xref: /openbmc/u-boot/README (revision 8faefadb7305b95d02df38bd2ea61429d59483e5)
1#
2# (C) Copyright 2000 - 2012
3# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4#
5# See file CREDITS for list of people who contributed to this
6# project.
7#
8# This program is free software; you can redistribute it and/or
9# modify it under the terms of the GNU General Public License as
10# published by the Free Software Foundation; either version 2 of
11# the License, or (at your option) any later version.
12#
13# This program is distributed in the hope that it will be useful,
14# but WITHOUT ANY WARRANTY; without even the implied warranty of
15# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the
16# GNU General Public License for more details.
17#
18# You should have received a copy of the GNU General Public License
19# along with this program; if not, write to the Free Software
20# Foundation, Inc., 59 Temple Place, Suite 330, Boston,
21# MA 02111-1307 USA
22#
23
24Summary:
25========
26
27This directory contains the source code for U-Boot, a boot loader for
28Embedded boards based on PowerPC, ARM, MIPS and several other
29processors, which can be installed in a boot ROM and used to
30initialize and test the hardware or to download and run application
31code.
32
33The development of U-Boot is closely related to Linux: some parts of
34the source code originate in the Linux source tree, we have some
35header files in common, and special provision has been made to
36support booting of Linux images.
37
38Some attention has been paid to make this software easily
39configurable and extendable. For instance, all monitor commands are
40implemented with the same call interface, so that it's very easy to
41add new commands. Also, instead of permanently adding rarely used
42code (for instance hardware test utilities) to the monitor, you can
43load and run it dynamically.
44
45
46Status:
47=======
48
49In general, all boards for which a configuration option exists in the
50Makefile have been tested to some extent and can be considered
51"working". In fact, many of them are used in production systems.
52
53In case of problems see the CHANGELOG and CREDITS files to find out
54who contributed the specific port. The MAINTAINERS file lists board
55maintainers.
56
57Note: There is no CHANGELOG file in the actual U-Boot source tree;
58it can be created dynamically from the Git log using:
59
60	make CHANGELOG
61
62
63Where to get help:
64==================
65
66In case you have questions about, problems with or contributions for
67U-Boot you should send a message to the U-Boot mailing list at
68<u-boot@lists.denx.de>. There is also an archive of previous traffic
69on the mailing list - please search the archive before asking FAQ's.
70Please see http://lists.denx.de/pipermail/u-boot and
71http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
72
73
74Where to get source code:
75=========================
76
77The U-Boot source code is maintained in the git repository at
78git://www.denx.de/git/u-boot.git ; you can browse it online at
79http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
80
81The "snapshot" links on this page allow you to download tarballs of
82any version you might be interested in. Official releases are also
83available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
84directory.
85
86Pre-built (and tested) images are available from
87ftp://ftp.denx.de/pub/u-boot/images/
88
89
90Where we come from:
91===================
92
93- start from 8xxrom sources
94- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
95- clean up code
96- make it easier to add custom boards
97- make it possible to add other [PowerPC] CPUs
98- extend functions, especially:
99  * Provide extended interface to Linux boot loader
100  * S-Record download
101  * network boot
102  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
103- create ARMBoot project (http://sourceforge.net/projects/armboot)
104- add other CPU families (starting with ARM)
105- create U-Boot project (http://sourceforge.net/projects/u-boot)
106- current project page: see http://www.denx.de/wiki/U-Boot
107
108
109Names and Spelling:
110===================
111
112The "official" name of this project is "Das U-Boot". The spelling
113"U-Boot" shall be used in all written text (documentation, comments
114in source files etc.). Example:
115
116	This is the README file for the U-Boot project.
117
118File names etc. shall be based on the string "u-boot". Examples:
119
120	include/asm-ppc/u-boot.h
121
122	#include <asm/u-boot.h>
123
124Variable names, preprocessor constants etc. shall be either based on
125the string "u_boot" or on "U_BOOT". Example:
126
127	U_BOOT_VERSION		u_boot_logo
128	IH_OS_U_BOOT		u_boot_hush_start
129
130
131Versioning:
132===========
133
134Starting with the release in October 2008, the names of the releases
135were changed from numerical release numbers without deeper meaning
136into a time stamp based numbering. Regular releases are identified by
137names consisting of the calendar year and month of the release date.
138Additional fields (if present) indicate release candidates or bug fix
139releases in "stable" maintenance trees.
140
141Examples:
142	U-Boot v2009.11	    - Release November 2009
143	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
144	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
145
146
147Directory Hierarchy:
148====================
149
150/arch			Architecture specific files
151  /arm			Files generic to ARM architecture
152    /cpu		CPU specific files
153      /arm720t		Files specific to ARM 720 CPUs
154      /arm920t		Files specific to ARM 920 CPUs
155	/at91		Files specific to Atmel AT91RM9200 CPU
156	/imx		Files specific to Freescale MC9328 i.MX CPUs
157	/s3c24x0	Files specific to Samsung S3C24X0 CPUs
158      /arm925t		Files specific to ARM 925 CPUs
159      /arm926ejs	Files specific to ARM 926 CPUs
160      /arm1136		Files specific to ARM 1136 CPUs
161      /ixp		Files specific to Intel XScale IXP CPUs
162      /pxa		Files specific to Intel XScale PXA CPUs
163      /s3c44b0		Files specific to Samsung S3C44B0 CPUs
164      /sa1100		Files specific to Intel StrongARM SA1100 CPUs
165    /lib		Architecture specific library files
166  /avr32		Files generic to AVR32 architecture
167    /cpu		CPU specific files
168    /lib		Architecture specific library files
169  /blackfin		Files generic to Analog Devices Blackfin architecture
170    /cpu		CPU specific files
171    /lib		Architecture specific library files
172  /x86			Files generic to x86 architecture
173    /cpu		CPU specific files
174    /lib		Architecture specific library files
175  /m68k			Files generic to m68k architecture
176    /cpu		CPU specific files
177      /mcf52x2		Files specific to Freescale ColdFire MCF52x2 CPUs
178      /mcf5227x		Files specific to Freescale ColdFire MCF5227x CPUs
179      /mcf532x		Files specific to Freescale ColdFire MCF5329 CPUs
180      /mcf5445x		Files specific to Freescale ColdFire MCF5445x CPUs
181      /mcf547x_8x	Files specific to Freescale ColdFire MCF547x_8x CPUs
182    /lib		Architecture specific library files
183  /microblaze		Files generic to microblaze architecture
184    /cpu		CPU specific files
185    /lib		Architecture specific library files
186  /mips			Files generic to MIPS architecture
187    /cpu		CPU specific files
188      /mips32		Files specific to MIPS32 CPUs
189      /xburst		Files specific to Ingenic XBurst CPUs
190    /lib		Architecture specific library files
191  /nds32		Files generic to NDS32 architecture
192    /cpu		CPU specific files
193      /n1213		Files specific to Andes Technology N1213 CPUs
194    /lib		Architecture specific library files
195  /nios2		Files generic to Altera NIOS2 architecture
196    /cpu		CPU specific files
197    /lib		Architecture specific library files
198  /powerpc		Files generic to PowerPC architecture
199    /cpu		CPU specific files
200      /74xx_7xx		Files specific to Freescale MPC74xx and 7xx CPUs
201      /mpc5xx		Files specific to Freescale MPC5xx CPUs
202      /mpc5xxx		Files specific to Freescale MPC5xxx CPUs
203      /mpc8xx		Files specific to Freescale MPC8xx CPUs
204      /mpc8220		Files specific to Freescale MPC8220 CPUs
205      /mpc824x		Files specific to Freescale MPC824x CPUs
206      /mpc8260		Files specific to Freescale MPC8260 CPUs
207      /mpc85xx		Files specific to Freescale MPC85xx CPUs
208      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
209    /lib		Architecture specific library files
210  /sh			Files generic to SH architecture
211    /cpu		CPU specific files
212      /sh2		Files specific to sh2 CPUs
213      /sh3		Files specific to sh3 CPUs
214      /sh4		Files specific to sh4 CPUs
215    /lib		Architecture specific library files
216  /sparc		Files generic to SPARC architecture
217    /cpu		CPU specific files
218      /leon2		Files specific to Gaisler LEON2 SPARC CPU
219      /leon3		Files specific to Gaisler LEON3 SPARC CPU
220    /lib		Architecture specific library files
221/api			Machine/arch independent API for external apps
222/board			Board dependent files
223/common			Misc architecture independent functions
224/disk			Code for disk drive partition handling
225/doc			Documentation (don't expect too much)
226/drivers		Commonly used device drivers
227/examples		Example code for standalone applications, etc.
228/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
229/include		Header Files
230/lib			Files generic to all architectures
231  /libfdt		Library files to support flattened device trees
232  /lzma			Library files to support LZMA decompression
233  /lzo			Library files to support LZO decompression
234/net			Networking code
235/post			Power On Self Test
236/rtc			Real Time Clock drivers
237/tools			Tools to build S-Record or U-Boot images, etc.
238
239Software Configuration:
240=======================
241
242Configuration is usually done using C preprocessor defines; the
243rationale behind that is to avoid dead code whenever possible.
244
245There are two classes of configuration variables:
246
247* Configuration _OPTIONS_:
248  These are selectable by the user and have names beginning with
249  "CONFIG_".
250
251* Configuration _SETTINGS_:
252  These depend on the hardware etc. and should not be meddled with if
253  you don't know what you're doing; they have names beginning with
254  "CONFIG_SYS_".
255
256Later we will add a configuration tool - probably similar to or even
257identical to what's used for the Linux kernel. Right now, we have to
258do the configuration by hand, which means creating some symbolic
259links and editing some configuration files. We use the TQM8xxL boards
260as an example here.
261
262
263Selection of Processor Architecture and Board Type:
264---------------------------------------------------
265
266For all supported boards there are ready-to-use default
267configurations available; just type "make <board_name>_config".
268
269Example: For a TQM823L module type:
270
271	cd u-boot
272	make TQM823L_config
273
274For the Cogent platform, you need to specify the CPU type as well;
275e.g. "make cogent_mpc8xx_config". And also configure the cogent
276directory according to the instructions in cogent/README.
277
278
279Configuration Options:
280----------------------
281
282Configuration depends on the combination of board and CPU type; all
283such information is kept in a configuration file
284"include/configs/<board_name>.h".
285
286Example: For a TQM823L module, all configuration settings are in
287"include/configs/TQM823L.h".
288
289
290Many of the options are named exactly as the corresponding Linux
291kernel configuration options. The intention is to make it easier to
292build a config tool - later.
293
294
295The following options need to be configured:
296
297- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
298
299- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
300
301- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
302		Define exactly one, e.g. CONFIG_ATSTK1002
303
304- CPU Module Type: (if CONFIG_COGENT is defined)
305		Define exactly one of
306		CONFIG_CMA286_60_OLD
307--- FIXME --- not tested yet:
308		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
309		CONFIG_CMA287_23, CONFIG_CMA287_50
310
311- Motherboard Type: (if CONFIG_COGENT is defined)
312		Define exactly one of
313		CONFIG_CMA101, CONFIG_CMA102
314
315- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
316		Define one or more of
317		CONFIG_CMA302
318
319- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
320		Define one or more of
321		CONFIG_LCD_HEARTBEAT	- update a character position on
322					  the LCD display every second with
323					  a "rotator" |\-/|\-/
324
325- Board flavour: (if CONFIG_MPC8260ADS is defined)
326		CONFIG_ADSTYPE
327		Possible values are:
328			CONFIG_SYS_8260ADS	- original MPC8260ADS
329			CONFIG_SYS_8266ADS	- MPC8266ADS
330			CONFIG_SYS_PQ2FADS	- PQ2FADS-ZU or PQ2FADS-VR
331			CONFIG_SYS_8272ADS	- MPC8272ADS
332
333- Marvell Family Member
334		CONFIG_SYS_MVFS		- define it if you want to enable
335					  multiple fs option at one time
336					  for marvell soc family
337
338- MPC824X Family Member (if CONFIG_MPC824X is defined)
339		Define exactly one of
340		CONFIG_MPC8240, CONFIG_MPC8245
341
342- 8xx CPU Options: (if using an MPC8xx CPU)
343		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
344					  get_gclk_freq() cannot work
345					  e.g. if there is no 32KHz
346					  reference PIT/RTC clock
347		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
348					  or XTAL/EXTAL)
349
350- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
351		CONFIG_SYS_8xx_CPUCLK_MIN
352		CONFIG_SYS_8xx_CPUCLK_MAX
353		CONFIG_8xx_CPUCLK_DEFAULT
354			See doc/README.MPC866
355
356		CONFIG_SYS_MEASURE_CPUCLK
357
358		Define this to measure the actual CPU clock instead
359		of relying on the correctness of the configured
360		values. Mostly useful for board bringup to make sure
361		the PLL is locked at the intended frequency. Note
362		that this requires a (stable) reference clock (32 kHz
363		RTC clock or CONFIG_SYS_8XX_XIN)
364
365		CONFIG_SYS_DELAYED_ICACHE
366
367		Define this option if you want to enable the
368		ICache only when Code runs from RAM.
369
370- 85xx CPU Options:
371		CONFIG_SYS_PPC64
372
373		Specifies that the core is a 64-bit PowerPC implementation (implements
374		the "64" category of the Power ISA). This is necessary for ePAPR
375		compliance, among other possible reasons.
376
377		CONFIG_SYS_FSL_TBCLK_DIV
378
379		Defines the core time base clock divider ratio compared to the
380		system clock.  On most PQ3 devices this is 8, on newer QorIQ
381		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
382
383		CONFIG_SYS_FSL_PCIE_COMPAT
384
385		Defines the string to utilize when trying to match PCIe device
386		tree nodes for the given platform.
387
388		CONFIG_SYS_PPC_E500_DEBUG_TLB
389
390		Enables a temporary TLB entry to be used during boot to work
391		around limitations in e500v1 and e500v2 external debugger
392		support. This reduces the portions of the boot code where
393		breakpoints and single stepping do not work.  The value of this
394		symbol should be set to the TLB1 entry to be used for this
395		purpose.
396
397		CONFIG_SYS_FSL_ERRATUM_A004510
398
399		Enables a workaround for erratum A004510.  If set,
400		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
401		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
402
403		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
404		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
405
406		Defines one or two SoC revisions (low 8 bits of SVR)
407		for which the A004510 workaround should be applied.
408
409		The rest of SVR is either not relevant to the decision
410		of whether the erratum is present (e.g. p2040 versus
411		p2041) or is implied by the build target, which controls
412		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
413
414		See Freescale App Note 4493 for more information about
415		this erratum.
416
417		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
418
419		This is the value to write into CCSR offset 0x18600
420		according to the A004510 workaround.
421
422- Generic CPU options:
423		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
424
425		Defines the endianess of the CPU. Implementation of those
426		values is arch specific.
427
428- Intel Monahans options:
429		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
430
431		Defines the Monahans run mode to oscillator
432		ratio. Valid values are 8, 16, 24, 31. The core
433		frequency is this value multiplied by 13 MHz.
434
435		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
436
437		Defines the Monahans turbo mode to oscillator
438		ratio. Valid values are 1 (default if undefined) and
439		2. The core frequency as calculated above is multiplied
440		by this value.
441
442- MIPS CPU options:
443		CONFIG_SYS_INIT_SP_OFFSET
444
445		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
446		pointer. This is needed for the temporary stack before
447		relocation.
448
449		CONFIG_SYS_MIPS_CACHE_MODE
450
451		Cache operation mode for the MIPS CPU.
452		See also arch/mips/include/asm/mipsregs.h.
453		Possible values are:
454			CONF_CM_CACHABLE_NO_WA
455			CONF_CM_CACHABLE_WA
456			CONF_CM_UNCACHED
457			CONF_CM_CACHABLE_NONCOHERENT
458			CONF_CM_CACHABLE_CE
459			CONF_CM_CACHABLE_COW
460			CONF_CM_CACHABLE_CUW
461			CONF_CM_CACHABLE_ACCELERATED
462
463		CONFIG_SYS_XWAY_EBU_BOOTCFG
464
465		Special option for Lantiq XWAY SoCs for booting from NOR flash.
466		See also arch/mips/cpu/mips32/start.S.
467
468		CONFIG_XWAY_SWAP_BYTES
469
470		Enable compilation of tools/xway-swap-bytes needed for Lantiq
471		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
472		be swapped if a flash programmer is used.
473
474- ARM options:
475		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
476
477		Select high exception vectors of the ARM core, e.g., do not
478		clear the V bit of the c1 register of CP15.
479
480		CONFIG_SYS_THUMB_BUILD
481
482		Use this flag to build U-Boot using the Thumb instruction
483		set for ARM architectures. Thumb instruction set provides
484		better code density. For ARM architectures that support
485		Thumb2 this flag will result in Thumb2 code generated by
486		GCC.
487
488		CONFIG_ARM_ERRATA_716044
489		CONFIG_ARM_ERRATA_742230
490		CONFIG_ARM_ERRATA_743622
491		CONFIG_ARM_ERRATA_751472
492
493		If set, the workarounds for these ARM errata are applied early
494		during U-Boot startup. Note that these options force the
495		workarounds to be applied; no CPU-type/version detection
496		exists, unlike the similar options in the Linux kernel. Do not
497		set these options unless they apply!
498
499- CPU timer options:
500		CONFIG_SYS_HZ
501
502		The frequency of the timer returned by get_timer().
503		get_timer() must operate in milliseconds and this CONFIG
504		option must be set to 1000.
505
506- Linux Kernel Interface:
507		CONFIG_CLOCKS_IN_MHZ
508
509		U-Boot stores all clock information in Hz
510		internally. For binary compatibility with older Linux
511		kernels (which expect the clocks passed in the
512		bd_info data to be in MHz) the environment variable
513		"clocks_in_mhz" can be defined so that U-Boot
514		converts clock data to MHZ before passing it to the
515		Linux kernel.
516		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
517		"clocks_in_mhz=1" is automatically included in the
518		default environment.
519
520		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
521
522		When transferring memsize parameter to linux, some versions
523		expect it to be in bytes, others in MB.
524		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
525
526		CONFIG_OF_LIBFDT
527
528		New kernel versions are expecting firmware settings to be
529		passed using flattened device trees (based on open firmware
530		concepts).
531
532		CONFIG_OF_LIBFDT
533		 * New libfdt-based support
534		 * Adds the "fdt" command
535		 * The bootm command automatically updates the fdt
536
537		OF_CPU - The proper name of the cpus node (only required for
538			MPC512X and MPC5xxx based boards).
539		OF_SOC - The proper name of the soc node (only required for
540			MPC512X and MPC5xxx based boards).
541		OF_TBCLK - The timebase frequency.
542		OF_STDOUT_PATH - The path to the console device
543
544		boards with QUICC Engines require OF_QE to set UCC MAC
545		addresses
546
547		CONFIG_OF_BOARD_SETUP
548
549		Board code has addition modification that it wants to make
550		to the flat device tree before handing it off to the kernel
551
552		CONFIG_OF_BOOT_CPU
553
554		This define fills in the correct boot CPU in the boot
555		param header, the default value is zero if undefined.
556
557		CONFIG_OF_IDE_FIXUP
558
559		U-Boot can detect if an IDE device is present or not.
560		If not, and this new config option is activated, U-Boot
561		removes the ATA node from the DTS before booting Linux,
562		so the Linux IDE driver does not probe the device and
563		crash. This is needed for buggy hardware (uc101) where
564		no pull down resistor is connected to the signal IDE5V_DD7.
565
566		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
567
568		This setting is mandatory for all boards that have only one
569		machine type and must be used to specify the machine type
570		number as it appears in the ARM machine registry
571		(see http://www.arm.linux.org.uk/developer/machines/).
572		Only boards that have multiple machine types supported
573		in a single configuration file and the machine type is
574		runtime discoverable, do not have to use this setting.
575
576- vxWorks boot parameters:
577
578		bootvx constructs a valid bootline using the following
579		environments variables: bootfile, ipaddr, serverip, hostname.
580		It loads the vxWorks image pointed bootfile.
581
582		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
583		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
584		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
585		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
586
587		CONFIG_SYS_VXWORKS_ADD_PARAMS
588
589		Add it at the end of the bootline. E.g "u=username pw=secret"
590
591		Note: If a "bootargs" environment is defined, it will overwride
592		the defaults discussed just above.
593
594- Cache Configuration:
595		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
596		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
597		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
598
599- Cache Configuration for ARM:
600		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
601				      controller
602		CONFIG_SYS_PL310_BASE - Physical base address of PL310
603					controller register space
604
605- Serial Ports:
606		CONFIG_PL010_SERIAL
607
608		Define this if you want support for Amba PrimeCell PL010 UARTs.
609
610		CONFIG_PL011_SERIAL
611
612		Define this if you want support for Amba PrimeCell PL011 UARTs.
613
614		CONFIG_PL011_CLOCK
615
616		If you have Amba PrimeCell PL011 UARTs, set this variable to
617		the clock speed of the UARTs.
618
619		CONFIG_PL01x_PORTS
620
621		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
622		define this to a list of base addresses for each (supported)
623		port. See e.g. include/configs/versatile.h
624
625		CONFIG_PL011_SERIAL_RLCR
626
627		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
628		have separate receive and transmit line control registers.  Set
629		this variable to initialize the extra register.
630
631		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
632
633		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
634		boot loader that has already initialized the UART.  Define this
635		variable to flush the UART at init time.
636
637		CONFIG_SYS_NS16550_BROKEN_TEMT
638
639		16550 UART set the Transmitter Empty (TEMT) Bit when all output
640		has finished and the transmitter is totally empty. U-Boot waits
641		for this bit to be set to initialize the serial console. On some
642		broken platforms this bit is not set in SPL making U-Boot to
643		hang while waiting for TEMT. Define this option to avoid it.
644
645
646- Console Interface:
647		Depending on board, define exactly one serial port
648		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
649		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
650		console by defining CONFIG_8xx_CONS_NONE
651
652		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
653		port routines must be defined elsewhere
654		(i.e. serial_init(), serial_getc(), ...)
655
656		CONFIG_CFB_CONSOLE
657		Enables console device for a color framebuffer. Needs following
658		defines (cf. smiLynxEM, i8042)
659			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
660						(default big endian)
661			VIDEO_HW_RECTFILL	graphic chip supports
662						rectangle fill
663						(cf. smiLynxEM)
664			VIDEO_HW_BITBLT		graphic chip supports
665						bit-blit (cf. smiLynxEM)
666			VIDEO_VISIBLE_COLS	visible pixel columns
667						(cols=pitch)
668			VIDEO_VISIBLE_ROWS	visible pixel rows
669			VIDEO_PIXEL_SIZE	bytes per pixel
670			VIDEO_DATA_FORMAT	graphic data format
671						(0-5, cf. cfb_console.c)
672			VIDEO_FB_ADRS		framebuffer address
673			VIDEO_KBD_INIT_FCT	keyboard int fct
674						(i.e. i8042_kbd_init())
675			VIDEO_TSTC_FCT		test char fct
676						(i.e. i8042_tstc)
677			VIDEO_GETC_FCT		get char fct
678						(i.e. i8042_getc)
679			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
680						(requires blink timer
681						cf. i8042.c)
682			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
683			CONFIG_CONSOLE_TIME	display time/date info in
684						upper right corner
685						(requires CONFIG_CMD_DATE)
686			CONFIG_VIDEO_LOGO	display Linux logo in
687						upper left corner
688			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
689						linux_logo.h for logo.
690						Requires CONFIG_VIDEO_LOGO
691			CONFIG_CONSOLE_EXTRA_INFO
692						additional board info beside
693						the logo
694
695		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
696		a limited number of ANSI escape sequences (cursor control,
697		erase functions and limited graphics rendition control).
698
699		When CONFIG_CFB_CONSOLE is defined, video console is
700		default i/o. Serial console can be forced with
701		environment 'console=serial'.
702
703		When CONFIG_SILENT_CONSOLE is defined, all console
704		messages (by U-Boot and Linux!) can be silenced with
705		the "silent" environment variable. See
706		doc/README.silent for more information.
707
708- Console Baudrate:
709		CONFIG_BAUDRATE - in bps
710		Select one of the baudrates listed in
711		CONFIG_SYS_BAUDRATE_TABLE, see below.
712		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
713
714- Console Rx buffer length
715		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
716		the maximum receive buffer length for the SMC.
717		This option is actual only for 82xx and 8xx possible.
718		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
719		must be defined, to setup the maximum idle timeout for
720		the SMC.
721
722- Pre-Console Buffer:
723		Prior to the console being initialised (i.e. serial UART
724		initialised etc) all console output is silently discarded.
725		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
726		buffer any console messages prior to the console being
727		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
728		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
729		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
730		bytes are output before the console is initialised, the
731		earlier bytes are discarded.
732
733		'Sane' compilers will generate smaller code if
734		CONFIG_PRE_CON_BUF_SZ is a power of 2
735
736- Safe printf() functions
737		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
738		the printf() functions. These are defined in
739		include/vsprintf.h and include snprintf(), vsnprintf() and
740		so on. Code size increase is approximately 300-500 bytes.
741		If this option is not given then these functions will
742		silently discard their buffer size argument - this means
743		you are not getting any overflow checking in this case.
744
745- Boot Delay:	CONFIG_BOOTDELAY - in seconds
746		Delay before automatically booting the default image;
747		set to -1 to disable autoboot.
748		set to -2 to autoboot with no delay and not check for abort
749		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
750
751		See doc/README.autoboot for these options that
752		work with CONFIG_BOOTDELAY. None are required.
753		CONFIG_BOOT_RETRY_TIME
754		CONFIG_BOOT_RETRY_MIN
755		CONFIG_AUTOBOOT_KEYED
756		CONFIG_AUTOBOOT_PROMPT
757		CONFIG_AUTOBOOT_DELAY_STR
758		CONFIG_AUTOBOOT_STOP_STR
759		CONFIG_AUTOBOOT_DELAY_STR2
760		CONFIG_AUTOBOOT_STOP_STR2
761		CONFIG_ZERO_BOOTDELAY_CHECK
762		CONFIG_RESET_TO_RETRY
763
764- Autoboot Command:
765		CONFIG_BOOTCOMMAND
766		Only needed when CONFIG_BOOTDELAY is enabled;
767		define a command string that is automatically executed
768		when no character is read on the console interface
769		within "Boot Delay" after reset.
770
771		CONFIG_BOOTARGS
772		This can be used to pass arguments to the bootm
773		command. The value of CONFIG_BOOTARGS goes into the
774		environment value "bootargs".
775
776		CONFIG_RAMBOOT and CONFIG_NFSBOOT
777		The value of these goes into the environment as
778		"ramboot" and "nfsboot" respectively, and can be used
779		as a convenience, when switching between booting from
780		RAM and NFS.
781
782- Pre-Boot Commands:
783		CONFIG_PREBOOT
784
785		When this option is #defined, the existence of the
786		environment variable "preboot" will be checked
787		immediately before starting the CONFIG_BOOTDELAY
788		countdown and/or running the auto-boot command resp.
789		entering interactive mode.
790
791		This feature is especially useful when "preboot" is
792		automatically generated or modified. For an example
793		see the LWMON board specific code: here "preboot" is
794		modified when the user holds down a certain
795		combination of keys on the (special) keyboard when
796		booting the systems
797
798- Serial Download Echo Mode:
799		CONFIG_LOADS_ECHO
800		If defined to 1, all characters received during a
801		serial download (using the "loads" command) are
802		echoed back. This might be needed by some terminal
803		emulations (like "cu"), but may as well just take
804		time on others. This setting #define's the initial
805		value of the "loads_echo" environment variable.
806
807- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
808		CONFIG_KGDB_BAUDRATE
809		Select one of the baudrates listed in
810		CONFIG_SYS_BAUDRATE_TABLE, see below.
811
812- Monitor Functions:
813		Monitor commands can be included or excluded
814		from the build by using the #include files
815		<config_cmd_all.h> and #undef'ing unwanted
816		commands, or using <config_cmd_default.h>
817		and augmenting with additional #define's
818		for wanted commands.
819
820		The default command configuration includes all commands
821		except those marked below with a "*".
822
823		CONFIG_CMD_ASKENV	* ask for env variable
824		CONFIG_CMD_BDI		  bdinfo
825		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
826		CONFIG_CMD_BMP		* BMP support
827		CONFIG_CMD_BSP		* Board specific commands
828		CONFIG_CMD_BOOTD	  bootd
829		CONFIG_CMD_CACHE	* icache, dcache
830		CONFIG_CMD_CONSOLE	  coninfo
831		CONFIG_CMD_CRC32	* crc32
832		CONFIG_CMD_DATE		* support for RTC, date/time...
833		CONFIG_CMD_DHCP		* DHCP support
834		CONFIG_CMD_DIAG		* Diagnostics
835		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
836		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
837		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
838		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
839		CONFIG_CMD_DTT		* Digital Therm and Thermostat
840		CONFIG_CMD_ECHO		  echo arguments
841		CONFIG_CMD_EDITENV	  edit env variable
842		CONFIG_CMD_EEPROM	* EEPROM read/write support
843		CONFIG_CMD_ELF		* bootelf, bootvx
844		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
845		CONFIG_CMD_ENV_FLAGS	* display details about env flags
846		CONFIG_CMD_EXPORTENV	* export the environment
847		CONFIG_CMD_EXT2		* ext2 command support
848		CONFIG_CMD_EXT4		* ext4 command support
849		CONFIG_CMD_SAVEENV	  saveenv
850		CONFIG_CMD_FDC		* Floppy Disk Support
851		CONFIG_CMD_FAT		* FAT command support
852		CONFIG_CMD_FDOS		* Dos diskette Support
853		CONFIG_CMD_FLASH	  flinfo, erase, protect
854		CONFIG_CMD_FPGA		  FPGA device initialization support
855		CONFIG_CMD_GETTIME	* Get time since boot
856		CONFIG_CMD_GO		* the 'go' command (exec code)
857		CONFIG_CMD_GREPENV	* search environment
858		CONFIG_CMD_HASH		* calculate hash / digest
859		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
860		CONFIG_CMD_I2C		* I2C serial bus support
861		CONFIG_CMD_IDE		* IDE harddisk support
862		CONFIG_CMD_IMI		  iminfo
863		CONFIG_CMD_IMLS		  List all images found in NOR flash
864		CONFIG_CMD_IMLS_NAND	  List all images found in NAND flash
865		CONFIG_CMD_IMMAP	* IMMR dump support
866		CONFIG_CMD_IMPORTENV	* import an environment
867		CONFIG_CMD_INI		* import data from an ini file into the env
868		CONFIG_CMD_IRQ		* irqinfo
869		CONFIG_CMD_ITEST	  Integer/string test of 2 values
870		CONFIG_CMD_JFFS2	* JFFS2 Support
871		CONFIG_CMD_KGDB		* kgdb
872		CONFIG_CMD_LDRINFO	  ldrinfo (display Blackfin loader)
873		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
874					  (169.254.*.*)
875		CONFIG_CMD_LOADB	  loadb
876		CONFIG_CMD_LOADS	  loads
877		CONFIG_CMD_MD5SUM	  print md5 message digest
878					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
879		CONFIG_CMD_MEMINFO	* Display detailed memory information
880		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
881					  loop, loopw
882		CONFIG_CMD_MEMTEST	  mtest
883		CONFIG_CMD_MISC		  Misc functions like sleep etc
884		CONFIG_CMD_MMC		* MMC memory mapped support
885		CONFIG_CMD_MII		* MII utility commands
886		CONFIG_CMD_MTDPARTS	* MTD partition support
887		CONFIG_CMD_NAND		* NAND support
888		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
889		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
890		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
891		CONFIG_CMD_PCI		* pciinfo
892		CONFIG_CMD_PCMCIA		* PCMCIA support
893		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
894					  host
895		CONFIG_CMD_PORTIO	* Port I/O
896		CONFIG_CMD_READ		* Read raw data from partition
897		CONFIG_CMD_REGINFO	* Register dump
898		CONFIG_CMD_RUN		  run command in env variable
899		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
900		CONFIG_CMD_SAVES	* save S record dump
901		CONFIG_CMD_SCSI		* SCSI Support
902		CONFIG_CMD_SDRAM	* print SDRAM configuration information
903					  (requires CONFIG_CMD_I2C)
904		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
905					  (4xx only)
906		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
907		CONFIG_CMD_SHA1SUM	  print sha1 memory digest
908					  (requires CONFIG_CMD_MEMORY)
909		CONFIG_CMD_SOURCE	  "source" command Support
910		CONFIG_CMD_SPI		* SPI serial bus support
911		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
912		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
913		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
914		CONFIG_CMD_TIMER	* access to the system tick timer
915		CONFIG_CMD_USB		* USB support
916		CONFIG_CMD_CDP		* Cisco Discover Protocol support
917		CONFIG_CMD_MFSL		* Microblaze FSL support
918
919
920		EXAMPLE: If you want all functions except of network
921		support you can write:
922
923		#include "config_cmd_all.h"
924		#undef CONFIG_CMD_NET
925
926	Other Commands:
927		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
928
929	Note:	Don't enable the "icache" and "dcache" commands
930		(configuration option CONFIG_CMD_CACHE) unless you know
931		what you (and your U-Boot users) are doing. Data
932		cache cannot be enabled on systems like the 8xx or
933		8260 (where accesses to the IMMR region must be
934		uncached), and it cannot be disabled on all other
935		systems where we (mis-) use the data cache to hold an
936		initial stack and some data.
937
938
939		XXX - this list needs to get updated!
940
941- Device tree:
942		CONFIG_OF_CONTROL
943		If this variable is defined, U-Boot will use a device tree
944		to configure its devices, instead of relying on statically
945		compiled #defines in the board file. This option is
946		experimental and only available on a few boards. The device
947		tree is available in the global data as gd->fdt_blob.
948
949		U-Boot needs to get its device tree from somewhere. This can
950		be done using one of the two options below:
951
952		CONFIG_OF_EMBED
953		If this variable is defined, U-Boot will embed a device tree
954		binary in its image. This device tree file should be in the
955		board directory and called <soc>-<board>.dts. The binary file
956		is then picked up in board_init_f() and made available through
957		the global data structure as gd->blob.
958
959		CONFIG_OF_SEPARATE
960		If this variable is defined, U-Boot will build a device tree
961		binary. It will be called u-boot.dtb. Architecture-specific
962		code will locate it at run-time. Generally this works by:
963
964			cat u-boot.bin u-boot.dtb >image.bin
965
966		and in fact, U-Boot does this for you, creating a file called
967		u-boot-dtb.bin which is useful in the common case. You can
968		still use the individual files if you need something more
969		exotic.
970
971- Watchdog:
972		CONFIG_WATCHDOG
973		If this variable is defined, it enables watchdog
974		support for the SoC. There must be support in the SoC
975		specific code for a watchdog. For the 8xx and 8260
976		CPUs, the SIU Watchdog feature is enabled in the SYPCR
977		register.  When supported for a specific SoC is
978		available, then no further board specific code should
979		be needed to use it.
980
981		CONFIG_HW_WATCHDOG
982		When using a watchdog circuitry external to the used
983		SoC, then define this variable and provide board
984		specific code for the "hw_watchdog_reset" function.
985
986- U-Boot Version:
987		CONFIG_VERSION_VARIABLE
988		If this variable is defined, an environment variable
989		named "ver" is created by U-Boot showing the U-Boot
990		version as printed by the "version" command.
991		Any change to this variable will be reverted at the
992		next reset.
993
994- Real-Time Clock:
995
996		When CONFIG_CMD_DATE is selected, the type of the RTC
997		has to be selected, too. Define exactly one of the
998		following options:
999
1000		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1001		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1002		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1003		CONFIG_RTC_MC146818	- use MC146818 RTC
1004		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1005		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1006		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1007		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1008		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1009		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1010		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1011		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1012					  RV3029 RTC.
1013
1014		Note that if the RTC uses I2C, then the I2C interface
1015		must also be configured. See I2C Support, below.
1016
1017- GPIO Support:
1018		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1019		CONFIG_PCA953X_INFO	- enable pca953x info command
1020
1021		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1022		chip-ngpio pairs that tell the PCA953X driver the number of
1023		pins supported by a particular chip.
1024
1025		Note that if the GPIO device uses I2C, then the I2C interface
1026		must also be configured. See I2C Support, below.
1027
1028- Timestamp Support:
1029
1030		When CONFIG_TIMESTAMP is selected, the timestamp
1031		(date and time) of an image is printed by image
1032		commands like bootm or iminfo. This option is
1033		automatically enabled when you select CONFIG_CMD_DATE .
1034
1035- Partition Labels (disklabels) Supported:
1036		Zero or more of the following:
1037		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1038		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1039				       Intel architecture, USB sticks, etc.
1040		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1041		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1042				       bootloader.  Note 2TB partition limit; see
1043				       disk/part_efi.c
1044		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1045
1046		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1047		CONFIG_CMD_SCSI) you must configure support for at
1048		least one non-MTD partition type as well.
1049
1050- IDE Reset method:
1051		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1052		board configurations files but used nowhere!
1053
1054		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1055		be performed by calling the function
1056			ide_set_reset(int reset)
1057		which has to be defined in a board specific file
1058
1059- ATAPI Support:
1060		CONFIG_ATAPI
1061
1062		Set this to enable ATAPI support.
1063
1064- LBA48 Support
1065		CONFIG_LBA48
1066
1067		Set this to enable support for disks larger than 137GB
1068		Also look at CONFIG_SYS_64BIT_LBA.
1069		Whithout these , LBA48 support uses 32bit variables and will 'only'
1070		support disks up to 2.1TB.
1071
1072		CONFIG_SYS_64BIT_LBA:
1073			When enabled, makes the IDE subsystem use 64bit sector addresses.
1074			Default is 32bit.
1075
1076- SCSI Support:
1077		At the moment only there is only support for the
1078		SYM53C8XX SCSI controller; define
1079		CONFIG_SCSI_SYM53C8XX to enable it.
1080
1081		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1082		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1083		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1084		maximum numbers of LUNs, SCSI ID's and target
1085		devices.
1086		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1087
1088                The environment variable 'scsidevs' is set to the number of
1089                SCSI devices found during the last scan.
1090
1091- NETWORK Support (PCI):
1092		CONFIG_E1000
1093		Support for Intel 8254x/8257x gigabit chips.
1094
1095		CONFIG_E1000_SPI
1096		Utility code for direct access to the SPI bus on Intel 8257x.
1097		This does not do anything useful unless you set at least one
1098		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1099
1100		CONFIG_E1000_SPI_GENERIC
1101		Allow generic access to the SPI bus on the Intel 8257x, for
1102		example with the "sspi" command.
1103
1104		CONFIG_CMD_E1000
1105		Management command for E1000 devices.  When used on devices
1106		with SPI support you can reprogram the EEPROM from U-Boot.
1107
1108		CONFIG_E1000_FALLBACK_MAC
1109		default MAC for empty EEPROM after production.
1110
1111		CONFIG_EEPRO100
1112		Support for Intel 82557/82559/82559ER chips.
1113		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1114		write routine for first time initialisation.
1115
1116		CONFIG_TULIP
1117		Support for Digital 2114x chips.
1118		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1119		modem chip initialisation (KS8761/QS6611).
1120
1121		CONFIG_NATSEMI
1122		Support for National dp83815 chips.
1123
1124		CONFIG_NS8382X
1125		Support for National dp8382[01] gigabit chips.
1126
1127- NETWORK Support (other):
1128
1129		CONFIG_DRIVER_AT91EMAC
1130		Support for AT91RM9200 EMAC.
1131
1132			CONFIG_RMII
1133			Define this to use reduced MII inteface
1134
1135			CONFIG_DRIVER_AT91EMAC_QUIET
1136			If this defined, the driver is quiet.
1137			The driver doen't show link status messages.
1138
1139		CONFIG_CALXEDA_XGMAC
1140		Support for the Calxeda XGMAC device
1141
1142		CONFIG_LAN91C96
1143		Support for SMSC's LAN91C96 chips.
1144
1145			CONFIG_LAN91C96_BASE
1146			Define this to hold the physical address
1147			of the LAN91C96's I/O space
1148
1149			CONFIG_LAN91C96_USE_32_BIT
1150			Define this to enable 32 bit addressing
1151
1152		CONFIG_SMC91111
1153		Support for SMSC's LAN91C111 chip
1154
1155			CONFIG_SMC91111_BASE
1156			Define this to hold the physical address
1157			of the device (I/O space)
1158
1159			CONFIG_SMC_USE_32_BIT
1160			Define this if data bus is 32 bits
1161
1162			CONFIG_SMC_USE_IOFUNCS
1163			Define this to use i/o functions instead of macros
1164			(some hardware wont work with macros)
1165
1166		CONFIG_DRIVER_TI_EMAC
1167		Support for davinci emac
1168
1169			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1170			Define this if you have more then 3 PHYs.
1171
1172		CONFIG_FTGMAC100
1173		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1174
1175			CONFIG_FTGMAC100_EGIGA
1176			Define this to use GE link update with gigabit PHY.
1177			Define this if FTGMAC100 is connected to gigabit PHY.
1178			If your system has 10/100 PHY only, it might not occur
1179			wrong behavior. Because PHY usually return timeout or
1180			useless data when polling gigabit status and gigabit
1181			control registers. This behavior won't affect the
1182			correctnessof 10/100 link speed update.
1183
1184		CONFIG_SMC911X
1185		Support for SMSC's LAN911x and LAN921x chips
1186
1187			CONFIG_SMC911X_BASE
1188			Define this to hold the physical address
1189			of the device (I/O space)
1190
1191			CONFIG_SMC911X_32_BIT
1192			Define this if data bus is 32 bits
1193
1194			CONFIG_SMC911X_16_BIT
1195			Define this if data bus is 16 bits. If your processor
1196			automatically converts one 32 bit word to two 16 bit
1197			words you may also try CONFIG_SMC911X_32_BIT.
1198
1199		CONFIG_SH_ETHER
1200		Support for Renesas on-chip Ethernet controller
1201
1202			CONFIG_SH_ETHER_USE_PORT
1203			Define the number of ports to be used
1204
1205			CONFIG_SH_ETHER_PHY_ADDR
1206			Define the ETH PHY's address
1207
1208			CONFIG_SH_ETHER_CACHE_WRITEBACK
1209			If this option is set, the driver enables cache flush.
1210
1211- TPM Support:
1212		CONFIG_GENERIC_LPC_TPM
1213		Support for generic parallel port TPM devices. Only one device
1214		per system is supported at this time.
1215
1216			CONFIG_TPM_TIS_BASE_ADDRESS
1217			Base address where the generic TPM device is mapped
1218			to. Contemporary x86 systems usually map it at
1219			0xfed40000.
1220
1221- USB Support:
1222		At the moment only the UHCI host controller is
1223		supported (PIP405, MIP405, MPC5200); define
1224		CONFIG_USB_UHCI to enable it.
1225		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1226		and define CONFIG_USB_STORAGE to enable the USB
1227		storage devices.
1228		Note:
1229		Supported are USB Keyboards and USB Floppy drives
1230		(TEAC FD-05PUB).
1231		MPC5200 USB requires additional defines:
1232			CONFIG_USB_CLOCK
1233				for 528 MHz Clock: 0x0001bbbb
1234			CONFIG_PSC3_USB
1235				for USB on PSC3
1236			CONFIG_USB_CONFIG
1237				for differential drivers: 0x00001000
1238				for single ended drivers: 0x00005000
1239				for differential drivers on PSC3: 0x00000100
1240				for single ended drivers on PSC3: 0x00004100
1241			CONFIG_SYS_USB_EVENT_POLL
1242				May be defined to allow interrupt polling
1243				instead of using asynchronous interrupts
1244
1245		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1246		txfilltuning field in the EHCI controller on reset.
1247
1248- USB Device:
1249		Define the below if you wish to use the USB console.
1250		Once firmware is rebuilt from a serial console issue the
1251		command "setenv stdin usbtty; setenv stdout usbtty" and
1252		attach your USB cable. The Unix command "dmesg" should print
1253		it has found a new device. The environment variable usbtty
1254		can be set to gserial or cdc_acm to enable your device to
1255		appear to a USB host as a Linux gserial device or a
1256		Common Device Class Abstract Control Model serial device.
1257		If you select usbtty = gserial you should be able to enumerate
1258		a Linux host by
1259		# modprobe usbserial vendor=0xVendorID product=0xProductID
1260		else if using cdc_acm, simply setting the environment
1261		variable usbtty to be cdc_acm should suffice. The following
1262		might be defined in YourBoardName.h
1263
1264			CONFIG_USB_DEVICE
1265			Define this to build a UDC device
1266
1267			CONFIG_USB_TTY
1268			Define this to have a tty type of device available to
1269			talk to the UDC device
1270
1271			CONFIG_USBD_HS
1272			Define this to enable the high speed support for usb
1273			device and usbtty. If this feature is enabled, a routine
1274			int is_usbd_high_speed(void)
1275			also needs to be defined by the driver to dynamically poll
1276			whether the enumeration has succeded at high speed or full
1277			speed.
1278
1279			CONFIG_SYS_CONSOLE_IS_IN_ENV
1280			Define this if you want stdin, stdout &/or stderr to
1281			be set to usbtty.
1282
1283			mpc8xx:
1284				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1285				Derive USB clock from external clock "blah"
1286				- CONFIG_SYS_USB_EXTC_CLK 0x02
1287
1288				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1289				Derive USB clock from brgclk
1290				- CONFIG_SYS_USB_BRG_CLK 0x04
1291
1292		If you have a USB-IF assigned VendorID then you may wish to
1293		define your own vendor specific values either in BoardName.h
1294		or directly in usbd_vendor_info.h. If you don't define
1295		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1296		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1297		should pretend to be a Linux device to it's target host.
1298
1299			CONFIG_USBD_MANUFACTURER
1300			Define this string as the name of your company for
1301			- CONFIG_USBD_MANUFACTURER "my company"
1302
1303			CONFIG_USBD_PRODUCT_NAME
1304			Define this string as the name of your product
1305			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1306
1307			CONFIG_USBD_VENDORID
1308			Define this as your assigned Vendor ID from the USB
1309			Implementors Forum. This *must* be a genuine Vendor ID
1310			to avoid polluting the USB namespace.
1311			- CONFIG_USBD_VENDORID 0xFFFF
1312
1313			CONFIG_USBD_PRODUCTID
1314			Define this as the unique Product ID
1315			for your device
1316			- CONFIG_USBD_PRODUCTID 0xFFFF
1317
1318- ULPI Layer Support:
1319		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1320		the generic ULPI layer. The generic layer accesses the ULPI PHY
1321		via the platform viewport, so you need both the genric layer and
1322		the viewport enabled. Currently only Chipidea/ARC based
1323		viewport is supported.
1324		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1325		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1326		If your ULPI phy needs a different reference clock than the
1327		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1328		the appropriate value in Hz.
1329
1330- MMC Support:
1331		The MMC controller on the Intel PXA is supported. To
1332		enable this define CONFIG_MMC. The MMC can be
1333		accessed from the boot prompt by mapping the device
1334		to physical memory similar to flash. Command line is
1335		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1336		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1337
1338		CONFIG_SH_MMCIF
1339		Support for Renesas on-chip MMCIF controller
1340
1341			CONFIG_SH_MMCIF_ADDR
1342			Define the base address of MMCIF registers
1343
1344			CONFIG_SH_MMCIF_CLK
1345			Define the clock frequency for MMCIF
1346
1347- Journaling Flash filesystem support:
1348		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1349		CONFIG_JFFS2_NAND_DEV
1350		Define these for a default partition on a NAND device
1351
1352		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1353		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1354		Define these for a default partition on a NOR device
1355
1356		CONFIG_SYS_JFFS_CUSTOM_PART
1357		Define this to create an own partition. You have to provide a
1358		function struct part_info* jffs2_part_info(int part_num)
1359
1360		If you define only one JFFS2 partition you may also want to
1361		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1362		to disable the command chpart. This is the default when you
1363		have not defined a custom partition
1364
1365- FAT(File Allocation Table) filesystem write function support:
1366		CONFIG_FAT_WRITE
1367
1368		Define this to enable support for saving memory data as a
1369		file in FAT formatted partition.
1370
1371		This will also enable the command "fatwrite" enabling the
1372		user to write files to FAT.
1373
1374CBFS (Coreboot Filesystem) support
1375		CONFIG_CMD_CBFS
1376
1377		Define this to enable support for reading from a Coreboot
1378		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1379		and cbfsload.
1380
1381- Keyboard Support:
1382		CONFIG_ISA_KEYBOARD
1383
1384		Define this to enable standard (PC-Style) keyboard
1385		support
1386
1387		CONFIG_I8042_KBD
1388		Standard PC keyboard driver with US (is default) and
1389		GERMAN key layout (switch via environment 'keymap=de') support.
1390		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1391		for cfb_console. Supports cursor blinking.
1392
1393- Video support:
1394		CONFIG_VIDEO
1395
1396		Define this to enable video support (for output to
1397		video).
1398
1399		CONFIG_VIDEO_CT69000
1400
1401		Enable Chips & Technologies 69000 Video chip
1402
1403		CONFIG_VIDEO_SMI_LYNXEM
1404		Enable Silicon Motion SMI 712/710/810 Video chip. The
1405		video output is selected via environment 'videoout'
1406		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1407		assumed.
1408
1409		For the CT69000 and SMI_LYNXEM drivers, videomode is
1410		selected via environment 'videomode'. Two different ways
1411		are possible:
1412		- "videomode=num"   'num' is a standard LiLo mode numbers.
1413		Following standard modes are supported	(* is default):
1414
1415		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1416		-------------+---------------------------------------------
1417		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1418		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1419		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1420		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1421		-------------+---------------------------------------------
1422		(i.e. setenv videomode 317; saveenv; reset;)
1423
1424		- "videomode=bootargs" all the video parameters are parsed
1425		from the bootargs. (See drivers/video/videomodes.c)
1426
1427
1428		CONFIG_VIDEO_SED13806
1429		Enable Epson SED13806 driver. This driver supports 8bpp
1430		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1431		or CONFIG_VIDEO_SED13806_16BPP
1432
1433		CONFIG_FSL_DIU_FB
1434		Enable the Freescale DIU video driver.	Reference boards for
1435		SOCs that have a DIU should define this macro to enable DIU
1436		support, and should also define these other macros:
1437
1438			CONFIG_SYS_DIU_ADDR
1439			CONFIG_VIDEO
1440			CONFIG_CMD_BMP
1441			CONFIG_CFB_CONSOLE
1442			CONFIG_VIDEO_SW_CURSOR
1443			CONFIG_VGA_AS_SINGLE_DEVICE
1444			CONFIG_VIDEO_LOGO
1445			CONFIG_VIDEO_BMP_LOGO
1446
1447		The DIU driver will look for the 'video-mode' environment
1448		variable, and if defined, enable the DIU as a console during
1449		boot.  See the documentation file README.video for a
1450		description of this variable.
1451
1452		CONFIG_VIDEO_VGA
1453
1454		Enable the VGA video / BIOS for x86. The alternative if you
1455		are using coreboot is to use the coreboot frame buffer
1456		driver.
1457
1458
1459- Keyboard Support:
1460		CONFIG_KEYBOARD
1461
1462		Define this to enable a custom keyboard support.
1463		This simply calls drv_keyboard_init() which must be
1464		defined in your board-specific files.
1465		The only board using this so far is RBC823.
1466
1467- LCD Support:	CONFIG_LCD
1468
1469		Define this to enable LCD support (for output to LCD
1470		display); also select one of the supported displays
1471		by defining one of these:
1472
1473		CONFIG_ATMEL_LCD:
1474
1475			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1476
1477		CONFIG_NEC_NL6448AC33:
1478
1479			NEC NL6448AC33-18. Active, color, single scan.
1480
1481		CONFIG_NEC_NL6448BC20
1482
1483			NEC NL6448BC20-08. 6.5", 640x480.
1484			Active, color, single scan.
1485
1486		CONFIG_NEC_NL6448BC33_54
1487
1488			NEC NL6448BC33-54. 10.4", 640x480.
1489			Active, color, single scan.
1490
1491		CONFIG_SHARP_16x9
1492
1493			Sharp 320x240. Active, color, single scan.
1494			It isn't 16x9, and I am not sure what it is.
1495
1496		CONFIG_SHARP_LQ64D341
1497
1498			Sharp LQ64D341 display, 640x480.
1499			Active, color, single scan.
1500
1501		CONFIG_HLD1045
1502
1503			HLD1045 display, 640x480.
1504			Active, color, single scan.
1505
1506		CONFIG_OPTREX_BW
1507
1508			Optrex	 CBL50840-2 NF-FW 99 22 M5
1509			or
1510			Hitachi	 LMG6912RPFC-00T
1511			or
1512			Hitachi	 SP14Q002
1513
1514			320x240. Black & white.
1515
1516		Normally display is black on white background; define
1517		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1518
1519		CONFIG_LCD_ALIGNMENT
1520
1521		Normally the LCD is page-aligned (tyically 4KB). If this is
1522		defined then the LCD will be aligned to this value instead.
1523		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1524		here, since it is cheaper to change data cache settings on
1525		a per-section basis.
1526
1527		CONFIG_CONSOLE_SCROLL_LINES
1528
1529		When the console need to be scrolled, this is the number of
1530		lines to scroll by. It defaults to 1. Increasing this makes
1531		the console jump but can help speed up operation when scrolling
1532		is slow.
1533
1534		CONFIG_LCD_BMP_RLE8
1535
1536		Support drawing of RLE8-compressed bitmaps on the LCD.
1537
1538		CONFIG_I2C_EDID
1539
1540		Enables an 'i2c edid' command which can read EDID
1541		information over I2C from an attached LCD display.
1542
1543- Splash Screen Support: CONFIG_SPLASH_SCREEN
1544
1545		If this option is set, the environment is checked for
1546		a variable "splashimage". If found, the usual display
1547		of logo, copyright and system information on the LCD
1548		is suppressed and the BMP image at the address
1549		specified in "splashimage" is loaded instead. The
1550		console is redirected to the "nulldev", too. This
1551		allows for a "silent" boot where a splash screen is
1552		loaded very quickly after power-on.
1553
1554		CONFIG_SPLASHIMAGE_GUARD
1555
1556		If this option is set, then U-Boot will prevent the environment
1557		variable "splashimage" from being set to a problematic address
1558		(see README.displaying-bmps and README.arm-unaligned-accesses).
1559		This option is useful for targets where, due to alignment
1560		restrictions, an improperly aligned BMP image will cause a data
1561		abort. If you think you will not have problems with unaligned
1562		accesses (for example because your toolchain prevents them)
1563		there is no need to set this option.
1564
1565		CONFIG_SPLASH_SCREEN_ALIGN
1566
1567		If this option is set the splash image can be freely positioned
1568		on the screen. Environment variable "splashpos" specifies the
1569		position as "x,y". If a positive number is given it is used as
1570		number of pixel from left/top. If a negative number is given it
1571		is used as number of pixel from right/bottom. You can also
1572		specify 'm' for centering the image.
1573
1574		Example:
1575		setenv splashpos m,m
1576			=> image at center of screen
1577
1578		setenv splashpos 30,20
1579			=> image at x = 30 and y = 20
1580
1581		setenv splashpos -10,m
1582			=> vertically centered image
1583			   at x = dspWidth - bmpWidth - 9
1584
1585		CONFIG_SPLASH_SCREEN_PREPARE
1586
1587		If this option is set then the board_splash_screen_prepare()
1588		function, which must be defined in your code, is called as part
1589		of the splash screen display sequence. It gives the board an
1590		opportunity to prepare the splash image data before it is
1591		processed and sent to the frame buffer by U-Boot.
1592
1593- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1594
1595		If this option is set, additionally to standard BMP
1596		images, gzipped BMP images can be displayed via the
1597		splashscreen support or the bmp command.
1598
1599- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1600
1601		If this option is set, 8-bit RLE compressed BMP images
1602		can be displayed via the splashscreen support or the
1603		bmp command.
1604
1605- Do compresssing for memory range:
1606		CONFIG_CMD_ZIP
1607
1608		If this option is set, it would use zlib deflate method
1609		to compress the specified memory at its best effort.
1610
1611- Compression support:
1612		CONFIG_BZIP2
1613
1614		If this option is set, support for bzip2 compressed
1615		images is included. If not, only uncompressed and gzip
1616		compressed images are supported.
1617
1618		NOTE: the bzip2 algorithm requires a lot of RAM, so
1619		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1620		be at least 4MB.
1621
1622		CONFIG_LZMA
1623
1624		If this option is set, support for lzma compressed
1625		images is included.
1626
1627		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1628		requires an amount of dynamic memory that is given by the
1629		formula:
1630
1631			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1632
1633		Where lc and lp stand for, respectively, Literal context bits
1634		and Literal pos bits.
1635
1636		This value is upper-bounded by 14MB in the worst case. Anyway,
1637		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1638		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1639		a very small buffer.
1640
1641		Use the lzmainfo tool to determinate the lc and lp values and
1642		then calculate the amount of needed dynamic memory (ensuring
1643		the appropriate CONFIG_SYS_MALLOC_LEN value).
1644
1645- MII/PHY support:
1646		CONFIG_PHY_ADDR
1647
1648		The address of PHY on MII bus.
1649
1650		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1651
1652		The clock frequency of the MII bus
1653
1654		CONFIG_PHY_GIGE
1655
1656		If this option is set, support for speed/duplex
1657		detection of gigabit PHY is included.
1658
1659		CONFIG_PHY_RESET_DELAY
1660
1661		Some PHY like Intel LXT971A need extra delay after
1662		reset before any MII register access is possible.
1663		For such PHY, set this option to the usec delay
1664		required. (minimum 300usec for LXT971A)
1665
1666		CONFIG_PHY_CMD_DELAY (ppc4xx)
1667
1668		Some PHY like Intel LXT971A need extra delay after
1669		command issued before MII status register can be read
1670
1671- Ethernet address:
1672		CONFIG_ETHADDR
1673		CONFIG_ETH1ADDR
1674		CONFIG_ETH2ADDR
1675		CONFIG_ETH3ADDR
1676		CONFIG_ETH4ADDR
1677		CONFIG_ETH5ADDR
1678
1679		Define a default value for Ethernet address to use
1680		for the respective Ethernet interface, in case this
1681		is not determined automatically.
1682
1683- IP address:
1684		CONFIG_IPADDR
1685
1686		Define a default value for the IP address to use for
1687		the default Ethernet interface, in case this is not
1688		determined through e.g. bootp.
1689		(Environment variable "ipaddr")
1690
1691- Server IP address:
1692		CONFIG_SERVERIP
1693
1694		Defines a default value for the IP address of a TFTP
1695		server to contact when using the "tftboot" command.
1696		(Environment variable "serverip")
1697
1698		CONFIG_KEEP_SERVERADDR
1699
1700		Keeps the server's MAC address, in the env 'serveraddr'
1701		for passing to bootargs (like Linux's netconsole option)
1702
1703- Gateway IP address:
1704		CONFIG_GATEWAYIP
1705
1706		Defines a default value for the IP address of the
1707		default router where packets to other networks are
1708		sent to.
1709		(Environment variable "gatewayip")
1710
1711- Subnet mask:
1712		CONFIG_NETMASK
1713
1714		Defines a default value for the subnet mask (or
1715		routing prefix) which is used to determine if an IP
1716		address belongs to the local subnet or needs to be
1717		forwarded through a router.
1718		(Environment variable "netmask")
1719
1720- Multicast TFTP Mode:
1721		CONFIG_MCAST_TFTP
1722
1723		Defines whether you want to support multicast TFTP as per
1724		rfc-2090; for example to work with atftp.  Lets lots of targets
1725		tftp down the same boot image concurrently.  Note: the Ethernet
1726		driver in use must provide a function: mcast() to join/leave a
1727		multicast group.
1728
1729- BOOTP Recovery Mode:
1730		CONFIG_BOOTP_RANDOM_DELAY
1731
1732		If you have many targets in a network that try to
1733		boot using BOOTP, you may want to avoid that all
1734		systems send out BOOTP requests at precisely the same
1735		moment (which would happen for instance at recovery
1736		from a power failure, when all systems will try to
1737		boot, thus flooding the BOOTP server. Defining
1738		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1739		inserted before sending out BOOTP requests. The
1740		following delays are inserted then:
1741
1742		1st BOOTP request:	delay 0 ... 1 sec
1743		2nd BOOTP request:	delay 0 ... 2 sec
1744		3rd BOOTP request:	delay 0 ... 4 sec
1745		4th and following
1746		BOOTP requests:		delay 0 ... 8 sec
1747
1748- DHCP Advanced Options:
1749		You can fine tune the DHCP functionality by defining
1750		CONFIG_BOOTP_* symbols:
1751
1752		CONFIG_BOOTP_SUBNETMASK
1753		CONFIG_BOOTP_GATEWAY
1754		CONFIG_BOOTP_HOSTNAME
1755		CONFIG_BOOTP_NISDOMAIN
1756		CONFIG_BOOTP_BOOTPATH
1757		CONFIG_BOOTP_BOOTFILESIZE
1758		CONFIG_BOOTP_DNS
1759		CONFIG_BOOTP_DNS2
1760		CONFIG_BOOTP_SEND_HOSTNAME
1761		CONFIG_BOOTP_NTPSERVER
1762		CONFIG_BOOTP_TIMEOFFSET
1763		CONFIG_BOOTP_VENDOREX
1764		CONFIG_BOOTP_MAY_FAIL
1765
1766		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1767		environment variable, not the BOOTP server.
1768
1769		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1770		after the configured retry count, the call will fail
1771		instead of starting over.  This can be used to fail over
1772		to Link-local IP address configuration if the DHCP server
1773		is not available.
1774
1775		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1776		serverip from a DHCP server, it is possible that more
1777		than one DNS serverip is offered to the client.
1778		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1779		serverip will be stored in the additional environment
1780		variable "dnsip2". The first DNS serverip is always
1781		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1782		is defined.
1783
1784		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1785		to do a dynamic update of a DNS server. To do this, they
1786		need the hostname of the DHCP requester.
1787		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1788		of the "hostname" environment variable is passed as
1789		option 12 to the DHCP server.
1790
1791		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1792
1793		A 32bit value in microseconds for a delay between
1794		receiving a "DHCP Offer" and sending the "DHCP Request".
1795		This fixes a problem with certain DHCP servers that don't
1796		respond 100% of the time to a "DHCP request". E.g. On an
1797		AT91RM9200 processor running at 180MHz, this delay needed
1798		to be *at least* 15,000 usec before a Windows Server 2003
1799		DHCP server would reply 100% of the time. I recommend at
1800		least 50,000 usec to be safe. The alternative is to hope
1801		that one of the retries will be successful but note that
1802		the DHCP timeout and retry process takes a longer than
1803		this delay.
1804
1805 - Link-local IP address negotiation:
1806		Negotiate with other link-local clients on the local network
1807		for an address that doesn't require explicit configuration.
1808		This is especially useful if a DHCP server cannot be guaranteed
1809		to exist in all environments that the device must operate.
1810
1811		See doc/README.link-local for more information.
1812
1813 - CDP Options:
1814		CONFIG_CDP_DEVICE_ID
1815
1816		The device id used in CDP trigger frames.
1817
1818		CONFIG_CDP_DEVICE_ID_PREFIX
1819
1820		A two character string which is prefixed to the MAC address
1821		of the device.
1822
1823		CONFIG_CDP_PORT_ID
1824
1825		A printf format string which contains the ascii name of
1826		the port. Normally is set to "eth%d" which sets
1827		eth0 for the first Ethernet, eth1 for the second etc.
1828
1829		CONFIG_CDP_CAPABILITIES
1830
1831		A 32bit integer which indicates the device capabilities;
1832		0x00000010 for a normal host which does not forwards.
1833
1834		CONFIG_CDP_VERSION
1835
1836		An ascii string containing the version of the software.
1837
1838		CONFIG_CDP_PLATFORM
1839
1840		An ascii string containing the name of the platform.
1841
1842		CONFIG_CDP_TRIGGER
1843
1844		A 32bit integer sent on the trigger.
1845
1846		CONFIG_CDP_POWER_CONSUMPTION
1847
1848		A 16bit integer containing the power consumption of the
1849		device in .1 of milliwatts.
1850
1851		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1852
1853		A byte containing the id of the VLAN.
1854
1855- Status LED:	CONFIG_STATUS_LED
1856
1857		Several configurations allow to display the current
1858		status using a LED. For instance, the LED will blink
1859		fast while running U-Boot code, stop blinking as
1860		soon as a reply to a BOOTP request was received, and
1861		start blinking slow once the Linux kernel is running
1862		(supported by a status LED driver in the Linux
1863		kernel). Defining CONFIG_STATUS_LED enables this
1864		feature in U-Boot.
1865
1866- CAN Support:	CONFIG_CAN_DRIVER
1867
1868		Defining CONFIG_CAN_DRIVER enables CAN driver support
1869		on those systems that support this (optional)
1870		feature, like the TQM8xxL modules.
1871
1872- I2C Support:	CONFIG_HARD_I2C | CONFIG_SOFT_I2C
1873
1874		These enable I2C serial bus commands. Defining either of
1875		(but not both of) CONFIG_HARD_I2C or CONFIG_SOFT_I2C will
1876		include the appropriate I2C driver for the selected CPU.
1877
1878		This will allow you to use i2c commands at the u-boot
1879		command line (as long as you set CONFIG_CMD_I2C in
1880		CONFIG_COMMANDS) and communicate with i2c based realtime
1881		clock chips. See common/cmd_i2c.c for a description of the
1882		command line interface.
1883
1884		CONFIG_HARD_I2C selects a hardware I2C controller.
1885
1886		CONFIG_SOFT_I2C configures u-boot to use a software (aka
1887		bit-banging) driver instead of CPM or similar hardware
1888		support for I2C.
1889
1890		There are several other quantities that must also be
1891		defined when you define CONFIG_HARD_I2C or CONFIG_SOFT_I2C.
1892
1893		In both cases you will need to define CONFIG_SYS_I2C_SPEED
1894		to be the frequency (in Hz) at which you wish your i2c bus
1895		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
1896		the CPU's i2c node address).
1897
1898		Now, the u-boot i2c code for the mpc8xx
1899		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
1900		and so its address should therefore be cleared to 0 (See,
1901		eg, MPC823e User's Manual p.16-473). So, set
1902		CONFIG_SYS_I2C_SLAVE to 0.
1903
1904		CONFIG_SYS_I2C_INIT_MPC5XXX
1905
1906		When a board is reset during an i2c bus transfer
1907		chips might think that the current transfer is still
1908		in progress.  Reset the slave devices by sending start
1909		commands until the slave device responds.
1910
1911		That's all that's required for CONFIG_HARD_I2C.
1912
1913		If you use the software i2c interface (CONFIG_SOFT_I2C)
1914		then the following macros need to be defined (examples are
1915		from include/configs/lwmon.h):
1916
1917		I2C_INIT
1918
1919		(Optional). Any commands necessary to enable the I2C
1920		controller or configure ports.
1921
1922		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1923
1924		I2C_PORT
1925
1926		(Only for MPC8260 CPU). The I/O port to use (the code
1927		assumes both bits are on the same port). Valid values
1928		are 0..3 for ports A..D.
1929
1930		I2C_ACTIVE
1931
1932		The code necessary to make the I2C data line active
1933		(driven).  If the data line is open collector, this
1934		define can be null.
1935
1936		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1937
1938		I2C_TRISTATE
1939
1940		The code necessary to make the I2C data line tri-stated
1941		(inactive).  If the data line is open collector, this
1942		define can be null.
1943
1944		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1945
1946		I2C_READ
1947
1948		Code that returns true if the I2C data line is high,
1949		false if it is low.
1950
1951		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1952
1953		I2C_SDA(bit)
1954
1955		If <bit> is true, sets the I2C data line high. If it
1956		is false, it clears it (low).
1957
1958		eg: #define I2C_SDA(bit) \
1959			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1960			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1961
1962		I2C_SCL(bit)
1963
1964		If <bit> is true, sets the I2C clock line high. If it
1965		is false, it clears it (low).
1966
1967		eg: #define I2C_SCL(bit) \
1968			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1969			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1970
1971		I2C_DELAY
1972
1973		This delay is invoked four times per clock cycle so this
1974		controls the rate of data transfer.  The data rate thus
1975		is 1 / (I2C_DELAY * 4). Often defined to be something
1976		like:
1977
1978		#define I2C_DELAY  udelay(2)
1979
1980		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1981
1982		If your arch supports the generic GPIO framework (asm/gpio.h),
1983		then you may alternatively define the two GPIOs that are to be
1984		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1985		have GPIO-based defaults assigned to them as appropriate.
1986
1987		You should define these to the GPIO value as given directly to
1988		the generic GPIO functions.
1989
1990		CONFIG_SYS_I2C_INIT_BOARD
1991
1992		When a board is reset during an i2c bus transfer
1993		chips might think that the current transfer is still
1994		in progress. On some boards it is possible to access
1995		the i2c SCLK line directly, either by using the
1996		processor pin as a GPIO or by having a second pin
1997		connected to the bus. If this option is defined a
1998		custom i2c_init_board() routine in boards/xxx/board.c
1999		is run early in the boot sequence.
2000
2001		CONFIG_SYS_I2C_BOARD_LATE_INIT
2002
2003		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2004		defined a custom i2c_board_late_init() routine in
2005		boards/xxx/board.c is run AFTER the operations in i2c_init()
2006		is completed. This callpoint can be used to unreset i2c bus
2007		using CPU i2c controller register accesses for CPUs whose i2c
2008		controller provide such a method. It is called at the end of
2009		i2c_init() to allow i2c_init operations to setup the i2c bus
2010		controller on the CPU (e.g. setting bus speed & slave address).
2011
2012		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2013
2014		This option enables configuration of bi_iic_fast[] flags
2015		in u-boot bd_info structure based on u-boot environment
2016		variable "i2cfast". (see also i2cfast)
2017
2018		CONFIG_I2C_MULTI_BUS
2019
2020		This option allows the use of multiple I2C buses, each of which
2021		must have a controller.	 At any point in time, only one bus is
2022		active.	 To switch to a different bus, use the 'i2c dev' command.
2023		Note that bus numbering is zero-based.
2024
2025		CONFIG_SYS_I2C_NOPROBES
2026
2027		This option specifies a list of I2C devices that will be skipped
2028		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2029		is set, specify a list of bus-device pairs.  Otherwise, specify
2030		a 1D array of device addresses
2031
2032		e.g.
2033			#undef	CONFIG_I2C_MULTI_BUS
2034			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2035
2036		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2037
2038			#define CONFIG_I2C_MULTI_BUS
2039			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2040
2041		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2042
2043		CONFIG_SYS_SPD_BUS_NUM
2044
2045		If defined, then this indicates the I2C bus number for DDR SPD.
2046		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2047
2048		CONFIG_SYS_RTC_BUS_NUM
2049
2050		If defined, then this indicates the I2C bus number for the RTC.
2051		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2052
2053		CONFIG_SYS_DTT_BUS_NUM
2054
2055		If defined, then this indicates the I2C bus number for the DTT.
2056		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2057
2058		CONFIG_SYS_I2C_DTT_ADDR:
2059
2060		If defined, specifies the I2C address of the DTT device.
2061		If not defined, then U-Boot uses predefined value for
2062		specified DTT device.
2063
2064		CONFIG_FSL_I2C
2065
2066		Define this option if you want to use Freescale's I2C driver in
2067		drivers/i2c/fsl_i2c.c.
2068
2069		CONFIG_I2C_MUX
2070
2071		Define this option if you have I2C devices reached over 1 .. n
2072		I2C Muxes like the pca9544a. This option addes a new I2C
2073		Command "i2c bus [muxtype:muxaddr:muxchannel]" which adds a
2074		new I2C Bus to the existing I2C Busses. If you select the
2075		new Bus with "i2c dev", u-bbot sends first the commandos for
2076		the muxes to activate this new "bus".
2077
2078		CONFIG_I2C_MULTI_BUS must be also defined, to use this
2079		feature!
2080
2081		Example:
2082		Adding a new I2C Bus reached over 2 pca9544a muxes
2083			The First mux with address 70 and channel 6
2084			The Second mux with address 71 and channel 4
2085
2086		=> i2c bus pca9544a:70:6:pca9544a:71:4
2087
2088		Use the "i2c bus" command without parameter, to get a list
2089		of I2C Busses with muxes:
2090
2091		=> i2c bus
2092		Busses reached over muxes:
2093		Bus ID: 2
2094		  reached over Mux(es):
2095		    pca9544a@70 ch: 4
2096		Bus ID: 3
2097		  reached over Mux(es):
2098		    pca9544a@70 ch: 6
2099		    pca9544a@71 ch: 4
2100		=>
2101
2102		If you now switch to the new I2C Bus 3 with "i2c dev 3"
2103		u-boot first sends the command to the mux@70 to enable
2104		channel 6, and then the command to the mux@71 to enable
2105		the channel 4.
2106
2107		After that, you can use the "normal" i2c commands as
2108		usual to communicate with your I2C devices behind
2109		the 2 muxes.
2110
2111		This option is actually implemented for the bitbanging
2112		algorithm in common/soft_i2c.c and for the Hardware I2C
2113		Bus on the MPC8260. But it should be not so difficult
2114		to add this option to other architectures.
2115
2116		CONFIG_SOFT_I2C_READ_REPEATED_START
2117
2118		defining this will force the i2c_read() function in
2119		the soft_i2c driver to perform an I2C repeated start
2120		between writing the address pointer and reading the
2121		data.  If this define is omitted the default behaviour
2122		of doing a stop-start sequence will be used.  Most I2C
2123		devices can use either method, but some require one or
2124		the other.
2125
2126- SPI Support:	CONFIG_SPI
2127
2128		Enables SPI driver (so far only tested with
2129		SPI EEPROM, also an instance works with Crystal A/D and
2130		D/As on the SACSng board)
2131
2132		CONFIG_SH_SPI
2133
2134		Enables the driver for SPI controller on SuperH. Currently
2135		only SH7757 is supported.
2136
2137		CONFIG_SPI_X
2138
2139		Enables extended (16-bit) SPI EEPROM addressing.
2140		(symmetrical to CONFIG_I2C_X)
2141
2142		CONFIG_SOFT_SPI
2143
2144		Enables a software (bit-bang) SPI driver rather than
2145		using hardware support. This is a general purpose
2146		driver that only requires three general I/O port pins
2147		(two outputs, one input) to function. If this is
2148		defined, the board configuration must define several
2149		SPI configuration items (port pins to use, etc). For
2150		an example, see include/configs/sacsng.h.
2151
2152		CONFIG_HARD_SPI
2153
2154		Enables a hardware SPI driver for general-purpose reads
2155		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2156		must define a list of chip-select function pointers.
2157		Currently supported on some MPC8xxx processors.	 For an
2158		example, see include/configs/mpc8349emds.h.
2159
2160		CONFIG_MXC_SPI
2161
2162		Enables the driver for the SPI controllers on i.MX and MXC
2163		SoCs. Currently i.MX31/35/51 are supported.
2164
2165- FPGA Support: CONFIG_FPGA
2166
2167		Enables FPGA subsystem.
2168
2169		CONFIG_FPGA_<vendor>
2170
2171		Enables support for specific chip vendors.
2172		(ALTERA, XILINX)
2173
2174		CONFIG_FPGA_<family>
2175
2176		Enables support for FPGA family.
2177		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2178
2179		CONFIG_FPGA_COUNT
2180
2181		Specify the number of FPGA devices to support.
2182
2183		CONFIG_SYS_FPGA_PROG_FEEDBACK
2184
2185		Enable printing of hash marks during FPGA configuration.
2186
2187		CONFIG_SYS_FPGA_CHECK_BUSY
2188
2189		Enable checks on FPGA configuration interface busy
2190		status by the configuration function. This option
2191		will require a board or device specific function to
2192		be written.
2193
2194		CONFIG_FPGA_DELAY
2195
2196		If defined, a function that provides delays in the FPGA
2197		configuration driver.
2198
2199		CONFIG_SYS_FPGA_CHECK_CTRLC
2200		Allow Control-C to interrupt FPGA configuration
2201
2202		CONFIG_SYS_FPGA_CHECK_ERROR
2203
2204		Check for configuration errors during FPGA bitfile
2205		loading. For example, abort during Virtex II
2206		configuration if the INIT_B line goes low (which
2207		indicated a CRC error).
2208
2209		CONFIG_SYS_FPGA_WAIT_INIT
2210
2211		Maximum time to wait for the INIT_B line to deassert
2212		after PROB_B has been deasserted during a Virtex II
2213		FPGA configuration sequence. The default time is 500
2214		ms.
2215
2216		CONFIG_SYS_FPGA_WAIT_BUSY
2217
2218		Maximum time to wait for BUSY to deassert during
2219		Virtex II FPGA configuration. The default is 5 ms.
2220
2221		CONFIG_SYS_FPGA_WAIT_CONFIG
2222
2223		Time to wait after FPGA configuration. The default is
2224		200 ms.
2225
2226- Configuration Management:
2227		CONFIG_IDENT_STRING
2228
2229		If defined, this string will be added to the U-Boot
2230		version information (U_BOOT_VERSION)
2231
2232- Vendor Parameter Protection:
2233
2234		U-Boot considers the values of the environment
2235		variables "serial#" (Board Serial Number) and
2236		"ethaddr" (Ethernet Address) to be parameters that
2237		are set once by the board vendor / manufacturer, and
2238		protects these variables from casual modification by
2239		the user. Once set, these variables are read-only,
2240		and write or delete attempts are rejected. You can
2241		change this behaviour:
2242
2243		If CONFIG_ENV_OVERWRITE is #defined in your config
2244		file, the write protection for vendor parameters is
2245		completely disabled. Anybody can change or delete
2246		these parameters.
2247
2248		Alternatively, if you #define _both_ CONFIG_ETHADDR
2249		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2250		Ethernet address is installed in the environment,
2251		which can be changed exactly ONCE by the user. [The
2252		serial# is unaffected by this, i. e. it remains
2253		read-only.]
2254
2255		The same can be accomplished in a more flexible way
2256		for any variable by configuring the type of access
2257		to allow for those variables in the ".flags" variable
2258		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2259
2260- Protected RAM:
2261		CONFIG_PRAM
2262
2263		Define this variable to enable the reservation of
2264		"protected RAM", i. e. RAM which is not overwritten
2265		by U-Boot. Define CONFIG_PRAM to hold the number of
2266		kB you want to reserve for pRAM. You can overwrite
2267		this default value by defining an environment
2268		variable "pram" to the number of kB you want to
2269		reserve. Note that the board info structure will
2270		still show the full amount of RAM. If pRAM is
2271		reserved, a new environment variable "mem" will
2272		automatically be defined to hold the amount of
2273		remaining RAM in a form that can be passed as boot
2274		argument to Linux, for instance like that:
2275
2276			setenv bootargs ... mem=\${mem}
2277			saveenv
2278
2279		This way you can tell Linux not to use this memory,
2280		either, which results in a memory region that will
2281		not be affected by reboots.
2282
2283		*WARNING* If your board configuration uses automatic
2284		detection of the RAM size, you must make sure that
2285		this memory test is non-destructive. So far, the
2286		following board configurations are known to be
2287		"pRAM-clean":
2288
2289			IVMS8, IVML24, SPD8xx, TQM8xxL,
2290			HERMES, IP860, RPXlite, LWMON,
2291			FLAGADM, TQM8260
2292
2293- Access to physical memory region (> 4GB)
2294		Some basic support is provided for operations on memory not
2295		normally accessible to U-Boot - e.g. some architectures
2296		support access to more than 4GB of memory on 32-bit
2297		machines using physical address extension or similar.
2298		Define CONFIG_PHYSMEM to access this basic support, which
2299		currently only supports clearing the memory.
2300
2301- Error Recovery:
2302		CONFIG_PANIC_HANG
2303
2304		Define this variable to stop the system in case of a
2305		fatal error, so that you have to reset it manually.
2306		This is probably NOT a good idea for an embedded
2307		system where you want the system to reboot
2308		automatically as fast as possible, but it may be
2309		useful during development since you can try to debug
2310		the conditions that lead to the situation.
2311
2312		CONFIG_NET_RETRY_COUNT
2313
2314		This variable defines the number of retries for
2315		network operations like ARP, RARP, TFTP, or BOOTP
2316		before giving up the operation. If not defined, a
2317		default value of 5 is used.
2318
2319		CONFIG_ARP_TIMEOUT
2320
2321		Timeout waiting for an ARP reply in milliseconds.
2322
2323		CONFIG_NFS_TIMEOUT
2324
2325		Timeout in milliseconds used in NFS protocol.
2326		If you encounter "ERROR: Cannot umount" in nfs command,
2327		try longer timeout such as
2328		#define CONFIG_NFS_TIMEOUT 10000UL
2329
2330- Command Interpreter:
2331		CONFIG_AUTO_COMPLETE
2332
2333		Enable auto completion of commands using TAB.
2334
2335		Note that this feature has NOT been implemented yet
2336		for the "hush" shell.
2337
2338
2339		CONFIG_SYS_HUSH_PARSER
2340
2341		Define this variable to enable the "hush" shell (from
2342		Busybox) as command line interpreter, thus enabling
2343		powerful command line syntax like
2344		if...then...else...fi conditionals or `&&' and '||'
2345		constructs ("shell scripts").
2346
2347		If undefined, you get the old, much simpler behaviour
2348		with a somewhat smaller memory footprint.
2349
2350
2351		CONFIG_SYS_PROMPT_HUSH_PS2
2352
2353		This defines the secondary prompt string, which is
2354		printed when the command interpreter needs more input
2355		to complete a command. Usually "> ".
2356
2357	Note:
2358
2359		In the current implementation, the local variables
2360		space and global environment variables space are
2361		separated. Local variables are those you define by
2362		simply typing `name=value'. To access a local
2363		variable later on, you have write `$name' or
2364		`${name}'; to execute the contents of a variable
2365		directly type `$name' at the command prompt.
2366
2367		Global environment variables are those you use
2368		setenv/printenv to work with. To run a command stored
2369		in such a variable, you need to use the run command,
2370		and you must not use the '$' sign to access them.
2371
2372		To store commands and special characters in a
2373		variable, please use double quotation marks
2374		surrounding the whole text of the variable, instead
2375		of the backslashes before semicolons and special
2376		symbols.
2377
2378- Commandline Editing and History:
2379		CONFIG_CMDLINE_EDITING
2380
2381		Enable editing and History functions for interactive
2382		commandline input operations
2383
2384- Default Environment:
2385		CONFIG_EXTRA_ENV_SETTINGS
2386
2387		Define this to contain any number of null terminated
2388		strings (variable = value pairs) that will be part of
2389		the default environment compiled into the boot image.
2390
2391		For example, place something like this in your
2392		board's config file:
2393
2394		#define CONFIG_EXTRA_ENV_SETTINGS \
2395			"myvar1=value1\0" \
2396			"myvar2=value2\0"
2397
2398		Warning: This method is based on knowledge about the
2399		internal format how the environment is stored by the
2400		U-Boot code. This is NOT an official, exported
2401		interface! Although it is unlikely that this format
2402		will change soon, there is no guarantee either.
2403		You better know what you are doing here.
2404
2405		Note: overly (ab)use of the default environment is
2406		discouraged. Make sure to check other ways to preset
2407		the environment like the "source" command or the
2408		boot command first.
2409
2410		CONFIG_ENV_VARS_UBOOT_CONFIG
2411
2412		Define this in order to add variables describing the
2413		U-Boot build configuration to the default environment.
2414		These will be named arch, cpu, board, vendor, and soc.
2415
2416		Enabling this option will cause the following to be defined:
2417
2418		- CONFIG_SYS_ARCH
2419		- CONFIG_SYS_CPU
2420		- CONFIG_SYS_BOARD
2421		- CONFIG_SYS_VENDOR
2422		- CONFIG_SYS_SOC
2423
2424		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2425
2426		Define this in order to add variables describing certain
2427		run-time determined information about the hardware to the
2428		environment.  These will be named board_name, board_rev.
2429
2430		CONFIG_DELAY_ENVIRONMENT
2431
2432		Normally the environment is loaded when the board is
2433		intialised so that it is available to U-Boot. This inhibits
2434		that so that the environment is not available until
2435		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2436		this is instead controlled by the value of
2437		/config/load-environment.
2438
2439- DataFlash Support:
2440		CONFIG_HAS_DATAFLASH
2441
2442		Defining this option enables DataFlash features and
2443		allows to read/write in Dataflash via the standard
2444		commands cp, md...
2445
2446- Serial Flash support
2447		CONFIG_CMD_SF
2448
2449		Defining this option enables SPI flash commands
2450		'sf probe/read/write/erase/update'.
2451
2452		Usage requires an initial 'probe' to define the serial
2453		flash parameters, followed by read/write/erase/update
2454		commands.
2455
2456		The following defaults may be provided by the platform
2457		to handle the common case when only a single serial
2458		flash is present on the system.
2459
2460		CONFIG_SF_DEFAULT_BUS		Bus identifier
2461		CONFIG_SF_DEFAULT_CS		Chip-select
2462		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2463		CONFIG_SF_DEFAULT_SPEED		in Hz
2464
2465		CONFIG_CMD_SF_TEST
2466
2467		Define this option to include a destructive SPI flash
2468		test ('sf test').
2469
2470- SystemACE Support:
2471		CONFIG_SYSTEMACE
2472
2473		Adding this option adds support for Xilinx SystemACE
2474		chips attached via some sort of local bus. The address
2475		of the chip must also be defined in the
2476		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2477
2478		#define CONFIG_SYSTEMACE
2479		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2480
2481		When SystemACE support is added, the "ace" device type
2482		becomes available to the fat commands, i.e. fatls.
2483
2484- TFTP Fixed UDP Port:
2485		CONFIG_TFTP_PORT
2486
2487		If this is defined, the environment variable tftpsrcp
2488		is used to supply the TFTP UDP source port value.
2489		If tftpsrcp isn't defined, the normal pseudo-random port
2490		number generator is used.
2491
2492		Also, the environment variable tftpdstp is used to supply
2493		the TFTP UDP destination port value.  If tftpdstp isn't
2494		defined, the normal port 69 is used.
2495
2496		The purpose for tftpsrcp is to allow a TFTP server to
2497		blindly start the TFTP transfer using the pre-configured
2498		target IP address and UDP port. This has the effect of
2499		"punching through" the (Windows XP) firewall, allowing
2500		the remainder of the TFTP transfer to proceed normally.
2501		A better solution is to properly configure the firewall,
2502		but sometimes that is not allowed.
2503
2504- Hashing support:
2505		CONFIG_CMD_HASH
2506
2507		This enables a generic 'hash' command which can produce
2508		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2509
2510		CONFIG_HASH_VERIFY
2511
2512		Enable the hash verify command (hash -v). This adds to code
2513		size a little.
2514
2515		CONFIG_SHA1 - support SHA1 hashing
2516		CONFIG_SHA256 - support SHA256 hashing
2517
2518		Note: There is also a sha1sum command, which should perhaps
2519		be deprecated in favour of 'hash sha1'.
2520
2521- Show boot progress:
2522		CONFIG_SHOW_BOOT_PROGRESS
2523
2524		Defining this option allows to add some board-
2525		specific code (calling a user-provided function
2526		"show_boot_progress(int)") that enables you to show
2527		the system's boot progress on some display (for
2528		example, some LED's) on your board. At the moment,
2529		the following checkpoints are implemented:
2530
2531- Detailed boot stage timing
2532		CONFIG_BOOTSTAGE
2533		Define this option to get detailed timing of each stage
2534		of the boot process.
2535
2536		CONFIG_BOOTSTAGE_USER_COUNT
2537		This is the number of available user bootstage records.
2538		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
2539		a new ID will be allocated from this stash. If you exceed
2540		the limit, recording will stop.
2541
2542		CONFIG_BOOTSTAGE_REPORT
2543		Define this to print a report before boot, similar to this:
2544
2545		Timer summary in microseconds:
2546		       Mark    Elapsed  Stage
2547			  0          0  reset
2548		  3,575,678  3,575,678  board_init_f start
2549		  3,575,695         17  arch_cpu_init A9
2550		  3,575,777         82  arch_cpu_init done
2551		  3,659,598     83,821  board_init_r start
2552		  3,910,375    250,777  main_loop
2553		 29,916,167 26,005,792  bootm_start
2554		 30,361,327    445,160  start_kernel
2555
2556		CONFIG_CMD_BOOTSTAGE
2557		Add a 'bootstage' command which supports printing a report
2558		and un/stashing of bootstage data.
2559
2560		CONFIG_BOOTSTAGE_FDT
2561		Stash the bootstage information in the FDT. A root 'bootstage'
2562		node is created with each bootstage id as a child. Each child
2563		has a 'name' property and either 'mark' containing the
2564		mark time in microsecond, or 'accum' containing the
2565		accumulated time for that bootstage id in microseconds.
2566		For example:
2567
2568		bootstage {
2569			154 {
2570				name = "board_init_f";
2571				mark = <3575678>;
2572			};
2573			170 {
2574				name = "lcd";
2575				accum = <33482>;
2576			};
2577		};
2578
2579		Code in the Linux kernel can find this in /proc/devicetree.
2580
2581Legacy uImage format:
2582
2583  Arg	Where			When
2584    1	common/cmd_bootm.c	before attempting to boot an image
2585   -1	common/cmd_bootm.c	Image header has bad	 magic number
2586    2	common/cmd_bootm.c	Image header has correct magic number
2587   -2	common/cmd_bootm.c	Image header has bad	 checksum
2588    3	common/cmd_bootm.c	Image header has correct checksum
2589   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2590    4	common/cmd_bootm.c	Image data   has correct checksum
2591   -4	common/cmd_bootm.c	Image is for unsupported architecture
2592    5	common/cmd_bootm.c	Architecture check OK
2593   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2594    6	common/cmd_bootm.c	Image Type check OK
2595   -6	common/cmd_bootm.c	gunzip uncompression error
2596   -7	common/cmd_bootm.c	Unimplemented compression type
2597    7	common/cmd_bootm.c	Uncompression OK
2598    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2599   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2600
2601    9	common/image.c		Start initial ramdisk verification
2602  -10	common/image.c		Ramdisk header has bad	   magic number
2603  -11	common/image.c		Ramdisk header has bad	   checksum
2604   10	common/image.c		Ramdisk header is OK
2605  -12	common/image.c		Ramdisk data   has bad	   checksum
2606   11	common/image.c		Ramdisk data   has correct checksum
2607   12	common/image.c		Ramdisk verification complete, start loading
2608  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2609   13	common/image.c		Start multifile image verification
2610   14	common/image.c		No initial ramdisk, no multifile, continue.
2611
2612   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2613
2614  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2615  -31	post/post.c		POST test failed, detected by post_output_backlog()
2616  -32	post/post.c		POST test failed, detected by post_run_single()
2617
2618   34	common/cmd_doc.c	before loading a Image from a DOC device
2619  -35	common/cmd_doc.c	Bad usage of "doc" command
2620   35	common/cmd_doc.c	correct usage of "doc" command
2621  -36	common/cmd_doc.c	No boot device
2622   36	common/cmd_doc.c	correct boot device
2623  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2624   37	common/cmd_doc.c	correct chip ID found, device available
2625  -38	common/cmd_doc.c	Read Error on boot device
2626   38	common/cmd_doc.c	reading Image header from DOC device OK
2627  -39	common/cmd_doc.c	Image header has bad magic number
2628   39	common/cmd_doc.c	Image header has correct magic number
2629  -40	common/cmd_doc.c	Error reading Image from DOC device
2630   40	common/cmd_doc.c	Image header has correct magic number
2631   41	common/cmd_ide.c	before loading a Image from a IDE device
2632  -42	common/cmd_ide.c	Bad usage of "ide" command
2633   42	common/cmd_ide.c	correct usage of "ide" command
2634  -43	common/cmd_ide.c	No boot device
2635   43	common/cmd_ide.c	boot device found
2636  -44	common/cmd_ide.c	Device not available
2637   44	common/cmd_ide.c	Device available
2638  -45	common/cmd_ide.c	wrong partition selected
2639   45	common/cmd_ide.c	partition selected
2640  -46	common/cmd_ide.c	Unknown partition table
2641   46	common/cmd_ide.c	valid partition table found
2642  -47	common/cmd_ide.c	Invalid partition type
2643   47	common/cmd_ide.c	correct partition type
2644  -48	common/cmd_ide.c	Error reading Image Header on boot device
2645   48	common/cmd_ide.c	reading Image Header from IDE device OK
2646  -49	common/cmd_ide.c	Image header has bad magic number
2647   49	common/cmd_ide.c	Image header has correct magic number
2648  -50	common/cmd_ide.c	Image header has bad	 checksum
2649   50	common/cmd_ide.c	Image header has correct checksum
2650  -51	common/cmd_ide.c	Error reading Image from IDE device
2651   51	common/cmd_ide.c	reading Image from IDE device OK
2652   52	common/cmd_nand.c	before loading a Image from a NAND device
2653  -53	common/cmd_nand.c	Bad usage of "nand" command
2654   53	common/cmd_nand.c	correct usage of "nand" command
2655  -54	common/cmd_nand.c	No boot device
2656   54	common/cmd_nand.c	boot device found
2657  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2658   55	common/cmd_nand.c	correct chip ID found, device available
2659  -56	common/cmd_nand.c	Error reading Image Header on boot device
2660   56	common/cmd_nand.c	reading Image Header from NAND device OK
2661  -57	common/cmd_nand.c	Image header has bad magic number
2662   57	common/cmd_nand.c	Image header has correct magic number
2663  -58	common/cmd_nand.c	Error reading Image from NAND device
2664   58	common/cmd_nand.c	reading Image from NAND device OK
2665
2666  -60	common/env_common.c	Environment has a bad CRC, using default
2667
2668   64	net/eth.c		starting with Ethernet configuration.
2669  -64	net/eth.c		no Ethernet found.
2670   65	net/eth.c		Ethernet found.
2671
2672  -80	common/cmd_net.c	usage wrong
2673   80	common/cmd_net.c	before calling NetLoop()
2674  -81	common/cmd_net.c	some error in NetLoop() occurred
2675   81	common/cmd_net.c	NetLoop() back without error
2676  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2677   82	common/cmd_net.c	trying automatic boot
2678   83	common/cmd_net.c	running "source" command
2679  -83	common/cmd_net.c	some error in automatic boot or "source" command
2680   84	common/cmd_net.c	end without errors
2681
2682FIT uImage format:
2683
2684  Arg	Where			When
2685  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2686 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2687  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2688 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2689  102	common/cmd_bootm.c	Kernel unit name specified
2690 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2691  103	common/cmd_bootm.c	Found configuration node
2692  104	common/cmd_bootm.c	Got kernel subimage node offset
2693 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2694  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2695 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2696  106	common/cmd_bootm.c	Architecture check OK
2697 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2698  107	common/cmd_bootm.c	Kernel subimage type OK
2699 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2700  108	common/cmd_bootm.c	Got kernel subimage data/size
2701 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2702 -109	common/cmd_bootm.c	Can't get kernel subimage type
2703 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2704 -111	common/cmd_bootm.c	Can't get kernel subimage os
2705 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2706 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2707
2708  120	common/image.c		Start initial ramdisk verification
2709 -120	common/image.c		Ramdisk FIT image has incorrect format
2710  121	common/image.c		Ramdisk FIT image has correct format
2711  122	common/image.c		No ramdisk subimage unit name, using configuration
2712 -122	common/image.c		Can't get configuration for ramdisk subimage
2713  123	common/image.c		Ramdisk unit name specified
2714 -124	common/image.c		Can't get ramdisk subimage node offset
2715  125	common/image.c		Got ramdisk subimage node offset
2716 -125	common/image.c		Ramdisk subimage hash verification failed
2717  126	common/image.c		Ramdisk subimage hash verification OK
2718 -126	common/image.c		Ramdisk subimage for unsupported architecture
2719  127	common/image.c		Architecture check OK
2720 -127	common/image.c		Can't get ramdisk subimage data/size
2721  128	common/image.c		Got ramdisk subimage data/size
2722  129	common/image.c		Can't get ramdisk load address
2723 -129	common/image.c		Got ramdisk load address
2724
2725 -130	common/cmd_doc.c	Incorrect FIT image format
2726  131	common/cmd_doc.c	FIT image format OK
2727
2728 -140	common/cmd_ide.c	Incorrect FIT image format
2729  141	common/cmd_ide.c	FIT image format OK
2730
2731 -150	common/cmd_nand.c	Incorrect FIT image format
2732  151	common/cmd_nand.c	FIT image format OK
2733
2734- FIT image support:
2735		CONFIG_FIT
2736		Enable support for the FIT uImage format.
2737
2738		CONFIG_FIT_BEST_MATCH
2739		When no configuration is explicitly selected, default to the
2740		one whose fdt's compatibility field best matches that of
2741		U-Boot itself. A match is considered "best" if it matches the
2742		most specific compatibility entry of U-Boot's fdt's root node.
2743		The order of entries in the configuration's fdt is ignored.
2744
2745- Standalone program support:
2746		CONFIG_STANDALONE_LOAD_ADDR
2747
2748		This option defines a board specific value for the
2749		address where standalone program gets loaded, thus
2750		overwriting the architecture dependent default
2751		settings.
2752
2753- Frame Buffer Address:
2754		CONFIG_FB_ADDR
2755
2756		Define CONFIG_FB_ADDR if you want to use specific
2757		address for frame buffer.  This is typically the case
2758		when using a graphics controller has separate video
2759		memory.  U-Boot will then place the frame buffer at
2760		the given address instead of dynamically reserving it
2761		in system RAM by calling lcd_setmem(), which grabs
2762		the memory for the frame buffer depending on the
2763		configured panel size.
2764
2765		Please see board_init_f function.
2766
2767- Automatic software updates via TFTP server
2768		CONFIG_UPDATE_TFTP
2769		CONFIG_UPDATE_TFTP_CNT_MAX
2770		CONFIG_UPDATE_TFTP_MSEC_MAX
2771
2772		These options enable and control the auto-update feature;
2773		for a more detailed description refer to doc/README.update.
2774
2775- MTD Support (mtdparts command, UBI support)
2776		CONFIG_MTD_DEVICE
2777
2778		Adds the MTD device infrastructure from the Linux kernel.
2779		Needed for mtdparts command support.
2780
2781		CONFIG_MTD_PARTITIONS
2782
2783		Adds the MTD partitioning infrastructure from the Linux
2784		kernel. Needed for UBI support.
2785
2786- SPL framework
2787		CONFIG_SPL
2788		Enable building of SPL globally.
2789
2790		CONFIG_SPL_LDSCRIPT
2791		LDSCRIPT for linking the SPL binary.
2792
2793		CONFIG_SPL_MAX_SIZE
2794		Maximum binary size (text, data and rodata) of the SPL binary.
2795
2796		CONFIG_SPL_TEXT_BASE
2797		TEXT_BASE for linking the SPL binary.
2798
2799		CONFIG_SPL_RELOC_TEXT_BASE
2800		Address to relocate to.  If unspecified, this is equal to
2801		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2802
2803		CONFIG_SPL_BSS_START_ADDR
2804		Link address for the BSS within the SPL binary.
2805
2806		CONFIG_SPL_BSS_MAX_SIZE
2807		Maximum binary size of the BSS section of the SPL binary.
2808
2809		CONFIG_SPL_STACK
2810		Adress of the start of the stack SPL will use
2811
2812		CONFIG_SPL_RELOC_STACK
2813		Adress of the start of the stack SPL will use after
2814		relocation.  If unspecified, this is equal to
2815		CONFIG_SPL_STACK.
2816
2817		CONFIG_SYS_SPL_MALLOC_START
2818		Starting address of the malloc pool used in SPL.
2819
2820		CONFIG_SYS_SPL_MALLOC_SIZE
2821		The size of the malloc pool used in SPL.
2822
2823		CONFIG_SPL_FRAMEWORK
2824		Enable the SPL framework under common/.  This framework
2825		supports MMC, NAND and YMODEM loading of U-Boot and NAND
2826		NAND loading of the Linux Kernel.
2827
2828		CONFIG_SPL_DISPLAY_PRINT
2829		For ARM, enable an optional function to print more information
2830		about the running system.
2831
2832		CONFIG_SPL_INIT_MINIMAL
2833		Arch init code should be built for a very small image
2834
2835		CONFIG_SPL_LIBCOMMON_SUPPORT
2836		Support for common/libcommon.o in SPL binary
2837
2838		CONFIG_SPL_LIBDISK_SUPPORT
2839		Support for disk/libdisk.o in SPL binary
2840
2841		CONFIG_SPL_I2C_SUPPORT
2842		Support for drivers/i2c/libi2c.o in SPL binary
2843
2844		CONFIG_SPL_GPIO_SUPPORT
2845		Support for drivers/gpio/libgpio.o in SPL binary
2846
2847		CONFIG_SPL_MMC_SUPPORT
2848		Support for drivers/mmc/libmmc.o in SPL binary
2849
2850		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
2851		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
2852		CONFIG_SYS_MMC_SD_FAT_BOOT_PARTITION
2853		Address, size and partition on the MMC to load U-Boot from
2854		when the MMC is being used in raw mode.
2855
2856		CONFIG_SPL_FAT_SUPPORT
2857		Support for fs/fat/libfat.o in SPL binary
2858
2859		CONFIG_SPL_FAT_LOAD_PAYLOAD_NAME
2860		Filename to read to load U-Boot when reading from FAT
2861
2862		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2863		Set this for NAND SPL on PPC mpc83xx targets, so that
2864		start.S waits for the rest of the SPL to load before
2865		continuing (the hardware starts execution after just
2866		loading the first page rather than the full 4K).
2867
2868		CONFIG_SPL_NAND_BASE
2869		Include nand_base.c in the SPL.  Requires
2870		CONFIG_SPL_NAND_DRIVERS.
2871
2872		CONFIG_SPL_NAND_DRIVERS
2873		SPL uses normal NAND drivers, not minimal drivers.
2874
2875		CONFIG_SPL_NAND_ECC
2876		Include standard software ECC in the SPL
2877
2878		CONFIG_SPL_NAND_SIMPLE
2879		Support for NAND boot using simple NAND drivers that
2880		expose the cmd_ctrl() interface.
2881
2882		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2883		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2884		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2885		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2886		CONFIG_SYS_NAND_ECCBYTES
2887		Defines the size and behavior of the NAND that SPL uses
2888		to read U-Boot
2889
2890		CONFIG_SYS_NAND_U_BOOT_OFFS
2891		Location in NAND to read U-Boot from
2892
2893		CONFIG_SYS_NAND_U_BOOT_DST
2894		Location in memory to load U-Boot to
2895
2896		CONFIG_SYS_NAND_U_BOOT_SIZE
2897		Size of image to load
2898
2899		CONFIG_SYS_NAND_U_BOOT_START
2900		Entry point in loaded image to jump to
2901
2902		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2903		Define this if you need to first read the OOB and then the
2904		data. This is used for example on davinci plattforms.
2905
2906		CONFIG_SPL_OMAP3_ID_NAND
2907		Support for an OMAP3-specific set of functions to return the
2908		ID and MFR of the first attached NAND chip, if present.
2909
2910		CONFIG_SPL_SERIAL_SUPPORT
2911		Support for drivers/serial/libserial.o in SPL binary
2912
2913		CONFIG_SPL_SPI_FLASH_SUPPORT
2914		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
2915
2916		CONFIG_SPL_SPI_SUPPORT
2917		Support for drivers/spi/libspi.o in SPL binary
2918
2919		CONFIG_SPL_RAM_DEVICE
2920		Support for running image already present in ram, in SPL binary
2921
2922		CONFIG_SPL_LIBGENERIC_SUPPORT
2923		Support for lib/libgeneric.o in SPL binary
2924
2925		CONFIG_SPL_PAD_TO
2926		Linker address to which the SPL should be padded before
2927		appending the SPL payload.
2928
2929		CONFIG_SPL_TARGET
2930		Final target image containing SPL and payload.  Some SPLs
2931		use an arch-specific makefile fragment instead, for
2932		example if more than one image needs to be produced.
2933
2934Modem Support:
2935--------------
2936
2937[so far only for SMDK2400 boards]
2938
2939- Modem support enable:
2940		CONFIG_MODEM_SUPPORT
2941
2942- RTS/CTS Flow control enable:
2943		CONFIG_HWFLOW
2944
2945- Modem debug support:
2946		CONFIG_MODEM_SUPPORT_DEBUG
2947
2948		Enables debugging stuff (char screen[1024], dbg())
2949		for modem support. Useful only with BDI2000.
2950
2951- Interrupt support (PPC):
2952
2953		There are common interrupt_init() and timer_interrupt()
2954		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2955		for CPU specific initialization. interrupt_init_cpu()
2956		should set decrementer_count to appropriate value. If
2957		CPU resets decrementer automatically after interrupt
2958		(ppc4xx) it should set decrementer_count to zero.
2959		timer_interrupt() calls timer_interrupt_cpu() for CPU
2960		specific handling. If board has watchdog / status_led
2961		/ other_activity_monitor it works automatically from
2962		general timer_interrupt().
2963
2964- General:
2965
2966		In the target system modem support is enabled when a
2967		specific key (key combination) is pressed during
2968		power-on. Otherwise U-Boot will boot normally
2969		(autoboot). The key_pressed() function is called from
2970		board_init(). Currently key_pressed() is a dummy
2971		function, returning 1 and thus enabling modem
2972		initialization.
2973
2974		If there are no modem init strings in the
2975		environment, U-Boot proceed to autoboot; the
2976		previous output (banner, info printfs) will be
2977		suppressed, though.
2978
2979		See also: doc/README.Modem
2980
2981Board initialization settings:
2982------------------------------
2983
2984During Initialization u-boot calls a number of board specific functions
2985to allow the preparation of board specific prerequisites, e.g. pin setup
2986before drivers are initialized. To enable these callbacks the
2987following configuration macros have to be defined. Currently this is
2988architecture specific, so please check arch/your_architecture/lib/board.c
2989typically in board_init_f() and board_init_r().
2990
2991- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2992- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2993- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2994- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2995
2996Configuration Settings:
2997-----------------------
2998
2999- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3000		undefine this when you're short of memory.
3001
3002- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3003		width of the commands listed in the 'help' command output.
3004
3005- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3006		prompt for user input.
3007
3008- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3009
3010- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3011
3012- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3013
3014- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3015		the application (usually a Linux kernel) when it is
3016		booted
3017
3018- CONFIG_SYS_BAUDRATE_TABLE:
3019		List of legal baudrate settings for this board.
3020
3021- CONFIG_SYS_CONSOLE_INFO_QUIET
3022		Suppress display of console information at boot.
3023
3024- CONFIG_SYS_CONSOLE_IS_IN_ENV
3025		If the board specific function
3026			extern int overwrite_console (void);
3027		returns 1, the stdin, stderr and stdout are switched to the
3028		serial port, else the settings in the environment are used.
3029
3030- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3031		Enable the call to overwrite_console().
3032
3033- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3034		Enable overwrite of previous console environment settings.
3035
3036- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3037		Begin and End addresses of the area used by the
3038		simple memory test.
3039
3040- CONFIG_SYS_ALT_MEMTEST:
3041		Enable an alternate, more extensive memory test.
3042
3043- CONFIG_SYS_MEMTEST_SCRATCH:
3044		Scratch address used by the alternate memory test
3045		You only need to set this if address zero isn't writeable
3046
3047- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3048		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3049		this specified memory area will get subtracted from the top
3050		(end) of RAM and won't get "touched" at all by U-Boot. By
3051		fixing up gd->ram_size the Linux kernel should gets passed
3052		the now "corrected" memory size and won't touch it either.
3053		This should work for arch/ppc and arch/powerpc. Only Linux
3054		board ports in arch/powerpc with bootwrapper support that
3055		recalculate the memory size from the SDRAM controller setup
3056		will have to get fixed in Linux additionally.
3057
3058		This option can be used as a workaround for the 440EPx/GRx
3059		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3060		be touched.
3061
3062		WARNING: Please make sure that this value is a multiple of
3063		the Linux page size (normally 4k). If this is not the case,
3064		then the end address of the Linux memory will be located at a
3065		non page size aligned address and this could cause major
3066		problems.
3067
3068- CONFIG_SYS_LOADS_BAUD_CHANGE:
3069		Enable temporary baudrate change while serial download
3070
3071- CONFIG_SYS_SDRAM_BASE:
3072		Physical start address of SDRAM. _Must_ be 0 here.
3073
3074- CONFIG_SYS_MBIO_BASE:
3075		Physical start address of Motherboard I/O (if using a
3076		Cogent motherboard)
3077
3078- CONFIG_SYS_FLASH_BASE:
3079		Physical start address of Flash memory.
3080
3081- CONFIG_SYS_MONITOR_BASE:
3082		Physical start address of boot monitor code (set by
3083		make config files to be same as the text base address
3084		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3085		CONFIG_SYS_FLASH_BASE when booting from flash.
3086
3087- CONFIG_SYS_MONITOR_LEN:
3088		Size of memory reserved for monitor code, used to
3089		determine _at_compile_time_ (!) if the environment is
3090		embedded within the U-Boot image, or in a separate
3091		flash sector.
3092
3093- CONFIG_SYS_MALLOC_LEN:
3094		Size of DRAM reserved for malloc() use.
3095
3096- CONFIG_SYS_BOOTM_LEN:
3097		Normally compressed uImages are limited to an
3098		uncompressed size of 8 MBytes. If this is not enough,
3099		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3100		to adjust this setting to your needs.
3101
3102- CONFIG_SYS_BOOTMAPSZ:
3103		Maximum size of memory mapped by the startup code of
3104		the Linux kernel; all data that must be processed by
3105		the Linux kernel (bd_info, boot arguments, FDT blob if
3106		used) must be put below this limit, unless "bootm_low"
3107		enviroment variable is defined and non-zero. In such case
3108		all data for the Linux kernel must be between "bootm_low"
3109		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3110		variable "bootm_mapsize" will override the value of
3111		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3112		then the value in "bootm_size" will be used instead.
3113
3114- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3115		Enable initrd_high functionality.  If defined then the
3116		initrd_high feature is enabled and the bootm ramdisk subcommand
3117		is enabled.
3118
3119- CONFIG_SYS_BOOT_GET_CMDLINE:
3120		Enables allocating and saving kernel cmdline in space between
3121		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3122
3123- CONFIG_SYS_BOOT_GET_KBD:
3124		Enables allocating and saving a kernel copy of the bd_info in
3125		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3126
3127- CONFIG_SYS_MAX_FLASH_BANKS:
3128		Max number of Flash memory banks
3129
3130- CONFIG_SYS_MAX_FLASH_SECT:
3131		Max number of sectors on a Flash chip
3132
3133- CONFIG_SYS_FLASH_ERASE_TOUT:
3134		Timeout for Flash erase operations (in ms)
3135
3136- CONFIG_SYS_FLASH_WRITE_TOUT:
3137		Timeout for Flash write operations (in ms)
3138
3139- CONFIG_SYS_FLASH_LOCK_TOUT
3140		Timeout for Flash set sector lock bit operation (in ms)
3141
3142- CONFIG_SYS_FLASH_UNLOCK_TOUT
3143		Timeout for Flash clear lock bits operation (in ms)
3144
3145- CONFIG_SYS_FLASH_PROTECTION
3146		If defined, hardware flash sectors protection is used
3147		instead of U-Boot software protection.
3148
3149- CONFIG_SYS_DIRECT_FLASH_TFTP:
3150
3151		Enable TFTP transfers directly to flash memory;
3152		without this option such a download has to be
3153		performed in two steps: (1) download to RAM, and (2)
3154		copy from RAM to flash.
3155
3156		The two-step approach is usually more reliable, since
3157		you can check if the download worked before you erase
3158		the flash, but in some situations (when system RAM is
3159		too limited to allow for a temporary copy of the
3160		downloaded image) this option may be very useful.
3161
3162- CONFIG_SYS_FLASH_CFI:
3163		Define if the flash driver uses extra elements in the
3164		common flash structure for storing flash geometry.
3165
3166- CONFIG_FLASH_CFI_DRIVER
3167		This option also enables the building of the cfi_flash driver
3168		in the drivers directory
3169
3170- CONFIG_FLASH_CFI_MTD
3171		This option enables the building of the cfi_mtd driver
3172		in the drivers directory. The driver exports CFI flash
3173		to the MTD layer.
3174
3175- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3176		Use buffered writes to flash.
3177
3178- CONFIG_FLASH_SPANSION_S29WS_N
3179		s29ws-n MirrorBit flash has non-standard addresses for buffered
3180		write commands.
3181
3182- CONFIG_SYS_FLASH_QUIET_TEST
3183		If this option is defined, the common CFI flash doesn't
3184		print it's warning upon not recognized FLASH banks. This
3185		is useful, if some of the configured banks are only
3186		optionally available.
3187
3188- CONFIG_FLASH_SHOW_PROGRESS
3189		If defined (must be an integer), print out countdown
3190		digits and dots.  Recommended value: 45 (9..1) for 80
3191		column displays, 15 (3..1) for 40 column displays.
3192
3193- CONFIG_SYS_RX_ETH_BUFFER:
3194		Defines the number of Ethernet receive buffers. On some
3195		Ethernet controllers it is recommended to set this value
3196		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3197		buffers can be full shortly after enabling the interface
3198		on high Ethernet traffic.
3199		Defaults to 4 if not defined.
3200
3201- CONFIG_ENV_MAX_ENTRIES
3202
3203	Maximum number of entries in the hash table that is used
3204	internally to store the environment settings. The default
3205	setting is supposed to be generous and should work in most
3206	cases. This setting can be used to tune behaviour; see
3207	lib/hashtable.c for details.
3208
3209- CONFIG_ENV_FLAGS_LIST_DEFAULT
3210- CONFIG_ENV_FLAGS_LIST_STATIC
3211	Enable validation of the values given to enviroment variables when
3212	calling env set.  Variables can be restricted to only decimal,
3213	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3214	the variables can also be restricted to IP address or MAC address.
3215
3216	The format of the list is:
3217		type_attribute = [s|d|x|b|i|m]
3218		access_atribute = [a|r|o|c]
3219		attributes = type_attribute[access_atribute]
3220		entry = variable_name[:attributes]
3221		list = entry[,list]
3222
3223	The type attributes are:
3224		s - String (default)
3225		d - Decimal
3226		x - Hexadecimal
3227		b - Boolean ([1yYtT|0nNfF])
3228		i - IP address
3229		m - MAC address
3230
3231	The access attributes are:
3232		a - Any (default)
3233		r - Read-only
3234		o - Write-once
3235		c - Change-default
3236
3237	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3238		Define this to a list (string) to define the ".flags"
3239		envirnoment variable in the default or embedded environment.
3240
3241	- CONFIG_ENV_FLAGS_LIST_STATIC
3242		Define this to a list (string) to define validation that
3243		should be done if an entry is not found in the ".flags"
3244		environment variable.  To override a setting in the static
3245		list, simply add an entry for the same variable name to the
3246		".flags" variable.
3247
3248- CONFIG_ENV_ACCESS_IGNORE_FORCE
3249	If defined, don't allow the -f switch to env set override variable
3250	access flags.
3251
3252- CONFIG_SYS_GENERIC_BOARD
3253	This selects the architecture-generic board system instead of the
3254	architecture-specific board files. It is intended to move boards
3255	to this new framework over time. Defining this will disable the
3256	arch/foo/lib/board.c file and use common/board_f.c and
3257	common/board_r.c instead. To use this option your architecture
3258	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
3259	its config.mk file). If you find problems enabling this option on
3260	your board please report the problem and send patches!
3261
3262- CONFIG_SYS_SYM_OFFSETS
3263	This is set by architectures that use offsets for link symbols
3264	instead of absolute values. So bss_start is obtained using an
3265	offset _bss_start_ofs from CONFIG_SYS_TEXT_BASE, rather than
3266	directly. You should not need to touch this setting.
3267
3268
3269The following definitions that deal with the placement and management
3270of environment data (variable area); in general, we support the
3271following configurations:
3272
3273- CONFIG_BUILD_ENVCRC:
3274
3275	Builds up envcrc with the target environment so that external utils
3276	may easily extract it and embed it in final U-Boot images.
3277
3278- CONFIG_ENV_IS_IN_FLASH:
3279
3280	Define this if the environment is in flash memory.
3281
3282	a) The environment occupies one whole flash sector, which is
3283	   "embedded" in the text segment with the U-Boot code. This
3284	   happens usually with "bottom boot sector" or "top boot
3285	   sector" type flash chips, which have several smaller
3286	   sectors at the start or the end. For instance, such a
3287	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3288	   such a case you would place the environment in one of the
3289	   4 kB sectors - with U-Boot code before and after it. With
3290	   "top boot sector" type flash chips, you would put the
3291	   environment in one of the last sectors, leaving a gap
3292	   between U-Boot and the environment.
3293
3294	- CONFIG_ENV_OFFSET:
3295
3296	   Offset of environment data (variable area) to the
3297	   beginning of flash memory; for instance, with bottom boot
3298	   type flash chips the second sector can be used: the offset
3299	   for this sector is given here.
3300
3301	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3302
3303	- CONFIG_ENV_ADDR:
3304
3305	   This is just another way to specify the start address of
3306	   the flash sector containing the environment (instead of
3307	   CONFIG_ENV_OFFSET).
3308
3309	- CONFIG_ENV_SECT_SIZE:
3310
3311	   Size of the sector containing the environment.
3312
3313
3314	b) Sometimes flash chips have few, equal sized, BIG sectors.
3315	   In such a case you don't want to spend a whole sector for
3316	   the environment.
3317
3318	- CONFIG_ENV_SIZE:
3319
3320	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3321	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3322	   of this flash sector for the environment. This saves
3323	   memory for the RAM copy of the environment.
3324
3325	   It may also save flash memory if you decide to use this
3326	   when your environment is "embedded" within U-Boot code,
3327	   since then the remainder of the flash sector could be used
3328	   for U-Boot code. It should be pointed out that this is
3329	   STRONGLY DISCOURAGED from a robustness point of view:
3330	   updating the environment in flash makes it always
3331	   necessary to erase the WHOLE sector. If something goes
3332	   wrong before the contents has been restored from a copy in
3333	   RAM, your target system will be dead.
3334
3335	- CONFIG_ENV_ADDR_REDUND
3336	  CONFIG_ENV_SIZE_REDUND
3337
3338	   These settings describe a second storage area used to hold
3339	   a redundant copy of the environment data, so that there is
3340	   a valid backup copy in case there is a power failure during
3341	   a "saveenv" operation.
3342
3343BE CAREFUL! Any changes to the flash layout, and some changes to the
3344source code will make it necessary to adapt <board>/u-boot.lds*
3345accordingly!
3346
3347
3348- CONFIG_ENV_IS_IN_NVRAM:
3349
3350	Define this if you have some non-volatile memory device
3351	(NVRAM, battery buffered SRAM) which you want to use for the
3352	environment.
3353
3354	- CONFIG_ENV_ADDR:
3355	- CONFIG_ENV_SIZE:
3356
3357	  These two #defines are used to determine the memory area you
3358	  want to use for environment. It is assumed that this memory
3359	  can just be read and written to, without any special
3360	  provision.
3361
3362BE CAREFUL! The first access to the environment happens quite early
3363in U-Boot initalization (when we try to get the setting of for the
3364console baudrate). You *MUST* have mapped your NVRAM area then, or
3365U-Boot will hang.
3366
3367Please note that even with NVRAM we still use a copy of the
3368environment in RAM: we could work on NVRAM directly, but we want to
3369keep settings there always unmodified except somebody uses "saveenv"
3370to save the current settings.
3371
3372
3373- CONFIG_ENV_IS_IN_EEPROM:
3374
3375	Use this if you have an EEPROM or similar serial access
3376	device and a driver for it.
3377
3378	- CONFIG_ENV_OFFSET:
3379	- CONFIG_ENV_SIZE:
3380
3381	  These two #defines specify the offset and size of the
3382	  environment area within the total memory of your EEPROM.
3383
3384	- CONFIG_SYS_I2C_EEPROM_ADDR:
3385	  If defined, specified the chip address of the EEPROM device.
3386	  The default address is zero.
3387
3388	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3389	  If defined, the number of bits used to address bytes in a
3390	  single page in the EEPROM device.  A 64 byte page, for example
3391	  would require six bits.
3392
3393	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3394	  If defined, the number of milliseconds to delay between
3395	  page writes.	The default is zero milliseconds.
3396
3397	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3398	  The length in bytes of the EEPROM memory array address.  Note
3399	  that this is NOT the chip address length!
3400
3401	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3402	  EEPROM chips that implement "address overflow" are ones
3403	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3404	  address and the extra bits end up in the "chip address" bit
3405	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3406	  byte chips.
3407
3408	  Note that we consider the length of the address field to
3409	  still be one byte because the extra address bits are hidden
3410	  in the chip address.
3411
3412	- CONFIG_SYS_EEPROM_SIZE:
3413	  The size in bytes of the EEPROM device.
3414
3415	- CONFIG_ENV_EEPROM_IS_ON_I2C
3416	  define this, if you have I2C and SPI activated, and your
3417	  EEPROM, which holds the environment, is on the I2C bus.
3418
3419	- CONFIG_I2C_ENV_EEPROM_BUS
3420	  if you have an Environment on an EEPROM reached over
3421	  I2C muxes, you can define here, how to reach this
3422	  EEPROM. For example:
3423
3424	  #define CONFIG_I2C_ENV_EEPROM_BUS	  "pca9547:70:d\0"
3425
3426	  EEPROM which holds the environment, is reached over
3427	  a pca9547 i2c mux with address 0x70, channel 3.
3428
3429- CONFIG_ENV_IS_IN_DATAFLASH:
3430
3431	Define this if you have a DataFlash memory device which you
3432	want to use for the environment.
3433
3434	- CONFIG_ENV_OFFSET:
3435	- CONFIG_ENV_ADDR:
3436	- CONFIG_ENV_SIZE:
3437
3438	  These three #defines specify the offset and size of the
3439	  environment area within the total memory of your DataFlash placed
3440	  at the specified address.
3441
3442- CONFIG_ENV_IS_IN_REMOTE:
3443
3444	Define this if you have a remote memory space which you
3445	want to use for the local device's environment.
3446
3447	- CONFIG_ENV_ADDR:
3448	- CONFIG_ENV_SIZE:
3449
3450	  These two #defines specify the address and size of the
3451	  environment area within the remote memory space. The
3452	  local device can get the environment from remote memory
3453	  space by SRIO or PCIE links.
3454
3455BE CAREFUL! For some special cases, the local device can not use
3456"saveenv" command. For example, the local device will get the
3457environment stored in a remote NOR flash by SRIO or PCIE link,
3458but it can not erase, write this NOR flash by SRIO or PCIE interface.
3459
3460- CONFIG_ENV_IS_IN_NAND:
3461
3462	Define this if you have a NAND device which you want to use
3463	for the environment.
3464
3465	- CONFIG_ENV_OFFSET:
3466	- CONFIG_ENV_SIZE:
3467
3468	  These two #defines specify the offset and size of the environment
3469	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3470	  aligned to an erase block boundary.
3471
3472	- CONFIG_ENV_OFFSET_REDUND (optional):
3473
3474	  This setting describes a second storage area of CONFIG_ENV_SIZE
3475	  size used to hold a redundant copy of the environment data, so
3476	  that there is a valid backup copy in case there is a power failure
3477	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
3478	  aligned to an erase block boundary.
3479
3480	- CONFIG_ENV_RANGE (optional):
3481
3482	  Specifies the length of the region in which the environment
3483	  can be written.  This should be a multiple of the NAND device's
3484	  block size.  Specifying a range with more erase blocks than
3485	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
3486	  the range to be avoided.
3487
3488	- CONFIG_ENV_OFFSET_OOB (optional):
3489
3490	  Enables support for dynamically retrieving the offset of the
3491	  environment from block zero's out-of-band data.  The
3492	  "nand env.oob" command can be used to record this offset.
3493	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
3494	  using CONFIG_ENV_OFFSET_OOB.
3495
3496- CONFIG_NAND_ENV_DST
3497
3498	Defines address in RAM to which the nand_spl code should copy the
3499	environment. If redundant environment is used, it will be copied to
3500	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3501
3502- CONFIG_SYS_SPI_INIT_OFFSET
3503
3504	Defines offset to the initial SPI buffer area in DPRAM. The
3505	area is used at an early stage (ROM part) if the environment
3506	is configured to reside in the SPI EEPROM: We need a 520 byte
3507	scratch DPRAM area. It is used between the two initialization
3508	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
3509	to be a good choice since it makes it far enough from the
3510	start of the data area as well as from the stack pointer.
3511
3512Please note that the environment is read-only until the monitor
3513has been relocated to RAM and a RAM copy of the environment has been
3514created; also, when using EEPROM you will have to use getenv_f()
3515until then to read environment variables.
3516
3517The environment is protected by a CRC32 checksum. Before the monitor
3518is relocated into RAM, as a result of a bad CRC you will be working
3519with the compiled-in default environment - *silently*!!! [This is
3520necessary, because the first environment variable we need is the
3521"baudrate" setting for the console - if we have a bad CRC, we don't
3522have any device yet where we could complain.]
3523
3524Note: once the monitor has been relocated, then it will complain if
3525the default environment is used; a new CRC is computed as soon as you
3526use the "saveenv" command to store a valid environment.
3527
3528- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3529		Echo the inverted Ethernet link state to the fault LED.
3530
3531		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3532		      also needs to be defined.
3533
3534- CONFIG_SYS_FAULT_MII_ADDR:
3535		MII address of the PHY to check for the Ethernet link state.
3536
3537- CONFIG_NS16550_MIN_FUNCTIONS:
3538		Define this if you desire to only have use of the NS16550_init
3539		and NS16550_putc functions for the serial driver located at
3540		drivers/serial/ns16550.c.  This option is useful for saving
3541		space for already greatly restricted images, including but not
3542		limited to NAND_SPL configurations.
3543
3544- CONFIG_DISPLAY_BOARDINFO
3545		Display information about the board that U-Boot is running on
3546		when U-Boot starts up. The board function checkboard() is called
3547		to do this.
3548
3549- CONFIG_DISPLAY_BOARDINFO_LATE
3550		Similar to the previous option, but display this information
3551		later, once stdio is running and output goes to the LCD, if
3552		present.
3553
3554Low Level (hardware related) configuration options:
3555---------------------------------------------------
3556
3557- CONFIG_SYS_CACHELINE_SIZE:
3558		Cache Line Size of the CPU.
3559
3560- CONFIG_SYS_DEFAULT_IMMR:
3561		Default address of the IMMR after system reset.
3562
3563		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
3564		and RPXsuper) to be able to adjust the position of
3565		the IMMR register after a reset.
3566
3567- CONFIG_SYS_CCSRBAR_DEFAULT:
3568		Default (power-on reset) physical address of CCSR on Freescale
3569		PowerPC SOCs.
3570
3571- CONFIG_SYS_CCSRBAR:
3572		Virtual address of CCSR.  On a 32-bit build, this is typically
3573		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3574
3575		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
3576		for cross-platform code that uses that macro instead.
3577
3578- CONFIG_SYS_CCSRBAR_PHYS:
3579		Physical address of CCSR.  CCSR can be relocated to a new
3580		physical address, if desired.  In this case, this macro should
3581		be set to that address.	 Otherwise, it should be set to the
3582		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3583		is typically relocated on 36-bit builds.  It is recommended
3584		that this macro be defined via the _HIGH and _LOW macros:
3585
3586		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3587			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3588
3589- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3590		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3591		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3592		used in assembly code, so it must not contain typecasts or
3593		integer size suffixes (e.g. "ULL").
3594
3595- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3596		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3597		used in assembly code, so it must not contain typecasts or
3598		integer size suffixes (e.g. "ULL").
3599
3600- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3601		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3602		forced to a value that ensures that CCSR is not relocated.
3603
3604- Floppy Disk Support:
3605		CONFIG_SYS_FDC_DRIVE_NUMBER
3606
3607		the default drive number (default value 0)
3608
3609		CONFIG_SYS_ISA_IO_STRIDE
3610
3611		defines the spacing between FDC chipset registers
3612		(default value 1)
3613
3614		CONFIG_SYS_ISA_IO_OFFSET
3615
3616		defines the offset of register from address. It
3617		depends on which part of the data bus is connected to
3618		the FDC chipset. (default value 0)
3619
3620		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3621		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3622		default value.
3623
3624		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3625		fdc_hw_init() is called at the beginning of the FDC
3626		setup. fdc_hw_init() must be provided by the board
3627		source code. It is used to make hardware dependant
3628		initializations.
3629
3630- CONFIG_IDE_AHB:
3631		Most IDE controllers were designed to be connected with PCI
3632		interface. Only few of them were designed for AHB interface.
3633		When software is doing ATA command and data transfer to
3634		IDE devices through IDE-AHB controller, some additional
3635		registers accessing to these kind of IDE-AHB controller
3636		is requierd.
3637
3638- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3639		DO NOT CHANGE unless you know exactly what you're
3640		doing! (11-4) [MPC8xx/82xx systems only]
3641
3642- CONFIG_SYS_INIT_RAM_ADDR:
3643
3644		Start address of memory area that can be used for
3645		initial data and stack; please note that this must be
3646		writable memory that is working WITHOUT special
3647		initialization, i. e. you CANNOT use normal RAM which
3648		will become available only after programming the
3649		memory controller and running certain initialization
3650		sequences.
3651
3652		U-Boot uses the following memory types:
3653		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
3654		- MPC824X: data cache
3655		- PPC4xx:  data cache
3656
3657- CONFIG_SYS_GBL_DATA_OFFSET:
3658
3659		Offset of the initial data structure in the memory
3660		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3661		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3662		data is located at the end of the available space
3663		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3664		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
3665		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3666		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3667
3668	Note:
3669		On the MPC824X (or other systems that use the data
3670		cache for initial memory) the address chosen for
3671		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3672		point to an otherwise UNUSED address space between
3673		the top of RAM and the start of the PCI space.
3674
3675- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
3676
3677- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
3678
3679- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
3680
3681- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
3682
3683- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
3684
3685- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3686
3687- CONFIG_SYS_OR_TIMING_SDRAM:
3688		SDRAM timing
3689
3690- CONFIG_SYS_MAMR_PTA:
3691		periodic timer for refresh
3692
3693- CONFIG_SYS_DER:	Debug Event Register (37-47)
3694
3695- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3696  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3697  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3698  CONFIG_SYS_BR1_PRELIM:
3699		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3700
3701- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3702  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3703  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3704		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3705
3706- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
3707  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
3708		Machine Mode Register and Memory Periodic Timer
3709		Prescaler definitions (SDRAM timing)
3710
3711- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
3712		enable I2C microcode relocation patch (MPC8xx);
3713		define relocation offset in DPRAM [DSP2]
3714
3715- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
3716		enable SMC microcode relocation patch (MPC8xx);
3717		define relocation offset in DPRAM [SMC1]
3718
3719- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
3720		enable SPI microcode relocation patch (MPC8xx);
3721		define relocation offset in DPRAM [SCC4]
3722
3723- CONFIG_SYS_USE_OSCCLK:
3724		Use OSCM clock mode on MBX8xx board. Be careful,
3725		wrong setting might damage your board. Read
3726		doc/README.MBX before setting this variable!
3727
3728- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
3729		Offset of the bootmode word in DPRAM used by post
3730		(Power On Self Tests). This definition overrides
3731		#define'd default value in commproc.h resp.
3732		cpm_8260.h.
3733
3734- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
3735  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
3736  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
3737  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
3738  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
3739  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
3740  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
3741  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
3742		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
3743
3744- CONFIG_PCI_DISABLE_PCIE:
3745		Disable PCI-Express on systems where it is supported but not
3746		required.
3747
3748- CONFIG_PCI_ENUM_ONLY
3749		Only scan through and get the devices on the busses.
3750		Don't do any setup work, presumably because someone or
3751		something has already done it, and we don't need to do it
3752		a second time.	Useful for platforms that are pre-booted
3753		by coreboot or similar.
3754
3755- CONFIG_SYS_SRIO:
3756		Chip has SRIO or not
3757
3758- CONFIG_SRIO1:
3759		Board has SRIO 1 port available
3760
3761- CONFIG_SRIO2:
3762		Board has SRIO 2 port available
3763
3764- CONFIG_SYS_SRIOn_MEM_VIRT:
3765		Virtual Address of SRIO port 'n' memory region
3766
3767- CONFIG_SYS_SRIOn_MEM_PHYS:
3768		Physical Address of SRIO port 'n' memory region
3769
3770- CONFIG_SYS_SRIOn_MEM_SIZE:
3771		Size of SRIO port 'n' memory region
3772
3773- CONFIG_SYS_NDFC_16
3774		Defined to tell the NDFC that the NAND chip is using a
3775		16 bit bus.
3776
3777- CONFIG_SYS_NDFC_EBC0_CFG
3778		Sets the EBC0_CFG register for the NDFC. If not defined
3779		a default value will be used.
3780
3781- CONFIG_SPD_EEPROM
3782		Get DDR timing information from an I2C EEPROM. Common
3783		with pluggable memory modules such as SODIMMs
3784
3785  SPD_EEPROM_ADDRESS
3786		I2C address of the SPD EEPROM
3787
3788- CONFIG_SYS_SPD_BUS_NUM
3789		If SPD EEPROM is on an I2C bus other than the first
3790		one, specify here. Note that the value must resolve
3791		to something your driver can deal with.
3792
3793- CONFIG_SYS_DDR_RAW_TIMING
3794		Get DDR timing information from other than SPD. Common with
3795		soldered DDR chips onboard without SPD. DDR raw timing
3796		parameters are extracted from datasheet and hard-coded into
3797		header files or board specific files.
3798
3799- CONFIG_FSL_DDR_INTERACTIVE
3800		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3801
3802- CONFIG_SYS_83XX_DDR_USES_CS0
3803		Only for 83xx systems. If specified, then DDR should
3804		be configured using CS0 and CS1 instead of CS2 and CS3.
3805
3806- CONFIG_ETHER_ON_FEC[12]
3807		Define to enable FEC[12] on a 8xx series processor.
3808
3809- CONFIG_FEC[12]_PHY
3810		Define to the hardcoded PHY address which corresponds
3811		to the given FEC; i. e.
3812			#define CONFIG_FEC1_PHY 4
3813		means that the PHY with address 4 is connected to FEC1
3814
3815		When set to -1, means to probe for first available.
3816
3817- CONFIG_FEC[12]_PHY_NORXERR
3818		The PHY does not have a RXERR line (RMII only).
3819		(so program the FEC to ignore it).
3820
3821- CONFIG_RMII
3822		Enable RMII mode for all FECs.
3823		Note that this is a global option, we can't
3824		have one FEC in standard MII mode and another in RMII mode.
3825
3826- CONFIG_CRC32_VERIFY
3827		Add a verify option to the crc32 command.
3828		The syntax is:
3829
3830		=> crc32 -v <address> <count> <crc32>
3831
3832		Where address/count indicate a memory area
3833		and crc32 is the correct crc32 which the
3834		area should have.
3835
3836- CONFIG_LOOPW
3837		Add the "loopw" memory command. This only takes effect if
3838		the memory commands are activated globally (CONFIG_CMD_MEM).
3839
3840- CONFIG_MX_CYCLIC
3841		Add the "mdc" and "mwc" memory commands. These are cyclic
3842		"md/mw" commands.
3843		Examples:
3844
3845		=> mdc.b 10 4 500
3846		This command will print 4 bytes (10,11,12,13) each 500 ms.
3847
3848		=> mwc.l 100 12345678 10
3849		This command will write 12345678 to address 100 all 10 ms.
3850
3851		This only takes effect if the memory commands are activated
3852		globally (CONFIG_CMD_MEM).
3853
3854- CONFIG_SKIP_LOWLEVEL_INIT
3855		[ARM, NDS32, MIPS only] If this variable is defined, then certain
3856		low level initializations (like setting up the memory
3857		controller) are omitted and/or U-Boot does not
3858		relocate itself into RAM.
3859
3860		Normally this variable MUST NOT be defined. The only
3861		exception is when U-Boot is loaded (to RAM) by some
3862		other boot loader or by a debugger which performs
3863		these initializations itself.
3864
3865- CONFIG_SPL_BUILD
3866		Modifies the behaviour of start.S when compiling a loader
3867		that is executed before the actual U-Boot. E.g. when
3868		compiling a NAND SPL.
3869
3870- CONFIG_ARCH_MAP_SYSMEM
3871		Generally U-Boot (and in particular the md command) uses
3872		effective address. It is therefore not necessary to regard
3873		U-Boot address as virtual addresses that need to be translated
3874		to physical addresses. However, sandbox requires this, since
3875		it maintains its own little RAM buffer which contains all
3876		addressable memory. This option causes some memory accesses
3877		to be mapped through map_sysmem() / unmap_sysmem().
3878
3879- CONFIG_USE_ARCH_MEMCPY
3880  CONFIG_USE_ARCH_MEMSET
3881		If these options are used a optimized version of memcpy/memset will
3882		be used if available. These functions may be faster under some
3883		conditions but may increase the binary size.
3884
3885- CONFIG_X86_RESET_VECTOR
3886		If defined, the x86 reset vector code is included. This is not
3887		needed when U-Boot is running from Coreboot.
3888
3889- CONFIG_SYS_MPUCLK
3890		Defines the MPU clock speed (in MHz).
3891
3892		NOTE : currently only supported on AM335x platforms.
3893
3894Freescale QE/FMAN Firmware Support:
3895-----------------------------------
3896
3897The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3898loading of "firmware", which is encoded in the QE firmware binary format.
3899This firmware often needs to be loaded during U-Boot booting, so macros
3900are used to identify the storage device (NOR flash, SPI, etc) and the address
3901within that device.
3902
3903- CONFIG_SYS_QE_FMAN_FW_ADDR
3904	The address in the storage device where the firmware is located.  The
3905	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3906	is also specified.
3907
3908- CONFIG_SYS_QE_FMAN_FW_LENGTH
3909	The maximum possible size of the firmware.  The firmware binary format
3910	has a field that specifies the actual size of the firmware, but it
3911	might not be possible to read any part of the firmware unless some
3912	local storage is allocated to hold the entire firmware first.
3913
3914- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3915	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3916	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3917	virtual address in NOR flash.
3918
3919- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3920	Specifies that QE/FMAN firmware is located in NAND flash.
3921	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3922
3923- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3924	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3925	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3926
3927- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
3928	Specifies that QE/FMAN firmware is located on the primary SPI
3929	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3930
3931- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3932	Specifies that QE/FMAN firmware is located in the remote (master)
3933	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3934	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3935	window->master inbound window->master LAW->the ucode address in
3936	master's memory space.
3937
3938Building the Software:
3939======================
3940
3941Building U-Boot has been tested in several native build environments
3942and in many different cross environments. Of course we cannot support
3943all possibly existing versions of cross development tools in all
3944(potentially obsolete) versions. In case of tool chain problems we
3945recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3946which is extensively used to build and test U-Boot.
3947
3948If you are not using a native environment, it is assumed that you
3949have GNU cross compiling tools available in your path. In this case,
3950you must set the environment variable CROSS_COMPILE in your shell.
3951Note that no changes to the Makefile or any other source files are
3952necessary. For example using the ELDK on a 4xx CPU, please enter:
3953
3954	$ CROSS_COMPILE=ppc_4xx-
3955	$ export CROSS_COMPILE
3956
3957Note: If you wish to generate Windows versions of the utilities in
3958      the tools directory you can use the MinGW toolchain
3959      (http://www.mingw.org).  Set your HOST tools to the MinGW
3960      toolchain and execute 'make tools'.  For example:
3961
3962       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3963
3964      Binaries such as tools/mkimage.exe will be created which can
3965      be executed on computers running Windows.
3966
3967U-Boot is intended to be simple to build. After installing the
3968sources you must configure U-Boot for one specific board type. This
3969is done by typing:
3970
3971	make NAME_config
3972
3973where "NAME_config" is the name of one of the existing configu-
3974rations; see boards.cfg for supported names.
3975
3976Note: for some board special configuration names may exist; check if
3977      additional information is available from the board vendor; for
3978      instance, the TQM823L systems are available without (standard)
3979      or with LCD support. You can select such additional "features"
3980      when choosing the configuration, i. e.
3981
3982      make TQM823L_config
3983	- will configure for a plain TQM823L, i. e. no LCD support
3984
3985      make TQM823L_LCD_config
3986	- will configure for a TQM823L with U-Boot console on LCD
3987
3988      etc.
3989
3990
3991Finally, type "make all", and you should get some working U-Boot
3992images ready for download to / installation on your system:
3993
3994- "u-boot.bin" is a raw binary image
3995- "u-boot" is an image in ELF binary format
3996- "u-boot.srec" is in Motorola S-Record format
3997
3998By default the build is performed locally and the objects are saved
3999in the source directory. One of the two methods can be used to change
4000this behavior and build U-Boot to some external directory:
4001
40021. Add O= to the make command line invocations:
4003
4004	make O=/tmp/build distclean
4005	make O=/tmp/build NAME_config
4006	make O=/tmp/build all
4007
40082. Set environment variable BUILD_DIR to point to the desired location:
4009
4010	export BUILD_DIR=/tmp/build
4011	make distclean
4012	make NAME_config
4013	make all
4014
4015Note that the command line "O=" setting overrides the BUILD_DIR environment
4016variable.
4017
4018
4019Please be aware that the Makefiles assume you are using GNU make, so
4020for instance on NetBSD you might need to use "gmake" instead of
4021native "make".
4022
4023
4024If the system board that you have is not listed, then you will need
4025to port U-Boot to your hardware platform. To do this, follow these
4026steps:
4027
40281.  Add a new configuration option for your board to the toplevel
4029    "boards.cfg" file, using the existing entries as examples.
4030    Follow the instructions there to keep the boards in order.
40312.  Create a new directory to hold your board specific code. Add any
4032    files you need. In your board directory, you will need at least
4033    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
40343.  Create a new configuration file "include/configs/<board>.h" for
4035    your board
40363.  If you're porting U-Boot to a new CPU, then also create a new
4037    directory to hold your CPU specific code. Add any files you need.
40384.  Run "make <board>_config" with your new name.
40395.  Type "make", and you should get a working "u-boot.srec" file
4040    to be installed on your target system.
40416.  Debug and solve any problems that might arise.
4042    [Of course, this last step is much harder than it sounds.]
4043
4044
4045Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4046==============================================================
4047
4048If you have modified U-Boot sources (for instance added a new board
4049or support for new devices, a new CPU, etc.) you are expected to
4050provide feedback to the other developers. The feedback normally takes
4051the form of a "patch", i. e. a context diff against a certain (latest
4052official or latest in the git repository) version of U-Boot sources.
4053
4054But before you submit such a patch, please verify that your modifi-
4055cation did not break existing code. At least make sure that *ALL* of
4056the supported boards compile WITHOUT ANY compiler warnings. To do so,
4057just run the "MAKEALL" script, which will configure and build U-Boot
4058for ALL supported system. Be warned, this will take a while. You can
4059select which (cross) compiler to use by passing a `CROSS_COMPILE'
4060environment variable to the script, i. e. to use the ELDK cross tools
4061you can type
4062
4063	CROSS_COMPILE=ppc_8xx- MAKEALL
4064
4065or to build on a native PowerPC system you can type
4066
4067	CROSS_COMPILE=' ' MAKEALL
4068
4069When using the MAKEALL script, the default behaviour is to build
4070U-Boot in the source directory. This location can be changed by
4071setting the BUILD_DIR environment variable. Also, for each target
4072built, the MAKEALL script saves two log files (<target>.ERR and
4073<target>.MAKEALL) in the <source dir>/LOG directory. This default
4074location can be changed by setting the MAKEALL_LOGDIR environment
4075variable. For example:
4076
4077	export BUILD_DIR=/tmp/build
4078	export MAKEALL_LOGDIR=/tmp/log
4079	CROSS_COMPILE=ppc_8xx- MAKEALL
4080
4081With the above settings build objects are saved in the /tmp/build,
4082log files are saved in the /tmp/log and the source tree remains clean
4083during the whole build process.
4084
4085
4086See also "U-Boot Porting Guide" below.
4087
4088
4089Monitor Commands - Overview:
4090============================
4091
4092go	- start application at address 'addr'
4093run	- run commands in an environment variable
4094bootm	- boot application image from memory
4095bootp	- boot image via network using BootP/TFTP protocol
4096bootz   - boot zImage from memory
4097tftpboot- boot image via network using TFTP protocol
4098	       and env variables "ipaddr" and "serverip"
4099	       (and eventually "gatewayip")
4100tftpput - upload a file via network using TFTP protocol
4101rarpboot- boot image via network using RARP/TFTP protocol
4102diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4103loads	- load S-Record file over serial line
4104loadb	- load binary file over serial line (kermit mode)
4105md	- memory display
4106mm	- memory modify (auto-incrementing)
4107nm	- memory modify (constant address)
4108mw	- memory write (fill)
4109cp	- memory copy
4110cmp	- memory compare
4111crc32	- checksum calculation
4112i2c	- I2C sub-system
4113sspi	- SPI utility commands
4114base	- print or set address offset
4115printenv- print environment variables
4116setenv	- set environment variables
4117saveenv - save environment variables to persistent storage
4118protect - enable or disable FLASH write protection
4119erase	- erase FLASH memory
4120flinfo	- print FLASH memory information
4121nand	- NAND memory operations (see doc/README.nand)
4122bdinfo	- print Board Info structure
4123iminfo	- print header information for application image
4124coninfo - print console devices and informations
4125ide	- IDE sub-system
4126loop	- infinite loop on address range
4127loopw	- infinite write loop on address range
4128mtest	- simple RAM test
4129icache	- enable or disable instruction cache
4130dcache	- enable or disable data cache
4131reset	- Perform RESET of the CPU
4132echo	- echo args to console
4133version - print monitor version
4134help	- print online help
4135?	- alias for 'help'
4136
4137
4138Monitor Commands - Detailed Description:
4139========================================
4140
4141TODO.
4142
4143For now: just type "help <command>".
4144
4145
4146Environment Variables:
4147======================
4148
4149U-Boot supports user configuration using Environment Variables which
4150can be made persistent by saving to Flash memory.
4151
4152Environment Variables are set using "setenv", printed using
4153"printenv", and saved to Flash using "saveenv". Using "setenv"
4154without a value can be used to delete a variable from the
4155environment. As long as you don't save the environment you are
4156working with an in-memory copy. In case the Flash area containing the
4157environment is erased by accident, a default environment is provided.
4158
4159Some configuration options can be set using Environment Variables.
4160
4161List of environment variables (most likely not complete):
4162
4163  baudrate	- see CONFIG_BAUDRATE
4164
4165  bootdelay	- see CONFIG_BOOTDELAY
4166
4167  bootcmd	- see CONFIG_BOOTCOMMAND
4168
4169  bootargs	- Boot arguments when booting an RTOS image
4170
4171  bootfile	- Name of the image to load with TFTP
4172
4173  bootm_low	- Memory range available for image processing in the bootm
4174		  command can be restricted. This variable is given as
4175		  a hexadecimal number and defines lowest address allowed
4176		  for use by the bootm command. See also "bootm_size"
4177		  environment variable. Address defined by "bootm_low" is
4178		  also the base of the initial memory mapping for the Linux
4179		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4180		  bootm_mapsize.
4181
4182  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4183		  This variable is given as a hexadecimal number and it
4184		  defines the size of the memory region starting at base
4185		  address bootm_low that is accessible by the Linux kernel
4186		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4187		  as the default value if it is defined, and bootm_size is
4188		  used otherwise.
4189
4190  bootm_size	- Memory range available for image processing in the bootm
4191		  command can be restricted. This variable is given as
4192		  a hexadecimal number and defines the size of the region
4193		  allowed for use by the bootm command. See also "bootm_low"
4194		  environment variable.
4195
4196  updatefile	- Location of the software update file on a TFTP server, used
4197		  by the automatic software update feature. Please refer to
4198		  documentation in doc/README.update for more details.
4199
4200  autoload	- if set to "no" (any string beginning with 'n'),
4201		  "bootp" will just load perform a lookup of the
4202		  configuration from the BOOTP server, but not try to
4203		  load any image using TFTP
4204
4205  autostart	- if set to "yes", an image loaded using the "bootp",
4206		  "rarpboot", "tftpboot" or "diskboot" commands will
4207		  be automatically started (by internally calling
4208		  "bootm")
4209
4210		  If set to "no", a standalone image passed to the
4211		  "bootm" command will be copied to the load address
4212		  (and eventually uncompressed), but NOT be started.
4213		  This can be used to load and uncompress arbitrary
4214		  data.
4215
4216  fdt_high	- if set this restricts the maximum address that the
4217		  flattened device tree will be copied into upon boot.
4218		  For example, if you have a system with 1 GB memory
4219		  at physical address 0x10000000, while Linux kernel
4220		  only recognizes the first 704 MB as low memory, you
4221		  may need to set fdt_high as 0x3C000000 to have the
4222		  device tree blob be copied to the maximum address
4223		  of the 704 MB low memory, so that Linux kernel can
4224		  access it during the boot procedure.
4225
4226		  If this is set to the special value 0xFFFFFFFF then
4227		  the fdt will not be copied at all on boot.  For this
4228		  to work it must reside in writable memory, have
4229		  sufficient padding on the end of it for u-boot to
4230		  add the information it needs into it, and the memory
4231		  must be accessible by the kernel.
4232
4233  fdtcontroladdr- if set this is the address of the control flattened
4234		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4235		  defined.
4236
4237  i2cfast	- (PPC405GP|PPC405EP only)
4238		  if set to 'y' configures Linux I2C driver for fast
4239		  mode (400kHZ). This environment variable is used in
4240		  initialization code. So, for changes to be effective
4241		  it must be saved and board must be reset.
4242
4243  initrd_high	- restrict positioning of initrd images:
4244		  If this variable is not set, initrd images will be
4245		  copied to the highest possible address in RAM; this
4246		  is usually what you want since it allows for
4247		  maximum initrd size. If for some reason you want to
4248		  make sure that the initrd image is loaded below the
4249		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4250		  variable to a value of "no" or "off" or "0".
4251		  Alternatively, you can set it to a maximum upper
4252		  address to use (U-Boot will still check that it
4253		  does not overwrite the U-Boot stack and data).
4254
4255		  For instance, when you have a system with 16 MB
4256		  RAM, and want to reserve 4 MB from use by Linux,
4257		  you can do this by adding "mem=12M" to the value of
4258		  the "bootargs" variable. However, now you must make
4259		  sure that the initrd image is placed in the first
4260		  12 MB as well - this can be done with
4261
4262		  setenv initrd_high 00c00000
4263
4264		  If you set initrd_high to 0xFFFFFFFF, this is an
4265		  indication to U-Boot that all addresses are legal
4266		  for the Linux kernel, including addresses in flash
4267		  memory. In this case U-Boot will NOT COPY the
4268		  ramdisk at all. This may be useful to reduce the
4269		  boot time on your system, but requires that this
4270		  feature is supported by your Linux kernel.
4271
4272  ipaddr	- IP address; needed for tftpboot command
4273
4274  loadaddr	- Default load address for commands like "bootp",
4275		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4276
4277  loads_echo	- see CONFIG_LOADS_ECHO
4278
4279  serverip	- TFTP server IP address; needed for tftpboot command
4280
4281  bootretry	- see CONFIG_BOOT_RETRY_TIME
4282
4283  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4284
4285  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4286
4287  ethprime	- controls which interface is used first.
4288
4289  ethact	- controls which interface is currently active.
4290		  For example you can do the following
4291
4292		  => setenv ethact FEC
4293		  => ping 192.168.0.1 # traffic sent on FEC
4294		  => setenv ethact SCC
4295		  => ping 10.0.0.1 # traffic sent on SCC
4296
4297  ethrotate	- When set to "no" U-Boot does not go through all
4298		  available network interfaces.
4299		  It just stays at the currently selected interface.
4300
4301  netretry	- When set to "no" each network operation will
4302		  either succeed or fail without retrying.
4303		  When set to "once" the network operation will
4304		  fail when all the available network interfaces
4305		  are tried once without success.
4306		  Useful on scripts which control the retry operation
4307		  themselves.
4308
4309  npe_ucode	- set load address for the NPE microcode
4310
4311  tftpsrcport	- If this is set, the value is used for TFTP's
4312		  UDP source port.
4313
4314  tftpdstport	- If this is set, the value is used for TFTP's UDP
4315		  destination port instead of the Well Know Port 69.
4316
4317  tftpblocksize - Block size to use for TFTP transfers; if not set,
4318		  we use the TFTP server's default block size
4319
4320  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4321		  seconds, minimum value is 1000 = 1 second). Defines
4322		  when a packet is considered to be lost so it has to
4323		  be retransmitted. The default is 5000 = 5 seconds.
4324		  Lowering this value may make downloads succeed
4325		  faster in networks with high packet loss rates or
4326		  with unreliable TFTP servers.
4327
4328  vlan		- When set to a value < 4095 the traffic over
4329		  Ethernet is encapsulated/received over 802.1q
4330		  VLAN tagged frames.
4331
4332The following image location variables contain the location of images
4333used in booting. The "Image" column gives the role of the image and is
4334not an environment variable name. The other columns are environment
4335variable names. "File Name" gives the name of the file on a TFTP
4336server, "RAM Address" gives the location in RAM the image will be
4337loaded to, and "Flash Location" gives the image's address in NOR
4338flash or offset in NAND flash.
4339
4340*Note* - these variables don't have to be defined for all boards, some
4341boards currenlty use other variables for these purposes, and some
4342boards use these variables for other purposes.
4343
4344Image		    File Name	     RAM Address       Flash Location
4345-----		    ---------	     -----------       --------------
4346u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4347Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4348device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4349ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4350
4351The following environment variables may be used and automatically
4352updated by the network boot commands ("bootp" and "rarpboot"),
4353depending the information provided by your boot server:
4354
4355  bootfile	- see above
4356  dnsip		- IP address of your Domain Name Server
4357  dnsip2	- IP address of your secondary Domain Name Server
4358  gatewayip	- IP address of the Gateway (Router) to use
4359  hostname	- Target hostname
4360  ipaddr	- see above
4361  netmask	- Subnet Mask
4362  rootpath	- Pathname of the root filesystem on the NFS server
4363  serverip	- see above
4364
4365
4366There are two special Environment Variables:
4367
4368  serial#	- contains hardware identification information such
4369		  as type string and/or serial number
4370  ethaddr	- Ethernet address
4371
4372These variables can be set only once (usually during manufacturing of
4373the board). U-Boot refuses to delete or overwrite these variables
4374once they have been set once.
4375
4376
4377Further special Environment Variables:
4378
4379  ver		- Contains the U-Boot version string as printed
4380		  with the "version" command. This variable is
4381		  readonly (see CONFIG_VERSION_VARIABLE).
4382
4383
4384Please note that changes to some configuration parameters may take
4385only effect after the next boot (yes, that's just like Windoze :-).
4386
4387
4388Callback functions for environment variables:
4389---------------------------------------------
4390
4391For some environment variables, the behavior of u-boot needs to change
4392when their values are changed.  This functionailty allows functions to
4393be associated with arbitrary variables.  On creation, overwrite, or
4394deletion, the callback will provide the opportunity for some side
4395effect to happen or for the change to be rejected.
4396
4397The callbacks are named and associated with a function using the
4398U_BOOT_ENV_CALLBACK macro in your board or driver code.
4399
4400These callbacks are associated with variables in one of two ways.  The
4401static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
4402in the board configuration to a string that defines a list of
4403associations.  The list must be in the following format:
4404
4405	entry = variable_name[:callback_name]
4406	list = entry[,list]
4407
4408If the callback name is not specified, then the callback is deleted.
4409Spaces are also allowed anywhere in the list.
4410
4411Callbacks can also be associated by defining the ".callbacks" variable
4412with the same list format above.  Any association in ".callbacks" will
4413override any association in the static list. You can define
4414CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
4415".callbacks" envirnoment variable in the default or embedded environment.
4416
4417
4418Command Line Parsing:
4419=====================
4420
4421There are two different command line parsers available with U-Boot:
4422the old "simple" one, and the much more powerful "hush" shell:
4423
4424Old, simple command line parser:
4425--------------------------------
4426
4427- supports environment variables (through setenv / saveenv commands)
4428- several commands on one line, separated by ';'
4429- variable substitution using "... ${name} ..." syntax
4430- special characters ('$', ';') can be escaped by prefixing with '\',
4431  for example:
4432	setenv bootcmd bootm \${address}
4433- You can also escape text by enclosing in single apostrophes, for example:
4434	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4435
4436Hush shell:
4437-----------
4438
4439- similar to Bourne shell, with control structures like
4440  if...then...else...fi, for...do...done; while...do...done,
4441  until...do...done, ...
4442- supports environment ("global") variables (through setenv / saveenv
4443  commands) and local shell variables (through standard shell syntax
4444  "name=value"); only environment variables can be used with "run"
4445  command
4446
4447General rules:
4448--------------
4449
4450(1) If a command line (or an environment variable executed by a "run"
4451    command) contains several commands separated by semicolon, and
4452    one of these commands fails, then the remaining commands will be
4453    executed anyway.
4454
4455(2) If you execute several variables with one call to run (i. e.
4456    calling run with a list of variables as arguments), any failing
4457    command will cause "run" to terminate, i. e. the remaining
4458    variables are not executed.
4459
4460Note for Redundant Ethernet Interfaces:
4461=======================================
4462
4463Some boards come with redundant Ethernet interfaces; U-Boot supports
4464such configurations and is capable of automatic selection of a
4465"working" interface when needed. MAC assignment works as follows:
4466
4467Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4468MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4469"eth1addr" (=>eth1), "eth2addr", ...
4470
4471If the network interface stores some valid MAC address (for instance
4472in SROM), this is used as default address if there is NO correspon-
4473ding setting in the environment; if the corresponding environment
4474variable is set, this overrides the settings in the card; that means:
4475
4476o If the SROM has a valid MAC address, and there is no address in the
4477  environment, the SROM's address is used.
4478
4479o If there is no valid address in the SROM, and a definition in the
4480  environment exists, then the value from the environment variable is
4481  used.
4482
4483o If both the SROM and the environment contain a MAC address, and
4484  both addresses are the same, this MAC address is used.
4485
4486o If both the SROM and the environment contain a MAC address, and the
4487  addresses differ, the value from the environment is used and a
4488  warning is printed.
4489
4490o If neither SROM nor the environment contain a MAC address, an error
4491  is raised.
4492
4493If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4494will be programmed into hardware as part of the initialization process.	 This
4495may be skipped by setting the appropriate 'ethmacskip' environment variable.
4496The naming convention is as follows:
4497"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4498
4499Image Formats:
4500==============
4501
4502U-Boot is capable of booting (and performing other auxiliary operations on)
4503images in two formats:
4504
4505New uImage format (FIT)
4506-----------------------
4507
4508Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4509to Flattened Device Tree). It allows the use of images with multiple
4510components (several kernels, ramdisks, etc.), with contents protected by
4511SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4512
4513
4514Old uImage format
4515-----------------
4516
4517Old image format is based on binary files which can be basically anything,
4518preceded by a special header; see the definitions in include/image.h for
4519details; basically, the header defines the following image properties:
4520
4521* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4522  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4523  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4524  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4525  INTEGRITY).
4526* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
4527  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4528  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4529* Compression Type (uncompressed, gzip, bzip2)
4530* Load Address
4531* Entry Point
4532* Image Name
4533* Image Timestamp
4534
4535The header is marked by a special Magic Number, and both the header
4536and the data portions of the image are secured against corruption by
4537CRC32 checksums.
4538
4539
4540Linux Support:
4541==============
4542
4543Although U-Boot should support any OS or standalone application
4544easily, the main focus has always been on Linux during the design of
4545U-Boot.
4546
4547U-Boot includes many features that so far have been part of some
4548special "boot loader" code within the Linux kernel. Also, any
4549"initrd" images to be used are no longer part of one big Linux image;
4550instead, kernel and "initrd" are separate images. This implementation
4551serves several purposes:
4552
4553- the same features can be used for other OS or standalone
4554  applications (for instance: using compressed images to reduce the
4555  Flash memory footprint)
4556
4557- it becomes much easier to port new Linux kernel versions because
4558  lots of low-level, hardware dependent stuff are done by U-Boot
4559
4560- the same Linux kernel image can now be used with different "initrd"
4561  images; of course this also means that different kernel images can
4562  be run with the same "initrd". This makes testing easier (you don't
4563  have to build a new "zImage.initrd" Linux image when you just
4564  change a file in your "initrd"). Also, a field-upgrade of the
4565  software is easier now.
4566
4567
4568Linux HOWTO:
4569============
4570
4571Porting Linux to U-Boot based systems:
4572---------------------------------------
4573
4574U-Boot cannot save you from doing all the necessary modifications to
4575configure the Linux device drivers for use with your target hardware
4576(no, we don't intend to provide a full virtual machine interface to
4577Linux :-).
4578
4579But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4580
4581Just make sure your machine specific header file (for instance
4582include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4583Information structure as we define in include/asm-<arch>/u-boot.h,
4584and make sure that your definition of IMAP_ADDR uses the same value
4585as your U-Boot configuration in CONFIG_SYS_IMMR.
4586
4587
4588Configuring the Linux kernel:
4589-----------------------------
4590
4591No specific requirements for U-Boot. Make sure you have some root
4592device (initial ramdisk, NFS) for your target system.
4593
4594
4595Building a Linux Image:
4596-----------------------
4597
4598With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4599not used. If you use recent kernel source, a new build target
4600"uImage" will exist which automatically builds an image usable by
4601U-Boot. Most older kernels also have support for a "pImage" target,
4602which was introduced for our predecessor project PPCBoot and uses a
4603100% compatible format.
4604
4605Example:
4606
4607	make TQM850L_config
4608	make oldconfig
4609	make dep
4610	make uImage
4611
4612The "uImage" build target uses a special tool (in 'tools/mkimage') to
4613encapsulate a compressed Linux kernel image with header	 information,
4614CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4615
4616* build a standard "vmlinux" kernel image (in ELF binary format):
4617
4618* convert the kernel into a raw binary image:
4619
4620	${CROSS_COMPILE}-objcopy -O binary \
4621				 -R .note -R .comment \
4622				 -S vmlinux linux.bin
4623
4624* compress the binary image:
4625
4626	gzip -9 linux.bin
4627
4628* package compressed binary image for U-Boot:
4629
4630	mkimage -A ppc -O linux -T kernel -C gzip \
4631		-a 0 -e 0 -n "Linux Kernel Image" \
4632		-d linux.bin.gz uImage
4633
4634
4635The "mkimage" tool can also be used to create ramdisk images for use
4636with U-Boot, either separated from the Linux kernel image, or
4637combined into one file. "mkimage" encapsulates the images with a 64
4638byte header containing information about target architecture,
4639operating system, image type, compression method, entry points, time
4640stamp, CRC32 checksums, etc.
4641
4642"mkimage" can be called in two ways: to verify existing images and
4643print the header information, or to build new images.
4644
4645In the first form (with "-l" option) mkimage lists the information
4646contained in the header of an existing U-Boot image; this includes
4647checksum verification:
4648
4649	tools/mkimage -l image
4650	  -l ==> list image header information
4651
4652The second form (with "-d" option) is used to build a U-Boot image
4653from a "data file" which is used as image payload:
4654
4655	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4656		      -n name -d data_file image
4657	  -A ==> set architecture to 'arch'
4658	  -O ==> set operating system to 'os'
4659	  -T ==> set image type to 'type'
4660	  -C ==> set compression type 'comp'
4661	  -a ==> set load address to 'addr' (hex)
4662	  -e ==> set entry point to 'ep' (hex)
4663	  -n ==> set image name to 'name'
4664	  -d ==> use image data from 'datafile'
4665
4666Right now, all Linux kernels for PowerPC systems use the same load
4667address (0x00000000), but the entry point address depends on the
4668kernel version:
4669
4670- 2.2.x kernels have the entry point at 0x0000000C,
4671- 2.3.x and later kernels have the entry point at 0x00000000.
4672
4673So a typical call to build a U-Boot image would read:
4674
4675	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4676	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4677	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4678	> examples/uImage.TQM850L
4679	Image Name:   2.4.4 kernel for TQM850L
4680	Created:      Wed Jul 19 02:34:59 2000
4681	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4682	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4683	Load Address: 0x00000000
4684	Entry Point:  0x00000000
4685
4686To verify the contents of the image (or check for corruption):
4687
4688	-> tools/mkimage -l examples/uImage.TQM850L
4689	Image Name:   2.4.4 kernel for TQM850L
4690	Created:      Wed Jul 19 02:34:59 2000
4691	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4692	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4693	Load Address: 0x00000000
4694	Entry Point:  0x00000000
4695
4696NOTE: for embedded systems where boot time is critical you can trade
4697speed for memory and install an UNCOMPRESSED image instead: this
4698needs more space in Flash, but boots much faster since it does not
4699need to be uncompressed:
4700
4701	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4702	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4703	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4704	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4705	> examples/uImage.TQM850L-uncompressed
4706	Image Name:   2.4.4 kernel for TQM850L
4707	Created:      Wed Jul 19 02:34:59 2000
4708	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4709	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4710	Load Address: 0x00000000
4711	Entry Point:  0x00000000
4712
4713
4714Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4715when your kernel is intended to use an initial ramdisk:
4716
4717	-> tools/mkimage -n 'Simple Ramdisk Image' \
4718	> -A ppc -O linux -T ramdisk -C gzip \
4719	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4720	Image Name:   Simple Ramdisk Image
4721	Created:      Wed Jan 12 14:01:50 2000
4722	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4723	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4724	Load Address: 0x00000000
4725	Entry Point:  0x00000000
4726
4727
4728Installing a Linux Image:
4729-------------------------
4730
4731To downloading a U-Boot image over the serial (console) interface,
4732you must convert the image to S-Record format:
4733
4734	objcopy -I binary -O srec examples/image examples/image.srec
4735
4736The 'objcopy' does not understand the information in the U-Boot
4737image header, so the resulting S-Record file will be relative to
4738address 0x00000000. To load it to a given address, you need to
4739specify the target address as 'offset' parameter with the 'loads'
4740command.
4741
4742Example: install the image to address 0x40100000 (which on the
4743TQM8xxL is in the first Flash bank):
4744
4745	=> erase 40100000 401FFFFF
4746
4747	.......... done
4748	Erased 8 sectors
4749
4750	=> loads 40100000
4751	## Ready for S-Record download ...
4752	~>examples/image.srec
4753	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4754	...
4755	15989 15990 15991 15992
4756	[file transfer complete]
4757	[connected]
4758	## Start Addr = 0x00000000
4759
4760
4761You can check the success of the download using the 'iminfo' command;
4762this includes a checksum verification so you can be sure no data
4763corruption happened:
4764
4765	=> imi 40100000
4766
4767	## Checking Image at 40100000 ...
4768	   Image Name:	 2.2.13 for initrd on TQM850L
4769	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4770	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4771	   Load Address: 00000000
4772	   Entry Point:	 0000000c
4773	   Verifying Checksum ... OK
4774
4775
4776Boot Linux:
4777-----------
4778
4779The "bootm" command is used to boot an application that is stored in
4780memory (RAM or Flash). In case of a Linux kernel image, the contents
4781of the "bootargs" environment variable is passed to the kernel as
4782parameters. You can check and modify this variable using the
4783"printenv" and "setenv" commands:
4784
4785
4786	=> printenv bootargs
4787	bootargs=root=/dev/ram
4788
4789	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4790
4791	=> printenv bootargs
4792	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4793
4794	=> bootm 40020000
4795	## Booting Linux kernel at 40020000 ...
4796	   Image Name:	 2.2.13 for NFS on TQM850L
4797	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4798	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4799	   Load Address: 00000000
4800	   Entry Point:	 0000000c
4801	   Verifying Checksum ... OK
4802	   Uncompressing Kernel Image ... OK
4803	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
4804	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4805	time_init: decrementer frequency = 187500000/60
4806	Calibrating delay loop... 49.77 BogoMIPS
4807	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4808	...
4809
4810If you want to boot a Linux kernel with initial RAM disk, you pass
4811the memory addresses of both the kernel and the initrd image (PPBCOOT
4812format!) to the "bootm" command:
4813
4814	=> imi 40100000 40200000
4815
4816	## Checking Image at 40100000 ...
4817	   Image Name:	 2.2.13 for initrd on TQM850L
4818	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4819	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4820	   Load Address: 00000000
4821	   Entry Point:	 0000000c
4822	   Verifying Checksum ... OK
4823
4824	## Checking Image at 40200000 ...
4825	   Image Name:	 Simple Ramdisk Image
4826	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4827	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4828	   Load Address: 00000000
4829	   Entry Point:	 00000000
4830	   Verifying Checksum ... OK
4831
4832	=> bootm 40100000 40200000
4833	## Booting Linux kernel at 40100000 ...
4834	   Image Name:	 2.2.13 for initrd on TQM850L
4835	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4836	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4837	   Load Address: 00000000
4838	   Entry Point:	 0000000c
4839	   Verifying Checksum ... OK
4840	   Uncompressing Kernel Image ... OK
4841	## Loading RAMDisk Image at 40200000 ...
4842	   Image Name:	 Simple Ramdisk Image
4843	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4844	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4845	   Load Address: 00000000
4846	   Entry Point:	 00000000
4847	   Verifying Checksum ... OK
4848	   Loading Ramdisk ... OK
4849	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
4850	Boot arguments: root=/dev/ram
4851	time_init: decrementer frequency = 187500000/60
4852	Calibrating delay loop... 49.77 BogoMIPS
4853	...
4854	RAMDISK: Compressed image found at block 0
4855	VFS: Mounted root (ext2 filesystem).
4856
4857	bash#
4858
4859Boot Linux and pass a flat device tree:
4860-----------
4861
4862First, U-Boot must be compiled with the appropriate defines. See the section
4863titled "Linux Kernel Interface" above for a more in depth explanation. The
4864following is an example of how to start a kernel and pass an updated
4865flat device tree:
4866
4867=> print oftaddr
4868oftaddr=0x300000
4869=> print oft
4870oft=oftrees/mpc8540ads.dtb
4871=> tftp $oftaddr $oft
4872Speed: 1000, full duplex
4873Using TSEC0 device
4874TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4875Filename 'oftrees/mpc8540ads.dtb'.
4876Load address: 0x300000
4877Loading: #
4878done
4879Bytes transferred = 4106 (100a hex)
4880=> tftp $loadaddr $bootfile
4881Speed: 1000, full duplex
4882Using TSEC0 device
4883TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4884Filename 'uImage'.
4885Load address: 0x200000
4886Loading:############
4887done
4888Bytes transferred = 1029407 (fb51f hex)
4889=> print loadaddr
4890loadaddr=200000
4891=> print oftaddr
4892oftaddr=0x300000
4893=> bootm $loadaddr - $oftaddr
4894## Booting image at 00200000 ...
4895   Image Name:	 Linux-2.6.17-dirty
4896   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4897   Data Size:	 1029343 Bytes = 1005.2 kB
4898   Load Address: 00000000
4899   Entry Point:	 00000000
4900   Verifying Checksum ... OK
4901   Uncompressing Kernel Image ... OK
4902Booting using flat device tree at 0x300000
4903Using MPC85xx ADS machine description
4904Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4905[snip]
4906
4907
4908More About U-Boot Image Types:
4909------------------------------
4910
4911U-Boot supports the following image types:
4912
4913   "Standalone Programs" are directly runnable in the environment
4914	provided by U-Boot; it is expected that (if they behave
4915	well) you can continue to work in U-Boot after return from
4916	the Standalone Program.
4917   "OS Kernel Images" are usually images of some Embedded OS which
4918	will take over control completely. Usually these programs
4919	will install their own set of exception handlers, device
4920	drivers, set up the MMU, etc. - this means, that you cannot
4921	expect to re-enter U-Boot except by resetting the CPU.
4922   "RAMDisk Images" are more or less just data blocks, and their
4923	parameters (address, size) are passed to an OS kernel that is
4924	being started.
4925   "Multi-File Images" contain several images, typically an OS
4926	(Linux) kernel image and one or more data images like
4927	RAMDisks. This construct is useful for instance when you want
4928	to boot over the network using BOOTP etc., where the boot
4929	server provides just a single image file, but you want to get
4930	for instance an OS kernel and a RAMDisk image.
4931
4932	"Multi-File Images" start with a list of image sizes, each
4933	image size (in bytes) specified by an "uint32_t" in network
4934	byte order. This list is terminated by an "(uint32_t)0".
4935	Immediately after the terminating 0 follow the images, one by
4936	one, all aligned on "uint32_t" boundaries (size rounded up to
4937	a multiple of 4 bytes).
4938
4939   "Firmware Images" are binary images containing firmware (like
4940	U-Boot or FPGA images) which usually will be programmed to
4941	flash memory.
4942
4943   "Script files" are command sequences that will be executed by
4944	U-Boot's command interpreter; this feature is especially
4945	useful when you configure U-Boot to use a real shell (hush)
4946	as command interpreter.
4947
4948Booting the Linux zImage:
4949-------------------------
4950
4951On some platforms, it's possible to boot Linux zImage. This is done
4952using the "bootz" command. The syntax of "bootz" command is the same
4953as the syntax of "bootm" command.
4954
4955Note, defining the CONFIG_SUPPORT_INITRD_RAW allows user to supply
4956kernel with raw initrd images. The syntax is slightly different, the
4957address of the initrd must be augmented by it's size, in the following
4958format: "<initrd addres>:<initrd size>".
4959
4960
4961Standalone HOWTO:
4962=================
4963
4964One of the features of U-Boot is that you can dynamically load and
4965run "standalone" applications, which can use some resources of
4966U-Boot like console I/O functions or interrupt services.
4967
4968Two simple examples are included with the sources:
4969
4970"Hello World" Demo:
4971-------------------
4972
4973'examples/hello_world.c' contains a small "Hello World" Demo
4974application; it is automatically compiled when you build U-Boot.
4975It's configured to run at address 0x00040004, so you can play with it
4976like that:
4977
4978	=> loads
4979	## Ready for S-Record download ...
4980	~>examples/hello_world.srec
4981	1 2 3 4 5 6 7 8 9 10 11 ...
4982	[file transfer complete]
4983	[connected]
4984	## Start Addr = 0x00040004
4985
4986	=> go 40004 Hello World! This is a test.
4987	## Starting application at 0x00040004 ...
4988	Hello World
4989	argc = 7
4990	argv[0] = "40004"
4991	argv[1] = "Hello"
4992	argv[2] = "World!"
4993	argv[3] = "This"
4994	argv[4] = "is"
4995	argv[5] = "a"
4996	argv[6] = "test."
4997	argv[7] = "<NULL>"
4998	Hit any key to exit ...
4999
5000	## Application terminated, rc = 0x0
5001
5002Another example, which demonstrates how to register a CPM interrupt
5003handler with the U-Boot code, can be found in 'examples/timer.c'.
5004Here, a CPM timer is set up to generate an interrupt every second.
5005The interrupt service routine is trivial, just printing a '.'
5006character, but this is just a demo program. The application can be
5007controlled by the following keys:
5008
5009	? - print current values og the CPM Timer registers
5010	b - enable interrupts and start timer
5011	e - stop timer and disable interrupts
5012	q - quit application
5013
5014	=> loads
5015	## Ready for S-Record download ...
5016	~>examples/timer.srec
5017	1 2 3 4 5 6 7 8 9 10 11 ...
5018	[file transfer complete]
5019	[connected]
5020	## Start Addr = 0x00040004
5021
5022	=> go 40004
5023	## Starting application at 0x00040004 ...
5024	TIMERS=0xfff00980
5025	Using timer 1
5026	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5027
5028Hit 'b':
5029	[q, b, e, ?] Set interval 1000000 us
5030	Enabling timer
5031Hit '?':
5032	[q, b, e, ?] ........
5033	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5034Hit '?':
5035	[q, b, e, ?] .
5036	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5037Hit '?':
5038	[q, b, e, ?] .
5039	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5040Hit '?':
5041	[q, b, e, ?] .
5042	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5043Hit 'e':
5044	[q, b, e, ?] ...Stopping timer
5045Hit 'q':
5046	[q, b, e, ?] ## Application terminated, rc = 0x0
5047
5048
5049Minicom warning:
5050================
5051
5052Over time, many people have reported problems when trying to use the
5053"minicom" terminal emulation program for serial download. I (wd)
5054consider minicom to be broken, and recommend not to use it. Under
5055Unix, I recommend to use C-Kermit for general purpose use (and
5056especially for kermit binary protocol download ("loadb" command), and
5057use "cu" for S-Record download ("loads" command).  See
5058http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5059for help with kermit.
5060
5061
5062Nevertheless, if you absolutely want to use it try adding this
5063configuration to your "File transfer protocols" section:
5064
5065	   Name	   Program			Name U/D FullScr IO-Red. Multi
5066	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5067	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5068
5069
5070NetBSD Notes:
5071=============
5072
5073Starting at version 0.9.2, U-Boot supports NetBSD both as host
5074(build U-Boot) and target system (boots NetBSD/mpc8xx).
5075
5076Building requires a cross environment; it is known to work on
5077NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5078need gmake since the Makefiles are not compatible with BSD make).
5079Note that the cross-powerpc package does not install include files;
5080attempting to build U-Boot will fail because <machine/ansi.h> is
5081missing.  This file has to be installed and patched manually:
5082
5083	# cd /usr/pkg/cross/powerpc-netbsd/include
5084	# mkdir powerpc
5085	# ln -s powerpc machine
5086	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5087	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5088
5089Native builds *don't* work due to incompatibilities between native
5090and U-Boot include files.
5091
5092Booting assumes that (the first part of) the image booted is a
5093stage-2 loader which in turn loads and then invokes the kernel
5094proper. Loader sources will eventually appear in the NetBSD source
5095tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5096meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5097
5098
5099Implementation Internals:
5100=========================
5101
5102The following is not intended to be a complete description of every
5103implementation detail. However, it should help to understand the
5104inner workings of U-Boot and make it easier to port it to custom
5105hardware.
5106
5107
5108Initial Stack, Global Data:
5109---------------------------
5110
5111The implementation of U-Boot is complicated by the fact that U-Boot
5112starts running out of ROM (flash memory), usually without access to
5113system RAM (because the memory controller is not initialized yet).
5114This means that we don't have writable Data or BSS segments, and BSS
5115is not initialized as zero. To be able to get a C environment working
5116at all, we have to allocate at least a minimal stack. Implementation
5117options for this are defined and restricted by the CPU used: Some CPU
5118models provide on-chip memory (like the IMMR area on MPC8xx and
5119MPC826x processors), on others (parts of) the data cache can be
5120locked as (mis-) used as memory, etc.
5121
5122	Chris Hallinan posted a good summary of these issues to the
5123	U-Boot mailing list:
5124
5125	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5126	From: "Chris Hallinan" <clh@net1plus.com>
5127	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5128	...
5129
5130	Correct me if I'm wrong, folks, but the way I understand it
5131	is this: Using DCACHE as initial RAM for Stack, etc, does not
5132	require any physical RAM backing up the cache. The cleverness
5133	is that the cache is being used as a temporary supply of
5134	necessary storage before the SDRAM controller is setup. It's
5135	beyond the scope of this list to explain the details, but you
5136	can see how this works by studying the cache architecture and
5137	operation in the architecture and processor-specific manuals.
5138
5139	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5140	is another option for the system designer to use as an
5141	initial stack/RAM area prior to SDRAM being available. Either
5142	option should work for you. Using CS 4 should be fine if your
5143	board designers haven't used it for something that would
5144	cause you grief during the initial boot! It is frequently not
5145	used.
5146
5147	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5148	with your processor/board/system design. The default value
5149	you will find in any recent u-boot distribution in
5150	walnut.h should work for you. I'd set it to a value larger
5151	than your SDRAM module. If you have a 64MB SDRAM module, set
5152	it above 400_0000. Just make sure your board has no resources
5153	that are supposed to respond to that address! That code in
5154	start.S has been around a while and should work as is when
5155	you get the config right.
5156
5157	-Chris Hallinan
5158	DS4.COM, Inc.
5159
5160It is essential to remember this, since it has some impact on the C
5161code for the initialization procedures:
5162
5163* Initialized global data (data segment) is read-only. Do not attempt
5164  to write it.
5165
5166* Do not use any uninitialized global data (or implicitely initialized
5167  as zero data - BSS segment) at all - this is undefined, initiali-
5168  zation is performed later (when relocating to RAM).
5169
5170* Stack space is very limited. Avoid big data buffers or things like
5171  that.
5172
5173Having only the stack as writable memory limits means we cannot use
5174normal global data to share information beween the code. But it
5175turned out that the implementation of U-Boot can be greatly
5176simplified by making a global data structure (gd_t) available to all
5177functions. We could pass a pointer to this data as argument to _all_
5178functions, but this would bloat the code. Instead we use a feature of
5179the GCC compiler (Global Register Variables) to share the data: we
5180place a pointer (gd) to the global data into a register which we
5181reserve for this purpose.
5182
5183When choosing a register for such a purpose we are restricted by the
5184relevant  (E)ABI  specifications for the current architecture, and by
5185GCC's implementation.
5186
5187For PowerPC, the following registers have specific use:
5188	R1:	stack pointer
5189	R2:	reserved for system use
5190	R3-R4:	parameter passing and return values
5191	R5-R10: parameter passing
5192	R13:	small data area pointer
5193	R30:	GOT pointer
5194	R31:	frame pointer
5195
5196	(U-Boot also uses R12 as internal GOT pointer. r12
5197	is a volatile register so r12 needs to be reset when
5198	going back and forth between asm and C)
5199
5200    ==> U-Boot will use R2 to hold a pointer to the global data
5201
5202    Note: on PPC, we could use a static initializer (since the
5203    address of the global data structure is known at compile time),
5204    but it turned out that reserving a register results in somewhat
5205    smaller code - although the code savings are not that big (on
5206    average for all boards 752 bytes for the whole U-Boot image,
5207    624 text + 127 data).
5208
5209On Blackfin, the normal C ABI (except for P3) is followed as documented here:
5210	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
5211
5212    ==> U-Boot will use P3 to hold a pointer to the global data
5213
5214On ARM, the following registers are used:
5215
5216	R0:	function argument word/integer result
5217	R1-R3:	function argument word
5218	R9:	GOT pointer
5219	R10:	stack limit (used only if stack checking if enabled)
5220	R11:	argument (frame) pointer
5221	R12:	temporary workspace
5222	R13:	stack pointer
5223	R14:	link register
5224	R15:	program counter
5225
5226    ==> U-Boot will use R8 to hold a pointer to the global data
5227
5228On Nios II, the ABI is documented here:
5229	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5230
5231    ==> U-Boot will use gp to hold a pointer to the global data
5232
5233    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5234    to access small data sections, so gp is free.
5235
5236On NDS32, the following registers are used:
5237
5238	R0-R1:	argument/return
5239	R2-R5:	argument
5240	R15:	temporary register for assembler
5241	R16:	trampoline register
5242	R28:	frame pointer (FP)
5243	R29:	global pointer (GP)
5244	R30:	link register (LP)
5245	R31:	stack pointer (SP)
5246	PC:	program counter (PC)
5247
5248    ==> U-Boot will use R10 to hold a pointer to the global data
5249
5250NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5251or current versions of GCC may "optimize" the code too much.
5252
5253Memory Management:
5254------------------
5255
5256U-Boot runs in system state and uses physical addresses, i.e. the
5257MMU is not used either for address mapping nor for memory protection.
5258
5259The available memory is mapped to fixed addresses using the memory
5260controller. In this process, a contiguous block is formed for each
5261memory type (Flash, SDRAM, SRAM), even when it consists of several
5262physical memory banks.
5263
5264U-Boot is installed in the first 128 kB of the first Flash bank (on
5265TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5266booting and sizing and initializing DRAM, the code relocates itself
5267to the upper end of DRAM. Immediately below the U-Boot code some
5268memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5269configuration setting]. Below that, a structure with global Board
5270Info data is placed, followed by the stack (growing downward).
5271
5272Additionally, some exception handler code is copied to the low 8 kB
5273of DRAM (0x00000000 ... 0x00001FFF).
5274
5275So a typical memory configuration with 16 MB of DRAM could look like
5276this:
5277
5278	0x0000 0000	Exception Vector code
5279	      :
5280	0x0000 1FFF
5281	0x0000 2000	Free for Application Use
5282	      :
5283	      :
5284
5285	      :
5286	      :
5287	0x00FB FF20	Monitor Stack (Growing downward)
5288	0x00FB FFAC	Board Info Data and permanent copy of global data
5289	0x00FC 0000	Malloc Arena
5290	      :
5291	0x00FD FFFF
5292	0x00FE 0000	RAM Copy of Monitor Code
5293	...		eventually: LCD or video framebuffer
5294	...		eventually: pRAM (Protected RAM - unchanged by reset)
5295	0x00FF FFFF	[End of RAM]
5296
5297
5298System Initialization:
5299----------------------
5300
5301In the reset configuration, U-Boot starts at the reset entry point
5302(on most PowerPC systems at address 0x00000100). Because of the reset
5303configuration for CS0# this is a mirror of the onboard Flash memory.
5304To be able to re-map memory U-Boot then jumps to its link address.
5305To be able to implement the initialization code in C, a (small!)
5306initial stack is set up in the internal Dual Ported RAM (in case CPUs
5307which provide such a feature like MPC8xx or MPC8260), or in a locked
5308part of the data cache. After that, U-Boot initializes the CPU core,
5309the caches and the SIU.
5310
5311Next, all (potentially) available memory banks are mapped using a
5312preliminary mapping. For example, we put them on 512 MB boundaries
5313(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5314on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5315programmed for SDRAM access. Using the temporary configuration, a
5316simple memory test is run that determines the size of the SDRAM
5317banks.
5318
5319When there is more than one SDRAM bank, and the banks are of
5320different size, the largest is mapped first. For equal size, the first
5321bank (CS2#) is mapped first. The first mapping is always for address
53220x00000000, with any additional banks following immediately to create
5323contiguous memory starting from 0.
5324
5325Then, the monitor installs itself at the upper end of the SDRAM area
5326and allocates memory for use by malloc() and for the global Board
5327Info data; also, the exception vector code is copied to the low RAM
5328pages, and the final stack is set up.
5329
5330Only after this relocation will you have a "normal" C environment;
5331until that you are restricted in several ways, mostly because you are
5332running from ROM, and because the code will have to be relocated to a
5333new address in RAM.
5334
5335
5336U-Boot Porting Guide:
5337----------------------
5338
5339[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5340list, October 2002]
5341
5342
5343int main(int argc, char *argv[])
5344{
5345	sighandler_t no_more_time;
5346
5347	signal(SIGALRM, no_more_time);
5348	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5349
5350	if (available_money > available_manpower) {
5351		Pay consultant to port U-Boot;
5352		return 0;
5353	}
5354
5355	Download latest U-Boot source;
5356
5357	Subscribe to u-boot mailing list;
5358
5359	if (clueless)
5360		email("Hi, I am new to U-Boot, how do I get started?");
5361
5362	while (learning) {
5363		Read the README file in the top level directory;
5364		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5365		Read applicable doc/*.README;
5366		Read the source, Luke;
5367		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5368	}
5369
5370	if (available_money > toLocalCurrency ($2500))
5371		Buy a BDI3000;
5372	else
5373		Add a lot of aggravation and time;
5374
5375	if (a similar board exists) {	/* hopefully... */
5376		cp -a board/<similar> board/<myboard>
5377		cp include/configs/<similar>.h include/configs/<myboard>.h
5378	} else {
5379		Create your own board support subdirectory;
5380		Create your own board include/configs/<myboard>.h file;
5381	}
5382	Edit new board/<myboard> files
5383	Edit new include/configs/<myboard>.h
5384
5385	while (!accepted) {
5386		while (!running) {
5387			do {
5388				Add / modify source code;
5389			} until (compiles);
5390			Debug;
5391			if (clueless)
5392				email("Hi, I am having problems...");
5393		}
5394		Send patch file to the U-Boot email list;
5395		if (reasonable critiques)
5396			Incorporate improvements from email list code review;
5397		else
5398			Defend code as written;
5399	}
5400
5401	return 0;
5402}
5403
5404void no_more_time (int sig)
5405{
5406      hire_a_guru();
5407}
5408
5409
5410Coding Standards:
5411-----------------
5412
5413All contributions to U-Boot should conform to the Linux kernel
5414coding style; see the file "Documentation/CodingStyle" and the script
5415"scripts/Lindent" in your Linux kernel source directory.
5416
5417Source files originating from a different project (for example the
5418MTD subsystem) are generally exempt from these guidelines and are not
5419reformated to ease subsequent migration to newer versions of those
5420sources.
5421
5422Please note that U-Boot is implemented in C (and to some small parts in
5423Assembler); no C++ is used, so please do not use C++ style comments (//)
5424in your code.
5425
5426Please also stick to the following formatting rules:
5427- remove any trailing white space
5428- use TAB characters for indentation and vertical alignment, not spaces
5429- make sure NOT to use DOS '\r\n' line feeds
5430- do not add more than 2 consecutive empty lines to source files
5431- do not add trailing empty lines to source files
5432
5433Submissions which do not conform to the standards may be returned
5434with a request to reformat the changes.
5435
5436
5437Submitting Patches:
5438-------------------
5439
5440Since the number of patches for U-Boot is growing, we need to
5441establish some rules. Submissions which do not conform to these rules
5442may be rejected, even when they contain important and valuable stuff.
5443
5444Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5445
5446Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5447see http://lists.denx.de/mailman/listinfo/u-boot
5448
5449When you send a patch, please include the following information with
5450it:
5451
5452* For bug fixes: a description of the bug and how your patch fixes
5453  this bug. Please try to include a way of demonstrating that the
5454  patch actually fixes something.
5455
5456* For new features: a description of the feature and your
5457  implementation.
5458
5459* A CHANGELOG entry as plaintext (separate from the patch)
5460
5461* For major contributions, your entry to the CREDITS file
5462
5463* When you add support for a new board, don't forget to add this
5464  board to the MAINTAINERS file, too.
5465
5466* If your patch adds new configuration options, don't forget to
5467  document these in the README file.
5468
5469* The patch itself. If you are using git (which is *strongly*
5470  recommended) you can easily generate the patch using the
5471  "git format-patch". If you then use "git send-email" to send it to
5472  the U-Boot mailing list, you will avoid most of the common problems
5473  with some other mail clients.
5474
5475  If you cannot use git, use "diff -purN OLD NEW". If your version of
5476  diff does not support these options, then get the latest version of
5477  GNU diff.
5478
5479  The current directory when running this command shall be the parent
5480  directory of the U-Boot source tree (i. e. please make sure that
5481  your patch includes sufficient directory information for the
5482  affected files).
5483
5484  We prefer patches as plain text. MIME attachments are discouraged,
5485  and compressed attachments must not be used.
5486
5487* If one logical set of modifications affects or creates several
5488  files, all these changes shall be submitted in a SINGLE patch file.
5489
5490* Changesets that contain different, unrelated modifications shall be
5491  submitted as SEPARATE patches, one patch per changeset.
5492
5493
5494Notes:
5495
5496* Before sending the patch, run the MAKEALL script on your patched
5497  source tree and make sure that no errors or warnings are reported
5498  for any of the boards.
5499
5500* Keep your modifications to the necessary minimum: A patch
5501  containing several unrelated changes or arbitrary reformats will be
5502  returned with a request to re-formatting / split it.
5503
5504* If you modify existing code, make sure that your new code does not
5505  add to the memory footprint of the code ;-) Small is beautiful!
5506  When adding new features, these should compile conditionally only
5507  (using #ifdef), and the resulting code with the new feature
5508  disabled must not need more memory than the old code without your
5509  modification.
5510
5511* Remember that there is a size limit of 100 kB per message on the
5512  u-boot mailing list. Bigger patches will be moderated. If they are
5513  reasonable and not too big, they will be acknowledged. But patches
5514  bigger than the size limit should be avoided.
5515