xref: /openbmc/u-boot/README (revision abb1678c)
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      /74xx_7xx		Files specific to Freescale MPC74xx and 7xx CPUs
186      /mpc5xx		Files specific to Freescale MPC5xx CPUs
187      /mpc5xxx		Files specific to Freescale MPC5xxx CPUs
188      /mpc8xx		Files specific to Freescale MPC8xx CPUs
189      /mpc824x		Files specific to Freescale MPC824x CPUs
190      /mpc8260		Files specific to Freescale MPC8260 CPUs
191      /mpc85xx		Files specific to Freescale MPC85xx CPUs
192      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
193    /lib		Architecture specific library files
194  /sh			Files generic to SH architecture
195    /cpu		CPU specific files
196      /sh2		Files specific to sh2 CPUs
197      /sh3		Files specific to sh3 CPUs
198      /sh4		Files specific to sh4 CPUs
199    /lib		Architecture specific library files
200  /sparc		Files generic to SPARC architecture
201    /cpu		CPU specific files
202      /leon2		Files specific to Gaisler LEON2 SPARC CPU
203      /leon3		Files specific to Gaisler LEON3 SPARC CPU
204    /lib		Architecture specific library files
205  /x86			Files generic to x86 architecture
206    /cpu		CPU specific files
207    /lib		Architecture specific library files
208/api			Machine/arch independent API for external apps
209/board			Board dependent files
210/common			Misc architecture independent functions
211/disk			Code for disk drive partition handling
212/doc			Documentation (don't expect too much)
213/drivers		Commonly used device drivers
214/dts			Contains Makefile for building internal U-Boot fdt.
215/examples		Example code for standalone applications, etc.
216/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
217/include		Header Files
218/lib			Files generic to all architectures
219  /libfdt		Library files to support flattened device trees
220  /lzma			Library files to support LZMA decompression
221  /lzo			Library files to support LZO decompression
222/net			Networking code
223/post			Power On Self Test
224/spl			Secondary Program Loader framework
225/tools			Tools to build S-Record or U-Boot images, etc.
226
227Software Configuration:
228=======================
229
230Configuration is usually done using C preprocessor defines; the
231rationale behind that is to avoid dead code whenever possible.
232
233There are two classes of configuration variables:
234
235* Configuration _OPTIONS_:
236  These are selectable by the user and have names beginning with
237  "CONFIG_".
238
239* Configuration _SETTINGS_:
240  These depend on the hardware etc. and should not be meddled with if
241  you don't know what you're doing; they have names beginning with
242  "CONFIG_SYS_".
243
244Later we will add a configuration tool - probably similar to or even
245identical to what's used for the Linux kernel. Right now, we have to
246do the configuration by hand, which means creating some symbolic
247links and editing some configuration files. We use the TQM8xxL boards
248as an example here.
249
250
251Selection of Processor Architecture and Board Type:
252---------------------------------------------------
253
254For all supported boards there are ready-to-use default
255configurations available; just type "make <board_name>_defconfig".
256
257Example: For a TQM823L module type:
258
259	cd u-boot
260	make TQM823L_defconfig
261
262For the Cogent platform, you need to specify the CPU type as well;
263e.g. "make cogent_mpc8xx_defconfig". And also configure the cogent
264directory according to the instructions in cogent/README.
265
266
267Sandbox Environment:
268--------------------
269
270U-Boot can be built natively to run on a Linux host using the 'sandbox'
271board. This allows feature development which is not board- or architecture-
272specific to be undertaken on a native platform. The sandbox is also used to
273run some of U-Boot's tests.
274
275See board/sandbox/README.sandbox for more details.
276
277
278Configuration Options:
279----------------------
280
281Configuration depends on the combination of board and CPU type; all
282such information is kept in a configuration file
283"include/configs/<board_name>.h".
284
285Example: For a TQM823L module, all configuration settings are in
286"include/configs/TQM823L.h".
287
288
289Many of the options are named exactly as the corresponding Linux
290kernel configuration options. The intention is to make it easier to
291build a config tool - later.
292
293
294The following options need to be configured:
295
296- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
297
298- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
299
300- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
301		Define exactly one, e.g. CONFIG_ATSTK1002
302
303- CPU Module Type: (if CONFIG_COGENT is defined)
304		Define exactly one of
305		CONFIG_CMA286_60_OLD
306--- FIXME --- not tested yet:
307		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
308		CONFIG_CMA287_23, CONFIG_CMA287_50
309
310- Motherboard Type: (if CONFIG_COGENT is defined)
311		Define exactly one of
312		CONFIG_CMA101, CONFIG_CMA102
313
314- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
315		Define one or more of
316		CONFIG_CMA302
317
318- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
319		Define one or more of
320		CONFIG_LCD_HEARTBEAT	- update a character position on
321					  the LCD display every second with
322					  a "rotator" |\-/|\-/
323
324- Marvell Family Member
325		CONFIG_SYS_MVFS		- define it if you want to enable
326					  multiple fs option at one time
327					  for marvell soc family
328
329- MPC824X Family Member (if CONFIG_MPC824X is defined)
330		Define exactly one of
331		CONFIG_MPC8240, CONFIG_MPC8245
332
333- 8xx CPU Options: (if using an MPC8xx CPU)
334		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
335					  get_gclk_freq() cannot work
336					  e.g. if there is no 32KHz
337					  reference PIT/RTC clock
338		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
339					  or XTAL/EXTAL)
340
341- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
342		CONFIG_SYS_8xx_CPUCLK_MIN
343		CONFIG_SYS_8xx_CPUCLK_MAX
344		CONFIG_8xx_CPUCLK_DEFAULT
345			See doc/README.MPC866
346
347		CONFIG_SYS_MEASURE_CPUCLK
348
349		Define this to measure the actual CPU clock instead
350		of relying on the correctness of the configured
351		values. Mostly useful for board bringup to make sure
352		the PLL is locked at the intended frequency. Note
353		that this requires a (stable) reference clock (32 kHz
354		RTC clock or CONFIG_SYS_8XX_XIN)
355
356		CONFIG_SYS_DELAYED_ICACHE
357
358		Define this option if you want to enable the
359		ICache only when Code runs from RAM.
360
361- 85xx CPU Options:
362		CONFIG_SYS_PPC64
363
364		Specifies that the core is a 64-bit PowerPC implementation (implements
365		the "64" category of the Power ISA). This is necessary for ePAPR
366		compliance, among other possible reasons.
367
368		CONFIG_SYS_FSL_TBCLK_DIV
369
370		Defines the core time base clock divider ratio compared to the
371		system clock.  On most PQ3 devices this is 8, on newer QorIQ
372		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
373
374		CONFIG_SYS_FSL_PCIE_COMPAT
375
376		Defines the string to utilize when trying to match PCIe device
377		tree nodes for the given platform.
378
379		CONFIG_SYS_PPC_E500_DEBUG_TLB
380
381		Enables a temporary TLB entry to be used during boot to work
382		around limitations in e500v1 and e500v2 external debugger
383		support. This reduces the portions of the boot code where
384		breakpoints and single stepping do not work.  The value of this
385		symbol should be set to the TLB1 entry to be used for this
386		purpose.
387
388		CONFIG_SYS_FSL_ERRATUM_A004510
389
390		Enables a workaround for erratum A004510.  If set,
391		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
392		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
393
394		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
395		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
396
397		Defines one or two SoC revisions (low 8 bits of SVR)
398		for which the A004510 workaround should be applied.
399
400		The rest of SVR is either not relevant to the decision
401		of whether the erratum is present (e.g. p2040 versus
402		p2041) or is implied by the build target, which controls
403		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
404
405		See Freescale App Note 4493 for more information about
406		this erratum.
407
408		CONFIG_A003399_NOR_WORKAROUND
409		Enables a workaround for IFC erratum A003399. It is only
410		requred during NOR boot.
411
412		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
413
414		This is the value to write into CCSR offset 0x18600
415		according to the A004510 workaround.
416
417		CONFIG_SYS_FSL_DSP_DDR_ADDR
418		This value denotes start offset of DDR memory which is
419		connected exclusively to the DSP cores.
420
421		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
422		This value denotes start offset of M2 memory
423		which is directly connected to the DSP core.
424
425		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
426		This value denotes start offset of M3 memory which is directly
427		connected to the DSP core.
428
429		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
430		This value denotes start offset of DSP CCSR space.
431
432		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
433		Single Source Clock is clocking mode present in some of FSL SoC's.
434		In this mode, a single differential clock is used to supply
435		clocks to the sysclock, ddrclock and usbclock.
436
437		CONFIG_SYS_CPC_REINIT_F
438		This CONFIG is defined when the CPC is configured as SRAM at the
439		time of U-boot entry and is required to be re-initialized.
440
441		CONFIG_DEEP_SLEEP
442		Inidcates this SoC supports deep sleep feature. If deep sleep is
443		supported, core will start to execute uboot when wakes up.
444
445- Generic CPU options:
446		CONFIG_SYS_GENERIC_GLOBAL_DATA
447		Defines global data is initialized in generic board board_init_f().
448		If this macro is defined, global data is created and cleared in
449		generic board board_init_f(). Without this macro, architecture/board
450		should initialize global data before calling board_init_f().
451
452		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
453
454		Defines the endianess of the CPU. Implementation of those
455		values is arch specific.
456
457		CONFIG_SYS_FSL_DDR
458		Freescale DDR driver in use. This type of DDR controller is
459		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
460		SoCs.
461
462		CONFIG_SYS_FSL_DDR_ADDR
463		Freescale DDR memory-mapped register base.
464
465		CONFIG_SYS_FSL_DDR_EMU
466		Specify emulator support for DDR. Some DDR features such as
467		deskew training are not available.
468
469		CONFIG_SYS_FSL_DDRC_GEN1
470		Freescale DDR1 controller.
471
472		CONFIG_SYS_FSL_DDRC_GEN2
473		Freescale DDR2 controller.
474
475		CONFIG_SYS_FSL_DDRC_GEN3
476		Freescale DDR3 controller.
477
478		CONFIG_SYS_FSL_DDRC_GEN4
479		Freescale DDR4 controller.
480
481		CONFIG_SYS_FSL_DDRC_ARM_GEN3
482		Freescale DDR3 controller for ARM-based SoCs.
483
484		CONFIG_SYS_FSL_DDR1
485		Board config to use DDR1. It can be enabled for SoCs with
486		Freescale DDR1 or DDR2 controllers, depending on the board
487		implemetation.
488
489		CONFIG_SYS_FSL_DDR2
490		Board config to use DDR2. It can be eanbeld for SoCs with
491		Freescale DDR2 or DDR3 controllers, depending on the board
492		implementation.
493
494		CONFIG_SYS_FSL_DDR3
495		Board config to use DDR3. It can be enabled for SoCs with
496		Freescale DDR3 or DDR3L controllers.
497
498		CONFIG_SYS_FSL_DDR3L
499		Board config to use DDR3L. It can be enabled for SoCs with
500		DDR3L controllers.
501
502		CONFIG_SYS_FSL_DDR4
503		Board config to use DDR4. It can be enabled for SoCs with
504		DDR4 controllers.
505
506		CONFIG_SYS_FSL_IFC_BE
507		Defines the IFC controller register space as Big Endian
508
509		CONFIG_SYS_FSL_IFC_LE
510		Defines the IFC controller register space as Little Endian
511
512		CONFIG_SYS_FSL_PBL_PBI
513		It enables addition of RCW (Power on reset configuration) in built image.
514		Please refer doc/README.pblimage for more details
515
516		CONFIG_SYS_FSL_PBL_RCW
517		It adds PBI(pre-boot instructions) commands in u-boot build image.
518		PBI commands can be used to configure SoC before it starts the execution.
519		Please refer doc/README.pblimage for more details
520
521		CONFIG_SPL_FSL_PBL
522		It adds a target to create boot binary having SPL binary in PBI format
523		concatenated with u-boot binary.
524
525		CONFIG_SYS_FSL_DDR_BE
526		Defines the DDR controller register space as Big Endian
527
528		CONFIG_SYS_FSL_DDR_LE
529		Defines the DDR controller register space as Little Endian
530
531		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
532		Physical address from the view of DDR controllers. It is the
533		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
534		it could be different for ARM SoCs.
535
536		CONFIG_SYS_FSL_DDR_INTLV_256B
537		DDR controller interleaving on 256-byte. This is a special
538		interleaving mode, handled by Dickens for Freescale layerscape
539		SoCs with ARM core.
540
541		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
542		Number of controllers used as main memory.
543
544		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
545		Number of controllers used for other than main memory.
546
547		CONFIG_SYS_FSL_SEC_BE
548		Defines the SEC controller register space as Big Endian
549
550		CONFIG_SYS_FSL_SEC_LE
551		Defines the SEC controller register space as Little Endian
552
553- Intel Monahans options:
554		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
555
556		Defines the Monahans run mode to oscillator
557		ratio. Valid values are 8, 16, 24, 31. The core
558		frequency is this value multiplied by 13 MHz.
559
560		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
561
562		Defines the Monahans turbo mode to oscillator
563		ratio. Valid values are 1 (default if undefined) and
564		2. The core frequency as calculated above is multiplied
565		by this value.
566
567- MIPS CPU options:
568		CONFIG_SYS_INIT_SP_OFFSET
569
570		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
571		pointer. This is needed for the temporary stack before
572		relocation.
573
574		CONFIG_SYS_MIPS_CACHE_MODE
575
576		Cache operation mode for the MIPS CPU.
577		See also arch/mips/include/asm/mipsregs.h.
578		Possible values are:
579			CONF_CM_CACHABLE_NO_WA
580			CONF_CM_CACHABLE_WA
581			CONF_CM_UNCACHED
582			CONF_CM_CACHABLE_NONCOHERENT
583			CONF_CM_CACHABLE_CE
584			CONF_CM_CACHABLE_COW
585			CONF_CM_CACHABLE_CUW
586			CONF_CM_CACHABLE_ACCELERATED
587
588		CONFIG_SYS_XWAY_EBU_BOOTCFG
589
590		Special option for Lantiq XWAY SoCs for booting from NOR flash.
591		See also arch/mips/cpu/mips32/start.S.
592
593		CONFIG_XWAY_SWAP_BYTES
594
595		Enable compilation of tools/xway-swap-bytes needed for Lantiq
596		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
597		be swapped if a flash programmer is used.
598
599- ARM options:
600		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
601
602		Select high exception vectors of the ARM core, e.g., do not
603		clear the V bit of the c1 register of CP15.
604
605		CONFIG_SYS_THUMB_BUILD
606
607		Use this flag to build U-Boot using the Thumb instruction
608		set for ARM architectures. Thumb instruction set provides
609		better code density. For ARM architectures that support
610		Thumb2 this flag will result in Thumb2 code generated by
611		GCC.
612
613		CONFIG_ARM_ERRATA_716044
614		CONFIG_ARM_ERRATA_742230
615		CONFIG_ARM_ERRATA_743622
616		CONFIG_ARM_ERRATA_751472
617		CONFIG_ARM_ERRATA_794072
618		CONFIG_ARM_ERRATA_761320
619
620		If set, the workarounds for these ARM errata are applied early
621		during U-Boot startup. Note that these options force the
622		workarounds to be applied; no CPU-type/version detection
623		exists, unlike the similar options in the Linux kernel. Do not
624		set these options unless they apply!
625
626- Linux Kernel Interface:
627		CONFIG_CLOCKS_IN_MHZ
628
629		U-Boot stores all clock information in Hz
630		internally. For binary compatibility with older Linux
631		kernels (which expect the clocks passed in the
632		bd_info data to be in MHz) the environment variable
633		"clocks_in_mhz" can be defined so that U-Boot
634		converts clock data to MHZ before passing it to the
635		Linux kernel.
636		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
637		"clocks_in_mhz=1" is automatically included in the
638		default environment.
639
640		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
641
642		When transferring memsize parameter to linux, some versions
643		expect it to be in bytes, others in MB.
644		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
645
646		CONFIG_OF_LIBFDT
647
648		New kernel versions are expecting firmware settings to be
649		passed using flattened device trees (based on open firmware
650		concepts).
651
652		CONFIG_OF_LIBFDT
653		 * New libfdt-based support
654		 * Adds the "fdt" command
655		 * The bootm command automatically updates the fdt
656
657		OF_CPU - The proper name of the cpus node (only required for
658			MPC512X and MPC5xxx based boards).
659		OF_SOC - The proper name of the soc node (only required for
660			MPC512X and MPC5xxx based boards).
661		OF_TBCLK - The timebase frequency.
662		OF_STDOUT_PATH - The path to the console device
663
664		boards with QUICC Engines require OF_QE to set UCC MAC
665		addresses
666
667		CONFIG_OF_BOARD_SETUP
668
669		Board code has addition modification that it wants to make
670		to the flat device tree before handing it off to the kernel
671
672		CONFIG_OF_BOOT_CPU
673
674		This define fills in the correct boot CPU in the boot
675		param header, the default value is zero if undefined.
676
677		CONFIG_OF_IDE_FIXUP
678
679		U-Boot can detect if an IDE device is present or not.
680		If not, and this new config option is activated, U-Boot
681		removes the ATA node from the DTS before booting Linux,
682		so the Linux IDE driver does not probe the device and
683		crash. This is needed for buggy hardware (uc101) where
684		no pull down resistor is connected to the signal IDE5V_DD7.
685
686		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
687
688		This setting is mandatory for all boards that have only one
689		machine type and must be used to specify the machine type
690		number as it appears in the ARM machine registry
691		(see http://www.arm.linux.org.uk/developer/machines/).
692		Only boards that have multiple machine types supported
693		in a single configuration file and the machine type is
694		runtime discoverable, do not have to use this setting.
695
696- vxWorks boot parameters:
697
698		bootvx constructs a valid bootline using the following
699		environments variables: bootfile, ipaddr, serverip, hostname.
700		It loads the vxWorks image pointed bootfile.
701
702		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
703		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
704		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
705		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
706
707		CONFIG_SYS_VXWORKS_ADD_PARAMS
708
709		Add it at the end of the bootline. E.g "u=username pw=secret"
710
711		Note: If a "bootargs" environment is defined, it will overwride
712		the defaults discussed just above.
713
714- Cache Configuration:
715		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
716		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
717		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
718
719- Cache Configuration for ARM:
720		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
721				      controller
722		CONFIG_SYS_PL310_BASE - Physical base address of PL310
723					controller register space
724
725- Serial Ports:
726		CONFIG_PL010_SERIAL
727
728		Define this if you want support for Amba PrimeCell PL010 UARTs.
729
730		CONFIG_PL011_SERIAL
731
732		Define this if you want support for Amba PrimeCell PL011 UARTs.
733
734		CONFIG_PL011_CLOCK
735
736		If you have Amba PrimeCell PL011 UARTs, set this variable to
737		the clock speed of the UARTs.
738
739		CONFIG_PL01x_PORTS
740
741		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
742		define this to a list of base addresses for each (supported)
743		port. See e.g. include/configs/versatile.h
744
745		CONFIG_PL011_SERIAL_RLCR
746
747		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
748		have separate receive and transmit line control registers.  Set
749		this variable to initialize the extra register.
750
751		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
752
753		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
754		boot loader that has already initialized the UART.  Define this
755		variable to flush the UART at init time.
756
757		CONFIG_SERIAL_HW_FLOW_CONTROL
758
759		Define this variable to enable hw flow control in serial driver.
760		Current user of this option is drivers/serial/nsl16550.c driver
761
762- Console Interface:
763		Depending on board, define exactly one serial port
764		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
765		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
766		console by defining CONFIG_8xx_CONS_NONE
767
768		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
769		port routines must be defined elsewhere
770		(i.e. serial_init(), serial_getc(), ...)
771
772		CONFIG_CFB_CONSOLE
773		Enables console device for a color framebuffer. Needs following
774		defines (cf. smiLynxEM, i8042)
775			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
776						(default big endian)
777			VIDEO_HW_RECTFILL	graphic chip supports
778						rectangle fill
779						(cf. smiLynxEM)
780			VIDEO_HW_BITBLT		graphic chip supports
781						bit-blit (cf. smiLynxEM)
782			VIDEO_VISIBLE_COLS	visible pixel columns
783						(cols=pitch)
784			VIDEO_VISIBLE_ROWS	visible pixel rows
785			VIDEO_PIXEL_SIZE	bytes per pixel
786			VIDEO_DATA_FORMAT	graphic data format
787						(0-5, cf. cfb_console.c)
788			VIDEO_FB_ADRS		framebuffer address
789			VIDEO_KBD_INIT_FCT	keyboard int fct
790						(i.e. i8042_kbd_init())
791			VIDEO_TSTC_FCT		test char fct
792						(i.e. i8042_tstc)
793			VIDEO_GETC_FCT		get char fct
794						(i.e. i8042_getc)
795			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
796						(requires blink timer
797						cf. i8042.c)
798			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
799			CONFIG_CONSOLE_TIME	display time/date info in
800						upper right corner
801						(requires CONFIG_CMD_DATE)
802			CONFIG_VIDEO_LOGO	display Linux logo in
803						upper left corner
804			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
805						linux_logo.h for logo.
806						Requires CONFIG_VIDEO_LOGO
807			CONFIG_CONSOLE_EXTRA_INFO
808						additional board info beside
809						the logo
810
811		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
812		a limited number of ANSI escape sequences (cursor control,
813		erase functions and limited graphics rendition control).
814
815		When CONFIG_CFB_CONSOLE is defined, video console is
816		default i/o. Serial console can be forced with
817		environment 'console=serial'.
818
819		When CONFIG_SILENT_CONSOLE is defined, all console
820		messages (by U-Boot and Linux!) can be silenced with
821		the "silent" environment variable. See
822		doc/README.silent for more information.
823
824		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
825			is 0x00.
826		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
827			is 0xa0.
828
829- Console Baudrate:
830		CONFIG_BAUDRATE - in bps
831		Select one of the baudrates listed in
832		CONFIG_SYS_BAUDRATE_TABLE, see below.
833		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
834
835- Console Rx buffer length
836		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
837		the maximum receive buffer length for the SMC.
838		This option is actual only for 82xx and 8xx possible.
839		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
840		must be defined, to setup the maximum idle timeout for
841		the SMC.
842
843- Pre-Console Buffer:
844		Prior to the console being initialised (i.e. serial UART
845		initialised etc) all console output is silently discarded.
846		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
847		buffer any console messages prior to the console being
848		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
849		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
850		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
851		bytes are output before the console is initialised, the
852		earlier bytes are discarded.
853
854		'Sane' compilers will generate smaller code if
855		CONFIG_PRE_CON_BUF_SZ is a power of 2
856
857- Safe printf() functions
858		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
859		the printf() functions. These are defined in
860		include/vsprintf.h and include snprintf(), vsnprintf() and
861		so on. Code size increase is approximately 300-500 bytes.
862		If this option is not given then these functions will
863		silently discard their buffer size argument - this means
864		you are not getting any overflow checking in this case.
865
866- Boot Delay:	CONFIG_BOOTDELAY - in seconds
867		Delay before automatically booting the default image;
868		set to -1 to disable autoboot.
869		set to -2 to autoboot with no delay and not check for abort
870		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
871
872		See doc/README.autoboot for these options that
873		work with CONFIG_BOOTDELAY. None are required.
874		CONFIG_BOOT_RETRY_TIME
875		CONFIG_BOOT_RETRY_MIN
876		CONFIG_AUTOBOOT_KEYED
877		CONFIG_AUTOBOOT_PROMPT
878		CONFIG_AUTOBOOT_DELAY_STR
879		CONFIG_AUTOBOOT_STOP_STR
880		CONFIG_AUTOBOOT_DELAY_STR2
881		CONFIG_AUTOBOOT_STOP_STR2
882		CONFIG_ZERO_BOOTDELAY_CHECK
883		CONFIG_RESET_TO_RETRY
884
885- Autoboot Command:
886		CONFIG_BOOTCOMMAND
887		Only needed when CONFIG_BOOTDELAY is enabled;
888		define a command string that is automatically executed
889		when no character is read on the console interface
890		within "Boot Delay" after reset.
891
892		CONFIG_BOOTARGS
893		This can be used to pass arguments to the bootm
894		command. The value of CONFIG_BOOTARGS goes into the
895		environment value "bootargs".
896
897		CONFIG_RAMBOOT and CONFIG_NFSBOOT
898		The value of these goes into the environment as
899		"ramboot" and "nfsboot" respectively, and can be used
900		as a convenience, when switching between booting from
901		RAM and NFS.
902
903- Bootcount:
904		CONFIG_BOOTCOUNT_LIMIT
905		Implements a mechanism for detecting a repeating reboot
906		cycle, see:
907		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
908
909		CONFIG_BOOTCOUNT_ENV
910		If no softreset save registers are found on the hardware
911		"bootcount" is stored in the environment. To prevent a
912		saveenv on all reboots, the environment variable
913		"upgrade_available" is used. If "upgrade_available" is
914		0, "bootcount" is always 0, if "upgrade_available" is
915		1 "bootcount" is incremented in the environment.
916		So the Userspace Applikation must set the "upgrade_available"
917		and "bootcount" variable to 0, if a boot was successfully.
918
919- Pre-Boot Commands:
920		CONFIG_PREBOOT
921
922		When this option is #defined, the existence of the
923		environment variable "preboot" will be checked
924		immediately before starting the CONFIG_BOOTDELAY
925		countdown and/or running the auto-boot command resp.
926		entering interactive mode.
927
928		This feature is especially useful when "preboot" is
929		automatically generated or modified. For an example
930		see the LWMON board specific code: here "preboot" is
931		modified when the user holds down a certain
932		combination of keys on the (special) keyboard when
933		booting the systems
934
935- Serial Download Echo Mode:
936		CONFIG_LOADS_ECHO
937		If defined to 1, all characters received during a
938		serial download (using the "loads" command) are
939		echoed back. This might be needed by some terminal
940		emulations (like "cu"), but may as well just take
941		time on others. This setting #define's the initial
942		value of the "loads_echo" environment variable.
943
944- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
945		CONFIG_KGDB_BAUDRATE
946		Select one of the baudrates listed in
947		CONFIG_SYS_BAUDRATE_TABLE, see below.
948
949- Monitor Functions:
950		Monitor commands can be included or excluded
951		from the build by using the #include files
952		<config_cmd_all.h> and #undef'ing unwanted
953		commands, or using <config_cmd_default.h>
954		and augmenting with additional #define's
955		for wanted commands.
956
957		The default command configuration includes all commands
958		except those marked below with a "*".
959
960		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
961		CONFIG_CMD_ASKENV	* ask for env variable
962		CONFIG_CMD_BDI		  bdinfo
963		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
964		CONFIG_CMD_BMP		* BMP support
965		CONFIG_CMD_BSP		* Board specific commands
966		CONFIG_CMD_BOOTD	  bootd
967		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
968		CONFIG_CMD_CACHE	* icache, dcache
969		CONFIG_CMD_CLK   	* clock command support
970		CONFIG_CMD_CONSOLE	  coninfo
971		CONFIG_CMD_CRC32	* crc32
972		CONFIG_CMD_DATE		* support for RTC, date/time...
973		CONFIG_CMD_DHCP		* DHCP support
974		CONFIG_CMD_DIAG		* Diagnostics
975		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
976		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
977		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
978		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
979		CONFIG_CMD_DTT		* Digital Therm and Thermostat
980		CONFIG_CMD_ECHO		  echo arguments
981		CONFIG_CMD_EDITENV	  edit env variable
982		CONFIG_CMD_EEPROM	* EEPROM read/write support
983		CONFIG_CMD_ELF		* bootelf, bootvx
984		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
985		CONFIG_CMD_ENV_FLAGS	* display details about env flags
986		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
987		CONFIG_CMD_EXPORTENV	* export the environment
988		CONFIG_CMD_EXT2		* ext2 command support
989		CONFIG_CMD_EXT4		* ext4 command support
990		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
991					  that work for multiple fs types
992		CONFIG_CMD_SAVEENV	  saveenv
993		CONFIG_CMD_FDC		* Floppy Disk Support
994		CONFIG_CMD_FAT		* FAT command support
995		CONFIG_CMD_FLASH	  flinfo, erase, protect
996		CONFIG_CMD_FPGA		  FPGA device initialization support
997		CONFIG_CMD_FUSE		* Device fuse support
998		CONFIG_CMD_GETTIME	* Get time since boot
999		CONFIG_CMD_GO		* the 'go' command (exec code)
1000		CONFIG_CMD_GREPENV	* search environment
1001		CONFIG_CMD_HASH		* calculate hash / digest
1002		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
1003		CONFIG_CMD_I2C		* I2C serial bus support
1004		CONFIG_CMD_IDE		* IDE harddisk support
1005		CONFIG_CMD_IMI		  iminfo
1006		CONFIG_CMD_IMLS		  List all images found in NOR flash
1007		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
1008		CONFIG_CMD_IMMAP	* IMMR dump support
1009		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
1010		CONFIG_CMD_IMPORTENV	* import an environment
1011		CONFIG_CMD_INI		* import data from an ini file into the env
1012		CONFIG_CMD_IRQ		* irqinfo
1013		CONFIG_CMD_ITEST	  Integer/string test of 2 values
1014		CONFIG_CMD_JFFS2	* JFFS2 Support
1015		CONFIG_CMD_KGDB		* kgdb
1016		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
1017		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
1018					  (169.254.*.*)
1019		CONFIG_CMD_LOADB	  loadb
1020		CONFIG_CMD_LOADS	  loads
1021		CONFIG_CMD_MD5SUM	* print md5 message digest
1022					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
1023		CONFIG_CMD_MEMINFO	* Display detailed memory information
1024		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
1025					  loop, loopw
1026		CONFIG_CMD_MEMTEST	* mtest
1027		CONFIG_CMD_MISC		  Misc functions like sleep etc
1028		CONFIG_CMD_MMC		* MMC memory mapped support
1029		CONFIG_CMD_MII		* MII utility commands
1030		CONFIG_CMD_MTDPARTS	* MTD partition support
1031		CONFIG_CMD_NAND		* NAND support
1032		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
1033		CONFIG_CMD_NFS		  NFS support
1034		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
1035		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
1036		CONFIG_CMD_PCI		* pciinfo
1037		CONFIG_CMD_PCMCIA		* PCMCIA support
1038		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
1039					  host
1040		CONFIG_CMD_PORTIO	* Port I/O
1041		CONFIG_CMD_READ		* Read raw data from partition
1042		CONFIG_CMD_REGINFO	* Register dump
1043		CONFIG_CMD_RUN		  run command in env variable
1044		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
1045		CONFIG_CMD_SAVES	* save S record dump
1046		CONFIG_CMD_SCSI		* SCSI Support
1047		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1048					  (requires CONFIG_CMD_I2C)
1049		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1050					  (4xx only)
1051		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1052		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1053					  (requires CONFIG_CMD_MEMORY)
1054		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1055		CONFIG_CMD_SOURCE	  "source" command Support
1056		CONFIG_CMD_SPI		* SPI serial bus support
1057		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1058		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1059		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1060		CONFIG_CMD_TIMER	* access to the system tick timer
1061		CONFIG_CMD_USB		* USB support
1062		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1063		CONFIG_CMD_MFSL		* Microblaze FSL support
1064		CONFIG_CMD_XIMG		  Load part of Multi Image
1065		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1066
1067		EXAMPLE: If you want all functions except of network
1068		support you can write:
1069
1070		#include "config_cmd_all.h"
1071		#undef CONFIG_CMD_NET
1072
1073	Other Commands:
1074		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1075
1076	Note:	Don't enable the "icache" and "dcache" commands
1077		(configuration option CONFIG_CMD_CACHE) unless you know
1078		what you (and your U-Boot users) are doing. Data
1079		cache cannot be enabled on systems like the 8xx or
1080		8260 (where accesses to the IMMR region must be
1081		uncached), and it cannot be disabled on all other
1082		systems where we (mis-) use the data cache to hold an
1083		initial stack and some data.
1084
1085
1086		XXX - this list needs to get updated!
1087
1088- Regular expression support:
1089		CONFIG_REGEX
1090		If this variable is defined, U-Boot is linked against
1091		the SLRE (Super Light Regular Expression) library,
1092		which adds regex support to some commands, as for
1093		example "env grep" and "setexpr".
1094
1095- Device tree:
1096		CONFIG_OF_CONTROL
1097		If this variable is defined, U-Boot will use a device tree
1098		to configure its devices, instead of relying on statically
1099		compiled #defines in the board file. This option is
1100		experimental and only available on a few boards. The device
1101		tree is available in the global data as gd->fdt_blob.
1102
1103		U-Boot needs to get its device tree from somewhere. This can
1104		be done using one of the two options below:
1105
1106		CONFIG_OF_EMBED
1107		If this variable is defined, U-Boot will embed a device tree
1108		binary in its image. This device tree file should be in the
1109		board directory and called <soc>-<board>.dts. The binary file
1110		is then picked up in board_init_f() and made available through
1111		the global data structure as gd->blob.
1112
1113		CONFIG_OF_SEPARATE
1114		If this variable is defined, U-Boot will build a device tree
1115		binary. It will be called u-boot.dtb. Architecture-specific
1116		code will locate it at run-time. Generally this works by:
1117
1118			cat u-boot.bin u-boot.dtb >image.bin
1119
1120		and in fact, U-Boot does this for you, creating a file called
1121		u-boot-dtb.bin which is useful in the common case. You can
1122		still use the individual files if you need something more
1123		exotic.
1124
1125- Watchdog:
1126		CONFIG_WATCHDOG
1127		If this variable is defined, it enables watchdog
1128		support for the SoC. There must be support in the SoC
1129		specific code for a watchdog. For the 8xx and 8260
1130		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1131		register.  When supported for a specific SoC is
1132		available, then no further board specific code should
1133		be needed to use it.
1134
1135		CONFIG_HW_WATCHDOG
1136		When using a watchdog circuitry external to the used
1137		SoC, then define this variable and provide board
1138		specific code for the "hw_watchdog_reset" function.
1139
1140- U-Boot Version:
1141		CONFIG_VERSION_VARIABLE
1142		If this variable is defined, an environment variable
1143		named "ver" is created by U-Boot showing the U-Boot
1144		version as printed by the "version" command.
1145		Any change to this variable will be reverted at the
1146		next reset.
1147
1148- Real-Time Clock:
1149
1150		When CONFIG_CMD_DATE is selected, the type of the RTC
1151		has to be selected, too. Define exactly one of the
1152		following options:
1153
1154		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1155		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1156		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1157		CONFIG_RTC_MC146818	- use MC146818 RTC
1158		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1159		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1160		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1161		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1162		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1163		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1164		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1165		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1166		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1167					  RV3029 RTC.
1168
1169		Note that if the RTC uses I2C, then the I2C interface
1170		must also be configured. See I2C Support, below.
1171
1172- GPIO Support:
1173		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1174
1175		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1176		chip-ngpio pairs that tell the PCA953X driver the number of
1177		pins supported by a particular chip.
1178
1179		Note that if the GPIO device uses I2C, then the I2C interface
1180		must also be configured. See I2C Support, below.
1181
1182- I/O tracing:
1183		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1184		accesses and can checksum them or write a list of them out
1185		to memory. See the 'iotrace' command for details. This is
1186		useful for testing device drivers since it can confirm that
1187		the driver behaves the same way before and after a code
1188		change. Currently this is supported on sandbox and arm. To
1189		add support for your architecture, add '#include <iotrace.h>'
1190		to the bottom of arch/<arch>/include/asm/io.h and test.
1191
1192		Example output from the 'iotrace stats' command is below.
1193		Note that if the trace buffer is exhausted, the checksum will
1194		still continue to operate.
1195
1196			iotrace is enabled
1197			Start:  10000000	(buffer start address)
1198			Size:   00010000	(buffer size)
1199			Offset: 00000120	(current buffer offset)
1200			Output: 10000120	(start + offset)
1201			Count:  00000018	(number of trace records)
1202			CRC32:  9526fb66	(CRC32 of all trace records)
1203
1204- Timestamp Support:
1205
1206		When CONFIG_TIMESTAMP is selected, the timestamp
1207		(date and time) of an image is printed by image
1208		commands like bootm or iminfo. This option is
1209		automatically enabled when you select CONFIG_CMD_DATE .
1210
1211- Partition Labels (disklabels) Supported:
1212		Zero or more of the following:
1213		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1214		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1215				       Intel architecture, USB sticks, etc.
1216		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1217		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1218				       bootloader.  Note 2TB partition limit; see
1219				       disk/part_efi.c
1220		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1221
1222		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1223		CONFIG_CMD_SCSI) you must configure support for at
1224		least one non-MTD partition type as well.
1225
1226- IDE Reset method:
1227		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1228		board configurations files but used nowhere!
1229
1230		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1231		be performed by calling the function
1232			ide_set_reset(int reset)
1233		which has to be defined in a board specific file
1234
1235- ATAPI Support:
1236		CONFIG_ATAPI
1237
1238		Set this to enable ATAPI support.
1239
1240- LBA48 Support
1241		CONFIG_LBA48
1242
1243		Set this to enable support for disks larger than 137GB
1244		Also look at CONFIG_SYS_64BIT_LBA.
1245		Whithout these , LBA48 support uses 32bit variables and will 'only'
1246		support disks up to 2.1TB.
1247
1248		CONFIG_SYS_64BIT_LBA:
1249			When enabled, makes the IDE subsystem use 64bit sector addresses.
1250			Default is 32bit.
1251
1252- SCSI Support:
1253		At the moment only there is only support for the
1254		SYM53C8XX SCSI controller; define
1255		CONFIG_SCSI_SYM53C8XX to enable it.
1256
1257		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1258		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1259		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1260		maximum numbers of LUNs, SCSI ID's and target
1261		devices.
1262		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1263
1264		The environment variable 'scsidevs' is set to the number of
1265		SCSI devices found during the last scan.
1266
1267- NETWORK Support (PCI):
1268		CONFIG_E1000
1269		Support for Intel 8254x/8257x gigabit chips.
1270
1271		CONFIG_E1000_SPI
1272		Utility code for direct access to the SPI bus on Intel 8257x.
1273		This does not do anything useful unless you set at least one
1274		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1275
1276		CONFIG_E1000_SPI_GENERIC
1277		Allow generic access to the SPI bus on the Intel 8257x, for
1278		example with the "sspi" command.
1279
1280		CONFIG_CMD_E1000
1281		Management command for E1000 devices.  When used on devices
1282		with SPI support you can reprogram the EEPROM from U-Boot.
1283
1284		CONFIG_E1000_FALLBACK_MAC
1285		default MAC for empty EEPROM after production.
1286
1287		CONFIG_EEPRO100
1288		Support for Intel 82557/82559/82559ER chips.
1289		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1290		write routine for first time initialisation.
1291
1292		CONFIG_TULIP
1293		Support for Digital 2114x chips.
1294		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1295		modem chip initialisation (KS8761/QS6611).
1296
1297		CONFIG_NATSEMI
1298		Support for National dp83815 chips.
1299
1300		CONFIG_NS8382X
1301		Support for National dp8382[01] gigabit chips.
1302
1303- NETWORK Support (other):
1304
1305		CONFIG_DRIVER_AT91EMAC
1306		Support for AT91RM9200 EMAC.
1307
1308			CONFIG_RMII
1309			Define this to use reduced MII inteface
1310
1311			CONFIG_DRIVER_AT91EMAC_QUIET
1312			If this defined, the driver is quiet.
1313			The driver doen't show link status messages.
1314
1315		CONFIG_CALXEDA_XGMAC
1316		Support for the Calxeda XGMAC device
1317
1318		CONFIG_LAN91C96
1319		Support for SMSC's LAN91C96 chips.
1320
1321			CONFIG_LAN91C96_BASE
1322			Define this to hold the physical address
1323			of the LAN91C96's I/O space
1324
1325			CONFIG_LAN91C96_USE_32_BIT
1326			Define this to enable 32 bit addressing
1327
1328		CONFIG_SMC91111
1329		Support for SMSC's LAN91C111 chip
1330
1331			CONFIG_SMC91111_BASE
1332			Define this to hold the physical address
1333			of the device (I/O space)
1334
1335			CONFIG_SMC_USE_32_BIT
1336			Define this if data bus is 32 bits
1337
1338			CONFIG_SMC_USE_IOFUNCS
1339			Define this to use i/o functions instead of macros
1340			(some hardware wont work with macros)
1341
1342		CONFIG_DRIVER_TI_EMAC
1343		Support for davinci emac
1344
1345			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1346			Define this if you have more then 3 PHYs.
1347
1348		CONFIG_FTGMAC100
1349		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1350
1351			CONFIG_FTGMAC100_EGIGA
1352			Define this to use GE link update with gigabit PHY.
1353			Define this if FTGMAC100 is connected to gigabit PHY.
1354			If your system has 10/100 PHY only, it might not occur
1355			wrong behavior. Because PHY usually return timeout or
1356			useless data when polling gigabit status and gigabit
1357			control registers. This behavior won't affect the
1358			correctnessof 10/100 link speed update.
1359
1360		CONFIG_SMC911X
1361		Support for SMSC's LAN911x and LAN921x chips
1362
1363			CONFIG_SMC911X_BASE
1364			Define this to hold the physical address
1365			of the device (I/O space)
1366
1367			CONFIG_SMC911X_32_BIT
1368			Define this if data bus is 32 bits
1369
1370			CONFIG_SMC911X_16_BIT
1371			Define this if data bus is 16 bits. If your processor
1372			automatically converts one 32 bit word to two 16 bit
1373			words you may also try CONFIG_SMC911X_32_BIT.
1374
1375		CONFIG_SH_ETHER
1376		Support for Renesas on-chip Ethernet controller
1377
1378			CONFIG_SH_ETHER_USE_PORT
1379			Define the number of ports to be used
1380
1381			CONFIG_SH_ETHER_PHY_ADDR
1382			Define the ETH PHY's address
1383
1384			CONFIG_SH_ETHER_CACHE_WRITEBACK
1385			If this option is set, the driver enables cache flush.
1386
1387- PWM Support:
1388		CONFIG_PWM_IMX
1389		Support for PWM modul on the imx6.
1390
1391- TPM Support:
1392		CONFIG_TPM
1393		Support TPM devices.
1394
1395		CONFIG_TPM_TIS_I2C
1396		Support for i2c bus TPM devices. Only one device
1397		per system is supported at this time.
1398
1399			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1400			Define the the i2c bus number for the TPM device
1401
1402			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1403			Define the TPM's address on the i2c bus
1404
1405			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1406			Define the burst count bytes upper limit
1407
1408		CONFIG_TPM_ATMEL_TWI
1409		Support for Atmel TWI TPM device. Requires I2C support.
1410
1411		CONFIG_TPM_TIS_LPC
1412		Support for generic parallel port TPM devices. Only one device
1413		per system is supported at this time.
1414
1415			CONFIG_TPM_TIS_BASE_ADDRESS
1416			Base address where the generic TPM device is mapped
1417			to. Contemporary x86 systems usually map it at
1418			0xfed40000.
1419
1420		CONFIG_CMD_TPM
1421		Add tpm monitor functions.
1422		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1423		provides monitor access to authorized functions.
1424
1425		CONFIG_TPM
1426		Define this to enable the TPM support library which provides
1427		functional interfaces to some TPM commands.
1428		Requires support for a TPM device.
1429
1430		CONFIG_TPM_AUTH_SESSIONS
1431		Define this to enable authorized functions in the TPM library.
1432		Requires CONFIG_TPM and CONFIG_SHA1.
1433
1434- USB Support:
1435		At the moment only the UHCI host controller is
1436		supported (PIP405, MIP405, MPC5200); define
1437		CONFIG_USB_UHCI to enable it.
1438		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1439		and define CONFIG_USB_STORAGE to enable the USB
1440		storage devices.
1441		Note:
1442		Supported are USB Keyboards and USB Floppy drives
1443		(TEAC FD-05PUB).
1444		MPC5200 USB requires additional defines:
1445			CONFIG_USB_CLOCK
1446				for 528 MHz Clock: 0x0001bbbb
1447			CONFIG_PSC3_USB
1448				for USB on PSC3
1449			CONFIG_USB_CONFIG
1450				for differential drivers: 0x00001000
1451				for single ended drivers: 0x00005000
1452				for differential drivers on PSC3: 0x00000100
1453				for single ended drivers on PSC3: 0x00004100
1454			CONFIG_SYS_USB_EVENT_POLL
1455				May be defined to allow interrupt polling
1456				instead of using asynchronous interrupts
1457
1458		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1459		txfilltuning field in the EHCI controller on reset.
1460
1461		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1462		HW module registers.
1463
1464- USB Device:
1465		Define the below if you wish to use the USB console.
1466		Once firmware is rebuilt from a serial console issue the
1467		command "setenv stdin usbtty; setenv stdout usbtty" and
1468		attach your USB cable. The Unix command "dmesg" should print
1469		it has found a new device. The environment variable usbtty
1470		can be set to gserial or cdc_acm to enable your device to
1471		appear to a USB host as a Linux gserial device or a
1472		Common Device Class Abstract Control Model serial device.
1473		If you select usbtty = gserial you should be able to enumerate
1474		a Linux host by
1475		# modprobe usbserial vendor=0xVendorID product=0xProductID
1476		else if using cdc_acm, simply setting the environment
1477		variable usbtty to be cdc_acm should suffice. The following
1478		might be defined in YourBoardName.h
1479
1480			CONFIG_USB_DEVICE
1481			Define this to build a UDC device
1482
1483			CONFIG_USB_TTY
1484			Define this to have a tty type of device available to
1485			talk to the UDC device
1486
1487			CONFIG_USBD_HS
1488			Define this to enable the high speed support for usb
1489			device and usbtty. If this feature is enabled, a routine
1490			int is_usbd_high_speed(void)
1491			also needs to be defined by the driver to dynamically poll
1492			whether the enumeration has succeded at high speed or full
1493			speed.
1494
1495			CONFIG_SYS_CONSOLE_IS_IN_ENV
1496			Define this if you want stdin, stdout &/or stderr to
1497			be set to usbtty.
1498
1499			mpc8xx:
1500				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1501				Derive USB clock from external clock "blah"
1502				- CONFIG_SYS_USB_EXTC_CLK 0x02
1503
1504				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1505				Derive USB clock from brgclk
1506				- CONFIG_SYS_USB_BRG_CLK 0x04
1507
1508		If you have a USB-IF assigned VendorID then you may wish to
1509		define your own vendor specific values either in BoardName.h
1510		or directly in usbd_vendor_info.h. If you don't define
1511		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1512		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1513		should pretend to be a Linux device to it's target host.
1514
1515			CONFIG_USBD_MANUFACTURER
1516			Define this string as the name of your company for
1517			- CONFIG_USBD_MANUFACTURER "my company"
1518
1519			CONFIG_USBD_PRODUCT_NAME
1520			Define this string as the name of your product
1521			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1522
1523			CONFIG_USBD_VENDORID
1524			Define this as your assigned Vendor ID from the USB
1525			Implementors Forum. This *must* be a genuine Vendor ID
1526			to avoid polluting the USB namespace.
1527			- CONFIG_USBD_VENDORID 0xFFFF
1528
1529			CONFIG_USBD_PRODUCTID
1530			Define this as the unique Product ID
1531			for your device
1532			- CONFIG_USBD_PRODUCTID 0xFFFF
1533
1534- ULPI Layer Support:
1535		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1536		the generic ULPI layer. The generic layer accesses the ULPI PHY
1537		via the platform viewport, so you need both the genric layer and
1538		the viewport enabled. Currently only Chipidea/ARC based
1539		viewport is supported.
1540		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1541		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1542		If your ULPI phy needs a different reference clock than the
1543		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1544		the appropriate value in Hz.
1545
1546- MMC Support:
1547		The MMC controller on the Intel PXA is supported. To
1548		enable this define CONFIG_MMC. The MMC can be
1549		accessed from the boot prompt by mapping the device
1550		to physical memory similar to flash. Command line is
1551		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1552		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1553
1554		CONFIG_SH_MMCIF
1555		Support for Renesas on-chip MMCIF controller
1556
1557			CONFIG_SH_MMCIF_ADDR
1558			Define the base address of MMCIF registers
1559
1560			CONFIG_SH_MMCIF_CLK
1561			Define the clock frequency for MMCIF
1562
1563		CONFIG_GENERIC_MMC
1564		Enable the generic MMC driver
1565
1566		CONFIG_SUPPORT_EMMC_BOOT
1567		Enable some additional features of the eMMC boot partitions.
1568
1569		CONFIG_SUPPORT_EMMC_RPMB
1570		Enable the commands for reading, writing and programming the
1571		key for the Replay Protection Memory Block partition in eMMC.
1572
1573- USB Device Firmware Update (DFU) class support:
1574		CONFIG_DFU_FUNCTION
1575		This enables the USB portion of the DFU USB class
1576
1577		CONFIG_CMD_DFU
1578		This enables the command "dfu" which is used to have
1579		U-Boot create a DFU class device via USB.  This command
1580		requires that the "dfu_alt_info" environment variable be
1581		set and define the alt settings to expose to the host.
1582
1583		CONFIG_DFU_MMC
1584		This enables support for exposing (e)MMC devices via DFU.
1585
1586		CONFIG_DFU_NAND
1587		This enables support for exposing NAND devices via DFU.
1588
1589		CONFIG_DFU_RAM
1590		This enables support for exposing RAM via DFU.
1591		Note: DFU spec refer to non-volatile memory usage, but
1592		allow usages beyond the scope of spec - here RAM usage,
1593		one that would help mostly the developer.
1594
1595		CONFIG_SYS_DFU_DATA_BUF_SIZE
1596		Dfu transfer uses a buffer before writing data to the
1597		raw storage device. Make the size (in bytes) of this buffer
1598		configurable. The size of this buffer is also configurable
1599		through the "dfu_bufsiz" environment variable.
1600
1601		CONFIG_SYS_DFU_MAX_FILE_SIZE
1602		When updating files rather than the raw storage device,
1603		we use a static buffer to copy the file into and then write
1604		the buffer once we've been given the whole file.  Define
1605		this to the maximum filesize (in bytes) for the buffer.
1606		Default is 4 MiB if undefined.
1607
1608		DFU_DEFAULT_POLL_TIMEOUT
1609		Poll timeout [ms], is the timeout a device can send to the
1610		host. The host must wait for this timeout before sending
1611		a subsequent DFU_GET_STATUS request to the device.
1612
1613		DFU_MANIFEST_POLL_TIMEOUT
1614		Poll timeout [ms], which the device sends to the host when
1615		entering dfuMANIFEST state. Host waits this timeout, before
1616		sending again an USB request to the device.
1617
1618- USB Device Android Fastboot support:
1619		CONFIG_CMD_FASTBOOT
1620		This enables the command "fastboot" which enables the Android
1621		fastboot mode for the platform's USB device. Fastboot is a USB
1622		protocol for downloading images, flashing and device control
1623		used on Android devices.
1624		See doc/README.android-fastboot for more information.
1625
1626		CONFIG_ANDROID_BOOT_IMAGE
1627		This enables support for booting images which use the Android
1628		image format header.
1629
1630		CONFIG_USB_FASTBOOT_BUF_ADDR
1631		The fastboot protocol requires a large memory buffer for
1632		downloads. Define this to the starting RAM address to use for
1633		downloaded images.
1634
1635		CONFIG_USB_FASTBOOT_BUF_SIZE
1636		The fastboot protocol requires a large memory buffer for
1637		downloads. This buffer should be as large as possible for a
1638		platform. Define this to the size available RAM for fastboot.
1639
1640		CONFIG_FASTBOOT_FLASH
1641		The fastboot protocol includes a "flash" command for writing
1642		the downloaded image to a non-volatile storage device. Define
1643		this to enable the "fastboot flash" command.
1644
1645		CONFIG_FASTBOOT_FLASH_MMC_DEV
1646		The fastboot "flash" command requires additional information
1647		regarding the non-volatile storage device. Define this to
1648		the eMMC device that fastboot should use to store the image.
1649
1650- Journaling Flash filesystem support:
1651		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1652		CONFIG_JFFS2_NAND_DEV
1653		Define these for a default partition on a NAND device
1654
1655		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1656		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1657		Define these for a default partition on a NOR device
1658
1659		CONFIG_SYS_JFFS_CUSTOM_PART
1660		Define this to create an own partition. You have to provide a
1661		function struct part_info* jffs2_part_info(int part_num)
1662
1663		If you define only one JFFS2 partition you may also want to
1664		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1665		to disable the command chpart. This is the default when you
1666		have not defined a custom partition
1667
1668- FAT(File Allocation Table) filesystem write function support:
1669		CONFIG_FAT_WRITE
1670
1671		Define this to enable support for saving memory data as a
1672		file in FAT formatted partition.
1673
1674		This will also enable the command "fatwrite" enabling the
1675		user to write files to FAT.
1676
1677CBFS (Coreboot Filesystem) support
1678		CONFIG_CMD_CBFS
1679
1680		Define this to enable support for reading from a Coreboot
1681		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1682		and cbfsload.
1683
1684- FAT(File Allocation Table) filesystem cluster size:
1685		CONFIG_FS_FAT_MAX_CLUSTSIZE
1686
1687		Define the max cluster size for fat operations else
1688		a default value of 65536 will be defined.
1689
1690- Keyboard Support:
1691		CONFIG_ISA_KEYBOARD
1692
1693		Define this to enable standard (PC-Style) keyboard
1694		support
1695
1696		CONFIG_I8042_KBD
1697		Standard PC keyboard driver with US (is default) and
1698		GERMAN key layout (switch via environment 'keymap=de') support.
1699		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1700		for cfb_console. Supports cursor blinking.
1701
1702		CONFIG_CROS_EC_KEYB
1703		Enables a Chrome OS keyboard using the CROS_EC interface.
1704		This uses CROS_EC to communicate with a second microcontroller
1705		which provides key scans on request.
1706
1707- Video support:
1708		CONFIG_VIDEO
1709
1710		Define this to enable video support (for output to
1711		video).
1712
1713		CONFIG_VIDEO_CT69000
1714
1715		Enable Chips & Technologies 69000 Video chip
1716
1717		CONFIG_VIDEO_SMI_LYNXEM
1718		Enable Silicon Motion SMI 712/710/810 Video chip. The
1719		video output is selected via environment 'videoout'
1720		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1721		assumed.
1722
1723		For the CT69000 and SMI_LYNXEM drivers, videomode is
1724		selected via environment 'videomode'. Two different ways
1725		are possible:
1726		- "videomode=num"   'num' is a standard LiLo mode numbers.
1727		Following standard modes are supported	(* is default):
1728
1729		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1730		-------------+---------------------------------------------
1731		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1732		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1733		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1734		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1735		-------------+---------------------------------------------
1736		(i.e. setenv videomode 317; saveenv; reset;)
1737
1738		- "videomode=bootargs" all the video parameters are parsed
1739		from the bootargs. (See drivers/video/videomodes.c)
1740
1741
1742		CONFIG_VIDEO_SED13806
1743		Enable Epson SED13806 driver. This driver supports 8bpp
1744		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1745		or CONFIG_VIDEO_SED13806_16BPP
1746
1747		CONFIG_FSL_DIU_FB
1748		Enable the Freescale DIU video driver.	Reference boards for
1749		SOCs that have a DIU should define this macro to enable DIU
1750		support, and should also define these other macros:
1751
1752			CONFIG_SYS_DIU_ADDR
1753			CONFIG_VIDEO
1754			CONFIG_CMD_BMP
1755			CONFIG_CFB_CONSOLE
1756			CONFIG_VIDEO_SW_CURSOR
1757			CONFIG_VGA_AS_SINGLE_DEVICE
1758			CONFIG_VIDEO_LOGO
1759			CONFIG_VIDEO_BMP_LOGO
1760
1761		The DIU driver will look for the 'video-mode' environment
1762		variable, and if defined, enable the DIU as a console during
1763		boot.  See the documentation file README.video for a
1764		description of this variable.
1765
1766		CONFIG_VIDEO_VGA
1767
1768		Enable the VGA video / BIOS for x86. The alternative if you
1769		are using coreboot is to use the coreboot frame buffer
1770		driver.
1771
1772
1773- Keyboard Support:
1774		CONFIG_KEYBOARD
1775
1776		Define this to enable a custom keyboard support.
1777		This simply calls drv_keyboard_init() which must be
1778		defined in your board-specific files.
1779		The only board using this so far is RBC823.
1780
1781- LCD Support:	CONFIG_LCD
1782
1783		Define this to enable LCD support (for output to LCD
1784		display); also select one of the supported displays
1785		by defining one of these:
1786
1787		CONFIG_ATMEL_LCD:
1788
1789			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1790
1791		CONFIG_NEC_NL6448AC33:
1792
1793			NEC NL6448AC33-18. Active, color, single scan.
1794
1795		CONFIG_NEC_NL6448BC20
1796
1797			NEC NL6448BC20-08. 6.5", 640x480.
1798			Active, color, single scan.
1799
1800		CONFIG_NEC_NL6448BC33_54
1801
1802			NEC NL6448BC33-54. 10.4", 640x480.
1803			Active, color, single scan.
1804
1805		CONFIG_SHARP_16x9
1806
1807			Sharp 320x240. Active, color, single scan.
1808			It isn't 16x9, and I am not sure what it is.
1809
1810		CONFIG_SHARP_LQ64D341
1811
1812			Sharp LQ64D341 display, 640x480.
1813			Active, color, single scan.
1814
1815		CONFIG_HLD1045
1816
1817			HLD1045 display, 640x480.
1818			Active, color, single scan.
1819
1820		CONFIG_OPTREX_BW
1821
1822			Optrex	 CBL50840-2 NF-FW 99 22 M5
1823			or
1824			Hitachi	 LMG6912RPFC-00T
1825			or
1826			Hitachi	 SP14Q002
1827
1828			320x240. Black & white.
1829
1830		Normally display is black on white background; define
1831		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1832
1833		CONFIG_LCD_ALIGNMENT
1834
1835		Normally the LCD is page-aligned (tyically 4KB). If this is
1836		defined then the LCD will be aligned to this value instead.
1837		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1838		here, since it is cheaper to change data cache settings on
1839		a per-section basis.
1840
1841		CONFIG_CONSOLE_SCROLL_LINES
1842
1843		When the console need to be scrolled, this is the number of
1844		lines to scroll by. It defaults to 1. Increasing this makes
1845		the console jump but can help speed up operation when scrolling
1846		is slow.
1847
1848		CONFIG_LCD_BMP_RLE8
1849
1850		Support drawing of RLE8-compressed bitmaps on the LCD.
1851
1852		CONFIG_I2C_EDID
1853
1854		Enables an 'i2c edid' command which can read EDID
1855		information over I2C from an attached LCD display.
1856
1857- Splash Screen Support: CONFIG_SPLASH_SCREEN
1858
1859		If this option is set, the environment is checked for
1860		a variable "splashimage". If found, the usual display
1861		of logo, copyright and system information on the LCD
1862		is suppressed and the BMP image at the address
1863		specified in "splashimage" is loaded instead. The
1864		console is redirected to the "nulldev", too. This
1865		allows for a "silent" boot where a splash screen is
1866		loaded very quickly after power-on.
1867
1868		CONFIG_SPLASHIMAGE_GUARD
1869
1870		If this option is set, then U-Boot will prevent the environment
1871		variable "splashimage" from being set to a problematic address
1872		(see README.displaying-bmps).
1873		This option is useful for targets where, due to alignment
1874		restrictions, an improperly aligned BMP image will cause a data
1875		abort. If you think you will not have problems with unaligned
1876		accesses (for example because your toolchain prevents them)
1877		there is no need to set this option.
1878
1879		CONFIG_SPLASH_SCREEN_ALIGN
1880
1881		If this option is set the splash image can be freely positioned
1882		on the screen. Environment variable "splashpos" specifies the
1883		position as "x,y". If a positive number is given it is used as
1884		number of pixel from left/top. If a negative number is given it
1885		is used as number of pixel from right/bottom. You can also
1886		specify 'm' for centering the image.
1887
1888		Example:
1889		setenv splashpos m,m
1890			=> image at center of screen
1891
1892		setenv splashpos 30,20
1893			=> image at x = 30 and y = 20
1894
1895		setenv splashpos -10,m
1896			=> vertically centered image
1897			   at x = dspWidth - bmpWidth - 9
1898
1899- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1900
1901		If this option is set, additionally to standard BMP
1902		images, gzipped BMP images can be displayed via the
1903		splashscreen support or the bmp command.
1904
1905- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1906
1907		If this option is set, 8-bit RLE compressed BMP images
1908		can be displayed via the splashscreen support or the
1909		bmp command.
1910
1911- Do compresssing for memory range:
1912		CONFIG_CMD_ZIP
1913
1914		If this option is set, it would use zlib deflate method
1915		to compress the specified memory at its best effort.
1916
1917- Compression support:
1918		CONFIG_GZIP
1919
1920		Enabled by default to support gzip compressed images.
1921
1922		CONFIG_BZIP2
1923
1924		If this option is set, support for bzip2 compressed
1925		images is included. If not, only uncompressed and gzip
1926		compressed images are supported.
1927
1928		NOTE: the bzip2 algorithm requires a lot of RAM, so
1929		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1930		be at least 4MB.
1931
1932		CONFIG_LZMA
1933
1934		If this option is set, support for lzma compressed
1935		images is included.
1936
1937		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1938		requires an amount of dynamic memory that is given by the
1939		formula:
1940
1941			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1942
1943		Where lc and lp stand for, respectively, Literal context bits
1944		and Literal pos bits.
1945
1946		This value is upper-bounded by 14MB in the worst case. Anyway,
1947		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1948		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1949		a very small buffer.
1950
1951		Use the lzmainfo tool to determinate the lc and lp values and
1952		then calculate the amount of needed dynamic memory (ensuring
1953		the appropriate CONFIG_SYS_MALLOC_LEN value).
1954
1955		CONFIG_LZO
1956
1957		If this option is set, support for LZO compressed images
1958		is included.
1959
1960- MII/PHY support:
1961		CONFIG_PHY_ADDR
1962
1963		The address of PHY on MII bus.
1964
1965		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1966
1967		The clock frequency of the MII bus
1968
1969		CONFIG_PHY_GIGE
1970
1971		If this option is set, support for speed/duplex
1972		detection of gigabit PHY is included.
1973
1974		CONFIG_PHY_RESET_DELAY
1975
1976		Some PHY like Intel LXT971A need extra delay after
1977		reset before any MII register access is possible.
1978		For such PHY, set this option to the usec delay
1979		required. (minimum 300usec for LXT971A)
1980
1981		CONFIG_PHY_CMD_DELAY (ppc4xx)
1982
1983		Some PHY like Intel LXT971A need extra delay after
1984		command issued before MII status register can be read
1985
1986- Ethernet address:
1987		CONFIG_ETHADDR
1988		CONFIG_ETH1ADDR
1989		CONFIG_ETH2ADDR
1990		CONFIG_ETH3ADDR
1991		CONFIG_ETH4ADDR
1992		CONFIG_ETH5ADDR
1993
1994		Define a default value for Ethernet address to use
1995		for the respective Ethernet interface, in case this
1996		is not determined automatically.
1997
1998- IP address:
1999		CONFIG_IPADDR
2000
2001		Define a default value for the IP address to use for
2002		the default Ethernet interface, in case this is not
2003		determined through e.g. bootp.
2004		(Environment variable "ipaddr")
2005
2006- Server IP address:
2007		CONFIG_SERVERIP
2008
2009		Defines a default value for the IP address of a TFTP
2010		server to contact when using the "tftboot" command.
2011		(Environment variable "serverip")
2012
2013		CONFIG_KEEP_SERVERADDR
2014
2015		Keeps the server's MAC address, in the env 'serveraddr'
2016		for passing to bootargs (like Linux's netconsole option)
2017
2018- Gateway IP address:
2019		CONFIG_GATEWAYIP
2020
2021		Defines a default value for the IP address of the
2022		default router where packets to other networks are
2023		sent to.
2024		(Environment variable "gatewayip")
2025
2026- Subnet mask:
2027		CONFIG_NETMASK
2028
2029		Defines a default value for the subnet mask (or
2030		routing prefix) which is used to determine if an IP
2031		address belongs to the local subnet or needs to be
2032		forwarded through a router.
2033		(Environment variable "netmask")
2034
2035- Multicast TFTP Mode:
2036		CONFIG_MCAST_TFTP
2037
2038		Defines whether you want to support multicast TFTP as per
2039		rfc-2090; for example to work with atftp.  Lets lots of targets
2040		tftp down the same boot image concurrently.  Note: the Ethernet
2041		driver in use must provide a function: mcast() to join/leave a
2042		multicast group.
2043
2044- BOOTP Recovery Mode:
2045		CONFIG_BOOTP_RANDOM_DELAY
2046
2047		If you have many targets in a network that try to
2048		boot using BOOTP, you may want to avoid that all
2049		systems send out BOOTP requests at precisely the same
2050		moment (which would happen for instance at recovery
2051		from a power failure, when all systems will try to
2052		boot, thus flooding the BOOTP server. Defining
2053		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
2054		inserted before sending out BOOTP requests. The
2055		following delays are inserted then:
2056
2057		1st BOOTP request:	delay 0 ... 1 sec
2058		2nd BOOTP request:	delay 0 ... 2 sec
2059		3rd BOOTP request:	delay 0 ... 4 sec
2060		4th and following
2061		BOOTP requests:		delay 0 ... 8 sec
2062
2063		CONFIG_BOOTP_ID_CACHE_SIZE
2064
2065		BOOTP packets are uniquely identified using a 32-bit ID. The
2066		server will copy the ID from client requests to responses and
2067		U-Boot will use this to determine if it is the destination of
2068		an incoming response. Some servers will check that addresses
2069		aren't in use before handing them out (usually using an ARP
2070		ping) and therefore take up to a few hundred milliseconds to
2071		respond. Network congestion may also influence the time it
2072		takes for a response to make it back to the client. If that
2073		time is too long, U-Boot will retransmit requests. In order
2074		to allow earlier responses to still be accepted after these
2075		retransmissions, U-Boot's BOOTP client keeps a small cache of
2076		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
2077		cache. The default is to keep IDs for up to four outstanding
2078		requests. Increasing this will allow U-Boot to accept offers
2079		from a BOOTP client in networks with unusually high latency.
2080
2081- DHCP Advanced Options:
2082		You can fine tune the DHCP functionality by defining
2083		CONFIG_BOOTP_* symbols:
2084
2085		CONFIG_BOOTP_SUBNETMASK
2086		CONFIG_BOOTP_GATEWAY
2087		CONFIG_BOOTP_HOSTNAME
2088		CONFIG_BOOTP_NISDOMAIN
2089		CONFIG_BOOTP_BOOTPATH
2090		CONFIG_BOOTP_BOOTFILESIZE
2091		CONFIG_BOOTP_DNS
2092		CONFIG_BOOTP_DNS2
2093		CONFIG_BOOTP_SEND_HOSTNAME
2094		CONFIG_BOOTP_NTPSERVER
2095		CONFIG_BOOTP_TIMEOFFSET
2096		CONFIG_BOOTP_VENDOREX
2097		CONFIG_BOOTP_MAY_FAIL
2098
2099		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
2100		environment variable, not the BOOTP server.
2101
2102		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
2103		after the configured retry count, the call will fail
2104		instead of starting over.  This can be used to fail over
2105		to Link-local IP address configuration if the DHCP server
2106		is not available.
2107
2108		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
2109		serverip from a DHCP server, it is possible that more
2110		than one DNS serverip is offered to the client.
2111		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
2112		serverip will be stored in the additional environment
2113		variable "dnsip2". The first DNS serverip is always
2114		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
2115		is defined.
2116
2117		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2118		to do a dynamic update of a DNS server. To do this, they
2119		need the hostname of the DHCP requester.
2120		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2121		of the "hostname" environment variable is passed as
2122		option 12 to the DHCP server.
2123
2124		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2125
2126		A 32bit value in microseconds for a delay between
2127		receiving a "DHCP Offer" and sending the "DHCP Request".
2128		This fixes a problem with certain DHCP servers that don't
2129		respond 100% of the time to a "DHCP request". E.g. On an
2130		AT91RM9200 processor running at 180MHz, this delay needed
2131		to be *at least* 15,000 usec before a Windows Server 2003
2132		DHCP server would reply 100% of the time. I recommend at
2133		least 50,000 usec to be safe. The alternative is to hope
2134		that one of the retries will be successful but note that
2135		the DHCP timeout and retry process takes a longer than
2136		this delay.
2137
2138 - Link-local IP address negotiation:
2139		Negotiate with other link-local clients on the local network
2140		for an address that doesn't require explicit configuration.
2141		This is especially useful if a DHCP server cannot be guaranteed
2142		to exist in all environments that the device must operate.
2143
2144		See doc/README.link-local for more information.
2145
2146 - CDP Options:
2147		CONFIG_CDP_DEVICE_ID
2148
2149		The device id used in CDP trigger frames.
2150
2151		CONFIG_CDP_DEVICE_ID_PREFIX
2152
2153		A two character string which is prefixed to the MAC address
2154		of the device.
2155
2156		CONFIG_CDP_PORT_ID
2157
2158		A printf format string which contains the ascii name of
2159		the port. Normally is set to "eth%d" which sets
2160		eth0 for the first Ethernet, eth1 for the second etc.
2161
2162		CONFIG_CDP_CAPABILITIES
2163
2164		A 32bit integer which indicates the device capabilities;
2165		0x00000010 for a normal host which does not forwards.
2166
2167		CONFIG_CDP_VERSION
2168
2169		An ascii string containing the version of the software.
2170
2171		CONFIG_CDP_PLATFORM
2172
2173		An ascii string containing the name of the platform.
2174
2175		CONFIG_CDP_TRIGGER
2176
2177		A 32bit integer sent on the trigger.
2178
2179		CONFIG_CDP_POWER_CONSUMPTION
2180
2181		A 16bit integer containing the power consumption of the
2182		device in .1 of milliwatts.
2183
2184		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2185
2186		A byte containing the id of the VLAN.
2187
2188- Status LED:	CONFIG_STATUS_LED
2189
2190		Several configurations allow to display the current
2191		status using a LED. For instance, the LED will blink
2192		fast while running U-Boot code, stop blinking as
2193		soon as a reply to a BOOTP request was received, and
2194		start blinking slow once the Linux kernel is running
2195		(supported by a status LED driver in the Linux
2196		kernel). Defining CONFIG_STATUS_LED enables this
2197		feature in U-Boot.
2198
2199		Additional options:
2200
2201		CONFIG_GPIO_LED
2202		The status LED can be connected to a GPIO pin.
2203		In such cases, the gpio_led driver can be used as a
2204		status LED backend implementation. Define CONFIG_GPIO_LED
2205		to include the gpio_led driver in the U-Boot binary.
2206
2207		CONFIG_GPIO_LED_INVERTED_TABLE
2208		Some GPIO connected LEDs may have inverted polarity in which
2209		case the GPIO high value corresponds to LED off state and
2210		GPIO low value corresponds to LED on state.
2211		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2212		with a list of GPIO LEDs that have inverted polarity.
2213
2214- CAN Support:	CONFIG_CAN_DRIVER
2215
2216		Defining CONFIG_CAN_DRIVER enables CAN driver support
2217		on those systems that support this (optional)
2218		feature, like the TQM8xxL modules.
2219
2220- I2C Support:	CONFIG_SYS_I2C
2221
2222		This enable the NEW i2c subsystem, and will allow you to use
2223		i2c commands at the u-boot command line (as long as you set
2224		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2225		based realtime clock chips or other i2c devices. See
2226		common/cmd_i2c.c for a description of the command line
2227		interface.
2228
2229		ported i2c driver to the new framework:
2230		- drivers/i2c/soft_i2c.c:
2231		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2232		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2233		    for defining speed and slave address
2234		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2235		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2236		    for defining speed and slave address
2237		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2238		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2239		    for defining speed and slave address
2240		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2241		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2242		    for defining speed and slave address
2243
2244		- drivers/i2c/fsl_i2c.c:
2245		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2246		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2247		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2248		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2249		    bus.
2250		  - If your board supports a second fsl i2c bus, define
2251		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2252		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2253		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2254		    second bus.
2255
2256		- drivers/i2c/tegra_i2c.c:
2257		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2258		  - This driver adds 4 i2c buses with a fix speed from
2259		    100000 and the slave addr 0!
2260
2261		- drivers/i2c/ppc4xx_i2c.c
2262		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2263		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2264		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2265
2266		- drivers/i2c/i2c_mxc.c
2267		  - activate this driver with CONFIG_SYS_I2C_MXC
2268		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2269		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2270		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2271		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2272		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2273		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2274		If thoses defines are not set, default value is 100000
2275		for speed, and 0 for slave.
2276
2277		- drivers/i2c/rcar_i2c.c:
2278		  - activate this driver with CONFIG_SYS_I2C_RCAR
2279		  - This driver adds 4 i2c buses
2280
2281		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2282		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2283		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2284		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2285		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2286		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2287		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2288		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2289		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2290
2291		- drivers/i2c/sh_i2c.c:
2292		  - activate this driver with CONFIG_SYS_I2C_SH
2293		  - This driver adds from 2 to 5 i2c buses
2294
2295		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2296		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2297		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2298		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2299		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2300		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2301		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2302		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2303		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2304		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2305		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2306		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2307		  - CONFIF_SYS_I2C_SH_NUM_CONTROLLERS for nummber of i2c buses
2308
2309		- drivers/i2c/omap24xx_i2c.c
2310		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2311		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2312		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2313		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2314		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2315		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2316		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2317		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2318		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2319		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2320		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2321
2322		- drivers/i2c/zynq_i2c.c
2323		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2324		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2325		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2326
2327		- drivers/i2c/s3c24x0_i2c.c:
2328		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2329		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2330		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2331		    with a fix speed from 100000 and the slave addr 0!
2332
2333		- drivers/i2c/ihs_i2c.c
2334		  - activate this driver with CONFIG_SYS_I2C_IHS
2335		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2336		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2337		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2338		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2339		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2340		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2341		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2342		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2343		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2344		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2345		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2346		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2347
2348		additional defines:
2349
2350		CONFIG_SYS_NUM_I2C_BUSES
2351		Hold the number of i2c busses you want to use. If you
2352		don't use/have i2c muxes on your i2c bus, this
2353		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2354		omit this define.
2355
2356		CONFIG_SYS_I2C_DIRECT_BUS
2357		define this, if you don't use i2c muxes on your hardware.
2358		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2359		omit this define.
2360
2361		CONFIG_SYS_I2C_MAX_HOPS
2362		define how many muxes are maximal consecutively connected
2363		on one i2c bus. If you not use i2c muxes, omit this
2364		define.
2365
2366		CONFIG_SYS_I2C_BUSES
2367		hold a list of busses you want to use, only used if
2368		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2369		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2370		CONFIG_SYS_NUM_I2C_BUSES = 9:
2371
2372		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2373					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2374					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2375					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2376					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2377					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2378					{1, {I2C_NULL_HOP}}, \
2379					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2380					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2381					}
2382
2383		which defines
2384			bus 0 on adapter 0 without a mux
2385			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2386			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2387			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2388			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2389			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2390			bus 6 on adapter 1 without a mux
2391			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2392			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2393
2394		If you do not have i2c muxes on your board, omit this define.
2395
2396- Legacy I2C Support:	CONFIG_HARD_I2C
2397
2398		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2399		provides the following compelling advantages:
2400
2401		- more than one i2c adapter is usable
2402		- approved multibus support
2403		- better i2c mux support
2404
2405		** Please consider updating your I2C driver now. **
2406
2407		These enable legacy I2C serial bus commands. Defining
2408		CONFIG_HARD_I2C will include the appropriate I2C driver
2409		for the selected CPU.
2410
2411		This will allow you to use i2c commands at the u-boot
2412		command line (as long as you set CONFIG_CMD_I2C in
2413		CONFIG_COMMANDS) and communicate with i2c based realtime
2414		clock chips. See common/cmd_i2c.c for a description of the
2415		command line interface.
2416
2417		CONFIG_HARD_I2C selects a hardware I2C controller.
2418
2419		There are several other quantities that must also be
2420		defined when you define CONFIG_HARD_I2C.
2421
2422		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2423		to be the frequency (in Hz) at which you wish your i2c bus
2424		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2425		the CPU's i2c node address).
2426
2427		Now, the u-boot i2c code for the mpc8xx
2428		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2429		and so its address should therefore be cleared to 0 (See,
2430		eg, MPC823e User's Manual p.16-473). So, set
2431		CONFIG_SYS_I2C_SLAVE to 0.
2432
2433		CONFIG_SYS_I2C_INIT_MPC5XXX
2434
2435		When a board is reset during an i2c bus transfer
2436		chips might think that the current transfer is still
2437		in progress.  Reset the slave devices by sending start
2438		commands until the slave device responds.
2439
2440		That's all that's required for CONFIG_HARD_I2C.
2441
2442		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2443		then the following macros need to be defined (examples are
2444		from include/configs/lwmon.h):
2445
2446		I2C_INIT
2447
2448		(Optional). Any commands necessary to enable the I2C
2449		controller or configure ports.
2450
2451		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2452
2453		I2C_PORT
2454
2455		(Only for MPC8260 CPU). The I/O port to use (the code
2456		assumes both bits are on the same port). Valid values
2457		are 0..3 for ports A..D.
2458
2459		I2C_ACTIVE
2460
2461		The code necessary to make the I2C data line active
2462		(driven).  If the data line is open collector, this
2463		define can be null.
2464
2465		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2466
2467		I2C_TRISTATE
2468
2469		The code necessary to make the I2C data line tri-stated
2470		(inactive).  If the data line is open collector, this
2471		define can be null.
2472
2473		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2474
2475		I2C_READ
2476
2477		Code that returns true if the I2C data line is high,
2478		false if it is low.
2479
2480		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2481
2482		I2C_SDA(bit)
2483
2484		If <bit> is true, sets the I2C data line high. If it
2485		is false, it clears it (low).
2486
2487		eg: #define I2C_SDA(bit) \
2488			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2489			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2490
2491		I2C_SCL(bit)
2492
2493		If <bit> is true, sets the I2C clock line high. If it
2494		is false, it clears it (low).
2495
2496		eg: #define I2C_SCL(bit) \
2497			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2498			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2499
2500		I2C_DELAY
2501
2502		This delay is invoked four times per clock cycle so this
2503		controls the rate of data transfer.  The data rate thus
2504		is 1 / (I2C_DELAY * 4). Often defined to be something
2505		like:
2506
2507		#define I2C_DELAY  udelay(2)
2508
2509		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2510
2511		If your arch supports the generic GPIO framework (asm/gpio.h),
2512		then you may alternatively define the two GPIOs that are to be
2513		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2514		have GPIO-based defaults assigned to them as appropriate.
2515
2516		You should define these to the GPIO value as given directly to
2517		the generic GPIO functions.
2518
2519		CONFIG_SYS_I2C_INIT_BOARD
2520
2521		When a board is reset during an i2c bus transfer
2522		chips might think that the current transfer is still
2523		in progress. On some boards it is possible to access
2524		the i2c SCLK line directly, either by using the
2525		processor pin as a GPIO or by having a second pin
2526		connected to the bus. If this option is defined a
2527		custom i2c_init_board() routine in boards/xxx/board.c
2528		is run early in the boot sequence.
2529
2530		CONFIG_SYS_I2C_BOARD_LATE_INIT
2531
2532		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2533		defined a custom i2c_board_late_init() routine in
2534		boards/xxx/board.c is run AFTER the operations in i2c_init()
2535		is completed. This callpoint can be used to unreset i2c bus
2536		using CPU i2c controller register accesses for CPUs whose i2c
2537		controller provide such a method. It is called at the end of
2538		i2c_init() to allow i2c_init operations to setup the i2c bus
2539		controller on the CPU (e.g. setting bus speed & slave address).
2540
2541		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2542
2543		This option enables configuration of bi_iic_fast[] flags
2544		in u-boot bd_info structure based on u-boot environment
2545		variable "i2cfast". (see also i2cfast)
2546
2547		CONFIG_I2C_MULTI_BUS
2548
2549		This option allows the use of multiple I2C buses, each of which
2550		must have a controller.	 At any point in time, only one bus is
2551		active.	 To switch to a different bus, use the 'i2c dev' command.
2552		Note that bus numbering is zero-based.
2553
2554		CONFIG_SYS_I2C_NOPROBES
2555
2556		This option specifies a list of I2C devices that will be skipped
2557		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2558		is set, specify a list of bus-device pairs.  Otherwise, specify
2559		a 1D array of device addresses
2560
2561		e.g.
2562			#undef	CONFIG_I2C_MULTI_BUS
2563			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2564
2565		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2566
2567			#define CONFIG_I2C_MULTI_BUS
2568			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2569
2570		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2571
2572		CONFIG_SYS_SPD_BUS_NUM
2573
2574		If defined, then this indicates the I2C bus number for DDR SPD.
2575		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2576
2577		CONFIG_SYS_RTC_BUS_NUM
2578
2579		If defined, then this indicates the I2C bus number for the RTC.
2580		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2581
2582		CONFIG_SYS_DTT_BUS_NUM
2583
2584		If defined, then this indicates the I2C bus number for the DTT.
2585		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2586
2587		CONFIG_SYS_I2C_DTT_ADDR:
2588
2589		If defined, specifies the I2C address of the DTT device.
2590		If not defined, then U-Boot uses predefined value for
2591		specified DTT device.
2592
2593		CONFIG_SOFT_I2C_READ_REPEATED_START
2594
2595		defining this will force the i2c_read() function in
2596		the soft_i2c driver to perform an I2C repeated start
2597		between writing the address pointer and reading the
2598		data.  If this define is omitted the default behaviour
2599		of doing a stop-start sequence will be used.  Most I2C
2600		devices can use either method, but some require one or
2601		the other.
2602
2603- SPI Support:	CONFIG_SPI
2604
2605		Enables SPI driver (so far only tested with
2606		SPI EEPROM, also an instance works with Crystal A/D and
2607		D/As on the SACSng board)
2608
2609		CONFIG_SH_SPI
2610
2611		Enables the driver for SPI controller on SuperH. Currently
2612		only SH7757 is supported.
2613
2614		CONFIG_SPI_X
2615
2616		Enables extended (16-bit) SPI EEPROM addressing.
2617		(symmetrical to CONFIG_I2C_X)
2618
2619		CONFIG_SOFT_SPI
2620
2621		Enables a software (bit-bang) SPI driver rather than
2622		using hardware support. This is a general purpose
2623		driver that only requires three general I/O port pins
2624		(two outputs, one input) to function. If this is
2625		defined, the board configuration must define several
2626		SPI configuration items (port pins to use, etc). For
2627		an example, see include/configs/sacsng.h.
2628
2629		CONFIG_HARD_SPI
2630
2631		Enables a hardware SPI driver for general-purpose reads
2632		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2633		must define a list of chip-select function pointers.
2634		Currently supported on some MPC8xxx processors.	 For an
2635		example, see include/configs/mpc8349emds.h.
2636
2637		CONFIG_MXC_SPI
2638
2639		Enables the driver for the SPI controllers on i.MX and MXC
2640		SoCs. Currently i.MX31/35/51 are supported.
2641
2642		CONFIG_SYS_SPI_MXC_WAIT
2643		Timeout for waiting until spi transfer completed.
2644		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2645
2646- FPGA Support: CONFIG_FPGA
2647
2648		Enables FPGA subsystem.
2649
2650		CONFIG_FPGA_<vendor>
2651
2652		Enables support for specific chip vendors.
2653		(ALTERA, XILINX)
2654
2655		CONFIG_FPGA_<family>
2656
2657		Enables support for FPGA family.
2658		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2659
2660		CONFIG_FPGA_COUNT
2661
2662		Specify the number of FPGA devices to support.
2663
2664		CONFIG_CMD_FPGA_LOADMK
2665
2666		Enable support for fpga loadmk command
2667
2668		CONFIG_CMD_FPGA_LOADP
2669
2670		Enable support for fpga loadp command - load partial bitstream
2671
2672		CONFIG_CMD_FPGA_LOADBP
2673
2674		Enable support for fpga loadbp command - load partial bitstream
2675		(Xilinx only)
2676
2677		CONFIG_SYS_FPGA_PROG_FEEDBACK
2678
2679		Enable printing of hash marks during FPGA configuration.
2680
2681		CONFIG_SYS_FPGA_CHECK_BUSY
2682
2683		Enable checks on FPGA configuration interface busy
2684		status by the configuration function. This option
2685		will require a board or device specific function to
2686		be written.
2687
2688		CONFIG_FPGA_DELAY
2689
2690		If defined, a function that provides delays in the FPGA
2691		configuration driver.
2692
2693		CONFIG_SYS_FPGA_CHECK_CTRLC
2694		Allow Control-C to interrupt FPGA configuration
2695
2696		CONFIG_SYS_FPGA_CHECK_ERROR
2697
2698		Check for configuration errors during FPGA bitfile
2699		loading. For example, abort during Virtex II
2700		configuration if the INIT_B line goes low (which
2701		indicated a CRC error).
2702
2703		CONFIG_SYS_FPGA_WAIT_INIT
2704
2705		Maximum time to wait for the INIT_B line to deassert
2706		after PROB_B has been deasserted during a Virtex II
2707		FPGA configuration sequence. The default time is 500
2708		ms.
2709
2710		CONFIG_SYS_FPGA_WAIT_BUSY
2711
2712		Maximum time to wait for BUSY to deassert during
2713		Virtex II FPGA configuration. The default is 5 ms.
2714
2715		CONFIG_SYS_FPGA_WAIT_CONFIG
2716
2717		Time to wait after FPGA configuration. The default is
2718		200 ms.
2719
2720- Configuration Management:
2721		CONFIG_BUILD_TARGET
2722
2723		Some SoCs need special image types (e.g. U-Boot binary
2724		with a special header) as build targets. By defining
2725		CONFIG_BUILD_TARGET in the SoC / board header, this
2726		special image will be automatically built upon calling
2727		make / MAKEALL.
2728
2729		CONFIG_IDENT_STRING
2730
2731		If defined, this string will be added to the U-Boot
2732		version information (U_BOOT_VERSION)
2733
2734- Vendor Parameter Protection:
2735
2736		U-Boot considers the values of the environment
2737		variables "serial#" (Board Serial Number) and
2738		"ethaddr" (Ethernet Address) to be parameters that
2739		are set once by the board vendor / manufacturer, and
2740		protects these variables from casual modification by
2741		the user. Once set, these variables are read-only,
2742		and write or delete attempts are rejected. You can
2743		change this behaviour:
2744
2745		If CONFIG_ENV_OVERWRITE is #defined in your config
2746		file, the write protection for vendor parameters is
2747		completely disabled. Anybody can change or delete
2748		these parameters.
2749
2750		Alternatively, if you #define _both_ CONFIG_ETHADDR
2751		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2752		Ethernet address is installed in the environment,
2753		which can be changed exactly ONCE by the user. [The
2754		serial# is unaffected by this, i. e. it remains
2755		read-only.]
2756
2757		The same can be accomplished in a more flexible way
2758		for any variable by configuring the type of access
2759		to allow for those variables in the ".flags" variable
2760		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2761
2762- Protected RAM:
2763		CONFIG_PRAM
2764
2765		Define this variable to enable the reservation of
2766		"protected RAM", i. e. RAM which is not overwritten
2767		by U-Boot. Define CONFIG_PRAM to hold the number of
2768		kB you want to reserve for pRAM. You can overwrite
2769		this default value by defining an environment
2770		variable "pram" to the number of kB you want to
2771		reserve. Note that the board info structure will
2772		still show the full amount of RAM. If pRAM is
2773		reserved, a new environment variable "mem" will
2774		automatically be defined to hold the amount of
2775		remaining RAM in a form that can be passed as boot
2776		argument to Linux, for instance like that:
2777
2778			setenv bootargs ... mem=\${mem}
2779			saveenv
2780
2781		This way you can tell Linux not to use this memory,
2782		either, which results in a memory region that will
2783		not be affected by reboots.
2784
2785		*WARNING* If your board configuration uses automatic
2786		detection of the RAM size, you must make sure that
2787		this memory test is non-destructive. So far, the
2788		following board configurations are known to be
2789		"pRAM-clean":
2790
2791			IVMS8, IVML24, SPD8xx, TQM8xxL,
2792			HERMES, IP860, RPXlite, LWMON,
2793			FLAGADM, TQM8260
2794
2795- Access to physical memory region (> 4GB)
2796		Some basic support is provided for operations on memory not
2797		normally accessible to U-Boot - e.g. some architectures
2798		support access to more than 4GB of memory on 32-bit
2799		machines using physical address extension or similar.
2800		Define CONFIG_PHYSMEM to access this basic support, which
2801		currently only supports clearing the memory.
2802
2803- Error Recovery:
2804		CONFIG_PANIC_HANG
2805
2806		Define this variable to stop the system in case of a
2807		fatal error, so that you have to reset it manually.
2808		This is probably NOT a good idea for an embedded
2809		system where you want the system to reboot
2810		automatically as fast as possible, but it may be
2811		useful during development since you can try to debug
2812		the conditions that lead to the situation.
2813
2814		CONFIG_NET_RETRY_COUNT
2815
2816		This variable defines the number of retries for
2817		network operations like ARP, RARP, TFTP, or BOOTP
2818		before giving up the operation. If not defined, a
2819		default value of 5 is used.
2820
2821		CONFIG_ARP_TIMEOUT
2822
2823		Timeout waiting for an ARP reply in milliseconds.
2824
2825		CONFIG_NFS_TIMEOUT
2826
2827		Timeout in milliseconds used in NFS protocol.
2828		If you encounter "ERROR: Cannot umount" in nfs command,
2829		try longer timeout such as
2830		#define CONFIG_NFS_TIMEOUT 10000UL
2831
2832- Command Interpreter:
2833		CONFIG_AUTO_COMPLETE
2834
2835		Enable auto completion of commands using TAB.
2836
2837		CONFIG_SYS_HUSH_PARSER
2838
2839		Define this variable to enable the "hush" shell (from
2840		Busybox) as command line interpreter, thus enabling
2841		powerful command line syntax like
2842		if...then...else...fi conditionals or `&&' and '||'
2843		constructs ("shell scripts").
2844
2845		If undefined, you get the old, much simpler behaviour
2846		with a somewhat smaller memory footprint.
2847
2848
2849		CONFIG_SYS_PROMPT_HUSH_PS2
2850
2851		This defines the secondary prompt string, which is
2852		printed when the command interpreter needs more input
2853		to complete a command. Usually "> ".
2854
2855	Note:
2856
2857		In the current implementation, the local variables
2858		space and global environment variables space are
2859		separated. Local variables are those you define by
2860		simply typing `name=value'. To access a local
2861		variable later on, you have write `$name' or
2862		`${name}'; to execute the contents of a variable
2863		directly type `$name' at the command prompt.
2864
2865		Global environment variables are those you use
2866		setenv/printenv to work with. To run a command stored
2867		in such a variable, you need to use the run command,
2868		and you must not use the '$' sign to access them.
2869
2870		To store commands and special characters in a
2871		variable, please use double quotation marks
2872		surrounding the whole text of the variable, instead
2873		of the backslashes before semicolons and special
2874		symbols.
2875
2876- Commandline Editing and History:
2877		CONFIG_CMDLINE_EDITING
2878
2879		Enable editing and History functions for interactive
2880		commandline input operations
2881
2882- Default Environment:
2883		CONFIG_EXTRA_ENV_SETTINGS
2884
2885		Define this to contain any number of null terminated
2886		strings (variable = value pairs) that will be part of
2887		the default environment compiled into the boot image.
2888
2889		For example, place something like this in your
2890		board's config file:
2891
2892		#define CONFIG_EXTRA_ENV_SETTINGS \
2893			"myvar1=value1\0" \
2894			"myvar2=value2\0"
2895
2896		Warning: This method is based on knowledge about the
2897		internal format how the environment is stored by the
2898		U-Boot code. This is NOT an official, exported
2899		interface! Although it is unlikely that this format
2900		will change soon, there is no guarantee either.
2901		You better know what you are doing here.
2902
2903		Note: overly (ab)use of the default environment is
2904		discouraged. Make sure to check other ways to preset
2905		the environment like the "source" command or the
2906		boot command first.
2907
2908		CONFIG_ENV_VARS_UBOOT_CONFIG
2909
2910		Define this in order to add variables describing the
2911		U-Boot build configuration to the default environment.
2912		These will be named arch, cpu, board, vendor, and soc.
2913
2914		Enabling this option will cause the following to be defined:
2915
2916		- CONFIG_SYS_ARCH
2917		- CONFIG_SYS_CPU
2918		- CONFIG_SYS_BOARD
2919		- CONFIG_SYS_VENDOR
2920		- CONFIG_SYS_SOC
2921
2922		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2923
2924		Define this in order to add variables describing certain
2925		run-time determined information about the hardware to the
2926		environment.  These will be named board_name, board_rev.
2927
2928		CONFIG_DELAY_ENVIRONMENT
2929
2930		Normally the environment is loaded when the board is
2931		intialised so that it is available to U-Boot. This inhibits
2932		that so that the environment is not available until
2933		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2934		this is instead controlled by the value of
2935		/config/load-environment.
2936
2937- DataFlash Support:
2938		CONFIG_HAS_DATAFLASH
2939
2940		Defining this option enables DataFlash features and
2941		allows to read/write in Dataflash via the standard
2942		commands cp, md...
2943
2944- Serial Flash support
2945		CONFIG_CMD_SF
2946
2947		Defining this option enables SPI flash commands
2948		'sf probe/read/write/erase/update'.
2949
2950		Usage requires an initial 'probe' to define the serial
2951		flash parameters, followed by read/write/erase/update
2952		commands.
2953
2954		The following defaults may be provided by the platform
2955		to handle the common case when only a single serial
2956		flash is present on the system.
2957
2958		CONFIG_SF_DEFAULT_BUS		Bus identifier
2959		CONFIG_SF_DEFAULT_CS		Chip-select
2960		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2961		CONFIG_SF_DEFAULT_SPEED		in Hz
2962
2963		CONFIG_CMD_SF_TEST
2964
2965		Define this option to include a destructive SPI flash
2966		test ('sf test').
2967
2968		CONFIG_SPI_FLASH_BAR		Ban/Extended Addr Reg
2969
2970		Define this option to use the Bank addr/Extended addr
2971		support on SPI flashes which has size > 16Mbytes.
2972
2973		CONFIG_SF_DUAL_FLASH		Dual flash memories
2974
2975		Define this option to use dual flash support where two flash
2976		memories can be connected with a given cs line.
2977		currently Xilinx Zynq qspi support these type of connections.
2978
2979		CONFIG_SYS_SPI_ST_ENABLE_WP_PIN
2980		enable the W#/Vpp signal to disable writing to the status
2981		register on ST MICRON flashes like the N25Q128.
2982		The status register write enable/disable bit, combined with
2983		the W#/VPP signal provides hardware data protection for the
2984		device as follows: When the enable/disable bit is set to 1,
2985		and the W#/VPP signal is driven LOW, the status register
2986		nonvolatile bits become read-only and the WRITE STATUS REGISTER
2987		operation will not execute. The only way to exit this
2988		hardware-protected mode is to drive W#/VPP HIGH.
2989
2990- SystemACE Support:
2991		CONFIG_SYSTEMACE
2992
2993		Adding this option adds support for Xilinx SystemACE
2994		chips attached via some sort of local bus. The address
2995		of the chip must also be defined in the
2996		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2997
2998		#define CONFIG_SYSTEMACE
2999		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
3000
3001		When SystemACE support is added, the "ace" device type
3002		becomes available to the fat commands, i.e. fatls.
3003
3004- TFTP Fixed UDP Port:
3005		CONFIG_TFTP_PORT
3006
3007		If this is defined, the environment variable tftpsrcp
3008		is used to supply the TFTP UDP source port value.
3009		If tftpsrcp isn't defined, the normal pseudo-random port
3010		number generator is used.
3011
3012		Also, the environment variable tftpdstp is used to supply
3013		the TFTP UDP destination port value.  If tftpdstp isn't
3014		defined, the normal port 69 is used.
3015
3016		The purpose for tftpsrcp is to allow a TFTP server to
3017		blindly start the TFTP transfer using the pre-configured
3018		target IP address and UDP port. This has the effect of
3019		"punching through" the (Windows XP) firewall, allowing
3020		the remainder of the TFTP transfer to proceed normally.
3021		A better solution is to properly configure the firewall,
3022		but sometimes that is not allowed.
3023
3024- Hashing support:
3025		CONFIG_CMD_HASH
3026
3027		This enables a generic 'hash' command which can produce
3028		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
3029
3030		CONFIG_HASH_VERIFY
3031
3032		Enable the hash verify command (hash -v). This adds to code
3033		size a little.
3034
3035		CONFIG_SHA1 - support SHA1 hashing
3036		CONFIG_SHA256 - support SHA256 hashing
3037
3038		Note: There is also a sha1sum command, which should perhaps
3039		be deprecated in favour of 'hash sha1'.
3040
3041- Freescale i.MX specific commands:
3042		CONFIG_CMD_HDMIDETECT
3043		This enables 'hdmidet' command which returns true if an
3044		HDMI monitor is detected.  This command is i.MX 6 specific.
3045
3046		CONFIG_CMD_BMODE
3047		This enables the 'bmode' (bootmode) command for forcing
3048		a boot from specific media.
3049
3050		This is useful for forcing the ROM's usb downloader to
3051		activate upon a watchdog reset which is nice when iterating
3052		on U-Boot.  Using the reset button or running bmode normal
3053		will set it back to normal.  This command currently
3054		supports i.MX53 and i.MX6.
3055
3056- Signing support:
3057		CONFIG_RSA
3058
3059		This enables the RSA algorithm used for FIT image verification
3060		in U-Boot. See doc/uImage.FIT/signature.txt for more information.
3061
3062		The signing part is build into mkimage regardless of this
3063		option.
3064
3065- bootcount support:
3066		CONFIG_BOOTCOUNT_LIMIT
3067
3068		This enables the bootcounter support, see:
3069		http://www.denx.de/wiki/DULG/UBootBootCountLimit
3070
3071		CONFIG_AT91SAM9XE
3072		enable special bootcounter support on at91sam9xe based boards.
3073		CONFIG_BLACKFIN
3074		enable special bootcounter support on blackfin based boards.
3075		CONFIG_SOC_DA8XX
3076		enable special bootcounter support on da850 based boards.
3077		CONFIG_BOOTCOUNT_RAM
3078		enable support for the bootcounter in RAM
3079		CONFIG_BOOTCOUNT_I2C
3080		enable support for the bootcounter on an i2c (like RTC) device.
3081			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
3082			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
3083						    the bootcounter.
3084			CONFIG_BOOTCOUNT_ALEN = address len
3085
3086- Show boot progress:
3087		CONFIG_SHOW_BOOT_PROGRESS
3088
3089		Defining this option allows to add some board-
3090		specific code (calling a user-provided function
3091		"show_boot_progress(int)") that enables you to show
3092		the system's boot progress on some display (for
3093		example, some LED's) on your board. At the moment,
3094		the following checkpoints are implemented:
3095
3096- Detailed boot stage timing
3097		CONFIG_BOOTSTAGE
3098		Define this option to get detailed timing of each stage
3099		of the boot process.
3100
3101		CONFIG_BOOTSTAGE_USER_COUNT
3102		This is the number of available user bootstage records.
3103		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
3104		a new ID will be allocated from this stash. If you exceed
3105		the limit, recording will stop.
3106
3107		CONFIG_BOOTSTAGE_REPORT
3108		Define this to print a report before boot, similar to this:
3109
3110		Timer summary in microseconds:
3111		       Mark    Elapsed  Stage
3112			  0          0  reset
3113		  3,575,678  3,575,678  board_init_f start
3114		  3,575,695         17  arch_cpu_init A9
3115		  3,575,777         82  arch_cpu_init done
3116		  3,659,598     83,821  board_init_r start
3117		  3,910,375    250,777  main_loop
3118		 29,916,167 26,005,792  bootm_start
3119		 30,361,327    445,160  start_kernel
3120
3121		CONFIG_CMD_BOOTSTAGE
3122		Add a 'bootstage' command which supports printing a report
3123		and un/stashing of bootstage data.
3124
3125		CONFIG_BOOTSTAGE_FDT
3126		Stash the bootstage information in the FDT. A root 'bootstage'
3127		node is created with each bootstage id as a child. Each child
3128		has a 'name' property and either 'mark' containing the
3129		mark time in microsecond, or 'accum' containing the
3130		accumulated time for that bootstage id in microseconds.
3131		For example:
3132
3133		bootstage {
3134			154 {
3135				name = "board_init_f";
3136				mark = <3575678>;
3137			};
3138			170 {
3139				name = "lcd";
3140				accum = <33482>;
3141			};
3142		};
3143
3144		Code in the Linux kernel can find this in /proc/devicetree.
3145
3146Legacy uImage format:
3147
3148  Arg	Where			When
3149    1	common/cmd_bootm.c	before attempting to boot an image
3150   -1	common/cmd_bootm.c	Image header has bad	 magic number
3151    2	common/cmd_bootm.c	Image header has correct magic number
3152   -2	common/cmd_bootm.c	Image header has bad	 checksum
3153    3	common/cmd_bootm.c	Image header has correct checksum
3154   -3	common/cmd_bootm.c	Image data   has bad	 checksum
3155    4	common/cmd_bootm.c	Image data   has correct checksum
3156   -4	common/cmd_bootm.c	Image is for unsupported architecture
3157    5	common/cmd_bootm.c	Architecture check OK
3158   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
3159    6	common/cmd_bootm.c	Image Type check OK
3160   -6	common/cmd_bootm.c	gunzip uncompression error
3161   -7	common/cmd_bootm.c	Unimplemented compression type
3162    7	common/cmd_bootm.c	Uncompression OK
3163    8	common/cmd_bootm.c	No uncompress/copy overwrite error
3164   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3165
3166    9	common/image.c		Start initial ramdisk verification
3167  -10	common/image.c		Ramdisk header has bad	   magic number
3168  -11	common/image.c		Ramdisk header has bad	   checksum
3169   10	common/image.c		Ramdisk header is OK
3170  -12	common/image.c		Ramdisk data   has bad	   checksum
3171   11	common/image.c		Ramdisk data   has correct checksum
3172   12	common/image.c		Ramdisk verification complete, start loading
3173  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3174   13	common/image.c		Start multifile image verification
3175   14	common/image.c		No initial ramdisk, no multifile, continue.
3176
3177   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3178
3179  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3180  -31	post/post.c		POST test failed, detected by post_output_backlog()
3181  -32	post/post.c		POST test failed, detected by post_run_single()
3182
3183   34	common/cmd_doc.c	before loading a Image from a DOC device
3184  -35	common/cmd_doc.c	Bad usage of "doc" command
3185   35	common/cmd_doc.c	correct usage of "doc" command
3186  -36	common/cmd_doc.c	No boot device
3187   36	common/cmd_doc.c	correct boot device
3188  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3189   37	common/cmd_doc.c	correct chip ID found, device available
3190  -38	common/cmd_doc.c	Read Error on boot device
3191   38	common/cmd_doc.c	reading Image header from DOC device OK
3192  -39	common/cmd_doc.c	Image header has bad magic number
3193   39	common/cmd_doc.c	Image header has correct magic number
3194  -40	common/cmd_doc.c	Error reading Image from DOC device
3195   40	common/cmd_doc.c	Image header has correct magic number
3196   41	common/cmd_ide.c	before loading a Image from a IDE device
3197  -42	common/cmd_ide.c	Bad usage of "ide" command
3198   42	common/cmd_ide.c	correct usage of "ide" command
3199  -43	common/cmd_ide.c	No boot device
3200   43	common/cmd_ide.c	boot device found
3201  -44	common/cmd_ide.c	Device not available
3202   44	common/cmd_ide.c	Device available
3203  -45	common/cmd_ide.c	wrong partition selected
3204   45	common/cmd_ide.c	partition selected
3205  -46	common/cmd_ide.c	Unknown partition table
3206   46	common/cmd_ide.c	valid partition table found
3207  -47	common/cmd_ide.c	Invalid partition type
3208   47	common/cmd_ide.c	correct partition type
3209  -48	common/cmd_ide.c	Error reading Image Header on boot device
3210   48	common/cmd_ide.c	reading Image Header from IDE device OK
3211  -49	common/cmd_ide.c	Image header has bad magic number
3212   49	common/cmd_ide.c	Image header has correct magic number
3213  -50	common/cmd_ide.c	Image header has bad	 checksum
3214   50	common/cmd_ide.c	Image header has correct checksum
3215  -51	common/cmd_ide.c	Error reading Image from IDE device
3216   51	common/cmd_ide.c	reading Image from IDE device OK
3217   52	common/cmd_nand.c	before loading a Image from a NAND device
3218  -53	common/cmd_nand.c	Bad usage of "nand" command
3219   53	common/cmd_nand.c	correct usage of "nand" command
3220  -54	common/cmd_nand.c	No boot device
3221   54	common/cmd_nand.c	boot device found
3222  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3223   55	common/cmd_nand.c	correct chip ID found, device available
3224  -56	common/cmd_nand.c	Error reading Image Header on boot device
3225   56	common/cmd_nand.c	reading Image Header from NAND device OK
3226  -57	common/cmd_nand.c	Image header has bad magic number
3227   57	common/cmd_nand.c	Image header has correct magic number
3228  -58	common/cmd_nand.c	Error reading Image from NAND device
3229   58	common/cmd_nand.c	reading Image from NAND device OK
3230
3231  -60	common/env_common.c	Environment has a bad CRC, using default
3232
3233   64	net/eth.c		starting with Ethernet configuration.
3234  -64	net/eth.c		no Ethernet found.
3235   65	net/eth.c		Ethernet found.
3236
3237  -80	common/cmd_net.c	usage wrong
3238   80	common/cmd_net.c	before calling NetLoop()
3239  -81	common/cmd_net.c	some error in NetLoop() occurred
3240   81	common/cmd_net.c	NetLoop() back without error
3241  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3242   82	common/cmd_net.c	trying automatic boot
3243   83	common/cmd_net.c	running "source" command
3244  -83	common/cmd_net.c	some error in automatic boot or "source" command
3245   84	common/cmd_net.c	end without errors
3246
3247FIT uImage format:
3248
3249  Arg	Where			When
3250  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3251 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3252  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3253 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3254  102	common/cmd_bootm.c	Kernel unit name specified
3255 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3256  103	common/cmd_bootm.c	Found configuration node
3257  104	common/cmd_bootm.c	Got kernel subimage node offset
3258 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3259  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3260 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3261  106	common/cmd_bootm.c	Architecture check OK
3262 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3263  107	common/cmd_bootm.c	Kernel subimage type OK
3264 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3265  108	common/cmd_bootm.c	Got kernel subimage data/size
3266 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3267 -109	common/cmd_bootm.c	Can't get kernel subimage type
3268 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3269 -111	common/cmd_bootm.c	Can't get kernel subimage os
3270 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3271 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3272
3273  120	common/image.c		Start initial ramdisk verification
3274 -120	common/image.c		Ramdisk FIT image has incorrect format
3275  121	common/image.c		Ramdisk FIT image has correct format
3276  122	common/image.c		No ramdisk subimage unit name, using configuration
3277 -122	common/image.c		Can't get configuration for ramdisk subimage
3278  123	common/image.c		Ramdisk unit name specified
3279 -124	common/image.c		Can't get ramdisk subimage node offset
3280  125	common/image.c		Got ramdisk subimage node offset
3281 -125	common/image.c		Ramdisk subimage hash verification failed
3282  126	common/image.c		Ramdisk subimage hash verification OK
3283 -126	common/image.c		Ramdisk subimage for unsupported architecture
3284  127	common/image.c		Architecture check OK
3285 -127	common/image.c		Can't get ramdisk subimage data/size
3286  128	common/image.c		Got ramdisk subimage data/size
3287  129	common/image.c		Can't get ramdisk load address
3288 -129	common/image.c		Got ramdisk load address
3289
3290 -130	common/cmd_doc.c	Incorrect FIT image format
3291  131	common/cmd_doc.c	FIT image format OK
3292
3293 -140	common/cmd_ide.c	Incorrect FIT image format
3294  141	common/cmd_ide.c	FIT image format OK
3295
3296 -150	common/cmd_nand.c	Incorrect FIT image format
3297  151	common/cmd_nand.c	FIT image format OK
3298
3299- legacy image format:
3300		CONFIG_IMAGE_FORMAT_LEGACY
3301		enables the legacy image format support in U-Boot.
3302
3303		Default:
3304		enabled if CONFIG_FIT_SIGNATURE is not defined.
3305
3306		CONFIG_DISABLE_IMAGE_LEGACY
3307		disable the legacy image format
3308
3309		This define is introduced, as the legacy image format is
3310		enabled per default for backward compatibility.
3311
3312- FIT image support:
3313		CONFIG_FIT
3314		Enable support for the FIT uImage format.
3315
3316		CONFIG_FIT_BEST_MATCH
3317		When no configuration is explicitly selected, default to the
3318		one whose fdt's compatibility field best matches that of
3319		U-Boot itself. A match is considered "best" if it matches the
3320		most specific compatibility entry of U-Boot's fdt's root node.
3321		The order of entries in the configuration's fdt is ignored.
3322
3323		CONFIG_FIT_SIGNATURE
3324		This option enables signature verification of FIT uImages,
3325		using a hash signed and verified using RSA. See
3326		doc/uImage.FIT/signature.txt for more details.
3327
3328		WARNING: When relying on signed FIT images with required
3329		signature check the legacy image format is default
3330		disabled. If a board need legacy image format support
3331		enable this through CONFIG_IMAGE_FORMAT_LEGACY
3332
3333		CONFIG_FIT_DISABLE_SHA256
3334		Supporting SHA256 hashes has quite an impact on binary size.
3335		For constrained systems sha256 hash support can be disabled
3336		with this option.
3337
3338- Standalone program support:
3339		CONFIG_STANDALONE_LOAD_ADDR
3340
3341		This option defines a board specific value for the
3342		address where standalone program gets loaded, thus
3343		overwriting the architecture dependent default
3344		settings.
3345
3346- Frame Buffer Address:
3347		CONFIG_FB_ADDR
3348
3349		Define CONFIG_FB_ADDR if you want to use specific
3350		address for frame buffer.  This is typically the case
3351		when using a graphics controller has separate video
3352		memory.  U-Boot will then place the frame buffer at
3353		the given address instead of dynamically reserving it
3354		in system RAM by calling lcd_setmem(), which grabs
3355		the memory for the frame buffer depending on the
3356		configured panel size.
3357
3358		Please see board_init_f function.
3359
3360- Automatic software updates via TFTP server
3361		CONFIG_UPDATE_TFTP
3362		CONFIG_UPDATE_TFTP_CNT_MAX
3363		CONFIG_UPDATE_TFTP_MSEC_MAX
3364
3365		These options enable and control the auto-update feature;
3366		for a more detailed description refer to doc/README.update.
3367
3368- MTD Support (mtdparts command, UBI support)
3369		CONFIG_MTD_DEVICE
3370
3371		Adds the MTD device infrastructure from the Linux kernel.
3372		Needed for mtdparts command support.
3373
3374		CONFIG_MTD_PARTITIONS
3375
3376		Adds the MTD partitioning infrastructure from the Linux
3377		kernel. Needed for UBI support.
3378
3379		CONFIG_MTD_NAND_VERIFY_WRITE
3380		verify if the written data is correct reread.
3381
3382- UBI support
3383		CONFIG_CMD_UBI
3384
3385		Adds commands for interacting with MTD partitions formatted
3386		with the UBI flash translation layer
3387
3388		Requires also defining CONFIG_RBTREE
3389
3390		CONFIG_UBI_SILENCE_MSG
3391
3392		Make the verbose messages from UBI stop printing.  This leaves
3393		warnings and errors enabled.
3394
3395
3396		CONFIG_MTD_UBI_WL_THRESHOLD
3397		This parameter defines the maximum difference between the highest
3398		erase counter value and the lowest erase counter value of eraseblocks
3399		of UBI devices. When this threshold is exceeded, UBI starts performing
3400		wear leveling by means of moving data from eraseblock with low erase
3401		counter to eraseblocks with high erase counter.
3402
3403		The default value should be OK for SLC NAND flashes, NOR flashes and
3404		other flashes which have eraseblock life-cycle 100000 or more.
3405		However, in case of MLC NAND flashes which typically have eraseblock
3406		life-cycle less than 10000, the threshold should be lessened (e.g.,
3407		to 128 or 256, although it does not have to be power of 2).
3408
3409		default: 4096
3410
3411		CONFIG_MTD_UBI_BEB_LIMIT
3412		This option specifies the maximum bad physical eraseblocks UBI
3413		expects on the MTD device (per 1024 eraseblocks). If the
3414		underlying flash does not admit of bad eraseblocks (e.g. NOR
3415		flash), this value is ignored.
3416
3417		NAND datasheets often specify the minimum and maximum NVM
3418		(Number of Valid Blocks) for the flashes' endurance lifetime.
3419		The maximum expected bad eraseblocks per 1024 eraseblocks
3420		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
3421		which gives 20 for most NANDs (MaxNVB is basically the total
3422		count of eraseblocks on the chip).
3423
3424		To put it differently, if this value is 20, UBI will try to
3425		reserve about 1.9% of physical eraseblocks for bad blocks
3426		handling. And that will be 1.9% of eraseblocks on the entire
3427		NAND chip, not just the MTD partition UBI attaches. This means
3428		that if you have, say, a NAND flash chip admits maximum 40 bad
3429		eraseblocks, and it is split on two MTD partitions of the same
3430		size, UBI will reserve 40 eraseblocks when attaching a
3431		partition.
3432
3433		default: 20
3434
3435		CONFIG_MTD_UBI_FASTMAP
3436		Fastmap is a mechanism which allows attaching an UBI device
3437		in nearly constant time. Instead of scanning the whole MTD device it
3438		only has to locate a checkpoint (called fastmap) on the device.
3439		The on-flash fastmap contains all information needed to attach
3440		the device. Using fastmap makes only sense on large devices where
3441		attaching by scanning takes long. UBI will not automatically install
3442		a fastmap on old images, but you can set the UBI parameter
3443		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
3444		that fastmap-enabled images are still usable with UBI implementations
3445		without	fastmap support. On typical flash devices the whole fastmap
3446		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
3447
3448		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
3449		Set this parameter to enable fastmap automatically on images
3450		without a fastmap.
3451		default: 0
3452
3453- UBIFS support
3454		CONFIG_CMD_UBIFS
3455
3456		Adds commands for interacting with UBI volumes formatted as
3457		UBIFS.  UBIFS is read-only in u-boot.
3458
3459		Requires UBI support as well as CONFIG_LZO
3460
3461		CONFIG_UBIFS_SILENCE_MSG
3462
3463		Make the verbose messages from UBIFS stop printing.  This leaves
3464		warnings and errors enabled.
3465
3466- SPL framework
3467		CONFIG_SPL
3468		Enable building of SPL globally.
3469
3470		CONFIG_SPL_LDSCRIPT
3471		LDSCRIPT for linking the SPL binary.
3472
3473		CONFIG_SPL_MAX_FOOTPRINT
3474		Maximum size in memory allocated to the SPL, BSS included.
3475		When defined, the linker checks that the actual memory
3476		used by SPL from _start to __bss_end does not exceed it.
3477		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3478		must not be both defined at the same time.
3479
3480		CONFIG_SPL_MAX_SIZE
3481		Maximum size of the SPL image (text, data, rodata, and
3482		linker lists sections), BSS excluded.
3483		When defined, the linker checks that the actual size does
3484		not exceed it.
3485
3486		CONFIG_SPL_TEXT_BASE
3487		TEXT_BASE for linking the SPL binary.
3488
3489		CONFIG_SPL_RELOC_TEXT_BASE
3490		Address to relocate to.  If unspecified, this is equal to
3491		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3492
3493		CONFIG_SPL_BSS_START_ADDR
3494		Link address for the BSS within the SPL binary.
3495
3496		CONFIG_SPL_BSS_MAX_SIZE
3497		Maximum size in memory allocated to the SPL BSS.
3498		When defined, the linker checks that the actual memory used
3499		by SPL from __bss_start to __bss_end does not exceed it.
3500		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3501		must not be both defined at the same time.
3502
3503		CONFIG_SPL_STACK
3504		Adress of the start of the stack SPL will use
3505
3506		CONFIG_SPL_RELOC_STACK
3507		Adress of the start of the stack SPL will use after
3508		relocation.  If unspecified, this is equal to
3509		CONFIG_SPL_STACK.
3510
3511		CONFIG_SYS_SPL_MALLOC_START
3512		Starting address of the malloc pool used in SPL.
3513
3514		CONFIG_SYS_SPL_MALLOC_SIZE
3515		The size of the malloc pool used in SPL.
3516
3517		CONFIG_SPL_FRAMEWORK
3518		Enable the SPL framework under common/.  This framework
3519		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3520		NAND loading of the Linux Kernel.
3521
3522		CONFIG_SPL_OS_BOOT
3523		Enable booting directly to an OS from SPL.
3524		See also: doc/README.falcon
3525
3526		CONFIG_SPL_DISPLAY_PRINT
3527		For ARM, enable an optional function to print more information
3528		about the running system.
3529
3530		CONFIG_SPL_INIT_MINIMAL
3531		Arch init code should be built for a very small image
3532
3533		CONFIG_SPL_LIBCOMMON_SUPPORT
3534		Support for common/libcommon.o in SPL binary
3535
3536		CONFIG_SPL_LIBDISK_SUPPORT
3537		Support for disk/libdisk.o in SPL binary
3538
3539		CONFIG_SPL_I2C_SUPPORT
3540		Support for drivers/i2c/libi2c.o in SPL binary
3541
3542		CONFIG_SPL_GPIO_SUPPORT
3543		Support for drivers/gpio/libgpio.o in SPL binary
3544
3545		CONFIG_SPL_MMC_SUPPORT
3546		Support for drivers/mmc/libmmc.o in SPL binary
3547
3548		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3549		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3550		CONFIG_SYS_MMC_SD_FS_BOOT_PARTITION
3551		Address, size and partition on the MMC to load U-Boot from
3552		when the MMC is being used in raw mode.
3553
3554		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3555		Sector to load kernel uImage from when MMC is being
3556		used in raw mode (for Falcon mode)
3557
3558		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3559		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3560		Sector and number of sectors to load kernel argument
3561		parameters from when MMC is being used in raw mode
3562		(for falcon mode)
3563
3564		CONFIG_SPL_FAT_SUPPORT
3565		Support for fs/fat/libfat.o in SPL binary
3566
3567		CONFIG_SPL_EXT_SUPPORT
3568		Support for EXT filesystem in SPL binary
3569
3570		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3571		Filename to read to load U-Boot when reading from filesystem
3572
3573		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3574		Filename to read to load kernel uImage when reading
3575		from filesystem (for Falcon mode)
3576
3577		CONFIG_SPL_FS_LOAD_ARGS_NAME
3578		Filename to read to load kernel argument parameters
3579		when reading from filesystem (for Falcon mode)
3580
3581		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3582		Set this for NAND SPL on PPC mpc83xx targets, so that
3583		start.S waits for the rest of the SPL to load before
3584		continuing (the hardware starts execution after just
3585		loading the first page rather than the full 4K).
3586
3587		CONFIG_SPL_SKIP_RELOCATE
3588		Avoid SPL relocation
3589
3590		CONFIG_SPL_NAND_BASE
3591		Include nand_base.c in the SPL.  Requires
3592		CONFIG_SPL_NAND_DRIVERS.
3593
3594		CONFIG_SPL_NAND_DRIVERS
3595		SPL uses normal NAND drivers, not minimal drivers.
3596
3597		CONFIG_SPL_NAND_ECC
3598		Include standard software ECC in the SPL
3599
3600		CONFIG_SPL_NAND_SIMPLE
3601		Support for NAND boot using simple NAND drivers that
3602		expose the cmd_ctrl() interface.
3603
3604		CONFIG_SPL_MTD_SUPPORT
3605		Support for the MTD subsystem within SPL.  Useful for
3606		environment on NAND support within SPL.
3607
3608		CONFIG_SPL_NAND_RAW_ONLY
3609		Support to boot only raw u-boot.bin images. Use this only
3610		if you need to save space.
3611
3612		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3613		Set for the SPL on PPC mpc8xxx targets, support for
3614		drivers/ddr/fsl/libddr.o in SPL binary.
3615
3616		CONFIG_SPL_COMMON_INIT_DDR
3617		Set for common ddr init with serial presence detect in
3618		SPL binary.
3619
3620		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3621		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3622		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3623		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3624		CONFIG_SYS_NAND_ECCBYTES
3625		Defines the size and behavior of the NAND that SPL uses
3626		to read U-Boot
3627
3628		CONFIG_SPL_NAND_BOOT
3629		Add support NAND boot
3630
3631		CONFIG_SYS_NAND_U_BOOT_OFFS
3632		Location in NAND to read U-Boot from
3633
3634		CONFIG_SYS_NAND_U_BOOT_DST
3635		Location in memory to load U-Boot to
3636
3637		CONFIG_SYS_NAND_U_BOOT_SIZE
3638		Size of image to load
3639
3640		CONFIG_SYS_NAND_U_BOOT_START
3641		Entry point in loaded image to jump to
3642
3643		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3644		Define this if you need to first read the OOB and then the
3645		data. This is used for example on davinci plattforms.
3646
3647		CONFIG_SPL_OMAP3_ID_NAND
3648		Support for an OMAP3-specific set of functions to return the
3649		ID and MFR of the first attached NAND chip, if present.
3650
3651		CONFIG_SPL_SERIAL_SUPPORT
3652		Support for drivers/serial/libserial.o in SPL binary
3653
3654		CONFIG_SPL_SPI_FLASH_SUPPORT
3655		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3656
3657		CONFIG_SPL_SPI_SUPPORT
3658		Support for drivers/spi/libspi.o in SPL binary
3659
3660		CONFIG_SPL_RAM_DEVICE
3661		Support for running image already present in ram, in SPL binary
3662
3663		CONFIG_SPL_LIBGENERIC_SUPPORT
3664		Support for lib/libgeneric.o in SPL binary
3665
3666		CONFIG_SPL_ENV_SUPPORT
3667		Support for the environment operating in SPL binary
3668
3669		CONFIG_SPL_NET_SUPPORT
3670		Support for the net/libnet.o in SPL binary.
3671		It conflicts with SPL env from storage medium specified by
3672		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3673
3674		CONFIG_SPL_PAD_TO
3675		Image offset to which the SPL should be padded before appending
3676		the SPL payload. By default, this is defined as
3677		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3678		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3679		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3680
3681		CONFIG_SPL_TARGET
3682		Final target image containing SPL and payload.  Some SPLs
3683		use an arch-specific makefile fragment instead, for
3684		example if more than one image needs to be produced.
3685
3686		CONFIG_FIT_SPL_PRINT
3687		Printing information about a FIT image adds quite a bit of
3688		code to SPL. So this is normally disabled in SPL. Use this
3689		option to re-enable it. This will affect the output of the
3690		bootm command when booting a FIT image.
3691
3692- TPL framework
3693		CONFIG_TPL
3694		Enable building of TPL globally.
3695
3696		CONFIG_TPL_PAD_TO
3697		Image offset to which the TPL should be padded before appending
3698		the TPL payload. By default, this is defined as
3699		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3700		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3701		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3702
3703Modem Support:
3704--------------
3705
3706[so far only for SMDK2400 boards]
3707
3708- Modem support enable:
3709		CONFIG_MODEM_SUPPORT
3710
3711- RTS/CTS Flow control enable:
3712		CONFIG_HWFLOW
3713
3714- Modem debug support:
3715		CONFIG_MODEM_SUPPORT_DEBUG
3716
3717		Enables debugging stuff (char screen[1024], dbg())
3718		for modem support. Useful only with BDI2000.
3719
3720- Interrupt support (PPC):
3721
3722		There are common interrupt_init() and timer_interrupt()
3723		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3724		for CPU specific initialization. interrupt_init_cpu()
3725		should set decrementer_count to appropriate value. If
3726		CPU resets decrementer automatically after interrupt
3727		(ppc4xx) it should set decrementer_count to zero.
3728		timer_interrupt() calls timer_interrupt_cpu() for CPU
3729		specific handling. If board has watchdog / status_led
3730		/ other_activity_monitor it works automatically from
3731		general timer_interrupt().
3732
3733- General:
3734
3735		In the target system modem support is enabled when a
3736		specific key (key combination) is pressed during
3737		power-on. Otherwise U-Boot will boot normally
3738		(autoboot). The key_pressed() function is called from
3739		board_init(). Currently key_pressed() is a dummy
3740		function, returning 1 and thus enabling modem
3741		initialization.
3742
3743		If there are no modem init strings in the
3744		environment, U-Boot proceed to autoboot; the
3745		previous output (banner, info printfs) will be
3746		suppressed, though.
3747
3748		See also: doc/README.Modem
3749
3750Board initialization settings:
3751------------------------------
3752
3753During Initialization u-boot calls a number of board specific functions
3754to allow the preparation of board specific prerequisites, e.g. pin setup
3755before drivers are initialized. To enable these callbacks the
3756following configuration macros have to be defined. Currently this is
3757architecture specific, so please check arch/your_architecture/lib/board.c
3758typically in board_init_f() and board_init_r().
3759
3760- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3761- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3762- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3763- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3764
3765Configuration Settings:
3766-----------------------
3767
3768- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3769		Optionally it can be defined to support 64-bit memory commands.
3770
3771- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3772		undefine this when you're short of memory.
3773
3774- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3775		width of the commands listed in the 'help' command output.
3776
3777- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3778		prompt for user input.
3779
3780- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3781
3782- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3783
3784- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3785
3786- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3787		the application (usually a Linux kernel) when it is
3788		booted
3789
3790- CONFIG_SYS_BAUDRATE_TABLE:
3791		List of legal baudrate settings for this board.
3792
3793- CONFIG_SYS_CONSOLE_INFO_QUIET
3794		Suppress display of console information at boot.
3795
3796- CONFIG_SYS_CONSOLE_IS_IN_ENV
3797		If the board specific function
3798			extern int overwrite_console (void);
3799		returns 1, the stdin, stderr and stdout are switched to the
3800		serial port, else the settings in the environment are used.
3801
3802- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3803		Enable the call to overwrite_console().
3804
3805- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3806		Enable overwrite of previous console environment settings.
3807
3808- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3809		Begin and End addresses of the area used by the
3810		simple memory test.
3811
3812- CONFIG_SYS_ALT_MEMTEST:
3813		Enable an alternate, more extensive memory test.
3814
3815- CONFIG_SYS_MEMTEST_SCRATCH:
3816		Scratch address used by the alternate memory test
3817		You only need to set this if address zero isn't writeable
3818
3819- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3820		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3821		this specified memory area will get subtracted from the top
3822		(end) of RAM and won't get "touched" at all by U-Boot. By
3823		fixing up gd->ram_size the Linux kernel should gets passed
3824		the now "corrected" memory size and won't touch it either.
3825		This should work for arch/ppc and arch/powerpc. Only Linux
3826		board ports in arch/powerpc with bootwrapper support that
3827		recalculate the memory size from the SDRAM controller setup
3828		will have to get fixed in Linux additionally.
3829
3830		This option can be used as a workaround for the 440EPx/GRx
3831		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3832		be touched.
3833
3834		WARNING: Please make sure that this value is a multiple of
3835		the Linux page size (normally 4k). If this is not the case,
3836		then the end address of the Linux memory will be located at a
3837		non page size aligned address and this could cause major
3838		problems.
3839
3840- CONFIG_SYS_LOADS_BAUD_CHANGE:
3841		Enable temporary baudrate change while serial download
3842
3843- CONFIG_SYS_SDRAM_BASE:
3844		Physical start address of SDRAM. _Must_ be 0 here.
3845
3846- CONFIG_SYS_MBIO_BASE:
3847		Physical start address of Motherboard I/O (if using a
3848		Cogent motherboard)
3849
3850- CONFIG_SYS_FLASH_BASE:
3851		Physical start address of Flash memory.
3852
3853- CONFIG_SYS_MONITOR_BASE:
3854		Physical start address of boot monitor code (set by
3855		make config files to be same as the text base address
3856		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3857		CONFIG_SYS_FLASH_BASE when booting from flash.
3858
3859- CONFIG_SYS_MONITOR_LEN:
3860		Size of memory reserved for monitor code, used to
3861		determine _at_compile_time_ (!) if the environment is
3862		embedded within the U-Boot image, or in a separate
3863		flash sector.
3864
3865- CONFIG_SYS_MALLOC_LEN:
3866		Size of DRAM reserved for malloc() use.
3867
3868- CONFIG_SYS_MALLOC_F_LEN
3869		Size of the malloc() pool for use before relocation. If
3870		this is defined, then a very simple malloc() implementation
3871		will become available before relocation. The address is just
3872		below the global data, and the stack is moved down to make
3873		space.
3874
3875		This feature allocates regions with increasing addresses
3876		within the region. calloc() is supported, but realloc()
3877		is not available. free() is supported but does nothing.
3878		The memory will be freed (or in fact just forgotton) when
3879		U-Boot relocates itself.
3880
3881		Pre-relocation malloc() is only supported on ARM and sandbox
3882		at present but is fairly easy to enable for other archs.
3883
3884- CONFIG_SYS_BOOTM_LEN:
3885		Normally compressed uImages are limited to an
3886		uncompressed size of 8 MBytes. If this is not enough,
3887		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3888		to adjust this setting to your needs.
3889
3890- CONFIG_SYS_BOOTMAPSZ:
3891		Maximum size of memory mapped by the startup code of
3892		the Linux kernel; all data that must be processed by
3893		the Linux kernel (bd_info, boot arguments, FDT blob if
3894		used) must be put below this limit, unless "bootm_low"
3895		environment variable is defined and non-zero. In such case
3896		all data for the Linux kernel must be between "bootm_low"
3897		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3898		variable "bootm_mapsize" will override the value of
3899		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3900		then the value in "bootm_size" will be used instead.
3901
3902- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3903		Enable initrd_high functionality.  If defined then the
3904		initrd_high feature is enabled and the bootm ramdisk subcommand
3905		is enabled.
3906
3907- CONFIG_SYS_BOOT_GET_CMDLINE:
3908		Enables allocating and saving kernel cmdline in space between
3909		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3910
3911- CONFIG_SYS_BOOT_GET_KBD:
3912		Enables allocating and saving a kernel copy of the bd_info in
3913		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3914
3915- CONFIG_SYS_MAX_FLASH_BANKS:
3916		Max number of Flash memory banks
3917
3918- CONFIG_SYS_MAX_FLASH_SECT:
3919		Max number of sectors on a Flash chip
3920
3921- CONFIG_SYS_FLASH_ERASE_TOUT:
3922		Timeout for Flash erase operations (in ms)
3923
3924- CONFIG_SYS_FLASH_WRITE_TOUT:
3925		Timeout for Flash write operations (in ms)
3926
3927- CONFIG_SYS_FLASH_LOCK_TOUT
3928		Timeout for Flash set sector lock bit operation (in ms)
3929
3930- CONFIG_SYS_FLASH_UNLOCK_TOUT
3931		Timeout for Flash clear lock bits operation (in ms)
3932
3933- CONFIG_SYS_FLASH_PROTECTION
3934		If defined, hardware flash sectors protection is used
3935		instead of U-Boot software protection.
3936
3937- CONFIG_SYS_DIRECT_FLASH_TFTP:
3938
3939		Enable TFTP transfers directly to flash memory;
3940		without this option such a download has to be
3941		performed in two steps: (1) download to RAM, and (2)
3942		copy from RAM to flash.
3943
3944		The two-step approach is usually more reliable, since
3945		you can check if the download worked before you erase
3946		the flash, but in some situations (when system RAM is
3947		too limited to allow for a temporary copy of the
3948		downloaded image) this option may be very useful.
3949
3950- CONFIG_SYS_FLASH_CFI:
3951		Define if the flash driver uses extra elements in the
3952		common flash structure for storing flash geometry.
3953
3954- CONFIG_FLASH_CFI_DRIVER
3955		This option also enables the building of the cfi_flash driver
3956		in the drivers directory
3957
3958- CONFIG_FLASH_CFI_MTD
3959		This option enables the building of the cfi_mtd driver
3960		in the drivers directory. The driver exports CFI flash
3961		to the MTD layer.
3962
3963- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3964		Use buffered writes to flash.
3965
3966- CONFIG_FLASH_SPANSION_S29WS_N
3967		s29ws-n MirrorBit flash has non-standard addresses for buffered
3968		write commands.
3969
3970- CONFIG_SYS_FLASH_QUIET_TEST
3971		If this option is defined, the common CFI flash doesn't
3972		print it's warning upon not recognized FLASH banks. This
3973		is useful, if some of the configured banks are only
3974		optionally available.
3975
3976- CONFIG_FLASH_SHOW_PROGRESS
3977		If defined (must be an integer), print out countdown
3978		digits and dots.  Recommended value: 45 (9..1) for 80
3979		column displays, 15 (3..1) for 40 column displays.
3980
3981- CONFIG_FLASH_VERIFY
3982		If defined, the content of the flash (destination) is compared
3983		against the source after the write operation. An error message
3984		will be printed when the contents are not identical.
3985		Please note that this option is useless in nearly all cases,
3986		since such flash programming errors usually are detected earlier
3987		while unprotecting/erasing/programming. Please only enable
3988		this option if you really know what you are doing.
3989
3990- CONFIG_SYS_RX_ETH_BUFFER:
3991		Defines the number of Ethernet receive buffers. On some
3992		Ethernet controllers it is recommended to set this value
3993		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3994		buffers can be full shortly after enabling the interface
3995		on high Ethernet traffic.
3996		Defaults to 4 if not defined.
3997
3998- CONFIG_ENV_MAX_ENTRIES
3999
4000	Maximum number of entries in the hash table that is used
4001	internally to store the environment settings. The default
4002	setting is supposed to be generous and should work in most
4003	cases. This setting can be used to tune behaviour; see
4004	lib/hashtable.c for details.
4005
4006- CONFIG_ENV_FLAGS_LIST_DEFAULT
4007- CONFIG_ENV_FLAGS_LIST_STATIC
4008	Enable validation of the values given to environment variables when
4009	calling env set.  Variables can be restricted to only decimal,
4010	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
4011	the variables can also be restricted to IP address or MAC address.
4012
4013	The format of the list is:
4014		type_attribute = [s|d|x|b|i|m]
4015		access_atribute = [a|r|o|c]
4016		attributes = type_attribute[access_atribute]
4017		entry = variable_name[:attributes]
4018		list = entry[,list]
4019
4020	The type attributes are:
4021		s - String (default)
4022		d - Decimal
4023		x - Hexadecimal
4024		b - Boolean ([1yYtT|0nNfF])
4025		i - IP address
4026		m - MAC address
4027
4028	The access attributes are:
4029		a - Any (default)
4030		r - Read-only
4031		o - Write-once
4032		c - Change-default
4033
4034	- CONFIG_ENV_FLAGS_LIST_DEFAULT
4035		Define this to a list (string) to define the ".flags"
4036		envirnoment variable in the default or embedded environment.
4037
4038	- CONFIG_ENV_FLAGS_LIST_STATIC
4039		Define this to a list (string) to define validation that
4040		should be done if an entry is not found in the ".flags"
4041		environment variable.  To override a setting in the static
4042		list, simply add an entry for the same variable name to the
4043		".flags" variable.
4044
4045- CONFIG_ENV_ACCESS_IGNORE_FORCE
4046	If defined, don't allow the -f switch to env set override variable
4047	access flags.
4048
4049- CONFIG_SYS_GENERIC_BOARD
4050	This selects the architecture-generic board system instead of the
4051	architecture-specific board files. It is intended to move boards
4052	to this new framework over time. Defining this will disable the
4053	arch/foo/lib/board.c file and use common/board_f.c and
4054	common/board_r.c instead. To use this option your architecture
4055	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
4056	its config.mk file). If you find problems enabling this option on
4057	your board please report the problem and send patches!
4058
4059- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
4060	This is set by OMAP boards for the max time that reset should
4061	be asserted. See doc/README.omap-reset-time for details on how
4062	the value can be calulated on a given board.
4063
4064- CONFIG_USE_STDINT
4065	If stdint.h is available with your toolchain you can define this
4066	option to enable it. You can provide option 'USE_STDINT=1' when
4067	building U-Boot to enable this.
4068
4069The following definitions that deal with the placement and management
4070of environment data (variable area); in general, we support the
4071following configurations:
4072
4073- CONFIG_BUILD_ENVCRC:
4074
4075	Builds up envcrc with the target environment so that external utils
4076	may easily extract it and embed it in final U-Boot images.
4077
4078- CONFIG_ENV_IS_IN_FLASH:
4079
4080	Define this if the environment is in flash memory.
4081
4082	a) The environment occupies one whole flash sector, which is
4083	   "embedded" in the text segment with the U-Boot code. This
4084	   happens usually with "bottom boot sector" or "top boot
4085	   sector" type flash chips, which have several smaller
4086	   sectors at the start or the end. For instance, such a
4087	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
4088	   such a case you would place the environment in one of the
4089	   4 kB sectors - with U-Boot code before and after it. With
4090	   "top boot sector" type flash chips, you would put the
4091	   environment in one of the last sectors, leaving a gap
4092	   between U-Boot and the environment.
4093
4094	- CONFIG_ENV_OFFSET:
4095
4096	   Offset of environment data (variable area) to the
4097	   beginning of flash memory; for instance, with bottom boot
4098	   type flash chips the second sector can be used: the offset
4099	   for this sector is given here.
4100
4101	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
4102
4103	- CONFIG_ENV_ADDR:
4104
4105	   This is just another way to specify the start address of
4106	   the flash sector containing the environment (instead of
4107	   CONFIG_ENV_OFFSET).
4108
4109	- CONFIG_ENV_SECT_SIZE:
4110
4111	   Size of the sector containing the environment.
4112
4113
4114	b) Sometimes flash chips have few, equal sized, BIG sectors.
4115	   In such a case you don't want to spend a whole sector for
4116	   the environment.
4117
4118	- CONFIG_ENV_SIZE:
4119
4120	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
4121	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
4122	   of this flash sector for the environment. This saves
4123	   memory for the RAM copy of the environment.
4124
4125	   It may also save flash memory if you decide to use this
4126	   when your environment is "embedded" within U-Boot code,
4127	   since then the remainder of the flash sector could be used
4128	   for U-Boot code. It should be pointed out that this is
4129	   STRONGLY DISCOURAGED from a robustness point of view:
4130	   updating the environment in flash makes it always
4131	   necessary to erase the WHOLE sector. If something goes
4132	   wrong before the contents has been restored from a copy in
4133	   RAM, your target system will be dead.
4134
4135	- CONFIG_ENV_ADDR_REDUND
4136	  CONFIG_ENV_SIZE_REDUND
4137
4138	   These settings describe a second storage area used to hold
4139	   a redundant copy of the environment data, so that there is
4140	   a valid backup copy in case there is a power failure during
4141	   a "saveenv" operation.
4142
4143BE CAREFUL! Any changes to the flash layout, and some changes to the
4144source code will make it necessary to adapt <board>/u-boot.lds*
4145accordingly!
4146
4147
4148- CONFIG_ENV_IS_IN_NVRAM:
4149
4150	Define this if you have some non-volatile memory device
4151	(NVRAM, battery buffered SRAM) which you want to use for the
4152	environment.
4153
4154	- CONFIG_ENV_ADDR:
4155	- CONFIG_ENV_SIZE:
4156
4157	  These two #defines are used to determine the memory area you
4158	  want to use for environment. It is assumed that this memory
4159	  can just be read and written to, without any special
4160	  provision.
4161
4162BE CAREFUL! The first access to the environment happens quite early
4163in U-Boot initalization (when we try to get the setting of for the
4164console baudrate). You *MUST* have mapped your NVRAM area then, or
4165U-Boot will hang.
4166
4167Please note that even with NVRAM we still use a copy of the
4168environment in RAM: we could work on NVRAM directly, but we want to
4169keep settings there always unmodified except somebody uses "saveenv"
4170to save the current settings.
4171
4172
4173- CONFIG_ENV_IS_IN_EEPROM:
4174
4175	Use this if you have an EEPROM or similar serial access
4176	device and a driver for it.
4177
4178	- CONFIG_ENV_OFFSET:
4179	- CONFIG_ENV_SIZE:
4180
4181	  These two #defines specify the offset and size of the
4182	  environment area within the total memory of your EEPROM.
4183
4184	- CONFIG_SYS_I2C_EEPROM_ADDR:
4185	  If defined, specified the chip address of the EEPROM device.
4186	  The default address is zero.
4187
4188	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
4189	  If defined, the number of bits used to address bytes in a
4190	  single page in the EEPROM device.  A 64 byte page, for example
4191	  would require six bits.
4192
4193	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
4194	  If defined, the number of milliseconds to delay between
4195	  page writes.	The default is zero milliseconds.
4196
4197	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
4198	  The length in bytes of the EEPROM memory array address.  Note
4199	  that this is NOT the chip address length!
4200
4201	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
4202	  EEPROM chips that implement "address overflow" are ones
4203	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
4204	  address and the extra bits end up in the "chip address" bit
4205	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
4206	  byte chips.
4207
4208	  Note that we consider the length of the address field to
4209	  still be one byte because the extra address bits are hidden
4210	  in the chip address.
4211
4212	- CONFIG_SYS_EEPROM_SIZE:
4213	  The size in bytes of the EEPROM device.
4214
4215	- CONFIG_ENV_EEPROM_IS_ON_I2C
4216	  define this, if you have I2C and SPI activated, and your
4217	  EEPROM, which holds the environment, is on the I2C bus.
4218
4219	- CONFIG_I2C_ENV_EEPROM_BUS
4220	  if you have an Environment on an EEPROM reached over
4221	  I2C muxes, you can define here, how to reach this
4222	  EEPROM. For example:
4223
4224	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
4225
4226	  EEPROM which holds the environment, is reached over
4227	  a pca9547 i2c mux with address 0x70, channel 3.
4228
4229- CONFIG_ENV_IS_IN_DATAFLASH:
4230
4231	Define this if you have a DataFlash memory device which you
4232	want to use for the environment.
4233
4234	- CONFIG_ENV_OFFSET:
4235	- CONFIG_ENV_ADDR:
4236	- CONFIG_ENV_SIZE:
4237
4238	  These three #defines specify the offset and size of the
4239	  environment area within the total memory of your DataFlash placed
4240	  at the specified address.
4241
4242- CONFIG_ENV_IS_IN_SPI_FLASH:
4243
4244	Define this if you have a SPI Flash memory device which you
4245	want to use for the environment.
4246
4247	- CONFIG_ENV_OFFSET:
4248	- CONFIG_ENV_SIZE:
4249
4250	  These two #defines specify the offset and size of the
4251	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
4252	  aligned to an erase sector boundary.
4253
4254	- CONFIG_ENV_SECT_SIZE:
4255
4256	  Define the SPI flash's sector size.
4257
4258	- CONFIG_ENV_OFFSET_REDUND (optional):
4259
4260	  This setting describes a second storage area of CONFIG_ENV_SIZE
4261	  size used to hold a redundant copy of the environment data, so
4262	  that there is a valid backup copy in case there is a power failure
4263	  during a "saveenv" operation. CONFIG_ENV_OFFSET_RENDUND must be
4264	  aligned to an erase sector boundary.
4265
4266	- CONFIG_ENV_SPI_BUS (optional):
4267	- CONFIG_ENV_SPI_CS (optional):
4268
4269	  Define the SPI bus and chip select. If not defined they will be 0.
4270
4271	- CONFIG_ENV_SPI_MAX_HZ (optional):
4272
4273	  Define the SPI max work clock. If not defined then use 1MHz.
4274
4275	- CONFIG_ENV_SPI_MODE (optional):
4276
4277	  Define the SPI work mode. If not defined then use SPI_MODE_3.
4278
4279- CONFIG_ENV_IS_IN_REMOTE:
4280
4281	Define this if you have a remote memory space which you
4282	want to use for the local device's environment.
4283
4284	- CONFIG_ENV_ADDR:
4285	- CONFIG_ENV_SIZE:
4286
4287	  These two #defines specify the address and size of the
4288	  environment area within the remote memory space. The
4289	  local device can get the environment from remote memory
4290	  space by SRIO or PCIE links.
4291
4292BE CAREFUL! For some special cases, the local device can not use
4293"saveenv" command. For example, the local device will get the
4294environment stored in a remote NOR flash by SRIO or PCIE link,
4295but it can not erase, write this NOR flash by SRIO or PCIE interface.
4296
4297- CONFIG_ENV_IS_IN_NAND:
4298
4299	Define this if you have a NAND device which you want to use
4300	for the environment.
4301
4302	- CONFIG_ENV_OFFSET:
4303	- CONFIG_ENV_SIZE:
4304
4305	  These two #defines specify the offset and size of the environment
4306	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4307	  aligned to an erase block boundary.
4308
4309	- CONFIG_ENV_OFFSET_REDUND (optional):
4310
4311	  This setting describes a second storage area of CONFIG_ENV_SIZE
4312	  size used to hold a redundant copy of the environment data, so
4313	  that there is a valid backup copy in case there is a power failure
4314	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
4315	  aligned to an erase block boundary.
4316
4317	- CONFIG_ENV_RANGE (optional):
4318
4319	  Specifies the length of the region in which the environment
4320	  can be written.  This should be a multiple of the NAND device's
4321	  block size.  Specifying a range with more erase blocks than
4322	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4323	  the range to be avoided.
4324
4325	- CONFIG_ENV_OFFSET_OOB (optional):
4326
4327	  Enables support for dynamically retrieving the offset of the
4328	  environment from block zero's out-of-band data.  The
4329	  "nand env.oob" command can be used to record this offset.
4330	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4331	  using CONFIG_ENV_OFFSET_OOB.
4332
4333- CONFIG_NAND_ENV_DST
4334
4335	Defines address in RAM to which the nand_spl code should copy the
4336	environment. If redundant environment is used, it will be copied to
4337	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4338
4339- CONFIG_ENV_IS_IN_UBI:
4340
4341	Define this if you have an UBI volume that you want to use for the
4342	environment.  This has the benefit of wear-leveling the environment
4343	accesses, which is important on NAND.
4344
4345	- CONFIG_ENV_UBI_PART:
4346
4347	  Define this to a string that is the mtd partition containing the UBI.
4348
4349	- CONFIG_ENV_UBI_VOLUME:
4350
4351	  Define this to the name of the volume that you want to store the
4352	  environment in.
4353
4354	- CONFIG_ENV_UBI_VOLUME_REDUND:
4355
4356	  Define this to the name of another volume to store a second copy of
4357	  the environment in.  This will enable redundant environments in UBI.
4358	  It is assumed that both volumes are in the same MTD partition.
4359
4360	- CONFIG_UBI_SILENCE_MSG
4361	- CONFIG_UBIFS_SILENCE_MSG
4362
4363	  You will probably want to define these to avoid a really noisy system
4364	  when storing the env in UBI.
4365
4366- CONFIG_ENV_IS_IN_FAT:
4367       Define this if you want to use the FAT file system for the environment.
4368
4369       - FAT_ENV_INTERFACE:
4370
4371         Define this to a string that is the name of the block device.
4372
4373       - FAT_ENV_DEV_AND_PART:
4374
4375         Define this to a string to specify the partition of the device. It can
4376         be as following:
4377
4378           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
4379               - "D:P": device D partition P. Error occurs if device D has no
4380                        partition table.
4381               - "D:0": device D.
4382               - "D" or "D:": device D partition 1 if device D has partition
4383                              table, or the whole device D if has no partition
4384                              table.
4385               - "D:auto": first partition in device D with bootable flag set.
4386                           If none, first valid paratition in device D. If no
4387                           partition table then means device D.
4388
4389       - FAT_ENV_FILE:
4390
4391         It's a string of the FAT file name. This file use to store the
4392         envrionment.
4393
4394       - CONFIG_FAT_WRITE:
4395         This should be defined. Otherwise it cannot save the envrionment file.
4396
4397- CONFIG_ENV_IS_IN_MMC:
4398
4399	Define this if you have an MMC device which you want to use for the
4400	environment.
4401
4402	- CONFIG_SYS_MMC_ENV_DEV:
4403
4404	  Specifies which MMC device the environment is stored in.
4405
4406	- CONFIG_SYS_MMC_ENV_PART (optional):
4407
4408	  Specifies which MMC partition the environment is stored in. If not
4409	  set, defaults to partition 0, the user area. Common values might be
4410	  1 (first MMC boot partition), 2 (second MMC boot partition).
4411
4412	- CONFIG_ENV_OFFSET:
4413	- CONFIG_ENV_SIZE:
4414
4415	  These two #defines specify the offset and size of the environment
4416	  area within the specified MMC device.
4417
4418	  If offset is positive (the usual case), it is treated as relative to
4419	  the start of the MMC partition. If offset is negative, it is treated
4420	  as relative to the end of the MMC partition. This can be useful if
4421	  your board may be fitted with different MMC devices, which have
4422	  different sizes for the MMC partitions, and you always want the
4423	  environment placed at the very end of the partition, to leave the
4424	  maximum possible space before it, to store other data.
4425
4426	  These two values are in units of bytes, but must be aligned to an
4427	  MMC sector boundary.
4428
4429	- CONFIG_ENV_OFFSET_REDUND (optional):
4430
4431	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4432	  hold a redundant copy of the environment data. This provides a
4433	  valid backup copy in case the other copy is corrupted, e.g. due
4434	  to a power failure during a "saveenv" operation.
4435
4436	  This value may also be positive or negative; this is handled in the
4437	  same way as CONFIG_ENV_OFFSET.
4438
4439	  This value is also in units of bytes, but must also be aligned to
4440	  an MMC sector boundary.
4441
4442	- CONFIG_ENV_SIZE_REDUND (optional):
4443
4444	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4445	  set. If this value is set, it must be set to the same value as
4446	  CONFIG_ENV_SIZE.
4447
4448- CONFIG_SYS_SPI_INIT_OFFSET
4449
4450	Defines offset to the initial SPI buffer area in DPRAM. The
4451	area is used at an early stage (ROM part) if the environment
4452	is configured to reside in the SPI EEPROM: We need a 520 byte
4453	scratch DPRAM area. It is used between the two initialization
4454	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4455	to be a good choice since it makes it far enough from the
4456	start of the data area as well as from the stack pointer.
4457
4458Please note that the environment is read-only until the monitor
4459has been relocated to RAM and a RAM copy of the environment has been
4460created; also, when using EEPROM you will have to use getenv_f()
4461until then to read environment variables.
4462
4463The environment is protected by a CRC32 checksum. Before the monitor
4464is relocated into RAM, as a result of a bad CRC you will be working
4465with the compiled-in default environment - *silently*!!! [This is
4466necessary, because the first environment variable we need is the
4467"baudrate" setting for the console - if we have a bad CRC, we don't
4468have any device yet where we could complain.]
4469
4470Note: once the monitor has been relocated, then it will complain if
4471the default environment is used; a new CRC is computed as soon as you
4472use the "saveenv" command to store a valid environment.
4473
4474- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4475		Echo the inverted Ethernet link state to the fault LED.
4476
4477		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4478		      also needs to be defined.
4479
4480- CONFIG_SYS_FAULT_MII_ADDR:
4481		MII address of the PHY to check for the Ethernet link state.
4482
4483- CONFIG_NS16550_MIN_FUNCTIONS:
4484		Define this if you desire to only have use of the NS16550_init
4485		and NS16550_putc functions for the serial driver located at
4486		drivers/serial/ns16550.c.  This option is useful for saving
4487		space for already greatly restricted images, including but not
4488		limited to NAND_SPL configurations.
4489
4490- CONFIG_DISPLAY_BOARDINFO
4491		Display information about the board that U-Boot is running on
4492		when U-Boot starts up. The board function checkboard() is called
4493		to do this.
4494
4495- CONFIG_DISPLAY_BOARDINFO_LATE
4496		Similar to the previous option, but display this information
4497		later, once stdio is running and output goes to the LCD, if
4498		present.
4499
4500- CONFIG_BOARD_SIZE_LIMIT:
4501		Maximum size of the U-Boot image. When defined, the
4502		build system checks that the actual size does not
4503		exceed it.
4504
4505Low Level (hardware related) configuration options:
4506---------------------------------------------------
4507
4508- CONFIG_SYS_CACHELINE_SIZE:
4509		Cache Line Size of the CPU.
4510
4511- CONFIG_SYS_DEFAULT_IMMR:
4512		Default address of the IMMR after system reset.
4513
4514		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4515		and RPXsuper) to be able to adjust the position of
4516		the IMMR register after a reset.
4517
4518- CONFIG_SYS_CCSRBAR_DEFAULT:
4519		Default (power-on reset) physical address of CCSR on Freescale
4520		PowerPC SOCs.
4521
4522- CONFIG_SYS_CCSRBAR:
4523		Virtual address of CCSR.  On a 32-bit build, this is typically
4524		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4525
4526		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4527		for cross-platform code that uses that macro instead.
4528
4529- CONFIG_SYS_CCSRBAR_PHYS:
4530		Physical address of CCSR.  CCSR can be relocated to a new
4531		physical address, if desired.  In this case, this macro should
4532		be set to that address.	 Otherwise, it should be set to the
4533		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4534		is typically relocated on 36-bit builds.  It is recommended
4535		that this macro be defined via the _HIGH and _LOW macros:
4536
4537		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4538			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4539
4540- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4541		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4542		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4543		used in assembly code, so it must not contain typecasts or
4544		integer size suffixes (e.g. "ULL").
4545
4546- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4547		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4548		used in assembly code, so it must not contain typecasts or
4549		integer size suffixes (e.g. "ULL").
4550
4551- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4552		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4553		forced to a value that ensures that CCSR is not relocated.
4554
4555- Floppy Disk Support:
4556		CONFIG_SYS_FDC_DRIVE_NUMBER
4557
4558		the default drive number (default value 0)
4559
4560		CONFIG_SYS_ISA_IO_STRIDE
4561
4562		defines the spacing between FDC chipset registers
4563		(default value 1)
4564
4565		CONFIG_SYS_ISA_IO_OFFSET
4566
4567		defines the offset of register from address. It
4568		depends on which part of the data bus is connected to
4569		the FDC chipset. (default value 0)
4570
4571		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4572		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4573		default value.
4574
4575		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4576		fdc_hw_init() is called at the beginning of the FDC
4577		setup. fdc_hw_init() must be provided by the board
4578		source code. It is used to make hardware dependant
4579		initializations.
4580
4581- CONFIG_IDE_AHB:
4582		Most IDE controllers were designed to be connected with PCI
4583		interface. Only few of them were designed for AHB interface.
4584		When software is doing ATA command and data transfer to
4585		IDE devices through IDE-AHB controller, some additional
4586		registers accessing to these kind of IDE-AHB controller
4587		is requierd.
4588
4589- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4590		DO NOT CHANGE unless you know exactly what you're
4591		doing! (11-4) [MPC8xx/82xx systems only]
4592
4593- CONFIG_SYS_INIT_RAM_ADDR:
4594
4595		Start address of memory area that can be used for
4596		initial data and stack; please note that this must be
4597		writable memory that is working WITHOUT special
4598		initialization, i. e. you CANNOT use normal RAM which
4599		will become available only after programming the
4600		memory controller and running certain initialization
4601		sequences.
4602
4603		U-Boot uses the following memory types:
4604		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4605		- MPC824X: data cache
4606		- PPC4xx:  data cache
4607
4608- CONFIG_SYS_GBL_DATA_OFFSET:
4609
4610		Offset of the initial data structure in the memory
4611		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4612		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4613		data is located at the end of the available space
4614		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4615		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4616		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4617		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4618
4619	Note:
4620		On the MPC824X (or other systems that use the data
4621		cache for initial memory) the address chosen for
4622		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4623		point to an otherwise UNUSED address space between
4624		the top of RAM and the start of the PCI space.
4625
4626- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4627
4628- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4629
4630- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4631
4632- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4633
4634- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4635
4636- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4637
4638- CONFIG_SYS_OR_TIMING_SDRAM:
4639		SDRAM timing
4640
4641- CONFIG_SYS_MAMR_PTA:
4642		periodic timer for refresh
4643
4644- CONFIG_SYS_DER:	Debug Event Register (37-47)
4645
4646- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4647  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4648  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4649  CONFIG_SYS_BR1_PRELIM:
4650		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4651
4652- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4653  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4654  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4655		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4656
4657- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4658  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4659		Machine Mode Register and Memory Periodic Timer
4660		Prescaler definitions (SDRAM timing)
4661
4662- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4663		enable I2C microcode relocation patch (MPC8xx);
4664		define relocation offset in DPRAM [DSP2]
4665
4666- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4667		enable SMC microcode relocation patch (MPC8xx);
4668		define relocation offset in DPRAM [SMC1]
4669
4670- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4671		enable SPI microcode relocation patch (MPC8xx);
4672		define relocation offset in DPRAM [SCC4]
4673
4674- CONFIG_SYS_USE_OSCCLK:
4675		Use OSCM clock mode on MBX8xx board. Be careful,
4676		wrong setting might damage your board. Read
4677		doc/README.MBX before setting this variable!
4678
4679- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4680		Offset of the bootmode word in DPRAM used by post
4681		(Power On Self Tests). This definition overrides
4682		#define'd default value in commproc.h resp.
4683		cpm_8260.h.
4684
4685- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4686  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4687  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4688  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4689  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4690  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4691  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4692  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4693		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4694
4695- CONFIG_PCI_DISABLE_PCIE:
4696		Disable PCI-Express on systems where it is supported but not
4697		required.
4698
4699- CONFIG_PCI_ENUM_ONLY
4700		Only scan through and get the devices on the busses.
4701		Don't do any setup work, presumably because someone or
4702		something has already done it, and we don't need to do it
4703		a second time.	Useful for platforms that are pre-booted
4704		by coreboot or similar.
4705
4706- CONFIG_PCI_INDIRECT_BRIDGE:
4707		Enable support for indirect PCI bridges.
4708
4709- CONFIG_SYS_SRIO:
4710		Chip has SRIO or not
4711
4712- CONFIG_SRIO1:
4713		Board has SRIO 1 port available
4714
4715- CONFIG_SRIO2:
4716		Board has SRIO 2 port available
4717
4718- CONFIG_SRIO_PCIE_BOOT_MASTER
4719		Board can support master function for Boot from SRIO and PCIE
4720
4721- CONFIG_SYS_SRIOn_MEM_VIRT:
4722		Virtual Address of SRIO port 'n' memory region
4723
4724- CONFIG_SYS_SRIOn_MEM_PHYS:
4725		Physical Address of SRIO port 'n' memory region
4726
4727- CONFIG_SYS_SRIOn_MEM_SIZE:
4728		Size of SRIO port 'n' memory region
4729
4730- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4731		Defined to tell the NAND controller that the NAND chip is using
4732		a 16 bit bus.
4733		Not all NAND drivers use this symbol.
4734		Example of drivers that use it:
4735		- drivers/mtd/nand/ndfc.c
4736		- drivers/mtd/nand/mxc_nand.c
4737
4738- CONFIG_SYS_NDFC_EBC0_CFG
4739		Sets the EBC0_CFG register for the NDFC. If not defined
4740		a default value will be used.
4741
4742- CONFIG_SPD_EEPROM
4743		Get DDR timing information from an I2C EEPROM. Common
4744		with pluggable memory modules such as SODIMMs
4745
4746  SPD_EEPROM_ADDRESS
4747		I2C address of the SPD EEPROM
4748
4749- CONFIG_SYS_SPD_BUS_NUM
4750		If SPD EEPROM is on an I2C bus other than the first
4751		one, specify here. Note that the value must resolve
4752		to something your driver can deal with.
4753
4754- CONFIG_SYS_DDR_RAW_TIMING
4755		Get DDR timing information from other than SPD. Common with
4756		soldered DDR chips onboard without SPD. DDR raw timing
4757		parameters are extracted from datasheet and hard-coded into
4758		header files or board specific files.
4759
4760- CONFIG_FSL_DDR_INTERACTIVE
4761		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4762
4763- CONFIG_SYS_83XX_DDR_USES_CS0
4764		Only for 83xx systems. If specified, then DDR should
4765		be configured using CS0 and CS1 instead of CS2 and CS3.
4766
4767- CONFIG_ETHER_ON_FEC[12]
4768		Define to enable FEC[12] on a 8xx series processor.
4769
4770- CONFIG_FEC[12]_PHY
4771		Define to the hardcoded PHY address which corresponds
4772		to the given FEC; i. e.
4773			#define CONFIG_FEC1_PHY 4
4774		means that the PHY with address 4 is connected to FEC1
4775
4776		When set to -1, means to probe for first available.
4777
4778- CONFIG_FEC[12]_PHY_NORXERR
4779		The PHY does not have a RXERR line (RMII only).
4780		(so program the FEC to ignore it).
4781
4782- CONFIG_RMII
4783		Enable RMII mode for all FECs.
4784		Note that this is a global option, we can't
4785		have one FEC in standard MII mode and another in RMII mode.
4786
4787- CONFIG_CRC32_VERIFY
4788		Add a verify option to the crc32 command.
4789		The syntax is:
4790
4791		=> crc32 -v <address> <count> <crc32>
4792
4793		Where address/count indicate a memory area
4794		and crc32 is the correct crc32 which the
4795		area should have.
4796
4797- CONFIG_LOOPW
4798		Add the "loopw" memory command. This only takes effect if
4799		the memory commands are activated globally (CONFIG_CMD_MEM).
4800
4801- CONFIG_MX_CYCLIC
4802		Add the "mdc" and "mwc" memory commands. These are cyclic
4803		"md/mw" commands.
4804		Examples:
4805
4806		=> mdc.b 10 4 500
4807		This command will print 4 bytes (10,11,12,13) each 500 ms.
4808
4809		=> mwc.l 100 12345678 10
4810		This command will write 12345678 to address 100 all 10 ms.
4811
4812		This only takes effect if the memory commands are activated
4813		globally (CONFIG_CMD_MEM).
4814
4815- CONFIG_SKIP_LOWLEVEL_INIT
4816		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4817		low level initializations (like setting up the memory
4818		controller) are omitted and/or U-Boot does not
4819		relocate itself into RAM.
4820
4821		Normally this variable MUST NOT be defined. The only
4822		exception is when U-Boot is loaded (to RAM) by some
4823		other boot loader or by a debugger which performs
4824		these initializations itself.
4825
4826- CONFIG_SPL_BUILD
4827		Modifies the behaviour of start.S when compiling a loader
4828		that is executed before the actual U-Boot. E.g. when
4829		compiling a NAND SPL.
4830
4831- CONFIG_TPL_BUILD
4832		Modifies the behaviour of start.S  when compiling a loader
4833		that is executed after the SPL and before the actual U-Boot.
4834		It is loaded by the SPL.
4835
4836- CONFIG_SYS_MPC85XX_NO_RESETVEC
4837		Only for 85xx systems. If this variable is specified, the section
4838		.resetvec is not kept and the section .bootpg is placed in the
4839		previous 4k of the .text section.
4840
4841- CONFIG_ARCH_MAP_SYSMEM
4842		Generally U-Boot (and in particular the md command) uses
4843		effective address. It is therefore not necessary to regard
4844		U-Boot address as virtual addresses that need to be translated
4845		to physical addresses. However, sandbox requires this, since
4846		it maintains its own little RAM buffer which contains all
4847		addressable memory. This option causes some memory accesses
4848		to be mapped through map_sysmem() / unmap_sysmem().
4849
4850- CONFIG_USE_ARCH_MEMCPY
4851  CONFIG_USE_ARCH_MEMSET
4852		If these options are used a optimized version of memcpy/memset will
4853		be used if available. These functions may be faster under some
4854		conditions but may increase the binary size.
4855
4856- CONFIG_X86_RESET_VECTOR
4857		If defined, the x86 reset vector code is included. This is not
4858		needed when U-Boot is running from Coreboot.
4859
4860- CONFIG_SYS_MPUCLK
4861		Defines the MPU clock speed (in MHz).
4862
4863		NOTE : currently only supported on AM335x platforms.
4864
4865- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4866		Enables the RTC32K OSC on AM33xx based plattforms
4867
4868- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4869		Option to disable subpage write in NAND driver
4870		driver that uses this:
4871		drivers/mtd/nand/davinci_nand.c
4872
4873Freescale QE/FMAN Firmware Support:
4874-----------------------------------
4875
4876The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4877loading of "firmware", which is encoded in the QE firmware binary format.
4878This firmware often needs to be loaded during U-Boot booting, so macros
4879are used to identify the storage device (NOR flash, SPI, etc) and the address
4880within that device.
4881
4882- CONFIG_SYS_FMAN_FW_ADDR
4883	The address in the storage device where the FMAN microcode is located.  The
4884	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4885	is also specified.
4886
4887- CONFIG_SYS_QE_FW_ADDR
4888	The address in the storage device where the QE microcode is located.  The
4889	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4890	is also specified.
4891
4892- CONFIG_SYS_QE_FMAN_FW_LENGTH
4893	The maximum possible size of the firmware.  The firmware binary format
4894	has a field that specifies the actual size of the firmware, but it
4895	might not be possible to read any part of the firmware unless some
4896	local storage is allocated to hold the entire firmware first.
4897
4898- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4899	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4900	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4901	virtual address in NOR flash.
4902
4903- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4904	Specifies that QE/FMAN firmware is located in NAND flash.
4905	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4906
4907- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4908	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4909	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4910
4911- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4912	Specifies that QE/FMAN firmware is located on the primary SPI
4913	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4914
4915- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4916	Specifies that QE/FMAN firmware is located in the remote (master)
4917	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4918	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4919	window->master inbound window->master LAW->the ucode address in
4920	master's memory space.
4921
4922Freescale Layerscape Management Complex Firmware Support:
4923---------------------------------------------------------
4924The Freescale Layerscape Management Complex (MC) supports the loading of
4925"firmware".
4926This firmware often needs to be loaded during U-Boot booting, so macros
4927are used to identify the storage device (NOR flash, SPI, etc) and the address
4928within that device.
4929
4930- CONFIG_FSL_MC_ENET
4931	Enable the MC driver for Layerscape SoCs.
4932
4933- CONFIG_SYS_LS_MC_FW_ADDR
4934	The address in the storage device where the firmware is located.  The
4935	meaning of this address depends on which CONFIG_SYS_LS_MC_FW_IN_xxx macro
4936	is also specified.
4937
4938- CONFIG_SYS_LS_MC_FW_LENGTH
4939	The maximum possible size of the firmware.  The firmware binary format
4940	has a field that specifies the actual size of the firmware, but it
4941	might not be possible to read any part of the firmware unless some
4942	local storage is allocated to hold the entire firmware first.
4943
4944- CONFIG_SYS_LS_MC_FW_IN_NOR
4945	Specifies that MC firmware is located in NOR flash, mapped as
4946	normal addressable memory via the LBC. CONFIG_SYS_LS_MC_FW_ADDR is the
4947	virtual address in NOR flash.
4948
4949Building the Software:
4950======================
4951
4952Building U-Boot has been tested in several native build environments
4953and in many different cross environments. Of course we cannot support
4954all possibly existing versions of cross development tools in all
4955(potentially obsolete) versions. In case of tool chain problems we
4956recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4957which is extensively used to build and test U-Boot.
4958
4959If you are not using a native environment, it is assumed that you
4960have GNU cross compiling tools available in your path. In this case,
4961you must set the environment variable CROSS_COMPILE in your shell.
4962Note that no changes to the Makefile or any other source files are
4963necessary. For example using the ELDK on a 4xx CPU, please enter:
4964
4965	$ CROSS_COMPILE=ppc_4xx-
4966	$ export CROSS_COMPILE
4967
4968Note: If you wish to generate Windows versions of the utilities in
4969      the tools directory you can use the MinGW toolchain
4970      (http://www.mingw.org).  Set your HOST tools to the MinGW
4971      toolchain and execute 'make tools'.  For example:
4972
4973       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4974
4975      Binaries such as tools/mkimage.exe will be created which can
4976      be executed on computers running Windows.
4977
4978U-Boot is intended to be simple to build. After installing the
4979sources you must configure U-Boot for one specific board type. This
4980is done by typing:
4981
4982	make NAME_defconfig
4983
4984where "NAME_defconfig" is the name of one of the existing configu-
4985rations; see boards.cfg for supported names.
4986
4987Note: for some board special configuration names may exist; check if
4988      additional information is available from the board vendor; for
4989      instance, the TQM823L systems are available without (standard)
4990      or with LCD support. You can select such additional "features"
4991      when choosing the configuration, i. e.
4992
4993      make TQM823L_defconfig
4994	- will configure for a plain TQM823L, i. e. no LCD support
4995
4996      make TQM823L_LCD_defconfig
4997	- will configure for a TQM823L with U-Boot console on LCD
4998
4999      etc.
5000
5001
5002Finally, type "make all", and you should get some working U-Boot
5003images ready for download to / installation on your system:
5004
5005- "u-boot.bin" is a raw binary image
5006- "u-boot" is an image in ELF binary format
5007- "u-boot.srec" is in Motorola S-Record format
5008
5009By default the build is performed locally and the objects are saved
5010in the source directory. One of the two methods can be used to change
5011this behavior and build U-Boot to some external directory:
5012
50131. Add O= to the make command line invocations:
5014
5015	make O=/tmp/build distclean
5016	make O=/tmp/build NAME_defconfig
5017	make O=/tmp/build all
5018
50192. Set environment variable KBUILD_OUTPUT to point to the desired location:
5020
5021	export KBUILD_OUTPUT=/tmp/build
5022	make distclean
5023	make NAME_defconfig
5024	make all
5025
5026Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
5027variable.
5028
5029
5030Please be aware that the Makefiles assume you are using GNU make, so
5031for instance on NetBSD you might need to use "gmake" instead of
5032native "make".
5033
5034
5035If the system board that you have is not listed, then you will need
5036to port U-Boot to your hardware platform. To do this, follow these
5037steps:
5038
50391.  Add a new configuration option for your board to the toplevel
5040    "boards.cfg" file, using the existing entries as examples.
5041    Follow the instructions there to keep the boards in order.
50422.  Create a new directory to hold your board specific code. Add any
5043    files you need. In your board directory, you will need at least
5044    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
50453.  Create a new configuration file "include/configs/<board>.h" for
5046    your board
50473.  If you're porting U-Boot to a new CPU, then also create a new
5048    directory to hold your CPU specific code. Add any files you need.
50494.  Run "make <board>_defconfig" with your new name.
50505.  Type "make", and you should get a working "u-boot.srec" file
5051    to be installed on your target system.
50526.  Debug and solve any problems that might arise.
5053    [Of course, this last step is much harder than it sounds.]
5054
5055
5056Testing of U-Boot Modifications, Ports to New Hardware, etc.:
5057==============================================================
5058
5059If you have modified U-Boot sources (for instance added a new board
5060or support for new devices, a new CPU, etc.) you are expected to
5061provide feedback to the other developers. The feedback normally takes
5062the form of a "patch", i. e. a context diff against a certain (latest
5063official or latest in the git repository) version of U-Boot sources.
5064
5065But before you submit such a patch, please verify that your modifi-
5066cation did not break existing code. At least make sure that *ALL* of
5067the supported boards compile WITHOUT ANY compiler warnings. To do so,
5068just run the "MAKEALL" script, which will configure and build U-Boot
5069for ALL supported system. Be warned, this will take a while. You can
5070select which (cross) compiler to use by passing a `CROSS_COMPILE'
5071environment variable to the script, i. e. to use the ELDK cross tools
5072you can type
5073
5074	CROSS_COMPILE=ppc_8xx- MAKEALL
5075
5076or to build on a native PowerPC system you can type
5077
5078	CROSS_COMPILE=' ' MAKEALL
5079
5080When using the MAKEALL script, the default behaviour is to build
5081U-Boot in the source directory. This location can be changed by
5082setting the BUILD_DIR environment variable. Also, for each target
5083built, the MAKEALL script saves two log files (<target>.ERR and
5084<target>.MAKEALL) in the <source dir>/LOG directory. This default
5085location can be changed by setting the MAKEALL_LOGDIR environment
5086variable. For example:
5087
5088	export BUILD_DIR=/tmp/build
5089	export MAKEALL_LOGDIR=/tmp/log
5090	CROSS_COMPILE=ppc_8xx- MAKEALL
5091
5092With the above settings build objects are saved in the /tmp/build,
5093log files are saved in the /tmp/log and the source tree remains clean
5094during the whole build process.
5095
5096
5097See also "U-Boot Porting Guide" below.
5098
5099
5100Monitor Commands - Overview:
5101============================
5102
5103go	- start application at address 'addr'
5104run	- run commands in an environment variable
5105bootm	- boot application image from memory
5106bootp	- boot image via network using BootP/TFTP protocol
5107bootz   - boot zImage from memory
5108tftpboot- boot image via network using TFTP protocol
5109	       and env variables "ipaddr" and "serverip"
5110	       (and eventually "gatewayip")
5111tftpput - upload a file via network using TFTP protocol
5112rarpboot- boot image via network using RARP/TFTP protocol
5113diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
5114loads	- load S-Record file over serial line
5115loadb	- load binary file over serial line (kermit mode)
5116md	- memory display
5117mm	- memory modify (auto-incrementing)
5118nm	- memory modify (constant address)
5119mw	- memory write (fill)
5120cp	- memory copy
5121cmp	- memory compare
5122crc32	- checksum calculation
5123i2c	- I2C sub-system
5124sspi	- SPI utility commands
5125base	- print or set address offset
5126printenv- print environment variables
5127setenv	- set environment variables
5128saveenv - save environment variables to persistent storage
5129protect - enable or disable FLASH write protection
5130erase	- erase FLASH memory
5131flinfo	- print FLASH memory information
5132nand	- NAND memory operations (see doc/README.nand)
5133bdinfo	- print Board Info structure
5134iminfo	- print header information for application image
5135coninfo - print console devices and informations
5136ide	- IDE sub-system
5137loop	- infinite loop on address range
5138loopw	- infinite write loop on address range
5139mtest	- simple RAM test
5140icache	- enable or disable instruction cache
5141dcache	- enable or disable data cache
5142reset	- Perform RESET of the CPU
5143echo	- echo args to console
5144version - print monitor version
5145help	- print online help
5146?	- alias for 'help'
5147
5148
5149Monitor Commands - Detailed Description:
5150========================================
5151
5152TODO.
5153
5154For now: just type "help <command>".
5155
5156
5157Environment Variables:
5158======================
5159
5160U-Boot supports user configuration using Environment Variables which
5161can be made persistent by saving to Flash memory.
5162
5163Environment Variables are set using "setenv", printed using
5164"printenv", and saved to Flash using "saveenv". Using "setenv"
5165without a value can be used to delete a variable from the
5166environment. As long as you don't save the environment you are
5167working with an in-memory copy. In case the Flash area containing the
5168environment is erased by accident, a default environment is provided.
5169
5170Some configuration options can be set using Environment Variables.
5171
5172List of environment variables (most likely not complete):
5173
5174  baudrate	- see CONFIG_BAUDRATE
5175
5176  bootdelay	- see CONFIG_BOOTDELAY
5177
5178  bootcmd	- see CONFIG_BOOTCOMMAND
5179
5180  bootargs	- Boot arguments when booting an RTOS image
5181
5182  bootfile	- Name of the image to load with TFTP
5183
5184  bootm_low	- Memory range available for image processing in the bootm
5185		  command can be restricted. This variable is given as
5186		  a hexadecimal number and defines lowest address allowed
5187		  for use by the bootm command. See also "bootm_size"
5188		  environment variable. Address defined by "bootm_low" is
5189		  also the base of the initial memory mapping for the Linux
5190		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
5191		  bootm_mapsize.
5192
5193  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
5194		  This variable is given as a hexadecimal number and it
5195		  defines the size of the memory region starting at base
5196		  address bootm_low that is accessible by the Linux kernel
5197		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
5198		  as the default value if it is defined, and bootm_size is
5199		  used otherwise.
5200
5201  bootm_size	- Memory range available for image processing in the bootm
5202		  command can be restricted. This variable is given as
5203		  a hexadecimal number and defines the size of the region
5204		  allowed for use by the bootm command. See also "bootm_low"
5205		  environment variable.
5206
5207  updatefile	- Location of the software update file on a TFTP server, used
5208		  by the automatic software update feature. Please refer to
5209		  documentation in doc/README.update for more details.
5210
5211  autoload	- if set to "no" (any string beginning with 'n'),
5212		  "bootp" will just load perform a lookup of the
5213		  configuration from the BOOTP server, but not try to
5214		  load any image using TFTP
5215
5216  autostart	- if set to "yes", an image loaded using the "bootp",
5217		  "rarpboot", "tftpboot" or "diskboot" commands will
5218		  be automatically started (by internally calling
5219		  "bootm")
5220
5221		  If set to "no", a standalone image passed to the
5222		  "bootm" command will be copied to the load address
5223		  (and eventually uncompressed), but NOT be started.
5224		  This can be used to load and uncompress arbitrary
5225		  data.
5226
5227  fdt_high	- if set this restricts the maximum address that the
5228		  flattened device tree will be copied into upon boot.
5229		  For example, if you have a system with 1 GB memory
5230		  at physical address 0x10000000, while Linux kernel
5231		  only recognizes the first 704 MB as low memory, you
5232		  may need to set fdt_high as 0x3C000000 to have the
5233		  device tree blob be copied to the maximum address
5234		  of the 704 MB low memory, so that Linux kernel can
5235		  access it during the boot procedure.
5236
5237		  If this is set to the special value 0xFFFFFFFF then
5238		  the fdt will not be copied at all on boot.  For this
5239		  to work it must reside in writable memory, have
5240		  sufficient padding on the end of it for u-boot to
5241		  add the information it needs into it, and the memory
5242		  must be accessible by the kernel.
5243
5244  fdtcontroladdr- if set this is the address of the control flattened
5245		  device tree used by U-Boot when CONFIG_OF_CONTROL is
5246		  defined.
5247
5248  i2cfast	- (PPC405GP|PPC405EP only)
5249		  if set to 'y' configures Linux I2C driver for fast
5250		  mode (400kHZ). This environment variable is used in
5251		  initialization code. So, for changes to be effective
5252		  it must be saved and board must be reset.
5253
5254  initrd_high	- restrict positioning of initrd images:
5255		  If this variable is not set, initrd images will be
5256		  copied to the highest possible address in RAM; this
5257		  is usually what you want since it allows for
5258		  maximum initrd size. If for some reason you want to
5259		  make sure that the initrd image is loaded below the
5260		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
5261		  variable to a value of "no" or "off" or "0".
5262		  Alternatively, you can set it to a maximum upper
5263		  address to use (U-Boot will still check that it
5264		  does not overwrite the U-Boot stack and data).
5265
5266		  For instance, when you have a system with 16 MB
5267		  RAM, and want to reserve 4 MB from use by Linux,
5268		  you can do this by adding "mem=12M" to the value of
5269		  the "bootargs" variable. However, now you must make
5270		  sure that the initrd image is placed in the first
5271		  12 MB as well - this can be done with
5272
5273		  setenv initrd_high 00c00000
5274
5275		  If you set initrd_high to 0xFFFFFFFF, this is an
5276		  indication to U-Boot that all addresses are legal
5277		  for the Linux kernel, including addresses in flash
5278		  memory. In this case U-Boot will NOT COPY the
5279		  ramdisk at all. This may be useful to reduce the
5280		  boot time on your system, but requires that this
5281		  feature is supported by your Linux kernel.
5282
5283  ipaddr	- IP address; needed for tftpboot command
5284
5285  loadaddr	- Default load address for commands like "bootp",
5286		  "rarpboot", "tftpboot", "loadb" or "diskboot"
5287
5288  loads_echo	- see CONFIG_LOADS_ECHO
5289
5290  serverip	- TFTP server IP address; needed for tftpboot command
5291
5292  bootretry	- see CONFIG_BOOT_RETRY_TIME
5293
5294  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
5295
5296  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
5297
5298  ethprime	- controls which interface is used first.
5299
5300  ethact	- controls which interface is currently active.
5301		  For example you can do the following
5302
5303		  => setenv ethact FEC
5304		  => ping 192.168.0.1 # traffic sent on FEC
5305		  => setenv ethact SCC
5306		  => ping 10.0.0.1 # traffic sent on SCC
5307
5308  ethrotate	- When set to "no" U-Boot does not go through all
5309		  available network interfaces.
5310		  It just stays at the currently selected interface.
5311
5312  netretry	- When set to "no" each network operation will
5313		  either succeed or fail without retrying.
5314		  When set to "once" the network operation will
5315		  fail when all the available network interfaces
5316		  are tried once without success.
5317		  Useful on scripts which control the retry operation
5318		  themselves.
5319
5320  npe_ucode	- set load address for the NPE microcode
5321
5322  silent_linux  - If set then linux will be told to boot silently, by
5323		  changing the console to be empty. If "yes" it will be
5324		  made silent. If "no" it will not be made silent. If
5325		  unset, then it will be made silent if the U-Boot console
5326		  is silent.
5327
5328  tftpsrcport	- If this is set, the value is used for TFTP's
5329		  UDP source port.
5330
5331  tftpdstport	- If this is set, the value is used for TFTP's UDP
5332		  destination port instead of the Well Know Port 69.
5333
5334  tftpblocksize - Block size to use for TFTP transfers; if not set,
5335		  we use the TFTP server's default block size
5336
5337  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
5338		  seconds, minimum value is 1000 = 1 second). Defines
5339		  when a packet is considered to be lost so it has to
5340		  be retransmitted. The default is 5000 = 5 seconds.
5341		  Lowering this value may make downloads succeed
5342		  faster in networks with high packet loss rates or
5343		  with unreliable TFTP servers.
5344
5345  vlan		- When set to a value < 4095 the traffic over
5346		  Ethernet is encapsulated/received over 802.1q
5347		  VLAN tagged frames.
5348
5349The following image location variables contain the location of images
5350used in booting. The "Image" column gives the role of the image and is
5351not an environment variable name. The other columns are environment
5352variable names. "File Name" gives the name of the file on a TFTP
5353server, "RAM Address" gives the location in RAM the image will be
5354loaded to, and "Flash Location" gives the image's address in NOR
5355flash or offset in NAND flash.
5356
5357*Note* - these variables don't have to be defined for all boards, some
5358boards currenlty use other variables for these purposes, and some
5359boards use these variables for other purposes.
5360
5361Image		    File Name	     RAM Address       Flash Location
5362-----		    ---------	     -----------       --------------
5363u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
5364Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
5365device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
5366ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
5367
5368The following environment variables may be used and automatically
5369updated by the network boot commands ("bootp" and "rarpboot"),
5370depending the information provided by your boot server:
5371
5372  bootfile	- see above
5373  dnsip		- IP address of your Domain Name Server
5374  dnsip2	- IP address of your secondary Domain Name Server
5375  gatewayip	- IP address of the Gateway (Router) to use
5376  hostname	- Target hostname
5377  ipaddr	- see above
5378  netmask	- Subnet Mask
5379  rootpath	- Pathname of the root filesystem on the NFS server
5380  serverip	- see above
5381
5382
5383There are two special Environment Variables:
5384
5385  serial#	- contains hardware identification information such
5386		  as type string and/or serial number
5387  ethaddr	- Ethernet address
5388
5389These variables can be set only once (usually during manufacturing of
5390the board). U-Boot refuses to delete or overwrite these variables
5391once they have been set once.
5392
5393
5394Further special Environment Variables:
5395
5396  ver		- Contains the U-Boot version string as printed
5397		  with the "version" command. This variable is
5398		  readonly (see CONFIG_VERSION_VARIABLE).
5399
5400
5401Please note that changes to some configuration parameters may take
5402only effect after the next boot (yes, that's just like Windoze :-).
5403
5404
5405Callback functions for environment variables:
5406---------------------------------------------
5407
5408For some environment variables, the behavior of u-boot needs to change
5409when their values are changed.  This functionailty allows functions to
5410be associated with arbitrary variables.  On creation, overwrite, or
5411deletion, the callback will provide the opportunity for some side
5412effect to happen or for the change to be rejected.
5413
5414The callbacks are named and associated with a function using the
5415U_BOOT_ENV_CALLBACK macro in your board or driver code.
5416
5417These callbacks are associated with variables in one of two ways.  The
5418static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5419in the board configuration to a string that defines a list of
5420associations.  The list must be in the following format:
5421
5422	entry = variable_name[:callback_name]
5423	list = entry[,list]
5424
5425If the callback name is not specified, then the callback is deleted.
5426Spaces are also allowed anywhere in the list.
5427
5428Callbacks can also be associated by defining the ".callbacks" variable
5429with the same list format above.  Any association in ".callbacks" will
5430override any association in the static list. You can define
5431CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5432".callbacks" envirnoment variable in the default or embedded environment.
5433
5434
5435Command Line Parsing:
5436=====================
5437
5438There are two different command line parsers available with U-Boot:
5439the old "simple" one, and the much more powerful "hush" shell:
5440
5441Old, simple command line parser:
5442--------------------------------
5443
5444- supports environment variables (through setenv / saveenv commands)
5445- several commands on one line, separated by ';'
5446- variable substitution using "... ${name} ..." syntax
5447- special characters ('$', ';') can be escaped by prefixing with '\',
5448  for example:
5449	setenv bootcmd bootm \${address}
5450- You can also escape text by enclosing in single apostrophes, for example:
5451	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5452
5453Hush shell:
5454-----------
5455
5456- similar to Bourne shell, with control structures like
5457  if...then...else...fi, for...do...done; while...do...done,
5458  until...do...done, ...
5459- supports environment ("global") variables (through setenv / saveenv
5460  commands) and local shell variables (through standard shell syntax
5461  "name=value"); only environment variables can be used with "run"
5462  command
5463
5464General rules:
5465--------------
5466
5467(1) If a command line (or an environment variable executed by a "run"
5468    command) contains several commands separated by semicolon, and
5469    one of these commands fails, then the remaining commands will be
5470    executed anyway.
5471
5472(2) If you execute several variables with one call to run (i. e.
5473    calling run with a list of variables as arguments), any failing
5474    command will cause "run" to terminate, i. e. the remaining
5475    variables are not executed.
5476
5477Note for Redundant Ethernet Interfaces:
5478=======================================
5479
5480Some boards come with redundant Ethernet interfaces; U-Boot supports
5481such configurations and is capable of automatic selection of a
5482"working" interface when needed. MAC assignment works as follows:
5483
5484Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5485MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5486"eth1addr" (=>eth1), "eth2addr", ...
5487
5488If the network interface stores some valid MAC address (for instance
5489in SROM), this is used as default address if there is NO correspon-
5490ding setting in the environment; if the corresponding environment
5491variable is set, this overrides the settings in the card; that means:
5492
5493o If the SROM has a valid MAC address, and there is no address in the
5494  environment, the SROM's address is used.
5495
5496o If there is no valid address in the SROM, and a definition in the
5497  environment exists, then the value from the environment variable is
5498  used.
5499
5500o If both the SROM and the environment contain a MAC address, and
5501  both addresses are the same, this MAC address is used.
5502
5503o If both the SROM and the environment contain a MAC address, and the
5504  addresses differ, the value from the environment is used and a
5505  warning is printed.
5506
5507o If neither SROM nor the environment contain a MAC address, an error
5508  is raised.
5509
5510If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5511will be programmed into hardware as part of the initialization process.	 This
5512may be skipped by setting the appropriate 'ethmacskip' environment variable.
5513The naming convention is as follows:
5514"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5515
5516Image Formats:
5517==============
5518
5519U-Boot is capable of booting (and performing other auxiliary operations on)
5520images in two formats:
5521
5522New uImage format (FIT)
5523-----------------------
5524
5525Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5526to Flattened Device Tree). It allows the use of images with multiple
5527components (several kernels, ramdisks, etc.), with contents protected by
5528SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5529
5530
5531Old uImage format
5532-----------------
5533
5534Old image format is based on binary files which can be basically anything,
5535preceded by a special header; see the definitions in include/image.h for
5536details; basically, the header defines the following image properties:
5537
5538* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5539  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5540  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5541  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5542  INTEGRITY).
5543* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5544  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5545  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5546* Compression Type (uncompressed, gzip, bzip2)
5547* Load Address
5548* Entry Point
5549* Image Name
5550* Image Timestamp
5551
5552The header is marked by a special Magic Number, and both the header
5553and the data portions of the image are secured against corruption by
5554CRC32 checksums.
5555
5556
5557Linux Support:
5558==============
5559
5560Although U-Boot should support any OS or standalone application
5561easily, the main focus has always been on Linux during the design of
5562U-Boot.
5563
5564U-Boot includes many features that so far have been part of some
5565special "boot loader" code within the Linux kernel. Also, any
5566"initrd" images to be used are no longer part of one big Linux image;
5567instead, kernel and "initrd" are separate images. This implementation
5568serves several purposes:
5569
5570- the same features can be used for other OS or standalone
5571  applications (for instance: using compressed images to reduce the
5572  Flash memory footprint)
5573
5574- it becomes much easier to port new Linux kernel versions because
5575  lots of low-level, hardware dependent stuff are done by U-Boot
5576
5577- the same Linux kernel image can now be used with different "initrd"
5578  images; of course this also means that different kernel images can
5579  be run with the same "initrd". This makes testing easier (you don't
5580  have to build a new "zImage.initrd" Linux image when you just
5581  change a file in your "initrd"). Also, a field-upgrade of the
5582  software is easier now.
5583
5584
5585Linux HOWTO:
5586============
5587
5588Porting Linux to U-Boot based systems:
5589---------------------------------------
5590
5591U-Boot cannot save you from doing all the necessary modifications to
5592configure the Linux device drivers for use with your target hardware
5593(no, we don't intend to provide a full virtual machine interface to
5594Linux :-).
5595
5596But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5597
5598Just make sure your machine specific header file (for instance
5599include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5600Information structure as we define in include/asm-<arch>/u-boot.h,
5601and make sure that your definition of IMAP_ADDR uses the same value
5602as your U-Boot configuration in CONFIG_SYS_IMMR.
5603
5604Note that U-Boot now has a driver model, a unified model for drivers.
5605If you are adding a new driver, plumb it into driver model. If there
5606is no uclass available, you are encouraged to create one. See
5607doc/driver-model.
5608
5609
5610Configuring the Linux kernel:
5611-----------------------------
5612
5613No specific requirements for U-Boot. Make sure you have some root
5614device (initial ramdisk, NFS) for your target system.
5615
5616
5617Building a Linux Image:
5618-----------------------
5619
5620With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5621not used. If you use recent kernel source, a new build target
5622"uImage" will exist which automatically builds an image usable by
5623U-Boot. Most older kernels also have support for a "pImage" target,
5624which was introduced for our predecessor project PPCBoot and uses a
5625100% compatible format.
5626
5627Example:
5628
5629	make TQM850L_defconfig
5630	make oldconfig
5631	make dep
5632	make uImage
5633
5634The "uImage" build target uses a special tool (in 'tools/mkimage') to
5635encapsulate a compressed Linux kernel image with header	 information,
5636CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5637
5638* build a standard "vmlinux" kernel image (in ELF binary format):
5639
5640* convert the kernel into a raw binary image:
5641
5642	${CROSS_COMPILE}-objcopy -O binary \
5643				 -R .note -R .comment \
5644				 -S vmlinux linux.bin
5645
5646* compress the binary image:
5647
5648	gzip -9 linux.bin
5649
5650* package compressed binary image for U-Boot:
5651
5652	mkimage -A ppc -O linux -T kernel -C gzip \
5653		-a 0 -e 0 -n "Linux Kernel Image" \
5654		-d linux.bin.gz uImage
5655
5656
5657The "mkimage" tool can also be used to create ramdisk images for use
5658with U-Boot, either separated from the Linux kernel image, or
5659combined into one file. "mkimage" encapsulates the images with a 64
5660byte header containing information about target architecture,
5661operating system, image type, compression method, entry points, time
5662stamp, CRC32 checksums, etc.
5663
5664"mkimage" can be called in two ways: to verify existing images and
5665print the header information, or to build new images.
5666
5667In the first form (with "-l" option) mkimage lists the information
5668contained in the header of an existing U-Boot image; this includes
5669checksum verification:
5670
5671	tools/mkimage -l image
5672	  -l ==> list image header information
5673
5674The second form (with "-d" option) is used to build a U-Boot image
5675from a "data file" which is used as image payload:
5676
5677	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5678		      -n name -d data_file image
5679	  -A ==> set architecture to 'arch'
5680	  -O ==> set operating system to 'os'
5681	  -T ==> set image type to 'type'
5682	  -C ==> set compression type 'comp'
5683	  -a ==> set load address to 'addr' (hex)
5684	  -e ==> set entry point to 'ep' (hex)
5685	  -n ==> set image name to 'name'
5686	  -d ==> use image data from 'datafile'
5687
5688Right now, all Linux kernels for PowerPC systems use the same load
5689address (0x00000000), but the entry point address depends on the
5690kernel version:
5691
5692- 2.2.x kernels have the entry point at 0x0000000C,
5693- 2.3.x and later kernels have the entry point at 0x00000000.
5694
5695So a typical call to build a U-Boot image would read:
5696
5697	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5698	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5699	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5700	> examples/uImage.TQM850L
5701	Image Name:   2.4.4 kernel for TQM850L
5702	Created:      Wed Jul 19 02:34:59 2000
5703	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5704	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5705	Load Address: 0x00000000
5706	Entry Point:  0x00000000
5707
5708To verify the contents of the image (or check for corruption):
5709
5710	-> tools/mkimage -l examples/uImage.TQM850L
5711	Image Name:   2.4.4 kernel for TQM850L
5712	Created:      Wed Jul 19 02:34:59 2000
5713	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5714	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5715	Load Address: 0x00000000
5716	Entry Point:  0x00000000
5717
5718NOTE: for embedded systems where boot time is critical you can trade
5719speed for memory and install an UNCOMPRESSED image instead: this
5720needs more space in Flash, but boots much faster since it does not
5721need to be uncompressed:
5722
5723	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5724	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5725	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5726	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5727	> examples/uImage.TQM850L-uncompressed
5728	Image Name:   2.4.4 kernel for TQM850L
5729	Created:      Wed Jul 19 02:34:59 2000
5730	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5731	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5732	Load Address: 0x00000000
5733	Entry Point:  0x00000000
5734
5735
5736Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5737when your kernel is intended to use an initial ramdisk:
5738
5739	-> tools/mkimage -n 'Simple Ramdisk Image' \
5740	> -A ppc -O linux -T ramdisk -C gzip \
5741	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5742	Image Name:   Simple Ramdisk Image
5743	Created:      Wed Jan 12 14:01:50 2000
5744	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5745	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5746	Load Address: 0x00000000
5747	Entry Point:  0x00000000
5748
5749The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5750option performs the converse operation of the mkimage's second form (the "-d"
5751option). Given an image built by mkimage, the dumpimage extracts a "data file"
5752from the image:
5753
5754	tools/dumpimage -i image -p position data_file
5755	  -i ==> extract from the 'image' a specific 'data_file', \
5756	   indexed by 'position'
5757
5758
5759Installing a Linux Image:
5760-------------------------
5761
5762To downloading a U-Boot image over the serial (console) interface,
5763you must convert the image to S-Record format:
5764
5765	objcopy -I binary -O srec examples/image examples/image.srec
5766
5767The 'objcopy' does not understand the information in the U-Boot
5768image header, so the resulting S-Record file will be relative to
5769address 0x00000000. To load it to a given address, you need to
5770specify the target address as 'offset' parameter with the 'loads'
5771command.
5772
5773Example: install the image to address 0x40100000 (which on the
5774TQM8xxL is in the first Flash bank):
5775
5776	=> erase 40100000 401FFFFF
5777
5778	.......... done
5779	Erased 8 sectors
5780
5781	=> loads 40100000
5782	## Ready for S-Record download ...
5783	~>examples/image.srec
5784	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5785	...
5786	15989 15990 15991 15992
5787	[file transfer complete]
5788	[connected]
5789	## Start Addr = 0x00000000
5790
5791
5792You can check the success of the download using the 'iminfo' command;
5793this includes a checksum verification so you can be sure no data
5794corruption happened:
5795
5796	=> imi 40100000
5797
5798	## Checking Image at 40100000 ...
5799	   Image Name:	 2.2.13 for initrd on TQM850L
5800	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5801	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5802	   Load Address: 00000000
5803	   Entry Point:	 0000000c
5804	   Verifying Checksum ... OK
5805
5806
5807Boot Linux:
5808-----------
5809
5810The "bootm" command is used to boot an application that is stored in
5811memory (RAM or Flash). In case of a Linux kernel image, the contents
5812of the "bootargs" environment variable is passed to the kernel as
5813parameters. You can check and modify this variable using the
5814"printenv" and "setenv" commands:
5815
5816
5817	=> printenv bootargs
5818	bootargs=root=/dev/ram
5819
5820	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5821
5822	=> printenv bootargs
5823	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5824
5825	=> bootm 40020000
5826	## Booting Linux kernel at 40020000 ...
5827	   Image Name:	 2.2.13 for NFS on TQM850L
5828	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5829	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5830	   Load Address: 00000000
5831	   Entry Point:	 0000000c
5832	   Verifying Checksum ... OK
5833	   Uncompressing Kernel Image ... OK
5834	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
5835	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5836	time_init: decrementer frequency = 187500000/60
5837	Calibrating delay loop... 49.77 BogoMIPS
5838	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5839	...
5840
5841If you want to boot a Linux kernel with initial RAM disk, you pass
5842the memory addresses of both the kernel and the initrd image (PPBCOOT
5843format!) to the "bootm" command:
5844
5845	=> imi 40100000 40200000
5846
5847	## Checking Image at 40100000 ...
5848	   Image Name:	 2.2.13 for initrd on TQM850L
5849	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5850	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5851	   Load Address: 00000000
5852	   Entry Point:	 0000000c
5853	   Verifying Checksum ... OK
5854
5855	## Checking Image at 40200000 ...
5856	   Image Name:	 Simple Ramdisk Image
5857	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5858	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5859	   Load Address: 00000000
5860	   Entry Point:	 00000000
5861	   Verifying Checksum ... OK
5862
5863	=> bootm 40100000 40200000
5864	## Booting Linux kernel at 40100000 ...
5865	   Image Name:	 2.2.13 for initrd on TQM850L
5866	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5867	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5868	   Load Address: 00000000
5869	   Entry Point:	 0000000c
5870	   Verifying Checksum ... OK
5871	   Uncompressing Kernel Image ... OK
5872	## Loading RAMDisk Image at 40200000 ...
5873	   Image Name:	 Simple Ramdisk Image
5874	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5875	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5876	   Load Address: 00000000
5877	   Entry Point:	 00000000
5878	   Verifying Checksum ... OK
5879	   Loading Ramdisk ... OK
5880	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
5881	Boot arguments: root=/dev/ram
5882	time_init: decrementer frequency = 187500000/60
5883	Calibrating delay loop... 49.77 BogoMIPS
5884	...
5885	RAMDISK: Compressed image found at block 0
5886	VFS: Mounted root (ext2 filesystem).
5887
5888	bash#
5889
5890Boot Linux and pass a flat device tree:
5891-----------
5892
5893First, U-Boot must be compiled with the appropriate defines. See the section
5894titled "Linux Kernel Interface" above for a more in depth explanation. The
5895following is an example of how to start a kernel and pass an updated
5896flat device tree:
5897
5898=> print oftaddr
5899oftaddr=0x300000
5900=> print oft
5901oft=oftrees/mpc8540ads.dtb
5902=> tftp $oftaddr $oft
5903Speed: 1000, full duplex
5904Using TSEC0 device
5905TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5906Filename 'oftrees/mpc8540ads.dtb'.
5907Load address: 0x300000
5908Loading: #
5909done
5910Bytes transferred = 4106 (100a hex)
5911=> tftp $loadaddr $bootfile
5912Speed: 1000, full duplex
5913Using TSEC0 device
5914TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5915Filename 'uImage'.
5916Load address: 0x200000
5917Loading:############
5918done
5919Bytes transferred = 1029407 (fb51f hex)
5920=> print loadaddr
5921loadaddr=200000
5922=> print oftaddr
5923oftaddr=0x300000
5924=> bootm $loadaddr - $oftaddr
5925## Booting image at 00200000 ...
5926   Image Name:	 Linux-2.6.17-dirty
5927   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5928   Data Size:	 1029343 Bytes = 1005.2 kB
5929   Load Address: 00000000
5930   Entry Point:	 00000000
5931   Verifying Checksum ... OK
5932   Uncompressing Kernel Image ... OK
5933Booting using flat device tree at 0x300000
5934Using MPC85xx ADS machine description
5935Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5936[snip]
5937
5938
5939More About U-Boot Image Types:
5940------------------------------
5941
5942U-Boot supports the following image types:
5943
5944   "Standalone Programs" are directly runnable in the environment
5945	provided by U-Boot; it is expected that (if they behave
5946	well) you can continue to work in U-Boot after return from
5947	the Standalone Program.
5948   "OS Kernel Images" are usually images of some Embedded OS which
5949	will take over control completely. Usually these programs
5950	will install their own set of exception handlers, device
5951	drivers, set up the MMU, etc. - this means, that you cannot
5952	expect to re-enter U-Boot except by resetting the CPU.
5953   "RAMDisk Images" are more or less just data blocks, and their
5954	parameters (address, size) are passed to an OS kernel that is
5955	being started.
5956   "Multi-File Images" contain several images, typically an OS
5957	(Linux) kernel image and one or more data images like
5958	RAMDisks. This construct is useful for instance when you want
5959	to boot over the network using BOOTP etc., where the boot
5960	server provides just a single image file, but you want to get
5961	for instance an OS kernel and a RAMDisk image.
5962
5963	"Multi-File Images" start with a list of image sizes, each
5964	image size (in bytes) specified by an "uint32_t" in network
5965	byte order. This list is terminated by an "(uint32_t)0".
5966	Immediately after the terminating 0 follow the images, one by
5967	one, all aligned on "uint32_t" boundaries (size rounded up to
5968	a multiple of 4 bytes).
5969
5970   "Firmware Images" are binary images containing firmware (like
5971	U-Boot or FPGA images) which usually will be programmed to
5972	flash memory.
5973
5974   "Script files" are command sequences that will be executed by
5975	U-Boot's command interpreter; this feature is especially
5976	useful when you configure U-Boot to use a real shell (hush)
5977	as command interpreter.
5978
5979Booting the Linux zImage:
5980-------------------------
5981
5982On some platforms, it's possible to boot Linux zImage. This is done
5983using the "bootz" command. The syntax of "bootz" command is the same
5984as the syntax of "bootm" command.
5985
5986Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5987kernel with raw initrd images. The syntax is slightly different, the
5988address of the initrd must be augmented by it's size, in the following
5989format: "<initrd addres>:<initrd size>".
5990
5991
5992Standalone HOWTO:
5993=================
5994
5995One of the features of U-Boot is that you can dynamically load and
5996run "standalone" applications, which can use some resources of
5997U-Boot like console I/O functions or interrupt services.
5998
5999Two simple examples are included with the sources:
6000
6001"Hello World" Demo:
6002-------------------
6003
6004'examples/hello_world.c' contains a small "Hello World" Demo
6005application; it is automatically compiled when you build U-Boot.
6006It's configured to run at address 0x00040004, so you can play with it
6007like that:
6008
6009	=> loads
6010	## Ready for S-Record download ...
6011	~>examples/hello_world.srec
6012	1 2 3 4 5 6 7 8 9 10 11 ...
6013	[file transfer complete]
6014	[connected]
6015	## Start Addr = 0x00040004
6016
6017	=> go 40004 Hello World! This is a test.
6018	## Starting application at 0x00040004 ...
6019	Hello World
6020	argc = 7
6021	argv[0] = "40004"
6022	argv[1] = "Hello"
6023	argv[2] = "World!"
6024	argv[3] = "This"
6025	argv[4] = "is"
6026	argv[5] = "a"
6027	argv[6] = "test."
6028	argv[7] = "<NULL>"
6029	Hit any key to exit ...
6030
6031	## Application terminated, rc = 0x0
6032
6033Another example, which demonstrates how to register a CPM interrupt
6034handler with the U-Boot code, can be found in 'examples/timer.c'.
6035Here, a CPM timer is set up to generate an interrupt every second.
6036The interrupt service routine is trivial, just printing a '.'
6037character, but this is just a demo program. The application can be
6038controlled by the following keys:
6039
6040	? - print current values og the CPM Timer registers
6041	b - enable interrupts and start timer
6042	e - stop timer and disable interrupts
6043	q - quit application
6044
6045	=> loads
6046	## Ready for S-Record download ...
6047	~>examples/timer.srec
6048	1 2 3 4 5 6 7 8 9 10 11 ...
6049	[file transfer complete]
6050	[connected]
6051	## Start Addr = 0x00040004
6052
6053	=> go 40004
6054	## Starting application at 0x00040004 ...
6055	TIMERS=0xfff00980
6056	Using timer 1
6057	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
6058
6059Hit 'b':
6060	[q, b, e, ?] Set interval 1000000 us
6061	Enabling timer
6062Hit '?':
6063	[q, b, e, ?] ........
6064	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
6065Hit '?':
6066	[q, b, e, ?] .
6067	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
6068Hit '?':
6069	[q, b, e, ?] .
6070	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
6071Hit '?':
6072	[q, b, e, ?] .
6073	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
6074Hit 'e':
6075	[q, b, e, ?] ...Stopping timer
6076Hit 'q':
6077	[q, b, e, ?] ## Application terminated, rc = 0x0
6078
6079
6080Minicom warning:
6081================
6082
6083Over time, many people have reported problems when trying to use the
6084"minicom" terminal emulation program for serial download. I (wd)
6085consider minicom to be broken, and recommend not to use it. Under
6086Unix, I recommend to use C-Kermit for general purpose use (and
6087especially for kermit binary protocol download ("loadb" command), and
6088use "cu" for S-Record download ("loads" command).  See
6089http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
6090for help with kermit.
6091
6092
6093Nevertheless, if you absolutely want to use it try adding this
6094configuration to your "File transfer protocols" section:
6095
6096	   Name	   Program			Name U/D FullScr IO-Red. Multi
6097	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
6098	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
6099
6100
6101NetBSD Notes:
6102=============
6103
6104Starting at version 0.9.2, U-Boot supports NetBSD both as host
6105(build U-Boot) and target system (boots NetBSD/mpc8xx).
6106
6107Building requires a cross environment; it is known to work on
6108NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
6109need gmake since the Makefiles are not compatible with BSD make).
6110Note that the cross-powerpc package does not install include files;
6111attempting to build U-Boot will fail because <machine/ansi.h> is
6112missing.  This file has to be installed and patched manually:
6113
6114	# cd /usr/pkg/cross/powerpc-netbsd/include
6115	# mkdir powerpc
6116	# ln -s powerpc machine
6117	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
6118	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
6119
6120Native builds *don't* work due to incompatibilities between native
6121and U-Boot include files.
6122
6123Booting assumes that (the first part of) the image booted is a
6124stage-2 loader which in turn loads and then invokes the kernel
6125proper. Loader sources will eventually appear in the NetBSD source
6126tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
6127meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
6128
6129
6130Implementation Internals:
6131=========================
6132
6133The following is not intended to be a complete description of every
6134implementation detail. However, it should help to understand the
6135inner workings of U-Boot and make it easier to port it to custom
6136hardware.
6137
6138
6139Initial Stack, Global Data:
6140---------------------------
6141
6142The implementation of U-Boot is complicated by the fact that U-Boot
6143starts running out of ROM (flash memory), usually without access to
6144system RAM (because the memory controller is not initialized yet).
6145This means that we don't have writable Data or BSS segments, and BSS
6146is not initialized as zero. To be able to get a C environment working
6147at all, we have to allocate at least a minimal stack. Implementation
6148options for this are defined and restricted by the CPU used: Some CPU
6149models provide on-chip memory (like the IMMR area on MPC8xx and
6150MPC826x processors), on others (parts of) the data cache can be
6151locked as (mis-) used as memory, etc.
6152
6153	Chris Hallinan posted a good summary of these issues to the
6154	U-Boot mailing list:
6155
6156	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
6157	From: "Chris Hallinan" <clh@net1plus.com>
6158	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
6159	...
6160
6161	Correct me if I'm wrong, folks, but the way I understand it
6162	is this: Using DCACHE as initial RAM for Stack, etc, does not
6163	require any physical RAM backing up the cache. The cleverness
6164	is that the cache is being used as a temporary supply of
6165	necessary storage before the SDRAM controller is setup. It's
6166	beyond the scope of this list to explain the details, but you
6167	can see how this works by studying the cache architecture and
6168	operation in the architecture and processor-specific manuals.
6169
6170	OCM is On Chip Memory, which I believe the 405GP has 4K. It
6171	is another option for the system designer to use as an
6172	initial stack/RAM area prior to SDRAM being available. Either
6173	option should work for you. Using CS 4 should be fine if your
6174	board designers haven't used it for something that would
6175	cause you grief during the initial boot! It is frequently not
6176	used.
6177
6178	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
6179	with your processor/board/system design. The default value
6180	you will find in any recent u-boot distribution in
6181	walnut.h should work for you. I'd set it to a value larger
6182	than your SDRAM module. If you have a 64MB SDRAM module, set
6183	it above 400_0000. Just make sure your board has no resources
6184	that are supposed to respond to that address! That code in
6185	start.S has been around a while and should work as is when
6186	you get the config right.
6187
6188	-Chris Hallinan
6189	DS4.COM, Inc.
6190
6191It is essential to remember this, since it has some impact on the C
6192code for the initialization procedures:
6193
6194* Initialized global data (data segment) is read-only. Do not attempt
6195  to write it.
6196
6197* Do not use any uninitialized global data (or implicitely initialized
6198  as zero data - BSS segment) at all - this is undefined, initiali-
6199  zation is performed later (when relocating to RAM).
6200
6201* Stack space is very limited. Avoid big data buffers or things like
6202  that.
6203
6204Having only the stack as writable memory limits means we cannot use
6205normal global data to share information beween the code. But it
6206turned out that the implementation of U-Boot can be greatly
6207simplified by making a global data structure (gd_t) available to all
6208functions. We could pass a pointer to this data as argument to _all_
6209functions, but this would bloat the code. Instead we use a feature of
6210the GCC compiler (Global Register Variables) to share the data: we
6211place a pointer (gd) to the global data into a register which we
6212reserve for this purpose.
6213
6214When choosing a register for such a purpose we are restricted by the
6215relevant  (E)ABI  specifications for the current architecture, and by
6216GCC's implementation.
6217
6218For PowerPC, the following registers have specific use:
6219	R1:	stack pointer
6220	R2:	reserved for system use
6221	R3-R4:	parameter passing and return values
6222	R5-R10: parameter passing
6223	R13:	small data area pointer
6224	R30:	GOT pointer
6225	R31:	frame pointer
6226
6227	(U-Boot also uses R12 as internal GOT pointer. r12
6228	is a volatile register so r12 needs to be reset when
6229	going back and forth between asm and C)
6230
6231    ==> U-Boot will use R2 to hold a pointer to the global data
6232
6233    Note: on PPC, we could use a static initializer (since the
6234    address of the global data structure is known at compile time),
6235    but it turned out that reserving a register results in somewhat
6236    smaller code - although the code savings are not that big (on
6237    average for all boards 752 bytes for the whole U-Boot image,
6238    624 text + 127 data).
6239
6240On Blackfin, the normal C ABI (except for P3) is followed as documented here:
6241	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
6242
6243    ==> U-Boot will use P3 to hold a pointer to the global data
6244
6245On ARM, the following registers are used:
6246
6247	R0:	function argument word/integer result
6248	R1-R3:	function argument word
6249	R9:	platform specific
6250	R10:	stack limit (used only if stack checking is enabled)
6251	R11:	argument (frame) pointer
6252	R12:	temporary workspace
6253	R13:	stack pointer
6254	R14:	link register
6255	R15:	program counter
6256
6257    ==> U-Boot will use R9 to hold a pointer to the global data
6258
6259    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
6260
6261On Nios II, the ABI is documented here:
6262	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
6263
6264    ==> U-Boot will use gp to hold a pointer to the global data
6265
6266    Note: on Nios II, we give "-G0" option to gcc and don't use gp
6267    to access small data sections, so gp is free.
6268
6269On NDS32, the following registers are used:
6270
6271	R0-R1:	argument/return
6272	R2-R5:	argument
6273	R15:	temporary register for assembler
6274	R16:	trampoline register
6275	R28:	frame pointer (FP)
6276	R29:	global pointer (GP)
6277	R30:	link register (LP)
6278	R31:	stack pointer (SP)
6279	PC:	program counter (PC)
6280
6281    ==> U-Boot will use R10 to hold a pointer to the global data
6282
6283NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
6284or current versions of GCC may "optimize" the code too much.
6285
6286Memory Management:
6287------------------
6288
6289U-Boot runs in system state and uses physical addresses, i.e. the
6290MMU is not used either for address mapping nor for memory protection.
6291
6292The available memory is mapped to fixed addresses using the memory
6293controller. In this process, a contiguous block is formed for each
6294memory type (Flash, SDRAM, SRAM), even when it consists of several
6295physical memory banks.
6296
6297U-Boot is installed in the first 128 kB of the first Flash bank (on
6298TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
6299booting and sizing and initializing DRAM, the code relocates itself
6300to the upper end of DRAM. Immediately below the U-Boot code some
6301memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
6302configuration setting]. Below that, a structure with global Board
6303Info data is placed, followed by the stack (growing downward).
6304
6305Additionally, some exception handler code is copied to the low 8 kB
6306of DRAM (0x00000000 ... 0x00001FFF).
6307
6308So a typical memory configuration with 16 MB of DRAM could look like
6309this:
6310
6311	0x0000 0000	Exception Vector code
6312	      :
6313	0x0000 1FFF
6314	0x0000 2000	Free for Application Use
6315	      :
6316	      :
6317
6318	      :
6319	      :
6320	0x00FB FF20	Monitor Stack (Growing downward)
6321	0x00FB FFAC	Board Info Data and permanent copy of global data
6322	0x00FC 0000	Malloc Arena
6323	      :
6324	0x00FD FFFF
6325	0x00FE 0000	RAM Copy of Monitor Code
6326	...		eventually: LCD or video framebuffer
6327	...		eventually: pRAM (Protected RAM - unchanged by reset)
6328	0x00FF FFFF	[End of RAM]
6329
6330
6331System Initialization:
6332----------------------
6333
6334In the reset configuration, U-Boot starts at the reset entry point
6335(on most PowerPC systems at address 0x00000100). Because of the reset
6336configuration for CS0# this is a mirror of the onboard Flash memory.
6337To be able to re-map memory U-Boot then jumps to its link address.
6338To be able to implement the initialization code in C, a (small!)
6339initial stack is set up in the internal Dual Ported RAM (in case CPUs
6340which provide such a feature like MPC8xx or MPC8260), or in a locked
6341part of the data cache. After that, U-Boot initializes the CPU core,
6342the caches and the SIU.
6343
6344Next, all (potentially) available memory banks are mapped using a
6345preliminary mapping. For example, we put them on 512 MB boundaries
6346(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
6347on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
6348programmed for SDRAM access. Using the temporary configuration, a
6349simple memory test is run that determines the size of the SDRAM
6350banks.
6351
6352When there is more than one SDRAM bank, and the banks are of
6353different size, the largest is mapped first. For equal size, the first
6354bank (CS2#) is mapped first. The first mapping is always for address
63550x00000000, with any additional banks following immediately to create
6356contiguous memory starting from 0.
6357
6358Then, the monitor installs itself at the upper end of the SDRAM area
6359and allocates memory for use by malloc() and for the global Board
6360Info data; also, the exception vector code is copied to the low RAM
6361pages, and the final stack is set up.
6362
6363Only after this relocation will you have a "normal" C environment;
6364until that you are restricted in several ways, mostly because you are
6365running from ROM, and because the code will have to be relocated to a
6366new address in RAM.
6367
6368
6369U-Boot Porting Guide:
6370----------------------
6371
6372[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
6373list, October 2002]
6374
6375
6376int main(int argc, char *argv[])
6377{
6378	sighandler_t no_more_time;
6379
6380	signal(SIGALRM, no_more_time);
6381	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6382
6383	if (available_money > available_manpower) {
6384		Pay consultant to port U-Boot;
6385		return 0;
6386	}
6387
6388	Download latest U-Boot source;
6389
6390	Subscribe to u-boot mailing list;
6391
6392	if (clueless)
6393		email("Hi, I am new to U-Boot, how do I get started?");
6394
6395	while (learning) {
6396		Read the README file in the top level directory;
6397		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6398		Read applicable doc/*.README;
6399		Read the source, Luke;
6400		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6401	}
6402
6403	if (available_money > toLocalCurrency ($2500))
6404		Buy a BDI3000;
6405	else
6406		Add a lot of aggravation and time;
6407
6408	if (a similar board exists) {	/* hopefully... */
6409		cp -a board/<similar> board/<myboard>
6410		cp include/configs/<similar>.h include/configs/<myboard>.h
6411	} else {
6412		Create your own board support subdirectory;
6413		Create your own board include/configs/<myboard>.h file;
6414	}
6415	Edit new board/<myboard> files
6416	Edit new include/configs/<myboard>.h
6417
6418	while (!accepted) {
6419		while (!running) {
6420			do {
6421				Add / modify source code;
6422			} until (compiles);
6423			Debug;
6424			if (clueless)
6425				email("Hi, I am having problems...");
6426		}
6427		Send patch file to the U-Boot email list;
6428		if (reasonable critiques)
6429			Incorporate improvements from email list code review;
6430		else
6431			Defend code as written;
6432	}
6433
6434	return 0;
6435}
6436
6437void no_more_time (int sig)
6438{
6439      hire_a_guru();
6440}
6441
6442
6443Coding Standards:
6444-----------------
6445
6446All contributions to U-Boot should conform to the Linux kernel
6447coding style; see the file "Documentation/CodingStyle" and the script
6448"scripts/Lindent" in your Linux kernel source directory.
6449
6450Source files originating from a different project (for example the
6451MTD subsystem) are generally exempt from these guidelines and are not
6452reformated to ease subsequent migration to newer versions of those
6453sources.
6454
6455Please note that U-Boot is implemented in C (and to some small parts in
6456Assembler); no C++ is used, so please do not use C++ style comments (//)
6457in your code.
6458
6459Please also stick to the following formatting rules:
6460- remove any trailing white space
6461- use TAB characters for indentation and vertical alignment, not spaces
6462- make sure NOT to use DOS '\r\n' line feeds
6463- do not add more than 2 consecutive empty lines to source files
6464- do not add trailing empty lines to source files
6465
6466Submissions which do not conform to the standards may be returned
6467with a request to reformat the changes.
6468
6469
6470Submitting Patches:
6471-------------------
6472
6473Since the number of patches for U-Boot is growing, we need to
6474establish some rules. Submissions which do not conform to these rules
6475may be rejected, even when they contain important and valuable stuff.
6476
6477Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6478
6479Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6480see http://lists.denx.de/mailman/listinfo/u-boot
6481
6482When you send a patch, please include the following information with
6483it:
6484
6485* For bug fixes: a description of the bug and how your patch fixes
6486  this bug. Please try to include a way of demonstrating that the
6487  patch actually fixes something.
6488
6489* For new features: a description of the feature and your
6490  implementation.
6491
6492* A CHANGELOG entry as plaintext (separate from the patch)
6493
6494* For major contributions, your entry to the CREDITS file
6495
6496* When you add support for a new board, don't forget to add a
6497  maintainer e-mail address to the boards.cfg file, too.
6498
6499* If your patch adds new configuration options, don't forget to
6500  document these in the README file.
6501
6502* The patch itself. If you are using git (which is *strongly*
6503  recommended) you can easily generate the patch using the
6504  "git format-patch". If you then use "git send-email" to send it to
6505  the U-Boot mailing list, you will avoid most of the common problems
6506  with some other mail clients.
6507
6508  If you cannot use git, use "diff -purN OLD NEW". If your version of
6509  diff does not support these options, then get the latest version of
6510  GNU diff.
6511
6512  The current directory when running this command shall be the parent
6513  directory of the U-Boot source tree (i. e. please make sure that
6514  your patch includes sufficient directory information for the
6515  affected files).
6516
6517  We prefer patches as plain text. MIME attachments are discouraged,
6518  and compressed attachments must not be used.
6519
6520* If one logical set of modifications affects or creates several
6521  files, all these changes shall be submitted in a SINGLE patch file.
6522
6523* Changesets that contain different, unrelated modifications shall be
6524  submitted as SEPARATE patches, one patch per changeset.
6525
6526
6527Notes:
6528
6529* Before sending the patch, run the MAKEALL script on your patched
6530  source tree and make sure that no errors or warnings are reported
6531  for any of the boards.
6532
6533* Keep your modifications to the necessary minimum: A patch
6534  containing several unrelated changes or arbitrary reformats will be
6535  returned with a request to re-formatting / split it.
6536
6537* If you modify existing code, make sure that your new code does not
6538  add to the memory footprint of the code ;-) Small is beautiful!
6539  When adding new features, these should compile conditionally only
6540  (using #ifdef), and the resulting code with the new feature
6541  disabled must not need more memory than the old code without your
6542  modification.
6543
6544* Remember that there is a size limit of 100 kB per message on the
6545  u-boot mailing list. Bigger patches will be moderated. If they are
6546  reasonable and not too big, they will be acknowledged. But patches
6547  bigger than the size limit should be avoided.
6548