xref: /openbmc/u-boot/README (revision 04735e9c5578dd4f3584be5454b9779e8e5c2af9)
1#
2# (C) Copyright 2000 - 2012
3# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4#
5# See file CREDITS for list of people who contributed to this
6# project.
7#
8# This program is free software; you can redistribute it and/or
9# modify it under the terms of the GNU General Public License as
10# published by the Free Software Foundation; either version 2 of
11# the License, or (at your option) any later version.
12#
13# This program is distributed in the hope that it will be useful,
14# but WITHOUT ANY WARRANTY; without even the implied warranty of
15# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the
16# GNU General Public License for more details.
17#
18# You should have received a copy of the GNU General Public License
19# along with this program; if not, write to the Free Software
20# Foundation, Inc., 59 Temple Place, Suite 330, Boston,
21# MA 02111-1307 USA
22#
23
24Summary:
25========
26
27This directory contains the source code for U-Boot, a boot loader for
28Embedded boards based on PowerPC, ARM, MIPS and several other
29processors, which can be installed in a boot ROM and used to
30initialize and test the hardware or to download and run application
31code.
32
33The development of U-Boot is closely related to Linux: some parts of
34the source code originate in the Linux source tree, we have some
35header files in common, and special provision has been made to
36support booting of Linux images.
37
38Some attention has been paid to make this software easily
39configurable and extendable. For instance, all monitor commands are
40implemented with the same call interface, so that it's very easy to
41add new commands. Also, instead of permanently adding rarely used
42code (for instance hardware test utilities) to the monitor, you can
43load and run it dynamically.
44
45
46Status:
47=======
48
49In general, all boards for which a configuration option exists in the
50Makefile have been tested to some extent and can be considered
51"working". In fact, many of them are used in production systems.
52
53In case of problems see the CHANGELOG and CREDITS files to find out
54who contributed the specific port. The MAINTAINERS file lists board
55maintainers.
56
57Note: There is no CHANGELOG file in the actual U-Boot source tree;
58it can be created dynamically from the Git log using:
59
60	make CHANGELOG
61
62
63Where to get help:
64==================
65
66In case you have questions about, problems with or contributions for
67U-Boot you should send a message to the U-Boot mailing list at
68<u-boot@lists.denx.de>. There is also an archive of previous traffic
69on the mailing list - please search the archive before asking FAQ's.
70Please see http://lists.denx.de/pipermail/u-boot and
71http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
72
73
74Where to get source code:
75=========================
76
77The U-Boot source code is maintained in the git repository at
78git://www.denx.de/git/u-boot.git ; you can browse it online at
79http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
80
81The "snapshot" links on this page allow you to download tarballs of
82any version you might be interested in. Official releases are also
83available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
84directory.
85
86Pre-built (and tested) images are available from
87ftp://ftp.denx.de/pub/u-boot/images/
88
89
90Where we come from:
91===================
92
93- start from 8xxrom sources
94- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
95- clean up code
96- make it easier to add custom boards
97- make it possible to add other [PowerPC] CPUs
98- extend functions, especially:
99  * Provide extended interface to Linux boot loader
100  * S-Record download
101  * network boot
102  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
103- create ARMBoot project (http://sourceforge.net/projects/armboot)
104- add other CPU families (starting with ARM)
105- create U-Boot project (http://sourceforge.net/projects/u-boot)
106- current project page: see http://www.denx.de/wiki/U-Boot
107
108
109Names and Spelling:
110===================
111
112The "official" name of this project is "Das U-Boot". The spelling
113"U-Boot" shall be used in all written text (documentation, comments
114in source files etc.). Example:
115
116	This is the README file for the U-Boot project.
117
118File names etc. shall be based on the string "u-boot". Examples:
119
120	include/asm-ppc/u-boot.h
121
122	#include <asm/u-boot.h>
123
124Variable names, preprocessor constants etc. shall be either based on
125the string "u_boot" or on "U_BOOT". Example:
126
127	U_BOOT_VERSION		u_boot_logo
128	IH_OS_U_BOOT		u_boot_hush_start
129
130
131Versioning:
132===========
133
134Starting with the release in October 2008, the names of the releases
135were changed from numerical release numbers without deeper meaning
136into a time stamp based numbering. Regular releases are identified by
137names consisting of the calendar year and month of the release date.
138Additional fields (if present) indicate release candidates or bug fix
139releases in "stable" maintenance trees.
140
141Examples:
142	U-Boot v2009.11	    - Release November 2009
143	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
144	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
145
146
147Directory Hierarchy:
148====================
149
150/arch			Architecture specific files
151  /arm			Files generic to ARM architecture
152    /cpu		CPU specific files
153      /arm720t		Files specific to ARM 720 CPUs
154      /arm920t		Files specific to ARM 920 CPUs
155	/at91		Files specific to Atmel AT91RM9200 CPU
156	/imx		Files specific to Freescale MC9328 i.MX CPUs
157	/s3c24x0	Files specific to Samsung S3C24X0 CPUs
158      /arm925t		Files specific to ARM 925 CPUs
159      /arm926ejs	Files specific to ARM 926 CPUs
160      /arm1136		Files specific to ARM 1136 CPUs
161      /ixp		Files specific to Intel XScale IXP CPUs
162      /pxa		Files specific to Intel XScale PXA CPUs
163      /s3c44b0		Files specific to Samsung S3C44B0 CPUs
164      /sa1100		Files specific to Intel StrongARM SA1100 CPUs
165    /lib		Architecture specific library files
166  /avr32		Files generic to AVR32 architecture
167    /cpu		CPU specific files
168    /lib		Architecture specific library files
169  /blackfin		Files generic to Analog Devices Blackfin architecture
170    /cpu		CPU specific files
171    /lib		Architecture specific library files
172  /x86			Files generic to x86 architecture
173    /cpu		CPU specific files
174    /lib		Architecture specific library files
175  /m68k			Files generic to m68k architecture
176    /cpu		CPU specific files
177      /mcf52x2		Files specific to Freescale ColdFire MCF52x2 CPUs
178      /mcf5227x		Files specific to Freescale ColdFire MCF5227x CPUs
179      /mcf532x		Files specific to Freescale ColdFire MCF5329 CPUs
180      /mcf5445x		Files specific to Freescale ColdFire MCF5445x CPUs
181      /mcf547x_8x	Files specific to Freescale ColdFire MCF547x_8x CPUs
182    /lib		Architecture specific library files
183  /microblaze		Files generic to microblaze architecture
184    /cpu		CPU specific files
185    /lib		Architecture specific library files
186  /mips			Files generic to MIPS architecture
187    /cpu		CPU specific files
188      /mips32		Files specific to MIPS32 CPUs
189      /xburst		Files specific to Ingenic XBurst CPUs
190    /lib		Architecture specific library files
191  /nds32		Files generic to NDS32 architecture
192    /cpu		CPU specific files
193      /n1213		Files specific to Andes Technology N1213 CPUs
194    /lib		Architecture specific library files
195  /nios2		Files generic to Altera NIOS2 architecture
196    /cpu		CPU specific files
197    /lib		Architecture specific library files
198  /powerpc		Files generic to PowerPC architecture
199    /cpu		CPU specific files
200      /74xx_7xx		Files specific to Freescale MPC74xx and 7xx CPUs
201      /mpc5xx		Files specific to Freescale MPC5xx CPUs
202      /mpc5xxx		Files specific to Freescale MPC5xxx CPUs
203      /mpc8xx		Files specific to Freescale MPC8xx CPUs
204      /mpc824x		Files specific to Freescale MPC824x CPUs
205      /mpc8260		Files specific to Freescale MPC8260 CPUs
206      /mpc85xx		Files specific to Freescale MPC85xx CPUs
207      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
208    /lib		Architecture specific library files
209  /sh			Files generic to SH architecture
210    /cpu		CPU specific files
211      /sh2		Files specific to sh2 CPUs
212      /sh3		Files specific to sh3 CPUs
213      /sh4		Files specific to sh4 CPUs
214    /lib		Architecture specific library files
215  /sparc		Files generic to SPARC architecture
216    /cpu		CPU specific files
217      /leon2		Files specific to Gaisler LEON2 SPARC CPU
218      /leon3		Files specific to Gaisler LEON3 SPARC CPU
219    /lib		Architecture specific library files
220/api			Machine/arch independent API for external apps
221/board			Board dependent files
222/common			Misc architecture independent functions
223/disk			Code for disk drive partition handling
224/doc			Documentation (don't expect too much)
225/drivers		Commonly used device drivers
226/examples		Example code for standalone applications, etc.
227/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
228/include		Header Files
229/lib			Files generic to all architectures
230  /libfdt		Library files to support flattened device trees
231  /lzma			Library files to support LZMA decompression
232  /lzo			Library files to support LZO decompression
233/net			Networking code
234/post			Power On Self Test
235/rtc			Real Time Clock drivers
236/tools			Tools to build S-Record or U-Boot images, etc.
237
238Software Configuration:
239=======================
240
241Configuration is usually done using C preprocessor defines; the
242rationale behind that is to avoid dead code whenever possible.
243
244There are two classes of configuration variables:
245
246* Configuration _OPTIONS_:
247  These are selectable by the user and have names beginning with
248  "CONFIG_".
249
250* Configuration _SETTINGS_:
251  These depend on the hardware etc. and should not be meddled with if
252  you don't know what you're doing; they have names beginning with
253  "CONFIG_SYS_".
254
255Later we will add a configuration tool - probably similar to or even
256identical to what's used for the Linux kernel. Right now, we have to
257do the configuration by hand, which means creating some symbolic
258links and editing some configuration files. We use the TQM8xxL boards
259as an example here.
260
261
262Selection of Processor Architecture and Board Type:
263---------------------------------------------------
264
265For all supported boards there are ready-to-use default
266configurations available; just type "make <board_name>_config".
267
268Example: For a TQM823L module type:
269
270	cd u-boot
271	make TQM823L_config
272
273For the Cogent platform, you need to specify the CPU type as well;
274e.g. "make cogent_mpc8xx_config". And also configure the cogent
275directory according to the instructions in cogent/README.
276
277
278Configuration Options:
279----------------------
280
281Configuration depends on the combination of board and CPU type; all
282such information is kept in a configuration file
283"include/configs/<board_name>.h".
284
285Example: For a TQM823L module, all configuration settings are in
286"include/configs/TQM823L.h".
287
288
289Many of the options are named exactly as the corresponding Linux
290kernel configuration options. The intention is to make it easier to
291build a config tool - later.
292
293
294The following options need to be configured:
295
296- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
297
298- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
299
300- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
301		Define exactly one, e.g. CONFIG_ATSTK1002
302
303- CPU Module Type: (if CONFIG_COGENT is defined)
304		Define exactly one of
305		CONFIG_CMA286_60_OLD
306--- FIXME --- not tested yet:
307		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
308		CONFIG_CMA287_23, CONFIG_CMA287_50
309
310- Motherboard Type: (if CONFIG_COGENT is defined)
311		Define exactly one of
312		CONFIG_CMA101, CONFIG_CMA102
313
314- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
315		Define one or more of
316		CONFIG_CMA302
317
318- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
319		Define one or more of
320		CONFIG_LCD_HEARTBEAT	- update a character position on
321					  the LCD display every second with
322					  a "rotator" |\-/|\-/
323
324- Board flavour: (if CONFIG_MPC8260ADS is defined)
325		CONFIG_ADSTYPE
326		Possible values are:
327			CONFIG_SYS_8260ADS	- original MPC8260ADS
328			CONFIG_SYS_8266ADS	- MPC8266ADS
329			CONFIG_SYS_PQ2FADS	- PQ2FADS-ZU or PQ2FADS-VR
330			CONFIG_SYS_8272ADS	- MPC8272ADS
331
332- Marvell Family Member
333		CONFIG_SYS_MVFS		- define it if you want to enable
334					  multiple fs option at one time
335					  for marvell soc family
336
337- MPC824X Family Member (if CONFIG_MPC824X is defined)
338		Define exactly one of
339		CONFIG_MPC8240, CONFIG_MPC8245
340
341- 8xx CPU Options: (if using an MPC8xx CPU)
342		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
343					  get_gclk_freq() cannot work
344					  e.g. if there is no 32KHz
345					  reference PIT/RTC clock
346		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
347					  or XTAL/EXTAL)
348
349- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
350		CONFIG_SYS_8xx_CPUCLK_MIN
351		CONFIG_SYS_8xx_CPUCLK_MAX
352		CONFIG_8xx_CPUCLK_DEFAULT
353			See doc/README.MPC866
354
355		CONFIG_SYS_MEASURE_CPUCLK
356
357		Define this to measure the actual CPU clock instead
358		of relying on the correctness of the configured
359		values. Mostly useful for board bringup to make sure
360		the PLL is locked at the intended frequency. Note
361		that this requires a (stable) reference clock (32 kHz
362		RTC clock or CONFIG_SYS_8XX_XIN)
363
364		CONFIG_SYS_DELAYED_ICACHE
365
366		Define this option if you want to enable the
367		ICache only when Code runs from RAM.
368
369- 85xx CPU Options:
370		CONFIG_SYS_PPC64
371
372		Specifies that the core is a 64-bit PowerPC implementation (implements
373		the "64" category of the Power ISA). This is necessary for ePAPR
374		compliance, among other possible reasons.
375
376		CONFIG_SYS_FSL_TBCLK_DIV
377
378		Defines the core time base clock divider ratio compared to the
379		system clock.  On most PQ3 devices this is 8, on newer QorIQ
380		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
381
382		CONFIG_SYS_FSL_PCIE_COMPAT
383
384		Defines the string to utilize when trying to match PCIe device
385		tree nodes for the given platform.
386
387		CONFIG_SYS_PPC_E500_DEBUG_TLB
388
389		Enables a temporary TLB entry to be used during boot to work
390		around limitations in e500v1 and e500v2 external debugger
391		support. This reduces the portions of the boot code where
392		breakpoints and single stepping do not work.  The value of this
393		symbol should be set to the TLB1 entry to be used for this
394		purpose.
395
396		CONFIG_SYS_FSL_ERRATUM_A004510
397
398		Enables a workaround for erratum A004510.  If set,
399		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
400		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
401
402		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
403		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
404
405		Defines one or two SoC revisions (low 8 bits of SVR)
406		for which the A004510 workaround should be applied.
407
408		The rest of SVR is either not relevant to the decision
409		of whether the erratum is present (e.g. p2040 versus
410		p2041) or is implied by the build target, which controls
411		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
412
413		See Freescale App Note 4493 for more information about
414		this erratum.
415
416		CONFIG_A003399_NOR_WORKAROUND
417		Enables a workaround for IFC erratum A003399. It is only
418		requred during NOR boot.
419
420		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
421
422		This is the value to write into CCSR offset 0x18600
423		according to the A004510 workaround.
424
425		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
426		This value denotes start offset of M2 memory
427		which is directly connected to the DSP core.
428
429		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
430		This value denotes start offset of DSP CCSR space.
431
432- Generic CPU options:
433		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
434
435		Defines the endianess of the CPU. Implementation of those
436		values is arch specific.
437
438- Intel Monahans options:
439		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
440
441		Defines the Monahans run mode to oscillator
442		ratio. Valid values are 8, 16, 24, 31. The core
443		frequency is this value multiplied by 13 MHz.
444
445		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
446
447		Defines the Monahans turbo mode to oscillator
448		ratio. Valid values are 1 (default if undefined) and
449		2. The core frequency as calculated above is multiplied
450		by this value.
451
452- MIPS CPU options:
453		CONFIG_SYS_INIT_SP_OFFSET
454
455		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
456		pointer. This is needed for the temporary stack before
457		relocation.
458
459		CONFIG_SYS_MIPS_CACHE_MODE
460
461		Cache operation mode for the MIPS CPU.
462		See also arch/mips/include/asm/mipsregs.h.
463		Possible values are:
464			CONF_CM_CACHABLE_NO_WA
465			CONF_CM_CACHABLE_WA
466			CONF_CM_UNCACHED
467			CONF_CM_CACHABLE_NONCOHERENT
468			CONF_CM_CACHABLE_CE
469			CONF_CM_CACHABLE_COW
470			CONF_CM_CACHABLE_CUW
471			CONF_CM_CACHABLE_ACCELERATED
472
473		CONFIG_SYS_XWAY_EBU_BOOTCFG
474
475		Special option for Lantiq XWAY SoCs for booting from NOR flash.
476		See also arch/mips/cpu/mips32/start.S.
477
478		CONFIG_XWAY_SWAP_BYTES
479
480		Enable compilation of tools/xway-swap-bytes needed for Lantiq
481		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
482		be swapped if a flash programmer is used.
483
484- ARM options:
485		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
486
487		Select high exception vectors of the ARM core, e.g., do not
488		clear the V bit of the c1 register of CP15.
489
490		CONFIG_SYS_THUMB_BUILD
491
492		Use this flag to build U-Boot using the Thumb instruction
493		set for ARM architectures. Thumb instruction set provides
494		better code density. For ARM architectures that support
495		Thumb2 this flag will result in Thumb2 code generated by
496		GCC.
497
498		CONFIG_ARM_ERRATA_716044
499		CONFIG_ARM_ERRATA_742230
500		CONFIG_ARM_ERRATA_743622
501		CONFIG_ARM_ERRATA_751472
502
503		If set, the workarounds for these ARM errata are applied early
504		during U-Boot startup. Note that these options force the
505		workarounds to be applied; no CPU-type/version detection
506		exists, unlike the similar options in the Linux kernel. Do not
507		set these options unless they apply!
508
509- CPU timer options:
510		CONFIG_SYS_HZ
511
512		The frequency of the timer returned by get_timer().
513		get_timer() must operate in milliseconds and this CONFIG
514		option must be set to 1000.
515
516- Linux Kernel Interface:
517		CONFIG_CLOCKS_IN_MHZ
518
519		U-Boot stores all clock information in Hz
520		internally. For binary compatibility with older Linux
521		kernels (which expect the clocks passed in the
522		bd_info data to be in MHz) the environment variable
523		"clocks_in_mhz" can be defined so that U-Boot
524		converts clock data to MHZ before passing it to the
525		Linux kernel.
526		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
527		"clocks_in_mhz=1" is automatically included in the
528		default environment.
529
530		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
531
532		When transferring memsize parameter to linux, some versions
533		expect it to be in bytes, others in MB.
534		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
535
536		CONFIG_OF_LIBFDT
537
538		New kernel versions are expecting firmware settings to be
539		passed using flattened device trees (based on open firmware
540		concepts).
541
542		CONFIG_OF_LIBFDT
543		 * New libfdt-based support
544		 * Adds the "fdt" command
545		 * The bootm command automatically updates the fdt
546
547		OF_CPU - The proper name of the cpus node (only required for
548			MPC512X and MPC5xxx based boards).
549		OF_SOC - The proper name of the soc node (only required for
550			MPC512X and MPC5xxx based boards).
551		OF_TBCLK - The timebase frequency.
552		OF_STDOUT_PATH - The path to the console device
553
554		boards with QUICC Engines require OF_QE to set UCC MAC
555		addresses
556
557		CONFIG_OF_BOARD_SETUP
558
559		Board code has addition modification that it wants to make
560		to the flat device tree before handing it off to the kernel
561
562		CONFIG_OF_BOOT_CPU
563
564		This define fills in the correct boot CPU in the boot
565		param header, the default value is zero if undefined.
566
567		CONFIG_OF_IDE_FIXUP
568
569		U-Boot can detect if an IDE device is present or not.
570		If not, and this new config option is activated, U-Boot
571		removes the ATA node from the DTS before booting Linux,
572		so the Linux IDE driver does not probe the device and
573		crash. This is needed for buggy hardware (uc101) where
574		no pull down resistor is connected to the signal IDE5V_DD7.
575
576		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
577
578		This setting is mandatory for all boards that have only one
579		machine type and must be used to specify the machine type
580		number as it appears in the ARM machine registry
581		(see http://www.arm.linux.org.uk/developer/machines/).
582		Only boards that have multiple machine types supported
583		in a single configuration file and the machine type is
584		runtime discoverable, do not have to use this setting.
585
586- vxWorks boot parameters:
587
588		bootvx constructs a valid bootline using the following
589		environments variables: bootfile, ipaddr, serverip, hostname.
590		It loads the vxWorks image pointed bootfile.
591
592		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
593		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
594		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
595		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
596
597		CONFIG_SYS_VXWORKS_ADD_PARAMS
598
599		Add it at the end of the bootline. E.g "u=username pw=secret"
600
601		Note: If a "bootargs" environment is defined, it will overwride
602		the defaults discussed just above.
603
604- Cache Configuration:
605		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
606		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
607		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
608
609- Cache Configuration for ARM:
610		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
611				      controller
612		CONFIG_SYS_PL310_BASE - Physical base address of PL310
613					controller register space
614
615- Serial Ports:
616		CONFIG_PL010_SERIAL
617
618		Define this if you want support for Amba PrimeCell PL010 UARTs.
619
620		CONFIG_PL011_SERIAL
621
622		Define this if you want support for Amba PrimeCell PL011 UARTs.
623
624		CONFIG_PL011_CLOCK
625
626		If you have Amba PrimeCell PL011 UARTs, set this variable to
627		the clock speed of the UARTs.
628
629		CONFIG_PL01x_PORTS
630
631		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
632		define this to a list of base addresses for each (supported)
633		port. See e.g. include/configs/versatile.h
634
635		CONFIG_PL011_SERIAL_RLCR
636
637		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
638		have separate receive and transmit line control registers.  Set
639		this variable to initialize the extra register.
640
641		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
642
643		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
644		boot loader that has already initialized the UART.  Define this
645		variable to flush the UART at init time.
646
647
648- Console Interface:
649		Depending on board, define exactly one serial port
650		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
651		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
652		console by defining CONFIG_8xx_CONS_NONE
653
654		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
655		port routines must be defined elsewhere
656		(i.e. serial_init(), serial_getc(), ...)
657
658		CONFIG_CFB_CONSOLE
659		Enables console device for a color framebuffer. Needs following
660		defines (cf. smiLynxEM, i8042)
661			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
662						(default big endian)
663			VIDEO_HW_RECTFILL	graphic chip supports
664						rectangle fill
665						(cf. smiLynxEM)
666			VIDEO_HW_BITBLT		graphic chip supports
667						bit-blit (cf. smiLynxEM)
668			VIDEO_VISIBLE_COLS	visible pixel columns
669						(cols=pitch)
670			VIDEO_VISIBLE_ROWS	visible pixel rows
671			VIDEO_PIXEL_SIZE	bytes per pixel
672			VIDEO_DATA_FORMAT	graphic data format
673						(0-5, cf. cfb_console.c)
674			VIDEO_FB_ADRS		framebuffer address
675			VIDEO_KBD_INIT_FCT	keyboard int fct
676						(i.e. i8042_kbd_init())
677			VIDEO_TSTC_FCT		test char fct
678						(i.e. i8042_tstc)
679			VIDEO_GETC_FCT		get char fct
680						(i.e. i8042_getc)
681			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
682						(requires blink timer
683						cf. i8042.c)
684			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
685			CONFIG_CONSOLE_TIME	display time/date info in
686						upper right corner
687						(requires CONFIG_CMD_DATE)
688			CONFIG_VIDEO_LOGO	display Linux logo in
689						upper left corner
690			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
691						linux_logo.h for logo.
692						Requires CONFIG_VIDEO_LOGO
693			CONFIG_CONSOLE_EXTRA_INFO
694						additional board info beside
695						the logo
696
697		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
698		a limited number of ANSI escape sequences (cursor control,
699		erase functions and limited graphics rendition control).
700
701		When CONFIG_CFB_CONSOLE is defined, video console is
702		default i/o. Serial console can be forced with
703		environment 'console=serial'.
704
705		When CONFIG_SILENT_CONSOLE is defined, all console
706		messages (by U-Boot and Linux!) can be silenced with
707		the "silent" environment variable. See
708		doc/README.silent for more information.
709
710- Console Baudrate:
711		CONFIG_BAUDRATE - in bps
712		Select one of the baudrates listed in
713		CONFIG_SYS_BAUDRATE_TABLE, see below.
714		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
715
716- Console Rx buffer length
717		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
718		the maximum receive buffer length for the SMC.
719		This option is actual only for 82xx and 8xx possible.
720		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
721		must be defined, to setup the maximum idle timeout for
722		the SMC.
723
724- Pre-Console Buffer:
725		Prior to the console being initialised (i.e. serial UART
726		initialised etc) all console output is silently discarded.
727		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
728		buffer any console messages prior to the console being
729		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
730		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
731		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
732		bytes are output before the console is initialised, the
733		earlier bytes are discarded.
734
735		'Sane' compilers will generate smaller code if
736		CONFIG_PRE_CON_BUF_SZ is a power of 2
737
738- Safe printf() functions
739		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
740		the printf() functions. These are defined in
741		include/vsprintf.h and include snprintf(), vsnprintf() and
742		so on. Code size increase is approximately 300-500 bytes.
743		If this option is not given then these functions will
744		silently discard their buffer size argument - this means
745		you are not getting any overflow checking in this case.
746
747- Boot Delay:	CONFIG_BOOTDELAY - in seconds
748		Delay before automatically booting the default image;
749		set to -1 to disable autoboot.
750		set to -2 to autoboot with no delay and not check for abort
751		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
752
753		See doc/README.autoboot for these options that
754		work with CONFIG_BOOTDELAY. None are required.
755		CONFIG_BOOT_RETRY_TIME
756		CONFIG_BOOT_RETRY_MIN
757		CONFIG_AUTOBOOT_KEYED
758		CONFIG_AUTOBOOT_PROMPT
759		CONFIG_AUTOBOOT_DELAY_STR
760		CONFIG_AUTOBOOT_STOP_STR
761		CONFIG_AUTOBOOT_DELAY_STR2
762		CONFIG_AUTOBOOT_STOP_STR2
763		CONFIG_ZERO_BOOTDELAY_CHECK
764		CONFIG_RESET_TO_RETRY
765
766- Autoboot Command:
767		CONFIG_BOOTCOMMAND
768		Only needed when CONFIG_BOOTDELAY is enabled;
769		define a command string that is automatically executed
770		when no character is read on the console interface
771		within "Boot Delay" after reset.
772
773		CONFIG_BOOTARGS
774		This can be used to pass arguments to the bootm
775		command. The value of CONFIG_BOOTARGS goes into the
776		environment value "bootargs".
777
778		CONFIG_RAMBOOT and CONFIG_NFSBOOT
779		The value of these goes into the environment as
780		"ramboot" and "nfsboot" respectively, and can be used
781		as a convenience, when switching between booting from
782		RAM and NFS.
783
784- Pre-Boot Commands:
785		CONFIG_PREBOOT
786
787		When this option is #defined, the existence of the
788		environment variable "preboot" will be checked
789		immediately before starting the CONFIG_BOOTDELAY
790		countdown and/or running the auto-boot command resp.
791		entering interactive mode.
792
793		This feature is especially useful when "preboot" is
794		automatically generated or modified. For an example
795		see the LWMON board specific code: here "preboot" is
796		modified when the user holds down a certain
797		combination of keys on the (special) keyboard when
798		booting the systems
799
800- Serial Download Echo Mode:
801		CONFIG_LOADS_ECHO
802		If defined to 1, all characters received during a
803		serial download (using the "loads" command) are
804		echoed back. This might be needed by some terminal
805		emulations (like "cu"), but may as well just take
806		time on others. This setting #define's the initial
807		value of the "loads_echo" environment variable.
808
809- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
810		CONFIG_KGDB_BAUDRATE
811		Select one of the baudrates listed in
812		CONFIG_SYS_BAUDRATE_TABLE, see below.
813
814- Monitor Functions:
815		Monitor commands can be included or excluded
816		from the build by using the #include files
817		<config_cmd_all.h> and #undef'ing unwanted
818		commands, or using <config_cmd_default.h>
819		and augmenting with additional #define's
820		for wanted commands.
821
822		The default command configuration includes all commands
823		except those marked below with a "*".
824
825		CONFIG_CMD_ASKENV	* ask for env variable
826		CONFIG_CMD_BDI		  bdinfo
827		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
828		CONFIG_CMD_BMP		* BMP support
829		CONFIG_CMD_BSP		* Board specific commands
830		CONFIG_CMD_BOOTD	  bootd
831		CONFIG_CMD_CACHE	* icache, dcache
832		CONFIG_CMD_CONSOLE	  coninfo
833		CONFIG_CMD_CRC32	* crc32
834		CONFIG_CMD_DATE		* support for RTC, date/time...
835		CONFIG_CMD_DHCP		* DHCP support
836		CONFIG_CMD_DIAG		* Diagnostics
837		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
838		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
839		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
840		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
841		CONFIG_CMD_DTT		* Digital Therm and Thermostat
842		CONFIG_CMD_ECHO		  echo arguments
843		CONFIG_CMD_EDITENV	  edit env variable
844		CONFIG_CMD_EEPROM	* EEPROM read/write support
845		CONFIG_CMD_ELF		* bootelf, bootvx
846		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
847		CONFIG_CMD_ENV_FLAGS	* display details about env flags
848		CONFIG_CMD_EXPORTENV	* export the environment
849		CONFIG_CMD_EXT2		* ext2 command support
850		CONFIG_CMD_EXT4		* ext4 command support
851		CONFIG_CMD_SAVEENV	  saveenv
852		CONFIG_CMD_FDC		* Floppy Disk Support
853		CONFIG_CMD_FAT		* FAT command support
854		CONFIG_CMD_FDOS		* Dos diskette Support
855		CONFIG_CMD_FLASH	  flinfo, erase, protect
856		CONFIG_CMD_FPGA		  FPGA device initialization support
857		CONFIG_CMD_FUSE		* Device fuse support
858		CONFIG_CMD_GETTIME	* Get time since boot
859		CONFIG_CMD_GO		* the 'go' command (exec code)
860		CONFIG_CMD_GREPENV	* search environment
861		CONFIG_CMD_HASH		* calculate hash / digest
862		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
863		CONFIG_CMD_I2C		* I2C serial bus support
864		CONFIG_CMD_IDE		* IDE harddisk support
865		CONFIG_CMD_IMI		  iminfo
866		CONFIG_CMD_IMLS		  List all images found in NOR flash
867		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
868		CONFIG_CMD_IMMAP	* IMMR dump support
869		CONFIG_CMD_IMPORTENV	* import an environment
870		CONFIG_CMD_INI		* import data from an ini file into the env
871		CONFIG_CMD_IRQ		* irqinfo
872		CONFIG_CMD_ITEST	  Integer/string test of 2 values
873		CONFIG_CMD_JFFS2	* JFFS2 Support
874		CONFIG_CMD_KGDB		* kgdb
875		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
876		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
877					  (169.254.*.*)
878		CONFIG_CMD_LOADB	  loadb
879		CONFIG_CMD_LOADS	  loads
880		CONFIG_CMD_MD5SUM	* print md5 message digest
881					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
882		CONFIG_CMD_MEMINFO	* Display detailed memory information
883		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
884					  loop, loopw
885		CONFIG_CMD_MEMTEST	* mtest
886		CONFIG_CMD_MISC		  Misc functions like sleep etc
887		CONFIG_CMD_MMC		* MMC memory mapped support
888		CONFIG_CMD_MII		* MII utility commands
889		CONFIG_CMD_MTDPARTS	* MTD partition support
890		CONFIG_CMD_NAND		* NAND support
891		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
892		CONFIG_CMD_NFS		  NFS support
893		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
894		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
895		CONFIG_CMD_PCI		* pciinfo
896		CONFIG_CMD_PCMCIA		* PCMCIA support
897		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
898					  host
899		CONFIG_CMD_PORTIO	* Port I/O
900		CONFIG_CMD_READ		* Read raw data from partition
901		CONFIG_CMD_REGINFO	* Register dump
902		CONFIG_CMD_RUN		  run command in env variable
903		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
904		CONFIG_CMD_SAVES	* save S record dump
905		CONFIG_CMD_SCSI		* SCSI Support
906		CONFIG_CMD_SDRAM	* print SDRAM configuration information
907					  (requires CONFIG_CMD_I2C)
908		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
909					  (4xx only)
910		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
911		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
912					  (requires CONFIG_CMD_MEMORY)
913		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
914		CONFIG_CMD_SOURCE	  "source" command Support
915		CONFIG_CMD_SPI		* SPI serial bus support
916		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
917		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
918		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
919		CONFIG_CMD_TIMER	* access to the system tick timer
920		CONFIG_CMD_USB		* USB support
921		CONFIG_CMD_CDP		* Cisco Discover Protocol support
922		CONFIG_CMD_MFSL		* Microblaze FSL support
923		CONFIG_CMD_XIMG		  Load part of Multi Image
924
925
926		EXAMPLE: If you want all functions except of network
927		support you can write:
928
929		#include "config_cmd_all.h"
930		#undef CONFIG_CMD_NET
931
932	Other Commands:
933		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
934
935	Note:	Don't enable the "icache" and "dcache" commands
936		(configuration option CONFIG_CMD_CACHE) unless you know
937		what you (and your U-Boot users) are doing. Data
938		cache cannot be enabled on systems like the 8xx or
939		8260 (where accesses to the IMMR region must be
940		uncached), and it cannot be disabled on all other
941		systems where we (mis-) use the data cache to hold an
942		initial stack and some data.
943
944
945		XXX - this list needs to get updated!
946
947- Regular expression support:
948		CONFIG_REGEX
949                If this variable is defined, U-Boot is linked against
950                the SLRE (Super Light Regular Expression) library,
951                which adds regex support to some commands, as for
952                example "env grep" and "setexpr".
953
954- Device tree:
955		CONFIG_OF_CONTROL
956		If this variable is defined, U-Boot will use a device tree
957		to configure its devices, instead of relying on statically
958		compiled #defines in the board file. This option is
959		experimental and only available on a few boards. The device
960		tree is available in the global data as gd->fdt_blob.
961
962		U-Boot needs to get its device tree from somewhere. This can
963		be done using one of the two options below:
964
965		CONFIG_OF_EMBED
966		If this variable is defined, U-Boot will embed a device tree
967		binary in its image. This device tree file should be in the
968		board directory and called <soc>-<board>.dts. The binary file
969		is then picked up in board_init_f() and made available through
970		the global data structure as gd->blob.
971
972		CONFIG_OF_SEPARATE
973		If this variable is defined, U-Boot will build a device tree
974		binary. It will be called u-boot.dtb. Architecture-specific
975		code will locate it at run-time. Generally this works by:
976
977			cat u-boot.bin u-boot.dtb >image.bin
978
979		and in fact, U-Boot does this for you, creating a file called
980		u-boot-dtb.bin which is useful in the common case. You can
981		still use the individual files if you need something more
982		exotic.
983
984- Watchdog:
985		CONFIG_WATCHDOG
986		If this variable is defined, it enables watchdog
987		support for the SoC. There must be support in the SoC
988		specific code for a watchdog. For the 8xx and 8260
989		CPUs, the SIU Watchdog feature is enabled in the SYPCR
990		register.  When supported for a specific SoC is
991		available, then no further board specific code should
992		be needed to use it.
993
994		CONFIG_HW_WATCHDOG
995		When using a watchdog circuitry external to the used
996		SoC, then define this variable and provide board
997		specific code for the "hw_watchdog_reset" function.
998
999- U-Boot Version:
1000		CONFIG_VERSION_VARIABLE
1001		If this variable is defined, an environment variable
1002		named "ver" is created by U-Boot showing the U-Boot
1003		version as printed by the "version" command.
1004		Any change to this variable will be reverted at the
1005		next reset.
1006
1007- Real-Time Clock:
1008
1009		When CONFIG_CMD_DATE is selected, the type of the RTC
1010		has to be selected, too. Define exactly one of the
1011		following options:
1012
1013		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1014		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1015		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1016		CONFIG_RTC_MC146818	- use MC146818 RTC
1017		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1018		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1019		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1020		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1021		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1022		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1023		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1024		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1025					  RV3029 RTC.
1026
1027		Note that if the RTC uses I2C, then the I2C interface
1028		must also be configured. See I2C Support, below.
1029
1030- GPIO Support:
1031		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1032		CONFIG_PCA953X_INFO	- enable pca953x info command
1033
1034		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1035		chip-ngpio pairs that tell the PCA953X driver the number of
1036		pins supported by a particular chip.
1037
1038		Note that if the GPIO device uses I2C, then the I2C interface
1039		must also be configured. See I2C Support, below.
1040
1041- Timestamp Support:
1042
1043		When CONFIG_TIMESTAMP is selected, the timestamp
1044		(date and time) of an image is printed by image
1045		commands like bootm or iminfo. This option is
1046		automatically enabled when you select CONFIG_CMD_DATE .
1047
1048- Partition Labels (disklabels) Supported:
1049		Zero or more of the following:
1050		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1051		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1052				       Intel architecture, USB sticks, etc.
1053		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1054		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1055				       bootloader.  Note 2TB partition limit; see
1056				       disk/part_efi.c
1057		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1058
1059		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1060		CONFIG_CMD_SCSI) you must configure support for at
1061		least one non-MTD partition type as well.
1062
1063- IDE Reset method:
1064		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1065		board configurations files but used nowhere!
1066
1067		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1068		be performed by calling the function
1069			ide_set_reset(int reset)
1070		which has to be defined in a board specific file
1071
1072- ATAPI Support:
1073		CONFIG_ATAPI
1074
1075		Set this to enable ATAPI support.
1076
1077- LBA48 Support
1078		CONFIG_LBA48
1079
1080		Set this to enable support for disks larger than 137GB
1081		Also look at CONFIG_SYS_64BIT_LBA.
1082		Whithout these , LBA48 support uses 32bit variables and will 'only'
1083		support disks up to 2.1TB.
1084
1085		CONFIG_SYS_64BIT_LBA:
1086			When enabled, makes the IDE subsystem use 64bit sector addresses.
1087			Default is 32bit.
1088
1089- SCSI Support:
1090		At the moment only there is only support for the
1091		SYM53C8XX SCSI controller; define
1092		CONFIG_SCSI_SYM53C8XX to enable it.
1093
1094		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1095		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1096		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1097		maximum numbers of LUNs, SCSI ID's and target
1098		devices.
1099		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1100
1101                The environment variable 'scsidevs' is set to the number of
1102                SCSI devices found during the last scan.
1103
1104- NETWORK Support (PCI):
1105		CONFIG_E1000
1106		Support for Intel 8254x/8257x gigabit chips.
1107
1108		CONFIG_E1000_SPI
1109		Utility code for direct access to the SPI bus on Intel 8257x.
1110		This does not do anything useful unless you set at least one
1111		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1112
1113		CONFIG_E1000_SPI_GENERIC
1114		Allow generic access to the SPI bus on the Intel 8257x, for
1115		example with the "sspi" command.
1116
1117		CONFIG_CMD_E1000
1118		Management command for E1000 devices.  When used on devices
1119		with SPI support you can reprogram the EEPROM from U-Boot.
1120
1121		CONFIG_E1000_FALLBACK_MAC
1122		default MAC for empty EEPROM after production.
1123
1124		CONFIG_EEPRO100
1125		Support for Intel 82557/82559/82559ER chips.
1126		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1127		write routine for first time initialisation.
1128
1129		CONFIG_TULIP
1130		Support for Digital 2114x chips.
1131		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1132		modem chip initialisation (KS8761/QS6611).
1133
1134		CONFIG_NATSEMI
1135		Support for National dp83815 chips.
1136
1137		CONFIG_NS8382X
1138		Support for National dp8382[01] gigabit chips.
1139
1140- NETWORK Support (other):
1141
1142		CONFIG_DRIVER_AT91EMAC
1143		Support for AT91RM9200 EMAC.
1144
1145			CONFIG_RMII
1146			Define this to use reduced MII inteface
1147
1148			CONFIG_DRIVER_AT91EMAC_QUIET
1149			If this defined, the driver is quiet.
1150			The driver doen't show link status messages.
1151
1152		CONFIG_CALXEDA_XGMAC
1153		Support for the Calxeda XGMAC device
1154
1155		CONFIG_LAN91C96
1156		Support for SMSC's LAN91C96 chips.
1157
1158			CONFIG_LAN91C96_BASE
1159			Define this to hold the physical address
1160			of the LAN91C96's I/O space
1161
1162			CONFIG_LAN91C96_USE_32_BIT
1163			Define this to enable 32 bit addressing
1164
1165		CONFIG_SMC91111
1166		Support for SMSC's LAN91C111 chip
1167
1168			CONFIG_SMC91111_BASE
1169			Define this to hold the physical address
1170			of the device (I/O space)
1171
1172			CONFIG_SMC_USE_32_BIT
1173			Define this if data bus is 32 bits
1174
1175			CONFIG_SMC_USE_IOFUNCS
1176			Define this to use i/o functions instead of macros
1177			(some hardware wont work with macros)
1178
1179		CONFIG_DRIVER_TI_EMAC
1180		Support for davinci emac
1181
1182			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1183			Define this if you have more then 3 PHYs.
1184
1185		CONFIG_FTGMAC100
1186		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1187
1188			CONFIG_FTGMAC100_EGIGA
1189			Define this to use GE link update with gigabit PHY.
1190			Define this if FTGMAC100 is connected to gigabit PHY.
1191			If your system has 10/100 PHY only, it might not occur
1192			wrong behavior. Because PHY usually return timeout or
1193			useless data when polling gigabit status and gigabit
1194			control registers. This behavior won't affect the
1195			correctnessof 10/100 link speed update.
1196
1197		CONFIG_SMC911X
1198		Support for SMSC's LAN911x and LAN921x chips
1199
1200			CONFIG_SMC911X_BASE
1201			Define this to hold the physical address
1202			of the device (I/O space)
1203
1204			CONFIG_SMC911X_32_BIT
1205			Define this if data bus is 32 bits
1206
1207			CONFIG_SMC911X_16_BIT
1208			Define this if data bus is 16 bits. If your processor
1209			automatically converts one 32 bit word to two 16 bit
1210			words you may also try CONFIG_SMC911X_32_BIT.
1211
1212		CONFIG_SH_ETHER
1213		Support for Renesas on-chip Ethernet controller
1214
1215			CONFIG_SH_ETHER_USE_PORT
1216			Define the number of ports to be used
1217
1218			CONFIG_SH_ETHER_PHY_ADDR
1219			Define the ETH PHY's address
1220
1221			CONFIG_SH_ETHER_CACHE_WRITEBACK
1222			If this option is set, the driver enables cache flush.
1223
1224- TPM Support:
1225		CONFIG_TPM
1226		Support TPM devices.
1227
1228		CONFIG_TPM_TIS_I2C
1229		Support for i2c bus TPM devices. Only one device
1230		per system is supported at this time.
1231
1232			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1233			Define the the i2c bus number for the TPM device
1234
1235			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1236			Define the TPM's address on the i2c bus
1237
1238			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1239			Define the burst count bytes upper limit
1240
1241		CONFIG_TPM_TIS_LPC
1242		Support for generic parallel port TPM devices. Only one device
1243		per system is supported at this time.
1244
1245			CONFIG_TPM_TIS_BASE_ADDRESS
1246			Base address where the generic TPM device is mapped
1247			to. Contemporary x86 systems usually map it at
1248			0xfed40000.
1249
1250- USB Support:
1251		At the moment only the UHCI host controller is
1252		supported (PIP405, MIP405, MPC5200); define
1253		CONFIG_USB_UHCI to enable it.
1254		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1255		and define CONFIG_USB_STORAGE to enable the USB
1256		storage devices.
1257		Note:
1258		Supported are USB Keyboards and USB Floppy drives
1259		(TEAC FD-05PUB).
1260		MPC5200 USB requires additional defines:
1261			CONFIG_USB_CLOCK
1262				for 528 MHz Clock: 0x0001bbbb
1263			CONFIG_PSC3_USB
1264				for USB on PSC3
1265			CONFIG_USB_CONFIG
1266				for differential drivers: 0x00001000
1267				for single ended drivers: 0x00005000
1268				for differential drivers on PSC3: 0x00000100
1269				for single ended drivers on PSC3: 0x00004100
1270			CONFIG_SYS_USB_EVENT_POLL
1271				May be defined to allow interrupt polling
1272				instead of using asynchronous interrupts
1273
1274		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1275		txfilltuning field in the EHCI controller on reset.
1276
1277		CONFIG_USB_HUB_MIN_POWER_ON_DELAY defines the minimum
1278		interval for usb hub power-on delay.(minimum 100msec)
1279
1280- USB Device:
1281		Define the below if you wish to use the USB console.
1282		Once firmware is rebuilt from a serial console issue the
1283		command "setenv stdin usbtty; setenv stdout usbtty" and
1284		attach your USB cable. The Unix command "dmesg" should print
1285		it has found a new device. The environment variable usbtty
1286		can be set to gserial or cdc_acm to enable your device to
1287		appear to a USB host as a Linux gserial device or a
1288		Common Device Class Abstract Control Model serial device.
1289		If you select usbtty = gserial you should be able to enumerate
1290		a Linux host by
1291		# modprobe usbserial vendor=0xVendorID product=0xProductID
1292		else if using cdc_acm, simply setting the environment
1293		variable usbtty to be cdc_acm should suffice. The following
1294		might be defined in YourBoardName.h
1295
1296			CONFIG_USB_DEVICE
1297			Define this to build a UDC device
1298
1299			CONFIG_USB_TTY
1300			Define this to have a tty type of device available to
1301			talk to the UDC device
1302
1303			CONFIG_USBD_HS
1304			Define this to enable the high speed support for usb
1305			device and usbtty. If this feature is enabled, a routine
1306			int is_usbd_high_speed(void)
1307			also needs to be defined by the driver to dynamically poll
1308			whether the enumeration has succeded at high speed or full
1309			speed.
1310
1311			CONFIG_SYS_CONSOLE_IS_IN_ENV
1312			Define this if you want stdin, stdout &/or stderr to
1313			be set to usbtty.
1314
1315			mpc8xx:
1316				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1317				Derive USB clock from external clock "blah"
1318				- CONFIG_SYS_USB_EXTC_CLK 0x02
1319
1320				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1321				Derive USB clock from brgclk
1322				- CONFIG_SYS_USB_BRG_CLK 0x04
1323
1324		If you have a USB-IF assigned VendorID then you may wish to
1325		define your own vendor specific values either in BoardName.h
1326		or directly in usbd_vendor_info.h. If you don't define
1327		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1328		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1329		should pretend to be a Linux device to it's target host.
1330
1331			CONFIG_USBD_MANUFACTURER
1332			Define this string as the name of your company for
1333			- CONFIG_USBD_MANUFACTURER "my company"
1334
1335			CONFIG_USBD_PRODUCT_NAME
1336			Define this string as the name of your product
1337			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1338
1339			CONFIG_USBD_VENDORID
1340			Define this as your assigned Vendor ID from the USB
1341			Implementors Forum. This *must* be a genuine Vendor ID
1342			to avoid polluting the USB namespace.
1343			- CONFIG_USBD_VENDORID 0xFFFF
1344
1345			CONFIG_USBD_PRODUCTID
1346			Define this as the unique Product ID
1347			for your device
1348			- CONFIG_USBD_PRODUCTID 0xFFFF
1349
1350- ULPI Layer Support:
1351		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1352		the generic ULPI layer. The generic layer accesses the ULPI PHY
1353		via the platform viewport, so you need both the genric layer and
1354		the viewport enabled. Currently only Chipidea/ARC based
1355		viewport is supported.
1356		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1357		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1358		If your ULPI phy needs a different reference clock than the
1359		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1360		the appropriate value in Hz.
1361
1362- MMC Support:
1363		The MMC controller on the Intel PXA is supported. To
1364		enable this define CONFIG_MMC. The MMC can be
1365		accessed from the boot prompt by mapping the device
1366		to physical memory similar to flash. Command line is
1367		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1368		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1369
1370		CONFIG_SH_MMCIF
1371		Support for Renesas on-chip MMCIF controller
1372
1373			CONFIG_SH_MMCIF_ADDR
1374			Define the base address of MMCIF registers
1375
1376			CONFIG_SH_MMCIF_CLK
1377			Define the clock frequency for MMCIF
1378
1379- USB Device Firmware Update (DFU) class support:
1380		CONFIG_DFU_FUNCTION
1381		This enables the USB portion of the DFU USB class
1382
1383		CONFIG_CMD_DFU
1384		This enables the command "dfu" which is used to have
1385		U-Boot create a DFU class device via USB.  This command
1386		requires that the "dfu_alt_info" environment variable be
1387		set and define the alt settings to expose to the host.
1388
1389		CONFIG_DFU_MMC
1390		This enables support for exposing (e)MMC devices via DFU.
1391
1392		CONFIG_DFU_NAND
1393		This enables support for exposing NAND devices via DFU.
1394
1395		CONFIG_SYS_DFU_DATA_BUF_SIZE
1396		Dfu transfer uses a buffer before writing data to the
1397		raw storage device. Make the size (in bytes) of this buffer
1398		configurable. The size of this buffer is also configurable
1399		through the "dfu_bufsiz" environment variable.
1400
1401		CONFIG_SYS_DFU_MAX_FILE_SIZE
1402		When updating files rather than the raw storage device,
1403		we use a static buffer to copy the file into and then write
1404		the buffer once we've been given the whole file.  Define
1405		this to the maximum filesize (in bytes) for the buffer.
1406		Default is 4 MiB if undefined.
1407
1408- Journaling Flash filesystem support:
1409		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1410		CONFIG_JFFS2_NAND_DEV
1411		Define these for a default partition on a NAND device
1412
1413		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1414		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1415		Define these for a default partition on a NOR device
1416
1417		CONFIG_SYS_JFFS_CUSTOM_PART
1418		Define this to create an own partition. You have to provide a
1419		function struct part_info* jffs2_part_info(int part_num)
1420
1421		If you define only one JFFS2 partition you may also want to
1422		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1423		to disable the command chpart. This is the default when you
1424		have not defined a custom partition
1425
1426- FAT(File Allocation Table) filesystem write function support:
1427		CONFIG_FAT_WRITE
1428
1429		Define this to enable support for saving memory data as a
1430		file in FAT formatted partition.
1431
1432		This will also enable the command "fatwrite" enabling the
1433		user to write files to FAT.
1434
1435CBFS (Coreboot Filesystem) support
1436		CONFIG_CMD_CBFS
1437
1438		Define this to enable support for reading from a Coreboot
1439		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1440		and cbfsload.
1441
1442- Keyboard Support:
1443		CONFIG_ISA_KEYBOARD
1444
1445		Define this to enable standard (PC-Style) keyboard
1446		support
1447
1448		CONFIG_I8042_KBD
1449		Standard PC keyboard driver with US (is default) and
1450		GERMAN key layout (switch via environment 'keymap=de') support.
1451		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1452		for cfb_console. Supports cursor blinking.
1453
1454		CONFIG_CROS_EC_KEYB
1455		Enables a Chrome OS keyboard using the CROS_EC interface.
1456		This uses CROS_EC to communicate with a second microcontroller
1457		which provides key scans on request.
1458
1459- Video support:
1460		CONFIG_VIDEO
1461
1462		Define this to enable video support (for output to
1463		video).
1464
1465		CONFIG_VIDEO_CT69000
1466
1467		Enable Chips & Technologies 69000 Video chip
1468
1469		CONFIG_VIDEO_SMI_LYNXEM
1470		Enable Silicon Motion SMI 712/710/810 Video chip. The
1471		video output is selected via environment 'videoout'
1472		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1473		assumed.
1474
1475		For the CT69000 and SMI_LYNXEM drivers, videomode is
1476		selected via environment 'videomode'. Two different ways
1477		are possible:
1478		- "videomode=num"   'num' is a standard LiLo mode numbers.
1479		Following standard modes are supported	(* is default):
1480
1481		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1482		-------------+---------------------------------------------
1483		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1484		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1485		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1486		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1487		-------------+---------------------------------------------
1488		(i.e. setenv videomode 317; saveenv; reset;)
1489
1490		- "videomode=bootargs" all the video parameters are parsed
1491		from the bootargs. (See drivers/video/videomodes.c)
1492
1493
1494		CONFIG_VIDEO_SED13806
1495		Enable Epson SED13806 driver. This driver supports 8bpp
1496		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1497		or CONFIG_VIDEO_SED13806_16BPP
1498
1499		CONFIG_FSL_DIU_FB
1500		Enable the Freescale DIU video driver.	Reference boards for
1501		SOCs that have a DIU should define this macro to enable DIU
1502		support, and should also define these other macros:
1503
1504			CONFIG_SYS_DIU_ADDR
1505			CONFIG_VIDEO
1506			CONFIG_CMD_BMP
1507			CONFIG_CFB_CONSOLE
1508			CONFIG_VIDEO_SW_CURSOR
1509			CONFIG_VGA_AS_SINGLE_DEVICE
1510			CONFIG_VIDEO_LOGO
1511			CONFIG_VIDEO_BMP_LOGO
1512
1513		The DIU driver will look for the 'video-mode' environment
1514		variable, and if defined, enable the DIU as a console during
1515		boot.  See the documentation file README.video for a
1516		description of this variable.
1517
1518		CONFIG_VIDEO_VGA
1519
1520		Enable the VGA video / BIOS for x86. The alternative if you
1521		are using coreboot is to use the coreboot frame buffer
1522		driver.
1523
1524
1525- Keyboard Support:
1526		CONFIG_KEYBOARD
1527
1528		Define this to enable a custom keyboard support.
1529		This simply calls drv_keyboard_init() which must be
1530		defined in your board-specific files.
1531		The only board using this so far is RBC823.
1532
1533- LCD Support:	CONFIG_LCD
1534
1535		Define this to enable LCD support (for output to LCD
1536		display); also select one of the supported displays
1537		by defining one of these:
1538
1539		CONFIG_ATMEL_LCD:
1540
1541			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1542
1543		CONFIG_NEC_NL6448AC33:
1544
1545			NEC NL6448AC33-18. Active, color, single scan.
1546
1547		CONFIG_NEC_NL6448BC20
1548
1549			NEC NL6448BC20-08. 6.5", 640x480.
1550			Active, color, single scan.
1551
1552		CONFIG_NEC_NL6448BC33_54
1553
1554			NEC NL6448BC33-54. 10.4", 640x480.
1555			Active, color, single scan.
1556
1557		CONFIG_SHARP_16x9
1558
1559			Sharp 320x240. Active, color, single scan.
1560			It isn't 16x9, and I am not sure what it is.
1561
1562		CONFIG_SHARP_LQ64D341
1563
1564			Sharp LQ64D341 display, 640x480.
1565			Active, color, single scan.
1566
1567		CONFIG_HLD1045
1568
1569			HLD1045 display, 640x480.
1570			Active, color, single scan.
1571
1572		CONFIG_OPTREX_BW
1573
1574			Optrex	 CBL50840-2 NF-FW 99 22 M5
1575			or
1576			Hitachi	 LMG6912RPFC-00T
1577			or
1578			Hitachi	 SP14Q002
1579
1580			320x240. Black & white.
1581
1582		Normally display is black on white background; define
1583		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1584
1585		CONFIG_LCD_ALIGNMENT
1586
1587		Normally the LCD is page-aligned (tyically 4KB). If this is
1588		defined then the LCD will be aligned to this value instead.
1589		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1590		here, since it is cheaper to change data cache settings on
1591		a per-section basis.
1592
1593		CONFIG_CONSOLE_SCROLL_LINES
1594
1595		When the console need to be scrolled, this is the number of
1596		lines to scroll by. It defaults to 1. Increasing this makes
1597		the console jump but can help speed up operation when scrolling
1598		is slow.
1599
1600		CONFIG_LCD_BMP_RLE8
1601
1602		Support drawing of RLE8-compressed bitmaps on the LCD.
1603
1604		CONFIG_I2C_EDID
1605
1606		Enables an 'i2c edid' command which can read EDID
1607		information over I2C from an attached LCD display.
1608
1609- Splash Screen Support: CONFIG_SPLASH_SCREEN
1610
1611		If this option is set, the environment is checked for
1612		a variable "splashimage". If found, the usual display
1613		of logo, copyright and system information on the LCD
1614		is suppressed and the BMP image at the address
1615		specified in "splashimage" is loaded instead. The
1616		console is redirected to the "nulldev", too. This
1617		allows for a "silent" boot where a splash screen is
1618		loaded very quickly after power-on.
1619
1620		CONFIG_SPLASHIMAGE_GUARD
1621
1622		If this option is set, then U-Boot will prevent the environment
1623		variable "splashimage" from being set to a problematic address
1624		(see README.displaying-bmps and README.arm-unaligned-accesses).
1625		This option is useful for targets where, due to alignment
1626		restrictions, an improperly aligned BMP image will cause a data
1627		abort. If you think you will not have problems with unaligned
1628		accesses (for example because your toolchain prevents them)
1629		there is no need to set this option.
1630
1631		CONFIG_SPLASH_SCREEN_ALIGN
1632
1633		If this option is set the splash image can be freely positioned
1634		on the screen. Environment variable "splashpos" specifies the
1635		position as "x,y". If a positive number is given it is used as
1636		number of pixel from left/top. If a negative number is given it
1637		is used as number of pixel from right/bottom. You can also
1638		specify 'm' for centering the image.
1639
1640		Example:
1641		setenv splashpos m,m
1642			=> image at center of screen
1643
1644		setenv splashpos 30,20
1645			=> image at x = 30 and y = 20
1646
1647		setenv splashpos -10,m
1648			=> vertically centered image
1649			   at x = dspWidth - bmpWidth - 9
1650
1651- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1652
1653		If this option is set, additionally to standard BMP
1654		images, gzipped BMP images can be displayed via the
1655		splashscreen support or the bmp command.
1656
1657- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1658
1659		If this option is set, 8-bit RLE compressed BMP images
1660		can be displayed via the splashscreen support or the
1661		bmp command.
1662
1663- Do compresssing for memory range:
1664		CONFIG_CMD_ZIP
1665
1666		If this option is set, it would use zlib deflate method
1667		to compress the specified memory at its best effort.
1668
1669- Compression support:
1670		CONFIG_BZIP2
1671
1672		If this option is set, support for bzip2 compressed
1673		images is included. If not, only uncompressed and gzip
1674		compressed images are supported.
1675
1676		NOTE: the bzip2 algorithm requires a lot of RAM, so
1677		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1678		be at least 4MB.
1679
1680		CONFIG_LZMA
1681
1682		If this option is set, support for lzma compressed
1683		images is included.
1684
1685		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1686		requires an amount of dynamic memory that is given by the
1687		formula:
1688
1689			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1690
1691		Where lc and lp stand for, respectively, Literal context bits
1692		and Literal pos bits.
1693
1694		This value is upper-bounded by 14MB in the worst case. Anyway,
1695		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1696		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1697		a very small buffer.
1698
1699		Use the lzmainfo tool to determinate the lc and lp values and
1700		then calculate the amount of needed dynamic memory (ensuring
1701		the appropriate CONFIG_SYS_MALLOC_LEN value).
1702
1703- MII/PHY support:
1704		CONFIG_PHY_ADDR
1705
1706		The address of PHY on MII bus.
1707
1708		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1709
1710		The clock frequency of the MII bus
1711
1712		CONFIG_PHY_GIGE
1713
1714		If this option is set, support for speed/duplex
1715		detection of gigabit PHY is included.
1716
1717		CONFIG_PHY_RESET_DELAY
1718
1719		Some PHY like Intel LXT971A need extra delay after
1720		reset before any MII register access is possible.
1721		For such PHY, set this option to the usec delay
1722		required. (minimum 300usec for LXT971A)
1723
1724		CONFIG_PHY_CMD_DELAY (ppc4xx)
1725
1726		Some PHY like Intel LXT971A need extra delay after
1727		command issued before MII status register can be read
1728
1729- Ethernet address:
1730		CONFIG_ETHADDR
1731		CONFIG_ETH1ADDR
1732		CONFIG_ETH2ADDR
1733		CONFIG_ETH3ADDR
1734		CONFIG_ETH4ADDR
1735		CONFIG_ETH5ADDR
1736
1737		Define a default value for Ethernet address to use
1738		for the respective Ethernet interface, in case this
1739		is not determined automatically.
1740
1741- IP address:
1742		CONFIG_IPADDR
1743
1744		Define a default value for the IP address to use for
1745		the default Ethernet interface, in case this is not
1746		determined through e.g. bootp.
1747		(Environment variable "ipaddr")
1748
1749- Server IP address:
1750		CONFIG_SERVERIP
1751
1752		Defines a default value for the IP address of a TFTP
1753		server to contact when using the "tftboot" command.
1754		(Environment variable "serverip")
1755
1756		CONFIG_KEEP_SERVERADDR
1757
1758		Keeps the server's MAC address, in the env 'serveraddr'
1759		for passing to bootargs (like Linux's netconsole option)
1760
1761- Gateway IP address:
1762		CONFIG_GATEWAYIP
1763
1764		Defines a default value for the IP address of the
1765		default router where packets to other networks are
1766		sent to.
1767		(Environment variable "gatewayip")
1768
1769- Subnet mask:
1770		CONFIG_NETMASK
1771
1772		Defines a default value for the subnet mask (or
1773		routing prefix) which is used to determine if an IP
1774		address belongs to the local subnet or needs to be
1775		forwarded through a router.
1776		(Environment variable "netmask")
1777
1778- Multicast TFTP Mode:
1779		CONFIG_MCAST_TFTP
1780
1781		Defines whether you want to support multicast TFTP as per
1782		rfc-2090; for example to work with atftp.  Lets lots of targets
1783		tftp down the same boot image concurrently.  Note: the Ethernet
1784		driver in use must provide a function: mcast() to join/leave a
1785		multicast group.
1786
1787- BOOTP Recovery Mode:
1788		CONFIG_BOOTP_RANDOM_DELAY
1789
1790		If you have many targets in a network that try to
1791		boot using BOOTP, you may want to avoid that all
1792		systems send out BOOTP requests at precisely the same
1793		moment (which would happen for instance at recovery
1794		from a power failure, when all systems will try to
1795		boot, thus flooding the BOOTP server. Defining
1796		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1797		inserted before sending out BOOTP requests. The
1798		following delays are inserted then:
1799
1800		1st BOOTP request:	delay 0 ... 1 sec
1801		2nd BOOTP request:	delay 0 ... 2 sec
1802		3rd BOOTP request:	delay 0 ... 4 sec
1803		4th and following
1804		BOOTP requests:		delay 0 ... 8 sec
1805
1806- DHCP Advanced Options:
1807		You can fine tune the DHCP functionality by defining
1808		CONFIG_BOOTP_* symbols:
1809
1810		CONFIG_BOOTP_SUBNETMASK
1811		CONFIG_BOOTP_GATEWAY
1812		CONFIG_BOOTP_HOSTNAME
1813		CONFIG_BOOTP_NISDOMAIN
1814		CONFIG_BOOTP_BOOTPATH
1815		CONFIG_BOOTP_BOOTFILESIZE
1816		CONFIG_BOOTP_DNS
1817		CONFIG_BOOTP_DNS2
1818		CONFIG_BOOTP_SEND_HOSTNAME
1819		CONFIG_BOOTP_NTPSERVER
1820		CONFIG_BOOTP_TIMEOFFSET
1821		CONFIG_BOOTP_VENDOREX
1822		CONFIG_BOOTP_MAY_FAIL
1823
1824		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1825		environment variable, not the BOOTP server.
1826
1827		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1828		after the configured retry count, the call will fail
1829		instead of starting over.  This can be used to fail over
1830		to Link-local IP address configuration if the DHCP server
1831		is not available.
1832
1833		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1834		serverip from a DHCP server, it is possible that more
1835		than one DNS serverip is offered to the client.
1836		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1837		serverip will be stored in the additional environment
1838		variable "dnsip2". The first DNS serverip is always
1839		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1840		is defined.
1841
1842		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1843		to do a dynamic update of a DNS server. To do this, they
1844		need the hostname of the DHCP requester.
1845		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1846		of the "hostname" environment variable is passed as
1847		option 12 to the DHCP server.
1848
1849		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1850
1851		A 32bit value in microseconds for a delay between
1852		receiving a "DHCP Offer" and sending the "DHCP Request".
1853		This fixes a problem with certain DHCP servers that don't
1854		respond 100% of the time to a "DHCP request". E.g. On an
1855		AT91RM9200 processor running at 180MHz, this delay needed
1856		to be *at least* 15,000 usec before a Windows Server 2003
1857		DHCP server would reply 100% of the time. I recommend at
1858		least 50,000 usec to be safe. The alternative is to hope
1859		that one of the retries will be successful but note that
1860		the DHCP timeout and retry process takes a longer than
1861		this delay.
1862
1863 - Link-local IP address negotiation:
1864		Negotiate with other link-local clients on the local network
1865		for an address that doesn't require explicit configuration.
1866		This is especially useful if a DHCP server cannot be guaranteed
1867		to exist in all environments that the device must operate.
1868
1869		See doc/README.link-local for more information.
1870
1871 - CDP Options:
1872		CONFIG_CDP_DEVICE_ID
1873
1874		The device id used in CDP trigger frames.
1875
1876		CONFIG_CDP_DEVICE_ID_PREFIX
1877
1878		A two character string which is prefixed to the MAC address
1879		of the device.
1880
1881		CONFIG_CDP_PORT_ID
1882
1883		A printf format string which contains the ascii name of
1884		the port. Normally is set to "eth%d" which sets
1885		eth0 for the first Ethernet, eth1 for the second etc.
1886
1887		CONFIG_CDP_CAPABILITIES
1888
1889		A 32bit integer which indicates the device capabilities;
1890		0x00000010 for a normal host which does not forwards.
1891
1892		CONFIG_CDP_VERSION
1893
1894		An ascii string containing the version of the software.
1895
1896		CONFIG_CDP_PLATFORM
1897
1898		An ascii string containing the name of the platform.
1899
1900		CONFIG_CDP_TRIGGER
1901
1902		A 32bit integer sent on the trigger.
1903
1904		CONFIG_CDP_POWER_CONSUMPTION
1905
1906		A 16bit integer containing the power consumption of the
1907		device in .1 of milliwatts.
1908
1909		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1910
1911		A byte containing the id of the VLAN.
1912
1913- Status LED:	CONFIG_STATUS_LED
1914
1915		Several configurations allow to display the current
1916		status using a LED. For instance, the LED will blink
1917		fast while running U-Boot code, stop blinking as
1918		soon as a reply to a BOOTP request was received, and
1919		start blinking slow once the Linux kernel is running
1920		(supported by a status LED driver in the Linux
1921		kernel). Defining CONFIG_STATUS_LED enables this
1922		feature in U-Boot.
1923
1924- CAN Support:	CONFIG_CAN_DRIVER
1925
1926		Defining CONFIG_CAN_DRIVER enables CAN driver support
1927		on those systems that support this (optional)
1928		feature, like the TQM8xxL modules.
1929
1930- I2C Support:	CONFIG_HARD_I2C | CONFIG_SOFT_I2C
1931
1932		These enable I2C serial bus commands. Defining either of
1933		(but not both of) CONFIG_HARD_I2C or CONFIG_SOFT_I2C will
1934		include the appropriate I2C driver for the selected CPU.
1935
1936		This will allow you to use i2c commands at the u-boot
1937		command line (as long as you set CONFIG_CMD_I2C in
1938		CONFIG_COMMANDS) and communicate with i2c based realtime
1939		clock chips. See common/cmd_i2c.c for a description of the
1940		command line interface.
1941
1942		CONFIG_HARD_I2C selects a hardware I2C controller.
1943
1944		CONFIG_SOFT_I2C configures u-boot to use a software (aka
1945		bit-banging) driver instead of CPM or similar hardware
1946		support for I2C.
1947
1948		There are several other quantities that must also be
1949		defined when you define CONFIG_HARD_I2C or CONFIG_SOFT_I2C.
1950
1951		In both cases you will need to define CONFIG_SYS_I2C_SPEED
1952		to be the frequency (in Hz) at which you wish your i2c bus
1953		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
1954		the CPU's i2c node address).
1955
1956		Now, the u-boot i2c code for the mpc8xx
1957		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
1958		and so its address should therefore be cleared to 0 (See,
1959		eg, MPC823e User's Manual p.16-473). So, set
1960		CONFIG_SYS_I2C_SLAVE to 0.
1961
1962		CONFIG_SYS_I2C_INIT_MPC5XXX
1963
1964		When a board is reset during an i2c bus transfer
1965		chips might think that the current transfer is still
1966		in progress.  Reset the slave devices by sending start
1967		commands until the slave device responds.
1968
1969		That's all that's required for CONFIG_HARD_I2C.
1970
1971		If you use the software i2c interface (CONFIG_SOFT_I2C)
1972		then the following macros need to be defined (examples are
1973		from include/configs/lwmon.h):
1974
1975		I2C_INIT
1976
1977		(Optional). Any commands necessary to enable the I2C
1978		controller or configure ports.
1979
1980		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1981
1982		I2C_PORT
1983
1984		(Only for MPC8260 CPU). The I/O port to use (the code
1985		assumes both bits are on the same port). Valid values
1986		are 0..3 for ports A..D.
1987
1988		I2C_ACTIVE
1989
1990		The code necessary to make the I2C data line active
1991		(driven).  If the data line is open collector, this
1992		define can be null.
1993
1994		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1995
1996		I2C_TRISTATE
1997
1998		The code necessary to make the I2C data line tri-stated
1999		(inactive).  If the data line is open collector, this
2000		define can be null.
2001
2002		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2003
2004		I2C_READ
2005
2006		Code that returns true if the I2C data line is high,
2007		false if it is low.
2008
2009		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2010
2011		I2C_SDA(bit)
2012
2013		If <bit> is true, sets the I2C data line high. If it
2014		is false, it clears it (low).
2015
2016		eg: #define I2C_SDA(bit) \
2017			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2018			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2019
2020		I2C_SCL(bit)
2021
2022		If <bit> is true, sets the I2C clock line high. If it
2023		is false, it clears it (low).
2024
2025		eg: #define I2C_SCL(bit) \
2026			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2027			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2028
2029		I2C_DELAY
2030
2031		This delay is invoked four times per clock cycle so this
2032		controls the rate of data transfer.  The data rate thus
2033		is 1 / (I2C_DELAY * 4). Often defined to be something
2034		like:
2035
2036		#define I2C_DELAY  udelay(2)
2037
2038		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2039
2040		If your arch supports the generic GPIO framework (asm/gpio.h),
2041		then you may alternatively define the two GPIOs that are to be
2042		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2043		have GPIO-based defaults assigned to them as appropriate.
2044
2045		You should define these to the GPIO value as given directly to
2046		the generic GPIO functions.
2047
2048		CONFIG_SYS_I2C_INIT_BOARD
2049
2050		When a board is reset during an i2c bus transfer
2051		chips might think that the current transfer is still
2052		in progress. On some boards it is possible to access
2053		the i2c SCLK line directly, either by using the
2054		processor pin as a GPIO or by having a second pin
2055		connected to the bus. If this option is defined a
2056		custom i2c_init_board() routine in boards/xxx/board.c
2057		is run early in the boot sequence.
2058
2059		CONFIG_SYS_I2C_BOARD_LATE_INIT
2060
2061		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2062		defined a custom i2c_board_late_init() routine in
2063		boards/xxx/board.c is run AFTER the operations in i2c_init()
2064		is completed. This callpoint can be used to unreset i2c bus
2065		using CPU i2c controller register accesses for CPUs whose i2c
2066		controller provide such a method. It is called at the end of
2067		i2c_init() to allow i2c_init operations to setup the i2c bus
2068		controller on the CPU (e.g. setting bus speed & slave address).
2069
2070		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2071
2072		This option enables configuration of bi_iic_fast[] flags
2073		in u-boot bd_info structure based on u-boot environment
2074		variable "i2cfast". (see also i2cfast)
2075
2076		CONFIG_I2C_MULTI_BUS
2077
2078		This option allows the use of multiple I2C buses, each of which
2079		must have a controller.	 At any point in time, only one bus is
2080		active.	 To switch to a different bus, use the 'i2c dev' command.
2081		Note that bus numbering is zero-based.
2082
2083		CONFIG_SYS_I2C_NOPROBES
2084
2085		This option specifies a list of I2C devices that will be skipped
2086		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2087		is set, specify a list of bus-device pairs.  Otherwise, specify
2088		a 1D array of device addresses
2089
2090		e.g.
2091			#undef	CONFIG_I2C_MULTI_BUS
2092			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2093
2094		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2095
2096			#define CONFIG_I2C_MULTI_BUS
2097			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2098
2099		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2100
2101		CONFIG_SYS_SPD_BUS_NUM
2102
2103		If defined, then this indicates the I2C bus number for DDR SPD.
2104		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2105
2106		CONFIG_SYS_RTC_BUS_NUM
2107
2108		If defined, then this indicates the I2C bus number for the RTC.
2109		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2110
2111		CONFIG_SYS_DTT_BUS_NUM
2112
2113		If defined, then this indicates the I2C bus number for the DTT.
2114		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2115
2116		CONFIG_SYS_I2C_DTT_ADDR:
2117
2118		If defined, specifies the I2C address of the DTT device.
2119		If not defined, then U-Boot uses predefined value for
2120		specified DTT device.
2121
2122		CONFIG_FSL_I2C
2123
2124		Define this option if you want to use Freescale's I2C driver in
2125		drivers/i2c/fsl_i2c.c.
2126
2127		CONFIG_I2C_MUX
2128
2129		Define this option if you have I2C devices reached over 1 .. n
2130		I2C Muxes like the pca9544a. This option addes a new I2C
2131		Command "i2c bus [muxtype:muxaddr:muxchannel]" which adds a
2132		new I2C Bus to the existing I2C Busses. If you select the
2133		new Bus with "i2c dev", u-bbot sends first the commandos for
2134		the muxes to activate this new "bus".
2135
2136		CONFIG_I2C_MULTI_BUS must be also defined, to use this
2137		feature!
2138
2139		Example:
2140		Adding a new I2C Bus reached over 2 pca9544a muxes
2141			The First mux with address 70 and channel 6
2142			The Second mux with address 71 and channel 4
2143
2144		=> i2c bus pca9544a:70:6:pca9544a:71:4
2145
2146		Use the "i2c bus" command without parameter, to get a list
2147		of I2C Busses with muxes:
2148
2149		=> i2c bus
2150		Busses reached over muxes:
2151		Bus ID: 2
2152		  reached over Mux(es):
2153		    pca9544a@70 ch: 4
2154		Bus ID: 3
2155		  reached over Mux(es):
2156		    pca9544a@70 ch: 6
2157		    pca9544a@71 ch: 4
2158		=>
2159
2160		If you now switch to the new I2C Bus 3 with "i2c dev 3"
2161		u-boot first sends the command to the mux@70 to enable
2162		channel 6, and then the command to the mux@71 to enable
2163		the channel 4.
2164
2165		After that, you can use the "normal" i2c commands as
2166		usual to communicate with your I2C devices behind
2167		the 2 muxes.
2168
2169		This option is actually implemented for the bitbanging
2170		algorithm in common/soft_i2c.c and for the Hardware I2C
2171		Bus on the MPC8260. But it should be not so difficult
2172		to add this option to other architectures.
2173
2174		CONFIG_SOFT_I2C_READ_REPEATED_START
2175
2176		defining this will force the i2c_read() function in
2177		the soft_i2c driver to perform an I2C repeated start
2178		between writing the address pointer and reading the
2179		data.  If this define is omitted the default behaviour
2180		of doing a stop-start sequence will be used.  Most I2C
2181		devices can use either method, but some require one or
2182		the other.
2183
2184- SPI Support:	CONFIG_SPI
2185
2186		Enables SPI driver (so far only tested with
2187		SPI EEPROM, also an instance works with Crystal A/D and
2188		D/As on the SACSng board)
2189
2190		CONFIG_SH_SPI
2191
2192		Enables the driver for SPI controller on SuperH. Currently
2193		only SH7757 is supported.
2194
2195		CONFIG_SPI_X
2196
2197		Enables extended (16-bit) SPI EEPROM addressing.
2198		(symmetrical to CONFIG_I2C_X)
2199
2200		CONFIG_SOFT_SPI
2201
2202		Enables a software (bit-bang) SPI driver rather than
2203		using hardware support. This is a general purpose
2204		driver that only requires three general I/O port pins
2205		(two outputs, one input) to function. If this is
2206		defined, the board configuration must define several
2207		SPI configuration items (port pins to use, etc). For
2208		an example, see include/configs/sacsng.h.
2209
2210		CONFIG_HARD_SPI
2211
2212		Enables a hardware SPI driver for general-purpose reads
2213		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2214		must define a list of chip-select function pointers.
2215		Currently supported on some MPC8xxx processors.	 For an
2216		example, see include/configs/mpc8349emds.h.
2217
2218		CONFIG_MXC_SPI
2219
2220		Enables the driver for the SPI controllers on i.MX and MXC
2221		SoCs. Currently i.MX31/35/51 are supported.
2222
2223- FPGA Support: CONFIG_FPGA
2224
2225		Enables FPGA subsystem.
2226
2227		CONFIG_FPGA_<vendor>
2228
2229		Enables support for specific chip vendors.
2230		(ALTERA, XILINX)
2231
2232		CONFIG_FPGA_<family>
2233
2234		Enables support for FPGA family.
2235		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2236
2237		CONFIG_FPGA_COUNT
2238
2239		Specify the number of FPGA devices to support.
2240
2241		CONFIG_SYS_FPGA_PROG_FEEDBACK
2242
2243		Enable printing of hash marks during FPGA configuration.
2244
2245		CONFIG_SYS_FPGA_CHECK_BUSY
2246
2247		Enable checks on FPGA configuration interface busy
2248		status by the configuration function. This option
2249		will require a board or device specific function to
2250		be written.
2251
2252		CONFIG_FPGA_DELAY
2253
2254		If defined, a function that provides delays in the FPGA
2255		configuration driver.
2256
2257		CONFIG_SYS_FPGA_CHECK_CTRLC
2258		Allow Control-C to interrupt FPGA configuration
2259
2260		CONFIG_SYS_FPGA_CHECK_ERROR
2261
2262		Check for configuration errors during FPGA bitfile
2263		loading. For example, abort during Virtex II
2264		configuration if the INIT_B line goes low (which
2265		indicated a CRC error).
2266
2267		CONFIG_SYS_FPGA_WAIT_INIT
2268
2269		Maximum time to wait for the INIT_B line to deassert
2270		after PROB_B has been deasserted during a Virtex II
2271		FPGA configuration sequence. The default time is 500
2272		ms.
2273
2274		CONFIG_SYS_FPGA_WAIT_BUSY
2275
2276		Maximum time to wait for BUSY to deassert during
2277		Virtex II FPGA configuration. The default is 5 ms.
2278
2279		CONFIG_SYS_FPGA_WAIT_CONFIG
2280
2281		Time to wait after FPGA configuration. The default is
2282		200 ms.
2283
2284- Configuration Management:
2285		CONFIG_IDENT_STRING
2286
2287		If defined, this string will be added to the U-Boot
2288		version information (U_BOOT_VERSION)
2289
2290- Vendor Parameter Protection:
2291
2292		U-Boot considers the values of the environment
2293		variables "serial#" (Board Serial Number) and
2294		"ethaddr" (Ethernet Address) to be parameters that
2295		are set once by the board vendor / manufacturer, and
2296		protects these variables from casual modification by
2297		the user. Once set, these variables are read-only,
2298		and write or delete attempts are rejected. You can
2299		change this behaviour:
2300
2301		If CONFIG_ENV_OVERWRITE is #defined in your config
2302		file, the write protection for vendor parameters is
2303		completely disabled. Anybody can change or delete
2304		these parameters.
2305
2306		Alternatively, if you #define _both_ CONFIG_ETHADDR
2307		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2308		Ethernet address is installed in the environment,
2309		which can be changed exactly ONCE by the user. [The
2310		serial# is unaffected by this, i. e. it remains
2311		read-only.]
2312
2313		The same can be accomplished in a more flexible way
2314		for any variable by configuring the type of access
2315		to allow for those variables in the ".flags" variable
2316		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2317
2318- Protected RAM:
2319		CONFIG_PRAM
2320
2321		Define this variable to enable the reservation of
2322		"protected RAM", i. e. RAM which is not overwritten
2323		by U-Boot. Define CONFIG_PRAM to hold the number of
2324		kB you want to reserve for pRAM. You can overwrite
2325		this default value by defining an environment
2326		variable "pram" to the number of kB you want to
2327		reserve. Note that the board info structure will
2328		still show the full amount of RAM. If pRAM is
2329		reserved, a new environment variable "mem" will
2330		automatically be defined to hold the amount of
2331		remaining RAM in a form that can be passed as boot
2332		argument to Linux, for instance like that:
2333
2334			setenv bootargs ... mem=\${mem}
2335			saveenv
2336
2337		This way you can tell Linux not to use this memory,
2338		either, which results in a memory region that will
2339		not be affected by reboots.
2340
2341		*WARNING* If your board configuration uses automatic
2342		detection of the RAM size, you must make sure that
2343		this memory test is non-destructive. So far, the
2344		following board configurations are known to be
2345		"pRAM-clean":
2346
2347			IVMS8, IVML24, SPD8xx, TQM8xxL,
2348			HERMES, IP860, RPXlite, LWMON,
2349			FLAGADM, TQM8260
2350
2351- Access to physical memory region (> 4GB)
2352		Some basic support is provided for operations on memory not
2353		normally accessible to U-Boot - e.g. some architectures
2354		support access to more than 4GB of memory on 32-bit
2355		machines using physical address extension or similar.
2356		Define CONFIG_PHYSMEM to access this basic support, which
2357		currently only supports clearing the memory.
2358
2359- Error Recovery:
2360		CONFIG_PANIC_HANG
2361
2362		Define this variable to stop the system in case of a
2363		fatal error, so that you have to reset it manually.
2364		This is probably NOT a good idea for an embedded
2365		system where you want the system to reboot
2366		automatically as fast as possible, but it may be
2367		useful during development since you can try to debug
2368		the conditions that lead to the situation.
2369
2370		CONFIG_NET_RETRY_COUNT
2371
2372		This variable defines the number of retries for
2373		network operations like ARP, RARP, TFTP, or BOOTP
2374		before giving up the operation. If not defined, a
2375		default value of 5 is used.
2376
2377		CONFIG_ARP_TIMEOUT
2378
2379		Timeout waiting for an ARP reply in milliseconds.
2380
2381		CONFIG_NFS_TIMEOUT
2382
2383		Timeout in milliseconds used in NFS protocol.
2384		If you encounter "ERROR: Cannot umount" in nfs command,
2385		try longer timeout such as
2386		#define CONFIG_NFS_TIMEOUT 10000UL
2387
2388- Command Interpreter:
2389		CONFIG_AUTO_COMPLETE
2390
2391		Enable auto completion of commands using TAB.
2392
2393		Note that this feature has NOT been implemented yet
2394		for the "hush" shell.
2395
2396
2397		CONFIG_SYS_HUSH_PARSER
2398
2399		Define this variable to enable the "hush" shell (from
2400		Busybox) as command line interpreter, thus enabling
2401		powerful command line syntax like
2402		if...then...else...fi conditionals or `&&' and '||'
2403		constructs ("shell scripts").
2404
2405		If undefined, you get the old, much simpler behaviour
2406		with a somewhat smaller memory footprint.
2407
2408
2409		CONFIG_SYS_PROMPT_HUSH_PS2
2410
2411		This defines the secondary prompt string, which is
2412		printed when the command interpreter needs more input
2413		to complete a command. Usually "> ".
2414
2415	Note:
2416
2417		In the current implementation, the local variables
2418		space and global environment variables space are
2419		separated. Local variables are those you define by
2420		simply typing `name=value'. To access a local
2421		variable later on, you have write `$name' or
2422		`${name}'; to execute the contents of a variable
2423		directly type `$name' at the command prompt.
2424
2425		Global environment variables are those you use
2426		setenv/printenv to work with. To run a command stored
2427		in such a variable, you need to use the run command,
2428		and you must not use the '$' sign to access them.
2429
2430		To store commands and special characters in a
2431		variable, please use double quotation marks
2432		surrounding the whole text of the variable, instead
2433		of the backslashes before semicolons and special
2434		symbols.
2435
2436- Commandline Editing and History:
2437		CONFIG_CMDLINE_EDITING
2438
2439		Enable editing and History functions for interactive
2440		commandline input operations
2441
2442- Default Environment:
2443		CONFIG_EXTRA_ENV_SETTINGS
2444
2445		Define this to contain any number of null terminated
2446		strings (variable = value pairs) that will be part of
2447		the default environment compiled into the boot image.
2448
2449		For example, place something like this in your
2450		board's config file:
2451
2452		#define CONFIG_EXTRA_ENV_SETTINGS \
2453			"myvar1=value1\0" \
2454			"myvar2=value2\0"
2455
2456		Warning: This method is based on knowledge about the
2457		internal format how the environment is stored by the
2458		U-Boot code. This is NOT an official, exported
2459		interface! Although it is unlikely that this format
2460		will change soon, there is no guarantee either.
2461		You better know what you are doing here.
2462
2463		Note: overly (ab)use of the default environment is
2464		discouraged. Make sure to check other ways to preset
2465		the environment like the "source" command or the
2466		boot command first.
2467
2468		CONFIG_ENV_VARS_UBOOT_CONFIG
2469
2470		Define this in order to add variables describing the
2471		U-Boot build configuration to the default environment.
2472		These will be named arch, cpu, board, vendor, and soc.
2473
2474		Enabling this option will cause the following to be defined:
2475
2476		- CONFIG_SYS_ARCH
2477		- CONFIG_SYS_CPU
2478		- CONFIG_SYS_BOARD
2479		- CONFIG_SYS_VENDOR
2480		- CONFIG_SYS_SOC
2481
2482		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2483
2484		Define this in order to add variables describing certain
2485		run-time determined information about the hardware to the
2486		environment.  These will be named board_name, board_rev.
2487
2488		CONFIG_DELAY_ENVIRONMENT
2489
2490		Normally the environment is loaded when the board is
2491		intialised so that it is available to U-Boot. This inhibits
2492		that so that the environment is not available until
2493		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2494		this is instead controlled by the value of
2495		/config/load-environment.
2496
2497- DataFlash Support:
2498		CONFIG_HAS_DATAFLASH
2499
2500		Defining this option enables DataFlash features and
2501		allows to read/write in Dataflash via the standard
2502		commands cp, md...
2503
2504- Serial Flash support
2505		CONFIG_CMD_SF
2506
2507		Defining this option enables SPI flash commands
2508		'sf probe/read/write/erase/update'.
2509
2510		Usage requires an initial 'probe' to define the serial
2511		flash parameters, followed by read/write/erase/update
2512		commands.
2513
2514		The following defaults may be provided by the platform
2515		to handle the common case when only a single serial
2516		flash is present on the system.
2517
2518		CONFIG_SF_DEFAULT_BUS		Bus identifier
2519		CONFIG_SF_DEFAULT_CS		Chip-select
2520		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2521		CONFIG_SF_DEFAULT_SPEED		in Hz
2522
2523		CONFIG_CMD_SF_TEST
2524
2525		Define this option to include a destructive SPI flash
2526		test ('sf test').
2527
2528		CONFIG_SPI_FLASH_BAR		Ban/Extended Addr Reg
2529
2530		Define this option to use the Bank addr/Extended addr
2531		support on SPI flashes which has size > 16Mbytes.
2532
2533- SystemACE Support:
2534		CONFIG_SYSTEMACE
2535
2536		Adding this option adds support for Xilinx SystemACE
2537		chips attached via some sort of local bus. The address
2538		of the chip must also be defined in the
2539		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2540
2541		#define CONFIG_SYSTEMACE
2542		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2543
2544		When SystemACE support is added, the "ace" device type
2545		becomes available to the fat commands, i.e. fatls.
2546
2547- TFTP Fixed UDP Port:
2548		CONFIG_TFTP_PORT
2549
2550		If this is defined, the environment variable tftpsrcp
2551		is used to supply the TFTP UDP source port value.
2552		If tftpsrcp isn't defined, the normal pseudo-random port
2553		number generator is used.
2554
2555		Also, the environment variable tftpdstp is used to supply
2556		the TFTP UDP destination port value.  If tftpdstp isn't
2557		defined, the normal port 69 is used.
2558
2559		The purpose for tftpsrcp is to allow a TFTP server to
2560		blindly start the TFTP transfer using the pre-configured
2561		target IP address and UDP port. This has the effect of
2562		"punching through" the (Windows XP) firewall, allowing
2563		the remainder of the TFTP transfer to proceed normally.
2564		A better solution is to properly configure the firewall,
2565		but sometimes that is not allowed.
2566
2567- Hashing support:
2568		CONFIG_CMD_HASH
2569
2570		This enables a generic 'hash' command which can produce
2571		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2572
2573		CONFIG_HASH_VERIFY
2574
2575		Enable the hash verify command (hash -v). This adds to code
2576		size a little.
2577
2578		CONFIG_SHA1 - support SHA1 hashing
2579		CONFIG_SHA256 - support SHA256 hashing
2580
2581		Note: There is also a sha1sum command, which should perhaps
2582		be deprecated in favour of 'hash sha1'.
2583
2584- Signing support:
2585		CONFIG_RSA
2586
2587		This enables the RSA algorithm used for FIT image verification
2588		in U-Boot. See doc/uImage/signature for more information.
2589
2590		The signing part is build into mkimage regardless of this
2591		option.
2592
2593
2594- Show boot progress:
2595		CONFIG_SHOW_BOOT_PROGRESS
2596
2597		Defining this option allows to add some board-
2598		specific code (calling a user-provided function
2599		"show_boot_progress(int)") that enables you to show
2600		the system's boot progress on some display (for
2601		example, some LED's) on your board. At the moment,
2602		the following checkpoints are implemented:
2603
2604- Detailed boot stage timing
2605		CONFIG_BOOTSTAGE
2606		Define this option to get detailed timing of each stage
2607		of the boot process.
2608
2609		CONFIG_BOOTSTAGE_USER_COUNT
2610		This is the number of available user bootstage records.
2611		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
2612		a new ID will be allocated from this stash. If you exceed
2613		the limit, recording will stop.
2614
2615		CONFIG_BOOTSTAGE_REPORT
2616		Define this to print a report before boot, similar to this:
2617
2618		Timer summary in microseconds:
2619		       Mark    Elapsed  Stage
2620			  0          0  reset
2621		  3,575,678  3,575,678  board_init_f start
2622		  3,575,695         17  arch_cpu_init A9
2623		  3,575,777         82  arch_cpu_init done
2624		  3,659,598     83,821  board_init_r start
2625		  3,910,375    250,777  main_loop
2626		 29,916,167 26,005,792  bootm_start
2627		 30,361,327    445,160  start_kernel
2628
2629		CONFIG_CMD_BOOTSTAGE
2630		Add a 'bootstage' command which supports printing a report
2631		and un/stashing of bootstage data.
2632
2633		CONFIG_BOOTSTAGE_FDT
2634		Stash the bootstage information in the FDT. A root 'bootstage'
2635		node is created with each bootstage id as a child. Each child
2636		has a 'name' property and either 'mark' containing the
2637		mark time in microsecond, or 'accum' containing the
2638		accumulated time for that bootstage id in microseconds.
2639		For example:
2640
2641		bootstage {
2642			154 {
2643				name = "board_init_f";
2644				mark = <3575678>;
2645			};
2646			170 {
2647				name = "lcd";
2648				accum = <33482>;
2649			};
2650		};
2651
2652		Code in the Linux kernel can find this in /proc/devicetree.
2653
2654Legacy uImage format:
2655
2656  Arg	Where			When
2657    1	common/cmd_bootm.c	before attempting to boot an image
2658   -1	common/cmd_bootm.c	Image header has bad	 magic number
2659    2	common/cmd_bootm.c	Image header has correct magic number
2660   -2	common/cmd_bootm.c	Image header has bad	 checksum
2661    3	common/cmd_bootm.c	Image header has correct checksum
2662   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2663    4	common/cmd_bootm.c	Image data   has correct checksum
2664   -4	common/cmd_bootm.c	Image is for unsupported architecture
2665    5	common/cmd_bootm.c	Architecture check OK
2666   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2667    6	common/cmd_bootm.c	Image Type check OK
2668   -6	common/cmd_bootm.c	gunzip uncompression error
2669   -7	common/cmd_bootm.c	Unimplemented compression type
2670    7	common/cmd_bootm.c	Uncompression OK
2671    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2672   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2673
2674    9	common/image.c		Start initial ramdisk verification
2675  -10	common/image.c		Ramdisk header has bad	   magic number
2676  -11	common/image.c		Ramdisk header has bad	   checksum
2677   10	common/image.c		Ramdisk header is OK
2678  -12	common/image.c		Ramdisk data   has bad	   checksum
2679   11	common/image.c		Ramdisk data   has correct checksum
2680   12	common/image.c		Ramdisk verification complete, start loading
2681  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2682   13	common/image.c		Start multifile image verification
2683   14	common/image.c		No initial ramdisk, no multifile, continue.
2684
2685   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2686
2687  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2688  -31	post/post.c		POST test failed, detected by post_output_backlog()
2689  -32	post/post.c		POST test failed, detected by post_run_single()
2690
2691   34	common/cmd_doc.c	before loading a Image from a DOC device
2692  -35	common/cmd_doc.c	Bad usage of "doc" command
2693   35	common/cmd_doc.c	correct usage of "doc" command
2694  -36	common/cmd_doc.c	No boot device
2695   36	common/cmd_doc.c	correct boot device
2696  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2697   37	common/cmd_doc.c	correct chip ID found, device available
2698  -38	common/cmd_doc.c	Read Error on boot device
2699   38	common/cmd_doc.c	reading Image header from DOC device OK
2700  -39	common/cmd_doc.c	Image header has bad magic number
2701   39	common/cmd_doc.c	Image header has correct magic number
2702  -40	common/cmd_doc.c	Error reading Image from DOC device
2703   40	common/cmd_doc.c	Image header has correct magic number
2704   41	common/cmd_ide.c	before loading a Image from a IDE device
2705  -42	common/cmd_ide.c	Bad usage of "ide" command
2706   42	common/cmd_ide.c	correct usage of "ide" command
2707  -43	common/cmd_ide.c	No boot device
2708   43	common/cmd_ide.c	boot device found
2709  -44	common/cmd_ide.c	Device not available
2710   44	common/cmd_ide.c	Device available
2711  -45	common/cmd_ide.c	wrong partition selected
2712   45	common/cmd_ide.c	partition selected
2713  -46	common/cmd_ide.c	Unknown partition table
2714   46	common/cmd_ide.c	valid partition table found
2715  -47	common/cmd_ide.c	Invalid partition type
2716   47	common/cmd_ide.c	correct partition type
2717  -48	common/cmd_ide.c	Error reading Image Header on boot device
2718   48	common/cmd_ide.c	reading Image Header from IDE device OK
2719  -49	common/cmd_ide.c	Image header has bad magic number
2720   49	common/cmd_ide.c	Image header has correct magic number
2721  -50	common/cmd_ide.c	Image header has bad	 checksum
2722   50	common/cmd_ide.c	Image header has correct checksum
2723  -51	common/cmd_ide.c	Error reading Image from IDE device
2724   51	common/cmd_ide.c	reading Image from IDE device OK
2725   52	common/cmd_nand.c	before loading a Image from a NAND device
2726  -53	common/cmd_nand.c	Bad usage of "nand" command
2727   53	common/cmd_nand.c	correct usage of "nand" command
2728  -54	common/cmd_nand.c	No boot device
2729   54	common/cmd_nand.c	boot device found
2730  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2731   55	common/cmd_nand.c	correct chip ID found, device available
2732  -56	common/cmd_nand.c	Error reading Image Header on boot device
2733   56	common/cmd_nand.c	reading Image Header from NAND device OK
2734  -57	common/cmd_nand.c	Image header has bad magic number
2735   57	common/cmd_nand.c	Image header has correct magic number
2736  -58	common/cmd_nand.c	Error reading Image from NAND device
2737   58	common/cmd_nand.c	reading Image from NAND device OK
2738
2739  -60	common/env_common.c	Environment has a bad CRC, using default
2740
2741   64	net/eth.c		starting with Ethernet configuration.
2742  -64	net/eth.c		no Ethernet found.
2743   65	net/eth.c		Ethernet found.
2744
2745  -80	common/cmd_net.c	usage wrong
2746   80	common/cmd_net.c	before calling NetLoop()
2747  -81	common/cmd_net.c	some error in NetLoop() occurred
2748   81	common/cmd_net.c	NetLoop() back without error
2749  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2750   82	common/cmd_net.c	trying automatic boot
2751   83	common/cmd_net.c	running "source" command
2752  -83	common/cmd_net.c	some error in automatic boot or "source" command
2753   84	common/cmd_net.c	end without errors
2754
2755FIT uImage format:
2756
2757  Arg	Where			When
2758  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2759 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2760  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2761 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2762  102	common/cmd_bootm.c	Kernel unit name specified
2763 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2764  103	common/cmd_bootm.c	Found configuration node
2765  104	common/cmd_bootm.c	Got kernel subimage node offset
2766 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2767  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2768 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2769  106	common/cmd_bootm.c	Architecture check OK
2770 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2771  107	common/cmd_bootm.c	Kernel subimage type OK
2772 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2773  108	common/cmd_bootm.c	Got kernel subimage data/size
2774 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2775 -109	common/cmd_bootm.c	Can't get kernel subimage type
2776 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2777 -111	common/cmd_bootm.c	Can't get kernel subimage os
2778 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2779 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2780
2781  120	common/image.c		Start initial ramdisk verification
2782 -120	common/image.c		Ramdisk FIT image has incorrect format
2783  121	common/image.c		Ramdisk FIT image has correct format
2784  122	common/image.c		No ramdisk subimage unit name, using configuration
2785 -122	common/image.c		Can't get configuration for ramdisk subimage
2786  123	common/image.c		Ramdisk unit name specified
2787 -124	common/image.c		Can't get ramdisk subimage node offset
2788  125	common/image.c		Got ramdisk subimage node offset
2789 -125	common/image.c		Ramdisk subimage hash verification failed
2790  126	common/image.c		Ramdisk subimage hash verification OK
2791 -126	common/image.c		Ramdisk subimage for unsupported architecture
2792  127	common/image.c		Architecture check OK
2793 -127	common/image.c		Can't get ramdisk subimage data/size
2794  128	common/image.c		Got ramdisk subimage data/size
2795  129	common/image.c		Can't get ramdisk load address
2796 -129	common/image.c		Got ramdisk load address
2797
2798 -130	common/cmd_doc.c	Incorrect FIT image format
2799  131	common/cmd_doc.c	FIT image format OK
2800
2801 -140	common/cmd_ide.c	Incorrect FIT image format
2802  141	common/cmd_ide.c	FIT image format OK
2803
2804 -150	common/cmd_nand.c	Incorrect FIT image format
2805  151	common/cmd_nand.c	FIT image format OK
2806
2807- FIT image support:
2808		CONFIG_FIT
2809		Enable support for the FIT uImage format.
2810
2811		CONFIG_FIT_BEST_MATCH
2812		When no configuration is explicitly selected, default to the
2813		one whose fdt's compatibility field best matches that of
2814		U-Boot itself. A match is considered "best" if it matches the
2815		most specific compatibility entry of U-Boot's fdt's root node.
2816		The order of entries in the configuration's fdt is ignored.
2817
2818		CONFIG_FIT_SIGNATURE
2819		This option enables signature verification of FIT uImages,
2820		using a hash signed and verified using RSA. See
2821		doc/uImage.FIT/signature.txt for more details.
2822
2823- Standalone program support:
2824		CONFIG_STANDALONE_LOAD_ADDR
2825
2826		This option defines a board specific value for the
2827		address where standalone program gets loaded, thus
2828		overwriting the architecture dependent default
2829		settings.
2830
2831- Frame Buffer Address:
2832		CONFIG_FB_ADDR
2833
2834		Define CONFIG_FB_ADDR if you want to use specific
2835		address for frame buffer.  This is typically the case
2836		when using a graphics controller has separate video
2837		memory.  U-Boot will then place the frame buffer at
2838		the given address instead of dynamically reserving it
2839		in system RAM by calling lcd_setmem(), which grabs
2840		the memory for the frame buffer depending on the
2841		configured panel size.
2842
2843		Please see board_init_f function.
2844
2845- Automatic software updates via TFTP server
2846		CONFIG_UPDATE_TFTP
2847		CONFIG_UPDATE_TFTP_CNT_MAX
2848		CONFIG_UPDATE_TFTP_MSEC_MAX
2849
2850		These options enable and control the auto-update feature;
2851		for a more detailed description refer to doc/README.update.
2852
2853- MTD Support (mtdparts command, UBI support)
2854		CONFIG_MTD_DEVICE
2855
2856		Adds the MTD device infrastructure from the Linux kernel.
2857		Needed for mtdparts command support.
2858
2859		CONFIG_MTD_PARTITIONS
2860
2861		Adds the MTD partitioning infrastructure from the Linux
2862		kernel. Needed for UBI support.
2863
2864- UBI support
2865		CONFIG_CMD_UBI
2866
2867		Adds commands for interacting with MTD partitions formatted
2868		with the UBI flash translation layer
2869
2870		Requires also defining CONFIG_RBTREE
2871
2872		CONFIG_UBI_SILENCE_MSG
2873
2874		Make the verbose messages from UBI stop printing.  This leaves
2875		warnings and errors enabled.
2876
2877- UBIFS support
2878		CONFIG_CMD_UBIFS
2879
2880		Adds commands for interacting with UBI volumes formatted as
2881		UBIFS.  UBIFS is read-only in u-boot.
2882
2883		Requires UBI support as well as CONFIG_LZO
2884
2885		CONFIG_UBIFS_SILENCE_MSG
2886
2887		Make the verbose messages from UBIFS stop printing.  This leaves
2888		warnings and errors enabled.
2889
2890- SPL framework
2891		CONFIG_SPL
2892		Enable building of SPL globally.
2893
2894		CONFIG_SPL_LDSCRIPT
2895		LDSCRIPT for linking the SPL binary.
2896
2897		CONFIG_SPL_MAX_FOOTPRINT
2898		Maximum size in memory allocated to the SPL, BSS included.
2899		When defined, the linker checks that the actual memory
2900		used by SPL from _start to __bss_end does not exceed it.
2901		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2902		must not be both defined at the same time.
2903
2904		CONFIG_SPL_MAX_SIZE
2905		Maximum size of the SPL image (text, data, rodata, and
2906		linker lists sections), BSS excluded.
2907		When defined, the linker checks that the actual size does
2908		not exceed it.
2909
2910		CONFIG_SPL_TEXT_BASE
2911		TEXT_BASE for linking the SPL binary.
2912
2913		CONFIG_SPL_RELOC_TEXT_BASE
2914		Address to relocate to.  If unspecified, this is equal to
2915		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2916
2917		CONFIG_SPL_BSS_START_ADDR
2918		Link address for the BSS within the SPL binary.
2919
2920		CONFIG_SPL_BSS_MAX_SIZE
2921		Maximum size in memory allocated to the SPL BSS.
2922		When defined, the linker checks that the actual memory used
2923		by SPL from __bss_start to __bss_end does not exceed it.
2924		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2925		must not be both defined at the same time.
2926
2927		CONFIG_SPL_STACK
2928		Adress of the start of the stack SPL will use
2929
2930		CONFIG_SPL_RELOC_STACK
2931		Adress of the start of the stack SPL will use after
2932		relocation.  If unspecified, this is equal to
2933		CONFIG_SPL_STACK.
2934
2935		CONFIG_SYS_SPL_MALLOC_START
2936		Starting address of the malloc pool used in SPL.
2937
2938		CONFIG_SYS_SPL_MALLOC_SIZE
2939		The size of the malloc pool used in SPL.
2940
2941		CONFIG_SPL_FRAMEWORK
2942		Enable the SPL framework under common/.  This framework
2943		supports MMC, NAND and YMODEM loading of U-Boot and NAND
2944		NAND loading of the Linux Kernel.
2945
2946		CONFIG_SPL_DISPLAY_PRINT
2947		For ARM, enable an optional function to print more information
2948		about the running system.
2949
2950		CONFIG_SPL_INIT_MINIMAL
2951		Arch init code should be built for a very small image
2952
2953		CONFIG_SPL_LIBCOMMON_SUPPORT
2954		Support for common/libcommon.o in SPL binary
2955
2956		CONFIG_SPL_LIBDISK_SUPPORT
2957		Support for disk/libdisk.o in SPL binary
2958
2959		CONFIG_SPL_I2C_SUPPORT
2960		Support for drivers/i2c/libi2c.o in SPL binary
2961
2962		CONFIG_SPL_GPIO_SUPPORT
2963		Support for drivers/gpio/libgpio.o in SPL binary
2964
2965		CONFIG_SPL_MMC_SUPPORT
2966		Support for drivers/mmc/libmmc.o in SPL binary
2967
2968		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
2969		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
2970		CONFIG_SYS_MMC_SD_FAT_BOOT_PARTITION
2971		Address, size and partition on the MMC to load U-Boot from
2972		when the MMC is being used in raw mode.
2973
2974		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2975		Sector to load kernel uImage from when MMC is being
2976		used in raw mode (for Falcon mode)
2977
2978		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2979		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2980		Sector and number of sectors to load kernel argument
2981		parameters from when MMC is being used in raw mode
2982		(for falcon mode)
2983
2984		CONFIG_SPL_FAT_SUPPORT
2985		Support for fs/fat/libfat.o in SPL binary
2986
2987		CONFIG_SPL_FAT_LOAD_PAYLOAD_NAME
2988		Filename to read to load U-Boot when reading from FAT
2989
2990		CONFIG_SPL_FAT_LOAD_KERNEL_NAME
2991		Filename to read to load kernel uImage when reading
2992		from FAT (for Falcon mode)
2993
2994		CONFIG_SPL_FAT_LOAD_ARGS_NAME
2995		Filename to read to load kernel argument parameters
2996		when reading from FAT (for Falcon mode)
2997
2998		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2999		Set this for NAND SPL on PPC mpc83xx targets, so that
3000		start.S waits for the rest of the SPL to load before
3001		continuing (the hardware starts execution after just
3002		loading the first page rather than the full 4K).
3003
3004		CONFIG_SPL_NAND_BASE
3005		Include nand_base.c in the SPL.  Requires
3006		CONFIG_SPL_NAND_DRIVERS.
3007
3008		CONFIG_SPL_NAND_DRIVERS
3009		SPL uses normal NAND drivers, not minimal drivers.
3010
3011		CONFIG_SPL_NAND_ECC
3012		Include standard software ECC in the SPL
3013
3014		CONFIG_SPL_NAND_SIMPLE
3015		Support for NAND boot using simple NAND drivers that
3016		expose the cmd_ctrl() interface.
3017
3018		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3019		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3020		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3021		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3022		CONFIG_SYS_NAND_ECCBYTES
3023		Defines the size and behavior of the NAND that SPL uses
3024		to read U-Boot
3025
3026		CONFIG_SYS_NAND_U_BOOT_OFFS
3027		Location in NAND to read U-Boot from
3028
3029		CONFIG_SYS_NAND_U_BOOT_DST
3030		Location in memory to load U-Boot to
3031
3032		CONFIG_SYS_NAND_U_BOOT_SIZE
3033		Size of image to load
3034
3035		CONFIG_SYS_NAND_U_BOOT_START
3036		Entry point in loaded image to jump to
3037
3038		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3039		Define this if you need to first read the OOB and then the
3040		data. This is used for example on davinci plattforms.
3041
3042		CONFIG_SPL_OMAP3_ID_NAND
3043		Support for an OMAP3-specific set of functions to return the
3044		ID and MFR of the first attached NAND chip, if present.
3045
3046		CONFIG_SPL_SERIAL_SUPPORT
3047		Support for drivers/serial/libserial.o in SPL binary
3048
3049		CONFIG_SPL_SPI_FLASH_SUPPORT
3050		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3051
3052		CONFIG_SPL_SPI_SUPPORT
3053		Support for drivers/spi/libspi.o in SPL binary
3054
3055		CONFIG_SPL_RAM_DEVICE
3056		Support for running image already present in ram, in SPL binary
3057
3058		CONFIG_SPL_LIBGENERIC_SUPPORT
3059		Support for lib/libgeneric.o in SPL binary
3060
3061		CONFIG_SPL_ENV_SUPPORT
3062		Support for the environment operating in SPL binary
3063
3064		CONFIG_SPL_NET_SUPPORT
3065		Support for the net/libnet.o in SPL binary.
3066		It conflicts with SPL env from storage medium specified by
3067		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3068
3069		CONFIG_SPL_PAD_TO
3070		Image offset to which the SPL should be padded before appending
3071		the SPL payload. By default, this is defined as
3072		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3073		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3074		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3075
3076		CONFIG_SPL_TARGET
3077		Final target image containing SPL and payload.  Some SPLs
3078		use an arch-specific makefile fragment instead, for
3079		example if more than one image needs to be produced.
3080
3081		CONFIG_FIT_SPL_PRINT
3082		Printing information about a FIT image adds quite a bit of
3083		code to SPL. So this is normally disabled in SPL. Use this
3084		option to re-enable it. This will affect the output of the
3085		bootm command when booting a FIT image.
3086
3087Modem Support:
3088--------------
3089
3090[so far only for SMDK2400 boards]
3091
3092- Modem support enable:
3093		CONFIG_MODEM_SUPPORT
3094
3095- RTS/CTS Flow control enable:
3096		CONFIG_HWFLOW
3097
3098- Modem debug support:
3099		CONFIG_MODEM_SUPPORT_DEBUG
3100
3101		Enables debugging stuff (char screen[1024], dbg())
3102		for modem support. Useful only with BDI2000.
3103
3104- Interrupt support (PPC):
3105
3106		There are common interrupt_init() and timer_interrupt()
3107		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3108		for CPU specific initialization. interrupt_init_cpu()
3109		should set decrementer_count to appropriate value. If
3110		CPU resets decrementer automatically after interrupt
3111		(ppc4xx) it should set decrementer_count to zero.
3112		timer_interrupt() calls timer_interrupt_cpu() for CPU
3113		specific handling. If board has watchdog / status_led
3114		/ other_activity_monitor it works automatically from
3115		general timer_interrupt().
3116
3117- General:
3118
3119		In the target system modem support is enabled when a
3120		specific key (key combination) is pressed during
3121		power-on. Otherwise U-Boot will boot normally
3122		(autoboot). The key_pressed() function is called from
3123		board_init(). Currently key_pressed() is a dummy
3124		function, returning 1 and thus enabling modem
3125		initialization.
3126
3127		If there are no modem init strings in the
3128		environment, U-Boot proceed to autoboot; the
3129		previous output (banner, info printfs) will be
3130		suppressed, though.
3131
3132		See also: doc/README.Modem
3133
3134Board initialization settings:
3135------------------------------
3136
3137During Initialization u-boot calls a number of board specific functions
3138to allow the preparation of board specific prerequisites, e.g. pin setup
3139before drivers are initialized. To enable these callbacks the
3140following configuration macros have to be defined. Currently this is
3141architecture specific, so please check arch/your_architecture/lib/board.c
3142typically in board_init_f() and board_init_r().
3143
3144- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3145- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3146- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3147- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3148
3149Configuration Settings:
3150-----------------------
3151
3152- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3153		undefine this when you're short of memory.
3154
3155- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3156		width of the commands listed in the 'help' command output.
3157
3158- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3159		prompt for user input.
3160
3161- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3162
3163- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3164
3165- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3166
3167- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3168		the application (usually a Linux kernel) when it is
3169		booted
3170
3171- CONFIG_SYS_BAUDRATE_TABLE:
3172		List of legal baudrate settings for this board.
3173
3174- CONFIG_SYS_CONSOLE_INFO_QUIET
3175		Suppress display of console information at boot.
3176
3177- CONFIG_SYS_CONSOLE_IS_IN_ENV
3178		If the board specific function
3179			extern int overwrite_console (void);
3180		returns 1, the stdin, stderr and stdout are switched to the
3181		serial port, else the settings in the environment are used.
3182
3183- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3184		Enable the call to overwrite_console().
3185
3186- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3187		Enable overwrite of previous console environment settings.
3188
3189- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3190		Begin and End addresses of the area used by the
3191		simple memory test.
3192
3193- CONFIG_SYS_ALT_MEMTEST:
3194		Enable an alternate, more extensive memory test.
3195
3196- CONFIG_SYS_MEMTEST_SCRATCH:
3197		Scratch address used by the alternate memory test
3198		You only need to set this if address zero isn't writeable
3199
3200- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3201		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3202		this specified memory area will get subtracted from the top
3203		(end) of RAM and won't get "touched" at all by U-Boot. By
3204		fixing up gd->ram_size the Linux kernel should gets passed
3205		the now "corrected" memory size and won't touch it either.
3206		This should work for arch/ppc and arch/powerpc. Only Linux
3207		board ports in arch/powerpc with bootwrapper support that
3208		recalculate the memory size from the SDRAM controller setup
3209		will have to get fixed in Linux additionally.
3210
3211		This option can be used as a workaround for the 440EPx/GRx
3212		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3213		be touched.
3214
3215		WARNING: Please make sure that this value is a multiple of
3216		the Linux page size (normally 4k). If this is not the case,
3217		then the end address of the Linux memory will be located at a
3218		non page size aligned address and this could cause major
3219		problems.
3220
3221- CONFIG_SYS_LOADS_BAUD_CHANGE:
3222		Enable temporary baudrate change while serial download
3223
3224- CONFIG_SYS_SDRAM_BASE:
3225		Physical start address of SDRAM. _Must_ be 0 here.
3226
3227- CONFIG_SYS_MBIO_BASE:
3228		Physical start address of Motherboard I/O (if using a
3229		Cogent motherboard)
3230
3231- CONFIG_SYS_FLASH_BASE:
3232		Physical start address of Flash memory.
3233
3234- CONFIG_SYS_MONITOR_BASE:
3235		Physical start address of boot monitor code (set by
3236		make config files to be same as the text base address
3237		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3238		CONFIG_SYS_FLASH_BASE when booting from flash.
3239
3240- CONFIG_SYS_MONITOR_LEN:
3241		Size of memory reserved for monitor code, used to
3242		determine _at_compile_time_ (!) if the environment is
3243		embedded within the U-Boot image, or in a separate
3244		flash sector.
3245
3246- CONFIG_SYS_MALLOC_LEN:
3247		Size of DRAM reserved for malloc() use.
3248
3249- CONFIG_SYS_BOOTM_LEN:
3250		Normally compressed uImages are limited to an
3251		uncompressed size of 8 MBytes. If this is not enough,
3252		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3253		to adjust this setting to your needs.
3254
3255- CONFIG_SYS_BOOTMAPSZ:
3256		Maximum size of memory mapped by the startup code of
3257		the Linux kernel; all data that must be processed by
3258		the Linux kernel (bd_info, boot arguments, FDT blob if
3259		used) must be put below this limit, unless "bootm_low"
3260		enviroment variable is defined and non-zero. In such case
3261		all data for the Linux kernel must be between "bootm_low"
3262		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3263		variable "bootm_mapsize" will override the value of
3264		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3265		then the value in "bootm_size" will be used instead.
3266
3267- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3268		Enable initrd_high functionality.  If defined then the
3269		initrd_high feature is enabled and the bootm ramdisk subcommand
3270		is enabled.
3271
3272- CONFIG_SYS_BOOT_GET_CMDLINE:
3273		Enables allocating and saving kernel cmdline in space between
3274		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3275
3276- CONFIG_SYS_BOOT_GET_KBD:
3277		Enables allocating and saving a kernel copy of the bd_info in
3278		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3279
3280- CONFIG_SYS_MAX_FLASH_BANKS:
3281		Max number of Flash memory banks
3282
3283- CONFIG_SYS_MAX_FLASH_SECT:
3284		Max number of sectors on a Flash chip
3285
3286- CONFIG_SYS_FLASH_ERASE_TOUT:
3287		Timeout for Flash erase operations (in ms)
3288
3289- CONFIG_SYS_FLASH_WRITE_TOUT:
3290		Timeout for Flash write operations (in ms)
3291
3292- CONFIG_SYS_FLASH_LOCK_TOUT
3293		Timeout for Flash set sector lock bit operation (in ms)
3294
3295- CONFIG_SYS_FLASH_UNLOCK_TOUT
3296		Timeout for Flash clear lock bits operation (in ms)
3297
3298- CONFIG_SYS_FLASH_PROTECTION
3299		If defined, hardware flash sectors protection is used
3300		instead of U-Boot software protection.
3301
3302- CONFIG_SYS_DIRECT_FLASH_TFTP:
3303
3304		Enable TFTP transfers directly to flash memory;
3305		without this option such a download has to be
3306		performed in two steps: (1) download to RAM, and (2)
3307		copy from RAM to flash.
3308
3309		The two-step approach is usually more reliable, since
3310		you can check if the download worked before you erase
3311		the flash, but in some situations (when system RAM is
3312		too limited to allow for a temporary copy of the
3313		downloaded image) this option may be very useful.
3314
3315- CONFIG_SYS_FLASH_CFI:
3316		Define if the flash driver uses extra elements in the
3317		common flash structure for storing flash geometry.
3318
3319- CONFIG_FLASH_CFI_DRIVER
3320		This option also enables the building of the cfi_flash driver
3321		in the drivers directory
3322
3323- CONFIG_FLASH_CFI_MTD
3324		This option enables the building of the cfi_mtd driver
3325		in the drivers directory. The driver exports CFI flash
3326		to the MTD layer.
3327
3328- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3329		Use buffered writes to flash.
3330
3331- CONFIG_FLASH_SPANSION_S29WS_N
3332		s29ws-n MirrorBit flash has non-standard addresses for buffered
3333		write commands.
3334
3335- CONFIG_SYS_FLASH_QUIET_TEST
3336		If this option is defined, the common CFI flash doesn't
3337		print it's warning upon not recognized FLASH banks. This
3338		is useful, if some of the configured banks are only
3339		optionally available.
3340
3341- CONFIG_FLASH_SHOW_PROGRESS
3342		If defined (must be an integer), print out countdown
3343		digits and dots.  Recommended value: 45 (9..1) for 80
3344		column displays, 15 (3..1) for 40 column displays.
3345
3346- CONFIG_FLASH_VERIFY
3347		If defined, the content of the flash (destination) is compared
3348		against the source after the write operation. An error message
3349		will be printed when the contents are not identical.
3350		Please note that this option is useless in nearly all cases,
3351		since such flash programming errors usually are detected earlier
3352		while unprotecting/erasing/programming. Please only enable
3353		this option if you really know what you are doing.
3354
3355- CONFIG_SYS_RX_ETH_BUFFER:
3356		Defines the number of Ethernet receive buffers. On some
3357		Ethernet controllers it is recommended to set this value
3358		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3359		buffers can be full shortly after enabling the interface
3360		on high Ethernet traffic.
3361		Defaults to 4 if not defined.
3362
3363- CONFIG_ENV_MAX_ENTRIES
3364
3365	Maximum number of entries in the hash table that is used
3366	internally to store the environment settings. The default
3367	setting is supposed to be generous and should work in most
3368	cases. This setting can be used to tune behaviour; see
3369	lib/hashtable.c for details.
3370
3371- CONFIG_ENV_FLAGS_LIST_DEFAULT
3372- CONFIG_ENV_FLAGS_LIST_STATIC
3373	Enable validation of the values given to enviroment variables when
3374	calling env set.  Variables can be restricted to only decimal,
3375	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3376	the variables can also be restricted to IP address or MAC address.
3377
3378	The format of the list is:
3379		type_attribute = [s|d|x|b|i|m]
3380		access_atribute = [a|r|o|c]
3381		attributes = type_attribute[access_atribute]
3382		entry = variable_name[:attributes]
3383		list = entry[,list]
3384
3385	The type attributes are:
3386		s - String (default)
3387		d - Decimal
3388		x - Hexadecimal
3389		b - Boolean ([1yYtT|0nNfF])
3390		i - IP address
3391		m - MAC address
3392
3393	The access attributes are:
3394		a - Any (default)
3395		r - Read-only
3396		o - Write-once
3397		c - Change-default
3398
3399	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3400		Define this to a list (string) to define the ".flags"
3401		envirnoment variable in the default or embedded environment.
3402
3403	- CONFIG_ENV_FLAGS_LIST_STATIC
3404		Define this to a list (string) to define validation that
3405		should be done if an entry is not found in the ".flags"
3406		environment variable.  To override a setting in the static
3407		list, simply add an entry for the same variable name to the
3408		".flags" variable.
3409
3410- CONFIG_ENV_ACCESS_IGNORE_FORCE
3411	If defined, don't allow the -f switch to env set override variable
3412	access flags.
3413
3414- CONFIG_SYS_GENERIC_BOARD
3415	This selects the architecture-generic board system instead of the
3416	architecture-specific board files. It is intended to move boards
3417	to this new framework over time. Defining this will disable the
3418	arch/foo/lib/board.c file and use common/board_f.c and
3419	common/board_r.c instead. To use this option your architecture
3420	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
3421	its config.mk file). If you find problems enabling this option on
3422	your board please report the problem and send patches!
3423
3424- CONFIG_SYS_SYM_OFFSETS
3425	This is set by architectures that use offsets for link symbols
3426	instead of absolute values. So bss_start is obtained using an
3427	offset _bss_start_ofs from CONFIG_SYS_TEXT_BASE, rather than
3428	directly. You should not need to touch this setting.
3429
3430- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
3431	This is set by OMAP boards for the max time that reset should
3432	be asserted. See doc/README.omap-reset-time for details on how
3433	the value can be calulated on a given board.
3434
3435The following definitions that deal with the placement and management
3436of environment data (variable area); in general, we support the
3437following configurations:
3438
3439- CONFIG_BUILD_ENVCRC:
3440
3441	Builds up envcrc with the target environment so that external utils
3442	may easily extract it and embed it in final U-Boot images.
3443
3444- CONFIG_ENV_IS_IN_FLASH:
3445
3446	Define this if the environment is in flash memory.
3447
3448	a) The environment occupies one whole flash sector, which is
3449	   "embedded" in the text segment with the U-Boot code. This
3450	   happens usually with "bottom boot sector" or "top boot
3451	   sector" type flash chips, which have several smaller
3452	   sectors at the start or the end. For instance, such a
3453	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3454	   such a case you would place the environment in one of the
3455	   4 kB sectors - with U-Boot code before and after it. With
3456	   "top boot sector" type flash chips, you would put the
3457	   environment in one of the last sectors, leaving a gap
3458	   between U-Boot and the environment.
3459
3460	- CONFIG_ENV_OFFSET:
3461
3462	   Offset of environment data (variable area) to the
3463	   beginning of flash memory; for instance, with bottom boot
3464	   type flash chips the second sector can be used: the offset
3465	   for this sector is given here.
3466
3467	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3468
3469	- CONFIG_ENV_ADDR:
3470
3471	   This is just another way to specify the start address of
3472	   the flash sector containing the environment (instead of
3473	   CONFIG_ENV_OFFSET).
3474
3475	- CONFIG_ENV_SECT_SIZE:
3476
3477	   Size of the sector containing the environment.
3478
3479
3480	b) Sometimes flash chips have few, equal sized, BIG sectors.
3481	   In such a case you don't want to spend a whole sector for
3482	   the environment.
3483
3484	- CONFIG_ENV_SIZE:
3485
3486	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3487	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3488	   of this flash sector for the environment. This saves
3489	   memory for the RAM copy of the environment.
3490
3491	   It may also save flash memory if you decide to use this
3492	   when your environment is "embedded" within U-Boot code,
3493	   since then the remainder of the flash sector could be used
3494	   for U-Boot code. It should be pointed out that this is
3495	   STRONGLY DISCOURAGED from a robustness point of view:
3496	   updating the environment in flash makes it always
3497	   necessary to erase the WHOLE sector. If something goes
3498	   wrong before the contents has been restored from a copy in
3499	   RAM, your target system will be dead.
3500
3501	- CONFIG_ENV_ADDR_REDUND
3502	  CONFIG_ENV_SIZE_REDUND
3503
3504	   These settings describe a second storage area used to hold
3505	   a redundant copy of the environment data, so that there is
3506	   a valid backup copy in case there is a power failure during
3507	   a "saveenv" operation.
3508
3509BE CAREFUL! Any changes to the flash layout, and some changes to the
3510source code will make it necessary to adapt <board>/u-boot.lds*
3511accordingly!
3512
3513
3514- CONFIG_ENV_IS_IN_NVRAM:
3515
3516	Define this if you have some non-volatile memory device
3517	(NVRAM, battery buffered SRAM) which you want to use for the
3518	environment.
3519
3520	- CONFIG_ENV_ADDR:
3521	- CONFIG_ENV_SIZE:
3522
3523	  These two #defines are used to determine the memory area you
3524	  want to use for environment. It is assumed that this memory
3525	  can just be read and written to, without any special
3526	  provision.
3527
3528BE CAREFUL! The first access to the environment happens quite early
3529in U-Boot initalization (when we try to get the setting of for the
3530console baudrate). You *MUST* have mapped your NVRAM area then, or
3531U-Boot will hang.
3532
3533Please note that even with NVRAM we still use a copy of the
3534environment in RAM: we could work on NVRAM directly, but we want to
3535keep settings there always unmodified except somebody uses "saveenv"
3536to save the current settings.
3537
3538
3539- CONFIG_ENV_IS_IN_EEPROM:
3540
3541	Use this if you have an EEPROM or similar serial access
3542	device and a driver for it.
3543
3544	- CONFIG_ENV_OFFSET:
3545	- CONFIG_ENV_SIZE:
3546
3547	  These two #defines specify the offset and size of the
3548	  environment area within the total memory of your EEPROM.
3549
3550	- CONFIG_SYS_I2C_EEPROM_ADDR:
3551	  If defined, specified the chip address of the EEPROM device.
3552	  The default address is zero.
3553
3554	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3555	  If defined, the number of bits used to address bytes in a
3556	  single page in the EEPROM device.  A 64 byte page, for example
3557	  would require six bits.
3558
3559	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3560	  If defined, the number of milliseconds to delay between
3561	  page writes.	The default is zero milliseconds.
3562
3563	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3564	  The length in bytes of the EEPROM memory array address.  Note
3565	  that this is NOT the chip address length!
3566
3567	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3568	  EEPROM chips that implement "address overflow" are ones
3569	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3570	  address and the extra bits end up in the "chip address" bit
3571	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3572	  byte chips.
3573
3574	  Note that we consider the length of the address field to
3575	  still be one byte because the extra address bits are hidden
3576	  in the chip address.
3577
3578	- CONFIG_SYS_EEPROM_SIZE:
3579	  The size in bytes of the EEPROM device.
3580
3581	- CONFIG_ENV_EEPROM_IS_ON_I2C
3582	  define this, if you have I2C and SPI activated, and your
3583	  EEPROM, which holds the environment, is on the I2C bus.
3584
3585	- CONFIG_I2C_ENV_EEPROM_BUS
3586	  if you have an Environment on an EEPROM reached over
3587	  I2C muxes, you can define here, how to reach this
3588	  EEPROM. For example:
3589
3590	  #define CONFIG_I2C_ENV_EEPROM_BUS	  "pca9547:70:d\0"
3591
3592	  EEPROM which holds the environment, is reached over
3593	  a pca9547 i2c mux with address 0x70, channel 3.
3594
3595- CONFIG_ENV_IS_IN_DATAFLASH:
3596
3597	Define this if you have a DataFlash memory device which you
3598	want to use for the environment.
3599
3600	- CONFIG_ENV_OFFSET:
3601	- CONFIG_ENV_ADDR:
3602	- CONFIG_ENV_SIZE:
3603
3604	  These three #defines specify the offset and size of the
3605	  environment area within the total memory of your DataFlash placed
3606	  at the specified address.
3607
3608- CONFIG_ENV_IS_IN_REMOTE:
3609
3610	Define this if you have a remote memory space which you
3611	want to use for the local device's environment.
3612
3613	- CONFIG_ENV_ADDR:
3614	- CONFIG_ENV_SIZE:
3615
3616	  These two #defines specify the address and size of the
3617	  environment area within the remote memory space. The
3618	  local device can get the environment from remote memory
3619	  space by SRIO or PCIE links.
3620
3621BE CAREFUL! For some special cases, the local device can not use
3622"saveenv" command. For example, the local device will get the
3623environment stored in a remote NOR flash by SRIO or PCIE link,
3624but it can not erase, write this NOR flash by SRIO or PCIE interface.
3625
3626- CONFIG_ENV_IS_IN_NAND:
3627
3628	Define this if you have a NAND device which you want to use
3629	for the environment.
3630
3631	- CONFIG_ENV_OFFSET:
3632	- CONFIG_ENV_SIZE:
3633
3634	  These two #defines specify the offset and size of the environment
3635	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3636	  aligned to an erase block boundary.
3637
3638	- CONFIG_ENV_OFFSET_REDUND (optional):
3639
3640	  This setting describes a second storage area of CONFIG_ENV_SIZE
3641	  size used to hold a redundant copy of the environment data, so
3642	  that there is a valid backup copy in case there is a power failure
3643	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
3644	  aligned to an erase block boundary.
3645
3646	- CONFIG_ENV_RANGE (optional):
3647
3648	  Specifies the length of the region in which the environment
3649	  can be written.  This should be a multiple of the NAND device's
3650	  block size.  Specifying a range with more erase blocks than
3651	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
3652	  the range to be avoided.
3653
3654	- CONFIG_ENV_OFFSET_OOB (optional):
3655
3656	  Enables support for dynamically retrieving the offset of the
3657	  environment from block zero's out-of-band data.  The
3658	  "nand env.oob" command can be used to record this offset.
3659	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
3660	  using CONFIG_ENV_OFFSET_OOB.
3661
3662- CONFIG_NAND_ENV_DST
3663
3664	Defines address in RAM to which the nand_spl code should copy the
3665	environment. If redundant environment is used, it will be copied to
3666	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3667
3668- CONFIG_ENV_IS_IN_UBI:
3669
3670	Define this if you have an UBI volume that you want to use for the
3671	environment.  This has the benefit of wear-leveling the environment
3672	accesses, which is important on NAND.
3673
3674	- CONFIG_ENV_UBI_PART:
3675
3676	  Define this to a string that is the mtd partition containing the UBI.
3677
3678	- CONFIG_ENV_UBI_VOLUME:
3679
3680	  Define this to the name of the volume that you want to store the
3681	  environment in.
3682
3683	- CONFIG_ENV_UBI_VOLUME_REDUND:
3684
3685	  Define this to the name of another volume to store a second copy of
3686	  the environment in.  This will enable redundant environments in UBI.
3687	  It is assumed that both volumes are in the same MTD partition.
3688
3689	- CONFIG_UBI_SILENCE_MSG
3690	- CONFIG_UBIFS_SILENCE_MSG
3691
3692	  You will probably want to define these to avoid a really noisy system
3693	  when storing the env in UBI.
3694
3695- CONFIG_ENV_IS_IN_MMC:
3696
3697	Define this if you have an MMC device which you want to use for the
3698	environment.
3699
3700	- CONFIG_SYS_MMC_ENV_DEV:
3701
3702	  Specifies which MMC device the environment is stored in.
3703
3704	- CONFIG_SYS_MMC_ENV_PART (optional):
3705
3706	  Specifies which MMC partition the environment is stored in. If not
3707	  set, defaults to partition 0, the user area. Common values might be
3708	  1 (first MMC boot partition), 2 (second MMC boot partition).
3709
3710	- CONFIG_ENV_OFFSET:
3711	- CONFIG_ENV_SIZE:
3712
3713	  These two #defines specify the offset and size of the environment
3714	  area within the specified MMC device.
3715
3716	  If offset is positive (the usual case), it is treated as relative to
3717	  the start of the MMC partition. If offset is negative, it is treated
3718	  as relative to the end of the MMC partition. This can be useful if
3719	  your board may be fitted with different MMC devices, which have
3720	  different sizes for the MMC partitions, and you always want the
3721	  environment placed at the very end of the partition, to leave the
3722	  maximum possible space before it, to store other data.
3723
3724	  These two values are in units of bytes, but must be aligned to an
3725	  MMC sector boundary.
3726
3727	- CONFIG_ENV_OFFSET_REDUND (optional):
3728
3729	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
3730	  hold a redundant copy of the environment data. This provides a
3731	  valid backup copy in case the other copy is corrupted, e.g. due
3732	  to a power failure during a "saveenv" operation.
3733
3734	  This value may also be positive or negative; this is handled in the
3735	  same way as CONFIG_ENV_OFFSET.
3736
3737	  This value is also in units of bytes, but must also be aligned to
3738	  an MMC sector boundary.
3739
3740	- CONFIG_ENV_SIZE_REDUND (optional):
3741
3742	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
3743	  set. If this value is set, it must be set to the same value as
3744	  CONFIG_ENV_SIZE.
3745
3746- CONFIG_SYS_SPI_INIT_OFFSET
3747
3748	Defines offset to the initial SPI buffer area in DPRAM. The
3749	area is used at an early stage (ROM part) if the environment
3750	is configured to reside in the SPI EEPROM: We need a 520 byte
3751	scratch DPRAM area. It is used between the two initialization
3752	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
3753	to be a good choice since it makes it far enough from the
3754	start of the data area as well as from the stack pointer.
3755
3756Please note that the environment is read-only until the monitor
3757has been relocated to RAM and a RAM copy of the environment has been
3758created; also, when using EEPROM you will have to use getenv_f()
3759until then to read environment variables.
3760
3761The environment is protected by a CRC32 checksum. Before the monitor
3762is relocated into RAM, as a result of a bad CRC you will be working
3763with the compiled-in default environment - *silently*!!! [This is
3764necessary, because the first environment variable we need is the
3765"baudrate" setting for the console - if we have a bad CRC, we don't
3766have any device yet where we could complain.]
3767
3768Note: once the monitor has been relocated, then it will complain if
3769the default environment is used; a new CRC is computed as soon as you
3770use the "saveenv" command to store a valid environment.
3771
3772- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3773		Echo the inverted Ethernet link state to the fault LED.
3774
3775		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3776		      also needs to be defined.
3777
3778- CONFIG_SYS_FAULT_MII_ADDR:
3779		MII address of the PHY to check for the Ethernet link state.
3780
3781- CONFIG_NS16550_MIN_FUNCTIONS:
3782		Define this if you desire to only have use of the NS16550_init
3783		and NS16550_putc functions for the serial driver located at
3784		drivers/serial/ns16550.c.  This option is useful for saving
3785		space for already greatly restricted images, including but not
3786		limited to NAND_SPL configurations.
3787
3788- CONFIG_DISPLAY_BOARDINFO
3789		Display information about the board that U-Boot is running on
3790		when U-Boot starts up. The board function checkboard() is called
3791		to do this.
3792
3793- CONFIG_DISPLAY_BOARDINFO_LATE
3794		Similar to the previous option, but display this information
3795		later, once stdio is running and output goes to the LCD, if
3796		present.
3797
3798Low Level (hardware related) configuration options:
3799---------------------------------------------------
3800
3801- CONFIG_SYS_CACHELINE_SIZE:
3802		Cache Line Size of the CPU.
3803
3804- CONFIG_SYS_DEFAULT_IMMR:
3805		Default address of the IMMR after system reset.
3806
3807		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
3808		and RPXsuper) to be able to adjust the position of
3809		the IMMR register after a reset.
3810
3811- CONFIG_SYS_CCSRBAR_DEFAULT:
3812		Default (power-on reset) physical address of CCSR on Freescale
3813		PowerPC SOCs.
3814
3815- CONFIG_SYS_CCSRBAR:
3816		Virtual address of CCSR.  On a 32-bit build, this is typically
3817		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3818
3819		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
3820		for cross-platform code that uses that macro instead.
3821
3822- CONFIG_SYS_CCSRBAR_PHYS:
3823		Physical address of CCSR.  CCSR can be relocated to a new
3824		physical address, if desired.  In this case, this macro should
3825		be set to that address.	 Otherwise, it should be set to the
3826		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3827		is typically relocated on 36-bit builds.  It is recommended
3828		that this macro be defined via the _HIGH and _LOW macros:
3829
3830		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3831			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3832
3833- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3834		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3835		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3836		used in assembly code, so it must not contain typecasts or
3837		integer size suffixes (e.g. "ULL").
3838
3839- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3840		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3841		used in assembly code, so it must not contain typecasts or
3842		integer size suffixes (e.g. "ULL").
3843
3844- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3845		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3846		forced to a value that ensures that CCSR is not relocated.
3847
3848- Floppy Disk Support:
3849		CONFIG_SYS_FDC_DRIVE_NUMBER
3850
3851		the default drive number (default value 0)
3852
3853		CONFIG_SYS_ISA_IO_STRIDE
3854
3855		defines the spacing between FDC chipset registers
3856		(default value 1)
3857
3858		CONFIG_SYS_ISA_IO_OFFSET
3859
3860		defines the offset of register from address. It
3861		depends on which part of the data bus is connected to
3862		the FDC chipset. (default value 0)
3863
3864		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3865		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3866		default value.
3867
3868		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3869		fdc_hw_init() is called at the beginning of the FDC
3870		setup. fdc_hw_init() must be provided by the board
3871		source code. It is used to make hardware dependant
3872		initializations.
3873
3874- CONFIG_IDE_AHB:
3875		Most IDE controllers were designed to be connected with PCI
3876		interface. Only few of them were designed for AHB interface.
3877		When software is doing ATA command and data transfer to
3878		IDE devices through IDE-AHB controller, some additional
3879		registers accessing to these kind of IDE-AHB controller
3880		is requierd.
3881
3882- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3883		DO NOT CHANGE unless you know exactly what you're
3884		doing! (11-4) [MPC8xx/82xx systems only]
3885
3886- CONFIG_SYS_INIT_RAM_ADDR:
3887
3888		Start address of memory area that can be used for
3889		initial data and stack; please note that this must be
3890		writable memory that is working WITHOUT special
3891		initialization, i. e. you CANNOT use normal RAM which
3892		will become available only after programming the
3893		memory controller and running certain initialization
3894		sequences.
3895
3896		U-Boot uses the following memory types:
3897		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
3898		- MPC824X: data cache
3899		- PPC4xx:  data cache
3900
3901- CONFIG_SYS_GBL_DATA_OFFSET:
3902
3903		Offset of the initial data structure in the memory
3904		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3905		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3906		data is located at the end of the available space
3907		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3908		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
3909		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3910		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3911
3912	Note:
3913		On the MPC824X (or other systems that use the data
3914		cache for initial memory) the address chosen for
3915		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3916		point to an otherwise UNUSED address space between
3917		the top of RAM and the start of the PCI space.
3918
3919- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
3920
3921- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
3922
3923- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
3924
3925- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
3926
3927- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
3928
3929- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3930
3931- CONFIG_SYS_OR_TIMING_SDRAM:
3932		SDRAM timing
3933
3934- CONFIG_SYS_MAMR_PTA:
3935		periodic timer for refresh
3936
3937- CONFIG_SYS_DER:	Debug Event Register (37-47)
3938
3939- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3940  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3941  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3942  CONFIG_SYS_BR1_PRELIM:
3943		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3944
3945- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3946  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3947  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3948		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3949
3950- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
3951  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
3952		Machine Mode Register and Memory Periodic Timer
3953		Prescaler definitions (SDRAM timing)
3954
3955- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
3956		enable I2C microcode relocation patch (MPC8xx);
3957		define relocation offset in DPRAM [DSP2]
3958
3959- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
3960		enable SMC microcode relocation patch (MPC8xx);
3961		define relocation offset in DPRAM [SMC1]
3962
3963- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
3964		enable SPI microcode relocation patch (MPC8xx);
3965		define relocation offset in DPRAM [SCC4]
3966
3967- CONFIG_SYS_USE_OSCCLK:
3968		Use OSCM clock mode on MBX8xx board. Be careful,
3969		wrong setting might damage your board. Read
3970		doc/README.MBX before setting this variable!
3971
3972- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
3973		Offset of the bootmode word in DPRAM used by post
3974		(Power On Self Tests). This definition overrides
3975		#define'd default value in commproc.h resp.
3976		cpm_8260.h.
3977
3978- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
3979  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
3980  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
3981  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
3982  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
3983  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
3984  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
3985  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
3986		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
3987
3988- CONFIG_PCI_DISABLE_PCIE:
3989		Disable PCI-Express on systems where it is supported but not
3990		required.
3991
3992- CONFIG_PCI_ENUM_ONLY
3993		Only scan through and get the devices on the busses.
3994		Don't do any setup work, presumably because someone or
3995		something has already done it, and we don't need to do it
3996		a second time.	Useful for platforms that are pre-booted
3997		by coreboot or similar.
3998
3999- CONFIG_PCI_INDIRECT_BRIDGE:
4000		Enable support for indirect PCI bridges.
4001
4002- CONFIG_SYS_SRIO:
4003		Chip has SRIO or not
4004
4005- CONFIG_SRIO1:
4006		Board has SRIO 1 port available
4007
4008- CONFIG_SRIO2:
4009		Board has SRIO 2 port available
4010
4011- CONFIG_SRIO_PCIE_BOOT_MASTER
4012		Board can support master function for Boot from SRIO and PCIE
4013
4014- CONFIG_SYS_SRIOn_MEM_VIRT:
4015		Virtual Address of SRIO port 'n' memory region
4016
4017- CONFIG_SYS_SRIOn_MEM_PHYS:
4018		Physical Address of SRIO port 'n' memory region
4019
4020- CONFIG_SYS_SRIOn_MEM_SIZE:
4021		Size of SRIO port 'n' memory region
4022
4023- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4024		Defined to tell the NAND controller that the NAND chip is using
4025		a 16 bit bus.
4026		Not all NAND drivers use this symbol.
4027		Example of drivers that use it:
4028		- drivers/mtd/nand/ndfc.c
4029		- drivers/mtd/nand/mxc_nand.c
4030
4031- CONFIG_SYS_NDFC_EBC0_CFG
4032		Sets the EBC0_CFG register for the NDFC. If not defined
4033		a default value will be used.
4034
4035- CONFIG_SPD_EEPROM
4036		Get DDR timing information from an I2C EEPROM. Common
4037		with pluggable memory modules such as SODIMMs
4038
4039  SPD_EEPROM_ADDRESS
4040		I2C address of the SPD EEPROM
4041
4042- CONFIG_SYS_SPD_BUS_NUM
4043		If SPD EEPROM is on an I2C bus other than the first
4044		one, specify here. Note that the value must resolve
4045		to something your driver can deal with.
4046
4047- CONFIG_SYS_DDR_RAW_TIMING
4048		Get DDR timing information from other than SPD. Common with
4049		soldered DDR chips onboard without SPD. DDR raw timing
4050		parameters are extracted from datasheet and hard-coded into
4051		header files or board specific files.
4052
4053- CONFIG_FSL_DDR_INTERACTIVE
4054		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4055
4056- CONFIG_SYS_83XX_DDR_USES_CS0
4057		Only for 83xx systems. If specified, then DDR should
4058		be configured using CS0 and CS1 instead of CS2 and CS3.
4059
4060- CONFIG_ETHER_ON_FEC[12]
4061		Define to enable FEC[12] on a 8xx series processor.
4062
4063- CONFIG_FEC[12]_PHY
4064		Define to the hardcoded PHY address which corresponds
4065		to the given FEC; i. e.
4066			#define CONFIG_FEC1_PHY 4
4067		means that the PHY with address 4 is connected to FEC1
4068
4069		When set to -1, means to probe for first available.
4070
4071- CONFIG_FEC[12]_PHY_NORXERR
4072		The PHY does not have a RXERR line (RMII only).
4073		(so program the FEC to ignore it).
4074
4075- CONFIG_RMII
4076		Enable RMII mode for all FECs.
4077		Note that this is a global option, we can't
4078		have one FEC in standard MII mode and another in RMII mode.
4079
4080- CONFIG_CRC32_VERIFY
4081		Add a verify option to the crc32 command.
4082		The syntax is:
4083
4084		=> crc32 -v <address> <count> <crc32>
4085
4086		Where address/count indicate a memory area
4087		and crc32 is the correct crc32 which the
4088		area should have.
4089
4090- CONFIG_LOOPW
4091		Add the "loopw" memory command. This only takes effect if
4092		the memory commands are activated globally (CONFIG_CMD_MEM).
4093
4094- CONFIG_MX_CYCLIC
4095		Add the "mdc" and "mwc" memory commands. These are cyclic
4096		"md/mw" commands.
4097		Examples:
4098
4099		=> mdc.b 10 4 500
4100		This command will print 4 bytes (10,11,12,13) each 500 ms.
4101
4102		=> mwc.l 100 12345678 10
4103		This command will write 12345678 to address 100 all 10 ms.
4104
4105		This only takes effect if the memory commands are activated
4106		globally (CONFIG_CMD_MEM).
4107
4108- CONFIG_SKIP_LOWLEVEL_INIT
4109		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4110		low level initializations (like setting up the memory
4111		controller) are omitted and/or U-Boot does not
4112		relocate itself into RAM.
4113
4114		Normally this variable MUST NOT be defined. The only
4115		exception is when U-Boot is loaded (to RAM) by some
4116		other boot loader or by a debugger which performs
4117		these initializations itself.
4118
4119- CONFIG_SPL_BUILD
4120		Modifies the behaviour of start.S when compiling a loader
4121		that is executed before the actual U-Boot. E.g. when
4122		compiling a NAND SPL.
4123
4124- CONFIG_SYS_MPC85XX_NO_RESETVEC
4125		Only for 85xx systems. If this variable is specified, the section
4126		.resetvec is not kept and the section .bootpg is placed in the
4127		previous 4k of the .text section.
4128
4129- CONFIG_ARCH_MAP_SYSMEM
4130		Generally U-Boot (and in particular the md command) uses
4131		effective address. It is therefore not necessary to regard
4132		U-Boot address as virtual addresses that need to be translated
4133		to physical addresses. However, sandbox requires this, since
4134		it maintains its own little RAM buffer which contains all
4135		addressable memory. This option causes some memory accesses
4136		to be mapped through map_sysmem() / unmap_sysmem().
4137
4138- CONFIG_USE_ARCH_MEMCPY
4139  CONFIG_USE_ARCH_MEMSET
4140		If these options are used a optimized version of memcpy/memset will
4141		be used if available. These functions may be faster under some
4142		conditions but may increase the binary size.
4143
4144- CONFIG_X86_RESET_VECTOR
4145		If defined, the x86 reset vector code is included. This is not
4146		needed when U-Boot is running from Coreboot.
4147
4148- CONFIG_SYS_MPUCLK
4149		Defines the MPU clock speed (in MHz).
4150
4151		NOTE : currently only supported on AM335x platforms.
4152
4153Freescale QE/FMAN Firmware Support:
4154-----------------------------------
4155
4156The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4157loading of "firmware", which is encoded in the QE firmware binary format.
4158This firmware often needs to be loaded during U-Boot booting, so macros
4159are used to identify the storage device (NOR flash, SPI, etc) and the address
4160within that device.
4161
4162- CONFIG_SYS_QE_FMAN_FW_ADDR
4163	The address in the storage device where the firmware is located.  The
4164	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4165	is also specified.
4166
4167- CONFIG_SYS_QE_FMAN_FW_LENGTH
4168	The maximum possible size of the firmware.  The firmware binary format
4169	has a field that specifies the actual size of the firmware, but it
4170	might not be possible to read any part of the firmware unless some
4171	local storage is allocated to hold the entire firmware first.
4172
4173- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4174	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4175	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4176	virtual address in NOR flash.
4177
4178- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4179	Specifies that QE/FMAN firmware is located in NAND flash.
4180	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4181
4182- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4183	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4184	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4185
4186- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4187	Specifies that QE/FMAN firmware is located on the primary SPI
4188	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4189
4190- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4191	Specifies that QE/FMAN firmware is located in the remote (master)
4192	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4193	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4194	window->master inbound window->master LAW->the ucode address in
4195	master's memory space.
4196
4197Building the Software:
4198======================
4199
4200Building U-Boot has been tested in several native build environments
4201and in many different cross environments. Of course we cannot support
4202all possibly existing versions of cross development tools in all
4203(potentially obsolete) versions. In case of tool chain problems we
4204recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4205which is extensively used to build and test U-Boot.
4206
4207If you are not using a native environment, it is assumed that you
4208have GNU cross compiling tools available in your path. In this case,
4209you must set the environment variable CROSS_COMPILE in your shell.
4210Note that no changes to the Makefile or any other source files are
4211necessary. For example using the ELDK on a 4xx CPU, please enter:
4212
4213	$ CROSS_COMPILE=ppc_4xx-
4214	$ export CROSS_COMPILE
4215
4216Note: If you wish to generate Windows versions of the utilities in
4217      the tools directory you can use the MinGW toolchain
4218      (http://www.mingw.org).  Set your HOST tools to the MinGW
4219      toolchain and execute 'make tools'.  For example:
4220
4221       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4222
4223      Binaries such as tools/mkimage.exe will be created which can
4224      be executed on computers running Windows.
4225
4226U-Boot is intended to be simple to build. After installing the
4227sources you must configure U-Boot for one specific board type. This
4228is done by typing:
4229
4230	make NAME_config
4231
4232where "NAME_config" is the name of one of the existing configu-
4233rations; see boards.cfg for supported names.
4234
4235Note: for some board special configuration names may exist; check if
4236      additional information is available from the board vendor; for
4237      instance, the TQM823L systems are available without (standard)
4238      or with LCD support. You can select such additional "features"
4239      when choosing the configuration, i. e.
4240
4241      make TQM823L_config
4242	- will configure for a plain TQM823L, i. e. no LCD support
4243
4244      make TQM823L_LCD_config
4245	- will configure for a TQM823L with U-Boot console on LCD
4246
4247      etc.
4248
4249
4250Finally, type "make all", and you should get some working U-Boot
4251images ready for download to / installation on your system:
4252
4253- "u-boot.bin" is a raw binary image
4254- "u-boot" is an image in ELF binary format
4255- "u-boot.srec" is in Motorola S-Record format
4256
4257By default the build is performed locally and the objects are saved
4258in the source directory. One of the two methods can be used to change
4259this behavior and build U-Boot to some external directory:
4260
42611. Add O= to the make command line invocations:
4262
4263	make O=/tmp/build distclean
4264	make O=/tmp/build NAME_config
4265	make O=/tmp/build all
4266
42672. Set environment variable BUILD_DIR to point to the desired location:
4268
4269	export BUILD_DIR=/tmp/build
4270	make distclean
4271	make NAME_config
4272	make all
4273
4274Note that the command line "O=" setting overrides the BUILD_DIR environment
4275variable.
4276
4277
4278Please be aware that the Makefiles assume you are using GNU make, so
4279for instance on NetBSD you might need to use "gmake" instead of
4280native "make".
4281
4282
4283If the system board that you have is not listed, then you will need
4284to port U-Boot to your hardware platform. To do this, follow these
4285steps:
4286
42871.  Add a new configuration option for your board to the toplevel
4288    "boards.cfg" file, using the existing entries as examples.
4289    Follow the instructions there to keep the boards in order.
42902.  Create a new directory to hold your board specific code. Add any
4291    files you need. In your board directory, you will need at least
4292    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
42933.  Create a new configuration file "include/configs/<board>.h" for
4294    your board
42953.  If you're porting U-Boot to a new CPU, then also create a new
4296    directory to hold your CPU specific code. Add any files you need.
42974.  Run "make <board>_config" with your new name.
42985.  Type "make", and you should get a working "u-boot.srec" file
4299    to be installed on your target system.
43006.  Debug and solve any problems that might arise.
4301    [Of course, this last step is much harder than it sounds.]
4302
4303
4304Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4305==============================================================
4306
4307If you have modified U-Boot sources (for instance added a new board
4308or support for new devices, a new CPU, etc.) you are expected to
4309provide feedback to the other developers. The feedback normally takes
4310the form of a "patch", i. e. a context diff against a certain (latest
4311official or latest in the git repository) version of U-Boot sources.
4312
4313But before you submit such a patch, please verify that your modifi-
4314cation did not break existing code. At least make sure that *ALL* of
4315the supported boards compile WITHOUT ANY compiler warnings. To do so,
4316just run the "MAKEALL" script, which will configure and build U-Boot
4317for ALL supported system. Be warned, this will take a while. You can
4318select which (cross) compiler to use by passing a `CROSS_COMPILE'
4319environment variable to the script, i. e. to use the ELDK cross tools
4320you can type
4321
4322	CROSS_COMPILE=ppc_8xx- MAKEALL
4323
4324or to build on a native PowerPC system you can type
4325
4326	CROSS_COMPILE=' ' MAKEALL
4327
4328When using the MAKEALL script, the default behaviour is to build
4329U-Boot in the source directory. This location can be changed by
4330setting the BUILD_DIR environment variable. Also, for each target
4331built, the MAKEALL script saves two log files (<target>.ERR and
4332<target>.MAKEALL) in the <source dir>/LOG directory. This default
4333location can be changed by setting the MAKEALL_LOGDIR environment
4334variable. For example:
4335
4336	export BUILD_DIR=/tmp/build
4337	export MAKEALL_LOGDIR=/tmp/log
4338	CROSS_COMPILE=ppc_8xx- MAKEALL
4339
4340With the above settings build objects are saved in the /tmp/build,
4341log files are saved in the /tmp/log and the source tree remains clean
4342during the whole build process.
4343
4344
4345See also "U-Boot Porting Guide" below.
4346
4347
4348Monitor Commands - Overview:
4349============================
4350
4351go	- start application at address 'addr'
4352run	- run commands in an environment variable
4353bootm	- boot application image from memory
4354bootp	- boot image via network using BootP/TFTP protocol
4355bootz   - boot zImage from memory
4356tftpboot- boot image via network using TFTP protocol
4357	       and env variables "ipaddr" and "serverip"
4358	       (and eventually "gatewayip")
4359tftpput - upload a file via network using TFTP protocol
4360rarpboot- boot image via network using RARP/TFTP protocol
4361diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4362loads	- load S-Record file over serial line
4363loadb	- load binary file over serial line (kermit mode)
4364md	- memory display
4365mm	- memory modify (auto-incrementing)
4366nm	- memory modify (constant address)
4367mw	- memory write (fill)
4368cp	- memory copy
4369cmp	- memory compare
4370crc32	- checksum calculation
4371i2c	- I2C sub-system
4372sspi	- SPI utility commands
4373base	- print or set address offset
4374printenv- print environment variables
4375setenv	- set environment variables
4376saveenv - save environment variables to persistent storage
4377protect - enable or disable FLASH write protection
4378erase	- erase FLASH memory
4379flinfo	- print FLASH memory information
4380nand	- NAND memory operations (see doc/README.nand)
4381bdinfo	- print Board Info structure
4382iminfo	- print header information for application image
4383coninfo - print console devices and informations
4384ide	- IDE sub-system
4385loop	- infinite loop on address range
4386loopw	- infinite write loop on address range
4387mtest	- simple RAM test
4388icache	- enable or disable instruction cache
4389dcache	- enable or disable data cache
4390reset	- Perform RESET of the CPU
4391echo	- echo args to console
4392version - print monitor version
4393help	- print online help
4394?	- alias for 'help'
4395
4396
4397Monitor Commands - Detailed Description:
4398========================================
4399
4400TODO.
4401
4402For now: just type "help <command>".
4403
4404
4405Environment Variables:
4406======================
4407
4408U-Boot supports user configuration using Environment Variables which
4409can be made persistent by saving to Flash memory.
4410
4411Environment Variables are set using "setenv", printed using
4412"printenv", and saved to Flash using "saveenv". Using "setenv"
4413without a value can be used to delete a variable from the
4414environment. As long as you don't save the environment you are
4415working with an in-memory copy. In case the Flash area containing the
4416environment is erased by accident, a default environment is provided.
4417
4418Some configuration options can be set using Environment Variables.
4419
4420List of environment variables (most likely not complete):
4421
4422  baudrate	- see CONFIG_BAUDRATE
4423
4424  bootdelay	- see CONFIG_BOOTDELAY
4425
4426  bootcmd	- see CONFIG_BOOTCOMMAND
4427
4428  bootargs	- Boot arguments when booting an RTOS image
4429
4430  bootfile	- Name of the image to load with TFTP
4431
4432  bootm_low	- Memory range available for image processing in the bootm
4433		  command can be restricted. This variable is given as
4434		  a hexadecimal number and defines lowest address allowed
4435		  for use by the bootm command. See also "bootm_size"
4436		  environment variable. Address defined by "bootm_low" is
4437		  also the base of the initial memory mapping for the Linux
4438		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4439		  bootm_mapsize.
4440
4441  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4442		  This variable is given as a hexadecimal number and it
4443		  defines the size of the memory region starting at base
4444		  address bootm_low that is accessible by the Linux kernel
4445		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4446		  as the default value if it is defined, and bootm_size is
4447		  used otherwise.
4448
4449  bootm_size	- Memory range available for image processing in the bootm
4450		  command can be restricted. This variable is given as
4451		  a hexadecimal number and defines the size of the region
4452		  allowed for use by the bootm command. See also "bootm_low"
4453		  environment variable.
4454
4455  updatefile	- Location of the software update file on a TFTP server, used
4456		  by the automatic software update feature. Please refer to
4457		  documentation in doc/README.update for more details.
4458
4459  autoload	- if set to "no" (any string beginning with 'n'),
4460		  "bootp" will just load perform a lookup of the
4461		  configuration from the BOOTP server, but not try to
4462		  load any image using TFTP
4463
4464  autostart	- if set to "yes", an image loaded using the "bootp",
4465		  "rarpboot", "tftpboot" or "diskboot" commands will
4466		  be automatically started (by internally calling
4467		  "bootm")
4468
4469		  If set to "no", a standalone image passed to the
4470		  "bootm" command will be copied to the load address
4471		  (and eventually uncompressed), but NOT be started.
4472		  This can be used to load and uncompress arbitrary
4473		  data.
4474
4475  fdt_high	- if set this restricts the maximum address that the
4476		  flattened device tree will be copied into upon boot.
4477		  For example, if you have a system with 1 GB memory
4478		  at physical address 0x10000000, while Linux kernel
4479		  only recognizes the first 704 MB as low memory, you
4480		  may need to set fdt_high as 0x3C000000 to have the
4481		  device tree blob be copied to the maximum address
4482		  of the 704 MB low memory, so that Linux kernel can
4483		  access it during the boot procedure.
4484
4485		  If this is set to the special value 0xFFFFFFFF then
4486		  the fdt will not be copied at all on boot.  For this
4487		  to work it must reside in writable memory, have
4488		  sufficient padding on the end of it for u-boot to
4489		  add the information it needs into it, and the memory
4490		  must be accessible by the kernel.
4491
4492  fdtcontroladdr- if set this is the address of the control flattened
4493		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4494		  defined.
4495
4496  i2cfast	- (PPC405GP|PPC405EP only)
4497		  if set to 'y' configures Linux I2C driver for fast
4498		  mode (400kHZ). This environment variable is used in
4499		  initialization code. So, for changes to be effective
4500		  it must be saved and board must be reset.
4501
4502  initrd_high	- restrict positioning of initrd images:
4503		  If this variable is not set, initrd images will be
4504		  copied to the highest possible address in RAM; this
4505		  is usually what you want since it allows for
4506		  maximum initrd size. If for some reason you want to
4507		  make sure that the initrd image is loaded below the
4508		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4509		  variable to a value of "no" or "off" or "0".
4510		  Alternatively, you can set it to a maximum upper
4511		  address to use (U-Boot will still check that it
4512		  does not overwrite the U-Boot stack and data).
4513
4514		  For instance, when you have a system with 16 MB
4515		  RAM, and want to reserve 4 MB from use by Linux,
4516		  you can do this by adding "mem=12M" to the value of
4517		  the "bootargs" variable. However, now you must make
4518		  sure that the initrd image is placed in the first
4519		  12 MB as well - this can be done with
4520
4521		  setenv initrd_high 00c00000
4522
4523		  If you set initrd_high to 0xFFFFFFFF, this is an
4524		  indication to U-Boot that all addresses are legal
4525		  for the Linux kernel, including addresses in flash
4526		  memory. In this case U-Boot will NOT COPY the
4527		  ramdisk at all. This may be useful to reduce the
4528		  boot time on your system, but requires that this
4529		  feature is supported by your Linux kernel.
4530
4531  ipaddr	- IP address; needed for tftpboot command
4532
4533  loadaddr	- Default load address for commands like "bootp",
4534		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4535
4536  loads_echo	- see CONFIG_LOADS_ECHO
4537
4538  serverip	- TFTP server IP address; needed for tftpboot command
4539
4540  bootretry	- see CONFIG_BOOT_RETRY_TIME
4541
4542  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4543
4544  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4545
4546  ethprime	- controls which interface is used first.
4547
4548  ethact	- controls which interface is currently active.
4549		  For example you can do the following
4550
4551		  => setenv ethact FEC
4552		  => ping 192.168.0.1 # traffic sent on FEC
4553		  => setenv ethact SCC
4554		  => ping 10.0.0.1 # traffic sent on SCC
4555
4556  ethrotate	- When set to "no" U-Boot does not go through all
4557		  available network interfaces.
4558		  It just stays at the currently selected interface.
4559
4560  netretry	- When set to "no" each network operation will
4561		  either succeed or fail without retrying.
4562		  When set to "once" the network operation will
4563		  fail when all the available network interfaces
4564		  are tried once without success.
4565		  Useful on scripts which control the retry operation
4566		  themselves.
4567
4568  npe_ucode	- set load address for the NPE microcode
4569
4570  tftpsrcport	- If this is set, the value is used for TFTP's
4571		  UDP source port.
4572
4573  tftpdstport	- If this is set, the value is used for TFTP's UDP
4574		  destination port instead of the Well Know Port 69.
4575
4576  tftpblocksize - Block size to use for TFTP transfers; if not set,
4577		  we use the TFTP server's default block size
4578
4579  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4580		  seconds, minimum value is 1000 = 1 second). Defines
4581		  when a packet is considered to be lost so it has to
4582		  be retransmitted. The default is 5000 = 5 seconds.
4583		  Lowering this value may make downloads succeed
4584		  faster in networks with high packet loss rates or
4585		  with unreliable TFTP servers.
4586
4587  vlan		- When set to a value < 4095 the traffic over
4588		  Ethernet is encapsulated/received over 802.1q
4589		  VLAN tagged frames.
4590
4591The following image location variables contain the location of images
4592used in booting. The "Image" column gives the role of the image and is
4593not an environment variable name. The other columns are environment
4594variable names. "File Name" gives the name of the file on a TFTP
4595server, "RAM Address" gives the location in RAM the image will be
4596loaded to, and "Flash Location" gives the image's address in NOR
4597flash or offset in NAND flash.
4598
4599*Note* - these variables don't have to be defined for all boards, some
4600boards currenlty use other variables for these purposes, and some
4601boards use these variables for other purposes.
4602
4603Image		    File Name	     RAM Address       Flash Location
4604-----		    ---------	     -----------       --------------
4605u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4606Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4607device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4608ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4609
4610The following environment variables may be used and automatically
4611updated by the network boot commands ("bootp" and "rarpboot"),
4612depending the information provided by your boot server:
4613
4614  bootfile	- see above
4615  dnsip		- IP address of your Domain Name Server
4616  dnsip2	- IP address of your secondary Domain Name Server
4617  gatewayip	- IP address of the Gateway (Router) to use
4618  hostname	- Target hostname
4619  ipaddr	- see above
4620  netmask	- Subnet Mask
4621  rootpath	- Pathname of the root filesystem on the NFS server
4622  serverip	- see above
4623
4624
4625There are two special Environment Variables:
4626
4627  serial#	- contains hardware identification information such
4628		  as type string and/or serial number
4629  ethaddr	- Ethernet address
4630
4631These variables can be set only once (usually during manufacturing of
4632the board). U-Boot refuses to delete or overwrite these variables
4633once they have been set once.
4634
4635
4636Further special Environment Variables:
4637
4638  ver		- Contains the U-Boot version string as printed
4639		  with the "version" command. This variable is
4640		  readonly (see CONFIG_VERSION_VARIABLE).
4641
4642
4643Please note that changes to some configuration parameters may take
4644only effect after the next boot (yes, that's just like Windoze :-).
4645
4646
4647Callback functions for environment variables:
4648---------------------------------------------
4649
4650For some environment variables, the behavior of u-boot needs to change
4651when their values are changed.  This functionailty allows functions to
4652be associated with arbitrary variables.  On creation, overwrite, or
4653deletion, the callback will provide the opportunity for some side
4654effect to happen or for the change to be rejected.
4655
4656The callbacks are named and associated with a function using the
4657U_BOOT_ENV_CALLBACK macro in your board or driver code.
4658
4659These callbacks are associated with variables in one of two ways.  The
4660static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
4661in the board configuration to a string that defines a list of
4662associations.  The list must be in the following format:
4663
4664	entry = variable_name[:callback_name]
4665	list = entry[,list]
4666
4667If the callback name is not specified, then the callback is deleted.
4668Spaces are also allowed anywhere in the list.
4669
4670Callbacks can also be associated by defining the ".callbacks" variable
4671with the same list format above.  Any association in ".callbacks" will
4672override any association in the static list. You can define
4673CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
4674".callbacks" envirnoment variable in the default or embedded environment.
4675
4676
4677Command Line Parsing:
4678=====================
4679
4680There are two different command line parsers available with U-Boot:
4681the old "simple" one, and the much more powerful "hush" shell:
4682
4683Old, simple command line parser:
4684--------------------------------
4685
4686- supports environment variables (through setenv / saveenv commands)
4687- several commands on one line, separated by ';'
4688- variable substitution using "... ${name} ..." syntax
4689- special characters ('$', ';') can be escaped by prefixing with '\',
4690  for example:
4691	setenv bootcmd bootm \${address}
4692- You can also escape text by enclosing in single apostrophes, for example:
4693	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4694
4695Hush shell:
4696-----------
4697
4698- similar to Bourne shell, with control structures like
4699  if...then...else...fi, for...do...done; while...do...done,
4700  until...do...done, ...
4701- supports environment ("global") variables (through setenv / saveenv
4702  commands) and local shell variables (through standard shell syntax
4703  "name=value"); only environment variables can be used with "run"
4704  command
4705
4706General rules:
4707--------------
4708
4709(1) If a command line (or an environment variable executed by a "run"
4710    command) contains several commands separated by semicolon, and
4711    one of these commands fails, then the remaining commands will be
4712    executed anyway.
4713
4714(2) If you execute several variables with one call to run (i. e.
4715    calling run with a list of variables as arguments), any failing
4716    command will cause "run" to terminate, i. e. the remaining
4717    variables are not executed.
4718
4719Note for Redundant Ethernet Interfaces:
4720=======================================
4721
4722Some boards come with redundant Ethernet interfaces; U-Boot supports
4723such configurations and is capable of automatic selection of a
4724"working" interface when needed. MAC assignment works as follows:
4725
4726Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4727MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4728"eth1addr" (=>eth1), "eth2addr", ...
4729
4730If the network interface stores some valid MAC address (for instance
4731in SROM), this is used as default address if there is NO correspon-
4732ding setting in the environment; if the corresponding environment
4733variable is set, this overrides the settings in the card; that means:
4734
4735o If the SROM has a valid MAC address, and there is no address in the
4736  environment, the SROM's address is used.
4737
4738o If there is no valid address in the SROM, and a definition in the
4739  environment exists, then the value from the environment variable is
4740  used.
4741
4742o If both the SROM and the environment contain a MAC address, and
4743  both addresses are the same, this MAC address is used.
4744
4745o If both the SROM and the environment contain a MAC address, and the
4746  addresses differ, the value from the environment is used and a
4747  warning is printed.
4748
4749o If neither SROM nor the environment contain a MAC address, an error
4750  is raised.
4751
4752If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4753will be programmed into hardware as part of the initialization process.	 This
4754may be skipped by setting the appropriate 'ethmacskip' environment variable.
4755The naming convention is as follows:
4756"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4757
4758Image Formats:
4759==============
4760
4761U-Boot is capable of booting (and performing other auxiliary operations on)
4762images in two formats:
4763
4764New uImage format (FIT)
4765-----------------------
4766
4767Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4768to Flattened Device Tree). It allows the use of images with multiple
4769components (several kernels, ramdisks, etc.), with contents protected by
4770SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4771
4772
4773Old uImage format
4774-----------------
4775
4776Old image format is based on binary files which can be basically anything,
4777preceded by a special header; see the definitions in include/image.h for
4778details; basically, the header defines the following image properties:
4779
4780* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4781  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4782  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4783  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4784  INTEGRITY).
4785* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
4786  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4787  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4788* Compression Type (uncompressed, gzip, bzip2)
4789* Load Address
4790* Entry Point
4791* Image Name
4792* Image Timestamp
4793
4794The header is marked by a special Magic Number, and both the header
4795and the data portions of the image are secured against corruption by
4796CRC32 checksums.
4797
4798
4799Linux Support:
4800==============
4801
4802Although U-Boot should support any OS or standalone application
4803easily, the main focus has always been on Linux during the design of
4804U-Boot.
4805
4806U-Boot includes many features that so far have been part of some
4807special "boot loader" code within the Linux kernel. Also, any
4808"initrd" images to be used are no longer part of one big Linux image;
4809instead, kernel and "initrd" are separate images. This implementation
4810serves several purposes:
4811
4812- the same features can be used for other OS or standalone
4813  applications (for instance: using compressed images to reduce the
4814  Flash memory footprint)
4815
4816- it becomes much easier to port new Linux kernel versions because
4817  lots of low-level, hardware dependent stuff are done by U-Boot
4818
4819- the same Linux kernel image can now be used with different "initrd"
4820  images; of course this also means that different kernel images can
4821  be run with the same "initrd". This makes testing easier (you don't
4822  have to build a new "zImage.initrd" Linux image when you just
4823  change a file in your "initrd"). Also, a field-upgrade of the
4824  software is easier now.
4825
4826
4827Linux HOWTO:
4828============
4829
4830Porting Linux to U-Boot based systems:
4831---------------------------------------
4832
4833U-Boot cannot save you from doing all the necessary modifications to
4834configure the Linux device drivers for use with your target hardware
4835(no, we don't intend to provide a full virtual machine interface to
4836Linux :-).
4837
4838But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4839
4840Just make sure your machine specific header file (for instance
4841include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4842Information structure as we define in include/asm-<arch>/u-boot.h,
4843and make sure that your definition of IMAP_ADDR uses the same value
4844as your U-Boot configuration in CONFIG_SYS_IMMR.
4845
4846
4847Configuring the Linux kernel:
4848-----------------------------
4849
4850No specific requirements for U-Boot. Make sure you have some root
4851device (initial ramdisk, NFS) for your target system.
4852
4853
4854Building a Linux Image:
4855-----------------------
4856
4857With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4858not used. If you use recent kernel source, a new build target
4859"uImage" will exist which automatically builds an image usable by
4860U-Boot. Most older kernels also have support for a "pImage" target,
4861which was introduced for our predecessor project PPCBoot and uses a
4862100% compatible format.
4863
4864Example:
4865
4866	make TQM850L_config
4867	make oldconfig
4868	make dep
4869	make uImage
4870
4871The "uImage" build target uses a special tool (in 'tools/mkimage') to
4872encapsulate a compressed Linux kernel image with header	 information,
4873CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4874
4875* build a standard "vmlinux" kernel image (in ELF binary format):
4876
4877* convert the kernel into a raw binary image:
4878
4879	${CROSS_COMPILE}-objcopy -O binary \
4880				 -R .note -R .comment \
4881				 -S vmlinux linux.bin
4882
4883* compress the binary image:
4884
4885	gzip -9 linux.bin
4886
4887* package compressed binary image for U-Boot:
4888
4889	mkimage -A ppc -O linux -T kernel -C gzip \
4890		-a 0 -e 0 -n "Linux Kernel Image" \
4891		-d linux.bin.gz uImage
4892
4893
4894The "mkimage" tool can also be used to create ramdisk images for use
4895with U-Boot, either separated from the Linux kernel image, or
4896combined into one file. "mkimage" encapsulates the images with a 64
4897byte header containing information about target architecture,
4898operating system, image type, compression method, entry points, time
4899stamp, CRC32 checksums, etc.
4900
4901"mkimage" can be called in two ways: to verify existing images and
4902print the header information, or to build new images.
4903
4904In the first form (with "-l" option) mkimage lists the information
4905contained in the header of an existing U-Boot image; this includes
4906checksum verification:
4907
4908	tools/mkimage -l image
4909	  -l ==> list image header information
4910
4911The second form (with "-d" option) is used to build a U-Boot image
4912from a "data file" which is used as image payload:
4913
4914	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4915		      -n name -d data_file image
4916	  -A ==> set architecture to 'arch'
4917	  -O ==> set operating system to 'os'
4918	  -T ==> set image type to 'type'
4919	  -C ==> set compression type 'comp'
4920	  -a ==> set load address to 'addr' (hex)
4921	  -e ==> set entry point to 'ep' (hex)
4922	  -n ==> set image name to 'name'
4923	  -d ==> use image data from 'datafile'
4924
4925Right now, all Linux kernels for PowerPC systems use the same load
4926address (0x00000000), but the entry point address depends on the
4927kernel version:
4928
4929- 2.2.x kernels have the entry point at 0x0000000C,
4930- 2.3.x and later kernels have the entry point at 0x00000000.
4931
4932So a typical call to build a U-Boot image would read:
4933
4934	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4935	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4936	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4937	> examples/uImage.TQM850L
4938	Image Name:   2.4.4 kernel for TQM850L
4939	Created:      Wed Jul 19 02:34:59 2000
4940	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4941	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4942	Load Address: 0x00000000
4943	Entry Point:  0x00000000
4944
4945To verify the contents of the image (or check for corruption):
4946
4947	-> tools/mkimage -l examples/uImage.TQM850L
4948	Image Name:   2.4.4 kernel for TQM850L
4949	Created:      Wed Jul 19 02:34:59 2000
4950	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4951	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4952	Load Address: 0x00000000
4953	Entry Point:  0x00000000
4954
4955NOTE: for embedded systems where boot time is critical you can trade
4956speed for memory and install an UNCOMPRESSED image instead: this
4957needs more space in Flash, but boots much faster since it does not
4958need to be uncompressed:
4959
4960	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4961	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4962	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4963	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4964	> examples/uImage.TQM850L-uncompressed
4965	Image Name:   2.4.4 kernel for TQM850L
4966	Created:      Wed Jul 19 02:34:59 2000
4967	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4968	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4969	Load Address: 0x00000000
4970	Entry Point:  0x00000000
4971
4972
4973Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4974when your kernel is intended to use an initial ramdisk:
4975
4976	-> tools/mkimage -n 'Simple Ramdisk Image' \
4977	> -A ppc -O linux -T ramdisk -C gzip \
4978	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4979	Image Name:   Simple Ramdisk Image
4980	Created:      Wed Jan 12 14:01:50 2000
4981	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4982	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4983	Load Address: 0x00000000
4984	Entry Point:  0x00000000
4985
4986
4987Installing a Linux Image:
4988-------------------------
4989
4990To downloading a U-Boot image over the serial (console) interface,
4991you must convert the image to S-Record format:
4992
4993	objcopy -I binary -O srec examples/image examples/image.srec
4994
4995The 'objcopy' does not understand the information in the U-Boot
4996image header, so the resulting S-Record file will be relative to
4997address 0x00000000. To load it to a given address, you need to
4998specify the target address as 'offset' parameter with the 'loads'
4999command.
5000
5001Example: install the image to address 0x40100000 (which on the
5002TQM8xxL is in the first Flash bank):
5003
5004	=> erase 40100000 401FFFFF
5005
5006	.......... done
5007	Erased 8 sectors
5008
5009	=> loads 40100000
5010	## Ready for S-Record download ...
5011	~>examples/image.srec
5012	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5013	...
5014	15989 15990 15991 15992
5015	[file transfer complete]
5016	[connected]
5017	## Start Addr = 0x00000000
5018
5019
5020You can check the success of the download using the 'iminfo' command;
5021this includes a checksum verification so you can be sure no data
5022corruption happened:
5023
5024	=> imi 40100000
5025
5026	## Checking Image at 40100000 ...
5027	   Image Name:	 2.2.13 for initrd on TQM850L
5028	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5029	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5030	   Load Address: 00000000
5031	   Entry Point:	 0000000c
5032	   Verifying Checksum ... OK
5033
5034
5035Boot Linux:
5036-----------
5037
5038The "bootm" command is used to boot an application that is stored in
5039memory (RAM or Flash). In case of a Linux kernel image, the contents
5040of the "bootargs" environment variable is passed to the kernel as
5041parameters. You can check and modify this variable using the
5042"printenv" and "setenv" commands:
5043
5044
5045	=> printenv bootargs
5046	bootargs=root=/dev/ram
5047
5048	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5049
5050	=> printenv bootargs
5051	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5052
5053	=> bootm 40020000
5054	## Booting Linux kernel at 40020000 ...
5055	   Image Name:	 2.2.13 for NFS on TQM850L
5056	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5057	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5058	   Load Address: 00000000
5059	   Entry Point:	 0000000c
5060	   Verifying Checksum ... OK
5061	   Uncompressing Kernel Image ... OK
5062	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
5063	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5064	time_init: decrementer frequency = 187500000/60
5065	Calibrating delay loop... 49.77 BogoMIPS
5066	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5067	...
5068
5069If you want to boot a Linux kernel with initial RAM disk, you pass
5070the memory addresses of both the kernel and the initrd image (PPBCOOT
5071format!) to the "bootm" command:
5072
5073	=> imi 40100000 40200000
5074
5075	## Checking Image at 40100000 ...
5076	   Image Name:	 2.2.13 for initrd on TQM850L
5077	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5078	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5079	   Load Address: 00000000
5080	   Entry Point:	 0000000c
5081	   Verifying Checksum ... OK
5082
5083	## Checking Image at 40200000 ...
5084	   Image Name:	 Simple Ramdisk Image
5085	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5086	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5087	   Load Address: 00000000
5088	   Entry Point:	 00000000
5089	   Verifying Checksum ... OK
5090
5091	=> bootm 40100000 40200000
5092	## Booting Linux kernel at 40100000 ...
5093	   Image Name:	 2.2.13 for initrd on TQM850L
5094	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5095	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5096	   Load Address: 00000000
5097	   Entry Point:	 0000000c
5098	   Verifying Checksum ... OK
5099	   Uncompressing Kernel Image ... OK
5100	## Loading RAMDisk Image at 40200000 ...
5101	   Image Name:	 Simple Ramdisk Image
5102	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5103	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5104	   Load Address: 00000000
5105	   Entry Point:	 00000000
5106	   Verifying Checksum ... OK
5107	   Loading Ramdisk ... OK
5108	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
5109	Boot arguments: root=/dev/ram
5110	time_init: decrementer frequency = 187500000/60
5111	Calibrating delay loop... 49.77 BogoMIPS
5112	...
5113	RAMDISK: Compressed image found at block 0
5114	VFS: Mounted root (ext2 filesystem).
5115
5116	bash#
5117
5118Boot Linux and pass a flat device tree:
5119-----------
5120
5121First, U-Boot must be compiled with the appropriate defines. See the section
5122titled "Linux Kernel Interface" above for a more in depth explanation. The
5123following is an example of how to start a kernel and pass an updated
5124flat device tree:
5125
5126=> print oftaddr
5127oftaddr=0x300000
5128=> print oft
5129oft=oftrees/mpc8540ads.dtb
5130=> tftp $oftaddr $oft
5131Speed: 1000, full duplex
5132Using TSEC0 device
5133TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5134Filename 'oftrees/mpc8540ads.dtb'.
5135Load address: 0x300000
5136Loading: #
5137done
5138Bytes transferred = 4106 (100a hex)
5139=> tftp $loadaddr $bootfile
5140Speed: 1000, full duplex
5141Using TSEC0 device
5142TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5143Filename 'uImage'.
5144Load address: 0x200000
5145Loading:############
5146done
5147Bytes transferred = 1029407 (fb51f hex)
5148=> print loadaddr
5149loadaddr=200000
5150=> print oftaddr
5151oftaddr=0x300000
5152=> bootm $loadaddr - $oftaddr
5153## Booting image at 00200000 ...
5154   Image Name:	 Linux-2.6.17-dirty
5155   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5156   Data Size:	 1029343 Bytes = 1005.2 kB
5157   Load Address: 00000000
5158   Entry Point:	 00000000
5159   Verifying Checksum ... OK
5160   Uncompressing Kernel Image ... OK
5161Booting using flat device tree at 0x300000
5162Using MPC85xx ADS machine description
5163Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5164[snip]
5165
5166
5167More About U-Boot Image Types:
5168------------------------------
5169
5170U-Boot supports the following image types:
5171
5172   "Standalone Programs" are directly runnable in the environment
5173	provided by U-Boot; it is expected that (if they behave
5174	well) you can continue to work in U-Boot after return from
5175	the Standalone Program.
5176   "OS Kernel Images" are usually images of some Embedded OS which
5177	will take over control completely. Usually these programs
5178	will install their own set of exception handlers, device
5179	drivers, set up the MMU, etc. - this means, that you cannot
5180	expect to re-enter U-Boot except by resetting the CPU.
5181   "RAMDisk Images" are more or less just data blocks, and their
5182	parameters (address, size) are passed to an OS kernel that is
5183	being started.
5184   "Multi-File Images" contain several images, typically an OS
5185	(Linux) kernel image and one or more data images like
5186	RAMDisks. This construct is useful for instance when you want
5187	to boot over the network using BOOTP etc., where the boot
5188	server provides just a single image file, but you want to get
5189	for instance an OS kernel and a RAMDisk image.
5190
5191	"Multi-File Images" start with a list of image sizes, each
5192	image size (in bytes) specified by an "uint32_t" in network
5193	byte order. This list is terminated by an "(uint32_t)0".
5194	Immediately after the terminating 0 follow the images, one by
5195	one, all aligned on "uint32_t" boundaries (size rounded up to
5196	a multiple of 4 bytes).
5197
5198   "Firmware Images" are binary images containing firmware (like
5199	U-Boot or FPGA images) which usually will be programmed to
5200	flash memory.
5201
5202   "Script files" are command sequences that will be executed by
5203	U-Boot's command interpreter; this feature is especially
5204	useful when you configure U-Boot to use a real shell (hush)
5205	as command interpreter.
5206
5207Booting the Linux zImage:
5208-------------------------
5209
5210On some platforms, it's possible to boot Linux zImage. This is done
5211using the "bootz" command. The syntax of "bootz" command is the same
5212as the syntax of "bootm" command.
5213
5214Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5215kernel with raw initrd images. The syntax is slightly different, the
5216address of the initrd must be augmented by it's size, in the following
5217format: "<initrd addres>:<initrd size>".
5218
5219
5220Standalone HOWTO:
5221=================
5222
5223One of the features of U-Boot is that you can dynamically load and
5224run "standalone" applications, which can use some resources of
5225U-Boot like console I/O functions or interrupt services.
5226
5227Two simple examples are included with the sources:
5228
5229"Hello World" Demo:
5230-------------------
5231
5232'examples/hello_world.c' contains a small "Hello World" Demo
5233application; it is automatically compiled when you build U-Boot.
5234It's configured to run at address 0x00040004, so you can play with it
5235like that:
5236
5237	=> loads
5238	## Ready for S-Record download ...
5239	~>examples/hello_world.srec
5240	1 2 3 4 5 6 7 8 9 10 11 ...
5241	[file transfer complete]
5242	[connected]
5243	## Start Addr = 0x00040004
5244
5245	=> go 40004 Hello World! This is a test.
5246	## Starting application at 0x00040004 ...
5247	Hello World
5248	argc = 7
5249	argv[0] = "40004"
5250	argv[1] = "Hello"
5251	argv[2] = "World!"
5252	argv[3] = "This"
5253	argv[4] = "is"
5254	argv[5] = "a"
5255	argv[6] = "test."
5256	argv[7] = "<NULL>"
5257	Hit any key to exit ...
5258
5259	## Application terminated, rc = 0x0
5260
5261Another example, which demonstrates how to register a CPM interrupt
5262handler with the U-Boot code, can be found in 'examples/timer.c'.
5263Here, a CPM timer is set up to generate an interrupt every second.
5264The interrupt service routine is trivial, just printing a '.'
5265character, but this is just a demo program. The application can be
5266controlled by the following keys:
5267
5268	? - print current values og the CPM Timer registers
5269	b - enable interrupts and start timer
5270	e - stop timer and disable interrupts
5271	q - quit application
5272
5273	=> loads
5274	## Ready for S-Record download ...
5275	~>examples/timer.srec
5276	1 2 3 4 5 6 7 8 9 10 11 ...
5277	[file transfer complete]
5278	[connected]
5279	## Start Addr = 0x00040004
5280
5281	=> go 40004
5282	## Starting application at 0x00040004 ...
5283	TIMERS=0xfff00980
5284	Using timer 1
5285	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5286
5287Hit 'b':
5288	[q, b, e, ?] Set interval 1000000 us
5289	Enabling timer
5290Hit '?':
5291	[q, b, e, ?] ........
5292	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5293Hit '?':
5294	[q, b, e, ?] .
5295	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5296Hit '?':
5297	[q, b, e, ?] .
5298	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5299Hit '?':
5300	[q, b, e, ?] .
5301	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5302Hit 'e':
5303	[q, b, e, ?] ...Stopping timer
5304Hit 'q':
5305	[q, b, e, ?] ## Application terminated, rc = 0x0
5306
5307
5308Minicom warning:
5309================
5310
5311Over time, many people have reported problems when trying to use the
5312"minicom" terminal emulation program for serial download. I (wd)
5313consider minicom to be broken, and recommend not to use it. Under
5314Unix, I recommend to use C-Kermit for general purpose use (and
5315especially for kermit binary protocol download ("loadb" command), and
5316use "cu" for S-Record download ("loads" command).  See
5317http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5318for help with kermit.
5319
5320
5321Nevertheless, if you absolutely want to use it try adding this
5322configuration to your "File transfer protocols" section:
5323
5324	   Name	   Program			Name U/D FullScr IO-Red. Multi
5325	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5326	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5327
5328
5329NetBSD Notes:
5330=============
5331
5332Starting at version 0.9.2, U-Boot supports NetBSD both as host
5333(build U-Boot) and target system (boots NetBSD/mpc8xx).
5334
5335Building requires a cross environment; it is known to work on
5336NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5337need gmake since the Makefiles are not compatible with BSD make).
5338Note that the cross-powerpc package does not install include files;
5339attempting to build U-Boot will fail because <machine/ansi.h> is
5340missing.  This file has to be installed and patched manually:
5341
5342	# cd /usr/pkg/cross/powerpc-netbsd/include
5343	# mkdir powerpc
5344	# ln -s powerpc machine
5345	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5346	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5347
5348Native builds *don't* work due to incompatibilities between native
5349and U-Boot include files.
5350
5351Booting assumes that (the first part of) the image booted is a
5352stage-2 loader which in turn loads and then invokes the kernel
5353proper. Loader sources will eventually appear in the NetBSD source
5354tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5355meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5356
5357
5358Implementation Internals:
5359=========================
5360
5361The following is not intended to be a complete description of every
5362implementation detail. However, it should help to understand the
5363inner workings of U-Boot and make it easier to port it to custom
5364hardware.
5365
5366
5367Initial Stack, Global Data:
5368---------------------------
5369
5370The implementation of U-Boot is complicated by the fact that U-Boot
5371starts running out of ROM (flash memory), usually without access to
5372system RAM (because the memory controller is not initialized yet).
5373This means that we don't have writable Data or BSS segments, and BSS
5374is not initialized as zero. To be able to get a C environment working
5375at all, we have to allocate at least a minimal stack. Implementation
5376options for this are defined and restricted by the CPU used: Some CPU
5377models provide on-chip memory (like the IMMR area on MPC8xx and
5378MPC826x processors), on others (parts of) the data cache can be
5379locked as (mis-) used as memory, etc.
5380
5381	Chris Hallinan posted a good summary of these issues to the
5382	U-Boot mailing list:
5383
5384	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5385	From: "Chris Hallinan" <clh@net1plus.com>
5386	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5387	...
5388
5389	Correct me if I'm wrong, folks, but the way I understand it
5390	is this: Using DCACHE as initial RAM for Stack, etc, does not
5391	require any physical RAM backing up the cache. The cleverness
5392	is that the cache is being used as a temporary supply of
5393	necessary storage before the SDRAM controller is setup. It's
5394	beyond the scope of this list to explain the details, but you
5395	can see how this works by studying the cache architecture and
5396	operation in the architecture and processor-specific manuals.
5397
5398	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5399	is another option for the system designer to use as an
5400	initial stack/RAM area prior to SDRAM being available. Either
5401	option should work for you. Using CS 4 should be fine if your
5402	board designers haven't used it for something that would
5403	cause you grief during the initial boot! It is frequently not
5404	used.
5405
5406	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5407	with your processor/board/system design. The default value
5408	you will find in any recent u-boot distribution in
5409	walnut.h should work for you. I'd set it to a value larger
5410	than your SDRAM module. If you have a 64MB SDRAM module, set
5411	it above 400_0000. Just make sure your board has no resources
5412	that are supposed to respond to that address! That code in
5413	start.S has been around a while and should work as is when
5414	you get the config right.
5415
5416	-Chris Hallinan
5417	DS4.COM, Inc.
5418
5419It is essential to remember this, since it has some impact on the C
5420code for the initialization procedures:
5421
5422* Initialized global data (data segment) is read-only. Do not attempt
5423  to write it.
5424
5425* Do not use any uninitialized global data (or implicitely initialized
5426  as zero data - BSS segment) at all - this is undefined, initiali-
5427  zation is performed later (when relocating to RAM).
5428
5429* Stack space is very limited. Avoid big data buffers or things like
5430  that.
5431
5432Having only the stack as writable memory limits means we cannot use
5433normal global data to share information beween the code. But it
5434turned out that the implementation of U-Boot can be greatly
5435simplified by making a global data structure (gd_t) available to all
5436functions. We could pass a pointer to this data as argument to _all_
5437functions, but this would bloat the code. Instead we use a feature of
5438the GCC compiler (Global Register Variables) to share the data: we
5439place a pointer (gd) to the global data into a register which we
5440reserve for this purpose.
5441
5442When choosing a register for such a purpose we are restricted by the
5443relevant  (E)ABI  specifications for the current architecture, and by
5444GCC's implementation.
5445
5446For PowerPC, the following registers have specific use:
5447	R1:	stack pointer
5448	R2:	reserved for system use
5449	R3-R4:	parameter passing and return values
5450	R5-R10: parameter passing
5451	R13:	small data area pointer
5452	R30:	GOT pointer
5453	R31:	frame pointer
5454
5455	(U-Boot also uses R12 as internal GOT pointer. r12
5456	is a volatile register so r12 needs to be reset when
5457	going back and forth between asm and C)
5458
5459    ==> U-Boot will use R2 to hold a pointer to the global data
5460
5461    Note: on PPC, we could use a static initializer (since the
5462    address of the global data structure is known at compile time),
5463    but it turned out that reserving a register results in somewhat
5464    smaller code - although the code savings are not that big (on
5465    average for all boards 752 bytes for the whole U-Boot image,
5466    624 text + 127 data).
5467
5468On Blackfin, the normal C ABI (except for P3) is followed as documented here:
5469	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
5470
5471    ==> U-Boot will use P3 to hold a pointer to the global data
5472
5473On ARM, the following registers are used:
5474
5475	R0:	function argument word/integer result
5476	R1-R3:	function argument word
5477	R9:	GOT pointer
5478	R10:	stack limit (used only if stack checking if enabled)
5479	R11:	argument (frame) pointer
5480	R12:	temporary workspace
5481	R13:	stack pointer
5482	R14:	link register
5483	R15:	program counter
5484
5485    ==> U-Boot will use R8 to hold a pointer to the global data
5486
5487On Nios II, the ABI is documented here:
5488	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5489
5490    ==> U-Boot will use gp to hold a pointer to the global data
5491
5492    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5493    to access small data sections, so gp is free.
5494
5495On NDS32, the following registers are used:
5496
5497	R0-R1:	argument/return
5498	R2-R5:	argument
5499	R15:	temporary register for assembler
5500	R16:	trampoline register
5501	R28:	frame pointer (FP)
5502	R29:	global pointer (GP)
5503	R30:	link register (LP)
5504	R31:	stack pointer (SP)
5505	PC:	program counter (PC)
5506
5507    ==> U-Boot will use R10 to hold a pointer to the global data
5508
5509NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5510or current versions of GCC may "optimize" the code too much.
5511
5512Memory Management:
5513------------------
5514
5515U-Boot runs in system state and uses physical addresses, i.e. the
5516MMU is not used either for address mapping nor for memory protection.
5517
5518The available memory is mapped to fixed addresses using the memory
5519controller. In this process, a contiguous block is formed for each
5520memory type (Flash, SDRAM, SRAM), even when it consists of several
5521physical memory banks.
5522
5523U-Boot is installed in the first 128 kB of the first Flash bank (on
5524TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5525booting and sizing and initializing DRAM, the code relocates itself
5526to the upper end of DRAM. Immediately below the U-Boot code some
5527memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5528configuration setting]. Below that, a structure with global Board
5529Info data is placed, followed by the stack (growing downward).
5530
5531Additionally, some exception handler code is copied to the low 8 kB
5532of DRAM (0x00000000 ... 0x00001FFF).
5533
5534So a typical memory configuration with 16 MB of DRAM could look like
5535this:
5536
5537	0x0000 0000	Exception Vector code
5538	      :
5539	0x0000 1FFF
5540	0x0000 2000	Free for Application Use
5541	      :
5542	      :
5543
5544	      :
5545	      :
5546	0x00FB FF20	Monitor Stack (Growing downward)
5547	0x00FB FFAC	Board Info Data and permanent copy of global data
5548	0x00FC 0000	Malloc Arena
5549	      :
5550	0x00FD FFFF
5551	0x00FE 0000	RAM Copy of Monitor Code
5552	...		eventually: LCD or video framebuffer
5553	...		eventually: pRAM (Protected RAM - unchanged by reset)
5554	0x00FF FFFF	[End of RAM]
5555
5556
5557System Initialization:
5558----------------------
5559
5560In the reset configuration, U-Boot starts at the reset entry point
5561(on most PowerPC systems at address 0x00000100). Because of the reset
5562configuration for CS0# this is a mirror of the onboard Flash memory.
5563To be able to re-map memory U-Boot then jumps to its link address.
5564To be able to implement the initialization code in C, a (small!)
5565initial stack is set up in the internal Dual Ported RAM (in case CPUs
5566which provide such a feature like MPC8xx or MPC8260), or in a locked
5567part of the data cache. After that, U-Boot initializes the CPU core,
5568the caches and the SIU.
5569
5570Next, all (potentially) available memory banks are mapped using a
5571preliminary mapping. For example, we put them on 512 MB boundaries
5572(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5573on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5574programmed for SDRAM access. Using the temporary configuration, a
5575simple memory test is run that determines the size of the SDRAM
5576banks.
5577
5578When there is more than one SDRAM bank, and the banks are of
5579different size, the largest is mapped first. For equal size, the first
5580bank (CS2#) is mapped first. The first mapping is always for address
55810x00000000, with any additional banks following immediately to create
5582contiguous memory starting from 0.
5583
5584Then, the monitor installs itself at the upper end of the SDRAM area
5585and allocates memory for use by malloc() and for the global Board
5586Info data; also, the exception vector code is copied to the low RAM
5587pages, and the final stack is set up.
5588
5589Only after this relocation will you have a "normal" C environment;
5590until that you are restricted in several ways, mostly because you are
5591running from ROM, and because the code will have to be relocated to a
5592new address in RAM.
5593
5594
5595U-Boot Porting Guide:
5596----------------------
5597
5598[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5599list, October 2002]
5600
5601
5602int main(int argc, char *argv[])
5603{
5604	sighandler_t no_more_time;
5605
5606	signal(SIGALRM, no_more_time);
5607	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5608
5609	if (available_money > available_manpower) {
5610		Pay consultant to port U-Boot;
5611		return 0;
5612	}
5613
5614	Download latest U-Boot source;
5615
5616	Subscribe to u-boot mailing list;
5617
5618	if (clueless)
5619		email("Hi, I am new to U-Boot, how do I get started?");
5620
5621	while (learning) {
5622		Read the README file in the top level directory;
5623		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5624		Read applicable doc/*.README;
5625		Read the source, Luke;
5626		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5627	}
5628
5629	if (available_money > toLocalCurrency ($2500))
5630		Buy a BDI3000;
5631	else
5632		Add a lot of aggravation and time;
5633
5634	if (a similar board exists) {	/* hopefully... */
5635		cp -a board/<similar> board/<myboard>
5636		cp include/configs/<similar>.h include/configs/<myboard>.h
5637	} else {
5638		Create your own board support subdirectory;
5639		Create your own board include/configs/<myboard>.h file;
5640	}
5641	Edit new board/<myboard> files
5642	Edit new include/configs/<myboard>.h
5643
5644	while (!accepted) {
5645		while (!running) {
5646			do {
5647				Add / modify source code;
5648			} until (compiles);
5649			Debug;
5650			if (clueless)
5651				email("Hi, I am having problems...");
5652		}
5653		Send patch file to the U-Boot email list;
5654		if (reasonable critiques)
5655			Incorporate improvements from email list code review;
5656		else
5657			Defend code as written;
5658	}
5659
5660	return 0;
5661}
5662
5663void no_more_time (int sig)
5664{
5665      hire_a_guru();
5666}
5667
5668
5669Coding Standards:
5670-----------------
5671
5672All contributions to U-Boot should conform to the Linux kernel
5673coding style; see the file "Documentation/CodingStyle" and the script
5674"scripts/Lindent" in your Linux kernel source directory.
5675
5676Source files originating from a different project (for example the
5677MTD subsystem) are generally exempt from these guidelines and are not
5678reformated to ease subsequent migration to newer versions of those
5679sources.
5680
5681Please note that U-Boot is implemented in C (and to some small parts in
5682Assembler); no C++ is used, so please do not use C++ style comments (//)
5683in your code.
5684
5685Please also stick to the following formatting rules:
5686- remove any trailing white space
5687- use TAB characters for indentation and vertical alignment, not spaces
5688- make sure NOT to use DOS '\r\n' line feeds
5689- do not add more than 2 consecutive empty lines to source files
5690- do not add trailing empty lines to source files
5691
5692Submissions which do not conform to the standards may be returned
5693with a request to reformat the changes.
5694
5695
5696Submitting Patches:
5697-------------------
5698
5699Since the number of patches for U-Boot is growing, we need to
5700establish some rules. Submissions which do not conform to these rules
5701may be rejected, even when they contain important and valuable stuff.
5702
5703Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5704
5705Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5706see http://lists.denx.de/mailman/listinfo/u-boot
5707
5708When you send a patch, please include the following information with
5709it:
5710
5711* For bug fixes: a description of the bug and how your patch fixes
5712  this bug. Please try to include a way of demonstrating that the
5713  patch actually fixes something.
5714
5715* For new features: a description of the feature and your
5716  implementation.
5717
5718* A CHANGELOG entry as plaintext (separate from the patch)
5719
5720* For major contributions, your entry to the CREDITS file
5721
5722* When you add support for a new board, don't forget to add this
5723  board to the MAINTAINERS file, too.
5724
5725* If your patch adds new configuration options, don't forget to
5726  document these in the README file.
5727
5728* The patch itself. If you are using git (which is *strongly*
5729  recommended) you can easily generate the patch using the
5730  "git format-patch". If you then use "git send-email" to send it to
5731  the U-Boot mailing list, you will avoid most of the common problems
5732  with some other mail clients.
5733
5734  If you cannot use git, use "diff -purN OLD NEW". If your version of
5735  diff does not support these options, then get the latest version of
5736  GNU diff.
5737
5738  The current directory when running this command shall be the parent
5739  directory of the U-Boot source tree (i. e. please make sure that
5740  your patch includes sufficient directory information for the
5741  affected files).
5742
5743  We prefer patches as plain text. MIME attachments are discouraged,
5744  and compressed attachments must not be used.
5745
5746* If one logical set of modifications affects or creates several
5747  files, all these changes shall be submitted in a SINGLE patch file.
5748
5749* Changesets that contain different, unrelated modifications shall be
5750  submitted as SEPARATE patches, one patch per changeset.
5751
5752
5753Notes:
5754
5755* Before sending the patch, run the MAKEALL script on your patched
5756  source tree and make sure that no errors or warnings are reported
5757  for any of the boards.
5758
5759* Keep your modifications to the necessary minimum: A patch
5760  containing several unrelated changes or arbitrary reformats will be
5761  returned with a request to re-formatting / split it.
5762
5763* If you modify existing code, make sure that your new code does not
5764  add to the memory footprint of the code ;-) Small is beautiful!
5765  When adding new features, these should compile conditionally only
5766  (using #ifdef), and the resulting code with the new feature
5767  disabled must not need more memory than the old code without your
5768  modification.
5769
5770* Remember that there is a size limit of 100 kB per message on the
5771  u-boot mailing list. Bigger patches will be moderated. If they are
5772  reasonable and not too big, they will be acknowledged. But patches
5773  bigger than the size limit should be avoided.
5774