xref: /openbmc/u-boot/README (revision 55c7a765)
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		CONFIG_ARM_ERRATA_801819
709
710- Tegra SoC options:
711		CONFIG_TEGRA_SUPPORT_NON_SECURE
712
713		Support executing U-Boot in non-secure (NS) mode. Certain
714		impossible actions will be skipped if the CPU is in NS mode,
715		such as ARM architectural timer initialization.
716
717- Linux Kernel Interface:
718		CONFIG_CLOCKS_IN_MHZ
719
720		U-Boot stores all clock information in Hz
721		internally. For binary compatibility with older Linux
722		kernels (which expect the clocks passed in the
723		bd_info data to be in MHz) the environment variable
724		"clocks_in_mhz" can be defined so that U-Boot
725		converts clock data to MHZ before passing it to the
726		Linux kernel.
727		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
728		"clocks_in_mhz=1" is automatically included in the
729		default environment.
730
731		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
732
733		When transferring memsize parameter to Linux, some versions
734		expect it to be in bytes, others in MB.
735		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
736
737		CONFIG_OF_LIBFDT
738
739		New kernel versions are expecting firmware settings to be
740		passed using flattened device trees (based on open firmware
741		concepts).
742
743		CONFIG_OF_LIBFDT
744		 * New libfdt-based support
745		 * Adds the "fdt" command
746		 * The bootm command automatically updates the fdt
747
748		OF_CPU - The proper name of the cpus node (only required for
749			MPC512X and MPC5xxx based boards).
750		OF_SOC - The proper name of the soc node (only required for
751			MPC512X and MPC5xxx based boards).
752		OF_TBCLK - The timebase frequency.
753		OF_STDOUT_PATH - The path to the console device
754
755		boards with QUICC Engines require OF_QE to set UCC MAC
756		addresses
757
758		CONFIG_OF_BOARD_SETUP
759
760		Board code has addition modification that it wants to make
761		to the flat device tree before handing it off to the kernel
762
763		CONFIG_OF_SYSTEM_SETUP
764
765		Other code has addition modification that it wants to make
766		to the flat device tree before handing it off to the kernel.
767		This causes ft_system_setup() to be called before booting
768		the kernel.
769
770		CONFIG_OF_BOOT_CPU
771
772		This define fills in the correct boot CPU in the boot
773		param header, the default value is zero if undefined.
774
775		CONFIG_OF_IDE_FIXUP
776
777		U-Boot can detect if an IDE device is present or not.
778		If not, and this new config option is activated, U-Boot
779		removes the ATA node from the DTS before booting Linux,
780		so the Linux IDE driver does not probe the device and
781		crash. This is needed for buggy hardware (uc101) where
782		no pull down resistor is connected to the signal IDE5V_DD7.
783
784		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
785
786		This setting is mandatory for all boards that have only one
787		machine type and must be used to specify the machine type
788		number as it appears in the ARM machine registry
789		(see http://www.arm.linux.org.uk/developer/machines/).
790		Only boards that have multiple machine types supported
791		in a single configuration file and the machine type is
792		runtime discoverable, do not have to use this setting.
793
794- vxWorks boot parameters:
795
796		bootvx constructs a valid bootline using the following
797		environments variables: bootfile, ipaddr, serverip, hostname.
798		It loads the vxWorks image pointed bootfile.
799
800		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
801		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
802		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
803		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
804
805		CONFIG_SYS_VXWORKS_ADD_PARAMS
806
807		Add it at the end of the bootline. E.g "u=username pw=secret"
808
809		Note: If a "bootargs" environment is defined, it will overwride
810		the defaults discussed just above.
811
812- Cache Configuration:
813		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
814		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
815		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
816
817- Cache Configuration for ARM:
818		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
819				      controller
820		CONFIG_SYS_PL310_BASE - Physical base address of PL310
821					controller register space
822
823- Serial Ports:
824		CONFIG_PL010_SERIAL
825
826		Define this if you want support for Amba PrimeCell PL010 UARTs.
827
828		CONFIG_PL011_SERIAL
829
830		Define this if you want support for Amba PrimeCell PL011 UARTs.
831
832		CONFIG_PL011_CLOCK
833
834		If you have Amba PrimeCell PL011 UARTs, set this variable to
835		the clock speed of the UARTs.
836
837		CONFIG_PL01x_PORTS
838
839		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
840		define this to a list of base addresses for each (supported)
841		port. See e.g. include/configs/versatile.h
842
843		CONFIG_PL011_SERIAL_RLCR
844
845		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
846		have separate receive and transmit line control registers.  Set
847		this variable to initialize the extra register.
848
849		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
850
851		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
852		boot loader that has already initialized the UART.  Define this
853		variable to flush the UART at init time.
854
855		CONFIG_SERIAL_HW_FLOW_CONTROL
856
857		Define this variable to enable hw flow control in serial driver.
858		Current user of this option is drivers/serial/nsl16550.c driver
859
860- Console Interface:
861		Depending on board, define exactly one serial port
862		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
863		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
864		console by defining CONFIG_8xx_CONS_NONE
865
866		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
867		port routines must be defined elsewhere
868		(i.e. serial_init(), serial_getc(), ...)
869
870		CONFIG_CFB_CONSOLE
871		Enables console device for a color framebuffer. Needs following
872		defines (cf. smiLynxEM, i8042)
873			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
874						(default big endian)
875			VIDEO_HW_RECTFILL	graphic chip supports
876						rectangle fill
877						(cf. smiLynxEM)
878			VIDEO_HW_BITBLT		graphic chip supports
879						bit-blit (cf. smiLynxEM)
880			VIDEO_VISIBLE_COLS	visible pixel columns
881						(cols=pitch)
882			VIDEO_VISIBLE_ROWS	visible pixel rows
883			VIDEO_PIXEL_SIZE	bytes per pixel
884			VIDEO_DATA_FORMAT	graphic data format
885						(0-5, cf. cfb_console.c)
886			VIDEO_FB_ADRS		framebuffer address
887			VIDEO_KBD_INIT_FCT	keyboard int fct
888						(i.e. i8042_kbd_init())
889			VIDEO_TSTC_FCT		test char fct
890						(i.e. i8042_tstc)
891			VIDEO_GETC_FCT		get char fct
892						(i.e. i8042_getc)
893			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
894						(requires blink timer
895						cf. i8042.c)
896			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
897			CONFIG_CONSOLE_TIME	display time/date info in
898						upper right corner
899						(requires CONFIG_CMD_DATE)
900			CONFIG_VIDEO_LOGO	display Linux logo in
901						upper left corner
902			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
903						linux_logo.h for logo.
904						Requires CONFIG_VIDEO_LOGO
905			CONFIG_CONSOLE_EXTRA_INFO
906						additional board info beside
907						the logo
908
909		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
910		a limited number of ANSI escape sequences (cursor control,
911		erase functions and limited graphics rendition control).
912
913		When CONFIG_CFB_CONSOLE is defined, video console is
914		default i/o. Serial console can be forced with
915		environment 'console=serial'.
916
917		When CONFIG_SILENT_CONSOLE is defined, all console
918		messages (by U-Boot and Linux!) can be silenced with
919		the "silent" environment variable. See
920		doc/README.silent for more information.
921
922		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
923			is 0x00.
924		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
925			is 0xa0.
926
927- Console Baudrate:
928		CONFIG_BAUDRATE - in bps
929		Select one of the baudrates listed in
930		CONFIG_SYS_BAUDRATE_TABLE, see below.
931		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
932
933- Console Rx buffer length
934		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
935		the maximum receive buffer length for the SMC.
936		This option is actual only for 82xx and 8xx possible.
937		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
938		must be defined, to setup the maximum idle timeout for
939		the SMC.
940
941- Pre-Console Buffer:
942		Prior to the console being initialised (i.e. serial UART
943		initialised etc) all console output is silently discarded.
944		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
945		buffer any console messages prior to the console being
946		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
947		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
948		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
949		bytes are output before the console is initialised, the
950		earlier bytes are discarded.
951
952		Note that when printing the buffer a copy is made on the
953		stack so CONFIG_PRE_CON_BUF_SZ must fit on the stack.
954
955		'Sane' compilers will generate smaller code if
956		CONFIG_PRE_CON_BUF_SZ is a power of 2
957
958- Safe printf() functions
959		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
960		the printf() functions. These are defined in
961		include/vsprintf.h and include snprintf(), vsnprintf() and
962		so on. Code size increase is approximately 300-500 bytes.
963		If this option is not given then these functions will
964		silently discard their buffer size argument - this means
965		you are not getting any overflow checking in this case.
966
967- Boot Delay:	CONFIG_BOOTDELAY - in seconds
968		Delay before automatically booting the default image;
969		set to -1 to disable autoboot.
970		set to -2 to autoboot with no delay and not check for abort
971		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
972
973		See doc/README.autoboot for these options that
974		work with CONFIG_BOOTDELAY. None are required.
975		CONFIG_BOOT_RETRY_TIME
976		CONFIG_BOOT_RETRY_MIN
977		CONFIG_AUTOBOOT_KEYED
978		CONFIG_AUTOBOOT_PROMPT
979		CONFIG_AUTOBOOT_DELAY_STR
980		CONFIG_AUTOBOOT_STOP_STR
981		CONFIG_ZERO_BOOTDELAY_CHECK
982		CONFIG_RESET_TO_RETRY
983
984- Autoboot Command:
985		CONFIG_BOOTCOMMAND
986		Only needed when CONFIG_BOOTDELAY is enabled;
987		define a command string that is automatically executed
988		when no character is read on the console interface
989		within "Boot Delay" after reset.
990
991		CONFIG_BOOTARGS
992		This can be used to pass arguments to the bootm
993		command. The value of CONFIG_BOOTARGS goes into the
994		environment value "bootargs".
995
996		CONFIG_RAMBOOT and CONFIG_NFSBOOT
997		The value of these goes into the environment as
998		"ramboot" and "nfsboot" respectively, and can be used
999		as a convenience, when switching between booting from
1000		RAM and NFS.
1001
1002- Bootcount:
1003		CONFIG_BOOTCOUNT_LIMIT
1004		Implements a mechanism for detecting a repeating reboot
1005		cycle, see:
1006		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
1007
1008		CONFIG_BOOTCOUNT_ENV
1009		If no softreset save registers are found on the hardware
1010		"bootcount" is stored in the environment. To prevent a
1011		saveenv on all reboots, the environment variable
1012		"upgrade_available" is used. If "upgrade_available" is
1013		0, "bootcount" is always 0, if "upgrade_available" is
1014		1 "bootcount" is incremented in the environment.
1015		So the Userspace Applikation must set the "upgrade_available"
1016		and "bootcount" variable to 0, if a boot was successfully.
1017
1018- Pre-Boot Commands:
1019		CONFIG_PREBOOT
1020
1021		When this option is #defined, the existence of the
1022		environment variable "preboot" will be checked
1023		immediately before starting the CONFIG_BOOTDELAY
1024		countdown and/or running the auto-boot command resp.
1025		entering interactive mode.
1026
1027		This feature is especially useful when "preboot" is
1028		automatically generated or modified. For an example
1029		see the LWMON board specific code: here "preboot" is
1030		modified when the user holds down a certain
1031		combination of keys on the (special) keyboard when
1032		booting the systems
1033
1034- Serial Download Echo Mode:
1035		CONFIG_LOADS_ECHO
1036		If defined to 1, all characters received during a
1037		serial download (using the "loads" command) are
1038		echoed back. This might be needed by some terminal
1039		emulations (like "cu"), but may as well just take
1040		time on others. This setting #define's the initial
1041		value of the "loads_echo" environment variable.
1042
1043- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
1044		CONFIG_KGDB_BAUDRATE
1045		Select one of the baudrates listed in
1046		CONFIG_SYS_BAUDRATE_TABLE, see below.
1047
1048- Monitor Functions:
1049		Monitor commands can be included or excluded
1050		from the build by using the #include files
1051		<config_cmd_all.h> and #undef'ing unwanted
1052		commands, or adding #define's for wanted commands.
1053
1054		The default command configuration includes all commands
1055		except those marked below with a "*".
1056
1057		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
1058		CONFIG_CMD_ASKENV	* ask for env variable
1059		CONFIG_CMD_BDI		  bdinfo
1060		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
1061		CONFIG_CMD_BMP		* BMP support
1062		CONFIG_CMD_BSP		* Board specific commands
1063		CONFIG_CMD_BOOTD	  bootd
1064		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
1065		CONFIG_CMD_CACHE	* icache, dcache
1066		CONFIG_CMD_CLK   	* clock command support
1067		CONFIG_CMD_CONSOLE	  coninfo
1068		CONFIG_CMD_CRC32	* crc32
1069		CONFIG_CMD_DATE		* support for RTC, date/time...
1070		CONFIG_CMD_DHCP		* DHCP support
1071		CONFIG_CMD_DIAG		* Diagnostics
1072		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
1073		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
1074		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
1075		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
1076		CONFIG_CMD_DTT		* Digital Therm and Thermostat
1077		CONFIG_CMD_ECHO		  echo arguments
1078		CONFIG_CMD_EDITENV	  edit env variable
1079		CONFIG_CMD_EEPROM	* EEPROM read/write support
1080		CONFIG_CMD_ELF		* bootelf, bootvx
1081		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
1082		CONFIG_CMD_ENV_FLAGS	* display details about env flags
1083		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
1084		CONFIG_CMD_EXPORTENV	* export the environment
1085		CONFIG_CMD_EXT2		* ext2 command support
1086		CONFIG_CMD_EXT4		* ext4 command support
1087		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
1088					  that work for multiple fs types
1089		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
1090		CONFIG_CMD_SAVEENV	  saveenv
1091		CONFIG_CMD_FDC		* Floppy Disk Support
1092		CONFIG_CMD_FAT		* FAT command support
1093		CONFIG_CMD_FLASH	  flinfo, erase, protect
1094		CONFIG_CMD_FPGA		  FPGA device initialization support
1095		CONFIG_CMD_FUSE		* Device fuse support
1096		CONFIG_CMD_GETTIME	* Get time since boot
1097		CONFIG_CMD_GO		* the 'go' command (exec code)
1098		CONFIG_CMD_GREPENV	* search environment
1099		CONFIG_CMD_HASH		* calculate hash / digest
1100		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
1101		CONFIG_CMD_I2C		* I2C serial bus support
1102		CONFIG_CMD_IDE		* IDE harddisk support
1103		CONFIG_CMD_IMI		  iminfo
1104		CONFIG_CMD_IMLS		  List all images found in NOR flash
1105		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
1106		CONFIG_CMD_IMMAP	* IMMR dump support
1107		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
1108		CONFIG_CMD_IMPORTENV	* import an environment
1109		CONFIG_CMD_INI		* import data from an ini file into the env
1110		CONFIG_CMD_IRQ		* irqinfo
1111		CONFIG_CMD_ITEST	  Integer/string test of 2 values
1112		CONFIG_CMD_JFFS2	* JFFS2 Support
1113		CONFIG_CMD_KGDB		* kgdb
1114		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
1115		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
1116					  (169.254.*.*)
1117		CONFIG_CMD_LOADB	  loadb
1118		CONFIG_CMD_LOADS	  loads
1119		CONFIG_CMD_MD5SUM	* print md5 message digest
1120					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
1121		CONFIG_CMD_MEMINFO	* Display detailed memory information
1122		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
1123					  loop, loopw
1124		CONFIG_CMD_MEMTEST	* mtest
1125		CONFIG_CMD_MISC		  Misc functions like sleep etc
1126		CONFIG_CMD_MMC		* MMC memory mapped support
1127		CONFIG_CMD_MII		* MII utility commands
1128		CONFIG_CMD_MTDPARTS	* MTD partition support
1129		CONFIG_CMD_NAND		* NAND support
1130		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
1131		CONFIG_CMD_NFS		  NFS support
1132		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
1133		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
1134		CONFIG_CMD_PCI		* pciinfo
1135		CONFIG_CMD_PCMCIA		* PCMCIA support
1136		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
1137					  host
1138		CONFIG_CMD_PORTIO	* Port I/O
1139		CONFIG_CMD_READ		* Read raw data from partition
1140		CONFIG_CMD_REGINFO	* Register dump
1141		CONFIG_CMD_RUN		  run command in env variable
1142		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
1143		CONFIG_CMD_SAVES	* save S record dump
1144		CONFIG_CMD_SCSI		* SCSI Support
1145		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1146					  (requires CONFIG_CMD_I2C)
1147		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1148					  (4xx only)
1149		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1150		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1151					  (requires CONFIG_CMD_MEMORY)
1152		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1153		CONFIG_CMD_SOURCE	  "source" command Support
1154		CONFIG_CMD_SPI		* SPI serial bus support
1155		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1156		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1157		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1158		CONFIG_CMD_TIMER	* access to the system tick timer
1159		CONFIG_CMD_USB		* USB support
1160		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1161		CONFIG_CMD_MFSL		* Microblaze FSL support
1162		CONFIG_CMD_XIMG		  Load part of Multi Image
1163		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1164
1165		EXAMPLE: If you want all functions except of network
1166		support you can write:
1167
1168		#include "config_cmd_all.h"
1169		#undef CONFIG_CMD_NET
1170
1171	Other Commands:
1172		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1173
1174	Note:	Don't enable the "icache" and "dcache" commands
1175		(configuration option CONFIG_CMD_CACHE) unless you know
1176		what you (and your U-Boot users) are doing. Data
1177		cache cannot be enabled on systems like the 8xx or
1178		8260 (where accesses to the IMMR region must be
1179		uncached), and it cannot be disabled on all other
1180		systems where we (mis-) use the data cache to hold an
1181		initial stack and some data.
1182
1183
1184		XXX - this list needs to get updated!
1185
1186- Regular expression support:
1187		CONFIG_REGEX
1188		If this variable is defined, U-Boot is linked against
1189		the SLRE (Super Light Regular Expression) library,
1190		which adds regex support to some commands, as for
1191		example "env grep" and "setexpr".
1192
1193- Device tree:
1194		CONFIG_OF_CONTROL
1195		If this variable is defined, U-Boot will use a device tree
1196		to configure its devices, instead of relying on statically
1197		compiled #defines in the board file. This option is
1198		experimental and only available on a few boards. The device
1199		tree is available in the global data as gd->fdt_blob.
1200
1201		U-Boot needs to get its device tree from somewhere. This can
1202		be done using one of the two options below:
1203
1204		CONFIG_OF_EMBED
1205		If this variable is defined, U-Boot will embed a device tree
1206		binary in its image. This device tree file should be in the
1207		board directory and called <soc>-<board>.dts. The binary file
1208		is then picked up in board_init_f() and made available through
1209		the global data structure as gd->blob.
1210
1211		CONFIG_OF_SEPARATE
1212		If this variable is defined, U-Boot will build a device tree
1213		binary. It will be called u-boot.dtb. Architecture-specific
1214		code will locate it at run-time. Generally this works by:
1215
1216			cat u-boot.bin u-boot.dtb >image.bin
1217
1218		and in fact, U-Boot does this for you, creating a file called
1219		u-boot-dtb.bin which is useful in the common case. You can
1220		still use the individual files if you need something more
1221		exotic.
1222
1223- Watchdog:
1224		CONFIG_WATCHDOG
1225		If this variable is defined, it enables watchdog
1226		support for the SoC. There must be support in the SoC
1227		specific code for a watchdog. For the 8xx and 8260
1228		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1229		register.  When supported for a specific SoC is
1230		available, then no further board specific code should
1231		be needed to use it.
1232
1233		CONFIG_HW_WATCHDOG
1234		When using a watchdog circuitry external to the used
1235		SoC, then define this variable and provide board
1236		specific code for the "hw_watchdog_reset" function.
1237
1238		CONFIG_AT91_HW_WDT_TIMEOUT
1239		specify the timeout in seconds. default 2 seconds.
1240
1241- U-Boot Version:
1242		CONFIG_VERSION_VARIABLE
1243		If this variable is defined, an environment variable
1244		named "ver" is created by U-Boot showing the U-Boot
1245		version as printed by the "version" command.
1246		Any change to this variable will be reverted at the
1247		next reset.
1248
1249- Real-Time Clock:
1250
1251		When CONFIG_CMD_DATE is selected, the type of the RTC
1252		has to be selected, too. Define exactly one of the
1253		following options:
1254
1255		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1256		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1257		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1258		CONFIG_RTC_MC146818	- use MC146818 RTC
1259		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1260		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1261		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1262		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1263		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1264		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1265		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1266		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1267		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1268					  RV3029 RTC.
1269
1270		Note that if the RTC uses I2C, then the I2C interface
1271		must also be configured. See I2C Support, below.
1272
1273- GPIO Support:
1274		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1275
1276		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1277		chip-ngpio pairs that tell the PCA953X driver the number of
1278		pins supported by a particular chip.
1279
1280		Note that if the GPIO device uses I2C, then the I2C interface
1281		must also be configured. See I2C Support, below.
1282
1283- I/O tracing:
1284		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1285		accesses and can checksum them or write a list of them out
1286		to memory. See the 'iotrace' command for details. This is
1287		useful for testing device drivers since it can confirm that
1288		the driver behaves the same way before and after a code
1289		change. Currently this is supported on sandbox and arm. To
1290		add support for your architecture, add '#include <iotrace.h>'
1291		to the bottom of arch/<arch>/include/asm/io.h and test.
1292
1293		Example output from the 'iotrace stats' command is below.
1294		Note that if the trace buffer is exhausted, the checksum will
1295		still continue to operate.
1296
1297			iotrace is enabled
1298			Start:  10000000	(buffer start address)
1299			Size:   00010000	(buffer size)
1300			Offset: 00000120	(current buffer offset)
1301			Output: 10000120	(start + offset)
1302			Count:  00000018	(number of trace records)
1303			CRC32:  9526fb66	(CRC32 of all trace records)
1304
1305- Timestamp Support:
1306
1307		When CONFIG_TIMESTAMP is selected, the timestamp
1308		(date and time) of an image is printed by image
1309		commands like bootm or iminfo. This option is
1310		automatically enabled when you select CONFIG_CMD_DATE .
1311
1312- Partition Labels (disklabels) Supported:
1313		Zero or more of the following:
1314		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1315		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1316				       Intel architecture, USB sticks, etc.
1317		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1318		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1319				       bootloader.  Note 2TB partition limit; see
1320				       disk/part_efi.c
1321		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1322
1323		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1324		CONFIG_CMD_SCSI) you must configure support for at
1325		least one non-MTD partition type as well.
1326
1327- IDE Reset method:
1328		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1329		board configurations files but used nowhere!
1330
1331		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1332		be performed by calling the function
1333			ide_set_reset(int reset)
1334		which has to be defined in a board specific file
1335
1336- ATAPI Support:
1337		CONFIG_ATAPI
1338
1339		Set this to enable ATAPI support.
1340
1341- LBA48 Support
1342		CONFIG_LBA48
1343
1344		Set this to enable support for disks larger than 137GB
1345		Also look at CONFIG_SYS_64BIT_LBA.
1346		Whithout these , LBA48 support uses 32bit variables and will 'only'
1347		support disks up to 2.1TB.
1348
1349		CONFIG_SYS_64BIT_LBA:
1350			When enabled, makes the IDE subsystem use 64bit sector addresses.
1351			Default is 32bit.
1352
1353- SCSI Support:
1354		At the moment only there is only support for the
1355		SYM53C8XX SCSI controller; define
1356		CONFIG_SCSI_SYM53C8XX to enable it.
1357
1358		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1359		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1360		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1361		maximum numbers of LUNs, SCSI ID's and target
1362		devices.
1363		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1364
1365		The environment variable 'scsidevs' is set to the number of
1366		SCSI devices found during the last scan.
1367
1368- NETWORK Support (PCI):
1369		CONFIG_E1000
1370		Support for Intel 8254x/8257x gigabit chips.
1371
1372		CONFIG_E1000_SPI
1373		Utility code for direct access to the SPI bus on Intel 8257x.
1374		This does not do anything useful unless you set at least one
1375		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1376
1377		CONFIG_E1000_SPI_GENERIC
1378		Allow generic access to the SPI bus on the Intel 8257x, for
1379		example with the "sspi" command.
1380
1381		CONFIG_CMD_E1000
1382		Management command for E1000 devices.  When used on devices
1383		with SPI support you can reprogram the EEPROM from U-Boot.
1384
1385		CONFIG_EEPRO100
1386		Support for Intel 82557/82559/82559ER chips.
1387		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1388		write routine for first time initialisation.
1389
1390		CONFIG_TULIP
1391		Support for Digital 2114x chips.
1392		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1393		modem chip initialisation (KS8761/QS6611).
1394
1395		CONFIG_NATSEMI
1396		Support for National dp83815 chips.
1397
1398		CONFIG_NS8382X
1399		Support for National dp8382[01] gigabit chips.
1400
1401- NETWORK Support (other):
1402
1403		CONFIG_DRIVER_AT91EMAC
1404		Support for AT91RM9200 EMAC.
1405
1406			CONFIG_RMII
1407			Define this to use reduced MII inteface
1408
1409			CONFIG_DRIVER_AT91EMAC_QUIET
1410			If this defined, the driver is quiet.
1411			The driver doen't show link status messages.
1412
1413		CONFIG_CALXEDA_XGMAC
1414		Support for the Calxeda XGMAC device
1415
1416		CONFIG_LAN91C96
1417		Support for SMSC's LAN91C96 chips.
1418
1419			CONFIG_LAN91C96_BASE
1420			Define this to hold the physical address
1421			of the LAN91C96's I/O space
1422
1423			CONFIG_LAN91C96_USE_32_BIT
1424			Define this to enable 32 bit addressing
1425
1426		CONFIG_SMC91111
1427		Support for SMSC's LAN91C111 chip
1428
1429			CONFIG_SMC91111_BASE
1430			Define this to hold the physical address
1431			of the device (I/O space)
1432
1433			CONFIG_SMC_USE_32_BIT
1434			Define this if data bus is 32 bits
1435
1436			CONFIG_SMC_USE_IOFUNCS
1437			Define this to use i/o functions instead of macros
1438			(some hardware wont work with macros)
1439
1440		CONFIG_DRIVER_TI_EMAC
1441		Support for davinci emac
1442
1443			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1444			Define this if you have more then 3 PHYs.
1445
1446		CONFIG_FTGMAC100
1447		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1448
1449			CONFIG_FTGMAC100_EGIGA
1450			Define this to use GE link update with gigabit PHY.
1451			Define this if FTGMAC100 is connected to gigabit PHY.
1452			If your system has 10/100 PHY only, it might not occur
1453			wrong behavior. Because PHY usually return timeout or
1454			useless data when polling gigabit status and gigabit
1455			control registers. This behavior won't affect the
1456			correctnessof 10/100 link speed update.
1457
1458		CONFIG_SMC911X
1459		Support for SMSC's LAN911x and LAN921x chips
1460
1461			CONFIG_SMC911X_BASE
1462			Define this to hold the physical address
1463			of the device (I/O space)
1464
1465			CONFIG_SMC911X_32_BIT
1466			Define this if data bus is 32 bits
1467
1468			CONFIG_SMC911X_16_BIT
1469			Define this if data bus is 16 bits. If your processor
1470			automatically converts one 32 bit word to two 16 bit
1471			words you may also try CONFIG_SMC911X_32_BIT.
1472
1473		CONFIG_SH_ETHER
1474		Support for Renesas on-chip Ethernet controller
1475
1476			CONFIG_SH_ETHER_USE_PORT
1477			Define the number of ports to be used
1478
1479			CONFIG_SH_ETHER_PHY_ADDR
1480			Define the ETH PHY's address
1481
1482			CONFIG_SH_ETHER_CACHE_WRITEBACK
1483			If this option is set, the driver enables cache flush.
1484
1485- PWM Support:
1486		CONFIG_PWM_IMX
1487		Support for PWM modul on the imx6.
1488
1489- TPM Support:
1490		CONFIG_TPM
1491		Support TPM devices.
1492
1493		CONFIG_TPM_TIS_I2C
1494		Support for i2c bus TPM devices. Only one device
1495		per system is supported at this time.
1496
1497			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1498			Define the burst count bytes upper limit
1499
1500		CONFIG_TPM_ATMEL_TWI
1501		Support for Atmel TWI TPM device. Requires I2C support.
1502
1503		CONFIG_TPM_TIS_LPC
1504		Support for generic parallel port TPM devices. Only one device
1505		per system is supported at this time.
1506
1507			CONFIG_TPM_TIS_BASE_ADDRESS
1508			Base address where the generic TPM device is mapped
1509			to. Contemporary x86 systems usually map it at
1510			0xfed40000.
1511
1512		CONFIG_CMD_TPM
1513		Add tpm monitor functions.
1514		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1515		provides monitor access to authorized functions.
1516
1517		CONFIG_TPM
1518		Define this to enable the TPM support library which provides
1519		functional interfaces to some TPM commands.
1520		Requires support for a TPM device.
1521
1522		CONFIG_TPM_AUTH_SESSIONS
1523		Define this to enable authorized functions in the TPM library.
1524		Requires CONFIG_TPM and CONFIG_SHA1.
1525
1526- USB Support:
1527		At the moment only the UHCI host controller is
1528		supported (PIP405, MIP405, MPC5200); define
1529		CONFIG_USB_UHCI to enable it.
1530		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1531		and define CONFIG_USB_STORAGE to enable the USB
1532		storage devices.
1533		Note:
1534		Supported are USB Keyboards and USB Floppy drives
1535		(TEAC FD-05PUB).
1536		MPC5200 USB requires additional defines:
1537			CONFIG_USB_CLOCK
1538				for 528 MHz Clock: 0x0001bbbb
1539			CONFIG_PSC3_USB
1540				for USB on PSC3
1541			CONFIG_USB_CONFIG
1542				for differential drivers: 0x00001000
1543				for single ended drivers: 0x00005000
1544				for differential drivers on PSC3: 0x00000100
1545				for single ended drivers on PSC3: 0x00004100
1546			CONFIG_SYS_USB_EVENT_POLL
1547				May be defined to allow interrupt polling
1548				instead of using asynchronous interrupts
1549
1550		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1551		txfilltuning field in the EHCI controller on reset.
1552
1553		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1554		HW module registers.
1555
1556- USB Device:
1557		Define the below if you wish to use the USB console.
1558		Once firmware is rebuilt from a serial console issue the
1559		command "setenv stdin usbtty; setenv stdout usbtty" and
1560		attach your USB cable. The Unix command "dmesg" should print
1561		it has found a new device. The environment variable usbtty
1562		can be set to gserial or cdc_acm to enable your device to
1563		appear to a USB host as a Linux gserial device or a
1564		Common Device Class Abstract Control Model serial device.
1565		If you select usbtty = gserial you should be able to enumerate
1566		a Linux host by
1567		# modprobe usbserial vendor=0xVendorID product=0xProductID
1568		else if using cdc_acm, simply setting the environment
1569		variable usbtty to be cdc_acm should suffice. The following
1570		might be defined in YourBoardName.h
1571
1572			CONFIG_USB_DEVICE
1573			Define this to build a UDC device
1574
1575			CONFIG_USB_TTY
1576			Define this to have a tty type of device available to
1577			talk to the UDC device
1578
1579			CONFIG_USBD_HS
1580			Define this to enable the high speed support for usb
1581			device and usbtty. If this feature is enabled, a routine
1582			int is_usbd_high_speed(void)
1583			also needs to be defined by the driver to dynamically poll
1584			whether the enumeration has succeded at high speed or full
1585			speed.
1586
1587			CONFIG_SYS_CONSOLE_IS_IN_ENV
1588			Define this if you want stdin, stdout &/or stderr to
1589			be set to usbtty.
1590
1591			mpc8xx:
1592				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1593				Derive USB clock from external clock "blah"
1594				- CONFIG_SYS_USB_EXTC_CLK 0x02
1595
1596				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1597				Derive USB clock from brgclk
1598				- CONFIG_SYS_USB_BRG_CLK 0x04
1599
1600		If you have a USB-IF assigned VendorID then you may wish to
1601		define your own vendor specific values either in BoardName.h
1602		or directly in usbd_vendor_info.h. If you don't define
1603		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1604		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1605		should pretend to be a Linux device to it's target host.
1606
1607			CONFIG_USBD_MANUFACTURER
1608			Define this string as the name of your company for
1609			- CONFIG_USBD_MANUFACTURER "my company"
1610
1611			CONFIG_USBD_PRODUCT_NAME
1612			Define this string as the name of your product
1613			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1614
1615			CONFIG_USBD_VENDORID
1616			Define this as your assigned Vendor ID from the USB
1617			Implementors Forum. This *must* be a genuine Vendor ID
1618			to avoid polluting the USB namespace.
1619			- CONFIG_USBD_VENDORID 0xFFFF
1620
1621			CONFIG_USBD_PRODUCTID
1622			Define this as the unique Product ID
1623			for your device
1624			- CONFIG_USBD_PRODUCTID 0xFFFF
1625
1626- ULPI Layer Support:
1627		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1628		the generic ULPI layer. The generic layer accesses the ULPI PHY
1629		via the platform viewport, so you need both the genric layer and
1630		the viewport enabled. Currently only Chipidea/ARC based
1631		viewport is supported.
1632		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1633		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1634		If your ULPI phy needs a different reference clock than the
1635		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1636		the appropriate value in Hz.
1637
1638- MMC Support:
1639		The MMC controller on the Intel PXA is supported. To
1640		enable this define CONFIG_MMC. The MMC can be
1641		accessed from the boot prompt by mapping the device
1642		to physical memory similar to flash. Command line is
1643		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1644		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1645
1646		CONFIG_SH_MMCIF
1647		Support for Renesas on-chip MMCIF controller
1648
1649			CONFIG_SH_MMCIF_ADDR
1650			Define the base address of MMCIF registers
1651
1652			CONFIG_SH_MMCIF_CLK
1653			Define the clock frequency for MMCIF
1654
1655		CONFIG_GENERIC_MMC
1656		Enable the generic MMC driver
1657
1658		CONFIG_SUPPORT_EMMC_BOOT
1659		Enable some additional features of the eMMC boot partitions.
1660
1661		CONFIG_SUPPORT_EMMC_RPMB
1662		Enable the commands for reading, writing and programming the
1663		key for the Replay Protection Memory Block partition in eMMC.
1664
1665- USB Device Firmware Update (DFU) class support:
1666		CONFIG_USB_FUNCTION_DFU
1667		This enables the USB portion of the DFU USB class
1668
1669		CONFIG_CMD_DFU
1670		This enables the command "dfu" which is used to have
1671		U-Boot create a DFU class device via USB.  This command
1672		requires that the "dfu_alt_info" environment variable be
1673		set and define the alt settings to expose to the host.
1674
1675		CONFIG_DFU_MMC
1676		This enables support for exposing (e)MMC devices via DFU.
1677
1678		CONFIG_DFU_NAND
1679		This enables support for exposing NAND devices via DFU.
1680
1681		CONFIG_DFU_RAM
1682		This enables support for exposing RAM via DFU.
1683		Note: DFU spec refer to non-volatile memory usage, but
1684		allow usages beyond the scope of spec - here RAM usage,
1685		one that would help mostly the developer.
1686
1687		CONFIG_SYS_DFU_DATA_BUF_SIZE
1688		Dfu transfer uses a buffer before writing data to the
1689		raw storage device. Make the size (in bytes) of this buffer
1690		configurable. The size of this buffer is also configurable
1691		through the "dfu_bufsiz" environment variable.
1692
1693		CONFIG_SYS_DFU_MAX_FILE_SIZE
1694		When updating files rather than the raw storage device,
1695		we use a static buffer to copy the file into and then write
1696		the buffer once we've been given the whole file.  Define
1697		this to the maximum filesize (in bytes) for the buffer.
1698		Default is 4 MiB if undefined.
1699
1700		DFU_DEFAULT_POLL_TIMEOUT
1701		Poll timeout [ms], is the timeout a device can send to the
1702		host. The host must wait for this timeout before sending
1703		a subsequent DFU_GET_STATUS request to the device.
1704
1705		DFU_MANIFEST_POLL_TIMEOUT
1706		Poll timeout [ms], which the device sends to the host when
1707		entering dfuMANIFEST state. Host waits this timeout, before
1708		sending again an USB request to the device.
1709
1710- USB Device Android Fastboot support:
1711		CONFIG_USB_FUNCTION_FASTBOOT
1712		This enables the USB part of the fastboot gadget
1713
1714		CONFIG_CMD_FASTBOOT
1715		This enables the command "fastboot" which enables the Android
1716		fastboot mode for the platform's USB device. Fastboot is a USB
1717		protocol for downloading images, flashing and device control
1718		used on Android devices.
1719		See doc/README.android-fastboot for more information.
1720
1721		CONFIG_ANDROID_BOOT_IMAGE
1722		This enables support for booting images which use the Android
1723		image format header.
1724
1725		CONFIG_FASTBOOT_BUF_ADDR
1726		The fastboot protocol requires a large memory buffer for
1727		downloads. Define this to the starting RAM address to use for
1728		downloaded images.
1729
1730		CONFIG_FASTBOOT_BUF_SIZE
1731		The fastboot protocol requires a large memory buffer for
1732		downloads. This buffer should be as large as possible for a
1733		platform. Define this to the size available RAM for fastboot.
1734
1735		CONFIG_FASTBOOT_FLASH
1736		The fastboot protocol includes a "flash" command for writing
1737		the downloaded image to a non-volatile storage device. Define
1738		this to enable the "fastboot flash" command.
1739
1740		CONFIG_FASTBOOT_FLASH_MMC_DEV
1741		The fastboot "flash" command requires additional information
1742		regarding the non-volatile storage device. Define this to
1743		the eMMC device that fastboot should use to store the image.
1744
1745		CONFIG_FASTBOOT_GPT_NAME
1746		The fastboot "flash" command supports writing the downloaded
1747		image to the Protective MBR and the Primary GUID Partition
1748		Table. (Additionally, this downloaded image is post-processed
1749		to generate and write the Backup GUID Partition Table.)
1750		This occurs when the specified "partition name" on the
1751		"fastboot flash" command line matches this value.
1752		Default is GPT_ENTRY_NAME (currently "gpt") if undefined.
1753
1754- Journaling Flash filesystem support:
1755		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1756		CONFIG_JFFS2_NAND_DEV
1757		Define these for a default partition on a NAND device
1758
1759		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1760		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1761		Define these for a default partition on a NOR device
1762
1763		CONFIG_SYS_JFFS_CUSTOM_PART
1764		Define this to create an own partition. You have to provide a
1765		function struct part_info* jffs2_part_info(int part_num)
1766
1767		If you define only one JFFS2 partition you may also want to
1768		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1769		to disable the command chpart. This is the default when you
1770		have not defined a custom partition
1771
1772- FAT(File Allocation Table) filesystem write function support:
1773		CONFIG_FAT_WRITE
1774
1775		Define this to enable support for saving memory data as a
1776		file in FAT formatted partition.
1777
1778		This will also enable the command "fatwrite" enabling the
1779		user to write files to FAT.
1780
1781CBFS (Coreboot Filesystem) support
1782		CONFIG_CMD_CBFS
1783
1784		Define this to enable support for reading from a Coreboot
1785		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1786		and cbfsload.
1787
1788- FAT(File Allocation Table) filesystem cluster size:
1789		CONFIG_FS_FAT_MAX_CLUSTSIZE
1790
1791		Define the max cluster size for fat operations else
1792		a default value of 65536 will be defined.
1793
1794- Keyboard Support:
1795		CONFIG_ISA_KEYBOARD
1796
1797		Define this to enable standard (PC-Style) keyboard
1798		support
1799
1800		CONFIG_I8042_KBD
1801		Standard PC keyboard driver with US (is default) and
1802		GERMAN key layout (switch via environment 'keymap=de') support.
1803		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1804		for cfb_console. Supports cursor blinking.
1805
1806		CONFIG_CROS_EC_KEYB
1807		Enables a Chrome OS keyboard using the CROS_EC interface.
1808		This uses CROS_EC to communicate with a second microcontroller
1809		which provides key scans on request.
1810
1811- Video support:
1812		CONFIG_VIDEO
1813
1814		Define this to enable video support (for output to
1815		video).
1816
1817		CONFIG_VIDEO_CT69000
1818
1819		Enable Chips & Technologies 69000 Video chip
1820
1821		CONFIG_VIDEO_SMI_LYNXEM
1822		Enable Silicon Motion SMI 712/710/810 Video chip. The
1823		video output is selected via environment 'videoout'
1824		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1825		assumed.
1826
1827		For the CT69000 and SMI_LYNXEM drivers, videomode is
1828		selected via environment 'videomode'. Two different ways
1829		are possible:
1830		- "videomode=num"   'num' is a standard LiLo mode numbers.
1831		Following standard modes are supported	(* is default):
1832
1833		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1834		-------------+---------------------------------------------
1835		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1836		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1837		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1838		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1839		-------------+---------------------------------------------
1840		(i.e. setenv videomode 317; saveenv; reset;)
1841
1842		- "videomode=bootargs" all the video parameters are parsed
1843		from the bootargs. (See drivers/video/videomodes.c)
1844
1845
1846		CONFIG_VIDEO_SED13806
1847		Enable Epson SED13806 driver. This driver supports 8bpp
1848		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1849		or CONFIG_VIDEO_SED13806_16BPP
1850
1851		CONFIG_FSL_DIU_FB
1852		Enable the Freescale DIU video driver.	Reference boards for
1853		SOCs that have a DIU should define this macro to enable DIU
1854		support, and should also define these other macros:
1855
1856			CONFIG_SYS_DIU_ADDR
1857			CONFIG_VIDEO
1858			CONFIG_CMD_BMP
1859			CONFIG_CFB_CONSOLE
1860			CONFIG_VIDEO_SW_CURSOR
1861			CONFIG_VGA_AS_SINGLE_DEVICE
1862			CONFIG_VIDEO_LOGO
1863			CONFIG_VIDEO_BMP_LOGO
1864
1865		The DIU driver will look for the 'video-mode' environment
1866		variable, and if defined, enable the DIU as a console during
1867		boot.  See the documentation file README.video for a
1868		description of this variable.
1869
1870
1871- Keyboard Support:
1872		CONFIG_KEYBOARD
1873
1874		Define this to enable a custom keyboard support.
1875		This simply calls drv_keyboard_init() which must be
1876		defined in your board-specific files.
1877		The only board using this so far is RBC823.
1878
1879- LCD Support:	CONFIG_LCD
1880
1881		Define this to enable LCD support (for output to LCD
1882		display); also select one of the supported displays
1883		by defining one of these:
1884
1885		CONFIG_ATMEL_LCD:
1886
1887			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1888
1889		CONFIG_NEC_NL6448AC33:
1890
1891			NEC NL6448AC33-18. Active, color, single scan.
1892
1893		CONFIG_NEC_NL6448BC20
1894
1895			NEC NL6448BC20-08. 6.5", 640x480.
1896			Active, color, single scan.
1897
1898		CONFIG_NEC_NL6448BC33_54
1899
1900			NEC NL6448BC33-54. 10.4", 640x480.
1901			Active, color, single scan.
1902
1903		CONFIG_SHARP_16x9
1904
1905			Sharp 320x240. Active, color, single scan.
1906			It isn't 16x9, and I am not sure what it is.
1907
1908		CONFIG_SHARP_LQ64D341
1909
1910			Sharp LQ64D341 display, 640x480.
1911			Active, color, single scan.
1912
1913		CONFIG_HLD1045
1914
1915			HLD1045 display, 640x480.
1916			Active, color, single scan.
1917
1918		CONFIG_OPTREX_BW
1919
1920			Optrex	 CBL50840-2 NF-FW 99 22 M5
1921			or
1922			Hitachi	 LMG6912RPFC-00T
1923			or
1924			Hitachi	 SP14Q002
1925
1926			320x240. Black & white.
1927
1928		Normally display is black on white background; define
1929		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1930
1931		CONFIG_LCD_ALIGNMENT
1932
1933		Normally the LCD is page-aligned (typically 4KB). If this is
1934		defined then the LCD will be aligned to this value instead.
1935		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1936		here, since it is cheaper to change data cache settings on
1937		a per-section basis.
1938
1939		CONFIG_CONSOLE_SCROLL_LINES
1940
1941		When the console need to be scrolled, this is the number of
1942		lines to scroll by. It defaults to 1. Increasing this makes
1943		the console jump but can help speed up operation when scrolling
1944		is slow.
1945
1946		CONFIG_LCD_ROTATION
1947
1948		Sometimes, for example if the display is mounted in portrait
1949		mode or even if it's mounted landscape but rotated by 180degree,
1950		we need to rotate our content of the display relative to the
1951		framebuffer, so that user can read the messages which are
1952		printed out.
1953		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1954		initialized with a given rotation from "vl_rot" out of
1955		"vidinfo_t" which is provided by the board specific code.
1956		The value for vl_rot is coded as following (matching to
1957		fbcon=rotate:<n> linux-kernel commandline):
1958		0 = no rotation respectively 0 degree
1959		1 = 90 degree rotation
1960		2 = 180 degree rotation
1961		3 = 270 degree rotation
1962
1963		If CONFIG_LCD_ROTATION is not defined, the console will be
1964		initialized with 0degree rotation.
1965
1966		CONFIG_LCD_BMP_RLE8
1967
1968		Support drawing of RLE8-compressed bitmaps on the LCD.
1969
1970		CONFIG_I2C_EDID
1971
1972		Enables an 'i2c edid' command which can read EDID
1973		information over I2C from an attached LCD display.
1974
1975- Splash Screen Support: CONFIG_SPLASH_SCREEN
1976
1977		If this option is set, the environment is checked for
1978		a variable "splashimage". If found, the usual display
1979		of logo, copyright and system information on the LCD
1980		is suppressed and the BMP image at the address
1981		specified in "splashimage" is loaded instead. The
1982		console is redirected to the "nulldev", too. This
1983		allows for a "silent" boot where a splash screen is
1984		loaded very quickly after power-on.
1985
1986		CONFIG_SPLASHIMAGE_GUARD
1987
1988		If this option is set, then U-Boot will prevent the environment
1989		variable "splashimage" from being set to a problematic address
1990		(see README.displaying-bmps).
1991		This option is useful for targets where, due to alignment
1992		restrictions, an improperly aligned BMP image will cause a data
1993		abort. If you think you will not have problems with unaligned
1994		accesses (for example because your toolchain prevents them)
1995		there is no need to set this option.
1996
1997		CONFIG_SPLASH_SCREEN_ALIGN
1998
1999		If this option is set the splash image can be freely positioned
2000		on the screen. Environment variable "splashpos" specifies the
2001		position as "x,y". If a positive number is given it is used as
2002		number of pixel from left/top. If a negative number is given it
2003		is used as number of pixel from right/bottom. You can also
2004		specify 'm' for centering the image.
2005
2006		Example:
2007		setenv splashpos m,m
2008			=> image at center of screen
2009
2010		setenv splashpos 30,20
2011			=> image at x = 30 and y = 20
2012
2013		setenv splashpos -10,m
2014			=> vertically centered image
2015			   at x = dspWidth - bmpWidth - 9
2016
2017- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
2018
2019		If this option is set, additionally to standard BMP
2020		images, gzipped BMP images can be displayed via the
2021		splashscreen support or the bmp command.
2022
2023- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
2024
2025		If this option is set, 8-bit RLE compressed BMP images
2026		can be displayed via the splashscreen support or the
2027		bmp command.
2028
2029- Do compressing for memory range:
2030		CONFIG_CMD_ZIP
2031
2032		If this option is set, it would use zlib deflate method
2033		to compress the specified memory at its best effort.
2034
2035- Compression support:
2036		CONFIG_GZIP
2037
2038		Enabled by default to support gzip compressed images.
2039
2040		CONFIG_BZIP2
2041
2042		If this option is set, support for bzip2 compressed
2043		images is included. If not, only uncompressed and gzip
2044		compressed images are supported.
2045
2046		NOTE: the bzip2 algorithm requires a lot of RAM, so
2047		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
2048		be at least 4MB.
2049
2050		CONFIG_LZMA
2051
2052		If this option is set, support for lzma compressed
2053		images is included.
2054
2055		Note: The LZMA algorithm adds between 2 and 4KB of code and it
2056		requires an amount of dynamic memory that is given by the
2057		formula:
2058
2059			(1846 + 768 << (lc + lp)) * sizeof(uint16)
2060
2061		Where lc and lp stand for, respectively, Literal context bits
2062		and Literal pos bits.
2063
2064		This value is upper-bounded by 14MB in the worst case. Anyway,
2065		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
2066		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
2067		a very small buffer.
2068
2069		Use the lzmainfo tool to determinate the lc and lp values and
2070		then calculate the amount of needed dynamic memory (ensuring
2071		the appropriate CONFIG_SYS_MALLOC_LEN value).
2072
2073		CONFIG_LZO
2074
2075		If this option is set, support for LZO compressed images
2076		is included.
2077
2078- MII/PHY support:
2079		CONFIG_PHY_ADDR
2080
2081		The address of PHY on MII bus.
2082
2083		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
2084
2085		The clock frequency of the MII bus
2086
2087		CONFIG_PHY_GIGE
2088
2089		If this option is set, support for speed/duplex
2090		detection of gigabit PHY is included.
2091
2092		CONFIG_PHY_RESET_DELAY
2093
2094		Some PHY like Intel LXT971A need extra delay after
2095		reset before any MII register access is possible.
2096		For such PHY, set this option to the usec delay
2097		required. (minimum 300usec for LXT971A)
2098
2099		CONFIG_PHY_CMD_DELAY (ppc4xx)
2100
2101		Some PHY like Intel LXT971A need extra delay after
2102		command issued before MII status register can be read
2103
2104- IP address:
2105		CONFIG_IPADDR
2106
2107		Define a default value for the IP address to use for
2108		the default Ethernet interface, in case this is not
2109		determined through e.g. bootp.
2110		(Environment variable "ipaddr")
2111
2112- Server IP address:
2113		CONFIG_SERVERIP
2114
2115		Defines a default value for the IP address of a TFTP
2116		server to contact when using the "tftboot" command.
2117		(Environment variable "serverip")
2118
2119		CONFIG_KEEP_SERVERADDR
2120
2121		Keeps the server's MAC address, in the env 'serveraddr'
2122		for passing to bootargs (like Linux's netconsole option)
2123
2124- Gateway IP address:
2125		CONFIG_GATEWAYIP
2126
2127		Defines a default value for the IP address of the
2128		default router where packets to other networks are
2129		sent to.
2130		(Environment variable "gatewayip")
2131
2132- Subnet mask:
2133		CONFIG_NETMASK
2134
2135		Defines a default value for the subnet mask (or
2136		routing prefix) which is used to determine if an IP
2137		address belongs to the local subnet or needs to be
2138		forwarded through a router.
2139		(Environment variable "netmask")
2140
2141- Multicast TFTP Mode:
2142		CONFIG_MCAST_TFTP
2143
2144		Defines whether you want to support multicast TFTP as per
2145		rfc-2090; for example to work with atftp.  Lets lots of targets
2146		tftp down the same boot image concurrently.  Note: the Ethernet
2147		driver in use must provide a function: mcast() to join/leave a
2148		multicast group.
2149
2150- BOOTP Recovery Mode:
2151		CONFIG_BOOTP_RANDOM_DELAY
2152
2153		If you have many targets in a network that try to
2154		boot using BOOTP, you may want to avoid that all
2155		systems send out BOOTP requests at precisely the same
2156		moment (which would happen for instance at recovery
2157		from a power failure, when all systems will try to
2158		boot, thus flooding the BOOTP server. Defining
2159		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
2160		inserted before sending out BOOTP requests. The
2161		following delays are inserted then:
2162
2163		1st BOOTP request:	delay 0 ... 1 sec
2164		2nd BOOTP request:	delay 0 ... 2 sec
2165		3rd BOOTP request:	delay 0 ... 4 sec
2166		4th and following
2167		BOOTP requests:		delay 0 ... 8 sec
2168
2169		CONFIG_BOOTP_ID_CACHE_SIZE
2170
2171		BOOTP packets are uniquely identified using a 32-bit ID. The
2172		server will copy the ID from client requests to responses and
2173		U-Boot will use this to determine if it is the destination of
2174		an incoming response. Some servers will check that addresses
2175		aren't in use before handing them out (usually using an ARP
2176		ping) and therefore take up to a few hundred milliseconds to
2177		respond. Network congestion may also influence the time it
2178		takes for a response to make it back to the client. If that
2179		time is too long, U-Boot will retransmit requests. In order
2180		to allow earlier responses to still be accepted after these
2181		retransmissions, U-Boot's BOOTP client keeps a small cache of
2182		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
2183		cache. The default is to keep IDs for up to four outstanding
2184		requests. Increasing this will allow U-Boot to accept offers
2185		from a BOOTP client in networks with unusually high latency.
2186
2187- DHCP Advanced Options:
2188		You can fine tune the DHCP functionality by defining
2189		CONFIG_BOOTP_* symbols:
2190
2191		CONFIG_BOOTP_SUBNETMASK
2192		CONFIG_BOOTP_GATEWAY
2193		CONFIG_BOOTP_HOSTNAME
2194		CONFIG_BOOTP_NISDOMAIN
2195		CONFIG_BOOTP_BOOTPATH
2196		CONFIG_BOOTP_BOOTFILESIZE
2197		CONFIG_BOOTP_DNS
2198		CONFIG_BOOTP_DNS2
2199		CONFIG_BOOTP_SEND_HOSTNAME
2200		CONFIG_BOOTP_NTPSERVER
2201		CONFIG_BOOTP_TIMEOFFSET
2202		CONFIG_BOOTP_VENDOREX
2203		CONFIG_BOOTP_MAY_FAIL
2204
2205		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
2206		environment variable, not the BOOTP server.
2207
2208		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
2209		after the configured retry count, the call will fail
2210		instead of starting over.  This can be used to fail over
2211		to Link-local IP address configuration if the DHCP server
2212		is not available.
2213
2214		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
2215		serverip from a DHCP server, it is possible that more
2216		than one DNS serverip is offered to the client.
2217		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
2218		serverip will be stored in the additional environment
2219		variable "dnsip2". The first DNS serverip is always
2220		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
2221		is defined.
2222
2223		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2224		to do a dynamic update of a DNS server. To do this, they
2225		need the hostname of the DHCP requester.
2226		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2227		of the "hostname" environment variable is passed as
2228		option 12 to the DHCP server.
2229
2230		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2231
2232		A 32bit value in microseconds for a delay between
2233		receiving a "DHCP Offer" and sending the "DHCP Request".
2234		This fixes a problem with certain DHCP servers that don't
2235		respond 100% of the time to a "DHCP request". E.g. On an
2236		AT91RM9200 processor running at 180MHz, this delay needed
2237		to be *at least* 15,000 usec before a Windows Server 2003
2238		DHCP server would reply 100% of the time. I recommend at
2239		least 50,000 usec to be safe. The alternative is to hope
2240		that one of the retries will be successful but note that
2241		the DHCP timeout and retry process takes a longer than
2242		this delay.
2243
2244 - Link-local IP address negotiation:
2245		Negotiate with other link-local clients on the local network
2246		for an address that doesn't require explicit configuration.
2247		This is especially useful if a DHCP server cannot be guaranteed
2248		to exist in all environments that the device must operate.
2249
2250		See doc/README.link-local for more information.
2251
2252 - CDP Options:
2253		CONFIG_CDP_DEVICE_ID
2254
2255		The device id used in CDP trigger frames.
2256
2257		CONFIG_CDP_DEVICE_ID_PREFIX
2258
2259		A two character string which is prefixed to the MAC address
2260		of the device.
2261
2262		CONFIG_CDP_PORT_ID
2263
2264		A printf format string which contains the ascii name of
2265		the port. Normally is set to "eth%d" which sets
2266		eth0 for the first Ethernet, eth1 for the second etc.
2267
2268		CONFIG_CDP_CAPABILITIES
2269
2270		A 32bit integer which indicates the device capabilities;
2271		0x00000010 for a normal host which does not forwards.
2272
2273		CONFIG_CDP_VERSION
2274
2275		An ascii string containing the version of the software.
2276
2277		CONFIG_CDP_PLATFORM
2278
2279		An ascii string containing the name of the platform.
2280
2281		CONFIG_CDP_TRIGGER
2282
2283		A 32bit integer sent on the trigger.
2284
2285		CONFIG_CDP_POWER_CONSUMPTION
2286
2287		A 16bit integer containing the power consumption of the
2288		device in .1 of milliwatts.
2289
2290		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2291
2292		A byte containing the id of the VLAN.
2293
2294- Status LED:	CONFIG_STATUS_LED
2295
2296		Several configurations allow to display the current
2297		status using a LED. For instance, the LED will blink
2298		fast while running U-Boot code, stop blinking as
2299		soon as a reply to a BOOTP request was received, and
2300		start blinking slow once the Linux kernel is running
2301		(supported by a status LED driver in the Linux
2302		kernel). Defining CONFIG_STATUS_LED enables this
2303		feature in U-Boot.
2304
2305		Additional options:
2306
2307		CONFIG_GPIO_LED
2308		The status LED can be connected to a GPIO pin.
2309		In such cases, the gpio_led driver can be used as a
2310		status LED backend implementation. Define CONFIG_GPIO_LED
2311		to include the gpio_led driver in the U-Boot binary.
2312
2313		CONFIG_GPIO_LED_INVERTED_TABLE
2314		Some GPIO connected LEDs may have inverted polarity in which
2315		case the GPIO high value corresponds to LED off state and
2316		GPIO low value corresponds to LED on state.
2317		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2318		with a list of GPIO LEDs that have inverted polarity.
2319
2320- CAN Support:	CONFIG_CAN_DRIVER
2321
2322		Defining CONFIG_CAN_DRIVER enables CAN driver support
2323		on those systems that support this (optional)
2324		feature, like the TQM8xxL modules.
2325
2326- I2C Support:	CONFIG_SYS_I2C
2327
2328		This enable the NEW i2c subsystem, and will allow you to use
2329		i2c commands at the u-boot command line (as long as you set
2330		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2331		based realtime clock chips or other i2c devices. See
2332		common/cmd_i2c.c for a description of the command line
2333		interface.
2334
2335		ported i2c driver to the new framework:
2336		- drivers/i2c/soft_i2c.c:
2337		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2338		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2339		    for defining speed and slave address
2340		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2341		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2342		    for defining speed and slave address
2343		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2344		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2345		    for defining speed and slave address
2346		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2347		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2348		    for defining speed and slave address
2349
2350		- drivers/i2c/fsl_i2c.c:
2351		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2352		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2353		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2354		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2355		    bus.
2356		  - If your board supports a second fsl i2c bus, define
2357		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2358		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2359		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2360		    second bus.
2361
2362		- drivers/i2c/tegra_i2c.c:
2363		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2364		  - This driver adds 4 i2c buses with a fix speed from
2365		    100000 and the slave addr 0!
2366
2367		- drivers/i2c/ppc4xx_i2c.c
2368		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2369		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2370		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2371
2372		- drivers/i2c/i2c_mxc.c
2373		  - activate this driver with CONFIG_SYS_I2C_MXC
2374		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2375		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2376		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2377		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2378		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2379		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2380		If those defines are not set, default value is 100000
2381		for speed, and 0 for slave.
2382		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
2383		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
2384
2385		- drivers/i2c/rcar_i2c.c:
2386		  - activate this driver with CONFIG_SYS_I2C_RCAR
2387		  - This driver adds 4 i2c buses
2388
2389		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2390		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2391		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2392		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2393		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2394		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2395		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2396		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2397		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2398
2399		- drivers/i2c/sh_i2c.c:
2400		  - activate this driver with CONFIG_SYS_I2C_SH
2401		  - This driver adds from 2 to 5 i2c buses
2402
2403		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2404		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2405		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2406		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2407		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2408		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2409		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2410		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2411		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2412		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2413		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2414		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2415		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2416
2417		- drivers/i2c/omap24xx_i2c.c
2418		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2419		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2420		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2421		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2422		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2423		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2424		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2425		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2426		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2427		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2428		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2429
2430		- drivers/i2c/zynq_i2c.c
2431		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2432		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2433		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2434
2435		- drivers/i2c/s3c24x0_i2c.c:
2436		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2437		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2438		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2439		    with a fix speed from 100000 and the slave addr 0!
2440
2441		- drivers/i2c/ihs_i2c.c
2442		  - activate this driver with CONFIG_SYS_I2C_IHS
2443		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2444		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2445		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2446		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2447		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2448		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2449		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2450		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2451		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2452		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2453		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2454		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2455
2456		additional defines:
2457
2458		CONFIG_SYS_NUM_I2C_BUSES
2459		Hold the number of i2c buses you want to use. If you
2460		don't use/have i2c muxes on your i2c bus, this
2461		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2462		omit this define.
2463
2464		CONFIG_SYS_I2C_DIRECT_BUS
2465		define this, if you don't use i2c muxes on your hardware.
2466		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2467		omit this define.
2468
2469		CONFIG_SYS_I2C_MAX_HOPS
2470		define how many muxes are maximal consecutively connected
2471		on one i2c bus. If you not use i2c muxes, omit this
2472		define.
2473
2474		CONFIG_SYS_I2C_BUSES
2475		hold a list of buses you want to use, only used if
2476		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2477		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2478		CONFIG_SYS_NUM_I2C_BUSES = 9:
2479
2480		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2481					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2482					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2483					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2484					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2485					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2486					{1, {I2C_NULL_HOP}}, \
2487					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2488					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2489					}
2490
2491		which defines
2492			bus 0 on adapter 0 without a mux
2493			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2494			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2495			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2496			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2497			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2498			bus 6 on adapter 1 without a mux
2499			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2500			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2501
2502		If you do not have i2c muxes on your board, omit this define.
2503
2504- Legacy I2C Support:	CONFIG_HARD_I2C
2505
2506		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2507		provides the following compelling advantages:
2508
2509		- more than one i2c adapter is usable
2510		- approved multibus support
2511		- better i2c mux support
2512
2513		** Please consider updating your I2C driver now. **
2514
2515		These enable legacy I2C serial bus commands. Defining
2516		CONFIG_HARD_I2C will include the appropriate I2C driver
2517		for the selected CPU.
2518
2519		This will allow you to use i2c commands at the u-boot
2520		command line (as long as you set CONFIG_CMD_I2C in
2521		CONFIG_COMMANDS) and communicate with i2c based realtime
2522		clock chips. See common/cmd_i2c.c for a description of the
2523		command line interface.
2524
2525		CONFIG_HARD_I2C selects a hardware I2C controller.
2526
2527		There are several other quantities that must also be
2528		defined when you define CONFIG_HARD_I2C.
2529
2530		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2531		to be the frequency (in Hz) at which you wish your i2c bus
2532		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2533		the CPU's i2c node address).
2534
2535		Now, the u-boot i2c code for the mpc8xx
2536		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2537		and so its address should therefore be cleared to 0 (See,
2538		eg, MPC823e User's Manual p.16-473). So, set
2539		CONFIG_SYS_I2C_SLAVE to 0.
2540
2541		CONFIG_SYS_I2C_INIT_MPC5XXX
2542
2543		When a board is reset during an i2c bus transfer
2544		chips might think that the current transfer is still
2545		in progress.  Reset the slave devices by sending start
2546		commands until the slave device responds.
2547
2548		That's all that's required for CONFIG_HARD_I2C.
2549
2550		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2551		then the following macros need to be defined (examples are
2552		from include/configs/lwmon.h):
2553
2554		I2C_INIT
2555
2556		(Optional). Any commands necessary to enable the I2C
2557		controller or configure ports.
2558
2559		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2560
2561		I2C_PORT
2562
2563		(Only for MPC8260 CPU). The I/O port to use (the code
2564		assumes both bits are on the same port). Valid values
2565		are 0..3 for ports A..D.
2566
2567		I2C_ACTIVE
2568
2569		The code necessary to make the I2C data line active
2570		(driven).  If the data line is open collector, this
2571		define can be null.
2572
2573		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2574
2575		I2C_TRISTATE
2576
2577		The code necessary to make the I2C data line tri-stated
2578		(inactive).  If the data line is open collector, this
2579		define can be null.
2580
2581		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2582
2583		I2C_READ
2584
2585		Code that returns true if the I2C data line is high,
2586		false if it is low.
2587
2588		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2589
2590		I2C_SDA(bit)
2591
2592		If <bit> is true, sets the I2C data line high. If it
2593		is false, it clears it (low).
2594
2595		eg: #define I2C_SDA(bit) \
2596			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2597			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2598
2599		I2C_SCL(bit)
2600
2601		If <bit> is true, sets the I2C clock line high. If it
2602		is false, it clears it (low).
2603
2604		eg: #define I2C_SCL(bit) \
2605			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2606			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2607
2608		I2C_DELAY
2609
2610		This delay is invoked four times per clock cycle so this
2611		controls the rate of data transfer.  The data rate thus
2612		is 1 / (I2C_DELAY * 4). Often defined to be something
2613		like:
2614
2615		#define I2C_DELAY  udelay(2)
2616
2617		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2618
2619		If your arch supports the generic GPIO framework (asm/gpio.h),
2620		then you may alternatively define the two GPIOs that are to be
2621		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2622		have GPIO-based defaults assigned to them as appropriate.
2623
2624		You should define these to the GPIO value as given directly to
2625		the generic GPIO functions.
2626
2627		CONFIG_SYS_I2C_INIT_BOARD
2628
2629		When a board is reset during an i2c bus transfer
2630		chips might think that the current transfer is still
2631		in progress. On some boards it is possible to access
2632		the i2c SCLK line directly, either by using the
2633		processor pin as a GPIO or by having a second pin
2634		connected to the bus. If this option is defined a
2635		custom i2c_init_board() routine in boards/xxx/board.c
2636		is run early in the boot sequence.
2637
2638		CONFIG_SYS_I2C_BOARD_LATE_INIT
2639
2640		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2641		defined a custom i2c_board_late_init() routine in
2642		boards/xxx/board.c is run AFTER the operations in i2c_init()
2643		is completed. This callpoint can be used to unreset i2c bus
2644		using CPU i2c controller register accesses for CPUs whose i2c
2645		controller provide such a method. It is called at the end of
2646		i2c_init() to allow i2c_init operations to setup the i2c bus
2647		controller on the CPU (e.g. setting bus speed & slave address).
2648
2649		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2650
2651		This option enables configuration of bi_iic_fast[] flags
2652		in u-boot bd_info structure based on u-boot environment
2653		variable "i2cfast". (see also i2cfast)
2654
2655		CONFIG_I2C_MULTI_BUS
2656
2657		This option allows the use of multiple I2C buses, each of which
2658		must have a controller.	 At any point in time, only one bus is
2659		active.	 To switch to a different bus, use the 'i2c dev' command.
2660		Note that bus numbering is zero-based.
2661
2662		CONFIG_SYS_I2C_NOPROBES
2663
2664		This option specifies a list of I2C devices that will be skipped
2665		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2666		is set, specify a list of bus-device pairs.  Otherwise, specify
2667		a 1D array of device addresses
2668
2669		e.g.
2670			#undef	CONFIG_I2C_MULTI_BUS
2671			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2672
2673		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2674
2675			#define CONFIG_I2C_MULTI_BUS
2676			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2677
2678		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2679
2680		CONFIG_SYS_SPD_BUS_NUM
2681
2682		If defined, then this indicates the I2C bus number for DDR SPD.
2683		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2684
2685		CONFIG_SYS_RTC_BUS_NUM
2686
2687		If defined, then this indicates the I2C bus number for the RTC.
2688		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2689
2690		CONFIG_SYS_DTT_BUS_NUM
2691
2692		If defined, then this indicates the I2C bus number for the DTT.
2693		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2694
2695		CONFIG_SYS_I2C_DTT_ADDR:
2696
2697		If defined, specifies the I2C address of the DTT device.
2698		If not defined, then U-Boot uses predefined value for
2699		specified DTT device.
2700
2701		CONFIG_SOFT_I2C_READ_REPEATED_START
2702
2703		defining this will force the i2c_read() function in
2704		the soft_i2c driver to perform an I2C repeated start
2705		between writing the address pointer and reading the
2706		data.  If this define is omitted the default behaviour
2707		of doing a stop-start sequence will be used.  Most I2C
2708		devices can use either method, but some require one or
2709		the other.
2710
2711- SPI Support:	CONFIG_SPI
2712
2713		Enables SPI driver (so far only tested with
2714		SPI EEPROM, also an instance works with Crystal A/D and
2715		D/As on the SACSng board)
2716
2717		CONFIG_SH_SPI
2718
2719		Enables the driver for SPI controller on SuperH. Currently
2720		only SH7757 is supported.
2721
2722		CONFIG_SPI_X
2723
2724		Enables extended (16-bit) SPI EEPROM addressing.
2725		(symmetrical to CONFIG_I2C_X)
2726
2727		CONFIG_SOFT_SPI
2728
2729		Enables a software (bit-bang) SPI driver rather than
2730		using hardware support. This is a general purpose
2731		driver that only requires three general I/O port pins
2732		(two outputs, one input) to function. If this is
2733		defined, the board configuration must define several
2734		SPI configuration items (port pins to use, etc). For
2735		an example, see include/configs/sacsng.h.
2736
2737		CONFIG_HARD_SPI
2738
2739		Enables a hardware SPI driver for general-purpose reads
2740		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2741		must define a list of chip-select function pointers.
2742		Currently supported on some MPC8xxx processors.	 For an
2743		example, see include/configs/mpc8349emds.h.
2744
2745		CONFIG_MXC_SPI
2746
2747		Enables the driver for the SPI controllers on i.MX and MXC
2748		SoCs. Currently i.MX31/35/51 are supported.
2749
2750		CONFIG_SYS_SPI_MXC_WAIT
2751		Timeout for waiting until spi transfer completed.
2752		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2753
2754- FPGA Support: CONFIG_FPGA
2755
2756		Enables FPGA subsystem.
2757
2758		CONFIG_FPGA_<vendor>
2759
2760		Enables support for specific chip vendors.
2761		(ALTERA, XILINX)
2762
2763		CONFIG_FPGA_<family>
2764
2765		Enables support for FPGA family.
2766		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2767
2768		CONFIG_FPGA_COUNT
2769
2770		Specify the number of FPGA devices to support.
2771
2772		CONFIG_CMD_FPGA_LOADMK
2773
2774		Enable support for fpga loadmk command
2775
2776		CONFIG_CMD_FPGA_LOADP
2777
2778		Enable support for fpga loadp command - load partial bitstream
2779
2780		CONFIG_CMD_FPGA_LOADBP
2781
2782		Enable support for fpga loadbp command - load partial bitstream
2783		(Xilinx only)
2784
2785		CONFIG_SYS_FPGA_PROG_FEEDBACK
2786
2787		Enable printing of hash marks during FPGA configuration.
2788
2789		CONFIG_SYS_FPGA_CHECK_BUSY
2790
2791		Enable checks on FPGA configuration interface busy
2792		status by the configuration function. This option
2793		will require a board or device specific function to
2794		be written.
2795
2796		CONFIG_FPGA_DELAY
2797
2798		If defined, a function that provides delays in the FPGA
2799		configuration driver.
2800
2801		CONFIG_SYS_FPGA_CHECK_CTRLC
2802		Allow Control-C to interrupt FPGA configuration
2803
2804		CONFIG_SYS_FPGA_CHECK_ERROR
2805
2806		Check for configuration errors during FPGA bitfile
2807		loading. For example, abort during Virtex II
2808		configuration if the INIT_B line goes low (which
2809		indicated a CRC error).
2810
2811		CONFIG_SYS_FPGA_WAIT_INIT
2812
2813		Maximum time to wait for the INIT_B line to de-assert
2814		after PROB_B has been de-asserted during a Virtex II
2815		FPGA configuration sequence. The default time is 500
2816		ms.
2817
2818		CONFIG_SYS_FPGA_WAIT_BUSY
2819
2820		Maximum time to wait for BUSY to de-assert during
2821		Virtex II FPGA configuration. The default is 5 ms.
2822
2823		CONFIG_SYS_FPGA_WAIT_CONFIG
2824
2825		Time to wait after FPGA configuration. The default is
2826		200 ms.
2827
2828- Configuration Management:
2829		CONFIG_BUILD_TARGET
2830
2831		Some SoCs need special image types (e.g. U-Boot binary
2832		with a special header) as build targets. By defining
2833		CONFIG_BUILD_TARGET in the SoC / board header, this
2834		special image will be automatically built upon calling
2835		make / MAKEALL.
2836
2837		CONFIG_IDENT_STRING
2838
2839		If defined, this string will be added to the U-Boot
2840		version information (U_BOOT_VERSION)
2841
2842- Vendor Parameter Protection:
2843
2844		U-Boot considers the values of the environment
2845		variables "serial#" (Board Serial Number) and
2846		"ethaddr" (Ethernet Address) to be parameters that
2847		are set once by the board vendor / manufacturer, and
2848		protects these variables from casual modification by
2849		the user. Once set, these variables are read-only,
2850		and write or delete attempts are rejected. You can
2851		change this behaviour:
2852
2853		If CONFIG_ENV_OVERWRITE is #defined in your config
2854		file, the write protection for vendor parameters is
2855		completely disabled. Anybody can change or delete
2856		these parameters.
2857
2858		Alternatively, if you define _both_ an ethaddr in the
2859		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2860		Ethernet address is installed in the environment,
2861		which can be changed exactly ONCE by the user. [The
2862		serial# is unaffected by this, i. e. it remains
2863		read-only.]
2864
2865		The same can be accomplished in a more flexible way
2866		for any variable by configuring the type of access
2867		to allow for those variables in the ".flags" variable
2868		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2869
2870- Protected RAM:
2871		CONFIG_PRAM
2872
2873		Define this variable to enable the reservation of
2874		"protected RAM", i. e. RAM which is not overwritten
2875		by U-Boot. Define CONFIG_PRAM to hold the number of
2876		kB you want to reserve for pRAM. You can overwrite
2877		this default value by defining an environment
2878		variable "pram" to the number of kB you want to
2879		reserve. Note that the board info structure will
2880		still show the full amount of RAM. If pRAM is
2881		reserved, a new environment variable "mem" will
2882		automatically be defined to hold the amount of
2883		remaining RAM in a form that can be passed as boot
2884		argument to Linux, for instance like that:
2885
2886			setenv bootargs ... mem=\${mem}
2887			saveenv
2888
2889		This way you can tell Linux not to use this memory,
2890		either, which results in a memory region that will
2891		not be affected by reboots.
2892
2893		*WARNING* If your board configuration uses automatic
2894		detection of the RAM size, you must make sure that
2895		this memory test is non-destructive. So far, the
2896		following board configurations are known to be
2897		"pRAM-clean":
2898
2899			IVMS8, IVML24, SPD8xx, TQM8xxL,
2900			HERMES, IP860, RPXlite, LWMON,
2901			FLAGADM, TQM8260
2902
2903- Access to physical memory region (> 4GB)
2904		Some basic support is provided for operations on memory not
2905		normally accessible to U-Boot - e.g. some architectures
2906		support access to more than 4GB of memory on 32-bit
2907		machines using physical address extension or similar.
2908		Define CONFIG_PHYSMEM to access this basic support, which
2909		currently only supports clearing the memory.
2910
2911- Error Recovery:
2912		CONFIG_PANIC_HANG
2913
2914		Define this variable to stop the system in case of a
2915		fatal error, so that you have to reset it manually.
2916		This is probably NOT a good idea for an embedded
2917		system where you want the system to reboot
2918		automatically as fast as possible, but it may be
2919		useful during development since you can try to debug
2920		the conditions that lead to the situation.
2921
2922		CONFIG_NET_RETRY_COUNT
2923
2924		This variable defines the number of retries for
2925		network operations like ARP, RARP, TFTP, or BOOTP
2926		before giving up the operation. If not defined, a
2927		default value of 5 is used.
2928
2929		CONFIG_ARP_TIMEOUT
2930
2931		Timeout waiting for an ARP reply in milliseconds.
2932
2933		CONFIG_NFS_TIMEOUT
2934
2935		Timeout in milliseconds used in NFS protocol.
2936		If you encounter "ERROR: Cannot umount" in nfs command,
2937		try longer timeout such as
2938		#define CONFIG_NFS_TIMEOUT 10000UL
2939
2940- Command Interpreter:
2941		CONFIG_AUTO_COMPLETE
2942
2943		Enable auto completion of commands using TAB.
2944
2945		CONFIG_SYS_PROMPT_HUSH_PS2
2946
2947		This defines the secondary prompt string, which is
2948		printed when the command interpreter needs more input
2949		to complete a command. Usually "> ".
2950
2951	Note:
2952
2953		In the current implementation, the local variables
2954		space and global environment variables space are
2955		separated. Local variables are those you define by
2956		simply typing `name=value'. To access a local
2957		variable later on, you have write `$name' or
2958		`${name}'; to execute the contents of a variable
2959		directly type `$name' at the command prompt.
2960
2961		Global environment variables are those you use
2962		setenv/printenv to work with. To run a command stored
2963		in such a variable, you need to use the run command,
2964		and you must not use the '$' sign to access them.
2965
2966		To store commands and special characters in a
2967		variable, please use double quotation marks
2968		surrounding the whole text of the variable, instead
2969		of the backslashes before semicolons and special
2970		symbols.
2971
2972- Command Line Editing and History:
2973		CONFIG_CMDLINE_EDITING
2974
2975		Enable editing and History functions for interactive
2976		command line input operations
2977
2978- Default Environment:
2979		CONFIG_EXTRA_ENV_SETTINGS
2980
2981		Define this to contain any number of null terminated
2982		strings (variable = value pairs) that will be part of
2983		the default environment compiled into the boot image.
2984
2985		For example, place something like this in your
2986		board's config file:
2987
2988		#define CONFIG_EXTRA_ENV_SETTINGS \
2989			"myvar1=value1\0" \
2990			"myvar2=value2\0"
2991
2992		Warning: This method is based on knowledge about the
2993		internal format how the environment is stored by the
2994		U-Boot code. This is NOT an official, exported
2995		interface! Although it is unlikely that this format
2996		will change soon, there is no guarantee either.
2997		You better know what you are doing here.
2998
2999		Note: overly (ab)use of the default environment is
3000		discouraged. Make sure to check other ways to preset
3001		the environment like the "source" command or the
3002		boot command first.
3003
3004		CONFIG_ENV_VARS_UBOOT_CONFIG
3005
3006		Define this in order to add variables describing the
3007		U-Boot build configuration to the default environment.
3008		These will be named arch, cpu, board, vendor, and soc.
3009
3010		Enabling this option will cause the following to be defined:
3011
3012		- CONFIG_SYS_ARCH
3013		- CONFIG_SYS_CPU
3014		- CONFIG_SYS_BOARD
3015		- CONFIG_SYS_VENDOR
3016		- CONFIG_SYS_SOC
3017
3018		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
3019
3020		Define this in order to add variables describing certain
3021		run-time determined information about the hardware to the
3022		environment.  These will be named board_name, board_rev.
3023
3024		CONFIG_DELAY_ENVIRONMENT
3025
3026		Normally the environment is loaded when the board is
3027		initialised so that it is available to U-Boot. This inhibits
3028		that so that the environment is not available until
3029		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
3030		this is instead controlled by the value of
3031		/config/load-environment.
3032
3033- Parallel Flash support:
3034		CONFIG_SYS_NO_FLASH
3035
3036		Traditionally U-boot was run on systems with parallel NOR
3037		flash. This option is used to disable support for parallel NOR
3038		flash. This option should be defined if the board does not have
3039		parallel flash.
3040
3041		If this option is not defined one of the generic flash drivers
3042		(e.g.  CONFIG_FLASH_CFI_DRIVER or CONFIG_ST_SMI) must be
3043		selected or the board must provide an implementation of the
3044		flash API (see include/flash.h).
3045
3046- DataFlash Support:
3047		CONFIG_HAS_DATAFLASH
3048
3049		Defining this option enables DataFlash features and
3050		allows to read/write in Dataflash via the standard
3051		commands cp, md...
3052
3053- Serial Flash support
3054		CONFIG_CMD_SF
3055
3056		Defining this option enables SPI flash commands
3057		'sf probe/read/write/erase/update'.
3058
3059		Usage requires an initial 'probe' to define the serial
3060		flash parameters, followed by read/write/erase/update
3061		commands.
3062
3063		The following defaults may be provided by the platform
3064		to handle the common case when only a single serial
3065		flash is present on the system.
3066
3067		CONFIG_SF_DEFAULT_BUS		Bus identifier
3068		CONFIG_SF_DEFAULT_CS		Chip-select
3069		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
3070		CONFIG_SF_DEFAULT_SPEED		in Hz
3071
3072		CONFIG_CMD_SF_TEST
3073
3074		Define this option to include a destructive SPI flash
3075		test ('sf test').
3076
3077		CONFIG_SF_DUAL_FLASH		Dual flash memories
3078
3079		Define this option to use dual flash support where two flash
3080		memories can be connected with a given cs line.
3081		Currently Xilinx Zynq qspi supports these type of connections.
3082
3083- SystemACE Support:
3084		CONFIG_SYSTEMACE
3085
3086		Adding this option adds support for Xilinx SystemACE
3087		chips attached via some sort of local bus. The address
3088		of the chip must also be defined in the
3089		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
3090
3091		#define CONFIG_SYSTEMACE
3092		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
3093
3094		When SystemACE support is added, the "ace" device type
3095		becomes available to the fat commands, i.e. fatls.
3096
3097- TFTP Fixed UDP Port:
3098		CONFIG_TFTP_PORT
3099
3100		If this is defined, the environment variable tftpsrcp
3101		is used to supply the TFTP UDP source port value.
3102		If tftpsrcp isn't defined, the normal pseudo-random port
3103		number generator is used.
3104
3105		Also, the environment variable tftpdstp is used to supply
3106		the TFTP UDP destination port value.  If tftpdstp isn't
3107		defined, the normal port 69 is used.
3108
3109		The purpose for tftpsrcp is to allow a TFTP server to
3110		blindly start the TFTP transfer using the pre-configured
3111		target IP address and UDP port. This has the effect of
3112		"punching through" the (Windows XP) firewall, allowing
3113		the remainder of the TFTP transfer to proceed normally.
3114		A better solution is to properly configure the firewall,
3115		but sometimes that is not allowed.
3116
3117- Hashing support:
3118		CONFIG_CMD_HASH
3119
3120		This enables a generic 'hash' command which can produce
3121		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
3122
3123		CONFIG_HASH_VERIFY
3124
3125		Enable the hash verify command (hash -v). This adds to code
3126		size a little.
3127
3128		CONFIG_SHA1 - This option enables support of hashing using SHA1
3129		algorithm. The hash is calculated in software.
3130		CONFIG_SHA256 - This option enables support of hashing using
3131		SHA256 algorithm. The hash is calculated in software.
3132		CONFIG_SHA_HW_ACCEL - This option enables hardware acceleration
3133		for SHA1/SHA256 hashing.
3134		This affects the 'hash' command and also the
3135		hash_lookup_algo() function.
3136		CONFIG_SHA_PROG_HW_ACCEL - This option enables
3137		hardware-acceleration for SHA1/SHA256 progressive hashing.
3138		Data can be streamed in a block at a time and the hashing
3139		is performed in hardware.
3140
3141		Note: There is also a sha1sum command, which should perhaps
3142		be deprecated in favour of 'hash sha1'.
3143
3144- Freescale i.MX specific commands:
3145		CONFIG_CMD_HDMIDETECT
3146		This enables 'hdmidet' command which returns true if an
3147		HDMI monitor is detected.  This command is i.MX 6 specific.
3148
3149		CONFIG_CMD_BMODE
3150		This enables the 'bmode' (bootmode) command for forcing
3151		a boot from specific media.
3152
3153		This is useful for forcing the ROM's usb downloader to
3154		activate upon a watchdog reset which is nice when iterating
3155		on U-Boot.  Using the reset button or running bmode normal
3156		will set it back to normal.  This command currently
3157		supports i.MX53 and i.MX6.
3158
3159- Signing support:
3160		CONFIG_RSA
3161
3162		This enables the RSA algorithm used for FIT image verification
3163		in U-Boot. See doc/uImage.FIT/signature.txt for more information.
3164
3165		The Modular Exponentiation algorithm in RSA is implemented using
3166		driver model. So CONFIG_DM needs to be enabled by default for this
3167		library to function.
3168
3169		The signing part is build into mkimage regardless of this
3170		option. The software based modular exponentiation is built into
3171		mkimage irrespective of this option.
3172
3173- bootcount support:
3174		CONFIG_BOOTCOUNT_LIMIT
3175
3176		This enables the bootcounter support, see:
3177		http://www.denx.de/wiki/DULG/UBootBootCountLimit
3178
3179		CONFIG_AT91SAM9XE
3180		enable special bootcounter support on at91sam9xe based boards.
3181		CONFIG_BLACKFIN
3182		enable special bootcounter support on blackfin based boards.
3183		CONFIG_SOC_DA8XX
3184		enable special bootcounter support on da850 based boards.
3185		CONFIG_BOOTCOUNT_RAM
3186		enable support for the bootcounter in RAM
3187		CONFIG_BOOTCOUNT_I2C
3188		enable support for the bootcounter on an i2c (like RTC) device.
3189			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
3190			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
3191						    the bootcounter.
3192			CONFIG_BOOTCOUNT_ALEN = address len
3193
3194- Show boot progress:
3195		CONFIG_SHOW_BOOT_PROGRESS
3196
3197		Defining this option allows to add some board-
3198		specific code (calling a user-provided function
3199		"show_boot_progress(int)") that enables you to show
3200		the system's boot progress on some display (for
3201		example, some LED's) on your board. At the moment,
3202		the following checkpoints are implemented:
3203
3204
3205Legacy uImage format:
3206
3207  Arg	Where			When
3208    1	common/cmd_bootm.c	before attempting to boot an image
3209   -1	common/cmd_bootm.c	Image header has bad	 magic number
3210    2	common/cmd_bootm.c	Image header has correct magic number
3211   -2	common/cmd_bootm.c	Image header has bad	 checksum
3212    3	common/cmd_bootm.c	Image header has correct checksum
3213   -3	common/cmd_bootm.c	Image data   has bad	 checksum
3214    4	common/cmd_bootm.c	Image data   has correct checksum
3215   -4	common/cmd_bootm.c	Image is for unsupported architecture
3216    5	common/cmd_bootm.c	Architecture check OK
3217   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
3218    6	common/cmd_bootm.c	Image Type check OK
3219   -6	common/cmd_bootm.c	gunzip uncompression error
3220   -7	common/cmd_bootm.c	Unimplemented compression type
3221    7	common/cmd_bootm.c	Uncompression OK
3222    8	common/cmd_bootm.c	No uncompress/copy overwrite error
3223   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3224
3225    9	common/image.c		Start initial ramdisk verification
3226  -10	common/image.c		Ramdisk header has bad	   magic number
3227  -11	common/image.c		Ramdisk header has bad	   checksum
3228   10	common/image.c		Ramdisk header is OK
3229  -12	common/image.c		Ramdisk data   has bad	   checksum
3230   11	common/image.c		Ramdisk data   has correct checksum
3231   12	common/image.c		Ramdisk verification complete, start loading
3232  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3233   13	common/image.c		Start multifile image verification
3234   14	common/image.c		No initial ramdisk, no multifile, continue.
3235
3236   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3237
3238  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3239  -31	post/post.c		POST test failed, detected by post_output_backlog()
3240  -32	post/post.c		POST test failed, detected by post_run_single()
3241
3242   34	common/cmd_doc.c	before loading a Image from a DOC device
3243  -35	common/cmd_doc.c	Bad usage of "doc" command
3244   35	common/cmd_doc.c	correct usage of "doc" command
3245  -36	common/cmd_doc.c	No boot device
3246   36	common/cmd_doc.c	correct boot device
3247  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3248   37	common/cmd_doc.c	correct chip ID found, device available
3249  -38	common/cmd_doc.c	Read Error on boot device
3250   38	common/cmd_doc.c	reading Image header from DOC device OK
3251  -39	common/cmd_doc.c	Image header has bad magic number
3252   39	common/cmd_doc.c	Image header has correct magic number
3253  -40	common/cmd_doc.c	Error reading Image from DOC device
3254   40	common/cmd_doc.c	Image header has correct magic number
3255   41	common/cmd_ide.c	before loading a Image from a IDE device
3256  -42	common/cmd_ide.c	Bad usage of "ide" command
3257   42	common/cmd_ide.c	correct usage of "ide" command
3258  -43	common/cmd_ide.c	No boot device
3259   43	common/cmd_ide.c	boot device found
3260  -44	common/cmd_ide.c	Device not available
3261   44	common/cmd_ide.c	Device available
3262  -45	common/cmd_ide.c	wrong partition selected
3263   45	common/cmd_ide.c	partition selected
3264  -46	common/cmd_ide.c	Unknown partition table
3265   46	common/cmd_ide.c	valid partition table found
3266  -47	common/cmd_ide.c	Invalid partition type
3267   47	common/cmd_ide.c	correct partition type
3268  -48	common/cmd_ide.c	Error reading Image Header on boot device
3269   48	common/cmd_ide.c	reading Image Header from IDE device OK
3270  -49	common/cmd_ide.c	Image header has bad magic number
3271   49	common/cmd_ide.c	Image header has correct magic number
3272  -50	common/cmd_ide.c	Image header has bad	 checksum
3273   50	common/cmd_ide.c	Image header has correct checksum
3274  -51	common/cmd_ide.c	Error reading Image from IDE device
3275   51	common/cmd_ide.c	reading Image from IDE device OK
3276   52	common/cmd_nand.c	before loading a Image from a NAND device
3277  -53	common/cmd_nand.c	Bad usage of "nand" command
3278   53	common/cmd_nand.c	correct usage of "nand" command
3279  -54	common/cmd_nand.c	No boot device
3280   54	common/cmd_nand.c	boot device found
3281  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3282   55	common/cmd_nand.c	correct chip ID found, device available
3283  -56	common/cmd_nand.c	Error reading Image Header on boot device
3284   56	common/cmd_nand.c	reading Image Header from NAND device OK
3285  -57	common/cmd_nand.c	Image header has bad magic number
3286   57	common/cmd_nand.c	Image header has correct magic number
3287  -58	common/cmd_nand.c	Error reading Image from NAND device
3288   58	common/cmd_nand.c	reading Image from NAND device OK
3289
3290  -60	common/env_common.c	Environment has a bad CRC, using default
3291
3292   64	net/eth.c		starting with Ethernet configuration.
3293  -64	net/eth.c		no Ethernet found.
3294   65	net/eth.c		Ethernet found.
3295
3296  -80	common/cmd_net.c	usage wrong
3297   80	common/cmd_net.c	before calling net_loop()
3298  -81	common/cmd_net.c	some error in net_loop() occurred
3299   81	common/cmd_net.c	net_loop() back without error
3300  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3301   82	common/cmd_net.c	trying automatic boot
3302   83	common/cmd_net.c	running "source" command
3303  -83	common/cmd_net.c	some error in automatic boot or "source" command
3304   84	common/cmd_net.c	end without errors
3305
3306FIT uImage format:
3307
3308  Arg	Where			When
3309  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3310 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3311  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3312 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3313  102	common/cmd_bootm.c	Kernel unit name specified
3314 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3315  103	common/cmd_bootm.c	Found configuration node
3316  104	common/cmd_bootm.c	Got kernel subimage node offset
3317 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3318  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3319 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3320  106	common/cmd_bootm.c	Architecture check OK
3321 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3322  107	common/cmd_bootm.c	Kernel subimage type OK
3323 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3324  108	common/cmd_bootm.c	Got kernel subimage data/size
3325 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3326 -109	common/cmd_bootm.c	Can't get kernel subimage type
3327 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3328 -111	common/cmd_bootm.c	Can't get kernel subimage os
3329 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3330 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3331
3332  120	common/image.c		Start initial ramdisk verification
3333 -120	common/image.c		Ramdisk FIT image has incorrect format
3334  121	common/image.c		Ramdisk FIT image has correct format
3335  122	common/image.c		No ramdisk subimage unit name, using configuration
3336 -122	common/image.c		Can't get configuration for ramdisk subimage
3337  123	common/image.c		Ramdisk unit name specified
3338 -124	common/image.c		Can't get ramdisk subimage node offset
3339  125	common/image.c		Got ramdisk subimage node offset
3340 -125	common/image.c		Ramdisk subimage hash verification failed
3341  126	common/image.c		Ramdisk subimage hash verification OK
3342 -126	common/image.c		Ramdisk subimage for unsupported architecture
3343  127	common/image.c		Architecture check OK
3344 -127	common/image.c		Can't get ramdisk subimage data/size
3345  128	common/image.c		Got ramdisk subimage data/size
3346  129	common/image.c		Can't get ramdisk load address
3347 -129	common/image.c		Got ramdisk load address
3348
3349 -130	common/cmd_doc.c	Incorrect FIT image format
3350  131	common/cmd_doc.c	FIT image format OK
3351
3352 -140	common/cmd_ide.c	Incorrect FIT image format
3353  141	common/cmd_ide.c	FIT image format OK
3354
3355 -150	common/cmd_nand.c	Incorrect FIT image format
3356  151	common/cmd_nand.c	FIT image format OK
3357
3358- legacy image format:
3359		CONFIG_IMAGE_FORMAT_LEGACY
3360		enables the legacy image format support in U-Boot.
3361
3362		Default:
3363		enabled if CONFIG_FIT_SIGNATURE is not defined.
3364
3365		CONFIG_DISABLE_IMAGE_LEGACY
3366		disable the legacy image format
3367
3368		This define is introduced, as the legacy image format is
3369		enabled per default for backward compatibility.
3370
3371- FIT image support:
3372		CONFIG_FIT
3373		Enable support for the FIT uImage format.
3374
3375		CONFIG_FIT_BEST_MATCH
3376		When no configuration is explicitly selected, default to the
3377		one whose fdt's compatibility field best matches that of
3378		U-Boot itself. A match is considered "best" if it matches the
3379		most specific compatibility entry of U-Boot's fdt's root node.
3380		The order of entries in the configuration's fdt is ignored.
3381
3382		CONFIG_FIT_SIGNATURE
3383		This option enables signature verification of FIT uImages,
3384		using a hash signed and verified using RSA. If
3385		CONFIG_SHA_PROG_HW_ACCEL is defined, i.e support for progressive
3386		hashing is available using hardware, RSA library will use it.
3387		See doc/uImage.FIT/signature.txt for more details.
3388
3389		WARNING: When relying on signed FIT images with required
3390		signature check the legacy image format is default
3391		disabled. If a board need legacy image format support
3392		enable this through CONFIG_IMAGE_FORMAT_LEGACY
3393
3394		CONFIG_FIT_DISABLE_SHA256
3395		Supporting SHA256 hashes has quite an impact on binary size.
3396		For constrained systems sha256 hash support can be disabled
3397		with this option.
3398
3399- Standalone program support:
3400		CONFIG_STANDALONE_LOAD_ADDR
3401
3402		This option defines a board specific value for the
3403		address where standalone program gets loaded, thus
3404		overwriting the architecture dependent default
3405		settings.
3406
3407- Frame Buffer Address:
3408		CONFIG_FB_ADDR
3409
3410		Define CONFIG_FB_ADDR if you want to use specific
3411		address for frame buffer.  This is typically the case
3412		when using a graphics controller has separate video
3413		memory.  U-Boot will then place the frame buffer at
3414		the given address instead of dynamically reserving it
3415		in system RAM by calling lcd_setmem(), which grabs
3416		the memory for the frame buffer depending on the
3417		configured panel size.
3418
3419		Please see board_init_f function.
3420
3421- Automatic software updates via TFTP server
3422		CONFIG_UPDATE_TFTP
3423		CONFIG_UPDATE_TFTP_CNT_MAX
3424		CONFIG_UPDATE_TFTP_MSEC_MAX
3425
3426		These options enable and control the auto-update feature;
3427		for a more detailed description refer to doc/README.update.
3428
3429- MTD Support (mtdparts command, UBI support)
3430		CONFIG_MTD_DEVICE
3431
3432		Adds the MTD device infrastructure from the Linux kernel.
3433		Needed for mtdparts command support.
3434
3435		CONFIG_MTD_PARTITIONS
3436
3437		Adds the MTD partitioning infrastructure from the Linux
3438		kernel. Needed for UBI support.
3439
3440- UBI support
3441		CONFIG_CMD_UBI
3442
3443		Adds commands for interacting with MTD partitions formatted
3444		with the UBI flash translation layer
3445
3446		Requires also defining CONFIG_RBTREE
3447
3448		CONFIG_UBI_SILENCE_MSG
3449
3450		Make the verbose messages from UBI stop printing.  This leaves
3451		warnings and errors enabled.
3452
3453
3454		CONFIG_MTD_UBI_WL_THRESHOLD
3455		This parameter defines the maximum difference between the highest
3456		erase counter value and the lowest erase counter value of eraseblocks
3457		of UBI devices. When this threshold is exceeded, UBI starts performing
3458		wear leveling by means of moving data from eraseblock with low erase
3459		counter to eraseblocks with high erase counter.
3460
3461		The default value should be OK for SLC NAND flashes, NOR flashes and
3462		other flashes which have eraseblock life-cycle 100000 or more.
3463		However, in case of MLC NAND flashes which typically have eraseblock
3464		life-cycle less than 10000, the threshold should be lessened (e.g.,
3465		to 128 or 256, although it does not have to be power of 2).
3466
3467		default: 4096
3468
3469		CONFIG_MTD_UBI_BEB_LIMIT
3470		This option specifies the maximum bad physical eraseblocks UBI
3471		expects on the MTD device (per 1024 eraseblocks). If the
3472		underlying flash does not admit of bad eraseblocks (e.g. NOR
3473		flash), this value is ignored.
3474
3475		NAND datasheets often specify the minimum and maximum NVM
3476		(Number of Valid Blocks) for the flashes' endurance lifetime.
3477		The maximum expected bad eraseblocks per 1024 eraseblocks
3478		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
3479		which gives 20 for most NANDs (MaxNVB is basically the total
3480		count of eraseblocks on the chip).
3481
3482		To put it differently, if this value is 20, UBI will try to
3483		reserve about 1.9% of physical eraseblocks for bad blocks
3484		handling. And that will be 1.9% of eraseblocks on the entire
3485		NAND chip, not just the MTD partition UBI attaches. This means
3486		that if you have, say, a NAND flash chip admits maximum 40 bad
3487		eraseblocks, and it is split on two MTD partitions of the same
3488		size, UBI will reserve 40 eraseblocks when attaching a
3489		partition.
3490
3491		default: 20
3492
3493		CONFIG_MTD_UBI_FASTMAP
3494		Fastmap is a mechanism which allows attaching an UBI device
3495		in nearly constant time. Instead of scanning the whole MTD device it
3496		only has to locate a checkpoint (called fastmap) on the device.
3497		The on-flash fastmap contains all information needed to attach
3498		the device. Using fastmap makes only sense on large devices where
3499		attaching by scanning takes long. UBI will not automatically install
3500		a fastmap on old images, but you can set the UBI parameter
3501		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
3502		that fastmap-enabled images are still usable with UBI implementations
3503		without	fastmap support. On typical flash devices the whole fastmap
3504		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
3505
3506		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
3507		Set this parameter to enable fastmap automatically on images
3508		without a fastmap.
3509		default: 0
3510
3511- UBIFS support
3512		CONFIG_CMD_UBIFS
3513
3514		Adds commands for interacting with UBI volumes formatted as
3515		UBIFS.  UBIFS is read-only in u-boot.
3516
3517		Requires UBI support as well as CONFIG_LZO
3518
3519		CONFIG_UBIFS_SILENCE_MSG
3520
3521		Make the verbose messages from UBIFS stop printing.  This leaves
3522		warnings and errors enabled.
3523
3524- SPL framework
3525		CONFIG_SPL
3526		Enable building of SPL globally.
3527
3528		CONFIG_SPL_LDSCRIPT
3529		LDSCRIPT for linking the SPL binary.
3530
3531		CONFIG_SPL_MAX_FOOTPRINT
3532		Maximum size in memory allocated to the SPL, BSS included.
3533		When defined, the linker checks that the actual memory
3534		used by SPL from _start to __bss_end does not exceed it.
3535		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3536		must not be both defined at the same time.
3537
3538		CONFIG_SPL_MAX_SIZE
3539		Maximum size of the SPL image (text, data, rodata, and
3540		linker lists sections), BSS excluded.
3541		When defined, the linker checks that the actual size does
3542		not exceed it.
3543
3544		CONFIG_SPL_TEXT_BASE
3545		TEXT_BASE for linking the SPL binary.
3546
3547		CONFIG_SPL_RELOC_TEXT_BASE
3548		Address to relocate to.  If unspecified, this is equal to
3549		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3550
3551		CONFIG_SPL_BSS_START_ADDR
3552		Link address for the BSS within the SPL binary.
3553
3554		CONFIG_SPL_BSS_MAX_SIZE
3555		Maximum size in memory allocated to the SPL BSS.
3556		When defined, the linker checks that the actual memory used
3557		by SPL from __bss_start to __bss_end does not exceed it.
3558		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3559		must not be both defined at the same time.
3560
3561		CONFIG_SPL_STACK
3562		Adress of the start of the stack SPL will use
3563
3564		CONFIG_SPL_PANIC_ON_RAW_IMAGE
3565		When defined, SPL will panic() if the image it has
3566		loaded does not have a signature.
3567		Defining this is useful when code which loads images
3568		in SPL cannot guarantee that absolutely all read errors
3569		will be caught.
3570		An example is the LPC32XX MLC NAND driver, which will
3571		consider that a completely unreadable NAND block is bad,
3572		and thus should be skipped silently.
3573
3574		CONFIG_SPL_RELOC_STACK
3575		Adress of the start of the stack SPL will use after
3576		relocation.  If unspecified, this is equal to
3577		CONFIG_SPL_STACK.
3578
3579		CONFIG_SYS_SPL_MALLOC_START
3580		Starting address of the malloc pool used in SPL.
3581
3582		CONFIG_SYS_SPL_MALLOC_SIZE
3583		The size of the malloc pool used in SPL.
3584
3585		CONFIG_SPL_FRAMEWORK
3586		Enable the SPL framework under common/.  This framework
3587		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3588		NAND loading of the Linux Kernel.
3589
3590		CONFIG_SPL_OS_BOOT
3591		Enable booting directly to an OS from SPL.
3592		See also: doc/README.falcon
3593
3594		CONFIG_SPL_DISPLAY_PRINT
3595		For ARM, enable an optional function to print more information
3596		about the running system.
3597
3598		CONFIG_SPL_INIT_MINIMAL
3599		Arch init code should be built for a very small image
3600
3601		CONFIG_SPL_LIBCOMMON_SUPPORT
3602		Support for common/libcommon.o in SPL binary
3603
3604		CONFIG_SPL_LIBDISK_SUPPORT
3605		Support for disk/libdisk.o in SPL binary
3606
3607		CONFIG_SPL_I2C_SUPPORT
3608		Support for drivers/i2c/libi2c.o in SPL binary
3609
3610		CONFIG_SPL_GPIO_SUPPORT
3611		Support for drivers/gpio/libgpio.o in SPL binary
3612
3613		CONFIG_SPL_MMC_SUPPORT
3614		Support for drivers/mmc/libmmc.o in SPL binary
3615
3616		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3617		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3618		Address and partition on the MMC to load U-Boot from
3619		when the MMC is being used in raw mode.
3620
3621		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3622		Partition on the MMC to load U-Boot from when the MMC is being
3623		used in raw mode
3624
3625		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3626		Sector to load kernel uImage from when MMC is being
3627		used in raw mode (for Falcon mode)
3628
3629		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3630		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3631		Sector and number of sectors to load kernel argument
3632		parameters from when MMC is being used in raw mode
3633		(for falcon mode)
3634
3635		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3636		Partition on the MMC to load U-Boot from when the MMC is being
3637		used in fs mode
3638
3639		CONFIG_SPL_FAT_SUPPORT
3640		Support for fs/fat/libfat.o in SPL binary
3641
3642		CONFIG_SPL_EXT_SUPPORT
3643		Support for EXT filesystem in SPL binary
3644
3645		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3646		Filename to read to load U-Boot when reading from filesystem
3647
3648		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3649		Filename to read to load kernel uImage when reading
3650		from filesystem (for Falcon mode)
3651
3652		CONFIG_SPL_FS_LOAD_ARGS_NAME
3653		Filename to read to load kernel argument parameters
3654		when reading from filesystem (for Falcon mode)
3655
3656		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3657		Set this for NAND SPL on PPC mpc83xx targets, so that
3658		start.S waits for the rest of the SPL to load before
3659		continuing (the hardware starts execution after just
3660		loading the first page rather than the full 4K).
3661
3662		CONFIG_SPL_SKIP_RELOCATE
3663		Avoid SPL relocation
3664
3665		CONFIG_SPL_NAND_BASE
3666		Include nand_base.c in the SPL.  Requires
3667		CONFIG_SPL_NAND_DRIVERS.
3668
3669		CONFIG_SPL_NAND_DRIVERS
3670		SPL uses normal NAND drivers, not minimal drivers.
3671
3672		CONFIG_SPL_NAND_ECC
3673		Include standard software ECC in the SPL
3674
3675		CONFIG_SPL_NAND_SIMPLE
3676		Support for NAND boot using simple NAND drivers that
3677		expose the cmd_ctrl() interface.
3678
3679		CONFIG_SPL_MTD_SUPPORT
3680		Support for the MTD subsystem within SPL.  Useful for
3681		environment on NAND support within SPL.
3682
3683		CONFIG_SPL_NAND_RAW_ONLY
3684		Support to boot only raw u-boot.bin images. Use this only
3685		if you need to save space.
3686
3687		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3688		Set for the SPL on PPC mpc8xxx targets, support for
3689		drivers/ddr/fsl/libddr.o in SPL binary.
3690
3691		CONFIG_SPL_COMMON_INIT_DDR
3692		Set for common ddr init with serial presence detect in
3693		SPL binary.
3694
3695		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3696		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3697		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3698		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3699		CONFIG_SYS_NAND_ECCBYTES
3700		Defines the size and behavior of the NAND that SPL uses
3701		to read U-Boot
3702
3703		CONFIG_SPL_NAND_BOOT
3704		Add support NAND boot
3705
3706		CONFIG_SYS_NAND_U_BOOT_OFFS
3707		Location in NAND to read U-Boot from
3708
3709		CONFIG_SYS_NAND_U_BOOT_DST
3710		Location in memory to load U-Boot to
3711
3712		CONFIG_SYS_NAND_U_BOOT_SIZE
3713		Size of image to load
3714
3715		CONFIG_SYS_NAND_U_BOOT_START
3716		Entry point in loaded image to jump to
3717
3718		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3719		Define this if you need to first read the OOB and then the
3720		data. This is used, for example, on davinci platforms.
3721
3722		CONFIG_SPL_OMAP3_ID_NAND
3723		Support for an OMAP3-specific set of functions to return the
3724		ID and MFR of the first attached NAND chip, if present.
3725
3726		CONFIG_SPL_SERIAL_SUPPORT
3727		Support for drivers/serial/libserial.o in SPL binary
3728
3729		CONFIG_SPL_SPI_FLASH_SUPPORT
3730		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3731
3732		CONFIG_SPL_SPI_SUPPORT
3733		Support for drivers/spi/libspi.o in SPL binary
3734
3735		CONFIG_SPL_RAM_DEVICE
3736		Support for running image already present in ram, in SPL binary
3737
3738		CONFIG_SPL_LIBGENERIC_SUPPORT
3739		Support for lib/libgeneric.o in SPL binary
3740
3741		CONFIG_SPL_ENV_SUPPORT
3742		Support for the environment operating in SPL binary
3743
3744		CONFIG_SPL_NET_SUPPORT
3745		Support for the net/libnet.o in SPL binary.
3746		It conflicts with SPL env from storage medium specified by
3747		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3748
3749		CONFIG_SPL_PAD_TO
3750		Image offset to which the SPL should be padded before appending
3751		the SPL payload. By default, this is defined as
3752		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3753		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3754		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3755
3756		CONFIG_SPL_TARGET
3757		Final target image containing SPL and payload.  Some SPLs
3758		use an arch-specific makefile fragment instead, for
3759		example if more than one image needs to be produced.
3760
3761		CONFIG_FIT_SPL_PRINT
3762		Printing information about a FIT image adds quite a bit of
3763		code to SPL. So this is normally disabled in SPL. Use this
3764		option to re-enable it. This will affect the output of the
3765		bootm command when booting a FIT image.
3766
3767- TPL framework
3768		CONFIG_TPL
3769		Enable building of TPL globally.
3770
3771		CONFIG_TPL_PAD_TO
3772		Image offset to which the TPL should be padded before appending
3773		the TPL payload. By default, this is defined as
3774		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3775		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3776		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3777
3778Modem Support:
3779--------------
3780
3781[so far only for SMDK2400 boards]
3782
3783- Modem support enable:
3784		CONFIG_MODEM_SUPPORT
3785
3786- RTS/CTS Flow control enable:
3787		CONFIG_HWFLOW
3788
3789- Modem debug support:
3790		CONFIG_MODEM_SUPPORT_DEBUG
3791
3792		Enables debugging stuff (char screen[1024], dbg())
3793		for modem support. Useful only with BDI2000.
3794
3795- Interrupt support (PPC):
3796
3797		There are common interrupt_init() and timer_interrupt()
3798		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3799		for CPU specific initialization. interrupt_init_cpu()
3800		should set decrementer_count to appropriate value. If
3801		CPU resets decrementer automatically after interrupt
3802		(ppc4xx) it should set decrementer_count to zero.
3803		timer_interrupt() calls timer_interrupt_cpu() for CPU
3804		specific handling. If board has watchdog / status_led
3805		/ other_activity_monitor it works automatically from
3806		general timer_interrupt().
3807
3808- General:
3809
3810		In the target system modem support is enabled when a
3811		specific key (key combination) is pressed during
3812		power-on. Otherwise U-Boot will boot normally
3813		(autoboot). The key_pressed() function is called from
3814		board_init(). Currently key_pressed() is a dummy
3815		function, returning 1 and thus enabling modem
3816		initialization.
3817
3818		If there are no modem init strings in the
3819		environment, U-Boot proceed to autoboot; the
3820		previous output (banner, info printfs) will be
3821		suppressed, though.
3822
3823		See also: doc/README.Modem
3824
3825Board initialization settings:
3826------------------------------
3827
3828During Initialization u-boot calls a number of board specific functions
3829to allow the preparation of board specific prerequisites, e.g. pin setup
3830before drivers are initialized. To enable these callbacks the
3831following configuration macros have to be defined. Currently this is
3832architecture specific, so please check arch/your_architecture/lib/board.c
3833typically in board_init_f() and board_init_r().
3834
3835- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3836- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3837- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3838- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3839
3840Configuration Settings:
3841-----------------------
3842
3843- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3844		Optionally it can be defined to support 64-bit memory commands.
3845
3846- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3847		undefine this when you're short of memory.
3848
3849- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3850		width of the commands listed in the 'help' command output.
3851
3852- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3853		prompt for user input.
3854
3855- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3856
3857- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3858
3859- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3860
3861- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3862		the application (usually a Linux kernel) when it is
3863		booted
3864
3865- CONFIG_SYS_BAUDRATE_TABLE:
3866		List of legal baudrate settings for this board.
3867
3868- CONFIG_SYS_CONSOLE_INFO_QUIET
3869		Suppress display of console information at boot.
3870
3871- CONFIG_SYS_CONSOLE_IS_IN_ENV
3872		If the board specific function
3873			extern int overwrite_console (void);
3874		returns 1, the stdin, stderr and stdout are switched to the
3875		serial port, else the settings in the environment are used.
3876
3877- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3878		Enable the call to overwrite_console().
3879
3880- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3881		Enable overwrite of previous console environment settings.
3882
3883- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3884		Begin and End addresses of the area used by the
3885		simple memory test.
3886
3887- CONFIG_SYS_ALT_MEMTEST:
3888		Enable an alternate, more extensive memory test.
3889
3890- CONFIG_SYS_MEMTEST_SCRATCH:
3891		Scratch address used by the alternate memory test
3892		You only need to set this if address zero isn't writeable
3893
3894- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3895		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3896		this specified memory area will get subtracted from the top
3897		(end) of RAM and won't get "touched" at all by U-Boot. By
3898		fixing up gd->ram_size the Linux kernel should gets passed
3899		the now "corrected" memory size and won't touch it either.
3900		This should work for arch/ppc and arch/powerpc. Only Linux
3901		board ports in arch/powerpc with bootwrapper support that
3902		recalculate the memory size from the SDRAM controller setup
3903		will have to get fixed in Linux additionally.
3904
3905		This option can be used as a workaround for the 440EPx/GRx
3906		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3907		be touched.
3908
3909		WARNING: Please make sure that this value is a multiple of
3910		the Linux page size (normally 4k). If this is not the case,
3911		then the end address of the Linux memory will be located at a
3912		non page size aligned address and this could cause major
3913		problems.
3914
3915- CONFIG_SYS_LOADS_BAUD_CHANGE:
3916		Enable temporary baudrate change while serial download
3917
3918- CONFIG_SYS_SDRAM_BASE:
3919		Physical start address of SDRAM. _Must_ be 0 here.
3920
3921- CONFIG_SYS_MBIO_BASE:
3922		Physical start address of Motherboard I/O (if using a
3923		Cogent motherboard)
3924
3925- CONFIG_SYS_FLASH_BASE:
3926		Physical start address of Flash memory.
3927
3928- CONFIG_SYS_MONITOR_BASE:
3929		Physical start address of boot monitor code (set by
3930		make config files to be same as the text base address
3931		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3932		CONFIG_SYS_FLASH_BASE when booting from flash.
3933
3934- CONFIG_SYS_MONITOR_LEN:
3935		Size of memory reserved for monitor code, used to
3936		determine _at_compile_time_ (!) if the environment is
3937		embedded within the U-Boot image, or in a separate
3938		flash sector.
3939
3940- CONFIG_SYS_MALLOC_LEN:
3941		Size of DRAM reserved for malloc() use.
3942
3943- CONFIG_SYS_MALLOC_F_LEN
3944		Size of the malloc() pool for use before relocation. If
3945		this is defined, then a very simple malloc() implementation
3946		will become available before relocation. The address is just
3947		below the global data, and the stack is moved down to make
3948		space.
3949
3950		This feature allocates regions with increasing addresses
3951		within the region. calloc() is supported, but realloc()
3952		is not available. free() is supported but does nothing.
3953		The memory will be freed (or in fact just forgotten) when
3954		U-Boot relocates itself.
3955
3956		Pre-relocation malloc() is only supported on ARM and sandbox
3957		at present but is fairly easy to enable for other archs.
3958
3959- CONFIG_SYS_MALLOC_SIMPLE
3960		Provides a simple and small malloc() and calloc() for those
3961		boards which do not use the full malloc in SPL (which is
3962		enabled with CONFIG_SYS_SPL_MALLOC_START).
3963
3964- CONFIG_SYS_NONCACHED_MEMORY:
3965		Size of non-cached memory area. This area of memory will be
3966		typically located right below the malloc() area and mapped
3967		uncached in the MMU. This is useful for drivers that would
3968		otherwise require a lot of explicit cache maintenance. For
3969		some drivers it's also impossible to properly maintain the
3970		cache. For example if the regions that need to be flushed
3971		are not a multiple of the cache-line size, *and* padding
3972		cannot be allocated between the regions to align them (i.e.
3973		if the HW requires a contiguous array of regions, and the
3974		size of each region is not cache-aligned), then a flush of
3975		one region may result in overwriting data that hardware has
3976		written to another region in the same cache-line. This can
3977		happen for example in network drivers where descriptors for
3978		buffers are typically smaller than the CPU cache-line (e.g.
3979		16 bytes vs. 32 or 64 bytes).
3980
3981		Non-cached memory is only supported on 32-bit ARM at present.
3982
3983- CONFIG_SYS_BOOTM_LEN:
3984		Normally compressed uImages are limited to an
3985		uncompressed size of 8 MBytes. If this is not enough,
3986		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3987		to adjust this setting to your needs.
3988
3989- CONFIG_SYS_BOOTMAPSZ:
3990		Maximum size of memory mapped by the startup code of
3991		the Linux kernel; all data that must be processed by
3992		the Linux kernel (bd_info, boot arguments, FDT blob if
3993		used) must be put below this limit, unless "bootm_low"
3994		environment variable is defined and non-zero. In such case
3995		all data for the Linux kernel must be between "bootm_low"
3996		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3997		variable "bootm_mapsize" will override the value of
3998		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3999		then the value in "bootm_size" will be used instead.
4000
4001- CONFIG_SYS_BOOT_RAMDISK_HIGH:
4002		Enable initrd_high functionality.  If defined then the
4003		initrd_high feature is enabled and the bootm ramdisk subcommand
4004		is enabled.
4005
4006- CONFIG_SYS_BOOT_GET_CMDLINE:
4007		Enables allocating and saving kernel cmdline in space between
4008		"bootm_low" and "bootm_low" + BOOTMAPSZ.
4009
4010- CONFIG_SYS_BOOT_GET_KBD:
4011		Enables allocating and saving a kernel copy of the bd_info in
4012		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
4013
4014- CONFIG_SYS_MAX_FLASH_BANKS:
4015		Max number of Flash memory banks
4016
4017- CONFIG_SYS_MAX_FLASH_SECT:
4018		Max number of sectors on a Flash chip
4019
4020- CONFIG_SYS_FLASH_ERASE_TOUT:
4021		Timeout for Flash erase operations (in ms)
4022
4023- CONFIG_SYS_FLASH_WRITE_TOUT:
4024		Timeout for Flash write operations (in ms)
4025
4026- CONFIG_SYS_FLASH_LOCK_TOUT
4027		Timeout for Flash set sector lock bit operation (in ms)
4028
4029- CONFIG_SYS_FLASH_UNLOCK_TOUT
4030		Timeout for Flash clear lock bits operation (in ms)
4031
4032- CONFIG_SYS_FLASH_PROTECTION
4033		If defined, hardware flash sectors protection is used
4034		instead of U-Boot software protection.
4035
4036- CONFIG_SYS_DIRECT_FLASH_TFTP:
4037
4038		Enable TFTP transfers directly to flash memory;
4039		without this option such a download has to be
4040		performed in two steps: (1) download to RAM, and (2)
4041		copy from RAM to flash.
4042
4043		The two-step approach is usually more reliable, since
4044		you can check if the download worked before you erase
4045		the flash, but in some situations (when system RAM is
4046		too limited to allow for a temporary copy of the
4047		downloaded image) this option may be very useful.
4048
4049- CONFIG_SYS_FLASH_CFI:
4050		Define if the flash driver uses extra elements in the
4051		common flash structure for storing flash geometry.
4052
4053- CONFIG_FLASH_CFI_DRIVER
4054		This option also enables the building of the cfi_flash driver
4055		in the drivers directory
4056
4057- CONFIG_FLASH_CFI_MTD
4058		This option enables the building of the cfi_mtd driver
4059		in the drivers directory. The driver exports CFI flash
4060		to the MTD layer.
4061
4062- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
4063		Use buffered writes to flash.
4064
4065- CONFIG_FLASH_SPANSION_S29WS_N
4066		s29ws-n MirrorBit flash has non-standard addresses for buffered
4067		write commands.
4068
4069- CONFIG_SYS_FLASH_QUIET_TEST
4070		If this option is defined, the common CFI flash doesn't
4071		print it's warning upon not recognized FLASH banks. This
4072		is useful, if some of the configured banks are only
4073		optionally available.
4074
4075- CONFIG_FLASH_SHOW_PROGRESS
4076		If defined (must be an integer), print out countdown
4077		digits and dots.  Recommended value: 45 (9..1) for 80
4078		column displays, 15 (3..1) for 40 column displays.
4079
4080- CONFIG_FLASH_VERIFY
4081		If defined, the content of the flash (destination) is compared
4082		against the source after the write operation. An error message
4083		will be printed when the contents are not identical.
4084		Please note that this option is useless in nearly all cases,
4085		since such flash programming errors usually are detected earlier
4086		while unprotecting/erasing/programming. Please only enable
4087		this option if you really know what you are doing.
4088
4089- CONFIG_SYS_RX_ETH_BUFFER:
4090		Defines the number of Ethernet receive buffers. On some
4091		Ethernet controllers it is recommended to set this value
4092		to 8 or even higher (EEPRO100 or 405 EMAC), since all
4093		buffers can be full shortly after enabling the interface
4094		on high Ethernet traffic.
4095		Defaults to 4 if not defined.
4096
4097- CONFIG_ENV_MAX_ENTRIES
4098
4099	Maximum number of entries in the hash table that is used
4100	internally to store the environment settings. The default
4101	setting is supposed to be generous and should work in most
4102	cases. This setting can be used to tune behaviour; see
4103	lib/hashtable.c for details.
4104
4105- CONFIG_ENV_FLAGS_LIST_DEFAULT
4106- CONFIG_ENV_FLAGS_LIST_STATIC
4107	Enable validation of the values given to environment variables when
4108	calling env set.  Variables can be restricted to only decimal,
4109	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
4110	the variables can also be restricted to IP address or MAC address.
4111
4112	The format of the list is:
4113		type_attribute = [s|d|x|b|i|m]
4114		access_attribute = [a|r|o|c]
4115		attributes = type_attribute[access_attribute]
4116		entry = variable_name[:attributes]
4117		list = entry[,list]
4118
4119	The type attributes are:
4120		s - String (default)
4121		d - Decimal
4122		x - Hexadecimal
4123		b - Boolean ([1yYtT|0nNfF])
4124		i - IP address
4125		m - MAC address
4126
4127	The access attributes are:
4128		a - Any (default)
4129		r - Read-only
4130		o - Write-once
4131		c - Change-default
4132
4133	- CONFIG_ENV_FLAGS_LIST_DEFAULT
4134		Define this to a list (string) to define the ".flags"
4135		environment variable in the default or embedded environment.
4136
4137	- CONFIG_ENV_FLAGS_LIST_STATIC
4138		Define this to a list (string) to define validation that
4139		should be done if an entry is not found in the ".flags"
4140		environment variable.  To override a setting in the static
4141		list, simply add an entry for the same variable name to the
4142		".flags" variable.
4143
4144	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
4145	regular expression. This allows multiple variables to define the same
4146	flags without explicitly listing them for each variable.
4147
4148- CONFIG_ENV_ACCESS_IGNORE_FORCE
4149	If defined, don't allow the -f switch to env set override variable
4150	access flags.
4151
4152- CONFIG_SYS_GENERIC_BOARD
4153	This selects the architecture-generic board system instead of the
4154	architecture-specific board files. It is intended to move boards
4155	to this new framework over time. Defining this will disable the
4156	arch/foo/lib/board.c file and use common/board_f.c and
4157	common/board_r.c instead. To use this option your architecture
4158	must support it (i.e. must select HAVE_GENERIC_BOARD in arch/Kconfig).
4159	If you find problems enabling this option on your board please report
4160	the problem and send patches!
4161
4162- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
4163	This is set by OMAP boards for the max time that reset should
4164	be asserted. See doc/README.omap-reset-time for details on how
4165	the value can be calculated on a given board.
4166
4167- CONFIG_USE_STDINT
4168	If stdint.h is available with your toolchain you can define this
4169	option to enable it. You can provide option 'USE_STDINT=1' when
4170	building U-Boot to enable this.
4171
4172The following definitions that deal with the placement and management
4173of environment data (variable area); in general, we support the
4174following configurations:
4175
4176- CONFIG_BUILD_ENVCRC:
4177
4178	Builds up envcrc with the target environment so that external utils
4179	may easily extract it and embed it in final U-Boot images.
4180
4181- CONFIG_ENV_IS_IN_FLASH:
4182
4183	Define this if the environment is in flash memory.
4184
4185	a) The environment occupies one whole flash sector, which is
4186	   "embedded" in the text segment with the U-Boot code. This
4187	   happens usually with "bottom boot sector" or "top boot
4188	   sector" type flash chips, which have several smaller
4189	   sectors at the start or the end. For instance, such a
4190	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
4191	   such a case you would place the environment in one of the
4192	   4 kB sectors - with U-Boot code before and after it. With
4193	   "top boot sector" type flash chips, you would put the
4194	   environment in one of the last sectors, leaving a gap
4195	   between U-Boot and the environment.
4196
4197	- CONFIG_ENV_OFFSET:
4198
4199	   Offset of environment data (variable area) to the
4200	   beginning of flash memory; for instance, with bottom boot
4201	   type flash chips the second sector can be used: the offset
4202	   for this sector is given here.
4203
4204	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
4205
4206	- CONFIG_ENV_ADDR:
4207
4208	   This is just another way to specify the start address of
4209	   the flash sector containing the environment (instead of
4210	   CONFIG_ENV_OFFSET).
4211
4212	- CONFIG_ENV_SECT_SIZE:
4213
4214	   Size of the sector containing the environment.
4215
4216
4217	b) Sometimes flash chips have few, equal sized, BIG sectors.
4218	   In such a case you don't want to spend a whole sector for
4219	   the environment.
4220
4221	- CONFIG_ENV_SIZE:
4222
4223	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
4224	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
4225	   of this flash sector for the environment. This saves
4226	   memory for the RAM copy of the environment.
4227
4228	   It may also save flash memory if you decide to use this
4229	   when your environment is "embedded" within U-Boot code,
4230	   since then the remainder of the flash sector could be used
4231	   for U-Boot code. It should be pointed out that this is
4232	   STRONGLY DISCOURAGED from a robustness point of view:
4233	   updating the environment in flash makes it always
4234	   necessary to erase the WHOLE sector. If something goes
4235	   wrong before the contents has been restored from a copy in
4236	   RAM, your target system will be dead.
4237
4238	- CONFIG_ENV_ADDR_REDUND
4239	  CONFIG_ENV_SIZE_REDUND
4240
4241	   These settings describe a second storage area used to hold
4242	   a redundant copy of the environment data, so that there is
4243	   a valid backup copy in case there is a power failure during
4244	   a "saveenv" operation.
4245
4246BE CAREFUL! Any changes to the flash layout, and some changes to the
4247source code will make it necessary to adapt <board>/u-boot.lds*
4248accordingly!
4249
4250
4251- CONFIG_ENV_IS_IN_NVRAM:
4252
4253	Define this if you have some non-volatile memory device
4254	(NVRAM, battery buffered SRAM) which you want to use for the
4255	environment.
4256
4257	- CONFIG_ENV_ADDR:
4258	- CONFIG_ENV_SIZE:
4259
4260	  These two #defines are used to determine the memory area you
4261	  want to use for environment. It is assumed that this memory
4262	  can just be read and written to, without any special
4263	  provision.
4264
4265BE CAREFUL! The first access to the environment happens quite early
4266in U-Boot initialization (when we try to get the setting of for the
4267console baudrate). You *MUST* have mapped your NVRAM area then, or
4268U-Boot will hang.
4269
4270Please note that even with NVRAM we still use a copy of the
4271environment in RAM: we could work on NVRAM directly, but we want to
4272keep settings there always unmodified except somebody uses "saveenv"
4273to save the current settings.
4274
4275
4276- CONFIG_ENV_IS_IN_EEPROM:
4277
4278	Use this if you have an EEPROM or similar serial access
4279	device and a driver for it.
4280
4281	- CONFIG_ENV_OFFSET:
4282	- CONFIG_ENV_SIZE:
4283
4284	  These two #defines specify the offset and size of the
4285	  environment area within the total memory of your EEPROM.
4286
4287	- CONFIG_SYS_I2C_EEPROM_ADDR:
4288	  If defined, specified the chip address of the EEPROM device.
4289	  The default address is zero.
4290
4291	- CONFIG_SYS_I2C_EEPROM_BUS:
4292	  If defined, specified the i2c bus of the EEPROM device.
4293
4294	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
4295	  If defined, the number of bits used to address bytes in a
4296	  single page in the EEPROM device.  A 64 byte page, for example
4297	  would require six bits.
4298
4299	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
4300	  If defined, the number of milliseconds to delay between
4301	  page writes.	The default is zero milliseconds.
4302
4303	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
4304	  The length in bytes of the EEPROM memory array address.  Note
4305	  that this is NOT the chip address length!
4306
4307	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
4308	  EEPROM chips that implement "address overflow" are ones
4309	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
4310	  address and the extra bits end up in the "chip address" bit
4311	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
4312	  byte chips.
4313
4314	  Note that we consider the length of the address field to
4315	  still be one byte because the extra address bits are hidden
4316	  in the chip address.
4317
4318	- CONFIG_SYS_EEPROM_SIZE:
4319	  The size in bytes of the EEPROM device.
4320
4321	- CONFIG_ENV_EEPROM_IS_ON_I2C
4322	  define this, if you have I2C and SPI activated, and your
4323	  EEPROM, which holds the environment, is on the I2C bus.
4324
4325	- CONFIG_I2C_ENV_EEPROM_BUS
4326	  if you have an Environment on an EEPROM reached over
4327	  I2C muxes, you can define here, how to reach this
4328	  EEPROM. For example:
4329
4330	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
4331
4332	  EEPROM which holds the environment, is reached over
4333	  a pca9547 i2c mux with address 0x70, channel 3.
4334
4335- CONFIG_ENV_IS_IN_DATAFLASH:
4336
4337	Define this if you have a DataFlash memory device which you
4338	want to use for the environment.
4339
4340	- CONFIG_ENV_OFFSET:
4341	- CONFIG_ENV_ADDR:
4342	- CONFIG_ENV_SIZE:
4343
4344	  These three #defines specify the offset and size of the
4345	  environment area within the total memory of your DataFlash placed
4346	  at the specified address.
4347
4348- CONFIG_ENV_IS_IN_SPI_FLASH:
4349
4350	Define this if you have a SPI Flash memory device which you
4351	want to use for the environment.
4352
4353	- CONFIG_ENV_OFFSET:
4354	- CONFIG_ENV_SIZE:
4355
4356	  These two #defines specify the offset and size of the
4357	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
4358	  aligned to an erase sector boundary.
4359
4360	- CONFIG_ENV_SECT_SIZE:
4361
4362	  Define the SPI flash's sector size.
4363
4364	- CONFIG_ENV_OFFSET_REDUND (optional):
4365
4366	  This setting describes a second storage area of CONFIG_ENV_SIZE
4367	  size used to hold a redundant copy of the environment data, so
4368	  that there is a valid backup copy in case there is a power failure
4369	  during a "saveenv" operation. CONFIG_ENV_OFFSET_RENDUND must be
4370	  aligned to an erase sector boundary.
4371
4372	- CONFIG_ENV_SPI_BUS (optional):
4373	- CONFIG_ENV_SPI_CS (optional):
4374
4375	  Define the SPI bus and chip select. If not defined they will be 0.
4376
4377	- CONFIG_ENV_SPI_MAX_HZ (optional):
4378
4379	  Define the SPI max work clock. If not defined then use 1MHz.
4380
4381	- CONFIG_ENV_SPI_MODE (optional):
4382
4383	  Define the SPI work mode. If not defined then use SPI_MODE_3.
4384
4385- CONFIG_ENV_IS_IN_REMOTE:
4386
4387	Define this if you have a remote memory space which you
4388	want to use for the local device's environment.
4389
4390	- CONFIG_ENV_ADDR:
4391	- CONFIG_ENV_SIZE:
4392
4393	  These two #defines specify the address and size of the
4394	  environment area within the remote memory space. The
4395	  local device can get the environment from remote memory
4396	  space by SRIO or PCIE links.
4397
4398BE CAREFUL! For some special cases, the local device can not use
4399"saveenv" command. For example, the local device will get the
4400environment stored in a remote NOR flash by SRIO or PCIE link,
4401but it can not erase, write this NOR flash by SRIO or PCIE interface.
4402
4403- CONFIG_ENV_IS_IN_NAND:
4404
4405	Define this if you have a NAND device which you want to use
4406	for the environment.
4407
4408	- CONFIG_ENV_OFFSET:
4409	- CONFIG_ENV_SIZE:
4410
4411	  These two #defines specify the offset and size of the environment
4412	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4413	  aligned to an erase block boundary.
4414
4415	- CONFIG_ENV_OFFSET_REDUND (optional):
4416
4417	  This setting describes a second storage area of CONFIG_ENV_SIZE
4418	  size used to hold a redundant copy of the environment data, so
4419	  that there is a valid backup copy in case there is a power failure
4420	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
4421	  aligned to an erase block boundary.
4422
4423	- CONFIG_ENV_RANGE (optional):
4424
4425	  Specifies the length of the region in which the environment
4426	  can be written.  This should be a multiple of the NAND device's
4427	  block size.  Specifying a range with more erase blocks than
4428	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4429	  the range to be avoided.
4430
4431	- CONFIG_ENV_OFFSET_OOB (optional):
4432
4433	  Enables support for dynamically retrieving the offset of the
4434	  environment from block zero's out-of-band data.  The
4435	  "nand env.oob" command can be used to record this offset.
4436	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4437	  using CONFIG_ENV_OFFSET_OOB.
4438
4439- CONFIG_NAND_ENV_DST
4440
4441	Defines address in RAM to which the nand_spl code should copy the
4442	environment. If redundant environment is used, it will be copied to
4443	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4444
4445- CONFIG_ENV_IS_IN_UBI:
4446
4447	Define this if you have an UBI volume that you want to use for the
4448	environment.  This has the benefit of wear-leveling the environment
4449	accesses, which is important on NAND.
4450
4451	- CONFIG_ENV_UBI_PART:
4452
4453	  Define this to a string that is the mtd partition containing the UBI.
4454
4455	- CONFIG_ENV_UBI_VOLUME:
4456
4457	  Define this to the name of the volume that you want to store the
4458	  environment in.
4459
4460	- CONFIG_ENV_UBI_VOLUME_REDUND:
4461
4462	  Define this to the name of another volume to store a second copy of
4463	  the environment in.  This will enable redundant environments in UBI.
4464	  It is assumed that both volumes are in the same MTD partition.
4465
4466	- CONFIG_UBI_SILENCE_MSG
4467	- CONFIG_UBIFS_SILENCE_MSG
4468
4469	  You will probably want to define these to avoid a really noisy system
4470	  when storing the env in UBI.
4471
4472- CONFIG_ENV_IS_IN_FAT:
4473       Define this if you want to use the FAT file system for the environment.
4474
4475       - FAT_ENV_INTERFACE:
4476
4477         Define this to a string that is the name of the block device.
4478
4479       - FAT_ENV_DEV_AND_PART:
4480
4481         Define this to a string to specify the partition of the device. It can
4482         be as following:
4483
4484           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
4485               - "D:P": device D partition P. Error occurs if device D has no
4486                        partition table.
4487               - "D:0": device D.
4488               - "D" or "D:": device D partition 1 if device D has partition
4489                              table, or the whole device D if has no partition
4490                              table.
4491               - "D:auto": first partition in device D with bootable flag set.
4492                           If none, first valid partition in device D. If no
4493                           partition table then means device D.
4494
4495       - FAT_ENV_FILE:
4496
4497         It's a string of the FAT file name. This file use to store the
4498         environment.
4499
4500       - CONFIG_FAT_WRITE:
4501         This should be defined. Otherwise it cannot save the environment file.
4502
4503- CONFIG_ENV_IS_IN_MMC:
4504
4505	Define this if you have an MMC device which you want to use for the
4506	environment.
4507
4508	- CONFIG_SYS_MMC_ENV_DEV:
4509
4510	  Specifies which MMC device the environment is stored in.
4511
4512	- CONFIG_SYS_MMC_ENV_PART (optional):
4513
4514	  Specifies which MMC partition the environment is stored in. If not
4515	  set, defaults to partition 0, the user area. Common values might be
4516	  1 (first MMC boot partition), 2 (second MMC boot partition).
4517
4518	- CONFIG_ENV_OFFSET:
4519	- CONFIG_ENV_SIZE:
4520
4521	  These two #defines specify the offset and size of the environment
4522	  area within the specified MMC device.
4523
4524	  If offset is positive (the usual case), it is treated as relative to
4525	  the start of the MMC partition. If offset is negative, it is treated
4526	  as relative to the end of the MMC partition. This can be useful if
4527	  your board may be fitted with different MMC devices, which have
4528	  different sizes for the MMC partitions, and you always want the
4529	  environment placed at the very end of the partition, to leave the
4530	  maximum possible space before it, to store other data.
4531
4532	  These two values are in units of bytes, but must be aligned to an
4533	  MMC sector boundary.
4534
4535	- CONFIG_ENV_OFFSET_REDUND (optional):
4536
4537	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4538	  hold a redundant copy of the environment data. This provides a
4539	  valid backup copy in case the other copy is corrupted, e.g. due
4540	  to a power failure during a "saveenv" operation.
4541
4542	  This value may also be positive or negative; this is handled in the
4543	  same way as CONFIG_ENV_OFFSET.
4544
4545	  This value is also in units of bytes, but must also be aligned to
4546	  an MMC sector boundary.
4547
4548	- CONFIG_ENV_SIZE_REDUND (optional):
4549
4550	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4551	  set. If this value is set, it must be set to the same value as
4552	  CONFIG_ENV_SIZE.
4553
4554- CONFIG_SYS_SPI_INIT_OFFSET
4555
4556	Defines offset to the initial SPI buffer area in DPRAM. The
4557	area is used at an early stage (ROM part) if the environment
4558	is configured to reside in the SPI EEPROM: We need a 520 byte
4559	scratch DPRAM area. It is used between the two initialization
4560	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4561	to be a good choice since it makes it far enough from the
4562	start of the data area as well as from the stack pointer.
4563
4564Please note that the environment is read-only until the monitor
4565has been relocated to RAM and a RAM copy of the environment has been
4566created; also, when using EEPROM you will have to use getenv_f()
4567until then to read environment variables.
4568
4569The environment is protected by a CRC32 checksum. Before the monitor
4570is relocated into RAM, as a result of a bad CRC you will be working
4571with the compiled-in default environment - *silently*!!! [This is
4572necessary, because the first environment variable we need is the
4573"baudrate" setting for the console - if we have a bad CRC, we don't
4574have any device yet where we could complain.]
4575
4576Note: once the monitor has been relocated, then it will complain if
4577the default environment is used; a new CRC is computed as soon as you
4578use the "saveenv" command to store a valid environment.
4579
4580- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4581		Echo the inverted Ethernet link state to the fault LED.
4582
4583		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4584		      also needs to be defined.
4585
4586- CONFIG_SYS_FAULT_MII_ADDR:
4587		MII address of the PHY to check for the Ethernet link state.
4588
4589- CONFIG_NS16550_MIN_FUNCTIONS:
4590		Define this if you desire to only have use of the NS16550_init
4591		and NS16550_putc functions for the serial driver located at
4592		drivers/serial/ns16550.c.  This option is useful for saving
4593		space for already greatly restricted images, including but not
4594		limited to NAND_SPL configurations.
4595
4596- CONFIG_DISPLAY_BOARDINFO
4597		Display information about the board that U-Boot is running on
4598		when U-Boot starts up. The board function checkboard() is called
4599		to do this.
4600
4601- CONFIG_DISPLAY_BOARDINFO_LATE
4602		Similar to the previous option, but display this information
4603		later, once stdio is running and output goes to the LCD, if
4604		present.
4605
4606- CONFIG_BOARD_SIZE_LIMIT:
4607		Maximum size of the U-Boot image. When defined, the
4608		build system checks that the actual size does not
4609		exceed it.
4610
4611Low Level (hardware related) configuration options:
4612---------------------------------------------------
4613
4614- CONFIG_SYS_CACHELINE_SIZE:
4615		Cache Line Size of the CPU.
4616
4617- CONFIG_SYS_DEFAULT_IMMR:
4618		Default address of the IMMR after system reset.
4619
4620		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4621		and RPXsuper) to be able to adjust the position of
4622		the IMMR register after a reset.
4623
4624- CONFIG_SYS_CCSRBAR_DEFAULT:
4625		Default (power-on reset) physical address of CCSR on Freescale
4626		PowerPC SOCs.
4627
4628- CONFIG_SYS_CCSRBAR:
4629		Virtual address of CCSR.  On a 32-bit build, this is typically
4630		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4631
4632		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4633		for cross-platform code that uses that macro instead.
4634
4635- CONFIG_SYS_CCSRBAR_PHYS:
4636		Physical address of CCSR.  CCSR can be relocated to a new
4637		physical address, if desired.  In this case, this macro should
4638		be set to that address.	 Otherwise, it should be set to the
4639		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4640		is typically relocated on 36-bit builds.  It is recommended
4641		that this macro be defined via the _HIGH and _LOW macros:
4642
4643		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4644			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4645
4646- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4647		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4648		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4649		used in assembly code, so it must not contain typecasts or
4650		integer size suffixes (e.g. "ULL").
4651
4652- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4653		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4654		used in assembly code, so it must not contain typecasts or
4655		integer size suffixes (e.g. "ULL").
4656
4657- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4658		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4659		forced to a value that ensures that CCSR is not relocated.
4660
4661- Floppy Disk Support:
4662		CONFIG_SYS_FDC_DRIVE_NUMBER
4663
4664		the default drive number (default value 0)
4665
4666		CONFIG_SYS_ISA_IO_STRIDE
4667
4668		defines the spacing between FDC chipset registers
4669		(default value 1)
4670
4671		CONFIG_SYS_ISA_IO_OFFSET
4672
4673		defines the offset of register from address. It
4674		depends on which part of the data bus is connected to
4675		the FDC chipset. (default value 0)
4676
4677		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4678		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4679		default value.
4680
4681		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4682		fdc_hw_init() is called at the beginning of the FDC
4683		setup. fdc_hw_init() must be provided by the board
4684		source code. It is used to make hardware-dependent
4685		initializations.
4686
4687- CONFIG_IDE_AHB:
4688		Most IDE controllers were designed to be connected with PCI
4689		interface. Only few of them were designed for AHB interface.
4690		When software is doing ATA command and data transfer to
4691		IDE devices through IDE-AHB controller, some additional
4692		registers accessing to these kind of IDE-AHB controller
4693		is required.
4694
4695- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4696		DO NOT CHANGE unless you know exactly what you're
4697		doing! (11-4) [MPC8xx/82xx systems only]
4698
4699- CONFIG_SYS_INIT_RAM_ADDR:
4700
4701		Start address of memory area that can be used for
4702		initial data and stack; please note that this must be
4703		writable memory that is working WITHOUT special
4704		initialization, i. e. you CANNOT use normal RAM which
4705		will become available only after programming the
4706		memory controller and running certain initialization
4707		sequences.
4708
4709		U-Boot uses the following memory types:
4710		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4711		- MPC824X: data cache
4712		- PPC4xx:  data cache
4713
4714- CONFIG_SYS_GBL_DATA_OFFSET:
4715
4716		Offset of the initial data structure in the memory
4717		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4718		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4719		data is located at the end of the available space
4720		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4721		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4722		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4723		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4724
4725	Note:
4726		On the MPC824X (or other systems that use the data
4727		cache for initial memory) the address chosen for
4728		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4729		point to an otherwise UNUSED address space between
4730		the top of RAM and the start of the PCI space.
4731
4732- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4733
4734- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4735
4736- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4737
4738- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4739
4740- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4741
4742- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4743
4744- CONFIG_SYS_OR_TIMING_SDRAM:
4745		SDRAM timing
4746
4747- CONFIG_SYS_MAMR_PTA:
4748		periodic timer for refresh
4749
4750- CONFIG_SYS_DER:	Debug Event Register (37-47)
4751
4752- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4753  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4754  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4755  CONFIG_SYS_BR1_PRELIM:
4756		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4757
4758- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4759  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4760  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4761		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4762
4763- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4764  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4765		Machine Mode Register and Memory Periodic Timer
4766		Prescaler definitions (SDRAM timing)
4767
4768- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4769		enable I2C microcode relocation patch (MPC8xx);
4770		define relocation offset in DPRAM [DSP2]
4771
4772- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4773		enable SMC microcode relocation patch (MPC8xx);
4774		define relocation offset in DPRAM [SMC1]
4775
4776- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4777		enable SPI microcode relocation patch (MPC8xx);
4778		define relocation offset in DPRAM [SCC4]
4779
4780- CONFIG_SYS_USE_OSCCLK:
4781		Use OSCM clock mode on MBX8xx board. Be careful,
4782		wrong setting might damage your board. Read
4783		doc/README.MBX before setting this variable!
4784
4785- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4786		Offset of the bootmode word in DPRAM used by post
4787		(Power On Self Tests). This definition overrides
4788		#define'd default value in commproc.h resp.
4789		cpm_8260.h.
4790
4791- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4792  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4793  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4794  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4795  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4796  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4797  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4798  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4799		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4800
4801- CONFIG_PCI_DISABLE_PCIE:
4802		Disable PCI-Express on systems where it is supported but not
4803		required.
4804
4805- CONFIG_PCI_ENUM_ONLY
4806		Only scan through and get the devices on the buses.
4807		Don't do any setup work, presumably because someone or
4808		something has already done it, and we don't need to do it
4809		a second time.	Useful for platforms that are pre-booted
4810		by coreboot or similar.
4811
4812- CONFIG_PCI_INDIRECT_BRIDGE:
4813		Enable support for indirect PCI bridges.
4814
4815- CONFIG_SYS_SRIO:
4816		Chip has SRIO or not
4817
4818- CONFIG_SRIO1:
4819		Board has SRIO 1 port available
4820
4821- CONFIG_SRIO2:
4822		Board has SRIO 2 port available
4823
4824- CONFIG_SRIO_PCIE_BOOT_MASTER
4825		Board can support master function for Boot from SRIO and PCIE
4826
4827- CONFIG_SYS_SRIOn_MEM_VIRT:
4828		Virtual Address of SRIO port 'n' memory region
4829
4830- CONFIG_SYS_SRIOn_MEM_PHYS:
4831		Physical Address of SRIO port 'n' memory region
4832
4833- CONFIG_SYS_SRIOn_MEM_SIZE:
4834		Size of SRIO port 'n' memory region
4835
4836- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4837		Defined to tell the NAND controller that the NAND chip is using
4838		a 16 bit bus.
4839		Not all NAND drivers use this symbol.
4840		Example of drivers that use it:
4841		- drivers/mtd/nand/ndfc.c
4842		- drivers/mtd/nand/mxc_nand.c
4843
4844- CONFIG_SYS_NDFC_EBC0_CFG
4845		Sets the EBC0_CFG register for the NDFC. If not defined
4846		a default value will be used.
4847
4848- CONFIG_SPD_EEPROM
4849		Get DDR timing information from an I2C EEPROM. Common
4850		with pluggable memory modules such as SODIMMs
4851
4852  SPD_EEPROM_ADDRESS
4853		I2C address of the SPD EEPROM
4854
4855- CONFIG_SYS_SPD_BUS_NUM
4856		If SPD EEPROM is on an I2C bus other than the first
4857		one, specify here. Note that the value must resolve
4858		to something your driver can deal with.
4859
4860- CONFIG_SYS_DDR_RAW_TIMING
4861		Get DDR timing information from other than SPD. Common with
4862		soldered DDR chips onboard without SPD. DDR raw timing
4863		parameters are extracted from datasheet and hard-coded into
4864		header files or board specific files.
4865
4866- CONFIG_FSL_DDR_INTERACTIVE
4867		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4868
4869- CONFIG_FSL_DDR_SYNC_REFRESH
4870		Enable sync of refresh for multiple controllers.
4871
4872- CONFIG_FSL_DDR_BIST
4873		Enable built-in memory test for Freescale DDR controllers.
4874
4875- CONFIG_SYS_83XX_DDR_USES_CS0
4876		Only for 83xx systems. If specified, then DDR should
4877		be configured using CS0 and CS1 instead of CS2 and CS3.
4878
4879- CONFIG_ETHER_ON_FEC[12]
4880		Define to enable FEC[12] on a 8xx series processor.
4881
4882- CONFIG_FEC[12]_PHY
4883		Define to the hardcoded PHY address which corresponds
4884		to the given FEC; i. e.
4885			#define CONFIG_FEC1_PHY 4
4886		means that the PHY with address 4 is connected to FEC1
4887
4888		When set to -1, means to probe for first available.
4889
4890- CONFIG_FEC[12]_PHY_NORXERR
4891		The PHY does not have a RXERR line (RMII only).
4892		(so program the FEC to ignore it).
4893
4894- CONFIG_RMII
4895		Enable RMII mode for all FECs.
4896		Note that this is a global option, we can't
4897		have one FEC in standard MII mode and another in RMII mode.
4898
4899- CONFIG_CRC32_VERIFY
4900		Add a verify option to the crc32 command.
4901		The syntax is:
4902
4903		=> crc32 -v <address> <count> <crc32>
4904
4905		Where address/count indicate a memory area
4906		and crc32 is the correct crc32 which the
4907		area should have.
4908
4909- CONFIG_LOOPW
4910		Add the "loopw" memory command. This only takes effect if
4911		the memory commands are activated globally (CONFIG_CMD_MEM).
4912
4913- CONFIG_MX_CYCLIC
4914		Add the "mdc" and "mwc" memory commands. These are cyclic
4915		"md/mw" commands.
4916		Examples:
4917
4918		=> mdc.b 10 4 500
4919		This command will print 4 bytes (10,11,12,13) each 500 ms.
4920
4921		=> mwc.l 100 12345678 10
4922		This command will write 12345678 to address 100 all 10 ms.
4923
4924		This only takes effect if the memory commands are activated
4925		globally (CONFIG_CMD_MEM).
4926
4927- CONFIG_SKIP_LOWLEVEL_INIT
4928		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4929		low level initializations (like setting up the memory
4930		controller) are omitted and/or U-Boot does not
4931		relocate itself into RAM.
4932
4933		Normally this variable MUST NOT be defined. The only
4934		exception is when U-Boot is loaded (to RAM) by some
4935		other boot loader or by a debugger which performs
4936		these initializations itself.
4937
4938- CONFIG_SPL_BUILD
4939		Modifies the behaviour of start.S when compiling a loader
4940		that is executed before the actual U-Boot. E.g. when
4941		compiling a NAND SPL.
4942
4943- CONFIG_TPL_BUILD
4944		Modifies the behaviour of start.S  when compiling a loader
4945		that is executed after the SPL and before the actual U-Boot.
4946		It is loaded by the SPL.
4947
4948- CONFIG_SYS_MPC85XX_NO_RESETVEC
4949		Only for 85xx systems. If this variable is specified, the section
4950		.resetvec is not kept and the section .bootpg is placed in the
4951		previous 4k of the .text section.
4952
4953- CONFIG_ARCH_MAP_SYSMEM
4954		Generally U-Boot (and in particular the md command) uses
4955		effective address. It is therefore not necessary to regard
4956		U-Boot address as virtual addresses that need to be translated
4957		to physical addresses. However, sandbox requires this, since
4958		it maintains its own little RAM buffer which contains all
4959		addressable memory. This option causes some memory accesses
4960		to be mapped through map_sysmem() / unmap_sysmem().
4961
4962- CONFIG_USE_ARCH_MEMCPY
4963  CONFIG_USE_ARCH_MEMSET
4964		If these options are used a optimized version of memcpy/memset will
4965		be used if available. These functions may be faster under some
4966		conditions but may increase the binary size.
4967
4968- CONFIG_X86_RESET_VECTOR
4969		If defined, the x86 reset vector code is included. This is not
4970		needed when U-Boot is running from Coreboot.
4971
4972- CONFIG_SYS_MPUCLK
4973		Defines the MPU clock speed (in MHz).
4974
4975		NOTE : currently only supported on AM335x platforms.
4976
4977- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4978		Enables the RTC32K OSC on AM33xx based plattforms
4979
4980- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4981		Option to disable subpage write in NAND driver
4982		driver that uses this:
4983		drivers/mtd/nand/davinci_nand.c
4984
4985Freescale QE/FMAN Firmware Support:
4986-----------------------------------
4987
4988The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4989loading of "firmware", which is encoded in the QE firmware binary format.
4990This firmware often needs to be loaded during U-Boot booting, so macros
4991are used to identify the storage device (NOR flash, SPI, etc) and the address
4992within that device.
4993
4994- CONFIG_SYS_FMAN_FW_ADDR
4995	The address in the storage device where the FMAN microcode is located.  The
4996	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4997	is also specified.
4998
4999- CONFIG_SYS_QE_FW_ADDR
5000	The address in the storage device where the QE microcode is located.  The
5001	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
5002	is also specified.
5003
5004- CONFIG_SYS_QE_FMAN_FW_LENGTH
5005	The maximum possible size of the firmware.  The firmware binary format
5006	has a field that specifies the actual size of the firmware, but it
5007	might not be possible to read any part of the firmware unless some
5008	local storage is allocated to hold the entire firmware first.
5009
5010- CONFIG_SYS_QE_FMAN_FW_IN_NOR
5011	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
5012	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
5013	virtual address in NOR flash.
5014
5015- CONFIG_SYS_QE_FMAN_FW_IN_NAND
5016	Specifies that QE/FMAN firmware is located in NAND flash.
5017	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
5018
5019- CONFIG_SYS_QE_FMAN_FW_IN_MMC
5020	Specifies that QE/FMAN firmware is located on the primary SD/MMC
5021	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
5022
5023- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
5024	Specifies that QE/FMAN firmware is located on the primary SPI
5025	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
5026
5027- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
5028	Specifies that QE/FMAN firmware is located in the remote (master)
5029	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
5030	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
5031	window->master inbound window->master LAW->the ucode address in
5032	master's memory space.
5033
5034Freescale Layerscape Management Complex Firmware Support:
5035---------------------------------------------------------
5036The Freescale Layerscape Management Complex (MC) supports the loading of
5037"firmware".
5038This firmware often needs to be loaded during U-Boot booting, so macros
5039are used to identify the storage device (NOR flash, SPI, etc) and the address
5040within that device.
5041
5042- CONFIG_FSL_MC_ENET
5043	Enable the MC driver for Layerscape SoCs.
5044
5045- CONFIG_SYS_LS_MC_FW_ADDR
5046	The address in the storage device where the firmware is located.  The
5047	meaning of this address depends on which CONFIG_SYS_LS_MC_FW_IN_xxx macro
5048	is also specified.
5049
5050- CONFIG_SYS_LS_MC_FW_LENGTH
5051	The maximum possible size of the firmware.  The firmware binary format
5052	has a field that specifies the actual size of the firmware, but it
5053	might not be possible to read any part of the firmware unless some
5054	local storage is allocated to hold the entire firmware first.
5055
5056- CONFIG_SYS_LS_MC_FW_IN_NOR
5057	Specifies that MC firmware is located in NOR flash, mapped as
5058	normal addressable memory via the LBC. CONFIG_SYS_LS_MC_FW_ADDR is the
5059	virtual address in NOR flash.
5060
5061Freescale Layerscape Debug Server Support:
5062-------------------------------------------
5063The Freescale Layerscape Debug Server Support supports the loading of
5064"Debug Server firmware" and triggering SP boot-rom.
5065This firmware often needs to be loaded during U-Boot booting.
5066
5067- CONFIG_FSL_DEBUG_SERVER
5068	Enable the Debug Server for Layerscape SoCs.
5069
5070- CONFIG_SYS_DEBUG_SERVER_DRAM_BLOCK_MIN_SIZE
5071	Define minimum DDR size required for debug server image
5072
5073- CONFIG_SYS_MEM_TOP_HIDE_MIN
5074	Define minimum DDR size to be hided from top of the DDR memory
5075
5076Reproducible builds
5077-------------------
5078
5079In order to achieve reproducible builds, timestamps used in the U-Boot build
5080process have to be set to a fixed value.
5081
5082This is done using the SOURCE_DATE_EPOCH environment variable.
5083SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
5084option for U-Boot or an environment variable in U-Boot.
5085
5086SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
5087
5088Building the Software:
5089======================
5090
5091Building U-Boot has been tested in several native build environments
5092and in many different cross environments. Of course we cannot support
5093all possibly existing versions of cross development tools in all
5094(potentially obsolete) versions. In case of tool chain problems we
5095recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
5096which is extensively used to build and test U-Boot.
5097
5098If you are not using a native environment, it is assumed that you
5099have GNU cross compiling tools available in your path. In this case,
5100you must set the environment variable CROSS_COMPILE in your shell.
5101Note that no changes to the Makefile or any other source files are
5102necessary. For example using the ELDK on a 4xx CPU, please enter:
5103
5104	$ CROSS_COMPILE=ppc_4xx-
5105	$ export CROSS_COMPILE
5106
5107Note: If you wish to generate Windows versions of the utilities in
5108      the tools directory you can use the MinGW toolchain
5109      (http://www.mingw.org).  Set your HOST tools to the MinGW
5110      toolchain and execute 'make tools'.  For example:
5111
5112       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
5113
5114      Binaries such as tools/mkimage.exe will be created which can
5115      be executed on computers running Windows.
5116
5117U-Boot is intended to be simple to build. After installing the
5118sources you must configure U-Boot for one specific board type. This
5119is done by typing:
5120
5121	make NAME_defconfig
5122
5123where "NAME_defconfig" is the name of one of the existing configu-
5124rations; see boards.cfg for supported names.
5125
5126Note: for some board special configuration names may exist; check if
5127      additional information is available from the board vendor; for
5128      instance, the TQM823L systems are available without (standard)
5129      or with LCD support. You can select such additional "features"
5130      when choosing the configuration, i. e.
5131
5132      make TQM823L_defconfig
5133	- will configure for a plain TQM823L, i. e. no LCD support
5134
5135      make TQM823L_LCD_defconfig
5136	- will configure for a TQM823L with U-Boot console on LCD
5137
5138      etc.
5139
5140
5141Finally, type "make all", and you should get some working U-Boot
5142images ready for download to / installation on your system:
5143
5144- "u-boot.bin" is a raw binary image
5145- "u-boot" is an image in ELF binary format
5146- "u-boot.srec" is in Motorola S-Record format
5147
5148By default the build is performed locally and the objects are saved
5149in the source directory. One of the two methods can be used to change
5150this behavior and build U-Boot to some external directory:
5151
51521. Add O= to the make command line invocations:
5153
5154	make O=/tmp/build distclean
5155	make O=/tmp/build NAME_defconfig
5156	make O=/tmp/build all
5157
51582. Set environment variable KBUILD_OUTPUT to point to the desired location:
5159
5160	export KBUILD_OUTPUT=/tmp/build
5161	make distclean
5162	make NAME_defconfig
5163	make all
5164
5165Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
5166variable.
5167
5168
5169Please be aware that the Makefiles assume you are using GNU make, so
5170for instance on NetBSD you might need to use "gmake" instead of
5171native "make".
5172
5173
5174If the system board that you have is not listed, then you will need
5175to port U-Boot to your hardware platform. To do this, follow these
5176steps:
5177
51781.  Add a new configuration option for your board to the toplevel
5179    "boards.cfg" file, using the existing entries as examples.
5180    Follow the instructions there to keep the boards in order.
51812.  Create a new directory to hold your board specific code. Add any
5182    files you need. In your board directory, you will need at least
5183    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
51843.  Create a new configuration file "include/configs/<board>.h" for
5185    your board
51863.  If you're porting U-Boot to a new CPU, then also create a new
5187    directory to hold your CPU specific code. Add any files you need.
51884.  Run "make <board>_defconfig" with your new name.
51895.  Type "make", and you should get a working "u-boot.srec" file
5190    to be installed on your target system.
51916.  Debug and solve any problems that might arise.
5192    [Of course, this last step is much harder than it sounds.]
5193
5194
5195Testing of U-Boot Modifications, Ports to New Hardware, etc.:
5196==============================================================
5197
5198If you have modified U-Boot sources (for instance added a new board
5199or support for new devices, a new CPU, etc.) you are expected to
5200provide feedback to the other developers. The feedback normally takes
5201the form of a "patch", i. e. a context diff against a certain (latest
5202official or latest in the git repository) version of U-Boot sources.
5203
5204But before you submit such a patch, please verify that your modifi-
5205cation did not break existing code. At least make sure that *ALL* of
5206the supported boards compile WITHOUT ANY compiler warnings. To do so,
5207just run the "MAKEALL" script, which will configure and build U-Boot
5208for ALL supported system. Be warned, this will take a while. You can
5209select which (cross) compiler to use by passing a `CROSS_COMPILE'
5210environment variable to the script, i. e. to use the ELDK cross tools
5211you can type
5212
5213	CROSS_COMPILE=ppc_8xx- MAKEALL
5214
5215or to build on a native PowerPC system you can type
5216
5217	CROSS_COMPILE=' ' MAKEALL
5218
5219When using the MAKEALL script, the default behaviour is to build
5220U-Boot in the source directory. This location can be changed by
5221setting the BUILD_DIR environment variable. Also, for each target
5222built, the MAKEALL script saves two log files (<target>.ERR and
5223<target>.MAKEALL) in the <source dir>/LOG directory. This default
5224location can be changed by setting the MAKEALL_LOGDIR environment
5225variable. For example:
5226
5227	export BUILD_DIR=/tmp/build
5228	export MAKEALL_LOGDIR=/tmp/log
5229	CROSS_COMPILE=ppc_8xx- MAKEALL
5230
5231With the above settings build objects are saved in the /tmp/build,
5232log files are saved in the /tmp/log and the source tree remains clean
5233during the whole build process.
5234
5235
5236See also "U-Boot Porting Guide" below.
5237
5238
5239Monitor Commands - Overview:
5240============================
5241
5242go	- start application at address 'addr'
5243run	- run commands in an environment variable
5244bootm	- boot application image from memory
5245bootp	- boot image via network using BootP/TFTP protocol
5246bootz   - boot zImage from memory
5247tftpboot- boot image via network using TFTP protocol
5248	       and env variables "ipaddr" and "serverip"
5249	       (and eventually "gatewayip")
5250tftpput - upload a file via network using TFTP protocol
5251rarpboot- boot image via network using RARP/TFTP protocol
5252diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
5253loads	- load S-Record file over serial line
5254loadb	- load binary file over serial line (kermit mode)
5255md	- memory display
5256mm	- memory modify (auto-incrementing)
5257nm	- memory modify (constant address)
5258mw	- memory write (fill)
5259cp	- memory copy
5260cmp	- memory compare
5261crc32	- checksum calculation
5262i2c	- I2C sub-system
5263sspi	- SPI utility commands
5264base	- print or set address offset
5265printenv- print environment variables
5266setenv	- set environment variables
5267saveenv - save environment variables to persistent storage
5268protect - enable or disable FLASH write protection
5269erase	- erase FLASH memory
5270flinfo	- print FLASH memory information
5271nand	- NAND memory operations (see doc/README.nand)
5272bdinfo	- print Board Info structure
5273iminfo	- print header information for application image
5274coninfo - print console devices and informations
5275ide	- IDE sub-system
5276loop	- infinite loop on address range
5277loopw	- infinite write loop on address range
5278mtest	- simple RAM test
5279icache	- enable or disable instruction cache
5280dcache	- enable or disable data cache
5281reset	- Perform RESET of the CPU
5282echo	- echo args to console
5283version - print monitor version
5284help	- print online help
5285?	- alias for 'help'
5286
5287
5288Monitor Commands - Detailed Description:
5289========================================
5290
5291TODO.
5292
5293For now: just type "help <command>".
5294
5295
5296Environment Variables:
5297======================
5298
5299U-Boot supports user configuration using Environment Variables which
5300can be made persistent by saving to Flash memory.
5301
5302Environment Variables are set using "setenv", printed using
5303"printenv", and saved to Flash using "saveenv". Using "setenv"
5304without a value can be used to delete a variable from the
5305environment. As long as you don't save the environment you are
5306working with an in-memory copy. In case the Flash area containing the
5307environment is erased by accident, a default environment is provided.
5308
5309Some configuration options can be set using Environment Variables.
5310
5311List of environment variables (most likely not complete):
5312
5313  baudrate	- see CONFIG_BAUDRATE
5314
5315  bootdelay	- see CONFIG_BOOTDELAY
5316
5317  bootcmd	- see CONFIG_BOOTCOMMAND
5318
5319  bootargs	- Boot arguments when booting an RTOS image
5320
5321  bootfile	- Name of the image to load with TFTP
5322
5323  bootm_low	- Memory range available for image processing in the bootm
5324		  command can be restricted. This variable is given as
5325		  a hexadecimal number and defines lowest address allowed
5326		  for use by the bootm command. See also "bootm_size"
5327		  environment variable. Address defined by "bootm_low" is
5328		  also the base of the initial memory mapping for the Linux
5329		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
5330		  bootm_mapsize.
5331
5332  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
5333		  This variable is given as a hexadecimal number and it
5334		  defines the size of the memory region starting at base
5335		  address bootm_low that is accessible by the Linux kernel
5336		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
5337		  as the default value if it is defined, and bootm_size is
5338		  used otherwise.
5339
5340  bootm_size	- Memory range available for image processing in the bootm
5341		  command can be restricted. This variable is given as
5342		  a hexadecimal number and defines the size of the region
5343		  allowed for use by the bootm command. See also "bootm_low"
5344		  environment variable.
5345
5346  updatefile	- Location of the software update file on a TFTP server, used
5347		  by the automatic software update feature. Please refer to
5348		  documentation in doc/README.update for more details.
5349
5350  autoload	- if set to "no" (any string beginning with 'n'),
5351		  "bootp" will just load perform a lookup of the
5352		  configuration from the BOOTP server, but not try to
5353		  load any image using TFTP
5354
5355  autostart	- if set to "yes", an image loaded using the "bootp",
5356		  "rarpboot", "tftpboot" or "diskboot" commands will
5357		  be automatically started (by internally calling
5358		  "bootm")
5359
5360		  If set to "no", a standalone image passed to the
5361		  "bootm" command will be copied to the load address
5362		  (and eventually uncompressed), but NOT be started.
5363		  This can be used to load and uncompress arbitrary
5364		  data.
5365
5366  fdt_high	- if set this restricts the maximum address that the
5367		  flattened device tree will be copied into upon boot.
5368		  For example, if you have a system with 1 GB memory
5369		  at physical address 0x10000000, while Linux kernel
5370		  only recognizes the first 704 MB as low memory, you
5371		  may need to set fdt_high as 0x3C000000 to have the
5372		  device tree blob be copied to the maximum address
5373		  of the 704 MB low memory, so that Linux kernel can
5374		  access it during the boot procedure.
5375
5376		  If this is set to the special value 0xFFFFFFFF then
5377		  the fdt will not be copied at all on boot.  For this
5378		  to work it must reside in writable memory, have
5379		  sufficient padding on the end of it for u-boot to
5380		  add the information it needs into it, and the memory
5381		  must be accessible by the kernel.
5382
5383  fdtcontroladdr- if set this is the address of the control flattened
5384		  device tree used by U-Boot when CONFIG_OF_CONTROL is
5385		  defined.
5386
5387  i2cfast	- (PPC405GP|PPC405EP only)
5388		  if set to 'y' configures Linux I2C driver for fast
5389		  mode (400kHZ). This environment variable is used in
5390		  initialization code. So, for changes to be effective
5391		  it must be saved and board must be reset.
5392
5393  initrd_high	- restrict positioning of initrd images:
5394		  If this variable is not set, initrd images will be
5395		  copied to the highest possible address in RAM; this
5396		  is usually what you want since it allows for
5397		  maximum initrd size. If for some reason you want to
5398		  make sure that the initrd image is loaded below the
5399		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
5400		  variable to a value of "no" or "off" or "0".
5401		  Alternatively, you can set it to a maximum upper
5402		  address to use (U-Boot will still check that it
5403		  does not overwrite the U-Boot stack and data).
5404
5405		  For instance, when you have a system with 16 MB
5406		  RAM, and want to reserve 4 MB from use by Linux,
5407		  you can do this by adding "mem=12M" to the value of
5408		  the "bootargs" variable. However, now you must make
5409		  sure that the initrd image is placed in the first
5410		  12 MB as well - this can be done with
5411
5412		  setenv initrd_high 00c00000
5413
5414		  If you set initrd_high to 0xFFFFFFFF, this is an
5415		  indication to U-Boot that all addresses are legal
5416		  for the Linux kernel, including addresses in flash
5417		  memory. In this case U-Boot will NOT COPY the
5418		  ramdisk at all. This may be useful to reduce the
5419		  boot time on your system, but requires that this
5420		  feature is supported by your Linux kernel.
5421
5422  ipaddr	- IP address; needed for tftpboot command
5423
5424  loadaddr	- Default load address for commands like "bootp",
5425		  "rarpboot", "tftpboot", "loadb" or "diskboot"
5426
5427  loads_echo	- see CONFIG_LOADS_ECHO
5428
5429  serverip	- TFTP server IP address; needed for tftpboot command
5430
5431  bootretry	- see CONFIG_BOOT_RETRY_TIME
5432
5433  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
5434
5435  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
5436
5437  ethprime	- controls which interface is used first.
5438
5439  ethact	- controls which interface is currently active.
5440		  For example you can do the following
5441
5442		  => setenv ethact FEC
5443		  => ping 192.168.0.1 # traffic sent on FEC
5444		  => setenv ethact SCC
5445		  => ping 10.0.0.1 # traffic sent on SCC
5446
5447  ethrotate	- When set to "no" U-Boot does not go through all
5448		  available network interfaces.
5449		  It just stays at the currently selected interface.
5450
5451  netretry	- When set to "no" each network operation will
5452		  either succeed or fail without retrying.
5453		  When set to "once" the network operation will
5454		  fail when all the available network interfaces
5455		  are tried once without success.
5456		  Useful on scripts which control the retry operation
5457		  themselves.
5458
5459  npe_ucode	- set load address for the NPE microcode
5460
5461  silent_linux  - If set then Linux will be told to boot silently, by
5462		  changing the console to be empty. If "yes" it will be
5463		  made silent. If "no" it will not be made silent. If
5464		  unset, then it will be made silent if the U-Boot console
5465		  is silent.
5466
5467  tftpsrcport	- If this is set, the value is used for TFTP's
5468		  UDP source port.
5469
5470  tftpdstport	- If this is set, the value is used for TFTP's UDP
5471		  destination port instead of the Well Know Port 69.
5472
5473  tftpblocksize - Block size to use for TFTP transfers; if not set,
5474		  we use the TFTP server's default block size
5475
5476  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
5477		  seconds, minimum value is 1000 = 1 second). Defines
5478		  when a packet is considered to be lost so it has to
5479		  be retransmitted. The default is 5000 = 5 seconds.
5480		  Lowering this value may make downloads succeed
5481		  faster in networks with high packet loss rates or
5482		  with unreliable TFTP servers.
5483
5484  vlan		- When set to a value < 4095 the traffic over
5485		  Ethernet is encapsulated/received over 802.1q
5486		  VLAN tagged frames.
5487
5488The following image location variables contain the location of images
5489used in booting. The "Image" column gives the role of the image and is
5490not an environment variable name. The other columns are environment
5491variable names. "File Name" gives the name of the file on a TFTP
5492server, "RAM Address" gives the location in RAM the image will be
5493loaded to, and "Flash Location" gives the image's address in NOR
5494flash or offset in NAND flash.
5495
5496*Note* - these variables don't have to be defined for all boards, some
5497boards currently use other variables for these purposes, and some
5498boards use these variables for other purposes.
5499
5500Image		    File Name	     RAM Address       Flash Location
5501-----		    ---------	     -----------       --------------
5502u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
5503Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
5504device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
5505ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
5506
5507The following environment variables may be used and automatically
5508updated by the network boot commands ("bootp" and "rarpboot"),
5509depending the information provided by your boot server:
5510
5511  bootfile	- see above
5512  dnsip		- IP address of your Domain Name Server
5513  dnsip2	- IP address of your secondary Domain Name Server
5514  gatewayip	- IP address of the Gateway (Router) to use
5515  hostname	- Target hostname
5516  ipaddr	- see above
5517  netmask	- Subnet Mask
5518  rootpath	- Pathname of the root filesystem on the NFS server
5519  serverip	- see above
5520
5521
5522There are two special Environment Variables:
5523
5524  serial#	- contains hardware identification information such
5525		  as type string and/or serial number
5526  ethaddr	- Ethernet address
5527
5528These variables can be set only once (usually during manufacturing of
5529the board). U-Boot refuses to delete or overwrite these variables
5530once they have been set once.
5531
5532
5533Further special Environment Variables:
5534
5535  ver		- Contains the U-Boot version string as printed
5536		  with the "version" command. This variable is
5537		  readonly (see CONFIG_VERSION_VARIABLE).
5538
5539
5540Please note that changes to some configuration parameters may take
5541only effect after the next boot (yes, that's just like Windoze :-).
5542
5543
5544Callback functions for environment variables:
5545---------------------------------------------
5546
5547For some environment variables, the behavior of u-boot needs to change
5548when their values are changed.  This functionality allows functions to
5549be associated with arbitrary variables.  On creation, overwrite, or
5550deletion, the callback will provide the opportunity for some side
5551effect to happen or for the change to be rejected.
5552
5553The callbacks are named and associated with a function using the
5554U_BOOT_ENV_CALLBACK macro in your board or driver code.
5555
5556These callbacks are associated with variables in one of two ways.  The
5557static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5558in the board configuration to a string that defines a list of
5559associations.  The list must be in the following format:
5560
5561	entry = variable_name[:callback_name]
5562	list = entry[,list]
5563
5564If the callback name is not specified, then the callback is deleted.
5565Spaces are also allowed anywhere in the list.
5566
5567Callbacks can also be associated by defining the ".callbacks" variable
5568with the same list format above.  Any association in ".callbacks" will
5569override any association in the static list. You can define
5570CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5571".callbacks" environment variable in the default or embedded environment.
5572
5573If CONFIG_REGEX is defined, the variable_name above is evaluated as a
5574regular expression. This allows multiple variables to be connected to
5575the same callback without explicitly listing them all out.
5576
5577
5578Command Line Parsing:
5579=====================
5580
5581There are two different command line parsers available with U-Boot:
5582the old "simple" one, and the much more powerful "hush" shell:
5583
5584Old, simple command line parser:
5585--------------------------------
5586
5587- supports environment variables (through setenv / saveenv commands)
5588- several commands on one line, separated by ';'
5589- variable substitution using "... ${name} ..." syntax
5590- special characters ('$', ';') can be escaped by prefixing with '\',
5591  for example:
5592	setenv bootcmd bootm \${address}
5593- You can also escape text by enclosing in single apostrophes, for example:
5594	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5595
5596Hush shell:
5597-----------
5598
5599- similar to Bourne shell, with control structures like
5600  if...then...else...fi, for...do...done; while...do...done,
5601  until...do...done, ...
5602- supports environment ("global") variables (through setenv / saveenv
5603  commands) and local shell variables (through standard shell syntax
5604  "name=value"); only environment variables can be used with "run"
5605  command
5606
5607General rules:
5608--------------
5609
5610(1) If a command line (or an environment variable executed by a "run"
5611    command) contains several commands separated by semicolon, and
5612    one of these commands fails, then the remaining commands will be
5613    executed anyway.
5614
5615(2) If you execute several variables with one call to run (i. e.
5616    calling run with a list of variables as arguments), any failing
5617    command will cause "run" to terminate, i. e. the remaining
5618    variables are not executed.
5619
5620Note for Redundant Ethernet Interfaces:
5621=======================================
5622
5623Some boards come with redundant Ethernet interfaces; U-Boot supports
5624such configurations and is capable of automatic selection of a
5625"working" interface when needed. MAC assignment works as follows:
5626
5627Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5628MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5629"eth1addr" (=>eth1), "eth2addr", ...
5630
5631If the network interface stores some valid MAC address (for instance
5632in SROM), this is used as default address if there is NO correspon-
5633ding setting in the environment; if the corresponding environment
5634variable is set, this overrides the settings in the card; that means:
5635
5636o If the SROM has a valid MAC address, and there is no address in the
5637  environment, the SROM's address is used.
5638
5639o If there is no valid address in the SROM, and a definition in the
5640  environment exists, then the value from the environment variable is
5641  used.
5642
5643o If both the SROM and the environment contain a MAC address, and
5644  both addresses are the same, this MAC address is used.
5645
5646o If both the SROM and the environment contain a MAC address, and the
5647  addresses differ, the value from the environment is used and a
5648  warning is printed.
5649
5650o If neither SROM nor the environment contain a MAC address, an error
5651  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
5652  a random, locally-assigned MAC is used.
5653
5654If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5655will be programmed into hardware as part of the initialization process.	 This
5656may be skipped by setting the appropriate 'ethmacskip' environment variable.
5657The naming convention is as follows:
5658"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5659
5660Image Formats:
5661==============
5662
5663U-Boot is capable of booting (and performing other auxiliary operations on)
5664images in two formats:
5665
5666New uImage format (FIT)
5667-----------------------
5668
5669Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5670to Flattened Device Tree). It allows the use of images with multiple
5671components (several kernels, ramdisks, etc.), with contents protected by
5672SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5673
5674
5675Old uImage format
5676-----------------
5677
5678Old image format is based on binary files which can be basically anything,
5679preceded by a special header; see the definitions in include/image.h for
5680details; basically, the header defines the following image properties:
5681
5682* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5683  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5684  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5685  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5686  INTEGRITY).
5687* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5688  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5689  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5690* Compression Type (uncompressed, gzip, bzip2)
5691* Load Address
5692* Entry Point
5693* Image Name
5694* Image Timestamp
5695
5696The header is marked by a special Magic Number, and both the header
5697and the data portions of the image are secured against corruption by
5698CRC32 checksums.
5699
5700
5701Linux Support:
5702==============
5703
5704Although U-Boot should support any OS or standalone application
5705easily, the main focus has always been on Linux during the design of
5706U-Boot.
5707
5708U-Boot includes many features that so far have been part of some
5709special "boot loader" code within the Linux kernel. Also, any
5710"initrd" images to be used are no longer part of one big Linux image;
5711instead, kernel and "initrd" are separate images. This implementation
5712serves several purposes:
5713
5714- the same features can be used for other OS or standalone
5715  applications (for instance: using compressed images to reduce the
5716  Flash memory footprint)
5717
5718- it becomes much easier to port new Linux kernel versions because
5719  lots of low-level, hardware dependent stuff are done by U-Boot
5720
5721- the same Linux kernel image can now be used with different "initrd"
5722  images; of course this also means that different kernel images can
5723  be run with the same "initrd". This makes testing easier (you don't
5724  have to build a new "zImage.initrd" Linux image when you just
5725  change a file in your "initrd"). Also, a field-upgrade of the
5726  software is easier now.
5727
5728
5729Linux HOWTO:
5730============
5731
5732Porting Linux to U-Boot based systems:
5733---------------------------------------
5734
5735U-Boot cannot save you from doing all the necessary modifications to
5736configure the Linux device drivers for use with your target hardware
5737(no, we don't intend to provide a full virtual machine interface to
5738Linux :-).
5739
5740But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5741
5742Just make sure your machine specific header file (for instance
5743include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5744Information structure as we define in include/asm-<arch>/u-boot.h,
5745and make sure that your definition of IMAP_ADDR uses the same value
5746as your U-Boot configuration in CONFIG_SYS_IMMR.
5747
5748Note that U-Boot now has a driver model, a unified model for drivers.
5749If you are adding a new driver, plumb it into driver model. If there
5750is no uclass available, you are encouraged to create one. See
5751doc/driver-model.
5752
5753
5754Configuring the Linux kernel:
5755-----------------------------
5756
5757No specific requirements for U-Boot. Make sure you have some root
5758device (initial ramdisk, NFS) for your target system.
5759
5760
5761Building a Linux Image:
5762-----------------------
5763
5764With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5765not used. If you use recent kernel source, a new build target
5766"uImage" will exist which automatically builds an image usable by
5767U-Boot. Most older kernels also have support for a "pImage" target,
5768which was introduced for our predecessor project PPCBoot and uses a
5769100% compatible format.
5770
5771Example:
5772
5773	make TQM850L_defconfig
5774	make oldconfig
5775	make dep
5776	make uImage
5777
5778The "uImage" build target uses a special tool (in 'tools/mkimage') to
5779encapsulate a compressed Linux kernel image with header	 information,
5780CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5781
5782* build a standard "vmlinux" kernel image (in ELF binary format):
5783
5784* convert the kernel into a raw binary image:
5785
5786	${CROSS_COMPILE}-objcopy -O binary \
5787				 -R .note -R .comment \
5788				 -S vmlinux linux.bin
5789
5790* compress the binary image:
5791
5792	gzip -9 linux.bin
5793
5794* package compressed binary image for U-Boot:
5795
5796	mkimage -A ppc -O linux -T kernel -C gzip \
5797		-a 0 -e 0 -n "Linux Kernel Image" \
5798		-d linux.bin.gz uImage
5799
5800
5801The "mkimage" tool can also be used to create ramdisk images for use
5802with U-Boot, either separated from the Linux kernel image, or
5803combined into one file. "mkimage" encapsulates the images with a 64
5804byte header containing information about target architecture,
5805operating system, image type, compression method, entry points, time
5806stamp, CRC32 checksums, etc.
5807
5808"mkimage" can be called in two ways: to verify existing images and
5809print the header information, or to build new images.
5810
5811In the first form (with "-l" option) mkimage lists the information
5812contained in the header of an existing U-Boot image; this includes
5813checksum verification:
5814
5815	tools/mkimage -l image
5816	  -l ==> list image header information
5817
5818The second form (with "-d" option) is used to build a U-Boot image
5819from a "data file" which is used as image payload:
5820
5821	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5822		      -n name -d data_file image
5823	  -A ==> set architecture to 'arch'
5824	  -O ==> set operating system to 'os'
5825	  -T ==> set image type to 'type'
5826	  -C ==> set compression type 'comp'
5827	  -a ==> set load address to 'addr' (hex)
5828	  -e ==> set entry point to 'ep' (hex)
5829	  -n ==> set image name to 'name'
5830	  -d ==> use image data from 'datafile'
5831
5832Right now, all Linux kernels for PowerPC systems use the same load
5833address (0x00000000), but the entry point address depends on the
5834kernel version:
5835
5836- 2.2.x kernels have the entry point at 0x0000000C,
5837- 2.3.x and later kernels have the entry point at 0x00000000.
5838
5839So a typical call to build a U-Boot image would read:
5840
5841	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5842	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5843	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5844	> examples/uImage.TQM850L
5845	Image Name:   2.4.4 kernel for TQM850L
5846	Created:      Wed Jul 19 02:34:59 2000
5847	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5848	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5849	Load Address: 0x00000000
5850	Entry Point:  0x00000000
5851
5852To verify the contents of the image (or check for corruption):
5853
5854	-> tools/mkimage -l examples/uImage.TQM850L
5855	Image Name:   2.4.4 kernel for TQM850L
5856	Created:      Wed Jul 19 02:34:59 2000
5857	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5858	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5859	Load Address: 0x00000000
5860	Entry Point:  0x00000000
5861
5862NOTE: for embedded systems where boot time is critical you can trade
5863speed for memory and install an UNCOMPRESSED image instead: this
5864needs more space in Flash, but boots much faster since it does not
5865need to be uncompressed:
5866
5867	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5868	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5869	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5870	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5871	> examples/uImage.TQM850L-uncompressed
5872	Image Name:   2.4.4 kernel for TQM850L
5873	Created:      Wed Jul 19 02:34:59 2000
5874	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5875	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5876	Load Address: 0x00000000
5877	Entry Point:  0x00000000
5878
5879
5880Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5881when your kernel is intended to use an initial ramdisk:
5882
5883	-> tools/mkimage -n 'Simple Ramdisk Image' \
5884	> -A ppc -O linux -T ramdisk -C gzip \
5885	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5886	Image Name:   Simple Ramdisk Image
5887	Created:      Wed Jan 12 14:01:50 2000
5888	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5889	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5890	Load Address: 0x00000000
5891	Entry Point:  0x00000000
5892
5893The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5894option performs the converse operation of the mkimage's second form (the "-d"
5895option). Given an image built by mkimage, the dumpimage extracts a "data file"
5896from the image:
5897
5898	tools/dumpimage -i image -T type -p position data_file
5899	  -i ==> extract from the 'image' a specific 'data_file'
5900	  -T ==> set image type to 'type'
5901	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5902
5903
5904Installing a Linux Image:
5905-------------------------
5906
5907To downloading a U-Boot image over the serial (console) interface,
5908you must convert the image to S-Record format:
5909
5910	objcopy -I binary -O srec examples/image examples/image.srec
5911
5912The 'objcopy' does not understand the information in the U-Boot
5913image header, so the resulting S-Record file will be relative to
5914address 0x00000000. To load it to a given address, you need to
5915specify the target address as 'offset' parameter with the 'loads'
5916command.
5917
5918Example: install the image to address 0x40100000 (which on the
5919TQM8xxL is in the first Flash bank):
5920
5921	=> erase 40100000 401FFFFF
5922
5923	.......... done
5924	Erased 8 sectors
5925
5926	=> loads 40100000
5927	## Ready for S-Record download ...
5928	~>examples/image.srec
5929	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5930	...
5931	15989 15990 15991 15992
5932	[file transfer complete]
5933	[connected]
5934	## Start Addr = 0x00000000
5935
5936
5937You can check the success of the download using the 'iminfo' command;
5938this includes a checksum verification so you can be sure no data
5939corruption happened:
5940
5941	=> imi 40100000
5942
5943	## Checking Image at 40100000 ...
5944	   Image Name:	 2.2.13 for initrd on TQM850L
5945	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5946	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5947	   Load Address: 00000000
5948	   Entry Point:	 0000000c
5949	   Verifying Checksum ... OK
5950
5951
5952Boot Linux:
5953-----------
5954
5955The "bootm" command is used to boot an application that is stored in
5956memory (RAM or Flash). In case of a Linux kernel image, the contents
5957of the "bootargs" environment variable is passed to the kernel as
5958parameters. You can check and modify this variable using the
5959"printenv" and "setenv" commands:
5960
5961
5962	=> printenv bootargs
5963	bootargs=root=/dev/ram
5964
5965	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5966
5967	=> printenv bootargs
5968	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5969
5970	=> bootm 40020000
5971	## Booting Linux kernel at 40020000 ...
5972	   Image Name:	 2.2.13 for NFS on TQM850L
5973	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5974	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5975	   Load Address: 00000000
5976	   Entry Point:	 0000000c
5977	   Verifying Checksum ... OK
5978	   Uncompressing Kernel Image ... OK
5979	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
5980	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5981	time_init: decrementer frequency = 187500000/60
5982	Calibrating delay loop... 49.77 BogoMIPS
5983	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5984	...
5985
5986If you want to boot a Linux kernel with initial RAM disk, you pass
5987the memory addresses of both the kernel and the initrd image (PPBCOOT
5988format!) to the "bootm" command:
5989
5990	=> imi 40100000 40200000
5991
5992	## Checking Image at 40100000 ...
5993	   Image Name:	 2.2.13 for initrd on TQM850L
5994	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5995	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5996	   Load Address: 00000000
5997	   Entry Point:	 0000000c
5998	   Verifying Checksum ... OK
5999
6000	## Checking Image at 40200000 ...
6001	   Image Name:	 Simple Ramdisk Image
6002	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
6003	   Data Size:	 566530 Bytes = 553 kB = 0 MB
6004	   Load Address: 00000000
6005	   Entry Point:	 00000000
6006	   Verifying Checksum ... OK
6007
6008	=> bootm 40100000 40200000
6009	## Booting Linux kernel at 40100000 ...
6010	   Image Name:	 2.2.13 for initrd on TQM850L
6011	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
6012	   Data Size:	 335725 Bytes = 327 kB = 0 MB
6013	   Load Address: 00000000
6014	   Entry Point:	 0000000c
6015	   Verifying Checksum ... OK
6016	   Uncompressing Kernel Image ... OK
6017	## Loading RAMDisk Image at 40200000 ...
6018	   Image Name:	 Simple Ramdisk Image
6019	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
6020	   Data Size:	 566530 Bytes = 553 kB = 0 MB
6021	   Load Address: 00000000
6022	   Entry Point:	 00000000
6023	   Verifying Checksum ... OK
6024	   Loading Ramdisk ... OK
6025	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
6026	Boot arguments: root=/dev/ram
6027	time_init: decrementer frequency = 187500000/60
6028	Calibrating delay loop... 49.77 BogoMIPS
6029	...
6030	RAMDISK: Compressed image found at block 0
6031	VFS: Mounted root (ext2 filesystem).
6032
6033	bash#
6034
6035Boot Linux and pass a flat device tree:
6036-----------
6037
6038First, U-Boot must be compiled with the appropriate defines. See the section
6039titled "Linux Kernel Interface" above for a more in depth explanation. The
6040following is an example of how to start a kernel and pass an updated
6041flat device tree:
6042
6043=> print oftaddr
6044oftaddr=0x300000
6045=> print oft
6046oft=oftrees/mpc8540ads.dtb
6047=> tftp $oftaddr $oft
6048Speed: 1000, full duplex
6049Using TSEC0 device
6050TFTP from server 192.168.1.1; our IP address is 192.168.1.101
6051Filename 'oftrees/mpc8540ads.dtb'.
6052Load address: 0x300000
6053Loading: #
6054done
6055Bytes transferred = 4106 (100a hex)
6056=> tftp $loadaddr $bootfile
6057Speed: 1000, full duplex
6058Using TSEC0 device
6059TFTP from server 192.168.1.1; our IP address is 192.168.1.2
6060Filename 'uImage'.
6061Load address: 0x200000
6062Loading:############
6063done
6064Bytes transferred = 1029407 (fb51f hex)
6065=> print loadaddr
6066loadaddr=200000
6067=> print oftaddr
6068oftaddr=0x300000
6069=> bootm $loadaddr - $oftaddr
6070## Booting image at 00200000 ...
6071   Image Name:	 Linux-2.6.17-dirty
6072   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
6073   Data Size:	 1029343 Bytes = 1005.2 kB
6074   Load Address: 00000000
6075   Entry Point:	 00000000
6076   Verifying Checksum ... OK
6077   Uncompressing Kernel Image ... OK
6078Booting using flat device tree at 0x300000
6079Using MPC85xx ADS machine description
6080Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
6081[snip]
6082
6083
6084More About U-Boot Image Types:
6085------------------------------
6086
6087U-Boot supports the following image types:
6088
6089   "Standalone Programs" are directly runnable in the environment
6090	provided by U-Boot; it is expected that (if they behave
6091	well) you can continue to work in U-Boot after return from
6092	the Standalone Program.
6093   "OS Kernel Images" are usually images of some Embedded OS which
6094	will take over control completely. Usually these programs
6095	will install their own set of exception handlers, device
6096	drivers, set up the MMU, etc. - this means, that you cannot
6097	expect to re-enter U-Boot except by resetting the CPU.
6098   "RAMDisk Images" are more or less just data blocks, and their
6099	parameters (address, size) are passed to an OS kernel that is
6100	being started.
6101   "Multi-File Images" contain several images, typically an OS
6102	(Linux) kernel image and one or more data images like
6103	RAMDisks. This construct is useful for instance when you want
6104	to boot over the network using BOOTP etc., where the boot
6105	server provides just a single image file, but you want to get
6106	for instance an OS kernel and a RAMDisk image.
6107
6108	"Multi-File Images" start with a list of image sizes, each
6109	image size (in bytes) specified by an "uint32_t" in network
6110	byte order. This list is terminated by an "(uint32_t)0".
6111	Immediately after the terminating 0 follow the images, one by
6112	one, all aligned on "uint32_t" boundaries (size rounded up to
6113	a multiple of 4 bytes).
6114
6115   "Firmware Images" are binary images containing firmware (like
6116	U-Boot or FPGA images) which usually will be programmed to
6117	flash memory.
6118
6119   "Script files" are command sequences that will be executed by
6120	U-Boot's command interpreter; this feature is especially
6121	useful when you configure U-Boot to use a real shell (hush)
6122	as command interpreter.
6123
6124Booting the Linux zImage:
6125-------------------------
6126
6127On some platforms, it's possible to boot Linux zImage. This is done
6128using the "bootz" command. The syntax of "bootz" command is the same
6129as the syntax of "bootm" command.
6130
6131Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
6132kernel with raw initrd images. The syntax is slightly different, the
6133address of the initrd must be augmented by it's size, in the following
6134format: "<initrd addres>:<initrd size>".
6135
6136
6137Standalone HOWTO:
6138=================
6139
6140One of the features of U-Boot is that you can dynamically load and
6141run "standalone" applications, which can use some resources of
6142U-Boot like console I/O functions or interrupt services.
6143
6144Two simple examples are included with the sources:
6145
6146"Hello World" Demo:
6147-------------------
6148
6149'examples/hello_world.c' contains a small "Hello World" Demo
6150application; it is automatically compiled when you build U-Boot.
6151It's configured to run at address 0x00040004, so you can play with it
6152like that:
6153
6154	=> loads
6155	## Ready for S-Record download ...
6156	~>examples/hello_world.srec
6157	1 2 3 4 5 6 7 8 9 10 11 ...
6158	[file transfer complete]
6159	[connected]
6160	## Start Addr = 0x00040004
6161
6162	=> go 40004 Hello World! This is a test.
6163	## Starting application at 0x00040004 ...
6164	Hello World
6165	argc = 7
6166	argv[0] = "40004"
6167	argv[1] = "Hello"
6168	argv[2] = "World!"
6169	argv[3] = "This"
6170	argv[4] = "is"
6171	argv[5] = "a"
6172	argv[6] = "test."
6173	argv[7] = "<NULL>"
6174	Hit any key to exit ...
6175
6176	## Application terminated, rc = 0x0
6177
6178Another example, which demonstrates how to register a CPM interrupt
6179handler with the U-Boot code, can be found in 'examples/timer.c'.
6180Here, a CPM timer is set up to generate an interrupt every second.
6181The interrupt service routine is trivial, just printing a '.'
6182character, but this is just a demo program. The application can be
6183controlled by the following keys:
6184
6185	? - print current values og the CPM Timer registers
6186	b - enable interrupts and start timer
6187	e - stop timer and disable interrupts
6188	q - quit application
6189
6190	=> loads
6191	## Ready for S-Record download ...
6192	~>examples/timer.srec
6193	1 2 3 4 5 6 7 8 9 10 11 ...
6194	[file transfer complete]
6195	[connected]
6196	## Start Addr = 0x00040004
6197
6198	=> go 40004
6199	## Starting application at 0x00040004 ...
6200	TIMERS=0xfff00980
6201	Using timer 1
6202	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
6203
6204Hit 'b':
6205	[q, b, e, ?] Set interval 1000000 us
6206	Enabling timer
6207Hit '?':
6208	[q, b, e, ?] ........
6209	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
6210Hit '?':
6211	[q, b, e, ?] .
6212	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
6213Hit '?':
6214	[q, b, e, ?] .
6215	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
6216Hit '?':
6217	[q, b, e, ?] .
6218	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
6219Hit 'e':
6220	[q, b, e, ?] ...Stopping timer
6221Hit 'q':
6222	[q, b, e, ?] ## Application terminated, rc = 0x0
6223
6224
6225Minicom warning:
6226================
6227
6228Over time, many people have reported problems when trying to use the
6229"minicom" terminal emulation program for serial download. I (wd)
6230consider minicom to be broken, and recommend not to use it. Under
6231Unix, I recommend to use C-Kermit for general purpose use (and
6232especially for kermit binary protocol download ("loadb" command), and
6233use "cu" for S-Record download ("loads" command).  See
6234http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
6235for help with kermit.
6236
6237
6238Nevertheless, if you absolutely want to use it try adding this
6239configuration to your "File transfer protocols" section:
6240
6241	   Name	   Program			Name U/D FullScr IO-Red. Multi
6242	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
6243	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
6244
6245
6246NetBSD Notes:
6247=============
6248
6249Starting at version 0.9.2, U-Boot supports NetBSD both as host
6250(build U-Boot) and target system (boots NetBSD/mpc8xx).
6251
6252Building requires a cross environment; it is known to work on
6253NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
6254need gmake since the Makefiles are not compatible with BSD make).
6255Note that the cross-powerpc package does not install include files;
6256attempting to build U-Boot will fail because <machine/ansi.h> is
6257missing.  This file has to be installed and patched manually:
6258
6259	# cd /usr/pkg/cross/powerpc-netbsd/include
6260	# mkdir powerpc
6261	# ln -s powerpc machine
6262	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
6263	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
6264
6265Native builds *don't* work due to incompatibilities between native
6266and U-Boot include files.
6267
6268Booting assumes that (the first part of) the image booted is a
6269stage-2 loader which in turn loads and then invokes the kernel
6270proper. Loader sources will eventually appear in the NetBSD source
6271tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
6272meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
6273
6274
6275Implementation Internals:
6276=========================
6277
6278The following is not intended to be a complete description of every
6279implementation detail. However, it should help to understand the
6280inner workings of U-Boot and make it easier to port it to custom
6281hardware.
6282
6283
6284Initial Stack, Global Data:
6285---------------------------
6286
6287The implementation of U-Boot is complicated by the fact that U-Boot
6288starts running out of ROM (flash memory), usually without access to
6289system RAM (because the memory controller is not initialized yet).
6290This means that we don't have writable Data or BSS segments, and BSS
6291is not initialized as zero. To be able to get a C environment working
6292at all, we have to allocate at least a minimal stack. Implementation
6293options for this are defined and restricted by the CPU used: Some CPU
6294models provide on-chip memory (like the IMMR area on MPC8xx and
6295MPC826x processors), on others (parts of) the data cache can be
6296locked as (mis-) used as memory, etc.
6297
6298	Chris Hallinan posted a good summary of these issues to the
6299	U-Boot mailing list:
6300
6301	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
6302	From: "Chris Hallinan" <clh@net1plus.com>
6303	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
6304	...
6305
6306	Correct me if I'm wrong, folks, but the way I understand it
6307	is this: Using DCACHE as initial RAM for Stack, etc, does not
6308	require any physical RAM backing up the cache. The cleverness
6309	is that the cache is being used as a temporary supply of
6310	necessary storage before the SDRAM controller is setup. It's
6311	beyond the scope of this list to explain the details, but you
6312	can see how this works by studying the cache architecture and
6313	operation in the architecture and processor-specific manuals.
6314
6315	OCM is On Chip Memory, which I believe the 405GP has 4K. It
6316	is another option for the system designer to use as an
6317	initial stack/RAM area prior to SDRAM being available. Either
6318	option should work for you. Using CS 4 should be fine if your
6319	board designers haven't used it for something that would
6320	cause you grief during the initial boot! It is frequently not
6321	used.
6322
6323	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
6324	with your processor/board/system design. The default value
6325	you will find in any recent u-boot distribution in
6326	walnut.h should work for you. I'd set it to a value larger
6327	than your SDRAM module. If you have a 64MB SDRAM module, set
6328	it above 400_0000. Just make sure your board has no resources
6329	that are supposed to respond to that address! That code in
6330	start.S has been around a while and should work as is when
6331	you get the config right.
6332
6333	-Chris Hallinan
6334	DS4.COM, Inc.
6335
6336It is essential to remember this, since it has some impact on the C
6337code for the initialization procedures:
6338
6339* Initialized global data (data segment) is read-only. Do not attempt
6340  to write it.
6341
6342* Do not use any uninitialized global data (or implicitly initialized
6343  as zero data - BSS segment) at all - this is undefined, initiali-
6344  zation is performed later (when relocating to RAM).
6345
6346* Stack space is very limited. Avoid big data buffers or things like
6347  that.
6348
6349Having only the stack as writable memory limits means we cannot use
6350normal global data to share information between the code. But it
6351turned out that the implementation of U-Boot can be greatly
6352simplified by making a global data structure (gd_t) available to all
6353functions. We could pass a pointer to this data as argument to _all_
6354functions, but this would bloat the code. Instead we use a feature of
6355the GCC compiler (Global Register Variables) to share the data: we
6356place a pointer (gd) to the global data into a register which we
6357reserve for this purpose.
6358
6359When choosing a register for such a purpose we are restricted by the
6360relevant  (E)ABI  specifications for the current architecture, and by
6361GCC's implementation.
6362
6363For PowerPC, the following registers have specific use:
6364	R1:	stack pointer
6365	R2:	reserved for system use
6366	R3-R4:	parameter passing and return values
6367	R5-R10: parameter passing
6368	R13:	small data area pointer
6369	R30:	GOT pointer
6370	R31:	frame pointer
6371
6372	(U-Boot also uses R12 as internal GOT pointer. r12
6373	is a volatile register so r12 needs to be reset when
6374	going back and forth between asm and C)
6375
6376    ==> U-Boot will use R2 to hold a pointer to the global data
6377
6378    Note: on PPC, we could use a static initializer (since the
6379    address of the global data structure is known at compile time),
6380    but it turned out that reserving a register results in somewhat
6381    smaller code - although the code savings are not that big (on
6382    average for all boards 752 bytes for the whole U-Boot image,
6383    624 text + 127 data).
6384
6385On Blackfin, the normal C ABI (except for P3) is followed as documented here:
6386	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
6387
6388    ==> U-Boot will use P3 to hold a pointer to the global data
6389
6390On ARM, the following registers are used:
6391
6392	R0:	function argument word/integer result
6393	R1-R3:	function argument word
6394	R9:	platform specific
6395	R10:	stack limit (used only if stack checking is enabled)
6396	R11:	argument (frame) pointer
6397	R12:	temporary workspace
6398	R13:	stack pointer
6399	R14:	link register
6400	R15:	program counter
6401
6402    ==> U-Boot will use R9 to hold a pointer to the global data
6403
6404    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
6405
6406On Nios II, the ABI is documented here:
6407	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
6408
6409    ==> U-Boot will use gp to hold a pointer to the global data
6410
6411    Note: on Nios II, we give "-G0" option to gcc and don't use gp
6412    to access small data sections, so gp is free.
6413
6414On NDS32, the following registers are used:
6415
6416	R0-R1:	argument/return
6417	R2-R5:	argument
6418	R15:	temporary register for assembler
6419	R16:	trampoline register
6420	R28:	frame pointer (FP)
6421	R29:	global pointer (GP)
6422	R30:	link register (LP)
6423	R31:	stack pointer (SP)
6424	PC:	program counter (PC)
6425
6426    ==> U-Boot will use R10 to hold a pointer to the global data
6427
6428NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
6429or current versions of GCC may "optimize" the code too much.
6430
6431Memory Management:
6432------------------
6433
6434U-Boot runs in system state and uses physical addresses, i.e. the
6435MMU is not used either for address mapping nor for memory protection.
6436
6437The available memory is mapped to fixed addresses using the memory
6438controller. In this process, a contiguous block is formed for each
6439memory type (Flash, SDRAM, SRAM), even when it consists of several
6440physical memory banks.
6441
6442U-Boot is installed in the first 128 kB of the first Flash bank (on
6443TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
6444booting and sizing and initializing DRAM, the code relocates itself
6445to the upper end of DRAM. Immediately below the U-Boot code some
6446memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
6447configuration setting]. Below that, a structure with global Board
6448Info data is placed, followed by the stack (growing downward).
6449
6450Additionally, some exception handler code is copied to the low 8 kB
6451of DRAM (0x00000000 ... 0x00001FFF).
6452
6453So a typical memory configuration with 16 MB of DRAM could look like
6454this:
6455
6456	0x0000 0000	Exception Vector code
6457	      :
6458	0x0000 1FFF
6459	0x0000 2000	Free for Application Use
6460	      :
6461	      :
6462
6463	      :
6464	      :
6465	0x00FB FF20	Monitor Stack (Growing downward)
6466	0x00FB FFAC	Board Info Data and permanent copy of global data
6467	0x00FC 0000	Malloc Arena
6468	      :
6469	0x00FD FFFF
6470	0x00FE 0000	RAM Copy of Monitor Code
6471	...		eventually: LCD or video framebuffer
6472	...		eventually: pRAM (Protected RAM - unchanged by reset)
6473	0x00FF FFFF	[End of RAM]
6474
6475
6476System Initialization:
6477----------------------
6478
6479In the reset configuration, U-Boot starts at the reset entry point
6480(on most PowerPC systems at address 0x00000100). Because of the reset
6481configuration for CS0# this is a mirror of the on board Flash memory.
6482To be able to re-map memory U-Boot then jumps to its link address.
6483To be able to implement the initialization code in C, a (small!)
6484initial stack is set up in the internal Dual Ported RAM (in case CPUs
6485which provide such a feature like MPC8xx or MPC8260), or in a locked
6486part of the data cache. After that, U-Boot initializes the CPU core,
6487the caches and the SIU.
6488
6489Next, all (potentially) available memory banks are mapped using a
6490preliminary mapping. For example, we put them on 512 MB boundaries
6491(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
6492on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
6493programmed for SDRAM access. Using the temporary configuration, a
6494simple memory test is run that determines the size of the SDRAM
6495banks.
6496
6497When there is more than one SDRAM bank, and the banks are of
6498different size, the largest is mapped first. For equal size, the first
6499bank (CS2#) is mapped first. The first mapping is always for address
65000x00000000, with any additional banks following immediately to create
6501contiguous memory starting from 0.
6502
6503Then, the monitor installs itself at the upper end of the SDRAM area
6504and allocates memory for use by malloc() and for the global Board
6505Info data; also, the exception vector code is copied to the low RAM
6506pages, and the final stack is set up.
6507
6508Only after this relocation will you have a "normal" C environment;
6509until that you are restricted in several ways, mostly because you are
6510running from ROM, and because the code will have to be relocated to a
6511new address in RAM.
6512
6513
6514U-Boot Porting Guide:
6515----------------------
6516
6517[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
6518list, October 2002]
6519
6520
6521int main(int argc, char *argv[])
6522{
6523	sighandler_t no_more_time;
6524
6525	signal(SIGALRM, no_more_time);
6526	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6527
6528	if (available_money > available_manpower) {
6529		Pay consultant to port U-Boot;
6530		return 0;
6531	}
6532
6533	Download latest U-Boot source;
6534
6535	Subscribe to u-boot mailing list;
6536
6537	if (clueless)
6538		email("Hi, I am new to U-Boot, how do I get started?");
6539
6540	while (learning) {
6541		Read the README file in the top level directory;
6542		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6543		Read applicable doc/*.README;
6544		Read the source, Luke;
6545		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6546	}
6547
6548	if (available_money > toLocalCurrency ($2500))
6549		Buy a BDI3000;
6550	else
6551		Add a lot of aggravation and time;
6552
6553	if (a similar board exists) {	/* hopefully... */
6554		cp -a board/<similar> board/<myboard>
6555		cp include/configs/<similar>.h include/configs/<myboard>.h
6556	} else {
6557		Create your own board support subdirectory;
6558		Create your own board include/configs/<myboard>.h file;
6559	}
6560	Edit new board/<myboard> files
6561	Edit new include/configs/<myboard>.h
6562
6563	while (!accepted) {
6564		while (!running) {
6565			do {
6566				Add / modify source code;
6567			} until (compiles);
6568			Debug;
6569			if (clueless)
6570				email("Hi, I am having problems...");
6571		}
6572		Send patch file to the U-Boot email list;
6573		if (reasonable critiques)
6574			Incorporate improvements from email list code review;
6575		else
6576			Defend code as written;
6577	}
6578
6579	return 0;
6580}
6581
6582void no_more_time (int sig)
6583{
6584      hire_a_guru();
6585}
6586
6587
6588Coding Standards:
6589-----------------
6590
6591All contributions to U-Boot should conform to the Linux kernel
6592coding style; see the file "Documentation/CodingStyle" and the script
6593"scripts/Lindent" in your Linux kernel source directory.
6594
6595Source files originating from a different project (for example the
6596MTD subsystem) are generally exempt from these guidelines and are not
6597reformatted to ease subsequent migration to newer versions of those
6598sources.
6599
6600Please note that U-Boot is implemented in C (and to some small parts in
6601Assembler); no C++ is used, so please do not use C++ style comments (//)
6602in your code.
6603
6604Please also stick to the following formatting rules:
6605- remove any trailing white space
6606- use TAB characters for indentation and vertical alignment, not spaces
6607- make sure NOT to use DOS '\r\n' line feeds
6608- do not add more than 2 consecutive empty lines to source files
6609- do not add trailing empty lines to source files
6610
6611Submissions which do not conform to the standards may be returned
6612with a request to reformat the changes.
6613
6614
6615Submitting Patches:
6616-------------------
6617
6618Since the number of patches for U-Boot is growing, we need to
6619establish some rules. Submissions which do not conform to these rules
6620may be rejected, even when they contain important and valuable stuff.
6621
6622Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6623
6624Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6625see http://lists.denx.de/mailman/listinfo/u-boot
6626
6627When you send a patch, please include the following information with
6628it:
6629
6630* For bug fixes: a description of the bug and how your patch fixes
6631  this bug. Please try to include a way of demonstrating that the
6632  patch actually fixes something.
6633
6634* For new features: a description of the feature and your
6635  implementation.
6636
6637* A CHANGELOG entry as plaintext (separate from the patch)
6638
6639* For major contributions, your entry to the CREDITS file
6640
6641* When you add support for a new board, don't forget to add a
6642  maintainer e-mail address to the boards.cfg file, too.
6643
6644* If your patch adds new configuration options, don't forget to
6645  document these in the README file.
6646
6647* The patch itself. If you are using git (which is *strongly*
6648  recommended) you can easily generate the patch using the
6649  "git format-patch". If you then use "git send-email" to send it to
6650  the U-Boot mailing list, you will avoid most of the common problems
6651  with some other mail clients.
6652
6653  If you cannot use git, use "diff -purN OLD NEW". If your version of
6654  diff does not support these options, then get the latest version of
6655  GNU diff.
6656
6657  The current directory when running this command shall be the parent
6658  directory of the U-Boot source tree (i. e. please make sure that
6659  your patch includes sufficient directory information for the
6660  affected files).
6661
6662  We prefer patches as plain text. MIME attachments are discouraged,
6663  and compressed attachments must not be used.
6664
6665* If one logical set of modifications affects or creates several
6666  files, all these changes shall be submitted in a SINGLE patch file.
6667
6668* Changesets that contain different, unrelated modifications shall be
6669  submitted as SEPARATE patches, one patch per changeset.
6670
6671
6672Notes:
6673
6674* Before sending the patch, run the MAKEALL script on your patched
6675  source tree and make sure that no errors or warnings are reported
6676  for any of the boards.
6677
6678* Keep your modifications to the necessary minimum: A patch
6679  containing several unrelated changes or arbitrary reformats will be
6680  returned with a request to re-formatting / split it.
6681
6682* If you modify existing code, make sure that your new code does not
6683  add to the memory footprint of the code ;-) Small is beautiful!
6684  When adding new features, these should compile conditionally only
6685  (using #ifdef), and the resulting code with the new feature
6686  disabled must not need more memory than the old code without your
6687  modification.
6688
6689* Remember that there is a size limit of 100 kB per message on the
6690  u-boot mailing list. Bigger patches will be moderated. If they are
6691  reasonable and not too big, they will be acknowledged. But patches
6692  bigger than the size limit should be avoided.
6693