xref: /openbmc/u-boot/README (revision 95de1e2f)
1#
2# (C) Copyright 2000 - 2013
3# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4#
5# SPDX-License-Identifier:	GPL-2.0+
6#
7
8Summary:
9========
10
11This directory contains the source code for U-Boot, a boot loader for
12Embedded boards based on PowerPC, ARM, MIPS and several other
13processors, which can be installed in a boot ROM and used to
14initialize and test the hardware or to download and run application
15code.
16
17The development of U-Boot is closely related to Linux: some parts of
18the source code originate in the Linux source tree, we have some
19header files in common, and special provision has been made to
20support booting of Linux images.
21
22Some attention has been paid to make this software easily
23configurable and extendable. For instance, all monitor commands are
24implemented with the same call interface, so that it's very easy to
25add new commands. Also, instead of permanently adding rarely used
26code (for instance hardware test utilities) to the monitor, you can
27load and run it dynamically.
28
29
30Status:
31=======
32
33In general, all boards for which a configuration option exists in the
34Makefile have been tested to some extent and can be considered
35"working". In fact, many of them are used in production systems.
36
37In case of problems see the CHANGELOG and CREDITS files to find out
38who contributed the specific port. The boards.cfg file lists board
39maintainers.
40
41Note: There is no CHANGELOG file in the actual U-Boot source tree;
42it can be created dynamically from the Git log using:
43
44	make CHANGELOG
45
46
47Where to get help:
48==================
49
50In case you have questions about, problems with or contributions for
51U-Boot you should send a message to the U-Boot mailing list at
52<u-boot@lists.denx.de>. There is also an archive of previous traffic
53on the mailing list - please search the archive before asking FAQ's.
54Please see http://lists.denx.de/pipermail/u-boot and
55http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
56
57
58Where to get source code:
59=========================
60
61The U-Boot source code is maintained in the git repository at
62git://www.denx.de/git/u-boot.git ; you can browse it online at
63http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
64
65The "snapshot" links on this page allow you to download tarballs of
66any version you might be interested in. Official releases are also
67available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
68directory.
69
70Pre-built (and tested) images are available from
71ftp://ftp.denx.de/pub/u-boot/images/
72
73
74Where we come from:
75===================
76
77- start from 8xxrom sources
78- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
79- clean up code
80- make it easier to add custom boards
81- make it possible to add other [PowerPC] CPUs
82- extend functions, especially:
83  * Provide extended interface to Linux boot loader
84  * S-Record download
85  * network boot
86  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
87- create ARMBoot project (http://sourceforge.net/projects/armboot)
88- add other CPU families (starting with ARM)
89- create U-Boot project (http://sourceforge.net/projects/u-boot)
90- current project page: see http://www.denx.de/wiki/U-Boot
91
92
93Names and Spelling:
94===================
95
96The "official" name of this project is "Das U-Boot". The spelling
97"U-Boot" shall be used in all written text (documentation, comments
98in source files etc.). Example:
99
100	This is the README file for the U-Boot project.
101
102File names etc. shall be based on the string "u-boot". Examples:
103
104	include/asm-ppc/u-boot.h
105
106	#include <asm/u-boot.h>
107
108Variable names, preprocessor constants etc. shall be either based on
109the string "u_boot" or on "U_BOOT". Example:
110
111	U_BOOT_VERSION		u_boot_logo
112	IH_OS_U_BOOT		u_boot_hush_start
113
114
115Versioning:
116===========
117
118Starting with the release in October 2008, the names of the releases
119were changed from numerical release numbers without deeper meaning
120into a time stamp based numbering. Regular releases are identified by
121names consisting of the calendar year and month of the release date.
122Additional fields (if present) indicate release candidates or bug fix
123releases in "stable" maintenance trees.
124
125Examples:
126	U-Boot v2009.11	    - Release November 2009
127	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
128	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
129
130
131Directory Hierarchy:
132====================
133
134/arch			Architecture specific files
135  /arc			Files generic to ARC architecture
136    /cpu		CPU specific files
137      /arc700		Files specific to ARC 700 CPUs
138    /lib		Architecture specific library files
139  /arm			Files generic to ARM architecture
140    /cpu		CPU specific files
141      /arm720t		Files specific to ARM 720 CPUs
142      /arm920t		Files specific to ARM 920 CPUs
143	/at91		Files specific to Atmel AT91RM9200 CPU
144	/imx		Files specific to Freescale MC9328 i.MX CPUs
145	/s3c24x0	Files specific to Samsung S3C24X0 CPUs
146      /arm926ejs	Files specific to ARM 926 CPUs
147      /arm1136		Files specific to ARM 1136 CPUs
148      /pxa		Files specific to Intel XScale PXA CPUs
149      /sa1100		Files specific to Intel StrongARM SA1100 CPUs
150    /lib		Architecture specific library files
151  /avr32		Files generic to AVR32 architecture
152    /cpu		CPU specific files
153    /lib		Architecture specific library files
154  /blackfin		Files generic to Analog Devices Blackfin architecture
155    /cpu		CPU specific files
156    /lib		Architecture specific library files
157  /m68k			Files generic to m68k architecture
158    /cpu		CPU specific files
159      /mcf52x2		Files specific to Freescale ColdFire MCF52x2 CPUs
160      /mcf5227x		Files specific to Freescale ColdFire MCF5227x CPUs
161      /mcf532x		Files specific to Freescale ColdFire MCF5329 CPUs
162      /mcf5445x		Files specific to Freescale ColdFire MCF5445x CPUs
163      /mcf547x_8x	Files specific to Freescale ColdFire MCF547x_8x CPUs
164    /lib		Architecture specific library files
165  /microblaze		Files generic to microblaze architecture
166    /cpu		CPU specific files
167    /lib		Architecture specific library files
168  /mips			Files generic to MIPS architecture
169    /cpu		CPU specific files
170      /mips32		Files specific to MIPS32 CPUs
171      /mips64		Files specific to MIPS64 CPUs
172    /lib		Architecture specific library files
173  /nds32		Files generic to NDS32 architecture
174    /cpu		CPU specific files
175      /n1213		Files specific to Andes Technology N1213 CPUs
176    /lib		Architecture specific library files
177  /nios2		Files generic to Altera NIOS2 architecture
178    /cpu		CPU specific files
179    /lib		Architecture specific library files
180  /openrisc		Files generic to OpenRISC architecture
181    /cpu		CPU specific files
182    /lib		Architecture specific library files
183  /powerpc		Files generic to PowerPC architecture
184    /cpu		CPU specific files
185      /mpc5xx		Files specific to Freescale MPC5xx CPUs
186      /mpc5xxx		Files specific to Freescale MPC5xxx CPUs
187      /mpc8xx		Files specific to Freescale MPC8xx CPUs
188      /mpc8260		Files specific to Freescale MPC8260 CPUs
189      /mpc85xx		Files specific to Freescale MPC85xx CPUs
190      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
191    /lib		Architecture specific library files
192  /sh			Files generic to SH architecture
193    /cpu		CPU specific files
194      /sh2		Files specific to sh2 CPUs
195      /sh3		Files specific to sh3 CPUs
196      /sh4		Files specific to sh4 CPUs
197    /lib		Architecture specific library files
198  /sparc		Files generic to SPARC architecture
199    /cpu		CPU specific files
200      /leon2		Files specific to Gaisler LEON2 SPARC CPU
201      /leon3		Files specific to Gaisler LEON3 SPARC CPU
202    /lib		Architecture specific library files
203  /x86			Files generic to x86 architecture
204    /cpu		CPU specific files
205    /lib		Architecture specific library files
206/api			Machine/arch independent API for external apps
207/board			Board dependent files
208/common			Misc architecture independent functions
209/disk			Code for disk drive partition handling
210/doc			Documentation (don't expect too much)
211/drivers		Commonly used device drivers
212/dts			Contains Makefile for building internal U-Boot fdt.
213/examples		Example code for standalone applications, etc.
214/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
215/include		Header Files
216/lib			Files generic to all architectures
217  /libfdt		Library files to support flattened device trees
218  /lzma			Library files to support LZMA decompression
219  /lzo			Library files to support LZO decompression
220/net			Networking code
221/post			Power On Self Test
222/spl			Secondary Program Loader framework
223/tools			Tools to build S-Record or U-Boot images, etc.
224
225Software Configuration:
226=======================
227
228Configuration is usually done using C preprocessor defines; the
229rationale behind that is to avoid dead code whenever possible.
230
231There are two classes of configuration variables:
232
233* Configuration _OPTIONS_:
234  These are selectable by the user and have names beginning with
235  "CONFIG_".
236
237* Configuration _SETTINGS_:
238  These depend on the hardware etc. and should not be meddled with if
239  you don't know what you're doing; they have names beginning with
240  "CONFIG_SYS_".
241
242Later we will add a configuration tool - probably similar to or even
243identical to what's used for the Linux kernel. Right now, we have to
244do the configuration by hand, which means creating some symbolic
245links and editing some configuration files. We use the TQM8xxL boards
246as an example here.
247
248
249Selection of Processor Architecture and Board Type:
250---------------------------------------------------
251
252For all supported boards there are ready-to-use default
253configurations available; just type "make <board_name>_defconfig".
254
255Example: For a TQM823L module type:
256
257	cd u-boot
258	make TQM823L_defconfig
259
260For the Cogent platform, you need to specify the CPU type as well;
261e.g. "make cogent_mpc8xx_defconfig". And also configure the cogent
262directory according to the instructions in cogent/README.
263
264
265Sandbox Environment:
266--------------------
267
268U-Boot can be built natively to run on a Linux host using the 'sandbox'
269board. This allows feature development which is not board- or architecture-
270specific to be undertaken on a native platform. The sandbox is also used to
271run some of U-Boot's tests.
272
273See board/sandbox/README.sandbox for more details.
274
275
276Board Initialisation Flow:
277--------------------------
278
279This is the intended start-up flow for boards. This should apply for both
280SPL and U-Boot proper (i.e. they both follow the same rules). At present SPL
281mostly uses a separate code path, but the funtion names and roles of each
282function are the same. Some boards or architectures may not conform to this.
283At least most ARM boards which use CONFIG_SPL_FRAMEWORK conform to this.
284
285Execution starts with start.S with three functions called during init after
286that. The purpose and limitations of each is described below.
287
288lowlevel_init():
289	- purpose: essential init to permit execution to reach board_init_f()
290	- no global_data or BSS
291	- there is no stack (ARMv7 may have one but it will soon be removed)
292	- must not set up SDRAM or use console
293	- must only do the bare minimum to allow execution to continue to
294		board_init_f()
295	- this is almost never needed
296	- return normally from this function
297
298board_init_f():
299	- purpose: set up the machine ready for running board_init_r():
300		i.e. SDRAM and serial UART
301	- global_data is available
302	- stack is in SRAM
303	- BSS is not available, so you cannot use global/static variables,
304		only stack variables and global_data
305
306	Non-SPL-specific notes:
307	- dram_init() is called to set up DRAM. If already done in SPL this
308		can do nothing
309
310	SPL-specific notes:
311	- you can override the entire board_init_f() function with your own
312		version as needed.
313	- preloader_console_init() can be called here in extremis
314	- should set up SDRAM, and anything needed to make the UART work
315	- these is no need to clear BSS, it will be done by crt0.S
316	- must return normally from this function (don't call board_init_r()
317		directly)
318
319Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
320this point the stack and global_data are relocated to below
321CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
322memory.
323
324board_init_r():
325	- purpose: main execution, common code
326	- global_data is available
327	- SDRAM is available
328	- BSS is available, all static/global variables can be used
329	- execution eventually continues to main_loop()
330
331	Non-SPL-specific notes:
332	- U-Boot is relocated to the top of memory and is now running from
333		there.
334
335	SPL-specific notes:
336	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
337		CONFIG_SPL_STACK_R_ADDR points into SDRAM
338	- preloader_console_init() can be called here - typically this is
339		done by defining CONFIG_SPL_BOARD_INIT and then supplying a
340		spl_board_init() function containing this call
341	- loads U-Boot or (in falcon mode) Linux
342
343
344
345Configuration Options:
346----------------------
347
348Configuration depends on the combination of board and CPU type; all
349such information is kept in a configuration file
350"include/configs/<board_name>.h".
351
352Example: For a TQM823L module, all configuration settings are in
353"include/configs/TQM823L.h".
354
355
356Many of the options are named exactly as the corresponding Linux
357kernel configuration options. The intention is to make it easier to
358build a config tool - later.
359
360
361The following options need to be configured:
362
363- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
364
365- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
366
367- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
368		Define exactly one, e.g. CONFIG_ATSTK1002
369
370- CPU Module Type: (if CONFIG_COGENT is defined)
371		Define exactly one of
372		CONFIG_CMA286_60_OLD
373--- FIXME --- not tested yet:
374		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
375		CONFIG_CMA287_23, CONFIG_CMA287_50
376
377- Motherboard Type: (if CONFIG_COGENT is defined)
378		Define exactly one of
379		CONFIG_CMA101, CONFIG_CMA102
380
381- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
382		Define one or more of
383		CONFIG_CMA302
384
385- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
386		Define one or more of
387		CONFIG_LCD_HEARTBEAT	- update a character position on
388					  the LCD display every second with
389					  a "rotator" |\-/|\-/
390
391- Marvell Family Member
392		CONFIG_SYS_MVFS		- define it if you want to enable
393					  multiple fs option at one time
394					  for marvell soc family
395
396- 8xx CPU Options: (if using an MPC8xx CPU)
397		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
398					  get_gclk_freq() cannot work
399					  e.g. if there is no 32KHz
400					  reference PIT/RTC clock
401		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
402					  or XTAL/EXTAL)
403
404- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
405		CONFIG_SYS_8xx_CPUCLK_MIN
406		CONFIG_SYS_8xx_CPUCLK_MAX
407		CONFIG_8xx_CPUCLK_DEFAULT
408			See doc/README.MPC866
409
410		CONFIG_SYS_MEASURE_CPUCLK
411
412		Define this to measure the actual CPU clock instead
413		of relying on the correctness of the configured
414		values. Mostly useful for board bringup to make sure
415		the PLL is locked at the intended frequency. Note
416		that this requires a (stable) reference clock (32 kHz
417		RTC clock or CONFIG_SYS_8XX_XIN)
418
419		CONFIG_SYS_DELAYED_ICACHE
420
421		Define this option if you want to enable the
422		ICache only when Code runs from RAM.
423
424- 85xx CPU Options:
425		CONFIG_SYS_PPC64
426
427		Specifies that the core is a 64-bit PowerPC implementation (implements
428		the "64" category of the Power ISA). This is necessary for ePAPR
429		compliance, among other possible reasons.
430
431		CONFIG_SYS_FSL_TBCLK_DIV
432
433		Defines the core time base clock divider ratio compared to the
434		system clock.  On most PQ3 devices this is 8, on newer QorIQ
435		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
436
437		CONFIG_SYS_FSL_PCIE_COMPAT
438
439		Defines the string to utilize when trying to match PCIe device
440		tree nodes for the given platform.
441
442		CONFIG_SYS_PPC_E500_DEBUG_TLB
443
444		Enables a temporary TLB entry to be used during boot to work
445		around limitations in e500v1 and e500v2 external debugger
446		support. This reduces the portions of the boot code where
447		breakpoints and single stepping do not work.  The value of this
448		symbol should be set to the TLB1 entry to be used for this
449		purpose.
450
451		CONFIG_SYS_FSL_ERRATUM_A004510
452
453		Enables a workaround for erratum A004510.  If set,
454		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
455		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
456
457		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
458		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
459
460		Defines one or two SoC revisions (low 8 bits of SVR)
461		for which the A004510 workaround should be applied.
462
463		The rest of SVR is either not relevant to the decision
464		of whether the erratum is present (e.g. p2040 versus
465		p2041) or is implied by the build target, which controls
466		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
467
468		See Freescale App Note 4493 for more information about
469		this erratum.
470
471		CONFIG_A003399_NOR_WORKAROUND
472		Enables a workaround for IFC erratum A003399. It is only
473		required during NOR boot.
474
475		CONFIG_A008044_WORKAROUND
476		Enables a workaround for T1040/T1042 erratum A008044. It is only
477		required during NAND boot and valid for Rev 1.0 SoC revision
478
479		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
480
481		This is the value to write into CCSR offset 0x18600
482		according to the A004510 workaround.
483
484		CONFIG_SYS_FSL_DSP_DDR_ADDR
485		This value denotes start offset of DDR memory which is
486		connected exclusively to the DSP cores.
487
488		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
489		This value denotes start offset of M2 memory
490		which is directly connected to the DSP core.
491
492		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
493		This value denotes start offset of M3 memory which is directly
494		connected to the DSP core.
495
496		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
497		This value denotes start offset of DSP CCSR space.
498
499		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
500		Single Source Clock is clocking mode present in some of FSL SoC's.
501		In this mode, a single differential clock is used to supply
502		clocks to the sysclock, ddrclock and usbclock.
503
504		CONFIG_SYS_CPC_REINIT_F
505		This CONFIG is defined when the CPC is configured as SRAM at the
506		time of U-boot entry and is required to be re-initialized.
507
508		CONFIG_DEEP_SLEEP
509		Indicates this SoC supports deep sleep feature. If deep sleep is
510		supported, core will start to execute uboot when wakes up.
511
512- Generic CPU options:
513		CONFIG_SYS_GENERIC_GLOBAL_DATA
514		Defines global data is initialized in generic board board_init_f().
515		If this macro is defined, global data is created and cleared in
516		generic board board_init_f(). Without this macro, architecture/board
517		should initialize global data before calling board_init_f().
518
519		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
520
521		Defines the endianess of the CPU. Implementation of those
522		values is arch specific.
523
524		CONFIG_SYS_FSL_DDR
525		Freescale DDR driver in use. This type of DDR controller is
526		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
527		SoCs.
528
529		CONFIG_SYS_FSL_DDR_ADDR
530		Freescale DDR memory-mapped register base.
531
532		CONFIG_SYS_FSL_DDR_EMU
533		Specify emulator support for DDR. Some DDR features such as
534		deskew training are not available.
535
536		CONFIG_SYS_FSL_DDRC_GEN1
537		Freescale DDR1 controller.
538
539		CONFIG_SYS_FSL_DDRC_GEN2
540		Freescale DDR2 controller.
541
542		CONFIG_SYS_FSL_DDRC_GEN3
543		Freescale DDR3 controller.
544
545		CONFIG_SYS_FSL_DDRC_GEN4
546		Freescale DDR4 controller.
547
548		CONFIG_SYS_FSL_DDRC_ARM_GEN3
549		Freescale DDR3 controller for ARM-based SoCs.
550
551		CONFIG_SYS_FSL_DDR1
552		Board config to use DDR1. It can be enabled for SoCs with
553		Freescale DDR1 or DDR2 controllers, depending on the board
554		implemetation.
555
556		CONFIG_SYS_FSL_DDR2
557		Board config to use DDR2. It can be eanbeld for SoCs with
558		Freescale DDR2 or DDR3 controllers, depending on the board
559		implementation.
560
561		CONFIG_SYS_FSL_DDR3
562		Board config to use DDR3. It can be enabled for SoCs with
563		Freescale DDR3 or DDR3L controllers.
564
565		CONFIG_SYS_FSL_DDR3L
566		Board config to use DDR3L. It can be enabled for SoCs with
567		DDR3L controllers.
568
569		CONFIG_SYS_FSL_DDR4
570		Board config to use DDR4. It can be enabled for SoCs with
571		DDR4 controllers.
572
573		CONFIG_SYS_FSL_IFC_BE
574		Defines the IFC controller register space as Big Endian
575
576		CONFIG_SYS_FSL_IFC_LE
577		Defines the IFC controller register space as Little Endian
578
579		CONFIG_SYS_FSL_PBL_PBI
580		It enables addition of RCW (Power on reset configuration) in built image.
581		Please refer doc/README.pblimage for more details
582
583		CONFIG_SYS_FSL_PBL_RCW
584		It adds PBI(pre-boot instructions) commands in u-boot build image.
585		PBI commands can be used to configure SoC before it starts the execution.
586		Please refer doc/README.pblimage for more details
587
588		CONFIG_SPL_FSL_PBL
589		It adds a target to create boot binary having SPL binary in PBI format
590		concatenated with u-boot binary.
591
592		CONFIG_SYS_FSL_DDR_BE
593		Defines the DDR controller register space as Big Endian
594
595		CONFIG_SYS_FSL_DDR_LE
596		Defines the DDR controller register space as Little Endian
597
598		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
599		Physical address from the view of DDR controllers. It is the
600		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
601		it could be different for ARM SoCs.
602
603		CONFIG_SYS_FSL_DDR_INTLV_256B
604		DDR controller interleaving on 256-byte. This is a special
605		interleaving mode, handled by Dickens for Freescale layerscape
606		SoCs with ARM core.
607
608		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
609		Number of controllers used as main memory.
610
611		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
612		Number of controllers used for other than main memory.
613
614		CONFIG_SYS_FSL_SEC_BE
615		Defines the SEC controller register space as Big Endian
616
617		CONFIG_SYS_FSL_SEC_LE
618		Defines the SEC controller register space as Little Endian
619
620- Intel Monahans options:
621		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
622
623		Defines the Monahans run mode to oscillator
624		ratio. Valid values are 8, 16, 24, 31. The core
625		frequency is this value multiplied by 13 MHz.
626
627		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
628
629		Defines the Monahans turbo mode to oscillator
630		ratio. Valid values are 1 (default if undefined) and
631		2. The core frequency as calculated above is multiplied
632		by this value.
633
634- MIPS CPU options:
635		CONFIG_SYS_INIT_SP_OFFSET
636
637		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
638		pointer. This is needed for the temporary stack before
639		relocation.
640
641		CONFIG_SYS_MIPS_CACHE_MODE
642
643		Cache operation mode for the MIPS CPU.
644		See also arch/mips/include/asm/mipsregs.h.
645		Possible values are:
646			CONF_CM_CACHABLE_NO_WA
647			CONF_CM_CACHABLE_WA
648			CONF_CM_UNCACHED
649			CONF_CM_CACHABLE_NONCOHERENT
650			CONF_CM_CACHABLE_CE
651			CONF_CM_CACHABLE_COW
652			CONF_CM_CACHABLE_CUW
653			CONF_CM_CACHABLE_ACCELERATED
654
655		CONFIG_SYS_XWAY_EBU_BOOTCFG
656
657		Special option for Lantiq XWAY SoCs for booting from NOR flash.
658		See also arch/mips/cpu/mips32/start.S.
659
660		CONFIG_XWAY_SWAP_BYTES
661
662		Enable compilation of tools/xway-swap-bytes needed for Lantiq
663		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
664		be swapped if a flash programmer is used.
665
666- ARM options:
667		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
668
669		Select high exception vectors of the ARM core, e.g., do not
670		clear the V bit of the c1 register of CP15.
671
672		CONFIG_SYS_THUMB_BUILD
673
674		Use this flag to build U-Boot using the Thumb instruction
675		set for ARM architectures. Thumb instruction set provides
676		better code density. For ARM architectures that support
677		Thumb2 this flag will result in Thumb2 code generated by
678		GCC.
679
680		CONFIG_ARM_ERRATA_716044
681		CONFIG_ARM_ERRATA_742230
682		CONFIG_ARM_ERRATA_743622
683		CONFIG_ARM_ERRATA_751472
684		CONFIG_ARM_ERRATA_794072
685		CONFIG_ARM_ERRATA_761320
686
687		If set, the workarounds for these ARM errata are applied early
688		during U-Boot startup. Note that these options force the
689		workarounds to be applied; no CPU-type/version detection
690		exists, unlike the similar options in the Linux kernel. Do not
691		set these options unless they apply!
692
693		COUNTER_FREQUENCY
694		Generic timer clock source frequency.
695
696		COUNTER_FREQUENCY_REAL
697		Generic timer clock source frequency if the real clock is
698		different from COUNTER_FREQUENCY, and can only be determined
699		at run time.
700
701		NOTE: The following can be machine specific errata. These
702		do have ability to provide rudimentary version and machine
703		specific checks, but expect no product checks.
704		CONFIG_ARM_ERRATA_430973
705		CONFIG_ARM_ERRATA_454179
706		CONFIG_ARM_ERRATA_621766
707		CONFIG_ARM_ERRATA_798870
708
709- Tegra SoC options:
710		CONFIG_TEGRA_SUPPORT_NON_SECURE
711
712		Support executing U-Boot in non-secure (NS) mode. Certain
713		impossible actions will be skipped if the CPU is in NS mode,
714		such as ARM architectural timer initialization.
715
716- Linux Kernel Interface:
717		CONFIG_CLOCKS_IN_MHZ
718
719		U-Boot stores all clock information in Hz
720		internally. For binary compatibility with older Linux
721		kernels (which expect the clocks passed in the
722		bd_info data to be in MHz) the environment variable
723		"clocks_in_mhz" can be defined so that U-Boot
724		converts clock data to MHZ before passing it to the
725		Linux kernel.
726		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
727		"clocks_in_mhz=1" is automatically included in the
728		default environment.
729
730		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
731
732		When transferring memsize parameter to Linux, some versions
733		expect it to be in bytes, others in MB.
734		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
735
736		CONFIG_OF_LIBFDT
737
738		New kernel versions are expecting firmware settings to be
739		passed using flattened device trees (based on open firmware
740		concepts).
741
742		CONFIG_OF_LIBFDT
743		 * New libfdt-based support
744		 * Adds the "fdt" command
745		 * The bootm command automatically updates the fdt
746
747		OF_CPU - The proper name of the cpus node (only required for
748			MPC512X and MPC5xxx based boards).
749		OF_SOC - The proper name of the soc node (only required for
750			MPC512X and MPC5xxx based boards).
751		OF_TBCLK - The timebase frequency.
752		OF_STDOUT_PATH - The path to the console device
753
754		boards with QUICC Engines require OF_QE to set UCC MAC
755		addresses
756
757		CONFIG_OF_BOARD_SETUP
758
759		Board code has addition modification that it wants to make
760		to the flat device tree before handing it off to the kernel
761
762		CONFIG_OF_SYSTEM_SETUP
763
764		Other code has addition modification that it wants to make
765		to the flat device tree before handing it off to the kernel.
766		This causes ft_system_setup() to be called before booting
767		the kernel.
768
769		CONFIG_OF_BOOT_CPU
770
771		This define fills in the correct boot CPU in the boot
772		param header, the default value is zero if undefined.
773
774		CONFIG_OF_IDE_FIXUP
775
776		U-Boot can detect if an IDE device is present or not.
777		If not, and this new config option is activated, U-Boot
778		removes the ATA node from the DTS before booting Linux,
779		so the Linux IDE driver does not probe the device and
780		crash. This is needed for buggy hardware (uc101) where
781		no pull down resistor is connected to the signal IDE5V_DD7.
782
783		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
784
785		This setting is mandatory for all boards that have only one
786		machine type and must be used to specify the machine type
787		number as it appears in the ARM machine registry
788		(see http://www.arm.linux.org.uk/developer/machines/).
789		Only boards that have multiple machine types supported
790		in a single configuration file and the machine type is
791		runtime discoverable, do not have to use this setting.
792
793- vxWorks boot parameters:
794
795		bootvx constructs a valid bootline using the following
796		environments variables: bootfile, ipaddr, serverip, hostname.
797		It loads the vxWorks image pointed bootfile.
798
799		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
800		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
801		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
802		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
803
804		CONFIG_SYS_VXWORKS_ADD_PARAMS
805
806		Add it at the end of the bootline. E.g "u=username pw=secret"
807
808		Note: If a "bootargs" environment is defined, it will overwride
809		the defaults discussed just above.
810
811- Cache Configuration:
812		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
813		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
814		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
815
816- Cache Configuration for ARM:
817		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
818				      controller
819		CONFIG_SYS_PL310_BASE - Physical base address of PL310
820					controller register space
821
822- Serial Ports:
823		CONFIG_PL010_SERIAL
824
825		Define this if you want support for Amba PrimeCell PL010 UARTs.
826
827		CONFIG_PL011_SERIAL
828
829		Define this if you want support for Amba PrimeCell PL011 UARTs.
830
831		CONFIG_PL011_CLOCK
832
833		If you have Amba PrimeCell PL011 UARTs, set this variable to
834		the clock speed of the UARTs.
835
836		CONFIG_PL01x_PORTS
837
838		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
839		define this to a list of base addresses for each (supported)
840		port. See e.g. include/configs/versatile.h
841
842		CONFIG_PL011_SERIAL_RLCR
843
844		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
845		have separate receive and transmit line control registers.  Set
846		this variable to initialize the extra register.
847
848		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
849
850		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
851		boot loader that has already initialized the UART.  Define this
852		variable to flush the UART at init time.
853
854		CONFIG_SERIAL_HW_FLOW_CONTROL
855
856		Define this variable to enable hw flow control in serial driver.
857		Current user of this option is drivers/serial/nsl16550.c driver
858
859- Console Interface:
860		Depending on board, define exactly one serial port
861		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
862		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
863		console by defining CONFIG_8xx_CONS_NONE
864
865		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
866		port routines must be defined elsewhere
867		(i.e. serial_init(), serial_getc(), ...)
868
869		CONFIG_CFB_CONSOLE
870		Enables console device for a color framebuffer. Needs following
871		defines (cf. smiLynxEM, i8042)
872			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
873						(default big endian)
874			VIDEO_HW_RECTFILL	graphic chip supports
875						rectangle fill
876						(cf. smiLynxEM)
877			VIDEO_HW_BITBLT		graphic chip supports
878						bit-blit (cf. smiLynxEM)
879			VIDEO_VISIBLE_COLS	visible pixel columns
880						(cols=pitch)
881			VIDEO_VISIBLE_ROWS	visible pixel rows
882			VIDEO_PIXEL_SIZE	bytes per pixel
883			VIDEO_DATA_FORMAT	graphic data format
884						(0-5, cf. cfb_console.c)
885			VIDEO_FB_ADRS		framebuffer address
886			VIDEO_KBD_INIT_FCT	keyboard int fct
887						(i.e. i8042_kbd_init())
888			VIDEO_TSTC_FCT		test char fct
889						(i.e. i8042_tstc)
890			VIDEO_GETC_FCT		get char fct
891						(i.e. i8042_getc)
892			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
893						(requires blink timer
894						cf. i8042.c)
895			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
896			CONFIG_CONSOLE_TIME	display time/date info in
897						upper right corner
898						(requires CONFIG_CMD_DATE)
899			CONFIG_VIDEO_LOGO	display Linux logo in
900						upper left corner
901			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
902						linux_logo.h for logo.
903						Requires CONFIG_VIDEO_LOGO
904			CONFIG_CONSOLE_EXTRA_INFO
905						additional board info beside
906						the logo
907
908		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
909		a limited number of ANSI escape sequences (cursor control,
910		erase functions and limited graphics rendition control).
911
912		When CONFIG_CFB_CONSOLE is defined, video console is
913		default i/o. Serial console can be forced with
914		environment 'console=serial'.
915
916		When CONFIG_SILENT_CONSOLE is defined, all console
917		messages (by U-Boot and Linux!) can be silenced with
918		the "silent" environment variable. See
919		doc/README.silent for more information.
920
921		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
922			is 0x00.
923		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
924			is 0xa0.
925
926- Console Baudrate:
927		CONFIG_BAUDRATE - in bps
928		Select one of the baudrates listed in
929		CONFIG_SYS_BAUDRATE_TABLE, see below.
930		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
931
932- Console Rx buffer length
933		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
934		the maximum receive buffer length for the SMC.
935		This option is actual only for 82xx and 8xx possible.
936		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
937		must be defined, to setup the maximum idle timeout for
938		the SMC.
939
940- Pre-Console Buffer:
941		Prior to the console being initialised (i.e. serial UART
942		initialised etc) all console output is silently discarded.
943		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
944		buffer any console messages prior to the console being
945		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
946		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
947		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
948		bytes are output before the console is initialised, the
949		earlier bytes are discarded.
950
951		Note that when printing the buffer a copy is made on the
952		stack so CONFIG_PRE_CON_BUF_SZ must fit on the stack.
953
954		'Sane' compilers will generate smaller code if
955		CONFIG_PRE_CON_BUF_SZ is a power of 2
956
957- Safe printf() functions
958		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
959		the printf() functions. These are defined in
960		include/vsprintf.h and include snprintf(), vsnprintf() and
961		so on. Code size increase is approximately 300-500 bytes.
962		If this option is not given then these functions will
963		silently discard their buffer size argument - this means
964		you are not getting any overflow checking in this case.
965
966- Boot Delay:	CONFIG_BOOTDELAY - in seconds
967		Delay before automatically booting the default image;
968		set to -1 to disable autoboot.
969		set to -2 to autoboot with no delay and not check for abort
970		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
971
972		See doc/README.autoboot for these options that
973		work with CONFIG_BOOTDELAY. None are required.
974		CONFIG_BOOT_RETRY_TIME
975		CONFIG_BOOT_RETRY_MIN
976		CONFIG_AUTOBOOT_KEYED
977		CONFIG_AUTOBOOT_PROMPT
978		CONFIG_AUTOBOOT_DELAY_STR
979		CONFIG_AUTOBOOT_STOP_STR
980		CONFIG_ZERO_BOOTDELAY_CHECK
981		CONFIG_RESET_TO_RETRY
982
983- Autoboot Command:
984		CONFIG_BOOTCOMMAND
985		Only needed when CONFIG_BOOTDELAY is enabled;
986		define a command string that is automatically executed
987		when no character is read on the console interface
988		within "Boot Delay" after reset.
989
990		CONFIG_BOOTARGS
991		This can be used to pass arguments to the bootm
992		command. The value of CONFIG_BOOTARGS goes into the
993		environment value "bootargs".
994
995		CONFIG_RAMBOOT and CONFIG_NFSBOOT
996		The value of these goes into the environment as
997		"ramboot" and "nfsboot" respectively, and can be used
998		as a convenience, when switching between booting from
999		RAM and NFS.
1000
1001- Bootcount:
1002		CONFIG_BOOTCOUNT_LIMIT
1003		Implements a mechanism for detecting a repeating reboot
1004		cycle, see:
1005		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
1006
1007		CONFIG_BOOTCOUNT_ENV
1008		If no softreset save registers are found on the hardware
1009		"bootcount" is stored in the environment. To prevent a
1010		saveenv on all reboots, the environment variable
1011		"upgrade_available" is used. If "upgrade_available" is
1012		0, "bootcount" is always 0, if "upgrade_available" is
1013		1 "bootcount" is incremented in the environment.
1014		So the Userspace Applikation must set the "upgrade_available"
1015		and "bootcount" variable to 0, if a boot was successfully.
1016
1017- Pre-Boot Commands:
1018		CONFIG_PREBOOT
1019
1020		When this option is #defined, the existence of the
1021		environment variable "preboot" will be checked
1022		immediately before starting the CONFIG_BOOTDELAY
1023		countdown and/or running the auto-boot command resp.
1024		entering interactive mode.
1025
1026		This feature is especially useful when "preboot" is
1027		automatically generated or modified. For an example
1028		see the LWMON board specific code: here "preboot" is
1029		modified when the user holds down a certain
1030		combination of keys on the (special) keyboard when
1031		booting the systems
1032
1033- Serial Download Echo Mode:
1034		CONFIG_LOADS_ECHO
1035		If defined to 1, all characters received during a
1036		serial download (using the "loads" command) are
1037		echoed back. This might be needed by some terminal
1038		emulations (like "cu"), but may as well just take
1039		time on others. This setting #define's the initial
1040		value of the "loads_echo" environment variable.
1041
1042- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
1043		CONFIG_KGDB_BAUDRATE
1044		Select one of the baudrates listed in
1045		CONFIG_SYS_BAUDRATE_TABLE, see below.
1046
1047- Monitor Functions:
1048		Monitor commands can be included or excluded
1049		from the build by using the #include files
1050		<config_cmd_all.h> and #undef'ing unwanted
1051		commands, or adding #define's for wanted commands.
1052
1053		The default command configuration includes all commands
1054		except those marked below with a "*".
1055
1056		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
1057		CONFIG_CMD_ASKENV	* ask for env variable
1058		CONFIG_CMD_BDI		  bdinfo
1059		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
1060		CONFIG_CMD_BMP		* BMP support
1061		CONFIG_CMD_BSP		* Board specific commands
1062		CONFIG_CMD_BOOTD	  bootd
1063		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
1064		CONFIG_CMD_CACHE	* icache, dcache
1065		CONFIG_CMD_CLK   	* clock command support
1066		CONFIG_CMD_CONSOLE	  coninfo
1067		CONFIG_CMD_CRC32	* crc32
1068		CONFIG_CMD_DATE		* support for RTC, date/time...
1069		CONFIG_CMD_DHCP		* DHCP support
1070		CONFIG_CMD_DIAG		* Diagnostics
1071		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
1072		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
1073		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
1074		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
1075		CONFIG_CMD_DTT		* Digital Therm and Thermostat
1076		CONFIG_CMD_ECHO		  echo arguments
1077		CONFIG_CMD_EDITENV	  edit env variable
1078		CONFIG_CMD_EEPROM	* EEPROM read/write support
1079		CONFIG_CMD_ELF		* bootelf, bootvx
1080		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
1081		CONFIG_CMD_ENV_FLAGS	* display details about env flags
1082		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
1083		CONFIG_CMD_EXPORTENV	* export the environment
1084		CONFIG_CMD_EXT2		* ext2 command support
1085		CONFIG_CMD_EXT4		* ext4 command support
1086		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
1087					  that work for multiple fs types
1088		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
1089		CONFIG_CMD_SAVEENV	  saveenv
1090		CONFIG_CMD_FDC		* Floppy Disk Support
1091		CONFIG_CMD_FAT		* FAT command support
1092		CONFIG_CMD_FLASH	  flinfo, erase, protect
1093		CONFIG_CMD_FPGA		  FPGA device initialization support
1094		CONFIG_CMD_FUSE		* Device fuse support
1095		CONFIG_CMD_GETTIME	* Get time since boot
1096		CONFIG_CMD_GO		* the 'go' command (exec code)
1097		CONFIG_CMD_GREPENV	* search environment
1098		CONFIG_CMD_HASH		* calculate hash / digest
1099		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
1100		CONFIG_CMD_I2C		* I2C serial bus support
1101		CONFIG_CMD_IDE		* IDE harddisk support
1102		CONFIG_CMD_IMI		  iminfo
1103		CONFIG_CMD_IMLS		  List all images found in NOR flash
1104		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
1105		CONFIG_CMD_IMMAP	* IMMR dump support
1106		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
1107		CONFIG_CMD_IMPORTENV	* import an environment
1108		CONFIG_CMD_INI		* import data from an ini file into the env
1109		CONFIG_CMD_IRQ		* irqinfo
1110		CONFIG_CMD_ITEST	  Integer/string test of 2 values
1111		CONFIG_CMD_JFFS2	* JFFS2 Support
1112		CONFIG_CMD_KGDB		* kgdb
1113		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
1114		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
1115					  (169.254.*.*)
1116		CONFIG_CMD_LOADB	  loadb
1117		CONFIG_CMD_LOADS	  loads
1118		CONFIG_CMD_MD5SUM	* print md5 message digest
1119					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
1120		CONFIG_CMD_MEMINFO	* Display detailed memory information
1121		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
1122					  loop, loopw
1123		CONFIG_CMD_MEMTEST	* mtest
1124		CONFIG_CMD_MISC		  Misc functions like sleep etc
1125		CONFIG_CMD_MMC		* MMC memory mapped support
1126		CONFIG_CMD_MII		* MII utility commands
1127		CONFIG_CMD_MTDPARTS	* MTD partition support
1128		CONFIG_CMD_NAND		* NAND support
1129		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
1130		CONFIG_CMD_NFS		  NFS support
1131		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
1132		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
1133		CONFIG_CMD_PCI		* pciinfo
1134		CONFIG_CMD_PCMCIA		* PCMCIA support
1135		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
1136					  host
1137		CONFIG_CMD_PORTIO	* Port I/O
1138		CONFIG_CMD_READ		* Read raw data from partition
1139		CONFIG_CMD_REGINFO	* Register dump
1140		CONFIG_CMD_RUN		  run command in env variable
1141		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
1142		CONFIG_CMD_SAVES	* save S record dump
1143		CONFIG_CMD_SCSI		* SCSI Support
1144		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1145					  (requires CONFIG_CMD_I2C)
1146		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1147					  (4xx only)
1148		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1149		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1150					  (requires CONFIG_CMD_MEMORY)
1151		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1152		CONFIG_CMD_SOURCE	  "source" command Support
1153		CONFIG_CMD_SPI		* SPI serial bus support
1154		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1155		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1156		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1157		CONFIG_CMD_TIMER	* access to the system tick timer
1158		CONFIG_CMD_USB		* USB support
1159		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1160		CONFIG_CMD_MFSL		* Microblaze FSL support
1161		CONFIG_CMD_XIMG		  Load part of Multi Image
1162		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1163
1164		EXAMPLE: If you want all functions except of network
1165		support you can write:
1166
1167		#include "config_cmd_all.h"
1168		#undef CONFIG_CMD_NET
1169
1170	Other Commands:
1171		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1172
1173	Note:	Don't enable the "icache" and "dcache" commands
1174		(configuration option CONFIG_CMD_CACHE) unless you know
1175		what you (and your U-Boot users) are doing. Data
1176		cache cannot be enabled on systems like the 8xx or
1177		8260 (where accesses to the IMMR region must be
1178		uncached), and it cannot be disabled on all other
1179		systems where we (mis-) use the data cache to hold an
1180		initial stack and some data.
1181
1182
1183		XXX - this list needs to get updated!
1184
1185- Regular expression support:
1186		CONFIG_REGEX
1187		If this variable is defined, U-Boot is linked against
1188		the SLRE (Super Light Regular Expression) library,
1189		which adds regex support to some commands, as for
1190		example "env grep" and "setexpr".
1191
1192- Device tree:
1193		CONFIG_OF_CONTROL
1194		If this variable is defined, U-Boot will use a device tree
1195		to configure its devices, instead of relying on statically
1196		compiled #defines in the board file. This option is
1197		experimental and only available on a few boards. The device
1198		tree is available in the global data as gd->fdt_blob.
1199
1200		U-Boot needs to get its device tree from somewhere. This can
1201		be done using one of the two options below:
1202
1203		CONFIG_OF_EMBED
1204		If this variable is defined, U-Boot will embed a device tree
1205		binary in its image. This device tree file should be in the
1206		board directory and called <soc>-<board>.dts. The binary file
1207		is then picked up in board_init_f() and made available through
1208		the global data structure as gd->blob.
1209
1210		CONFIG_OF_SEPARATE
1211		If this variable is defined, U-Boot will build a device tree
1212		binary. It will be called u-boot.dtb. Architecture-specific
1213		code will locate it at run-time. Generally this works by:
1214
1215			cat u-boot.bin u-boot.dtb >image.bin
1216
1217		and in fact, U-Boot does this for you, creating a file called
1218		u-boot-dtb.bin which is useful in the common case. You can
1219		still use the individual files if you need something more
1220		exotic.
1221
1222- Watchdog:
1223		CONFIG_WATCHDOG
1224		If this variable is defined, it enables watchdog
1225		support for the SoC. There must be support in the SoC
1226		specific code for a watchdog. For the 8xx and 8260
1227		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1228		register.  When supported for a specific SoC is
1229		available, then no further board specific code should
1230		be needed to use it.
1231
1232		CONFIG_HW_WATCHDOG
1233		When using a watchdog circuitry external to the used
1234		SoC, then define this variable and provide board
1235		specific code for the "hw_watchdog_reset" function.
1236
1237		CONFIG_AT91_HW_WDT_TIMEOUT
1238		specify the timeout in seconds. default 2 seconds.
1239
1240- U-Boot Version:
1241		CONFIG_VERSION_VARIABLE
1242		If this variable is defined, an environment variable
1243		named "ver" is created by U-Boot showing the U-Boot
1244		version as printed by the "version" command.
1245		Any change to this variable will be reverted at the
1246		next reset.
1247
1248- Real-Time Clock:
1249
1250		When CONFIG_CMD_DATE is selected, the type of the RTC
1251		has to be selected, too. Define exactly one of the
1252		following options:
1253
1254		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1255		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1256		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1257		CONFIG_RTC_MC146818	- use MC146818 RTC
1258		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1259		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1260		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1261		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1262		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1263		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1264		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1265		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1266		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1267					  RV3029 RTC.
1268
1269		Note that if the RTC uses I2C, then the I2C interface
1270		must also be configured. See I2C Support, below.
1271
1272- GPIO Support:
1273		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1274
1275		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1276		chip-ngpio pairs that tell the PCA953X driver the number of
1277		pins supported by a particular chip.
1278
1279		Note that if the GPIO device uses I2C, then the I2C interface
1280		must also be configured. See I2C Support, below.
1281
1282- I/O tracing:
1283		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1284		accesses and can checksum them or write a list of them out
1285		to memory. See the 'iotrace' command for details. This is
1286		useful for testing device drivers since it can confirm that
1287		the driver behaves the same way before and after a code
1288		change. Currently this is supported on sandbox and arm. To
1289		add support for your architecture, add '#include <iotrace.h>'
1290		to the bottom of arch/<arch>/include/asm/io.h and test.
1291
1292		Example output from the 'iotrace stats' command is below.
1293		Note that if the trace buffer is exhausted, the checksum will
1294		still continue to operate.
1295
1296			iotrace is enabled
1297			Start:  10000000	(buffer start address)
1298			Size:   00010000	(buffer size)
1299			Offset: 00000120	(current buffer offset)
1300			Output: 10000120	(start + offset)
1301			Count:  00000018	(number of trace records)
1302			CRC32:  9526fb66	(CRC32 of all trace records)
1303
1304- Timestamp Support:
1305
1306		When CONFIG_TIMESTAMP is selected, the timestamp
1307		(date and time) of an image is printed by image
1308		commands like bootm or iminfo. This option is
1309		automatically enabled when you select CONFIG_CMD_DATE .
1310
1311- Partition Labels (disklabels) Supported:
1312		Zero or more of the following:
1313		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1314		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1315				       Intel architecture, USB sticks, etc.
1316		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1317		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1318				       bootloader.  Note 2TB partition limit; see
1319				       disk/part_efi.c
1320		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1321
1322		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1323		CONFIG_CMD_SCSI) you must configure support for at
1324		least one non-MTD partition type as well.
1325
1326- IDE Reset method:
1327		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1328		board configurations files but used nowhere!
1329
1330		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1331		be performed by calling the function
1332			ide_set_reset(int reset)
1333		which has to be defined in a board specific file
1334
1335- ATAPI Support:
1336		CONFIG_ATAPI
1337
1338		Set this to enable ATAPI support.
1339
1340- LBA48 Support
1341		CONFIG_LBA48
1342
1343		Set this to enable support for disks larger than 137GB
1344		Also look at CONFIG_SYS_64BIT_LBA.
1345		Whithout these , LBA48 support uses 32bit variables and will 'only'
1346		support disks up to 2.1TB.
1347
1348		CONFIG_SYS_64BIT_LBA:
1349			When enabled, makes the IDE subsystem use 64bit sector addresses.
1350			Default is 32bit.
1351
1352- SCSI Support:
1353		At the moment only there is only support for the
1354		SYM53C8XX SCSI controller; define
1355		CONFIG_SCSI_SYM53C8XX to enable it.
1356
1357		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1358		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1359		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1360		maximum numbers of LUNs, SCSI ID's and target
1361		devices.
1362		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1363
1364		The environment variable 'scsidevs' is set to the number of
1365		SCSI devices found during the last scan.
1366
1367- NETWORK Support (PCI):
1368		CONFIG_E1000
1369		Support for Intel 8254x/8257x gigabit chips.
1370
1371		CONFIG_E1000_SPI
1372		Utility code for direct access to the SPI bus on Intel 8257x.
1373		This does not do anything useful unless you set at least one
1374		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1375
1376		CONFIG_E1000_SPI_GENERIC
1377		Allow generic access to the SPI bus on the Intel 8257x, for
1378		example with the "sspi" command.
1379
1380		CONFIG_CMD_E1000
1381		Management command for E1000 devices.  When used on devices
1382		with SPI support you can reprogram the EEPROM from U-Boot.
1383
1384		CONFIG_E1000_FALLBACK_MAC
1385		default MAC for empty EEPROM after production.
1386
1387		CONFIG_EEPRO100
1388		Support for Intel 82557/82559/82559ER chips.
1389		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1390		write routine for first time initialisation.
1391
1392		CONFIG_TULIP
1393		Support for Digital 2114x chips.
1394		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1395		modem chip initialisation (KS8761/QS6611).
1396
1397		CONFIG_NATSEMI
1398		Support for National dp83815 chips.
1399
1400		CONFIG_NS8382X
1401		Support for National dp8382[01] gigabit chips.
1402
1403- NETWORK Support (other):
1404
1405		CONFIG_DRIVER_AT91EMAC
1406		Support for AT91RM9200 EMAC.
1407
1408			CONFIG_RMII
1409			Define this to use reduced MII inteface
1410
1411			CONFIG_DRIVER_AT91EMAC_QUIET
1412			If this defined, the driver is quiet.
1413			The driver doen't show link status messages.
1414
1415		CONFIG_CALXEDA_XGMAC
1416		Support for the Calxeda XGMAC device
1417
1418		CONFIG_LAN91C96
1419		Support for SMSC's LAN91C96 chips.
1420
1421			CONFIG_LAN91C96_BASE
1422			Define this to hold the physical address
1423			of the LAN91C96's I/O space
1424
1425			CONFIG_LAN91C96_USE_32_BIT
1426			Define this to enable 32 bit addressing
1427
1428		CONFIG_SMC91111
1429		Support for SMSC's LAN91C111 chip
1430
1431			CONFIG_SMC91111_BASE
1432			Define this to hold the physical address
1433			of the device (I/O space)
1434
1435			CONFIG_SMC_USE_32_BIT
1436			Define this if data bus is 32 bits
1437
1438			CONFIG_SMC_USE_IOFUNCS
1439			Define this to use i/o functions instead of macros
1440			(some hardware wont work with macros)
1441
1442		CONFIG_DRIVER_TI_EMAC
1443		Support for davinci emac
1444
1445			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1446			Define this if you have more then 3 PHYs.
1447
1448		CONFIG_FTGMAC100
1449		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1450
1451			CONFIG_FTGMAC100_EGIGA
1452			Define this to use GE link update with gigabit PHY.
1453			Define this if FTGMAC100 is connected to gigabit PHY.
1454			If your system has 10/100 PHY only, it might not occur
1455			wrong behavior. Because PHY usually return timeout or
1456			useless data when polling gigabit status and gigabit
1457			control registers. This behavior won't affect the
1458			correctnessof 10/100 link speed update.
1459
1460		CONFIG_SMC911X
1461		Support for SMSC's LAN911x and LAN921x chips
1462
1463			CONFIG_SMC911X_BASE
1464			Define this to hold the physical address
1465			of the device (I/O space)
1466
1467			CONFIG_SMC911X_32_BIT
1468			Define this if data bus is 32 bits
1469
1470			CONFIG_SMC911X_16_BIT
1471			Define this if data bus is 16 bits. If your processor
1472			automatically converts one 32 bit word to two 16 bit
1473			words you may also try CONFIG_SMC911X_32_BIT.
1474
1475		CONFIG_SH_ETHER
1476		Support for Renesas on-chip Ethernet controller
1477
1478			CONFIG_SH_ETHER_USE_PORT
1479			Define the number of ports to be used
1480
1481			CONFIG_SH_ETHER_PHY_ADDR
1482			Define the ETH PHY's address
1483
1484			CONFIG_SH_ETHER_CACHE_WRITEBACK
1485			If this option is set, the driver enables cache flush.
1486
1487- PWM Support:
1488		CONFIG_PWM_IMX
1489		Support for PWM modul on the imx6.
1490
1491- TPM Support:
1492		CONFIG_TPM
1493		Support TPM devices.
1494
1495		CONFIG_TPM_TIS_I2C
1496		Support for i2c bus TPM devices. Only one device
1497		per system is supported at this time.
1498
1499			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1500			Define the the i2c bus number for the TPM device
1501
1502			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1503			Define the TPM's address on the i2c bus
1504
1505			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1506			Define the burst count bytes upper limit
1507
1508		CONFIG_TPM_ATMEL_TWI
1509		Support for Atmel TWI TPM device. Requires I2C support.
1510
1511		CONFIG_TPM_TIS_LPC
1512		Support for generic parallel port TPM devices. Only one device
1513		per system is supported at this time.
1514
1515			CONFIG_TPM_TIS_BASE_ADDRESS
1516			Base address where the generic TPM device is mapped
1517			to. Contemporary x86 systems usually map it at
1518			0xfed40000.
1519
1520		CONFIG_CMD_TPM
1521		Add tpm monitor functions.
1522		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1523		provides monitor access to authorized functions.
1524
1525		CONFIG_TPM
1526		Define this to enable the TPM support library which provides
1527		functional interfaces to some TPM commands.
1528		Requires support for a TPM device.
1529
1530		CONFIG_TPM_AUTH_SESSIONS
1531		Define this to enable authorized functions in the TPM library.
1532		Requires CONFIG_TPM and CONFIG_SHA1.
1533
1534- USB Support:
1535		At the moment only the UHCI host controller is
1536		supported (PIP405, MIP405, MPC5200); define
1537		CONFIG_USB_UHCI to enable it.
1538		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1539		and define CONFIG_USB_STORAGE to enable the USB
1540		storage devices.
1541		Note:
1542		Supported are USB Keyboards and USB Floppy drives
1543		(TEAC FD-05PUB).
1544		MPC5200 USB requires additional defines:
1545			CONFIG_USB_CLOCK
1546				for 528 MHz Clock: 0x0001bbbb
1547			CONFIG_PSC3_USB
1548				for USB on PSC3
1549			CONFIG_USB_CONFIG
1550				for differential drivers: 0x00001000
1551				for single ended drivers: 0x00005000
1552				for differential drivers on PSC3: 0x00000100
1553				for single ended drivers on PSC3: 0x00004100
1554			CONFIG_SYS_USB_EVENT_POLL
1555				May be defined to allow interrupt polling
1556				instead of using asynchronous interrupts
1557
1558		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1559		txfilltuning field in the EHCI controller on reset.
1560
1561		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1562		HW module registers.
1563
1564- USB Device:
1565		Define the below if you wish to use the USB console.
1566		Once firmware is rebuilt from a serial console issue the
1567		command "setenv stdin usbtty; setenv stdout usbtty" and
1568		attach your USB cable. The Unix command "dmesg" should print
1569		it has found a new device. The environment variable usbtty
1570		can be set to gserial or cdc_acm to enable your device to
1571		appear to a USB host as a Linux gserial device or a
1572		Common Device Class Abstract Control Model serial device.
1573		If you select usbtty = gserial you should be able to enumerate
1574		a Linux host by
1575		# modprobe usbserial vendor=0xVendorID product=0xProductID
1576		else if using cdc_acm, simply setting the environment
1577		variable usbtty to be cdc_acm should suffice. The following
1578		might be defined in YourBoardName.h
1579
1580			CONFIG_USB_DEVICE
1581			Define this to build a UDC device
1582
1583			CONFIG_USB_TTY
1584			Define this to have a tty type of device available to
1585			talk to the UDC device
1586
1587			CONFIG_USBD_HS
1588			Define this to enable the high speed support for usb
1589			device and usbtty. If this feature is enabled, a routine
1590			int is_usbd_high_speed(void)
1591			also needs to be defined by the driver to dynamically poll
1592			whether the enumeration has succeded at high speed or full
1593			speed.
1594
1595			CONFIG_SYS_CONSOLE_IS_IN_ENV
1596			Define this if you want stdin, stdout &/or stderr to
1597			be set to usbtty.
1598
1599			mpc8xx:
1600				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1601				Derive USB clock from external clock "blah"
1602				- CONFIG_SYS_USB_EXTC_CLK 0x02
1603
1604				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1605				Derive USB clock from brgclk
1606				- CONFIG_SYS_USB_BRG_CLK 0x04
1607
1608		If you have a USB-IF assigned VendorID then you may wish to
1609		define your own vendor specific values either in BoardName.h
1610		or directly in usbd_vendor_info.h. If you don't define
1611		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1612		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1613		should pretend to be a Linux device to it's target host.
1614
1615			CONFIG_USBD_MANUFACTURER
1616			Define this string as the name of your company for
1617			- CONFIG_USBD_MANUFACTURER "my company"
1618
1619			CONFIG_USBD_PRODUCT_NAME
1620			Define this string as the name of your product
1621			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1622
1623			CONFIG_USBD_VENDORID
1624			Define this as your assigned Vendor ID from the USB
1625			Implementors Forum. This *must* be a genuine Vendor ID
1626			to avoid polluting the USB namespace.
1627			- CONFIG_USBD_VENDORID 0xFFFF
1628
1629			CONFIG_USBD_PRODUCTID
1630			Define this as the unique Product ID
1631			for your device
1632			- CONFIG_USBD_PRODUCTID 0xFFFF
1633
1634- ULPI Layer Support:
1635		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1636		the generic ULPI layer. The generic layer accesses the ULPI PHY
1637		via the platform viewport, so you need both the genric layer and
1638		the viewport enabled. Currently only Chipidea/ARC based
1639		viewport is supported.
1640		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1641		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1642		If your ULPI phy needs a different reference clock than the
1643		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1644		the appropriate value in Hz.
1645
1646- MMC Support:
1647		The MMC controller on the Intel PXA is supported. To
1648		enable this define CONFIG_MMC. The MMC can be
1649		accessed from the boot prompt by mapping the device
1650		to physical memory similar to flash. Command line is
1651		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1652		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1653
1654		CONFIG_SH_MMCIF
1655		Support for Renesas on-chip MMCIF controller
1656
1657			CONFIG_SH_MMCIF_ADDR
1658			Define the base address of MMCIF registers
1659
1660			CONFIG_SH_MMCIF_CLK
1661			Define the clock frequency for MMCIF
1662
1663		CONFIG_GENERIC_MMC
1664		Enable the generic MMC driver
1665
1666		CONFIG_SUPPORT_EMMC_BOOT
1667		Enable some additional features of the eMMC boot partitions.
1668
1669		CONFIG_SUPPORT_EMMC_RPMB
1670		Enable the commands for reading, writing and programming the
1671		key for the Replay Protection Memory Block partition in eMMC.
1672
1673- USB Device Firmware Update (DFU) class support:
1674		CONFIG_USB_FUNCTION_DFU
1675		This enables the USB portion of the DFU USB class
1676
1677		CONFIG_CMD_DFU
1678		This enables the command "dfu" which is used to have
1679		U-Boot create a DFU class device via USB.  This command
1680		requires that the "dfu_alt_info" environment variable be
1681		set and define the alt settings to expose to the host.
1682
1683		CONFIG_DFU_MMC
1684		This enables support for exposing (e)MMC devices via DFU.
1685
1686		CONFIG_DFU_NAND
1687		This enables support for exposing NAND devices via DFU.
1688
1689		CONFIG_DFU_RAM
1690		This enables support for exposing RAM via DFU.
1691		Note: DFU spec refer to non-volatile memory usage, but
1692		allow usages beyond the scope of spec - here RAM usage,
1693		one that would help mostly the developer.
1694
1695		CONFIG_SYS_DFU_DATA_BUF_SIZE
1696		Dfu transfer uses a buffer before writing data to the
1697		raw storage device. Make the size (in bytes) of this buffer
1698		configurable. The size of this buffer is also configurable
1699		through the "dfu_bufsiz" environment variable.
1700
1701		CONFIG_SYS_DFU_MAX_FILE_SIZE
1702		When updating files rather than the raw storage device,
1703		we use a static buffer to copy the file into and then write
1704		the buffer once we've been given the whole file.  Define
1705		this to the maximum filesize (in bytes) for the buffer.
1706		Default is 4 MiB if undefined.
1707
1708		DFU_DEFAULT_POLL_TIMEOUT
1709		Poll timeout [ms], is the timeout a device can send to the
1710		host. The host must wait for this timeout before sending
1711		a subsequent DFU_GET_STATUS request to the device.
1712
1713		DFU_MANIFEST_POLL_TIMEOUT
1714		Poll timeout [ms], which the device sends to the host when
1715		entering dfuMANIFEST state. Host waits this timeout, before
1716		sending again an USB request to the device.
1717
1718- USB Device Android Fastboot support:
1719		CONFIG_USB_FUNCTION_FASTBOOT
1720		This enables the USB part of the fastboot gadget
1721
1722		CONFIG_CMD_FASTBOOT
1723		This enables the command "fastboot" which enables the Android
1724		fastboot mode for the platform's USB device. Fastboot is a USB
1725		protocol for downloading images, flashing and device control
1726		used on Android devices.
1727		See doc/README.android-fastboot for more information.
1728
1729		CONFIG_ANDROID_BOOT_IMAGE
1730		This enables support for booting images which use the Android
1731		image format header.
1732
1733		CONFIG_FASTBOOT_BUF_ADDR
1734		The fastboot protocol requires a large memory buffer for
1735		downloads. Define this to the starting RAM address to use for
1736		downloaded images.
1737
1738		CONFIG_FASTBOOT_BUF_SIZE
1739		The fastboot protocol requires a large memory buffer for
1740		downloads. This buffer should be as large as possible for a
1741		platform. Define this to the size available RAM for fastboot.
1742
1743		CONFIG_FASTBOOT_FLASH
1744		The fastboot protocol includes a "flash" command for writing
1745		the downloaded image to a non-volatile storage device. Define
1746		this to enable the "fastboot flash" command.
1747
1748		CONFIG_FASTBOOT_FLASH_MMC_DEV
1749		The fastboot "flash" command requires additional information
1750		regarding the non-volatile storage device. Define this to
1751		the eMMC device that fastboot should use to store the image.
1752
1753		CONFIG_FASTBOOT_GPT_NAME
1754		The fastboot "flash" command supports writing the downloaded
1755		image to the Protective MBR and the Primary GUID Partition
1756		Table. (Additionally, this downloaded image is post-processed
1757		to generate and write the Backup GUID Partition Table.)
1758		This occurs when the specified "partition name" on the
1759		"fastboot flash" command line matches this value.
1760		Default is GPT_ENTRY_NAME (currently "gpt") if undefined.
1761
1762- Journaling Flash filesystem support:
1763		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1764		CONFIG_JFFS2_NAND_DEV
1765		Define these for a default partition on a NAND device
1766
1767		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1768		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1769		Define these for a default partition on a NOR device
1770
1771		CONFIG_SYS_JFFS_CUSTOM_PART
1772		Define this to create an own partition. You have to provide a
1773		function struct part_info* jffs2_part_info(int part_num)
1774
1775		If you define only one JFFS2 partition you may also want to
1776		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1777		to disable the command chpart. This is the default when you
1778		have not defined a custom partition
1779
1780- FAT(File Allocation Table) filesystem write function support:
1781		CONFIG_FAT_WRITE
1782
1783		Define this to enable support for saving memory data as a
1784		file in FAT formatted partition.
1785
1786		This will also enable the command "fatwrite" enabling the
1787		user to write files to FAT.
1788
1789CBFS (Coreboot Filesystem) support
1790		CONFIG_CMD_CBFS
1791
1792		Define this to enable support for reading from a Coreboot
1793		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1794		and cbfsload.
1795
1796- FAT(File Allocation Table) filesystem cluster size:
1797		CONFIG_FS_FAT_MAX_CLUSTSIZE
1798
1799		Define the max cluster size for fat operations else
1800		a default value of 65536 will be defined.
1801
1802- Keyboard Support:
1803		CONFIG_ISA_KEYBOARD
1804
1805		Define this to enable standard (PC-Style) keyboard
1806		support
1807
1808		CONFIG_I8042_KBD
1809		Standard PC keyboard driver with US (is default) and
1810		GERMAN key layout (switch via environment 'keymap=de') support.
1811		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1812		for cfb_console. Supports cursor blinking.
1813
1814		CONFIG_CROS_EC_KEYB
1815		Enables a Chrome OS keyboard using the CROS_EC interface.
1816		This uses CROS_EC to communicate with a second microcontroller
1817		which provides key scans on request.
1818
1819- Video support:
1820		CONFIG_VIDEO
1821
1822		Define this to enable video support (for output to
1823		video).
1824
1825		CONFIG_VIDEO_CT69000
1826
1827		Enable Chips & Technologies 69000 Video chip
1828
1829		CONFIG_VIDEO_SMI_LYNXEM
1830		Enable Silicon Motion SMI 712/710/810 Video chip. The
1831		video output is selected via environment 'videoout'
1832		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1833		assumed.
1834
1835		For the CT69000 and SMI_LYNXEM drivers, videomode is
1836		selected via environment 'videomode'. Two different ways
1837		are possible:
1838		- "videomode=num"   'num' is a standard LiLo mode numbers.
1839		Following standard modes are supported	(* is default):
1840
1841		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1842		-------------+---------------------------------------------
1843		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1844		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1845		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1846		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1847		-------------+---------------------------------------------
1848		(i.e. setenv videomode 317; saveenv; reset;)
1849
1850		- "videomode=bootargs" all the video parameters are parsed
1851		from the bootargs. (See drivers/video/videomodes.c)
1852
1853
1854		CONFIG_VIDEO_SED13806
1855		Enable Epson SED13806 driver. This driver supports 8bpp
1856		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1857		or CONFIG_VIDEO_SED13806_16BPP
1858
1859		CONFIG_FSL_DIU_FB
1860		Enable the Freescale DIU video driver.	Reference boards for
1861		SOCs that have a DIU should define this macro to enable DIU
1862		support, and should also define these other macros:
1863
1864			CONFIG_SYS_DIU_ADDR
1865			CONFIG_VIDEO
1866			CONFIG_CMD_BMP
1867			CONFIG_CFB_CONSOLE
1868			CONFIG_VIDEO_SW_CURSOR
1869			CONFIG_VGA_AS_SINGLE_DEVICE
1870			CONFIG_VIDEO_LOGO
1871			CONFIG_VIDEO_BMP_LOGO
1872
1873		The DIU driver will look for the 'video-mode' environment
1874		variable, and if defined, enable the DIU as a console during
1875		boot.  See the documentation file README.video for a
1876		description of this variable.
1877
1878
1879- Keyboard Support:
1880		CONFIG_KEYBOARD
1881
1882		Define this to enable a custom keyboard support.
1883		This simply calls drv_keyboard_init() which must be
1884		defined in your board-specific files.
1885		The only board using this so far is RBC823.
1886
1887- LCD Support:	CONFIG_LCD
1888
1889		Define this to enable LCD support (for output to LCD
1890		display); also select one of the supported displays
1891		by defining one of these:
1892
1893		CONFIG_ATMEL_LCD:
1894
1895			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1896
1897		CONFIG_NEC_NL6448AC33:
1898
1899			NEC NL6448AC33-18. Active, color, single scan.
1900
1901		CONFIG_NEC_NL6448BC20
1902
1903			NEC NL6448BC20-08. 6.5", 640x480.
1904			Active, color, single scan.
1905
1906		CONFIG_NEC_NL6448BC33_54
1907
1908			NEC NL6448BC33-54. 10.4", 640x480.
1909			Active, color, single scan.
1910
1911		CONFIG_SHARP_16x9
1912
1913			Sharp 320x240. Active, color, single scan.
1914			It isn't 16x9, and I am not sure what it is.
1915
1916		CONFIG_SHARP_LQ64D341
1917
1918			Sharp LQ64D341 display, 640x480.
1919			Active, color, single scan.
1920
1921		CONFIG_HLD1045
1922
1923			HLD1045 display, 640x480.
1924			Active, color, single scan.
1925
1926		CONFIG_OPTREX_BW
1927
1928			Optrex	 CBL50840-2 NF-FW 99 22 M5
1929			or
1930			Hitachi	 LMG6912RPFC-00T
1931			or
1932			Hitachi	 SP14Q002
1933
1934			320x240. Black & white.
1935
1936		Normally display is black on white background; define
1937		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1938
1939		CONFIG_LCD_ALIGNMENT
1940
1941		Normally the LCD is page-aligned (typically 4KB). If this is
1942		defined then the LCD will be aligned to this value instead.
1943		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1944		here, since it is cheaper to change data cache settings on
1945		a per-section basis.
1946
1947		CONFIG_CONSOLE_SCROLL_LINES
1948
1949		When the console need to be scrolled, this is the number of
1950		lines to scroll by. It defaults to 1. Increasing this makes
1951		the console jump but can help speed up operation when scrolling
1952		is slow.
1953
1954		CONFIG_LCD_ROTATION
1955
1956		Sometimes, for example if the display is mounted in portrait
1957		mode or even if it's mounted landscape but rotated by 180degree,
1958		we need to rotate our content of the display relative to the
1959		framebuffer, so that user can read the messages which are
1960		printed out.
1961		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1962		initialized with a given rotation from "vl_rot" out of
1963		"vidinfo_t" which is provided by the board specific code.
1964		The value for vl_rot is coded as following (matching to
1965		fbcon=rotate:<n> linux-kernel commandline):
1966		0 = no rotation respectively 0 degree
1967		1 = 90 degree rotation
1968		2 = 180 degree rotation
1969		3 = 270 degree rotation
1970
1971		If CONFIG_LCD_ROTATION is not defined, the console will be
1972		initialized with 0degree rotation.
1973
1974		CONFIG_LCD_BMP_RLE8
1975
1976		Support drawing of RLE8-compressed bitmaps on the LCD.
1977
1978		CONFIG_I2C_EDID
1979
1980		Enables an 'i2c edid' command which can read EDID
1981		information over I2C from an attached LCD display.
1982
1983- Splash Screen Support: CONFIG_SPLASH_SCREEN
1984
1985		If this option is set, the environment is checked for
1986		a variable "splashimage". If found, the usual display
1987		of logo, copyright and system information on the LCD
1988		is suppressed and the BMP image at the address
1989		specified in "splashimage" is loaded instead. The
1990		console is redirected to the "nulldev", too. This
1991		allows for a "silent" boot where a splash screen is
1992		loaded very quickly after power-on.
1993
1994		CONFIG_SPLASHIMAGE_GUARD
1995
1996		If this option is set, then U-Boot will prevent the environment
1997		variable "splashimage" from being set to a problematic address
1998		(see README.displaying-bmps).
1999		This option is useful for targets where, due to alignment
2000		restrictions, an improperly aligned BMP image will cause a data
2001		abort. If you think you will not have problems with unaligned
2002		accesses (for example because your toolchain prevents them)
2003		there is no need to set this option.
2004
2005		CONFIG_SPLASH_SCREEN_ALIGN
2006
2007		If this option is set the splash image can be freely positioned
2008		on the screen. Environment variable "splashpos" specifies the
2009		position as "x,y". If a positive number is given it is used as
2010		number of pixel from left/top. If a negative number is given it
2011		is used as number of pixel from right/bottom. You can also
2012		specify 'm' for centering the image.
2013
2014		Example:
2015		setenv splashpos m,m
2016			=> image at center of screen
2017
2018		setenv splashpos 30,20
2019			=> image at x = 30 and y = 20
2020
2021		setenv splashpos -10,m
2022			=> vertically centered image
2023			   at x = dspWidth - bmpWidth - 9
2024
2025- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
2026
2027		If this option is set, additionally to standard BMP
2028		images, gzipped BMP images can be displayed via the
2029		splashscreen support or the bmp command.
2030
2031- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
2032
2033		If this option is set, 8-bit RLE compressed BMP images
2034		can be displayed via the splashscreen support or the
2035		bmp command.
2036
2037- Do compressing for memory range:
2038		CONFIG_CMD_ZIP
2039
2040		If this option is set, it would use zlib deflate method
2041		to compress the specified memory at its best effort.
2042
2043- Compression support:
2044		CONFIG_GZIP
2045
2046		Enabled by default to support gzip compressed images.
2047
2048		CONFIG_BZIP2
2049
2050		If this option is set, support for bzip2 compressed
2051		images is included. If not, only uncompressed and gzip
2052		compressed images are supported.
2053
2054		NOTE: the bzip2 algorithm requires a lot of RAM, so
2055		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
2056		be at least 4MB.
2057
2058		CONFIG_LZMA
2059
2060		If this option is set, support for lzma compressed
2061		images is included.
2062
2063		Note: The LZMA algorithm adds between 2 and 4KB of code and it
2064		requires an amount of dynamic memory that is given by the
2065		formula:
2066
2067			(1846 + 768 << (lc + lp)) * sizeof(uint16)
2068
2069		Where lc and lp stand for, respectively, Literal context bits
2070		and Literal pos bits.
2071
2072		This value is upper-bounded by 14MB in the worst case. Anyway,
2073		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
2074		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
2075		a very small buffer.
2076
2077		Use the lzmainfo tool to determinate the lc and lp values and
2078		then calculate the amount of needed dynamic memory (ensuring
2079		the appropriate CONFIG_SYS_MALLOC_LEN value).
2080
2081		CONFIG_LZO
2082
2083		If this option is set, support for LZO compressed images
2084		is included.
2085
2086- MII/PHY support:
2087		CONFIG_PHY_ADDR
2088
2089		The address of PHY on MII bus.
2090
2091		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
2092
2093		The clock frequency of the MII bus
2094
2095		CONFIG_PHY_GIGE
2096
2097		If this option is set, support for speed/duplex
2098		detection of gigabit PHY is included.
2099
2100		CONFIG_PHY_RESET_DELAY
2101
2102		Some PHY like Intel LXT971A need extra delay after
2103		reset before any MII register access is possible.
2104		For such PHY, set this option to the usec delay
2105		required. (minimum 300usec for LXT971A)
2106
2107		CONFIG_PHY_CMD_DELAY (ppc4xx)
2108
2109		Some PHY like Intel LXT971A need extra delay after
2110		command issued before MII status register can be read
2111
2112- IP address:
2113		CONFIG_IPADDR
2114
2115		Define a default value for the IP address to use for
2116		the default Ethernet interface, in case this is not
2117		determined through e.g. bootp.
2118		(Environment variable "ipaddr")
2119
2120- Server IP address:
2121		CONFIG_SERVERIP
2122
2123		Defines a default value for the IP address of a TFTP
2124		server to contact when using the "tftboot" command.
2125		(Environment variable "serverip")
2126
2127		CONFIG_KEEP_SERVERADDR
2128
2129		Keeps the server's MAC address, in the env 'serveraddr'
2130		for passing to bootargs (like Linux's netconsole option)
2131
2132- Gateway IP address:
2133		CONFIG_GATEWAYIP
2134
2135		Defines a default value for the IP address of the
2136		default router where packets to other networks are
2137		sent to.
2138		(Environment variable "gatewayip")
2139
2140- Subnet mask:
2141		CONFIG_NETMASK
2142
2143		Defines a default value for the subnet mask (or
2144		routing prefix) which is used to determine if an IP
2145		address belongs to the local subnet or needs to be
2146		forwarded through a router.
2147		(Environment variable "netmask")
2148
2149- Multicast TFTP Mode:
2150		CONFIG_MCAST_TFTP
2151
2152		Defines whether you want to support multicast TFTP as per
2153		rfc-2090; for example to work with atftp.  Lets lots of targets
2154		tftp down the same boot image concurrently.  Note: the Ethernet
2155		driver in use must provide a function: mcast() to join/leave a
2156		multicast group.
2157
2158- BOOTP Recovery Mode:
2159		CONFIG_BOOTP_RANDOM_DELAY
2160
2161		If you have many targets in a network that try to
2162		boot using BOOTP, you may want to avoid that all
2163		systems send out BOOTP requests at precisely the same
2164		moment (which would happen for instance at recovery
2165		from a power failure, when all systems will try to
2166		boot, thus flooding the BOOTP server. Defining
2167		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
2168		inserted before sending out BOOTP requests. The
2169		following delays are inserted then:
2170
2171		1st BOOTP request:	delay 0 ... 1 sec
2172		2nd BOOTP request:	delay 0 ... 2 sec
2173		3rd BOOTP request:	delay 0 ... 4 sec
2174		4th and following
2175		BOOTP requests:		delay 0 ... 8 sec
2176
2177		CONFIG_BOOTP_ID_CACHE_SIZE
2178
2179		BOOTP packets are uniquely identified using a 32-bit ID. The
2180		server will copy the ID from client requests to responses and
2181		U-Boot will use this to determine if it is the destination of
2182		an incoming response. Some servers will check that addresses
2183		aren't in use before handing them out (usually using an ARP
2184		ping) and therefore take up to a few hundred milliseconds to
2185		respond. Network congestion may also influence the time it
2186		takes for a response to make it back to the client. If that
2187		time is too long, U-Boot will retransmit requests. In order
2188		to allow earlier responses to still be accepted after these
2189		retransmissions, U-Boot's BOOTP client keeps a small cache of
2190		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
2191		cache. The default is to keep IDs for up to four outstanding
2192		requests. Increasing this will allow U-Boot to accept offers
2193		from a BOOTP client in networks with unusually high latency.
2194
2195- DHCP Advanced Options:
2196		You can fine tune the DHCP functionality by defining
2197		CONFIG_BOOTP_* symbols:
2198
2199		CONFIG_BOOTP_SUBNETMASK
2200		CONFIG_BOOTP_GATEWAY
2201		CONFIG_BOOTP_HOSTNAME
2202		CONFIG_BOOTP_NISDOMAIN
2203		CONFIG_BOOTP_BOOTPATH
2204		CONFIG_BOOTP_BOOTFILESIZE
2205		CONFIG_BOOTP_DNS
2206		CONFIG_BOOTP_DNS2
2207		CONFIG_BOOTP_SEND_HOSTNAME
2208		CONFIG_BOOTP_NTPSERVER
2209		CONFIG_BOOTP_TIMEOFFSET
2210		CONFIG_BOOTP_VENDOREX
2211		CONFIG_BOOTP_MAY_FAIL
2212
2213		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
2214		environment variable, not the BOOTP server.
2215
2216		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
2217		after the configured retry count, the call will fail
2218		instead of starting over.  This can be used to fail over
2219		to Link-local IP address configuration if the DHCP server
2220		is not available.
2221
2222		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
2223		serverip from a DHCP server, it is possible that more
2224		than one DNS serverip is offered to the client.
2225		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
2226		serverip will be stored in the additional environment
2227		variable "dnsip2". The first DNS serverip is always
2228		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
2229		is defined.
2230
2231		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2232		to do a dynamic update of a DNS server. To do this, they
2233		need the hostname of the DHCP requester.
2234		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2235		of the "hostname" environment variable is passed as
2236		option 12 to the DHCP server.
2237
2238		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2239
2240		A 32bit value in microseconds for a delay between
2241		receiving a "DHCP Offer" and sending the "DHCP Request".
2242		This fixes a problem with certain DHCP servers that don't
2243		respond 100% of the time to a "DHCP request". E.g. On an
2244		AT91RM9200 processor running at 180MHz, this delay needed
2245		to be *at least* 15,000 usec before a Windows Server 2003
2246		DHCP server would reply 100% of the time. I recommend at
2247		least 50,000 usec to be safe. The alternative is to hope
2248		that one of the retries will be successful but note that
2249		the DHCP timeout and retry process takes a longer than
2250		this delay.
2251
2252 - Link-local IP address negotiation:
2253		Negotiate with other link-local clients on the local network
2254		for an address that doesn't require explicit configuration.
2255		This is especially useful if a DHCP server cannot be guaranteed
2256		to exist in all environments that the device must operate.
2257
2258		See doc/README.link-local for more information.
2259
2260 - CDP Options:
2261		CONFIG_CDP_DEVICE_ID
2262
2263		The device id used in CDP trigger frames.
2264
2265		CONFIG_CDP_DEVICE_ID_PREFIX
2266
2267		A two character string which is prefixed to the MAC address
2268		of the device.
2269
2270		CONFIG_CDP_PORT_ID
2271
2272		A printf format string which contains the ascii name of
2273		the port. Normally is set to "eth%d" which sets
2274		eth0 for the first Ethernet, eth1 for the second etc.
2275
2276		CONFIG_CDP_CAPABILITIES
2277
2278		A 32bit integer which indicates the device capabilities;
2279		0x00000010 for a normal host which does not forwards.
2280
2281		CONFIG_CDP_VERSION
2282
2283		An ascii string containing the version of the software.
2284
2285		CONFIG_CDP_PLATFORM
2286
2287		An ascii string containing the name of the platform.
2288
2289		CONFIG_CDP_TRIGGER
2290
2291		A 32bit integer sent on the trigger.
2292
2293		CONFIG_CDP_POWER_CONSUMPTION
2294
2295		A 16bit integer containing the power consumption of the
2296		device in .1 of milliwatts.
2297
2298		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2299
2300		A byte containing the id of the VLAN.
2301
2302- Status LED:	CONFIG_STATUS_LED
2303
2304		Several configurations allow to display the current
2305		status using a LED. For instance, the LED will blink
2306		fast while running U-Boot code, stop blinking as
2307		soon as a reply to a BOOTP request was received, and
2308		start blinking slow once the Linux kernel is running
2309		(supported by a status LED driver in the Linux
2310		kernel). Defining CONFIG_STATUS_LED enables this
2311		feature in U-Boot.
2312
2313		Additional options:
2314
2315		CONFIG_GPIO_LED
2316		The status LED can be connected to a GPIO pin.
2317		In such cases, the gpio_led driver can be used as a
2318		status LED backend implementation. Define CONFIG_GPIO_LED
2319		to include the gpio_led driver in the U-Boot binary.
2320
2321		CONFIG_GPIO_LED_INVERTED_TABLE
2322		Some GPIO connected LEDs may have inverted polarity in which
2323		case the GPIO high value corresponds to LED off state and
2324		GPIO low value corresponds to LED on state.
2325		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2326		with a list of GPIO LEDs that have inverted polarity.
2327
2328- CAN Support:	CONFIG_CAN_DRIVER
2329
2330		Defining CONFIG_CAN_DRIVER enables CAN driver support
2331		on those systems that support this (optional)
2332		feature, like the TQM8xxL modules.
2333
2334- I2C Support:	CONFIG_SYS_I2C
2335
2336		This enable the NEW i2c subsystem, and will allow you to use
2337		i2c commands at the u-boot command line (as long as you set
2338		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2339		based realtime clock chips or other i2c devices. See
2340		common/cmd_i2c.c for a description of the command line
2341		interface.
2342
2343		ported i2c driver to the new framework:
2344		- drivers/i2c/soft_i2c.c:
2345		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2346		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2347		    for defining speed and slave address
2348		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2349		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2350		    for defining speed and slave address
2351		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2352		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2353		    for defining speed and slave address
2354		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2355		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2356		    for defining speed and slave address
2357
2358		- drivers/i2c/fsl_i2c.c:
2359		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2360		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2361		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2362		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2363		    bus.
2364		  - If your board supports a second fsl i2c bus, define
2365		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2366		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2367		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2368		    second bus.
2369
2370		- drivers/i2c/tegra_i2c.c:
2371		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2372		  - This driver adds 4 i2c buses with a fix speed from
2373		    100000 and the slave addr 0!
2374
2375		- drivers/i2c/ppc4xx_i2c.c
2376		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2377		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2378		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2379
2380		- drivers/i2c/i2c_mxc.c
2381		  - activate this driver with CONFIG_SYS_I2C_MXC
2382		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2383		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2384		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2385		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2386		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2387		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2388		If those defines are not set, default value is 100000
2389		for speed, and 0 for slave.
2390		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
2391		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
2392
2393		- drivers/i2c/rcar_i2c.c:
2394		  - activate this driver with CONFIG_SYS_I2C_RCAR
2395		  - This driver adds 4 i2c buses
2396
2397		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2398		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2399		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2400		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2401		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2402		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2403		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2404		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2405		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2406
2407		- drivers/i2c/sh_i2c.c:
2408		  - activate this driver with CONFIG_SYS_I2C_SH
2409		  - This driver adds from 2 to 5 i2c buses
2410
2411		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2412		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2413		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2414		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2415		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2416		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2417		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2418		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2419		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2420		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2421		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2422		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2423		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2424
2425		- drivers/i2c/omap24xx_i2c.c
2426		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2427		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2428		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2429		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2430		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2431		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2432		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2433		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2434		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2435		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2436		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2437
2438		- drivers/i2c/zynq_i2c.c
2439		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2440		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2441		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2442
2443		- drivers/i2c/s3c24x0_i2c.c:
2444		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2445		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2446		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2447		    with a fix speed from 100000 and the slave addr 0!
2448
2449		- drivers/i2c/ihs_i2c.c
2450		  - activate this driver with CONFIG_SYS_I2C_IHS
2451		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2452		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2453		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2454		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2455		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2456		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2457		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2458		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2459		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2460		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2461		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2462		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2463
2464		additional defines:
2465
2466		CONFIG_SYS_NUM_I2C_BUSES
2467		Hold the number of i2c buses you want to use. If you
2468		don't use/have i2c muxes on your i2c bus, this
2469		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2470		omit this define.
2471
2472		CONFIG_SYS_I2C_DIRECT_BUS
2473		define this, if you don't use i2c muxes on your hardware.
2474		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2475		omit this define.
2476
2477		CONFIG_SYS_I2C_MAX_HOPS
2478		define how many muxes are maximal consecutively connected
2479		on one i2c bus. If you not use i2c muxes, omit this
2480		define.
2481
2482		CONFIG_SYS_I2C_BUSES
2483		hold a list of buses you want to use, only used if
2484		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2485		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2486		CONFIG_SYS_NUM_I2C_BUSES = 9:
2487
2488		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2489					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2490					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2491					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2492					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2493					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2494					{1, {I2C_NULL_HOP}}, \
2495					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2496					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2497					}
2498
2499		which defines
2500			bus 0 on adapter 0 without a mux
2501			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2502			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2503			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2504			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2505			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2506			bus 6 on adapter 1 without a mux
2507			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2508			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2509
2510		If you do not have i2c muxes on your board, omit this define.
2511
2512- Legacy I2C Support:	CONFIG_HARD_I2C
2513
2514		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2515		provides the following compelling advantages:
2516
2517		- more than one i2c adapter is usable
2518		- approved multibus support
2519		- better i2c mux support
2520
2521		** Please consider updating your I2C driver now. **
2522
2523		These enable legacy I2C serial bus commands. Defining
2524		CONFIG_HARD_I2C will include the appropriate I2C driver
2525		for the selected CPU.
2526
2527		This will allow you to use i2c commands at the u-boot
2528		command line (as long as you set CONFIG_CMD_I2C in
2529		CONFIG_COMMANDS) and communicate with i2c based realtime
2530		clock chips. See common/cmd_i2c.c for a description of the
2531		command line interface.
2532
2533		CONFIG_HARD_I2C selects a hardware I2C controller.
2534
2535		There are several other quantities that must also be
2536		defined when you define CONFIG_HARD_I2C.
2537
2538		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2539		to be the frequency (in Hz) at which you wish your i2c bus
2540		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2541		the CPU's i2c node address).
2542
2543		Now, the u-boot i2c code for the mpc8xx
2544		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2545		and so its address should therefore be cleared to 0 (See,
2546		eg, MPC823e User's Manual p.16-473). So, set
2547		CONFIG_SYS_I2C_SLAVE to 0.
2548
2549		CONFIG_SYS_I2C_INIT_MPC5XXX
2550
2551		When a board is reset during an i2c bus transfer
2552		chips might think that the current transfer is still
2553		in progress.  Reset the slave devices by sending start
2554		commands until the slave device responds.
2555
2556		That's all that's required for CONFIG_HARD_I2C.
2557
2558		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2559		then the following macros need to be defined (examples are
2560		from include/configs/lwmon.h):
2561
2562		I2C_INIT
2563
2564		(Optional). Any commands necessary to enable the I2C
2565		controller or configure ports.
2566
2567		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2568
2569		I2C_PORT
2570
2571		(Only for MPC8260 CPU). The I/O port to use (the code
2572		assumes both bits are on the same port). Valid values
2573		are 0..3 for ports A..D.
2574
2575		I2C_ACTIVE
2576
2577		The code necessary to make the I2C data line active
2578		(driven).  If the data line is open collector, this
2579		define can be null.
2580
2581		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2582
2583		I2C_TRISTATE
2584
2585		The code necessary to make the I2C data line tri-stated
2586		(inactive).  If the data line is open collector, this
2587		define can be null.
2588
2589		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2590
2591		I2C_READ
2592
2593		Code that returns true if the I2C data line is high,
2594		false if it is low.
2595
2596		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2597
2598		I2C_SDA(bit)
2599
2600		If <bit> is true, sets the I2C data line high. If it
2601		is false, it clears it (low).
2602
2603		eg: #define I2C_SDA(bit) \
2604			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2605			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2606
2607		I2C_SCL(bit)
2608
2609		If <bit> is true, sets the I2C clock line high. If it
2610		is false, it clears it (low).
2611
2612		eg: #define I2C_SCL(bit) \
2613			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2614			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2615
2616		I2C_DELAY
2617
2618		This delay is invoked four times per clock cycle so this
2619		controls the rate of data transfer.  The data rate thus
2620		is 1 / (I2C_DELAY * 4). Often defined to be something
2621		like:
2622
2623		#define I2C_DELAY  udelay(2)
2624
2625		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2626
2627		If your arch supports the generic GPIO framework (asm/gpio.h),
2628		then you may alternatively define the two GPIOs that are to be
2629		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2630		have GPIO-based defaults assigned to them as appropriate.
2631
2632		You should define these to the GPIO value as given directly to
2633		the generic GPIO functions.
2634
2635		CONFIG_SYS_I2C_INIT_BOARD
2636
2637		When a board is reset during an i2c bus transfer
2638		chips might think that the current transfer is still
2639		in progress. On some boards it is possible to access
2640		the i2c SCLK line directly, either by using the
2641		processor pin as a GPIO or by having a second pin
2642		connected to the bus. If this option is defined a
2643		custom i2c_init_board() routine in boards/xxx/board.c
2644		is run early in the boot sequence.
2645
2646		CONFIG_SYS_I2C_BOARD_LATE_INIT
2647
2648		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2649		defined a custom i2c_board_late_init() routine in
2650		boards/xxx/board.c is run AFTER the operations in i2c_init()
2651		is completed. This callpoint can be used to unreset i2c bus
2652		using CPU i2c controller register accesses for CPUs whose i2c
2653		controller provide such a method. It is called at the end of
2654		i2c_init() to allow i2c_init operations to setup the i2c bus
2655		controller on the CPU (e.g. setting bus speed & slave address).
2656
2657		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2658
2659		This option enables configuration of bi_iic_fast[] flags
2660		in u-boot bd_info structure based on u-boot environment
2661		variable "i2cfast". (see also i2cfast)
2662
2663		CONFIG_I2C_MULTI_BUS
2664
2665		This option allows the use of multiple I2C buses, each of which
2666		must have a controller.	 At any point in time, only one bus is
2667		active.	 To switch to a different bus, use the 'i2c dev' command.
2668		Note that bus numbering is zero-based.
2669
2670		CONFIG_SYS_I2C_NOPROBES
2671
2672		This option specifies a list of I2C devices that will be skipped
2673		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2674		is set, specify a list of bus-device pairs.  Otherwise, specify
2675		a 1D array of device addresses
2676
2677		e.g.
2678			#undef	CONFIG_I2C_MULTI_BUS
2679			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2680
2681		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2682
2683			#define CONFIG_I2C_MULTI_BUS
2684			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2685
2686		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2687
2688		CONFIG_SYS_SPD_BUS_NUM
2689
2690		If defined, then this indicates the I2C bus number for DDR SPD.
2691		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2692
2693		CONFIG_SYS_RTC_BUS_NUM
2694
2695		If defined, then this indicates the I2C bus number for the RTC.
2696		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2697
2698		CONFIG_SYS_DTT_BUS_NUM
2699
2700		If defined, then this indicates the I2C bus number for the DTT.
2701		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2702
2703		CONFIG_SYS_I2C_DTT_ADDR:
2704
2705		If defined, specifies the I2C address of the DTT device.
2706		If not defined, then U-Boot uses predefined value for
2707		specified DTT device.
2708
2709		CONFIG_SOFT_I2C_READ_REPEATED_START
2710
2711		defining this will force the i2c_read() function in
2712		the soft_i2c driver to perform an I2C repeated start
2713		between writing the address pointer and reading the
2714		data.  If this define is omitted the default behaviour
2715		of doing a stop-start sequence will be used.  Most I2C
2716		devices can use either method, but some require one or
2717		the other.
2718
2719- SPI Support:	CONFIG_SPI
2720
2721		Enables SPI driver (so far only tested with
2722		SPI EEPROM, also an instance works with Crystal A/D and
2723		D/As on the SACSng board)
2724
2725		CONFIG_SH_SPI
2726
2727		Enables the driver for SPI controller on SuperH. Currently
2728		only SH7757 is supported.
2729
2730		CONFIG_SPI_X
2731
2732		Enables extended (16-bit) SPI EEPROM addressing.
2733		(symmetrical to CONFIG_I2C_X)
2734
2735		CONFIG_SOFT_SPI
2736
2737		Enables a software (bit-bang) SPI driver rather than
2738		using hardware support. This is a general purpose
2739		driver that only requires three general I/O port pins
2740		(two outputs, one input) to function. If this is
2741		defined, the board configuration must define several
2742		SPI configuration items (port pins to use, etc). For
2743		an example, see include/configs/sacsng.h.
2744
2745		CONFIG_HARD_SPI
2746
2747		Enables a hardware SPI driver for general-purpose reads
2748		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2749		must define a list of chip-select function pointers.
2750		Currently supported on some MPC8xxx processors.	 For an
2751		example, see include/configs/mpc8349emds.h.
2752
2753		CONFIG_MXC_SPI
2754
2755		Enables the driver for the SPI controllers on i.MX and MXC
2756		SoCs. Currently i.MX31/35/51 are supported.
2757
2758		CONFIG_SYS_SPI_MXC_WAIT
2759		Timeout for waiting until spi transfer completed.
2760		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2761
2762- FPGA Support: CONFIG_FPGA
2763
2764		Enables FPGA subsystem.
2765
2766		CONFIG_FPGA_<vendor>
2767
2768		Enables support for specific chip vendors.
2769		(ALTERA, XILINX)
2770
2771		CONFIG_FPGA_<family>
2772
2773		Enables support for FPGA family.
2774		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2775
2776		CONFIG_FPGA_COUNT
2777
2778		Specify the number of FPGA devices to support.
2779
2780		CONFIG_CMD_FPGA_LOADMK
2781
2782		Enable support for fpga loadmk command
2783
2784		CONFIG_CMD_FPGA_LOADP
2785
2786		Enable support for fpga loadp command - load partial bitstream
2787
2788		CONFIG_CMD_FPGA_LOADBP
2789
2790		Enable support for fpga loadbp command - load partial bitstream
2791		(Xilinx only)
2792
2793		CONFIG_SYS_FPGA_PROG_FEEDBACK
2794
2795		Enable printing of hash marks during FPGA configuration.
2796
2797		CONFIG_SYS_FPGA_CHECK_BUSY
2798
2799		Enable checks on FPGA configuration interface busy
2800		status by the configuration function. This option
2801		will require a board or device specific function to
2802		be written.
2803
2804		CONFIG_FPGA_DELAY
2805
2806		If defined, a function that provides delays in the FPGA
2807		configuration driver.
2808
2809		CONFIG_SYS_FPGA_CHECK_CTRLC
2810		Allow Control-C to interrupt FPGA configuration
2811
2812		CONFIG_SYS_FPGA_CHECK_ERROR
2813
2814		Check for configuration errors during FPGA bitfile
2815		loading. For example, abort during Virtex II
2816		configuration if the INIT_B line goes low (which
2817		indicated a CRC error).
2818
2819		CONFIG_SYS_FPGA_WAIT_INIT
2820
2821		Maximum time to wait for the INIT_B line to de-assert
2822		after PROB_B has been de-asserted during a Virtex II
2823		FPGA configuration sequence. The default time is 500
2824		ms.
2825
2826		CONFIG_SYS_FPGA_WAIT_BUSY
2827
2828		Maximum time to wait for BUSY to de-assert during
2829		Virtex II FPGA configuration. The default is 5 ms.
2830
2831		CONFIG_SYS_FPGA_WAIT_CONFIG
2832
2833		Time to wait after FPGA configuration. The default is
2834		200 ms.
2835
2836- Configuration Management:
2837		CONFIG_BUILD_TARGET
2838
2839		Some SoCs need special image types (e.g. U-Boot binary
2840		with a special header) as build targets. By defining
2841		CONFIG_BUILD_TARGET in the SoC / board header, this
2842		special image will be automatically built upon calling
2843		make / MAKEALL.
2844
2845		CONFIG_IDENT_STRING
2846
2847		If defined, this string will be added to the U-Boot
2848		version information (U_BOOT_VERSION)
2849
2850- Vendor Parameter Protection:
2851
2852		U-Boot considers the values of the environment
2853		variables "serial#" (Board Serial Number) and
2854		"ethaddr" (Ethernet Address) to be parameters that
2855		are set once by the board vendor / manufacturer, and
2856		protects these variables from casual modification by
2857		the user. Once set, these variables are read-only,
2858		and write or delete attempts are rejected. You can
2859		change this behaviour:
2860
2861		If CONFIG_ENV_OVERWRITE is #defined in your config
2862		file, the write protection for vendor parameters is
2863		completely disabled. Anybody can change or delete
2864		these parameters.
2865
2866		Alternatively, if you define _both_ an ethaddr in the
2867		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2868		Ethernet address is installed in the environment,
2869		which can be changed exactly ONCE by the user. [The
2870		serial# is unaffected by this, i. e. it remains
2871		read-only.]
2872
2873		The same can be accomplished in a more flexible way
2874		for any variable by configuring the type of access
2875		to allow for those variables in the ".flags" variable
2876		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2877
2878- Protected RAM:
2879		CONFIG_PRAM
2880
2881		Define this variable to enable the reservation of
2882		"protected RAM", i. e. RAM which is not overwritten
2883		by U-Boot. Define CONFIG_PRAM to hold the number of
2884		kB you want to reserve for pRAM. You can overwrite
2885		this default value by defining an environment
2886		variable "pram" to the number of kB you want to
2887		reserve. Note that the board info structure will
2888		still show the full amount of RAM. If pRAM is
2889		reserved, a new environment variable "mem" will
2890		automatically be defined to hold the amount of
2891		remaining RAM in a form that can be passed as boot
2892		argument to Linux, for instance like that:
2893
2894			setenv bootargs ... mem=\${mem}
2895			saveenv
2896
2897		This way you can tell Linux not to use this memory,
2898		either, which results in a memory region that will
2899		not be affected by reboots.
2900
2901		*WARNING* If your board configuration uses automatic
2902		detection of the RAM size, you must make sure that
2903		this memory test is non-destructive. So far, the
2904		following board configurations are known to be
2905		"pRAM-clean":
2906
2907			IVMS8, IVML24, SPD8xx, TQM8xxL,
2908			HERMES, IP860, RPXlite, LWMON,
2909			FLAGADM, TQM8260
2910
2911- Access to physical memory region (> 4GB)
2912		Some basic support is provided for operations on memory not
2913		normally accessible to U-Boot - e.g. some architectures
2914		support access to more than 4GB of memory on 32-bit
2915		machines using physical address extension or similar.
2916		Define CONFIG_PHYSMEM to access this basic support, which
2917		currently only supports clearing the memory.
2918
2919- Error Recovery:
2920		CONFIG_PANIC_HANG
2921
2922		Define this variable to stop the system in case of a
2923		fatal error, so that you have to reset it manually.
2924		This is probably NOT a good idea for an embedded
2925		system where you want the system to reboot
2926		automatically as fast as possible, but it may be
2927		useful during development since you can try to debug
2928		the conditions that lead to the situation.
2929
2930		CONFIG_NET_RETRY_COUNT
2931
2932		This variable defines the number of retries for
2933		network operations like ARP, RARP, TFTP, or BOOTP
2934		before giving up the operation. If not defined, a
2935		default value of 5 is used.
2936
2937		CONFIG_ARP_TIMEOUT
2938
2939		Timeout waiting for an ARP reply in milliseconds.
2940
2941		CONFIG_NFS_TIMEOUT
2942
2943		Timeout in milliseconds used in NFS protocol.
2944		If you encounter "ERROR: Cannot umount" in nfs command,
2945		try longer timeout such as
2946		#define CONFIG_NFS_TIMEOUT 10000UL
2947
2948- Command Interpreter:
2949		CONFIG_AUTO_COMPLETE
2950
2951		Enable auto completion of commands using TAB.
2952
2953		CONFIG_SYS_PROMPT_HUSH_PS2
2954
2955		This defines the secondary prompt string, which is
2956		printed when the command interpreter needs more input
2957		to complete a command. Usually "> ".
2958
2959	Note:
2960
2961		In the current implementation, the local variables
2962		space and global environment variables space are
2963		separated. Local variables are those you define by
2964		simply typing `name=value'. To access a local
2965		variable later on, you have write `$name' or
2966		`${name}'; to execute the contents of a variable
2967		directly type `$name' at the command prompt.
2968
2969		Global environment variables are those you use
2970		setenv/printenv to work with. To run a command stored
2971		in such a variable, you need to use the run command,
2972		and you must not use the '$' sign to access them.
2973
2974		To store commands and special characters in a
2975		variable, please use double quotation marks
2976		surrounding the whole text of the variable, instead
2977		of the backslashes before semicolons and special
2978		symbols.
2979
2980- Command Line Editing and History:
2981		CONFIG_CMDLINE_EDITING
2982
2983		Enable editing and History functions for interactive
2984		command line input operations
2985
2986- Default Environment:
2987		CONFIG_EXTRA_ENV_SETTINGS
2988
2989		Define this to contain any number of null terminated
2990		strings (variable = value pairs) that will be part of
2991		the default environment compiled into the boot image.
2992
2993		For example, place something like this in your
2994		board's config file:
2995
2996		#define CONFIG_EXTRA_ENV_SETTINGS \
2997			"myvar1=value1\0" \
2998			"myvar2=value2\0"
2999
3000		Warning: This method is based on knowledge about the
3001		internal format how the environment is stored by the
3002		U-Boot code. This is NOT an official, exported
3003		interface! Although it is unlikely that this format
3004		will change soon, there is no guarantee either.
3005		You better know what you are doing here.
3006
3007		Note: overly (ab)use of the default environment is
3008		discouraged. Make sure to check other ways to preset
3009		the environment like the "source" command or the
3010		boot command first.
3011
3012		CONFIG_ENV_VARS_UBOOT_CONFIG
3013
3014		Define this in order to add variables describing the
3015		U-Boot build configuration to the default environment.
3016		These will be named arch, cpu, board, vendor, and soc.
3017
3018		Enabling this option will cause the following to be defined:
3019
3020		- CONFIG_SYS_ARCH
3021		- CONFIG_SYS_CPU
3022		- CONFIG_SYS_BOARD
3023		- CONFIG_SYS_VENDOR
3024		- CONFIG_SYS_SOC
3025
3026		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
3027
3028		Define this in order to add variables describing certain
3029		run-time determined information about the hardware to the
3030		environment.  These will be named board_name, board_rev.
3031
3032		CONFIG_DELAY_ENVIRONMENT
3033
3034		Normally the environment is loaded when the board is
3035		initialised so that it is available to U-Boot. This inhibits
3036		that so that the environment is not available until
3037		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
3038		this is instead controlled by the value of
3039		/config/load-environment.
3040
3041- Parallel Flash support:
3042		CONFIG_SYS_NO_FLASH
3043
3044		Traditionally U-boot was run on systems with parallel NOR
3045		flash. This option is used to disable support for parallel NOR
3046		flash. This option should be defined if the board does not have
3047		parallel flash.
3048
3049		If this option is not defined one of the generic flash drivers
3050		(e.g.  CONFIG_FLASH_CFI_DRIVER or CONFIG_ST_SMI) must be
3051		selected or the board must provide an implementation of the
3052		flash API (see include/flash.h).
3053
3054- DataFlash Support:
3055		CONFIG_HAS_DATAFLASH
3056
3057		Defining this option enables DataFlash features and
3058		allows to read/write in Dataflash via the standard
3059		commands cp, md...
3060
3061- Serial Flash support
3062		CONFIG_CMD_SF
3063
3064		Defining this option enables SPI flash commands
3065		'sf probe/read/write/erase/update'.
3066
3067		Usage requires an initial 'probe' to define the serial
3068		flash parameters, followed by read/write/erase/update
3069		commands.
3070
3071		The following defaults may be provided by the platform
3072		to handle the common case when only a single serial
3073		flash is present on the system.
3074
3075		CONFIG_SF_DEFAULT_BUS		Bus identifier
3076		CONFIG_SF_DEFAULT_CS		Chip-select
3077		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
3078		CONFIG_SF_DEFAULT_SPEED		in Hz
3079
3080		CONFIG_CMD_SF_TEST
3081
3082		Define this option to include a destructive SPI flash
3083		test ('sf test').
3084
3085		CONFIG_SF_DUAL_FLASH		Dual flash memories
3086
3087		Define this option to use dual flash support where two flash
3088		memories can be connected with a given cs line.
3089		Currently Xilinx Zynq qspi supports these type of connections.
3090
3091- SystemACE Support:
3092		CONFIG_SYSTEMACE
3093
3094		Adding this option adds support for Xilinx SystemACE
3095		chips attached via some sort of local bus. The address
3096		of the chip must also be defined in the
3097		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
3098
3099		#define CONFIG_SYSTEMACE
3100		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
3101
3102		When SystemACE support is added, the "ace" device type
3103		becomes available to the fat commands, i.e. fatls.
3104
3105- TFTP Fixed UDP Port:
3106		CONFIG_TFTP_PORT
3107
3108		If this is defined, the environment variable tftpsrcp
3109		is used to supply the TFTP UDP source port value.
3110		If tftpsrcp isn't defined, the normal pseudo-random port
3111		number generator is used.
3112
3113		Also, the environment variable tftpdstp is used to supply
3114		the TFTP UDP destination port value.  If tftpdstp isn't
3115		defined, the normal port 69 is used.
3116
3117		The purpose for tftpsrcp is to allow a TFTP server to
3118		blindly start the TFTP transfer using the pre-configured
3119		target IP address and UDP port. This has the effect of
3120		"punching through" the (Windows XP) firewall, allowing
3121		the remainder of the TFTP transfer to proceed normally.
3122		A better solution is to properly configure the firewall,
3123		but sometimes that is not allowed.
3124
3125- Hashing support:
3126		CONFIG_CMD_HASH
3127
3128		This enables a generic 'hash' command which can produce
3129		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
3130
3131		CONFIG_HASH_VERIFY
3132
3133		Enable the hash verify command (hash -v). This adds to code
3134		size a little.
3135
3136		CONFIG_SHA1 - This option enables support of hashing using SHA1
3137		algorithm. The hash is calculated in software.
3138		CONFIG_SHA256 - This option enables support of hashing using
3139		SHA256 algorithm. The hash is calculated in software.
3140		CONFIG_SHA_HW_ACCEL - This option enables hardware acceleration
3141		for SHA1/SHA256 hashing.
3142		This affects the 'hash' command and also the
3143		hash_lookup_algo() function.
3144		CONFIG_SHA_PROG_HW_ACCEL - This option enables
3145		hardware-acceleration for SHA1/SHA256 progressive hashing.
3146		Data can be streamed in a block at a time and the hashing
3147		is performed in hardware.
3148
3149		Note: There is also a sha1sum command, which should perhaps
3150		be deprecated in favour of 'hash sha1'.
3151
3152- Freescale i.MX specific commands:
3153		CONFIG_CMD_HDMIDETECT
3154		This enables 'hdmidet' command which returns true if an
3155		HDMI monitor is detected.  This command is i.MX 6 specific.
3156
3157		CONFIG_CMD_BMODE
3158		This enables the 'bmode' (bootmode) command for forcing
3159		a boot from specific media.
3160
3161		This is useful for forcing the ROM's usb downloader to
3162		activate upon a watchdog reset which is nice when iterating
3163		on U-Boot.  Using the reset button or running bmode normal
3164		will set it back to normal.  This command currently
3165		supports i.MX53 and i.MX6.
3166
3167- Signing support:
3168		CONFIG_RSA
3169
3170		This enables the RSA algorithm used for FIT image verification
3171		in U-Boot. See doc/uImage.FIT/signature.txt for more information.
3172
3173		The Modular Exponentiation algorithm in RSA is implemented using
3174		driver model. So CONFIG_DM needs to be enabled by default for this
3175		library to function.
3176
3177		The signing part is build into mkimage regardless of this
3178		option. The software based modular exponentiation is built into
3179		mkimage irrespective of this option.
3180
3181- bootcount support:
3182		CONFIG_BOOTCOUNT_LIMIT
3183
3184		This enables the bootcounter support, see:
3185		http://www.denx.de/wiki/DULG/UBootBootCountLimit
3186
3187		CONFIG_AT91SAM9XE
3188		enable special bootcounter support on at91sam9xe based boards.
3189		CONFIG_BLACKFIN
3190		enable special bootcounter support on blackfin based boards.
3191		CONFIG_SOC_DA8XX
3192		enable special bootcounter support on da850 based boards.
3193		CONFIG_BOOTCOUNT_RAM
3194		enable support for the bootcounter in RAM
3195		CONFIG_BOOTCOUNT_I2C
3196		enable support for the bootcounter on an i2c (like RTC) device.
3197			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
3198			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
3199						    the bootcounter.
3200			CONFIG_BOOTCOUNT_ALEN = address len
3201
3202- Show boot progress:
3203		CONFIG_SHOW_BOOT_PROGRESS
3204
3205		Defining this option allows to add some board-
3206		specific code (calling a user-provided function
3207		"show_boot_progress(int)") that enables you to show
3208		the system's boot progress on some display (for
3209		example, some LED's) on your board. At the moment,
3210		the following checkpoints are implemented:
3211
3212
3213Legacy uImage format:
3214
3215  Arg	Where			When
3216    1	common/cmd_bootm.c	before attempting to boot an image
3217   -1	common/cmd_bootm.c	Image header has bad	 magic number
3218    2	common/cmd_bootm.c	Image header has correct magic number
3219   -2	common/cmd_bootm.c	Image header has bad	 checksum
3220    3	common/cmd_bootm.c	Image header has correct checksum
3221   -3	common/cmd_bootm.c	Image data   has bad	 checksum
3222    4	common/cmd_bootm.c	Image data   has correct checksum
3223   -4	common/cmd_bootm.c	Image is for unsupported architecture
3224    5	common/cmd_bootm.c	Architecture check OK
3225   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
3226    6	common/cmd_bootm.c	Image Type check OK
3227   -6	common/cmd_bootm.c	gunzip uncompression error
3228   -7	common/cmd_bootm.c	Unimplemented compression type
3229    7	common/cmd_bootm.c	Uncompression OK
3230    8	common/cmd_bootm.c	No uncompress/copy overwrite error
3231   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3232
3233    9	common/image.c		Start initial ramdisk verification
3234  -10	common/image.c		Ramdisk header has bad	   magic number
3235  -11	common/image.c		Ramdisk header has bad	   checksum
3236   10	common/image.c		Ramdisk header is OK
3237  -12	common/image.c		Ramdisk data   has bad	   checksum
3238   11	common/image.c		Ramdisk data   has correct checksum
3239   12	common/image.c		Ramdisk verification complete, start loading
3240  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3241   13	common/image.c		Start multifile image verification
3242   14	common/image.c		No initial ramdisk, no multifile, continue.
3243
3244   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3245
3246  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3247  -31	post/post.c		POST test failed, detected by post_output_backlog()
3248  -32	post/post.c		POST test failed, detected by post_run_single()
3249
3250   34	common/cmd_doc.c	before loading a Image from a DOC device
3251  -35	common/cmd_doc.c	Bad usage of "doc" command
3252   35	common/cmd_doc.c	correct usage of "doc" command
3253  -36	common/cmd_doc.c	No boot device
3254   36	common/cmd_doc.c	correct boot device
3255  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3256   37	common/cmd_doc.c	correct chip ID found, device available
3257  -38	common/cmd_doc.c	Read Error on boot device
3258   38	common/cmd_doc.c	reading Image header from DOC device OK
3259  -39	common/cmd_doc.c	Image header has bad magic number
3260   39	common/cmd_doc.c	Image header has correct magic number
3261  -40	common/cmd_doc.c	Error reading Image from DOC device
3262   40	common/cmd_doc.c	Image header has correct magic number
3263   41	common/cmd_ide.c	before loading a Image from a IDE device
3264  -42	common/cmd_ide.c	Bad usage of "ide" command
3265   42	common/cmd_ide.c	correct usage of "ide" command
3266  -43	common/cmd_ide.c	No boot device
3267   43	common/cmd_ide.c	boot device found
3268  -44	common/cmd_ide.c	Device not available
3269   44	common/cmd_ide.c	Device available
3270  -45	common/cmd_ide.c	wrong partition selected
3271   45	common/cmd_ide.c	partition selected
3272  -46	common/cmd_ide.c	Unknown partition table
3273   46	common/cmd_ide.c	valid partition table found
3274  -47	common/cmd_ide.c	Invalid partition type
3275   47	common/cmd_ide.c	correct partition type
3276  -48	common/cmd_ide.c	Error reading Image Header on boot device
3277   48	common/cmd_ide.c	reading Image Header from IDE device OK
3278  -49	common/cmd_ide.c	Image header has bad magic number
3279   49	common/cmd_ide.c	Image header has correct magic number
3280  -50	common/cmd_ide.c	Image header has bad	 checksum
3281   50	common/cmd_ide.c	Image header has correct checksum
3282  -51	common/cmd_ide.c	Error reading Image from IDE device
3283   51	common/cmd_ide.c	reading Image from IDE device OK
3284   52	common/cmd_nand.c	before loading a Image from a NAND device
3285  -53	common/cmd_nand.c	Bad usage of "nand" command
3286   53	common/cmd_nand.c	correct usage of "nand" command
3287  -54	common/cmd_nand.c	No boot device
3288   54	common/cmd_nand.c	boot device found
3289  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3290   55	common/cmd_nand.c	correct chip ID found, device available
3291  -56	common/cmd_nand.c	Error reading Image Header on boot device
3292   56	common/cmd_nand.c	reading Image Header from NAND device OK
3293  -57	common/cmd_nand.c	Image header has bad magic number
3294   57	common/cmd_nand.c	Image header has correct magic number
3295  -58	common/cmd_nand.c	Error reading Image from NAND device
3296   58	common/cmd_nand.c	reading Image from NAND device OK
3297
3298  -60	common/env_common.c	Environment has a bad CRC, using default
3299
3300   64	net/eth.c		starting with Ethernet configuration.
3301  -64	net/eth.c		no Ethernet found.
3302   65	net/eth.c		Ethernet found.
3303
3304  -80	common/cmd_net.c	usage wrong
3305   80	common/cmd_net.c	before calling net_loop()
3306  -81	common/cmd_net.c	some error in net_loop() occurred
3307   81	common/cmd_net.c	net_loop() back without error
3308  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3309   82	common/cmd_net.c	trying automatic boot
3310   83	common/cmd_net.c	running "source" command
3311  -83	common/cmd_net.c	some error in automatic boot or "source" command
3312   84	common/cmd_net.c	end without errors
3313
3314FIT uImage format:
3315
3316  Arg	Where			When
3317  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3318 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3319  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3320 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3321  102	common/cmd_bootm.c	Kernel unit name specified
3322 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3323  103	common/cmd_bootm.c	Found configuration node
3324  104	common/cmd_bootm.c	Got kernel subimage node offset
3325 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3326  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3327 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3328  106	common/cmd_bootm.c	Architecture check OK
3329 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3330  107	common/cmd_bootm.c	Kernel subimage type OK
3331 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3332  108	common/cmd_bootm.c	Got kernel subimage data/size
3333 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3334 -109	common/cmd_bootm.c	Can't get kernel subimage type
3335 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3336 -111	common/cmd_bootm.c	Can't get kernel subimage os
3337 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3338 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3339
3340  120	common/image.c		Start initial ramdisk verification
3341 -120	common/image.c		Ramdisk FIT image has incorrect format
3342  121	common/image.c		Ramdisk FIT image has correct format
3343  122	common/image.c		No ramdisk subimage unit name, using configuration
3344 -122	common/image.c		Can't get configuration for ramdisk subimage
3345  123	common/image.c		Ramdisk unit name specified
3346 -124	common/image.c		Can't get ramdisk subimage node offset
3347  125	common/image.c		Got ramdisk subimage node offset
3348 -125	common/image.c		Ramdisk subimage hash verification failed
3349  126	common/image.c		Ramdisk subimage hash verification OK
3350 -126	common/image.c		Ramdisk subimage for unsupported architecture
3351  127	common/image.c		Architecture check OK
3352 -127	common/image.c		Can't get ramdisk subimage data/size
3353  128	common/image.c		Got ramdisk subimage data/size
3354  129	common/image.c		Can't get ramdisk load address
3355 -129	common/image.c		Got ramdisk load address
3356
3357 -130	common/cmd_doc.c	Incorrect FIT image format
3358  131	common/cmd_doc.c	FIT image format OK
3359
3360 -140	common/cmd_ide.c	Incorrect FIT image format
3361  141	common/cmd_ide.c	FIT image format OK
3362
3363 -150	common/cmd_nand.c	Incorrect FIT image format
3364  151	common/cmd_nand.c	FIT image format OK
3365
3366- legacy image format:
3367		CONFIG_IMAGE_FORMAT_LEGACY
3368		enables the legacy image format support in U-Boot.
3369
3370		Default:
3371		enabled if CONFIG_FIT_SIGNATURE is not defined.
3372
3373		CONFIG_DISABLE_IMAGE_LEGACY
3374		disable the legacy image format
3375
3376		This define is introduced, as the legacy image format is
3377		enabled per default for backward compatibility.
3378
3379- FIT image support:
3380		CONFIG_FIT
3381		Enable support for the FIT uImage format.
3382
3383		CONFIG_FIT_BEST_MATCH
3384		When no configuration is explicitly selected, default to the
3385		one whose fdt's compatibility field best matches that of
3386		U-Boot itself. A match is considered "best" if it matches the
3387		most specific compatibility entry of U-Boot's fdt's root node.
3388		The order of entries in the configuration's fdt is ignored.
3389
3390		CONFIG_FIT_SIGNATURE
3391		This option enables signature verification of FIT uImages,
3392		using a hash signed and verified using RSA. If
3393		CONFIG_SHA_PROG_HW_ACCEL is defined, i.e support for progressive
3394		hashing is available using hardware, RSA library will use it.
3395		See doc/uImage.FIT/signature.txt for more details.
3396
3397		WARNING: When relying on signed FIT images with required
3398		signature check the legacy image format is default
3399		disabled. If a board need legacy image format support
3400		enable this through CONFIG_IMAGE_FORMAT_LEGACY
3401
3402		CONFIG_FIT_DISABLE_SHA256
3403		Supporting SHA256 hashes has quite an impact on binary size.
3404		For constrained systems sha256 hash support can be disabled
3405		with this option.
3406
3407- Standalone program support:
3408		CONFIG_STANDALONE_LOAD_ADDR
3409
3410		This option defines a board specific value for the
3411		address where standalone program gets loaded, thus
3412		overwriting the architecture dependent default
3413		settings.
3414
3415- Frame Buffer Address:
3416		CONFIG_FB_ADDR
3417
3418		Define CONFIG_FB_ADDR if you want to use specific
3419		address for frame buffer.  This is typically the case
3420		when using a graphics controller has separate video
3421		memory.  U-Boot will then place the frame buffer at
3422		the given address instead of dynamically reserving it
3423		in system RAM by calling lcd_setmem(), which grabs
3424		the memory for the frame buffer depending on the
3425		configured panel size.
3426
3427		Please see board_init_f function.
3428
3429- Automatic software updates via TFTP server
3430		CONFIG_UPDATE_TFTP
3431		CONFIG_UPDATE_TFTP_CNT_MAX
3432		CONFIG_UPDATE_TFTP_MSEC_MAX
3433
3434		These options enable and control the auto-update feature;
3435		for a more detailed description refer to doc/README.update.
3436
3437- MTD Support (mtdparts command, UBI support)
3438		CONFIG_MTD_DEVICE
3439
3440		Adds the MTD device infrastructure from the Linux kernel.
3441		Needed for mtdparts command support.
3442
3443		CONFIG_MTD_PARTITIONS
3444
3445		Adds the MTD partitioning infrastructure from the Linux
3446		kernel. Needed for UBI support.
3447
3448- UBI support
3449		CONFIG_CMD_UBI
3450
3451		Adds commands for interacting with MTD partitions formatted
3452		with the UBI flash translation layer
3453
3454		Requires also defining CONFIG_RBTREE
3455
3456		CONFIG_UBI_SILENCE_MSG
3457
3458		Make the verbose messages from UBI stop printing.  This leaves
3459		warnings and errors enabled.
3460
3461
3462		CONFIG_MTD_UBI_WL_THRESHOLD
3463		This parameter defines the maximum difference between the highest
3464		erase counter value and the lowest erase counter value of eraseblocks
3465		of UBI devices. When this threshold is exceeded, UBI starts performing
3466		wear leveling by means of moving data from eraseblock with low erase
3467		counter to eraseblocks with high erase counter.
3468
3469		The default value should be OK for SLC NAND flashes, NOR flashes and
3470		other flashes which have eraseblock life-cycle 100000 or more.
3471		However, in case of MLC NAND flashes which typically have eraseblock
3472		life-cycle less than 10000, the threshold should be lessened (e.g.,
3473		to 128 or 256, although it does not have to be power of 2).
3474
3475		default: 4096
3476
3477		CONFIG_MTD_UBI_BEB_LIMIT
3478		This option specifies the maximum bad physical eraseblocks UBI
3479		expects on the MTD device (per 1024 eraseblocks). If the
3480		underlying flash does not admit of bad eraseblocks (e.g. NOR
3481		flash), this value is ignored.
3482
3483		NAND datasheets often specify the minimum and maximum NVM
3484		(Number of Valid Blocks) for the flashes' endurance lifetime.
3485		The maximum expected bad eraseblocks per 1024 eraseblocks
3486		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
3487		which gives 20 for most NANDs (MaxNVB is basically the total
3488		count of eraseblocks on the chip).
3489
3490		To put it differently, if this value is 20, UBI will try to
3491		reserve about 1.9% of physical eraseblocks for bad blocks
3492		handling. And that will be 1.9% of eraseblocks on the entire
3493		NAND chip, not just the MTD partition UBI attaches. This means
3494		that if you have, say, a NAND flash chip admits maximum 40 bad
3495		eraseblocks, and it is split on two MTD partitions of the same
3496		size, UBI will reserve 40 eraseblocks when attaching a
3497		partition.
3498
3499		default: 20
3500
3501		CONFIG_MTD_UBI_FASTMAP
3502		Fastmap is a mechanism which allows attaching an UBI device
3503		in nearly constant time. Instead of scanning the whole MTD device it
3504		only has to locate a checkpoint (called fastmap) on the device.
3505		The on-flash fastmap contains all information needed to attach
3506		the device. Using fastmap makes only sense on large devices where
3507		attaching by scanning takes long. UBI will not automatically install
3508		a fastmap on old images, but you can set the UBI parameter
3509		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
3510		that fastmap-enabled images are still usable with UBI implementations
3511		without	fastmap support. On typical flash devices the whole fastmap
3512		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
3513
3514		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
3515		Set this parameter to enable fastmap automatically on images
3516		without a fastmap.
3517		default: 0
3518
3519- UBIFS support
3520		CONFIG_CMD_UBIFS
3521
3522		Adds commands for interacting with UBI volumes formatted as
3523		UBIFS.  UBIFS is read-only in u-boot.
3524
3525		Requires UBI support as well as CONFIG_LZO
3526
3527		CONFIG_UBIFS_SILENCE_MSG
3528
3529		Make the verbose messages from UBIFS stop printing.  This leaves
3530		warnings and errors enabled.
3531
3532- SPL framework
3533		CONFIG_SPL
3534		Enable building of SPL globally.
3535
3536		CONFIG_SPL_LDSCRIPT
3537		LDSCRIPT for linking the SPL binary.
3538
3539		CONFIG_SPL_MAX_FOOTPRINT
3540		Maximum size in memory allocated to the SPL, BSS included.
3541		When defined, the linker checks that the actual memory
3542		used by SPL from _start to __bss_end does not exceed it.
3543		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3544		must not be both defined at the same time.
3545
3546		CONFIG_SPL_MAX_SIZE
3547		Maximum size of the SPL image (text, data, rodata, and
3548		linker lists sections), BSS excluded.
3549		When defined, the linker checks that the actual size does
3550		not exceed it.
3551
3552		CONFIG_SPL_TEXT_BASE
3553		TEXT_BASE for linking the SPL binary.
3554
3555		CONFIG_SPL_RELOC_TEXT_BASE
3556		Address to relocate to.  If unspecified, this is equal to
3557		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3558
3559		CONFIG_SPL_BSS_START_ADDR
3560		Link address for the BSS within the SPL binary.
3561
3562		CONFIG_SPL_BSS_MAX_SIZE
3563		Maximum size in memory allocated to the SPL BSS.
3564		When defined, the linker checks that the actual memory used
3565		by SPL from __bss_start to __bss_end does not exceed it.
3566		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3567		must not be both defined at the same time.
3568
3569		CONFIG_SPL_STACK
3570		Adress of the start of the stack SPL will use
3571
3572		CONFIG_SPL_PANIC_ON_RAW_IMAGE
3573		When defined, SPL will panic() if the image it has
3574		loaded does not have a signature.
3575		Defining this is useful when code which loads images
3576		in SPL cannot guarantee that absolutely all read errors
3577		will be caught.
3578		An example is the LPC32XX MLC NAND driver, which will
3579		consider that a completely unreadable NAND block is bad,
3580		and thus should be skipped silently.
3581
3582		CONFIG_SPL_RELOC_STACK
3583		Adress of the start of the stack SPL will use after
3584		relocation.  If unspecified, this is equal to
3585		CONFIG_SPL_STACK.
3586
3587		CONFIG_SYS_SPL_MALLOC_START
3588		Starting address of the malloc pool used in SPL.
3589
3590		CONFIG_SYS_SPL_MALLOC_SIZE
3591		The size of the malloc pool used in SPL.
3592
3593		CONFIG_SPL_FRAMEWORK
3594		Enable the SPL framework under common/.  This framework
3595		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3596		NAND loading of the Linux Kernel.
3597
3598		CONFIG_SPL_OS_BOOT
3599		Enable booting directly to an OS from SPL.
3600		See also: doc/README.falcon
3601
3602		CONFIG_SPL_DISPLAY_PRINT
3603		For ARM, enable an optional function to print more information
3604		about the running system.
3605
3606		CONFIG_SPL_INIT_MINIMAL
3607		Arch init code should be built for a very small image
3608
3609		CONFIG_SPL_LIBCOMMON_SUPPORT
3610		Support for common/libcommon.o in SPL binary
3611
3612		CONFIG_SPL_LIBDISK_SUPPORT
3613		Support for disk/libdisk.o in SPL binary
3614
3615		CONFIG_SPL_I2C_SUPPORT
3616		Support for drivers/i2c/libi2c.o in SPL binary
3617
3618		CONFIG_SPL_GPIO_SUPPORT
3619		Support for drivers/gpio/libgpio.o in SPL binary
3620
3621		CONFIG_SPL_MMC_SUPPORT
3622		Support for drivers/mmc/libmmc.o in SPL binary
3623
3624		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3625		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3626		Address and partition on the MMC to load U-Boot from
3627		when the MMC is being used in raw mode.
3628
3629		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3630		Partition on the MMC to load U-Boot from when the MMC is being
3631		used in raw mode
3632
3633		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3634		Sector to load kernel uImage from when MMC is being
3635		used in raw mode (for Falcon mode)
3636
3637		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3638		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3639		Sector and number of sectors to load kernel argument
3640		parameters from when MMC is being used in raw mode
3641		(for falcon mode)
3642
3643		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3644		Partition on the MMC to load U-Boot from when the MMC is being
3645		used in fs mode
3646
3647		CONFIG_SPL_FAT_SUPPORT
3648		Support for fs/fat/libfat.o in SPL binary
3649
3650		CONFIG_SPL_EXT_SUPPORT
3651		Support for EXT filesystem in SPL binary
3652
3653		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3654		Filename to read to load U-Boot when reading from filesystem
3655
3656		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3657		Filename to read to load kernel uImage when reading
3658		from filesystem (for Falcon mode)
3659
3660		CONFIG_SPL_FS_LOAD_ARGS_NAME
3661		Filename to read to load kernel argument parameters
3662		when reading from filesystem (for Falcon mode)
3663
3664		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3665		Set this for NAND SPL on PPC mpc83xx targets, so that
3666		start.S waits for the rest of the SPL to load before
3667		continuing (the hardware starts execution after just
3668		loading the first page rather than the full 4K).
3669
3670		CONFIG_SPL_SKIP_RELOCATE
3671		Avoid SPL relocation
3672
3673		CONFIG_SPL_NAND_BASE
3674		Include nand_base.c in the SPL.  Requires
3675		CONFIG_SPL_NAND_DRIVERS.
3676
3677		CONFIG_SPL_NAND_DRIVERS
3678		SPL uses normal NAND drivers, not minimal drivers.
3679
3680		CONFIG_SPL_NAND_ECC
3681		Include standard software ECC in the SPL
3682
3683		CONFIG_SPL_NAND_SIMPLE
3684		Support for NAND boot using simple NAND drivers that
3685		expose the cmd_ctrl() interface.
3686
3687		CONFIG_SPL_MTD_SUPPORT
3688		Support for the MTD subsystem within SPL.  Useful for
3689		environment on NAND support within SPL.
3690
3691		CONFIG_SPL_NAND_RAW_ONLY
3692		Support to boot only raw u-boot.bin images. Use this only
3693		if you need to save space.
3694
3695		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3696		Set for the SPL on PPC mpc8xxx targets, support for
3697		drivers/ddr/fsl/libddr.o in SPL binary.
3698
3699		CONFIG_SPL_COMMON_INIT_DDR
3700		Set for common ddr init with serial presence detect in
3701		SPL binary.
3702
3703		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3704		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3705		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3706		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3707		CONFIG_SYS_NAND_ECCBYTES
3708		Defines the size and behavior of the NAND that SPL uses
3709		to read U-Boot
3710
3711		CONFIG_SPL_NAND_BOOT
3712		Add support NAND boot
3713
3714		CONFIG_SYS_NAND_U_BOOT_OFFS
3715		Location in NAND to read U-Boot from
3716
3717		CONFIG_SYS_NAND_U_BOOT_DST
3718		Location in memory to load U-Boot to
3719
3720		CONFIG_SYS_NAND_U_BOOT_SIZE
3721		Size of image to load
3722
3723		CONFIG_SYS_NAND_U_BOOT_START
3724		Entry point in loaded image to jump to
3725
3726		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3727		Define this if you need to first read the OOB and then the
3728		data. This is used, for example, on davinci platforms.
3729
3730		CONFIG_SPL_OMAP3_ID_NAND
3731		Support for an OMAP3-specific set of functions to return the
3732		ID and MFR of the first attached NAND chip, if present.
3733
3734		CONFIG_SPL_SERIAL_SUPPORT
3735		Support for drivers/serial/libserial.o in SPL binary
3736
3737		CONFIG_SPL_SPI_FLASH_SUPPORT
3738		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3739
3740		CONFIG_SPL_SPI_SUPPORT
3741		Support for drivers/spi/libspi.o in SPL binary
3742
3743		CONFIG_SPL_RAM_DEVICE
3744		Support for running image already present in ram, in SPL binary
3745
3746		CONFIG_SPL_LIBGENERIC_SUPPORT
3747		Support for lib/libgeneric.o in SPL binary
3748
3749		CONFIG_SPL_ENV_SUPPORT
3750		Support for the environment operating in SPL binary
3751
3752		CONFIG_SPL_NET_SUPPORT
3753		Support for the net/libnet.o in SPL binary.
3754		It conflicts with SPL env from storage medium specified by
3755		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3756
3757		CONFIG_SPL_PAD_TO
3758		Image offset to which the SPL should be padded before appending
3759		the SPL payload. By default, this is defined as
3760		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3761		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3762		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3763
3764		CONFIG_SPL_TARGET
3765		Final target image containing SPL and payload.  Some SPLs
3766		use an arch-specific makefile fragment instead, for
3767		example if more than one image needs to be produced.
3768
3769		CONFIG_FIT_SPL_PRINT
3770		Printing information about a FIT image adds quite a bit of
3771		code to SPL. So this is normally disabled in SPL. Use this
3772		option to re-enable it. This will affect the output of the
3773		bootm command when booting a FIT image.
3774
3775- TPL framework
3776		CONFIG_TPL
3777		Enable building of TPL globally.
3778
3779		CONFIG_TPL_PAD_TO
3780		Image offset to which the TPL should be padded before appending
3781		the TPL payload. By default, this is defined as
3782		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3783		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3784		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3785
3786Modem Support:
3787--------------
3788
3789[so far only for SMDK2400 boards]
3790
3791- Modem support enable:
3792		CONFIG_MODEM_SUPPORT
3793
3794- RTS/CTS Flow control enable:
3795		CONFIG_HWFLOW
3796
3797- Modem debug support:
3798		CONFIG_MODEM_SUPPORT_DEBUG
3799
3800		Enables debugging stuff (char screen[1024], dbg())
3801		for modem support. Useful only with BDI2000.
3802
3803- Interrupt support (PPC):
3804
3805		There are common interrupt_init() and timer_interrupt()
3806		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3807		for CPU specific initialization. interrupt_init_cpu()
3808		should set decrementer_count to appropriate value. If
3809		CPU resets decrementer automatically after interrupt
3810		(ppc4xx) it should set decrementer_count to zero.
3811		timer_interrupt() calls timer_interrupt_cpu() for CPU
3812		specific handling. If board has watchdog / status_led
3813		/ other_activity_monitor it works automatically from
3814		general timer_interrupt().
3815
3816- General:
3817
3818		In the target system modem support is enabled when a
3819		specific key (key combination) is pressed during
3820		power-on. Otherwise U-Boot will boot normally
3821		(autoboot). The key_pressed() function is called from
3822		board_init(). Currently key_pressed() is a dummy
3823		function, returning 1 and thus enabling modem
3824		initialization.
3825
3826		If there are no modem init strings in the
3827		environment, U-Boot proceed to autoboot; the
3828		previous output (banner, info printfs) will be
3829		suppressed, though.
3830
3831		See also: doc/README.Modem
3832
3833Board initialization settings:
3834------------------------------
3835
3836During Initialization u-boot calls a number of board specific functions
3837to allow the preparation of board specific prerequisites, e.g. pin setup
3838before drivers are initialized. To enable these callbacks the
3839following configuration macros have to be defined. Currently this is
3840architecture specific, so please check arch/your_architecture/lib/board.c
3841typically in board_init_f() and board_init_r().
3842
3843- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3844- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3845- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3846- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3847
3848Configuration Settings:
3849-----------------------
3850
3851- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3852		Optionally it can be defined to support 64-bit memory commands.
3853
3854- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3855		undefine this when you're short of memory.
3856
3857- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3858		width of the commands listed in the 'help' command output.
3859
3860- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3861		prompt for user input.
3862
3863- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3864
3865- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3866
3867- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3868
3869- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3870		the application (usually a Linux kernel) when it is
3871		booted
3872
3873- CONFIG_SYS_BAUDRATE_TABLE:
3874		List of legal baudrate settings for this board.
3875
3876- CONFIG_SYS_CONSOLE_INFO_QUIET
3877		Suppress display of console information at boot.
3878
3879- CONFIG_SYS_CONSOLE_IS_IN_ENV
3880		If the board specific function
3881			extern int overwrite_console (void);
3882		returns 1, the stdin, stderr and stdout are switched to the
3883		serial port, else the settings in the environment are used.
3884
3885- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3886		Enable the call to overwrite_console().
3887
3888- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3889		Enable overwrite of previous console environment settings.
3890
3891- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3892		Begin and End addresses of the area used by the
3893		simple memory test.
3894
3895- CONFIG_SYS_ALT_MEMTEST:
3896		Enable an alternate, more extensive memory test.
3897
3898- CONFIG_SYS_MEMTEST_SCRATCH:
3899		Scratch address used by the alternate memory test
3900		You only need to set this if address zero isn't writeable
3901
3902- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3903		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3904		this specified memory area will get subtracted from the top
3905		(end) of RAM and won't get "touched" at all by U-Boot. By
3906		fixing up gd->ram_size the Linux kernel should gets passed
3907		the now "corrected" memory size and won't touch it either.
3908		This should work for arch/ppc and arch/powerpc. Only Linux
3909		board ports in arch/powerpc with bootwrapper support that
3910		recalculate the memory size from the SDRAM controller setup
3911		will have to get fixed in Linux additionally.
3912
3913		This option can be used as a workaround for the 440EPx/GRx
3914		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3915		be touched.
3916
3917		WARNING: Please make sure that this value is a multiple of
3918		the Linux page size (normally 4k). If this is not the case,
3919		then the end address of the Linux memory will be located at a
3920		non page size aligned address and this could cause major
3921		problems.
3922
3923- CONFIG_SYS_LOADS_BAUD_CHANGE:
3924		Enable temporary baudrate change while serial download
3925
3926- CONFIG_SYS_SDRAM_BASE:
3927		Physical start address of SDRAM. _Must_ be 0 here.
3928
3929- CONFIG_SYS_MBIO_BASE:
3930		Physical start address of Motherboard I/O (if using a
3931		Cogent motherboard)
3932
3933- CONFIG_SYS_FLASH_BASE:
3934		Physical start address of Flash memory.
3935
3936- CONFIG_SYS_MONITOR_BASE:
3937		Physical start address of boot monitor code (set by
3938		make config files to be same as the text base address
3939		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3940		CONFIG_SYS_FLASH_BASE when booting from flash.
3941
3942- CONFIG_SYS_MONITOR_LEN:
3943		Size of memory reserved for monitor code, used to
3944		determine _at_compile_time_ (!) if the environment is
3945		embedded within the U-Boot image, or in a separate
3946		flash sector.
3947
3948- CONFIG_SYS_MALLOC_LEN:
3949		Size of DRAM reserved for malloc() use.
3950
3951- CONFIG_SYS_MALLOC_F_LEN
3952		Size of the malloc() pool for use before relocation. If
3953		this is defined, then a very simple malloc() implementation
3954		will become available before relocation. The address is just
3955		below the global data, and the stack is moved down to make
3956		space.
3957
3958		This feature allocates regions with increasing addresses
3959		within the region. calloc() is supported, but realloc()
3960		is not available. free() is supported but does nothing.
3961		The memory will be freed (or in fact just forgotten) when
3962		U-Boot relocates itself.
3963
3964		Pre-relocation malloc() is only supported on ARM and sandbox
3965		at present but is fairly easy to enable for other archs.
3966
3967- CONFIG_SYS_MALLOC_SIMPLE
3968		Provides a simple and small malloc() and calloc() for those
3969		boards which do not use the full malloc in SPL (which is
3970		enabled with CONFIG_SYS_SPL_MALLOC_START).
3971
3972- CONFIG_SYS_NONCACHED_MEMORY:
3973		Size of non-cached memory area. This area of memory will be
3974		typically located right below the malloc() area and mapped
3975		uncached in the MMU. This is useful for drivers that would
3976		otherwise require a lot of explicit cache maintenance. For
3977		some drivers it's also impossible to properly maintain the
3978		cache. For example if the regions that need to be flushed
3979		are not a multiple of the cache-line size, *and* padding
3980		cannot be allocated between the regions to align them (i.e.
3981		if the HW requires a contiguous array of regions, and the
3982		size of each region is not cache-aligned), then a flush of
3983		one region may result in overwriting data that hardware has
3984		written to another region in the same cache-line. This can
3985		happen for example in network drivers where descriptors for
3986		buffers are typically smaller than the CPU cache-line (e.g.
3987		16 bytes vs. 32 or 64 bytes).
3988
3989		Non-cached memory is only supported on 32-bit ARM at present.
3990
3991- CONFIG_SYS_BOOTM_LEN:
3992		Normally compressed uImages are limited to an
3993		uncompressed size of 8 MBytes. If this is not enough,
3994		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3995		to adjust this setting to your needs.
3996
3997- CONFIG_SYS_BOOTMAPSZ:
3998		Maximum size of memory mapped by the startup code of
3999		the Linux kernel; all data that must be processed by
4000		the Linux kernel (bd_info, boot arguments, FDT blob if
4001		used) must be put below this limit, unless "bootm_low"
4002		environment variable is defined and non-zero. In such case
4003		all data for the Linux kernel must be between "bootm_low"
4004		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
4005		variable "bootm_mapsize" will override the value of
4006		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
4007		then the value in "bootm_size" will be used instead.
4008
4009- CONFIG_SYS_BOOT_RAMDISK_HIGH:
4010		Enable initrd_high functionality.  If defined then the
4011		initrd_high feature is enabled and the bootm ramdisk subcommand
4012		is enabled.
4013
4014- CONFIG_SYS_BOOT_GET_CMDLINE:
4015		Enables allocating and saving kernel cmdline in space between
4016		"bootm_low" and "bootm_low" + BOOTMAPSZ.
4017
4018- CONFIG_SYS_BOOT_GET_KBD:
4019		Enables allocating and saving a kernel copy of the bd_info in
4020		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
4021
4022- CONFIG_SYS_MAX_FLASH_BANKS:
4023		Max number of Flash memory banks
4024
4025- CONFIG_SYS_MAX_FLASH_SECT:
4026		Max number of sectors on a Flash chip
4027
4028- CONFIG_SYS_FLASH_ERASE_TOUT:
4029		Timeout for Flash erase operations (in ms)
4030
4031- CONFIG_SYS_FLASH_WRITE_TOUT:
4032		Timeout for Flash write operations (in ms)
4033
4034- CONFIG_SYS_FLASH_LOCK_TOUT
4035		Timeout for Flash set sector lock bit operation (in ms)
4036
4037- CONFIG_SYS_FLASH_UNLOCK_TOUT
4038		Timeout for Flash clear lock bits operation (in ms)
4039
4040- CONFIG_SYS_FLASH_PROTECTION
4041		If defined, hardware flash sectors protection is used
4042		instead of U-Boot software protection.
4043
4044- CONFIG_SYS_DIRECT_FLASH_TFTP:
4045
4046		Enable TFTP transfers directly to flash memory;
4047		without this option such a download has to be
4048		performed in two steps: (1) download to RAM, and (2)
4049		copy from RAM to flash.
4050
4051		The two-step approach is usually more reliable, since
4052		you can check if the download worked before you erase
4053		the flash, but in some situations (when system RAM is
4054		too limited to allow for a temporary copy of the
4055		downloaded image) this option may be very useful.
4056
4057- CONFIG_SYS_FLASH_CFI:
4058		Define if the flash driver uses extra elements in the
4059		common flash structure for storing flash geometry.
4060
4061- CONFIG_FLASH_CFI_DRIVER
4062		This option also enables the building of the cfi_flash driver
4063		in the drivers directory
4064
4065- CONFIG_FLASH_CFI_MTD
4066		This option enables the building of the cfi_mtd driver
4067		in the drivers directory. The driver exports CFI flash
4068		to the MTD layer.
4069
4070- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
4071		Use buffered writes to flash.
4072
4073- CONFIG_FLASH_SPANSION_S29WS_N
4074		s29ws-n MirrorBit flash has non-standard addresses for buffered
4075		write commands.
4076
4077- CONFIG_SYS_FLASH_QUIET_TEST
4078		If this option is defined, the common CFI flash doesn't
4079		print it's warning upon not recognized FLASH banks. This
4080		is useful, if some of the configured banks are only
4081		optionally available.
4082
4083- CONFIG_FLASH_SHOW_PROGRESS
4084		If defined (must be an integer), print out countdown
4085		digits and dots.  Recommended value: 45 (9..1) for 80
4086		column displays, 15 (3..1) for 40 column displays.
4087
4088- CONFIG_FLASH_VERIFY
4089		If defined, the content of the flash (destination) is compared
4090		against the source after the write operation. An error message
4091		will be printed when the contents are not identical.
4092		Please note that this option is useless in nearly all cases,
4093		since such flash programming errors usually are detected earlier
4094		while unprotecting/erasing/programming. Please only enable
4095		this option if you really know what you are doing.
4096
4097- CONFIG_SYS_RX_ETH_BUFFER:
4098		Defines the number of Ethernet receive buffers. On some
4099		Ethernet controllers it is recommended to set this value
4100		to 8 or even higher (EEPRO100 or 405 EMAC), since all
4101		buffers can be full shortly after enabling the interface
4102		on high Ethernet traffic.
4103		Defaults to 4 if not defined.
4104
4105- CONFIG_ENV_MAX_ENTRIES
4106
4107	Maximum number of entries in the hash table that is used
4108	internally to store the environment settings. The default
4109	setting is supposed to be generous and should work in most
4110	cases. This setting can be used to tune behaviour; see
4111	lib/hashtable.c for details.
4112
4113- CONFIG_ENV_FLAGS_LIST_DEFAULT
4114- CONFIG_ENV_FLAGS_LIST_STATIC
4115	Enable validation of the values given to environment variables when
4116	calling env set.  Variables can be restricted to only decimal,
4117	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
4118	the variables can also be restricted to IP address or MAC address.
4119
4120	The format of the list is:
4121		type_attribute = [s|d|x|b|i|m]
4122		access_attribute = [a|r|o|c]
4123		attributes = type_attribute[access_attribute]
4124		entry = variable_name[:attributes]
4125		list = entry[,list]
4126
4127	The type attributes are:
4128		s - String (default)
4129		d - Decimal
4130		x - Hexadecimal
4131		b - Boolean ([1yYtT|0nNfF])
4132		i - IP address
4133		m - MAC address
4134
4135	The access attributes are:
4136		a - Any (default)
4137		r - Read-only
4138		o - Write-once
4139		c - Change-default
4140
4141	- CONFIG_ENV_FLAGS_LIST_DEFAULT
4142		Define this to a list (string) to define the ".flags"
4143		environment variable in the default or embedded environment.
4144
4145	- CONFIG_ENV_FLAGS_LIST_STATIC
4146		Define this to a list (string) to define validation that
4147		should be done if an entry is not found in the ".flags"
4148		environment variable.  To override a setting in the static
4149		list, simply add an entry for the same variable name to the
4150		".flags" variable.
4151
4152	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
4153	regular expression. This allows multiple variables to define the same
4154	flags without explicitly listing them for each variable.
4155
4156- CONFIG_ENV_ACCESS_IGNORE_FORCE
4157	If defined, don't allow the -f switch to env set override variable
4158	access flags.
4159
4160- CONFIG_SYS_GENERIC_BOARD
4161	This selects the architecture-generic board system instead of the
4162	architecture-specific board files. It is intended to move boards
4163	to this new framework over time. Defining this will disable the
4164	arch/foo/lib/board.c file and use common/board_f.c and
4165	common/board_r.c instead. To use this option your architecture
4166	must support it (i.e. must select HAVE_GENERIC_BOARD in arch/Kconfig).
4167	If you find problems enabling this option on your board please report
4168	the problem and send patches!
4169
4170- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
4171	This is set by OMAP boards for the max time that reset should
4172	be asserted. See doc/README.omap-reset-time for details on how
4173	the value can be calculated on a given board.
4174
4175- CONFIG_USE_STDINT
4176	If stdint.h is available with your toolchain you can define this
4177	option to enable it. You can provide option 'USE_STDINT=1' when
4178	building U-Boot to enable this.
4179
4180The following definitions that deal with the placement and management
4181of environment data (variable area); in general, we support the
4182following configurations:
4183
4184- CONFIG_BUILD_ENVCRC:
4185
4186	Builds up envcrc with the target environment so that external utils
4187	may easily extract it and embed it in final U-Boot images.
4188
4189- CONFIG_ENV_IS_IN_FLASH:
4190
4191	Define this if the environment is in flash memory.
4192
4193	a) The environment occupies one whole flash sector, which is
4194	   "embedded" in the text segment with the U-Boot code. This
4195	   happens usually with "bottom boot sector" or "top boot
4196	   sector" type flash chips, which have several smaller
4197	   sectors at the start or the end. For instance, such a
4198	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
4199	   such a case you would place the environment in one of the
4200	   4 kB sectors - with U-Boot code before and after it. With
4201	   "top boot sector" type flash chips, you would put the
4202	   environment in one of the last sectors, leaving a gap
4203	   between U-Boot and the environment.
4204
4205	- CONFIG_ENV_OFFSET:
4206
4207	   Offset of environment data (variable area) to the
4208	   beginning of flash memory; for instance, with bottom boot
4209	   type flash chips the second sector can be used: the offset
4210	   for this sector is given here.
4211
4212	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
4213
4214	- CONFIG_ENV_ADDR:
4215
4216	   This is just another way to specify the start address of
4217	   the flash sector containing the environment (instead of
4218	   CONFIG_ENV_OFFSET).
4219
4220	- CONFIG_ENV_SECT_SIZE:
4221
4222	   Size of the sector containing the environment.
4223
4224
4225	b) Sometimes flash chips have few, equal sized, BIG sectors.
4226	   In such a case you don't want to spend a whole sector for
4227	   the environment.
4228
4229	- CONFIG_ENV_SIZE:
4230
4231	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
4232	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
4233	   of this flash sector for the environment. This saves
4234	   memory for the RAM copy of the environment.
4235
4236	   It may also save flash memory if you decide to use this
4237	   when your environment is "embedded" within U-Boot code,
4238	   since then the remainder of the flash sector could be used
4239	   for U-Boot code. It should be pointed out that this is
4240	   STRONGLY DISCOURAGED from a robustness point of view:
4241	   updating the environment in flash makes it always
4242	   necessary to erase the WHOLE sector. If something goes
4243	   wrong before the contents has been restored from a copy in
4244	   RAM, your target system will be dead.
4245
4246	- CONFIG_ENV_ADDR_REDUND
4247	  CONFIG_ENV_SIZE_REDUND
4248
4249	   These settings describe a second storage area used to hold
4250	   a redundant copy of the environment data, so that there is
4251	   a valid backup copy in case there is a power failure during
4252	   a "saveenv" operation.
4253
4254BE CAREFUL! Any changes to the flash layout, and some changes to the
4255source code will make it necessary to adapt <board>/u-boot.lds*
4256accordingly!
4257
4258
4259- CONFIG_ENV_IS_IN_NVRAM:
4260
4261	Define this if you have some non-volatile memory device
4262	(NVRAM, battery buffered SRAM) which you want to use for the
4263	environment.
4264
4265	- CONFIG_ENV_ADDR:
4266	- CONFIG_ENV_SIZE:
4267
4268	  These two #defines are used to determine the memory area you
4269	  want to use for environment. It is assumed that this memory
4270	  can just be read and written to, without any special
4271	  provision.
4272
4273BE CAREFUL! The first access to the environment happens quite early
4274in U-Boot initialization (when we try to get the setting of for the
4275console baudrate). You *MUST* have mapped your NVRAM area then, or
4276U-Boot will hang.
4277
4278Please note that even with NVRAM we still use a copy of the
4279environment in RAM: we could work on NVRAM directly, but we want to
4280keep settings there always unmodified except somebody uses "saveenv"
4281to save the current settings.
4282
4283
4284- CONFIG_ENV_IS_IN_EEPROM:
4285
4286	Use this if you have an EEPROM or similar serial access
4287	device and a driver for it.
4288
4289	- CONFIG_ENV_OFFSET:
4290	- CONFIG_ENV_SIZE:
4291
4292	  These two #defines specify the offset and size of the
4293	  environment area within the total memory of your EEPROM.
4294
4295	- CONFIG_SYS_I2C_EEPROM_ADDR:
4296	  If defined, specified the chip address of the EEPROM device.
4297	  The default address is zero.
4298
4299	- CONFIG_SYS_I2C_EEPROM_BUS:
4300	  If defined, specified the i2c bus of the EEPROM device.
4301
4302	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
4303	  If defined, the number of bits used to address bytes in a
4304	  single page in the EEPROM device.  A 64 byte page, for example
4305	  would require six bits.
4306
4307	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
4308	  If defined, the number of milliseconds to delay between
4309	  page writes.	The default is zero milliseconds.
4310
4311	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
4312	  The length in bytes of the EEPROM memory array address.  Note
4313	  that this is NOT the chip address length!
4314
4315	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
4316	  EEPROM chips that implement "address overflow" are ones
4317	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
4318	  address and the extra bits end up in the "chip address" bit
4319	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
4320	  byte chips.
4321
4322	  Note that we consider the length of the address field to
4323	  still be one byte because the extra address bits are hidden
4324	  in the chip address.
4325
4326	- CONFIG_SYS_EEPROM_SIZE:
4327	  The size in bytes of the EEPROM device.
4328
4329	- CONFIG_ENV_EEPROM_IS_ON_I2C
4330	  define this, if you have I2C and SPI activated, and your
4331	  EEPROM, which holds the environment, is on the I2C bus.
4332
4333	- CONFIG_I2C_ENV_EEPROM_BUS
4334	  if you have an Environment on an EEPROM reached over
4335	  I2C muxes, you can define here, how to reach this
4336	  EEPROM. For example:
4337
4338	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
4339
4340	  EEPROM which holds the environment, is reached over
4341	  a pca9547 i2c mux with address 0x70, channel 3.
4342
4343- CONFIG_ENV_IS_IN_DATAFLASH:
4344
4345	Define this if you have a DataFlash memory device which you
4346	want to use for the environment.
4347
4348	- CONFIG_ENV_OFFSET:
4349	- CONFIG_ENV_ADDR:
4350	- CONFIG_ENV_SIZE:
4351
4352	  These three #defines specify the offset and size of the
4353	  environment area within the total memory of your DataFlash placed
4354	  at the specified address.
4355
4356- CONFIG_ENV_IS_IN_SPI_FLASH:
4357
4358	Define this if you have a SPI Flash memory device which you
4359	want to use for the environment.
4360
4361	- CONFIG_ENV_OFFSET:
4362	- CONFIG_ENV_SIZE:
4363
4364	  These two #defines specify the offset and size of the
4365	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
4366	  aligned to an erase sector boundary.
4367
4368	- CONFIG_ENV_SECT_SIZE:
4369
4370	  Define the SPI flash's sector size.
4371
4372	- CONFIG_ENV_OFFSET_REDUND (optional):
4373
4374	  This setting describes a second storage area of CONFIG_ENV_SIZE
4375	  size used to hold a redundant copy of the environment data, so
4376	  that there is a valid backup copy in case there is a power failure
4377	  during a "saveenv" operation. CONFIG_ENV_OFFSET_RENDUND must be
4378	  aligned to an erase sector boundary.
4379
4380	- CONFIG_ENV_SPI_BUS (optional):
4381	- CONFIG_ENV_SPI_CS (optional):
4382
4383	  Define the SPI bus and chip select. If not defined they will be 0.
4384
4385	- CONFIG_ENV_SPI_MAX_HZ (optional):
4386
4387	  Define the SPI max work clock. If not defined then use 1MHz.
4388
4389	- CONFIG_ENV_SPI_MODE (optional):
4390
4391	  Define the SPI work mode. If not defined then use SPI_MODE_3.
4392
4393- CONFIG_ENV_IS_IN_REMOTE:
4394
4395	Define this if you have a remote memory space which you
4396	want to use for the local device's environment.
4397
4398	- CONFIG_ENV_ADDR:
4399	- CONFIG_ENV_SIZE:
4400
4401	  These two #defines specify the address and size of the
4402	  environment area within the remote memory space. The
4403	  local device can get the environment from remote memory
4404	  space by SRIO or PCIE links.
4405
4406BE CAREFUL! For some special cases, the local device can not use
4407"saveenv" command. For example, the local device will get the
4408environment stored in a remote NOR flash by SRIO or PCIE link,
4409but it can not erase, write this NOR flash by SRIO or PCIE interface.
4410
4411- CONFIG_ENV_IS_IN_NAND:
4412
4413	Define this if you have a NAND device which you want to use
4414	for the environment.
4415
4416	- CONFIG_ENV_OFFSET:
4417	- CONFIG_ENV_SIZE:
4418
4419	  These two #defines specify the offset and size of the environment
4420	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4421	  aligned to an erase block boundary.
4422
4423	- CONFIG_ENV_OFFSET_REDUND (optional):
4424
4425	  This setting describes a second storage area of CONFIG_ENV_SIZE
4426	  size used to hold a redundant copy of the environment data, so
4427	  that there is a valid backup copy in case there is a power failure
4428	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
4429	  aligned to an erase block boundary.
4430
4431	- CONFIG_ENV_RANGE (optional):
4432
4433	  Specifies the length of the region in which the environment
4434	  can be written.  This should be a multiple of the NAND device's
4435	  block size.  Specifying a range with more erase blocks than
4436	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4437	  the range to be avoided.
4438
4439	- CONFIG_ENV_OFFSET_OOB (optional):
4440
4441	  Enables support for dynamically retrieving the offset of the
4442	  environment from block zero's out-of-band data.  The
4443	  "nand env.oob" command can be used to record this offset.
4444	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4445	  using CONFIG_ENV_OFFSET_OOB.
4446
4447- CONFIG_NAND_ENV_DST
4448
4449	Defines address in RAM to which the nand_spl code should copy the
4450	environment. If redundant environment is used, it will be copied to
4451	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4452
4453- CONFIG_ENV_IS_IN_UBI:
4454
4455	Define this if you have an UBI volume that you want to use for the
4456	environment.  This has the benefit of wear-leveling the environment
4457	accesses, which is important on NAND.
4458
4459	- CONFIG_ENV_UBI_PART:
4460
4461	  Define this to a string that is the mtd partition containing the UBI.
4462
4463	- CONFIG_ENV_UBI_VOLUME:
4464
4465	  Define this to the name of the volume that you want to store the
4466	  environment in.
4467
4468	- CONFIG_ENV_UBI_VOLUME_REDUND:
4469
4470	  Define this to the name of another volume to store a second copy of
4471	  the environment in.  This will enable redundant environments in UBI.
4472	  It is assumed that both volumes are in the same MTD partition.
4473
4474	- CONFIG_UBI_SILENCE_MSG
4475	- CONFIG_UBIFS_SILENCE_MSG
4476
4477	  You will probably want to define these to avoid a really noisy system
4478	  when storing the env in UBI.
4479
4480- CONFIG_ENV_IS_IN_FAT:
4481       Define this if you want to use the FAT file system for the environment.
4482
4483       - FAT_ENV_INTERFACE:
4484
4485         Define this to a string that is the name of the block device.
4486
4487       - FAT_ENV_DEV_AND_PART:
4488
4489         Define this to a string to specify the partition of the device. It can
4490         be as following:
4491
4492           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
4493               - "D:P": device D partition P. Error occurs if device D has no
4494                        partition table.
4495               - "D:0": device D.
4496               - "D" or "D:": device D partition 1 if device D has partition
4497                              table, or the whole device D if has no partition
4498                              table.
4499               - "D:auto": first partition in device D with bootable flag set.
4500                           If none, first valid partition in device D. If no
4501                           partition table then means device D.
4502
4503       - FAT_ENV_FILE:
4504
4505         It's a string of the FAT file name. This file use to store the
4506         environment.
4507
4508       - CONFIG_FAT_WRITE:
4509         This should be defined. Otherwise it cannot save the environment file.
4510
4511- CONFIG_ENV_IS_IN_MMC:
4512
4513	Define this if you have an MMC device which you want to use for the
4514	environment.
4515
4516	- CONFIG_SYS_MMC_ENV_DEV:
4517
4518	  Specifies which MMC device the environment is stored in.
4519
4520	- CONFIG_SYS_MMC_ENV_PART (optional):
4521
4522	  Specifies which MMC partition the environment is stored in. If not
4523	  set, defaults to partition 0, the user area. Common values might be
4524	  1 (first MMC boot partition), 2 (second MMC boot partition).
4525
4526	- CONFIG_ENV_OFFSET:
4527	- CONFIG_ENV_SIZE:
4528
4529	  These two #defines specify the offset and size of the environment
4530	  area within the specified MMC device.
4531
4532	  If offset is positive (the usual case), it is treated as relative to
4533	  the start of the MMC partition. If offset is negative, it is treated
4534	  as relative to the end of the MMC partition. This can be useful if
4535	  your board may be fitted with different MMC devices, which have
4536	  different sizes for the MMC partitions, and you always want the
4537	  environment placed at the very end of the partition, to leave the
4538	  maximum possible space before it, to store other data.
4539
4540	  These two values are in units of bytes, but must be aligned to an
4541	  MMC sector boundary.
4542
4543	- CONFIG_ENV_OFFSET_REDUND (optional):
4544
4545	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4546	  hold a redundant copy of the environment data. This provides a
4547	  valid backup copy in case the other copy is corrupted, e.g. due
4548	  to a power failure during a "saveenv" operation.
4549
4550	  This value may also be positive or negative; this is handled in the
4551	  same way as CONFIG_ENV_OFFSET.
4552
4553	  This value is also in units of bytes, but must also be aligned to
4554	  an MMC sector boundary.
4555
4556	- CONFIG_ENV_SIZE_REDUND (optional):
4557
4558	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4559	  set. If this value is set, it must be set to the same value as
4560	  CONFIG_ENV_SIZE.
4561
4562- CONFIG_SYS_SPI_INIT_OFFSET
4563
4564	Defines offset to the initial SPI buffer area in DPRAM. The
4565	area is used at an early stage (ROM part) if the environment
4566	is configured to reside in the SPI EEPROM: We need a 520 byte
4567	scratch DPRAM area. It is used between the two initialization
4568	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4569	to be a good choice since it makes it far enough from the
4570	start of the data area as well as from the stack pointer.
4571
4572Please note that the environment is read-only until the monitor
4573has been relocated to RAM and a RAM copy of the environment has been
4574created; also, when using EEPROM you will have to use getenv_f()
4575until then to read environment variables.
4576
4577The environment is protected by a CRC32 checksum. Before the monitor
4578is relocated into RAM, as a result of a bad CRC you will be working
4579with the compiled-in default environment - *silently*!!! [This is
4580necessary, because the first environment variable we need is the
4581"baudrate" setting for the console - if we have a bad CRC, we don't
4582have any device yet where we could complain.]
4583
4584Note: once the monitor has been relocated, then it will complain if
4585the default environment is used; a new CRC is computed as soon as you
4586use the "saveenv" command to store a valid environment.
4587
4588- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4589		Echo the inverted Ethernet link state to the fault LED.
4590
4591		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4592		      also needs to be defined.
4593
4594- CONFIG_SYS_FAULT_MII_ADDR:
4595		MII address of the PHY to check for the Ethernet link state.
4596
4597- CONFIG_NS16550_MIN_FUNCTIONS:
4598		Define this if you desire to only have use of the NS16550_init
4599		and NS16550_putc functions for the serial driver located at
4600		drivers/serial/ns16550.c.  This option is useful for saving
4601		space for already greatly restricted images, including but not
4602		limited to NAND_SPL configurations.
4603
4604- CONFIG_DISPLAY_BOARDINFO
4605		Display information about the board that U-Boot is running on
4606		when U-Boot starts up. The board function checkboard() is called
4607		to do this.
4608
4609- CONFIG_DISPLAY_BOARDINFO_LATE
4610		Similar to the previous option, but display this information
4611		later, once stdio is running and output goes to the LCD, if
4612		present.
4613
4614- CONFIG_BOARD_SIZE_LIMIT:
4615		Maximum size of the U-Boot image. When defined, the
4616		build system checks that the actual size does not
4617		exceed it.
4618
4619Low Level (hardware related) configuration options:
4620---------------------------------------------------
4621
4622- CONFIG_SYS_CACHELINE_SIZE:
4623		Cache Line Size of the CPU.
4624
4625- CONFIG_SYS_DEFAULT_IMMR:
4626		Default address of the IMMR after system reset.
4627
4628		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4629		and RPXsuper) to be able to adjust the position of
4630		the IMMR register after a reset.
4631
4632- CONFIG_SYS_CCSRBAR_DEFAULT:
4633		Default (power-on reset) physical address of CCSR on Freescale
4634		PowerPC SOCs.
4635
4636- CONFIG_SYS_CCSRBAR:
4637		Virtual address of CCSR.  On a 32-bit build, this is typically
4638		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4639
4640		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4641		for cross-platform code that uses that macro instead.
4642
4643- CONFIG_SYS_CCSRBAR_PHYS:
4644		Physical address of CCSR.  CCSR can be relocated to a new
4645		physical address, if desired.  In this case, this macro should
4646		be set to that address.	 Otherwise, it should be set to the
4647		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4648		is typically relocated on 36-bit builds.  It is recommended
4649		that this macro be defined via the _HIGH and _LOW macros:
4650
4651		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4652			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4653
4654- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4655		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4656		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4657		used in assembly code, so it must not contain typecasts or
4658		integer size suffixes (e.g. "ULL").
4659
4660- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4661		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4662		used in assembly code, so it must not contain typecasts or
4663		integer size suffixes (e.g. "ULL").
4664
4665- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4666		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4667		forced to a value that ensures that CCSR is not relocated.
4668
4669- Floppy Disk Support:
4670		CONFIG_SYS_FDC_DRIVE_NUMBER
4671
4672		the default drive number (default value 0)
4673
4674		CONFIG_SYS_ISA_IO_STRIDE
4675
4676		defines the spacing between FDC chipset registers
4677		(default value 1)
4678
4679		CONFIG_SYS_ISA_IO_OFFSET
4680
4681		defines the offset of register from address. It
4682		depends on which part of the data bus is connected to
4683		the FDC chipset. (default value 0)
4684
4685		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4686		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4687		default value.
4688
4689		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4690		fdc_hw_init() is called at the beginning of the FDC
4691		setup. fdc_hw_init() must be provided by the board
4692		source code. It is used to make hardware-dependent
4693		initializations.
4694
4695- CONFIG_IDE_AHB:
4696		Most IDE controllers were designed to be connected with PCI
4697		interface. Only few of them were designed for AHB interface.
4698		When software is doing ATA command and data transfer to
4699		IDE devices through IDE-AHB controller, some additional
4700		registers accessing to these kind of IDE-AHB controller
4701		is required.
4702
4703- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4704		DO NOT CHANGE unless you know exactly what you're
4705		doing! (11-4) [MPC8xx/82xx systems only]
4706
4707- CONFIG_SYS_INIT_RAM_ADDR:
4708
4709		Start address of memory area that can be used for
4710		initial data and stack; please note that this must be
4711		writable memory that is working WITHOUT special
4712		initialization, i. e. you CANNOT use normal RAM which
4713		will become available only after programming the
4714		memory controller and running certain initialization
4715		sequences.
4716
4717		U-Boot uses the following memory types:
4718		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4719		- MPC824X: data cache
4720		- PPC4xx:  data cache
4721
4722- CONFIG_SYS_GBL_DATA_OFFSET:
4723
4724		Offset of the initial data structure in the memory
4725		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4726		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4727		data is located at the end of the available space
4728		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4729		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4730		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4731		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4732
4733	Note:
4734		On the MPC824X (or other systems that use the data
4735		cache for initial memory) the address chosen for
4736		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4737		point to an otherwise UNUSED address space between
4738		the top of RAM and the start of the PCI space.
4739
4740- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4741
4742- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4743
4744- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4745
4746- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4747
4748- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4749
4750- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4751
4752- CONFIG_SYS_OR_TIMING_SDRAM:
4753		SDRAM timing
4754
4755- CONFIG_SYS_MAMR_PTA:
4756		periodic timer for refresh
4757
4758- CONFIG_SYS_DER:	Debug Event Register (37-47)
4759
4760- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4761  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4762  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4763  CONFIG_SYS_BR1_PRELIM:
4764		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4765
4766- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4767  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4768  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4769		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4770
4771- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4772  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4773		Machine Mode Register and Memory Periodic Timer
4774		Prescaler definitions (SDRAM timing)
4775
4776- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4777		enable I2C microcode relocation patch (MPC8xx);
4778		define relocation offset in DPRAM [DSP2]
4779
4780- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4781		enable SMC microcode relocation patch (MPC8xx);
4782		define relocation offset in DPRAM [SMC1]
4783
4784- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4785		enable SPI microcode relocation patch (MPC8xx);
4786		define relocation offset in DPRAM [SCC4]
4787
4788- CONFIG_SYS_USE_OSCCLK:
4789		Use OSCM clock mode on MBX8xx board. Be careful,
4790		wrong setting might damage your board. Read
4791		doc/README.MBX before setting this variable!
4792
4793- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4794		Offset of the bootmode word in DPRAM used by post
4795		(Power On Self Tests). This definition overrides
4796		#define'd default value in commproc.h resp.
4797		cpm_8260.h.
4798
4799- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4800  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4801  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4802  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4803  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4804  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4805  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4806  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4807		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4808
4809- CONFIG_PCI_DISABLE_PCIE:
4810		Disable PCI-Express on systems where it is supported but not
4811		required.
4812
4813- CONFIG_PCI_ENUM_ONLY
4814		Only scan through and get the devices on the buses.
4815		Don't do any setup work, presumably because someone or
4816		something has already done it, and we don't need to do it
4817		a second time.	Useful for platforms that are pre-booted
4818		by coreboot or similar.
4819
4820- CONFIG_PCI_INDIRECT_BRIDGE:
4821		Enable support for indirect PCI bridges.
4822
4823- CONFIG_SYS_SRIO:
4824		Chip has SRIO or not
4825
4826- CONFIG_SRIO1:
4827		Board has SRIO 1 port available
4828
4829- CONFIG_SRIO2:
4830		Board has SRIO 2 port available
4831
4832- CONFIG_SRIO_PCIE_BOOT_MASTER
4833		Board can support master function for Boot from SRIO and PCIE
4834
4835- CONFIG_SYS_SRIOn_MEM_VIRT:
4836		Virtual Address of SRIO port 'n' memory region
4837
4838- CONFIG_SYS_SRIOn_MEM_PHYS:
4839		Physical Address of SRIO port 'n' memory region
4840
4841- CONFIG_SYS_SRIOn_MEM_SIZE:
4842		Size of SRIO port 'n' memory region
4843
4844- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4845		Defined to tell the NAND controller that the NAND chip is using
4846		a 16 bit bus.
4847		Not all NAND drivers use this symbol.
4848		Example of drivers that use it:
4849		- drivers/mtd/nand/ndfc.c
4850		- drivers/mtd/nand/mxc_nand.c
4851
4852- CONFIG_SYS_NDFC_EBC0_CFG
4853		Sets the EBC0_CFG register for the NDFC. If not defined
4854		a default value will be used.
4855
4856- CONFIG_SPD_EEPROM
4857		Get DDR timing information from an I2C EEPROM. Common
4858		with pluggable memory modules such as SODIMMs
4859
4860  SPD_EEPROM_ADDRESS
4861		I2C address of the SPD EEPROM
4862
4863- CONFIG_SYS_SPD_BUS_NUM
4864		If SPD EEPROM is on an I2C bus other than the first
4865		one, specify here. Note that the value must resolve
4866		to something your driver can deal with.
4867
4868- CONFIG_SYS_DDR_RAW_TIMING
4869		Get DDR timing information from other than SPD. Common with
4870		soldered DDR chips onboard without SPD. DDR raw timing
4871		parameters are extracted from datasheet and hard-coded into
4872		header files or board specific files.
4873
4874- CONFIG_FSL_DDR_INTERACTIVE
4875		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4876
4877- CONFIG_FSL_DDR_SYNC_REFRESH
4878		Enable sync of refresh for multiple controllers.
4879
4880- CONFIG_FSL_DDR_BIST
4881		Enable built-in memory test for Freescale DDR controllers.
4882
4883- CONFIG_SYS_83XX_DDR_USES_CS0
4884		Only for 83xx systems. If specified, then DDR should
4885		be configured using CS0 and CS1 instead of CS2 and CS3.
4886
4887- CONFIG_ETHER_ON_FEC[12]
4888		Define to enable FEC[12] on a 8xx series processor.
4889
4890- CONFIG_FEC[12]_PHY
4891		Define to the hardcoded PHY address which corresponds
4892		to the given FEC; i. e.
4893			#define CONFIG_FEC1_PHY 4
4894		means that the PHY with address 4 is connected to FEC1
4895
4896		When set to -1, means to probe for first available.
4897
4898- CONFIG_FEC[12]_PHY_NORXERR
4899		The PHY does not have a RXERR line (RMII only).
4900		(so program the FEC to ignore it).
4901
4902- CONFIG_RMII
4903		Enable RMII mode for all FECs.
4904		Note that this is a global option, we can't
4905		have one FEC in standard MII mode and another in RMII mode.
4906
4907- CONFIG_CRC32_VERIFY
4908		Add a verify option to the crc32 command.
4909		The syntax is:
4910
4911		=> crc32 -v <address> <count> <crc32>
4912
4913		Where address/count indicate a memory area
4914		and crc32 is the correct crc32 which the
4915		area should have.
4916
4917- CONFIG_LOOPW
4918		Add the "loopw" memory command. This only takes effect if
4919		the memory commands are activated globally (CONFIG_CMD_MEM).
4920
4921- CONFIG_MX_CYCLIC
4922		Add the "mdc" and "mwc" memory commands. These are cyclic
4923		"md/mw" commands.
4924		Examples:
4925
4926		=> mdc.b 10 4 500
4927		This command will print 4 bytes (10,11,12,13) each 500 ms.
4928
4929		=> mwc.l 100 12345678 10
4930		This command will write 12345678 to address 100 all 10 ms.
4931
4932		This only takes effect if the memory commands are activated
4933		globally (CONFIG_CMD_MEM).
4934
4935- CONFIG_SKIP_LOWLEVEL_INIT
4936		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4937		low level initializations (like setting up the memory
4938		controller) are omitted and/or U-Boot does not
4939		relocate itself into RAM.
4940
4941		Normally this variable MUST NOT be defined. The only
4942		exception is when U-Boot is loaded (to RAM) by some
4943		other boot loader or by a debugger which performs
4944		these initializations itself.
4945
4946- CONFIG_SPL_BUILD
4947		Modifies the behaviour of start.S when compiling a loader
4948		that is executed before the actual U-Boot. E.g. when
4949		compiling a NAND SPL.
4950
4951- CONFIG_TPL_BUILD
4952		Modifies the behaviour of start.S  when compiling a loader
4953		that is executed after the SPL and before the actual U-Boot.
4954		It is loaded by the SPL.
4955
4956- CONFIG_SYS_MPC85XX_NO_RESETVEC
4957		Only for 85xx systems. If this variable is specified, the section
4958		.resetvec is not kept and the section .bootpg is placed in the
4959		previous 4k of the .text section.
4960
4961- CONFIG_ARCH_MAP_SYSMEM
4962		Generally U-Boot (and in particular the md command) uses
4963		effective address. It is therefore not necessary to regard
4964		U-Boot address as virtual addresses that need to be translated
4965		to physical addresses. However, sandbox requires this, since
4966		it maintains its own little RAM buffer which contains all
4967		addressable memory. This option causes some memory accesses
4968		to be mapped through map_sysmem() / unmap_sysmem().
4969
4970- CONFIG_USE_ARCH_MEMCPY
4971  CONFIG_USE_ARCH_MEMSET
4972		If these options are used a optimized version of memcpy/memset will
4973		be used if available. These functions may be faster under some
4974		conditions but may increase the binary size.
4975
4976- CONFIG_X86_RESET_VECTOR
4977		If defined, the x86 reset vector code is included. This is not
4978		needed when U-Boot is running from Coreboot.
4979
4980- CONFIG_SYS_MPUCLK
4981		Defines the MPU clock speed (in MHz).
4982
4983		NOTE : currently only supported on AM335x platforms.
4984
4985- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4986		Enables the RTC32K OSC on AM33xx based plattforms
4987
4988- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4989		Option to disable subpage write in NAND driver
4990		driver that uses this:
4991		drivers/mtd/nand/davinci_nand.c
4992
4993Freescale QE/FMAN Firmware Support:
4994-----------------------------------
4995
4996The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4997loading of "firmware", which is encoded in the QE firmware binary format.
4998This firmware often needs to be loaded during U-Boot booting, so macros
4999are used to identify the storage device (NOR flash, SPI, etc) and the address
5000within that device.
5001
5002- CONFIG_SYS_FMAN_FW_ADDR
5003	The address in the storage device where the FMAN microcode is located.  The
5004	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
5005	is also specified.
5006
5007- CONFIG_SYS_QE_FW_ADDR
5008	The address in the storage device where the QE microcode is located.  The
5009	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
5010	is also specified.
5011
5012- CONFIG_SYS_QE_FMAN_FW_LENGTH
5013	The maximum possible size of the firmware.  The firmware binary format
5014	has a field that specifies the actual size of the firmware, but it
5015	might not be possible to read any part of the firmware unless some
5016	local storage is allocated to hold the entire firmware first.
5017
5018- CONFIG_SYS_QE_FMAN_FW_IN_NOR
5019	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
5020	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
5021	virtual address in NOR flash.
5022
5023- CONFIG_SYS_QE_FMAN_FW_IN_NAND
5024	Specifies that QE/FMAN firmware is located in NAND flash.
5025	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
5026
5027- CONFIG_SYS_QE_FMAN_FW_IN_MMC
5028	Specifies that QE/FMAN firmware is located on the primary SD/MMC
5029	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
5030
5031- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
5032	Specifies that QE/FMAN firmware is located on the primary SPI
5033	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
5034
5035- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
5036	Specifies that QE/FMAN firmware is located in the remote (master)
5037	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
5038	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
5039	window->master inbound window->master LAW->the ucode address in
5040	master's memory space.
5041
5042Freescale Layerscape Management Complex Firmware Support:
5043---------------------------------------------------------
5044The Freescale Layerscape Management Complex (MC) supports the loading of
5045"firmware".
5046This firmware often needs to be loaded during U-Boot booting, so macros
5047are used to identify the storage device (NOR flash, SPI, etc) and the address
5048within that device.
5049
5050- CONFIG_FSL_MC_ENET
5051	Enable the MC driver for Layerscape SoCs.
5052
5053- CONFIG_SYS_LS_MC_FW_ADDR
5054	The address in the storage device where the firmware is located.  The
5055	meaning of this address depends on which CONFIG_SYS_LS_MC_FW_IN_xxx macro
5056	is also specified.
5057
5058- CONFIG_SYS_LS_MC_FW_LENGTH
5059	The maximum possible size of the firmware.  The firmware binary format
5060	has a field that specifies the actual size of the firmware, but it
5061	might not be possible to read any part of the firmware unless some
5062	local storage is allocated to hold the entire firmware first.
5063
5064- CONFIG_SYS_LS_MC_FW_IN_NOR
5065	Specifies that MC firmware is located in NOR flash, mapped as
5066	normal addressable memory via the LBC. CONFIG_SYS_LS_MC_FW_ADDR is the
5067	virtual address in NOR flash.
5068
5069Freescale Layerscape Debug Server Support:
5070-------------------------------------------
5071The Freescale Layerscape Debug Server Support supports the loading of
5072"Debug Server firmware" and triggering SP boot-rom.
5073This firmware often needs to be loaded during U-Boot booting.
5074
5075- CONFIG_FSL_DEBUG_SERVER
5076	Enable the Debug Server for Layerscape SoCs.
5077
5078- CONFIG_SYS_DEBUG_SERVER_DRAM_BLOCK_MIN_SIZE
5079	Define minimum DDR size required for debug server image
5080
5081- CONFIG_SYS_MEM_TOP_HIDE_MIN
5082	Define minimum DDR size to be hided from top of the DDR memory
5083
5084Reproducible builds
5085-------------------
5086
5087In order to achieve reproducible builds, timestamps used in the U-Boot build
5088process have to be set to a fixed value.
5089
5090This is done using the SOURCE_DATE_EPOCH environment variable.
5091SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
5092option for U-Boot or an environment variable in U-Boot.
5093
5094SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
5095
5096Building the Software:
5097======================
5098
5099Building U-Boot has been tested in several native build environments
5100and in many different cross environments. Of course we cannot support
5101all possibly existing versions of cross development tools in all
5102(potentially obsolete) versions. In case of tool chain problems we
5103recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
5104which is extensively used to build and test U-Boot.
5105
5106If you are not using a native environment, it is assumed that you
5107have GNU cross compiling tools available in your path. In this case,
5108you must set the environment variable CROSS_COMPILE in your shell.
5109Note that no changes to the Makefile or any other source files are
5110necessary. For example using the ELDK on a 4xx CPU, please enter:
5111
5112	$ CROSS_COMPILE=ppc_4xx-
5113	$ export CROSS_COMPILE
5114
5115Note: If you wish to generate Windows versions of the utilities in
5116      the tools directory you can use the MinGW toolchain
5117      (http://www.mingw.org).  Set your HOST tools to the MinGW
5118      toolchain and execute 'make tools'.  For example:
5119
5120       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
5121
5122      Binaries such as tools/mkimage.exe will be created which can
5123      be executed on computers running Windows.
5124
5125U-Boot is intended to be simple to build. After installing the
5126sources you must configure U-Boot for one specific board type. This
5127is done by typing:
5128
5129	make NAME_defconfig
5130
5131where "NAME_defconfig" is the name of one of the existing configu-
5132rations; see boards.cfg for supported names.
5133
5134Note: for some board special configuration names may exist; check if
5135      additional information is available from the board vendor; for
5136      instance, the TQM823L systems are available without (standard)
5137      or with LCD support. You can select such additional "features"
5138      when choosing the configuration, i. e.
5139
5140      make TQM823L_defconfig
5141	- will configure for a plain TQM823L, i. e. no LCD support
5142
5143      make TQM823L_LCD_defconfig
5144	- will configure for a TQM823L with U-Boot console on LCD
5145
5146      etc.
5147
5148
5149Finally, type "make all", and you should get some working U-Boot
5150images ready for download to / installation on your system:
5151
5152- "u-boot.bin" is a raw binary image
5153- "u-boot" is an image in ELF binary format
5154- "u-boot.srec" is in Motorola S-Record format
5155
5156By default the build is performed locally and the objects are saved
5157in the source directory. One of the two methods can be used to change
5158this behavior and build U-Boot to some external directory:
5159
51601. Add O= to the make command line invocations:
5161
5162	make O=/tmp/build distclean
5163	make O=/tmp/build NAME_defconfig
5164	make O=/tmp/build all
5165
51662. Set environment variable KBUILD_OUTPUT to point to the desired location:
5167
5168	export KBUILD_OUTPUT=/tmp/build
5169	make distclean
5170	make NAME_defconfig
5171	make all
5172
5173Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
5174variable.
5175
5176
5177Please be aware that the Makefiles assume you are using GNU make, so
5178for instance on NetBSD you might need to use "gmake" instead of
5179native "make".
5180
5181
5182If the system board that you have is not listed, then you will need
5183to port U-Boot to your hardware platform. To do this, follow these
5184steps:
5185
51861.  Add a new configuration option for your board to the toplevel
5187    "boards.cfg" file, using the existing entries as examples.
5188    Follow the instructions there to keep the boards in order.
51892.  Create a new directory to hold your board specific code. Add any
5190    files you need. In your board directory, you will need at least
5191    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
51923.  Create a new configuration file "include/configs/<board>.h" for
5193    your board
51943.  If you're porting U-Boot to a new CPU, then also create a new
5195    directory to hold your CPU specific code. Add any files you need.
51964.  Run "make <board>_defconfig" with your new name.
51975.  Type "make", and you should get a working "u-boot.srec" file
5198    to be installed on your target system.
51996.  Debug and solve any problems that might arise.
5200    [Of course, this last step is much harder than it sounds.]
5201
5202
5203Testing of U-Boot Modifications, Ports to New Hardware, etc.:
5204==============================================================
5205
5206If you have modified U-Boot sources (for instance added a new board
5207or support for new devices, a new CPU, etc.) you are expected to
5208provide feedback to the other developers. The feedback normally takes
5209the form of a "patch", i. e. a context diff against a certain (latest
5210official or latest in the git repository) version of U-Boot sources.
5211
5212But before you submit such a patch, please verify that your modifi-
5213cation did not break existing code. At least make sure that *ALL* of
5214the supported boards compile WITHOUT ANY compiler warnings. To do so,
5215just run the "MAKEALL" script, which will configure and build U-Boot
5216for ALL supported system. Be warned, this will take a while. You can
5217select which (cross) compiler to use by passing a `CROSS_COMPILE'
5218environment variable to the script, i. e. to use the ELDK cross tools
5219you can type
5220
5221	CROSS_COMPILE=ppc_8xx- MAKEALL
5222
5223or to build on a native PowerPC system you can type
5224
5225	CROSS_COMPILE=' ' MAKEALL
5226
5227When using the MAKEALL script, the default behaviour is to build
5228U-Boot in the source directory. This location can be changed by
5229setting the BUILD_DIR environment variable. Also, for each target
5230built, the MAKEALL script saves two log files (<target>.ERR and
5231<target>.MAKEALL) in the <source dir>/LOG directory. This default
5232location can be changed by setting the MAKEALL_LOGDIR environment
5233variable. For example:
5234
5235	export BUILD_DIR=/tmp/build
5236	export MAKEALL_LOGDIR=/tmp/log
5237	CROSS_COMPILE=ppc_8xx- MAKEALL
5238
5239With the above settings build objects are saved in the /tmp/build,
5240log files are saved in the /tmp/log and the source tree remains clean
5241during the whole build process.
5242
5243
5244See also "U-Boot Porting Guide" below.
5245
5246
5247Monitor Commands - Overview:
5248============================
5249
5250go	- start application at address 'addr'
5251run	- run commands in an environment variable
5252bootm	- boot application image from memory
5253bootp	- boot image via network using BootP/TFTP protocol
5254bootz   - boot zImage from memory
5255tftpboot- boot image via network using TFTP protocol
5256	       and env variables "ipaddr" and "serverip"
5257	       (and eventually "gatewayip")
5258tftpput - upload a file via network using TFTP protocol
5259rarpboot- boot image via network using RARP/TFTP protocol
5260diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
5261loads	- load S-Record file over serial line
5262loadb	- load binary file over serial line (kermit mode)
5263md	- memory display
5264mm	- memory modify (auto-incrementing)
5265nm	- memory modify (constant address)
5266mw	- memory write (fill)
5267cp	- memory copy
5268cmp	- memory compare
5269crc32	- checksum calculation
5270i2c	- I2C sub-system
5271sspi	- SPI utility commands
5272base	- print or set address offset
5273printenv- print environment variables
5274setenv	- set environment variables
5275saveenv - save environment variables to persistent storage
5276protect - enable or disable FLASH write protection
5277erase	- erase FLASH memory
5278flinfo	- print FLASH memory information
5279nand	- NAND memory operations (see doc/README.nand)
5280bdinfo	- print Board Info structure
5281iminfo	- print header information for application image
5282coninfo - print console devices and informations
5283ide	- IDE sub-system
5284loop	- infinite loop on address range
5285loopw	- infinite write loop on address range
5286mtest	- simple RAM test
5287icache	- enable or disable instruction cache
5288dcache	- enable or disable data cache
5289reset	- Perform RESET of the CPU
5290echo	- echo args to console
5291version - print monitor version
5292help	- print online help
5293?	- alias for 'help'
5294
5295
5296Monitor Commands - Detailed Description:
5297========================================
5298
5299TODO.
5300
5301For now: just type "help <command>".
5302
5303
5304Environment Variables:
5305======================
5306
5307U-Boot supports user configuration using Environment Variables which
5308can be made persistent by saving to Flash memory.
5309
5310Environment Variables are set using "setenv", printed using
5311"printenv", and saved to Flash using "saveenv". Using "setenv"
5312without a value can be used to delete a variable from the
5313environment. As long as you don't save the environment you are
5314working with an in-memory copy. In case the Flash area containing the
5315environment is erased by accident, a default environment is provided.
5316
5317Some configuration options can be set using Environment Variables.
5318
5319List of environment variables (most likely not complete):
5320
5321  baudrate	- see CONFIG_BAUDRATE
5322
5323  bootdelay	- see CONFIG_BOOTDELAY
5324
5325  bootcmd	- see CONFIG_BOOTCOMMAND
5326
5327  bootargs	- Boot arguments when booting an RTOS image
5328
5329  bootfile	- Name of the image to load with TFTP
5330
5331  bootm_low	- Memory range available for image processing in the bootm
5332		  command can be restricted. This variable is given as
5333		  a hexadecimal number and defines lowest address allowed
5334		  for use by the bootm command. See also "bootm_size"
5335		  environment variable. Address defined by "bootm_low" is
5336		  also the base of the initial memory mapping for the Linux
5337		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
5338		  bootm_mapsize.
5339
5340  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
5341		  This variable is given as a hexadecimal number and it
5342		  defines the size of the memory region starting at base
5343		  address bootm_low that is accessible by the Linux kernel
5344		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
5345		  as the default value if it is defined, and bootm_size is
5346		  used otherwise.
5347
5348  bootm_size	- Memory range available for image processing in the bootm
5349		  command can be restricted. This variable is given as
5350		  a hexadecimal number and defines the size of the region
5351		  allowed for use by the bootm command. See also "bootm_low"
5352		  environment variable.
5353
5354  updatefile	- Location of the software update file on a TFTP server, used
5355		  by the automatic software update feature. Please refer to
5356		  documentation in doc/README.update for more details.
5357
5358  autoload	- if set to "no" (any string beginning with 'n'),
5359		  "bootp" will just load perform a lookup of the
5360		  configuration from the BOOTP server, but not try to
5361		  load any image using TFTP
5362
5363  autostart	- if set to "yes", an image loaded using the "bootp",
5364		  "rarpboot", "tftpboot" or "diskboot" commands will
5365		  be automatically started (by internally calling
5366		  "bootm")
5367
5368		  If set to "no", a standalone image passed to the
5369		  "bootm" command will be copied to the load address
5370		  (and eventually uncompressed), but NOT be started.
5371		  This can be used to load and uncompress arbitrary
5372		  data.
5373
5374  fdt_high	- if set this restricts the maximum address that the
5375		  flattened device tree will be copied into upon boot.
5376		  For example, if you have a system with 1 GB memory
5377		  at physical address 0x10000000, while Linux kernel
5378		  only recognizes the first 704 MB as low memory, you
5379		  may need to set fdt_high as 0x3C000000 to have the
5380		  device tree blob be copied to the maximum address
5381		  of the 704 MB low memory, so that Linux kernel can
5382		  access it during the boot procedure.
5383
5384		  If this is set to the special value 0xFFFFFFFF then
5385		  the fdt will not be copied at all on boot.  For this
5386		  to work it must reside in writable memory, have
5387		  sufficient padding on the end of it for u-boot to
5388		  add the information it needs into it, and the memory
5389		  must be accessible by the kernel.
5390
5391  fdtcontroladdr- if set this is the address of the control flattened
5392		  device tree used by U-Boot when CONFIG_OF_CONTROL is
5393		  defined.
5394
5395  i2cfast	- (PPC405GP|PPC405EP only)
5396		  if set to 'y' configures Linux I2C driver for fast
5397		  mode (400kHZ). This environment variable is used in
5398		  initialization code. So, for changes to be effective
5399		  it must be saved and board must be reset.
5400
5401  initrd_high	- restrict positioning of initrd images:
5402		  If this variable is not set, initrd images will be
5403		  copied to the highest possible address in RAM; this
5404		  is usually what you want since it allows for
5405		  maximum initrd size. If for some reason you want to
5406		  make sure that the initrd image is loaded below the
5407		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
5408		  variable to a value of "no" or "off" or "0".
5409		  Alternatively, you can set it to a maximum upper
5410		  address to use (U-Boot will still check that it
5411		  does not overwrite the U-Boot stack and data).
5412
5413		  For instance, when you have a system with 16 MB
5414		  RAM, and want to reserve 4 MB from use by Linux,
5415		  you can do this by adding "mem=12M" to the value of
5416		  the "bootargs" variable. However, now you must make
5417		  sure that the initrd image is placed in the first
5418		  12 MB as well - this can be done with
5419
5420		  setenv initrd_high 00c00000
5421
5422		  If you set initrd_high to 0xFFFFFFFF, this is an
5423		  indication to U-Boot that all addresses are legal
5424		  for the Linux kernel, including addresses in flash
5425		  memory. In this case U-Boot will NOT COPY the
5426		  ramdisk at all. This may be useful to reduce the
5427		  boot time on your system, but requires that this
5428		  feature is supported by your Linux kernel.
5429
5430  ipaddr	- IP address; needed for tftpboot command
5431
5432  loadaddr	- Default load address for commands like "bootp",
5433		  "rarpboot", "tftpboot", "loadb" or "diskboot"
5434
5435  loads_echo	- see CONFIG_LOADS_ECHO
5436
5437  serverip	- TFTP server IP address; needed for tftpboot command
5438
5439  bootretry	- see CONFIG_BOOT_RETRY_TIME
5440
5441  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
5442
5443  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
5444
5445  ethprime	- controls which interface is used first.
5446
5447  ethact	- controls which interface is currently active.
5448		  For example you can do the following
5449
5450		  => setenv ethact FEC
5451		  => ping 192.168.0.1 # traffic sent on FEC
5452		  => setenv ethact SCC
5453		  => ping 10.0.0.1 # traffic sent on SCC
5454
5455  ethrotate	- When set to "no" U-Boot does not go through all
5456		  available network interfaces.
5457		  It just stays at the currently selected interface.
5458
5459  netretry	- When set to "no" each network operation will
5460		  either succeed or fail without retrying.
5461		  When set to "once" the network operation will
5462		  fail when all the available network interfaces
5463		  are tried once without success.
5464		  Useful on scripts which control the retry operation
5465		  themselves.
5466
5467  npe_ucode	- set load address for the NPE microcode
5468
5469  silent_linux  - If set then Linux will be told to boot silently, by
5470		  changing the console to be empty. If "yes" it will be
5471		  made silent. If "no" it will not be made silent. If
5472		  unset, then it will be made silent if the U-Boot console
5473		  is silent.
5474
5475  tftpsrcport	- If this is set, the value is used for TFTP's
5476		  UDP source port.
5477
5478  tftpdstport	- If this is set, the value is used for TFTP's UDP
5479		  destination port instead of the Well Know Port 69.
5480
5481  tftpblocksize - Block size to use for TFTP transfers; if not set,
5482		  we use the TFTP server's default block size
5483
5484  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
5485		  seconds, minimum value is 1000 = 1 second). Defines
5486		  when a packet is considered to be lost so it has to
5487		  be retransmitted. The default is 5000 = 5 seconds.
5488		  Lowering this value may make downloads succeed
5489		  faster in networks with high packet loss rates or
5490		  with unreliable TFTP servers.
5491
5492  vlan		- When set to a value < 4095 the traffic over
5493		  Ethernet is encapsulated/received over 802.1q
5494		  VLAN tagged frames.
5495
5496The following image location variables contain the location of images
5497used in booting. The "Image" column gives the role of the image and is
5498not an environment variable name. The other columns are environment
5499variable names. "File Name" gives the name of the file on a TFTP
5500server, "RAM Address" gives the location in RAM the image will be
5501loaded to, and "Flash Location" gives the image's address in NOR
5502flash or offset in NAND flash.
5503
5504*Note* - these variables don't have to be defined for all boards, some
5505boards currently use other variables for these purposes, and some
5506boards use these variables for other purposes.
5507
5508Image		    File Name	     RAM Address       Flash Location
5509-----		    ---------	     -----------       --------------
5510u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
5511Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
5512device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
5513ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
5514
5515The following environment variables may be used and automatically
5516updated by the network boot commands ("bootp" and "rarpboot"),
5517depending the information provided by your boot server:
5518
5519  bootfile	- see above
5520  dnsip		- IP address of your Domain Name Server
5521  dnsip2	- IP address of your secondary Domain Name Server
5522  gatewayip	- IP address of the Gateway (Router) to use
5523  hostname	- Target hostname
5524  ipaddr	- see above
5525  netmask	- Subnet Mask
5526  rootpath	- Pathname of the root filesystem on the NFS server
5527  serverip	- see above
5528
5529
5530There are two special Environment Variables:
5531
5532  serial#	- contains hardware identification information such
5533		  as type string and/or serial number
5534  ethaddr	- Ethernet address
5535
5536These variables can be set only once (usually during manufacturing of
5537the board). U-Boot refuses to delete or overwrite these variables
5538once they have been set once.
5539
5540
5541Further special Environment Variables:
5542
5543  ver		- Contains the U-Boot version string as printed
5544		  with the "version" command. This variable is
5545		  readonly (see CONFIG_VERSION_VARIABLE).
5546
5547
5548Please note that changes to some configuration parameters may take
5549only effect after the next boot (yes, that's just like Windoze :-).
5550
5551
5552Callback functions for environment variables:
5553---------------------------------------------
5554
5555For some environment variables, the behavior of u-boot needs to change
5556when their values are changed.  This functionality allows functions to
5557be associated with arbitrary variables.  On creation, overwrite, or
5558deletion, the callback will provide the opportunity for some side
5559effect to happen or for the change to be rejected.
5560
5561The callbacks are named and associated with a function using the
5562U_BOOT_ENV_CALLBACK macro in your board or driver code.
5563
5564These callbacks are associated with variables in one of two ways.  The
5565static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5566in the board configuration to a string that defines a list of
5567associations.  The list must be in the following format:
5568
5569	entry = variable_name[:callback_name]
5570	list = entry[,list]
5571
5572If the callback name is not specified, then the callback is deleted.
5573Spaces are also allowed anywhere in the list.
5574
5575Callbacks can also be associated by defining the ".callbacks" variable
5576with the same list format above.  Any association in ".callbacks" will
5577override any association in the static list. You can define
5578CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5579".callbacks" environment variable in the default or embedded environment.
5580
5581If CONFIG_REGEX is defined, the variable_name above is evaluated as a
5582regular expression. This allows multiple variables to be connected to
5583the same callback without explicitly listing them all out.
5584
5585
5586Command Line Parsing:
5587=====================
5588
5589There are two different command line parsers available with U-Boot:
5590the old "simple" one, and the much more powerful "hush" shell:
5591
5592Old, simple command line parser:
5593--------------------------------
5594
5595- supports environment variables (through setenv / saveenv commands)
5596- several commands on one line, separated by ';'
5597- variable substitution using "... ${name} ..." syntax
5598- special characters ('$', ';') can be escaped by prefixing with '\',
5599  for example:
5600	setenv bootcmd bootm \${address}
5601- You can also escape text by enclosing in single apostrophes, for example:
5602	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5603
5604Hush shell:
5605-----------
5606
5607- similar to Bourne shell, with control structures like
5608  if...then...else...fi, for...do...done; while...do...done,
5609  until...do...done, ...
5610- supports environment ("global") variables (through setenv / saveenv
5611  commands) and local shell variables (through standard shell syntax
5612  "name=value"); only environment variables can be used with "run"
5613  command
5614
5615General rules:
5616--------------
5617
5618(1) If a command line (or an environment variable executed by a "run"
5619    command) contains several commands separated by semicolon, and
5620    one of these commands fails, then the remaining commands will be
5621    executed anyway.
5622
5623(2) If you execute several variables with one call to run (i. e.
5624    calling run with a list of variables as arguments), any failing
5625    command will cause "run" to terminate, i. e. the remaining
5626    variables are not executed.
5627
5628Note for Redundant Ethernet Interfaces:
5629=======================================
5630
5631Some boards come with redundant Ethernet interfaces; U-Boot supports
5632such configurations and is capable of automatic selection of a
5633"working" interface when needed. MAC assignment works as follows:
5634
5635Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5636MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5637"eth1addr" (=>eth1), "eth2addr", ...
5638
5639If the network interface stores some valid MAC address (for instance
5640in SROM), this is used as default address if there is NO correspon-
5641ding setting in the environment; if the corresponding environment
5642variable is set, this overrides the settings in the card; that means:
5643
5644o If the SROM has a valid MAC address, and there is no address in the
5645  environment, the SROM's address is used.
5646
5647o If there is no valid address in the SROM, and a definition in the
5648  environment exists, then the value from the environment variable is
5649  used.
5650
5651o If both the SROM and the environment contain a MAC address, and
5652  both addresses are the same, this MAC address is used.
5653
5654o If both the SROM and the environment contain a MAC address, and the
5655  addresses differ, the value from the environment is used and a
5656  warning is printed.
5657
5658o If neither SROM nor the environment contain a MAC address, an error
5659  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
5660  a random, locally-assigned MAC is used.
5661
5662If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5663will be programmed into hardware as part of the initialization process.	 This
5664may be skipped by setting the appropriate 'ethmacskip' environment variable.
5665The naming convention is as follows:
5666"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5667
5668Image Formats:
5669==============
5670
5671U-Boot is capable of booting (and performing other auxiliary operations on)
5672images in two formats:
5673
5674New uImage format (FIT)
5675-----------------------
5676
5677Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5678to Flattened Device Tree). It allows the use of images with multiple
5679components (several kernels, ramdisks, etc.), with contents protected by
5680SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5681
5682
5683Old uImage format
5684-----------------
5685
5686Old image format is based on binary files which can be basically anything,
5687preceded by a special header; see the definitions in include/image.h for
5688details; basically, the header defines the following image properties:
5689
5690* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5691  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5692  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5693  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5694  INTEGRITY).
5695* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5696  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5697  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5698* Compression Type (uncompressed, gzip, bzip2)
5699* Load Address
5700* Entry Point
5701* Image Name
5702* Image Timestamp
5703
5704The header is marked by a special Magic Number, and both the header
5705and the data portions of the image are secured against corruption by
5706CRC32 checksums.
5707
5708
5709Linux Support:
5710==============
5711
5712Although U-Boot should support any OS or standalone application
5713easily, the main focus has always been on Linux during the design of
5714U-Boot.
5715
5716U-Boot includes many features that so far have been part of some
5717special "boot loader" code within the Linux kernel. Also, any
5718"initrd" images to be used are no longer part of one big Linux image;
5719instead, kernel and "initrd" are separate images. This implementation
5720serves several purposes:
5721
5722- the same features can be used for other OS or standalone
5723  applications (for instance: using compressed images to reduce the
5724  Flash memory footprint)
5725
5726- it becomes much easier to port new Linux kernel versions because
5727  lots of low-level, hardware dependent stuff are done by U-Boot
5728
5729- the same Linux kernel image can now be used with different "initrd"
5730  images; of course this also means that different kernel images can
5731  be run with the same "initrd". This makes testing easier (you don't
5732  have to build a new "zImage.initrd" Linux image when you just
5733  change a file in your "initrd"). Also, a field-upgrade of the
5734  software is easier now.
5735
5736
5737Linux HOWTO:
5738============
5739
5740Porting Linux to U-Boot based systems:
5741---------------------------------------
5742
5743U-Boot cannot save you from doing all the necessary modifications to
5744configure the Linux device drivers for use with your target hardware
5745(no, we don't intend to provide a full virtual machine interface to
5746Linux :-).
5747
5748But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5749
5750Just make sure your machine specific header file (for instance
5751include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5752Information structure as we define in include/asm-<arch>/u-boot.h,
5753and make sure that your definition of IMAP_ADDR uses the same value
5754as your U-Boot configuration in CONFIG_SYS_IMMR.
5755
5756Note that U-Boot now has a driver model, a unified model for drivers.
5757If you are adding a new driver, plumb it into driver model. If there
5758is no uclass available, you are encouraged to create one. See
5759doc/driver-model.
5760
5761
5762Configuring the Linux kernel:
5763-----------------------------
5764
5765No specific requirements for U-Boot. Make sure you have some root
5766device (initial ramdisk, NFS) for your target system.
5767
5768
5769Building a Linux Image:
5770-----------------------
5771
5772With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5773not used. If you use recent kernel source, a new build target
5774"uImage" will exist which automatically builds an image usable by
5775U-Boot. Most older kernels also have support for a "pImage" target,
5776which was introduced for our predecessor project PPCBoot and uses a
5777100% compatible format.
5778
5779Example:
5780
5781	make TQM850L_defconfig
5782	make oldconfig
5783	make dep
5784	make uImage
5785
5786The "uImage" build target uses a special tool (in 'tools/mkimage') to
5787encapsulate a compressed Linux kernel image with header	 information,
5788CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5789
5790* build a standard "vmlinux" kernel image (in ELF binary format):
5791
5792* convert the kernel into a raw binary image:
5793
5794	${CROSS_COMPILE}-objcopy -O binary \
5795				 -R .note -R .comment \
5796				 -S vmlinux linux.bin
5797
5798* compress the binary image:
5799
5800	gzip -9 linux.bin
5801
5802* package compressed binary image for U-Boot:
5803
5804	mkimage -A ppc -O linux -T kernel -C gzip \
5805		-a 0 -e 0 -n "Linux Kernel Image" \
5806		-d linux.bin.gz uImage
5807
5808
5809The "mkimage" tool can also be used to create ramdisk images for use
5810with U-Boot, either separated from the Linux kernel image, or
5811combined into one file. "mkimage" encapsulates the images with a 64
5812byte header containing information about target architecture,
5813operating system, image type, compression method, entry points, time
5814stamp, CRC32 checksums, etc.
5815
5816"mkimage" can be called in two ways: to verify existing images and
5817print the header information, or to build new images.
5818
5819In the first form (with "-l" option) mkimage lists the information
5820contained in the header of an existing U-Boot image; this includes
5821checksum verification:
5822
5823	tools/mkimage -l image
5824	  -l ==> list image header information
5825
5826The second form (with "-d" option) is used to build a U-Boot image
5827from a "data file" which is used as image payload:
5828
5829	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5830		      -n name -d data_file image
5831	  -A ==> set architecture to 'arch'
5832	  -O ==> set operating system to 'os'
5833	  -T ==> set image type to 'type'
5834	  -C ==> set compression type 'comp'
5835	  -a ==> set load address to 'addr' (hex)
5836	  -e ==> set entry point to 'ep' (hex)
5837	  -n ==> set image name to 'name'
5838	  -d ==> use image data from 'datafile'
5839
5840Right now, all Linux kernels for PowerPC systems use the same load
5841address (0x00000000), but the entry point address depends on the
5842kernel version:
5843
5844- 2.2.x kernels have the entry point at 0x0000000C,
5845- 2.3.x and later kernels have the entry point at 0x00000000.
5846
5847So a typical call to build a U-Boot image would read:
5848
5849	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5850	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5851	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5852	> examples/uImage.TQM850L
5853	Image Name:   2.4.4 kernel for TQM850L
5854	Created:      Wed Jul 19 02:34:59 2000
5855	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5856	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5857	Load Address: 0x00000000
5858	Entry Point:  0x00000000
5859
5860To verify the contents of the image (or check for corruption):
5861
5862	-> tools/mkimage -l examples/uImage.TQM850L
5863	Image Name:   2.4.4 kernel for TQM850L
5864	Created:      Wed Jul 19 02:34:59 2000
5865	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5866	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5867	Load Address: 0x00000000
5868	Entry Point:  0x00000000
5869
5870NOTE: for embedded systems where boot time is critical you can trade
5871speed for memory and install an UNCOMPRESSED image instead: this
5872needs more space in Flash, but boots much faster since it does not
5873need to be uncompressed:
5874
5875	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5876	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5877	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5878	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5879	> examples/uImage.TQM850L-uncompressed
5880	Image Name:   2.4.4 kernel for TQM850L
5881	Created:      Wed Jul 19 02:34:59 2000
5882	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5883	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5884	Load Address: 0x00000000
5885	Entry Point:  0x00000000
5886
5887
5888Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5889when your kernel is intended to use an initial ramdisk:
5890
5891	-> tools/mkimage -n 'Simple Ramdisk Image' \
5892	> -A ppc -O linux -T ramdisk -C gzip \
5893	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5894	Image Name:   Simple Ramdisk Image
5895	Created:      Wed Jan 12 14:01:50 2000
5896	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5897	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5898	Load Address: 0x00000000
5899	Entry Point:  0x00000000
5900
5901The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5902option performs the converse operation of the mkimage's second form (the "-d"
5903option). Given an image built by mkimage, the dumpimage extracts a "data file"
5904from the image:
5905
5906	tools/dumpimage -i image -T type -p position data_file
5907	  -i ==> extract from the 'image' a specific 'data_file'
5908	  -T ==> set image type to 'type'
5909	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5910
5911
5912Installing a Linux Image:
5913-------------------------
5914
5915To downloading a U-Boot image over the serial (console) interface,
5916you must convert the image to S-Record format:
5917
5918	objcopy -I binary -O srec examples/image examples/image.srec
5919
5920The 'objcopy' does not understand the information in the U-Boot
5921image header, so the resulting S-Record file will be relative to
5922address 0x00000000. To load it to a given address, you need to
5923specify the target address as 'offset' parameter with the 'loads'
5924command.
5925
5926Example: install the image to address 0x40100000 (which on the
5927TQM8xxL is in the first Flash bank):
5928
5929	=> erase 40100000 401FFFFF
5930
5931	.......... done
5932	Erased 8 sectors
5933
5934	=> loads 40100000
5935	## Ready for S-Record download ...
5936	~>examples/image.srec
5937	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5938	...
5939	15989 15990 15991 15992
5940	[file transfer complete]
5941	[connected]
5942	## Start Addr = 0x00000000
5943
5944
5945You can check the success of the download using the 'iminfo' command;
5946this includes a checksum verification so you can be sure no data
5947corruption happened:
5948
5949	=> imi 40100000
5950
5951	## Checking Image at 40100000 ...
5952	   Image Name:	 2.2.13 for initrd on TQM850L
5953	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5954	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5955	   Load Address: 00000000
5956	   Entry Point:	 0000000c
5957	   Verifying Checksum ... OK
5958
5959
5960Boot Linux:
5961-----------
5962
5963The "bootm" command is used to boot an application that is stored in
5964memory (RAM or Flash). In case of a Linux kernel image, the contents
5965of the "bootargs" environment variable is passed to the kernel as
5966parameters. You can check and modify this variable using the
5967"printenv" and "setenv" commands:
5968
5969
5970	=> printenv bootargs
5971	bootargs=root=/dev/ram
5972
5973	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5974
5975	=> printenv bootargs
5976	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5977
5978	=> bootm 40020000
5979	## Booting Linux kernel at 40020000 ...
5980	   Image Name:	 2.2.13 for NFS on TQM850L
5981	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5982	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5983	   Load Address: 00000000
5984	   Entry Point:	 0000000c
5985	   Verifying Checksum ... OK
5986	   Uncompressing Kernel Image ... OK
5987	Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000
5988	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5989	time_init: decrementer frequency = 187500000/60
5990	Calibrating delay loop... 49.77 BogoMIPS
5991	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5992	...
5993
5994If you want to boot a Linux kernel with initial RAM disk, you pass
5995the memory addresses of both the kernel and the initrd image (PPBCOOT
5996format!) to the "bootm" command:
5997
5998	=> imi 40100000 40200000
5999
6000	## Checking Image at 40100000 ...
6001	   Image Name:	 2.2.13 for initrd on TQM850L
6002	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
6003	   Data Size:	 335725 Bytes = 327 kB = 0 MB
6004	   Load Address: 00000000
6005	   Entry Point:	 0000000c
6006	   Verifying Checksum ... OK
6007
6008	## Checking Image at 40200000 ...
6009	   Image Name:	 Simple Ramdisk Image
6010	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
6011	   Data Size:	 566530 Bytes = 553 kB = 0 MB
6012	   Load Address: 00000000
6013	   Entry Point:	 00000000
6014	   Verifying Checksum ... OK
6015
6016	=> bootm 40100000 40200000
6017	## Booting Linux kernel at 40100000 ...
6018	   Image Name:	 2.2.13 for initrd on TQM850L
6019	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
6020	   Data Size:	 335725 Bytes = 327 kB = 0 MB
6021	   Load Address: 00000000
6022	   Entry Point:	 0000000c
6023	   Verifying Checksum ... OK
6024	   Uncompressing Kernel Image ... OK
6025	## Loading RAMDisk Image at 40200000 ...
6026	   Image Name:	 Simple Ramdisk Image
6027	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
6028	   Data Size:	 566530 Bytes = 553 kB = 0 MB
6029	   Load Address: 00000000
6030	   Entry Point:	 00000000
6031	   Verifying Checksum ... OK
6032	   Loading Ramdisk ... OK
6033	Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000
6034	Boot arguments: root=/dev/ram
6035	time_init: decrementer frequency = 187500000/60
6036	Calibrating delay loop... 49.77 BogoMIPS
6037	...
6038	RAMDISK: Compressed image found at block 0
6039	VFS: Mounted root (ext2 filesystem).
6040
6041	bash#
6042
6043Boot Linux and pass a flat device tree:
6044-----------
6045
6046First, U-Boot must be compiled with the appropriate defines. See the section
6047titled "Linux Kernel Interface" above for a more in depth explanation. The
6048following is an example of how to start a kernel and pass an updated
6049flat device tree:
6050
6051=> print oftaddr
6052oftaddr=0x300000
6053=> print oft
6054oft=oftrees/mpc8540ads.dtb
6055=> tftp $oftaddr $oft
6056Speed: 1000, full duplex
6057Using TSEC0 device
6058TFTP from server 192.168.1.1; our IP address is 192.168.1.101
6059Filename 'oftrees/mpc8540ads.dtb'.
6060Load address: 0x300000
6061Loading: #
6062done
6063Bytes transferred = 4106 (100a hex)
6064=> tftp $loadaddr $bootfile
6065Speed: 1000, full duplex
6066Using TSEC0 device
6067TFTP from server 192.168.1.1; our IP address is 192.168.1.2
6068Filename 'uImage'.
6069Load address: 0x200000
6070Loading:############
6071done
6072Bytes transferred = 1029407 (fb51f hex)
6073=> print loadaddr
6074loadaddr=200000
6075=> print oftaddr
6076oftaddr=0x300000
6077=> bootm $loadaddr - $oftaddr
6078## Booting image at 00200000 ...
6079   Image Name:	 Linux-2.6.17-dirty
6080   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
6081   Data Size:	 1029343 Bytes = 1005.2 kB
6082   Load Address: 00000000
6083   Entry Point:	 00000000
6084   Verifying Checksum ... OK
6085   Uncompressing Kernel Image ... OK
6086Booting using flat device tree at 0x300000
6087Using MPC85xx ADS machine description
6088Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
6089[snip]
6090
6091
6092More About U-Boot Image Types:
6093------------------------------
6094
6095U-Boot supports the following image types:
6096
6097   "Standalone Programs" are directly runnable in the environment
6098	provided by U-Boot; it is expected that (if they behave
6099	well) you can continue to work in U-Boot after return from
6100	the Standalone Program.
6101   "OS Kernel Images" are usually images of some Embedded OS which
6102	will take over control completely. Usually these programs
6103	will install their own set of exception handlers, device
6104	drivers, set up the MMU, etc. - this means, that you cannot
6105	expect to re-enter U-Boot except by resetting the CPU.
6106   "RAMDisk Images" are more or less just data blocks, and their
6107	parameters (address, size) are passed to an OS kernel that is
6108	being started.
6109   "Multi-File Images" contain several images, typically an OS
6110	(Linux) kernel image and one or more data images like
6111	RAMDisks. This construct is useful for instance when you want
6112	to boot over the network using BOOTP etc., where the boot
6113	server provides just a single image file, but you want to get
6114	for instance an OS kernel and a RAMDisk image.
6115
6116	"Multi-File Images" start with a list of image sizes, each
6117	image size (in bytes) specified by an "uint32_t" in network
6118	byte order. This list is terminated by an "(uint32_t)0".
6119	Immediately after the terminating 0 follow the images, one by
6120	one, all aligned on "uint32_t" boundaries (size rounded up to
6121	a multiple of 4 bytes).
6122
6123   "Firmware Images" are binary images containing firmware (like
6124	U-Boot or FPGA images) which usually will be programmed to
6125	flash memory.
6126
6127   "Script files" are command sequences that will be executed by
6128	U-Boot's command interpreter; this feature is especially
6129	useful when you configure U-Boot to use a real shell (hush)
6130	as command interpreter.
6131
6132Booting the Linux zImage:
6133-------------------------
6134
6135On some platforms, it's possible to boot Linux zImage. This is done
6136using the "bootz" command. The syntax of "bootz" command is the same
6137as the syntax of "bootm" command.
6138
6139Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
6140kernel with raw initrd images. The syntax is slightly different, the
6141address of the initrd must be augmented by it's size, in the following
6142format: "<initrd addres>:<initrd size>".
6143
6144
6145Standalone HOWTO:
6146=================
6147
6148One of the features of U-Boot is that you can dynamically load and
6149run "standalone" applications, which can use some resources of
6150U-Boot like console I/O functions or interrupt services.
6151
6152Two simple examples are included with the sources:
6153
6154"Hello World" Demo:
6155-------------------
6156
6157'examples/hello_world.c' contains a small "Hello World" Demo
6158application; it is automatically compiled when you build U-Boot.
6159It's configured to run at address 0x00040004, so you can play with it
6160like that:
6161
6162	=> loads
6163	## Ready for S-Record download ...
6164	~>examples/hello_world.srec
6165	1 2 3 4 5 6 7 8 9 10 11 ...
6166	[file transfer complete]
6167	[connected]
6168	## Start Addr = 0x00040004
6169
6170	=> go 40004 Hello World! This is a test.
6171	## Starting application at 0x00040004 ...
6172	Hello World
6173	argc = 7
6174	argv[0] = "40004"
6175	argv[1] = "Hello"
6176	argv[2] = "World!"
6177	argv[3] = "This"
6178	argv[4] = "is"
6179	argv[5] = "a"
6180	argv[6] = "test."
6181	argv[7] = "<NULL>"
6182	Hit any key to exit ...
6183
6184	## Application terminated, rc = 0x0
6185
6186Another example, which demonstrates how to register a CPM interrupt
6187handler with the U-Boot code, can be found in 'examples/timer.c'.
6188Here, a CPM timer is set up to generate an interrupt every second.
6189The interrupt service routine is trivial, just printing a '.'
6190character, but this is just a demo program. The application can be
6191controlled by the following keys:
6192
6193	? - print current values og the CPM Timer registers
6194	b - enable interrupts and start timer
6195	e - stop timer and disable interrupts
6196	q - quit application
6197
6198	=> loads
6199	## Ready for S-Record download ...
6200	~>examples/timer.srec
6201	1 2 3 4 5 6 7 8 9 10 11 ...
6202	[file transfer complete]
6203	[connected]
6204	## Start Addr = 0x00040004
6205
6206	=> go 40004
6207	## Starting application at 0x00040004 ...
6208	TIMERS=0xfff00980
6209	Using timer 1
6210	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
6211
6212Hit 'b':
6213	[q, b, e, ?] Set interval 1000000 us
6214	Enabling timer
6215Hit '?':
6216	[q, b, e, ?] ........
6217	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
6218Hit '?':
6219	[q, b, e, ?] .
6220	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
6221Hit '?':
6222	[q, b, e, ?] .
6223	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
6224Hit '?':
6225	[q, b, e, ?] .
6226	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
6227Hit 'e':
6228	[q, b, e, ?] ...Stopping timer
6229Hit 'q':
6230	[q, b, e, ?] ## Application terminated, rc = 0x0
6231
6232
6233Minicom warning:
6234================
6235
6236Over time, many people have reported problems when trying to use the
6237"minicom" terminal emulation program for serial download. I (wd)
6238consider minicom to be broken, and recommend not to use it. Under
6239Unix, I recommend to use C-Kermit for general purpose use (and
6240especially for kermit binary protocol download ("loadb" command), and
6241use "cu" for S-Record download ("loads" command).  See
6242http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
6243for help with kermit.
6244
6245
6246Nevertheless, if you absolutely want to use it try adding this
6247configuration to your "File transfer protocols" section:
6248
6249	   Name	   Program			Name U/D FullScr IO-Red. Multi
6250	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
6251	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
6252
6253
6254NetBSD Notes:
6255=============
6256
6257Starting at version 0.9.2, U-Boot supports NetBSD both as host
6258(build U-Boot) and target system (boots NetBSD/mpc8xx).
6259
6260Building requires a cross environment; it is known to work on
6261NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
6262need gmake since the Makefiles are not compatible with BSD make).
6263Note that the cross-powerpc package does not install include files;
6264attempting to build U-Boot will fail because <machine/ansi.h> is
6265missing.  This file has to be installed and patched manually:
6266
6267	# cd /usr/pkg/cross/powerpc-netbsd/include
6268	# mkdir powerpc
6269	# ln -s powerpc machine
6270	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
6271	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
6272
6273Native builds *don't* work due to incompatibilities between native
6274and U-Boot include files.
6275
6276Booting assumes that (the first part of) the image booted is a
6277stage-2 loader which in turn loads and then invokes the kernel
6278proper. Loader sources will eventually appear in the NetBSD source
6279tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
6280meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
6281
6282
6283Implementation Internals:
6284=========================
6285
6286The following is not intended to be a complete description of every
6287implementation detail. However, it should help to understand the
6288inner workings of U-Boot and make it easier to port it to custom
6289hardware.
6290
6291
6292Initial Stack, Global Data:
6293---------------------------
6294
6295The implementation of U-Boot is complicated by the fact that U-Boot
6296starts running out of ROM (flash memory), usually without access to
6297system RAM (because the memory controller is not initialized yet).
6298This means that we don't have writable Data or BSS segments, and BSS
6299is not initialized as zero. To be able to get a C environment working
6300at all, we have to allocate at least a minimal stack. Implementation
6301options for this are defined and restricted by the CPU used: Some CPU
6302models provide on-chip memory (like the IMMR area on MPC8xx and
6303MPC826x processors), on others (parts of) the data cache can be
6304locked as (mis-) used as memory, etc.
6305
6306	Chris Hallinan posted a good summary of these issues to the
6307	U-Boot mailing list:
6308
6309	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
6310	From: "Chris Hallinan" <clh@net1plus.com>
6311	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
6312	...
6313
6314	Correct me if I'm wrong, folks, but the way I understand it
6315	is this: Using DCACHE as initial RAM for Stack, etc, does not
6316	require any physical RAM backing up the cache. The cleverness
6317	is that the cache is being used as a temporary supply of
6318	necessary storage before the SDRAM controller is setup. It's
6319	beyond the scope of this list to explain the details, but you
6320	can see how this works by studying the cache architecture and
6321	operation in the architecture and processor-specific manuals.
6322
6323	OCM is On Chip Memory, which I believe the 405GP has 4K. It
6324	is another option for the system designer to use as an
6325	initial stack/RAM area prior to SDRAM being available. Either
6326	option should work for you. Using CS 4 should be fine if your
6327	board designers haven't used it for something that would
6328	cause you grief during the initial boot! It is frequently not
6329	used.
6330
6331	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
6332	with your processor/board/system design. The default value
6333	you will find in any recent u-boot distribution in
6334	walnut.h should work for you. I'd set it to a value larger
6335	than your SDRAM module. If you have a 64MB SDRAM module, set
6336	it above 400_0000. Just make sure your board has no resources
6337	that are supposed to respond to that address! That code in
6338	start.S has been around a while and should work as is when
6339	you get the config right.
6340
6341	-Chris Hallinan
6342	DS4.COM, Inc.
6343
6344It is essential to remember this, since it has some impact on the C
6345code for the initialization procedures:
6346
6347* Initialized global data (data segment) is read-only. Do not attempt
6348  to write it.
6349
6350* Do not use any uninitialized global data (or implicitly initialized
6351  as zero data - BSS segment) at all - this is undefined, initiali-
6352  zation is performed later (when relocating to RAM).
6353
6354* Stack space is very limited. Avoid big data buffers or things like
6355  that.
6356
6357Having only the stack as writable memory limits means we cannot use
6358normal global data to share information between the code. But it
6359turned out that the implementation of U-Boot can be greatly
6360simplified by making a global data structure (gd_t) available to all
6361functions. We could pass a pointer to this data as argument to _all_
6362functions, but this would bloat the code. Instead we use a feature of
6363the GCC compiler (Global Register Variables) to share the data: we
6364place a pointer (gd) to the global data into a register which we
6365reserve for this purpose.
6366
6367When choosing a register for such a purpose we are restricted by the
6368relevant  (E)ABI  specifications for the current architecture, and by
6369GCC's implementation.
6370
6371For PowerPC, the following registers have specific use:
6372	R1:	stack pointer
6373	R2:	reserved for system use
6374	R3-R4:	parameter passing and return values
6375	R5-R10: parameter passing
6376	R13:	small data area pointer
6377	R30:	GOT pointer
6378	R31:	frame pointer
6379
6380	(U-Boot also uses R12 as internal GOT pointer. r12
6381	is a volatile register so r12 needs to be reset when
6382	going back and forth between asm and C)
6383
6384    ==> U-Boot will use R2 to hold a pointer to the global data
6385
6386    Note: on PPC, we could use a static initializer (since the
6387    address of the global data structure is known at compile time),
6388    but it turned out that reserving a register results in somewhat
6389    smaller code - although the code savings are not that big (on
6390    average for all boards 752 bytes for the whole U-Boot image,
6391    624 text + 127 data).
6392
6393On Blackfin, the normal C ABI (except for P3) is followed as documented here:
6394	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
6395
6396    ==> U-Boot will use P3 to hold a pointer to the global data
6397
6398On ARM, the following registers are used:
6399
6400	R0:	function argument word/integer result
6401	R1-R3:	function argument word
6402	R9:	platform specific
6403	R10:	stack limit (used only if stack checking is enabled)
6404	R11:	argument (frame) pointer
6405	R12:	temporary workspace
6406	R13:	stack pointer
6407	R14:	link register
6408	R15:	program counter
6409
6410    ==> U-Boot will use R9 to hold a pointer to the global data
6411
6412    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
6413
6414On Nios II, the ABI is documented here:
6415	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
6416
6417    ==> U-Boot will use gp to hold a pointer to the global data
6418
6419    Note: on Nios II, we give "-G0" option to gcc and don't use gp
6420    to access small data sections, so gp is free.
6421
6422On NDS32, the following registers are used:
6423
6424	R0-R1:	argument/return
6425	R2-R5:	argument
6426	R15:	temporary register for assembler
6427	R16:	trampoline register
6428	R28:	frame pointer (FP)
6429	R29:	global pointer (GP)
6430	R30:	link register (LP)
6431	R31:	stack pointer (SP)
6432	PC:	program counter (PC)
6433
6434    ==> U-Boot will use R10 to hold a pointer to the global data
6435
6436NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
6437or current versions of GCC may "optimize" the code too much.
6438
6439Memory Management:
6440------------------
6441
6442U-Boot runs in system state and uses physical addresses, i.e. the
6443MMU is not used either for address mapping nor for memory protection.
6444
6445The available memory is mapped to fixed addresses using the memory
6446controller. In this process, a contiguous block is formed for each
6447memory type (Flash, SDRAM, SRAM), even when it consists of several
6448physical memory banks.
6449
6450U-Boot is installed in the first 128 kB of the first Flash bank (on
6451TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
6452booting and sizing and initializing DRAM, the code relocates itself
6453to the upper end of DRAM. Immediately below the U-Boot code some
6454memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
6455configuration setting]. Below that, a structure with global Board
6456Info data is placed, followed by the stack (growing downward).
6457
6458Additionally, some exception handler code is copied to the low 8 kB
6459of DRAM (0x00000000 ... 0x00001FFF).
6460
6461So a typical memory configuration with 16 MB of DRAM could look like
6462this:
6463
6464	0x0000 0000	Exception Vector code
6465	      :
6466	0x0000 1FFF
6467	0x0000 2000	Free for Application Use
6468	      :
6469	      :
6470
6471	      :
6472	      :
6473	0x00FB FF20	Monitor Stack (Growing downward)
6474	0x00FB FFAC	Board Info Data and permanent copy of global data
6475	0x00FC 0000	Malloc Arena
6476	      :
6477	0x00FD FFFF
6478	0x00FE 0000	RAM Copy of Monitor Code
6479	...		eventually: LCD or video framebuffer
6480	...		eventually: pRAM (Protected RAM - unchanged by reset)
6481	0x00FF FFFF	[End of RAM]
6482
6483
6484System Initialization:
6485----------------------
6486
6487In the reset configuration, U-Boot starts at the reset entry point
6488(on most PowerPC systems at address 0x00000100). Because of the reset
6489configuration for CS0# this is a mirror of the on board Flash memory.
6490To be able to re-map memory U-Boot then jumps to its link address.
6491To be able to implement the initialization code in C, a (small!)
6492initial stack is set up in the internal Dual Ported RAM (in case CPUs
6493which provide such a feature like MPC8xx or MPC8260), or in a locked
6494part of the data cache. After that, U-Boot initializes the CPU core,
6495the caches and the SIU.
6496
6497Next, all (potentially) available memory banks are mapped using a
6498preliminary mapping. For example, we put them on 512 MB boundaries
6499(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
6500on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
6501programmed for SDRAM access. Using the temporary configuration, a
6502simple memory test is run that determines the size of the SDRAM
6503banks.
6504
6505When there is more than one SDRAM bank, and the banks are of
6506different size, the largest is mapped first. For equal size, the first
6507bank (CS2#) is mapped first. The first mapping is always for address
65080x00000000, with any additional banks following immediately to create
6509contiguous memory starting from 0.
6510
6511Then, the monitor installs itself at the upper end of the SDRAM area
6512and allocates memory for use by malloc() and for the global Board
6513Info data; also, the exception vector code is copied to the low RAM
6514pages, and the final stack is set up.
6515
6516Only after this relocation will you have a "normal" C environment;
6517until that you are restricted in several ways, mostly because you are
6518running from ROM, and because the code will have to be relocated to a
6519new address in RAM.
6520
6521
6522U-Boot Porting Guide:
6523----------------------
6524
6525[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
6526list, October 2002]
6527
6528
6529int main(int argc, char *argv[])
6530{
6531	sighandler_t no_more_time;
6532
6533	signal(SIGALRM, no_more_time);
6534	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6535
6536	if (available_money > available_manpower) {
6537		Pay consultant to port U-Boot;
6538		return 0;
6539	}
6540
6541	Download latest U-Boot source;
6542
6543	Subscribe to u-boot mailing list;
6544
6545	if (clueless)
6546		email("Hi, I am new to U-Boot, how do I get started?");
6547
6548	while (learning) {
6549		Read the README file in the top level directory;
6550		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6551		Read applicable doc/*.README;
6552		Read the source, Luke;
6553		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6554	}
6555
6556	if (available_money > toLocalCurrency ($2500))
6557		Buy a BDI3000;
6558	else
6559		Add a lot of aggravation and time;
6560
6561	if (a similar board exists) {	/* hopefully... */
6562		cp -a board/<similar> board/<myboard>
6563		cp include/configs/<similar>.h include/configs/<myboard>.h
6564	} else {
6565		Create your own board support subdirectory;
6566		Create your own board include/configs/<myboard>.h file;
6567	}
6568	Edit new board/<myboard> files
6569	Edit new include/configs/<myboard>.h
6570
6571	while (!accepted) {
6572		while (!running) {
6573			do {
6574				Add / modify source code;
6575			} until (compiles);
6576			Debug;
6577			if (clueless)
6578				email("Hi, I am having problems...");
6579		}
6580		Send patch file to the U-Boot email list;
6581		if (reasonable critiques)
6582			Incorporate improvements from email list code review;
6583		else
6584			Defend code as written;
6585	}
6586
6587	return 0;
6588}
6589
6590void no_more_time (int sig)
6591{
6592      hire_a_guru();
6593}
6594
6595
6596Coding Standards:
6597-----------------
6598
6599All contributions to U-Boot should conform to the Linux kernel
6600coding style; see the file "Documentation/CodingStyle" and the script
6601"scripts/Lindent" in your Linux kernel source directory.
6602
6603Source files originating from a different project (for example the
6604MTD subsystem) are generally exempt from these guidelines and are not
6605reformatted to ease subsequent migration to newer versions of those
6606sources.
6607
6608Please note that U-Boot is implemented in C (and to some small parts in
6609Assembler); no C++ is used, so please do not use C++ style comments (//)
6610in your code.
6611
6612Please also stick to the following formatting rules:
6613- remove any trailing white space
6614- use TAB characters for indentation and vertical alignment, not spaces
6615- make sure NOT to use DOS '\r\n' line feeds
6616- do not add more than 2 consecutive empty lines to source files
6617- do not add trailing empty lines to source files
6618
6619Submissions which do not conform to the standards may be returned
6620with a request to reformat the changes.
6621
6622
6623Submitting Patches:
6624-------------------
6625
6626Since the number of patches for U-Boot is growing, we need to
6627establish some rules. Submissions which do not conform to these rules
6628may be rejected, even when they contain important and valuable stuff.
6629
6630Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6631
6632Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6633see http://lists.denx.de/mailman/listinfo/u-boot
6634
6635When you send a patch, please include the following information with
6636it:
6637
6638* For bug fixes: a description of the bug and how your patch fixes
6639  this bug. Please try to include a way of demonstrating that the
6640  patch actually fixes something.
6641
6642* For new features: a description of the feature and your
6643  implementation.
6644
6645* A CHANGELOG entry as plaintext (separate from the patch)
6646
6647* For major contributions, your entry to the CREDITS file
6648
6649* When you add support for a new board, don't forget to add a
6650  maintainer e-mail address to the boards.cfg file, too.
6651
6652* If your patch adds new configuration options, don't forget to
6653  document these in the README file.
6654
6655* The patch itself. If you are using git (which is *strongly*
6656  recommended) you can easily generate the patch using the
6657  "git format-patch". If you then use "git send-email" to send it to
6658  the U-Boot mailing list, you will avoid most of the common problems
6659  with some other mail clients.
6660
6661  If you cannot use git, use "diff -purN OLD NEW". If your version of
6662  diff does not support these options, then get the latest version of
6663  GNU diff.
6664
6665  The current directory when running this command shall be the parent
6666  directory of the U-Boot source tree (i. e. please make sure that
6667  your patch includes sufficient directory information for the
6668  affected files).
6669
6670  We prefer patches as plain text. MIME attachments are discouraged,
6671  and compressed attachments must not be used.
6672
6673* If one logical set of modifications affects or creates several
6674  files, all these changes shall be submitted in a SINGLE patch file.
6675
6676* Changesets that contain different, unrelated modifications shall be
6677  submitted as SEPARATE patches, one patch per changeset.
6678
6679
6680Notes:
6681
6682* Before sending the patch, run the MAKEALL script on your patched
6683  source tree and make sure that no errors or warnings are reported
6684  for any of the boards.
6685
6686* Keep your modifications to the necessary minimum: A patch
6687  containing several unrelated changes or arbitrary reformats will be
6688  returned with a request to re-formatting / split it.
6689
6690* If you modify existing code, make sure that your new code does not
6691  add to the memory footprint of the code ;-) Small is beautiful!
6692  When adding new features, these should compile conditionally only
6693  (using #ifdef), and the resulting code with the new feature
6694  disabled must not need more memory than the old code without your
6695  modification.
6696
6697* Remember that there is a size limit of 100 kB per message on the
6698  u-boot mailing list. Bigger patches will be moderated. If they are
6699  reasonable and not too big, they will be acknowledged. But patches
6700  bigger than the size limit should be avoided.
6701