xref: /openbmc/u-boot/README (revision d7c865bdf2588c5f5936cc92fe679c68397196e3)
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		NOTE: The following can be machine specific errata. These
694		do have ability to provide rudimentary version and machine
695		specific checks, but expect no product checks.
696		CONFIG_ARM_ERRATA_430973
697		CONFIG_ARM_ERRATA_454179
698		CONFIG_ARM_ERRATA_621766
699		CONFIG_ARM_ERRATA_798870
700
701- Tegra SoC options:
702		CONFIG_TEGRA_SUPPORT_NON_SECURE
703
704		Support executing U-Boot in non-secure (NS) mode. Certain
705		impossible actions will be skipped if the CPU is in NS mode,
706		such as ARM architectural timer initialization.
707
708- Linux Kernel Interface:
709		CONFIG_CLOCKS_IN_MHZ
710
711		U-Boot stores all clock information in Hz
712		internally. For binary compatibility with older Linux
713		kernels (which expect the clocks passed in the
714		bd_info data to be in MHz) the environment variable
715		"clocks_in_mhz" can be defined so that U-Boot
716		converts clock data to MHZ before passing it to the
717		Linux kernel.
718		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
719		"clocks_in_mhz=1" is automatically included in the
720		default environment.
721
722		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
723
724		When transferring memsize parameter to Linux, some versions
725		expect it to be in bytes, others in MB.
726		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
727
728		CONFIG_OF_LIBFDT
729
730		New kernel versions are expecting firmware settings to be
731		passed using flattened device trees (based on open firmware
732		concepts).
733
734		CONFIG_OF_LIBFDT
735		 * New libfdt-based support
736		 * Adds the "fdt" command
737		 * The bootm command automatically updates the fdt
738
739		OF_CPU - The proper name of the cpus node (only required for
740			MPC512X and MPC5xxx based boards).
741		OF_SOC - The proper name of the soc node (only required for
742			MPC512X and MPC5xxx based boards).
743		OF_TBCLK - The timebase frequency.
744		OF_STDOUT_PATH - The path to the console device
745
746		boards with QUICC Engines require OF_QE to set UCC MAC
747		addresses
748
749		CONFIG_OF_BOARD_SETUP
750
751		Board code has addition modification that it wants to make
752		to the flat device tree before handing it off to the kernel
753
754		CONFIG_OF_SYSTEM_SETUP
755
756		Other code has addition modification that it wants to make
757		to the flat device tree before handing it off to the kernel.
758		This causes ft_system_setup() to be called before booting
759		the kernel.
760
761		CONFIG_OF_BOOT_CPU
762
763		This define fills in the correct boot CPU in the boot
764		param header, the default value is zero if undefined.
765
766		CONFIG_OF_IDE_FIXUP
767
768		U-Boot can detect if an IDE device is present or not.
769		If not, and this new config option is activated, U-Boot
770		removes the ATA node from the DTS before booting Linux,
771		so the Linux IDE driver does not probe the device and
772		crash. This is needed for buggy hardware (uc101) where
773		no pull down resistor is connected to the signal IDE5V_DD7.
774
775		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
776
777		This setting is mandatory for all boards that have only one
778		machine type and must be used to specify the machine type
779		number as it appears in the ARM machine registry
780		(see http://www.arm.linux.org.uk/developer/machines/).
781		Only boards that have multiple machine types supported
782		in a single configuration file and the machine type is
783		runtime discoverable, do not have to use this setting.
784
785- vxWorks boot parameters:
786
787		bootvx constructs a valid bootline using the following
788		environments variables: bootfile, ipaddr, serverip, hostname.
789		It loads the vxWorks image pointed bootfile.
790
791		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
792		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
793		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
794		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
795
796		CONFIG_SYS_VXWORKS_ADD_PARAMS
797
798		Add it at the end of the bootline. E.g "u=username pw=secret"
799
800		Note: If a "bootargs" environment is defined, it will overwride
801		the defaults discussed just above.
802
803- Cache Configuration:
804		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
805		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
806		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
807
808- Cache Configuration for ARM:
809		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
810				      controller
811		CONFIG_SYS_PL310_BASE - Physical base address of PL310
812					controller register space
813
814- Serial Ports:
815		CONFIG_PL010_SERIAL
816
817		Define this if you want support for Amba PrimeCell PL010 UARTs.
818
819		CONFIG_PL011_SERIAL
820
821		Define this if you want support for Amba PrimeCell PL011 UARTs.
822
823		CONFIG_PL011_CLOCK
824
825		If you have Amba PrimeCell PL011 UARTs, set this variable to
826		the clock speed of the UARTs.
827
828		CONFIG_PL01x_PORTS
829
830		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
831		define this to a list of base addresses for each (supported)
832		port. See e.g. include/configs/versatile.h
833
834		CONFIG_PL011_SERIAL_RLCR
835
836		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
837		have separate receive and transmit line control registers.  Set
838		this variable to initialize the extra register.
839
840		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
841
842		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
843		boot loader that has already initialized the UART.  Define this
844		variable to flush the UART at init time.
845
846		CONFIG_SERIAL_HW_FLOW_CONTROL
847
848		Define this variable to enable hw flow control in serial driver.
849		Current user of this option is drivers/serial/nsl16550.c driver
850
851- Console Interface:
852		Depending on board, define exactly one serial port
853		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
854		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
855		console by defining CONFIG_8xx_CONS_NONE
856
857		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
858		port routines must be defined elsewhere
859		(i.e. serial_init(), serial_getc(), ...)
860
861		CONFIG_CFB_CONSOLE
862		Enables console device for a color framebuffer. Needs following
863		defines (cf. smiLynxEM, i8042)
864			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
865						(default big endian)
866			VIDEO_HW_RECTFILL	graphic chip supports
867						rectangle fill
868						(cf. smiLynxEM)
869			VIDEO_HW_BITBLT		graphic chip supports
870						bit-blit (cf. smiLynxEM)
871			VIDEO_VISIBLE_COLS	visible pixel columns
872						(cols=pitch)
873			VIDEO_VISIBLE_ROWS	visible pixel rows
874			VIDEO_PIXEL_SIZE	bytes per pixel
875			VIDEO_DATA_FORMAT	graphic data format
876						(0-5, cf. cfb_console.c)
877			VIDEO_FB_ADRS		framebuffer address
878			VIDEO_KBD_INIT_FCT	keyboard int fct
879						(i.e. i8042_kbd_init())
880			VIDEO_TSTC_FCT		test char fct
881						(i.e. i8042_tstc)
882			VIDEO_GETC_FCT		get char fct
883						(i.e. i8042_getc)
884			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
885						(requires blink timer
886						cf. i8042.c)
887			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
888			CONFIG_CONSOLE_TIME	display time/date info in
889						upper right corner
890						(requires CONFIG_CMD_DATE)
891			CONFIG_VIDEO_LOGO	display Linux logo in
892						upper left corner
893			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
894						linux_logo.h for logo.
895						Requires CONFIG_VIDEO_LOGO
896			CONFIG_CONSOLE_EXTRA_INFO
897						additional board info beside
898						the logo
899
900		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
901		a limited number of ANSI escape sequences (cursor control,
902		erase functions and limited graphics rendition control).
903
904		When CONFIG_CFB_CONSOLE is defined, video console is
905		default i/o. Serial console can be forced with
906		environment 'console=serial'.
907
908		When CONFIG_SILENT_CONSOLE is defined, all console
909		messages (by U-Boot and Linux!) can be silenced with
910		the "silent" environment variable. See
911		doc/README.silent for more information.
912
913		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
914			is 0x00.
915		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
916			is 0xa0.
917
918- Console Baudrate:
919		CONFIG_BAUDRATE - in bps
920		Select one of the baudrates listed in
921		CONFIG_SYS_BAUDRATE_TABLE, see below.
922		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
923
924- Console Rx buffer length
925		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
926		the maximum receive buffer length for the SMC.
927		This option is actual only for 82xx and 8xx possible.
928		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
929		must be defined, to setup the maximum idle timeout for
930		the SMC.
931
932- Pre-Console Buffer:
933		Prior to the console being initialised (i.e. serial UART
934		initialised etc) all console output is silently discarded.
935		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
936		buffer any console messages prior to the console being
937		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
938		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
939		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
940		bytes are output before the console is initialised, the
941		earlier bytes are discarded.
942
943		'Sane' compilers will generate smaller code if
944		CONFIG_PRE_CON_BUF_SZ is a power of 2
945
946- Safe printf() functions
947		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
948		the printf() functions. These are defined in
949		include/vsprintf.h and include snprintf(), vsnprintf() and
950		so on. Code size increase is approximately 300-500 bytes.
951		If this option is not given then these functions will
952		silently discard their buffer size argument - this means
953		you are not getting any overflow checking in this case.
954
955- Boot Delay:	CONFIG_BOOTDELAY - in seconds
956		Delay before automatically booting the default image;
957		set to -1 to disable autoboot.
958		set to -2 to autoboot with no delay and not check for abort
959		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
960
961		See doc/README.autoboot for these options that
962		work with CONFIG_BOOTDELAY. None are required.
963		CONFIG_BOOT_RETRY_TIME
964		CONFIG_BOOT_RETRY_MIN
965		CONFIG_AUTOBOOT_KEYED
966		CONFIG_AUTOBOOT_PROMPT
967		CONFIG_AUTOBOOT_DELAY_STR
968		CONFIG_AUTOBOOT_STOP_STR
969		CONFIG_AUTOBOOT_DELAY_STR2
970		CONFIG_AUTOBOOT_STOP_STR2
971		CONFIG_ZERO_BOOTDELAY_CHECK
972		CONFIG_RESET_TO_RETRY
973
974- Autoboot Command:
975		CONFIG_BOOTCOMMAND
976		Only needed when CONFIG_BOOTDELAY is enabled;
977		define a command string that is automatically executed
978		when no character is read on the console interface
979		within "Boot Delay" after reset.
980
981		CONFIG_BOOTARGS
982		This can be used to pass arguments to the bootm
983		command. The value of CONFIG_BOOTARGS goes into the
984		environment value "bootargs".
985
986		CONFIG_RAMBOOT and CONFIG_NFSBOOT
987		The value of these goes into the environment as
988		"ramboot" and "nfsboot" respectively, and can be used
989		as a convenience, when switching between booting from
990		RAM and NFS.
991
992- Bootcount:
993		CONFIG_BOOTCOUNT_LIMIT
994		Implements a mechanism for detecting a repeating reboot
995		cycle, see:
996		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
997
998		CONFIG_BOOTCOUNT_ENV
999		If no softreset save registers are found on the hardware
1000		"bootcount" is stored in the environment. To prevent a
1001		saveenv on all reboots, the environment variable
1002		"upgrade_available" is used. If "upgrade_available" is
1003		0, "bootcount" is always 0, if "upgrade_available" is
1004		1 "bootcount" is incremented in the environment.
1005		So the Userspace Applikation must set the "upgrade_available"
1006		and "bootcount" variable to 0, if a boot was successfully.
1007
1008- Pre-Boot Commands:
1009		CONFIG_PREBOOT
1010
1011		When this option is #defined, the existence of the
1012		environment variable "preboot" will be checked
1013		immediately before starting the CONFIG_BOOTDELAY
1014		countdown and/or running the auto-boot command resp.
1015		entering interactive mode.
1016
1017		This feature is especially useful when "preboot" is
1018		automatically generated or modified. For an example
1019		see the LWMON board specific code: here "preboot" is
1020		modified when the user holds down a certain
1021		combination of keys on the (special) keyboard when
1022		booting the systems
1023
1024- Serial Download Echo Mode:
1025		CONFIG_LOADS_ECHO
1026		If defined to 1, all characters received during a
1027		serial download (using the "loads" command) are
1028		echoed back. This might be needed by some terminal
1029		emulations (like "cu"), but may as well just take
1030		time on others. This setting #define's the initial
1031		value of the "loads_echo" environment variable.
1032
1033- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
1034		CONFIG_KGDB_BAUDRATE
1035		Select one of the baudrates listed in
1036		CONFIG_SYS_BAUDRATE_TABLE, see below.
1037
1038- Monitor Functions:
1039		Monitor commands can be included or excluded
1040		from the build by using the #include files
1041		<config_cmd_all.h> and #undef'ing unwanted
1042		commands, or using <config_cmd_default.h>
1043		and augmenting with additional #define's
1044		for wanted commands.
1045
1046		The default command configuration includes all commands
1047		except those marked below with a "*".
1048
1049		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
1050		CONFIG_CMD_ASKENV	* ask for env variable
1051		CONFIG_CMD_BDI		  bdinfo
1052		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
1053		CONFIG_CMD_BMP		* BMP support
1054		CONFIG_CMD_BSP		* Board specific commands
1055		CONFIG_CMD_BOOTD	  bootd
1056		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
1057		CONFIG_CMD_CACHE	* icache, dcache
1058		CONFIG_CMD_CLK   	* clock command support
1059		CONFIG_CMD_CONSOLE	  coninfo
1060		CONFIG_CMD_CRC32	* crc32
1061		CONFIG_CMD_DATE		* support for RTC, date/time...
1062		CONFIG_CMD_DHCP		* DHCP support
1063		CONFIG_CMD_DIAG		* Diagnostics
1064		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
1065		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
1066		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
1067		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
1068		CONFIG_CMD_DTT		* Digital Therm and Thermostat
1069		CONFIG_CMD_ECHO		  echo arguments
1070		CONFIG_CMD_EDITENV	  edit env variable
1071		CONFIG_CMD_EEPROM	* EEPROM read/write support
1072		CONFIG_CMD_ELF		* bootelf, bootvx
1073		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
1074		CONFIG_CMD_ENV_FLAGS	* display details about env flags
1075		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
1076		CONFIG_CMD_EXPORTENV	* export the environment
1077		CONFIG_CMD_EXT2		* ext2 command support
1078		CONFIG_CMD_EXT4		* ext4 command support
1079		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
1080					  that work for multiple fs types
1081		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
1082		CONFIG_CMD_SAVEENV	  saveenv
1083		CONFIG_CMD_FDC		* Floppy Disk Support
1084		CONFIG_CMD_FAT		* FAT command support
1085		CONFIG_CMD_FLASH	  flinfo, erase, protect
1086		CONFIG_CMD_FPGA		  FPGA device initialization support
1087		CONFIG_CMD_FUSE		* Device fuse support
1088		CONFIG_CMD_GETTIME	* Get time since boot
1089		CONFIG_CMD_GO		* the 'go' command (exec code)
1090		CONFIG_CMD_GREPENV	* search environment
1091		CONFIG_CMD_HASH		* calculate hash / digest
1092		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
1093		CONFIG_CMD_I2C		* I2C serial bus support
1094		CONFIG_CMD_IDE		* IDE harddisk support
1095		CONFIG_CMD_IMI		  iminfo
1096		CONFIG_CMD_IMLS		  List all images found in NOR flash
1097		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
1098		CONFIG_CMD_IMMAP	* IMMR dump support
1099		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
1100		CONFIG_CMD_IMPORTENV	* import an environment
1101		CONFIG_CMD_INI		* import data from an ini file into the env
1102		CONFIG_CMD_IRQ		* irqinfo
1103		CONFIG_CMD_ITEST	  Integer/string test of 2 values
1104		CONFIG_CMD_JFFS2	* JFFS2 Support
1105		CONFIG_CMD_KGDB		* kgdb
1106		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
1107		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
1108					  (169.254.*.*)
1109		CONFIG_CMD_LOADB	  loadb
1110		CONFIG_CMD_LOADS	  loads
1111		CONFIG_CMD_MD5SUM	* print md5 message digest
1112					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
1113		CONFIG_CMD_MEMINFO	* Display detailed memory information
1114		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
1115					  loop, loopw
1116		CONFIG_CMD_MEMTEST	* mtest
1117		CONFIG_CMD_MISC		  Misc functions like sleep etc
1118		CONFIG_CMD_MMC		* MMC memory mapped support
1119		CONFIG_CMD_MII		* MII utility commands
1120		CONFIG_CMD_MTDPARTS	* MTD partition support
1121		CONFIG_CMD_NAND		* NAND support
1122		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
1123		CONFIG_CMD_NFS		  NFS support
1124		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
1125		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
1126		CONFIG_CMD_PCI		* pciinfo
1127		CONFIG_CMD_PCMCIA		* PCMCIA support
1128		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
1129					  host
1130		CONFIG_CMD_PORTIO	* Port I/O
1131		CONFIG_CMD_READ		* Read raw data from partition
1132		CONFIG_CMD_REGINFO	* Register dump
1133		CONFIG_CMD_RUN		  run command in env variable
1134		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
1135		CONFIG_CMD_SAVES	* save S record dump
1136		CONFIG_CMD_SCSI		* SCSI Support
1137		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1138					  (requires CONFIG_CMD_I2C)
1139		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1140					  (4xx only)
1141		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1142		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1143					  (requires CONFIG_CMD_MEMORY)
1144		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1145		CONFIG_CMD_SOURCE	  "source" command Support
1146		CONFIG_CMD_SPI		* SPI serial bus support
1147		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1148		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1149		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1150		CONFIG_CMD_TIMER	* access to the system tick timer
1151		CONFIG_CMD_USB		* USB support
1152		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1153		CONFIG_CMD_MFSL		* Microblaze FSL support
1154		CONFIG_CMD_XIMG		  Load part of Multi Image
1155		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1156
1157		EXAMPLE: If you want all functions except of network
1158		support you can write:
1159
1160		#include "config_cmd_all.h"
1161		#undef CONFIG_CMD_NET
1162
1163	Other Commands:
1164		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1165
1166	Note:	Don't enable the "icache" and "dcache" commands
1167		(configuration option CONFIG_CMD_CACHE) unless you know
1168		what you (and your U-Boot users) are doing. Data
1169		cache cannot be enabled on systems like the 8xx or
1170		8260 (where accesses to the IMMR region must be
1171		uncached), and it cannot be disabled on all other
1172		systems where we (mis-) use the data cache to hold an
1173		initial stack and some data.
1174
1175
1176		XXX - this list needs to get updated!
1177
1178- Regular expression support:
1179		CONFIG_REGEX
1180		If this variable is defined, U-Boot is linked against
1181		the SLRE (Super Light Regular Expression) library,
1182		which adds regex support to some commands, as for
1183		example "env grep" and "setexpr".
1184
1185- Device tree:
1186		CONFIG_OF_CONTROL
1187		If this variable is defined, U-Boot will use a device tree
1188		to configure its devices, instead of relying on statically
1189		compiled #defines in the board file. This option is
1190		experimental and only available on a few boards. The device
1191		tree is available in the global data as gd->fdt_blob.
1192
1193		U-Boot needs to get its device tree from somewhere. This can
1194		be done using one of the two options below:
1195
1196		CONFIG_OF_EMBED
1197		If this variable is defined, U-Boot will embed a device tree
1198		binary in its image. This device tree file should be in the
1199		board directory and called <soc>-<board>.dts. The binary file
1200		is then picked up in board_init_f() and made available through
1201		the global data structure as gd->blob.
1202
1203		CONFIG_OF_SEPARATE
1204		If this variable is defined, U-Boot will build a device tree
1205		binary. It will be called u-boot.dtb. Architecture-specific
1206		code will locate it at run-time. Generally this works by:
1207
1208			cat u-boot.bin u-boot.dtb >image.bin
1209
1210		and in fact, U-Boot does this for you, creating a file called
1211		u-boot-dtb.bin which is useful in the common case. You can
1212		still use the individual files if you need something more
1213		exotic.
1214
1215- Watchdog:
1216		CONFIG_WATCHDOG
1217		If this variable is defined, it enables watchdog
1218		support for the SoC. There must be support in the SoC
1219		specific code for a watchdog. For the 8xx and 8260
1220		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1221		register.  When supported for a specific SoC is
1222		available, then no further board specific code should
1223		be needed to use it.
1224
1225		CONFIG_HW_WATCHDOG
1226		When using a watchdog circuitry external to the used
1227		SoC, then define this variable and provide board
1228		specific code for the "hw_watchdog_reset" function.
1229
1230		CONFIG_AT91_HW_WDT_TIMEOUT
1231		specify the timeout in seconds. default 2 seconds.
1232
1233- U-Boot Version:
1234		CONFIG_VERSION_VARIABLE
1235		If this variable is defined, an environment variable
1236		named "ver" is created by U-Boot showing the U-Boot
1237		version as printed by the "version" command.
1238		Any change to this variable will be reverted at the
1239		next reset.
1240
1241- Real-Time Clock:
1242
1243		When CONFIG_CMD_DATE is selected, the type of the RTC
1244		has to be selected, too. Define exactly one of the
1245		following options:
1246
1247		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1248		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1249		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1250		CONFIG_RTC_MC146818	- use MC146818 RTC
1251		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1252		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1253		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1254		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1255		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1256		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1257		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1258		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1259		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1260					  RV3029 RTC.
1261
1262		Note that if the RTC uses I2C, then the I2C interface
1263		must also be configured. See I2C Support, below.
1264
1265- GPIO Support:
1266		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1267
1268		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1269		chip-ngpio pairs that tell the PCA953X driver the number of
1270		pins supported by a particular chip.
1271
1272		Note that if the GPIO device uses I2C, then the I2C interface
1273		must also be configured. See I2C Support, below.
1274
1275- I/O tracing:
1276		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1277		accesses and can checksum them or write a list of them out
1278		to memory. See the 'iotrace' command for details. This is
1279		useful for testing device drivers since it can confirm that
1280		the driver behaves the same way before and after a code
1281		change. Currently this is supported on sandbox and arm. To
1282		add support for your architecture, add '#include <iotrace.h>'
1283		to the bottom of arch/<arch>/include/asm/io.h and test.
1284
1285		Example output from the 'iotrace stats' command is below.
1286		Note that if the trace buffer is exhausted, the checksum will
1287		still continue to operate.
1288
1289			iotrace is enabled
1290			Start:  10000000	(buffer start address)
1291			Size:   00010000	(buffer size)
1292			Offset: 00000120	(current buffer offset)
1293			Output: 10000120	(start + offset)
1294			Count:  00000018	(number of trace records)
1295			CRC32:  9526fb66	(CRC32 of all trace records)
1296
1297- Timestamp Support:
1298
1299		When CONFIG_TIMESTAMP is selected, the timestamp
1300		(date and time) of an image is printed by image
1301		commands like bootm or iminfo. This option is
1302		automatically enabled when you select CONFIG_CMD_DATE .
1303
1304- Partition Labels (disklabels) Supported:
1305		Zero or more of the following:
1306		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1307		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1308				       Intel architecture, USB sticks, etc.
1309		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1310		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1311				       bootloader.  Note 2TB partition limit; see
1312				       disk/part_efi.c
1313		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1314
1315		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1316		CONFIG_CMD_SCSI) you must configure support for at
1317		least one non-MTD partition type as well.
1318
1319- IDE Reset method:
1320		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1321		board configurations files but used nowhere!
1322
1323		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1324		be performed by calling the function
1325			ide_set_reset(int reset)
1326		which has to be defined in a board specific file
1327
1328- ATAPI Support:
1329		CONFIG_ATAPI
1330
1331		Set this to enable ATAPI support.
1332
1333- LBA48 Support
1334		CONFIG_LBA48
1335
1336		Set this to enable support for disks larger than 137GB
1337		Also look at CONFIG_SYS_64BIT_LBA.
1338		Whithout these , LBA48 support uses 32bit variables and will 'only'
1339		support disks up to 2.1TB.
1340
1341		CONFIG_SYS_64BIT_LBA:
1342			When enabled, makes the IDE subsystem use 64bit sector addresses.
1343			Default is 32bit.
1344
1345- SCSI Support:
1346		At the moment only there is only support for the
1347		SYM53C8XX SCSI controller; define
1348		CONFIG_SCSI_SYM53C8XX to enable it.
1349
1350		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1351		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1352		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1353		maximum numbers of LUNs, SCSI ID's and target
1354		devices.
1355		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1356
1357		The environment variable 'scsidevs' is set to the number of
1358		SCSI devices found during the last scan.
1359
1360- NETWORK Support (PCI):
1361		CONFIG_E1000
1362		Support for Intel 8254x/8257x gigabit chips.
1363
1364		CONFIG_E1000_SPI
1365		Utility code for direct access to the SPI bus on Intel 8257x.
1366		This does not do anything useful unless you set at least one
1367		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1368
1369		CONFIG_E1000_SPI_GENERIC
1370		Allow generic access to the SPI bus on the Intel 8257x, for
1371		example with the "sspi" command.
1372
1373		CONFIG_CMD_E1000
1374		Management command for E1000 devices.  When used on devices
1375		with SPI support you can reprogram the EEPROM from U-Boot.
1376
1377		CONFIG_E1000_FALLBACK_MAC
1378		default MAC for empty EEPROM after production.
1379
1380		CONFIG_EEPRO100
1381		Support for Intel 82557/82559/82559ER chips.
1382		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1383		write routine for first time initialisation.
1384
1385		CONFIG_TULIP
1386		Support for Digital 2114x chips.
1387		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1388		modem chip initialisation (KS8761/QS6611).
1389
1390		CONFIG_NATSEMI
1391		Support for National dp83815 chips.
1392
1393		CONFIG_NS8382X
1394		Support for National dp8382[01] gigabit chips.
1395
1396- NETWORK Support (other):
1397
1398		CONFIG_DRIVER_AT91EMAC
1399		Support for AT91RM9200 EMAC.
1400
1401			CONFIG_RMII
1402			Define this to use reduced MII inteface
1403
1404			CONFIG_DRIVER_AT91EMAC_QUIET
1405			If this defined, the driver is quiet.
1406			The driver doen't show link status messages.
1407
1408		CONFIG_CALXEDA_XGMAC
1409		Support for the Calxeda XGMAC device
1410
1411		CONFIG_LAN91C96
1412		Support for SMSC's LAN91C96 chips.
1413
1414			CONFIG_LAN91C96_BASE
1415			Define this to hold the physical address
1416			of the LAN91C96's I/O space
1417
1418			CONFIG_LAN91C96_USE_32_BIT
1419			Define this to enable 32 bit addressing
1420
1421		CONFIG_SMC91111
1422		Support for SMSC's LAN91C111 chip
1423
1424			CONFIG_SMC91111_BASE
1425			Define this to hold the physical address
1426			of the device (I/O space)
1427
1428			CONFIG_SMC_USE_32_BIT
1429			Define this if data bus is 32 bits
1430
1431			CONFIG_SMC_USE_IOFUNCS
1432			Define this to use i/o functions instead of macros
1433			(some hardware wont work with macros)
1434
1435		CONFIG_DRIVER_TI_EMAC
1436		Support for davinci emac
1437
1438			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1439			Define this if you have more then 3 PHYs.
1440
1441		CONFIG_FTGMAC100
1442		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1443
1444			CONFIG_FTGMAC100_EGIGA
1445			Define this to use GE link update with gigabit PHY.
1446			Define this if FTGMAC100 is connected to gigabit PHY.
1447			If your system has 10/100 PHY only, it might not occur
1448			wrong behavior. Because PHY usually return timeout or
1449			useless data when polling gigabit status and gigabit
1450			control registers. This behavior won't affect the
1451			correctnessof 10/100 link speed update.
1452
1453		CONFIG_SMC911X
1454		Support for SMSC's LAN911x and LAN921x chips
1455
1456			CONFIG_SMC911X_BASE
1457			Define this to hold the physical address
1458			of the device (I/O space)
1459
1460			CONFIG_SMC911X_32_BIT
1461			Define this if data bus is 32 bits
1462
1463			CONFIG_SMC911X_16_BIT
1464			Define this if data bus is 16 bits. If your processor
1465			automatically converts one 32 bit word to two 16 bit
1466			words you may also try CONFIG_SMC911X_32_BIT.
1467
1468		CONFIG_SH_ETHER
1469		Support for Renesas on-chip Ethernet controller
1470
1471			CONFIG_SH_ETHER_USE_PORT
1472			Define the number of ports to be used
1473
1474			CONFIG_SH_ETHER_PHY_ADDR
1475			Define the ETH PHY's address
1476
1477			CONFIG_SH_ETHER_CACHE_WRITEBACK
1478			If this option is set, the driver enables cache flush.
1479
1480- PWM Support:
1481		CONFIG_PWM_IMX
1482		Support for PWM modul on the imx6.
1483
1484- TPM Support:
1485		CONFIG_TPM
1486		Support TPM devices.
1487
1488		CONFIG_TPM_TIS_I2C
1489		Support for i2c bus TPM devices. Only one device
1490		per system is supported at this time.
1491
1492			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1493			Define the the i2c bus number for the TPM device
1494
1495			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1496			Define the TPM's address on the i2c bus
1497
1498			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1499			Define the burst count bytes upper limit
1500
1501		CONFIG_TPM_ATMEL_TWI
1502		Support for Atmel TWI TPM device. Requires I2C support.
1503
1504		CONFIG_TPM_TIS_LPC
1505		Support for generic parallel port TPM devices. Only one device
1506		per system is supported at this time.
1507
1508			CONFIG_TPM_TIS_BASE_ADDRESS
1509			Base address where the generic TPM device is mapped
1510			to. Contemporary x86 systems usually map it at
1511			0xfed40000.
1512
1513		CONFIG_CMD_TPM
1514		Add tpm monitor functions.
1515		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1516		provides monitor access to authorized functions.
1517
1518		CONFIG_TPM
1519		Define this to enable the TPM support library which provides
1520		functional interfaces to some TPM commands.
1521		Requires support for a TPM device.
1522
1523		CONFIG_TPM_AUTH_SESSIONS
1524		Define this to enable authorized functions in the TPM library.
1525		Requires CONFIG_TPM and CONFIG_SHA1.
1526
1527- USB Support:
1528		At the moment only the UHCI host controller is
1529		supported (PIP405, MIP405, MPC5200); define
1530		CONFIG_USB_UHCI to enable it.
1531		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1532		and define CONFIG_USB_STORAGE to enable the USB
1533		storage devices.
1534		Note:
1535		Supported are USB Keyboards and USB Floppy drives
1536		(TEAC FD-05PUB).
1537		MPC5200 USB requires additional defines:
1538			CONFIG_USB_CLOCK
1539				for 528 MHz Clock: 0x0001bbbb
1540			CONFIG_PSC3_USB
1541				for USB on PSC3
1542			CONFIG_USB_CONFIG
1543				for differential drivers: 0x00001000
1544				for single ended drivers: 0x00005000
1545				for differential drivers on PSC3: 0x00000100
1546				for single ended drivers on PSC3: 0x00004100
1547			CONFIG_SYS_USB_EVENT_POLL
1548				May be defined to allow interrupt polling
1549				instead of using asynchronous interrupts
1550
1551		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1552		txfilltuning field in the EHCI controller on reset.
1553
1554		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1555		HW module registers.
1556
1557- USB Device:
1558		Define the below if you wish to use the USB console.
1559		Once firmware is rebuilt from a serial console issue the
1560		command "setenv stdin usbtty; setenv stdout usbtty" and
1561		attach your USB cable. The Unix command "dmesg" should print
1562		it has found a new device. The environment variable usbtty
1563		can be set to gserial or cdc_acm to enable your device to
1564		appear to a USB host as a Linux gserial device or a
1565		Common Device Class Abstract Control Model serial device.
1566		If you select usbtty = gserial you should be able to enumerate
1567		a Linux host by
1568		# modprobe usbserial vendor=0xVendorID product=0xProductID
1569		else if using cdc_acm, simply setting the environment
1570		variable usbtty to be cdc_acm should suffice. The following
1571		might be defined in YourBoardName.h
1572
1573			CONFIG_USB_DEVICE
1574			Define this to build a UDC device
1575
1576			CONFIG_USB_TTY
1577			Define this to have a tty type of device available to
1578			talk to the UDC device
1579
1580			CONFIG_USBD_HS
1581			Define this to enable the high speed support for usb
1582			device and usbtty. If this feature is enabled, a routine
1583			int is_usbd_high_speed(void)
1584			also needs to be defined by the driver to dynamically poll
1585			whether the enumeration has succeded at high speed or full
1586			speed.
1587
1588			CONFIG_SYS_CONSOLE_IS_IN_ENV
1589			Define this if you want stdin, stdout &/or stderr to
1590			be set to usbtty.
1591
1592			mpc8xx:
1593				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1594				Derive USB clock from external clock "blah"
1595				- CONFIG_SYS_USB_EXTC_CLK 0x02
1596
1597				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1598				Derive USB clock from brgclk
1599				- CONFIG_SYS_USB_BRG_CLK 0x04
1600
1601		If you have a USB-IF assigned VendorID then you may wish to
1602		define your own vendor specific values either in BoardName.h
1603		or directly in usbd_vendor_info.h. If you don't define
1604		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1605		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1606		should pretend to be a Linux device to it's target host.
1607
1608			CONFIG_USBD_MANUFACTURER
1609			Define this string as the name of your company for
1610			- CONFIG_USBD_MANUFACTURER "my company"
1611
1612			CONFIG_USBD_PRODUCT_NAME
1613			Define this string as the name of your product
1614			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1615
1616			CONFIG_USBD_VENDORID
1617			Define this as your assigned Vendor ID from the USB
1618			Implementors Forum. This *must* be a genuine Vendor ID
1619			to avoid polluting the USB namespace.
1620			- CONFIG_USBD_VENDORID 0xFFFF
1621
1622			CONFIG_USBD_PRODUCTID
1623			Define this as the unique Product ID
1624			for your device
1625			- CONFIG_USBD_PRODUCTID 0xFFFF
1626
1627- ULPI Layer Support:
1628		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1629		the generic ULPI layer. The generic layer accesses the ULPI PHY
1630		via the platform viewport, so you need both the genric layer and
1631		the viewport enabled. Currently only Chipidea/ARC based
1632		viewport is supported.
1633		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1634		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1635		If your ULPI phy needs a different reference clock than the
1636		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1637		the appropriate value in Hz.
1638
1639- MMC Support:
1640		The MMC controller on the Intel PXA is supported. To
1641		enable this define CONFIG_MMC. The MMC can be
1642		accessed from the boot prompt by mapping the device
1643		to physical memory similar to flash. Command line is
1644		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1645		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1646
1647		CONFIG_SH_MMCIF
1648		Support for Renesas on-chip MMCIF controller
1649
1650			CONFIG_SH_MMCIF_ADDR
1651			Define the base address of MMCIF registers
1652
1653			CONFIG_SH_MMCIF_CLK
1654			Define the clock frequency for MMCIF
1655
1656		CONFIG_GENERIC_MMC
1657		Enable the generic MMC driver
1658
1659		CONFIG_SUPPORT_EMMC_BOOT
1660		Enable some additional features of the eMMC boot partitions.
1661
1662		CONFIG_SUPPORT_EMMC_RPMB
1663		Enable the commands for reading, writing and programming the
1664		key for the Replay Protection Memory Block partition in eMMC.
1665
1666- USB Device Firmware Update (DFU) class support:
1667		CONFIG_DFU_FUNCTION
1668		This enables the USB portion of the DFU USB class
1669
1670		CONFIG_CMD_DFU
1671		This enables the command "dfu" which is used to have
1672		U-Boot create a DFU class device via USB.  This command
1673		requires that the "dfu_alt_info" environment variable be
1674		set and define the alt settings to expose to the host.
1675
1676		CONFIG_DFU_MMC
1677		This enables support for exposing (e)MMC devices via DFU.
1678
1679		CONFIG_DFU_NAND
1680		This enables support for exposing NAND devices via DFU.
1681
1682		CONFIG_DFU_RAM
1683		This enables support for exposing RAM via DFU.
1684		Note: DFU spec refer to non-volatile memory usage, but
1685		allow usages beyond the scope of spec - here RAM usage,
1686		one that would help mostly the developer.
1687
1688		CONFIG_SYS_DFU_DATA_BUF_SIZE
1689		Dfu transfer uses a buffer before writing data to the
1690		raw storage device. Make the size (in bytes) of this buffer
1691		configurable. The size of this buffer is also configurable
1692		through the "dfu_bufsiz" environment variable.
1693
1694		CONFIG_SYS_DFU_MAX_FILE_SIZE
1695		When updating files rather than the raw storage device,
1696		we use a static buffer to copy the file into and then write
1697		the buffer once we've been given the whole file.  Define
1698		this to the maximum filesize (in bytes) for the buffer.
1699		Default is 4 MiB if undefined.
1700
1701		DFU_DEFAULT_POLL_TIMEOUT
1702		Poll timeout [ms], is the timeout a device can send to the
1703		host. The host must wait for this timeout before sending
1704		a subsequent DFU_GET_STATUS request to the device.
1705
1706		DFU_MANIFEST_POLL_TIMEOUT
1707		Poll timeout [ms], which the device sends to the host when
1708		entering dfuMANIFEST state. Host waits this timeout, before
1709		sending again an USB request to the device.
1710
1711- USB Device Android Fastboot support:
1712		CONFIG_CMD_FASTBOOT
1713		This enables the command "fastboot" which enables the Android
1714		fastboot mode for the platform's USB device. Fastboot is a USB
1715		protocol for downloading images, flashing and device control
1716		used on Android devices.
1717		See doc/README.android-fastboot for more information.
1718
1719		CONFIG_ANDROID_BOOT_IMAGE
1720		This enables support for booting images which use the Android
1721		image format header.
1722
1723		CONFIG_USB_FASTBOOT_BUF_ADDR
1724		The fastboot protocol requires a large memory buffer for
1725		downloads. Define this to the starting RAM address to use for
1726		downloaded images.
1727
1728		CONFIG_USB_FASTBOOT_BUF_SIZE
1729		The fastboot protocol requires a large memory buffer for
1730		downloads. This buffer should be as large as possible for a
1731		platform. Define this to the size available RAM for fastboot.
1732
1733		CONFIG_FASTBOOT_FLASH
1734		The fastboot protocol includes a "flash" command for writing
1735		the downloaded image to a non-volatile storage device. Define
1736		this to enable the "fastboot flash" command.
1737
1738		CONFIG_FASTBOOT_FLASH_MMC_DEV
1739		The fastboot "flash" command requires additional information
1740		regarding the non-volatile storage device. Define this to
1741		the eMMC device that fastboot should use to store the image.
1742
1743		CONFIG_FASTBOOT_GPT_NAME
1744		The fastboot "flash" command supports writing the downloaded
1745		image to the Protective MBR and the Primary GUID Partition
1746		Table. (Additionally, this downloaded image is post-processed
1747		to generate and write the Backup GUID Partition Table.)
1748		This occurs when the specified "partition name" on the
1749		"fastboot flash" command line matches this value.
1750		Default is GPT_ENTRY_NAME (currently "gpt") if undefined.
1751
1752- Journaling Flash filesystem support:
1753		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1754		CONFIG_JFFS2_NAND_DEV
1755		Define these for a default partition on a NAND device
1756
1757		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1758		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1759		Define these for a default partition on a NOR device
1760
1761		CONFIG_SYS_JFFS_CUSTOM_PART
1762		Define this to create an own partition. You have to provide a
1763		function struct part_info* jffs2_part_info(int part_num)
1764
1765		If you define only one JFFS2 partition you may also want to
1766		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1767		to disable the command chpart. This is the default when you
1768		have not defined a custom partition
1769
1770- FAT(File Allocation Table) filesystem write function support:
1771		CONFIG_FAT_WRITE
1772
1773		Define this to enable support for saving memory data as a
1774		file in FAT formatted partition.
1775
1776		This will also enable the command "fatwrite" enabling the
1777		user to write files to FAT.
1778
1779CBFS (Coreboot Filesystem) support
1780		CONFIG_CMD_CBFS
1781
1782		Define this to enable support for reading from a Coreboot
1783		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1784		and cbfsload.
1785
1786- FAT(File Allocation Table) filesystem cluster size:
1787		CONFIG_FS_FAT_MAX_CLUSTSIZE
1788
1789		Define the max cluster size for fat operations else
1790		a default value of 65536 will be defined.
1791
1792- Keyboard Support:
1793		CONFIG_ISA_KEYBOARD
1794
1795		Define this to enable standard (PC-Style) keyboard
1796		support
1797
1798		CONFIG_I8042_KBD
1799		Standard PC keyboard driver with US (is default) and
1800		GERMAN key layout (switch via environment 'keymap=de') support.
1801		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1802		for cfb_console. Supports cursor blinking.
1803
1804		CONFIG_CROS_EC_KEYB
1805		Enables a Chrome OS keyboard using the CROS_EC interface.
1806		This uses CROS_EC to communicate with a second microcontroller
1807		which provides key scans on request.
1808
1809- Video support:
1810		CONFIG_VIDEO
1811
1812		Define this to enable video support (for output to
1813		video).
1814
1815		CONFIG_VIDEO_CT69000
1816
1817		Enable Chips & Technologies 69000 Video chip
1818
1819		CONFIG_VIDEO_SMI_LYNXEM
1820		Enable Silicon Motion SMI 712/710/810 Video chip. The
1821		video output is selected via environment 'videoout'
1822		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1823		assumed.
1824
1825		For the CT69000 and SMI_LYNXEM drivers, videomode is
1826		selected via environment 'videomode'. Two different ways
1827		are possible:
1828		- "videomode=num"   'num' is a standard LiLo mode numbers.
1829		Following standard modes are supported	(* is default):
1830
1831		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1832		-------------+---------------------------------------------
1833		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1834		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1835		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1836		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1837		-------------+---------------------------------------------
1838		(i.e. setenv videomode 317; saveenv; reset;)
1839
1840		- "videomode=bootargs" all the video parameters are parsed
1841		from the bootargs. (See drivers/video/videomodes.c)
1842
1843
1844		CONFIG_VIDEO_SED13806
1845		Enable Epson SED13806 driver. This driver supports 8bpp
1846		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1847		or CONFIG_VIDEO_SED13806_16BPP
1848
1849		CONFIG_FSL_DIU_FB
1850		Enable the Freescale DIU video driver.	Reference boards for
1851		SOCs that have a DIU should define this macro to enable DIU
1852		support, and should also define these other macros:
1853
1854			CONFIG_SYS_DIU_ADDR
1855			CONFIG_VIDEO
1856			CONFIG_CMD_BMP
1857			CONFIG_CFB_CONSOLE
1858			CONFIG_VIDEO_SW_CURSOR
1859			CONFIG_VGA_AS_SINGLE_DEVICE
1860			CONFIG_VIDEO_LOGO
1861			CONFIG_VIDEO_BMP_LOGO
1862
1863		The DIU driver will look for the 'video-mode' environment
1864		variable, and if defined, enable the DIU as a console during
1865		boot.  See the documentation file README.video for a
1866		description of this variable.
1867
1868		CONFIG_VIDEO_VGA
1869
1870		Enable the VGA video / BIOS for x86. The alternative if you
1871		are using coreboot is to use the coreboot frame buffer
1872		driver.
1873
1874
1875- Keyboard Support:
1876		CONFIG_KEYBOARD
1877
1878		Define this to enable a custom keyboard support.
1879		This simply calls drv_keyboard_init() which must be
1880		defined in your board-specific files.
1881		The only board using this so far is RBC823.
1882
1883- LCD Support:	CONFIG_LCD
1884
1885		Define this to enable LCD support (for output to LCD
1886		display); also select one of the supported displays
1887		by defining one of these:
1888
1889		CONFIG_ATMEL_LCD:
1890
1891			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1892
1893		CONFIG_NEC_NL6448AC33:
1894
1895			NEC NL6448AC33-18. Active, color, single scan.
1896
1897		CONFIG_NEC_NL6448BC20
1898
1899			NEC NL6448BC20-08. 6.5", 640x480.
1900			Active, color, single scan.
1901
1902		CONFIG_NEC_NL6448BC33_54
1903
1904			NEC NL6448BC33-54. 10.4", 640x480.
1905			Active, color, single scan.
1906
1907		CONFIG_SHARP_16x9
1908
1909			Sharp 320x240. Active, color, single scan.
1910			It isn't 16x9, and I am not sure what it is.
1911
1912		CONFIG_SHARP_LQ64D341
1913
1914			Sharp LQ64D341 display, 640x480.
1915			Active, color, single scan.
1916
1917		CONFIG_HLD1045
1918
1919			HLD1045 display, 640x480.
1920			Active, color, single scan.
1921
1922		CONFIG_OPTREX_BW
1923
1924			Optrex	 CBL50840-2 NF-FW 99 22 M5
1925			or
1926			Hitachi	 LMG6912RPFC-00T
1927			or
1928			Hitachi	 SP14Q002
1929
1930			320x240. Black & white.
1931
1932		Normally display is black on white background; define
1933		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1934
1935		CONFIG_LCD_ALIGNMENT
1936
1937		Normally the LCD is page-aligned (typically 4KB). If this is
1938		defined then the LCD will be aligned to this value instead.
1939		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1940		here, since it is cheaper to change data cache settings on
1941		a per-section basis.
1942
1943		CONFIG_CONSOLE_SCROLL_LINES
1944
1945		When the console need to be scrolled, this is the number of
1946		lines to scroll by. It defaults to 1. Increasing this makes
1947		the console jump but can help speed up operation when scrolling
1948		is slow.
1949
1950		CONFIG_LCD_BMP_RLE8
1951
1952		Support drawing of RLE8-compressed bitmaps on the LCD.
1953
1954		CONFIG_I2C_EDID
1955
1956		Enables an 'i2c edid' command which can read EDID
1957		information over I2C from an attached LCD display.
1958
1959- Splash Screen Support: CONFIG_SPLASH_SCREEN
1960
1961		If this option is set, the environment is checked for
1962		a variable "splashimage". If found, the usual display
1963		of logo, copyright and system information on the LCD
1964		is suppressed and the BMP image at the address
1965		specified in "splashimage" is loaded instead. The
1966		console is redirected to the "nulldev", too. This
1967		allows for a "silent" boot where a splash screen is
1968		loaded very quickly after power-on.
1969
1970		CONFIG_SPLASHIMAGE_GUARD
1971
1972		If this option is set, then U-Boot will prevent the environment
1973		variable "splashimage" from being set to a problematic address
1974		(see README.displaying-bmps).
1975		This option is useful for targets where, due to alignment
1976		restrictions, an improperly aligned BMP image will cause a data
1977		abort. If you think you will not have problems with unaligned
1978		accesses (for example because your toolchain prevents them)
1979		there is no need to set this option.
1980
1981		CONFIG_SPLASH_SCREEN_ALIGN
1982
1983		If this option is set the splash image can be freely positioned
1984		on the screen. Environment variable "splashpos" specifies the
1985		position as "x,y". If a positive number is given it is used as
1986		number of pixel from left/top. If a negative number is given it
1987		is used as number of pixel from right/bottom. You can also
1988		specify 'm' for centering the image.
1989
1990		Example:
1991		setenv splashpos m,m
1992			=> image at center of screen
1993
1994		setenv splashpos 30,20
1995			=> image at x = 30 and y = 20
1996
1997		setenv splashpos -10,m
1998			=> vertically centered image
1999			   at x = dspWidth - bmpWidth - 9
2000
2001- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
2002
2003		If this option is set, additionally to standard BMP
2004		images, gzipped BMP images can be displayed via the
2005		splashscreen support or the bmp command.
2006
2007- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
2008
2009		If this option is set, 8-bit RLE compressed BMP images
2010		can be displayed via the splashscreen support or the
2011		bmp command.
2012
2013- Do compressing for memory range:
2014		CONFIG_CMD_ZIP
2015
2016		If this option is set, it would use zlib deflate method
2017		to compress the specified memory at its best effort.
2018
2019- Compression support:
2020		CONFIG_GZIP
2021
2022		Enabled by default to support gzip compressed images.
2023
2024		CONFIG_BZIP2
2025
2026		If this option is set, support for bzip2 compressed
2027		images is included. If not, only uncompressed and gzip
2028		compressed images are supported.
2029
2030		NOTE: the bzip2 algorithm requires a lot of RAM, so
2031		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
2032		be at least 4MB.
2033
2034		CONFIG_LZMA
2035
2036		If this option is set, support for lzma compressed
2037		images is included.
2038
2039		Note: The LZMA algorithm adds between 2 and 4KB of code and it
2040		requires an amount of dynamic memory that is given by the
2041		formula:
2042
2043			(1846 + 768 << (lc + lp)) * sizeof(uint16)
2044
2045		Where lc and lp stand for, respectively, Literal context bits
2046		and Literal pos bits.
2047
2048		This value is upper-bounded by 14MB in the worst case. Anyway,
2049		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
2050		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
2051		a very small buffer.
2052
2053		Use the lzmainfo tool to determinate the lc and lp values and
2054		then calculate the amount of needed dynamic memory (ensuring
2055		the appropriate CONFIG_SYS_MALLOC_LEN value).
2056
2057		CONFIG_LZO
2058
2059		If this option is set, support for LZO compressed images
2060		is included.
2061
2062- MII/PHY support:
2063		CONFIG_PHY_ADDR
2064
2065		The address of PHY on MII bus.
2066
2067		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
2068
2069		The clock frequency of the MII bus
2070
2071		CONFIG_PHY_GIGE
2072
2073		If this option is set, support for speed/duplex
2074		detection of gigabit PHY is included.
2075
2076		CONFIG_PHY_RESET_DELAY
2077
2078		Some PHY like Intel LXT971A need extra delay after
2079		reset before any MII register access is possible.
2080		For such PHY, set this option to the usec delay
2081		required. (minimum 300usec for LXT971A)
2082
2083		CONFIG_PHY_CMD_DELAY (ppc4xx)
2084
2085		Some PHY like Intel LXT971A need extra delay after
2086		command issued before MII status register can be read
2087
2088- Ethernet address:
2089		CONFIG_ETHADDR
2090		CONFIG_ETH1ADDR
2091		CONFIG_ETH2ADDR
2092		CONFIG_ETH3ADDR
2093		CONFIG_ETH4ADDR
2094		CONFIG_ETH5ADDR
2095
2096		Define a default value for Ethernet address to use
2097		for the respective Ethernet interface, in case this
2098		is not determined automatically.
2099
2100- IP address:
2101		CONFIG_IPADDR
2102
2103		Define a default value for the IP address to use for
2104		the default Ethernet interface, in case this is not
2105		determined through e.g. bootp.
2106		(Environment variable "ipaddr")
2107
2108- Server IP address:
2109		CONFIG_SERVERIP
2110
2111		Defines a default value for the IP address of a TFTP
2112		server to contact when using the "tftboot" command.
2113		(Environment variable "serverip")
2114
2115		CONFIG_KEEP_SERVERADDR
2116
2117		Keeps the server's MAC address, in the env 'serveraddr'
2118		for passing to bootargs (like Linux's netconsole option)
2119
2120- Gateway IP address:
2121		CONFIG_GATEWAYIP
2122
2123		Defines a default value for the IP address of the
2124		default router where packets to other networks are
2125		sent to.
2126		(Environment variable "gatewayip")
2127
2128- Subnet mask:
2129		CONFIG_NETMASK
2130
2131		Defines a default value for the subnet mask (or
2132		routing prefix) which is used to determine if an IP
2133		address belongs to the local subnet or needs to be
2134		forwarded through a router.
2135		(Environment variable "netmask")
2136
2137- Multicast TFTP Mode:
2138		CONFIG_MCAST_TFTP
2139
2140		Defines whether you want to support multicast TFTP as per
2141		rfc-2090; for example to work with atftp.  Lets lots of targets
2142		tftp down the same boot image concurrently.  Note: the Ethernet
2143		driver in use must provide a function: mcast() to join/leave a
2144		multicast group.
2145
2146- BOOTP Recovery Mode:
2147		CONFIG_BOOTP_RANDOM_DELAY
2148
2149		If you have many targets in a network that try to
2150		boot using BOOTP, you may want to avoid that all
2151		systems send out BOOTP requests at precisely the same
2152		moment (which would happen for instance at recovery
2153		from a power failure, when all systems will try to
2154		boot, thus flooding the BOOTP server. Defining
2155		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
2156		inserted before sending out BOOTP requests. The
2157		following delays are inserted then:
2158
2159		1st BOOTP request:	delay 0 ... 1 sec
2160		2nd BOOTP request:	delay 0 ... 2 sec
2161		3rd BOOTP request:	delay 0 ... 4 sec
2162		4th and following
2163		BOOTP requests:		delay 0 ... 8 sec
2164
2165		CONFIG_BOOTP_ID_CACHE_SIZE
2166
2167		BOOTP packets are uniquely identified using a 32-bit ID. The
2168		server will copy the ID from client requests to responses and
2169		U-Boot will use this to determine if it is the destination of
2170		an incoming response. Some servers will check that addresses
2171		aren't in use before handing them out (usually using an ARP
2172		ping) and therefore take up to a few hundred milliseconds to
2173		respond. Network congestion may also influence the time it
2174		takes for a response to make it back to the client. If that
2175		time is too long, U-Boot will retransmit requests. In order
2176		to allow earlier responses to still be accepted after these
2177		retransmissions, U-Boot's BOOTP client keeps a small cache of
2178		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
2179		cache. The default is to keep IDs for up to four outstanding
2180		requests. Increasing this will allow U-Boot to accept offers
2181		from a BOOTP client in networks with unusually high latency.
2182
2183- DHCP Advanced Options:
2184		You can fine tune the DHCP functionality by defining
2185		CONFIG_BOOTP_* symbols:
2186
2187		CONFIG_BOOTP_SUBNETMASK
2188		CONFIG_BOOTP_GATEWAY
2189		CONFIG_BOOTP_HOSTNAME
2190		CONFIG_BOOTP_NISDOMAIN
2191		CONFIG_BOOTP_BOOTPATH
2192		CONFIG_BOOTP_BOOTFILESIZE
2193		CONFIG_BOOTP_DNS
2194		CONFIG_BOOTP_DNS2
2195		CONFIG_BOOTP_SEND_HOSTNAME
2196		CONFIG_BOOTP_NTPSERVER
2197		CONFIG_BOOTP_TIMEOFFSET
2198		CONFIG_BOOTP_VENDOREX
2199		CONFIG_BOOTP_MAY_FAIL
2200
2201		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
2202		environment variable, not the BOOTP server.
2203
2204		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
2205		after the configured retry count, the call will fail
2206		instead of starting over.  This can be used to fail over
2207		to Link-local IP address configuration if the DHCP server
2208		is not available.
2209
2210		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
2211		serverip from a DHCP server, it is possible that more
2212		than one DNS serverip is offered to the client.
2213		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
2214		serverip will be stored in the additional environment
2215		variable "dnsip2". The first DNS serverip is always
2216		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
2217		is defined.
2218
2219		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2220		to do a dynamic update of a DNS server. To do this, they
2221		need the hostname of the DHCP requester.
2222		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2223		of the "hostname" environment variable is passed as
2224		option 12 to the DHCP server.
2225
2226		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2227
2228		A 32bit value in microseconds for a delay between
2229		receiving a "DHCP Offer" and sending the "DHCP Request".
2230		This fixes a problem with certain DHCP servers that don't
2231		respond 100% of the time to a "DHCP request". E.g. On an
2232		AT91RM9200 processor running at 180MHz, this delay needed
2233		to be *at least* 15,000 usec before a Windows Server 2003
2234		DHCP server would reply 100% of the time. I recommend at
2235		least 50,000 usec to be safe. The alternative is to hope
2236		that one of the retries will be successful but note that
2237		the DHCP timeout and retry process takes a longer than
2238		this delay.
2239
2240 - Link-local IP address negotiation:
2241		Negotiate with other link-local clients on the local network
2242		for an address that doesn't require explicit configuration.
2243		This is especially useful if a DHCP server cannot be guaranteed
2244		to exist in all environments that the device must operate.
2245
2246		See doc/README.link-local for more information.
2247
2248 - CDP Options:
2249		CONFIG_CDP_DEVICE_ID
2250
2251		The device id used in CDP trigger frames.
2252
2253		CONFIG_CDP_DEVICE_ID_PREFIX
2254
2255		A two character string which is prefixed to the MAC address
2256		of the device.
2257
2258		CONFIG_CDP_PORT_ID
2259
2260		A printf format string which contains the ascii name of
2261		the port. Normally is set to "eth%d" which sets
2262		eth0 for the first Ethernet, eth1 for the second etc.
2263
2264		CONFIG_CDP_CAPABILITIES
2265
2266		A 32bit integer which indicates the device capabilities;
2267		0x00000010 for a normal host which does not forwards.
2268
2269		CONFIG_CDP_VERSION
2270
2271		An ascii string containing the version of the software.
2272
2273		CONFIG_CDP_PLATFORM
2274
2275		An ascii string containing the name of the platform.
2276
2277		CONFIG_CDP_TRIGGER
2278
2279		A 32bit integer sent on the trigger.
2280
2281		CONFIG_CDP_POWER_CONSUMPTION
2282
2283		A 16bit integer containing the power consumption of the
2284		device in .1 of milliwatts.
2285
2286		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2287
2288		A byte containing the id of the VLAN.
2289
2290- Status LED:	CONFIG_STATUS_LED
2291
2292		Several configurations allow to display the current
2293		status using a LED. For instance, the LED will blink
2294		fast while running U-Boot code, stop blinking as
2295		soon as a reply to a BOOTP request was received, and
2296		start blinking slow once the Linux kernel is running
2297		(supported by a status LED driver in the Linux
2298		kernel). Defining CONFIG_STATUS_LED enables this
2299		feature in U-Boot.
2300
2301		Additional options:
2302
2303		CONFIG_GPIO_LED
2304		The status LED can be connected to a GPIO pin.
2305		In such cases, the gpio_led driver can be used as a
2306		status LED backend implementation. Define CONFIG_GPIO_LED
2307		to include the gpio_led driver in the U-Boot binary.
2308
2309		CONFIG_GPIO_LED_INVERTED_TABLE
2310		Some GPIO connected LEDs may have inverted polarity in which
2311		case the GPIO high value corresponds to LED off state and
2312		GPIO low value corresponds to LED on state.
2313		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2314		with a list of GPIO LEDs that have inverted polarity.
2315
2316- CAN Support:	CONFIG_CAN_DRIVER
2317
2318		Defining CONFIG_CAN_DRIVER enables CAN driver support
2319		on those systems that support this (optional)
2320		feature, like the TQM8xxL modules.
2321
2322- I2C Support:	CONFIG_SYS_I2C
2323
2324		This enable the NEW i2c subsystem, and will allow you to use
2325		i2c commands at the u-boot command line (as long as you set
2326		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2327		based realtime clock chips or other i2c devices. See
2328		common/cmd_i2c.c for a description of the command line
2329		interface.
2330
2331		ported i2c driver to the new framework:
2332		- drivers/i2c/soft_i2c.c:
2333		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2334		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2335		    for defining speed and slave address
2336		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2337		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2338		    for defining speed and slave address
2339		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2340		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2341		    for defining speed and slave address
2342		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2343		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2344		    for defining speed and slave address
2345
2346		- drivers/i2c/fsl_i2c.c:
2347		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2348		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2349		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2350		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2351		    bus.
2352		  - If your board supports a second fsl i2c bus, define
2353		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2354		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2355		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2356		    second bus.
2357
2358		- drivers/i2c/tegra_i2c.c:
2359		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2360		  - This driver adds 4 i2c buses with a fix speed from
2361		    100000 and the slave addr 0!
2362
2363		- drivers/i2c/ppc4xx_i2c.c
2364		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2365		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2366		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2367
2368		- drivers/i2c/i2c_mxc.c
2369		  - activate this driver with CONFIG_SYS_I2C_MXC
2370		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2371		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2372		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2373		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2374		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2375		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2376		If those defines are not set, default value is 100000
2377		for speed, and 0 for slave.
2378
2379		- drivers/i2c/rcar_i2c.c:
2380		  - activate this driver with CONFIG_SYS_I2C_RCAR
2381		  - This driver adds 4 i2c buses
2382
2383		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2384		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2385		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2386		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2387		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2388		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2389		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2390		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2391		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2392
2393		- drivers/i2c/sh_i2c.c:
2394		  - activate this driver with CONFIG_SYS_I2C_SH
2395		  - This driver adds from 2 to 5 i2c buses
2396
2397		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2398		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2399		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2400		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2401		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2402		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2403		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2404		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2405		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2406		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2407		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2408		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2409		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2410
2411		- drivers/i2c/omap24xx_i2c.c
2412		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2413		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2414		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2415		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2416		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2417		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2418		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2419		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2420		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2421		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2422		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2423
2424		- drivers/i2c/zynq_i2c.c
2425		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2426		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2427		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2428
2429		- drivers/i2c/s3c24x0_i2c.c:
2430		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2431		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2432		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2433		    with a fix speed from 100000 and the slave addr 0!
2434
2435		- drivers/i2c/ihs_i2c.c
2436		  - activate this driver with CONFIG_SYS_I2C_IHS
2437		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2438		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2439		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2440		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2441		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2442		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2443		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2444		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2445		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2446		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2447		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2448		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2449
2450		additional defines:
2451
2452		CONFIG_SYS_NUM_I2C_BUSES
2453		Hold the number of i2c buses you want to use. If you
2454		don't use/have i2c muxes on your i2c bus, this
2455		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2456		omit this define.
2457
2458		CONFIG_SYS_I2C_DIRECT_BUS
2459		define this, if you don't use i2c muxes on your hardware.
2460		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2461		omit this define.
2462
2463		CONFIG_SYS_I2C_MAX_HOPS
2464		define how many muxes are maximal consecutively connected
2465		on one i2c bus. If you not use i2c muxes, omit this
2466		define.
2467
2468		CONFIG_SYS_I2C_BUSES
2469		hold a list of buses you want to use, only used if
2470		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2471		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2472		CONFIG_SYS_NUM_I2C_BUSES = 9:
2473
2474		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2475					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2476					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2477					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2478					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2479					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2480					{1, {I2C_NULL_HOP}}, \
2481					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2482					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2483					}
2484
2485		which defines
2486			bus 0 on adapter 0 without a mux
2487			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2488			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2489			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2490			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2491			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2492			bus 6 on adapter 1 without a mux
2493			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2494			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2495
2496		If you do not have i2c muxes on your board, omit this define.
2497
2498- Legacy I2C Support:	CONFIG_HARD_I2C
2499
2500		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2501		provides the following compelling advantages:
2502
2503		- more than one i2c adapter is usable
2504		- approved multibus support
2505		- better i2c mux support
2506
2507		** Please consider updating your I2C driver now. **
2508
2509		These enable legacy I2C serial bus commands. Defining
2510		CONFIG_HARD_I2C will include the appropriate I2C driver
2511		for the selected CPU.
2512
2513		This will allow you to use i2c commands at the u-boot
2514		command line (as long as you set CONFIG_CMD_I2C in
2515		CONFIG_COMMANDS) and communicate with i2c based realtime
2516		clock chips. See common/cmd_i2c.c for a description of the
2517		command line interface.
2518
2519		CONFIG_HARD_I2C selects a hardware I2C controller.
2520
2521		There are several other quantities that must also be
2522		defined when you define CONFIG_HARD_I2C.
2523
2524		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2525		to be the frequency (in Hz) at which you wish your i2c bus
2526		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2527		the CPU's i2c node address).
2528
2529		Now, the u-boot i2c code for the mpc8xx
2530		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2531		and so its address should therefore be cleared to 0 (See,
2532		eg, MPC823e User's Manual p.16-473). So, set
2533		CONFIG_SYS_I2C_SLAVE to 0.
2534
2535		CONFIG_SYS_I2C_INIT_MPC5XXX
2536
2537		When a board is reset during an i2c bus transfer
2538		chips might think that the current transfer is still
2539		in progress.  Reset the slave devices by sending start
2540		commands until the slave device responds.
2541
2542		That's all that's required for CONFIG_HARD_I2C.
2543
2544		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2545		then the following macros need to be defined (examples are
2546		from include/configs/lwmon.h):
2547
2548		I2C_INIT
2549
2550		(Optional). Any commands necessary to enable the I2C
2551		controller or configure ports.
2552
2553		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2554
2555		I2C_PORT
2556
2557		(Only for MPC8260 CPU). The I/O port to use (the code
2558		assumes both bits are on the same port). Valid values
2559		are 0..3 for ports A..D.
2560
2561		I2C_ACTIVE
2562
2563		The code necessary to make the I2C data line active
2564		(driven).  If the data line is open collector, this
2565		define can be null.
2566
2567		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2568
2569		I2C_TRISTATE
2570
2571		The code necessary to make the I2C data line tri-stated
2572		(inactive).  If the data line is open collector, this
2573		define can be null.
2574
2575		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2576
2577		I2C_READ
2578
2579		Code that returns true if the I2C data line is high,
2580		false if it is low.
2581
2582		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2583
2584		I2C_SDA(bit)
2585
2586		If <bit> is true, sets the I2C data line high. If it
2587		is false, it clears it (low).
2588
2589		eg: #define I2C_SDA(bit) \
2590			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2591			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2592
2593		I2C_SCL(bit)
2594
2595		If <bit> is true, sets the I2C clock line high. If it
2596		is false, it clears it (low).
2597
2598		eg: #define I2C_SCL(bit) \
2599			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2600			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2601
2602		I2C_DELAY
2603
2604		This delay is invoked four times per clock cycle so this
2605		controls the rate of data transfer.  The data rate thus
2606		is 1 / (I2C_DELAY * 4). Often defined to be something
2607		like:
2608
2609		#define I2C_DELAY  udelay(2)
2610
2611		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2612
2613		If your arch supports the generic GPIO framework (asm/gpio.h),
2614		then you may alternatively define the two GPIOs that are to be
2615		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2616		have GPIO-based defaults assigned to them as appropriate.
2617
2618		You should define these to the GPIO value as given directly to
2619		the generic GPIO functions.
2620
2621		CONFIG_SYS_I2C_INIT_BOARD
2622
2623		When a board is reset during an i2c bus transfer
2624		chips might think that the current transfer is still
2625		in progress. On some boards it is possible to access
2626		the i2c SCLK line directly, either by using the
2627		processor pin as a GPIO or by having a second pin
2628		connected to the bus. If this option is defined a
2629		custom i2c_init_board() routine in boards/xxx/board.c
2630		is run early in the boot sequence.
2631
2632		CONFIG_SYS_I2C_BOARD_LATE_INIT
2633
2634		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2635		defined a custom i2c_board_late_init() routine in
2636		boards/xxx/board.c is run AFTER the operations in i2c_init()
2637		is completed. This callpoint can be used to unreset i2c bus
2638		using CPU i2c controller register accesses for CPUs whose i2c
2639		controller provide such a method. It is called at the end of
2640		i2c_init() to allow i2c_init operations to setup the i2c bus
2641		controller on the CPU (e.g. setting bus speed & slave address).
2642
2643		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2644
2645		This option enables configuration of bi_iic_fast[] flags
2646		in u-boot bd_info structure based on u-boot environment
2647		variable "i2cfast". (see also i2cfast)
2648
2649		CONFIG_I2C_MULTI_BUS
2650
2651		This option allows the use of multiple I2C buses, each of which
2652		must have a controller.	 At any point in time, only one bus is
2653		active.	 To switch to a different bus, use the 'i2c dev' command.
2654		Note that bus numbering is zero-based.
2655
2656		CONFIG_SYS_I2C_NOPROBES
2657
2658		This option specifies a list of I2C devices that will be skipped
2659		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2660		is set, specify a list of bus-device pairs.  Otherwise, specify
2661		a 1D array of device addresses
2662
2663		e.g.
2664			#undef	CONFIG_I2C_MULTI_BUS
2665			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2666
2667		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2668
2669			#define CONFIG_I2C_MULTI_BUS
2670			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2671
2672		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2673
2674		CONFIG_SYS_SPD_BUS_NUM
2675
2676		If defined, then this indicates the I2C bus number for DDR SPD.
2677		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2678
2679		CONFIG_SYS_RTC_BUS_NUM
2680
2681		If defined, then this indicates the I2C bus number for the RTC.
2682		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2683
2684		CONFIG_SYS_DTT_BUS_NUM
2685
2686		If defined, then this indicates the I2C bus number for the DTT.
2687		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2688
2689		CONFIG_SYS_I2C_DTT_ADDR:
2690
2691		If defined, specifies the I2C address of the DTT device.
2692		If not defined, then U-Boot uses predefined value for
2693		specified DTT device.
2694
2695		CONFIG_SOFT_I2C_READ_REPEATED_START
2696
2697		defining this will force the i2c_read() function in
2698		the soft_i2c driver to perform an I2C repeated start
2699		between writing the address pointer and reading the
2700		data.  If this define is omitted the default behaviour
2701		of doing a stop-start sequence will be used.  Most I2C
2702		devices can use either method, but some require one or
2703		the other.
2704
2705- SPI Support:	CONFIG_SPI
2706
2707		Enables SPI driver (so far only tested with
2708		SPI EEPROM, also an instance works with Crystal A/D and
2709		D/As on the SACSng board)
2710
2711		CONFIG_SH_SPI
2712
2713		Enables the driver for SPI controller on SuperH. Currently
2714		only SH7757 is supported.
2715
2716		CONFIG_SPI_X
2717
2718		Enables extended (16-bit) SPI EEPROM addressing.
2719		(symmetrical to CONFIG_I2C_X)
2720
2721		CONFIG_SOFT_SPI
2722
2723		Enables a software (bit-bang) SPI driver rather than
2724		using hardware support. This is a general purpose
2725		driver that only requires three general I/O port pins
2726		(two outputs, one input) to function. If this is
2727		defined, the board configuration must define several
2728		SPI configuration items (port pins to use, etc). For
2729		an example, see include/configs/sacsng.h.
2730
2731		CONFIG_HARD_SPI
2732
2733		Enables a hardware SPI driver for general-purpose reads
2734		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2735		must define a list of chip-select function pointers.
2736		Currently supported on some MPC8xxx processors.	 For an
2737		example, see include/configs/mpc8349emds.h.
2738
2739		CONFIG_MXC_SPI
2740
2741		Enables the driver for the SPI controllers on i.MX and MXC
2742		SoCs. Currently i.MX31/35/51 are supported.
2743
2744		CONFIG_SYS_SPI_MXC_WAIT
2745		Timeout for waiting until spi transfer completed.
2746		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2747
2748- FPGA Support: CONFIG_FPGA
2749
2750		Enables FPGA subsystem.
2751
2752		CONFIG_FPGA_<vendor>
2753
2754		Enables support for specific chip vendors.
2755		(ALTERA, XILINX)
2756
2757		CONFIG_FPGA_<family>
2758
2759		Enables support for FPGA family.
2760		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2761
2762		CONFIG_FPGA_COUNT
2763
2764		Specify the number of FPGA devices to support.
2765
2766		CONFIG_CMD_FPGA_LOADMK
2767
2768		Enable support for fpga loadmk command
2769
2770		CONFIG_CMD_FPGA_LOADP
2771
2772		Enable support for fpga loadp command - load partial bitstream
2773
2774		CONFIG_CMD_FPGA_LOADBP
2775
2776		Enable support for fpga loadbp command - load partial bitstream
2777		(Xilinx only)
2778
2779		CONFIG_SYS_FPGA_PROG_FEEDBACK
2780
2781		Enable printing of hash marks during FPGA configuration.
2782
2783		CONFIG_SYS_FPGA_CHECK_BUSY
2784
2785		Enable checks on FPGA configuration interface busy
2786		status by the configuration function. This option
2787		will require a board or device specific function to
2788		be written.
2789
2790		CONFIG_FPGA_DELAY
2791
2792		If defined, a function that provides delays in the FPGA
2793		configuration driver.
2794
2795		CONFIG_SYS_FPGA_CHECK_CTRLC
2796		Allow Control-C to interrupt FPGA configuration
2797
2798		CONFIG_SYS_FPGA_CHECK_ERROR
2799
2800		Check for configuration errors during FPGA bitfile
2801		loading. For example, abort during Virtex II
2802		configuration if the INIT_B line goes low (which
2803		indicated a CRC error).
2804
2805		CONFIG_SYS_FPGA_WAIT_INIT
2806
2807		Maximum time to wait for the INIT_B line to de-assert
2808		after PROB_B has been de-asserted during a Virtex II
2809		FPGA configuration sequence. The default time is 500
2810		ms.
2811
2812		CONFIG_SYS_FPGA_WAIT_BUSY
2813
2814		Maximum time to wait for BUSY to de-assert during
2815		Virtex II FPGA configuration. The default is 5 ms.
2816
2817		CONFIG_SYS_FPGA_WAIT_CONFIG
2818
2819		Time to wait after FPGA configuration. The default is
2820		200 ms.
2821
2822- Configuration Management:
2823		CONFIG_BUILD_TARGET
2824
2825		Some SoCs need special image types (e.g. U-Boot binary
2826		with a special header) as build targets. By defining
2827		CONFIG_BUILD_TARGET in the SoC / board header, this
2828		special image will be automatically built upon calling
2829		make / MAKEALL.
2830
2831		CONFIG_IDENT_STRING
2832
2833		If defined, this string will be added to the U-Boot
2834		version information (U_BOOT_VERSION)
2835
2836- Vendor Parameter Protection:
2837
2838		U-Boot considers the values of the environment
2839		variables "serial#" (Board Serial Number) and
2840		"ethaddr" (Ethernet Address) to be parameters that
2841		are set once by the board vendor / manufacturer, and
2842		protects these variables from casual modification by
2843		the user. Once set, these variables are read-only,
2844		and write or delete attempts are rejected. You can
2845		change this behaviour:
2846
2847		If CONFIG_ENV_OVERWRITE is #defined in your config
2848		file, the write protection for vendor parameters is
2849		completely disabled. Anybody can change or delete
2850		these parameters.
2851
2852		Alternatively, if you #define _both_ CONFIG_ETHADDR
2853		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2854		Ethernet address is installed in the environment,
2855		which can be changed exactly ONCE by the user. [The
2856		serial# is unaffected by this, i. e. it remains
2857		read-only.]
2858
2859		The same can be accomplished in a more flexible way
2860		for any variable by configuring the type of access
2861		to allow for those variables in the ".flags" variable
2862		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2863
2864- Protected RAM:
2865		CONFIG_PRAM
2866
2867		Define this variable to enable the reservation of
2868		"protected RAM", i. e. RAM which is not overwritten
2869		by U-Boot. Define CONFIG_PRAM to hold the number of
2870		kB you want to reserve for pRAM. You can overwrite
2871		this default value by defining an environment
2872		variable "pram" to the number of kB you want to
2873		reserve. Note that the board info structure will
2874		still show the full amount of RAM. If pRAM is
2875		reserved, a new environment variable "mem" will
2876		automatically be defined to hold the amount of
2877		remaining RAM in a form that can be passed as boot
2878		argument to Linux, for instance like that:
2879
2880			setenv bootargs ... mem=\${mem}
2881			saveenv
2882
2883		This way you can tell Linux not to use this memory,
2884		either, which results in a memory region that will
2885		not be affected by reboots.
2886
2887		*WARNING* If your board configuration uses automatic
2888		detection of the RAM size, you must make sure that
2889		this memory test is non-destructive. So far, the
2890		following board configurations are known to be
2891		"pRAM-clean":
2892
2893			IVMS8, IVML24, SPD8xx, TQM8xxL,
2894			HERMES, IP860, RPXlite, LWMON,
2895			FLAGADM, TQM8260
2896
2897- Access to physical memory region (> 4GB)
2898		Some basic support is provided for operations on memory not
2899		normally accessible to U-Boot - e.g. some architectures
2900		support access to more than 4GB of memory on 32-bit
2901		machines using physical address extension or similar.
2902		Define CONFIG_PHYSMEM to access this basic support, which
2903		currently only supports clearing the memory.
2904
2905- Error Recovery:
2906		CONFIG_PANIC_HANG
2907
2908		Define this variable to stop the system in case of a
2909		fatal error, so that you have to reset it manually.
2910		This is probably NOT a good idea for an embedded
2911		system where you want the system to reboot
2912		automatically as fast as possible, but it may be
2913		useful during development since you can try to debug
2914		the conditions that lead to the situation.
2915
2916		CONFIG_NET_RETRY_COUNT
2917
2918		This variable defines the number of retries for
2919		network operations like ARP, RARP, TFTP, or BOOTP
2920		before giving up the operation. If not defined, a
2921		default value of 5 is used.
2922
2923		CONFIG_ARP_TIMEOUT
2924
2925		Timeout waiting for an ARP reply in milliseconds.
2926
2927		CONFIG_NFS_TIMEOUT
2928
2929		Timeout in milliseconds used in NFS protocol.
2930		If you encounter "ERROR: Cannot umount" in nfs command,
2931		try longer timeout such as
2932		#define CONFIG_NFS_TIMEOUT 10000UL
2933
2934- Command Interpreter:
2935		CONFIG_AUTO_COMPLETE
2936
2937		Enable auto completion of commands using TAB.
2938
2939		CONFIG_SYS_PROMPT_HUSH_PS2
2940
2941		This defines the secondary prompt string, which is
2942		printed when the command interpreter needs more input
2943		to complete a command. Usually "> ".
2944
2945	Note:
2946
2947		In the current implementation, the local variables
2948		space and global environment variables space are
2949		separated. Local variables are those you define by
2950		simply typing `name=value'. To access a local
2951		variable later on, you have write `$name' or
2952		`${name}'; to execute the contents of a variable
2953		directly type `$name' at the command prompt.
2954
2955		Global environment variables are those you use
2956		setenv/printenv to work with. To run a command stored
2957		in such a variable, you need to use the run command,
2958		and you must not use the '$' sign to access them.
2959
2960		To store commands and special characters in a
2961		variable, please use double quotation marks
2962		surrounding the whole text of the variable, instead
2963		of the backslashes before semicolons and special
2964		symbols.
2965
2966- Command Line Editing and History:
2967		CONFIG_CMDLINE_EDITING
2968
2969		Enable editing and History functions for interactive
2970		command line input operations
2971
2972- Default Environment:
2973		CONFIG_EXTRA_ENV_SETTINGS
2974
2975		Define this to contain any number of null terminated
2976		strings (variable = value pairs) that will be part of
2977		the default environment compiled into the boot image.
2978
2979		For example, place something like this in your
2980		board's config file:
2981
2982		#define CONFIG_EXTRA_ENV_SETTINGS \
2983			"myvar1=value1\0" \
2984			"myvar2=value2\0"
2985
2986		Warning: This method is based on knowledge about the
2987		internal format how the environment is stored by the
2988		U-Boot code. This is NOT an official, exported
2989		interface! Although it is unlikely that this format
2990		will change soon, there is no guarantee either.
2991		You better know what you are doing here.
2992
2993		Note: overly (ab)use of the default environment is
2994		discouraged. Make sure to check other ways to preset
2995		the environment like the "source" command or the
2996		boot command first.
2997
2998		CONFIG_ENV_VARS_UBOOT_CONFIG
2999
3000		Define this in order to add variables describing the
3001		U-Boot build configuration to the default environment.
3002		These will be named arch, cpu, board, vendor, and soc.
3003
3004		Enabling this option will cause the following to be defined:
3005
3006		- CONFIG_SYS_ARCH
3007		- CONFIG_SYS_CPU
3008		- CONFIG_SYS_BOARD
3009		- CONFIG_SYS_VENDOR
3010		- CONFIG_SYS_SOC
3011
3012		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
3013
3014		Define this in order to add variables describing certain
3015		run-time determined information about the hardware to the
3016		environment.  These will be named board_name, board_rev.
3017
3018		CONFIG_DELAY_ENVIRONMENT
3019
3020		Normally the environment is loaded when the board is
3021		initialised so that it is available to U-Boot. This inhibits
3022		that so that the environment is not available until
3023		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
3024		this is instead controlled by the value of
3025		/config/load-environment.
3026
3027- DataFlash Support:
3028		CONFIG_HAS_DATAFLASH
3029
3030		Defining this option enables DataFlash features and
3031		allows to read/write in Dataflash via the standard
3032		commands cp, md...
3033
3034- Serial Flash support
3035		CONFIG_CMD_SF
3036
3037		Defining this option enables SPI flash commands
3038		'sf probe/read/write/erase/update'.
3039
3040		Usage requires an initial 'probe' to define the serial
3041		flash parameters, followed by read/write/erase/update
3042		commands.
3043
3044		The following defaults may be provided by the platform
3045		to handle the common case when only a single serial
3046		flash is present on the system.
3047
3048		CONFIG_SF_DEFAULT_BUS		Bus identifier
3049		CONFIG_SF_DEFAULT_CS		Chip-select
3050		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
3051		CONFIG_SF_DEFAULT_SPEED		in Hz
3052
3053		CONFIG_CMD_SF_TEST
3054
3055		Define this option to include a destructive SPI flash
3056		test ('sf test').
3057
3058		CONFIG_SPI_FLASH_BAR		Ban/Extended Addr Reg
3059
3060		Define this option to use the Bank addr/Extended addr
3061		support on SPI flashes which has size > 16Mbytes.
3062
3063		CONFIG_SF_DUAL_FLASH		Dual flash memories
3064
3065		Define this option to use dual flash support where two flash
3066		memories can be connected with a given cs line.
3067		Currently Xilinx Zynq qspi supports these type of connections.
3068
3069		CONFIG_SYS_SPI_ST_ENABLE_WP_PIN
3070		enable the W#/Vpp signal to disable writing to the status
3071		register on ST MICRON flashes like the N25Q128.
3072		The status register write enable/disable bit, combined with
3073		the W#/VPP signal provides hardware data protection for the
3074		device as follows: When the enable/disable bit is set to 1,
3075		and the W#/VPP signal is driven LOW, the status register
3076		nonvolatile bits become read-only and the WRITE STATUS REGISTER
3077		operation will not execute. The only way to exit this
3078		hardware-protected mode is to drive W#/VPP HIGH.
3079
3080- SystemACE Support:
3081		CONFIG_SYSTEMACE
3082
3083		Adding this option adds support for Xilinx SystemACE
3084		chips attached via some sort of local bus. The address
3085		of the chip must also be defined in the
3086		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
3087
3088		#define CONFIG_SYSTEMACE
3089		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
3090
3091		When SystemACE support is added, the "ace" device type
3092		becomes available to the fat commands, i.e. fatls.
3093
3094- TFTP Fixed UDP Port:
3095		CONFIG_TFTP_PORT
3096
3097		If this is defined, the environment variable tftpsrcp
3098		is used to supply the TFTP UDP source port value.
3099		If tftpsrcp isn't defined, the normal pseudo-random port
3100		number generator is used.
3101
3102		Also, the environment variable tftpdstp is used to supply
3103		the TFTP UDP destination port value.  If tftpdstp isn't
3104		defined, the normal port 69 is used.
3105
3106		The purpose for tftpsrcp is to allow a TFTP server to
3107		blindly start the TFTP transfer using the pre-configured
3108		target IP address and UDP port. This has the effect of
3109		"punching through" the (Windows XP) firewall, allowing
3110		the remainder of the TFTP transfer to proceed normally.
3111		A better solution is to properly configure the firewall,
3112		but sometimes that is not allowed.
3113
3114- Hashing support:
3115		CONFIG_CMD_HASH
3116
3117		This enables a generic 'hash' command which can produce
3118		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
3119
3120		CONFIG_HASH_VERIFY
3121
3122		Enable the hash verify command (hash -v). This adds to code
3123		size a little.
3124
3125		CONFIG_SHA1 - This option enables support of hashing using SHA1
3126		algorithm. The hash is calculated in software.
3127		CONFIG_SHA256 - This option enables support of hashing using
3128		SHA256 algorithm. The hash is calculated in software.
3129		CONFIG_SHA_HW_ACCEL - This option enables hardware acceleration
3130		for SHA1/SHA256 hashing.
3131		This affects the 'hash' command and also the
3132		hash_lookup_algo() function.
3133		CONFIG_SHA_PROG_HW_ACCEL - This option enables
3134		hardware-acceleration for SHA1/SHA256 progressive hashing.
3135		Data can be streamed in a block at a time and the hashing
3136		is performed in hardware.
3137
3138		Note: There is also a sha1sum command, which should perhaps
3139		be deprecated in favour of 'hash sha1'.
3140
3141- Freescale i.MX specific commands:
3142		CONFIG_CMD_HDMIDETECT
3143		This enables 'hdmidet' command which returns true if an
3144		HDMI monitor is detected.  This command is i.MX 6 specific.
3145
3146		CONFIG_CMD_BMODE
3147		This enables the 'bmode' (bootmode) command for forcing
3148		a boot from specific media.
3149
3150		This is useful for forcing the ROM's usb downloader to
3151		activate upon a watchdog reset which is nice when iterating
3152		on U-Boot.  Using the reset button or running bmode normal
3153		will set it back to normal.  This command currently
3154		supports i.MX53 and i.MX6.
3155
3156- Signing support:
3157		CONFIG_RSA
3158
3159		This enables the RSA algorithm used for FIT image verification
3160		in U-Boot. See doc/uImage.FIT/signature.txt for more information.
3161
3162		The Modular Exponentiation algorithm in RSA is implemented using
3163		driver model. So CONFIG_DM needs to be enabled by default for this
3164		library to function.
3165
3166		The signing part is build into mkimage regardless of this
3167		option. The software based modular exponentiation is built into
3168		mkimage irrespective of this option.
3169
3170- bootcount support:
3171		CONFIG_BOOTCOUNT_LIMIT
3172
3173		This enables the bootcounter support, see:
3174		http://www.denx.de/wiki/DULG/UBootBootCountLimit
3175
3176		CONFIG_AT91SAM9XE
3177		enable special bootcounter support on at91sam9xe based boards.
3178		CONFIG_BLACKFIN
3179		enable special bootcounter support on blackfin based boards.
3180		CONFIG_SOC_DA8XX
3181		enable special bootcounter support on da850 based boards.
3182		CONFIG_BOOTCOUNT_RAM
3183		enable support for the bootcounter in RAM
3184		CONFIG_BOOTCOUNT_I2C
3185		enable support for the bootcounter on an i2c (like RTC) device.
3186			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
3187			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
3188						    the bootcounter.
3189			CONFIG_BOOTCOUNT_ALEN = address len
3190
3191- Show boot progress:
3192		CONFIG_SHOW_BOOT_PROGRESS
3193
3194		Defining this option allows to add some board-
3195		specific code (calling a user-provided function
3196		"show_boot_progress(int)") that enables you to show
3197		the system's boot progress on some display (for
3198		example, some LED's) on your board. At the moment,
3199		the following checkpoints are implemented:
3200
3201
3202Legacy uImage format:
3203
3204  Arg	Where			When
3205    1	common/cmd_bootm.c	before attempting to boot an image
3206   -1	common/cmd_bootm.c	Image header has bad	 magic number
3207    2	common/cmd_bootm.c	Image header has correct magic number
3208   -2	common/cmd_bootm.c	Image header has bad	 checksum
3209    3	common/cmd_bootm.c	Image header has correct checksum
3210   -3	common/cmd_bootm.c	Image data   has bad	 checksum
3211    4	common/cmd_bootm.c	Image data   has correct checksum
3212   -4	common/cmd_bootm.c	Image is for unsupported architecture
3213    5	common/cmd_bootm.c	Architecture check OK
3214   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
3215    6	common/cmd_bootm.c	Image Type check OK
3216   -6	common/cmd_bootm.c	gunzip uncompression error
3217   -7	common/cmd_bootm.c	Unimplemented compression type
3218    7	common/cmd_bootm.c	Uncompression OK
3219    8	common/cmd_bootm.c	No uncompress/copy overwrite error
3220   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3221
3222    9	common/image.c		Start initial ramdisk verification
3223  -10	common/image.c		Ramdisk header has bad	   magic number
3224  -11	common/image.c		Ramdisk header has bad	   checksum
3225   10	common/image.c		Ramdisk header is OK
3226  -12	common/image.c		Ramdisk data   has bad	   checksum
3227   11	common/image.c		Ramdisk data   has correct checksum
3228   12	common/image.c		Ramdisk verification complete, start loading
3229  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3230   13	common/image.c		Start multifile image verification
3231   14	common/image.c		No initial ramdisk, no multifile, continue.
3232
3233   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3234
3235  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3236  -31	post/post.c		POST test failed, detected by post_output_backlog()
3237  -32	post/post.c		POST test failed, detected by post_run_single()
3238
3239   34	common/cmd_doc.c	before loading a Image from a DOC device
3240  -35	common/cmd_doc.c	Bad usage of "doc" command
3241   35	common/cmd_doc.c	correct usage of "doc" command
3242  -36	common/cmd_doc.c	No boot device
3243   36	common/cmd_doc.c	correct boot device
3244  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3245   37	common/cmd_doc.c	correct chip ID found, device available
3246  -38	common/cmd_doc.c	Read Error on boot device
3247   38	common/cmd_doc.c	reading Image header from DOC device OK
3248  -39	common/cmd_doc.c	Image header has bad magic number
3249   39	common/cmd_doc.c	Image header has correct magic number
3250  -40	common/cmd_doc.c	Error reading Image from DOC device
3251   40	common/cmd_doc.c	Image header has correct magic number
3252   41	common/cmd_ide.c	before loading a Image from a IDE device
3253  -42	common/cmd_ide.c	Bad usage of "ide" command
3254   42	common/cmd_ide.c	correct usage of "ide" command
3255  -43	common/cmd_ide.c	No boot device
3256   43	common/cmd_ide.c	boot device found
3257  -44	common/cmd_ide.c	Device not available
3258   44	common/cmd_ide.c	Device available
3259  -45	common/cmd_ide.c	wrong partition selected
3260   45	common/cmd_ide.c	partition selected
3261  -46	common/cmd_ide.c	Unknown partition table
3262   46	common/cmd_ide.c	valid partition table found
3263  -47	common/cmd_ide.c	Invalid partition type
3264   47	common/cmd_ide.c	correct partition type
3265  -48	common/cmd_ide.c	Error reading Image Header on boot device
3266   48	common/cmd_ide.c	reading Image Header from IDE device OK
3267  -49	common/cmd_ide.c	Image header has bad magic number
3268   49	common/cmd_ide.c	Image header has correct magic number
3269  -50	common/cmd_ide.c	Image header has bad	 checksum
3270   50	common/cmd_ide.c	Image header has correct checksum
3271  -51	common/cmd_ide.c	Error reading Image from IDE device
3272   51	common/cmd_ide.c	reading Image from IDE device OK
3273   52	common/cmd_nand.c	before loading a Image from a NAND device
3274  -53	common/cmd_nand.c	Bad usage of "nand" command
3275   53	common/cmd_nand.c	correct usage of "nand" command
3276  -54	common/cmd_nand.c	No boot device
3277   54	common/cmd_nand.c	boot device found
3278  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3279   55	common/cmd_nand.c	correct chip ID found, device available
3280  -56	common/cmd_nand.c	Error reading Image Header on boot device
3281   56	common/cmd_nand.c	reading Image Header from NAND device OK
3282  -57	common/cmd_nand.c	Image header has bad magic number
3283   57	common/cmd_nand.c	Image header has correct magic number
3284  -58	common/cmd_nand.c	Error reading Image from NAND device
3285   58	common/cmd_nand.c	reading Image from NAND device OK
3286
3287  -60	common/env_common.c	Environment has a bad CRC, using default
3288
3289   64	net/eth.c		starting with Ethernet configuration.
3290  -64	net/eth.c		no Ethernet found.
3291   65	net/eth.c		Ethernet found.
3292
3293  -80	common/cmd_net.c	usage wrong
3294   80	common/cmd_net.c	before calling net_loop()
3295  -81	common/cmd_net.c	some error in net_loop() occurred
3296   81	common/cmd_net.c	net_loop() back without error
3297  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3298   82	common/cmd_net.c	trying automatic boot
3299   83	common/cmd_net.c	running "source" command
3300  -83	common/cmd_net.c	some error in automatic boot or "source" command
3301   84	common/cmd_net.c	end without errors
3302
3303FIT uImage format:
3304
3305  Arg	Where			When
3306  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3307 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3308  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3309 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3310  102	common/cmd_bootm.c	Kernel unit name specified
3311 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3312  103	common/cmd_bootm.c	Found configuration node
3313  104	common/cmd_bootm.c	Got kernel subimage node offset
3314 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3315  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3316 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3317  106	common/cmd_bootm.c	Architecture check OK
3318 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3319  107	common/cmd_bootm.c	Kernel subimage type OK
3320 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3321  108	common/cmd_bootm.c	Got kernel subimage data/size
3322 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3323 -109	common/cmd_bootm.c	Can't get kernel subimage type
3324 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3325 -111	common/cmd_bootm.c	Can't get kernel subimage os
3326 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3327 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3328
3329  120	common/image.c		Start initial ramdisk verification
3330 -120	common/image.c		Ramdisk FIT image has incorrect format
3331  121	common/image.c		Ramdisk FIT image has correct format
3332  122	common/image.c		No ramdisk subimage unit name, using configuration
3333 -122	common/image.c		Can't get configuration for ramdisk subimage
3334  123	common/image.c		Ramdisk unit name specified
3335 -124	common/image.c		Can't get ramdisk subimage node offset
3336  125	common/image.c		Got ramdisk subimage node offset
3337 -125	common/image.c		Ramdisk subimage hash verification failed
3338  126	common/image.c		Ramdisk subimage hash verification OK
3339 -126	common/image.c		Ramdisk subimage for unsupported architecture
3340  127	common/image.c		Architecture check OK
3341 -127	common/image.c		Can't get ramdisk subimage data/size
3342  128	common/image.c		Got ramdisk subimage data/size
3343  129	common/image.c		Can't get ramdisk load address
3344 -129	common/image.c		Got ramdisk load address
3345
3346 -130	common/cmd_doc.c	Incorrect FIT image format
3347  131	common/cmd_doc.c	FIT image format OK
3348
3349 -140	common/cmd_ide.c	Incorrect FIT image format
3350  141	common/cmd_ide.c	FIT image format OK
3351
3352 -150	common/cmd_nand.c	Incorrect FIT image format
3353  151	common/cmd_nand.c	FIT image format OK
3354
3355- legacy image format:
3356		CONFIG_IMAGE_FORMAT_LEGACY
3357		enables the legacy image format support in U-Boot.
3358
3359		Default:
3360		enabled if CONFIG_FIT_SIGNATURE is not defined.
3361
3362		CONFIG_DISABLE_IMAGE_LEGACY
3363		disable the legacy image format
3364
3365		This define is introduced, as the legacy image format is
3366		enabled per default for backward compatibility.
3367
3368- FIT image support:
3369		CONFIG_FIT
3370		Enable support for the FIT uImage format.
3371
3372		CONFIG_FIT_BEST_MATCH
3373		When no configuration is explicitly selected, default to the
3374		one whose fdt's compatibility field best matches that of
3375		U-Boot itself. A match is considered "best" if it matches the
3376		most specific compatibility entry of U-Boot's fdt's root node.
3377		The order of entries in the configuration's fdt is ignored.
3378
3379		CONFIG_FIT_SIGNATURE
3380		This option enables signature verification of FIT uImages,
3381		using a hash signed and verified using RSA. If
3382		CONFIG_SHA_PROG_HW_ACCEL is defined, i.e support for progressive
3383		hashing is available using hardware, RSA library will use it.
3384		See doc/uImage.FIT/signature.txt for more details.
3385
3386		WARNING: When relying on signed FIT images with required
3387		signature check the legacy image format is default
3388		disabled. If a board need legacy image format support
3389		enable this through CONFIG_IMAGE_FORMAT_LEGACY
3390
3391		CONFIG_FIT_DISABLE_SHA256
3392		Supporting SHA256 hashes has quite an impact on binary size.
3393		For constrained systems sha256 hash support can be disabled
3394		with this option.
3395
3396- Standalone program support:
3397		CONFIG_STANDALONE_LOAD_ADDR
3398
3399		This option defines a board specific value for the
3400		address where standalone program gets loaded, thus
3401		overwriting the architecture dependent default
3402		settings.
3403
3404- Frame Buffer Address:
3405		CONFIG_FB_ADDR
3406
3407		Define CONFIG_FB_ADDR if you want to use specific
3408		address for frame buffer.  This is typically the case
3409		when using a graphics controller has separate video
3410		memory.  U-Boot will then place the frame buffer at
3411		the given address instead of dynamically reserving it
3412		in system RAM by calling lcd_setmem(), which grabs
3413		the memory for the frame buffer depending on the
3414		configured panel size.
3415
3416		Please see board_init_f function.
3417
3418- Automatic software updates via TFTP server
3419		CONFIG_UPDATE_TFTP
3420		CONFIG_UPDATE_TFTP_CNT_MAX
3421		CONFIG_UPDATE_TFTP_MSEC_MAX
3422
3423		These options enable and control the auto-update feature;
3424		for a more detailed description refer to doc/README.update.
3425
3426- MTD Support (mtdparts command, UBI support)
3427		CONFIG_MTD_DEVICE
3428
3429		Adds the MTD device infrastructure from the Linux kernel.
3430		Needed for mtdparts command support.
3431
3432		CONFIG_MTD_PARTITIONS
3433
3434		Adds the MTD partitioning infrastructure from the Linux
3435		kernel. Needed for UBI support.
3436
3437- UBI support
3438		CONFIG_CMD_UBI
3439
3440		Adds commands for interacting with MTD partitions formatted
3441		with the UBI flash translation layer
3442
3443		Requires also defining CONFIG_RBTREE
3444
3445		CONFIG_UBI_SILENCE_MSG
3446
3447		Make the verbose messages from UBI stop printing.  This leaves
3448		warnings and errors enabled.
3449
3450
3451		CONFIG_MTD_UBI_WL_THRESHOLD
3452		This parameter defines the maximum difference between the highest
3453		erase counter value and the lowest erase counter value of eraseblocks
3454		of UBI devices. When this threshold is exceeded, UBI starts performing
3455		wear leveling by means of moving data from eraseblock with low erase
3456		counter to eraseblocks with high erase counter.
3457
3458		The default value should be OK for SLC NAND flashes, NOR flashes and
3459		other flashes which have eraseblock life-cycle 100000 or more.
3460		However, in case of MLC NAND flashes which typically have eraseblock
3461		life-cycle less than 10000, the threshold should be lessened (e.g.,
3462		to 128 or 256, although it does not have to be power of 2).
3463
3464		default: 4096
3465
3466		CONFIG_MTD_UBI_BEB_LIMIT
3467		This option specifies the maximum bad physical eraseblocks UBI
3468		expects on the MTD device (per 1024 eraseblocks). If the
3469		underlying flash does not admit of bad eraseblocks (e.g. NOR
3470		flash), this value is ignored.
3471
3472		NAND datasheets often specify the minimum and maximum NVM
3473		(Number of Valid Blocks) for the flashes' endurance lifetime.
3474		The maximum expected bad eraseblocks per 1024 eraseblocks
3475		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
3476		which gives 20 for most NANDs (MaxNVB is basically the total
3477		count of eraseblocks on the chip).
3478
3479		To put it differently, if this value is 20, UBI will try to
3480		reserve about 1.9% of physical eraseblocks for bad blocks
3481		handling. And that will be 1.9% of eraseblocks on the entire
3482		NAND chip, not just the MTD partition UBI attaches. This means
3483		that if you have, say, a NAND flash chip admits maximum 40 bad
3484		eraseblocks, and it is split on two MTD partitions of the same
3485		size, UBI will reserve 40 eraseblocks when attaching a
3486		partition.
3487
3488		default: 20
3489
3490		CONFIG_MTD_UBI_FASTMAP
3491		Fastmap is a mechanism which allows attaching an UBI device
3492		in nearly constant time. Instead of scanning the whole MTD device it
3493		only has to locate a checkpoint (called fastmap) on the device.
3494		The on-flash fastmap contains all information needed to attach
3495		the device. Using fastmap makes only sense on large devices where
3496		attaching by scanning takes long. UBI will not automatically install
3497		a fastmap on old images, but you can set the UBI parameter
3498		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
3499		that fastmap-enabled images are still usable with UBI implementations
3500		without	fastmap support. On typical flash devices the whole fastmap
3501		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
3502
3503		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
3504		Set this parameter to enable fastmap automatically on images
3505		without a fastmap.
3506		default: 0
3507
3508- UBIFS support
3509		CONFIG_CMD_UBIFS
3510
3511		Adds commands for interacting with UBI volumes formatted as
3512		UBIFS.  UBIFS is read-only in u-boot.
3513
3514		Requires UBI support as well as CONFIG_LZO
3515
3516		CONFIG_UBIFS_SILENCE_MSG
3517
3518		Make the verbose messages from UBIFS stop printing.  This leaves
3519		warnings and errors enabled.
3520
3521- SPL framework
3522		CONFIG_SPL
3523		Enable building of SPL globally.
3524
3525		CONFIG_SPL_LDSCRIPT
3526		LDSCRIPT for linking the SPL binary.
3527
3528		CONFIG_SPL_MAX_FOOTPRINT
3529		Maximum size in memory allocated to the SPL, BSS included.
3530		When defined, the linker checks that the actual memory
3531		used by SPL from _start to __bss_end does not exceed it.
3532		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3533		must not be both defined at the same time.
3534
3535		CONFIG_SPL_MAX_SIZE
3536		Maximum size of the SPL image (text, data, rodata, and
3537		linker lists sections), BSS excluded.
3538		When defined, the linker checks that the actual size does
3539		not exceed it.
3540
3541		CONFIG_SPL_TEXT_BASE
3542		TEXT_BASE for linking the SPL binary.
3543
3544		CONFIG_SPL_RELOC_TEXT_BASE
3545		Address to relocate to.  If unspecified, this is equal to
3546		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3547
3548		CONFIG_SPL_BSS_START_ADDR
3549		Link address for the BSS within the SPL binary.
3550
3551		CONFIG_SPL_BSS_MAX_SIZE
3552		Maximum size in memory allocated to the SPL BSS.
3553		When defined, the linker checks that the actual memory used
3554		by SPL from __bss_start to __bss_end does not exceed it.
3555		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3556		must not be both defined at the same time.
3557
3558		CONFIG_SPL_STACK
3559		Adress of the start of the stack SPL will use
3560
3561		CONFIG_SPL_PANIC_ON_RAW_IMAGE
3562		When defined, SPL will panic() if the image it has
3563		loaded does not have a signature.
3564		Defining this is useful when code which loads images
3565		in SPL cannot guarantee that absolutely all read errors
3566		will be caught.
3567		An example is the LPC32XX MLC NAND driver, which will
3568		consider that a completely unreadable NAND block is bad,
3569		and thus should be skipped silently.
3570
3571		CONFIG_SPL_RELOC_STACK
3572		Adress of the start of the stack SPL will use after
3573		relocation.  If unspecified, this is equal to
3574		CONFIG_SPL_STACK.
3575
3576		CONFIG_SYS_SPL_MALLOC_START
3577		Starting address of the malloc pool used in SPL.
3578
3579		CONFIG_SYS_SPL_MALLOC_SIZE
3580		The size of the malloc pool used in SPL.
3581
3582		CONFIG_SPL_FRAMEWORK
3583		Enable the SPL framework under common/.  This framework
3584		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3585		NAND loading of the Linux Kernel.
3586
3587		CONFIG_SPL_OS_BOOT
3588		Enable booting directly to an OS from SPL.
3589		See also: doc/README.falcon
3590
3591		CONFIG_SPL_DISPLAY_PRINT
3592		For ARM, enable an optional function to print more information
3593		about the running system.
3594
3595		CONFIG_SPL_INIT_MINIMAL
3596		Arch init code should be built for a very small image
3597
3598		CONFIG_SPL_LIBCOMMON_SUPPORT
3599		Support for common/libcommon.o in SPL binary
3600
3601		CONFIG_SPL_LIBDISK_SUPPORT
3602		Support for disk/libdisk.o in SPL binary
3603
3604		CONFIG_SPL_I2C_SUPPORT
3605		Support for drivers/i2c/libi2c.o in SPL binary
3606
3607		CONFIG_SPL_GPIO_SUPPORT
3608		Support for drivers/gpio/libgpio.o in SPL binary
3609
3610		CONFIG_SPL_MMC_SUPPORT
3611		Support for drivers/mmc/libmmc.o in SPL binary
3612
3613		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3614		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3615		Address and partition on the MMC to load U-Boot from
3616		when the MMC is being used in raw mode.
3617
3618		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3619		Partition on the MMC to load U-Boot from when the MMC is being
3620		used in raw mode
3621
3622		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3623		Sector to load kernel uImage from when MMC is being
3624		used in raw mode (for Falcon mode)
3625
3626		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3627		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3628		Sector and number of sectors to load kernel argument
3629		parameters from when MMC is being used in raw mode
3630		(for falcon mode)
3631
3632		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3633		Partition on the MMC to load U-Boot from when the MMC is being
3634		used in fs mode
3635
3636		CONFIG_SPL_FAT_SUPPORT
3637		Support for fs/fat/libfat.o in SPL binary
3638
3639		CONFIG_SPL_EXT_SUPPORT
3640		Support for EXT filesystem in SPL binary
3641
3642		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3643		Filename to read to load U-Boot when reading from filesystem
3644
3645		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3646		Filename to read to load kernel uImage when reading
3647		from filesystem (for Falcon mode)
3648
3649		CONFIG_SPL_FS_LOAD_ARGS_NAME
3650		Filename to read to load kernel argument parameters
3651		when reading from filesystem (for Falcon mode)
3652
3653		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3654		Set this for NAND SPL on PPC mpc83xx targets, so that
3655		start.S waits for the rest of the SPL to load before
3656		continuing (the hardware starts execution after just
3657		loading the first page rather than the full 4K).
3658
3659		CONFIG_SPL_SKIP_RELOCATE
3660		Avoid SPL relocation
3661
3662		CONFIG_SPL_NAND_BASE
3663		Include nand_base.c in the SPL.  Requires
3664		CONFIG_SPL_NAND_DRIVERS.
3665
3666		CONFIG_SPL_NAND_DRIVERS
3667		SPL uses normal NAND drivers, not minimal drivers.
3668
3669		CONFIG_SPL_NAND_ECC
3670		Include standard software ECC in the SPL
3671
3672		CONFIG_SPL_NAND_SIMPLE
3673		Support for NAND boot using simple NAND drivers that
3674		expose the cmd_ctrl() interface.
3675
3676		CONFIG_SPL_MTD_SUPPORT
3677		Support for the MTD subsystem within SPL.  Useful for
3678		environment on NAND support within SPL.
3679
3680		CONFIG_SPL_NAND_RAW_ONLY
3681		Support to boot only raw u-boot.bin images. Use this only
3682		if you need to save space.
3683
3684		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3685		Set for the SPL on PPC mpc8xxx targets, support for
3686		drivers/ddr/fsl/libddr.o in SPL binary.
3687
3688		CONFIG_SPL_COMMON_INIT_DDR
3689		Set for common ddr init with serial presence detect in
3690		SPL binary.
3691
3692		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3693		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3694		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3695		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3696		CONFIG_SYS_NAND_ECCBYTES
3697		Defines the size and behavior of the NAND that SPL uses
3698		to read U-Boot
3699
3700		CONFIG_SPL_NAND_BOOT
3701		Add support NAND boot
3702
3703		CONFIG_SYS_NAND_U_BOOT_OFFS
3704		Location in NAND to read U-Boot from
3705
3706		CONFIG_SYS_NAND_U_BOOT_DST
3707		Location in memory to load U-Boot to
3708
3709		CONFIG_SYS_NAND_U_BOOT_SIZE
3710		Size of image to load
3711
3712		CONFIG_SYS_NAND_U_BOOT_START
3713		Entry point in loaded image to jump to
3714
3715		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3716		Define this if you need to first read the OOB and then the
3717		data. This is used, for example, on davinci platforms.
3718
3719		CONFIG_SPL_OMAP3_ID_NAND
3720		Support for an OMAP3-specific set of functions to return the
3721		ID and MFR of the first attached NAND chip, if present.
3722
3723		CONFIG_SPL_SERIAL_SUPPORT
3724		Support for drivers/serial/libserial.o in SPL binary
3725
3726		CONFIG_SPL_SPI_FLASH_SUPPORT
3727		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3728
3729		CONFIG_SPL_SPI_SUPPORT
3730		Support for drivers/spi/libspi.o in SPL binary
3731
3732		CONFIG_SPL_RAM_DEVICE
3733		Support for running image already present in ram, in SPL binary
3734
3735		CONFIG_SPL_LIBGENERIC_SUPPORT
3736		Support for lib/libgeneric.o in SPL binary
3737
3738		CONFIG_SPL_ENV_SUPPORT
3739		Support for the environment operating in SPL binary
3740
3741		CONFIG_SPL_NET_SUPPORT
3742		Support for the net/libnet.o in SPL binary.
3743		It conflicts with SPL env from storage medium specified by
3744		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3745
3746		CONFIG_SPL_PAD_TO
3747		Image offset to which the SPL should be padded before appending
3748		the SPL payload. By default, this is defined as
3749		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3750		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3751		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3752
3753		CONFIG_SPL_TARGET
3754		Final target image containing SPL and payload.  Some SPLs
3755		use an arch-specific makefile fragment instead, for
3756		example if more than one image needs to be produced.
3757
3758		CONFIG_FIT_SPL_PRINT
3759		Printing information about a FIT image adds quite a bit of
3760		code to SPL. So this is normally disabled in SPL. Use this
3761		option to re-enable it. This will affect the output of the
3762		bootm command when booting a FIT image.
3763
3764- TPL framework
3765		CONFIG_TPL
3766		Enable building of TPL globally.
3767
3768		CONFIG_TPL_PAD_TO
3769		Image offset to which the TPL should be padded before appending
3770		the TPL payload. By default, this is defined as
3771		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3772		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3773		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3774
3775Modem Support:
3776--------------
3777
3778[so far only for SMDK2400 boards]
3779
3780- Modem support enable:
3781		CONFIG_MODEM_SUPPORT
3782
3783- RTS/CTS Flow control enable:
3784		CONFIG_HWFLOW
3785
3786- Modem debug support:
3787		CONFIG_MODEM_SUPPORT_DEBUG
3788
3789		Enables debugging stuff (char screen[1024], dbg())
3790		for modem support. Useful only with BDI2000.
3791
3792- Interrupt support (PPC):
3793
3794		There are common interrupt_init() and timer_interrupt()
3795		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3796		for CPU specific initialization. interrupt_init_cpu()
3797		should set decrementer_count to appropriate value. If
3798		CPU resets decrementer automatically after interrupt
3799		(ppc4xx) it should set decrementer_count to zero.
3800		timer_interrupt() calls timer_interrupt_cpu() for CPU
3801		specific handling. If board has watchdog / status_led
3802		/ other_activity_monitor it works automatically from
3803		general timer_interrupt().
3804
3805- General:
3806
3807		In the target system modem support is enabled when a
3808		specific key (key combination) is pressed during
3809		power-on. Otherwise U-Boot will boot normally
3810		(autoboot). The key_pressed() function is called from
3811		board_init(). Currently key_pressed() is a dummy
3812		function, returning 1 and thus enabling modem
3813		initialization.
3814
3815		If there are no modem init strings in the
3816		environment, U-Boot proceed to autoboot; the
3817		previous output (banner, info printfs) will be
3818		suppressed, though.
3819
3820		See also: doc/README.Modem
3821
3822Board initialization settings:
3823------------------------------
3824
3825During Initialization u-boot calls a number of board specific functions
3826to allow the preparation of board specific prerequisites, e.g. pin setup
3827before drivers are initialized. To enable these callbacks the
3828following configuration macros have to be defined. Currently this is
3829architecture specific, so please check arch/your_architecture/lib/board.c
3830typically in board_init_f() and board_init_r().
3831
3832- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3833- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3834- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3835- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3836
3837Configuration Settings:
3838-----------------------
3839
3840- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3841		Optionally it can be defined to support 64-bit memory commands.
3842
3843- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3844		undefine this when you're short of memory.
3845
3846- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3847		width of the commands listed in the 'help' command output.
3848
3849- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3850		prompt for user input.
3851
3852- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3853
3854- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3855
3856- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3857
3858- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3859		the application (usually a Linux kernel) when it is
3860		booted
3861
3862- CONFIG_SYS_BAUDRATE_TABLE:
3863		List of legal baudrate settings for this board.
3864
3865- CONFIG_SYS_CONSOLE_INFO_QUIET
3866		Suppress display of console information at boot.
3867
3868- CONFIG_SYS_CONSOLE_IS_IN_ENV
3869		If the board specific function
3870			extern int overwrite_console (void);
3871		returns 1, the stdin, stderr and stdout are switched to the
3872		serial port, else the settings in the environment are used.
3873
3874- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3875		Enable the call to overwrite_console().
3876
3877- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3878		Enable overwrite of previous console environment settings.
3879
3880- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3881		Begin and End addresses of the area used by the
3882		simple memory test.
3883
3884- CONFIG_SYS_ALT_MEMTEST:
3885		Enable an alternate, more extensive memory test.
3886
3887- CONFIG_SYS_MEMTEST_SCRATCH:
3888		Scratch address used by the alternate memory test
3889		You only need to set this if address zero isn't writeable
3890
3891- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3892		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3893		this specified memory area will get subtracted from the top
3894		(end) of RAM and won't get "touched" at all by U-Boot. By
3895		fixing up gd->ram_size the Linux kernel should gets passed
3896		the now "corrected" memory size and won't touch it either.
3897		This should work for arch/ppc and arch/powerpc. Only Linux
3898		board ports in arch/powerpc with bootwrapper support that
3899		recalculate the memory size from the SDRAM controller setup
3900		will have to get fixed in Linux additionally.
3901
3902		This option can be used as a workaround for the 440EPx/GRx
3903		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3904		be touched.
3905
3906		WARNING: Please make sure that this value is a multiple of
3907		the Linux page size (normally 4k). If this is not the case,
3908		then the end address of the Linux memory will be located at a
3909		non page size aligned address and this could cause major
3910		problems.
3911
3912- CONFIG_SYS_LOADS_BAUD_CHANGE:
3913		Enable temporary baudrate change while serial download
3914
3915- CONFIG_SYS_SDRAM_BASE:
3916		Physical start address of SDRAM. _Must_ be 0 here.
3917
3918- CONFIG_SYS_MBIO_BASE:
3919		Physical start address of Motherboard I/O (if using a
3920		Cogent motherboard)
3921
3922- CONFIG_SYS_FLASH_BASE:
3923		Physical start address of Flash memory.
3924
3925- CONFIG_SYS_MONITOR_BASE:
3926		Physical start address of boot monitor code (set by
3927		make config files to be same as the text base address
3928		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3929		CONFIG_SYS_FLASH_BASE when booting from flash.
3930
3931- CONFIG_SYS_MONITOR_LEN:
3932		Size of memory reserved for monitor code, used to
3933		determine _at_compile_time_ (!) if the environment is
3934		embedded within the U-Boot image, or in a separate
3935		flash sector.
3936
3937- CONFIG_SYS_MALLOC_LEN:
3938		Size of DRAM reserved for malloc() use.
3939
3940- CONFIG_SYS_MALLOC_F_LEN
3941		Size of the malloc() pool for use before relocation. If
3942		this is defined, then a very simple malloc() implementation
3943		will become available before relocation. The address is just
3944		below the global data, and the stack is moved down to make
3945		space.
3946
3947		This feature allocates regions with increasing addresses
3948		within the region. calloc() is supported, but realloc()
3949		is not available. free() is supported but does nothing.
3950		The memory will be freed (or in fact just forgotten) when
3951		U-Boot relocates itself.
3952
3953		Pre-relocation malloc() is only supported on ARM and sandbox
3954		at present but is fairly easy to enable for other archs.
3955
3956- CONFIG_SYS_MALLOC_SIMPLE
3957		Provides a simple and small malloc() and calloc() for those
3958		boards which do not use the full malloc in SPL (which is
3959		enabled with CONFIG_SYS_SPL_MALLOC_START).
3960
3961- CONFIG_SYS_NONCACHED_MEMORY:
3962		Size of non-cached memory area. This area of memory will be
3963		typically located right below the malloc() area and mapped
3964		uncached in the MMU. This is useful for drivers that would
3965		otherwise require a lot of explicit cache maintenance. For
3966		some drivers it's also impossible to properly maintain the
3967		cache. For example if the regions that need to be flushed
3968		are not a multiple of the cache-line size, *and* padding
3969		cannot be allocated between the regions to align them (i.e.
3970		if the HW requires a contiguous array of regions, and the
3971		size of each region is not cache-aligned), then a flush of
3972		one region may result in overwriting data that hardware has
3973		written to another region in the same cache-line. This can
3974		happen for example in network drivers where descriptors for
3975		buffers are typically smaller than the CPU cache-line (e.g.
3976		16 bytes vs. 32 or 64 bytes).
3977
3978		Non-cached memory is only supported on 32-bit ARM at present.
3979
3980- CONFIG_SYS_BOOTM_LEN:
3981		Normally compressed uImages are limited to an
3982		uncompressed size of 8 MBytes. If this is not enough,
3983		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3984		to adjust this setting to your needs.
3985
3986- CONFIG_SYS_BOOTMAPSZ:
3987		Maximum size of memory mapped by the startup code of
3988		the Linux kernel; all data that must be processed by
3989		the Linux kernel (bd_info, boot arguments, FDT blob if
3990		used) must be put below this limit, unless "bootm_low"
3991		environment variable is defined and non-zero. In such case
3992		all data for the Linux kernel must be between "bootm_low"
3993		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3994		variable "bootm_mapsize" will override the value of
3995		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3996		then the value in "bootm_size" will be used instead.
3997
3998- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3999		Enable initrd_high functionality.  If defined then the
4000		initrd_high feature is enabled and the bootm ramdisk subcommand
4001		is enabled.
4002
4003- CONFIG_SYS_BOOT_GET_CMDLINE:
4004		Enables allocating and saving kernel cmdline in space between
4005		"bootm_low" and "bootm_low" + BOOTMAPSZ.
4006
4007- CONFIG_SYS_BOOT_GET_KBD:
4008		Enables allocating and saving a kernel copy of the bd_info in
4009		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
4010
4011- CONFIG_SYS_MAX_FLASH_BANKS:
4012		Max number of Flash memory banks
4013
4014- CONFIG_SYS_MAX_FLASH_SECT:
4015		Max number of sectors on a Flash chip
4016
4017- CONFIG_SYS_FLASH_ERASE_TOUT:
4018		Timeout for Flash erase operations (in ms)
4019
4020- CONFIG_SYS_FLASH_WRITE_TOUT:
4021		Timeout for Flash write operations (in ms)
4022
4023- CONFIG_SYS_FLASH_LOCK_TOUT
4024		Timeout for Flash set sector lock bit operation (in ms)
4025
4026- CONFIG_SYS_FLASH_UNLOCK_TOUT
4027		Timeout for Flash clear lock bits operation (in ms)
4028
4029- CONFIG_SYS_FLASH_PROTECTION
4030		If defined, hardware flash sectors protection is used
4031		instead of U-Boot software protection.
4032
4033- CONFIG_SYS_DIRECT_FLASH_TFTP:
4034
4035		Enable TFTP transfers directly to flash memory;
4036		without this option such a download has to be
4037		performed in two steps: (1) download to RAM, and (2)
4038		copy from RAM to flash.
4039
4040		The two-step approach is usually more reliable, since
4041		you can check if the download worked before you erase
4042		the flash, but in some situations (when system RAM is
4043		too limited to allow for a temporary copy of the
4044		downloaded image) this option may be very useful.
4045
4046- CONFIG_SYS_FLASH_CFI:
4047		Define if the flash driver uses extra elements in the
4048		common flash structure for storing flash geometry.
4049
4050- CONFIG_FLASH_CFI_DRIVER
4051		This option also enables the building of the cfi_flash driver
4052		in the drivers directory
4053
4054- CONFIG_FLASH_CFI_MTD
4055		This option enables the building of the cfi_mtd driver
4056		in the drivers directory. The driver exports CFI flash
4057		to the MTD layer.
4058
4059- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
4060		Use buffered writes to flash.
4061
4062- CONFIG_FLASH_SPANSION_S29WS_N
4063		s29ws-n MirrorBit flash has non-standard addresses for buffered
4064		write commands.
4065
4066- CONFIG_SYS_FLASH_QUIET_TEST
4067		If this option is defined, the common CFI flash doesn't
4068		print it's warning upon not recognized FLASH banks. This
4069		is useful, if some of the configured banks are only
4070		optionally available.
4071
4072- CONFIG_FLASH_SHOW_PROGRESS
4073		If defined (must be an integer), print out countdown
4074		digits and dots.  Recommended value: 45 (9..1) for 80
4075		column displays, 15 (3..1) for 40 column displays.
4076
4077- CONFIG_FLASH_VERIFY
4078		If defined, the content of the flash (destination) is compared
4079		against the source after the write operation. An error message
4080		will be printed when the contents are not identical.
4081		Please note that this option is useless in nearly all cases,
4082		since such flash programming errors usually are detected earlier
4083		while unprotecting/erasing/programming. Please only enable
4084		this option if you really know what you are doing.
4085
4086- CONFIG_SYS_RX_ETH_BUFFER:
4087		Defines the number of Ethernet receive buffers. On some
4088		Ethernet controllers it is recommended to set this value
4089		to 8 or even higher (EEPRO100 or 405 EMAC), since all
4090		buffers can be full shortly after enabling the interface
4091		on high Ethernet traffic.
4092		Defaults to 4 if not defined.
4093
4094- CONFIG_ENV_MAX_ENTRIES
4095
4096	Maximum number of entries in the hash table that is used
4097	internally to store the environment settings. The default
4098	setting is supposed to be generous and should work in most
4099	cases. This setting can be used to tune behaviour; see
4100	lib/hashtable.c for details.
4101
4102- CONFIG_ENV_FLAGS_LIST_DEFAULT
4103- CONFIG_ENV_FLAGS_LIST_STATIC
4104	Enable validation of the values given to environment variables when
4105	calling env set.  Variables can be restricted to only decimal,
4106	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
4107	the variables can also be restricted to IP address or MAC address.
4108
4109	The format of the list is:
4110		type_attribute = [s|d|x|b|i|m]
4111		access_attribute = [a|r|o|c]
4112		attributes = type_attribute[access_attribute]
4113		entry = variable_name[:attributes]
4114		list = entry[,list]
4115
4116	The type attributes are:
4117		s - String (default)
4118		d - Decimal
4119		x - Hexadecimal
4120		b - Boolean ([1yYtT|0nNfF])
4121		i - IP address
4122		m - MAC address
4123
4124	The access attributes are:
4125		a - Any (default)
4126		r - Read-only
4127		o - Write-once
4128		c - Change-default
4129
4130	- CONFIG_ENV_FLAGS_LIST_DEFAULT
4131		Define this to a list (string) to define the ".flags"
4132		environment variable in the default or embedded environment.
4133
4134	- CONFIG_ENV_FLAGS_LIST_STATIC
4135		Define this to a list (string) to define validation that
4136		should be done if an entry is not found in the ".flags"
4137		environment variable.  To override a setting in the static
4138		list, simply add an entry for the same variable name to the
4139		".flags" variable.
4140
4141- CONFIG_ENV_ACCESS_IGNORE_FORCE
4142	If defined, don't allow the -f switch to env set override variable
4143	access flags.
4144
4145- CONFIG_SYS_GENERIC_BOARD
4146	This selects the architecture-generic board system instead of the
4147	architecture-specific board files. It is intended to move boards
4148	to this new framework over time. Defining this will disable the
4149	arch/foo/lib/board.c file and use common/board_f.c and
4150	common/board_r.c instead. To use this option your architecture
4151	must support it (i.e. must select HAVE_GENERIC_BOARD in arch/Kconfig).
4152	If you find problems enabling this option on your board please report
4153	the problem and send patches!
4154
4155- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
4156	This is set by OMAP boards for the max time that reset should
4157	be asserted. See doc/README.omap-reset-time for details on how
4158	the value can be calculated on a given board.
4159
4160- CONFIG_USE_STDINT
4161	If stdint.h is available with your toolchain you can define this
4162	option to enable it. You can provide option 'USE_STDINT=1' when
4163	building U-Boot to enable this.
4164
4165The following definitions that deal with the placement and management
4166of environment data (variable area); in general, we support the
4167following configurations:
4168
4169- CONFIG_BUILD_ENVCRC:
4170
4171	Builds up envcrc with the target environment so that external utils
4172	may easily extract it and embed it in final U-Boot images.
4173
4174- CONFIG_ENV_IS_IN_FLASH:
4175
4176	Define this if the environment is in flash memory.
4177
4178	a) The environment occupies one whole flash sector, which is
4179	   "embedded" in the text segment with the U-Boot code. This
4180	   happens usually with "bottom boot sector" or "top boot
4181	   sector" type flash chips, which have several smaller
4182	   sectors at the start or the end. For instance, such a
4183	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
4184	   such a case you would place the environment in one of the
4185	   4 kB sectors - with U-Boot code before and after it. With
4186	   "top boot sector" type flash chips, you would put the
4187	   environment in one of the last sectors, leaving a gap
4188	   between U-Boot and the environment.
4189
4190	- CONFIG_ENV_OFFSET:
4191
4192	   Offset of environment data (variable area) to the
4193	   beginning of flash memory; for instance, with bottom boot
4194	   type flash chips the second sector can be used: the offset
4195	   for this sector is given here.
4196
4197	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
4198
4199	- CONFIG_ENV_ADDR:
4200
4201	   This is just another way to specify the start address of
4202	   the flash sector containing the environment (instead of
4203	   CONFIG_ENV_OFFSET).
4204
4205	- CONFIG_ENV_SECT_SIZE:
4206
4207	   Size of the sector containing the environment.
4208
4209
4210	b) Sometimes flash chips have few, equal sized, BIG sectors.
4211	   In such a case you don't want to spend a whole sector for
4212	   the environment.
4213
4214	- CONFIG_ENV_SIZE:
4215
4216	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
4217	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
4218	   of this flash sector for the environment. This saves
4219	   memory for the RAM copy of the environment.
4220
4221	   It may also save flash memory if you decide to use this
4222	   when your environment is "embedded" within U-Boot code,
4223	   since then the remainder of the flash sector could be used
4224	   for U-Boot code. It should be pointed out that this is
4225	   STRONGLY DISCOURAGED from a robustness point of view:
4226	   updating the environment in flash makes it always
4227	   necessary to erase the WHOLE sector. If something goes
4228	   wrong before the contents has been restored from a copy in
4229	   RAM, your target system will be dead.
4230
4231	- CONFIG_ENV_ADDR_REDUND
4232	  CONFIG_ENV_SIZE_REDUND
4233
4234	   These settings describe a second storage area used to hold
4235	   a redundant copy of the environment data, so that there is
4236	   a valid backup copy in case there is a power failure during
4237	   a "saveenv" operation.
4238
4239BE CAREFUL! Any changes to the flash layout, and some changes to the
4240source code will make it necessary to adapt <board>/u-boot.lds*
4241accordingly!
4242
4243
4244- CONFIG_ENV_IS_IN_NVRAM:
4245
4246	Define this if you have some non-volatile memory device
4247	(NVRAM, battery buffered SRAM) which you want to use for the
4248	environment.
4249
4250	- CONFIG_ENV_ADDR:
4251	- CONFIG_ENV_SIZE:
4252
4253	  These two #defines are used to determine the memory area you
4254	  want to use for environment. It is assumed that this memory
4255	  can just be read and written to, without any special
4256	  provision.
4257
4258BE CAREFUL! The first access to the environment happens quite early
4259in U-Boot initialization (when we try to get the setting of for the
4260console baudrate). You *MUST* have mapped your NVRAM area then, or
4261U-Boot will hang.
4262
4263Please note that even with NVRAM we still use a copy of the
4264environment in RAM: we could work on NVRAM directly, but we want to
4265keep settings there always unmodified except somebody uses "saveenv"
4266to save the current settings.
4267
4268
4269- CONFIG_ENV_IS_IN_EEPROM:
4270
4271	Use this if you have an EEPROM or similar serial access
4272	device and a driver for it.
4273
4274	- CONFIG_ENV_OFFSET:
4275	- CONFIG_ENV_SIZE:
4276
4277	  These two #defines specify the offset and size of the
4278	  environment area within the total memory of your EEPROM.
4279
4280	- CONFIG_SYS_I2C_EEPROM_ADDR:
4281	  If defined, specified the chip address of the EEPROM device.
4282	  The default address is zero.
4283
4284	- CONFIG_SYS_I2C_EEPROM_BUS:
4285	  If defined, specified the i2c bus of the EEPROM device.
4286
4287	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
4288	  If defined, the number of bits used to address bytes in a
4289	  single page in the EEPROM device.  A 64 byte page, for example
4290	  would require six bits.
4291
4292	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
4293	  If defined, the number of milliseconds to delay between
4294	  page writes.	The default is zero milliseconds.
4295
4296	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
4297	  The length in bytes of the EEPROM memory array address.  Note
4298	  that this is NOT the chip address length!
4299
4300	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
4301	  EEPROM chips that implement "address overflow" are ones
4302	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
4303	  address and the extra bits end up in the "chip address" bit
4304	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
4305	  byte chips.
4306
4307	  Note that we consider the length of the address field to
4308	  still be one byte because the extra address bits are hidden
4309	  in the chip address.
4310
4311	- CONFIG_SYS_EEPROM_SIZE:
4312	  The size in bytes of the EEPROM device.
4313
4314	- CONFIG_ENV_EEPROM_IS_ON_I2C
4315	  define this, if you have I2C and SPI activated, and your
4316	  EEPROM, which holds the environment, is on the I2C bus.
4317
4318	- CONFIG_I2C_ENV_EEPROM_BUS
4319	  if you have an Environment on an EEPROM reached over
4320	  I2C muxes, you can define here, how to reach this
4321	  EEPROM. For example:
4322
4323	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
4324
4325	  EEPROM which holds the environment, is reached over
4326	  a pca9547 i2c mux with address 0x70, channel 3.
4327
4328- CONFIG_ENV_IS_IN_DATAFLASH:
4329
4330	Define this if you have a DataFlash memory device which you
4331	want to use for the environment.
4332
4333	- CONFIG_ENV_OFFSET:
4334	- CONFIG_ENV_ADDR:
4335	- CONFIG_ENV_SIZE:
4336
4337	  These three #defines specify the offset and size of the
4338	  environment area within the total memory of your DataFlash placed
4339	  at the specified address.
4340
4341- CONFIG_ENV_IS_IN_SPI_FLASH:
4342
4343	Define this if you have a SPI Flash memory device which you
4344	want to use for the environment.
4345
4346	- CONFIG_ENV_OFFSET:
4347	- CONFIG_ENV_SIZE:
4348
4349	  These two #defines specify the offset and size of the
4350	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
4351	  aligned to an erase sector boundary.
4352
4353	- CONFIG_ENV_SECT_SIZE:
4354
4355	  Define the SPI flash's sector size.
4356
4357	- CONFIG_ENV_OFFSET_REDUND (optional):
4358
4359	  This setting describes a second storage area of CONFIG_ENV_SIZE
4360	  size used to hold a redundant copy of the environment data, so
4361	  that there is a valid backup copy in case there is a power failure
4362	  during a "saveenv" operation. CONFIG_ENV_OFFSET_RENDUND must be
4363	  aligned to an erase sector boundary.
4364
4365	- CONFIG_ENV_SPI_BUS (optional):
4366	- CONFIG_ENV_SPI_CS (optional):
4367
4368	  Define the SPI bus and chip select. If not defined they will be 0.
4369
4370	- CONFIG_ENV_SPI_MAX_HZ (optional):
4371
4372	  Define the SPI max work clock. If not defined then use 1MHz.
4373
4374	- CONFIG_ENV_SPI_MODE (optional):
4375
4376	  Define the SPI work mode. If not defined then use SPI_MODE_3.
4377
4378- CONFIG_ENV_IS_IN_REMOTE:
4379
4380	Define this if you have a remote memory space which you
4381	want to use for the local device's environment.
4382
4383	- CONFIG_ENV_ADDR:
4384	- CONFIG_ENV_SIZE:
4385
4386	  These two #defines specify the address and size of the
4387	  environment area within the remote memory space. The
4388	  local device can get the environment from remote memory
4389	  space by SRIO or PCIE links.
4390
4391BE CAREFUL! For some special cases, the local device can not use
4392"saveenv" command. For example, the local device will get the
4393environment stored in a remote NOR flash by SRIO or PCIE link,
4394but it can not erase, write this NOR flash by SRIO or PCIE interface.
4395
4396- CONFIG_ENV_IS_IN_NAND:
4397
4398	Define this if you have a NAND device which you want to use
4399	for the environment.
4400
4401	- CONFIG_ENV_OFFSET:
4402	- CONFIG_ENV_SIZE:
4403
4404	  These two #defines specify the offset and size of the environment
4405	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4406	  aligned to an erase block boundary.
4407
4408	- CONFIG_ENV_OFFSET_REDUND (optional):
4409
4410	  This setting describes a second storage area of CONFIG_ENV_SIZE
4411	  size used to hold a redundant copy of the environment data, so
4412	  that there is a valid backup copy in case there is a power failure
4413	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
4414	  aligned to an erase block boundary.
4415
4416	- CONFIG_ENV_RANGE (optional):
4417
4418	  Specifies the length of the region in which the environment
4419	  can be written.  This should be a multiple of the NAND device's
4420	  block size.  Specifying a range with more erase blocks than
4421	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4422	  the range to be avoided.
4423
4424	- CONFIG_ENV_OFFSET_OOB (optional):
4425
4426	  Enables support for dynamically retrieving the offset of the
4427	  environment from block zero's out-of-band data.  The
4428	  "nand env.oob" command can be used to record this offset.
4429	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4430	  using CONFIG_ENV_OFFSET_OOB.
4431
4432- CONFIG_NAND_ENV_DST
4433
4434	Defines address in RAM to which the nand_spl code should copy the
4435	environment. If redundant environment is used, it will be copied to
4436	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4437
4438- CONFIG_ENV_IS_IN_UBI:
4439
4440	Define this if you have an UBI volume that you want to use for the
4441	environment.  This has the benefit of wear-leveling the environment
4442	accesses, which is important on NAND.
4443
4444	- CONFIG_ENV_UBI_PART:
4445
4446	  Define this to a string that is the mtd partition containing the UBI.
4447
4448	- CONFIG_ENV_UBI_VOLUME:
4449
4450	  Define this to the name of the volume that you want to store the
4451	  environment in.
4452
4453	- CONFIG_ENV_UBI_VOLUME_REDUND:
4454
4455	  Define this to the name of another volume to store a second copy of
4456	  the environment in.  This will enable redundant environments in UBI.
4457	  It is assumed that both volumes are in the same MTD partition.
4458
4459	- CONFIG_UBI_SILENCE_MSG
4460	- CONFIG_UBIFS_SILENCE_MSG
4461
4462	  You will probably want to define these to avoid a really noisy system
4463	  when storing the env in UBI.
4464
4465- CONFIG_ENV_IS_IN_FAT:
4466       Define this if you want to use the FAT file system for the environment.
4467
4468       - FAT_ENV_INTERFACE:
4469
4470         Define this to a string that is the name of the block device.
4471
4472       - FAT_ENV_DEV_AND_PART:
4473
4474         Define this to a string to specify the partition of the device. It can
4475         be as following:
4476
4477           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
4478               - "D:P": device D partition P. Error occurs if device D has no
4479                        partition table.
4480               - "D:0": device D.
4481               - "D" or "D:": device D partition 1 if device D has partition
4482                              table, or the whole device D if has no partition
4483                              table.
4484               - "D:auto": first partition in device D with bootable flag set.
4485                           If none, first valid partition in device D. If no
4486                           partition table then means device D.
4487
4488       - FAT_ENV_FILE:
4489
4490         It's a string of the FAT file name. This file use to store the
4491         environment.
4492
4493       - CONFIG_FAT_WRITE:
4494         This should be defined. Otherwise it cannot save the environment file.
4495
4496- CONFIG_ENV_IS_IN_MMC:
4497
4498	Define this if you have an MMC device which you want to use for the
4499	environment.
4500
4501	- CONFIG_SYS_MMC_ENV_DEV:
4502
4503	  Specifies which MMC device the environment is stored in.
4504
4505	- CONFIG_SYS_MMC_ENV_PART (optional):
4506
4507	  Specifies which MMC partition the environment is stored in. If not
4508	  set, defaults to partition 0, the user area. Common values might be
4509	  1 (first MMC boot partition), 2 (second MMC boot partition).
4510
4511	- CONFIG_ENV_OFFSET:
4512	- CONFIG_ENV_SIZE:
4513
4514	  These two #defines specify the offset and size of the environment
4515	  area within the specified MMC device.
4516
4517	  If offset is positive (the usual case), it is treated as relative to
4518	  the start of the MMC partition. If offset is negative, it is treated
4519	  as relative to the end of the MMC partition. This can be useful if
4520	  your board may be fitted with different MMC devices, which have
4521	  different sizes for the MMC partitions, and you always want the
4522	  environment placed at the very end of the partition, to leave the
4523	  maximum possible space before it, to store other data.
4524
4525	  These two values are in units of bytes, but must be aligned to an
4526	  MMC sector boundary.
4527
4528	- CONFIG_ENV_OFFSET_REDUND (optional):
4529
4530	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4531	  hold a redundant copy of the environment data. This provides a
4532	  valid backup copy in case the other copy is corrupted, e.g. due
4533	  to a power failure during a "saveenv" operation.
4534
4535	  This value may also be positive or negative; this is handled in the
4536	  same way as CONFIG_ENV_OFFSET.
4537
4538	  This value is also in units of bytes, but must also be aligned to
4539	  an MMC sector boundary.
4540
4541	- CONFIG_ENV_SIZE_REDUND (optional):
4542
4543	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4544	  set. If this value is set, it must be set to the same value as
4545	  CONFIG_ENV_SIZE.
4546
4547- CONFIG_SYS_SPI_INIT_OFFSET
4548
4549	Defines offset to the initial SPI buffer area in DPRAM. The
4550	area is used at an early stage (ROM part) if the environment
4551	is configured to reside in the SPI EEPROM: We need a 520 byte
4552	scratch DPRAM area. It is used between the two initialization
4553	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4554	to be a good choice since it makes it far enough from the
4555	start of the data area as well as from the stack pointer.
4556
4557Please note that the environment is read-only until the monitor
4558has been relocated to RAM and a RAM copy of the environment has been
4559created; also, when using EEPROM you will have to use getenv_f()
4560until then to read environment variables.
4561
4562The environment is protected by a CRC32 checksum. Before the monitor
4563is relocated into RAM, as a result of a bad CRC you will be working
4564with the compiled-in default environment - *silently*!!! [This is
4565necessary, because the first environment variable we need is the
4566"baudrate" setting for the console - if we have a bad CRC, we don't
4567have any device yet where we could complain.]
4568
4569Note: once the monitor has been relocated, then it will complain if
4570the default environment is used; a new CRC is computed as soon as you
4571use the "saveenv" command to store a valid environment.
4572
4573- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4574		Echo the inverted Ethernet link state to the fault LED.
4575
4576		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4577		      also needs to be defined.
4578
4579- CONFIG_SYS_FAULT_MII_ADDR:
4580		MII address of the PHY to check for the Ethernet link state.
4581
4582- CONFIG_NS16550_MIN_FUNCTIONS:
4583		Define this if you desire to only have use of the NS16550_init
4584		and NS16550_putc functions for the serial driver located at
4585		drivers/serial/ns16550.c.  This option is useful for saving
4586		space for already greatly restricted images, including but not
4587		limited to NAND_SPL configurations.
4588
4589- CONFIG_DISPLAY_BOARDINFO
4590		Display information about the board that U-Boot is running on
4591		when U-Boot starts up. The board function checkboard() is called
4592		to do this.
4593
4594- CONFIG_DISPLAY_BOARDINFO_LATE
4595		Similar to the previous option, but display this information
4596		later, once stdio is running and output goes to the LCD, if
4597		present.
4598
4599- CONFIG_BOARD_SIZE_LIMIT:
4600		Maximum size of the U-Boot image. When defined, the
4601		build system checks that the actual size does not
4602		exceed it.
4603
4604Low Level (hardware related) configuration options:
4605---------------------------------------------------
4606
4607- CONFIG_SYS_CACHELINE_SIZE:
4608		Cache Line Size of the CPU.
4609
4610- CONFIG_SYS_DEFAULT_IMMR:
4611		Default address of the IMMR after system reset.
4612
4613		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4614		and RPXsuper) to be able to adjust the position of
4615		the IMMR register after a reset.
4616
4617- CONFIG_SYS_CCSRBAR_DEFAULT:
4618		Default (power-on reset) physical address of CCSR on Freescale
4619		PowerPC SOCs.
4620
4621- CONFIG_SYS_CCSRBAR:
4622		Virtual address of CCSR.  On a 32-bit build, this is typically
4623		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4624
4625		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4626		for cross-platform code that uses that macro instead.
4627
4628- CONFIG_SYS_CCSRBAR_PHYS:
4629		Physical address of CCSR.  CCSR can be relocated to a new
4630		physical address, if desired.  In this case, this macro should
4631		be set to that address.	 Otherwise, it should be set to the
4632		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4633		is typically relocated on 36-bit builds.  It is recommended
4634		that this macro be defined via the _HIGH and _LOW macros:
4635
4636		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4637			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4638
4639- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4640		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4641		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4642		used in assembly code, so it must not contain typecasts or
4643		integer size suffixes (e.g. "ULL").
4644
4645- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4646		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4647		used in assembly code, so it must not contain typecasts or
4648		integer size suffixes (e.g. "ULL").
4649
4650- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4651		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4652		forced to a value that ensures that CCSR is not relocated.
4653
4654- Floppy Disk Support:
4655		CONFIG_SYS_FDC_DRIVE_NUMBER
4656
4657		the default drive number (default value 0)
4658
4659		CONFIG_SYS_ISA_IO_STRIDE
4660
4661		defines the spacing between FDC chipset registers
4662		(default value 1)
4663
4664		CONFIG_SYS_ISA_IO_OFFSET
4665
4666		defines the offset of register from address. It
4667		depends on which part of the data bus is connected to
4668		the FDC chipset. (default value 0)
4669
4670		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4671		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4672		default value.
4673
4674		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4675		fdc_hw_init() is called at the beginning of the FDC
4676		setup. fdc_hw_init() must be provided by the board
4677		source code. It is used to make hardware-dependent
4678		initializations.
4679
4680- CONFIG_IDE_AHB:
4681		Most IDE controllers were designed to be connected with PCI
4682		interface. Only few of them were designed for AHB interface.
4683		When software is doing ATA command and data transfer to
4684		IDE devices through IDE-AHB controller, some additional
4685		registers accessing to these kind of IDE-AHB controller
4686		is required.
4687
4688- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4689		DO NOT CHANGE unless you know exactly what you're
4690		doing! (11-4) [MPC8xx/82xx systems only]
4691
4692- CONFIG_SYS_INIT_RAM_ADDR:
4693
4694		Start address of memory area that can be used for
4695		initial data and stack; please note that this must be
4696		writable memory that is working WITHOUT special
4697		initialization, i. e. you CANNOT use normal RAM which
4698		will become available only after programming the
4699		memory controller and running certain initialization
4700		sequences.
4701
4702		U-Boot uses the following memory types:
4703		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4704		- MPC824X: data cache
4705		- PPC4xx:  data cache
4706
4707- CONFIG_SYS_GBL_DATA_OFFSET:
4708
4709		Offset of the initial data structure in the memory
4710		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4711		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4712		data is located at the end of the available space
4713		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4714		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4715		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4716		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4717
4718	Note:
4719		On the MPC824X (or other systems that use the data
4720		cache for initial memory) the address chosen for
4721		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4722		point to an otherwise UNUSED address space between
4723		the top of RAM and the start of the PCI space.
4724
4725- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4726
4727- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4728
4729- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4730
4731- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4732
4733- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4734
4735- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4736
4737- CONFIG_SYS_OR_TIMING_SDRAM:
4738		SDRAM timing
4739
4740- CONFIG_SYS_MAMR_PTA:
4741		periodic timer for refresh
4742
4743- CONFIG_SYS_DER:	Debug Event Register (37-47)
4744
4745- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4746  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4747  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4748  CONFIG_SYS_BR1_PRELIM:
4749		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4750
4751- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4752  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4753  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4754		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4755
4756- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4757  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4758		Machine Mode Register and Memory Periodic Timer
4759		Prescaler definitions (SDRAM timing)
4760
4761- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4762		enable I2C microcode relocation patch (MPC8xx);
4763		define relocation offset in DPRAM [DSP2]
4764
4765- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4766		enable SMC microcode relocation patch (MPC8xx);
4767		define relocation offset in DPRAM [SMC1]
4768
4769- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4770		enable SPI microcode relocation patch (MPC8xx);
4771		define relocation offset in DPRAM [SCC4]
4772
4773- CONFIG_SYS_USE_OSCCLK:
4774		Use OSCM clock mode on MBX8xx board. Be careful,
4775		wrong setting might damage your board. Read
4776		doc/README.MBX before setting this variable!
4777
4778- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4779		Offset of the bootmode word in DPRAM used by post
4780		(Power On Self Tests). This definition overrides
4781		#define'd default value in commproc.h resp.
4782		cpm_8260.h.
4783
4784- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4785  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4786  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4787  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4788  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4789  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4790  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4791  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4792		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4793
4794- CONFIG_PCI_DISABLE_PCIE:
4795		Disable PCI-Express on systems where it is supported but not
4796		required.
4797
4798- CONFIG_PCI_ENUM_ONLY
4799		Only scan through and get the devices on the buses.
4800		Don't do any setup work, presumably because someone or
4801		something has already done it, and we don't need to do it
4802		a second time.	Useful for platforms that are pre-booted
4803		by coreboot or similar.
4804
4805- CONFIG_PCI_INDIRECT_BRIDGE:
4806		Enable support for indirect PCI bridges.
4807
4808- CONFIG_SYS_SRIO:
4809		Chip has SRIO or not
4810
4811- CONFIG_SRIO1:
4812		Board has SRIO 1 port available
4813
4814- CONFIG_SRIO2:
4815		Board has SRIO 2 port available
4816
4817- CONFIG_SRIO_PCIE_BOOT_MASTER
4818		Board can support master function for Boot from SRIO and PCIE
4819
4820- CONFIG_SYS_SRIOn_MEM_VIRT:
4821		Virtual Address of SRIO port 'n' memory region
4822
4823- CONFIG_SYS_SRIOn_MEM_PHYS:
4824		Physical Address of SRIO port 'n' memory region
4825
4826- CONFIG_SYS_SRIOn_MEM_SIZE:
4827		Size of SRIO port 'n' memory region
4828
4829- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4830		Defined to tell the NAND controller that the NAND chip is using
4831		a 16 bit bus.
4832		Not all NAND drivers use this symbol.
4833		Example of drivers that use it:
4834		- drivers/mtd/nand/ndfc.c
4835		- drivers/mtd/nand/mxc_nand.c
4836
4837- CONFIG_SYS_NDFC_EBC0_CFG
4838		Sets the EBC0_CFG register for the NDFC. If not defined
4839		a default value will be used.
4840
4841- CONFIG_SPD_EEPROM
4842		Get DDR timing information from an I2C EEPROM. Common
4843		with pluggable memory modules such as SODIMMs
4844
4845  SPD_EEPROM_ADDRESS
4846		I2C address of the SPD EEPROM
4847
4848- CONFIG_SYS_SPD_BUS_NUM
4849		If SPD EEPROM is on an I2C bus other than the first
4850		one, specify here. Note that the value must resolve
4851		to something your driver can deal with.
4852
4853- CONFIG_SYS_DDR_RAW_TIMING
4854		Get DDR timing information from other than SPD. Common with
4855		soldered DDR chips onboard without SPD. DDR raw timing
4856		parameters are extracted from datasheet and hard-coded into
4857		header files or board specific files.
4858
4859- CONFIG_FSL_DDR_INTERACTIVE
4860		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4861
4862- CONFIG_FSL_DDR_SYNC_REFRESH
4863		Enable sync of refresh for multiple controllers.
4864
4865- CONFIG_SYS_83XX_DDR_USES_CS0
4866		Only for 83xx systems. If specified, then DDR should
4867		be configured using CS0 and CS1 instead of CS2 and CS3.
4868
4869- CONFIG_ETHER_ON_FEC[12]
4870		Define to enable FEC[12] on a 8xx series processor.
4871
4872- CONFIG_FEC[12]_PHY
4873		Define to the hardcoded PHY address which corresponds
4874		to the given FEC; i. e.
4875			#define CONFIG_FEC1_PHY 4
4876		means that the PHY with address 4 is connected to FEC1
4877
4878		When set to -1, means to probe for first available.
4879
4880- CONFIG_FEC[12]_PHY_NORXERR
4881		The PHY does not have a RXERR line (RMII only).
4882		(so program the FEC to ignore it).
4883
4884- CONFIG_RMII
4885		Enable RMII mode for all FECs.
4886		Note that this is a global option, we can't
4887		have one FEC in standard MII mode and another in RMII mode.
4888
4889- CONFIG_CRC32_VERIFY
4890		Add a verify option to the crc32 command.
4891		The syntax is:
4892
4893		=> crc32 -v <address> <count> <crc32>
4894
4895		Where address/count indicate a memory area
4896		and crc32 is the correct crc32 which the
4897		area should have.
4898
4899- CONFIG_LOOPW
4900		Add the "loopw" memory command. This only takes effect if
4901		the memory commands are activated globally (CONFIG_CMD_MEM).
4902
4903- CONFIG_MX_CYCLIC
4904		Add the "mdc" and "mwc" memory commands. These are cyclic
4905		"md/mw" commands.
4906		Examples:
4907
4908		=> mdc.b 10 4 500
4909		This command will print 4 bytes (10,11,12,13) each 500 ms.
4910
4911		=> mwc.l 100 12345678 10
4912		This command will write 12345678 to address 100 all 10 ms.
4913
4914		This only takes effect if the memory commands are activated
4915		globally (CONFIG_CMD_MEM).
4916
4917- CONFIG_SKIP_LOWLEVEL_INIT
4918		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4919		low level initializations (like setting up the memory
4920		controller) are omitted and/or U-Boot does not
4921		relocate itself into RAM.
4922
4923		Normally this variable MUST NOT be defined. The only
4924		exception is when U-Boot is loaded (to RAM) by some
4925		other boot loader or by a debugger which performs
4926		these initializations itself.
4927
4928- CONFIG_SPL_BUILD
4929		Modifies the behaviour of start.S when compiling a loader
4930		that is executed before the actual U-Boot. E.g. when
4931		compiling a NAND SPL.
4932
4933- CONFIG_TPL_BUILD
4934		Modifies the behaviour of start.S  when compiling a loader
4935		that is executed after the SPL and before the actual U-Boot.
4936		It is loaded by the SPL.
4937
4938- CONFIG_SYS_MPC85XX_NO_RESETVEC
4939		Only for 85xx systems. If this variable is specified, the section
4940		.resetvec is not kept and the section .bootpg is placed in the
4941		previous 4k of the .text section.
4942
4943- CONFIG_ARCH_MAP_SYSMEM
4944		Generally U-Boot (and in particular the md command) uses
4945		effective address. It is therefore not necessary to regard
4946		U-Boot address as virtual addresses that need to be translated
4947		to physical addresses. However, sandbox requires this, since
4948		it maintains its own little RAM buffer which contains all
4949		addressable memory. This option causes some memory accesses
4950		to be mapped through map_sysmem() / unmap_sysmem().
4951
4952- CONFIG_USE_ARCH_MEMCPY
4953  CONFIG_USE_ARCH_MEMSET
4954		If these options are used a optimized version of memcpy/memset will
4955		be used if available. These functions may be faster under some
4956		conditions but may increase the binary size.
4957
4958- CONFIG_X86_RESET_VECTOR
4959		If defined, the x86 reset vector code is included. This is not
4960		needed when U-Boot is running from Coreboot.
4961
4962- CONFIG_SYS_MPUCLK
4963		Defines the MPU clock speed (in MHz).
4964
4965		NOTE : currently only supported on AM335x platforms.
4966
4967- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4968		Enables the RTC32K OSC on AM33xx based plattforms
4969
4970- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4971		Option to disable subpage write in NAND driver
4972		driver that uses this:
4973		drivers/mtd/nand/davinci_nand.c
4974
4975Freescale QE/FMAN Firmware Support:
4976-----------------------------------
4977
4978The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4979loading of "firmware", which is encoded in the QE firmware binary format.
4980This firmware often needs to be loaded during U-Boot booting, so macros
4981are used to identify the storage device (NOR flash, SPI, etc) and the address
4982within that device.
4983
4984- CONFIG_SYS_FMAN_FW_ADDR
4985	The address in the storage device where the FMAN microcode is located.  The
4986	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4987	is also specified.
4988
4989- CONFIG_SYS_QE_FW_ADDR
4990	The address in the storage device where the QE microcode is located.  The
4991	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4992	is also specified.
4993
4994- CONFIG_SYS_QE_FMAN_FW_LENGTH
4995	The maximum possible size of the firmware.  The firmware binary format
4996	has a field that specifies the actual size of the firmware, but it
4997	might not be possible to read any part of the firmware unless some
4998	local storage is allocated to hold the entire firmware first.
4999
5000- CONFIG_SYS_QE_FMAN_FW_IN_NOR
5001	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
5002	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
5003	virtual address in NOR flash.
5004
5005- CONFIG_SYS_QE_FMAN_FW_IN_NAND
5006	Specifies that QE/FMAN firmware is located in NAND flash.
5007	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
5008
5009- CONFIG_SYS_QE_FMAN_FW_IN_MMC
5010	Specifies that QE/FMAN firmware is located on the primary SD/MMC
5011	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
5012
5013- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
5014	Specifies that QE/FMAN firmware is located on the primary SPI
5015	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
5016
5017- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
5018	Specifies that QE/FMAN firmware is located in the remote (master)
5019	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
5020	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
5021	window->master inbound window->master LAW->the ucode address in
5022	master's memory space.
5023
5024Freescale Layerscape Management Complex Firmware Support:
5025---------------------------------------------------------
5026The Freescale Layerscape Management Complex (MC) supports the loading of
5027"firmware".
5028This firmware often needs to be loaded during U-Boot booting, so macros
5029are used to identify the storage device (NOR flash, SPI, etc) and the address
5030within that device.
5031
5032- CONFIG_FSL_MC_ENET
5033	Enable the MC driver for Layerscape SoCs.
5034
5035- CONFIG_SYS_LS_MC_FW_ADDR
5036	The address in the storage device where the firmware is located.  The
5037	meaning of this address depends on which CONFIG_SYS_LS_MC_FW_IN_xxx macro
5038	is also specified.
5039
5040- CONFIG_SYS_LS_MC_FW_LENGTH
5041	The maximum possible size of the firmware.  The firmware binary format
5042	has a field that specifies the actual size of the firmware, but it
5043	might not be possible to read any part of the firmware unless some
5044	local storage is allocated to hold the entire firmware first.
5045
5046- CONFIG_SYS_LS_MC_FW_IN_NOR
5047	Specifies that MC firmware is located in NOR flash, mapped as
5048	normal addressable memory via the LBC. CONFIG_SYS_LS_MC_FW_ADDR is the
5049	virtual address in NOR flash.
5050
5051Building the Software:
5052======================
5053
5054Building U-Boot has been tested in several native build environments
5055and in many different cross environments. Of course we cannot support
5056all possibly existing versions of cross development tools in all
5057(potentially obsolete) versions. In case of tool chain problems we
5058recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
5059which is extensively used to build and test U-Boot.
5060
5061If you are not using a native environment, it is assumed that you
5062have GNU cross compiling tools available in your path. In this case,
5063you must set the environment variable CROSS_COMPILE in your shell.
5064Note that no changes to the Makefile or any other source files are
5065necessary. For example using the ELDK on a 4xx CPU, please enter:
5066
5067	$ CROSS_COMPILE=ppc_4xx-
5068	$ export CROSS_COMPILE
5069
5070Note: If you wish to generate Windows versions of the utilities in
5071      the tools directory you can use the MinGW toolchain
5072      (http://www.mingw.org).  Set your HOST tools to the MinGW
5073      toolchain and execute 'make tools'.  For example:
5074
5075       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
5076
5077      Binaries such as tools/mkimage.exe will be created which can
5078      be executed on computers running Windows.
5079
5080U-Boot is intended to be simple to build. After installing the
5081sources you must configure U-Boot for one specific board type. This
5082is done by typing:
5083
5084	make NAME_defconfig
5085
5086where "NAME_defconfig" is the name of one of the existing configu-
5087rations; see boards.cfg for supported names.
5088
5089Note: for some board special configuration names may exist; check if
5090      additional information is available from the board vendor; for
5091      instance, the TQM823L systems are available without (standard)
5092      or with LCD support. You can select such additional "features"
5093      when choosing the configuration, i. e.
5094
5095      make TQM823L_defconfig
5096	- will configure for a plain TQM823L, i. e. no LCD support
5097
5098      make TQM823L_LCD_defconfig
5099	- will configure for a TQM823L with U-Boot console on LCD
5100
5101      etc.
5102
5103
5104Finally, type "make all", and you should get some working U-Boot
5105images ready for download to / installation on your system:
5106
5107- "u-boot.bin" is a raw binary image
5108- "u-boot" is an image in ELF binary format
5109- "u-boot.srec" is in Motorola S-Record format
5110
5111By default the build is performed locally and the objects are saved
5112in the source directory. One of the two methods can be used to change
5113this behavior and build U-Boot to some external directory:
5114
51151. Add O= to the make command line invocations:
5116
5117	make O=/tmp/build distclean
5118	make O=/tmp/build NAME_defconfig
5119	make O=/tmp/build all
5120
51212. Set environment variable KBUILD_OUTPUT to point to the desired location:
5122
5123	export KBUILD_OUTPUT=/tmp/build
5124	make distclean
5125	make NAME_defconfig
5126	make all
5127
5128Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
5129variable.
5130
5131
5132Please be aware that the Makefiles assume you are using GNU make, so
5133for instance on NetBSD you might need to use "gmake" instead of
5134native "make".
5135
5136
5137If the system board that you have is not listed, then you will need
5138to port U-Boot to your hardware platform. To do this, follow these
5139steps:
5140
51411.  Add a new configuration option for your board to the toplevel
5142    "boards.cfg" file, using the existing entries as examples.
5143    Follow the instructions there to keep the boards in order.
51442.  Create a new directory to hold your board specific code. Add any
5145    files you need. In your board directory, you will need at least
5146    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
51473.  Create a new configuration file "include/configs/<board>.h" for
5148    your board
51493.  If you're porting U-Boot to a new CPU, then also create a new
5150    directory to hold your CPU specific code. Add any files you need.
51514.  Run "make <board>_defconfig" with your new name.
51525.  Type "make", and you should get a working "u-boot.srec" file
5153    to be installed on your target system.
51546.  Debug and solve any problems that might arise.
5155    [Of course, this last step is much harder than it sounds.]
5156
5157
5158Testing of U-Boot Modifications, Ports to New Hardware, etc.:
5159==============================================================
5160
5161If you have modified U-Boot sources (for instance added a new board
5162or support for new devices, a new CPU, etc.) you are expected to
5163provide feedback to the other developers. The feedback normally takes
5164the form of a "patch", i. e. a context diff against a certain (latest
5165official or latest in the git repository) version of U-Boot sources.
5166
5167But before you submit such a patch, please verify that your modifi-
5168cation did not break existing code. At least make sure that *ALL* of
5169the supported boards compile WITHOUT ANY compiler warnings. To do so,
5170just run the "MAKEALL" script, which will configure and build U-Boot
5171for ALL supported system. Be warned, this will take a while. You can
5172select which (cross) compiler to use by passing a `CROSS_COMPILE'
5173environment variable to the script, i. e. to use the ELDK cross tools
5174you can type
5175
5176	CROSS_COMPILE=ppc_8xx- MAKEALL
5177
5178or to build on a native PowerPC system you can type
5179
5180	CROSS_COMPILE=' ' MAKEALL
5181
5182When using the MAKEALL script, the default behaviour is to build
5183U-Boot in the source directory. This location can be changed by
5184setting the BUILD_DIR environment variable. Also, for each target
5185built, the MAKEALL script saves two log files (<target>.ERR and
5186<target>.MAKEALL) in the <source dir>/LOG directory. This default
5187location can be changed by setting the MAKEALL_LOGDIR environment
5188variable. For example:
5189
5190	export BUILD_DIR=/tmp/build
5191	export MAKEALL_LOGDIR=/tmp/log
5192	CROSS_COMPILE=ppc_8xx- MAKEALL
5193
5194With the above settings build objects are saved in the /tmp/build,
5195log files are saved in the /tmp/log and the source tree remains clean
5196during the whole build process.
5197
5198
5199See also "U-Boot Porting Guide" below.
5200
5201
5202Monitor Commands - Overview:
5203============================
5204
5205go	- start application at address 'addr'
5206run	- run commands in an environment variable
5207bootm	- boot application image from memory
5208bootp	- boot image via network using BootP/TFTP protocol
5209bootz   - boot zImage from memory
5210tftpboot- boot image via network using TFTP protocol
5211	       and env variables "ipaddr" and "serverip"
5212	       (and eventually "gatewayip")
5213tftpput - upload a file via network using TFTP protocol
5214rarpboot- boot image via network using RARP/TFTP protocol
5215diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
5216loads	- load S-Record file over serial line
5217loadb	- load binary file over serial line (kermit mode)
5218md	- memory display
5219mm	- memory modify (auto-incrementing)
5220nm	- memory modify (constant address)
5221mw	- memory write (fill)
5222cp	- memory copy
5223cmp	- memory compare
5224crc32	- checksum calculation
5225i2c	- I2C sub-system
5226sspi	- SPI utility commands
5227base	- print or set address offset
5228printenv- print environment variables
5229setenv	- set environment variables
5230saveenv - save environment variables to persistent storage
5231protect - enable or disable FLASH write protection
5232erase	- erase FLASH memory
5233flinfo	- print FLASH memory information
5234nand	- NAND memory operations (see doc/README.nand)
5235bdinfo	- print Board Info structure
5236iminfo	- print header information for application image
5237coninfo - print console devices and informations
5238ide	- IDE sub-system
5239loop	- infinite loop on address range
5240loopw	- infinite write loop on address range
5241mtest	- simple RAM test
5242icache	- enable or disable instruction cache
5243dcache	- enable or disable data cache
5244reset	- Perform RESET of the CPU
5245echo	- echo args to console
5246version - print monitor version
5247help	- print online help
5248?	- alias for 'help'
5249
5250
5251Monitor Commands - Detailed Description:
5252========================================
5253
5254TODO.
5255
5256For now: just type "help <command>".
5257
5258
5259Environment Variables:
5260======================
5261
5262U-Boot supports user configuration using Environment Variables which
5263can be made persistent by saving to Flash memory.
5264
5265Environment Variables are set using "setenv", printed using
5266"printenv", and saved to Flash using "saveenv". Using "setenv"
5267without a value can be used to delete a variable from the
5268environment. As long as you don't save the environment you are
5269working with an in-memory copy. In case the Flash area containing the
5270environment is erased by accident, a default environment is provided.
5271
5272Some configuration options can be set using Environment Variables.
5273
5274List of environment variables (most likely not complete):
5275
5276  baudrate	- see CONFIG_BAUDRATE
5277
5278  bootdelay	- see CONFIG_BOOTDELAY
5279
5280  bootcmd	- see CONFIG_BOOTCOMMAND
5281
5282  bootargs	- Boot arguments when booting an RTOS image
5283
5284  bootfile	- Name of the image to load with TFTP
5285
5286  bootm_low	- Memory range available for image processing in the bootm
5287		  command can be restricted. This variable is given as
5288		  a hexadecimal number and defines lowest address allowed
5289		  for use by the bootm command. See also "bootm_size"
5290		  environment variable. Address defined by "bootm_low" is
5291		  also the base of the initial memory mapping for the Linux
5292		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
5293		  bootm_mapsize.
5294
5295  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
5296		  This variable is given as a hexadecimal number and it
5297		  defines the size of the memory region starting at base
5298		  address bootm_low that is accessible by the Linux kernel
5299		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
5300		  as the default value if it is defined, and bootm_size is
5301		  used otherwise.
5302
5303  bootm_size	- Memory range available for image processing in the bootm
5304		  command can be restricted. This variable is given as
5305		  a hexadecimal number and defines the size of the region
5306		  allowed for use by the bootm command. See also "bootm_low"
5307		  environment variable.
5308
5309  updatefile	- Location of the software update file on a TFTP server, used
5310		  by the automatic software update feature. Please refer to
5311		  documentation in doc/README.update for more details.
5312
5313  autoload	- if set to "no" (any string beginning with 'n'),
5314		  "bootp" will just load perform a lookup of the
5315		  configuration from the BOOTP server, but not try to
5316		  load any image using TFTP
5317
5318  autostart	- if set to "yes", an image loaded using the "bootp",
5319		  "rarpboot", "tftpboot" or "diskboot" commands will
5320		  be automatically started (by internally calling
5321		  "bootm")
5322
5323		  If set to "no", a standalone image passed to the
5324		  "bootm" command will be copied to the load address
5325		  (and eventually uncompressed), but NOT be started.
5326		  This can be used to load and uncompress arbitrary
5327		  data.
5328
5329  fdt_high	- if set this restricts the maximum address that the
5330		  flattened device tree will be copied into upon boot.
5331		  For example, if you have a system with 1 GB memory
5332		  at physical address 0x10000000, while Linux kernel
5333		  only recognizes the first 704 MB as low memory, you
5334		  may need to set fdt_high as 0x3C000000 to have the
5335		  device tree blob be copied to the maximum address
5336		  of the 704 MB low memory, so that Linux kernel can
5337		  access it during the boot procedure.
5338
5339		  If this is set to the special value 0xFFFFFFFF then
5340		  the fdt will not be copied at all on boot.  For this
5341		  to work it must reside in writable memory, have
5342		  sufficient padding on the end of it for u-boot to
5343		  add the information it needs into it, and the memory
5344		  must be accessible by the kernel.
5345
5346  fdtcontroladdr- if set this is the address of the control flattened
5347		  device tree used by U-Boot when CONFIG_OF_CONTROL is
5348		  defined.
5349
5350  i2cfast	- (PPC405GP|PPC405EP only)
5351		  if set to 'y' configures Linux I2C driver for fast
5352		  mode (400kHZ). This environment variable is used in
5353		  initialization code. So, for changes to be effective
5354		  it must be saved and board must be reset.
5355
5356  initrd_high	- restrict positioning of initrd images:
5357		  If this variable is not set, initrd images will be
5358		  copied to the highest possible address in RAM; this
5359		  is usually what you want since it allows for
5360		  maximum initrd size. If for some reason you want to
5361		  make sure that the initrd image is loaded below the
5362		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
5363		  variable to a value of "no" or "off" or "0".
5364		  Alternatively, you can set it to a maximum upper
5365		  address to use (U-Boot will still check that it
5366		  does not overwrite the U-Boot stack and data).
5367
5368		  For instance, when you have a system with 16 MB
5369		  RAM, and want to reserve 4 MB from use by Linux,
5370		  you can do this by adding "mem=12M" to the value of
5371		  the "bootargs" variable. However, now you must make
5372		  sure that the initrd image is placed in the first
5373		  12 MB as well - this can be done with
5374
5375		  setenv initrd_high 00c00000
5376
5377		  If you set initrd_high to 0xFFFFFFFF, this is an
5378		  indication to U-Boot that all addresses are legal
5379		  for the Linux kernel, including addresses in flash
5380		  memory. In this case U-Boot will NOT COPY the
5381		  ramdisk at all. This may be useful to reduce the
5382		  boot time on your system, but requires that this
5383		  feature is supported by your Linux kernel.
5384
5385  ipaddr	- IP address; needed for tftpboot command
5386
5387  loadaddr	- Default load address for commands like "bootp",
5388		  "rarpboot", "tftpboot", "loadb" or "diskboot"
5389
5390  loads_echo	- see CONFIG_LOADS_ECHO
5391
5392  serverip	- TFTP server IP address; needed for tftpboot command
5393
5394  bootretry	- see CONFIG_BOOT_RETRY_TIME
5395
5396  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
5397
5398  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
5399
5400  ethprime	- controls which interface is used first.
5401
5402  ethact	- controls which interface is currently active.
5403		  For example you can do the following
5404
5405		  => setenv ethact FEC
5406		  => ping 192.168.0.1 # traffic sent on FEC
5407		  => setenv ethact SCC
5408		  => ping 10.0.0.1 # traffic sent on SCC
5409
5410  ethrotate	- When set to "no" U-Boot does not go through all
5411		  available network interfaces.
5412		  It just stays at the currently selected interface.
5413
5414  netretry	- When set to "no" each network operation will
5415		  either succeed or fail without retrying.
5416		  When set to "once" the network operation will
5417		  fail when all the available network interfaces
5418		  are tried once without success.
5419		  Useful on scripts which control the retry operation
5420		  themselves.
5421
5422  npe_ucode	- set load address for the NPE microcode
5423
5424  silent_linux  - If set then Linux will be told to boot silently, by
5425		  changing the console to be empty. If "yes" it will be
5426		  made silent. If "no" it will not be made silent. If
5427		  unset, then it will be made silent if the U-Boot console
5428		  is silent.
5429
5430  tftpsrcport	- If this is set, the value is used for TFTP's
5431		  UDP source port.
5432
5433  tftpdstport	- If this is set, the value is used for TFTP's UDP
5434		  destination port instead of the Well Know Port 69.
5435
5436  tftpblocksize - Block size to use for TFTP transfers; if not set,
5437		  we use the TFTP server's default block size
5438
5439  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
5440		  seconds, minimum value is 1000 = 1 second). Defines
5441		  when a packet is considered to be lost so it has to
5442		  be retransmitted. The default is 5000 = 5 seconds.
5443		  Lowering this value may make downloads succeed
5444		  faster in networks with high packet loss rates or
5445		  with unreliable TFTP servers.
5446
5447  vlan		- When set to a value < 4095 the traffic over
5448		  Ethernet is encapsulated/received over 802.1q
5449		  VLAN tagged frames.
5450
5451The following image location variables contain the location of images
5452used in booting. The "Image" column gives the role of the image and is
5453not an environment variable name. The other columns are environment
5454variable names. "File Name" gives the name of the file on a TFTP
5455server, "RAM Address" gives the location in RAM the image will be
5456loaded to, and "Flash Location" gives the image's address in NOR
5457flash or offset in NAND flash.
5458
5459*Note* - these variables don't have to be defined for all boards, some
5460boards currenlty use other variables for these purposes, and some
5461boards use these variables for other purposes.
5462
5463Image		    File Name	     RAM Address       Flash Location
5464-----		    ---------	     -----------       --------------
5465u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
5466Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
5467device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
5468ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
5469
5470The following environment variables may be used and automatically
5471updated by the network boot commands ("bootp" and "rarpboot"),
5472depending the information provided by your boot server:
5473
5474  bootfile	- see above
5475  dnsip		- IP address of your Domain Name Server
5476  dnsip2	- IP address of your secondary Domain Name Server
5477  gatewayip	- IP address of the Gateway (Router) to use
5478  hostname	- Target hostname
5479  ipaddr	- see above
5480  netmask	- Subnet Mask
5481  rootpath	- Pathname of the root filesystem on the NFS server
5482  serverip	- see above
5483
5484
5485There are two special Environment Variables:
5486
5487  serial#	- contains hardware identification information such
5488		  as type string and/or serial number
5489  ethaddr	- Ethernet address
5490
5491These variables can be set only once (usually during manufacturing of
5492the board). U-Boot refuses to delete or overwrite these variables
5493once they have been set once.
5494
5495
5496Further special Environment Variables:
5497
5498  ver		- Contains the U-Boot version string as printed
5499		  with the "version" command. This variable is
5500		  readonly (see CONFIG_VERSION_VARIABLE).
5501
5502
5503Please note that changes to some configuration parameters may take
5504only effect after the next boot (yes, that's just like Windoze :-).
5505
5506
5507Callback functions for environment variables:
5508---------------------------------------------
5509
5510For some environment variables, the behavior of u-boot needs to change
5511when their values are changed.  This functionality allows functions to
5512be associated with arbitrary variables.  On creation, overwrite, or
5513deletion, the callback will provide the opportunity for some side
5514effect to happen or for the change to be rejected.
5515
5516The callbacks are named and associated with a function using the
5517U_BOOT_ENV_CALLBACK macro in your board or driver code.
5518
5519These callbacks are associated with variables in one of two ways.  The
5520static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5521in the board configuration to a string that defines a list of
5522associations.  The list must be in the following format:
5523
5524	entry = variable_name[:callback_name]
5525	list = entry[,list]
5526
5527If the callback name is not specified, then the callback is deleted.
5528Spaces are also allowed anywhere in the list.
5529
5530Callbacks can also be associated by defining the ".callbacks" variable
5531with the same list format above.  Any association in ".callbacks" will
5532override any association in the static list. You can define
5533CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5534".callbacks" environment variable in the default or embedded environment.
5535
5536
5537Command Line Parsing:
5538=====================
5539
5540There are two different command line parsers available with U-Boot:
5541the old "simple" one, and the much more powerful "hush" shell:
5542
5543Old, simple command line parser:
5544--------------------------------
5545
5546- supports environment variables (through setenv / saveenv commands)
5547- several commands on one line, separated by ';'
5548- variable substitution using "... ${name} ..." syntax
5549- special characters ('$', ';') can be escaped by prefixing with '\',
5550  for example:
5551	setenv bootcmd bootm \${address}
5552- You can also escape text by enclosing in single apostrophes, for example:
5553	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5554
5555Hush shell:
5556-----------
5557
5558- similar to Bourne shell, with control structures like
5559  if...then...else...fi, for...do...done; while...do...done,
5560  until...do...done, ...
5561- supports environment ("global") variables (through setenv / saveenv
5562  commands) and local shell variables (through standard shell syntax
5563  "name=value"); only environment variables can be used with "run"
5564  command
5565
5566General rules:
5567--------------
5568
5569(1) If a command line (or an environment variable executed by a "run"
5570    command) contains several commands separated by semicolon, and
5571    one of these commands fails, then the remaining commands will be
5572    executed anyway.
5573
5574(2) If you execute several variables with one call to run (i. e.
5575    calling run with a list of variables as arguments), any failing
5576    command will cause "run" to terminate, i. e. the remaining
5577    variables are not executed.
5578
5579Note for Redundant Ethernet Interfaces:
5580=======================================
5581
5582Some boards come with redundant Ethernet interfaces; U-Boot supports
5583such configurations and is capable of automatic selection of a
5584"working" interface when needed. MAC assignment works as follows:
5585
5586Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5587MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5588"eth1addr" (=>eth1), "eth2addr", ...
5589
5590If the network interface stores some valid MAC address (for instance
5591in SROM), this is used as default address if there is NO correspon-
5592ding setting in the environment; if the corresponding environment
5593variable is set, this overrides the settings in the card; that means:
5594
5595o If the SROM has a valid MAC address, and there is no address in the
5596  environment, the SROM's address is used.
5597
5598o If there is no valid address in the SROM, and a definition in the
5599  environment exists, then the value from the environment variable is
5600  used.
5601
5602o If both the SROM and the environment contain a MAC address, and
5603  both addresses are the same, this MAC address is used.
5604
5605o If both the SROM and the environment contain a MAC address, and the
5606  addresses differ, the value from the environment is used and a
5607  warning is printed.
5608
5609o If neither SROM nor the environment contain a MAC address, an error
5610  is raised.
5611
5612If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5613will be programmed into hardware as part of the initialization process.	 This
5614may be skipped by setting the appropriate 'ethmacskip' environment variable.
5615The naming convention is as follows:
5616"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5617
5618Image Formats:
5619==============
5620
5621U-Boot is capable of booting (and performing other auxiliary operations on)
5622images in two formats:
5623
5624New uImage format (FIT)
5625-----------------------
5626
5627Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5628to Flattened Device Tree). It allows the use of images with multiple
5629components (several kernels, ramdisks, etc.), with contents protected by
5630SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5631
5632
5633Old uImage format
5634-----------------
5635
5636Old image format is based on binary files which can be basically anything,
5637preceded by a special header; see the definitions in include/image.h for
5638details; basically, the header defines the following image properties:
5639
5640* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5641  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5642  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5643  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5644  INTEGRITY).
5645* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5646  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5647  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5648* Compression Type (uncompressed, gzip, bzip2)
5649* Load Address
5650* Entry Point
5651* Image Name
5652* Image Timestamp
5653
5654The header is marked by a special Magic Number, and both the header
5655and the data portions of the image are secured against corruption by
5656CRC32 checksums.
5657
5658
5659Linux Support:
5660==============
5661
5662Although U-Boot should support any OS or standalone application
5663easily, the main focus has always been on Linux during the design of
5664U-Boot.
5665
5666U-Boot includes many features that so far have been part of some
5667special "boot loader" code within the Linux kernel. Also, any
5668"initrd" images to be used are no longer part of one big Linux image;
5669instead, kernel and "initrd" are separate images. This implementation
5670serves several purposes:
5671
5672- the same features can be used for other OS or standalone
5673  applications (for instance: using compressed images to reduce the
5674  Flash memory footprint)
5675
5676- it becomes much easier to port new Linux kernel versions because
5677  lots of low-level, hardware dependent stuff are done by U-Boot
5678
5679- the same Linux kernel image can now be used with different "initrd"
5680  images; of course this also means that different kernel images can
5681  be run with the same "initrd". This makes testing easier (you don't
5682  have to build a new "zImage.initrd" Linux image when you just
5683  change a file in your "initrd"). Also, a field-upgrade of the
5684  software is easier now.
5685
5686
5687Linux HOWTO:
5688============
5689
5690Porting Linux to U-Boot based systems:
5691---------------------------------------
5692
5693U-Boot cannot save you from doing all the necessary modifications to
5694configure the Linux device drivers for use with your target hardware
5695(no, we don't intend to provide a full virtual machine interface to
5696Linux :-).
5697
5698But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5699
5700Just make sure your machine specific header file (for instance
5701include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5702Information structure as we define in include/asm-<arch>/u-boot.h,
5703and make sure that your definition of IMAP_ADDR uses the same value
5704as your U-Boot configuration in CONFIG_SYS_IMMR.
5705
5706Note that U-Boot now has a driver model, a unified model for drivers.
5707If you are adding a new driver, plumb it into driver model. If there
5708is no uclass available, you are encouraged to create one. See
5709doc/driver-model.
5710
5711
5712Configuring the Linux kernel:
5713-----------------------------
5714
5715No specific requirements for U-Boot. Make sure you have some root
5716device (initial ramdisk, NFS) for your target system.
5717
5718
5719Building a Linux Image:
5720-----------------------
5721
5722With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5723not used. If you use recent kernel source, a new build target
5724"uImage" will exist which automatically builds an image usable by
5725U-Boot. Most older kernels also have support for a "pImage" target,
5726which was introduced for our predecessor project PPCBoot and uses a
5727100% compatible format.
5728
5729Example:
5730
5731	make TQM850L_defconfig
5732	make oldconfig
5733	make dep
5734	make uImage
5735
5736The "uImage" build target uses a special tool (in 'tools/mkimage') to
5737encapsulate a compressed Linux kernel image with header	 information,
5738CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5739
5740* build a standard "vmlinux" kernel image (in ELF binary format):
5741
5742* convert the kernel into a raw binary image:
5743
5744	${CROSS_COMPILE}-objcopy -O binary \
5745				 -R .note -R .comment \
5746				 -S vmlinux linux.bin
5747
5748* compress the binary image:
5749
5750	gzip -9 linux.bin
5751
5752* package compressed binary image for U-Boot:
5753
5754	mkimage -A ppc -O linux -T kernel -C gzip \
5755		-a 0 -e 0 -n "Linux Kernel Image" \
5756		-d linux.bin.gz uImage
5757
5758
5759The "mkimage" tool can also be used to create ramdisk images for use
5760with U-Boot, either separated from the Linux kernel image, or
5761combined into one file. "mkimage" encapsulates the images with a 64
5762byte header containing information about target architecture,
5763operating system, image type, compression method, entry points, time
5764stamp, CRC32 checksums, etc.
5765
5766"mkimage" can be called in two ways: to verify existing images and
5767print the header information, or to build new images.
5768
5769In the first form (with "-l" option) mkimage lists the information
5770contained in the header of an existing U-Boot image; this includes
5771checksum verification:
5772
5773	tools/mkimage -l image
5774	  -l ==> list image header information
5775
5776The second form (with "-d" option) is used to build a U-Boot image
5777from a "data file" which is used as image payload:
5778
5779	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5780		      -n name -d data_file image
5781	  -A ==> set architecture to 'arch'
5782	  -O ==> set operating system to 'os'
5783	  -T ==> set image type to 'type'
5784	  -C ==> set compression type 'comp'
5785	  -a ==> set load address to 'addr' (hex)
5786	  -e ==> set entry point to 'ep' (hex)
5787	  -n ==> set image name to 'name'
5788	  -d ==> use image data from 'datafile'
5789
5790Right now, all Linux kernels for PowerPC systems use the same load
5791address (0x00000000), but the entry point address depends on the
5792kernel version:
5793
5794- 2.2.x kernels have the entry point at 0x0000000C,
5795- 2.3.x and later kernels have the entry point at 0x00000000.
5796
5797So a typical call to build a U-Boot image would read:
5798
5799	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5800	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5801	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5802	> examples/uImage.TQM850L
5803	Image Name:   2.4.4 kernel for TQM850L
5804	Created:      Wed Jul 19 02:34:59 2000
5805	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5806	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5807	Load Address: 0x00000000
5808	Entry Point:  0x00000000
5809
5810To verify the contents of the image (or check for corruption):
5811
5812	-> tools/mkimage -l examples/uImage.TQM850L
5813	Image Name:   2.4.4 kernel for TQM850L
5814	Created:      Wed Jul 19 02:34:59 2000
5815	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5816	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5817	Load Address: 0x00000000
5818	Entry Point:  0x00000000
5819
5820NOTE: for embedded systems where boot time is critical you can trade
5821speed for memory and install an UNCOMPRESSED image instead: this
5822needs more space in Flash, but boots much faster since it does not
5823need to be uncompressed:
5824
5825	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5826	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5827	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5828	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5829	> examples/uImage.TQM850L-uncompressed
5830	Image Name:   2.4.4 kernel for TQM850L
5831	Created:      Wed Jul 19 02:34:59 2000
5832	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5833	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5834	Load Address: 0x00000000
5835	Entry Point:  0x00000000
5836
5837
5838Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5839when your kernel is intended to use an initial ramdisk:
5840
5841	-> tools/mkimage -n 'Simple Ramdisk Image' \
5842	> -A ppc -O linux -T ramdisk -C gzip \
5843	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5844	Image Name:   Simple Ramdisk Image
5845	Created:      Wed Jan 12 14:01:50 2000
5846	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5847	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5848	Load Address: 0x00000000
5849	Entry Point:  0x00000000
5850
5851The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5852option performs the converse operation of the mkimage's second form (the "-d"
5853option). Given an image built by mkimage, the dumpimage extracts a "data file"
5854from the image:
5855
5856	tools/dumpimage -i image -T type -p position data_file
5857	  -i ==> extract from the 'image' a specific 'data_file'
5858	  -T ==> set image type to 'type'
5859	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5860
5861
5862Installing a Linux Image:
5863-------------------------
5864
5865To downloading a U-Boot image over the serial (console) interface,
5866you must convert the image to S-Record format:
5867
5868	objcopy -I binary -O srec examples/image examples/image.srec
5869
5870The 'objcopy' does not understand the information in the U-Boot
5871image header, so the resulting S-Record file will be relative to
5872address 0x00000000. To load it to a given address, you need to
5873specify the target address as 'offset' parameter with the 'loads'
5874command.
5875
5876Example: install the image to address 0x40100000 (which on the
5877TQM8xxL is in the first Flash bank):
5878
5879	=> erase 40100000 401FFFFF
5880
5881	.......... done
5882	Erased 8 sectors
5883
5884	=> loads 40100000
5885	## Ready for S-Record download ...
5886	~>examples/image.srec
5887	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5888	...
5889	15989 15990 15991 15992
5890	[file transfer complete]
5891	[connected]
5892	## Start Addr = 0x00000000
5893
5894
5895You can check the success of the download using the 'iminfo' command;
5896this includes a checksum verification so you can be sure no data
5897corruption happened:
5898
5899	=> imi 40100000
5900
5901	## Checking Image at 40100000 ...
5902	   Image Name:	 2.2.13 for initrd on TQM850L
5903	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5904	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5905	   Load Address: 00000000
5906	   Entry Point:	 0000000c
5907	   Verifying Checksum ... OK
5908
5909
5910Boot Linux:
5911-----------
5912
5913The "bootm" command is used to boot an application that is stored in
5914memory (RAM or Flash). In case of a Linux kernel image, the contents
5915of the "bootargs" environment variable is passed to the kernel as
5916parameters. You can check and modify this variable using the
5917"printenv" and "setenv" commands:
5918
5919
5920	=> printenv bootargs
5921	bootargs=root=/dev/ram
5922
5923	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5924
5925	=> printenv bootargs
5926	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5927
5928	=> bootm 40020000
5929	## Booting Linux kernel at 40020000 ...
5930	   Image Name:	 2.2.13 for NFS on TQM850L
5931	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5932	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5933	   Load Address: 00000000
5934	   Entry Point:	 0000000c
5935	   Verifying Checksum ... OK
5936	   Uncompressing Kernel Image ... OK
5937	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
5938	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5939	time_init: decrementer frequency = 187500000/60
5940	Calibrating delay loop... 49.77 BogoMIPS
5941	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5942	...
5943
5944If you want to boot a Linux kernel with initial RAM disk, you pass
5945the memory addresses of both the kernel and the initrd image (PPBCOOT
5946format!) to the "bootm" command:
5947
5948	=> imi 40100000 40200000
5949
5950	## Checking Image at 40100000 ...
5951	   Image Name:	 2.2.13 for initrd on TQM850L
5952	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5953	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5954	   Load Address: 00000000
5955	   Entry Point:	 0000000c
5956	   Verifying Checksum ... OK
5957
5958	## Checking Image at 40200000 ...
5959	   Image Name:	 Simple Ramdisk Image
5960	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5961	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5962	   Load Address: 00000000
5963	   Entry Point:	 00000000
5964	   Verifying Checksum ... OK
5965
5966	=> bootm 40100000 40200000
5967	## Booting Linux kernel at 40100000 ...
5968	   Image Name:	 2.2.13 for initrd on TQM850L
5969	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5970	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5971	   Load Address: 00000000
5972	   Entry Point:	 0000000c
5973	   Verifying Checksum ... OK
5974	   Uncompressing Kernel Image ... OK
5975	## Loading RAMDisk Image at 40200000 ...
5976	   Image Name:	 Simple Ramdisk Image
5977	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5978	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5979	   Load Address: 00000000
5980	   Entry Point:	 00000000
5981	   Verifying Checksum ... OK
5982	   Loading Ramdisk ... OK
5983	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
5984	Boot arguments: root=/dev/ram
5985	time_init: decrementer frequency = 187500000/60
5986	Calibrating delay loop... 49.77 BogoMIPS
5987	...
5988	RAMDISK: Compressed image found at block 0
5989	VFS: Mounted root (ext2 filesystem).
5990
5991	bash#
5992
5993Boot Linux and pass a flat device tree:
5994-----------
5995
5996First, U-Boot must be compiled with the appropriate defines. See the section
5997titled "Linux Kernel Interface" above for a more in depth explanation. The
5998following is an example of how to start a kernel and pass an updated
5999flat device tree:
6000
6001=> print oftaddr
6002oftaddr=0x300000
6003=> print oft
6004oft=oftrees/mpc8540ads.dtb
6005=> tftp $oftaddr $oft
6006Speed: 1000, full duplex
6007Using TSEC0 device
6008TFTP from server 192.168.1.1; our IP address is 192.168.1.101
6009Filename 'oftrees/mpc8540ads.dtb'.
6010Load address: 0x300000
6011Loading: #
6012done
6013Bytes transferred = 4106 (100a hex)
6014=> tftp $loadaddr $bootfile
6015Speed: 1000, full duplex
6016Using TSEC0 device
6017TFTP from server 192.168.1.1; our IP address is 192.168.1.2
6018Filename 'uImage'.
6019Load address: 0x200000
6020Loading:############
6021done
6022Bytes transferred = 1029407 (fb51f hex)
6023=> print loadaddr
6024loadaddr=200000
6025=> print oftaddr
6026oftaddr=0x300000
6027=> bootm $loadaddr - $oftaddr
6028## Booting image at 00200000 ...
6029   Image Name:	 Linux-2.6.17-dirty
6030   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
6031   Data Size:	 1029343 Bytes = 1005.2 kB
6032   Load Address: 00000000
6033   Entry Point:	 00000000
6034   Verifying Checksum ... OK
6035   Uncompressing Kernel Image ... OK
6036Booting using flat device tree at 0x300000
6037Using MPC85xx ADS machine description
6038Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
6039[snip]
6040
6041
6042More About U-Boot Image Types:
6043------------------------------
6044
6045U-Boot supports the following image types:
6046
6047   "Standalone Programs" are directly runnable in the environment
6048	provided by U-Boot; it is expected that (if they behave
6049	well) you can continue to work in U-Boot after return from
6050	the Standalone Program.
6051   "OS Kernel Images" are usually images of some Embedded OS which
6052	will take over control completely. Usually these programs
6053	will install their own set of exception handlers, device
6054	drivers, set up the MMU, etc. - this means, that you cannot
6055	expect to re-enter U-Boot except by resetting the CPU.
6056   "RAMDisk Images" are more or less just data blocks, and their
6057	parameters (address, size) are passed to an OS kernel that is
6058	being started.
6059   "Multi-File Images" contain several images, typically an OS
6060	(Linux) kernel image and one or more data images like
6061	RAMDisks. This construct is useful for instance when you want
6062	to boot over the network using BOOTP etc., where the boot
6063	server provides just a single image file, but you want to get
6064	for instance an OS kernel and a RAMDisk image.
6065
6066	"Multi-File Images" start with a list of image sizes, each
6067	image size (in bytes) specified by an "uint32_t" in network
6068	byte order. This list is terminated by an "(uint32_t)0".
6069	Immediately after the terminating 0 follow the images, one by
6070	one, all aligned on "uint32_t" boundaries (size rounded up to
6071	a multiple of 4 bytes).
6072
6073   "Firmware Images" are binary images containing firmware (like
6074	U-Boot or FPGA images) which usually will be programmed to
6075	flash memory.
6076
6077   "Script files" are command sequences that will be executed by
6078	U-Boot's command interpreter; this feature is especially
6079	useful when you configure U-Boot to use a real shell (hush)
6080	as command interpreter.
6081
6082Booting the Linux zImage:
6083-------------------------
6084
6085On some platforms, it's possible to boot Linux zImage. This is done
6086using the "bootz" command. The syntax of "bootz" command is the same
6087as the syntax of "bootm" command.
6088
6089Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
6090kernel with raw initrd images. The syntax is slightly different, the
6091address of the initrd must be augmented by it's size, in the following
6092format: "<initrd addres>:<initrd size>".
6093
6094
6095Standalone HOWTO:
6096=================
6097
6098One of the features of U-Boot is that you can dynamically load and
6099run "standalone" applications, which can use some resources of
6100U-Boot like console I/O functions or interrupt services.
6101
6102Two simple examples are included with the sources:
6103
6104"Hello World" Demo:
6105-------------------
6106
6107'examples/hello_world.c' contains a small "Hello World" Demo
6108application; it is automatically compiled when you build U-Boot.
6109It's configured to run at address 0x00040004, so you can play with it
6110like that:
6111
6112	=> loads
6113	## Ready for S-Record download ...
6114	~>examples/hello_world.srec
6115	1 2 3 4 5 6 7 8 9 10 11 ...
6116	[file transfer complete]
6117	[connected]
6118	## Start Addr = 0x00040004
6119
6120	=> go 40004 Hello World! This is a test.
6121	## Starting application at 0x00040004 ...
6122	Hello World
6123	argc = 7
6124	argv[0] = "40004"
6125	argv[1] = "Hello"
6126	argv[2] = "World!"
6127	argv[3] = "This"
6128	argv[4] = "is"
6129	argv[5] = "a"
6130	argv[6] = "test."
6131	argv[7] = "<NULL>"
6132	Hit any key to exit ...
6133
6134	## Application terminated, rc = 0x0
6135
6136Another example, which demonstrates how to register a CPM interrupt
6137handler with the U-Boot code, can be found in 'examples/timer.c'.
6138Here, a CPM timer is set up to generate an interrupt every second.
6139The interrupt service routine is trivial, just printing a '.'
6140character, but this is just a demo program. The application can be
6141controlled by the following keys:
6142
6143	? - print current values og the CPM Timer registers
6144	b - enable interrupts and start timer
6145	e - stop timer and disable interrupts
6146	q - quit application
6147
6148	=> loads
6149	## Ready for S-Record download ...
6150	~>examples/timer.srec
6151	1 2 3 4 5 6 7 8 9 10 11 ...
6152	[file transfer complete]
6153	[connected]
6154	## Start Addr = 0x00040004
6155
6156	=> go 40004
6157	## Starting application at 0x00040004 ...
6158	TIMERS=0xfff00980
6159	Using timer 1
6160	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
6161
6162Hit 'b':
6163	[q, b, e, ?] Set interval 1000000 us
6164	Enabling timer
6165Hit '?':
6166	[q, b, e, ?] ........
6167	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
6168Hit '?':
6169	[q, b, e, ?] .
6170	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
6171Hit '?':
6172	[q, b, e, ?] .
6173	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
6174Hit '?':
6175	[q, b, e, ?] .
6176	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
6177Hit 'e':
6178	[q, b, e, ?] ...Stopping timer
6179Hit 'q':
6180	[q, b, e, ?] ## Application terminated, rc = 0x0
6181
6182
6183Minicom warning:
6184================
6185
6186Over time, many people have reported problems when trying to use the
6187"minicom" terminal emulation program for serial download. I (wd)
6188consider minicom to be broken, and recommend not to use it. Under
6189Unix, I recommend to use C-Kermit for general purpose use (and
6190especially for kermit binary protocol download ("loadb" command), and
6191use "cu" for S-Record download ("loads" command).  See
6192http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
6193for help with kermit.
6194
6195
6196Nevertheless, if you absolutely want to use it try adding this
6197configuration to your "File transfer protocols" section:
6198
6199	   Name	   Program			Name U/D FullScr IO-Red. Multi
6200	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
6201	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
6202
6203
6204NetBSD Notes:
6205=============
6206
6207Starting at version 0.9.2, U-Boot supports NetBSD both as host
6208(build U-Boot) and target system (boots NetBSD/mpc8xx).
6209
6210Building requires a cross environment; it is known to work on
6211NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
6212need gmake since the Makefiles are not compatible with BSD make).
6213Note that the cross-powerpc package does not install include files;
6214attempting to build U-Boot will fail because <machine/ansi.h> is
6215missing.  This file has to be installed and patched manually:
6216
6217	# cd /usr/pkg/cross/powerpc-netbsd/include
6218	# mkdir powerpc
6219	# ln -s powerpc machine
6220	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
6221	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
6222
6223Native builds *don't* work due to incompatibilities between native
6224and U-Boot include files.
6225
6226Booting assumes that (the first part of) the image booted is a
6227stage-2 loader which in turn loads and then invokes the kernel
6228proper. Loader sources will eventually appear in the NetBSD source
6229tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
6230meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
6231
6232
6233Implementation Internals:
6234=========================
6235
6236The following is not intended to be a complete description of every
6237implementation detail. However, it should help to understand the
6238inner workings of U-Boot and make it easier to port it to custom
6239hardware.
6240
6241
6242Initial Stack, Global Data:
6243---------------------------
6244
6245The implementation of U-Boot is complicated by the fact that U-Boot
6246starts running out of ROM (flash memory), usually without access to
6247system RAM (because the memory controller is not initialized yet).
6248This means that we don't have writable Data or BSS segments, and BSS
6249is not initialized as zero. To be able to get a C environment working
6250at all, we have to allocate at least a minimal stack. Implementation
6251options for this are defined and restricted by the CPU used: Some CPU
6252models provide on-chip memory (like the IMMR area on MPC8xx and
6253MPC826x processors), on others (parts of) the data cache can be
6254locked as (mis-) used as memory, etc.
6255
6256	Chris Hallinan posted a good summary of these issues to the
6257	U-Boot mailing list:
6258
6259	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
6260	From: "Chris Hallinan" <clh@net1plus.com>
6261	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
6262	...
6263
6264	Correct me if I'm wrong, folks, but the way I understand it
6265	is this: Using DCACHE as initial RAM for Stack, etc, does not
6266	require any physical RAM backing up the cache. The cleverness
6267	is that the cache is being used as a temporary supply of
6268	necessary storage before the SDRAM controller is setup. It's
6269	beyond the scope of this list to explain the details, but you
6270	can see how this works by studying the cache architecture and
6271	operation in the architecture and processor-specific manuals.
6272
6273	OCM is On Chip Memory, which I believe the 405GP has 4K. It
6274	is another option for the system designer to use as an
6275	initial stack/RAM area prior to SDRAM being available. Either
6276	option should work for you. Using CS 4 should be fine if your
6277	board designers haven't used it for something that would
6278	cause you grief during the initial boot! It is frequently not
6279	used.
6280
6281	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
6282	with your processor/board/system design. The default value
6283	you will find in any recent u-boot distribution in
6284	walnut.h should work for you. I'd set it to a value larger
6285	than your SDRAM module. If you have a 64MB SDRAM module, set
6286	it above 400_0000. Just make sure your board has no resources
6287	that are supposed to respond to that address! That code in
6288	start.S has been around a while and should work as is when
6289	you get the config right.
6290
6291	-Chris Hallinan
6292	DS4.COM, Inc.
6293
6294It is essential to remember this, since it has some impact on the C
6295code for the initialization procedures:
6296
6297* Initialized global data (data segment) is read-only. Do not attempt
6298  to write it.
6299
6300* Do not use any uninitialized global data (or implicitly initialized
6301  as zero data - BSS segment) at all - this is undefined, initiali-
6302  zation is performed later (when relocating to RAM).
6303
6304* Stack space is very limited. Avoid big data buffers or things like
6305  that.
6306
6307Having only the stack as writable memory limits means we cannot use
6308normal global data to share information between the code. But it
6309turned out that the implementation of U-Boot can be greatly
6310simplified by making a global data structure (gd_t) available to all
6311functions. We could pass a pointer to this data as argument to _all_
6312functions, but this would bloat the code. Instead we use a feature of
6313the GCC compiler (Global Register Variables) to share the data: we
6314place a pointer (gd) to the global data into a register which we
6315reserve for this purpose.
6316
6317When choosing a register for such a purpose we are restricted by the
6318relevant  (E)ABI  specifications for the current architecture, and by
6319GCC's implementation.
6320
6321For PowerPC, the following registers have specific use:
6322	R1:	stack pointer
6323	R2:	reserved for system use
6324	R3-R4:	parameter passing and return values
6325	R5-R10: parameter passing
6326	R13:	small data area pointer
6327	R30:	GOT pointer
6328	R31:	frame pointer
6329
6330	(U-Boot also uses R12 as internal GOT pointer. r12
6331	is a volatile register so r12 needs to be reset when
6332	going back and forth between asm and C)
6333
6334    ==> U-Boot will use R2 to hold a pointer to the global data
6335
6336    Note: on PPC, we could use a static initializer (since the
6337    address of the global data structure is known at compile time),
6338    but it turned out that reserving a register results in somewhat
6339    smaller code - although the code savings are not that big (on
6340    average for all boards 752 bytes for the whole U-Boot image,
6341    624 text + 127 data).
6342
6343On Blackfin, the normal C ABI (except for P3) is followed as documented here:
6344	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
6345
6346    ==> U-Boot will use P3 to hold a pointer to the global data
6347
6348On ARM, the following registers are used:
6349
6350	R0:	function argument word/integer result
6351	R1-R3:	function argument word
6352	R9:	platform specific
6353	R10:	stack limit (used only if stack checking is enabled)
6354	R11:	argument (frame) pointer
6355	R12:	temporary workspace
6356	R13:	stack pointer
6357	R14:	link register
6358	R15:	program counter
6359
6360    ==> U-Boot will use R9 to hold a pointer to the global data
6361
6362    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
6363
6364On Nios II, the ABI is documented here:
6365	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
6366
6367    ==> U-Boot will use gp to hold a pointer to the global data
6368
6369    Note: on Nios II, we give "-G0" option to gcc and don't use gp
6370    to access small data sections, so gp is free.
6371
6372On NDS32, the following registers are used:
6373
6374	R0-R1:	argument/return
6375	R2-R5:	argument
6376	R15:	temporary register for assembler
6377	R16:	trampoline register
6378	R28:	frame pointer (FP)
6379	R29:	global pointer (GP)
6380	R30:	link register (LP)
6381	R31:	stack pointer (SP)
6382	PC:	program counter (PC)
6383
6384    ==> U-Boot will use R10 to hold a pointer to the global data
6385
6386NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
6387or current versions of GCC may "optimize" the code too much.
6388
6389Memory Management:
6390------------------
6391
6392U-Boot runs in system state and uses physical addresses, i.e. the
6393MMU is not used either for address mapping nor for memory protection.
6394
6395The available memory is mapped to fixed addresses using the memory
6396controller. In this process, a contiguous block is formed for each
6397memory type (Flash, SDRAM, SRAM), even when it consists of several
6398physical memory banks.
6399
6400U-Boot is installed in the first 128 kB of the first Flash bank (on
6401TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
6402booting and sizing and initializing DRAM, the code relocates itself
6403to the upper end of DRAM. Immediately below the U-Boot code some
6404memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
6405configuration setting]. Below that, a structure with global Board
6406Info data is placed, followed by the stack (growing downward).
6407
6408Additionally, some exception handler code is copied to the low 8 kB
6409of DRAM (0x00000000 ... 0x00001FFF).
6410
6411So a typical memory configuration with 16 MB of DRAM could look like
6412this:
6413
6414	0x0000 0000	Exception Vector code
6415	      :
6416	0x0000 1FFF
6417	0x0000 2000	Free for Application Use
6418	      :
6419	      :
6420
6421	      :
6422	      :
6423	0x00FB FF20	Monitor Stack (Growing downward)
6424	0x00FB FFAC	Board Info Data and permanent copy of global data
6425	0x00FC 0000	Malloc Arena
6426	      :
6427	0x00FD FFFF
6428	0x00FE 0000	RAM Copy of Monitor Code
6429	...		eventually: LCD or video framebuffer
6430	...		eventually: pRAM (Protected RAM - unchanged by reset)
6431	0x00FF FFFF	[End of RAM]
6432
6433
6434System Initialization:
6435----------------------
6436
6437In the reset configuration, U-Boot starts at the reset entry point
6438(on most PowerPC systems at address 0x00000100). Because of the reset
6439configuration for CS0# this is a mirror of the on board Flash memory.
6440To be able to re-map memory U-Boot then jumps to its link address.
6441To be able to implement the initialization code in C, a (small!)
6442initial stack is set up in the internal Dual Ported RAM (in case CPUs
6443which provide such a feature like MPC8xx or MPC8260), or in a locked
6444part of the data cache. After that, U-Boot initializes the CPU core,
6445the caches and the SIU.
6446
6447Next, all (potentially) available memory banks are mapped using a
6448preliminary mapping. For example, we put them on 512 MB boundaries
6449(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
6450on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
6451programmed for SDRAM access. Using the temporary configuration, a
6452simple memory test is run that determines the size of the SDRAM
6453banks.
6454
6455When there is more than one SDRAM bank, and the banks are of
6456different size, the largest is mapped first. For equal size, the first
6457bank (CS2#) is mapped first. The first mapping is always for address
64580x00000000, with any additional banks following immediately to create
6459contiguous memory starting from 0.
6460
6461Then, the monitor installs itself at the upper end of the SDRAM area
6462and allocates memory for use by malloc() and for the global Board
6463Info data; also, the exception vector code is copied to the low RAM
6464pages, and the final stack is set up.
6465
6466Only after this relocation will you have a "normal" C environment;
6467until that you are restricted in several ways, mostly because you are
6468running from ROM, and because the code will have to be relocated to a
6469new address in RAM.
6470
6471
6472U-Boot Porting Guide:
6473----------------------
6474
6475[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
6476list, October 2002]
6477
6478
6479int main(int argc, char *argv[])
6480{
6481	sighandler_t no_more_time;
6482
6483	signal(SIGALRM, no_more_time);
6484	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6485
6486	if (available_money > available_manpower) {
6487		Pay consultant to port U-Boot;
6488		return 0;
6489	}
6490
6491	Download latest U-Boot source;
6492
6493	Subscribe to u-boot mailing list;
6494
6495	if (clueless)
6496		email("Hi, I am new to U-Boot, how do I get started?");
6497
6498	while (learning) {
6499		Read the README file in the top level directory;
6500		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6501		Read applicable doc/*.README;
6502		Read the source, Luke;
6503		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6504	}
6505
6506	if (available_money > toLocalCurrency ($2500))
6507		Buy a BDI3000;
6508	else
6509		Add a lot of aggravation and time;
6510
6511	if (a similar board exists) {	/* hopefully... */
6512		cp -a board/<similar> board/<myboard>
6513		cp include/configs/<similar>.h include/configs/<myboard>.h
6514	} else {
6515		Create your own board support subdirectory;
6516		Create your own board include/configs/<myboard>.h file;
6517	}
6518	Edit new board/<myboard> files
6519	Edit new include/configs/<myboard>.h
6520
6521	while (!accepted) {
6522		while (!running) {
6523			do {
6524				Add / modify source code;
6525			} until (compiles);
6526			Debug;
6527			if (clueless)
6528				email("Hi, I am having problems...");
6529		}
6530		Send patch file to the U-Boot email list;
6531		if (reasonable critiques)
6532			Incorporate improvements from email list code review;
6533		else
6534			Defend code as written;
6535	}
6536
6537	return 0;
6538}
6539
6540void no_more_time (int sig)
6541{
6542      hire_a_guru();
6543}
6544
6545
6546Coding Standards:
6547-----------------
6548
6549All contributions to U-Boot should conform to the Linux kernel
6550coding style; see the file "Documentation/CodingStyle" and the script
6551"scripts/Lindent" in your Linux kernel source directory.
6552
6553Source files originating from a different project (for example the
6554MTD subsystem) are generally exempt from these guidelines and are not
6555reformatted to ease subsequent migration to newer versions of those
6556sources.
6557
6558Please note that U-Boot is implemented in C (and to some small parts in
6559Assembler); no C++ is used, so please do not use C++ style comments (//)
6560in your code.
6561
6562Please also stick to the following formatting rules:
6563- remove any trailing white space
6564- use TAB characters for indentation and vertical alignment, not spaces
6565- make sure NOT to use DOS '\r\n' line feeds
6566- do not add more than 2 consecutive empty lines to source files
6567- do not add trailing empty lines to source files
6568
6569Submissions which do not conform to the standards may be returned
6570with a request to reformat the changes.
6571
6572
6573Submitting Patches:
6574-------------------
6575
6576Since the number of patches for U-Boot is growing, we need to
6577establish some rules. Submissions which do not conform to these rules
6578may be rejected, even when they contain important and valuable stuff.
6579
6580Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6581
6582Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6583see http://lists.denx.de/mailman/listinfo/u-boot
6584
6585When you send a patch, please include the following information with
6586it:
6587
6588* For bug fixes: a description of the bug and how your patch fixes
6589  this bug. Please try to include a way of demonstrating that the
6590  patch actually fixes something.
6591
6592* For new features: a description of the feature and your
6593  implementation.
6594
6595* A CHANGELOG entry as plaintext (separate from the patch)
6596
6597* For major contributions, your entry to the CREDITS file
6598
6599* When you add support for a new board, don't forget to add a
6600  maintainer e-mail address to the boards.cfg file, too.
6601
6602* If your patch adds new configuration options, don't forget to
6603  document these in the README file.
6604
6605* The patch itself. If you are using git (which is *strongly*
6606  recommended) you can easily generate the patch using the
6607  "git format-patch". If you then use "git send-email" to send it to
6608  the U-Boot mailing list, you will avoid most of the common problems
6609  with some other mail clients.
6610
6611  If you cannot use git, use "diff -purN OLD NEW". If your version of
6612  diff does not support these options, then get the latest version of
6613  GNU diff.
6614
6615  The current directory when running this command shall be the parent
6616  directory of the U-Boot source tree (i. e. please make sure that
6617  your patch includes sufficient directory information for the
6618  affected files).
6619
6620  We prefer patches as plain text. MIME attachments are discouraged,
6621  and compressed attachments must not be used.
6622
6623* If one logical set of modifications affects or creates several
6624  files, all these changes shall be submitted in a SINGLE patch file.
6625
6626* Changesets that contain different, unrelated modifications shall be
6627  submitted as SEPARATE patches, one patch per changeset.
6628
6629
6630Notes:
6631
6632* Before sending the patch, run the MAKEALL script on your patched
6633  source tree and make sure that no errors or warnings are reported
6634  for any of the boards.
6635
6636* Keep your modifications to the necessary minimum: A patch
6637  containing several unrelated changes or arbitrary reformats will be
6638  returned with a request to re-formatting / split it.
6639
6640* If you modify existing code, make sure that your new code does not
6641  add to the memory footprint of the code ;-) Small is beautiful!
6642  When adding new features, these should compile conditionally only
6643  (using #ifdef), and the resulting code with the new feature
6644  disabled must not need more memory than the old code without your
6645  modification.
6646
6647* Remember that there is a size limit of 100 kB per message on the
6648  u-boot mailing list. Bigger patches will be moderated. If they are
6649  reasonable and not too big, they will be acknowledged. But patches
6650  bigger than the size limit should be avoided.
6651