xref: /openbmc/u-boot/README (revision e5f00f0180994b7ab218e904b3426f1c66eb6da7)
1 #
2 # (C) Copyright 2000 - 2013
3 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4 #
5 # SPDX-License-Identifier:	GPL-2.0+
6 #
7 
8 Summary:
9 ========
10 
11 This directory contains the source code for U-Boot, a boot loader for
12 Embedded boards based on PowerPC, ARM, MIPS and several other
13 processors, which can be installed in a boot ROM and used to
14 initialize and test the hardware or to download and run application
15 code.
16 
17 The development of U-Boot is closely related to Linux: some parts of
18 the source code originate in the Linux source tree, we have some
19 header files in common, and special provision has been made to
20 support booting of Linux images.
21 
22 Some attention has been paid to make this software easily
23 configurable and extendable. For instance, all monitor commands are
24 implemented with the same call interface, so that it's very easy to
25 add new commands. Also, instead of permanently adding rarely used
26 code (for instance hardware test utilities) to the monitor, you can
27 load and run it dynamically.
28 
29 
30 Status:
31 =======
32 
33 In general, all boards for which a configuration option exists in the
34 Makefile have been tested to some extent and can be considered
35 "working". In fact, many of them are used in production systems.
36 
37 In case of problems see the CHANGELOG file to find out who contributed
38 the specific port. In addition, there are various MAINTAINERS files
39 scattered throughout the U-Boot source identifying the people or
40 companies responsible for various boards and subsystems.
41 
42 Note: As of August, 2010, there is no longer a CHANGELOG file in the
43 actual U-Boot source tree; however, it can be created dynamically
44 from the Git log using:
45 
46 	make CHANGELOG
47 
48 
49 Where to get help:
50 ==================
51 
52 In case you have questions about, problems with or contributions for
53 U-Boot, you should send a message to the U-Boot mailing list at
54 <u-boot@lists.denx.de>. There is also an archive of previous traffic
55 on the mailing list - please search the archive before asking FAQ's.
56 Please see http://lists.denx.de/pipermail/u-boot and
57 http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
58 
59 
60 Where to get source code:
61 =========================
62 
63 The U-Boot source code is maintained in the Git repository at
64 git://www.denx.de/git/u-boot.git ; you can browse it online at
65 http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
66 
67 The "snapshot" links on this page allow you to download tarballs of
68 any version you might be interested in. Official releases are also
69 available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
70 directory.
71 
72 Pre-built (and tested) images are available from
73 ftp://ftp.denx.de/pub/u-boot/images/
74 
75 
76 Where we come from:
77 ===================
78 
79 - start from 8xxrom sources
80 - create PPCBoot project (http://sourceforge.net/projects/ppcboot)
81 - clean up code
82 - make it easier to add custom boards
83 - make it possible to add other [PowerPC] CPUs
84 - extend functions, especially:
85   * Provide extended interface to Linux boot loader
86   * S-Record download
87   * network boot
88   * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
89 - create ARMBoot project (http://sourceforge.net/projects/armboot)
90 - add other CPU families (starting with ARM)
91 - create U-Boot project (http://sourceforge.net/projects/u-boot)
92 - current project page: see http://www.denx.de/wiki/U-Boot
93 
94 
95 Names and Spelling:
96 ===================
97 
98 The "official" name of this project is "Das U-Boot". The spelling
99 "U-Boot" shall be used in all written text (documentation, comments
100 in source files etc.). Example:
101 
102 	This is the README file for the U-Boot project.
103 
104 File names etc. shall be based on the string "u-boot". Examples:
105 
106 	include/asm-ppc/u-boot.h
107 
108 	#include <asm/u-boot.h>
109 
110 Variable names, preprocessor constants etc. shall be either based on
111 the string "u_boot" or on "U_BOOT". Example:
112 
113 	U_BOOT_VERSION		u_boot_logo
114 	IH_OS_U_BOOT		u_boot_hush_start
115 
116 
117 Versioning:
118 ===========
119 
120 Starting with the release in October 2008, the names of the releases
121 were changed from numerical release numbers without deeper meaning
122 into a time stamp based numbering. Regular releases are identified by
123 names consisting of the calendar year and month of the release date.
124 Additional fields (if present) indicate release candidates or bug fix
125 releases in "stable" maintenance trees.
126 
127 Examples:
128 	U-Boot v2009.11	    - Release November 2009
129 	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
130 	U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
131 
132 
133 Directory Hierarchy:
134 ====================
135 
136 /arch			Architecture specific files
137   /arc			Files generic to ARC architecture
138   /arm			Files generic to ARM architecture
139   /avr32		Files generic to AVR32 architecture
140   /m68k			Files generic to m68k architecture
141   /microblaze		Files generic to microblaze architecture
142   /mips			Files generic to MIPS architecture
143   /nds32		Files generic to NDS32 architecture
144   /nios2		Files generic to Altera NIOS2 architecture
145   /openrisc		Files generic to OpenRISC architecture
146   /powerpc		Files generic to PowerPC architecture
147   /sandbox		Files generic to HW-independent "sandbox"
148   /sh			Files generic to SH architecture
149   /x86			Files generic to x86 architecture
150 /api			Machine/arch independent API for external apps
151 /board			Board dependent files
152 /cmd			U-Boot commands functions
153 /common			Misc architecture independent functions
154 /configs		Board default configuration files
155 /disk			Code for disk drive partition handling
156 /doc			Documentation (don't expect too much)
157 /drivers		Commonly used device drivers
158 /dts			Contains Makefile for building internal U-Boot fdt.
159 /examples		Example code for standalone applications, etc.
160 /fs			Filesystem code (cramfs, ext2, jffs2, etc.)
161 /include		Header Files
162 /lib			Library routines generic to all architectures
163 /Licenses		Various license files
164 /net			Networking code
165 /post			Power On Self Test
166 /scripts		Various build scripts and Makefiles
167 /test			Various unit test files
168 /tools			Tools to build S-Record or U-Boot images, etc.
169 
170 Software Configuration:
171 =======================
172 
173 Configuration is usually done using C preprocessor defines; the
174 rationale behind that is to avoid dead code whenever possible.
175 
176 There are two classes of configuration variables:
177 
178 * Configuration _OPTIONS_:
179   These are selectable by the user and have names beginning with
180   "CONFIG_".
181 
182 * Configuration _SETTINGS_:
183   These depend on the hardware etc. and should not be meddled with if
184   you don't know what you're doing; they have names beginning with
185   "CONFIG_SYS_".
186 
187 Previously, all configuration was done by hand, which involved creating
188 symbolic links and editing configuration files manually. More recently,
189 U-Boot has added the Kbuild infrastructure used by the Linux kernel,
190 allowing you to use the "make menuconfig" command to configure your
191 build.
192 
193 
194 Selection of Processor Architecture and Board Type:
195 ---------------------------------------------------
196 
197 For all supported boards there are ready-to-use default
198 configurations available; just type "make <board_name>_defconfig".
199 
200 Example: For a TQM823L module type:
201 
202 	cd u-boot
203 	make TQM823L_defconfig
204 
205 Note: If you're looking for the default configuration file for a board
206 you're sure used to be there but is now missing, check the file
207 doc/README.scrapyard for a list of no longer supported boards.
208 
209 Sandbox Environment:
210 --------------------
211 
212 U-Boot can be built natively to run on a Linux host using the 'sandbox'
213 board. This allows feature development which is not board- or architecture-
214 specific to be undertaken on a native platform. The sandbox is also used to
215 run some of U-Boot's tests.
216 
217 See board/sandbox/README.sandbox for more details.
218 
219 
220 Board Initialisation Flow:
221 --------------------------
222 
223 This is the intended start-up flow for boards. This should apply for both
224 SPL and U-Boot proper (i.e. they both follow the same rules).
225 
226 Note: "SPL" stands for "Secondary Program Loader," which is explained in
227 more detail later in this file.
228 
229 At present, SPL mostly uses a separate code path, but the function names
230 and roles of each function are the same. Some boards or architectures
231 may not conform to this.  At least most ARM boards which use
232 CONFIG_SPL_FRAMEWORK conform to this.
233 
234 Execution typically starts with an architecture-specific (and possibly
235 CPU-specific) start.S file, such as:
236 
237 	- arch/arm/cpu/armv7/start.S
238 	- arch/powerpc/cpu/mpc83xx/start.S
239 	- arch/mips/cpu/start.S
240 
241 and so on. From there, three functions are called; the purpose and
242 limitations of each of these functions are described below.
243 
244 lowlevel_init():
245 	- purpose: essential init to permit execution to reach board_init_f()
246 	- no global_data or BSS
247 	- there is no stack (ARMv7 may have one but it will soon be removed)
248 	- must not set up SDRAM or use console
249 	- must only do the bare minimum to allow execution to continue to
250 		board_init_f()
251 	- this is almost never needed
252 	- return normally from this function
253 
254 board_init_f():
255 	- purpose: set up the machine ready for running board_init_r():
256 		i.e. SDRAM and serial UART
257 	- global_data is available
258 	- stack is in SRAM
259 	- BSS is not available, so you cannot use global/static variables,
260 		only stack variables and global_data
261 
262 	Non-SPL-specific notes:
263 	- dram_init() is called to set up DRAM. If already done in SPL this
264 		can do nothing
265 
266 	SPL-specific notes:
267 	- you can override the entire board_init_f() function with your own
268 		version as needed.
269 	- preloader_console_init() can be called here in extremis
270 	- should set up SDRAM, and anything needed to make the UART work
271 	- these is no need to clear BSS, it will be done by crt0.S
272 	- must return normally from this function (don't call board_init_r()
273 		directly)
274 
275 Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
276 this point the stack and global_data are relocated to below
277 CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
278 memory.
279 
280 board_init_r():
281 	- purpose: main execution, common code
282 	- global_data is available
283 	- SDRAM is available
284 	- BSS is available, all static/global variables can be used
285 	- execution eventually continues to main_loop()
286 
287 	Non-SPL-specific notes:
288 	- U-Boot is relocated to the top of memory and is now running from
289 		there.
290 
291 	SPL-specific notes:
292 	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
293 		CONFIG_SPL_STACK_R_ADDR points into SDRAM
294 	- preloader_console_init() can be called here - typically this is
295 		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
296 		spl_board_init() function containing this call
297 	- loads U-Boot or (in falcon mode) Linux
298 
299 
300 
301 Configuration Options:
302 ----------------------
303 
304 Configuration depends on the combination of board and CPU type; all
305 such information is kept in a configuration file
306 "include/configs/<board_name>.h".
307 
308 Example: For a TQM823L module, all configuration settings are in
309 "include/configs/TQM823L.h".
310 
311 
312 Many of the options are named exactly as the corresponding Linux
313 kernel configuration options. The intention is to make it easier to
314 build a config tool - later.
315 
316 
317 The following options need to be configured:
318 
319 - CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
320 
321 - Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
322 
323 - CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
324 		Define exactly one, e.g. CONFIG_ATSTK1002
325 
326 - Marvell Family Member
327 		CONFIG_SYS_MVFS		- define it if you want to enable
328 					  multiple fs option at one time
329 					  for marvell soc family
330 
331 - 8xx CPU Options: (if using an MPC8xx CPU)
332 		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
333 					  get_gclk_freq() cannot work
334 					  e.g. if there is no 32KHz
335 					  reference PIT/RTC clock
336 		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
337 					  or XTAL/EXTAL)
338 
339 - 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
340 		CONFIG_SYS_8xx_CPUCLK_MIN
341 		CONFIG_SYS_8xx_CPUCLK_MAX
342 		CONFIG_8xx_CPUCLK_DEFAULT
343 			See doc/README.MPC866
344 
345 		CONFIG_SYS_MEASURE_CPUCLK
346 
347 		Define this to measure the actual CPU clock instead
348 		of relying on the correctness of the configured
349 		values. Mostly useful for board bringup to make sure
350 		the PLL is locked at the intended frequency. Note
351 		that this requires a (stable) reference clock (32 kHz
352 		RTC clock or CONFIG_SYS_8XX_XIN)
353 
354 		CONFIG_SYS_DELAYED_ICACHE
355 
356 		Define this option if you want to enable the
357 		ICache only when Code runs from RAM.
358 
359 - 85xx CPU Options:
360 		CONFIG_SYS_PPC64
361 
362 		Specifies that the core is a 64-bit PowerPC implementation (implements
363 		the "64" category of the Power ISA). This is necessary for ePAPR
364 		compliance, among other possible reasons.
365 
366 		CONFIG_SYS_FSL_TBCLK_DIV
367 
368 		Defines the core time base clock divider ratio compared to the
369 		system clock.  On most PQ3 devices this is 8, on newer QorIQ
370 		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
371 
372 		CONFIG_SYS_FSL_PCIE_COMPAT
373 
374 		Defines the string to utilize when trying to match PCIe device
375 		tree nodes for the given platform.
376 
377 		CONFIG_SYS_FSL_ERRATUM_A004510
378 
379 		Enables a workaround for erratum A004510.  If set,
380 		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
381 		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
382 
383 		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
384 		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
385 
386 		Defines one or two SoC revisions (low 8 bits of SVR)
387 		for which the A004510 workaround should be applied.
388 
389 		The rest of SVR is either not relevant to the decision
390 		of whether the erratum is present (e.g. p2040 versus
391 		p2041) or is implied by the build target, which controls
392 		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
393 
394 		See Freescale App Note 4493 for more information about
395 		this erratum.
396 
397 		CONFIG_A003399_NOR_WORKAROUND
398 		Enables a workaround for IFC erratum A003399. It is only
399 		required during NOR boot.
400 
401 		CONFIG_A008044_WORKAROUND
402 		Enables a workaround for T1040/T1042 erratum A008044. It is only
403 		required during NAND boot and valid for Rev 1.0 SoC revision
404 
405 		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
406 
407 		This is the value to write into CCSR offset 0x18600
408 		according to the A004510 workaround.
409 
410 		CONFIG_SYS_FSL_DSP_DDR_ADDR
411 		This value denotes start offset of DDR memory which is
412 		connected exclusively to the DSP cores.
413 
414 		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
415 		This value denotes start offset of M2 memory
416 		which is directly connected to the DSP core.
417 
418 		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
419 		This value denotes start offset of M3 memory which is directly
420 		connected to the DSP core.
421 
422 		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
423 		This value denotes start offset of DSP CCSR space.
424 
425 		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
426 		Single Source Clock is clocking mode present in some of FSL SoC's.
427 		In this mode, a single differential clock is used to supply
428 		clocks to the sysclock, ddrclock and usbclock.
429 
430 		CONFIG_SYS_CPC_REINIT_F
431 		This CONFIG is defined when the CPC is configured as SRAM at the
432 		time of U-Boot entry and is required to be re-initialized.
433 
434 		CONFIG_DEEP_SLEEP
435 		Indicates this SoC supports deep sleep feature. If deep sleep is
436 		supported, core will start to execute uboot when wakes up.
437 
438 - Generic CPU options:
439 		CONFIG_SYS_GENERIC_GLOBAL_DATA
440 		Defines global data is initialized in generic board board_init_f().
441 		If this macro is defined, global data is created and cleared in
442 		generic board board_init_f(). Without this macro, architecture/board
443 		should initialize global data before calling board_init_f().
444 
445 		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
446 
447 		Defines the endianess of the CPU. Implementation of those
448 		values is arch specific.
449 
450 		CONFIG_SYS_FSL_DDR
451 		Freescale DDR driver in use. This type of DDR controller is
452 		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
453 		SoCs.
454 
455 		CONFIG_SYS_FSL_DDR_ADDR
456 		Freescale DDR memory-mapped register base.
457 
458 		CONFIG_SYS_FSL_DDR_EMU
459 		Specify emulator support for DDR. Some DDR features such as
460 		deskew training are not available.
461 
462 		CONFIG_SYS_FSL_DDRC_GEN1
463 		Freescale DDR1 controller.
464 
465 		CONFIG_SYS_FSL_DDRC_GEN2
466 		Freescale DDR2 controller.
467 
468 		CONFIG_SYS_FSL_DDRC_GEN3
469 		Freescale DDR3 controller.
470 
471 		CONFIG_SYS_FSL_DDRC_GEN4
472 		Freescale DDR4 controller.
473 
474 		CONFIG_SYS_FSL_DDRC_ARM_GEN3
475 		Freescale DDR3 controller for ARM-based SoCs.
476 
477 		CONFIG_SYS_FSL_DDR1
478 		Board config to use DDR1. It can be enabled for SoCs with
479 		Freescale DDR1 or DDR2 controllers, depending on the board
480 		implemetation.
481 
482 		CONFIG_SYS_FSL_DDR2
483 		Board config to use DDR2. It can be enabled for SoCs with
484 		Freescale DDR2 or DDR3 controllers, depending on the board
485 		implementation.
486 
487 		CONFIG_SYS_FSL_DDR3
488 		Board config to use DDR3. It can be enabled for SoCs with
489 		Freescale DDR3 or DDR3L controllers.
490 
491 		CONFIG_SYS_FSL_DDR3L
492 		Board config to use DDR3L. It can be enabled for SoCs with
493 		DDR3L controllers.
494 
495 		CONFIG_SYS_FSL_DDR4
496 		Board config to use DDR4. It can be enabled for SoCs with
497 		DDR4 controllers.
498 
499 		CONFIG_SYS_FSL_IFC_BE
500 		Defines the IFC controller register space as Big Endian
501 
502 		CONFIG_SYS_FSL_IFC_LE
503 		Defines the IFC controller register space as Little Endian
504 
505 		CONFIG_SYS_FSL_IFC_CLK_DIV
506 		Defines divider of platform clock(clock input to IFC controller).
507 
508 		CONFIG_SYS_FSL_LBC_CLK_DIV
509 		Defines divider of platform clock(clock input to eLBC controller).
510 
511 		CONFIG_SYS_FSL_PBL_PBI
512 		It enables addition of RCW (Power on reset configuration) in built image.
513 		Please refer doc/README.pblimage for more details
514 
515 		CONFIG_SYS_FSL_PBL_RCW
516 		It adds PBI(pre-boot instructions) commands in u-boot build image.
517 		PBI commands can be used to configure SoC before it starts the execution.
518 		Please refer doc/README.pblimage for more details
519 
520 		CONFIG_SPL_FSL_PBL
521 		It adds a target to create boot binary having SPL binary in PBI format
522 		concatenated with u-boot binary.
523 
524 		CONFIG_SYS_FSL_DDR_BE
525 		Defines the DDR controller register space as Big Endian
526 
527 		CONFIG_SYS_FSL_DDR_LE
528 		Defines the DDR controller register space as Little Endian
529 
530 		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
531 		Physical address from the view of DDR controllers. It is the
532 		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
533 		it could be different for ARM SoCs.
534 
535 		CONFIG_SYS_FSL_DDR_INTLV_256B
536 		DDR controller interleaving on 256-byte. This is a special
537 		interleaving mode, handled by Dickens for Freescale layerscape
538 		SoCs with ARM core.
539 
540 		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
541 		Number of controllers used as main memory.
542 
543 		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
544 		Number of controllers used for other than main memory.
545 
546 		CONFIG_SYS_FSL_HAS_DP_DDR
547 		Defines the SoC has DP-DDR used for DPAA.
548 
549 		CONFIG_SYS_FSL_SEC_BE
550 		Defines the SEC controller register space as Big Endian
551 
552 		CONFIG_SYS_FSL_SEC_LE
553 		Defines the SEC controller register space as Little Endian
554 
555 - MIPS CPU options:
556 		CONFIG_SYS_INIT_SP_OFFSET
557 
558 		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
559 		pointer. This is needed for the temporary stack before
560 		relocation.
561 
562 		CONFIG_SYS_MIPS_CACHE_MODE
563 
564 		Cache operation mode for the MIPS CPU.
565 		See also arch/mips/include/asm/mipsregs.h.
566 		Possible values are:
567 			CONF_CM_CACHABLE_NO_WA
568 			CONF_CM_CACHABLE_WA
569 			CONF_CM_UNCACHED
570 			CONF_CM_CACHABLE_NONCOHERENT
571 			CONF_CM_CACHABLE_CE
572 			CONF_CM_CACHABLE_COW
573 			CONF_CM_CACHABLE_CUW
574 			CONF_CM_CACHABLE_ACCELERATED
575 
576 		CONFIG_SYS_XWAY_EBU_BOOTCFG
577 
578 		Special option for Lantiq XWAY SoCs for booting from NOR flash.
579 		See also arch/mips/cpu/mips32/start.S.
580 
581 		CONFIG_XWAY_SWAP_BYTES
582 
583 		Enable compilation of tools/xway-swap-bytes needed for Lantiq
584 		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
585 		be swapped if a flash programmer is used.
586 
587 - ARM options:
588 		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
589 
590 		Select high exception vectors of the ARM core, e.g., do not
591 		clear the V bit of the c1 register of CP15.
592 
593 		COUNTER_FREQUENCY
594 		Generic timer clock source frequency.
595 
596 		COUNTER_FREQUENCY_REAL
597 		Generic timer clock source frequency if the real clock is
598 		different from COUNTER_FREQUENCY, and can only be determined
599 		at run time.
600 
601 - Tegra SoC options:
602 		CONFIG_TEGRA_SUPPORT_NON_SECURE
603 
604 		Support executing U-Boot in non-secure (NS) mode. Certain
605 		impossible actions will be skipped if the CPU is in NS mode,
606 		such as ARM architectural timer initialization.
607 
608 - Linux Kernel Interface:
609 		CONFIG_CLOCKS_IN_MHZ
610 
611 		U-Boot stores all clock information in Hz
612 		internally. For binary compatibility with older Linux
613 		kernels (which expect the clocks passed in the
614 		bd_info data to be in MHz) the environment variable
615 		"clocks_in_mhz" can be defined so that U-Boot
616 		converts clock data to MHZ before passing it to the
617 		Linux kernel.
618 		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
619 		"clocks_in_mhz=1" is automatically included in the
620 		default environment.
621 
622 		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
623 
624 		When transferring memsize parameter to Linux, some versions
625 		expect it to be in bytes, others in MB.
626 		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
627 
628 		CONFIG_OF_LIBFDT
629 
630 		New kernel versions are expecting firmware settings to be
631 		passed using flattened device trees (based on open firmware
632 		concepts).
633 
634 		CONFIG_OF_LIBFDT
635 		 * New libfdt-based support
636 		 * Adds the "fdt" command
637 		 * The bootm command automatically updates the fdt
638 
639 		OF_CPU - The proper name of the cpus node (only required for
640 			MPC512X and MPC5xxx based boards).
641 		OF_SOC - The proper name of the soc node (only required for
642 			MPC512X and MPC5xxx based boards).
643 		OF_TBCLK - The timebase frequency.
644 		OF_STDOUT_PATH - The path to the console device
645 
646 		boards with QUICC Engines require OF_QE to set UCC MAC
647 		addresses
648 
649 		CONFIG_OF_BOARD_SETUP
650 
651 		Board code has addition modification that it wants to make
652 		to the flat device tree before handing it off to the kernel
653 
654 		CONFIG_OF_SYSTEM_SETUP
655 
656 		Other code has addition modification that it wants to make
657 		to the flat device tree before handing it off to the kernel.
658 		This causes ft_system_setup() to be called before booting
659 		the kernel.
660 
661 		CONFIG_OF_IDE_FIXUP
662 
663 		U-Boot can detect if an IDE device is present or not.
664 		If not, and this new config option is activated, U-Boot
665 		removes the ATA node from the DTS before booting Linux,
666 		so the Linux IDE driver does not probe the device and
667 		crash. This is needed for buggy hardware (uc101) where
668 		no pull down resistor is connected to the signal IDE5V_DD7.
669 
670 		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
671 
672 		This setting is mandatory for all boards that have only one
673 		machine type and must be used to specify the machine type
674 		number as it appears in the ARM machine registry
675 		(see http://www.arm.linux.org.uk/developer/machines/).
676 		Only boards that have multiple machine types supported
677 		in a single configuration file and the machine type is
678 		runtime discoverable, do not have to use this setting.
679 
680 - vxWorks boot parameters:
681 
682 		bootvx constructs a valid bootline using the following
683 		environments variables: bootdev, bootfile, ipaddr, netmask,
684 		serverip, gatewayip, hostname, othbootargs.
685 		It loads the vxWorks image pointed bootfile.
686 
687 		Note: If a "bootargs" environment is defined, it will overwride
688 		the defaults discussed just above.
689 
690 - Cache Configuration:
691 		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
692 		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
693 		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
694 
695 - Cache Configuration for ARM:
696 		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
697 				      controller
698 		CONFIG_SYS_PL310_BASE - Physical base address of PL310
699 					controller register space
700 
701 - Serial Ports:
702 		CONFIG_PL010_SERIAL
703 
704 		Define this if you want support for Amba PrimeCell PL010 UARTs.
705 
706 		CONFIG_PL011_SERIAL
707 
708 		Define this if you want support for Amba PrimeCell PL011 UARTs.
709 
710 		CONFIG_PL011_CLOCK
711 
712 		If you have Amba PrimeCell PL011 UARTs, set this variable to
713 		the clock speed of the UARTs.
714 
715 		CONFIG_PL01x_PORTS
716 
717 		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
718 		define this to a list of base addresses for each (supported)
719 		port. See e.g. include/configs/versatile.h
720 
721 		CONFIG_SERIAL_HW_FLOW_CONTROL
722 
723 		Define this variable to enable hw flow control in serial driver.
724 		Current user of this option is drivers/serial/nsl16550.c driver
725 
726 - Console Interface:
727 		Depending on board, define exactly one serial port
728 		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
729 		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
730 		console by defining CONFIG_8xx_CONS_NONE
731 
732 		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
733 		port routines must be defined elsewhere
734 		(i.e. serial_init(), serial_getc(), ...)
735 
736 - Console Baudrate:
737 		CONFIG_BAUDRATE - in bps
738 		Select one of the baudrates listed in
739 		CONFIG_SYS_BAUDRATE_TABLE, see below.
740 		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
741 
742 - Console Rx buffer length
743 		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
744 		the maximum receive buffer length for the SMC.
745 		This option is actual only for 82xx and 8xx possible.
746 		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
747 		must be defined, to setup the maximum idle timeout for
748 		the SMC.
749 
750 - Autoboot Command:
751 		CONFIG_BOOTCOMMAND
752 		Only needed when CONFIG_BOOTDELAY is enabled;
753 		define a command string that is automatically executed
754 		when no character is read on the console interface
755 		within "Boot Delay" after reset.
756 
757 		CONFIG_BOOTARGS
758 		This can be used to pass arguments to the bootm
759 		command. The value of CONFIG_BOOTARGS goes into the
760 		environment value "bootargs".
761 
762 		CONFIG_RAMBOOT and CONFIG_NFSBOOT
763 		The value of these goes into the environment as
764 		"ramboot" and "nfsboot" respectively, and can be used
765 		as a convenience, when switching between booting from
766 		RAM and NFS.
767 
768 - Bootcount:
769 		CONFIG_BOOTCOUNT_LIMIT
770 		Implements a mechanism for detecting a repeating reboot
771 		cycle, see:
772 		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
773 
774 		CONFIG_BOOTCOUNT_ENV
775 		If no softreset save registers are found on the hardware
776 		"bootcount" is stored in the environment. To prevent a
777 		saveenv on all reboots, the environment variable
778 		"upgrade_available" is used. If "upgrade_available" is
779 		0, "bootcount" is always 0, if "upgrade_available" is
780 		1 "bootcount" is incremented in the environment.
781 		So the Userspace Applikation must set the "upgrade_available"
782 		and "bootcount" variable to 0, if a boot was successfully.
783 
784 - Pre-Boot Commands:
785 		CONFIG_PREBOOT
786 
787 		When this option is #defined, the existence of the
788 		environment variable "preboot" will be checked
789 		immediately before starting the CONFIG_BOOTDELAY
790 		countdown and/or running the auto-boot command resp.
791 		entering interactive mode.
792 
793 		This feature is especially useful when "preboot" is
794 		automatically generated or modified. For an example
795 		see the LWMON board specific code: here "preboot" is
796 		modified when the user holds down a certain
797 		combination of keys on the (special) keyboard when
798 		booting the systems
799 
800 - Serial Download Echo Mode:
801 		CONFIG_LOADS_ECHO
802 		If defined to 1, all characters received during a
803 		serial download (using the "loads" command) are
804 		echoed back. This might be needed by some terminal
805 		emulations (like "cu"), but may as well just take
806 		time on others. This setting #define's the initial
807 		value of the "loads_echo" environment variable.
808 
809 - Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
810 		CONFIG_KGDB_BAUDRATE
811 		Select one of the baudrates listed in
812 		CONFIG_SYS_BAUDRATE_TABLE, see below.
813 
814 - Monitor Functions:
815 		Monitor commands can be included or excluded
816 		from the build by using the #include files
817 		<config_cmd_all.h> and #undef'ing unwanted
818 		commands, or adding #define's for wanted commands.
819 
820 		The default command configuration includes all commands
821 		except those marked below with a "*".
822 
823 		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
824 		CONFIG_CMD_ASKENV	* ask for env variable
825 		CONFIG_CMD_BDI		  bdinfo
826 		CONFIG_CMD_BOOTD	  bootd
827 		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
828 		CONFIG_CMD_CACHE	* icache, dcache
829 		CONFIG_CMD_CONSOLE	  coninfo
830 		CONFIG_CMD_DHCP		* DHCP support
831 		CONFIG_CMD_DIAG		* Diagnostics
832 		CONFIG_CMD_ECHO		  echo arguments
833 		CONFIG_CMD_EDITENV	  edit env variable
834 		CONFIG_CMD_ELF		* bootelf, bootvx
835 		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
836 		CONFIG_CMD_EXPORTENV	* export the environment
837 		CONFIG_CMD_EXT2		* ext2 command support
838 		CONFIG_CMD_EXT4		* ext4 command support
839 		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
840 					  that work for multiple fs types
841 		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
842 		CONFIG_CMD_SAVEENV	  saveenv
843 		CONFIG_CMD_FAT		* FAT command support
844 		CONFIG_CMD_FLASH	  flinfo, erase, protect
845 		CONFIG_CMD_FPGA		  FPGA device initialization support
846 		CONFIG_CMD_GO		* the 'go' command (exec code)
847 		CONFIG_CMD_GREPENV	* search environment
848 		CONFIG_CMD_I2C		* I2C serial bus support
849 		CONFIG_CMD_IMI		  iminfo
850 		CONFIG_CMD_IMLS		  List all images found in NOR flash
851 		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
852 		CONFIG_CMD_IMPORTENV	* import an environment
853 		CONFIG_CMD_INI		* import data from an ini file into the env
854 		CONFIG_CMD_ITEST	  Integer/string test of 2 values
855 		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
856 		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
857 					  (169.254.*.*)
858 		CONFIG_CMD_LOADB	  loadb
859 		CONFIG_CMD_LOADS	  loads
860 		CONFIG_CMD_MD5SUM	* print md5 message digest
861 					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
862 		CONFIG_CMD_MEMINFO	* Display detailed memory information
863 		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
864 					  loop, loopw
865 		CONFIG_CMD_MEMTEST	* mtest
866 		CONFIG_CMD_MISC		  Misc functions like sleep etc
867 		CONFIG_CMD_MMC		* MMC memory mapped support
868 		CONFIG_CMD_MII		* MII utility commands
869 		CONFIG_CMD_MTDPARTS	* MTD partition support
870 		CONFIG_CMD_NAND		* NAND support
871 		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
872 		CONFIG_CMD_NFS		  NFS support
873 		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
874 		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
875 		CONFIG_CMD_PCI		* pciinfo
876 		CONFIG_CMD_PCMCIA		* PCMCIA support
877 		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
878 					  host
879 		CONFIG_CMD_PORTIO	* Port I/O
880 		CONFIG_CMD_READ		* Read raw data from partition
881 		CONFIG_CMD_REGINFO	* Register dump
882 		CONFIG_CMD_RUN		  run command in env variable
883 		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
884 		CONFIG_CMD_SAVES	* save S record dump
885 		CONFIG_SCSI		* SCSI Support
886 		CONFIG_CMD_SDRAM	* print SDRAM configuration information
887 					  (requires CONFIG_CMD_I2C)
888 		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
889 					  (4xx only)
890 		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
891 		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
892 		CONFIG_CMD_SOURCE	  "source" command Support
893 		CONFIG_CMD_SPI		* SPI serial bus support
894 		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
895 		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
896 		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
897 		CONFIG_CMD_TIMER	* access to the system tick timer
898 		CONFIG_CMD_USB		* USB support
899 		CONFIG_CMD_CDP		* Cisco Discover Protocol support
900 		CONFIG_CMD_MFSL		* Microblaze FSL support
901 		CONFIG_CMD_XIMG		  Load part of Multi Image
902 		CONFIG_CMD_UUID		* Generate random UUID or GUID string
903 
904 		EXAMPLE: If you want all functions except of network
905 		support you can write:
906 
907 		#include "config_cmd_all.h"
908 		#undef CONFIG_CMD_NET
909 
910 	Other Commands:
911 		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
912 
913 	Note:	Don't enable the "icache" and "dcache" commands
914 		(configuration option CONFIG_CMD_CACHE) unless you know
915 		what you (and your U-Boot users) are doing. Data
916 		cache cannot be enabled on systems like the 8xx or
917 		8260 (where accesses to the IMMR region must be
918 		uncached), and it cannot be disabled on all other
919 		systems where we (mis-) use the data cache to hold an
920 		initial stack and some data.
921 
922 
923 		XXX - this list needs to get updated!
924 
925 - Removal of commands
926 		If no commands are needed to boot, you can disable
927 		CONFIG_CMDLINE to remove them. In this case, the command line
928 		will not be available, and when U-Boot wants to execute the
929 		boot command (on start-up) it will call board_run_command()
930 		instead. This can reduce image size significantly for very
931 		simple boot procedures.
932 
933 - Regular expression support:
934 		CONFIG_REGEX
935 		If this variable is defined, U-Boot is linked against
936 		the SLRE (Super Light Regular Expression) library,
937 		which adds regex support to some commands, as for
938 		example "env grep" and "setexpr".
939 
940 - Device tree:
941 		CONFIG_OF_CONTROL
942 		If this variable is defined, U-Boot will use a device tree
943 		to configure its devices, instead of relying on statically
944 		compiled #defines in the board file. This option is
945 		experimental and only available on a few boards. The device
946 		tree is available in the global data as gd->fdt_blob.
947 
948 		U-Boot needs to get its device tree from somewhere. This can
949 		be done using one of the three options below:
950 
951 		CONFIG_OF_EMBED
952 		If this variable is defined, U-Boot will embed a device tree
953 		binary in its image. This device tree file should be in the
954 		board directory and called <soc>-<board>.dts. The binary file
955 		is then picked up in board_init_f() and made available through
956 		the global data structure as gd->blob.
957 
958 		CONFIG_OF_SEPARATE
959 		If this variable is defined, U-Boot will build a device tree
960 		binary. It will be called u-boot.dtb. Architecture-specific
961 		code will locate it at run-time. Generally this works by:
962 
963 			cat u-boot.bin u-boot.dtb >image.bin
964 
965 		and in fact, U-Boot does this for you, creating a file called
966 		u-boot-dtb.bin which is useful in the common case. You can
967 		still use the individual files if you need something more
968 		exotic.
969 
970 		CONFIG_OF_BOARD
971 		If this variable is defined, U-Boot will use the device tree
972 		provided by the board at runtime instead of embedding one with
973 		the image. Only boards defining board_fdt_blob_setup() support
974 		this option (see include/fdtdec.h file).
975 
976 - Watchdog:
977 		CONFIG_WATCHDOG
978 		If this variable is defined, it enables watchdog
979 		support for the SoC. There must be support in the SoC
980 		specific code for a watchdog. For the 8xx and 8260
981 		CPUs, the SIU Watchdog feature is enabled in the SYPCR
982 		register.  When supported for a specific SoC is
983 		available, then no further board specific code should
984 		be needed to use it.
985 
986 		CONFIG_HW_WATCHDOG
987 		When using a watchdog circuitry external to the used
988 		SoC, then define this variable and provide board
989 		specific code for the "hw_watchdog_reset" function.
990 
991 		CONFIG_AT91_HW_WDT_TIMEOUT
992 		specify the timeout in seconds. default 2 seconds.
993 
994 - U-Boot Version:
995 		CONFIG_VERSION_VARIABLE
996 		If this variable is defined, an environment variable
997 		named "ver" is created by U-Boot showing the U-Boot
998 		version as printed by the "version" command.
999 		Any change to this variable will be reverted at the
1000 		next reset.
1001 
1002 - Real-Time Clock:
1003 
1004 		When CONFIG_CMD_DATE is selected, the type of the RTC
1005 		has to be selected, too. Define exactly one of the
1006 		following options:
1007 
1008 		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1009 		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1010 		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1011 		CONFIG_RTC_MC146818	- use MC146818 RTC
1012 		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1013 		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1014 		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1015 		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1016 		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1017 		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1018 		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1019 		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1020 		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1021 					  RV3029 RTC.
1022 
1023 		Note that if the RTC uses I2C, then the I2C interface
1024 		must also be configured. See I2C Support, below.
1025 
1026 - GPIO Support:
1027 		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1028 
1029 		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1030 		chip-ngpio pairs that tell the PCA953X driver the number of
1031 		pins supported by a particular chip.
1032 
1033 		Note that if the GPIO device uses I2C, then the I2C interface
1034 		must also be configured. See I2C Support, below.
1035 
1036 - I/O tracing:
1037 		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1038 		accesses and can checksum them or write a list of them out
1039 		to memory. See the 'iotrace' command for details. This is
1040 		useful for testing device drivers since it can confirm that
1041 		the driver behaves the same way before and after a code
1042 		change. Currently this is supported on sandbox and arm. To
1043 		add support for your architecture, add '#include <iotrace.h>'
1044 		to the bottom of arch/<arch>/include/asm/io.h and test.
1045 
1046 		Example output from the 'iotrace stats' command is below.
1047 		Note that if the trace buffer is exhausted, the checksum will
1048 		still continue to operate.
1049 
1050 			iotrace is enabled
1051 			Start:  10000000	(buffer start address)
1052 			Size:   00010000	(buffer size)
1053 			Offset: 00000120	(current buffer offset)
1054 			Output: 10000120	(start + offset)
1055 			Count:  00000018	(number of trace records)
1056 			CRC32:  9526fb66	(CRC32 of all trace records)
1057 
1058 - Timestamp Support:
1059 
1060 		When CONFIG_TIMESTAMP is selected, the timestamp
1061 		(date and time) of an image is printed by image
1062 		commands like bootm or iminfo. This option is
1063 		automatically enabled when you select CONFIG_CMD_DATE .
1064 
1065 - Partition Labels (disklabels) Supported:
1066 		Zero or more of the following:
1067 		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1068 		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1069 				       Intel architecture, USB sticks, etc.
1070 		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1071 		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1072 				       bootloader.  Note 2TB partition limit; see
1073 				       disk/part_efi.c
1074 		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1075 
1076 		If IDE or SCSI support is enabled (CONFIG_IDE or
1077 		CONFIG_SCSI) you must configure support for at
1078 		least one non-MTD partition type as well.
1079 
1080 - IDE Reset method:
1081 		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1082 		board configurations files but used nowhere!
1083 
1084 		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1085 		be performed by calling the function
1086 			ide_set_reset(int reset)
1087 		which has to be defined in a board specific file
1088 
1089 - ATAPI Support:
1090 		CONFIG_ATAPI
1091 
1092 		Set this to enable ATAPI support.
1093 
1094 - LBA48 Support
1095 		CONFIG_LBA48
1096 
1097 		Set this to enable support for disks larger than 137GB
1098 		Also look at CONFIG_SYS_64BIT_LBA.
1099 		Whithout these , LBA48 support uses 32bit variables and will 'only'
1100 		support disks up to 2.1TB.
1101 
1102 		CONFIG_SYS_64BIT_LBA:
1103 			When enabled, makes the IDE subsystem use 64bit sector addresses.
1104 			Default is 32bit.
1105 
1106 - SCSI Support:
1107 		At the moment only there is only support for the
1108 		SYM53C8XX SCSI controller; define
1109 		CONFIG_SCSI_SYM53C8XX to enable it.
1110 
1111 		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1112 		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1113 		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1114 		maximum numbers of LUNs, SCSI ID's and target
1115 		devices.
1116 		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1117 
1118 		The environment variable 'scsidevs' is set to the number of
1119 		SCSI devices found during the last scan.
1120 
1121 - NETWORK Support (PCI):
1122 		CONFIG_E1000
1123 		Support for Intel 8254x/8257x gigabit chips.
1124 
1125 		CONFIG_E1000_SPI
1126 		Utility code for direct access to the SPI bus on Intel 8257x.
1127 		This does not do anything useful unless you set at least one
1128 		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1129 
1130 		CONFIG_E1000_SPI_GENERIC
1131 		Allow generic access to the SPI bus on the Intel 8257x, for
1132 		example with the "sspi" command.
1133 
1134 		CONFIG_CMD_E1000
1135 		Management command for E1000 devices.  When used on devices
1136 		with SPI support you can reprogram the EEPROM from U-Boot.
1137 
1138 		CONFIG_EEPRO100
1139 		Support for Intel 82557/82559/82559ER chips.
1140 		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1141 		write routine for first time initialisation.
1142 
1143 		CONFIG_TULIP
1144 		Support for Digital 2114x chips.
1145 		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1146 		modem chip initialisation (KS8761/QS6611).
1147 
1148 		CONFIG_NATSEMI
1149 		Support for National dp83815 chips.
1150 
1151 		CONFIG_NS8382X
1152 		Support for National dp8382[01] gigabit chips.
1153 
1154 - NETWORK Support (other):
1155 
1156 		CONFIG_DRIVER_AT91EMAC
1157 		Support for AT91RM9200 EMAC.
1158 
1159 			CONFIG_RMII
1160 			Define this to use reduced MII inteface
1161 
1162 			CONFIG_DRIVER_AT91EMAC_QUIET
1163 			If this defined, the driver is quiet.
1164 			The driver doen't show link status messages.
1165 
1166 		CONFIG_CALXEDA_XGMAC
1167 		Support for the Calxeda XGMAC device
1168 
1169 		CONFIG_LAN91C96
1170 		Support for SMSC's LAN91C96 chips.
1171 
1172 			CONFIG_LAN91C96_USE_32_BIT
1173 			Define this to enable 32 bit addressing
1174 
1175 		CONFIG_SMC91111
1176 		Support for SMSC's LAN91C111 chip
1177 
1178 			CONFIG_SMC91111_BASE
1179 			Define this to hold the physical address
1180 			of the device (I/O space)
1181 
1182 			CONFIG_SMC_USE_32_BIT
1183 			Define this if data bus is 32 bits
1184 
1185 			CONFIG_SMC_USE_IOFUNCS
1186 			Define this to use i/o functions instead of macros
1187 			(some hardware wont work with macros)
1188 
1189 		CONFIG_DRIVER_TI_EMAC
1190 		Support for davinci emac
1191 
1192 			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1193 			Define this if you have more then 3 PHYs.
1194 
1195 		CONFIG_FTGMAC100
1196 		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1197 
1198 			CONFIG_FTGMAC100_EGIGA
1199 			Define this to use GE link update with gigabit PHY.
1200 			Define this if FTGMAC100 is connected to gigabit PHY.
1201 			If your system has 10/100 PHY only, it might not occur
1202 			wrong behavior. Because PHY usually return timeout or
1203 			useless data when polling gigabit status and gigabit
1204 			control registers. This behavior won't affect the
1205 			correctnessof 10/100 link speed update.
1206 
1207 		CONFIG_SMC911X
1208 		Support for SMSC's LAN911x and LAN921x chips
1209 
1210 			CONFIG_SMC911X_BASE
1211 			Define this to hold the physical address
1212 			of the device (I/O space)
1213 
1214 			CONFIG_SMC911X_32_BIT
1215 			Define this if data bus is 32 bits
1216 
1217 			CONFIG_SMC911X_16_BIT
1218 			Define this if data bus is 16 bits. If your processor
1219 			automatically converts one 32 bit word to two 16 bit
1220 			words you may also try CONFIG_SMC911X_32_BIT.
1221 
1222 		CONFIG_SH_ETHER
1223 		Support for Renesas on-chip Ethernet controller
1224 
1225 			CONFIG_SH_ETHER_USE_PORT
1226 			Define the number of ports to be used
1227 
1228 			CONFIG_SH_ETHER_PHY_ADDR
1229 			Define the ETH PHY's address
1230 
1231 			CONFIG_SH_ETHER_CACHE_WRITEBACK
1232 			If this option is set, the driver enables cache flush.
1233 
1234 - PWM Support:
1235 		CONFIG_PWM_IMX
1236 		Support for PWM module on the imx6.
1237 
1238 - TPM Support:
1239 		CONFIG_TPM
1240 		Support TPM devices.
1241 
1242 		CONFIG_TPM_TIS_INFINEON
1243 		Support for Infineon i2c bus TPM devices. Only one device
1244 		per system is supported at this time.
1245 
1246 			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1247 			Define the burst count bytes upper limit
1248 
1249 		CONFIG_TPM_ST33ZP24
1250 		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1251 
1252 			CONFIG_TPM_ST33ZP24_I2C
1253 			Support for STMicroelectronics ST33ZP24 I2C devices.
1254 			Requires TPM_ST33ZP24 and I2C.
1255 
1256 			CONFIG_TPM_ST33ZP24_SPI
1257 			Support for STMicroelectronics ST33ZP24 SPI devices.
1258 			Requires TPM_ST33ZP24 and SPI.
1259 
1260 		CONFIG_TPM_ATMEL_TWI
1261 		Support for Atmel TWI TPM device. Requires I2C support.
1262 
1263 		CONFIG_TPM_TIS_LPC
1264 		Support for generic parallel port TPM devices. Only one device
1265 		per system is supported at this time.
1266 
1267 			CONFIG_TPM_TIS_BASE_ADDRESS
1268 			Base address where the generic TPM device is mapped
1269 			to. Contemporary x86 systems usually map it at
1270 			0xfed40000.
1271 
1272 		CONFIG_CMD_TPM
1273 		Add tpm monitor functions.
1274 		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1275 		provides monitor access to authorized functions.
1276 
1277 		CONFIG_TPM
1278 		Define this to enable the TPM support library which provides
1279 		functional interfaces to some TPM commands.
1280 		Requires support for a TPM device.
1281 
1282 		CONFIG_TPM_AUTH_SESSIONS
1283 		Define this to enable authorized functions in the TPM library.
1284 		Requires CONFIG_TPM and CONFIG_SHA1.
1285 
1286 - USB Support:
1287 		At the moment only the UHCI host controller is
1288 		supported (PIP405, MIP405, MPC5200); define
1289 		CONFIG_USB_UHCI to enable it.
1290 		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1291 		and define CONFIG_USB_STORAGE to enable the USB
1292 		storage devices.
1293 		Note:
1294 		Supported are USB Keyboards and USB Floppy drives
1295 		(TEAC FD-05PUB).
1296 		MPC5200 USB requires additional defines:
1297 			CONFIG_USB_CLOCK
1298 				for 528 MHz Clock: 0x0001bbbb
1299 			CONFIG_PSC3_USB
1300 				for USB on PSC3
1301 			CONFIG_USB_CONFIG
1302 				for differential drivers: 0x00001000
1303 				for single ended drivers: 0x00005000
1304 				for differential drivers on PSC3: 0x00000100
1305 				for single ended drivers on PSC3: 0x00004100
1306 			CONFIG_SYS_USB_EVENT_POLL
1307 				May be defined to allow interrupt polling
1308 				instead of using asynchronous interrupts
1309 
1310 		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1311 		txfilltuning field in the EHCI controller on reset.
1312 
1313 		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1314 		HW module registers.
1315 
1316 - USB Device:
1317 		Define the below if you wish to use the USB console.
1318 		Once firmware is rebuilt from a serial console issue the
1319 		command "setenv stdin usbtty; setenv stdout usbtty" and
1320 		attach your USB cable. The Unix command "dmesg" should print
1321 		it has found a new device. The environment variable usbtty
1322 		can be set to gserial or cdc_acm to enable your device to
1323 		appear to a USB host as a Linux gserial device or a
1324 		Common Device Class Abstract Control Model serial device.
1325 		If you select usbtty = gserial you should be able to enumerate
1326 		a Linux host by
1327 		# modprobe usbserial vendor=0xVendorID product=0xProductID
1328 		else if using cdc_acm, simply setting the environment
1329 		variable usbtty to be cdc_acm should suffice. The following
1330 		might be defined in YourBoardName.h
1331 
1332 			CONFIG_USB_DEVICE
1333 			Define this to build a UDC device
1334 
1335 			CONFIG_USB_TTY
1336 			Define this to have a tty type of device available to
1337 			talk to the UDC device
1338 
1339 			CONFIG_USBD_HS
1340 			Define this to enable the high speed support for usb
1341 			device and usbtty. If this feature is enabled, a routine
1342 			int is_usbd_high_speed(void)
1343 			also needs to be defined by the driver to dynamically poll
1344 			whether the enumeration has succeded at high speed or full
1345 			speed.
1346 
1347 			CONFIG_SYS_CONSOLE_IS_IN_ENV
1348 			Define this if you want stdin, stdout &/or stderr to
1349 			be set to usbtty.
1350 
1351 			mpc8xx:
1352 				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1353 				Derive USB clock from external clock "blah"
1354 				- CONFIG_SYS_USB_EXTC_CLK 0x02
1355 
1356 		If you have a USB-IF assigned VendorID then you may wish to
1357 		define your own vendor specific values either in BoardName.h
1358 		or directly in usbd_vendor_info.h. If you don't define
1359 		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1360 		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1361 		should pretend to be a Linux device to it's target host.
1362 
1363 			CONFIG_USBD_MANUFACTURER
1364 			Define this string as the name of your company for
1365 			- CONFIG_USBD_MANUFACTURER "my company"
1366 
1367 			CONFIG_USBD_PRODUCT_NAME
1368 			Define this string as the name of your product
1369 			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1370 
1371 			CONFIG_USBD_VENDORID
1372 			Define this as your assigned Vendor ID from the USB
1373 			Implementors Forum. This *must* be a genuine Vendor ID
1374 			to avoid polluting the USB namespace.
1375 			- CONFIG_USBD_VENDORID 0xFFFF
1376 
1377 			CONFIG_USBD_PRODUCTID
1378 			Define this as the unique Product ID
1379 			for your device
1380 			- CONFIG_USBD_PRODUCTID 0xFFFF
1381 
1382 - ULPI Layer Support:
1383 		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1384 		the generic ULPI layer. The generic layer accesses the ULPI PHY
1385 		via the platform viewport, so you need both the genric layer and
1386 		the viewport enabled. Currently only Chipidea/ARC based
1387 		viewport is supported.
1388 		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1389 		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1390 		If your ULPI phy needs a different reference clock than the
1391 		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1392 		the appropriate value in Hz.
1393 
1394 - MMC Support:
1395 		The MMC controller on the Intel PXA is supported. To
1396 		enable this define CONFIG_MMC. The MMC can be
1397 		accessed from the boot prompt by mapping the device
1398 		to physical memory similar to flash. Command line is
1399 		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1400 		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1401 
1402 		CONFIG_SH_MMCIF
1403 		Support for Renesas on-chip MMCIF controller
1404 
1405 			CONFIG_SH_MMCIF_ADDR
1406 			Define the base address of MMCIF registers
1407 
1408 			CONFIG_SH_MMCIF_CLK
1409 			Define the clock frequency for MMCIF
1410 
1411 		CONFIG_SUPPORT_EMMC_BOOT
1412 		Enable some additional features of the eMMC boot partitions.
1413 
1414 		CONFIG_SUPPORT_EMMC_RPMB
1415 		Enable the commands for reading, writing and programming the
1416 		key for the Replay Protection Memory Block partition in eMMC.
1417 
1418 - USB Device Firmware Update (DFU) class support:
1419 		CONFIG_USB_FUNCTION_DFU
1420 		This enables the USB portion of the DFU USB class
1421 
1422 		CONFIG_CMD_DFU
1423 		This enables the command "dfu" which is used to have
1424 		U-Boot create a DFU class device via USB.  This command
1425 		requires that the "dfu_alt_info" environment variable be
1426 		set and define the alt settings to expose to the host.
1427 
1428 		CONFIG_DFU_MMC
1429 		This enables support for exposing (e)MMC devices via DFU.
1430 
1431 		CONFIG_DFU_NAND
1432 		This enables support for exposing NAND devices via DFU.
1433 
1434 		CONFIG_DFU_RAM
1435 		This enables support for exposing RAM via DFU.
1436 		Note: DFU spec refer to non-volatile memory usage, but
1437 		allow usages beyond the scope of spec - here RAM usage,
1438 		one that would help mostly the developer.
1439 
1440 		CONFIG_SYS_DFU_DATA_BUF_SIZE
1441 		Dfu transfer uses a buffer before writing data to the
1442 		raw storage device. Make the size (in bytes) of this buffer
1443 		configurable. The size of this buffer is also configurable
1444 		through the "dfu_bufsiz" environment variable.
1445 
1446 		CONFIG_SYS_DFU_MAX_FILE_SIZE
1447 		When updating files rather than the raw storage device,
1448 		we use a static buffer to copy the file into and then write
1449 		the buffer once we've been given the whole file.  Define
1450 		this to the maximum filesize (in bytes) for the buffer.
1451 		Default is 4 MiB if undefined.
1452 
1453 		DFU_DEFAULT_POLL_TIMEOUT
1454 		Poll timeout [ms], is the timeout a device can send to the
1455 		host. The host must wait for this timeout before sending
1456 		a subsequent DFU_GET_STATUS request to the device.
1457 
1458 		DFU_MANIFEST_POLL_TIMEOUT
1459 		Poll timeout [ms], which the device sends to the host when
1460 		entering dfuMANIFEST state. Host waits this timeout, before
1461 		sending again an USB request to the device.
1462 
1463 - USB Device Android Fastboot support:
1464 		CONFIG_USB_FUNCTION_FASTBOOT
1465 		This enables the USB part of the fastboot gadget
1466 
1467 		CONFIG_CMD_FASTBOOT
1468 		This enables the command "fastboot" which enables the Android
1469 		fastboot mode for the platform's USB device. Fastboot is a USB
1470 		protocol for downloading images, flashing and device control
1471 		used on Android devices.
1472 		See doc/README.android-fastboot for more information.
1473 
1474 		CONFIG_ANDROID_BOOT_IMAGE
1475 		This enables support for booting images which use the Android
1476 		image format header.
1477 
1478 		CONFIG_FASTBOOT_BUF_ADDR
1479 		The fastboot protocol requires a large memory buffer for
1480 		downloads. Define this to the starting RAM address to use for
1481 		downloaded images.
1482 
1483 		CONFIG_FASTBOOT_BUF_SIZE
1484 		The fastboot protocol requires a large memory buffer for
1485 		downloads. This buffer should be as large as possible for a
1486 		platform. Define this to the size available RAM for fastboot.
1487 
1488 		CONFIG_FASTBOOT_FLASH
1489 		The fastboot protocol includes a "flash" command for writing
1490 		the downloaded image to a non-volatile storage device. Define
1491 		this to enable the "fastboot flash" command.
1492 
1493 		CONFIG_FASTBOOT_FLASH_MMC_DEV
1494 		The fastboot "flash" command requires additional information
1495 		regarding the non-volatile storage device. Define this to
1496 		the eMMC device that fastboot should use to store the image.
1497 
1498 		CONFIG_FASTBOOT_GPT_NAME
1499 		The fastboot "flash" command supports writing the downloaded
1500 		image to the Protective MBR and the Primary GUID Partition
1501 		Table. (Additionally, this downloaded image is post-processed
1502 		to generate and write the Backup GUID Partition Table.)
1503 		This occurs when the specified "partition name" on the
1504 		"fastboot flash" command line matches this value.
1505 		The default is "gpt" if undefined.
1506 
1507 		CONFIG_FASTBOOT_MBR_NAME
1508 		The fastboot "flash" command supports writing the downloaded
1509 		image to DOS MBR.
1510 		This occurs when the "partition name" specified on the
1511 		"fastboot flash" command line matches this value.
1512 		If not defined the default value "mbr" is used.
1513 
1514 - Journaling Flash filesystem support:
1515 		CONFIG_JFFS2_NAND
1516 		Define these for a default partition on a NAND device
1517 
1518 		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1519 		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1520 		Define these for a default partition on a NOR device
1521 
1522 - FAT(File Allocation Table) filesystem write function support:
1523 		CONFIG_FAT_WRITE
1524 
1525 		Define this to enable support for saving memory data as a
1526 		file in FAT formatted partition.
1527 
1528 		This will also enable the command "fatwrite" enabling the
1529 		user to write files to FAT.
1530 
1531 - FAT(File Allocation Table) filesystem cluster size:
1532 		CONFIG_FS_FAT_MAX_CLUSTSIZE
1533 
1534 		Define the max cluster size for fat operations else
1535 		a default value of 65536 will be defined.
1536 
1537 - Keyboard Support:
1538 		See Kconfig help for available keyboard drivers.
1539 
1540 		CONFIG_KEYBOARD
1541 
1542 		Define this to enable a custom keyboard support.
1543 		This simply calls drv_keyboard_init() which must be
1544 		defined in your board-specific files. This option is deprecated
1545 		and is only used by novena. For new boards, use driver model
1546 		instead.
1547 
1548 - Video support:
1549 		CONFIG_FSL_DIU_FB
1550 		Enable the Freescale DIU video driver.	Reference boards for
1551 		SOCs that have a DIU should define this macro to enable DIU
1552 		support, and should also define these other macros:
1553 
1554 			CONFIG_SYS_DIU_ADDR
1555 			CONFIG_VIDEO
1556 			CONFIG_CFB_CONSOLE
1557 			CONFIG_VIDEO_SW_CURSOR
1558 			CONFIG_VGA_AS_SINGLE_DEVICE
1559 			CONFIG_VIDEO_LOGO
1560 			CONFIG_VIDEO_BMP_LOGO
1561 
1562 		The DIU driver will look for the 'video-mode' environment
1563 		variable, and if defined, enable the DIU as a console during
1564 		boot.  See the documentation file doc/README.video for a
1565 		description of this variable.
1566 
1567 - LCD Support:	CONFIG_LCD
1568 
1569 		Define this to enable LCD support (for output to LCD
1570 		display); also select one of the supported displays
1571 		by defining one of these:
1572 
1573 		CONFIG_ATMEL_LCD:
1574 
1575 			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1576 
1577 		CONFIG_NEC_NL6448AC33:
1578 
1579 			NEC NL6448AC33-18. Active, color, single scan.
1580 
1581 		CONFIG_NEC_NL6448BC20
1582 
1583 			NEC NL6448BC20-08. 6.5", 640x480.
1584 			Active, color, single scan.
1585 
1586 		CONFIG_NEC_NL6448BC33_54
1587 
1588 			NEC NL6448BC33-54. 10.4", 640x480.
1589 			Active, color, single scan.
1590 
1591 		CONFIG_SHARP_16x9
1592 
1593 			Sharp 320x240. Active, color, single scan.
1594 			It isn't 16x9, and I am not sure what it is.
1595 
1596 		CONFIG_SHARP_LQ64D341
1597 
1598 			Sharp LQ64D341 display, 640x480.
1599 			Active, color, single scan.
1600 
1601 		CONFIG_HLD1045
1602 
1603 			HLD1045 display, 640x480.
1604 			Active, color, single scan.
1605 
1606 		CONFIG_OPTREX_BW
1607 
1608 			Optrex	 CBL50840-2 NF-FW 99 22 M5
1609 			or
1610 			Hitachi	 LMG6912RPFC-00T
1611 			or
1612 			Hitachi	 SP14Q002
1613 
1614 			320x240. Black & white.
1615 
1616 		CONFIG_LCD_ALIGNMENT
1617 
1618 		Normally the LCD is page-aligned (typically 4KB). If this is
1619 		defined then the LCD will be aligned to this value instead.
1620 		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1621 		here, since it is cheaper to change data cache settings on
1622 		a per-section basis.
1623 
1624 
1625 		CONFIG_LCD_ROTATION
1626 
1627 		Sometimes, for example if the display is mounted in portrait
1628 		mode or even if it's mounted landscape but rotated by 180degree,
1629 		we need to rotate our content of the display relative to the
1630 		framebuffer, so that user can read the messages which are
1631 		printed out.
1632 		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1633 		initialized with a given rotation from "vl_rot" out of
1634 		"vidinfo_t" which is provided by the board specific code.
1635 		The value for vl_rot is coded as following (matching to
1636 		fbcon=rotate:<n> linux-kernel commandline):
1637 		0 = no rotation respectively 0 degree
1638 		1 = 90 degree rotation
1639 		2 = 180 degree rotation
1640 		3 = 270 degree rotation
1641 
1642 		If CONFIG_LCD_ROTATION is not defined, the console will be
1643 		initialized with 0degree rotation.
1644 
1645 		CONFIG_LCD_BMP_RLE8
1646 
1647 		Support drawing of RLE8-compressed bitmaps on the LCD.
1648 
1649 		CONFIG_I2C_EDID
1650 
1651 		Enables an 'i2c edid' command which can read EDID
1652 		information over I2C from an attached LCD display.
1653 
1654 - Splash Screen Support: CONFIG_SPLASH_SCREEN
1655 
1656 		If this option is set, the environment is checked for
1657 		a variable "splashimage". If found, the usual display
1658 		of logo, copyright and system information on the LCD
1659 		is suppressed and the BMP image at the address
1660 		specified in "splashimage" is loaded instead. The
1661 		console is redirected to the "nulldev", too. This
1662 		allows for a "silent" boot where a splash screen is
1663 		loaded very quickly after power-on.
1664 
1665 		CONFIG_SPLASHIMAGE_GUARD
1666 
1667 		If this option is set, then U-Boot will prevent the environment
1668 		variable "splashimage" from being set to a problematic address
1669 		(see doc/README.displaying-bmps).
1670 		This option is useful for targets where, due to alignment
1671 		restrictions, an improperly aligned BMP image will cause a data
1672 		abort. If you think you will not have problems with unaligned
1673 		accesses (for example because your toolchain prevents them)
1674 		there is no need to set this option.
1675 
1676 		CONFIG_SPLASH_SCREEN_ALIGN
1677 
1678 		If this option is set the splash image can be freely positioned
1679 		on the screen. Environment variable "splashpos" specifies the
1680 		position as "x,y". If a positive number is given it is used as
1681 		number of pixel from left/top. If a negative number is given it
1682 		is used as number of pixel from right/bottom. You can also
1683 		specify 'm' for centering the image.
1684 
1685 		Example:
1686 		setenv splashpos m,m
1687 			=> image at center of screen
1688 
1689 		setenv splashpos 30,20
1690 			=> image at x = 30 and y = 20
1691 
1692 		setenv splashpos -10,m
1693 			=> vertically centered image
1694 			   at x = dspWidth - bmpWidth - 9
1695 
1696 - Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1697 
1698 		If this option is set, additionally to standard BMP
1699 		images, gzipped BMP images can be displayed via the
1700 		splashscreen support or the bmp command.
1701 
1702 - Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1703 
1704 		If this option is set, 8-bit RLE compressed BMP images
1705 		can be displayed via the splashscreen support or the
1706 		bmp command.
1707 
1708 - Compression support:
1709 		CONFIG_GZIP
1710 
1711 		Enabled by default to support gzip compressed images.
1712 
1713 		CONFIG_BZIP2
1714 
1715 		If this option is set, support for bzip2 compressed
1716 		images is included. If not, only uncompressed and gzip
1717 		compressed images are supported.
1718 
1719 		NOTE: the bzip2 algorithm requires a lot of RAM, so
1720 		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1721 		be at least 4MB.
1722 
1723 		CONFIG_LZO
1724 
1725 		If this option is set, support for LZO compressed images
1726 		is included.
1727 
1728 - MII/PHY support:
1729 		CONFIG_PHY_ADDR
1730 
1731 		The address of PHY on MII bus.
1732 
1733 		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1734 
1735 		The clock frequency of the MII bus
1736 
1737 		CONFIG_PHY_GIGE
1738 
1739 		If this option is set, support for speed/duplex
1740 		detection of gigabit PHY is included.
1741 
1742 		CONFIG_PHY_RESET_DELAY
1743 
1744 		Some PHY like Intel LXT971A need extra delay after
1745 		reset before any MII register access is possible.
1746 		For such PHY, set this option to the usec delay
1747 		required. (minimum 300usec for LXT971A)
1748 
1749 		CONFIG_PHY_CMD_DELAY (ppc4xx)
1750 
1751 		Some PHY like Intel LXT971A need extra delay after
1752 		command issued before MII status register can be read
1753 
1754 - IP address:
1755 		CONFIG_IPADDR
1756 
1757 		Define a default value for the IP address to use for
1758 		the default Ethernet interface, in case this is not
1759 		determined through e.g. bootp.
1760 		(Environment variable "ipaddr")
1761 
1762 - Server IP address:
1763 		CONFIG_SERVERIP
1764 
1765 		Defines a default value for the IP address of a TFTP
1766 		server to contact when using the "tftboot" command.
1767 		(Environment variable "serverip")
1768 
1769 		CONFIG_KEEP_SERVERADDR
1770 
1771 		Keeps the server's MAC address, in the env 'serveraddr'
1772 		for passing to bootargs (like Linux's netconsole option)
1773 
1774 - Gateway IP address:
1775 		CONFIG_GATEWAYIP
1776 
1777 		Defines a default value for the IP address of the
1778 		default router where packets to other networks are
1779 		sent to.
1780 		(Environment variable "gatewayip")
1781 
1782 - Subnet mask:
1783 		CONFIG_NETMASK
1784 
1785 		Defines a default value for the subnet mask (or
1786 		routing prefix) which is used to determine if an IP
1787 		address belongs to the local subnet or needs to be
1788 		forwarded through a router.
1789 		(Environment variable "netmask")
1790 
1791 - Multicast TFTP Mode:
1792 		CONFIG_MCAST_TFTP
1793 
1794 		Defines whether you want to support multicast TFTP as per
1795 		rfc-2090; for example to work with atftp.  Lets lots of targets
1796 		tftp down the same boot image concurrently.  Note: the Ethernet
1797 		driver in use must provide a function: mcast() to join/leave a
1798 		multicast group.
1799 
1800 - BOOTP Recovery Mode:
1801 		CONFIG_BOOTP_RANDOM_DELAY
1802 
1803 		If you have many targets in a network that try to
1804 		boot using BOOTP, you may want to avoid that all
1805 		systems send out BOOTP requests at precisely the same
1806 		moment (which would happen for instance at recovery
1807 		from a power failure, when all systems will try to
1808 		boot, thus flooding the BOOTP server. Defining
1809 		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1810 		inserted before sending out BOOTP requests. The
1811 		following delays are inserted then:
1812 
1813 		1st BOOTP request:	delay 0 ... 1 sec
1814 		2nd BOOTP request:	delay 0 ... 2 sec
1815 		3rd BOOTP request:	delay 0 ... 4 sec
1816 		4th and following
1817 		BOOTP requests:		delay 0 ... 8 sec
1818 
1819 		CONFIG_BOOTP_ID_CACHE_SIZE
1820 
1821 		BOOTP packets are uniquely identified using a 32-bit ID. The
1822 		server will copy the ID from client requests to responses and
1823 		U-Boot will use this to determine if it is the destination of
1824 		an incoming response. Some servers will check that addresses
1825 		aren't in use before handing them out (usually using an ARP
1826 		ping) and therefore take up to a few hundred milliseconds to
1827 		respond. Network congestion may also influence the time it
1828 		takes for a response to make it back to the client. If that
1829 		time is too long, U-Boot will retransmit requests. In order
1830 		to allow earlier responses to still be accepted after these
1831 		retransmissions, U-Boot's BOOTP client keeps a small cache of
1832 		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1833 		cache. The default is to keep IDs for up to four outstanding
1834 		requests. Increasing this will allow U-Boot to accept offers
1835 		from a BOOTP client in networks with unusually high latency.
1836 
1837 - DHCP Advanced Options:
1838 		You can fine tune the DHCP functionality by defining
1839 		CONFIG_BOOTP_* symbols:
1840 
1841 		CONFIG_BOOTP_SUBNETMASK
1842 		CONFIG_BOOTP_GATEWAY
1843 		CONFIG_BOOTP_HOSTNAME
1844 		CONFIG_BOOTP_NISDOMAIN
1845 		CONFIG_BOOTP_BOOTPATH
1846 		CONFIG_BOOTP_BOOTFILESIZE
1847 		CONFIG_BOOTP_DNS
1848 		CONFIG_BOOTP_DNS2
1849 		CONFIG_BOOTP_SEND_HOSTNAME
1850 		CONFIG_BOOTP_NTPSERVER
1851 		CONFIG_BOOTP_TIMEOFFSET
1852 		CONFIG_BOOTP_VENDOREX
1853 		CONFIG_BOOTP_MAY_FAIL
1854 
1855 		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1856 		environment variable, not the BOOTP server.
1857 
1858 		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1859 		after the configured retry count, the call will fail
1860 		instead of starting over.  This can be used to fail over
1861 		to Link-local IP address configuration if the DHCP server
1862 		is not available.
1863 
1864 		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1865 		serverip from a DHCP server, it is possible that more
1866 		than one DNS serverip is offered to the client.
1867 		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1868 		serverip will be stored in the additional environment
1869 		variable "dnsip2". The first DNS serverip is always
1870 		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1871 		is defined.
1872 
1873 		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1874 		to do a dynamic update of a DNS server. To do this, they
1875 		need the hostname of the DHCP requester.
1876 		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1877 		of the "hostname" environment variable is passed as
1878 		option 12 to the DHCP server.
1879 
1880 		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1881 
1882 		A 32bit value in microseconds for a delay between
1883 		receiving a "DHCP Offer" and sending the "DHCP Request".
1884 		This fixes a problem with certain DHCP servers that don't
1885 		respond 100% of the time to a "DHCP request". E.g. On an
1886 		AT91RM9200 processor running at 180MHz, this delay needed
1887 		to be *at least* 15,000 usec before a Windows Server 2003
1888 		DHCP server would reply 100% of the time. I recommend at
1889 		least 50,000 usec to be safe. The alternative is to hope
1890 		that one of the retries will be successful but note that
1891 		the DHCP timeout and retry process takes a longer than
1892 		this delay.
1893 
1894  - Link-local IP address negotiation:
1895 		Negotiate with other link-local clients on the local network
1896 		for an address that doesn't require explicit configuration.
1897 		This is especially useful if a DHCP server cannot be guaranteed
1898 		to exist in all environments that the device must operate.
1899 
1900 		See doc/README.link-local for more information.
1901 
1902  - CDP Options:
1903 		CONFIG_CDP_DEVICE_ID
1904 
1905 		The device id used in CDP trigger frames.
1906 
1907 		CONFIG_CDP_DEVICE_ID_PREFIX
1908 
1909 		A two character string which is prefixed to the MAC address
1910 		of the device.
1911 
1912 		CONFIG_CDP_PORT_ID
1913 
1914 		A printf format string which contains the ascii name of
1915 		the port. Normally is set to "eth%d" which sets
1916 		eth0 for the first Ethernet, eth1 for the second etc.
1917 
1918 		CONFIG_CDP_CAPABILITIES
1919 
1920 		A 32bit integer which indicates the device capabilities;
1921 		0x00000010 for a normal host which does not forwards.
1922 
1923 		CONFIG_CDP_VERSION
1924 
1925 		An ascii string containing the version of the software.
1926 
1927 		CONFIG_CDP_PLATFORM
1928 
1929 		An ascii string containing the name of the platform.
1930 
1931 		CONFIG_CDP_TRIGGER
1932 
1933 		A 32bit integer sent on the trigger.
1934 
1935 		CONFIG_CDP_POWER_CONSUMPTION
1936 
1937 		A 16bit integer containing the power consumption of the
1938 		device in .1 of milliwatts.
1939 
1940 		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1941 
1942 		A byte containing the id of the VLAN.
1943 
1944 - Status LED:	CONFIG_LED_STATUS
1945 
1946 		Several configurations allow to display the current
1947 		status using a LED. For instance, the LED will blink
1948 		fast while running U-Boot code, stop blinking as
1949 		soon as a reply to a BOOTP request was received, and
1950 		start blinking slow once the Linux kernel is running
1951 		(supported by a status LED driver in the Linux
1952 		kernel). Defining CONFIG_LED_STATUS enables this
1953 		feature in U-Boot.
1954 
1955 		Additional options:
1956 
1957 		CONFIG_LED_STATUS_GPIO
1958 		The status LED can be connected to a GPIO pin.
1959 		In such cases, the gpio_led driver can be used as a
1960 		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1961 		to include the gpio_led driver in the U-Boot binary.
1962 
1963 		CONFIG_GPIO_LED_INVERTED_TABLE
1964 		Some GPIO connected LEDs may have inverted polarity in which
1965 		case the GPIO high value corresponds to LED off state and
1966 		GPIO low value corresponds to LED on state.
1967 		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1968 		with a list of GPIO LEDs that have inverted polarity.
1969 
1970 - CAN Support:	CONFIG_CAN_DRIVER
1971 
1972 		Defining CONFIG_CAN_DRIVER enables CAN driver support
1973 		on those systems that support this (optional)
1974 		feature, like the TQM8xxL modules.
1975 
1976 - I2C Support:	CONFIG_SYS_I2C
1977 
1978 		This enable the NEW i2c subsystem, and will allow you to use
1979 		i2c commands at the u-boot command line (as long as you set
1980 		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1981 		based realtime clock chips or other i2c devices. See
1982 		common/cmd_i2c.c for a description of the command line
1983 		interface.
1984 
1985 		ported i2c driver to the new framework:
1986 		- drivers/i2c/soft_i2c.c:
1987 		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1988 		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1989 		    for defining speed and slave address
1990 		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1991 		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1992 		    for defining speed and slave address
1993 		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1994 		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1995 		    for defining speed and slave address
1996 		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1997 		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1998 		    for defining speed and slave address
1999 
2000 		- drivers/i2c/fsl_i2c.c:
2001 		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2002 		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2003 		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2004 		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2005 		    bus.
2006 		  - If your board supports a second fsl i2c bus, define
2007 		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2008 		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2009 		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2010 		    second bus.
2011 
2012 		- drivers/i2c/tegra_i2c.c:
2013 		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2014 		  - This driver adds 4 i2c buses with a fix speed from
2015 		    100000 and the slave addr 0!
2016 
2017 		- drivers/i2c/ppc4xx_i2c.c
2018 		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2019 		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2020 		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2021 
2022 		- drivers/i2c/i2c_mxc.c
2023 		  - activate this driver with CONFIG_SYS_I2C_MXC
2024 		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
2025 		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
2026 		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
2027 		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
2028 		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2029 		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2030 		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2031 		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2032 		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2033 		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2034 		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
2035 		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
2036 		If those defines are not set, default value is 100000
2037 		for speed, and 0 for slave.
2038 
2039 		- drivers/i2c/rcar_i2c.c:
2040 		  - activate this driver with CONFIG_SYS_I2C_RCAR
2041 		  - This driver adds 4 i2c buses
2042 
2043 		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2044 		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2045 		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2046 		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2047 		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2048 		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2049 		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2050 		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2051 		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2052 
2053 		- drivers/i2c/sh_i2c.c:
2054 		  - activate this driver with CONFIG_SYS_I2C_SH
2055 		  - This driver adds from 2 to 5 i2c buses
2056 
2057 		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2058 		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2059 		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2060 		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2061 		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2062 		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2063 		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2064 		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2065 		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2066 		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2067 		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2068 
2069 		- drivers/i2c/omap24xx_i2c.c
2070 		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2071 		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2072 		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2073 		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2074 		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2075 		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2076 		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2077 		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2078 		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2079 		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2080 		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2081 
2082 		- drivers/i2c/zynq_i2c.c
2083 		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2084 		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2085 		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2086 
2087 		- drivers/i2c/s3c24x0_i2c.c:
2088 		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2089 		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2090 		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2091 		    with a fix speed from 100000 and the slave addr 0!
2092 
2093 		- drivers/i2c/ihs_i2c.c
2094 		  - activate this driver with CONFIG_SYS_I2C_IHS
2095 		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2096 		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2097 		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2098 		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2099 		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2100 		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2101 		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2102 		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2103 		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2104 		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2105 		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2106 		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2107 		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
2108 		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
2109 		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
2110 		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
2111 		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
2112 		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
2113 		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
2114 		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
2115 		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
2116 
2117 		additional defines:
2118 
2119 		CONFIG_SYS_NUM_I2C_BUSES
2120 		Hold the number of i2c buses you want to use.
2121 
2122 		CONFIG_SYS_I2C_DIRECT_BUS
2123 		define this, if you don't use i2c muxes on your hardware.
2124 		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2125 		omit this define.
2126 
2127 		CONFIG_SYS_I2C_MAX_HOPS
2128 		define how many muxes are maximal consecutively connected
2129 		on one i2c bus. If you not use i2c muxes, omit this
2130 		define.
2131 
2132 		CONFIG_SYS_I2C_BUSES
2133 		hold a list of buses you want to use, only used if
2134 		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2135 		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2136 		CONFIG_SYS_NUM_I2C_BUSES = 9:
2137 
2138 		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2139 					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2140 					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2141 					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2142 					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2143 					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2144 					{1, {I2C_NULL_HOP}}, \
2145 					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2146 					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2147 					}
2148 
2149 		which defines
2150 			bus 0 on adapter 0 without a mux
2151 			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2152 			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2153 			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2154 			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2155 			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2156 			bus 6 on adapter 1 without a mux
2157 			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2158 			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2159 
2160 		If you do not have i2c muxes on your board, omit this define.
2161 
2162 - Legacy I2C Support:
2163 		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2164 		then the following macros need to be defined (examples are
2165 		from include/configs/lwmon.h):
2166 
2167 		I2C_INIT
2168 
2169 		(Optional). Any commands necessary to enable the I2C
2170 		controller or configure ports.
2171 
2172 		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2173 
2174 		I2C_PORT
2175 
2176 		(Only for MPC8260 CPU). The I/O port to use (the code
2177 		assumes both bits are on the same port). Valid values
2178 		are 0..3 for ports A..D.
2179 
2180 		I2C_ACTIVE
2181 
2182 		The code necessary to make the I2C data line active
2183 		(driven).  If the data line is open collector, this
2184 		define can be null.
2185 
2186 		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2187 
2188 		I2C_TRISTATE
2189 
2190 		The code necessary to make the I2C data line tri-stated
2191 		(inactive).  If the data line is open collector, this
2192 		define can be null.
2193 
2194 		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2195 
2196 		I2C_READ
2197 
2198 		Code that returns true if the I2C data line is high,
2199 		false if it is low.
2200 
2201 		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2202 
2203 		I2C_SDA(bit)
2204 
2205 		If <bit> is true, sets the I2C data line high. If it
2206 		is false, it clears it (low).
2207 
2208 		eg: #define I2C_SDA(bit) \
2209 			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2210 			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2211 
2212 		I2C_SCL(bit)
2213 
2214 		If <bit> is true, sets the I2C clock line high. If it
2215 		is false, it clears it (low).
2216 
2217 		eg: #define I2C_SCL(bit) \
2218 			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2219 			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2220 
2221 		I2C_DELAY
2222 
2223 		This delay is invoked four times per clock cycle so this
2224 		controls the rate of data transfer.  The data rate thus
2225 		is 1 / (I2C_DELAY * 4). Often defined to be something
2226 		like:
2227 
2228 		#define I2C_DELAY  udelay(2)
2229 
2230 		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2231 
2232 		If your arch supports the generic GPIO framework (asm/gpio.h),
2233 		then you may alternatively define the two GPIOs that are to be
2234 		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2235 		have GPIO-based defaults assigned to them as appropriate.
2236 
2237 		You should define these to the GPIO value as given directly to
2238 		the generic GPIO functions.
2239 
2240 		CONFIG_SYS_I2C_INIT_BOARD
2241 
2242 		When a board is reset during an i2c bus transfer
2243 		chips might think that the current transfer is still
2244 		in progress. On some boards it is possible to access
2245 		the i2c SCLK line directly, either by using the
2246 		processor pin as a GPIO or by having a second pin
2247 		connected to the bus. If this option is defined a
2248 		custom i2c_init_board() routine in boards/xxx/board.c
2249 		is run early in the boot sequence.
2250 
2251 		CONFIG_I2C_MULTI_BUS
2252 
2253 		This option allows the use of multiple I2C buses, each of which
2254 		must have a controller.	 At any point in time, only one bus is
2255 		active.	 To switch to a different bus, use the 'i2c dev' command.
2256 		Note that bus numbering is zero-based.
2257 
2258 		CONFIG_SYS_I2C_NOPROBES
2259 
2260 		This option specifies a list of I2C devices that will be skipped
2261 		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2262 		is set, specify a list of bus-device pairs.  Otherwise, specify
2263 		a 1D array of device addresses
2264 
2265 		e.g.
2266 			#undef	CONFIG_I2C_MULTI_BUS
2267 			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2268 
2269 		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2270 
2271 			#define CONFIG_I2C_MULTI_BUS
2272 			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2273 
2274 		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2275 
2276 		CONFIG_SYS_SPD_BUS_NUM
2277 
2278 		If defined, then this indicates the I2C bus number for DDR SPD.
2279 		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2280 
2281 		CONFIG_SYS_RTC_BUS_NUM
2282 
2283 		If defined, then this indicates the I2C bus number for the RTC.
2284 		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2285 
2286 		CONFIG_SOFT_I2C_READ_REPEATED_START
2287 
2288 		defining this will force the i2c_read() function in
2289 		the soft_i2c driver to perform an I2C repeated start
2290 		between writing the address pointer and reading the
2291 		data.  If this define is omitted the default behaviour
2292 		of doing a stop-start sequence will be used.  Most I2C
2293 		devices can use either method, but some require one or
2294 		the other.
2295 
2296 - SPI Support:	CONFIG_SPI
2297 
2298 		Enables SPI driver (so far only tested with
2299 		SPI EEPROM, also an instance works with Crystal A/D and
2300 		D/As on the SACSng board)
2301 
2302 		CONFIG_SH_SPI
2303 
2304 		Enables the driver for SPI controller on SuperH. Currently
2305 		only SH7757 is supported.
2306 
2307 		CONFIG_SOFT_SPI
2308 
2309 		Enables a software (bit-bang) SPI driver rather than
2310 		using hardware support. This is a general purpose
2311 		driver that only requires three general I/O port pins
2312 		(two outputs, one input) to function. If this is
2313 		defined, the board configuration must define several
2314 		SPI configuration items (port pins to use, etc). For
2315 		an example, see include/configs/sacsng.h.
2316 
2317 		CONFIG_HARD_SPI
2318 
2319 		Enables a hardware SPI driver for general-purpose reads
2320 		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2321 		must define a list of chip-select function pointers.
2322 		Currently supported on some MPC8xxx processors.	 For an
2323 		example, see include/configs/mpc8349emds.h.
2324 
2325 		CONFIG_MXC_SPI
2326 
2327 		Enables the driver for the SPI controllers on i.MX and MXC
2328 		SoCs. Currently i.MX31/35/51 are supported.
2329 
2330 		CONFIG_SYS_SPI_MXC_WAIT
2331 		Timeout for waiting until spi transfer completed.
2332 		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2333 
2334 - FPGA Support: CONFIG_FPGA
2335 
2336 		Enables FPGA subsystem.
2337 
2338 		CONFIG_FPGA_<vendor>
2339 
2340 		Enables support for specific chip vendors.
2341 		(ALTERA, XILINX)
2342 
2343 		CONFIG_FPGA_<family>
2344 
2345 		Enables support for FPGA family.
2346 		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2347 
2348 		CONFIG_FPGA_COUNT
2349 
2350 		Specify the number of FPGA devices to support.
2351 
2352 		CONFIG_SYS_FPGA_PROG_FEEDBACK
2353 
2354 		Enable printing of hash marks during FPGA configuration.
2355 
2356 		CONFIG_SYS_FPGA_CHECK_BUSY
2357 
2358 		Enable checks on FPGA configuration interface busy
2359 		status by the configuration function. This option
2360 		will require a board or device specific function to
2361 		be written.
2362 
2363 		CONFIG_FPGA_DELAY
2364 
2365 		If defined, a function that provides delays in the FPGA
2366 		configuration driver.
2367 
2368 		CONFIG_SYS_FPGA_CHECK_CTRLC
2369 		Allow Control-C to interrupt FPGA configuration
2370 
2371 		CONFIG_SYS_FPGA_CHECK_ERROR
2372 
2373 		Check for configuration errors during FPGA bitfile
2374 		loading. For example, abort during Virtex II
2375 		configuration if the INIT_B line goes low (which
2376 		indicated a CRC error).
2377 
2378 		CONFIG_SYS_FPGA_WAIT_INIT
2379 
2380 		Maximum time to wait for the INIT_B line to de-assert
2381 		after PROB_B has been de-asserted during a Virtex II
2382 		FPGA configuration sequence. The default time is 500
2383 		ms.
2384 
2385 		CONFIG_SYS_FPGA_WAIT_BUSY
2386 
2387 		Maximum time to wait for BUSY to de-assert during
2388 		Virtex II FPGA configuration. The default is 5 ms.
2389 
2390 		CONFIG_SYS_FPGA_WAIT_CONFIG
2391 
2392 		Time to wait after FPGA configuration. The default is
2393 		200 ms.
2394 
2395 - Configuration Management:
2396 		CONFIG_BUILD_TARGET
2397 
2398 		Some SoCs need special image types (e.g. U-Boot binary
2399 		with a special header) as build targets. By defining
2400 		CONFIG_BUILD_TARGET in the SoC / board header, this
2401 		special image will be automatically built upon calling
2402 		make / buildman.
2403 
2404 		CONFIG_IDENT_STRING
2405 
2406 		If defined, this string will be added to the U-Boot
2407 		version information (U_BOOT_VERSION)
2408 
2409 - Vendor Parameter Protection:
2410 
2411 		U-Boot considers the values of the environment
2412 		variables "serial#" (Board Serial Number) and
2413 		"ethaddr" (Ethernet Address) to be parameters that
2414 		are set once by the board vendor / manufacturer, and
2415 		protects these variables from casual modification by
2416 		the user. Once set, these variables are read-only,
2417 		and write or delete attempts are rejected. You can
2418 		change this behaviour:
2419 
2420 		If CONFIG_ENV_OVERWRITE is #defined in your config
2421 		file, the write protection for vendor parameters is
2422 		completely disabled. Anybody can change or delete
2423 		these parameters.
2424 
2425 		Alternatively, if you define _both_ an ethaddr in the
2426 		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2427 		Ethernet address is installed in the environment,
2428 		which can be changed exactly ONCE by the user. [The
2429 		serial# is unaffected by this, i. e. it remains
2430 		read-only.]
2431 
2432 		The same can be accomplished in a more flexible way
2433 		for any variable by configuring the type of access
2434 		to allow for those variables in the ".flags" variable
2435 		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2436 
2437 - Protected RAM:
2438 		CONFIG_PRAM
2439 
2440 		Define this variable to enable the reservation of
2441 		"protected RAM", i. e. RAM which is not overwritten
2442 		by U-Boot. Define CONFIG_PRAM to hold the number of
2443 		kB you want to reserve for pRAM. You can overwrite
2444 		this default value by defining an environment
2445 		variable "pram" to the number of kB you want to
2446 		reserve. Note that the board info structure will
2447 		still show the full amount of RAM. If pRAM is
2448 		reserved, a new environment variable "mem" will
2449 		automatically be defined to hold the amount of
2450 		remaining RAM in a form that can be passed as boot
2451 		argument to Linux, for instance like that:
2452 
2453 			setenv bootargs ... mem=\${mem}
2454 			saveenv
2455 
2456 		This way you can tell Linux not to use this memory,
2457 		either, which results in a memory region that will
2458 		not be affected by reboots.
2459 
2460 		*WARNING* If your board configuration uses automatic
2461 		detection of the RAM size, you must make sure that
2462 		this memory test is non-destructive. So far, the
2463 		following board configurations are known to be
2464 		"pRAM-clean":
2465 
2466 			IVMS8, IVML24, SPD8xx, TQM8xxL,
2467 			HERMES, IP860, RPXlite, LWMON,
2468 			FLAGADM, TQM8260
2469 
2470 - Access to physical memory region (> 4GB)
2471 		Some basic support is provided for operations on memory not
2472 		normally accessible to U-Boot - e.g. some architectures
2473 		support access to more than 4GB of memory on 32-bit
2474 		machines using physical address extension or similar.
2475 		Define CONFIG_PHYSMEM to access this basic support, which
2476 		currently only supports clearing the memory.
2477 
2478 - Error Recovery:
2479 		CONFIG_PANIC_HANG
2480 
2481 		Define this variable to stop the system in case of a
2482 		fatal error, so that you have to reset it manually.
2483 		This is probably NOT a good idea for an embedded
2484 		system where you want the system to reboot
2485 		automatically as fast as possible, but it may be
2486 		useful during development since you can try to debug
2487 		the conditions that lead to the situation.
2488 
2489 		CONFIG_NET_RETRY_COUNT
2490 
2491 		This variable defines the number of retries for
2492 		network operations like ARP, RARP, TFTP, or BOOTP
2493 		before giving up the operation. If not defined, a
2494 		default value of 5 is used.
2495 
2496 		CONFIG_ARP_TIMEOUT
2497 
2498 		Timeout waiting for an ARP reply in milliseconds.
2499 
2500 		CONFIG_NFS_TIMEOUT
2501 
2502 		Timeout in milliseconds used in NFS protocol.
2503 		If you encounter "ERROR: Cannot umount" in nfs command,
2504 		try longer timeout such as
2505 		#define CONFIG_NFS_TIMEOUT 10000UL
2506 
2507 - Command Interpreter:
2508 		CONFIG_AUTO_COMPLETE
2509 
2510 		Enable auto completion of commands using TAB.
2511 
2512 		CONFIG_SYS_PROMPT_HUSH_PS2
2513 
2514 		This defines the secondary prompt string, which is
2515 		printed when the command interpreter needs more input
2516 		to complete a command. Usually "> ".
2517 
2518 	Note:
2519 
2520 		In the current implementation, the local variables
2521 		space and global environment variables space are
2522 		separated. Local variables are those you define by
2523 		simply typing `name=value'. To access a local
2524 		variable later on, you have write `$name' or
2525 		`${name}'; to execute the contents of a variable
2526 		directly type `$name' at the command prompt.
2527 
2528 		Global environment variables are those you use
2529 		setenv/printenv to work with. To run a command stored
2530 		in such a variable, you need to use the run command,
2531 		and you must not use the '$' sign to access them.
2532 
2533 		To store commands and special characters in a
2534 		variable, please use double quotation marks
2535 		surrounding the whole text of the variable, instead
2536 		of the backslashes before semicolons and special
2537 		symbols.
2538 
2539 - Command Line Editing and History:
2540 		CONFIG_CMDLINE_EDITING
2541 
2542 		Enable editing and History functions for interactive
2543 		command line input operations
2544 
2545 - Command Line PS1/PS2 support:
2546 		CONFIG_CMDLINE_PS_SUPPORT
2547 
2548 		Enable support for changing the command prompt string
2549 		at run-time. Only static string is supported so far.
2550 		The string is obtained from environment variables PS1
2551 		and PS2.
2552 
2553 - Default Environment:
2554 		CONFIG_EXTRA_ENV_SETTINGS
2555 
2556 		Define this to contain any number of null terminated
2557 		strings (variable = value pairs) that will be part of
2558 		the default environment compiled into the boot image.
2559 
2560 		For example, place something like this in your
2561 		board's config file:
2562 
2563 		#define CONFIG_EXTRA_ENV_SETTINGS \
2564 			"myvar1=value1\0" \
2565 			"myvar2=value2\0"
2566 
2567 		Warning: This method is based on knowledge about the
2568 		internal format how the environment is stored by the
2569 		U-Boot code. This is NOT an official, exported
2570 		interface! Although it is unlikely that this format
2571 		will change soon, there is no guarantee either.
2572 		You better know what you are doing here.
2573 
2574 		Note: overly (ab)use of the default environment is
2575 		discouraged. Make sure to check other ways to preset
2576 		the environment like the "source" command or the
2577 		boot command first.
2578 
2579 		CONFIG_ENV_VARS_UBOOT_CONFIG
2580 
2581 		Define this in order to add variables describing the
2582 		U-Boot build configuration to the default environment.
2583 		These will be named arch, cpu, board, vendor, and soc.
2584 
2585 		Enabling this option will cause the following to be defined:
2586 
2587 		- CONFIG_SYS_ARCH
2588 		- CONFIG_SYS_CPU
2589 		- CONFIG_SYS_BOARD
2590 		- CONFIG_SYS_VENDOR
2591 		- CONFIG_SYS_SOC
2592 
2593 		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2594 
2595 		Define this in order to add variables describing certain
2596 		run-time determined information about the hardware to the
2597 		environment.  These will be named board_name, board_rev.
2598 
2599 		CONFIG_DELAY_ENVIRONMENT
2600 
2601 		Normally the environment is loaded when the board is
2602 		initialised so that it is available to U-Boot. This inhibits
2603 		that so that the environment is not available until
2604 		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2605 		this is instead controlled by the value of
2606 		/config/load-environment.
2607 
2608 - DataFlash Support:
2609 		CONFIG_HAS_DATAFLASH
2610 
2611 		Defining this option enables DataFlash features and
2612 		allows to read/write in Dataflash via the standard
2613 		commands cp, md...
2614 
2615 - Serial Flash support
2616 		CONFIG_CMD_SF
2617 
2618 		Defining this option enables SPI flash commands
2619 		'sf probe/read/write/erase/update'.
2620 
2621 		Usage requires an initial 'probe' to define the serial
2622 		flash parameters, followed by read/write/erase/update
2623 		commands.
2624 
2625 		The following defaults may be provided by the platform
2626 		to handle the common case when only a single serial
2627 		flash is present on the system.
2628 
2629 		CONFIG_SF_DEFAULT_BUS		Bus identifier
2630 		CONFIG_SF_DEFAULT_CS		Chip-select
2631 		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2632 		CONFIG_SF_DEFAULT_SPEED		in Hz
2633 
2634 		CONFIG_CMD_SF_TEST
2635 
2636 		Define this option to include a destructive SPI flash
2637 		test ('sf test').
2638 
2639 		CONFIG_SF_DUAL_FLASH		Dual flash memories
2640 
2641 		Define this option to use dual flash support where two flash
2642 		memories can be connected with a given cs line.
2643 		Currently Xilinx Zynq qspi supports these type of connections.
2644 
2645 - SystemACE Support:
2646 		CONFIG_SYSTEMACE
2647 
2648 		Adding this option adds support for Xilinx SystemACE
2649 		chips attached via some sort of local bus. The address
2650 		of the chip must also be defined in the
2651 		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2652 
2653 		#define CONFIG_SYSTEMACE
2654 		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2655 
2656 		When SystemACE support is added, the "ace" device type
2657 		becomes available to the fat commands, i.e. fatls.
2658 
2659 - TFTP Fixed UDP Port:
2660 		CONFIG_TFTP_PORT
2661 
2662 		If this is defined, the environment variable tftpsrcp
2663 		is used to supply the TFTP UDP source port value.
2664 		If tftpsrcp isn't defined, the normal pseudo-random port
2665 		number generator is used.
2666 
2667 		Also, the environment variable tftpdstp is used to supply
2668 		the TFTP UDP destination port value.  If tftpdstp isn't
2669 		defined, the normal port 69 is used.
2670 
2671 		The purpose for tftpsrcp is to allow a TFTP server to
2672 		blindly start the TFTP transfer using the pre-configured
2673 		target IP address and UDP port. This has the effect of
2674 		"punching through" the (Windows XP) firewall, allowing
2675 		the remainder of the TFTP transfer to proceed normally.
2676 		A better solution is to properly configure the firewall,
2677 		but sometimes that is not allowed.
2678 
2679 - bootcount support:
2680 		CONFIG_BOOTCOUNT_LIMIT
2681 
2682 		This enables the bootcounter support, see:
2683 		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2684 
2685 		CONFIG_AT91SAM9XE
2686 		enable special bootcounter support on at91sam9xe based boards.
2687 		CONFIG_SOC_DA8XX
2688 		enable special bootcounter support on da850 based boards.
2689 		CONFIG_BOOTCOUNT_RAM
2690 		enable support for the bootcounter in RAM
2691 		CONFIG_BOOTCOUNT_I2C
2692 		enable support for the bootcounter on an i2c (like RTC) device.
2693 			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2694 			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2695 						    the bootcounter.
2696 			CONFIG_BOOTCOUNT_ALEN = address len
2697 
2698 - Show boot progress:
2699 		CONFIG_SHOW_BOOT_PROGRESS
2700 
2701 		Defining this option allows to add some board-
2702 		specific code (calling a user-provided function
2703 		"show_boot_progress(int)") that enables you to show
2704 		the system's boot progress on some display (for
2705 		example, some LED's) on your board. At the moment,
2706 		the following checkpoints are implemented:
2707 
2708 
2709 Legacy uImage format:
2710 
2711   Arg	Where			When
2712     1	common/cmd_bootm.c	before attempting to boot an image
2713    -1	common/cmd_bootm.c	Image header has bad	 magic number
2714     2	common/cmd_bootm.c	Image header has correct magic number
2715    -2	common/cmd_bootm.c	Image header has bad	 checksum
2716     3	common/cmd_bootm.c	Image header has correct checksum
2717    -3	common/cmd_bootm.c	Image data   has bad	 checksum
2718     4	common/cmd_bootm.c	Image data   has correct checksum
2719    -4	common/cmd_bootm.c	Image is for unsupported architecture
2720     5	common/cmd_bootm.c	Architecture check OK
2721    -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2722     6	common/cmd_bootm.c	Image Type check OK
2723    -6	common/cmd_bootm.c	gunzip uncompression error
2724    -7	common/cmd_bootm.c	Unimplemented compression type
2725     7	common/cmd_bootm.c	Uncompression OK
2726     8	common/cmd_bootm.c	No uncompress/copy overwrite error
2727    -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2728 
2729     9	common/image.c		Start initial ramdisk verification
2730   -10	common/image.c		Ramdisk header has bad	   magic number
2731   -11	common/image.c		Ramdisk header has bad	   checksum
2732    10	common/image.c		Ramdisk header is OK
2733   -12	common/image.c		Ramdisk data   has bad	   checksum
2734    11	common/image.c		Ramdisk data   has correct checksum
2735    12	common/image.c		Ramdisk verification complete, start loading
2736   -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2737    13	common/image.c		Start multifile image verification
2738    14	common/image.c		No initial ramdisk, no multifile, continue.
2739 
2740    15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2741 
2742   -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2743   -31	post/post.c		POST test failed, detected by post_output_backlog()
2744   -32	post/post.c		POST test failed, detected by post_run_single()
2745 
2746    34	common/cmd_doc.c	before loading a Image from a DOC device
2747   -35	common/cmd_doc.c	Bad usage of "doc" command
2748    35	common/cmd_doc.c	correct usage of "doc" command
2749   -36	common/cmd_doc.c	No boot device
2750    36	common/cmd_doc.c	correct boot device
2751   -37	common/cmd_doc.c	Unknown Chip ID on boot device
2752    37	common/cmd_doc.c	correct chip ID found, device available
2753   -38	common/cmd_doc.c	Read Error on boot device
2754    38	common/cmd_doc.c	reading Image header from DOC device OK
2755   -39	common/cmd_doc.c	Image header has bad magic number
2756    39	common/cmd_doc.c	Image header has correct magic number
2757   -40	common/cmd_doc.c	Error reading Image from DOC device
2758    40	common/cmd_doc.c	Image header has correct magic number
2759    41	common/cmd_ide.c	before loading a Image from a IDE device
2760   -42	common/cmd_ide.c	Bad usage of "ide" command
2761    42	common/cmd_ide.c	correct usage of "ide" command
2762   -43	common/cmd_ide.c	No boot device
2763    43	common/cmd_ide.c	boot device found
2764   -44	common/cmd_ide.c	Device not available
2765    44	common/cmd_ide.c	Device available
2766   -45	common/cmd_ide.c	wrong partition selected
2767    45	common/cmd_ide.c	partition selected
2768   -46	common/cmd_ide.c	Unknown partition table
2769    46	common/cmd_ide.c	valid partition table found
2770   -47	common/cmd_ide.c	Invalid partition type
2771    47	common/cmd_ide.c	correct partition type
2772   -48	common/cmd_ide.c	Error reading Image Header on boot device
2773    48	common/cmd_ide.c	reading Image Header from IDE device OK
2774   -49	common/cmd_ide.c	Image header has bad magic number
2775    49	common/cmd_ide.c	Image header has correct magic number
2776   -50	common/cmd_ide.c	Image header has bad	 checksum
2777    50	common/cmd_ide.c	Image header has correct checksum
2778   -51	common/cmd_ide.c	Error reading Image from IDE device
2779    51	common/cmd_ide.c	reading Image from IDE device OK
2780    52	common/cmd_nand.c	before loading a Image from a NAND device
2781   -53	common/cmd_nand.c	Bad usage of "nand" command
2782    53	common/cmd_nand.c	correct usage of "nand" command
2783   -54	common/cmd_nand.c	No boot device
2784    54	common/cmd_nand.c	boot device found
2785   -55	common/cmd_nand.c	Unknown Chip ID on boot device
2786    55	common/cmd_nand.c	correct chip ID found, device available
2787   -56	common/cmd_nand.c	Error reading Image Header on boot device
2788    56	common/cmd_nand.c	reading Image Header from NAND device OK
2789   -57	common/cmd_nand.c	Image header has bad magic number
2790    57	common/cmd_nand.c	Image header has correct magic number
2791   -58	common/cmd_nand.c	Error reading Image from NAND device
2792    58	common/cmd_nand.c	reading Image from NAND device OK
2793 
2794   -60	common/env_common.c	Environment has a bad CRC, using default
2795 
2796    64	net/eth.c		starting with Ethernet configuration.
2797   -64	net/eth.c		no Ethernet found.
2798    65	net/eth.c		Ethernet found.
2799 
2800   -80	common/cmd_net.c	usage wrong
2801    80	common/cmd_net.c	before calling net_loop()
2802   -81	common/cmd_net.c	some error in net_loop() occurred
2803    81	common/cmd_net.c	net_loop() back without error
2804   -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2805    82	common/cmd_net.c	trying automatic boot
2806    83	common/cmd_net.c	running "source" command
2807   -83	common/cmd_net.c	some error in automatic boot or "source" command
2808    84	common/cmd_net.c	end without errors
2809 
2810 FIT uImage format:
2811 
2812   Arg	Where			When
2813   100	common/cmd_bootm.c	Kernel FIT Image has correct format
2814  -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2815   101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2816  -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2817   102	common/cmd_bootm.c	Kernel unit name specified
2818  -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2819   103	common/cmd_bootm.c	Found configuration node
2820   104	common/cmd_bootm.c	Got kernel subimage node offset
2821  -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2822   105	common/cmd_bootm.c	Kernel subimage hash verification OK
2823  -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2824   106	common/cmd_bootm.c	Architecture check OK
2825  -106	common/cmd_bootm.c	Kernel subimage has wrong type
2826   107	common/cmd_bootm.c	Kernel subimage type OK
2827  -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2828   108	common/cmd_bootm.c	Got kernel subimage data/size
2829  -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2830  -109	common/cmd_bootm.c	Can't get kernel subimage type
2831  -110	common/cmd_bootm.c	Can't get kernel subimage comp
2832  -111	common/cmd_bootm.c	Can't get kernel subimage os
2833  -112	common/cmd_bootm.c	Can't get kernel subimage load address
2834  -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2835 
2836   120	common/image.c		Start initial ramdisk verification
2837  -120	common/image.c		Ramdisk FIT image has incorrect format
2838   121	common/image.c		Ramdisk FIT image has correct format
2839   122	common/image.c		No ramdisk subimage unit name, using configuration
2840  -122	common/image.c		Can't get configuration for ramdisk subimage
2841   123	common/image.c		Ramdisk unit name specified
2842  -124	common/image.c		Can't get ramdisk subimage node offset
2843   125	common/image.c		Got ramdisk subimage node offset
2844  -125	common/image.c		Ramdisk subimage hash verification failed
2845   126	common/image.c		Ramdisk subimage hash verification OK
2846  -126	common/image.c		Ramdisk subimage for unsupported architecture
2847   127	common/image.c		Architecture check OK
2848  -127	common/image.c		Can't get ramdisk subimage data/size
2849   128	common/image.c		Got ramdisk subimage data/size
2850   129	common/image.c		Can't get ramdisk load address
2851  -129	common/image.c		Got ramdisk load address
2852 
2853  -130	common/cmd_doc.c	Incorrect FIT image format
2854   131	common/cmd_doc.c	FIT image format OK
2855 
2856  -140	common/cmd_ide.c	Incorrect FIT image format
2857   141	common/cmd_ide.c	FIT image format OK
2858 
2859  -150	common/cmd_nand.c	Incorrect FIT image format
2860   151	common/cmd_nand.c	FIT image format OK
2861 
2862 - legacy image format:
2863 		CONFIG_IMAGE_FORMAT_LEGACY
2864 		enables the legacy image format support in U-Boot.
2865 
2866 		Default:
2867 		enabled if CONFIG_FIT_SIGNATURE is not defined.
2868 
2869 		CONFIG_DISABLE_IMAGE_LEGACY
2870 		disable the legacy image format
2871 
2872 		This define is introduced, as the legacy image format is
2873 		enabled per default for backward compatibility.
2874 
2875 - Standalone program support:
2876 		CONFIG_STANDALONE_LOAD_ADDR
2877 
2878 		This option defines a board specific value for the
2879 		address where standalone program gets loaded, thus
2880 		overwriting the architecture dependent default
2881 		settings.
2882 
2883 - Frame Buffer Address:
2884 		CONFIG_FB_ADDR
2885 
2886 		Define CONFIG_FB_ADDR if you want to use specific
2887 		address for frame buffer.  This is typically the case
2888 		when using a graphics controller has separate video
2889 		memory.  U-Boot will then place the frame buffer at
2890 		the given address instead of dynamically reserving it
2891 		in system RAM by calling lcd_setmem(), which grabs
2892 		the memory for the frame buffer depending on the
2893 		configured panel size.
2894 
2895 		Please see board_init_f function.
2896 
2897 - Automatic software updates via TFTP server
2898 		CONFIG_UPDATE_TFTP
2899 		CONFIG_UPDATE_TFTP_CNT_MAX
2900 		CONFIG_UPDATE_TFTP_MSEC_MAX
2901 
2902 		These options enable and control the auto-update feature;
2903 		for a more detailed description refer to doc/README.update.
2904 
2905 - MTD Support (mtdparts command, UBI support)
2906 		CONFIG_MTD_DEVICE
2907 
2908 		Adds the MTD device infrastructure from the Linux kernel.
2909 		Needed for mtdparts command support.
2910 
2911 		CONFIG_MTD_PARTITIONS
2912 
2913 		Adds the MTD partitioning infrastructure from the Linux
2914 		kernel. Needed for UBI support.
2915 
2916 - UBI support
2917 		CONFIG_CMD_UBI
2918 
2919 		Adds commands for interacting with MTD partitions formatted
2920 		with the UBI flash translation layer
2921 
2922 		Requires also defining CONFIG_RBTREE
2923 
2924 		CONFIG_UBI_SILENCE_MSG
2925 
2926 		Make the verbose messages from UBI stop printing.  This leaves
2927 		warnings and errors enabled.
2928 
2929 
2930 		CONFIG_MTD_UBI_WL_THRESHOLD
2931 		This parameter defines the maximum difference between the highest
2932 		erase counter value and the lowest erase counter value of eraseblocks
2933 		of UBI devices. When this threshold is exceeded, UBI starts performing
2934 		wear leveling by means of moving data from eraseblock with low erase
2935 		counter to eraseblocks with high erase counter.
2936 
2937 		The default value should be OK for SLC NAND flashes, NOR flashes and
2938 		other flashes which have eraseblock life-cycle 100000 or more.
2939 		However, in case of MLC NAND flashes which typically have eraseblock
2940 		life-cycle less than 10000, the threshold should be lessened (e.g.,
2941 		to 128 or 256, although it does not have to be power of 2).
2942 
2943 		default: 4096
2944 
2945 		CONFIG_MTD_UBI_BEB_LIMIT
2946 		This option specifies the maximum bad physical eraseblocks UBI
2947 		expects on the MTD device (per 1024 eraseblocks). If the
2948 		underlying flash does not admit of bad eraseblocks (e.g. NOR
2949 		flash), this value is ignored.
2950 
2951 		NAND datasheets often specify the minimum and maximum NVM
2952 		(Number of Valid Blocks) for the flashes' endurance lifetime.
2953 		The maximum expected bad eraseblocks per 1024 eraseblocks
2954 		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2955 		which gives 20 for most NANDs (MaxNVB is basically the total
2956 		count of eraseblocks on the chip).
2957 
2958 		To put it differently, if this value is 20, UBI will try to
2959 		reserve about 1.9% of physical eraseblocks for bad blocks
2960 		handling. And that will be 1.9% of eraseblocks on the entire
2961 		NAND chip, not just the MTD partition UBI attaches. This means
2962 		that if you have, say, a NAND flash chip admits maximum 40 bad
2963 		eraseblocks, and it is split on two MTD partitions of the same
2964 		size, UBI will reserve 40 eraseblocks when attaching a
2965 		partition.
2966 
2967 		default: 20
2968 
2969 		CONFIG_MTD_UBI_FASTMAP
2970 		Fastmap is a mechanism which allows attaching an UBI device
2971 		in nearly constant time. Instead of scanning the whole MTD device it
2972 		only has to locate a checkpoint (called fastmap) on the device.
2973 		The on-flash fastmap contains all information needed to attach
2974 		the device. Using fastmap makes only sense on large devices where
2975 		attaching by scanning takes long. UBI will not automatically install
2976 		a fastmap on old images, but you can set the UBI parameter
2977 		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2978 		that fastmap-enabled images are still usable with UBI implementations
2979 		without	fastmap support. On typical flash devices the whole fastmap
2980 		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2981 
2982 		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2983 		Set this parameter to enable fastmap automatically on images
2984 		without a fastmap.
2985 		default: 0
2986 
2987 		CONFIG_MTD_UBI_FM_DEBUG
2988 		Enable UBI fastmap debug
2989 		default: 0
2990 
2991 - UBIFS support
2992 		CONFIG_CMD_UBIFS
2993 
2994 		Adds commands for interacting with UBI volumes formatted as
2995 		UBIFS.  UBIFS is read-only in u-boot.
2996 
2997 		Requires UBI support as well as CONFIG_LZO
2998 
2999 		CONFIG_UBIFS_SILENCE_MSG
3000 
3001 		Make the verbose messages from UBIFS stop printing.  This leaves
3002 		warnings and errors enabled.
3003 
3004 - SPL framework
3005 		CONFIG_SPL
3006 		Enable building of SPL globally.
3007 
3008 		CONFIG_SPL_LDSCRIPT
3009 		LDSCRIPT for linking the SPL binary.
3010 
3011 		CONFIG_SPL_MAX_FOOTPRINT
3012 		Maximum size in memory allocated to the SPL, BSS included.
3013 		When defined, the linker checks that the actual memory
3014 		used by SPL from _start to __bss_end does not exceed it.
3015 		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3016 		must not be both defined at the same time.
3017 
3018 		CONFIG_SPL_MAX_SIZE
3019 		Maximum size of the SPL image (text, data, rodata, and
3020 		linker lists sections), BSS excluded.
3021 		When defined, the linker checks that the actual size does
3022 		not exceed it.
3023 
3024 		CONFIG_SPL_TEXT_BASE
3025 		TEXT_BASE for linking the SPL binary.
3026 
3027 		CONFIG_SPL_RELOC_TEXT_BASE
3028 		Address to relocate to.  If unspecified, this is equal to
3029 		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3030 
3031 		CONFIG_SPL_BSS_START_ADDR
3032 		Link address for the BSS within the SPL binary.
3033 
3034 		CONFIG_SPL_BSS_MAX_SIZE
3035 		Maximum size in memory allocated to the SPL BSS.
3036 		When defined, the linker checks that the actual memory used
3037 		by SPL from __bss_start to __bss_end does not exceed it.
3038 		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3039 		must not be both defined at the same time.
3040 
3041 		CONFIG_SPL_STACK
3042 		Adress of the start of the stack SPL will use
3043 
3044 		CONFIG_SPL_PANIC_ON_RAW_IMAGE
3045 		When defined, SPL will panic() if the image it has
3046 		loaded does not have a signature.
3047 		Defining this is useful when code which loads images
3048 		in SPL cannot guarantee that absolutely all read errors
3049 		will be caught.
3050 		An example is the LPC32XX MLC NAND driver, which will
3051 		consider that a completely unreadable NAND block is bad,
3052 		and thus should be skipped silently.
3053 
3054 		CONFIG_SPL_RELOC_STACK
3055 		Adress of the start of the stack SPL will use after
3056 		relocation.  If unspecified, this is equal to
3057 		CONFIG_SPL_STACK.
3058 
3059 		CONFIG_SYS_SPL_MALLOC_START
3060 		Starting address of the malloc pool used in SPL.
3061 		When this option is set the full malloc is used in SPL and
3062 		it is set up by spl_init() and before that, the simple malloc()
3063 		can be used if CONFIG_SYS_MALLOC_F is defined.
3064 
3065 		CONFIG_SYS_SPL_MALLOC_SIZE
3066 		The size of the malloc pool used in SPL.
3067 
3068 		CONFIG_SPL_FRAMEWORK
3069 		Enable the SPL framework under common/.  This framework
3070 		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3071 		NAND loading of the Linux Kernel.
3072 
3073 		CONFIG_SPL_OS_BOOT
3074 		Enable booting directly to an OS from SPL.
3075 		See also: doc/README.falcon
3076 
3077 		CONFIG_SPL_DISPLAY_PRINT
3078 		For ARM, enable an optional function to print more information
3079 		about the running system.
3080 
3081 		CONFIG_SPL_INIT_MINIMAL
3082 		Arch init code should be built for a very small image
3083 
3084 		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3085 		Partition on the MMC to load U-Boot from when the MMC is being
3086 		used in raw mode
3087 
3088 		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3089 		Sector to load kernel uImage from when MMC is being
3090 		used in raw mode (for Falcon mode)
3091 
3092 		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3093 		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3094 		Sector and number of sectors to load kernel argument
3095 		parameters from when MMC is being used in raw mode
3096 		(for falcon mode)
3097 
3098 		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3099 		Partition on the MMC to load U-Boot from when the MMC is being
3100 		used in fs mode
3101 
3102 		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3103 		Filename to read to load U-Boot when reading from filesystem
3104 
3105 		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3106 		Filename to read to load kernel uImage when reading
3107 		from filesystem (for Falcon mode)
3108 
3109 		CONFIG_SPL_FS_LOAD_ARGS_NAME
3110 		Filename to read to load kernel argument parameters
3111 		when reading from filesystem (for Falcon mode)
3112 
3113 		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3114 		Set this for NAND SPL on PPC mpc83xx targets, so that
3115 		start.S waits for the rest of the SPL to load before
3116 		continuing (the hardware starts execution after just
3117 		loading the first page rather than the full 4K).
3118 
3119 		CONFIG_SPL_SKIP_RELOCATE
3120 		Avoid SPL relocation
3121 
3122 		CONFIG_SPL_NAND_BASE
3123 		Include nand_base.c in the SPL.  Requires
3124 		CONFIG_SPL_NAND_DRIVERS.
3125 
3126 		CONFIG_SPL_NAND_DRIVERS
3127 		SPL uses normal NAND drivers, not minimal drivers.
3128 
3129 		CONFIG_SPL_NAND_ECC
3130 		Include standard software ECC in the SPL
3131 
3132 		CONFIG_SPL_NAND_SIMPLE
3133 		Support for NAND boot using simple NAND drivers that
3134 		expose the cmd_ctrl() interface.
3135 
3136 		CONFIG_SPL_UBI
3137 		Support for a lightweight UBI (fastmap) scanner and
3138 		loader
3139 
3140 		CONFIG_SPL_NAND_RAW_ONLY
3141 		Support to boot only raw u-boot.bin images. Use this only
3142 		if you need to save space.
3143 
3144 		CONFIG_SPL_COMMON_INIT_DDR
3145 		Set for common ddr init with serial presence detect in
3146 		SPL binary.
3147 
3148 		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3149 		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3150 		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3151 		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3152 		CONFIG_SYS_NAND_ECCBYTES
3153 		Defines the size and behavior of the NAND that SPL uses
3154 		to read U-Boot
3155 
3156 		CONFIG_SPL_NAND_BOOT
3157 		Add support NAND boot
3158 
3159 		CONFIG_SYS_NAND_U_BOOT_OFFS
3160 		Location in NAND to read U-Boot from
3161 
3162 		CONFIG_SYS_NAND_U_BOOT_DST
3163 		Location in memory to load U-Boot to
3164 
3165 		CONFIG_SYS_NAND_U_BOOT_SIZE
3166 		Size of image to load
3167 
3168 		CONFIG_SYS_NAND_U_BOOT_START
3169 		Entry point in loaded image to jump to
3170 
3171 		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3172 		Define this if you need to first read the OOB and then the
3173 		data. This is used, for example, on davinci platforms.
3174 
3175 		CONFIG_SPL_OMAP3_ID_NAND
3176 		Support for an OMAP3-specific set of functions to return the
3177 		ID and MFR of the first attached NAND chip, if present.
3178 
3179 		CONFIG_SPL_RAM_DEVICE
3180 		Support for running image already present in ram, in SPL binary
3181 
3182 		CONFIG_SPL_PAD_TO
3183 		Image offset to which the SPL should be padded before appending
3184 		the SPL payload. By default, this is defined as
3185 		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3186 		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3187 		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3188 
3189 		CONFIG_SPL_TARGET
3190 		Final target image containing SPL and payload.  Some SPLs
3191 		use an arch-specific makefile fragment instead, for
3192 		example if more than one image needs to be produced.
3193 
3194 		CONFIG_FIT_SPL_PRINT
3195 		Printing information about a FIT image adds quite a bit of
3196 		code to SPL. So this is normally disabled in SPL. Use this
3197 		option to re-enable it. This will affect the output of the
3198 		bootm command when booting a FIT image.
3199 
3200 - TPL framework
3201 		CONFIG_TPL
3202 		Enable building of TPL globally.
3203 
3204 		CONFIG_TPL_PAD_TO
3205 		Image offset to which the TPL should be padded before appending
3206 		the TPL payload. By default, this is defined as
3207 		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3208 		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3209 		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3210 
3211 - Interrupt support (PPC):
3212 
3213 		There are common interrupt_init() and timer_interrupt()
3214 		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3215 		for CPU specific initialization. interrupt_init_cpu()
3216 		should set decrementer_count to appropriate value. If
3217 		CPU resets decrementer automatically after interrupt
3218 		(ppc4xx) it should set decrementer_count to zero.
3219 		timer_interrupt() calls timer_interrupt_cpu() for CPU
3220 		specific handling. If board has watchdog / status_led
3221 		/ other_activity_monitor it works automatically from
3222 		general timer_interrupt().
3223 
3224 
3225 Board initialization settings:
3226 ------------------------------
3227 
3228 During Initialization u-boot calls a number of board specific functions
3229 to allow the preparation of board specific prerequisites, e.g. pin setup
3230 before drivers are initialized. To enable these callbacks the
3231 following configuration macros have to be defined. Currently this is
3232 architecture specific, so please check arch/your_architecture/lib/board.c
3233 typically in board_init_f() and board_init_r().
3234 
3235 - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3236 - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3237 - CONFIG_BOARD_LATE_INIT: Call board_late_init()
3238 - CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3239 
3240 Configuration Settings:
3241 -----------------------
3242 
3243 - CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3244 		Optionally it can be defined to support 64-bit memory commands.
3245 
3246 - CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3247 		undefine this when you're short of memory.
3248 
3249 - CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3250 		width of the commands listed in the 'help' command output.
3251 
3252 - CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3253 		prompt for user input.
3254 
3255 - CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3256 
3257 - CONFIG_SYS_PBSIZE:	Buffer size for Console output
3258 
3259 - CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3260 
3261 - CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3262 		the application (usually a Linux kernel) when it is
3263 		booted
3264 
3265 - CONFIG_SYS_BAUDRATE_TABLE:
3266 		List of legal baudrate settings for this board.
3267 
3268 - CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3269 		Begin and End addresses of the area used by the
3270 		simple memory test.
3271 
3272 - CONFIG_SYS_ALT_MEMTEST:
3273 		Enable an alternate, more extensive memory test.
3274 
3275 - CONFIG_SYS_MEMTEST_SCRATCH:
3276 		Scratch address used by the alternate memory test
3277 		You only need to set this if address zero isn't writeable
3278 
3279 - CONFIG_SYS_MEM_RESERVE_SECURE
3280 		Only implemented for ARMv8 for now.
3281 		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
3282 		is substracted from total RAM and won't be reported to OS.
3283 		This memory can be used as secure memory. A variable
3284 		gd->arch.secure_ram is used to track the location. In systems
3285 		the RAM base is not zero, or RAM is divided into banks,
3286 		this variable needs to be recalcuated to get the address.
3287 
3288 - CONFIG_SYS_MEM_TOP_HIDE:
3289 		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3290 		this specified memory area will get subtracted from the top
3291 		(end) of RAM and won't get "touched" at all by U-Boot. By
3292 		fixing up gd->ram_size the Linux kernel should gets passed
3293 		the now "corrected" memory size and won't touch it either.
3294 		This should work for arch/ppc and arch/powerpc. Only Linux
3295 		board ports in arch/powerpc with bootwrapper support that
3296 		recalculate the memory size from the SDRAM controller setup
3297 		will have to get fixed in Linux additionally.
3298 
3299 		This option can be used as a workaround for the 440EPx/GRx
3300 		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3301 		be touched.
3302 
3303 		WARNING: Please make sure that this value is a multiple of
3304 		the Linux page size (normally 4k). If this is not the case,
3305 		then the end address of the Linux memory will be located at a
3306 		non page size aligned address and this could cause major
3307 		problems.
3308 
3309 - CONFIG_SYS_LOADS_BAUD_CHANGE:
3310 		Enable temporary baudrate change while serial download
3311 
3312 - CONFIG_SYS_SDRAM_BASE:
3313 		Physical start address of SDRAM. _Must_ be 0 here.
3314 
3315 - CONFIG_SYS_FLASH_BASE:
3316 		Physical start address of Flash memory.
3317 
3318 - CONFIG_SYS_MONITOR_BASE:
3319 		Physical start address of boot monitor code (set by
3320 		make config files to be same as the text base address
3321 		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3322 		CONFIG_SYS_FLASH_BASE when booting from flash.
3323 
3324 - CONFIG_SYS_MONITOR_LEN:
3325 		Size of memory reserved for monitor code, used to
3326 		determine _at_compile_time_ (!) if the environment is
3327 		embedded within the U-Boot image, or in a separate
3328 		flash sector.
3329 
3330 - CONFIG_SYS_MALLOC_LEN:
3331 		Size of DRAM reserved for malloc() use.
3332 
3333 - CONFIG_SYS_MALLOC_F_LEN
3334 		Size of the malloc() pool for use before relocation. If
3335 		this is defined, then a very simple malloc() implementation
3336 		will become available before relocation. The address is just
3337 		below the global data, and the stack is moved down to make
3338 		space.
3339 
3340 		This feature allocates regions with increasing addresses
3341 		within the region. calloc() is supported, but realloc()
3342 		is not available. free() is supported but does nothing.
3343 		The memory will be freed (or in fact just forgotten) when
3344 		U-Boot relocates itself.
3345 
3346 - CONFIG_SYS_MALLOC_SIMPLE
3347 		Provides a simple and small malloc() and calloc() for those
3348 		boards which do not use the full malloc in SPL (which is
3349 		enabled with CONFIG_SYS_SPL_MALLOC_START).
3350 
3351 - CONFIG_SYS_NONCACHED_MEMORY:
3352 		Size of non-cached memory area. This area of memory will be
3353 		typically located right below the malloc() area and mapped
3354 		uncached in the MMU. This is useful for drivers that would
3355 		otherwise require a lot of explicit cache maintenance. For
3356 		some drivers it's also impossible to properly maintain the
3357 		cache. For example if the regions that need to be flushed
3358 		are not a multiple of the cache-line size, *and* padding
3359 		cannot be allocated between the regions to align them (i.e.
3360 		if the HW requires a contiguous array of regions, and the
3361 		size of each region is not cache-aligned), then a flush of
3362 		one region may result in overwriting data that hardware has
3363 		written to another region in the same cache-line. This can
3364 		happen for example in network drivers where descriptors for
3365 		buffers are typically smaller than the CPU cache-line (e.g.
3366 		16 bytes vs. 32 or 64 bytes).
3367 
3368 		Non-cached memory is only supported on 32-bit ARM at present.
3369 
3370 - CONFIG_SYS_BOOTM_LEN:
3371 		Normally compressed uImages are limited to an
3372 		uncompressed size of 8 MBytes. If this is not enough,
3373 		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3374 		to adjust this setting to your needs.
3375 
3376 - CONFIG_SYS_BOOTMAPSZ:
3377 		Maximum size of memory mapped by the startup code of
3378 		the Linux kernel; all data that must be processed by
3379 		the Linux kernel (bd_info, boot arguments, FDT blob if
3380 		used) must be put below this limit, unless "bootm_low"
3381 		environment variable is defined and non-zero. In such case
3382 		all data for the Linux kernel must be between "bootm_low"
3383 		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3384 		variable "bootm_mapsize" will override the value of
3385 		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3386 		then the value in "bootm_size" will be used instead.
3387 
3388 - CONFIG_SYS_BOOT_RAMDISK_HIGH:
3389 		Enable initrd_high functionality.  If defined then the
3390 		initrd_high feature is enabled and the bootm ramdisk subcommand
3391 		is enabled.
3392 
3393 - CONFIG_SYS_BOOT_GET_CMDLINE:
3394 		Enables allocating and saving kernel cmdline in space between
3395 		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3396 
3397 - CONFIG_SYS_BOOT_GET_KBD:
3398 		Enables allocating and saving a kernel copy of the bd_info in
3399 		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3400 
3401 - CONFIG_SYS_MAX_FLASH_BANKS:
3402 		Max number of Flash memory banks
3403 
3404 - CONFIG_SYS_MAX_FLASH_SECT:
3405 		Max number of sectors on a Flash chip
3406 
3407 - CONFIG_SYS_FLASH_ERASE_TOUT:
3408 		Timeout for Flash erase operations (in ms)
3409 
3410 - CONFIG_SYS_FLASH_WRITE_TOUT:
3411 		Timeout for Flash write operations (in ms)
3412 
3413 - CONFIG_SYS_FLASH_LOCK_TOUT
3414 		Timeout for Flash set sector lock bit operation (in ms)
3415 
3416 - CONFIG_SYS_FLASH_UNLOCK_TOUT
3417 		Timeout for Flash clear lock bits operation (in ms)
3418 
3419 - CONFIG_SYS_FLASH_PROTECTION
3420 		If defined, hardware flash sectors protection is used
3421 		instead of U-Boot software protection.
3422 
3423 - CONFIG_SYS_DIRECT_FLASH_TFTP:
3424 
3425 		Enable TFTP transfers directly to flash memory;
3426 		without this option such a download has to be
3427 		performed in two steps: (1) download to RAM, and (2)
3428 		copy from RAM to flash.
3429 
3430 		The two-step approach is usually more reliable, since
3431 		you can check if the download worked before you erase
3432 		the flash, but in some situations (when system RAM is
3433 		too limited to allow for a temporary copy of the
3434 		downloaded image) this option may be very useful.
3435 
3436 - CONFIG_SYS_FLASH_CFI:
3437 		Define if the flash driver uses extra elements in the
3438 		common flash structure for storing flash geometry.
3439 
3440 - CONFIG_FLASH_CFI_DRIVER
3441 		This option also enables the building of the cfi_flash driver
3442 		in the drivers directory
3443 
3444 - CONFIG_FLASH_CFI_MTD
3445 		This option enables the building of the cfi_mtd driver
3446 		in the drivers directory. The driver exports CFI flash
3447 		to the MTD layer.
3448 
3449 - CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3450 		Use buffered writes to flash.
3451 
3452 - CONFIG_FLASH_SPANSION_S29WS_N
3453 		s29ws-n MirrorBit flash has non-standard addresses for buffered
3454 		write commands.
3455 
3456 - CONFIG_SYS_FLASH_QUIET_TEST
3457 		If this option is defined, the common CFI flash doesn't
3458 		print it's warning upon not recognized FLASH banks. This
3459 		is useful, if some of the configured banks are only
3460 		optionally available.
3461 
3462 - CONFIG_FLASH_SHOW_PROGRESS
3463 		If defined (must be an integer), print out countdown
3464 		digits and dots.  Recommended value: 45 (9..1) for 80
3465 		column displays, 15 (3..1) for 40 column displays.
3466 
3467 - CONFIG_FLASH_VERIFY
3468 		If defined, the content of the flash (destination) is compared
3469 		against the source after the write operation. An error message
3470 		will be printed when the contents are not identical.
3471 		Please note that this option is useless in nearly all cases,
3472 		since such flash programming errors usually are detected earlier
3473 		while unprotecting/erasing/programming. Please only enable
3474 		this option if you really know what you are doing.
3475 
3476 - CONFIG_SYS_RX_ETH_BUFFER:
3477 		Defines the number of Ethernet receive buffers. On some
3478 		Ethernet controllers it is recommended to set this value
3479 		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3480 		buffers can be full shortly after enabling the interface
3481 		on high Ethernet traffic.
3482 		Defaults to 4 if not defined.
3483 
3484 - CONFIG_ENV_MAX_ENTRIES
3485 
3486 	Maximum number of entries in the hash table that is used
3487 	internally to store the environment settings. The default
3488 	setting is supposed to be generous and should work in most
3489 	cases. This setting can be used to tune behaviour; see
3490 	lib/hashtable.c for details.
3491 
3492 - CONFIG_ENV_FLAGS_LIST_DEFAULT
3493 - CONFIG_ENV_FLAGS_LIST_STATIC
3494 	Enable validation of the values given to environment variables when
3495 	calling env set.  Variables can be restricted to only decimal,
3496 	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3497 	the variables can also be restricted to IP address or MAC address.
3498 
3499 	The format of the list is:
3500 		type_attribute = [s|d|x|b|i|m]
3501 		access_attribute = [a|r|o|c]
3502 		attributes = type_attribute[access_attribute]
3503 		entry = variable_name[:attributes]
3504 		list = entry[,list]
3505 
3506 	The type attributes are:
3507 		s - String (default)
3508 		d - Decimal
3509 		x - Hexadecimal
3510 		b - Boolean ([1yYtT|0nNfF])
3511 		i - IP address
3512 		m - MAC address
3513 
3514 	The access attributes are:
3515 		a - Any (default)
3516 		r - Read-only
3517 		o - Write-once
3518 		c - Change-default
3519 
3520 	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3521 		Define this to a list (string) to define the ".flags"
3522 		environment variable in the default or embedded environment.
3523 
3524 	- CONFIG_ENV_FLAGS_LIST_STATIC
3525 		Define this to a list (string) to define validation that
3526 		should be done if an entry is not found in the ".flags"
3527 		environment variable.  To override a setting in the static
3528 		list, simply add an entry for the same variable name to the
3529 		".flags" variable.
3530 
3531 	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3532 	regular expression. This allows multiple variables to define the same
3533 	flags without explicitly listing them for each variable.
3534 
3535 - CONFIG_ENV_ACCESS_IGNORE_FORCE
3536 	If defined, don't allow the -f switch to env set override variable
3537 	access flags.
3538 
3539 - CONFIG_USE_STDINT
3540 	If stdint.h is available with your toolchain you can define this
3541 	option to enable it. You can provide option 'USE_STDINT=1' when
3542 	building U-Boot to enable this.
3543 
3544 The following definitions that deal with the placement and management
3545 of environment data (variable area); in general, we support the
3546 following configurations:
3547 
3548 - CONFIG_BUILD_ENVCRC:
3549 
3550 	Builds up envcrc with the target environment so that external utils
3551 	may easily extract it and embed it in final U-Boot images.
3552 
3553 - CONFIG_ENV_IS_IN_FLASH:
3554 
3555 	Define this if the environment is in flash memory.
3556 
3557 	a) The environment occupies one whole flash sector, which is
3558 	   "embedded" in the text segment with the U-Boot code. This
3559 	   happens usually with "bottom boot sector" or "top boot
3560 	   sector" type flash chips, which have several smaller
3561 	   sectors at the start or the end. For instance, such a
3562 	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3563 	   such a case you would place the environment in one of the
3564 	   4 kB sectors - with U-Boot code before and after it. With
3565 	   "top boot sector" type flash chips, you would put the
3566 	   environment in one of the last sectors, leaving a gap
3567 	   between U-Boot and the environment.
3568 
3569 	- CONFIG_ENV_OFFSET:
3570 
3571 	   Offset of environment data (variable area) to the
3572 	   beginning of flash memory; for instance, with bottom boot
3573 	   type flash chips the second sector can be used: the offset
3574 	   for this sector is given here.
3575 
3576 	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3577 
3578 	- CONFIG_ENV_ADDR:
3579 
3580 	   This is just another way to specify the start address of
3581 	   the flash sector containing the environment (instead of
3582 	   CONFIG_ENV_OFFSET).
3583 
3584 	- CONFIG_ENV_SECT_SIZE:
3585 
3586 	   Size of the sector containing the environment.
3587 
3588 
3589 	b) Sometimes flash chips have few, equal sized, BIG sectors.
3590 	   In such a case you don't want to spend a whole sector for
3591 	   the environment.
3592 
3593 	- CONFIG_ENV_SIZE:
3594 
3595 	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3596 	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3597 	   of this flash sector for the environment. This saves
3598 	   memory for the RAM copy of the environment.
3599 
3600 	   It may also save flash memory if you decide to use this
3601 	   when your environment is "embedded" within U-Boot code,
3602 	   since then the remainder of the flash sector could be used
3603 	   for U-Boot code. It should be pointed out that this is
3604 	   STRONGLY DISCOURAGED from a robustness point of view:
3605 	   updating the environment in flash makes it always
3606 	   necessary to erase the WHOLE sector. If something goes
3607 	   wrong before the contents has been restored from a copy in
3608 	   RAM, your target system will be dead.
3609 
3610 	- CONFIG_ENV_ADDR_REDUND
3611 	  CONFIG_ENV_SIZE_REDUND
3612 
3613 	   These settings describe a second storage area used to hold
3614 	   a redundant copy of the environment data, so that there is
3615 	   a valid backup copy in case there is a power failure during
3616 	   a "saveenv" operation.
3617 
3618 BE CAREFUL! Any changes to the flash layout, and some changes to the
3619 source code will make it necessary to adapt <board>/u-boot.lds*
3620 accordingly!
3621 
3622 
3623 - CONFIG_ENV_IS_IN_NVRAM:
3624 
3625 	Define this if you have some non-volatile memory device
3626 	(NVRAM, battery buffered SRAM) which you want to use for the
3627 	environment.
3628 
3629 	- CONFIG_ENV_ADDR:
3630 	- CONFIG_ENV_SIZE:
3631 
3632 	  These two #defines are used to determine the memory area you
3633 	  want to use for environment. It is assumed that this memory
3634 	  can just be read and written to, without any special
3635 	  provision.
3636 
3637 BE CAREFUL! The first access to the environment happens quite early
3638 in U-Boot initialization (when we try to get the setting of for the
3639 console baudrate). You *MUST* have mapped your NVRAM area then, or
3640 U-Boot will hang.
3641 
3642 Please note that even with NVRAM we still use a copy of the
3643 environment in RAM: we could work on NVRAM directly, but we want to
3644 keep settings there always unmodified except somebody uses "saveenv"
3645 to save the current settings.
3646 
3647 
3648 - CONFIG_ENV_IS_IN_EEPROM:
3649 
3650 	Use this if you have an EEPROM or similar serial access
3651 	device and a driver for it.
3652 
3653 	- CONFIG_ENV_OFFSET:
3654 	- CONFIG_ENV_SIZE:
3655 
3656 	  These two #defines specify the offset and size of the
3657 	  environment area within the total memory of your EEPROM.
3658 
3659 	- CONFIG_SYS_I2C_EEPROM_ADDR:
3660 	  If defined, specified the chip address of the EEPROM device.
3661 	  The default address is zero.
3662 
3663 	- CONFIG_SYS_I2C_EEPROM_BUS:
3664 	  If defined, specified the i2c bus of the EEPROM device.
3665 
3666 	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3667 	  If defined, the number of bits used to address bytes in a
3668 	  single page in the EEPROM device.  A 64 byte page, for example
3669 	  would require six bits.
3670 
3671 	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3672 	  If defined, the number of milliseconds to delay between
3673 	  page writes.	The default is zero milliseconds.
3674 
3675 	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3676 	  The length in bytes of the EEPROM memory array address.  Note
3677 	  that this is NOT the chip address length!
3678 
3679 	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3680 	  EEPROM chips that implement "address overflow" are ones
3681 	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3682 	  address and the extra bits end up in the "chip address" bit
3683 	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3684 	  byte chips.
3685 
3686 	  Note that we consider the length of the address field to
3687 	  still be one byte because the extra address bits are hidden
3688 	  in the chip address.
3689 
3690 	- CONFIG_SYS_EEPROM_SIZE:
3691 	  The size in bytes of the EEPROM device.
3692 
3693 	- CONFIG_ENV_EEPROM_IS_ON_I2C
3694 	  define this, if you have I2C and SPI activated, and your
3695 	  EEPROM, which holds the environment, is on the I2C bus.
3696 
3697 	- CONFIG_I2C_ENV_EEPROM_BUS
3698 	  if you have an Environment on an EEPROM reached over
3699 	  I2C muxes, you can define here, how to reach this
3700 	  EEPROM. For example:
3701 
3702 	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
3703 
3704 	  EEPROM which holds the environment, is reached over
3705 	  a pca9547 i2c mux with address 0x70, channel 3.
3706 
3707 - CONFIG_ENV_IS_IN_DATAFLASH:
3708 
3709 	Define this if you have a DataFlash memory device which you
3710 	want to use for the environment.
3711 
3712 	- CONFIG_ENV_OFFSET:
3713 	- CONFIG_ENV_ADDR:
3714 	- CONFIG_ENV_SIZE:
3715 
3716 	  These three #defines specify the offset and size of the
3717 	  environment area within the total memory of your DataFlash placed
3718 	  at the specified address.
3719 
3720 - CONFIG_ENV_IS_IN_SPI_FLASH:
3721 
3722 	Define this if you have a SPI Flash memory device which you
3723 	want to use for the environment.
3724 
3725 	- CONFIG_ENV_OFFSET:
3726 	- CONFIG_ENV_SIZE:
3727 
3728 	  These two #defines specify the offset and size of the
3729 	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
3730 	  aligned to an erase sector boundary.
3731 
3732 	- CONFIG_ENV_SECT_SIZE:
3733 
3734 	  Define the SPI flash's sector size.
3735 
3736 	- CONFIG_ENV_OFFSET_REDUND (optional):
3737 
3738 	  This setting describes a second storage area of CONFIG_ENV_SIZE
3739 	  size used to hold a redundant copy of the environment data, so
3740 	  that there is a valid backup copy in case there is a power failure
3741 	  during a "saveenv" operation. CONFIG_ENV_OFFSET_REDUND must be
3742 	  aligned to an erase sector boundary.
3743 
3744 	- CONFIG_ENV_SPI_BUS (optional):
3745 	- CONFIG_ENV_SPI_CS (optional):
3746 
3747 	  Define the SPI bus and chip select. If not defined they will be 0.
3748 
3749 	- CONFIG_ENV_SPI_MAX_HZ (optional):
3750 
3751 	  Define the SPI max work clock. If not defined then use 1MHz.
3752 
3753 	- CONFIG_ENV_SPI_MODE (optional):
3754 
3755 	  Define the SPI work mode. If not defined then use SPI_MODE_3.
3756 
3757 - CONFIG_ENV_IS_IN_REMOTE:
3758 
3759 	Define this if you have a remote memory space which you
3760 	want to use for the local device's environment.
3761 
3762 	- CONFIG_ENV_ADDR:
3763 	- CONFIG_ENV_SIZE:
3764 
3765 	  These two #defines specify the address and size of the
3766 	  environment area within the remote memory space. The
3767 	  local device can get the environment from remote memory
3768 	  space by SRIO or PCIE links.
3769 
3770 BE CAREFUL! For some special cases, the local device can not use
3771 "saveenv" command. For example, the local device will get the
3772 environment stored in a remote NOR flash by SRIO or PCIE link,
3773 but it can not erase, write this NOR flash by SRIO or PCIE interface.
3774 
3775 - CONFIG_ENV_IS_IN_NAND:
3776 
3777 	Define this if you have a NAND device which you want to use
3778 	for the environment.
3779 
3780 	- CONFIG_ENV_OFFSET:
3781 	- CONFIG_ENV_SIZE:
3782 
3783 	  These two #defines specify the offset and size of the environment
3784 	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3785 	  aligned to an erase block boundary.
3786 
3787 	- CONFIG_ENV_OFFSET_REDUND (optional):
3788 
3789 	  This setting describes a second storage area of CONFIG_ENV_SIZE
3790 	  size used to hold a redundant copy of the environment data, so
3791 	  that there is a valid backup copy in case there is a power failure
3792 	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_REDUND must be
3793 	  aligned to an erase block boundary.
3794 
3795 	- CONFIG_ENV_RANGE (optional):
3796 
3797 	  Specifies the length of the region in which the environment
3798 	  can be written.  This should be a multiple of the NAND device's
3799 	  block size.  Specifying a range with more erase blocks than
3800 	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
3801 	  the range to be avoided.
3802 
3803 	- CONFIG_ENV_OFFSET_OOB (optional):
3804 
3805 	  Enables support for dynamically retrieving the offset of the
3806 	  environment from block zero's out-of-band data.  The
3807 	  "nand env.oob" command can be used to record this offset.
3808 	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
3809 	  using CONFIG_ENV_OFFSET_OOB.
3810 
3811 - CONFIG_NAND_ENV_DST
3812 
3813 	Defines address in RAM to which the nand_spl code should copy the
3814 	environment. If redundant environment is used, it will be copied to
3815 	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3816 
3817 - CONFIG_ENV_IS_IN_UBI:
3818 
3819 	Define this if you have an UBI volume that you want to use for the
3820 	environment.  This has the benefit of wear-leveling the environment
3821 	accesses, which is important on NAND.
3822 
3823 	- CONFIG_ENV_UBI_PART:
3824 
3825 	  Define this to a string that is the mtd partition containing the UBI.
3826 
3827 	- CONFIG_ENV_UBI_VOLUME:
3828 
3829 	  Define this to the name of the volume that you want to store the
3830 	  environment in.
3831 
3832 	- CONFIG_ENV_UBI_VOLUME_REDUND:
3833 
3834 	  Define this to the name of another volume to store a second copy of
3835 	  the environment in.  This will enable redundant environments in UBI.
3836 	  It is assumed that both volumes are in the same MTD partition.
3837 
3838 	- CONFIG_UBI_SILENCE_MSG
3839 	- CONFIG_UBIFS_SILENCE_MSG
3840 
3841 	  You will probably want to define these to avoid a really noisy system
3842 	  when storing the env in UBI.
3843 
3844 - CONFIG_ENV_IS_IN_FAT:
3845        Define this if you want to use the FAT file system for the environment.
3846 
3847        - FAT_ENV_INTERFACE:
3848 
3849          Define this to a string that is the name of the block device.
3850 
3851        - FAT_ENV_DEVICE_AND_PART:
3852 
3853          Define this to a string to specify the partition of the device. It can
3854          be as following:
3855 
3856            "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
3857                - "D:P": device D partition P. Error occurs if device D has no
3858                         partition table.
3859                - "D:0": device D.
3860                - "D" or "D:": device D partition 1 if device D has partition
3861                               table, or the whole device D if has no partition
3862                               table.
3863                - "D:auto": first partition in device D with bootable flag set.
3864                            If none, first valid partition in device D. If no
3865                            partition table then means device D.
3866 
3867        - FAT_ENV_FILE:
3868 
3869          It's a string of the FAT file name. This file use to store the
3870          environment.
3871 
3872        - CONFIG_FAT_WRITE:
3873          This should be defined. Otherwise it cannot save the environment file.
3874 
3875 - CONFIG_ENV_IS_IN_MMC:
3876 
3877 	Define this if you have an MMC device which you want to use for the
3878 	environment.
3879 
3880 	- CONFIG_SYS_MMC_ENV_DEV:
3881 
3882 	  Specifies which MMC device the environment is stored in.
3883 
3884 	- CONFIG_SYS_MMC_ENV_PART (optional):
3885 
3886 	  Specifies which MMC partition the environment is stored in. If not
3887 	  set, defaults to partition 0, the user area. Common values might be
3888 	  1 (first MMC boot partition), 2 (second MMC boot partition).
3889 
3890 	- CONFIG_ENV_OFFSET:
3891 	- CONFIG_ENV_SIZE:
3892 
3893 	  These two #defines specify the offset and size of the environment
3894 	  area within the specified MMC device.
3895 
3896 	  If offset is positive (the usual case), it is treated as relative to
3897 	  the start of the MMC partition. If offset is negative, it is treated
3898 	  as relative to the end of the MMC partition. This can be useful if
3899 	  your board may be fitted with different MMC devices, which have
3900 	  different sizes for the MMC partitions, and you always want the
3901 	  environment placed at the very end of the partition, to leave the
3902 	  maximum possible space before it, to store other data.
3903 
3904 	  These two values are in units of bytes, but must be aligned to an
3905 	  MMC sector boundary.
3906 
3907 	- CONFIG_ENV_OFFSET_REDUND (optional):
3908 
3909 	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
3910 	  hold a redundant copy of the environment data. This provides a
3911 	  valid backup copy in case the other copy is corrupted, e.g. due
3912 	  to a power failure during a "saveenv" operation.
3913 
3914 	  This value may also be positive or negative; this is handled in the
3915 	  same way as CONFIG_ENV_OFFSET.
3916 
3917 	  This value is also in units of bytes, but must also be aligned to
3918 	  an MMC sector boundary.
3919 
3920 	- CONFIG_ENV_SIZE_REDUND (optional):
3921 
3922 	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
3923 	  set. If this value is set, it must be set to the same value as
3924 	  CONFIG_ENV_SIZE.
3925 
3926 - CONFIG_SYS_SPI_INIT_OFFSET
3927 
3928 	Defines offset to the initial SPI buffer area in DPRAM. The
3929 	area is used at an early stage (ROM part) if the environment
3930 	is configured to reside in the SPI EEPROM: We need a 520 byte
3931 	scratch DPRAM area. It is used between the two initialization
3932 	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
3933 	to be a good choice since it makes it far enough from the
3934 	start of the data area as well as from the stack pointer.
3935 
3936 Please note that the environment is read-only until the monitor
3937 has been relocated to RAM and a RAM copy of the environment has been
3938 created; also, when using EEPROM you will have to use getenv_f()
3939 until then to read environment variables.
3940 
3941 The environment is protected by a CRC32 checksum. Before the monitor
3942 is relocated into RAM, as a result of a bad CRC you will be working
3943 with the compiled-in default environment - *silently*!!! [This is
3944 necessary, because the first environment variable we need is the
3945 "baudrate" setting for the console - if we have a bad CRC, we don't
3946 have any device yet where we could complain.]
3947 
3948 Note: once the monitor has been relocated, then it will complain if
3949 the default environment is used; a new CRC is computed as soon as you
3950 use the "saveenv" command to store a valid environment.
3951 
3952 - CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3953 		Echo the inverted Ethernet link state to the fault LED.
3954 
3955 		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3956 		      also needs to be defined.
3957 
3958 - CONFIG_SYS_FAULT_MII_ADDR:
3959 		MII address of the PHY to check for the Ethernet link state.
3960 
3961 - CONFIG_NS16550_MIN_FUNCTIONS:
3962 		Define this if you desire to only have use of the NS16550_init
3963 		and NS16550_putc functions for the serial driver located at
3964 		drivers/serial/ns16550.c.  This option is useful for saving
3965 		space for already greatly restricted images, including but not
3966 		limited to NAND_SPL configurations.
3967 
3968 - CONFIG_DISPLAY_BOARDINFO
3969 		Display information about the board that U-Boot is running on
3970 		when U-Boot starts up. The board function checkboard() is called
3971 		to do this.
3972 
3973 - CONFIG_DISPLAY_BOARDINFO_LATE
3974 		Similar to the previous option, but display this information
3975 		later, once stdio is running and output goes to the LCD, if
3976 		present.
3977 
3978 - CONFIG_BOARD_SIZE_LIMIT:
3979 		Maximum size of the U-Boot image. When defined, the
3980 		build system checks that the actual size does not
3981 		exceed it.
3982 
3983 Low Level (hardware related) configuration options:
3984 ---------------------------------------------------
3985 
3986 - CONFIG_SYS_CACHELINE_SIZE:
3987 		Cache Line Size of the CPU.
3988 
3989 - CONFIG_SYS_DEFAULT_IMMR:
3990 		Default address of the IMMR after system reset.
3991 
3992 		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
3993 		and RPXsuper) to be able to adjust the position of
3994 		the IMMR register after a reset.
3995 
3996 - CONFIG_SYS_CCSRBAR_DEFAULT:
3997 		Default (power-on reset) physical address of CCSR on Freescale
3998 		PowerPC SOCs.
3999 
4000 - CONFIG_SYS_CCSRBAR:
4001 		Virtual address of CCSR.  On a 32-bit build, this is typically
4002 		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4003 
4004 		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4005 		for cross-platform code that uses that macro instead.
4006 
4007 - CONFIG_SYS_CCSRBAR_PHYS:
4008 		Physical address of CCSR.  CCSR can be relocated to a new
4009 		physical address, if desired.  In this case, this macro should
4010 		be set to that address.	 Otherwise, it should be set to the
4011 		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4012 		is typically relocated on 36-bit builds.  It is recommended
4013 		that this macro be defined via the _HIGH and _LOW macros:
4014 
4015 		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4016 			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4017 
4018 - CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4019 		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4020 		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4021 		used in assembly code, so it must not contain typecasts or
4022 		integer size suffixes (e.g. "ULL").
4023 
4024 - CONFIG_SYS_CCSRBAR_PHYS_LOW:
4025 		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4026 		used in assembly code, so it must not contain typecasts or
4027 		integer size suffixes (e.g. "ULL").
4028 
4029 - CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4030 		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4031 		forced to a value that ensures that CCSR is not relocated.
4032 
4033 - Floppy Disk Support:
4034 		CONFIG_SYS_FDC_DRIVE_NUMBER
4035 
4036 		the default drive number (default value 0)
4037 
4038 		CONFIG_SYS_ISA_IO_STRIDE
4039 
4040 		defines the spacing between FDC chipset registers
4041 		(default value 1)
4042 
4043 		CONFIG_SYS_ISA_IO_OFFSET
4044 
4045 		defines the offset of register from address. It
4046 		depends on which part of the data bus is connected to
4047 		the FDC chipset. (default value 0)
4048 
4049 		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4050 		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4051 		default value.
4052 
4053 		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4054 		fdc_hw_init() is called at the beginning of the FDC
4055 		setup. fdc_hw_init() must be provided by the board
4056 		source code. It is used to make hardware-dependent
4057 		initializations.
4058 
4059 - CONFIG_IDE_AHB:
4060 		Most IDE controllers were designed to be connected with PCI
4061 		interface. Only few of them were designed for AHB interface.
4062 		When software is doing ATA command and data transfer to
4063 		IDE devices through IDE-AHB controller, some additional
4064 		registers accessing to these kind of IDE-AHB controller
4065 		is required.
4066 
4067 - CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4068 		DO NOT CHANGE unless you know exactly what you're
4069 		doing! (11-4) [MPC8xx/82xx systems only]
4070 
4071 - CONFIG_SYS_INIT_RAM_ADDR:
4072 
4073 		Start address of memory area that can be used for
4074 		initial data and stack; please note that this must be
4075 		writable memory that is working WITHOUT special
4076 		initialization, i. e. you CANNOT use normal RAM which
4077 		will become available only after programming the
4078 		memory controller and running certain initialization
4079 		sequences.
4080 
4081 		U-Boot uses the following memory types:
4082 		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4083 		- MPC824X: data cache
4084 		- PPC4xx:  data cache
4085 
4086 - CONFIG_SYS_GBL_DATA_OFFSET:
4087 
4088 		Offset of the initial data structure in the memory
4089 		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4090 		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4091 		data is located at the end of the available space
4092 		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4093 		GENERATED_GBL_DATA_SIZE), and the initial stack is just
4094 		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4095 		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4096 
4097 	Note:
4098 		On the MPC824X (or other systems that use the data
4099 		cache for initial memory) the address chosen for
4100 		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4101 		point to an otherwise UNUSED address space between
4102 		the top of RAM and the start of the PCI space.
4103 
4104 - CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4105 
4106 - CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4107 
4108 - CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4109 
4110 - CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4111 
4112 - CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4113 
4114 - CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4115 
4116 - CONFIG_SYS_OR_TIMING_SDRAM:
4117 		SDRAM timing
4118 
4119 - CONFIG_SYS_MAMR_PTA:
4120 		periodic timer for refresh
4121 
4122 - CONFIG_SYS_DER:	Debug Event Register (37-47)
4123 
4124 - FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4125   CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4126   CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4127   CONFIG_SYS_BR1_PRELIM:
4128 		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4129 
4130 - SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4131   CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4132   CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4133 		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4134 
4135 - CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4136   CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4137 		Machine Mode Register and Memory Periodic Timer
4138 		Prescaler definitions (SDRAM timing)
4139 
4140 - CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4141 		enable I2C microcode relocation patch (MPC8xx);
4142 		define relocation offset in DPRAM [DSP2]
4143 
4144 - CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4145 		enable SMC microcode relocation patch (MPC8xx);
4146 		define relocation offset in DPRAM [SMC1]
4147 
4148 - CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4149 		enable SPI microcode relocation patch (MPC8xx);
4150 		define relocation offset in DPRAM [SCC4]
4151 
4152 - CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4153 		Offset of the bootmode word in DPRAM used by post
4154 		(Power On Self Tests). This definition overrides
4155 		#define'd default value in commproc.h resp.
4156 		cpm_8260.h.
4157 
4158 - CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4159   CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4160   CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4161   CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4162   CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4163   CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4164   CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4165   CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4166 		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4167 
4168 - CONFIG_PCI_DISABLE_PCIE:
4169 		Disable PCI-Express on systems where it is supported but not
4170 		required.
4171 
4172 - CONFIG_PCI_ENUM_ONLY
4173 		Only scan through and get the devices on the buses.
4174 		Don't do any setup work, presumably because someone or
4175 		something has already done it, and we don't need to do it
4176 		a second time.	Useful for platforms that are pre-booted
4177 		by coreboot or similar.
4178 
4179 - CONFIG_PCI_INDIRECT_BRIDGE:
4180 		Enable support for indirect PCI bridges.
4181 
4182 - CONFIG_SYS_SRIO:
4183 		Chip has SRIO or not
4184 
4185 - CONFIG_SRIO1:
4186 		Board has SRIO 1 port available
4187 
4188 - CONFIG_SRIO2:
4189 		Board has SRIO 2 port available
4190 
4191 - CONFIG_SRIO_PCIE_BOOT_MASTER
4192 		Board can support master function for Boot from SRIO and PCIE
4193 
4194 - CONFIG_SYS_SRIOn_MEM_VIRT:
4195 		Virtual Address of SRIO port 'n' memory region
4196 
4197 - CONFIG_SYS_SRIOn_MEM_PHYS:
4198 		Physical Address of SRIO port 'n' memory region
4199 
4200 - CONFIG_SYS_SRIOn_MEM_SIZE:
4201 		Size of SRIO port 'n' memory region
4202 
4203 - CONFIG_SYS_NAND_BUSWIDTH_16BIT
4204 		Defined to tell the NAND controller that the NAND chip is using
4205 		a 16 bit bus.
4206 		Not all NAND drivers use this symbol.
4207 		Example of drivers that use it:
4208 		- drivers/mtd/nand/ndfc.c
4209 		- drivers/mtd/nand/mxc_nand.c
4210 
4211 - CONFIG_SYS_NDFC_EBC0_CFG
4212 		Sets the EBC0_CFG register for the NDFC. If not defined
4213 		a default value will be used.
4214 
4215 - CONFIG_SPD_EEPROM
4216 		Get DDR timing information from an I2C EEPROM. Common
4217 		with pluggable memory modules such as SODIMMs
4218 
4219   SPD_EEPROM_ADDRESS
4220 		I2C address of the SPD EEPROM
4221 
4222 - CONFIG_SYS_SPD_BUS_NUM
4223 		If SPD EEPROM is on an I2C bus other than the first
4224 		one, specify here. Note that the value must resolve
4225 		to something your driver can deal with.
4226 
4227 - CONFIG_SYS_DDR_RAW_TIMING
4228 		Get DDR timing information from other than SPD. Common with
4229 		soldered DDR chips onboard without SPD. DDR raw timing
4230 		parameters are extracted from datasheet and hard-coded into
4231 		header files or board specific files.
4232 
4233 - CONFIG_FSL_DDR_INTERACTIVE
4234 		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4235 
4236 - CONFIG_FSL_DDR_SYNC_REFRESH
4237 		Enable sync of refresh for multiple controllers.
4238 
4239 - CONFIG_FSL_DDR_BIST
4240 		Enable built-in memory test for Freescale DDR controllers.
4241 
4242 - CONFIG_SYS_83XX_DDR_USES_CS0
4243 		Only for 83xx systems. If specified, then DDR should
4244 		be configured using CS0 and CS1 instead of CS2 and CS3.
4245 
4246 - CONFIG_ETHER_ON_FEC[12]
4247 		Define to enable FEC[12] on a 8xx series processor.
4248 
4249 - CONFIG_FEC[12]_PHY
4250 		Define to the hardcoded PHY address which corresponds
4251 		to the given FEC; i. e.
4252 			#define CONFIG_FEC1_PHY 4
4253 		means that the PHY with address 4 is connected to FEC1
4254 
4255 		When set to -1, means to probe for first available.
4256 
4257 - CONFIG_FEC[12]_PHY_NORXERR
4258 		The PHY does not have a RXERR line (RMII only).
4259 		(so program the FEC to ignore it).
4260 
4261 - CONFIG_RMII
4262 		Enable RMII mode for all FECs.
4263 		Note that this is a global option, we can't
4264 		have one FEC in standard MII mode and another in RMII mode.
4265 
4266 - CONFIG_CRC32_VERIFY
4267 		Add a verify option to the crc32 command.
4268 		The syntax is:
4269 
4270 		=> crc32 -v <address> <count> <crc32>
4271 
4272 		Where address/count indicate a memory area
4273 		and crc32 is the correct crc32 which the
4274 		area should have.
4275 
4276 - CONFIG_LOOPW
4277 		Add the "loopw" memory command. This only takes effect if
4278 		the memory commands are activated globally (CONFIG_CMD_MEM).
4279 
4280 - CONFIG_MX_CYCLIC
4281 		Add the "mdc" and "mwc" memory commands. These are cyclic
4282 		"md/mw" commands.
4283 		Examples:
4284 
4285 		=> mdc.b 10 4 500
4286 		This command will print 4 bytes (10,11,12,13) each 500 ms.
4287 
4288 		=> mwc.l 100 12345678 10
4289 		This command will write 12345678 to address 100 all 10 ms.
4290 
4291 		This only takes effect if the memory commands are activated
4292 		globally (CONFIG_CMD_MEM).
4293 
4294 - CONFIG_SKIP_LOWLEVEL_INIT
4295 		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4296 		low level initializations (like setting up the memory
4297 		controller) are omitted and/or U-Boot does not
4298 		relocate itself into RAM.
4299 
4300 		Normally this variable MUST NOT be defined. The only
4301 		exception is when U-Boot is loaded (to RAM) by some
4302 		other boot loader or by a debugger which performs
4303 		these initializations itself.
4304 
4305 - CONFIG_SKIP_LOWLEVEL_INIT_ONLY
4306 		[ARM926EJ-S only] This allows just the call to lowlevel_init()
4307 		to be skipped. The normal CP15 init (such as enabling the
4308 		instruction cache) is still performed.
4309 
4310 - CONFIG_SPL_BUILD
4311 		Modifies the behaviour of start.S when compiling a loader
4312 		that is executed before the actual U-Boot. E.g. when
4313 		compiling a NAND SPL.
4314 
4315 - CONFIG_TPL_BUILD
4316 		Modifies the behaviour of start.S  when compiling a loader
4317 		that is executed after the SPL and before the actual U-Boot.
4318 		It is loaded by the SPL.
4319 
4320 - CONFIG_SYS_MPC85XX_NO_RESETVEC
4321 		Only for 85xx systems. If this variable is specified, the section
4322 		.resetvec is not kept and the section .bootpg is placed in the
4323 		previous 4k of the .text section.
4324 
4325 - CONFIG_ARCH_MAP_SYSMEM
4326 		Generally U-Boot (and in particular the md command) uses
4327 		effective address. It is therefore not necessary to regard
4328 		U-Boot address as virtual addresses that need to be translated
4329 		to physical addresses. However, sandbox requires this, since
4330 		it maintains its own little RAM buffer which contains all
4331 		addressable memory. This option causes some memory accesses
4332 		to be mapped through map_sysmem() / unmap_sysmem().
4333 
4334 - CONFIG_X86_RESET_VECTOR
4335 		If defined, the x86 reset vector code is included. This is not
4336 		needed when U-Boot is running from Coreboot.
4337 
4338 - CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4339 		Enables the RTC32K OSC on AM33xx based plattforms
4340 
4341 - CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4342 		Option to disable subpage write in NAND driver
4343 		driver that uses this:
4344 		drivers/mtd/nand/davinci_nand.c
4345 
4346 Freescale QE/FMAN Firmware Support:
4347 -----------------------------------
4348 
4349 The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4350 loading of "firmware", which is encoded in the QE firmware binary format.
4351 This firmware often needs to be loaded during U-Boot booting, so macros
4352 are used to identify the storage device (NOR flash, SPI, etc) and the address
4353 within that device.
4354 
4355 - CONFIG_SYS_FMAN_FW_ADDR
4356 	The address in the storage device where the FMAN microcode is located.  The
4357 	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4358 	is also specified.
4359 
4360 - CONFIG_SYS_QE_FW_ADDR
4361 	The address in the storage device where the QE microcode is located.  The
4362 	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4363 	is also specified.
4364 
4365 - CONFIG_SYS_QE_FMAN_FW_LENGTH
4366 	The maximum possible size of the firmware.  The firmware binary format
4367 	has a field that specifies the actual size of the firmware, but it
4368 	might not be possible to read any part of the firmware unless some
4369 	local storage is allocated to hold the entire firmware first.
4370 
4371 - CONFIG_SYS_QE_FMAN_FW_IN_NOR
4372 	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4373 	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4374 	virtual address in NOR flash.
4375 
4376 - CONFIG_SYS_QE_FMAN_FW_IN_NAND
4377 	Specifies that QE/FMAN firmware is located in NAND flash.
4378 	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4379 
4380 - CONFIG_SYS_QE_FMAN_FW_IN_MMC
4381 	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4382 	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4383 
4384 - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4385 	Specifies that QE/FMAN firmware is located in the remote (master)
4386 	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4387 	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4388 	window->master inbound window->master LAW->the ucode address in
4389 	master's memory space.
4390 
4391 Freescale Layerscape Management Complex Firmware Support:
4392 ---------------------------------------------------------
4393 The Freescale Layerscape Management Complex (MC) supports the loading of
4394 "firmware".
4395 This firmware often needs to be loaded during U-Boot booting, so macros
4396 are used to identify the storage device (NOR flash, SPI, etc) and the address
4397 within that device.
4398 
4399 - CONFIG_FSL_MC_ENET
4400 	Enable the MC driver for Layerscape SoCs.
4401 
4402 Freescale Layerscape Debug Server Support:
4403 -------------------------------------------
4404 The Freescale Layerscape Debug Server Support supports the loading of
4405 "Debug Server firmware" and triggering SP boot-rom.
4406 This firmware often needs to be loaded during U-Boot booting.
4407 
4408 - CONFIG_SYS_MC_RSV_MEM_ALIGN
4409 	Define alignment of reserved memory MC requires
4410 
4411 Reproducible builds
4412 -------------------
4413 
4414 In order to achieve reproducible builds, timestamps used in the U-Boot build
4415 process have to be set to a fixed value.
4416 
4417 This is done using the SOURCE_DATE_EPOCH environment variable.
4418 SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
4419 option for U-Boot or an environment variable in U-Boot.
4420 
4421 SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
4422 
4423 Building the Software:
4424 ======================
4425 
4426 Building U-Boot has been tested in several native build environments
4427 and in many different cross environments. Of course we cannot support
4428 all possibly existing versions of cross development tools in all
4429 (potentially obsolete) versions. In case of tool chain problems we
4430 recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4431 which is extensively used to build and test U-Boot.
4432 
4433 If you are not using a native environment, it is assumed that you
4434 have GNU cross compiling tools available in your path. In this case,
4435 you must set the environment variable CROSS_COMPILE in your shell.
4436 Note that no changes to the Makefile or any other source files are
4437 necessary. For example using the ELDK on a 4xx CPU, please enter:
4438 
4439 	$ CROSS_COMPILE=ppc_4xx-
4440 	$ export CROSS_COMPILE
4441 
4442 Note: If you wish to generate Windows versions of the utilities in
4443       the tools directory you can use the MinGW toolchain
4444       (http://www.mingw.org).  Set your HOST tools to the MinGW
4445       toolchain and execute 'make tools'.  For example:
4446 
4447        $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4448 
4449       Binaries such as tools/mkimage.exe will be created which can
4450       be executed on computers running Windows.
4451 
4452 U-Boot is intended to be simple to build. After installing the
4453 sources you must configure U-Boot for one specific board type. This
4454 is done by typing:
4455 
4456 	make NAME_defconfig
4457 
4458 where "NAME_defconfig" is the name of one of the existing configu-
4459 rations; see boards.cfg for supported names.
4460 
4461 Note: for some board special configuration names may exist; check if
4462       additional information is available from the board vendor; for
4463       instance, the TQM823L systems are available without (standard)
4464       or with LCD support. You can select such additional "features"
4465       when choosing the configuration, i. e.
4466 
4467       make TQM823L_defconfig
4468 	- will configure for a plain TQM823L, i. e. no LCD support
4469 
4470       make TQM823L_LCD_defconfig
4471 	- will configure for a TQM823L with U-Boot console on LCD
4472 
4473       etc.
4474 
4475 
4476 Finally, type "make all", and you should get some working U-Boot
4477 images ready for download to / installation on your system:
4478 
4479 - "u-boot.bin" is a raw binary image
4480 - "u-boot" is an image in ELF binary format
4481 - "u-boot.srec" is in Motorola S-Record format
4482 
4483 By default the build is performed locally and the objects are saved
4484 in the source directory. One of the two methods can be used to change
4485 this behavior and build U-Boot to some external directory:
4486 
4487 1. Add O= to the make command line invocations:
4488 
4489 	make O=/tmp/build distclean
4490 	make O=/tmp/build NAME_defconfig
4491 	make O=/tmp/build all
4492 
4493 2. Set environment variable KBUILD_OUTPUT to point to the desired location:
4494 
4495 	export KBUILD_OUTPUT=/tmp/build
4496 	make distclean
4497 	make NAME_defconfig
4498 	make all
4499 
4500 Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
4501 variable.
4502 
4503 
4504 Please be aware that the Makefiles assume you are using GNU make, so
4505 for instance on NetBSD you might need to use "gmake" instead of
4506 native "make".
4507 
4508 
4509 If the system board that you have is not listed, then you will need
4510 to port U-Boot to your hardware platform. To do this, follow these
4511 steps:
4512 
4513 1.  Create a new directory to hold your board specific code. Add any
4514     files you need. In your board directory, you will need at least
4515     the "Makefile" and a "<board>.c".
4516 2.  Create a new configuration file "include/configs/<board>.h" for
4517     your board.
4518 3.  If you're porting U-Boot to a new CPU, then also create a new
4519     directory to hold your CPU specific code. Add any files you need.
4520 4.  Run "make <board>_defconfig" with your new name.
4521 5.  Type "make", and you should get a working "u-boot.srec" file
4522     to be installed on your target system.
4523 6.  Debug and solve any problems that might arise.
4524     [Of course, this last step is much harder than it sounds.]
4525 
4526 
4527 Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4528 ==============================================================
4529 
4530 If you have modified U-Boot sources (for instance added a new board
4531 or support for new devices, a new CPU, etc.) you are expected to
4532 provide feedback to the other developers. The feedback normally takes
4533 the form of a "patch", i. e. a context diff against a certain (latest
4534 official or latest in the git repository) version of U-Boot sources.
4535 
4536 But before you submit such a patch, please verify that your modifi-
4537 cation did not break existing code. At least make sure that *ALL* of
4538 the supported boards compile WITHOUT ANY compiler warnings. To do so,
4539 just run the buildman script (tools/buildman/buildman), which will
4540 configure and build U-Boot for ALL supported system. Be warned, this
4541 will take a while. Please see the buildman README, or run 'buildman -H'
4542 for documentation.
4543 
4544 
4545 See also "U-Boot Porting Guide" below.
4546 
4547 
4548 Monitor Commands - Overview:
4549 ============================
4550 
4551 go	- start application at address 'addr'
4552 run	- run commands in an environment variable
4553 bootm	- boot application image from memory
4554 bootp	- boot image via network using BootP/TFTP protocol
4555 bootz   - boot zImage from memory
4556 tftpboot- boot image via network using TFTP protocol
4557 	       and env variables "ipaddr" and "serverip"
4558 	       (and eventually "gatewayip")
4559 tftpput - upload a file via network using TFTP protocol
4560 rarpboot- boot image via network using RARP/TFTP protocol
4561 diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4562 loads	- load S-Record file over serial line
4563 loadb	- load binary file over serial line (kermit mode)
4564 md	- memory display
4565 mm	- memory modify (auto-incrementing)
4566 nm	- memory modify (constant address)
4567 mw	- memory write (fill)
4568 cp	- memory copy
4569 cmp	- memory compare
4570 crc32	- checksum calculation
4571 i2c	- I2C sub-system
4572 sspi	- SPI utility commands
4573 base	- print or set address offset
4574 printenv- print environment variables
4575 setenv	- set environment variables
4576 saveenv - save environment variables to persistent storage
4577 protect - enable or disable FLASH write protection
4578 erase	- erase FLASH memory
4579 flinfo	- print FLASH memory information
4580 nand	- NAND memory operations (see doc/README.nand)
4581 bdinfo	- print Board Info structure
4582 iminfo	- print header information for application image
4583 coninfo - print console devices and informations
4584 ide	- IDE sub-system
4585 loop	- infinite loop on address range
4586 loopw	- infinite write loop on address range
4587 mtest	- simple RAM test
4588 icache	- enable or disable instruction cache
4589 dcache	- enable or disable data cache
4590 reset	- Perform RESET of the CPU
4591 echo	- echo args to console
4592 version - print monitor version
4593 help	- print online help
4594 ?	- alias for 'help'
4595 
4596 
4597 Monitor Commands - Detailed Description:
4598 ========================================
4599 
4600 TODO.
4601 
4602 For now: just type "help <command>".
4603 
4604 
4605 Environment Variables:
4606 ======================
4607 
4608 U-Boot supports user configuration using Environment Variables which
4609 can be made persistent by saving to Flash memory.
4610 
4611 Environment Variables are set using "setenv", printed using
4612 "printenv", and saved to Flash using "saveenv". Using "setenv"
4613 without a value can be used to delete a variable from the
4614 environment. As long as you don't save the environment you are
4615 working with an in-memory copy. In case the Flash area containing the
4616 environment is erased by accident, a default environment is provided.
4617 
4618 Some configuration options can be set using Environment Variables.
4619 
4620 List of environment variables (most likely not complete):
4621 
4622   baudrate	- see CONFIG_BAUDRATE
4623 
4624   bootdelay	- see CONFIG_BOOTDELAY
4625 
4626   bootcmd	- see CONFIG_BOOTCOMMAND
4627 
4628   bootargs	- Boot arguments when booting an RTOS image
4629 
4630   bootfile	- Name of the image to load with TFTP
4631 
4632   bootm_low	- Memory range available for image processing in the bootm
4633 		  command can be restricted. This variable is given as
4634 		  a hexadecimal number and defines lowest address allowed
4635 		  for use by the bootm command. See also "bootm_size"
4636 		  environment variable. Address defined by "bootm_low" is
4637 		  also the base of the initial memory mapping for the Linux
4638 		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4639 		  bootm_mapsize.
4640 
4641   bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4642 		  This variable is given as a hexadecimal number and it
4643 		  defines the size of the memory region starting at base
4644 		  address bootm_low that is accessible by the Linux kernel
4645 		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4646 		  as the default value if it is defined, and bootm_size is
4647 		  used otherwise.
4648 
4649   bootm_size	- Memory range available for image processing in the bootm
4650 		  command can be restricted. This variable is given as
4651 		  a hexadecimal number and defines the size of the region
4652 		  allowed for use by the bootm command. See also "bootm_low"
4653 		  environment variable.
4654 
4655   updatefile	- Location of the software update file on a TFTP server, used
4656 		  by the automatic software update feature. Please refer to
4657 		  documentation in doc/README.update for more details.
4658 
4659   autoload	- if set to "no" (any string beginning with 'n'),
4660 		  "bootp" will just load perform a lookup of the
4661 		  configuration from the BOOTP server, but not try to
4662 		  load any image using TFTP
4663 
4664   autostart	- if set to "yes", an image loaded using the "bootp",
4665 		  "rarpboot", "tftpboot" or "diskboot" commands will
4666 		  be automatically started (by internally calling
4667 		  "bootm")
4668 
4669 		  If set to "no", a standalone image passed to the
4670 		  "bootm" command will be copied to the load address
4671 		  (and eventually uncompressed), but NOT be started.
4672 		  This can be used to load and uncompress arbitrary
4673 		  data.
4674 
4675   fdt_high	- if set this restricts the maximum address that the
4676 		  flattened device tree will be copied into upon boot.
4677 		  For example, if you have a system with 1 GB memory
4678 		  at physical address 0x10000000, while Linux kernel
4679 		  only recognizes the first 704 MB as low memory, you
4680 		  may need to set fdt_high as 0x3C000000 to have the
4681 		  device tree blob be copied to the maximum address
4682 		  of the 704 MB low memory, so that Linux kernel can
4683 		  access it during the boot procedure.
4684 
4685 		  If this is set to the special value 0xFFFFFFFF then
4686 		  the fdt will not be copied at all on boot.  For this
4687 		  to work it must reside in writable memory, have
4688 		  sufficient padding on the end of it for u-boot to
4689 		  add the information it needs into it, and the memory
4690 		  must be accessible by the kernel.
4691 
4692   fdtcontroladdr- if set this is the address of the control flattened
4693 		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4694 		  defined.
4695 
4696   i2cfast	- (PPC405GP|PPC405EP only)
4697 		  if set to 'y' configures Linux I2C driver for fast
4698 		  mode (400kHZ). This environment variable is used in
4699 		  initialization code. So, for changes to be effective
4700 		  it must be saved and board must be reset.
4701 
4702   initrd_high	- restrict positioning of initrd images:
4703 		  If this variable is not set, initrd images will be
4704 		  copied to the highest possible address in RAM; this
4705 		  is usually what you want since it allows for
4706 		  maximum initrd size. If for some reason you want to
4707 		  make sure that the initrd image is loaded below the
4708 		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4709 		  variable to a value of "no" or "off" or "0".
4710 		  Alternatively, you can set it to a maximum upper
4711 		  address to use (U-Boot will still check that it
4712 		  does not overwrite the U-Boot stack and data).
4713 
4714 		  For instance, when you have a system with 16 MB
4715 		  RAM, and want to reserve 4 MB from use by Linux,
4716 		  you can do this by adding "mem=12M" to the value of
4717 		  the "bootargs" variable. However, now you must make
4718 		  sure that the initrd image is placed in the first
4719 		  12 MB as well - this can be done with
4720 
4721 		  setenv initrd_high 00c00000
4722 
4723 		  If you set initrd_high to 0xFFFFFFFF, this is an
4724 		  indication to U-Boot that all addresses are legal
4725 		  for the Linux kernel, including addresses in flash
4726 		  memory. In this case U-Boot will NOT COPY the
4727 		  ramdisk at all. This may be useful to reduce the
4728 		  boot time on your system, but requires that this
4729 		  feature is supported by your Linux kernel.
4730 
4731   ipaddr	- IP address; needed for tftpboot command
4732 
4733   loadaddr	- Default load address for commands like "bootp",
4734 		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4735 
4736   loads_echo	- see CONFIG_LOADS_ECHO
4737 
4738   serverip	- TFTP server IP address; needed for tftpboot command
4739 
4740   bootretry	- see CONFIG_BOOT_RETRY_TIME
4741 
4742   bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4743 
4744   bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4745 
4746   ethprime	- controls which interface is used first.
4747 
4748   ethact	- controls which interface is currently active.
4749 		  For example you can do the following
4750 
4751 		  => setenv ethact FEC
4752 		  => ping 192.168.0.1 # traffic sent on FEC
4753 		  => setenv ethact SCC
4754 		  => ping 10.0.0.1 # traffic sent on SCC
4755 
4756   ethrotate	- When set to "no" U-Boot does not go through all
4757 		  available network interfaces.
4758 		  It just stays at the currently selected interface.
4759 
4760   netretry	- When set to "no" each network operation will
4761 		  either succeed or fail without retrying.
4762 		  When set to "once" the network operation will
4763 		  fail when all the available network interfaces
4764 		  are tried once without success.
4765 		  Useful on scripts which control the retry operation
4766 		  themselves.
4767 
4768   npe_ucode	- set load address for the NPE microcode
4769 
4770   silent_linux  - If set then Linux will be told to boot silently, by
4771 		  changing the console to be empty. If "yes" it will be
4772 		  made silent. If "no" it will not be made silent. If
4773 		  unset, then it will be made silent if the U-Boot console
4774 		  is silent.
4775 
4776   tftpsrcp	- If this is set, the value is used for TFTP's
4777 		  UDP source port.
4778 
4779   tftpdstp	- If this is set, the value is used for TFTP's UDP
4780 		  destination port instead of the Well Know Port 69.
4781 
4782   tftpblocksize - Block size to use for TFTP transfers; if not set,
4783 		  we use the TFTP server's default block size
4784 
4785   tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4786 		  seconds, minimum value is 1000 = 1 second). Defines
4787 		  when a packet is considered to be lost so it has to
4788 		  be retransmitted. The default is 5000 = 5 seconds.
4789 		  Lowering this value may make downloads succeed
4790 		  faster in networks with high packet loss rates or
4791 		  with unreliable TFTP servers.
4792 
4793   tftptimeoutcountmax	- maximum count of TFTP timeouts (no
4794 		  unit, minimum value = 0). Defines how many timeouts
4795 		  can happen during a single file transfer before that
4796 		  transfer is aborted. The default is 10, and 0 means
4797 		  'no timeouts allowed'. Increasing this value may help
4798 		  downloads succeed with high packet loss rates, or with
4799 		  unreliable TFTP servers or client hardware.
4800 
4801   vlan		- When set to a value < 4095 the traffic over
4802 		  Ethernet is encapsulated/received over 802.1q
4803 		  VLAN tagged frames.
4804 
4805   bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
4806 		  Unsigned value, in milliseconds. If not set, the period will
4807 		  be either the default (28000), or a value based on
4808 		  CONFIG_NET_RETRY_COUNT, if defined. This value has
4809 		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
4810 
4811 The following image location variables contain the location of images
4812 used in booting. The "Image" column gives the role of the image and is
4813 not an environment variable name. The other columns are environment
4814 variable names. "File Name" gives the name of the file on a TFTP
4815 server, "RAM Address" gives the location in RAM the image will be
4816 loaded to, and "Flash Location" gives the image's address in NOR
4817 flash or offset in NAND flash.
4818 
4819 *Note* - these variables don't have to be defined for all boards, some
4820 boards currently use other variables for these purposes, and some
4821 boards use these variables for other purposes.
4822 
4823 Image		    File Name	     RAM Address       Flash Location
4824 -----		    ---------	     -----------       --------------
4825 u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4826 Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4827 device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4828 ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4829 
4830 The following environment variables may be used and automatically
4831 updated by the network boot commands ("bootp" and "rarpboot"),
4832 depending the information provided by your boot server:
4833 
4834   bootfile	- see above
4835   dnsip		- IP address of your Domain Name Server
4836   dnsip2	- IP address of your secondary Domain Name Server
4837   gatewayip	- IP address of the Gateway (Router) to use
4838   hostname	- Target hostname
4839   ipaddr	- see above
4840   netmask	- Subnet Mask
4841   rootpath	- Pathname of the root filesystem on the NFS server
4842   serverip	- see above
4843 
4844 
4845 There are two special Environment Variables:
4846 
4847   serial#	- contains hardware identification information such
4848 		  as type string and/or serial number
4849   ethaddr	- Ethernet address
4850 
4851 These variables can be set only once (usually during manufacturing of
4852 the board). U-Boot refuses to delete or overwrite these variables
4853 once they have been set once.
4854 
4855 
4856 Further special Environment Variables:
4857 
4858   ver		- Contains the U-Boot version string as printed
4859 		  with the "version" command. This variable is
4860 		  readonly (see CONFIG_VERSION_VARIABLE).
4861 
4862 
4863 Please note that changes to some configuration parameters may take
4864 only effect after the next boot (yes, that's just like Windoze :-).
4865 
4866 
4867 Callback functions for environment variables:
4868 ---------------------------------------------
4869 
4870 For some environment variables, the behavior of u-boot needs to change
4871 when their values are changed.  This functionality allows functions to
4872 be associated with arbitrary variables.  On creation, overwrite, or
4873 deletion, the callback will provide the opportunity for some side
4874 effect to happen or for the change to be rejected.
4875 
4876 The callbacks are named and associated with a function using the
4877 U_BOOT_ENV_CALLBACK macro in your board or driver code.
4878 
4879 These callbacks are associated with variables in one of two ways.  The
4880 static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
4881 in the board configuration to a string that defines a list of
4882 associations.  The list must be in the following format:
4883 
4884 	entry = variable_name[:callback_name]
4885 	list = entry[,list]
4886 
4887 If the callback name is not specified, then the callback is deleted.
4888 Spaces are also allowed anywhere in the list.
4889 
4890 Callbacks can also be associated by defining the ".callbacks" variable
4891 with the same list format above.  Any association in ".callbacks" will
4892 override any association in the static list. You can define
4893 CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
4894 ".callbacks" environment variable in the default or embedded environment.
4895 
4896 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
4897 regular expression. This allows multiple variables to be connected to
4898 the same callback without explicitly listing them all out.
4899 
4900 
4901 Command Line Parsing:
4902 =====================
4903 
4904 There are two different command line parsers available with U-Boot:
4905 the old "simple" one, and the much more powerful "hush" shell:
4906 
4907 Old, simple command line parser:
4908 --------------------------------
4909 
4910 - supports environment variables (through setenv / saveenv commands)
4911 - several commands on one line, separated by ';'
4912 - variable substitution using "... ${name} ..." syntax
4913 - special characters ('$', ';') can be escaped by prefixing with '\',
4914   for example:
4915 	setenv bootcmd bootm \${address}
4916 - You can also escape text by enclosing in single apostrophes, for example:
4917 	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4918 
4919 Hush shell:
4920 -----------
4921 
4922 - similar to Bourne shell, with control structures like
4923   if...then...else...fi, for...do...done; while...do...done,
4924   until...do...done, ...
4925 - supports environment ("global") variables (through setenv / saveenv
4926   commands) and local shell variables (through standard shell syntax
4927   "name=value"); only environment variables can be used with "run"
4928   command
4929 
4930 General rules:
4931 --------------
4932 
4933 (1) If a command line (or an environment variable executed by a "run"
4934     command) contains several commands separated by semicolon, and
4935     one of these commands fails, then the remaining commands will be
4936     executed anyway.
4937 
4938 (2) If you execute several variables with one call to run (i. e.
4939     calling run with a list of variables as arguments), any failing
4940     command will cause "run" to terminate, i. e. the remaining
4941     variables are not executed.
4942 
4943 Note for Redundant Ethernet Interfaces:
4944 =======================================
4945 
4946 Some boards come with redundant Ethernet interfaces; U-Boot supports
4947 such configurations and is capable of automatic selection of a
4948 "working" interface when needed. MAC assignment works as follows:
4949 
4950 Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4951 MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4952 "eth1addr" (=>eth1), "eth2addr", ...
4953 
4954 If the network interface stores some valid MAC address (for instance
4955 in SROM), this is used as default address if there is NO correspon-
4956 ding setting in the environment; if the corresponding environment
4957 variable is set, this overrides the settings in the card; that means:
4958 
4959 o If the SROM has a valid MAC address, and there is no address in the
4960   environment, the SROM's address is used.
4961 
4962 o If there is no valid address in the SROM, and a definition in the
4963   environment exists, then the value from the environment variable is
4964   used.
4965 
4966 o If both the SROM and the environment contain a MAC address, and
4967   both addresses are the same, this MAC address is used.
4968 
4969 o If both the SROM and the environment contain a MAC address, and the
4970   addresses differ, the value from the environment is used and a
4971   warning is printed.
4972 
4973 o If neither SROM nor the environment contain a MAC address, an error
4974   is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4975   a random, locally-assigned MAC is used.
4976 
4977 If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4978 will be programmed into hardware as part of the initialization process.	 This
4979 may be skipped by setting the appropriate 'ethmacskip' environment variable.
4980 The naming convention is as follows:
4981 "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4982 
4983 Image Formats:
4984 ==============
4985 
4986 U-Boot is capable of booting (and performing other auxiliary operations on)
4987 images in two formats:
4988 
4989 New uImage format (FIT)
4990 -----------------------
4991 
4992 Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4993 to Flattened Device Tree). It allows the use of images with multiple
4994 components (several kernels, ramdisks, etc.), with contents protected by
4995 SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4996 
4997 
4998 Old uImage format
4999 -----------------
5000 
5001 Old image format is based on binary files which can be basically anything,
5002 preceded by a special header; see the definitions in include/image.h for
5003 details; basically, the header defines the following image properties:
5004 
5005 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5006   4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5007   LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5008   Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5009   INTEGRITY).
5010 * Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5011   IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5012   Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5013 * Compression Type (uncompressed, gzip, bzip2)
5014 * Load Address
5015 * Entry Point
5016 * Image Name
5017 * Image Timestamp
5018 
5019 The header is marked by a special Magic Number, and both the header
5020 and the data portions of the image are secured against corruption by
5021 CRC32 checksums.
5022 
5023 
5024 Linux Support:
5025 ==============
5026 
5027 Although U-Boot should support any OS or standalone application
5028 easily, the main focus has always been on Linux during the design of
5029 U-Boot.
5030 
5031 U-Boot includes many features that so far have been part of some
5032 special "boot loader" code within the Linux kernel. Also, any
5033 "initrd" images to be used are no longer part of one big Linux image;
5034 instead, kernel and "initrd" are separate images. This implementation
5035 serves several purposes:
5036 
5037 - the same features can be used for other OS or standalone
5038   applications (for instance: using compressed images to reduce the
5039   Flash memory footprint)
5040 
5041 - it becomes much easier to port new Linux kernel versions because
5042   lots of low-level, hardware dependent stuff are done by U-Boot
5043 
5044 - the same Linux kernel image can now be used with different "initrd"
5045   images; of course this also means that different kernel images can
5046   be run with the same "initrd". This makes testing easier (you don't
5047   have to build a new "zImage.initrd" Linux image when you just
5048   change a file in your "initrd"). Also, a field-upgrade of the
5049   software is easier now.
5050 
5051 
5052 Linux HOWTO:
5053 ============
5054 
5055 Porting Linux to U-Boot based systems:
5056 ---------------------------------------
5057 
5058 U-Boot cannot save you from doing all the necessary modifications to
5059 configure the Linux device drivers for use with your target hardware
5060 (no, we don't intend to provide a full virtual machine interface to
5061 Linux :-).
5062 
5063 But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5064 
5065 Just make sure your machine specific header file (for instance
5066 include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5067 Information structure as we define in include/asm-<arch>/u-boot.h,
5068 and make sure that your definition of IMAP_ADDR uses the same value
5069 as your U-Boot configuration in CONFIG_SYS_IMMR.
5070 
5071 Note that U-Boot now has a driver model, a unified model for drivers.
5072 If you are adding a new driver, plumb it into driver model. If there
5073 is no uclass available, you are encouraged to create one. See
5074 doc/driver-model.
5075 
5076 
5077 Configuring the Linux kernel:
5078 -----------------------------
5079 
5080 No specific requirements for U-Boot. Make sure you have some root
5081 device (initial ramdisk, NFS) for your target system.
5082 
5083 
5084 Building a Linux Image:
5085 -----------------------
5086 
5087 With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5088 not used. If you use recent kernel source, a new build target
5089 "uImage" will exist which automatically builds an image usable by
5090 U-Boot. Most older kernels also have support for a "pImage" target,
5091 which was introduced for our predecessor project PPCBoot and uses a
5092 100% compatible format.
5093 
5094 Example:
5095 
5096 	make TQM850L_defconfig
5097 	make oldconfig
5098 	make dep
5099 	make uImage
5100 
5101 The "uImage" build target uses a special tool (in 'tools/mkimage') to
5102 encapsulate a compressed Linux kernel image with header	 information,
5103 CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5104 
5105 * build a standard "vmlinux" kernel image (in ELF binary format):
5106 
5107 * convert the kernel into a raw binary image:
5108 
5109 	${CROSS_COMPILE}-objcopy -O binary \
5110 				 -R .note -R .comment \
5111 				 -S vmlinux linux.bin
5112 
5113 * compress the binary image:
5114 
5115 	gzip -9 linux.bin
5116 
5117 * package compressed binary image for U-Boot:
5118 
5119 	mkimage -A ppc -O linux -T kernel -C gzip \
5120 		-a 0 -e 0 -n "Linux Kernel Image" \
5121 		-d linux.bin.gz uImage
5122 
5123 
5124 The "mkimage" tool can also be used to create ramdisk images for use
5125 with U-Boot, either separated from the Linux kernel image, or
5126 combined into one file. "mkimage" encapsulates the images with a 64
5127 byte header containing information about target architecture,
5128 operating system, image type, compression method, entry points, time
5129 stamp, CRC32 checksums, etc.
5130 
5131 "mkimage" can be called in two ways: to verify existing images and
5132 print the header information, or to build new images.
5133 
5134 In the first form (with "-l" option) mkimage lists the information
5135 contained in the header of an existing U-Boot image; this includes
5136 checksum verification:
5137 
5138 	tools/mkimage -l image
5139 	  -l ==> list image header information
5140 
5141 The second form (with "-d" option) is used to build a U-Boot image
5142 from a "data file" which is used as image payload:
5143 
5144 	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5145 		      -n name -d data_file image
5146 	  -A ==> set architecture to 'arch'
5147 	  -O ==> set operating system to 'os'
5148 	  -T ==> set image type to 'type'
5149 	  -C ==> set compression type 'comp'
5150 	  -a ==> set load address to 'addr' (hex)
5151 	  -e ==> set entry point to 'ep' (hex)
5152 	  -n ==> set image name to 'name'
5153 	  -d ==> use image data from 'datafile'
5154 
5155 Right now, all Linux kernels for PowerPC systems use the same load
5156 address (0x00000000), but the entry point address depends on the
5157 kernel version:
5158 
5159 - 2.2.x kernels have the entry point at 0x0000000C,
5160 - 2.3.x and later kernels have the entry point at 0x00000000.
5161 
5162 So a typical call to build a U-Boot image would read:
5163 
5164 	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5165 	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5166 	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5167 	> examples/uImage.TQM850L
5168 	Image Name:   2.4.4 kernel for TQM850L
5169 	Created:      Wed Jul 19 02:34:59 2000
5170 	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5171 	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5172 	Load Address: 0x00000000
5173 	Entry Point:  0x00000000
5174 
5175 To verify the contents of the image (or check for corruption):
5176 
5177 	-> tools/mkimage -l examples/uImage.TQM850L
5178 	Image Name:   2.4.4 kernel for TQM850L
5179 	Created:      Wed Jul 19 02:34:59 2000
5180 	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5181 	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5182 	Load Address: 0x00000000
5183 	Entry Point:  0x00000000
5184 
5185 NOTE: for embedded systems where boot time is critical you can trade
5186 speed for memory and install an UNCOMPRESSED image instead: this
5187 needs more space in Flash, but boots much faster since it does not
5188 need to be uncompressed:
5189 
5190 	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5191 	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5192 	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5193 	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5194 	> examples/uImage.TQM850L-uncompressed
5195 	Image Name:   2.4.4 kernel for TQM850L
5196 	Created:      Wed Jul 19 02:34:59 2000
5197 	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5198 	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5199 	Load Address: 0x00000000
5200 	Entry Point:  0x00000000
5201 
5202 
5203 Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5204 when your kernel is intended to use an initial ramdisk:
5205 
5206 	-> tools/mkimage -n 'Simple Ramdisk Image' \
5207 	> -A ppc -O linux -T ramdisk -C gzip \
5208 	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5209 	Image Name:   Simple Ramdisk Image
5210 	Created:      Wed Jan 12 14:01:50 2000
5211 	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5212 	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5213 	Load Address: 0x00000000
5214 	Entry Point:  0x00000000
5215 
5216 The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5217 option performs the converse operation of the mkimage's second form (the "-d"
5218 option). Given an image built by mkimage, the dumpimage extracts a "data file"
5219 from the image:
5220 
5221 	tools/dumpimage -i image -T type -p position data_file
5222 	  -i ==> extract from the 'image' a specific 'data_file'
5223 	  -T ==> set image type to 'type'
5224 	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5225 
5226 
5227 Installing a Linux Image:
5228 -------------------------
5229 
5230 To downloading a U-Boot image over the serial (console) interface,
5231 you must convert the image to S-Record format:
5232 
5233 	objcopy -I binary -O srec examples/image examples/image.srec
5234 
5235 The 'objcopy' does not understand the information in the U-Boot
5236 image header, so the resulting S-Record file will be relative to
5237 address 0x00000000. To load it to a given address, you need to
5238 specify the target address as 'offset' parameter with the 'loads'
5239 command.
5240 
5241 Example: install the image to address 0x40100000 (which on the
5242 TQM8xxL is in the first Flash bank):
5243 
5244 	=> erase 40100000 401FFFFF
5245 
5246 	.......... done
5247 	Erased 8 sectors
5248 
5249 	=> loads 40100000
5250 	## Ready for S-Record download ...
5251 	~>examples/image.srec
5252 	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5253 	...
5254 	15989 15990 15991 15992
5255 	[file transfer complete]
5256 	[connected]
5257 	## Start Addr = 0x00000000
5258 
5259 
5260 You can check the success of the download using the 'iminfo' command;
5261 this includes a checksum verification so you can be sure no data
5262 corruption happened:
5263 
5264 	=> imi 40100000
5265 
5266 	## Checking Image at 40100000 ...
5267 	   Image Name:	 2.2.13 for initrd on TQM850L
5268 	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5269 	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5270 	   Load Address: 00000000
5271 	   Entry Point:	 0000000c
5272 	   Verifying Checksum ... OK
5273 
5274 
5275 Boot Linux:
5276 -----------
5277 
5278 The "bootm" command is used to boot an application that is stored in
5279 memory (RAM or Flash). In case of a Linux kernel image, the contents
5280 of the "bootargs" environment variable is passed to the kernel as
5281 parameters. You can check and modify this variable using the
5282 "printenv" and "setenv" commands:
5283 
5284 
5285 	=> printenv bootargs
5286 	bootargs=root=/dev/ram
5287 
5288 	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5289 
5290 	=> printenv bootargs
5291 	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5292 
5293 	=> bootm 40020000
5294 	## Booting Linux kernel at 40020000 ...
5295 	   Image Name:	 2.2.13 for NFS on TQM850L
5296 	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5297 	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5298 	   Load Address: 00000000
5299 	   Entry Point:	 0000000c
5300 	   Verifying Checksum ... OK
5301 	   Uncompressing Kernel Image ... OK
5302 	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
5303 	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5304 	time_init: decrementer frequency = 187500000/60
5305 	Calibrating delay loop... 49.77 BogoMIPS
5306 	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5307 	...
5308 
5309 If you want to boot a Linux kernel with initial RAM disk, you pass
5310 the memory addresses of both the kernel and the initrd image (PPBCOOT
5311 format!) to the "bootm" command:
5312 
5313 	=> imi 40100000 40200000
5314 
5315 	## Checking Image at 40100000 ...
5316 	   Image Name:	 2.2.13 for initrd on TQM850L
5317 	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5318 	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5319 	   Load Address: 00000000
5320 	   Entry Point:	 0000000c
5321 	   Verifying Checksum ... OK
5322 
5323 	## Checking Image at 40200000 ...
5324 	   Image Name:	 Simple Ramdisk Image
5325 	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5326 	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5327 	   Load Address: 00000000
5328 	   Entry Point:	 00000000
5329 	   Verifying Checksum ... OK
5330 
5331 	=> bootm 40100000 40200000
5332 	## Booting Linux kernel at 40100000 ...
5333 	   Image Name:	 2.2.13 for initrd on TQM850L
5334 	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5335 	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5336 	   Load Address: 00000000
5337 	   Entry Point:	 0000000c
5338 	   Verifying Checksum ... OK
5339 	   Uncompressing Kernel Image ... OK
5340 	## Loading RAMDisk Image at 40200000 ...
5341 	   Image Name:	 Simple Ramdisk Image
5342 	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5343 	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5344 	   Load Address: 00000000
5345 	   Entry Point:	 00000000
5346 	   Verifying Checksum ... OK
5347 	   Loading Ramdisk ... OK
5348 	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
5349 	Boot arguments: root=/dev/ram
5350 	time_init: decrementer frequency = 187500000/60
5351 	Calibrating delay loop... 49.77 BogoMIPS
5352 	...
5353 	RAMDISK: Compressed image found at block 0
5354 	VFS: Mounted root (ext2 filesystem).
5355 
5356 	bash#
5357 
5358 Boot Linux and pass a flat device tree:
5359 -----------
5360 
5361 First, U-Boot must be compiled with the appropriate defines. See the section
5362 titled "Linux Kernel Interface" above for a more in depth explanation. The
5363 following is an example of how to start a kernel and pass an updated
5364 flat device tree:
5365 
5366 => print oftaddr
5367 oftaddr=0x300000
5368 => print oft
5369 oft=oftrees/mpc8540ads.dtb
5370 => tftp $oftaddr $oft
5371 Speed: 1000, full duplex
5372 Using TSEC0 device
5373 TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5374 Filename 'oftrees/mpc8540ads.dtb'.
5375 Load address: 0x300000
5376 Loading: #
5377 done
5378 Bytes transferred = 4106 (100a hex)
5379 => tftp $loadaddr $bootfile
5380 Speed: 1000, full duplex
5381 Using TSEC0 device
5382 TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5383 Filename 'uImage'.
5384 Load address: 0x200000
5385 Loading:############
5386 done
5387 Bytes transferred = 1029407 (fb51f hex)
5388 => print loadaddr
5389 loadaddr=200000
5390 => print oftaddr
5391 oftaddr=0x300000
5392 => bootm $loadaddr - $oftaddr
5393 ## Booting image at 00200000 ...
5394    Image Name:	 Linux-2.6.17-dirty
5395    Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5396    Data Size:	 1029343 Bytes = 1005.2 kB
5397    Load Address: 00000000
5398    Entry Point:	 00000000
5399    Verifying Checksum ... OK
5400    Uncompressing Kernel Image ... OK
5401 Booting using flat device tree at 0x300000
5402 Using MPC85xx ADS machine description
5403 Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5404 [snip]
5405 
5406 
5407 More About U-Boot Image Types:
5408 ------------------------------
5409 
5410 U-Boot supports the following image types:
5411 
5412    "Standalone Programs" are directly runnable in the environment
5413 	provided by U-Boot; it is expected that (if they behave
5414 	well) you can continue to work in U-Boot after return from
5415 	the Standalone Program.
5416    "OS Kernel Images" are usually images of some Embedded OS which
5417 	will take over control completely. Usually these programs
5418 	will install their own set of exception handlers, device
5419 	drivers, set up the MMU, etc. - this means, that you cannot
5420 	expect to re-enter U-Boot except by resetting the CPU.
5421    "RAMDisk Images" are more or less just data blocks, and their
5422 	parameters (address, size) are passed to an OS kernel that is
5423 	being started.
5424    "Multi-File Images" contain several images, typically an OS
5425 	(Linux) kernel image and one or more data images like
5426 	RAMDisks. This construct is useful for instance when you want
5427 	to boot over the network using BOOTP etc., where the boot
5428 	server provides just a single image file, but you want to get
5429 	for instance an OS kernel and a RAMDisk image.
5430 
5431 	"Multi-File Images" start with a list of image sizes, each
5432 	image size (in bytes) specified by an "uint32_t" in network
5433 	byte order. This list is terminated by an "(uint32_t)0".
5434 	Immediately after the terminating 0 follow the images, one by
5435 	one, all aligned on "uint32_t" boundaries (size rounded up to
5436 	a multiple of 4 bytes).
5437 
5438    "Firmware Images" are binary images containing firmware (like
5439 	U-Boot or FPGA images) which usually will be programmed to
5440 	flash memory.
5441 
5442    "Script files" are command sequences that will be executed by
5443 	U-Boot's command interpreter; this feature is especially
5444 	useful when you configure U-Boot to use a real shell (hush)
5445 	as command interpreter.
5446 
5447 Booting the Linux zImage:
5448 -------------------------
5449 
5450 On some platforms, it's possible to boot Linux zImage. This is done
5451 using the "bootz" command. The syntax of "bootz" command is the same
5452 as the syntax of "bootm" command.
5453 
5454 Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5455 kernel with raw initrd images. The syntax is slightly different, the
5456 address of the initrd must be augmented by it's size, in the following
5457 format: "<initrd addres>:<initrd size>".
5458 
5459 
5460 Standalone HOWTO:
5461 =================
5462 
5463 One of the features of U-Boot is that you can dynamically load and
5464 run "standalone" applications, which can use some resources of
5465 U-Boot like console I/O functions or interrupt services.
5466 
5467 Two simple examples are included with the sources:
5468 
5469 "Hello World" Demo:
5470 -------------------
5471 
5472 'examples/hello_world.c' contains a small "Hello World" Demo
5473 application; it is automatically compiled when you build U-Boot.
5474 It's configured to run at address 0x00040004, so you can play with it
5475 like that:
5476 
5477 	=> loads
5478 	## Ready for S-Record download ...
5479 	~>examples/hello_world.srec
5480 	1 2 3 4 5 6 7 8 9 10 11 ...
5481 	[file transfer complete]
5482 	[connected]
5483 	## Start Addr = 0x00040004
5484 
5485 	=> go 40004 Hello World! This is a test.
5486 	## Starting application at 0x00040004 ...
5487 	Hello World
5488 	argc = 7
5489 	argv[0] = "40004"
5490 	argv[1] = "Hello"
5491 	argv[2] = "World!"
5492 	argv[3] = "This"
5493 	argv[4] = "is"
5494 	argv[5] = "a"
5495 	argv[6] = "test."
5496 	argv[7] = "<NULL>"
5497 	Hit any key to exit ...
5498 
5499 	## Application terminated, rc = 0x0
5500 
5501 Another example, which demonstrates how to register a CPM interrupt
5502 handler with the U-Boot code, can be found in 'examples/timer.c'.
5503 Here, a CPM timer is set up to generate an interrupt every second.
5504 The interrupt service routine is trivial, just printing a '.'
5505 character, but this is just a demo program. The application can be
5506 controlled by the following keys:
5507 
5508 	? - print current values og the CPM Timer registers
5509 	b - enable interrupts and start timer
5510 	e - stop timer and disable interrupts
5511 	q - quit application
5512 
5513 	=> loads
5514 	## Ready for S-Record download ...
5515 	~>examples/timer.srec
5516 	1 2 3 4 5 6 7 8 9 10 11 ...
5517 	[file transfer complete]
5518 	[connected]
5519 	## Start Addr = 0x00040004
5520 
5521 	=> go 40004
5522 	## Starting application at 0x00040004 ...
5523 	TIMERS=0xfff00980
5524 	Using timer 1
5525 	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5526 
5527 Hit 'b':
5528 	[q, b, e, ?] Set interval 1000000 us
5529 	Enabling timer
5530 Hit '?':
5531 	[q, b, e, ?] ........
5532 	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5533 Hit '?':
5534 	[q, b, e, ?] .
5535 	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5536 Hit '?':
5537 	[q, b, e, ?] .
5538 	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5539 Hit '?':
5540 	[q, b, e, ?] .
5541 	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5542 Hit 'e':
5543 	[q, b, e, ?] ...Stopping timer
5544 Hit 'q':
5545 	[q, b, e, ?] ## Application terminated, rc = 0x0
5546 
5547 
5548 Minicom warning:
5549 ================
5550 
5551 Over time, many people have reported problems when trying to use the
5552 "minicom" terminal emulation program for serial download. I (wd)
5553 consider minicom to be broken, and recommend not to use it. Under
5554 Unix, I recommend to use C-Kermit for general purpose use (and
5555 especially for kermit binary protocol download ("loadb" command), and
5556 use "cu" for S-Record download ("loads" command).  See
5557 http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5558 for help with kermit.
5559 
5560 
5561 Nevertheless, if you absolutely want to use it try adding this
5562 configuration to your "File transfer protocols" section:
5563 
5564 	   Name	   Program			Name U/D FullScr IO-Red. Multi
5565 	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5566 	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5567 
5568 
5569 NetBSD Notes:
5570 =============
5571 
5572 Starting at version 0.9.2, U-Boot supports NetBSD both as host
5573 (build U-Boot) and target system (boots NetBSD/mpc8xx).
5574 
5575 Building requires a cross environment; it is known to work on
5576 NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5577 need gmake since the Makefiles are not compatible with BSD make).
5578 Note that the cross-powerpc package does not install include files;
5579 attempting to build U-Boot will fail because <machine/ansi.h> is
5580 missing.  This file has to be installed and patched manually:
5581 
5582 	# cd /usr/pkg/cross/powerpc-netbsd/include
5583 	# mkdir powerpc
5584 	# ln -s powerpc machine
5585 	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5586 	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5587 
5588 Native builds *don't* work due to incompatibilities between native
5589 and U-Boot include files.
5590 
5591 Booting assumes that (the first part of) the image booted is a
5592 stage-2 loader which in turn loads and then invokes the kernel
5593 proper. Loader sources will eventually appear in the NetBSD source
5594 tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5595 meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5596 
5597 
5598 Implementation Internals:
5599 =========================
5600 
5601 The following is not intended to be a complete description of every
5602 implementation detail. However, it should help to understand the
5603 inner workings of U-Boot and make it easier to port it to custom
5604 hardware.
5605 
5606 
5607 Initial Stack, Global Data:
5608 ---------------------------
5609 
5610 The implementation of U-Boot is complicated by the fact that U-Boot
5611 starts running out of ROM (flash memory), usually without access to
5612 system RAM (because the memory controller is not initialized yet).
5613 This means that we don't have writable Data or BSS segments, and BSS
5614 is not initialized as zero. To be able to get a C environment working
5615 at all, we have to allocate at least a minimal stack. Implementation
5616 options for this are defined and restricted by the CPU used: Some CPU
5617 models provide on-chip memory (like the IMMR area on MPC8xx and
5618 MPC826x processors), on others (parts of) the data cache can be
5619 locked as (mis-) used as memory, etc.
5620 
5621 	Chris Hallinan posted a good summary of these issues to the
5622 	U-Boot mailing list:
5623 
5624 	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5625 	From: "Chris Hallinan" <clh@net1plus.com>
5626 	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5627 	...
5628 
5629 	Correct me if I'm wrong, folks, but the way I understand it
5630 	is this: Using DCACHE as initial RAM for Stack, etc, does not
5631 	require any physical RAM backing up the cache. The cleverness
5632 	is that the cache is being used as a temporary supply of
5633 	necessary storage before the SDRAM controller is setup. It's
5634 	beyond the scope of this list to explain the details, but you
5635 	can see how this works by studying the cache architecture and
5636 	operation in the architecture and processor-specific manuals.
5637 
5638 	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5639 	is another option for the system designer to use as an
5640 	initial stack/RAM area prior to SDRAM being available. Either
5641 	option should work for you. Using CS 4 should be fine if your
5642 	board designers haven't used it for something that would
5643 	cause you grief during the initial boot! It is frequently not
5644 	used.
5645 
5646 	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5647 	with your processor/board/system design. The default value
5648 	you will find in any recent u-boot distribution in
5649 	walnut.h should work for you. I'd set it to a value larger
5650 	than your SDRAM module. If you have a 64MB SDRAM module, set
5651 	it above 400_0000. Just make sure your board has no resources
5652 	that are supposed to respond to that address! That code in
5653 	start.S has been around a while and should work as is when
5654 	you get the config right.
5655 
5656 	-Chris Hallinan
5657 	DS4.COM, Inc.
5658 
5659 It is essential to remember this, since it has some impact on the C
5660 code for the initialization procedures:
5661 
5662 * Initialized global data (data segment) is read-only. Do not attempt
5663   to write it.
5664 
5665 * Do not use any uninitialized global data (or implicitly initialized
5666   as zero data - BSS segment) at all - this is undefined, initiali-
5667   zation is performed later (when relocating to RAM).
5668 
5669 * Stack space is very limited. Avoid big data buffers or things like
5670   that.
5671 
5672 Having only the stack as writable memory limits means we cannot use
5673 normal global data to share information between the code. But it
5674 turned out that the implementation of U-Boot can be greatly
5675 simplified by making a global data structure (gd_t) available to all
5676 functions. We could pass a pointer to this data as argument to _all_
5677 functions, but this would bloat the code. Instead we use a feature of
5678 the GCC compiler (Global Register Variables) to share the data: we
5679 place a pointer (gd) to the global data into a register which we
5680 reserve for this purpose.
5681 
5682 When choosing a register for such a purpose we are restricted by the
5683 relevant  (E)ABI  specifications for the current architecture, and by
5684 GCC's implementation.
5685 
5686 For PowerPC, the following registers have specific use:
5687 	R1:	stack pointer
5688 	R2:	reserved for system use
5689 	R3-R4:	parameter passing and return values
5690 	R5-R10: parameter passing
5691 	R13:	small data area pointer
5692 	R30:	GOT pointer
5693 	R31:	frame pointer
5694 
5695 	(U-Boot also uses R12 as internal GOT pointer. r12
5696 	is a volatile register so r12 needs to be reset when
5697 	going back and forth between asm and C)
5698 
5699     ==> U-Boot will use R2 to hold a pointer to the global data
5700 
5701     Note: on PPC, we could use a static initializer (since the
5702     address of the global data structure is known at compile time),
5703     but it turned out that reserving a register results in somewhat
5704     smaller code - although the code savings are not that big (on
5705     average for all boards 752 bytes for the whole U-Boot image,
5706     624 text + 127 data).
5707 
5708 On ARM, the following registers are used:
5709 
5710 	R0:	function argument word/integer result
5711 	R1-R3:	function argument word
5712 	R9:	platform specific
5713 	R10:	stack limit (used only if stack checking is enabled)
5714 	R11:	argument (frame) pointer
5715 	R12:	temporary workspace
5716 	R13:	stack pointer
5717 	R14:	link register
5718 	R15:	program counter
5719 
5720     ==> U-Boot will use R9 to hold a pointer to the global data
5721 
5722     Note: on ARM, only R_ARM_RELATIVE relocations are supported.
5723 
5724 On Nios II, the ABI is documented here:
5725 	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5726 
5727     ==> U-Boot will use gp to hold a pointer to the global data
5728 
5729     Note: on Nios II, we give "-G0" option to gcc and don't use gp
5730     to access small data sections, so gp is free.
5731 
5732 On NDS32, the following registers are used:
5733 
5734 	R0-R1:	argument/return
5735 	R2-R5:	argument
5736 	R15:	temporary register for assembler
5737 	R16:	trampoline register
5738 	R28:	frame pointer (FP)
5739 	R29:	global pointer (GP)
5740 	R30:	link register (LP)
5741 	R31:	stack pointer (SP)
5742 	PC:	program counter (PC)
5743 
5744     ==> U-Boot will use R10 to hold a pointer to the global data
5745 
5746 NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5747 or current versions of GCC may "optimize" the code too much.
5748 
5749 Memory Management:
5750 ------------------
5751 
5752 U-Boot runs in system state and uses physical addresses, i.e. the
5753 MMU is not used either for address mapping nor for memory protection.
5754 
5755 The available memory is mapped to fixed addresses using the memory
5756 controller. In this process, a contiguous block is formed for each
5757 memory type (Flash, SDRAM, SRAM), even when it consists of several
5758 physical memory banks.
5759 
5760 U-Boot is installed in the first 128 kB of the first Flash bank (on
5761 TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5762 booting and sizing and initializing DRAM, the code relocates itself
5763 to the upper end of DRAM. Immediately below the U-Boot code some
5764 memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5765 configuration setting]. Below that, a structure with global Board
5766 Info data is placed, followed by the stack (growing downward).
5767 
5768 Additionally, some exception handler code is copied to the low 8 kB
5769 of DRAM (0x00000000 ... 0x00001FFF).
5770 
5771 So a typical memory configuration with 16 MB of DRAM could look like
5772 this:
5773 
5774 	0x0000 0000	Exception Vector code
5775 	      :
5776 	0x0000 1FFF
5777 	0x0000 2000	Free for Application Use
5778 	      :
5779 	      :
5780 
5781 	      :
5782 	      :
5783 	0x00FB FF20	Monitor Stack (Growing downward)
5784 	0x00FB FFAC	Board Info Data and permanent copy of global data
5785 	0x00FC 0000	Malloc Arena
5786 	      :
5787 	0x00FD FFFF
5788 	0x00FE 0000	RAM Copy of Monitor Code
5789 	...		eventually: LCD or video framebuffer
5790 	...		eventually: pRAM (Protected RAM - unchanged by reset)
5791 	0x00FF FFFF	[End of RAM]
5792 
5793 
5794 System Initialization:
5795 ----------------------
5796 
5797 In the reset configuration, U-Boot starts at the reset entry point
5798 (on most PowerPC systems at address 0x00000100). Because of the reset
5799 configuration for CS0# this is a mirror of the on board Flash memory.
5800 To be able to re-map memory U-Boot then jumps to its link address.
5801 To be able to implement the initialization code in C, a (small!)
5802 initial stack is set up in the internal Dual Ported RAM (in case CPUs
5803 which provide such a feature like MPC8xx or MPC8260), or in a locked
5804 part of the data cache. After that, U-Boot initializes the CPU core,
5805 the caches and the SIU.
5806 
5807 Next, all (potentially) available memory banks are mapped using a
5808 preliminary mapping. For example, we put them on 512 MB boundaries
5809 (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5810 on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5811 programmed for SDRAM access. Using the temporary configuration, a
5812 simple memory test is run that determines the size of the SDRAM
5813 banks.
5814 
5815 When there is more than one SDRAM bank, and the banks are of
5816 different size, the largest is mapped first. For equal size, the first
5817 bank (CS2#) is mapped first. The first mapping is always for address
5818 0x00000000, with any additional banks following immediately to create
5819 contiguous memory starting from 0.
5820 
5821 Then, the monitor installs itself at the upper end of the SDRAM area
5822 and allocates memory for use by malloc() and for the global Board
5823 Info data; also, the exception vector code is copied to the low RAM
5824 pages, and the final stack is set up.
5825 
5826 Only after this relocation will you have a "normal" C environment;
5827 until that you are restricted in several ways, mostly because you are
5828 running from ROM, and because the code will have to be relocated to a
5829 new address in RAM.
5830 
5831 
5832 U-Boot Porting Guide:
5833 ----------------------
5834 
5835 [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5836 list, October 2002]
5837 
5838 
5839 int main(int argc, char *argv[])
5840 {
5841 	sighandler_t no_more_time;
5842 
5843 	signal(SIGALRM, no_more_time);
5844 	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5845 
5846 	if (available_money > available_manpower) {
5847 		Pay consultant to port U-Boot;
5848 		return 0;
5849 	}
5850 
5851 	Download latest U-Boot source;
5852 
5853 	Subscribe to u-boot mailing list;
5854 
5855 	if (clueless)
5856 		email("Hi, I am new to U-Boot, how do I get started?");
5857 
5858 	while (learning) {
5859 		Read the README file in the top level directory;
5860 		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5861 		Read applicable doc/*.README;
5862 		Read the source, Luke;
5863 		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5864 	}
5865 
5866 	if (available_money > toLocalCurrency ($2500))
5867 		Buy a BDI3000;
5868 	else
5869 		Add a lot of aggravation and time;
5870 
5871 	if (a similar board exists) {	/* hopefully... */
5872 		cp -a board/<similar> board/<myboard>
5873 		cp include/configs/<similar>.h include/configs/<myboard>.h
5874 	} else {
5875 		Create your own board support subdirectory;
5876 		Create your own board include/configs/<myboard>.h file;
5877 	}
5878 	Edit new board/<myboard> files
5879 	Edit new include/configs/<myboard>.h
5880 
5881 	while (!accepted) {
5882 		while (!running) {
5883 			do {
5884 				Add / modify source code;
5885 			} until (compiles);
5886 			Debug;
5887 			if (clueless)
5888 				email("Hi, I am having problems...");
5889 		}
5890 		Send patch file to the U-Boot email list;
5891 		if (reasonable critiques)
5892 			Incorporate improvements from email list code review;
5893 		else
5894 			Defend code as written;
5895 	}
5896 
5897 	return 0;
5898 }
5899 
5900 void no_more_time (int sig)
5901 {
5902       hire_a_guru();
5903 }
5904 
5905 
5906 Coding Standards:
5907 -----------------
5908 
5909 All contributions to U-Boot should conform to the Linux kernel
5910 coding style; see the file "Documentation/CodingStyle" and the script
5911 "scripts/Lindent" in your Linux kernel source directory.
5912 
5913 Source files originating from a different project (for example the
5914 MTD subsystem) are generally exempt from these guidelines and are not
5915 reformatted to ease subsequent migration to newer versions of those
5916 sources.
5917 
5918 Please note that U-Boot is implemented in C (and to some small parts in
5919 Assembler); no C++ is used, so please do not use C++ style comments (//)
5920 in your code.
5921 
5922 Please also stick to the following formatting rules:
5923 - remove any trailing white space
5924 - use TAB characters for indentation and vertical alignment, not spaces
5925 - make sure NOT to use DOS '\r\n' line feeds
5926 - do not add more than 2 consecutive empty lines to source files
5927 - do not add trailing empty lines to source files
5928 
5929 Submissions which do not conform to the standards may be returned
5930 with a request to reformat the changes.
5931 
5932 
5933 Submitting Patches:
5934 -------------------
5935 
5936 Since the number of patches for U-Boot is growing, we need to
5937 establish some rules. Submissions which do not conform to these rules
5938 may be rejected, even when they contain important and valuable stuff.
5939 
5940 Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5941 
5942 Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5943 see http://lists.denx.de/mailman/listinfo/u-boot
5944 
5945 When you send a patch, please include the following information with
5946 it:
5947 
5948 * For bug fixes: a description of the bug and how your patch fixes
5949   this bug. Please try to include a way of demonstrating that the
5950   patch actually fixes something.
5951 
5952 * For new features: a description of the feature and your
5953   implementation.
5954 
5955 * A CHANGELOG entry as plaintext (separate from the patch)
5956 
5957 * For major contributions, add a MAINTAINERS file with your
5958   information and associated file and directory references.
5959 
5960 * When you add support for a new board, don't forget to add a
5961   maintainer e-mail address to the boards.cfg file, too.
5962 
5963 * If your patch adds new configuration options, don't forget to
5964   document these in the README file.
5965 
5966 * The patch itself. If you are using git (which is *strongly*
5967   recommended) you can easily generate the patch using the
5968   "git format-patch". If you then use "git send-email" to send it to
5969   the U-Boot mailing list, you will avoid most of the common problems
5970   with some other mail clients.
5971 
5972   If you cannot use git, use "diff -purN OLD NEW". If your version of
5973   diff does not support these options, then get the latest version of
5974   GNU diff.
5975 
5976   The current directory when running this command shall be the parent
5977   directory of the U-Boot source tree (i. e. please make sure that
5978   your patch includes sufficient directory information for the
5979   affected files).
5980 
5981   We prefer patches as plain text. MIME attachments are discouraged,
5982   and compressed attachments must not be used.
5983 
5984 * If one logical set of modifications affects or creates several
5985   files, all these changes shall be submitted in a SINGLE patch file.
5986 
5987 * Changesets that contain different, unrelated modifications shall be
5988   submitted as SEPARATE patches, one patch per changeset.
5989 
5990 
5991 Notes:
5992 
5993 * Before sending the patch, run the buildman script on your patched
5994   source tree and make sure that no errors or warnings are reported
5995   for any of the boards.
5996 
5997 * Keep your modifications to the necessary minimum: A patch
5998   containing several unrelated changes or arbitrary reformats will be
5999   returned with a request to re-formatting / split it.
6000 
6001 * If you modify existing code, make sure that your new code does not
6002   add to the memory footprint of the code ;-) Small is beautiful!
6003   When adding new features, these should compile conditionally only
6004   (using #ifdef), and the resulting code with the new feature
6005   disabled must not need more memory than the old code without your
6006   modification.
6007 
6008 * Remember that there is a size limit of 100 kB per message on the
6009   u-boot mailing list. Bigger patches will be moderated. If they are
6010   reasonable and not too big, they will be acknowledged. But patches
6011   bigger than the size limit should be avoided.
6012