xref: /openbmc/u-boot/README (revision 33699df12cbcd9bfa609dc7fb5a0a69c029449e9)
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
57
58Where to get help:
59==================
60
61In case you have questions about, problems with or contributions for
62U-Boot you should send a message to the U-Boot mailing list at
63<u-boot@lists.denx.de>. There is also an archive of previous traffic
64on the mailing list - please search the archive before asking FAQ's.
65Please see http://lists.denx.de/pipermail/u-boot and
66http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
67
68
69Where to get source code:
70=========================
71
72The U-Boot source code is maintained in the git repository at
73git://www.denx.de/git/u-boot.git ; you can browse it online at
74http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
75
76The "snapshot" links on this page allow you to download tarballs of
77any version you might be interested in. Official releases are also
78available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
79directory.
80
81Pre-built (and tested) images are available from
82ftp://ftp.denx.de/pub/u-boot/images/
83
84
85Where we come from:
86===================
87
88- start from 8xxrom sources
89- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
90- clean up code
91- make it easier to add custom boards
92- make it possible to add other [PowerPC] CPUs
93- extend functions, especially:
94  * Provide extended interface to Linux boot loader
95  * S-Record download
96  * network boot
97  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
98- create ARMBoot project (http://sourceforge.net/projects/armboot)
99- add other CPU families (starting with ARM)
100- create U-Boot project (http://sourceforge.net/projects/u-boot)
101- current project page: see http://www.denx.de/wiki/U-Boot
102
103
104Names and Spelling:
105===================
106
107The "official" name of this project is "Das U-Boot". The spelling
108"U-Boot" shall be used in all written text (documentation, comments
109in source files etc.). Example:
110
111	This is the README file for the U-Boot project.
112
113File names etc. shall be based on the string "u-boot". Examples:
114
115	include/asm-ppc/u-boot.h
116
117	#include <asm/u-boot.h>
118
119Variable names, preprocessor constants etc. shall be either based on
120the string "u_boot" or on "U_BOOT". Example:
121
122	U_BOOT_VERSION		u_boot_logo
123	IH_OS_U_BOOT		u_boot_hush_start
124
125
126Versioning:
127===========
128
129Starting with the release in October 2008, the names of the releases
130were changed from numerical release numbers without deeper meaning
131into a time stamp based numbering. Regular releases are identified by
132names consisting of the calendar year and month of the release date.
133Additional fields (if present) indicate release candidates or bug fix
134releases in "stable" maintenance trees.
135
136Examples:
137	U-Boot v2009.11	    - Release November 2009
138	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
139	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
140
141
142Directory Hierarchy:
143====================
144
145/arch			Architecture specific files
146  /arm			Files generic to ARM architecture
147    /cpu		CPU specific files
148      /arm720t		Files specific to ARM 720 CPUs
149      /arm920t		Files specific to ARM 920 CPUs
150	/at91		Files specific to Atmel AT91RM9200 CPU
151	/imx		Files specific to Freescale MC9328 i.MX CPUs
152	/s3c24x0	Files specific to Samsung S3C24X0 CPUs
153      /arm925t		Files specific to ARM 925 CPUs
154      /arm926ejs	Files specific to ARM 926 CPUs
155      /arm1136		Files specific to ARM 1136 CPUs
156      /ixp		Files specific to Intel XScale IXP CPUs
157      /pxa		Files specific to Intel XScale PXA CPUs
158      /s3c44b0		Files specific to Samsung S3C44B0 CPUs
159      /sa1100		Files specific to Intel StrongARM SA1100 CPUs
160    /lib		Architecture specific library files
161  /avr32		Files generic to AVR32 architecture
162    /cpu		CPU specific files
163    /lib		Architecture specific library files
164  /blackfin		Files generic to Analog Devices Blackfin architecture
165    /cpu		CPU specific files
166    /lib		Architecture specific library files
167  /x86			Files generic to x86 architecture
168    /cpu		CPU specific files
169    /lib		Architecture specific library files
170  /m68k			Files generic to m68k architecture
171    /cpu		CPU specific files
172      /mcf52x2		Files specific to Freescale ColdFire MCF52x2 CPUs
173      /mcf5227x		Files specific to Freescale ColdFire MCF5227x CPUs
174      /mcf532x		Files specific to Freescale ColdFire MCF5329 CPUs
175      /mcf5445x		Files specific to Freescale ColdFire MCF5445x CPUs
176      /mcf547x_8x	Files specific to Freescale ColdFire MCF547x_8x CPUs
177    /lib		Architecture specific library files
178  /microblaze		Files generic to microblaze architecture
179    /cpu		CPU specific files
180    /lib		Architecture specific library files
181  /mips			Files generic to MIPS architecture
182    /cpu		CPU specific files
183      /mips32		Files specific to MIPS32 CPUs
184      /xburst		Files specific to Ingenic XBurst CPUs
185    /lib		Architecture specific library files
186  /nds32		Files generic to NDS32 architecture
187    /cpu		CPU specific files
188      /n1213		Files specific to Andes Technology N1213 CPUs
189    /lib		Architecture specific library files
190  /nios2		Files generic to Altera NIOS2 architecture
191    /cpu		CPU specific files
192    /lib		Architecture specific library files
193  /powerpc		Files generic to PowerPC architecture
194    /cpu		CPU specific files
195      /74xx_7xx		Files specific to Freescale MPC74xx and 7xx CPUs
196      /mpc5xx		Files specific to Freescale MPC5xx CPUs
197      /mpc5xxx		Files specific to Freescale MPC5xxx CPUs
198      /mpc8xx		Files specific to Freescale MPC8xx CPUs
199      /mpc8220		Files specific to Freescale MPC8220 CPUs
200      /mpc824x		Files specific to Freescale MPC824x CPUs
201      /mpc8260		Files specific to Freescale MPC8260 CPUs
202      /mpc85xx		Files specific to Freescale MPC85xx CPUs
203      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
204    /lib		Architecture specific library files
205  /sh			Files generic to SH architecture
206    /cpu		CPU specific files
207      /sh2		Files specific to sh2 CPUs
208      /sh3		Files specific to sh3 CPUs
209      /sh4		Files specific to sh4 CPUs
210    /lib		Architecture specific library files
211  /sparc		Files generic to SPARC architecture
212    /cpu		CPU specific files
213      /leon2		Files specific to Gaisler LEON2 SPARC CPU
214      /leon3		Files specific to Gaisler LEON3 SPARC CPU
215    /lib		Architecture specific library files
216/api			Machine/arch independent API for external apps
217/board			Board dependent files
218/common			Misc architecture independent functions
219/disk			Code for disk drive partition handling
220/doc			Documentation (don't expect too much)
221/drivers		Commonly used device drivers
222/examples		Example code for standalone applications, etc.
223/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
224/include		Header Files
225/lib			Files generic to all architectures
226  /libfdt		Library files to support flattened device trees
227  /lzma			Library files to support LZMA decompression
228  /lzo			Library files to support LZO decompression
229/net			Networking code
230/post			Power On Self Test
231/rtc			Real Time Clock drivers
232/tools			Tools to build S-Record or U-Boot images, etc.
233
234Software Configuration:
235=======================
236
237Configuration is usually done using C preprocessor defines; the
238rationale behind that is to avoid dead code whenever possible.
239
240There are two classes of configuration variables:
241
242* Configuration _OPTIONS_:
243  These are selectable by the user and have names beginning with
244  "CONFIG_".
245
246* Configuration _SETTINGS_:
247  These depend on the hardware etc. and should not be meddled with if
248  you don't know what you're doing; they have names beginning with
249  "CONFIG_SYS_".
250
251Later we will add a configuration tool - probably similar to or even
252identical to what's used for the Linux kernel. Right now, we have to
253do the configuration by hand, which means creating some symbolic
254links and editing some configuration files. We use the TQM8xxL boards
255as an example here.
256
257
258Selection of Processor Architecture and Board Type:
259---------------------------------------------------
260
261For all supported boards there are ready-to-use default
262configurations available; just type "make <board_name>_config".
263
264Example: For a TQM823L module type:
265
266	cd u-boot
267	make TQM823L_config
268
269For the Cogent platform, you need to specify the CPU type as well;
270e.g. "make cogent_mpc8xx_config". And also configure the cogent
271directory according to the instructions in cogent/README.
272
273
274Configuration Options:
275----------------------
276
277Configuration depends on the combination of board and CPU type; all
278such information is kept in a configuration file
279"include/configs/<board_name>.h".
280
281Example: For a TQM823L module, all configuration settings are in
282"include/configs/TQM823L.h".
283
284
285Many of the options are named exactly as the corresponding Linux
286kernel configuration options. The intention is to make it easier to
287build a config tool - later.
288
289
290The following options need to be configured:
291
292- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
293
294- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
295
296- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
297		Define exactly one, e.g. CONFIG_ATSTK1002
298
299- CPU Module Type: (if CONFIG_COGENT is defined)
300		Define exactly one of
301		CONFIG_CMA286_60_OLD
302--- FIXME --- not tested yet:
303		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
304		CONFIG_CMA287_23, CONFIG_CMA287_50
305
306- Motherboard Type: (if CONFIG_COGENT is defined)
307		Define exactly one of
308		CONFIG_CMA101, CONFIG_CMA102
309
310- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
311		Define one or more of
312		CONFIG_CMA302
313
314- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
315		Define one or more of
316		CONFIG_LCD_HEARTBEAT	- update a character position on
317					  the LCD display every second with
318					  a "rotator" |\-/|\-/
319
320- Board flavour: (if CONFIG_MPC8260ADS is defined)
321		CONFIG_ADSTYPE
322		Possible values are:
323			CONFIG_SYS_8260ADS	- original MPC8260ADS
324			CONFIG_SYS_8266ADS	- MPC8266ADS
325			CONFIG_SYS_PQ2FADS	- PQ2FADS-ZU or PQ2FADS-VR
326			CONFIG_SYS_8272ADS	- MPC8272ADS
327
328- Marvell Family Member
329		CONFIG_SYS_MVFS		- define it if you want to enable
330					  multiple fs option at one time
331					  for marvell soc family
332
333- MPC824X Family Member (if CONFIG_MPC824X is defined)
334		Define exactly one of
335		CONFIG_MPC8240, CONFIG_MPC8245
336
337- 8xx CPU Options: (if using an MPC8xx CPU)
338		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
339					  get_gclk_freq() cannot work
340					  e.g. if there is no 32KHz
341					  reference PIT/RTC clock
342		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
343					  or XTAL/EXTAL)
344
345- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
346		CONFIG_SYS_8xx_CPUCLK_MIN
347		CONFIG_SYS_8xx_CPUCLK_MAX
348		CONFIG_8xx_CPUCLK_DEFAULT
349			See doc/README.MPC866
350
351		CONFIG_SYS_MEASURE_CPUCLK
352
353		Define this to measure the actual CPU clock instead
354		of relying on the correctness of the configured
355		values. Mostly useful for board bringup to make sure
356		the PLL is locked at the intended frequency. Note
357		that this requires a (stable) reference clock (32 kHz
358		RTC clock or CONFIG_SYS_8XX_XIN)
359
360		CONFIG_SYS_DELAYED_ICACHE
361
362		Define this option if you want to enable the
363		ICache only when Code runs from RAM.
364
365- 85xx CPU Options:
366		CONFIG_SYS_PPC64
367
368		Specifies that the core is a 64-bit PowerPC implementation (implements
369		the "64" category of the Power ISA). This is necessary for ePAPR
370		compliance, among other possible reasons.
371
372		CONFIG_SYS_FSL_TBCLK_DIV
373
374		Defines the core time base clock divider ratio compared to the
375		system clock.  On most PQ3 devices this is 8, on newer QorIQ
376		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
377
378		CONFIG_SYS_FSL_PCIE_COMPAT
379
380		Defines the string to utilize when trying to match PCIe device
381		tree nodes for the given platform.
382
383		CONFIG_SYS_PPC_E500_DEBUG_TLB
384
385		Enables a temporary TLB entry to be used during boot to work
386		around limitations in e500v1 and e500v2 external debugger
387		support. This reduces the portions of the boot code where
388		breakpoints and single stepping do not work.  The value of this
389		symbol should be set to the TLB1 entry to be used for this
390		purpose.
391
392		CONFIG_SYS_FSL_ERRATUM_A004510
393
394		Enables a workaround for erratum A004510.  If set,
395		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
396		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
397
398		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
399		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
400
401		Defines one or two SoC revisions (low 8 bits of SVR)
402		for which the A004510 workaround should be applied.
403
404		The rest of SVR is either not relevant to the decision
405		of whether the erratum is present (e.g. p2040 versus
406		p2041) or is implied by the build target, which controls
407		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
408
409		See Freescale App Note 4493 for more information about
410		this erratum.
411
412		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
413
414		This is the value to write into CCSR offset 0x18600
415		according to the A004510 workaround.
416
417- Generic CPU options:
418		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
419
420		Defines the endianess of the CPU. Implementation of those
421		values is arch specific.
422
423- Intel Monahans options:
424		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
425
426		Defines the Monahans run mode to oscillator
427		ratio. Valid values are 8, 16, 24, 31. The core
428		frequency is this value multiplied by 13 MHz.
429
430		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
431
432		Defines the Monahans turbo mode to oscillator
433		ratio. Valid values are 1 (default if undefined) and
434		2. The core frequency as calculated above is multiplied
435		by this value.
436
437- MIPS CPU options:
438		CONFIG_SYS_INIT_SP_OFFSET
439
440		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
441		pointer. This is needed for the temporary stack before
442		relocation.
443
444		CONFIG_SYS_MIPS_CACHE_MODE
445
446		Cache operation mode for the MIPS CPU.
447		See also arch/mips/include/asm/mipsregs.h.
448		Possible values are:
449			CONF_CM_CACHABLE_NO_WA
450			CONF_CM_CACHABLE_WA
451			CONF_CM_UNCACHED
452			CONF_CM_CACHABLE_NONCOHERENT
453			CONF_CM_CACHABLE_CE
454			CONF_CM_CACHABLE_COW
455			CONF_CM_CACHABLE_CUW
456			CONF_CM_CACHABLE_ACCELERATED
457
458		CONFIG_SYS_XWAY_EBU_BOOTCFG
459
460		Special option for Lantiq XWAY SoCs for booting from NOR flash.
461		See also arch/mips/cpu/mips32/start.S.
462
463		CONFIG_XWAY_SWAP_BYTES
464
465		Enable compilation of tools/xway-swap-bytes needed for Lantiq
466		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
467		be swapped if a flash programmer is used.
468
469- ARM options:
470		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
471
472		Select high exception vectors of the ARM core, e.g., do not
473		clear the V bit of the c1 register of CP15.
474
475		CONFIG_SYS_THUMB_BUILD
476
477		Use this flag to build U-Boot using the Thumb instruction
478		set for ARM architectures. Thumb instruction set provides
479		better code density. For ARM architectures that support
480		Thumb2 this flag will result in Thumb2 code generated by
481		GCC.
482
483- Linux Kernel Interface:
484		CONFIG_CLOCKS_IN_MHZ
485
486		U-Boot stores all clock information in Hz
487		internally. For binary compatibility with older Linux
488		kernels (which expect the clocks passed in the
489		bd_info data to be in MHz) the environment variable
490		"clocks_in_mhz" can be defined so that U-Boot
491		converts clock data to MHZ before passing it to the
492		Linux kernel.
493		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
494		"clocks_in_mhz=1" is automatically included in the
495		default environment.
496
497		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
498
499		When transferring memsize parameter to linux, some versions
500		expect it to be in bytes, others in MB.
501		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
502
503		CONFIG_OF_LIBFDT
504
505		New kernel versions are expecting firmware settings to be
506		passed using flattened device trees (based on open firmware
507		concepts).
508
509		CONFIG_OF_LIBFDT
510		 * New libfdt-based support
511		 * Adds the "fdt" command
512		 * The bootm command automatically updates the fdt
513
514		OF_CPU - The proper name of the cpus node (only required for
515			MPC512X and MPC5xxx based boards).
516		OF_SOC - The proper name of the soc node (only required for
517			MPC512X and MPC5xxx based boards).
518		OF_TBCLK - The timebase frequency.
519		OF_STDOUT_PATH - The path to the console device
520
521		boards with QUICC Engines require OF_QE to set UCC MAC
522		addresses
523
524		CONFIG_OF_BOARD_SETUP
525
526		Board code has addition modification that it wants to make
527		to the flat device tree before handing it off to the kernel
528
529		CONFIG_OF_BOOT_CPU
530
531		This define fills in the correct boot CPU in the boot
532		param header, the default value is zero if undefined.
533
534		CONFIG_OF_IDE_FIXUP
535
536		U-Boot can detect if an IDE device is present or not.
537		If not, and this new config option is activated, U-Boot
538		removes the ATA node from the DTS before booting Linux,
539		so the Linux IDE driver does not probe the device and
540		crash. This is needed for buggy hardware (uc101) where
541		no pull down resistor is connected to the signal IDE5V_DD7.
542
543		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
544
545		This setting is mandatory for all boards that have only one
546		machine type and must be used to specify the machine type
547		number as it appears in the ARM machine registry
548		(see http://www.arm.linux.org.uk/developer/machines/).
549		Only boards that have multiple machine types supported
550		in a single configuration file and the machine type is
551		runtime discoverable, do not have to use this setting.
552
553- vxWorks boot parameters:
554
555		bootvx constructs a valid bootline using the following
556		environments variables: bootfile, ipaddr, serverip, hostname.
557		It loads the vxWorks image pointed bootfile.
558
559		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
560		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
561		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
562		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
563
564		CONFIG_SYS_VXWORKS_ADD_PARAMS
565
566		Add it at the end of the bootline. E.g "u=username pw=secret"
567
568		Note: If a "bootargs" environment is defined, it will overwride
569		the defaults discussed just above.
570
571- Cache Configuration:
572		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
573		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
574		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
575
576- Cache Configuration for ARM:
577		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
578				      controller
579		CONFIG_SYS_PL310_BASE - Physical base address of PL310
580					controller register space
581
582- Serial Ports:
583		CONFIG_PL010_SERIAL
584
585		Define this if you want support for Amba PrimeCell PL010 UARTs.
586
587		CONFIG_PL011_SERIAL
588
589		Define this if you want support for Amba PrimeCell PL011 UARTs.
590
591		CONFIG_PL011_CLOCK
592
593		If you have Amba PrimeCell PL011 UARTs, set this variable to
594		the clock speed of the UARTs.
595
596		CONFIG_PL01x_PORTS
597
598		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
599		define this to a list of base addresses for each (supported)
600		port. See e.g. include/configs/versatile.h
601
602		CONFIG_PL011_SERIAL_RLCR
603
604		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
605		have separate receive and transmit line control registers.  Set
606		this variable to initialize the extra register.
607
608		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
609
610		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
611		boot loader that has already initialized the UART.  Define this
612		variable to flush the UART at init time.
613
614
615- Console Interface:
616		Depending on board, define exactly one serial port
617		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
618		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
619		console by defining CONFIG_8xx_CONS_NONE
620
621		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
622		port routines must be defined elsewhere
623		(i.e. serial_init(), serial_getc(), ...)
624
625		CONFIG_CFB_CONSOLE
626		Enables console device for a color framebuffer. Needs following
627		defines (cf. smiLynxEM, i8042)
628			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
629						(default big endian)
630			VIDEO_HW_RECTFILL	graphic chip supports
631						rectangle fill
632						(cf. smiLynxEM)
633			VIDEO_HW_BITBLT		graphic chip supports
634						bit-blit (cf. smiLynxEM)
635			VIDEO_VISIBLE_COLS	visible pixel columns
636						(cols=pitch)
637			VIDEO_VISIBLE_ROWS	visible pixel rows
638			VIDEO_PIXEL_SIZE	bytes per pixel
639			VIDEO_DATA_FORMAT	graphic data format
640						(0-5, cf. cfb_console.c)
641			VIDEO_FB_ADRS		framebuffer address
642			VIDEO_KBD_INIT_FCT	keyboard int fct
643						(i.e. i8042_kbd_init())
644			VIDEO_TSTC_FCT		test char fct
645						(i.e. i8042_tstc)
646			VIDEO_GETC_FCT		get char fct
647						(i.e. i8042_getc)
648			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
649						(requires blink timer
650						cf. i8042.c)
651			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
652			CONFIG_CONSOLE_TIME	display time/date info in
653						upper right corner
654						(requires CONFIG_CMD_DATE)
655			CONFIG_VIDEO_LOGO	display Linux logo in
656						upper left corner
657			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
658						linux_logo.h for logo.
659						Requires CONFIG_VIDEO_LOGO
660			CONFIG_CONSOLE_EXTRA_INFO
661						additional board info beside
662						the logo
663
664		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
665		a limited number of ANSI escape sequences (cursor control,
666		erase functions and limited graphics rendition control).
667
668		When CONFIG_CFB_CONSOLE is defined, video console is
669		default i/o. Serial console can be forced with
670		environment 'console=serial'.
671
672		When CONFIG_SILENT_CONSOLE is defined, all console
673		messages (by U-Boot and Linux!) can be silenced with
674		the "silent" environment variable. See
675		doc/README.silent for more information.
676
677- Console Baudrate:
678		CONFIG_BAUDRATE - in bps
679		Select one of the baudrates listed in
680		CONFIG_SYS_BAUDRATE_TABLE, see below.
681		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
682
683- Console Rx buffer length
684		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
685		the maximum receive buffer length for the SMC.
686		This option is actual only for 82xx and 8xx possible.
687		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
688		must be defined, to setup the maximum idle timeout for
689		the SMC.
690
691- Pre-Console Buffer:
692		Prior to the console being initialised (i.e. serial UART
693		initialised etc) all console output is silently discarded.
694		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
695		buffer any console messages prior to the console being
696		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
697		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
698		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
699		bytes are output before the console is initialised, the
700		earlier bytes are discarded.
701
702		'Sane' compilers will generate smaller code if
703		CONFIG_PRE_CON_BUF_SZ is a power of 2
704
705- Safe printf() functions
706		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
707		the printf() functions. These are defined in
708		include/vsprintf.h and include snprintf(), vsnprintf() and
709		so on. Code size increase is approximately 300-500 bytes.
710		If this option is not given then these functions will
711		silently discard their buffer size argument - this means
712		you are not getting any overflow checking in this case.
713
714- Boot Delay:	CONFIG_BOOTDELAY - in seconds
715		Delay before automatically booting the default image;
716		set to -1 to disable autoboot.
717		set to -2 to autoboot with no delay and not check for abort
718		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
719
720		See doc/README.autoboot for these options that
721		work with CONFIG_BOOTDELAY. None are required.
722		CONFIG_BOOT_RETRY_TIME
723		CONFIG_BOOT_RETRY_MIN
724		CONFIG_AUTOBOOT_KEYED
725		CONFIG_AUTOBOOT_PROMPT
726		CONFIG_AUTOBOOT_DELAY_STR
727		CONFIG_AUTOBOOT_STOP_STR
728		CONFIG_AUTOBOOT_DELAY_STR2
729		CONFIG_AUTOBOOT_STOP_STR2
730		CONFIG_ZERO_BOOTDELAY_CHECK
731		CONFIG_RESET_TO_RETRY
732
733- Autoboot Command:
734		CONFIG_BOOTCOMMAND
735		Only needed when CONFIG_BOOTDELAY is enabled;
736		define a command string that is automatically executed
737		when no character is read on the console interface
738		within "Boot Delay" after reset.
739
740		CONFIG_BOOTARGS
741		This can be used to pass arguments to the bootm
742		command. The value of CONFIG_BOOTARGS goes into the
743		environment value "bootargs".
744
745		CONFIG_RAMBOOT and CONFIG_NFSBOOT
746		The value of these goes into the environment as
747		"ramboot" and "nfsboot" respectively, and can be used
748		as a convenience, when switching between booting from
749		RAM and NFS.
750
751- Pre-Boot Commands:
752		CONFIG_PREBOOT
753
754		When this option is #defined, the existence of the
755		environment variable "preboot" will be checked
756		immediately before starting the CONFIG_BOOTDELAY
757		countdown and/or running the auto-boot command resp.
758		entering interactive mode.
759
760		This feature is especially useful when "preboot" is
761		automatically generated or modified. For an example
762		see the LWMON board specific code: here "preboot" is
763		modified when the user holds down a certain
764		combination of keys on the (special) keyboard when
765		booting the systems
766
767- Serial Download Echo Mode:
768		CONFIG_LOADS_ECHO
769		If defined to 1, all characters received during a
770		serial download (using the "loads" command) are
771		echoed back. This might be needed by some terminal
772		emulations (like "cu"), but may as well just take
773		time on others. This setting #define's the initial
774		value of the "loads_echo" environment variable.
775
776- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
777		CONFIG_KGDB_BAUDRATE
778		Select one of the baudrates listed in
779		CONFIG_SYS_BAUDRATE_TABLE, see below.
780
781- Monitor Functions:
782		Monitor commands can be included or excluded
783		from the build by using the #include files
784		<config_cmd_all.h> and #undef'ing unwanted
785		commands, or using <config_cmd_default.h>
786		and augmenting with additional #define's
787		for wanted commands.
788
789		The default command configuration includes all commands
790		except those marked below with a "*".
791
792		CONFIG_CMD_ASKENV	* ask for env variable
793		CONFIG_CMD_BDI		  bdinfo
794		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
795		CONFIG_CMD_BMP		* BMP support
796		CONFIG_CMD_BSP		* Board specific commands
797		CONFIG_CMD_BOOTD	  bootd
798		CONFIG_CMD_CACHE	* icache, dcache
799		CONFIG_CMD_CONSOLE	  coninfo
800		CONFIG_CMD_CRC32	* crc32
801		CONFIG_CMD_DATE		* support for RTC, date/time...
802		CONFIG_CMD_DHCP		* DHCP support
803		CONFIG_CMD_DIAG		* Diagnostics
804		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
805		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
806		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
807		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
808		CONFIG_CMD_DTT		* Digital Therm and Thermostat
809		CONFIG_CMD_ECHO		  echo arguments
810		CONFIG_CMD_EDITENV	  edit env variable
811		CONFIG_CMD_EEPROM	* EEPROM read/write support
812		CONFIG_CMD_ELF		* bootelf, bootvx
813		CONFIG_CMD_EXPORTENV	* export the environment
814		CONFIG_CMD_EXT2		* ext2 command support
815		CONFIG_CMD_EXT4		* ext4 command support
816		CONFIG_CMD_SAVEENV	  saveenv
817		CONFIG_CMD_FDC		* Floppy Disk Support
818		CONFIG_CMD_FAT		* FAT command support
819		CONFIG_CMD_FDOS		* Dos diskette Support
820		CONFIG_CMD_FLASH	  flinfo, erase, protect
821		CONFIG_CMD_FPGA		  FPGA device initialization support
822		CONFIG_CMD_GO		* the 'go' command (exec code)
823		CONFIG_CMD_GREPENV	* search environment
824		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
825		CONFIG_CMD_I2C		* I2C serial bus support
826		CONFIG_CMD_IDE		* IDE harddisk support
827		CONFIG_CMD_IMI		  iminfo
828		CONFIG_CMD_IMLS		  List all found images
829		CONFIG_CMD_IMMAP	* IMMR dump support
830		CONFIG_CMD_IMPORTENV	* import an environment
831		CONFIG_CMD_INI		* import data from an ini file into the env
832		CONFIG_CMD_IRQ		* irqinfo
833		CONFIG_CMD_ITEST	  Integer/string test of 2 values
834		CONFIG_CMD_JFFS2	* JFFS2 Support
835		CONFIG_CMD_KGDB		* kgdb
836		CONFIG_CMD_LDRINFO	  ldrinfo (display Blackfin loader)
837		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
838					  (169.254.*.*)
839		CONFIG_CMD_LOADB	  loadb
840		CONFIG_CMD_LOADS	  loads
841		CONFIG_CMD_MD5SUM	  print md5 message digest
842					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
843		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
844					  loop, loopw, mtest
845		CONFIG_CMD_MISC		  Misc functions like sleep etc
846		CONFIG_CMD_MMC		* MMC memory mapped support
847		CONFIG_CMD_MII		* MII utility commands
848		CONFIG_CMD_MTDPARTS	* MTD partition support
849		CONFIG_CMD_NAND		* NAND support
850		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
851		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
852		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
853		CONFIG_CMD_PCI		* pciinfo
854		CONFIG_CMD_PCMCIA		* PCMCIA support
855		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
856					  host
857		CONFIG_CMD_PORTIO	* Port I/O
858		CONFIG_CMD_REGINFO	* Register dump
859		CONFIG_CMD_RUN		  run command in env variable
860		CONFIG_CMD_SAVES	* save S record dump
861		CONFIG_CMD_SCSI		* SCSI Support
862		CONFIG_CMD_SDRAM	* print SDRAM configuration information
863					  (requires CONFIG_CMD_I2C)
864		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
865					  (4xx only)
866		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
867		CONFIG_CMD_SHA1SUM	  print sha1 memory digest
868					  (requires CONFIG_CMD_MEMORY)
869		CONFIG_CMD_SOURCE	  "source" command Support
870		CONFIG_CMD_SPI		* SPI serial bus support
871		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
872		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
873		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
874		CONFIG_CMD_TIMER	* access to the system tick timer
875		CONFIG_CMD_USB		* USB support
876		CONFIG_CMD_CDP		* Cisco Discover Protocol support
877		CONFIG_CMD_MFSL		* Microblaze FSL support
878
879
880		EXAMPLE: If you want all functions except of network
881		support you can write:
882
883		#include "config_cmd_all.h"
884		#undef CONFIG_CMD_NET
885
886	Other Commands:
887		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
888
889	Note:	Don't enable the "icache" and "dcache" commands
890		(configuration option CONFIG_CMD_CACHE) unless you know
891		what you (and your U-Boot users) are doing. Data
892		cache cannot be enabled on systems like the 8xx or
893		8260 (where accesses to the IMMR region must be
894		uncached), and it cannot be disabled on all other
895		systems where we (mis-) use the data cache to hold an
896		initial stack and some data.
897
898
899		XXX - this list needs to get updated!
900
901- Device tree:
902		CONFIG_OF_CONTROL
903		If this variable is defined, U-Boot will use a device tree
904		to configure its devices, instead of relying on statically
905		compiled #defines in the board file. This option is
906		experimental and only available on a few boards. The device
907		tree is available in the global data as gd->fdt_blob.
908
909		U-Boot needs to get its device tree from somewhere. This can
910		be done using one of the two options below:
911
912		CONFIG_OF_EMBED
913		If this variable is defined, U-Boot will embed a device tree
914		binary in its image. This device tree file should be in the
915		board directory and called <soc>-<board>.dts. The binary file
916		is then picked up in board_init_f() and made available through
917		the global data structure as gd->blob.
918
919		CONFIG_OF_SEPARATE
920		If this variable is defined, U-Boot will build a device tree
921		binary. It will be called u-boot.dtb. Architecture-specific
922		code will locate it at run-time. Generally this works by:
923
924			cat u-boot.bin u-boot.dtb >image.bin
925
926		and in fact, U-Boot does this for you, creating a file called
927		u-boot-dtb.bin which is useful in the common case. You can
928		still use the individual files if you need something more
929		exotic.
930
931- Watchdog:
932		CONFIG_WATCHDOG
933		If this variable is defined, it enables watchdog
934		support for the SoC. There must be support in the SoC
935		specific code for a watchdog. For the 8xx and 8260
936		CPUs, the SIU Watchdog feature is enabled in the SYPCR
937		register.  When supported for a specific SoC is
938		available, then no further board specific code should
939		be needed to use it.
940
941		CONFIG_HW_WATCHDOG
942		When using a watchdog circuitry external to the used
943		SoC, then define this variable and provide board
944		specific code for the "hw_watchdog_reset" function.
945
946- U-Boot Version:
947		CONFIG_VERSION_VARIABLE
948		If this variable is defined, an environment variable
949		named "ver" is created by U-Boot showing the U-Boot
950		version as printed by the "version" command.
951		Any change to this variable will be reverted at the
952		next reset.
953
954- Real-Time Clock:
955
956		When CONFIG_CMD_DATE is selected, the type of the RTC
957		has to be selected, too. Define exactly one of the
958		following options:
959
960		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
961		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
962		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
963		CONFIG_RTC_MC146818	- use MC146818 RTC
964		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
965		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
966		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
967		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
968		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
969		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
970		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
971		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
972					  RV3029 RTC.
973
974		Note that if the RTC uses I2C, then the I2C interface
975		must also be configured. See I2C Support, below.
976
977- GPIO Support:
978		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
979		CONFIG_PCA953X_INFO	- enable pca953x info command
980
981		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
982		chip-ngpio pairs that tell the PCA953X driver the number of
983		pins supported by a particular chip.
984
985		Note that if the GPIO device uses I2C, then the I2C interface
986		must also be configured. See I2C Support, below.
987
988- Timestamp Support:
989
990		When CONFIG_TIMESTAMP is selected, the timestamp
991		(date and time) of an image is printed by image
992		commands like bootm or iminfo. This option is
993		automatically enabled when you select CONFIG_CMD_DATE .
994
995- Partition Labels (disklabels) Supported:
996		Zero or more of the following:
997		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
998		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
999				       Intel architecture, USB sticks, etc.
1000		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1001		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1002				       bootloader.  Note 2TB partition limit; see
1003				       disk/part_efi.c
1004		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1005
1006		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1007		CONFIG_CMD_SCSI) you must configure support for at
1008		least one non-MTD partition type as well.
1009
1010- IDE Reset method:
1011		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1012		board configurations files but used nowhere!
1013
1014		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1015		be performed by calling the function
1016			ide_set_reset(int reset)
1017		which has to be defined in a board specific file
1018
1019- ATAPI Support:
1020		CONFIG_ATAPI
1021
1022		Set this to enable ATAPI support.
1023
1024- LBA48 Support
1025		CONFIG_LBA48
1026
1027		Set this to enable support for disks larger than 137GB
1028		Also look at CONFIG_SYS_64BIT_LBA.
1029		Whithout these , LBA48 support uses 32bit variables and will 'only'
1030		support disks up to 2.1TB.
1031
1032		CONFIG_SYS_64BIT_LBA:
1033			When enabled, makes the IDE subsystem use 64bit sector addresses.
1034			Default is 32bit.
1035
1036- SCSI Support:
1037		At the moment only there is only support for the
1038		SYM53C8XX SCSI controller; define
1039		CONFIG_SCSI_SYM53C8XX to enable it.
1040
1041		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1042		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1043		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1044		maximum numbers of LUNs, SCSI ID's and target
1045		devices.
1046		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1047
1048                The environment variable 'scsidevs' is set to the number of
1049                SCSI devices found during the last scan.
1050
1051- NETWORK Support (PCI):
1052		CONFIG_E1000
1053		Support for Intel 8254x/8257x gigabit chips.
1054
1055		CONFIG_E1000_SPI
1056		Utility code for direct access to the SPI bus on Intel 8257x.
1057		This does not do anything useful unless you set at least one
1058		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1059
1060		CONFIG_E1000_SPI_GENERIC
1061		Allow generic access to the SPI bus on the Intel 8257x, for
1062		example with the "sspi" command.
1063
1064		CONFIG_CMD_E1000
1065		Management command for E1000 devices.  When used on devices
1066		with SPI support you can reprogram the EEPROM from U-Boot.
1067
1068		CONFIG_E1000_FALLBACK_MAC
1069		default MAC for empty EEPROM after production.
1070
1071		CONFIG_EEPRO100
1072		Support for Intel 82557/82559/82559ER chips.
1073		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1074		write routine for first time initialisation.
1075
1076		CONFIG_TULIP
1077		Support for Digital 2114x chips.
1078		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1079		modem chip initialisation (KS8761/QS6611).
1080
1081		CONFIG_NATSEMI
1082		Support for National dp83815 chips.
1083
1084		CONFIG_NS8382X
1085		Support for National dp8382[01] gigabit chips.
1086
1087- NETWORK Support (other):
1088
1089		CONFIG_DRIVER_AT91EMAC
1090		Support for AT91RM9200 EMAC.
1091
1092			CONFIG_RMII
1093			Define this to use reduced MII inteface
1094
1095			CONFIG_DRIVER_AT91EMAC_QUIET
1096			If this defined, the driver is quiet.
1097			The driver doen't show link status messages.
1098
1099		CONFIG_CALXEDA_XGMAC
1100		Support for the Calxeda XGMAC device
1101
1102		CONFIG_LAN91C96
1103		Support for SMSC's LAN91C96 chips.
1104
1105			CONFIG_LAN91C96_BASE
1106			Define this to hold the physical address
1107			of the LAN91C96's I/O space
1108
1109			CONFIG_LAN91C96_USE_32_BIT
1110			Define this to enable 32 bit addressing
1111
1112		CONFIG_SMC91111
1113		Support for SMSC's LAN91C111 chip
1114
1115			CONFIG_SMC91111_BASE
1116			Define this to hold the physical address
1117			of the device (I/O space)
1118
1119			CONFIG_SMC_USE_32_BIT
1120			Define this if data bus is 32 bits
1121
1122			CONFIG_SMC_USE_IOFUNCS
1123			Define this to use i/o functions instead of macros
1124			(some hardware wont work with macros)
1125
1126		CONFIG_DRIVER_TI_EMAC
1127		Support for davinci emac
1128
1129			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1130			Define this if you have more then 3 PHYs.
1131
1132		CONFIG_FTGMAC100
1133		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1134
1135			CONFIG_FTGMAC100_EGIGA
1136			Define this to use GE link update with gigabit PHY.
1137			Define this if FTGMAC100 is connected to gigabit PHY.
1138			If your system has 10/100 PHY only, it might not occur
1139			wrong behavior. Because PHY usually return timeout or
1140			useless data when polling gigabit status and gigabit
1141			control registers. This behavior won't affect the
1142			correctnessof 10/100 link speed update.
1143
1144		CONFIG_SMC911X
1145		Support for SMSC's LAN911x and LAN921x chips
1146
1147			CONFIG_SMC911X_BASE
1148			Define this to hold the physical address
1149			of the device (I/O space)
1150
1151			CONFIG_SMC911X_32_BIT
1152			Define this if data bus is 32 bits
1153
1154			CONFIG_SMC911X_16_BIT
1155			Define this if data bus is 16 bits. If your processor
1156			automatically converts one 32 bit word to two 16 bit
1157			words you may also try CONFIG_SMC911X_32_BIT.
1158
1159		CONFIG_SH_ETHER
1160		Support for Renesas on-chip Ethernet controller
1161
1162			CONFIG_SH_ETHER_USE_PORT
1163			Define the number of ports to be used
1164
1165			CONFIG_SH_ETHER_PHY_ADDR
1166			Define the ETH PHY's address
1167
1168			CONFIG_SH_ETHER_CACHE_WRITEBACK
1169			If this option is set, the driver enables cache flush.
1170
1171- TPM Support:
1172		CONFIG_GENERIC_LPC_TPM
1173		Support for generic parallel port TPM devices. Only one device
1174		per system is supported at this time.
1175
1176			CONFIG_TPM_TIS_BASE_ADDRESS
1177			Base address where the generic TPM device is mapped
1178			to. Contemporary x86 systems usually map it at
1179			0xfed40000.
1180
1181- USB Support:
1182		At the moment only the UHCI host controller is
1183		supported (PIP405, MIP405, MPC5200); define
1184		CONFIG_USB_UHCI to enable it.
1185		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1186		and define CONFIG_USB_STORAGE to enable the USB
1187		storage devices.
1188		Note:
1189		Supported are USB Keyboards and USB Floppy drives
1190		(TEAC FD-05PUB).
1191		MPC5200 USB requires additional defines:
1192			CONFIG_USB_CLOCK
1193				for 528 MHz Clock: 0x0001bbbb
1194			CONFIG_PSC3_USB
1195				for USB on PSC3
1196			CONFIG_USB_CONFIG
1197				for differential drivers: 0x00001000
1198				for single ended drivers: 0x00005000
1199				for differential drivers on PSC3: 0x00000100
1200				for single ended drivers on PSC3: 0x00004100
1201			CONFIG_SYS_USB_EVENT_POLL
1202				May be defined to allow interrupt polling
1203				instead of using asynchronous interrupts
1204
1205		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1206		txfilltuning field in the EHCI controller on reset.
1207
1208- USB Device:
1209		Define the below if you wish to use the USB console.
1210		Once firmware is rebuilt from a serial console issue the
1211		command "setenv stdin usbtty; setenv stdout usbtty" and
1212		attach your USB cable. The Unix command "dmesg" should print
1213		it has found a new device. The environment variable usbtty
1214		can be set to gserial or cdc_acm to enable your device to
1215		appear to a USB host as a Linux gserial device or a
1216		Common Device Class Abstract Control Model serial device.
1217		If you select usbtty = gserial you should be able to enumerate
1218		a Linux host by
1219		# modprobe usbserial vendor=0xVendorID product=0xProductID
1220		else if using cdc_acm, simply setting the environment
1221		variable usbtty to be cdc_acm should suffice. The following
1222		might be defined in YourBoardName.h
1223
1224			CONFIG_USB_DEVICE
1225			Define this to build a UDC device
1226
1227			CONFIG_USB_TTY
1228			Define this to have a tty type of device available to
1229			talk to the UDC device
1230
1231			CONFIG_USBD_HS
1232			Define this to enable the high speed support for usb
1233			device and usbtty. If this feature is enabled, a routine
1234			int is_usbd_high_speed(void)
1235			also needs to be defined by the driver to dynamically poll
1236			whether the enumeration has succeded at high speed or full
1237			speed.
1238
1239			CONFIG_SYS_CONSOLE_IS_IN_ENV
1240			Define this if you want stdin, stdout &/or stderr to
1241			be set to usbtty.
1242
1243			mpc8xx:
1244				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1245				Derive USB clock from external clock "blah"
1246				- CONFIG_SYS_USB_EXTC_CLK 0x02
1247
1248				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1249				Derive USB clock from brgclk
1250				- CONFIG_SYS_USB_BRG_CLK 0x04
1251
1252		If you have a USB-IF assigned VendorID then you may wish to
1253		define your own vendor specific values either in BoardName.h
1254		or directly in usbd_vendor_info.h. If you don't define
1255		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1256		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1257		should pretend to be a Linux device to it's target host.
1258
1259			CONFIG_USBD_MANUFACTURER
1260			Define this string as the name of your company for
1261			- CONFIG_USBD_MANUFACTURER "my company"
1262
1263			CONFIG_USBD_PRODUCT_NAME
1264			Define this string as the name of your product
1265			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1266
1267			CONFIG_USBD_VENDORID
1268			Define this as your assigned Vendor ID from the USB
1269			Implementors Forum. This *must* be a genuine Vendor ID
1270			to avoid polluting the USB namespace.
1271			- CONFIG_USBD_VENDORID 0xFFFF
1272
1273			CONFIG_USBD_PRODUCTID
1274			Define this as the unique Product ID
1275			for your device
1276			- CONFIG_USBD_PRODUCTID 0xFFFF
1277
1278- ULPI Layer Support:
1279		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1280		the generic ULPI layer. The generic layer accesses the ULPI PHY
1281		via the platform viewport, so you need both the genric layer and
1282		the viewport enabled. Currently only Chipidea/ARC based
1283		viewport is supported.
1284		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1285		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1286		If your ULPI phy needs a different reference clock than the
1287		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1288		the appropriate value in Hz.
1289
1290- MMC Support:
1291		The MMC controller on the Intel PXA is supported. To
1292		enable this define CONFIG_MMC. The MMC can be
1293		accessed from the boot prompt by mapping the device
1294		to physical memory similar to flash. Command line is
1295		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1296		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1297
1298		CONFIG_SH_MMCIF
1299		Support for Renesas on-chip MMCIF controller
1300
1301			CONFIG_SH_MMCIF_ADDR
1302			Define the base address of MMCIF registers
1303
1304			CONFIG_SH_MMCIF_CLK
1305			Define the clock frequency for MMCIF
1306
1307- Journaling Flash filesystem support:
1308		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1309		CONFIG_JFFS2_NAND_DEV
1310		Define these for a default partition on a NAND device
1311
1312		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1313		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1314		Define these for a default partition on a NOR device
1315
1316		CONFIG_SYS_JFFS_CUSTOM_PART
1317		Define this to create an own partition. You have to provide a
1318		function struct part_info* jffs2_part_info(int part_num)
1319
1320		If you define only one JFFS2 partition you may also want to
1321		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1322		to disable the command chpart. This is the default when you
1323		have not defined a custom partition
1324
1325- FAT(File Allocation Table) filesystem write function support:
1326		CONFIG_FAT_WRITE
1327
1328		Define this to enable support for saving memory data as a
1329		file in FAT formatted partition.
1330
1331		This will also enable the command "fatwrite" enabling the
1332		user to write files to FAT.
1333
1334CBFS (Coreboot Filesystem) support
1335		CONFIG_CMD_CBFS
1336
1337		Define this to enable support for reading from a Coreboot
1338		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1339		and cbfsload.
1340
1341- Keyboard Support:
1342		CONFIG_ISA_KEYBOARD
1343
1344		Define this to enable standard (PC-Style) keyboard
1345		support
1346
1347		CONFIG_I8042_KBD
1348		Standard PC keyboard driver with US (is default) and
1349		GERMAN key layout (switch via environment 'keymap=de') support.
1350		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1351		for cfb_console. Supports cursor blinking.
1352
1353- Video support:
1354		CONFIG_VIDEO
1355
1356		Define this to enable video support (for output to
1357		video).
1358
1359		CONFIG_VIDEO_CT69000
1360
1361		Enable Chips & Technologies 69000 Video chip
1362
1363		CONFIG_VIDEO_SMI_LYNXEM
1364		Enable Silicon Motion SMI 712/710/810 Video chip. The
1365		video output is selected via environment 'videoout'
1366		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1367		assumed.
1368
1369		For the CT69000 and SMI_LYNXEM drivers, videomode is
1370		selected via environment 'videomode'. Two different ways
1371		are possible:
1372		- "videomode=num"   'num' is a standard LiLo mode numbers.
1373		Following standard modes are supported	(* is default):
1374
1375		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1376		-------------+---------------------------------------------
1377		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1378		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1379		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1380		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1381		-------------+---------------------------------------------
1382		(i.e. setenv videomode 317; saveenv; reset;)
1383
1384		- "videomode=bootargs" all the video parameters are parsed
1385		from the bootargs. (See drivers/video/videomodes.c)
1386
1387
1388		CONFIG_VIDEO_SED13806
1389		Enable Epson SED13806 driver. This driver supports 8bpp
1390		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1391		or CONFIG_VIDEO_SED13806_16BPP
1392
1393		CONFIG_FSL_DIU_FB
1394		Enable the Freescale DIU video driver.	Reference boards for
1395		SOCs that have a DIU should define this macro to enable DIU
1396		support, and should also define these other macros:
1397
1398			CONFIG_SYS_DIU_ADDR
1399			CONFIG_VIDEO
1400			CONFIG_CMD_BMP
1401			CONFIG_CFB_CONSOLE
1402			CONFIG_VIDEO_SW_CURSOR
1403			CONFIG_VGA_AS_SINGLE_DEVICE
1404			CONFIG_VIDEO_LOGO
1405			CONFIG_VIDEO_BMP_LOGO
1406
1407		The DIU driver will look for the 'video-mode' environment
1408		variable, and if defined, enable the DIU as a console during
1409		boot.  See the documentation file README.video for a
1410		description of this variable.
1411
1412- Keyboard Support:
1413		CONFIG_KEYBOARD
1414
1415		Define this to enable a custom keyboard support.
1416		This simply calls drv_keyboard_init() which must be
1417		defined in your board-specific files.
1418		The only board using this so far is RBC823.
1419
1420- LCD Support:	CONFIG_LCD
1421
1422		Define this to enable LCD support (for output to LCD
1423		display); also select one of the supported displays
1424		by defining one of these:
1425
1426		CONFIG_ATMEL_LCD:
1427
1428			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1429
1430		CONFIG_NEC_NL6448AC33:
1431
1432			NEC NL6448AC33-18. Active, color, single scan.
1433
1434		CONFIG_NEC_NL6448BC20
1435
1436			NEC NL6448BC20-08. 6.5", 640x480.
1437			Active, color, single scan.
1438
1439		CONFIG_NEC_NL6448BC33_54
1440
1441			NEC NL6448BC33-54. 10.4", 640x480.
1442			Active, color, single scan.
1443
1444		CONFIG_SHARP_16x9
1445
1446			Sharp 320x240. Active, color, single scan.
1447			It isn't 16x9, and I am not sure what it is.
1448
1449		CONFIG_SHARP_LQ64D341
1450
1451			Sharp LQ64D341 display, 640x480.
1452			Active, color, single scan.
1453
1454		CONFIG_HLD1045
1455
1456			HLD1045 display, 640x480.
1457			Active, color, single scan.
1458
1459		CONFIG_OPTREX_BW
1460
1461			Optrex	 CBL50840-2 NF-FW 99 22 M5
1462			or
1463			Hitachi	 LMG6912RPFC-00T
1464			or
1465			Hitachi	 SP14Q002
1466
1467			320x240. Black & white.
1468
1469		Normally display is black on white background; define
1470		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1471
1472		CONFIG_LCD_BMP_RLE8
1473
1474		Support drawing of RLE8-compressed bitmaps on the LCD.
1475
1476
1477- Splash Screen Support: CONFIG_SPLASH_SCREEN
1478
1479		If this option is set, the environment is checked for
1480		a variable "splashimage". If found, the usual display
1481		of logo, copyright and system information on the LCD
1482		is suppressed and the BMP image at the address
1483		specified in "splashimage" is loaded instead. The
1484		console is redirected to the "nulldev", too. This
1485		allows for a "silent" boot where a splash screen is
1486		loaded very quickly after power-on.
1487
1488		CONFIG_SPLASH_SCREEN_ALIGN
1489
1490		If this option is set the splash image can be freely positioned
1491		on the screen. Environment variable "splashpos" specifies the
1492		position as "x,y". If a positive number is given it is used as
1493		number of pixel from left/top. If a negative number is given it
1494		is used as number of pixel from right/bottom. You can also
1495		specify 'm' for centering the image.
1496
1497		Example:
1498		setenv splashpos m,m
1499			=> image at center of screen
1500
1501		setenv splashpos 30,20
1502			=> image at x = 30 and y = 20
1503
1504		setenv splashpos -10,m
1505			=> vertically centered image
1506			   at x = dspWidth - bmpWidth - 9
1507
1508- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1509
1510		If this option is set, additionally to standard BMP
1511		images, gzipped BMP images can be displayed via the
1512		splashscreen support or the bmp command.
1513
1514- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1515
1516		If this option is set, 8-bit RLE compressed BMP images
1517		can be displayed via the splashscreen support or the
1518		bmp command.
1519
1520- Do compresssing for memory range:
1521		CONFIG_CMD_ZIP
1522
1523		If this option is set, it would use zlib deflate method
1524		to compress the specified memory at its best effort.
1525
1526- Compression support:
1527		CONFIG_BZIP2
1528
1529		If this option is set, support for bzip2 compressed
1530		images is included. If not, only uncompressed and gzip
1531		compressed images are supported.
1532
1533		NOTE: the bzip2 algorithm requires a lot of RAM, so
1534		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1535		be at least 4MB.
1536
1537		CONFIG_LZMA
1538
1539		If this option is set, support for lzma compressed
1540		images is included.
1541
1542		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1543		requires an amount of dynamic memory that is given by the
1544		formula:
1545
1546			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1547
1548		Where lc and lp stand for, respectively, Literal context bits
1549		and Literal pos bits.
1550
1551		This value is upper-bounded by 14MB in the worst case. Anyway,
1552		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1553		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1554		a very small buffer.
1555
1556		Use the lzmainfo tool to determinate the lc and lp values and
1557		then calculate the amount of needed dynamic memory (ensuring
1558		the appropriate CONFIG_SYS_MALLOC_LEN value).
1559
1560- MII/PHY support:
1561		CONFIG_PHY_ADDR
1562
1563		The address of PHY on MII bus.
1564
1565		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1566
1567		The clock frequency of the MII bus
1568
1569		CONFIG_PHY_GIGE
1570
1571		If this option is set, support for speed/duplex
1572		detection of gigabit PHY is included.
1573
1574		CONFIG_PHY_RESET_DELAY
1575
1576		Some PHY like Intel LXT971A need extra delay after
1577		reset before any MII register access is possible.
1578		For such PHY, set this option to the usec delay
1579		required. (minimum 300usec for LXT971A)
1580
1581		CONFIG_PHY_CMD_DELAY (ppc4xx)
1582
1583		Some PHY like Intel LXT971A need extra delay after
1584		command issued before MII status register can be read
1585
1586- Ethernet address:
1587		CONFIG_ETHADDR
1588		CONFIG_ETH1ADDR
1589		CONFIG_ETH2ADDR
1590		CONFIG_ETH3ADDR
1591		CONFIG_ETH4ADDR
1592		CONFIG_ETH5ADDR
1593
1594		Define a default value for Ethernet address to use
1595		for the respective Ethernet interface, in case this
1596		is not determined automatically.
1597
1598- IP address:
1599		CONFIG_IPADDR
1600
1601		Define a default value for the IP address to use for
1602		the default Ethernet interface, in case this is not
1603		determined through e.g. bootp.
1604		(Environment variable "ipaddr")
1605
1606- Server IP address:
1607		CONFIG_SERVERIP
1608
1609		Defines a default value for the IP address of a TFTP
1610		server to contact when using the "tftboot" command.
1611		(Environment variable "serverip")
1612
1613		CONFIG_KEEP_SERVERADDR
1614
1615		Keeps the server's MAC address, in the env 'serveraddr'
1616		for passing to bootargs (like Linux's netconsole option)
1617
1618- Gateway IP address:
1619		CONFIG_GATEWAYIP
1620
1621		Defines a default value for the IP address of the
1622		default router where packets to other networks are
1623		sent to.
1624		(Environment variable "gatewayip")
1625
1626- Subnet mask:
1627		CONFIG_NETMASK
1628
1629		Defines a default value for the subnet mask (or
1630		routing prefix) which is used to determine if an IP
1631		address belongs to the local subnet or needs to be
1632		forwarded through a router.
1633		(Environment variable "netmask")
1634
1635- Multicast TFTP Mode:
1636		CONFIG_MCAST_TFTP
1637
1638		Defines whether you want to support multicast TFTP as per
1639		rfc-2090; for example to work with atftp.  Lets lots of targets
1640		tftp down the same boot image concurrently.  Note: the Ethernet
1641		driver in use must provide a function: mcast() to join/leave a
1642		multicast group.
1643
1644- BOOTP Recovery Mode:
1645		CONFIG_BOOTP_RANDOM_DELAY
1646
1647		If you have many targets in a network that try to
1648		boot using BOOTP, you may want to avoid that all
1649		systems send out BOOTP requests at precisely the same
1650		moment (which would happen for instance at recovery
1651		from a power failure, when all systems will try to
1652		boot, thus flooding the BOOTP server. Defining
1653		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1654		inserted before sending out BOOTP requests. The
1655		following delays are inserted then:
1656
1657		1st BOOTP request:	delay 0 ... 1 sec
1658		2nd BOOTP request:	delay 0 ... 2 sec
1659		3rd BOOTP request:	delay 0 ... 4 sec
1660		4th and following
1661		BOOTP requests:		delay 0 ... 8 sec
1662
1663- DHCP Advanced Options:
1664		You can fine tune the DHCP functionality by defining
1665		CONFIG_BOOTP_* symbols:
1666
1667		CONFIG_BOOTP_SUBNETMASK
1668		CONFIG_BOOTP_GATEWAY
1669		CONFIG_BOOTP_HOSTNAME
1670		CONFIG_BOOTP_NISDOMAIN
1671		CONFIG_BOOTP_BOOTPATH
1672		CONFIG_BOOTP_BOOTFILESIZE
1673		CONFIG_BOOTP_DNS
1674		CONFIG_BOOTP_DNS2
1675		CONFIG_BOOTP_SEND_HOSTNAME
1676		CONFIG_BOOTP_NTPSERVER
1677		CONFIG_BOOTP_TIMEOFFSET
1678		CONFIG_BOOTP_VENDOREX
1679		CONFIG_BOOTP_MAY_FAIL
1680
1681		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1682		environment variable, not the BOOTP server.
1683
1684		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1685		after the configured retry count, the call will fail
1686		instead of starting over.  This can be used to fail over
1687		to Link-local IP address configuration if the DHCP server
1688		is not available.
1689
1690		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1691		serverip from a DHCP server, it is possible that more
1692		than one DNS serverip is offered to the client.
1693		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1694		serverip will be stored in the additional environment
1695		variable "dnsip2". The first DNS serverip is always
1696		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1697		is defined.
1698
1699		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1700		to do a dynamic update of a DNS server. To do this, they
1701		need the hostname of the DHCP requester.
1702		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1703		of the "hostname" environment variable is passed as
1704		option 12 to the DHCP server.
1705
1706		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1707
1708		A 32bit value in microseconds for a delay between
1709		receiving a "DHCP Offer" and sending the "DHCP Request".
1710		This fixes a problem with certain DHCP servers that don't
1711		respond 100% of the time to a "DHCP request". E.g. On an
1712		AT91RM9200 processor running at 180MHz, this delay needed
1713		to be *at least* 15,000 usec before a Windows Server 2003
1714		DHCP server would reply 100% of the time. I recommend at
1715		least 50,000 usec to be safe. The alternative is to hope
1716		that one of the retries will be successful but note that
1717		the DHCP timeout and retry process takes a longer than
1718		this delay.
1719
1720 - Link-local IP address negotiation:
1721		Negotiate with other link-local clients on the local network
1722		for an address that doesn't require explicit configuration.
1723		This is especially useful if a DHCP server cannot be guaranteed
1724		to exist in all environments that the device must operate.
1725
1726		See doc/README.link-local for more information.
1727
1728 - CDP Options:
1729		CONFIG_CDP_DEVICE_ID
1730
1731		The device id used in CDP trigger frames.
1732
1733		CONFIG_CDP_DEVICE_ID_PREFIX
1734
1735		A two character string which is prefixed to the MAC address
1736		of the device.
1737
1738		CONFIG_CDP_PORT_ID
1739
1740		A printf format string which contains the ascii name of
1741		the port. Normally is set to "eth%d" which sets
1742		eth0 for the first Ethernet, eth1 for the second etc.
1743
1744		CONFIG_CDP_CAPABILITIES
1745
1746		A 32bit integer which indicates the device capabilities;
1747		0x00000010 for a normal host which does not forwards.
1748
1749		CONFIG_CDP_VERSION
1750
1751		An ascii string containing the version of the software.
1752
1753		CONFIG_CDP_PLATFORM
1754
1755		An ascii string containing the name of the platform.
1756
1757		CONFIG_CDP_TRIGGER
1758
1759		A 32bit integer sent on the trigger.
1760
1761		CONFIG_CDP_POWER_CONSUMPTION
1762
1763		A 16bit integer containing the power consumption of the
1764		device in .1 of milliwatts.
1765
1766		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1767
1768		A byte containing the id of the VLAN.
1769
1770- Status LED:	CONFIG_STATUS_LED
1771
1772		Several configurations allow to display the current
1773		status using a LED. For instance, the LED will blink
1774		fast while running U-Boot code, stop blinking as
1775		soon as a reply to a BOOTP request was received, and
1776		start blinking slow once the Linux kernel is running
1777		(supported by a status LED driver in the Linux
1778		kernel). Defining CONFIG_STATUS_LED enables this
1779		feature in U-Boot.
1780
1781- CAN Support:	CONFIG_CAN_DRIVER
1782
1783		Defining CONFIG_CAN_DRIVER enables CAN driver support
1784		on those systems that support this (optional)
1785		feature, like the TQM8xxL modules.
1786
1787- I2C Support:	CONFIG_HARD_I2C | CONFIG_SOFT_I2C
1788
1789		These enable I2C serial bus commands. Defining either of
1790		(but not both of) CONFIG_HARD_I2C or CONFIG_SOFT_I2C will
1791		include the appropriate I2C driver for the selected CPU.
1792
1793		This will allow you to use i2c commands at the u-boot
1794		command line (as long as you set CONFIG_CMD_I2C in
1795		CONFIG_COMMANDS) and communicate with i2c based realtime
1796		clock chips. See common/cmd_i2c.c for a description of the
1797		command line interface.
1798
1799		CONFIG_HARD_I2C selects a hardware I2C controller.
1800
1801		CONFIG_SOFT_I2C configures u-boot to use a software (aka
1802		bit-banging) driver instead of CPM or similar hardware
1803		support for I2C.
1804
1805		There are several other quantities that must also be
1806		defined when you define CONFIG_HARD_I2C or CONFIG_SOFT_I2C.
1807
1808		In both cases you will need to define CONFIG_SYS_I2C_SPEED
1809		to be the frequency (in Hz) at which you wish your i2c bus
1810		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
1811		the CPU's i2c node address).
1812
1813		Now, the u-boot i2c code for the mpc8xx
1814		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
1815		and so its address should therefore be cleared to 0 (See,
1816		eg, MPC823e User's Manual p.16-473). So, set
1817		CONFIG_SYS_I2C_SLAVE to 0.
1818
1819		CONFIG_SYS_I2C_INIT_MPC5XXX
1820
1821		When a board is reset during an i2c bus transfer
1822		chips might think that the current transfer is still
1823		in progress.  Reset the slave devices by sending start
1824		commands until the slave device responds.
1825
1826		That's all that's required for CONFIG_HARD_I2C.
1827
1828		If you use the software i2c interface (CONFIG_SOFT_I2C)
1829		then the following macros need to be defined (examples are
1830		from include/configs/lwmon.h):
1831
1832		I2C_INIT
1833
1834		(Optional). Any commands necessary to enable the I2C
1835		controller or configure ports.
1836
1837		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1838
1839		I2C_PORT
1840
1841		(Only for MPC8260 CPU). The I/O port to use (the code
1842		assumes both bits are on the same port). Valid values
1843		are 0..3 for ports A..D.
1844
1845		I2C_ACTIVE
1846
1847		The code necessary to make the I2C data line active
1848		(driven).  If the data line is open collector, this
1849		define can be null.
1850
1851		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1852
1853		I2C_TRISTATE
1854
1855		The code necessary to make the I2C data line tri-stated
1856		(inactive).  If the data line is open collector, this
1857		define can be null.
1858
1859		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1860
1861		I2C_READ
1862
1863		Code that returns TRUE if the I2C data line is high,
1864		FALSE if it is low.
1865
1866		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1867
1868		I2C_SDA(bit)
1869
1870		If <bit> is TRUE, sets the I2C data line high. If it
1871		is FALSE, it clears it (low).
1872
1873		eg: #define I2C_SDA(bit) \
1874			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1875			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1876
1877		I2C_SCL(bit)
1878
1879		If <bit> is TRUE, sets the I2C clock line high. If it
1880		is FALSE, it clears it (low).
1881
1882		eg: #define I2C_SCL(bit) \
1883			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1884			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1885
1886		I2C_DELAY
1887
1888		This delay is invoked four times per clock cycle so this
1889		controls the rate of data transfer.  The data rate thus
1890		is 1 / (I2C_DELAY * 4). Often defined to be something
1891		like:
1892
1893		#define I2C_DELAY  udelay(2)
1894
1895		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1896
1897		If your arch supports the generic GPIO framework (asm/gpio.h),
1898		then you may alternatively define the two GPIOs that are to be
1899		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1900		have GPIO-based defaults assigned to them as appropriate.
1901
1902		You should define these to the GPIO value as given directly to
1903		the generic GPIO functions.
1904
1905		CONFIG_SYS_I2C_INIT_BOARD
1906
1907		When a board is reset during an i2c bus transfer
1908		chips might think that the current transfer is still
1909		in progress. On some boards it is possible to access
1910		the i2c SCLK line directly, either by using the
1911		processor pin as a GPIO or by having a second pin
1912		connected to the bus. If this option is defined a
1913		custom i2c_init_board() routine in boards/xxx/board.c
1914		is run early in the boot sequence.
1915
1916		CONFIG_SYS_I2C_BOARD_LATE_INIT
1917
1918		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
1919		defined a custom i2c_board_late_init() routine in
1920		boards/xxx/board.c is run AFTER the operations in i2c_init()
1921		is completed. This callpoint can be used to unreset i2c bus
1922		using CPU i2c controller register accesses for CPUs whose i2c
1923		controller provide such a method. It is called at the end of
1924		i2c_init() to allow i2c_init operations to setup the i2c bus
1925		controller on the CPU (e.g. setting bus speed & slave address).
1926
1927		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
1928
1929		This option enables configuration of bi_iic_fast[] flags
1930		in u-boot bd_info structure based on u-boot environment
1931		variable "i2cfast". (see also i2cfast)
1932
1933		CONFIG_I2C_MULTI_BUS
1934
1935		This option allows the use of multiple I2C buses, each of which
1936		must have a controller.	 At any point in time, only one bus is
1937		active.	 To switch to a different bus, use the 'i2c dev' command.
1938		Note that bus numbering is zero-based.
1939
1940		CONFIG_SYS_I2C_NOPROBES
1941
1942		This option specifies a list of I2C devices that will be skipped
1943		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1944		is set, specify a list of bus-device pairs.  Otherwise, specify
1945		a 1D array of device addresses
1946
1947		e.g.
1948			#undef	CONFIG_I2C_MULTI_BUS
1949			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1950
1951		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1952
1953			#define CONFIG_I2C_MULTI_BUS
1954			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1955
1956		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1957
1958		CONFIG_SYS_SPD_BUS_NUM
1959
1960		If defined, then this indicates the I2C bus number for DDR SPD.
1961		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1962
1963		CONFIG_SYS_RTC_BUS_NUM
1964
1965		If defined, then this indicates the I2C bus number for the RTC.
1966		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1967
1968		CONFIG_SYS_DTT_BUS_NUM
1969
1970		If defined, then this indicates the I2C bus number for the DTT.
1971		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
1972
1973		CONFIG_SYS_I2C_DTT_ADDR:
1974
1975		If defined, specifies the I2C address of the DTT device.
1976		If not defined, then U-Boot uses predefined value for
1977		specified DTT device.
1978
1979		CONFIG_FSL_I2C
1980
1981		Define this option if you want to use Freescale's I2C driver in
1982		drivers/i2c/fsl_i2c.c.
1983
1984		CONFIG_I2C_MUX
1985
1986		Define this option if you have I2C devices reached over 1 .. n
1987		I2C Muxes like the pca9544a. This option addes a new I2C
1988		Command "i2c bus [muxtype:muxaddr:muxchannel]" which adds a
1989		new I2C Bus to the existing I2C Busses. If you select the
1990		new Bus with "i2c dev", u-bbot sends first the commandos for
1991		the muxes to activate this new "bus".
1992
1993		CONFIG_I2C_MULTI_BUS must be also defined, to use this
1994		feature!
1995
1996		Example:
1997		Adding a new I2C Bus reached over 2 pca9544a muxes
1998			The First mux with address 70 and channel 6
1999			The Second mux with address 71 and channel 4
2000
2001		=> i2c bus pca9544a:70:6:pca9544a:71:4
2002
2003		Use the "i2c bus" command without parameter, to get a list
2004		of I2C Busses with muxes:
2005
2006		=> i2c bus
2007		Busses reached over muxes:
2008		Bus ID: 2
2009		  reached over Mux(es):
2010		    pca9544a@70 ch: 4
2011		Bus ID: 3
2012		  reached over Mux(es):
2013		    pca9544a@70 ch: 6
2014		    pca9544a@71 ch: 4
2015		=>
2016
2017		If you now switch to the new I2C Bus 3 with "i2c dev 3"
2018		u-boot first sends the command to the mux@70 to enable
2019		channel 6, and then the command to the mux@71 to enable
2020		the channel 4.
2021
2022		After that, you can use the "normal" i2c commands as
2023		usual to communicate with your I2C devices behind
2024		the 2 muxes.
2025
2026		This option is actually implemented for the bitbanging
2027		algorithm in common/soft_i2c.c and for the Hardware I2C
2028		Bus on the MPC8260. But it should be not so difficult
2029		to add this option to other architectures.
2030
2031		CONFIG_SOFT_I2C_READ_REPEATED_START
2032
2033		defining this will force the i2c_read() function in
2034		the soft_i2c driver to perform an I2C repeated start
2035		between writing the address pointer and reading the
2036		data.  If this define is omitted the default behaviour
2037		of doing a stop-start sequence will be used.  Most I2C
2038		devices can use either method, but some require one or
2039		the other.
2040
2041- SPI Support:	CONFIG_SPI
2042
2043		Enables SPI driver (so far only tested with
2044		SPI EEPROM, also an instance works with Crystal A/D and
2045		D/As on the SACSng board)
2046
2047		CONFIG_SH_SPI
2048
2049		Enables the driver for SPI controller on SuperH. Currently
2050		only SH7757 is supported.
2051
2052		CONFIG_SPI_X
2053
2054		Enables extended (16-bit) SPI EEPROM addressing.
2055		(symmetrical to CONFIG_I2C_X)
2056
2057		CONFIG_SOFT_SPI
2058
2059		Enables a software (bit-bang) SPI driver rather than
2060		using hardware support. This is a general purpose
2061		driver that only requires three general I/O port pins
2062		(two outputs, one input) to function. If this is
2063		defined, the board configuration must define several
2064		SPI configuration items (port pins to use, etc). For
2065		an example, see include/configs/sacsng.h.
2066
2067		CONFIG_HARD_SPI
2068
2069		Enables a hardware SPI driver for general-purpose reads
2070		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2071		must define a list of chip-select function pointers.
2072		Currently supported on some MPC8xxx processors.	 For an
2073		example, see include/configs/mpc8349emds.h.
2074
2075		CONFIG_MXC_SPI
2076
2077		Enables the driver for the SPI controllers on i.MX and MXC
2078		SoCs. Currently i.MX31/35/51 are supported.
2079
2080- FPGA Support: CONFIG_FPGA
2081
2082		Enables FPGA subsystem.
2083
2084		CONFIG_FPGA_<vendor>
2085
2086		Enables support for specific chip vendors.
2087		(ALTERA, XILINX)
2088
2089		CONFIG_FPGA_<family>
2090
2091		Enables support for FPGA family.
2092		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2093
2094		CONFIG_FPGA_COUNT
2095
2096		Specify the number of FPGA devices to support.
2097
2098		CONFIG_SYS_FPGA_PROG_FEEDBACK
2099
2100		Enable printing of hash marks during FPGA configuration.
2101
2102		CONFIG_SYS_FPGA_CHECK_BUSY
2103
2104		Enable checks on FPGA configuration interface busy
2105		status by the configuration function. This option
2106		will require a board or device specific function to
2107		be written.
2108
2109		CONFIG_FPGA_DELAY
2110
2111		If defined, a function that provides delays in the FPGA
2112		configuration driver.
2113
2114		CONFIG_SYS_FPGA_CHECK_CTRLC
2115		Allow Control-C to interrupt FPGA configuration
2116
2117		CONFIG_SYS_FPGA_CHECK_ERROR
2118
2119		Check for configuration errors during FPGA bitfile
2120		loading. For example, abort during Virtex II
2121		configuration if the INIT_B line goes low (which
2122		indicated a CRC error).
2123
2124		CONFIG_SYS_FPGA_WAIT_INIT
2125
2126		Maximum time to wait for the INIT_B line to deassert
2127		after PROB_B has been deasserted during a Virtex II
2128		FPGA configuration sequence. The default time is 500
2129		ms.
2130
2131		CONFIG_SYS_FPGA_WAIT_BUSY
2132
2133		Maximum time to wait for BUSY to deassert during
2134		Virtex II FPGA configuration. The default is 5 ms.
2135
2136		CONFIG_SYS_FPGA_WAIT_CONFIG
2137
2138		Time to wait after FPGA configuration. The default is
2139		200 ms.
2140
2141- Configuration Management:
2142		CONFIG_IDENT_STRING
2143
2144		If defined, this string will be added to the U-Boot
2145		version information (U_BOOT_VERSION)
2146
2147- Vendor Parameter Protection:
2148
2149		U-Boot considers the values of the environment
2150		variables "serial#" (Board Serial Number) and
2151		"ethaddr" (Ethernet Address) to be parameters that
2152		are set once by the board vendor / manufacturer, and
2153		protects these variables from casual modification by
2154		the user. Once set, these variables are read-only,
2155		and write or delete attempts are rejected. You can
2156		change this behaviour:
2157
2158		If CONFIG_ENV_OVERWRITE is #defined in your config
2159		file, the write protection for vendor parameters is
2160		completely disabled. Anybody can change or delete
2161		these parameters.
2162
2163		Alternatively, if you #define _both_ CONFIG_ETHADDR
2164		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2165		Ethernet address is installed in the environment,
2166		which can be changed exactly ONCE by the user. [The
2167		serial# is unaffected by this, i. e. it remains
2168		read-only.]
2169
2170- Protected RAM:
2171		CONFIG_PRAM
2172
2173		Define this variable to enable the reservation of
2174		"protected RAM", i. e. RAM which is not overwritten
2175		by U-Boot. Define CONFIG_PRAM to hold the number of
2176		kB you want to reserve for pRAM. You can overwrite
2177		this default value by defining an environment
2178		variable "pram" to the number of kB you want to
2179		reserve. Note that the board info structure will
2180		still show the full amount of RAM. If pRAM is
2181		reserved, a new environment variable "mem" will
2182		automatically be defined to hold the amount of
2183		remaining RAM in a form that can be passed as boot
2184		argument to Linux, for instance like that:
2185
2186			setenv bootargs ... mem=\${mem}
2187			saveenv
2188
2189		This way you can tell Linux not to use this memory,
2190		either, which results in a memory region that will
2191		not be affected by reboots.
2192
2193		*WARNING* If your board configuration uses automatic
2194		detection of the RAM size, you must make sure that
2195		this memory test is non-destructive. So far, the
2196		following board configurations are known to be
2197		"pRAM-clean":
2198
2199			IVMS8, IVML24, SPD8xx, TQM8xxL,
2200			HERMES, IP860, RPXlite, LWMON,
2201			FLAGADM, TQM8260
2202
2203- Error Recovery:
2204		CONFIG_PANIC_HANG
2205
2206		Define this variable to stop the system in case of a
2207		fatal error, so that you have to reset it manually.
2208		This is probably NOT a good idea for an embedded
2209		system where you want the system to reboot
2210		automatically as fast as possible, but it may be
2211		useful during development since you can try to debug
2212		the conditions that lead to the situation.
2213
2214		CONFIG_NET_RETRY_COUNT
2215
2216		This variable defines the number of retries for
2217		network operations like ARP, RARP, TFTP, or BOOTP
2218		before giving up the operation. If not defined, a
2219		default value of 5 is used.
2220
2221		CONFIG_ARP_TIMEOUT
2222
2223		Timeout waiting for an ARP reply in milliseconds.
2224
2225		CONFIG_NFS_TIMEOUT
2226
2227		Timeout in milliseconds used in NFS protocol.
2228		If you encounter "ERROR: Cannot umount" in nfs command,
2229		try longer timeout such as
2230		#define CONFIG_NFS_TIMEOUT 10000UL
2231
2232- Command Interpreter:
2233		CONFIG_AUTO_COMPLETE
2234
2235		Enable auto completion of commands using TAB.
2236
2237		Note that this feature has NOT been implemented yet
2238		for the "hush" shell.
2239
2240
2241		CONFIG_SYS_HUSH_PARSER
2242
2243		Define this variable to enable the "hush" shell (from
2244		Busybox) as command line interpreter, thus enabling
2245		powerful command line syntax like
2246		if...then...else...fi conditionals or `&&' and '||'
2247		constructs ("shell scripts").
2248
2249		If undefined, you get the old, much simpler behaviour
2250		with a somewhat smaller memory footprint.
2251
2252
2253		CONFIG_SYS_PROMPT_HUSH_PS2
2254
2255		This defines the secondary prompt string, which is
2256		printed when the command interpreter needs more input
2257		to complete a command. Usually "> ".
2258
2259	Note:
2260
2261		In the current implementation, the local variables
2262		space and global environment variables space are
2263		separated. Local variables are those you define by
2264		simply typing `name=value'. To access a local
2265		variable later on, you have write `$name' or
2266		`${name}'; to execute the contents of a variable
2267		directly type `$name' at the command prompt.
2268
2269		Global environment variables are those you use
2270		setenv/printenv to work with. To run a command stored
2271		in such a variable, you need to use the run command,
2272		and you must not use the '$' sign to access them.
2273
2274		To store commands and special characters in a
2275		variable, please use double quotation marks
2276		surrounding the whole text of the variable, instead
2277		of the backslashes before semicolons and special
2278		symbols.
2279
2280- Commandline Editing and History:
2281		CONFIG_CMDLINE_EDITING
2282
2283		Enable editing and History functions for interactive
2284		commandline input operations
2285
2286- Default Environment:
2287		CONFIG_EXTRA_ENV_SETTINGS
2288
2289		Define this to contain any number of null terminated
2290		strings (variable = value pairs) that will be part of
2291		the default environment compiled into the boot image.
2292
2293		For example, place something like this in your
2294		board's config file:
2295
2296		#define CONFIG_EXTRA_ENV_SETTINGS \
2297			"myvar1=value1\0" \
2298			"myvar2=value2\0"
2299
2300		Warning: This method is based on knowledge about the
2301		internal format how the environment is stored by the
2302		U-Boot code. This is NOT an official, exported
2303		interface! Although it is unlikely that this format
2304		will change soon, there is no guarantee either.
2305		You better know what you are doing here.
2306
2307		Note: overly (ab)use of the default environment is
2308		discouraged. Make sure to check other ways to preset
2309		the environment like the "source" command or the
2310		boot command first.
2311
2312		CONFIG_ENV_VARS_UBOOT_CONFIG
2313
2314		Define this in order to add variables describing the
2315		U-Boot build configuration to the default environment.
2316		These will be named arch, cpu, board, vendor, and soc.
2317
2318		Enabling this option will cause the following to be defined:
2319
2320		- CONFIG_SYS_ARCH
2321		- CONFIG_SYS_CPU
2322		- CONFIG_SYS_BOARD
2323		- CONFIG_SYS_VENDOR
2324		- CONFIG_SYS_SOC
2325
2326		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2327
2328		Define this in order to add variables describing certain
2329		run-time determined information about the hardware to the
2330		environment.  These will be named board_name, board_rev.
2331
2332- DataFlash Support:
2333		CONFIG_HAS_DATAFLASH
2334
2335		Defining this option enables DataFlash features and
2336		allows to read/write in Dataflash via the standard
2337		commands cp, md...
2338
2339- Serial Flash support
2340		CONFIG_CMD_SF
2341
2342		Defining this option enables SPI flash commands
2343		'sf probe/read/write/erase/update'.
2344
2345		Usage requires an initial 'probe' to define the serial
2346		flash parameters, followed by read/write/erase/update
2347		commands.
2348
2349		The following defaults may be provided by the platform
2350		to handle the common case when only a single serial
2351		flash is present on the system.
2352
2353		CONFIG_SF_DEFAULT_BUS		Bus identifier
2354		CONFIG_SF_DEFAULT_CS		Chip-select
2355		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2356		CONFIG_SF_DEFAULT_SPEED		in Hz
2357
2358- SystemACE Support:
2359		CONFIG_SYSTEMACE
2360
2361		Adding this option adds support for Xilinx SystemACE
2362		chips attached via some sort of local bus. The address
2363		of the chip must also be defined in the
2364		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2365
2366		#define CONFIG_SYSTEMACE
2367		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2368
2369		When SystemACE support is added, the "ace" device type
2370		becomes available to the fat commands, i.e. fatls.
2371
2372- TFTP Fixed UDP Port:
2373		CONFIG_TFTP_PORT
2374
2375		If this is defined, the environment variable tftpsrcp
2376		is used to supply the TFTP UDP source port value.
2377		If tftpsrcp isn't defined, the normal pseudo-random port
2378		number generator is used.
2379
2380		Also, the environment variable tftpdstp is used to supply
2381		the TFTP UDP destination port value.  If tftpdstp isn't
2382		defined, the normal port 69 is used.
2383
2384		The purpose for tftpsrcp is to allow a TFTP server to
2385		blindly start the TFTP transfer using the pre-configured
2386		target IP address and UDP port. This has the effect of
2387		"punching through" the (Windows XP) firewall, allowing
2388		the remainder of the TFTP transfer to proceed normally.
2389		A better solution is to properly configure the firewall,
2390		but sometimes that is not allowed.
2391
2392- Show boot progress:
2393		CONFIG_SHOW_BOOT_PROGRESS
2394
2395		Defining this option allows to add some board-
2396		specific code (calling a user-provided function
2397		"show_boot_progress(int)") that enables you to show
2398		the system's boot progress on some display (for
2399		example, some LED's) on your board. At the moment,
2400		the following checkpoints are implemented:
2401
2402- Detailed boot stage timing
2403		CONFIG_BOOTSTAGE
2404		Define this option to get detailed timing of each stage
2405		of the boot process.
2406
2407		CONFIG_BOOTSTAGE_USER_COUNT
2408		This is the number of available user bootstage records.
2409		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
2410		a new ID will be allocated from this stash. If you exceed
2411		the limit, recording will stop.
2412
2413		CONFIG_BOOTSTAGE_REPORT
2414		Define this to print a report before boot, similar to this:
2415
2416		Timer summary in microseconds:
2417		       Mark    Elapsed  Stage
2418			  0          0  reset
2419		  3,575,678  3,575,678  board_init_f start
2420		  3,575,695         17  arch_cpu_init A9
2421		  3,575,777         82  arch_cpu_init done
2422		  3,659,598     83,821  board_init_r start
2423		  3,910,375    250,777  main_loop
2424		 29,916,167 26,005,792  bootm_start
2425		 30,361,327    445,160  start_kernel
2426
2427		CONFIG_CMD_BOOTSTAGE
2428		Add a 'bootstage' command which supports printing a report
2429		and un/stashing of bootstage data.
2430
2431		CONFIG_BOOTSTAGE_FDT
2432		Stash the bootstage information in the FDT. A root 'bootstage'
2433		node is created with each bootstage id as a child. Each child
2434		has a 'name' property and either 'mark' containing the
2435		mark time in microsecond, or 'accum' containing the
2436		accumulated time for that bootstage id in microseconds.
2437		For example:
2438
2439		bootstage {
2440			154 {
2441				name = "board_init_f";
2442				mark = <3575678>;
2443			};
2444			170 {
2445				name = "lcd";
2446				accum = <33482>;
2447			};
2448		};
2449
2450		Code in the Linux kernel can find this in /proc/devicetree.
2451
2452Legacy uImage format:
2453
2454  Arg	Where			When
2455    1	common/cmd_bootm.c	before attempting to boot an image
2456   -1	common/cmd_bootm.c	Image header has bad	 magic number
2457    2	common/cmd_bootm.c	Image header has correct magic number
2458   -2	common/cmd_bootm.c	Image header has bad	 checksum
2459    3	common/cmd_bootm.c	Image header has correct checksum
2460   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2461    4	common/cmd_bootm.c	Image data   has correct checksum
2462   -4	common/cmd_bootm.c	Image is for unsupported architecture
2463    5	common/cmd_bootm.c	Architecture check OK
2464   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2465    6	common/cmd_bootm.c	Image Type check OK
2466   -6	common/cmd_bootm.c	gunzip uncompression error
2467   -7	common/cmd_bootm.c	Unimplemented compression type
2468    7	common/cmd_bootm.c	Uncompression OK
2469    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2470   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2471
2472    9	common/image.c		Start initial ramdisk verification
2473  -10	common/image.c		Ramdisk header has bad	   magic number
2474  -11	common/image.c		Ramdisk header has bad	   checksum
2475   10	common/image.c		Ramdisk header is OK
2476  -12	common/image.c		Ramdisk data   has bad	   checksum
2477   11	common/image.c		Ramdisk data   has correct checksum
2478   12	common/image.c		Ramdisk verification complete, start loading
2479  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2480   13	common/image.c		Start multifile image verification
2481   14	common/image.c		No initial ramdisk, no multifile, continue.
2482
2483   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2484
2485  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2486  -31	post/post.c		POST test failed, detected by post_output_backlog()
2487  -32	post/post.c		POST test failed, detected by post_run_single()
2488
2489   34	common/cmd_doc.c	before loading a Image from a DOC device
2490  -35	common/cmd_doc.c	Bad usage of "doc" command
2491   35	common/cmd_doc.c	correct usage of "doc" command
2492  -36	common/cmd_doc.c	No boot device
2493   36	common/cmd_doc.c	correct boot device
2494  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2495   37	common/cmd_doc.c	correct chip ID found, device available
2496  -38	common/cmd_doc.c	Read Error on boot device
2497   38	common/cmd_doc.c	reading Image header from DOC device OK
2498  -39	common/cmd_doc.c	Image header has bad magic number
2499   39	common/cmd_doc.c	Image header has correct magic number
2500  -40	common/cmd_doc.c	Error reading Image from DOC device
2501   40	common/cmd_doc.c	Image header has correct magic number
2502   41	common/cmd_ide.c	before loading a Image from a IDE device
2503  -42	common/cmd_ide.c	Bad usage of "ide" command
2504   42	common/cmd_ide.c	correct usage of "ide" command
2505  -43	common/cmd_ide.c	No boot device
2506   43	common/cmd_ide.c	boot device found
2507  -44	common/cmd_ide.c	Device not available
2508   44	common/cmd_ide.c	Device available
2509  -45	common/cmd_ide.c	wrong partition selected
2510   45	common/cmd_ide.c	partition selected
2511  -46	common/cmd_ide.c	Unknown partition table
2512   46	common/cmd_ide.c	valid partition table found
2513  -47	common/cmd_ide.c	Invalid partition type
2514   47	common/cmd_ide.c	correct partition type
2515  -48	common/cmd_ide.c	Error reading Image Header on boot device
2516   48	common/cmd_ide.c	reading Image Header from IDE device OK
2517  -49	common/cmd_ide.c	Image header has bad magic number
2518   49	common/cmd_ide.c	Image header has correct magic number
2519  -50	common/cmd_ide.c	Image header has bad	 checksum
2520   50	common/cmd_ide.c	Image header has correct checksum
2521  -51	common/cmd_ide.c	Error reading Image from IDE device
2522   51	common/cmd_ide.c	reading Image from IDE device OK
2523   52	common/cmd_nand.c	before loading a Image from a NAND device
2524  -53	common/cmd_nand.c	Bad usage of "nand" command
2525   53	common/cmd_nand.c	correct usage of "nand" command
2526  -54	common/cmd_nand.c	No boot device
2527   54	common/cmd_nand.c	boot device found
2528  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2529   55	common/cmd_nand.c	correct chip ID found, device available
2530  -56	common/cmd_nand.c	Error reading Image Header on boot device
2531   56	common/cmd_nand.c	reading Image Header from NAND device OK
2532  -57	common/cmd_nand.c	Image header has bad magic number
2533   57	common/cmd_nand.c	Image header has correct magic number
2534  -58	common/cmd_nand.c	Error reading Image from NAND device
2535   58	common/cmd_nand.c	reading Image from NAND device OK
2536
2537  -60	common/env_common.c	Environment has a bad CRC, using default
2538
2539   64	net/eth.c		starting with Ethernet configuration.
2540  -64	net/eth.c		no Ethernet found.
2541   65	net/eth.c		Ethernet found.
2542
2543  -80	common/cmd_net.c	usage wrong
2544   80	common/cmd_net.c	before calling NetLoop()
2545  -81	common/cmd_net.c	some error in NetLoop() occurred
2546   81	common/cmd_net.c	NetLoop() back without error
2547  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2548   82	common/cmd_net.c	trying automatic boot
2549   83	common/cmd_net.c	running "source" command
2550  -83	common/cmd_net.c	some error in automatic boot or "source" command
2551   84	common/cmd_net.c	end without errors
2552
2553FIT uImage format:
2554
2555  Arg	Where			When
2556  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2557 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2558  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2559 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2560  102	common/cmd_bootm.c	Kernel unit name specified
2561 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2562  103	common/cmd_bootm.c	Found configuration node
2563  104	common/cmd_bootm.c	Got kernel subimage node offset
2564 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2565  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2566 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2567  106	common/cmd_bootm.c	Architecture check OK
2568 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2569  107	common/cmd_bootm.c	Kernel subimage type OK
2570 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2571  108	common/cmd_bootm.c	Got kernel subimage data/size
2572 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2573 -109	common/cmd_bootm.c	Can't get kernel subimage type
2574 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2575 -111	common/cmd_bootm.c	Can't get kernel subimage os
2576 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2577 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2578
2579  120	common/image.c		Start initial ramdisk verification
2580 -120	common/image.c		Ramdisk FIT image has incorrect format
2581  121	common/image.c		Ramdisk FIT image has correct format
2582  122	common/image.c		No ramdisk subimage unit name, using configuration
2583 -122	common/image.c		Can't get configuration for ramdisk subimage
2584  123	common/image.c		Ramdisk unit name specified
2585 -124	common/image.c		Can't get ramdisk subimage node offset
2586  125	common/image.c		Got ramdisk subimage node offset
2587 -125	common/image.c		Ramdisk subimage hash verification failed
2588  126	common/image.c		Ramdisk subimage hash verification OK
2589 -126	common/image.c		Ramdisk subimage for unsupported architecture
2590  127	common/image.c		Architecture check OK
2591 -127	common/image.c		Can't get ramdisk subimage data/size
2592  128	common/image.c		Got ramdisk subimage data/size
2593  129	common/image.c		Can't get ramdisk load address
2594 -129	common/image.c		Got ramdisk load address
2595
2596 -130	common/cmd_doc.c	Incorrect FIT image format
2597  131	common/cmd_doc.c	FIT image format OK
2598
2599 -140	common/cmd_ide.c	Incorrect FIT image format
2600  141	common/cmd_ide.c	FIT image format OK
2601
2602 -150	common/cmd_nand.c	Incorrect FIT image format
2603  151	common/cmd_nand.c	FIT image format OK
2604
2605- FIT image support:
2606		CONFIG_FIT
2607		Enable support for the FIT uImage format.
2608
2609		CONFIG_FIT_BEST_MATCH
2610		When no configuration is explicitly selected, default to the
2611		one whose fdt's compatibility field best matches that of
2612		U-Boot itself. A match is considered "best" if it matches the
2613		most specific compatibility entry of U-Boot's fdt's root node.
2614		The order of entries in the configuration's fdt is ignored.
2615
2616- Standalone program support:
2617		CONFIG_STANDALONE_LOAD_ADDR
2618
2619		This option defines a board specific value for the
2620		address where standalone program gets loaded, thus
2621		overwriting the architecture dependent default
2622		settings.
2623
2624- Frame Buffer Address:
2625		CONFIG_FB_ADDR
2626
2627		Define CONFIG_FB_ADDR if you want to use specific
2628		address for frame buffer.
2629		Then system will reserve the frame buffer address to
2630		defined address instead of lcd_setmem (this function
2631		grabs the memory for frame buffer by panel's size).
2632
2633		Please see board_init_f function.
2634
2635- Automatic software updates via TFTP server
2636		CONFIG_UPDATE_TFTP
2637		CONFIG_UPDATE_TFTP_CNT_MAX
2638		CONFIG_UPDATE_TFTP_MSEC_MAX
2639
2640		These options enable and control the auto-update feature;
2641		for a more detailed description refer to doc/README.update.
2642
2643- MTD Support (mtdparts command, UBI support)
2644		CONFIG_MTD_DEVICE
2645
2646		Adds the MTD device infrastructure from the Linux kernel.
2647		Needed for mtdparts command support.
2648
2649		CONFIG_MTD_PARTITIONS
2650
2651		Adds the MTD partitioning infrastructure from the Linux
2652		kernel. Needed for UBI support.
2653
2654- SPL framework
2655		CONFIG_SPL
2656		Enable building of SPL globally.
2657
2658		CONFIG_SPL_LDSCRIPT
2659		LDSCRIPT for linking the SPL binary.
2660
2661		CONFIG_SPL_MAX_SIZE
2662		Maximum binary size (text, data and rodata) of the SPL binary.
2663
2664		CONFIG_SPL_TEXT_BASE
2665		TEXT_BASE for linking the SPL binary.
2666
2667		CONFIG_SPL_RELOC_TEXT_BASE
2668		Address to relocate to.  If unspecified, this is equal to
2669		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2670
2671		CONFIG_SPL_BSS_START_ADDR
2672		Link address for the BSS within the SPL binary.
2673
2674		CONFIG_SPL_BSS_MAX_SIZE
2675		Maximum binary size of the BSS section of the SPL binary.
2676
2677		CONFIG_SPL_STACK
2678		Adress of the start of the stack SPL will use
2679
2680		CONFIG_SPL_RELOC_STACK
2681		Adress of the start of the stack SPL will use after
2682		relocation.  If unspecified, this is equal to
2683		CONFIG_SPL_STACK.
2684
2685		CONFIG_SYS_SPL_MALLOC_START
2686		Starting address of the malloc pool used in SPL.
2687
2688		CONFIG_SYS_SPL_MALLOC_SIZE
2689		The size of the malloc pool used in SPL.
2690
2691		CONFIG_SPL_FRAMEWORK
2692		Enable the SPL framework under common/.  This framework
2693		supports MMC, NAND and YMODEM loading of U-Boot and NAND
2694		NAND loading of the Linux Kernel.
2695
2696		CONFIG_SPL_DISPLAY_PRINT
2697		For ARM, enable an optional function to print more information
2698		about the running system.
2699
2700		CONFIG_SPL_INIT_MINIMAL
2701		Arch init code should be built for a very small image
2702
2703		CONFIG_SPL_LIBCOMMON_SUPPORT
2704		Support for common/libcommon.o in SPL binary
2705
2706		CONFIG_SPL_LIBDISK_SUPPORT
2707		Support for disk/libdisk.o in SPL binary
2708
2709		CONFIG_SPL_I2C_SUPPORT
2710		Support for drivers/i2c/libi2c.o in SPL binary
2711
2712		CONFIG_SPL_GPIO_SUPPORT
2713		Support for drivers/gpio/libgpio.o in SPL binary
2714
2715		CONFIG_SPL_MMC_SUPPORT
2716		Support for drivers/mmc/libmmc.o in SPL binary
2717
2718		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
2719		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
2720		CONFIG_SYS_MMC_SD_FAT_BOOT_PARTITION
2721		Address, size and partition on the MMC to load U-Boot from
2722		when the MMC is being used in raw mode.
2723
2724		CONFIG_SPL_FAT_SUPPORT
2725		Support for fs/fat/libfat.o in SPL binary
2726
2727		CONFIG_SPL_FAT_LOAD_PAYLOAD_NAME
2728		Filename to read to load U-Boot when reading from FAT
2729
2730		CONFIG_SPL_NAND_BASE
2731		Include nand_base.c in the SPL.  Requires
2732		CONFIG_SPL_NAND_DRIVERS.
2733
2734		CONFIG_SPL_NAND_DRIVERS
2735		SPL uses normal NAND drivers, not minimal drivers.
2736
2737		CONFIG_SPL_NAND_ECC
2738		Include standard software ECC in the SPL
2739
2740		CONFIG_SPL_NAND_SIMPLE
2741		Support for NAND boot using simple NAND drivers that
2742		expose the cmd_ctrl() interface.
2743
2744		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2745		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2746		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2747		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2748		CONFIG_SYS_NAND_ECCBYTES
2749		Defines the size and behavior of the NAND that SPL uses
2750		to read U-Boot
2751
2752		CONFIG_SYS_NAND_U_BOOT_OFFS
2753		Location in NAND to read U-Boot from
2754
2755		CONFIG_SYS_NAND_U_BOOT_DST
2756		Location in memory to load U-Boot to
2757
2758		CONFIG_SYS_NAND_U_BOOT_SIZE
2759		Size of image to load
2760
2761		CONFIG_SYS_NAND_U_BOOT_START
2762		Entry point in loaded image to jump to
2763
2764		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2765		Define this if you need to first read the OOB and then the
2766		data. This is used for example on davinci plattforms.
2767
2768		CONFIG_SPL_OMAP3_ID_NAND
2769		Support for an OMAP3-specific set of functions to return the
2770		ID and MFR of the first attached NAND chip, if present.
2771
2772		CONFIG_SPL_SERIAL_SUPPORT
2773		Support for drivers/serial/libserial.o in SPL binary
2774
2775		CONFIG_SPL_SPI_FLASH_SUPPORT
2776		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
2777
2778		CONFIG_SPL_SPI_SUPPORT
2779		Support for drivers/spi/libspi.o in SPL binary
2780
2781		CONFIG_SPL_RAM_DEVICE
2782		Support for running image already present in ram, in SPL binary
2783
2784		CONFIG_SPL_LIBGENERIC_SUPPORT
2785		Support for lib/libgeneric.o in SPL binary
2786
2787		CONFIG_SPL_TARGET
2788		Final target image containing SPL and payload.  Some SPLs
2789		use an arch-specific makefile fragment instead, for
2790		example if more than one image needs to be produced.
2791
2792Modem Support:
2793--------------
2794
2795[so far only for SMDK2400 boards]
2796
2797- Modem support enable:
2798		CONFIG_MODEM_SUPPORT
2799
2800- RTS/CTS Flow control enable:
2801		CONFIG_HWFLOW
2802
2803- Modem debug support:
2804		CONFIG_MODEM_SUPPORT_DEBUG
2805
2806		Enables debugging stuff (char screen[1024], dbg())
2807		for modem support. Useful only with BDI2000.
2808
2809- Interrupt support (PPC):
2810
2811		There are common interrupt_init() and timer_interrupt()
2812		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2813		for CPU specific initialization. interrupt_init_cpu()
2814		should set decrementer_count to appropriate value. If
2815		CPU resets decrementer automatically after interrupt
2816		(ppc4xx) it should set decrementer_count to zero.
2817		timer_interrupt() calls timer_interrupt_cpu() for CPU
2818		specific handling. If board has watchdog / status_led
2819		/ other_activity_monitor it works automatically from
2820		general timer_interrupt().
2821
2822- General:
2823
2824		In the target system modem support is enabled when a
2825		specific key (key combination) is pressed during
2826		power-on. Otherwise U-Boot will boot normally
2827		(autoboot). The key_pressed() function is called from
2828		board_init(). Currently key_pressed() is a dummy
2829		function, returning 1 and thus enabling modem
2830		initialization.
2831
2832		If there are no modem init strings in the
2833		environment, U-Boot proceed to autoboot; the
2834		previous output (banner, info printfs) will be
2835		suppressed, though.
2836
2837		See also: doc/README.Modem
2838
2839Board initialization settings:
2840------------------------------
2841
2842During Initialization u-boot calls a number of board specific functions
2843to allow the preparation of board specific prerequisites, e.g. pin setup
2844before drivers are initialized. To enable these callbacks the
2845following configuration macros have to be defined. Currently this is
2846architecture specific, so please check arch/your_architecture/lib/board.c
2847typically in board_init_f() and board_init_r().
2848
2849- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2850- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2851- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2852- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2853
2854Configuration Settings:
2855-----------------------
2856
2857- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2858		undefine this when you're short of memory.
2859
2860- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2861		width of the commands listed in the 'help' command output.
2862
2863- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2864		prompt for user input.
2865
2866- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2867
2868- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2869
2870- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2871
2872- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2873		the application (usually a Linux kernel) when it is
2874		booted
2875
2876- CONFIG_SYS_BAUDRATE_TABLE:
2877		List of legal baudrate settings for this board.
2878
2879- CONFIG_SYS_CONSOLE_INFO_QUIET
2880		Suppress display of console information at boot.
2881
2882- CONFIG_SYS_CONSOLE_IS_IN_ENV
2883		If the board specific function
2884			extern int overwrite_console (void);
2885		returns 1, the stdin, stderr and stdout are switched to the
2886		serial port, else the settings in the environment are used.
2887
2888- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
2889		Enable the call to overwrite_console().
2890
2891- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
2892		Enable overwrite of previous console environment settings.
2893
2894- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2895		Begin and End addresses of the area used by the
2896		simple memory test.
2897
2898- CONFIG_SYS_ALT_MEMTEST:
2899		Enable an alternate, more extensive memory test.
2900
2901- CONFIG_SYS_MEMTEST_SCRATCH:
2902		Scratch address used by the alternate memory test
2903		You only need to set this if address zero isn't writeable
2904
2905- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
2906		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2907		this specified memory area will get subtracted from the top
2908		(end) of RAM and won't get "touched" at all by U-Boot. By
2909		fixing up gd->ram_size the Linux kernel should gets passed
2910		the now "corrected" memory size and won't touch it either.
2911		This should work for arch/ppc and arch/powerpc. Only Linux
2912		board ports in arch/powerpc with bootwrapper support that
2913		recalculate the memory size from the SDRAM controller setup
2914		will have to get fixed in Linux additionally.
2915
2916		This option can be used as a workaround for the 440EPx/GRx
2917		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2918		be touched.
2919
2920		WARNING: Please make sure that this value is a multiple of
2921		the Linux page size (normally 4k). If this is not the case,
2922		then the end address of the Linux memory will be located at a
2923		non page size aligned address and this could cause major
2924		problems.
2925
2926- CONFIG_SYS_TFTP_LOADADDR:
2927		Default load address for network file downloads
2928
2929- CONFIG_SYS_LOADS_BAUD_CHANGE:
2930		Enable temporary baudrate change while serial download
2931
2932- CONFIG_SYS_SDRAM_BASE:
2933		Physical start address of SDRAM. _Must_ be 0 here.
2934
2935- CONFIG_SYS_MBIO_BASE:
2936		Physical start address of Motherboard I/O (if using a
2937		Cogent motherboard)
2938
2939- CONFIG_SYS_FLASH_BASE:
2940		Physical start address of Flash memory.
2941
2942- CONFIG_SYS_MONITOR_BASE:
2943		Physical start address of boot monitor code (set by
2944		make config files to be same as the text base address
2945		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2946		CONFIG_SYS_FLASH_BASE when booting from flash.
2947
2948- CONFIG_SYS_MONITOR_LEN:
2949		Size of memory reserved for monitor code, used to
2950		determine _at_compile_time_ (!) if the environment is
2951		embedded within the U-Boot image, or in a separate
2952		flash sector.
2953
2954- CONFIG_SYS_MALLOC_LEN:
2955		Size of DRAM reserved for malloc() use.
2956
2957- CONFIG_SYS_BOOTM_LEN:
2958		Normally compressed uImages are limited to an
2959		uncompressed size of 8 MBytes. If this is not enough,
2960		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2961		to adjust this setting to your needs.
2962
2963- CONFIG_SYS_BOOTMAPSZ:
2964		Maximum size of memory mapped by the startup code of
2965		the Linux kernel; all data that must be processed by
2966		the Linux kernel (bd_info, boot arguments, FDT blob if
2967		used) must be put below this limit, unless "bootm_low"
2968		enviroment variable is defined and non-zero. In such case
2969		all data for the Linux kernel must be between "bootm_low"
2970		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2971		variable "bootm_mapsize" will override the value of
2972		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2973		then the value in "bootm_size" will be used instead.
2974
2975- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2976		Enable initrd_high functionality.  If defined then the
2977		initrd_high feature is enabled and the bootm ramdisk subcommand
2978		is enabled.
2979
2980- CONFIG_SYS_BOOT_GET_CMDLINE:
2981		Enables allocating and saving kernel cmdline in space between
2982		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2983
2984- CONFIG_SYS_BOOT_GET_KBD:
2985		Enables allocating and saving a kernel copy of the bd_info in
2986		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2987
2988- CONFIG_SYS_MAX_FLASH_BANKS:
2989		Max number of Flash memory banks
2990
2991- CONFIG_SYS_MAX_FLASH_SECT:
2992		Max number of sectors on a Flash chip
2993
2994- CONFIG_SYS_FLASH_ERASE_TOUT:
2995		Timeout for Flash erase operations (in ms)
2996
2997- CONFIG_SYS_FLASH_WRITE_TOUT:
2998		Timeout for Flash write operations (in ms)
2999
3000- CONFIG_SYS_FLASH_LOCK_TOUT
3001		Timeout for Flash set sector lock bit operation (in ms)
3002
3003- CONFIG_SYS_FLASH_UNLOCK_TOUT
3004		Timeout for Flash clear lock bits operation (in ms)
3005
3006- CONFIG_SYS_FLASH_PROTECTION
3007		If defined, hardware flash sectors protection is used
3008		instead of U-Boot software protection.
3009
3010- CONFIG_SYS_DIRECT_FLASH_TFTP:
3011
3012		Enable TFTP transfers directly to flash memory;
3013		without this option such a download has to be
3014		performed in two steps: (1) download to RAM, and (2)
3015		copy from RAM to flash.
3016
3017		The two-step approach is usually more reliable, since
3018		you can check if the download worked before you erase
3019		the flash, but in some situations (when system RAM is
3020		too limited to allow for a temporary copy of the
3021		downloaded image) this option may be very useful.
3022
3023- CONFIG_SYS_FLASH_CFI:
3024		Define if the flash driver uses extra elements in the
3025		common flash structure for storing flash geometry.
3026
3027- CONFIG_FLASH_CFI_DRIVER
3028		This option also enables the building of the cfi_flash driver
3029		in the drivers directory
3030
3031- CONFIG_FLASH_CFI_MTD
3032		This option enables the building of the cfi_mtd driver
3033		in the drivers directory. The driver exports CFI flash
3034		to the MTD layer.
3035
3036- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3037		Use buffered writes to flash.
3038
3039- CONFIG_FLASH_SPANSION_S29WS_N
3040		s29ws-n MirrorBit flash has non-standard addresses for buffered
3041		write commands.
3042
3043- CONFIG_SYS_FLASH_QUIET_TEST
3044		If this option is defined, the common CFI flash doesn't
3045		print it's warning upon not recognized FLASH banks. This
3046		is useful, if some of the configured banks are only
3047		optionally available.
3048
3049- CONFIG_FLASH_SHOW_PROGRESS
3050		If defined (must be an integer), print out countdown
3051		digits and dots.  Recommended value: 45 (9..1) for 80
3052		column displays, 15 (3..1) for 40 column displays.
3053
3054- CONFIG_SYS_RX_ETH_BUFFER:
3055		Defines the number of Ethernet receive buffers. On some
3056		Ethernet controllers it is recommended to set this value
3057		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3058		buffers can be full shortly after enabling the interface
3059		on high Ethernet traffic.
3060		Defaults to 4 if not defined.
3061
3062- CONFIG_ENV_MAX_ENTRIES
3063
3064	Maximum number of entries in the hash table that is used
3065	internally to store the environment settings. The default
3066	setting is supposed to be generous and should work in most
3067	cases. This setting can be used to tune behaviour; see
3068	lib/hashtable.c for details.
3069
3070The following definitions that deal with the placement and management
3071of environment data (variable area); in general, we support the
3072following configurations:
3073
3074- CONFIG_BUILD_ENVCRC:
3075
3076	Builds up envcrc with the target environment so that external utils
3077	may easily extract it and embed it in final U-Boot images.
3078
3079- CONFIG_ENV_IS_IN_FLASH:
3080
3081	Define this if the environment is in flash memory.
3082
3083	a) The environment occupies one whole flash sector, which is
3084	   "embedded" in the text segment with the U-Boot code. This
3085	   happens usually with "bottom boot sector" or "top boot
3086	   sector" type flash chips, which have several smaller
3087	   sectors at the start or the end. For instance, such a
3088	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3089	   such a case you would place the environment in one of the
3090	   4 kB sectors - with U-Boot code before and after it. With
3091	   "top boot sector" type flash chips, you would put the
3092	   environment in one of the last sectors, leaving a gap
3093	   between U-Boot and the environment.
3094
3095	- CONFIG_ENV_OFFSET:
3096
3097	   Offset of environment data (variable area) to the
3098	   beginning of flash memory; for instance, with bottom boot
3099	   type flash chips the second sector can be used: the offset
3100	   for this sector is given here.
3101
3102	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3103
3104	- CONFIG_ENV_ADDR:
3105
3106	   This is just another way to specify the start address of
3107	   the flash sector containing the environment (instead of
3108	   CONFIG_ENV_OFFSET).
3109
3110	- CONFIG_ENV_SECT_SIZE:
3111
3112	   Size of the sector containing the environment.
3113
3114
3115	b) Sometimes flash chips have few, equal sized, BIG sectors.
3116	   In such a case you don't want to spend a whole sector for
3117	   the environment.
3118
3119	- CONFIG_ENV_SIZE:
3120
3121	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3122	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3123	   of this flash sector for the environment. This saves
3124	   memory for the RAM copy of the environment.
3125
3126	   It may also save flash memory if you decide to use this
3127	   when your environment is "embedded" within U-Boot code,
3128	   since then the remainder of the flash sector could be used
3129	   for U-Boot code. It should be pointed out that this is
3130	   STRONGLY DISCOURAGED from a robustness point of view:
3131	   updating the environment in flash makes it always
3132	   necessary to erase the WHOLE sector. If something goes
3133	   wrong before the contents has been restored from a copy in
3134	   RAM, your target system will be dead.
3135
3136	- CONFIG_ENV_ADDR_REDUND
3137	  CONFIG_ENV_SIZE_REDUND
3138
3139	   These settings describe a second storage area used to hold
3140	   a redundant copy of the environment data, so that there is
3141	   a valid backup copy in case there is a power failure during
3142	   a "saveenv" operation.
3143
3144BE CAREFUL! Any changes to the flash layout, and some changes to the
3145source code will make it necessary to adapt <board>/u-boot.lds*
3146accordingly!
3147
3148
3149- CONFIG_ENV_IS_IN_NVRAM:
3150
3151	Define this if you have some non-volatile memory device
3152	(NVRAM, battery buffered SRAM) which you want to use for the
3153	environment.
3154
3155	- CONFIG_ENV_ADDR:
3156	- CONFIG_ENV_SIZE:
3157
3158	  These two #defines are used to determine the memory area you
3159	  want to use for environment. It is assumed that this memory
3160	  can just be read and written to, without any special
3161	  provision.
3162
3163BE CAREFUL! The first access to the environment happens quite early
3164in U-Boot initalization (when we try to get the setting of for the
3165console baudrate). You *MUST* have mapped your NVRAM area then, or
3166U-Boot will hang.
3167
3168Please note that even with NVRAM we still use a copy of the
3169environment in RAM: we could work on NVRAM directly, but we want to
3170keep settings there always unmodified except somebody uses "saveenv"
3171to save the current settings.
3172
3173
3174- CONFIG_ENV_IS_IN_EEPROM:
3175
3176	Use this if you have an EEPROM or similar serial access
3177	device and a driver for it.
3178
3179	- CONFIG_ENV_OFFSET:
3180	- CONFIG_ENV_SIZE:
3181
3182	  These two #defines specify the offset and size of the
3183	  environment area within the total memory of your EEPROM.
3184
3185	- CONFIG_SYS_I2C_EEPROM_ADDR:
3186	  If defined, specified the chip address of the EEPROM device.
3187	  The default address is zero.
3188
3189	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3190	  If defined, the number of bits used to address bytes in a
3191	  single page in the EEPROM device.  A 64 byte page, for example
3192	  would require six bits.
3193
3194	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3195	  If defined, the number of milliseconds to delay between
3196	  page writes.	The default is zero milliseconds.
3197
3198	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3199	  The length in bytes of the EEPROM memory array address.  Note
3200	  that this is NOT the chip address length!
3201
3202	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3203	  EEPROM chips that implement "address overflow" are ones
3204	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3205	  address and the extra bits end up in the "chip address" bit
3206	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3207	  byte chips.
3208
3209	  Note that we consider the length of the address field to
3210	  still be one byte because the extra address bits are hidden
3211	  in the chip address.
3212
3213	- CONFIG_SYS_EEPROM_SIZE:
3214	  The size in bytes of the EEPROM device.
3215
3216	- CONFIG_ENV_EEPROM_IS_ON_I2C
3217	  define this, if you have I2C and SPI activated, and your
3218	  EEPROM, which holds the environment, is on the I2C bus.
3219
3220	- CONFIG_I2C_ENV_EEPROM_BUS
3221	  if you have an Environment on an EEPROM reached over
3222	  I2C muxes, you can define here, how to reach this
3223	  EEPROM. For example:
3224
3225	  #define CONFIG_I2C_ENV_EEPROM_BUS	  "pca9547:70:d\0"
3226
3227	  EEPROM which holds the environment, is reached over
3228	  a pca9547 i2c mux with address 0x70, channel 3.
3229
3230- CONFIG_ENV_IS_IN_DATAFLASH:
3231
3232	Define this if you have a DataFlash memory device which you
3233	want to use for the environment.
3234
3235	- CONFIG_ENV_OFFSET:
3236	- CONFIG_ENV_ADDR:
3237	- CONFIG_ENV_SIZE:
3238
3239	  These three #defines specify the offset and size of the
3240	  environment area within the total memory of your DataFlash placed
3241	  at the specified address.
3242
3243- CONFIG_ENV_IS_IN_REMOTE:
3244
3245	Define this if you have a remote memory space which you
3246	want to use for the local device's environment.
3247
3248	- CONFIG_ENV_ADDR:
3249	- CONFIG_ENV_SIZE:
3250
3251	  These two #defines specify the address and size of the
3252	  environment area within the remote memory space. The
3253	  local device can get the environment from remote memory
3254	  space by SRIO or PCIE links.
3255
3256BE CAREFUL! For some special cases, the local device can not use
3257"saveenv" command. For example, the local device will get the
3258environment stored in a remote NOR flash by SRIO or PCIE link,
3259but it can not erase, write this NOR flash by SRIO or PCIE interface.
3260
3261- CONFIG_ENV_IS_IN_NAND:
3262
3263	Define this if you have a NAND device which you want to use
3264	for the environment.
3265
3266	- CONFIG_ENV_OFFSET:
3267	- CONFIG_ENV_SIZE:
3268
3269	  These two #defines specify the offset and size of the environment
3270	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3271	  aligned to an erase block boundary.
3272
3273	- CONFIG_ENV_OFFSET_REDUND (optional):
3274
3275	  This setting describes a second storage area of CONFIG_ENV_SIZE
3276	  size used to hold a redundant copy of the environment data, so
3277	  that there is a valid backup copy in case there is a power failure
3278	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
3279	  aligned to an erase block boundary.
3280
3281	- CONFIG_ENV_RANGE (optional):
3282
3283	  Specifies the length of the region in which the environment
3284	  can be written.  This should be a multiple of the NAND device's
3285	  block size.  Specifying a range with more erase blocks than
3286	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
3287	  the range to be avoided.
3288
3289	- CONFIG_ENV_OFFSET_OOB (optional):
3290
3291	  Enables support for dynamically retrieving the offset of the
3292	  environment from block zero's out-of-band data.  The
3293	  "nand env.oob" command can be used to record this offset.
3294	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
3295	  using CONFIG_ENV_OFFSET_OOB.
3296
3297- CONFIG_NAND_ENV_DST
3298
3299	Defines address in RAM to which the nand_spl code should copy the
3300	environment. If redundant environment is used, it will be copied to
3301	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3302
3303- CONFIG_SYS_SPI_INIT_OFFSET
3304
3305	Defines offset to the initial SPI buffer area in DPRAM. The
3306	area is used at an early stage (ROM part) if the environment
3307	is configured to reside in the SPI EEPROM: We need a 520 byte
3308	scratch DPRAM area. It is used between the two initialization
3309	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
3310	to be a good choice since it makes it far enough from the
3311	start of the data area as well as from the stack pointer.
3312
3313Please note that the environment is read-only until the monitor
3314has been relocated to RAM and a RAM copy of the environment has been
3315created; also, when using EEPROM you will have to use getenv_f()
3316until then to read environment variables.
3317
3318The environment is protected by a CRC32 checksum. Before the monitor
3319is relocated into RAM, as a result of a bad CRC you will be working
3320with the compiled-in default environment - *silently*!!! [This is
3321necessary, because the first environment variable we need is the
3322"baudrate" setting for the console - if we have a bad CRC, we don't
3323have any device yet where we could complain.]
3324
3325Note: once the monitor has been relocated, then it will complain if
3326the default environment is used; a new CRC is computed as soon as you
3327use the "saveenv" command to store a valid environment.
3328
3329- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3330		Echo the inverted Ethernet link state to the fault LED.
3331
3332		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3333		      also needs to be defined.
3334
3335- CONFIG_SYS_FAULT_MII_ADDR:
3336		MII address of the PHY to check for the Ethernet link state.
3337
3338- CONFIG_NS16550_MIN_FUNCTIONS:
3339		Define this if you desire to only have use of the NS16550_init
3340		and NS16550_putc functions for the serial driver located at
3341		drivers/serial/ns16550.c.  This option is useful for saving
3342		space for already greatly restricted images, including but not
3343		limited to NAND_SPL configurations.
3344
3345Low Level (hardware related) configuration options:
3346---------------------------------------------------
3347
3348- CONFIG_SYS_CACHELINE_SIZE:
3349		Cache Line Size of the CPU.
3350
3351- CONFIG_SYS_DEFAULT_IMMR:
3352		Default address of the IMMR after system reset.
3353
3354		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
3355		and RPXsuper) to be able to adjust the position of
3356		the IMMR register after a reset.
3357
3358- CONFIG_SYS_CCSRBAR_DEFAULT:
3359		Default (power-on reset) physical address of CCSR on Freescale
3360		PowerPC SOCs.
3361
3362- CONFIG_SYS_CCSRBAR:
3363		Virtual address of CCSR.  On a 32-bit build, this is typically
3364		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3365
3366		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
3367		for cross-platform code that uses that macro instead.
3368
3369- CONFIG_SYS_CCSRBAR_PHYS:
3370		Physical address of CCSR.  CCSR can be relocated to a new
3371		physical address, if desired.  In this case, this macro should
3372		be set to that address.	 Otherwise, it should be set to the
3373		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3374		is typically relocated on 36-bit builds.  It is recommended
3375		that this macro be defined via the _HIGH and _LOW macros:
3376
3377		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3378			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3379
3380- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3381		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3382		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3383		used in assembly code, so it must not contain typecasts or
3384		integer size suffixes (e.g. "ULL").
3385
3386- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3387		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3388		used in assembly code, so it must not contain typecasts or
3389		integer size suffixes (e.g. "ULL").
3390
3391- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3392		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3393		forced to a value that ensures that CCSR is not relocated.
3394
3395- Floppy Disk Support:
3396		CONFIG_SYS_FDC_DRIVE_NUMBER
3397
3398		the default drive number (default value 0)
3399
3400		CONFIG_SYS_ISA_IO_STRIDE
3401
3402		defines the spacing between FDC chipset registers
3403		(default value 1)
3404
3405		CONFIG_SYS_ISA_IO_OFFSET
3406
3407		defines the offset of register from address. It
3408		depends on which part of the data bus is connected to
3409		the FDC chipset. (default value 0)
3410
3411		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3412		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3413		default value.
3414
3415		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3416		fdc_hw_init() is called at the beginning of the FDC
3417		setup. fdc_hw_init() must be provided by the board
3418		source code. It is used to make hardware dependant
3419		initializations.
3420
3421- CONFIG_IDE_AHB:
3422		Most IDE controllers were designed to be connected with PCI
3423		interface. Only few of them were designed for AHB interface.
3424		When software is doing ATA command and data transfer to
3425		IDE devices through IDE-AHB controller, some additional
3426		registers accessing to these kind of IDE-AHB controller
3427		is requierd.
3428
3429- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3430		DO NOT CHANGE unless you know exactly what you're
3431		doing! (11-4) [MPC8xx/82xx systems only]
3432
3433- CONFIG_SYS_INIT_RAM_ADDR:
3434
3435		Start address of memory area that can be used for
3436		initial data and stack; please note that this must be
3437		writable memory that is working WITHOUT special
3438		initialization, i. e. you CANNOT use normal RAM which
3439		will become available only after programming the
3440		memory controller and running certain initialization
3441		sequences.
3442
3443		U-Boot uses the following memory types:
3444		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
3445		- MPC824X: data cache
3446		- PPC4xx:  data cache
3447
3448- CONFIG_SYS_GBL_DATA_OFFSET:
3449
3450		Offset of the initial data structure in the memory
3451		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3452		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3453		data is located at the end of the available space
3454		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3455		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
3456		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3457		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3458
3459	Note:
3460		On the MPC824X (or other systems that use the data
3461		cache for initial memory) the address chosen for
3462		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3463		point to an otherwise UNUSED address space between
3464		the top of RAM and the start of the PCI space.
3465
3466- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
3467
3468- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
3469
3470- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
3471
3472- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
3473
3474- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
3475
3476- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3477
3478- CONFIG_SYS_OR_TIMING_SDRAM:
3479		SDRAM timing
3480
3481- CONFIG_SYS_MAMR_PTA:
3482		periodic timer for refresh
3483
3484- CONFIG_SYS_DER:	Debug Event Register (37-47)
3485
3486- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3487  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3488  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3489  CONFIG_SYS_BR1_PRELIM:
3490		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3491
3492- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3493  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3494  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3495		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3496
3497- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
3498  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
3499		Machine Mode Register and Memory Periodic Timer
3500		Prescaler definitions (SDRAM timing)
3501
3502- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
3503		enable I2C microcode relocation patch (MPC8xx);
3504		define relocation offset in DPRAM [DSP2]
3505
3506- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
3507		enable SMC microcode relocation patch (MPC8xx);
3508		define relocation offset in DPRAM [SMC1]
3509
3510- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
3511		enable SPI microcode relocation patch (MPC8xx);
3512		define relocation offset in DPRAM [SCC4]
3513
3514- CONFIG_SYS_USE_OSCCLK:
3515		Use OSCM clock mode on MBX8xx board. Be careful,
3516		wrong setting might damage your board. Read
3517		doc/README.MBX before setting this variable!
3518
3519- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
3520		Offset of the bootmode word in DPRAM used by post
3521		(Power On Self Tests). This definition overrides
3522		#define'd default value in commproc.h resp.
3523		cpm_8260.h.
3524
3525- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
3526  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
3527  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
3528  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
3529  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
3530  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
3531  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
3532  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
3533		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
3534
3535- CONFIG_PCI_DISABLE_PCIE:
3536		Disable PCI-Express on systems where it is supported but not
3537		required.
3538
3539- CONFIG_PCI_ENUM_ONLY
3540		Only scan through and get the devices on the busses.
3541		Don't do any setup work, presumably because someone or
3542		something has already done it, and we don't need to do it
3543		a second time.	Useful for platforms that are pre-booted
3544		by coreboot or similar.
3545
3546- CONFIG_SYS_SRIO:
3547		Chip has SRIO or not
3548
3549- CONFIG_SRIO1:
3550		Board has SRIO 1 port available
3551
3552- CONFIG_SRIO2:
3553		Board has SRIO 2 port available
3554
3555- CONFIG_SYS_SRIOn_MEM_VIRT:
3556		Virtual Address of SRIO port 'n' memory region
3557
3558- CONFIG_SYS_SRIOn_MEM_PHYS:
3559		Physical Address of SRIO port 'n' memory region
3560
3561- CONFIG_SYS_SRIOn_MEM_SIZE:
3562		Size of SRIO port 'n' memory region
3563
3564- CONFIG_SYS_NDFC_16
3565		Defined to tell the NDFC that the NAND chip is using a
3566		16 bit bus.
3567
3568- CONFIG_SYS_NDFC_EBC0_CFG
3569		Sets the EBC0_CFG register for the NDFC. If not defined
3570		a default value will be used.
3571
3572- CONFIG_SPD_EEPROM
3573		Get DDR timing information from an I2C EEPROM. Common
3574		with pluggable memory modules such as SODIMMs
3575
3576  SPD_EEPROM_ADDRESS
3577		I2C address of the SPD EEPROM
3578
3579- CONFIG_SYS_SPD_BUS_NUM
3580		If SPD EEPROM is on an I2C bus other than the first
3581		one, specify here. Note that the value must resolve
3582		to something your driver can deal with.
3583
3584- CONFIG_SYS_DDR_RAW_TIMING
3585		Get DDR timing information from other than SPD. Common with
3586		soldered DDR chips onboard without SPD. DDR raw timing
3587		parameters are extracted from datasheet and hard-coded into
3588		header files or board specific files.
3589
3590- CONFIG_FSL_DDR_INTERACTIVE
3591		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3592
3593- CONFIG_SYS_83XX_DDR_USES_CS0
3594		Only for 83xx systems. If specified, then DDR should
3595		be configured using CS0 and CS1 instead of CS2 and CS3.
3596
3597- CONFIG_ETHER_ON_FEC[12]
3598		Define to enable FEC[12] on a 8xx series processor.
3599
3600- CONFIG_FEC[12]_PHY
3601		Define to the hardcoded PHY address which corresponds
3602		to the given FEC; i. e.
3603			#define CONFIG_FEC1_PHY 4
3604		means that the PHY with address 4 is connected to FEC1
3605
3606		When set to -1, means to probe for first available.
3607
3608- CONFIG_FEC[12]_PHY_NORXERR
3609		The PHY does not have a RXERR line (RMII only).
3610		(so program the FEC to ignore it).
3611
3612- CONFIG_RMII
3613		Enable RMII mode for all FECs.
3614		Note that this is a global option, we can't
3615		have one FEC in standard MII mode and another in RMII mode.
3616
3617- CONFIG_CRC32_VERIFY
3618		Add a verify option to the crc32 command.
3619		The syntax is:
3620
3621		=> crc32 -v <address> <count> <crc32>
3622
3623		Where address/count indicate a memory area
3624		and crc32 is the correct crc32 which the
3625		area should have.
3626
3627- CONFIG_LOOPW
3628		Add the "loopw" memory command. This only takes effect if
3629		the memory commands are activated globally (CONFIG_CMD_MEM).
3630
3631- CONFIG_MX_CYCLIC
3632		Add the "mdc" and "mwc" memory commands. These are cyclic
3633		"md/mw" commands.
3634		Examples:
3635
3636		=> mdc.b 10 4 500
3637		This command will print 4 bytes (10,11,12,13) each 500 ms.
3638
3639		=> mwc.l 100 12345678 10
3640		This command will write 12345678 to address 100 all 10 ms.
3641
3642		This only takes effect if the memory commands are activated
3643		globally (CONFIG_CMD_MEM).
3644
3645- CONFIG_SKIP_LOWLEVEL_INIT
3646		[ARM, NDS32, MIPS only] If this variable is defined, then certain
3647		low level initializations (like setting up the memory
3648		controller) are omitted and/or U-Boot does not
3649		relocate itself into RAM.
3650
3651		Normally this variable MUST NOT be defined. The only
3652		exception is when U-Boot is loaded (to RAM) by some
3653		other boot loader or by a debugger which performs
3654		these initializations itself.
3655
3656- CONFIG_SPL_BUILD
3657		Modifies the behaviour of start.S when compiling a loader
3658		that is executed before the actual U-Boot. E.g. when
3659		compiling a NAND SPL.
3660
3661- CONFIG_USE_ARCH_MEMCPY
3662  CONFIG_USE_ARCH_MEMSET
3663		If these options are used a optimized version of memcpy/memset will
3664		be used if available. These functions may be faster under some
3665		conditions but may increase the binary size.
3666
3667- CONFIG_X86_NO_RESET_VECTOR
3668		If defined, the x86 reset vector code is excluded. You will need
3669		to do this when U-Boot is running from Coreboot.
3670
3671- CONFIG_X86_NO_REAL_MODE
3672		If defined, x86 real mode code is omitted. This assumes a
3673		32-bit environment where such code is not needed. You will
3674		need to do this when U-Boot is running from Coreboot.
3675
3676
3677Freescale QE/FMAN Firmware Support:
3678-----------------------------------
3679
3680The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3681loading of "firmware", which is encoded in the QE firmware binary format.
3682This firmware often needs to be loaded during U-Boot booting, so macros
3683are used to identify the storage device (NOR flash, SPI, etc) and the address
3684within that device.
3685
3686- CONFIG_SYS_QE_FMAN_FW_ADDR
3687	The address in the storage device where the firmware is located.  The
3688	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3689	is also specified.
3690
3691- CONFIG_SYS_QE_FMAN_FW_LENGTH
3692	The maximum possible size of the firmware.  The firmware binary format
3693	has a field that specifies the actual size of the firmware, but it
3694	might not be possible to read any part of the firmware unless some
3695	local storage is allocated to hold the entire firmware first.
3696
3697- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3698	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3699	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3700	virtual address in NOR flash.
3701
3702- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3703	Specifies that QE/FMAN firmware is located in NAND flash.
3704	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3705
3706- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3707	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3708	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3709
3710- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
3711	Specifies that QE/FMAN firmware is located on the primary SPI
3712	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3713
3714- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3715	Specifies that QE/FMAN firmware is located in the remote (master)
3716	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3717	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3718	window->master inbound window->master LAW->the ucode address in
3719	master's memory space.
3720
3721Building the Software:
3722======================
3723
3724Building U-Boot has been tested in several native build environments
3725and in many different cross environments. Of course we cannot support
3726all possibly existing versions of cross development tools in all
3727(potentially obsolete) versions. In case of tool chain problems we
3728recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3729which is extensively used to build and test U-Boot.
3730
3731If you are not using a native environment, it is assumed that you
3732have GNU cross compiling tools available in your path. In this case,
3733you must set the environment variable CROSS_COMPILE in your shell.
3734Note that no changes to the Makefile or any other source files are
3735necessary. For example using the ELDK on a 4xx CPU, please enter:
3736
3737	$ CROSS_COMPILE=ppc_4xx-
3738	$ export CROSS_COMPILE
3739
3740Note: If you wish to generate Windows versions of the utilities in
3741      the tools directory you can use the MinGW toolchain
3742      (http://www.mingw.org).  Set your HOST tools to the MinGW
3743      toolchain and execute 'make tools'.  For example:
3744
3745       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3746
3747      Binaries such as tools/mkimage.exe will be created which can
3748      be executed on computers running Windows.
3749
3750U-Boot is intended to be simple to build. After installing the
3751sources you must configure U-Boot for one specific board type. This
3752is done by typing:
3753
3754	make NAME_config
3755
3756where "NAME_config" is the name of one of the existing configu-
3757rations; see boards.cfg for supported names.
3758
3759Note: for some board special configuration names may exist; check if
3760      additional information is available from the board vendor; for
3761      instance, the TQM823L systems are available without (standard)
3762      or with LCD support. You can select such additional "features"
3763      when choosing the configuration, i. e.
3764
3765      make TQM823L_config
3766	- will configure for a plain TQM823L, i. e. no LCD support
3767
3768      make TQM823L_LCD_config
3769	- will configure for a TQM823L with U-Boot console on LCD
3770
3771      etc.
3772
3773
3774Finally, type "make all", and you should get some working U-Boot
3775images ready for download to / installation on your system:
3776
3777- "u-boot.bin" is a raw binary image
3778- "u-boot" is an image in ELF binary format
3779- "u-boot.srec" is in Motorola S-Record format
3780
3781By default the build is performed locally and the objects are saved
3782in the source directory. One of the two methods can be used to change
3783this behavior and build U-Boot to some external directory:
3784
37851. Add O= to the make command line invocations:
3786
3787	make O=/tmp/build distclean
3788	make O=/tmp/build NAME_config
3789	make O=/tmp/build all
3790
37912. Set environment variable BUILD_DIR to point to the desired location:
3792
3793	export BUILD_DIR=/tmp/build
3794	make distclean
3795	make NAME_config
3796	make all
3797
3798Note that the command line "O=" setting overrides the BUILD_DIR environment
3799variable.
3800
3801
3802Please be aware that the Makefiles assume you are using GNU make, so
3803for instance on NetBSD you might need to use "gmake" instead of
3804native "make".
3805
3806
3807If the system board that you have is not listed, then you will need
3808to port U-Boot to your hardware platform. To do this, follow these
3809steps:
3810
38111.  Add a new configuration option for your board to the toplevel
3812    "boards.cfg" file, using the existing entries as examples.
3813    Follow the instructions there to keep the boards in order.
38142.  Create a new directory to hold your board specific code. Add any
3815    files you need. In your board directory, you will need at least
3816    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
38173.  Create a new configuration file "include/configs/<board>.h" for
3818    your board
38193.  If you're porting U-Boot to a new CPU, then also create a new
3820    directory to hold your CPU specific code. Add any files you need.
38214.  Run "make <board>_config" with your new name.
38225.  Type "make", and you should get a working "u-boot.srec" file
3823    to be installed on your target system.
38246.  Debug and solve any problems that might arise.
3825    [Of course, this last step is much harder than it sounds.]
3826
3827
3828Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3829==============================================================
3830
3831If you have modified U-Boot sources (for instance added a new board
3832or support for new devices, a new CPU, etc.) you are expected to
3833provide feedback to the other developers. The feedback normally takes
3834the form of a "patch", i. e. a context diff against a certain (latest
3835official or latest in the git repository) version of U-Boot sources.
3836
3837But before you submit such a patch, please verify that your modifi-
3838cation did not break existing code. At least make sure that *ALL* of
3839the supported boards compile WITHOUT ANY compiler warnings. To do so,
3840just run the "MAKEALL" script, which will configure and build U-Boot
3841for ALL supported system. Be warned, this will take a while. You can
3842select which (cross) compiler to use by passing a `CROSS_COMPILE'
3843environment variable to the script, i. e. to use the ELDK cross tools
3844you can type
3845
3846	CROSS_COMPILE=ppc_8xx- MAKEALL
3847
3848or to build on a native PowerPC system you can type
3849
3850	CROSS_COMPILE=' ' MAKEALL
3851
3852When using the MAKEALL script, the default behaviour is to build
3853U-Boot in the source directory. This location can be changed by
3854setting the BUILD_DIR environment variable. Also, for each target
3855built, the MAKEALL script saves two log files (<target>.ERR and
3856<target>.MAKEALL) in the <source dir>/LOG directory. This default
3857location can be changed by setting the MAKEALL_LOGDIR environment
3858variable. For example:
3859
3860	export BUILD_DIR=/tmp/build
3861	export MAKEALL_LOGDIR=/tmp/log
3862	CROSS_COMPILE=ppc_8xx- MAKEALL
3863
3864With the above settings build objects are saved in the /tmp/build,
3865log files are saved in the /tmp/log and the source tree remains clean
3866during the whole build process.
3867
3868
3869See also "U-Boot Porting Guide" below.
3870
3871
3872Monitor Commands - Overview:
3873============================
3874
3875go	- start application at address 'addr'
3876run	- run commands in an environment variable
3877bootm	- boot application image from memory
3878bootp	- boot image via network using BootP/TFTP protocol
3879bootz   - boot zImage from memory
3880tftpboot- boot image via network using TFTP protocol
3881	       and env variables "ipaddr" and "serverip"
3882	       (and eventually "gatewayip")
3883tftpput - upload a file via network using TFTP protocol
3884rarpboot- boot image via network using RARP/TFTP protocol
3885diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3886loads	- load S-Record file over serial line
3887loadb	- load binary file over serial line (kermit mode)
3888md	- memory display
3889mm	- memory modify (auto-incrementing)
3890nm	- memory modify (constant address)
3891mw	- memory write (fill)
3892cp	- memory copy
3893cmp	- memory compare
3894crc32	- checksum calculation
3895i2c	- I2C sub-system
3896sspi	- SPI utility commands
3897base	- print or set address offset
3898printenv- print environment variables
3899setenv	- set environment variables
3900saveenv - save environment variables to persistent storage
3901protect - enable or disable FLASH write protection
3902erase	- erase FLASH memory
3903flinfo	- print FLASH memory information
3904nand	- NAND memory operations (see doc/README.nand)
3905bdinfo	- print Board Info structure
3906iminfo	- print header information for application image
3907coninfo - print console devices and informations
3908ide	- IDE sub-system
3909loop	- infinite loop on address range
3910loopw	- infinite write loop on address range
3911mtest	- simple RAM test
3912icache	- enable or disable instruction cache
3913dcache	- enable or disable data cache
3914reset	- Perform RESET of the CPU
3915echo	- echo args to console
3916version - print monitor version
3917help	- print online help
3918?	- alias for 'help'
3919
3920
3921Monitor Commands - Detailed Description:
3922========================================
3923
3924TODO.
3925
3926For now: just type "help <command>".
3927
3928
3929Environment Variables:
3930======================
3931
3932U-Boot supports user configuration using Environment Variables which
3933can be made persistent by saving to Flash memory.
3934
3935Environment Variables are set using "setenv", printed using
3936"printenv", and saved to Flash using "saveenv". Using "setenv"
3937without a value can be used to delete a variable from the
3938environment. As long as you don't save the environment you are
3939working with an in-memory copy. In case the Flash area containing the
3940environment is erased by accident, a default environment is provided.
3941
3942Some configuration options can be set using Environment Variables.
3943
3944List of environment variables (most likely not complete):
3945
3946  baudrate	- see CONFIG_BAUDRATE
3947
3948  bootdelay	- see CONFIG_BOOTDELAY
3949
3950  bootcmd	- see CONFIG_BOOTCOMMAND
3951
3952  bootargs	- Boot arguments when booting an RTOS image
3953
3954  bootfile	- Name of the image to load with TFTP
3955
3956  bootm_low	- Memory range available for image processing in the bootm
3957		  command can be restricted. This variable is given as
3958		  a hexadecimal number and defines lowest address allowed
3959		  for use by the bootm command. See also "bootm_size"
3960		  environment variable. Address defined by "bootm_low" is
3961		  also the base of the initial memory mapping for the Linux
3962		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3963		  bootm_mapsize.
3964
3965  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3966		  This variable is given as a hexadecimal number and it
3967		  defines the size of the memory region starting at base
3968		  address bootm_low that is accessible by the Linux kernel
3969		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3970		  as the default value if it is defined, and bootm_size is
3971		  used otherwise.
3972
3973  bootm_size	- Memory range available for image processing in the bootm
3974		  command can be restricted. This variable is given as
3975		  a hexadecimal number and defines the size of the region
3976		  allowed for use by the bootm command. See also "bootm_low"
3977		  environment variable.
3978
3979  updatefile	- Location of the software update file on a TFTP server, used
3980		  by the automatic software update feature. Please refer to
3981		  documentation in doc/README.update for more details.
3982
3983  autoload	- if set to "no" (any string beginning with 'n'),
3984		  "bootp" will just load perform a lookup of the
3985		  configuration from the BOOTP server, but not try to
3986		  load any image using TFTP
3987
3988  autostart	- if set to "yes", an image loaded using the "bootp",
3989		  "rarpboot", "tftpboot" or "diskboot" commands will
3990		  be automatically started (by internally calling
3991		  "bootm")
3992
3993		  If set to "no", a standalone image passed to the
3994		  "bootm" command will be copied to the load address
3995		  (and eventually uncompressed), but NOT be started.
3996		  This can be used to load and uncompress arbitrary
3997		  data.
3998
3999  fdt_high	- if set this restricts the maximum address that the
4000		  flattened device tree will be copied into upon boot.
4001		  For example, if you have a system with 1 GB memory
4002		  at physical address 0x10000000, while Linux kernel
4003		  only recognizes the first 704 MB as low memory, you
4004		  may need to set fdt_high as 0x3C000000 to have the
4005		  device tree blob be copied to the maximum address
4006		  of the 704 MB low memory, so that Linux kernel can
4007		  access it during the boot procedure.
4008
4009		  If this is set to the special value 0xFFFFFFFF then
4010		  the fdt will not be copied at all on boot.  For this
4011		  to work it must reside in writable memory, have
4012		  sufficient padding on the end of it for u-boot to
4013		  add the information it needs into it, and the memory
4014		  must be accessible by the kernel.
4015
4016  fdtcontroladdr- if set this is the address of the control flattened
4017		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4018		  defined.
4019
4020  i2cfast	- (PPC405GP|PPC405EP only)
4021		  if set to 'y' configures Linux I2C driver for fast
4022		  mode (400kHZ). This environment variable is used in
4023		  initialization code. So, for changes to be effective
4024		  it must be saved and board must be reset.
4025
4026  initrd_high	- restrict positioning of initrd images:
4027		  If this variable is not set, initrd images will be
4028		  copied to the highest possible address in RAM; this
4029		  is usually what you want since it allows for
4030		  maximum initrd size. If for some reason you want to
4031		  make sure that the initrd image is loaded below the
4032		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4033		  variable to a value of "no" or "off" or "0".
4034		  Alternatively, you can set it to a maximum upper
4035		  address to use (U-Boot will still check that it
4036		  does not overwrite the U-Boot stack and data).
4037
4038		  For instance, when you have a system with 16 MB
4039		  RAM, and want to reserve 4 MB from use by Linux,
4040		  you can do this by adding "mem=12M" to the value of
4041		  the "bootargs" variable. However, now you must make
4042		  sure that the initrd image is placed in the first
4043		  12 MB as well - this can be done with
4044
4045		  setenv initrd_high 00c00000
4046
4047		  If you set initrd_high to 0xFFFFFFFF, this is an
4048		  indication to U-Boot that all addresses are legal
4049		  for the Linux kernel, including addresses in flash
4050		  memory. In this case U-Boot will NOT COPY the
4051		  ramdisk at all. This may be useful to reduce the
4052		  boot time on your system, but requires that this
4053		  feature is supported by your Linux kernel.
4054
4055  ipaddr	- IP address; needed for tftpboot command
4056
4057  loadaddr	- Default load address for commands like "bootp",
4058		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4059
4060  loads_echo	- see CONFIG_LOADS_ECHO
4061
4062  serverip	- TFTP server IP address; needed for tftpboot command
4063
4064  bootretry	- see CONFIG_BOOT_RETRY_TIME
4065
4066  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4067
4068  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4069
4070  ethprime	- controls which interface is used first.
4071
4072  ethact	- controls which interface is currently active.
4073		  For example you can do the following
4074
4075		  => setenv ethact FEC
4076		  => ping 192.168.0.1 # traffic sent on FEC
4077		  => setenv ethact SCC
4078		  => ping 10.0.0.1 # traffic sent on SCC
4079
4080  ethrotate	- When set to "no" U-Boot does not go through all
4081		  available network interfaces.
4082		  It just stays at the currently selected interface.
4083
4084  netretry	- When set to "no" each network operation will
4085		  either succeed or fail without retrying.
4086		  When set to "once" the network operation will
4087		  fail when all the available network interfaces
4088		  are tried once without success.
4089		  Useful on scripts which control the retry operation
4090		  themselves.
4091
4092  npe_ucode	- set load address for the NPE microcode
4093
4094  tftpsrcport	- If this is set, the value is used for TFTP's
4095		  UDP source port.
4096
4097  tftpdstport	- If this is set, the value is used for TFTP's UDP
4098		  destination port instead of the Well Know Port 69.
4099
4100  tftpblocksize - Block size to use for TFTP transfers; if not set,
4101		  we use the TFTP server's default block size
4102
4103  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4104		  seconds, minimum value is 1000 = 1 second). Defines
4105		  when a packet is considered to be lost so it has to
4106		  be retransmitted. The default is 5000 = 5 seconds.
4107		  Lowering this value may make downloads succeed
4108		  faster in networks with high packet loss rates or
4109		  with unreliable TFTP servers.
4110
4111  vlan		- When set to a value < 4095 the traffic over
4112		  Ethernet is encapsulated/received over 802.1q
4113		  VLAN tagged frames.
4114
4115The following image location variables contain the location of images
4116used in booting. The "Image" column gives the role of the image and is
4117not an environment variable name. The other columns are environment
4118variable names. "File Name" gives the name of the file on a TFTP
4119server, "RAM Address" gives the location in RAM the image will be
4120loaded to, and "Flash Location" gives the image's address in NOR
4121flash or offset in NAND flash.
4122
4123*Note* - these variables don't have to be defined for all boards, some
4124boards currenlty use other variables for these purposes, and some
4125boards use these variables for other purposes.
4126
4127Image		    File Name	     RAM Address       Flash Location
4128-----		    ---------	     -----------       --------------
4129u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4130Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4131device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4132ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4133
4134The following environment variables may be used and automatically
4135updated by the network boot commands ("bootp" and "rarpboot"),
4136depending the information provided by your boot server:
4137
4138  bootfile	- see above
4139  dnsip		- IP address of your Domain Name Server
4140  dnsip2	- IP address of your secondary Domain Name Server
4141  gatewayip	- IP address of the Gateway (Router) to use
4142  hostname	- Target hostname
4143  ipaddr	- see above
4144  netmask	- Subnet Mask
4145  rootpath	- Pathname of the root filesystem on the NFS server
4146  serverip	- see above
4147
4148
4149There are two special Environment Variables:
4150
4151  serial#	- contains hardware identification information such
4152		  as type string and/or serial number
4153  ethaddr	- Ethernet address
4154
4155These variables can be set only once (usually during manufacturing of
4156the board). U-Boot refuses to delete or overwrite these variables
4157once they have been set once.
4158
4159
4160Further special Environment Variables:
4161
4162  ver		- Contains the U-Boot version string as printed
4163		  with the "version" command. This variable is
4164		  readonly (see CONFIG_VERSION_VARIABLE).
4165
4166
4167Please note that changes to some configuration parameters may take
4168only effect after the next boot (yes, that's just like Windoze :-).
4169
4170
4171Command Line Parsing:
4172=====================
4173
4174There are two different command line parsers available with U-Boot:
4175the old "simple" one, and the much more powerful "hush" shell:
4176
4177Old, simple command line parser:
4178--------------------------------
4179
4180- supports environment variables (through setenv / saveenv commands)
4181- several commands on one line, separated by ';'
4182- variable substitution using "... ${name} ..." syntax
4183- special characters ('$', ';') can be escaped by prefixing with '\',
4184  for example:
4185	setenv bootcmd bootm \${address}
4186- You can also escape text by enclosing in single apostrophes, for example:
4187	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4188
4189Hush shell:
4190-----------
4191
4192- similar to Bourne shell, with control structures like
4193  if...then...else...fi, for...do...done; while...do...done,
4194  until...do...done, ...
4195- supports environment ("global") variables (through setenv / saveenv
4196  commands) and local shell variables (through standard shell syntax
4197  "name=value"); only environment variables can be used with "run"
4198  command
4199
4200General rules:
4201--------------
4202
4203(1) If a command line (or an environment variable executed by a "run"
4204    command) contains several commands separated by semicolon, and
4205    one of these commands fails, then the remaining commands will be
4206    executed anyway.
4207
4208(2) If you execute several variables with one call to run (i. e.
4209    calling run with a list of variables as arguments), any failing
4210    command will cause "run" to terminate, i. e. the remaining
4211    variables are not executed.
4212
4213Note for Redundant Ethernet Interfaces:
4214=======================================
4215
4216Some boards come with redundant Ethernet interfaces; U-Boot supports
4217such configurations and is capable of automatic selection of a
4218"working" interface when needed. MAC assignment works as follows:
4219
4220Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4221MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4222"eth1addr" (=>eth1), "eth2addr", ...
4223
4224If the network interface stores some valid MAC address (for instance
4225in SROM), this is used as default address if there is NO correspon-
4226ding setting in the environment; if the corresponding environment
4227variable is set, this overrides the settings in the card; that means:
4228
4229o If the SROM has a valid MAC address, and there is no address in the
4230  environment, the SROM's address is used.
4231
4232o If there is no valid address in the SROM, and a definition in the
4233  environment exists, then the value from the environment variable is
4234  used.
4235
4236o If both the SROM and the environment contain a MAC address, and
4237  both addresses are the same, this MAC address is used.
4238
4239o If both the SROM and the environment contain a MAC address, and the
4240  addresses differ, the value from the environment is used and a
4241  warning is printed.
4242
4243o If neither SROM nor the environment contain a MAC address, an error
4244  is raised.
4245
4246If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4247will be programmed into hardware as part of the initialization process.	 This
4248may be skipped by setting the appropriate 'ethmacskip' environment variable.
4249The naming convention is as follows:
4250"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4251
4252Image Formats:
4253==============
4254
4255U-Boot is capable of booting (and performing other auxiliary operations on)
4256images in two formats:
4257
4258New uImage format (FIT)
4259-----------------------
4260
4261Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4262to Flattened Device Tree). It allows the use of images with multiple
4263components (several kernels, ramdisks, etc.), with contents protected by
4264SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4265
4266
4267Old uImage format
4268-----------------
4269
4270Old image format is based on binary files which can be basically anything,
4271preceded by a special header; see the definitions in include/image.h for
4272details; basically, the header defines the following image properties:
4273
4274* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4275  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4276  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4277  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4278  INTEGRITY).
4279* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
4280  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4281  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4282* Compression Type (uncompressed, gzip, bzip2)
4283* Load Address
4284* Entry Point
4285* Image Name
4286* Image Timestamp
4287
4288The header is marked by a special Magic Number, and both the header
4289and the data portions of the image are secured against corruption by
4290CRC32 checksums.
4291
4292
4293Linux Support:
4294==============
4295
4296Although U-Boot should support any OS or standalone application
4297easily, the main focus has always been on Linux during the design of
4298U-Boot.
4299
4300U-Boot includes many features that so far have been part of some
4301special "boot loader" code within the Linux kernel. Also, any
4302"initrd" images to be used are no longer part of one big Linux image;
4303instead, kernel and "initrd" are separate images. This implementation
4304serves several purposes:
4305
4306- the same features can be used for other OS or standalone
4307  applications (for instance: using compressed images to reduce the
4308  Flash memory footprint)
4309
4310- it becomes much easier to port new Linux kernel versions because
4311  lots of low-level, hardware dependent stuff are done by U-Boot
4312
4313- the same Linux kernel image can now be used with different "initrd"
4314  images; of course this also means that different kernel images can
4315  be run with the same "initrd". This makes testing easier (you don't
4316  have to build a new "zImage.initrd" Linux image when you just
4317  change a file in your "initrd"). Also, a field-upgrade of the
4318  software is easier now.
4319
4320
4321Linux HOWTO:
4322============
4323
4324Porting Linux to U-Boot based systems:
4325---------------------------------------
4326
4327U-Boot cannot save you from doing all the necessary modifications to
4328configure the Linux device drivers for use with your target hardware
4329(no, we don't intend to provide a full virtual machine interface to
4330Linux :-).
4331
4332But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4333
4334Just make sure your machine specific header file (for instance
4335include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4336Information structure as we define in include/asm-<arch>/u-boot.h,
4337and make sure that your definition of IMAP_ADDR uses the same value
4338as your U-Boot configuration in CONFIG_SYS_IMMR.
4339
4340
4341Configuring the Linux kernel:
4342-----------------------------
4343
4344No specific requirements for U-Boot. Make sure you have some root
4345device (initial ramdisk, NFS) for your target system.
4346
4347
4348Building a Linux Image:
4349-----------------------
4350
4351With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4352not used. If you use recent kernel source, a new build target
4353"uImage" will exist which automatically builds an image usable by
4354U-Boot. Most older kernels also have support for a "pImage" target,
4355which was introduced for our predecessor project PPCBoot and uses a
4356100% compatible format.
4357
4358Example:
4359
4360	make TQM850L_config
4361	make oldconfig
4362	make dep
4363	make uImage
4364
4365The "uImage" build target uses a special tool (in 'tools/mkimage') to
4366encapsulate a compressed Linux kernel image with header	 information,
4367CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4368
4369* build a standard "vmlinux" kernel image (in ELF binary format):
4370
4371* convert the kernel into a raw binary image:
4372
4373	${CROSS_COMPILE}-objcopy -O binary \
4374				 -R .note -R .comment \
4375				 -S vmlinux linux.bin
4376
4377* compress the binary image:
4378
4379	gzip -9 linux.bin
4380
4381* package compressed binary image for U-Boot:
4382
4383	mkimage -A ppc -O linux -T kernel -C gzip \
4384		-a 0 -e 0 -n "Linux Kernel Image" \
4385		-d linux.bin.gz uImage
4386
4387
4388The "mkimage" tool can also be used to create ramdisk images for use
4389with U-Boot, either separated from the Linux kernel image, or
4390combined into one file. "mkimage" encapsulates the images with a 64
4391byte header containing information about target architecture,
4392operating system, image type, compression method, entry points, time
4393stamp, CRC32 checksums, etc.
4394
4395"mkimage" can be called in two ways: to verify existing images and
4396print the header information, or to build new images.
4397
4398In the first form (with "-l" option) mkimage lists the information
4399contained in the header of an existing U-Boot image; this includes
4400checksum verification:
4401
4402	tools/mkimage -l image
4403	  -l ==> list image header information
4404
4405The second form (with "-d" option) is used to build a U-Boot image
4406from a "data file" which is used as image payload:
4407
4408	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4409		      -n name -d data_file image
4410	  -A ==> set architecture to 'arch'
4411	  -O ==> set operating system to 'os'
4412	  -T ==> set image type to 'type'
4413	  -C ==> set compression type 'comp'
4414	  -a ==> set load address to 'addr' (hex)
4415	  -e ==> set entry point to 'ep' (hex)
4416	  -n ==> set image name to 'name'
4417	  -d ==> use image data from 'datafile'
4418
4419Right now, all Linux kernels for PowerPC systems use the same load
4420address (0x00000000), but the entry point address depends on the
4421kernel version:
4422
4423- 2.2.x kernels have the entry point at 0x0000000C,
4424- 2.3.x and later kernels have the entry point at 0x00000000.
4425
4426So a typical call to build a U-Boot image would read:
4427
4428	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4429	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4430	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4431	> examples/uImage.TQM850L
4432	Image Name:   2.4.4 kernel for TQM850L
4433	Created:      Wed Jul 19 02:34:59 2000
4434	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4435	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4436	Load Address: 0x00000000
4437	Entry Point:  0x00000000
4438
4439To verify the contents of the image (or check for corruption):
4440
4441	-> tools/mkimage -l examples/uImage.TQM850L
4442	Image Name:   2.4.4 kernel for TQM850L
4443	Created:      Wed Jul 19 02:34:59 2000
4444	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4445	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4446	Load Address: 0x00000000
4447	Entry Point:  0x00000000
4448
4449NOTE: for embedded systems where boot time is critical you can trade
4450speed for memory and install an UNCOMPRESSED image instead: this
4451needs more space in Flash, but boots much faster since it does not
4452need to be uncompressed:
4453
4454	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4455	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4456	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4457	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4458	> examples/uImage.TQM850L-uncompressed
4459	Image Name:   2.4.4 kernel for TQM850L
4460	Created:      Wed Jul 19 02:34:59 2000
4461	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4462	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4463	Load Address: 0x00000000
4464	Entry Point:  0x00000000
4465
4466
4467Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4468when your kernel is intended to use an initial ramdisk:
4469
4470	-> tools/mkimage -n 'Simple Ramdisk Image' \
4471	> -A ppc -O linux -T ramdisk -C gzip \
4472	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4473	Image Name:   Simple Ramdisk Image
4474	Created:      Wed Jan 12 14:01:50 2000
4475	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4476	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4477	Load Address: 0x00000000
4478	Entry Point:  0x00000000
4479
4480
4481Installing a Linux Image:
4482-------------------------
4483
4484To downloading a U-Boot image over the serial (console) interface,
4485you must convert the image to S-Record format:
4486
4487	objcopy -I binary -O srec examples/image examples/image.srec
4488
4489The 'objcopy' does not understand the information in the U-Boot
4490image header, so the resulting S-Record file will be relative to
4491address 0x00000000. To load it to a given address, you need to
4492specify the target address as 'offset' parameter with the 'loads'
4493command.
4494
4495Example: install the image to address 0x40100000 (which on the
4496TQM8xxL is in the first Flash bank):
4497
4498	=> erase 40100000 401FFFFF
4499
4500	.......... done
4501	Erased 8 sectors
4502
4503	=> loads 40100000
4504	## Ready for S-Record download ...
4505	~>examples/image.srec
4506	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4507	...
4508	15989 15990 15991 15992
4509	[file transfer complete]
4510	[connected]
4511	## Start Addr = 0x00000000
4512
4513
4514You can check the success of the download using the 'iminfo' command;
4515this includes a checksum verification so you can be sure no data
4516corruption happened:
4517
4518	=> imi 40100000
4519
4520	## Checking Image at 40100000 ...
4521	   Image Name:	 2.2.13 for initrd on TQM850L
4522	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4523	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4524	   Load Address: 00000000
4525	   Entry Point:	 0000000c
4526	   Verifying Checksum ... OK
4527
4528
4529Boot Linux:
4530-----------
4531
4532The "bootm" command is used to boot an application that is stored in
4533memory (RAM or Flash). In case of a Linux kernel image, the contents
4534of the "bootargs" environment variable is passed to the kernel as
4535parameters. You can check and modify this variable using the
4536"printenv" and "setenv" commands:
4537
4538
4539	=> printenv bootargs
4540	bootargs=root=/dev/ram
4541
4542	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4543
4544	=> printenv bootargs
4545	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4546
4547	=> bootm 40020000
4548	## Booting Linux kernel at 40020000 ...
4549	   Image Name:	 2.2.13 for NFS on TQM850L
4550	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4551	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4552	   Load Address: 00000000
4553	   Entry Point:	 0000000c
4554	   Verifying Checksum ... OK
4555	   Uncompressing Kernel Image ... OK
4556	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
4557	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4558	time_init: decrementer frequency = 187500000/60
4559	Calibrating delay loop... 49.77 BogoMIPS
4560	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4561	...
4562
4563If you want to boot a Linux kernel with initial RAM disk, you pass
4564the memory addresses of both the kernel and the initrd image (PPBCOOT
4565format!) to the "bootm" command:
4566
4567	=> imi 40100000 40200000
4568
4569	## Checking Image at 40100000 ...
4570	   Image Name:	 2.2.13 for initrd on TQM850L
4571	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4572	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4573	   Load Address: 00000000
4574	   Entry Point:	 0000000c
4575	   Verifying Checksum ... OK
4576
4577	## Checking Image at 40200000 ...
4578	   Image Name:	 Simple Ramdisk Image
4579	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4580	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4581	   Load Address: 00000000
4582	   Entry Point:	 00000000
4583	   Verifying Checksum ... OK
4584
4585	=> bootm 40100000 40200000
4586	## Booting Linux kernel at 40100000 ...
4587	   Image Name:	 2.2.13 for initrd on TQM850L
4588	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4589	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4590	   Load Address: 00000000
4591	   Entry Point:	 0000000c
4592	   Verifying Checksum ... OK
4593	   Uncompressing Kernel Image ... OK
4594	## Loading RAMDisk Image at 40200000 ...
4595	   Image Name:	 Simple Ramdisk Image
4596	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4597	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4598	   Load Address: 00000000
4599	   Entry Point:	 00000000
4600	   Verifying Checksum ... OK
4601	   Loading Ramdisk ... OK
4602	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
4603	Boot arguments: root=/dev/ram
4604	time_init: decrementer frequency = 187500000/60
4605	Calibrating delay loop... 49.77 BogoMIPS
4606	...
4607	RAMDISK: Compressed image found at block 0
4608	VFS: Mounted root (ext2 filesystem).
4609
4610	bash#
4611
4612Boot Linux and pass a flat device tree:
4613-----------
4614
4615First, U-Boot must be compiled with the appropriate defines. See the section
4616titled "Linux Kernel Interface" above for a more in depth explanation. The
4617following is an example of how to start a kernel and pass an updated
4618flat device tree:
4619
4620=> print oftaddr
4621oftaddr=0x300000
4622=> print oft
4623oft=oftrees/mpc8540ads.dtb
4624=> tftp $oftaddr $oft
4625Speed: 1000, full duplex
4626Using TSEC0 device
4627TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4628Filename 'oftrees/mpc8540ads.dtb'.
4629Load address: 0x300000
4630Loading: #
4631done
4632Bytes transferred = 4106 (100a hex)
4633=> tftp $loadaddr $bootfile
4634Speed: 1000, full duplex
4635Using TSEC0 device
4636TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4637Filename 'uImage'.
4638Load address: 0x200000
4639Loading:############
4640done
4641Bytes transferred = 1029407 (fb51f hex)
4642=> print loadaddr
4643loadaddr=200000
4644=> print oftaddr
4645oftaddr=0x300000
4646=> bootm $loadaddr - $oftaddr
4647## Booting image at 00200000 ...
4648   Image Name:	 Linux-2.6.17-dirty
4649   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4650   Data Size:	 1029343 Bytes = 1005.2 kB
4651   Load Address: 00000000
4652   Entry Point:	 00000000
4653   Verifying Checksum ... OK
4654   Uncompressing Kernel Image ... OK
4655Booting using flat device tree at 0x300000
4656Using MPC85xx ADS machine description
4657Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4658[snip]
4659
4660
4661More About U-Boot Image Types:
4662------------------------------
4663
4664U-Boot supports the following image types:
4665
4666   "Standalone Programs" are directly runnable in the environment
4667	provided by U-Boot; it is expected that (if they behave
4668	well) you can continue to work in U-Boot after return from
4669	the Standalone Program.
4670   "OS Kernel Images" are usually images of some Embedded OS which
4671	will take over control completely. Usually these programs
4672	will install their own set of exception handlers, device
4673	drivers, set up the MMU, etc. - this means, that you cannot
4674	expect to re-enter U-Boot except by resetting the CPU.
4675   "RAMDisk Images" are more or less just data blocks, and their
4676	parameters (address, size) are passed to an OS kernel that is
4677	being started.
4678   "Multi-File Images" contain several images, typically an OS
4679	(Linux) kernel image and one or more data images like
4680	RAMDisks. This construct is useful for instance when you want
4681	to boot over the network using BOOTP etc., where the boot
4682	server provides just a single image file, but you want to get
4683	for instance an OS kernel and a RAMDisk image.
4684
4685	"Multi-File Images" start with a list of image sizes, each
4686	image size (in bytes) specified by an "uint32_t" in network
4687	byte order. This list is terminated by an "(uint32_t)0".
4688	Immediately after the terminating 0 follow the images, one by
4689	one, all aligned on "uint32_t" boundaries (size rounded up to
4690	a multiple of 4 bytes).
4691
4692   "Firmware Images" are binary images containing firmware (like
4693	U-Boot or FPGA images) which usually will be programmed to
4694	flash memory.
4695
4696   "Script files" are command sequences that will be executed by
4697	U-Boot's command interpreter; this feature is especially
4698	useful when you configure U-Boot to use a real shell (hush)
4699	as command interpreter.
4700
4701Booting the Linux zImage:
4702-------------------------
4703
4704On some platforms, it's possible to boot Linux zImage. This is done
4705using the "bootz" command. The syntax of "bootz" command is the same
4706as the syntax of "bootm" command.
4707
4708Note, defining the CONFIG_SUPPORT_INITRD_RAW allows user to supply
4709kernel with raw initrd images. The syntax is slightly different, the
4710address of the initrd must be augmented by it's size, in the following
4711format: "<initrd addres>:<initrd size>".
4712
4713
4714Standalone HOWTO:
4715=================
4716
4717One of the features of U-Boot is that you can dynamically load and
4718run "standalone" applications, which can use some resources of
4719U-Boot like console I/O functions or interrupt services.
4720
4721Two simple examples are included with the sources:
4722
4723"Hello World" Demo:
4724-------------------
4725
4726'examples/hello_world.c' contains a small "Hello World" Demo
4727application; it is automatically compiled when you build U-Boot.
4728It's configured to run at address 0x00040004, so you can play with it
4729like that:
4730
4731	=> loads
4732	## Ready for S-Record download ...
4733	~>examples/hello_world.srec
4734	1 2 3 4 5 6 7 8 9 10 11 ...
4735	[file transfer complete]
4736	[connected]
4737	## Start Addr = 0x00040004
4738
4739	=> go 40004 Hello World! This is a test.
4740	## Starting application at 0x00040004 ...
4741	Hello World
4742	argc = 7
4743	argv[0] = "40004"
4744	argv[1] = "Hello"
4745	argv[2] = "World!"
4746	argv[3] = "This"
4747	argv[4] = "is"
4748	argv[5] = "a"
4749	argv[6] = "test."
4750	argv[7] = "<NULL>"
4751	Hit any key to exit ...
4752
4753	## Application terminated, rc = 0x0
4754
4755Another example, which demonstrates how to register a CPM interrupt
4756handler with the U-Boot code, can be found in 'examples/timer.c'.
4757Here, a CPM timer is set up to generate an interrupt every second.
4758The interrupt service routine is trivial, just printing a '.'
4759character, but this is just a demo program. The application can be
4760controlled by the following keys:
4761
4762	? - print current values og the CPM Timer registers
4763	b - enable interrupts and start timer
4764	e - stop timer and disable interrupts
4765	q - quit application
4766
4767	=> loads
4768	## Ready for S-Record download ...
4769	~>examples/timer.srec
4770	1 2 3 4 5 6 7 8 9 10 11 ...
4771	[file transfer complete]
4772	[connected]
4773	## Start Addr = 0x00040004
4774
4775	=> go 40004
4776	## Starting application at 0x00040004 ...
4777	TIMERS=0xfff00980
4778	Using timer 1
4779	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4780
4781Hit 'b':
4782	[q, b, e, ?] Set interval 1000000 us
4783	Enabling timer
4784Hit '?':
4785	[q, b, e, ?] ........
4786	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4787Hit '?':
4788	[q, b, e, ?] .
4789	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4790Hit '?':
4791	[q, b, e, ?] .
4792	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4793Hit '?':
4794	[q, b, e, ?] .
4795	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4796Hit 'e':
4797	[q, b, e, ?] ...Stopping timer
4798Hit 'q':
4799	[q, b, e, ?] ## Application terminated, rc = 0x0
4800
4801
4802Minicom warning:
4803================
4804
4805Over time, many people have reported problems when trying to use the
4806"minicom" terminal emulation program for serial download. I (wd)
4807consider minicom to be broken, and recommend not to use it. Under
4808Unix, I recommend to use C-Kermit for general purpose use (and
4809especially for kermit binary protocol download ("loadb" command), and
4810use "cu" for S-Record download ("loads" command).  See
4811http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4812for help with kermit.
4813
4814
4815Nevertheless, if you absolutely want to use it try adding this
4816configuration to your "File transfer protocols" section:
4817
4818	   Name	   Program			Name U/D FullScr IO-Red. Multi
4819	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4820	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4821
4822
4823NetBSD Notes:
4824=============
4825
4826Starting at version 0.9.2, U-Boot supports NetBSD both as host
4827(build U-Boot) and target system (boots NetBSD/mpc8xx).
4828
4829Building requires a cross environment; it is known to work on
4830NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4831need gmake since the Makefiles are not compatible with BSD make).
4832Note that the cross-powerpc package does not install include files;
4833attempting to build U-Boot will fail because <machine/ansi.h> is
4834missing.  This file has to be installed and patched manually:
4835
4836	# cd /usr/pkg/cross/powerpc-netbsd/include
4837	# mkdir powerpc
4838	# ln -s powerpc machine
4839	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4840	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4841
4842Native builds *don't* work due to incompatibilities between native
4843and U-Boot include files.
4844
4845Booting assumes that (the first part of) the image booted is a
4846stage-2 loader which in turn loads and then invokes the kernel
4847proper. Loader sources will eventually appear in the NetBSD source
4848tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4849meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4850
4851
4852Implementation Internals:
4853=========================
4854
4855The following is not intended to be a complete description of every
4856implementation detail. However, it should help to understand the
4857inner workings of U-Boot and make it easier to port it to custom
4858hardware.
4859
4860
4861Initial Stack, Global Data:
4862---------------------------
4863
4864The implementation of U-Boot is complicated by the fact that U-Boot
4865starts running out of ROM (flash memory), usually without access to
4866system RAM (because the memory controller is not initialized yet).
4867This means that we don't have writable Data or BSS segments, and BSS
4868is not initialized as zero. To be able to get a C environment working
4869at all, we have to allocate at least a minimal stack. Implementation
4870options for this are defined and restricted by the CPU used: Some CPU
4871models provide on-chip memory (like the IMMR area on MPC8xx and
4872MPC826x processors), on others (parts of) the data cache can be
4873locked as (mis-) used as memory, etc.
4874
4875	Chris Hallinan posted a good summary of these issues to the
4876	U-Boot mailing list:
4877
4878	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4879	From: "Chris Hallinan" <clh@net1plus.com>
4880	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4881	...
4882
4883	Correct me if I'm wrong, folks, but the way I understand it
4884	is this: Using DCACHE as initial RAM for Stack, etc, does not
4885	require any physical RAM backing up the cache. The cleverness
4886	is that the cache is being used as a temporary supply of
4887	necessary storage before the SDRAM controller is setup. It's
4888	beyond the scope of this list to explain the details, but you
4889	can see how this works by studying the cache architecture and
4890	operation in the architecture and processor-specific manuals.
4891
4892	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4893	is another option for the system designer to use as an
4894	initial stack/RAM area prior to SDRAM being available. Either
4895	option should work for you. Using CS 4 should be fine if your
4896	board designers haven't used it for something that would
4897	cause you grief during the initial boot! It is frequently not
4898	used.
4899
4900	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4901	with your processor/board/system design. The default value
4902	you will find in any recent u-boot distribution in
4903	walnut.h should work for you. I'd set it to a value larger
4904	than your SDRAM module. If you have a 64MB SDRAM module, set
4905	it above 400_0000. Just make sure your board has no resources
4906	that are supposed to respond to that address! That code in
4907	start.S has been around a while and should work as is when
4908	you get the config right.
4909
4910	-Chris Hallinan
4911	DS4.COM, Inc.
4912
4913It is essential to remember this, since it has some impact on the C
4914code for the initialization procedures:
4915
4916* Initialized global data (data segment) is read-only. Do not attempt
4917  to write it.
4918
4919* Do not use any uninitialized global data (or implicitely initialized
4920  as zero data - BSS segment) at all - this is undefined, initiali-
4921  zation is performed later (when relocating to RAM).
4922
4923* Stack space is very limited. Avoid big data buffers or things like
4924  that.
4925
4926Having only the stack as writable memory limits means we cannot use
4927normal global data to share information beween the code. But it
4928turned out that the implementation of U-Boot can be greatly
4929simplified by making a global data structure (gd_t) available to all
4930functions. We could pass a pointer to this data as argument to _all_
4931functions, but this would bloat the code. Instead we use a feature of
4932the GCC compiler (Global Register Variables) to share the data: we
4933place a pointer (gd) to the global data into a register which we
4934reserve for this purpose.
4935
4936When choosing a register for such a purpose we are restricted by the
4937relevant  (E)ABI  specifications for the current architecture, and by
4938GCC's implementation.
4939
4940For PowerPC, the following registers have specific use:
4941	R1:	stack pointer
4942	R2:	reserved for system use
4943	R3-R4:	parameter passing and return values
4944	R5-R10: parameter passing
4945	R13:	small data area pointer
4946	R30:	GOT pointer
4947	R31:	frame pointer
4948
4949	(U-Boot also uses R12 as internal GOT pointer. r12
4950	is a volatile register so r12 needs to be reset when
4951	going back and forth between asm and C)
4952
4953    ==> U-Boot will use R2 to hold a pointer to the global data
4954
4955    Note: on PPC, we could use a static initializer (since the
4956    address of the global data structure is known at compile time),
4957    but it turned out that reserving a register results in somewhat
4958    smaller code - although the code savings are not that big (on
4959    average for all boards 752 bytes for the whole U-Boot image,
4960    624 text + 127 data).
4961
4962On Blackfin, the normal C ABI (except for P3) is followed as documented here:
4963	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
4964
4965    ==> U-Boot will use P3 to hold a pointer to the global data
4966
4967On ARM, the following registers are used:
4968
4969	R0:	function argument word/integer result
4970	R1-R3:	function argument word
4971	R9:	GOT pointer
4972	R10:	stack limit (used only if stack checking if enabled)
4973	R11:	argument (frame) pointer
4974	R12:	temporary workspace
4975	R13:	stack pointer
4976	R14:	link register
4977	R15:	program counter
4978
4979    ==> U-Boot will use R8 to hold a pointer to the global data
4980
4981On Nios II, the ABI is documented here:
4982	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4983
4984    ==> U-Boot will use gp to hold a pointer to the global data
4985
4986    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4987    to access small data sections, so gp is free.
4988
4989On NDS32, the following registers are used:
4990
4991	R0-R1:	argument/return
4992	R2-R5:	argument
4993	R15:	temporary register for assembler
4994	R16:	trampoline register
4995	R28:	frame pointer (FP)
4996	R29:	global pointer (GP)
4997	R30:	link register (LP)
4998	R31:	stack pointer (SP)
4999	PC:	program counter (PC)
5000
5001    ==> U-Boot will use R10 to hold a pointer to the global data
5002
5003NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5004or current versions of GCC may "optimize" the code too much.
5005
5006Memory Management:
5007------------------
5008
5009U-Boot runs in system state and uses physical addresses, i.e. the
5010MMU is not used either for address mapping nor for memory protection.
5011
5012The available memory is mapped to fixed addresses using the memory
5013controller. In this process, a contiguous block is formed for each
5014memory type (Flash, SDRAM, SRAM), even when it consists of several
5015physical memory banks.
5016
5017U-Boot is installed in the first 128 kB of the first Flash bank (on
5018TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5019booting and sizing and initializing DRAM, the code relocates itself
5020to the upper end of DRAM. Immediately below the U-Boot code some
5021memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5022configuration setting]. Below that, a structure with global Board
5023Info data is placed, followed by the stack (growing downward).
5024
5025Additionally, some exception handler code is copied to the low 8 kB
5026of DRAM (0x00000000 ... 0x00001FFF).
5027
5028So a typical memory configuration with 16 MB of DRAM could look like
5029this:
5030
5031	0x0000 0000	Exception Vector code
5032	      :
5033	0x0000 1FFF
5034	0x0000 2000	Free for Application Use
5035	      :
5036	      :
5037
5038	      :
5039	      :
5040	0x00FB FF20	Monitor Stack (Growing downward)
5041	0x00FB FFAC	Board Info Data and permanent copy of global data
5042	0x00FC 0000	Malloc Arena
5043	      :
5044	0x00FD FFFF
5045	0x00FE 0000	RAM Copy of Monitor Code
5046	...		eventually: LCD or video framebuffer
5047	...		eventually: pRAM (Protected RAM - unchanged by reset)
5048	0x00FF FFFF	[End of RAM]
5049
5050
5051System Initialization:
5052----------------------
5053
5054In the reset configuration, U-Boot starts at the reset entry point
5055(on most PowerPC systems at address 0x00000100). Because of the reset
5056configuration for CS0# this is a mirror of the onboard Flash memory.
5057To be able to re-map memory U-Boot then jumps to its link address.
5058To be able to implement the initialization code in C, a (small!)
5059initial stack is set up in the internal Dual Ported RAM (in case CPUs
5060which provide such a feature like MPC8xx or MPC8260), or in a locked
5061part of the data cache. After that, U-Boot initializes the CPU core,
5062the caches and the SIU.
5063
5064Next, all (potentially) available memory banks are mapped using a
5065preliminary mapping. For example, we put them on 512 MB boundaries
5066(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5067on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5068programmed for SDRAM access. Using the temporary configuration, a
5069simple memory test is run that determines the size of the SDRAM
5070banks.
5071
5072When there is more than one SDRAM bank, and the banks are of
5073different size, the largest is mapped first. For equal size, the first
5074bank (CS2#) is mapped first. The first mapping is always for address
50750x00000000, with any additional banks following immediately to create
5076contiguous memory starting from 0.
5077
5078Then, the monitor installs itself at the upper end of the SDRAM area
5079and allocates memory for use by malloc() and for the global Board
5080Info data; also, the exception vector code is copied to the low RAM
5081pages, and the final stack is set up.
5082
5083Only after this relocation will you have a "normal" C environment;
5084until that you are restricted in several ways, mostly because you are
5085running from ROM, and because the code will have to be relocated to a
5086new address in RAM.
5087
5088
5089U-Boot Porting Guide:
5090----------------------
5091
5092[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5093list, October 2002]
5094
5095
5096int main(int argc, char *argv[])
5097{
5098	sighandler_t no_more_time;
5099
5100	signal(SIGALRM, no_more_time);
5101	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5102
5103	if (available_money > available_manpower) {
5104		Pay consultant to port U-Boot;
5105		return 0;
5106	}
5107
5108	Download latest U-Boot source;
5109
5110	Subscribe to u-boot mailing list;
5111
5112	if (clueless)
5113		email("Hi, I am new to U-Boot, how do I get started?");
5114
5115	while (learning) {
5116		Read the README file in the top level directory;
5117		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5118		Read applicable doc/*.README;
5119		Read the source, Luke;
5120		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5121	}
5122
5123	if (available_money > toLocalCurrency ($2500))
5124		Buy a BDI3000;
5125	else
5126		Add a lot of aggravation and time;
5127
5128	if (a similar board exists) {	/* hopefully... */
5129		cp -a board/<similar> board/<myboard>
5130		cp include/configs/<similar>.h include/configs/<myboard>.h
5131	} else {
5132		Create your own board support subdirectory;
5133		Create your own board include/configs/<myboard>.h file;
5134	}
5135	Edit new board/<myboard> files
5136	Edit new include/configs/<myboard>.h
5137
5138	while (!accepted) {
5139		while (!running) {
5140			do {
5141				Add / modify source code;
5142			} until (compiles);
5143			Debug;
5144			if (clueless)
5145				email("Hi, I am having problems...");
5146		}
5147		Send patch file to the U-Boot email list;
5148		if (reasonable critiques)
5149			Incorporate improvements from email list code review;
5150		else
5151			Defend code as written;
5152	}
5153
5154	return 0;
5155}
5156
5157void no_more_time (int sig)
5158{
5159      hire_a_guru();
5160}
5161
5162
5163Coding Standards:
5164-----------------
5165
5166All contributions to U-Boot should conform to the Linux kernel
5167coding style; see the file "Documentation/CodingStyle" and the script
5168"scripts/Lindent" in your Linux kernel source directory.
5169
5170Source files originating from a different project (for example the
5171MTD subsystem) are generally exempt from these guidelines and are not
5172reformated to ease subsequent migration to newer versions of those
5173sources.
5174
5175Please note that U-Boot is implemented in C (and to some small parts in
5176Assembler); no C++ is used, so please do not use C++ style comments (//)
5177in your code.
5178
5179Please also stick to the following formatting rules:
5180- remove any trailing white space
5181- use TAB characters for indentation and vertical alignment, not spaces
5182- make sure NOT to use DOS '\r\n' line feeds
5183- do not add more than 2 consecutive empty lines to source files
5184- do not add trailing empty lines to source files
5185
5186Submissions which do not conform to the standards may be returned
5187with a request to reformat the changes.
5188
5189
5190Submitting Patches:
5191-------------------
5192
5193Since the number of patches for U-Boot is growing, we need to
5194establish some rules. Submissions which do not conform to these rules
5195may be rejected, even when they contain important and valuable stuff.
5196
5197Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5198
5199Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5200see http://lists.denx.de/mailman/listinfo/u-boot
5201
5202When you send a patch, please include the following information with
5203it:
5204
5205* For bug fixes: a description of the bug and how your patch fixes
5206  this bug. Please try to include a way of demonstrating that the
5207  patch actually fixes something.
5208
5209* For new features: a description of the feature and your
5210  implementation.
5211
5212* A CHANGELOG entry as plaintext (separate from the patch)
5213
5214* For major contributions, your entry to the CREDITS file
5215
5216* When you add support for a new board, don't forget to add this
5217  board to the MAINTAINERS file, too.
5218
5219* If your patch adds new configuration options, don't forget to
5220  document these in the README file.
5221
5222* The patch itself. If you are using git (which is *strongly*
5223  recommended) you can easily generate the patch using the
5224  "git format-patch". If you then use "git send-email" to send it to
5225  the U-Boot mailing list, you will avoid most of the common problems
5226  with some other mail clients.
5227
5228  If you cannot use git, use "diff -purN OLD NEW". If your version of
5229  diff does not support these options, then get the latest version of
5230  GNU diff.
5231
5232  The current directory when running this command shall be the parent
5233  directory of the U-Boot source tree (i. e. please make sure that
5234  your patch includes sufficient directory information for the
5235  affected files).
5236
5237  We prefer patches as plain text. MIME attachments are discouraged,
5238  and compressed attachments must not be used.
5239
5240* If one logical set of modifications affects or creates several
5241  files, all these changes shall be submitted in a SINGLE patch file.
5242
5243* Changesets that contain different, unrelated modifications shall be
5244  submitted as SEPARATE patches, one patch per changeset.
5245
5246
5247Notes:
5248
5249* Before sending the patch, run the MAKEALL script on your patched
5250  source tree and make sure that no errors or warnings are reported
5251  for any of the boards.
5252
5253* Keep your modifications to the necessary minimum: A patch
5254  containing several unrelated changes or arbitrary reformats will be
5255  returned with a request to re-formatting / split it.
5256
5257* If you modify existing code, make sure that your new code does not
5258  add to the memory footprint of the code ;-) Small is beautiful!
5259  When adding new features, these should compile conditionally only
5260  (using #ifdef), and the resulting code with the new feature
5261  disabled must not need more memory than the old code without your
5262  modification.
5263
5264* Remember that there is a size limit of 100 kB per message on the
5265  u-boot mailing list. Bigger patches will be moderated. If they are
5266  reasonable and not too big, they will be acknowledged. But patches
5267  bigger than the size limit should be avoided.
5268