xref: /rk3399_rockchip-uboot/README (revision b7588e3bdcdb2ee073a6a66a4c882b23feaaa0e6)
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  /arm			Files generic to ARM architecture
136    /cpu		CPU specific files
137      /arm720t		Files specific to ARM 720 CPUs
138      /arm920t		Files specific to ARM 920 CPUs
139	/at91		Files specific to Atmel AT91RM9200 CPU
140	/imx		Files specific to Freescale MC9328 i.MX CPUs
141	/s3c24x0	Files specific to Samsung S3C24X0 CPUs
142      /arm926ejs	Files specific to ARM 926 CPUs
143      /arm1136		Files specific to ARM 1136 CPUs
144      /pxa		Files specific to Intel XScale PXA CPUs
145      /sa1100		Files specific to Intel StrongARM SA1100 CPUs
146    /lib		Architecture specific library files
147  /avr32		Files generic to AVR32 architecture
148    /cpu		CPU specific files
149    /lib		Architecture specific library files
150  /blackfin		Files generic to Analog Devices Blackfin architecture
151    /cpu		CPU specific files
152    /lib		Architecture specific library files
153  /m68k			Files generic to m68k architecture
154    /cpu		CPU specific files
155      /mcf52x2		Files specific to Freescale ColdFire MCF52x2 CPUs
156      /mcf5227x		Files specific to Freescale ColdFire MCF5227x CPUs
157      /mcf532x		Files specific to Freescale ColdFire MCF5329 CPUs
158      /mcf5445x		Files specific to Freescale ColdFire MCF5445x CPUs
159      /mcf547x_8x	Files specific to Freescale ColdFire MCF547x_8x CPUs
160    /lib		Architecture specific library files
161  /microblaze		Files generic to microblaze architecture
162    /cpu		CPU specific files
163    /lib		Architecture specific library files
164  /mips			Files generic to MIPS architecture
165    /cpu		CPU specific files
166      /mips32		Files specific to MIPS32 CPUs
167      /xburst		Files specific to Ingenic XBurst CPUs
168    /lib		Architecture specific library files
169  /nds32		Files generic to NDS32 architecture
170    /cpu		CPU specific files
171      /n1213		Files specific to Andes Technology N1213 CPUs
172    /lib		Architecture specific library files
173  /nios2		Files generic to Altera NIOS2 architecture
174    /cpu		CPU specific files
175    /lib		Architecture specific library files
176  /openrisc		Files generic to OpenRISC architecture
177    /cpu		CPU specific files
178    /lib		Architecture specific library files
179  /powerpc		Files generic to PowerPC architecture
180    /cpu		CPU specific files
181      /74xx_7xx		Files specific to Freescale MPC74xx and 7xx CPUs
182      /mpc5xx		Files specific to Freescale MPC5xx CPUs
183      /mpc5xxx		Files specific to Freescale MPC5xxx CPUs
184      /mpc8xx		Files specific to Freescale MPC8xx CPUs
185      /mpc824x		Files specific to Freescale MPC824x CPUs
186      /mpc8260		Files specific to Freescale MPC8260 CPUs
187      /mpc85xx		Files specific to Freescale MPC85xx CPUs
188      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
189    /lib		Architecture specific library files
190  /sh			Files generic to SH architecture
191    /cpu		CPU specific files
192      /sh2		Files specific to sh2 CPUs
193      /sh3		Files specific to sh3 CPUs
194      /sh4		Files specific to sh4 CPUs
195    /lib		Architecture specific library files
196  /sparc		Files generic to SPARC architecture
197    /cpu		CPU specific files
198      /leon2		Files specific to Gaisler LEON2 SPARC CPU
199      /leon3		Files specific to Gaisler LEON3 SPARC CPU
200    /lib		Architecture specific library files
201  /x86			Files generic to x86 architecture
202    /cpu		CPU specific files
203    /lib		Architecture specific library files
204/api			Machine/arch independent API for external apps
205/board			Board dependent files
206/common			Misc architecture independent functions
207/disk			Code for disk drive partition handling
208/doc			Documentation (don't expect too much)
209/drivers		Commonly used device drivers
210/dts			Contains Makefile for building internal U-Boot fdt.
211/examples		Example code for standalone applications, etc.
212/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
213/include		Header Files
214/lib			Files generic to all architectures
215  /libfdt		Library files to support flattened device trees
216  /lzma			Library files to support LZMA decompression
217  /lzo			Library files to support LZO decompression
218/net			Networking code
219/post			Power On Self Test
220/spl			Secondary Program Loader framework
221/tools			Tools to build S-Record or U-Boot images, etc.
222
223Software Configuration:
224=======================
225
226Configuration is usually done using C preprocessor defines; the
227rationale behind that is to avoid dead code whenever possible.
228
229There are two classes of configuration variables:
230
231* Configuration _OPTIONS_:
232  These are selectable by the user and have names beginning with
233  "CONFIG_".
234
235* Configuration _SETTINGS_:
236  These depend on the hardware etc. and should not be meddled with if
237  you don't know what you're doing; they have names beginning with
238  "CONFIG_SYS_".
239
240Later we will add a configuration tool - probably similar to or even
241identical to what's used for the Linux kernel. Right now, we have to
242do the configuration by hand, which means creating some symbolic
243links and editing some configuration files. We use the TQM8xxL boards
244as an example here.
245
246
247Selection of Processor Architecture and Board Type:
248---------------------------------------------------
249
250For all supported boards there are ready-to-use default
251configurations available; just type "make <board_name>_config".
252
253Example: For a TQM823L module type:
254
255	cd u-boot
256	make TQM823L_config
257
258For the Cogent platform, you need to specify the CPU type as well;
259e.g. "make cogent_mpc8xx_config". And also configure the cogent
260directory according to the instructions in cogent/README.
261
262
263Configuration Options:
264----------------------
265
266Configuration depends on the combination of board and CPU type; all
267such information is kept in a configuration file
268"include/configs/<board_name>.h".
269
270Example: For a TQM823L module, all configuration settings are in
271"include/configs/TQM823L.h".
272
273
274Many of the options are named exactly as the corresponding Linux
275kernel configuration options. The intention is to make it easier to
276build a config tool - later.
277
278
279The following options need to be configured:
280
281- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
282
283- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
284
285- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
286		Define exactly one, e.g. CONFIG_ATSTK1002
287
288- CPU Module Type: (if CONFIG_COGENT is defined)
289		Define exactly one of
290		CONFIG_CMA286_60_OLD
291--- FIXME --- not tested yet:
292		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
293		CONFIG_CMA287_23, CONFIG_CMA287_50
294
295- Motherboard Type: (if CONFIG_COGENT is defined)
296		Define exactly one of
297		CONFIG_CMA101, CONFIG_CMA102
298
299- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
300		Define one or more of
301		CONFIG_CMA302
302
303- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
304		Define one or more of
305		CONFIG_LCD_HEARTBEAT	- update a character position on
306					  the LCD display every second with
307					  a "rotator" |\-/|\-/
308
309- Board flavour: (if CONFIG_MPC8260ADS is defined)
310		CONFIG_ADSTYPE
311		Possible values are:
312			CONFIG_SYS_8260ADS	- original MPC8260ADS
313			CONFIG_SYS_8266ADS	- MPC8266ADS
314			CONFIG_SYS_PQ2FADS	- PQ2FADS-ZU or PQ2FADS-VR
315			CONFIG_SYS_8272ADS	- MPC8272ADS
316
317- Marvell Family Member
318		CONFIG_SYS_MVFS		- define it if you want to enable
319					  multiple fs option at one time
320					  for marvell soc family
321
322- MPC824X Family Member (if CONFIG_MPC824X is defined)
323		Define exactly one of
324		CONFIG_MPC8240, CONFIG_MPC8245
325
326- 8xx CPU Options: (if using an MPC8xx CPU)
327		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
328					  get_gclk_freq() cannot work
329					  e.g. if there is no 32KHz
330					  reference PIT/RTC clock
331		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
332					  or XTAL/EXTAL)
333
334- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
335		CONFIG_SYS_8xx_CPUCLK_MIN
336		CONFIG_SYS_8xx_CPUCLK_MAX
337		CONFIG_8xx_CPUCLK_DEFAULT
338			See doc/README.MPC866
339
340		CONFIG_SYS_MEASURE_CPUCLK
341
342		Define this to measure the actual CPU clock instead
343		of relying on the correctness of the configured
344		values. Mostly useful for board bringup to make sure
345		the PLL is locked at the intended frequency. Note
346		that this requires a (stable) reference clock (32 kHz
347		RTC clock or CONFIG_SYS_8XX_XIN)
348
349		CONFIG_SYS_DELAYED_ICACHE
350
351		Define this option if you want to enable the
352		ICache only when Code runs from RAM.
353
354- 85xx CPU Options:
355		CONFIG_SYS_PPC64
356
357		Specifies that the core is a 64-bit PowerPC implementation (implements
358		the "64" category of the Power ISA). This is necessary for ePAPR
359		compliance, among other possible reasons.
360
361		CONFIG_SYS_FSL_TBCLK_DIV
362
363		Defines the core time base clock divider ratio compared to the
364		system clock.  On most PQ3 devices this is 8, on newer QorIQ
365		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
366
367		CONFIG_SYS_FSL_PCIE_COMPAT
368
369		Defines the string to utilize when trying to match PCIe device
370		tree nodes for the given platform.
371
372		CONFIG_SYS_PPC_E500_DEBUG_TLB
373
374		Enables a temporary TLB entry to be used during boot to work
375		around limitations in e500v1 and e500v2 external debugger
376		support. This reduces the portions of the boot code where
377		breakpoints and single stepping do not work.  The value of this
378		symbol should be set to the TLB1 entry to be used for this
379		purpose.
380
381		CONFIG_SYS_FSL_ERRATUM_A004510
382
383		Enables a workaround for erratum A004510.  If set,
384		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
385		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
386
387		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
388		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
389
390		Defines one or two SoC revisions (low 8 bits of SVR)
391		for which the A004510 workaround should be applied.
392
393		The rest of SVR is either not relevant to the decision
394		of whether the erratum is present (e.g. p2040 versus
395		p2041) or is implied by the build target, which controls
396		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
397
398		See Freescale App Note 4493 for more information about
399		this erratum.
400
401		CONFIG_A003399_NOR_WORKAROUND
402		Enables a workaround for IFC erratum A003399. It is only
403		requred during NOR boot.
404
405		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
406
407		This is the value to write into CCSR offset 0x18600
408		according to the A004510 workaround.
409
410		CONFIG_SYS_FSL_DSP_DDR_ADDR
411		This value denotes start offset of DDR memory which is
412		connected exclusively to the DSP cores.
413
414		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
415		This value denotes start offset of M2 memory
416		which is directly connected to the DSP core.
417
418		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
419		This value denotes start offset of M3 memory which is directly
420		connected to the DSP core.
421
422		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
423		This value denotes start offset of DSP CCSR space.
424
425		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
426		Single Source Clock is clocking mode present in some of FSL SoC's.
427		In this mode, a single differential clock is used to supply
428		clocks to the sysclock, ddrclock and usbclock.
429
430- Generic CPU options:
431		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
432
433		Defines the endianess of the CPU. Implementation of those
434		values is arch specific.
435
436		CONFIG_SYS_FSL_DDR
437		Freescale DDR driver in use. This type of DDR controller is
438		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
439		SoCs.
440
441		CONFIG_SYS_FSL_DDR_ADDR
442		Freescale DDR memory-mapped register base.
443
444		CONFIG_SYS_FSL_DDR_EMU
445		Specify emulator support for DDR. Some DDR features such as
446		deskew training are not available.
447
448		CONFIG_SYS_FSL_DDRC_GEN1
449		Freescale DDR1 controller.
450
451		CONFIG_SYS_FSL_DDRC_GEN2
452		Freescale DDR2 controller.
453
454		CONFIG_SYS_FSL_DDRC_GEN3
455		Freescale DDR3 controller.
456
457		CONFIG_SYS_FSL_DDRC_ARM_GEN3
458		Freescale DDR3 controller for ARM-based SoCs.
459
460		CONFIG_SYS_FSL_DDR1
461		Board config to use DDR1. It can be enabled for SoCs with
462		Freescale DDR1 or DDR2 controllers, depending on the board
463		implemetation.
464
465		CONFIG_SYS_FSL_DDR2
466		Board config to use DDR2. It can be eanbeld for SoCs with
467		Freescale DDR2 or DDR3 controllers, depending on the board
468		implementation.
469
470		CONFIG_SYS_FSL_DDR3
471		Board config to use DDR3. It can be enabled for SoCs with
472		Freescale DDR3 controllers.
473
474		CONFIG_SYS_FSL_IFC_BE
475		Defines the IFC controller register space as Big Endian
476
477		CONFIG_SYS_FSL_IFC_LE
478		Defines the IFC controller register space as Little Endian
479
480		CONFIG_SYS_FSL_PBL_PBI
481		It enables addition of RCW (Power on reset configuration) in built image.
482		Please refer doc/README.pblimage for more details
483
484		CONFIG_SYS_FSL_PBL_RCW
485		It adds PBI(pre-boot instructions) commands in u-boot build image.
486		PBI commands can be used to configure SoC before it starts the execution.
487		Please refer doc/README.pblimage for more details
488
489		CONFIG_SYS_FSL_DDR_BE
490		Defines the DDR controller register space as Big Endian
491
492		CONFIG_SYS_FSL_DDR_LE
493		Defines the DDR controller register space as Little Endian
494
495		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
496		Physical address from the view of DDR controllers. It is the
497		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
498		it could be different for ARM SoCs.
499
500		CONFIG_SYS_FSL_DDR_INTLV_256B
501		DDR controller interleaving on 256-byte. This is a special
502		interleaving mode, handled by Dickens for Freescale layerscape
503		SoCs with ARM core.
504
505- Intel Monahans options:
506		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
507
508		Defines the Monahans run mode to oscillator
509		ratio. Valid values are 8, 16, 24, 31. The core
510		frequency is this value multiplied by 13 MHz.
511
512		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
513
514		Defines the Monahans turbo mode to oscillator
515		ratio. Valid values are 1 (default if undefined) and
516		2. The core frequency as calculated above is multiplied
517		by this value.
518
519- MIPS CPU options:
520		CONFIG_SYS_INIT_SP_OFFSET
521
522		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
523		pointer. This is needed for the temporary stack before
524		relocation.
525
526		CONFIG_SYS_MIPS_CACHE_MODE
527
528		Cache operation mode for the MIPS CPU.
529		See also arch/mips/include/asm/mipsregs.h.
530		Possible values are:
531			CONF_CM_CACHABLE_NO_WA
532			CONF_CM_CACHABLE_WA
533			CONF_CM_UNCACHED
534			CONF_CM_CACHABLE_NONCOHERENT
535			CONF_CM_CACHABLE_CE
536			CONF_CM_CACHABLE_COW
537			CONF_CM_CACHABLE_CUW
538			CONF_CM_CACHABLE_ACCELERATED
539
540		CONFIG_SYS_XWAY_EBU_BOOTCFG
541
542		Special option for Lantiq XWAY SoCs for booting from NOR flash.
543		See also arch/mips/cpu/mips32/start.S.
544
545		CONFIG_XWAY_SWAP_BYTES
546
547		Enable compilation of tools/xway-swap-bytes needed for Lantiq
548		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
549		be swapped if a flash programmer is used.
550
551- ARM options:
552		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
553
554		Select high exception vectors of the ARM core, e.g., do not
555		clear the V bit of the c1 register of CP15.
556
557		CONFIG_SYS_THUMB_BUILD
558
559		Use this flag to build U-Boot using the Thumb instruction
560		set for ARM architectures. Thumb instruction set provides
561		better code density. For ARM architectures that support
562		Thumb2 this flag will result in Thumb2 code generated by
563		GCC.
564
565		CONFIG_ARM_ERRATA_716044
566		CONFIG_ARM_ERRATA_742230
567		CONFIG_ARM_ERRATA_743622
568		CONFIG_ARM_ERRATA_751472
569		CONFIG_ARM_ERRATA_794072
570		CONFIG_ARM_ERRATA_761320
571
572		If set, the workarounds for these ARM errata are applied early
573		during U-Boot startup. Note that these options force the
574		workarounds to be applied; no CPU-type/version detection
575		exists, unlike the similar options in the Linux kernel. Do not
576		set these options unless they apply!
577
578- CPU timer options:
579		CONFIG_SYS_HZ
580
581		The frequency of the timer returned by get_timer().
582		get_timer() must operate in milliseconds and this CONFIG
583		option must be set to 1000.
584
585- Linux Kernel Interface:
586		CONFIG_CLOCKS_IN_MHZ
587
588		U-Boot stores all clock information in Hz
589		internally. For binary compatibility with older Linux
590		kernels (which expect the clocks passed in the
591		bd_info data to be in MHz) the environment variable
592		"clocks_in_mhz" can be defined so that U-Boot
593		converts clock data to MHZ before passing it to the
594		Linux kernel.
595		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
596		"clocks_in_mhz=1" is automatically included in the
597		default environment.
598
599		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
600
601		When transferring memsize parameter to linux, some versions
602		expect it to be in bytes, others in MB.
603		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
604
605		CONFIG_OF_LIBFDT
606
607		New kernel versions are expecting firmware settings to be
608		passed using flattened device trees (based on open firmware
609		concepts).
610
611		CONFIG_OF_LIBFDT
612		 * New libfdt-based support
613		 * Adds the "fdt" command
614		 * The bootm command automatically updates the fdt
615
616		OF_CPU - The proper name of the cpus node (only required for
617			MPC512X and MPC5xxx based boards).
618		OF_SOC - The proper name of the soc node (only required for
619			MPC512X and MPC5xxx based boards).
620		OF_TBCLK - The timebase frequency.
621		OF_STDOUT_PATH - The path to the console device
622
623		boards with QUICC Engines require OF_QE to set UCC MAC
624		addresses
625
626		CONFIG_OF_BOARD_SETUP
627
628		Board code has addition modification that it wants to make
629		to the flat device tree before handing it off to the kernel
630
631		CONFIG_OF_BOOT_CPU
632
633		This define fills in the correct boot CPU in the boot
634		param header, the default value is zero if undefined.
635
636		CONFIG_OF_IDE_FIXUP
637
638		U-Boot can detect if an IDE device is present or not.
639		If not, and this new config option is activated, U-Boot
640		removes the ATA node from the DTS before booting Linux,
641		so the Linux IDE driver does not probe the device and
642		crash. This is needed for buggy hardware (uc101) where
643		no pull down resistor is connected to the signal IDE5V_DD7.
644
645		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
646
647		This setting is mandatory for all boards that have only one
648		machine type and must be used to specify the machine type
649		number as it appears in the ARM machine registry
650		(see http://www.arm.linux.org.uk/developer/machines/).
651		Only boards that have multiple machine types supported
652		in a single configuration file and the machine type is
653		runtime discoverable, do not have to use this setting.
654
655- vxWorks boot parameters:
656
657		bootvx constructs a valid bootline using the following
658		environments variables: bootfile, ipaddr, serverip, hostname.
659		It loads the vxWorks image pointed bootfile.
660
661		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
662		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
663		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
664		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
665
666		CONFIG_SYS_VXWORKS_ADD_PARAMS
667
668		Add it at the end of the bootline. E.g "u=username pw=secret"
669
670		Note: If a "bootargs" environment is defined, it will overwride
671		the defaults discussed just above.
672
673- Cache Configuration:
674		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
675		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
676		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
677
678- Cache Configuration for ARM:
679		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
680				      controller
681		CONFIG_SYS_PL310_BASE - Physical base address of PL310
682					controller register space
683
684- Serial Ports:
685		CONFIG_PL010_SERIAL
686
687		Define this if you want support for Amba PrimeCell PL010 UARTs.
688
689		CONFIG_PL011_SERIAL
690
691		Define this if you want support for Amba PrimeCell PL011 UARTs.
692
693		CONFIG_PL011_CLOCK
694
695		If you have Amba PrimeCell PL011 UARTs, set this variable to
696		the clock speed of the UARTs.
697
698		CONFIG_PL01x_PORTS
699
700		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
701		define this to a list of base addresses for each (supported)
702		port. See e.g. include/configs/versatile.h
703
704		CONFIG_PL011_SERIAL_RLCR
705
706		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
707		have separate receive and transmit line control registers.  Set
708		this variable to initialize the extra register.
709
710		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
711
712		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
713		boot loader that has already initialized the UART.  Define this
714		variable to flush the UART at init time.
715
716
717- Console Interface:
718		Depending on board, define exactly one serial port
719		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
720		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
721		console by defining CONFIG_8xx_CONS_NONE
722
723		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
724		port routines must be defined elsewhere
725		(i.e. serial_init(), serial_getc(), ...)
726
727		CONFIG_CFB_CONSOLE
728		Enables console device for a color framebuffer. Needs following
729		defines (cf. smiLynxEM, i8042)
730			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
731						(default big endian)
732			VIDEO_HW_RECTFILL	graphic chip supports
733						rectangle fill
734						(cf. smiLynxEM)
735			VIDEO_HW_BITBLT		graphic chip supports
736						bit-blit (cf. smiLynxEM)
737			VIDEO_VISIBLE_COLS	visible pixel columns
738						(cols=pitch)
739			VIDEO_VISIBLE_ROWS	visible pixel rows
740			VIDEO_PIXEL_SIZE	bytes per pixel
741			VIDEO_DATA_FORMAT	graphic data format
742						(0-5, cf. cfb_console.c)
743			VIDEO_FB_ADRS		framebuffer address
744			VIDEO_KBD_INIT_FCT	keyboard int fct
745						(i.e. i8042_kbd_init())
746			VIDEO_TSTC_FCT		test char fct
747						(i.e. i8042_tstc)
748			VIDEO_GETC_FCT		get char fct
749						(i.e. i8042_getc)
750			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
751						(requires blink timer
752						cf. i8042.c)
753			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
754			CONFIG_CONSOLE_TIME	display time/date info in
755						upper right corner
756						(requires CONFIG_CMD_DATE)
757			CONFIG_VIDEO_LOGO	display Linux logo in
758						upper left corner
759			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
760						linux_logo.h for logo.
761						Requires CONFIG_VIDEO_LOGO
762			CONFIG_CONSOLE_EXTRA_INFO
763						additional board info beside
764						the logo
765
766		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
767		a limited number of ANSI escape sequences (cursor control,
768		erase functions and limited graphics rendition control).
769
770		When CONFIG_CFB_CONSOLE is defined, video console is
771		default i/o. Serial console can be forced with
772		environment 'console=serial'.
773
774		When CONFIG_SILENT_CONSOLE is defined, all console
775		messages (by U-Boot and Linux!) can be silenced with
776		the "silent" environment variable. See
777		doc/README.silent for more information.
778
779		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
780			is 0x00.
781		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
782			is 0xa0.
783
784- Console Baudrate:
785		CONFIG_BAUDRATE - in bps
786		Select one of the baudrates listed in
787		CONFIG_SYS_BAUDRATE_TABLE, see below.
788		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
789
790- Console Rx buffer length
791		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
792		the maximum receive buffer length for the SMC.
793		This option is actual only for 82xx and 8xx possible.
794		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
795		must be defined, to setup the maximum idle timeout for
796		the SMC.
797
798- Pre-Console Buffer:
799		Prior to the console being initialised (i.e. serial UART
800		initialised etc) all console output is silently discarded.
801		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
802		buffer any console messages prior to the console being
803		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
804		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
805		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
806		bytes are output before the console is initialised, the
807		earlier bytes are discarded.
808
809		'Sane' compilers will generate smaller code if
810		CONFIG_PRE_CON_BUF_SZ is a power of 2
811
812- Safe printf() functions
813		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
814		the printf() functions. These are defined in
815		include/vsprintf.h and include snprintf(), vsnprintf() and
816		so on. Code size increase is approximately 300-500 bytes.
817		If this option is not given then these functions will
818		silently discard their buffer size argument - this means
819		you are not getting any overflow checking in this case.
820
821- Boot Delay:	CONFIG_BOOTDELAY - in seconds
822		Delay before automatically booting the default image;
823		set to -1 to disable autoboot.
824		set to -2 to autoboot with no delay and not check for abort
825		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
826
827		See doc/README.autoboot for these options that
828		work with CONFIG_BOOTDELAY. None are required.
829		CONFIG_BOOT_RETRY_TIME
830		CONFIG_BOOT_RETRY_MIN
831		CONFIG_AUTOBOOT_KEYED
832		CONFIG_AUTOBOOT_PROMPT
833		CONFIG_AUTOBOOT_DELAY_STR
834		CONFIG_AUTOBOOT_STOP_STR
835		CONFIG_AUTOBOOT_DELAY_STR2
836		CONFIG_AUTOBOOT_STOP_STR2
837		CONFIG_ZERO_BOOTDELAY_CHECK
838		CONFIG_RESET_TO_RETRY
839
840- Autoboot Command:
841		CONFIG_BOOTCOMMAND
842		Only needed when CONFIG_BOOTDELAY is enabled;
843		define a command string that is automatically executed
844		when no character is read on the console interface
845		within "Boot Delay" after reset.
846
847		CONFIG_BOOTARGS
848		This can be used to pass arguments to the bootm
849		command. The value of CONFIG_BOOTARGS goes into the
850		environment value "bootargs".
851
852		CONFIG_RAMBOOT and CONFIG_NFSBOOT
853		The value of these goes into the environment as
854		"ramboot" and "nfsboot" respectively, and can be used
855		as a convenience, when switching between booting from
856		RAM and NFS.
857
858- Bootcount:
859		CONFIG_BOOTCOUNT_LIMIT
860		Implements a mechanism for detecting a repeating reboot
861		cycle, see:
862		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
863
864		CONFIG_BOOTCOUNT_ENV
865		If no softreset save registers are found on the hardware
866		"bootcount" is stored in the environment. To prevent a
867		saveenv on all reboots, the environment variable
868		"upgrade_available" is used. If "upgrade_available" is
869		0, "bootcount" is always 0, if "upgrade_available" is
870		1 "bootcount" is incremented in the environment.
871		So the Userspace Applikation must set the "upgrade_available"
872		and "bootcount" variable to 0, if a boot was successfully.
873
874- Pre-Boot Commands:
875		CONFIG_PREBOOT
876
877		When this option is #defined, the existence of the
878		environment variable "preboot" will be checked
879		immediately before starting the CONFIG_BOOTDELAY
880		countdown and/or running the auto-boot command resp.
881		entering interactive mode.
882
883		This feature is especially useful when "preboot" is
884		automatically generated or modified. For an example
885		see the LWMON board specific code: here "preboot" is
886		modified when the user holds down a certain
887		combination of keys on the (special) keyboard when
888		booting the systems
889
890- Serial Download Echo Mode:
891		CONFIG_LOADS_ECHO
892		If defined to 1, all characters received during a
893		serial download (using the "loads" command) are
894		echoed back. This might be needed by some terminal
895		emulations (like "cu"), but may as well just take
896		time on others. This setting #define's the initial
897		value of the "loads_echo" environment variable.
898
899- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
900		CONFIG_KGDB_BAUDRATE
901		Select one of the baudrates listed in
902		CONFIG_SYS_BAUDRATE_TABLE, see below.
903
904- Monitor Functions:
905		Monitor commands can be included or excluded
906		from the build by using the #include files
907		<config_cmd_all.h> and #undef'ing unwanted
908		commands, or using <config_cmd_default.h>
909		and augmenting with additional #define's
910		for wanted commands.
911
912		The default command configuration includes all commands
913		except those marked below with a "*".
914
915		CONFIG_CMD_ASKENV	* ask for env variable
916		CONFIG_CMD_BDI		  bdinfo
917		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
918		CONFIG_CMD_BMP		* BMP support
919		CONFIG_CMD_BSP		* Board specific commands
920		CONFIG_CMD_BOOTD	  bootd
921		CONFIG_CMD_CACHE	* icache, dcache
922		CONFIG_CMD_CLK   	* clock command support
923		CONFIG_CMD_CONSOLE	  coninfo
924		CONFIG_CMD_CRC32	* crc32
925		CONFIG_CMD_DATE		* support for RTC, date/time...
926		CONFIG_CMD_DHCP		* DHCP support
927		CONFIG_CMD_DIAG		* Diagnostics
928		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
929		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
930		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
931		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
932		CONFIG_CMD_DTT		* Digital Therm and Thermostat
933		CONFIG_CMD_ECHO		  echo arguments
934		CONFIG_CMD_EDITENV	  edit env variable
935		CONFIG_CMD_EEPROM	* EEPROM read/write support
936		CONFIG_CMD_ELF		* bootelf, bootvx
937		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
938		CONFIG_CMD_ENV_FLAGS	* display details about env flags
939		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
940		CONFIG_CMD_EXPORTENV	* export the environment
941		CONFIG_CMD_EXT2		* ext2 command support
942		CONFIG_CMD_EXT4		* ext4 command support
943		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
944					  that work for multiple fs types
945		CONFIG_CMD_SAVEENV	  saveenv
946		CONFIG_CMD_FDC		* Floppy Disk Support
947		CONFIG_CMD_FAT		* FAT command support
948		CONFIG_CMD_FLASH	  flinfo, erase, protect
949		CONFIG_CMD_FPGA		  FPGA device initialization support
950		CONFIG_CMD_FUSE		* Device fuse support
951		CONFIG_CMD_GETTIME	* Get time since boot
952		CONFIG_CMD_GO		* the 'go' command (exec code)
953		CONFIG_CMD_GREPENV	* search environment
954		CONFIG_CMD_HASH		* calculate hash / digest
955		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
956		CONFIG_CMD_I2C		* I2C serial bus support
957		CONFIG_CMD_IDE		* IDE harddisk support
958		CONFIG_CMD_IMI		  iminfo
959		CONFIG_CMD_IMLS		  List all images found in NOR flash
960		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
961		CONFIG_CMD_IMMAP	* IMMR dump support
962		CONFIG_CMD_IMPORTENV	* import an environment
963		CONFIG_CMD_INI		* import data from an ini file into the env
964		CONFIG_CMD_IRQ		* irqinfo
965		CONFIG_CMD_ITEST	  Integer/string test of 2 values
966		CONFIG_CMD_JFFS2	* JFFS2 Support
967		CONFIG_CMD_KGDB		* kgdb
968		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
969		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
970					  (169.254.*.*)
971		CONFIG_CMD_LOADB	  loadb
972		CONFIG_CMD_LOADS	  loads
973		CONFIG_CMD_MD5SUM	* print md5 message digest
974					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
975		CONFIG_CMD_MEMINFO	* Display detailed memory information
976		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
977					  loop, loopw
978		CONFIG_CMD_MEMTEST	* mtest
979		CONFIG_CMD_MISC		  Misc functions like sleep etc
980		CONFIG_CMD_MMC		* MMC memory mapped support
981		CONFIG_CMD_MII		* MII utility commands
982		CONFIG_CMD_MTDPARTS	* MTD partition support
983		CONFIG_CMD_NAND		* NAND support
984		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
985		CONFIG_CMD_NFS		  NFS support
986		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
987		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
988		CONFIG_CMD_PCI		* pciinfo
989		CONFIG_CMD_PCMCIA		* PCMCIA support
990		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
991					  host
992		CONFIG_CMD_PORTIO	* Port I/O
993		CONFIG_CMD_READ		* Read raw data from partition
994		CONFIG_CMD_REGINFO	* Register dump
995		CONFIG_CMD_RUN		  run command in env variable
996		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
997		CONFIG_CMD_SAVES	* save S record dump
998		CONFIG_CMD_SCSI		* SCSI Support
999		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1000					  (requires CONFIG_CMD_I2C)
1001		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1002					  (4xx only)
1003		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1004		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1005					  (requires CONFIG_CMD_MEMORY)
1006		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1007		CONFIG_CMD_SOURCE	  "source" command Support
1008		CONFIG_CMD_SPI		* SPI serial bus support
1009		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1010		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1011		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1012		CONFIG_CMD_TIMER	* access to the system tick timer
1013		CONFIG_CMD_USB		* USB support
1014		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1015		CONFIG_CMD_MFSL		* Microblaze FSL support
1016		CONFIG_CMD_XIMG		  Load part of Multi Image
1017
1018
1019		EXAMPLE: If you want all functions except of network
1020		support you can write:
1021
1022		#include "config_cmd_all.h"
1023		#undef CONFIG_CMD_NET
1024
1025	Other Commands:
1026		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1027
1028	Note:	Don't enable the "icache" and "dcache" commands
1029		(configuration option CONFIG_CMD_CACHE) unless you know
1030		what you (and your U-Boot users) are doing. Data
1031		cache cannot be enabled on systems like the 8xx or
1032		8260 (where accesses to the IMMR region must be
1033		uncached), and it cannot be disabled on all other
1034		systems where we (mis-) use the data cache to hold an
1035		initial stack and some data.
1036
1037
1038		XXX - this list needs to get updated!
1039
1040- Regular expression support:
1041		CONFIG_REGEX
1042		If this variable is defined, U-Boot is linked against
1043		the SLRE (Super Light Regular Expression) library,
1044		which adds regex support to some commands, as for
1045		example "env grep" and "setexpr".
1046
1047- Device tree:
1048		CONFIG_OF_CONTROL
1049		If this variable is defined, U-Boot will use a device tree
1050		to configure its devices, instead of relying on statically
1051		compiled #defines in the board file. This option is
1052		experimental and only available on a few boards. The device
1053		tree is available in the global data as gd->fdt_blob.
1054
1055		U-Boot needs to get its device tree from somewhere. This can
1056		be done using one of the two options below:
1057
1058		CONFIG_OF_EMBED
1059		If this variable is defined, U-Boot will embed a device tree
1060		binary in its image. This device tree file should be in the
1061		board directory and called <soc>-<board>.dts. The binary file
1062		is then picked up in board_init_f() and made available through
1063		the global data structure as gd->blob.
1064
1065		CONFIG_OF_SEPARATE
1066		If this variable is defined, U-Boot will build a device tree
1067		binary. It will be called u-boot.dtb. Architecture-specific
1068		code will locate it at run-time. Generally this works by:
1069
1070			cat u-boot.bin u-boot.dtb >image.bin
1071
1072		and in fact, U-Boot does this for you, creating a file called
1073		u-boot-dtb.bin which is useful in the common case. You can
1074		still use the individual files if you need something more
1075		exotic.
1076
1077- Watchdog:
1078		CONFIG_WATCHDOG
1079		If this variable is defined, it enables watchdog
1080		support for the SoC. There must be support in the SoC
1081		specific code for a watchdog. For the 8xx and 8260
1082		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1083		register.  When supported for a specific SoC is
1084		available, then no further board specific code should
1085		be needed to use it.
1086
1087		CONFIG_HW_WATCHDOG
1088		When using a watchdog circuitry external to the used
1089		SoC, then define this variable and provide board
1090		specific code for the "hw_watchdog_reset" function.
1091
1092- U-Boot Version:
1093		CONFIG_VERSION_VARIABLE
1094		If this variable is defined, an environment variable
1095		named "ver" is created by U-Boot showing the U-Boot
1096		version as printed by the "version" command.
1097		Any change to this variable will be reverted at the
1098		next reset.
1099
1100- Real-Time Clock:
1101
1102		When CONFIG_CMD_DATE is selected, the type of the RTC
1103		has to be selected, too. Define exactly one of the
1104		following options:
1105
1106		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1107		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1108		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1109		CONFIG_RTC_MC146818	- use MC146818 RTC
1110		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1111		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1112		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1113		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1114		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1115		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1116		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1117		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1118					  RV3029 RTC.
1119
1120		Note that if the RTC uses I2C, then the I2C interface
1121		must also be configured. See I2C Support, below.
1122
1123- GPIO Support:
1124		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1125
1126		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1127		chip-ngpio pairs that tell the PCA953X driver the number of
1128		pins supported by a particular chip.
1129
1130		Note that if the GPIO device uses I2C, then the I2C interface
1131		must also be configured. See I2C Support, below.
1132
1133- Timestamp Support:
1134
1135		When CONFIG_TIMESTAMP is selected, the timestamp
1136		(date and time) of an image is printed by image
1137		commands like bootm or iminfo. This option is
1138		automatically enabled when you select CONFIG_CMD_DATE .
1139
1140- Partition Labels (disklabels) Supported:
1141		Zero or more of the following:
1142		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1143		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1144				       Intel architecture, USB sticks, etc.
1145		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1146		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1147				       bootloader.  Note 2TB partition limit; see
1148				       disk/part_efi.c
1149		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1150
1151		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1152		CONFIG_CMD_SCSI) you must configure support for at
1153		least one non-MTD partition type as well.
1154
1155- IDE Reset method:
1156		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1157		board configurations files but used nowhere!
1158
1159		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1160		be performed by calling the function
1161			ide_set_reset(int reset)
1162		which has to be defined in a board specific file
1163
1164- ATAPI Support:
1165		CONFIG_ATAPI
1166
1167		Set this to enable ATAPI support.
1168
1169- LBA48 Support
1170		CONFIG_LBA48
1171
1172		Set this to enable support for disks larger than 137GB
1173		Also look at CONFIG_SYS_64BIT_LBA.
1174		Whithout these , LBA48 support uses 32bit variables and will 'only'
1175		support disks up to 2.1TB.
1176
1177		CONFIG_SYS_64BIT_LBA:
1178			When enabled, makes the IDE subsystem use 64bit sector addresses.
1179			Default is 32bit.
1180
1181- SCSI Support:
1182		At the moment only there is only support for the
1183		SYM53C8XX SCSI controller; define
1184		CONFIG_SCSI_SYM53C8XX to enable it.
1185
1186		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1187		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1188		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1189		maximum numbers of LUNs, SCSI ID's and target
1190		devices.
1191		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1192
1193		The environment variable 'scsidevs' is set to the number of
1194		SCSI devices found during the last scan.
1195
1196- NETWORK Support (PCI):
1197		CONFIG_E1000
1198		Support for Intel 8254x/8257x gigabit chips.
1199
1200		CONFIG_E1000_SPI
1201		Utility code for direct access to the SPI bus on Intel 8257x.
1202		This does not do anything useful unless you set at least one
1203		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1204
1205		CONFIG_E1000_SPI_GENERIC
1206		Allow generic access to the SPI bus on the Intel 8257x, for
1207		example with the "sspi" command.
1208
1209		CONFIG_CMD_E1000
1210		Management command for E1000 devices.  When used on devices
1211		with SPI support you can reprogram the EEPROM from U-Boot.
1212
1213		CONFIG_E1000_FALLBACK_MAC
1214		default MAC for empty EEPROM after production.
1215
1216		CONFIG_EEPRO100
1217		Support for Intel 82557/82559/82559ER chips.
1218		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1219		write routine for first time initialisation.
1220
1221		CONFIG_TULIP
1222		Support for Digital 2114x chips.
1223		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1224		modem chip initialisation (KS8761/QS6611).
1225
1226		CONFIG_NATSEMI
1227		Support for National dp83815 chips.
1228
1229		CONFIG_NS8382X
1230		Support for National dp8382[01] gigabit chips.
1231
1232- NETWORK Support (other):
1233
1234		CONFIG_DRIVER_AT91EMAC
1235		Support for AT91RM9200 EMAC.
1236
1237			CONFIG_RMII
1238			Define this to use reduced MII inteface
1239
1240			CONFIG_DRIVER_AT91EMAC_QUIET
1241			If this defined, the driver is quiet.
1242			The driver doen't show link status messages.
1243
1244		CONFIG_CALXEDA_XGMAC
1245		Support for the Calxeda XGMAC device
1246
1247		CONFIG_LAN91C96
1248		Support for SMSC's LAN91C96 chips.
1249
1250			CONFIG_LAN91C96_BASE
1251			Define this to hold the physical address
1252			of the LAN91C96's I/O space
1253
1254			CONFIG_LAN91C96_USE_32_BIT
1255			Define this to enable 32 bit addressing
1256
1257		CONFIG_SMC91111
1258		Support for SMSC's LAN91C111 chip
1259
1260			CONFIG_SMC91111_BASE
1261			Define this to hold the physical address
1262			of the device (I/O space)
1263
1264			CONFIG_SMC_USE_32_BIT
1265			Define this if data bus is 32 bits
1266
1267			CONFIG_SMC_USE_IOFUNCS
1268			Define this to use i/o functions instead of macros
1269			(some hardware wont work with macros)
1270
1271		CONFIG_DRIVER_TI_EMAC
1272		Support for davinci emac
1273
1274			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1275			Define this if you have more then 3 PHYs.
1276
1277		CONFIG_FTGMAC100
1278		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1279
1280			CONFIG_FTGMAC100_EGIGA
1281			Define this to use GE link update with gigabit PHY.
1282			Define this if FTGMAC100 is connected to gigabit PHY.
1283			If your system has 10/100 PHY only, it might not occur
1284			wrong behavior. Because PHY usually return timeout or
1285			useless data when polling gigabit status and gigabit
1286			control registers. This behavior won't affect the
1287			correctnessof 10/100 link speed update.
1288
1289		CONFIG_SMC911X
1290		Support for SMSC's LAN911x and LAN921x chips
1291
1292			CONFIG_SMC911X_BASE
1293			Define this to hold the physical address
1294			of the device (I/O space)
1295
1296			CONFIG_SMC911X_32_BIT
1297			Define this if data bus is 32 bits
1298
1299			CONFIG_SMC911X_16_BIT
1300			Define this if data bus is 16 bits. If your processor
1301			automatically converts one 32 bit word to two 16 bit
1302			words you may also try CONFIG_SMC911X_32_BIT.
1303
1304		CONFIG_SH_ETHER
1305		Support for Renesas on-chip Ethernet controller
1306
1307			CONFIG_SH_ETHER_USE_PORT
1308			Define the number of ports to be used
1309
1310			CONFIG_SH_ETHER_PHY_ADDR
1311			Define the ETH PHY's address
1312
1313			CONFIG_SH_ETHER_CACHE_WRITEBACK
1314			If this option is set, the driver enables cache flush.
1315
1316- TPM Support:
1317		CONFIG_TPM
1318		Support TPM devices.
1319
1320		CONFIG_TPM_TIS_I2C
1321		Support for i2c bus TPM devices. Only one device
1322		per system is supported at this time.
1323
1324			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1325			Define the the i2c bus number for the TPM device
1326
1327			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1328			Define the TPM's address on the i2c bus
1329
1330			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1331			Define the burst count bytes upper limit
1332
1333		CONFIG_TPM_ATMEL_TWI
1334		Support for Atmel TWI TPM device. Requires I2C support.
1335
1336		CONFIG_TPM_TIS_LPC
1337		Support for generic parallel port TPM devices. Only one device
1338		per system is supported at this time.
1339
1340			CONFIG_TPM_TIS_BASE_ADDRESS
1341			Base address where the generic TPM device is mapped
1342			to. Contemporary x86 systems usually map it at
1343			0xfed40000.
1344
1345		CONFIG_CMD_TPM
1346		Add tpm monitor functions.
1347		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1348		provides monitor access to authorized functions.
1349
1350		CONFIG_TPM
1351		Define this to enable the TPM support library which provides
1352		functional interfaces to some TPM commands.
1353		Requires support for a TPM device.
1354
1355		CONFIG_TPM_AUTH_SESSIONS
1356		Define this to enable authorized functions in the TPM library.
1357		Requires CONFIG_TPM and CONFIG_SHA1.
1358
1359- USB Support:
1360		At the moment only the UHCI host controller is
1361		supported (PIP405, MIP405, MPC5200); define
1362		CONFIG_USB_UHCI to enable it.
1363		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1364		and define CONFIG_USB_STORAGE to enable the USB
1365		storage devices.
1366		Note:
1367		Supported are USB Keyboards and USB Floppy drives
1368		(TEAC FD-05PUB).
1369		MPC5200 USB requires additional defines:
1370			CONFIG_USB_CLOCK
1371				for 528 MHz Clock: 0x0001bbbb
1372			CONFIG_PSC3_USB
1373				for USB on PSC3
1374			CONFIG_USB_CONFIG
1375				for differential drivers: 0x00001000
1376				for single ended drivers: 0x00005000
1377				for differential drivers on PSC3: 0x00000100
1378				for single ended drivers on PSC3: 0x00004100
1379			CONFIG_SYS_USB_EVENT_POLL
1380				May be defined to allow interrupt polling
1381				instead of using asynchronous interrupts
1382
1383		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1384		txfilltuning field in the EHCI controller on reset.
1385
1386		CONFIG_USB_HUB_MIN_POWER_ON_DELAY defines the minimum
1387		interval for usb hub power-on delay.(minimum 100msec)
1388
1389- USB Device:
1390		Define the below if you wish to use the USB console.
1391		Once firmware is rebuilt from a serial console issue the
1392		command "setenv stdin usbtty; setenv stdout usbtty" and
1393		attach your USB cable. The Unix command "dmesg" should print
1394		it has found a new device. The environment variable usbtty
1395		can be set to gserial or cdc_acm to enable your device to
1396		appear to a USB host as a Linux gserial device or a
1397		Common Device Class Abstract Control Model serial device.
1398		If you select usbtty = gserial you should be able to enumerate
1399		a Linux host by
1400		# modprobe usbserial vendor=0xVendorID product=0xProductID
1401		else if using cdc_acm, simply setting the environment
1402		variable usbtty to be cdc_acm should suffice. The following
1403		might be defined in YourBoardName.h
1404
1405			CONFIG_USB_DEVICE
1406			Define this to build a UDC device
1407
1408			CONFIG_USB_TTY
1409			Define this to have a tty type of device available to
1410			talk to the UDC device
1411
1412			CONFIG_USBD_HS
1413			Define this to enable the high speed support for usb
1414			device and usbtty. If this feature is enabled, a routine
1415			int is_usbd_high_speed(void)
1416			also needs to be defined by the driver to dynamically poll
1417			whether the enumeration has succeded at high speed or full
1418			speed.
1419
1420			CONFIG_SYS_CONSOLE_IS_IN_ENV
1421			Define this if you want stdin, stdout &/or stderr to
1422			be set to usbtty.
1423
1424			mpc8xx:
1425				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1426				Derive USB clock from external clock "blah"
1427				- CONFIG_SYS_USB_EXTC_CLK 0x02
1428
1429				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1430				Derive USB clock from brgclk
1431				- CONFIG_SYS_USB_BRG_CLK 0x04
1432
1433		If you have a USB-IF assigned VendorID then you may wish to
1434		define your own vendor specific values either in BoardName.h
1435		or directly in usbd_vendor_info.h. If you don't define
1436		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1437		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1438		should pretend to be a Linux device to it's target host.
1439
1440			CONFIG_USBD_MANUFACTURER
1441			Define this string as the name of your company for
1442			- CONFIG_USBD_MANUFACTURER "my company"
1443
1444			CONFIG_USBD_PRODUCT_NAME
1445			Define this string as the name of your product
1446			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1447
1448			CONFIG_USBD_VENDORID
1449			Define this as your assigned Vendor ID from the USB
1450			Implementors Forum. This *must* be a genuine Vendor ID
1451			to avoid polluting the USB namespace.
1452			- CONFIG_USBD_VENDORID 0xFFFF
1453
1454			CONFIG_USBD_PRODUCTID
1455			Define this as the unique Product ID
1456			for your device
1457			- CONFIG_USBD_PRODUCTID 0xFFFF
1458
1459		Some USB device drivers may need to check USB cable attachment.
1460		In this case you can enable following config in BoardName.h:
1461			CONFIG_USB_CABLE_CHECK
1462			This enables function definition:
1463			- usb_cable_connected() in include/usb.h
1464			Implementation of this function is board-specific.
1465
1466- ULPI Layer Support:
1467		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1468		the generic ULPI layer. The generic layer accesses the ULPI PHY
1469		via the platform viewport, so you need both the genric layer and
1470		the viewport enabled. Currently only Chipidea/ARC based
1471		viewport is supported.
1472		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1473		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1474		If your ULPI phy needs a different reference clock than the
1475		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1476		the appropriate value in Hz.
1477
1478- MMC Support:
1479		The MMC controller on the Intel PXA is supported. To
1480		enable this define CONFIG_MMC. The MMC can be
1481		accessed from the boot prompt by mapping the device
1482		to physical memory similar to flash. Command line is
1483		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1484		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1485
1486		CONFIG_SH_MMCIF
1487		Support for Renesas on-chip MMCIF controller
1488
1489			CONFIG_SH_MMCIF_ADDR
1490			Define the base address of MMCIF registers
1491
1492			CONFIG_SH_MMCIF_CLK
1493			Define the clock frequency for MMCIF
1494
1495- USB Device Firmware Update (DFU) class support:
1496		CONFIG_DFU_FUNCTION
1497		This enables the USB portion of the DFU USB class
1498
1499		CONFIG_CMD_DFU
1500		This enables the command "dfu" which is used to have
1501		U-Boot create a DFU class device via USB.  This command
1502		requires that the "dfu_alt_info" environment variable be
1503		set and define the alt settings to expose to the host.
1504
1505		CONFIG_DFU_MMC
1506		This enables support for exposing (e)MMC devices via DFU.
1507
1508		CONFIG_DFU_NAND
1509		This enables support for exposing NAND devices via DFU.
1510
1511		CONFIG_DFU_RAM
1512		This enables support for exposing RAM via DFU.
1513		Note: DFU spec refer to non-volatile memory usage, but
1514		allow usages beyond the scope of spec - here RAM usage,
1515		one that would help mostly the developer.
1516
1517		CONFIG_SYS_DFU_DATA_BUF_SIZE
1518		Dfu transfer uses a buffer before writing data to the
1519		raw storage device. Make the size (in bytes) of this buffer
1520		configurable. The size of this buffer is also configurable
1521		through the "dfu_bufsiz" environment variable.
1522
1523		CONFIG_SYS_DFU_MAX_FILE_SIZE
1524		When updating files rather than the raw storage device,
1525		we use a static buffer to copy the file into and then write
1526		the buffer once we've been given the whole file.  Define
1527		this to the maximum filesize (in bytes) for the buffer.
1528		Default is 4 MiB if undefined.
1529
1530- Journaling Flash filesystem support:
1531		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1532		CONFIG_JFFS2_NAND_DEV
1533		Define these for a default partition on a NAND device
1534
1535		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1536		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1537		Define these for a default partition on a NOR device
1538
1539		CONFIG_SYS_JFFS_CUSTOM_PART
1540		Define this to create an own partition. You have to provide a
1541		function struct part_info* jffs2_part_info(int part_num)
1542
1543		If you define only one JFFS2 partition you may also want to
1544		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1545		to disable the command chpart. This is the default when you
1546		have not defined a custom partition
1547
1548- FAT(File Allocation Table) filesystem write function support:
1549		CONFIG_FAT_WRITE
1550
1551		Define this to enable support for saving memory data as a
1552		file in FAT formatted partition.
1553
1554		This will also enable the command "fatwrite" enabling the
1555		user to write files to FAT.
1556
1557CBFS (Coreboot Filesystem) support
1558		CONFIG_CMD_CBFS
1559
1560		Define this to enable support for reading from a Coreboot
1561		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1562		and cbfsload.
1563
1564- Keyboard Support:
1565		CONFIG_ISA_KEYBOARD
1566
1567		Define this to enable standard (PC-Style) keyboard
1568		support
1569
1570		CONFIG_I8042_KBD
1571		Standard PC keyboard driver with US (is default) and
1572		GERMAN key layout (switch via environment 'keymap=de') support.
1573		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1574		for cfb_console. Supports cursor blinking.
1575
1576		CONFIG_CROS_EC_KEYB
1577		Enables a Chrome OS keyboard using the CROS_EC interface.
1578		This uses CROS_EC to communicate with a second microcontroller
1579		which provides key scans on request.
1580
1581- Video support:
1582		CONFIG_VIDEO
1583
1584		Define this to enable video support (for output to
1585		video).
1586
1587		CONFIG_VIDEO_CT69000
1588
1589		Enable Chips & Technologies 69000 Video chip
1590
1591		CONFIG_VIDEO_SMI_LYNXEM
1592		Enable Silicon Motion SMI 712/710/810 Video chip. The
1593		video output is selected via environment 'videoout'
1594		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1595		assumed.
1596
1597		For the CT69000 and SMI_LYNXEM drivers, videomode is
1598		selected via environment 'videomode'. Two different ways
1599		are possible:
1600		- "videomode=num"   'num' is a standard LiLo mode numbers.
1601		Following standard modes are supported	(* is default):
1602
1603		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1604		-------------+---------------------------------------------
1605		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1606		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1607		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1608		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1609		-------------+---------------------------------------------
1610		(i.e. setenv videomode 317; saveenv; reset;)
1611
1612		- "videomode=bootargs" all the video parameters are parsed
1613		from the bootargs. (See drivers/video/videomodes.c)
1614
1615
1616		CONFIG_VIDEO_SED13806
1617		Enable Epson SED13806 driver. This driver supports 8bpp
1618		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1619		or CONFIG_VIDEO_SED13806_16BPP
1620
1621		CONFIG_FSL_DIU_FB
1622		Enable the Freescale DIU video driver.	Reference boards for
1623		SOCs that have a DIU should define this macro to enable DIU
1624		support, and should also define these other macros:
1625
1626			CONFIG_SYS_DIU_ADDR
1627			CONFIG_VIDEO
1628			CONFIG_CMD_BMP
1629			CONFIG_CFB_CONSOLE
1630			CONFIG_VIDEO_SW_CURSOR
1631			CONFIG_VGA_AS_SINGLE_DEVICE
1632			CONFIG_VIDEO_LOGO
1633			CONFIG_VIDEO_BMP_LOGO
1634
1635		The DIU driver will look for the 'video-mode' environment
1636		variable, and if defined, enable the DIU as a console during
1637		boot.  See the documentation file README.video for a
1638		description of this variable.
1639
1640		CONFIG_VIDEO_VGA
1641
1642		Enable the VGA video / BIOS for x86. The alternative if you
1643		are using coreboot is to use the coreboot frame buffer
1644		driver.
1645
1646
1647- Keyboard Support:
1648		CONFIG_KEYBOARD
1649
1650		Define this to enable a custom keyboard support.
1651		This simply calls drv_keyboard_init() which must be
1652		defined in your board-specific files.
1653		The only board using this so far is RBC823.
1654
1655- LCD Support:	CONFIG_LCD
1656
1657		Define this to enable LCD support (for output to LCD
1658		display); also select one of the supported displays
1659		by defining one of these:
1660
1661		CONFIG_ATMEL_LCD:
1662
1663			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1664
1665		CONFIG_NEC_NL6448AC33:
1666
1667			NEC NL6448AC33-18. Active, color, single scan.
1668
1669		CONFIG_NEC_NL6448BC20
1670
1671			NEC NL6448BC20-08. 6.5", 640x480.
1672			Active, color, single scan.
1673
1674		CONFIG_NEC_NL6448BC33_54
1675
1676			NEC NL6448BC33-54. 10.4", 640x480.
1677			Active, color, single scan.
1678
1679		CONFIG_SHARP_16x9
1680
1681			Sharp 320x240. Active, color, single scan.
1682			It isn't 16x9, and I am not sure what it is.
1683
1684		CONFIG_SHARP_LQ64D341
1685
1686			Sharp LQ64D341 display, 640x480.
1687			Active, color, single scan.
1688
1689		CONFIG_HLD1045
1690
1691			HLD1045 display, 640x480.
1692			Active, color, single scan.
1693
1694		CONFIG_OPTREX_BW
1695
1696			Optrex	 CBL50840-2 NF-FW 99 22 M5
1697			or
1698			Hitachi	 LMG6912RPFC-00T
1699			or
1700			Hitachi	 SP14Q002
1701
1702			320x240. Black & white.
1703
1704		Normally display is black on white background; define
1705		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1706
1707		CONFIG_LCD_ALIGNMENT
1708
1709		Normally the LCD is page-aligned (tyically 4KB). If this is
1710		defined then the LCD will be aligned to this value instead.
1711		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1712		here, since it is cheaper to change data cache settings on
1713		a per-section basis.
1714
1715		CONFIG_CONSOLE_SCROLL_LINES
1716
1717		When the console need to be scrolled, this is the number of
1718		lines to scroll by. It defaults to 1. Increasing this makes
1719		the console jump but can help speed up operation when scrolling
1720		is slow.
1721
1722		CONFIG_LCD_BMP_RLE8
1723
1724		Support drawing of RLE8-compressed bitmaps on the LCD.
1725
1726		CONFIG_I2C_EDID
1727
1728		Enables an 'i2c edid' command which can read EDID
1729		information over I2C from an attached LCD display.
1730
1731- Splash Screen Support: CONFIG_SPLASH_SCREEN
1732
1733		If this option is set, the environment is checked for
1734		a variable "splashimage". If found, the usual display
1735		of logo, copyright and system information on the LCD
1736		is suppressed and the BMP image at the address
1737		specified in "splashimage" is loaded instead. The
1738		console is redirected to the "nulldev", too. This
1739		allows for a "silent" boot where a splash screen is
1740		loaded very quickly after power-on.
1741
1742		CONFIG_SPLASHIMAGE_GUARD
1743
1744		If this option is set, then U-Boot will prevent the environment
1745		variable "splashimage" from being set to a problematic address
1746		(see README.displaying-bmps).
1747		This option is useful for targets where, due to alignment
1748		restrictions, an improperly aligned BMP image will cause a data
1749		abort. If you think you will not have problems with unaligned
1750		accesses (for example because your toolchain prevents them)
1751		there is no need to set this option.
1752
1753		CONFIG_SPLASH_SCREEN_ALIGN
1754
1755		If this option is set the splash image can be freely positioned
1756		on the screen. Environment variable "splashpos" specifies the
1757		position as "x,y". If a positive number is given it is used as
1758		number of pixel from left/top. If a negative number is given it
1759		is used as number of pixel from right/bottom. You can also
1760		specify 'm' for centering the image.
1761
1762		Example:
1763		setenv splashpos m,m
1764			=> image at center of screen
1765
1766		setenv splashpos 30,20
1767			=> image at x = 30 and y = 20
1768
1769		setenv splashpos -10,m
1770			=> vertically centered image
1771			   at x = dspWidth - bmpWidth - 9
1772
1773- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1774
1775		If this option is set, additionally to standard BMP
1776		images, gzipped BMP images can be displayed via the
1777		splashscreen support or the bmp command.
1778
1779- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1780
1781		If this option is set, 8-bit RLE compressed BMP images
1782		can be displayed via the splashscreen support or the
1783		bmp command.
1784
1785- Do compresssing for memory range:
1786		CONFIG_CMD_ZIP
1787
1788		If this option is set, it would use zlib deflate method
1789		to compress the specified memory at its best effort.
1790
1791- Compression support:
1792		CONFIG_GZIP
1793
1794		Enabled by default to support gzip compressed images.
1795
1796		CONFIG_BZIP2
1797
1798		If this option is set, support for bzip2 compressed
1799		images is included. If not, only uncompressed and gzip
1800		compressed images are supported.
1801
1802		NOTE: the bzip2 algorithm requires a lot of RAM, so
1803		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1804		be at least 4MB.
1805
1806		CONFIG_LZMA
1807
1808		If this option is set, support for lzma compressed
1809		images is included.
1810
1811		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1812		requires an amount of dynamic memory that is given by the
1813		formula:
1814
1815			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1816
1817		Where lc and lp stand for, respectively, Literal context bits
1818		and Literal pos bits.
1819
1820		This value is upper-bounded by 14MB in the worst case. Anyway,
1821		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1822		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1823		a very small buffer.
1824
1825		Use the lzmainfo tool to determinate the lc and lp values and
1826		then calculate the amount of needed dynamic memory (ensuring
1827		the appropriate CONFIG_SYS_MALLOC_LEN value).
1828
1829		CONFIG_LZO
1830
1831		If this option is set, support for LZO compressed images
1832		is included.
1833
1834- MII/PHY support:
1835		CONFIG_PHY_ADDR
1836
1837		The address of PHY on MII bus.
1838
1839		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1840
1841		The clock frequency of the MII bus
1842
1843		CONFIG_PHY_GIGE
1844
1845		If this option is set, support for speed/duplex
1846		detection of gigabit PHY is included.
1847
1848		CONFIG_PHY_RESET_DELAY
1849
1850		Some PHY like Intel LXT971A need extra delay after
1851		reset before any MII register access is possible.
1852		For such PHY, set this option to the usec delay
1853		required. (minimum 300usec for LXT971A)
1854
1855		CONFIG_PHY_CMD_DELAY (ppc4xx)
1856
1857		Some PHY like Intel LXT971A need extra delay after
1858		command issued before MII status register can be read
1859
1860- Ethernet address:
1861		CONFIG_ETHADDR
1862		CONFIG_ETH1ADDR
1863		CONFIG_ETH2ADDR
1864		CONFIG_ETH3ADDR
1865		CONFIG_ETH4ADDR
1866		CONFIG_ETH5ADDR
1867
1868		Define a default value for Ethernet address to use
1869		for the respective Ethernet interface, in case this
1870		is not determined automatically.
1871
1872- IP address:
1873		CONFIG_IPADDR
1874
1875		Define a default value for the IP address to use for
1876		the default Ethernet interface, in case this is not
1877		determined through e.g. bootp.
1878		(Environment variable "ipaddr")
1879
1880- Server IP address:
1881		CONFIG_SERVERIP
1882
1883		Defines a default value for the IP address of a TFTP
1884		server to contact when using the "tftboot" command.
1885		(Environment variable "serverip")
1886
1887		CONFIG_KEEP_SERVERADDR
1888
1889		Keeps the server's MAC address, in the env 'serveraddr'
1890		for passing to bootargs (like Linux's netconsole option)
1891
1892- Gateway IP address:
1893		CONFIG_GATEWAYIP
1894
1895		Defines a default value for the IP address of the
1896		default router where packets to other networks are
1897		sent to.
1898		(Environment variable "gatewayip")
1899
1900- Subnet mask:
1901		CONFIG_NETMASK
1902
1903		Defines a default value for the subnet mask (or
1904		routing prefix) which is used to determine if an IP
1905		address belongs to the local subnet or needs to be
1906		forwarded through a router.
1907		(Environment variable "netmask")
1908
1909- Multicast TFTP Mode:
1910		CONFIG_MCAST_TFTP
1911
1912		Defines whether you want to support multicast TFTP as per
1913		rfc-2090; for example to work with atftp.  Lets lots of targets
1914		tftp down the same boot image concurrently.  Note: the Ethernet
1915		driver in use must provide a function: mcast() to join/leave a
1916		multicast group.
1917
1918- BOOTP Recovery Mode:
1919		CONFIG_BOOTP_RANDOM_DELAY
1920
1921		If you have many targets in a network that try to
1922		boot using BOOTP, you may want to avoid that all
1923		systems send out BOOTP requests at precisely the same
1924		moment (which would happen for instance at recovery
1925		from a power failure, when all systems will try to
1926		boot, thus flooding the BOOTP server. Defining
1927		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1928		inserted before sending out BOOTP requests. The
1929		following delays are inserted then:
1930
1931		1st BOOTP request:	delay 0 ... 1 sec
1932		2nd BOOTP request:	delay 0 ... 2 sec
1933		3rd BOOTP request:	delay 0 ... 4 sec
1934		4th and following
1935		BOOTP requests:		delay 0 ... 8 sec
1936
1937- DHCP Advanced Options:
1938		You can fine tune the DHCP functionality by defining
1939		CONFIG_BOOTP_* symbols:
1940
1941		CONFIG_BOOTP_SUBNETMASK
1942		CONFIG_BOOTP_GATEWAY
1943		CONFIG_BOOTP_HOSTNAME
1944		CONFIG_BOOTP_NISDOMAIN
1945		CONFIG_BOOTP_BOOTPATH
1946		CONFIG_BOOTP_BOOTFILESIZE
1947		CONFIG_BOOTP_DNS
1948		CONFIG_BOOTP_DNS2
1949		CONFIG_BOOTP_SEND_HOSTNAME
1950		CONFIG_BOOTP_NTPSERVER
1951		CONFIG_BOOTP_TIMEOFFSET
1952		CONFIG_BOOTP_VENDOREX
1953		CONFIG_BOOTP_MAY_FAIL
1954
1955		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1956		environment variable, not the BOOTP server.
1957
1958		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1959		after the configured retry count, the call will fail
1960		instead of starting over.  This can be used to fail over
1961		to Link-local IP address configuration if the DHCP server
1962		is not available.
1963
1964		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1965		serverip from a DHCP server, it is possible that more
1966		than one DNS serverip is offered to the client.
1967		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1968		serverip will be stored in the additional environment
1969		variable "dnsip2". The first DNS serverip is always
1970		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1971		is defined.
1972
1973		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1974		to do a dynamic update of a DNS server. To do this, they
1975		need the hostname of the DHCP requester.
1976		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1977		of the "hostname" environment variable is passed as
1978		option 12 to the DHCP server.
1979
1980		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1981
1982		A 32bit value in microseconds for a delay between
1983		receiving a "DHCP Offer" and sending the "DHCP Request".
1984		This fixes a problem with certain DHCP servers that don't
1985		respond 100% of the time to a "DHCP request". E.g. On an
1986		AT91RM9200 processor running at 180MHz, this delay needed
1987		to be *at least* 15,000 usec before a Windows Server 2003
1988		DHCP server would reply 100% of the time. I recommend at
1989		least 50,000 usec to be safe. The alternative is to hope
1990		that one of the retries will be successful but note that
1991		the DHCP timeout and retry process takes a longer than
1992		this delay.
1993
1994 - Link-local IP address negotiation:
1995		Negotiate with other link-local clients on the local network
1996		for an address that doesn't require explicit configuration.
1997		This is especially useful if a DHCP server cannot be guaranteed
1998		to exist in all environments that the device must operate.
1999
2000		See doc/README.link-local for more information.
2001
2002 - CDP Options:
2003		CONFIG_CDP_DEVICE_ID
2004
2005		The device id used in CDP trigger frames.
2006
2007		CONFIG_CDP_DEVICE_ID_PREFIX
2008
2009		A two character string which is prefixed to the MAC address
2010		of the device.
2011
2012		CONFIG_CDP_PORT_ID
2013
2014		A printf format string which contains the ascii name of
2015		the port. Normally is set to "eth%d" which sets
2016		eth0 for the first Ethernet, eth1 for the second etc.
2017
2018		CONFIG_CDP_CAPABILITIES
2019
2020		A 32bit integer which indicates the device capabilities;
2021		0x00000010 for a normal host which does not forwards.
2022
2023		CONFIG_CDP_VERSION
2024
2025		An ascii string containing the version of the software.
2026
2027		CONFIG_CDP_PLATFORM
2028
2029		An ascii string containing the name of the platform.
2030
2031		CONFIG_CDP_TRIGGER
2032
2033		A 32bit integer sent on the trigger.
2034
2035		CONFIG_CDP_POWER_CONSUMPTION
2036
2037		A 16bit integer containing the power consumption of the
2038		device in .1 of milliwatts.
2039
2040		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2041
2042		A byte containing the id of the VLAN.
2043
2044- Status LED:	CONFIG_STATUS_LED
2045
2046		Several configurations allow to display the current
2047		status using a LED. For instance, the LED will blink
2048		fast while running U-Boot code, stop blinking as
2049		soon as a reply to a BOOTP request was received, and
2050		start blinking slow once the Linux kernel is running
2051		(supported by a status LED driver in the Linux
2052		kernel). Defining CONFIG_STATUS_LED enables this
2053		feature in U-Boot.
2054
2055		Additional options:
2056
2057		CONFIG_GPIO_LED
2058		The status LED can be connected to a GPIO pin.
2059		In such cases, the gpio_led driver can be used as a
2060		status LED backend implementation. Define CONFIG_GPIO_LED
2061		to include the gpio_led driver in the U-Boot binary.
2062
2063		CONFIG_GPIO_LED_INVERTED_TABLE
2064		Some GPIO connected LEDs may have inverted polarity in which
2065		case the GPIO high value corresponds to LED off state and
2066		GPIO low value corresponds to LED on state.
2067		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2068		with a list of GPIO LEDs that have inverted polarity.
2069
2070- CAN Support:	CONFIG_CAN_DRIVER
2071
2072		Defining CONFIG_CAN_DRIVER enables CAN driver support
2073		on those systems that support this (optional)
2074		feature, like the TQM8xxL modules.
2075
2076- I2C Support:	CONFIG_SYS_I2C
2077
2078		This enable the NEW i2c subsystem, and will allow you to use
2079		i2c commands at the u-boot command line (as long as you set
2080		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2081		based realtime clock chips or other i2c devices. See
2082		common/cmd_i2c.c for a description of the command line
2083		interface.
2084
2085		ported i2c driver to the new framework:
2086		- drivers/i2c/soft_i2c.c:
2087		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2088		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2089		    for defining speed and slave address
2090		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2091		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2092		    for defining speed and slave address
2093		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2094		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2095		    for defining speed and slave address
2096		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2097		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2098		    for defining speed and slave address
2099
2100		- drivers/i2c/fsl_i2c.c:
2101		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2102		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2103		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2104		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2105		    bus.
2106		  - If your board supports a second fsl i2c bus, define
2107		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2108		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2109		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2110		    second bus.
2111
2112		- drivers/i2c/tegra_i2c.c:
2113		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2114		  - This driver adds 4 i2c buses with a fix speed from
2115		    100000 and the slave addr 0!
2116
2117		- drivers/i2c/ppc4xx_i2c.c
2118		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2119		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2120		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2121
2122		- drivers/i2c/i2c_mxc.c
2123		  - activate this driver with CONFIG_SYS_I2C_MXC
2124		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2125		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2126		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2127		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2128		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2129		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2130		If thoses defines are not set, default value is 100000
2131		for speed, and 0 for slave.
2132
2133		- drivers/i2c/rcar_i2c.c:
2134		  - activate this driver with CONFIG_SYS_I2C_RCAR
2135		  - This driver adds 4 i2c buses
2136
2137		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2138		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2139		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2140		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2141		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2142		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2143		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2144		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2145		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2146
2147		- drivers/i2c/sh_i2c.c:
2148		  - activate this driver with CONFIG_SYS_I2C_SH
2149		  - This driver adds from 2 to 5 i2c buses
2150
2151		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2152		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2153		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2154		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2155		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2156		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2157		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2158		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2159		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2160		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2161		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2162		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2163		  - CONFIF_SYS_I2C_SH_NUM_CONTROLLERS for nummber of i2c buses
2164
2165		- drivers/i2c/omap24xx_i2c.c
2166		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2167		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2168		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2169		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2170		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2171		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2172		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2173		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2174		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2175		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2176		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2177
2178		- drivers/i2c/zynq_i2c.c
2179		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2180		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2181		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2182
2183		- drivers/i2c/s3c24x0_i2c.c:
2184		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2185		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2186		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2187		    with a fix speed from 100000 and the slave addr 0!
2188
2189		additional defines:
2190
2191		CONFIG_SYS_NUM_I2C_BUSES
2192		Hold the number of i2c busses you want to use. If you
2193		don't use/have i2c muxes on your i2c bus, this
2194		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2195		omit this define.
2196
2197		CONFIG_SYS_I2C_DIRECT_BUS
2198		define this, if you don't use i2c muxes on your hardware.
2199		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2200		omit this define.
2201
2202		CONFIG_SYS_I2C_MAX_HOPS
2203		define how many muxes are maximal consecutively connected
2204		on one i2c bus. If you not use i2c muxes, omit this
2205		define.
2206
2207		CONFIG_SYS_I2C_BUSES
2208		hold a list of busses you want to use, only used if
2209		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2210		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2211		CONFIG_SYS_NUM_I2C_BUSES = 9:
2212
2213		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2214					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2215					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2216					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2217					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2218					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2219					{1, {I2C_NULL_HOP}}, \
2220					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2221					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2222					}
2223
2224		which defines
2225			bus 0 on adapter 0 without a mux
2226			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2227			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2228			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2229			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2230			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2231			bus 6 on adapter 1 without a mux
2232			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2233			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2234
2235		If you do not have i2c muxes on your board, omit this define.
2236
2237- Legacy I2C Support:	CONFIG_HARD_I2C
2238
2239		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2240		provides the following compelling advantages:
2241
2242		- more than one i2c adapter is usable
2243		- approved multibus support
2244		- better i2c mux support
2245
2246		** Please consider updating your I2C driver now. **
2247
2248		These enable legacy I2C serial bus commands. Defining
2249		CONFIG_HARD_I2C will include the appropriate I2C driver
2250		for the selected CPU.
2251
2252		This will allow you to use i2c commands at the u-boot
2253		command line (as long as you set CONFIG_CMD_I2C in
2254		CONFIG_COMMANDS) and communicate with i2c based realtime
2255		clock chips. See common/cmd_i2c.c for a description of the
2256		command line interface.
2257
2258		CONFIG_HARD_I2C selects a hardware I2C controller.
2259
2260		There are several other quantities that must also be
2261		defined when you define CONFIG_HARD_I2C.
2262
2263		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2264		to be the frequency (in Hz) at which you wish your i2c bus
2265		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2266		the CPU's i2c node address).
2267
2268		Now, the u-boot i2c code for the mpc8xx
2269		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2270		and so its address should therefore be cleared to 0 (See,
2271		eg, MPC823e User's Manual p.16-473). So, set
2272		CONFIG_SYS_I2C_SLAVE to 0.
2273
2274		CONFIG_SYS_I2C_INIT_MPC5XXX
2275
2276		When a board is reset during an i2c bus transfer
2277		chips might think that the current transfer is still
2278		in progress.  Reset the slave devices by sending start
2279		commands until the slave device responds.
2280
2281		That's all that's required for CONFIG_HARD_I2C.
2282
2283		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2284		then the following macros need to be defined (examples are
2285		from include/configs/lwmon.h):
2286
2287		I2C_INIT
2288
2289		(Optional). Any commands necessary to enable the I2C
2290		controller or configure ports.
2291
2292		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2293
2294		I2C_PORT
2295
2296		(Only for MPC8260 CPU). The I/O port to use (the code
2297		assumes both bits are on the same port). Valid values
2298		are 0..3 for ports A..D.
2299
2300		I2C_ACTIVE
2301
2302		The code necessary to make the I2C data line active
2303		(driven).  If the data line is open collector, this
2304		define can be null.
2305
2306		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2307
2308		I2C_TRISTATE
2309
2310		The code necessary to make the I2C data line tri-stated
2311		(inactive).  If the data line is open collector, this
2312		define can be null.
2313
2314		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2315
2316		I2C_READ
2317
2318		Code that returns true if the I2C data line is high,
2319		false if it is low.
2320
2321		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2322
2323		I2C_SDA(bit)
2324
2325		If <bit> is true, sets the I2C data line high. If it
2326		is false, it clears it (low).
2327
2328		eg: #define I2C_SDA(bit) \
2329			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2330			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2331
2332		I2C_SCL(bit)
2333
2334		If <bit> is true, sets the I2C clock line high. If it
2335		is false, it clears it (low).
2336
2337		eg: #define I2C_SCL(bit) \
2338			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2339			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2340
2341		I2C_DELAY
2342
2343		This delay is invoked four times per clock cycle so this
2344		controls the rate of data transfer.  The data rate thus
2345		is 1 / (I2C_DELAY * 4). Often defined to be something
2346		like:
2347
2348		#define I2C_DELAY  udelay(2)
2349
2350		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2351
2352		If your arch supports the generic GPIO framework (asm/gpio.h),
2353		then you may alternatively define the two GPIOs that are to be
2354		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2355		have GPIO-based defaults assigned to them as appropriate.
2356
2357		You should define these to the GPIO value as given directly to
2358		the generic GPIO functions.
2359
2360		CONFIG_SYS_I2C_INIT_BOARD
2361
2362		When a board is reset during an i2c bus transfer
2363		chips might think that the current transfer is still
2364		in progress. On some boards it is possible to access
2365		the i2c SCLK line directly, either by using the
2366		processor pin as a GPIO or by having a second pin
2367		connected to the bus. If this option is defined a
2368		custom i2c_init_board() routine in boards/xxx/board.c
2369		is run early in the boot sequence.
2370
2371		CONFIG_SYS_I2C_BOARD_LATE_INIT
2372
2373		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2374		defined a custom i2c_board_late_init() routine in
2375		boards/xxx/board.c is run AFTER the operations in i2c_init()
2376		is completed. This callpoint can be used to unreset i2c bus
2377		using CPU i2c controller register accesses for CPUs whose i2c
2378		controller provide such a method. It is called at the end of
2379		i2c_init() to allow i2c_init operations to setup the i2c bus
2380		controller on the CPU (e.g. setting bus speed & slave address).
2381
2382		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2383
2384		This option enables configuration of bi_iic_fast[] flags
2385		in u-boot bd_info structure based on u-boot environment
2386		variable "i2cfast". (see also i2cfast)
2387
2388		CONFIG_I2C_MULTI_BUS
2389
2390		This option allows the use of multiple I2C buses, each of which
2391		must have a controller.	 At any point in time, only one bus is
2392		active.	 To switch to a different bus, use the 'i2c dev' command.
2393		Note that bus numbering is zero-based.
2394
2395		CONFIG_SYS_I2C_NOPROBES
2396
2397		This option specifies a list of I2C devices that will be skipped
2398		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2399		is set, specify a list of bus-device pairs.  Otherwise, specify
2400		a 1D array of device addresses
2401
2402		e.g.
2403			#undef	CONFIG_I2C_MULTI_BUS
2404			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2405
2406		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2407
2408			#define CONFIG_I2C_MULTI_BUS
2409			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2410
2411		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2412
2413		CONFIG_SYS_SPD_BUS_NUM
2414
2415		If defined, then this indicates the I2C bus number for DDR SPD.
2416		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2417
2418		CONFIG_SYS_RTC_BUS_NUM
2419
2420		If defined, then this indicates the I2C bus number for the RTC.
2421		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2422
2423		CONFIG_SYS_DTT_BUS_NUM
2424
2425		If defined, then this indicates the I2C bus number for the DTT.
2426		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2427
2428		CONFIG_SYS_I2C_DTT_ADDR:
2429
2430		If defined, specifies the I2C address of the DTT device.
2431		If not defined, then U-Boot uses predefined value for
2432		specified DTT device.
2433
2434		CONFIG_SOFT_I2C_READ_REPEATED_START
2435
2436		defining this will force the i2c_read() function in
2437		the soft_i2c driver to perform an I2C repeated start
2438		between writing the address pointer and reading the
2439		data.  If this define is omitted the default behaviour
2440		of doing a stop-start sequence will be used.  Most I2C
2441		devices can use either method, but some require one or
2442		the other.
2443
2444- SPI Support:	CONFIG_SPI
2445
2446		Enables SPI driver (so far only tested with
2447		SPI EEPROM, also an instance works with Crystal A/D and
2448		D/As on the SACSng board)
2449
2450		CONFIG_SH_SPI
2451
2452		Enables the driver for SPI controller on SuperH. Currently
2453		only SH7757 is supported.
2454
2455		CONFIG_SPI_X
2456
2457		Enables extended (16-bit) SPI EEPROM addressing.
2458		(symmetrical to CONFIG_I2C_X)
2459
2460		CONFIG_SOFT_SPI
2461
2462		Enables a software (bit-bang) SPI driver rather than
2463		using hardware support. This is a general purpose
2464		driver that only requires three general I/O port pins
2465		(two outputs, one input) to function. If this is
2466		defined, the board configuration must define several
2467		SPI configuration items (port pins to use, etc). For
2468		an example, see include/configs/sacsng.h.
2469
2470		CONFIG_HARD_SPI
2471
2472		Enables a hardware SPI driver for general-purpose reads
2473		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2474		must define a list of chip-select function pointers.
2475		Currently supported on some MPC8xxx processors.	 For an
2476		example, see include/configs/mpc8349emds.h.
2477
2478		CONFIG_MXC_SPI
2479
2480		Enables the driver for the SPI controllers on i.MX and MXC
2481		SoCs. Currently i.MX31/35/51 are supported.
2482
2483- FPGA Support: CONFIG_FPGA
2484
2485		Enables FPGA subsystem.
2486
2487		CONFIG_FPGA_<vendor>
2488
2489		Enables support for specific chip vendors.
2490		(ALTERA, XILINX)
2491
2492		CONFIG_FPGA_<family>
2493
2494		Enables support for FPGA family.
2495		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2496
2497		CONFIG_FPGA_COUNT
2498
2499		Specify the number of FPGA devices to support.
2500
2501		CONFIG_SYS_FPGA_PROG_FEEDBACK
2502
2503		Enable printing of hash marks during FPGA configuration.
2504
2505		CONFIG_SYS_FPGA_CHECK_BUSY
2506
2507		Enable checks on FPGA configuration interface busy
2508		status by the configuration function. This option
2509		will require a board or device specific function to
2510		be written.
2511
2512		CONFIG_FPGA_DELAY
2513
2514		If defined, a function that provides delays in the FPGA
2515		configuration driver.
2516
2517		CONFIG_SYS_FPGA_CHECK_CTRLC
2518		Allow Control-C to interrupt FPGA configuration
2519
2520		CONFIG_SYS_FPGA_CHECK_ERROR
2521
2522		Check for configuration errors during FPGA bitfile
2523		loading. For example, abort during Virtex II
2524		configuration if the INIT_B line goes low (which
2525		indicated a CRC error).
2526
2527		CONFIG_SYS_FPGA_WAIT_INIT
2528
2529		Maximum time to wait for the INIT_B line to deassert
2530		after PROB_B has been deasserted during a Virtex II
2531		FPGA configuration sequence. The default time is 500
2532		ms.
2533
2534		CONFIG_SYS_FPGA_WAIT_BUSY
2535
2536		Maximum time to wait for BUSY to deassert during
2537		Virtex II FPGA configuration. The default is 5 ms.
2538
2539		CONFIG_SYS_FPGA_WAIT_CONFIG
2540
2541		Time to wait after FPGA configuration. The default is
2542		200 ms.
2543
2544- Configuration Management:
2545		CONFIG_IDENT_STRING
2546
2547		If defined, this string will be added to the U-Boot
2548		version information (U_BOOT_VERSION)
2549
2550- Vendor Parameter Protection:
2551
2552		U-Boot considers the values of the environment
2553		variables "serial#" (Board Serial Number) and
2554		"ethaddr" (Ethernet Address) to be parameters that
2555		are set once by the board vendor / manufacturer, and
2556		protects these variables from casual modification by
2557		the user. Once set, these variables are read-only,
2558		and write or delete attempts are rejected. You can
2559		change this behaviour:
2560
2561		If CONFIG_ENV_OVERWRITE is #defined in your config
2562		file, the write protection for vendor parameters is
2563		completely disabled. Anybody can change or delete
2564		these parameters.
2565
2566		Alternatively, if you #define _both_ CONFIG_ETHADDR
2567		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2568		Ethernet address is installed in the environment,
2569		which can be changed exactly ONCE by the user. [The
2570		serial# is unaffected by this, i. e. it remains
2571		read-only.]
2572
2573		The same can be accomplished in a more flexible way
2574		for any variable by configuring the type of access
2575		to allow for those variables in the ".flags" variable
2576		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2577
2578- Protected RAM:
2579		CONFIG_PRAM
2580
2581		Define this variable to enable the reservation of
2582		"protected RAM", i. e. RAM which is not overwritten
2583		by U-Boot. Define CONFIG_PRAM to hold the number of
2584		kB you want to reserve for pRAM. You can overwrite
2585		this default value by defining an environment
2586		variable "pram" to the number of kB you want to
2587		reserve. Note that the board info structure will
2588		still show the full amount of RAM. If pRAM is
2589		reserved, a new environment variable "mem" will
2590		automatically be defined to hold the amount of
2591		remaining RAM in a form that can be passed as boot
2592		argument to Linux, for instance like that:
2593
2594			setenv bootargs ... mem=\${mem}
2595			saveenv
2596
2597		This way you can tell Linux not to use this memory,
2598		either, which results in a memory region that will
2599		not be affected by reboots.
2600
2601		*WARNING* If your board configuration uses automatic
2602		detection of the RAM size, you must make sure that
2603		this memory test is non-destructive. So far, the
2604		following board configurations are known to be
2605		"pRAM-clean":
2606
2607			IVMS8, IVML24, SPD8xx, TQM8xxL,
2608			HERMES, IP860, RPXlite, LWMON,
2609			FLAGADM, TQM8260
2610
2611- Access to physical memory region (> 4GB)
2612		Some basic support is provided for operations on memory not
2613		normally accessible to U-Boot - e.g. some architectures
2614		support access to more than 4GB of memory on 32-bit
2615		machines using physical address extension or similar.
2616		Define CONFIG_PHYSMEM to access this basic support, which
2617		currently only supports clearing the memory.
2618
2619- Error Recovery:
2620		CONFIG_PANIC_HANG
2621
2622		Define this variable to stop the system in case of a
2623		fatal error, so that you have to reset it manually.
2624		This is probably NOT a good idea for an embedded
2625		system where you want the system to reboot
2626		automatically as fast as possible, but it may be
2627		useful during development since you can try to debug
2628		the conditions that lead to the situation.
2629
2630		CONFIG_NET_RETRY_COUNT
2631
2632		This variable defines the number of retries for
2633		network operations like ARP, RARP, TFTP, or BOOTP
2634		before giving up the operation. If not defined, a
2635		default value of 5 is used.
2636
2637		CONFIG_ARP_TIMEOUT
2638
2639		Timeout waiting for an ARP reply in milliseconds.
2640
2641		CONFIG_NFS_TIMEOUT
2642
2643		Timeout in milliseconds used in NFS protocol.
2644		If you encounter "ERROR: Cannot umount" in nfs command,
2645		try longer timeout such as
2646		#define CONFIG_NFS_TIMEOUT 10000UL
2647
2648- Command Interpreter:
2649		CONFIG_AUTO_COMPLETE
2650
2651		Enable auto completion of commands using TAB.
2652
2653		Note that this feature has NOT been implemented yet
2654		for the "hush" shell.
2655
2656
2657		CONFIG_SYS_HUSH_PARSER
2658
2659		Define this variable to enable the "hush" shell (from
2660		Busybox) as command line interpreter, thus enabling
2661		powerful command line syntax like
2662		if...then...else...fi conditionals or `&&' and '||'
2663		constructs ("shell scripts").
2664
2665		If undefined, you get the old, much simpler behaviour
2666		with a somewhat smaller memory footprint.
2667
2668
2669		CONFIG_SYS_PROMPT_HUSH_PS2
2670
2671		This defines the secondary prompt string, which is
2672		printed when the command interpreter needs more input
2673		to complete a command. Usually "> ".
2674
2675	Note:
2676
2677		In the current implementation, the local variables
2678		space and global environment variables space are
2679		separated. Local variables are those you define by
2680		simply typing `name=value'. To access a local
2681		variable later on, you have write `$name' or
2682		`${name}'; to execute the contents of a variable
2683		directly type `$name' at the command prompt.
2684
2685		Global environment variables are those you use
2686		setenv/printenv to work with. To run a command stored
2687		in such a variable, you need to use the run command,
2688		and you must not use the '$' sign to access them.
2689
2690		To store commands and special characters in a
2691		variable, please use double quotation marks
2692		surrounding the whole text of the variable, instead
2693		of the backslashes before semicolons and special
2694		symbols.
2695
2696- Commandline Editing and History:
2697		CONFIG_CMDLINE_EDITING
2698
2699		Enable editing and History functions for interactive
2700		commandline input operations
2701
2702- Default Environment:
2703		CONFIG_EXTRA_ENV_SETTINGS
2704
2705		Define this to contain any number of null terminated
2706		strings (variable = value pairs) that will be part of
2707		the default environment compiled into the boot image.
2708
2709		For example, place something like this in your
2710		board's config file:
2711
2712		#define CONFIG_EXTRA_ENV_SETTINGS \
2713			"myvar1=value1\0" \
2714			"myvar2=value2\0"
2715
2716		Warning: This method is based on knowledge about the
2717		internal format how the environment is stored by the
2718		U-Boot code. This is NOT an official, exported
2719		interface! Although it is unlikely that this format
2720		will change soon, there is no guarantee either.
2721		You better know what you are doing here.
2722
2723		Note: overly (ab)use of the default environment is
2724		discouraged. Make sure to check other ways to preset
2725		the environment like the "source" command or the
2726		boot command first.
2727
2728		CONFIG_ENV_VARS_UBOOT_CONFIG
2729
2730		Define this in order to add variables describing the
2731		U-Boot build configuration to the default environment.
2732		These will be named arch, cpu, board, vendor, and soc.
2733
2734		Enabling this option will cause the following to be defined:
2735
2736		- CONFIG_SYS_ARCH
2737		- CONFIG_SYS_CPU
2738		- CONFIG_SYS_BOARD
2739		- CONFIG_SYS_VENDOR
2740		- CONFIG_SYS_SOC
2741
2742		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2743
2744		Define this in order to add variables describing certain
2745		run-time determined information about the hardware to the
2746		environment.  These will be named board_name, board_rev.
2747
2748		CONFIG_DELAY_ENVIRONMENT
2749
2750		Normally the environment is loaded when the board is
2751		intialised so that it is available to U-Boot. This inhibits
2752		that so that the environment is not available until
2753		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2754		this is instead controlled by the value of
2755		/config/load-environment.
2756
2757- DataFlash Support:
2758		CONFIG_HAS_DATAFLASH
2759
2760		Defining this option enables DataFlash features and
2761		allows to read/write in Dataflash via the standard
2762		commands cp, md...
2763
2764- Serial Flash support
2765		CONFIG_CMD_SF
2766
2767		Defining this option enables SPI flash commands
2768		'sf probe/read/write/erase/update'.
2769
2770		Usage requires an initial 'probe' to define the serial
2771		flash parameters, followed by read/write/erase/update
2772		commands.
2773
2774		The following defaults may be provided by the platform
2775		to handle the common case when only a single serial
2776		flash is present on the system.
2777
2778		CONFIG_SF_DEFAULT_BUS		Bus identifier
2779		CONFIG_SF_DEFAULT_CS		Chip-select
2780		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2781		CONFIG_SF_DEFAULT_SPEED		in Hz
2782
2783		CONFIG_CMD_SF_TEST
2784
2785		Define this option to include a destructive SPI flash
2786		test ('sf test').
2787
2788		CONFIG_SPI_FLASH_BAR		Ban/Extended Addr Reg
2789
2790		Define this option to use the Bank addr/Extended addr
2791		support on SPI flashes which has size > 16Mbytes.
2792
2793		CONFIG_SF_DUAL_FLASH		Dual flash memories
2794
2795		Define this option to use dual flash support where two flash
2796		memories can be connected with a given cs line.
2797		currently Xilinx Zynq qspi support these type of connections.
2798
2799- SystemACE Support:
2800		CONFIG_SYSTEMACE
2801
2802		Adding this option adds support for Xilinx SystemACE
2803		chips attached via some sort of local bus. The address
2804		of the chip must also be defined in the
2805		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2806
2807		#define CONFIG_SYSTEMACE
2808		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2809
2810		When SystemACE support is added, the "ace" device type
2811		becomes available to the fat commands, i.e. fatls.
2812
2813- TFTP Fixed UDP Port:
2814		CONFIG_TFTP_PORT
2815
2816		If this is defined, the environment variable tftpsrcp
2817		is used to supply the TFTP UDP source port value.
2818		If tftpsrcp isn't defined, the normal pseudo-random port
2819		number generator is used.
2820
2821		Also, the environment variable tftpdstp is used to supply
2822		the TFTP UDP destination port value.  If tftpdstp isn't
2823		defined, the normal port 69 is used.
2824
2825		The purpose for tftpsrcp is to allow a TFTP server to
2826		blindly start the TFTP transfer using the pre-configured
2827		target IP address and UDP port. This has the effect of
2828		"punching through" the (Windows XP) firewall, allowing
2829		the remainder of the TFTP transfer to proceed normally.
2830		A better solution is to properly configure the firewall,
2831		but sometimes that is not allowed.
2832
2833- Hashing support:
2834		CONFIG_CMD_HASH
2835
2836		This enables a generic 'hash' command which can produce
2837		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2838
2839		CONFIG_HASH_VERIFY
2840
2841		Enable the hash verify command (hash -v). This adds to code
2842		size a little.
2843
2844		CONFIG_SHA1 - support SHA1 hashing
2845		CONFIG_SHA256 - support SHA256 hashing
2846
2847		Note: There is also a sha1sum command, which should perhaps
2848		be deprecated in favour of 'hash sha1'.
2849
2850- Freescale i.MX specific commands:
2851		CONFIG_CMD_HDMIDETECT
2852		This enables 'hdmidet' command which returns true if an
2853		HDMI monitor is detected.  This command is i.MX 6 specific.
2854
2855		CONFIG_CMD_BMODE
2856		This enables the 'bmode' (bootmode) command for forcing
2857		a boot from specific media.
2858
2859		This is useful for forcing the ROM's usb downloader to
2860		activate upon a watchdog reset which is nice when iterating
2861		on U-Boot.  Using the reset button or running bmode normal
2862		will set it back to normal.  This command currently
2863		supports i.MX53 and i.MX6.
2864
2865- Signing support:
2866		CONFIG_RSA
2867
2868		This enables the RSA algorithm used for FIT image verification
2869		in U-Boot. See doc/uImage.FIT/signature.txt for more information.
2870
2871		The signing part is build into mkimage regardless of this
2872		option.
2873
2874- bootcount support:
2875		CONFIG_BOOTCOUNT_LIMIT
2876
2877		This enables the bootcounter support, see:
2878		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2879
2880		CONFIG_AT91SAM9XE
2881		enable special bootcounter support on at91sam9xe based boards.
2882		CONFIG_BLACKFIN
2883		enable special bootcounter support on blackfin based boards.
2884		CONFIG_SOC_DA8XX
2885		enable special bootcounter support on da850 based boards.
2886		CONFIG_BOOTCOUNT_RAM
2887		enable support for the bootcounter in RAM
2888		CONFIG_BOOTCOUNT_I2C
2889		enable support for the bootcounter on an i2c (like RTC) device.
2890			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2891			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2892						    the bootcounter.
2893			CONFIG_BOOTCOUNT_ALEN = address len
2894
2895- Show boot progress:
2896		CONFIG_SHOW_BOOT_PROGRESS
2897
2898		Defining this option allows to add some board-
2899		specific code (calling a user-provided function
2900		"show_boot_progress(int)") that enables you to show
2901		the system's boot progress on some display (for
2902		example, some LED's) on your board. At the moment,
2903		the following checkpoints are implemented:
2904
2905- Detailed boot stage timing
2906		CONFIG_BOOTSTAGE
2907		Define this option to get detailed timing of each stage
2908		of the boot process.
2909
2910		CONFIG_BOOTSTAGE_USER_COUNT
2911		This is the number of available user bootstage records.
2912		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
2913		a new ID will be allocated from this stash. If you exceed
2914		the limit, recording will stop.
2915
2916		CONFIG_BOOTSTAGE_REPORT
2917		Define this to print a report before boot, similar to this:
2918
2919		Timer summary in microseconds:
2920		       Mark    Elapsed  Stage
2921			  0          0  reset
2922		  3,575,678  3,575,678  board_init_f start
2923		  3,575,695         17  arch_cpu_init A9
2924		  3,575,777         82  arch_cpu_init done
2925		  3,659,598     83,821  board_init_r start
2926		  3,910,375    250,777  main_loop
2927		 29,916,167 26,005,792  bootm_start
2928		 30,361,327    445,160  start_kernel
2929
2930		CONFIG_CMD_BOOTSTAGE
2931		Add a 'bootstage' command which supports printing a report
2932		and un/stashing of bootstage data.
2933
2934		CONFIG_BOOTSTAGE_FDT
2935		Stash the bootstage information in the FDT. A root 'bootstage'
2936		node is created with each bootstage id as a child. Each child
2937		has a 'name' property and either 'mark' containing the
2938		mark time in microsecond, or 'accum' containing the
2939		accumulated time for that bootstage id in microseconds.
2940		For example:
2941
2942		bootstage {
2943			154 {
2944				name = "board_init_f";
2945				mark = <3575678>;
2946			};
2947			170 {
2948				name = "lcd";
2949				accum = <33482>;
2950			};
2951		};
2952
2953		Code in the Linux kernel can find this in /proc/devicetree.
2954
2955Legacy uImage format:
2956
2957  Arg	Where			When
2958    1	common/cmd_bootm.c	before attempting to boot an image
2959   -1	common/cmd_bootm.c	Image header has bad	 magic number
2960    2	common/cmd_bootm.c	Image header has correct magic number
2961   -2	common/cmd_bootm.c	Image header has bad	 checksum
2962    3	common/cmd_bootm.c	Image header has correct checksum
2963   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2964    4	common/cmd_bootm.c	Image data   has correct checksum
2965   -4	common/cmd_bootm.c	Image is for unsupported architecture
2966    5	common/cmd_bootm.c	Architecture check OK
2967   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2968    6	common/cmd_bootm.c	Image Type check OK
2969   -6	common/cmd_bootm.c	gunzip uncompression error
2970   -7	common/cmd_bootm.c	Unimplemented compression type
2971    7	common/cmd_bootm.c	Uncompression OK
2972    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2973   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2974
2975    9	common/image.c		Start initial ramdisk verification
2976  -10	common/image.c		Ramdisk header has bad	   magic number
2977  -11	common/image.c		Ramdisk header has bad	   checksum
2978   10	common/image.c		Ramdisk header is OK
2979  -12	common/image.c		Ramdisk data   has bad	   checksum
2980   11	common/image.c		Ramdisk data   has correct checksum
2981   12	common/image.c		Ramdisk verification complete, start loading
2982  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2983   13	common/image.c		Start multifile image verification
2984   14	common/image.c		No initial ramdisk, no multifile, continue.
2985
2986   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2987
2988  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2989  -31	post/post.c		POST test failed, detected by post_output_backlog()
2990  -32	post/post.c		POST test failed, detected by post_run_single()
2991
2992   34	common/cmd_doc.c	before loading a Image from a DOC device
2993  -35	common/cmd_doc.c	Bad usage of "doc" command
2994   35	common/cmd_doc.c	correct usage of "doc" command
2995  -36	common/cmd_doc.c	No boot device
2996   36	common/cmd_doc.c	correct boot device
2997  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2998   37	common/cmd_doc.c	correct chip ID found, device available
2999  -38	common/cmd_doc.c	Read Error on boot device
3000   38	common/cmd_doc.c	reading Image header from DOC device OK
3001  -39	common/cmd_doc.c	Image header has bad magic number
3002   39	common/cmd_doc.c	Image header has correct magic number
3003  -40	common/cmd_doc.c	Error reading Image from DOC device
3004   40	common/cmd_doc.c	Image header has correct magic number
3005   41	common/cmd_ide.c	before loading a Image from a IDE device
3006  -42	common/cmd_ide.c	Bad usage of "ide" command
3007   42	common/cmd_ide.c	correct usage of "ide" command
3008  -43	common/cmd_ide.c	No boot device
3009   43	common/cmd_ide.c	boot device found
3010  -44	common/cmd_ide.c	Device not available
3011   44	common/cmd_ide.c	Device available
3012  -45	common/cmd_ide.c	wrong partition selected
3013   45	common/cmd_ide.c	partition selected
3014  -46	common/cmd_ide.c	Unknown partition table
3015   46	common/cmd_ide.c	valid partition table found
3016  -47	common/cmd_ide.c	Invalid partition type
3017   47	common/cmd_ide.c	correct partition type
3018  -48	common/cmd_ide.c	Error reading Image Header on boot device
3019   48	common/cmd_ide.c	reading Image Header from IDE device OK
3020  -49	common/cmd_ide.c	Image header has bad magic number
3021   49	common/cmd_ide.c	Image header has correct magic number
3022  -50	common/cmd_ide.c	Image header has bad	 checksum
3023   50	common/cmd_ide.c	Image header has correct checksum
3024  -51	common/cmd_ide.c	Error reading Image from IDE device
3025   51	common/cmd_ide.c	reading Image from IDE device OK
3026   52	common/cmd_nand.c	before loading a Image from a NAND device
3027  -53	common/cmd_nand.c	Bad usage of "nand" command
3028   53	common/cmd_nand.c	correct usage of "nand" command
3029  -54	common/cmd_nand.c	No boot device
3030   54	common/cmd_nand.c	boot device found
3031  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3032   55	common/cmd_nand.c	correct chip ID found, device available
3033  -56	common/cmd_nand.c	Error reading Image Header on boot device
3034   56	common/cmd_nand.c	reading Image Header from NAND device OK
3035  -57	common/cmd_nand.c	Image header has bad magic number
3036   57	common/cmd_nand.c	Image header has correct magic number
3037  -58	common/cmd_nand.c	Error reading Image from NAND device
3038   58	common/cmd_nand.c	reading Image from NAND device OK
3039
3040  -60	common/env_common.c	Environment has a bad CRC, using default
3041
3042   64	net/eth.c		starting with Ethernet configuration.
3043  -64	net/eth.c		no Ethernet found.
3044   65	net/eth.c		Ethernet found.
3045
3046  -80	common/cmd_net.c	usage wrong
3047   80	common/cmd_net.c	before calling NetLoop()
3048  -81	common/cmd_net.c	some error in NetLoop() occurred
3049   81	common/cmd_net.c	NetLoop() back without error
3050  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3051   82	common/cmd_net.c	trying automatic boot
3052   83	common/cmd_net.c	running "source" command
3053  -83	common/cmd_net.c	some error in automatic boot or "source" command
3054   84	common/cmd_net.c	end without errors
3055
3056FIT uImage format:
3057
3058  Arg	Where			When
3059  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3060 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3061  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3062 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3063  102	common/cmd_bootm.c	Kernel unit name specified
3064 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3065  103	common/cmd_bootm.c	Found configuration node
3066  104	common/cmd_bootm.c	Got kernel subimage node offset
3067 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3068  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3069 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3070  106	common/cmd_bootm.c	Architecture check OK
3071 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3072  107	common/cmd_bootm.c	Kernel subimage type OK
3073 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3074  108	common/cmd_bootm.c	Got kernel subimage data/size
3075 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3076 -109	common/cmd_bootm.c	Can't get kernel subimage type
3077 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3078 -111	common/cmd_bootm.c	Can't get kernel subimage os
3079 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3080 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3081
3082  120	common/image.c		Start initial ramdisk verification
3083 -120	common/image.c		Ramdisk FIT image has incorrect format
3084  121	common/image.c		Ramdisk FIT image has correct format
3085  122	common/image.c		No ramdisk subimage unit name, using configuration
3086 -122	common/image.c		Can't get configuration for ramdisk subimage
3087  123	common/image.c		Ramdisk unit name specified
3088 -124	common/image.c		Can't get ramdisk subimage node offset
3089  125	common/image.c		Got ramdisk subimage node offset
3090 -125	common/image.c		Ramdisk subimage hash verification failed
3091  126	common/image.c		Ramdisk subimage hash verification OK
3092 -126	common/image.c		Ramdisk subimage for unsupported architecture
3093  127	common/image.c		Architecture check OK
3094 -127	common/image.c		Can't get ramdisk subimage data/size
3095  128	common/image.c		Got ramdisk subimage data/size
3096  129	common/image.c		Can't get ramdisk load address
3097 -129	common/image.c		Got ramdisk load address
3098
3099 -130	common/cmd_doc.c	Incorrect FIT image format
3100  131	common/cmd_doc.c	FIT image format OK
3101
3102 -140	common/cmd_ide.c	Incorrect FIT image format
3103  141	common/cmd_ide.c	FIT image format OK
3104
3105 -150	common/cmd_nand.c	Incorrect FIT image format
3106  151	common/cmd_nand.c	FIT image format OK
3107
3108- FIT image support:
3109		CONFIG_FIT
3110		Enable support for the FIT uImage format.
3111
3112		CONFIG_FIT_BEST_MATCH
3113		When no configuration is explicitly selected, default to the
3114		one whose fdt's compatibility field best matches that of
3115		U-Boot itself. A match is considered "best" if it matches the
3116		most specific compatibility entry of U-Boot's fdt's root node.
3117		The order of entries in the configuration's fdt is ignored.
3118
3119		CONFIG_FIT_SIGNATURE
3120		This option enables signature verification of FIT uImages,
3121		using a hash signed and verified using RSA. See
3122		doc/uImage.FIT/signature.txt for more details.
3123
3124- Standalone program support:
3125		CONFIG_STANDALONE_LOAD_ADDR
3126
3127		This option defines a board specific value for the
3128		address where standalone program gets loaded, thus
3129		overwriting the architecture dependent default
3130		settings.
3131
3132- Frame Buffer Address:
3133		CONFIG_FB_ADDR
3134
3135		Define CONFIG_FB_ADDR if you want to use specific
3136		address for frame buffer.  This is typically the case
3137		when using a graphics controller has separate video
3138		memory.  U-Boot will then place the frame buffer at
3139		the given address instead of dynamically reserving it
3140		in system RAM by calling lcd_setmem(), which grabs
3141		the memory for the frame buffer depending on the
3142		configured panel size.
3143
3144		Please see board_init_f function.
3145
3146- Automatic software updates via TFTP server
3147		CONFIG_UPDATE_TFTP
3148		CONFIG_UPDATE_TFTP_CNT_MAX
3149		CONFIG_UPDATE_TFTP_MSEC_MAX
3150
3151		These options enable and control the auto-update feature;
3152		for a more detailed description refer to doc/README.update.
3153
3154- MTD Support (mtdparts command, UBI support)
3155		CONFIG_MTD_DEVICE
3156
3157		Adds the MTD device infrastructure from the Linux kernel.
3158		Needed for mtdparts command support.
3159
3160		CONFIG_MTD_PARTITIONS
3161
3162		Adds the MTD partitioning infrastructure from the Linux
3163		kernel. Needed for UBI support.
3164
3165- UBI support
3166		CONFIG_CMD_UBI
3167
3168		Adds commands for interacting with MTD partitions formatted
3169		with the UBI flash translation layer
3170
3171		Requires also defining CONFIG_RBTREE
3172
3173		CONFIG_UBI_SILENCE_MSG
3174
3175		Make the verbose messages from UBI stop printing.  This leaves
3176		warnings and errors enabled.
3177
3178- UBIFS support
3179		CONFIG_CMD_UBIFS
3180
3181		Adds commands for interacting with UBI volumes formatted as
3182		UBIFS.  UBIFS is read-only in u-boot.
3183
3184		Requires UBI support as well as CONFIG_LZO
3185
3186		CONFIG_UBIFS_SILENCE_MSG
3187
3188		Make the verbose messages from UBIFS stop printing.  This leaves
3189		warnings and errors enabled.
3190
3191- SPL framework
3192		CONFIG_SPL
3193		Enable building of SPL globally.
3194
3195		CONFIG_SPL_LDSCRIPT
3196		LDSCRIPT for linking the SPL binary.
3197
3198		CONFIG_SPL_MAX_FOOTPRINT
3199		Maximum size in memory allocated to the SPL, BSS included.
3200		When defined, the linker checks that the actual memory
3201		used by SPL from _start to __bss_end does not exceed it.
3202		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3203		must not be both defined at the same time.
3204
3205		CONFIG_SPL_MAX_SIZE
3206		Maximum size of the SPL image (text, data, rodata, and
3207		linker lists sections), BSS excluded.
3208		When defined, the linker checks that the actual size does
3209		not exceed it.
3210
3211		CONFIG_SPL_TEXT_BASE
3212		TEXT_BASE for linking the SPL binary.
3213
3214		CONFIG_SPL_RELOC_TEXT_BASE
3215		Address to relocate to.  If unspecified, this is equal to
3216		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3217
3218		CONFIG_SPL_BSS_START_ADDR
3219		Link address for the BSS within the SPL binary.
3220
3221		CONFIG_SPL_BSS_MAX_SIZE
3222		Maximum size in memory allocated to the SPL BSS.
3223		When defined, the linker checks that the actual memory used
3224		by SPL from __bss_start to __bss_end does not exceed it.
3225		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3226		must not be both defined at the same time.
3227
3228		CONFIG_SPL_STACK
3229		Adress of the start of the stack SPL will use
3230
3231		CONFIG_SPL_RELOC_STACK
3232		Adress of the start of the stack SPL will use after
3233		relocation.  If unspecified, this is equal to
3234		CONFIG_SPL_STACK.
3235
3236		CONFIG_SYS_SPL_MALLOC_START
3237		Starting address of the malloc pool used in SPL.
3238
3239		CONFIG_SYS_SPL_MALLOC_SIZE
3240		The size of the malloc pool used in SPL.
3241
3242		CONFIG_SPL_FRAMEWORK
3243		Enable the SPL framework under common/.  This framework
3244		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3245		NAND loading of the Linux Kernel.
3246
3247		CONFIG_SPL_DISPLAY_PRINT
3248		For ARM, enable an optional function to print more information
3249		about the running system.
3250
3251		CONFIG_SPL_INIT_MINIMAL
3252		Arch init code should be built for a very small image
3253
3254		CONFIG_SPL_LIBCOMMON_SUPPORT
3255		Support for common/libcommon.o in SPL binary
3256
3257		CONFIG_SPL_LIBDISK_SUPPORT
3258		Support for disk/libdisk.o in SPL binary
3259
3260		CONFIG_SPL_I2C_SUPPORT
3261		Support for drivers/i2c/libi2c.o in SPL binary
3262
3263		CONFIG_SPL_GPIO_SUPPORT
3264		Support for drivers/gpio/libgpio.o in SPL binary
3265
3266		CONFIG_SPL_MMC_SUPPORT
3267		Support for drivers/mmc/libmmc.o in SPL binary
3268
3269		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3270		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3271		CONFIG_SYS_MMC_SD_FAT_BOOT_PARTITION
3272		Address, size and partition on the MMC to load U-Boot from
3273		when the MMC is being used in raw mode.
3274
3275		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3276		Sector to load kernel uImage from when MMC is being
3277		used in raw mode (for Falcon mode)
3278
3279		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3280		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3281		Sector and number of sectors to load kernel argument
3282		parameters from when MMC is being used in raw mode
3283		(for falcon mode)
3284
3285		CONFIG_SPL_FAT_SUPPORT
3286		Support for fs/fat/libfat.o in SPL binary
3287
3288		CONFIG_SPL_FAT_LOAD_PAYLOAD_NAME
3289		Filename to read to load U-Boot when reading from FAT
3290
3291		CONFIG_SPL_FAT_LOAD_KERNEL_NAME
3292		Filename to read to load kernel uImage when reading
3293		from FAT (for Falcon mode)
3294
3295		CONFIG_SPL_FAT_LOAD_ARGS_NAME
3296		Filename to read to load kernel argument parameters
3297		when reading from FAT (for Falcon mode)
3298
3299		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3300		Set this for NAND SPL on PPC mpc83xx targets, so that
3301		start.S waits for the rest of the SPL to load before
3302		continuing (the hardware starts execution after just
3303		loading the first page rather than the full 4K).
3304
3305		CONFIG_SPL_NAND_BASE
3306		Include nand_base.c in the SPL.  Requires
3307		CONFIG_SPL_NAND_DRIVERS.
3308
3309		CONFIG_SPL_NAND_DRIVERS
3310		SPL uses normal NAND drivers, not minimal drivers.
3311
3312		CONFIG_SPL_NAND_ECC
3313		Include standard software ECC in the SPL
3314
3315		CONFIG_SPL_NAND_SIMPLE
3316		Support for NAND boot using simple NAND drivers that
3317		expose the cmd_ctrl() interface.
3318
3319		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3320		Set for the SPL on PPC mpc8xxx targets, support for
3321		drivers/ddr/fsl/libddr.o in SPL binary.
3322
3323		CONFIG_SPL_COMMON_INIT_DDR
3324		Set for common ddr init with serial presence detect in
3325		SPL binary.
3326
3327		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3328		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3329		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3330		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3331		CONFIG_SYS_NAND_ECCBYTES
3332		Defines the size and behavior of the NAND that SPL uses
3333		to read U-Boot
3334
3335		CONFIG_SPL_NAND_BOOT
3336		Add support NAND boot
3337
3338		CONFIG_SYS_NAND_U_BOOT_OFFS
3339		Location in NAND to read U-Boot from
3340
3341		CONFIG_SYS_NAND_U_BOOT_DST
3342		Location in memory to load U-Boot to
3343
3344		CONFIG_SYS_NAND_U_BOOT_SIZE
3345		Size of image to load
3346
3347		CONFIG_SYS_NAND_U_BOOT_START
3348		Entry point in loaded image to jump to
3349
3350		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3351		Define this if you need to first read the OOB and then the
3352		data. This is used for example on davinci plattforms.
3353
3354		CONFIG_SPL_OMAP3_ID_NAND
3355		Support for an OMAP3-specific set of functions to return the
3356		ID and MFR of the first attached NAND chip, if present.
3357
3358		CONFIG_SPL_SERIAL_SUPPORT
3359		Support for drivers/serial/libserial.o in SPL binary
3360
3361		CONFIG_SPL_SPI_FLASH_SUPPORT
3362		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3363
3364		CONFIG_SPL_SPI_SUPPORT
3365		Support for drivers/spi/libspi.o in SPL binary
3366
3367		CONFIG_SPL_RAM_DEVICE
3368		Support for running image already present in ram, in SPL binary
3369
3370		CONFIG_SPL_LIBGENERIC_SUPPORT
3371		Support for lib/libgeneric.o in SPL binary
3372
3373		CONFIG_SPL_ENV_SUPPORT
3374		Support for the environment operating in SPL binary
3375
3376		CONFIG_SPL_NET_SUPPORT
3377		Support for the net/libnet.o in SPL binary.
3378		It conflicts with SPL env from storage medium specified by
3379		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3380
3381		CONFIG_SPL_PAD_TO
3382		Image offset to which the SPL should be padded before appending
3383		the SPL payload. By default, this is defined as
3384		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3385		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3386		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3387
3388		CONFIG_SPL_TARGET
3389		Final target image containing SPL and payload.  Some SPLs
3390		use an arch-specific makefile fragment instead, for
3391		example if more than one image needs to be produced.
3392
3393		CONFIG_FIT_SPL_PRINT
3394		Printing information about a FIT image adds quite a bit of
3395		code to SPL. So this is normally disabled in SPL. Use this
3396		option to re-enable it. This will affect the output of the
3397		bootm command when booting a FIT image.
3398
3399- TPL framework
3400		CONFIG_TPL
3401		Enable building of TPL globally.
3402
3403		CONFIG_TPL_PAD_TO
3404		Image offset to which the TPL should be padded before appending
3405		the TPL payload. By default, this is defined as
3406		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3407		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3408		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3409
3410Modem Support:
3411--------------
3412
3413[so far only for SMDK2400 boards]
3414
3415- Modem support enable:
3416		CONFIG_MODEM_SUPPORT
3417
3418- RTS/CTS Flow control enable:
3419		CONFIG_HWFLOW
3420
3421- Modem debug support:
3422		CONFIG_MODEM_SUPPORT_DEBUG
3423
3424		Enables debugging stuff (char screen[1024], dbg())
3425		for modem support. Useful only with BDI2000.
3426
3427- Interrupt support (PPC):
3428
3429		There are common interrupt_init() and timer_interrupt()
3430		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3431		for CPU specific initialization. interrupt_init_cpu()
3432		should set decrementer_count to appropriate value. If
3433		CPU resets decrementer automatically after interrupt
3434		(ppc4xx) it should set decrementer_count to zero.
3435		timer_interrupt() calls timer_interrupt_cpu() for CPU
3436		specific handling. If board has watchdog / status_led
3437		/ other_activity_monitor it works automatically from
3438		general timer_interrupt().
3439
3440- General:
3441
3442		In the target system modem support is enabled when a
3443		specific key (key combination) is pressed during
3444		power-on. Otherwise U-Boot will boot normally
3445		(autoboot). The key_pressed() function is called from
3446		board_init(). Currently key_pressed() is a dummy
3447		function, returning 1 and thus enabling modem
3448		initialization.
3449
3450		If there are no modem init strings in the
3451		environment, U-Boot proceed to autoboot; the
3452		previous output (banner, info printfs) will be
3453		suppressed, though.
3454
3455		See also: doc/README.Modem
3456
3457Board initialization settings:
3458------------------------------
3459
3460During Initialization u-boot calls a number of board specific functions
3461to allow the preparation of board specific prerequisites, e.g. pin setup
3462before drivers are initialized. To enable these callbacks the
3463following configuration macros have to be defined. Currently this is
3464architecture specific, so please check arch/your_architecture/lib/board.c
3465typically in board_init_f() and board_init_r().
3466
3467- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3468- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3469- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3470- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3471
3472Configuration Settings:
3473-----------------------
3474
3475- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3476		Optionally it can be defined to support 64-bit memory commands.
3477
3478- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3479		undefine this when you're short of memory.
3480
3481- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3482		width of the commands listed in the 'help' command output.
3483
3484- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3485		prompt for user input.
3486
3487- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3488
3489- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3490
3491- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3492
3493- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3494		the application (usually a Linux kernel) when it is
3495		booted
3496
3497- CONFIG_SYS_BAUDRATE_TABLE:
3498		List of legal baudrate settings for this board.
3499
3500- CONFIG_SYS_CONSOLE_INFO_QUIET
3501		Suppress display of console information at boot.
3502
3503- CONFIG_SYS_CONSOLE_IS_IN_ENV
3504		If the board specific function
3505			extern int overwrite_console (void);
3506		returns 1, the stdin, stderr and stdout are switched to the
3507		serial port, else the settings in the environment are used.
3508
3509- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3510		Enable the call to overwrite_console().
3511
3512- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3513		Enable overwrite of previous console environment settings.
3514
3515- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3516		Begin and End addresses of the area used by the
3517		simple memory test.
3518
3519- CONFIG_SYS_ALT_MEMTEST:
3520		Enable an alternate, more extensive memory test.
3521
3522- CONFIG_SYS_MEMTEST_SCRATCH:
3523		Scratch address used by the alternate memory test
3524		You only need to set this if address zero isn't writeable
3525
3526- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3527		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3528		this specified memory area will get subtracted from the top
3529		(end) of RAM and won't get "touched" at all by U-Boot. By
3530		fixing up gd->ram_size the Linux kernel should gets passed
3531		the now "corrected" memory size and won't touch it either.
3532		This should work for arch/ppc and arch/powerpc. Only Linux
3533		board ports in arch/powerpc with bootwrapper support that
3534		recalculate the memory size from the SDRAM controller setup
3535		will have to get fixed in Linux additionally.
3536
3537		This option can be used as a workaround for the 440EPx/GRx
3538		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3539		be touched.
3540
3541		WARNING: Please make sure that this value is a multiple of
3542		the Linux page size (normally 4k). If this is not the case,
3543		then the end address of the Linux memory will be located at a
3544		non page size aligned address and this could cause major
3545		problems.
3546
3547- CONFIG_SYS_LOADS_BAUD_CHANGE:
3548		Enable temporary baudrate change while serial download
3549
3550- CONFIG_SYS_SDRAM_BASE:
3551		Physical start address of SDRAM. _Must_ be 0 here.
3552
3553- CONFIG_SYS_MBIO_BASE:
3554		Physical start address of Motherboard I/O (if using a
3555		Cogent motherboard)
3556
3557- CONFIG_SYS_FLASH_BASE:
3558		Physical start address of Flash memory.
3559
3560- CONFIG_SYS_MONITOR_BASE:
3561		Physical start address of boot monitor code (set by
3562		make config files to be same as the text base address
3563		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3564		CONFIG_SYS_FLASH_BASE when booting from flash.
3565
3566- CONFIG_SYS_MONITOR_LEN:
3567		Size of memory reserved for monitor code, used to
3568		determine _at_compile_time_ (!) if the environment is
3569		embedded within the U-Boot image, or in a separate
3570		flash sector.
3571
3572- CONFIG_SYS_MALLOC_LEN:
3573		Size of DRAM reserved for malloc() use.
3574
3575- CONFIG_SYS_BOOTM_LEN:
3576		Normally compressed uImages are limited to an
3577		uncompressed size of 8 MBytes. If this is not enough,
3578		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3579		to adjust this setting to your needs.
3580
3581- CONFIG_SYS_BOOTMAPSZ:
3582		Maximum size of memory mapped by the startup code of
3583		the Linux kernel; all data that must be processed by
3584		the Linux kernel (bd_info, boot arguments, FDT blob if
3585		used) must be put below this limit, unless "bootm_low"
3586		environment variable is defined and non-zero. In such case
3587		all data for the Linux kernel must be between "bootm_low"
3588		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3589		variable "bootm_mapsize" will override the value of
3590		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3591		then the value in "bootm_size" will be used instead.
3592
3593- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3594		Enable initrd_high functionality.  If defined then the
3595		initrd_high feature is enabled and the bootm ramdisk subcommand
3596		is enabled.
3597
3598- CONFIG_SYS_BOOT_GET_CMDLINE:
3599		Enables allocating and saving kernel cmdline in space between
3600		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3601
3602- CONFIG_SYS_BOOT_GET_KBD:
3603		Enables allocating and saving a kernel copy of the bd_info in
3604		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3605
3606- CONFIG_SYS_MAX_FLASH_BANKS:
3607		Max number of Flash memory banks
3608
3609- CONFIG_SYS_MAX_FLASH_SECT:
3610		Max number of sectors on a Flash chip
3611
3612- CONFIG_SYS_FLASH_ERASE_TOUT:
3613		Timeout for Flash erase operations (in ms)
3614
3615- CONFIG_SYS_FLASH_WRITE_TOUT:
3616		Timeout for Flash write operations (in ms)
3617
3618- CONFIG_SYS_FLASH_LOCK_TOUT
3619		Timeout for Flash set sector lock bit operation (in ms)
3620
3621- CONFIG_SYS_FLASH_UNLOCK_TOUT
3622		Timeout for Flash clear lock bits operation (in ms)
3623
3624- CONFIG_SYS_FLASH_PROTECTION
3625		If defined, hardware flash sectors protection is used
3626		instead of U-Boot software protection.
3627
3628- CONFIG_SYS_DIRECT_FLASH_TFTP:
3629
3630		Enable TFTP transfers directly to flash memory;
3631		without this option such a download has to be
3632		performed in two steps: (1) download to RAM, and (2)
3633		copy from RAM to flash.
3634
3635		The two-step approach is usually more reliable, since
3636		you can check if the download worked before you erase
3637		the flash, but in some situations (when system RAM is
3638		too limited to allow for a temporary copy of the
3639		downloaded image) this option may be very useful.
3640
3641- CONFIG_SYS_FLASH_CFI:
3642		Define if the flash driver uses extra elements in the
3643		common flash structure for storing flash geometry.
3644
3645- CONFIG_FLASH_CFI_DRIVER
3646		This option also enables the building of the cfi_flash driver
3647		in the drivers directory
3648
3649- CONFIG_FLASH_CFI_MTD
3650		This option enables the building of the cfi_mtd driver
3651		in the drivers directory. The driver exports CFI flash
3652		to the MTD layer.
3653
3654- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3655		Use buffered writes to flash.
3656
3657- CONFIG_FLASH_SPANSION_S29WS_N
3658		s29ws-n MirrorBit flash has non-standard addresses for buffered
3659		write commands.
3660
3661- CONFIG_SYS_FLASH_QUIET_TEST
3662		If this option is defined, the common CFI flash doesn't
3663		print it's warning upon not recognized FLASH banks. This
3664		is useful, if some of the configured banks are only
3665		optionally available.
3666
3667- CONFIG_FLASH_SHOW_PROGRESS
3668		If defined (must be an integer), print out countdown
3669		digits and dots.  Recommended value: 45 (9..1) for 80
3670		column displays, 15 (3..1) for 40 column displays.
3671
3672- CONFIG_FLASH_VERIFY
3673		If defined, the content of the flash (destination) is compared
3674		against the source after the write operation. An error message
3675		will be printed when the contents are not identical.
3676		Please note that this option is useless in nearly all cases,
3677		since such flash programming errors usually are detected earlier
3678		while unprotecting/erasing/programming. Please only enable
3679		this option if you really know what you are doing.
3680
3681- CONFIG_SYS_RX_ETH_BUFFER:
3682		Defines the number of Ethernet receive buffers. On some
3683		Ethernet controllers it is recommended to set this value
3684		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3685		buffers can be full shortly after enabling the interface
3686		on high Ethernet traffic.
3687		Defaults to 4 if not defined.
3688
3689- CONFIG_ENV_MAX_ENTRIES
3690
3691	Maximum number of entries in the hash table that is used
3692	internally to store the environment settings. The default
3693	setting is supposed to be generous and should work in most
3694	cases. This setting can be used to tune behaviour; see
3695	lib/hashtable.c for details.
3696
3697- CONFIG_ENV_FLAGS_LIST_DEFAULT
3698- CONFIG_ENV_FLAGS_LIST_STATIC
3699	Enable validation of the values given to environment variables when
3700	calling env set.  Variables can be restricted to only decimal,
3701	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3702	the variables can also be restricted to IP address or MAC address.
3703
3704	The format of the list is:
3705		type_attribute = [s|d|x|b|i|m]
3706		access_atribute = [a|r|o|c]
3707		attributes = type_attribute[access_atribute]
3708		entry = variable_name[:attributes]
3709		list = entry[,list]
3710
3711	The type attributes are:
3712		s - String (default)
3713		d - Decimal
3714		x - Hexadecimal
3715		b - Boolean ([1yYtT|0nNfF])
3716		i - IP address
3717		m - MAC address
3718
3719	The access attributes are:
3720		a - Any (default)
3721		r - Read-only
3722		o - Write-once
3723		c - Change-default
3724
3725	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3726		Define this to a list (string) to define the ".flags"
3727		envirnoment variable in the default or embedded environment.
3728
3729	- CONFIG_ENV_FLAGS_LIST_STATIC
3730		Define this to a list (string) to define validation that
3731		should be done if an entry is not found in the ".flags"
3732		environment variable.  To override a setting in the static
3733		list, simply add an entry for the same variable name to the
3734		".flags" variable.
3735
3736- CONFIG_ENV_ACCESS_IGNORE_FORCE
3737	If defined, don't allow the -f switch to env set override variable
3738	access flags.
3739
3740- CONFIG_SYS_GENERIC_BOARD
3741	This selects the architecture-generic board system instead of the
3742	architecture-specific board files. It is intended to move boards
3743	to this new framework over time. Defining this will disable the
3744	arch/foo/lib/board.c file and use common/board_f.c and
3745	common/board_r.c instead. To use this option your architecture
3746	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
3747	its config.mk file). If you find problems enabling this option on
3748	your board please report the problem and send patches!
3749
3750- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
3751	This is set by OMAP boards for the max time that reset should
3752	be asserted. See doc/README.omap-reset-time for details on how
3753	the value can be calulated on a given board.
3754
3755The following definitions that deal with the placement and management
3756of environment data (variable area); in general, we support the
3757following configurations:
3758
3759- CONFIG_BUILD_ENVCRC:
3760
3761	Builds up envcrc with the target environment so that external utils
3762	may easily extract it and embed it in final U-Boot images.
3763
3764- CONFIG_ENV_IS_IN_FLASH:
3765
3766	Define this if the environment is in flash memory.
3767
3768	a) The environment occupies one whole flash sector, which is
3769	   "embedded" in the text segment with the U-Boot code. This
3770	   happens usually with "bottom boot sector" or "top boot
3771	   sector" type flash chips, which have several smaller
3772	   sectors at the start or the end. For instance, such a
3773	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3774	   such a case you would place the environment in one of the
3775	   4 kB sectors - with U-Boot code before and after it. With
3776	   "top boot sector" type flash chips, you would put the
3777	   environment in one of the last sectors, leaving a gap
3778	   between U-Boot and the environment.
3779
3780	- CONFIG_ENV_OFFSET:
3781
3782	   Offset of environment data (variable area) to the
3783	   beginning of flash memory; for instance, with bottom boot
3784	   type flash chips the second sector can be used: the offset
3785	   for this sector is given here.
3786
3787	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3788
3789	- CONFIG_ENV_ADDR:
3790
3791	   This is just another way to specify the start address of
3792	   the flash sector containing the environment (instead of
3793	   CONFIG_ENV_OFFSET).
3794
3795	- CONFIG_ENV_SECT_SIZE:
3796
3797	   Size of the sector containing the environment.
3798
3799
3800	b) Sometimes flash chips have few, equal sized, BIG sectors.
3801	   In such a case you don't want to spend a whole sector for
3802	   the environment.
3803
3804	- CONFIG_ENV_SIZE:
3805
3806	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3807	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3808	   of this flash sector for the environment. This saves
3809	   memory for the RAM copy of the environment.
3810
3811	   It may also save flash memory if you decide to use this
3812	   when your environment is "embedded" within U-Boot code,
3813	   since then the remainder of the flash sector could be used
3814	   for U-Boot code. It should be pointed out that this is
3815	   STRONGLY DISCOURAGED from a robustness point of view:
3816	   updating the environment in flash makes it always
3817	   necessary to erase the WHOLE sector. If something goes
3818	   wrong before the contents has been restored from a copy in
3819	   RAM, your target system will be dead.
3820
3821	- CONFIG_ENV_ADDR_REDUND
3822	  CONFIG_ENV_SIZE_REDUND
3823
3824	   These settings describe a second storage area used to hold
3825	   a redundant copy of the environment data, so that there is
3826	   a valid backup copy in case there is a power failure during
3827	   a "saveenv" operation.
3828
3829BE CAREFUL! Any changes to the flash layout, and some changes to the
3830source code will make it necessary to adapt <board>/u-boot.lds*
3831accordingly!
3832
3833
3834- CONFIG_ENV_IS_IN_NVRAM:
3835
3836	Define this if you have some non-volatile memory device
3837	(NVRAM, battery buffered SRAM) which you want to use for the
3838	environment.
3839
3840	- CONFIG_ENV_ADDR:
3841	- CONFIG_ENV_SIZE:
3842
3843	  These two #defines are used to determine the memory area you
3844	  want to use for environment. It is assumed that this memory
3845	  can just be read and written to, without any special
3846	  provision.
3847
3848BE CAREFUL! The first access to the environment happens quite early
3849in U-Boot initalization (when we try to get the setting of for the
3850console baudrate). You *MUST* have mapped your NVRAM area then, or
3851U-Boot will hang.
3852
3853Please note that even with NVRAM we still use a copy of the
3854environment in RAM: we could work on NVRAM directly, but we want to
3855keep settings there always unmodified except somebody uses "saveenv"
3856to save the current settings.
3857
3858
3859- CONFIG_ENV_IS_IN_EEPROM:
3860
3861	Use this if you have an EEPROM or similar serial access
3862	device and a driver for it.
3863
3864	- CONFIG_ENV_OFFSET:
3865	- CONFIG_ENV_SIZE:
3866
3867	  These two #defines specify the offset and size of the
3868	  environment area within the total memory of your EEPROM.
3869
3870	- CONFIG_SYS_I2C_EEPROM_ADDR:
3871	  If defined, specified the chip address of the EEPROM device.
3872	  The default address is zero.
3873
3874	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3875	  If defined, the number of bits used to address bytes in a
3876	  single page in the EEPROM device.  A 64 byte page, for example
3877	  would require six bits.
3878
3879	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3880	  If defined, the number of milliseconds to delay between
3881	  page writes.	The default is zero milliseconds.
3882
3883	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3884	  The length in bytes of the EEPROM memory array address.  Note
3885	  that this is NOT the chip address length!
3886
3887	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3888	  EEPROM chips that implement "address overflow" are ones
3889	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3890	  address and the extra bits end up in the "chip address" bit
3891	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3892	  byte chips.
3893
3894	  Note that we consider the length of the address field to
3895	  still be one byte because the extra address bits are hidden
3896	  in the chip address.
3897
3898	- CONFIG_SYS_EEPROM_SIZE:
3899	  The size in bytes of the EEPROM device.
3900
3901	- CONFIG_ENV_EEPROM_IS_ON_I2C
3902	  define this, if you have I2C and SPI activated, and your
3903	  EEPROM, which holds the environment, is on the I2C bus.
3904
3905	- CONFIG_I2C_ENV_EEPROM_BUS
3906	  if you have an Environment on an EEPROM reached over
3907	  I2C muxes, you can define here, how to reach this
3908	  EEPROM. For example:
3909
3910	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
3911
3912	  EEPROM which holds the environment, is reached over
3913	  a pca9547 i2c mux with address 0x70, channel 3.
3914
3915- CONFIG_ENV_IS_IN_DATAFLASH:
3916
3917	Define this if you have a DataFlash memory device which you
3918	want to use for the environment.
3919
3920	- CONFIG_ENV_OFFSET:
3921	- CONFIG_ENV_ADDR:
3922	- CONFIG_ENV_SIZE:
3923
3924	  These three #defines specify the offset and size of the
3925	  environment area within the total memory of your DataFlash placed
3926	  at the specified address.
3927
3928- CONFIG_ENV_IS_IN_REMOTE:
3929
3930	Define this if you have a remote memory space which you
3931	want to use for the local device's environment.
3932
3933	- CONFIG_ENV_ADDR:
3934	- CONFIG_ENV_SIZE:
3935
3936	  These two #defines specify the address and size of the
3937	  environment area within the remote memory space. The
3938	  local device can get the environment from remote memory
3939	  space by SRIO or PCIE links.
3940
3941BE CAREFUL! For some special cases, the local device can not use
3942"saveenv" command. For example, the local device will get the
3943environment stored in a remote NOR flash by SRIO or PCIE link,
3944but it can not erase, write this NOR flash by SRIO or PCIE interface.
3945
3946- CONFIG_ENV_IS_IN_NAND:
3947
3948	Define this if you have a NAND device which you want to use
3949	for the environment.
3950
3951	- CONFIG_ENV_OFFSET:
3952	- CONFIG_ENV_SIZE:
3953
3954	  These two #defines specify the offset and size of the environment
3955	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3956	  aligned to an erase block boundary.
3957
3958	- CONFIG_ENV_OFFSET_REDUND (optional):
3959
3960	  This setting describes a second storage area of CONFIG_ENV_SIZE
3961	  size used to hold a redundant copy of the environment data, so
3962	  that there is a valid backup copy in case there is a power failure
3963	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
3964	  aligned to an erase block boundary.
3965
3966	- CONFIG_ENV_RANGE (optional):
3967
3968	  Specifies the length of the region in which the environment
3969	  can be written.  This should be a multiple of the NAND device's
3970	  block size.  Specifying a range with more erase blocks than
3971	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
3972	  the range to be avoided.
3973
3974	- CONFIG_ENV_OFFSET_OOB (optional):
3975
3976	  Enables support for dynamically retrieving the offset of the
3977	  environment from block zero's out-of-band data.  The
3978	  "nand env.oob" command can be used to record this offset.
3979	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
3980	  using CONFIG_ENV_OFFSET_OOB.
3981
3982- CONFIG_NAND_ENV_DST
3983
3984	Defines address in RAM to which the nand_spl code should copy the
3985	environment. If redundant environment is used, it will be copied to
3986	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3987
3988- CONFIG_ENV_IS_IN_UBI:
3989
3990	Define this if you have an UBI volume that you want to use for the
3991	environment.  This has the benefit of wear-leveling the environment
3992	accesses, which is important on NAND.
3993
3994	- CONFIG_ENV_UBI_PART:
3995
3996	  Define this to a string that is the mtd partition containing the UBI.
3997
3998	- CONFIG_ENV_UBI_VOLUME:
3999
4000	  Define this to the name of the volume that you want to store the
4001	  environment in.
4002
4003	- CONFIG_ENV_UBI_VOLUME_REDUND:
4004
4005	  Define this to the name of another volume to store a second copy of
4006	  the environment in.  This will enable redundant environments in UBI.
4007	  It is assumed that both volumes are in the same MTD partition.
4008
4009	- CONFIG_UBI_SILENCE_MSG
4010	- CONFIG_UBIFS_SILENCE_MSG
4011
4012	  You will probably want to define these to avoid a really noisy system
4013	  when storing the env in UBI.
4014
4015- CONFIG_ENV_IS_IN_MMC:
4016
4017	Define this if you have an MMC device which you want to use for the
4018	environment.
4019
4020	- CONFIG_SYS_MMC_ENV_DEV:
4021
4022	  Specifies which MMC device the environment is stored in.
4023
4024	- CONFIG_SYS_MMC_ENV_PART (optional):
4025
4026	  Specifies which MMC partition the environment is stored in. If not
4027	  set, defaults to partition 0, the user area. Common values might be
4028	  1 (first MMC boot partition), 2 (second MMC boot partition).
4029
4030	- CONFIG_ENV_OFFSET:
4031	- CONFIG_ENV_SIZE:
4032
4033	  These two #defines specify the offset and size of the environment
4034	  area within the specified MMC device.
4035
4036	  If offset is positive (the usual case), it is treated as relative to
4037	  the start of the MMC partition. If offset is negative, it is treated
4038	  as relative to the end of the MMC partition. This can be useful if
4039	  your board may be fitted with different MMC devices, which have
4040	  different sizes for the MMC partitions, and you always want the
4041	  environment placed at the very end of the partition, to leave the
4042	  maximum possible space before it, to store other data.
4043
4044	  These two values are in units of bytes, but must be aligned to an
4045	  MMC sector boundary.
4046
4047	- CONFIG_ENV_OFFSET_REDUND (optional):
4048
4049	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4050	  hold a redundant copy of the environment data. This provides a
4051	  valid backup copy in case the other copy is corrupted, e.g. due
4052	  to a power failure during a "saveenv" operation.
4053
4054	  This value may also be positive or negative; this is handled in the
4055	  same way as CONFIG_ENV_OFFSET.
4056
4057	  This value is also in units of bytes, but must also be aligned to
4058	  an MMC sector boundary.
4059
4060	- CONFIG_ENV_SIZE_REDUND (optional):
4061
4062	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4063	  set. If this value is set, it must be set to the same value as
4064	  CONFIG_ENV_SIZE.
4065
4066- CONFIG_SYS_SPI_INIT_OFFSET
4067
4068	Defines offset to the initial SPI buffer area in DPRAM. The
4069	area is used at an early stage (ROM part) if the environment
4070	is configured to reside in the SPI EEPROM: We need a 520 byte
4071	scratch DPRAM area. It is used between the two initialization
4072	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4073	to be a good choice since it makes it far enough from the
4074	start of the data area as well as from the stack pointer.
4075
4076Please note that the environment is read-only until the monitor
4077has been relocated to RAM and a RAM copy of the environment has been
4078created; also, when using EEPROM you will have to use getenv_f()
4079until then to read environment variables.
4080
4081The environment is protected by a CRC32 checksum. Before the monitor
4082is relocated into RAM, as a result of a bad CRC you will be working
4083with the compiled-in default environment - *silently*!!! [This is
4084necessary, because the first environment variable we need is the
4085"baudrate" setting for the console - if we have a bad CRC, we don't
4086have any device yet where we could complain.]
4087
4088Note: once the monitor has been relocated, then it will complain if
4089the default environment is used; a new CRC is computed as soon as you
4090use the "saveenv" command to store a valid environment.
4091
4092- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4093		Echo the inverted Ethernet link state to the fault LED.
4094
4095		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4096		      also needs to be defined.
4097
4098- CONFIG_SYS_FAULT_MII_ADDR:
4099		MII address of the PHY to check for the Ethernet link state.
4100
4101- CONFIG_NS16550_MIN_FUNCTIONS:
4102		Define this if you desire to only have use of the NS16550_init
4103		and NS16550_putc functions for the serial driver located at
4104		drivers/serial/ns16550.c.  This option is useful for saving
4105		space for already greatly restricted images, including but not
4106		limited to NAND_SPL configurations.
4107
4108- CONFIG_DISPLAY_BOARDINFO
4109		Display information about the board that U-Boot is running on
4110		when U-Boot starts up. The board function checkboard() is called
4111		to do this.
4112
4113- CONFIG_DISPLAY_BOARDINFO_LATE
4114		Similar to the previous option, but display this information
4115		later, once stdio is running and output goes to the LCD, if
4116		present.
4117
4118Low Level (hardware related) configuration options:
4119---------------------------------------------------
4120
4121- CONFIG_SYS_CACHELINE_SIZE:
4122		Cache Line Size of the CPU.
4123
4124- CONFIG_SYS_DEFAULT_IMMR:
4125		Default address of the IMMR after system reset.
4126
4127		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4128		and RPXsuper) to be able to adjust the position of
4129		the IMMR register after a reset.
4130
4131- CONFIG_SYS_CCSRBAR_DEFAULT:
4132		Default (power-on reset) physical address of CCSR on Freescale
4133		PowerPC SOCs.
4134
4135- CONFIG_SYS_CCSRBAR:
4136		Virtual address of CCSR.  On a 32-bit build, this is typically
4137		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4138
4139		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4140		for cross-platform code that uses that macro instead.
4141
4142- CONFIG_SYS_CCSRBAR_PHYS:
4143		Physical address of CCSR.  CCSR can be relocated to a new
4144		physical address, if desired.  In this case, this macro should
4145		be set to that address.	 Otherwise, it should be set to the
4146		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4147		is typically relocated on 36-bit builds.  It is recommended
4148		that this macro be defined via the _HIGH and _LOW macros:
4149
4150		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4151			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4152
4153- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4154		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4155		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4156		used in assembly code, so it must not contain typecasts or
4157		integer size suffixes (e.g. "ULL").
4158
4159- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4160		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4161		used in assembly code, so it must not contain typecasts or
4162		integer size suffixes (e.g. "ULL").
4163
4164- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4165		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4166		forced to a value that ensures that CCSR is not relocated.
4167
4168- Floppy Disk Support:
4169		CONFIG_SYS_FDC_DRIVE_NUMBER
4170
4171		the default drive number (default value 0)
4172
4173		CONFIG_SYS_ISA_IO_STRIDE
4174
4175		defines the spacing between FDC chipset registers
4176		(default value 1)
4177
4178		CONFIG_SYS_ISA_IO_OFFSET
4179
4180		defines the offset of register from address. It
4181		depends on which part of the data bus is connected to
4182		the FDC chipset. (default value 0)
4183
4184		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4185		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4186		default value.
4187
4188		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4189		fdc_hw_init() is called at the beginning of the FDC
4190		setup. fdc_hw_init() must be provided by the board
4191		source code. It is used to make hardware dependant
4192		initializations.
4193
4194- CONFIG_IDE_AHB:
4195		Most IDE controllers were designed to be connected with PCI
4196		interface. Only few of them were designed for AHB interface.
4197		When software is doing ATA command and data transfer to
4198		IDE devices through IDE-AHB controller, some additional
4199		registers accessing to these kind of IDE-AHB controller
4200		is requierd.
4201
4202- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4203		DO NOT CHANGE unless you know exactly what you're
4204		doing! (11-4) [MPC8xx/82xx systems only]
4205
4206- CONFIG_SYS_INIT_RAM_ADDR:
4207
4208		Start address of memory area that can be used for
4209		initial data and stack; please note that this must be
4210		writable memory that is working WITHOUT special
4211		initialization, i. e. you CANNOT use normal RAM which
4212		will become available only after programming the
4213		memory controller and running certain initialization
4214		sequences.
4215
4216		U-Boot uses the following memory types:
4217		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4218		- MPC824X: data cache
4219		- PPC4xx:  data cache
4220
4221- CONFIG_SYS_GBL_DATA_OFFSET:
4222
4223		Offset of the initial data structure in the memory
4224		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4225		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4226		data is located at the end of the available space
4227		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4228		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4229		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4230		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4231
4232	Note:
4233		On the MPC824X (or other systems that use the data
4234		cache for initial memory) the address chosen for
4235		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4236		point to an otherwise UNUSED address space between
4237		the top of RAM and the start of the PCI space.
4238
4239- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4240
4241- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4242
4243- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4244
4245- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4246
4247- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4248
4249- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4250
4251- CONFIG_SYS_OR_TIMING_SDRAM:
4252		SDRAM timing
4253
4254- CONFIG_SYS_MAMR_PTA:
4255		periodic timer for refresh
4256
4257- CONFIG_SYS_DER:	Debug Event Register (37-47)
4258
4259- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4260  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4261  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4262  CONFIG_SYS_BR1_PRELIM:
4263		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4264
4265- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4266  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4267  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4268		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4269
4270- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4271  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4272		Machine Mode Register and Memory Periodic Timer
4273		Prescaler definitions (SDRAM timing)
4274
4275- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4276		enable I2C microcode relocation patch (MPC8xx);
4277		define relocation offset in DPRAM [DSP2]
4278
4279- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4280		enable SMC microcode relocation patch (MPC8xx);
4281		define relocation offset in DPRAM [SMC1]
4282
4283- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4284		enable SPI microcode relocation patch (MPC8xx);
4285		define relocation offset in DPRAM [SCC4]
4286
4287- CONFIG_SYS_USE_OSCCLK:
4288		Use OSCM clock mode on MBX8xx board. Be careful,
4289		wrong setting might damage your board. Read
4290		doc/README.MBX before setting this variable!
4291
4292- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4293		Offset of the bootmode word in DPRAM used by post
4294		(Power On Self Tests). This definition overrides
4295		#define'd default value in commproc.h resp.
4296		cpm_8260.h.
4297
4298- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4299  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4300  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4301  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4302  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4303  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4304  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4305  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4306		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4307
4308- CONFIG_PCI_DISABLE_PCIE:
4309		Disable PCI-Express on systems where it is supported but not
4310		required.
4311
4312- CONFIG_PCI_ENUM_ONLY
4313		Only scan through and get the devices on the busses.
4314		Don't do any setup work, presumably because someone or
4315		something has already done it, and we don't need to do it
4316		a second time.	Useful for platforms that are pre-booted
4317		by coreboot or similar.
4318
4319- CONFIG_PCI_INDIRECT_BRIDGE:
4320		Enable support for indirect PCI bridges.
4321
4322- CONFIG_SYS_SRIO:
4323		Chip has SRIO or not
4324
4325- CONFIG_SRIO1:
4326		Board has SRIO 1 port available
4327
4328- CONFIG_SRIO2:
4329		Board has SRIO 2 port available
4330
4331- CONFIG_SRIO_PCIE_BOOT_MASTER
4332		Board can support master function for Boot from SRIO and PCIE
4333
4334- CONFIG_SYS_SRIOn_MEM_VIRT:
4335		Virtual Address of SRIO port 'n' memory region
4336
4337- CONFIG_SYS_SRIOn_MEM_PHYS:
4338		Physical Address of SRIO port 'n' memory region
4339
4340- CONFIG_SYS_SRIOn_MEM_SIZE:
4341		Size of SRIO port 'n' memory region
4342
4343- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4344		Defined to tell the NAND controller that the NAND chip is using
4345		a 16 bit bus.
4346		Not all NAND drivers use this symbol.
4347		Example of drivers that use it:
4348		- drivers/mtd/nand/ndfc.c
4349		- drivers/mtd/nand/mxc_nand.c
4350
4351- CONFIG_SYS_NDFC_EBC0_CFG
4352		Sets the EBC0_CFG register for the NDFC. If not defined
4353		a default value will be used.
4354
4355- CONFIG_SPD_EEPROM
4356		Get DDR timing information from an I2C EEPROM. Common
4357		with pluggable memory modules such as SODIMMs
4358
4359  SPD_EEPROM_ADDRESS
4360		I2C address of the SPD EEPROM
4361
4362- CONFIG_SYS_SPD_BUS_NUM
4363		If SPD EEPROM is on an I2C bus other than the first
4364		one, specify here. Note that the value must resolve
4365		to something your driver can deal with.
4366
4367- CONFIG_SYS_DDR_RAW_TIMING
4368		Get DDR timing information from other than SPD. Common with
4369		soldered DDR chips onboard without SPD. DDR raw timing
4370		parameters are extracted from datasheet and hard-coded into
4371		header files or board specific files.
4372
4373- CONFIG_FSL_DDR_INTERACTIVE
4374		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4375
4376- CONFIG_SYS_83XX_DDR_USES_CS0
4377		Only for 83xx systems. If specified, then DDR should
4378		be configured using CS0 and CS1 instead of CS2 and CS3.
4379
4380- CONFIG_ETHER_ON_FEC[12]
4381		Define to enable FEC[12] on a 8xx series processor.
4382
4383- CONFIG_FEC[12]_PHY
4384		Define to the hardcoded PHY address which corresponds
4385		to the given FEC; i. e.
4386			#define CONFIG_FEC1_PHY 4
4387		means that the PHY with address 4 is connected to FEC1
4388
4389		When set to -1, means to probe for first available.
4390
4391- CONFIG_FEC[12]_PHY_NORXERR
4392		The PHY does not have a RXERR line (RMII only).
4393		(so program the FEC to ignore it).
4394
4395- CONFIG_RMII
4396		Enable RMII mode for all FECs.
4397		Note that this is a global option, we can't
4398		have one FEC in standard MII mode and another in RMII mode.
4399
4400- CONFIG_CRC32_VERIFY
4401		Add a verify option to the crc32 command.
4402		The syntax is:
4403
4404		=> crc32 -v <address> <count> <crc32>
4405
4406		Where address/count indicate a memory area
4407		and crc32 is the correct crc32 which the
4408		area should have.
4409
4410- CONFIG_LOOPW
4411		Add the "loopw" memory command. This only takes effect if
4412		the memory commands are activated globally (CONFIG_CMD_MEM).
4413
4414- CONFIG_MX_CYCLIC
4415		Add the "mdc" and "mwc" memory commands. These are cyclic
4416		"md/mw" commands.
4417		Examples:
4418
4419		=> mdc.b 10 4 500
4420		This command will print 4 bytes (10,11,12,13) each 500 ms.
4421
4422		=> mwc.l 100 12345678 10
4423		This command will write 12345678 to address 100 all 10 ms.
4424
4425		This only takes effect if the memory commands are activated
4426		globally (CONFIG_CMD_MEM).
4427
4428- CONFIG_SKIP_LOWLEVEL_INIT
4429		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4430		low level initializations (like setting up the memory
4431		controller) are omitted and/or U-Boot does not
4432		relocate itself into RAM.
4433
4434		Normally this variable MUST NOT be defined. The only
4435		exception is when U-Boot is loaded (to RAM) by some
4436		other boot loader or by a debugger which performs
4437		these initializations itself.
4438
4439- CONFIG_SPL_BUILD
4440		Modifies the behaviour of start.S when compiling a loader
4441		that is executed before the actual U-Boot. E.g. when
4442		compiling a NAND SPL.
4443
4444- CONFIG_TPL_BUILD
4445		Modifies the behaviour of start.S  when compiling a loader
4446		that is executed after the SPL and before the actual U-Boot.
4447		It is loaded by the SPL.
4448
4449- CONFIG_SYS_MPC85XX_NO_RESETVEC
4450		Only for 85xx systems. If this variable is specified, the section
4451		.resetvec is not kept and the section .bootpg is placed in the
4452		previous 4k of the .text section.
4453
4454- CONFIG_ARCH_MAP_SYSMEM
4455		Generally U-Boot (and in particular the md command) uses
4456		effective address. It is therefore not necessary to regard
4457		U-Boot address as virtual addresses that need to be translated
4458		to physical addresses. However, sandbox requires this, since
4459		it maintains its own little RAM buffer which contains all
4460		addressable memory. This option causes some memory accesses
4461		to be mapped through map_sysmem() / unmap_sysmem().
4462
4463- CONFIG_USE_ARCH_MEMCPY
4464  CONFIG_USE_ARCH_MEMSET
4465		If these options are used a optimized version of memcpy/memset will
4466		be used if available. These functions may be faster under some
4467		conditions but may increase the binary size.
4468
4469- CONFIG_X86_RESET_VECTOR
4470		If defined, the x86 reset vector code is included. This is not
4471		needed when U-Boot is running from Coreboot.
4472
4473- CONFIG_SYS_MPUCLK
4474		Defines the MPU clock speed (in MHz).
4475
4476		NOTE : currently only supported on AM335x platforms.
4477
4478- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4479		Enables the RTC32K OSC on AM33xx based plattforms
4480
4481Freescale QE/FMAN Firmware Support:
4482-----------------------------------
4483
4484The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4485loading of "firmware", which is encoded in the QE firmware binary format.
4486This firmware often needs to be loaded during U-Boot booting, so macros
4487are used to identify the storage device (NOR flash, SPI, etc) and the address
4488within that device.
4489
4490- CONFIG_SYS_QE_FMAN_FW_ADDR
4491	The address in the storage device where the firmware is located.  The
4492	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4493	is also specified.
4494
4495- CONFIG_SYS_QE_FMAN_FW_LENGTH
4496	The maximum possible size of the firmware.  The firmware binary format
4497	has a field that specifies the actual size of the firmware, but it
4498	might not be possible to read any part of the firmware unless some
4499	local storage is allocated to hold the entire firmware first.
4500
4501- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4502	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4503	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4504	virtual address in NOR flash.
4505
4506- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4507	Specifies that QE/FMAN firmware is located in NAND flash.
4508	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4509
4510- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4511	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4512	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4513
4514- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4515	Specifies that QE/FMAN firmware is located on the primary SPI
4516	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4517
4518- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4519	Specifies that QE/FMAN firmware is located in the remote (master)
4520	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4521	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4522	window->master inbound window->master LAW->the ucode address in
4523	master's memory space.
4524
4525Building the Software:
4526======================
4527
4528Building U-Boot has been tested in several native build environments
4529and in many different cross environments. Of course we cannot support
4530all possibly existing versions of cross development tools in all
4531(potentially obsolete) versions. In case of tool chain problems we
4532recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4533which is extensively used to build and test U-Boot.
4534
4535If you are not using a native environment, it is assumed that you
4536have GNU cross compiling tools available in your path. In this case,
4537you must set the environment variable CROSS_COMPILE in your shell.
4538Note that no changes to the Makefile or any other source files are
4539necessary. For example using the ELDK on a 4xx CPU, please enter:
4540
4541	$ CROSS_COMPILE=ppc_4xx-
4542	$ export CROSS_COMPILE
4543
4544Note: If you wish to generate Windows versions of the utilities in
4545      the tools directory you can use the MinGW toolchain
4546      (http://www.mingw.org).  Set your HOST tools to the MinGW
4547      toolchain and execute 'make tools'.  For example:
4548
4549       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4550
4551      Binaries such as tools/mkimage.exe will be created which can
4552      be executed on computers running Windows.
4553
4554U-Boot is intended to be simple to build. After installing the
4555sources you must configure U-Boot for one specific board type. This
4556is done by typing:
4557
4558	make NAME_config
4559
4560where "NAME_config" is the name of one of the existing configu-
4561rations; see boards.cfg for supported names.
4562
4563Note: for some board special configuration names may exist; check if
4564      additional information is available from the board vendor; for
4565      instance, the TQM823L systems are available without (standard)
4566      or with LCD support. You can select such additional "features"
4567      when choosing the configuration, i. e.
4568
4569      make TQM823L_config
4570	- will configure for a plain TQM823L, i. e. no LCD support
4571
4572      make TQM823L_LCD_config
4573	- will configure for a TQM823L with U-Boot console on LCD
4574
4575      etc.
4576
4577
4578Finally, type "make all", and you should get some working U-Boot
4579images ready for download to / installation on your system:
4580
4581- "u-boot.bin" is a raw binary image
4582- "u-boot" is an image in ELF binary format
4583- "u-boot.srec" is in Motorola S-Record format
4584
4585By default the build is performed locally and the objects are saved
4586in the source directory. One of the two methods can be used to change
4587this behavior and build U-Boot to some external directory:
4588
45891. Add O= to the make command line invocations:
4590
4591	make O=/tmp/build distclean
4592	make O=/tmp/build NAME_config
4593	make O=/tmp/build all
4594
45952. Set environment variable BUILD_DIR to point to the desired location:
4596
4597	export BUILD_DIR=/tmp/build
4598	make distclean
4599	make NAME_config
4600	make all
4601
4602Note that the command line "O=" setting overrides the BUILD_DIR environment
4603variable.
4604
4605
4606Please be aware that the Makefiles assume you are using GNU make, so
4607for instance on NetBSD you might need to use "gmake" instead of
4608native "make".
4609
4610
4611If the system board that you have is not listed, then you will need
4612to port U-Boot to your hardware platform. To do this, follow these
4613steps:
4614
46151.  Add a new configuration option for your board to the toplevel
4616    "boards.cfg" file, using the existing entries as examples.
4617    Follow the instructions there to keep the boards in order.
46182.  Create a new directory to hold your board specific code. Add any
4619    files you need. In your board directory, you will need at least
4620    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
46213.  Create a new configuration file "include/configs/<board>.h" for
4622    your board
46233.  If you're porting U-Boot to a new CPU, then also create a new
4624    directory to hold your CPU specific code. Add any files you need.
46254.  Run "make <board>_config" with your new name.
46265.  Type "make", and you should get a working "u-boot.srec" file
4627    to be installed on your target system.
46286.  Debug and solve any problems that might arise.
4629    [Of course, this last step is much harder than it sounds.]
4630
4631
4632Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4633==============================================================
4634
4635If you have modified U-Boot sources (for instance added a new board
4636or support for new devices, a new CPU, etc.) you are expected to
4637provide feedback to the other developers. The feedback normally takes
4638the form of a "patch", i. e. a context diff against a certain (latest
4639official or latest in the git repository) version of U-Boot sources.
4640
4641But before you submit such a patch, please verify that your modifi-
4642cation did not break existing code. At least make sure that *ALL* of
4643the supported boards compile WITHOUT ANY compiler warnings. To do so,
4644just run the "MAKEALL" script, which will configure and build U-Boot
4645for ALL supported system. Be warned, this will take a while. You can
4646select which (cross) compiler to use by passing a `CROSS_COMPILE'
4647environment variable to the script, i. e. to use the ELDK cross tools
4648you can type
4649
4650	CROSS_COMPILE=ppc_8xx- MAKEALL
4651
4652or to build on a native PowerPC system you can type
4653
4654	CROSS_COMPILE=' ' MAKEALL
4655
4656When using the MAKEALL script, the default behaviour is to build
4657U-Boot in the source directory. This location can be changed by
4658setting the BUILD_DIR environment variable. Also, for each target
4659built, the MAKEALL script saves two log files (<target>.ERR and
4660<target>.MAKEALL) in the <source dir>/LOG directory. This default
4661location can be changed by setting the MAKEALL_LOGDIR environment
4662variable. For example:
4663
4664	export BUILD_DIR=/tmp/build
4665	export MAKEALL_LOGDIR=/tmp/log
4666	CROSS_COMPILE=ppc_8xx- MAKEALL
4667
4668With the above settings build objects are saved in the /tmp/build,
4669log files are saved in the /tmp/log and the source tree remains clean
4670during the whole build process.
4671
4672
4673See also "U-Boot Porting Guide" below.
4674
4675
4676Monitor Commands - Overview:
4677============================
4678
4679go	- start application at address 'addr'
4680run	- run commands in an environment variable
4681bootm	- boot application image from memory
4682bootp	- boot image via network using BootP/TFTP protocol
4683bootz   - boot zImage from memory
4684tftpboot- boot image via network using TFTP protocol
4685	       and env variables "ipaddr" and "serverip"
4686	       (and eventually "gatewayip")
4687tftpput - upload a file via network using TFTP protocol
4688rarpboot- boot image via network using RARP/TFTP protocol
4689diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4690loads	- load S-Record file over serial line
4691loadb	- load binary file over serial line (kermit mode)
4692md	- memory display
4693mm	- memory modify (auto-incrementing)
4694nm	- memory modify (constant address)
4695mw	- memory write (fill)
4696cp	- memory copy
4697cmp	- memory compare
4698crc32	- checksum calculation
4699i2c	- I2C sub-system
4700sspi	- SPI utility commands
4701base	- print or set address offset
4702printenv- print environment variables
4703setenv	- set environment variables
4704saveenv - save environment variables to persistent storage
4705protect - enable or disable FLASH write protection
4706erase	- erase FLASH memory
4707flinfo	- print FLASH memory information
4708nand	- NAND memory operations (see doc/README.nand)
4709bdinfo	- print Board Info structure
4710iminfo	- print header information for application image
4711coninfo - print console devices and informations
4712ide	- IDE sub-system
4713loop	- infinite loop on address range
4714loopw	- infinite write loop on address range
4715mtest	- simple RAM test
4716icache	- enable or disable instruction cache
4717dcache	- enable or disable data cache
4718reset	- Perform RESET of the CPU
4719echo	- echo args to console
4720version - print monitor version
4721help	- print online help
4722?	- alias for 'help'
4723
4724
4725Monitor Commands - Detailed Description:
4726========================================
4727
4728TODO.
4729
4730For now: just type "help <command>".
4731
4732
4733Environment Variables:
4734======================
4735
4736U-Boot supports user configuration using Environment Variables which
4737can be made persistent by saving to Flash memory.
4738
4739Environment Variables are set using "setenv", printed using
4740"printenv", and saved to Flash using "saveenv". Using "setenv"
4741without a value can be used to delete a variable from the
4742environment. As long as you don't save the environment you are
4743working with an in-memory copy. In case the Flash area containing the
4744environment is erased by accident, a default environment is provided.
4745
4746Some configuration options can be set using Environment Variables.
4747
4748List of environment variables (most likely not complete):
4749
4750  baudrate	- see CONFIG_BAUDRATE
4751
4752  bootdelay	- see CONFIG_BOOTDELAY
4753
4754  bootcmd	- see CONFIG_BOOTCOMMAND
4755
4756  bootargs	- Boot arguments when booting an RTOS image
4757
4758  bootfile	- Name of the image to load with TFTP
4759
4760  bootm_low	- Memory range available for image processing in the bootm
4761		  command can be restricted. This variable is given as
4762		  a hexadecimal number and defines lowest address allowed
4763		  for use by the bootm command. See also "bootm_size"
4764		  environment variable. Address defined by "bootm_low" is
4765		  also the base of the initial memory mapping for the Linux
4766		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4767		  bootm_mapsize.
4768
4769  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4770		  This variable is given as a hexadecimal number and it
4771		  defines the size of the memory region starting at base
4772		  address bootm_low that is accessible by the Linux kernel
4773		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4774		  as the default value if it is defined, and bootm_size is
4775		  used otherwise.
4776
4777  bootm_size	- Memory range available for image processing in the bootm
4778		  command can be restricted. This variable is given as
4779		  a hexadecimal number and defines the size of the region
4780		  allowed for use by the bootm command. See also "bootm_low"
4781		  environment variable.
4782
4783  updatefile	- Location of the software update file on a TFTP server, used
4784		  by the automatic software update feature. Please refer to
4785		  documentation in doc/README.update for more details.
4786
4787  autoload	- if set to "no" (any string beginning with 'n'),
4788		  "bootp" will just load perform a lookup of the
4789		  configuration from the BOOTP server, but not try to
4790		  load any image using TFTP
4791
4792  autostart	- if set to "yes", an image loaded using the "bootp",
4793		  "rarpboot", "tftpboot" or "diskboot" commands will
4794		  be automatically started (by internally calling
4795		  "bootm")
4796
4797		  If set to "no", a standalone image passed to the
4798		  "bootm" command will be copied to the load address
4799		  (and eventually uncompressed), but NOT be started.
4800		  This can be used to load and uncompress arbitrary
4801		  data.
4802
4803  fdt_high	- if set this restricts the maximum address that the
4804		  flattened device tree will be copied into upon boot.
4805		  For example, if you have a system with 1 GB memory
4806		  at physical address 0x10000000, while Linux kernel
4807		  only recognizes the first 704 MB as low memory, you
4808		  may need to set fdt_high as 0x3C000000 to have the
4809		  device tree blob be copied to the maximum address
4810		  of the 704 MB low memory, so that Linux kernel can
4811		  access it during the boot procedure.
4812
4813		  If this is set to the special value 0xFFFFFFFF then
4814		  the fdt will not be copied at all on boot.  For this
4815		  to work it must reside in writable memory, have
4816		  sufficient padding on the end of it for u-boot to
4817		  add the information it needs into it, and the memory
4818		  must be accessible by the kernel.
4819
4820  fdtcontroladdr- if set this is the address of the control flattened
4821		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4822		  defined.
4823
4824  i2cfast	- (PPC405GP|PPC405EP only)
4825		  if set to 'y' configures Linux I2C driver for fast
4826		  mode (400kHZ). This environment variable is used in
4827		  initialization code. So, for changes to be effective
4828		  it must be saved and board must be reset.
4829
4830  initrd_high	- restrict positioning of initrd images:
4831		  If this variable is not set, initrd images will be
4832		  copied to the highest possible address in RAM; this
4833		  is usually what you want since it allows for
4834		  maximum initrd size. If for some reason you want to
4835		  make sure that the initrd image is loaded below the
4836		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4837		  variable to a value of "no" or "off" or "0".
4838		  Alternatively, you can set it to a maximum upper
4839		  address to use (U-Boot will still check that it
4840		  does not overwrite the U-Boot stack and data).
4841
4842		  For instance, when you have a system with 16 MB
4843		  RAM, and want to reserve 4 MB from use by Linux,
4844		  you can do this by adding "mem=12M" to the value of
4845		  the "bootargs" variable. However, now you must make
4846		  sure that the initrd image is placed in the first
4847		  12 MB as well - this can be done with
4848
4849		  setenv initrd_high 00c00000
4850
4851		  If you set initrd_high to 0xFFFFFFFF, this is an
4852		  indication to U-Boot that all addresses are legal
4853		  for the Linux kernel, including addresses in flash
4854		  memory. In this case U-Boot will NOT COPY the
4855		  ramdisk at all. This may be useful to reduce the
4856		  boot time on your system, but requires that this
4857		  feature is supported by your Linux kernel.
4858
4859  ipaddr	- IP address; needed for tftpboot command
4860
4861  loadaddr	- Default load address for commands like "bootp",
4862		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4863
4864  loads_echo	- see CONFIG_LOADS_ECHO
4865
4866  serverip	- TFTP server IP address; needed for tftpboot command
4867
4868  bootretry	- see CONFIG_BOOT_RETRY_TIME
4869
4870  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4871
4872  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4873
4874  ethprime	- controls which interface is used first.
4875
4876  ethact	- controls which interface is currently active.
4877		  For example you can do the following
4878
4879		  => setenv ethact FEC
4880		  => ping 192.168.0.1 # traffic sent on FEC
4881		  => setenv ethact SCC
4882		  => ping 10.0.0.1 # traffic sent on SCC
4883
4884  ethrotate	- When set to "no" U-Boot does not go through all
4885		  available network interfaces.
4886		  It just stays at the currently selected interface.
4887
4888  netretry	- When set to "no" each network operation will
4889		  either succeed or fail without retrying.
4890		  When set to "once" the network operation will
4891		  fail when all the available network interfaces
4892		  are tried once without success.
4893		  Useful on scripts which control the retry operation
4894		  themselves.
4895
4896  npe_ucode	- set load address for the NPE microcode
4897
4898  silent_linux  - If set then linux will be told to boot silently, by
4899		  changing the console to be empty. If "yes" it will be
4900		  made silent. If "no" it will not be made silent. If
4901		  unset, then it will be made silent if the U-Boot console
4902		  is silent.
4903
4904  tftpsrcport	- If this is set, the value is used for TFTP's
4905		  UDP source port.
4906
4907  tftpdstport	- If this is set, the value is used for TFTP's UDP
4908		  destination port instead of the Well Know Port 69.
4909
4910  tftpblocksize - Block size to use for TFTP transfers; if not set,
4911		  we use the TFTP server's default block size
4912
4913  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4914		  seconds, minimum value is 1000 = 1 second). Defines
4915		  when a packet is considered to be lost so it has to
4916		  be retransmitted. The default is 5000 = 5 seconds.
4917		  Lowering this value may make downloads succeed
4918		  faster in networks with high packet loss rates or
4919		  with unreliable TFTP servers.
4920
4921  vlan		- When set to a value < 4095 the traffic over
4922		  Ethernet is encapsulated/received over 802.1q
4923		  VLAN tagged frames.
4924
4925The following image location variables contain the location of images
4926used in booting. The "Image" column gives the role of the image and is
4927not an environment variable name. The other columns are environment
4928variable names. "File Name" gives the name of the file on a TFTP
4929server, "RAM Address" gives the location in RAM the image will be
4930loaded to, and "Flash Location" gives the image's address in NOR
4931flash or offset in NAND flash.
4932
4933*Note* - these variables don't have to be defined for all boards, some
4934boards currenlty use other variables for these purposes, and some
4935boards use these variables for other purposes.
4936
4937Image		    File Name	     RAM Address       Flash Location
4938-----		    ---------	     -----------       --------------
4939u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4940Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4941device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4942ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4943
4944The following environment variables may be used and automatically
4945updated by the network boot commands ("bootp" and "rarpboot"),
4946depending the information provided by your boot server:
4947
4948  bootfile	- see above
4949  dnsip		- IP address of your Domain Name Server
4950  dnsip2	- IP address of your secondary Domain Name Server
4951  gatewayip	- IP address of the Gateway (Router) to use
4952  hostname	- Target hostname
4953  ipaddr	- see above
4954  netmask	- Subnet Mask
4955  rootpath	- Pathname of the root filesystem on the NFS server
4956  serverip	- see above
4957
4958
4959There are two special Environment Variables:
4960
4961  serial#	- contains hardware identification information such
4962		  as type string and/or serial number
4963  ethaddr	- Ethernet address
4964
4965These variables can be set only once (usually during manufacturing of
4966the board). U-Boot refuses to delete or overwrite these variables
4967once they have been set once.
4968
4969
4970Further special Environment Variables:
4971
4972  ver		- Contains the U-Boot version string as printed
4973		  with the "version" command. This variable is
4974		  readonly (see CONFIG_VERSION_VARIABLE).
4975
4976
4977Please note that changes to some configuration parameters may take
4978only effect after the next boot (yes, that's just like Windoze :-).
4979
4980
4981Callback functions for environment variables:
4982---------------------------------------------
4983
4984For some environment variables, the behavior of u-boot needs to change
4985when their values are changed.  This functionailty allows functions to
4986be associated with arbitrary variables.  On creation, overwrite, or
4987deletion, the callback will provide the opportunity for some side
4988effect to happen or for the change to be rejected.
4989
4990The callbacks are named and associated with a function using the
4991U_BOOT_ENV_CALLBACK macro in your board or driver code.
4992
4993These callbacks are associated with variables in one of two ways.  The
4994static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
4995in the board configuration to a string that defines a list of
4996associations.  The list must be in the following format:
4997
4998	entry = variable_name[:callback_name]
4999	list = entry[,list]
5000
5001If the callback name is not specified, then the callback is deleted.
5002Spaces are also allowed anywhere in the list.
5003
5004Callbacks can also be associated by defining the ".callbacks" variable
5005with the same list format above.  Any association in ".callbacks" will
5006override any association in the static list. You can define
5007CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5008".callbacks" envirnoment variable in the default or embedded environment.
5009
5010
5011Command Line Parsing:
5012=====================
5013
5014There are two different command line parsers available with U-Boot:
5015the old "simple" one, and the much more powerful "hush" shell:
5016
5017Old, simple command line parser:
5018--------------------------------
5019
5020- supports environment variables (through setenv / saveenv commands)
5021- several commands on one line, separated by ';'
5022- variable substitution using "... ${name} ..." syntax
5023- special characters ('$', ';') can be escaped by prefixing with '\',
5024  for example:
5025	setenv bootcmd bootm \${address}
5026- You can also escape text by enclosing in single apostrophes, for example:
5027	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5028
5029Hush shell:
5030-----------
5031
5032- similar to Bourne shell, with control structures like
5033  if...then...else...fi, for...do...done; while...do...done,
5034  until...do...done, ...
5035- supports environment ("global") variables (through setenv / saveenv
5036  commands) and local shell variables (through standard shell syntax
5037  "name=value"); only environment variables can be used with "run"
5038  command
5039
5040General rules:
5041--------------
5042
5043(1) If a command line (or an environment variable executed by a "run"
5044    command) contains several commands separated by semicolon, and
5045    one of these commands fails, then the remaining commands will be
5046    executed anyway.
5047
5048(2) If you execute several variables with one call to run (i. e.
5049    calling run with a list of variables as arguments), any failing
5050    command will cause "run" to terminate, i. e. the remaining
5051    variables are not executed.
5052
5053Note for Redundant Ethernet Interfaces:
5054=======================================
5055
5056Some boards come with redundant Ethernet interfaces; U-Boot supports
5057such configurations and is capable of automatic selection of a
5058"working" interface when needed. MAC assignment works as follows:
5059
5060Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5061MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5062"eth1addr" (=>eth1), "eth2addr", ...
5063
5064If the network interface stores some valid MAC address (for instance
5065in SROM), this is used as default address if there is NO correspon-
5066ding setting in the environment; if the corresponding environment
5067variable is set, this overrides the settings in the card; that means:
5068
5069o If the SROM has a valid MAC address, and there is no address in the
5070  environment, the SROM's address is used.
5071
5072o If there is no valid address in the SROM, and a definition in the
5073  environment exists, then the value from the environment variable is
5074  used.
5075
5076o If both the SROM and the environment contain a MAC address, and
5077  both addresses are the same, this MAC address is used.
5078
5079o If both the SROM and the environment contain a MAC address, and the
5080  addresses differ, the value from the environment is used and a
5081  warning is printed.
5082
5083o If neither SROM nor the environment contain a MAC address, an error
5084  is raised.
5085
5086If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5087will be programmed into hardware as part of the initialization process.	 This
5088may be skipped by setting the appropriate 'ethmacskip' environment variable.
5089The naming convention is as follows:
5090"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5091
5092Image Formats:
5093==============
5094
5095U-Boot is capable of booting (and performing other auxiliary operations on)
5096images in two formats:
5097
5098New uImage format (FIT)
5099-----------------------
5100
5101Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5102to Flattened Device Tree). It allows the use of images with multiple
5103components (several kernels, ramdisks, etc.), with contents protected by
5104SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5105
5106
5107Old uImage format
5108-----------------
5109
5110Old image format is based on binary files which can be basically anything,
5111preceded by a special header; see the definitions in include/image.h for
5112details; basically, the header defines the following image properties:
5113
5114* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5115  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5116  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5117  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5118  INTEGRITY).
5119* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5120  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5121  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5122* Compression Type (uncompressed, gzip, bzip2)
5123* Load Address
5124* Entry Point
5125* Image Name
5126* Image Timestamp
5127
5128The header is marked by a special Magic Number, and both the header
5129and the data portions of the image are secured against corruption by
5130CRC32 checksums.
5131
5132
5133Linux Support:
5134==============
5135
5136Although U-Boot should support any OS or standalone application
5137easily, the main focus has always been on Linux during the design of
5138U-Boot.
5139
5140U-Boot includes many features that so far have been part of some
5141special "boot loader" code within the Linux kernel. Also, any
5142"initrd" images to be used are no longer part of one big Linux image;
5143instead, kernel and "initrd" are separate images. This implementation
5144serves several purposes:
5145
5146- the same features can be used for other OS or standalone
5147  applications (for instance: using compressed images to reduce the
5148  Flash memory footprint)
5149
5150- it becomes much easier to port new Linux kernel versions because
5151  lots of low-level, hardware dependent stuff are done by U-Boot
5152
5153- the same Linux kernel image can now be used with different "initrd"
5154  images; of course this also means that different kernel images can
5155  be run with the same "initrd". This makes testing easier (you don't
5156  have to build a new "zImage.initrd" Linux image when you just
5157  change a file in your "initrd"). Also, a field-upgrade of the
5158  software is easier now.
5159
5160
5161Linux HOWTO:
5162============
5163
5164Porting Linux to U-Boot based systems:
5165---------------------------------------
5166
5167U-Boot cannot save you from doing all the necessary modifications to
5168configure the Linux device drivers for use with your target hardware
5169(no, we don't intend to provide a full virtual machine interface to
5170Linux :-).
5171
5172But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5173
5174Just make sure your machine specific header file (for instance
5175include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5176Information structure as we define in include/asm-<arch>/u-boot.h,
5177and make sure that your definition of IMAP_ADDR uses the same value
5178as your U-Boot configuration in CONFIG_SYS_IMMR.
5179
5180
5181Configuring the Linux kernel:
5182-----------------------------
5183
5184No specific requirements for U-Boot. Make sure you have some root
5185device (initial ramdisk, NFS) for your target system.
5186
5187
5188Building a Linux Image:
5189-----------------------
5190
5191With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5192not used. If you use recent kernel source, a new build target
5193"uImage" will exist which automatically builds an image usable by
5194U-Boot. Most older kernels also have support for a "pImage" target,
5195which was introduced for our predecessor project PPCBoot and uses a
5196100% compatible format.
5197
5198Example:
5199
5200	make TQM850L_config
5201	make oldconfig
5202	make dep
5203	make uImage
5204
5205The "uImage" build target uses a special tool (in 'tools/mkimage') to
5206encapsulate a compressed Linux kernel image with header	 information,
5207CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5208
5209* build a standard "vmlinux" kernel image (in ELF binary format):
5210
5211* convert the kernel into a raw binary image:
5212
5213	${CROSS_COMPILE}-objcopy -O binary \
5214				 -R .note -R .comment \
5215				 -S vmlinux linux.bin
5216
5217* compress the binary image:
5218
5219	gzip -9 linux.bin
5220
5221* package compressed binary image for U-Boot:
5222
5223	mkimage -A ppc -O linux -T kernel -C gzip \
5224		-a 0 -e 0 -n "Linux Kernel Image" \
5225		-d linux.bin.gz uImage
5226
5227
5228The "mkimage" tool can also be used to create ramdisk images for use
5229with U-Boot, either separated from the Linux kernel image, or
5230combined into one file. "mkimage" encapsulates the images with a 64
5231byte header containing information about target architecture,
5232operating system, image type, compression method, entry points, time
5233stamp, CRC32 checksums, etc.
5234
5235"mkimage" can be called in two ways: to verify existing images and
5236print the header information, or to build new images.
5237
5238In the first form (with "-l" option) mkimage lists the information
5239contained in the header of an existing U-Boot image; this includes
5240checksum verification:
5241
5242	tools/mkimage -l image
5243	  -l ==> list image header information
5244
5245The second form (with "-d" option) is used to build a U-Boot image
5246from a "data file" which is used as image payload:
5247
5248	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5249		      -n name -d data_file image
5250	  -A ==> set architecture to 'arch'
5251	  -O ==> set operating system to 'os'
5252	  -T ==> set image type to 'type'
5253	  -C ==> set compression type 'comp'
5254	  -a ==> set load address to 'addr' (hex)
5255	  -e ==> set entry point to 'ep' (hex)
5256	  -n ==> set image name to 'name'
5257	  -d ==> use image data from 'datafile'
5258
5259Right now, all Linux kernels for PowerPC systems use the same load
5260address (0x00000000), but the entry point address depends on the
5261kernel version:
5262
5263- 2.2.x kernels have the entry point at 0x0000000C,
5264- 2.3.x and later kernels have the entry point at 0x00000000.
5265
5266So a typical call to build a U-Boot image would read:
5267
5268	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5269	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5270	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5271	> examples/uImage.TQM850L
5272	Image Name:   2.4.4 kernel for TQM850L
5273	Created:      Wed Jul 19 02:34:59 2000
5274	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5275	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5276	Load Address: 0x00000000
5277	Entry Point:  0x00000000
5278
5279To verify the contents of the image (or check for corruption):
5280
5281	-> tools/mkimage -l examples/uImage.TQM850L
5282	Image Name:   2.4.4 kernel for TQM850L
5283	Created:      Wed Jul 19 02:34:59 2000
5284	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5285	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5286	Load Address: 0x00000000
5287	Entry Point:  0x00000000
5288
5289NOTE: for embedded systems where boot time is critical you can trade
5290speed for memory and install an UNCOMPRESSED image instead: this
5291needs more space in Flash, but boots much faster since it does not
5292need to be uncompressed:
5293
5294	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5295	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5296	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5297	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5298	> examples/uImage.TQM850L-uncompressed
5299	Image Name:   2.4.4 kernel for TQM850L
5300	Created:      Wed Jul 19 02:34:59 2000
5301	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5302	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5303	Load Address: 0x00000000
5304	Entry Point:  0x00000000
5305
5306
5307Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5308when your kernel is intended to use an initial ramdisk:
5309
5310	-> tools/mkimage -n 'Simple Ramdisk Image' \
5311	> -A ppc -O linux -T ramdisk -C gzip \
5312	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5313	Image Name:   Simple Ramdisk Image
5314	Created:      Wed Jan 12 14:01:50 2000
5315	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5316	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5317	Load Address: 0x00000000
5318	Entry Point:  0x00000000
5319
5320The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5321option performs the converse operation of the mkimage's second form (the "-d"
5322option). Given an image built by mkimage, the dumpimage extracts a "data file"
5323from the image:
5324
5325	tools/dumpimage -i image -p position data_file
5326	  -i ==> extract from the 'image' a specific 'data_file', \
5327	   indexed by 'position'
5328
5329
5330Installing a Linux Image:
5331-------------------------
5332
5333To downloading a U-Boot image over the serial (console) interface,
5334you must convert the image to S-Record format:
5335
5336	objcopy -I binary -O srec examples/image examples/image.srec
5337
5338The 'objcopy' does not understand the information in the U-Boot
5339image header, so the resulting S-Record file will be relative to
5340address 0x00000000. To load it to a given address, you need to
5341specify the target address as 'offset' parameter with the 'loads'
5342command.
5343
5344Example: install the image to address 0x40100000 (which on the
5345TQM8xxL is in the first Flash bank):
5346
5347	=> erase 40100000 401FFFFF
5348
5349	.......... done
5350	Erased 8 sectors
5351
5352	=> loads 40100000
5353	## Ready for S-Record download ...
5354	~>examples/image.srec
5355	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5356	...
5357	15989 15990 15991 15992
5358	[file transfer complete]
5359	[connected]
5360	## Start Addr = 0x00000000
5361
5362
5363You can check the success of the download using the 'iminfo' command;
5364this includes a checksum verification so you can be sure no data
5365corruption happened:
5366
5367	=> imi 40100000
5368
5369	## Checking Image at 40100000 ...
5370	   Image Name:	 2.2.13 for initrd on TQM850L
5371	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5372	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5373	   Load Address: 00000000
5374	   Entry Point:	 0000000c
5375	   Verifying Checksum ... OK
5376
5377
5378Boot Linux:
5379-----------
5380
5381The "bootm" command is used to boot an application that is stored in
5382memory (RAM or Flash). In case of a Linux kernel image, the contents
5383of the "bootargs" environment variable is passed to the kernel as
5384parameters. You can check and modify this variable using the
5385"printenv" and "setenv" commands:
5386
5387
5388	=> printenv bootargs
5389	bootargs=root=/dev/ram
5390
5391	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5392
5393	=> printenv bootargs
5394	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5395
5396	=> bootm 40020000
5397	## Booting Linux kernel at 40020000 ...
5398	   Image Name:	 2.2.13 for NFS on TQM850L
5399	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5400	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5401	   Load Address: 00000000
5402	   Entry Point:	 0000000c
5403	   Verifying Checksum ... OK
5404	   Uncompressing Kernel Image ... OK
5405	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
5406	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5407	time_init: decrementer frequency = 187500000/60
5408	Calibrating delay loop... 49.77 BogoMIPS
5409	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5410	...
5411
5412If you want to boot a Linux kernel with initial RAM disk, you pass
5413the memory addresses of both the kernel and the initrd image (PPBCOOT
5414format!) to the "bootm" command:
5415
5416	=> imi 40100000 40200000
5417
5418	## Checking Image at 40100000 ...
5419	   Image Name:	 2.2.13 for initrd on TQM850L
5420	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5421	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5422	   Load Address: 00000000
5423	   Entry Point:	 0000000c
5424	   Verifying Checksum ... OK
5425
5426	## Checking Image at 40200000 ...
5427	   Image Name:	 Simple Ramdisk Image
5428	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5429	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5430	   Load Address: 00000000
5431	   Entry Point:	 00000000
5432	   Verifying Checksum ... OK
5433
5434	=> bootm 40100000 40200000
5435	## Booting Linux kernel at 40100000 ...
5436	   Image Name:	 2.2.13 for initrd on TQM850L
5437	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5438	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5439	   Load Address: 00000000
5440	   Entry Point:	 0000000c
5441	   Verifying Checksum ... OK
5442	   Uncompressing Kernel Image ... OK
5443	## Loading RAMDisk Image at 40200000 ...
5444	   Image Name:	 Simple Ramdisk Image
5445	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5446	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5447	   Load Address: 00000000
5448	   Entry Point:	 00000000
5449	   Verifying Checksum ... OK
5450	   Loading Ramdisk ... OK
5451	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
5452	Boot arguments: root=/dev/ram
5453	time_init: decrementer frequency = 187500000/60
5454	Calibrating delay loop... 49.77 BogoMIPS
5455	...
5456	RAMDISK: Compressed image found at block 0
5457	VFS: Mounted root (ext2 filesystem).
5458
5459	bash#
5460
5461Boot Linux and pass a flat device tree:
5462-----------
5463
5464First, U-Boot must be compiled with the appropriate defines. See the section
5465titled "Linux Kernel Interface" above for a more in depth explanation. The
5466following is an example of how to start a kernel and pass an updated
5467flat device tree:
5468
5469=> print oftaddr
5470oftaddr=0x300000
5471=> print oft
5472oft=oftrees/mpc8540ads.dtb
5473=> tftp $oftaddr $oft
5474Speed: 1000, full duplex
5475Using TSEC0 device
5476TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5477Filename 'oftrees/mpc8540ads.dtb'.
5478Load address: 0x300000
5479Loading: #
5480done
5481Bytes transferred = 4106 (100a hex)
5482=> tftp $loadaddr $bootfile
5483Speed: 1000, full duplex
5484Using TSEC0 device
5485TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5486Filename 'uImage'.
5487Load address: 0x200000
5488Loading:############
5489done
5490Bytes transferred = 1029407 (fb51f hex)
5491=> print loadaddr
5492loadaddr=200000
5493=> print oftaddr
5494oftaddr=0x300000
5495=> bootm $loadaddr - $oftaddr
5496## Booting image at 00200000 ...
5497   Image Name:	 Linux-2.6.17-dirty
5498   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5499   Data Size:	 1029343 Bytes = 1005.2 kB
5500   Load Address: 00000000
5501   Entry Point:	 00000000
5502   Verifying Checksum ... OK
5503   Uncompressing Kernel Image ... OK
5504Booting using flat device tree at 0x300000
5505Using MPC85xx ADS machine description
5506Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5507[snip]
5508
5509
5510More About U-Boot Image Types:
5511------------------------------
5512
5513U-Boot supports the following image types:
5514
5515   "Standalone Programs" are directly runnable in the environment
5516	provided by U-Boot; it is expected that (if they behave
5517	well) you can continue to work in U-Boot after return from
5518	the Standalone Program.
5519   "OS Kernel Images" are usually images of some Embedded OS which
5520	will take over control completely. Usually these programs
5521	will install their own set of exception handlers, device
5522	drivers, set up the MMU, etc. - this means, that you cannot
5523	expect to re-enter U-Boot except by resetting the CPU.
5524   "RAMDisk Images" are more or less just data blocks, and their
5525	parameters (address, size) are passed to an OS kernel that is
5526	being started.
5527   "Multi-File Images" contain several images, typically an OS
5528	(Linux) kernel image and one or more data images like
5529	RAMDisks. This construct is useful for instance when you want
5530	to boot over the network using BOOTP etc., where the boot
5531	server provides just a single image file, but you want to get
5532	for instance an OS kernel and a RAMDisk image.
5533
5534	"Multi-File Images" start with a list of image sizes, each
5535	image size (in bytes) specified by an "uint32_t" in network
5536	byte order. This list is terminated by an "(uint32_t)0".
5537	Immediately after the terminating 0 follow the images, one by
5538	one, all aligned on "uint32_t" boundaries (size rounded up to
5539	a multiple of 4 bytes).
5540
5541   "Firmware Images" are binary images containing firmware (like
5542	U-Boot or FPGA images) which usually will be programmed to
5543	flash memory.
5544
5545   "Script files" are command sequences that will be executed by
5546	U-Boot's command interpreter; this feature is especially
5547	useful when you configure U-Boot to use a real shell (hush)
5548	as command interpreter.
5549
5550Booting the Linux zImage:
5551-------------------------
5552
5553On some platforms, it's possible to boot Linux zImage. This is done
5554using the "bootz" command. The syntax of "bootz" command is the same
5555as the syntax of "bootm" command.
5556
5557Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5558kernel with raw initrd images. The syntax is slightly different, the
5559address of the initrd must be augmented by it's size, in the following
5560format: "<initrd addres>:<initrd size>".
5561
5562
5563Standalone HOWTO:
5564=================
5565
5566One of the features of U-Boot is that you can dynamically load and
5567run "standalone" applications, which can use some resources of
5568U-Boot like console I/O functions or interrupt services.
5569
5570Two simple examples are included with the sources:
5571
5572"Hello World" Demo:
5573-------------------
5574
5575'examples/hello_world.c' contains a small "Hello World" Demo
5576application; it is automatically compiled when you build U-Boot.
5577It's configured to run at address 0x00040004, so you can play with it
5578like that:
5579
5580	=> loads
5581	## Ready for S-Record download ...
5582	~>examples/hello_world.srec
5583	1 2 3 4 5 6 7 8 9 10 11 ...
5584	[file transfer complete]
5585	[connected]
5586	## Start Addr = 0x00040004
5587
5588	=> go 40004 Hello World! This is a test.
5589	## Starting application at 0x00040004 ...
5590	Hello World
5591	argc = 7
5592	argv[0] = "40004"
5593	argv[1] = "Hello"
5594	argv[2] = "World!"
5595	argv[3] = "This"
5596	argv[4] = "is"
5597	argv[5] = "a"
5598	argv[6] = "test."
5599	argv[7] = "<NULL>"
5600	Hit any key to exit ...
5601
5602	## Application terminated, rc = 0x0
5603
5604Another example, which demonstrates how to register a CPM interrupt
5605handler with the U-Boot code, can be found in 'examples/timer.c'.
5606Here, a CPM timer is set up to generate an interrupt every second.
5607The interrupt service routine is trivial, just printing a '.'
5608character, but this is just a demo program. The application can be
5609controlled by the following keys:
5610
5611	? - print current values og the CPM Timer registers
5612	b - enable interrupts and start timer
5613	e - stop timer and disable interrupts
5614	q - quit application
5615
5616	=> loads
5617	## Ready for S-Record download ...
5618	~>examples/timer.srec
5619	1 2 3 4 5 6 7 8 9 10 11 ...
5620	[file transfer complete]
5621	[connected]
5622	## Start Addr = 0x00040004
5623
5624	=> go 40004
5625	## Starting application at 0x00040004 ...
5626	TIMERS=0xfff00980
5627	Using timer 1
5628	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5629
5630Hit 'b':
5631	[q, b, e, ?] Set interval 1000000 us
5632	Enabling timer
5633Hit '?':
5634	[q, b, e, ?] ........
5635	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5636Hit '?':
5637	[q, b, e, ?] .
5638	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5639Hit '?':
5640	[q, b, e, ?] .
5641	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5642Hit '?':
5643	[q, b, e, ?] .
5644	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5645Hit 'e':
5646	[q, b, e, ?] ...Stopping timer
5647Hit 'q':
5648	[q, b, e, ?] ## Application terminated, rc = 0x0
5649
5650
5651Minicom warning:
5652================
5653
5654Over time, many people have reported problems when trying to use the
5655"minicom" terminal emulation program for serial download. I (wd)
5656consider minicom to be broken, and recommend not to use it. Under
5657Unix, I recommend to use C-Kermit for general purpose use (and
5658especially for kermit binary protocol download ("loadb" command), and
5659use "cu" for S-Record download ("loads" command).  See
5660http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5661for help with kermit.
5662
5663
5664Nevertheless, if you absolutely want to use it try adding this
5665configuration to your "File transfer protocols" section:
5666
5667	   Name	   Program			Name U/D FullScr IO-Red. Multi
5668	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5669	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5670
5671
5672NetBSD Notes:
5673=============
5674
5675Starting at version 0.9.2, U-Boot supports NetBSD both as host
5676(build U-Boot) and target system (boots NetBSD/mpc8xx).
5677
5678Building requires a cross environment; it is known to work on
5679NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5680need gmake since the Makefiles are not compatible with BSD make).
5681Note that the cross-powerpc package does not install include files;
5682attempting to build U-Boot will fail because <machine/ansi.h> is
5683missing.  This file has to be installed and patched manually:
5684
5685	# cd /usr/pkg/cross/powerpc-netbsd/include
5686	# mkdir powerpc
5687	# ln -s powerpc machine
5688	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5689	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5690
5691Native builds *don't* work due to incompatibilities between native
5692and U-Boot include files.
5693
5694Booting assumes that (the first part of) the image booted is a
5695stage-2 loader which in turn loads and then invokes the kernel
5696proper. Loader sources will eventually appear in the NetBSD source
5697tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5698meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5699
5700
5701Implementation Internals:
5702=========================
5703
5704The following is not intended to be a complete description of every
5705implementation detail. However, it should help to understand the
5706inner workings of U-Boot and make it easier to port it to custom
5707hardware.
5708
5709
5710Initial Stack, Global Data:
5711---------------------------
5712
5713The implementation of U-Boot is complicated by the fact that U-Boot
5714starts running out of ROM (flash memory), usually without access to
5715system RAM (because the memory controller is not initialized yet).
5716This means that we don't have writable Data or BSS segments, and BSS
5717is not initialized as zero. To be able to get a C environment working
5718at all, we have to allocate at least a minimal stack. Implementation
5719options for this are defined and restricted by the CPU used: Some CPU
5720models provide on-chip memory (like the IMMR area on MPC8xx and
5721MPC826x processors), on others (parts of) the data cache can be
5722locked as (mis-) used as memory, etc.
5723
5724	Chris Hallinan posted a good summary of these issues to the
5725	U-Boot mailing list:
5726
5727	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5728	From: "Chris Hallinan" <clh@net1plus.com>
5729	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5730	...
5731
5732	Correct me if I'm wrong, folks, but the way I understand it
5733	is this: Using DCACHE as initial RAM for Stack, etc, does not
5734	require any physical RAM backing up the cache. The cleverness
5735	is that the cache is being used as a temporary supply of
5736	necessary storage before the SDRAM controller is setup. It's
5737	beyond the scope of this list to explain the details, but you
5738	can see how this works by studying the cache architecture and
5739	operation in the architecture and processor-specific manuals.
5740
5741	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5742	is another option for the system designer to use as an
5743	initial stack/RAM area prior to SDRAM being available. Either
5744	option should work for you. Using CS 4 should be fine if your
5745	board designers haven't used it for something that would
5746	cause you grief during the initial boot! It is frequently not
5747	used.
5748
5749	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5750	with your processor/board/system design. The default value
5751	you will find in any recent u-boot distribution in
5752	walnut.h should work for you. I'd set it to a value larger
5753	than your SDRAM module. If you have a 64MB SDRAM module, set
5754	it above 400_0000. Just make sure your board has no resources
5755	that are supposed to respond to that address! That code in
5756	start.S has been around a while and should work as is when
5757	you get the config right.
5758
5759	-Chris Hallinan
5760	DS4.COM, Inc.
5761
5762It is essential to remember this, since it has some impact on the C
5763code for the initialization procedures:
5764
5765* Initialized global data (data segment) is read-only. Do not attempt
5766  to write it.
5767
5768* Do not use any uninitialized global data (or implicitely initialized
5769  as zero data - BSS segment) at all - this is undefined, initiali-
5770  zation is performed later (when relocating to RAM).
5771
5772* Stack space is very limited. Avoid big data buffers or things like
5773  that.
5774
5775Having only the stack as writable memory limits means we cannot use
5776normal global data to share information beween the code. But it
5777turned out that the implementation of U-Boot can be greatly
5778simplified by making a global data structure (gd_t) available to all
5779functions. We could pass a pointer to this data as argument to _all_
5780functions, but this would bloat the code. Instead we use a feature of
5781the GCC compiler (Global Register Variables) to share the data: we
5782place a pointer (gd) to the global data into a register which we
5783reserve for this purpose.
5784
5785When choosing a register for such a purpose we are restricted by the
5786relevant  (E)ABI  specifications for the current architecture, and by
5787GCC's implementation.
5788
5789For PowerPC, the following registers have specific use:
5790	R1:	stack pointer
5791	R2:	reserved for system use
5792	R3-R4:	parameter passing and return values
5793	R5-R10: parameter passing
5794	R13:	small data area pointer
5795	R30:	GOT pointer
5796	R31:	frame pointer
5797
5798	(U-Boot also uses R12 as internal GOT pointer. r12
5799	is a volatile register so r12 needs to be reset when
5800	going back and forth between asm and C)
5801
5802    ==> U-Boot will use R2 to hold a pointer to the global data
5803
5804    Note: on PPC, we could use a static initializer (since the
5805    address of the global data structure is known at compile time),
5806    but it turned out that reserving a register results in somewhat
5807    smaller code - although the code savings are not that big (on
5808    average for all boards 752 bytes for the whole U-Boot image,
5809    624 text + 127 data).
5810
5811On Blackfin, the normal C ABI (except for P3) is followed as documented here:
5812	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
5813
5814    ==> U-Boot will use P3 to hold a pointer to the global data
5815
5816On ARM, the following registers are used:
5817
5818	R0:	function argument word/integer result
5819	R1-R3:	function argument word
5820	R9:	platform specific
5821	R10:	stack limit (used only if stack checking is enabled)
5822	R11:	argument (frame) pointer
5823	R12:	temporary workspace
5824	R13:	stack pointer
5825	R14:	link register
5826	R15:	program counter
5827
5828    ==> U-Boot will use R9 to hold a pointer to the global data
5829
5830    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
5831
5832On Nios II, the ABI is documented here:
5833	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5834
5835    ==> U-Boot will use gp to hold a pointer to the global data
5836
5837    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5838    to access small data sections, so gp is free.
5839
5840On NDS32, the following registers are used:
5841
5842	R0-R1:	argument/return
5843	R2-R5:	argument
5844	R15:	temporary register for assembler
5845	R16:	trampoline register
5846	R28:	frame pointer (FP)
5847	R29:	global pointer (GP)
5848	R30:	link register (LP)
5849	R31:	stack pointer (SP)
5850	PC:	program counter (PC)
5851
5852    ==> U-Boot will use R10 to hold a pointer to the global data
5853
5854NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5855or current versions of GCC may "optimize" the code too much.
5856
5857Memory Management:
5858------------------
5859
5860U-Boot runs in system state and uses physical addresses, i.e. the
5861MMU is not used either for address mapping nor for memory protection.
5862
5863The available memory is mapped to fixed addresses using the memory
5864controller. In this process, a contiguous block is formed for each
5865memory type (Flash, SDRAM, SRAM), even when it consists of several
5866physical memory banks.
5867
5868U-Boot is installed in the first 128 kB of the first Flash bank (on
5869TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5870booting and sizing and initializing DRAM, the code relocates itself
5871to the upper end of DRAM. Immediately below the U-Boot code some
5872memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5873configuration setting]. Below that, a structure with global Board
5874Info data is placed, followed by the stack (growing downward).
5875
5876Additionally, some exception handler code is copied to the low 8 kB
5877of DRAM (0x00000000 ... 0x00001FFF).
5878
5879So a typical memory configuration with 16 MB of DRAM could look like
5880this:
5881
5882	0x0000 0000	Exception Vector code
5883	      :
5884	0x0000 1FFF
5885	0x0000 2000	Free for Application Use
5886	      :
5887	      :
5888
5889	      :
5890	      :
5891	0x00FB FF20	Monitor Stack (Growing downward)
5892	0x00FB FFAC	Board Info Data and permanent copy of global data
5893	0x00FC 0000	Malloc Arena
5894	      :
5895	0x00FD FFFF
5896	0x00FE 0000	RAM Copy of Monitor Code
5897	...		eventually: LCD or video framebuffer
5898	...		eventually: pRAM (Protected RAM - unchanged by reset)
5899	0x00FF FFFF	[End of RAM]
5900
5901
5902System Initialization:
5903----------------------
5904
5905In the reset configuration, U-Boot starts at the reset entry point
5906(on most PowerPC systems at address 0x00000100). Because of the reset
5907configuration for CS0# this is a mirror of the onboard Flash memory.
5908To be able to re-map memory U-Boot then jumps to its link address.
5909To be able to implement the initialization code in C, a (small!)
5910initial stack is set up in the internal Dual Ported RAM (in case CPUs
5911which provide such a feature like MPC8xx or MPC8260), or in a locked
5912part of the data cache. After that, U-Boot initializes the CPU core,
5913the caches and the SIU.
5914
5915Next, all (potentially) available memory banks are mapped using a
5916preliminary mapping. For example, we put them on 512 MB boundaries
5917(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5918on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5919programmed for SDRAM access. Using the temporary configuration, a
5920simple memory test is run that determines the size of the SDRAM
5921banks.
5922
5923When there is more than one SDRAM bank, and the banks are of
5924different size, the largest is mapped first. For equal size, the first
5925bank (CS2#) is mapped first. The first mapping is always for address
59260x00000000, with any additional banks following immediately to create
5927contiguous memory starting from 0.
5928
5929Then, the monitor installs itself at the upper end of the SDRAM area
5930and allocates memory for use by malloc() and for the global Board
5931Info data; also, the exception vector code is copied to the low RAM
5932pages, and the final stack is set up.
5933
5934Only after this relocation will you have a "normal" C environment;
5935until that you are restricted in several ways, mostly because you are
5936running from ROM, and because the code will have to be relocated to a
5937new address in RAM.
5938
5939
5940U-Boot Porting Guide:
5941----------------------
5942
5943[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5944list, October 2002]
5945
5946
5947int main(int argc, char *argv[])
5948{
5949	sighandler_t no_more_time;
5950
5951	signal(SIGALRM, no_more_time);
5952	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5953
5954	if (available_money > available_manpower) {
5955		Pay consultant to port U-Boot;
5956		return 0;
5957	}
5958
5959	Download latest U-Boot source;
5960
5961	Subscribe to u-boot mailing list;
5962
5963	if (clueless)
5964		email("Hi, I am new to U-Boot, how do I get started?");
5965
5966	while (learning) {
5967		Read the README file in the top level directory;
5968		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5969		Read applicable doc/*.README;
5970		Read the source, Luke;
5971		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5972	}
5973
5974	if (available_money > toLocalCurrency ($2500))
5975		Buy a BDI3000;
5976	else
5977		Add a lot of aggravation and time;
5978
5979	if (a similar board exists) {	/* hopefully... */
5980		cp -a board/<similar> board/<myboard>
5981		cp include/configs/<similar>.h include/configs/<myboard>.h
5982	} else {
5983		Create your own board support subdirectory;
5984		Create your own board include/configs/<myboard>.h file;
5985	}
5986	Edit new board/<myboard> files
5987	Edit new include/configs/<myboard>.h
5988
5989	while (!accepted) {
5990		while (!running) {
5991			do {
5992				Add / modify source code;
5993			} until (compiles);
5994			Debug;
5995			if (clueless)
5996				email("Hi, I am having problems...");
5997		}
5998		Send patch file to the U-Boot email list;
5999		if (reasonable critiques)
6000			Incorporate improvements from email list code review;
6001		else
6002			Defend code as written;
6003	}
6004
6005	return 0;
6006}
6007
6008void no_more_time (int sig)
6009{
6010      hire_a_guru();
6011}
6012
6013
6014Coding Standards:
6015-----------------
6016
6017All contributions to U-Boot should conform to the Linux kernel
6018coding style; see the file "Documentation/CodingStyle" and the script
6019"scripts/Lindent" in your Linux kernel source directory.
6020
6021Source files originating from a different project (for example the
6022MTD subsystem) are generally exempt from these guidelines and are not
6023reformated to ease subsequent migration to newer versions of those
6024sources.
6025
6026Please note that U-Boot is implemented in C (and to some small parts in
6027Assembler); no C++ is used, so please do not use C++ style comments (//)
6028in your code.
6029
6030Please also stick to the following formatting rules:
6031- remove any trailing white space
6032- use TAB characters for indentation and vertical alignment, not spaces
6033- make sure NOT to use DOS '\r\n' line feeds
6034- do not add more than 2 consecutive empty lines to source files
6035- do not add trailing empty lines to source files
6036
6037Submissions which do not conform to the standards may be returned
6038with a request to reformat the changes.
6039
6040
6041Submitting Patches:
6042-------------------
6043
6044Since the number of patches for U-Boot is growing, we need to
6045establish some rules. Submissions which do not conform to these rules
6046may be rejected, even when they contain important and valuable stuff.
6047
6048Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6049
6050Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6051see http://lists.denx.de/mailman/listinfo/u-boot
6052
6053When you send a patch, please include the following information with
6054it:
6055
6056* For bug fixes: a description of the bug and how your patch fixes
6057  this bug. Please try to include a way of demonstrating that the
6058  patch actually fixes something.
6059
6060* For new features: a description of the feature and your
6061  implementation.
6062
6063* A CHANGELOG entry as plaintext (separate from the patch)
6064
6065* For major contributions, your entry to the CREDITS file
6066
6067* When you add support for a new board, don't forget to add a
6068  maintainer e-mail address to the boards.cfg file, too.
6069
6070* If your patch adds new configuration options, don't forget to
6071  document these in the README file.
6072
6073* The patch itself. If you are using git (which is *strongly*
6074  recommended) you can easily generate the patch using the
6075  "git format-patch". If you then use "git send-email" to send it to
6076  the U-Boot mailing list, you will avoid most of the common problems
6077  with some other mail clients.
6078
6079  If you cannot use git, use "diff -purN OLD NEW". If your version of
6080  diff does not support these options, then get the latest version of
6081  GNU diff.
6082
6083  The current directory when running this command shall be the parent
6084  directory of the U-Boot source tree (i. e. please make sure that
6085  your patch includes sufficient directory information for the
6086  affected files).
6087
6088  We prefer patches as plain text. MIME attachments are discouraged,
6089  and compressed attachments must not be used.
6090
6091* If one logical set of modifications affects or creates several
6092  files, all these changes shall be submitted in a SINGLE patch file.
6093
6094* Changesets that contain different, unrelated modifications shall be
6095  submitted as SEPARATE patches, one patch per changeset.
6096
6097
6098Notes:
6099
6100* Before sending the patch, run the MAKEALL script on your patched
6101  source tree and make sure that no errors or warnings are reported
6102  for any of the boards.
6103
6104* Keep your modifications to the necessary minimum: A patch
6105  containing several unrelated changes or arbitrary reformats will be
6106  returned with a request to re-formatting / split it.
6107
6108* If you modify existing code, make sure that your new code does not
6109  add to the memory footprint of the code ;-) Small is beautiful!
6110  When adding new features, these should compile conditionally only
6111  (using #ifdef), and the resulting code with the new feature
6112  disabled must not need more memory than the old code without your
6113  modification.
6114
6115* Remember that there is a size limit of 100 kB per message on the
6116  u-boot mailing list. Bigger patches will be moderated. If they are
6117  reasonable and not too big, they will be acknowledged. But patches
6118  bigger than the size limit should be avoided.
6119