xref: /openbmc/u-boot/README (revision c6832a96)
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_FAT_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_FAT_LOAD_PAYLOAD_NAME
3568		Filename to read to load U-Boot when reading from FAT
3569
3570		CONFIG_SPL_FAT_LOAD_KERNEL_NAME
3571		Filename to read to load kernel uImage when reading
3572		from FAT (for Falcon mode)
3573
3574		CONFIG_SPL_FAT_LOAD_ARGS_NAME
3575		Filename to read to load kernel argument parameters
3576		when reading from FAT (for Falcon mode)
3577
3578		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3579		Set this for NAND SPL on PPC mpc83xx targets, so that
3580		start.S waits for the rest of the SPL to load before
3581		continuing (the hardware starts execution after just
3582		loading the first page rather than the full 4K).
3583
3584		CONFIG_SPL_SKIP_RELOCATE
3585		Avoid SPL relocation
3586
3587		CONFIG_SPL_NAND_BASE
3588		Include nand_base.c in the SPL.  Requires
3589		CONFIG_SPL_NAND_DRIVERS.
3590
3591		CONFIG_SPL_NAND_DRIVERS
3592		SPL uses normal NAND drivers, not minimal drivers.
3593
3594		CONFIG_SPL_NAND_ECC
3595		Include standard software ECC in the SPL
3596
3597		CONFIG_SPL_NAND_SIMPLE
3598		Support for NAND boot using simple NAND drivers that
3599		expose the cmd_ctrl() interface.
3600
3601		CONFIG_SPL_MTD_SUPPORT
3602		Support for the MTD subsystem within SPL.  Useful for
3603		environment on NAND support within SPL.
3604
3605		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3606		Set for the SPL on PPC mpc8xxx targets, support for
3607		drivers/ddr/fsl/libddr.o in SPL binary.
3608
3609		CONFIG_SPL_COMMON_INIT_DDR
3610		Set for common ddr init with serial presence detect in
3611		SPL binary.
3612
3613		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3614		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3615		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3616		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3617		CONFIG_SYS_NAND_ECCBYTES
3618		Defines the size and behavior of the NAND that SPL uses
3619		to read U-Boot
3620
3621		CONFIG_SPL_NAND_BOOT
3622		Add support NAND boot
3623
3624		CONFIG_SYS_NAND_U_BOOT_OFFS
3625		Location in NAND to read U-Boot from
3626
3627		CONFIG_SYS_NAND_U_BOOT_DST
3628		Location in memory to load U-Boot to
3629
3630		CONFIG_SYS_NAND_U_BOOT_SIZE
3631		Size of image to load
3632
3633		CONFIG_SYS_NAND_U_BOOT_START
3634		Entry point in loaded image to jump to
3635
3636		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3637		Define this if you need to first read the OOB and then the
3638		data. This is used for example on davinci plattforms.
3639
3640		CONFIG_SPL_OMAP3_ID_NAND
3641		Support for an OMAP3-specific set of functions to return the
3642		ID and MFR of the first attached NAND chip, if present.
3643
3644		CONFIG_SPL_SERIAL_SUPPORT
3645		Support for drivers/serial/libserial.o in SPL binary
3646
3647		CONFIG_SPL_SPI_FLASH_SUPPORT
3648		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3649
3650		CONFIG_SPL_SPI_SUPPORT
3651		Support for drivers/spi/libspi.o in SPL binary
3652
3653		CONFIG_SPL_RAM_DEVICE
3654		Support for running image already present in ram, in SPL binary
3655
3656		CONFIG_SPL_LIBGENERIC_SUPPORT
3657		Support for lib/libgeneric.o in SPL binary
3658
3659		CONFIG_SPL_ENV_SUPPORT
3660		Support for the environment operating in SPL binary
3661
3662		CONFIG_SPL_NET_SUPPORT
3663		Support for the net/libnet.o in SPL binary.
3664		It conflicts with SPL env from storage medium specified by
3665		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3666
3667		CONFIG_SPL_PAD_TO
3668		Image offset to which the SPL should be padded before appending
3669		the SPL payload. By default, this is defined as
3670		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3671		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3672		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3673
3674		CONFIG_SPL_TARGET
3675		Final target image containing SPL and payload.  Some SPLs
3676		use an arch-specific makefile fragment instead, for
3677		example if more than one image needs to be produced.
3678
3679		CONFIG_FIT_SPL_PRINT
3680		Printing information about a FIT image adds quite a bit of
3681		code to SPL. So this is normally disabled in SPL. Use this
3682		option to re-enable it. This will affect the output of the
3683		bootm command when booting a FIT image.
3684
3685- TPL framework
3686		CONFIG_TPL
3687		Enable building of TPL globally.
3688
3689		CONFIG_TPL_PAD_TO
3690		Image offset to which the TPL should be padded before appending
3691		the TPL payload. By default, this is defined as
3692		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3693		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3694		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3695
3696Modem Support:
3697--------------
3698
3699[so far only for SMDK2400 boards]
3700
3701- Modem support enable:
3702		CONFIG_MODEM_SUPPORT
3703
3704- RTS/CTS Flow control enable:
3705		CONFIG_HWFLOW
3706
3707- Modem debug support:
3708		CONFIG_MODEM_SUPPORT_DEBUG
3709
3710		Enables debugging stuff (char screen[1024], dbg())
3711		for modem support. Useful only with BDI2000.
3712
3713- Interrupt support (PPC):
3714
3715		There are common interrupt_init() and timer_interrupt()
3716		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3717		for CPU specific initialization. interrupt_init_cpu()
3718		should set decrementer_count to appropriate value. If
3719		CPU resets decrementer automatically after interrupt
3720		(ppc4xx) it should set decrementer_count to zero.
3721		timer_interrupt() calls timer_interrupt_cpu() for CPU
3722		specific handling. If board has watchdog / status_led
3723		/ other_activity_monitor it works automatically from
3724		general timer_interrupt().
3725
3726- General:
3727
3728		In the target system modem support is enabled when a
3729		specific key (key combination) is pressed during
3730		power-on. Otherwise U-Boot will boot normally
3731		(autoboot). The key_pressed() function is called from
3732		board_init(). Currently key_pressed() is a dummy
3733		function, returning 1 and thus enabling modem
3734		initialization.
3735
3736		If there are no modem init strings in the
3737		environment, U-Boot proceed to autoboot; the
3738		previous output (banner, info printfs) will be
3739		suppressed, though.
3740
3741		See also: doc/README.Modem
3742
3743Board initialization settings:
3744------------------------------
3745
3746During Initialization u-boot calls a number of board specific functions
3747to allow the preparation of board specific prerequisites, e.g. pin setup
3748before drivers are initialized. To enable these callbacks the
3749following configuration macros have to be defined. Currently this is
3750architecture specific, so please check arch/your_architecture/lib/board.c
3751typically in board_init_f() and board_init_r().
3752
3753- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3754- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3755- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3756- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3757
3758Configuration Settings:
3759-----------------------
3760
3761- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3762		Optionally it can be defined to support 64-bit memory commands.
3763
3764- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3765		undefine this when you're short of memory.
3766
3767- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3768		width of the commands listed in the 'help' command output.
3769
3770- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3771		prompt for user input.
3772
3773- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3774
3775- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3776
3777- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3778
3779- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3780		the application (usually a Linux kernel) when it is
3781		booted
3782
3783- CONFIG_SYS_BAUDRATE_TABLE:
3784		List of legal baudrate settings for this board.
3785
3786- CONFIG_SYS_CONSOLE_INFO_QUIET
3787		Suppress display of console information at boot.
3788
3789- CONFIG_SYS_CONSOLE_IS_IN_ENV
3790		If the board specific function
3791			extern int overwrite_console (void);
3792		returns 1, the stdin, stderr and stdout are switched to the
3793		serial port, else the settings in the environment are used.
3794
3795- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3796		Enable the call to overwrite_console().
3797
3798- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3799		Enable overwrite of previous console environment settings.
3800
3801- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3802		Begin and End addresses of the area used by the
3803		simple memory test.
3804
3805- CONFIG_SYS_ALT_MEMTEST:
3806		Enable an alternate, more extensive memory test.
3807
3808- CONFIG_SYS_MEMTEST_SCRATCH:
3809		Scratch address used by the alternate memory test
3810		You only need to set this if address zero isn't writeable
3811
3812- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3813		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3814		this specified memory area will get subtracted from the top
3815		(end) of RAM and won't get "touched" at all by U-Boot. By
3816		fixing up gd->ram_size the Linux kernel should gets passed
3817		the now "corrected" memory size and won't touch it either.
3818		This should work for arch/ppc and arch/powerpc. Only Linux
3819		board ports in arch/powerpc with bootwrapper support that
3820		recalculate the memory size from the SDRAM controller setup
3821		will have to get fixed in Linux additionally.
3822
3823		This option can be used as a workaround for the 440EPx/GRx
3824		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3825		be touched.
3826
3827		WARNING: Please make sure that this value is a multiple of
3828		the Linux page size (normally 4k). If this is not the case,
3829		then the end address of the Linux memory will be located at a
3830		non page size aligned address and this could cause major
3831		problems.
3832
3833- CONFIG_SYS_LOADS_BAUD_CHANGE:
3834		Enable temporary baudrate change while serial download
3835
3836- CONFIG_SYS_SDRAM_BASE:
3837		Physical start address of SDRAM. _Must_ be 0 here.
3838
3839- CONFIG_SYS_MBIO_BASE:
3840		Physical start address of Motherboard I/O (if using a
3841		Cogent motherboard)
3842
3843- CONFIG_SYS_FLASH_BASE:
3844		Physical start address of Flash memory.
3845
3846- CONFIG_SYS_MONITOR_BASE:
3847		Physical start address of boot monitor code (set by
3848		make config files to be same as the text base address
3849		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3850		CONFIG_SYS_FLASH_BASE when booting from flash.
3851
3852- CONFIG_SYS_MONITOR_LEN:
3853		Size of memory reserved for monitor code, used to
3854		determine _at_compile_time_ (!) if the environment is
3855		embedded within the U-Boot image, or in a separate
3856		flash sector.
3857
3858- CONFIG_SYS_MALLOC_LEN:
3859		Size of DRAM reserved for malloc() use.
3860
3861- CONFIG_SYS_MALLOC_F_LEN
3862		Size of the malloc() pool for use before relocation. If
3863		this is defined, then a very simple malloc() implementation
3864		will become available before relocation. The address is just
3865		below the global data, and the stack is moved down to make
3866		space.
3867
3868		This feature allocates regions with increasing addresses
3869		within the region. calloc() is supported, but realloc()
3870		is not available. free() is supported but does nothing.
3871		The memory will be freed (or in fact just forgotton) when
3872		U-Boot relocates itself.
3873
3874		Pre-relocation malloc() is only supported on ARM and sandbox
3875		at present but is fairly easy to enable for other archs.
3876
3877- CONFIG_SYS_BOOTM_LEN:
3878		Normally compressed uImages are limited to an
3879		uncompressed size of 8 MBytes. If this is not enough,
3880		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3881		to adjust this setting to your needs.
3882
3883- CONFIG_SYS_BOOTMAPSZ:
3884		Maximum size of memory mapped by the startup code of
3885		the Linux kernel; all data that must be processed by
3886		the Linux kernel (bd_info, boot arguments, FDT blob if
3887		used) must be put below this limit, unless "bootm_low"
3888		environment variable is defined and non-zero. In such case
3889		all data for the Linux kernel must be between "bootm_low"
3890		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3891		variable "bootm_mapsize" will override the value of
3892		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3893		then the value in "bootm_size" will be used instead.
3894
3895- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3896		Enable initrd_high functionality.  If defined then the
3897		initrd_high feature is enabled and the bootm ramdisk subcommand
3898		is enabled.
3899
3900- CONFIG_SYS_BOOT_GET_CMDLINE:
3901		Enables allocating and saving kernel cmdline in space between
3902		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3903
3904- CONFIG_SYS_BOOT_GET_KBD:
3905		Enables allocating and saving a kernel copy of the bd_info in
3906		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3907
3908- CONFIG_SYS_MAX_FLASH_BANKS:
3909		Max number of Flash memory banks
3910
3911- CONFIG_SYS_MAX_FLASH_SECT:
3912		Max number of sectors on a Flash chip
3913
3914- CONFIG_SYS_FLASH_ERASE_TOUT:
3915		Timeout for Flash erase operations (in ms)
3916
3917- CONFIG_SYS_FLASH_WRITE_TOUT:
3918		Timeout for Flash write operations (in ms)
3919
3920- CONFIG_SYS_FLASH_LOCK_TOUT
3921		Timeout for Flash set sector lock bit operation (in ms)
3922
3923- CONFIG_SYS_FLASH_UNLOCK_TOUT
3924		Timeout for Flash clear lock bits operation (in ms)
3925
3926- CONFIG_SYS_FLASH_PROTECTION
3927		If defined, hardware flash sectors protection is used
3928		instead of U-Boot software protection.
3929
3930- CONFIG_SYS_DIRECT_FLASH_TFTP:
3931
3932		Enable TFTP transfers directly to flash memory;
3933		without this option such a download has to be
3934		performed in two steps: (1) download to RAM, and (2)
3935		copy from RAM to flash.
3936
3937		The two-step approach is usually more reliable, since
3938		you can check if the download worked before you erase
3939		the flash, but in some situations (when system RAM is
3940		too limited to allow for a temporary copy of the
3941		downloaded image) this option may be very useful.
3942
3943- CONFIG_SYS_FLASH_CFI:
3944		Define if the flash driver uses extra elements in the
3945		common flash structure for storing flash geometry.
3946
3947- CONFIG_FLASH_CFI_DRIVER
3948		This option also enables the building of the cfi_flash driver
3949		in the drivers directory
3950
3951- CONFIG_FLASH_CFI_MTD
3952		This option enables the building of the cfi_mtd driver
3953		in the drivers directory. The driver exports CFI flash
3954		to the MTD layer.
3955
3956- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3957		Use buffered writes to flash.
3958
3959- CONFIG_FLASH_SPANSION_S29WS_N
3960		s29ws-n MirrorBit flash has non-standard addresses for buffered
3961		write commands.
3962
3963- CONFIG_SYS_FLASH_QUIET_TEST
3964		If this option is defined, the common CFI flash doesn't
3965		print it's warning upon not recognized FLASH banks. This
3966		is useful, if some of the configured banks are only
3967		optionally available.
3968
3969- CONFIG_FLASH_SHOW_PROGRESS
3970		If defined (must be an integer), print out countdown
3971		digits and dots.  Recommended value: 45 (9..1) for 80
3972		column displays, 15 (3..1) for 40 column displays.
3973
3974- CONFIG_FLASH_VERIFY
3975		If defined, the content of the flash (destination) is compared
3976		against the source after the write operation. An error message
3977		will be printed when the contents are not identical.
3978		Please note that this option is useless in nearly all cases,
3979		since such flash programming errors usually are detected earlier
3980		while unprotecting/erasing/programming. Please only enable
3981		this option if you really know what you are doing.
3982
3983- CONFIG_SYS_RX_ETH_BUFFER:
3984		Defines the number of Ethernet receive buffers. On some
3985		Ethernet controllers it is recommended to set this value
3986		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3987		buffers can be full shortly after enabling the interface
3988		on high Ethernet traffic.
3989		Defaults to 4 if not defined.
3990
3991- CONFIG_ENV_MAX_ENTRIES
3992
3993	Maximum number of entries in the hash table that is used
3994	internally to store the environment settings. The default
3995	setting is supposed to be generous and should work in most
3996	cases. This setting can be used to tune behaviour; see
3997	lib/hashtable.c for details.
3998
3999- CONFIG_ENV_FLAGS_LIST_DEFAULT
4000- CONFIG_ENV_FLAGS_LIST_STATIC
4001	Enable validation of the values given to environment variables when
4002	calling env set.  Variables can be restricted to only decimal,
4003	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
4004	the variables can also be restricted to IP address or MAC address.
4005
4006	The format of the list is:
4007		type_attribute = [s|d|x|b|i|m]
4008		access_atribute = [a|r|o|c]
4009		attributes = type_attribute[access_atribute]
4010		entry = variable_name[:attributes]
4011		list = entry[,list]
4012
4013	The type attributes are:
4014		s - String (default)
4015		d - Decimal
4016		x - Hexadecimal
4017		b - Boolean ([1yYtT|0nNfF])
4018		i - IP address
4019		m - MAC address
4020
4021	The access attributes are:
4022		a - Any (default)
4023		r - Read-only
4024		o - Write-once
4025		c - Change-default
4026
4027	- CONFIG_ENV_FLAGS_LIST_DEFAULT
4028		Define this to a list (string) to define the ".flags"
4029		envirnoment variable in the default or embedded environment.
4030
4031	- CONFIG_ENV_FLAGS_LIST_STATIC
4032		Define this to a list (string) to define validation that
4033		should be done if an entry is not found in the ".flags"
4034		environment variable.  To override a setting in the static
4035		list, simply add an entry for the same variable name to the
4036		".flags" variable.
4037
4038- CONFIG_ENV_ACCESS_IGNORE_FORCE
4039	If defined, don't allow the -f switch to env set override variable
4040	access flags.
4041
4042- CONFIG_SYS_GENERIC_BOARD
4043	This selects the architecture-generic board system instead of the
4044	architecture-specific board files. It is intended to move boards
4045	to this new framework over time. Defining this will disable the
4046	arch/foo/lib/board.c file and use common/board_f.c and
4047	common/board_r.c instead. To use this option your architecture
4048	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
4049	its config.mk file). If you find problems enabling this option on
4050	your board please report the problem and send patches!
4051
4052- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
4053	This is set by OMAP boards for the max time that reset should
4054	be asserted. See doc/README.omap-reset-time for details on how
4055	the value can be calulated on a given board.
4056
4057The following definitions that deal with the placement and management
4058of environment data (variable area); in general, we support the
4059following configurations:
4060
4061- CONFIG_BUILD_ENVCRC:
4062
4063	Builds up envcrc with the target environment so that external utils
4064	may easily extract it and embed it in final U-Boot images.
4065
4066- CONFIG_ENV_IS_IN_FLASH:
4067
4068	Define this if the environment is in flash memory.
4069
4070	a) The environment occupies one whole flash sector, which is
4071	   "embedded" in the text segment with the U-Boot code. This
4072	   happens usually with "bottom boot sector" or "top boot
4073	   sector" type flash chips, which have several smaller
4074	   sectors at the start or the end. For instance, such a
4075	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
4076	   such a case you would place the environment in one of the
4077	   4 kB sectors - with U-Boot code before and after it. With
4078	   "top boot sector" type flash chips, you would put the
4079	   environment in one of the last sectors, leaving a gap
4080	   between U-Boot and the environment.
4081
4082	- CONFIG_ENV_OFFSET:
4083
4084	   Offset of environment data (variable area) to the
4085	   beginning of flash memory; for instance, with bottom boot
4086	   type flash chips the second sector can be used: the offset
4087	   for this sector is given here.
4088
4089	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
4090
4091	- CONFIG_ENV_ADDR:
4092
4093	   This is just another way to specify the start address of
4094	   the flash sector containing the environment (instead of
4095	   CONFIG_ENV_OFFSET).
4096
4097	- CONFIG_ENV_SECT_SIZE:
4098
4099	   Size of the sector containing the environment.
4100
4101
4102	b) Sometimes flash chips have few, equal sized, BIG sectors.
4103	   In such a case you don't want to spend a whole sector for
4104	   the environment.
4105
4106	- CONFIG_ENV_SIZE:
4107
4108	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
4109	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
4110	   of this flash sector for the environment. This saves
4111	   memory for the RAM copy of the environment.
4112
4113	   It may also save flash memory if you decide to use this
4114	   when your environment is "embedded" within U-Boot code,
4115	   since then the remainder of the flash sector could be used
4116	   for U-Boot code. It should be pointed out that this is
4117	   STRONGLY DISCOURAGED from a robustness point of view:
4118	   updating the environment in flash makes it always
4119	   necessary to erase the WHOLE sector. If something goes
4120	   wrong before the contents has been restored from a copy in
4121	   RAM, your target system will be dead.
4122
4123	- CONFIG_ENV_ADDR_REDUND
4124	  CONFIG_ENV_SIZE_REDUND
4125
4126	   These settings describe a second storage area used to hold
4127	   a redundant copy of the environment data, so that there is
4128	   a valid backup copy in case there is a power failure during
4129	   a "saveenv" operation.
4130
4131BE CAREFUL! Any changes to the flash layout, and some changes to the
4132source code will make it necessary to adapt <board>/u-boot.lds*
4133accordingly!
4134
4135
4136- CONFIG_ENV_IS_IN_NVRAM:
4137
4138	Define this if you have some non-volatile memory device
4139	(NVRAM, battery buffered SRAM) which you want to use for the
4140	environment.
4141
4142	- CONFIG_ENV_ADDR:
4143	- CONFIG_ENV_SIZE:
4144
4145	  These two #defines are used to determine the memory area you
4146	  want to use for environment. It is assumed that this memory
4147	  can just be read and written to, without any special
4148	  provision.
4149
4150BE CAREFUL! The first access to the environment happens quite early
4151in U-Boot initalization (when we try to get the setting of for the
4152console baudrate). You *MUST* have mapped your NVRAM area then, or
4153U-Boot will hang.
4154
4155Please note that even with NVRAM we still use a copy of the
4156environment in RAM: we could work on NVRAM directly, but we want to
4157keep settings there always unmodified except somebody uses "saveenv"
4158to save the current settings.
4159
4160
4161- CONFIG_ENV_IS_IN_EEPROM:
4162
4163	Use this if you have an EEPROM or similar serial access
4164	device and a driver for it.
4165
4166	- CONFIG_ENV_OFFSET:
4167	- CONFIG_ENV_SIZE:
4168
4169	  These two #defines specify the offset and size of the
4170	  environment area within the total memory of your EEPROM.
4171
4172	- CONFIG_SYS_I2C_EEPROM_ADDR:
4173	  If defined, specified the chip address of the EEPROM device.
4174	  The default address is zero.
4175
4176	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
4177	  If defined, the number of bits used to address bytes in a
4178	  single page in the EEPROM device.  A 64 byte page, for example
4179	  would require six bits.
4180
4181	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
4182	  If defined, the number of milliseconds to delay between
4183	  page writes.	The default is zero milliseconds.
4184
4185	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
4186	  The length in bytes of the EEPROM memory array address.  Note
4187	  that this is NOT the chip address length!
4188
4189	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
4190	  EEPROM chips that implement "address overflow" are ones
4191	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
4192	  address and the extra bits end up in the "chip address" bit
4193	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
4194	  byte chips.
4195
4196	  Note that we consider the length of the address field to
4197	  still be one byte because the extra address bits are hidden
4198	  in the chip address.
4199
4200	- CONFIG_SYS_EEPROM_SIZE:
4201	  The size in bytes of the EEPROM device.
4202
4203	- CONFIG_ENV_EEPROM_IS_ON_I2C
4204	  define this, if you have I2C and SPI activated, and your
4205	  EEPROM, which holds the environment, is on the I2C bus.
4206
4207	- CONFIG_I2C_ENV_EEPROM_BUS
4208	  if you have an Environment on an EEPROM reached over
4209	  I2C muxes, you can define here, how to reach this
4210	  EEPROM. For example:
4211
4212	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
4213
4214	  EEPROM which holds the environment, is reached over
4215	  a pca9547 i2c mux with address 0x70, channel 3.
4216
4217- CONFIG_ENV_IS_IN_DATAFLASH:
4218
4219	Define this if you have a DataFlash memory device which you
4220	want to use for the environment.
4221
4222	- CONFIG_ENV_OFFSET:
4223	- CONFIG_ENV_ADDR:
4224	- CONFIG_ENV_SIZE:
4225
4226	  These three #defines specify the offset and size of the
4227	  environment area within the total memory of your DataFlash placed
4228	  at the specified address.
4229
4230- CONFIG_ENV_IS_IN_SPI_FLASH:
4231
4232	Define this if you have a SPI Flash memory device which you
4233	want to use for the environment.
4234
4235	- CONFIG_ENV_OFFSET:
4236	- CONFIG_ENV_SIZE:
4237
4238	  These two #defines specify the offset and size of the
4239	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
4240	  aligned to an erase sector boundary.
4241
4242	- CONFIG_ENV_SECT_SIZE:
4243
4244	  Define the SPI flash's sector size.
4245
4246	- CONFIG_ENV_OFFSET_REDUND (optional):
4247
4248	  This setting describes a second storage area of CONFIG_ENV_SIZE
4249	  size used to hold a redundant copy of the environment data, so
4250	  that there is a valid backup copy in case there is a power failure
4251	  during a "saveenv" operation. CONFIG_ENV_OFFSET_RENDUND must be
4252	  aligned to an erase sector boundary.
4253
4254	- CONFIG_ENV_SPI_BUS (optional):
4255	- CONFIG_ENV_SPI_CS (optional):
4256
4257	  Define the SPI bus and chip select. If not defined they will be 0.
4258
4259	- CONFIG_ENV_SPI_MAX_HZ (optional):
4260
4261	  Define the SPI max work clock. If not defined then use 1MHz.
4262
4263	- CONFIG_ENV_SPI_MODE (optional):
4264
4265	  Define the SPI work mode. If not defined then use SPI_MODE_3.
4266
4267- CONFIG_ENV_IS_IN_REMOTE:
4268
4269	Define this if you have a remote memory space which you
4270	want to use for the local device's environment.
4271
4272	- CONFIG_ENV_ADDR:
4273	- CONFIG_ENV_SIZE:
4274
4275	  These two #defines specify the address and size of the
4276	  environment area within the remote memory space. The
4277	  local device can get the environment from remote memory
4278	  space by SRIO or PCIE links.
4279
4280BE CAREFUL! For some special cases, the local device can not use
4281"saveenv" command. For example, the local device will get the
4282environment stored in a remote NOR flash by SRIO or PCIE link,
4283but it can not erase, write this NOR flash by SRIO or PCIE interface.
4284
4285- CONFIG_ENV_IS_IN_NAND:
4286
4287	Define this if you have a NAND device which you want to use
4288	for the environment.
4289
4290	- CONFIG_ENV_OFFSET:
4291	- CONFIG_ENV_SIZE:
4292
4293	  These two #defines specify the offset and size of the environment
4294	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4295	  aligned to an erase block boundary.
4296
4297	- CONFIG_ENV_OFFSET_REDUND (optional):
4298
4299	  This setting describes a second storage area of CONFIG_ENV_SIZE
4300	  size used to hold a redundant copy of the environment data, so
4301	  that there is a valid backup copy in case there is a power failure
4302	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
4303	  aligned to an erase block boundary.
4304
4305	- CONFIG_ENV_RANGE (optional):
4306
4307	  Specifies the length of the region in which the environment
4308	  can be written.  This should be a multiple of the NAND device's
4309	  block size.  Specifying a range with more erase blocks than
4310	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4311	  the range to be avoided.
4312
4313	- CONFIG_ENV_OFFSET_OOB (optional):
4314
4315	  Enables support for dynamically retrieving the offset of the
4316	  environment from block zero's out-of-band data.  The
4317	  "nand env.oob" command can be used to record this offset.
4318	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4319	  using CONFIG_ENV_OFFSET_OOB.
4320
4321- CONFIG_NAND_ENV_DST
4322
4323	Defines address in RAM to which the nand_spl code should copy the
4324	environment. If redundant environment is used, it will be copied to
4325	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4326
4327- CONFIG_ENV_IS_IN_UBI:
4328
4329	Define this if you have an UBI volume that you want to use for the
4330	environment.  This has the benefit of wear-leveling the environment
4331	accesses, which is important on NAND.
4332
4333	- CONFIG_ENV_UBI_PART:
4334
4335	  Define this to a string that is the mtd partition containing the UBI.
4336
4337	- CONFIG_ENV_UBI_VOLUME:
4338
4339	  Define this to the name of the volume that you want to store the
4340	  environment in.
4341
4342	- CONFIG_ENV_UBI_VOLUME_REDUND:
4343
4344	  Define this to the name of another volume to store a second copy of
4345	  the environment in.  This will enable redundant environments in UBI.
4346	  It is assumed that both volumes are in the same MTD partition.
4347
4348	- CONFIG_UBI_SILENCE_MSG
4349	- CONFIG_UBIFS_SILENCE_MSG
4350
4351	  You will probably want to define these to avoid a really noisy system
4352	  when storing the env in UBI.
4353
4354- CONFIG_ENV_IS_IN_FAT:
4355       Define this if you want to use the FAT file system for the environment.
4356
4357       - FAT_ENV_INTERFACE:
4358
4359         Define this to a string that is the name of the block device.
4360
4361       - FAT_ENV_DEV_AND_PART:
4362
4363         Define this to a string to specify the partition of the device. It can
4364         be as following:
4365
4366           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
4367               - "D:P": device D partition P. Error occurs if device D has no
4368                        partition table.
4369               - "D:0": device D.
4370               - "D" or "D:": device D partition 1 if device D has partition
4371                              table, or the whole device D if has no partition
4372                              table.
4373               - "D:auto": first partition in device D with bootable flag set.
4374                           If none, first valid paratition in device D. If no
4375                           partition table then means device D.
4376
4377       - FAT_ENV_FILE:
4378
4379         It's a string of the FAT file name. This file use to store the
4380         envrionment.
4381
4382       - CONFIG_FAT_WRITE:
4383         This should be defined. Otherwise it cannot save the envrionment file.
4384
4385- CONFIG_ENV_IS_IN_MMC:
4386
4387	Define this if you have an MMC device which you want to use for the
4388	environment.
4389
4390	- CONFIG_SYS_MMC_ENV_DEV:
4391
4392	  Specifies which MMC device the environment is stored in.
4393
4394	- CONFIG_SYS_MMC_ENV_PART (optional):
4395
4396	  Specifies which MMC partition the environment is stored in. If not
4397	  set, defaults to partition 0, the user area. Common values might be
4398	  1 (first MMC boot partition), 2 (second MMC boot partition).
4399
4400	- CONFIG_ENV_OFFSET:
4401	- CONFIG_ENV_SIZE:
4402
4403	  These two #defines specify the offset and size of the environment
4404	  area within the specified MMC device.
4405
4406	  If offset is positive (the usual case), it is treated as relative to
4407	  the start of the MMC partition. If offset is negative, it is treated
4408	  as relative to the end of the MMC partition. This can be useful if
4409	  your board may be fitted with different MMC devices, which have
4410	  different sizes for the MMC partitions, and you always want the
4411	  environment placed at the very end of the partition, to leave the
4412	  maximum possible space before it, to store other data.
4413
4414	  These two values are in units of bytes, but must be aligned to an
4415	  MMC sector boundary.
4416
4417	- CONFIG_ENV_OFFSET_REDUND (optional):
4418
4419	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4420	  hold a redundant copy of the environment data. This provides a
4421	  valid backup copy in case the other copy is corrupted, e.g. due
4422	  to a power failure during a "saveenv" operation.
4423
4424	  This value may also be positive or negative; this is handled in the
4425	  same way as CONFIG_ENV_OFFSET.
4426
4427	  This value is also in units of bytes, but must also be aligned to
4428	  an MMC sector boundary.
4429
4430	- CONFIG_ENV_SIZE_REDUND (optional):
4431
4432	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4433	  set. If this value is set, it must be set to the same value as
4434	  CONFIG_ENV_SIZE.
4435
4436- CONFIG_SYS_SPI_INIT_OFFSET
4437
4438	Defines offset to the initial SPI buffer area in DPRAM. The
4439	area is used at an early stage (ROM part) if the environment
4440	is configured to reside in the SPI EEPROM: We need a 520 byte
4441	scratch DPRAM area. It is used between the two initialization
4442	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4443	to be a good choice since it makes it far enough from the
4444	start of the data area as well as from the stack pointer.
4445
4446Please note that the environment is read-only until the monitor
4447has been relocated to RAM and a RAM copy of the environment has been
4448created; also, when using EEPROM you will have to use getenv_f()
4449until then to read environment variables.
4450
4451The environment is protected by a CRC32 checksum. Before the monitor
4452is relocated into RAM, as a result of a bad CRC you will be working
4453with the compiled-in default environment - *silently*!!! [This is
4454necessary, because the first environment variable we need is the
4455"baudrate" setting for the console - if we have a bad CRC, we don't
4456have any device yet where we could complain.]
4457
4458Note: once the monitor has been relocated, then it will complain if
4459the default environment is used; a new CRC is computed as soon as you
4460use the "saveenv" command to store a valid environment.
4461
4462- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4463		Echo the inverted Ethernet link state to the fault LED.
4464
4465		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4466		      also needs to be defined.
4467
4468- CONFIG_SYS_FAULT_MII_ADDR:
4469		MII address of the PHY to check for the Ethernet link state.
4470
4471- CONFIG_NS16550_MIN_FUNCTIONS:
4472		Define this if you desire to only have use of the NS16550_init
4473		and NS16550_putc functions for the serial driver located at
4474		drivers/serial/ns16550.c.  This option is useful for saving
4475		space for already greatly restricted images, including but not
4476		limited to NAND_SPL configurations.
4477
4478- CONFIG_DISPLAY_BOARDINFO
4479		Display information about the board that U-Boot is running on
4480		when U-Boot starts up. The board function checkboard() is called
4481		to do this.
4482
4483- CONFIG_DISPLAY_BOARDINFO_LATE
4484		Similar to the previous option, but display this information
4485		later, once stdio is running and output goes to the LCD, if
4486		present.
4487
4488- CONFIG_BOARD_SIZE_LIMIT:
4489		Maximum size of the U-Boot image. When defined, the
4490		build system checks that the actual size does not
4491		exceed it.
4492
4493Low Level (hardware related) configuration options:
4494---------------------------------------------------
4495
4496- CONFIG_SYS_CACHELINE_SIZE:
4497		Cache Line Size of the CPU.
4498
4499- CONFIG_SYS_DEFAULT_IMMR:
4500		Default address of the IMMR after system reset.
4501
4502		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4503		and RPXsuper) to be able to adjust the position of
4504		the IMMR register after a reset.
4505
4506- CONFIG_SYS_CCSRBAR_DEFAULT:
4507		Default (power-on reset) physical address of CCSR on Freescale
4508		PowerPC SOCs.
4509
4510- CONFIG_SYS_CCSRBAR:
4511		Virtual address of CCSR.  On a 32-bit build, this is typically
4512		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4513
4514		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4515		for cross-platform code that uses that macro instead.
4516
4517- CONFIG_SYS_CCSRBAR_PHYS:
4518		Physical address of CCSR.  CCSR can be relocated to a new
4519		physical address, if desired.  In this case, this macro should
4520		be set to that address.	 Otherwise, it should be set to the
4521		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4522		is typically relocated on 36-bit builds.  It is recommended
4523		that this macro be defined via the _HIGH and _LOW macros:
4524
4525		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4526			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4527
4528- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4529		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4530		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4531		used in assembly code, so it must not contain typecasts or
4532		integer size suffixes (e.g. "ULL").
4533
4534- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4535		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4536		used in assembly code, so it must not contain typecasts or
4537		integer size suffixes (e.g. "ULL").
4538
4539- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4540		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4541		forced to a value that ensures that CCSR is not relocated.
4542
4543- Floppy Disk Support:
4544		CONFIG_SYS_FDC_DRIVE_NUMBER
4545
4546		the default drive number (default value 0)
4547
4548		CONFIG_SYS_ISA_IO_STRIDE
4549
4550		defines the spacing between FDC chipset registers
4551		(default value 1)
4552
4553		CONFIG_SYS_ISA_IO_OFFSET
4554
4555		defines the offset of register from address. It
4556		depends on which part of the data bus is connected to
4557		the FDC chipset. (default value 0)
4558
4559		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4560		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4561		default value.
4562
4563		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4564		fdc_hw_init() is called at the beginning of the FDC
4565		setup. fdc_hw_init() must be provided by the board
4566		source code. It is used to make hardware dependant
4567		initializations.
4568
4569- CONFIG_IDE_AHB:
4570		Most IDE controllers were designed to be connected with PCI
4571		interface. Only few of them were designed for AHB interface.
4572		When software is doing ATA command and data transfer to
4573		IDE devices through IDE-AHB controller, some additional
4574		registers accessing to these kind of IDE-AHB controller
4575		is requierd.
4576
4577- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4578		DO NOT CHANGE unless you know exactly what you're
4579		doing! (11-4) [MPC8xx/82xx systems only]
4580
4581- CONFIG_SYS_INIT_RAM_ADDR:
4582
4583		Start address of memory area that can be used for
4584		initial data and stack; please note that this must be
4585		writable memory that is working WITHOUT special
4586		initialization, i. e. you CANNOT use normal RAM which
4587		will become available only after programming the
4588		memory controller and running certain initialization
4589		sequences.
4590
4591		U-Boot uses the following memory types:
4592		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4593		- MPC824X: data cache
4594		- PPC4xx:  data cache
4595
4596- CONFIG_SYS_GBL_DATA_OFFSET:
4597
4598		Offset of the initial data structure in the memory
4599		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4600		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4601		data is located at the end of the available space
4602		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4603		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4604		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4605		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4606
4607	Note:
4608		On the MPC824X (or other systems that use the data
4609		cache for initial memory) the address chosen for
4610		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4611		point to an otherwise UNUSED address space between
4612		the top of RAM and the start of the PCI space.
4613
4614- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4615
4616- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4617
4618- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4619
4620- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4621
4622- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4623
4624- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4625
4626- CONFIG_SYS_OR_TIMING_SDRAM:
4627		SDRAM timing
4628
4629- CONFIG_SYS_MAMR_PTA:
4630		periodic timer for refresh
4631
4632- CONFIG_SYS_DER:	Debug Event Register (37-47)
4633
4634- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4635  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4636  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4637  CONFIG_SYS_BR1_PRELIM:
4638		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4639
4640- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4641  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4642  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4643		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4644
4645- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4646  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4647		Machine Mode Register and Memory Periodic Timer
4648		Prescaler definitions (SDRAM timing)
4649
4650- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4651		enable I2C microcode relocation patch (MPC8xx);
4652		define relocation offset in DPRAM [DSP2]
4653
4654- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4655		enable SMC microcode relocation patch (MPC8xx);
4656		define relocation offset in DPRAM [SMC1]
4657
4658- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4659		enable SPI microcode relocation patch (MPC8xx);
4660		define relocation offset in DPRAM [SCC4]
4661
4662- CONFIG_SYS_USE_OSCCLK:
4663		Use OSCM clock mode on MBX8xx board. Be careful,
4664		wrong setting might damage your board. Read
4665		doc/README.MBX before setting this variable!
4666
4667- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4668		Offset of the bootmode word in DPRAM used by post
4669		(Power On Self Tests). This definition overrides
4670		#define'd default value in commproc.h resp.
4671		cpm_8260.h.
4672
4673- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4674  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4675  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4676  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4677  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4678  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4679  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4680  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4681		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4682
4683- CONFIG_PCI_DISABLE_PCIE:
4684		Disable PCI-Express on systems where it is supported but not
4685		required.
4686
4687- CONFIG_PCI_ENUM_ONLY
4688		Only scan through and get the devices on the busses.
4689		Don't do any setup work, presumably because someone or
4690		something has already done it, and we don't need to do it
4691		a second time.	Useful for platforms that are pre-booted
4692		by coreboot or similar.
4693
4694- CONFIG_PCI_INDIRECT_BRIDGE:
4695		Enable support for indirect PCI bridges.
4696
4697- CONFIG_SYS_SRIO:
4698		Chip has SRIO or not
4699
4700- CONFIG_SRIO1:
4701		Board has SRIO 1 port available
4702
4703- CONFIG_SRIO2:
4704		Board has SRIO 2 port available
4705
4706- CONFIG_SRIO_PCIE_BOOT_MASTER
4707		Board can support master function for Boot from SRIO and PCIE
4708
4709- CONFIG_SYS_SRIOn_MEM_VIRT:
4710		Virtual Address of SRIO port 'n' memory region
4711
4712- CONFIG_SYS_SRIOn_MEM_PHYS:
4713		Physical Address of SRIO port 'n' memory region
4714
4715- CONFIG_SYS_SRIOn_MEM_SIZE:
4716		Size of SRIO port 'n' memory region
4717
4718- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4719		Defined to tell the NAND controller that the NAND chip is using
4720		a 16 bit bus.
4721		Not all NAND drivers use this symbol.
4722		Example of drivers that use it:
4723		- drivers/mtd/nand/ndfc.c
4724		- drivers/mtd/nand/mxc_nand.c
4725
4726- CONFIG_SYS_NDFC_EBC0_CFG
4727		Sets the EBC0_CFG register for the NDFC. If not defined
4728		a default value will be used.
4729
4730- CONFIG_SPD_EEPROM
4731		Get DDR timing information from an I2C EEPROM. Common
4732		with pluggable memory modules such as SODIMMs
4733
4734  SPD_EEPROM_ADDRESS
4735		I2C address of the SPD EEPROM
4736
4737- CONFIG_SYS_SPD_BUS_NUM
4738		If SPD EEPROM is on an I2C bus other than the first
4739		one, specify here. Note that the value must resolve
4740		to something your driver can deal with.
4741
4742- CONFIG_SYS_DDR_RAW_TIMING
4743		Get DDR timing information from other than SPD. Common with
4744		soldered DDR chips onboard without SPD. DDR raw timing
4745		parameters are extracted from datasheet and hard-coded into
4746		header files or board specific files.
4747
4748- CONFIG_FSL_DDR_INTERACTIVE
4749		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4750
4751- CONFIG_SYS_83XX_DDR_USES_CS0
4752		Only for 83xx systems. If specified, then DDR should
4753		be configured using CS0 and CS1 instead of CS2 and CS3.
4754
4755- CONFIG_ETHER_ON_FEC[12]
4756		Define to enable FEC[12] on a 8xx series processor.
4757
4758- CONFIG_FEC[12]_PHY
4759		Define to the hardcoded PHY address which corresponds
4760		to the given FEC; i. e.
4761			#define CONFIG_FEC1_PHY 4
4762		means that the PHY with address 4 is connected to FEC1
4763
4764		When set to -1, means to probe for first available.
4765
4766- CONFIG_FEC[12]_PHY_NORXERR
4767		The PHY does not have a RXERR line (RMII only).
4768		(so program the FEC to ignore it).
4769
4770- CONFIG_RMII
4771		Enable RMII mode for all FECs.
4772		Note that this is a global option, we can't
4773		have one FEC in standard MII mode and another in RMII mode.
4774
4775- CONFIG_CRC32_VERIFY
4776		Add a verify option to the crc32 command.
4777		The syntax is:
4778
4779		=> crc32 -v <address> <count> <crc32>
4780
4781		Where address/count indicate a memory area
4782		and crc32 is the correct crc32 which the
4783		area should have.
4784
4785- CONFIG_LOOPW
4786		Add the "loopw" memory command. This only takes effect if
4787		the memory commands are activated globally (CONFIG_CMD_MEM).
4788
4789- CONFIG_MX_CYCLIC
4790		Add the "mdc" and "mwc" memory commands. These are cyclic
4791		"md/mw" commands.
4792		Examples:
4793
4794		=> mdc.b 10 4 500
4795		This command will print 4 bytes (10,11,12,13) each 500 ms.
4796
4797		=> mwc.l 100 12345678 10
4798		This command will write 12345678 to address 100 all 10 ms.
4799
4800		This only takes effect if the memory commands are activated
4801		globally (CONFIG_CMD_MEM).
4802
4803- CONFIG_SKIP_LOWLEVEL_INIT
4804		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4805		low level initializations (like setting up the memory
4806		controller) are omitted and/or U-Boot does not
4807		relocate itself into RAM.
4808
4809		Normally this variable MUST NOT be defined. The only
4810		exception is when U-Boot is loaded (to RAM) by some
4811		other boot loader or by a debugger which performs
4812		these initializations itself.
4813
4814- CONFIG_SPL_BUILD
4815		Modifies the behaviour of start.S when compiling a loader
4816		that is executed before the actual U-Boot. E.g. when
4817		compiling a NAND SPL.
4818
4819- CONFIG_TPL_BUILD
4820		Modifies the behaviour of start.S  when compiling a loader
4821		that is executed after the SPL and before the actual U-Boot.
4822		It is loaded by the SPL.
4823
4824- CONFIG_SYS_MPC85XX_NO_RESETVEC
4825		Only for 85xx systems. If this variable is specified, the section
4826		.resetvec is not kept and the section .bootpg is placed in the
4827		previous 4k of the .text section.
4828
4829- CONFIG_ARCH_MAP_SYSMEM
4830		Generally U-Boot (and in particular the md command) uses
4831		effective address. It is therefore not necessary to regard
4832		U-Boot address as virtual addresses that need to be translated
4833		to physical addresses. However, sandbox requires this, since
4834		it maintains its own little RAM buffer which contains all
4835		addressable memory. This option causes some memory accesses
4836		to be mapped through map_sysmem() / unmap_sysmem().
4837
4838- CONFIG_USE_ARCH_MEMCPY
4839  CONFIG_USE_ARCH_MEMSET
4840		If these options are used a optimized version of memcpy/memset will
4841		be used if available. These functions may be faster under some
4842		conditions but may increase the binary size.
4843
4844- CONFIG_X86_RESET_VECTOR
4845		If defined, the x86 reset vector code is included. This is not
4846		needed when U-Boot is running from Coreboot.
4847
4848- CONFIG_SYS_MPUCLK
4849		Defines the MPU clock speed (in MHz).
4850
4851		NOTE : currently only supported on AM335x platforms.
4852
4853- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4854		Enables the RTC32K OSC on AM33xx based plattforms
4855
4856- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4857		Option to disable subpage write in NAND driver
4858		driver that uses this:
4859		drivers/mtd/nand/davinci_nand.c
4860
4861Freescale QE/FMAN Firmware Support:
4862-----------------------------------
4863
4864The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4865loading of "firmware", which is encoded in the QE firmware binary format.
4866This firmware often needs to be loaded during U-Boot booting, so macros
4867are used to identify the storage device (NOR flash, SPI, etc) and the address
4868within that device.
4869
4870- CONFIG_SYS_FMAN_FW_ADDR
4871	The address in the storage device where the FMAN microcode is located.  The
4872	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4873	is also specified.
4874
4875- CONFIG_SYS_QE_FW_ADDR
4876	The address in the storage device where the QE microcode is located.  The
4877	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4878	is also specified.
4879
4880- CONFIG_SYS_QE_FMAN_FW_LENGTH
4881	The maximum possible size of the firmware.  The firmware binary format
4882	has a field that specifies the actual size of the firmware, but it
4883	might not be possible to read any part of the firmware unless some
4884	local storage is allocated to hold the entire firmware first.
4885
4886- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4887	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4888	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4889	virtual address in NOR flash.
4890
4891- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4892	Specifies that QE/FMAN firmware is located in NAND flash.
4893	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4894
4895- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4896	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4897	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4898
4899- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4900	Specifies that QE/FMAN firmware is located on the primary SPI
4901	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4902
4903- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4904	Specifies that QE/FMAN firmware is located in the remote (master)
4905	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4906	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4907	window->master inbound window->master LAW->the ucode address in
4908	master's memory space.
4909
4910Freescale Layerscape Management Complex Firmware Support:
4911---------------------------------------------------------
4912The Freescale Layerscape Management Complex (MC) supports the loading of
4913"firmware".
4914This firmware often needs to be loaded during U-Boot booting, so macros
4915are used to identify the storage device (NOR flash, SPI, etc) and the address
4916within that device.
4917
4918- CONFIG_FSL_MC_ENET
4919	Enable the MC driver for Layerscape SoCs.
4920
4921- CONFIG_SYS_LS_MC_FW_ADDR
4922	The address in the storage device where the firmware is located.  The
4923	meaning of this address depends on which CONFIG_SYS_LS_MC_FW_IN_xxx macro
4924	is also specified.
4925
4926- CONFIG_SYS_LS_MC_FW_LENGTH
4927	The maximum possible size of the firmware.  The firmware binary format
4928	has a field that specifies the actual size of the firmware, but it
4929	might not be possible to read any part of the firmware unless some
4930	local storage is allocated to hold the entire firmware first.
4931
4932- CONFIG_SYS_LS_MC_FW_IN_NOR
4933	Specifies that MC firmware is located in NOR flash, mapped as
4934	normal addressable memory via the LBC. CONFIG_SYS_LS_MC_FW_ADDR is the
4935	virtual address in NOR flash.
4936
4937Building the Software:
4938======================
4939
4940Building U-Boot has been tested in several native build environments
4941and in many different cross environments. Of course we cannot support
4942all possibly existing versions of cross development tools in all
4943(potentially obsolete) versions. In case of tool chain problems we
4944recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4945which is extensively used to build and test U-Boot.
4946
4947If you are not using a native environment, it is assumed that you
4948have GNU cross compiling tools available in your path. In this case,
4949you must set the environment variable CROSS_COMPILE in your shell.
4950Note that no changes to the Makefile or any other source files are
4951necessary. For example using the ELDK on a 4xx CPU, please enter:
4952
4953	$ CROSS_COMPILE=ppc_4xx-
4954	$ export CROSS_COMPILE
4955
4956Note: If you wish to generate Windows versions of the utilities in
4957      the tools directory you can use the MinGW toolchain
4958      (http://www.mingw.org).  Set your HOST tools to the MinGW
4959      toolchain and execute 'make tools'.  For example:
4960
4961       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4962
4963      Binaries such as tools/mkimage.exe will be created which can
4964      be executed on computers running Windows.
4965
4966U-Boot is intended to be simple to build. After installing the
4967sources you must configure U-Boot for one specific board type. This
4968is done by typing:
4969
4970	make NAME_defconfig
4971
4972where "NAME_defconfig" is the name of one of the existing configu-
4973rations; see boards.cfg for supported names.
4974
4975Note: for some board special configuration names may exist; check if
4976      additional information is available from the board vendor; for
4977      instance, the TQM823L systems are available without (standard)
4978      or with LCD support. You can select such additional "features"
4979      when choosing the configuration, i. e.
4980
4981      make TQM823L_defconfig
4982	- will configure for a plain TQM823L, i. e. no LCD support
4983
4984      make TQM823L_LCD_defconfig
4985	- will configure for a TQM823L with U-Boot console on LCD
4986
4987      etc.
4988
4989
4990Finally, type "make all", and you should get some working U-Boot
4991images ready for download to / installation on your system:
4992
4993- "u-boot.bin" is a raw binary image
4994- "u-boot" is an image in ELF binary format
4995- "u-boot.srec" is in Motorola S-Record format
4996
4997By default the build is performed locally and the objects are saved
4998in the source directory. One of the two methods can be used to change
4999this behavior and build U-Boot to some external directory:
5000
50011. Add O= to the make command line invocations:
5002
5003	make O=/tmp/build distclean
5004	make O=/tmp/build NAME_defconfig
5005	make O=/tmp/build all
5006
50072. Set environment variable BUILD_DIR to point to the desired location:
5008
5009	export BUILD_DIR=/tmp/build
5010	make distclean
5011	make NAME_defconfig
5012	make all
5013
5014Note that the command line "O=" setting overrides the BUILD_DIR environment
5015variable.
5016
5017
5018Please be aware that the Makefiles assume you are using GNU make, so
5019for instance on NetBSD you might need to use "gmake" instead of
5020native "make".
5021
5022
5023If the system board that you have is not listed, then you will need
5024to port U-Boot to your hardware platform. To do this, follow these
5025steps:
5026
50271.  Add a new configuration option for your board to the toplevel
5028    "boards.cfg" file, using the existing entries as examples.
5029    Follow the instructions there to keep the boards in order.
50302.  Create a new directory to hold your board specific code. Add any
5031    files you need. In your board directory, you will need at least
5032    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
50333.  Create a new configuration file "include/configs/<board>.h" for
5034    your board
50353.  If you're porting U-Boot to a new CPU, then also create a new
5036    directory to hold your CPU specific code. Add any files you need.
50374.  Run "make <board>_defconfig" with your new name.
50385.  Type "make", and you should get a working "u-boot.srec" file
5039    to be installed on your target system.
50406.  Debug and solve any problems that might arise.
5041    [Of course, this last step is much harder than it sounds.]
5042
5043
5044Testing of U-Boot Modifications, Ports to New Hardware, etc.:
5045==============================================================
5046
5047If you have modified U-Boot sources (for instance added a new board
5048or support for new devices, a new CPU, etc.) you are expected to
5049provide feedback to the other developers. The feedback normally takes
5050the form of a "patch", i. e. a context diff against a certain (latest
5051official or latest in the git repository) version of U-Boot sources.
5052
5053But before you submit such a patch, please verify that your modifi-
5054cation did not break existing code. At least make sure that *ALL* of
5055the supported boards compile WITHOUT ANY compiler warnings. To do so,
5056just run the "MAKEALL" script, which will configure and build U-Boot
5057for ALL supported system. Be warned, this will take a while. You can
5058select which (cross) compiler to use by passing a `CROSS_COMPILE'
5059environment variable to the script, i. e. to use the ELDK cross tools
5060you can type
5061
5062	CROSS_COMPILE=ppc_8xx- MAKEALL
5063
5064or to build on a native PowerPC system you can type
5065
5066	CROSS_COMPILE=' ' MAKEALL
5067
5068When using the MAKEALL script, the default behaviour is to build
5069U-Boot in the source directory. This location can be changed by
5070setting the BUILD_DIR environment variable. Also, for each target
5071built, the MAKEALL script saves two log files (<target>.ERR and
5072<target>.MAKEALL) in the <source dir>/LOG directory. This default
5073location can be changed by setting the MAKEALL_LOGDIR environment
5074variable. For example:
5075
5076	export BUILD_DIR=/tmp/build
5077	export MAKEALL_LOGDIR=/tmp/log
5078	CROSS_COMPILE=ppc_8xx- MAKEALL
5079
5080With the above settings build objects are saved in the /tmp/build,
5081log files are saved in the /tmp/log and the source tree remains clean
5082during the whole build process.
5083
5084
5085See also "U-Boot Porting Guide" below.
5086
5087
5088Monitor Commands - Overview:
5089============================
5090
5091go	- start application at address 'addr'
5092run	- run commands in an environment variable
5093bootm	- boot application image from memory
5094bootp	- boot image via network using BootP/TFTP protocol
5095bootz   - boot zImage from memory
5096tftpboot- boot image via network using TFTP protocol
5097	       and env variables "ipaddr" and "serverip"
5098	       (and eventually "gatewayip")
5099tftpput - upload a file via network using TFTP protocol
5100rarpboot- boot image via network using RARP/TFTP protocol
5101diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
5102loads	- load S-Record file over serial line
5103loadb	- load binary file over serial line (kermit mode)
5104md	- memory display
5105mm	- memory modify (auto-incrementing)
5106nm	- memory modify (constant address)
5107mw	- memory write (fill)
5108cp	- memory copy
5109cmp	- memory compare
5110crc32	- checksum calculation
5111i2c	- I2C sub-system
5112sspi	- SPI utility commands
5113base	- print or set address offset
5114printenv- print environment variables
5115setenv	- set environment variables
5116saveenv - save environment variables to persistent storage
5117protect - enable or disable FLASH write protection
5118erase	- erase FLASH memory
5119flinfo	- print FLASH memory information
5120nand	- NAND memory operations (see doc/README.nand)
5121bdinfo	- print Board Info structure
5122iminfo	- print header information for application image
5123coninfo - print console devices and informations
5124ide	- IDE sub-system
5125loop	- infinite loop on address range
5126loopw	- infinite write loop on address range
5127mtest	- simple RAM test
5128icache	- enable or disable instruction cache
5129dcache	- enable or disable data cache
5130reset	- Perform RESET of the CPU
5131echo	- echo args to console
5132version - print monitor version
5133help	- print online help
5134?	- alias for 'help'
5135
5136
5137Monitor Commands - Detailed Description:
5138========================================
5139
5140TODO.
5141
5142For now: just type "help <command>".
5143
5144
5145Environment Variables:
5146======================
5147
5148U-Boot supports user configuration using Environment Variables which
5149can be made persistent by saving to Flash memory.
5150
5151Environment Variables are set using "setenv", printed using
5152"printenv", and saved to Flash using "saveenv". Using "setenv"
5153without a value can be used to delete a variable from the
5154environment. As long as you don't save the environment you are
5155working with an in-memory copy. In case the Flash area containing the
5156environment is erased by accident, a default environment is provided.
5157
5158Some configuration options can be set using Environment Variables.
5159
5160List of environment variables (most likely not complete):
5161
5162  baudrate	- see CONFIG_BAUDRATE
5163
5164  bootdelay	- see CONFIG_BOOTDELAY
5165
5166  bootcmd	- see CONFIG_BOOTCOMMAND
5167
5168  bootargs	- Boot arguments when booting an RTOS image
5169
5170  bootfile	- Name of the image to load with TFTP
5171
5172  bootm_low	- Memory range available for image processing in the bootm
5173		  command can be restricted. This variable is given as
5174		  a hexadecimal number and defines lowest address allowed
5175		  for use by the bootm command. See also "bootm_size"
5176		  environment variable. Address defined by "bootm_low" is
5177		  also the base of the initial memory mapping for the Linux
5178		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
5179		  bootm_mapsize.
5180
5181  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
5182		  This variable is given as a hexadecimal number and it
5183		  defines the size of the memory region starting at base
5184		  address bootm_low that is accessible by the Linux kernel
5185		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
5186		  as the default value if it is defined, and bootm_size is
5187		  used otherwise.
5188
5189  bootm_size	- Memory range available for image processing in the bootm
5190		  command can be restricted. This variable is given as
5191		  a hexadecimal number and defines the size of the region
5192		  allowed for use by the bootm command. See also "bootm_low"
5193		  environment variable.
5194
5195  updatefile	- Location of the software update file on a TFTP server, used
5196		  by the automatic software update feature. Please refer to
5197		  documentation in doc/README.update for more details.
5198
5199  autoload	- if set to "no" (any string beginning with 'n'),
5200		  "bootp" will just load perform a lookup of the
5201		  configuration from the BOOTP server, but not try to
5202		  load any image using TFTP
5203
5204  autostart	- if set to "yes", an image loaded using the "bootp",
5205		  "rarpboot", "tftpboot" or "diskboot" commands will
5206		  be automatically started (by internally calling
5207		  "bootm")
5208
5209		  If set to "no", a standalone image passed to the
5210		  "bootm" command will be copied to the load address
5211		  (and eventually uncompressed), but NOT be started.
5212		  This can be used to load and uncompress arbitrary
5213		  data.
5214
5215  fdt_high	- if set this restricts the maximum address that the
5216		  flattened device tree will be copied into upon boot.
5217		  For example, if you have a system with 1 GB memory
5218		  at physical address 0x10000000, while Linux kernel
5219		  only recognizes the first 704 MB as low memory, you
5220		  may need to set fdt_high as 0x3C000000 to have the
5221		  device tree blob be copied to the maximum address
5222		  of the 704 MB low memory, so that Linux kernel can
5223		  access it during the boot procedure.
5224
5225		  If this is set to the special value 0xFFFFFFFF then
5226		  the fdt will not be copied at all on boot.  For this
5227		  to work it must reside in writable memory, have
5228		  sufficient padding on the end of it for u-boot to
5229		  add the information it needs into it, and the memory
5230		  must be accessible by the kernel.
5231
5232  fdtcontroladdr- if set this is the address of the control flattened
5233		  device tree used by U-Boot when CONFIG_OF_CONTROL is
5234		  defined.
5235
5236  i2cfast	- (PPC405GP|PPC405EP only)
5237		  if set to 'y' configures Linux I2C driver for fast
5238		  mode (400kHZ). This environment variable is used in
5239		  initialization code. So, for changes to be effective
5240		  it must be saved and board must be reset.
5241
5242  initrd_high	- restrict positioning of initrd images:
5243		  If this variable is not set, initrd images will be
5244		  copied to the highest possible address in RAM; this
5245		  is usually what you want since it allows for
5246		  maximum initrd size. If for some reason you want to
5247		  make sure that the initrd image is loaded below the
5248		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
5249		  variable to a value of "no" or "off" or "0".
5250		  Alternatively, you can set it to a maximum upper
5251		  address to use (U-Boot will still check that it
5252		  does not overwrite the U-Boot stack and data).
5253
5254		  For instance, when you have a system with 16 MB
5255		  RAM, and want to reserve 4 MB from use by Linux,
5256		  you can do this by adding "mem=12M" to the value of
5257		  the "bootargs" variable. However, now you must make
5258		  sure that the initrd image is placed in the first
5259		  12 MB as well - this can be done with
5260
5261		  setenv initrd_high 00c00000
5262
5263		  If you set initrd_high to 0xFFFFFFFF, this is an
5264		  indication to U-Boot that all addresses are legal
5265		  for the Linux kernel, including addresses in flash
5266		  memory. In this case U-Boot will NOT COPY the
5267		  ramdisk at all. This may be useful to reduce the
5268		  boot time on your system, but requires that this
5269		  feature is supported by your Linux kernel.
5270
5271  ipaddr	- IP address; needed for tftpboot command
5272
5273  loadaddr	- Default load address for commands like "bootp",
5274		  "rarpboot", "tftpboot", "loadb" or "diskboot"
5275
5276  loads_echo	- see CONFIG_LOADS_ECHO
5277
5278  serverip	- TFTP server IP address; needed for tftpboot command
5279
5280  bootretry	- see CONFIG_BOOT_RETRY_TIME
5281
5282  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
5283
5284  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
5285
5286  ethprime	- controls which interface is used first.
5287
5288  ethact	- controls which interface is currently active.
5289		  For example you can do the following
5290
5291		  => setenv ethact FEC
5292		  => ping 192.168.0.1 # traffic sent on FEC
5293		  => setenv ethact SCC
5294		  => ping 10.0.0.1 # traffic sent on SCC
5295
5296  ethrotate	- When set to "no" U-Boot does not go through all
5297		  available network interfaces.
5298		  It just stays at the currently selected interface.
5299
5300  netretry	- When set to "no" each network operation will
5301		  either succeed or fail without retrying.
5302		  When set to "once" the network operation will
5303		  fail when all the available network interfaces
5304		  are tried once without success.
5305		  Useful on scripts which control the retry operation
5306		  themselves.
5307
5308  npe_ucode	- set load address for the NPE microcode
5309
5310  silent_linux  - If set then linux will be told to boot silently, by
5311		  changing the console to be empty. If "yes" it will be
5312		  made silent. If "no" it will not be made silent. If
5313		  unset, then it will be made silent if the U-Boot console
5314		  is silent.
5315
5316  tftpsrcport	- If this is set, the value is used for TFTP's
5317		  UDP source port.
5318
5319  tftpdstport	- If this is set, the value is used for TFTP's UDP
5320		  destination port instead of the Well Know Port 69.
5321
5322  tftpblocksize - Block size to use for TFTP transfers; if not set,
5323		  we use the TFTP server's default block size
5324
5325  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
5326		  seconds, minimum value is 1000 = 1 second). Defines
5327		  when a packet is considered to be lost so it has to
5328		  be retransmitted. The default is 5000 = 5 seconds.
5329		  Lowering this value may make downloads succeed
5330		  faster in networks with high packet loss rates or
5331		  with unreliable TFTP servers.
5332
5333  vlan		- When set to a value < 4095 the traffic over
5334		  Ethernet is encapsulated/received over 802.1q
5335		  VLAN tagged frames.
5336
5337The following image location variables contain the location of images
5338used in booting. The "Image" column gives the role of the image and is
5339not an environment variable name. The other columns are environment
5340variable names. "File Name" gives the name of the file on a TFTP
5341server, "RAM Address" gives the location in RAM the image will be
5342loaded to, and "Flash Location" gives the image's address in NOR
5343flash or offset in NAND flash.
5344
5345*Note* - these variables don't have to be defined for all boards, some
5346boards currenlty use other variables for these purposes, and some
5347boards use these variables for other purposes.
5348
5349Image		    File Name	     RAM Address       Flash Location
5350-----		    ---------	     -----------       --------------
5351u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
5352Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
5353device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
5354ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
5355
5356The following environment variables may be used and automatically
5357updated by the network boot commands ("bootp" and "rarpboot"),
5358depending the information provided by your boot server:
5359
5360  bootfile	- see above
5361  dnsip		- IP address of your Domain Name Server
5362  dnsip2	- IP address of your secondary Domain Name Server
5363  gatewayip	- IP address of the Gateway (Router) to use
5364  hostname	- Target hostname
5365  ipaddr	- see above
5366  netmask	- Subnet Mask
5367  rootpath	- Pathname of the root filesystem on the NFS server
5368  serverip	- see above
5369
5370
5371There are two special Environment Variables:
5372
5373  serial#	- contains hardware identification information such
5374		  as type string and/or serial number
5375  ethaddr	- Ethernet address
5376
5377These variables can be set only once (usually during manufacturing of
5378the board). U-Boot refuses to delete or overwrite these variables
5379once they have been set once.
5380
5381
5382Further special Environment Variables:
5383
5384  ver		- Contains the U-Boot version string as printed
5385		  with the "version" command. This variable is
5386		  readonly (see CONFIG_VERSION_VARIABLE).
5387
5388
5389Please note that changes to some configuration parameters may take
5390only effect after the next boot (yes, that's just like Windoze :-).
5391
5392
5393Callback functions for environment variables:
5394---------------------------------------------
5395
5396For some environment variables, the behavior of u-boot needs to change
5397when their values are changed.  This functionailty allows functions to
5398be associated with arbitrary variables.  On creation, overwrite, or
5399deletion, the callback will provide the opportunity for some side
5400effect to happen or for the change to be rejected.
5401
5402The callbacks are named and associated with a function using the
5403U_BOOT_ENV_CALLBACK macro in your board or driver code.
5404
5405These callbacks are associated with variables in one of two ways.  The
5406static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5407in the board configuration to a string that defines a list of
5408associations.  The list must be in the following format:
5409
5410	entry = variable_name[:callback_name]
5411	list = entry[,list]
5412
5413If the callback name is not specified, then the callback is deleted.
5414Spaces are also allowed anywhere in the list.
5415
5416Callbacks can also be associated by defining the ".callbacks" variable
5417with the same list format above.  Any association in ".callbacks" will
5418override any association in the static list. You can define
5419CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5420".callbacks" envirnoment variable in the default or embedded environment.
5421
5422
5423Command Line Parsing:
5424=====================
5425
5426There are two different command line parsers available with U-Boot:
5427the old "simple" one, and the much more powerful "hush" shell:
5428
5429Old, simple command line parser:
5430--------------------------------
5431
5432- supports environment variables (through setenv / saveenv commands)
5433- several commands on one line, separated by ';'
5434- variable substitution using "... ${name} ..." syntax
5435- special characters ('$', ';') can be escaped by prefixing with '\',
5436  for example:
5437	setenv bootcmd bootm \${address}
5438- You can also escape text by enclosing in single apostrophes, for example:
5439	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5440
5441Hush shell:
5442-----------
5443
5444- similar to Bourne shell, with control structures like
5445  if...then...else...fi, for...do...done; while...do...done,
5446  until...do...done, ...
5447- supports environment ("global") variables (through setenv / saveenv
5448  commands) and local shell variables (through standard shell syntax
5449  "name=value"); only environment variables can be used with "run"
5450  command
5451
5452General rules:
5453--------------
5454
5455(1) If a command line (or an environment variable executed by a "run"
5456    command) contains several commands separated by semicolon, and
5457    one of these commands fails, then the remaining commands will be
5458    executed anyway.
5459
5460(2) If you execute several variables with one call to run (i. e.
5461    calling run with a list of variables as arguments), any failing
5462    command will cause "run" to terminate, i. e. the remaining
5463    variables are not executed.
5464
5465Note for Redundant Ethernet Interfaces:
5466=======================================
5467
5468Some boards come with redundant Ethernet interfaces; U-Boot supports
5469such configurations and is capable of automatic selection of a
5470"working" interface when needed. MAC assignment works as follows:
5471
5472Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5473MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5474"eth1addr" (=>eth1), "eth2addr", ...
5475
5476If the network interface stores some valid MAC address (for instance
5477in SROM), this is used as default address if there is NO correspon-
5478ding setting in the environment; if the corresponding environment
5479variable is set, this overrides the settings in the card; that means:
5480
5481o If the SROM has a valid MAC address, and there is no address in the
5482  environment, the SROM's address is used.
5483
5484o If there is no valid address in the SROM, and a definition in the
5485  environment exists, then the value from the environment variable is
5486  used.
5487
5488o If both the SROM and the environment contain a MAC address, and
5489  both addresses are the same, this MAC address is used.
5490
5491o If both the SROM and the environment contain a MAC address, and the
5492  addresses differ, the value from the environment is used and a
5493  warning is printed.
5494
5495o If neither SROM nor the environment contain a MAC address, an error
5496  is raised.
5497
5498If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5499will be programmed into hardware as part of the initialization process.	 This
5500may be skipped by setting the appropriate 'ethmacskip' environment variable.
5501The naming convention is as follows:
5502"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5503
5504Image Formats:
5505==============
5506
5507U-Boot is capable of booting (and performing other auxiliary operations on)
5508images in two formats:
5509
5510New uImage format (FIT)
5511-----------------------
5512
5513Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5514to Flattened Device Tree). It allows the use of images with multiple
5515components (several kernels, ramdisks, etc.), with contents protected by
5516SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5517
5518
5519Old uImage format
5520-----------------
5521
5522Old image format is based on binary files which can be basically anything,
5523preceded by a special header; see the definitions in include/image.h for
5524details; basically, the header defines the following image properties:
5525
5526* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5527  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5528  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5529  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5530  INTEGRITY).
5531* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5532  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5533  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5534* Compression Type (uncompressed, gzip, bzip2)
5535* Load Address
5536* Entry Point
5537* Image Name
5538* Image Timestamp
5539
5540The header is marked by a special Magic Number, and both the header
5541and the data portions of the image are secured against corruption by
5542CRC32 checksums.
5543
5544
5545Linux Support:
5546==============
5547
5548Although U-Boot should support any OS or standalone application
5549easily, the main focus has always been on Linux during the design of
5550U-Boot.
5551
5552U-Boot includes many features that so far have been part of some
5553special "boot loader" code within the Linux kernel. Also, any
5554"initrd" images to be used are no longer part of one big Linux image;
5555instead, kernel and "initrd" are separate images. This implementation
5556serves several purposes:
5557
5558- the same features can be used for other OS or standalone
5559  applications (for instance: using compressed images to reduce the
5560  Flash memory footprint)
5561
5562- it becomes much easier to port new Linux kernel versions because
5563  lots of low-level, hardware dependent stuff are done by U-Boot
5564
5565- the same Linux kernel image can now be used with different "initrd"
5566  images; of course this also means that different kernel images can
5567  be run with the same "initrd". This makes testing easier (you don't
5568  have to build a new "zImage.initrd" Linux image when you just
5569  change a file in your "initrd"). Also, a field-upgrade of the
5570  software is easier now.
5571
5572
5573Linux HOWTO:
5574============
5575
5576Porting Linux to U-Boot based systems:
5577---------------------------------------
5578
5579U-Boot cannot save you from doing all the necessary modifications to
5580configure the Linux device drivers for use with your target hardware
5581(no, we don't intend to provide a full virtual machine interface to
5582Linux :-).
5583
5584But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5585
5586Just make sure your machine specific header file (for instance
5587include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5588Information structure as we define in include/asm-<arch>/u-boot.h,
5589and make sure that your definition of IMAP_ADDR uses the same value
5590as your U-Boot configuration in CONFIG_SYS_IMMR.
5591
5592Note that U-Boot now has a driver model, a unified model for drivers.
5593If you are adding a new driver, plumb it into driver model. If there
5594is no uclass available, you are encouraged to create one. See
5595doc/driver-model.
5596
5597
5598Configuring the Linux kernel:
5599-----------------------------
5600
5601No specific requirements for U-Boot. Make sure you have some root
5602device (initial ramdisk, NFS) for your target system.
5603
5604
5605Building a Linux Image:
5606-----------------------
5607
5608With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5609not used. If you use recent kernel source, a new build target
5610"uImage" will exist which automatically builds an image usable by
5611U-Boot. Most older kernels also have support for a "pImage" target,
5612which was introduced for our predecessor project PPCBoot and uses a
5613100% compatible format.
5614
5615Example:
5616
5617	make TQM850L_defconfig
5618	make oldconfig
5619	make dep
5620	make uImage
5621
5622The "uImage" build target uses a special tool (in 'tools/mkimage') to
5623encapsulate a compressed Linux kernel image with header	 information,
5624CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5625
5626* build a standard "vmlinux" kernel image (in ELF binary format):
5627
5628* convert the kernel into a raw binary image:
5629
5630	${CROSS_COMPILE}-objcopy -O binary \
5631				 -R .note -R .comment \
5632				 -S vmlinux linux.bin
5633
5634* compress the binary image:
5635
5636	gzip -9 linux.bin
5637
5638* package compressed binary image for U-Boot:
5639
5640	mkimage -A ppc -O linux -T kernel -C gzip \
5641		-a 0 -e 0 -n "Linux Kernel Image" \
5642		-d linux.bin.gz uImage
5643
5644
5645The "mkimage" tool can also be used to create ramdisk images for use
5646with U-Boot, either separated from the Linux kernel image, or
5647combined into one file. "mkimage" encapsulates the images with a 64
5648byte header containing information about target architecture,
5649operating system, image type, compression method, entry points, time
5650stamp, CRC32 checksums, etc.
5651
5652"mkimage" can be called in two ways: to verify existing images and
5653print the header information, or to build new images.
5654
5655In the first form (with "-l" option) mkimage lists the information
5656contained in the header of an existing U-Boot image; this includes
5657checksum verification:
5658
5659	tools/mkimage -l image
5660	  -l ==> list image header information
5661
5662The second form (with "-d" option) is used to build a U-Boot image
5663from a "data file" which is used as image payload:
5664
5665	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5666		      -n name -d data_file image
5667	  -A ==> set architecture to 'arch'
5668	  -O ==> set operating system to 'os'
5669	  -T ==> set image type to 'type'
5670	  -C ==> set compression type 'comp'
5671	  -a ==> set load address to 'addr' (hex)
5672	  -e ==> set entry point to 'ep' (hex)
5673	  -n ==> set image name to 'name'
5674	  -d ==> use image data from 'datafile'
5675
5676Right now, all Linux kernels for PowerPC systems use the same load
5677address (0x00000000), but the entry point address depends on the
5678kernel version:
5679
5680- 2.2.x kernels have the entry point at 0x0000000C,
5681- 2.3.x and later kernels have the entry point at 0x00000000.
5682
5683So a typical call to build a U-Boot image would read:
5684
5685	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5686	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5687	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5688	> examples/uImage.TQM850L
5689	Image Name:   2.4.4 kernel for TQM850L
5690	Created:      Wed Jul 19 02:34:59 2000
5691	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5692	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5693	Load Address: 0x00000000
5694	Entry Point:  0x00000000
5695
5696To verify the contents of the image (or check for corruption):
5697
5698	-> tools/mkimage -l examples/uImage.TQM850L
5699	Image Name:   2.4.4 kernel for TQM850L
5700	Created:      Wed Jul 19 02:34:59 2000
5701	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5702	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5703	Load Address: 0x00000000
5704	Entry Point:  0x00000000
5705
5706NOTE: for embedded systems where boot time is critical you can trade
5707speed for memory and install an UNCOMPRESSED image instead: this
5708needs more space in Flash, but boots much faster since it does not
5709need to be uncompressed:
5710
5711	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5712	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5713	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5714	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5715	> examples/uImage.TQM850L-uncompressed
5716	Image Name:   2.4.4 kernel for TQM850L
5717	Created:      Wed Jul 19 02:34:59 2000
5718	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5719	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5720	Load Address: 0x00000000
5721	Entry Point:  0x00000000
5722
5723
5724Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5725when your kernel is intended to use an initial ramdisk:
5726
5727	-> tools/mkimage -n 'Simple Ramdisk Image' \
5728	> -A ppc -O linux -T ramdisk -C gzip \
5729	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5730	Image Name:   Simple Ramdisk Image
5731	Created:      Wed Jan 12 14:01:50 2000
5732	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5733	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5734	Load Address: 0x00000000
5735	Entry Point:  0x00000000
5736
5737The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5738option performs the converse operation of the mkimage's second form (the "-d"
5739option). Given an image built by mkimage, the dumpimage extracts a "data file"
5740from the image:
5741
5742	tools/dumpimage -i image -p position data_file
5743	  -i ==> extract from the 'image' a specific 'data_file', \
5744	   indexed by 'position'
5745
5746
5747Installing a Linux Image:
5748-------------------------
5749
5750To downloading a U-Boot image over the serial (console) interface,
5751you must convert the image to S-Record format:
5752
5753	objcopy -I binary -O srec examples/image examples/image.srec
5754
5755The 'objcopy' does not understand the information in the U-Boot
5756image header, so the resulting S-Record file will be relative to
5757address 0x00000000. To load it to a given address, you need to
5758specify the target address as 'offset' parameter with the 'loads'
5759command.
5760
5761Example: install the image to address 0x40100000 (which on the
5762TQM8xxL is in the first Flash bank):
5763
5764	=> erase 40100000 401FFFFF
5765
5766	.......... done
5767	Erased 8 sectors
5768
5769	=> loads 40100000
5770	## Ready for S-Record download ...
5771	~>examples/image.srec
5772	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5773	...
5774	15989 15990 15991 15992
5775	[file transfer complete]
5776	[connected]
5777	## Start Addr = 0x00000000
5778
5779
5780You can check the success of the download using the 'iminfo' command;
5781this includes a checksum verification so you can be sure no data
5782corruption happened:
5783
5784	=> imi 40100000
5785
5786	## Checking Image at 40100000 ...
5787	   Image Name:	 2.2.13 for initrd on TQM850L
5788	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5789	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5790	   Load Address: 00000000
5791	   Entry Point:	 0000000c
5792	   Verifying Checksum ... OK
5793
5794
5795Boot Linux:
5796-----------
5797
5798The "bootm" command is used to boot an application that is stored in
5799memory (RAM or Flash). In case of a Linux kernel image, the contents
5800of the "bootargs" environment variable is passed to the kernel as
5801parameters. You can check and modify this variable using the
5802"printenv" and "setenv" commands:
5803
5804
5805	=> printenv bootargs
5806	bootargs=root=/dev/ram
5807
5808	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5809
5810	=> printenv bootargs
5811	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5812
5813	=> bootm 40020000
5814	## Booting Linux kernel at 40020000 ...
5815	   Image Name:	 2.2.13 for NFS on TQM850L
5816	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5817	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5818	   Load Address: 00000000
5819	   Entry Point:	 0000000c
5820	   Verifying Checksum ... OK
5821	   Uncompressing Kernel Image ... OK
5822	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
5823	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5824	time_init: decrementer frequency = 187500000/60
5825	Calibrating delay loop... 49.77 BogoMIPS
5826	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5827	...
5828
5829If you want to boot a Linux kernel with initial RAM disk, you pass
5830the memory addresses of both the kernel and the initrd image (PPBCOOT
5831format!) to the "bootm" command:
5832
5833	=> imi 40100000 40200000
5834
5835	## Checking Image at 40100000 ...
5836	   Image Name:	 2.2.13 for initrd on TQM850L
5837	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5838	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5839	   Load Address: 00000000
5840	   Entry Point:	 0000000c
5841	   Verifying Checksum ... OK
5842
5843	## Checking Image at 40200000 ...
5844	   Image Name:	 Simple Ramdisk Image
5845	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5846	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5847	   Load Address: 00000000
5848	   Entry Point:	 00000000
5849	   Verifying Checksum ... OK
5850
5851	=> bootm 40100000 40200000
5852	## Booting Linux kernel at 40100000 ...
5853	   Image Name:	 2.2.13 for initrd on TQM850L
5854	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5855	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5856	   Load Address: 00000000
5857	   Entry Point:	 0000000c
5858	   Verifying Checksum ... OK
5859	   Uncompressing Kernel Image ... OK
5860	## Loading RAMDisk Image at 40200000 ...
5861	   Image Name:	 Simple Ramdisk Image
5862	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5863	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5864	   Load Address: 00000000
5865	   Entry Point:	 00000000
5866	   Verifying Checksum ... OK
5867	   Loading Ramdisk ... OK
5868	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
5869	Boot arguments: root=/dev/ram
5870	time_init: decrementer frequency = 187500000/60
5871	Calibrating delay loop... 49.77 BogoMIPS
5872	...
5873	RAMDISK: Compressed image found at block 0
5874	VFS: Mounted root (ext2 filesystem).
5875
5876	bash#
5877
5878Boot Linux and pass a flat device tree:
5879-----------
5880
5881First, U-Boot must be compiled with the appropriate defines. See the section
5882titled "Linux Kernel Interface" above for a more in depth explanation. The
5883following is an example of how to start a kernel and pass an updated
5884flat device tree:
5885
5886=> print oftaddr
5887oftaddr=0x300000
5888=> print oft
5889oft=oftrees/mpc8540ads.dtb
5890=> tftp $oftaddr $oft
5891Speed: 1000, full duplex
5892Using TSEC0 device
5893TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5894Filename 'oftrees/mpc8540ads.dtb'.
5895Load address: 0x300000
5896Loading: #
5897done
5898Bytes transferred = 4106 (100a hex)
5899=> tftp $loadaddr $bootfile
5900Speed: 1000, full duplex
5901Using TSEC0 device
5902TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5903Filename 'uImage'.
5904Load address: 0x200000
5905Loading:############
5906done
5907Bytes transferred = 1029407 (fb51f hex)
5908=> print loadaddr
5909loadaddr=200000
5910=> print oftaddr
5911oftaddr=0x300000
5912=> bootm $loadaddr - $oftaddr
5913## Booting image at 00200000 ...
5914   Image Name:	 Linux-2.6.17-dirty
5915   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5916   Data Size:	 1029343 Bytes = 1005.2 kB
5917   Load Address: 00000000
5918   Entry Point:	 00000000
5919   Verifying Checksum ... OK
5920   Uncompressing Kernel Image ... OK
5921Booting using flat device tree at 0x300000
5922Using MPC85xx ADS machine description
5923Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5924[snip]
5925
5926
5927More About U-Boot Image Types:
5928------------------------------
5929
5930U-Boot supports the following image types:
5931
5932   "Standalone Programs" are directly runnable in the environment
5933	provided by U-Boot; it is expected that (if they behave
5934	well) you can continue to work in U-Boot after return from
5935	the Standalone Program.
5936   "OS Kernel Images" are usually images of some Embedded OS which
5937	will take over control completely. Usually these programs
5938	will install their own set of exception handlers, device
5939	drivers, set up the MMU, etc. - this means, that you cannot
5940	expect to re-enter U-Boot except by resetting the CPU.
5941   "RAMDisk Images" are more or less just data blocks, and their
5942	parameters (address, size) are passed to an OS kernel that is
5943	being started.
5944   "Multi-File Images" contain several images, typically an OS
5945	(Linux) kernel image and one or more data images like
5946	RAMDisks. This construct is useful for instance when you want
5947	to boot over the network using BOOTP etc., where the boot
5948	server provides just a single image file, but you want to get
5949	for instance an OS kernel and a RAMDisk image.
5950
5951	"Multi-File Images" start with a list of image sizes, each
5952	image size (in bytes) specified by an "uint32_t" in network
5953	byte order. This list is terminated by an "(uint32_t)0".
5954	Immediately after the terminating 0 follow the images, one by
5955	one, all aligned on "uint32_t" boundaries (size rounded up to
5956	a multiple of 4 bytes).
5957
5958   "Firmware Images" are binary images containing firmware (like
5959	U-Boot or FPGA images) which usually will be programmed to
5960	flash memory.
5961
5962   "Script files" are command sequences that will be executed by
5963	U-Boot's command interpreter; this feature is especially
5964	useful when you configure U-Boot to use a real shell (hush)
5965	as command interpreter.
5966
5967Booting the Linux zImage:
5968-------------------------
5969
5970On some platforms, it's possible to boot Linux zImage. This is done
5971using the "bootz" command. The syntax of "bootz" command is the same
5972as the syntax of "bootm" command.
5973
5974Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5975kernel with raw initrd images. The syntax is slightly different, the
5976address of the initrd must be augmented by it's size, in the following
5977format: "<initrd addres>:<initrd size>".
5978
5979
5980Standalone HOWTO:
5981=================
5982
5983One of the features of U-Boot is that you can dynamically load and
5984run "standalone" applications, which can use some resources of
5985U-Boot like console I/O functions or interrupt services.
5986
5987Two simple examples are included with the sources:
5988
5989"Hello World" Demo:
5990-------------------
5991
5992'examples/hello_world.c' contains a small "Hello World" Demo
5993application; it is automatically compiled when you build U-Boot.
5994It's configured to run at address 0x00040004, so you can play with it
5995like that:
5996
5997	=> loads
5998	## Ready for S-Record download ...
5999	~>examples/hello_world.srec
6000	1 2 3 4 5 6 7 8 9 10 11 ...
6001	[file transfer complete]
6002	[connected]
6003	## Start Addr = 0x00040004
6004
6005	=> go 40004 Hello World! This is a test.
6006	## Starting application at 0x00040004 ...
6007	Hello World
6008	argc = 7
6009	argv[0] = "40004"
6010	argv[1] = "Hello"
6011	argv[2] = "World!"
6012	argv[3] = "This"
6013	argv[4] = "is"
6014	argv[5] = "a"
6015	argv[6] = "test."
6016	argv[7] = "<NULL>"
6017	Hit any key to exit ...
6018
6019	## Application terminated, rc = 0x0
6020
6021Another example, which demonstrates how to register a CPM interrupt
6022handler with the U-Boot code, can be found in 'examples/timer.c'.
6023Here, a CPM timer is set up to generate an interrupt every second.
6024The interrupt service routine is trivial, just printing a '.'
6025character, but this is just a demo program. The application can be
6026controlled by the following keys:
6027
6028	? - print current values og the CPM Timer registers
6029	b - enable interrupts and start timer
6030	e - stop timer and disable interrupts
6031	q - quit application
6032
6033	=> loads
6034	## Ready for S-Record download ...
6035	~>examples/timer.srec
6036	1 2 3 4 5 6 7 8 9 10 11 ...
6037	[file transfer complete]
6038	[connected]
6039	## Start Addr = 0x00040004
6040
6041	=> go 40004
6042	## Starting application at 0x00040004 ...
6043	TIMERS=0xfff00980
6044	Using timer 1
6045	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
6046
6047Hit 'b':
6048	[q, b, e, ?] Set interval 1000000 us
6049	Enabling timer
6050Hit '?':
6051	[q, b, e, ?] ........
6052	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
6053Hit '?':
6054	[q, b, e, ?] .
6055	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
6056Hit '?':
6057	[q, b, e, ?] .
6058	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
6059Hit '?':
6060	[q, b, e, ?] .
6061	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
6062Hit 'e':
6063	[q, b, e, ?] ...Stopping timer
6064Hit 'q':
6065	[q, b, e, ?] ## Application terminated, rc = 0x0
6066
6067
6068Minicom warning:
6069================
6070
6071Over time, many people have reported problems when trying to use the
6072"minicom" terminal emulation program for serial download. I (wd)
6073consider minicom to be broken, and recommend not to use it. Under
6074Unix, I recommend to use C-Kermit for general purpose use (and
6075especially for kermit binary protocol download ("loadb" command), and
6076use "cu" for S-Record download ("loads" command).  See
6077http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
6078for help with kermit.
6079
6080
6081Nevertheless, if you absolutely want to use it try adding this
6082configuration to your "File transfer protocols" section:
6083
6084	   Name	   Program			Name U/D FullScr IO-Red. Multi
6085	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
6086	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
6087
6088
6089NetBSD Notes:
6090=============
6091
6092Starting at version 0.9.2, U-Boot supports NetBSD both as host
6093(build U-Boot) and target system (boots NetBSD/mpc8xx).
6094
6095Building requires a cross environment; it is known to work on
6096NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
6097need gmake since the Makefiles are not compatible with BSD make).
6098Note that the cross-powerpc package does not install include files;
6099attempting to build U-Boot will fail because <machine/ansi.h> is
6100missing.  This file has to be installed and patched manually:
6101
6102	# cd /usr/pkg/cross/powerpc-netbsd/include
6103	# mkdir powerpc
6104	# ln -s powerpc machine
6105	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
6106	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
6107
6108Native builds *don't* work due to incompatibilities between native
6109and U-Boot include files.
6110
6111Booting assumes that (the first part of) the image booted is a
6112stage-2 loader which in turn loads and then invokes the kernel
6113proper. Loader sources will eventually appear in the NetBSD source
6114tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
6115meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
6116
6117
6118Implementation Internals:
6119=========================
6120
6121The following is not intended to be a complete description of every
6122implementation detail. However, it should help to understand the
6123inner workings of U-Boot and make it easier to port it to custom
6124hardware.
6125
6126
6127Initial Stack, Global Data:
6128---------------------------
6129
6130The implementation of U-Boot is complicated by the fact that U-Boot
6131starts running out of ROM (flash memory), usually without access to
6132system RAM (because the memory controller is not initialized yet).
6133This means that we don't have writable Data or BSS segments, and BSS
6134is not initialized as zero. To be able to get a C environment working
6135at all, we have to allocate at least a minimal stack. Implementation
6136options for this are defined and restricted by the CPU used: Some CPU
6137models provide on-chip memory (like the IMMR area on MPC8xx and
6138MPC826x processors), on others (parts of) the data cache can be
6139locked as (mis-) used as memory, etc.
6140
6141	Chris Hallinan posted a good summary of these issues to the
6142	U-Boot mailing list:
6143
6144	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
6145	From: "Chris Hallinan" <clh@net1plus.com>
6146	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
6147	...
6148
6149	Correct me if I'm wrong, folks, but the way I understand it
6150	is this: Using DCACHE as initial RAM for Stack, etc, does not
6151	require any physical RAM backing up the cache. The cleverness
6152	is that the cache is being used as a temporary supply of
6153	necessary storage before the SDRAM controller is setup. It's
6154	beyond the scope of this list to explain the details, but you
6155	can see how this works by studying the cache architecture and
6156	operation in the architecture and processor-specific manuals.
6157
6158	OCM is On Chip Memory, which I believe the 405GP has 4K. It
6159	is another option for the system designer to use as an
6160	initial stack/RAM area prior to SDRAM being available. Either
6161	option should work for you. Using CS 4 should be fine if your
6162	board designers haven't used it for something that would
6163	cause you grief during the initial boot! It is frequently not
6164	used.
6165
6166	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
6167	with your processor/board/system design. The default value
6168	you will find in any recent u-boot distribution in
6169	walnut.h should work for you. I'd set it to a value larger
6170	than your SDRAM module. If you have a 64MB SDRAM module, set
6171	it above 400_0000. Just make sure your board has no resources
6172	that are supposed to respond to that address! That code in
6173	start.S has been around a while and should work as is when
6174	you get the config right.
6175
6176	-Chris Hallinan
6177	DS4.COM, Inc.
6178
6179It is essential to remember this, since it has some impact on the C
6180code for the initialization procedures:
6181
6182* Initialized global data (data segment) is read-only. Do not attempt
6183  to write it.
6184
6185* Do not use any uninitialized global data (or implicitely initialized
6186  as zero data - BSS segment) at all - this is undefined, initiali-
6187  zation is performed later (when relocating to RAM).
6188
6189* Stack space is very limited. Avoid big data buffers or things like
6190  that.
6191
6192Having only the stack as writable memory limits means we cannot use
6193normal global data to share information beween the code. But it
6194turned out that the implementation of U-Boot can be greatly
6195simplified by making a global data structure (gd_t) available to all
6196functions. We could pass a pointer to this data as argument to _all_
6197functions, but this would bloat the code. Instead we use a feature of
6198the GCC compiler (Global Register Variables) to share the data: we
6199place a pointer (gd) to the global data into a register which we
6200reserve for this purpose.
6201
6202When choosing a register for such a purpose we are restricted by the
6203relevant  (E)ABI  specifications for the current architecture, and by
6204GCC's implementation.
6205
6206For PowerPC, the following registers have specific use:
6207	R1:	stack pointer
6208	R2:	reserved for system use
6209	R3-R4:	parameter passing and return values
6210	R5-R10: parameter passing
6211	R13:	small data area pointer
6212	R30:	GOT pointer
6213	R31:	frame pointer
6214
6215	(U-Boot also uses R12 as internal GOT pointer. r12
6216	is a volatile register so r12 needs to be reset when
6217	going back and forth between asm and C)
6218
6219    ==> U-Boot will use R2 to hold a pointer to the global data
6220
6221    Note: on PPC, we could use a static initializer (since the
6222    address of the global data structure is known at compile time),
6223    but it turned out that reserving a register results in somewhat
6224    smaller code - although the code savings are not that big (on
6225    average for all boards 752 bytes for the whole U-Boot image,
6226    624 text + 127 data).
6227
6228On Blackfin, the normal C ABI (except for P3) is followed as documented here:
6229	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
6230
6231    ==> U-Boot will use P3 to hold a pointer to the global data
6232
6233On ARM, the following registers are used:
6234
6235	R0:	function argument word/integer result
6236	R1-R3:	function argument word
6237	R9:	platform specific
6238	R10:	stack limit (used only if stack checking is enabled)
6239	R11:	argument (frame) pointer
6240	R12:	temporary workspace
6241	R13:	stack pointer
6242	R14:	link register
6243	R15:	program counter
6244
6245    ==> U-Boot will use R9 to hold a pointer to the global data
6246
6247    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
6248
6249On Nios II, the ABI is documented here:
6250	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
6251
6252    ==> U-Boot will use gp to hold a pointer to the global data
6253
6254    Note: on Nios II, we give "-G0" option to gcc and don't use gp
6255    to access small data sections, so gp is free.
6256
6257On NDS32, the following registers are used:
6258
6259	R0-R1:	argument/return
6260	R2-R5:	argument
6261	R15:	temporary register for assembler
6262	R16:	trampoline register
6263	R28:	frame pointer (FP)
6264	R29:	global pointer (GP)
6265	R30:	link register (LP)
6266	R31:	stack pointer (SP)
6267	PC:	program counter (PC)
6268
6269    ==> U-Boot will use R10 to hold a pointer to the global data
6270
6271NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
6272or current versions of GCC may "optimize" the code too much.
6273
6274Memory Management:
6275------------------
6276
6277U-Boot runs in system state and uses physical addresses, i.e. the
6278MMU is not used either for address mapping nor for memory protection.
6279
6280The available memory is mapped to fixed addresses using the memory
6281controller. In this process, a contiguous block is formed for each
6282memory type (Flash, SDRAM, SRAM), even when it consists of several
6283physical memory banks.
6284
6285U-Boot is installed in the first 128 kB of the first Flash bank (on
6286TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
6287booting and sizing and initializing DRAM, the code relocates itself
6288to the upper end of DRAM. Immediately below the U-Boot code some
6289memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
6290configuration setting]. Below that, a structure with global Board
6291Info data is placed, followed by the stack (growing downward).
6292
6293Additionally, some exception handler code is copied to the low 8 kB
6294of DRAM (0x00000000 ... 0x00001FFF).
6295
6296So a typical memory configuration with 16 MB of DRAM could look like
6297this:
6298
6299	0x0000 0000	Exception Vector code
6300	      :
6301	0x0000 1FFF
6302	0x0000 2000	Free for Application Use
6303	      :
6304	      :
6305
6306	      :
6307	      :
6308	0x00FB FF20	Monitor Stack (Growing downward)
6309	0x00FB FFAC	Board Info Data and permanent copy of global data
6310	0x00FC 0000	Malloc Arena
6311	      :
6312	0x00FD FFFF
6313	0x00FE 0000	RAM Copy of Monitor Code
6314	...		eventually: LCD or video framebuffer
6315	...		eventually: pRAM (Protected RAM - unchanged by reset)
6316	0x00FF FFFF	[End of RAM]
6317
6318
6319System Initialization:
6320----------------------
6321
6322In the reset configuration, U-Boot starts at the reset entry point
6323(on most PowerPC systems at address 0x00000100). Because of the reset
6324configuration for CS0# this is a mirror of the onboard Flash memory.
6325To be able to re-map memory U-Boot then jumps to its link address.
6326To be able to implement the initialization code in C, a (small!)
6327initial stack is set up in the internal Dual Ported RAM (in case CPUs
6328which provide such a feature like MPC8xx or MPC8260), or in a locked
6329part of the data cache. After that, U-Boot initializes the CPU core,
6330the caches and the SIU.
6331
6332Next, all (potentially) available memory banks are mapped using a
6333preliminary mapping. For example, we put them on 512 MB boundaries
6334(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
6335on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
6336programmed for SDRAM access. Using the temporary configuration, a
6337simple memory test is run that determines the size of the SDRAM
6338banks.
6339
6340When there is more than one SDRAM bank, and the banks are of
6341different size, the largest is mapped first. For equal size, the first
6342bank (CS2#) is mapped first. The first mapping is always for address
63430x00000000, with any additional banks following immediately to create
6344contiguous memory starting from 0.
6345
6346Then, the monitor installs itself at the upper end of the SDRAM area
6347and allocates memory for use by malloc() and for the global Board
6348Info data; also, the exception vector code is copied to the low RAM
6349pages, and the final stack is set up.
6350
6351Only after this relocation will you have a "normal" C environment;
6352until that you are restricted in several ways, mostly because you are
6353running from ROM, and because the code will have to be relocated to a
6354new address in RAM.
6355
6356
6357U-Boot Porting Guide:
6358----------------------
6359
6360[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
6361list, October 2002]
6362
6363
6364int main(int argc, char *argv[])
6365{
6366	sighandler_t no_more_time;
6367
6368	signal(SIGALRM, no_more_time);
6369	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6370
6371	if (available_money > available_manpower) {
6372		Pay consultant to port U-Boot;
6373		return 0;
6374	}
6375
6376	Download latest U-Boot source;
6377
6378	Subscribe to u-boot mailing list;
6379
6380	if (clueless)
6381		email("Hi, I am new to U-Boot, how do I get started?");
6382
6383	while (learning) {
6384		Read the README file in the top level directory;
6385		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6386		Read applicable doc/*.README;
6387		Read the source, Luke;
6388		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6389	}
6390
6391	if (available_money > toLocalCurrency ($2500))
6392		Buy a BDI3000;
6393	else
6394		Add a lot of aggravation and time;
6395
6396	if (a similar board exists) {	/* hopefully... */
6397		cp -a board/<similar> board/<myboard>
6398		cp include/configs/<similar>.h include/configs/<myboard>.h
6399	} else {
6400		Create your own board support subdirectory;
6401		Create your own board include/configs/<myboard>.h file;
6402	}
6403	Edit new board/<myboard> files
6404	Edit new include/configs/<myboard>.h
6405
6406	while (!accepted) {
6407		while (!running) {
6408			do {
6409				Add / modify source code;
6410			} until (compiles);
6411			Debug;
6412			if (clueless)
6413				email("Hi, I am having problems...");
6414		}
6415		Send patch file to the U-Boot email list;
6416		if (reasonable critiques)
6417			Incorporate improvements from email list code review;
6418		else
6419			Defend code as written;
6420	}
6421
6422	return 0;
6423}
6424
6425void no_more_time (int sig)
6426{
6427      hire_a_guru();
6428}
6429
6430
6431Coding Standards:
6432-----------------
6433
6434All contributions to U-Boot should conform to the Linux kernel
6435coding style; see the file "Documentation/CodingStyle" and the script
6436"scripts/Lindent" in your Linux kernel source directory.
6437
6438Source files originating from a different project (for example the
6439MTD subsystem) are generally exempt from these guidelines and are not
6440reformated to ease subsequent migration to newer versions of those
6441sources.
6442
6443Please note that U-Boot is implemented in C (and to some small parts in
6444Assembler); no C++ is used, so please do not use C++ style comments (//)
6445in your code.
6446
6447Please also stick to the following formatting rules:
6448- remove any trailing white space
6449- use TAB characters for indentation and vertical alignment, not spaces
6450- make sure NOT to use DOS '\r\n' line feeds
6451- do not add more than 2 consecutive empty lines to source files
6452- do not add trailing empty lines to source files
6453
6454Submissions which do not conform to the standards may be returned
6455with a request to reformat the changes.
6456
6457
6458Submitting Patches:
6459-------------------
6460
6461Since the number of patches for U-Boot is growing, we need to
6462establish some rules. Submissions which do not conform to these rules
6463may be rejected, even when they contain important and valuable stuff.
6464
6465Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6466
6467Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6468see http://lists.denx.de/mailman/listinfo/u-boot
6469
6470When you send a patch, please include the following information with
6471it:
6472
6473* For bug fixes: a description of the bug and how your patch fixes
6474  this bug. Please try to include a way of demonstrating that the
6475  patch actually fixes something.
6476
6477* For new features: a description of the feature and your
6478  implementation.
6479
6480* A CHANGELOG entry as plaintext (separate from the patch)
6481
6482* For major contributions, your entry to the CREDITS file
6483
6484* When you add support for a new board, don't forget to add a
6485  maintainer e-mail address to the boards.cfg file, too.
6486
6487* If your patch adds new configuration options, don't forget to
6488  document these in the README file.
6489
6490* The patch itself. If you are using git (which is *strongly*
6491  recommended) you can easily generate the patch using the
6492  "git format-patch". If you then use "git send-email" to send it to
6493  the U-Boot mailing list, you will avoid most of the common problems
6494  with some other mail clients.
6495
6496  If you cannot use git, use "diff -purN OLD NEW". If your version of
6497  diff does not support these options, then get the latest version of
6498  GNU diff.
6499
6500  The current directory when running this command shall be the parent
6501  directory of the U-Boot source tree (i. e. please make sure that
6502  your patch includes sufficient directory information for the
6503  affected files).
6504
6505  We prefer patches as plain text. MIME attachments are discouraged,
6506  and compressed attachments must not be used.
6507
6508* If one logical set of modifications affects or creates several
6509  files, all these changes shall be submitted in a SINGLE patch file.
6510
6511* Changesets that contain different, unrelated modifications shall be
6512  submitted as SEPARATE patches, one patch per changeset.
6513
6514
6515Notes:
6516
6517* Before sending the patch, run the MAKEALL script on your patched
6518  source tree and make sure that no errors or warnings are reported
6519  for any of the boards.
6520
6521* Keep your modifications to the necessary minimum: A patch
6522  containing several unrelated changes or arbitrary reformats will be
6523  returned with a request to re-formatting / split it.
6524
6525* If you modify existing code, make sure that your new code does not
6526  add to the memory footprint of the code ;-) Small is beautiful!
6527  When adding new features, these should compile conditionally only
6528  (using #ifdef), and the resulting code with the new feature
6529  disabled must not need more memory than the old code without your
6530  modification.
6531
6532* Remember that there is a size limit of 100 kB per message on the
6533  u-boot mailing list. Bigger patches will be moderated. If they are
6534  reasonable and not too big, they will be acknowledged. But patches
6535  bigger than the size limit should be avoided.
6536