xref: /openbmc/u-boot/README (revision e0a0cbf2)
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- Splash Screen Support: CONFIG_SPLASH_SCREEN
1473
1474		If this option is set, the environment is checked for
1475		a variable "splashimage". If found, the usual display
1476		of logo, copyright and system information on the LCD
1477		is suppressed and the BMP image at the address
1478		specified in "splashimage" is loaded instead. The
1479		console is redirected to the "nulldev", too. This
1480		allows for a "silent" boot where a splash screen is
1481		loaded very quickly after power-on.
1482
1483		CONFIG_SPLASH_SCREEN_ALIGN
1484
1485		If this option is set the splash image can be freely positioned
1486		on the screen. Environment variable "splashpos" specifies the
1487		position as "x,y". If a positive number is given it is used as
1488		number of pixel from left/top. If a negative number is given it
1489		is used as number of pixel from right/bottom. You can also
1490		specify 'm' for centering the image.
1491
1492		Example:
1493		setenv splashpos m,m
1494			=> image at center of screen
1495
1496		setenv splashpos 30,20
1497			=> image at x = 30 and y = 20
1498
1499		setenv splashpos -10,m
1500			=> vertically centered image
1501			   at x = dspWidth - bmpWidth - 9
1502
1503- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1504
1505		If this option is set, additionally to standard BMP
1506		images, gzipped BMP images can be displayed via the
1507		splashscreen support or the bmp command.
1508
1509- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1510
1511		If this option is set, 8-bit RLE compressed BMP images
1512		can be displayed via the splashscreen support or the
1513		bmp command.
1514
1515- Do compresssing for memory range:
1516		CONFIG_CMD_ZIP
1517
1518		If this option is set, it would use zlib deflate method
1519		to compress the specified memory at its best effort.
1520
1521- Compression support:
1522		CONFIG_BZIP2
1523
1524		If this option is set, support for bzip2 compressed
1525		images is included. If not, only uncompressed and gzip
1526		compressed images are supported.
1527
1528		NOTE: the bzip2 algorithm requires a lot of RAM, so
1529		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1530		be at least 4MB.
1531
1532		CONFIG_LZMA
1533
1534		If this option is set, support for lzma compressed
1535		images is included.
1536
1537		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1538		requires an amount of dynamic memory that is given by the
1539		formula:
1540
1541			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1542
1543		Where lc and lp stand for, respectively, Literal context bits
1544		and Literal pos bits.
1545
1546		This value is upper-bounded by 14MB in the worst case. Anyway,
1547		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1548		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1549		a very small buffer.
1550
1551		Use the lzmainfo tool to determinate the lc and lp values and
1552		then calculate the amount of needed dynamic memory (ensuring
1553		the appropriate CONFIG_SYS_MALLOC_LEN value).
1554
1555- MII/PHY support:
1556		CONFIG_PHY_ADDR
1557
1558		The address of PHY on MII bus.
1559
1560		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1561
1562		The clock frequency of the MII bus
1563
1564		CONFIG_PHY_GIGE
1565
1566		If this option is set, support for speed/duplex
1567		detection of gigabit PHY is included.
1568
1569		CONFIG_PHY_RESET_DELAY
1570
1571		Some PHY like Intel LXT971A need extra delay after
1572		reset before any MII register access is possible.
1573		For such PHY, set this option to the usec delay
1574		required. (minimum 300usec for LXT971A)
1575
1576		CONFIG_PHY_CMD_DELAY (ppc4xx)
1577
1578		Some PHY like Intel LXT971A need extra delay after
1579		command issued before MII status register can be read
1580
1581- Ethernet address:
1582		CONFIG_ETHADDR
1583		CONFIG_ETH1ADDR
1584		CONFIG_ETH2ADDR
1585		CONFIG_ETH3ADDR
1586		CONFIG_ETH4ADDR
1587		CONFIG_ETH5ADDR
1588
1589		Define a default value for Ethernet address to use
1590		for the respective Ethernet interface, in case this
1591		is not determined automatically.
1592
1593- IP address:
1594		CONFIG_IPADDR
1595
1596		Define a default value for the IP address to use for
1597		the default Ethernet interface, in case this is not
1598		determined through e.g. bootp.
1599		(Environment variable "ipaddr")
1600
1601- Server IP address:
1602		CONFIG_SERVERIP
1603
1604		Defines a default value for the IP address of a TFTP
1605		server to contact when using the "tftboot" command.
1606		(Environment variable "serverip")
1607
1608		CONFIG_KEEP_SERVERADDR
1609
1610		Keeps the server's MAC address, in the env 'serveraddr'
1611		for passing to bootargs (like Linux's netconsole option)
1612
1613- Gateway IP address:
1614		CONFIG_GATEWAYIP
1615
1616		Defines a default value for the IP address of the
1617		default router where packets to other networks are
1618		sent to.
1619		(Environment variable "gatewayip")
1620
1621- Subnet mask:
1622		CONFIG_NETMASK
1623
1624		Defines a default value for the subnet mask (or
1625		routing prefix) which is used to determine if an IP
1626		address belongs to the local subnet or needs to be
1627		forwarded through a router.
1628		(Environment variable "netmask")
1629
1630- Multicast TFTP Mode:
1631		CONFIG_MCAST_TFTP
1632
1633		Defines whether you want to support multicast TFTP as per
1634		rfc-2090; for example to work with atftp.  Lets lots of targets
1635		tftp down the same boot image concurrently.  Note: the Ethernet
1636		driver in use must provide a function: mcast() to join/leave a
1637		multicast group.
1638
1639- BOOTP Recovery Mode:
1640		CONFIG_BOOTP_RANDOM_DELAY
1641
1642		If you have many targets in a network that try to
1643		boot using BOOTP, you may want to avoid that all
1644		systems send out BOOTP requests at precisely the same
1645		moment (which would happen for instance at recovery
1646		from a power failure, when all systems will try to
1647		boot, thus flooding the BOOTP server. Defining
1648		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1649		inserted before sending out BOOTP requests. The
1650		following delays are inserted then:
1651
1652		1st BOOTP request:	delay 0 ... 1 sec
1653		2nd BOOTP request:	delay 0 ... 2 sec
1654		3rd BOOTP request:	delay 0 ... 4 sec
1655		4th and following
1656		BOOTP requests:		delay 0 ... 8 sec
1657
1658- DHCP Advanced Options:
1659		You can fine tune the DHCP functionality by defining
1660		CONFIG_BOOTP_* symbols:
1661
1662		CONFIG_BOOTP_SUBNETMASK
1663		CONFIG_BOOTP_GATEWAY
1664		CONFIG_BOOTP_HOSTNAME
1665		CONFIG_BOOTP_NISDOMAIN
1666		CONFIG_BOOTP_BOOTPATH
1667		CONFIG_BOOTP_BOOTFILESIZE
1668		CONFIG_BOOTP_DNS
1669		CONFIG_BOOTP_DNS2
1670		CONFIG_BOOTP_SEND_HOSTNAME
1671		CONFIG_BOOTP_NTPSERVER
1672		CONFIG_BOOTP_TIMEOFFSET
1673		CONFIG_BOOTP_VENDOREX
1674		CONFIG_BOOTP_MAY_FAIL
1675
1676		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1677		environment variable, not the BOOTP server.
1678
1679		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1680		after the configured retry count, the call will fail
1681		instead of starting over.  This can be used to fail over
1682		to Link-local IP address configuration if the DHCP server
1683		is not available.
1684
1685		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1686		serverip from a DHCP server, it is possible that more
1687		than one DNS serverip is offered to the client.
1688		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1689		serverip will be stored in the additional environment
1690		variable "dnsip2". The first DNS serverip is always
1691		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1692		is defined.
1693
1694		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1695		to do a dynamic update of a DNS server. To do this, they
1696		need the hostname of the DHCP requester.
1697		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1698		of the "hostname" environment variable is passed as
1699		option 12 to the DHCP server.
1700
1701		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1702
1703		A 32bit value in microseconds for a delay between
1704		receiving a "DHCP Offer" and sending the "DHCP Request".
1705		This fixes a problem with certain DHCP servers that don't
1706		respond 100% of the time to a "DHCP request". E.g. On an
1707		AT91RM9200 processor running at 180MHz, this delay needed
1708		to be *at least* 15,000 usec before a Windows Server 2003
1709		DHCP server would reply 100% of the time. I recommend at
1710		least 50,000 usec to be safe. The alternative is to hope
1711		that one of the retries will be successful but note that
1712		the DHCP timeout and retry process takes a longer than
1713		this delay.
1714
1715 - Link-local IP address negotiation:
1716		Negotiate with other link-local clients on the local network
1717		for an address that doesn't require explicit configuration.
1718		This is especially useful if a DHCP server cannot be guaranteed
1719		to exist in all environments that the device must operate.
1720
1721		See doc/README.link-local for more information.
1722
1723 - CDP Options:
1724		CONFIG_CDP_DEVICE_ID
1725
1726		The device id used in CDP trigger frames.
1727
1728		CONFIG_CDP_DEVICE_ID_PREFIX
1729
1730		A two character string which is prefixed to the MAC address
1731		of the device.
1732
1733		CONFIG_CDP_PORT_ID
1734
1735		A printf format string which contains the ascii name of
1736		the port. Normally is set to "eth%d" which sets
1737		eth0 for the first Ethernet, eth1 for the second etc.
1738
1739		CONFIG_CDP_CAPABILITIES
1740
1741		A 32bit integer which indicates the device capabilities;
1742		0x00000010 for a normal host which does not forwards.
1743
1744		CONFIG_CDP_VERSION
1745
1746		An ascii string containing the version of the software.
1747
1748		CONFIG_CDP_PLATFORM
1749
1750		An ascii string containing the name of the platform.
1751
1752		CONFIG_CDP_TRIGGER
1753
1754		A 32bit integer sent on the trigger.
1755
1756		CONFIG_CDP_POWER_CONSUMPTION
1757
1758		A 16bit integer containing the power consumption of the
1759		device in .1 of milliwatts.
1760
1761		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1762
1763		A byte containing the id of the VLAN.
1764
1765- Status LED:	CONFIG_STATUS_LED
1766
1767		Several configurations allow to display the current
1768		status using a LED. For instance, the LED will blink
1769		fast while running U-Boot code, stop blinking as
1770		soon as a reply to a BOOTP request was received, and
1771		start blinking slow once the Linux kernel is running
1772		(supported by a status LED driver in the Linux
1773		kernel). Defining CONFIG_STATUS_LED enables this
1774		feature in U-Boot.
1775
1776- CAN Support:	CONFIG_CAN_DRIVER
1777
1778		Defining CONFIG_CAN_DRIVER enables CAN driver support
1779		on those systems that support this (optional)
1780		feature, like the TQM8xxL modules.
1781
1782- I2C Support:	CONFIG_HARD_I2C | CONFIG_SOFT_I2C
1783
1784		These enable I2C serial bus commands. Defining either of
1785		(but not both of) CONFIG_HARD_I2C or CONFIG_SOFT_I2C will
1786		include the appropriate I2C driver for the selected CPU.
1787
1788		This will allow you to use i2c commands at the u-boot
1789		command line (as long as you set CONFIG_CMD_I2C in
1790		CONFIG_COMMANDS) and communicate with i2c based realtime
1791		clock chips. See common/cmd_i2c.c for a description of the
1792		command line interface.
1793
1794		CONFIG_HARD_I2C selects a hardware I2C controller.
1795
1796		CONFIG_SOFT_I2C configures u-boot to use a software (aka
1797		bit-banging) driver instead of CPM or similar hardware
1798		support for I2C.
1799
1800		There are several other quantities that must also be
1801		defined when you define CONFIG_HARD_I2C or CONFIG_SOFT_I2C.
1802
1803		In both cases you will need to define CONFIG_SYS_I2C_SPEED
1804		to be the frequency (in Hz) at which you wish your i2c bus
1805		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
1806		the CPU's i2c node address).
1807
1808		Now, the u-boot i2c code for the mpc8xx
1809		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
1810		and so its address should therefore be cleared to 0 (See,
1811		eg, MPC823e User's Manual p.16-473). So, set
1812		CONFIG_SYS_I2C_SLAVE to 0.
1813
1814		CONFIG_SYS_I2C_INIT_MPC5XXX
1815
1816		When a board is reset during an i2c bus transfer
1817		chips might think that the current transfer is still
1818		in progress.  Reset the slave devices by sending start
1819		commands until the slave device responds.
1820
1821		That's all that's required for CONFIG_HARD_I2C.
1822
1823		If you use the software i2c interface (CONFIG_SOFT_I2C)
1824		then the following macros need to be defined (examples are
1825		from include/configs/lwmon.h):
1826
1827		I2C_INIT
1828
1829		(Optional). Any commands necessary to enable the I2C
1830		controller or configure ports.
1831
1832		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1833
1834		I2C_PORT
1835
1836		(Only for MPC8260 CPU). The I/O port to use (the code
1837		assumes both bits are on the same port). Valid values
1838		are 0..3 for ports A..D.
1839
1840		I2C_ACTIVE
1841
1842		The code necessary to make the I2C data line active
1843		(driven).  If the data line is open collector, this
1844		define can be null.
1845
1846		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1847
1848		I2C_TRISTATE
1849
1850		The code necessary to make the I2C data line tri-stated
1851		(inactive).  If the data line is open collector, this
1852		define can be null.
1853
1854		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1855
1856		I2C_READ
1857
1858		Code that returns TRUE if the I2C data line is high,
1859		FALSE if it is low.
1860
1861		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1862
1863		I2C_SDA(bit)
1864
1865		If <bit> is TRUE, sets the I2C data line high. If it
1866		is FALSE, it clears it (low).
1867
1868		eg: #define I2C_SDA(bit) \
1869			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1870			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1871
1872		I2C_SCL(bit)
1873
1874		If <bit> is TRUE, sets the I2C clock line high. If it
1875		is FALSE, it clears it (low).
1876
1877		eg: #define I2C_SCL(bit) \
1878			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1879			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1880
1881		I2C_DELAY
1882
1883		This delay is invoked four times per clock cycle so this
1884		controls the rate of data transfer.  The data rate thus
1885		is 1 / (I2C_DELAY * 4). Often defined to be something
1886		like:
1887
1888		#define I2C_DELAY  udelay(2)
1889
1890		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1891
1892		If your arch supports the generic GPIO framework (asm/gpio.h),
1893		then you may alternatively define the two GPIOs that are to be
1894		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1895		have GPIO-based defaults assigned to them as appropriate.
1896
1897		You should define these to the GPIO value as given directly to
1898		the generic GPIO functions.
1899
1900		CONFIG_SYS_I2C_INIT_BOARD
1901
1902		When a board is reset during an i2c bus transfer
1903		chips might think that the current transfer is still
1904		in progress. On some boards it is possible to access
1905		the i2c SCLK line directly, either by using the
1906		processor pin as a GPIO or by having a second pin
1907		connected to the bus. If this option is defined a
1908		custom i2c_init_board() routine in boards/xxx/board.c
1909		is run early in the boot sequence.
1910
1911		CONFIG_SYS_I2C_BOARD_LATE_INIT
1912
1913		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
1914		defined a custom i2c_board_late_init() routine in
1915		boards/xxx/board.c is run AFTER the operations in i2c_init()
1916		is completed. This callpoint can be used to unreset i2c bus
1917		using CPU i2c controller register accesses for CPUs whose i2c
1918		controller provide such a method. It is called at the end of
1919		i2c_init() to allow i2c_init operations to setup the i2c bus
1920		controller on the CPU (e.g. setting bus speed & slave address).
1921
1922		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
1923
1924		This option enables configuration of bi_iic_fast[] flags
1925		in u-boot bd_info structure based on u-boot environment
1926		variable "i2cfast". (see also i2cfast)
1927
1928		CONFIG_I2C_MULTI_BUS
1929
1930		This option allows the use of multiple I2C buses, each of which
1931		must have a controller.	 At any point in time, only one bus is
1932		active.	 To switch to a different bus, use the 'i2c dev' command.
1933		Note that bus numbering is zero-based.
1934
1935		CONFIG_SYS_I2C_NOPROBES
1936
1937		This option specifies a list of I2C devices that will be skipped
1938		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1939		is set, specify a list of bus-device pairs.  Otherwise, specify
1940		a 1D array of device addresses
1941
1942		e.g.
1943			#undef	CONFIG_I2C_MULTI_BUS
1944			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1945
1946		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1947
1948			#define CONFIG_I2C_MULTI_BUS
1949			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1950
1951		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1952
1953		CONFIG_SYS_SPD_BUS_NUM
1954
1955		If defined, then this indicates the I2C bus number for DDR SPD.
1956		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1957
1958		CONFIG_SYS_RTC_BUS_NUM
1959
1960		If defined, then this indicates the I2C bus number for the RTC.
1961		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1962
1963		CONFIG_SYS_DTT_BUS_NUM
1964
1965		If defined, then this indicates the I2C bus number for the DTT.
1966		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
1967
1968		CONFIG_SYS_I2C_DTT_ADDR:
1969
1970		If defined, specifies the I2C address of the DTT device.
1971		If not defined, then U-Boot uses predefined value for
1972		specified DTT device.
1973
1974		CONFIG_FSL_I2C
1975
1976		Define this option if you want to use Freescale's I2C driver in
1977		drivers/i2c/fsl_i2c.c.
1978
1979		CONFIG_I2C_MUX
1980
1981		Define this option if you have I2C devices reached over 1 .. n
1982		I2C Muxes like the pca9544a. This option addes a new I2C
1983		Command "i2c bus [muxtype:muxaddr:muxchannel]" which adds a
1984		new I2C Bus to the existing I2C Busses. If you select the
1985		new Bus with "i2c dev", u-bbot sends first the commandos for
1986		the muxes to activate this new "bus".
1987
1988		CONFIG_I2C_MULTI_BUS must be also defined, to use this
1989		feature!
1990
1991		Example:
1992		Adding a new I2C Bus reached over 2 pca9544a muxes
1993			The First mux with address 70 and channel 6
1994			The Second mux with address 71 and channel 4
1995
1996		=> i2c bus pca9544a:70:6:pca9544a:71:4
1997
1998		Use the "i2c bus" command without parameter, to get a list
1999		of I2C Busses with muxes:
2000
2001		=> i2c bus
2002		Busses reached over muxes:
2003		Bus ID: 2
2004		  reached over Mux(es):
2005		    pca9544a@70 ch: 4
2006		Bus ID: 3
2007		  reached over Mux(es):
2008		    pca9544a@70 ch: 6
2009		    pca9544a@71 ch: 4
2010		=>
2011
2012		If you now switch to the new I2C Bus 3 with "i2c dev 3"
2013		u-boot first sends the command to the mux@70 to enable
2014		channel 6, and then the command to the mux@71 to enable
2015		the channel 4.
2016
2017		After that, you can use the "normal" i2c commands as
2018		usual to communicate with your I2C devices behind
2019		the 2 muxes.
2020
2021		This option is actually implemented for the bitbanging
2022		algorithm in common/soft_i2c.c and for the Hardware I2C
2023		Bus on the MPC8260. But it should be not so difficult
2024		to add this option to other architectures.
2025
2026		CONFIG_SOFT_I2C_READ_REPEATED_START
2027
2028		defining this will force the i2c_read() function in
2029		the soft_i2c driver to perform an I2C repeated start
2030		between writing the address pointer and reading the
2031		data.  If this define is omitted the default behaviour
2032		of doing a stop-start sequence will be used.  Most I2C
2033		devices can use either method, but some require one or
2034		the other.
2035
2036- SPI Support:	CONFIG_SPI
2037
2038		Enables SPI driver (so far only tested with
2039		SPI EEPROM, also an instance works with Crystal A/D and
2040		D/As on the SACSng board)
2041
2042		CONFIG_SH_SPI
2043
2044		Enables the driver for SPI controller on SuperH. Currently
2045		only SH7757 is supported.
2046
2047		CONFIG_SPI_X
2048
2049		Enables extended (16-bit) SPI EEPROM addressing.
2050		(symmetrical to CONFIG_I2C_X)
2051
2052		CONFIG_SOFT_SPI
2053
2054		Enables a software (bit-bang) SPI driver rather than
2055		using hardware support. This is a general purpose
2056		driver that only requires three general I/O port pins
2057		(two outputs, one input) to function. If this is
2058		defined, the board configuration must define several
2059		SPI configuration items (port pins to use, etc). For
2060		an example, see include/configs/sacsng.h.
2061
2062		CONFIG_HARD_SPI
2063
2064		Enables a hardware SPI driver for general-purpose reads
2065		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2066		must define a list of chip-select function pointers.
2067		Currently supported on some MPC8xxx processors.	 For an
2068		example, see include/configs/mpc8349emds.h.
2069
2070		CONFIG_MXC_SPI
2071
2072		Enables the driver for the SPI controllers on i.MX and MXC
2073		SoCs. Currently i.MX31/35/51 are supported.
2074
2075- FPGA Support: CONFIG_FPGA
2076
2077		Enables FPGA subsystem.
2078
2079		CONFIG_FPGA_<vendor>
2080
2081		Enables support for specific chip vendors.
2082		(ALTERA, XILINX)
2083
2084		CONFIG_FPGA_<family>
2085
2086		Enables support for FPGA family.
2087		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2088
2089		CONFIG_FPGA_COUNT
2090
2091		Specify the number of FPGA devices to support.
2092
2093		CONFIG_SYS_FPGA_PROG_FEEDBACK
2094
2095		Enable printing of hash marks during FPGA configuration.
2096
2097		CONFIG_SYS_FPGA_CHECK_BUSY
2098
2099		Enable checks on FPGA configuration interface busy
2100		status by the configuration function. This option
2101		will require a board or device specific function to
2102		be written.
2103
2104		CONFIG_FPGA_DELAY
2105
2106		If defined, a function that provides delays in the FPGA
2107		configuration driver.
2108
2109		CONFIG_SYS_FPGA_CHECK_CTRLC
2110		Allow Control-C to interrupt FPGA configuration
2111
2112		CONFIG_SYS_FPGA_CHECK_ERROR
2113
2114		Check for configuration errors during FPGA bitfile
2115		loading. For example, abort during Virtex II
2116		configuration if the INIT_B line goes low (which
2117		indicated a CRC error).
2118
2119		CONFIG_SYS_FPGA_WAIT_INIT
2120
2121		Maximum time to wait for the INIT_B line to deassert
2122		after PROB_B has been deasserted during a Virtex II
2123		FPGA configuration sequence. The default time is 500
2124		ms.
2125
2126		CONFIG_SYS_FPGA_WAIT_BUSY
2127
2128		Maximum time to wait for BUSY to deassert during
2129		Virtex II FPGA configuration. The default is 5 ms.
2130
2131		CONFIG_SYS_FPGA_WAIT_CONFIG
2132
2133		Time to wait after FPGA configuration. The default is
2134		200 ms.
2135
2136- Configuration Management:
2137		CONFIG_IDENT_STRING
2138
2139		If defined, this string will be added to the U-Boot
2140		version information (U_BOOT_VERSION)
2141
2142- Vendor Parameter Protection:
2143
2144		U-Boot considers the values of the environment
2145		variables "serial#" (Board Serial Number) and
2146		"ethaddr" (Ethernet Address) to be parameters that
2147		are set once by the board vendor / manufacturer, and
2148		protects these variables from casual modification by
2149		the user. Once set, these variables are read-only,
2150		and write or delete attempts are rejected. You can
2151		change this behaviour:
2152
2153		If CONFIG_ENV_OVERWRITE is #defined in your config
2154		file, the write protection for vendor parameters is
2155		completely disabled. Anybody can change or delete
2156		these parameters.
2157
2158		Alternatively, if you #define _both_ CONFIG_ETHADDR
2159		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2160		Ethernet address is installed in the environment,
2161		which can be changed exactly ONCE by the user. [The
2162		serial# is unaffected by this, i. e. it remains
2163		read-only.]
2164
2165- Protected RAM:
2166		CONFIG_PRAM
2167
2168		Define this variable to enable the reservation of
2169		"protected RAM", i. e. RAM which is not overwritten
2170		by U-Boot. Define CONFIG_PRAM to hold the number of
2171		kB you want to reserve for pRAM. You can overwrite
2172		this default value by defining an environment
2173		variable "pram" to the number of kB you want to
2174		reserve. Note that the board info structure will
2175		still show the full amount of RAM. If pRAM is
2176		reserved, a new environment variable "mem" will
2177		automatically be defined to hold the amount of
2178		remaining RAM in a form that can be passed as boot
2179		argument to Linux, for instance like that:
2180
2181			setenv bootargs ... mem=\${mem}
2182			saveenv
2183
2184		This way you can tell Linux not to use this memory,
2185		either, which results in a memory region that will
2186		not be affected by reboots.
2187
2188		*WARNING* If your board configuration uses automatic
2189		detection of the RAM size, you must make sure that
2190		this memory test is non-destructive. So far, the
2191		following board configurations are known to be
2192		"pRAM-clean":
2193
2194			IVMS8, IVML24, SPD8xx, TQM8xxL,
2195			HERMES, IP860, RPXlite, LWMON,
2196			FLAGADM, TQM8260
2197
2198- Error Recovery:
2199		CONFIG_PANIC_HANG
2200
2201		Define this variable to stop the system in case of a
2202		fatal error, so that you have to reset it manually.
2203		This is probably NOT a good idea for an embedded
2204		system where you want the system to reboot
2205		automatically as fast as possible, but it may be
2206		useful during development since you can try to debug
2207		the conditions that lead to the situation.
2208
2209		CONFIG_NET_RETRY_COUNT
2210
2211		This variable defines the number of retries for
2212		network operations like ARP, RARP, TFTP, or BOOTP
2213		before giving up the operation. If not defined, a
2214		default value of 5 is used.
2215
2216		CONFIG_ARP_TIMEOUT
2217
2218		Timeout waiting for an ARP reply in milliseconds.
2219
2220		CONFIG_NFS_TIMEOUT
2221
2222		Timeout in milliseconds used in NFS protocol.
2223		If you encounter "ERROR: Cannot umount" in nfs command,
2224		try longer timeout such as
2225		#define CONFIG_NFS_TIMEOUT 10000UL
2226
2227- Command Interpreter:
2228		CONFIG_AUTO_COMPLETE
2229
2230		Enable auto completion of commands using TAB.
2231
2232		Note that this feature has NOT been implemented yet
2233		for the "hush" shell.
2234
2235
2236		CONFIG_SYS_HUSH_PARSER
2237
2238		Define this variable to enable the "hush" shell (from
2239		Busybox) as command line interpreter, thus enabling
2240		powerful command line syntax like
2241		if...then...else...fi conditionals or `&&' and '||'
2242		constructs ("shell scripts").
2243
2244		If undefined, you get the old, much simpler behaviour
2245		with a somewhat smaller memory footprint.
2246
2247
2248		CONFIG_SYS_PROMPT_HUSH_PS2
2249
2250		This defines the secondary prompt string, which is
2251		printed when the command interpreter needs more input
2252		to complete a command. Usually "> ".
2253
2254	Note:
2255
2256		In the current implementation, the local variables
2257		space and global environment variables space are
2258		separated. Local variables are those you define by
2259		simply typing `name=value'. To access a local
2260		variable later on, you have write `$name' or
2261		`${name}'; to execute the contents of a variable
2262		directly type `$name' at the command prompt.
2263
2264		Global environment variables are those you use
2265		setenv/printenv to work with. To run a command stored
2266		in such a variable, you need to use the run command,
2267		and you must not use the '$' sign to access them.
2268
2269		To store commands and special characters in a
2270		variable, please use double quotation marks
2271		surrounding the whole text of the variable, instead
2272		of the backslashes before semicolons and special
2273		symbols.
2274
2275- Commandline Editing and History:
2276		CONFIG_CMDLINE_EDITING
2277
2278		Enable editing and History functions for interactive
2279		commandline input operations
2280
2281- Default Environment:
2282		CONFIG_EXTRA_ENV_SETTINGS
2283
2284		Define this to contain any number of null terminated
2285		strings (variable = value pairs) that will be part of
2286		the default environment compiled into the boot image.
2287
2288		For example, place something like this in your
2289		board's config file:
2290
2291		#define CONFIG_EXTRA_ENV_SETTINGS \
2292			"myvar1=value1\0" \
2293			"myvar2=value2\0"
2294
2295		Warning: This method is based on knowledge about the
2296		internal format how the environment is stored by the
2297		U-Boot code. This is NOT an official, exported
2298		interface! Although it is unlikely that this format
2299		will change soon, there is no guarantee either.
2300		You better know what you are doing here.
2301
2302		Note: overly (ab)use of the default environment is
2303		discouraged. Make sure to check other ways to preset
2304		the environment like the "source" command or the
2305		boot command first.
2306
2307		CONFIG_ENV_VARS_UBOOT_CONFIG
2308
2309		Define this in order to add variables describing the
2310		U-Boot build configuration to the default environment.
2311		These will be named arch, cpu, board, vendor, and soc.
2312
2313		Enabling this option will cause the following to be defined:
2314
2315		- CONFIG_SYS_ARCH
2316		- CONFIG_SYS_CPU
2317		- CONFIG_SYS_BOARD
2318		- CONFIG_SYS_VENDOR
2319		- CONFIG_SYS_SOC
2320
2321		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2322
2323		Define this in order to add variables describing certain
2324		run-time determined information about the hardware to the
2325		environment.  These will be named board_name, board_rev.
2326
2327- DataFlash Support:
2328		CONFIG_HAS_DATAFLASH
2329
2330		Defining this option enables DataFlash features and
2331		allows to read/write in Dataflash via the standard
2332		commands cp, md...
2333
2334- Serial Flash support
2335		CONFIG_CMD_SF
2336
2337		Defining this option enables SPI flash commands
2338		'sf probe/read/write/erase/update'.
2339
2340		Usage requires an initial 'probe' to define the serial
2341		flash parameters, followed by read/write/erase/update
2342		commands.
2343
2344		The following defaults may be provided by the platform
2345		to handle the common case when only a single serial
2346		flash is present on the system.
2347
2348		CONFIG_SF_DEFAULT_BUS		Bus identifier
2349		CONFIG_SF_DEFAULT_CS		Chip-select
2350		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2351		CONFIG_SF_DEFAULT_SPEED		in Hz
2352
2353- SystemACE Support:
2354		CONFIG_SYSTEMACE
2355
2356		Adding this option adds support for Xilinx SystemACE
2357		chips attached via some sort of local bus. The address
2358		of the chip must also be defined in the
2359		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2360
2361		#define CONFIG_SYSTEMACE
2362		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2363
2364		When SystemACE support is added, the "ace" device type
2365		becomes available to the fat commands, i.e. fatls.
2366
2367- TFTP Fixed UDP Port:
2368		CONFIG_TFTP_PORT
2369
2370		If this is defined, the environment variable tftpsrcp
2371		is used to supply the TFTP UDP source port value.
2372		If tftpsrcp isn't defined, the normal pseudo-random port
2373		number generator is used.
2374
2375		Also, the environment variable tftpdstp is used to supply
2376		the TFTP UDP destination port value.  If tftpdstp isn't
2377		defined, the normal port 69 is used.
2378
2379		The purpose for tftpsrcp is to allow a TFTP server to
2380		blindly start the TFTP transfer using the pre-configured
2381		target IP address and UDP port. This has the effect of
2382		"punching through" the (Windows XP) firewall, allowing
2383		the remainder of the TFTP transfer to proceed normally.
2384		A better solution is to properly configure the firewall,
2385		but sometimes that is not allowed.
2386
2387- Show boot progress:
2388		CONFIG_SHOW_BOOT_PROGRESS
2389
2390		Defining this option allows to add some board-
2391		specific code (calling a user-provided function
2392		"show_boot_progress(int)") that enables you to show
2393		the system's boot progress on some display (for
2394		example, some LED's) on your board. At the moment,
2395		the following checkpoints are implemented:
2396
2397- Detailed boot stage timing
2398		CONFIG_BOOTSTAGE
2399		Define this option to get detailed timing of each stage
2400		of the boot process.
2401
2402		CONFIG_BOOTSTAGE_USER_COUNT
2403		This is the number of available user bootstage records.
2404		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
2405		a new ID will be allocated from this stash. If you exceed
2406		the limit, recording will stop.
2407
2408		CONFIG_BOOTSTAGE_REPORT
2409		Define this to print a report before boot, similar to this:
2410
2411		Timer summary in microseconds:
2412		       Mark    Elapsed  Stage
2413			  0          0  reset
2414		  3,575,678  3,575,678  board_init_f start
2415		  3,575,695         17  arch_cpu_init A9
2416		  3,575,777         82  arch_cpu_init done
2417		  3,659,598     83,821  board_init_r start
2418		  3,910,375    250,777  main_loop
2419		 29,916,167 26,005,792  bootm_start
2420		 30,361,327    445,160  start_kernel
2421
2422		CONFIG_CMD_BOOTSTAGE
2423		Add a 'bootstage' command which supports printing a report
2424		and un/stashing of bootstage data.
2425
2426		CONFIG_BOOTSTAGE_FDT
2427		Stash the bootstage information in the FDT. A root 'bootstage'
2428		node is created with each bootstage id as a child. Each child
2429		has a 'name' property and either 'mark' containing the
2430		mark time in microsecond, or 'accum' containing the
2431		accumulated time for that bootstage id in microseconds.
2432		For example:
2433
2434		bootstage {
2435			154 {
2436				name = "board_init_f";
2437				mark = <3575678>;
2438			};
2439			170 {
2440				name = "lcd";
2441				accum = <33482>;
2442			};
2443		};
2444
2445		Code in the Linux kernel can find this in /proc/devicetree.
2446
2447Legacy uImage format:
2448
2449  Arg	Where			When
2450    1	common/cmd_bootm.c	before attempting to boot an image
2451   -1	common/cmd_bootm.c	Image header has bad	 magic number
2452    2	common/cmd_bootm.c	Image header has correct magic number
2453   -2	common/cmd_bootm.c	Image header has bad	 checksum
2454    3	common/cmd_bootm.c	Image header has correct checksum
2455   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2456    4	common/cmd_bootm.c	Image data   has correct checksum
2457   -4	common/cmd_bootm.c	Image is for unsupported architecture
2458    5	common/cmd_bootm.c	Architecture check OK
2459   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2460    6	common/cmd_bootm.c	Image Type check OK
2461   -6	common/cmd_bootm.c	gunzip uncompression error
2462   -7	common/cmd_bootm.c	Unimplemented compression type
2463    7	common/cmd_bootm.c	Uncompression OK
2464    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2465   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2466
2467    9	common/image.c		Start initial ramdisk verification
2468  -10	common/image.c		Ramdisk header has bad	   magic number
2469  -11	common/image.c		Ramdisk header has bad	   checksum
2470   10	common/image.c		Ramdisk header is OK
2471  -12	common/image.c		Ramdisk data   has bad	   checksum
2472   11	common/image.c		Ramdisk data   has correct checksum
2473   12	common/image.c		Ramdisk verification complete, start loading
2474  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2475   13	common/image.c		Start multifile image verification
2476   14	common/image.c		No initial ramdisk, no multifile, continue.
2477
2478   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2479
2480  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2481  -31	post/post.c		POST test failed, detected by post_output_backlog()
2482  -32	post/post.c		POST test failed, detected by post_run_single()
2483
2484   34	common/cmd_doc.c	before loading a Image from a DOC device
2485  -35	common/cmd_doc.c	Bad usage of "doc" command
2486   35	common/cmd_doc.c	correct usage of "doc" command
2487  -36	common/cmd_doc.c	No boot device
2488   36	common/cmd_doc.c	correct boot device
2489  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2490   37	common/cmd_doc.c	correct chip ID found, device available
2491  -38	common/cmd_doc.c	Read Error on boot device
2492   38	common/cmd_doc.c	reading Image header from DOC device OK
2493  -39	common/cmd_doc.c	Image header has bad magic number
2494   39	common/cmd_doc.c	Image header has correct magic number
2495  -40	common/cmd_doc.c	Error reading Image from DOC device
2496   40	common/cmd_doc.c	Image header has correct magic number
2497   41	common/cmd_ide.c	before loading a Image from a IDE device
2498  -42	common/cmd_ide.c	Bad usage of "ide" command
2499   42	common/cmd_ide.c	correct usage of "ide" command
2500  -43	common/cmd_ide.c	No boot device
2501   43	common/cmd_ide.c	boot device found
2502  -44	common/cmd_ide.c	Device not available
2503   44	common/cmd_ide.c	Device available
2504  -45	common/cmd_ide.c	wrong partition selected
2505   45	common/cmd_ide.c	partition selected
2506  -46	common/cmd_ide.c	Unknown partition table
2507   46	common/cmd_ide.c	valid partition table found
2508  -47	common/cmd_ide.c	Invalid partition type
2509   47	common/cmd_ide.c	correct partition type
2510  -48	common/cmd_ide.c	Error reading Image Header on boot device
2511   48	common/cmd_ide.c	reading Image Header from IDE device OK
2512  -49	common/cmd_ide.c	Image header has bad magic number
2513   49	common/cmd_ide.c	Image header has correct magic number
2514  -50	common/cmd_ide.c	Image header has bad	 checksum
2515   50	common/cmd_ide.c	Image header has correct checksum
2516  -51	common/cmd_ide.c	Error reading Image from IDE device
2517   51	common/cmd_ide.c	reading Image from IDE device OK
2518   52	common/cmd_nand.c	before loading a Image from a NAND device
2519  -53	common/cmd_nand.c	Bad usage of "nand" command
2520   53	common/cmd_nand.c	correct usage of "nand" command
2521  -54	common/cmd_nand.c	No boot device
2522   54	common/cmd_nand.c	boot device found
2523  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2524   55	common/cmd_nand.c	correct chip ID found, device available
2525  -56	common/cmd_nand.c	Error reading Image Header on boot device
2526   56	common/cmd_nand.c	reading Image Header from NAND device OK
2527  -57	common/cmd_nand.c	Image header has bad magic number
2528   57	common/cmd_nand.c	Image header has correct magic number
2529  -58	common/cmd_nand.c	Error reading Image from NAND device
2530   58	common/cmd_nand.c	reading Image from NAND device OK
2531
2532  -60	common/env_common.c	Environment has a bad CRC, using default
2533
2534   64	net/eth.c		starting with Ethernet configuration.
2535  -64	net/eth.c		no Ethernet found.
2536   65	net/eth.c		Ethernet found.
2537
2538  -80	common/cmd_net.c	usage wrong
2539   80	common/cmd_net.c	before calling NetLoop()
2540  -81	common/cmd_net.c	some error in NetLoop() occurred
2541   81	common/cmd_net.c	NetLoop() back without error
2542  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2543   82	common/cmd_net.c	trying automatic boot
2544   83	common/cmd_net.c	running "source" command
2545  -83	common/cmd_net.c	some error in automatic boot or "source" command
2546   84	common/cmd_net.c	end without errors
2547
2548FIT uImage format:
2549
2550  Arg	Where			When
2551  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2552 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2553  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2554 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2555  102	common/cmd_bootm.c	Kernel unit name specified
2556 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2557  103	common/cmd_bootm.c	Found configuration node
2558  104	common/cmd_bootm.c	Got kernel subimage node offset
2559 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2560  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2561 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2562  106	common/cmd_bootm.c	Architecture check OK
2563 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2564  107	common/cmd_bootm.c	Kernel subimage type OK
2565 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2566  108	common/cmd_bootm.c	Got kernel subimage data/size
2567 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2568 -109	common/cmd_bootm.c	Can't get kernel subimage type
2569 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2570 -111	common/cmd_bootm.c	Can't get kernel subimage os
2571 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2572 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2573
2574  120	common/image.c		Start initial ramdisk verification
2575 -120	common/image.c		Ramdisk FIT image has incorrect format
2576  121	common/image.c		Ramdisk FIT image has correct format
2577  122	common/image.c		No ramdisk subimage unit name, using configuration
2578 -122	common/image.c		Can't get configuration for ramdisk subimage
2579  123	common/image.c		Ramdisk unit name specified
2580 -124	common/image.c		Can't get ramdisk subimage node offset
2581  125	common/image.c		Got ramdisk subimage node offset
2582 -125	common/image.c		Ramdisk subimage hash verification failed
2583  126	common/image.c		Ramdisk subimage hash verification OK
2584 -126	common/image.c		Ramdisk subimage for unsupported architecture
2585  127	common/image.c		Architecture check OK
2586 -127	common/image.c		Can't get ramdisk subimage data/size
2587  128	common/image.c		Got ramdisk subimage data/size
2588  129	common/image.c		Can't get ramdisk load address
2589 -129	common/image.c		Got ramdisk load address
2590
2591 -130	common/cmd_doc.c	Incorrect FIT image format
2592  131	common/cmd_doc.c	FIT image format OK
2593
2594 -140	common/cmd_ide.c	Incorrect FIT image format
2595  141	common/cmd_ide.c	FIT image format OK
2596
2597 -150	common/cmd_nand.c	Incorrect FIT image format
2598  151	common/cmd_nand.c	FIT image format OK
2599
2600- Standalone program support:
2601		CONFIG_STANDALONE_LOAD_ADDR
2602
2603		This option defines a board specific value for the
2604		address where standalone program gets loaded, thus
2605		overwriting the architecture dependent default
2606		settings.
2607
2608- Frame Buffer Address:
2609		CONFIG_FB_ADDR
2610
2611		Define CONFIG_FB_ADDR if you want to use specific
2612		address for frame buffer.
2613		Then system will reserve the frame buffer address to
2614		defined address instead of lcd_setmem (this function
2615		grabs the memory for frame buffer by panel's size).
2616
2617		Please see board_init_f function.
2618
2619- Automatic software updates via TFTP server
2620		CONFIG_UPDATE_TFTP
2621		CONFIG_UPDATE_TFTP_CNT_MAX
2622		CONFIG_UPDATE_TFTP_MSEC_MAX
2623
2624		These options enable and control the auto-update feature;
2625		for a more detailed description refer to doc/README.update.
2626
2627- MTD Support (mtdparts command, UBI support)
2628		CONFIG_MTD_DEVICE
2629
2630		Adds the MTD device infrastructure from the Linux kernel.
2631		Needed for mtdparts command support.
2632
2633		CONFIG_MTD_PARTITIONS
2634
2635		Adds the MTD partitioning infrastructure from the Linux
2636		kernel. Needed for UBI support.
2637
2638- SPL framework
2639		CONFIG_SPL
2640		Enable building of SPL globally.
2641
2642		CONFIG_SPL_LDSCRIPT
2643		LDSCRIPT for linking the SPL binary.
2644
2645		CONFIG_SPL_MAX_SIZE
2646		Maximum binary size (text, data and rodata) of the SPL binary.
2647
2648		CONFIG_SPL_TEXT_BASE
2649		TEXT_BASE for linking the SPL binary.
2650
2651		CONFIG_SPL_BSS_START_ADDR
2652		Link address for the BSS within the SPL binary.
2653
2654		CONFIG_SPL_BSS_MAX_SIZE
2655		Maximum binary size of the BSS section of the SPL binary.
2656
2657		CONFIG_SPL_STACK
2658		Adress of the start of the stack SPL will use
2659
2660		CONFIG_SYS_SPL_MALLOC_START
2661		Starting address of the malloc pool used in SPL.
2662
2663		CONFIG_SYS_SPL_MALLOC_SIZE
2664		The size of the malloc pool used in SPL.
2665
2666		CONFIG_SPL_FRAMEWORK
2667		Enable the SPL framework under common/.  This framework
2668		supports MMC, NAND and YMODEM loading of U-Boot and NAND
2669		NAND loading of the Linux Kernel.
2670
2671		CONFIG_SPL_DISPLAY_PRINT
2672		For ARM, enable an optional function to print more information
2673		about the running system.
2674
2675		CONFIG_SPL_LIBCOMMON_SUPPORT
2676		Support for common/libcommon.o in SPL binary
2677
2678		CONFIG_SPL_LIBDISK_SUPPORT
2679		Support for disk/libdisk.o in SPL binary
2680
2681		CONFIG_SPL_I2C_SUPPORT
2682		Support for drivers/i2c/libi2c.o in SPL binary
2683
2684		CONFIG_SPL_GPIO_SUPPORT
2685		Support for drivers/gpio/libgpio.o in SPL binary
2686
2687		CONFIG_SPL_MMC_SUPPORT
2688		Support for drivers/mmc/libmmc.o in SPL binary
2689
2690		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
2691		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
2692		CONFIG_SYS_MMC_SD_FAT_BOOT_PARTITION
2693		Address, size and partition on the MMC to load U-Boot from
2694		when the MMC is being used in raw mode.
2695
2696		CONFIG_SPL_FAT_SUPPORT
2697		Support for fs/fat/libfat.o in SPL binary
2698
2699		CONFIG_SPL_FAT_LOAD_PAYLOAD_NAME
2700		Filename to read to load U-Boot when reading from FAT
2701
2702		CONFIG_SPL_NAND_SIMPLE
2703		Support for drivers/mtd/nand/libnand.o in SPL binary
2704
2705		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2706		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2707		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2708		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2709		CONFIG_SYS_NAND_ECCBYTES
2710		Defines the size and behavior of the NAND that SPL uses
2711		to read U-Boot with CONFIG_SPL_NAND_SIMPLE
2712
2713		CONFIG_SYS_NAND_U_BOOT_OFFS
2714		Location in NAND for CONFIG_SPL_NAND_SIMPLE to read U-Boot
2715		from.
2716
2717		CONFIG_SYS_NAND_U_BOOT_START
2718		Location in memory for CONFIG_SPL_NAND_SIMPLE to load U-Boot
2719		to.
2720
2721		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2722		Define this if you need to first read the OOB and then the
2723		data. This is used for example on davinci plattforms.
2724
2725		CONFIG_SPL_OMAP3_ID_NAND
2726		Support for an OMAP3-specific set of functions to return the
2727		ID and MFR of the first attached NAND chip, if present.
2728
2729		CONFIG_SPL_SERIAL_SUPPORT
2730		Support for drivers/serial/libserial.o in SPL binary
2731
2732		CONFIG_SPL_SPI_FLASH_SUPPORT
2733		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
2734
2735		CONFIG_SPL_SPI_SUPPORT
2736		Support for drivers/spi/libspi.o in SPL binary
2737
2738		CONFIG_SPL_RAM_DEVICE
2739		Support for running image already present in ram, in SPL binary
2740
2741		CONFIG_SPL_LIBGENERIC_SUPPORT
2742		Support for lib/libgeneric.o in SPL binary
2743
2744Modem Support:
2745--------------
2746
2747[so far only for SMDK2400 boards]
2748
2749- Modem support enable:
2750		CONFIG_MODEM_SUPPORT
2751
2752- RTS/CTS Flow control enable:
2753		CONFIG_HWFLOW
2754
2755- Modem debug support:
2756		CONFIG_MODEM_SUPPORT_DEBUG
2757
2758		Enables debugging stuff (char screen[1024], dbg())
2759		for modem support. Useful only with BDI2000.
2760
2761- Interrupt support (PPC):
2762
2763		There are common interrupt_init() and timer_interrupt()
2764		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2765		for CPU specific initialization. interrupt_init_cpu()
2766		should set decrementer_count to appropriate value. If
2767		CPU resets decrementer automatically after interrupt
2768		(ppc4xx) it should set decrementer_count to zero.
2769		timer_interrupt() calls timer_interrupt_cpu() for CPU
2770		specific handling. If board has watchdog / status_led
2771		/ other_activity_monitor it works automatically from
2772		general timer_interrupt().
2773
2774- General:
2775
2776		In the target system modem support is enabled when a
2777		specific key (key combination) is pressed during
2778		power-on. Otherwise U-Boot will boot normally
2779		(autoboot). The key_pressed() function is called from
2780		board_init(). Currently key_pressed() is a dummy
2781		function, returning 1 and thus enabling modem
2782		initialization.
2783
2784		If there are no modem init strings in the
2785		environment, U-Boot proceed to autoboot; the
2786		previous output (banner, info printfs) will be
2787		suppressed, though.
2788
2789		See also: doc/README.Modem
2790
2791Board initialization settings:
2792------------------------------
2793
2794During Initialization u-boot calls a number of board specific functions
2795to allow the preparation of board specific prerequisites, e.g. pin setup
2796before drivers are initialized. To enable these callbacks the
2797following configuration macros have to be defined. Currently this is
2798architecture specific, so please check arch/your_architecture/lib/board.c
2799typically in board_init_f() and board_init_r().
2800
2801- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2802- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2803- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2804- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2805
2806Configuration Settings:
2807-----------------------
2808
2809- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2810		undefine this when you're short of memory.
2811
2812- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2813		width of the commands listed in the 'help' command output.
2814
2815- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2816		prompt for user input.
2817
2818- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2819
2820- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2821
2822- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2823
2824- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2825		the application (usually a Linux kernel) when it is
2826		booted
2827
2828- CONFIG_SYS_BAUDRATE_TABLE:
2829		List of legal baudrate settings for this board.
2830
2831- CONFIG_SYS_CONSOLE_INFO_QUIET
2832		Suppress display of console information at boot.
2833
2834- CONFIG_SYS_CONSOLE_IS_IN_ENV
2835		If the board specific function
2836			extern int overwrite_console (void);
2837		returns 1, the stdin, stderr and stdout are switched to the
2838		serial port, else the settings in the environment are used.
2839
2840- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
2841		Enable the call to overwrite_console().
2842
2843- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
2844		Enable overwrite of previous console environment settings.
2845
2846- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2847		Begin and End addresses of the area used by the
2848		simple memory test.
2849
2850- CONFIG_SYS_ALT_MEMTEST:
2851		Enable an alternate, more extensive memory test.
2852
2853- CONFIG_SYS_MEMTEST_SCRATCH:
2854		Scratch address used by the alternate memory test
2855		You only need to set this if address zero isn't writeable
2856
2857- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
2858		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2859		this specified memory area will get subtracted from the top
2860		(end) of RAM and won't get "touched" at all by U-Boot. By
2861		fixing up gd->ram_size the Linux kernel should gets passed
2862		the now "corrected" memory size and won't touch it either.
2863		This should work for arch/ppc and arch/powerpc. Only Linux
2864		board ports in arch/powerpc with bootwrapper support that
2865		recalculate the memory size from the SDRAM controller setup
2866		will have to get fixed in Linux additionally.
2867
2868		This option can be used as a workaround for the 440EPx/GRx
2869		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2870		be touched.
2871
2872		WARNING: Please make sure that this value is a multiple of
2873		the Linux page size (normally 4k). If this is not the case,
2874		then the end address of the Linux memory will be located at a
2875		non page size aligned address and this could cause major
2876		problems.
2877
2878- CONFIG_SYS_TFTP_LOADADDR:
2879		Default load address for network file downloads
2880
2881- CONFIG_SYS_LOADS_BAUD_CHANGE:
2882		Enable temporary baudrate change while serial download
2883
2884- CONFIG_SYS_SDRAM_BASE:
2885		Physical start address of SDRAM. _Must_ be 0 here.
2886
2887- CONFIG_SYS_MBIO_BASE:
2888		Physical start address of Motherboard I/O (if using a
2889		Cogent motherboard)
2890
2891- CONFIG_SYS_FLASH_BASE:
2892		Physical start address of Flash memory.
2893
2894- CONFIG_SYS_MONITOR_BASE:
2895		Physical start address of boot monitor code (set by
2896		make config files to be same as the text base address
2897		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2898		CONFIG_SYS_FLASH_BASE when booting from flash.
2899
2900- CONFIG_SYS_MONITOR_LEN:
2901		Size of memory reserved for monitor code, used to
2902		determine _at_compile_time_ (!) if the environment is
2903		embedded within the U-Boot image, or in a separate
2904		flash sector.
2905
2906- CONFIG_SYS_MALLOC_LEN:
2907		Size of DRAM reserved for malloc() use.
2908
2909- CONFIG_SYS_BOOTM_LEN:
2910		Normally compressed uImages are limited to an
2911		uncompressed size of 8 MBytes. If this is not enough,
2912		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2913		to adjust this setting to your needs.
2914
2915- CONFIG_SYS_BOOTMAPSZ:
2916		Maximum size of memory mapped by the startup code of
2917		the Linux kernel; all data that must be processed by
2918		the Linux kernel (bd_info, boot arguments, FDT blob if
2919		used) must be put below this limit, unless "bootm_low"
2920		enviroment variable is defined and non-zero. In such case
2921		all data for the Linux kernel must be between "bootm_low"
2922		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2923		variable "bootm_mapsize" will override the value of
2924		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2925		then the value in "bootm_size" will be used instead.
2926
2927- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2928		Enable initrd_high functionality.  If defined then the
2929		initrd_high feature is enabled and the bootm ramdisk subcommand
2930		is enabled.
2931
2932- CONFIG_SYS_BOOT_GET_CMDLINE:
2933		Enables allocating and saving kernel cmdline in space between
2934		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2935
2936- CONFIG_SYS_BOOT_GET_KBD:
2937		Enables allocating and saving a kernel copy of the bd_info in
2938		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2939
2940- CONFIG_SYS_MAX_FLASH_BANKS:
2941		Max number of Flash memory banks
2942
2943- CONFIG_SYS_MAX_FLASH_SECT:
2944		Max number of sectors on a Flash chip
2945
2946- CONFIG_SYS_FLASH_ERASE_TOUT:
2947		Timeout for Flash erase operations (in ms)
2948
2949- CONFIG_SYS_FLASH_WRITE_TOUT:
2950		Timeout for Flash write operations (in ms)
2951
2952- CONFIG_SYS_FLASH_LOCK_TOUT
2953		Timeout for Flash set sector lock bit operation (in ms)
2954
2955- CONFIG_SYS_FLASH_UNLOCK_TOUT
2956		Timeout for Flash clear lock bits operation (in ms)
2957
2958- CONFIG_SYS_FLASH_PROTECTION
2959		If defined, hardware flash sectors protection is used
2960		instead of U-Boot software protection.
2961
2962- CONFIG_SYS_DIRECT_FLASH_TFTP:
2963
2964		Enable TFTP transfers directly to flash memory;
2965		without this option such a download has to be
2966		performed in two steps: (1) download to RAM, and (2)
2967		copy from RAM to flash.
2968
2969		The two-step approach is usually more reliable, since
2970		you can check if the download worked before you erase
2971		the flash, but in some situations (when system RAM is
2972		too limited to allow for a temporary copy of the
2973		downloaded image) this option may be very useful.
2974
2975- CONFIG_SYS_FLASH_CFI:
2976		Define if the flash driver uses extra elements in the
2977		common flash structure for storing flash geometry.
2978
2979- CONFIG_FLASH_CFI_DRIVER
2980		This option also enables the building of the cfi_flash driver
2981		in the drivers directory
2982
2983- CONFIG_FLASH_CFI_MTD
2984		This option enables the building of the cfi_mtd driver
2985		in the drivers directory. The driver exports CFI flash
2986		to the MTD layer.
2987
2988- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2989		Use buffered writes to flash.
2990
2991- CONFIG_FLASH_SPANSION_S29WS_N
2992		s29ws-n MirrorBit flash has non-standard addresses for buffered
2993		write commands.
2994
2995- CONFIG_SYS_FLASH_QUIET_TEST
2996		If this option is defined, the common CFI flash doesn't
2997		print it's warning upon not recognized FLASH banks. This
2998		is useful, if some of the configured banks are only
2999		optionally available.
3000
3001- CONFIG_FLASH_SHOW_PROGRESS
3002		If defined (must be an integer), print out countdown
3003		digits and dots.  Recommended value: 45 (9..1) for 80
3004		column displays, 15 (3..1) for 40 column displays.
3005
3006- CONFIG_SYS_RX_ETH_BUFFER:
3007		Defines the number of Ethernet receive buffers. On some
3008		Ethernet controllers it is recommended to set this value
3009		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3010		buffers can be full shortly after enabling the interface
3011		on high Ethernet traffic.
3012		Defaults to 4 if not defined.
3013
3014- CONFIG_ENV_MAX_ENTRIES
3015
3016	Maximum number of entries in the hash table that is used
3017	internally to store the environment settings. The default
3018	setting is supposed to be generous and should work in most
3019	cases. This setting can be used to tune behaviour; see
3020	lib/hashtable.c for details.
3021
3022The following definitions that deal with the placement and management
3023of environment data (variable area); in general, we support the
3024following configurations:
3025
3026- CONFIG_BUILD_ENVCRC:
3027
3028	Builds up envcrc with the target environment so that external utils
3029	may easily extract it and embed it in final U-Boot images.
3030
3031- CONFIG_ENV_IS_IN_FLASH:
3032
3033	Define this if the environment is in flash memory.
3034
3035	a) The environment occupies one whole flash sector, which is
3036	   "embedded" in the text segment with the U-Boot code. This
3037	   happens usually with "bottom boot sector" or "top boot
3038	   sector" type flash chips, which have several smaller
3039	   sectors at the start or the end. For instance, such a
3040	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3041	   such a case you would place the environment in one of the
3042	   4 kB sectors - with U-Boot code before and after it. With
3043	   "top boot sector" type flash chips, you would put the
3044	   environment in one of the last sectors, leaving a gap
3045	   between U-Boot and the environment.
3046
3047	- CONFIG_ENV_OFFSET:
3048
3049	   Offset of environment data (variable area) to the
3050	   beginning of flash memory; for instance, with bottom boot
3051	   type flash chips the second sector can be used: the offset
3052	   for this sector is given here.
3053
3054	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3055
3056	- CONFIG_ENV_ADDR:
3057
3058	   This is just another way to specify the start address of
3059	   the flash sector containing the environment (instead of
3060	   CONFIG_ENV_OFFSET).
3061
3062	- CONFIG_ENV_SECT_SIZE:
3063
3064	   Size of the sector containing the environment.
3065
3066
3067	b) Sometimes flash chips have few, equal sized, BIG sectors.
3068	   In such a case you don't want to spend a whole sector for
3069	   the environment.
3070
3071	- CONFIG_ENV_SIZE:
3072
3073	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3074	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3075	   of this flash sector for the environment. This saves
3076	   memory for the RAM copy of the environment.
3077
3078	   It may also save flash memory if you decide to use this
3079	   when your environment is "embedded" within U-Boot code,
3080	   since then the remainder of the flash sector could be used
3081	   for U-Boot code. It should be pointed out that this is
3082	   STRONGLY DISCOURAGED from a robustness point of view:
3083	   updating the environment in flash makes it always
3084	   necessary to erase the WHOLE sector. If something goes
3085	   wrong before the contents has been restored from a copy in
3086	   RAM, your target system will be dead.
3087
3088	- CONFIG_ENV_ADDR_REDUND
3089	  CONFIG_ENV_SIZE_REDUND
3090
3091	   These settings describe a second storage area used to hold
3092	   a redundant copy of the environment data, so that there is
3093	   a valid backup copy in case there is a power failure during
3094	   a "saveenv" operation.
3095
3096BE CAREFUL! Any changes to the flash layout, and some changes to the
3097source code will make it necessary to adapt <board>/u-boot.lds*
3098accordingly!
3099
3100
3101- CONFIG_ENV_IS_IN_NVRAM:
3102
3103	Define this if you have some non-volatile memory device
3104	(NVRAM, battery buffered SRAM) which you want to use for the
3105	environment.
3106
3107	- CONFIG_ENV_ADDR:
3108	- CONFIG_ENV_SIZE:
3109
3110	  These two #defines are used to determine the memory area you
3111	  want to use for environment. It is assumed that this memory
3112	  can just be read and written to, without any special
3113	  provision.
3114
3115BE CAREFUL! The first access to the environment happens quite early
3116in U-Boot initalization (when we try to get the setting of for the
3117console baudrate). You *MUST* have mapped your NVRAM area then, or
3118U-Boot will hang.
3119
3120Please note that even with NVRAM we still use a copy of the
3121environment in RAM: we could work on NVRAM directly, but we want to
3122keep settings there always unmodified except somebody uses "saveenv"
3123to save the current settings.
3124
3125
3126- CONFIG_ENV_IS_IN_EEPROM:
3127
3128	Use this if you have an EEPROM or similar serial access
3129	device and a driver for it.
3130
3131	- CONFIG_ENV_OFFSET:
3132	- CONFIG_ENV_SIZE:
3133
3134	  These two #defines specify the offset and size of the
3135	  environment area within the total memory of your EEPROM.
3136
3137	- CONFIG_SYS_I2C_EEPROM_ADDR:
3138	  If defined, specified the chip address of the EEPROM device.
3139	  The default address is zero.
3140
3141	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3142	  If defined, the number of bits used to address bytes in a
3143	  single page in the EEPROM device.  A 64 byte page, for example
3144	  would require six bits.
3145
3146	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3147	  If defined, the number of milliseconds to delay between
3148	  page writes.	The default is zero milliseconds.
3149
3150	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3151	  The length in bytes of the EEPROM memory array address.  Note
3152	  that this is NOT the chip address length!
3153
3154	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3155	  EEPROM chips that implement "address overflow" are ones
3156	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3157	  address and the extra bits end up in the "chip address" bit
3158	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3159	  byte chips.
3160
3161	  Note that we consider the length of the address field to
3162	  still be one byte because the extra address bits are hidden
3163	  in the chip address.
3164
3165	- CONFIG_SYS_EEPROM_SIZE:
3166	  The size in bytes of the EEPROM device.
3167
3168	- CONFIG_ENV_EEPROM_IS_ON_I2C
3169	  define this, if you have I2C and SPI activated, and your
3170	  EEPROM, which holds the environment, is on the I2C bus.
3171
3172	- CONFIG_I2C_ENV_EEPROM_BUS
3173	  if you have an Environment on an EEPROM reached over
3174	  I2C muxes, you can define here, how to reach this
3175	  EEPROM. For example:
3176
3177	  #define CONFIG_I2C_ENV_EEPROM_BUS	  "pca9547:70:d\0"
3178
3179	  EEPROM which holds the environment, is reached over
3180	  a pca9547 i2c mux with address 0x70, channel 3.
3181
3182- CONFIG_ENV_IS_IN_DATAFLASH:
3183
3184	Define this if you have a DataFlash memory device which you
3185	want to use for the environment.
3186
3187	- CONFIG_ENV_OFFSET:
3188	- CONFIG_ENV_ADDR:
3189	- CONFIG_ENV_SIZE:
3190
3191	  These three #defines specify the offset and size of the
3192	  environment area within the total memory of your DataFlash placed
3193	  at the specified address.
3194
3195- CONFIG_ENV_IS_IN_REMOTE:
3196
3197	Define this if you have a remote memory space which you
3198	want to use for the local device's environment.
3199
3200	- CONFIG_ENV_ADDR:
3201	- CONFIG_ENV_SIZE:
3202
3203	  These two #defines specify the address and size of the
3204	  environment area within the remote memory space. The
3205	  local device can get the environment from remote memory
3206	  space by SRIO or PCIE links.
3207
3208BE CAREFUL! For some special cases, the local device can not use
3209"saveenv" command. For example, the local device will get the
3210environment stored in a remote NOR flash by SRIO or PCIE link,
3211but it can not erase, write this NOR flash by SRIO or PCIE interface.
3212
3213- CONFIG_ENV_IS_IN_NAND:
3214
3215	Define this if you have a NAND device which you want to use
3216	for the environment.
3217
3218	- CONFIG_ENV_OFFSET:
3219	- CONFIG_ENV_SIZE:
3220
3221	  These two #defines specify the offset and size of the environment
3222	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3223	  aligned to an erase block boundary.
3224
3225	- CONFIG_ENV_OFFSET_REDUND (optional):
3226
3227	  This setting describes a second storage area of CONFIG_ENV_SIZE
3228	  size used to hold a redundant copy of the environment data, so
3229	  that there is a valid backup copy in case there is a power failure
3230	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
3231	  aligned to an erase block boundary.
3232
3233	- CONFIG_ENV_RANGE (optional):
3234
3235	  Specifies the length of the region in which the environment
3236	  can be written.  This should be a multiple of the NAND device's
3237	  block size.  Specifying a range with more erase blocks than
3238	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
3239	  the range to be avoided.
3240
3241	- CONFIG_ENV_OFFSET_OOB (optional):
3242
3243	  Enables support for dynamically retrieving the offset of the
3244	  environment from block zero's out-of-band data.  The
3245	  "nand env.oob" command can be used to record this offset.
3246	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
3247	  using CONFIG_ENV_OFFSET_OOB.
3248
3249- CONFIG_NAND_ENV_DST
3250
3251	Defines address in RAM to which the nand_spl code should copy the
3252	environment. If redundant environment is used, it will be copied to
3253	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3254
3255- CONFIG_SYS_SPI_INIT_OFFSET
3256
3257	Defines offset to the initial SPI buffer area in DPRAM. The
3258	area is used at an early stage (ROM part) if the environment
3259	is configured to reside in the SPI EEPROM: We need a 520 byte
3260	scratch DPRAM area. It is used between the two initialization
3261	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
3262	to be a good choice since it makes it far enough from the
3263	start of the data area as well as from the stack pointer.
3264
3265Please note that the environment is read-only until the monitor
3266has been relocated to RAM and a RAM copy of the environment has been
3267created; also, when using EEPROM you will have to use getenv_f()
3268until then to read environment variables.
3269
3270The environment is protected by a CRC32 checksum. Before the monitor
3271is relocated into RAM, as a result of a bad CRC you will be working
3272with the compiled-in default environment - *silently*!!! [This is
3273necessary, because the first environment variable we need is the
3274"baudrate" setting for the console - if we have a bad CRC, we don't
3275have any device yet where we could complain.]
3276
3277Note: once the monitor has been relocated, then it will complain if
3278the default environment is used; a new CRC is computed as soon as you
3279use the "saveenv" command to store a valid environment.
3280
3281- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3282		Echo the inverted Ethernet link state to the fault LED.
3283
3284		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3285		      also needs to be defined.
3286
3287- CONFIG_SYS_FAULT_MII_ADDR:
3288		MII address of the PHY to check for the Ethernet link state.
3289
3290- CONFIG_NS16550_MIN_FUNCTIONS:
3291		Define this if you desire to only have use of the NS16550_init
3292		and NS16550_putc functions for the serial driver located at
3293		drivers/serial/ns16550.c.  This option is useful for saving
3294		space for already greatly restricted images, including but not
3295		limited to NAND_SPL configurations.
3296
3297Low Level (hardware related) configuration options:
3298---------------------------------------------------
3299
3300- CONFIG_SYS_CACHELINE_SIZE:
3301		Cache Line Size of the CPU.
3302
3303- CONFIG_SYS_DEFAULT_IMMR:
3304		Default address of the IMMR after system reset.
3305
3306		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
3307		and RPXsuper) to be able to adjust the position of
3308		the IMMR register after a reset.
3309
3310- CONFIG_SYS_CCSRBAR_DEFAULT:
3311		Default (power-on reset) physical address of CCSR on Freescale
3312		PowerPC SOCs.
3313
3314- CONFIG_SYS_CCSRBAR:
3315		Virtual address of CCSR.  On a 32-bit build, this is typically
3316		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3317
3318		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
3319		for cross-platform code that uses that macro instead.
3320
3321- CONFIG_SYS_CCSRBAR_PHYS:
3322		Physical address of CCSR.  CCSR can be relocated to a new
3323		physical address, if desired.  In this case, this macro should
3324		be set to that address.	 Otherwise, it should be set to the
3325		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3326		is typically relocated on 36-bit builds.  It is recommended
3327		that this macro be defined via the _HIGH and _LOW macros:
3328
3329		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3330			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3331
3332- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3333		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3334		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3335		used in assembly code, so it must not contain typecasts or
3336		integer size suffixes (e.g. "ULL").
3337
3338- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3339		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3340		used in assembly code, so it must not contain typecasts or
3341		integer size suffixes (e.g. "ULL").
3342
3343- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3344		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3345		forced to a value that ensures that CCSR is not relocated.
3346
3347- Floppy Disk Support:
3348		CONFIG_SYS_FDC_DRIVE_NUMBER
3349
3350		the default drive number (default value 0)
3351
3352		CONFIG_SYS_ISA_IO_STRIDE
3353
3354		defines the spacing between FDC chipset registers
3355		(default value 1)
3356
3357		CONFIG_SYS_ISA_IO_OFFSET
3358
3359		defines the offset of register from address. It
3360		depends on which part of the data bus is connected to
3361		the FDC chipset. (default value 0)
3362
3363		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3364		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3365		default value.
3366
3367		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3368		fdc_hw_init() is called at the beginning of the FDC
3369		setup. fdc_hw_init() must be provided by the board
3370		source code. It is used to make hardware dependant
3371		initializations.
3372
3373- CONFIG_IDE_AHB:
3374		Most IDE controllers were designed to be connected with PCI
3375		interface. Only few of them were designed for AHB interface.
3376		When software is doing ATA command and data transfer to
3377		IDE devices through IDE-AHB controller, some additional
3378		registers accessing to these kind of IDE-AHB controller
3379		is requierd.
3380
3381- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3382		DO NOT CHANGE unless you know exactly what you're
3383		doing! (11-4) [MPC8xx/82xx systems only]
3384
3385- CONFIG_SYS_INIT_RAM_ADDR:
3386
3387		Start address of memory area that can be used for
3388		initial data and stack; please note that this must be
3389		writable memory that is working WITHOUT special
3390		initialization, i. e. you CANNOT use normal RAM which
3391		will become available only after programming the
3392		memory controller and running certain initialization
3393		sequences.
3394
3395		U-Boot uses the following memory types:
3396		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
3397		- MPC824X: data cache
3398		- PPC4xx:  data cache
3399
3400- CONFIG_SYS_GBL_DATA_OFFSET:
3401
3402		Offset of the initial data structure in the memory
3403		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3404		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3405		data is located at the end of the available space
3406		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3407		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
3408		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3409		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3410
3411	Note:
3412		On the MPC824X (or other systems that use the data
3413		cache for initial memory) the address chosen for
3414		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3415		point to an otherwise UNUSED address space between
3416		the top of RAM and the start of the PCI space.
3417
3418- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
3419
3420- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
3421
3422- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
3423
3424- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
3425
3426- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
3427
3428- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3429
3430- CONFIG_SYS_OR_TIMING_SDRAM:
3431		SDRAM timing
3432
3433- CONFIG_SYS_MAMR_PTA:
3434		periodic timer for refresh
3435
3436- CONFIG_SYS_DER:	Debug Event Register (37-47)
3437
3438- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3439  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3440  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3441  CONFIG_SYS_BR1_PRELIM:
3442		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3443
3444- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3445  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3446  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3447		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3448
3449- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
3450  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
3451		Machine Mode Register and Memory Periodic Timer
3452		Prescaler definitions (SDRAM timing)
3453
3454- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
3455		enable I2C microcode relocation patch (MPC8xx);
3456		define relocation offset in DPRAM [DSP2]
3457
3458- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
3459		enable SMC microcode relocation patch (MPC8xx);
3460		define relocation offset in DPRAM [SMC1]
3461
3462- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
3463		enable SPI microcode relocation patch (MPC8xx);
3464		define relocation offset in DPRAM [SCC4]
3465
3466- CONFIG_SYS_USE_OSCCLK:
3467		Use OSCM clock mode on MBX8xx board. Be careful,
3468		wrong setting might damage your board. Read
3469		doc/README.MBX before setting this variable!
3470
3471- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
3472		Offset of the bootmode word in DPRAM used by post
3473		(Power On Self Tests). This definition overrides
3474		#define'd default value in commproc.h resp.
3475		cpm_8260.h.
3476
3477- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
3478  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
3479  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
3480  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
3481  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
3482  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
3483  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
3484  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
3485		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
3486
3487- CONFIG_PCI_DISABLE_PCIE:
3488		Disable PCI-Express on systems where it is supported but not
3489		required.
3490
3491- CONFIG_PCI_ENUM_ONLY
3492		Only scan through and get the devices on the busses.
3493		Don't do any setup work, presumably because someone or
3494		something has already done it, and we don't need to do it
3495		a second time.	Useful for platforms that are pre-booted
3496		by coreboot or similar.
3497
3498- CONFIG_SYS_SRIO:
3499		Chip has SRIO or not
3500
3501- CONFIG_SRIO1:
3502		Board has SRIO 1 port available
3503
3504- CONFIG_SRIO2:
3505		Board has SRIO 2 port available
3506
3507- CONFIG_SYS_SRIOn_MEM_VIRT:
3508		Virtual Address of SRIO port 'n' memory region
3509
3510- CONFIG_SYS_SRIOn_MEM_PHYS:
3511		Physical Address of SRIO port 'n' memory region
3512
3513- CONFIG_SYS_SRIOn_MEM_SIZE:
3514		Size of SRIO port 'n' memory region
3515
3516- CONFIG_SYS_NDFC_16
3517		Defined to tell the NDFC that the NAND chip is using a
3518		16 bit bus.
3519
3520- CONFIG_SYS_NDFC_EBC0_CFG
3521		Sets the EBC0_CFG register for the NDFC. If not defined
3522		a default value will be used.
3523
3524- CONFIG_SPD_EEPROM
3525		Get DDR timing information from an I2C EEPROM. Common
3526		with pluggable memory modules such as SODIMMs
3527
3528  SPD_EEPROM_ADDRESS
3529		I2C address of the SPD EEPROM
3530
3531- CONFIG_SYS_SPD_BUS_NUM
3532		If SPD EEPROM is on an I2C bus other than the first
3533		one, specify here. Note that the value must resolve
3534		to something your driver can deal with.
3535
3536- CONFIG_SYS_DDR_RAW_TIMING
3537		Get DDR timing information from other than SPD. Common with
3538		soldered DDR chips onboard without SPD. DDR raw timing
3539		parameters are extracted from datasheet and hard-coded into
3540		header files or board specific files.
3541
3542- CONFIG_FSL_DDR_INTERACTIVE
3543		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3544
3545- CONFIG_SYS_83XX_DDR_USES_CS0
3546		Only for 83xx systems. If specified, then DDR should
3547		be configured using CS0 and CS1 instead of CS2 and CS3.
3548
3549- CONFIG_ETHER_ON_FEC[12]
3550		Define to enable FEC[12] on a 8xx series processor.
3551
3552- CONFIG_FEC[12]_PHY
3553		Define to the hardcoded PHY address which corresponds
3554		to the given FEC; i. e.
3555			#define CONFIG_FEC1_PHY 4
3556		means that the PHY with address 4 is connected to FEC1
3557
3558		When set to -1, means to probe for first available.
3559
3560- CONFIG_FEC[12]_PHY_NORXERR
3561		The PHY does not have a RXERR line (RMII only).
3562		(so program the FEC to ignore it).
3563
3564- CONFIG_RMII
3565		Enable RMII mode for all FECs.
3566		Note that this is a global option, we can't
3567		have one FEC in standard MII mode and another in RMII mode.
3568
3569- CONFIG_CRC32_VERIFY
3570		Add a verify option to the crc32 command.
3571		The syntax is:
3572
3573		=> crc32 -v <address> <count> <crc32>
3574
3575		Where address/count indicate a memory area
3576		and crc32 is the correct crc32 which the
3577		area should have.
3578
3579- CONFIG_LOOPW
3580		Add the "loopw" memory command. This only takes effect if
3581		the memory commands are activated globally (CONFIG_CMD_MEM).
3582
3583- CONFIG_MX_CYCLIC
3584		Add the "mdc" and "mwc" memory commands. These are cyclic
3585		"md/mw" commands.
3586		Examples:
3587
3588		=> mdc.b 10 4 500
3589		This command will print 4 bytes (10,11,12,13) each 500 ms.
3590
3591		=> mwc.l 100 12345678 10
3592		This command will write 12345678 to address 100 all 10 ms.
3593
3594		This only takes effect if the memory commands are activated
3595		globally (CONFIG_CMD_MEM).
3596
3597- CONFIG_SKIP_LOWLEVEL_INIT
3598		[ARM, NDS32, MIPS only] If this variable is defined, then certain
3599		low level initializations (like setting up the memory
3600		controller) are omitted and/or U-Boot does not
3601		relocate itself into RAM.
3602
3603		Normally this variable MUST NOT be defined. The only
3604		exception is when U-Boot is loaded (to RAM) by some
3605		other boot loader or by a debugger which performs
3606		these initializations itself.
3607
3608- CONFIG_SPL_BUILD
3609		Modifies the behaviour of start.S when compiling a loader
3610		that is executed before the actual U-Boot. E.g. when
3611		compiling a NAND SPL.
3612
3613- CONFIG_USE_ARCH_MEMCPY
3614  CONFIG_USE_ARCH_MEMSET
3615		If these options are used a optimized version of memcpy/memset will
3616		be used if available. These functions may be faster under some
3617		conditions but may increase the binary size.
3618
3619Freescale QE/FMAN Firmware Support:
3620-----------------------------------
3621
3622The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3623loading of "firmware", which is encoded in the QE firmware binary format.
3624This firmware often needs to be loaded during U-Boot booting, so macros
3625are used to identify the storage device (NOR flash, SPI, etc) and the address
3626within that device.
3627
3628- CONFIG_SYS_QE_FMAN_FW_ADDR
3629	The address in the storage device where the firmware is located.  The
3630	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3631	is also specified.
3632
3633- CONFIG_SYS_QE_FMAN_FW_LENGTH
3634	The maximum possible size of the firmware.  The firmware binary format
3635	has a field that specifies the actual size of the firmware, but it
3636	might not be possible to read any part of the firmware unless some
3637	local storage is allocated to hold the entire firmware first.
3638
3639- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3640	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3641	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3642	virtual address in NOR flash.
3643
3644- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3645	Specifies that QE/FMAN firmware is located in NAND flash.
3646	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3647
3648- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3649	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3650	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3651
3652- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
3653	Specifies that QE/FMAN firmware is located on the primary SPI
3654	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3655
3656- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3657	Specifies that QE/FMAN firmware is located in the remote (master)
3658	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3659	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3660	window->master inbound window->master LAW->the ucode address in
3661	master's memory space.
3662
3663Building the Software:
3664======================
3665
3666Building U-Boot has been tested in several native build environments
3667and in many different cross environments. Of course we cannot support
3668all possibly existing versions of cross development tools in all
3669(potentially obsolete) versions. In case of tool chain problems we
3670recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3671which is extensively used to build and test U-Boot.
3672
3673If you are not using a native environment, it is assumed that you
3674have GNU cross compiling tools available in your path. In this case,
3675you must set the environment variable CROSS_COMPILE in your shell.
3676Note that no changes to the Makefile or any other source files are
3677necessary. For example using the ELDK on a 4xx CPU, please enter:
3678
3679	$ CROSS_COMPILE=ppc_4xx-
3680	$ export CROSS_COMPILE
3681
3682Note: If you wish to generate Windows versions of the utilities in
3683      the tools directory you can use the MinGW toolchain
3684      (http://www.mingw.org).  Set your HOST tools to the MinGW
3685      toolchain and execute 'make tools'.  For example:
3686
3687       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3688
3689      Binaries such as tools/mkimage.exe will be created which can
3690      be executed on computers running Windows.
3691
3692U-Boot is intended to be simple to build. After installing the
3693sources you must configure U-Boot for one specific board type. This
3694is done by typing:
3695
3696	make NAME_config
3697
3698where "NAME_config" is the name of one of the existing configu-
3699rations; see boards.cfg for supported names.
3700
3701Note: for some board special configuration names may exist; check if
3702      additional information is available from the board vendor; for
3703      instance, the TQM823L systems are available without (standard)
3704      or with LCD support. You can select such additional "features"
3705      when choosing the configuration, i. e.
3706
3707      make TQM823L_config
3708	- will configure for a plain TQM823L, i. e. no LCD support
3709
3710      make TQM823L_LCD_config
3711	- will configure for a TQM823L with U-Boot console on LCD
3712
3713      etc.
3714
3715
3716Finally, type "make all", and you should get some working U-Boot
3717images ready for download to / installation on your system:
3718
3719- "u-boot.bin" is a raw binary image
3720- "u-boot" is an image in ELF binary format
3721- "u-boot.srec" is in Motorola S-Record format
3722
3723By default the build is performed locally and the objects are saved
3724in the source directory. One of the two methods can be used to change
3725this behavior and build U-Boot to some external directory:
3726
37271. Add O= to the make command line invocations:
3728
3729	make O=/tmp/build distclean
3730	make O=/tmp/build NAME_config
3731	make O=/tmp/build all
3732
37332. Set environment variable BUILD_DIR to point to the desired location:
3734
3735	export BUILD_DIR=/tmp/build
3736	make distclean
3737	make NAME_config
3738	make all
3739
3740Note that the command line "O=" setting overrides the BUILD_DIR environment
3741variable.
3742
3743
3744Please be aware that the Makefiles assume you are using GNU make, so
3745for instance on NetBSD you might need to use "gmake" instead of
3746native "make".
3747
3748
3749If the system board that you have is not listed, then you will need
3750to port U-Boot to your hardware platform. To do this, follow these
3751steps:
3752
37531.  Add a new configuration option for your board to the toplevel
3754    "boards.cfg" file, using the existing entries as examples.
3755    Follow the instructions there to keep the boards in order.
37562.  Create a new directory to hold your board specific code. Add any
3757    files you need. In your board directory, you will need at least
3758    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
37593.  Create a new configuration file "include/configs/<board>.h" for
3760    your board
37613.  If you're porting U-Boot to a new CPU, then also create a new
3762    directory to hold your CPU specific code. Add any files you need.
37634.  Run "make <board>_config" with your new name.
37645.  Type "make", and you should get a working "u-boot.srec" file
3765    to be installed on your target system.
37666.  Debug and solve any problems that might arise.
3767    [Of course, this last step is much harder than it sounds.]
3768
3769
3770Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3771==============================================================
3772
3773If you have modified U-Boot sources (for instance added a new board
3774or support for new devices, a new CPU, etc.) you are expected to
3775provide feedback to the other developers. The feedback normally takes
3776the form of a "patch", i. e. a context diff against a certain (latest
3777official or latest in the git repository) version of U-Boot sources.
3778
3779But before you submit such a patch, please verify that your modifi-
3780cation did not break existing code. At least make sure that *ALL* of
3781the supported boards compile WITHOUT ANY compiler warnings. To do so,
3782just run the "MAKEALL" script, which will configure and build U-Boot
3783for ALL supported system. Be warned, this will take a while. You can
3784select which (cross) compiler to use by passing a `CROSS_COMPILE'
3785environment variable to the script, i. e. to use the ELDK cross tools
3786you can type
3787
3788	CROSS_COMPILE=ppc_8xx- MAKEALL
3789
3790or to build on a native PowerPC system you can type
3791
3792	CROSS_COMPILE=' ' MAKEALL
3793
3794When using the MAKEALL script, the default behaviour is to build
3795U-Boot in the source directory. This location can be changed by
3796setting the BUILD_DIR environment variable. Also, for each target
3797built, the MAKEALL script saves two log files (<target>.ERR and
3798<target>.MAKEALL) in the <source dir>/LOG directory. This default
3799location can be changed by setting the MAKEALL_LOGDIR environment
3800variable. For example:
3801
3802	export BUILD_DIR=/tmp/build
3803	export MAKEALL_LOGDIR=/tmp/log
3804	CROSS_COMPILE=ppc_8xx- MAKEALL
3805
3806With the above settings build objects are saved in the /tmp/build,
3807log files are saved in the /tmp/log and the source tree remains clean
3808during the whole build process.
3809
3810
3811See also "U-Boot Porting Guide" below.
3812
3813
3814Monitor Commands - Overview:
3815============================
3816
3817go	- start application at address 'addr'
3818run	- run commands in an environment variable
3819bootm	- boot application image from memory
3820bootp	- boot image via network using BootP/TFTP protocol
3821bootz   - boot zImage from memory
3822tftpboot- boot image via network using TFTP protocol
3823	       and env variables "ipaddr" and "serverip"
3824	       (and eventually "gatewayip")
3825tftpput - upload a file via network using TFTP protocol
3826rarpboot- boot image via network using RARP/TFTP protocol
3827diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3828loads	- load S-Record file over serial line
3829loadb	- load binary file over serial line (kermit mode)
3830md	- memory display
3831mm	- memory modify (auto-incrementing)
3832nm	- memory modify (constant address)
3833mw	- memory write (fill)
3834cp	- memory copy
3835cmp	- memory compare
3836crc32	- checksum calculation
3837i2c	- I2C sub-system
3838sspi	- SPI utility commands
3839base	- print or set address offset
3840printenv- print environment variables
3841setenv	- set environment variables
3842saveenv - save environment variables to persistent storage
3843protect - enable or disable FLASH write protection
3844erase	- erase FLASH memory
3845flinfo	- print FLASH memory information
3846bdinfo	- print Board Info structure
3847iminfo	- print header information for application image
3848coninfo - print console devices and informations
3849ide	- IDE sub-system
3850loop	- infinite loop on address range
3851loopw	- infinite write loop on address range
3852mtest	- simple RAM test
3853icache	- enable or disable instruction cache
3854dcache	- enable or disable data cache
3855reset	- Perform RESET of the CPU
3856echo	- echo args to console
3857version - print monitor version
3858help	- print online help
3859?	- alias for 'help'
3860
3861
3862Monitor Commands - Detailed Description:
3863========================================
3864
3865TODO.
3866
3867For now: just type "help <command>".
3868
3869
3870Environment Variables:
3871======================
3872
3873U-Boot supports user configuration using Environment Variables which
3874can be made persistent by saving to Flash memory.
3875
3876Environment Variables are set using "setenv", printed using
3877"printenv", and saved to Flash using "saveenv". Using "setenv"
3878without a value can be used to delete a variable from the
3879environment. As long as you don't save the environment you are
3880working with an in-memory copy. In case the Flash area containing the
3881environment is erased by accident, a default environment is provided.
3882
3883Some configuration options can be set using Environment Variables.
3884
3885List of environment variables (most likely not complete):
3886
3887  baudrate	- see CONFIG_BAUDRATE
3888
3889  bootdelay	- see CONFIG_BOOTDELAY
3890
3891  bootcmd	- see CONFIG_BOOTCOMMAND
3892
3893  bootargs	- Boot arguments when booting an RTOS image
3894
3895  bootfile	- Name of the image to load with TFTP
3896
3897  bootm_low	- Memory range available for image processing in the bootm
3898		  command can be restricted. This variable is given as
3899		  a hexadecimal number and defines lowest address allowed
3900		  for use by the bootm command. See also "bootm_size"
3901		  environment variable. Address defined by "bootm_low" is
3902		  also the base of the initial memory mapping for the Linux
3903		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3904		  bootm_mapsize.
3905
3906  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3907		  This variable is given as a hexadecimal number and it
3908		  defines the size of the memory region starting at base
3909		  address bootm_low that is accessible by the Linux kernel
3910		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3911		  as the default value if it is defined, and bootm_size is
3912		  used otherwise.
3913
3914  bootm_size	- Memory range available for image processing in the bootm
3915		  command can be restricted. This variable is given as
3916		  a hexadecimal number and defines the size of the region
3917		  allowed for use by the bootm command. See also "bootm_low"
3918		  environment variable.
3919
3920  updatefile	- Location of the software update file on a TFTP server, used
3921		  by the automatic software update feature. Please refer to
3922		  documentation in doc/README.update for more details.
3923
3924  autoload	- if set to "no" (any string beginning with 'n'),
3925		  "bootp" will just load perform a lookup of the
3926		  configuration from the BOOTP server, but not try to
3927		  load any image using TFTP
3928
3929  autostart	- if set to "yes", an image loaded using the "bootp",
3930		  "rarpboot", "tftpboot" or "diskboot" commands will
3931		  be automatically started (by internally calling
3932		  "bootm")
3933
3934		  If set to "no", a standalone image passed to the
3935		  "bootm" command will be copied to the load address
3936		  (and eventually uncompressed), but NOT be started.
3937		  This can be used to load and uncompress arbitrary
3938		  data.
3939
3940  fdt_high	- if set this restricts the maximum address that the
3941		  flattened device tree will be copied into upon boot.
3942		  For example, if you have a system with 1 GB memory
3943		  at physical address 0x10000000, while Linux kernel
3944		  only recognizes the first 704 MB as low memory, you
3945		  may need to set fdt_high as 0x3C000000 to have the
3946		  device tree blob be copied to the maximum address
3947		  of the 704 MB low memory, so that Linux kernel can
3948		  access it during the boot procedure.
3949
3950		  If this is set to the special value 0xFFFFFFFF then
3951		  the fdt will not be copied at all on boot.  For this
3952		  to work it must reside in writable memory, have
3953		  sufficient padding on the end of it for u-boot to
3954		  add the information it needs into it, and the memory
3955		  must be accessible by the kernel.
3956
3957  fdtcontroladdr- if set this is the address of the control flattened
3958		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3959		  defined.
3960
3961  i2cfast	- (PPC405GP|PPC405EP only)
3962		  if set to 'y' configures Linux I2C driver for fast
3963		  mode (400kHZ). This environment variable is used in
3964		  initialization code. So, for changes to be effective
3965		  it must be saved and board must be reset.
3966
3967  initrd_high	- restrict positioning of initrd images:
3968		  If this variable is not set, initrd images will be
3969		  copied to the highest possible address in RAM; this
3970		  is usually what you want since it allows for
3971		  maximum initrd size. If for some reason you want to
3972		  make sure that the initrd image is loaded below the
3973		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3974		  variable to a value of "no" or "off" or "0".
3975		  Alternatively, you can set it to a maximum upper
3976		  address to use (U-Boot will still check that it
3977		  does not overwrite the U-Boot stack and data).
3978
3979		  For instance, when you have a system with 16 MB
3980		  RAM, and want to reserve 4 MB from use by Linux,
3981		  you can do this by adding "mem=12M" to the value of
3982		  the "bootargs" variable. However, now you must make
3983		  sure that the initrd image is placed in the first
3984		  12 MB as well - this can be done with
3985
3986		  setenv initrd_high 00c00000
3987
3988		  If you set initrd_high to 0xFFFFFFFF, this is an
3989		  indication to U-Boot that all addresses are legal
3990		  for the Linux kernel, including addresses in flash
3991		  memory. In this case U-Boot will NOT COPY the
3992		  ramdisk at all. This may be useful to reduce the
3993		  boot time on your system, but requires that this
3994		  feature is supported by your Linux kernel.
3995
3996  ipaddr	- IP address; needed for tftpboot command
3997
3998  loadaddr	- Default load address for commands like "bootp",
3999		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4000
4001  loads_echo	- see CONFIG_LOADS_ECHO
4002
4003  serverip	- TFTP server IP address; needed for tftpboot command
4004
4005  bootretry	- see CONFIG_BOOT_RETRY_TIME
4006
4007  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4008
4009  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4010
4011  ethprime	- controls which interface is used first.
4012
4013  ethact	- controls which interface is currently active.
4014		  For example you can do the following
4015
4016		  => setenv ethact FEC
4017		  => ping 192.168.0.1 # traffic sent on FEC
4018		  => setenv ethact SCC
4019		  => ping 10.0.0.1 # traffic sent on SCC
4020
4021  ethrotate	- When set to "no" U-Boot does not go through all
4022		  available network interfaces.
4023		  It just stays at the currently selected interface.
4024
4025  netretry	- When set to "no" each network operation will
4026		  either succeed or fail without retrying.
4027		  When set to "once" the network operation will
4028		  fail when all the available network interfaces
4029		  are tried once without success.
4030		  Useful on scripts which control the retry operation
4031		  themselves.
4032
4033  npe_ucode	- set load address for the NPE microcode
4034
4035  tftpsrcport	- If this is set, the value is used for TFTP's
4036		  UDP source port.
4037
4038  tftpdstport	- If this is set, the value is used for TFTP's UDP
4039		  destination port instead of the Well Know Port 69.
4040
4041  tftpblocksize - Block size to use for TFTP transfers; if not set,
4042		  we use the TFTP server's default block size
4043
4044  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4045		  seconds, minimum value is 1000 = 1 second). Defines
4046		  when a packet is considered to be lost so it has to
4047		  be retransmitted. The default is 5000 = 5 seconds.
4048		  Lowering this value may make downloads succeed
4049		  faster in networks with high packet loss rates or
4050		  with unreliable TFTP servers.
4051
4052  vlan		- When set to a value < 4095 the traffic over
4053		  Ethernet is encapsulated/received over 802.1q
4054		  VLAN tagged frames.
4055
4056The following image location variables contain the location of images
4057used in booting. The "Image" column gives the role of the image and is
4058not an environment variable name. The other columns are environment
4059variable names. "File Name" gives the name of the file on a TFTP
4060server, "RAM Address" gives the location in RAM the image will be
4061loaded to, and "Flash Location" gives the image's address in NOR
4062flash or offset in NAND flash.
4063
4064*Note* - these variables don't have to be defined for all boards, some
4065boards currenlty use other variables for these purposes, and some
4066boards use these variables for other purposes.
4067
4068Image		    File Name	     RAM Address       Flash Location
4069-----		    ---------	     -----------       --------------
4070u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4071Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4072device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4073ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4074
4075The following environment variables may be used and automatically
4076updated by the network boot commands ("bootp" and "rarpboot"),
4077depending the information provided by your boot server:
4078
4079  bootfile	- see above
4080  dnsip		- IP address of your Domain Name Server
4081  dnsip2	- IP address of your secondary Domain Name Server
4082  gatewayip	- IP address of the Gateway (Router) to use
4083  hostname	- Target hostname
4084  ipaddr	- see above
4085  netmask	- Subnet Mask
4086  rootpath	- Pathname of the root filesystem on the NFS server
4087  serverip	- see above
4088
4089
4090There are two special Environment Variables:
4091
4092  serial#	- contains hardware identification information such
4093		  as type string and/or serial number
4094  ethaddr	- Ethernet address
4095
4096These variables can be set only once (usually during manufacturing of
4097the board). U-Boot refuses to delete or overwrite these variables
4098once they have been set once.
4099
4100
4101Further special Environment Variables:
4102
4103  ver		- Contains the U-Boot version string as printed
4104		  with the "version" command. This variable is
4105		  readonly (see CONFIG_VERSION_VARIABLE).
4106
4107
4108Please note that changes to some configuration parameters may take
4109only effect after the next boot (yes, that's just like Windoze :-).
4110
4111
4112Command Line Parsing:
4113=====================
4114
4115There are two different command line parsers available with U-Boot:
4116the old "simple" one, and the much more powerful "hush" shell:
4117
4118Old, simple command line parser:
4119--------------------------------
4120
4121- supports environment variables (through setenv / saveenv commands)
4122- several commands on one line, separated by ';'
4123- variable substitution using "... ${name} ..." syntax
4124- special characters ('$', ';') can be escaped by prefixing with '\',
4125  for example:
4126	setenv bootcmd bootm \${address}
4127- You can also escape text by enclosing in single apostrophes, for example:
4128	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4129
4130Hush shell:
4131-----------
4132
4133- similar to Bourne shell, with control structures like
4134  if...then...else...fi, for...do...done; while...do...done,
4135  until...do...done, ...
4136- supports environment ("global") variables (through setenv / saveenv
4137  commands) and local shell variables (through standard shell syntax
4138  "name=value"); only environment variables can be used with "run"
4139  command
4140
4141General rules:
4142--------------
4143
4144(1) If a command line (or an environment variable executed by a "run"
4145    command) contains several commands separated by semicolon, and
4146    one of these commands fails, then the remaining commands will be
4147    executed anyway.
4148
4149(2) If you execute several variables with one call to run (i. e.
4150    calling run with a list of variables as arguments), any failing
4151    command will cause "run" to terminate, i. e. the remaining
4152    variables are not executed.
4153
4154Note for Redundant Ethernet Interfaces:
4155=======================================
4156
4157Some boards come with redundant Ethernet interfaces; U-Boot supports
4158such configurations and is capable of automatic selection of a
4159"working" interface when needed. MAC assignment works as follows:
4160
4161Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4162MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4163"eth1addr" (=>eth1), "eth2addr", ...
4164
4165If the network interface stores some valid MAC address (for instance
4166in SROM), this is used as default address if there is NO correspon-
4167ding setting in the environment; if the corresponding environment
4168variable is set, this overrides the settings in the card; that means:
4169
4170o If the SROM has a valid MAC address, and there is no address in the
4171  environment, the SROM's address is used.
4172
4173o If there is no valid address in the SROM, and a definition in the
4174  environment exists, then the value from the environment variable is
4175  used.
4176
4177o If both the SROM and the environment contain a MAC address, and
4178  both addresses are the same, this MAC address is used.
4179
4180o If both the SROM and the environment contain a MAC address, and the
4181  addresses differ, the value from the environment is used and a
4182  warning is printed.
4183
4184o If neither SROM nor the environment contain a MAC address, an error
4185  is raised.
4186
4187If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4188will be programmed into hardware as part of the initialization process.	 This
4189may be skipped by setting the appropriate 'ethmacskip' environment variable.
4190The naming convention is as follows:
4191"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4192
4193Image Formats:
4194==============
4195
4196U-Boot is capable of booting (and performing other auxiliary operations on)
4197images in two formats:
4198
4199New uImage format (FIT)
4200-----------------------
4201
4202Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4203to Flattened Device Tree). It allows the use of images with multiple
4204components (several kernels, ramdisks, etc.), with contents protected by
4205SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4206
4207
4208Old uImage format
4209-----------------
4210
4211Old image format is based on binary files which can be basically anything,
4212preceded by a special header; see the definitions in include/image.h for
4213details; basically, the header defines the following image properties:
4214
4215* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4216  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4217  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4218  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4219  INTEGRITY).
4220* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
4221  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4222  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4223* Compression Type (uncompressed, gzip, bzip2)
4224* Load Address
4225* Entry Point
4226* Image Name
4227* Image Timestamp
4228
4229The header is marked by a special Magic Number, and both the header
4230and the data portions of the image are secured against corruption by
4231CRC32 checksums.
4232
4233
4234Linux Support:
4235==============
4236
4237Although U-Boot should support any OS or standalone application
4238easily, the main focus has always been on Linux during the design of
4239U-Boot.
4240
4241U-Boot includes many features that so far have been part of some
4242special "boot loader" code within the Linux kernel. Also, any
4243"initrd" images to be used are no longer part of one big Linux image;
4244instead, kernel and "initrd" are separate images. This implementation
4245serves several purposes:
4246
4247- the same features can be used for other OS or standalone
4248  applications (for instance: using compressed images to reduce the
4249  Flash memory footprint)
4250
4251- it becomes much easier to port new Linux kernel versions because
4252  lots of low-level, hardware dependent stuff are done by U-Boot
4253
4254- the same Linux kernel image can now be used with different "initrd"
4255  images; of course this also means that different kernel images can
4256  be run with the same "initrd". This makes testing easier (you don't
4257  have to build a new "zImage.initrd" Linux image when you just
4258  change a file in your "initrd"). Also, a field-upgrade of the
4259  software is easier now.
4260
4261
4262Linux HOWTO:
4263============
4264
4265Porting Linux to U-Boot based systems:
4266---------------------------------------
4267
4268U-Boot cannot save you from doing all the necessary modifications to
4269configure the Linux device drivers for use with your target hardware
4270(no, we don't intend to provide a full virtual machine interface to
4271Linux :-).
4272
4273But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4274
4275Just make sure your machine specific header file (for instance
4276include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4277Information structure as we define in include/asm-<arch>/u-boot.h,
4278and make sure that your definition of IMAP_ADDR uses the same value
4279as your U-Boot configuration in CONFIG_SYS_IMMR.
4280
4281
4282Configuring the Linux kernel:
4283-----------------------------
4284
4285No specific requirements for U-Boot. Make sure you have some root
4286device (initial ramdisk, NFS) for your target system.
4287
4288
4289Building a Linux Image:
4290-----------------------
4291
4292With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4293not used. If you use recent kernel source, a new build target
4294"uImage" will exist which automatically builds an image usable by
4295U-Boot. Most older kernels also have support for a "pImage" target,
4296which was introduced for our predecessor project PPCBoot and uses a
4297100% compatible format.
4298
4299Example:
4300
4301	make TQM850L_config
4302	make oldconfig
4303	make dep
4304	make uImage
4305
4306The "uImage" build target uses a special tool (in 'tools/mkimage') to
4307encapsulate a compressed Linux kernel image with header	 information,
4308CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4309
4310* build a standard "vmlinux" kernel image (in ELF binary format):
4311
4312* convert the kernel into a raw binary image:
4313
4314	${CROSS_COMPILE}-objcopy -O binary \
4315				 -R .note -R .comment \
4316				 -S vmlinux linux.bin
4317
4318* compress the binary image:
4319
4320	gzip -9 linux.bin
4321
4322* package compressed binary image for U-Boot:
4323
4324	mkimage -A ppc -O linux -T kernel -C gzip \
4325		-a 0 -e 0 -n "Linux Kernel Image" \
4326		-d linux.bin.gz uImage
4327
4328
4329The "mkimage" tool can also be used to create ramdisk images for use
4330with U-Boot, either separated from the Linux kernel image, or
4331combined into one file. "mkimage" encapsulates the images with a 64
4332byte header containing information about target architecture,
4333operating system, image type, compression method, entry points, time
4334stamp, CRC32 checksums, etc.
4335
4336"mkimage" can be called in two ways: to verify existing images and
4337print the header information, or to build new images.
4338
4339In the first form (with "-l" option) mkimage lists the information
4340contained in the header of an existing U-Boot image; this includes
4341checksum verification:
4342
4343	tools/mkimage -l image
4344	  -l ==> list image header information
4345
4346The second form (with "-d" option) is used to build a U-Boot image
4347from a "data file" which is used as image payload:
4348
4349	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4350		      -n name -d data_file image
4351	  -A ==> set architecture to 'arch'
4352	  -O ==> set operating system to 'os'
4353	  -T ==> set image type to 'type'
4354	  -C ==> set compression type 'comp'
4355	  -a ==> set load address to 'addr' (hex)
4356	  -e ==> set entry point to 'ep' (hex)
4357	  -n ==> set image name to 'name'
4358	  -d ==> use image data from 'datafile'
4359
4360Right now, all Linux kernels for PowerPC systems use the same load
4361address (0x00000000), but the entry point address depends on the
4362kernel version:
4363
4364- 2.2.x kernels have the entry point at 0x0000000C,
4365- 2.3.x and later kernels have the entry point at 0x00000000.
4366
4367So a typical call to build a U-Boot image would read:
4368
4369	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4370	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4371	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4372	> examples/uImage.TQM850L
4373	Image Name:   2.4.4 kernel for TQM850L
4374	Created:      Wed Jul 19 02:34:59 2000
4375	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4376	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4377	Load Address: 0x00000000
4378	Entry Point:  0x00000000
4379
4380To verify the contents of the image (or check for corruption):
4381
4382	-> tools/mkimage -l examples/uImage.TQM850L
4383	Image Name:   2.4.4 kernel for TQM850L
4384	Created:      Wed Jul 19 02:34:59 2000
4385	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4386	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4387	Load Address: 0x00000000
4388	Entry Point:  0x00000000
4389
4390NOTE: for embedded systems where boot time is critical you can trade
4391speed for memory and install an UNCOMPRESSED image instead: this
4392needs more space in Flash, but boots much faster since it does not
4393need to be uncompressed:
4394
4395	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4396	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4397	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4398	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4399	> examples/uImage.TQM850L-uncompressed
4400	Image Name:   2.4.4 kernel for TQM850L
4401	Created:      Wed Jul 19 02:34:59 2000
4402	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4403	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4404	Load Address: 0x00000000
4405	Entry Point:  0x00000000
4406
4407
4408Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4409when your kernel is intended to use an initial ramdisk:
4410
4411	-> tools/mkimage -n 'Simple Ramdisk Image' \
4412	> -A ppc -O linux -T ramdisk -C gzip \
4413	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4414	Image Name:   Simple Ramdisk Image
4415	Created:      Wed Jan 12 14:01:50 2000
4416	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4417	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4418	Load Address: 0x00000000
4419	Entry Point:  0x00000000
4420
4421
4422Installing a Linux Image:
4423-------------------------
4424
4425To downloading a U-Boot image over the serial (console) interface,
4426you must convert the image to S-Record format:
4427
4428	objcopy -I binary -O srec examples/image examples/image.srec
4429
4430The 'objcopy' does not understand the information in the U-Boot
4431image header, so the resulting S-Record file will be relative to
4432address 0x00000000. To load it to a given address, you need to
4433specify the target address as 'offset' parameter with the 'loads'
4434command.
4435
4436Example: install the image to address 0x40100000 (which on the
4437TQM8xxL is in the first Flash bank):
4438
4439	=> erase 40100000 401FFFFF
4440
4441	.......... done
4442	Erased 8 sectors
4443
4444	=> loads 40100000
4445	## Ready for S-Record download ...
4446	~>examples/image.srec
4447	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4448	...
4449	15989 15990 15991 15992
4450	[file transfer complete]
4451	[connected]
4452	## Start Addr = 0x00000000
4453
4454
4455You can check the success of the download using the 'iminfo' command;
4456this includes a checksum verification so you can be sure no data
4457corruption happened:
4458
4459	=> imi 40100000
4460
4461	## Checking Image at 40100000 ...
4462	   Image Name:	 2.2.13 for initrd on TQM850L
4463	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4464	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4465	   Load Address: 00000000
4466	   Entry Point:	 0000000c
4467	   Verifying Checksum ... OK
4468
4469
4470Boot Linux:
4471-----------
4472
4473The "bootm" command is used to boot an application that is stored in
4474memory (RAM or Flash). In case of a Linux kernel image, the contents
4475of the "bootargs" environment variable is passed to the kernel as
4476parameters. You can check and modify this variable using the
4477"printenv" and "setenv" commands:
4478
4479
4480	=> printenv bootargs
4481	bootargs=root=/dev/ram
4482
4483	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4484
4485	=> printenv bootargs
4486	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4487
4488	=> bootm 40020000
4489	## Booting Linux kernel at 40020000 ...
4490	   Image Name:	 2.2.13 for NFS on TQM850L
4491	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4492	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4493	   Load Address: 00000000
4494	   Entry Point:	 0000000c
4495	   Verifying Checksum ... OK
4496	   Uncompressing Kernel Image ... OK
4497	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
4498	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4499	time_init: decrementer frequency = 187500000/60
4500	Calibrating delay loop... 49.77 BogoMIPS
4501	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4502	...
4503
4504If you want to boot a Linux kernel with initial RAM disk, you pass
4505the memory addresses of both the kernel and the initrd image (PPBCOOT
4506format!) to the "bootm" command:
4507
4508	=> imi 40100000 40200000
4509
4510	## Checking Image at 40100000 ...
4511	   Image Name:	 2.2.13 for initrd on TQM850L
4512	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4513	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4514	   Load Address: 00000000
4515	   Entry Point:	 0000000c
4516	   Verifying Checksum ... OK
4517
4518	## Checking Image at 40200000 ...
4519	   Image Name:	 Simple Ramdisk Image
4520	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4521	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4522	   Load Address: 00000000
4523	   Entry Point:	 00000000
4524	   Verifying Checksum ... OK
4525
4526	=> bootm 40100000 40200000
4527	## Booting Linux kernel at 40100000 ...
4528	   Image Name:	 2.2.13 for initrd on TQM850L
4529	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4530	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4531	   Load Address: 00000000
4532	   Entry Point:	 0000000c
4533	   Verifying Checksum ... OK
4534	   Uncompressing Kernel Image ... OK
4535	## Loading RAMDisk Image at 40200000 ...
4536	   Image Name:	 Simple Ramdisk Image
4537	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4538	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4539	   Load Address: 00000000
4540	   Entry Point:	 00000000
4541	   Verifying Checksum ... OK
4542	   Loading Ramdisk ... OK
4543	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
4544	Boot arguments: root=/dev/ram
4545	time_init: decrementer frequency = 187500000/60
4546	Calibrating delay loop... 49.77 BogoMIPS
4547	...
4548	RAMDISK: Compressed image found at block 0
4549	VFS: Mounted root (ext2 filesystem).
4550
4551	bash#
4552
4553Boot Linux and pass a flat device tree:
4554-----------
4555
4556First, U-Boot must be compiled with the appropriate defines. See the section
4557titled "Linux Kernel Interface" above for a more in depth explanation. The
4558following is an example of how to start a kernel and pass an updated
4559flat device tree:
4560
4561=> print oftaddr
4562oftaddr=0x300000
4563=> print oft
4564oft=oftrees/mpc8540ads.dtb
4565=> tftp $oftaddr $oft
4566Speed: 1000, full duplex
4567Using TSEC0 device
4568TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4569Filename 'oftrees/mpc8540ads.dtb'.
4570Load address: 0x300000
4571Loading: #
4572done
4573Bytes transferred = 4106 (100a hex)
4574=> tftp $loadaddr $bootfile
4575Speed: 1000, full duplex
4576Using TSEC0 device
4577TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4578Filename 'uImage'.
4579Load address: 0x200000
4580Loading:############
4581done
4582Bytes transferred = 1029407 (fb51f hex)
4583=> print loadaddr
4584loadaddr=200000
4585=> print oftaddr
4586oftaddr=0x300000
4587=> bootm $loadaddr - $oftaddr
4588## Booting image at 00200000 ...
4589   Image Name:	 Linux-2.6.17-dirty
4590   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4591   Data Size:	 1029343 Bytes = 1005.2 kB
4592   Load Address: 00000000
4593   Entry Point:	 00000000
4594   Verifying Checksum ... OK
4595   Uncompressing Kernel Image ... OK
4596Booting using flat device tree at 0x300000
4597Using MPC85xx ADS machine description
4598Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4599[snip]
4600
4601
4602More About U-Boot Image Types:
4603------------------------------
4604
4605U-Boot supports the following image types:
4606
4607   "Standalone Programs" are directly runnable in the environment
4608	provided by U-Boot; it is expected that (if they behave
4609	well) you can continue to work in U-Boot after return from
4610	the Standalone Program.
4611   "OS Kernel Images" are usually images of some Embedded OS which
4612	will take over control completely. Usually these programs
4613	will install their own set of exception handlers, device
4614	drivers, set up the MMU, etc. - this means, that you cannot
4615	expect to re-enter U-Boot except by resetting the CPU.
4616   "RAMDisk Images" are more or less just data blocks, and their
4617	parameters (address, size) are passed to an OS kernel that is
4618	being started.
4619   "Multi-File Images" contain several images, typically an OS
4620	(Linux) kernel image and one or more data images like
4621	RAMDisks. This construct is useful for instance when you want
4622	to boot over the network using BOOTP etc., where the boot
4623	server provides just a single image file, but you want to get
4624	for instance an OS kernel and a RAMDisk image.
4625
4626	"Multi-File Images" start with a list of image sizes, each
4627	image size (in bytes) specified by an "uint32_t" in network
4628	byte order. This list is terminated by an "(uint32_t)0".
4629	Immediately after the terminating 0 follow the images, one by
4630	one, all aligned on "uint32_t" boundaries (size rounded up to
4631	a multiple of 4 bytes).
4632
4633   "Firmware Images" are binary images containing firmware (like
4634	U-Boot or FPGA images) which usually will be programmed to
4635	flash memory.
4636
4637   "Script files" are command sequences that will be executed by
4638	U-Boot's command interpreter; this feature is especially
4639	useful when you configure U-Boot to use a real shell (hush)
4640	as command interpreter.
4641
4642Booting the Linux zImage:
4643-------------------------
4644
4645On some platforms, it's possible to boot Linux zImage. This is done
4646using the "bootz" command. The syntax of "bootz" command is the same
4647as the syntax of "bootm" command.
4648
4649Note, defining the CONFIG_SUPPORT_INITRD_RAW allows user to supply
4650kernel with raw initrd images. The syntax is slightly different, the
4651address of the initrd must be augmented by it's size, in the following
4652format: "<initrd addres>:<initrd size>".
4653
4654
4655Standalone HOWTO:
4656=================
4657
4658One of the features of U-Boot is that you can dynamically load and
4659run "standalone" applications, which can use some resources of
4660U-Boot like console I/O functions or interrupt services.
4661
4662Two simple examples are included with the sources:
4663
4664"Hello World" Demo:
4665-------------------
4666
4667'examples/hello_world.c' contains a small "Hello World" Demo
4668application; it is automatically compiled when you build U-Boot.
4669It's configured to run at address 0x00040004, so you can play with it
4670like that:
4671
4672	=> loads
4673	## Ready for S-Record download ...
4674	~>examples/hello_world.srec
4675	1 2 3 4 5 6 7 8 9 10 11 ...
4676	[file transfer complete]
4677	[connected]
4678	## Start Addr = 0x00040004
4679
4680	=> go 40004 Hello World! This is a test.
4681	## Starting application at 0x00040004 ...
4682	Hello World
4683	argc = 7
4684	argv[0] = "40004"
4685	argv[1] = "Hello"
4686	argv[2] = "World!"
4687	argv[3] = "This"
4688	argv[4] = "is"
4689	argv[5] = "a"
4690	argv[6] = "test."
4691	argv[7] = "<NULL>"
4692	Hit any key to exit ...
4693
4694	## Application terminated, rc = 0x0
4695
4696Another example, which demonstrates how to register a CPM interrupt
4697handler with the U-Boot code, can be found in 'examples/timer.c'.
4698Here, a CPM timer is set up to generate an interrupt every second.
4699The interrupt service routine is trivial, just printing a '.'
4700character, but this is just a demo program. The application can be
4701controlled by the following keys:
4702
4703	? - print current values og the CPM Timer registers
4704	b - enable interrupts and start timer
4705	e - stop timer and disable interrupts
4706	q - quit application
4707
4708	=> loads
4709	## Ready for S-Record download ...
4710	~>examples/timer.srec
4711	1 2 3 4 5 6 7 8 9 10 11 ...
4712	[file transfer complete]
4713	[connected]
4714	## Start Addr = 0x00040004
4715
4716	=> go 40004
4717	## Starting application at 0x00040004 ...
4718	TIMERS=0xfff00980
4719	Using timer 1
4720	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4721
4722Hit 'b':
4723	[q, b, e, ?] Set interval 1000000 us
4724	Enabling timer
4725Hit '?':
4726	[q, b, e, ?] ........
4727	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4728Hit '?':
4729	[q, b, e, ?] .
4730	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4731Hit '?':
4732	[q, b, e, ?] .
4733	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4734Hit '?':
4735	[q, b, e, ?] .
4736	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4737Hit 'e':
4738	[q, b, e, ?] ...Stopping timer
4739Hit 'q':
4740	[q, b, e, ?] ## Application terminated, rc = 0x0
4741
4742
4743Minicom warning:
4744================
4745
4746Over time, many people have reported problems when trying to use the
4747"minicom" terminal emulation program for serial download. I (wd)
4748consider minicom to be broken, and recommend not to use it. Under
4749Unix, I recommend to use C-Kermit for general purpose use (and
4750especially for kermit binary protocol download ("loadb" command), and
4751use "cu" for S-Record download ("loads" command).  See
4752http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4753for help with kermit.
4754
4755
4756Nevertheless, if you absolutely want to use it try adding this
4757configuration to your "File transfer protocols" section:
4758
4759	   Name	   Program			Name U/D FullScr IO-Red. Multi
4760	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4761	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4762
4763
4764NetBSD Notes:
4765=============
4766
4767Starting at version 0.9.2, U-Boot supports NetBSD both as host
4768(build U-Boot) and target system (boots NetBSD/mpc8xx).
4769
4770Building requires a cross environment; it is known to work on
4771NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4772need gmake since the Makefiles are not compatible with BSD make).
4773Note that the cross-powerpc package does not install include files;
4774attempting to build U-Boot will fail because <machine/ansi.h> is
4775missing.  This file has to be installed and patched manually:
4776
4777	# cd /usr/pkg/cross/powerpc-netbsd/include
4778	# mkdir powerpc
4779	# ln -s powerpc machine
4780	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4781	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4782
4783Native builds *don't* work due to incompatibilities between native
4784and U-Boot include files.
4785
4786Booting assumes that (the first part of) the image booted is a
4787stage-2 loader which in turn loads and then invokes the kernel
4788proper. Loader sources will eventually appear in the NetBSD source
4789tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4790meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4791
4792
4793Implementation Internals:
4794=========================
4795
4796The following is not intended to be a complete description of every
4797implementation detail. However, it should help to understand the
4798inner workings of U-Boot and make it easier to port it to custom
4799hardware.
4800
4801
4802Initial Stack, Global Data:
4803---------------------------
4804
4805The implementation of U-Boot is complicated by the fact that U-Boot
4806starts running out of ROM (flash memory), usually without access to
4807system RAM (because the memory controller is not initialized yet).
4808This means that we don't have writable Data or BSS segments, and BSS
4809is not initialized as zero. To be able to get a C environment working
4810at all, we have to allocate at least a minimal stack. Implementation
4811options for this are defined and restricted by the CPU used: Some CPU
4812models provide on-chip memory (like the IMMR area on MPC8xx and
4813MPC826x processors), on others (parts of) the data cache can be
4814locked as (mis-) used as memory, etc.
4815
4816	Chris Hallinan posted a good summary of these issues to the
4817	U-Boot mailing list:
4818
4819	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4820	From: "Chris Hallinan" <clh@net1plus.com>
4821	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4822	...
4823
4824	Correct me if I'm wrong, folks, but the way I understand it
4825	is this: Using DCACHE as initial RAM for Stack, etc, does not
4826	require any physical RAM backing up the cache. The cleverness
4827	is that the cache is being used as a temporary supply of
4828	necessary storage before the SDRAM controller is setup. It's
4829	beyond the scope of this list to explain the details, but you
4830	can see how this works by studying the cache architecture and
4831	operation in the architecture and processor-specific manuals.
4832
4833	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4834	is another option for the system designer to use as an
4835	initial stack/RAM area prior to SDRAM being available. Either
4836	option should work for you. Using CS 4 should be fine if your
4837	board designers haven't used it for something that would
4838	cause you grief during the initial boot! It is frequently not
4839	used.
4840
4841	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4842	with your processor/board/system design. The default value
4843	you will find in any recent u-boot distribution in
4844	walnut.h should work for you. I'd set it to a value larger
4845	than your SDRAM module. If you have a 64MB SDRAM module, set
4846	it above 400_0000. Just make sure your board has no resources
4847	that are supposed to respond to that address! That code in
4848	start.S has been around a while and should work as is when
4849	you get the config right.
4850
4851	-Chris Hallinan
4852	DS4.COM, Inc.
4853
4854It is essential to remember this, since it has some impact on the C
4855code for the initialization procedures:
4856
4857* Initialized global data (data segment) is read-only. Do not attempt
4858  to write it.
4859
4860* Do not use any uninitialized global data (or implicitely initialized
4861  as zero data - BSS segment) at all - this is undefined, initiali-
4862  zation is performed later (when relocating to RAM).
4863
4864* Stack space is very limited. Avoid big data buffers or things like
4865  that.
4866
4867Having only the stack as writable memory limits means we cannot use
4868normal global data to share information beween the code. But it
4869turned out that the implementation of U-Boot can be greatly
4870simplified by making a global data structure (gd_t) available to all
4871functions. We could pass a pointer to this data as argument to _all_
4872functions, but this would bloat the code. Instead we use a feature of
4873the GCC compiler (Global Register Variables) to share the data: we
4874place a pointer (gd) to the global data into a register which we
4875reserve for this purpose.
4876
4877When choosing a register for such a purpose we are restricted by the
4878relevant  (E)ABI  specifications for the current architecture, and by
4879GCC's implementation.
4880
4881For PowerPC, the following registers have specific use:
4882	R1:	stack pointer
4883	R2:	reserved for system use
4884	R3-R4:	parameter passing and return values
4885	R5-R10: parameter passing
4886	R13:	small data area pointer
4887	R30:	GOT pointer
4888	R31:	frame pointer
4889
4890	(U-Boot also uses R12 as internal GOT pointer. r12
4891	is a volatile register so r12 needs to be reset when
4892	going back and forth between asm and C)
4893
4894    ==> U-Boot will use R2 to hold a pointer to the global data
4895
4896    Note: on PPC, we could use a static initializer (since the
4897    address of the global data structure is known at compile time),
4898    but it turned out that reserving a register results in somewhat
4899    smaller code - although the code savings are not that big (on
4900    average for all boards 752 bytes for the whole U-Boot image,
4901    624 text + 127 data).
4902
4903On Blackfin, the normal C ABI (except for P3) is followed as documented here:
4904	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
4905
4906    ==> U-Boot will use P3 to hold a pointer to the global data
4907
4908On ARM, the following registers are used:
4909
4910	R0:	function argument word/integer result
4911	R1-R3:	function argument word
4912	R9:	GOT pointer
4913	R10:	stack limit (used only if stack checking if enabled)
4914	R11:	argument (frame) pointer
4915	R12:	temporary workspace
4916	R13:	stack pointer
4917	R14:	link register
4918	R15:	program counter
4919
4920    ==> U-Boot will use R8 to hold a pointer to the global data
4921
4922On Nios II, the ABI is documented here:
4923	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4924
4925    ==> U-Boot will use gp to hold a pointer to the global data
4926
4927    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4928    to access small data sections, so gp is free.
4929
4930On NDS32, the following registers are used:
4931
4932	R0-R1:	argument/return
4933	R2-R5:	argument
4934	R15:	temporary register for assembler
4935	R16:	trampoline register
4936	R28:	frame pointer (FP)
4937	R29:	global pointer (GP)
4938	R30:	link register (LP)
4939	R31:	stack pointer (SP)
4940	PC:	program counter (PC)
4941
4942    ==> U-Boot will use R10 to hold a pointer to the global data
4943
4944NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4945or current versions of GCC may "optimize" the code too much.
4946
4947Memory Management:
4948------------------
4949
4950U-Boot runs in system state and uses physical addresses, i.e. the
4951MMU is not used either for address mapping nor for memory protection.
4952
4953The available memory is mapped to fixed addresses using the memory
4954controller. In this process, a contiguous block is formed for each
4955memory type (Flash, SDRAM, SRAM), even when it consists of several
4956physical memory banks.
4957
4958U-Boot is installed in the first 128 kB of the first Flash bank (on
4959TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4960booting and sizing and initializing DRAM, the code relocates itself
4961to the upper end of DRAM. Immediately below the U-Boot code some
4962memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4963configuration setting]. Below that, a structure with global Board
4964Info data is placed, followed by the stack (growing downward).
4965
4966Additionally, some exception handler code is copied to the low 8 kB
4967of DRAM (0x00000000 ... 0x00001FFF).
4968
4969So a typical memory configuration with 16 MB of DRAM could look like
4970this:
4971
4972	0x0000 0000	Exception Vector code
4973	      :
4974	0x0000 1FFF
4975	0x0000 2000	Free for Application Use
4976	      :
4977	      :
4978
4979	      :
4980	      :
4981	0x00FB FF20	Monitor Stack (Growing downward)
4982	0x00FB FFAC	Board Info Data and permanent copy of global data
4983	0x00FC 0000	Malloc Arena
4984	      :
4985	0x00FD FFFF
4986	0x00FE 0000	RAM Copy of Monitor Code
4987	...		eventually: LCD or video framebuffer
4988	...		eventually: pRAM (Protected RAM - unchanged by reset)
4989	0x00FF FFFF	[End of RAM]
4990
4991
4992System Initialization:
4993----------------------
4994
4995In the reset configuration, U-Boot starts at the reset entry point
4996(on most PowerPC systems at address 0x00000100). Because of the reset
4997configuration for CS0# this is a mirror of the onboard Flash memory.
4998To be able to re-map memory U-Boot then jumps to its link address.
4999To be able to implement the initialization code in C, a (small!)
5000initial stack is set up in the internal Dual Ported RAM (in case CPUs
5001which provide such a feature like MPC8xx or MPC8260), or in a locked
5002part of the data cache. After that, U-Boot initializes the CPU core,
5003the caches and the SIU.
5004
5005Next, all (potentially) available memory banks are mapped using a
5006preliminary mapping. For example, we put them on 512 MB boundaries
5007(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5008on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5009programmed for SDRAM access. Using the temporary configuration, a
5010simple memory test is run that determines the size of the SDRAM
5011banks.
5012
5013When there is more than one SDRAM bank, and the banks are of
5014different size, the largest is mapped first. For equal size, the first
5015bank (CS2#) is mapped first. The first mapping is always for address
50160x00000000, with any additional banks following immediately to create
5017contiguous memory starting from 0.
5018
5019Then, the monitor installs itself at the upper end of the SDRAM area
5020and allocates memory for use by malloc() and for the global Board
5021Info data; also, the exception vector code is copied to the low RAM
5022pages, and the final stack is set up.
5023
5024Only after this relocation will you have a "normal" C environment;
5025until that you are restricted in several ways, mostly because you are
5026running from ROM, and because the code will have to be relocated to a
5027new address in RAM.
5028
5029
5030U-Boot Porting Guide:
5031----------------------
5032
5033[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5034list, October 2002]
5035
5036
5037int main(int argc, char *argv[])
5038{
5039	sighandler_t no_more_time;
5040
5041	signal(SIGALRM, no_more_time);
5042	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5043
5044	if (available_money > available_manpower) {
5045		Pay consultant to port U-Boot;
5046		return 0;
5047	}
5048
5049	Download latest U-Boot source;
5050
5051	Subscribe to u-boot mailing list;
5052
5053	if (clueless)
5054		email("Hi, I am new to U-Boot, how do I get started?");
5055
5056	while (learning) {
5057		Read the README file in the top level directory;
5058		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5059		Read applicable doc/*.README;
5060		Read the source, Luke;
5061		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5062	}
5063
5064	if (available_money > toLocalCurrency ($2500))
5065		Buy a BDI3000;
5066	else
5067		Add a lot of aggravation and time;
5068
5069	if (a similar board exists) {	/* hopefully... */
5070		cp -a board/<similar> board/<myboard>
5071		cp include/configs/<similar>.h include/configs/<myboard>.h
5072	} else {
5073		Create your own board support subdirectory;
5074		Create your own board include/configs/<myboard>.h file;
5075	}
5076	Edit new board/<myboard> files
5077	Edit new include/configs/<myboard>.h
5078
5079	while (!accepted) {
5080		while (!running) {
5081			do {
5082				Add / modify source code;
5083			} until (compiles);
5084			Debug;
5085			if (clueless)
5086				email("Hi, I am having problems...");
5087		}
5088		Send patch file to the U-Boot email list;
5089		if (reasonable critiques)
5090			Incorporate improvements from email list code review;
5091		else
5092			Defend code as written;
5093	}
5094
5095	return 0;
5096}
5097
5098void no_more_time (int sig)
5099{
5100      hire_a_guru();
5101}
5102
5103
5104Coding Standards:
5105-----------------
5106
5107All contributions to U-Boot should conform to the Linux kernel
5108coding style; see the file "Documentation/CodingStyle" and the script
5109"scripts/Lindent" in your Linux kernel source directory.
5110
5111Source files originating from a different project (for example the
5112MTD subsystem) are generally exempt from these guidelines and are not
5113reformated to ease subsequent migration to newer versions of those
5114sources.
5115
5116Please note that U-Boot is implemented in C (and to some small parts in
5117Assembler); no C++ is used, so please do not use C++ style comments (//)
5118in your code.
5119
5120Please also stick to the following formatting rules:
5121- remove any trailing white space
5122- use TAB characters for indentation and vertical alignment, not spaces
5123- make sure NOT to use DOS '\r\n' line feeds
5124- do not add more than 2 consecutive empty lines to source files
5125- do not add trailing empty lines to source files
5126
5127Submissions which do not conform to the standards may be returned
5128with a request to reformat the changes.
5129
5130
5131Submitting Patches:
5132-------------------
5133
5134Since the number of patches for U-Boot is growing, we need to
5135establish some rules. Submissions which do not conform to these rules
5136may be rejected, even when they contain important and valuable stuff.
5137
5138Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5139
5140Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5141see http://lists.denx.de/mailman/listinfo/u-boot
5142
5143When you send a patch, please include the following information with
5144it:
5145
5146* For bug fixes: a description of the bug and how your patch fixes
5147  this bug. Please try to include a way of demonstrating that the
5148  patch actually fixes something.
5149
5150* For new features: a description of the feature and your
5151  implementation.
5152
5153* A CHANGELOG entry as plaintext (separate from the patch)
5154
5155* For major contributions, your entry to the CREDITS file
5156
5157* When you add support for a new board, don't forget to add this
5158  board to the MAINTAINERS file, too.
5159
5160* If your patch adds new configuration options, don't forget to
5161  document these in the README file.
5162
5163* The patch itself. If you are using git (which is *strongly*
5164  recommended) you can easily generate the patch using the
5165  "git format-patch". If you then use "git send-email" to send it to
5166  the U-Boot mailing list, you will avoid most of the common problems
5167  with some other mail clients.
5168
5169  If you cannot use git, use "diff -purN OLD NEW". If your version of
5170  diff does not support these options, then get the latest version of
5171  GNU diff.
5172
5173  The current directory when running this command shall be the parent
5174  directory of the U-Boot source tree (i. e. please make sure that
5175  your patch includes sufficient directory information for the
5176  affected files).
5177
5178  We prefer patches as plain text. MIME attachments are discouraged,
5179  and compressed attachments must not be used.
5180
5181* If one logical set of modifications affects or creates several
5182  files, all these changes shall be submitted in a SINGLE patch file.
5183
5184* Changesets that contain different, unrelated modifications shall be
5185  submitted as SEPARATE patches, one patch per changeset.
5186
5187
5188Notes:
5189
5190* Before sending the patch, run the MAKEALL script on your patched
5191  source tree and make sure that no errors or warnings are reported
5192  for any of the boards.
5193
5194* Keep your modifications to the necessary minimum: A patch
5195  containing several unrelated changes or arbitrary reformats will be
5196  returned with a request to re-formatting / split it.
5197
5198* If you modify existing code, make sure that your new code does not
5199  add to the memory footprint of the code ;-) Small is beautiful!
5200  When adding new features, these should compile conditionally only
5201  (using #ifdef), and the resulting code with the new feature
5202  disabled must not need more memory than the old code without your
5203  modification.
5204
5205* Remember that there is a size limit of 100 kB per message on the
5206  u-boot mailing list. Bigger patches will be moderated. If they are
5207  reasonable and not too big, they will be acknowledged. But patches
5208  bigger than the size limit should be avoided.
5209