xref: /openbmc/u-boot/README (revision 9386f96ca952529378f64b65633e38fdd8708307)
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- Linux Kernel Interface:
489		CONFIG_CLOCKS_IN_MHZ
490
491		U-Boot stores all clock information in Hz
492		internally. For binary compatibility with older Linux
493		kernels (which expect the clocks passed in the
494		bd_info data to be in MHz) the environment variable
495		"clocks_in_mhz" can be defined so that U-Boot
496		converts clock data to MHZ before passing it to the
497		Linux kernel.
498		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
499		"clocks_in_mhz=1" is automatically included in the
500		default environment.
501
502		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
503
504		When transferring memsize parameter to linux, some versions
505		expect it to be in bytes, others in MB.
506		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
507
508		CONFIG_OF_LIBFDT
509
510		New kernel versions are expecting firmware settings to be
511		passed using flattened device trees (based on open firmware
512		concepts).
513
514		CONFIG_OF_LIBFDT
515		 * New libfdt-based support
516		 * Adds the "fdt" command
517		 * The bootm command automatically updates the fdt
518
519		OF_CPU - The proper name of the cpus node (only required for
520			MPC512X and MPC5xxx based boards).
521		OF_SOC - The proper name of the soc node (only required for
522			MPC512X and MPC5xxx based boards).
523		OF_TBCLK - The timebase frequency.
524		OF_STDOUT_PATH - The path to the console device
525
526		boards with QUICC Engines require OF_QE to set UCC MAC
527		addresses
528
529		CONFIG_OF_BOARD_SETUP
530
531		Board code has addition modification that it wants to make
532		to the flat device tree before handing it off to the kernel
533
534		CONFIG_OF_BOOT_CPU
535
536		This define fills in the correct boot CPU in the boot
537		param header, the default value is zero if undefined.
538
539		CONFIG_OF_IDE_FIXUP
540
541		U-Boot can detect if an IDE device is present or not.
542		If not, and this new config option is activated, U-Boot
543		removes the ATA node from the DTS before booting Linux,
544		so the Linux IDE driver does not probe the device and
545		crash. This is needed for buggy hardware (uc101) where
546		no pull down resistor is connected to the signal IDE5V_DD7.
547
548		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
549
550		This setting is mandatory for all boards that have only one
551		machine type and must be used to specify the machine type
552		number as it appears in the ARM machine registry
553		(see http://www.arm.linux.org.uk/developer/machines/).
554		Only boards that have multiple machine types supported
555		in a single configuration file and the machine type is
556		runtime discoverable, do not have to use this setting.
557
558- vxWorks boot parameters:
559
560		bootvx constructs a valid bootline using the following
561		environments variables: bootfile, ipaddr, serverip, hostname.
562		It loads the vxWorks image pointed bootfile.
563
564		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
565		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
566		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
567		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
568
569		CONFIG_SYS_VXWORKS_ADD_PARAMS
570
571		Add it at the end of the bootline. E.g "u=username pw=secret"
572
573		Note: If a "bootargs" environment is defined, it will overwride
574		the defaults discussed just above.
575
576- Cache Configuration:
577		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
578		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
579		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
580
581- Cache Configuration for ARM:
582		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
583				      controller
584		CONFIG_SYS_PL310_BASE - Physical base address of PL310
585					controller register space
586
587- Serial Ports:
588		CONFIG_PL010_SERIAL
589
590		Define this if you want support for Amba PrimeCell PL010 UARTs.
591
592		CONFIG_PL011_SERIAL
593
594		Define this if you want support for Amba PrimeCell PL011 UARTs.
595
596		CONFIG_PL011_CLOCK
597
598		If you have Amba PrimeCell PL011 UARTs, set this variable to
599		the clock speed of the UARTs.
600
601		CONFIG_PL01x_PORTS
602
603		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
604		define this to a list of base addresses for each (supported)
605		port. See e.g. include/configs/versatile.h
606
607		CONFIG_PL011_SERIAL_RLCR
608
609		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
610		have separate receive and transmit line control registers.  Set
611		this variable to initialize the extra register.
612
613		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
614
615		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
616		boot loader that has already initialized the UART.  Define this
617		variable to flush the UART at init time.
618
619
620- Console Interface:
621		Depending on board, define exactly one serial port
622		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
623		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
624		console by defining CONFIG_8xx_CONS_NONE
625
626		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
627		port routines must be defined elsewhere
628		(i.e. serial_init(), serial_getc(), ...)
629
630		CONFIG_CFB_CONSOLE
631		Enables console device for a color framebuffer. Needs following
632		defines (cf. smiLynxEM, i8042)
633			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
634						(default big endian)
635			VIDEO_HW_RECTFILL	graphic chip supports
636						rectangle fill
637						(cf. smiLynxEM)
638			VIDEO_HW_BITBLT		graphic chip supports
639						bit-blit (cf. smiLynxEM)
640			VIDEO_VISIBLE_COLS	visible pixel columns
641						(cols=pitch)
642			VIDEO_VISIBLE_ROWS	visible pixel rows
643			VIDEO_PIXEL_SIZE	bytes per pixel
644			VIDEO_DATA_FORMAT	graphic data format
645						(0-5, cf. cfb_console.c)
646			VIDEO_FB_ADRS		framebuffer address
647			VIDEO_KBD_INIT_FCT	keyboard int fct
648						(i.e. i8042_kbd_init())
649			VIDEO_TSTC_FCT		test char fct
650						(i.e. i8042_tstc)
651			VIDEO_GETC_FCT		get char fct
652						(i.e. i8042_getc)
653			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
654						(requires blink timer
655						cf. i8042.c)
656			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
657			CONFIG_CONSOLE_TIME	display time/date info in
658						upper right corner
659						(requires CONFIG_CMD_DATE)
660			CONFIG_VIDEO_LOGO	display Linux logo in
661						upper left corner
662			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
663						linux_logo.h for logo.
664						Requires CONFIG_VIDEO_LOGO
665			CONFIG_CONSOLE_EXTRA_INFO
666						additional board info beside
667						the logo
668
669		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
670		a limited number of ANSI escape sequences (cursor control,
671		erase functions and limited graphics rendition control).
672
673		When CONFIG_CFB_CONSOLE is defined, video console is
674		default i/o. Serial console can be forced with
675		environment 'console=serial'.
676
677		When CONFIG_SILENT_CONSOLE is defined, all console
678		messages (by U-Boot and Linux!) can be silenced with
679		the "silent" environment variable. See
680		doc/README.silent for more information.
681
682- Console Baudrate:
683		CONFIG_BAUDRATE - in bps
684		Select one of the baudrates listed in
685		CONFIG_SYS_BAUDRATE_TABLE, see below.
686		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
687
688- Console Rx buffer length
689		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
690		the maximum receive buffer length for the SMC.
691		This option is actual only for 82xx and 8xx possible.
692		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
693		must be defined, to setup the maximum idle timeout for
694		the SMC.
695
696- Pre-Console Buffer:
697		Prior to the console being initialised (i.e. serial UART
698		initialised etc) all console output is silently discarded.
699		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
700		buffer any console messages prior to the console being
701		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
702		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
703		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
704		bytes are output before the console is initialised, the
705		earlier bytes are discarded.
706
707		'Sane' compilers will generate smaller code if
708		CONFIG_PRE_CON_BUF_SZ is a power of 2
709
710- Safe printf() functions
711		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
712		the printf() functions. These are defined in
713		include/vsprintf.h and include snprintf(), vsnprintf() and
714		so on. Code size increase is approximately 300-500 bytes.
715		If this option is not given then these functions will
716		silently discard their buffer size argument - this means
717		you are not getting any overflow checking in this case.
718
719- Boot Delay:	CONFIG_BOOTDELAY - in seconds
720		Delay before automatically booting the default image;
721		set to -1 to disable autoboot.
722		set to -2 to autoboot with no delay and not check for abort
723		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
724
725		See doc/README.autoboot for these options that
726		work with CONFIG_BOOTDELAY. None are required.
727		CONFIG_BOOT_RETRY_TIME
728		CONFIG_BOOT_RETRY_MIN
729		CONFIG_AUTOBOOT_KEYED
730		CONFIG_AUTOBOOT_PROMPT
731		CONFIG_AUTOBOOT_DELAY_STR
732		CONFIG_AUTOBOOT_STOP_STR
733		CONFIG_AUTOBOOT_DELAY_STR2
734		CONFIG_AUTOBOOT_STOP_STR2
735		CONFIG_ZERO_BOOTDELAY_CHECK
736		CONFIG_RESET_TO_RETRY
737
738- Autoboot Command:
739		CONFIG_BOOTCOMMAND
740		Only needed when CONFIG_BOOTDELAY is enabled;
741		define a command string that is automatically executed
742		when no character is read on the console interface
743		within "Boot Delay" after reset.
744
745		CONFIG_BOOTARGS
746		This can be used to pass arguments to the bootm
747		command. The value of CONFIG_BOOTARGS goes into the
748		environment value "bootargs".
749
750		CONFIG_RAMBOOT and CONFIG_NFSBOOT
751		The value of these goes into the environment as
752		"ramboot" and "nfsboot" respectively, and can be used
753		as a convenience, when switching between booting from
754		RAM and NFS.
755
756- Pre-Boot Commands:
757		CONFIG_PREBOOT
758
759		When this option is #defined, the existence of the
760		environment variable "preboot" will be checked
761		immediately before starting the CONFIG_BOOTDELAY
762		countdown and/or running the auto-boot command resp.
763		entering interactive mode.
764
765		This feature is especially useful when "preboot" is
766		automatically generated or modified. For an example
767		see the LWMON board specific code: here "preboot" is
768		modified when the user holds down a certain
769		combination of keys on the (special) keyboard when
770		booting the systems
771
772- Serial Download Echo Mode:
773		CONFIG_LOADS_ECHO
774		If defined to 1, all characters received during a
775		serial download (using the "loads" command) are
776		echoed back. This might be needed by some terminal
777		emulations (like "cu"), but may as well just take
778		time on others. This setting #define's the initial
779		value of the "loads_echo" environment variable.
780
781- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
782		CONFIG_KGDB_BAUDRATE
783		Select one of the baudrates listed in
784		CONFIG_SYS_BAUDRATE_TABLE, see below.
785
786- Monitor Functions:
787		Monitor commands can be included or excluded
788		from the build by using the #include files
789		<config_cmd_all.h> and #undef'ing unwanted
790		commands, or using <config_cmd_default.h>
791		and augmenting with additional #define's
792		for wanted commands.
793
794		The default command configuration includes all commands
795		except those marked below with a "*".
796
797		CONFIG_CMD_ASKENV	* ask for env variable
798		CONFIG_CMD_BDI		  bdinfo
799		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
800		CONFIG_CMD_BMP		* BMP support
801		CONFIG_CMD_BSP		* Board specific commands
802		CONFIG_CMD_BOOTD	  bootd
803		CONFIG_CMD_CACHE	* icache, dcache
804		CONFIG_CMD_CONSOLE	  coninfo
805		CONFIG_CMD_CRC32	* crc32
806		CONFIG_CMD_DATE		* support for RTC, date/time...
807		CONFIG_CMD_DHCP		* DHCP support
808		CONFIG_CMD_DIAG		* Diagnostics
809		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
810		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
811		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
812		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
813		CONFIG_CMD_DTT		* Digital Therm and Thermostat
814		CONFIG_CMD_ECHO		  echo arguments
815		CONFIG_CMD_EDITENV	  edit env variable
816		CONFIG_CMD_EEPROM	* EEPROM read/write support
817		CONFIG_CMD_ELF		* bootelf, bootvx
818		CONFIG_CMD_EXPORTENV	* export the environment
819		CONFIG_CMD_EXT2		* ext2 command support
820		CONFIG_CMD_EXT4		* ext4 command support
821		CONFIG_CMD_SAVEENV	  saveenv
822		CONFIG_CMD_FDC		* Floppy Disk Support
823		CONFIG_CMD_FAT		* FAT command support
824		CONFIG_CMD_FDOS		* Dos diskette Support
825		CONFIG_CMD_FLASH	  flinfo, erase, protect
826		CONFIG_CMD_FPGA		  FPGA device initialization support
827		CONFIG_CMD_GETTIME	* Get time since boot
828		CONFIG_CMD_GO		* the 'go' command (exec code)
829		CONFIG_CMD_GREPENV	* search environment
830		CONFIG_CMD_HASH		* calculate hash / digest
831		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
832		CONFIG_CMD_I2C		* I2C serial bus support
833		CONFIG_CMD_IDE		* IDE harddisk support
834		CONFIG_CMD_IMI		  iminfo
835		CONFIG_CMD_IMLS		  List all found images
836		CONFIG_CMD_IMMAP	* IMMR dump support
837		CONFIG_CMD_IMPORTENV	* import an environment
838		CONFIG_CMD_INI		* import data from an ini file into the env
839		CONFIG_CMD_IRQ		* irqinfo
840		CONFIG_CMD_ITEST	  Integer/string test of 2 values
841		CONFIG_CMD_JFFS2	* JFFS2 Support
842		CONFIG_CMD_KGDB		* kgdb
843		CONFIG_CMD_LDRINFO	  ldrinfo (display Blackfin loader)
844		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
845					  (169.254.*.*)
846		CONFIG_CMD_LOADB	  loadb
847		CONFIG_CMD_LOADS	  loads
848		CONFIG_CMD_MD5SUM	  print md5 message digest
849					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
850		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
851					  loop, loopw, mtest
852		CONFIG_CMD_MISC		  Misc functions like sleep etc
853		CONFIG_CMD_MMC		* MMC memory mapped support
854		CONFIG_CMD_MII		* MII utility commands
855		CONFIG_CMD_MTDPARTS	* MTD partition support
856		CONFIG_CMD_NAND		* NAND support
857		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
858		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
859		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
860		CONFIG_CMD_PCI		* pciinfo
861		CONFIG_CMD_PCMCIA		* PCMCIA support
862		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
863					  host
864		CONFIG_CMD_PORTIO	* Port I/O
865		CONFIG_CMD_READ		* Read raw data from partition
866		CONFIG_CMD_REGINFO	* Register dump
867		CONFIG_CMD_RUN		  run command in env variable
868		CONFIG_CMD_SAVES	* save S record dump
869		CONFIG_CMD_SCSI		* SCSI Support
870		CONFIG_CMD_SDRAM	* print SDRAM configuration information
871					  (requires CONFIG_CMD_I2C)
872		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
873					  (4xx only)
874		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
875		CONFIG_CMD_SHA1SUM	  print sha1 memory digest
876					  (requires CONFIG_CMD_MEMORY)
877		CONFIG_CMD_SOURCE	  "source" command Support
878		CONFIG_CMD_SPI		* SPI serial bus support
879		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
880		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
881		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
882		CONFIG_CMD_TIMER	* access to the system tick timer
883		CONFIG_CMD_USB		* USB support
884		CONFIG_CMD_CDP		* Cisco Discover Protocol support
885		CONFIG_CMD_MFSL		* Microblaze FSL support
886
887
888		EXAMPLE: If you want all functions except of network
889		support you can write:
890
891		#include "config_cmd_all.h"
892		#undef CONFIG_CMD_NET
893
894	Other Commands:
895		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
896
897	Note:	Don't enable the "icache" and "dcache" commands
898		(configuration option CONFIG_CMD_CACHE) unless you know
899		what you (and your U-Boot users) are doing. Data
900		cache cannot be enabled on systems like the 8xx or
901		8260 (where accesses to the IMMR region must be
902		uncached), and it cannot be disabled on all other
903		systems where we (mis-) use the data cache to hold an
904		initial stack and some data.
905
906
907		XXX - this list needs to get updated!
908
909- Device tree:
910		CONFIG_OF_CONTROL
911		If this variable is defined, U-Boot will use a device tree
912		to configure its devices, instead of relying on statically
913		compiled #defines in the board file. This option is
914		experimental and only available on a few boards. The device
915		tree is available in the global data as gd->fdt_blob.
916
917		U-Boot needs to get its device tree from somewhere. This can
918		be done using one of the two options below:
919
920		CONFIG_OF_EMBED
921		If this variable is defined, U-Boot will embed a device tree
922		binary in its image. This device tree file should be in the
923		board directory and called <soc>-<board>.dts. The binary file
924		is then picked up in board_init_f() and made available through
925		the global data structure as gd->blob.
926
927		CONFIG_OF_SEPARATE
928		If this variable is defined, U-Boot will build a device tree
929		binary. It will be called u-boot.dtb. Architecture-specific
930		code will locate it at run-time. Generally this works by:
931
932			cat u-boot.bin u-boot.dtb >image.bin
933
934		and in fact, U-Boot does this for you, creating a file called
935		u-boot-dtb.bin which is useful in the common case. You can
936		still use the individual files if you need something more
937		exotic.
938
939- Watchdog:
940		CONFIG_WATCHDOG
941		If this variable is defined, it enables watchdog
942		support for the SoC. There must be support in the SoC
943		specific code for a watchdog. For the 8xx and 8260
944		CPUs, the SIU Watchdog feature is enabled in the SYPCR
945		register.  When supported for a specific SoC is
946		available, then no further board specific code should
947		be needed to use it.
948
949		CONFIG_HW_WATCHDOG
950		When using a watchdog circuitry external to the used
951		SoC, then define this variable and provide board
952		specific code for the "hw_watchdog_reset" function.
953
954- U-Boot Version:
955		CONFIG_VERSION_VARIABLE
956		If this variable is defined, an environment variable
957		named "ver" is created by U-Boot showing the U-Boot
958		version as printed by the "version" command.
959		Any change to this variable will be reverted at the
960		next reset.
961
962- Real-Time Clock:
963
964		When CONFIG_CMD_DATE is selected, the type of the RTC
965		has to be selected, too. Define exactly one of the
966		following options:
967
968		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
969		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
970		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
971		CONFIG_RTC_MC146818	- use MC146818 RTC
972		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
973		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
974		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
975		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
976		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
977		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
978		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
979		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
980					  RV3029 RTC.
981
982		Note that if the RTC uses I2C, then the I2C interface
983		must also be configured. See I2C Support, below.
984
985- GPIO Support:
986		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
987		CONFIG_PCA953X_INFO	- enable pca953x info command
988
989		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
990		chip-ngpio pairs that tell the PCA953X driver the number of
991		pins supported by a particular chip.
992
993		Note that if the GPIO device uses I2C, then the I2C interface
994		must also be configured. See I2C Support, below.
995
996- Timestamp Support:
997
998		When CONFIG_TIMESTAMP is selected, the timestamp
999		(date and time) of an image is printed by image
1000		commands like bootm or iminfo. This option is
1001		automatically enabled when you select CONFIG_CMD_DATE .
1002
1003- Partition Labels (disklabels) Supported:
1004		Zero or more of the following:
1005		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1006		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1007				       Intel architecture, USB sticks, etc.
1008		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1009		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1010				       bootloader.  Note 2TB partition limit; see
1011				       disk/part_efi.c
1012		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1013
1014		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1015		CONFIG_CMD_SCSI) you must configure support for at
1016		least one non-MTD partition type as well.
1017
1018- IDE Reset method:
1019		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1020		board configurations files but used nowhere!
1021
1022		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1023		be performed by calling the function
1024			ide_set_reset(int reset)
1025		which has to be defined in a board specific file
1026
1027- ATAPI Support:
1028		CONFIG_ATAPI
1029
1030		Set this to enable ATAPI support.
1031
1032- LBA48 Support
1033		CONFIG_LBA48
1034
1035		Set this to enable support for disks larger than 137GB
1036		Also look at CONFIG_SYS_64BIT_LBA.
1037		Whithout these , LBA48 support uses 32bit variables and will 'only'
1038		support disks up to 2.1TB.
1039
1040		CONFIG_SYS_64BIT_LBA:
1041			When enabled, makes the IDE subsystem use 64bit sector addresses.
1042			Default is 32bit.
1043
1044- SCSI Support:
1045		At the moment only there is only support for the
1046		SYM53C8XX SCSI controller; define
1047		CONFIG_SCSI_SYM53C8XX to enable it.
1048
1049		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1050		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1051		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1052		maximum numbers of LUNs, SCSI ID's and target
1053		devices.
1054		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1055
1056                The environment variable 'scsidevs' is set to the number of
1057                SCSI devices found during the last scan.
1058
1059- NETWORK Support (PCI):
1060		CONFIG_E1000
1061		Support for Intel 8254x/8257x gigabit chips.
1062
1063		CONFIG_E1000_SPI
1064		Utility code for direct access to the SPI bus on Intel 8257x.
1065		This does not do anything useful unless you set at least one
1066		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1067
1068		CONFIG_E1000_SPI_GENERIC
1069		Allow generic access to the SPI bus on the Intel 8257x, for
1070		example with the "sspi" command.
1071
1072		CONFIG_CMD_E1000
1073		Management command for E1000 devices.  When used on devices
1074		with SPI support you can reprogram the EEPROM from U-Boot.
1075
1076		CONFIG_E1000_FALLBACK_MAC
1077		default MAC for empty EEPROM after production.
1078
1079		CONFIG_EEPRO100
1080		Support for Intel 82557/82559/82559ER chips.
1081		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1082		write routine for first time initialisation.
1083
1084		CONFIG_TULIP
1085		Support for Digital 2114x chips.
1086		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1087		modem chip initialisation (KS8761/QS6611).
1088
1089		CONFIG_NATSEMI
1090		Support for National dp83815 chips.
1091
1092		CONFIG_NS8382X
1093		Support for National dp8382[01] gigabit chips.
1094
1095- NETWORK Support (other):
1096
1097		CONFIG_DRIVER_AT91EMAC
1098		Support for AT91RM9200 EMAC.
1099
1100			CONFIG_RMII
1101			Define this to use reduced MII inteface
1102
1103			CONFIG_DRIVER_AT91EMAC_QUIET
1104			If this defined, the driver is quiet.
1105			The driver doen't show link status messages.
1106
1107		CONFIG_CALXEDA_XGMAC
1108		Support for the Calxeda XGMAC device
1109
1110		CONFIG_LAN91C96
1111		Support for SMSC's LAN91C96 chips.
1112
1113			CONFIG_LAN91C96_BASE
1114			Define this to hold the physical address
1115			of the LAN91C96's I/O space
1116
1117			CONFIG_LAN91C96_USE_32_BIT
1118			Define this to enable 32 bit addressing
1119
1120		CONFIG_SMC91111
1121		Support for SMSC's LAN91C111 chip
1122
1123			CONFIG_SMC91111_BASE
1124			Define this to hold the physical address
1125			of the device (I/O space)
1126
1127			CONFIG_SMC_USE_32_BIT
1128			Define this if data bus is 32 bits
1129
1130			CONFIG_SMC_USE_IOFUNCS
1131			Define this to use i/o functions instead of macros
1132			(some hardware wont work with macros)
1133
1134		CONFIG_DRIVER_TI_EMAC
1135		Support for davinci emac
1136
1137			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1138			Define this if you have more then 3 PHYs.
1139
1140		CONFIG_FTGMAC100
1141		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1142
1143			CONFIG_FTGMAC100_EGIGA
1144			Define this to use GE link update with gigabit PHY.
1145			Define this if FTGMAC100 is connected to gigabit PHY.
1146			If your system has 10/100 PHY only, it might not occur
1147			wrong behavior. Because PHY usually return timeout or
1148			useless data when polling gigabit status and gigabit
1149			control registers. This behavior won't affect the
1150			correctnessof 10/100 link speed update.
1151
1152		CONFIG_SMC911X
1153		Support for SMSC's LAN911x and LAN921x chips
1154
1155			CONFIG_SMC911X_BASE
1156			Define this to hold the physical address
1157			of the device (I/O space)
1158
1159			CONFIG_SMC911X_32_BIT
1160			Define this if data bus is 32 bits
1161
1162			CONFIG_SMC911X_16_BIT
1163			Define this if data bus is 16 bits. If your processor
1164			automatically converts one 32 bit word to two 16 bit
1165			words you may also try CONFIG_SMC911X_32_BIT.
1166
1167		CONFIG_SH_ETHER
1168		Support for Renesas on-chip Ethernet controller
1169
1170			CONFIG_SH_ETHER_USE_PORT
1171			Define the number of ports to be used
1172
1173			CONFIG_SH_ETHER_PHY_ADDR
1174			Define the ETH PHY's address
1175
1176			CONFIG_SH_ETHER_CACHE_WRITEBACK
1177			If this option is set, the driver enables cache flush.
1178
1179- TPM Support:
1180		CONFIG_GENERIC_LPC_TPM
1181		Support for generic parallel port TPM devices. Only one device
1182		per system is supported at this time.
1183
1184			CONFIG_TPM_TIS_BASE_ADDRESS
1185			Base address where the generic TPM device is mapped
1186			to. Contemporary x86 systems usually map it at
1187			0xfed40000.
1188
1189- USB Support:
1190		At the moment only the UHCI host controller is
1191		supported (PIP405, MIP405, MPC5200); define
1192		CONFIG_USB_UHCI to enable it.
1193		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1194		and define CONFIG_USB_STORAGE to enable the USB
1195		storage devices.
1196		Note:
1197		Supported are USB Keyboards and USB Floppy drives
1198		(TEAC FD-05PUB).
1199		MPC5200 USB requires additional defines:
1200			CONFIG_USB_CLOCK
1201				for 528 MHz Clock: 0x0001bbbb
1202			CONFIG_PSC3_USB
1203				for USB on PSC3
1204			CONFIG_USB_CONFIG
1205				for differential drivers: 0x00001000
1206				for single ended drivers: 0x00005000
1207				for differential drivers on PSC3: 0x00000100
1208				for single ended drivers on PSC3: 0x00004100
1209			CONFIG_SYS_USB_EVENT_POLL
1210				May be defined to allow interrupt polling
1211				instead of using asynchronous interrupts
1212
1213		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1214		txfilltuning field in the EHCI controller on reset.
1215
1216- USB Device:
1217		Define the below if you wish to use the USB console.
1218		Once firmware is rebuilt from a serial console issue the
1219		command "setenv stdin usbtty; setenv stdout usbtty" and
1220		attach your USB cable. The Unix command "dmesg" should print
1221		it has found a new device. The environment variable usbtty
1222		can be set to gserial or cdc_acm to enable your device to
1223		appear to a USB host as a Linux gserial device or a
1224		Common Device Class Abstract Control Model serial device.
1225		If you select usbtty = gserial you should be able to enumerate
1226		a Linux host by
1227		# modprobe usbserial vendor=0xVendorID product=0xProductID
1228		else if using cdc_acm, simply setting the environment
1229		variable usbtty to be cdc_acm should suffice. The following
1230		might be defined in YourBoardName.h
1231
1232			CONFIG_USB_DEVICE
1233			Define this to build a UDC device
1234
1235			CONFIG_USB_TTY
1236			Define this to have a tty type of device available to
1237			talk to the UDC device
1238
1239			CONFIG_USBD_HS
1240			Define this to enable the high speed support for usb
1241			device and usbtty. If this feature is enabled, a routine
1242			int is_usbd_high_speed(void)
1243			also needs to be defined by the driver to dynamically poll
1244			whether the enumeration has succeded at high speed or full
1245			speed.
1246
1247			CONFIG_SYS_CONSOLE_IS_IN_ENV
1248			Define this if you want stdin, stdout &/or stderr to
1249			be set to usbtty.
1250
1251			mpc8xx:
1252				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1253				Derive USB clock from external clock "blah"
1254				- CONFIG_SYS_USB_EXTC_CLK 0x02
1255
1256				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1257				Derive USB clock from brgclk
1258				- CONFIG_SYS_USB_BRG_CLK 0x04
1259
1260		If you have a USB-IF assigned VendorID then you may wish to
1261		define your own vendor specific values either in BoardName.h
1262		or directly in usbd_vendor_info.h. If you don't define
1263		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1264		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1265		should pretend to be a Linux device to it's target host.
1266
1267			CONFIG_USBD_MANUFACTURER
1268			Define this string as the name of your company for
1269			- CONFIG_USBD_MANUFACTURER "my company"
1270
1271			CONFIG_USBD_PRODUCT_NAME
1272			Define this string as the name of your product
1273			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1274
1275			CONFIG_USBD_VENDORID
1276			Define this as your assigned Vendor ID from the USB
1277			Implementors Forum. This *must* be a genuine Vendor ID
1278			to avoid polluting the USB namespace.
1279			- CONFIG_USBD_VENDORID 0xFFFF
1280
1281			CONFIG_USBD_PRODUCTID
1282			Define this as the unique Product ID
1283			for your device
1284			- CONFIG_USBD_PRODUCTID 0xFFFF
1285
1286- ULPI Layer Support:
1287		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1288		the generic ULPI layer. The generic layer accesses the ULPI PHY
1289		via the platform viewport, so you need both the genric layer and
1290		the viewport enabled. Currently only Chipidea/ARC based
1291		viewport is supported.
1292		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1293		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1294		If your ULPI phy needs a different reference clock than the
1295		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1296		the appropriate value in Hz.
1297
1298- MMC Support:
1299		The MMC controller on the Intel PXA is supported. To
1300		enable this define CONFIG_MMC. The MMC can be
1301		accessed from the boot prompt by mapping the device
1302		to physical memory similar to flash. Command line is
1303		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1304		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1305
1306		CONFIG_SH_MMCIF
1307		Support for Renesas on-chip MMCIF controller
1308
1309			CONFIG_SH_MMCIF_ADDR
1310			Define the base address of MMCIF registers
1311
1312			CONFIG_SH_MMCIF_CLK
1313			Define the clock frequency for MMCIF
1314
1315- Journaling Flash filesystem support:
1316		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1317		CONFIG_JFFS2_NAND_DEV
1318		Define these for a default partition on a NAND device
1319
1320		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1321		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1322		Define these for a default partition on a NOR device
1323
1324		CONFIG_SYS_JFFS_CUSTOM_PART
1325		Define this to create an own partition. You have to provide a
1326		function struct part_info* jffs2_part_info(int part_num)
1327
1328		If you define only one JFFS2 partition you may also want to
1329		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1330		to disable the command chpart. This is the default when you
1331		have not defined a custom partition
1332
1333- FAT(File Allocation Table) filesystem write function support:
1334		CONFIG_FAT_WRITE
1335
1336		Define this to enable support for saving memory data as a
1337		file in FAT formatted partition.
1338
1339		This will also enable the command "fatwrite" enabling the
1340		user to write files to FAT.
1341
1342CBFS (Coreboot Filesystem) support
1343		CONFIG_CMD_CBFS
1344
1345		Define this to enable support for reading from a Coreboot
1346		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1347		and cbfsload.
1348
1349- Keyboard Support:
1350		CONFIG_ISA_KEYBOARD
1351
1352		Define this to enable standard (PC-Style) keyboard
1353		support
1354
1355		CONFIG_I8042_KBD
1356		Standard PC keyboard driver with US (is default) and
1357		GERMAN key layout (switch via environment 'keymap=de') support.
1358		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1359		for cfb_console. Supports cursor blinking.
1360
1361- Video support:
1362		CONFIG_VIDEO
1363
1364		Define this to enable video support (for output to
1365		video).
1366
1367		CONFIG_VIDEO_CT69000
1368
1369		Enable Chips & Technologies 69000 Video chip
1370
1371		CONFIG_VIDEO_SMI_LYNXEM
1372		Enable Silicon Motion SMI 712/710/810 Video chip. The
1373		video output is selected via environment 'videoout'
1374		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1375		assumed.
1376
1377		For the CT69000 and SMI_LYNXEM drivers, videomode is
1378		selected via environment 'videomode'. Two different ways
1379		are possible:
1380		- "videomode=num"   'num' is a standard LiLo mode numbers.
1381		Following standard modes are supported	(* is default):
1382
1383		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1384		-------------+---------------------------------------------
1385		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1386		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1387		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1388		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1389		-------------+---------------------------------------------
1390		(i.e. setenv videomode 317; saveenv; reset;)
1391
1392		- "videomode=bootargs" all the video parameters are parsed
1393		from the bootargs. (See drivers/video/videomodes.c)
1394
1395
1396		CONFIG_VIDEO_SED13806
1397		Enable Epson SED13806 driver. This driver supports 8bpp
1398		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1399		or CONFIG_VIDEO_SED13806_16BPP
1400
1401		CONFIG_FSL_DIU_FB
1402		Enable the Freescale DIU video driver.	Reference boards for
1403		SOCs that have a DIU should define this macro to enable DIU
1404		support, and should also define these other macros:
1405
1406			CONFIG_SYS_DIU_ADDR
1407			CONFIG_VIDEO
1408			CONFIG_CMD_BMP
1409			CONFIG_CFB_CONSOLE
1410			CONFIG_VIDEO_SW_CURSOR
1411			CONFIG_VGA_AS_SINGLE_DEVICE
1412			CONFIG_VIDEO_LOGO
1413			CONFIG_VIDEO_BMP_LOGO
1414
1415		The DIU driver will look for the 'video-mode' environment
1416		variable, and if defined, enable the DIU as a console during
1417		boot.  See the documentation file README.video for a
1418		description of this variable.
1419
1420		CONFIG_VIDEO_VGA
1421
1422		Enable the VGA video / BIOS for x86. The alternative if you
1423		are using coreboot is to use the coreboot frame buffer
1424		driver.
1425
1426
1427- Keyboard Support:
1428		CONFIG_KEYBOARD
1429
1430		Define this to enable a custom keyboard support.
1431		This simply calls drv_keyboard_init() which must be
1432		defined in your board-specific files.
1433		The only board using this so far is RBC823.
1434
1435- LCD Support:	CONFIG_LCD
1436
1437		Define this to enable LCD support (for output to LCD
1438		display); also select one of the supported displays
1439		by defining one of these:
1440
1441		CONFIG_ATMEL_LCD:
1442
1443			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1444
1445		CONFIG_NEC_NL6448AC33:
1446
1447			NEC NL6448AC33-18. Active, color, single scan.
1448
1449		CONFIG_NEC_NL6448BC20
1450
1451			NEC NL6448BC20-08. 6.5", 640x480.
1452			Active, color, single scan.
1453
1454		CONFIG_NEC_NL6448BC33_54
1455
1456			NEC NL6448BC33-54. 10.4", 640x480.
1457			Active, color, single scan.
1458
1459		CONFIG_SHARP_16x9
1460
1461			Sharp 320x240. Active, color, single scan.
1462			It isn't 16x9, and I am not sure what it is.
1463
1464		CONFIG_SHARP_LQ64D341
1465
1466			Sharp LQ64D341 display, 640x480.
1467			Active, color, single scan.
1468
1469		CONFIG_HLD1045
1470
1471			HLD1045 display, 640x480.
1472			Active, color, single scan.
1473
1474		CONFIG_OPTREX_BW
1475
1476			Optrex	 CBL50840-2 NF-FW 99 22 M5
1477			or
1478			Hitachi	 LMG6912RPFC-00T
1479			or
1480			Hitachi	 SP14Q002
1481
1482			320x240. Black & white.
1483
1484		Normally display is black on white background; define
1485		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1486
1487		CONFIG_LCD_BMP_RLE8
1488
1489		Support drawing of RLE8-compressed bitmaps on the LCD.
1490
1491		CONFIG_I2C_EDID
1492
1493		Enables an 'i2c edid' command which can read EDID
1494		information over I2C from an attached LCD display.
1495
1496
1497- Splash Screen Support: CONFIG_SPLASH_SCREEN
1498
1499		If this option is set, the environment is checked for
1500		a variable "splashimage". If found, the usual display
1501		of logo, copyright and system information on the LCD
1502		is suppressed and the BMP image at the address
1503		specified in "splashimage" is loaded instead. The
1504		console is redirected to the "nulldev", too. This
1505		allows for a "silent" boot where a splash screen is
1506		loaded very quickly after power-on.
1507
1508		CONFIG_SPLASH_SCREEN_ALIGN
1509
1510		If this option is set the splash image can be freely positioned
1511		on the screen. Environment variable "splashpos" specifies the
1512		position as "x,y". If a positive number is given it is used as
1513		number of pixel from left/top. If a negative number is given it
1514		is used as number of pixel from right/bottom. You can also
1515		specify 'm' for centering the image.
1516
1517		Example:
1518		setenv splashpos m,m
1519			=> image at center of screen
1520
1521		setenv splashpos 30,20
1522			=> image at x = 30 and y = 20
1523
1524		setenv splashpos -10,m
1525			=> vertically centered image
1526			   at x = dspWidth - bmpWidth - 9
1527
1528- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1529
1530		If this option is set, additionally to standard BMP
1531		images, gzipped BMP images can be displayed via the
1532		splashscreen support or the bmp command.
1533
1534- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1535
1536		If this option is set, 8-bit RLE compressed BMP images
1537		can be displayed via the splashscreen support or the
1538		bmp command.
1539
1540- Do compresssing for memory range:
1541		CONFIG_CMD_ZIP
1542
1543		If this option is set, it would use zlib deflate method
1544		to compress the specified memory at its best effort.
1545
1546- Compression support:
1547		CONFIG_BZIP2
1548
1549		If this option is set, support for bzip2 compressed
1550		images is included. If not, only uncompressed and gzip
1551		compressed images are supported.
1552
1553		NOTE: the bzip2 algorithm requires a lot of RAM, so
1554		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1555		be at least 4MB.
1556
1557		CONFIG_LZMA
1558
1559		If this option is set, support for lzma compressed
1560		images is included.
1561
1562		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1563		requires an amount of dynamic memory that is given by the
1564		formula:
1565
1566			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1567
1568		Where lc and lp stand for, respectively, Literal context bits
1569		and Literal pos bits.
1570
1571		This value is upper-bounded by 14MB in the worst case. Anyway,
1572		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1573		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1574		a very small buffer.
1575
1576		Use the lzmainfo tool to determinate the lc and lp values and
1577		then calculate the amount of needed dynamic memory (ensuring
1578		the appropriate CONFIG_SYS_MALLOC_LEN value).
1579
1580- MII/PHY support:
1581		CONFIG_PHY_ADDR
1582
1583		The address of PHY on MII bus.
1584
1585		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1586
1587		The clock frequency of the MII bus
1588
1589		CONFIG_PHY_GIGE
1590
1591		If this option is set, support for speed/duplex
1592		detection of gigabit PHY is included.
1593
1594		CONFIG_PHY_RESET_DELAY
1595
1596		Some PHY like Intel LXT971A need extra delay after
1597		reset before any MII register access is possible.
1598		For such PHY, set this option to the usec delay
1599		required. (minimum 300usec for LXT971A)
1600
1601		CONFIG_PHY_CMD_DELAY (ppc4xx)
1602
1603		Some PHY like Intel LXT971A need extra delay after
1604		command issued before MII status register can be read
1605
1606- Ethernet address:
1607		CONFIG_ETHADDR
1608		CONFIG_ETH1ADDR
1609		CONFIG_ETH2ADDR
1610		CONFIG_ETH3ADDR
1611		CONFIG_ETH4ADDR
1612		CONFIG_ETH5ADDR
1613
1614		Define a default value for Ethernet address to use
1615		for the respective Ethernet interface, in case this
1616		is not determined automatically.
1617
1618- IP address:
1619		CONFIG_IPADDR
1620
1621		Define a default value for the IP address to use for
1622		the default Ethernet interface, in case this is not
1623		determined through e.g. bootp.
1624		(Environment variable "ipaddr")
1625
1626- Server IP address:
1627		CONFIG_SERVERIP
1628
1629		Defines a default value for the IP address of a TFTP
1630		server to contact when using the "tftboot" command.
1631		(Environment variable "serverip")
1632
1633		CONFIG_KEEP_SERVERADDR
1634
1635		Keeps the server's MAC address, in the env 'serveraddr'
1636		for passing to bootargs (like Linux's netconsole option)
1637
1638- Gateway IP address:
1639		CONFIG_GATEWAYIP
1640
1641		Defines a default value for the IP address of the
1642		default router where packets to other networks are
1643		sent to.
1644		(Environment variable "gatewayip")
1645
1646- Subnet mask:
1647		CONFIG_NETMASK
1648
1649		Defines a default value for the subnet mask (or
1650		routing prefix) which is used to determine if an IP
1651		address belongs to the local subnet or needs to be
1652		forwarded through a router.
1653		(Environment variable "netmask")
1654
1655- Multicast TFTP Mode:
1656		CONFIG_MCAST_TFTP
1657
1658		Defines whether you want to support multicast TFTP as per
1659		rfc-2090; for example to work with atftp.  Lets lots of targets
1660		tftp down the same boot image concurrently.  Note: the Ethernet
1661		driver in use must provide a function: mcast() to join/leave a
1662		multicast group.
1663
1664- BOOTP Recovery Mode:
1665		CONFIG_BOOTP_RANDOM_DELAY
1666
1667		If you have many targets in a network that try to
1668		boot using BOOTP, you may want to avoid that all
1669		systems send out BOOTP requests at precisely the same
1670		moment (which would happen for instance at recovery
1671		from a power failure, when all systems will try to
1672		boot, thus flooding the BOOTP server. Defining
1673		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1674		inserted before sending out BOOTP requests. The
1675		following delays are inserted then:
1676
1677		1st BOOTP request:	delay 0 ... 1 sec
1678		2nd BOOTP request:	delay 0 ... 2 sec
1679		3rd BOOTP request:	delay 0 ... 4 sec
1680		4th and following
1681		BOOTP requests:		delay 0 ... 8 sec
1682
1683- DHCP Advanced Options:
1684		You can fine tune the DHCP functionality by defining
1685		CONFIG_BOOTP_* symbols:
1686
1687		CONFIG_BOOTP_SUBNETMASK
1688		CONFIG_BOOTP_GATEWAY
1689		CONFIG_BOOTP_HOSTNAME
1690		CONFIG_BOOTP_NISDOMAIN
1691		CONFIG_BOOTP_BOOTPATH
1692		CONFIG_BOOTP_BOOTFILESIZE
1693		CONFIG_BOOTP_DNS
1694		CONFIG_BOOTP_DNS2
1695		CONFIG_BOOTP_SEND_HOSTNAME
1696		CONFIG_BOOTP_NTPSERVER
1697		CONFIG_BOOTP_TIMEOFFSET
1698		CONFIG_BOOTP_VENDOREX
1699		CONFIG_BOOTP_MAY_FAIL
1700
1701		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1702		environment variable, not the BOOTP server.
1703
1704		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1705		after the configured retry count, the call will fail
1706		instead of starting over.  This can be used to fail over
1707		to Link-local IP address configuration if the DHCP server
1708		is not available.
1709
1710		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1711		serverip from a DHCP server, it is possible that more
1712		than one DNS serverip is offered to the client.
1713		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1714		serverip will be stored in the additional environment
1715		variable "dnsip2". The first DNS serverip is always
1716		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1717		is defined.
1718
1719		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1720		to do a dynamic update of a DNS server. To do this, they
1721		need the hostname of the DHCP requester.
1722		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1723		of the "hostname" environment variable is passed as
1724		option 12 to the DHCP server.
1725
1726		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1727
1728		A 32bit value in microseconds for a delay between
1729		receiving a "DHCP Offer" and sending the "DHCP Request".
1730		This fixes a problem with certain DHCP servers that don't
1731		respond 100% of the time to a "DHCP request". E.g. On an
1732		AT91RM9200 processor running at 180MHz, this delay needed
1733		to be *at least* 15,000 usec before a Windows Server 2003
1734		DHCP server would reply 100% of the time. I recommend at
1735		least 50,000 usec to be safe. The alternative is to hope
1736		that one of the retries will be successful but note that
1737		the DHCP timeout and retry process takes a longer than
1738		this delay.
1739
1740 - Link-local IP address negotiation:
1741		Negotiate with other link-local clients on the local network
1742		for an address that doesn't require explicit configuration.
1743		This is especially useful if a DHCP server cannot be guaranteed
1744		to exist in all environments that the device must operate.
1745
1746		See doc/README.link-local for more information.
1747
1748 - CDP Options:
1749		CONFIG_CDP_DEVICE_ID
1750
1751		The device id used in CDP trigger frames.
1752
1753		CONFIG_CDP_DEVICE_ID_PREFIX
1754
1755		A two character string which is prefixed to the MAC address
1756		of the device.
1757
1758		CONFIG_CDP_PORT_ID
1759
1760		A printf format string which contains the ascii name of
1761		the port. Normally is set to "eth%d" which sets
1762		eth0 for the first Ethernet, eth1 for the second etc.
1763
1764		CONFIG_CDP_CAPABILITIES
1765
1766		A 32bit integer which indicates the device capabilities;
1767		0x00000010 for a normal host which does not forwards.
1768
1769		CONFIG_CDP_VERSION
1770
1771		An ascii string containing the version of the software.
1772
1773		CONFIG_CDP_PLATFORM
1774
1775		An ascii string containing the name of the platform.
1776
1777		CONFIG_CDP_TRIGGER
1778
1779		A 32bit integer sent on the trigger.
1780
1781		CONFIG_CDP_POWER_CONSUMPTION
1782
1783		A 16bit integer containing the power consumption of the
1784		device in .1 of milliwatts.
1785
1786		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1787
1788		A byte containing the id of the VLAN.
1789
1790- Status LED:	CONFIG_STATUS_LED
1791
1792		Several configurations allow to display the current
1793		status using a LED. For instance, the LED will blink
1794		fast while running U-Boot code, stop blinking as
1795		soon as a reply to a BOOTP request was received, and
1796		start blinking slow once the Linux kernel is running
1797		(supported by a status LED driver in the Linux
1798		kernel). Defining CONFIG_STATUS_LED enables this
1799		feature in U-Boot.
1800
1801- CAN Support:	CONFIG_CAN_DRIVER
1802
1803		Defining CONFIG_CAN_DRIVER enables CAN driver support
1804		on those systems that support this (optional)
1805		feature, like the TQM8xxL modules.
1806
1807- I2C Support:	CONFIG_HARD_I2C | CONFIG_SOFT_I2C
1808
1809		These enable I2C serial bus commands. Defining either of
1810		(but not both of) CONFIG_HARD_I2C or CONFIG_SOFT_I2C will
1811		include the appropriate I2C driver for the selected CPU.
1812
1813		This will allow you to use i2c commands at the u-boot
1814		command line (as long as you set CONFIG_CMD_I2C in
1815		CONFIG_COMMANDS) and communicate with i2c based realtime
1816		clock chips. See common/cmd_i2c.c for a description of the
1817		command line interface.
1818
1819		CONFIG_HARD_I2C selects a hardware I2C controller.
1820
1821		CONFIG_SOFT_I2C configures u-boot to use a software (aka
1822		bit-banging) driver instead of CPM or similar hardware
1823		support for I2C.
1824
1825		There are several other quantities that must also be
1826		defined when you define CONFIG_HARD_I2C or CONFIG_SOFT_I2C.
1827
1828		In both cases you will need to define CONFIG_SYS_I2C_SPEED
1829		to be the frequency (in Hz) at which you wish your i2c bus
1830		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
1831		the CPU's i2c node address).
1832
1833		Now, the u-boot i2c code for the mpc8xx
1834		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
1835		and so its address should therefore be cleared to 0 (See,
1836		eg, MPC823e User's Manual p.16-473). So, set
1837		CONFIG_SYS_I2C_SLAVE to 0.
1838
1839		CONFIG_SYS_I2C_INIT_MPC5XXX
1840
1841		When a board is reset during an i2c bus transfer
1842		chips might think that the current transfer is still
1843		in progress.  Reset the slave devices by sending start
1844		commands until the slave device responds.
1845
1846		That's all that's required for CONFIG_HARD_I2C.
1847
1848		If you use the software i2c interface (CONFIG_SOFT_I2C)
1849		then the following macros need to be defined (examples are
1850		from include/configs/lwmon.h):
1851
1852		I2C_INIT
1853
1854		(Optional). Any commands necessary to enable the I2C
1855		controller or configure ports.
1856
1857		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1858
1859		I2C_PORT
1860
1861		(Only for MPC8260 CPU). The I/O port to use (the code
1862		assumes both bits are on the same port). Valid values
1863		are 0..3 for ports A..D.
1864
1865		I2C_ACTIVE
1866
1867		The code necessary to make the I2C data line active
1868		(driven).  If the data line is open collector, this
1869		define can be null.
1870
1871		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1872
1873		I2C_TRISTATE
1874
1875		The code necessary to make the I2C data line tri-stated
1876		(inactive).  If the data line is open collector, this
1877		define can be null.
1878
1879		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1880
1881		I2C_READ
1882
1883		Code that returns TRUE if the I2C data line is high,
1884		FALSE if it is low.
1885
1886		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1887
1888		I2C_SDA(bit)
1889
1890		If <bit> is TRUE, sets the I2C data line high. If it
1891		is FALSE, it clears it (low).
1892
1893		eg: #define I2C_SDA(bit) \
1894			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1895			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1896
1897		I2C_SCL(bit)
1898
1899		If <bit> is TRUE, sets the I2C clock line high. If it
1900		is FALSE, it clears it (low).
1901
1902		eg: #define I2C_SCL(bit) \
1903			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1904			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1905
1906		I2C_DELAY
1907
1908		This delay is invoked four times per clock cycle so this
1909		controls the rate of data transfer.  The data rate thus
1910		is 1 / (I2C_DELAY * 4). Often defined to be something
1911		like:
1912
1913		#define I2C_DELAY  udelay(2)
1914
1915		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1916
1917		If your arch supports the generic GPIO framework (asm/gpio.h),
1918		then you may alternatively define the two GPIOs that are to be
1919		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1920		have GPIO-based defaults assigned to them as appropriate.
1921
1922		You should define these to the GPIO value as given directly to
1923		the generic GPIO functions.
1924
1925		CONFIG_SYS_I2C_INIT_BOARD
1926
1927		When a board is reset during an i2c bus transfer
1928		chips might think that the current transfer is still
1929		in progress. On some boards it is possible to access
1930		the i2c SCLK line directly, either by using the
1931		processor pin as a GPIO or by having a second pin
1932		connected to the bus. If this option is defined a
1933		custom i2c_init_board() routine in boards/xxx/board.c
1934		is run early in the boot sequence.
1935
1936		CONFIG_SYS_I2C_BOARD_LATE_INIT
1937
1938		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
1939		defined a custom i2c_board_late_init() routine in
1940		boards/xxx/board.c is run AFTER the operations in i2c_init()
1941		is completed. This callpoint can be used to unreset i2c bus
1942		using CPU i2c controller register accesses for CPUs whose i2c
1943		controller provide such a method. It is called at the end of
1944		i2c_init() to allow i2c_init operations to setup the i2c bus
1945		controller on the CPU (e.g. setting bus speed & slave address).
1946
1947		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
1948
1949		This option enables configuration of bi_iic_fast[] flags
1950		in u-boot bd_info structure based on u-boot environment
1951		variable "i2cfast". (see also i2cfast)
1952
1953		CONFIG_I2C_MULTI_BUS
1954
1955		This option allows the use of multiple I2C buses, each of which
1956		must have a controller.	 At any point in time, only one bus is
1957		active.	 To switch to a different bus, use the 'i2c dev' command.
1958		Note that bus numbering is zero-based.
1959
1960		CONFIG_SYS_I2C_NOPROBES
1961
1962		This option specifies a list of I2C devices that will be skipped
1963		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1964		is set, specify a list of bus-device pairs.  Otherwise, specify
1965		a 1D array of device addresses
1966
1967		e.g.
1968			#undef	CONFIG_I2C_MULTI_BUS
1969			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1970
1971		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1972
1973			#define CONFIG_I2C_MULTI_BUS
1974			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1975
1976		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1977
1978		CONFIG_SYS_SPD_BUS_NUM
1979
1980		If defined, then this indicates the I2C bus number for DDR SPD.
1981		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1982
1983		CONFIG_SYS_RTC_BUS_NUM
1984
1985		If defined, then this indicates the I2C bus number for the RTC.
1986		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1987
1988		CONFIG_SYS_DTT_BUS_NUM
1989
1990		If defined, then this indicates the I2C bus number for the DTT.
1991		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
1992
1993		CONFIG_SYS_I2C_DTT_ADDR:
1994
1995		If defined, specifies the I2C address of the DTT device.
1996		If not defined, then U-Boot uses predefined value for
1997		specified DTT device.
1998
1999		CONFIG_FSL_I2C
2000
2001		Define this option if you want to use Freescale's I2C driver in
2002		drivers/i2c/fsl_i2c.c.
2003
2004		CONFIG_I2C_MUX
2005
2006		Define this option if you have I2C devices reached over 1 .. n
2007		I2C Muxes like the pca9544a. This option addes a new I2C
2008		Command "i2c bus [muxtype:muxaddr:muxchannel]" which adds a
2009		new I2C Bus to the existing I2C Busses. If you select the
2010		new Bus with "i2c dev", u-bbot sends first the commandos for
2011		the muxes to activate this new "bus".
2012
2013		CONFIG_I2C_MULTI_BUS must be also defined, to use this
2014		feature!
2015
2016		Example:
2017		Adding a new I2C Bus reached over 2 pca9544a muxes
2018			The First mux with address 70 and channel 6
2019			The Second mux with address 71 and channel 4
2020
2021		=> i2c bus pca9544a:70:6:pca9544a:71:4
2022
2023		Use the "i2c bus" command without parameter, to get a list
2024		of I2C Busses with muxes:
2025
2026		=> i2c bus
2027		Busses reached over muxes:
2028		Bus ID: 2
2029		  reached over Mux(es):
2030		    pca9544a@70 ch: 4
2031		Bus ID: 3
2032		  reached over Mux(es):
2033		    pca9544a@70 ch: 6
2034		    pca9544a@71 ch: 4
2035		=>
2036
2037		If you now switch to the new I2C Bus 3 with "i2c dev 3"
2038		u-boot first sends the command to the mux@70 to enable
2039		channel 6, and then the command to the mux@71 to enable
2040		the channel 4.
2041
2042		After that, you can use the "normal" i2c commands as
2043		usual to communicate with your I2C devices behind
2044		the 2 muxes.
2045
2046		This option is actually implemented for the bitbanging
2047		algorithm in common/soft_i2c.c and for the Hardware I2C
2048		Bus on the MPC8260. But it should be not so difficult
2049		to add this option to other architectures.
2050
2051		CONFIG_SOFT_I2C_READ_REPEATED_START
2052
2053		defining this will force the i2c_read() function in
2054		the soft_i2c driver to perform an I2C repeated start
2055		between writing the address pointer and reading the
2056		data.  If this define is omitted the default behaviour
2057		of doing a stop-start sequence will be used.  Most I2C
2058		devices can use either method, but some require one or
2059		the other.
2060
2061- SPI Support:	CONFIG_SPI
2062
2063		Enables SPI driver (so far only tested with
2064		SPI EEPROM, also an instance works with Crystal A/D and
2065		D/As on the SACSng board)
2066
2067		CONFIG_SH_SPI
2068
2069		Enables the driver for SPI controller on SuperH. Currently
2070		only SH7757 is supported.
2071
2072		CONFIG_SPI_X
2073
2074		Enables extended (16-bit) SPI EEPROM addressing.
2075		(symmetrical to CONFIG_I2C_X)
2076
2077		CONFIG_SOFT_SPI
2078
2079		Enables a software (bit-bang) SPI driver rather than
2080		using hardware support. This is a general purpose
2081		driver that only requires three general I/O port pins
2082		(two outputs, one input) to function. If this is
2083		defined, the board configuration must define several
2084		SPI configuration items (port pins to use, etc). For
2085		an example, see include/configs/sacsng.h.
2086
2087		CONFIG_HARD_SPI
2088
2089		Enables a hardware SPI driver for general-purpose reads
2090		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2091		must define a list of chip-select function pointers.
2092		Currently supported on some MPC8xxx processors.	 For an
2093		example, see include/configs/mpc8349emds.h.
2094
2095		CONFIG_MXC_SPI
2096
2097		Enables the driver for the SPI controllers on i.MX and MXC
2098		SoCs. Currently i.MX31/35/51 are supported.
2099
2100- FPGA Support: CONFIG_FPGA
2101
2102		Enables FPGA subsystem.
2103
2104		CONFIG_FPGA_<vendor>
2105
2106		Enables support for specific chip vendors.
2107		(ALTERA, XILINX)
2108
2109		CONFIG_FPGA_<family>
2110
2111		Enables support for FPGA family.
2112		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2113
2114		CONFIG_FPGA_COUNT
2115
2116		Specify the number of FPGA devices to support.
2117
2118		CONFIG_SYS_FPGA_PROG_FEEDBACK
2119
2120		Enable printing of hash marks during FPGA configuration.
2121
2122		CONFIG_SYS_FPGA_CHECK_BUSY
2123
2124		Enable checks on FPGA configuration interface busy
2125		status by the configuration function. This option
2126		will require a board or device specific function to
2127		be written.
2128
2129		CONFIG_FPGA_DELAY
2130
2131		If defined, a function that provides delays in the FPGA
2132		configuration driver.
2133
2134		CONFIG_SYS_FPGA_CHECK_CTRLC
2135		Allow Control-C to interrupt FPGA configuration
2136
2137		CONFIG_SYS_FPGA_CHECK_ERROR
2138
2139		Check for configuration errors during FPGA bitfile
2140		loading. For example, abort during Virtex II
2141		configuration if the INIT_B line goes low (which
2142		indicated a CRC error).
2143
2144		CONFIG_SYS_FPGA_WAIT_INIT
2145
2146		Maximum time to wait for the INIT_B line to deassert
2147		after PROB_B has been deasserted during a Virtex II
2148		FPGA configuration sequence. The default time is 500
2149		ms.
2150
2151		CONFIG_SYS_FPGA_WAIT_BUSY
2152
2153		Maximum time to wait for BUSY to deassert during
2154		Virtex II FPGA configuration. The default is 5 ms.
2155
2156		CONFIG_SYS_FPGA_WAIT_CONFIG
2157
2158		Time to wait after FPGA configuration. The default is
2159		200 ms.
2160
2161- Configuration Management:
2162		CONFIG_IDENT_STRING
2163
2164		If defined, this string will be added to the U-Boot
2165		version information (U_BOOT_VERSION)
2166
2167- Vendor Parameter Protection:
2168
2169		U-Boot considers the values of the environment
2170		variables "serial#" (Board Serial Number) and
2171		"ethaddr" (Ethernet Address) to be parameters that
2172		are set once by the board vendor / manufacturer, and
2173		protects these variables from casual modification by
2174		the user. Once set, these variables are read-only,
2175		and write or delete attempts are rejected. You can
2176		change this behaviour:
2177
2178		If CONFIG_ENV_OVERWRITE is #defined in your config
2179		file, the write protection for vendor parameters is
2180		completely disabled. Anybody can change or delete
2181		these parameters.
2182
2183		Alternatively, if you #define _both_ CONFIG_ETHADDR
2184		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2185		Ethernet address is installed in the environment,
2186		which can be changed exactly ONCE by the user. [The
2187		serial# is unaffected by this, i. e. it remains
2188		read-only.]
2189
2190- Protected RAM:
2191		CONFIG_PRAM
2192
2193		Define this variable to enable the reservation of
2194		"protected RAM", i. e. RAM which is not overwritten
2195		by U-Boot. Define CONFIG_PRAM to hold the number of
2196		kB you want to reserve for pRAM. You can overwrite
2197		this default value by defining an environment
2198		variable "pram" to the number of kB you want to
2199		reserve. Note that the board info structure will
2200		still show the full amount of RAM. If pRAM is
2201		reserved, a new environment variable "mem" will
2202		automatically be defined to hold the amount of
2203		remaining RAM in a form that can be passed as boot
2204		argument to Linux, for instance like that:
2205
2206			setenv bootargs ... mem=\${mem}
2207			saveenv
2208
2209		This way you can tell Linux not to use this memory,
2210		either, which results in a memory region that will
2211		not be affected by reboots.
2212
2213		*WARNING* If your board configuration uses automatic
2214		detection of the RAM size, you must make sure that
2215		this memory test is non-destructive. So far, the
2216		following board configurations are known to be
2217		"pRAM-clean":
2218
2219			IVMS8, IVML24, SPD8xx, TQM8xxL,
2220			HERMES, IP860, RPXlite, LWMON,
2221			FLAGADM, TQM8260
2222
2223- Access to physical memory region (> 4GB)
2224		Some basic support is provided for operations on memory not
2225		normally accessible to U-Boot - e.g. some architectures
2226		support access to more than 4GB of memory on 32-bit
2227		machines using physical address extension or similar.
2228		Define CONFIG_PHYSMEM to access this basic support, which
2229		currently only supports clearing the memory.
2230
2231- Error Recovery:
2232		CONFIG_PANIC_HANG
2233
2234		Define this variable to stop the system in case of a
2235		fatal error, so that you have to reset it manually.
2236		This is probably NOT a good idea for an embedded
2237		system where you want the system to reboot
2238		automatically as fast as possible, but it may be
2239		useful during development since you can try to debug
2240		the conditions that lead to the situation.
2241
2242		CONFIG_NET_RETRY_COUNT
2243
2244		This variable defines the number of retries for
2245		network operations like ARP, RARP, TFTP, or BOOTP
2246		before giving up the operation. If not defined, a
2247		default value of 5 is used.
2248
2249		CONFIG_ARP_TIMEOUT
2250
2251		Timeout waiting for an ARP reply in milliseconds.
2252
2253		CONFIG_NFS_TIMEOUT
2254
2255		Timeout in milliseconds used in NFS protocol.
2256		If you encounter "ERROR: Cannot umount" in nfs command,
2257		try longer timeout such as
2258		#define CONFIG_NFS_TIMEOUT 10000UL
2259
2260- Command Interpreter:
2261		CONFIG_AUTO_COMPLETE
2262
2263		Enable auto completion of commands using TAB.
2264
2265		Note that this feature has NOT been implemented yet
2266		for the "hush" shell.
2267
2268
2269		CONFIG_SYS_HUSH_PARSER
2270
2271		Define this variable to enable the "hush" shell (from
2272		Busybox) as command line interpreter, thus enabling
2273		powerful command line syntax like
2274		if...then...else...fi conditionals or `&&' and '||'
2275		constructs ("shell scripts").
2276
2277		If undefined, you get the old, much simpler behaviour
2278		with a somewhat smaller memory footprint.
2279
2280
2281		CONFIG_SYS_PROMPT_HUSH_PS2
2282
2283		This defines the secondary prompt string, which is
2284		printed when the command interpreter needs more input
2285		to complete a command. Usually "> ".
2286
2287	Note:
2288
2289		In the current implementation, the local variables
2290		space and global environment variables space are
2291		separated. Local variables are those you define by
2292		simply typing `name=value'. To access a local
2293		variable later on, you have write `$name' or
2294		`${name}'; to execute the contents of a variable
2295		directly type `$name' at the command prompt.
2296
2297		Global environment variables are those you use
2298		setenv/printenv to work with. To run a command stored
2299		in such a variable, you need to use the run command,
2300		and you must not use the '$' sign to access them.
2301
2302		To store commands and special characters in a
2303		variable, please use double quotation marks
2304		surrounding the whole text of the variable, instead
2305		of the backslashes before semicolons and special
2306		symbols.
2307
2308- Commandline Editing and History:
2309		CONFIG_CMDLINE_EDITING
2310
2311		Enable editing and History functions for interactive
2312		commandline input operations
2313
2314- Default Environment:
2315		CONFIG_EXTRA_ENV_SETTINGS
2316
2317		Define this to contain any number of null terminated
2318		strings (variable = value pairs) that will be part of
2319		the default environment compiled into the boot image.
2320
2321		For example, place something like this in your
2322		board's config file:
2323
2324		#define CONFIG_EXTRA_ENV_SETTINGS \
2325			"myvar1=value1\0" \
2326			"myvar2=value2\0"
2327
2328		Warning: This method is based on knowledge about the
2329		internal format how the environment is stored by the
2330		U-Boot code. This is NOT an official, exported
2331		interface! Although it is unlikely that this format
2332		will change soon, there is no guarantee either.
2333		You better know what you are doing here.
2334
2335		Note: overly (ab)use of the default environment is
2336		discouraged. Make sure to check other ways to preset
2337		the environment like the "source" command or the
2338		boot command first.
2339
2340		CONFIG_ENV_VARS_UBOOT_CONFIG
2341
2342		Define this in order to add variables describing the
2343		U-Boot build configuration to the default environment.
2344		These will be named arch, cpu, board, vendor, and soc.
2345
2346		Enabling this option will cause the following to be defined:
2347
2348		- CONFIG_SYS_ARCH
2349		- CONFIG_SYS_CPU
2350		- CONFIG_SYS_BOARD
2351		- CONFIG_SYS_VENDOR
2352		- CONFIG_SYS_SOC
2353
2354		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2355
2356		Define this in order to add variables describing certain
2357		run-time determined information about the hardware to the
2358		environment.  These will be named board_name, board_rev.
2359
2360- DataFlash Support:
2361		CONFIG_HAS_DATAFLASH
2362
2363		Defining this option enables DataFlash features and
2364		allows to read/write in Dataflash via the standard
2365		commands cp, md...
2366
2367- Serial Flash support
2368		CONFIG_CMD_SF
2369
2370		Defining this option enables SPI flash commands
2371		'sf probe/read/write/erase/update'.
2372
2373		Usage requires an initial 'probe' to define the serial
2374		flash parameters, followed by read/write/erase/update
2375		commands.
2376
2377		The following defaults may be provided by the platform
2378		to handle the common case when only a single serial
2379		flash is present on the system.
2380
2381		CONFIG_SF_DEFAULT_BUS		Bus identifier
2382		CONFIG_SF_DEFAULT_CS		Chip-select
2383		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2384		CONFIG_SF_DEFAULT_SPEED		in Hz
2385
2386- SystemACE Support:
2387		CONFIG_SYSTEMACE
2388
2389		Adding this option adds support for Xilinx SystemACE
2390		chips attached via some sort of local bus. The address
2391		of the chip must also be defined in the
2392		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2393
2394		#define CONFIG_SYSTEMACE
2395		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2396
2397		When SystemACE support is added, the "ace" device type
2398		becomes available to the fat commands, i.e. fatls.
2399
2400- TFTP Fixed UDP Port:
2401		CONFIG_TFTP_PORT
2402
2403		If this is defined, the environment variable tftpsrcp
2404		is used to supply the TFTP UDP source port value.
2405		If tftpsrcp isn't defined, the normal pseudo-random port
2406		number generator is used.
2407
2408		Also, the environment variable tftpdstp is used to supply
2409		the TFTP UDP destination port value.  If tftpdstp isn't
2410		defined, the normal port 69 is used.
2411
2412		The purpose for tftpsrcp is to allow a TFTP server to
2413		blindly start the TFTP transfer using the pre-configured
2414		target IP address and UDP port. This has the effect of
2415		"punching through" the (Windows XP) firewall, allowing
2416		the remainder of the TFTP transfer to proceed normally.
2417		A better solution is to properly configure the firewall,
2418		but sometimes that is not allowed.
2419
2420- Hashing support:
2421		CONFIG_CMD_HASH
2422
2423		This enables a generic 'hash' command which can produce
2424		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2425
2426		CONFIG_HASH_VERIFY
2427
2428		Enable the hash verify command (hash -v). This adds to code
2429		size a little.
2430
2431		CONFIG_SHA1 - support SHA1 hashing
2432		CONFIG_SHA256 - support SHA256 hashing
2433
2434		Note: There is also a sha1sum command, which should perhaps
2435		be deprecated in favour of 'hash sha1'.
2436
2437- Show boot progress:
2438		CONFIG_SHOW_BOOT_PROGRESS
2439
2440		Defining this option allows to add some board-
2441		specific code (calling a user-provided function
2442		"show_boot_progress(int)") that enables you to show
2443		the system's boot progress on some display (for
2444		example, some LED's) on your board. At the moment,
2445		the following checkpoints are implemented:
2446
2447- Detailed boot stage timing
2448		CONFIG_BOOTSTAGE
2449		Define this option to get detailed timing of each stage
2450		of the boot process.
2451
2452		CONFIG_BOOTSTAGE_USER_COUNT
2453		This is the number of available user bootstage records.
2454		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
2455		a new ID will be allocated from this stash. If you exceed
2456		the limit, recording will stop.
2457
2458		CONFIG_BOOTSTAGE_REPORT
2459		Define this to print a report before boot, similar to this:
2460
2461		Timer summary in microseconds:
2462		       Mark    Elapsed  Stage
2463			  0          0  reset
2464		  3,575,678  3,575,678  board_init_f start
2465		  3,575,695         17  arch_cpu_init A9
2466		  3,575,777         82  arch_cpu_init done
2467		  3,659,598     83,821  board_init_r start
2468		  3,910,375    250,777  main_loop
2469		 29,916,167 26,005,792  bootm_start
2470		 30,361,327    445,160  start_kernel
2471
2472		CONFIG_CMD_BOOTSTAGE
2473		Add a 'bootstage' command which supports printing a report
2474		and un/stashing of bootstage data.
2475
2476		CONFIG_BOOTSTAGE_FDT
2477		Stash the bootstage information in the FDT. A root 'bootstage'
2478		node is created with each bootstage id as a child. Each child
2479		has a 'name' property and either 'mark' containing the
2480		mark time in microsecond, or 'accum' containing the
2481		accumulated time for that bootstage id in microseconds.
2482		For example:
2483
2484		bootstage {
2485			154 {
2486				name = "board_init_f";
2487				mark = <3575678>;
2488			};
2489			170 {
2490				name = "lcd";
2491				accum = <33482>;
2492			};
2493		};
2494
2495		Code in the Linux kernel can find this in /proc/devicetree.
2496
2497Legacy uImage format:
2498
2499  Arg	Where			When
2500    1	common/cmd_bootm.c	before attempting to boot an image
2501   -1	common/cmd_bootm.c	Image header has bad	 magic number
2502    2	common/cmd_bootm.c	Image header has correct magic number
2503   -2	common/cmd_bootm.c	Image header has bad	 checksum
2504    3	common/cmd_bootm.c	Image header has correct checksum
2505   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2506    4	common/cmd_bootm.c	Image data   has correct checksum
2507   -4	common/cmd_bootm.c	Image is for unsupported architecture
2508    5	common/cmd_bootm.c	Architecture check OK
2509   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2510    6	common/cmd_bootm.c	Image Type check OK
2511   -6	common/cmd_bootm.c	gunzip uncompression error
2512   -7	common/cmd_bootm.c	Unimplemented compression type
2513    7	common/cmd_bootm.c	Uncompression OK
2514    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2515   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2516
2517    9	common/image.c		Start initial ramdisk verification
2518  -10	common/image.c		Ramdisk header has bad	   magic number
2519  -11	common/image.c		Ramdisk header has bad	   checksum
2520   10	common/image.c		Ramdisk header is OK
2521  -12	common/image.c		Ramdisk data   has bad	   checksum
2522   11	common/image.c		Ramdisk data   has correct checksum
2523   12	common/image.c		Ramdisk verification complete, start loading
2524  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2525   13	common/image.c		Start multifile image verification
2526   14	common/image.c		No initial ramdisk, no multifile, continue.
2527
2528   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2529
2530  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2531  -31	post/post.c		POST test failed, detected by post_output_backlog()
2532  -32	post/post.c		POST test failed, detected by post_run_single()
2533
2534   34	common/cmd_doc.c	before loading a Image from a DOC device
2535  -35	common/cmd_doc.c	Bad usage of "doc" command
2536   35	common/cmd_doc.c	correct usage of "doc" command
2537  -36	common/cmd_doc.c	No boot device
2538   36	common/cmd_doc.c	correct boot device
2539  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2540   37	common/cmd_doc.c	correct chip ID found, device available
2541  -38	common/cmd_doc.c	Read Error on boot device
2542   38	common/cmd_doc.c	reading Image header from DOC device OK
2543  -39	common/cmd_doc.c	Image header has bad magic number
2544   39	common/cmd_doc.c	Image header has correct magic number
2545  -40	common/cmd_doc.c	Error reading Image from DOC device
2546   40	common/cmd_doc.c	Image header has correct magic number
2547   41	common/cmd_ide.c	before loading a Image from a IDE device
2548  -42	common/cmd_ide.c	Bad usage of "ide" command
2549   42	common/cmd_ide.c	correct usage of "ide" command
2550  -43	common/cmd_ide.c	No boot device
2551   43	common/cmd_ide.c	boot device found
2552  -44	common/cmd_ide.c	Device not available
2553   44	common/cmd_ide.c	Device available
2554  -45	common/cmd_ide.c	wrong partition selected
2555   45	common/cmd_ide.c	partition selected
2556  -46	common/cmd_ide.c	Unknown partition table
2557   46	common/cmd_ide.c	valid partition table found
2558  -47	common/cmd_ide.c	Invalid partition type
2559   47	common/cmd_ide.c	correct partition type
2560  -48	common/cmd_ide.c	Error reading Image Header on boot device
2561   48	common/cmd_ide.c	reading Image Header from IDE device OK
2562  -49	common/cmd_ide.c	Image header has bad magic number
2563   49	common/cmd_ide.c	Image header has correct magic number
2564  -50	common/cmd_ide.c	Image header has bad	 checksum
2565   50	common/cmd_ide.c	Image header has correct checksum
2566  -51	common/cmd_ide.c	Error reading Image from IDE device
2567   51	common/cmd_ide.c	reading Image from IDE device OK
2568   52	common/cmd_nand.c	before loading a Image from a NAND device
2569  -53	common/cmd_nand.c	Bad usage of "nand" command
2570   53	common/cmd_nand.c	correct usage of "nand" command
2571  -54	common/cmd_nand.c	No boot device
2572   54	common/cmd_nand.c	boot device found
2573  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2574   55	common/cmd_nand.c	correct chip ID found, device available
2575  -56	common/cmd_nand.c	Error reading Image Header on boot device
2576   56	common/cmd_nand.c	reading Image Header from NAND device OK
2577  -57	common/cmd_nand.c	Image header has bad magic number
2578   57	common/cmd_nand.c	Image header has correct magic number
2579  -58	common/cmd_nand.c	Error reading Image from NAND device
2580   58	common/cmd_nand.c	reading Image from NAND device OK
2581
2582  -60	common/env_common.c	Environment has a bad CRC, using default
2583
2584   64	net/eth.c		starting with Ethernet configuration.
2585  -64	net/eth.c		no Ethernet found.
2586   65	net/eth.c		Ethernet found.
2587
2588  -80	common/cmd_net.c	usage wrong
2589   80	common/cmd_net.c	before calling NetLoop()
2590  -81	common/cmd_net.c	some error in NetLoop() occurred
2591   81	common/cmd_net.c	NetLoop() back without error
2592  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2593   82	common/cmd_net.c	trying automatic boot
2594   83	common/cmd_net.c	running "source" command
2595  -83	common/cmd_net.c	some error in automatic boot or "source" command
2596   84	common/cmd_net.c	end without errors
2597
2598FIT uImage format:
2599
2600  Arg	Where			When
2601  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2602 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2603  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2604 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2605  102	common/cmd_bootm.c	Kernel unit name specified
2606 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2607  103	common/cmd_bootm.c	Found configuration node
2608  104	common/cmd_bootm.c	Got kernel subimage node offset
2609 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2610  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2611 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2612  106	common/cmd_bootm.c	Architecture check OK
2613 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2614  107	common/cmd_bootm.c	Kernel subimage type OK
2615 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2616  108	common/cmd_bootm.c	Got kernel subimage data/size
2617 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2618 -109	common/cmd_bootm.c	Can't get kernel subimage type
2619 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2620 -111	common/cmd_bootm.c	Can't get kernel subimage os
2621 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2622 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2623
2624  120	common/image.c		Start initial ramdisk verification
2625 -120	common/image.c		Ramdisk FIT image has incorrect format
2626  121	common/image.c		Ramdisk FIT image has correct format
2627  122	common/image.c		No ramdisk subimage unit name, using configuration
2628 -122	common/image.c		Can't get configuration for ramdisk subimage
2629  123	common/image.c		Ramdisk unit name specified
2630 -124	common/image.c		Can't get ramdisk subimage node offset
2631  125	common/image.c		Got ramdisk subimage node offset
2632 -125	common/image.c		Ramdisk subimage hash verification failed
2633  126	common/image.c		Ramdisk subimage hash verification OK
2634 -126	common/image.c		Ramdisk subimage for unsupported architecture
2635  127	common/image.c		Architecture check OK
2636 -127	common/image.c		Can't get ramdisk subimage data/size
2637  128	common/image.c		Got ramdisk subimage data/size
2638  129	common/image.c		Can't get ramdisk load address
2639 -129	common/image.c		Got ramdisk load address
2640
2641 -130	common/cmd_doc.c	Incorrect FIT image format
2642  131	common/cmd_doc.c	FIT image format OK
2643
2644 -140	common/cmd_ide.c	Incorrect FIT image format
2645  141	common/cmd_ide.c	FIT image format OK
2646
2647 -150	common/cmd_nand.c	Incorrect FIT image format
2648  151	common/cmd_nand.c	FIT image format OK
2649
2650- FIT image support:
2651		CONFIG_FIT
2652		Enable support for the FIT uImage format.
2653
2654		CONFIG_FIT_BEST_MATCH
2655		When no configuration is explicitly selected, default to the
2656		one whose fdt's compatibility field best matches that of
2657		U-Boot itself. A match is considered "best" if it matches the
2658		most specific compatibility entry of U-Boot's fdt's root node.
2659		The order of entries in the configuration's fdt is ignored.
2660
2661- Standalone program support:
2662		CONFIG_STANDALONE_LOAD_ADDR
2663
2664		This option defines a board specific value for the
2665		address where standalone program gets loaded, thus
2666		overwriting the architecture dependent default
2667		settings.
2668
2669- Frame Buffer Address:
2670		CONFIG_FB_ADDR
2671
2672		Define CONFIG_FB_ADDR if you want to use specific
2673		address for frame buffer.
2674		Then system will reserve the frame buffer address to
2675		defined address instead of lcd_setmem (this function
2676		grabs the memory for frame buffer by panel's size).
2677
2678		Please see board_init_f function.
2679
2680- Automatic software updates via TFTP server
2681		CONFIG_UPDATE_TFTP
2682		CONFIG_UPDATE_TFTP_CNT_MAX
2683		CONFIG_UPDATE_TFTP_MSEC_MAX
2684
2685		These options enable and control the auto-update feature;
2686		for a more detailed description refer to doc/README.update.
2687
2688- MTD Support (mtdparts command, UBI support)
2689		CONFIG_MTD_DEVICE
2690
2691		Adds the MTD device infrastructure from the Linux kernel.
2692		Needed for mtdparts command support.
2693
2694		CONFIG_MTD_PARTITIONS
2695
2696		Adds the MTD partitioning infrastructure from the Linux
2697		kernel. Needed for UBI support.
2698
2699- SPL framework
2700		CONFIG_SPL
2701		Enable building of SPL globally.
2702
2703		CONFIG_SPL_LDSCRIPT
2704		LDSCRIPT for linking the SPL binary.
2705
2706		CONFIG_SPL_MAX_SIZE
2707		Maximum binary size (text, data and rodata) of the SPL binary.
2708
2709		CONFIG_SPL_TEXT_BASE
2710		TEXT_BASE for linking the SPL binary.
2711
2712		CONFIG_SPL_RELOC_TEXT_BASE
2713		Address to relocate to.  If unspecified, this is equal to
2714		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2715
2716		CONFIG_SPL_BSS_START_ADDR
2717		Link address for the BSS within the SPL binary.
2718
2719		CONFIG_SPL_BSS_MAX_SIZE
2720		Maximum binary size of the BSS section of the SPL binary.
2721
2722		CONFIG_SPL_STACK
2723		Adress of the start of the stack SPL will use
2724
2725		CONFIG_SPL_RELOC_STACK
2726		Adress of the start of the stack SPL will use after
2727		relocation.  If unspecified, this is equal to
2728		CONFIG_SPL_STACK.
2729
2730		CONFIG_SYS_SPL_MALLOC_START
2731		Starting address of the malloc pool used in SPL.
2732
2733		CONFIG_SYS_SPL_MALLOC_SIZE
2734		The size of the malloc pool used in SPL.
2735
2736		CONFIG_SPL_FRAMEWORK
2737		Enable the SPL framework under common/.  This framework
2738		supports MMC, NAND and YMODEM loading of U-Boot and NAND
2739		NAND loading of the Linux Kernel.
2740
2741		CONFIG_SPL_DISPLAY_PRINT
2742		For ARM, enable an optional function to print more information
2743		about the running system.
2744
2745		CONFIG_SPL_INIT_MINIMAL
2746		Arch init code should be built for a very small image
2747
2748		CONFIG_SPL_LIBCOMMON_SUPPORT
2749		Support for common/libcommon.o in SPL binary
2750
2751		CONFIG_SPL_LIBDISK_SUPPORT
2752		Support for disk/libdisk.o in SPL binary
2753
2754		CONFIG_SPL_I2C_SUPPORT
2755		Support for drivers/i2c/libi2c.o in SPL binary
2756
2757		CONFIG_SPL_GPIO_SUPPORT
2758		Support for drivers/gpio/libgpio.o in SPL binary
2759
2760		CONFIG_SPL_MMC_SUPPORT
2761		Support for drivers/mmc/libmmc.o in SPL binary
2762
2763		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
2764		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
2765		CONFIG_SYS_MMC_SD_FAT_BOOT_PARTITION
2766		Address, size and partition on the MMC to load U-Boot from
2767		when the MMC is being used in raw mode.
2768
2769		CONFIG_SPL_FAT_SUPPORT
2770		Support for fs/fat/libfat.o in SPL binary
2771
2772		CONFIG_SPL_FAT_LOAD_PAYLOAD_NAME
2773		Filename to read to load U-Boot when reading from FAT
2774
2775		CONFIG_SPL_NAND_BASE
2776		Include nand_base.c in the SPL.  Requires
2777		CONFIG_SPL_NAND_DRIVERS.
2778
2779		CONFIG_SPL_NAND_DRIVERS
2780		SPL uses normal NAND drivers, not minimal drivers.
2781
2782		CONFIG_SPL_NAND_ECC
2783		Include standard software ECC in the SPL
2784
2785		CONFIG_SPL_NAND_SIMPLE
2786		Support for NAND boot using simple NAND drivers that
2787		expose the cmd_ctrl() interface.
2788
2789		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2790		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2791		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2792		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2793		CONFIG_SYS_NAND_ECCBYTES
2794		Defines the size and behavior of the NAND that SPL uses
2795		to read U-Boot
2796
2797		CONFIG_SYS_NAND_U_BOOT_OFFS
2798		Location in NAND to read U-Boot from
2799
2800		CONFIG_SYS_NAND_U_BOOT_DST
2801		Location in memory to load U-Boot to
2802
2803		CONFIG_SYS_NAND_U_BOOT_SIZE
2804		Size of image to load
2805
2806		CONFIG_SYS_NAND_U_BOOT_START
2807		Entry point in loaded image to jump to
2808
2809		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2810		Define this if you need to first read the OOB and then the
2811		data. This is used for example on davinci plattforms.
2812
2813		CONFIG_SPL_OMAP3_ID_NAND
2814		Support for an OMAP3-specific set of functions to return the
2815		ID and MFR of the first attached NAND chip, if present.
2816
2817		CONFIG_SPL_SERIAL_SUPPORT
2818		Support for drivers/serial/libserial.o in SPL binary
2819
2820		CONFIG_SPL_SPI_FLASH_SUPPORT
2821		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
2822
2823		CONFIG_SPL_SPI_SUPPORT
2824		Support for drivers/spi/libspi.o in SPL binary
2825
2826		CONFIG_SPL_RAM_DEVICE
2827		Support for running image already present in ram, in SPL binary
2828
2829		CONFIG_SPL_LIBGENERIC_SUPPORT
2830		Support for lib/libgeneric.o in SPL binary
2831
2832		CONFIG_SPL_TARGET
2833		Final target image containing SPL and payload.  Some SPLs
2834		use an arch-specific makefile fragment instead, for
2835		example if more than one image needs to be produced.
2836
2837Modem Support:
2838--------------
2839
2840[so far only for SMDK2400 boards]
2841
2842- Modem support enable:
2843		CONFIG_MODEM_SUPPORT
2844
2845- RTS/CTS Flow control enable:
2846		CONFIG_HWFLOW
2847
2848- Modem debug support:
2849		CONFIG_MODEM_SUPPORT_DEBUG
2850
2851		Enables debugging stuff (char screen[1024], dbg())
2852		for modem support. Useful only with BDI2000.
2853
2854- Interrupt support (PPC):
2855
2856		There are common interrupt_init() and timer_interrupt()
2857		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2858		for CPU specific initialization. interrupt_init_cpu()
2859		should set decrementer_count to appropriate value. If
2860		CPU resets decrementer automatically after interrupt
2861		(ppc4xx) it should set decrementer_count to zero.
2862		timer_interrupt() calls timer_interrupt_cpu() for CPU
2863		specific handling. If board has watchdog / status_led
2864		/ other_activity_monitor it works automatically from
2865		general timer_interrupt().
2866
2867- General:
2868
2869		In the target system modem support is enabled when a
2870		specific key (key combination) is pressed during
2871		power-on. Otherwise U-Boot will boot normally
2872		(autoboot). The key_pressed() function is called from
2873		board_init(). Currently key_pressed() is a dummy
2874		function, returning 1 and thus enabling modem
2875		initialization.
2876
2877		If there are no modem init strings in the
2878		environment, U-Boot proceed to autoboot; the
2879		previous output (banner, info printfs) will be
2880		suppressed, though.
2881
2882		See also: doc/README.Modem
2883
2884Board initialization settings:
2885------------------------------
2886
2887During Initialization u-boot calls a number of board specific functions
2888to allow the preparation of board specific prerequisites, e.g. pin setup
2889before drivers are initialized. To enable these callbacks the
2890following configuration macros have to be defined. Currently this is
2891architecture specific, so please check arch/your_architecture/lib/board.c
2892typically in board_init_f() and board_init_r().
2893
2894- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2895- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2896- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2897- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2898
2899Configuration Settings:
2900-----------------------
2901
2902- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2903		undefine this when you're short of memory.
2904
2905- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2906		width of the commands listed in the 'help' command output.
2907
2908- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2909		prompt for user input.
2910
2911- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2912
2913- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2914
2915- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2916
2917- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2918		the application (usually a Linux kernel) when it is
2919		booted
2920
2921- CONFIG_SYS_BAUDRATE_TABLE:
2922		List of legal baudrate settings for this board.
2923
2924- CONFIG_SYS_CONSOLE_INFO_QUIET
2925		Suppress display of console information at boot.
2926
2927- CONFIG_SYS_CONSOLE_IS_IN_ENV
2928		If the board specific function
2929			extern int overwrite_console (void);
2930		returns 1, the stdin, stderr and stdout are switched to the
2931		serial port, else the settings in the environment are used.
2932
2933- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
2934		Enable the call to overwrite_console().
2935
2936- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
2937		Enable overwrite of previous console environment settings.
2938
2939- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2940		Begin and End addresses of the area used by the
2941		simple memory test.
2942
2943- CONFIG_SYS_ALT_MEMTEST:
2944		Enable an alternate, more extensive memory test.
2945
2946- CONFIG_SYS_MEMTEST_SCRATCH:
2947		Scratch address used by the alternate memory test
2948		You only need to set this if address zero isn't writeable
2949
2950- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
2951		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2952		this specified memory area will get subtracted from the top
2953		(end) of RAM and won't get "touched" at all by U-Boot. By
2954		fixing up gd->ram_size the Linux kernel should gets passed
2955		the now "corrected" memory size and won't touch it either.
2956		This should work for arch/ppc and arch/powerpc. Only Linux
2957		board ports in arch/powerpc with bootwrapper support that
2958		recalculate the memory size from the SDRAM controller setup
2959		will have to get fixed in Linux additionally.
2960
2961		This option can be used as a workaround for the 440EPx/GRx
2962		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2963		be touched.
2964
2965		WARNING: Please make sure that this value is a multiple of
2966		the Linux page size (normally 4k). If this is not the case,
2967		then the end address of the Linux memory will be located at a
2968		non page size aligned address and this could cause major
2969		problems.
2970
2971- CONFIG_SYS_TFTP_LOADADDR:
2972		Default load address for network file downloads
2973
2974- CONFIG_SYS_LOADS_BAUD_CHANGE:
2975		Enable temporary baudrate change while serial download
2976
2977- CONFIG_SYS_SDRAM_BASE:
2978		Physical start address of SDRAM. _Must_ be 0 here.
2979
2980- CONFIG_SYS_MBIO_BASE:
2981		Physical start address of Motherboard I/O (if using a
2982		Cogent motherboard)
2983
2984- CONFIG_SYS_FLASH_BASE:
2985		Physical start address of Flash memory.
2986
2987- CONFIG_SYS_MONITOR_BASE:
2988		Physical start address of boot monitor code (set by
2989		make config files to be same as the text base address
2990		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2991		CONFIG_SYS_FLASH_BASE when booting from flash.
2992
2993- CONFIG_SYS_MONITOR_LEN:
2994		Size of memory reserved for monitor code, used to
2995		determine _at_compile_time_ (!) if the environment is
2996		embedded within the U-Boot image, or in a separate
2997		flash sector.
2998
2999- CONFIG_SYS_MALLOC_LEN:
3000		Size of DRAM reserved for malloc() use.
3001
3002- CONFIG_SYS_BOOTM_LEN:
3003		Normally compressed uImages are limited to an
3004		uncompressed size of 8 MBytes. If this is not enough,
3005		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3006		to adjust this setting to your needs.
3007
3008- CONFIG_SYS_BOOTMAPSZ:
3009		Maximum size of memory mapped by the startup code of
3010		the Linux kernel; all data that must be processed by
3011		the Linux kernel (bd_info, boot arguments, FDT blob if
3012		used) must be put below this limit, unless "bootm_low"
3013		enviroment variable is defined and non-zero. In such case
3014		all data for the Linux kernel must be between "bootm_low"
3015		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3016		variable "bootm_mapsize" will override the value of
3017		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3018		then the value in "bootm_size" will be used instead.
3019
3020- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3021		Enable initrd_high functionality.  If defined then the
3022		initrd_high feature is enabled and the bootm ramdisk subcommand
3023		is enabled.
3024
3025- CONFIG_SYS_BOOT_GET_CMDLINE:
3026		Enables allocating and saving kernel cmdline in space between
3027		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3028
3029- CONFIG_SYS_BOOT_GET_KBD:
3030		Enables allocating and saving a kernel copy of the bd_info in
3031		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3032
3033- CONFIG_SYS_MAX_FLASH_BANKS:
3034		Max number of Flash memory banks
3035
3036- CONFIG_SYS_MAX_FLASH_SECT:
3037		Max number of sectors on a Flash chip
3038
3039- CONFIG_SYS_FLASH_ERASE_TOUT:
3040		Timeout for Flash erase operations (in ms)
3041
3042- CONFIG_SYS_FLASH_WRITE_TOUT:
3043		Timeout for Flash write operations (in ms)
3044
3045- CONFIG_SYS_FLASH_LOCK_TOUT
3046		Timeout for Flash set sector lock bit operation (in ms)
3047
3048- CONFIG_SYS_FLASH_UNLOCK_TOUT
3049		Timeout for Flash clear lock bits operation (in ms)
3050
3051- CONFIG_SYS_FLASH_PROTECTION
3052		If defined, hardware flash sectors protection is used
3053		instead of U-Boot software protection.
3054
3055- CONFIG_SYS_DIRECT_FLASH_TFTP:
3056
3057		Enable TFTP transfers directly to flash memory;
3058		without this option such a download has to be
3059		performed in two steps: (1) download to RAM, and (2)
3060		copy from RAM to flash.
3061
3062		The two-step approach is usually more reliable, since
3063		you can check if the download worked before you erase
3064		the flash, but in some situations (when system RAM is
3065		too limited to allow for a temporary copy of the
3066		downloaded image) this option may be very useful.
3067
3068- CONFIG_SYS_FLASH_CFI:
3069		Define if the flash driver uses extra elements in the
3070		common flash structure for storing flash geometry.
3071
3072- CONFIG_FLASH_CFI_DRIVER
3073		This option also enables the building of the cfi_flash driver
3074		in the drivers directory
3075
3076- CONFIG_FLASH_CFI_MTD
3077		This option enables the building of the cfi_mtd driver
3078		in the drivers directory. The driver exports CFI flash
3079		to the MTD layer.
3080
3081- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3082		Use buffered writes to flash.
3083
3084- CONFIG_FLASH_SPANSION_S29WS_N
3085		s29ws-n MirrorBit flash has non-standard addresses for buffered
3086		write commands.
3087
3088- CONFIG_SYS_FLASH_QUIET_TEST
3089		If this option is defined, the common CFI flash doesn't
3090		print it's warning upon not recognized FLASH banks. This
3091		is useful, if some of the configured banks are only
3092		optionally available.
3093
3094- CONFIG_FLASH_SHOW_PROGRESS
3095		If defined (must be an integer), print out countdown
3096		digits and dots.  Recommended value: 45 (9..1) for 80
3097		column displays, 15 (3..1) for 40 column displays.
3098
3099- CONFIG_SYS_RX_ETH_BUFFER:
3100		Defines the number of Ethernet receive buffers. On some
3101		Ethernet controllers it is recommended to set this value
3102		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3103		buffers can be full shortly after enabling the interface
3104		on high Ethernet traffic.
3105		Defaults to 4 if not defined.
3106
3107- CONFIG_ENV_MAX_ENTRIES
3108
3109	Maximum number of entries in the hash table that is used
3110	internally to store the environment settings. The default
3111	setting is supposed to be generous and should work in most
3112	cases. This setting can be used to tune behaviour; see
3113	lib/hashtable.c for details.
3114
3115The following definitions that deal with the placement and management
3116of environment data (variable area); in general, we support the
3117following configurations:
3118
3119- CONFIG_BUILD_ENVCRC:
3120
3121	Builds up envcrc with the target environment so that external utils
3122	may easily extract it and embed it in final U-Boot images.
3123
3124- CONFIG_ENV_IS_IN_FLASH:
3125
3126	Define this if the environment is in flash memory.
3127
3128	a) The environment occupies one whole flash sector, which is
3129	   "embedded" in the text segment with the U-Boot code. This
3130	   happens usually with "bottom boot sector" or "top boot
3131	   sector" type flash chips, which have several smaller
3132	   sectors at the start or the end. For instance, such a
3133	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3134	   such a case you would place the environment in one of the
3135	   4 kB sectors - with U-Boot code before and after it. With
3136	   "top boot sector" type flash chips, you would put the
3137	   environment in one of the last sectors, leaving a gap
3138	   between U-Boot and the environment.
3139
3140	- CONFIG_ENV_OFFSET:
3141
3142	   Offset of environment data (variable area) to the
3143	   beginning of flash memory; for instance, with bottom boot
3144	   type flash chips the second sector can be used: the offset
3145	   for this sector is given here.
3146
3147	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3148
3149	- CONFIG_ENV_ADDR:
3150
3151	   This is just another way to specify the start address of
3152	   the flash sector containing the environment (instead of
3153	   CONFIG_ENV_OFFSET).
3154
3155	- CONFIG_ENV_SECT_SIZE:
3156
3157	   Size of the sector containing the environment.
3158
3159
3160	b) Sometimes flash chips have few, equal sized, BIG sectors.
3161	   In such a case you don't want to spend a whole sector for
3162	   the environment.
3163
3164	- CONFIG_ENV_SIZE:
3165
3166	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3167	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3168	   of this flash sector for the environment. This saves
3169	   memory for the RAM copy of the environment.
3170
3171	   It may also save flash memory if you decide to use this
3172	   when your environment is "embedded" within U-Boot code,
3173	   since then the remainder of the flash sector could be used
3174	   for U-Boot code. It should be pointed out that this is
3175	   STRONGLY DISCOURAGED from a robustness point of view:
3176	   updating the environment in flash makes it always
3177	   necessary to erase the WHOLE sector. If something goes
3178	   wrong before the contents has been restored from a copy in
3179	   RAM, your target system will be dead.
3180
3181	- CONFIG_ENV_ADDR_REDUND
3182	  CONFIG_ENV_SIZE_REDUND
3183
3184	   These settings describe a second storage area used to hold
3185	   a redundant copy of the environment data, so that there is
3186	   a valid backup copy in case there is a power failure during
3187	   a "saveenv" operation.
3188
3189BE CAREFUL! Any changes to the flash layout, and some changes to the
3190source code will make it necessary to adapt <board>/u-boot.lds*
3191accordingly!
3192
3193
3194- CONFIG_ENV_IS_IN_NVRAM:
3195
3196	Define this if you have some non-volatile memory device
3197	(NVRAM, battery buffered SRAM) which you want to use for the
3198	environment.
3199
3200	- CONFIG_ENV_ADDR:
3201	- CONFIG_ENV_SIZE:
3202
3203	  These two #defines are used to determine the memory area you
3204	  want to use for environment. It is assumed that this memory
3205	  can just be read and written to, without any special
3206	  provision.
3207
3208BE CAREFUL! The first access to the environment happens quite early
3209in U-Boot initalization (when we try to get the setting of for the
3210console baudrate). You *MUST* have mapped your NVRAM area then, or
3211U-Boot will hang.
3212
3213Please note that even with NVRAM we still use a copy of the
3214environment in RAM: we could work on NVRAM directly, but we want to
3215keep settings there always unmodified except somebody uses "saveenv"
3216to save the current settings.
3217
3218
3219- CONFIG_ENV_IS_IN_EEPROM:
3220
3221	Use this if you have an EEPROM or similar serial access
3222	device and a driver for it.
3223
3224	- CONFIG_ENV_OFFSET:
3225	- CONFIG_ENV_SIZE:
3226
3227	  These two #defines specify the offset and size of the
3228	  environment area within the total memory of your EEPROM.
3229
3230	- CONFIG_SYS_I2C_EEPROM_ADDR:
3231	  If defined, specified the chip address of the EEPROM device.
3232	  The default address is zero.
3233
3234	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3235	  If defined, the number of bits used to address bytes in a
3236	  single page in the EEPROM device.  A 64 byte page, for example
3237	  would require six bits.
3238
3239	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3240	  If defined, the number of milliseconds to delay between
3241	  page writes.	The default is zero milliseconds.
3242
3243	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3244	  The length in bytes of the EEPROM memory array address.  Note
3245	  that this is NOT the chip address length!
3246
3247	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3248	  EEPROM chips that implement "address overflow" are ones
3249	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3250	  address and the extra bits end up in the "chip address" bit
3251	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3252	  byte chips.
3253
3254	  Note that we consider the length of the address field to
3255	  still be one byte because the extra address bits are hidden
3256	  in the chip address.
3257
3258	- CONFIG_SYS_EEPROM_SIZE:
3259	  The size in bytes of the EEPROM device.
3260
3261	- CONFIG_ENV_EEPROM_IS_ON_I2C
3262	  define this, if you have I2C and SPI activated, and your
3263	  EEPROM, which holds the environment, is on the I2C bus.
3264
3265	- CONFIG_I2C_ENV_EEPROM_BUS
3266	  if you have an Environment on an EEPROM reached over
3267	  I2C muxes, you can define here, how to reach this
3268	  EEPROM. For example:
3269
3270	  #define CONFIG_I2C_ENV_EEPROM_BUS	  "pca9547:70:d\0"
3271
3272	  EEPROM which holds the environment, is reached over
3273	  a pca9547 i2c mux with address 0x70, channel 3.
3274
3275- CONFIG_ENV_IS_IN_DATAFLASH:
3276
3277	Define this if you have a DataFlash memory device which you
3278	want to use for the environment.
3279
3280	- CONFIG_ENV_OFFSET:
3281	- CONFIG_ENV_ADDR:
3282	- CONFIG_ENV_SIZE:
3283
3284	  These three #defines specify the offset and size of the
3285	  environment area within the total memory of your DataFlash placed
3286	  at the specified address.
3287
3288- CONFIG_ENV_IS_IN_REMOTE:
3289
3290	Define this if you have a remote memory space which you
3291	want to use for the local device's environment.
3292
3293	- CONFIG_ENV_ADDR:
3294	- CONFIG_ENV_SIZE:
3295
3296	  These two #defines specify the address and size of the
3297	  environment area within the remote memory space. The
3298	  local device can get the environment from remote memory
3299	  space by SRIO or PCIE links.
3300
3301BE CAREFUL! For some special cases, the local device can not use
3302"saveenv" command. For example, the local device will get the
3303environment stored in a remote NOR flash by SRIO or PCIE link,
3304but it can not erase, write this NOR flash by SRIO or PCIE interface.
3305
3306- CONFIG_ENV_IS_IN_NAND:
3307
3308	Define this if you have a NAND device which you want to use
3309	for the environment.
3310
3311	- CONFIG_ENV_OFFSET:
3312	- CONFIG_ENV_SIZE:
3313
3314	  These two #defines specify the offset and size of the environment
3315	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3316	  aligned to an erase block boundary.
3317
3318	- CONFIG_ENV_OFFSET_REDUND (optional):
3319
3320	  This setting describes a second storage area of CONFIG_ENV_SIZE
3321	  size used to hold a redundant copy of the environment data, so
3322	  that there is a valid backup copy in case there is a power failure
3323	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
3324	  aligned to an erase block boundary.
3325
3326	- CONFIG_ENV_RANGE (optional):
3327
3328	  Specifies the length of the region in which the environment
3329	  can be written.  This should be a multiple of the NAND device's
3330	  block size.  Specifying a range with more erase blocks than
3331	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
3332	  the range to be avoided.
3333
3334	- CONFIG_ENV_OFFSET_OOB (optional):
3335
3336	  Enables support for dynamically retrieving the offset of the
3337	  environment from block zero's out-of-band data.  The
3338	  "nand env.oob" command can be used to record this offset.
3339	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
3340	  using CONFIG_ENV_OFFSET_OOB.
3341
3342- CONFIG_NAND_ENV_DST
3343
3344	Defines address in RAM to which the nand_spl code should copy the
3345	environment. If redundant environment is used, it will be copied to
3346	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3347
3348- CONFIG_SYS_SPI_INIT_OFFSET
3349
3350	Defines offset to the initial SPI buffer area in DPRAM. The
3351	area is used at an early stage (ROM part) if the environment
3352	is configured to reside in the SPI EEPROM: We need a 520 byte
3353	scratch DPRAM area. It is used between the two initialization
3354	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
3355	to be a good choice since it makes it far enough from the
3356	start of the data area as well as from the stack pointer.
3357
3358Please note that the environment is read-only until the monitor
3359has been relocated to RAM and a RAM copy of the environment has been
3360created; also, when using EEPROM you will have to use getenv_f()
3361until then to read environment variables.
3362
3363The environment is protected by a CRC32 checksum. Before the monitor
3364is relocated into RAM, as a result of a bad CRC you will be working
3365with the compiled-in default environment - *silently*!!! [This is
3366necessary, because the first environment variable we need is the
3367"baudrate" setting for the console - if we have a bad CRC, we don't
3368have any device yet where we could complain.]
3369
3370Note: once the monitor has been relocated, then it will complain if
3371the default environment is used; a new CRC is computed as soon as you
3372use the "saveenv" command to store a valid environment.
3373
3374- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3375		Echo the inverted Ethernet link state to the fault LED.
3376
3377		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3378		      also needs to be defined.
3379
3380- CONFIG_SYS_FAULT_MII_ADDR:
3381		MII address of the PHY to check for the Ethernet link state.
3382
3383- CONFIG_NS16550_MIN_FUNCTIONS:
3384		Define this if you desire to only have use of the NS16550_init
3385		and NS16550_putc functions for the serial driver located at
3386		drivers/serial/ns16550.c.  This option is useful for saving
3387		space for already greatly restricted images, including but not
3388		limited to NAND_SPL configurations.
3389
3390Low Level (hardware related) configuration options:
3391---------------------------------------------------
3392
3393- CONFIG_SYS_CACHELINE_SIZE:
3394		Cache Line Size of the CPU.
3395
3396- CONFIG_SYS_DEFAULT_IMMR:
3397		Default address of the IMMR after system reset.
3398
3399		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
3400		and RPXsuper) to be able to adjust the position of
3401		the IMMR register after a reset.
3402
3403- CONFIG_SYS_CCSRBAR_DEFAULT:
3404		Default (power-on reset) physical address of CCSR on Freescale
3405		PowerPC SOCs.
3406
3407- CONFIG_SYS_CCSRBAR:
3408		Virtual address of CCSR.  On a 32-bit build, this is typically
3409		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3410
3411		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
3412		for cross-platform code that uses that macro instead.
3413
3414- CONFIG_SYS_CCSRBAR_PHYS:
3415		Physical address of CCSR.  CCSR can be relocated to a new
3416		physical address, if desired.  In this case, this macro should
3417		be set to that address.	 Otherwise, it should be set to the
3418		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3419		is typically relocated on 36-bit builds.  It is recommended
3420		that this macro be defined via the _HIGH and _LOW macros:
3421
3422		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3423			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3424
3425- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3426		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3427		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3428		used in assembly code, so it must not contain typecasts or
3429		integer size suffixes (e.g. "ULL").
3430
3431- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3432		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3433		used in assembly code, so it must not contain typecasts or
3434		integer size suffixes (e.g. "ULL").
3435
3436- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3437		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3438		forced to a value that ensures that CCSR is not relocated.
3439
3440- Floppy Disk Support:
3441		CONFIG_SYS_FDC_DRIVE_NUMBER
3442
3443		the default drive number (default value 0)
3444
3445		CONFIG_SYS_ISA_IO_STRIDE
3446
3447		defines the spacing between FDC chipset registers
3448		(default value 1)
3449
3450		CONFIG_SYS_ISA_IO_OFFSET
3451
3452		defines the offset of register from address. It
3453		depends on which part of the data bus is connected to
3454		the FDC chipset. (default value 0)
3455
3456		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3457		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3458		default value.
3459
3460		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3461		fdc_hw_init() is called at the beginning of the FDC
3462		setup. fdc_hw_init() must be provided by the board
3463		source code. It is used to make hardware dependant
3464		initializations.
3465
3466- CONFIG_IDE_AHB:
3467		Most IDE controllers were designed to be connected with PCI
3468		interface. Only few of them were designed for AHB interface.
3469		When software is doing ATA command and data transfer to
3470		IDE devices through IDE-AHB controller, some additional
3471		registers accessing to these kind of IDE-AHB controller
3472		is requierd.
3473
3474- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3475		DO NOT CHANGE unless you know exactly what you're
3476		doing! (11-4) [MPC8xx/82xx systems only]
3477
3478- CONFIG_SYS_INIT_RAM_ADDR:
3479
3480		Start address of memory area that can be used for
3481		initial data and stack; please note that this must be
3482		writable memory that is working WITHOUT special
3483		initialization, i. e. you CANNOT use normal RAM which
3484		will become available only after programming the
3485		memory controller and running certain initialization
3486		sequences.
3487
3488		U-Boot uses the following memory types:
3489		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
3490		- MPC824X: data cache
3491		- PPC4xx:  data cache
3492
3493- CONFIG_SYS_GBL_DATA_OFFSET:
3494
3495		Offset of the initial data structure in the memory
3496		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3497		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3498		data is located at the end of the available space
3499		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3500		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
3501		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3502		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3503
3504	Note:
3505		On the MPC824X (or other systems that use the data
3506		cache for initial memory) the address chosen for
3507		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3508		point to an otherwise UNUSED address space between
3509		the top of RAM and the start of the PCI space.
3510
3511- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
3512
3513- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
3514
3515- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
3516
3517- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
3518
3519- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
3520
3521- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3522
3523- CONFIG_SYS_OR_TIMING_SDRAM:
3524		SDRAM timing
3525
3526- CONFIG_SYS_MAMR_PTA:
3527		periodic timer for refresh
3528
3529- CONFIG_SYS_DER:	Debug Event Register (37-47)
3530
3531- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3532  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3533  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3534  CONFIG_SYS_BR1_PRELIM:
3535		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3536
3537- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3538  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3539  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3540		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3541
3542- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
3543  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
3544		Machine Mode Register and Memory Periodic Timer
3545		Prescaler definitions (SDRAM timing)
3546
3547- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
3548		enable I2C microcode relocation patch (MPC8xx);
3549		define relocation offset in DPRAM [DSP2]
3550
3551- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
3552		enable SMC microcode relocation patch (MPC8xx);
3553		define relocation offset in DPRAM [SMC1]
3554
3555- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
3556		enable SPI microcode relocation patch (MPC8xx);
3557		define relocation offset in DPRAM [SCC4]
3558
3559- CONFIG_SYS_USE_OSCCLK:
3560		Use OSCM clock mode on MBX8xx board. Be careful,
3561		wrong setting might damage your board. Read
3562		doc/README.MBX before setting this variable!
3563
3564- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
3565		Offset of the bootmode word in DPRAM used by post
3566		(Power On Self Tests). This definition overrides
3567		#define'd default value in commproc.h resp.
3568		cpm_8260.h.
3569
3570- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
3571  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
3572  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
3573  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
3574  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
3575  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
3576  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
3577  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
3578		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
3579
3580- CONFIG_PCI_DISABLE_PCIE:
3581		Disable PCI-Express on systems where it is supported but not
3582		required.
3583
3584- CONFIG_PCI_ENUM_ONLY
3585		Only scan through and get the devices on the busses.
3586		Don't do any setup work, presumably because someone or
3587		something has already done it, and we don't need to do it
3588		a second time.	Useful for platforms that are pre-booted
3589		by coreboot or similar.
3590
3591- CONFIG_SYS_SRIO:
3592		Chip has SRIO or not
3593
3594- CONFIG_SRIO1:
3595		Board has SRIO 1 port available
3596
3597- CONFIG_SRIO2:
3598		Board has SRIO 2 port available
3599
3600- CONFIG_SYS_SRIOn_MEM_VIRT:
3601		Virtual Address of SRIO port 'n' memory region
3602
3603- CONFIG_SYS_SRIOn_MEM_PHYS:
3604		Physical Address of SRIO port 'n' memory region
3605
3606- CONFIG_SYS_SRIOn_MEM_SIZE:
3607		Size of SRIO port 'n' memory region
3608
3609- CONFIG_SYS_NDFC_16
3610		Defined to tell the NDFC that the NAND chip is using a
3611		16 bit bus.
3612
3613- CONFIG_SYS_NDFC_EBC0_CFG
3614		Sets the EBC0_CFG register for the NDFC. If not defined
3615		a default value will be used.
3616
3617- CONFIG_SPD_EEPROM
3618		Get DDR timing information from an I2C EEPROM. Common
3619		with pluggable memory modules such as SODIMMs
3620
3621  SPD_EEPROM_ADDRESS
3622		I2C address of the SPD EEPROM
3623
3624- CONFIG_SYS_SPD_BUS_NUM
3625		If SPD EEPROM is on an I2C bus other than the first
3626		one, specify here. Note that the value must resolve
3627		to something your driver can deal with.
3628
3629- CONFIG_SYS_DDR_RAW_TIMING
3630		Get DDR timing information from other than SPD. Common with
3631		soldered DDR chips onboard without SPD. DDR raw timing
3632		parameters are extracted from datasheet and hard-coded into
3633		header files or board specific files.
3634
3635- CONFIG_FSL_DDR_INTERACTIVE
3636		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3637
3638- CONFIG_SYS_83XX_DDR_USES_CS0
3639		Only for 83xx systems. If specified, then DDR should
3640		be configured using CS0 and CS1 instead of CS2 and CS3.
3641
3642- CONFIG_ETHER_ON_FEC[12]
3643		Define to enable FEC[12] on a 8xx series processor.
3644
3645- CONFIG_FEC[12]_PHY
3646		Define to the hardcoded PHY address which corresponds
3647		to the given FEC; i. e.
3648			#define CONFIG_FEC1_PHY 4
3649		means that the PHY with address 4 is connected to FEC1
3650
3651		When set to -1, means to probe for first available.
3652
3653- CONFIG_FEC[12]_PHY_NORXERR
3654		The PHY does not have a RXERR line (RMII only).
3655		(so program the FEC to ignore it).
3656
3657- CONFIG_RMII
3658		Enable RMII mode for all FECs.
3659		Note that this is a global option, we can't
3660		have one FEC in standard MII mode and another in RMII mode.
3661
3662- CONFIG_CRC32_VERIFY
3663		Add a verify option to the crc32 command.
3664		The syntax is:
3665
3666		=> crc32 -v <address> <count> <crc32>
3667
3668		Where address/count indicate a memory area
3669		and crc32 is the correct crc32 which the
3670		area should have.
3671
3672- CONFIG_LOOPW
3673		Add the "loopw" memory command. This only takes effect if
3674		the memory commands are activated globally (CONFIG_CMD_MEM).
3675
3676- CONFIG_MX_CYCLIC
3677		Add the "mdc" and "mwc" memory commands. These are cyclic
3678		"md/mw" commands.
3679		Examples:
3680
3681		=> mdc.b 10 4 500
3682		This command will print 4 bytes (10,11,12,13) each 500 ms.
3683
3684		=> mwc.l 100 12345678 10
3685		This command will write 12345678 to address 100 all 10 ms.
3686
3687		This only takes effect if the memory commands are activated
3688		globally (CONFIG_CMD_MEM).
3689
3690- CONFIG_SKIP_LOWLEVEL_INIT
3691		[ARM, NDS32, MIPS only] If this variable is defined, then certain
3692		low level initializations (like setting up the memory
3693		controller) are omitted and/or U-Boot does not
3694		relocate itself into RAM.
3695
3696		Normally this variable MUST NOT be defined. The only
3697		exception is when U-Boot is loaded (to RAM) by some
3698		other boot loader or by a debugger which performs
3699		these initializations itself.
3700
3701- CONFIG_SPL_BUILD
3702		Modifies the behaviour of start.S when compiling a loader
3703		that is executed before the actual U-Boot. E.g. when
3704		compiling a NAND SPL.
3705
3706- CONFIG_USE_ARCH_MEMCPY
3707  CONFIG_USE_ARCH_MEMSET
3708		If these options are used a optimized version of memcpy/memset will
3709		be used if available. These functions may be faster under some
3710		conditions but may increase the binary size.
3711
3712- CONFIG_X86_NO_RESET_VECTOR
3713		If defined, the x86 reset vector code is excluded. You will need
3714		to do this when U-Boot is running from Coreboot.
3715
3716- CONFIG_X86_NO_REAL_MODE
3717		If defined, x86 real mode code is omitted. This assumes a
3718		32-bit environment where such code is not needed. You will
3719		need to do this when U-Boot is running from Coreboot.
3720
3721
3722Freescale QE/FMAN Firmware Support:
3723-----------------------------------
3724
3725The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3726loading of "firmware", which is encoded in the QE firmware binary format.
3727This firmware often needs to be loaded during U-Boot booting, so macros
3728are used to identify the storage device (NOR flash, SPI, etc) and the address
3729within that device.
3730
3731- CONFIG_SYS_QE_FMAN_FW_ADDR
3732	The address in the storage device where the firmware is located.  The
3733	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3734	is also specified.
3735
3736- CONFIG_SYS_QE_FMAN_FW_LENGTH
3737	The maximum possible size of the firmware.  The firmware binary format
3738	has a field that specifies the actual size of the firmware, but it
3739	might not be possible to read any part of the firmware unless some
3740	local storage is allocated to hold the entire firmware first.
3741
3742- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3743	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3744	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3745	virtual address in NOR flash.
3746
3747- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3748	Specifies that QE/FMAN firmware is located in NAND flash.
3749	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3750
3751- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3752	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3753	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3754
3755- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
3756	Specifies that QE/FMAN firmware is located on the primary SPI
3757	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3758
3759- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3760	Specifies that QE/FMAN firmware is located in the remote (master)
3761	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3762	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3763	window->master inbound window->master LAW->the ucode address in
3764	master's memory space.
3765
3766Building the Software:
3767======================
3768
3769Building U-Boot has been tested in several native build environments
3770and in many different cross environments. Of course we cannot support
3771all possibly existing versions of cross development tools in all
3772(potentially obsolete) versions. In case of tool chain problems we
3773recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3774which is extensively used to build and test U-Boot.
3775
3776If you are not using a native environment, it is assumed that you
3777have GNU cross compiling tools available in your path. In this case,
3778you must set the environment variable CROSS_COMPILE in your shell.
3779Note that no changes to the Makefile or any other source files are
3780necessary. For example using the ELDK on a 4xx CPU, please enter:
3781
3782	$ CROSS_COMPILE=ppc_4xx-
3783	$ export CROSS_COMPILE
3784
3785Note: If you wish to generate Windows versions of the utilities in
3786      the tools directory you can use the MinGW toolchain
3787      (http://www.mingw.org).  Set your HOST tools to the MinGW
3788      toolchain and execute 'make tools'.  For example:
3789
3790       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3791
3792      Binaries such as tools/mkimage.exe will be created which can
3793      be executed on computers running Windows.
3794
3795U-Boot is intended to be simple to build. After installing the
3796sources you must configure U-Boot for one specific board type. This
3797is done by typing:
3798
3799	make NAME_config
3800
3801where "NAME_config" is the name of one of the existing configu-
3802rations; see boards.cfg for supported names.
3803
3804Note: for some board special configuration names may exist; check if
3805      additional information is available from the board vendor; for
3806      instance, the TQM823L systems are available without (standard)
3807      or with LCD support. You can select such additional "features"
3808      when choosing the configuration, i. e.
3809
3810      make TQM823L_config
3811	- will configure for a plain TQM823L, i. e. no LCD support
3812
3813      make TQM823L_LCD_config
3814	- will configure for a TQM823L with U-Boot console on LCD
3815
3816      etc.
3817
3818
3819Finally, type "make all", and you should get some working U-Boot
3820images ready for download to / installation on your system:
3821
3822- "u-boot.bin" is a raw binary image
3823- "u-boot" is an image in ELF binary format
3824- "u-boot.srec" is in Motorola S-Record format
3825
3826By default the build is performed locally and the objects are saved
3827in the source directory. One of the two methods can be used to change
3828this behavior and build U-Boot to some external directory:
3829
38301. Add O= to the make command line invocations:
3831
3832	make O=/tmp/build distclean
3833	make O=/tmp/build NAME_config
3834	make O=/tmp/build all
3835
38362. Set environment variable BUILD_DIR to point to the desired location:
3837
3838	export BUILD_DIR=/tmp/build
3839	make distclean
3840	make NAME_config
3841	make all
3842
3843Note that the command line "O=" setting overrides the BUILD_DIR environment
3844variable.
3845
3846
3847Please be aware that the Makefiles assume you are using GNU make, so
3848for instance on NetBSD you might need to use "gmake" instead of
3849native "make".
3850
3851
3852If the system board that you have is not listed, then you will need
3853to port U-Boot to your hardware platform. To do this, follow these
3854steps:
3855
38561.  Add a new configuration option for your board to the toplevel
3857    "boards.cfg" file, using the existing entries as examples.
3858    Follow the instructions there to keep the boards in order.
38592.  Create a new directory to hold your board specific code. Add any
3860    files you need. In your board directory, you will need at least
3861    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
38623.  Create a new configuration file "include/configs/<board>.h" for
3863    your board
38643.  If you're porting U-Boot to a new CPU, then also create a new
3865    directory to hold your CPU specific code. Add any files you need.
38664.  Run "make <board>_config" with your new name.
38675.  Type "make", and you should get a working "u-boot.srec" file
3868    to be installed on your target system.
38696.  Debug and solve any problems that might arise.
3870    [Of course, this last step is much harder than it sounds.]
3871
3872
3873Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3874==============================================================
3875
3876If you have modified U-Boot sources (for instance added a new board
3877or support for new devices, a new CPU, etc.) you are expected to
3878provide feedback to the other developers. The feedback normally takes
3879the form of a "patch", i. e. a context diff against a certain (latest
3880official or latest in the git repository) version of U-Boot sources.
3881
3882But before you submit such a patch, please verify that your modifi-
3883cation did not break existing code. At least make sure that *ALL* of
3884the supported boards compile WITHOUT ANY compiler warnings. To do so,
3885just run the "MAKEALL" script, which will configure and build U-Boot
3886for ALL supported system. Be warned, this will take a while. You can
3887select which (cross) compiler to use by passing a `CROSS_COMPILE'
3888environment variable to the script, i. e. to use the ELDK cross tools
3889you can type
3890
3891	CROSS_COMPILE=ppc_8xx- MAKEALL
3892
3893or to build on a native PowerPC system you can type
3894
3895	CROSS_COMPILE=' ' MAKEALL
3896
3897When using the MAKEALL script, the default behaviour is to build
3898U-Boot in the source directory. This location can be changed by
3899setting the BUILD_DIR environment variable. Also, for each target
3900built, the MAKEALL script saves two log files (<target>.ERR and
3901<target>.MAKEALL) in the <source dir>/LOG directory. This default
3902location can be changed by setting the MAKEALL_LOGDIR environment
3903variable. For example:
3904
3905	export BUILD_DIR=/tmp/build
3906	export MAKEALL_LOGDIR=/tmp/log
3907	CROSS_COMPILE=ppc_8xx- MAKEALL
3908
3909With the above settings build objects are saved in the /tmp/build,
3910log files are saved in the /tmp/log and the source tree remains clean
3911during the whole build process.
3912
3913
3914See also "U-Boot Porting Guide" below.
3915
3916
3917Monitor Commands - Overview:
3918============================
3919
3920go	- start application at address 'addr'
3921run	- run commands in an environment variable
3922bootm	- boot application image from memory
3923bootp	- boot image via network using BootP/TFTP protocol
3924bootz   - boot zImage from memory
3925tftpboot- boot image via network using TFTP protocol
3926	       and env variables "ipaddr" and "serverip"
3927	       (and eventually "gatewayip")
3928tftpput - upload a file via network using TFTP protocol
3929rarpboot- boot image via network using RARP/TFTP protocol
3930diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3931loads	- load S-Record file over serial line
3932loadb	- load binary file over serial line (kermit mode)
3933md	- memory display
3934mm	- memory modify (auto-incrementing)
3935nm	- memory modify (constant address)
3936mw	- memory write (fill)
3937cp	- memory copy
3938cmp	- memory compare
3939crc32	- checksum calculation
3940i2c	- I2C sub-system
3941sspi	- SPI utility commands
3942base	- print or set address offset
3943printenv- print environment variables
3944setenv	- set environment variables
3945saveenv - save environment variables to persistent storage
3946protect - enable or disable FLASH write protection
3947erase	- erase FLASH memory
3948flinfo	- print FLASH memory information
3949nand	- NAND memory operations (see doc/README.nand)
3950bdinfo	- print Board Info structure
3951iminfo	- print header information for application image
3952coninfo - print console devices and informations
3953ide	- IDE sub-system
3954loop	- infinite loop on address range
3955loopw	- infinite write loop on address range
3956mtest	- simple RAM test
3957icache	- enable or disable instruction cache
3958dcache	- enable or disable data cache
3959reset	- Perform RESET of the CPU
3960echo	- echo args to console
3961version - print monitor version
3962help	- print online help
3963?	- alias for 'help'
3964
3965
3966Monitor Commands - Detailed Description:
3967========================================
3968
3969TODO.
3970
3971For now: just type "help <command>".
3972
3973
3974Environment Variables:
3975======================
3976
3977U-Boot supports user configuration using Environment Variables which
3978can be made persistent by saving to Flash memory.
3979
3980Environment Variables are set using "setenv", printed using
3981"printenv", and saved to Flash using "saveenv". Using "setenv"
3982without a value can be used to delete a variable from the
3983environment. As long as you don't save the environment you are
3984working with an in-memory copy. In case the Flash area containing the
3985environment is erased by accident, a default environment is provided.
3986
3987Some configuration options can be set using Environment Variables.
3988
3989List of environment variables (most likely not complete):
3990
3991  baudrate	- see CONFIG_BAUDRATE
3992
3993  bootdelay	- see CONFIG_BOOTDELAY
3994
3995  bootcmd	- see CONFIG_BOOTCOMMAND
3996
3997  bootargs	- Boot arguments when booting an RTOS image
3998
3999  bootfile	- Name of the image to load with TFTP
4000
4001  bootm_low	- Memory range available for image processing in the bootm
4002		  command can be restricted. This variable is given as
4003		  a hexadecimal number and defines lowest address allowed
4004		  for use by the bootm command. See also "bootm_size"
4005		  environment variable. Address defined by "bootm_low" is
4006		  also the base of the initial memory mapping for the Linux
4007		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4008		  bootm_mapsize.
4009
4010  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4011		  This variable is given as a hexadecimal number and it
4012		  defines the size of the memory region starting at base
4013		  address bootm_low that is accessible by the Linux kernel
4014		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4015		  as the default value if it is defined, and bootm_size is
4016		  used otherwise.
4017
4018  bootm_size	- Memory range available for image processing in the bootm
4019		  command can be restricted. This variable is given as
4020		  a hexadecimal number and defines the size of the region
4021		  allowed for use by the bootm command. See also "bootm_low"
4022		  environment variable.
4023
4024  updatefile	- Location of the software update file on a TFTP server, used
4025		  by the automatic software update feature. Please refer to
4026		  documentation in doc/README.update for more details.
4027
4028  autoload	- if set to "no" (any string beginning with 'n'),
4029		  "bootp" will just load perform a lookup of the
4030		  configuration from the BOOTP server, but not try to
4031		  load any image using TFTP
4032
4033  autostart	- if set to "yes", an image loaded using the "bootp",
4034		  "rarpboot", "tftpboot" or "diskboot" commands will
4035		  be automatically started (by internally calling
4036		  "bootm")
4037
4038		  If set to "no", a standalone image passed to the
4039		  "bootm" command will be copied to the load address
4040		  (and eventually uncompressed), but NOT be started.
4041		  This can be used to load and uncompress arbitrary
4042		  data.
4043
4044  fdt_high	- if set this restricts the maximum address that the
4045		  flattened device tree will be copied into upon boot.
4046		  For example, if you have a system with 1 GB memory
4047		  at physical address 0x10000000, while Linux kernel
4048		  only recognizes the first 704 MB as low memory, you
4049		  may need to set fdt_high as 0x3C000000 to have the
4050		  device tree blob be copied to the maximum address
4051		  of the 704 MB low memory, so that Linux kernel can
4052		  access it during the boot procedure.
4053
4054		  If this is set to the special value 0xFFFFFFFF then
4055		  the fdt will not be copied at all on boot.  For this
4056		  to work it must reside in writable memory, have
4057		  sufficient padding on the end of it for u-boot to
4058		  add the information it needs into it, and the memory
4059		  must be accessible by the kernel.
4060
4061  fdtcontroladdr- if set this is the address of the control flattened
4062		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4063		  defined.
4064
4065  i2cfast	- (PPC405GP|PPC405EP only)
4066		  if set to 'y' configures Linux I2C driver for fast
4067		  mode (400kHZ). This environment variable is used in
4068		  initialization code. So, for changes to be effective
4069		  it must be saved and board must be reset.
4070
4071  initrd_high	- restrict positioning of initrd images:
4072		  If this variable is not set, initrd images will be
4073		  copied to the highest possible address in RAM; this
4074		  is usually what you want since it allows for
4075		  maximum initrd size. If for some reason you want to
4076		  make sure that the initrd image is loaded below the
4077		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4078		  variable to a value of "no" or "off" or "0".
4079		  Alternatively, you can set it to a maximum upper
4080		  address to use (U-Boot will still check that it
4081		  does not overwrite the U-Boot stack and data).
4082
4083		  For instance, when you have a system with 16 MB
4084		  RAM, and want to reserve 4 MB from use by Linux,
4085		  you can do this by adding "mem=12M" to the value of
4086		  the "bootargs" variable. However, now you must make
4087		  sure that the initrd image is placed in the first
4088		  12 MB as well - this can be done with
4089
4090		  setenv initrd_high 00c00000
4091
4092		  If you set initrd_high to 0xFFFFFFFF, this is an
4093		  indication to U-Boot that all addresses are legal
4094		  for the Linux kernel, including addresses in flash
4095		  memory. In this case U-Boot will NOT COPY the
4096		  ramdisk at all. This may be useful to reduce the
4097		  boot time on your system, but requires that this
4098		  feature is supported by your Linux kernel.
4099
4100  ipaddr	- IP address; needed for tftpboot command
4101
4102  loadaddr	- Default load address for commands like "bootp",
4103		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4104
4105  loads_echo	- see CONFIG_LOADS_ECHO
4106
4107  serverip	- TFTP server IP address; needed for tftpboot command
4108
4109  bootretry	- see CONFIG_BOOT_RETRY_TIME
4110
4111  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4112
4113  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4114
4115  ethprime	- controls which interface is used first.
4116
4117  ethact	- controls which interface is currently active.
4118		  For example you can do the following
4119
4120		  => setenv ethact FEC
4121		  => ping 192.168.0.1 # traffic sent on FEC
4122		  => setenv ethact SCC
4123		  => ping 10.0.0.1 # traffic sent on SCC
4124
4125  ethrotate	- When set to "no" U-Boot does not go through all
4126		  available network interfaces.
4127		  It just stays at the currently selected interface.
4128
4129  netretry	- When set to "no" each network operation will
4130		  either succeed or fail without retrying.
4131		  When set to "once" the network operation will
4132		  fail when all the available network interfaces
4133		  are tried once without success.
4134		  Useful on scripts which control the retry operation
4135		  themselves.
4136
4137  npe_ucode	- set load address for the NPE microcode
4138
4139  tftpsrcport	- If this is set, the value is used for TFTP's
4140		  UDP source port.
4141
4142  tftpdstport	- If this is set, the value is used for TFTP's UDP
4143		  destination port instead of the Well Know Port 69.
4144
4145  tftpblocksize - Block size to use for TFTP transfers; if not set,
4146		  we use the TFTP server's default block size
4147
4148  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4149		  seconds, minimum value is 1000 = 1 second). Defines
4150		  when a packet is considered to be lost so it has to
4151		  be retransmitted. The default is 5000 = 5 seconds.
4152		  Lowering this value may make downloads succeed
4153		  faster in networks with high packet loss rates or
4154		  with unreliable TFTP servers.
4155
4156  vlan		- When set to a value < 4095 the traffic over
4157		  Ethernet is encapsulated/received over 802.1q
4158		  VLAN tagged frames.
4159
4160The following image location variables contain the location of images
4161used in booting. The "Image" column gives the role of the image and is
4162not an environment variable name. The other columns are environment
4163variable names. "File Name" gives the name of the file on a TFTP
4164server, "RAM Address" gives the location in RAM the image will be
4165loaded to, and "Flash Location" gives the image's address in NOR
4166flash or offset in NAND flash.
4167
4168*Note* - these variables don't have to be defined for all boards, some
4169boards currenlty use other variables for these purposes, and some
4170boards use these variables for other purposes.
4171
4172Image		    File Name	     RAM Address       Flash Location
4173-----		    ---------	     -----------       --------------
4174u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4175Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4176device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4177ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4178
4179The following environment variables may be used and automatically
4180updated by the network boot commands ("bootp" and "rarpboot"),
4181depending the information provided by your boot server:
4182
4183  bootfile	- see above
4184  dnsip		- IP address of your Domain Name Server
4185  dnsip2	- IP address of your secondary Domain Name Server
4186  gatewayip	- IP address of the Gateway (Router) to use
4187  hostname	- Target hostname
4188  ipaddr	- see above
4189  netmask	- Subnet Mask
4190  rootpath	- Pathname of the root filesystem on the NFS server
4191  serverip	- see above
4192
4193
4194There are two special Environment Variables:
4195
4196  serial#	- contains hardware identification information such
4197		  as type string and/or serial number
4198  ethaddr	- Ethernet address
4199
4200These variables can be set only once (usually during manufacturing of
4201the board). U-Boot refuses to delete or overwrite these variables
4202once they have been set once.
4203
4204
4205Further special Environment Variables:
4206
4207  ver		- Contains the U-Boot version string as printed
4208		  with the "version" command. This variable is
4209		  readonly (see CONFIG_VERSION_VARIABLE).
4210
4211
4212Please note that changes to some configuration parameters may take
4213only effect after the next boot (yes, that's just like Windoze :-).
4214
4215
4216Command Line Parsing:
4217=====================
4218
4219There are two different command line parsers available with U-Boot:
4220the old "simple" one, and the much more powerful "hush" shell:
4221
4222Old, simple command line parser:
4223--------------------------------
4224
4225- supports environment variables (through setenv / saveenv commands)
4226- several commands on one line, separated by ';'
4227- variable substitution using "... ${name} ..." syntax
4228- special characters ('$', ';') can be escaped by prefixing with '\',
4229  for example:
4230	setenv bootcmd bootm \${address}
4231- You can also escape text by enclosing in single apostrophes, for example:
4232	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4233
4234Hush shell:
4235-----------
4236
4237- similar to Bourne shell, with control structures like
4238  if...then...else...fi, for...do...done; while...do...done,
4239  until...do...done, ...
4240- supports environment ("global") variables (through setenv / saveenv
4241  commands) and local shell variables (through standard shell syntax
4242  "name=value"); only environment variables can be used with "run"
4243  command
4244
4245General rules:
4246--------------
4247
4248(1) If a command line (or an environment variable executed by a "run"
4249    command) contains several commands separated by semicolon, and
4250    one of these commands fails, then the remaining commands will be
4251    executed anyway.
4252
4253(2) If you execute several variables with one call to run (i. e.
4254    calling run with a list of variables as arguments), any failing
4255    command will cause "run" to terminate, i. e. the remaining
4256    variables are not executed.
4257
4258Note for Redundant Ethernet Interfaces:
4259=======================================
4260
4261Some boards come with redundant Ethernet interfaces; U-Boot supports
4262such configurations and is capable of automatic selection of a
4263"working" interface when needed. MAC assignment works as follows:
4264
4265Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4266MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4267"eth1addr" (=>eth1), "eth2addr", ...
4268
4269If the network interface stores some valid MAC address (for instance
4270in SROM), this is used as default address if there is NO correspon-
4271ding setting in the environment; if the corresponding environment
4272variable is set, this overrides the settings in the card; that means:
4273
4274o If the SROM has a valid MAC address, and there is no address in the
4275  environment, the SROM's address is used.
4276
4277o If there is no valid address in the SROM, and a definition in the
4278  environment exists, then the value from the environment variable is
4279  used.
4280
4281o If both the SROM and the environment contain a MAC address, and
4282  both addresses are the same, this MAC address is used.
4283
4284o If both the SROM and the environment contain a MAC address, and the
4285  addresses differ, the value from the environment is used and a
4286  warning is printed.
4287
4288o If neither SROM nor the environment contain a MAC address, an error
4289  is raised.
4290
4291If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4292will be programmed into hardware as part of the initialization process.	 This
4293may be skipped by setting the appropriate 'ethmacskip' environment variable.
4294The naming convention is as follows:
4295"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4296
4297Image Formats:
4298==============
4299
4300U-Boot is capable of booting (and performing other auxiliary operations on)
4301images in two formats:
4302
4303New uImage format (FIT)
4304-----------------------
4305
4306Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4307to Flattened Device Tree). It allows the use of images with multiple
4308components (several kernels, ramdisks, etc.), with contents protected by
4309SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4310
4311
4312Old uImage format
4313-----------------
4314
4315Old image format is based on binary files which can be basically anything,
4316preceded by a special header; see the definitions in include/image.h for
4317details; basically, the header defines the following image properties:
4318
4319* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4320  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4321  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4322  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4323  INTEGRITY).
4324* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
4325  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4326  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4327* Compression Type (uncompressed, gzip, bzip2)
4328* Load Address
4329* Entry Point
4330* Image Name
4331* Image Timestamp
4332
4333The header is marked by a special Magic Number, and both the header
4334and the data portions of the image are secured against corruption by
4335CRC32 checksums.
4336
4337
4338Linux Support:
4339==============
4340
4341Although U-Boot should support any OS or standalone application
4342easily, the main focus has always been on Linux during the design of
4343U-Boot.
4344
4345U-Boot includes many features that so far have been part of some
4346special "boot loader" code within the Linux kernel. Also, any
4347"initrd" images to be used are no longer part of one big Linux image;
4348instead, kernel and "initrd" are separate images. This implementation
4349serves several purposes:
4350
4351- the same features can be used for other OS or standalone
4352  applications (for instance: using compressed images to reduce the
4353  Flash memory footprint)
4354
4355- it becomes much easier to port new Linux kernel versions because
4356  lots of low-level, hardware dependent stuff are done by U-Boot
4357
4358- the same Linux kernel image can now be used with different "initrd"
4359  images; of course this also means that different kernel images can
4360  be run with the same "initrd". This makes testing easier (you don't
4361  have to build a new "zImage.initrd" Linux image when you just
4362  change a file in your "initrd"). Also, a field-upgrade of the
4363  software is easier now.
4364
4365
4366Linux HOWTO:
4367============
4368
4369Porting Linux to U-Boot based systems:
4370---------------------------------------
4371
4372U-Boot cannot save you from doing all the necessary modifications to
4373configure the Linux device drivers for use with your target hardware
4374(no, we don't intend to provide a full virtual machine interface to
4375Linux :-).
4376
4377But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4378
4379Just make sure your machine specific header file (for instance
4380include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4381Information structure as we define in include/asm-<arch>/u-boot.h,
4382and make sure that your definition of IMAP_ADDR uses the same value
4383as your U-Boot configuration in CONFIG_SYS_IMMR.
4384
4385
4386Configuring the Linux kernel:
4387-----------------------------
4388
4389No specific requirements for U-Boot. Make sure you have some root
4390device (initial ramdisk, NFS) for your target system.
4391
4392
4393Building a Linux Image:
4394-----------------------
4395
4396With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4397not used. If you use recent kernel source, a new build target
4398"uImage" will exist which automatically builds an image usable by
4399U-Boot. Most older kernels also have support for a "pImage" target,
4400which was introduced for our predecessor project PPCBoot and uses a
4401100% compatible format.
4402
4403Example:
4404
4405	make TQM850L_config
4406	make oldconfig
4407	make dep
4408	make uImage
4409
4410The "uImage" build target uses a special tool (in 'tools/mkimage') to
4411encapsulate a compressed Linux kernel image with header	 information,
4412CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4413
4414* build a standard "vmlinux" kernel image (in ELF binary format):
4415
4416* convert the kernel into a raw binary image:
4417
4418	${CROSS_COMPILE}-objcopy -O binary \
4419				 -R .note -R .comment \
4420				 -S vmlinux linux.bin
4421
4422* compress the binary image:
4423
4424	gzip -9 linux.bin
4425
4426* package compressed binary image for U-Boot:
4427
4428	mkimage -A ppc -O linux -T kernel -C gzip \
4429		-a 0 -e 0 -n "Linux Kernel Image" \
4430		-d linux.bin.gz uImage
4431
4432
4433The "mkimage" tool can also be used to create ramdisk images for use
4434with U-Boot, either separated from the Linux kernel image, or
4435combined into one file. "mkimage" encapsulates the images with a 64
4436byte header containing information about target architecture,
4437operating system, image type, compression method, entry points, time
4438stamp, CRC32 checksums, etc.
4439
4440"mkimage" can be called in two ways: to verify existing images and
4441print the header information, or to build new images.
4442
4443In the first form (with "-l" option) mkimage lists the information
4444contained in the header of an existing U-Boot image; this includes
4445checksum verification:
4446
4447	tools/mkimage -l image
4448	  -l ==> list image header information
4449
4450The second form (with "-d" option) is used to build a U-Boot image
4451from a "data file" which is used as image payload:
4452
4453	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4454		      -n name -d data_file image
4455	  -A ==> set architecture to 'arch'
4456	  -O ==> set operating system to 'os'
4457	  -T ==> set image type to 'type'
4458	  -C ==> set compression type 'comp'
4459	  -a ==> set load address to 'addr' (hex)
4460	  -e ==> set entry point to 'ep' (hex)
4461	  -n ==> set image name to 'name'
4462	  -d ==> use image data from 'datafile'
4463
4464Right now, all Linux kernels for PowerPC systems use the same load
4465address (0x00000000), but the entry point address depends on the
4466kernel version:
4467
4468- 2.2.x kernels have the entry point at 0x0000000C,
4469- 2.3.x and later kernels have the entry point at 0x00000000.
4470
4471So a typical call to build a U-Boot image would read:
4472
4473	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4474	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4475	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4476	> examples/uImage.TQM850L
4477	Image Name:   2.4.4 kernel for TQM850L
4478	Created:      Wed Jul 19 02:34:59 2000
4479	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4480	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4481	Load Address: 0x00000000
4482	Entry Point:  0x00000000
4483
4484To verify the contents of the image (or check for corruption):
4485
4486	-> tools/mkimage -l examples/uImage.TQM850L
4487	Image Name:   2.4.4 kernel for TQM850L
4488	Created:      Wed Jul 19 02:34:59 2000
4489	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4490	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4491	Load Address: 0x00000000
4492	Entry Point:  0x00000000
4493
4494NOTE: for embedded systems where boot time is critical you can trade
4495speed for memory and install an UNCOMPRESSED image instead: this
4496needs more space in Flash, but boots much faster since it does not
4497need to be uncompressed:
4498
4499	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4500	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4501	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4502	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4503	> examples/uImage.TQM850L-uncompressed
4504	Image Name:   2.4.4 kernel for TQM850L
4505	Created:      Wed Jul 19 02:34:59 2000
4506	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4507	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4508	Load Address: 0x00000000
4509	Entry Point:  0x00000000
4510
4511
4512Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4513when your kernel is intended to use an initial ramdisk:
4514
4515	-> tools/mkimage -n 'Simple Ramdisk Image' \
4516	> -A ppc -O linux -T ramdisk -C gzip \
4517	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4518	Image Name:   Simple Ramdisk Image
4519	Created:      Wed Jan 12 14:01:50 2000
4520	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4521	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4522	Load Address: 0x00000000
4523	Entry Point:  0x00000000
4524
4525
4526Installing a Linux Image:
4527-------------------------
4528
4529To downloading a U-Boot image over the serial (console) interface,
4530you must convert the image to S-Record format:
4531
4532	objcopy -I binary -O srec examples/image examples/image.srec
4533
4534The 'objcopy' does not understand the information in the U-Boot
4535image header, so the resulting S-Record file will be relative to
4536address 0x00000000. To load it to a given address, you need to
4537specify the target address as 'offset' parameter with the 'loads'
4538command.
4539
4540Example: install the image to address 0x40100000 (which on the
4541TQM8xxL is in the first Flash bank):
4542
4543	=> erase 40100000 401FFFFF
4544
4545	.......... done
4546	Erased 8 sectors
4547
4548	=> loads 40100000
4549	## Ready for S-Record download ...
4550	~>examples/image.srec
4551	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4552	...
4553	15989 15990 15991 15992
4554	[file transfer complete]
4555	[connected]
4556	## Start Addr = 0x00000000
4557
4558
4559You can check the success of the download using the 'iminfo' command;
4560this includes a checksum verification so you can be sure no data
4561corruption happened:
4562
4563	=> imi 40100000
4564
4565	## Checking Image at 40100000 ...
4566	   Image Name:	 2.2.13 for initrd on TQM850L
4567	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4568	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4569	   Load Address: 00000000
4570	   Entry Point:	 0000000c
4571	   Verifying Checksum ... OK
4572
4573
4574Boot Linux:
4575-----------
4576
4577The "bootm" command is used to boot an application that is stored in
4578memory (RAM or Flash). In case of a Linux kernel image, the contents
4579of the "bootargs" environment variable is passed to the kernel as
4580parameters. You can check and modify this variable using the
4581"printenv" and "setenv" commands:
4582
4583
4584	=> printenv bootargs
4585	bootargs=root=/dev/ram
4586
4587	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4588
4589	=> printenv bootargs
4590	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4591
4592	=> bootm 40020000
4593	## Booting Linux kernel at 40020000 ...
4594	   Image Name:	 2.2.13 for NFS on TQM850L
4595	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4596	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4597	   Load Address: 00000000
4598	   Entry Point:	 0000000c
4599	   Verifying Checksum ... OK
4600	   Uncompressing Kernel Image ... OK
4601	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
4602	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4603	time_init: decrementer frequency = 187500000/60
4604	Calibrating delay loop... 49.77 BogoMIPS
4605	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4606	...
4607
4608If you want to boot a Linux kernel with initial RAM disk, you pass
4609the memory addresses of both the kernel and the initrd image (PPBCOOT
4610format!) to the "bootm" command:
4611
4612	=> imi 40100000 40200000
4613
4614	## Checking Image at 40100000 ...
4615	   Image Name:	 2.2.13 for initrd on TQM850L
4616	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4617	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4618	   Load Address: 00000000
4619	   Entry Point:	 0000000c
4620	   Verifying Checksum ... OK
4621
4622	## Checking Image at 40200000 ...
4623	   Image Name:	 Simple Ramdisk Image
4624	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4625	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4626	   Load Address: 00000000
4627	   Entry Point:	 00000000
4628	   Verifying Checksum ... OK
4629
4630	=> bootm 40100000 40200000
4631	## Booting Linux kernel at 40100000 ...
4632	   Image Name:	 2.2.13 for initrd on TQM850L
4633	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4634	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4635	   Load Address: 00000000
4636	   Entry Point:	 0000000c
4637	   Verifying Checksum ... OK
4638	   Uncompressing Kernel Image ... OK
4639	## Loading RAMDisk Image at 40200000 ...
4640	   Image Name:	 Simple Ramdisk Image
4641	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4642	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4643	   Load Address: 00000000
4644	   Entry Point:	 00000000
4645	   Verifying Checksum ... OK
4646	   Loading Ramdisk ... OK
4647	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
4648	Boot arguments: root=/dev/ram
4649	time_init: decrementer frequency = 187500000/60
4650	Calibrating delay loop... 49.77 BogoMIPS
4651	...
4652	RAMDISK: Compressed image found at block 0
4653	VFS: Mounted root (ext2 filesystem).
4654
4655	bash#
4656
4657Boot Linux and pass a flat device tree:
4658-----------
4659
4660First, U-Boot must be compiled with the appropriate defines. See the section
4661titled "Linux Kernel Interface" above for a more in depth explanation. The
4662following is an example of how to start a kernel and pass an updated
4663flat device tree:
4664
4665=> print oftaddr
4666oftaddr=0x300000
4667=> print oft
4668oft=oftrees/mpc8540ads.dtb
4669=> tftp $oftaddr $oft
4670Speed: 1000, full duplex
4671Using TSEC0 device
4672TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4673Filename 'oftrees/mpc8540ads.dtb'.
4674Load address: 0x300000
4675Loading: #
4676done
4677Bytes transferred = 4106 (100a hex)
4678=> tftp $loadaddr $bootfile
4679Speed: 1000, full duplex
4680Using TSEC0 device
4681TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4682Filename 'uImage'.
4683Load address: 0x200000
4684Loading:############
4685done
4686Bytes transferred = 1029407 (fb51f hex)
4687=> print loadaddr
4688loadaddr=200000
4689=> print oftaddr
4690oftaddr=0x300000
4691=> bootm $loadaddr - $oftaddr
4692## Booting image at 00200000 ...
4693   Image Name:	 Linux-2.6.17-dirty
4694   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4695   Data Size:	 1029343 Bytes = 1005.2 kB
4696   Load Address: 00000000
4697   Entry Point:	 00000000
4698   Verifying Checksum ... OK
4699   Uncompressing Kernel Image ... OK
4700Booting using flat device tree at 0x300000
4701Using MPC85xx ADS machine description
4702Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4703[snip]
4704
4705
4706More About U-Boot Image Types:
4707------------------------------
4708
4709U-Boot supports the following image types:
4710
4711   "Standalone Programs" are directly runnable in the environment
4712	provided by U-Boot; it is expected that (if they behave
4713	well) you can continue to work in U-Boot after return from
4714	the Standalone Program.
4715   "OS Kernel Images" are usually images of some Embedded OS which
4716	will take over control completely. Usually these programs
4717	will install their own set of exception handlers, device
4718	drivers, set up the MMU, etc. - this means, that you cannot
4719	expect to re-enter U-Boot except by resetting the CPU.
4720   "RAMDisk Images" are more or less just data blocks, and their
4721	parameters (address, size) are passed to an OS kernel that is
4722	being started.
4723   "Multi-File Images" contain several images, typically an OS
4724	(Linux) kernel image and one or more data images like
4725	RAMDisks. This construct is useful for instance when you want
4726	to boot over the network using BOOTP etc., where the boot
4727	server provides just a single image file, but you want to get
4728	for instance an OS kernel and a RAMDisk image.
4729
4730	"Multi-File Images" start with a list of image sizes, each
4731	image size (in bytes) specified by an "uint32_t" in network
4732	byte order. This list is terminated by an "(uint32_t)0".
4733	Immediately after the terminating 0 follow the images, one by
4734	one, all aligned on "uint32_t" boundaries (size rounded up to
4735	a multiple of 4 bytes).
4736
4737   "Firmware Images" are binary images containing firmware (like
4738	U-Boot or FPGA images) which usually will be programmed to
4739	flash memory.
4740
4741   "Script files" are command sequences that will be executed by
4742	U-Boot's command interpreter; this feature is especially
4743	useful when you configure U-Boot to use a real shell (hush)
4744	as command interpreter.
4745
4746Booting the Linux zImage:
4747-------------------------
4748
4749On some platforms, it's possible to boot Linux zImage. This is done
4750using the "bootz" command. The syntax of "bootz" command is the same
4751as the syntax of "bootm" command.
4752
4753Note, defining the CONFIG_SUPPORT_INITRD_RAW allows user to supply
4754kernel with raw initrd images. The syntax is slightly different, the
4755address of the initrd must be augmented by it's size, in the following
4756format: "<initrd addres>:<initrd size>".
4757
4758
4759Standalone HOWTO:
4760=================
4761
4762One of the features of U-Boot is that you can dynamically load and
4763run "standalone" applications, which can use some resources of
4764U-Boot like console I/O functions or interrupt services.
4765
4766Two simple examples are included with the sources:
4767
4768"Hello World" Demo:
4769-------------------
4770
4771'examples/hello_world.c' contains a small "Hello World" Demo
4772application; it is automatically compiled when you build U-Boot.
4773It's configured to run at address 0x00040004, so you can play with it
4774like that:
4775
4776	=> loads
4777	## Ready for S-Record download ...
4778	~>examples/hello_world.srec
4779	1 2 3 4 5 6 7 8 9 10 11 ...
4780	[file transfer complete]
4781	[connected]
4782	## Start Addr = 0x00040004
4783
4784	=> go 40004 Hello World! This is a test.
4785	## Starting application at 0x00040004 ...
4786	Hello World
4787	argc = 7
4788	argv[0] = "40004"
4789	argv[1] = "Hello"
4790	argv[2] = "World!"
4791	argv[3] = "This"
4792	argv[4] = "is"
4793	argv[5] = "a"
4794	argv[6] = "test."
4795	argv[7] = "<NULL>"
4796	Hit any key to exit ...
4797
4798	## Application terminated, rc = 0x0
4799
4800Another example, which demonstrates how to register a CPM interrupt
4801handler with the U-Boot code, can be found in 'examples/timer.c'.
4802Here, a CPM timer is set up to generate an interrupt every second.
4803The interrupt service routine is trivial, just printing a '.'
4804character, but this is just a demo program. The application can be
4805controlled by the following keys:
4806
4807	? - print current values og the CPM Timer registers
4808	b - enable interrupts and start timer
4809	e - stop timer and disable interrupts
4810	q - quit application
4811
4812	=> loads
4813	## Ready for S-Record download ...
4814	~>examples/timer.srec
4815	1 2 3 4 5 6 7 8 9 10 11 ...
4816	[file transfer complete]
4817	[connected]
4818	## Start Addr = 0x00040004
4819
4820	=> go 40004
4821	## Starting application at 0x00040004 ...
4822	TIMERS=0xfff00980
4823	Using timer 1
4824	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4825
4826Hit 'b':
4827	[q, b, e, ?] Set interval 1000000 us
4828	Enabling timer
4829Hit '?':
4830	[q, b, e, ?] ........
4831	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4832Hit '?':
4833	[q, b, e, ?] .
4834	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4835Hit '?':
4836	[q, b, e, ?] .
4837	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4838Hit '?':
4839	[q, b, e, ?] .
4840	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4841Hit 'e':
4842	[q, b, e, ?] ...Stopping timer
4843Hit 'q':
4844	[q, b, e, ?] ## Application terminated, rc = 0x0
4845
4846
4847Minicom warning:
4848================
4849
4850Over time, many people have reported problems when trying to use the
4851"minicom" terminal emulation program for serial download. I (wd)
4852consider minicom to be broken, and recommend not to use it. Under
4853Unix, I recommend to use C-Kermit for general purpose use (and
4854especially for kermit binary protocol download ("loadb" command), and
4855use "cu" for S-Record download ("loads" command).  See
4856http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4857for help with kermit.
4858
4859
4860Nevertheless, if you absolutely want to use it try adding this
4861configuration to your "File transfer protocols" section:
4862
4863	   Name	   Program			Name U/D FullScr IO-Red. Multi
4864	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4865	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4866
4867
4868NetBSD Notes:
4869=============
4870
4871Starting at version 0.9.2, U-Boot supports NetBSD both as host
4872(build U-Boot) and target system (boots NetBSD/mpc8xx).
4873
4874Building requires a cross environment; it is known to work on
4875NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4876need gmake since the Makefiles are not compatible with BSD make).
4877Note that the cross-powerpc package does not install include files;
4878attempting to build U-Boot will fail because <machine/ansi.h> is
4879missing.  This file has to be installed and patched manually:
4880
4881	# cd /usr/pkg/cross/powerpc-netbsd/include
4882	# mkdir powerpc
4883	# ln -s powerpc machine
4884	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4885	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4886
4887Native builds *don't* work due to incompatibilities between native
4888and U-Boot include files.
4889
4890Booting assumes that (the first part of) the image booted is a
4891stage-2 loader which in turn loads and then invokes the kernel
4892proper. Loader sources will eventually appear in the NetBSD source
4893tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4894meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4895
4896
4897Implementation Internals:
4898=========================
4899
4900The following is not intended to be a complete description of every
4901implementation detail. However, it should help to understand the
4902inner workings of U-Boot and make it easier to port it to custom
4903hardware.
4904
4905
4906Initial Stack, Global Data:
4907---------------------------
4908
4909The implementation of U-Boot is complicated by the fact that U-Boot
4910starts running out of ROM (flash memory), usually without access to
4911system RAM (because the memory controller is not initialized yet).
4912This means that we don't have writable Data or BSS segments, and BSS
4913is not initialized as zero. To be able to get a C environment working
4914at all, we have to allocate at least a minimal stack. Implementation
4915options for this are defined and restricted by the CPU used: Some CPU
4916models provide on-chip memory (like the IMMR area on MPC8xx and
4917MPC826x processors), on others (parts of) the data cache can be
4918locked as (mis-) used as memory, etc.
4919
4920	Chris Hallinan posted a good summary of these issues to the
4921	U-Boot mailing list:
4922
4923	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4924	From: "Chris Hallinan" <clh@net1plus.com>
4925	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4926	...
4927
4928	Correct me if I'm wrong, folks, but the way I understand it
4929	is this: Using DCACHE as initial RAM for Stack, etc, does not
4930	require any physical RAM backing up the cache. The cleverness
4931	is that the cache is being used as a temporary supply of
4932	necessary storage before the SDRAM controller is setup. It's
4933	beyond the scope of this list to explain the details, but you
4934	can see how this works by studying the cache architecture and
4935	operation in the architecture and processor-specific manuals.
4936
4937	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4938	is another option for the system designer to use as an
4939	initial stack/RAM area prior to SDRAM being available. Either
4940	option should work for you. Using CS 4 should be fine if your
4941	board designers haven't used it for something that would
4942	cause you grief during the initial boot! It is frequently not
4943	used.
4944
4945	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4946	with your processor/board/system design. The default value
4947	you will find in any recent u-boot distribution in
4948	walnut.h should work for you. I'd set it to a value larger
4949	than your SDRAM module. If you have a 64MB SDRAM module, set
4950	it above 400_0000. Just make sure your board has no resources
4951	that are supposed to respond to that address! That code in
4952	start.S has been around a while and should work as is when
4953	you get the config right.
4954
4955	-Chris Hallinan
4956	DS4.COM, Inc.
4957
4958It is essential to remember this, since it has some impact on the C
4959code for the initialization procedures:
4960
4961* Initialized global data (data segment) is read-only. Do not attempt
4962  to write it.
4963
4964* Do not use any uninitialized global data (or implicitely initialized
4965  as zero data - BSS segment) at all - this is undefined, initiali-
4966  zation is performed later (when relocating to RAM).
4967
4968* Stack space is very limited. Avoid big data buffers or things like
4969  that.
4970
4971Having only the stack as writable memory limits means we cannot use
4972normal global data to share information beween the code. But it
4973turned out that the implementation of U-Boot can be greatly
4974simplified by making a global data structure (gd_t) available to all
4975functions. We could pass a pointer to this data as argument to _all_
4976functions, but this would bloat the code. Instead we use a feature of
4977the GCC compiler (Global Register Variables) to share the data: we
4978place a pointer (gd) to the global data into a register which we
4979reserve for this purpose.
4980
4981When choosing a register for such a purpose we are restricted by the
4982relevant  (E)ABI  specifications for the current architecture, and by
4983GCC's implementation.
4984
4985For PowerPC, the following registers have specific use:
4986	R1:	stack pointer
4987	R2:	reserved for system use
4988	R3-R4:	parameter passing and return values
4989	R5-R10: parameter passing
4990	R13:	small data area pointer
4991	R30:	GOT pointer
4992	R31:	frame pointer
4993
4994	(U-Boot also uses R12 as internal GOT pointer. r12
4995	is a volatile register so r12 needs to be reset when
4996	going back and forth between asm and C)
4997
4998    ==> U-Boot will use R2 to hold a pointer to the global data
4999
5000    Note: on PPC, we could use a static initializer (since the
5001    address of the global data structure is known at compile time),
5002    but it turned out that reserving a register results in somewhat
5003    smaller code - although the code savings are not that big (on
5004    average for all boards 752 bytes for the whole U-Boot image,
5005    624 text + 127 data).
5006
5007On Blackfin, the normal C ABI (except for P3) is followed as documented here:
5008	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
5009
5010    ==> U-Boot will use P3 to hold a pointer to the global data
5011
5012On ARM, the following registers are used:
5013
5014	R0:	function argument word/integer result
5015	R1-R3:	function argument word
5016	R9:	GOT pointer
5017	R10:	stack limit (used only if stack checking if enabled)
5018	R11:	argument (frame) pointer
5019	R12:	temporary workspace
5020	R13:	stack pointer
5021	R14:	link register
5022	R15:	program counter
5023
5024    ==> U-Boot will use R8 to hold a pointer to the global data
5025
5026On Nios II, the ABI is documented here:
5027	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5028
5029    ==> U-Boot will use gp to hold a pointer to the global data
5030
5031    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5032    to access small data sections, so gp is free.
5033
5034On NDS32, the following registers are used:
5035
5036	R0-R1:	argument/return
5037	R2-R5:	argument
5038	R15:	temporary register for assembler
5039	R16:	trampoline register
5040	R28:	frame pointer (FP)
5041	R29:	global pointer (GP)
5042	R30:	link register (LP)
5043	R31:	stack pointer (SP)
5044	PC:	program counter (PC)
5045
5046    ==> U-Boot will use R10 to hold a pointer to the global data
5047
5048NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5049or current versions of GCC may "optimize" the code too much.
5050
5051Memory Management:
5052------------------
5053
5054U-Boot runs in system state and uses physical addresses, i.e. the
5055MMU is not used either for address mapping nor for memory protection.
5056
5057The available memory is mapped to fixed addresses using the memory
5058controller. In this process, a contiguous block is formed for each
5059memory type (Flash, SDRAM, SRAM), even when it consists of several
5060physical memory banks.
5061
5062U-Boot is installed in the first 128 kB of the first Flash bank (on
5063TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5064booting and sizing and initializing DRAM, the code relocates itself
5065to the upper end of DRAM. Immediately below the U-Boot code some
5066memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5067configuration setting]. Below that, a structure with global Board
5068Info data is placed, followed by the stack (growing downward).
5069
5070Additionally, some exception handler code is copied to the low 8 kB
5071of DRAM (0x00000000 ... 0x00001FFF).
5072
5073So a typical memory configuration with 16 MB of DRAM could look like
5074this:
5075
5076	0x0000 0000	Exception Vector code
5077	      :
5078	0x0000 1FFF
5079	0x0000 2000	Free for Application Use
5080	      :
5081	      :
5082
5083	      :
5084	      :
5085	0x00FB FF20	Monitor Stack (Growing downward)
5086	0x00FB FFAC	Board Info Data and permanent copy of global data
5087	0x00FC 0000	Malloc Arena
5088	      :
5089	0x00FD FFFF
5090	0x00FE 0000	RAM Copy of Monitor Code
5091	...		eventually: LCD or video framebuffer
5092	...		eventually: pRAM (Protected RAM - unchanged by reset)
5093	0x00FF FFFF	[End of RAM]
5094
5095
5096System Initialization:
5097----------------------
5098
5099In the reset configuration, U-Boot starts at the reset entry point
5100(on most PowerPC systems at address 0x00000100). Because of the reset
5101configuration for CS0# this is a mirror of the onboard Flash memory.
5102To be able to re-map memory U-Boot then jumps to its link address.
5103To be able to implement the initialization code in C, a (small!)
5104initial stack is set up in the internal Dual Ported RAM (in case CPUs
5105which provide such a feature like MPC8xx or MPC8260), or in a locked
5106part of the data cache. After that, U-Boot initializes the CPU core,
5107the caches and the SIU.
5108
5109Next, all (potentially) available memory banks are mapped using a
5110preliminary mapping. For example, we put them on 512 MB boundaries
5111(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5112on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5113programmed for SDRAM access. Using the temporary configuration, a
5114simple memory test is run that determines the size of the SDRAM
5115banks.
5116
5117When there is more than one SDRAM bank, and the banks are of
5118different size, the largest is mapped first. For equal size, the first
5119bank (CS2#) is mapped first. The first mapping is always for address
51200x00000000, with any additional banks following immediately to create
5121contiguous memory starting from 0.
5122
5123Then, the monitor installs itself at the upper end of the SDRAM area
5124and allocates memory for use by malloc() and for the global Board
5125Info data; also, the exception vector code is copied to the low RAM
5126pages, and the final stack is set up.
5127
5128Only after this relocation will you have a "normal" C environment;
5129until that you are restricted in several ways, mostly because you are
5130running from ROM, and because the code will have to be relocated to a
5131new address in RAM.
5132
5133
5134U-Boot Porting Guide:
5135----------------------
5136
5137[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5138list, October 2002]
5139
5140
5141int main(int argc, char *argv[])
5142{
5143	sighandler_t no_more_time;
5144
5145	signal(SIGALRM, no_more_time);
5146	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5147
5148	if (available_money > available_manpower) {
5149		Pay consultant to port U-Boot;
5150		return 0;
5151	}
5152
5153	Download latest U-Boot source;
5154
5155	Subscribe to u-boot mailing list;
5156
5157	if (clueless)
5158		email("Hi, I am new to U-Boot, how do I get started?");
5159
5160	while (learning) {
5161		Read the README file in the top level directory;
5162		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5163		Read applicable doc/*.README;
5164		Read the source, Luke;
5165		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5166	}
5167
5168	if (available_money > toLocalCurrency ($2500))
5169		Buy a BDI3000;
5170	else
5171		Add a lot of aggravation and time;
5172
5173	if (a similar board exists) {	/* hopefully... */
5174		cp -a board/<similar> board/<myboard>
5175		cp include/configs/<similar>.h include/configs/<myboard>.h
5176	} else {
5177		Create your own board support subdirectory;
5178		Create your own board include/configs/<myboard>.h file;
5179	}
5180	Edit new board/<myboard> files
5181	Edit new include/configs/<myboard>.h
5182
5183	while (!accepted) {
5184		while (!running) {
5185			do {
5186				Add / modify source code;
5187			} until (compiles);
5188			Debug;
5189			if (clueless)
5190				email("Hi, I am having problems...");
5191		}
5192		Send patch file to the U-Boot email list;
5193		if (reasonable critiques)
5194			Incorporate improvements from email list code review;
5195		else
5196			Defend code as written;
5197	}
5198
5199	return 0;
5200}
5201
5202void no_more_time (int sig)
5203{
5204      hire_a_guru();
5205}
5206
5207
5208Coding Standards:
5209-----------------
5210
5211All contributions to U-Boot should conform to the Linux kernel
5212coding style; see the file "Documentation/CodingStyle" and the script
5213"scripts/Lindent" in your Linux kernel source directory.
5214
5215Source files originating from a different project (for example the
5216MTD subsystem) are generally exempt from these guidelines and are not
5217reformated to ease subsequent migration to newer versions of those
5218sources.
5219
5220Please note that U-Boot is implemented in C (and to some small parts in
5221Assembler); no C++ is used, so please do not use C++ style comments (//)
5222in your code.
5223
5224Please also stick to the following formatting rules:
5225- remove any trailing white space
5226- use TAB characters for indentation and vertical alignment, not spaces
5227- make sure NOT to use DOS '\r\n' line feeds
5228- do not add more than 2 consecutive empty lines to source files
5229- do not add trailing empty lines to source files
5230
5231Submissions which do not conform to the standards may be returned
5232with a request to reformat the changes.
5233
5234
5235Submitting Patches:
5236-------------------
5237
5238Since the number of patches for U-Boot is growing, we need to
5239establish some rules. Submissions which do not conform to these rules
5240may be rejected, even when they contain important and valuable stuff.
5241
5242Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5243
5244Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5245see http://lists.denx.de/mailman/listinfo/u-boot
5246
5247When you send a patch, please include the following information with
5248it:
5249
5250* For bug fixes: a description of the bug and how your patch fixes
5251  this bug. Please try to include a way of demonstrating that the
5252  patch actually fixes something.
5253
5254* For new features: a description of the feature and your
5255  implementation.
5256
5257* A CHANGELOG entry as plaintext (separate from the patch)
5258
5259* For major contributions, your entry to the CREDITS file
5260
5261* When you add support for a new board, don't forget to add this
5262  board to the MAINTAINERS file, too.
5263
5264* If your patch adds new configuration options, don't forget to
5265  document these in the README file.
5266
5267* The patch itself. If you are using git (which is *strongly*
5268  recommended) you can easily generate the patch using the
5269  "git format-patch". If you then use "git send-email" to send it to
5270  the U-Boot mailing list, you will avoid most of the common problems
5271  with some other mail clients.
5272
5273  If you cannot use git, use "diff -purN OLD NEW". If your version of
5274  diff does not support these options, then get the latest version of
5275  GNU diff.
5276
5277  The current directory when running this command shall be the parent
5278  directory of the U-Boot source tree (i. e. please make sure that
5279  your patch includes sufficient directory information for the
5280  affected files).
5281
5282  We prefer patches as plain text. MIME attachments are discouraged,
5283  and compressed attachments must not be used.
5284
5285* If one logical set of modifications affects or creates several
5286  files, all these changes shall be submitted in a SINGLE patch file.
5287
5288* Changesets that contain different, unrelated modifications shall be
5289  submitted as SEPARATE patches, one patch per changeset.
5290
5291
5292Notes:
5293
5294* Before sending the patch, run the MAKEALL script on your patched
5295  source tree and make sure that no errors or warnings are reported
5296  for any of the boards.
5297
5298* Keep your modifications to the necessary minimum: A patch
5299  containing several unrelated changes or arbitrary reformats will be
5300  returned with a request to re-formatting / split it.
5301
5302* If you modify existing code, make sure that your new code does not
5303  add to the memory footprint of the code ;-) Small is beautiful!
5304  When adding new features, these should compile conditionally only
5305  (using #ifdef), and the resulting code with the new feature
5306  disabled must not need more memory than the old code without your
5307  modification.
5308
5309* Remember that there is a size limit of 100 kB per message on the
5310  u-boot mailing list. Bigger patches will be moderated. If they are
5311  reasonable and not too big, they will be acknowledged. But patches
5312  bigger than the size limit should be avoided.
5313