xref: /openbmc/u-boot/README (revision 5d0c74e6)
1#
2# (C) Copyright 2000 - 2013
3# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4#
5# SPDX-License-Identifier:	GPL-2.0+
6#
7
8Summary:
9========
10
11This directory contains the source code for U-Boot, a boot loader for
12Embedded boards based on PowerPC, ARM, MIPS and several other
13processors, which can be installed in a boot ROM and used to
14initialize and test the hardware or to download and run application
15code.
16
17The development of U-Boot is closely related to Linux: some parts of
18the source code originate in the Linux source tree, we have some
19header files in common, and special provision has been made to
20support booting of Linux images.
21
22Some attention has been paid to make this software easily
23configurable and extendable. For instance, all monitor commands are
24implemented with the same call interface, so that it's very easy to
25add new commands. Also, instead of permanently adding rarely used
26code (for instance hardware test utilities) to the monitor, you can
27load and run it dynamically.
28
29
30Status:
31=======
32
33In general, all boards for which a configuration option exists in the
34Makefile have been tested to some extent and can be considered
35"working". In fact, many of them are used in production systems.
36
37In case of problems see the CHANGELOG file to find out who contributed
38the specific port. In addition, there are various MAINTAINERS files
39scattered throughout the U-Boot source identifying the people or
40companies responsible for various boards and subsystems.
41
42Note: As of August, 2010, there is no longer a CHANGELOG file in the
43actual U-Boot source tree; however, it can be created dynamically
44from the Git log using:
45
46	make CHANGELOG
47
48
49Where to get help:
50==================
51
52In case you have questions about, problems with or contributions for
53U-Boot, you should send a message to the U-Boot mailing list at
54<u-boot@lists.denx.de>. There is also an archive of previous traffic
55on the mailing list - please search the archive before asking FAQ's.
56Please see http://lists.denx.de/pipermail/u-boot and
57http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
58
59
60Where to get source code:
61=========================
62
63The U-Boot source code is maintained in the Git repository at
64git://www.denx.de/git/u-boot.git ; you can browse it online at
65http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
66
67The "snapshot" links on this page allow you to download tarballs of
68any version you might be interested in. Official releases are also
69available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
70directory.
71
72Pre-built (and tested) images are available from
73ftp://ftp.denx.de/pub/u-boot/images/
74
75
76Where we come from:
77===================
78
79- start from 8xxrom sources
80- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
81- clean up code
82- make it easier to add custom boards
83- make it possible to add other [PowerPC] CPUs
84- extend functions, especially:
85  * Provide extended interface to Linux boot loader
86  * S-Record download
87  * network boot
88  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
89- create ARMBoot project (http://sourceforge.net/projects/armboot)
90- add other CPU families (starting with ARM)
91- create U-Boot project (http://sourceforge.net/projects/u-boot)
92- current project page: see http://www.denx.de/wiki/U-Boot
93
94
95Names and Spelling:
96===================
97
98The "official" name of this project is "Das U-Boot". The spelling
99"U-Boot" shall be used in all written text (documentation, comments
100in source files etc.). Example:
101
102	This is the README file for the U-Boot project.
103
104File names etc. shall be based on the string "u-boot". Examples:
105
106	include/asm-ppc/u-boot.h
107
108	#include <asm/u-boot.h>
109
110Variable names, preprocessor constants etc. shall be either based on
111the string "u_boot" or on "U_BOOT". Example:
112
113	U_BOOT_VERSION		u_boot_logo
114	IH_OS_U_BOOT		u_boot_hush_start
115
116
117Versioning:
118===========
119
120Starting with the release in October 2008, the names of the releases
121were changed from numerical release numbers without deeper meaning
122into a time stamp based numbering. Regular releases are identified by
123names consisting of the calendar year and month of the release date.
124Additional fields (if present) indicate release candidates or bug fix
125releases in "stable" maintenance trees.
126
127Examples:
128	U-Boot v2009.11	    - Release November 2009
129	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
130	U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
131
132
133Directory Hierarchy:
134====================
135
136/arch			Architecture specific files
137  /arc			Files generic to ARC architecture
138  /arm			Files generic to ARM architecture
139  /m68k			Files generic to m68k architecture
140  /microblaze		Files generic to microblaze architecture
141  /mips			Files generic to MIPS architecture
142  /nds32		Files generic to NDS32 architecture
143  /nios2		Files generic to Altera NIOS2 architecture
144  /openrisc		Files generic to OpenRISC architecture
145  /powerpc		Files generic to PowerPC architecture
146  /riscv		Files generic to RISC-V architecture
147  /sandbox		Files generic to HW-independent "sandbox"
148  /sh			Files generic to SH architecture
149  /x86			Files generic to x86 architecture
150/api			Machine/arch independent API for external apps
151/board			Board dependent files
152/cmd			U-Boot commands functions
153/common			Misc architecture independent functions
154/configs		Board default configuration files
155/disk			Code for disk drive partition handling
156/doc			Documentation (don't expect too much)
157/drivers		Commonly used device drivers
158/dts			Contains Makefile for building internal U-Boot fdt.
159/examples		Example code for standalone applications, etc.
160/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
161/include		Header Files
162/lib			Library routines generic to all architectures
163/Licenses		Various license files
164/net			Networking code
165/post			Power On Self Test
166/scripts		Various build scripts and Makefiles
167/test			Various unit test files
168/tools			Tools to build S-Record or U-Boot images, etc.
169
170Software Configuration:
171=======================
172
173Configuration is usually done using C preprocessor defines; the
174rationale behind that is to avoid dead code whenever possible.
175
176There are two classes of configuration variables:
177
178* Configuration _OPTIONS_:
179  These are selectable by the user and have names beginning with
180  "CONFIG_".
181
182* Configuration _SETTINGS_:
183  These depend on the hardware etc. and should not be meddled with if
184  you don't know what you're doing; they have names beginning with
185  "CONFIG_SYS_".
186
187Previously, all configuration was done by hand, which involved creating
188symbolic links and editing configuration files manually. More recently,
189U-Boot has added the Kbuild infrastructure used by the Linux kernel,
190allowing you to use the "make menuconfig" command to configure your
191build.
192
193
194Selection of Processor Architecture and Board Type:
195---------------------------------------------------
196
197For all supported boards there are ready-to-use default
198configurations available; just type "make <board_name>_defconfig".
199
200Example: For a TQM823L module type:
201
202	cd u-boot
203	make TQM823L_defconfig
204
205Note: If you're looking for the default configuration file for a board
206you're sure used to be there but is now missing, check the file
207doc/README.scrapyard for a list of no longer supported boards.
208
209Sandbox Environment:
210--------------------
211
212U-Boot can be built natively to run on a Linux host using the 'sandbox'
213board. This allows feature development which is not board- or architecture-
214specific to be undertaken on a native platform. The sandbox is also used to
215run some of U-Boot's tests.
216
217See board/sandbox/README.sandbox for more details.
218
219
220Board Initialisation Flow:
221--------------------------
222
223This is the intended start-up flow for boards. This should apply for both
224SPL and U-Boot proper (i.e. they both follow the same rules).
225
226Note: "SPL" stands for "Secondary Program Loader," which is explained in
227more detail later in this file.
228
229At present, SPL mostly uses a separate code path, but the function names
230and roles of each function are the same. Some boards or architectures
231may not conform to this.  At least most ARM boards which use
232CONFIG_SPL_FRAMEWORK conform to this.
233
234Execution typically starts with an architecture-specific (and possibly
235CPU-specific) start.S file, such as:
236
237	- arch/arm/cpu/armv7/start.S
238	- arch/powerpc/cpu/mpc83xx/start.S
239	- arch/mips/cpu/start.S
240
241and so on. From there, three functions are called; the purpose and
242limitations of each of these functions are described below.
243
244lowlevel_init():
245	- purpose: essential init to permit execution to reach board_init_f()
246	- no global_data or BSS
247	- there is no stack (ARMv7 may have one but it will soon be removed)
248	- must not set up SDRAM or use console
249	- must only do the bare minimum to allow execution to continue to
250		board_init_f()
251	- this is almost never needed
252	- return normally from this function
253
254board_init_f():
255	- purpose: set up the machine ready for running board_init_r():
256		i.e. SDRAM and serial UART
257	- global_data is available
258	- stack is in SRAM
259	- BSS is not available, so you cannot use global/static variables,
260		only stack variables and global_data
261
262	Non-SPL-specific notes:
263	- dram_init() is called to set up DRAM. If already done in SPL this
264		can do nothing
265
266	SPL-specific notes:
267	- you can override the entire board_init_f() function with your own
268		version as needed.
269	- preloader_console_init() can be called here in extremis
270	- should set up SDRAM, and anything needed to make the UART work
271	- these is no need to clear BSS, it will be done by crt0.S
272	- must return normally from this function (don't call board_init_r()
273		directly)
274
275Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
276this point the stack and global_data are relocated to below
277CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
278memory.
279
280board_init_r():
281	- purpose: main execution, common code
282	- global_data is available
283	- SDRAM is available
284	- BSS is available, all static/global variables can be used
285	- execution eventually continues to main_loop()
286
287	Non-SPL-specific notes:
288	- U-Boot is relocated to the top of memory and is now running from
289		there.
290
291	SPL-specific notes:
292	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
293		CONFIG_SPL_STACK_R_ADDR points into SDRAM
294	- preloader_console_init() can be called here - typically this is
295		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
296		spl_board_init() function containing this call
297	- loads U-Boot or (in falcon mode) Linux
298
299
300
301Configuration Options:
302----------------------
303
304Configuration depends on the combination of board and CPU type; all
305such information is kept in a configuration file
306"include/configs/<board_name>.h".
307
308Example: For a TQM823L module, all configuration settings are in
309"include/configs/TQM823L.h".
310
311
312Many of the options are named exactly as the corresponding Linux
313kernel configuration options. The intention is to make it easier to
314build a config tool - later.
315
316- ARM Platform Bus Type(CCI):
317		CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
318		provides full cache coherency between two clusters of multi-core
319		CPUs and I/O coherency for devices and I/O masters
320
321		CONFIG_SYS_FSL_HAS_CCI400
322
323		Defined For SoC that has cache coherent interconnect
324		CCN-400
325
326		CONFIG_SYS_FSL_HAS_CCN504
327
328		Defined for SoC that has cache coherent interconnect CCN-504
329
330The following options need to be configured:
331
332- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
333
334- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
335
336- Marvell Family Member
337		CONFIG_SYS_MVFS		- define it if you want to enable
338					  multiple fs option at one time
339					  for marvell soc family
340
341- 85xx CPU Options:
342		CONFIG_SYS_PPC64
343
344		Specifies that the core is a 64-bit PowerPC implementation (implements
345		the "64" category of the Power ISA). This is necessary for ePAPR
346		compliance, among other possible reasons.
347
348		CONFIG_SYS_FSL_TBCLK_DIV
349
350		Defines the core time base clock divider ratio compared to the
351		system clock.  On most PQ3 devices this is 8, on newer QorIQ
352		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
353
354		CONFIG_SYS_FSL_PCIE_COMPAT
355
356		Defines the string to utilize when trying to match PCIe device
357		tree nodes for the given platform.
358
359		CONFIG_SYS_FSL_ERRATUM_A004510
360
361		Enables a workaround for erratum A004510.  If set,
362		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
363		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
364
365		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
366		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
367
368		Defines one or two SoC revisions (low 8 bits of SVR)
369		for which the A004510 workaround should be applied.
370
371		The rest of SVR is either not relevant to the decision
372		of whether the erratum is present (e.g. p2040 versus
373		p2041) or is implied by the build target, which controls
374		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
375
376		See Freescale App Note 4493 for more information about
377		this erratum.
378
379		CONFIG_A003399_NOR_WORKAROUND
380		Enables a workaround for IFC erratum A003399. It is only
381		required during NOR boot.
382
383		CONFIG_A008044_WORKAROUND
384		Enables a workaround for T1040/T1042 erratum A008044. It is only
385		required during NAND boot and valid for Rev 1.0 SoC revision
386
387		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
388
389		This is the value to write into CCSR offset 0x18600
390		according to the A004510 workaround.
391
392		CONFIG_SYS_FSL_DSP_DDR_ADDR
393		This value denotes start offset of DDR memory which is
394		connected exclusively to the DSP cores.
395
396		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
397		This value denotes start offset of M2 memory
398		which is directly connected to the DSP core.
399
400		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
401		This value denotes start offset of M3 memory which is directly
402		connected to the DSP core.
403
404		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
405		This value denotes start offset of DSP CCSR space.
406
407		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
408		Single Source Clock is clocking mode present in some of FSL SoC's.
409		In this mode, a single differential clock is used to supply
410		clocks to the sysclock, ddrclock and usbclock.
411
412		CONFIG_SYS_CPC_REINIT_F
413		This CONFIG is defined when the CPC is configured as SRAM at the
414		time of U-Boot entry and is required to be re-initialized.
415
416		CONFIG_DEEP_SLEEP
417		Indicates this SoC supports deep sleep feature. If deep sleep is
418		supported, core will start to execute uboot when wakes up.
419
420- Generic CPU options:
421		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
422
423		Defines the endianess of the CPU. Implementation of those
424		values is arch specific.
425
426		CONFIG_SYS_FSL_DDR
427		Freescale DDR driver in use. This type of DDR controller is
428		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
429		SoCs.
430
431		CONFIG_SYS_FSL_DDR_ADDR
432		Freescale DDR memory-mapped register base.
433
434		CONFIG_SYS_FSL_DDR_EMU
435		Specify emulator support for DDR. Some DDR features such as
436		deskew training are not available.
437
438		CONFIG_SYS_FSL_DDRC_GEN1
439		Freescale DDR1 controller.
440
441		CONFIG_SYS_FSL_DDRC_GEN2
442		Freescale DDR2 controller.
443
444		CONFIG_SYS_FSL_DDRC_GEN3
445		Freescale DDR3 controller.
446
447		CONFIG_SYS_FSL_DDRC_GEN4
448		Freescale DDR4 controller.
449
450		CONFIG_SYS_FSL_DDRC_ARM_GEN3
451		Freescale DDR3 controller for ARM-based SoCs.
452
453		CONFIG_SYS_FSL_DDR1
454		Board config to use DDR1. It can be enabled for SoCs with
455		Freescale DDR1 or DDR2 controllers, depending on the board
456		implemetation.
457
458		CONFIG_SYS_FSL_DDR2
459		Board config to use DDR2. It can be enabled for SoCs with
460		Freescale DDR2 or DDR3 controllers, depending on the board
461		implementation.
462
463		CONFIG_SYS_FSL_DDR3
464		Board config to use DDR3. It can be enabled for SoCs with
465		Freescale DDR3 or DDR3L controllers.
466
467		CONFIG_SYS_FSL_DDR3L
468		Board config to use DDR3L. It can be enabled for SoCs with
469		DDR3L controllers.
470
471		CONFIG_SYS_FSL_DDR4
472		Board config to use DDR4. It can be enabled for SoCs with
473		DDR4 controllers.
474
475		CONFIG_SYS_FSL_IFC_BE
476		Defines the IFC controller register space as Big Endian
477
478		CONFIG_SYS_FSL_IFC_LE
479		Defines the IFC controller register space as Little Endian
480
481		CONFIG_SYS_FSL_IFC_CLK_DIV
482		Defines divider of platform clock(clock input to IFC controller).
483
484		CONFIG_SYS_FSL_LBC_CLK_DIV
485		Defines divider of platform clock(clock input to eLBC controller).
486
487		CONFIG_SYS_FSL_PBL_PBI
488		It enables addition of RCW (Power on reset configuration) in built image.
489		Please refer doc/README.pblimage for more details
490
491		CONFIG_SYS_FSL_PBL_RCW
492		It adds PBI(pre-boot instructions) commands in u-boot build image.
493		PBI commands can be used to configure SoC before it starts the execution.
494		Please refer doc/README.pblimage for more details
495
496		CONFIG_SPL_FSL_PBL
497		It adds a target to create boot binary having SPL binary in PBI format
498		concatenated with u-boot binary.
499
500		CONFIG_SYS_FSL_DDR_BE
501		Defines the DDR controller register space as Big Endian
502
503		CONFIG_SYS_FSL_DDR_LE
504		Defines the DDR controller register space as Little Endian
505
506		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
507		Physical address from the view of DDR controllers. It is the
508		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
509		it could be different for ARM SoCs.
510
511		CONFIG_SYS_FSL_DDR_INTLV_256B
512		DDR controller interleaving on 256-byte. This is a special
513		interleaving mode, handled by Dickens for Freescale layerscape
514		SoCs with ARM core.
515
516		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
517		Number of controllers used as main memory.
518
519		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
520		Number of controllers used for other than main memory.
521
522		CONFIG_SYS_FSL_HAS_DP_DDR
523		Defines the SoC has DP-DDR used for DPAA.
524
525		CONFIG_SYS_FSL_SEC_BE
526		Defines the SEC controller register space as Big Endian
527
528		CONFIG_SYS_FSL_SEC_LE
529		Defines the SEC controller register space as Little Endian
530
531- MIPS CPU options:
532		CONFIG_SYS_INIT_SP_OFFSET
533
534		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
535		pointer. This is needed for the temporary stack before
536		relocation.
537
538		CONFIG_SYS_MIPS_CACHE_MODE
539
540		Cache operation mode for the MIPS CPU.
541		See also arch/mips/include/asm/mipsregs.h.
542		Possible values are:
543			CONF_CM_CACHABLE_NO_WA
544			CONF_CM_CACHABLE_WA
545			CONF_CM_UNCACHED
546			CONF_CM_CACHABLE_NONCOHERENT
547			CONF_CM_CACHABLE_CE
548			CONF_CM_CACHABLE_COW
549			CONF_CM_CACHABLE_CUW
550			CONF_CM_CACHABLE_ACCELERATED
551
552		CONFIG_SYS_XWAY_EBU_BOOTCFG
553
554		Special option for Lantiq XWAY SoCs for booting from NOR flash.
555		See also arch/mips/cpu/mips32/start.S.
556
557		CONFIG_XWAY_SWAP_BYTES
558
559		Enable compilation of tools/xway-swap-bytes needed for Lantiq
560		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
561		be swapped if a flash programmer is used.
562
563- ARM options:
564		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
565
566		Select high exception vectors of the ARM core, e.g., do not
567		clear the V bit of the c1 register of CP15.
568
569		COUNTER_FREQUENCY
570		Generic timer clock source frequency.
571
572		COUNTER_FREQUENCY_REAL
573		Generic timer clock source frequency if the real clock is
574		different from COUNTER_FREQUENCY, and can only be determined
575		at run time.
576
577- Tegra SoC options:
578		CONFIG_TEGRA_SUPPORT_NON_SECURE
579
580		Support executing U-Boot in non-secure (NS) mode. Certain
581		impossible actions will be skipped if the CPU is in NS mode,
582		such as ARM architectural timer initialization.
583
584- Linux Kernel Interface:
585		CONFIG_CLOCKS_IN_MHZ
586
587		U-Boot stores all clock information in Hz
588		internally. For binary compatibility with older Linux
589		kernels (which expect the clocks passed in the
590		bd_info data to be in MHz) the environment variable
591		"clocks_in_mhz" can be defined so that U-Boot
592		converts clock data to MHZ before passing it to the
593		Linux kernel.
594		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
595		"clocks_in_mhz=1" is automatically included in the
596		default environment.
597
598		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
599
600		When transferring memsize parameter to Linux, some versions
601		expect it to be in bytes, others in MB.
602		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
603
604		CONFIG_OF_LIBFDT
605
606		New kernel versions are expecting firmware settings to be
607		passed using flattened device trees (based on open firmware
608		concepts).
609
610		CONFIG_OF_LIBFDT
611		 * New libfdt-based support
612		 * Adds the "fdt" command
613		 * The bootm command automatically updates the fdt
614
615		OF_TBCLK - The timebase frequency.
616		OF_STDOUT_PATH - The path to the console device
617
618		boards with QUICC Engines require OF_QE to set UCC MAC
619		addresses
620
621		CONFIG_OF_BOARD_SETUP
622
623		Board code has addition modification that it wants to make
624		to the flat device tree before handing it off to the kernel
625
626		CONFIG_OF_SYSTEM_SETUP
627
628		Other code has addition modification that it wants to make
629		to the flat device tree before handing it off to the kernel.
630		This causes ft_system_setup() to be called before booting
631		the kernel.
632
633		CONFIG_OF_IDE_FIXUP
634
635		U-Boot can detect if an IDE device is present or not.
636		If not, and this new config option is activated, U-Boot
637		removes the ATA node from the DTS before booting Linux,
638		so the Linux IDE driver does not probe the device and
639		crash. This is needed for buggy hardware (uc101) where
640		no pull down resistor is connected to the signal IDE5V_DD7.
641
642		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
643
644		This setting is mandatory for all boards that have only one
645		machine type and must be used to specify the machine type
646		number as it appears in the ARM machine registry
647		(see http://www.arm.linux.org.uk/developer/machines/).
648		Only boards that have multiple machine types supported
649		in a single configuration file and the machine type is
650		runtime discoverable, do not have to use this setting.
651
652- vxWorks boot parameters:
653
654		bootvx constructs a valid bootline using the following
655		environments variables: bootdev, bootfile, ipaddr, netmask,
656		serverip, gatewayip, hostname, othbootargs.
657		It loads the vxWorks image pointed bootfile.
658
659		Note: If a "bootargs" environment is defined, it will overwride
660		the defaults discussed just above.
661
662- Cache Configuration:
663		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
664		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
665		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
666
667- Cache Configuration for ARM:
668		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
669				      controller
670		CONFIG_SYS_PL310_BASE - Physical base address of PL310
671					controller register space
672
673- Serial Ports:
674		CONFIG_PL010_SERIAL
675
676		Define this if you want support for Amba PrimeCell PL010 UARTs.
677
678		CONFIG_PL011_SERIAL
679
680		Define this if you want support for Amba PrimeCell PL011 UARTs.
681
682		CONFIG_PL011_CLOCK
683
684		If you have Amba PrimeCell PL011 UARTs, set this variable to
685		the clock speed of the UARTs.
686
687		CONFIG_PL01x_PORTS
688
689		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
690		define this to a list of base addresses for each (supported)
691		port. See e.g. include/configs/versatile.h
692
693		CONFIG_SERIAL_HW_FLOW_CONTROL
694
695		Define this variable to enable hw flow control in serial driver.
696		Current user of this option is drivers/serial/nsl16550.c driver
697
698- Console Baudrate:
699		CONFIG_BAUDRATE - in bps
700		Select one of the baudrates listed in
701		CONFIG_SYS_BAUDRATE_TABLE, see below.
702
703- Autoboot Command:
704		CONFIG_BOOTCOMMAND
705		Only needed when CONFIG_BOOTDELAY is enabled;
706		define a command string that is automatically executed
707		when no character is read on the console interface
708		within "Boot Delay" after reset.
709
710		CONFIG_RAMBOOT and CONFIG_NFSBOOT
711		The value of these goes into the environment as
712		"ramboot" and "nfsboot" respectively, and can be used
713		as a convenience, when switching between booting from
714		RAM and NFS.
715
716- Pre-Boot Commands:
717		CONFIG_PREBOOT
718
719		When this option is #defined, the existence of the
720		environment variable "preboot" will be checked
721		immediately before starting the CONFIG_BOOTDELAY
722		countdown and/or running the auto-boot command resp.
723		entering interactive mode.
724
725		This feature is especially useful when "preboot" is
726		automatically generated or modified. For an example
727		see the LWMON board specific code: here "preboot" is
728		modified when the user holds down a certain
729		combination of keys on the (special) keyboard when
730		booting the systems
731
732- Serial Download Echo Mode:
733		CONFIG_LOADS_ECHO
734		If defined to 1, all characters received during a
735		serial download (using the "loads" command) are
736		echoed back. This might be needed by some terminal
737		emulations (like "cu"), but may as well just take
738		time on others. This setting #define's the initial
739		value of the "loads_echo" environment variable.
740
741- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
742		CONFIG_KGDB_BAUDRATE
743		Select one of the baudrates listed in
744		CONFIG_SYS_BAUDRATE_TABLE, see below.
745
746- Removal of commands
747		If no commands are needed to boot, you can disable
748		CONFIG_CMDLINE to remove them. In this case, the command line
749		will not be available, and when U-Boot wants to execute the
750		boot command (on start-up) it will call board_run_command()
751		instead. This can reduce image size significantly for very
752		simple boot procedures.
753
754- Regular expression support:
755		CONFIG_REGEX
756		If this variable is defined, U-Boot is linked against
757		the SLRE (Super Light Regular Expression) library,
758		which adds regex support to some commands, as for
759		example "env grep" and "setexpr".
760
761- Device tree:
762		CONFIG_OF_CONTROL
763		If this variable is defined, U-Boot will use a device tree
764		to configure its devices, instead of relying on statically
765		compiled #defines in the board file. This option is
766		experimental and only available on a few boards. The device
767		tree is available in the global data as gd->fdt_blob.
768
769		U-Boot needs to get its device tree from somewhere. This can
770		be done using one of the three options below:
771
772		CONFIG_OF_EMBED
773		If this variable is defined, U-Boot will embed a device tree
774		binary in its image. This device tree file should be in the
775		board directory and called <soc>-<board>.dts. The binary file
776		is then picked up in board_init_f() and made available through
777		the global data structure as gd->fdt_blob.
778
779		CONFIG_OF_SEPARATE
780		If this variable is defined, U-Boot will build a device tree
781		binary. It will be called u-boot.dtb. Architecture-specific
782		code will locate it at run-time. Generally this works by:
783
784			cat u-boot.bin u-boot.dtb >image.bin
785
786		and in fact, U-Boot does this for you, creating a file called
787		u-boot-dtb.bin which is useful in the common case. You can
788		still use the individual files if you need something more
789		exotic.
790
791		CONFIG_OF_BOARD
792		If this variable is defined, U-Boot will use the device tree
793		provided by the board at runtime instead of embedding one with
794		the image. Only boards defining board_fdt_blob_setup() support
795		this option (see include/fdtdec.h file).
796
797- Watchdog:
798		CONFIG_WATCHDOG
799		If this variable is defined, it enables watchdog
800		support for the SoC. There must be support in the SoC
801		specific code for a watchdog. For the 8xx
802		CPUs, the SIU Watchdog feature is enabled in the SYPCR
803		register.  When supported for a specific SoC is
804		available, then no further board specific code should
805		be needed to use it.
806
807		CONFIG_HW_WATCHDOG
808		When using a watchdog circuitry external to the used
809		SoC, then define this variable and provide board
810		specific code for the "hw_watchdog_reset" function.
811
812		CONFIG_AT91_HW_WDT_TIMEOUT
813		specify the timeout in seconds. default 2 seconds.
814
815- U-Boot Version:
816		CONFIG_VERSION_VARIABLE
817		If this variable is defined, an environment variable
818		named "ver" is created by U-Boot showing the U-Boot
819		version as printed by the "version" command.
820		Any change to this variable will be reverted at the
821		next reset.
822
823- Real-Time Clock:
824
825		When CONFIG_CMD_DATE is selected, the type of the RTC
826		has to be selected, too. Define exactly one of the
827		following options:
828
829		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
830		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
831		CONFIG_RTC_MC146818	- use MC146818 RTC
832		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
833		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
834		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
835		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
836		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
837		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
838		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
839		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
840		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
841					  RV3029 RTC.
842
843		Note that if the RTC uses I2C, then the I2C interface
844		must also be configured. See I2C Support, below.
845
846- GPIO Support:
847		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
848
849		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
850		chip-ngpio pairs that tell the PCA953X driver the number of
851		pins supported by a particular chip.
852
853		Note that if the GPIO device uses I2C, then the I2C interface
854		must also be configured. See I2C Support, below.
855
856- I/O tracing:
857		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
858		accesses and can checksum them or write a list of them out
859		to memory. See the 'iotrace' command for details. This is
860		useful for testing device drivers since it can confirm that
861		the driver behaves the same way before and after a code
862		change. Currently this is supported on sandbox and arm. To
863		add support for your architecture, add '#include <iotrace.h>'
864		to the bottom of arch/<arch>/include/asm/io.h and test.
865
866		Example output from the 'iotrace stats' command is below.
867		Note that if the trace buffer is exhausted, the checksum will
868		still continue to operate.
869
870			iotrace is enabled
871			Start:  10000000	(buffer start address)
872			Size:   00010000	(buffer size)
873			Offset: 00000120	(current buffer offset)
874			Output: 10000120	(start + offset)
875			Count:  00000018	(number of trace records)
876			CRC32:  9526fb66	(CRC32 of all trace records)
877
878- Timestamp Support:
879
880		When CONFIG_TIMESTAMP is selected, the timestamp
881		(date and time) of an image is printed by image
882		commands like bootm or iminfo. This option is
883		automatically enabled when you select CONFIG_CMD_DATE .
884
885- Partition Labels (disklabels) Supported:
886		Zero or more of the following:
887		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
888		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
889		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
890				       bootloader.  Note 2TB partition limit; see
891				       disk/part_efi.c
892		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
893
894		If IDE or SCSI support is enabled (CONFIG_IDE or
895		CONFIG_SCSI) you must configure support for at
896		least one non-MTD partition type as well.
897
898- IDE Reset method:
899		CONFIG_IDE_RESET_ROUTINE - this is defined in several
900		board configurations files but used nowhere!
901
902		CONFIG_IDE_RESET - is this is defined, IDE Reset will
903		be performed by calling the function
904			ide_set_reset(int reset)
905		which has to be defined in a board specific file
906
907- ATAPI Support:
908		CONFIG_ATAPI
909
910		Set this to enable ATAPI support.
911
912- LBA48 Support
913		CONFIG_LBA48
914
915		Set this to enable support for disks larger than 137GB
916		Also look at CONFIG_SYS_64BIT_LBA.
917		Whithout these , LBA48 support uses 32bit variables and will 'only'
918		support disks up to 2.1TB.
919
920		CONFIG_SYS_64BIT_LBA:
921			When enabled, makes the IDE subsystem use 64bit sector addresses.
922			Default is 32bit.
923
924- SCSI Support:
925		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
926		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
927		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
928		maximum numbers of LUNs, SCSI ID's and target
929		devices.
930
931		The environment variable 'scsidevs' is set to the number of
932		SCSI devices found during the last scan.
933
934- NETWORK Support (PCI):
935		CONFIG_E1000
936		Support for Intel 8254x/8257x gigabit chips.
937
938		CONFIG_E1000_SPI
939		Utility code for direct access to the SPI bus on Intel 8257x.
940		This does not do anything useful unless you set at least one
941		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
942
943		CONFIG_E1000_SPI_GENERIC
944		Allow generic access to the SPI bus on the Intel 8257x, for
945		example with the "sspi" command.
946
947		CONFIG_EEPRO100
948		Support for Intel 82557/82559/82559ER chips.
949		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
950		write routine for first time initialisation.
951
952		CONFIG_TULIP
953		Support for Digital 2114x chips.
954		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
955		modem chip initialisation (KS8761/QS6611).
956
957		CONFIG_NATSEMI
958		Support for National dp83815 chips.
959
960		CONFIG_NS8382X
961		Support for National dp8382[01] gigabit chips.
962
963- NETWORK Support (other):
964
965		CONFIG_DRIVER_AT91EMAC
966		Support for AT91RM9200 EMAC.
967
968			CONFIG_RMII
969			Define this to use reduced MII inteface
970
971			CONFIG_DRIVER_AT91EMAC_QUIET
972			If this defined, the driver is quiet.
973			The driver doen't show link status messages.
974
975		CONFIG_CALXEDA_XGMAC
976		Support for the Calxeda XGMAC device
977
978		CONFIG_LAN91C96
979		Support for SMSC's LAN91C96 chips.
980
981			CONFIG_LAN91C96_USE_32_BIT
982			Define this to enable 32 bit addressing
983
984		CONFIG_SMC91111
985		Support for SMSC's LAN91C111 chip
986
987			CONFIG_SMC91111_BASE
988			Define this to hold the physical address
989			of the device (I/O space)
990
991			CONFIG_SMC_USE_32_BIT
992			Define this if data bus is 32 bits
993
994			CONFIG_SMC_USE_IOFUNCS
995			Define this to use i/o functions instead of macros
996			(some hardware wont work with macros)
997
998		CONFIG_DRIVER_TI_EMAC
999		Support for davinci emac
1000
1001			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1002			Define this if you have more then 3 PHYs.
1003
1004		CONFIG_FTGMAC100
1005		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1006
1007			CONFIG_FTGMAC100_EGIGA
1008			Define this to use GE link update with gigabit PHY.
1009			Define this if FTGMAC100 is connected to gigabit PHY.
1010			If your system has 10/100 PHY only, it might not occur
1011			wrong behavior. Because PHY usually return timeout or
1012			useless data when polling gigabit status and gigabit
1013			control registers. This behavior won't affect the
1014			correctnessof 10/100 link speed update.
1015
1016		CONFIG_SH_ETHER
1017		Support for Renesas on-chip Ethernet controller
1018
1019			CONFIG_SH_ETHER_USE_PORT
1020			Define the number of ports to be used
1021
1022			CONFIG_SH_ETHER_PHY_ADDR
1023			Define the ETH PHY's address
1024
1025			CONFIG_SH_ETHER_CACHE_WRITEBACK
1026			If this option is set, the driver enables cache flush.
1027
1028- PWM Support:
1029		CONFIG_PWM_IMX
1030		Support for PWM module on the imx6.
1031
1032- TPM Support:
1033		CONFIG_TPM
1034		Support TPM devices.
1035
1036		CONFIG_TPM_TIS_INFINEON
1037		Support for Infineon i2c bus TPM devices. Only one device
1038		per system is supported at this time.
1039
1040			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1041			Define the burst count bytes upper limit
1042
1043		CONFIG_TPM_ST33ZP24
1044		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1045
1046			CONFIG_TPM_ST33ZP24_I2C
1047			Support for STMicroelectronics ST33ZP24 I2C devices.
1048			Requires TPM_ST33ZP24 and I2C.
1049
1050			CONFIG_TPM_ST33ZP24_SPI
1051			Support for STMicroelectronics ST33ZP24 SPI devices.
1052			Requires TPM_ST33ZP24 and SPI.
1053
1054		CONFIG_TPM_ATMEL_TWI
1055		Support for Atmel TWI TPM device. Requires I2C support.
1056
1057		CONFIG_TPM_TIS_LPC
1058		Support for generic parallel port TPM devices. Only one device
1059		per system is supported at this time.
1060
1061			CONFIG_TPM_TIS_BASE_ADDRESS
1062			Base address where the generic TPM device is mapped
1063			to. Contemporary x86 systems usually map it at
1064			0xfed40000.
1065
1066		CONFIG_TPM
1067		Define this to enable the TPM support library which provides
1068		functional interfaces to some TPM commands.
1069		Requires support for a TPM device.
1070
1071		CONFIG_TPM_AUTH_SESSIONS
1072		Define this to enable authorized functions in the TPM library.
1073		Requires CONFIG_TPM and CONFIG_SHA1.
1074
1075- USB Support:
1076		At the moment only the UHCI host controller is
1077		supported (PIP405, MIP405); define
1078		CONFIG_USB_UHCI to enable it.
1079		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1080		and define CONFIG_USB_STORAGE to enable the USB
1081		storage devices.
1082		Note:
1083		Supported are USB Keyboards and USB Floppy drives
1084		(TEAC FD-05PUB).
1085
1086		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1087		txfilltuning field in the EHCI controller on reset.
1088
1089		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1090		HW module registers.
1091
1092- USB Device:
1093		Define the below if you wish to use the USB console.
1094		Once firmware is rebuilt from a serial console issue the
1095		command "setenv stdin usbtty; setenv stdout usbtty" and
1096		attach your USB cable. The Unix command "dmesg" should print
1097		it has found a new device. The environment variable usbtty
1098		can be set to gserial or cdc_acm to enable your device to
1099		appear to a USB host as a Linux gserial device or a
1100		Common Device Class Abstract Control Model serial device.
1101		If you select usbtty = gserial you should be able to enumerate
1102		a Linux host by
1103		# modprobe usbserial vendor=0xVendorID product=0xProductID
1104		else if using cdc_acm, simply setting the environment
1105		variable usbtty to be cdc_acm should suffice. The following
1106		might be defined in YourBoardName.h
1107
1108			CONFIG_USB_DEVICE
1109			Define this to build a UDC device
1110
1111			CONFIG_USB_TTY
1112			Define this to have a tty type of device available to
1113			talk to the UDC device
1114
1115			CONFIG_USBD_HS
1116			Define this to enable the high speed support for usb
1117			device and usbtty. If this feature is enabled, a routine
1118			int is_usbd_high_speed(void)
1119			also needs to be defined by the driver to dynamically poll
1120			whether the enumeration has succeded at high speed or full
1121			speed.
1122
1123			CONFIG_SYS_CONSOLE_IS_IN_ENV
1124			Define this if you want stdin, stdout &/or stderr to
1125			be set to usbtty.
1126
1127		If you have a USB-IF assigned VendorID then you may wish to
1128		define your own vendor specific values either in BoardName.h
1129		or directly in usbd_vendor_info.h. If you don't define
1130		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1131		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1132		should pretend to be a Linux device to it's target host.
1133
1134			CONFIG_USBD_MANUFACTURER
1135			Define this string as the name of your company for
1136			- CONFIG_USBD_MANUFACTURER "my company"
1137
1138			CONFIG_USBD_PRODUCT_NAME
1139			Define this string as the name of your product
1140			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1141
1142			CONFIG_USBD_VENDORID
1143			Define this as your assigned Vendor ID from the USB
1144			Implementors Forum. This *must* be a genuine Vendor ID
1145			to avoid polluting the USB namespace.
1146			- CONFIG_USBD_VENDORID 0xFFFF
1147
1148			CONFIG_USBD_PRODUCTID
1149			Define this as the unique Product ID
1150			for your device
1151			- CONFIG_USBD_PRODUCTID 0xFFFF
1152
1153- ULPI Layer Support:
1154		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1155		the generic ULPI layer. The generic layer accesses the ULPI PHY
1156		via the platform viewport, so you need both the genric layer and
1157		the viewport enabled. Currently only Chipidea/ARC based
1158		viewport is supported.
1159		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1160		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1161		If your ULPI phy needs a different reference clock than the
1162		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1163		the appropriate value in Hz.
1164
1165- MMC Support:
1166		The MMC controller on the Intel PXA is supported. To
1167		enable this define CONFIG_MMC. The MMC can be
1168		accessed from the boot prompt by mapping the device
1169		to physical memory similar to flash. Command line is
1170		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1171		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1172
1173		CONFIG_SH_MMCIF
1174		Support for Renesas on-chip MMCIF controller
1175
1176			CONFIG_SH_MMCIF_ADDR
1177			Define the base address of MMCIF registers
1178
1179			CONFIG_SH_MMCIF_CLK
1180			Define the clock frequency for MMCIF
1181
1182		CONFIG_SUPPORT_EMMC_BOOT
1183		Enable some additional features of the eMMC boot partitions.
1184
1185		CONFIG_SUPPORT_EMMC_RPMB
1186		Enable the commands for reading, writing and programming the
1187		key for the Replay Protection Memory Block partition in eMMC.
1188
1189- USB Device Firmware Update (DFU) class support:
1190		CONFIG_DFU_OVER_USB
1191		This enables the USB portion of the DFU USB class
1192
1193		CONFIG_DFU_MMC
1194		This enables support for exposing (e)MMC devices via DFU.
1195
1196		CONFIG_DFU_NAND
1197		This enables support for exposing NAND devices via DFU.
1198
1199		CONFIG_DFU_RAM
1200		This enables support for exposing RAM via DFU.
1201		Note: DFU spec refer to non-volatile memory usage, but
1202		allow usages beyond the scope of spec - here RAM usage,
1203		one that would help mostly the developer.
1204
1205		CONFIG_SYS_DFU_DATA_BUF_SIZE
1206		Dfu transfer uses a buffer before writing data to the
1207		raw storage device. Make the size (in bytes) of this buffer
1208		configurable. The size of this buffer is also configurable
1209		through the "dfu_bufsiz" environment variable.
1210
1211		CONFIG_SYS_DFU_MAX_FILE_SIZE
1212		When updating files rather than the raw storage device,
1213		we use a static buffer to copy the file into and then write
1214		the buffer once we've been given the whole file.  Define
1215		this to the maximum filesize (in bytes) for the buffer.
1216		Default is 4 MiB if undefined.
1217
1218		DFU_DEFAULT_POLL_TIMEOUT
1219		Poll timeout [ms], is the timeout a device can send to the
1220		host. The host must wait for this timeout before sending
1221		a subsequent DFU_GET_STATUS request to the device.
1222
1223		DFU_MANIFEST_POLL_TIMEOUT
1224		Poll timeout [ms], which the device sends to the host when
1225		entering dfuMANIFEST state. Host waits this timeout, before
1226		sending again an USB request to the device.
1227
1228- Journaling Flash filesystem support:
1229		CONFIG_JFFS2_NAND
1230		Define these for a default partition on a NAND device
1231
1232		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1233		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1234		Define these for a default partition on a NOR device
1235
1236- Keyboard Support:
1237		See Kconfig help for available keyboard drivers.
1238
1239		CONFIG_KEYBOARD
1240
1241		Define this to enable a custom keyboard support.
1242		This simply calls drv_keyboard_init() which must be
1243		defined in your board-specific files. This option is deprecated
1244		and is only used by novena. For new boards, use driver model
1245		instead.
1246
1247- Video support:
1248		CONFIG_FSL_DIU_FB
1249		Enable the Freescale DIU video driver.	Reference boards for
1250		SOCs that have a DIU should define this macro to enable DIU
1251		support, and should also define these other macros:
1252
1253			CONFIG_SYS_DIU_ADDR
1254			CONFIG_VIDEO
1255			CONFIG_CFB_CONSOLE
1256			CONFIG_VIDEO_SW_CURSOR
1257			CONFIG_VGA_AS_SINGLE_DEVICE
1258			CONFIG_VIDEO_LOGO
1259			CONFIG_VIDEO_BMP_LOGO
1260
1261		The DIU driver will look for the 'video-mode' environment
1262		variable, and if defined, enable the DIU as a console during
1263		boot.  See the documentation file doc/README.video for a
1264		description of this variable.
1265
1266- LCD Support:	CONFIG_LCD
1267
1268		Define this to enable LCD support (for output to LCD
1269		display); also select one of the supported displays
1270		by defining one of these:
1271
1272		CONFIG_ATMEL_LCD:
1273
1274			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1275
1276		CONFIG_NEC_NL6448AC33:
1277
1278			NEC NL6448AC33-18. Active, color, single scan.
1279
1280		CONFIG_NEC_NL6448BC20
1281
1282			NEC NL6448BC20-08. 6.5", 640x480.
1283			Active, color, single scan.
1284
1285		CONFIG_NEC_NL6448BC33_54
1286
1287			NEC NL6448BC33-54. 10.4", 640x480.
1288			Active, color, single scan.
1289
1290		CONFIG_SHARP_16x9
1291
1292			Sharp 320x240. Active, color, single scan.
1293			It isn't 16x9, and I am not sure what it is.
1294
1295		CONFIG_SHARP_LQ64D341
1296
1297			Sharp LQ64D341 display, 640x480.
1298			Active, color, single scan.
1299
1300		CONFIG_HLD1045
1301
1302			HLD1045 display, 640x480.
1303			Active, color, single scan.
1304
1305		CONFIG_OPTREX_BW
1306
1307			Optrex	 CBL50840-2 NF-FW 99 22 M5
1308			or
1309			Hitachi	 LMG6912RPFC-00T
1310			or
1311			Hitachi	 SP14Q002
1312
1313			320x240. Black & white.
1314
1315		CONFIG_LCD_ALIGNMENT
1316
1317		Normally the LCD is page-aligned (typically 4KB). If this is
1318		defined then the LCD will be aligned to this value instead.
1319		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1320		here, since it is cheaper to change data cache settings on
1321		a per-section basis.
1322
1323
1324		CONFIG_LCD_ROTATION
1325
1326		Sometimes, for example if the display is mounted in portrait
1327		mode or even if it's mounted landscape but rotated by 180degree,
1328		we need to rotate our content of the display relative to the
1329		framebuffer, so that user can read the messages which are
1330		printed out.
1331		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1332		initialized with a given rotation from "vl_rot" out of
1333		"vidinfo_t" which is provided by the board specific code.
1334		The value for vl_rot is coded as following (matching to
1335		fbcon=rotate:<n> linux-kernel commandline):
1336		0 = no rotation respectively 0 degree
1337		1 = 90 degree rotation
1338		2 = 180 degree rotation
1339		3 = 270 degree rotation
1340
1341		If CONFIG_LCD_ROTATION is not defined, the console will be
1342		initialized with 0degree rotation.
1343
1344		CONFIG_LCD_BMP_RLE8
1345
1346		Support drawing of RLE8-compressed bitmaps on the LCD.
1347
1348		CONFIG_I2C_EDID
1349
1350		Enables an 'i2c edid' command which can read EDID
1351		information over I2C from an attached LCD display.
1352
1353- Splash Screen Support: CONFIG_SPLASH_SCREEN
1354
1355		If this option is set, the environment is checked for
1356		a variable "splashimage". If found, the usual display
1357		of logo, copyright and system information on the LCD
1358		is suppressed and the BMP image at the address
1359		specified in "splashimage" is loaded instead. The
1360		console is redirected to the "nulldev", too. This
1361		allows for a "silent" boot where a splash screen is
1362		loaded very quickly after power-on.
1363
1364		CONFIG_SPLASHIMAGE_GUARD
1365
1366		If this option is set, then U-Boot will prevent the environment
1367		variable "splashimage" from being set to a problematic address
1368		(see doc/README.displaying-bmps).
1369		This option is useful for targets where, due to alignment
1370		restrictions, an improperly aligned BMP image will cause a data
1371		abort. If you think you will not have problems with unaligned
1372		accesses (for example because your toolchain prevents them)
1373		there is no need to set this option.
1374
1375		CONFIG_SPLASH_SCREEN_ALIGN
1376
1377		If this option is set the splash image can be freely positioned
1378		on the screen. Environment variable "splashpos" specifies the
1379		position as "x,y". If a positive number is given it is used as
1380		number of pixel from left/top. If a negative number is given it
1381		is used as number of pixel from right/bottom. You can also
1382		specify 'm' for centering the image.
1383
1384		Example:
1385		setenv splashpos m,m
1386			=> image at center of screen
1387
1388		setenv splashpos 30,20
1389			=> image at x = 30 and y = 20
1390
1391		setenv splashpos -10,m
1392			=> vertically centered image
1393			   at x = dspWidth - bmpWidth - 9
1394
1395- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1396
1397		If this option is set, additionally to standard BMP
1398		images, gzipped BMP images can be displayed via the
1399		splashscreen support or the bmp command.
1400
1401- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1402
1403		If this option is set, 8-bit RLE compressed BMP images
1404		can be displayed via the splashscreen support or the
1405		bmp command.
1406
1407- Compression support:
1408		CONFIG_GZIP
1409
1410		Enabled by default to support gzip compressed images.
1411
1412		CONFIG_BZIP2
1413
1414		If this option is set, support for bzip2 compressed
1415		images is included. If not, only uncompressed and gzip
1416		compressed images are supported.
1417
1418		NOTE: the bzip2 algorithm requires a lot of RAM, so
1419		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1420		be at least 4MB.
1421
1422- MII/PHY support:
1423		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1424
1425		The clock frequency of the MII bus
1426
1427		CONFIG_PHY_RESET_DELAY
1428
1429		Some PHY like Intel LXT971A need extra delay after
1430		reset before any MII register access is possible.
1431		For such PHY, set this option to the usec delay
1432		required. (minimum 300usec for LXT971A)
1433
1434		CONFIG_PHY_CMD_DELAY (ppc4xx)
1435
1436		Some PHY like Intel LXT971A need extra delay after
1437		command issued before MII status register can be read
1438
1439- IP address:
1440		CONFIG_IPADDR
1441
1442		Define a default value for the IP address to use for
1443		the default Ethernet interface, in case this is not
1444		determined through e.g. bootp.
1445		(Environment variable "ipaddr")
1446
1447- Server IP address:
1448		CONFIG_SERVERIP
1449
1450		Defines a default value for the IP address of a TFTP
1451		server to contact when using the "tftboot" command.
1452		(Environment variable "serverip")
1453
1454		CONFIG_KEEP_SERVERADDR
1455
1456		Keeps the server's MAC address, in the env 'serveraddr'
1457		for passing to bootargs (like Linux's netconsole option)
1458
1459- Gateway IP address:
1460		CONFIG_GATEWAYIP
1461
1462		Defines a default value for the IP address of the
1463		default router where packets to other networks are
1464		sent to.
1465		(Environment variable "gatewayip")
1466
1467- Subnet mask:
1468		CONFIG_NETMASK
1469
1470		Defines a default value for the subnet mask (or
1471		routing prefix) which is used to determine if an IP
1472		address belongs to the local subnet or needs to be
1473		forwarded through a router.
1474		(Environment variable "netmask")
1475
1476- Multicast TFTP Mode:
1477		CONFIG_MCAST_TFTP
1478
1479		Defines whether you want to support multicast TFTP as per
1480		rfc-2090; for example to work with atftp.  Lets lots of targets
1481		tftp down the same boot image concurrently.  Note: the Ethernet
1482		driver in use must provide a function: mcast() to join/leave a
1483		multicast group.
1484
1485- BOOTP Recovery Mode:
1486		CONFIG_BOOTP_RANDOM_DELAY
1487
1488		If you have many targets in a network that try to
1489		boot using BOOTP, you may want to avoid that all
1490		systems send out BOOTP requests at precisely the same
1491		moment (which would happen for instance at recovery
1492		from a power failure, when all systems will try to
1493		boot, thus flooding the BOOTP server. Defining
1494		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1495		inserted before sending out BOOTP requests. The
1496		following delays are inserted then:
1497
1498		1st BOOTP request:	delay 0 ... 1 sec
1499		2nd BOOTP request:	delay 0 ... 2 sec
1500		3rd BOOTP request:	delay 0 ... 4 sec
1501		4th and following
1502		BOOTP requests:		delay 0 ... 8 sec
1503
1504		CONFIG_BOOTP_ID_CACHE_SIZE
1505
1506		BOOTP packets are uniquely identified using a 32-bit ID. The
1507		server will copy the ID from client requests to responses and
1508		U-Boot will use this to determine if it is the destination of
1509		an incoming response. Some servers will check that addresses
1510		aren't in use before handing them out (usually using an ARP
1511		ping) and therefore take up to a few hundred milliseconds to
1512		respond. Network congestion may also influence the time it
1513		takes for a response to make it back to the client. If that
1514		time is too long, U-Boot will retransmit requests. In order
1515		to allow earlier responses to still be accepted after these
1516		retransmissions, U-Boot's BOOTP client keeps a small cache of
1517		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1518		cache. The default is to keep IDs for up to four outstanding
1519		requests. Increasing this will allow U-Boot to accept offers
1520		from a BOOTP client in networks with unusually high latency.
1521
1522- DHCP Advanced Options:
1523		You can fine tune the DHCP functionality by defining
1524		CONFIG_BOOTP_* symbols:
1525
1526		CONFIG_BOOTP_NISDOMAIN
1527		CONFIG_BOOTP_BOOTFILESIZE
1528		CONFIG_BOOTP_SEND_HOSTNAME
1529		CONFIG_BOOTP_NTPSERVER
1530		CONFIG_BOOTP_TIMEOFFSET
1531		CONFIG_BOOTP_VENDOREX
1532		CONFIG_BOOTP_MAY_FAIL
1533
1534		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1535		environment variable, not the BOOTP server.
1536
1537		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1538		after the configured retry count, the call will fail
1539		instead of starting over.  This can be used to fail over
1540		to Link-local IP address configuration if the DHCP server
1541		is not available.
1542
1543		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1544		to do a dynamic update of a DNS server. To do this, they
1545		need the hostname of the DHCP requester.
1546		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1547		of the "hostname" environment variable is passed as
1548		option 12 to the DHCP server.
1549
1550		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1551
1552		A 32bit value in microseconds for a delay between
1553		receiving a "DHCP Offer" and sending the "DHCP Request".
1554		This fixes a problem with certain DHCP servers that don't
1555		respond 100% of the time to a "DHCP request". E.g. On an
1556		AT91RM9200 processor running at 180MHz, this delay needed
1557		to be *at least* 15,000 usec before a Windows Server 2003
1558		DHCP server would reply 100% of the time. I recommend at
1559		least 50,000 usec to be safe. The alternative is to hope
1560		that one of the retries will be successful but note that
1561		the DHCP timeout and retry process takes a longer than
1562		this delay.
1563
1564 - Link-local IP address negotiation:
1565		Negotiate with other link-local clients on the local network
1566		for an address that doesn't require explicit configuration.
1567		This is especially useful if a DHCP server cannot be guaranteed
1568		to exist in all environments that the device must operate.
1569
1570		See doc/README.link-local for more information.
1571
1572 - MAC address from environment variables
1573
1574		FDT_SEQ_MACADDR_FROM_ENV
1575
1576		Fix-up device tree with MAC addresses fetched sequentially from
1577		environment variables. This config work on assumption that
1578		non-usable ethernet node of device-tree are either not present
1579		or their status has been marked as "disabled".
1580
1581 - CDP Options:
1582		CONFIG_CDP_DEVICE_ID
1583
1584		The device id used in CDP trigger frames.
1585
1586		CONFIG_CDP_DEVICE_ID_PREFIX
1587
1588		A two character string which is prefixed to the MAC address
1589		of the device.
1590
1591		CONFIG_CDP_PORT_ID
1592
1593		A printf format string which contains the ascii name of
1594		the port. Normally is set to "eth%d" which sets
1595		eth0 for the first Ethernet, eth1 for the second etc.
1596
1597		CONFIG_CDP_CAPABILITIES
1598
1599		A 32bit integer which indicates the device capabilities;
1600		0x00000010 for a normal host which does not forwards.
1601
1602		CONFIG_CDP_VERSION
1603
1604		An ascii string containing the version of the software.
1605
1606		CONFIG_CDP_PLATFORM
1607
1608		An ascii string containing the name of the platform.
1609
1610		CONFIG_CDP_TRIGGER
1611
1612		A 32bit integer sent on the trigger.
1613
1614		CONFIG_CDP_POWER_CONSUMPTION
1615
1616		A 16bit integer containing the power consumption of the
1617		device in .1 of milliwatts.
1618
1619		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1620
1621		A byte containing the id of the VLAN.
1622
1623- Status LED:	CONFIG_LED_STATUS
1624
1625		Several configurations allow to display the current
1626		status using a LED. For instance, the LED will blink
1627		fast while running U-Boot code, stop blinking as
1628		soon as a reply to a BOOTP request was received, and
1629		start blinking slow once the Linux kernel is running
1630		(supported by a status LED driver in the Linux
1631		kernel). Defining CONFIG_LED_STATUS enables this
1632		feature in U-Boot.
1633
1634		Additional options:
1635
1636		CONFIG_LED_STATUS_GPIO
1637		The status LED can be connected to a GPIO pin.
1638		In such cases, the gpio_led driver can be used as a
1639		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1640		to include the gpio_led driver in the U-Boot binary.
1641
1642		CONFIG_GPIO_LED_INVERTED_TABLE
1643		Some GPIO connected LEDs may have inverted polarity in which
1644		case the GPIO high value corresponds to LED off state and
1645		GPIO low value corresponds to LED on state.
1646		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1647		with a list of GPIO LEDs that have inverted polarity.
1648
1649- I2C Support:	CONFIG_SYS_I2C
1650
1651		This enable the NEW i2c subsystem, and will allow you to use
1652		i2c commands at the u-boot command line (as long as you set
1653		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1654		based realtime clock chips or other i2c devices. See
1655		common/cmd_i2c.c for a description of the command line
1656		interface.
1657
1658		ported i2c driver to the new framework:
1659		- drivers/i2c/soft_i2c.c:
1660		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1661		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1662		    for defining speed and slave address
1663		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1664		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1665		    for defining speed and slave address
1666		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1667		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1668		    for defining speed and slave address
1669		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1670		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1671		    for defining speed and slave address
1672
1673		- drivers/i2c/fsl_i2c.c:
1674		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1675		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1676		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1677		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1678		    bus.
1679		  - If your board supports a second fsl i2c bus, define
1680		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1681		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1682		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1683		    second bus.
1684
1685		- drivers/i2c/tegra_i2c.c:
1686		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1687		  - This driver adds 4 i2c buses with a fix speed from
1688		    100000 and the slave addr 0!
1689
1690		- drivers/i2c/ppc4xx_i2c.c
1691		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1692		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1693		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1694
1695		- drivers/i2c/i2c_mxc.c
1696		  - activate this driver with CONFIG_SYS_I2C_MXC
1697		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1698		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1699		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1700		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1701		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1702		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1703		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1704		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1705		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1706		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1707		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1708		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1709		If those defines are not set, default value is 100000
1710		for speed, and 0 for slave.
1711
1712		- drivers/i2c/rcar_i2c.c:
1713		  - activate this driver with CONFIG_SYS_I2C_RCAR
1714		  - This driver adds 4 i2c buses
1715
1716		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1717		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1718		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1719		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1720		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1721		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1722		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1723		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1724		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1725
1726		- drivers/i2c/sh_i2c.c:
1727		  - activate this driver with CONFIG_SYS_I2C_SH
1728		  - This driver adds from 2 to 5 i2c buses
1729
1730		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1731		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1732		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1733		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1734		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1735		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1736		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1737		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1738		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1739		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1740		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1741
1742		- drivers/i2c/omap24xx_i2c.c
1743		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1744		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1745		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1746		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1747		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1748		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1749		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1750		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1751		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1752		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1753		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1754
1755		- drivers/i2c/zynq_i2c.c
1756		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1757		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1758		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1759
1760		- drivers/i2c/s3c24x0_i2c.c:
1761		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1762		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1763		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1764		    with a fix speed from 100000 and the slave addr 0!
1765
1766		- drivers/i2c/ihs_i2c.c
1767		  - activate this driver with CONFIG_SYS_I2C_IHS
1768		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1769		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1770		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1771		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1772		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1773		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1774		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1775		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1776		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1777		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1778		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1779		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1780		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1781		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1782		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1783		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1784		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1785		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1786		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1787		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1788		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1789
1790		additional defines:
1791
1792		CONFIG_SYS_NUM_I2C_BUSES
1793		Hold the number of i2c buses you want to use.
1794
1795		CONFIG_SYS_I2C_DIRECT_BUS
1796		define this, if you don't use i2c muxes on your hardware.
1797		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1798		omit this define.
1799
1800		CONFIG_SYS_I2C_MAX_HOPS
1801		define how many muxes are maximal consecutively connected
1802		on one i2c bus. If you not use i2c muxes, omit this
1803		define.
1804
1805		CONFIG_SYS_I2C_BUSES
1806		hold a list of buses you want to use, only used if
1807		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1808		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1809		CONFIG_SYS_NUM_I2C_BUSES = 9:
1810
1811		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1812					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1813					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1814					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1815					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1816					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1817					{1, {I2C_NULL_HOP}}, \
1818					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1819					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1820					}
1821
1822		which defines
1823			bus 0 on adapter 0 without a mux
1824			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1825			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1826			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1827			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1828			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1829			bus 6 on adapter 1 without a mux
1830			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1831			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1832
1833		If you do not have i2c muxes on your board, omit this define.
1834
1835- Legacy I2C Support:
1836		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1837		then the following macros need to be defined (examples are
1838		from include/configs/lwmon.h):
1839
1840		I2C_INIT
1841
1842		(Optional). Any commands necessary to enable the I2C
1843		controller or configure ports.
1844
1845		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1846
1847		I2C_ACTIVE
1848
1849		The code necessary to make the I2C data line active
1850		(driven).  If the data line is open collector, this
1851		define can be null.
1852
1853		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1854
1855		I2C_TRISTATE
1856
1857		The code necessary to make the I2C data line tri-stated
1858		(inactive).  If the data line is open collector, this
1859		define can be null.
1860
1861		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1862
1863		I2C_READ
1864
1865		Code that returns true if the I2C data line is high,
1866		false if it is low.
1867
1868		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1869
1870		I2C_SDA(bit)
1871
1872		If <bit> is true, sets the I2C data line high. If it
1873		is false, it clears it (low).
1874
1875		eg: #define I2C_SDA(bit) \
1876			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1877			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1878
1879		I2C_SCL(bit)
1880
1881		If <bit> is true, sets the I2C clock line high. If it
1882		is false, it clears it (low).
1883
1884		eg: #define I2C_SCL(bit) \
1885			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1886			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1887
1888		I2C_DELAY
1889
1890		This delay is invoked four times per clock cycle so this
1891		controls the rate of data transfer.  The data rate thus
1892		is 1 / (I2C_DELAY * 4). Often defined to be something
1893		like:
1894
1895		#define I2C_DELAY  udelay(2)
1896
1897		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1898
1899		If your arch supports the generic GPIO framework (asm/gpio.h),
1900		then you may alternatively define the two GPIOs that are to be
1901		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1902		have GPIO-based defaults assigned to them as appropriate.
1903
1904		You should define these to the GPIO value as given directly to
1905		the generic GPIO functions.
1906
1907		CONFIG_SYS_I2C_INIT_BOARD
1908
1909		When a board is reset during an i2c bus transfer
1910		chips might think that the current transfer is still
1911		in progress. On some boards it is possible to access
1912		the i2c SCLK line directly, either by using the
1913		processor pin as a GPIO or by having a second pin
1914		connected to the bus. If this option is defined a
1915		custom i2c_init_board() routine in boards/xxx/board.c
1916		is run early in the boot sequence.
1917
1918		CONFIG_I2C_MULTI_BUS
1919
1920		This option allows the use of multiple I2C buses, each of which
1921		must have a controller.	 At any point in time, only one bus is
1922		active.	 To switch to a different bus, use the 'i2c dev' command.
1923		Note that bus numbering is zero-based.
1924
1925		CONFIG_SYS_I2C_NOPROBES
1926
1927		This option specifies a list of I2C devices that will be skipped
1928		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1929		is set, specify a list of bus-device pairs.  Otherwise, specify
1930		a 1D array of device addresses
1931
1932		e.g.
1933			#undef	CONFIG_I2C_MULTI_BUS
1934			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1935
1936		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1937
1938			#define CONFIG_I2C_MULTI_BUS
1939			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1940
1941		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1942
1943		CONFIG_SYS_SPD_BUS_NUM
1944
1945		If defined, then this indicates the I2C bus number for DDR SPD.
1946		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1947
1948		CONFIG_SYS_RTC_BUS_NUM
1949
1950		If defined, then this indicates the I2C bus number for the RTC.
1951		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1952
1953		CONFIG_SOFT_I2C_READ_REPEATED_START
1954
1955		defining this will force the i2c_read() function in
1956		the soft_i2c driver to perform an I2C repeated start
1957		between writing the address pointer and reading the
1958		data.  If this define is omitted the default behaviour
1959		of doing a stop-start sequence will be used.  Most I2C
1960		devices can use either method, but some require one or
1961		the other.
1962
1963- SPI Support:	CONFIG_SPI
1964
1965		Enables SPI driver (so far only tested with
1966		SPI EEPROM, also an instance works with Crystal A/D and
1967		D/As on the SACSng board)
1968
1969		CONFIG_SOFT_SPI
1970
1971		Enables a software (bit-bang) SPI driver rather than
1972		using hardware support. This is a general purpose
1973		driver that only requires three general I/O port pins
1974		(two outputs, one input) to function. If this is
1975		defined, the board configuration must define several
1976		SPI configuration items (port pins to use, etc). For
1977		an example, see include/configs/sacsng.h.
1978
1979		CONFIG_HARD_SPI
1980
1981		Enables a hardware SPI driver for general-purpose reads
1982		and writes.  As with CONFIG_SOFT_SPI, the board configuration
1983		must define a list of chip-select function pointers.
1984		Currently supported on some MPC8xxx processors.	 For an
1985		example, see include/configs/mpc8349emds.h.
1986
1987		CONFIG_SYS_SPI_MXC_WAIT
1988		Timeout for waiting until spi transfer completed.
1989		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1990
1991- FPGA Support: CONFIG_FPGA
1992
1993		Enables FPGA subsystem.
1994
1995		CONFIG_FPGA_<vendor>
1996
1997		Enables support for specific chip vendors.
1998		(ALTERA, XILINX)
1999
2000		CONFIG_FPGA_<family>
2001
2002		Enables support for FPGA family.
2003		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2004
2005		CONFIG_FPGA_COUNT
2006
2007		Specify the number of FPGA devices to support.
2008
2009		CONFIG_SYS_FPGA_PROG_FEEDBACK
2010
2011		Enable printing of hash marks during FPGA configuration.
2012
2013		CONFIG_SYS_FPGA_CHECK_BUSY
2014
2015		Enable checks on FPGA configuration interface busy
2016		status by the configuration function. This option
2017		will require a board or device specific function to
2018		be written.
2019
2020		CONFIG_FPGA_DELAY
2021
2022		If defined, a function that provides delays in the FPGA
2023		configuration driver.
2024
2025		CONFIG_SYS_FPGA_CHECK_CTRLC
2026		Allow Control-C to interrupt FPGA configuration
2027
2028		CONFIG_SYS_FPGA_CHECK_ERROR
2029
2030		Check for configuration errors during FPGA bitfile
2031		loading. For example, abort during Virtex II
2032		configuration if the INIT_B line goes low (which
2033		indicated a CRC error).
2034
2035		CONFIG_SYS_FPGA_WAIT_INIT
2036
2037		Maximum time to wait for the INIT_B line to de-assert
2038		after PROB_B has been de-asserted during a Virtex II
2039		FPGA configuration sequence. The default time is 500
2040		ms.
2041
2042		CONFIG_SYS_FPGA_WAIT_BUSY
2043
2044		Maximum time to wait for BUSY to de-assert during
2045		Virtex II FPGA configuration. The default is 5 ms.
2046
2047		CONFIG_SYS_FPGA_WAIT_CONFIG
2048
2049		Time to wait after FPGA configuration. The default is
2050		200 ms.
2051
2052- Configuration Management:
2053		CONFIG_BUILD_TARGET
2054
2055		Some SoCs need special image types (e.g. U-Boot binary
2056		with a special header) as build targets. By defining
2057		CONFIG_BUILD_TARGET in the SoC / board header, this
2058		special image will be automatically built upon calling
2059		make / buildman.
2060
2061		CONFIG_IDENT_STRING
2062
2063		If defined, this string will be added to the U-Boot
2064		version information (U_BOOT_VERSION)
2065
2066- Vendor Parameter Protection:
2067
2068		U-Boot considers the values of the environment
2069		variables "serial#" (Board Serial Number) and
2070		"ethaddr" (Ethernet Address) to be parameters that
2071		are set once by the board vendor / manufacturer, and
2072		protects these variables from casual modification by
2073		the user. Once set, these variables are read-only,
2074		and write or delete attempts are rejected. You can
2075		change this behaviour:
2076
2077		If CONFIG_ENV_OVERWRITE is #defined in your config
2078		file, the write protection for vendor parameters is
2079		completely disabled. Anybody can change or delete
2080		these parameters.
2081
2082		Alternatively, if you define _both_ an ethaddr in the
2083		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2084		Ethernet address is installed in the environment,
2085		which can be changed exactly ONCE by the user. [The
2086		serial# is unaffected by this, i. e. it remains
2087		read-only.]
2088
2089		The same can be accomplished in a more flexible way
2090		for any variable by configuring the type of access
2091		to allow for those variables in the ".flags" variable
2092		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2093
2094- Protected RAM:
2095		CONFIG_PRAM
2096
2097		Define this variable to enable the reservation of
2098		"protected RAM", i. e. RAM which is not overwritten
2099		by U-Boot. Define CONFIG_PRAM to hold the number of
2100		kB you want to reserve for pRAM. You can overwrite
2101		this default value by defining an environment
2102		variable "pram" to the number of kB you want to
2103		reserve. Note that the board info structure will
2104		still show the full amount of RAM. If pRAM is
2105		reserved, a new environment variable "mem" will
2106		automatically be defined to hold the amount of
2107		remaining RAM in a form that can be passed as boot
2108		argument to Linux, for instance like that:
2109
2110			setenv bootargs ... mem=\${mem}
2111			saveenv
2112
2113		This way you can tell Linux not to use this memory,
2114		either, which results in a memory region that will
2115		not be affected by reboots.
2116
2117		*WARNING* If your board configuration uses automatic
2118		detection of the RAM size, you must make sure that
2119		this memory test is non-destructive. So far, the
2120		following board configurations are known to be
2121		"pRAM-clean":
2122
2123			IVMS8, IVML24, SPD8xx,
2124			HERMES, IP860, RPXlite, LWMON,
2125			FLAGADM
2126
2127- Access to physical memory region (> 4GB)
2128		Some basic support is provided for operations on memory not
2129		normally accessible to U-Boot - e.g. some architectures
2130		support access to more than 4GB of memory on 32-bit
2131		machines using physical address extension or similar.
2132		Define CONFIG_PHYSMEM to access this basic support, which
2133		currently only supports clearing the memory.
2134
2135- Error Recovery:
2136		CONFIG_NET_RETRY_COUNT
2137
2138		This variable defines the number of retries for
2139		network operations like ARP, RARP, TFTP, or BOOTP
2140		before giving up the operation. If not defined, a
2141		default value of 5 is used.
2142
2143		CONFIG_ARP_TIMEOUT
2144
2145		Timeout waiting for an ARP reply in milliseconds.
2146
2147		CONFIG_NFS_TIMEOUT
2148
2149		Timeout in milliseconds used in NFS protocol.
2150		If you encounter "ERROR: Cannot umount" in nfs command,
2151		try longer timeout such as
2152		#define CONFIG_NFS_TIMEOUT 10000UL
2153
2154- Command Interpreter:
2155		CONFIG_SYS_PROMPT_HUSH_PS2
2156
2157		This defines the secondary prompt string, which is
2158		printed when the command interpreter needs more input
2159		to complete a command. Usually "> ".
2160
2161	Note:
2162
2163		In the current implementation, the local variables
2164		space and global environment variables space are
2165		separated. Local variables are those you define by
2166		simply typing `name=value'. To access a local
2167		variable later on, you have write `$name' or
2168		`${name}'; to execute the contents of a variable
2169		directly type `$name' at the command prompt.
2170
2171		Global environment variables are those you use
2172		setenv/printenv to work with. To run a command stored
2173		in such a variable, you need to use the run command,
2174		and you must not use the '$' sign to access them.
2175
2176		To store commands and special characters in a
2177		variable, please use double quotation marks
2178		surrounding the whole text of the variable, instead
2179		of the backslashes before semicolons and special
2180		symbols.
2181
2182- Command Line Editing and History:
2183		CONFIG_CMDLINE_PS_SUPPORT
2184
2185		Enable support for changing the command prompt string
2186		at run-time. Only static string is supported so far.
2187		The string is obtained from environment variables PS1
2188		and PS2.
2189
2190- Default Environment:
2191		CONFIG_EXTRA_ENV_SETTINGS
2192
2193		Define this to contain any number of null terminated
2194		strings (variable = value pairs) that will be part of
2195		the default environment compiled into the boot image.
2196
2197		For example, place something like this in your
2198		board's config file:
2199
2200		#define CONFIG_EXTRA_ENV_SETTINGS \
2201			"myvar1=value1\0" \
2202			"myvar2=value2\0"
2203
2204		Warning: This method is based on knowledge about the
2205		internal format how the environment is stored by the
2206		U-Boot code. This is NOT an official, exported
2207		interface! Although it is unlikely that this format
2208		will change soon, there is no guarantee either.
2209		You better know what you are doing here.
2210
2211		Note: overly (ab)use of the default environment is
2212		discouraged. Make sure to check other ways to preset
2213		the environment like the "source" command or the
2214		boot command first.
2215
2216		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2217
2218		Define this in order to add variables describing certain
2219		run-time determined information about the hardware to the
2220		environment.  These will be named board_name, board_rev.
2221
2222		CONFIG_DELAY_ENVIRONMENT
2223
2224		Normally the environment is loaded when the board is
2225		initialised so that it is available to U-Boot. This inhibits
2226		that so that the environment is not available until
2227		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2228		this is instead controlled by the value of
2229		/config/load-environment.
2230
2231- Serial Flash support
2232		Usage requires an initial 'sf probe' to define the serial
2233		flash parameters, followed by read/write/erase/update
2234		commands.
2235
2236		The following defaults may be provided by the platform
2237		to handle the common case when only a single serial
2238		flash is present on the system.
2239
2240		CONFIG_SF_DEFAULT_BUS		Bus identifier
2241		CONFIG_SF_DEFAULT_CS		Chip-select
2242		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2243		CONFIG_SF_DEFAULT_SPEED		in Hz
2244
2245
2246- TFTP Fixed UDP Port:
2247		CONFIG_TFTP_PORT
2248
2249		If this is defined, the environment variable tftpsrcp
2250		is used to supply the TFTP UDP source port value.
2251		If tftpsrcp isn't defined, the normal pseudo-random port
2252		number generator is used.
2253
2254		Also, the environment variable tftpdstp is used to supply
2255		the TFTP UDP destination port value.  If tftpdstp isn't
2256		defined, the normal port 69 is used.
2257
2258		The purpose for tftpsrcp is to allow a TFTP server to
2259		blindly start the TFTP transfer using the pre-configured
2260		target IP address and UDP port. This has the effect of
2261		"punching through" the (Windows XP) firewall, allowing
2262		the remainder of the TFTP transfer to proceed normally.
2263		A better solution is to properly configure the firewall,
2264		but sometimes that is not allowed.
2265
2266- Show boot progress:
2267		CONFIG_SHOW_BOOT_PROGRESS
2268
2269		Defining this option allows to add some board-
2270		specific code (calling a user-provided function
2271		"show_boot_progress(int)") that enables you to show
2272		the system's boot progress on some display (for
2273		example, some LED's) on your board. At the moment,
2274		the following checkpoints are implemented:
2275
2276
2277Legacy uImage format:
2278
2279  Arg	Where			When
2280    1	common/cmd_bootm.c	before attempting to boot an image
2281   -1	common/cmd_bootm.c	Image header has bad	 magic number
2282    2	common/cmd_bootm.c	Image header has correct magic number
2283   -2	common/cmd_bootm.c	Image header has bad	 checksum
2284    3	common/cmd_bootm.c	Image header has correct checksum
2285   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2286    4	common/cmd_bootm.c	Image data   has correct checksum
2287   -4	common/cmd_bootm.c	Image is for unsupported architecture
2288    5	common/cmd_bootm.c	Architecture check OK
2289   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2290    6	common/cmd_bootm.c	Image Type check OK
2291   -6	common/cmd_bootm.c	gunzip uncompression error
2292   -7	common/cmd_bootm.c	Unimplemented compression type
2293    7	common/cmd_bootm.c	Uncompression OK
2294    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2295   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2296
2297    9	common/image.c		Start initial ramdisk verification
2298  -10	common/image.c		Ramdisk header has bad	   magic number
2299  -11	common/image.c		Ramdisk header has bad	   checksum
2300   10	common/image.c		Ramdisk header is OK
2301  -12	common/image.c		Ramdisk data   has bad	   checksum
2302   11	common/image.c		Ramdisk data   has correct checksum
2303   12	common/image.c		Ramdisk verification complete, start loading
2304  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2305   13	common/image.c		Start multifile image verification
2306   14	common/image.c		No initial ramdisk, no multifile, continue.
2307
2308   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2309
2310  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2311  -31	post/post.c		POST test failed, detected by post_output_backlog()
2312  -32	post/post.c		POST test failed, detected by post_run_single()
2313
2314   34	common/cmd_doc.c	before loading a Image from a DOC device
2315  -35	common/cmd_doc.c	Bad usage of "doc" command
2316   35	common/cmd_doc.c	correct usage of "doc" command
2317  -36	common/cmd_doc.c	No boot device
2318   36	common/cmd_doc.c	correct boot device
2319  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2320   37	common/cmd_doc.c	correct chip ID found, device available
2321  -38	common/cmd_doc.c	Read Error on boot device
2322   38	common/cmd_doc.c	reading Image header from DOC device OK
2323  -39	common/cmd_doc.c	Image header has bad magic number
2324   39	common/cmd_doc.c	Image header has correct magic number
2325  -40	common/cmd_doc.c	Error reading Image from DOC device
2326   40	common/cmd_doc.c	Image header has correct magic number
2327   41	common/cmd_ide.c	before loading a Image from a IDE device
2328  -42	common/cmd_ide.c	Bad usage of "ide" command
2329   42	common/cmd_ide.c	correct usage of "ide" command
2330  -43	common/cmd_ide.c	No boot device
2331   43	common/cmd_ide.c	boot device found
2332  -44	common/cmd_ide.c	Device not available
2333   44	common/cmd_ide.c	Device available
2334  -45	common/cmd_ide.c	wrong partition selected
2335   45	common/cmd_ide.c	partition selected
2336  -46	common/cmd_ide.c	Unknown partition table
2337   46	common/cmd_ide.c	valid partition table found
2338  -47	common/cmd_ide.c	Invalid partition type
2339   47	common/cmd_ide.c	correct partition type
2340  -48	common/cmd_ide.c	Error reading Image Header on boot device
2341   48	common/cmd_ide.c	reading Image Header from IDE device OK
2342  -49	common/cmd_ide.c	Image header has bad magic number
2343   49	common/cmd_ide.c	Image header has correct magic number
2344  -50	common/cmd_ide.c	Image header has bad	 checksum
2345   50	common/cmd_ide.c	Image header has correct checksum
2346  -51	common/cmd_ide.c	Error reading Image from IDE device
2347   51	common/cmd_ide.c	reading Image from IDE device OK
2348   52	common/cmd_nand.c	before loading a Image from a NAND device
2349  -53	common/cmd_nand.c	Bad usage of "nand" command
2350   53	common/cmd_nand.c	correct usage of "nand" command
2351  -54	common/cmd_nand.c	No boot device
2352   54	common/cmd_nand.c	boot device found
2353  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2354   55	common/cmd_nand.c	correct chip ID found, device available
2355  -56	common/cmd_nand.c	Error reading Image Header on boot device
2356   56	common/cmd_nand.c	reading Image Header from NAND device OK
2357  -57	common/cmd_nand.c	Image header has bad magic number
2358   57	common/cmd_nand.c	Image header has correct magic number
2359  -58	common/cmd_nand.c	Error reading Image from NAND device
2360   58	common/cmd_nand.c	reading Image from NAND device OK
2361
2362  -60	common/env_common.c	Environment has a bad CRC, using default
2363
2364   64	net/eth.c		starting with Ethernet configuration.
2365  -64	net/eth.c		no Ethernet found.
2366   65	net/eth.c		Ethernet found.
2367
2368  -80	common/cmd_net.c	usage wrong
2369   80	common/cmd_net.c	before calling net_loop()
2370  -81	common/cmd_net.c	some error in net_loop() occurred
2371   81	common/cmd_net.c	net_loop() back without error
2372  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2373   82	common/cmd_net.c	trying automatic boot
2374   83	common/cmd_net.c	running "source" command
2375  -83	common/cmd_net.c	some error in automatic boot or "source" command
2376   84	common/cmd_net.c	end without errors
2377
2378FIT uImage format:
2379
2380  Arg	Where			When
2381  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2382 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2383  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2384 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2385  102	common/cmd_bootm.c	Kernel unit name specified
2386 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2387  103	common/cmd_bootm.c	Found configuration node
2388  104	common/cmd_bootm.c	Got kernel subimage node offset
2389 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2390  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2391 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2392  106	common/cmd_bootm.c	Architecture check OK
2393 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2394  107	common/cmd_bootm.c	Kernel subimage type OK
2395 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2396  108	common/cmd_bootm.c	Got kernel subimage data/size
2397 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2398 -109	common/cmd_bootm.c	Can't get kernel subimage type
2399 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2400 -111	common/cmd_bootm.c	Can't get kernel subimage os
2401 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2402 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2403
2404  120	common/image.c		Start initial ramdisk verification
2405 -120	common/image.c		Ramdisk FIT image has incorrect format
2406  121	common/image.c		Ramdisk FIT image has correct format
2407  122	common/image.c		No ramdisk subimage unit name, using configuration
2408 -122	common/image.c		Can't get configuration for ramdisk subimage
2409  123	common/image.c		Ramdisk unit name specified
2410 -124	common/image.c		Can't get ramdisk subimage node offset
2411  125	common/image.c		Got ramdisk subimage node offset
2412 -125	common/image.c		Ramdisk subimage hash verification failed
2413  126	common/image.c		Ramdisk subimage hash verification OK
2414 -126	common/image.c		Ramdisk subimage for unsupported architecture
2415  127	common/image.c		Architecture check OK
2416 -127	common/image.c		Can't get ramdisk subimage data/size
2417  128	common/image.c		Got ramdisk subimage data/size
2418  129	common/image.c		Can't get ramdisk load address
2419 -129	common/image.c		Got ramdisk load address
2420
2421 -130	common/cmd_doc.c	Incorrect FIT image format
2422  131	common/cmd_doc.c	FIT image format OK
2423
2424 -140	common/cmd_ide.c	Incorrect FIT image format
2425  141	common/cmd_ide.c	FIT image format OK
2426
2427 -150	common/cmd_nand.c	Incorrect FIT image format
2428  151	common/cmd_nand.c	FIT image format OK
2429
2430- legacy image format:
2431		CONFIG_IMAGE_FORMAT_LEGACY
2432		enables the legacy image format support in U-Boot.
2433
2434		Default:
2435		enabled if CONFIG_FIT_SIGNATURE is not defined.
2436
2437		CONFIG_DISABLE_IMAGE_LEGACY
2438		disable the legacy image format
2439
2440		This define is introduced, as the legacy image format is
2441		enabled per default for backward compatibility.
2442
2443- Standalone program support:
2444		CONFIG_STANDALONE_LOAD_ADDR
2445
2446		This option defines a board specific value for the
2447		address where standalone program gets loaded, thus
2448		overwriting the architecture dependent default
2449		settings.
2450
2451- Frame Buffer Address:
2452		CONFIG_FB_ADDR
2453
2454		Define CONFIG_FB_ADDR if you want to use specific
2455		address for frame buffer.  This is typically the case
2456		when using a graphics controller has separate video
2457		memory.  U-Boot will then place the frame buffer at
2458		the given address instead of dynamically reserving it
2459		in system RAM by calling lcd_setmem(), which grabs
2460		the memory for the frame buffer depending on the
2461		configured panel size.
2462
2463		Please see board_init_f function.
2464
2465- Automatic software updates via TFTP server
2466		CONFIG_UPDATE_TFTP
2467		CONFIG_UPDATE_TFTP_CNT_MAX
2468		CONFIG_UPDATE_TFTP_MSEC_MAX
2469
2470		These options enable and control the auto-update feature;
2471		for a more detailed description refer to doc/README.update.
2472
2473- MTD Support (mtdparts command, UBI support)
2474		CONFIG_MTD_DEVICE
2475
2476		Adds the MTD device infrastructure from the Linux kernel.
2477		Needed for mtdparts command support.
2478
2479		CONFIG_MTD_PARTITIONS
2480
2481		Adds the MTD partitioning infrastructure from the Linux
2482		kernel. Needed for UBI support.
2483
2484- UBI support
2485		CONFIG_UBI_SILENCE_MSG
2486
2487		Make the verbose messages from UBI stop printing.  This leaves
2488		warnings and errors enabled.
2489
2490
2491		CONFIG_MTD_UBI_WL_THRESHOLD
2492		This parameter defines the maximum difference between the highest
2493		erase counter value and the lowest erase counter value of eraseblocks
2494		of UBI devices. When this threshold is exceeded, UBI starts performing
2495		wear leveling by means of moving data from eraseblock with low erase
2496		counter to eraseblocks with high erase counter.
2497
2498		The default value should be OK for SLC NAND flashes, NOR flashes and
2499		other flashes which have eraseblock life-cycle 100000 or more.
2500		However, in case of MLC NAND flashes which typically have eraseblock
2501		life-cycle less than 10000, the threshold should be lessened (e.g.,
2502		to 128 or 256, although it does not have to be power of 2).
2503
2504		default: 4096
2505
2506		CONFIG_MTD_UBI_BEB_LIMIT
2507		This option specifies the maximum bad physical eraseblocks UBI
2508		expects on the MTD device (per 1024 eraseblocks). If the
2509		underlying flash does not admit of bad eraseblocks (e.g. NOR
2510		flash), this value is ignored.
2511
2512		NAND datasheets often specify the minimum and maximum NVM
2513		(Number of Valid Blocks) for the flashes' endurance lifetime.
2514		The maximum expected bad eraseblocks per 1024 eraseblocks
2515		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2516		which gives 20 for most NANDs (MaxNVB is basically the total
2517		count of eraseblocks on the chip).
2518
2519		To put it differently, if this value is 20, UBI will try to
2520		reserve about 1.9% of physical eraseblocks for bad blocks
2521		handling. And that will be 1.9% of eraseblocks on the entire
2522		NAND chip, not just the MTD partition UBI attaches. This means
2523		that if you have, say, a NAND flash chip admits maximum 40 bad
2524		eraseblocks, and it is split on two MTD partitions of the same
2525		size, UBI will reserve 40 eraseblocks when attaching a
2526		partition.
2527
2528		default: 20
2529
2530		CONFIG_MTD_UBI_FASTMAP
2531		Fastmap is a mechanism which allows attaching an UBI device
2532		in nearly constant time. Instead of scanning the whole MTD device it
2533		only has to locate a checkpoint (called fastmap) on the device.
2534		The on-flash fastmap contains all information needed to attach
2535		the device. Using fastmap makes only sense on large devices where
2536		attaching by scanning takes long. UBI will not automatically install
2537		a fastmap on old images, but you can set the UBI parameter
2538		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2539		that fastmap-enabled images are still usable with UBI implementations
2540		without	fastmap support. On typical flash devices the whole fastmap
2541		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2542
2543		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2544		Set this parameter to enable fastmap automatically on images
2545		without a fastmap.
2546		default: 0
2547
2548		CONFIG_MTD_UBI_FM_DEBUG
2549		Enable UBI fastmap debug
2550		default: 0
2551
2552- UBIFS support
2553		CONFIG_UBIFS_SILENCE_MSG
2554
2555		Make the verbose messages from UBIFS stop printing.  This leaves
2556		warnings and errors enabled.
2557
2558- SPL framework
2559		CONFIG_SPL
2560		Enable building of SPL globally.
2561
2562		CONFIG_SPL_LDSCRIPT
2563		LDSCRIPT for linking the SPL binary.
2564
2565		CONFIG_SPL_MAX_FOOTPRINT
2566		Maximum size in memory allocated to the SPL, BSS included.
2567		When defined, the linker checks that the actual memory
2568		used by SPL from _start to __bss_end does not exceed it.
2569		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2570		must not be both defined at the same time.
2571
2572		CONFIG_SPL_MAX_SIZE
2573		Maximum size of the SPL image (text, data, rodata, and
2574		linker lists sections), BSS excluded.
2575		When defined, the linker checks that the actual size does
2576		not exceed it.
2577
2578		CONFIG_SPL_TEXT_BASE
2579		TEXT_BASE for linking the SPL binary.
2580
2581		CONFIG_SPL_RELOC_TEXT_BASE
2582		Address to relocate to.  If unspecified, this is equal to
2583		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2584
2585		CONFIG_SPL_BSS_START_ADDR
2586		Link address for the BSS within the SPL binary.
2587
2588		CONFIG_SPL_BSS_MAX_SIZE
2589		Maximum size in memory allocated to the SPL BSS.
2590		When defined, the linker checks that the actual memory used
2591		by SPL from __bss_start to __bss_end does not exceed it.
2592		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2593		must not be both defined at the same time.
2594
2595		CONFIG_SPL_STACK
2596		Adress of the start of the stack SPL will use
2597
2598		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2599		When defined, SPL will panic() if the image it has
2600		loaded does not have a signature.
2601		Defining this is useful when code which loads images
2602		in SPL cannot guarantee that absolutely all read errors
2603		will be caught.
2604		An example is the LPC32XX MLC NAND driver, which will
2605		consider that a completely unreadable NAND block is bad,
2606		and thus should be skipped silently.
2607
2608		CONFIG_SPL_RELOC_STACK
2609		Adress of the start of the stack SPL will use after
2610		relocation.  If unspecified, this is equal to
2611		CONFIG_SPL_STACK.
2612
2613		CONFIG_SYS_SPL_MALLOC_START
2614		Starting address of the malloc pool used in SPL.
2615		When this option is set the full malloc is used in SPL and
2616		it is set up by spl_init() and before that, the simple malloc()
2617		can be used if CONFIG_SYS_MALLOC_F is defined.
2618
2619		CONFIG_SYS_SPL_MALLOC_SIZE
2620		The size of the malloc pool used in SPL.
2621
2622		CONFIG_SPL_OS_BOOT
2623		Enable booting directly to an OS from SPL.
2624		See also: doc/README.falcon
2625
2626		CONFIG_SPL_DISPLAY_PRINT
2627		For ARM, enable an optional function to print more information
2628		about the running system.
2629
2630		CONFIG_SPL_INIT_MINIMAL
2631		Arch init code should be built for a very small image
2632
2633		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2634		Partition on the MMC to load U-Boot from when the MMC is being
2635		used in raw mode
2636
2637		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2638		Sector to load kernel uImage from when MMC is being
2639		used in raw mode (for Falcon mode)
2640
2641		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2642		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2643		Sector and number of sectors to load kernel argument
2644		parameters from when MMC is being used in raw mode
2645		(for falcon mode)
2646
2647		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2648		Partition on the MMC to load U-Boot from when the MMC is being
2649		used in fs mode
2650
2651		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2652		Filename to read to load U-Boot when reading from filesystem
2653
2654		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2655		Filename to read to load kernel uImage when reading
2656		from filesystem (for Falcon mode)
2657
2658		CONFIG_SPL_FS_LOAD_ARGS_NAME
2659		Filename to read to load kernel argument parameters
2660		when reading from filesystem (for Falcon mode)
2661
2662		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2663		Set this for NAND SPL on PPC mpc83xx targets, so that
2664		start.S waits for the rest of the SPL to load before
2665		continuing (the hardware starts execution after just
2666		loading the first page rather than the full 4K).
2667
2668		CONFIG_SPL_SKIP_RELOCATE
2669		Avoid SPL relocation
2670
2671		CONFIG_SPL_NAND_BASE
2672		Include nand_base.c in the SPL.  Requires
2673		CONFIG_SPL_NAND_DRIVERS.
2674
2675		CONFIG_SPL_NAND_DRIVERS
2676		SPL uses normal NAND drivers, not minimal drivers.
2677
2678		CONFIG_SPL_NAND_ECC
2679		Include standard software ECC in the SPL
2680
2681		CONFIG_SPL_NAND_SIMPLE
2682		Support for NAND boot using simple NAND drivers that
2683		expose the cmd_ctrl() interface.
2684
2685		CONFIG_SPL_UBI
2686		Support for a lightweight UBI (fastmap) scanner and
2687		loader
2688
2689		CONFIG_SPL_NAND_RAW_ONLY
2690		Support to boot only raw u-boot.bin images. Use this only
2691		if you need to save space.
2692
2693		CONFIG_SPL_COMMON_INIT_DDR
2694		Set for common ddr init with serial presence detect in
2695		SPL binary.
2696
2697		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2698		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2699		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2700		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2701		CONFIG_SYS_NAND_ECCBYTES
2702		Defines the size and behavior of the NAND that SPL uses
2703		to read U-Boot
2704
2705		CONFIG_SPL_NAND_BOOT
2706		Add support NAND boot
2707
2708		CONFIG_SYS_NAND_U_BOOT_OFFS
2709		Location in NAND to read U-Boot from
2710
2711		CONFIG_SYS_NAND_U_BOOT_DST
2712		Location in memory to load U-Boot to
2713
2714		CONFIG_SYS_NAND_U_BOOT_SIZE
2715		Size of image to load
2716
2717		CONFIG_SYS_NAND_U_BOOT_START
2718		Entry point in loaded image to jump to
2719
2720		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2721		Define this if you need to first read the OOB and then the
2722		data. This is used, for example, on davinci platforms.
2723
2724		CONFIG_SPL_RAM_DEVICE
2725		Support for running image already present in ram, in SPL binary
2726
2727		CONFIG_SPL_PAD_TO
2728		Image offset to which the SPL should be padded before appending
2729		the SPL payload. By default, this is defined as
2730		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2731		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2732		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2733
2734		CONFIG_SPL_TARGET
2735		Final target image containing SPL and payload.  Some SPLs
2736		use an arch-specific makefile fragment instead, for
2737		example if more than one image needs to be produced.
2738
2739		CONFIG_FIT_SPL_PRINT
2740		Printing information about a FIT image adds quite a bit of
2741		code to SPL. So this is normally disabled in SPL. Use this
2742		option to re-enable it. This will affect the output of the
2743		bootm command when booting a FIT image.
2744
2745- TPL framework
2746		CONFIG_TPL
2747		Enable building of TPL globally.
2748
2749		CONFIG_TPL_PAD_TO
2750		Image offset to which the TPL should be padded before appending
2751		the TPL payload. By default, this is defined as
2752		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2753		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2754		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2755
2756- Interrupt support (PPC):
2757
2758		There are common interrupt_init() and timer_interrupt()
2759		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2760		for CPU specific initialization. interrupt_init_cpu()
2761		should set decrementer_count to appropriate value. If
2762		CPU resets decrementer automatically after interrupt
2763		(ppc4xx) it should set decrementer_count to zero.
2764		timer_interrupt() calls timer_interrupt_cpu() for CPU
2765		specific handling. If board has watchdog / status_led
2766		/ other_activity_monitor it works automatically from
2767		general timer_interrupt().
2768
2769
2770Board initialization settings:
2771------------------------------
2772
2773During Initialization u-boot calls a number of board specific functions
2774to allow the preparation of board specific prerequisites, e.g. pin setup
2775before drivers are initialized. To enable these callbacks the
2776following configuration macros have to be defined. Currently this is
2777architecture specific, so please check arch/your_architecture/lib/board.c
2778typically in board_init_f() and board_init_r().
2779
2780- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2781- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2782- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2783- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2784
2785Configuration Settings:
2786-----------------------
2787
2788- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2789		Optionally it can be defined to support 64-bit memory commands.
2790
2791- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2792		undefine this when you're short of memory.
2793
2794- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2795		width of the commands listed in the 'help' command output.
2796
2797- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2798		prompt for user input.
2799
2800- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2801
2802- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2803
2804- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2805
2806- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2807		the application (usually a Linux kernel) when it is
2808		booted
2809
2810- CONFIG_SYS_BAUDRATE_TABLE:
2811		List of legal baudrate settings for this board.
2812
2813- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2814		Begin and End addresses of the area used by the
2815		simple memory test.
2816
2817- CONFIG_SYS_ALT_MEMTEST:
2818		Enable an alternate, more extensive memory test.
2819
2820- CONFIG_SYS_MEMTEST_SCRATCH:
2821		Scratch address used by the alternate memory test
2822		You only need to set this if address zero isn't writeable
2823
2824- CONFIG_SYS_MEM_RESERVE_SECURE
2825		Only implemented for ARMv8 for now.
2826		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2827		is substracted from total RAM and won't be reported to OS.
2828		This memory can be used as secure memory. A variable
2829		gd->arch.secure_ram is used to track the location. In systems
2830		the RAM base is not zero, or RAM is divided into banks,
2831		this variable needs to be recalcuated to get the address.
2832
2833- CONFIG_SYS_MEM_TOP_HIDE:
2834		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2835		this specified memory area will get subtracted from the top
2836		(end) of RAM and won't get "touched" at all by U-Boot. By
2837		fixing up gd->ram_size the Linux kernel should gets passed
2838		the now "corrected" memory size and won't touch it either.
2839		This should work for arch/ppc and arch/powerpc. Only Linux
2840		board ports in arch/powerpc with bootwrapper support that
2841		recalculate the memory size from the SDRAM controller setup
2842		will have to get fixed in Linux additionally.
2843
2844		This option can be used as a workaround for the 440EPx/GRx
2845		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2846		be touched.
2847
2848		WARNING: Please make sure that this value is a multiple of
2849		the Linux page size (normally 4k). If this is not the case,
2850		then the end address of the Linux memory will be located at a
2851		non page size aligned address and this could cause major
2852		problems.
2853
2854- CONFIG_SYS_LOADS_BAUD_CHANGE:
2855		Enable temporary baudrate change while serial download
2856
2857- CONFIG_SYS_SDRAM_BASE:
2858		Physical start address of SDRAM. _Must_ be 0 here.
2859
2860- CONFIG_SYS_FLASH_BASE:
2861		Physical start address of Flash memory.
2862
2863- CONFIG_SYS_MONITOR_BASE:
2864		Physical start address of boot monitor code (set by
2865		make config files to be same as the text base address
2866		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2867		CONFIG_SYS_FLASH_BASE when booting from flash.
2868
2869- CONFIG_SYS_MONITOR_LEN:
2870		Size of memory reserved for monitor code, used to
2871		determine _at_compile_time_ (!) if the environment is
2872		embedded within the U-Boot image, or in a separate
2873		flash sector.
2874
2875- CONFIG_SYS_MALLOC_LEN:
2876		Size of DRAM reserved for malloc() use.
2877
2878- CONFIG_SYS_MALLOC_F_LEN
2879		Size of the malloc() pool for use before relocation. If
2880		this is defined, then a very simple malloc() implementation
2881		will become available before relocation. The address is just
2882		below the global data, and the stack is moved down to make
2883		space.
2884
2885		This feature allocates regions with increasing addresses
2886		within the region. calloc() is supported, but realloc()
2887		is not available. free() is supported but does nothing.
2888		The memory will be freed (or in fact just forgotten) when
2889		U-Boot relocates itself.
2890
2891- CONFIG_SYS_MALLOC_SIMPLE
2892		Provides a simple and small malloc() and calloc() for those
2893		boards which do not use the full malloc in SPL (which is
2894		enabled with CONFIG_SYS_SPL_MALLOC_START).
2895
2896- CONFIG_SYS_NONCACHED_MEMORY:
2897		Size of non-cached memory area. This area of memory will be
2898		typically located right below the malloc() area and mapped
2899		uncached in the MMU. This is useful for drivers that would
2900		otherwise require a lot of explicit cache maintenance. For
2901		some drivers it's also impossible to properly maintain the
2902		cache. For example if the regions that need to be flushed
2903		are not a multiple of the cache-line size, *and* padding
2904		cannot be allocated between the regions to align them (i.e.
2905		if the HW requires a contiguous array of regions, and the
2906		size of each region is not cache-aligned), then a flush of
2907		one region may result in overwriting data that hardware has
2908		written to another region in the same cache-line. This can
2909		happen for example in network drivers where descriptors for
2910		buffers are typically smaller than the CPU cache-line (e.g.
2911		16 bytes vs. 32 or 64 bytes).
2912
2913		Non-cached memory is only supported on 32-bit ARM at present.
2914
2915- CONFIG_SYS_BOOTM_LEN:
2916		Normally compressed uImages are limited to an
2917		uncompressed size of 8 MBytes. If this is not enough,
2918		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2919		to adjust this setting to your needs.
2920
2921- CONFIG_SYS_BOOTMAPSZ:
2922		Maximum size of memory mapped by the startup code of
2923		the Linux kernel; all data that must be processed by
2924		the Linux kernel (bd_info, boot arguments, FDT blob if
2925		used) must be put below this limit, unless "bootm_low"
2926		environment variable is defined and non-zero. In such case
2927		all data for the Linux kernel must be between "bootm_low"
2928		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2929		variable "bootm_mapsize" will override the value of
2930		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2931		then the value in "bootm_size" will be used instead.
2932
2933- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2934		Enable initrd_high functionality.  If defined then the
2935		initrd_high feature is enabled and the bootm ramdisk subcommand
2936		is enabled.
2937
2938- CONFIG_SYS_BOOT_GET_CMDLINE:
2939		Enables allocating and saving kernel cmdline in space between
2940		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2941
2942- CONFIG_SYS_BOOT_GET_KBD:
2943		Enables allocating and saving a kernel copy of the bd_info in
2944		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2945
2946- CONFIG_SYS_MAX_FLASH_BANKS:
2947		Max number of Flash memory banks
2948
2949- CONFIG_SYS_MAX_FLASH_SECT:
2950		Max number of sectors on a Flash chip
2951
2952- CONFIG_SYS_FLASH_ERASE_TOUT:
2953		Timeout for Flash erase operations (in ms)
2954
2955- CONFIG_SYS_FLASH_WRITE_TOUT:
2956		Timeout for Flash write operations (in ms)
2957
2958- CONFIG_SYS_FLASH_LOCK_TOUT
2959		Timeout for Flash set sector lock bit operation (in ms)
2960
2961- CONFIG_SYS_FLASH_UNLOCK_TOUT
2962		Timeout for Flash clear lock bits operation (in ms)
2963
2964- CONFIG_SYS_FLASH_PROTECTION
2965		If defined, hardware flash sectors protection is used
2966		instead of U-Boot software protection.
2967
2968- CONFIG_SYS_DIRECT_FLASH_TFTP:
2969
2970		Enable TFTP transfers directly to flash memory;
2971		without this option such a download has to be
2972		performed in two steps: (1) download to RAM, and (2)
2973		copy from RAM to flash.
2974
2975		The two-step approach is usually more reliable, since
2976		you can check if the download worked before you erase
2977		the flash, but in some situations (when system RAM is
2978		too limited to allow for a temporary copy of the
2979		downloaded image) this option may be very useful.
2980
2981- CONFIG_SYS_FLASH_CFI:
2982		Define if the flash driver uses extra elements in the
2983		common flash structure for storing flash geometry.
2984
2985- CONFIG_FLASH_CFI_DRIVER
2986		This option also enables the building of the cfi_flash driver
2987		in the drivers directory
2988
2989- CONFIG_FLASH_CFI_MTD
2990		This option enables the building of the cfi_mtd driver
2991		in the drivers directory. The driver exports CFI flash
2992		to the MTD layer.
2993
2994- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2995		Use buffered writes to flash.
2996
2997- CONFIG_FLASH_SPANSION_S29WS_N
2998		s29ws-n MirrorBit flash has non-standard addresses for buffered
2999		write commands.
3000
3001- CONFIG_SYS_FLASH_QUIET_TEST
3002		If this option is defined, the common CFI flash doesn't
3003		print it's warning upon not recognized FLASH banks. This
3004		is useful, if some of the configured banks are only
3005		optionally available.
3006
3007- CONFIG_FLASH_SHOW_PROGRESS
3008		If defined (must be an integer), print out countdown
3009		digits and dots.  Recommended value: 45 (9..1) for 80
3010		column displays, 15 (3..1) for 40 column displays.
3011
3012- CONFIG_FLASH_VERIFY
3013		If defined, the content of the flash (destination) is compared
3014		against the source after the write operation. An error message
3015		will be printed when the contents are not identical.
3016		Please note that this option is useless in nearly all cases,
3017		since such flash programming errors usually are detected earlier
3018		while unprotecting/erasing/programming. Please only enable
3019		this option if you really know what you are doing.
3020
3021- CONFIG_SYS_RX_ETH_BUFFER:
3022		Defines the number of Ethernet receive buffers. On some
3023		Ethernet controllers it is recommended to set this value
3024		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3025		buffers can be full shortly after enabling the interface
3026		on high Ethernet traffic.
3027		Defaults to 4 if not defined.
3028
3029- CONFIG_ENV_MAX_ENTRIES
3030
3031	Maximum number of entries in the hash table that is used
3032	internally to store the environment settings. The default
3033	setting is supposed to be generous and should work in most
3034	cases. This setting can be used to tune behaviour; see
3035	lib/hashtable.c for details.
3036
3037- CONFIG_ENV_FLAGS_LIST_DEFAULT
3038- CONFIG_ENV_FLAGS_LIST_STATIC
3039	Enable validation of the values given to environment variables when
3040	calling env set.  Variables can be restricted to only decimal,
3041	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3042	the variables can also be restricted to IP address or MAC address.
3043
3044	The format of the list is:
3045		type_attribute = [s|d|x|b|i|m]
3046		access_attribute = [a|r|o|c]
3047		attributes = type_attribute[access_attribute]
3048		entry = variable_name[:attributes]
3049		list = entry[,list]
3050
3051	The type attributes are:
3052		s - String (default)
3053		d - Decimal
3054		x - Hexadecimal
3055		b - Boolean ([1yYtT|0nNfF])
3056		i - IP address
3057		m - MAC address
3058
3059	The access attributes are:
3060		a - Any (default)
3061		r - Read-only
3062		o - Write-once
3063		c - Change-default
3064
3065	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3066		Define this to a list (string) to define the ".flags"
3067		environment variable in the default or embedded environment.
3068
3069	- CONFIG_ENV_FLAGS_LIST_STATIC
3070		Define this to a list (string) to define validation that
3071		should be done if an entry is not found in the ".flags"
3072		environment variable.  To override a setting in the static
3073		list, simply add an entry for the same variable name to the
3074		".flags" variable.
3075
3076	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3077	regular expression. This allows multiple variables to define the same
3078	flags without explicitly listing them for each variable.
3079
3080- CONFIG_ENV_ACCESS_IGNORE_FORCE
3081	If defined, don't allow the -f switch to env set override variable
3082	access flags.
3083
3084- CONFIG_USE_STDINT
3085	If stdint.h is available with your toolchain you can define this
3086	option to enable it. You can provide option 'USE_STDINT=1' when
3087	building U-Boot to enable this.
3088
3089The following definitions that deal with the placement and management
3090of environment data (variable area); in general, we support the
3091following configurations:
3092
3093- CONFIG_BUILD_ENVCRC:
3094
3095	Builds up envcrc with the target environment so that external utils
3096	may easily extract it and embed it in final U-Boot images.
3097
3098BE CAREFUL! The first access to the environment happens quite early
3099in U-Boot initialization (when we try to get the setting of for the
3100console baudrate). You *MUST* have mapped your NVRAM area then, or
3101U-Boot will hang.
3102
3103Please note that even with NVRAM we still use a copy of the
3104environment in RAM: we could work on NVRAM directly, but we want to
3105keep settings there always unmodified except somebody uses "saveenv"
3106to save the current settings.
3107
3108BE CAREFUL! For some special cases, the local device can not use
3109"saveenv" command. For example, the local device will get the
3110environment stored in a remote NOR flash by SRIO or PCIE link,
3111but it can not erase, write this NOR flash by SRIO or PCIE interface.
3112
3113- CONFIG_NAND_ENV_DST
3114
3115	Defines address in RAM to which the nand_spl code should copy the
3116	environment. If redundant environment is used, it will be copied to
3117	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3118
3119Please note that the environment is read-only until the monitor
3120has been relocated to RAM and a RAM copy of the environment has been
3121created; also, when using EEPROM you will have to use env_get_f()
3122until then to read environment variables.
3123
3124The environment is protected by a CRC32 checksum. Before the monitor
3125is relocated into RAM, as a result of a bad CRC you will be working
3126with the compiled-in default environment - *silently*!!! [This is
3127necessary, because the first environment variable we need is the
3128"baudrate" setting for the console - if we have a bad CRC, we don't
3129have any device yet where we could complain.]
3130
3131Note: once the monitor has been relocated, then it will complain if
3132the default environment is used; a new CRC is computed as soon as you
3133use the "saveenv" command to store a valid environment.
3134
3135- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3136		Echo the inverted Ethernet link state to the fault LED.
3137
3138		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3139		      also needs to be defined.
3140
3141- CONFIG_SYS_FAULT_MII_ADDR:
3142		MII address of the PHY to check for the Ethernet link state.
3143
3144- CONFIG_NS16550_MIN_FUNCTIONS:
3145		Define this if you desire to only have use of the NS16550_init
3146		and NS16550_putc functions for the serial driver located at
3147		drivers/serial/ns16550.c.  This option is useful for saving
3148		space for already greatly restricted images, including but not
3149		limited to NAND_SPL configurations.
3150
3151- CONFIG_DISPLAY_BOARDINFO
3152		Display information about the board that U-Boot is running on
3153		when U-Boot starts up. The board function checkboard() is called
3154		to do this.
3155
3156- CONFIG_DISPLAY_BOARDINFO_LATE
3157		Similar to the previous option, but display this information
3158		later, once stdio is running and output goes to the LCD, if
3159		present.
3160
3161- CONFIG_BOARD_SIZE_LIMIT:
3162		Maximum size of the U-Boot image. When defined, the
3163		build system checks that the actual size does not
3164		exceed it.
3165
3166Low Level (hardware related) configuration options:
3167---------------------------------------------------
3168
3169- CONFIG_SYS_CACHELINE_SIZE:
3170		Cache Line Size of the CPU.
3171
3172- CONFIG_SYS_CCSRBAR_DEFAULT:
3173		Default (power-on reset) physical address of CCSR on Freescale
3174		PowerPC SOCs.
3175
3176- CONFIG_SYS_CCSRBAR:
3177		Virtual address of CCSR.  On a 32-bit build, this is typically
3178		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3179
3180- CONFIG_SYS_CCSRBAR_PHYS:
3181		Physical address of CCSR.  CCSR can be relocated to a new
3182		physical address, if desired.  In this case, this macro should
3183		be set to that address.	 Otherwise, it should be set to the
3184		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3185		is typically relocated on 36-bit builds.  It is recommended
3186		that this macro be defined via the _HIGH and _LOW macros:
3187
3188		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3189			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3190
3191- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3192		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3193		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3194		used in assembly code, so it must not contain typecasts or
3195		integer size suffixes (e.g. "ULL").
3196
3197- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3198		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3199		used in assembly code, so it must not contain typecasts or
3200		integer size suffixes (e.g. "ULL").
3201
3202- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3203		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3204		forced to a value that ensures that CCSR is not relocated.
3205
3206- Floppy Disk Support:
3207		CONFIG_SYS_FDC_DRIVE_NUMBER
3208
3209		the default drive number (default value 0)
3210
3211		CONFIG_SYS_ISA_IO_STRIDE
3212
3213		defines the spacing between FDC chipset registers
3214		(default value 1)
3215
3216		CONFIG_SYS_ISA_IO_OFFSET
3217
3218		defines the offset of register from address. It
3219		depends on which part of the data bus is connected to
3220		the FDC chipset. (default value 0)
3221
3222		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3223		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3224		default value.
3225
3226		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3227		fdc_hw_init() is called at the beginning of the FDC
3228		setup. fdc_hw_init() must be provided by the board
3229		source code. It is used to make hardware-dependent
3230		initializations.
3231
3232- CONFIG_IDE_AHB:
3233		Most IDE controllers were designed to be connected with PCI
3234		interface. Only few of them were designed for AHB interface.
3235		When software is doing ATA command and data transfer to
3236		IDE devices through IDE-AHB controller, some additional
3237		registers accessing to these kind of IDE-AHB controller
3238		is required.
3239
3240- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3241		DO NOT CHANGE unless you know exactly what you're
3242		doing! (11-4) [MPC8xx systems only]
3243
3244- CONFIG_SYS_INIT_RAM_ADDR:
3245
3246		Start address of memory area that can be used for
3247		initial data and stack; please note that this must be
3248		writable memory that is working WITHOUT special
3249		initialization, i. e. you CANNOT use normal RAM which
3250		will become available only after programming the
3251		memory controller and running certain initialization
3252		sequences.
3253
3254		U-Boot uses the following memory types:
3255		- MPC8xx: IMMR (internal memory of the CPU)
3256
3257- CONFIG_SYS_GBL_DATA_OFFSET:
3258
3259		Offset of the initial data structure in the memory
3260		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3261		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3262		data is located at the end of the available space
3263		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3264		GENERATED_GBL_DATA_SIZE), and the initial stack is just
3265		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3266		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3267
3268	Note:
3269		On the MPC824X (or other systems that use the data
3270		cache for initial memory) the address chosen for
3271		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3272		point to an otherwise UNUSED address space between
3273		the top of RAM and the start of the PCI space.
3274
3275- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3276
3277- CONFIG_SYS_OR_TIMING_SDRAM:
3278		SDRAM timing
3279
3280- CONFIG_SYS_MAMR_PTA:
3281		periodic timer for refresh
3282
3283- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3284  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3285  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3286  CONFIG_SYS_BR1_PRELIM:
3287		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3288
3289- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3290  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3291  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3292		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3293
3294- CONFIG_PCI_ENUM_ONLY
3295		Only scan through and get the devices on the buses.
3296		Don't do any setup work, presumably because someone or
3297		something has already done it, and we don't need to do it
3298		a second time.	Useful for platforms that are pre-booted
3299		by coreboot or similar.
3300
3301- CONFIG_PCI_INDIRECT_BRIDGE:
3302		Enable support for indirect PCI bridges.
3303
3304- CONFIG_SYS_SRIO:
3305		Chip has SRIO or not
3306
3307- CONFIG_SRIO1:
3308		Board has SRIO 1 port available
3309
3310- CONFIG_SRIO2:
3311		Board has SRIO 2 port available
3312
3313- CONFIG_SRIO_PCIE_BOOT_MASTER
3314		Board can support master function for Boot from SRIO and PCIE
3315
3316- CONFIG_SYS_SRIOn_MEM_VIRT:
3317		Virtual Address of SRIO port 'n' memory region
3318
3319- CONFIG_SYS_SRIOn_MEM_PHYS:
3320		Physical Address of SRIO port 'n' memory region
3321
3322- CONFIG_SYS_SRIOn_MEM_SIZE:
3323		Size of SRIO port 'n' memory region
3324
3325- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3326		Defined to tell the NAND controller that the NAND chip is using
3327		a 16 bit bus.
3328		Not all NAND drivers use this symbol.
3329		Example of drivers that use it:
3330		- drivers/mtd/nand/ndfc.c
3331		- drivers/mtd/nand/mxc_nand.c
3332
3333- CONFIG_SYS_NDFC_EBC0_CFG
3334		Sets the EBC0_CFG register for the NDFC. If not defined
3335		a default value will be used.
3336
3337- CONFIG_SPD_EEPROM
3338		Get DDR timing information from an I2C EEPROM. Common
3339		with pluggable memory modules such as SODIMMs
3340
3341  SPD_EEPROM_ADDRESS
3342		I2C address of the SPD EEPROM
3343
3344- CONFIG_SYS_SPD_BUS_NUM
3345		If SPD EEPROM is on an I2C bus other than the first
3346		one, specify here. Note that the value must resolve
3347		to something your driver can deal with.
3348
3349- CONFIG_SYS_DDR_RAW_TIMING
3350		Get DDR timing information from other than SPD. Common with
3351		soldered DDR chips onboard without SPD. DDR raw timing
3352		parameters are extracted from datasheet and hard-coded into
3353		header files or board specific files.
3354
3355- CONFIG_FSL_DDR_INTERACTIVE
3356		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3357
3358- CONFIG_FSL_DDR_SYNC_REFRESH
3359		Enable sync of refresh for multiple controllers.
3360
3361- CONFIG_FSL_DDR_BIST
3362		Enable built-in memory test for Freescale DDR controllers.
3363
3364- CONFIG_SYS_83XX_DDR_USES_CS0
3365		Only for 83xx systems. If specified, then DDR should
3366		be configured using CS0 and CS1 instead of CS2 and CS3.
3367
3368- CONFIG_RMII
3369		Enable RMII mode for all FECs.
3370		Note that this is a global option, we can't
3371		have one FEC in standard MII mode and another in RMII mode.
3372
3373- CONFIG_CRC32_VERIFY
3374		Add a verify option to the crc32 command.
3375		The syntax is:
3376
3377		=> crc32 -v <address> <count> <crc32>
3378
3379		Where address/count indicate a memory area
3380		and crc32 is the correct crc32 which the
3381		area should have.
3382
3383- CONFIG_LOOPW
3384		Add the "loopw" memory command. This only takes effect if
3385		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3386
3387- CONFIG_MX_CYCLIC
3388		Add the "mdc" and "mwc" memory commands. These are cyclic
3389		"md/mw" commands.
3390		Examples:
3391
3392		=> mdc.b 10 4 500
3393		This command will print 4 bytes (10,11,12,13) each 500 ms.
3394
3395		=> mwc.l 100 12345678 10
3396		This command will write 12345678 to address 100 all 10 ms.
3397
3398		This only takes effect if the memory commands are activated
3399		globally (CONFIG_CMD_MEMORY).
3400
3401- CONFIG_SKIP_LOWLEVEL_INIT
3402		[ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3403		low level initializations (like setting up the memory
3404		controller) are omitted and/or U-Boot does not
3405		relocate itself into RAM.
3406
3407		Normally this variable MUST NOT be defined. The only
3408		exception is when U-Boot is loaded (to RAM) by some
3409		other boot loader or by a debugger which performs
3410		these initializations itself.
3411
3412- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3413		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3414		to be skipped. The normal CP15 init (such as enabling the
3415		instruction cache) is still performed.
3416
3417- CONFIG_SPL_BUILD
3418		Modifies the behaviour of start.S when compiling a loader
3419		that is executed before the actual U-Boot. E.g. when
3420		compiling a NAND SPL.
3421
3422- CONFIG_TPL_BUILD
3423		Modifies the behaviour of start.S  when compiling a loader
3424		that is executed after the SPL and before the actual U-Boot.
3425		It is loaded by the SPL.
3426
3427- CONFIG_SYS_MPC85XX_NO_RESETVEC
3428		Only for 85xx systems. If this variable is specified, the section
3429		.resetvec is not kept and the section .bootpg is placed in the
3430		previous 4k of the .text section.
3431
3432- CONFIG_ARCH_MAP_SYSMEM
3433		Generally U-Boot (and in particular the md command) uses
3434		effective address. It is therefore not necessary to regard
3435		U-Boot address as virtual addresses that need to be translated
3436		to physical addresses. However, sandbox requires this, since
3437		it maintains its own little RAM buffer which contains all
3438		addressable memory. This option causes some memory accesses
3439		to be mapped through map_sysmem() / unmap_sysmem().
3440
3441- CONFIG_X86_RESET_VECTOR
3442		If defined, the x86 reset vector code is included. This is not
3443		needed when U-Boot is running from Coreboot.
3444
3445- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
3446		Enables the RTC32K OSC on AM33xx based plattforms
3447
3448- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3449		Option to disable subpage write in NAND driver
3450		driver that uses this:
3451		drivers/mtd/nand/davinci_nand.c
3452
3453Freescale QE/FMAN Firmware Support:
3454-----------------------------------
3455
3456The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3457loading of "firmware", which is encoded in the QE firmware binary format.
3458This firmware often needs to be loaded during U-Boot booting, so macros
3459are used to identify the storage device (NOR flash, SPI, etc) and the address
3460within that device.
3461
3462- CONFIG_SYS_FMAN_FW_ADDR
3463	The address in the storage device where the FMAN microcode is located.  The
3464	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3465	is also specified.
3466
3467- CONFIG_SYS_QE_FW_ADDR
3468	The address in the storage device where the QE microcode is located.  The
3469	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3470	is also specified.
3471
3472- CONFIG_SYS_QE_FMAN_FW_LENGTH
3473	The maximum possible size of the firmware.  The firmware binary format
3474	has a field that specifies the actual size of the firmware, but it
3475	might not be possible to read any part of the firmware unless some
3476	local storage is allocated to hold the entire firmware first.
3477
3478- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3479	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3480	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3481	virtual address in NOR flash.
3482
3483- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3484	Specifies that QE/FMAN firmware is located in NAND flash.
3485	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3486
3487- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3488	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3489	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3490
3491- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3492	Specifies that QE/FMAN firmware is located in the remote (master)
3493	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3494	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3495	window->master inbound window->master LAW->the ucode address in
3496	master's memory space.
3497
3498Freescale Layerscape Management Complex Firmware Support:
3499---------------------------------------------------------
3500The Freescale Layerscape Management Complex (MC) supports the loading of
3501"firmware".
3502This firmware often needs to be loaded during U-Boot booting, so macros
3503are used to identify the storage device (NOR flash, SPI, etc) and the address
3504within that device.
3505
3506- CONFIG_FSL_MC_ENET
3507	Enable the MC driver for Layerscape SoCs.
3508
3509Freescale Layerscape Debug Server Support:
3510-------------------------------------------
3511The Freescale Layerscape Debug Server Support supports the loading of
3512"Debug Server firmware" and triggering SP boot-rom.
3513This firmware often needs to be loaded during U-Boot booting.
3514
3515- CONFIG_SYS_MC_RSV_MEM_ALIGN
3516	Define alignment of reserved memory MC requires
3517
3518Reproducible builds
3519-------------------
3520
3521In order to achieve reproducible builds, timestamps used in the U-Boot build
3522process have to be set to a fixed value.
3523
3524This is done using the SOURCE_DATE_EPOCH environment variable.
3525SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3526option for U-Boot or an environment variable in U-Boot.
3527
3528SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3529
3530Building the Software:
3531======================
3532
3533Building U-Boot has been tested in several native build environments
3534and in many different cross environments. Of course we cannot support
3535all possibly existing versions of cross development tools in all
3536(potentially obsolete) versions. In case of tool chain problems we
3537recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3538which is extensively used to build and test U-Boot.
3539
3540If you are not using a native environment, it is assumed that you
3541have GNU cross compiling tools available in your path. In this case,
3542you must set the environment variable CROSS_COMPILE in your shell.
3543Note that no changes to the Makefile or any other source files are
3544necessary. For example using the ELDK on a 4xx CPU, please enter:
3545
3546	$ CROSS_COMPILE=ppc_4xx-
3547	$ export CROSS_COMPILE
3548
3549Note: If you wish to generate Windows versions of the utilities in
3550      the tools directory you can use the MinGW toolchain
3551      (http://www.mingw.org).  Set your HOST tools to the MinGW
3552      toolchain and execute 'make tools'.  For example:
3553
3554       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3555
3556      Binaries such as tools/mkimage.exe will be created which can
3557      be executed on computers running Windows.
3558
3559U-Boot is intended to be simple to build. After installing the
3560sources you must configure U-Boot for one specific board type. This
3561is done by typing:
3562
3563	make NAME_defconfig
3564
3565where "NAME_defconfig" is the name of one of the existing configu-
3566rations; see boards.cfg for supported names.
3567
3568Note: for some board special configuration names may exist; check if
3569      additional information is available from the board vendor; for
3570      instance, the TQM823L systems are available without (standard)
3571      or with LCD support. You can select such additional "features"
3572      when choosing the configuration, i. e.
3573
3574      make TQM823L_defconfig
3575	- will configure for a plain TQM823L, i. e. no LCD support
3576
3577      make TQM823L_LCD_defconfig
3578	- will configure for a TQM823L with U-Boot console on LCD
3579
3580      etc.
3581
3582
3583Finally, type "make all", and you should get some working U-Boot
3584images ready for download to / installation on your system:
3585
3586- "u-boot.bin" is a raw binary image
3587- "u-boot" is an image in ELF binary format
3588- "u-boot.srec" is in Motorola S-Record format
3589
3590By default the build is performed locally and the objects are saved
3591in the source directory. One of the two methods can be used to change
3592this behavior and build U-Boot to some external directory:
3593
35941. Add O= to the make command line invocations:
3595
3596	make O=/tmp/build distclean
3597	make O=/tmp/build NAME_defconfig
3598	make O=/tmp/build all
3599
36002. Set environment variable KBUILD_OUTPUT to point to the desired location:
3601
3602	export KBUILD_OUTPUT=/tmp/build
3603	make distclean
3604	make NAME_defconfig
3605	make all
3606
3607Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3608variable.
3609
3610User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3611setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3612For example to treat all compiler warnings as errors:
3613
3614	make KCFLAGS=-Werror
3615
3616Please be aware that the Makefiles assume you are using GNU make, so
3617for instance on NetBSD you might need to use "gmake" instead of
3618native "make".
3619
3620
3621If the system board that you have is not listed, then you will need
3622to port U-Boot to your hardware platform. To do this, follow these
3623steps:
3624
36251.  Create a new directory to hold your board specific code. Add any
3626    files you need. In your board directory, you will need at least
3627    the "Makefile" and a "<board>.c".
36282.  Create a new configuration file "include/configs/<board>.h" for
3629    your board.
36303.  If you're porting U-Boot to a new CPU, then also create a new
3631    directory to hold your CPU specific code. Add any files you need.
36324.  Run "make <board>_defconfig" with your new name.
36335.  Type "make", and you should get a working "u-boot.srec" file
3634    to be installed on your target system.
36356.  Debug and solve any problems that might arise.
3636    [Of course, this last step is much harder than it sounds.]
3637
3638
3639Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3640==============================================================
3641
3642If you have modified U-Boot sources (for instance added a new board
3643or support for new devices, a new CPU, etc.) you are expected to
3644provide feedback to the other developers. The feedback normally takes
3645the form of a "patch", i. e. a context diff against a certain (latest
3646official or latest in the git repository) version of U-Boot sources.
3647
3648But before you submit such a patch, please verify that your modifi-
3649cation did not break existing code. At least make sure that *ALL* of
3650the supported boards compile WITHOUT ANY compiler warnings. To do so,
3651just run the buildman script (tools/buildman/buildman), which will
3652configure and build U-Boot for ALL supported system. Be warned, this
3653will take a while. Please see the buildman README, or run 'buildman -H'
3654for documentation.
3655
3656
3657See also "U-Boot Porting Guide" below.
3658
3659
3660Monitor Commands - Overview:
3661============================
3662
3663go	- start application at address 'addr'
3664run	- run commands in an environment variable
3665bootm	- boot application image from memory
3666bootp	- boot image via network using BootP/TFTP protocol
3667bootz   - boot zImage from memory
3668tftpboot- boot image via network using TFTP protocol
3669	       and env variables "ipaddr" and "serverip"
3670	       (and eventually "gatewayip")
3671tftpput - upload a file via network using TFTP protocol
3672rarpboot- boot image via network using RARP/TFTP protocol
3673diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3674loads	- load S-Record file over serial line
3675loadb	- load binary file over serial line (kermit mode)
3676md	- memory display
3677mm	- memory modify (auto-incrementing)
3678nm	- memory modify (constant address)
3679mw	- memory write (fill)
3680cp	- memory copy
3681cmp	- memory compare
3682crc32	- checksum calculation
3683i2c	- I2C sub-system
3684sspi	- SPI utility commands
3685base	- print or set address offset
3686printenv- print environment variables
3687setenv	- set environment variables
3688saveenv - save environment variables to persistent storage
3689protect - enable or disable FLASH write protection
3690erase	- erase FLASH memory
3691flinfo	- print FLASH memory information
3692nand	- NAND memory operations (see doc/README.nand)
3693bdinfo	- print Board Info structure
3694iminfo	- print header information for application image
3695coninfo - print console devices and informations
3696ide	- IDE sub-system
3697loop	- infinite loop on address range
3698loopw	- infinite write loop on address range
3699mtest	- simple RAM test
3700icache	- enable or disable instruction cache
3701dcache	- enable or disable data cache
3702reset	- Perform RESET of the CPU
3703echo	- echo args to console
3704version - print monitor version
3705help	- print online help
3706?	- alias for 'help'
3707
3708
3709Monitor Commands - Detailed Description:
3710========================================
3711
3712TODO.
3713
3714For now: just type "help <command>".
3715
3716
3717Environment Variables:
3718======================
3719
3720U-Boot supports user configuration using Environment Variables which
3721can be made persistent by saving to Flash memory.
3722
3723Environment Variables are set using "setenv", printed using
3724"printenv", and saved to Flash using "saveenv". Using "setenv"
3725without a value can be used to delete a variable from the
3726environment. As long as you don't save the environment you are
3727working with an in-memory copy. In case the Flash area containing the
3728environment is erased by accident, a default environment is provided.
3729
3730Some configuration options can be set using Environment Variables.
3731
3732List of environment variables (most likely not complete):
3733
3734  baudrate	- see CONFIG_BAUDRATE
3735
3736  bootdelay	- see CONFIG_BOOTDELAY
3737
3738  bootcmd	- see CONFIG_BOOTCOMMAND
3739
3740  bootargs	- Boot arguments when booting an RTOS image
3741
3742  bootfile	- Name of the image to load with TFTP
3743
3744  bootm_low	- Memory range available for image processing in the bootm
3745		  command can be restricted. This variable is given as
3746		  a hexadecimal number and defines lowest address allowed
3747		  for use by the bootm command. See also "bootm_size"
3748		  environment variable. Address defined by "bootm_low" is
3749		  also the base of the initial memory mapping for the Linux
3750		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3751		  bootm_mapsize.
3752
3753  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3754		  This variable is given as a hexadecimal number and it
3755		  defines the size of the memory region starting at base
3756		  address bootm_low that is accessible by the Linux kernel
3757		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3758		  as the default value if it is defined, and bootm_size is
3759		  used otherwise.
3760
3761  bootm_size	- Memory range available for image processing in the bootm
3762		  command can be restricted. This variable is given as
3763		  a hexadecimal number and defines the size of the region
3764		  allowed for use by the bootm command. See also "bootm_low"
3765		  environment variable.
3766
3767  updatefile	- Location of the software update file on a TFTP server, used
3768		  by the automatic software update feature. Please refer to
3769		  documentation in doc/README.update for more details.
3770
3771  autoload	- if set to "no" (any string beginning with 'n'),
3772		  "bootp" will just load perform a lookup of the
3773		  configuration from the BOOTP server, but not try to
3774		  load any image using TFTP
3775
3776  autostart	- if set to "yes", an image loaded using the "bootp",
3777		  "rarpboot", "tftpboot" or "diskboot" commands will
3778		  be automatically started (by internally calling
3779		  "bootm")
3780
3781		  If set to "no", a standalone image passed to the
3782		  "bootm" command will be copied to the load address
3783		  (and eventually uncompressed), but NOT be started.
3784		  This can be used to load and uncompress arbitrary
3785		  data.
3786
3787  fdt_high	- if set this restricts the maximum address that the
3788		  flattened device tree will be copied into upon boot.
3789		  For example, if you have a system with 1 GB memory
3790		  at physical address 0x10000000, while Linux kernel
3791		  only recognizes the first 704 MB as low memory, you
3792		  may need to set fdt_high as 0x3C000000 to have the
3793		  device tree blob be copied to the maximum address
3794		  of the 704 MB low memory, so that Linux kernel can
3795		  access it during the boot procedure.
3796
3797		  If this is set to the special value 0xFFFFFFFF then
3798		  the fdt will not be copied at all on boot.  For this
3799		  to work it must reside in writable memory, have
3800		  sufficient padding on the end of it for u-boot to
3801		  add the information it needs into it, and the memory
3802		  must be accessible by the kernel.
3803
3804  fdtcontroladdr- if set this is the address of the control flattened
3805		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3806		  defined.
3807
3808  i2cfast	- (PPC405GP|PPC405EP only)
3809		  if set to 'y' configures Linux I2C driver for fast
3810		  mode (400kHZ). This environment variable is used in
3811		  initialization code. So, for changes to be effective
3812		  it must be saved and board must be reset.
3813
3814  initrd_high	- restrict positioning of initrd images:
3815		  If this variable is not set, initrd images will be
3816		  copied to the highest possible address in RAM; this
3817		  is usually what you want since it allows for
3818		  maximum initrd size. If for some reason you want to
3819		  make sure that the initrd image is loaded below the
3820		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3821		  variable to a value of "no" or "off" or "0".
3822		  Alternatively, you can set it to a maximum upper
3823		  address to use (U-Boot will still check that it
3824		  does not overwrite the U-Boot stack and data).
3825
3826		  For instance, when you have a system with 16 MB
3827		  RAM, and want to reserve 4 MB from use by Linux,
3828		  you can do this by adding "mem=12M" to the value of
3829		  the "bootargs" variable. However, now you must make
3830		  sure that the initrd image is placed in the first
3831		  12 MB as well - this can be done with
3832
3833		  setenv initrd_high 00c00000
3834
3835		  If you set initrd_high to 0xFFFFFFFF, this is an
3836		  indication to U-Boot that all addresses are legal
3837		  for the Linux kernel, including addresses in flash
3838		  memory. In this case U-Boot will NOT COPY the
3839		  ramdisk at all. This may be useful to reduce the
3840		  boot time on your system, but requires that this
3841		  feature is supported by your Linux kernel.
3842
3843  ipaddr	- IP address; needed for tftpboot command
3844
3845  loadaddr	- Default load address for commands like "bootp",
3846		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3847
3848  loads_echo	- see CONFIG_LOADS_ECHO
3849
3850  serverip	- TFTP server IP address; needed for tftpboot command
3851
3852  bootretry	- see CONFIG_BOOT_RETRY_TIME
3853
3854  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3855
3856  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3857
3858  ethprime	- controls which interface is used first.
3859
3860  ethact	- controls which interface is currently active.
3861		  For example you can do the following
3862
3863		  => setenv ethact FEC
3864		  => ping 192.168.0.1 # traffic sent on FEC
3865		  => setenv ethact SCC
3866		  => ping 10.0.0.1 # traffic sent on SCC
3867
3868  ethrotate	- When set to "no" U-Boot does not go through all
3869		  available network interfaces.
3870		  It just stays at the currently selected interface.
3871
3872  netretry	- When set to "no" each network operation will
3873		  either succeed or fail without retrying.
3874		  When set to "once" the network operation will
3875		  fail when all the available network interfaces
3876		  are tried once without success.
3877		  Useful on scripts which control the retry operation
3878		  themselves.
3879
3880  npe_ucode	- set load address for the NPE microcode
3881
3882  silent_linux  - If set then Linux will be told to boot silently, by
3883		  changing the console to be empty. If "yes" it will be
3884		  made silent. If "no" it will not be made silent. If
3885		  unset, then it will be made silent if the U-Boot console
3886		  is silent.
3887
3888  tftpsrcp	- If this is set, the value is used for TFTP's
3889		  UDP source port.
3890
3891  tftpdstp	- If this is set, the value is used for TFTP's UDP
3892		  destination port instead of the Well Know Port 69.
3893
3894  tftpblocksize - Block size to use for TFTP transfers; if not set,
3895		  we use the TFTP server's default block size
3896
3897  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3898		  seconds, minimum value is 1000 = 1 second). Defines
3899		  when a packet is considered to be lost so it has to
3900		  be retransmitted. The default is 5000 = 5 seconds.
3901		  Lowering this value may make downloads succeed
3902		  faster in networks with high packet loss rates or
3903		  with unreliable TFTP servers.
3904
3905  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
3906		  unit, minimum value = 0). Defines how many timeouts
3907		  can happen during a single file transfer before that
3908		  transfer is aborted. The default is 10, and 0 means
3909		  'no timeouts allowed'. Increasing this value may help
3910		  downloads succeed with high packet loss rates, or with
3911		  unreliable TFTP servers or client hardware.
3912
3913  vlan		- When set to a value < 4095 the traffic over
3914		  Ethernet is encapsulated/received over 802.1q
3915		  VLAN tagged frames.
3916
3917  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
3918		  Unsigned value, in milliseconds. If not set, the period will
3919		  be either the default (28000), or a value based on
3920		  CONFIG_NET_RETRY_COUNT, if defined. This value has
3921		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3922
3923The following image location variables contain the location of images
3924used in booting. The "Image" column gives the role of the image and is
3925not an environment variable name. The other columns are environment
3926variable names. "File Name" gives the name of the file on a TFTP
3927server, "RAM Address" gives the location in RAM the image will be
3928loaded to, and "Flash Location" gives the image's address in NOR
3929flash or offset in NAND flash.
3930
3931*Note* - these variables don't have to be defined for all boards, some
3932boards currently use other variables for these purposes, and some
3933boards use these variables for other purposes.
3934
3935Image		    File Name	     RAM Address       Flash Location
3936-----		    ---------	     -----------       --------------
3937u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
3938Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
3939device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
3940ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
3941
3942The following environment variables may be used and automatically
3943updated by the network boot commands ("bootp" and "rarpboot"),
3944depending the information provided by your boot server:
3945
3946  bootfile	- see above
3947  dnsip		- IP address of your Domain Name Server
3948  dnsip2	- IP address of your secondary Domain Name Server
3949  gatewayip	- IP address of the Gateway (Router) to use
3950  hostname	- Target hostname
3951  ipaddr	- see above
3952  netmask	- Subnet Mask
3953  rootpath	- Pathname of the root filesystem on the NFS server
3954  serverip	- see above
3955
3956
3957There are two special Environment Variables:
3958
3959  serial#	- contains hardware identification information such
3960		  as type string and/or serial number
3961  ethaddr	- Ethernet address
3962
3963These variables can be set only once (usually during manufacturing of
3964the board). U-Boot refuses to delete or overwrite these variables
3965once they have been set once.
3966
3967
3968Further special Environment Variables:
3969
3970  ver		- Contains the U-Boot version string as printed
3971		  with the "version" command. This variable is
3972		  readonly (see CONFIG_VERSION_VARIABLE).
3973
3974
3975Please note that changes to some configuration parameters may take
3976only effect after the next boot (yes, that's just like Windoze :-).
3977
3978
3979Callback functions for environment variables:
3980---------------------------------------------
3981
3982For some environment variables, the behavior of u-boot needs to change
3983when their values are changed.  This functionality allows functions to
3984be associated with arbitrary variables.  On creation, overwrite, or
3985deletion, the callback will provide the opportunity for some side
3986effect to happen or for the change to be rejected.
3987
3988The callbacks are named and associated with a function using the
3989U_BOOT_ENV_CALLBACK macro in your board or driver code.
3990
3991These callbacks are associated with variables in one of two ways.  The
3992static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3993in the board configuration to a string that defines a list of
3994associations.  The list must be in the following format:
3995
3996	entry = variable_name[:callback_name]
3997	list = entry[,list]
3998
3999If the callback name is not specified, then the callback is deleted.
4000Spaces are also allowed anywhere in the list.
4001
4002Callbacks can also be associated by defining the ".callbacks" variable
4003with the same list format above.  Any association in ".callbacks" will
4004override any association in the static list. You can define
4005CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
4006".callbacks" environment variable in the default or embedded environment.
4007
4008If CONFIG_REGEX is defined, the variable_name above is evaluated as a
4009regular expression. This allows multiple variables to be connected to
4010the same callback without explicitly listing them all out.
4011
4012
4013Command Line Parsing:
4014=====================
4015
4016There are two different command line parsers available with U-Boot:
4017the old "simple" one, and the much more powerful "hush" shell:
4018
4019Old, simple command line parser:
4020--------------------------------
4021
4022- supports environment variables (through setenv / saveenv commands)
4023- several commands on one line, separated by ';'
4024- variable substitution using "... ${name} ..." syntax
4025- special characters ('$', ';') can be escaped by prefixing with '\',
4026  for example:
4027	setenv bootcmd bootm \${address}
4028- You can also escape text by enclosing in single apostrophes, for example:
4029	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4030
4031Hush shell:
4032-----------
4033
4034- similar to Bourne shell, with control structures like
4035  if...then...else...fi, for...do...done; while...do...done,
4036  until...do...done, ...
4037- supports environment ("global") variables (through setenv / saveenv
4038  commands) and local shell variables (through standard shell syntax
4039  "name=value"); only environment variables can be used with "run"
4040  command
4041
4042General rules:
4043--------------
4044
4045(1) If a command line (or an environment variable executed by a "run"
4046    command) contains several commands separated by semicolon, and
4047    one of these commands fails, then the remaining commands will be
4048    executed anyway.
4049
4050(2) If you execute several variables with one call to run (i. e.
4051    calling run with a list of variables as arguments), any failing
4052    command will cause "run" to terminate, i. e. the remaining
4053    variables are not executed.
4054
4055Note for Redundant Ethernet Interfaces:
4056=======================================
4057
4058Some boards come with redundant Ethernet interfaces; U-Boot supports
4059such configurations and is capable of automatic selection of a
4060"working" interface when needed. MAC assignment works as follows:
4061
4062Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4063MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4064"eth1addr" (=>eth1), "eth2addr", ...
4065
4066If the network interface stores some valid MAC address (for instance
4067in SROM), this is used as default address if there is NO correspon-
4068ding setting in the environment; if the corresponding environment
4069variable is set, this overrides the settings in the card; that means:
4070
4071o If the SROM has a valid MAC address, and there is no address in the
4072  environment, the SROM's address is used.
4073
4074o If there is no valid address in the SROM, and a definition in the
4075  environment exists, then the value from the environment variable is
4076  used.
4077
4078o If both the SROM and the environment contain a MAC address, and
4079  both addresses are the same, this MAC address is used.
4080
4081o If both the SROM and the environment contain a MAC address, and the
4082  addresses differ, the value from the environment is used and a
4083  warning is printed.
4084
4085o If neither SROM nor the environment contain a MAC address, an error
4086  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4087  a random, locally-assigned MAC is used.
4088
4089If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4090will be programmed into hardware as part of the initialization process.	 This
4091may be skipped by setting the appropriate 'ethmacskip' environment variable.
4092The naming convention is as follows:
4093"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4094
4095Image Formats:
4096==============
4097
4098U-Boot is capable of booting (and performing other auxiliary operations on)
4099images in two formats:
4100
4101New uImage format (FIT)
4102-----------------------
4103
4104Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4105to Flattened Device Tree). It allows the use of images with multiple
4106components (several kernels, ramdisks, etc.), with contents protected by
4107SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4108
4109
4110Old uImage format
4111-----------------
4112
4113Old image format is based on binary files which can be basically anything,
4114preceded by a special header; see the definitions in include/image.h for
4115details; basically, the header defines the following image properties:
4116
4117* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4118  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4119  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4120  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4121  INTEGRITY).
4122* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4123  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4124  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4125* Compression Type (uncompressed, gzip, bzip2)
4126* Load Address
4127* Entry Point
4128* Image Name
4129* Image Timestamp
4130
4131The header is marked by a special Magic Number, and both the header
4132and the data portions of the image are secured against corruption by
4133CRC32 checksums.
4134
4135
4136Linux Support:
4137==============
4138
4139Although U-Boot should support any OS or standalone application
4140easily, the main focus has always been on Linux during the design of
4141U-Boot.
4142
4143U-Boot includes many features that so far have been part of some
4144special "boot loader" code within the Linux kernel. Also, any
4145"initrd" images to be used are no longer part of one big Linux image;
4146instead, kernel and "initrd" are separate images. This implementation
4147serves several purposes:
4148
4149- the same features can be used for other OS or standalone
4150  applications (for instance: using compressed images to reduce the
4151  Flash memory footprint)
4152
4153- it becomes much easier to port new Linux kernel versions because
4154  lots of low-level, hardware dependent stuff are done by U-Boot
4155
4156- the same Linux kernel image can now be used with different "initrd"
4157  images; of course this also means that different kernel images can
4158  be run with the same "initrd". This makes testing easier (you don't
4159  have to build a new "zImage.initrd" Linux image when you just
4160  change a file in your "initrd"). Also, a field-upgrade of the
4161  software is easier now.
4162
4163
4164Linux HOWTO:
4165============
4166
4167Porting Linux to U-Boot based systems:
4168---------------------------------------
4169
4170U-Boot cannot save you from doing all the necessary modifications to
4171configure the Linux device drivers for use with your target hardware
4172(no, we don't intend to provide a full virtual machine interface to
4173Linux :-).
4174
4175But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4176
4177Just make sure your machine specific header file (for instance
4178include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4179Information structure as we define in include/asm-<arch>/u-boot.h,
4180and make sure that your definition of IMAP_ADDR uses the same value
4181as your U-Boot configuration in CONFIG_SYS_IMMR.
4182
4183Note that U-Boot now has a driver model, a unified model for drivers.
4184If you are adding a new driver, plumb it into driver model. If there
4185is no uclass available, you are encouraged to create one. See
4186doc/driver-model.
4187
4188
4189Configuring the Linux kernel:
4190-----------------------------
4191
4192No specific requirements for U-Boot. Make sure you have some root
4193device (initial ramdisk, NFS) for your target system.
4194
4195
4196Building a Linux Image:
4197-----------------------
4198
4199With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4200not used. If you use recent kernel source, a new build target
4201"uImage" will exist which automatically builds an image usable by
4202U-Boot. Most older kernels also have support for a "pImage" target,
4203which was introduced for our predecessor project PPCBoot and uses a
4204100% compatible format.
4205
4206Example:
4207
4208	make TQM850L_defconfig
4209	make oldconfig
4210	make dep
4211	make uImage
4212
4213The "uImage" build target uses a special tool (in 'tools/mkimage') to
4214encapsulate a compressed Linux kernel image with header	 information,
4215CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4216
4217* build a standard "vmlinux" kernel image (in ELF binary format):
4218
4219* convert the kernel into a raw binary image:
4220
4221	${CROSS_COMPILE}-objcopy -O binary \
4222				 -R .note -R .comment \
4223				 -S vmlinux linux.bin
4224
4225* compress the binary image:
4226
4227	gzip -9 linux.bin
4228
4229* package compressed binary image for U-Boot:
4230
4231	mkimage -A ppc -O linux -T kernel -C gzip \
4232		-a 0 -e 0 -n "Linux Kernel Image" \
4233		-d linux.bin.gz uImage
4234
4235
4236The "mkimage" tool can also be used to create ramdisk images for use
4237with U-Boot, either separated from the Linux kernel image, or
4238combined into one file. "mkimage" encapsulates the images with a 64
4239byte header containing information about target architecture,
4240operating system, image type, compression method, entry points, time
4241stamp, CRC32 checksums, etc.
4242
4243"mkimage" can be called in two ways: to verify existing images and
4244print the header information, or to build new images.
4245
4246In the first form (with "-l" option) mkimage lists the information
4247contained in the header of an existing U-Boot image; this includes
4248checksum verification:
4249
4250	tools/mkimage -l image
4251	  -l ==> list image header information
4252
4253The second form (with "-d" option) is used to build a U-Boot image
4254from a "data file" which is used as image payload:
4255
4256	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4257		      -n name -d data_file image
4258	  -A ==> set architecture to 'arch'
4259	  -O ==> set operating system to 'os'
4260	  -T ==> set image type to 'type'
4261	  -C ==> set compression type 'comp'
4262	  -a ==> set load address to 'addr' (hex)
4263	  -e ==> set entry point to 'ep' (hex)
4264	  -n ==> set image name to 'name'
4265	  -d ==> use image data from 'datafile'
4266
4267Right now, all Linux kernels for PowerPC systems use the same load
4268address (0x00000000), but the entry point address depends on the
4269kernel version:
4270
4271- 2.2.x kernels have the entry point at 0x0000000C,
4272- 2.3.x and later kernels have the entry point at 0x00000000.
4273
4274So a typical call to build a U-Boot image would read:
4275
4276	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4277	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4278	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4279	> examples/uImage.TQM850L
4280	Image Name:   2.4.4 kernel for TQM850L
4281	Created:      Wed Jul 19 02:34:59 2000
4282	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4283	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4284	Load Address: 0x00000000
4285	Entry Point:  0x00000000
4286
4287To verify the contents of the image (or check for corruption):
4288
4289	-> tools/mkimage -l examples/uImage.TQM850L
4290	Image Name:   2.4.4 kernel for TQM850L
4291	Created:      Wed Jul 19 02:34:59 2000
4292	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4293	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4294	Load Address: 0x00000000
4295	Entry Point:  0x00000000
4296
4297NOTE: for embedded systems where boot time is critical you can trade
4298speed for memory and install an UNCOMPRESSED image instead: this
4299needs more space in Flash, but boots much faster since it does not
4300need to be uncompressed:
4301
4302	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4303	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4304	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4305	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4306	> examples/uImage.TQM850L-uncompressed
4307	Image Name:   2.4.4 kernel for TQM850L
4308	Created:      Wed Jul 19 02:34:59 2000
4309	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4310	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4311	Load Address: 0x00000000
4312	Entry Point:  0x00000000
4313
4314
4315Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4316when your kernel is intended to use an initial ramdisk:
4317
4318	-> tools/mkimage -n 'Simple Ramdisk Image' \
4319	> -A ppc -O linux -T ramdisk -C gzip \
4320	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4321	Image Name:   Simple Ramdisk Image
4322	Created:      Wed Jan 12 14:01:50 2000
4323	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4324	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4325	Load Address: 0x00000000
4326	Entry Point:  0x00000000
4327
4328The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4329option performs the converse operation of the mkimage's second form (the "-d"
4330option). Given an image built by mkimage, the dumpimage extracts a "data file"
4331from the image:
4332
4333	tools/dumpimage -i image -T type -p position data_file
4334	  -i ==> extract from the 'image' a specific 'data_file'
4335	  -T ==> set image type to 'type'
4336	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4337
4338
4339Installing a Linux Image:
4340-------------------------
4341
4342To downloading a U-Boot image over the serial (console) interface,
4343you must convert the image to S-Record format:
4344
4345	objcopy -I binary -O srec examples/image examples/image.srec
4346
4347The 'objcopy' does not understand the information in the U-Boot
4348image header, so the resulting S-Record file will be relative to
4349address 0x00000000. To load it to a given address, you need to
4350specify the target address as 'offset' parameter with the 'loads'
4351command.
4352
4353Example: install the image to address 0x40100000 (which on the
4354TQM8xxL is in the first Flash bank):
4355
4356	=> erase 40100000 401FFFFF
4357
4358	.......... done
4359	Erased 8 sectors
4360
4361	=> loads 40100000
4362	## Ready for S-Record download ...
4363	~>examples/image.srec
4364	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4365	...
4366	15989 15990 15991 15992
4367	[file transfer complete]
4368	[connected]
4369	## Start Addr = 0x00000000
4370
4371
4372You can check the success of the download using the 'iminfo' command;
4373this includes a checksum verification so you can be sure no data
4374corruption happened:
4375
4376	=> imi 40100000
4377
4378	## Checking Image 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
4386
4387Boot Linux:
4388-----------
4389
4390The "bootm" command is used to boot an application that is stored in
4391memory (RAM or Flash). In case of a Linux kernel image, the contents
4392of the "bootargs" environment variable is passed to the kernel as
4393parameters. You can check and modify this variable using the
4394"printenv" and "setenv" commands:
4395
4396
4397	=> printenv bootargs
4398	bootargs=root=/dev/ram
4399
4400	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4401
4402	=> printenv bootargs
4403	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4404
4405	=> bootm 40020000
4406	## Booting Linux kernel at 40020000 ...
4407	   Image Name:	 2.2.13 for NFS on TQM850L
4408	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4409	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4410	   Load Address: 00000000
4411	   Entry Point:	 0000000c
4412	   Verifying Checksum ... OK
4413	   Uncompressing Kernel Image ... OK
4414	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
4415	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4416	time_init: decrementer frequency = 187500000/60
4417	Calibrating delay loop... 49.77 BogoMIPS
4418	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4419	...
4420
4421If you want to boot a Linux kernel with initial RAM disk, you pass
4422the memory addresses of both the kernel and the initrd image (PPBCOOT
4423format!) to the "bootm" command:
4424
4425	=> imi 40100000 40200000
4426
4427	## Checking Image at 40100000 ...
4428	   Image Name:	 2.2.13 for initrd on TQM850L
4429	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4430	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4431	   Load Address: 00000000
4432	   Entry Point:	 0000000c
4433	   Verifying Checksum ... OK
4434
4435	## Checking Image at 40200000 ...
4436	   Image Name:	 Simple Ramdisk Image
4437	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4438	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4439	   Load Address: 00000000
4440	   Entry Point:	 00000000
4441	   Verifying Checksum ... OK
4442
4443	=> bootm 40100000 40200000
4444	## Booting Linux kernel at 40100000 ...
4445	   Image Name:	 2.2.13 for initrd on TQM850L
4446	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4447	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4448	   Load Address: 00000000
4449	   Entry Point:	 0000000c
4450	   Verifying Checksum ... OK
4451	   Uncompressing Kernel Image ... OK
4452	## Loading RAMDisk Image at 40200000 ...
4453	   Image Name:	 Simple Ramdisk Image
4454	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4455	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4456	   Load Address: 00000000
4457	   Entry Point:	 00000000
4458	   Verifying Checksum ... OK
4459	   Loading Ramdisk ... OK
4460	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
4461	Boot arguments: root=/dev/ram
4462	time_init: decrementer frequency = 187500000/60
4463	Calibrating delay loop... 49.77 BogoMIPS
4464	...
4465	RAMDISK: Compressed image found at block 0
4466	VFS: Mounted root (ext2 filesystem).
4467
4468	bash#
4469
4470Boot Linux and pass a flat device tree:
4471-----------
4472
4473First, U-Boot must be compiled with the appropriate defines. See the section
4474titled "Linux Kernel Interface" above for a more in depth explanation. The
4475following is an example of how to start a kernel and pass an updated
4476flat device tree:
4477
4478=> print oftaddr
4479oftaddr=0x300000
4480=> print oft
4481oft=oftrees/mpc8540ads.dtb
4482=> tftp $oftaddr $oft
4483Speed: 1000, full duplex
4484Using TSEC0 device
4485TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4486Filename 'oftrees/mpc8540ads.dtb'.
4487Load address: 0x300000
4488Loading: #
4489done
4490Bytes transferred = 4106 (100a hex)
4491=> tftp $loadaddr $bootfile
4492Speed: 1000, full duplex
4493Using TSEC0 device
4494TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4495Filename 'uImage'.
4496Load address: 0x200000
4497Loading:############
4498done
4499Bytes transferred = 1029407 (fb51f hex)
4500=> print loadaddr
4501loadaddr=200000
4502=> print oftaddr
4503oftaddr=0x300000
4504=> bootm $loadaddr - $oftaddr
4505## Booting image at 00200000 ...
4506   Image Name:	 Linux-2.6.17-dirty
4507   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4508   Data Size:	 1029343 Bytes = 1005.2 kB
4509   Load Address: 00000000
4510   Entry Point:	 00000000
4511   Verifying Checksum ... OK
4512   Uncompressing Kernel Image ... OK
4513Booting using flat device tree at 0x300000
4514Using MPC85xx ADS machine description
4515Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4516[snip]
4517
4518
4519More About U-Boot Image Types:
4520------------------------------
4521
4522U-Boot supports the following image types:
4523
4524   "Standalone Programs" are directly runnable in the environment
4525	provided by U-Boot; it is expected that (if they behave
4526	well) you can continue to work in U-Boot after return from
4527	the Standalone Program.
4528   "OS Kernel Images" are usually images of some Embedded OS which
4529	will take over control completely. Usually these programs
4530	will install their own set of exception handlers, device
4531	drivers, set up the MMU, etc. - this means, that you cannot
4532	expect to re-enter U-Boot except by resetting the CPU.
4533   "RAMDisk Images" are more or less just data blocks, and their
4534	parameters (address, size) are passed to an OS kernel that is
4535	being started.
4536   "Multi-File Images" contain several images, typically an OS
4537	(Linux) kernel image and one or more data images like
4538	RAMDisks. This construct is useful for instance when you want
4539	to boot over the network using BOOTP etc., where the boot
4540	server provides just a single image file, but you want to get
4541	for instance an OS kernel and a RAMDisk image.
4542
4543	"Multi-File Images" start with a list of image sizes, each
4544	image size (in bytes) specified by an "uint32_t" in network
4545	byte order. This list is terminated by an "(uint32_t)0".
4546	Immediately after the terminating 0 follow the images, one by
4547	one, all aligned on "uint32_t" boundaries (size rounded up to
4548	a multiple of 4 bytes).
4549
4550   "Firmware Images" are binary images containing firmware (like
4551	U-Boot or FPGA images) which usually will be programmed to
4552	flash memory.
4553
4554   "Script files" are command sequences that will be executed by
4555	U-Boot's command interpreter; this feature is especially
4556	useful when you configure U-Boot to use a real shell (hush)
4557	as command interpreter.
4558
4559Booting the Linux zImage:
4560-------------------------
4561
4562On some platforms, it's possible to boot Linux zImage. This is done
4563using the "bootz" command. The syntax of "bootz" command is the same
4564as the syntax of "bootm" command.
4565
4566Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4567kernel with raw initrd images. The syntax is slightly different, the
4568address of the initrd must be augmented by it's size, in the following
4569format: "<initrd addres>:<initrd size>".
4570
4571
4572Standalone HOWTO:
4573=================
4574
4575One of the features of U-Boot is that you can dynamically load and
4576run "standalone" applications, which can use some resources of
4577U-Boot like console I/O functions or interrupt services.
4578
4579Two simple examples are included with the sources:
4580
4581"Hello World" Demo:
4582-------------------
4583
4584'examples/hello_world.c' contains a small "Hello World" Demo
4585application; it is automatically compiled when you build U-Boot.
4586It's configured to run at address 0x00040004, so you can play with it
4587like that:
4588
4589	=> loads
4590	## Ready for S-Record download ...
4591	~>examples/hello_world.srec
4592	1 2 3 4 5 6 7 8 9 10 11 ...
4593	[file transfer complete]
4594	[connected]
4595	## Start Addr = 0x00040004
4596
4597	=> go 40004 Hello World! This is a test.
4598	## Starting application at 0x00040004 ...
4599	Hello World
4600	argc = 7
4601	argv[0] = "40004"
4602	argv[1] = "Hello"
4603	argv[2] = "World!"
4604	argv[3] = "This"
4605	argv[4] = "is"
4606	argv[5] = "a"
4607	argv[6] = "test."
4608	argv[7] = "<NULL>"
4609	Hit any key to exit ...
4610
4611	## Application terminated, rc = 0x0
4612
4613Another example, which demonstrates how to register a CPM interrupt
4614handler with the U-Boot code, can be found in 'examples/timer.c'.
4615Here, a CPM timer is set up to generate an interrupt every second.
4616The interrupt service routine is trivial, just printing a '.'
4617character, but this is just a demo program. The application can be
4618controlled by the following keys:
4619
4620	? - print current values og the CPM Timer registers
4621	b - enable interrupts and start timer
4622	e - stop timer and disable interrupts
4623	q - quit application
4624
4625	=> loads
4626	## Ready for S-Record download ...
4627	~>examples/timer.srec
4628	1 2 3 4 5 6 7 8 9 10 11 ...
4629	[file transfer complete]
4630	[connected]
4631	## Start Addr = 0x00040004
4632
4633	=> go 40004
4634	## Starting application at 0x00040004 ...
4635	TIMERS=0xfff00980
4636	Using timer 1
4637	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4638
4639Hit 'b':
4640	[q, b, e, ?] Set interval 1000000 us
4641	Enabling timer
4642Hit '?':
4643	[q, b, e, ?] ........
4644	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4645Hit '?':
4646	[q, b, e, ?] .
4647	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4648Hit '?':
4649	[q, b, e, ?] .
4650	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4651Hit '?':
4652	[q, b, e, ?] .
4653	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4654Hit 'e':
4655	[q, b, e, ?] ...Stopping timer
4656Hit 'q':
4657	[q, b, e, ?] ## Application terminated, rc = 0x0
4658
4659
4660Minicom warning:
4661================
4662
4663Over time, many people have reported problems when trying to use the
4664"minicom" terminal emulation program for serial download. I (wd)
4665consider minicom to be broken, and recommend not to use it. Under
4666Unix, I recommend to use C-Kermit for general purpose use (and
4667especially for kermit binary protocol download ("loadb" command), and
4668use "cu" for S-Record download ("loads" command).  See
4669http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4670for help with kermit.
4671
4672
4673Nevertheless, if you absolutely want to use it try adding this
4674configuration to your "File transfer protocols" section:
4675
4676	   Name	   Program			Name U/D FullScr IO-Red. Multi
4677	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4678	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4679
4680
4681NetBSD Notes:
4682=============
4683
4684Starting at version 0.9.2, U-Boot supports NetBSD both as host
4685(build U-Boot) and target system (boots NetBSD/mpc8xx).
4686
4687Building requires a cross environment; it is known to work on
4688NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4689need gmake since the Makefiles are not compatible with BSD make).
4690Note that the cross-powerpc package does not install include files;
4691attempting to build U-Boot will fail because <machine/ansi.h> is
4692missing.  This file has to be installed and patched manually:
4693
4694	# cd /usr/pkg/cross/powerpc-netbsd/include
4695	# mkdir powerpc
4696	# ln -s powerpc machine
4697	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4698	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4699
4700Native builds *don't* work due to incompatibilities between native
4701and U-Boot include files.
4702
4703Booting assumes that (the first part of) the image booted is a
4704stage-2 loader which in turn loads and then invokes the kernel
4705proper. Loader sources will eventually appear in the NetBSD source
4706tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4707meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4708
4709
4710Implementation Internals:
4711=========================
4712
4713The following is not intended to be a complete description of every
4714implementation detail. However, it should help to understand the
4715inner workings of U-Boot and make it easier to port it to custom
4716hardware.
4717
4718
4719Initial Stack, Global Data:
4720---------------------------
4721
4722The implementation of U-Boot is complicated by the fact that U-Boot
4723starts running out of ROM (flash memory), usually without access to
4724system RAM (because the memory controller is not initialized yet).
4725This means that we don't have writable Data or BSS segments, and BSS
4726is not initialized as zero. To be able to get a C environment working
4727at all, we have to allocate at least a minimal stack. Implementation
4728options for this are defined and restricted by the CPU used: Some CPU
4729models provide on-chip memory (like the IMMR area on MPC8xx and
4730MPC826x processors), on others (parts of) the data cache can be
4731locked as (mis-) used as memory, etc.
4732
4733	Chris Hallinan posted a good summary of these issues to the
4734	U-Boot mailing list:
4735
4736	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4737	From: "Chris Hallinan" <clh@net1plus.com>
4738	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4739	...
4740
4741	Correct me if I'm wrong, folks, but the way I understand it
4742	is this: Using DCACHE as initial RAM for Stack, etc, does not
4743	require any physical RAM backing up the cache. The cleverness
4744	is that the cache is being used as a temporary supply of
4745	necessary storage before the SDRAM controller is setup. It's
4746	beyond the scope of this list to explain the details, but you
4747	can see how this works by studying the cache architecture and
4748	operation in the architecture and processor-specific manuals.
4749
4750	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4751	is another option for the system designer to use as an
4752	initial stack/RAM area prior to SDRAM being available. Either
4753	option should work for you. Using CS 4 should be fine if your
4754	board designers haven't used it for something that would
4755	cause you grief during the initial boot! It is frequently not
4756	used.
4757
4758	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4759	with your processor/board/system design. The default value
4760	you will find in any recent u-boot distribution in
4761	walnut.h should work for you. I'd set it to a value larger
4762	than your SDRAM module. If you have a 64MB SDRAM module, set
4763	it above 400_0000. Just make sure your board has no resources
4764	that are supposed to respond to that address! That code in
4765	start.S has been around a while and should work as is when
4766	you get the config right.
4767
4768	-Chris Hallinan
4769	DS4.COM, Inc.
4770
4771It is essential to remember this, since it has some impact on the C
4772code for the initialization procedures:
4773
4774* Initialized global data (data segment) is read-only. Do not attempt
4775  to write it.
4776
4777* Do not use any uninitialized global data (or implicitly initialized
4778  as zero data - BSS segment) at all - this is undefined, initiali-
4779  zation is performed later (when relocating to RAM).
4780
4781* Stack space is very limited. Avoid big data buffers or things like
4782  that.
4783
4784Having only the stack as writable memory limits means we cannot use
4785normal global data to share information between the code. But it
4786turned out that the implementation of U-Boot can be greatly
4787simplified by making a global data structure (gd_t) available to all
4788functions. We could pass a pointer to this data as argument to _all_
4789functions, but this would bloat the code. Instead we use a feature of
4790the GCC compiler (Global Register Variables) to share the data: we
4791place a pointer (gd) to the global data into a register which we
4792reserve for this purpose.
4793
4794When choosing a register for such a purpose we are restricted by the
4795relevant  (E)ABI  specifications for the current architecture, and by
4796GCC's implementation.
4797
4798For PowerPC, the following registers have specific use:
4799	R1:	stack pointer
4800	R2:	reserved for system use
4801	R3-R4:	parameter passing and return values
4802	R5-R10: parameter passing
4803	R13:	small data area pointer
4804	R30:	GOT pointer
4805	R31:	frame pointer
4806
4807	(U-Boot also uses R12 as internal GOT pointer. r12
4808	is a volatile register so r12 needs to be reset when
4809	going back and forth between asm and C)
4810
4811    ==> U-Boot will use R2 to hold a pointer to the global data
4812
4813    Note: on PPC, we could use a static initializer (since the
4814    address of the global data structure is known at compile time),
4815    but it turned out that reserving a register results in somewhat
4816    smaller code - although the code savings are not that big (on
4817    average for all boards 752 bytes for the whole U-Boot image,
4818    624 text + 127 data).
4819
4820On ARM, the following registers are used:
4821
4822	R0:	function argument word/integer result
4823	R1-R3:	function argument word
4824	R9:	platform specific
4825	R10:	stack limit (used only if stack checking is enabled)
4826	R11:	argument (frame) pointer
4827	R12:	temporary workspace
4828	R13:	stack pointer
4829	R14:	link register
4830	R15:	program counter
4831
4832    ==> U-Boot will use R9 to hold a pointer to the global data
4833
4834    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4835
4836On Nios II, the ABI is documented here:
4837	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4838
4839    ==> U-Boot will use gp to hold a pointer to the global data
4840
4841    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4842    to access small data sections, so gp is free.
4843
4844On NDS32, the following registers are used:
4845
4846	R0-R1:	argument/return
4847	R2-R5:	argument
4848	R15:	temporary register for assembler
4849	R16:	trampoline register
4850	R28:	frame pointer (FP)
4851	R29:	global pointer (GP)
4852	R30:	link register (LP)
4853	R31:	stack pointer (SP)
4854	PC:	program counter (PC)
4855
4856    ==> U-Boot will use R10 to hold a pointer to the global data
4857
4858NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4859or current versions of GCC may "optimize" the code too much.
4860
4861On RISC-V, the following registers are used:
4862
4863	x0: hard-wired zero (zero)
4864	x1: return address (ra)
4865	x2:	stack pointer (sp)
4866	x3:	global pointer (gp)
4867	x4:	thread pointer (tp)
4868	x5:	link register (t0)
4869	x8:	frame pointer (fp)
4870	x10-x11:	arguments/return values (a0-1)
4871	x12-x17:	arguments (a2-7)
4872	x28-31:	 temporaries (t3-6)
4873	pc:	program counter (pc)
4874
4875    ==> U-Boot will use gp to hold a pointer to the global data
4876
4877Memory Management:
4878------------------
4879
4880U-Boot runs in system state and uses physical addresses, i.e. the
4881MMU is not used either for address mapping nor for memory protection.
4882
4883The available memory is mapped to fixed addresses using the memory
4884controller. In this process, a contiguous block is formed for each
4885memory type (Flash, SDRAM, SRAM), even when it consists of several
4886physical memory banks.
4887
4888U-Boot is installed in the first 128 kB of the first Flash bank (on
4889TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4890booting and sizing and initializing DRAM, the code relocates itself
4891to the upper end of DRAM. Immediately below the U-Boot code some
4892memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4893configuration setting]. Below that, a structure with global Board
4894Info data is placed, followed by the stack (growing downward).
4895
4896Additionally, some exception handler code is copied to the low 8 kB
4897of DRAM (0x00000000 ... 0x00001FFF).
4898
4899So a typical memory configuration with 16 MB of DRAM could look like
4900this:
4901
4902	0x0000 0000	Exception Vector code
4903	      :
4904	0x0000 1FFF
4905	0x0000 2000	Free for Application Use
4906	      :
4907	      :
4908
4909	      :
4910	      :
4911	0x00FB FF20	Monitor Stack (Growing downward)
4912	0x00FB FFAC	Board Info Data and permanent copy of global data
4913	0x00FC 0000	Malloc Arena
4914	      :
4915	0x00FD FFFF
4916	0x00FE 0000	RAM Copy of Monitor Code
4917	...		eventually: LCD or video framebuffer
4918	...		eventually: pRAM (Protected RAM - unchanged by reset)
4919	0x00FF FFFF	[End of RAM]
4920
4921
4922System Initialization:
4923----------------------
4924
4925In the reset configuration, U-Boot starts at the reset entry point
4926(on most PowerPC systems at address 0x00000100). Because of the reset
4927configuration for CS0# this is a mirror of the on board Flash memory.
4928To be able to re-map memory U-Boot then jumps to its link address.
4929To be able to implement the initialization code in C, a (small!)
4930initial stack is set up in the internal Dual Ported RAM (in case CPUs
4931which provide such a feature like), or in a locked part of the data
4932cache. After that, U-Boot initializes the CPU core, the caches and
4933the SIU.
4934
4935Next, all (potentially) available memory banks are mapped using a
4936preliminary mapping. For example, we put them on 512 MB boundaries
4937(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4938on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4939programmed for SDRAM access. Using the temporary configuration, a
4940simple memory test is run that determines the size of the SDRAM
4941banks.
4942
4943When there is more than one SDRAM bank, and the banks are of
4944different size, the largest is mapped first. For equal size, the first
4945bank (CS2#) is mapped first. The first mapping is always for address
49460x00000000, with any additional banks following immediately to create
4947contiguous memory starting from 0.
4948
4949Then, the monitor installs itself at the upper end of the SDRAM area
4950and allocates memory for use by malloc() and for the global Board
4951Info data; also, the exception vector code is copied to the low RAM
4952pages, and the final stack is set up.
4953
4954Only after this relocation will you have a "normal" C environment;
4955until that you are restricted in several ways, mostly because you are
4956running from ROM, and because the code will have to be relocated to a
4957new address in RAM.
4958
4959
4960U-Boot Porting Guide:
4961----------------------
4962
4963[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4964list, October 2002]
4965
4966
4967int main(int argc, char *argv[])
4968{
4969	sighandler_t no_more_time;
4970
4971	signal(SIGALRM, no_more_time);
4972	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4973
4974	if (available_money > available_manpower) {
4975		Pay consultant to port U-Boot;
4976		return 0;
4977	}
4978
4979	Download latest U-Boot source;
4980
4981	Subscribe to u-boot mailing list;
4982
4983	if (clueless)
4984		email("Hi, I am new to U-Boot, how do I get started?");
4985
4986	while (learning) {
4987		Read the README file in the top level directory;
4988		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4989		Read applicable doc/*.README;
4990		Read the source, Luke;
4991		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
4992	}
4993
4994	if (available_money > toLocalCurrency ($2500))
4995		Buy a BDI3000;
4996	else
4997		Add a lot of aggravation and time;
4998
4999	if (a similar board exists) {	/* hopefully... */
5000		cp -a board/<similar> board/<myboard>
5001		cp include/configs/<similar>.h include/configs/<myboard>.h
5002	} else {
5003		Create your own board support subdirectory;
5004		Create your own board include/configs/<myboard>.h file;
5005	}
5006	Edit new board/<myboard> files
5007	Edit new include/configs/<myboard>.h
5008
5009	while (!accepted) {
5010		while (!running) {
5011			do {
5012				Add / modify source code;
5013			} until (compiles);
5014			Debug;
5015			if (clueless)
5016				email("Hi, I am having problems...");
5017		}
5018		Send patch file to the U-Boot email list;
5019		if (reasonable critiques)
5020			Incorporate improvements from email list code review;
5021		else
5022			Defend code as written;
5023	}
5024
5025	return 0;
5026}
5027
5028void no_more_time (int sig)
5029{
5030      hire_a_guru();
5031}
5032
5033
5034Coding Standards:
5035-----------------
5036
5037All contributions to U-Boot should conform to the Linux kernel
5038coding style; see the kernel coding style guide at
5039https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
5040script "scripts/Lindent" in your Linux kernel source directory.
5041
5042Source files originating from a different project (for example the
5043MTD subsystem) are generally exempt from these guidelines and are not
5044reformatted to ease subsequent migration to newer versions of those
5045sources.
5046
5047Please note that U-Boot is implemented in C (and to some small parts in
5048Assembler); no C++ is used, so please do not use C++ style comments (//)
5049in your code.
5050
5051Please also stick to the following formatting rules:
5052- remove any trailing white space
5053- use TAB characters for indentation and vertical alignment, not spaces
5054- make sure NOT to use DOS '\r\n' line feeds
5055- do not add more than 2 consecutive empty lines to source files
5056- do not add trailing empty lines to source files
5057
5058Submissions which do not conform to the standards may be returned
5059with a request to reformat the changes.
5060
5061
5062Submitting Patches:
5063-------------------
5064
5065Since the number of patches for U-Boot is growing, we need to
5066establish some rules. Submissions which do not conform to these rules
5067may be rejected, even when they contain important and valuable stuff.
5068
5069Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5070
5071Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5072see https://lists.denx.de/listinfo/u-boot
5073
5074When you send a patch, please include the following information with
5075it:
5076
5077* For bug fixes: a description of the bug and how your patch fixes
5078  this bug. Please try to include a way of demonstrating that the
5079  patch actually fixes something.
5080
5081* For new features: a description of the feature and your
5082  implementation.
5083
5084* A CHANGELOG entry as plaintext (separate from the patch)
5085
5086* For major contributions, add a MAINTAINERS file with your
5087  information and associated file and directory references.
5088
5089* When you add support for a new board, don't forget to add a
5090  maintainer e-mail address to the boards.cfg file, too.
5091
5092* If your patch adds new configuration options, don't forget to
5093  document these in the README file.
5094
5095* The patch itself. If you are using git (which is *strongly*
5096  recommended) you can easily generate the patch using the
5097  "git format-patch". If you then use "git send-email" to send it to
5098  the U-Boot mailing list, you will avoid most of the common problems
5099  with some other mail clients.
5100
5101  If you cannot use git, use "diff -purN OLD NEW". If your version of
5102  diff does not support these options, then get the latest version of
5103  GNU diff.
5104
5105  The current directory when running this command shall be the parent
5106  directory of the U-Boot source tree (i. e. please make sure that
5107  your patch includes sufficient directory information for the
5108  affected files).
5109
5110  We prefer patches as plain text. MIME attachments are discouraged,
5111  and compressed attachments must not be used.
5112
5113* If one logical set of modifications affects or creates several
5114  files, all these changes shall be submitted in a SINGLE patch file.
5115
5116* Changesets that contain different, unrelated modifications shall be
5117  submitted as SEPARATE patches, one patch per changeset.
5118
5119
5120Notes:
5121
5122* Before sending the patch, run the buildman script on your patched
5123  source tree and make sure that no errors or warnings are reported
5124  for any of the boards.
5125
5126* Keep your modifications to the necessary minimum: A patch
5127  containing several unrelated changes or arbitrary reformats will be
5128  returned with a request to re-formatting / split it.
5129
5130* If you modify existing code, make sure that your new code does not
5131  add to the memory footprint of the code ;-) Small is beautiful!
5132  When adding new features, these should compile conditionally only
5133  (using #ifdef), and the resulting code with the new feature
5134  disabled must not need more memory than the old code without your
5135  modification.
5136
5137* Remember that there is a size limit of 100 kB per message on the
5138  u-boot mailing list. Bigger patches will be moderated. If they are
5139  reasonable and not too big, they will be acknowledged. But patches
5140  bigger than the size limit should be avoided.
5141