xref: /openbmc/u-boot/README (revision feaa7856f50ec5bbf843d533ee223aedd845452c)
1 # SPDX-License-Identifier: GPL-2.0+
2 #
3 # (C) Copyright 2000 - 2013
4 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
5 
6 Summary:
7 ========
8 
9 This directory contains the source code for U-Boot, a boot loader for
10 Embedded boards based on PowerPC, ARM, MIPS and several other
11 processors, which can be installed in a boot ROM and used to
12 initialize and test the hardware or to download and run application
13 code.
14 
15 The development of U-Boot is closely related to Linux: some parts of
16 the source code originate in the Linux source tree, we have some
17 header files in common, and special provision has been made to
18 support booting of Linux images.
19 
20 Some attention has been paid to make this software easily
21 configurable and extendable. For instance, all monitor commands are
22 implemented with the same call interface, so that it's very easy to
23 add new commands. Also, instead of permanently adding rarely used
24 code (for instance hardware test utilities) to the monitor, you can
25 load and run it dynamically.
26 
27 
28 Status:
29 =======
30 
31 In general, all boards for which a configuration option exists in the
32 Makefile have been tested to some extent and can be considered
33 "working". In fact, many of them are used in production systems.
34 
35 In case of problems see the CHANGELOG file to find out who contributed
36 the specific port. In addition, there are various MAINTAINERS files
37 scattered throughout the U-Boot source identifying the people or
38 companies responsible for various boards and subsystems.
39 
40 Note: As of August, 2010, there is no longer a CHANGELOG file in the
41 actual U-Boot source tree; however, it can be created dynamically
42 from the Git log using:
43 
44 	make CHANGELOG
45 
46 
47 Where to get help:
48 ==================
49 
50 In case you have questions about, problems with or contributions for
51 U-Boot, you should send a message to the U-Boot mailing list at
52 <u-boot@lists.denx.de>. There is also an archive of previous traffic
53 on the mailing list - please search the archive before asking FAQ's.
54 Please see http://lists.denx.de/pipermail/u-boot and
55 http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
56 
57 
58 Where to get source code:
59 =========================
60 
61 The U-Boot source code is maintained in the Git repository at
62 git://www.denx.de/git/u-boot.git ; you can browse it online at
63 http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
64 
65 The "snapshot" links on this page allow you to download tarballs of
66 any version you might be interested in. Official releases are also
67 available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
68 directory.
69 
70 Pre-built (and tested) images are available from
71 ftp://ftp.denx.de/pub/u-boot/images/
72 
73 
74 Where we come from:
75 ===================
76 
77 - start from 8xxrom sources
78 - create PPCBoot project (http://sourceforge.net/projects/ppcboot)
79 - clean up code
80 - make it easier to add custom boards
81 - make it possible to add other [PowerPC] CPUs
82 - extend functions, especially:
83   * Provide extended interface to Linux boot loader
84   * S-Record download
85   * network boot
86   * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
87 - create ARMBoot project (http://sourceforge.net/projects/armboot)
88 - add other CPU families (starting with ARM)
89 - create U-Boot project (http://sourceforge.net/projects/u-boot)
90 - current project page: see http://www.denx.de/wiki/U-Boot
91 
92 
93 Names and Spelling:
94 ===================
95 
96 The "official" name of this project is "Das U-Boot". The spelling
97 "U-Boot" shall be used in all written text (documentation, comments
98 in source files etc.). Example:
99 
100 	This is the README file for the U-Boot project.
101 
102 File names etc. shall be based on the string "u-boot". Examples:
103 
104 	include/asm-ppc/u-boot.h
105 
106 	#include <asm/u-boot.h>
107 
108 Variable names, preprocessor constants etc. shall be either based on
109 the string "u_boot" or on "U_BOOT". Example:
110 
111 	U_BOOT_VERSION		u_boot_logo
112 	IH_OS_U_BOOT		u_boot_hush_start
113 
114 
115 Versioning:
116 ===========
117 
118 Starting with the release in October 2008, the names of the releases
119 were changed from numerical release numbers without deeper meaning
120 into a time stamp based numbering. Regular releases are identified by
121 names consisting of the calendar year and month of the release date.
122 Additional fields (if present) indicate release candidates or bug fix
123 releases in "stable" maintenance trees.
124 
125 Examples:
126 	U-Boot v2009.11	    - Release November 2009
127 	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
128 	U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
129 
130 
131 Directory Hierarchy:
132 ====================
133 
134 /arch			Architecture specific files
135   /arc			Files generic to ARC architecture
136   /arm			Files generic to ARM architecture
137   /m68k			Files generic to m68k architecture
138   /microblaze		Files generic to microblaze architecture
139   /mips			Files generic to MIPS architecture
140   /nds32		Files generic to NDS32 architecture
141   /nios2		Files generic to Altera NIOS2 architecture
142   /openrisc		Files generic to OpenRISC architecture
143   /powerpc		Files generic to PowerPC architecture
144   /riscv		Files generic to RISC-V architecture
145   /sandbox		Files generic to HW-independent "sandbox"
146   /sh			Files generic to SH architecture
147   /x86			Files generic to x86 architecture
148 /api			Machine/arch independent API for external apps
149 /board			Board dependent files
150 /cmd			U-Boot commands functions
151 /common			Misc architecture independent functions
152 /configs		Board default configuration files
153 /disk			Code for disk drive partition handling
154 /doc			Documentation (don't expect too much)
155 /drivers		Commonly used device drivers
156 /dts			Contains Makefile for building internal U-Boot fdt.
157 /examples		Example code for standalone applications, etc.
158 /fs			Filesystem code (cramfs, ext2, jffs2, etc.)
159 /include		Header Files
160 /lib			Library routines generic to all architectures
161 /Licenses		Various license files
162 /net			Networking code
163 /post			Power On Self Test
164 /scripts		Various build scripts and Makefiles
165 /test			Various unit test files
166 /tools			Tools to build S-Record or U-Boot images, etc.
167 
168 Software Configuration:
169 =======================
170 
171 Configuration is usually done using C preprocessor defines; the
172 rationale behind that is to avoid dead code whenever possible.
173 
174 There are two classes of configuration variables:
175 
176 * Configuration _OPTIONS_:
177   These are selectable by the user and have names beginning with
178   "CONFIG_".
179 
180 * Configuration _SETTINGS_:
181   These depend on the hardware etc. and should not be meddled with if
182   you don't know what you're doing; they have names beginning with
183   "CONFIG_SYS_".
184 
185 Previously, all configuration was done by hand, which involved creating
186 symbolic links and editing configuration files manually. More recently,
187 U-Boot has added the Kbuild infrastructure used by the Linux kernel,
188 allowing you to use the "make menuconfig" command to configure your
189 build.
190 
191 
192 Selection of Processor Architecture and Board Type:
193 ---------------------------------------------------
194 
195 For all supported boards there are ready-to-use default
196 configurations available; just type "make <board_name>_defconfig".
197 
198 Example: For a TQM823L module type:
199 
200 	cd u-boot
201 	make TQM823L_defconfig
202 
203 Note: If you're looking for the default configuration file for a board
204 you're sure used to be there but is now missing, check the file
205 doc/README.scrapyard for a list of no longer supported boards.
206 
207 Sandbox Environment:
208 --------------------
209 
210 U-Boot can be built natively to run on a Linux host using the 'sandbox'
211 board. This allows feature development which is not board- or architecture-
212 specific to be undertaken on a native platform. The sandbox is also used to
213 run some of U-Boot's tests.
214 
215 See board/sandbox/README.sandbox for more details.
216 
217 
218 Board Initialisation Flow:
219 --------------------------
220 
221 This is the intended start-up flow for boards. This should apply for both
222 SPL and U-Boot proper (i.e. they both follow the same rules).
223 
224 Note: "SPL" stands for "Secondary Program Loader," which is explained in
225 more detail later in this file.
226 
227 At present, SPL mostly uses a separate code path, but the function names
228 and roles of each function are the same. Some boards or architectures
229 may not conform to this.  At least most ARM boards which use
230 CONFIG_SPL_FRAMEWORK conform to this.
231 
232 Execution typically starts with an architecture-specific (and possibly
233 CPU-specific) start.S file, such as:
234 
235 	- arch/arm/cpu/armv7/start.S
236 	- arch/powerpc/cpu/mpc83xx/start.S
237 	- arch/mips/cpu/start.S
238 
239 and so on. From there, three functions are called; the purpose and
240 limitations of each of these functions are described below.
241 
242 lowlevel_init():
243 	- purpose: essential init to permit execution to reach board_init_f()
244 	- no global_data or BSS
245 	- there is no stack (ARMv7 may have one but it will soon be removed)
246 	- must not set up SDRAM or use console
247 	- must only do the bare minimum to allow execution to continue to
248 		board_init_f()
249 	- this is almost never needed
250 	- return normally from this function
251 
252 board_init_f():
253 	- purpose: set up the machine ready for running board_init_r():
254 		i.e. SDRAM and serial UART
255 	- global_data is available
256 	- stack is in SRAM
257 	- BSS is not available, so you cannot use global/static variables,
258 		only stack variables and global_data
259 
260 	Non-SPL-specific notes:
261 	- dram_init() is called to set up DRAM. If already done in SPL this
262 		can do nothing
263 
264 	SPL-specific notes:
265 	- you can override the entire board_init_f() function with your own
266 		version as needed.
267 	- preloader_console_init() can be called here in extremis
268 	- should set up SDRAM, and anything needed to make the UART work
269 	- these is no need to clear BSS, it will be done by crt0.S
270 	- must return normally from this function (don't call board_init_r()
271 		directly)
272 
273 Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
274 this point the stack and global_data are relocated to below
275 CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
276 memory.
277 
278 board_init_r():
279 	- purpose: main execution, common code
280 	- global_data is available
281 	- SDRAM is available
282 	- BSS is available, all static/global variables can be used
283 	- execution eventually continues to main_loop()
284 
285 	Non-SPL-specific notes:
286 	- U-Boot is relocated to the top of memory and is now running from
287 		there.
288 
289 	SPL-specific notes:
290 	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
291 		CONFIG_SPL_STACK_R_ADDR points into SDRAM
292 	- preloader_console_init() can be called here - typically this is
293 		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
294 		spl_board_init() function containing this call
295 	- loads U-Boot or (in falcon mode) Linux
296 
297 
298 
299 Configuration Options:
300 ----------------------
301 
302 Configuration depends on the combination of board and CPU type; all
303 such information is kept in a configuration file
304 "include/configs/<board_name>.h".
305 
306 Example: For a TQM823L module, all configuration settings are in
307 "include/configs/TQM823L.h".
308 
309 
310 Many of the options are named exactly as the corresponding Linux
311 kernel configuration options. The intention is to make it easier to
312 build a config tool - later.
313 
314 - ARM Platform Bus Type(CCI):
315 		CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
316 		provides full cache coherency between two clusters of multi-core
317 		CPUs and I/O coherency for devices and I/O masters
318 
319 		CONFIG_SYS_FSL_HAS_CCI400
320 
321 		Defined For SoC that has cache coherent interconnect
322 		CCN-400
323 
324 		CONFIG_SYS_FSL_HAS_CCN504
325 
326 		Defined for SoC that has cache coherent interconnect CCN-504
327 
328 The following options need to be configured:
329 
330 - CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
331 
332 - Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
333 
334 - 85xx CPU Options:
335 		CONFIG_SYS_PPC64
336 
337 		Specifies that the core is a 64-bit PowerPC implementation (implements
338 		the "64" category of the Power ISA). This is necessary for ePAPR
339 		compliance, among other possible reasons.
340 
341 		CONFIG_SYS_FSL_TBCLK_DIV
342 
343 		Defines the core time base clock divider ratio compared to the
344 		system clock.  On most PQ3 devices this is 8, on newer QorIQ
345 		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
346 
347 		CONFIG_SYS_FSL_PCIE_COMPAT
348 
349 		Defines the string to utilize when trying to match PCIe device
350 		tree nodes for the given platform.
351 
352 		CONFIG_SYS_FSL_ERRATUM_A004510
353 
354 		Enables a workaround for erratum A004510.  If set,
355 		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
356 		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
357 
358 		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
359 		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
360 
361 		Defines one or two SoC revisions (low 8 bits of SVR)
362 		for which the A004510 workaround should be applied.
363 
364 		The rest of SVR is either not relevant to the decision
365 		of whether the erratum is present (e.g. p2040 versus
366 		p2041) or is implied by the build target, which controls
367 		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
368 
369 		See Freescale App Note 4493 for more information about
370 		this erratum.
371 
372 		CONFIG_A003399_NOR_WORKAROUND
373 		Enables a workaround for IFC erratum A003399. It is only
374 		required during NOR boot.
375 
376 		CONFIG_A008044_WORKAROUND
377 		Enables a workaround for T1040/T1042 erratum A008044. It is only
378 		required during NAND boot and valid for Rev 1.0 SoC revision
379 
380 		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
381 
382 		This is the value to write into CCSR offset 0x18600
383 		according to the A004510 workaround.
384 
385 		CONFIG_SYS_FSL_DSP_DDR_ADDR
386 		This value denotes start offset of DDR memory which is
387 		connected exclusively to the DSP cores.
388 
389 		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
390 		This value denotes start offset of M2 memory
391 		which is directly connected to the DSP core.
392 
393 		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
394 		This value denotes start offset of M3 memory which is directly
395 		connected to the DSP core.
396 
397 		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
398 		This value denotes start offset of DSP CCSR space.
399 
400 		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
401 		Single Source Clock is clocking mode present in some of FSL SoC's.
402 		In this mode, a single differential clock is used to supply
403 		clocks to the sysclock, ddrclock and usbclock.
404 
405 		CONFIG_SYS_CPC_REINIT_F
406 		This CONFIG is defined when the CPC is configured as SRAM at the
407 		time of U-Boot entry and is required to be re-initialized.
408 
409 		CONFIG_DEEP_SLEEP
410 		Indicates this SoC supports deep sleep feature. If deep sleep is
411 		supported, core will start to execute uboot when wakes up.
412 
413 - Generic CPU options:
414 		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
415 
416 		Defines the endianess of the CPU. Implementation of those
417 		values is arch specific.
418 
419 		CONFIG_SYS_FSL_DDR
420 		Freescale DDR driver in use. This type of DDR controller is
421 		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
422 		SoCs.
423 
424 		CONFIG_SYS_FSL_DDR_ADDR
425 		Freescale DDR memory-mapped register base.
426 
427 		CONFIG_SYS_FSL_DDR_EMU
428 		Specify emulator support for DDR. Some DDR features such as
429 		deskew training are not available.
430 
431 		CONFIG_SYS_FSL_DDRC_GEN1
432 		Freescale DDR1 controller.
433 
434 		CONFIG_SYS_FSL_DDRC_GEN2
435 		Freescale DDR2 controller.
436 
437 		CONFIG_SYS_FSL_DDRC_GEN3
438 		Freescale DDR3 controller.
439 
440 		CONFIG_SYS_FSL_DDRC_GEN4
441 		Freescale DDR4 controller.
442 
443 		CONFIG_SYS_FSL_DDRC_ARM_GEN3
444 		Freescale DDR3 controller for ARM-based SoCs.
445 
446 		CONFIG_SYS_FSL_DDR1
447 		Board config to use DDR1. It can be enabled for SoCs with
448 		Freescale DDR1 or DDR2 controllers, depending on the board
449 		implemetation.
450 
451 		CONFIG_SYS_FSL_DDR2
452 		Board config to use DDR2. It can be enabled for SoCs with
453 		Freescale DDR2 or DDR3 controllers, depending on the board
454 		implementation.
455 
456 		CONFIG_SYS_FSL_DDR3
457 		Board config to use DDR3. It can be enabled for SoCs with
458 		Freescale DDR3 or DDR3L controllers.
459 
460 		CONFIG_SYS_FSL_DDR3L
461 		Board config to use DDR3L. It can be enabled for SoCs with
462 		DDR3L controllers.
463 
464 		CONFIG_SYS_FSL_DDR4
465 		Board config to use DDR4. It can be enabled for SoCs with
466 		DDR4 controllers.
467 
468 		CONFIG_SYS_FSL_IFC_BE
469 		Defines the IFC controller register space as Big Endian
470 
471 		CONFIG_SYS_FSL_IFC_LE
472 		Defines the IFC controller register space as Little Endian
473 
474 		CONFIG_SYS_FSL_IFC_CLK_DIV
475 		Defines divider of platform clock(clock input to IFC controller).
476 
477 		CONFIG_SYS_FSL_LBC_CLK_DIV
478 		Defines divider of platform clock(clock input to eLBC controller).
479 
480 		CONFIG_SYS_FSL_PBL_PBI
481 		It enables addition of RCW (Power on reset configuration) in built image.
482 		Please refer doc/README.pblimage for more details
483 
484 		CONFIG_SYS_FSL_PBL_RCW
485 		It adds PBI(pre-boot instructions) commands in u-boot build image.
486 		PBI commands can be used to configure SoC before it starts the execution.
487 		Please refer doc/README.pblimage for more details
488 
489 		CONFIG_SPL_FSL_PBL
490 		It adds a target to create boot binary having SPL binary in PBI format
491 		concatenated with u-boot binary.
492 
493 		CONFIG_SYS_FSL_DDR_BE
494 		Defines the DDR controller register space as Big Endian
495 
496 		CONFIG_SYS_FSL_DDR_LE
497 		Defines the DDR controller register space as Little Endian
498 
499 		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
500 		Physical address from the view of DDR controllers. It is the
501 		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
502 		it could be different for ARM SoCs.
503 
504 		CONFIG_SYS_FSL_DDR_INTLV_256B
505 		DDR controller interleaving on 256-byte. This is a special
506 		interleaving mode, handled by Dickens for Freescale layerscape
507 		SoCs with ARM core.
508 
509 		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
510 		Number of controllers used as main memory.
511 
512 		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
513 		Number of controllers used for other than main memory.
514 
515 		CONFIG_SYS_FSL_HAS_DP_DDR
516 		Defines the SoC has DP-DDR used for DPAA.
517 
518 		CONFIG_SYS_FSL_SEC_BE
519 		Defines the SEC controller register space as Big Endian
520 
521 		CONFIG_SYS_FSL_SEC_LE
522 		Defines the SEC controller register space as Little Endian
523 
524 - MIPS CPU options:
525 		CONFIG_SYS_INIT_SP_OFFSET
526 
527 		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
528 		pointer. This is needed for the temporary stack before
529 		relocation.
530 
531 		CONFIG_SYS_MIPS_CACHE_MODE
532 
533 		Cache operation mode for the MIPS CPU.
534 		See also arch/mips/include/asm/mipsregs.h.
535 		Possible values are:
536 			CONF_CM_CACHABLE_NO_WA
537 			CONF_CM_CACHABLE_WA
538 			CONF_CM_UNCACHED
539 			CONF_CM_CACHABLE_NONCOHERENT
540 			CONF_CM_CACHABLE_CE
541 			CONF_CM_CACHABLE_COW
542 			CONF_CM_CACHABLE_CUW
543 			CONF_CM_CACHABLE_ACCELERATED
544 
545 		CONFIG_SYS_XWAY_EBU_BOOTCFG
546 
547 		Special option for Lantiq XWAY SoCs for booting from NOR flash.
548 		See also arch/mips/cpu/mips32/start.S.
549 
550 		CONFIG_XWAY_SWAP_BYTES
551 
552 		Enable compilation of tools/xway-swap-bytes needed for Lantiq
553 		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
554 		be swapped if a flash programmer is used.
555 
556 - ARM options:
557 		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
558 
559 		Select high exception vectors of the ARM core, e.g., do not
560 		clear the V bit of the c1 register of CP15.
561 
562 		COUNTER_FREQUENCY
563 		Generic timer clock source frequency.
564 
565 		COUNTER_FREQUENCY_REAL
566 		Generic timer clock source frequency if the real clock is
567 		different from COUNTER_FREQUENCY, and can only be determined
568 		at run time.
569 
570 - Tegra SoC options:
571 		CONFIG_TEGRA_SUPPORT_NON_SECURE
572 
573 		Support executing U-Boot in non-secure (NS) mode. Certain
574 		impossible actions will be skipped if the CPU is in NS mode,
575 		such as ARM architectural timer initialization.
576 
577 - Linux Kernel Interface:
578 		CONFIG_CLOCKS_IN_MHZ
579 
580 		U-Boot stores all clock information in Hz
581 		internally. For binary compatibility with older Linux
582 		kernels (which expect the clocks passed in the
583 		bd_info data to be in MHz) the environment variable
584 		"clocks_in_mhz" can be defined so that U-Boot
585 		converts clock data to MHZ before passing it to the
586 		Linux kernel.
587 		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
588 		"clocks_in_mhz=1" is automatically included in the
589 		default environment.
590 
591 		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
592 
593 		When transferring memsize parameter to Linux, some versions
594 		expect it to be in bytes, others in MB.
595 		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
596 
597 		CONFIG_OF_LIBFDT
598 
599 		New kernel versions are expecting firmware settings to be
600 		passed using flattened device trees (based on open firmware
601 		concepts).
602 
603 		CONFIG_OF_LIBFDT
604 		 * New libfdt-based support
605 		 * Adds the "fdt" command
606 		 * The bootm command automatically updates the fdt
607 
608 		OF_TBCLK - The timebase frequency.
609 		OF_STDOUT_PATH - The path to the console device
610 
611 		boards with QUICC Engines require OF_QE to set UCC MAC
612 		addresses
613 
614 		CONFIG_OF_BOARD_SETUP
615 
616 		Board code has addition modification that it wants to make
617 		to the flat device tree before handing it off to the kernel
618 
619 		CONFIG_OF_SYSTEM_SETUP
620 
621 		Other code has addition modification that it wants to make
622 		to the flat device tree before handing it off to the kernel.
623 		This causes ft_system_setup() to be called before booting
624 		the kernel.
625 
626 		CONFIG_OF_IDE_FIXUP
627 
628 		U-Boot can detect if an IDE device is present or not.
629 		If not, and this new config option is activated, U-Boot
630 		removes the ATA node from the DTS before booting Linux,
631 		so the Linux IDE driver does not probe the device and
632 		crash. This is needed for buggy hardware (uc101) where
633 		no pull down resistor is connected to the signal IDE5V_DD7.
634 
635 		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
636 
637 		This setting is mandatory for all boards that have only one
638 		machine type and must be used to specify the machine type
639 		number as it appears in the ARM machine registry
640 		(see http://www.arm.linux.org.uk/developer/machines/).
641 		Only boards that have multiple machine types supported
642 		in a single configuration file and the machine type is
643 		runtime discoverable, do not have to use this setting.
644 
645 - vxWorks boot parameters:
646 
647 		bootvx constructs a valid bootline using the following
648 		environments variables: bootdev, bootfile, ipaddr, netmask,
649 		serverip, gatewayip, hostname, othbootargs.
650 		It loads the vxWorks image pointed bootfile.
651 
652 		Note: If a "bootargs" environment is defined, it will overwride
653 		the defaults discussed just above.
654 
655 - Cache Configuration:
656 		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
657 		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
658 		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
659 
660 - Cache Configuration for ARM:
661 		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
662 				      controller
663 		CONFIG_SYS_PL310_BASE - Physical base address of PL310
664 					controller register space
665 
666 - Serial Ports:
667 		CONFIG_PL010_SERIAL
668 
669 		Define this if you want support for Amba PrimeCell PL010 UARTs.
670 
671 		CONFIG_PL011_SERIAL
672 
673 		Define this if you want support for Amba PrimeCell PL011 UARTs.
674 
675 		CONFIG_PL011_CLOCK
676 
677 		If you have Amba PrimeCell PL011 UARTs, set this variable to
678 		the clock speed of the UARTs.
679 
680 		CONFIG_PL01x_PORTS
681 
682 		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
683 		define this to a list of base addresses for each (supported)
684 		port. See e.g. include/configs/versatile.h
685 
686 		CONFIG_SERIAL_HW_FLOW_CONTROL
687 
688 		Define this variable to enable hw flow control in serial driver.
689 		Current user of this option is drivers/serial/nsl16550.c driver
690 
691 - Console Baudrate:
692 		CONFIG_BAUDRATE - in bps
693 		Select one of the baudrates listed in
694 		CONFIG_SYS_BAUDRATE_TABLE, see below.
695 
696 - Autoboot Command:
697 		CONFIG_BOOTCOMMAND
698 		Only needed when CONFIG_BOOTDELAY is enabled;
699 		define a command string that is automatically executed
700 		when no character is read on the console interface
701 		within "Boot Delay" after reset.
702 
703 		CONFIG_RAMBOOT and CONFIG_NFSBOOT
704 		The value of these goes into the environment as
705 		"ramboot" and "nfsboot" respectively, and can be used
706 		as a convenience, when switching between booting from
707 		RAM and NFS.
708 
709 - Pre-Boot Commands:
710 		CONFIG_PREBOOT
711 
712 		When this option is #defined, the existence of the
713 		environment variable "preboot" will be checked
714 		immediately before starting the CONFIG_BOOTDELAY
715 		countdown and/or running the auto-boot command resp.
716 		entering interactive mode.
717 
718 		This feature is especially useful when "preboot" is
719 		automatically generated or modified. For an example
720 		see the LWMON board specific code: here "preboot" is
721 		modified when the user holds down a certain
722 		combination of keys on the (special) keyboard when
723 		booting the systems
724 
725 - Serial Download Echo Mode:
726 		CONFIG_LOADS_ECHO
727 		If defined to 1, all characters received during a
728 		serial download (using the "loads" command) are
729 		echoed back. This might be needed by some terminal
730 		emulations (like "cu"), but may as well just take
731 		time on others. This setting #define's the initial
732 		value of the "loads_echo" environment variable.
733 
734 - Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
735 		CONFIG_KGDB_BAUDRATE
736 		Select one of the baudrates listed in
737 		CONFIG_SYS_BAUDRATE_TABLE, see below.
738 
739 - Removal of commands
740 		If no commands are needed to boot, you can disable
741 		CONFIG_CMDLINE to remove them. In this case, the command line
742 		will not be available, and when U-Boot wants to execute the
743 		boot command (on start-up) it will call board_run_command()
744 		instead. This can reduce image size significantly for very
745 		simple boot procedures.
746 
747 - Regular expression support:
748 		CONFIG_REGEX
749 		If this variable is defined, U-Boot is linked against
750 		the SLRE (Super Light Regular Expression) library,
751 		which adds regex support to some commands, as for
752 		example "env grep" and "setexpr".
753 
754 - Device tree:
755 		CONFIG_OF_CONTROL
756 		If this variable is defined, U-Boot will use a device tree
757 		to configure its devices, instead of relying on statically
758 		compiled #defines in the board file. This option is
759 		experimental and only available on a few boards. The device
760 		tree is available in the global data as gd->fdt_blob.
761 
762 		U-Boot needs to get its device tree from somewhere. This can
763 		be done using one of the three options below:
764 
765 		CONFIG_OF_EMBED
766 		If this variable is defined, U-Boot will embed a device tree
767 		binary in its image. This device tree file should be in the
768 		board directory and called <soc>-<board>.dts. The binary file
769 		is then picked up in board_init_f() and made available through
770 		the global data structure as gd->fdt_blob.
771 
772 		CONFIG_OF_SEPARATE
773 		If this variable is defined, U-Boot will build a device tree
774 		binary. It will be called u-boot.dtb. Architecture-specific
775 		code will locate it at run-time. Generally this works by:
776 
777 			cat u-boot.bin u-boot.dtb >image.bin
778 
779 		and in fact, U-Boot does this for you, creating a file called
780 		u-boot-dtb.bin which is useful in the common case. You can
781 		still use the individual files if you need something more
782 		exotic.
783 
784 		CONFIG_OF_BOARD
785 		If this variable is defined, U-Boot will use the device tree
786 		provided by the board at runtime instead of embedding one with
787 		the image. Only boards defining board_fdt_blob_setup() support
788 		this option (see include/fdtdec.h file).
789 
790 - Watchdog:
791 		CONFIG_WATCHDOG
792 		If this variable is defined, it enables watchdog
793 		support for the SoC. There must be support in the SoC
794 		specific code for a watchdog. For the 8xx
795 		CPUs, the SIU Watchdog feature is enabled in the SYPCR
796 		register.  When supported for a specific SoC is
797 		available, then no further board specific code should
798 		be needed to use it.
799 
800 		CONFIG_HW_WATCHDOG
801 		When using a watchdog circuitry external to the used
802 		SoC, then define this variable and provide board
803 		specific code for the "hw_watchdog_reset" function.
804 
805 		CONFIG_AT91_HW_WDT_TIMEOUT
806 		specify the timeout in seconds. default 2 seconds.
807 
808 - Real-Time Clock:
809 
810 		When CONFIG_CMD_DATE is selected, the type of the RTC
811 		has to be selected, too. Define exactly one of the
812 		following options:
813 
814 		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
815 		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
816 		CONFIG_RTC_MC146818	- use MC146818 RTC
817 		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
818 		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
819 		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
820 		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
821 		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
822 		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
823 		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
824 		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
825 		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
826 					  RV3029 RTC.
827 
828 		Note that if the RTC uses I2C, then the I2C interface
829 		must also be configured. See I2C Support, below.
830 
831 - GPIO Support:
832 		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
833 
834 		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
835 		chip-ngpio pairs that tell the PCA953X driver the number of
836 		pins supported by a particular chip.
837 
838 		Note that if the GPIO device uses I2C, then the I2C interface
839 		must also be configured. See I2C Support, below.
840 
841 - I/O tracing:
842 		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
843 		accesses and can checksum them or write a list of them out
844 		to memory. See the 'iotrace' command for details. This is
845 		useful for testing device drivers since it can confirm that
846 		the driver behaves the same way before and after a code
847 		change. Currently this is supported on sandbox and arm. To
848 		add support for your architecture, add '#include <iotrace.h>'
849 		to the bottom of arch/<arch>/include/asm/io.h and test.
850 
851 		Example output from the 'iotrace stats' command is below.
852 		Note that if the trace buffer is exhausted, the checksum will
853 		still continue to operate.
854 
855 			iotrace is enabled
856 			Start:  10000000	(buffer start address)
857 			Size:   00010000	(buffer size)
858 			Offset: 00000120	(current buffer offset)
859 			Output: 10000120	(start + offset)
860 			Count:  00000018	(number of trace records)
861 			CRC32:  9526fb66	(CRC32 of all trace records)
862 
863 - Timestamp Support:
864 
865 		When CONFIG_TIMESTAMP is selected, the timestamp
866 		(date and time) of an image is printed by image
867 		commands like bootm or iminfo. This option is
868 		automatically enabled when you select CONFIG_CMD_DATE .
869 
870 - Partition Labels (disklabels) Supported:
871 		Zero or more of the following:
872 		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
873 		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
874 		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
875 				       bootloader.  Note 2TB partition limit; see
876 				       disk/part_efi.c
877 		CONFIG_SCSI) you must configure support for at
878 		least one non-MTD partition type as well.
879 
880 - IDE Reset method:
881 		CONFIG_IDE_RESET_ROUTINE - this is defined in several
882 		board configurations files but used nowhere!
883 
884 		CONFIG_IDE_RESET - is this is defined, IDE Reset will
885 		be performed by calling the function
886 			ide_set_reset(int reset)
887 		which has to be defined in a board specific file
888 
889 - ATAPI Support:
890 		CONFIG_ATAPI
891 
892 		Set this to enable ATAPI support.
893 
894 - LBA48 Support
895 		CONFIG_LBA48
896 
897 		Set this to enable support for disks larger than 137GB
898 		Also look at CONFIG_SYS_64BIT_LBA.
899 		Whithout these , LBA48 support uses 32bit variables and will 'only'
900 		support disks up to 2.1TB.
901 
902 		CONFIG_SYS_64BIT_LBA:
903 			When enabled, makes the IDE subsystem use 64bit sector addresses.
904 			Default is 32bit.
905 
906 - SCSI Support:
907 		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
908 		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
909 		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
910 		maximum numbers of LUNs, SCSI ID's and target
911 		devices.
912 
913 		The environment variable 'scsidevs' is set to the number of
914 		SCSI devices found during the last scan.
915 
916 - NETWORK Support (PCI):
917 		CONFIG_E1000
918 		Support for Intel 8254x/8257x gigabit chips.
919 
920 		CONFIG_E1000_SPI
921 		Utility code for direct access to the SPI bus on Intel 8257x.
922 		This does not do anything useful unless you set at least one
923 		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
924 
925 		CONFIG_E1000_SPI_GENERIC
926 		Allow generic access to the SPI bus on the Intel 8257x, for
927 		example with the "sspi" command.
928 
929 		CONFIG_EEPRO100
930 		Support for Intel 82557/82559/82559ER chips.
931 		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
932 		write routine for first time initialisation.
933 
934 		CONFIG_TULIP
935 		Support for Digital 2114x chips.
936 		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
937 		modem chip initialisation (KS8761/QS6611).
938 
939 		CONFIG_NATSEMI
940 		Support for National dp83815 chips.
941 
942 		CONFIG_NS8382X
943 		Support for National dp8382[01] gigabit chips.
944 
945 - NETWORK Support (other):
946 
947 		CONFIG_DRIVER_AT91EMAC
948 		Support for AT91RM9200 EMAC.
949 
950 			CONFIG_RMII
951 			Define this to use reduced MII inteface
952 
953 			CONFIG_DRIVER_AT91EMAC_QUIET
954 			If this defined, the driver is quiet.
955 			The driver doen't show link status messages.
956 
957 		CONFIG_CALXEDA_XGMAC
958 		Support for the Calxeda XGMAC device
959 
960 		CONFIG_LAN91C96
961 		Support for SMSC's LAN91C96 chips.
962 
963 			CONFIG_LAN91C96_USE_32_BIT
964 			Define this to enable 32 bit addressing
965 
966 		CONFIG_SMC91111
967 		Support for SMSC's LAN91C111 chip
968 
969 			CONFIG_SMC91111_BASE
970 			Define this to hold the physical address
971 			of the device (I/O space)
972 
973 			CONFIG_SMC_USE_32_BIT
974 			Define this if data bus is 32 bits
975 
976 			CONFIG_SMC_USE_IOFUNCS
977 			Define this to use i/o functions instead of macros
978 			(some hardware wont work with macros)
979 
980 		CONFIG_DRIVER_TI_EMAC
981 		Support for davinci emac
982 
983 			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
984 			Define this if you have more then 3 PHYs.
985 
986 		CONFIG_FTGMAC100
987 		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
988 
989 			CONFIG_FTGMAC100_EGIGA
990 			Define this to use GE link update with gigabit PHY.
991 			Define this if FTGMAC100 is connected to gigabit PHY.
992 			If your system has 10/100 PHY only, it might not occur
993 			wrong behavior. Because PHY usually return timeout or
994 			useless data when polling gigabit status and gigabit
995 			control registers. This behavior won't affect the
996 			correctnessof 10/100 link speed update.
997 
998 		CONFIG_SH_ETHER
999 		Support for Renesas on-chip Ethernet controller
1000 
1001 			CONFIG_SH_ETHER_USE_PORT
1002 			Define the number of ports to be used
1003 
1004 			CONFIG_SH_ETHER_PHY_ADDR
1005 			Define the ETH PHY's address
1006 
1007 			CONFIG_SH_ETHER_CACHE_WRITEBACK
1008 			If this option is set, the driver enables cache flush.
1009 
1010 - PWM Support:
1011 		CONFIG_PWM_IMX
1012 		Support for PWM module on the imx6.
1013 
1014 - TPM Support:
1015 		CONFIG_TPM
1016 		Support TPM devices.
1017 
1018 		CONFIG_TPM_TIS_INFINEON
1019 		Support for Infineon i2c bus TPM devices. Only one device
1020 		per system is supported at this time.
1021 
1022 			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1023 			Define the burst count bytes upper limit
1024 
1025 		CONFIG_TPM_ST33ZP24
1026 		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1027 
1028 			CONFIG_TPM_ST33ZP24_I2C
1029 			Support for STMicroelectronics ST33ZP24 I2C devices.
1030 			Requires TPM_ST33ZP24 and I2C.
1031 
1032 			CONFIG_TPM_ST33ZP24_SPI
1033 			Support for STMicroelectronics ST33ZP24 SPI devices.
1034 			Requires TPM_ST33ZP24 and SPI.
1035 
1036 		CONFIG_TPM_ATMEL_TWI
1037 		Support for Atmel TWI TPM device. Requires I2C support.
1038 
1039 		CONFIG_TPM_TIS_LPC
1040 		Support for generic parallel port TPM devices. Only one device
1041 		per system is supported at this time.
1042 
1043 			CONFIG_TPM_TIS_BASE_ADDRESS
1044 			Base address where the generic TPM device is mapped
1045 			to. Contemporary x86 systems usually map it at
1046 			0xfed40000.
1047 
1048 		CONFIG_TPM
1049 		Define this to enable the TPM support library which provides
1050 		functional interfaces to some TPM commands.
1051 		Requires support for a TPM device.
1052 
1053 		CONFIG_TPM_AUTH_SESSIONS
1054 		Define this to enable authorized functions in the TPM library.
1055 		Requires CONFIG_TPM and CONFIG_SHA1.
1056 
1057 - USB Support:
1058 		At the moment only the UHCI host controller is
1059 		supported (PIP405, MIP405); define
1060 		CONFIG_USB_UHCI to enable it.
1061 		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1062 		and define CONFIG_USB_STORAGE to enable the USB
1063 		storage devices.
1064 		Note:
1065 		Supported are USB Keyboards and USB Floppy drives
1066 		(TEAC FD-05PUB).
1067 
1068 		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1069 		txfilltuning field in the EHCI controller on reset.
1070 
1071 		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1072 		HW module registers.
1073 
1074 - USB Device:
1075 		Define the below if you wish to use the USB console.
1076 		Once firmware is rebuilt from a serial console issue the
1077 		command "setenv stdin usbtty; setenv stdout usbtty" and
1078 		attach your USB cable. The Unix command "dmesg" should print
1079 		it has found a new device. The environment variable usbtty
1080 		can be set to gserial or cdc_acm to enable your device to
1081 		appear to a USB host as a Linux gserial device or a
1082 		Common Device Class Abstract Control Model serial device.
1083 		If you select usbtty = gserial you should be able to enumerate
1084 		a Linux host by
1085 		# modprobe usbserial vendor=0xVendorID product=0xProductID
1086 		else if using cdc_acm, simply setting the environment
1087 		variable usbtty to be cdc_acm should suffice. The following
1088 		might be defined in YourBoardName.h
1089 
1090 			CONFIG_USB_DEVICE
1091 			Define this to build a UDC device
1092 
1093 			CONFIG_USB_TTY
1094 			Define this to have a tty type of device available to
1095 			talk to the UDC device
1096 
1097 			CONFIG_USBD_HS
1098 			Define this to enable the high speed support for usb
1099 			device and usbtty. If this feature is enabled, a routine
1100 			int is_usbd_high_speed(void)
1101 			also needs to be defined by the driver to dynamically poll
1102 			whether the enumeration has succeded at high speed or full
1103 			speed.
1104 
1105 			CONFIG_SYS_CONSOLE_IS_IN_ENV
1106 			Define this if you want stdin, stdout &/or stderr to
1107 			be set to usbtty.
1108 
1109 		If you have a USB-IF assigned VendorID then you may wish to
1110 		define your own vendor specific values either in BoardName.h
1111 		or directly in usbd_vendor_info.h. If you don't define
1112 		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1113 		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1114 		should pretend to be a Linux device to it's target host.
1115 
1116 			CONFIG_USBD_MANUFACTURER
1117 			Define this string as the name of your company for
1118 			- CONFIG_USBD_MANUFACTURER "my company"
1119 
1120 			CONFIG_USBD_PRODUCT_NAME
1121 			Define this string as the name of your product
1122 			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1123 
1124 			CONFIG_USBD_VENDORID
1125 			Define this as your assigned Vendor ID from the USB
1126 			Implementors Forum. This *must* be a genuine Vendor ID
1127 			to avoid polluting the USB namespace.
1128 			- CONFIG_USBD_VENDORID 0xFFFF
1129 
1130 			CONFIG_USBD_PRODUCTID
1131 			Define this as the unique Product ID
1132 			for your device
1133 			- CONFIG_USBD_PRODUCTID 0xFFFF
1134 
1135 - ULPI Layer Support:
1136 		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1137 		the generic ULPI layer. The generic layer accesses the ULPI PHY
1138 		via the platform viewport, so you need both the genric layer and
1139 		the viewport enabled. Currently only Chipidea/ARC based
1140 		viewport is supported.
1141 		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1142 		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1143 		If your ULPI phy needs a different reference clock than the
1144 		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1145 		the appropriate value in Hz.
1146 
1147 - MMC Support:
1148 		The MMC controller on the Intel PXA is supported. To
1149 		enable this define CONFIG_MMC. The MMC can be
1150 		accessed from the boot prompt by mapping the device
1151 		to physical memory similar to flash. Command line is
1152 		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1153 		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1154 
1155 		CONFIG_SH_MMCIF
1156 		Support for Renesas on-chip MMCIF controller
1157 
1158 			CONFIG_SH_MMCIF_ADDR
1159 			Define the base address of MMCIF registers
1160 
1161 			CONFIG_SH_MMCIF_CLK
1162 			Define the clock frequency for MMCIF
1163 
1164 		CONFIG_SUPPORT_EMMC_BOOT
1165 		Enable some additional features of the eMMC boot partitions.
1166 
1167 - USB Device Firmware Update (DFU) class support:
1168 		CONFIG_DFU_OVER_USB
1169 		This enables the USB portion of the DFU USB class
1170 
1171 		CONFIG_DFU_MMC
1172 		This enables support for exposing (e)MMC devices via DFU.
1173 
1174 		CONFIG_DFU_NAND
1175 		This enables support for exposing NAND devices via DFU.
1176 
1177 		CONFIG_DFU_RAM
1178 		This enables support for exposing RAM via DFU.
1179 		Note: DFU spec refer to non-volatile memory usage, but
1180 		allow usages beyond the scope of spec - here RAM usage,
1181 		one that would help mostly the developer.
1182 
1183 		CONFIG_SYS_DFU_DATA_BUF_SIZE
1184 		Dfu transfer uses a buffer before writing data to the
1185 		raw storage device. Make the size (in bytes) of this buffer
1186 		configurable. The size of this buffer is also configurable
1187 		through the "dfu_bufsiz" environment variable.
1188 
1189 		CONFIG_SYS_DFU_MAX_FILE_SIZE
1190 		When updating files rather than the raw storage device,
1191 		we use a static buffer to copy the file into and then write
1192 		the buffer once we've been given the whole file.  Define
1193 		this to the maximum filesize (in bytes) for the buffer.
1194 		Default is 4 MiB if undefined.
1195 
1196 		DFU_DEFAULT_POLL_TIMEOUT
1197 		Poll timeout [ms], is the timeout a device can send to the
1198 		host. The host must wait for this timeout before sending
1199 		a subsequent DFU_GET_STATUS request to the device.
1200 
1201 		DFU_MANIFEST_POLL_TIMEOUT
1202 		Poll timeout [ms], which the device sends to the host when
1203 		entering dfuMANIFEST state. Host waits this timeout, before
1204 		sending again an USB request to the device.
1205 
1206 - Journaling Flash filesystem support:
1207 		CONFIG_JFFS2_NAND
1208 		Define these for a default partition on a NAND device
1209 
1210 		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1211 		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1212 		Define these for a default partition on a NOR device
1213 
1214 - Keyboard Support:
1215 		See Kconfig help for available keyboard drivers.
1216 
1217 		CONFIG_KEYBOARD
1218 
1219 		Define this to enable a custom keyboard support.
1220 		This simply calls drv_keyboard_init() which must be
1221 		defined in your board-specific files. This option is deprecated
1222 		and is only used by novena. For new boards, use driver model
1223 		instead.
1224 
1225 - Video support:
1226 		CONFIG_FSL_DIU_FB
1227 		Enable the Freescale DIU video driver.	Reference boards for
1228 		SOCs that have a DIU should define this macro to enable DIU
1229 		support, and should also define these other macros:
1230 
1231 			CONFIG_SYS_DIU_ADDR
1232 			CONFIG_VIDEO
1233 			CONFIG_CFB_CONSOLE
1234 			CONFIG_VIDEO_SW_CURSOR
1235 			CONFIG_VGA_AS_SINGLE_DEVICE
1236 			CONFIG_VIDEO_LOGO
1237 			CONFIG_VIDEO_BMP_LOGO
1238 
1239 		The DIU driver will look for the 'video-mode' environment
1240 		variable, and if defined, enable the DIU as a console during
1241 		boot.  See the documentation file doc/README.video for a
1242 		description of this variable.
1243 
1244 - LCD Support:	CONFIG_LCD
1245 
1246 		Define this to enable LCD support (for output to LCD
1247 		display); also select one of the supported displays
1248 		by defining one of these:
1249 
1250 		CONFIG_ATMEL_LCD:
1251 
1252 			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1253 
1254 		CONFIG_NEC_NL6448AC33:
1255 
1256 			NEC NL6448AC33-18. Active, color, single scan.
1257 
1258 		CONFIG_NEC_NL6448BC20
1259 
1260 			NEC NL6448BC20-08. 6.5", 640x480.
1261 			Active, color, single scan.
1262 
1263 		CONFIG_NEC_NL6448BC33_54
1264 
1265 			NEC NL6448BC33-54. 10.4", 640x480.
1266 			Active, color, single scan.
1267 
1268 		CONFIG_SHARP_16x9
1269 
1270 			Sharp 320x240. Active, color, single scan.
1271 			It isn't 16x9, and I am not sure what it is.
1272 
1273 		CONFIG_SHARP_LQ64D341
1274 
1275 			Sharp LQ64D341 display, 640x480.
1276 			Active, color, single scan.
1277 
1278 		CONFIG_HLD1045
1279 
1280 			HLD1045 display, 640x480.
1281 			Active, color, single scan.
1282 
1283 		CONFIG_OPTREX_BW
1284 
1285 			Optrex	 CBL50840-2 NF-FW 99 22 M5
1286 			or
1287 			Hitachi	 LMG6912RPFC-00T
1288 			or
1289 			Hitachi	 SP14Q002
1290 
1291 			320x240. Black & white.
1292 
1293 		CONFIG_LCD_ALIGNMENT
1294 
1295 		Normally the LCD is page-aligned (typically 4KB). If this is
1296 		defined then the LCD will be aligned to this value instead.
1297 		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1298 		here, since it is cheaper to change data cache settings on
1299 		a per-section basis.
1300 
1301 
1302 		CONFIG_LCD_ROTATION
1303 
1304 		Sometimes, for example if the display is mounted in portrait
1305 		mode or even if it's mounted landscape but rotated by 180degree,
1306 		we need to rotate our content of the display relative to the
1307 		framebuffer, so that user can read the messages which are
1308 		printed out.
1309 		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1310 		initialized with a given rotation from "vl_rot" out of
1311 		"vidinfo_t" which is provided by the board specific code.
1312 		The value for vl_rot is coded as following (matching to
1313 		fbcon=rotate:<n> linux-kernel commandline):
1314 		0 = no rotation respectively 0 degree
1315 		1 = 90 degree rotation
1316 		2 = 180 degree rotation
1317 		3 = 270 degree rotation
1318 
1319 		If CONFIG_LCD_ROTATION is not defined, the console will be
1320 		initialized with 0degree rotation.
1321 
1322 		CONFIG_LCD_BMP_RLE8
1323 
1324 		Support drawing of RLE8-compressed bitmaps on the LCD.
1325 
1326 		CONFIG_I2C_EDID
1327 
1328 		Enables an 'i2c edid' command which can read EDID
1329 		information over I2C from an attached LCD display.
1330 
1331 - Splash Screen Support: CONFIG_SPLASH_SCREEN
1332 
1333 		If this option is set, the environment is checked for
1334 		a variable "splashimage". If found, the usual display
1335 		of logo, copyright and system information on the LCD
1336 		is suppressed and the BMP image at the address
1337 		specified in "splashimage" is loaded instead. The
1338 		console is redirected to the "nulldev", too. This
1339 		allows for a "silent" boot where a splash screen is
1340 		loaded very quickly after power-on.
1341 
1342 		CONFIG_SPLASHIMAGE_GUARD
1343 
1344 		If this option is set, then U-Boot will prevent the environment
1345 		variable "splashimage" from being set to a problematic address
1346 		(see doc/README.displaying-bmps).
1347 		This option is useful for targets where, due to alignment
1348 		restrictions, an improperly aligned BMP image will cause a data
1349 		abort. If you think you will not have problems with unaligned
1350 		accesses (for example because your toolchain prevents them)
1351 		there is no need to set this option.
1352 
1353 		CONFIG_SPLASH_SCREEN_ALIGN
1354 
1355 		If this option is set the splash image can be freely positioned
1356 		on the screen. Environment variable "splashpos" specifies the
1357 		position as "x,y". If a positive number is given it is used as
1358 		number of pixel from left/top. If a negative number is given it
1359 		is used as number of pixel from right/bottom. You can also
1360 		specify 'm' for centering the image.
1361 
1362 		Example:
1363 		setenv splashpos m,m
1364 			=> image at center of screen
1365 
1366 		setenv splashpos 30,20
1367 			=> image at x = 30 and y = 20
1368 
1369 		setenv splashpos -10,m
1370 			=> vertically centered image
1371 			   at x = dspWidth - bmpWidth - 9
1372 
1373 - Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1374 
1375 		If this option is set, additionally to standard BMP
1376 		images, gzipped BMP images can be displayed via the
1377 		splashscreen support or the bmp command.
1378 
1379 - Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1380 
1381 		If this option is set, 8-bit RLE compressed BMP images
1382 		can be displayed via the splashscreen support or the
1383 		bmp command.
1384 
1385 - Compression support:
1386 		CONFIG_GZIP
1387 
1388 		Enabled by default to support gzip compressed images.
1389 
1390 		CONFIG_BZIP2
1391 
1392 		If this option is set, support for bzip2 compressed
1393 		images is included. If not, only uncompressed and gzip
1394 		compressed images are supported.
1395 
1396 		NOTE: the bzip2 algorithm requires a lot of RAM, so
1397 		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1398 		be at least 4MB.
1399 
1400 - MII/PHY support:
1401 		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1402 
1403 		The clock frequency of the MII bus
1404 
1405 		CONFIG_PHY_RESET_DELAY
1406 
1407 		Some PHY like Intel LXT971A need extra delay after
1408 		reset before any MII register access is possible.
1409 		For such PHY, set this option to the usec delay
1410 		required. (minimum 300usec for LXT971A)
1411 
1412 		CONFIG_PHY_CMD_DELAY (ppc4xx)
1413 
1414 		Some PHY like Intel LXT971A need extra delay after
1415 		command issued before MII status register can be read
1416 
1417 - IP address:
1418 		CONFIG_IPADDR
1419 
1420 		Define a default value for the IP address to use for
1421 		the default Ethernet interface, in case this is not
1422 		determined through e.g. bootp.
1423 		(Environment variable "ipaddr")
1424 
1425 - Server IP address:
1426 		CONFIG_SERVERIP
1427 
1428 		Defines a default value for the IP address of a TFTP
1429 		server to contact when using the "tftboot" command.
1430 		(Environment variable "serverip")
1431 
1432 		CONFIG_KEEP_SERVERADDR
1433 
1434 		Keeps the server's MAC address, in the env 'serveraddr'
1435 		for passing to bootargs (like Linux's netconsole option)
1436 
1437 - Gateway IP address:
1438 		CONFIG_GATEWAYIP
1439 
1440 		Defines a default value for the IP address of the
1441 		default router where packets to other networks are
1442 		sent to.
1443 		(Environment variable "gatewayip")
1444 
1445 - Subnet mask:
1446 		CONFIG_NETMASK
1447 
1448 		Defines a default value for the subnet mask (or
1449 		routing prefix) which is used to determine if an IP
1450 		address belongs to the local subnet or needs to be
1451 		forwarded through a router.
1452 		(Environment variable "netmask")
1453 
1454 - Multicast TFTP Mode:
1455 		CONFIG_MCAST_TFTP
1456 
1457 		Defines whether you want to support multicast TFTP as per
1458 		rfc-2090; for example to work with atftp.  Lets lots of targets
1459 		tftp down the same boot image concurrently.  Note: the Ethernet
1460 		driver in use must provide a function: mcast() to join/leave a
1461 		multicast group.
1462 
1463 - BOOTP Recovery Mode:
1464 		CONFIG_BOOTP_RANDOM_DELAY
1465 
1466 		If you have many targets in a network that try to
1467 		boot using BOOTP, you may want to avoid that all
1468 		systems send out BOOTP requests at precisely the same
1469 		moment (which would happen for instance at recovery
1470 		from a power failure, when all systems will try to
1471 		boot, thus flooding the BOOTP server. Defining
1472 		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1473 		inserted before sending out BOOTP requests. The
1474 		following delays are inserted then:
1475 
1476 		1st BOOTP request:	delay 0 ... 1 sec
1477 		2nd BOOTP request:	delay 0 ... 2 sec
1478 		3rd BOOTP request:	delay 0 ... 4 sec
1479 		4th and following
1480 		BOOTP requests:		delay 0 ... 8 sec
1481 
1482 		CONFIG_BOOTP_ID_CACHE_SIZE
1483 
1484 		BOOTP packets are uniquely identified using a 32-bit ID. The
1485 		server will copy the ID from client requests to responses and
1486 		U-Boot will use this to determine if it is the destination of
1487 		an incoming response. Some servers will check that addresses
1488 		aren't in use before handing them out (usually using an ARP
1489 		ping) and therefore take up to a few hundred milliseconds to
1490 		respond. Network congestion may also influence the time it
1491 		takes for a response to make it back to the client. If that
1492 		time is too long, U-Boot will retransmit requests. In order
1493 		to allow earlier responses to still be accepted after these
1494 		retransmissions, U-Boot's BOOTP client keeps a small cache of
1495 		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1496 		cache. The default is to keep IDs for up to four outstanding
1497 		requests. Increasing this will allow U-Boot to accept offers
1498 		from a BOOTP client in networks with unusually high latency.
1499 
1500 - DHCP Advanced Options:
1501 		You can fine tune the DHCP functionality by defining
1502 		CONFIG_BOOTP_* symbols:
1503 
1504 		CONFIG_BOOTP_NISDOMAIN
1505 		CONFIG_BOOTP_BOOTFILESIZE
1506 		CONFIG_BOOTP_SEND_HOSTNAME
1507 		CONFIG_BOOTP_NTPSERVER
1508 		CONFIG_BOOTP_TIMEOFFSET
1509 		CONFIG_BOOTP_VENDOREX
1510 		CONFIG_BOOTP_MAY_FAIL
1511 
1512 		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1513 		environment variable, not the BOOTP server.
1514 
1515 		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1516 		after the configured retry count, the call will fail
1517 		instead of starting over.  This can be used to fail over
1518 		to Link-local IP address configuration if the DHCP server
1519 		is not available.
1520 
1521 		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1522 		to do a dynamic update of a DNS server. To do this, they
1523 		need the hostname of the DHCP requester.
1524 		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1525 		of the "hostname" environment variable is passed as
1526 		option 12 to the DHCP server.
1527 
1528 		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1529 
1530 		A 32bit value in microseconds for a delay between
1531 		receiving a "DHCP Offer" and sending the "DHCP Request".
1532 		This fixes a problem with certain DHCP servers that don't
1533 		respond 100% of the time to a "DHCP request". E.g. On an
1534 		AT91RM9200 processor running at 180MHz, this delay needed
1535 		to be *at least* 15,000 usec before a Windows Server 2003
1536 		DHCP server would reply 100% of the time. I recommend at
1537 		least 50,000 usec to be safe. The alternative is to hope
1538 		that one of the retries will be successful but note that
1539 		the DHCP timeout and retry process takes a longer than
1540 		this delay.
1541 
1542  - Link-local IP address negotiation:
1543 		Negotiate with other link-local clients on the local network
1544 		for an address that doesn't require explicit configuration.
1545 		This is especially useful if a DHCP server cannot be guaranteed
1546 		to exist in all environments that the device must operate.
1547 
1548 		See doc/README.link-local for more information.
1549 
1550  - MAC address from environment variables
1551 
1552 		FDT_SEQ_MACADDR_FROM_ENV
1553 
1554 		Fix-up device tree with MAC addresses fetched sequentially from
1555 		environment variables. This config work on assumption that
1556 		non-usable ethernet node of device-tree are either not present
1557 		or their status has been marked as "disabled".
1558 
1559  - CDP Options:
1560 		CONFIG_CDP_DEVICE_ID
1561 
1562 		The device id used in CDP trigger frames.
1563 
1564 		CONFIG_CDP_DEVICE_ID_PREFIX
1565 
1566 		A two character string which is prefixed to the MAC address
1567 		of the device.
1568 
1569 		CONFIG_CDP_PORT_ID
1570 
1571 		A printf format string which contains the ascii name of
1572 		the port. Normally is set to "eth%d" which sets
1573 		eth0 for the first Ethernet, eth1 for the second etc.
1574 
1575 		CONFIG_CDP_CAPABILITIES
1576 
1577 		A 32bit integer which indicates the device capabilities;
1578 		0x00000010 for a normal host which does not forwards.
1579 
1580 		CONFIG_CDP_VERSION
1581 
1582 		An ascii string containing the version of the software.
1583 
1584 		CONFIG_CDP_PLATFORM
1585 
1586 		An ascii string containing the name of the platform.
1587 
1588 		CONFIG_CDP_TRIGGER
1589 
1590 		A 32bit integer sent on the trigger.
1591 
1592 		CONFIG_CDP_POWER_CONSUMPTION
1593 
1594 		A 16bit integer containing the power consumption of the
1595 		device in .1 of milliwatts.
1596 
1597 		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1598 
1599 		A byte containing the id of the VLAN.
1600 
1601 - Status LED:	CONFIG_LED_STATUS
1602 
1603 		Several configurations allow to display the current
1604 		status using a LED. For instance, the LED will blink
1605 		fast while running U-Boot code, stop blinking as
1606 		soon as a reply to a BOOTP request was received, and
1607 		start blinking slow once the Linux kernel is running
1608 		(supported by a status LED driver in the Linux
1609 		kernel). Defining CONFIG_LED_STATUS enables this
1610 		feature in U-Boot.
1611 
1612 		Additional options:
1613 
1614 		CONFIG_LED_STATUS_GPIO
1615 		The status LED can be connected to a GPIO pin.
1616 		In such cases, the gpio_led driver can be used as a
1617 		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1618 		to include the gpio_led driver in the U-Boot binary.
1619 
1620 		CONFIG_GPIO_LED_INVERTED_TABLE
1621 		Some GPIO connected LEDs may have inverted polarity in which
1622 		case the GPIO high value corresponds to LED off state and
1623 		GPIO low value corresponds to LED on state.
1624 		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1625 		with a list of GPIO LEDs that have inverted polarity.
1626 
1627 - I2C Support:	CONFIG_SYS_I2C
1628 
1629 		This enable the NEW i2c subsystem, and will allow you to use
1630 		i2c commands at the u-boot command line (as long as you set
1631 		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1632 		based realtime clock chips or other i2c devices. See
1633 		common/cmd_i2c.c for a description of the command line
1634 		interface.
1635 
1636 		ported i2c driver to the new framework:
1637 		- drivers/i2c/soft_i2c.c:
1638 		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1639 		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1640 		    for defining speed and slave address
1641 		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1642 		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1643 		    for defining speed and slave address
1644 		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1645 		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1646 		    for defining speed and slave address
1647 		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1648 		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1649 		    for defining speed and slave address
1650 
1651 		- drivers/i2c/fsl_i2c.c:
1652 		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1653 		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1654 		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1655 		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1656 		    bus.
1657 		  - If your board supports a second fsl i2c bus, define
1658 		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1659 		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1660 		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1661 		    second bus.
1662 
1663 		- drivers/i2c/tegra_i2c.c:
1664 		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1665 		  - This driver adds 4 i2c buses with a fix speed from
1666 		    100000 and the slave addr 0!
1667 
1668 		- drivers/i2c/ppc4xx_i2c.c
1669 		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1670 		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1671 		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1672 
1673 		- drivers/i2c/i2c_mxc.c
1674 		  - activate this driver with CONFIG_SYS_I2C_MXC
1675 		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1676 		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1677 		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1678 		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1679 		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1680 		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1681 		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1682 		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1683 		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1684 		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1685 		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1686 		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1687 		If those defines are not set, default value is 100000
1688 		for speed, and 0 for slave.
1689 
1690 		- drivers/i2c/rcar_i2c.c:
1691 		  - activate this driver with CONFIG_SYS_I2C_RCAR
1692 		  - This driver adds 4 i2c buses
1693 
1694 		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1695 		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1696 		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1697 		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1698 		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1699 		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1700 		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1701 		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1702 		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1703 
1704 		- drivers/i2c/sh_i2c.c:
1705 		  - activate this driver with CONFIG_SYS_I2C_SH
1706 		  - This driver adds from 2 to 5 i2c buses
1707 
1708 		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1709 		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1710 		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1711 		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1712 		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1713 		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1714 		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1715 		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1716 		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1717 		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1718 		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1719 
1720 		- drivers/i2c/omap24xx_i2c.c
1721 		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1722 		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1723 		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1724 		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1725 		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1726 		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1727 		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1728 		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1729 		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1730 		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1731 		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1732 
1733 		- drivers/i2c/zynq_i2c.c
1734 		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1735 		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1736 		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1737 
1738 		- drivers/i2c/s3c24x0_i2c.c:
1739 		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1740 		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1741 		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1742 		    with a fix speed from 100000 and the slave addr 0!
1743 
1744 		- drivers/i2c/ihs_i2c.c
1745 		  - activate this driver with CONFIG_SYS_I2C_IHS
1746 		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1747 		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1748 		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1749 		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1750 		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1751 		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1752 		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1753 		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1754 		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1755 		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1756 		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1757 		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1758 		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1759 		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1760 		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1761 		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1762 		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1763 		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1764 		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1765 		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1766 		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1767 
1768 		additional defines:
1769 
1770 		CONFIG_SYS_NUM_I2C_BUSES
1771 		Hold the number of i2c buses you want to use.
1772 
1773 		CONFIG_SYS_I2C_DIRECT_BUS
1774 		define this, if you don't use i2c muxes on your hardware.
1775 		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1776 		omit this define.
1777 
1778 		CONFIG_SYS_I2C_MAX_HOPS
1779 		define how many muxes are maximal consecutively connected
1780 		on one i2c bus. If you not use i2c muxes, omit this
1781 		define.
1782 
1783 		CONFIG_SYS_I2C_BUSES
1784 		hold a list of buses you want to use, only used if
1785 		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1786 		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1787 		CONFIG_SYS_NUM_I2C_BUSES = 9:
1788 
1789 		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1790 					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1791 					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1792 					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1793 					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1794 					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1795 					{1, {I2C_NULL_HOP}}, \
1796 					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1797 					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1798 					}
1799 
1800 		which defines
1801 			bus 0 on adapter 0 without a mux
1802 			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1803 			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1804 			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1805 			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1806 			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1807 			bus 6 on adapter 1 without a mux
1808 			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1809 			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1810 
1811 		If you do not have i2c muxes on your board, omit this define.
1812 
1813 - Legacy I2C Support:
1814 		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1815 		then the following macros need to be defined (examples are
1816 		from include/configs/lwmon.h):
1817 
1818 		I2C_INIT
1819 
1820 		(Optional). Any commands necessary to enable the I2C
1821 		controller or configure ports.
1822 
1823 		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1824 
1825 		I2C_ACTIVE
1826 
1827 		The code necessary to make the I2C data line active
1828 		(driven).  If the data line is open collector, this
1829 		define can be null.
1830 
1831 		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1832 
1833 		I2C_TRISTATE
1834 
1835 		The code necessary to make the I2C data line tri-stated
1836 		(inactive).  If the data line is open collector, this
1837 		define can be null.
1838 
1839 		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1840 
1841 		I2C_READ
1842 
1843 		Code that returns true if the I2C data line is high,
1844 		false if it is low.
1845 
1846 		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1847 
1848 		I2C_SDA(bit)
1849 
1850 		If <bit> is true, sets the I2C data line high. If it
1851 		is false, it clears it (low).
1852 
1853 		eg: #define I2C_SDA(bit) \
1854 			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1855 			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1856 
1857 		I2C_SCL(bit)
1858 
1859 		If <bit> is true, sets the I2C clock line high. If it
1860 		is false, it clears it (low).
1861 
1862 		eg: #define I2C_SCL(bit) \
1863 			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1864 			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1865 
1866 		I2C_DELAY
1867 
1868 		This delay is invoked four times per clock cycle so this
1869 		controls the rate of data transfer.  The data rate thus
1870 		is 1 / (I2C_DELAY * 4). Often defined to be something
1871 		like:
1872 
1873 		#define I2C_DELAY  udelay(2)
1874 
1875 		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1876 
1877 		If your arch supports the generic GPIO framework (asm/gpio.h),
1878 		then you may alternatively define the two GPIOs that are to be
1879 		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1880 		have GPIO-based defaults assigned to them as appropriate.
1881 
1882 		You should define these to the GPIO value as given directly to
1883 		the generic GPIO functions.
1884 
1885 		CONFIG_SYS_I2C_INIT_BOARD
1886 
1887 		When a board is reset during an i2c bus transfer
1888 		chips might think that the current transfer is still
1889 		in progress. On some boards it is possible to access
1890 		the i2c SCLK line directly, either by using the
1891 		processor pin as a GPIO or by having a second pin
1892 		connected to the bus. If this option is defined a
1893 		custom i2c_init_board() routine in boards/xxx/board.c
1894 		is run early in the boot sequence.
1895 
1896 		CONFIG_I2C_MULTI_BUS
1897 
1898 		This option allows the use of multiple I2C buses, each of which
1899 		must have a controller.	 At any point in time, only one bus is
1900 		active.	 To switch to a different bus, use the 'i2c dev' command.
1901 		Note that bus numbering is zero-based.
1902 
1903 		CONFIG_SYS_I2C_NOPROBES
1904 
1905 		This option specifies a list of I2C devices that will be skipped
1906 		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1907 		is set, specify a list of bus-device pairs.  Otherwise, specify
1908 		a 1D array of device addresses
1909 
1910 		e.g.
1911 			#undef	CONFIG_I2C_MULTI_BUS
1912 			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1913 
1914 		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1915 
1916 			#define CONFIG_I2C_MULTI_BUS
1917 			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1918 
1919 		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1920 
1921 		CONFIG_SYS_SPD_BUS_NUM
1922 
1923 		If defined, then this indicates the I2C bus number for DDR SPD.
1924 		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1925 
1926 		CONFIG_SYS_RTC_BUS_NUM
1927 
1928 		If defined, then this indicates the I2C bus number for the RTC.
1929 		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1930 
1931 		CONFIG_SOFT_I2C_READ_REPEATED_START
1932 
1933 		defining this will force the i2c_read() function in
1934 		the soft_i2c driver to perform an I2C repeated start
1935 		between writing the address pointer and reading the
1936 		data.  If this define is omitted the default behaviour
1937 		of doing a stop-start sequence will be used.  Most I2C
1938 		devices can use either method, but some require one or
1939 		the other.
1940 
1941 - SPI Support:	CONFIG_SPI
1942 
1943 		Enables SPI driver (so far only tested with
1944 		SPI EEPROM, also an instance works with Crystal A/D and
1945 		D/As on the SACSng board)
1946 
1947 		CONFIG_SOFT_SPI
1948 
1949 		Enables a software (bit-bang) SPI driver rather than
1950 		using hardware support. This is a general purpose
1951 		driver that only requires three general I/O port pins
1952 		(two outputs, one input) to function. If this is
1953 		defined, the board configuration must define several
1954 		SPI configuration items (port pins to use, etc). For
1955 		an example, see include/configs/sacsng.h.
1956 
1957 		CONFIG_HARD_SPI
1958 
1959 		Enables a hardware SPI driver for general-purpose reads
1960 		and writes.  As with CONFIG_SOFT_SPI, the board configuration
1961 		must define a list of chip-select function pointers.
1962 		Currently supported on some MPC8xxx processors.	 For an
1963 		example, see include/configs/mpc8349emds.h.
1964 
1965 		CONFIG_SYS_SPI_MXC_WAIT
1966 		Timeout for waiting until spi transfer completed.
1967 		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1968 
1969 - FPGA Support: CONFIG_FPGA
1970 
1971 		Enables FPGA subsystem.
1972 
1973 		CONFIG_FPGA_<vendor>
1974 
1975 		Enables support for specific chip vendors.
1976 		(ALTERA, XILINX)
1977 
1978 		CONFIG_FPGA_<family>
1979 
1980 		Enables support for FPGA family.
1981 		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1982 
1983 		CONFIG_FPGA_COUNT
1984 
1985 		Specify the number of FPGA devices to support.
1986 
1987 		CONFIG_SYS_FPGA_PROG_FEEDBACK
1988 
1989 		Enable printing of hash marks during FPGA configuration.
1990 
1991 		CONFIG_SYS_FPGA_CHECK_BUSY
1992 
1993 		Enable checks on FPGA configuration interface busy
1994 		status by the configuration function. This option
1995 		will require a board or device specific function to
1996 		be written.
1997 
1998 		CONFIG_FPGA_DELAY
1999 
2000 		If defined, a function that provides delays in the FPGA
2001 		configuration driver.
2002 
2003 		CONFIG_SYS_FPGA_CHECK_CTRLC
2004 		Allow Control-C to interrupt FPGA configuration
2005 
2006 		CONFIG_SYS_FPGA_CHECK_ERROR
2007 
2008 		Check for configuration errors during FPGA bitfile
2009 		loading. For example, abort during Virtex II
2010 		configuration if the INIT_B line goes low (which
2011 		indicated a CRC error).
2012 
2013 		CONFIG_SYS_FPGA_WAIT_INIT
2014 
2015 		Maximum time to wait for the INIT_B line to de-assert
2016 		after PROB_B has been de-asserted during a Virtex II
2017 		FPGA configuration sequence. The default time is 500
2018 		ms.
2019 
2020 		CONFIG_SYS_FPGA_WAIT_BUSY
2021 
2022 		Maximum time to wait for BUSY to de-assert during
2023 		Virtex II FPGA configuration. The default is 5 ms.
2024 
2025 		CONFIG_SYS_FPGA_WAIT_CONFIG
2026 
2027 		Time to wait after FPGA configuration. The default is
2028 		200 ms.
2029 
2030 - Configuration Management:
2031 		CONFIG_BUILD_TARGET
2032 
2033 		Some SoCs need special image types (e.g. U-Boot binary
2034 		with a special header) as build targets. By defining
2035 		CONFIG_BUILD_TARGET in the SoC / board header, this
2036 		special image will be automatically built upon calling
2037 		make / buildman.
2038 
2039 		CONFIG_IDENT_STRING
2040 
2041 		If defined, this string will be added to the U-Boot
2042 		version information (U_BOOT_VERSION)
2043 
2044 - Vendor Parameter Protection:
2045 
2046 		U-Boot considers the values of the environment
2047 		variables "serial#" (Board Serial Number) and
2048 		"ethaddr" (Ethernet Address) to be parameters that
2049 		are set once by the board vendor / manufacturer, and
2050 		protects these variables from casual modification by
2051 		the user. Once set, these variables are read-only,
2052 		and write or delete attempts are rejected. You can
2053 		change this behaviour:
2054 
2055 		If CONFIG_ENV_OVERWRITE is #defined in your config
2056 		file, the write protection for vendor parameters is
2057 		completely disabled. Anybody can change or delete
2058 		these parameters.
2059 
2060 		Alternatively, if you define _both_ an ethaddr in the
2061 		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2062 		Ethernet address is installed in the environment,
2063 		which can be changed exactly ONCE by the user. [The
2064 		serial# is unaffected by this, i. e. it remains
2065 		read-only.]
2066 
2067 		The same can be accomplished in a more flexible way
2068 		for any variable by configuring the type of access
2069 		to allow for those variables in the ".flags" variable
2070 		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2071 
2072 - Protected RAM:
2073 		CONFIG_PRAM
2074 
2075 		Define this variable to enable the reservation of
2076 		"protected RAM", i. e. RAM which is not overwritten
2077 		by U-Boot. Define CONFIG_PRAM to hold the number of
2078 		kB you want to reserve for pRAM. You can overwrite
2079 		this default value by defining an environment
2080 		variable "pram" to the number of kB you want to
2081 		reserve. Note that the board info structure will
2082 		still show the full amount of RAM. If pRAM is
2083 		reserved, a new environment variable "mem" will
2084 		automatically be defined to hold the amount of
2085 		remaining RAM in a form that can be passed as boot
2086 		argument to Linux, for instance like that:
2087 
2088 			setenv bootargs ... mem=\${mem}
2089 			saveenv
2090 
2091 		This way you can tell Linux not to use this memory,
2092 		either, which results in a memory region that will
2093 		not be affected by reboots.
2094 
2095 		*WARNING* If your board configuration uses automatic
2096 		detection of the RAM size, you must make sure that
2097 		this memory test is non-destructive. So far, the
2098 		following board configurations are known to be
2099 		"pRAM-clean":
2100 
2101 			IVMS8, IVML24, SPD8xx,
2102 			HERMES, IP860, RPXlite, LWMON,
2103 			FLAGADM
2104 
2105 - Access to physical memory region (> 4GB)
2106 		Some basic support is provided for operations on memory not
2107 		normally accessible to U-Boot - e.g. some architectures
2108 		support access to more than 4GB of memory on 32-bit
2109 		machines using physical address extension or similar.
2110 		Define CONFIG_PHYSMEM to access this basic support, which
2111 		currently only supports clearing the memory.
2112 
2113 - Error Recovery:
2114 		CONFIG_NET_RETRY_COUNT
2115 
2116 		This variable defines the number of retries for
2117 		network operations like ARP, RARP, TFTP, or BOOTP
2118 		before giving up the operation. If not defined, a
2119 		default value of 5 is used.
2120 
2121 		CONFIG_ARP_TIMEOUT
2122 
2123 		Timeout waiting for an ARP reply in milliseconds.
2124 
2125 		CONFIG_NFS_TIMEOUT
2126 
2127 		Timeout in milliseconds used in NFS protocol.
2128 		If you encounter "ERROR: Cannot umount" in nfs command,
2129 		try longer timeout such as
2130 		#define CONFIG_NFS_TIMEOUT 10000UL
2131 
2132 - Command Interpreter:
2133 		CONFIG_SYS_PROMPT_HUSH_PS2
2134 
2135 		This defines the secondary prompt string, which is
2136 		printed when the command interpreter needs more input
2137 		to complete a command. Usually "> ".
2138 
2139 	Note:
2140 
2141 		In the current implementation, the local variables
2142 		space and global environment variables space are
2143 		separated. Local variables are those you define by
2144 		simply typing `name=value'. To access a local
2145 		variable later on, you have write `$name' or
2146 		`${name}'; to execute the contents of a variable
2147 		directly type `$name' at the command prompt.
2148 
2149 		Global environment variables are those you use
2150 		setenv/printenv to work with. To run a command stored
2151 		in such a variable, you need to use the run command,
2152 		and you must not use the '$' sign to access them.
2153 
2154 		To store commands and special characters in a
2155 		variable, please use double quotation marks
2156 		surrounding the whole text of the variable, instead
2157 		of the backslashes before semicolons and special
2158 		symbols.
2159 
2160 - Command Line Editing and History:
2161 		CONFIG_CMDLINE_PS_SUPPORT
2162 
2163 		Enable support for changing the command prompt string
2164 		at run-time. Only static string is supported so far.
2165 		The string is obtained from environment variables PS1
2166 		and PS2.
2167 
2168 - Default Environment:
2169 		CONFIG_EXTRA_ENV_SETTINGS
2170 
2171 		Define this to contain any number of null terminated
2172 		strings (variable = value pairs) that will be part of
2173 		the default environment compiled into the boot image.
2174 
2175 		For example, place something like this in your
2176 		board's config file:
2177 
2178 		#define CONFIG_EXTRA_ENV_SETTINGS \
2179 			"myvar1=value1\0" \
2180 			"myvar2=value2\0"
2181 
2182 		Warning: This method is based on knowledge about the
2183 		internal format how the environment is stored by the
2184 		U-Boot code. This is NOT an official, exported
2185 		interface! Although it is unlikely that this format
2186 		will change soon, there is no guarantee either.
2187 		You better know what you are doing here.
2188 
2189 		Note: overly (ab)use of the default environment is
2190 		discouraged. Make sure to check other ways to preset
2191 		the environment like the "source" command or the
2192 		boot command first.
2193 
2194 		CONFIG_DELAY_ENVIRONMENT
2195 
2196 		Normally the environment is loaded when the board is
2197 		initialised so that it is available to U-Boot. This inhibits
2198 		that so that the environment is not available until
2199 		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2200 		this is instead controlled by the value of
2201 		/config/load-environment.
2202 
2203 - Serial Flash support
2204 		Usage requires an initial 'sf probe' to define the serial
2205 		flash parameters, followed by read/write/erase/update
2206 		commands.
2207 
2208 		The following defaults may be provided by the platform
2209 		to handle the common case when only a single serial
2210 		flash is present on the system.
2211 
2212 		CONFIG_SF_DEFAULT_BUS		Bus identifier
2213 		CONFIG_SF_DEFAULT_CS		Chip-select
2214 		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2215 		CONFIG_SF_DEFAULT_SPEED		in Hz
2216 
2217 
2218 - TFTP Fixed UDP Port:
2219 		CONFIG_TFTP_PORT
2220 
2221 		If this is defined, the environment variable tftpsrcp
2222 		is used to supply the TFTP UDP source port value.
2223 		If tftpsrcp isn't defined, the normal pseudo-random port
2224 		number generator is used.
2225 
2226 		Also, the environment variable tftpdstp is used to supply
2227 		the TFTP UDP destination port value.  If tftpdstp isn't
2228 		defined, the normal port 69 is used.
2229 
2230 		The purpose for tftpsrcp is to allow a TFTP server to
2231 		blindly start the TFTP transfer using the pre-configured
2232 		target IP address and UDP port. This has the effect of
2233 		"punching through" the (Windows XP) firewall, allowing
2234 		the remainder of the TFTP transfer to proceed normally.
2235 		A better solution is to properly configure the firewall,
2236 		but sometimes that is not allowed.
2237 
2238 - Show boot progress:
2239 		CONFIG_SHOW_BOOT_PROGRESS
2240 
2241 		Defining this option allows to add some board-
2242 		specific code (calling a user-provided function
2243 		"show_boot_progress(int)") that enables you to show
2244 		the system's boot progress on some display (for
2245 		example, some LED's) on your board. At the moment,
2246 		the following checkpoints are implemented:
2247 
2248 
2249 Legacy uImage format:
2250 
2251   Arg	Where			When
2252     1	common/cmd_bootm.c	before attempting to boot an image
2253    -1	common/cmd_bootm.c	Image header has bad	 magic number
2254     2	common/cmd_bootm.c	Image header has correct magic number
2255    -2	common/cmd_bootm.c	Image header has bad	 checksum
2256     3	common/cmd_bootm.c	Image header has correct checksum
2257    -3	common/cmd_bootm.c	Image data   has bad	 checksum
2258     4	common/cmd_bootm.c	Image data   has correct checksum
2259    -4	common/cmd_bootm.c	Image is for unsupported architecture
2260     5	common/cmd_bootm.c	Architecture check OK
2261    -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2262     6	common/cmd_bootm.c	Image Type check OK
2263    -6	common/cmd_bootm.c	gunzip uncompression error
2264    -7	common/cmd_bootm.c	Unimplemented compression type
2265     7	common/cmd_bootm.c	Uncompression OK
2266     8	common/cmd_bootm.c	No uncompress/copy overwrite error
2267    -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2268 
2269     9	common/image.c		Start initial ramdisk verification
2270   -10	common/image.c		Ramdisk header has bad	   magic number
2271   -11	common/image.c		Ramdisk header has bad	   checksum
2272    10	common/image.c		Ramdisk header is OK
2273   -12	common/image.c		Ramdisk data   has bad	   checksum
2274    11	common/image.c		Ramdisk data   has correct checksum
2275    12	common/image.c		Ramdisk verification complete, start loading
2276   -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2277    13	common/image.c		Start multifile image verification
2278    14	common/image.c		No initial ramdisk, no multifile, continue.
2279 
2280    15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2281 
2282   -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2283   -31	post/post.c		POST test failed, detected by post_output_backlog()
2284   -32	post/post.c		POST test failed, detected by post_run_single()
2285 
2286    34	common/cmd_doc.c	before loading a Image from a DOC device
2287   -35	common/cmd_doc.c	Bad usage of "doc" command
2288    35	common/cmd_doc.c	correct usage of "doc" command
2289   -36	common/cmd_doc.c	No boot device
2290    36	common/cmd_doc.c	correct boot device
2291   -37	common/cmd_doc.c	Unknown Chip ID on boot device
2292    37	common/cmd_doc.c	correct chip ID found, device available
2293   -38	common/cmd_doc.c	Read Error on boot device
2294    38	common/cmd_doc.c	reading Image header from DOC device OK
2295   -39	common/cmd_doc.c	Image header has bad magic number
2296    39	common/cmd_doc.c	Image header has correct magic number
2297   -40	common/cmd_doc.c	Error reading Image from DOC device
2298    40	common/cmd_doc.c	Image header has correct magic number
2299    41	common/cmd_ide.c	before loading a Image from a IDE device
2300   -42	common/cmd_ide.c	Bad usage of "ide" command
2301    42	common/cmd_ide.c	correct usage of "ide" command
2302   -43	common/cmd_ide.c	No boot device
2303    43	common/cmd_ide.c	boot device found
2304   -44	common/cmd_ide.c	Device not available
2305    44	common/cmd_ide.c	Device available
2306   -45	common/cmd_ide.c	wrong partition selected
2307    45	common/cmd_ide.c	partition selected
2308   -46	common/cmd_ide.c	Unknown partition table
2309    46	common/cmd_ide.c	valid partition table found
2310   -47	common/cmd_ide.c	Invalid partition type
2311    47	common/cmd_ide.c	correct partition type
2312   -48	common/cmd_ide.c	Error reading Image Header on boot device
2313    48	common/cmd_ide.c	reading Image Header from IDE device OK
2314   -49	common/cmd_ide.c	Image header has bad magic number
2315    49	common/cmd_ide.c	Image header has correct magic number
2316   -50	common/cmd_ide.c	Image header has bad	 checksum
2317    50	common/cmd_ide.c	Image header has correct checksum
2318   -51	common/cmd_ide.c	Error reading Image from IDE device
2319    51	common/cmd_ide.c	reading Image from IDE device OK
2320    52	common/cmd_nand.c	before loading a Image from a NAND device
2321   -53	common/cmd_nand.c	Bad usage of "nand" command
2322    53	common/cmd_nand.c	correct usage of "nand" command
2323   -54	common/cmd_nand.c	No boot device
2324    54	common/cmd_nand.c	boot device found
2325   -55	common/cmd_nand.c	Unknown Chip ID on boot device
2326    55	common/cmd_nand.c	correct chip ID found, device available
2327   -56	common/cmd_nand.c	Error reading Image Header on boot device
2328    56	common/cmd_nand.c	reading Image Header from NAND device OK
2329   -57	common/cmd_nand.c	Image header has bad magic number
2330    57	common/cmd_nand.c	Image header has correct magic number
2331   -58	common/cmd_nand.c	Error reading Image from NAND device
2332    58	common/cmd_nand.c	reading Image from NAND device OK
2333 
2334   -60	common/env_common.c	Environment has a bad CRC, using default
2335 
2336    64	net/eth.c		starting with Ethernet configuration.
2337   -64	net/eth.c		no Ethernet found.
2338    65	net/eth.c		Ethernet found.
2339 
2340   -80	common/cmd_net.c	usage wrong
2341    80	common/cmd_net.c	before calling net_loop()
2342   -81	common/cmd_net.c	some error in net_loop() occurred
2343    81	common/cmd_net.c	net_loop() back without error
2344   -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2345    82	common/cmd_net.c	trying automatic boot
2346    83	common/cmd_net.c	running "source" command
2347   -83	common/cmd_net.c	some error in automatic boot or "source" command
2348    84	common/cmd_net.c	end without errors
2349 
2350 FIT uImage format:
2351 
2352   Arg	Where			When
2353   100	common/cmd_bootm.c	Kernel FIT Image has correct format
2354  -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2355   101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2356  -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2357   102	common/cmd_bootm.c	Kernel unit name specified
2358  -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2359   103	common/cmd_bootm.c	Found configuration node
2360   104	common/cmd_bootm.c	Got kernel subimage node offset
2361  -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2362   105	common/cmd_bootm.c	Kernel subimage hash verification OK
2363  -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2364   106	common/cmd_bootm.c	Architecture check OK
2365  -106	common/cmd_bootm.c	Kernel subimage has wrong type
2366   107	common/cmd_bootm.c	Kernel subimage type OK
2367  -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2368   108	common/cmd_bootm.c	Got kernel subimage data/size
2369  -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2370  -109	common/cmd_bootm.c	Can't get kernel subimage type
2371  -110	common/cmd_bootm.c	Can't get kernel subimage comp
2372  -111	common/cmd_bootm.c	Can't get kernel subimage os
2373  -112	common/cmd_bootm.c	Can't get kernel subimage load address
2374  -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2375 
2376   120	common/image.c		Start initial ramdisk verification
2377  -120	common/image.c		Ramdisk FIT image has incorrect format
2378   121	common/image.c		Ramdisk FIT image has correct format
2379   122	common/image.c		No ramdisk subimage unit name, using configuration
2380  -122	common/image.c		Can't get configuration for ramdisk subimage
2381   123	common/image.c		Ramdisk unit name specified
2382  -124	common/image.c		Can't get ramdisk subimage node offset
2383   125	common/image.c		Got ramdisk subimage node offset
2384  -125	common/image.c		Ramdisk subimage hash verification failed
2385   126	common/image.c		Ramdisk subimage hash verification OK
2386  -126	common/image.c		Ramdisk subimage for unsupported architecture
2387   127	common/image.c		Architecture check OK
2388  -127	common/image.c		Can't get ramdisk subimage data/size
2389   128	common/image.c		Got ramdisk subimage data/size
2390   129	common/image.c		Can't get ramdisk load address
2391  -129	common/image.c		Got ramdisk load address
2392 
2393  -130	common/cmd_doc.c	Incorrect FIT image format
2394   131	common/cmd_doc.c	FIT image format OK
2395 
2396  -140	common/cmd_ide.c	Incorrect FIT image format
2397   141	common/cmd_ide.c	FIT image format OK
2398 
2399  -150	common/cmd_nand.c	Incorrect FIT image format
2400   151	common/cmd_nand.c	FIT image format OK
2401 
2402 - Standalone program support:
2403 		CONFIG_STANDALONE_LOAD_ADDR
2404 
2405 		This option defines a board specific value for the
2406 		address where standalone program gets loaded, thus
2407 		overwriting the architecture dependent default
2408 		settings.
2409 
2410 - Frame Buffer Address:
2411 		CONFIG_FB_ADDR
2412 
2413 		Define CONFIG_FB_ADDR if you want to use specific
2414 		address for frame buffer.  This is typically the case
2415 		when using a graphics controller has separate video
2416 		memory.  U-Boot will then place the frame buffer at
2417 		the given address instead of dynamically reserving it
2418 		in system RAM by calling lcd_setmem(), which grabs
2419 		the memory for the frame buffer depending on the
2420 		configured panel size.
2421 
2422 		Please see board_init_f function.
2423 
2424 - Automatic software updates via TFTP server
2425 		CONFIG_UPDATE_TFTP
2426 		CONFIG_UPDATE_TFTP_CNT_MAX
2427 		CONFIG_UPDATE_TFTP_MSEC_MAX
2428 
2429 		These options enable and control the auto-update feature;
2430 		for a more detailed description refer to doc/README.update.
2431 
2432 - MTD Support (mtdparts command, UBI support)
2433 		CONFIG_MTD_UBI_WL_THRESHOLD
2434 		This parameter defines the maximum difference between the highest
2435 		erase counter value and the lowest erase counter value of eraseblocks
2436 		of UBI devices. When this threshold is exceeded, UBI starts performing
2437 		wear leveling by means of moving data from eraseblock with low erase
2438 		counter to eraseblocks with high erase counter.
2439 
2440 		The default value should be OK for SLC NAND flashes, NOR flashes and
2441 		other flashes which have eraseblock life-cycle 100000 or more.
2442 		However, in case of MLC NAND flashes which typically have eraseblock
2443 		life-cycle less than 10000, the threshold should be lessened (e.g.,
2444 		to 128 or 256, although it does not have to be power of 2).
2445 
2446 		default: 4096
2447 
2448 		CONFIG_MTD_UBI_BEB_LIMIT
2449 		This option specifies the maximum bad physical eraseblocks UBI
2450 		expects on the MTD device (per 1024 eraseblocks). If the
2451 		underlying flash does not admit of bad eraseblocks (e.g. NOR
2452 		flash), this value is ignored.
2453 
2454 		NAND datasheets often specify the minimum and maximum NVM
2455 		(Number of Valid Blocks) for the flashes' endurance lifetime.
2456 		The maximum expected bad eraseblocks per 1024 eraseblocks
2457 		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2458 		which gives 20 for most NANDs (MaxNVB is basically the total
2459 		count of eraseblocks on the chip).
2460 
2461 		To put it differently, if this value is 20, UBI will try to
2462 		reserve about 1.9% of physical eraseblocks for bad blocks
2463 		handling. And that will be 1.9% of eraseblocks on the entire
2464 		NAND chip, not just the MTD partition UBI attaches. This means
2465 		that if you have, say, a NAND flash chip admits maximum 40 bad
2466 		eraseblocks, and it is split on two MTD partitions of the same
2467 		size, UBI will reserve 40 eraseblocks when attaching a
2468 		partition.
2469 
2470 		default: 20
2471 
2472 		CONFIG_MTD_UBI_FASTMAP
2473 		Fastmap is a mechanism which allows attaching an UBI device
2474 		in nearly constant time. Instead of scanning the whole MTD device it
2475 		only has to locate a checkpoint (called fastmap) on the device.
2476 		The on-flash fastmap contains all information needed to attach
2477 		the device. Using fastmap makes only sense on large devices where
2478 		attaching by scanning takes long. UBI will not automatically install
2479 		a fastmap on old images, but you can set the UBI parameter
2480 		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2481 		that fastmap-enabled images are still usable with UBI implementations
2482 		without	fastmap support. On typical flash devices the whole fastmap
2483 		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2484 
2485 		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2486 		Set this parameter to enable fastmap automatically on images
2487 		without a fastmap.
2488 		default: 0
2489 
2490 		CONFIG_MTD_UBI_FM_DEBUG
2491 		Enable UBI fastmap debug
2492 		default: 0
2493 
2494 - SPL framework
2495 		CONFIG_SPL
2496 		Enable building of SPL globally.
2497 
2498 		CONFIG_SPL_LDSCRIPT
2499 		LDSCRIPT for linking the SPL binary.
2500 
2501 		CONFIG_SPL_MAX_FOOTPRINT
2502 		Maximum size in memory allocated to the SPL, BSS included.
2503 		When defined, the linker checks that the actual memory
2504 		used by SPL from _start to __bss_end does not exceed it.
2505 		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2506 		must not be both defined at the same time.
2507 
2508 		CONFIG_SPL_MAX_SIZE
2509 		Maximum size of the SPL image (text, data, rodata, and
2510 		linker lists sections), BSS excluded.
2511 		When defined, the linker checks that the actual size does
2512 		not exceed it.
2513 
2514 		CONFIG_SPL_TEXT_BASE
2515 		TEXT_BASE for linking the SPL binary.
2516 
2517 		CONFIG_SPL_RELOC_TEXT_BASE
2518 		Address to relocate to.  If unspecified, this is equal to
2519 		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2520 
2521 		CONFIG_SPL_BSS_START_ADDR
2522 		Link address for the BSS within the SPL binary.
2523 
2524 		CONFIG_SPL_BSS_MAX_SIZE
2525 		Maximum size in memory allocated to the SPL BSS.
2526 		When defined, the linker checks that the actual memory used
2527 		by SPL from __bss_start to __bss_end does not exceed it.
2528 		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2529 		must not be both defined at the same time.
2530 
2531 		CONFIG_SPL_STACK
2532 		Adress of the start of the stack SPL will use
2533 
2534 		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2535 		When defined, SPL will panic() if the image it has
2536 		loaded does not have a signature.
2537 		Defining this is useful when code which loads images
2538 		in SPL cannot guarantee that absolutely all read errors
2539 		will be caught.
2540 		An example is the LPC32XX MLC NAND driver, which will
2541 		consider that a completely unreadable NAND block is bad,
2542 		and thus should be skipped silently.
2543 
2544 		CONFIG_SPL_RELOC_STACK
2545 		Adress of the start of the stack SPL will use after
2546 		relocation.  If unspecified, this is equal to
2547 		CONFIG_SPL_STACK.
2548 
2549 		CONFIG_SYS_SPL_MALLOC_START
2550 		Starting address of the malloc pool used in SPL.
2551 		When this option is set the full malloc is used in SPL and
2552 		it is set up by spl_init() and before that, the simple malloc()
2553 		can be used if CONFIG_SYS_MALLOC_F is defined.
2554 
2555 		CONFIG_SYS_SPL_MALLOC_SIZE
2556 		The size of the malloc pool used in SPL.
2557 
2558 		CONFIG_SPL_OS_BOOT
2559 		Enable booting directly to an OS from SPL.
2560 		See also: doc/README.falcon
2561 
2562 		CONFIG_SPL_DISPLAY_PRINT
2563 		For ARM, enable an optional function to print more information
2564 		about the running system.
2565 
2566 		CONFIG_SPL_INIT_MINIMAL
2567 		Arch init code should be built for a very small image
2568 
2569 		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2570 		Partition on the MMC to load U-Boot from when the MMC is being
2571 		used in raw mode
2572 
2573 		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2574 		Sector to load kernel uImage from when MMC is being
2575 		used in raw mode (for Falcon mode)
2576 
2577 		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2578 		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2579 		Sector and number of sectors to load kernel argument
2580 		parameters from when MMC is being used in raw mode
2581 		(for falcon mode)
2582 
2583 		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2584 		Partition on the MMC to load U-Boot from when the MMC is being
2585 		used in fs mode
2586 
2587 		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2588 		Filename to read to load U-Boot when reading from filesystem
2589 
2590 		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2591 		Filename to read to load kernel uImage when reading
2592 		from filesystem (for Falcon mode)
2593 
2594 		CONFIG_SPL_FS_LOAD_ARGS_NAME
2595 		Filename to read to load kernel argument parameters
2596 		when reading from filesystem (for Falcon mode)
2597 
2598 		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2599 		Set this for NAND SPL on PPC mpc83xx targets, so that
2600 		start.S waits for the rest of the SPL to load before
2601 		continuing (the hardware starts execution after just
2602 		loading the first page rather than the full 4K).
2603 
2604 		CONFIG_SPL_SKIP_RELOCATE
2605 		Avoid SPL relocation
2606 
2607 		CONFIG_SPL_NAND_BASE
2608 		Include nand_base.c in the SPL.  Requires
2609 		CONFIG_SPL_NAND_DRIVERS.
2610 
2611 		CONFIG_SPL_NAND_DRIVERS
2612 		SPL uses normal NAND drivers, not minimal drivers.
2613 
2614 		CONFIG_SPL_NAND_IDENT
2615 		SPL uses the chip ID list to identify the NAND flash.
2616 		Requires CONFIG_SPL_NAND_BASE.
2617 
2618 		CONFIG_SPL_NAND_ECC
2619 		Include standard software ECC in the SPL
2620 
2621 		CONFIG_SPL_NAND_SIMPLE
2622 		Support for NAND boot using simple NAND drivers that
2623 		expose the cmd_ctrl() interface.
2624 
2625 		CONFIG_SPL_UBI
2626 		Support for a lightweight UBI (fastmap) scanner and
2627 		loader
2628 
2629 		CONFIG_SPL_NAND_RAW_ONLY
2630 		Support to boot only raw u-boot.bin images. Use this only
2631 		if you need to save space.
2632 
2633 		CONFIG_SPL_COMMON_INIT_DDR
2634 		Set for common ddr init with serial presence detect in
2635 		SPL binary.
2636 
2637 		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2638 		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2639 		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2640 		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2641 		CONFIG_SYS_NAND_ECCBYTES
2642 		Defines the size and behavior of the NAND that SPL uses
2643 		to read U-Boot
2644 
2645 		CONFIG_SPL_NAND_BOOT
2646 		Add support NAND boot
2647 
2648 		CONFIG_SYS_NAND_U_BOOT_OFFS
2649 		Location in NAND to read U-Boot from
2650 
2651 		CONFIG_SYS_NAND_U_BOOT_DST
2652 		Location in memory to load U-Boot to
2653 
2654 		CONFIG_SYS_NAND_U_BOOT_SIZE
2655 		Size of image to load
2656 
2657 		CONFIG_SYS_NAND_U_BOOT_START
2658 		Entry point in loaded image to jump to
2659 
2660 		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2661 		Define this if you need to first read the OOB and then the
2662 		data. This is used, for example, on davinci platforms.
2663 
2664 		CONFIG_SPL_RAM_DEVICE
2665 		Support for running image already present in ram, in SPL binary
2666 
2667 		CONFIG_SPL_PAD_TO
2668 		Image offset to which the SPL should be padded before appending
2669 		the SPL payload. By default, this is defined as
2670 		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2671 		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2672 		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2673 
2674 		CONFIG_SPL_TARGET
2675 		Final target image containing SPL and payload.  Some SPLs
2676 		use an arch-specific makefile fragment instead, for
2677 		example if more than one image needs to be produced.
2678 
2679 		CONFIG_SPL_FIT_PRINT
2680 		Printing information about a FIT image adds quite a bit of
2681 		code to SPL. So this is normally disabled in SPL. Use this
2682 		option to re-enable it. This will affect the output of the
2683 		bootm command when booting a FIT image.
2684 
2685 - TPL framework
2686 		CONFIG_TPL
2687 		Enable building of TPL globally.
2688 
2689 		CONFIG_TPL_PAD_TO
2690 		Image offset to which the TPL should be padded before appending
2691 		the TPL payload. By default, this is defined as
2692 		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2693 		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2694 		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2695 
2696 - Interrupt support (PPC):
2697 
2698 		There are common interrupt_init() and timer_interrupt()
2699 		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2700 		for CPU specific initialization. interrupt_init_cpu()
2701 		should set decrementer_count to appropriate value. If
2702 		CPU resets decrementer automatically after interrupt
2703 		(ppc4xx) it should set decrementer_count to zero.
2704 		timer_interrupt() calls timer_interrupt_cpu() for CPU
2705 		specific handling. If board has watchdog / status_led
2706 		/ other_activity_monitor it works automatically from
2707 		general timer_interrupt().
2708 
2709 
2710 Board initialization settings:
2711 ------------------------------
2712 
2713 During Initialization u-boot calls a number of board specific functions
2714 to allow the preparation of board specific prerequisites, e.g. pin setup
2715 before drivers are initialized. To enable these callbacks the
2716 following configuration macros have to be defined. Currently this is
2717 architecture specific, so please check arch/your_architecture/lib/board.c
2718 typically in board_init_f() and board_init_r().
2719 
2720 - CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2721 - CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2722 - CONFIG_BOARD_LATE_INIT: Call board_late_init()
2723 - CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2724 
2725 Configuration Settings:
2726 -----------------------
2727 
2728 - CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2729 		Optionally it can be defined to support 64-bit memory commands.
2730 
2731 - CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2732 		undefine this when you're short of memory.
2733 
2734 - CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2735 		width of the commands listed in the 'help' command output.
2736 
2737 - CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2738 		prompt for user input.
2739 
2740 - CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2741 
2742 - CONFIG_SYS_PBSIZE:	Buffer size for Console output
2743 
2744 - CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2745 
2746 - CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2747 		the application (usually a Linux kernel) when it is
2748 		booted
2749 
2750 - CONFIG_SYS_BAUDRATE_TABLE:
2751 		List of legal baudrate settings for this board.
2752 
2753 - CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2754 		Begin and End addresses of the area used by the
2755 		simple memory test.
2756 
2757 - CONFIG_SYS_MEMTEST_SCRATCH:
2758 		Scratch address used by the alternate memory test
2759 		You only need to set this if address zero isn't writeable
2760 
2761 - CONFIG_SYS_MEM_RESERVE_SECURE
2762 		Only implemented for ARMv8 for now.
2763 		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2764 		is substracted from total RAM and won't be reported to OS.
2765 		This memory can be used as secure memory. A variable
2766 		gd->arch.secure_ram is used to track the location. In systems
2767 		the RAM base is not zero, or RAM is divided into banks,
2768 		this variable needs to be recalcuated to get the address.
2769 
2770 - CONFIG_SYS_MEM_TOP_HIDE:
2771 		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2772 		this specified memory area will get subtracted from the top
2773 		(end) of RAM and won't get "touched" at all by U-Boot. By
2774 		fixing up gd->ram_size the Linux kernel should gets passed
2775 		the now "corrected" memory size and won't touch it either.
2776 		This should work for arch/ppc and arch/powerpc. Only Linux
2777 		board ports in arch/powerpc with bootwrapper support that
2778 		recalculate the memory size from the SDRAM controller setup
2779 		will have to get fixed in Linux additionally.
2780 
2781 		This option can be used as a workaround for the 440EPx/GRx
2782 		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2783 		be touched.
2784 
2785 		WARNING: Please make sure that this value is a multiple of
2786 		the Linux page size (normally 4k). If this is not the case,
2787 		then the end address of the Linux memory will be located at a
2788 		non page size aligned address and this could cause major
2789 		problems.
2790 
2791 - CONFIG_SYS_LOADS_BAUD_CHANGE:
2792 		Enable temporary baudrate change while serial download
2793 
2794 - CONFIG_SYS_SDRAM_BASE:
2795 		Physical start address of SDRAM. _Must_ be 0 here.
2796 
2797 - CONFIG_SYS_FLASH_BASE:
2798 		Physical start address of Flash memory.
2799 
2800 - CONFIG_SYS_MONITOR_BASE:
2801 		Physical start address of boot monitor code (set by
2802 		make config files to be same as the text base address
2803 		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2804 		CONFIG_SYS_FLASH_BASE when booting from flash.
2805 
2806 - CONFIG_SYS_MONITOR_LEN:
2807 		Size of memory reserved for monitor code, used to
2808 		determine _at_compile_time_ (!) if the environment is
2809 		embedded within the U-Boot image, or in a separate
2810 		flash sector.
2811 
2812 - CONFIG_SYS_MALLOC_LEN:
2813 		Size of DRAM reserved for malloc() use.
2814 
2815 - CONFIG_SYS_MALLOC_F_LEN
2816 		Size of the malloc() pool for use before relocation. If
2817 		this is defined, then a very simple malloc() implementation
2818 		will become available before relocation. The address is just
2819 		below the global data, and the stack is moved down to make
2820 		space.
2821 
2822 		This feature allocates regions with increasing addresses
2823 		within the region. calloc() is supported, but realloc()
2824 		is not available. free() is supported but does nothing.
2825 		The memory will be freed (or in fact just forgotten) when
2826 		U-Boot relocates itself.
2827 
2828 - CONFIG_SYS_MALLOC_SIMPLE
2829 		Provides a simple and small malloc() and calloc() for those
2830 		boards which do not use the full malloc in SPL (which is
2831 		enabled with CONFIG_SYS_SPL_MALLOC_START).
2832 
2833 - CONFIG_SYS_NONCACHED_MEMORY:
2834 		Size of non-cached memory area. This area of memory will be
2835 		typically located right below the malloc() area and mapped
2836 		uncached in the MMU. This is useful for drivers that would
2837 		otherwise require a lot of explicit cache maintenance. For
2838 		some drivers it's also impossible to properly maintain the
2839 		cache. For example if the regions that need to be flushed
2840 		are not a multiple of the cache-line size, *and* padding
2841 		cannot be allocated between the regions to align them (i.e.
2842 		if the HW requires a contiguous array of regions, and the
2843 		size of each region is not cache-aligned), then a flush of
2844 		one region may result in overwriting data that hardware has
2845 		written to another region in the same cache-line. This can
2846 		happen for example in network drivers where descriptors for
2847 		buffers are typically smaller than the CPU cache-line (e.g.
2848 		16 bytes vs. 32 or 64 bytes).
2849 
2850 		Non-cached memory is only supported on 32-bit ARM at present.
2851 
2852 - CONFIG_SYS_BOOTM_LEN:
2853 		Normally compressed uImages are limited to an
2854 		uncompressed size of 8 MBytes. If this is not enough,
2855 		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2856 		to adjust this setting to your needs.
2857 
2858 - CONFIG_SYS_BOOTMAPSZ:
2859 		Maximum size of memory mapped by the startup code of
2860 		the Linux kernel; all data that must be processed by
2861 		the Linux kernel (bd_info, boot arguments, FDT blob if
2862 		used) must be put below this limit, unless "bootm_low"
2863 		environment variable is defined and non-zero. In such case
2864 		all data for the Linux kernel must be between "bootm_low"
2865 		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2866 		variable "bootm_mapsize" will override the value of
2867 		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2868 		then the value in "bootm_size" will be used instead.
2869 
2870 - CONFIG_SYS_BOOT_RAMDISK_HIGH:
2871 		Enable initrd_high functionality.  If defined then the
2872 		initrd_high feature is enabled and the bootm ramdisk subcommand
2873 		is enabled.
2874 
2875 - CONFIG_SYS_BOOT_GET_CMDLINE:
2876 		Enables allocating and saving kernel cmdline in space between
2877 		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2878 
2879 - CONFIG_SYS_BOOT_GET_KBD:
2880 		Enables allocating and saving a kernel copy of the bd_info in
2881 		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2882 
2883 - CONFIG_SYS_MAX_FLASH_BANKS:
2884 		Max number of Flash memory banks
2885 
2886 - CONFIG_SYS_MAX_FLASH_SECT:
2887 		Max number of sectors on a Flash chip
2888 
2889 - CONFIG_SYS_FLASH_ERASE_TOUT:
2890 		Timeout for Flash erase operations (in ms)
2891 
2892 - CONFIG_SYS_FLASH_WRITE_TOUT:
2893 		Timeout for Flash write operations (in ms)
2894 
2895 - CONFIG_SYS_FLASH_LOCK_TOUT
2896 		Timeout for Flash set sector lock bit operation (in ms)
2897 
2898 - CONFIG_SYS_FLASH_UNLOCK_TOUT
2899 		Timeout for Flash clear lock bits operation (in ms)
2900 
2901 - CONFIG_SYS_FLASH_PROTECTION
2902 		If defined, hardware flash sectors protection is used
2903 		instead of U-Boot software protection.
2904 
2905 - CONFIG_SYS_DIRECT_FLASH_TFTP:
2906 
2907 		Enable TFTP transfers directly to flash memory;
2908 		without this option such a download has to be
2909 		performed in two steps: (1) download to RAM, and (2)
2910 		copy from RAM to flash.
2911 
2912 		The two-step approach is usually more reliable, since
2913 		you can check if the download worked before you erase
2914 		the flash, but in some situations (when system RAM is
2915 		too limited to allow for a temporary copy of the
2916 		downloaded image) this option may be very useful.
2917 
2918 - CONFIG_SYS_FLASH_CFI:
2919 		Define if the flash driver uses extra elements in the
2920 		common flash structure for storing flash geometry.
2921 
2922 - CONFIG_FLASH_CFI_DRIVER
2923 		This option also enables the building of the cfi_flash driver
2924 		in the drivers directory
2925 
2926 - CONFIG_FLASH_CFI_MTD
2927 		This option enables the building of the cfi_mtd driver
2928 		in the drivers directory. The driver exports CFI flash
2929 		to the MTD layer.
2930 
2931 - CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2932 		Use buffered writes to flash.
2933 
2934 - CONFIG_FLASH_SPANSION_S29WS_N
2935 		s29ws-n MirrorBit flash has non-standard addresses for buffered
2936 		write commands.
2937 
2938 - CONFIG_SYS_FLASH_QUIET_TEST
2939 		If this option is defined, the common CFI flash doesn't
2940 		print it's warning upon not recognized FLASH banks. This
2941 		is useful, if some of the configured banks are only
2942 		optionally available.
2943 
2944 - CONFIG_FLASH_SHOW_PROGRESS
2945 		If defined (must be an integer), print out countdown
2946 		digits and dots.  Recommended value: 45 (9..1) for 80
2947 		column displays, 15 (3..1) for 40 column displays.
2948 
2949 - CONFIG_FLASH_VERIFY
2950 		If defined, the content of the flash (destination) is compared
2951 		against the source after the write operation. An error message
2952 		will be printed when the contents are not identical.
2953 		Please note that this option is useless in nearly all cases,
2954 		since such flash programming errors usually are detected earlier
2955 		while unprotecting/erasing/programming. Please only enable
2956 		this option if you really know what you are doing.
2957 
2958 - CONFIG_SYS_RX_ETH_BUFFER:
2959 		Defines the number of Ethernet receive buffers. On some
2960 		Ethernet controllers it is recommended to set this value
2961 		to 8 or even higher (EEPRO100 or 405 EMAC), since all
2962 		buffers can be full shortly after enabling the interface
2963 		on high Ethernet traffic.
2964 		Defaults to 4 if not defined.
2965 
2966 - CONFIG_ENV_MAX_ENTRIES
2967 
2968 	Maximum number of entries in the hash table that is used
2969 	internally to store the environment settings. The default
2970 	setting is supposed to be generous and should work in most
2971 	cases. This setting can be used to tune behaviour; see
2972 	lib/hashtable.c for details.
2973 
2974 - CONFIG_ENV_FLAGS_LIST_DEFAULT
2975 - CONFIG_ENV_FLAGS_LIST_STATIC
2976 	Enable validation of the values given to environment variables when
2977 	calling env set.  Variables can be restricted to only decimal,
2978 	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2979 	the variables can also be restricted to IP address or MAC address.
2980 
2981 	The format of the list is:
2982 		type_attribute = [s|d|x|b|i|m]
2983 		access_attribute = [a|r|o|c]
2984 		attributes = type_attribute[access_attribute]
2985 		entry = variable_name[:attributes]
2986 		list = entry[,list]
2987 
2988 	The type attributes are:
2989 		s - String (default)
2990 		d - Decimal
2991 		x - Hexadecimal
2992 		b - Boolean ([1yYtT|0nNfF])
2993 		i - IP address
2994 		m - MAC address
2995 
2996 	The access attributes are:
2997 		a - Any (default)
2998 		r - Read-only
2999 		o - Write-once
3000 		c - Change-default
3001 
3002 	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3003 		Define this to a list (string) to define the ".flags"
3004 		environment variable in the default or embedded environment.
3005 
3006 	- CONFIG_ENV_FLAGS_LIST_STATIC
3007 		Define this to a list (string) to define validation that
3008 		should be done if an entry is not found in the ".flags"
3009 		environment variable.  To override a setting in the static
3010 		list, simply add an entry for the same variable name to the
3011 		".flags" variable.
3012 
3013 	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3014 	regular expression. This allows multiple variables to define the same
3015 	flags without explicitly listing them for each variable.
3016 
3017 - CONFIG_ENV_ACCESS_IGNORE_FORCE
3018 	If defined, don't allow the -f switch to env set override variable
3019 	access flags.
3020 
3021 - CONFIG_USE_STDINT
3022 	If stdint.h is available with your toolchain you can define this
3023 	option to enable it. You can provide option 'USE_STDINT=1' when
3024 	building U-Boot to enable this.
3025 
3026 The following definitions that deal with the placement and management
3027 of environment data (variable area); in general, we support the
3028 following configurations:
3029 
3030 - CONFIG_BUILD_ENVCRC:
3031 
3032 	Builds up envcrc with the target environment so that external utils
3033 	may easily extract it and embed it in final U-Boot images.
3034 
3035 BE CAREFUL! The first access to the environment happens quite early
3036 in U-Boot initialization (when we try to get the setting of for the
3037 console baudrate). You *MUST* have mapped your NVRAM area then, or
3038 U-Boot will hang.
3039 
3040 Please note that even with NVRAM we still use a copy of the
3041 environment in RAM: we could work on NVRAM directly, but we want to
3042 keep settings there always unmodified except somebody uses "saveenv"
3043 to save the current settings.
3044 
3045 BE CAREFUL! For some special cases, the local device can not use
3046 "saveenv" command. For example, the local device will get the
3047 environment stored in a remote NOR flash by SRIO or PCIE link,
3048 but it can not erase, write this NOR flash by SRIO or PCIE interface.
3049 
3050 - CONFIG_NAND_ENV_DST
3051 
3052 	Defines address in RAM to which the nand_spl code should copy the
3053 	environment. If redundant environment is used, it will be copied to
3054 	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3055 
3056 Please note that the environment is read-only until the monitor
3057 has been relocated to RAM and a RAM copy of the environment has been
3058 created; also, when using EEPROM you will have to use env_get_f()
3059 until then to read environment variables.
3060 
3061 The environment is protected by a CRC32 checksum. Before the monitor
3062 is relocated into RAM, as a result of a bad CRC you will be working
3063 with the compiled-in default environment - *silently*!!! [This is
3064 necessary, because the first environment variable we need is the
3065 "baudrate" setting for the console - if we have a bad CRC, we don't
3066 have any device yet where we could complain.]
3067 
3068 Note: once the monitor has been relocated, then it will complain if
3069 the default environment is used; a new CRC is computed as soon as you
3070 use the "saveenv" command to store a valid environment.
3071 
3072 - CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3073 		Echo the inverted Ethernet link state to the fault LED.
3074 
3075 		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3076 		      also needs to be defined.
3077 
3078 - CONFIG_SYS_FAULT_MII_ADDR:
3079 		MII address of the PHY to check for the Ethernet link state.
3080 
3081 - CONFIG_NS16550_MIN_FUNCTIONS:
3082 		Define this if you desire to only have use of the NS16550_init
3083 		and NS16550_putc functions for the serial driver located at
3084 		drivers/serial/ns16550.c.  This option is useful for saving
3085 		space for already greatly restricted images, including but not
3086 		limited to NAND_SPL configurations.
3087 
3088 - CONFIG_DISPLAY_BOARDINFO
3089 		Display information about the board that U-Boot is running on
3090 		when U-Boot starts up. The board function checkboard() is called
3091 		to do this.
3092 
3093 - CONFIG_DISPLAY_BOARDINFO_LATE
3094 		Similar to the previous option, but display this information
3095 		later, once stdio is running and output goes to the LCD, if
3096 		present.
3097 
3098 - CONFIG_BOARD_SIZE_LIMIT:
3099 		Maximum size of the U-Boot image. When defined, the
3100 		build system checks that the actual size does not
3101 		exceed it.
3102 
3103 Low Level (hardware related) configuration options:
3104 ---------------------------------------------------
3105 
3106 - CONFIG_SYS_CACHELINE_SIZE:
3107 		Cache Line Size of the CPU.
3108 
3109 - CONFIG_SYS_CCSRBAR_DEFAULT:
3110 		Default (power-on reset) physical address of CCSR on Freescale
3111 		PowerPC SOCs.
3112 
3113 - CONFIG_SYS_CCSRBAR:
3114 		Virtual address of CCSR.  On a 32-bit build, this is typically
3115 		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3116 
3117 - CONFIG_SYS_CCSRBAR_PHYS:
3118 		Physical address of CCSR.  CCSR can be relocated to a new
3119 		physical address, if desired.  In this case, this macro should
3120 		be set to that address.	 Otherwise, it should be set to the
3121 		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3122 		is typically relocated on 36-bit builds.  It is recommended
3123 		that this macro be defined via the _HIGH and _LOW macros:
3124 
3125 		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3126 			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3127 
3128 - CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3129 		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3130 		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3131 		used in assembly code, so it must not contain typecasts or
3132 		integer size suffixes (e.g. "ULL").
3133 
3134 - CONFIG_SYS_CCSRBAR_PHYS_LOW:
3135 		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3136 		used in assembly code, so it must not contain typecasts or
3137 		integer size suffixes (e.g. "ULL").
3138 
3139 - CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3140 		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3141 		forced to a value that ensures that CCSR is not relocated.
3142 
3143 - Floppy Disk Support:
3144 		CONFIG_SYS_FDC_DRIVE_NUMBER
3145 
3146 		the default drive number (default value 0)
3147 
3148 		CONFIG_SYS_ISA_IO_STRIDE
3149 
3150 		defines the spacing between FDC chipset registers
3151 		(default value 1)
3152 
3153 		CONFIG_SYS_ISA_IO_OFFSET
3154 
3155 		defines the offset of register from address. It
3156 		depends on which part of the data bus is connected to
3157 		the FDC chipset. (default value 0)
3158 
3159 		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3160 		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3161 		default value.
3162 
3163 		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3164 		fdc_hw_init() is called at the beginning of the FDC
3165 		setup. fdc_hw_init() must be provided by the board
3166 		source code. It is used to make hardware-dependent
3167 		initializations.
3168 
3169 - CONFIG_IDE_AHB:
3170 		Most IDE controllers were designed to be connected with PCI
3171 		interface. Only few of them were designed for AHB interface.
3172 		When software is doing ATA command and data transfer to
3173 		IDE devices through IDE-AHB controller, some additional
3174 		registers accessing to these kind of IDE-AHB controller
3175 		is required.
3176 
3177 - CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3178 		DO NOT CHANGE unless you know exactly what you're
3179 		doing! (11-4) [MPC8xx systems only]
3180 
3181 - CONFIG_SYS_INIT_RAM_ADDR:
3182 
3183 		Start address of memory area that can be used for
3184 		initial data and stack; please note that this must be
3185 		writable memory that is working WITHOUT special
3186 		initialization, i. e. you CANNOT use normal RAM which
3187 		will become available only after programming the
3188 		memory controller and running certain initialization
3189 		sequences.
3190 
3191 		U-Boot uses the following memory types:
3192 		- MPC8xx: IMMR (internal memory of the CPU)
3193 
3194 - CONFIG_SYS_GBL_DATA_OFFSET:
3195 
3196 		Offset of the initial data structure in the memory
3197 		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3198 		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3199 		data is located at the end of the available space
3200 		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3201 		GENERATED_GBL_DATA_SIZE), and the initial stack is just
3202 		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3203 		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3204 
3205 	Note:
3206 		On the MPC824X (or other systems that use the data
3207 		cache for initial memory) the address chosen for
3208 		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3209 		point to an otherwise UNUSED address space between
3210 		the top of RAM and the start of the PCI space.
3211 
3212 - CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3213 
3214 - CONFIG_SYS_OR_TIMING_SDRAM:
3215 		SDRAM timing
3216 
3217 - CONFIG_SYS_MAMR_PTA:
3218 		periodic timer for refresh
3219 
3220 - FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3221   CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3222   CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3223   CONFIG_SYS_BR1_PRELIM:
3224 		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3225 
3226 - SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3227   CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3228   CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3229 		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3230 
3231 - CONFIG_PCI_ENUM_ONLY
3232 		Only scan through and get the devices on the buses.
3233 		Don't do any setup work, presumably because someone or
3234 		something has already done it, and we don't need to do it
3235 		a second time.	Useful for platforms that are pre-booted
3236 		by coreboot or similar.
3237 
3238 - CONFIG_PCI_INDIRECT_BRIDGE:
3239 		Enable support for indirect PCI bridges.
3240 
3241 - CONFIG_SYS_SRIO:
3242 		Chip has SRIO or not
3243 
3244 - CONFIG_SRIO1:
3245 		Board has SRIO 1 port available
3246 
3247 - CONFIG_SRIO2:
3248 		Board has SRIO 2 port available
3249 
3250 - CONFIG_SRIO_PCIE_BOOT_MASTER
3251 		Board can support master function for Boot from SRIO and PCIE
3252 
3253 - CONFIG_SYS_SRIOn_MEM_VIRT:
3254 		Virtual Address of SRIO port 'n' memory region
3255 
3256 - CONFIG_SYS_SRIOn_MEM_PHYS:
3257 		Physical Address of SRIO port 'n' memory region
3258 
3259 - CONFIG_SYS_SRIOn_MEM_SIZE:
3260 		Size of SRIO port 'n' memory region
3261 
3262 - CONFIG_SYS_NAND_BUSWIDTH_16BIT
3263 		Defined to tell the NAND controller that the NAND chip is using
3264 		a 16 bit bus.
3265 		Not all NAND drivers use this symbol.
3266 		Example of drivers that use it:
3267 		- drivers/mtd/nand/ndfc.c
3268 		- drivers/mtd/nand/mxc_nand.c
3269 
3270 - CONFIG_SYS_NDFC_EBC0_CFG
3271 		Sets the EBC0_CFG register for the NDFC. If not defined
3272 		a default value will be used.
3273 
3274 - CONFIG_SPD_EEPROM
3275 		Get DDR timing information from an I2C EEPROM. Common
3276 		with pluggable memory modules such as SODIMMs
3277 
3278   SPD_EEPROM_ADDRESS
3279 		I2C address of the SPD EEPROM
3280 
3281 - CONFIG_SYS_SPD_BUS_NUM
3282 		If SPD EEPROM is on an I2C bus other than the first
3283 		one, specify here. Note that the value must resolve
3284 		to something your driver can deal with.
3285 
3286 - CONFIG_SYS_DDR_RAW_TIMING
3287 		Get DDR timing information from other than SPD. Common with
3288 		soldered DDR chips onboard without SPD. DDR raw timing
3289 		parameters are extracted from datasheet and hard-coded into
3290 		header files or board specific files.
3291 
3292 - CONFIG_FSL_DDR_INTERACTIVE
3293 		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3294 
3295 - CONFIG_FSL_DDR_SYNC_REFRESH
3296 		Enable sync of refresh for multiple controllers.
3297 
3298 - CONFIG_FSL_DDR_BIST
3299 		Enable built-in memory test for Freescale DDR controllers.
3300 
3301 - CONFIG_SYS_83XX_DDR_USES_CS0
3302 		Only for 83xx systems. If specified, then DDR should
3303 		be configured using CS0 and CS1 instead of CS2 and CS3.
3304 
3305 - CONFIG_RMII
3306 		Enable RMII mode for all FECs.
3307 		Note that this is a global option, we can't
3308 		have one FEC in standard MII mode and another in RMII mode.
3309 
3310 - CONFIG_CRC32_VERIFY
3311 		Add a verify option to the crc32 command.
3312 		The syntax is:
3313 
3314 		=> crc32 -v <address> <count> <crc32>
3315 
3316 		Where address/count indicate a memory area
3317 		and crc32 is the correct crc32 which the
3318 		area should have.
3319 
3320 - CONFIG_LOOPW
3321 		Add the "loopw" memory command. This only takes effect if
3322 		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3323 
3324 - CONFIG_MX_CYCLIC
3325 		Add the "mdc" and "mwc" memory commands. These are cyclic
3326 		"md/mw" commands.
3327 		Examples:
3328 
3329 		=> mdc.b 10 4 500
3330 		This command will print 4 bytes (10,11,12,13) each 500 ms.
3331 
3332 		=> mwc.l 100 12345678 10
3333 		This command will write 12345678 to address 100 all 10 ms.
3334 
3335 		This only takes effect if the memory commands are activated
3336 		globally (CONFIG_CMD_MEMORY).
3337 
3338 - CONFIG_SKIP_LOWLEVEL_INIT
3339 		[ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3340 		low level initializations (like setting up the memory
3341 		controller) are omitted and/or U-Boot does not
3342 		relocate itself into RAM.
3343 
3344 		Normally this variable MUST NOT be defined. The only
3345 		exception is when U-Boot is loaded (to RAM) by some
3346 		other boot loader or by a debugger which performs
3347 		these initializations itself.
3348 
3349 - CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3350 		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3351 		to be skipped. The normal CP15 init (such as enabling the
3352 		instruction cache) is still performed.
3353 
3354 - CONFIG_SPL_BUILD
3355 		Modifies the behaviour of start.S when compiling a loader
3356 		that is executed before the actual U-Boot. E.g. when
3357 		compiling a NAND SPL.
3358 
3359 - CONFIG_TPL_BUILD
3360 		Modifies the behaviour of start.S  when compiling a loader
3361 		that is executed after the SPL and before the actual U-Boot.
3362 		It is loaded by the SPL.
3363 
3364 - CONFIG_SYS_MPC85XX_NO_RESETVEC
3365 		Only for 85xx systems. If this variable is specified, the section
3366 		.resetvec is not kept and the section .bootpg is placed in the
3367 		previous 4k of the .text section.
3368 
3369 - CONFIG_ARCH_MAP_SYSMEM
3370 		Generally U-Boot (and in particular the md command) uses
3371 		effective address. It is therefore not necessary to regard
3372 		U-Boot address as virtual addresses that need to be translated
3373 		to physical addresses. However, sandbox requires this, since
3374 		it maintains its own little RAM buffer which contains all
3375 		addressable memory. This option causes some memory accesses
3376 		to be mapped through map_sysmem() / unmap_sysmem().
3377 
3378 - CONFIG_X86_RESET_VECTOR
3379 		If defined, the x86 reset vector code is included. This is not
3380 		needed when U-Boot is running from Coreboot.
3381 
3382 - CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3383 		Option to disable subpage write in NAND driver
3384 		driver that uses this:
3385 		drivers/mtd/nand/davinci_nand.c
3386 
3387 Freescale QE/FMAN Firmware Support:
3388 -----------------------------------
3389 
3390 The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3391 loading of "firmware", which is encoded in the QE firmware binary format.
3392 This firmware often needs to be loaded during U-Boot booting, so macros
3393 are used to identify the storage device (NOR flash, SPI, etc) and the address
3394 within that device.
3395 
3396 - CONFIG_SYS_FMAN_FW_ADDR
3397 	The address in the storage device where the FMAN microcode is located.  The
3398 	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3399 	is also specified.
3400 
3401 - CONFIG_SYS_QE_FW_ADDR
3402 	The address in the storage device where the QE microcode is located.  The
3403 	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3404 	is also specified.
3405 
3406 - CONFIG_SYS_QE_FMAN_FW_LENGTH
3407 	The maximum possible size of the firmware.  The firmware binary format
3408 	has a field that specifies the actual size of the firmware, but it
3409 	might not be possible to read any part of the firmware unless some
3410 	local storage is allocated to hold the entire firmware first.
3411 
3412 - CONFIG_SYS_QE_FMAN_FW_IN_NOR
3413 	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3414 	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3415 	virtual address in NOR flash.
3416 
3417 - CONFIG_SYS_QE_FMAN_FW_IN_NAND
3418 	Specifies that QE/FMAN firmware is located in NAND flash.
3419 	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3420 
3421 - CONFIG_SYS_QE_FMAN_FW_IN_MMC
3422 	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3423 	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3424 
3425 - CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3426 	Specifies that QE/FMAN firmware is located in the remote (master)
3427 	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3428 	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3429 	window->master inbound window->master LAW->the ucode address in
3430 	master's memory space.
3431 
3432 Freescale Layerscape Management Complex Firmware Support:
3433 ---------------------------------------------------------
3434 The Freescale Layerscape Management Complex (MC) supports the loading of
3435 "firmware".
3436 This firmware often needs to be loaded during U-Boot booting, so macros
3437 are used to identify the storage device (NOR flash, SPI, etc) and the address
3438 within that device.
3439 
3440 - CONFIG_FSL_MC_ENET
3441 	Enable the MC driver for Layerscape SoCs.
3442 
3443 Freescale Layerscape Debug Server Support:
3444 -------------------------------------------
3445 The Freescale Layerscape Debug Server Support supports the loading of
3446 "Debug Server firmware" and triggering SP boot-rom.
3447 This firmware often needs to be loaded during U-Boot booting.
3448 
3449 - CONFIG_SYS_MC_RSV_MEM_ALIGN
3450 	Define alignment of reserved memory MC requires
3451 
3452 Reproducible builds
3453 -------------------
3454 
3455 In order to achieve reproducible builds, timestamps used in the U-Boot build
3456 process have to be set to a fixed value.
3457 
3458 This is done using the SOURCE_DATE_EPOCH environment variable.
3459 SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3460 option for U-Boot or an environment variable in U-Boot.
3461 
3462 SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3463 
3464 Building the Software:
3465 ======================
3466 
3467 Building U-Boot has been tested in several native build environments
3468 and in many different cross environments. Of course we cannot support
3469 all possibly existing versions of cross development tools in all
3470 (potentially obsolete) versions. In case of tool chain problems we
3471 recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3472 which is extensively used to build and test U-Boot.
3473 
3474 If you are not using a native environment, it is assumed that you
3475 have GNU cross compiling tools available in your path. In this case,
3476 you must set the environment variable CROSS_COMPILE in your shell.
3477 Note that no changes to the Makefile or any other source files are
3478 necessary. For example using the ELDK on a 4xx CPU, please enter:
3479 
3480 	$ CROSS_COMPILE=ppc_4xx-
3481 	$ export CROSS_COMPILE
3482 
3483 Note: If you wish to generate Windows versions of the utilities in
3484       the tools directory you can use the MinGW toolchain
3485       (http://www.mingw.org).  Set your HOST tools to the MinGW
3486       toolchain and execute 'make tools'.  For example:
3487 
3488        $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3489 
3490       Binaries such as tools/mkimage.exe will be created which can
3491       be executed on computers running Windows.
3492 
3493 U-Boot is intended to be simple to build. After installing the
3494 sources you must configure U-Boot for one specific board type. This
3495 is done by typing:
3496 
3497 	make NAME_defconfig
3498 
3499 where "NAME_defconfig" is the name of one of the existing configu-
3500 rations; see boards.cfg for supported names.
3501 
3502 Note: for some board special configuration names may exist; check if
3503       additional information is available from the board vendor; for
3504       instance, the TQM823L systems are available without (standard)
3505       or with LCD support. You can select such additional "features"
3506       when choosing the configuration, i. e.
3507 
3508       make TQM823L_defconfig
3509 	- will configure for a plain TQM823L, i. e. no LCD support
3510 
3511       make TQM823L_LCD_defconfig
3512 	- will configure for a TQM823L with U-Boot console on LCD
3513 
3514       etc.
3515 
3516 
3517 Finally, type "make all", and you should get some working U-Boot
3518 images ready for download to / installation on your system:
3519 
3520 - "u-boot.bin" is a raw binary image
3521 - "u-boot" is an image in ELF binary format
3522 - "u-boot.srec" is in Motorola S-Record format
3523 
3524 By default the build is performed locally and the objects are saved
3525 in the source directory. One of the two methods can be used to change
3526 this behavior and build U-Boot to some external directory:
3527 
3528 1. Add O= to the make command line invocations:
3529 
3530 	make O=/tmp/build distclean
3531 	make O=/tmp/build NAME_defconfig
3532 	make O=/tmp/build all
3533 
3534 2. Set environment variable KBUILD_OUTPUT to point to the desired location:
3535 
3536 	export KBUILD_OUTPUT=/tmp/build
3537 	make distclean
3538 	make NAME_defconfig
3539 	make all
3540 
3541 Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3542 variable.
3543 
3544 User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3545 setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3546 For example to treat all compiler warnings as errors:
3547 
3548 	make KCFLAGS=-Werror
3549 
3550 Please be aware that the Makefiles assume you are using GNU make, so
3551 for instance on NetBSD you might need to use "gmake" instead of
3552 native "make".
3553 
3554 
3555 If the system board that you have is not listed, then you will need
3556 to port U-Boot to your hardware platform. To do this, follow these
3557 steps:
3558 
3559 1.  Create a new directory to hold your board specific code. Add any
3560     files you need. In your board directory, you will need at least
3561     the "Makefile" and a "<board>.c".
3562 2.  Create a new configuration file "include/configs/<board>.h" for
3563     your board.
3564 3.  If you're porting U-Boot to a new CPU, then also create a new
3565     directory to hold your CPU specific code. Add any files you need.
3566 4.  Run "make <board>_defconfig" with your new name.
3567 5.  Type "make", and you should get a working "u-boot.srec" file
3568     to be installed on your target system.
3569 6.  Debug and solve any problems that might arise.
3570     [Of course, this last step is much harder than it sounds.]
3571 
3572 
3573 Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3574 ==============================================================
3575 
3576 If you have modified U-Boot sources (for instance added a new board
3577 or support for new devices, a new CPU, etc.) you are expected to
3578 provide feedback to the other developers. The feedback normally takes
3579 the form of a "patch", i. e. a context diff against a certain (latest
3580 official or latest in the git repository) version of U-Boot sources.
3581 
3582 But before you submit such a patch, please verify that your modifi-
3583 cation did not break existing code. At least make sure that *ALL* of
3584 the supported boards compile WITHOUT ANY compiler warnings. To do so,
3585 just run the buildman script (tools/buildman/buildman), which will
3586 configure and build U-Boot for ALL supported system. Be warned, this
3587 will take a while. Please see the buildman README, or run 'buildman -H'
3588 for documentation.
3589 
3590 
3591 See also "U-Boot Porting Guide" below.
3592 
3593 
3594 Monitor Commands - Overview:
3595 ============================
3596 
3597 go	- start application at address 'addr'
3598 run	- run commands in an environment variable
3599 bootm	- boot application image from memory
3600 bootp	- boot image via network using BootP/TFTP protocol
3601 bootz   - boot zImage from memory
3602 tftpboot- boot image via network using TFTP protocol
3603 	       and env variables "ipaddr" and "serverip"
3604 	       (and eventually "gatewayip")
3605 tftpput - upload a file via network using TFTP protocol
3606 rarpboot- boot image via network using RARP/TFTP protocol
3607 diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3608 loads	- load S-Record file over serial line
3609 loadb	- load binary file over serial line (kermit mode)
3610 md	- memory display
3611 mm	- memory modify (auto-incrementing)
3612 nm	- memory modify (constant address)
3613 mw	- memory write (fill)
3614 cp	- memory copy
3615 cmp	- memory compare
3616 crc32	- checksum calculation
3617 i2c	- I2C sub-system
3618 sspi	- SPI utility commands
3619 base	- print or set address offset
3620 printenv- print environment variables
3621 setenv	- set environment variables
3622 saveenv - save environment variables to persistent storage
3623 protect - enable or disable FLASH write protection
3624 erase	- erase FLASH memory
3625 flinfo	- print FLASH memory information
3626 nand	- NAND memory operations (see doc/README.nand)
3627 bdinfo	- print Board Info structure
3628 iminfo	- print header information for application image
3629 coninfo - print console devices and informations
3630 ide	- IDE sub-system
3631 loop	- infinite loop on address range
3632 loopw	- infinite write loop on address range
3633 mtest	- simple RAM test
3634 icache	- enable or disable instruction cache
3635 dcache	- enable or disable data cache
3636 reset	- Perform RESET of the CPU
3637 echo	- echo args to console
3638 version - print monitor version
3639 help	- print online help
3640 ?	- alias for 'help'
3641 
3642 
3643 Monitor Commands - Detailed Description:
3644 ========================================
3645 
3646 TODO.
3647 
3648 For now: just type "help <command>".
3649 
3650 
3651 Environment Variables:
3652 ======================
3653 
3654 U-Boot supports user configuration using Environment Variables which
3655 can be made persistent by saving to Flash memory.
3656 
3657 Environment Variables are set using "setenv", printed using
3658 "printenv", and saved to Flash using "saveenv". Using "setenv"
3659 without a value can be used to delete a variable from the
3660 environment. As long as you don't save the environment you are
3661 working with an in-memory copy. In case the Flash area containing the
3662 environment is erased by accident, a default environment is provided.
3663 
3664 Some configuration options can be set using Environment Variables.
3665 
3666 List of environment variables (most likely not complete):
3667 
3668   baudrate	- see CONFIG_BAUDRATE
3669 
3670   bootdelay	- see CONFIG_BOOTDELAY
3671 
3672   bootcmd	- see CONFIG_BOOTCOMMAND
3673 
3674   bootargs	- Boot arguments when booting an RTOS image
3675 
3676   bootfile	- Name of the image to load with TFTP
3677 
3678   bootm_low	- Memory range available for image processing in the bootm
3679 		  command can be restricted. This variable is given as
3680 		  a hexadecimal number and defines lowest address allowed
3681 		  for use by the bootm command. See also "bootm_size"
3682 		  environment variable. Address defined by "bootm_low" is
3683 		  also the base of the initial memory mapping for the Linux
3684 		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3685 		  bootm_mapsize.
3686 
3687   bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3688 		  This variable is given as a hexadecimal number and it
3689 		  defines the size of the memory region starting at base
3690 		  address bootm_low that is accessible by the Linux kernel
3691 		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3692 		  as the default value if it is defined, and bootm_size is
3693 		  used otherwise.
3694 
3695   bootm_size	- Memory range available for image processing in the bootm
3696 		  command can be restricted. This variable is given as
3697 		  a hexadecimal number and defines the size of the region
3698 		  allowed for use by the bootm command. See also "bootm_low"
3699 		  environment variable.
3700 
3701   updatefile	- Location of the software update file on a TFTP server, used
3702 		  by the automatic software update feature. Please refer to
3703 		  documentation in doc/README.update for more details.
3704 
3705   autoload	- if set to "no" (any string beginning with 'n'),
3706 		  "bootp" will just load perform a lookup of the
3707 		  configuration from the BOOTP server, but not try to
3708 		  load any image using TFTP
3709 
3710   autostart	- if set to "yes", an image loaded using the "bootp",
3711 		  "rarpboot", "tftpboot" or "diskboot" commands will
3712 		  be automatically started (by internally calling
3713 		  "bootm")
3714 
3715 		  If set to "no", a standalone image passed to the
3716 		  "bootm" command will be copied to the load address
3717 		  (and eventually uncompressed), but NOT be started.
3718 		  This can be used to load and uncompress arbitrary
3719 		  data.
3720 
3721   fdt_high	- if set this restricts the maximum address that the
3722 		  flattened device tree will be copied into upon boot.
3723 		  For example, if you have a system with 1 GB memory
3724 		  at physical address 0x10000000, while Linux kernel
3725 		  only recognizes the first 704 MB as low memory, you
3726 		  may need to set fdt_high as 0x3C000000 to have the
3727 		  device tree blob be copied to the maximum address
3728 		  of the 704 MB low memory, so that Linux kernel can
3729 		  access it during the boot procedure.
3730 
3731 		  If this is set to the special value 0xFFFFFFFF then
3732 		  the fdt will not be copied at all on boot.  For this
3733 		  to work it must reside in writable memory, have
3734 		  sufficient padding on the end of it for u-boot to
3735 		  add the information it needs into it, and the memory
3736 		  must be accessible by the kernel.
3737 
3738   fdtcontroladdr- if set this is the address of the control flattened
3739 		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3740 		  defined.
3741 
3742   i2cfast	- (PPC405GP|PPC405EP only)
3743 		  if set to 'y' configures Linux I2C driver for fast
3744 		  mode (400kHZ). This environment variable is used in
3745 		  initialization code. So, for changes to be effective
3746 		  it must be saved and board must be reset.
3747 
3748   initrd_high	- restrict positioning of initrd images:
3749 		  If this variable is not set, initrd images will be
3750 		  copied to the highest possible address in RAM; this
3751 		  is usually what you want since it allows for
3752 		  maximum initrd size. If for some reason you want to
3753 		  make sure that the initrd image is loaded below the
3754 		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3755 		  variable to a value of "no" or "off" or "0".
3756 		  Alternatively, you can set it to a maximum upper
3757 		  address to use (U-Boot will still check that it
3758 		  does not overwrite the U-Boot stack and data).
3759 
3760 		  For instance, when you have a system with 16 MB
3761 		  RAM, and want to reserve 4 MB from use by Linux,
3762 		  you can do this by adding "mem=12M" to the value of
3763 		  the "bootargs" variable. However, now you must make
3764 		  sure that the initrd image is placed in the first
3765 		  12 MB as well - this can be done with
3766 
3767 		  setenv initrd_high 00c00000
3768 
3769 		  If you set initrd_high to 0xFFFFFFFF, this is an
3770 		  indication to U-Boot that all addresses are legal
3771 		  for the Linux kernel, including addresses in flash
3772 		  memory. In this case U-Boot will NOT COPY the
3773 		  ramdisk at all. This may be useful to reduce the
3774 		  boot time on your system, but requires that this
3775 		  feature is supported by your Linux kernel.
3776 
3777   ipaddr	- IP address; needed for tftpboot command
3778 
3779   loadaddr	- Default load address for commands like "bootp",
3780 		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3781 
3782   loads_echo	- see CONFIG_LOADS_ECHO
3783 
3784   serverip	- TFTP server IP address; needed for tftpboot command
3785 
3786   bootretry	- see CONFIG_BOOT_RETRY_TIME
3787 
3788   bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3789 
3790   bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3791 
3792   ethprime	- controls which interface is used first.
3793 
3794   ethact	- controls which interface is currently active.
3795 		  For example you can do the following
3796 
3797 		  => setenv ethact FEC
3798 		  => ping 192.168.0.1 # traffic sent on FEC
3799 		  => setenv ethact SCC
3800 		  => ping 10.0.0.1 # traffic sent on SCC
3801 
3802   ethrotate	- When set to "no" U-Boot does not go through all
3803 		  available network interfaces.
3804 		  It just stays at the currently selected interface.
3805 
3806   netretry	- When set to "no" each network operation will
3807 		  either succeed or fail without retrying.
3808 		  When set to "once" the network operation will
3809 		  fail when all the available network interfaces
3810 		  are tried once without success.
3811 		  Useful on scripts which control the retry operation
3812 		  themselves.
3813 
3814   npe_ucode	- set load address for the NPE microcode
3815 
3816   silent_linux  - If set then Linux will be told to boot silently, by
3817 		  changing the console to be empty. If "yes" it will be
3818 		  made silent. If "no" it will not be made silent. If
3819 		  unset, then it will be made silent if the U-Boot console
3820 		  is silent.
3821 
3822   tftpsrcp	- If this is set, the value is used for TFTP's
3823 		  UDP source port.
3824 
3825   tftpdstp	- If this is set, the value is used for TFTP's UDP
3826 		  destination port instead of the Well Know Port 69.
3827 
3828   tftpblocksize - Block size to use for TFTP transfers; if not set,
3829 		  we use the TFTP server's default block size
3830 
3831   tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3832 		  seconds, minimum value is 1000 = 1 second). Defines
3833 		  when a packet is considered to be lost so it has to
3834 		  be retransmitted. The default is 5000 = 5 seconds.
3835 		  Lowering this value may make downloads succeed
3836 		  faster in networks with high packet loss rates or
3837 		  with unreliable TFTP servers.
3838 
3839   tftptimeoutcountmax	- maximum count of TFTP timeouts (no
3840 		  unit, minimum value = 0). Defines how many timeouts
3841 		  can happen during a single file transfer before that
3842 		  transfer is aborted. The default is 10, and 0 means
3843 		  'no timeouts allowed'. Increasing this value may help
3844 		  downloads succeed with high packet loss rates, or with
3845 		  unreliable TFTP servers or client hardware.
3846 
3847   vlan		- When set to a value < 4095 the traffic over
3848 		  Ethernet is encapsulated/received over 802.1q
3849 		  VLAN tagged frames.
3850 
3851   bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
3852 		  Unsigned value, in milliseconds. If not set, the period will
3853 		  be either the default (28000), or a value based on
3854 		  CONFIG_NET_RETRY_COUNT, if defined. This value has
3855 		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3856 
3857 The following image location variables contain the location of images
3858 used in booting. The "Image" column gives the role of the image and is
3859 not an environment variable name. The other columns are environment
3860 variable names. "File Name" gives the name of the file on a TFTP
3861 server, "RAM Address" gives the location in RAM the image will be
3862 loaded to, and "Flash Location" gives the image's address in NOR
3863 flash or offset in NAND flash.
3864 
3865 *Note* - these variables don't have to be defined for all boards, some
3866 boards currently use other variables for these purposes, and some
3867 boards use these variables for other purposes.
3868 
3869 Image		    File Name	     RAM Address       Flash Location
3870 -----		    ---------	     -----------       --------------
3871 u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
3872 Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
3873 device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
3874 ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
3875 
3876 The following environment variables may be used and automatically
3877 updated by the network boot commands ("bootp" and "rarpboot"),
3878 depending the information provided by your boot server:
3879 
3880   bootfile	- see above
3881   dnsip		- IP address of your Domain Name Server
3882   dnsip2	- IP address of your secondary Domain Name Server
3883   gatewayip	- IP address of the Gateway (Router) to use
3884   hostname	- Target hostname
3885   ipaddr	- see above
3886   netmask	- Subnet Mask
3887   rootpath	- Pathname of the root filesystem on the NFS server
3888   serverip	- see above
3889 
3890 
3891 There are two special Environment Variables:
3892 
3893   serial#	- contains hardware identification information such
3894 		  as type string and/or serial number
3895   ethaddr	- Ethernet address
3896 
3897 These variables can be set only once (usually during manufacturing of
3898 the board). U-Boot refuses to delete or overwrite these variables
3899 once they have been set once.
3900 
3901 
3902 Further special Environment Variables:
3903 
3904   ver		- Contains the U-Boot version string as printed
3905 		  with the "version" command. This variable is
3906 		  readonly (see CONFIG_VERSION_VARIABLE).
3907 
3908 
3909 Please note that changes to some configuration parameters may take
3910 only effect after the next boot (yes, that's just like Windoze :-).
3911 
3912 
3913 Callback functions for environment variables:
3914 ---------------------------------------------
3915 
3916 For some environment variables, the behavior of u-boot needs to change
3917 when their values are changed.  This functionality allows functions to
3918 be associated with arbitrary variables.  On creation, overwrite, or
3919 deletion, the callback will provide the opportunity for some side
3920 effect to happen or for the change to be rejected.
3921 
3922 The callbacks are named and associated with a function using the
3923 U_BOOT_ENV_CALLBACK macro in your board or driver code.
3924 
3925 These callbacks are associated with variables in one of two ways.  The
3926 static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3927 in the board configuration to a string that defines a list of
3928 associations.  The list must be in the following format:
3929 
3930 	entry = variable_name[:callback_name]
3931 	list = entry[,list]
3932 
3933 If the callback name is not specified, then the callback is deleted.
3934 Spaces are also allowed anywhere in the list.
3935 
3936 Callbacks can also be associated by defining the ".callbacks" variable
3937 with the same list format above.  Any association in ".callbacks" will
3938 override any association in the static list. You can define
3939 CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3940 ".callbacks" environment variable in the default or embedded environment.
3941 
3942 If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3943 regular expression. This allows multiple variables to be connected to
3944 the same callback without explicitly listing them all out.
3945 
3946 
3947 Command Line Parsing:
3948 =====================
3949 
3950 There are two different command line parsers available with U-Boot:
3951 the old "simple" one, and the much more powerful "hush" shell:
3952 
3953 Old, simple command line parser:
3954 --------------------------------
3955 
3956 - supports environment variables (through setenv / saveenv commands)
3957 - several commands on one line, separated by ';'
3958 - variable substitution using "... ${name} ..." syntax
3959 - special characters ('$', ';') can be escaped by prefixing with '\',
3960   for example:
3961 	setenv bootcmd bootm \${address}
3962 - You can also escape text by enclosing in single apostrophes, for example:
3963 	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3964 
3965 Hush shell:
3966 -----------
3967 
3968 - similar to Bourne shell, with control structures like
3969   if...then...else...fi, for...do...done; while...do...done,
3970   until...do...done, ...
3971 - supports environment ("global") variables (through setenv / saveenv
3972   commands) and local shell variables (through standard shell syntax
3973   "name=value"); only environment variables can be used with "run"
3974   command
3975 
3976 General rules:
3977 --------------
3978 
3979 (1) If a command line (or an environment variable executed by a "run"
3980     command) contains several commands separated by semicolon, and
3981     one of these commands fails, then the remaining commands will be
3982     executed anyway.
3983 
3984 (2) If you execute several variables with one call to run (i. e.
3985     calling run with a list of variables as arguments), any failing
3986     command will cause "run" to terminate, i. e. the remaining
3987     variables are not executed.
3988 
3989 Note for Redundant Ethernet Interfaces:
3990 =======================================
3991 
3992 Some boards come with redundant Ethernet interfaces; U-Boot supports
3993 such configurations and is capable of automatic selection of a
3994 "working" interface when needed. MAC assignment works as follows:
3995 
3996 Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3997 MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3998 "eth1addr" (=>eth1), "eth2addr", ...
3999 
4000 If the network interface stores some valid MAC address (for instance
4001 in SROM), this is used as default address if there is NO correspon-
4002 ding setting in the environment; if the corresponding environment
4003 variable is set, this overrides the settings in the card; that means:
4004 
4005 o If the SROM has a valid MAC address, and there is no address in the
4006   environment, the SROM's address is used.
4007 
4008 o If there is no valid address in the SROM, and a definition in the
4009   environment exists, then the value from the environment variable is
4010   used.
4011 
4012 o If both the SROM and the environment contain a MAC address, and
4013   both addresses are the same, this MAC address is used.
4014 
4015 o If both the SROM and the environment contain a MAC address, and the
4016   addresses differ, the value from the environment is used and a
4017   warning is printed.
4018 
4019 o If neither SROM nor the environment contain a MAC address, an error
4020   is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4021   a random, locally-assigned MAC is used.
4022 
4023 If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4024 will be programmed into hardware as part of the initialization process.	 This
4025 may be skipped by setting the appropriate 'ethmacskip' environment variable.
4026 The naming convention is as follows:
4027 "ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4028 
4029 Image Formats:
4030 ==============
4031 
4032 U-Boot is capable of booting (and performing other auxiliary operations on)
4033 images in two formats:
4034 
4035 New uImage format (FIT)
4036 -----------------------
4037 
4038 Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4039 to Flattened Device Tree). It allows the use of images with multiple
4040 components (several kernels, ramdisks, etc.), with contents protected by
4041 SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4042 
4043 
4044 Old uImage format
4045 -----------------
4046 
4047 Old image format is based on binary files which can be basically anything,
4048 preceded by a special header; see the definitions in include/image.h for
4049 details; basically, the header defines the following image properties:
4050 
4051 * Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4052   4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4053   LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4054   Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4055   INTEGRITY).
4056 * Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4057   IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4058   Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4059 * Compression Type (uncompressed, gzip, bzip2)
4060 * Load Address
4061 * Entry Point
4062 * Image Name
4063 * Image Timestamp
4064 
4065 The header is marked by a special Magic Number, and both the header
4066 and the data portions of the image are secured against corruption by
4067 CRC32 checksums.
4068 
4069 
4070 Linux Support:
4071 ==============
4072 
4073 Although U-Boot should support any OS or standalone application
4074 easily, the main focus has always been on Linux during the design of
4075 U-Boot.
4076 
4077 U-Boot includes many features that so far have been part of some
4078 special "boot loader" code within the Linux kernel. Also, any
4079 "initrd" images to be used are no longer part of one big Linux image;
4080 instead, kernel and "initrd" are separate images. This implementation
4081 serves several purposes:
4082 
4083 - the same features can be used for other OS or standalone
4084   applications (for instance: using compressed images to reduce the
4085   Flash memory footprint)
4086 
4087 - it becomes much easier to port new Linux kernel versions because
4088   lots of low-level, hardware dependent stuff are done by U-Boot
4089 
4090 - the same Linux kernel image can now be used with different "initrd"
4091   images; of course this also means that different kernel images can
4092   be run with the same "initrd". This makes testing easier (you don't
4093   have to build a new "zImage.initrd" Linux image when you just
4094   change a file in your "initrd"). Also, a field-upgrade of the
4095   software is easier now.
4096 
4097 
4098 Linux HOWTO:
4099 ============
4100 
4101 Porting Linux to U-Boot based systems:
4102 ---------------------------------------
4103 
4104 U-Boot cannot save you from doing all the necessary modifications to
4105 configure the Linux device drivers for use with your target hardware
4106 (no, we don't intend to provide a full virtual machine interface to
4107 Linux :-).
4108 
4109 But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4110 
4111 Just make sure your machine specific header file (for instance
4112 include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4113 Information structure as we define in include/asm-<arch>/u-boot.h,
4114 and make sure that your definition of IMAP_ADDR uses the same value
4115 as your U-Boot configuration in CONFIG_SYS_IMMR.
4116 
4117 Note that U-Boot now has a driver model, a unified model for drivers.
4118 If you are adding a new driver, plumb it into driver model. If there
4119 is no uclass available, you are encouraged to create one. See
4120 doc/driver-model.
4121 
4122 
4123 Configuring the Linux kernel:
4124 -----------------------------
4125 
4126 No specific requirements for U-Boot. Make sure you have some root
4127 device (initial ramdisk, NFS) for your target system.
4128 
4129 
4130 Building a Linux Image:
4131 -----------------------
4132 
4133 With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4134 not used. If you use recent kernel source, a new build target
4135 "uImage" will exist which automatically builds an image usable by
4136 U-Boot. Most older kernels also have support for a "pImage" target,
4137 which was introduced for our predecessor project PPCBoot and uses a
4138 100% compatible format.
4139 
4140 Example:
4141 
4142 	make TQM850L_defconfig
4143 	make oldconfig
4144 	make dep
4145 	make uImage
4146 
4147 The "uImage" build target uses a special tool (in 'tools/mkimage') to
4148 encapsulate a compressed Linux kernel image with header	 information,
4149 CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4150 
4151 * build a standard "vmlinux" kernel image (in ELF binary format):
4152 
4153 * convert the kernel into a raw binary image:
4154 
4155 	${CROSS_COMPILE}-objcopy -O binary \
4156 				 -R .note -R .comment \
4157 				 -S vmlinux linux.bin
4158 
4159 * compress the binary image:
4160 
4161 	gzip -9 linux.bin
4162 
4163 * package compressed binary image for U-Boot:
4164 
4165 	mkimage -A ppc -O linux -T kernel -C gzip \
4166 		-a 0 -e 0 -n "Linux Kernel Image" \
4167 		-d linux.bin.gz uImage
4168 
4169 
4170 The "mkimage" tool can also be used to create ramdisk images for use
4171 with U-Boot, either separated from the Linux kernel image, or
4172 combined into one file. "mkimage" encapsulates the images with a 64
4173 byte header containing information about target architecture,
4174 operating system, image type, compression method, entry points, time
4175 stamp, CRC32 checksums, etc.
4176 
4177 "mkimage" can be called in two ways: to verify existing images and
4178 print the header information, or to build new images.
4179 
4180 In the first form (with "-l" option) mkimage lists the information
4181 contained in the header of an existing U-Boot image; this includes
4182 checksum verification:
4183 
4184 	tools/mkimage -l image
4185 	  -l ==> list image header information
4186 
4187 The second form (with "-d" option) is used to build a U-Boot image
4188 from a "data file" which is used as image payload:
4189 
4190 	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4191 		      -n name -d data_file image
4192 	  -A ==> set architecture to 'arch'
4193 	  -O ==> set operating system to 'os'
4194 	  -T ==> set image type to 'type'
4195 	  -C ==> set compression type 'comp'
4196 	  -a ==> set load address to 'addr' (hex)
4197 	  -e ==> set entry point to 'ep' (hex)
4198 	  -n ==> set image name to 'name'
4199 	  -d ==> use image data from 'datafile'
4200 
4201 Right now, all Linux kernels for PowerPC systems use the same load
4202 address (0x00000000), but the entry point address depends on the
4203 kernel version:
4204 
4205 - 2.2.x kernels have the entry point at 0x0000000C,
4206 - 2.3.x and later kernels have the entry point at 0x00000000.
4207 
4208 So a typical call to build a U-Boot image would read:
4209 
4210 	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4211 	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4212 	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4213 	> examples/uImage.TQM850L
4214 	Image Name:   2.4.4 kernel for TQM850L
4215 	Created:      Wed Jul 19 02:34:59 2000
4216 	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4217 	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4218 	Load Address: 0x00000000
4219 	Entry Point:  0x00000000
4220 
4221 To verify the contents of the image (or check for corruption):
4222 
4223 	-> tools/mkimage -l examples/uImage.TQM850L
4224 	Image Name:   2.4.4 kernel for TQM850L
4225 	Created:      Wed Jul 19 02:34:59 2000
4226 	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4227 	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4228 	Load Address: 0x00000000
4229 	Entry Point:  0x00000000
4230 
4231 NOTE: for embedded systems where boot time is critical you can trade
4232 speed for memory and install an UNCOMPRESSED image instead: this
4233 needs more space in Flash, but boots much faster since it does not
4234 need to be uncompressed:
4235 
4236 	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4237 	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4238 	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4239 	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4240 	> examples/uImage.TQM850L-uncompressed
4241 	Image Name:   2.4.4 kernel for TQM850L
4242 	Created:      Wed Jul 19 02:34:59 2000
4243 	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4244 	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4245 	Load Address: 0x00000000
4246 	Entry Point:  0x00000000
4247 
4248 
4249 Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4250 when your kernel is intended to use an initial ramdisk:
4251 
4252 	-> tools/mkimage -n 'Simple Ramdisk Image' \
4253 	> -A ppc -O linux -T ramdisk -C gzip \
4254 	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4255 	Image Name:   Simple Ramdisk Image
4256 	Created:      Wed Jan 12 14:01:50 2000
4257 	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4258 	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4259 	Load Address: 0x00000000
4260 	Entry Point:  0x00000000
4261 
4262 The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4263 option performs the converse operation of the mkimage's second form (the "-d"
4264 option). Given an image built by mkimage, the dumpimage extracts a "data file"
4265 from the image:
4266 
4267 	tools/dumpimage -i image -T type -p position data_file
4268 	  -i ==> extract from the 'image' a specific 'data_file'
4269 	  -T ==> set image type to 'type'
4270 	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4271 
4272 
4273 Installing a Linux Image:
4274 -------------------------
4275 
4276 To downloading a U-Boot image over the serial (console) interface,
4277 you must convert the image to S-Record format:
4278 
4279 	objcopy -I binary -O srec examples/image examples/image.srec
4280 
4281 The 'objcopy' does not understand the information in the U-Boot
4282 image header, so the resulting S-Record file will be relative to
4283 address 0x00000000. To load it to a given address, you need to
4284 specify the target address as 'offset' parameter with the 'loads'
4285 command.
4286 
4287 Example: install the image to address 0x40100000 (which on the
4288 TQM8xxL is in the first Flash bank):
4289 
4290 	=> erase 40100000 401FFFFF
4291 
4292 	.......... done
4293 	Erased 8 sectors
4294 
4295 	=> loads 40100000
4296 	## Ready for S-Record download ...
4297 	~>examples/image.srec
4298 	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4299 	...
4300 	15989 15990 15991 15992
4301 	[file transfer complete]
4302 	[connected]
4303 	## Start Addr = 0x00000000
4304 
4305 
4306 You can check the success of the download using the 'iminfo' command;
4307 this includes a checksum verification so you can be sure no data
4308 corruption happened:
4309 
4310 	=> imi 40100000
4311 
4312 	## Checking Image at 40100000 ...
4313 	   Image Name:	 2.2.13 for initrd on TQM850L
4314 	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4315 	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4316 	   Load Address: 00000000
4317 	   Entry Point:	 0000000c
4318 	   Verifying Checksum ... OK
4319 
4320 
4321 Boot Linux:
4322 -----------
4323 
4324 The "bootm" command is used to boot an application that is stored in
4325 memory (RAM or Flash). In case of a Linux kernel image, the contents
4326 of the "bootargs" environment variable is passed to the kernel as
4327 parameters. You can check and modify this variable using the
4328 "printenv" and "setenv" commands:
4329 
4330 
4331 	=> printenv bootargs
4332 	bootargs=root=/dev/ram
4333 
4334 	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4335 
4336 	=> printenv bootargs
4337 	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4338 
4339 	=> bootm 40020000
4340 	## Booting Linux kernel at 40020000 ...
4341 	   Image Name:	 2.2.13 for NFS on TQM850L
4342 	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4343 	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4344 	   Load Address: 00000000
4345 	   Entry Point:	 0000000c
4346 	   Verifying Checksum ... OK
4347 	   Uncompressing Kernel Image ... OK
4348 	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
4349 	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4350 	time_init: decrementer frequency = 187500000/60
4351 	Calibrating delay loop... 49.77 BogoMIPS
4352 	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4353 	...
4354 
4355 If you want to boot a Linux kernel with initial RAM disk, you pass
4356 the memory addresses of both the kernel and the initrd image (PPBCOOT
4357 format!) to the "bootm" command:
4358 
4359 	=> imi 40100000 40200000
4360 
4361 	## Checking Image at 40100000 ...
4362 	   Image Name:	 2.2.13 for initrd on TQM850L
4363 	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4364 	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4365 	   Load Address: 00000000
4366 	   Entry Point:	 0000000c
4367 	   Verifying Checksum ... OK
4368 
4369 	## Checking Image at 40200000 ...
4370 	   Image Name:	 Simple Ramdisk Image
4371 	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4372 	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4373 	   Load Address: 00000000
4374 	   Entry Point:	 00000000
4375 	   Verifying Checksum ... OK
4376 
4377 	=> bootm 40100000 40200000
4378 	## Booting Linux kernel at 40100000 ...
4379 	   Image Name:	 2.2.13 for initrd on TQM850L
4380 	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4381 	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4382 	   Load Address: 00000000
4383 	   Entry Point:	 0000000c
4384 	   Verifying Checksum ... OK
4385 	   Uncompressing Kernel Image ... OK
4386 	## Loading RAMDisk Image at 40200000 ...
4387 	   Image Name:	 Simple Ramdisk Image
4388 	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4389 	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4390 	   Load Address: 00000000
4391 	   Entry Point:	 00000000
4392 	   Verifying Checksum ... OK
4393 	   Loading Ramdisk ... OK
4394 	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
4395 	Boot arguments: root=/dev/ram
4396 	time_init: decrementer frequency = 187500000/60
4397 	Calibrating delay loop... 49.77 BogoMIPS
4398 	...
4399 	RAMDISK: Compressed image found at block 0
4400 	VFS: Mounted root (ext2 filesystem).
4401 
4402 	bash#
4403 
4404 Boot Linux and pass a flat device tree:
4405 -----------
4406 
4407 First, U-Boot must be compiled with the appropriate defines. See the section
4408 titled "Linux Kernel Interface" above for a more in depth explanation. The
4409 following is an example of how to start a kernel and pass an updated
4410 flat device tree:
4411 
4412 => print oftaddr
4413 oftaddr=0x300000
4414 => print oft
4415 oft=oftrees/mpc8540ads.dtb
4416 => tftp $oftaddr $oft
4417 Speed: 1000, full duplex
4418 Using TSEC0 device
4419 TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4420 Filename 'oftrees/mpc8540ads.dtb'.
4421 Load address: 0x300000
4422 Loading: #
4423 done
4424 Bytes transferred = 4106 (100a hex)
4425 => tftp $loadaddr $bootfile
4426 Speed: 1000, full duplex
4427 Using TSEC0 device
4428 TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4429 Filename 'uImage'.
4430 Load address: 0x200000
4431 Loading:############
4432 done
4433 Bytes transferred = 1029407 (fb51f hex)
4434 => print loadaddr
4435 loadaddr=200000
4436 => print oftaddr
4437 oftaddr=0x300000
4438 => bootm $loadaddr - $oftaddr
4439 ## Booting image at 00200000 ...
4440    Image Name:	 Linux-2.6.17-dirty
4441    Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4442    Data Size:	 1029343 Bytes = 1005.2 kB
4443    Load Address: 00000000
4444    Entry Point:	 00000000
4445    Verifying Checksum ... OK
4446    Uncompressing Kernel Image ... OK
4447 Booting using flat device tree at 0x300000
4448 Using MPC85xx ADS machine description
4449 Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4450 [snip]
4451 
4452 
4453 More About U-Boot Image Types:
4454 ------------------------------
4455 
4456 U-Boot supports the following image types:
4457 
4458    "Standalone Programs" are directly runnable in the environment
4459 	provided by U-Boot; it is expected that (if they behave
4460 	well) you can continue to work in U-Boot after return from
4461 	the Standalone Program.
4462    "OS Kernel Images" are usually images of some Embedded OS which
4463 	will take over control completely. Usually these programs
4464 	will install their own set of exception handlers, device
4465 	drivers, set up the MMU, etc. - this means, that you cannot
4466 	expect to re-enter U-Boot except by resetting the CPU.
4467    "RAMDisk Images" are more or less just data blocks, and their
4468 	parameters (address, size) are passed to an OS kernel that is
4469 	being started.
4470    "Multi-File Images" contain several images, typically an OS
4471 	(Linux) kernel image and one or more data images like
4472 	RAMDisks. This construct is useful for instance when you want
4473 	to boot over the network using BOOTP etc., where the boot
4474 	server provides just a single image file, but you want to get
4475 	for instance an OS kernel and a RAMDisk image.
4476 
4477 	"Multi-File Images" start with a list of image sizes, each
4478 	image size (in bytes) specified by an "uint32_t" in network
4479 	byte order. This list is terminated by an "(uint32_t)0".
4480 	Immediately after the terminating 0 follow the images, one by
4481 	one, all aligned on "uint32_t" boundaries (size rounded up to
4482 	a multiple of 4 bytes).
4483 
4484    "Firmware Images" are binary images containing firmware (like
4485 	U-Boot or FPGA images) which usually will be programmed to
4486 	flash memory.
4487 
4488    "Script files" are command sequences that will be executed by
4489 	U-Boot's command interpreter; this feature is especially
4490 	useful when you configure U-Boot to use a real shell (hush)
4491 	as command interpreter.
4492 
4493 Booting the Linux zImage:
4494 -------------------------
4495 
4496 On some platforms, it's possible to boot Linux zImage. This is done
4497 using the "bootz" command. The syntax of "bootz" command is the same
4498 as the syntax of "bootm" command.
4499 
4500 Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4501 kernel with raw initrd images. The syntax is slightly different, the
4502 address of the initrd must be augmented by it's size, in the following
4503 format: "<initrd addres>:<initrd size>".
4504 
4505 
4506 Standalone HOWTO:
4507 =================
4508 
4509 One of the features of U-Boot is that you can dynamically load and
4510 run "standalone" applications, which can use some resources of
4511 U-Boot like console I/O functions or interrupt services.
4512 
4513 Two simple examples are included with the sources:
4514 
4515 "Hello World" Demo:
4516 -------------------
4517 
4518 'examples/hello_world.c' contains a small "Hello World" Demo
4519 application; it is automatically compiled when you build U-Boot.
4520 It's configured to run at address 0x00040004, so you can play with it
4521 like that:
4522 
4523 	=> loads
4524 	## Ready for S-Record download ...
4525 	~>examples/hello_world.srec
4526 	1 2 3 4 5 6 7 8 9 10 11 ...
4527 	[file transfer complete]
4528 	[connected]
4529 	## Start Addr = 0x00040004
4530 
4531 	=> go 40004 Hello World! This is a test.
4532 	## Starting application at 0x00040004 ...
4533 	Hello World
4534 	argc = 7
4535 	argv[0] = "40004"
4536 	argv[1] = "Hello"
4537 	argv[2] = "World!"
4538 	argv[3] = "This"
4539 	argv[4] = "is"
4540 	argv[5] = "a"
4541 	argv[6] = "test."
4542 	argv[7] = "<NULL>"
4543 	Hit any key to exit ...
4544 
4545 	## Application terminated, rc = 0x0
4546 
4547 Another example, which demonstrates how to register a CPM interrupt
4548 handler with the U-Boot code, can be found in 'examples/timer.c'.
4549 Here, a CPM timer is set up to generate an interrupt every second.
4550 The interrupt service routine is trivial, just printing a '.'
4551 character, but this is just a demo program. The application can be
4552 controlled by the following keys:
4553 
4554 	? - print current values og the CPM Timer registers
4555 	b - enable interrupts and start timer
4556 	e - stop timer and disable interrupts
4557 	q - quit application
4558 
4559 	=> loads
4560 	## Ready for S-Record download ...
4561 	~>examples/timer.srec
4562 	1 2 3 4 5 6 7 8 9 10 11 ...
4563 	[file transfer complete]
4564 	[connected]
4565 	## Start Addr = 0x00040004
4566 
4567 	=> go 40004
4568 	## Starting application at 0x00040004 ...
4569 	TIMERS=0xfff00980
4570 	Using timer 1
4571 	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4572 
4573 Hit 'b':
4574 	[q, b, e, ?] Set interval 1000000 us
4575 	Enabling timer
4576 Hit '?':
4577 	[q, b, e, ?] ........
4578 	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4579 Hit '?':
4580 	[q, b, e, ?] .
4581 	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4582 Hit '?':
4583 	[q, b, e, ?] .
4584 	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4585 Hit '?':
4586 	[q, b, e, ?] .
4587 	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4588 Hit 'e':
4589 	[q, b, e, ?] ...Stopping timer
4590 Hit 'q':
4591 	[q, b, e, ?] ## Application terminated, rc = 0x0
4592 
4593 
4594 Minicom warning:
4595 ================
4596 
4597 Over time, many people have reported problems when trying to use the
4598 "minicom" terminal emulation program for serial download. I (wd)
4599 consider minicom to be broken, and recommend not to use it. Under
4600 Unix, I recommend to use C-Kermit for general purpose use (and
4601 especially for kermit binary protocol download ("loadb" command), and
4602 use "cu" for S-Record download ("loads" command).  See
4603 http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4604 for help with kermit.
4605 
4606 
4607 Nevertheless, if you absolutely want to use it try adding this
4608 configuration to your "File transfer protocols" section:
4609 
4610 	   Name	   Program			Name U/D FullScr IO-Red. Multi
4611 	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4612 	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4613 
4614 
4615 NetBSD Notes:
4616 =============
4617 
4618 Starting at version 0.9.2, U-Boot supports NetBSD both as host
4619 (build U-Boot) and target system (boots NetBSD/mpc8xx).
4620 
4621 Building requires a cross environment; it is known to work on
4622 NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4623 need gmake since the Makefiles are not compatible with BSD make).
4624 Note that the cross-powerpc package does not install include files;
4625 attempting to build U-Boot will fail because <machine/ansi.h> is
4626 missing.  This file has to be installed and patched manually:
4627 
4628 	# cd /usr/pkg/cross/powerpc-netbsd/include
4629 	# mkdir powerpc
4630 	# ln -s powerpc machine
4631 	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4632 	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4633 
4634 Native builds *don't* work due to incompatibilities between native
4635 and U-Boot include files.
4636 
4637 Booting assumes that (the first part of) the image booted is a
4638 stage-2 loader which in turn loads and then invokes the kernel
4639 proper. Loader sources will eventually appear in the NetBSD source
4640 tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4641 meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4642 
4643 
4644 Implementation Internals:
4645 =========================
4646 
4647 The following is not intended to be a complete description of every
4648 implementation detail. However, it should help to understand the
4649 inner workings of U-Boot and make it easier to port it to custom
4650 hardware.
4651 
4652 
4653 Initial Stack, Global Data:
4654 ---------------------------
4655 
4656 The implementation of U-Boot is complicated by the fact that U-Boot
4657 starts running out of ROM (flash memory), usually without access to
4658 system RAM (because the memory controller is not initialized yet).
4659 This means that we don't have writable Data or BSS segments, and BSS
4660 is not initialized as zero. To be able to get a C environment working
4661 at all, we have to allocate at least a minimal stack. Implementation
4662 options for this are defined and restricted by the CPU used: Some CPU
4663 models provide on-chip memory (like the IMMR area on MPC8xx and
4664 MPC826x processors), on others (parts of) the data cache can be
4665 locked as (mis-) used as memory, etc.
4666 
4667 	Chris Hallinan posted a good summary of these issues to the
4668 	U-Boot mailing list:
4669 
4670 	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4671 	From: "Chris Hallinan" <clh@net1plus.com>
4672 	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4673 	...
4674 
4675 	Correct me if I'm wrong, folks, but the way I understand it
4676 	is this: Using DCACHE as initial RAM for Stack, etc, does not
4677 	require any physical RAM backing up the cache. The cleverness
4678 	is that the cache is being used as a temporary supply of
4679 	necessary storage before the SDRAM controller is setup. It's
4680 	beyond the scope of this list to explain the details, but you
4681 	can see how this works by studying the cache architecture and
4682 	operation in the architecture and processor-specific manuals.
4683 
4684 	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4685 	is another option for the system designer to use as an
4686 	initial stack/RAM area prior to SDRAM being available. Either
4687 	option should work for you. Using CS 4 should be fine if your
4688 	board designers haven't used it for something that would
4689 	cause you grief during the initial boot! It is frequently not
4690 	used.
4691 
4692 	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4693 	with your processor/board/system design. The default value
4694 	you will find in any recent u-boot distribution in
4695 	walnut.h should work for you. I'd set it to a value larger
4696 	than your SDRAM module. If you have a 64MB SDRAM module, set
4697 	it above 400_0000. Just make sure your board has no resources
4698 	that are supposed to respond to that address! That code in
4699 	start.S has been around a while and should work as is when
4700 	you get the config right.
4701 
4702 	-Chris Hallinan
4703 	DS4.COM, Inc.
4704 
4705 It is essential to remember this, since it has some impact on the C
4706 code for the initialization procedures:
4707 
4708 * Initialized global data (data segment) is read-only. Do not attempt
4709   to write it.
4710 
4711 * Do not use any uninitialized global data (or implicitly initialized
4712   as zero data - BSS segment) at all - this is undefined, initiali-
4713   zation is performed later (when relocating to RAM).
4714 
4715 * Stack space is very limited. Avoid big data buffers or things like
4716   that.
4717 
4718 Having only the stack as writable memory limits means we cannot use
4719 normal global data to share information between the code. But it
4720 turned out that the implementation of U-Boot can be greatly
4721 simplified by making a global data structure (gd_t) available to all
4722 functions. We could pass a pointer to this data as argument to _all_
4723 functions, but this would bloat the code. Instead we use a feature of
4724 the GCC compiler (Global Register Variables) to share the data: we
4725 place a pointer (gd) to the global data into a register which we
4726 reserve for this purpose.
4727 
4728 When choosing a register for such a purpose we are restricted by the
4729 relevant  (E)ABI  specifications for the current architecture, and by
4730 GCC's implementation.
4731 
4732 For PowerPC, the following registers have specific use:
4733 	R1:	stack pointer
4734 	R2:	reserved for system use
4735 	R3-R4:	parameter passing and return values
4736 	R5-R10: parameter passing
4737 	R13:	small data area pointer
4738 	R30:	GOT pointer
4739 	R31:	frame pointer
4740 
4741 	(U-Boot also uses R12 as internal GOT pointer. r12
4742 	is a volatile register so r12 needs to be reset when
4743 	going back and forth between asm and C)
4744 
4745     ==> U-Boot will use R2 to hold a pointer to the global data
4746 
4747     Note: on PPC, we could use a static initializer (since the
4748     address of the global data structure is known at compile time),
4749     but it turned out that reserving a register results in somewhat
4750     smaller code - although the code savings are not that big (on
4751     average for all boards 752 bytes for the whole U-Boot image,
4752     624 text + 127 data).
4753 
4754 On ARM, the following registers are used:
4755 
4756 	R0:	function argument word/integer result
4757 	R1-R3:	function argument word
4758 	R9:	platform specific
4759 	R10:	stack limit (used only if stack checking is enabled)
4760 	R11:	argument (frame) pointer
4761 	R12:	temporary workspace
4762 	R13:	stack pointer
4763 	R14:	link register
4764 	R15:	program counter
4765 
4766     ==> U-Boot will use R9 to hold a pointer to the global data
4767 
4768     Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4769 
4770 On Nios II, the ABI is documented here:
4771 	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4772 
4773     ==> U-Boot will use gp to hold a pointer to the global data
4774 
4775     Note: on Nios II, we give "-G0" option to gcc and don't use gp
4776     to access small data sections, so gp is free.
4777 
4778 On NDS32, the following registers are used:
4779 
4780 	R0-R1:	argument/return
4781 	R2-R5:	argument
4782 	R15:	temporary register for assembler
4783 	R16:	trampoline register
4784 	R28:	frame pointer (FP)
4785 	R29:	global pointer (GP)
4786 	R30:	link register (LP)
4787 	R31:	stack pointer (SP)
4788 	PC:	program counter (PC)
4789 
4790     ==> U-Boot will use R10 to hold a pointer to the global data
4791 
4792 NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4793 or current versions of GCC may "optimize" the code too much.
4794 
4795 On RISC-V, the following registers are used:
4796 
4797 	x0: hard-wired zero (zero)
4798 	x1: return address (ra)
4799 	x2:	stack pointer (sp)
4800 	x3:	global pointer (gp)
4801 	x4:	thread pointer (tp)
4802 	x5:	link register (t0)
4803 	x8:	frame pointer (fp)
4804 	x10-x11:	arguments/return values (a0-1)
4805 	x12-x17:	arguments (a2-7)
4806 	x28-31:	 temporaries (t3-6)
4807 	pc:	program counter (pc)
4808 
4809     ==> U-Boot will use gp to hold a pointer to the global data
4810 
4811 Memory Management:
4812 ------------------
4813 
4814 U-Boot runs in system state and uses physical addresses, i.e. the
4815 MMU is not used either for address mapping nor for memory protection.
4816 
4817 The available memory is mapped to fixed addresses using the memory
4818 controller. In this process, a contiguous block is formed for each
4819 memory type (Flash, SDRAM, SRAM), even when it consists of several
4820 physical memory banks.
4821 
4822 U-Boot is installed in the first 128 kB of the first Flash bank (on
4823 TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4824 booting and sizing and initializing DRAM, the code relocates itself
4825 to the upper end of DRAM. Immediately below the U-Boot code some
4826 memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4827 configuration setting]. Below that, a structure with global Board
4828 Info data is placed, followed by the stack (growing downward).
4829 
4830 Additionally, some exception handler code is copied to the low 8 kB
4831 of DRAM (0x00000000 ... 0x00001FFF).
4832 
4833 So a typical memory configuration with 16 MB of DRAM could look like
4834 this:
4835 
4836 	0x0000 0000	Exception Vector code
4837 	      :
4838 	0x0000 1FFF
4839 	0x0000 2000	Free for Application Use
4840 	      :
4841 	      :
4842 
4843 	      :
4844 	      :
4845 	0x00FB FF20	Monitor Stack (Growing downward)
4846 	0x00FB FFAC	Board Info Data and permanent copy of global data
4847 	0x00FC 0000	Malloc Arena
4848 	      :
4849 	0x00FD FFFF
4850 	0x00FE 0000	RAM Copy of Monitor Code
4851 	...		eventually: LCD or video framebuffer
4852 	...		eventually: pRAM (Protected RAM - unchanged by reset)
4853 	0x00FF FFFF	[End of RAM]
4854 
4855 
4856 System Initialization:
4857 ----------------------
4858 
4859 In the reset configuration, U-Boot starts at the reset entry point
4860 (on most PowerPC systems at address 0x00000100). Because of the reset
4861 configuration for CS0# this is a mirror of the on board Flash memory.
4862 To be able to re-map memory U-Boot then jumps to its link address.
4863 To be able to implement the initialization code in C, a (small!)
4864 initial stack is set up in the internal Dual Ported RAM (in case CPUs
4865 which provide such a feature like), or in a locked part of the data
4866 cache. After that, U-Boot initializes the CPU core, the caches and
4867 the SIU.
4868 
4869 Next, all (potentially) available memory banks are mapped using a
4870 preliminary mapping. For example, we put them on 512 MB boundaries
4871 (multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4872 on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4873 programmed for SDRAM access. Using the temporary configuration, a
4874 simple memory test is run that determines the size of the SDRAM
4875 banks.
4876 
4877 When there is more than one SDRAM bank, and the banks are of
4878 different size, the largest is mapped first. For equal size, the first
4879 bank (CS2#) is mapped first. The first mapping is always for address
4880 0x00000000, with any additional banks following immediately to create
4881 contiguous memory starting from 0.
4882 
4883 Then, the monitor installs itself at the upper end of the SDRAM area
4884 and allocates memory for use by malloc() and for the global Board
4885 Info data; also, the exception vector code is copied to the low RAM
4886 pages, and the final stack is set up.
4887 
4888 Only after this relocation will you have a "normal" C environment;
4889 until that you are restricted in several ways, mostly because you are
4890 running from ROM, and because the code will have to be relocated to a
4891 new address in RAM.
4892 
4893 
4894 U-Boot Porting Guide:
4895 ----------------------
4896 
4897 [Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4898 list, October 2002]
4899 
4900 
4901 int main(int argc, char *argv[])
4902 {
4903 	sighandler_t no_more_time;
4904 
4905 	signal(SIGALRM, no_more_time);
4906 	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4907 
4908 	if (available_money > available_manpower) {
4909 		Pay consultant to port U-Boot;
4910 		return 0;
4911 	}
4912 
4913 	Download latest U-Boot source;
4914 
4915 	Subscribe to u-boot mailing list;
4916 
4917 	if (clueless)
4918 		email("Hi, I am new to U-Boot, how do I get started?");
4919 
4920 	while (learning) {
4921 		Read the README file in the top level directory;
4922 		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4923 		Read applicable doc/*.README;
4924 		Read the source, Luke;
4925 		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
4926 	}
4927 
4928 	if (available_money > toLocalCurrency ($2500))
4929 		Buy a BDI3000;
4930 	else
4931 		Add a lot of aggravation and time;
4932 
4933 	if (a similar board exists) {	/* hopefully... */
4934 		cp -a board/<similar> board/<myboard>
4935 		cp include/configs/<similar>.h include/configs/<myboard>.h
4936 	} else {
4937 		Create your own board support subdirectory;
4938 		Create your own board include/configs/<myboard>.h file;
4939 	}
4940 	Edit new board/<myboard> files
4941 	Edit new include/configs/<myboard>.h
4942 
4943 	while (!accepted) {
4944 		while (!running) {
4945 			do {
4946 				Add / modify source code;
4947 			} until (compiles);
4948 			Debug;
4949 			if (clueless)
4950 				email("Hi, I am having problems...");
4951 		}
4952 		Send patch file to the U-Boot email list;
4953 		if (reasonable critiques)
4954 			Incorporate improvements from email list code review;
4955 		else
4956 			Defend code as written;
4957 	}
4958 
4959 	return 0;
4960 }
4961 
4962 void no_more_time (int sig)
4963 {
4964       hire_a_guru();
4965 }
4966 
4967 
4968 Coding Standards:
4969 -----------------
4970 
4971 All contributions to U-Boot should conform to the Linux kernel
4972 coding style; see the kernel coding style guide at
4973 https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4974 script "scripts/Lindent" in your Linux kernel source directory.
4975 
4976 Source files originating from a different project (for example the
4977 MTD subsystem) are generally exempt from these guidelines and are not
4978 reformatted to ease subsequent migration to newer versions of those
4979 sources.
4980 
4981 Please note that U-Boot is implemented in C (and to some small parts in
4982 Assembler); no C++ is used, so please do not use C++ style comments (//)
4983 in your code.
4984 
4985 Please also stick to the following formatting rules:
4986 - remove any trailing white space
4987 - use TAB characters for indentation and vertical alignment, not spaces
4988 - make sure NOT to use DOS '\r\n' line feeds
4989 - do not add more than 2 consecutive empty lines to source files
4990 - do not add trailing empty lines to source files
4991 
4992 Submissions which do not conform to the standards may be returned
4993 with a request to reformat the changes.
4994 
4995 
4996 Submitting Patches:
4997 -------------------
4998 
4999 Since the number of patches for U-Boot is growing, we need to
5000 establish some rules. Submissions which do not conform to these rules
5001 may be rejected, even when they contain important and valuable stuff.
5002 
5003 Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5004 
5005 Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5006 see https://lists.denx.de/listinfo/u-boot
5007 
5008 When you send a patch, please include the following information with
5009 it:
5010 
5011 * For bug fixes: a description of the bug and how your patch fixes
5012   this bug. Please try to include a way of demonstrating that the
5013   patch actually fixes something.
5014 
5015 * For new features: a description of the feature and your
5016   implementation.
5017 
5018 * A CHANGELOG entry as plaintext (separate from the patch)
5019 
5020 * For major contributions, add a MAINTAINERS file with your
5021   information and associated file and directory references.
5022 
5023 * When you add support for a new board, don't forget to add a
5024   maintainer e-mail address to the boards.cfg file, too.
5025 
5026 * If your patch adds new configuration options, don't forget to
5027   document these in the README file.
5028 
5029 * The patch itself. If you are using git (which is *strongly*
5030   recommended) you can easily generate the patch using the
5031   "git format-patch". If you then use "git send-email" to send it to
5032   the U-Boot mailing list, you will avoid most of the common problems
5033   with some other mail clients.
5034 
5035   If you cannot use git, use "diff -purN OLD NEW". If your version of
5036   diff does not support these options, then get the latest version of
5037   GNU diff.
5038 
5039   The current directory when running this command shall be the parent
5040   directory of the U-Boot source tree (i. e. please make sure that
5041   your patch includes sufficient directory information for the
5042   affected files).
5043 
5044   We prefer patches as plain text. MIME attachments are discouraged,
5045   and compressed attachments must not be used.
5046 
5047 * If one logical set of modifications affects or creates several
5048   files, all these changes shall be submitted in a SINGLE patch file.
5049 
5050 * Changesets that contain different, unrelated modifications shall be
5051   submitted as SEPARATE patches, one patch per changeset.
5052 
5053 
5054 Notes:
5055 
5056 * Before sending the patch, run the buildman script on your patched
5057   source tree and make sure that no errors or warnings are reported
5058   for any of the boards.
5059 
5060 * Keep your modifications to the necessary minimum: A patch
5061   containing several unrelated changes or arbitrary reformats will be
5062   returned with a request to re-formatting / split it.
5063 
5064 * If you modify existing code, make sure that your new code does not
5065   add to the memory footprint of the code ;-) Small is beautiful!
5066   When adding new features, these should compile conditionally only
5067   (using #ifdef), and the resulting code with the new feature
5068   disabled must not need more memory than the old code without your
5069   modification.
5070 
5071 * Remember that there is a size limit of 100 kB per message on the
5072   u-boot mailing list. Bigger patches will be moderated. If they are
5073   reasonable and not too big, they will be acknowledged. But patches
5074   bigger than the size limit should be avoided.
5075