xref: /openbmc/u-boot/README (revision b1420c81)
1#
2# (C) Copyright 2000 - 2013
3# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4#
5# SPDX-License-Identifier:	GPL-2.0+
6#
7
8Summary:
9========
10
11This directory contains the source code for U-Boot, a boot loader for
12Embedded boards based on PowerPC, ARM, MIPS and several other
13processors, which can be installed in a boot ROM and used to
14initialize and test the hardware or to download and run application
15code.
16
17The development of U-Boot is closely related to Linux: some parts of
18the source code originate in the Linux source tree, we have some
19header files in common, and special provision has been made to
20support booting of Linux images.
21
22Some attention has been paid to make this software easily
23configurable and extendable. For instance, all monitor commands are
24implemented with the same call interface, so that it's very easy to
25add new commands. Also, instead of permanently adding rarely used
26code (for instance hardware test utilities) to the monitor, you can
27load and run it dynamically.
28
29
30Status:
31=======
32
33In general, all boards for which a configuration option exists in the
34Makefile have been tested to some extent and can be considered
35"working". In fact, many of them are used in production systems.
36
37In case of problems see the CHANGELOG and CREDITS files to find out
38who contributed the specific port. The boards.cfg file lists board
39maintainers.
40
41Note: There is no CHANGELOG file in the actual U-Boot source tree;
42it can be created dynamically from the Git log using:
43
44	make CHANGELOG
45
46
47Where to get help:
48==================
49
50In case you have questions about, problems with or contributions for
51U-Boot you should send a message to the U-Boot mailing list at
52<u-boot@lists.denx.de>. There is also an archive of previous traffic
53on the mailing list - please search the archive before asking FAQ's.
54Please see http://lists.denx.de/pipermail/u-boot and
55http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
56
57
58Where to get source code:
59=========================
60
61The U-Boot source code is maintained in the git repository at
62git://www.denx.de/git/u-boot.git ; you can browse it online at
63http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
64
65The "snapshot" links on this page allow you to download tarballs of
66any version you might be interested in. Official releases are also
67available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
68directory.
69
70Pre-built (and tested) images are available from
71ftp://ftp.denx.de/pub/u-boot/images/
72
73
74Where we come from:
75===================
76
77- start from 8xxrom sources
78- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
79- clean up code
80- make it easier to add custom boards
81- make it possible to add other [PowerPC] CPUs
82- extend functions, especially:
83  * Provide extended interface to Linux boot loader
84  * S-Record download
85  * network boot
86  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
87- create ARMBoot project (http://sourceforge.net/projects/armboot)
88- add other CPU families (starting with ARM)
89- create U-Boot project (http://sourceforge.net/projects/u-boot)
90- current project page: see http://www.denx.de/wiki/U-Boot
91
92
93Names and Spelling:
94===================
95
96The "official" name of this project is "Das U-Boot". The spelling
97"U-Boot" shall be used in all written text (documentation, comments
98in source files etc.). Example:
99
100	This is the README file for the U-Boot project.
101
102File names etc. shall be based on the string "u-boot". Examples:
103
104	include/asm-ppc/u-boot.h
105
106	#include <asm/u-boot.h>
107
108Variable names, preprocessor constants etc. shall be either based on
109the string "u_boot" or on "U_BOOT". Example:
110
111	U_BOOT_VERSION		u_boot_logo
112	IH_OS_U_BOOT		u_boot_hush_start
113
114
115Versioning:
116===========
117
118Starting with the release in October 2008, the names of the releases
119were changed from numerical release numbers without deeper meaning
120into a time stamp based numbering. Regular releases are identified by
121names consisting of the calendar year and month of the release date.
122Additional fields (if present) indicate release candidates or bug fix
123releases in "stable" maintenance trees.
124
125Examples:
126	U-Boot v2009.11	    - Release November 2009
127	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
128	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
129
130
131Directory Hierarchy:
132====================
133
134/arch			Architecture specific files
135  /arc			Files generic to ARC architecture
136    /cpu		CPU specific files
137      /arc700		Files specific to ARC 700 CPUs
138    /lib		Architecture specific library files
139  /arm			Files generic to ARM architecture
140    /cpu		CPU specific files
141      /arm720t		Files specific to ARM 720 CPUs
142      /arm920t		Files specific to ARM 920 CPUs
143	/at91		Files specific to Atmel AT91RM9200 CPU
144	/imx		Files specific to Freescale MC9328 i.MX CPUs
145	/s3c24x0	Files specific to Samsung S3C24X0 CPUs
146      /arm926ejs	Files specific to ARM 926 CPUs
147      /arm1136		Files specific to ARM 1136 CPUs
148      /pxa		Files specific to Intel XScale PXA CPUs
149      /sa1100		Files specific to Intel StrongARM SA1100 CPUs
150    /lib		Architecture specific library files
151  /avr32		Files generic to AVR32 architecture
152    /cpu		CPU specific files
153    /lib		Architecture specific library files
154  /blackfin		Files generic to Analog Devices Blackfin architecture
155    /cpu		CPU specific files
156    /lib		Architecture specific library files
157  /m68k			Files generic to m68k architecture
158    /cpu		CPU specific files
159      /mcf52x2		Files specific to Freescale ColdFire MCF52x2 CPUs
160      /mcf5227x		Files specific to Freescale ColdFire MCF5227x CPUs
161      /mcf532x		Files specific to Freescale ColdFire MCF5329 CPUs
162      /mcf5445x		Files specific to Freescale ColdFire MCF5445x CPUs
163      /mcf547x_8x	Files specific to Freescale ColdFire MCF547x_8x CPUs
164    /lib		Architecture specific library files
165  /microblaze		Files generic to microblaze architecture
166    /cpu		CPU specific files
167    /lib		Architecture specific library files
168  /mips			Files generic to MIPS architecture
169    /cpu		CPU specific files
170      /mips32		Files specific to MIPS32 CPUs
171      /mips64		Files specific to MIPS64 CPUs
172    /lib		Architecture specific library files
173  /nds32		Files generic to NDS32 architecture
174    /cpu		CPU specific files
175      /n1213		Files specific to Andes Technology N1213 CPUs
176    /lib		Architecture specific library files
177  /nios2		Files generic to Altera NIOS2 architecture
178    /cpu		CPU specific files
179    /lib		Architecture specific library files
180  /openrisc		Files generic to OpenRISC architecture
181    /cpu		CPU specific files
182    /lib		Architecture specific library files
183  /powerpc		Files generic to PowerPC architecture
184    /cpu		CPU specific files
185      /mpc5xx		Files specific to Freescale MPC5xx CPUs
186      /mpc5xxx		Files specific to Freescale MPC5xxx CPUs
187      /mpc8xx		Files specific to Freescale MPC8xx CPUs
188      /mpc8260		Files specific to Freescale MPC8260 CPUs
189      /mpc85xx		Files specific to Freescale MPC85xx CPUs
190      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
191    /lib		Architecture specific library files
192  /sh			Files generic to SH architecture
193    /cpu		CPU specific files
194      /sh2		Files specific to sh2 CPUs
195      /sh3		Files specific to sh3 CPUs
196      /sh4		Files specific to sh4 CPUs
197    /lib		Architecture specific library files
198  /sparc		Files generic to SPARC architecture
199    /cpu		CPU specific files
200      /leon2		Files specific to Gaisler LEON2 SPARC CPU
201      /leon3		Files specific to Gaisler LEON3 SPARC CPU
202    /lib		Architecture specific library files
203  /x86			Files generic to x86 architecture
204    /cpu		CPU specific files
205    /lib		Architecture specific library files
206/api			Machine/arch independent API for external apps
207/board			Board dependent files
208/common			Misc architecture independent functions
209/disk			Code for disk drive partition handling
210/doc			Documentation (don't expect too much)
211/drivers		Commonly used device drivers
212/dts			Contains Makefile for building internal U-Boot fdt.
213/examples		Example code for standalone applications, etc.
214/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
215/include		Header Files
216/lib			Files generic to all architectures
217  /libfdt		Library files to support flattened device trees
218  /lzma			Library files to support LZMA decompression
219  /lzo			Library files to support LZO decompression
220/net			Networking code
221/post			Power On Self Test
222/spl			Secondary Program Loader framework
223/tools			Tools to build S-Record or U-Boot images, etc.
224
225Software Configuration:
226=======================
227
228Configuration is usually done using C preprocessor defines; the
229rationale behind that is to avoid dead code whenever possible.
230
231There are two classes of configuration variables:
232
233* Configuration _OPTIONS_:
234  These are selectable by the user and have names beginning with
235  "CONFIG_".
236
237* Configuration _SETTINGS_:
238  These depend on the hardware etc. and should not be meddled with if
239  you don't know what you're doing; they have names beginning with
240  "CONFIG_SYS_".
241
242Later we will add a configuration tool - probably similar to or even
243identical to what's used for the Linux kernel. Right now, we have to
244do the configuration by hand, which means creating some symbolic
245links and editing some configuration files. We use the TQM8xxL boards
246as an example here.
247
248
249Selection of Processor Architecture and Board Type:
250---------------------------------------------------
251
252For all supported boards there are ready-to-use default
253configurations available; just type "make <board_name>_defconfig".
254
255Example: For a TQM823L module type:
256
257	cd u-boot
258	make TQM823L_defconfig
259
260For the Cogent platform, you need to specify the CPU type as well;
261e.g. "make cogent_mpc8xx_defconfig". And also configure the cogent
262directory according to the instructions in cogent/README.
263
264
265Sandbox Environment:
266--------------------
267
268U-Boot can be built natively to run on a Linux host using the 'sandbox'
269board. This allows feature development which is not board- or architecture-
270specific to be undertaken on a native platform. The sandbox is also used to
271run some of U-Boot's tests.
272
273See board/sandbox/README.sandbox for more details.
274
275
276Configuration Options:
277----------------------
278
279Configuration depends on the combination of board and CPU type; all
280such information is kept in a configuration file
281"include/configs/<board_name>.h".
282
283Example: For a TQM823L module, all configuration settings are in
284"include/configs/TQM823L.h".
285
286
287Many of the options are named exactly as the corresponding Linux
288kernel configuration options. The intention is to make it easier to
289build a config tool - later.
290
291
292The following options need to be configured:
293
294- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
295
296- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
297
298- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
299		Define exactly one, e.g. CONFIG_ATSTK1002
300
301- CPU Module Type: (if CONFIG_COGENT is defined)
302		Define exactly one of
303		CONFIG_CMA286_60_OLD
304--- FIXME --- not tested yet:
305		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
306		CONFIG_CMA287_23, CONFIG_CMA287_50
307
308- Motherboard Type: (if CONFIG_COGENT is defined)
309		Define exactly one of
310		CONFIG_CMA101, CONFIG_CMA102
311
312- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
313		Define one or more of
314		CONFIG_CMA302
315
316- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
317		Define one or more of
318		CONFIG_LCD_HEARTBEAT	- update a character position on
319					  the LCD display every second with
320					  a "rotator" |\-/|\-/
321
322- Marvell Family Member
323		CONFIG_SYS_MVFS		- define it if you want to enable
324					  multiple fs option at one time
325					  for marvell soc family
326
327- 8xx CPU Options: (if using an MPC8xx CPU)
328		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
329					  get_gclk_freq() cannot work
330					  e.g. if there is no 32KHz
331					  reference PIT/RTC clock
332		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
333					  or XTAL/EXTAL)
334
335- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
336		CONFIG_SYS_8xx_CPUCLK_MIN
337		CONFIG_SYS_8xx_CPUCLK_MAX
338		CONFIG_8xx_CPUCLK_DEFAULT
339			See doc/README.MPC866
340
341		CONFIG_SYS_MEASURE_CPUCLK
342
343		Define this to measure the actual CPU clock instead
344		of relying on the correctness of the configured
345		values. Mostly useful for board bringup to make sure
346		the PLL is locked at the intended frequency. Note
347		that this requires a (stable) reference clock (32 kHz
348		RTC clock or CONFIG_SYS_8XX_XIN)
349
350		CONFIG_SYS_DELAYED_ICACHE
351
352		Define this option if you want to enable the
353		ICache only when Code runs from RAM.
354
355- 85xx CPU Options:
356		CONFIG_SYS_PPC64
357
358		Specifies that the core is a 64-bit PowerPC implementation (implements
359		the "64" category of the Power ISA). This is necessary for ePAPR
360		compliance, among other possible reasons.
361
362		CONFIG_SYS_FSL_TBCLK_DIV
363
364		Defines the core time base clock divider ratio compared to the
365		system clock.  On most PQ3 devices this is 8, on newer QorIQ
366		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
367
368		CONFIG_SYS_FSL_PCIE_COMPAT
369
370		Defines the string to utilize when trying to match PCIe device
371		tree nodes for the given platform.
372
373		CONFIG_SYS_PPC_E500_DEBUG_TLB
374
375		Enables a temporary TLB entry to be used during boot to work
376		around limitations in e500v1 and e500v2 external debugger
377		support. This reduces the portions of the boot code where
378		breakpoints and single stepping do not work.  The value of this
379		symbol should be set to the TLB1 entry to be used for this
380		purpose.
381
382		CONFIG_SYS_FSL_ERRATUM_A004510
383
384		Enables a workaround for erratum A004510.  If set,
385		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
386		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
387
388		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
389		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
390
391		Defines one or two SoC revisions (low 8 bits of SVR)
392		for which the A004510 workaround should be applied.
393
394		The rest of SVR is either not relevant to the decision
395		of whether the erratum is present (e.g. p2040 versus
396		p2041) or is implied by the build target, which controls
397		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
398
399		See Freescale App Note 4493 for more information about
400		this erratum.
401
402		CONFIG_A003399_NOR_WORKAROUND
403		Enables a workaround for IFC erratum A003399. It is only
404		required during NOR boot.
405
406		CONFIG_A008044_WORKAROUND
407		Enables a workaround for T1040/T1042 erratum A008044. It is only
408		required during NAND boot and valid for Rev 1.0 SoC revision
409
410		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
411
412		This is the value to write into CCSR offset 0x18600
413		according to the A004510 workaround.
414
415		CONFIG_SYS_FSL_DSP_DDR_ADDR
416		This value denotes start offset of DDR memory which is
417		connected exclusively to the DSP cores.
418
419		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
420		This value denotes start offset of M2 memory
421		which is directly connected to the DSP core.
422
423		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
424		This value denotes start offset of M3 memory which is directly
425		connected to the DSP core.
426
427		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
428		This value denotes start offset of DSP CCSR space.
429
430		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
431		Single Source Clock is clocking mode present in some of FSL SoC's.
432		In this mode, a single differential clock is used to supply
433		clocks to the sysclock, ddrclock and usbclock.
434
435		CONFIG_SYS_CPC_REINIT_F
436		This CONFIG is defined when the CPC is configured as SRAM at the
437		time of U-boot entry and is required to be re-initialized.
438
439		CONFIG_DEEP_SLEEP
440		Indicates this SoC supports deep sleep feature. If deep sleep is
441		supported, core will start to execute uboot when wakes up.
442
443- Generic CPU options:
444		CONFIG_SYS_GENERIC_GLOBAL_DATA
445		Defines global data is initialized in generic board board_init_f().
446		If this macro is defined, global data is created and cleared in
447		generic board board_init_f(). Without this macro, architecture/board
448		should initialize global data before calling board_init_f().
449
450		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
451
452		Defines the endianess of the CPU. Implementation of those
453		values is arch specific.
454
455		CONFIG_SYS_FSL_DDR
456		Freescale DDR driver in use. This type of DDR controller is
457		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
458		SoCs.
459
460		CONFIG_SYS_FSL_DDR_ADDR
461		Freescale DDR memory-mapped register base.
462
463		CONFIG_SYS_FSL_DDR_EMU
464		Specify emulator support for DDR. Some DDR features such as
465		deskew training are not available.
466
467		CONFIG_SYS_FSL_DDRC_GEN1
468		Freescale DDR1 controller.
469
470		CONFIG_SYS_FSL_DDRC_GEN2
471		Freescale DDR2 controller.
472
473		CONFIG_SYS_FSL_DDRC_GEN3
474		Freescale DDR3 controller.
475
476		CONFIG_SYS_FSL_DDRC_GEN4
477		Freescale DDR4 controller.
478
479		CONFIG_SYS_FSL_DDRC_ARM_GEN3
480		Freescale DDR3 controller for ARM-based SoCs.
481
482		CONFIG_SYS_FSL_DDR1
483		Board config to use DDR1. It can be enabled for SoCs with
484		Freescale DDR1 or DDR2 controllers, depending on the board
485		implemetation.
486
487		CONFIG_SYS_FSL_DDR2
488		Board config to use DDR2. It can be eanbeld for SoCs with
489		Freescale DDR2 or DDR3 controllers, depending on the board
490		implementation.
491
492		CONFIG_SYS_FSL_DDR3
493		Board config to use DDR3. It can be enabled for SoCs with
494		Freescale DDR3 or DDR3L controllers.
495
496		CONFIG_SYS_FSL_DDR3L
497		Board config to use DDR3L. It can be enabled for SoCs with
498		DDR3L controllers.
499
500		CONFIG_SYS_FSL_DDR4
501		Board config to use DDR4. It can be enabled for SoCs with
502		DDR4 controllers.
503
504		CONFIG_SYS_FSL_IFC_BE
505		Defines the IFC controller register space as Big Endian
506
507		CONFIG_SYS_FSL_IFC_LE
508		Defines the IFC controller register space as Little Endian
509
510		CONFIG_SYS_FSL_PBL_PBI
511		It enables addition of RCW (Power on reset configuration) in built image.
512		Please refer doc/README.pblimage for more details
513
514		CONFIG_SYS_FSL_PBL_RCW
515		It adds PBI(pre-boot instructions) commands in u-boot build image.
516		PBI commands can be used to configure SoC before it starts the execution.
517		Please refer doc/README.pblimage for more details
518
519		CONFIG_SPL_FSL_PBL
520		It adds a target to create boot binary having SPL binary in PBI format
521		concatenated with u-boot binary.
522
523		CONFIG_SYS_FSL_DDR_BE
524		Defines the DDR controller register space as Big Endian
525
526		CONFIG_SYS_FSL_DDR_LE
527		Defines the DDR controller register space as Little Endian
528
529		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
530		Physical address from the view of DDR controllers. It is the
531		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
532		it could be different for ARM SoCs.
533
534		CONFIG_SYS_FSL_DDR_INTLV_256B
535		DDR controller interleaving on 256-byte. This is a special
536		interleaving mode, handled by Dickens for Freescale layerscape
537		SoCs with ARM core.
538
539		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
540		Number of controllers used as main memory.
541
542		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
543		Number of controllers used for other than main memory.
544
545		CONFIG_SYS_FSL_SEC_BE
546		Defines the SEC controller register space as Big Endian
547
548		CONFIG_SYS_FSL_SEC_LE
549		Defines the SEC controller register space as Little Endian
550
551- Intel Monahans options:
552		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
553
554		Defines the Monahans run mode to oscillator
555		ratio. Valid values are 8, 16, 24, 31. The core
556		frequency is this value multiplied by 13 MHz.
557
558		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
559
560		Defines the Monahans turbo mode to oscillator
561		ratio. Valid values are 1 (default if undefined) and
562		2. The core frequency as calculated above is multiplied
563		by this value.
564
565- MIPS CPU options:
566		CONFIG_SYS_INIT_SP_OFFSET
567
568		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
569		pointer. This is needed for the temporary stack before
570		relocation.
571
572		CONFIG_SYS_MIPS_CACHE_MODE
573
574		Cache operation mode for the MIPS CPU.
575		See also arch/mips/include/asm/mipsregs.h.
576		Possible values are:
577			CONF_CM_CACHABLE_NO_WA
578			CONF_CM_CACHABLE_WA
579			CONF_CM_UNCACHED
580			CONF_CM_CACHABLE_NONCOHERENT
581			CONF_CM_CACHABLE_CE
582			CONF_CM_CACHABLE_COW
583			CONF_CM_CACHABLE_CUW
584			CONF_CM_CACHABLE_ACCELERATED
585
586		CONFIG_SYS_XWAY_EBU_BOOTCFG
587
588		Special option for Lantiq XWAY SoCs for booting from NOR flash.
589		See also arch/mips/cpu/mips32/start.S.
590
591		CONFIG_XWAY_SWAP_BYTES
592
593		Enable compilation of tools/xway-swap-bytes needed for Lantiq
594		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
595		be swapped if a flash programmer is used.
596
597- ARM options:
598		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
599
600		Select high exception vectors of the ARM core, e.g., do not
601		clear the V bit of the c1 register of CP15.
602
603		CONFIG_SYS_THUMB_BUILD
604
605		Use this flag to build U-Boot using the Thumb instruction
606		set for ARM architectures. Thumb instruction set provides
607		better code density. For ARM architectures that support
608		Thumb2 this flag will result in Thumb2 code generated by
609		GCC.
610
611		CONFIG_ARM_ERRATA_716044
612		CONFIG_ARM_ERRATA_742230
613		CONFIG_ARM_ERRATA_743622
614		CONFIG_ARM_ERRATA_751472
615		CONFIG_ARM_ERRATA_794072
616		CONFIG_ARM_ERRATA_761320
617
618		If set, the workarounds for these ARM errata are applied early
619		during U-Boot startup. Note that these options force the
620		workarounds to be applied; no CPU-type/version detection
621		exists, unlike the similar options in the Linux kernel. Do not
622		set these options unless they apply!
623
624- Driver Model
625		Driver model is a new framework for devices in U-Boot
626		introduced in early 2014. U-Boot is being progressively
627		moved over to this. It offers a consistent device structure,
628		supports grouping devices into classes and has built-in
629		handling of platform data and device tree.
630
631		To enable transition to driver model in a relatively
632		painful fashion, each subsystem can be independently
633		switched between the legacy/ad-hoc approach and the new
634		driver model using the options below. Also, many uclass
635		interfaces include compatibility features which may be
636		removed once the conversion of that subsystem is complete.
637		As a result, the API provided by the subsystem may in fact
638		not change with driver model.
639
640		See doc/driver-model/README.txt for more information.
641
642		CONFIG_DM
643
644		Enable driver model. This brings in the core support,
645		including scanning of platform data on start-up. If
646		CONFIG_OF_CONTROL is enabled, the device tree will be
647		scanned also when available.
648
649		CONFIG_CMD_DM
650
651		Enable driver model test commands. These allow you to print
652		out the driver model tree and the uclasses.
653
654		CONFIG_DM_DEMO
655
656		Enable some demo devices and the 'demo' command. These are
657		really only useful for playing around while trying to
658		understand driver model in sandbox.
659
660		CONFIG_SPL_DM
661
662		Enable driver model in SPL. You will need to provide a
663		suitable malloc() implementation. If you are not using the
664		full malloc() enabled by CONFIG_SYS_SPL_MALLOC_START,
665		consider using CONFIG_SYS_MALLOC_SIMPLE. In that case you
666		must provide CONFIG_SYS_MALLOC_F_LEN to set the size.
667		In most cases driver model will only allocate a few uclasses
668		and devices in SPL, so 1KB should be enable. See
669		CONFIG_SYS_MALLOC_F_LEN for more details on how to enable
670		it.
671
672		CONFIG_DM_SERIAL
673
674		Enable driver model for serial. This replaces
675		drivers/serial/serial.c with the serial uclass, which
676		implements serial_putc() etc. The uclass interface is
677		defined in include/serial.h.
678
679		CONFIG_DM_GPIO
680
681		Enable driver model for GPIO access. The standard GPIO
682		interface (gpio_get_value(), etc.) is then implemented by
683		the GPIO uclass. Drivers provide methods to query the
684		particular GPIOs that they provide. The uclass interface
685		is defined in include/asm-generic/gpio.h.
686
687		CONFIG_DM_SPI
688
689		Enable driver model for SPI. The SPI slave interface
690		(spi_setup_slave(), spi_xfer(), etc.) is then implemented by
691		the SPI uclass. Drivers provide methods to access the SPI
692		buses that they control. The uclass interface is defined in
693		include/spi.h. The existing spi_slave structure is attached
694		as 'parent data' to every slave on each bus. Slaves
695		typically use driver-private data instead of extending the
696		spi_slave structure.
697
698		CONFIG_DM_SPI_FLASH
699
700		Enable driver model for SPI flash. This SPI flash interface
701		(spi_flash_probe(), spi_flash_write(), etc.) is then
702		implemented by the SPI flash uclass. There is one standard
703		SPI flash driver which knows how to probe most chips
704		supported by U-Boot. The uclass interface is defined in
705		include/spi_flash.h, but is currently fully compatible
706		with the old interface to avoid confusion and duplication
707		during the transition parent. SPI and SPI flash must be
708		enabled together (it is not possible to use driver model
709		for one and not the other).
710
711		CONFIG_DM_CROS_EC
712
713		Enable driver model for the Chrome OS EC interface. This
714		allows the cros_ec SPI driver to operate with CONFIG_DM_SPI
715		but otherwise makes few changes. Since cros_ec also supports
716		I2C and LPC (which don't support driver model yet), a full
717		conversion is not yet possible.
718
719
720		** Code size options: The following options are enabled by
721		default except in SPL. Enable them explicitly to get these
722		features in SPL.
723
724		CONFIG_DM_WARN
725
726		Enable the dm_warn() function. This can use up quite a bit
727		of space for its strings.
728
729		CONFIG_DM_STDIO
730
731		Enable registering a serial device with the stdio library.
732
733		CONFIG_DM_DEVICE_REMOVE
734
735		Enable removing of devices.
736
737
738- Linux Kernel Interface:
739		CONFIG_CLOCKS_IN_MHZ
740
741		U-Boot stores all clock information in Hz
742		internally. For binary compatibility with older Linux
743		kernels (which expect the clocks passed in the
744		bd_info data to be in MHz) the environment variable
745		"clocks_in_mhz" can be defined so that U-Boot
746		converts clock data to MHZ before passing it to the
747		Linux kernel.
748		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
749		"clocks_in_mhz=1" is automatically included in the
750		default environment.
751
752		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
753
754		When transferring memsize parameter to Linux, some versions
755		expect it to be in bytes, others in MB.
756		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
757
758		CONFIG_OF_LIBFDT
759
760		New kernel versions are expecting firmware settings to be
761		passed using flattened device trees (based on open firmware
762		concepts).
763
764		CONFIG_OF_LIBFDT
765		 * New libfdt-based support
766		 * Adds the "fdt" command
767		 * The bootm command automatically updates the fdt
768
769		OF_CPU - The proper name of the cpus node (only required for
770			MPC512X and MPC5xxx based boards).
771		OF_SOC - The proper name of the soc node (only required for
772			MPC512X and MPC5xxx based boards).
773		OF_TBCLK - The timebase frequency.
774		OF_STDOUT_PATH - The path to the console device
775
776		boards with QUICC Engines require OF_QE to set UCC MAC
777		addresses
778
779		CONFIG_OF_BOARD_SETUP
780
781		Board code has addition modification that it wants to make
782		to the flat device tree before handing it off to the kernel
783
784		CONFIG_OF_SYSTEM_SETUP
785
786		Other code has addition modification that it wants to make
787		to the flat device tree before handing it off to the kernel.
788		This causes ft_system_setup() to be called before booting
789		the kernel.
790
791		CONFIG_OF_BOOT_CPU
792
793		This define fills in the correct boot CPU in the boot
794		param header, the default value is zero if undefined.
795
796		CONFIG_OF_IDE_FIXUP
797
798		U-Boot can detect if an IDE device is present or not.
799		If not, and this new config option is activated, U-Boot
800		removes the ATA node from the DTS before booting Linux,
801		so the Linux IDE driver does not probe the device and
802		crash. This is needed for buggy hardware (uc101) where
803		no pull down resistor is connected to the signal IDE5V_DD7.
804
805		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
806
807		This setting is mandatory for all boards that have only one
808		machine type and must be used to specify the machine type
809		number as it appears in the ARM machine registry
810		(see http://www.arm.linux.org.uk/developer/machines/).
811		Only boards that have multiple machine types supported
812		in a single configuration file and the machine type is
813		runtime discoverable, do not have to use this setting.
814
815- vxWorks boot parameters:
816
817		bootvx constructs a valid bootline using the following
818		environments variables: bootfile, ipaddr, serverip, hostname.
819		It loads the vxWorks image pointed bootfile.
820
821		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
822		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
823		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
824		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
825
826		CONFIG_SYS_VXWORKS_ADD_PARAMS
827
828		Add it at the end of the bootline. E.g "u=username pw=secret"
829
830		Note: If a "bootargs" environment is defined, it will overwride
831		the defaults discussed just above.
832
833- Cache Configuration:
834		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
835		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
836		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
837
838- Cache Configuration for ARM:
839		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
840				      controller
841		CONFIG_SYS_PL310_BASE - Physical base address of PL310
842					controller register space
843
844- Serial Ports:
845		CONFIG_PL010_SERIAL
846
847		Define this if you want support for Amba PrimeCell PL010 UARTs.
848
849		CONFIG_PL011_SERIAL
850
851		Define this if you want support for Amba PrimeCell PL011 UARTs.
852
853		CONFIG_PL011_CLOCK
854
855		If you have Amba PrimeCell PL011 UARTs, set this variable to
856		the clock speed of the UARTs.
857
858		CONFIG_PL01x_PORTS
859
860		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
861		define this to a list of base addresses for each (supported)
862		port. See e.g. include/configs/versatile.h
863
864		CONFIG_PL011_SERIAL_RLCR
865
866		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
867		have separate receive and transmit line control registers.  Set
868		this variable to initialize the extra register.
869
870		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
871
872		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
873		boot loader that has already initialized the UART.  Define this
874		variable to flush the UART at init time.
875
876		CONFIG_SERIAL_HW_FLOW_CONTROL
877
878		Define this variable to enable hw flow control in serial driver.
879		Current user of this option is drivers/serial/nsl16550.c driver
880
881- Console Interface:
882		Depending on board, define exactly one serial port
883		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
884		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
885		console by defining CONFIG_8xx_CONS_NONE
886
887		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
888		port routines must be defined elsewhere
889		(i.e. serial_init(), serial_getc(), ...)
890
891		CONFIG_CFB_CONSOLE
892		Enables console device for a color framebuffer. Needs following
893		defines (cf. smiLynxEM, i8042)
894			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
895						(default big endian)
896			VIDEO_HW_RECTFILL	graphic chip supports
897						rectangle fill
898						(cf. smiLynxEM)
899			VIDEO_HW_BITBLT		graphic chip supports
900						bit-blit (cf. smiLynxEM)
901			VIDEO_VISIBLE_COLS	visible pixel columns
902						(cols=pitch)
903			VIDEO_VISIBLE_ROWS	visible pixel rows
904			VIDEO_PIXEL_SIZE	bytes per pixel
905			VIDEO_DATA_FORMAT	graphic data format
906						(0-5, cf. cfb_console.c)
907			VIDEO_FB_ADRS		framebuffer address
908			VIDEO_KBD_INIT_FCT	keyboard int fct
909						(i.e. i8042_kbd_init())
910			VIDEO_TSTC_FCT		test char fct
911						(i.e. i8042_tstc)
912			VIDEO_GETC_FCT		get char fct
913						(i.e. i8042_getc)
914			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
915						(requires blink timer
916						cf. i8042.c)
917			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
918			CONFIG_CONSOLE_TIME	display time/date info in
919						upper right corner
920						(requires CONFIG_CMD_DATE)
921			CONFIG_VIDEO_LOGO	display Linux logo in
922						upper left corner
923			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
924						linux_logo.h for logo.
925						Requires CONFIG_VIDEO_LOGO
926			CONFIG_CONSOLE_EXTRA_INFO
927						additional board info beside
928						the logo
929
930		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
931		a limited number of ANSI escape sequences (cursor control,
932		erase functions and limited graphics rendition control).
933
934		When CONFIG_CFB_CONSOLE is defined, video console is
935		default i/o. Serial console can be forced with
936		environment 'console=serial'.
937
938		When CONFIG_SILENT_CONSOLE is defined, all console
939		messages (by U-Boot and Linux!) can be silenced with
940		the "silent" environment variable. See
941		doc/README.silent for more information.
942
943		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
944			is 0x00.
945		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
946			is 0xa0.
947
948- Console Baudrate:
949		CONFIG_BAUDRATE - in bps
950		Select one of the baudrates listed in
951		CONFIG_SYS_BAUDRATE_TABLE, see below.
952		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
953
954- Console Rx buffer length
955		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
956		the maximum receive buffer length for the SMC.
957		This option is actual only for 82xx and 8xx possible.
958		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
959		must be defined, to setup the maximum idle timeout for
960		the SMC.
961
962- Pre-Console Buffer:
963		Prior to the console being initialised (i.e. serial UART
964		initialised etc) all console output is silently discarded.
965		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
966		buffer any console messages prior to the console being
967		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
968		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
969		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
970		bytes are output before the console is initialised, the
971		earlier bytes are discarded.
972
973		'Sane' compilers will generate smaller code if
974		CONFIG_PRE_CON_BUF_SZ is a power of 2
975
976- Safe printf() functions
977		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
978		the printf() functions. These are defined in
979		include/vsprintf.h and include snprintf(), vsnprintf() and
980		so on. Code size increase is approximately 300-500 bytes.
981		If this option is not given then these functions will
982		silently discard their buffer size argument - this means
983		you are not getting any overflow checking in this case.
984
985- Boot Delay:	CONFIG_BOOTDELAY - in seconds
986		Delay before automatically booting the default image;
987		set to -1 to disable autoboot.
988		set to -2 to autoboot with no delay and not check for abort
989		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
990
991		See doc/README.autoboot for these options that
992		work with CONFIG_BOOTDELAY. None are required.
993		CONFIG_BOOT_RETRY_TIME
994		CONFIG_BOOT_RETRY_MIN
995		CONFIG_AUTOBOOT_KEYED
996		CONFIG_AUTOBOOT_PROMPT
997		CONFIG_AUTOBOOT_DELAY_STR
998		CONFIG_AUTOBOOT_STOP_STR
999		CONFIG_AUTOBOOT_DELAY_STR2
1000		CONFIG_AUTOBOOT_STOP_STR2
1001		CONFIG_ZERO_BOOTDELAY_CHECK
1002		CONFIG_RESET_TO_RETRY
1003
1004- Autoboot Command:
1005		CONFIG_BOOTCOMMAND
1006		Only needed when CONFIG_BOOTDELAY is enabled;
1007		define a command string that is automatically executed
1008		when no character is read on the console interface
1009		within "Boot Delay" after reset.
1010
1011		CONFIG_BOOTARGS
1012		This can be used to pass arguments to the bootm
1013		command. The value of CONFIG_BOOTARGS goes into the
1014		environment value "bootargs".
1015
1016		CONFIG_RAMBOOT and CONFIG_NFSBOOT
1017		The value of these goes into the environment as
1018		"ramboot" and "nfsboot" respectively, and can be used
1019		as a convenience, when switching between booting from
1020		RAM and NFS.
1021
1022- Bootcount:
1023		CONFIG_BOOTCOUNT_LIMIT
1024		Implements a mechanism for detecting a repeating reboot
1025		cycle, see:
1026		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
1027
1028		CONFIG_BOOTCOUNT_ENV
1029		If no softreset save registers are found on the hardware
1030		"bootcount" is stored in the environment. To prevent a
1031		saveenv on all reboots, the environment variable
1032		"upgrade_available" is used. If "upgrade_available" is
1033		0, "bootcount" is always 0, if "upgrade_available" is
1034		1 "bootcount" is incremented in the environment.
1035		So the Userspace Applikation must set the "upgrade_available"
1036		and "bootcount" variable to 0, if a boot was successfully.
1037
1038- Pre-Boot Commands:
1039		CONFIG_PREBOOT
1040
1041		When this option is #defined, the existence of the
1042		environment variable "preboot" will be checked
1043		immediately before starting the CONFIG_BOOTDELAY
1044		countdown and/or running the auto-boot command resp.
1045		entering interactive mode.
1046
1047		This feature is especially useful when "preboot" is
1048		automatically generated or modified. For an example
1049		see the LWMON board specific code: here "preboot" is
1050		modified when the user holds down a certain
1051		combination of keys on the (special) keyboard when
1052		booting the systems
1053
1054- Serial Download Echo Mode:
1055		CONFIG_LOADS_ECHO
1056		If defined to 1, all characters received during a
1057		serial download (using the "loads" command) are
1058		echoed back. This might be needed by some terminal
1059		emulations (like "cu"), but may as well just take
1060		time on others. This setting #define's the initial
1061		value of the "loads_echo" environment variable.
1062
1063- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
1064		CONFIG_KGDB_BAUDRATE
1065		Select one of the baudrates listed in
1066		CONFIG_SYS_BAUDRATE_TABLE, see below.
1067
1068- Monitor Functions:
1069		Monitor commands can be included or excluded
1070		from the build by using the #include files
1071		<config_cmd_all.h> and #undef'ing unwanted
1072		commands, or using <config_cmd_default.h>
1073		and augmenting with additional #define's
1074		for wanted commands.
1075
1076		The default command configuration includes all commands
1077		except those marked below with a "*".
1078
1079		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
1080		CONFIG_CMD_ASKENV	* ask for env variable
1081		CONFIG_CMD_BDI		  bdinfo
1082		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
1083		CONFIG_CMD_BMP		* BMP support
1084		CONFIG_CMD_BSP		* Board specific commands
1085		CONFIG_CMD_BOOTD	  bootd
1086		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
1087		CONFIG_CMD_CACHE	* icache, dcache
1088		CONFIG_CMD_CLK   	* clock command support
1089		CONFIG_CMD_CONSOLE	  coninfo
1090		CONFIG_CMD_CRC32	* crc32
1091		CONFIG_CMD_DATE		* support for RTC, date/time...
1092		CONFIG_CMD_DHCP		* DHCP support
1093		CONFIG_CMD_DIAG		* Diagnostics
1094		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
1095		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
1096		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
1097		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
1098		CONFIG_CMD_DTT		* Digital Therm and Thermostat
1099		CONFIG_CMD_ECHO		  echo arguments
1100		CONFIG_CMD_EDITENV	  edit env variable
1101		CONFIG_CMD_EEPROM	* EEPROM read/write support
1102		CONFIG_CMD_ELF		* bootelf, bootvx
1103		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
1104		CONFIG_CMD_ENV_FLAGS	* display details about env flags
1105		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
1106		CONFIG_CMD_EXPORTENV	* export the environment
1107		CONFIG_CMD_EXT2		* ext2 command support
1108		CONFIG_CMD_EXT4		* ext4 command support
1109		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
1110					  that work for multiple fs types
1111		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
1112		CONFIG_CMD_SAVEENV	  saveenv
1113		CONFIG_CMD_FDC		* Floppy Disk Support
1114		CONFIG_CMD_FAT		* FAT command support
1115		CONFIG_CMD_FLASH	  flinfo, erase, protect
1116		CONFIG_CMD_FPGA		  FPGA device initialization support
1117		CONFIG_CMD_FUSE		* Device fuse support
1118		CONFIG_CMD_GETTIME	* Get time since boot
1119		CONFIG_CMD_GO		* the 'go' command (exec code)
1120		CONFIG_CMD_GREPENV	* search environment
1121		CONFIG_CMD_HASH		* calculate hash / digest
1122		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
1123		CONFIG_CMD_I2C		* I2C serial bus support
1124		CONFIG_CMD_IDE		* IDE harddisk support
1125		CONFIG_CMD_IMI		  iminfo
1126		CONFIG_CMD_IMLS		  List all images found in NOR flash
1127		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
1128		CONFIG_CMD_IMMAP	* IMMR dump support
1129		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
1130		CONFIG_CMD_IMPORTENV	* import an environment
1131		CONFIG_CMD_INI		* import data from an ini file into the env
1132		CONFIG_CMD_IRQ		* irqinfo
1133		CONFIG_CMD_ITEST	  Integer/string test of 2 values
1134		CONFIG_CMD_JFFS2	* JFFS2 Support
1135		CONFIG_CMD_KGDB		* kgdb
1136		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
1137		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
1138					  (169.254.*.*)
1139		CONFIG_CMD_LOADB	  loadb
1140		CONFIG_CMD_LOADS	  loads
1141		CONFIG_CMD_MD5SUM	* print md5 message digest
1142					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
1143		CONFIG_CMD_MEMINFO	* Display detailed memory information
1144		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
1145					  loop, loopw
1146		CONFIG_CMD_MEMTEST	* mtest
1147		CONFIG_CMD_MISC		  Misc functions like sleep etc
1148		CONFIG_CMD_MMC		* MMC memory mapped support
1149		CONFIG_CMD_MII		* MII utility commands
1150		CONFIG_CMD_MTDPARTS	* MTD partition support
1151		CONFIG_CMD_NAND		* NAND support
1152		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
1153		CONFIG_CMD_NFS		  NFS support
1154		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
1155		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
1156		CONFIG_CMD_PCI		* pciinfo
1157		CONFIG_CMD_PCMCIA		* PCMCIA support
1158		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
1159					  host
1160		CONFIG_CMD_PORTIO	* Port I/O
1161		CONFIG_CMD_READ		* Read raw data from partition
1162		CONFIG_CMD_REGINFO	* Register dump
1163		CONFIG_CMD_RUN		  run command in env variable
1164		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
1165		CONFIG_CMD_SAVES	* save S record dump
1166		CONFIG_CMD_SCSI		* SCSI Support
1167		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1168					  (requires CONFIG_CMD_I2C)
1169		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1170					  (4xx only)
1171		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1172		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1173					  (requires CONFIG_CMD_MEMORY)
1174		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1175		CONFIG_CMD_SOURCE	  "source" command Support
1176		CONFIG_CMD_SPI		* SPI serial bus support
1177		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1178		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1179		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1180		CONFIG_CMD_TIMER	* access to the system tick timer
1181		CONFIG_CMD_USB		* USB support
1182		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1183		CONFIG_CMD_MFSL		* Microblaze FSL support
1184		CONFIG_CMD_XIMG		  Load part of Multi Image
1185		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1186
1187		EXAMPLE: If you want all functions except of network
1188		support you can write:
1189
1190		#include "config_cmd_all.h"
1191		#undef CONFIG_CMD_NET
1192
1193	Other Commands:
1194		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1195
1196	Note:	Don't enable the "icache" and "dcache" commands
1197		(configuration option CONFIG_CMD_CACHE) unless you know
1198		what you (and your U-Boot users) are doing. Data
1199		cache cannot be enabled on systems like the 8xx or
1200		8260 (where accesses to the IMMR region must be
1201		uncached), and it cannot be disabled on all other
1202		systems where we (mis-) use the data cache to hold an
1203		initial stack and some data.
1204
1205
1206		XXX - this list needs to get updated!
1207
1208- Regular expression support:
1209		CONFIG_REGEX
1210		If this variable is defined, U-Boot is linked against
1211		the SLRE (Super Light Regular Expression) library,
1212		which adds regex support to some commands, as for
1213		example "env grep" and "setexpr".
1214
1215- Device tree:
1216		CONFIG_OF_CONTROL
1217		If this variable is defined, U-Boot will use a device tree
1218		to configure its devices, instead of relying on statically
1219		compiled #defines in the board file. This option is
1220		experimental and only available on a few boards. The device
1221		tree is available in the global data as gd->fdt_blob.
1222
1223		U-Boot needs to get its device tree from somewhere. This can
1224		be done using one of the two options below:
1225
1226		CONFIG_OF_EMBED
1227		If this variable is defined, U-Boot will embed a device tree
1228		binary in its image. This device tree file should be in the
1229		board directory and called <soc>-<board>.dts. The binary file
1230		is then picked up in board_init_f() and made available through
1231		the global data structure as gd->blob.
1232
1233		CONFIG_OF_SEPARATE
1234		If this variable is defined, U-Boot will build a device tree
1235		binary. It will be called u-boot.dtb. Architecture-specific
1236		code will locate it at run-time. Generally this works by:
1237
1238			cat u-boot.bin u-boot.dtb >image.bin
1239
1240		and in fact, U-Boot does this for you, creating a file called
1241		u-boot-dtb.bin which is useful in the common case. You can
1242		still use the individual files if you need something more
1243		exotic.
1244
1245- Watchdog:
1246		CONFIG_WATCHDOG
1247		If this variable is defined, it enables watchdog
1248		support for the SoC. There must be support in the SoC
1249		specific code for a watchdog. For the 8xx and 8260
1250		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1251		register.  When supported for a specific SoC is
1252		available, then no further board specific code should
1253		be needed to use it.
1254
1255		CONFIG_HW_WATCHDOG
1256		When using a watchdog circuitry external to the used
1257		SoC, then define this variable and provide board
1258		specific code for the "hw_watchdog_reset" function.
1259
1260- U-Boot Version:
1261		CONFIG_VERSION_VARIABLE
1262		If this variable is defined, an environment variable
1263		named "ver" is created by U-Boot showing the U-Boot
1264		version as printed by the "version" command.
1265		Any change to this variable will be reverted at the
1266		next reset.
1267
1268- Real-Time Clock:
1269
1270		When CONFIG_CMD_DATE is selected, the type of the RTC
1271		has to be selected, too. Define exactly one of the
1272		following options:
1273
1274		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1275		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1276		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1277		CONFIG_RTC_MC146818	- use MC146818 RTC
1278		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1279		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1280		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1281		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1282		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1283		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1284		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1285		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1286		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1287					  RV3029 RTC.
1288
1289		Note that if the RTC uses I2C, then the I2C interface
1290		must also be configured. See I2C Support, below.
1291
1292- GPIO Support:
1293		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1294
1295		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1296		chip-ngpio pairs that tell the PCA953X driver the number of
1297		pins supported by a particular chip.
1298
1299		Note that if the GPIO device uses I2C, then the I2C interface
1300		must also be configured. See I2C Support, below.
1301
1302- I/O tracing:
1303		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1304		accesses and can checksum them or write a list of them out
1305		to memory. See the 'iotrace' command for details. This is
1306		useful for testing device drivers since it can confirm that
1307		the driver behaves the same way before and after a code
1308		change. Currently this is supported on sandbox and arm. To
1309		add support for your architecture, add '#include <iotrace.h>'
1310		to the bottom of arch/<arch>/include/asm/io.h and test.
1311
1312		Example output from the 'iotrace stats' command is below.
1313		Note that if the trace buffer is exhausted, the checksum will
1314		still continue to operate.
1315
1316			iotrace is enabled
1317			Start:  10000000	(buffer start address)
1318			Size:   00010000	(buffer size)
1319			Offset: 00000120	(current buffer offset)
1320			Output: 10000120	(start + offset)
1321			Count:  00000018	(number of trace records)
1322			CRC32:  9526fb66	(CRC32 of all trace records)
1323
1324- Timestamp Support:
1325
1326		When CONFIG_TIMESTAMP is selected, the timestamp
1327		(date and time) of an image is printed by image
1328		commands like bootm or iminfo. This option is
1329		automatically enabled when you select CONFIG_CMD_DATE .
1330
1331- Partition Labels (disklabels) Supported:
1332		Zero or more of the following:
1333		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1334		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1335				       Intel architecture, USB sticks, etc.
1336		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1337		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1338				       bootloader.  Note 2TB partition limit; see
1339				       disk/part_efi.c
1340		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1341
1342		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1343		CONFIG_CMD_SCSI) you must configure support for at
1344		least one non-MTD partition type as well.
1345
1346- IDE Reset method:
1347		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1348		board configurations files but used nowhere!
1349
1350		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1351		be performed by calling the function
1352			ide_set_reset(int reset)
1353		which has to be defined in a board specific file
1354
1355- ATAPI Support:
1356		CONFIG_ATAPI
1357
1358		Set this to enable ATAPI support.
1359
1360- LBA48 Support
1361		CONFIG_LBA48
1362
1363		Set this to enable support for disks larger than 137GB
1364		Also look at CONFIG_SYS_64BIT_LBA.
1365		Whithout these , LBA48 support uses 32bit variables and will 'only'
1366		support disks up to 2.1TB.
1367
1368		CONFIG_SYS_64BIT_LBA:
1369			When enabled, makes the IDE subsystem use 64bit sector addresses.
1370			Default is 32bit.
1371
1372- SCSI Support:
1373		At the moment only there is only support for the
1374		SYM53C8XX SCSI controller; define
1375		CONFIG_SCSI_SYM53C8XX to enable it.
1376
1377		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1378		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1379		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1380		maximum numbers of LUNs, SCSI ID's and target
1381		devices.
1382		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1383
1384		The environment variable 'scsidevs' is set to the number of
1385		SCSI devices found during the last scan.
1386
1387- NETWORK Support (PCI):
1388		CONFIG_E1000
1389		Support for Intel 8254x/8257x gigabit chips.
1390
1391		CONFIG_E1000_SPI
1392		Utility code for direct access to the SPI bus on Intel 8257x.
1393		This does not do anything useful unless you set at least one
1394		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1395
1396		CONFIG_E1000_SPI_GENERIC
1397		Allow generic access to the SPI bus on the Intel 8257x, for
1398		example with the "sspi" command.
1399
1400		CONFIG_CMD_E1000
1401		Management command for E1000 devices.  When used on devices
1402		with SPI support you can reprogram the EEPROM from U-Boot.
1403
1404		CONFIG_E1000_FALLBACK_MAC
1405		default MAC for empty EEPROM after production.
1406
1407		CONFIG_EEPRO100
1408		Support for Intel 82557/82559/82559ER chips.
1409		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1410		write routine for first time initialisation.
1411
1412		CONFIG_TULIP
1413		Support for Digital 2114x chips.
1414		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1415		modem chip initialisation (KS8761/QS6611).
1416
1417		CONFIG_NATSEMI
1418		Support for National dp83815 chips.
1419
1420		CONFIG_NS8382X
1421		Support for National dp8382[01] gigabit chips.
1422
1423- NETWORK Support (other):
1424
1425		CONFIG_DRIVER_AT91EMAC
1426		Support for AT91RM9200 EMAC.
1427
1428			CONFIG_RMII
1429			Define this to use reduced MII inteface
1430
1431			CONFIG_DRIVER_AT91EMAC_QUIET
1432			If this defined, the driver is quiet.
1433			The driver doen't show link status messages.
1434
1435		CONFIG_CALXEDA_XGMAC
1436		Support for the Calxeda XGMAC device
1437
1438		CONFIG_LAN91C96
1439		Support for SMSC's LAN91C96 chips.
1440
1441			CONFIG_LAN91C96_BASE
1442			Define this to hold the physical address
1443			of the LAN91C96's I/O space
1444
1445			CONFIG_LAN91C96_USE_32_BIT
1446			Define this to enable 32 bit addressing
1447
1448		CONFIG_SMC91111
1449		Support for SMSC's LAN91C111 chip
1450
1451			CONFIG_SMC91111_BASE
1452			Define this to hold the physical address
1453			of the device (I/O space)
1454
1455			CONFIG_SMC_USE_32_BIT
1456			Define this if data bus is 32 bits
1457
1458			CONFIG_SMC_USE_IOFUNCS
1459			Define this to use i/o functions instead of macros
1460			(some hardware wont work with macros)
1461
1462		CONFIG_DRIVER_TI_EMAC
1463		Support for davinci emac
1464
1465			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1466			Define this if you have more then 3 PHYs.
1467
1468		CONFIG_FTGMAC100
1469		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1470
1471			CONFIG_FTGMAC100_EGIGA
1472			Define this to use GE link update with gigabit PHY.
1473			Define this if FTGMAC100 is connected to gigabit PHY.
1474			If your system has 10/100 PHY only, it might not occur
1475			wrong behavior. Because PHY usually return timeout or
1476			useless data when polling gigabit status and gigabit
1477			control registers. This behavior won't affect the
1478			correctnessof 10/100 link speed update.
1479
1480		CONFIG_SMC911X
1481		Support for SMSC's LAN911x and LAN921x chips
1482
1483			CONFIG_SMC911X_BASE
1484			Define this to hold the physical address
1485			of the device (I/O space)
1486
1487			CONFIG_SMC911X_32_BIT
1488			Define this if data bus is 32 bits
1489
1490			CONFIG_SMC911X_16_BIT
1491			Define this if data bus is 16 bits. If your processor
1492			automatically converts one 32 bit word to two 16 bit
1493			words you may also try CONFIG_SMC911X_32_BIT.
1494
1495		CONFIG_SH_ETHER
1496		Support for Renesas on-chip Ethernet controller
1497
1498			CONFIG_SH_ETHER_USE_PORT
1499			Define the number of ports to be used
1500
1501			CONFIG_SH_ETHER_PHY_ADDR
1502			Define the ETH PHY's address
1503
1504			CONFIG_SH_ETHER_CACHE_WRITEBACK
1505			If this option is set, the driver enables cache flush.
1506
1507- PWM Support:
1508		CONFIG_PWM_IMX
1509		Support for PWM modul on the imx6.
1510
1511- TPM Support:
1512		CONFIG_TPM
1513		Support TPM devices.
1514
1515		CONFIG_TPM_TIS_I2C
1516		Support for i2c bus TPM devices. Only one device
1517		per system is supported at this time.
1518
1519			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1520			Define the the i2c bus number for the TPM device
1521
1522			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1523			Define the TPM's address on the i2c bus
1524
1525			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1526			Define the burst count bytes upper limit
1527
1528		CONFIG_TPM_ATMEL_TWI
1529		Support for Atmel TWI TPM device. Requires I2C support.
1530
1531		CONFIG_TPM_TIS_LPC
1532		Support for generic parallel port TPM devices. Only one device
1533		per system is supported at this time.
1534
1535			CONFIG_TPM_TIS_BASE_ADDRESS
1536			Base address where the generic TPM device is mapped
1537			to. Contemporary x86 systems usually map it at
1538			0xfed40000.
1539
1540		CONFIG_CMD_TPM
1541		Add tpm monitor functions.
1542		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1543		provides monitor access to authorized functions.
1544
1545		CONFIG_TPM
1546		Define this to enable the TPM support library which provides
1547		functional interfaces to some TPM commands.
1548		Requires support for a TPM device.
1549
1550		CONFIG_TPM_AUTH_SESSIONS
1551		Define this to enable authorized functions in the TPM library.
1552		Requires CONFIG_TPM and CONFIG_SHA1.
1553
1554- USB Support:
1555		At the moment only the UHCI host controller is
1556		supported (PIP405, MIP405, MPC5200); define
1557		CONFIG_USB_UHCI to enable it.
1558		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1559		and define CONFIG_USB_STORAGE to enable the USB
1560		storage devices.
1561		Note:
1562		Supported are USB Keyboards and USB Floppy drives
1563		(TEAC FD-05PUB).
1564		MPC5200 USB requires additional defines:
1565			CONFIG_USB_CLOCK
1566				for 528 MHz Clock: 0x0001bbbb
1567			CONFIG_PSC3_USB
1568				for USB on PSC3
1569			CONFIG_USB_CONFIG
1570				for differential drivers: 0x00001000
1571				for single ended drivers: 0x00005000
1572				for differential drivers on PSC3: 0x00000100
1573				for single ended drivers on PSC3: 0x00004100
1574			CONFIG_SYS_USB_EVENT_POLL
1575				May be defined to allow interrupt polling
1576				instead of using asynchronous interrupts
1577
1578		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1579		txfilltuning field in the EHCI controller on reset.
1580
1581		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1582		HW module registers.
1583
1584- USB Device:
1585		Define the below if you wish to use the USB console.
1586		Once firmware is rebuilt from a serial console issue the
1587		command "setenv stdin usbtty; setenv stdout usbtty" and
1588		attach your USB cable. The Unix command "dmesg" should print
1589		it has found a new device. The environment variable usbtty
1590		can be set to gserial or cdc_acm to enable your device to
1591		appear to a USB host as a Linux gserial device or a
1592		Common Device Class Abstract Control Model serial device.
1593		If you select usbtty = gserial you should be able to enumerate
1594		a Linux host by
1595		# modprobe usbserial vendor=0xVendorID product=0xProductID
1596		else if using cdc_acm, simply setting the environment
1597		variable usbtty to be cdc_acm should suffice. The following
1598		might be defined in YourBoardName.h
1599
1600			CONFIG_USB_DEVICE
1601			Define this to build a UDC device
1602
1603			CONFIG_USB_TTY
1604			Define this to have a tty type of device available to
1605			talk to the UDC device
1606
1607			CONFIG_USBD_HS
1608			Define this to enable the high speed support for usb
1609			device and usbtty. If this feature is enabled, a routine
1610			int is_usbd_high_speed(void)
1611			also needs to be defined by the driver to dynamically poll
1612			whether the enumeration has succeded at high speed or full
1613			speed.
1614
1615			CONFIG_SYS_CONSOLE_IS_IN_ENV
1616			Define this if you want stdin, stdout &/or stderr to
1617			be set to usbtty.
1618
1619			mpc8xx:
1620				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1621				Derive USB clock from external clock "blah"
1622				- CONFIG_SYS_USB_EXTC_CLK 0x02
1623
1624				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1625				Derive USB clock from brgclk
1626				- CONFIG_SYS_USB_BRG_CLK 0x04
1627
1628		If you have a USB-IF assigned VendorID then you may wish to
1629		define your own vendor specific values either in BoardName.h
1630		or directly in usbd_vendor_info.h. If you don't define
1631		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1632		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1633		should pretend to be a Linux device to it's target host.
1634
1635			CONFIG_USBD_MANUFACTURER
1636			Define this string as the name of your company for
1637			- CONFIG_USBD_MANUFACTURER "my company"
1638
1639			CONFIG_USBD_PRODUCT_NAME
1640			Define this string as the name of your product
1641			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1642
1643			CONFIG_USBD_VENDORID
1644			Define this as your assigned Vendor ID from the USB
1645			Implementors Forum. This *must* be a genuine Vendor ID
1646			to avoid polluting the USB namespace.
1647			- CONFIG_USBD_VENDORID 0xFFFF
1648
1649			CONFIG_USBD_PRODUCTID
1650			Define this as the unique Product ID
1651			for your device
1652			- CONFIG_USBD_PRODUCTID 0xFFFF
1653
1654- ULPI Layer Support:
1655		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1656		the generic ULPI layer. The generic layer accesses the ULPI PHY
1657		via the platform viewport, so you need both the genric layer and
1658		the viewport enabled. Currently only Chipidea/ARC based
1659		viewport is supported.
1660		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1661		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1662		If your ULPI phy needs a different reference clock than the
1663		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1664		the appropriate value in Hz.
1665
1666- MMC Support:
1667		The MMC controller on the Intel PXA is supported. To
1668		enable this define CONFIG_MMC. The MMC can be
1669		accessed from the boot prompt by mapping the device
1670		to physical memory similar to flash. Command line is
1671		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1672		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1673
1674		CONFIG_SH_MMCIF
1675		Support for Renesas on-chip MMCIF controller
1676
1677			CONFIG_SH_MMCIF_ADDR
1678			Define the base address of MMCIF registers
1679
1680			CONFIG_SH_MMCIF_CLK
1681			Define the clock frequency for MMCIF
1682
1683		CONFIG_GENERIC_MMC
1684		Enable the generic MMC driver
1685
1686		CONFIG_SUPPORT_EMMC_BOOT
1687		Enable some additional features of the eMMC boot partitions.
1688
1689		CONFIG_SUPPORT_EMMC_RPMB
1690		Enable the commands for reading, writing and programming the
1691		key for the Replay Protection Memory Block partition in eMMC.
1692
1693- USB Device Firmware Update (DFU) class support:
1694		CONFIG_DFU_FUNCTION
1695		This enables the USB portion of the DFU USB class
1696
1697		CONFIG_CMD_DFU
1698		This enables the command "dfu" which is used to have
1699		U-Boot create a DFU class device via USB.  This command
1700		requires that the "dfu_alt_info" environment variable be
1701		set and define the alt settings to expose to the host.
1702
1703		CONFIG_DFU_MMC
1704		This enables support for exposing (e)MMC devices via DFU.
1705
1706		CONFIG_DFU_NAND
1707		This enables support for exposing NAND devices via DFU.
1708
1709		CONFIG_DFU_RAM
1710		This enables support for exposing RAM via DFU.
1711		Note: DFU spec refer to non-volatile memory usage, but
1712		allow usages beyond the scope of spec - here RAM usage,
1713		one that would help mostly the developer.
1714
1715		CONFIG_SYS_DFU_DATA_BUF_SIZE
1716		Dfu transfer uses a buffer before writing data to the
1717		raw storage device. Make the size (in bytes) of this buffer
1718		configurable. The size of this buffer is also configurable
1719		through the "dfu_bufsiz" environment variable.
1720
1721		CONFIG_SYS_DFU_MAX_FILE_SIZE
1722		When updating files rather than the raw storage device,
1723		we use a static buffer to copy the file into and then write
1724		the buffer once we've been given the whole file.  Define
1725		this to the maximum filesize (in bytes) for the buffer.
1726		Default is 4 MiB if undefined.
1727
1728		DFU_DEFAULT_POLL_TIMEOUT
1729		Poll timeout [ms], is the timeout a device can send to the
1730		host. The host must wait for this timeout before sending
1731		a subsequent DFU_GET_STATUS request to the device.
1732
1733		DFU_MANIFEST_POLL_TIMEOUT
1734		Poll timeout [ms], which the device sends to the host when
1735		entering dfuMANIFEST state. Host waits this timeout, before
1736		sending again an USB request to the device.
1737
1738- USB Device Android Fastboot support:
1739		CONFIG_CMD_FASTBOOT
1740		This enables the command "fastboot" which enables the Android
1741		fastboot mode for the platform's USB device. Fastboot is a USB
1742		protocol for downloading images, flashing and device control
1743		used on Android devices.
1744		See doc/README.android-fastboot for more information.
1745
1746		CONFIG_ANDROID_BOOT_IMAGE
1747		This enables support for booting images which use the Android
1748		image format header.
1749
1750		CONFIG_USB_FASTBOOT_BUF_ADDR
1751		The fastboot protocol requires a large memory buffer for
1752		downloads. Define this to the starting RAM address to use for
1753		downloaded images.
1754
1755		CONFIG_USB_FASTBOOT_BUF_SIZE
1756		The fastboot protocol requires a large memory buffer for
1757		downloads. This buffer should be as large as possible for a
1758		platform. Define this to the size available RAM for fastboot.
1759
1760		CONFIG_FASTBOOT_FLASH
1761		The fastboot protocol includes a "flash" command for writing
1762		the downloaded image to a non-volatile storage device. Define
1763		this to enable the "fastboot flash" command.
1764
1765		CONFIG_FASTBOOT_FLASH_MMC_DEV
1766		The fastboot "flash" command requires additional information
1767		regarding the non-volatile storage device. Define this to
1768		the eMMC device that fastboot should use to store the image.
1769
1770		CONFIG_FASTBOOT_GPT_NAME
1771		The fastboot "flash" command supports writing the downloaded
1772		image to the Protective MBR and the Primary GUID Partition
1773		Table. (Additionally, this downloaded image is post-processed
1774		to generate and write the Backup GUID Partition Table.)
1775		This occurs when the specified "partition name" on the
1776		"fastboot flash" command line matches this value.
1777		Default is GPT_ENTRY_NAME (currently "gpt") if undefined.
1778
1779- Journaling Flash filesystem support:
1780		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1781		CONFIG_JFFS2_NAND_DEV
1782		Define these for a default partition on a NAND device
1783
1784		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1785		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1786		Define these for a default partition on a NOR device
1787
1788		CONFIG_SYS_JFFS_CUSTOM_PART
1789		Define this to create an own partition. You have to provide a
1790		function struct part_info* jffs2_part_info(int part_num)
1791
1792		If you define only one JFFS2 partition you may also want to
1793		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1794		to disable the command chpart. This is the default when you
1795		have not defined a custom partition
1796
1797- FAT(File Allocation Table) filesystem write function support:
1798		CONFIG_FAT_WRITE
1799
1800		Define this to enable support for saving memory data as a
1801		file in FAT formatted partition.
1802
1803		This will also enable the command "fatwrite" enabling the
1804		user to write files to FAT.
1805
1806CBFS (Coreboot Filesystem) support
1807		CONFIG_CMD_CBFS
1808
1809		Define this to enable support for reading from a Coreboot
1810		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1811		and cbfsload.
1812
1813- FAT(File Allocation Table) filesystem cluster size:
1814		CONFIG_FS_FAT_MAX_CLUSTSIZE
1815
1816		Define the max cluster size for fat operations else
1817		a default value of 65536 will be defined.
1818
1819- Keyboard Support:
1820		CONFIG_ISA_KEYBOARD
1821
1822		Define this to enable standard (PC-Style) keyboard
1823		support
1824
1825		CONFIG_I8042_KBD
1826		Standard PC keyboard driver with US (is default) and
1827		GERMAN key layout (switch via environment 'keymap=de') support.
1828		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1829		for cfb_console. Supports cursor blinking.
1830
1831		CONFIG_CROS_EC_KEYB
1832		Enables a Chrome OS keyboard using the CROS_EC interface.
1833		This uses CROS_EC to communicate with a second microcontroller
1834		which provides key scans on request.
1835
1836- Video support:
1837		CONFIG_VIDEO
1838
1839		Define this to enable video support (for output to
1840		video).
1841
1842		CONFIG_VIDEO_CT69000
1843
1844		Enable Chips & Technologies 69000 Video chip
1845
1846		CONFIG_VIDEO_SMI_LYNXEM
1847		Enable Silicon Motion SMI 712/710/810 Video chip. The
1848		video output is selected via environment 'videoout'
1849		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1850		assumed.
1851
1852		For the CT69000 and SMI_LYNXEM drivers, videomode is
1853		selected via environment 'videomode'. Two different ways
1854		are possible:
1855		- "videomode=num"   'num' is a standard LiLo mode numbers.
1856		Following standard modes are supported	(* is default):
1857
1858		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1859		-------------+---------------------------------------------
1860		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1861		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1862		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1863		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1864		-------------+---------------------------------------------
1865		(i.e. setenv videomode 317; saveenv; reset;)
1866
1867		- "videomode=bootargs" all the video parameters are parsed
1868		from the bootargs. (See drivers/video/videomodes.c)
1869
1870
1871		CONFIG_VIDEO_SED13806
1872		Enable Epson SED13806 driver. This driver supports 8bpp
1873		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1874		or CONFIG_VIDEO_SED13806_16BPP
1875
1876		CONFIG_FSL_DIU_FB
1877		Enable the Freescale DIU video driver.	Reference boards for
1878		SOCs that have a DIU should define this macro to enable DIU
1879		support, and should also define these other macros:
1880
1881			CONFIG_SYS_DIU_ADDR
1882			CONFIG_VIDEO
1883			CONFIG_CMD_BMP
1884			CONFIG_CFB_CONSOLE
1885			CONFIG_VIDEO_SW_CURSOR
1886			CONFIG_VGA_AS_SINGLE_DEVICE
1887			CONFIG_VIDEO_LOGO
1888			CONFIG_VIDEO_BMP_LOGO
1889
1890		The DIU driver will look for the 'video-mode' environment
1891		variable, and if defined, enable the DIU as a console during
1892		boot.  See the documentation file README.video for a
1893		description of this variable.
1894
1895		CONFIG_VIDEO_VGA
1896
1897		Enable the VGA video / BIOS for x86. The alternative if you
1898		are using coreboot is to use the coreboot frame buffer
1899		driver.
1900
1901
1902- Keyboard Support:
1903		CONFIG_KEYBOARD
1904
1905		Define this to enable a custom keyboard support.
1906		This simply calls drv_keyboard_init() which must be
1907		defined in your board-specific files.
1908		The only board using this so far is RBC823.
1909
1910- LCD Support:	CONFIG_LCD
1911
1912		Define this to enable LCD support (for output to LCD
1913		display); also select one of the supported displays
1914		by defining one of these:
1915
1916		CONFIG_ATMEL_LCD:
1917
1918			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1919
1920		CONFIG_NEC_NL6448AC33:
1921
1922			NEC NL6448AC33-18. Active, color, single scan.
1923
1924		CONFIG_NEC_NL6448BC20
1925
1926			NEC NL6448BC20-08. 6.5", 640x480.
1927			Active, color, single scan.
1928
1929		CONFIG_NEC_NL6448BC33_54
1930
1931			NEC NL6448BC33-54. 10.4", 640x480.
1932			Active, color, single scan.
1933
1934		CONFIG_SHARP_16x9
1935
1936			Sharp 320x240. Active, color, single scan.
1937			It isn't 16x9, and I am not sure what it is.
1938
1939		CONFIG_SHARP_LQ64D341
1940
1941			Sharp LQ64D341 display, 640x480.
1942			Active, color, single scan.
1943
1944		CONFIG_HLD1045
1945
1946			HLD1045 display, 640x480.
1947			Active, color, single scan.
1948
1949		CONFIG_OPTREX_BW
1950
1951			Optrex	 CBL50840-2 NF-FW 99 22 M5
1952			or
1953			Hitachi	 LMG6912RPFC-00T
1954			or
1955			Hitachi	 SP14Q002
1956
1957			320x240. Black & white.
1958
1959		Normally display is black on white background; define
1960		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1961
1962		CONFIG_LCD_ALIGNMENT
1963
1964		Normally the LCD is page-aligned (typically 4KB). If this is
1965		defined then the LCD will be aligned to this value instead.
1966		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1967		here, since it is cheaper to change data cache settings on
1968		a per-section basis.
1969
1970		CONFIG_CONSOLE_SCROLL_LINES
1971
1972		When the console need to be scrolled, this is the number of
1973		lines to scroll by. It defaults to 1. Increasing this makes
1974		the console jump but can help speed up operation when scrolling
1975		is slow.
1976
1977		CONFIG_LCD_BMP_RLE8
1978
1979		Support drawing of RLE8-compressed bitmaps on the LCD.
1980
1981		CONFIG_I2C_EDID
1982
1983		Enables an 'i2c edid' command which can read EDID
1984		information over I2C from an attached LCD display.
1985
1986- Splash Screen Support: CONFIG_SPLASH_SCREEN
1987
1988		If this option is set, the environment is checked for
1989		a variable "splashimage". If found, the usual display
1990		of logo, copyright and system information on the LCD
1991		is suppressed and the BMP image at the address
1992		specified in "splashimage" is loaded instead. The
1993		console is redirected to the "nulldev", too. This
1994		allows for a "silent" boot where a splash screen is
1995		loaded very quickly after power-on.
1996
1997		CONFIG_SPLASHIMAGE_GUARD
1998
1999		If this option is set, then U-Boot will prevent the environment
2000		variable "splashimage" from being set to a problematic address
2001		(see README.displaying-bmps).
2002		This option is useful for targets where, due to alignment
2003		restrictions, an improperly aligned BMP image will cause a data
2004		abort. If you think you will not have problems with unaligned
2005		accesses (for example because your toolchain prevents them)
2006		there is no need to set this option.
2007
2008		CONFIG_SPLASH_SCREEN_ALIGN
2009
2010		If this option is set the splash image can be freely positioned
2011		on the screen. Environment variable "splashpos" specifies the
2012		position as "x,y". If a positive number is given it is used as
2013		number of pixel from left/top. If a negative number is given it
2014		is used as number of pixel from right/bottom. You can also
2015		specify 'm' for centering the image.
2016
2017		Example:
2018		setenv splashpos m,m
2019			=> image at center of screen
2020
2021		setenv splashpos 30,20
2022			=> image at x = 30 and y = 20
2023
2024		setenv splashpos -10,m
2025			=> vertically centered image
2026			   at x = dspWidth - bmpWidth - 9
2027
2028- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
2029
2030		If this option is set, additionally to standard BMP
2031		images, gzipped BMP images can be displayed via the
2032		splashscreen support or the bmp command.
2033
2034- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
2035
2036		If this option is set, 8-bit RLE compressed BMP images
2037		can be displayed via the splashscreen support or the
2038		bmp command.
2039
2040- Do compressing for memory range:
2041		CONFIG_CMD_ZIP
2042
2043		If this option is set, it would use zlib deflate method
2044		to compress the specified memory at its best effort.
2045
2046- Compression support:
2047		CONFIG_GZIP
2048
2049		Enabled by default to support gzip compressed images.
2050
2051		CONFIG_BZIP2
2052
2053		If this option is set, support for bzip2 compressed
2054		images is included. If not, only uncompressed and gzip
2055		compressed images are supported.
2056
2057		NOTE: the bzip2 algorithm requires a lot of RAM, so
2058		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
2059		be at least 4MB.
2060
2061		CONFIG_LZMA
2062
2063		If this option is set, support for lzma compressed
2064		images is included.
2065
2066		Note: The LZMA algorithm adds between 2 and 4KB of code and it
2067		requires an amount of dynamic memory that is given by the
2068		formula:
2069
2070			(1846 + 768 << (lc + lp)) * sizeof(uint16)
2071
2072		Where lc and lp stand for, respectively, Literal context bits
2073		and Literal pos bits.
2074
2075		This value is upper-bounded by 14MB in the worst case. Anyway,
2076		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
2077		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
2078		a very small buffer.
2079
2080		Use the lzmainfo tool to determinate the lc and lp values and
2081		then calculate the amount of needed dynamic memory (ensuring
2082		the appropriate CONFIG_SYS_MALLOC_LEN value).
2083
2084		CONFIG_LZO
2085
2086		If this option is set, support for LZO compressed images
2087		is included.
2088
2089- MII/PHY support:
2090		CONFIG_PHY_ADDR
2091
2092		The address of PHY on MII bus.
2093
2094		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
2095
2096		The clock frequency of the MII bus
2097
2098		CONFIG_PHY_GIGE
2099
2100		If this option is set, support for speed/duplex
2101		detection of gigabit PHY is included.
2102
2103		CONFIG_PHY_RESET_DELAY
2104
2105		Some PHY like Intel LXT971A need extra delay after
2106		reset before any MII register access is possible.
2107		For such PHY, set this option to the usec delay
2108		required. (minimum 300usec for LXT971A)
2109
2110		CONFIG_PHY_CMD_DELAY (ppc4xx)
2111
2112		Some PHY like Intel LXT971A need extra delay after
2113		command issued before MII status register can be read
2114
2115- Ethernet address:
2116		CONFIG_ETHADDR
2117		CONFIG_ETH1ADDR
2118		CONFIG_ETH2ADDR
2119		CONFIG_ETH3ADDR
2120		CONFIG_ETH4ADDR
2121		CONFIG_ETH5ADDR
2122
2123		Define a default value for Ethernet address to use
2124		for the respective Ethernet interface, in case this
2125		is not determined automatically.
2126
2127- IP address:
2128		CONFIG_IPADDR
2129
2130		Define a default value for the IP address to use for
2131		the default Ethernet interface, in case this is not
2132		determined through e.g. bootp.
2133		(Environment variable "ipaddr")
2134
2135- Server IP address:
2136		CONFIG_SERVERIP
2137
2138		Defines a default value for the IP address of a TFTP
2139		server to contact when using the "tftboot" command.
2140		(Environment variable "serverip")
2141
2142		CONFIG_KEEP_SERVERADDR
2143
2144		Keeps the server's MAC address, in the env 'serveraddr'
2145		for passing to bootargs (like Linux's netconsole option)
2146
2147- Gateway IP address:
2148		CONFIG_GATEWAYIP
2149
2150		Defines a default value for the IP address of the
2151		default router where packets to other networks are
2152		sent to.
2153		(Environment variable "gatewayip")
2154
2155- Subnet mask:
2156		CONFIG_NETMASK
2157
2158		Defines a default value for the subnet mask (or
2159		routing prefix) which is used to determine if an IP
2160		address belongs to the local subnet or needs to be
2161		forwarded through a router.
2162		(Environment variable "netmask")
2163
2164- Multicast TFTP Mode:
2165		CONFIG_MCAST_TFTP
2166
2167		Defines whether you want to support multicast TFTP as per
2168		rfc-2090; for example to work with atftp.  Lets lots of targets
2169		tftp down the same boot image concurrently.  Note: the Ethernet
2170		driver in use must provide a function: mcast() to join/leave a
2171		multicast group.
2172
2173- BOOTP Recovery Mode:
2174		CONFIG_BOOTP_RANDOM_DELAY
2175
2176		If you have many targets in a network that try to
2177		boot using BOOTP, you may want to avoid that all
2178		systems send out BOOTP requests at precisely the same
2179		moment (which would happen for instance at recovery
2180		from a power failure, when all systems will try to
2181		boot, thus flooding the BOOTP server. Defining
2182		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
2183		inserted before sending out BOOTP requests. The
2184		following delays are inserted then:
2185
2186		1st BOOTP request:	delay 0 ... 1 sec
2187		2nd BOOTP request:	delay 0 ... 2 sec
2188		3rd BOOTP request:	delay 0 ... 4 sec
2189		4th and following
2190		BOOTP requests:		delay 0 ... 8 sec
2191
2192		CONFIG_BOOTP_ID_CACHE_SIZE
2193
2194		BOOTP packets are uniquely identified using a 32-bit ID. The
2195		server will copy the ID from client requests to responses and
2196		U-Boot will use this to determine if it is the destination of
2197		an incoming response. Some servers will check that addresses
2198		aren't in use before handing them out (usually using an ARP
2199		ping) and therefore take up to a few hundred milliseconds to
2200		respond. Network congestion may also influence the time it
2201		takes for a response to make it back to the client. If that
2202		time is too long, U-Boot will retransmit requests. In order
2203		to allow earlier responses to still be accepted after these
2204		retransmissions, U-Boot's BOOTP client keeps a small cache of
2205		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
2206		cache. The default is to keep IDs for up to four outstanding
2207		requests. Increasing this will allow U-Boot to accept offers
2208		from a BOOTP client in networks with unusually high latency.
2209
2210- DHCP Advanced Options:
2211		You can fine tune the DHCP functionality by defining
2212		CONFIG_BOOTP_* symbols:
2213
2214		CONFIG_BOOTP_SUBNETMASK
2215		CONFIG_BOOTP_GATEWAY
2216		CONFIG_BOOTP_HOSTNAME
2217		CONFIG_BOOTP_NISDOMAIN
2218		CONFIG_BOOTP_BOOTPATH
2219		CONFIG_BOOTP_BOOTFILESIZE
2220		CONFIG_BOOTP_DNS
2221		CONFIG_BOOTP_DNS2
2222		CONFIG_BOOTP_SEND_HOSTNAME
2223		CONFIG_BOOTP_NTPSERVER
2224		CONFIG_BOOTP_TIMEOFFSET
2225		CONFIG_BOOTP_VENDOREX
2226		CONFIG_BOOTP_MAY_FAIL
2227
2228		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
2229		environment variable, not the BOOTP server.
2230
2231		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
2232		after the configured retry count, the call will fail
2233		instead of starting over.  This can be used to fail over
2234		to Link-local IP address configuration if the DHCP server
2235		is not available.
2236
2237		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
2238		serverip from a DHCP server, it is possible that more
2239		than one DNS serverip is offered to the client.
2240		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
2241		serverip will be stored in the additional environment
2242		variable "dnsip2". The first DNS serverip is always
2243		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
2244		is defined.
2245
2246		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2247		to do a dynamic update of a DNS server. To do this, they
2248		need the hostname of the DHCP requester.
2249		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2250		of the "hostname" environment variable is passed as
2251		option 12 to the DHCP server.
2252
2253		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2254
2255		A 32bit value in microseconds for a delay between
2256		receiving a "DHCP Offer" and sending the "DHCP Request".
2257		This fixes a problem with certain DHCP servers that don't
2258		respond 100% of the time to a "DHCP request". E.g. On an
2259		AT91RM9200 processor running at 180MHz, this delay needed
2260		to be *at least* 15,000 usec before a Windows Server 2003
2261		DHCP server would reply 100% of the time. I recommend at
2262		least 50,000 usec to be safe. The alternative is to hope
2263		that one of the retries will be successful but note that
2264		the DHCP timeout and retry process takes a longer than
2265		this delay.
2266
2267 - Link-local IP address negotiation:
2268		Negotiate with other link-local clients on the local network
2269		for an address that doesn't require explicit configuration.
2270		This is especially useful if a DHCP server cannot be guaranteed
2271		to exist in all environments that the device must operate.
2272
2273		See doc/README.link-local for more information.
2274
2275 - CDP Options:
2276		CONFIG_CDP_DEVICE_ID
2277
2278		The device id used in CDP trigger frames.
2279
2280		CONFIG_CDP_DEVICE_ID_PREFIX
2281
2282		A two character string which is prefixed to the MAC address
2283		of the device.
2284
2285		CONFIG_CDP_PORT_ID
2286
2287		A printf format string which contains the ascii name of
2288		the port. Normally is set to "eth%d" which sets
2289		eth0 for the first Ethernet, eth1 for the second etc.
2290
2291		CONFIG_CDP_CAPABILITIES
2292
2293		A 32bit integer which indicates the device capabilities;
2294		0x00000010 for a normal host which does not forwards.
2295
2296		CONFIG_CDP_VERSION
2297
2298		An ascii string containing the version of the software.
2299
2300		CONFIG_CDP_PLATFORM
2301
2302		An ascii string containing the name of the platform.
2303
2304		CONFIG_CDP_TRIGGER
2305
2306		A 32bit integer sent on the trigger.
2307
2308		CONFIG_CDP_POWER_CONSUMPTION
2309
2310		A 16bit integer containing the power consumption of the
2311		device in .1 of milliwatts.
2312
2313		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2314
2315		A byte containing the id of the VLAN.
2316
2317- Status LED:	CONFIG_STATUS_LED
2318
2319		Several configurations allow to display the current
2320		status using a LED. For instance, the LED will blink
2321		fast while running U-Boot code, stop blinking as
2322		soon as a reply to a BOOTP request was received, and
2323		start blinking slow once the Linux kernel is running
2324		(supported by a status LED driver in the Linux
2325		kernel). Defining CONFIG_STATUS_LED enables this
2326		feature in U-Boot.
2327
2328		Additional options:
2329
2330		CONFIG_GPIO_LED
2331		The status LED can be connected to a GPIO pin.
2332		In such cases, the gpio_led driver can be used as a
2333		status LED backend implementation. Define CONFIG_GPIO_LED
2334		to include the gpio_led driver in the U-Boot binary.
2335
2336		CONFIG_GPIO_LED_INVERTED_TABLE
2337		Some GPIO connected LEDs may have inverted polarity in which
2338		case the GPIO high value corresponds to LED off state and
2339		GPIO low value corresponds to LED on state.
2340		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2341		with a list of GPIO LEDs that have inverted polarity.
2342
2343- CAN Support:	CONFIG_CAN_DRIVER
2344
2345		Defining CONFIG_CAN_DRIVER enables CAN driver support
2346		on those systems that support this (optional)
2347		feature, like the TQM8xxL modules.
2348
2349- I2C Support:	CONFIG_SYS_I2C
2350
2351		This enable the NEW i2c subsystem, and will allow you to use
2352		i2c commands at the u-boot command line (as long as you set
2353		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2354		based realtime clock chips or other i2c devices. See
2355		common/cmd_i2c.c for a description of the command line
2356		interface.
2357
2358		ported i2c driver to the new framework:
2359		- drivers/i2c/soft_i2c.c:
2360		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2361		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2362		    for defining speed and slave address
2363		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2364		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2365		    for defining speed and slave address
2366		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2367		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2368		    for defining speed and slave address
2369		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2370		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2371		    for defining speed and slave address
2372
2373		- drivers/i2c/fsl_i2c.c:
2374		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2375		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2376		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2377		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2378		    bus.
2379		  - If your board supports a second fsl i2c bus, define
2380		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2381		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2382		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2383		    second bus.
2384
2385		- drivers/i2c/tegra_i2c.c:
2386		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2387		  - This driver adds 4 i2c buses with a fix speed from
2388		    100000 and the slave addr 0!
2389
2390		- drivers/i2c/ppc4xx_i2c.c
2391		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2392		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2393		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2394
2395		- drivers/i2c/i2c_mxc.c
2396		  - activate this driver with CONFIG_SYS_I2C_MXC
2397		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2398		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2399		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2400		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2401		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2402		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2403		If those defines are not set, default value is 100000
2404		for speed, and 0 for slave.
2405
2406		- drivers/i2c/rcar_i2c.c:
2407		  - activate this driver with CONFIG_SYS_I2C_RCAR
2408		  - This driver adds 4 i2c buses
2409
2410		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2411		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2412		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2413		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2414		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2415		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2416		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2417		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2418		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2419
2420		- drivers/i2c/sh_i2c.c:
2421		  - activate this driver with CONFIG_SYS_I2C_SH
2422		  - This driver adds from 2 to 5 i2c buses
2423
2424		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2425		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2426		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2427		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2428		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2429		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2430		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2431		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2432		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2433		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2434		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2435		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2436		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2437
2438		- drivers/i2c/omap24xx_i2c.c
2439		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2440		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2441		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2442		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2443		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2444		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2445		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2446		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2447		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2448		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2449		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2450
2451		- drivers/i2c/zynq_i2c.c
2452		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2453		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2454		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2455
2456		- drivers/i2c/s3c24x0_i2c.c:
2457		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2458		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2459		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2460		    with a fix speed from 100000 and the slave addr 0!
2461
2462		- drivers/i2c/ihs_i2c.c
2463		  - activate this driver with CONFIG_SYS_I2C_IHS
2464		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2465		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2466		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2467		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2468		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2469		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2470		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2471		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2472		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2473		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2474		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2475		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2476
2477		additional defines:
2478
2479		CONFIG_SYS_NUM_I2C_BUSES
2480		Hold the number of i2c buses you want to use. If you
2481		don't use/have i2c muxes on your i2c bus, this
2482		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2483		omit this define.
2484
2485		CONFIG_SYS_I2C_DIRECT_BUS
2486		define this, if you don't use i2c muxes on your hardware.
2487		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2488		omit this define.
2489
2490		CONFIG_SYS_I2C_MAX_HOPS
2491		define how many muxes are maximal consecutively connected
2492		on one i2c bus. If you not use i2c muxes, omit this
2493		define.
2494
2495		CONFIG_SYS_I2C_BUSES
2496		hold a list of buses you want to use, only used if
2497		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2498		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2499		CONFIG_SYS_NUM_I2C_BUSES = 9:
2500
2501		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2502					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2503					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2504					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2505					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2506					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2507					{1, {I2C_NULL_HOP}}, \
2508					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2509					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2510					}
2511
2512		which defines
2513			bus 0 on adapter 0 without a mux
2514			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2515			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2516			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2517			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2518			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2519			bus 6 on adapter 1 without a mux
2520			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2521			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2522
2523		If you do not have i2c muxes on your board, omit this define.
2524
2525- Legacy I2C Support:	CONFIG_HARD_I2C
2526
2527		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2528		provides the following compelling advantages:
2529
2530		- more than one i2c adapter is usable
2531		- approved multibus support
2532		- better i2c mux support
2533
2534		** Please consider updating your I2C driver now. **
2535
2536		These enable legacy I2C serial bus commands. Defining
2537		CONFIG_HARD_I2C will include the appropriate I2C driver
2538		for the selected CPU.
2539
2540		This will allow you to use i2c commands at the u-boot
2541		command line (as long as you set CONFIG_CMD_I2C in
2542		CONFIG_COMMANDS) and communicate with i2c based realtime
2543		clock chips. See common/cmd_i2c.c for a description of the
2544		command line interface.
2545
2546		CONFIG_HARD_I2C selects a hardware I2C controller.
2547
2548		There are several other quantities that must also be
2549		defined when you define CONFIG_HARD_I2C.
2550
2551		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2552		to be the frequency (in Hz) at which you wish your i2c bus
2553		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2554		the CPU's i2c node address).
2555
2556		Now, the u-boot i2c code for the mpc8xx
2557		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2558		and so its address should therefore be cleared to 0 (See,
2559		eg, MPC823e User's Manual p.16-473). So, set
2560		CONFIG_SYS_I2C_SLAVE to 0.
2561
2562		CONFIG_SYS_I2C_INIT_MPC5XXX
2563
2564		When a board is reset during an i2c bus transfer
2565		chips might think that the current transfer is still
2566		in progress.  Reset the slave devices by sending start
2567		commands until the slave device responds.
2568
2569		That's all that's required for CONFIG_HARD_I2C.
2570
2571		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2572		then the following macros need to be defined (examples are
2573		from include/configs/lwmon.h):
2574
2575		I2C_INIT
2576
2577		(Optional). Any commands necessary to enable the I2C
2578		controller or configure ports.
2579
2580		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2581
2582		I2C_PORT
2583
2584		(Only for MPC8260 CPU). The I/O port to use (the code
2585		assumes both bits are on the same port). Valid values
2586		are 0..3 for ports A..D.
2587
2588		I2C_ACTIVE
2589
2590		The code necessary to make the I2C data line active
2591		(driven).  If the data line is open collector, this
2592		define can be null.
2593
2594		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2595
2596		I2C_TRISTATE
2597
2598		The code necessary to make the I2C data line tri-stated
2599		(inactive).  If the data line is open collector, this
2600		define can be null.
2601
2602		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2603
2604		I2C_READ
2605
2606		Code that returns true if the I2C data line is high,
2607		false if it is low.
2608
2609		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2610
2611		I2C_SDA(bit)
2612
2613		If <bit> is true, sets the I2C data line high. If it
2614		is false, it clears it (low).
2615
2616		eg: #define I2C_SDA(bit) \
2617			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2618			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2619
2620		I2C_SCL(bit)
2621
2622		If <bit> is true, sets the I2C clock line high. If it
2623		is false, it clears it (low).
2624
2625		eg: #define I2C_SCL(bit) \
2626			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2627			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2628
2629		I2C_DELAY
2630
2631		This delay is invoked four times per clock cycle so this
2632		controls the rate of data transfer.  The data rate thus
2633		is 1 / (I2C_DELAY * 4). Often defined to be something
2634		like:
2635
2636		#define I2C_DELAY  udelay(2)
2637
2638		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2639
2640		If your arch supports the generic GPIO framework (asm/gpio.h),
2641		then you may alternatively define the two GPIOs that are to be
2642		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2643		have GPIO-based defaults assigned to them as appropriate.
2644
2645		You should define these to the GPIO value as given directly to
2646		the generic GPIO functions.
2647
2648		CONFIG_SYS_I2C_INIT_BOARD
2649
2650		When a board is reset during an i2c bus transfer
2651		chips might think that the current transfer is still
2652		in progress. On some boards it is possible to access
2653		the i2c SCLK line directly, either by using the
2654		processor pin as a GPIO or by having a second pin
2655		connected to the bus. If this option is defined a
2656		custom i2c_init_board() routine in boards/xxx/board.c
2657		is run early in the boot sequence.
2658
2659		CONFIG_SYS_I2C_BOARD_LATE_INIT
2660
2661		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2662		defined a custom i2c_board_late_init() routine in
2663		boards/xxx/board.c is run AFTER the operations in i2c_init()
2664		is completed. This callpoint can be used to unreset i2c bus
2665		using CPU i2c controller register accesses for CPUs whose i2c
2666		controller provide such a method. It is called at the end of
2667		i2c_init() to allow i2c_init operations to setup the i2c bus
2668		controller on the CPU (e.g. setting bus speed & slave address).
2669
2670		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2671
2672		This option enables configuration of bi_iic_fast[] flags
2673		in u-boot bd_info structure based on u-boot environment
2674		variable "i2cfast". (see also i2cfast)
2675
2676		CONFIG_I2C_MULTI_BUS
2677
2678		This option allows the use of multiple I2C buses, each of which
2679		must have a controller.	 At any point in time, only one bus is
2680		active.	 To switch to a different bus, use the 'i2c dev' command.
2681		Note that bus numbering is zero-based.
2682
2683		CONFIG_SYS_I2C_NOPROBES
2684
2685		This option specifies a list of I2C devices that will be skipped
2686		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2687		is set, specify a list of bus-device pairs.  Otherwise, specify
2688		a 1D array of device addresses
2689
2690		e.g.
2691			#undef	CONFIG_I2C_MULTI_BUS
2692			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2693
2694		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2695
2696			#define CONFIG_I2C_MULTI_BUS
2697			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2698
2699		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2700
2701		CONFIG_SYS_SPD_BUS_NUM
2702
2703		If defined, then this indicates the I2C bus number for DDR SPD.
2704		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2705
2706		CONFIG_SYS_RTC_BUS_NUM
2707
2708		If defined, then this indicates the I2C bus number for the RTC.
2709		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2710
2711		CONFIG_SYS_DTT_BUS_NUM
2712
2713		If defined, then this indicates the I2C bus number for the DTT.
2714		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2715
2716		CONFIG_SYS_I2C_DTT_ADDR:
2717
2718		If defined, specifies the I2C address of the DTT device.
2719		If not defined, then U-Boot uses predefined value for
2720		specified DTT device.
2721
2722		CONFIG_SOFT_I2C_READ_REPEATED_START
2723
2724		defining this will force the i2c_read() function in
2725		the soft_i2c driver to perform an I2C repeated start
2726		between writing the address pointer and reading the
2727		data.  If this define is omitted the default behaviour
2728		of doing a stop-start sequence will be used.  Most I2C
2729		devices can use either method, but some require one or
2730		the other.
2731
2732- SPI Support:	CONFIG_SPI
2733
2734		Enables SPI driver (so far only tested with
2735		SPI EEPROM, also an instance works with Crystal A/D and
2736		D/As on the SACSng board)
2737
2738		CONFIG_SH_SPI
2739
2740		Enables the driver for SPI controller on SuperH. Currently
2741		only SH7757 is supported.
2742
2743		CONFIG_SPI_X
2744
2745		Enables extended (16-bit) SPI EEPROM addressing.
2746		(symmetrical to CONFIG_I2C_X)
2747
2748		CONFIG_SOFT_SPI
2749
2750		Enables a software (bit-bang) SPI driver rather than
2751		using hardware support. This is a general purpose
2752		driver that only requires three general I/O port pins
2753		(two outputs, one input) to function. If this is
2754		defined, the board configuration must define several
2755		SPI configuration items (port pins to use, etc). For
2756		an example, see include/configs/sacsng.h.
2757
2758		CONFIG_HARD_SPI
2759
2760		Enables a hardware SPI driver for general-purpose reads
2761		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2762		must define a list of chip-select function pointers.
2763		Currently supported on some MPC8xxx processors.	 For an
2764		example, see include/configs/mpc8349emds.h.
2765
2766		CONFIG_MXC_SPI
2767
2768		Enables the driver for the SPI controllers on i.MX and MXC
2769		SoCs. Currently i.MX31/35/51 are supported.
2770
2771		CONFIG_SYS_SPI_MXC_WAIT
2772		Timeout for waiting until spi transfer completed.
2773		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2774
2775- FPGA Support: CONFIG_FPGA
2776
2777		Enables FPGA subsystem.
2778
2779		CONFIG_FPGA_<vendor>
2780
2781		Enables support for specific chip vendors.
2782		(ALTERA, XILINX)
2783
2784		CONFIG_FPGA_<family>
2785
2786		Enables support for FPGA family.
2787		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2788
2789		CONFIG_FPGA_COUNT
2790
2791		Specify the number of FPGA devices to support.
2792
2793		CONFIG_CMD_FPGA_LOADMK
2794
2795		Enable support for fpga loadmk command
2796
2797		CONFIG_CMD_FPGA_LOADP
2798
2799		Enable support for fpga loadp command - load partial bitstream
2800
2801		CONFIG_CMD_FPGA_LOADBP
2802
2803		Enable support for fpga loadbp command - load partial bitstream
2804		(Xilinx only)
2805
2806		CONFIG_SYS_FPGA_PROG_FEEDBACK
2807
2808		Enable printing of hash marks during FPGA configuration.
2809
2810		CONFIG_SYS_FPGA_CHECK_BUSY
2811
2812		Enable checks on FPGA configuration interface busy
2813		status by the configuration function. This option
2814		will require a board or device specific function to
2815		be written.
2816
2817		CONFIG_FPGA_DELAY
2818
2819		If defined, a function that provides delays in the FPGA
2820		configuration driver.
2821
2822		CONFIG_SYS_FPGA_CHECK_CTRLC
2823		Allow Control-C to interrupt FPGA configuration
2824
2825		CONFIG_SYS_FPGA_CHECK_ERROR
2826
2827		Check for configuration errors during FPGA bitfile
2828		loading. For example, abort during Virtex II
2829		configuration if the INIT_B line goes low (which
2830		indicated a CRC error).
2831
2832		CONFIG_SYS_FPGA_WAIT_INIT
2833
2834		Maximum time to wait for the INIT_B line to de-assert
2835		after PROB_B has been de-asserted during a Virtex II
2836		FPGA configuration sequence. The default time is 500
2837		ms.
2838
2839		CONFIG_SYS_FPGA_WAIT_BUSY
2840
2841		Maximum time to wait for BUSY to de-assert during
2842		Virtex II FPGA configuration. The default is 5 ms.
2843
2844		CONFIG_SYS_FPGA_WAIT_CONFIG
2845
2846		Time to wait after FPGA configuration. The default is
2847		200 ms.
2848
2849- Configuration Management:
2850		CONFIG_BUILD_TARGET
2851
2852		Some SoCs need special image types (e.g. U-Boot binary
2853		with a special header) as build targets. By defining
2854		CONFIG_BUILD_TARGET in the SoC / board header, this
2855		special image will be automatically built upon calling
2856		make / MAKEALL.
2857
2858		CONFIG_IDENT_STRING
2859
2860		If defined, this string will be added to the U-Boot
2861		version information (U_BOOT_VERSION)
2862
2863- Vendor Parameter Protection:
2864
2865		U-Boot considers the values of the environment
2866		variables "serial#" (Board Serial Number) and
2867		"ethaddr" (Ethernet Address) to be parameters that
2868		are set once by the board vendor / manufacturer, and
2869		protects these variables from casual modification by
2870		the user. Once set, these variables are read-only,
2871		and write or delete attempts are rejected. You can
2872		change this behaviour:
2873
2874		If CONFIG_ENV_OVERWRITE is #defined in your config
2875		file, the write protection for vendor parameters is
2876		completely disabled. Anybody can change or delete
2877		these parameters.
2878
2879		Alternatively, if you #define _both_ CONFIG_ETHADDR
2880		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2881		Ethernet address is installed in the environment,
2882		which can be changed exactly ONCE by the user. [The
2883		serial# is unaffected by this, i. e. it remains
2884		read-only.]
2885
2886		The same can be accomplished in a more flexible way
2887		for any variable by configuring the type of access
2888		to allow for those variables in the ".flags" variable
2889		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2890
2891- Protected RAM:
2892		CONFIG_PRAM
2893
2894		Define this variable to enable the reservation of
2895		"protected RAM", i. e. RAM which is not overwritten
2896		by U-Boot. Define CONFIG_PRAM to hold the number of
2897		kB you want to reserve for pRAM. You can overwrite
2898		this default value by defining an environment
2899		variable "pram" to the number of kB you want to
2900		reserve. Note that the board info structure will
2901		still show the full amount of RAM. If pRAM is
2902		reserved, a new environment variable "mem" will
2903		automatically be defined to hold the amount of
2904		remaining RAM in a form that can be passed as boot
2905		argument to Linux, for instance like that:
2906
2907			setenv bootargs ... mem=\${mem}
2908			saveenv
2909
2910		This way you can tell Linux not to use this memory,
2911		either, which results in a memory region that will
2912		not be affected by reboots.
2913
2914		*WARNING* If your board configuration uses automatic
2915		detection of the RAM size, you must make sure that
2916		this memory test is non-destructive. So far, the
2917		following board configurations are known to be
2918		"pRAM-clean":
2919
2920			IVMS8, IVML24, SPD8xx, TQM8xxL,
2921			HERMES, IP860, RPXlite, LWMON,
2922			FLAGADM, TQM8260
2923
2924- Access to physical memory region (> 4GB)
2925		Some basic support is provided for operations on memory not
2926		normally accessible to U-Boot - e.g. some architectures
2927		support access to more than 4GB of memory on 32-bit
2928		machines using physical address extension or similar.
2929		Define CONFIG_PHYSMEM to access this basic support, which
2930		currently only supports clearing the memory.
2931
2932- Error Recovery:
2933		CONFIG_PANIC_HANG
2934
2935		Define this variable to stop the system in case of a
2936		fatal error, so that you have to reset it manually.
2937		This is probably NOT a good idea for an embedded
2938		system where you want the system to reboot
2939		automatically as fast as possible, but it may be
2940		useful during development since you can try to debug
2941		the conditions that lead to the situation.
2942
2943		CONFIG_NET_RETRY_COUNT
2944
2945		This variable defines the number of retries for
2946		network operations like ARP, RARP, TFTP, or BOOTP
2947		before giving up the operation. If not defined, a
2948		default value of 5 is used.
2949
2950		CONFIG_ARP_TIMEOUT
2951
2952		Timeout waiting for an ARP reply in milliseconds.
2953
2954		CONFIG_NFS_TIMEOUT
2955
2956		Timeout in milliseconds used in NFS protocol.
2957		If you encounter "ERROR: Cannot umount" in nfs command,
2958		try longer timeout such as
2959		#define CONFIG_NFS_TIMEOUT 10000UL
2960
2961- Command Interpreter:
2962		CONFIG_AUTO_COMPLETE
2963
2964		Enable auto completion of commands using TAB.
2965
2966		CONFIG_SYS_PROMPT_HUSH_PS2
2967
2968		This defines the secondary prompt string, which is
2969		printed when the command interpreter needs more input
2970		to complete a command. Usually "> ".
2971
2972	Note:
2973
2974		In the current implementation, the local variables
2975		space and global environment variables space are
2976		separated. Local variables are those you define by
2977		simply typing `name=value'. To access a local
2978		variable later on, you have write `$name' or
2979		`${name}'; to execute the contents of a variable
2980		directly type `$name' at the command prompt.
2981
2982		Global environment variables are those you use
2983		setenv/printenv to work with. To run a command stored
2984		in such a variable, you need to use the run command,
2985		and you must not use the '$' sign to access them.
2986
2987		To store commands and special characters in a
2988		variable, please use double quotation marks
2989		surrounding the whole text of the variable, instead
2990		of the backslashes before semicolons and special
2991		symbols.
2992
2993- Command Line Editing and History:
2994		CONFIG_CMDLINE_EDITING
2995
2996		Enable editing and History functions for interactive
2997		command line input operations
2998
2999- Default Environment:
3000		CONFIG_EXTRA_ENV_SETTINGS
3001
3002		Define this to contain any number of null terminated
3003		strings (variable = value pairs) that will be part of
3004		the default environment compiled into the boot image.
3005
3006		For example, place something like this in your
3007		board's config file:
3008
3009		#define CONFIG_EXTRA_ENV_SETTINGS \
3010			"myvar1=value1\0" \
3011			"myvar2=value2\0"
3012
3013		Warning: This method is based on knowledge about the
3014		internal format how the environment is stored by the
3015		U-Boot code. This is NOT an official, exported
3016		interface! Although it is unlikely that this format
3017		will change soon, there is no guarantee either.
3018		You better know what you are doing here.
3019
3020		Note: overly (ab)use of the default environment is
3021		discouraged. Make sure to check other ways to preset
3022		the environment like the "source" command or the
3023		boot command first.
3024
3025		CONFIG_ENV_VARS_UBOOT_CONFIG
3026
3027		Define this in order to add variables describing the
3028		U-Boot build configuration to the default environment.
3029		These will be named arch, cpu, board, vendor, and soc.
3030
3031		Enabling this option will cause the following to be defined:
3032
3033		- CONFIG_SYS_ARCH
3034		- CONFIG_SYS_CPU
3035		- CONFIG_SYS_BOARD
3036		- CONFIG_SYS_VENDOR
3037		- CONFIG_SYS_SOC
3038
3039		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
3040
3041		Define this in order to add variables describing certain
3042		run-time determined information about the hardware to the
3043		environment.  These will be named board_name, board_rev.
3044
3045		CONFIG_DELAY_ENVIRONMENT
3046
3047		Normally the environment is loaded when the board is
3048		initialised so that it is available to U-Boot. This inhibits
3049		that so that the environment is not available until
3050		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
3051		this is instead controlled by the value of
3052		/config/load-environment.
3053
3054- DataFlash Support:
3055		CONFIG_HAS_DATAFLASH
3056
3057		Defining this option enables DataFlash features and
3058		allows to read/write in Dataflash via the standard
3059		commands cp, md...
3060
3061- Serial Flash support
3062		CONFIG_CMD_SF
3063
3064		Defining this option enables SPI flash commands
3065		'sf probe/read/write/erase/update'.
3066
3067		Usage requires an initial 'probe' to define the serial
3068		flash parameters, followed by read/write/erase/update
3069		commands.
3070
3071		The following defaults may be provided by the platform
3072		to handle the common case when only a single serial
3073		flash is present on the system.
3074
3075		CONFIG_SF_DEFAULT_BUS		Bus identifier
3076		CONFIG_SF_DEFAULT_CS		Chip-select
3077		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
3078		CONFIG_SF_DEFAULT_SPEED		in Hz
3079
3080		CONFIG_CMD_SF_TEST
3081
3082		Define this option to include a destructive SPI flash
3083		test ('sf test').
3084
3085		CONFIG_SPI_FLASH_BAR		Ban/Extended Addr Reg
3086
3087		Define this option to use the Bank addr/Extended addr
3088		support on SPI flashes which has size > 16Mbytes.
3089
3090		CONFIG_SF_DUAL_FLASH		Dual flash memories
3091
3092		Define this option to use dual flash support where two flash
3093		memories can be connected with a given cs line.
3094		Currently Xilinx Zynq qspi supports these type of connections.
3095
3096		CONFIG_SYS_SPI_ST_ENABLE_WP_PIN
3097		enable the W#/Vpp signal to disable writing to the status
3098		register on ST MICRON flashes like the N25Q128.
3099		The status register write enable/disable bit, combined with
3100		the W#/VPP signal provides hardware data protection for the
3101		device as follows: When the enable/disable bit is set to 1,
3102		and the W#/VPP signal is driven LOW, the status register
3103		nonvolatile bits become read-only and the WRITE STATUS REGISTER
3104		operation will not execute. The only way to exit this
3105		hardware-protected mode is to drive W#/VPP HIGH.
3106
3107- SystemACE Support:
3108		CONFIG_SYSTEMACE
3109
3110		Adding this option adds support for Xilinx SystemACE
3111		chips attached via some sort of local bus. The address
3112		of the chip must also be defined in the
3113		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
3114
3115		#define CONFIG_SYSTEMACE
3116		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
3117
3118		When SystemACE support is added, the "ace" device type
3119		becomes available to the fat commands, i.e. fatls.
3120
3121- TFTP Fixed UDP Port:
3122		CONFIG_TFTP_PORT
3123
3124		If this is defined, the environment variable tftpsrcp
3125		is used to supply the TFTP UDP source port value.
3126		If tftpsrcp isn't defined, the normal pseudo-random port
3127		number generator is used.
3128
3129		Also, the environment variable tftpdstp is used to supply
3130		the TFTP UDP destination port value.  If tftpdstp isn't
3131		defined, the normal port 69 is used.
3132
3133		The purpose for tftpsrcp is to allow a TFTP server to
3134		blindly start the TFTP transfer using the pre-configured
3135		target IP address and UDP port. This has the effect of
3136		"punching through" the (Windows XP) firewall, allowing
3137		the remainder of the TFTP transfer to proceed normally.
3138		A better solution is to properly configure the firewall,
3139		but sometimes that is not allowed.
3140
3141- Hashing support:
3142		CONFIG_CMD_HASH
3143
3144		This enables a generic 'hash' command which can produce
3145		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
3146
3147		CONFIG_HASH_VERIFY
3148
3149		Enable the hash verify command (hash -v). This adds to code
3150		size a little.
3151
3152		CONFIG_SHA1 - support SHA1 hashing
3153		CONFIG_SHA256 - support SHA256 hashing
3154
3155		Note: There is also a sha1sum command, which should perhaps
3156		be deprecated in favour of 'hash sha1'.
3157
3158- Freescale i.MX specific commands:
3159		CONFIG_CMD_HDMIDETECT
3160		This enables 'hdmidet' command which returns true if an
3161		HDMI monitor is detected.  This command is i.MX 6 specific.
3162
3163		CONFIG_CMD_BMODE
3164		This enables the 'bmode' (bootmode) command for forcing
3165		a boot from specific media.
3166
3167		This is useful for forcing the ROM's usb downloader to
3168		activate upon a watchdog reset which is nice when iterating
3169		on U-Boot.  Using the reset button or running bmode normal
3170		will set it back to normal.  This command currently
3171		supports i.MX53 and i.MX6.
3172
3173- Signing support:
3174		CONFIG_RSA
3175
3176		This enables the RSA algorithm used for FIT image verification
3177		in U-Boot. See doc/uImage.FIT/signature.txt for more information.
3178
3179		The Modular Exponentiation algorithm in RSA is implemented using
3180		driver model. So CONFIG_DM needs to be enabled by default for this
3181		library to function.
3182
3183		The signing part is build into mkimage regardless of this
3184		option. The software based modular exponentiation is built into
3185		mkimage irrespective of this option.
3186
3187- bootcount support:
3188		CONFIG_BOOTCOUNT_LIMIT
3189
3190		This enables the bootcounter support, see:
3191		http://www.denx.de/wiki/DULG/UBootBootCountLimit
3192
3193		CONFIG_AT91SAM9XE
3194		enable special bootcounter support on at91sam9xe based boards.
3195		CONFIG_BLACKFIN
3196		enable special bootcounter support on blackfin based boards.
3197		CONFIG_SOC_DA8XX
3198		enable special bootcounter support on da850 based boards.
3199		CONFIG_BOOTCOUNT_RAM
3200		enable support for the bootcounter in RAM
3201		CONFIG_BOOTCOUNT_I2C
3202		enable support for the bootcounter on an i2c (like RTC) device.
3203			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
3204			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
3205						    the bootcounter.
3206			CONFIG_BOOTCOUNT_ALEN = address len
3207
3208- Show boot progress:
3209		CONFIG_SHOW_BOOT_PROGRESS
3210
3211		Defining this option allows to add some board-
3212		specific code (calling a user-provided function
3213		"show_boot_progress(int)") that enables you to show
3214		the system's boot progress on some display (for
3215		example, some LED's) on your board. At the moment,
3216		the following checkpoints are implemented:
3217
3218- Detailed boot stage timing
3219		CONFIG_BOOTSTAGE
3220		Define this option to get detailed timing of each stage
3221		of the boot process.
3222
3223		CONFIG_BOOTSTAGE_USER_COUNT
3224		This is the number of available user bootstage records.
3225		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
3226		a new ID will be allocated from this stash. If you exceed
3227		the limit, recording will stop.
3228
3229		CONFIG_BOOTSTAGE_REPORT
3230		Define this to print a report before boot, similar to this:
3231
3232		Timer summary in microseconds:
3233		       Mark    Elapsed  Stage
3234			  0          0  reset
3235		  3,575,678  3,575,678  board_init_f start
3236		  3,575,695         17  arch_cpu_init A9
3237		  3,575,777         82  arch_cpu_init done
3238		  3,659,598     83,821  board_init_r start
3239		  3,910,375    250,777  main_loop
3240		 29,916,167 26,005,792  bootm_start
3241		 30,361,327    445,160  start_kernel
3242
3243		CONFIG_CMD_BOOTSTAGE
3244		Add a 'bootstage' command which supports printing a report
3245		and un/stashing of bootstage data.
3246
3247		CONFIG_BOOTSTAGE_FDT
3248		Stash the bootstage information in the FDT. A root 'bootstage'
3249		node is created with each bootstage id as a child. Each child
3250		has a 'name' property and either 'mark' containing the
3251		mark time in microsecond, or 'accum' containing the
3252		accumulated time for that bootstage id in microseconds.
3253		For example:
3254
3255		bootstage {
3256			154 {
3257				name = "board_init_f";
3258				mark = <3575678>;
3259			};
3260			170 {
3261				name = "lcd";
3262				accum = <33482>;
3263			};
3264		};
3265
3266		Code in the Linux kernel can find this in /proc/devicetree.
3267
3268Legacy uImage format:
3269
3270  Arg	Where			When
3271    1	common/cmd_bootm.c	before attempting to boot an image
3272   -1	common/cmd_bootm.c	Image header has bad	 magic number
3273    2	common/cmd_bootm.c	Image header has correct magic number
3274   -2	common/cmd_bootm.c	Image header has bad	 checksum
3275    3	common/cmd_bootm.c	Image header has correct checksum
3276   -3	common/cmd_bootm.c	Image data   has bad	 checksum
3277    4	common/cmd_bootm.c	Image data   has correct checksum
3278   -4	common/cmd_bootm.c	Image is for unsupported architecture
3279    5	common/cmd_bootm.c	Architecture check OK
3280   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
3281    6	common/cmd_bootm.c	Image Type check OK
3282   -6	common/cmd_bootm.c	gunzip uncompression error
3283   -7	common/cmd_bootm.c	Unimplemented compression type
3284    7	common/cmd_bootm.c	Uncompression OK
3285    8	common/cmd_bootm.c	No uncompress/copy overwrite error
3286   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3287
3288    9	common/image.c		Start initial ramdisk verification
3289  -10	common/image.c		Ramdisk header has bad	   magic number
3290  -11	common/image.c		Ramdisk header has bad	   checksum
3291   10	common/image.c		Ramdisk header is OK
3292  -12	common/image.c		Ramdisk data   has bad	   checksum
3293   11	common/image.c		Ramdisk data   has correct checksum
3294   12	common/image.c		Ramdisk verification complete, start loading
3295  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3296   13	common/image.c		Start multifile image verification
3297   14	common/image.c		No initial ramdisk, no multifile, continue.
3298
3299   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3300
3301  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3302  -31	post/post.c		POST test failed, detected by post_output_backlog()
3303  -32	post/post.c		POST test failed, detected by post_run_single()
3304
3305   34	common/cmd_doc.c	before loading a Image from a DOC device
3306  -35	common/cmd_doc.c	Bad usage of "doc" command
3307   35	common/cmd_doc.c	correct usage of "doc" command
3308  -36	common/cmd_doc.c	No boot device
3309   36	common/cmd_doc.c	correct boot device
3310  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3311   37	common/cmd_doc.c	correct chip ID found, device available
3312  -38	common/cmd_doc.c	Read Error on boot device
3313   38	common/cmd_doc.c	reading Image header from DOC device OK
3314  -39	common/cmd_doc.c	Image header has bad magic number
3315   39	common/cmd_doc.c	Image header has correct magic number
3316  -40	common/cmd_doc.c	Error reading Image from DOC device
3317   40	common/cmd_doc.c	Image header has correct magic number
3318   41	common/cmd_ide.c	before loading a Image from a IDE device
3319  -42	common/cmd_ide.c	Bad usage of "ide" command
3320   42	common/cmd_ide.c	correct usage of "ide" command
3321  -43	common/cmd_ide.c	No boot device
3322   43	common/cmd_ide.c	boot device found
3323  -44	common/cmd_ide.c	Device not available
3324   44	common/cmd_ide.c	Device available
3325  -45	common/cmd_ide.c	wrong partition selected
3326   45	common/cmd_ide.c	partition selected
3327  -46	common/cmd_ide.c	Unknown partition table
3328   46	common/cmd_ide.c	valid partition table found
3329  -47	common/cmd_ide.c	Invalid partition type
3330   47	common/cmd_ide.c	correct partition type
3331  -48	common/cmd_ide.c	Error reading Image Header on boot device
3332   48	common/cmd_ide.c	reading Image Header from IDE device OK
3333  -49	common/cmd_ide.c	Image header has bad magic number
3334   49	common/cmd_ide.c	Image header has correct magic number
3335  -50	common/cmd_ide.c	Image header has bad	 checksum
3336   50	common/cmd_ide.c	Image header has correct checksum
3337  -51	common/cmd_ide.c	Error reading Image from IDE device
3338   51	common/cmd_ide.c	reading Image from IDE device OK
3339   52	common/cmd_nand.c	before loading a Image from a NAND device
3340  -53	common/cmd_nand.c	Bad usage of "nand" command
3341   53	common/cmd_nand.c	correct usage of "nand" command
3342  -54	common/cmd_nand.c	No boot device
3343   54	common/cmd_nand.c	boot device found
3344  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3345   55	common/cmd_nand.c	correct chip ID found, device available
3346  -56	common/cmd_nand.c	Error reading Image Header on boot device
3347   56	common/cmd_nand.c	reading Image Header from NAND device OK
3348  -57	common/cmd_nand.c	Image header has bad magic number
3349   57	common/cmd_nand.c	Image header has correct magic number
3350  -58	common/cmd_nand.c	Error reading Image from NAND device
3351   58	common/cmd_nand.c	reading Image from NAND device OK
3352
3353  -60	common/env_common.c	Environment has a bad CRC, using default
3354
3355   64	net/eth.c		starting with Ethernet configuration.
3356  -64	net/eth.c		no Ethernet found.
3357   65	net/eth.c		Ethernet found.
3358
3359  -80	common/cmd_net.c	usage wrong
3360   80	common/cmd_net.c	before calling NetLoop()
3361  -81	common/cmd_net.c	some error in NetLoop() occurred
3362   81	common/cmd_net.c	NetLoop() back without error
3363  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3364   82	common/cmd_net.c	trying automatic boot
3365   83	common/cmd_net.c	running "source" command
3366  -83	common/cmd_net.c	some error in automatic boot or "source" command
3367   84	common/cmd_net.c	end without errors
3368
3369FIT uImage format:
3370
3371  Arg	Where			When
3372  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3373 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3374  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3375 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3376  102	common/cmd_bootm.c	Kernel unit name specified
3377 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3378  103	common/cmd_bootm.c	Found configuration node
3379  104	common/cmd_bootm.c	Got kernel subimage node offset
3380 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3381  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3382 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3383  106	common/cmd_bootm.c	Architecture check OK
3384 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3385  107	common/cmd_bootm.c	Kernel subimage type OK
3386 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3387  108	common/cmd_bootm.c	Got kernel subimage data/size
3388 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3389 -109	common/cmd_bootm.c	Can't get kernel subimage type
3390 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3391 -111	common/cmd_bootm.c	Can't get kernel subimage os
3392 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3393 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3394
3395  120	common/image.c		Start initial ramdisk verification
3396 -120	common/image.c		Ramdisk FIT image has incorrect format
3397  121	common/image.c		Ramdisk FIT image has correct format
3398  122	common/image.c		No ramdisk subimage unit name, using configuration
3399 -122	common/image.c		Can't get configuration for ramdisk subimage
3400  123	common/image.c		Ramdisk unit name specified
3401 -124	common/image.c		Can't get ramdisk subimage node offset
3402  125	common/image.c		Got ramdisk subimage node offset
3403 -125	common/image.c		Ramdisk subimage hash verification failed
3404  126	common/image.c		Ramdisk subimage hash verification OK
3405 -126	common/image.c		Ramdisk subimage for unsupported architecture
3406  127	common/image.c		Architecture check OK
3407 -127	common/image.c		Can't get ramdisk subimage data/size
3408  128	common/image.c		Got ramdisk subimage data/size
3409  129	common/image.c		Can't get ramdisk load address
3410 -129	common/image.c		Got ramdisk load address
3411
3412 -130	common/cmd_doc.c	Incorrect FIT image format
3413  131	common/cmd_doc.c	FIT image format OK
3414
3415 -140	common/cmd_ide.c	Incorrect FIT image format
3416  141	common/cmd_ide.c	FIT image format OK
3417
3418 -150	common/cmd_nand.c	Incorrect FIT image format
3419  151	common/cmd_nand.c	FIT image format OK
3420
3421- legacy image format:
3422		CONFIG_IMAGE_FORMAT_LEGACY
3423		enables the legacy image format support in U-Boot.
3424
3425		Default:
3426		enabled if CONFIG_FIT_SIGNATURE is not defined.
3427
3428		CONFIG_DISABLE_IMAGE_LEGACY
3429		disable the legacy image format
3430
3431		This define is introduced, as the legacy image format is
3432		enabled per default for backward compatibility.
3433
3434- FIT image support:
3435		CONFIG_FIT
3436		Enable support for the FIT uImage format.
3437
3438		CONFIG_FIT_BEST_MATCH
3439		When no configuration is explicitly selected, default to the
3440		one whose fdt's compatibility field best matches that of
3441		U-Boot itself. A match is considered "best" if it matches the
3442		most specific compatibility entry of U-Boot's fdt's root node.
3443		The order of entries in the configuration's fdt is ignored.
3444
3445		CONFIG_FIT_SIGNATURE
3446		This option enables signature verification of FIT uImages,
3447		using a hash signed and verified using RSA. See
3448		doc/uImage.FIT/signature.txt for more details.
3449
3450		WARNING: When relying on signed FIT images with required
3451		signature check the legacy image format is default
3452		disabled. If a board need legacy image format support
3453		enable this through CONFIG_IMAGE_FORMAT_LEGACY
3454
3455		CONFIG_FIT_DISABLE_SHA256
3456		Supporting SHA256 hashes has quite an impact on binary size.
3457		For constrained systems sha256 hash support can be disabled
3458		with this option.
3459
3460- Standalone program support:
3461		CONFIG_STANDALONE_LOAD_ADDR
3462
3463		This option defines a board specific value for the
3464		address where standalone program gets loaded, thus
3465		overwriting the architecture dependent default
3466		settings.
3467
3468- Frame Buffer Address:
3469		CONFIG_FB_ADDR
3470
3471		Define CONFIG_FB_ADDR if you want to use specific
3472		address for frame buffer.  This is typically the case
3473		when using a graphics controller has separate video
3474		memory.  U-Boot will then place the frame buffer at
3475		the given address instead of dynamically reserving it
3476		in system RAM by calling lcd_setmem(), which grabs
3477		the memory for the frame buffer depending on the
3478		configured panel size.
3479
3480		Please see board_init_f function.
3481
3482- Automatic software updates via TFTP server
3483		CONFIG_UPDATE_TFTP
3484		CONFIG_UPDATE_TFTP_CNT_MAX
3485		CONFIG_UPDATE_TFTP_MSEC_MAX
3486
3487		These options enable and control the auto-update feature;
3488		for a more detailed description refer to doc/README.update.
3489
3490- MTD Support (mtdparts command, UBI support)
3491		CONFIG_MTD_DEVICE
3492
3493		Adds the MTD device infrastructure from the Linux kernel.
3494		Needed for mtdparts command support.
3495
3496		CONFIG_MTD_PARTITIONS
3497
3498		Adds the MTD partitioning infrastructure from the Linux
3499		kernel. Needed for UBI support.
3500
3501		CONFIG_MTD_NAND_VERIFY_WRITE
3502		verify if the written data is correct reread.
3503
3504- UBI support
3505		CONFIG_CMD_UBI
3506
3507		Adds commands for interacting with MTD partitions formatted
3508		with the UBI flash translation layer
3509
3510		Requires also defining CONFIG_RBTREE
3511
3512		CONFIG_UBI_SILENCE_MSG
3513
3514		Make the verbose messages from UBI stop printing.  This leaves
3515		warnings and errors enabled.
3516
3517
3518		CONFIG_MTD_UBI_WL_THRESHOLD
3519		This parameter defines the maximum difference between the highest
3520		erase counter value and the lowest erase counter value of eraseblocks
3521		of UBI devices. When this threshold is exceeded, UBI starts performing
3522		wear leveling by means of moving data from eraseblock with low erase
3523		counter to eraseblocks with high erase counter.
3524
3525		The default value should be OK for SLC NAND flashes, NOR flashes and
3526		other flashes which have eraseblock life-cycle 100000 or more.
3527		However, in case of MLC NAND flashes which typically have eraseblock
3528		life-cycle less than 10000, the threshold should be lessened (e.g.,
3529		to 128 or 256, although it does not have to be power of 2).
3530
3531		default: 4096
3532
3533		CONFIG_MTD_UBI_BEB_LIMIT
3534		This option specifies the maximum bad physical eraseblocks UBI
3535		expects on the MTD device (per 1024 eraseblocks). If the
3536		underlying flash does not admit of bad eraseblocks (e.g. NOR
3537		flash), this value is ignored.
3538
3539		NAND datasheets often specify the minimum and maximum NVM
3540		(Number of Valid Blocks) for the flashes' endurance lifetime.
3541		The maximum expected bad eraseblocks per 1024 eraseblocks
3542		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
3543		which gives 20 for most NANDs (MaxNVB is basically the total
3544		count of eraseblocks on the chip).
3545
3546		To put it differently, if this value is 20, UBI will try to
3547		reserve about 1.9% of physical eraseblocks for bad blocks
3548		handling. And that will be 1.9% of eraseblocks on the entire
3549		NAND chip, not just the MTD partition UBI attaches. This means
3550		that if you have, say, a NAND flash chip admits maximum 40 bad
3551		eraseblocks, and it is split on two MTD partitions of the same
3552		size, UBI will reserve 40 eraseblocks when attaching a
3553		partition.
3554
3555		default: 20
3556
3557		CONFIG_MTD_UBI_FASTMAP
3558		Fastmap is a mechanism which allows attaching an UBI device
3559		in nearly constant time. Instead of scanning the whole MTD device it
3560		only has to locate a checkpoint (called fastmap) on the device.
3561		The on-flash fastmap contains all information needed to attach
3562		the device. Using fastmap makes only sense on large devices where
3563		attaching by scanning takes long. UBI will not automatically install
3564		a fastmap on old images, but you can set the UBI parameter
3565		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
3566		that fastmap-enabled images are still usable with UBI implementations
3567		without	fastmap support. On typical flash devices the whole fastmap
3568		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
3569
3570		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
3571		Set this parameter to enable fastmap automatically on images
3572		without a fastmap.
3573		default: 0
3574
3575- UBIFS support
3576		CONFIG_CMD_UBIFS
3577
3578		Adds commands for interacting with UBI volumes formatted as
3579		UBIFS.  UBIFS is read-only in u-boot.
3580
3581		Requires UBI support as well as CONFIG_LZO
3582
3583		CONFIG_UBIFS_SILENCE_MSG
3584
3585		Make the verbose messages from UBIFS stop printing.  This leaves
3586		warnings and errors enabled.
3587
3588- SPL framework
3589		CONFIG_SPL
3590		Enable building of SPL globally.
3591
3592		CONFIG_SPL_LDSCRIPT
3593		LDSCRIPT for linking the SPL binary.
3594
3595		CONFIG_SPL_MAX_FOOTPRINT
3596		Maximum size in memory allocated to the SPL, BSS included.
3597		When defined, the linker checks that the actual memory
3598		used by SPL from _start to __bss_end does not exceed it.
3599		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3600		must not be both defined at the same time.
3601
3602		CONFIG_SPL_MAX_SIZE
3603		Maximum size of the SPL image (text, data, rodata, and
3604		linker lists sections), BSS excluded.
3605		When defined, the linker checks that the actual size does
3606		not exceed it.
3607
3608		CONFIG_SPL_TEXT_BASE
3609		TEXT_BASE for linking the SPL binary.
3610
3611		CONFIG_SPL_RELOC_TEXT_BASE
3612		Address to relocate to.  If unspecified, this is equal to
3613		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3614
3615		CONFIG_SPL_BSS_START_ADDR
3616		Link address for the BSS within the SPL binary.
3617
3618		CONFIG_SPL_BSS_MAX_SIZE
3619		Maximum size in memory allocated to the SPL BSS.
3620		When defined, the linker checks that the actual memory used
3621		by SPL from __bss_start to __bss_end does not exceed it.
3622		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3623		must not be both defined at the same time.
3624
3625		CONFIG_SPL_STACK
3626		Adress of the start of the stack SPL will use
3627
3628		CONFIG_SPL_RELOC_STACK
3629		Adress of the start of the stack SPL will use after
3630		relocation.  If unspecified, this is equal to
3631		CONFIG_SPL_STACK.
3632
3633		CONFIG_SYS_SPL_MALLOC_START
3634		Starting address of the malloc pool used in SPL.
3635
3636		CONFIG_SYS_SPL_MALLOC_SIZE
3637		The size of the malloc pool used in SPL.
3638
3639		CONFIG_SPL_FRAMEWORK
3640		Enable the SPL framework under common/.  This framework
3641		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3642		NAND loading of the Linux Kernel.
3643
3644		CONFIG_SPL_OS_BOOT
3645		Enable booting directly to an OS from SPL.
3646		See also: doc/README.falcon
3647
3648		CONFIG_SPL_DISPLAY_PRINT
3649		For ARM, enable an optional function to print more information
3650		about the running system.
3651
3652		CONFIG_SPL_INIT_MINIMAL
3653		Arch init code should be built for a very small image
3654
3655		CONFIG_SPL_LIBCOMMON_SUPPORT
3656		Support for common/libcommon.o in SPL binary
3657
3658		CONFIG_SPL_LIBDISK_SUPPORT
3659		Support for disk/libdisk.o in SPL binary
3660
3661		CONFIG_SPL_I2C_SUPPORT
3662		Support for drivers/i2c/libi2c.o in SPL binary
3663
3664		CONFIG_SPL_GPIO_SUPPORT
3665		Support for drivers/gpio/libgpio.o in SPL binary
3666
3667		CONFIG_SPL_MMC_SUPPORT
3668		Support for drivers/mmc/libmmc.o in SPL binary
3669
3670		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3671		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3672		Address and partition on the MMC to load U-Boot from
3673		when the MMC is being used in raw mode.
3674
3675		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3676		Partition on the MMC to load U-Boot from when the MMC is being
3677		used in raw mode
3678
3679		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3680		Sector to load kernel uImage from when MMC is being
3681		used in raw mode (for Falcon mode)
3682
3683		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3684		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3685		Sector and number of sectors to load kernel argument
3686		parameters from when MMC is being used in raw mode
3687		(for falcon mode)
3688
3689		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3690		Partition on the MMC to load U-Boot from when the MMC is being
3691		used in fs mode
3692
3693		CONFIG_SPL_FAT_SUPPORT
3694		Support for fs/fat/libfat.o in SPL binary
3695
3696		CONFIG_SPL_EXT_SUPPORT
3697		Support for EXT filesystem in SPL binary
3698
3699		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3700		Filename to read to load U-Boot when reading from filesystem
3701
3702		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3703		Filename to read to load kernel uImage when reading
3704		from filesystem (for Falcon mode)
3705
3706		CONFIG_SPL_FS_LOAD_ARGS_NAME
3707		Filename to read to load kernel argument parameters
3708		when reading from filesystem (for Falcon mode)
3709
3710		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3711		Set this for NAND SPL on PPC mpc83xx targets, so that
3712		start.S waits for the rest of the SPL to load before
3713		continuing (the hardware starts execution after just
3714		loading the first page rather than the full 4K).
3715
3716		CONFIG_SPL_SKIP_RELOCATE
3717		Avoid SPL relocation
3718
3719		CONFIG_SPL_NAND_BASE
3720		Include nand_base.c in the SPL.  Requires
3721		CONFIG_SPL_NAND_DRIVERS.
3722
3723		CONFIG_SPL_NAND_DRIVERS
3724		SPL uses normal NAND drivers, not minimal drivers.
3725
3726		CONFIG_SPL_NAND_ECC
3727		Include standard software ECC in the SPL
3728
3729		CONFIG_SPL_NAND_SIMPLE
3730		Support for NAND boot using simple NAND drivers that
3731		expose the cmd_ctrl() interface.
3732
3733		CONFIG_SPL_MTD_SUPPORT
3734		Support for the MTD subsystem within SPL.  Useful for
3735		environment on NAND support within SPL.
3736
3737		CONFIG_SPL_NAND_RAW_ONLY
3738		Support to boot only raw u-boot.bin images. Use this only
3739		if you need to save space.
3740
3741		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3742		Set for the SPL on PPC mpc8xxx targets, support for
3743		drivers/ddr/fsl/libddr.o in SPL binary.
3744
3745		CONFIG_SPL_COMMON_INIT_DDR
3746		Set for common ddr init with serial presence detect in
3747		SPL binary.
3748
3749		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3750		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3751		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3752		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3753		CONFIG_SYS_NAND_ECCBYTES
3754		Defines the size and behavior of the NAND that SPL uses
3755		to read U-Boot
3756
3757		CONFIG_SPL_NAND_BOOT
3758		Add support NAND boot
3759
3760		CONFIG_SYS_NAND_U_BOOT_OFFS
3761		Location in NAND to read U-Boot from
3762
3763		CONFIG_SYS_NAND_U_BOOT_DST
3764		Location in memory to load U-Boot to
3765
3766		CONFIG_SYS_NAND_U_BOOT_SIZE
3767		Size of image to load
3768
3769		CONFIG_SYS_NAND_U_BOOT_START
3770		Entry point in loaded image to jump to
3771
3772		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3773		Define this if you need to first read the OOB and then the
3774		data. This is used, for example, on davinci platforms.
3775
3776		CONFIG_SPL_OMAP3_ID_NAND
3777		Support for an OMAP3-specific set of functions to return the
3778		ID and MFR of the first attached NAND chip, if present.
3779
3780		CONFIG_SPL_SERIAL_SUPPORT
3781		Support for drivers/serial/libserial.o in SPL binary
3782
3783		CONFIG_SPL_SPI_FLASH_SUPPORT
3784		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3785
3786		CONFIG_SPL_SPI_SUPPORT
3787		Support for drivers/spi/libspi.o in SPL binary
3788
3789		CONFIG_SPL_RAM_DEVICE
3790		Support for running image already present in ram, in SPL binary
3791
3792		CONFIG_SPL_LIBGENERIC_SUPPORT
3793		Support for lib/libgeneric.o in SPL binary
3794
3795		CONFIG_SPL_ENV_SUPPORT
3796		Support for the environment operating in SPL binary
3797
3798		CONFIG_SPL_NET_SUPPORT
3799		Support for the net/libnet.o in SPL binary.
3800		It conflicts with SPL env from storage medium specified by
3801		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3802
3803		CONFIG_SPL_PAD_TO
3804		Image offset to which the SPL should be padded before appending
3805		the SPL payload. By default, this is defined as
3806		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3807		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3808		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3809
3810		CONFIG_SPL_TARGET
3811		Final target image containing SPL and payload.  Some SPLs
3812		use an arch-specific makefile fragment instead, for
3813		example if more than one image needs to be produced.
3814
3815		CONFIG_FIT_SPL_PRINT
3816		Printing information about a FIT image adds quite a bit of
3817		code to SPL. So this is normally disabled in SPL. Use this
3818		option to re-enable it. This will affect the output of the
3819		bootm command when booting a FIT image.
3820
3821- TPL framework
3822		CONFIG_TPL
3823		Enable building of TPL globally.
3824
3825		CONFIG_TPL_PAD_TO
3826		Image offset to which the TPL should be padded before appending
3827		the TPL payload. By default, this is defined as
3828		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3829		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3830		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3831
3832Modem Support:
3833--------------
3834
3835[so far only for SMDK2400 boards]
3836
3837- Modem support enable:
3838		CONFIG_MODEM_SUPPORT
3839
3840- RTS/CTS Flow control enable:
3841		CONFIG_HWFLOW
3842
3843- Modem debug support:
3844		CONFIG_MODEM_SUPPORT_DEBUG
3845
3846		Enables debugging stuff (char screen[1024], dbg())
3847		for modem support. Useful only with BDI2000.
3848
3849- Interrupt support (PPC):
3850
3851		There are common interrupt_init() and timer_interrupt()
3852		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3853		for CPU specific initialization. interrupt_init_cpu()
3854		should set decrementer_count to appropriate value. If
3855		CPU resets decrementer automatically after interrupt
3856		(ppc4xx) it should set decrementer_count to zero.
3857		timer_interrupt() calls timer_interrupt_cpu() for CPU
3858		specific handling. If board has watchdog / status_led
3859		/ other_activity_monitor it works automatically from
3860		general timer_interrupt().
3861
3862- General:
3863
3864		In the target system modem support is enabled when a
3865		specific key (key combination) is pressed during
3866		power-on. Otherwise U-Boot will boot normally
3867		(autoboot). The key_pressed() function is called from
3868		board_init(). Currently key_pressed() is a dummy
3869		function, returning 1 and thus enabling modem
3870		initialization.
3871
3872		If there are no modem init strings in the
3873		environment, U-Boot proceed to autoboot; the
3874		previous output (banner, info printfs) will be
3875		suppressed, though.
3876
3877		See also: doc/README.Modem
3878
3879Board initialization settings:
3880------------------------------
3881
3882During Initialization u-boot calls a number of board specific functions
3883to allow the preparation of board specific prerequisites, e.g. pin setup
3884before drivers are initialized. To enable these callbacks the
3885following configuration macros have to be defined. Currently this is
3886architecture specific, so please check arch/your_architecture/lib/board.c
3887typically in board_init_f() and board_init_r().
3888
3889- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3890- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3891- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3892- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3893
3894Configuration Settings:
3895-----------------------
3896
3897- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3898		Optionally it can be defined to support 64-bit memory commands.
3899
3900- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3901		undefine this when you're short of memory.
3902
3903- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3904		width of the commands listed in the 'help' command output.
3905
3906- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3907		prompt for user input.
3908
3909- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3910
3911- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3912
3913- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3914
3915- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3916		the application (usually a Linux kernel) when it is
3917		booted
3918
3919- CONFIG_SYS_BAUDRATE_TABLE:
3920		List of legal baudrate settings for this board.
3921
3922- CONFIG_SYS_CONSOLE_INFO_QUIET
3923		Suppress display of console information at boot.
3924
3925- CONFIG_SYS_CONSOLE_IS_IN_ENV
3926		If the board specific function
3927			extern int overwrite_console (void);
3928		returns 1, the stdin, stderr and stdout are switched to the
3929		serial port, else the settings in the environment are used.
3930
3931- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3932		Enable the call to overwrite_console().
3933
3934- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3935		Enable overwrite of previous console environment settings.
3936
3937- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3938		Begin and End addresses of the area used by the
3939		simple memory test.
3940
3941- CONFIG_SYS_ALT_MEMTEST:
3942		Enable an alternate, more extensive memory test.
3943
3944- CONFIG_SYS_MEMTEST_SCRATCH:
3945		Scratch address used by the alternate memory test
3946		You only need to set this if address zero isn't writeable
3947
3948- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3949		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3950		this specified memory area will get subtracted from the top
3951		(end) of RAM and won't get "touched" at all by U-Boot. By
3952		fixing up gd->ram_size the Linux kernel should gets passed
3953		the now "corrected" memory size and won't touch it either.
3954		This should work for arch/ppc and arch/powerpc. Only Linux
3955		board ports in arch/powerpc with bootwrapper support that
3956		recalculate the memory size from the SDRAM controller setup
3957		will have to get fixed in Linux additionally.
3958
3959		This option can be used as a workaround for the 440EPx/GRx
3960		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3961		be touched.
3962
3963		WARNING: Please make sure that this value is a multiple of
3964		the Linux page size (normally 4k). If this is not the case,
3965		then the end address of the Linux memory will be located at a
3966		non page size aligned address and this could cause major
3967		problems.
3968
3969- CONFIG_SYS_LOADS_BAUD_CHANGE:
3970		Enable temporary baudrate change while serial download
3971
3972- CONFIG_SYS_SDRAM_BASE:
3973		Physical start address of SDRAM. _Must_ be 0 here.
3974
3975- CONFIG_SYS_MBIO_BASE:
3976		Physical start address of Motherboard I/O (if using a
3977		Cogent motherboard)
3978
3979- CONFIG_SYS_FLASH_BASE:
3980		Physical start address of Flash memory.
3981
3982- CONFIG_SYS_MONITOR_BASE:
3983		Physical start address of boot monitor code (set by
3984		make config files to be same as the text base address
3985		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3986		CONFIG_SYS_FLASH_BASE when booting from flash.
3987
3988- CONFIG_SYS_MONITOR_LEN:
3989		Size of memory reserved for monitor code, used to
3990		determine _at_compile_time_ (!) if the environment is
3991		embedded within the U-Boot image, or in a separate
3992		flash sector.
3993
3994- CONFIG_SYS_MALLOC_LEN:
3995		Size of DRAM reserved for malloc() use.
3996
3997- CONFIG_SYS_MALLOC_F_LEN
3998		Size of the malloc() pool for use before relocation. If
3999		this is defined, then a very simple malloc() implementation
4000		will become available before relocation. The address is just
4001		below the global data, and the stack is moved down to make
4002		space.
4003
4004		This feature allocates regions with increasing addresses
4005		within the region. calloc() is supported, but realloc()
4006		is not available. free() is supported but does nothing.
4007		The memory will be freed (or in fact just forgotten) when
4008		U-Boot relocates itself.
4009
4010		Pre-relocation malloc() is only supported on ARM and sandbox
4011		at present but is fairly easy to enable for other archs.
4012
4013- CONFIG_SYS_MALLOC_SIMPLE
4014		Provides a simple and small malloc() and calloc() for those
4015		boards which do not use the full malloc in SPL (which is
4016		enabled with CONFIG_SYS_SPL_MALLOC_START).
4017
4018- CONFIG_SYS_NONCACHED_MEMORY:
4019		Size of non-cached memory area. This area of memory will be
4020		typically located right below the malloc() area and mapped
4021		uncached in the MMU. This is useful for drivers that would
4022		otherwise require a lot of explicit cache maintenance. For
4023		some drivers it's also impossible to properly maintain the
4024		cache. For example if the regions that need to be flushed
4025		are not a multiple of the cache-line size, *and* padding
4026		cannot be allocated between the regions to align them (i.e.
4027		if the HW requires a contiguous array of regions, and the
4028		size of each region is not cache-aligned), then a flush of
4029		one region may result in overwriting data that hardware has
4030		written to another region in the same cache-line. This can
4031		happen for example in network drivers where descriptors for
4032		buffers are typically smaller than the CPU cache-line (e.g.
4033		16 bytes vs. 32 or 64 bytes).
4034
4035		Non-cached memory is only supported on 32-bit ARM at present.
4036
4037- CONFIG_SYS_BOOTM_LEN:
4038		Normally compressed uImages are limited to an
4039		uncompressed size of 8 MBytes. If this is not enough,
4040		you can define CONFIG_SYS_BOOTM_LEN in your board config file
4041		to adjust this setting to your needs.
4042
4043- CONFIG_SYS_BOOTMAPSZ:
4044		Maximum size of memory mapped by the startup code of
4045		the Linux kernel; all data that must be processed by
4046		the Linux kernel (bd_info, boot arguments, FDT blob if
4047		used) must be put below this limit, unless "bootm_low"
4048		environment variable is defined and non-zero. In such case
4049		all data for the Linux kernel must be between "bootm_low"
4050		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
4051		variable "bootm_mapsize" will override the value of
4052		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
4053		then the value in "bootm_size" will be used instead.
4054
4055- CONFIG_SYS_BOOT_RAMDISK_HIGH:
4056		Enable initrd_high functionality.  If defined then the
4057		initrd_high feature is enabled and the bootm ramdisk subcommand
4058		is enabled.
4059
4060- CONFIG_SYS_BOOT_GET_CMDLINE:
4061		Enables allocating and saving kernel cmdline in space between
4062		"bootm_low" and "bootm_low" + BOOTMAPSZ.
4063
4064- CONFIG_SYS_BOOT_GET_KBD:
4065		Enables allocating and saving a kernel copy of the bd_info in
4066		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
4067
4068- CONFIG_SYS_MAX_FLASH_BANKS:
4069		Max number of Flash memory banks
4070
4071- CONFIG_SYS_MAX_FLASH_SECT:
4072		Max number of sectors on a Flash chip
4073
4074- CONFIG_SYS_FLASH_ERASE_TOUT:
4075		Timeout for Flash erase operations (in ms)
4076
4077- CONFIG_SYS_FLASH_WRITE_TOUT:
4078		Timeout for Flash write operations (in ms)
4079
4080- CONFIG_SYS_FLASH_LOCK_TOUT
4081		Timeout for Flash set sector lock bit operation (in ms)
4082
4083- CONFIG_SYS_FLASH_UNLOCK_TOUT
4084		Timeout for Flash clear lock bits operation (in ms)
4085
4086- CONFIG_SYS_FLASH_PROTECTION
4087		If defined, hardware flash sectors protection is used
4088		instead of U-Boot software protection.
4089
4090- CONFIG_SYS_DIRECT_FLASH_TFTP:
4091
4092		Enable TFTP transfers directly to flash memory;
4093		without this option such a download has to be
4094		performed in two steps: (1) download to RAM, and (2)
4095		copy from RAM to flash.
4096
4097		The two-step approach is usually more reliable, since
4098		you can check if the download worked before you erase
4099		the flash, but in some situations (when system RAM is
4100		too limited to allow for a temporary copy of the
4101		downloaded image) this option may be very useful.
4102
4103- CONFIG_SYS_FLASH_CFI:
4104		Define if the flash driver uses extra elements in the
4105		common flash structure for storing flash geometry.
4106
4107- CONFIG_FLASH_CFI_DRIVER
4108		This option also enables the building of the cfi_flash driver
4109		in the drivers directory
4110
4111- CONFIG_FLASH_CFI_MTD
4112		This option enables the building of the cfi_mtd driver
4113		in the drivers directory. The driver exports CFI flash
4114		to the MTD layer.
4115
4116- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
4117		Use buffered writes to flash.
4118
4119- CONFIG_FLASH_SPANSION_S29WS_N
4120		s29ws-n MirrorBit flash has non-standard addresses for buffered
4121		write commands.
4122
4123- CONFIG_SYS_FLASH_QUIET_TEST
4124		If this option is defined, the common CFI flash doesn't
4125		print it's warning upon not recognized FLASH banks. This
4126		is useful, if some of the configured banks are only
4127		optionally available.
4128
4129- CONFIG_FLASH_SHOW_PROGRESS
4130		If defined (must be an integer), print out countdown
4131		digits and dots.  Recommended value: 45 (9..1) for 80
4132		column displays, 15 (3..1) for 40 column displays.
4133
4134- CONFIG_FLASH_VERIFY
4135		If defined, the content of the flash (destination) is compared
4136		against the source after the write operation. An error message
4137		will be printed when the contents are not identical.
4138		Please note that this option is useless in nearly all cases,
4139		since such flash programming errors usually are detected earlier
4140		while unprotecting/erasing/programming. Please only enable
4141		this option if you really know what you are doing.
4142
4143- CONFIG_SYS_RX_ETH_BUFFER:
4144		Defines the number of Ethernet receive buffers. On some
4145		Ethernet controllers it is recommended to set this value
4146		to 8 or even higher (EEPRO100 or 405 EMAC), since all
4147		buffers can be full shortly after enabling the interface
4148		on high Ethernet traffic.
4149		Defaults to 4 if not defined.
4150
4151- CONFIG_ENV_MAX_ENTRIES
4152
4153	Maximum number of entries in the hash table that is used
4154	internally to store the environment settings. The default
4155	setting is supposed to be generous and should work in most
4156	cases. This setting can be used to tune behaviour; see
4157	lib/hashtable.c for details.
4158
4159- CONFIG_ENV_FLAGS_LIST_DEFAULT
4160- CONFIG_ENV_FLAGS_LIST_STATIC
4161	Enable validation of the values given to environment variables when
4162	calling env set.  Variables can be restricted to only decimal,
4163	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
4164	the variables can also be restricted to IP address or MAC address.
4165
4166	The format of the list is:
4167		type_attribute = [s|d|x|b|i|m]
4168		access_attribute = [a|r|o|c]
4169		attributes = type_attribute[access_attribute]
4170		entry = variable_name[:attributes]
4171		list = entry[,list]
4172
4173	The type attributes are:
4174		s - String (default)
4175		d - Decimal
4176		x - Hexadecimal
4177		b - Boolean ([1yYtT|0nNfF])
4178		i - IP address
4179		m - MAC address
4180
4181	The access attributes are:
4182		a - Any (default)
4183		r - Read-only
4184		o - Write-once
4185		c - Change-default
4186
4187	- CONFIG_ENV_FLAGS_LIST_DEFAULT
4188		Define this to a list (string) to define the ".flags"
4189		environment variable in the default or embedded environment.
4190
4191	- CONFIG_ENV_FLAGS_LIST_STATIC
4192		Define this to a list (string) to define validation that
4193		should be done if an entry is not found in the ".flags"
4194		environment variable.  To override a setting in the static
4195		list, simply add an entry for the same variable name to the
4196		".flags" variable.
4197
4198- CONFIG_ENV_ACCESS_IGNORE_FORCE
4199	If defined, don't allow the -f switch to env set override variable
4200	access flags.
4201
4202- CONFIG_SYS_GENERIC_BOARD
4203	This selects the architecture-generic board system instead of the
4204	architecture-specific board files. It is intended to move boards
4205	to this new framework over time. Defining this will disable the
4206	arch/foo/lib/board.c file and use common/board_f.c and
4207	common/board_r.c instead. To use this option your architecture
4208	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
4209	its config.mk file). If you find problems enabling this option on
4210	your board please report the problem and send patches!
4211
4212- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
4213	This is set by OMAP boards for the max time that reset should
4214	be asserted. See doc/README.omap-reset-time for details on how
4215	the value can be calculated on a given board.
4216
4217- CONFIG_USE_STDINT
4218	If stdint.h is available with your toolchain you can define this
4219	option to enable it. You can provide option 'USE_STDINT=1' when
4220	building U-Boot to enable this.
4221
4222The following definitions that deal with the placement and management
4223of environment data (variable area); in general, we support the
4224following configurations:
4225
4226- CONFIG_BUILD_ENVCRC:
4227
4228	Builds up envcrc with the target environment so that external utils
4229	may easily extract it and embed it in final U-Boot images.
4230
4231- CONFIG_ENV_IS_IN_FLASH:
4232
4233	Define this if the environment is in flash memory.
4234
4235	a) The environment occupies one whole flash sector, which is
4236	   "embedded" in the text segment with the U-Boot code. This
4237	   happens usually with "bottom boot sector" or "top boot
4238	   sector" type flash chips, which have several smaller
4239	   sectors at the start or the end. For instance, such a
4240	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
4241	   such a case you would place the environment in one of the
4242	   4 kB sectors - with U-Boot code before and after it. With
4243	   "top boot sector" type flash chips, you would put the
4244	   environment in one of the last sectors, leaving a gap
4245	   between U-Boot and the environment.
4246
4247	- CONFIG_ENV_OFFSET:
4248
4249	   Offset of environment data (variable area) to the
4250	   beginning of flash memory; for instance, with bottom boot
4251	   type flash chips the second sector can be used: the offset
4252	   for this sector is given here.
4253
4254	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
4255
4256	- CONFIG_ENV_ADDR:
4257
4258	   This is just another way to specify the start address of
4259	   the flash sector containing the environment (instead of
4260	   CONFIG_ENV_OFFSET).
4261
4262	- CONFIG_ENV_SECT_SIZE:
4263
4264	   Size of the sector containing the environment.
4265
4266
4267	b) Sometimes flash chips have few, equal sized, BIG sectors.
4268	   In such a case you don't want to spend a whole sector for
4269	   the environment.
4270
4271	- CONFIG_ENV_SIZE:
4272
4273	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
4274	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
4275	   of this flash sector for the environment. This saves
4276	   memory for the RAM copy of the environment.
4277
4278	   It may also save flash memory if you decide to use this
4279	   when your environment is "embedded" within U-Boot code,
4280	   since then the remainder of the flash sector could be used
4281	   for U-Boot code. It should be pointed out that this is
4282	   STRONGLY DISCOURAGED from a robustness point of view:
4283	   updating the environment in flash makes it always
4284	   necessary to erase the WHOLE sector. If something goes
4285	   wrong before the contents has been restored from a copy in
4286	   RAM, your target system will be dead.
4287
4288	- CONFIG_ENV_ADDR_REDUND
4289	  CONFIG_ENV_SIZE_REDUND
4290
4291	   These settings describe a second storage area used to hold
4292	   a redundant copy of the environment data, so that there is
4293	   a valid backup copy in case there is a power failure during
4294	   a "saveenv" operation.
4295
4296BE CAREFUL! Any changes to the flash layout, and some changes to the
4297source code will make it necessary to adapt <board>/u-boot.lds*
4298accordingly!
4299
4300
4301- CONFIG_ENV_IS_IN_NVRAM:
4302
4303	Define this if you have some non-volatile memory device
4304	(NVRAM, battery buffered SRAM) which you want to use for the
4305	environment.
4306
4307	- CONFIG_ENV_ADDR:
4308	- CONFIG_ENV_SIZE:
4309
4310	  These two #defines are used to determine the memory area you
4311	  want to use for environment. It is assumed that this memory
4312	  can just be read and written to, without any special
4313	  provision.
4314
4315BE CAREFUL! The first access to the environment happens quite early
4316in U-Boot initialization (when we try to get the setting of for the
4317console baudrate). You *MUST* have mapped your NVRAM area then, or
4318U-Boot will hang.
4319
4320Please note that even with NVRAM we still use a copy of the
4321environment in RAM: we could work on NVRAM directly, but we want to
4322keep settings there always unmodified except somebody uses "saveenv"
4323to save the current settings.
4324
4325
4326- CONFIG_ENV_IS_IN_EEPROM:
4327
4328	Use this if you have an EEPROM or similar serial access
4329	device and a driver for it.
4330
4331	- CONFIG_ENV_OFFSET:
4332	- CONFIG_ENV_SIZE:
4333
4334	  These two #defines specify the offset and size of the
4335	  environment area within the total memory of your EEPROM.
4336
4337	- CONFIG_SYS_I2C_EEPROM_ADDR:
4338	  If defined, specified the chip address of the EEPROM device.
4339	  The default address is zero.
4340
4341	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
4342	  If defined, the number of bits used to address bytes in a
4343	  single page in the EEPROM device.  A 64 byte page, for example
4344	  would require six bits.
4345
4346	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
4347	  If defined, the number of milliseconds to delay between
4348	  page writes.	The default is zero milliseconds.
4349
4350	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
4351	  The length in bytes of the EEPROM memory array address.  Note
4352	  that this is NOT the chip address length!
4353
4354	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
4355	  EEPROM chips that implement "address overflow" are ones
4356	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
4357	  address and the extra bits end up in the "chip address" bit
4358	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
4359	  byte chips.
4360
4361	  Note that we consider the length of the address field to
4362	  still be one byte because the extra address bits are hidden
4363	  in the chip address.
4364
4365	- CONFIG_SYS_EEPROM_SIZE:
4366	  The size in bytes of the EEPROM device.
4367
4368	- CONFIG_ENV_EEPROM_IS_ON_I2C
4369	  define this, if you have I2C and SPI activated, and your
4370	  EEPROM, which holds the environment, is on the I2C bus.
4371
4372	- CONFIG_I2C_ENV_EEPROM_BUS
4373	  if you have an Environment on an EEPROM reached over
4374	  I2C muxes, you can define here, how to reach this
4375	  EEPROM. For example:
4376
4377	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
4378
4379	  EEPROM which holds the environment, is reached over
4380	  a pca9547 i2c mux with address 0x70, channel 3.
4381
4382- CONFIG_ENV_IS_IN_DATAFLASH:
4383
4384	Define this if you have a DataFlash memory device which you
4385	want to use for the environment.
4386
4387	- CONFIG_ENV_OFFSET:
4388	- CONFIG_ENV_ADDR:
4389	- CONFIG_ENV_SIZE:
4390
4391	  These three #defines specify the offset and size of the
4392	  environment area within the total memory of your DataFlash placed
4393	  at the specified address.
4394
4395- CONFIG_ENV_IS_IN_SPI_FLASH:
4396
4397	Define this if you have a SPI Flash memory device which you
4398	want to use for the environment.
4399
4400	- CONFIG_ENV_OFFSET:
4401	- CONFIG_ENV_SIZE:
4402
4403	  These two #defines specify the offset and size of the
4404	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
4405	  aligned to an erase sector boundary.
4406
4407	- CONFIG_ENV_SECT_SIZE:
4408
4409	  Define the SPI flash's sector size.
4410
4411	- CONFIG_ENV_OFFSET_REDUND (optional):
4412
4413	  This setting describes a second storage area of CONFIG_ENV_SIZE
4414	  size used to hold a redundant copy of the environment data, so
4415	  that there is a valid backup copy in case there is a power failure
4416	  during a "saveenv" operation. CONFIG_ENV_OFFSET_RENDUND must be
4417	  aligned to an erase sector boundary.
4418
4419	- CONFIG_ENV_SPI_BUS (optional):
4420	- CONFIG_ENV_SPI_CS (optional):
4421
4422	  Define the SPI bus and chip select. If not defined they will be 0.
4423
4424	- CONFIG_ENV_SPI_MAX_HZ (optional):
4425
4426	  Define the SPI max work clock. If not defined then use 1MHz.
4427
4428	- CONFIG_ENV_SPI_MODE (optional):
4429
4430	  Define the SPI work mode. If not defined then use SPI_MODE_3.
4431
4432- CONFIG_ENV_IS_IN_REMOTE:
4433
4434	Define this if you have a remote memory space which you
4435	want to use for the local device's environment.
4436
4437	- CONFIG_ENV_ADDR:
4438	- CONFIG_ENV_SIZE:
4439
4440	  These two #defines specify the address and size of the
4441	  environment area within the remote memory space. The
4442	  local device can get the environment from remote memory
4443	  space by SRIO or PCIE links.
4444
4445BE CAREFUL! For some special cases, the local device can not use
4446"saveenv" command. For example, the local device will get the
4447environment stored in a remote NOR flash by SRIO or PCIE link,
4448but it can not erase, write this NOR flash by SRIO or PCIE interface.
4449
4450- CONFIG_ENV_IS_IN_NAND:
4451
4452	Define this if you have a NAND device which you want to use
4453	for the environment.
4454
4455	- CONFIG_ENV_OFFSET:
4456	- CONFIG_ENV_SIZE:
4457
4458	  These two #defines specify the offset and size of the environment
4459	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4460	  aligned to an erase block boundary.
4461
4462	- CONFIG_ENV_OFFSET_REDUND (optional):
4463
4464	  This setting describes a second storage area of CONFIG_ENV_SIZE
4465	  size used to hold a redundant copy of the environment data, so
4466	  that there is a valid backup copy in case there is a power failure
4467	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
4468	  aligned to an erase block boundary.
4469
4470	- CONFIG_ENV_RANGE (optional):
4471
4472	  Specifies the length of the region in which the environment
4473	  can be written.  This should be a multiple of the NAND device's
4474	  block size.  Specifying a range with more erase blocks than
4475	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4476	  the range to be avoided.
4477
4478	- CONFIG_ENV_OFFSET_OOB (optional):
4479
4480	  Enables support for dynamically retrieving the offset of the
4481	  environment from block zero's out-of-band data.  The
4482	  "nand env.oob" command can be used to record this offset.
4483	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4484	  using CONFIG_ENV_OFFSET_OOB.
4485
4486- CONFIG_NAND_ENV_DST
4487
4488	Defines address in RAM to which the nand_spl code should copy the
4489	environment. If redundant environment is used, it will be copied to
4490	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4491
4492- CONFIG_ENV_IS_IN_UBI:
4493
4494	Define this if you have an UBI volume that you want to use for the
4495	environment.  This has the benefit of wear-leveling the environment
4496	accesses, which is important on NAND.
4497
4498	- CONFIG_ENV_UBI_PART:
4499
4500	  Define this to a string that is the mtd partition containing the UBI.
4501
4502	- CONFIG_ENV_UBI_VOLUME:
4503
4504	  Define this to the name of the volume that you want to store the
4505	  environment in.
4506
4507	- CONFIG_ENV_UBI_VOLUME_REDUND:
4508
4509	  Define this to the name of another volume to store a second copy of
4510	  the environment in.  This will enable redundant environments in UBI.
4511	  It is assumed that both volumes are in the same MTD partition.
4512
4513	- CONFIG_UBI_SILENCE_MSG
4514	- CONFIG_UBIFS_SILENCE_MSG
4515
4516	  You will probably want to define these to avoid a really noisy system
4517	  when storing the env in UBI.
4518
4519- CONFIG_ENV_IS_IN_FAT:
4520       Define this if you want to use the FAT file system for the environment.
4521
4522       - FAT_ENV_INTERFACE:
4523
4524         Define this to a string that is the name of the block device.
4525
4526       - FAT_ENV_DEV_AND_PART:
4527
4528         Define this to a string to specify the partition of the device. It can
4529         be as following:
4530
4531           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
4532               - "D:P": device D partition P. Error occurs if device D has no
4533                        partition table.
4534               - "D:0": device D.
4535               - "D" or "D:": device D partition 1 if device D has partition
4536                              table, or the whole device D if has no partition
4537                              table.
4538               - "D:auto": first partition in device D with bootable flag set.
4539                           If none, first valid partition in device D. If no
4540                           partition table then means device D.
4541
4542       - FAT_ENV_FILE:
4543
4544         It's a string of the FAT file name. This file use to store the
4545         environment.
4546
4547       - CONFIG_FAT_WRITE:
4548         This should be defined. Otherwise it cannot save the environment file.
4549
4550- CONFIG_ENV_IS_IN_MMC:
4551
4552	Define this if you have an MMC device which you want to use for the
4553	environment.
4554
4555	- CONFIG_SYS_MMC_ENV_DEV:
4556
4557	  Specifies which MMC device the environment is stored in.
4558
4559	- CONFIG_SYS_MMC_ENV_PART (optional):
4560
4561	  Specifies which MMC partition the environment is stored in. If not
4562	  set, defaults to partition 0, the user area. Common values might be
4563	  1 (first MMC boot partition), 2 (second MMC boot partition).
4564
4565	- CONFIG_ENV_OFFSET:
4566	- CONFIG_ENV_SIZE:
4567
4568	  These two #defines specify the offset and size of the environment
4569	  area within the specified MMC device.
4570
4571	  If offset is positive (the usual case), it is treated as relative to
4572	  the start of the MMC partition. If offset is negative, it is treated
4573	  as relative to the end of the MMC partition. This can be useful if
4574	  your board may be fitted with different MMC devices, which have
4575	  different sizes for the MMC partitions, and you always want the
4576	  environment placed at the very end of the partition, to leave the
4577	  maximum possible space before it, to store other data.
4578
4579	  These two values are in units of bytes, but must be aligned to an
4580	  MMC sector boundary.
4581
4582	- CONFIG_ENV_OFFSET_REDUND (optional):
4583
4584	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4585	  hold a redundant copy of the environment data. This provides a
4586	  valid backup copy in case the other copy is corrupted, e.g. due
4587	  to a power failure during a "saveenv" operation.
4588
4589	  This value may also be positive or negative; this is handled in the
4590	  same way as CONFIG_ENV_OFFSET.
4591
4592	  This value is also in units of bytes, but must also be aligned to
4593	  an MMC sector boundary.
4594
4595	- CONFIG_ENV_SIZE_REDUND (optional):
4596
4597	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4598	  set. If this value is set, it must be set to the same value as
4599	  CONFIG_ENV_SIZE.
4600
4601- CONFIG_SYS_SPI_INIT_OFFSET
4602
4603	Defines offset to the initial SPI buffer area in DPRAM. The
4604	area is used at an early stage (ROM part) if the environment
4605	is configured to reside in the SPI EEPROM: We need a 520 byte
4606	scratch DPRAM area. It is used between the two initialization
4607	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4608	to be a good choice since it makes it far enough from the
4609	start of the data area as well as from the stack pointer.
4610
4611Please note that the environment is read-only until the monitor
4612has been relocated to RAM and a RAM copy of the environment has been
4613created; also, when using EEPROM you will have to use getenv_f()
4614until then to read environment variables.
4615
4616The environment is protected by a CRC32 checksum. Before the monitor
4617is relocated into RAM, as a result of a bad CRC you will be working
4618with the compiled-in default environment - *silently*!!! [This is
4619necessary, because the first environment variable we need is the
4620"baudrate" setting for the console - if we have a bad CRC, we don't
4621have any device yet where we could complain.]
4622
4623Note: once the monitor has been relocated, then it will complain if
4624the default environment is used; a new CRC is computed as soon as you
4625use the "saveenv" command to store a valid environment.
4626
4627- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4628		Echo the inverted Ethernet link state to the fault LED.
4629
4630		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4631		      also needs to be defined.
4632
4633- CONFIG_SYS_FAULT_MII_ADDR:
4634		MII address of the PHY to check for the Ethernet link state.
4635
4636- CONFIG_NS16550_MIN_FUNCTIONS:
4637		Define this if you desire to only have use of the NS16550_init
4638		and NS16550_putc functions for the serial driver located at
4639		drivers/serial/ns16550.c.  This option is useful for saving
4640		space for already greatly restricted images, including but not
4641		limited to NAND_SPL configurations.
4642
4643- CONFIG_DISPLAY_BOARDINFO
4644		Display information about the board that U-Boot is running on
4645		when U-Boot starts up. The board function checkboard() is called
4646		to do this.
4647
4648- CONFIG_DISPLAY_BOARDINFO_LATE
4649		Similar to the previous option, but display this information
4650		later, once stdio is running and output goes to the LCD, if
4651		present.
4652
4653- CONFIG_BOARD_SIZE_LIMIT:
4654		Maximum size of the U-Boot image. When defined, the
4655		build system checks that the actual size does not
4656		exceed it.
4657
4658Low Level (hardware related) configuration options:
4659---------------------------------------------------
4660
4661- CONFIG_SYS_CACHELINE_SIZE:
4662		Cache Line Size of the CPU.
4663
4664- CONFIG_SYS_DEFAULT_IMMR:
4665		Default address of the IMMR after system reset.
4666
4667		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4668		and RPXsuper) to be able to adjust the position of
4669		the IMMR register after a reset.
4670
4671- CONFIG_SYS_CCSRBAR_DEFAULT:
4672		Default (power-on reset) physical address of CCSR on Freescale
4673		PowerPC SOCs.
4674
4675- CONFIG_SYS_CCSRBAR:
4676		Virtual address of CCSR.  On a 32-bit build, this is typically
4677		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4678
4679		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4680		for cross-platform code that uses that macro instead.
4681
4682- CONFIG_SYS_CCSRBAR_PHYS:
4683		Physical address of CCSR.  CCSR can be relocated to a new
4684		physical address, if desired.  In this case, this macro should
4685		be set to that address.	 Otherwise, it should be set to the
4686		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4687		is typically relocated on 36-bit builds.  It is recommended
4688		that this macro be defined via the _HIGH and _LOW macros:
4689
4690		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4691			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4692
4693- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4694		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4695		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4696		used in assembly code, so it must not contain typecasts or
4697		integer size suffixes (e.g. "ULL").
4698
4699- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4700		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4701		used in assembly code, so it must not contain typecasts or
4702		integer size suffixes (e.g. "ULL").
4703
4704- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4705		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4706		forced to a value that ensures that CCSR is not relocated.
4707
4708- Floppy Disk Support:
4709		CONFIG_SYS_FDC_DRIVE_NUMBER
4710
4711		the default drive number (default value 0)
4712
4713		CONFIG_SYS_ISA_IO_STRIDE
4714
4715		defines the spacing between FDC chipset registers
4716		(default value 1)
4717
4718		CONFIG_SYS_ISA_IO_OFFSET
4719
4720		defines the offset of register from address. It
4721		depends on which part of the data bus is connected to
4722		the FDC chipset. (default value 0)
4723
4724		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4725		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4726		default value.
4727
4728		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4729		fdc_hw_init() is called at the beginning of the FDC
4730		setup. fdc_hw_init() must be provided by the board
4731		source code. It is used to make hardware-dependent
4732		initializations.
4733
4734- CONFIG_IDE_AHB:
4735		Most IDE controllers were designed to be connected with PCI
4736		interface. Only few of them were designed for AHB interface.
4737		When software is doing ATA command and data transfer to
4738		IDE devices through IDE-AHB controller, some additional
4739		registers accessing to these kind of IDE-AHB controller
4740		is required.
4741
4742- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4743		DO NOT CHANGE unless you know exactly what you're
4744		doing! (11-4) [MPC8xx/82xx systems only]
4745
4746- CONFIG_SYS_INIT_RAM_ADDR:
4747
4748		Start address of memory area that can be used for
4749		initial data and stack; please note that this must be
4750		writable memory that is working WITHOUT special
4751		initialization, i. e. you CANNOT use normal RAM which
4752		will become available only after programming the
4753		memory controller and running certain initialization
4754		sequences.
4755
4756		U-Boot uses the following memory types:
4757		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4758		- MPC824X: data cache
4759		- PPC4xx:  data cache
4760
4761- CONFIG_SYS_GBL_DATA_OFFSET:
4762
4763		Offset of the initial data structure in the memory
4764		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4765		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4766		data is located at the end of the available space
4767		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4768		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4769		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4770		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4771
4772	Note:
4773		On the MPC824X (or other systems that use the data
4774		cache for initial memory) the address chosen for
4775		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4776		point to an otherwise UNUSED address space between
4777		the top of RAM and the start of the PCI space.
4778
4779- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4780
4781- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4782
4783- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4784
4785- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4786
4787- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4788
4789- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4790
4791- CONFIG_SYS_OR_TIMING_SDRAM:
4792		SDRAM timing
4793
4794- CONFIG_SYS_MAMR_PTA:
4795		periodic timer for refresh
4796
4797- CONFIG_SYS_DER:	Debug Event Register (37-47)
4798
4799- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4800  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4801  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4802  CONFIG_SYS_BR1_PRELIM:
4803		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4804
4805- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4806  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4807  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4808		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4809
4810- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4811  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4812		Machine Mode Register and Memory Periodic Timer
4813		Prescaler definitions (SDRAM timing)
4814
4815- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4816		enable I2C microcode relocation patch (MPC8xx);
4817		define relocation offset in DPRAM [DSP2]
4818
4819- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4820		enable SMC microcode relocation patch (MPC8xx);
4821		define relocation offset in DPRAM [SMC1]
4822
4823- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4824		enable SPI microcode relocation patch (MPC8xx);
4825		define relocation offset in DPRAM [SCC4]
4826
4827- CONFIG_SYS_USE_OSCCLK:
4828		Use OSCM clock mode on MBX8xx board. Be careful,
4829		wrong setting might damage your board. Read
4830		doc/README.MBX before setting this variable!
4831
4832- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4833		Offset of the bootmode word in DPRAM used by post
4834		(Power On Self Tests). This definition overrides
4835		#define'd default value in commproc.h resp.
4836		cpm_8260.h.
4837
4838- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4839  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4840  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4841  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4842  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4843  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4844  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4845  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4846		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4847
4848- CONFIG_PCI_DISABLE_PCIE:
4849		Disable PCI-Express on systems where it is supported but not
4850		required.
4851
4852- CONFIG_PCI_ENUM_ONLY
4853		Only scan through and get the devices on the buses.
4854		Don't do any setup work, presumably because someone or
4855		something has already done it, and we don't need to do it
4856		a second time.	Useful for platforms that are pre-booted
4857		by coreboot or similar.
4858
4859- CONFIG_PCI_INDIRECT_BRIDGE:
4860		Enable support for indirect PCI bridges.
4861
4862- CONFIG_SYS_SRIO:
4863		Chip has SRIO or not
4864
4865- CONFIG_SRIO1:
4866		Board has SRIO 1 port available
4867
4868- CONFIG_SRIO2:
4869		Board has SRIO 2 port available
4870
4871- CONFIG_SRIO_PCIE_BOOT_MASTER
4872		Board can support master function for Boot from SRIO and PCIE
4873
4874- CONFIG_SYS_SRIOn_MEM_VIRT:
4875		Virtual Address of SRIO port 'n' memory region
4876
4877- CONFIG_SYS_SRIOn_MEM_PHYS:
4878		Physical Address of SRIO port 'n' memory region
4879
4880- CONFIG_SYS_SRIOn_MEM_SIZE:
4881		Size of SRIO port 'n' memory region
4882
4883- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4884		Defined to tell the NAND controller that the NAND chip is using
4885		a 16 bit bus.
4886		Not all NAND drivers use this symbol.
4887		Example of drivers that use it:
4888		- drivers/mtd/nand/ndfc.c
4889		- drivers/mtd/nand/mxc_nand.c
4890
4891- CONFIG_SYS_NDFC_EBC0_CFG
4892		Sets the EBC0_CFG register for the NDFC. If not defined
4893		a default value will be used.
4894
4895- CONFIG_SPD_EEPROM
4896		Get DDR timing information from an I2C EEPROM. Common
4897		with pluggable memory modules such as SODIMMs
4898
4899  SPD_EEPROM_ADDRESS
4900		I2C address of the SPD EEPROM
4901
4902- CONFIG_SYS_SPD_BUS_NUM
4903		If SPD EEPROM is on an I2C bus other than the first
4904		one, specify here. Note that the value must resolve
4905		to something your driver can deal with.
4906
4907- CONFIG_SYS_DDR_RAW_TIMING
4908		Get DDR timing information from other than SPD. Common with
4909		soldered DDR chips onboard without SPD. DDR raw timing
4910		parameters are extracted from datasheet and hard-coded into
4911		header files or board specific files.
4912
4913- CONFIG_FSL_DDR_INTERACTIVE
4914		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4915
4916- CONFIG_SYS_83XX_DDR_USES_CS0
4917		Only for 83xx systems. If specified, then DDR should
4918		be configured using CS0 and CS1 instead of CS2 and CS3.
4919
4920- CONFIG_ETHER_ON_FEC[12]
4921		Define to enable FEC[12] on a 8xx series processor.
4922
4923- CONFIG_FEC[12]_PHY
4924		Define to the hardcoded PHY address which corresponds
4925		to the given FEC; i. e.
4926			#define CONFIG_FEC1_PHY 4
4927		means that the PHY with address 4 is connected to FEC1
4928
4929		When set to -1, means to probe for first available.
4930
4931- CONFIG_FEC[12]_PHY_NORXERR
4932		The PHY does not have a RXERR line (RMII only).
4933		(so program the FEC to ignore it).
4934
4935- CONFIG_RMII
4936		Enable RMII mode for all FECs.
4937		Note that this is a global option, we can't
4938		have one FEC in standard MII mode and another in RMII mode.
4939
4940- CONFIG_CRC32_VERIFY
4941		Add a verify option to the crc32 command.
4942		The syntax is:
4943
4944		=> crc32 -v <address> <count> <crc32>
4945
4946		Where address/count indicate a memory area
4947		and crc32 is the correct crc32 which the
4948		area should have.
4949
4950- CONFIG_LOOPW
4951		Add the "loopw" memory command. This only takes effect if
4952		the memory commands are activated globally (CONFIG_CMD_MEM).
4953
4954- CONFIG_MX_CYCLIC
4955		Add the "mdc" and "mwc" memory commands. These are cyclic
4956		"md/mw" commands.
4957		Examples:
4958
4959		=> mdc.b 10 4 500
4960		This command will print 4 bytes (10,11,12,13) each 500 ms.
4961
4962		=> mwc.l 100 12345678 10
4963		This command will write 12345678 to address 100 all 10 ms.
4964
4965		This only takes effect if the memory commands are activated
4966		globally (CONFIG_CMD_MEM).
4967
4968- CONFIG_SKIP_LOWLEVEL_INIT
4969		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4970		low level initializations (like setting up the memory
4971		controller) are omitted and/or U-Boot does not
4972		relocate itself into RAM.
4973
4974		Normally this variable MUST NOT be defined. The only
4975		exception is when U-Boot is loaded (to RAM) by some
4976		other boot loader or by a debugger which performs
4977		these initializations itself.
4978
4979- CONFIG_SPL_BUILD
4980		Modifies the behaviour of start.S when compiling a loader
4981		that is executed before the actual U-Boot. E.g. when
4982		compiling a NAND SPL.
4983
4984- CONFIG_TPL_BUILD
4985		Modifies the behaviour of start.S  when compiling a loader
4986		that is executed after the SPL and before the actual U-Boot.
4987		It is loaded by the SPL.
4988
4989- CONFIG_SYS_MPC85XX_NO_RESETVEC
4990		Only for 85xx systems. If this variable is specified, the section
4991		.resetvec is not kept and the section .bootpg is placed in the
4992		previous 4k of the .text section.
4993
4994- CONFIG_ARCH_MAP_SYSMEM
4995		Generally U-Boot (and in particular the md command) uses
4996		effective address. It is therefore not necessary to regard
4997		U-Boot address as virtual addresses that need to be translated
4998		to physical addresses. However, sandbox requires this, since
4999		it maintains its own little RAM buffer which contains all
5000		addressable memory. This option causes some memory accesses
5001		to be mapped through map_sysmem() / unmap_sysmem().
5002
5003- CONFIG_USE_ARCH_MEMCPY
5004  CONFIG_USE_ARCH_MEMSET
5005		If these options are used a optimized version of memcpy/memset will
5006		be used if available. These functions may be faster under some
5007		conditions but may increase the binary size.
5008
5009- CONFIG_X86_RESET_VECTOR
5010		If defined, the x86 reset vector code is included. This is not
5011		needed when U-Boot is running from Coreboot.
5012
5013- CONFIG_SYS_MPUCLK
5014		Defines the MPU clock speed (in MHz).
5015
5016		NOTE : currently only supported on AM335x platforms.
5017
5018- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
5019		Enables the RTC32K OSC on AM33xx based plattforms
5020
5021- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
5022		Option to disable subpage write in NAND driver
5023		driver that uses this:
5024		drivers/mtd/nand/davinci_nand.c
5025
5026Freescale QE/FMAN Firmware Support:
5027-----------------------------------
5028
5029The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
5030loading of "firmware", which is encoded in the QE firmware binary format.
5031This firmware often needs to be loaded during U-Boot booting, so macros
5032are used to identify the storage device (NOR flash, SPI, etc) and the address
5033within that device.
5034
5035- CONFIG_SYS_FMAN_FW_ADDR
5036	The address in the storage device where the FMAN microcode is located.  The
5037	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
5038	is also specified.
5039
5040- CONFIG_SYS_QE_FW_ADDR
5041	The address in the storage device where the QE microcode is located.  The
5042	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
5043	is also specified.
5044
5045- CONFIG_SYS_QE_FMAN_FW_LENGTH
5046	The maximum possible size of the firmware.  The firmware binary format
5047	has a field that specifies the actual size of the firmware, but it
5048	might not be possible to read any part of the firmware unless some
5049	local storage is allocated to hold the entire firmware first.
5050
5051- CONFIG_SYS_QE_FMAN_FW_IN_NOR
5052	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
5053	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
5054	virtual address in NOR flash.
5055
5056- CONFIG_SYS_QE_FMAN_FW_IN_NAND
5057	Specifies that QE/FMAN firmware is located in NAND flash.
5058	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
5059
5060- CONFIG_SYS_QE_FMAN_FW_IN_MMC
5061	Specifies that QE/FMAN firmware is located on the primary SD/MMC
5062	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
5063
5064- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
5065	Specifies that QE/FMAN firmware is located on the primary SPI
5066	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
5067
5068- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
5069	Specifies that QE/FMAN firmware is located in the remote (master)
5070	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
5071	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
5072	window->master inbound window->master LAW->the ucode address in
5073	master's memory space.
5074
5075Freescale Layerscape Management Complex Firmware Support:
5076---------------------------------------------------------
5077The Freescale Layerscape Management Complex (MC) supports the loading of
5078"firmware".
5079This firmware often needs to be loaded during U-Boot booting, so macros
5080are used to identify the storage device (NOR flash, SPI, etc) and the address
5081within that device.
5082
5083- CONFIG_FSL_MC_ENET
5084	Enable the MC driver for Layerscape SoCs.
5085
5086- CONFIG_SYS_LS_MC_FW_ADDR
5087	The address in the storage device where the firmware is located.  The
5088	meaning of this address depends on which CONFIG_SYS_LS_MC_FW_IN_xxx macro
5089	is also specified.
5090
5091- CONFIG_SYS_LS_MC_FW_LENGTH
5092	The maximum possible size of the firmware.  The firmware binary format
5093	has a field that specifies the actual size of the firmware, but it
5094	might not be possible to read any part of the firmware unless some
5095	local storage is allocated to hold the entire firmware first.
5096
5097- CONFIG_SYS_LS_MC_FW_IN_NOR
5098	Specifies that MC firmware is located in NOR flash, mapped as
5099	normal addressable memory via the LBC. CONFIG_SYS_LS_MC_FW_ADDR is the
5100	virtual address in NOR flash.
5101
5102Building the Software:
5103======================
5104
5105Building U-Boot has been tested in several native build environments
5106and in many different cross environments. Of course we cannot support
5107all possibly existing versions of cross development tools in all
5108(potentially obsolete) versions. In case of tool chain problems we
5109recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
5110which is extensively used to build and test U-Boot.
5111
5112If you are not using a native environment, it is assumed that you
5113have GNU cross compiling tools available in your path. In this case,
5114you must set the environment variable CROSS_COMPILE in your shell.
5115Note that no changes to the Makefile or any other source files are
5116necessary. For example using the ELDK on a 4xx CPU, please enter:
5117
5118	$ CROSS_COMPILE=ppc_4xx-
5119	$ export CROSS_COMPILE
5120
5121Note: If you wish to generate Windows versions of the utilities in
5122      the tools directory you can use the MinGW toolchain
5123      (http://www.mingw.org).  Set your HOST tools to the MinGW
5124      toolchain and execute 'make tools'.  For example:
5125
5126       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
5127
5128      Binaries such as tools/mkimage.exe will be created which can
5129      be executed on computers running Windows.
5130
5131U-Boot is intended to be simple to build. After installing the
5132sources you must configure U-Boot for one specific board type. This
5133is done by typing:
5134
5135	make NAME_defconfig
5136
5137where "NAME_defconfig" is the name of one of the existing configu-
5138rations; see boards.cfg for supported names.
5139
5140Note: for some board special configuration names may exist; check if
5141      additional information is available from the board vendor; for
5142      instance, the TQM823L systems are available without (standard)
5143      or with LCD support. You can select such additional "features"
5144      when choosing the configuration, i. e.
5145
5146      make TQM823L_defconfig
5147	- will configure for a plain TQM823L, i. e. no LCD support
5148
5149      make TQM823L_LCD_defconfig
5150	- will configure for a TQM823L with U-Boot console on LCD
5151
5152      etc.
5153
5154
5155Finally, type "make all", and you should get some working U-Boot
5156images ready for download to / installation on your system:
5157
5158- "u-boot.bin" is a raw binary image
5159- "u-boot" is an image in ELF binary format
5160- "u-boot.srec" is in Motorola S-Record format
5161
5162By default the build is performed locally and the objects are saved
5163in the source directory. One of the two methods can be used to change
5164this behavior and build U-Boot to some external directory:
5165
51661. Add O= to the make command line invocations:
5167
5168	make O=/tmp/build distclean
5169	make O=/tmp/build NAME_defconfig
5170	make O=/tmp/build all
5171
51722. Set environment variable KBUILD_OUTPUT to point to the desired location:
5173
5174	export KBUILD_OUTPUT=/tmp/build
5175	make distclean
5176	make NAME_defconfig
5177	make all
5178
5179Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
5180variable.
5181
5182
5183Please be aware that the Makefiles assume you are using GNU make, so
5184for instance on NetBSD you might need to use "gmake" instead of
5185native "make".
5186
5187
5188If the system board that you have is not listed, then you will need
5189to port U-Boot to your hardware platform. To do this, follow these
5190steps:
5191
51921.  Add a new configuration option for your board to the toplevel
5193    "boards.cfg" file, using the existing entries as examples.
5194    Follow the instructions there to keep the boards in order.
51952.  Create a new directory to hold your board specific code. Add any
5196    files you need. In your board directory, you will need at least
5197    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
51983.  Create a new configuration file "include/configs/<board>.h" for
5199    your board
52003.  If you're porting U-Boot to a new CPU, then also create a new
5201    directory to hold your CPU specific code. Add any files you need.
52024.  Run "make <board>_defconfig" with your new name.
52035.  Type "make", and you should get a working "u-boot.srec" file
5204    to be installed on your target system.
52056.  Debug and solve any problems that might arise.
5206    [Of course, this last step is much harder than it sounds.]
5207
5208
5209Testing of U-Boot Modifications, Ports to New Hardware, etc.:
5210==============================================================
5211
5212If you have modified U-Boot sources (for instance added a new board
5213or support for new devices, a new CPU, etc.) you are expected to
5214provide feedback to the other developers. The feedback normally takes
5215the form of a "patch", i. e. a context diff against a certain (latest
5216official or latest in the git repository) version of U-Boot sources.
5217
5218But before you submit such a patch, please verify that your modifi-
5219cation did not break existing code. At least make sure that *ALL* of
5220the supported boards compile WITHOUT ANY compiler warnings. To do so,
5221just run the "MAKEALL" script, which will configure and build U-Boot
5222for ALL supported system. Be warned, this will take a while. You can
5223select which (cross) compiler to use by passing a `CROSS_COMPILE'
5224environment variable to the script, i. e. to use the ELDK cross tools
5225you can type
5226
5227	CROSS_COMPILE=ppc_8xx- MAKEALL
5228
5229or to build on a native PowerPC system you can type
5230
5231	CROSS_COMPILE=' ' MAKEALL
5232
5233When using the MAKEALL script, the default behaviour is to build
5234U-Boot in the source directory. This location can be changed by
5235setting the BUILD_DIR environment variable. Also, for each target
5236built, the MAKEALL script saves two log files (<target>.ERR and
5237<target>.MAKEALL) in the <source dir>/LOG directory. This default
5238location can be changed by setting the MAKEALL_LOGDIR environment
5239variable. For example:
5240
5241	export BUILD_DIR=/tmp/build
5242	export MAKEALL_LOGDIR=/tmp/log
5243	CROSS_COMPILE=ppc_8xx- MAKEALL
5244
5245With the above settings build objects are saved in the /tmp/build,
5246log files are saved in the /tmp/log and the source tree remains clean
5247during the whole build process.
5248
5249
5250See also "U-Boot Porting Guide" below.
5251
5252
5253Monitor Commands - Overview:
5254============================
5255
5256go	- start application at address 'addr'
5257run	- run commands in an environment variable
5258bootm	- boot application image from memory
5259bootp	- boot image via network using BootP/TFTP protocol
5260bootz   - boot zImage from memory
5261tftpboot- boot image via network using TFTP protocol
5262	       and env variables "ipaddr" and "serverip"
5263	       (and eventually "gatewayip")
5264tftpput - upload a file via network using TFTP protocol
5265rarpboot- boot image via network using RARP/TFTP protocol
5266diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
5267loads	- load S-Record file over serial line
5268loadb	- load binary file over serial line (kermit mode)
5269md	- memory display
5270mm	- memory modify (auto-incrementing)
5271nm	- memory modify (constant address)
5272mw	- memory write (fill)
5273cp	- memory copy
5274cmp	- memory compare
5275crc32	- checksum calculation
5276i2c	- I2C sub-system
5277sspi	- SPI utility commands
5278base	- print or set address offset
5279printenv- print environment variables
5280setenv	- set environment variables
5281saveenv - save environment variables to persistent storage
5282protect - enable or disable FLASH write protection
5283erase	- erase FLASH memory
5284flinfo	- print FLASH memory information
5285nand	- NAND memory operations (see doc/README.nand)
5286bdinfo	- print Board Info structure
5287iminfo	- print header information for application image
5288coninfo - print console devices and informations
5289ide	- IDE sub-system
5290loop	- infinite loop on address range
5291loopw	- infinite write loop on address range
5292mtest	- simple RAM test
5293icache	- enable or disable instruction cache
5294dcache	- enable or disable data cache
5295reset	- Perform RESET of the CPU
5296echo	- echo args to console
5297version - print monitor version
5298help	- print online help
5299?	- alias for 'help'
5300
5301
5302Monitor Commands - Detailed Description:
5303========================================
5304
5305TODO.
5306
5307For now: just type "help <command>".
5308
5309
5310Environment Variables:
5311======================
5312
5313U-Boot supports user configuration using Environment Variables which
5314can be made persistent by saving to Flash memory.
5315
5316Environment Variables are set using "setenv", printed using
5317"printenv", and saved to Flash using "saveenv". Using "setenv"
5318without a value can be used to delete a variable from the
5319environment. As long as you don't save the environment you are
5320working with an in-memory copy. In case the Flash area containing the
5321environment is erased by accident, a default environment is provided.
5322
5323Some configuration options can be set using Environment Variables.
5324
5325List of environment variables (most likely not complete):
5326
5327  baudrate	- see CONFIG_BAUDRATE
5328
5329  bootdelay	- see CONFIG_BOOTDELAY
5330
5331  bootcmd	- see CONFIG_BOOTCOMMAND
5332
5333  bootargs	- Boot arguments when booting an RTOS image
5334
5335  bootfile	- Name of the image to load with TFTP
5336
5337  bootm_low	- Memory range available for image processing in the bootm
5338		  command can be restricted. This variable is given as
5339		  a hexadecimal number and defines lowest address allowed
5340		  for use by the bootm command. See also "bootm_size"
5341		  environment variable. Address defined by "bootm_low" is
5342		  also the base of the initial memory mapping for the Linux
5343		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
5344		  bootm_mapsize.
5345
5346  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
5347		  This variable is given as a hexadecimal number and it
5348		  defines the size of the memory region starting at base
5349		  address bootm_low that is accessible by the Linux kernel
5350		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
5351		  as the default value if it is defined, and bootm_size is
5352		  used otherwise.
5353
5354  bootm_size	- Memory range available for image processing in the bootm
5355		  command can be restricted. This variable is given as
5356		  a hexadecimal number and defines the size of the region
5357		  allowed for use by the bootm command. See also "bootm_low"
5358		  environment variable.
5359
5360  updatefile	- Location of the software update file on a TFTP server, used
5361		  by the automatic software update feature. Please refer to
5362		  documentation in doc/README.update for more details.
5363
5364  autoload	- if set to "no" (any string beginning with 'n'),
5365		  "bootp" will just load perform a lookup of the
5366		  configuration from the BOOTP server, but not try to
5367		  load any image using TFTP
5368
5369  autostart	- if set to "yes", an image loaded using the "bootp",
5370		  "rarpboot", "tftpboot" or "diskboot" commands will
5371		  be automatically started (by internally calling
5372		  "bootm")
5373
5374		  If set to "no", a standalone image passed to the
5375		  "bootm" command will be copied to the load address
5376		  (and eventually uncompressed), but NOT be started.
5377		  This can be used to load and uncompress arbitrary
5378		  data.
5379
5380  fdt_high	- if set this restricts the maximum address that the
5381		  flattened device tree will be copied into upon boot.
5382		  For example, if you have a system with 1 GB memory
5383		  at physical address 0x10000000, while Linux kernel
5384		  only recognizes the first 704 MB as low memory, you
5385		  may need to set fdt_high as 0x3C000000 to have the
5386		  device tree blob be copied to the maximum address
5387		  of the 704 MB low memory, so that Linux kernel can
5388		  access it during the boot procedure.
5389
5390		  If this is set to the special value 0xFFFFFFFF then
5391		  the fdt will not be copied at all on boot.  For this
5392		  to work it must reside in writable memory, have
5393		  sufficient padding on the end of it for u-boot to
5394		  add the information it needs into it, and the memory
5395		  must be accessible by the kernel.
5396
5397  fdtcontroladdr- if set this is the address of the control flattened
5398		  device tree used by U-Boot when CONFIG_OF_CONTROL is
5399		  defined.
5400
5401  i2cfast	- (PPC405GP|PPC405EP only)
5402		  if set to 'y' configures Linux I2C driver for fast
5403		  mode (400kHZ). This environment variable is used in
5404		  initialization code. So, for changes to be effective
5405		  it must be saved and board must be reset.
5406
5407  initrd_high	- restrict positioning of initrd images:
5408		  If this variable is not set, initrd images will be
5409		  copied to the highest possible address in RAM; this
5410		  is usually what you want since it allows for
5411		  maximum initrd size. If for some reason you want to
5412		  make sure that the initrd image is loaded below the
5413		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
5414		  variable to a value of "no" or "off" or "0".
5415		  Alternatively, you can set it to a maximum upper
5416		  address to use (U-Boot will still check that it
5417		  does not overwrite the U-Boot stack and data).
5418
5419		  For instance, when you have a system with 16 MB
5420		  RAM, and want to reserve 4 MB from use by Linux,
5421		  you can do this by adding "mem=12M" to the value of
5422		  the "bootargs" variable. However, now you must make
5423		  sure that the initrd image is placed in the first
5424		  12 MB as well - this can be done with
5425
5426		  setenv initrd_high 00c00000
5427
5428		  If you set initrd_high to 0xFFFFFFFF, this is an
5429		  indication to U-Boot that all addresses are legal
5430		  for the Linux kernel, including addresses in flash
5431		  memory. In this case U-Boot will NOT COPY the
5432		  ramdisk at all. This may be useful to reduce the
5433		  boot time on your system, but requires that this
5434		  feature is supported by your Linux kernel.
5435
5436  ipaddr	- IP address; needed for tftpboot command
5437
5438  loadaddr	- Default load address for commands like "bootp",
5439		  "rarpboot", "tftpboot", "loadb" or "diskboot"
5440
5441  loads_echo	- see CONFIG_LOADS_ECHO
5442
5443  serverip	- TFTP server IP address; needed for tftpboot command
5444
5445  bootretry	- see CONFIG_BOOT_RETRY_TIME
5446
5447  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
5448
5449  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
5450
5451  ethprime	- controls which interface is used first.
5452
5453  ethact	- controls which interface is currently active.
5454		  For example you can do the following
5455
5456		  => setenv ethact FEC
5457		  => ping 192.168.0.1 # traffic sent on FEC
5458		  => setenv ethact SCC
5459		  => ping 10.0.0.1 # traffic sent on SCC
5460
5461  ethrotate	- When set to "no" U-Boot does not go through all
5462		  available network interfaces.
5463		  It just stays at the currently selected interface.
5464
5465  netretry	- When set to "no" each network operation will
5466		  either succeed or fail without retrying.
5467		  When set to "once" the network operation will
5468		  fail when all the available network interfaces
5469		  are tried once without success.
5470		  Useful on scripts which control the retry operation
5471		  themselves.
5472
5473  npe_ucode	- set load address for the NPE microcode
5474
5475  silent_linux  - If set then Linux will be told to boot silently, by
5476		  changing the console to be empty. If "yes" it will be
5477		  made silent. If "no" it will not be made silent. If
5478		  unset, then it will be made silent if the U-Boot console
5479		  is silent.
5480
5481  tftpsrcport	- If this is set, the value is used for TFTP's
5482		  UDP source port.
5483
5484  tftpdstport	- If this is set, the value is used for TFTP's UDP
5485		  destination port instead of the Well Know Port 69.
5486
5487  tftpblocksize - Block size to use for TFTP transfers; if not set,
5488		  we use the TFTP server's default block size
5489
5490  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
5491		  seconds, minimum value is 1000 = 1 second). Defines
5492		  when a packet is considered to be lost so it has to
5493		  be retransmitted. The default is 5000 = 5 seconds.
5494		  Lowering this value may make downloads succeed
5495		  faster in networks with high packet loss rates or
5496		  with unreliable TFTP servers.
5497
5498  vlan		- When set to a value < 4095 the traffic over
5499		  Ethernet is encapsulated/received over 802.1q
5500		  VLAN tagged frames.
5501
5502The following image location variables contain the location of images
5503used in booting. The "Image" column gives the role of the image and is
5504not an environment variable name. The other columns are environment
5505variable names. "File Name" gives the name of the file on a TFTP
5506server, "RAM Address" gives the location in RAM the image will be
5507loaded to, and "Flash Location" gives the image's address in NOR
5508flash or offset in NAND flash.
5509
5510*Note* - these variables don't have to be defined for all boards, some
5511boards currenlty use other variables for these purposes, and some
5512boards use these variables for other purposes.
5513
5514Image		    File Name	     RAM Address       Flash Location
5515-----		    ---------	     -----------       --------------
5516u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
5517Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
5518device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
5519ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
5520
5521The following environment variables may be used and automatically
5522updated by the network boot commands ("bootp" and "rarpboot"),
5523depending the information provided by your boot server:
5524
5525  bootfile	- see above
5526  dnsip		- IP address of your Domain Name Server
5527  dnsip2	- IP address of your secondary Domain Name Server
5528  gatewayip	- IP address of the Gateway (Router) to use
5529  hostname	- Target hostname
5530  ipaddr	- see above
5531  netmask	- Subnet Mask
5532  rootpath	- Pathname of the root filesystem on the NFS server
5533  serverip	- see above
5534
5535
5536There are two special Environment Variables:
5537
5538  serial#	- contains hardware identification information such
5539		  as type string and/or serial number
5540  ethaddr	- Ethernet address
5541
5542These variables can be set only once (usually during manufacturing of
5543the board). U-Boot refuses to delete or overwrite these variables
5544once they have been set once.
5545
5546
5547Further special Environment Variables:
5548
5549  ver		- Contains the U-Boot version string as printed
5550		  with the "version" command. This variable is
5551		  readonly (see CONFIG_VERSION_VARIABLE).
5552
5553
5554Please note that changes to some configuration parameters may take
5555only effect after the next boot (yes, that's just like Windoze :-).
5556
5557
5558Callback functions for environment variables:
5559---------------------------------------------
5560
5561For some environment variables, the behavior of u-boot needs to change
5562when their values are changed.  This functionality allows functions to
5563be associated with arbitrary variables.  On creation, overwrite, or
5564deletion, the callback will provide the opportunity for some side
5565effect to happen or for the change to be rejected.
5566
5567The callbacks are named and associated with a function using the
5568U_BOOT_ENV_CALLBACK macro in your board or driver code.
5569
5570These callbacks are associated with variables in one of two ways.  The
5571static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5572in the board configuration to a string that defines a list of
5573associations.  The list must be in the following format:
5574
5575	entry = variable_name[:callback_name]
5576	list = entry[,list]
5577
5578If the callback name is not specified, then the callback is deleted.
5579Spaces are also allowed anywhere in the list.
5580
5581Callbacks can also be associated by defining the ".callbacks" variable
5582with the same list format above.  Any association in ".callbacks" will
5583override any association in the static list. You can define
5584CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5585".callbacks" environment variable in the default or embedded environment.
5586
5587
5588Command Line Parsing:
5589=====================
5590
5591There are two different command line parsers available with U-Boot:
5592the old "simple" one, and the much more powerful "hush" shell:
5593
5594Old, simple command line parser:
5595--------------------------------
5596
5597- supports environment variables (through setenv / saveenv commands)
5598- several commands on one line, separated by ';'
5599- variable substitution using "... ${name} ..." syntax
5600- special characters ('$', ';') can be escaped by prefixing with '\',
5601  for example:
5602	setenv bootcmd bootm \${address}
5603- You can also escape text by enclosing in single apostrophes, for example:
5604	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5605
5606Hush shell:
5607-----------
5608
5609- similar to Bourne shell, with control structures like
5610  if...then...else...fi, for...do...done; while...do...done,
5611  until...do...done, ...
5612- supports environment ("global") variables (through setenv / saveenv
5613  commands) and local shell variables (through standard shell syntax
5614  "name=value"); only environment variables can be used with "run"
5615  command
5616
5617General rules:
5618--------------
5619
5620(1) If a command line (or an environment variable executed by a "run"
5621    command) contains several commands separated by semicolon, and
5622    one of these commands fails, then the remaining commands will be
5623    executed anyway.
5624
5625(2) If you execute several variables with one call to run (i. e.
5626    calling run with a list of variables as arguments), any failing
5627    command will cause "run" to terminate, i. e. the remaining
5628    variables are not executed.
5629
5630Note for Redundant Ethernet Interfaces:
5631=======================================
5632
5633Some boards come with redundant Ethernet interfaces; U-Boot supports
5634such configurations and is capable of automatic selection of a
5635"working" interface when needed. MAC assignment works as follows:
5636
5637Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5638MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5639"eth1addr" (=>eth1), "eth2addr", ...
5640
5641If the network interface stores some valid MAC address (for instance
5642in SROM), this is used as default address if there is NO correspon-
5643ding setting in the environment; if the corresponding environment
5644variable is set, this overrides the settings in the card; that means:
5645
5646o If the SROM has a valid MAC address, and there is no address in the
5647  environment, the SROM's address is used.
5648
5649o If there is no valid address in the SROM, and a definition in the
5650  environment exists, then the value from the environment variable is
5651  used.
5652
5653o If both the SROM and the environment contain a MAC address, and
5654  both addresses are the same, this MAC address is used.
5655
5656o If both the SROM and the environment contain a MAC address, and the
5657  addresses differ, the value from the environment is used and a
5658  warning is printed.
5659
5660o If neither SROM nor the environment contain a MAC address, an error
5661  is raised.
5662
5663If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5664will be programmed into hardware as part of the initialization process.	 This
5665may be skipped by setting the appropriate 'ethmacskip' environment variable.
5666The naming convention is as follows:
5667"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5668
5669Image Formats:
5670==============
5671
5672U-Boot is capable of booting (and performing other auxiliary operations on)
5673images in two formats:
5674
5675New uImage format (FIT)
5676-----------------------
5677
5678Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5679to Flattened Device Tree). It allows the use of images with multiple
5680components (several kernels, ramdisks, etc.), with contents protected by
5681SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5682
5683
5684Old uImage format
5685-----------------
5686
5687Old image format is based on binary files which can be basically anything,
5688preceded by a special header; see the definitions in include/image.h for
5689details; basically, the header defines the following image properties:
5690
5691* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5692  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5693  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5694  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5695  INTEGRITY).
5696* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5697  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5698  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5699* Compression Type (uncompressed, gzip, bzip2)
5700* Load Address
5701* Entry Point
5702* Image Name
5703* Image Timestamp
5704
5705The header is marked by a special Magic Number, and both the header
5706and the data portions of the image are secured against corruption by
5707CRC32 checksums.
5708
5709
5710Linux Support:
5711==============
5712
5713Although U-Boot should support any OS or standalone application
5714easily, the main focus has always been on Linux during the design of
5715U-Boot.
5716
5717U-Boot includes many features that so far have been part of some
5718special "boot loader" code within the Linux kernel. Also, any
5719"initrd" images to be used are no longer part of one big Linux image;
5720instead, kernel and "initrd" are separate images. This implementation
5721serves several purposes:
5722
5723- the same features can be used for other OS or standalone
5724  applications (for instance: using compressed images to reduce the
5725  Flash memory footprint)
5726
5727- it becomes much easier to port new Linux kernel versions because
5728  lots of low-level, hardware dependent stuff are done by U-Boot
5729
5730- the same Linux kernel image can now be used with different "initrd"
5731  images; of course this also means that different kernel images can
5732  be run with the same "initrd". This makes testing easier (you don't
5733  have to build a new "zImage.initrd" Linux image when you just
5734  change a file in your "initrd"). Also, a field-upgrade of the
5735  software is easier now.
5736
5737
5738Linux HOWTO:
5739============
5740
5741Porting Linux to U-Boot based systems:
5742---------------------------------------
5743
5744U-Boot cannot save you from doing all the necessary modifications to
5745configure the Linux device drivers for use with your target hardware
5746(no, we don't intend to provide a full virtual machine interface to
5747Linux :-).
5748
5749But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5750
5751Just make sure your machine specific header file (for instance
5752include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5753Information structure as we define in include/asm-<arch>/u-boot.h,
5754and make sure that your definition of IMAP_ADDR uses the same value
5755as your U-Boot configuration in CONFIG_SYS_IMMR.
5756
5757Note that U-Boot now has a driver model, a unified model for drivers.
5758If you are adding a new driver, plumb it into driver model. If there
5759is no uclass available, you are encouraged to create one. See
5760doc/driver-model.
5761
5762
5763Configuring the Linux kernel:
5764-----------------------------
5765
5766No specific requirements for U-Boot. Make sure you have some root
5767device (initial ramdisk, NFS) for your target system.
5768
5769
5770Building a Linux Image:
5771-----------------------
5772
5773With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5774not used. If you use recent kernel source, a new build target
5775"uImage" will exist which automatically builds an image usable by
5776U-Boot. Most older kernels also have support for a "pImage" target,
5777which was introduced for our predecessor project PPCBoot and uses a
5778100% compatible format.
5779
5780Example:
5781
5782	make TQM850L_defconfig
5783	make oldconfig
5784	make dep
5785	make uImage
5786
5787The "uImage" build target uses a special tool (in 'tools/mkimage') to
5788encapsulate a compressed Linux kernel image with header	 information,
5789CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5790
5791* build a standard "vmlinux" kernel image (in ELF binary format):
5792
5793* convert the kernel into a raw binary image:
5794
5795	${CROSS_COMPILE}-objcopy -O binary \
5796				 -R .note -R .comment \
5797				 -S vmlinux linux.bin
5798
5799* compress the binary image:
5800
5801	gzip -9 linux.bin
5802
5803* package compressed binary image for U-Boot:
5804
5805	mkimage -A ppc -O linux -T kernel -C gzip \
5806		-a 0 -e 0 -n "Linux Kernel Image" \
5807		-d linux.bin.gz uImage
5808
5809
5810The "mkimage" tool can also be used to create ramdisk images for use
5811with U-Boot, either separated from the Linux kernel image, or
5812combined into one file. "mkimage" encapsulates the images with a 64
5813byte header containing information about target architecture,
5814operating system, image type, compression method, entry points, time
5815stamp, CRC32 checksums, etc.
5816
5817"mkimage" can be called in two ways: to verify existing images and
5818print the header information, or to build new images.
5819
5820In the first form (with "-l" option) mkimage lists the information
5821contained in the header of an existing U-Boot image; this includes
5822checksum verification:
5823
5824	tools/mkimage -l image
5825	  -l ==> list image header information
5826
5827The second form (with "-d" option) is used to build a U-Boot image
5828from a "data file" which is used as image payload:
5829
5830	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5831		      -n name -d data_file image
5832	  -A ==> set architecture to 'arch'
5833	  -O ==> set operating system to 'os'
5834	  -T ==> set image type to 'type'
5835	  -C ==> set compression type 'comp'
5836	  -a ==> set load address to 'addr' (hex)
5837	  -e ==> set entry point to 'ep' (hex)
5838	  -n ==> set image name to 'name'
5839	  -d ==> use image data from 'datafile'
5840
5841Right now, all Linux kernels for PowerPC systems use the same load
5842address (0x00000000), but the entry point address depends on the
5843kernel version:
5844
5845- 2.2.x kernels have the entry point at 0x0000000C,
5846- 2.3.x and later kernels have the entry point at 0x00000000.
5847
5848So a typical call to build a U-Boot image would read:
5849
5850	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5851	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5852	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5853	> examples/uImage.TQM850L
5854	Image Name:   2.4.4 kernel for TQM850L
5855	Created:      Wed Jul 19 02:34:59 2000
5856	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5857	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5858	Load Address: 0x00000000
5859	Entry Point:  0x00000000
5860
5861To verify the contents of the image (or check for corruption):
5862
5863	-> tools/mkimage -l examples/uImage.TQM850L
5864	Image Name:   2.4.4 kernel for TQM850L
5865	Created:      Wed Jul 19 02:34:59 2000
5866	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5867	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5868	Load Address: 0x00000000
5869	Entry Point:  0x00000000
5870
5871NOTE: for embedded systems where boot time is critical you can trade
5872speed for memory and install an UNCOMPRESSED image instead: this
5873needs more space in Flash, but boots much faster since it does not
5874need to be uncompressed:
5875
5876	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5877	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5878	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5879	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5880	> examples/uImage.TQM850L-uncompressed
5881	Image Name:   2.4.4 kernel for TQM850L
5882	Created:      Wed Jul 19 02:34:59 2000
5883	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5884	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5885	Load Address: 0x00000000
5886	Entry Point:  0x00000000
5887
5888
5889Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5890when your kernel is intended to use an initial ramdisk:
5891
5892	-> tools/mkimage -n 'Simple Ramdisk Image' \
5893	> -A ppc -O linux -T ramdisk -C gzip \
5894	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5895	Image Name:   Simple Ramdisk Image
5896	Created:      Wed Jan 12 14:01:50 2000
5897	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5898	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5899	Load Address: 0x00000000
5900	Entry Point:  0x00000000
5901
5902The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5903option performs the converse operation of the mkimage's second form (the "-d"
5904option). Given an image built by mkimage, the dumpimage extracts a "data file"
5905from the image:
5906
5907	tools/dumpimage -i image -T type -p position data_file
5908	  -i ==> extract from the 'image' a specific 'data_file'
5909	  -T ==> set image type to 'type'
5910	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5911
5912
5913Installing a Linux Image:
5914-------------------------
5915
5916To downloading a U-Boot image over the serial (console) interface,
5917you must convert the image to S-Record format:
5918
5919	objcopy -I binary -O srec examples/image examples/image.srec
5920
5921The 'objcopy' does not understand the information in the U-Boot
5922image header, so the resulting S-Record file will be relative to
5923address 0x00000000. To load it to a given address, you need to
5924specify the target address as 'offset' parameter with the 'loads'
5925command.
5926
5927Example: install the image to address 0x40100000 (which on the
5928TQM8xxL is in the first Flash bank):
5929
5930	=> erase 40100000 401FFFFF
5931
5932	.......... done
5933	Erased 8 sectors
5934
5935	=> loads 40100000
5936	## Ready for S-Record download ...
5937	~>examples/image.srec
5938	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5939	...
5940	15989 15990 15991 15992
5941	[file transfer complete]
5942	[connected]
5943	## Start Addr = 0x00000000
5944
5945
5946You can check the success of the download using the 'iminfo' command;
5947this includes a checksum verification so you can be sure no data
5948corruption happened:
5949
5950	=> imi 40100000
5951
5952	## Checking Image at 40100000 ...
5953	   Image Name:	 2.2.13 for initrd on TQM850L
5954	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5955	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5956	   Load Address: 00000000
5957	   Entry Point:	 0000000c
5958	   Verifying Checksum ... OK
5959
5960
5961Boot Linux:
5962-----------
5963
5964The "bootm" command is used to boot an application that is stored in
5965memory (RAM or Flash). In case of a Linux kernel image, the contents
5966of the "bootargs" environment variable is passed to the kernel as
5967parameters. You can check and modify this variable using the
5968"printenv" and "setenv" commands:
5969
5970
5971	=> printenv bootargs
5972	bootargs=root=/dev/ram
5973
5974	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5975
5976	=> printenv bootargs
5977	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5978
5979	=> bootm 40020000
5980	## Booting Linux kernel at 40020000 ...
5981	   Image Name:	 2.2.13 for NFS on TQM850L
5982	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5983	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5984	   Load Address: 00000000
5985	   Entry Point:	 0000000c
5986	   Verifying Checksum ... OK
5987	   Uncompressing Kernel Image ... OK
5988	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
5989	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5990	time_init: decrementer frequency = 187500000/60
5991	Calibrating delay loop... 49.77 BogoMIPS
5992	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5993	...
5994
5995If you want to boot a Linux kernel with initial RAM disk, you pass
5996the memory addresses of both the kernel and the initrd image (PPBCOOT
5997format!) to the "bootm" command:
5998
5999	=> imi 40100000 40200000
6000
6001	## Checking Image at 40100000 ...
6002	   Image Name:	 2.2.13 for initrd on TQM850L
6003	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
6004	   Data Size:	 335725 Bytes = 327 kB = 0 MB
6005	   Load Address: 00000000
6006	   Entry Point:	 0000000c
6007	   Verifying Checksum ... OK
6008
6009	## Checking Image at 40200000 ...
6010	   Image Name:	 Simple Ramdisk Image
6011	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
6012	   Data Size:	 566530 Bytes = 553 kB = 0 MB
6013	   Load Address: 00000000
6014	   Entry Point:	 00000000
6015	   Verifying Checksum ... OK
6016
6017	=> bootm 40100000 40200000
6018	## Booting Linux kernel at 40100000 ...
6019	   Image Name:	 2.2.13 for initrd on TQM850L
6020	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
6021	   Data Size:	 335725 Bytes = 327 kB = 0 MB
6022	   Load Address: 00000000
6023	   Entry Point:	 0000000c
6024	   Verifying Checksum ... OK
6025	   Uncompressing Kernel Image ... OK
6026	## Loading RAMDisk Image at 40200000 ...
6027	   Image Name:	 Simple Ramdisk Image
6028	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
6029	   Data Size:	 566530 Bytes = 553 kB = 0 MB
6030	   Load Address: 00000000
6031	   Entry Point:	 00000000
6032	   Verifying Checksum ... OK
6033	   Loading Ramdisk ... OK
6034	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
6035	Boot arguments: root=/dev/ram
6036	time_init: decrementer frequency = 187500000/60
6037	Calibrating delay loop... 49.77 BogoMIPS
6038	...
6039	RAMDISK: Compressed image found at block 0
6040	VFS: Mounted root (ext2 filesystem).
6041
6042	bash#
6043
6044Boot Linux and pass a flat device tree:
6045-----------
6046
6047First, U-Boot must be compiled with the appropriate defines. See the section
6048titled "Linux Kernel Interface" above for a more in depth explanation. The
6049following is an example of how to start a kernel and pass an updated
6050flat device tree:
6051
6052=> print oftaddr
6053oftaddr=0x300000
6054=> print oft
6055oft=oftrees/mpc8540ads.dtb
6056=> tftp $oftaddr $oft
6057Speed: 1000, full duplex
6058Using TSEC0 device
6059TFTP from server 192.168.1.1; our IP address is 192.168.1.101
6060Filename 'oftrees/mpc8540ads.dtb'.
6061Load address: 0x300000
6062Loading: #
6063done
6064Bytes transferred = 4106 (100a hex)
6065=> tftp $loadaddr $bootfile
6066Speed: 1000, full duplex
6067Using TSEC0 device
6068TFTP from server 192.168.1.1; our IP address is 192.168.1.2
6069Filename 'uImage'.
6070Load address: 0x200000
6071Loading:############
6072done
6073Bytes transferred = 1029407 (fb51f hex)
6074=> print loadaddr
6075loadaddr=200000
6076=> print oftaddr
6077oftaddr=0x300000
6078=> bootm $loadaddr - $oftaddr
6079## Booting image at 00200000 ...
6080   Image Name:	 Linux-2.6.17-dirty
6081   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
6082   Data Size:	 1029343 Bytes = 1005.2 kB
6083   Load Address: 00000000
6084   Entry Point:	 00000000
6085   Verifying Checksum ... OK
6086   Uncompressing Kernel Image ... OK
6087Booting using flat device tree at 0x300000
6088Using MPC85xx ADS machine description
6089Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
6090[snip]
6091
6092
6093More About U-Boot Image Types:
6094------------------------------
6095
6096U-Boot supports the following image types:
6097
6098   "Standalone Programs" are directly runnable in the environment
6099	provided by U-Boot; it is expected that (if they behave
6100	well) you can continue to work in U-Boot after return from
6101	the Standalone Program.
6102   "OS Kernel Images" are usually images of some Embedded OS which
6103	will take over control completely. Usually these programs
6104	will install their own set of exception handlers, device
6105	drivers, set up the MMU, etc. - this means, that you cannot
6106	expect to re-enter U-Boot except by resetting the CPU.
6107   "RAMDisk Images" are more or less just data blocks, and their
6108	parameters (address, size) are passed to an OS kernel that is
6109	being started.
6110   "Multi-File Images" contain several images, typically an OS
6111	(Linux) kernel image and one or more data images like
6112	RAMDisks. This construct is useful for instance when you want
6113	to boot over the network using BOOTP etc., where the boot
6114	server provides just a single image file, but you want to get
6115	for instance an OS kernel and a RAMDisk image.
6116
6117	"Multi-File Images" start with a list of image sizes, each
6118	image size (in bytes) specified by an "uint32_t" in network
6119	byte order. This list is terminated by an "(uint32_t)0".
6120	Immediately after the terminating 0 follow the images, one by
6121	one, all aligned on "uint32_t" boundaries (size rounded up to
6122	a multiple of 4 bytes).
6123
6124   "Firmware Images" are binary images containing firmware (like
6125	U-Boot or FPGA images) which usually will be programmed to
6126	flash memory.
6127
6128   "Script files" are command sequences that will be executed by
6129	U-Boot's command interpreter; this feature is especially
6130	useful when you configure U-Boot to use a real shell (hush)
6131	as command interpreter.
6132
6133Booting the Linux zImage:
6134-------------------------
6135
6136On some platforms, it's possible to boot Linux zImage. This is done
6137using the "bootz" command. The syntax of "bootz" command is the same
6138as the syntax of "bootm" command.
6139
6140Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
6141kernel with raw initrd images. The syntax is slightly different, the
6142address of the initrd must be augmented by it's size, in the following
6143format: "<initrd addres>:<initrd size>".
6144
6145
6146Standalone HOWTO:
6147=================
6148
6149One of the features of U-Boot is that you can dynamically load and
6150run "standalone" applications, which can use some resources of
6151U-Boot like console I/O functions or interrupt services.
6152
6153Two simple examples are included with the sources:
6154
6155"Hello World" Demo:
6156-------------------
6157
6158'examples/hello_world.c' contains a small "Hello World" Demo
6159application; it is automatically compiled when you build U-Boot.
6160It's configured to run at address 0x00040004, so you can play with it
6161like that:
6162
6163	=> loads
6164	## Ready for S-Record download ...
6165	~>examples/hello_world.srec
6166	1 2 3 4 5 6 7 8 9 10 11 ...
6167	[file transfer complete]
6168	[connected]
6169	## Start Addr = 0x00040004
6170
6171	=> go 40004 Hello World! This is a test.
6172	## Starting application at 0x00040004 ...
6173	Hello World
6174	argc = 7
6175	argv[0] = "40004"
6176	argv[1] = "Hello"
6177	argv[2] = "World!"
6178	argv[3] = "This"
6179	argv[4] = "is"
6180	argv[5] = "a"
6181	argv[6] = "test."
6182	argv[7] = "<NULL>"
6183	Hit any key to exit ...
6184
6185	## Application terminated, rc = 0x0
6186
6187Another example, which demonstrates how to register a CPM interrupt
6188handler with the U-Boot code, can be found in 'examples/timer.c'.
6189Here, a CPM timer is set up to generate an interrupt every second.
6190The interrupt service routine is trivial, just printing a '.'
6191character, but this is just a demo program. The application can be
6192controlled by the following keys:
6193
6194	? - print current values og the CPM Timer registers
6195	b - enable interrupts and start timer
6196	e - stop timer and disable interrupts
6197	q - quit application
6198
6199	=> loads
6200	## Ready for S-Record download ...
6201	~>examples/timer.srec
6202	1 2 3 4 5 6 7 8 9 10 11 ...
6203	[file transfer complete]
6204	[connected]
6205	## Start Addr = 0x00040004
6206
6207	=> go 40004
6208	## Starting application at 0x00040004 ...
6209	TIMERS=0xfff00980
6210	Using timer 1
6211	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
6212
6213Hit 'b':
6214	[q, b, e, ?] Set interval 1000000 us
6215	Enabling timer
6216Hit '?':
6217	[q, b, e, ?] ........
6218	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
6219Hit '?':
6220	[q, b, e, ?] .
6221	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
6222Hit '?':
6223	[q, b, e, ?] .
6224	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
6225Hit '?':
6226	[q, b, e, ?] .
6227	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
6228Hit 'e':
6229	[q, b, e, ?] ...Stopping timer
6230Hit 'q':
6231	[q, b, e, ?] ## Application terminated, rc = 0x0
6232
6233
6234Minicom warning:
6235================
6236
6237Over time, many people have reported problems when trying to use the
6238"minicom" terminal emulation program for serial download. I (wd)
6239consider minicom to be broken, and recommend not to use it. Under
6240Unix, I recommend to use C-Kermit for general purpose use (and
6241especially for kermit binary protocol download ("loadb" command), and
6242use "cu" for S-Record download ("loads" command).  See
6243http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
6244for help with kermit.
6245
6246
6247Nevertheless, if you absolutely want to use it try adding this
6248configuration to your "File transfer protocols" section:
6249
6250	   Name	   Program			Name U/D FullScr IO-Red. Multi
6251	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
6252	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
6253
6254
6255NetBSD Notes:
6256=============
6257
6258Starting at version 0.9.2, U-Boot supports NetBSD both as host
6259(build U-Boot) and target system (boots NetBSD/mpc8xx).
6260
6261Building requires a cross environment; it is known to work on
6262NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
6263need gmake since the Makefiles are not compatible with BSD make).
6264Note that the cross-powerpc package does not install include files;
6265attempting to build U-Boot will fail because <machine/ansi.h> is
6266missing.  This file has to be installed and patched manually:
6267
6268	# cd /usr/pkg/cross/powerpc-netbsd/include
6269	# mkdir powerpc
6270	# ln -s powerpc machine
6271	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
6272	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
6273
6274Native builds *don't* work due to incompatibilities between native
6275and U-Boot include files.
6276
6277Booting assumes that (the first part of) the image booted is a
6278stage-2 loader which in turn loads and then invokes the kernel
6279proper. Loader sources will eventually appear in the NetBSD source
6280tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
6281meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
6282
6283
6284Implementation Internals:
6285=========================
6286
6287The following is not intended to be a complete description of every
6288implementation detail. However, it should help to understand the
6289inner workings of U-Boot and make it easier to port it to custom
6290hardware.
6291
6292
6293Initial Stack, Global Data:
6294---------------------------
6295
6296The implementation of U-Boot is complicated by the fact that U-Boot
6297starts running out of ROM (flash memory), usually without access to
6298system RAM (because the memory controller is not initialized yet).
6299This means that we don't have writable Data or BSS segments, and BSS
6300is not initialized as zero. To be able to get a C environment working
6301at all, we have to allocate at least a minimal stack. Implementation
6302options for this are defined and restricted by the CPU used: Some CPU
6303models provide on-chip memory (like the IMMR area on MPC8xx and
6304MPC826x processors), on others (parts of) the data cache can be
6305locked as (mis-) used as memory, etc.
6306
6307	Chris Hallinan posted a good summary of these issues to the
6308	U-Boot mailing list:
6309
6310	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
6311	From: "Chris Hallinan" <clh@net1plus.com>
6312	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
6313	...
6314
6315	Correct me if I'm wrong, folks, but the way I understand it
6316	is this: Using DCACHE as initial RAM for Stack, etc, does not
6317	require any physical RAM backing up the cache. The cleverness
6318	is that the cache is being used as a temporary supply of
6319	necessary storage before the SDRAM controller is setup. It's
6320	beyond the scope of this list to explain the details, but you
6321	can see how this works by studying the cache architecture and
6322	operation in the architecture and processor-specific manuals.
6323
6324	OCM is On Chip Memory, which I believe the 405GP has 4K. It
6325	is another option for the system designer to use as an
6326	initial stack/RAM area prior to SDRAM being available. Either
6327	option should work for you. Using CS 4 should be fine if your
6328	board designers haven't used it for something that would
6329	cause you grief during the initial boot! It is frequently not
6330	used.
6331
6332	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
6333	with your processor/board/system design. The default value
6334	you will find in any recent u-boot distribution in
6335	walnut.h should work for you. I'd set it to a value larger
6336	than your SDRAM module. If you have a 64MB SDRAM module, set
6337	it above 400_0000. Just make sure your board has no resources
6338	that are supposed to respond to that address! That code in
6339	start.S has been around a while and should work as is when
6340	you get the config right.
6341
6342	-Chris Hallinan
6343	DS4.COM, Inc.
6344
6345It is essential to remember this, since it has some impact on the C
6346code for the initialization procedures:
6347
6348* Initialized global data (data segment) is read-only. Do not attempt
6349  to write it.
6350
6351* Do not use any uninitialized global data (or implicitly initialized
6352  as zero data - BSS segment) at all - this is undefined, initiali-
6353  zation is performed later (when relocating to RAM).
6354
6355* Stack space is very limited. Avoid big data buffers or things like
6356  that.
6357
6358Having only the stack as writable memory limits means we cannot use
6359normal global data to share information between the code. But it
6360turned out that the implementation of U-Boot can be greatly
6361simplified by making a global data structure (gd_t) available to all
6362functions. We could pass a pointer to this data as argument to _all_
6363functions, but this would bloat the code. Instead we use a feature of
6364the GCC compiler (Global Register Variables) to share the data: we
6365place a pointer (gd) to the global data into a register which we
6366reserve for this purpose.
6367
6368When choosing a register for such a purpose we are restricted by the
6369relevant  (E)ABI  specifications for the current architecture, and by
6370GCC's implementation.
6371
6372For PowerPC, the following registers have specific use:
6373	R1:	stack pointer
6374	R2:	reserved for system use
6375	R3-R4:	parameter passing and return values
6376	R5-R10: parameter passing
6377	R13:	small data area pointer
6378	R30:	GOT pointer
6379	R31:	frame pointer
6380
6381	(U-Boot also uses R12 as internal GOT pointer. r12
6382	is a volatile register so r12 needs to be reset when
6383	going back and forth between asm and C)
6384
6385    ==> U-Boot will use R2 to hold a pointer to the global data
6386
6387    Note: on PPC, we could use a static initializer (since the
6388    address of the global data structure is known at compile time),
6389    but it turned out that reserving a register results in somewhat
6390    smaller code - although the code savings are not that big (on
6391    average for all boards 752 bytes for the whole U-Boot image,
6392    624 text + 127 data).
6393
6394On Blackfin, the normal C ABI (except for P3) is followed as documented here:
6395	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
6396
6397    ==> U-Boot will use P3 to hold a pointer to the global data
6398
6399On ARM, the following registers are used:
6400
6401	R0:	function argument word/integer result
6402	R1-R3:	function argument word
6403	R9:	platform specific
6404	R10:	stack limit (used only if stack checking is enabled)
6405	R11:	argument (frame) pointer
6406	R12:	temporary workspace
6407	R13:	stack pointer
6408	R14:	link register
6409	R15:	program counter
6410
6411    ==> U-Boot will use R9 to hold a pointer to the global data
6412
6413    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
6414
6415On Nios II, the ABI is documented here:
6416	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
6417
6418    ==> U-Boot will use gp to hold a pointer to the global data
6419
6420    Note: on Nios II, we give "-G0" option to gcc and don't use gp
6421    to access small data sections, so gp is free.
6422
6423On NDS32, the following registers are used:
6424
6425	R0-R1:	argument/return
6426	R2-R5:	argument
6427	R15:	temporary register for assembler
6428	R16:	trampoline register
6429	R28:	frame pointer (FP)
6430	R29:	global pointer (GP)
6431	R30:	link register (LP)
6432	R31:	stack pointer (SP)
6433	PC:	program counter (PC)
6434
6435    ==> U-Boot will use R10 to hold a pointer to the global data
6436
6437NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
6438or current versions of GCC may "optimize" the code too much.
6439
6440Memory Management:
6441------------------
6442
6443U-Boot runs in system state and uses physical addresses, i.e. the
6444MMU is not used either for address mapping nor for memory protection.
6445
6446The available memory is mapped to fixed addresses using the memory
6447controller. In this process, a contiguous block is formed for each
6448memory type (Flash, SDRAM, SRAM), even when it consists of several
6449physical memory banks.
6450
6451U-Boot is installed in the first 128 kB of the first Flash bank (on
6452TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
6453booting and sizing and initializing DRAM, the code relocates itself
6454to the upper end of DRAM. Immediately below the U-Boot code some
6455memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
6456configuration setting]. Below that, a structure with global Board
6457Info data is placed, followed by the stack (growing downward).
6458
6459Additionally, some exception handler code is copied to the low 8 kB
6460of DRAM (0x00000000 ... 0x00001FFF).
6461
6462So a typical memory configuration with 16 MB of DRAM could look like
6463this:
6464
6465	0x0000 0000	Exception Vector code
6466	      :
6467	0x0000 1FFF
6468	0x0000 2000	Free for Application Use
6469	      :
6470	      :
6471
6472	      :
6473	      :
6474	0x00FB FF20	Monitor Stack (Growing downward)
6475	0x00FB FFAC	Board Info Data and permanent copy of global data
6476	0x00FC 0000	Malloc Arena
6477	      :
6478	0x00FD FFFF
6479	0x00FE 0000	RAM Copy of Monitor Code
6480	...		eventually: LCD or video framebuffer
6481	...		eventually: pRAM (Protected RAM - unchanged by reset)
6482	0x00FF FFFF	[End of RAM]
6483
6484
6485System Initialization:
6486----------------------
6487
6488In the reset configuration, U-Boot starts at the reset entry point
6489(on most PowerPC systems at address 0x00000100). Because of the reset
6490configuration for CS0# this is a mirror of the on board Flash memory.
6491To be able to re-map memory U-Boot then jumps to its link address.
6492To be able to implement the initialization code in C, a (small!)
6493initial stack is set up in the internal Dual Ported RAM (in case CPUs
6494which provide such a feature like MPC8xx or MPC8260), or in a locked
6495part of the data cache. After that, U-Boot initializes the CPU core,
6496the caches and the SIU.
6497
6498Next, all (potentially) available memory banks are mapped using a
6499preliminary mapping. For example, we put them on 512 MB boundaries
6500(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
6501on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
6502programmed for SDRAM access. Using the temporary configuration, a
6503simple memory test is run that determines the size of the SDRAM
6504banks.
6505
6506When there is more than one SDRAM bank, and the banks are of
6507different size, the largest is mapped first. For equal size, the first
6508bank (CS2#) is mapped first. The first mapping is always for address
65090x00000000, with any additional banks following immediately to create
6510contiguous memory starting from 0.
6511
6512Then, the monitor installs itself at the upper end of the SDRAM area
6513and allocates memory for use by malloc() and for the global Board
6514Info data; also, the exception vector code is copied to the low RAM
6515pages, and the final stack is set up.
6516
6517Only after this relocation will you have a "normal" C environment;
6518until that you are restricted in several ways, mostly because you are
6519running from ROM, and because the code will have to be relocated to a
6520new address in RAM.
6521
6522
6523U-Boot Porting Guide:
6524----------------------
6525
6526[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
6527list, October 2002]
6528
6529
6530int main(int argc, char *argv[])
6531{
6532	sighandler_t no_more_time;
6533
6534	signal(SIGALRM, no_more_time);
6535	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6536
6537	if (available_money > available_manpower) {
6538		Pay consultant to port U-Boot;
6539		return 0;
6540	}
6541
6542	Download latest U-Boot source;
6543
6544	Subscribe to u-boot mailing list;
6545
6546	if (clueless)
6547		email("Hi, I am new to U-Boot, how do I get started?");
6548
6549	while (learning) {
6550		Read the README file in the top level directory;
6551		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6552		Read applicable doc/*.README;
6553		Read the source, Luke;
6554		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6555	}
6556
6557	if (available_money > toLocalCurrency ($2500))
6558		Buy a BDI3000;
6559	else
6560		Add a lot of aggravation and time;
6561
6562	if (a similar board exists) {	/* hopefully... */
6563		cp -a board/<similar> board/<myboard>
6564		cp include/configs/<similar>.h include/configs/<myboard>.h
6565	} else {
6566		Create your own board support subdirectory;
6567		Create your own board include/configs/<myboard>.h file;
6568	}
6569	Edit new board/<myboard> files
6570	Edit new include/configs/<myboard>.h
6571
6572	while (!accepted) {
6573		while (!running) {
6574			do {
6575				Add / modify source code;
6576			} until (compiles);
6577			Debug;
6578			if (clueless)
6579				email("Hi, I am having problems...");
6580		}
6581		Send patch file to the U-Boot email list;
6582		if (reasonable critiques)
6583			Incorporate improvements from email list code review;
6584		else
6585			Defend code as written;
6586	}
6587
6588	return 0;
6589}
6590
6591void no_more_time (int sig)
6592{
6593      hire_a_guru();
6594}
6595
6596
6597Coding Standards:
6598-----------------
6599
6600All contributions to U-Boot should conform to the Linux kernel
6601coding style; see the file "Documentation/CodingStyle" and the script
6602"scripts/Lindent" in your Linux kernel source directory.
6603
6604Source files originating from a different project (for example the
6605MTD subsystem) are generally exempt from these guidelines and are not
6606reformatted to ease subsequent migration to newer versions of those
6607sources.
6608
6609Please note that U-Boot is implemented in C (and to some small parts in
6610Assembler); no C++ is used, so please do not use C++ style comments (//)
6611in your code.
6612
6613Please also stick to the following formatting rules:
6614- remove any trailing white space
6615- use TAB characters for indentation and vertical alignment, not spaces
6616- make sure NOT to use DOS '\r\n' line feeds
6617- do not add more than 2 consecutive empty lines to source files
6618- do not add trailing empty lines to source files
6619
6620Submissions which do not conform to the standards may be returned
6621with a request to reformat the changes.
6622
6623
6624Submitting Patches:
6625-------------------
6626
6627Since the number of patches for U-Boot is growing, we need to
6628establish some rules. Submissions which do not conform to these rules
6629may be rejected, even when they contain important and valuable stuff.
6630
6631Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6632
6633Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6634see http://lists.denx.de/mailman/listinfo/u-boot
6635
6636When you send a patch, please include the following information with
6637it:
6638
6639* For bug fixes: a description of the bug and how your patch fixes
6640  this bug. Please try to include a way of demonstrating that the
6641  patch actually fixes something.
6642
6643* For new features: a description of the feature and your
6644  implementation.
6645
6646* A CHANGELOG entry as plaintext (separate from the patch)
6647
6648* For major contributions, your entry to the CREDITS file
6649
6650* When you add support for a new board, don't forget to add a
6651  maintainer e-mail address to the boards.cfg file, too.
6652
6653* If your patch adds new configuration options, don't forget to
6654  document these in the README file.
6655
6656* The patch itself. If you are using git (which is *strongly*
6657  recommended) you can easily generate the patch using the
6658  "git format-patch". If you then use "git send-email" to send it to
6659  the U-Boot mailing list, you will avoid most of the common problems
6660  with some other mail clients.
6661
6662  If you cannot use git, use "diff -purN OLD NEW". If your version of
6663  diff does not support these options, then get the latest version of
6664  GNU diff.
6665
6666  The current directory when running this command shall be the parent
6667  directory of the U-Boot source tree (i. e. please make sure that
6668  your patch includes sufficient directory information for the
6669  affected files).
6670
6671  We prefer patches as plain text. MIME attachments are discouraged,
6672  and compressed attachments must not be used.
6673
6674* If one logical set of modifications affects or creates several
6675  files, all these changes shall be submitted in a SINGLE patch file.
6676
6677* Changesets that contain different, unrelated modifications shall be
6678  submitted as SEPARATE patches, one patch per changeset.
6679
6680
6681Notes:
6682
6683* Before sending the patch, run the MAKEALL script on your patched
6684  source tree and make sure that no errors or warnings are reported
6685  for any of the boards.
6686
6687* Keep your modifications to the necessary minimum: A patch
6688  containing several unrelated changes or arbitrary reformats will be
6689  returned with a request to re-formatting / split it.
6690
6691* If you modify existing code, make sure that your new code does not
6692  add to the memory footprint of the code ;-) Small is beautiful!
6693  When adding new features, these should compile conditionally only
6694  (using #ifdef), and the resulting code with the new feature
6695  disabled must not need more memory than the old code without your
6696  modification.
6697
6698* Remember that there is a size limit of 100 kB per message on the
6699  u-boot mailing list. Bigger patches will be moderated. If they are
6700  reasonable and not too big, they will be acknowledged. But patches
6701  bigger than the size limit should be avoided.
6702