xref: /openbmc/u-boot/README (revision 66dae3bb)
1# SPDX-License-Identifier: GPL-2.0+
2#
3# (C) Copyright 2000 - 2013
4# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
5
6Summary:
7========
8
9This directory contains the source code for U-Boot, a boot loader for
10Embedded boards based on PowerPC, ARM, MIPS and several other
11processors, which can be installed in a boot ROM and used to
12initialize and test the hardware or to download and run application
13code.
14
15The development of U-Boot is closely related to Linux: some parts of
16the source code originate in the Linux source tree, we have some
17header files in common, and special provision has been made to
18support booting of Linux images.
19
20Some attention has been paid to make this software easily
21configurable and extendable. For instance, all monitor commands are
22implemented with the same call interface, so that it's very easy to
23add new commands. Also, instead of permanently adding rarely used
24code (for instance hardware test utilities) to the monitor, you can
25load and run it dynamically.
26
27
28Status:
29=======
30
31In general, all boards for which a configuration option exists in the
32Makefile have been tested to some extent and can be considered
33"working". In fact, many of them are used in production systems.
34
35In case of problems see the CHANGELOG file to find out who contributed
36the specific port. In addition, there are various MAINTAINERS files
37scattered throughout the U-Boot source identifying the people or
38companies responsible for various boards and subsystems.
39
40Note: As of August, 2010, there is no longer a CHANGELOG file in the
41actual U-Boot source tree; however, it can be created dynamically
42from the Git log using:
43
44	make CHANGELOG
45
46
47Where to get help:
48==================
49
50In case you have questions about, problems with or contributions for
51U-Boot, you should send a message to the U-Boot mailing list at
52<u-boot@lists.denx.de>. There is also an archive of previous traffic
53on the mailing list - please search the archive before asking FAQ's.
54Please see http://lists.denx.de/pipermail/u-boot and
55http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
56
57
58Where to get source code:
59=========================
60
61The U-Boot source code is maintained in the Git repository at
62git://www.denx.de/git/u-boot.git ; you can browse it online at
63http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
64
65The "snapshot" links on this page allow you to download tarballs of
66any version you might be interested in. Official releases are also
67available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
68directory.
69
70Pre-built (and tested) images are available from
71ftp://ftp.denx.de/pub/u-boot/images/
72
73
74Where we come from:
75===================
76
77- start from 8xxrom sources
78- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
79- clean up code
80- make it easier to add custom boards
81- make it possible to add other [PowerPC] CPUs
82- extend functions, especially:
83  * Provide extended interface to Linux boot loader
84  * S-Record download
85  * network boot
86  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
87- create ARMBoot project (http://sourceforge.net/projects/armboot)
88- add other CPU families (starting with ARM)
89- create U-Boot project (http://sourceforge.net/projects/u-boot)
90- current project page: see http://www.denx.de/wiki/U-Boot
91
92
93Names and Spelling:
94===================
95
96The "official" name of this project is "Das U-Boot". The spelling
97"U-Boot" shall be used in all written text (documentation, comments
98in source files etc.). Example:
99
100	This is the README file for the U-Boot project.
101
102File names etc. shall be based on the string "u-boot". Examples:
103
104	include/asm-ppc/u-boot.h
105
106	#include <asm/u-boot.h>
107
108Variable names, preprocessor constants etc. shall be either based on
109the string "u_boot" or on "U_BOOT". Example:
110
111	U_BOOT_VERSION		u_boot_logo
112	IH_OS_U_BOOT		u_boot_hush_start
113
114
115Versioning:
116===========
117
118Starting with the release in October 2008, the names of the releases
119were changed from numerical release numbers without deeper meaning
120into a time stamp based numbering. Regular releases are identified by
121names consisting of the calendar year and month of the release date.
122Additional fields (if present) indicate release candidates or bug fix
123releases in "stable" maintenance trees.
124
125Examples:
126	U-Boot v2009.11	    - Release November 2009
127	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
128	U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
129
130
131Directory Hierarchy:
132====================
133
134/arch			Architecture specific files
135  /arc			Files generic to ARC architecture
136  /arm			Files generic to ARM architecture
137  /m68k			Files generic to m68k architecture
138  /microblaze		Files generic to microblaze architecture
139  /mips			Files generic to MIPS architecture
140  /nds32		Files generic to NDS32 architecture
141  /nios2		Files generic to Altera NIOS2 architecture
142  /openrisc		Files generic to OpenRISC architecture
143  /powerpc		Files generic to PowerPC architecture
144  /riscv		Files generic to RISC-V architecture
145  /sandbox		Files generic to HW-independent "sandbox"
146  /sh			Files generic to SH architecture
147  /x86			Files generic to x86 architecture
148/api			Machine/arch independent API for external apps
149/board			Board dependent files
150/cmd			U-Boot commands functions
151/common			Misc architecture independent functions
152/configs		Board default configuration files
153/disk			Code for disk drive partition handling
154/doc			Documentation (don't expect too much)
155/drivers		Commonly used device drivers
156/dts			Contains Makefile for building internal U-Boot fdt.
157/examples		Example code for standalone applications, etc.
158/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
159/include		Header Files
160/lib			Library routines generic to all architectures
161/Licenses		Various license files
162/net			Networking code
163/post			Power On Self Test
164/scripts		Various build scripts and Makefiles
165/test			Various unit test files
166/tools			Tools to build S-Record or U-Boot images, etc.
167
168Software Configuration:
169=======================
170
171Configuration is usually done using C preprocessor defines; the
172rationale behind that is to avoid dead code whenever possible.
173
174There are two classes of configuration variables:
175
176* Configuration _OPTIONS_:
177  These are selectable by the user and have names beginning with
178  "CONFIG_".
179
180* Configuration _SETTINGS_:
181  These depend on the hardware etc. and should not be meddled with if
182  you don't know what you're doing; they have names beginning with
183  "CONFIG_SYS_".
184
185Previously, all configuration was done by hand, which involved creating
186symbolic links and editing configuration files manually. More recently,
187U-Boot has added the Kbuild infrastructure used by the Linux kernel,
188allowing you to use the "make menuconfig" command to configure your
189build.
190
191
192Selection of Processor Architecture and Board Type:
193---------------------------------------------------
194
195For all supported boards there are ready-to-use default
196configurations available; just type "make <board_name>_defconfig".
197
198Example: For a TQM823L module type:
199
200	cd u-boot
201	make TQM823L_defconfig
202
203Note: If you're looking for the default configuration file for a board
204you're sure used to be there but is now missing, check the file
205doc/README.scrapyard for a list of no longer supported boards.
206
207Sandbox Environment:
208--------------------
209
210U-Boot can be built natively to run on a Linux host using the 'sandbox'
211board. This allows feature development which is not board- or architecture-
212specific to be undertaken on a native platform. The sandbox is also used to
213run some of U-Boot's tests.
214
215See board/sandbox/README.sandbox for more details.
216
217
218Board Initialisation Flow:
219--------------------------
220
221This is the intended start-up flow for boards. This should apply for both
222SPL and U-Boot proper (i.e. they both follow the same rules).
223
224Note: "SPL" stands for "Secondary Program Loader," which is explained in
225more detail later in this file.
226
227At present, SPL mostly uses a separate code path, but the function names
228and roles of each function are the same. Some boards or architectures
229may not conform to this.  At least most ARM boards which use
230CONFIG_SPL_FRAMEWORK conform to this.
231
232Execution typically starts with an architecture-specific (and possibly
233CPU-specific) start.S file, such as:
234
235	- arch/arm/cpu/armv7/start.S
236	- arch/powerpc/cpu/mpc83xx/start.S
237	- arch/mips/cpu/start.S
238
239and so on. From there, three functions are called; the purpose and
240limitations of each of these functions are described below.
241
242lowlevel_init():
243	- purpose: essential init to permit execution to reach board_init_f()
244	- no global_data or BSS
245	- there is no stack (ARMv7 may have one but it will soon be removed)
246	- must not set up SDRAM or use console
247	- must only do the bare minimum to allow execution to continue to
248		board_init_f()
249	- this is almost never needed
250	- return normally from this function
251
252board_init_f():
253	- purpose: set up the machine ready for running board_init_r():
254		i.e. SDRAM and serial UART
255	- global_data is available
256	- stack is in SRAM
257	- BSS is not available, so you cannot use global/static variables,
258		only stack variables and global_data
259
260	Non-SPL-specific notes:
261	- dram_init() is called to set up DRAM. If already done in SPL this
262		can do nothing
263
264	SPL-specific notes:
265	- you can override the entire board_init_f() function with your own
266		version as needed.
267	- preloader_console_init() can be called here in extremis
268	- should set up SDRAM, and anything needed to make the UART work
269	- these is no need to clear BSS, it will be done by crt0.S
270	- must return normally from this function (don't call board_init_r()
271		directly)
272
273Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
274this point the stack and global_data are relocated to below
275CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
276memory.
277
278board_init_r():
279	- purpose: main execution, common code
280	- global_data is available
281	- SDRAM is available
282	- BSS is available, all static/global variables can be used
283	- execution eventually continues to main_loop()
284
285	Non-SPL-specific notes:
286	- U-Boot is relocated to the top of memory and is now running from
287		there.
288
289	SPL-specific notes:
290	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
291		CONFIG_SPL_STACK_R_ADDR points into SDRAM
292	- preloader_console_init() can be called here - typically this is
293		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
294		spl_board_init() function containing this call
295	- loads U-Boot or (in falcon mode) Linux
296
297
298
299Configuration Options:
300----------------------
301
302Configuration depends on the combination of board and CPU type; all
303such information is kept in a configuration file
304"include/configs/<board_name>.h".
305
306Example: For a TQM823L module, all configuration settings are in
307"include/configs/TQM823L.h".
308
309
310Many of the options are named exactly as the corresponding Linux
311kernel configuration options. The intention is to make it easier to
312build a config tool - later.
313
314- ARM Platform Bus Type(CCI):
315		CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
316		provides full cache coherency between two clusters of multi-core
317		CPUs and I/O coherency for devices and I/O masters
318
319		CONFIG_SYS_FSL_HAS_CCI400
320
321		Defined For SoC that has cache coherent interconnect
322		CCN-400
323
324		CONFIG_SYS_FSL_HAS_CCN504
325
326		Defined for SoC that has cache coherent interconnect CCN-504
327
328The following options need to be configured:
329
330- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
331
332- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
333
334- 85xx CPU Options:
335		CONFIG_SYS_PPC64
336
337		Specifies that the core is a 64-bit PowerPC implementation (implements
338		the "64" category of the Power ISA). This is necessary for ePAPR
339		compliance, among other possible reasons.
340
341		CONFIG_SYS_FSL_TBCLK_DIV
342
343		Defines the core time base clock divider ratio compared to the
344		system clock.  On most PQ3 devices this is 8, on newer QorIQ
345		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
346
347		CONFIG_SYS_FSL_PCIE_COMPAT
348
349		Defines the string to utilize when trying to match PCIe device
350		tree nodes for the given platform.
351
352		CONFIG_SYS_FSL_ERRATUM_A004510
353
354		Enables a workaround for erratum A004510.  If set,
355		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
356		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
357
358		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
359		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
360
361		Defines one or two SoC revisions (low 8 bits of SVR)
362		for which the A004510 workaround should be applied.
363
364		The rest of SVR is either not relevant to the decision
365		of whether the erratum is present (e.g. p2040 versus
366		p2041) or is implied by the build target, which controls
367		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
368
369		See Freescale App Note 4493 for more information about
370		this erratum.
371
372		CONFIG_A003399_NOR_WORKAROUND
373		Enables a workaround for IFC erratum A003399. It is only
374		required during NOR boot.
375
376		CONFIG_A008044_WORKAROUND
377		Enables a workaround for T1040/T1042 erratum A008044. It is only
378		required during NAND boot and valid for Rev 1.0 SoC revision
379
380		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
381
382		This is the value to write into CCSR offset 0x18600
383		according to the A004510 workaround.
384
385		CONFIG_SYS_FSL_DSP_DDR_ADDR
386		This value denotes start offset of DDR memory which is
387		connected exclusively to the DSP cores.
388
389		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
390		This value denotes start offset of M2 memory
391		which is directly connected to the DSP core.
392
393		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
394		This value denotes start offset of M3 memory which is directly
395		connected to the DSP core.
396
397		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
398		This value denotes start offset of DSP CCSR space.
399
400		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
401		Single Source Clock is clocking mode present in some of FSL SoC's.
402		In this mode, a single differential clock is used to supply
403		clocks to the sysclock, ddrclock and usbclock.
404
405		CONFIG_SYS_CPC_REINIT_F
406		This CONFIG is defined when the CPC is configured as SRAM at the
407		time of U-Boot entry and is required to be re-initialized.
408
409		CONFIG_DEEP_SLEEP
410		Indicates this SoC supports deep sleep feature. If deep sleep is
411		supported, core will start to execute uboot when wakes up.
412
413- Generic CPU options:
414		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
415
416		Defines the endianess of the CPU. Implementation of those
417		values is arch specific.
418
419		CONFIG_SYS_FSL_DDR
420		Freescale DDR driver in use. This type of DDR controller is
421		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
422		SoCs.
423
424		CONFIG_SYS_FSL_DDR_ADDR
425		Freescale DDR memory-mapped register base.
426
427		CONFIG_SYS_FSL_DDR_EMU
428		Specify emulator support for DDR. Some DDR features such as
429		deskew training are not available.
430
431		CONFIG_SYS_FSL_DDRC_GEN1
432		Freescale DDR1 controller.
433
434		CONFIG_SYS_FSL_DDRC_GEN2
435		Freescale DDR2 controller.
436
437		CONFIG_SYS_FSL_DDRC_GEN3
438		Freescale DDR3 controller.
439
440		CONFIG_SYS_FSL_DDRC_GEN4
441		Freescale DDR4 controller.
442
443		CONFIG_SYS_FSL_DDRC_ARM_GEN3
444		Freescale DDR3 controller for ARM-based SoCs.
445
446		CONFIG_SYS_FSL_DDR1
447		Board config to use DDR1. It can be enabled for SoCs with
448		Freescale DDR1 or DDR2 controllers, depending on the board
449		implemetation.
450
451		CONFIG_SYS_FSL_DDR2
452		Board config to use DDR2. It can be enabled for SoCs with
453		Freescale DDR2 or DDR3 controllers, depending on the board
454		implementation.
455
456		CONFIG_SYS_FSL_DDR3
457		Board config to use DDR3. It can be enabled for SoCs with
458		Freescale DDR3 or DDR3L controllers.
459
460		CONFIG_SYS_FSL_DDR3L
461		Board config to use DDR3L. It can be enabled for SoCs with
462		DDR3L controllers.
463
464		CONFIG_SYS_FSL_DDR4
465		Board config to use DDR4. It can be enabled for SoCs with
466		DDR4 controllers.
467
468		CONFIG_SYS_FSL_IFC_BE
469		Defines the IFC controller register space as Big Endian
470
471		CONFIG_SYS_FSL_IFC_LE
472		Defines the IFC controller register space as Little Endian
473
474		CONFIG_SYS_FSL_IFC_CLK_DIV
475		Defines divider of platform clock(clock input to IFC controller).
476
477		CONFIG_SYS_FSL_LBC_CLK_DIV
478		Defines divider of platform clock(clock input to eLBC controller).
479
480		CONFIG_SYS_FSL_PBL_PBI
481		It enables addition of RCW (Power on reset configuration) in built image.
482		Please refer doc/README.pblimage for more details
483
484		CONFIG_SYS_FSL_PBL_RCW
485		It adds PBI(pre-boot instructions) commands in u-boot build image.
486		PBI commands can be used to configure SoC before it starts the execution.
487		Please refer doc/README.pblimage for more details
488
489		CONFIG_SPL_FSL_PBL
490		It adds a target to create boot binary having SPL binary in PBI format
491		concatenated with u-boot binary.
492
493		CONFIG_SYS_FSL_DDR_BE
494		Defines the DDR controller register space as Big Endian
495
496		CONFIG_SYS_FSL_DDR_LE
497		Defines the DDR controller register space as Little Endian
498
499		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
500		Physical address from the view of DDR controllers. It is the
501		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
502		it could be different for ARM SoCs.
503
504		CONFIG_SYS_FSL_DDR_INTLV_256B
505		DDR controller interleaving on 256-byte. This is a special
506		interleaving mode, handled by Dickens for Freescale layerscape
507		SoCs with ARM core.
508
509		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
510		Number of controllers used as main memory.
511
512		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
513		Number of controllers used for other than main memory.
514
515		CONFIG_SYS_FSL_HAS_DP_DDR
516		Defines the SoC has DP-DDR used for DPAA.
517
518		CONFIG_SYS_FSL_SEC_BE
519		Defines the SEC controller register space as Big Endian
520
521		CONFIG_SYS_FSL_SEC_LE
522		Defines the SEC controller register space as Little Endian
523
524- MIPS CPU options:
525		CONFIG_SYS_INIT_SP_OFFSET
526
527		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
528		pointer. This is needed for the temporary stack before
529		relocation.
530
531		CONFIG_SYS_MIPS_CACHE_MODE
532
533		Cache operation mode for the MIPS CPU.
534		See also arch/mips/include/asm/mipsregs.h.
535		Possible values are:
536			CONF_CM_CACHABLE_NO_WA
537			CONF_CM_CACHABLE_WA
538			CONF_CM_UNCACHED
539			CONF_CM_CACHABLE_NONCOHERENT
540			CONF_CM_CACHABLE_CE
541			CONF_CM_CACHABLE_COW
542			CONF_CM_CACHABLE_CUW
543			CONF_CM_CACHABLE_ACCELERATED
544
545		CONFIG_SYS_XWAY_EBU_BOOTCFG
546
547		Special option for Lantiq XWAY SoCs for booting from NOR flash.
548		See also arch/mips/cpu/mips32/start.S.
549
550		CONFIG_XWAY_SWAP_BYTES
551
552		Enable compilation of tools/xway-swap-bytes needed for Lantiq
553		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
554		be swapped if a flash programmer is used.
555
556- ARM options:
557		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
558
559		Select high exception vectors of the ARM core, e.g., do not
560		clear the V bit of the c1 register of CP15.
561
562		COUNTER_FREQUENCY
563		Generic timer clock source frequency.
564
565		COUNTER_FREQUENCY_REAL
566		Generic timer clock source frequency if the real clock is
567		different from COUNTER_FREQUENCY, and can only be determined
568		at run time.
569
570- Tegra SoC options:
571		CONFIG_TEGRA_SUPPORT_NON_SECURE
572
573		Support executing U-Boot in non-secure (NS) mode. Certain
574		impossible actions will be skipped if the CPU is in NS mode,
575		such as ARM architectural timer initialization.
576
577- Linux Kernel Interface:
578		CONFIG_CLOCKS_IN_MHZ
579
580		U-Boot stores all clock information in Hz
581		internally. For binary compatibility with older Linux
582		kernels (which expect the clocks passed in the
583		bd_info data to be in MHz) the environment variable
584		"clocks_in_mhz" can be defined so that U-Boot
585		converts clock data to MHZ before passing it to the
586		Linux kernel.
587		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
588		"clocks_in_mhz=1" is automatically included in the
589		default environment.
590
591		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
592
593		When transferring memsize parameter to Linux, some versions
594		expect it to be in bytes, others in MB.
595		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
596
597		CONFIG_OF_LIBFDT
598
599		New kernel versions are expecting firmware settings to be
600		passed using flattened device trees (based on open firmware
601		concepts).
602
603		CONFIG_OF_LIBFDT
604		 * New libfdt-based support
605		 * Adds the "fdt" command
606		 * The bootm command automatically updates the fdt
607
608		OF_TBCLK - The timebase frequency.
609		OF_STDOUT_PATH - The path to the console device
610
611		boards with QUICC Engines require OF_QE to set UCC MAC
612		addresses
613
614		CONFIG_OF_BOARD_SETUP
615
616		Board code has addition modification that it wants to make
617		to the flat device tree before handing it off to the kernel
618
619		CONFIG_OF_SYSTEM_SETUP
620
621		Other code has addition modification that it wants to make
622		to the flat device tree before handing it off to the kernel.
623		This causes ft_system_setup() to be called before booting
624		the kernel.
625
626		CONFIG_OF_IDE_FIXUP
627
628		U-Boot can detect if an IDE device is present or not.
629		If not, and this new config option is activated, U-Boot
630		removes the ATA node from the DTS before booting Linux,
631		so the Linux IDE driver does not probe the device and
632		crash. This is needed for buggy hardware (uc101) where
633		no pull down resistor is connected to the signal IDE5V_DD7.
634
635		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
636
637		This setting is mandatory for all boards that have only one
638		machine type and must be used to specify the machine type
639		number as it appears in the ARM machine registry
640		(see http://www.arm.linux.org.uk/developer/machines/).
641		Only boards that have multiple machine types supported
642		in a single configuration file and the machine type is
643		runtime discoverable, do not have to use this setting.
644
645- vxWorks boot parameters:
646
647		bootvx constructs a valid bootline using the following
648		environments variables: bootdev, bootfile, ipaddr, netmask,
649		serverip, gatewayip, hostname, othbootargs.
650		It loads the vxWorks image pointed bootfile.
651
652		Note: If a "bootargs" environment is defined, it will overwride
653		the defaults discussed just above.
654
655- Cache Configuration:
656		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
657		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
658		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
659
660- Cache Configuration for ARM:
661		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
662				      controller
663		CONFIG_SYS_PL310_BASE - Physical base address of PL310
664					controller register space
665
666- Serial Ports:
667		CONFIG_PL010_SERIAL
668
669		Define this if you want support for Amba PrimeCell PL010 UARTs.
670
671		CONFIG_PL011_SERIAL
672
673		Define this if you want support for Amba PrimeCell PL011 UARTs.
674
675		CONFIG_PL011_CLOCK
676
677		If you have Amba PrimeCell PL011 UARTs, set this variable to
678		the clock speed of the UARTs.
679
680		CONFIG_PL01x_PORTS
681
682		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
683		define this to a list of base addresses for each (supported)
684		port. See e.g. include/configs/versatile.h
685
686		CONFIG_SERIAL_HW_FLOW_CONTROL
687
688		Define this variable to enable hw flow control in serial driver.
689		Current user of this option is drivers/serial/nsl16550.c driver
690
691- Console Baudrate:
692		CONFIG_BAUDRATE - in bps
693		Select one of the baudrates listed in
694		CONFIG_SYS_BAUDRATE_TABLE, see below.
695
696- Autoboot Command:
697		CONFIG_BOOTCOMMAND
698		Only needed when CONFIG_BOOTDELAY is enabled;
699		define a command string that is automatically executed
700		when no character is read on the console interface
701		within "Boot Delay" after reset.
702
703		CONFIG_RAMBOOT and CONFIG_NFSBOOT
704		The value of these goes into the environment as
705		"ramboot" and "nfsboot" respectively, and can be used
706		as a convenience, when switching between booting from
707		RAM and NFS.
708
709- Pre-Boot Commands:
710		CONFIG_PREBOOT
711
712		When this option is #defined, the existence of the
713		environment variable "preboot" will be checked
714		immediately before starting the CONFIG_BOOTDELAY
715		countdown and/or running the auto-boot command resp.
716		entering interactive mode.
717
718		This feature is especially useful when "preboot" is
719		automatically generated or modified. For an example
720		see the LWMON board specific code: here "preboot" is
721		modified when the user holds down a certain
722		combination of keys on the (special) keyboard when
723		booting the systems
724
725- Serial Download Echo Mode:
726		CONFIG_LOADS_ECHO
727		If defined to 1, all characters received during a
728		serial download (using the "loads" command) are
729		echoed back. This might be needed by some terminal
730		emulations (like "cu"), but may as well just take
731		time on others. This setting #define's the initial
732		value of the "loads_echo" environment variable.
733
734- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
735		CONFIG_KGDB_BAUDRATE
736		Select one of the baudrates listed in
737		CONFIG_SYS_BAUDRATE_TABLE, see below.
738
739- Removal of commands
740		If no commands are needed to boot, you can disable
741		CONFIG_CMDLINE to remove them. In this case, the command line
742		will not be available, and when U-Boot wants to execute the
743		boot command (on start-up) it will call board_run_command()
744		instead. This can reduce image size significantly for very
745		simple boot procedures.
746
747- Regular expression support:
748		CONFIG_REGEX
749		If this variable is defined, U-Boot is linked against
750		the SLRE (Super Light Regular Expression) library,
751		which adds regex support to some commands, as for
752		example "env grep" and "setexpr".
753
754- Device tree:
755		CONFIG_OF_CONTROL
756		If this variable is defined, U-Boot will use a device tree
757		to configure its devices, instead of relying on statically
758		compiled #defines in the board file. This option is
759		experimental and only available on a few boards. The device
760		tree is available in the global data as gd->fdt_blob.
761
762		U-Boot needs to get its device tree from somewhere. This can
763		be done using one of the three options below:
764
765		CONFIG_OF_EMBED
766		If this variable is defined, U-Boot will embed a device tree
767		binary in its image. This device tree file should be in the
768		board directory and called <soc>-<board>.dts. The binary file
769		is then picked up in board_init_f() and made available through
770		the global data structure as gd->fdt_blob.
771
772		CONFIG_OF_SEPARATE
773		If this variable is defined, U-Boot will build a device tree
774		binary. It will be called u-boot.dtb. Architecture-specific
775		code will locate it at run-time. Generally this works by:
776
777			cat u-boot.bin u-boot.dtb >image.bin
778
779		and in fact, U-Boot does this for you, creating a file called
780		u-boot-dtb.bin which is useful in the common case. You can
781		still use the individual files if you need something more
782		exotic.
783
784		CONFIG_OF_BOARD
785		If this variable is defined, U-Boot will use the device tree
786		provided by the board at runtime instead of embedding one with
787		the image. Only boards defining board_fdt_blob_setup() support
788		this option (see include/fdtdec.h file).
789
790- Watchdog:
791		CONFIG_WATCHDOG
792		If this variable is defined, it enables watchdog
793		support for the SoC. There must be support in the SoC
794		specific code for a watchdog. For the 8xx
795		CPUs, the SIU Watchdog feature is enabled in the SYPCR
796		register.  When supported for a specific SoC is
797		available, then no further board specific code should
798		be needed to use it.
799
800		CONFIG_HW_WATCHDOG
801		When using a watchdog circuitry external to the used
802		SoC, then define this variable and provide board
803		specific code for the "hw_watchdog_reset" function.
804
805		CONFIG_AT91_HW_WDT_TIMEOUT
806		specify the timeout in seconds. default 2 seconds.
807
808- Real-Time Clock:
809
810		When CONFIG_CMD_DATE is selected, the type of the RTC
811		has to be selected, too. Define exactly one of the
812		following options:
813
814		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
815		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
816		CONFIG_RTC_MC146818	- use MC146818 RTC
817		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
818		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
819		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
820		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
821		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
822		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
823		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
824		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
825		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
826					  RV3029 RTC.
827
828		Note that if the RTC uses I2C, then the I2C interface
829		must also be configured. See I2C Support, below.
830
831- GPIO Support:
832		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
833
834		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
835		chip-ngpio pairs that tell the PCA953X driver the number of
836		pins supported by a particular chip.
837
838		Note that if the GPIO device uses I2C, then the I2C interface
839		must also be configured. See I2C Support, below.
840
841- I/O tracing:
842		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
843		accesses and can checksum them or write a list of them out
844		to memory. See the 'iotrace' command for details. This is
845		useful for testing device drivers since it can confirm that
846		the driver behaves the same way before and after a code
847		change. Currently this is supported on sandbox and arm. To
848		add support for your architecture, add '#include <iotrace.h>'
849		to the bottom of arch/<arch>/include/asm/io.h and test.
850
851		Example output from the 'iotrace stats' command is below.
852		Note that if the trace buffer is exhausted, the checksum will
853		still continue to operate.
854
855			iotrace is enabled
856			Start:  10000000	(buffer start address)
857			Size:   00010000	(buffer size)
858			Offset: 00000120	(current buffer offset)
859			Output: 10000120	(start + offset)
860			Count:  00000018	(number of trace records)
861			CRC32:  9526fb66	(CRC32 of all trace records)
862
863- Timestamp Support:
864
865		When CONFIG_TIMESTAMP is selected, the timestamp
866		(date and time) of an image is printed by image
867		commands like bootm or iminfo. This option is
868		automatically enabled when you select CONFIG_CMD_DATE .
869
870- Partition Labels (disklabels) Supported:
871		Zero or more of the following:
872		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
873		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
874		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
875				       bootloader.  Note 2TB partition limit; see
876				       disk/part_efi.c
877		CONFIG_SCSI) you must configure support for at
878		least one non-MTD partition type as well.
879
880- IDE Reset method:
881		CONFIG_IDE_RESET_ROUTINE - this is defined in several
882		board configurations files but used nowhere!
883
884		CONFIG_IDE_RESET - is this is defined, IDE Reset will
885		be performed by calling the function
886			ide_set_reset(int reset)
887		which has to be defined in a board specific file
888
889- ATAPI Support:
890		CONFIG_ATAPI
891
892		Set this to enable ATAPI support.
893
894- LBA48 Support
895		CONFIG_LBA48
896
897		Set this to enable support for disks larger than 137GB
898		Also look at CONFIG_SYS_64BIT_LBA.
899		Whithout these , LBA48 support uses 32bit variables and will 'only'
900		support disks up to 2.1TB.
901
902		CONFIG_SYS_64BIT_LBA:
903			When enabled, makes the IDE subsystem use 64bit sector addresses.
904			Default is 32bit.
905
906- SCSI Support:
907		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
908		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
909		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
910		maximum numbers of LUNs, SCSI ID's and target
911		devices.
912
913		The environment variable 'scsidevs' is set to the number of
914		SCSI devices found during the last scan.
915
916- NETWORK Support (PCI):
917		CONFIG_E1000
918		Support for Intel 8254x/8257x gigabit chips.
919
920		CONFIG_E1000_SPI
921		Utility code for direct access to the SPI bus on Intel 8257x.
922		This does not do anything useful unless you set at least one
923		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
924
925		CONFIG_E1000_SPI_GENERIC
926		Allow generic access to the SPI bus on the Intel 8257x, for
927		example with the "sspi" command.
928
929		CONFIG_EEPRO100
930		Support for Intel 82557/82559/82559ER chips.
931		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
932		write routine for first time initialisation.
933
934		CONFIG_TULIP
935		Support for Digital 2114x chips.
936		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
937		modem chip initialisation (KS8761/QS6611).
938
939		CONFIG_NATSEMI
940		Support for National dp83815 chips.
941
942		CONFIG_NS8382X
943		Support for National dp8382[01] gigabit chips.
944
945- NETWORK Support (other):
946
947		CONFIG_DRIVER_AT91EMAC
948		Support for AT91RM9200 EMAC.
949
950			CONFIG_RMII
951			Define this to use reduced MII inteface
952
953			CONFIG_DRIVER_AT91EMAC_QUIET
954			If this defined, the driver is quiet.
955			The driver doen't show link status messages.
956
957		CONFIG_CALXEDA_XGMAC
958		Support for the Calxeda XGMAC device
959
960		CONFIG_LAN91C96
961		Support for SMSC's LAN91C96 chips.
962
963			CONFIG_LAN91C96_USE_32_BIT
964			Define this to enable 32 bit addressing
965
966		CONFIG_SMC91111
967		Support for SMSC's LAN91C111 chip
968
969			CONFIG_SMC91111_BASE
970			Define this to hold the physical address
971			of the device (I/O space)
972
973			CONFIG_SMC_USE_32_BIT
974			Define this if data bus is 32 bits
975
976			CONFIG_SMC_USE_IOFUNCS
977			Define this to use i/o functions instead of macros
978			(some hardware wont work with macros)
979
980		CONFIG_DRIVER_TI_EMAC
981		Support for davinci emac
982
983			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
984			Define this if you have more then 3 PHYs.
985
986		CONFIG_FTGMAC100
987		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
988
989			CONFIG_FTGMAC100_EGIGA
990			Define this to use GE link update with gigabit PHY.
991			Define this if FTGMAC100 is connected to gigabit PHY.
992			If your system has 10/100 PHY only, it might not occur
993			wrong behavior. Because PHY usually return timeout or
994			useless data when polling gigabit status and gigabit
995			control registers. This behavior won't affect the
996			correctnessof 10/100 link speed update.
997
998		CONFIG_SH_ETHER
999		Support for Renesas on-chip Ethernet controller
1000
1001			CONFIG_SH_ETHER_USE_PORT
1002			Define the number of ports to be used
1003
1004			CONFIG_SH_ETHER_PHY_ADDR
1005			Define the ETH PHY's address
1006
1007			CONFIG_SH_ETHER_CACHE_WRITEBACK
1008			If this option is set, the driver enables cache flush.
1009
1010- PWM Support:
1011		CONFIG_PWM_IMX
1012		Support for PWM module on the imx6.
1013
1014- TPM Support:
1015		CONFIG_TPM
1016		Support TPM devices.
1017
1018		CONFIG_TPM_TIS_INFINEON
1019		Support for Infineon i2c bus TPM devices. Only one device
1020		per system is supported at this time.
1021
1022			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1023			Define the burst count bytes upper limit
1024
1025		CONFIG_TPM_ST33ZP24
1026		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1027
1028			CONFIG_TPM_ST33ZP24_I2C
1029			Support for STMicroelectronics ST33ZP24 I2C devices.
1030			Requires TPM_ST33ZP24 and I2C.
1031
1032			CONFIG_TPM_ST33ZP24_SPI
1033			Support for STMicroelectronics ST33ZP24 SPI devices.
1034			Requires TPM_ST33ZP24 and SPI.
1035
1036		CONFIG_TPM_ATMEL_TWI
1037		Support for Atmel TWI TPM device. Requires I2C support.
1038
1039		CONFIG_TPM_TIS_LPC
1040		Support for generic parallel port TPM devices. Only one device
1041		per system is supported at this time.
1042
1043			CONFIG_TPM_TIS_BASE_ADDRESS
1044			Base address where the generic TPM device is mapped
1045			to. Contemporary x86 systems usually map it at
1046			0xfed40000.
1047
1048		CONFIG_TPM
1049		Define this to enable the TPM support library which provides
1050		functional interfaces to some TPM commands.
1051		Requires support for a TPM device.
1052
1053		CONFIG_TPM_AUTH_SESSIONS
1054		Define this to enable authorized functions in the TPM library.
1055		Requires CONFIG_TPM and CONFIG_SHA1.
1056
1057- USB Support:
1058		At the moment only the UHCI host controller is
1059		supported (PIP405, MIP405); define
1060		CONFIG_USB_UHCI to enable it.
1061		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1062		and define CONFIG_USB_STORAGE to enable the USB
1063		storage devices.
1064		Note:
1065		Supported are USB Keyboards and USB Floppy drives
1066		(TEAC FD-05PUB).
1067
1068		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1069		txfilltuning field in the EHCI controller on reset.
1070
1071		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1072		HW module registers.
1073
1074- USB Device:
1075		Define the below if you wish to use the USB console.
1076		Once firmware is rebuilt from a serial console issue the
1077		command "setenv stdin usbtty; setenv stdout usbtty" and
1078		attach your USB cable. The Unix command "dmesg" should print
1079		it has found a new device. The environment variable usbtty
1080		can be set to gserial or cdc_acm to enable your device to
1081		appear to a USB host as a Linux gserial device or a
1082		Common Device Class Abstract Control Model serial device.
1083		If you select usbtty = gserial you should be able to enumerate
1084		a Linux host by
1085		# modprobe usbserial vendor=0xVendorID product=0xProductID
1086		else if using cdc_acm, simply setting the environment
1087		variable usbtty to be cdc_acm should suffice. The following
1088		might be defined in YourBoardName.h
1089
1090			CONFIG_USB_DEVICE
1091			Define this to build a UDC device
1092
1093			CONFIG_USB_TTY
1094			Define this to have a tty type of device available to
1095			talk to the UDC device
1096
1097			CONFIG_USBD_HS
1098			Define this to enable the high speed support for usb
1099			device and usbtty. If this feature is enabled, a routine
1100			int is_usbd_high_speed(void)
1101			also needs to be defined by the driver to dynamically poll
1102			whether the enumeration has succeded at high speed or full
1103			speed.
1104
1105			CONFIG_SYS_CONSOLE_IS_IN_ENV
1106			Define this if you want stdin, stdout &/or stderr to
1107			be set to usbtty.
1108
1109		If you have a USB-IF assigned VendorID then you may wish to
1110		define your own vendor specific values either in BoardName.h
1111		or directly in usbd_vendor_info.h. If you don't define
1112		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1113		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1114		should pretend to be a Linux device to it's target host.
1115
1116			CONFIG_USBD_MANUFACTURER
1117			Define this string as the name of your company for
1118			- CONFIG_USBD_MANUFACTURER "my company"
1119
1120			CONFIG_USBD_PRODUCT_NAME
1121			Define this string as the name of your product
1122			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1123
1124			CONFIG_USBD_VENDORID
1125			Define this as your assigned Vendor ID from the USB
1126			Implementors Forum. This *must* be a genuine Vendor ID
1127			to avoid polluting the USB namespace.
1128			- CONFIG_USBD_VENDORID 0xFFFF
1129
1130			CONFIG_USBD_PRODUCTID
1131			Define this as the unique Product ID
1132			for your device
1133			- CONFIG_USBD_PRODUCTID 0xFFFF
1134
1135- ULPI Layer Support:
1136		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1137		the generic ULPI layer. The generic layer accesses the ULPI PHY
1138		via the platform viewport, so you need both the genric layer and
1139		the viewport enabled. Currently only Chipidea/ARC based
1140		viewport is supported.
1141		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1142		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1143		If your ULPI phy needs a different reference clock than the
1144		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1145		the appropriate value in Hz.
1146
1147- MMC Support:
1148		The MMC controller on the Intel PXA is supported. To
1149		enable this define CONFIG_MMC. The MMC can be
1150		accessed from the boot prompt by mapping the device
1151		to physical memory similar to flash. Command line is
1152		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1153		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1154
1155		CONFIG_SH_MMCIF
1156		Support for Renesas on-chip MMCIF controller
1157
1158			CONFIG_SH_MMCIF_ADDR
1159			Define the base address of MMCIF registers
1160
1161			CONFIG_SH_MMCIF_CLK
1162			Define the clock frequency for MMCIF
1163
1164		CONFIG_SUPPORT_EMMC_BOOT
1165		Enable some additional features of the eMMC boot partitions.
1166
1167- USB Device Firmware Update (DFU) class support:
1168		CONFIG_DFU_OVER_USB
1169		This enables the USB portion of the DFU USB class
1170
1171		CONFIG_DFU_MMC
1172		This enables support for exposing (e)MMC devices via DFU.
1173
1174		CONFIG_DFU_NAND
1175		This enables support for exposing NAND devices via DFU.
1176
1177		CONFIG_DFU_RAM
1178		This enables support for exposing RAM via DFU.
1179		Note: DFU spec refer to non-volatile memory usage, but
1180		allow usages beyond the scope of spec - here RAM usage,
1181		one that would help mostly the developer.
1182
1183		CONFIG_SYS_DFU_DATA_BUF_SIZE
1184		Dfu transfer uses a buffer before writing data to the
1185		raw storage device. Make the size (in bytes) of this buffer
1186		configurable. The size of this buffer is also configurable
1187		through the "dfu_bufsiz" environment variable.
1188
1189		CONFIG_SYS_DFU_MAX_FILE_SIZE
1190		When updating files rather than the raw storage device,
1191		we use a static buffer to copy the file into and then write
1192		the buffer once we've been given the whole file.  Define
1193		this to the maximum filesize (in bytes) for the buffer.
1194		Default is 4 MiB if undefined.
1195
1196		DFU_DEFAULT_POLL_TIMEOUT
1197		Poll timeout [ms], is the timeout a device can send to the
1198		host. The host must wait for this timeout before sending
1199		a subsequent DFU_GET_STATUS request to the device.
1200
1201		DFU_MANIFEST_POLL_TIMEOUT
1202		Poll timeout [ms], which the device sends to the host when
1203		entering dfuMANIFEST state. Host waits this timeout, before
1204		sending again an USB request to the device.
1205
1206- Journaling Flash filesystem support:
1207		CONFIG_JFFS2_NAND
1208		Define these for a default partition on a NAND device
1209
1210		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1211		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1212		Define these for a default partition on a NOR device
1213
1214- Keyboard Support:
1215		See Kconfig help for available keyboard drivers.
1216
1217		CONFIG_KEYBOARD
1218
1219		Define this to enable a custom keyboard support.
1220		This simply calls drv_keyboard_init() which must be
1221		defined in your board-specific files. This option is deprecated
1222		and is only used by novena. For new boards, use driver model
1223		instead.
1224
1225- Video support:
1226		CONFIG_FSL_DIU_FB
1227		Enable the Freescale DIU video driver.	Reference boards for
1228		SOCs that have a DIU should define this macro to enable DIU
1229		support, and should also define these other macros:
1230
1231			CONFIG_SYS_DIU_ADDR
1232			CONFIG_VIDEO
1233			CONFIG_CFB_CONSOLE
1234			CONFIG_VIDEO_SW_CURSOR
1235			CONFIG_VGA_AS_SINGLE_DEVICE
1236			CONFIG_VIDEO_LOGO
1237			CONFIG_VIDEO_BMP_LOGO
1238
1239		The DIU driver will look for the 'video-mode' environment
1240		variable, and if defined, enable the DIU as a console during
1241		boot.  See the documentation file doc/README.video for a
1242		description of this variable.
1243
1244- LCD Support:	CONFIG_LCD
1245
1246		Define this to enable LCD support (for output to LCD
1247		display); also select one of the supported displays
1248		by defining one of these:
1249
1250		CONFIG_ATMEL_LCD:
1251
1252			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1253
1254		CONFIG_NEC_NL6448AC33:
1255
1256			NEC NL6448AC33-18. Active, color, single scan.
1257
1258		CONFIG_NEC_NL6448BC20
1259
1260			NEC NL6448BC20-08. 6.5", 640x480.
1261			Active, color, single scan.
1262
1263		CONFIG_NEC_NL6448BC33_54
1264
1265			NEC NL6448BC33-54. 10.4", 640x480.
1266			Active, color, single scan.
1267
1268		CONFIG_SHARP_16x9
1269
1270			Sharp 320x240. Active, color, single scan.
1271			It isn't 16x9, and I am not sure what it is.
1272
1273		CONFIG_SHARP_LQ64D341
1274
1275			Sharp LQ64D341 display, 640x480.
1276			Active, color, single scan.
1277
1278		CONFIG_HLD1045
1279
1280			HLD1045 display, 640x480.
1281			Active, color, single scan.
1282
1283		CONFIG_OPTREX_BW
1284
1285			Optrex	 CBL50840-2 NF-FW 99 22 M5
1286			or
1287			Hitachi	 LMG6912RPFC-00T
1288			or
1289			Hitachi	 SP14Q002
1290
1291			320x240. Black & white.
1292
1293		CONFIG_LCD_ALIGNMENT
1294
1295		Normally the LCD is page-aligned (typically 4KB). If this is
1296		defined then the LCD will be aligned to this value instead.
1297		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1298		here, since it is cheaper to change data cache settings on
1299		a per-section basis.
1300
1301
1302		CONFIG_LCD_ROTATION
1303
1304		Sometimes, for example if the display is mounted in portrait
1305		mode or even if it's mounted landscape but rotated by 180degree,
1306		we need to rotate our content of the display relative to the
1307		framebuffer, so that user can read the messages which are
1308		printed out.
1309		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1310		initialized with a given rotation from "vl_rot" out of
1311		"vidinfo_t" which is provided by the board specific code.
1312		The value for vl_rot is coded as following (matching to
1313		fbcon=rotate:<n> linux-kernel commandline):
1314		0 = no rotation respectively 0 degree
1315		1 = 90 degree rotation
1316		2 = 180 degree rotation
1317		3 = 270 degree rotation
1318
1319		If CONFIG_LCD_ROTATION is not defined, the console will be
1320		initialized with 0degree rotation.
1321
1322		CONFIG_LCD_BMP_RLE8
1323
1324		Support drawing of RLE8-compressed bitmaps on the LCD.
1325
1326		CONFIG_I2C_EDID
1327
1328		Enables an 'i2c edid' command which can read EDID
1329		information over I2C from an attached LCD display.
1330
1331- Splash Screen Support: CONFIG_SPLASH_SCREEN
1332
1333		If this option is set, the environment is checked for
1334		a variable "splashimage". If found, the usual display
1335		of logo, copyright and system information on the LCD
1336		is suppressed and the BMP image at the address
1337		specified in "splashimage" is loaded instead. The
1338		console is redirected to the "nulldev", too. This
1339		allows for a "silent" boot where a splash screen is
1340		loaded very quickly after power-on.
1341
1342		CONFIG_SPLASHIMAGE_GUARD
1343
1344		If this option is set, then U-Boot will prevent the environment
1345		variable "splashimage" from being set to a problematic address
1346		(see doc/README.displaying-bmps).
1347		This option is useful for targets where, due to alignment
1348		restrictions, an improperly aligned BMP image will cause a data
1349		abort. If you think you will not have problems with unaligned
1350		accesses (for example because your toolchain prevents them)
1351		there is no need to set this option.
1352
1353		CONFIG_SPLASH_SCREEN_ALIGN
1354
1355		If this option is set the splash image can be freely positioned
1356		on the screen. Environment variable "splashpos" specifies the
1357		position as "x,y". If a positive number is given it is used as
1358		number of pixel from left/top. If a negative number is given it
1359		is used as number of pixel from right/bottom. You can also
1360		specify 'm' for centering the image.
1361
1362		Example:
1363		setenv splashpos m,m
1364			=> image at center of screen
1365
1366		setenv splashpos 30,20
1367			=> image at x = 30 and y = 20
1368
1369		setenv splashpos -10,m
1370			=> vertically centered image
1371			   at x = dspWidth - bmpWidth - 9
1372
1373- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1374
1375		If this option is set, additionally to standard BMP
1376		images, gzipped BMP images can be displayed via the
1377		splashscreen support or the bmp command.
1378
1379- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1380
1381		If this option is set, 8-bit RLE compressed BMP images
1382		can be displayed via the splashscreen support or the
1383		bmp command.
1384
1385- Compression support:
1386		CONFIG_GZIP
1387
1388		Enabled by default to support gzip compressed images.
1389
1390		CONFIG_BZIP2
1391
1392		If this option is set, support for bzip2 compressed
1393		images is included. If not, only uncompressed and gzip
1394		compressed images are supported.
1395
1396		NOTE: the bzip2 algorithm requires a lot of RAM, so
1397		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1398		be at least 4MB.
1399
1400- MII/PHY support:
1401		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1402
1403		The clock frequency of the MII bus
1404
1405		CONFIG_PHY_RESET_DELAY
1406
1407		Some PHY like Intel LXT971A need extra delay after
1408		reset before any MII register access is possible.
1409		For such PHY, set this option to the usec delay
1410		required. (minimum 300usec for LXT971A)
1411
1412		CONFIG_PHY_CMD_DELAY (ppc4xx)
1413
1414		Some PHY like Intel LXT971A need extra delay after
1415		command issued before MII status register can be read
1416
1417- IP address:
1418		CONFIG_IPADDR
1419
1420		Define a default value for the IP address to use for
1421		the default Ethernet interface, in case this is not
1422		determined through e.g. bootp.
1423		(Environment variable "ipaddr")
1424
1425- Server IP address:
1426		CONFIG_SERVERIP
1427
1428		Defines a default value for the IP address of a TFTP
1429		server to contact when using the "tftboot" command.
1430		(Environment variable "serverip")
1431
1432		CONFIG_KEEP_SERVERADDR
1433
1434		Keeps the server's MAC address, in the env 'serveraddr'
1435		for passing to bootargs (like Linux's netconsole option)
1436
1437- Gateway IP address:
1438		CONFIG_GATEWAYIP
1439
1440		Defines a default value for the IP address of the
1441		default router where packets to other networks are
1442		sent to.
1443		(Environment variable "gatewayip")
1444
1445- Subnet mask:
1446		CONFIG_NETMASK
1447
1448		Defines a default value for the subnet mask (or
1449		routing prefix) which is used to determine if an IP
1450		address belongs to the local subnet or needs to be
1451		forwarded through a router.
1452		(Environment variable "netmask")
1453
1454- Multicast TFTP Mode:
1455		CONFIG_MCAST_TFTP
1456
1457		Defines whether you want to support multicast TFTP as per
1458		rfc-2090; for example to work with atftp.  Lets lots of targets
1459		tftp down the same boot image concurrently.  Note: the Ethernet
1460		driver in use must provide a function: mcast() to join/leave a
1461		multicast group.
1462
1463- BOOTP Recovery Mode:
1464		CONFIG_BOOTP_RANDOM_DELAY
1465
1466		If you have many targets in a network that try to
1467		boot using BOOTP, you may want to avoid that all
1468		systems send out BOOTP requests at precisely the same
1469		moment (which would happen for instance at recovery
1470		from a power failure, when all systems will try to
1471		boot, thus flooding the BOOTP server. Defining
1472		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1473		inserted before sending out BOOTP requests. The
1474		following delays are inserted then:
1475
1476		1st BOOTP request:	delay 0 ... 1 sec
1477		2nd BOOTP request:	delay 0 ... 2 sec
1478		3rd BOOTP request:	delay 0 ... 4 sec
1479		4th and following
1480		BOOTP requests:		delay 0 ... 8 sec
1481
1482		CONFIG_BOOTP_ID_CACHE_SIZE
1483
1484		BOOTP packets are uniquely identified using a 32-bit ID. The
1485		server will copy the ID from client requests to responses and
1486		U-Boot will use this to determine if it is the destination of
1487		an incoming response. Some servers will check that addresses
1488		aren't in use before handing them out (usually using an ARP
1489		ping) and therefore take up to a few hundred milliseconds to
1490		respond. Network congestion may also influence the time it
1491		takes for a response to make it back to the client. If that
1492		time is too long, U-Boot will retransmit requests. In order
1493		to allow earlier responses to still be accepted after these
1494		retransmissions, U-Boot's BOOTP client keeps a small cache of
1495		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1496		cache. The default is to keep IDs for up to four outstanding
1497		requests. Increasing this will allow U-Boot to accept offers
1498		from a BOOTP client in networks with unusually high latency.
1499
1500- DHCP Advanced Options:
1501		You can fine tune the DHCP functionality by defining
1502		CONFIG_BOOTP_* symbols:
1503
1504		CONFIG_BOOTP_NISDOMAIN
1505		CONFIG_BOOTP_BOOTFILESIZE
1506		CONFIG_BOOTP_SEND_HOSTNAME
1507		CONFIG_BOOTP_NTPSERVER
1508		CONFIG_BOOTP_TIMEOFFSET
1509		CONFIG_BOOTP_VENDOREX
1510		CONFIG_BOOTP_MAY_FAIL
1511
1512		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1513		environment variable, not the BOOTP server.
1514
1515		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1516		after the configured retry count, the call will fail
1517		instead of starting over.  This can be used to fail over
1518		to Link-local IP address configuration if the DHCP server
1519		is not available.
1520
1521		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1522		to do a dynamic update of a DNS server. To do this, they
1523		need the hostname of the DHCP requester.
1524		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1525		of the "hostname" environment variable is passed as
1526		option 12 to the DHCP server.
1527
1528		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1529
1530		A 32bit value in microseconds for a delay between
1531		receiving a "DHCP Offer" and sending the "DHCP Request".
1532		This fixes a problem with certain DHCP servers that don't
1533		respond 100% of the time to a "DHCP request". E.g. On an
1534		AT91RM9200 processor running at 180MHz, this delay needed
1535		to be *at least* 15,000 usec before a Windows Server 2003
1536		DHCP server would reply 100% of the time. I recommend at
1537		least 50,000 usec to be safe. The alternative is to hope
1538		that one of the retries will be successful but note that
1539		the DHCP timeout and retry process takes a longer than
1540		this delay.
1541
1542 - Link-local IP address negotiation:
1543		Negotiate with other link-local clients on the local network
1544		for an address that doesn't require explicit configuration.
1545		This is especially useful if a DHCP server cannot be guaranteed
1546		to exist in all environments that the device must operate.
1547
1548		See doc/README.link-local for more information.
1549
1550 - MAC address from environment variables
1551
1552		FDT_SEQ_MACADDR_FROM_ENV
1553
1554		Fix-up device tree with MAC addresses fetched sequentially from
1555		environment variables. This config work on assumption that
1556		non-usable ethernet node of device-tree are either not present
1557		or their status has been marked as "disabled".
1558
1559 - CDP Options:
1560		CONFIG_CDP_DEVICE_ID
1561
1562		The device id used in CDP trigger frames.
1563
1564		CONFIG_CDP_DEVICE_ID_PREFIX
1565
1566		A two character string which is prefixed to the MAC address
1567		of the device.
1568
1569		CONFIG_CDP_PORT_ID
1570
1571		A printf format string which contains the ascii name of
1572		the port. Normally is set to "eth%d" which sets
1573		eth0 for the first Ethernet, eth1 for the second etc.
1574
1575		CONFIG_CDP_CAPABILITIES
1576
1577		A 32bit integer which indicates the device capabilities;
1578		0x00000010 for a normal host which does not forwards.
1579
1580		CONFIG_CDP_VERSION
1581
1582		An ascii string containing the version of the software.
1583
1584		CONFIG_CDP_PLATFORM
1585
1586		An ascii string containing the name of the platform.
1587
1588		CONFIG_CDP_TRIGGER
1589
1590		A 32bit integer sent on the trigger.
1591
1592		CONFIG_CDP_POWER_CONSUMPTION
1593
1594		A 16bit integer containing the power consumption of the
1595		device in .1 of milliwatts.
1596
1597		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1598
1599		A byte containing the id of the VLAN.
1600
1601- Status LED:	CONFIG_LED_STATUS
1602
1603		Several configurations allow to display the current
1604		status using a LED. For instance, the LED will blink
1605		fast while running U-Boot code, stop blinking as
1606		soon as a reply to a BOOTP request was received, and
1607		start blinking slow once the Linux kernel is running
1608		(supported by a status LED driver in the Linux
1609		kernel). Defining CONFIG_LED_STATUS enables this
1610		feature in U-Boot.
1611
1612		Additional options:
1613
1614		CONFIG_LED_STATUS_GPIO
1615		The status LED can be connected to a GPIO pin.
1616		In such cases, the gpio_led driver can be used as a
1617		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1618		to include the gpio_led driver in the U-Boot binary.
1619
1620		CONFIG_GPIO_LED_INVERTED_TABLE
1621		Some GPIO connected LEDs may have inverted polarity in which
1622		case the GPIO high value corresponds to LED off state and
1623		GPIO low value corresponds to LED on state.
1624		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1625		with a list of GPIO LEDs that have inverted polarity.
1626
1627- I2C Support:	CONFIG_SYS_I2C
1628
1629		This enable the NEW i2c subsystem, and will allow you to use
1630		i2c commands at the u-boot command line (as long as you set
1631		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1632		based realtime clock chips or other i2c devices. See
1633		common/cmd_i2c.c for a description of the command line
1634		interface.
1635
1636		ported i2c driver to the new framework:
1637		- drivers/i2c/soft_i2c.c:
1638		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1639		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1640		    for defining speed and slave address
1641		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1642		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1643		    for defining speed and slave address
1644		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1645		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1646		    for defining speed and slave address
1647		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1648		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1649		    for defining speed and slave address
1650
1651		- drivers/i2c/fsl_i2c.c:
1652		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1653		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1654		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1655		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1656		    bus.
1657		  - If your board supports a second fsl i2c bus, define
1658		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1659		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1660		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1661		    second bus.
1662
1663		- drivers/i2c/tegra_i2c.c:
1664		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1665		  - This driver adds 4 i2c buses with a fix speed from
1666		    100000 and the slave addr 0!
1667
1668		- drivers/i2c/ppc4xx_i2c.c
1669		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1670		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1671		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1672
1673		- drivers/i2c/i2c_mxc.c
1674		  - activate this driver with CONFIG_SYS_I2C_MXC
1675		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1676		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1677		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1678		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1679		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1680		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1681		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1682		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1683		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1684		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1685		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1686		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1687		If those defines are not set, default value is 100000
1688		for speed, and 0 for slave.
1689
1690		- drivers/i2c/rcar_i2c.c:
1691		  - activate this driver with CONFIG_SYS_I2C_RCAR
1692		  - This driver adds 4 i2c buses
1693
1694		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1695		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1696		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1697		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1698		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1699		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1700		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1701		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1702		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1703
1704		- drivers/i2c/sh_i2c.c:
1705		  - activate this driver with CONFIG_SYS_I2C_SH
1706		  - This driver adds from 2 to 5 i2c buses
1707
1708		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1709		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1710		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1711		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1712		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1713		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1714		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1715		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1716		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1717		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1718		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1719
1720		- drivers/i2c/omap24xx_i2c.c
1721		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1722		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1723		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1724		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1725		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1726		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1727		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1728		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1729		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1730		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1731		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1732
1733		- drivers/i2c/zynq_i2c.c
1734		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1735		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1736		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1737
1738		- drivers/i2c/s3c24x0_i2c.c:
1739		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1740		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1741		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1742		    with a fix speed from 100000 and the slave addr 0!
1743
1744		- drivers/i2c/ihs_i2c.c
1745		  - activate this driver with CONFIG_SYS_I2C_IHS
1746		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1747		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1748		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1749		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1750		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1751		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1752		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1753		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1754		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1755		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1756		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1757		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1758		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1759		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1760		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1761		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1762		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1763		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1764		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1765		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1766		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1767
1768		additional defines:
1769
1770		CONFIG_SYS_NUM_I2C_BUSES
1771		Hold the number of i2c buses you want to use.
1772
1773		CONFIG_SYS_I2C_DIRECT_BUS
1774		define this, if you don't use i2c muxes on your hardware.
1775		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1776		omit this define.
1777
1778		CONFIG_SYS_I2C_MAX_HOPS
1779		define how many muxes are maximal consecutively connected
1780		on one i2c bus. If you not use i2c muxes, omit this
1781		define.
1782
1783		CONFIG_SYS_I2C_BUSES
1784		hold a list of buses you want to use, only used if
1785		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1786		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1787		CONFIG_SYS_NUM_I2C_BUSES = 9:
1788
1789		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1790					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1791					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1792					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1793					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1794					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1795					{1, {I2C_NULL_HOP}}, \
1796					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1797					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1798					}
1799
1800		which defines
1801			bus 0 on adapter 0 without a mux
1802			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1803			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1804			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1805			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1806			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1807			bus 6 on adapter 1 without a mux
1808			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1809			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1810
1811		If you do not have i2c muxes on your board, omit this define.
1812
1813- Legacy I2C Support:
1814		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1815		then the following macros need to be defined (examples are
1816		from include/configs/lwmon.h):
1817
1818		I2C_INIT
1819
1820		(Optional). Any commands necessary to enable the I2C
1821		controller or configure ports.
1822
1823		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1824
1825		I2C_ACTIVE
1826
1827		The code necessary to make the I2C data line active
1828		(driven).  If the data line is open collector, this
1829		define can be null.
1830
1831		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1832
1833		I2C_TRISTATE
1834
1835		The code necessary to make the I2C data line tri-stated
1836		(inactive).  If the data line is open collector, this
1837		define can be null.
1838
1839		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1840
1841		I2C_READ
1842
1843		Code that returns true if the I2C data line is high,
1844		false if it is low.
1845
1846		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1847
1848		I2C_SDA(bit)
1849
1850		If <bit> is true, sets the I2C data line high. If it
1851		is false, it clears it (low).
1852
1853		eg: #define I2C_SDA(bit) \
1854			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1855			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1856
1857		I2C_SCL(bit)
1858
1859		If <bit> is true, sets the I2C clock line high. If it
1860		is false, it clears it (low).
1861
1862		eg: #define I2C_SCL(bit) \
1863			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1864			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1865
1866		I2C_DELAY
1867
1868		This delay is invoked four times per clock cycle so this
1869		controls the rate of data transfer.  The data rate thus
1870		is 1 / (I2C_DELAY * 4). Often defined to be something
1871		like:
1872
1873		#define I2C_DELAY  udelay(2)
1874
1875		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1876
1877		If your arch supports the generic GPIO framework (asm/gpio.h),
1878		then you may alternatively define the two GPIOs that are to be
1879		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1880		have GPIO-based defaults assigned to them as appropriate.
1881
1882		You should define these to the GPIO value as given directly to
1883		the generic GPIO functions.
1884
1885		CONFIG_SYS_I2C_INIT_BOARD
1886
1887		When a board is reset during an i2c bus transfer
1888		chips might think that the current transfer is still
1889		in progress. On some boards it is possible to access
1890		the i2c SCLK line directly, either by using the
1891		processor pin as a GPIO or by having a second pin
1892		connected to the bus. If this option is defined a
1893		custom i2c_init_board() routine in boards/xxx/board.c
1894		is run early in the boot sequence.
1895
1896		CONFIG_I2C_MULTI_BUS
1897
1898		This option allows the use of multiple I2C buses, each of which
1899		must have a controller.	 At any point in time, only one bus is
1900		active.	 To switch to a different bus, use the 'i2c dev' command.
1901		Note that bus numbering is zero-based.
1902
1903		CONFIG_SYS_I2C_NOPROBES
1904
1905		This option specifies a list of I2C devices that will be skipped
1906		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1907		is set, specify a list of bus-device pairs.  Otherwise, specify
1908		a 1D array of device addresses
1909
1910		e.g.
1911			#undef	CONFIG_I2C_MULTI_BUS
1912			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1913
1914		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1915
1916			#define CONFIG_I2C_MULTI_BUS
1917			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1918
1919		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1920
1921		CONFIG_SYS_SPD_BUS_NUM
1922
1923		If defined, then this indicates the I2C bus number for DDR SPD.
1924		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1925
1926		CONFIG_SYS_RTC_BUS_NUM
1927
1928		If defined, then this indicates the I2C bus number for the RTC.
1929		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1930
1931		CONFIG_SOFT_I2C_READ_REPEATED_START
1932
1933		defining this will force the i2c_read() function in
1934		the soft_i2c driver to perform an I2C repeated start
1935		between writing the address pointer and reading the
1936		data.  If this define is omitted the default behaviour
1937		of doing a stop-start sequence will be used.  Most I2C
1938		devices can use either method, but some require one or
1939		the other.
1940
1941- SPI Support:	CONFIG_SPI
1942
1943		Enables SPI driver (so far only tested with
1944		SPI EEPROM, also an instance works with Crystal A/D and
1945		D/As on the SACSng board)
1946
1947		CONFIG_SOFT_SPI
1948
1949		Enables a software (bit-bang) SPI driver rather than
1950		using hardware support. This is a general purpose
1951		driver that only requires three general I/O port pins
1952		(two outputs, one input) to function. If this is
1953		defined, the board configuration must define several
1954		SPI configuration items (port pins to use, etc). For
1955		an example, see include/configs/sacsng.h.
1956
1957		CONFIG_HARD_SPI
1958
1959		Enables a hardware SPI driver for general-purpose reads
1960		and writes.  As with CONFIG_SOFT_SPI, the board configuration
1961		must define a list of chip-select function pointers.
1962		Currently supported on some MPC8xxx processors.	 For an
1963		example, see include/configs/mpc8349emds.h.
1964
1965		CONFIG_SYS_SPI_MXC_WAIT
1966		Timeout for waiting until spi transfer completed.
1967		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1968
1969- FPGA Support: CONFIG_FPGA
1970
1971		Enables FPGA subsystem.
1972
1973		CONFIG_FPGA_<vendor>
1974
1975		Enables support for specific chip vendors.
1976		(ALTERA, XILINX)
1977
1978		CONFIG_FPGA_<family>
1979
1980		Enables support for FPGA family.
1981		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1982
1983		CONFIG_FPGA_COUNT
1984
1985		Specify the number of FPGA devices to support.
1986
1987		CONFIG_SYS_FPGA_PROG_FEEDBACK
1988
1989		Enable printing of hash marks during FPGA configuration.
1990
1991		CONFIG_SYS_FPGA_CHECK_BUSY
1992
1993		Enable checks on FPGA configuration interface busy
1994		status by the configuration function. This option
1995		will require a board or device specific function to
1996		be written.
1997
1998		CONFIG_FPGA_DELAY
1999
2000		If defined, a function that provides delays in the FPGA
2001		configuration driver.
2002
2003		CONFIG_SYS_FPGA_CHECK_CTRLC
2004		Allow Control-C to interrupt FPGA configuration
2005
2006		CONFIG_SYS_FPGA_CHECK_ERROR
2007
2008		Check for configuration errors during FPGA bitfile
2009		loading. For example, abort during Virtex II
2010		configuration if the INIT_B line goes low (which
2011		indicated a CRC error).
2012
2013		CONFIG_SYS_FPGA_WAIT_INIT
2014
2015		Maximum time to wait for the INIT_B line to de-assert
2016		after PROB_B has been de-asserted during a Virtex II
2017		FPGA configuration sequence. The default time is 500
2018		ms.
2019
2020		CONFIG_SYS_FPGA_WAIT_BUSY
2021
2022		Maximum time to wait for BUSY to de-assert during
2023		Virtex II FPGA configuration. The default is 5 ms.
2024
2025		CONFIG_SYS_FPGA_WAIT_CONFIG
2026
2027		Time to wait after FPGA configuration. The default is
2028		200 ms.
2029
2030- Configuration Management:
2031		CONFIG_BUILD_TARGET
2032
2033		Some SoCs need special image types (e.g. U-Boot binary
2034		with a special header) as build targets. By defining
2035		CONFIG_BUILD_TARGET in the SoC / board header, this
2036		special image will be automatically built upon calling
2037		make / buildman.
2038
2039		CONFIG_IDENT_STRING
2040
2041		If defined, this string will be added to the U-Boot
2042		version information (U_BOOT_VERSION)
2043
2044- Vendor Parameter Protection:
2045
2046		U-Boot considers the values of the environment
2047		variables "serial#" (Board Serial Number) and
2048		"ethaddr" (Ethernet Address) to be parameters that
2049		are set once by the board vendor / manufacturer, and
2050		protects these variables from casual modification by
2051		the user. Once set, these variables are read-only,
2052		and write or delete attempts are rejected. You can
2053		change this behaviour:
2054
2055		If CONFIG_ENV_OVERWRITE is #defined in your config
2056		file, the write protection for vendor parameters is
2057		completely disabled. Anybody can change or delete
2058		these parameters.
2059
2060		Alternatively, if you define _both_ an ethaddr in the
2061		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2062		Ethernet address is installed in the environment,
2063		which can be changed exactly ONCE by the user. [The
2064		serial# is unaffected by this, i. e. it remains
2065		read-only.]
2066
2067		The same can be accomplished in a more flexible way
2068		for any variable by configuring the type of access
2069		to allow for those variables in the ".flags" variable
2070		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2071
2072- Protected RAM:
2073		CONFIG_PRAM
2074
2075		Define this variable to enable the reservation of
2076		"protected RAM", i. e. RAM which is not overwritten
2077		by U-Boot. Define CONFIG_PRAM to hold the number of
2078		kB you want to reserve for pRAM. You can overwrite
2079		this default value by defining an environment
2080		variable "pram" to the number of kB you want to
2081		reserve. Note that the board info structure will
2082		still show the full amount of RAM. If pRAM is
2083		reserved, a new environment variable "mem" will
2084		automatically be defined to hold the amount of
2085		remaining RAM in a form that can be passed as boot
2086		argument to Linux, for instance like that:
2087
2088			setenv bootargs ... mem=\${mem}
2089			saveenv
2090
2091		This way you can tell Linux not to use this memory,
2092		either, which results in a memory region that will
2093		not be affected by reboots.
2094
2095		*WARNING* If your board configuration uses automatic
2096		detection of the RAM size, you must make sure that
2097		this memory test is non-destructive. So far, the
2098		following board configurations are known to be
2099		"pRAM-clean":
2100
2101			IVMS8, IVML24, SPD8xx,
2102			HERMES, IP860, RPXlite, LWMON,
2103			FLAGADM
2104
2105- Access to physical memory region (> 4GB)
2106		Some basic support is provided for operations on memory not
2107		normally accessible to U-Boot - e.g. some architectures
2108		support access to more than 4GB of memory on 32-bit
2109		machines using physical address extension or similar.
2110		Define CONFIG_PHYSMEM to access this basic support, which
2111		currently only supports clearing the memory.
2112
2113- Error Recovery:
2114		CONFIG_NET_RETRY_COUNT
2115
2116		This variable defines the number of retries for
2117		network operations like ARP, RARP, TFTP, or BOOTP
2118		before giving up the operation. If not defined, a
2119		default value of 5 is used.
2120
2121		CONFIG_ARP_TIMEOUT
2122
2123		Timeout waiting for an ARP reply in milliseconds.
2124
2125		CONFIG_NFS_TIMEOUT
2126
2127		Timeout in milliseconds used in NFS protocol.
2128		If you encounter "ERROR: Cannot umount" in nfs command,
2129		try longer timeout such as
2130		#define CONFIG_NFS_TIMEOUT 10000UL
2131
2132- Command Interpreter:
2133		CONFIG_SYS_PROMPT_HUSH_PS2
2134
2135		This defines the secondary prompt string, which is
2136		printed when the command interpreter needs more input
2137		to complete a command. Usually "> ".
2138
2139	Note:
2140
2141		In the current implementation, the local variables
2142		space and global environment variables space are
2143		separated. Local variables are those you define by
2144		simply typing `name=value'. To access a local
2145		variable later on, you have write `$name' or
2146		`${name}'; to execute the contents of a variable
2147		directly type `$name' at the command prompt.
2148
2149		Global environment variables are those you use
2150		setenv/printenv to work with. To run a command stored
2151		in such a variable, you need to use the run command,
2152		and you must not use the '$' sign to access them.
2153
2154		To store commands and special characters in a
2155		variable, please use double quotation marks
2156		surrounding the whole text of the variable, instead
2157		of the backslashes before semicolons and special
2158		symbols.
2159
2160- Command Line Editing and History:
2161		CONFIG_CMDLINE_PS_SUPPORT
2162
2163		Enable support for changing the command prompt string
2164		at run-time. Only static string is supported so far.
2165		The string is obtained from environment variables PS1
2166		and PS2.
2167
2168- Default Environment:
2169		CONFIG_EXTRA_ENV_SETTINGS
2170
2171		Define this to contain any number of null terminated
2172		strings (variable = value pairs) that will be part of
2173		the default environment compiled into the boot image.
2174
2175		For example, place something like this in your
2176		board's config file:
2177
2178		#define CONFIG_EXTRA_ENV_SETTINGS \
2179			"myvar1=value1\0" \
2180			"myvar2=value2\0"
2181
2182		Warning: This method is based on knowledge about the
2183		internal format how the environment is stored by the
2184		U-Boot code. This is NOT an official, exported
2185		interface! Although it is unlikely that this format
2186		will change soon, there is no guarantee either.
2187		You better know what you are doing here.
2188
2189		Note: overly (ab)use of the default environment is
2190		discouraged. Make sure to check other ways to preset
2191		the environment like the "source" command or the
2192		boot command first.
2193
2194		CONFIG_DELAY_ENVIRONMENT
2195
2196		Normally the environment is loaded when the board is
2197		initialised so that it is available to U-Boot. This inhibits
2198		that so that the environment is not available until
2199		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2200		this is instead controlled by the value of
2201		/config/load-environment.
2202
2203- Serial Flash support
2204		Usage requires an initial 'sf probe' to define the serial
2205		flash parameters, followed by read/write/erase/update
2206		commands.
2207
2208		The following defaults may be provided by the platform
2209		to handle the common case when only a single serial
2210		flash is present on the system.
2211
2212		CONFIG_SF_DEFAULT_BUS		Bus identifier
2213		CONFIG_SF_DEFAULT_CS		Chip-select
2214		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2215		CONFIG_SF_DEFAULT_SPEED		in Hz
2216
2217
2218- TFTP Fixed UDP Port:
2219		CONFIG_TFTP_PORT
2220
2221		If this is defined, the environment variable tftpsrcp
2222		is used to supply the TFTP UDP source port value.
2223		If tftpsrcp isn't defined, the normal pseudo-random port
2224		number generator is used.
2225
2226		Also, the environment variable tftpdstp is used to supply
2227		the TFTP UDP destination port value.  If tftpdstp isn't
2228		defined, the normal port 69 is used.
2229
2230		The purpose for tftpsrcp is to allow a TFTP server to
2231		blindly start the TFTP transfer using the pre-configured
2232		target IP address and UDP port. This has the effect of
2233		"punching through" the (Windows XP) firewall, allowing
2234		the remainder of the TFTP transfer to proceed normally.
2235		A better solution is to properly configure the firewall,
2236		but sometimes that is not allowed.
2237
2238- Show boot progress:
2239		CONFIG_SHOW_BOOT_PROGRESS
2240
2241		Defining this option allows to add some board-
2242		specific code (calling a user-provided function
2243		"show_boot_progress(int)") that enables you to show
2244		the system's boot progress on some display (for
2245		example, some LED's) on your board. At the moment,
2246		the following checkpoints are implemented:
2247
2248
2249Legacy uImage format:
2250
2251  Arg	Where			When
2252    1	common/cmd_bootm.c	before attempting to boot an image
2253   -1	common/cmd_bootm.c	Image header has bad	 magic number
2254    2	common/cmd_bootm.c	Image header has correct magic number
2255   -2	common/cmd_bootm.c	Image header has bad	 checksum
2256    3	common/cmd_bootm.c	Image header has correct checksum
2257   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2258    4	common/cmd_bootm.c	Image data   has correct checksum
2259   -4	common/cmd_bootm.c	Image is for unsupported architecture
2260    5	common/cmd_bootm.c	Architecture check OK
2261   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2262    6	common/cmd_bootm.c	Image Type check OK
2263   -6	common/cmd_bootm.c	gunzip uncompression error
2264   -7	common/cmd_bootm.c	Unimplemented compression type
2265    7	common/cmd_bootm.c	Uncompression OK
2266    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2267   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2268
2269    9	common/image.c		Start initial ramdisk verification
2270  -10	common/image.c		Ramdisk header has bad	   magic number
2271  -11	common/image.c		Ramdisk header has bad	   checksum
2272   10	common/image.c		Ramdisk header is OK
2273  -12	common/image.c		Ramdisk data   has bad	   checksum
2274   11	common/image.c		Ramdisk data   has correct checksum
2275   12	common/image.c		Ramdisk verification complete, start loading
2276  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2277   13	common/image.c		Start multifile image verification
2278   14	common/image.c		No initial ramdisk, no multifile, continue.
2279
2280   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2281
2282  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2283  -31	post/post.c		POST test failed, detected by post_output_backlog()
2284  -32	post/post.c		POST test failed, detected by post_run_single()
2285
2286   34	common/cmd_doc.c	before loading a Image from a DOC device
2287  -35	common/cmd_doc.c	Bad usage of "doc" command
2288   35	common/cmd_doc.c	correct usage of "doc" command
2289  -36	common/cmd_doc.c	No boot device
2290   36	common/cmd_doc.c	correct boot device
2291  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2292   37	common/cmd_doc.c	correct chip ID found, device available
2293  -38	common/cmd_doc.c	Read Error on boot device
2294   38	common/cmd_doc.c	reading Image header from DOC device OK
2295  -39	common/cmd_doc.c	Image header has bad magic number
2296   39	common/cmd_doc.c	Image header has correct magic number
2297  -40	common/cmd_doc.c	Error reading Image from DOC device
2298   40	common/cmd_doc.c	Image header has correct magic number
2299   41	common/cmd_ide.c	before loading a Image from a IDE device
2300  -42	common/cmd_ide.c	Bad usage of "ide" command
2301   42	common/cmd_ide.c	correct usage of "ide" command
2302  -43	common/cmd_ide.c	No boot device
2303   43	common/cmd_ide.c	boot device found
2304  -44	common/cmd_ide.c	Device not available
2305   44	common/cmd_ide.c	Device available
2306  -45	common/cmd_ide.c	wrong partition selected
2307   45	common/cmd_ide.c	partition selected
2308  -46	common/cmd_ide.c	Unknown partition table
2309   46	common/cmd_ide.c	valid partition table found
2310  -47	common/cmd_ide.c	Invalid partition type
2311   47	common/cmd_ide.c	correct partition type
2312  -48	common/cmd_ide.c	Error reading Image Header on boot device
2313   48	common/cmd_ide.c	reading Image Header from IDE device OK
2314  -49	common/cmd_ide.c	Image header has bad magic number
2315   49	common/cmd_ide.c	Image header has correct magic number
2316  -50	common/cmd_ide.c	Image header has bad	 checksum
2317   50	common/cmd_ide.c	Image header has correct checksum
2318  -51	common/cmd_ide.c	Error reading Image from IDE device
2319   51	common/cmd_ide.c	reading Image from IDE device OK
2320   52	common/cmd_nand.c	before loading a Image from a NAND device
2321  -53	common/cmd_nand.c	Bad usage of "nand" command
2322   53	common/cmd_nand.c	correct usage of "nand" command
2323  -54	common/cmd_nand.c	No boot device
2324   54	common/cmd_nand.c	boot device found
2325  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2326   55	common/cmd_nand.c	correct chip ID found, device available
2327  -56	common/cmd_nand.c	Error reading Image Header on boot device
2328   56	common/cmd_nand.c	reading Image Header from NAND device OK
2329  -57	common/cmd_nand.c	Image header has bad magic number
2330   57	common/cmd_nand.c	Image header has correct magic number
2331  -58	common/cmd_nand.c	Error reading Image from NAND device
2332   58	common/cmd_nand.c	reading Image from NAND device OK
2333
2334  -60	common/env_common.c	Environment has a bad CRC, using default
2335
2336   64	net/eth.c		starting with Ethernet configuration.
2337  -64	net/eth.c		no Ethernet found.
2338   65	net/eth.c		Ethernet found.
2339
2340  -80	common/cmd_net.c	usage wrong
2341   80	common/cmd_net.c	before calling net_loop()
2342  -81	common/cmd_net.c	some error in net_loop() occurred
2343   81	common/cmd_net.c	net_loop() back without error
2344  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2345   82	common/cmd_net.c	trying automatic boot
2346   83	common/cmd_net.c	running "source" command
2347  -83	common/cmd_net.c	some error in automatic boot or "source" command
2348   84	common/cmd_net.c	end without errors
2349
2350FIT uImage format:
2351
2352  Arg	Where			When
2353  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2354 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2355  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2356 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2357  102	common/cmd_bootm.c	Kernel unit name specified
2358 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2359  103	common/cmd_bootm.c	Found configuration node
2360  104	common/cmd_bootm.c	Got kernel subimage node offset
2361 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2362  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2363 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2364  106	common/cmd_bootm.c	Architecture check OK
2365 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2366  107	common/cmd_bootm.c	Kernel subimage type OK
2367 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2368  108	common/cmd_bootm.c	Got kernel subimage data/size
2369 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2370 -109	common/cmd_bootm.c	Can't get kernel subimage type
2371 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2372 -111	common/cmd_bootm.c	Can't get kernel subimage os
2373 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2374 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2375
2376  120	common/image.c		Start initial ramdisk verification
2377 -120	common/image.c		Ramdisk FIT image has incorrect format
2378  121	common/image.c		Ramdisk FIT image has correct format
2379  122	common/image.c		No ramdisk subimage unit name, using configuration
2380 -122	common/image.c		Can't get configuration for ramdisk subimage
2381  123	common/image.c		Ramdisk unit name specified
2382 -124	common/image.c		Can't get ramdisk subimage node offset
2383  125	common/image.c		Got ramdisk subimage node offset
2384 -125	common/image.c		Ramdisk subimage hash verification failed
2385  126	common/image.c		Ramdisk subimage hash verification OK
2386 -126	common/image.c		Ramdisk subimage for unsupported architecture
2387  127	common/image.c		Architecture check OK
2388 -127	common/image.c		Can't get ramdisk subimage data/size
2389  128	common/image.c		Got ramdisk subimage data/size
2390  129	common/image.c		Can't get ramdisk load address
2391 -129	common/image.c		Got ramdisk load address
2392
2393 -130	common/cmd_doc.c	Incorrect FIT image format
2394  131	common/cmd_doc.c	FIT image format OK
2395
2396 -140	common/cmd_ide.c	Incorrect FIT image format
2397  141	common/cmd_ide.c	FIT image format OK
2398
2399 -150	common/cmd_nand.c	Incorrect FIT image format
2400  151	common/cmd_nand.c	FIT image format OK
2401
2402- Standalone program support:
2403		CONFIG_STANDALONE_LOAD_ADDR
2404
2405		This option defines a board specific value for the
2406		address where standalone program gets loaded, thus
2407		overwriting the architecture dependent default
2408		settings.
2409
2410- Frame Buffer Address:
2411		CONFIG_FB_ADDR
2412
2413		Define CONFIG_FB_ADDR if you want to use specific
2414		address for frame buffer.  This is typically the case
2415		when using a graphics controller has separate video
2416		memory.  U-Boot will then place the frame buffer at
2417		the given address instead of dynamically reserving it
2418		in system RAM by calling lcd_setmem(), which grabs
2419		the memory for the frame buffer depending on the
2420		configured panel size.
2421
2422		Please see board_init_f function.
2423
2424- Automatic software updates via TFTP server
2425		CONFIG_UPDATE_TFTP
2426		CONFIG_UPDATE_TFTP_CNT_MAX
2427		CONFIG_UPDATE_TFTP_MSEC_MAX
2428
2429		These options enable and control the auto-update feature;
2430		for a more detailed description refer to doc/README.update.
2431
2432- MTD Support (mtdparts command, UBI support)
2433		CONFIG_MTD_UBI_WL_THRESHOLD
2434		This parameter defines the maximum difference between the highest
2435		erase counter value and the lowest erase counter value of eraseblocks
2436		of UBI devices. When this threshold is exceeded, UBI starts performing
2437		wear leveling by means of moving data from eraseblock with low erase
2438		counter to eraseblocks with high erase counter.
2439
2440		The default value should be OK for SLC NAND flashes, NOR flashes and
2441		other flashes which have eraseblock life-cycle 100000 or more.
2442		However, in case of MLC NAND flashes which typically have eraseblock
2443		life-cycle less than 10000, the threshold should be lessened (e.g.,
2444		to 128 or 256, although it does not have to be power of 2).
2445
2446		default: 4096
2447
2448		CONFIG_MTD_UBI_BEB_LIMIT
2449		This option specifies the maximum bad physical eraseblocks UBI
2450		expects on the MTD device (per 1024 eraseblocks). If the
2451		underlying flash does not admit of bad eraseblocks (e.g. NOR
2452		flash), this value is ignored.
2453
2454		NAND datasheets often specify the minimum and maximum NVM
2455		(Number of Valid Blocks) for the flashes' endurance lifetime.
2456		The maximum expected bad eraseblocks per 1024 eraseblocks
2457		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2458		which gives 20 for most NANDs (MaxNVB is basically the total
2459		count of eraseblocks on the chip).
2460
2461		To put it differently, if this value is 20, UBI will try to
2462		reserve about 1.9% of physical eraseblocks for bad blocks
2463		handling. And that will be 1.9% of eraseblocks on the entire
2464		NAND chip, not just the MTD partition UBI attaches. This means
2465		that if you have, say, a NAND flash chip admits maximum 40 bad
2466		eraseblocks, and it is split on two MTD partitions of the same
2467		size, UBI will reserve 40 eraseblocks when attaching a
2468		partition.
2469
2470		default: 20
2471
2472		CONFIG_MTD_UBI_FASTMAP
2473		Fastmap is a mechanism which allows attaching an UBI device
2474		in nearly constant time. Instead of scanning the whole MTD device it
2475		only has to locate a checkpoint (called fastmap) on the device.
2476		The on-flash fastmap contains all information needed to attach
2477		the device. Using fastmap makes only sense on large devices where
2478		attaching by scanning takes long. UBI will not automatically install
2479		a fastmap on old images, but you can set the UBI parameter
2480		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2481		that fastmap-enabled images are still usable with UBI implementations
2482		without	fastmap support. On typical flash devices the whole fastmap
2483		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2484
2485		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2486		Set this parameter to enable fastmap automatically on images
2487		without a fastmap.
2488		default: 0
2489
2490		CONFIG_MTD_UBI_FM_DEBUG
2491		Enable UBI fastmap debug
2492		default: 0
2493
2494- SPL framework
2495		CONFIG_SPL
2496		Enable building of SPL globally.
2497
2498		CONFIG_SPL_LDSCRIPT
2499		LDSCRIPT for linking the SPL binary.
2500
2501		CONFIG_SPL_MAX_FOOTPRINT
2502		Maximum size in memory allocated to the SPL, BSS included.
2503		When defined, the linker checks that the actual memory
2504		used by SPL from _start to __bss_end does not exceed it.
2505		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2506		must not be both defined at the same time.
2507
2508		CONFIG_SPL_MAX_SIZE
2509		Maximum size of the SPL image (text, data, rodata, and
2510		linker lists sections), BSS excluded.
2511		When defined, the linker checks that the actual size does
2512		not exceed it.
2513
2514		CONFIG_SPL_TEXT_BASE
2515		TEXT_BASE for linking the SPL binary.
2516
2517		CONFIG_SPL_RELOC_TEXT_BASE
2518		Address to relocate to.  If unspecified, this is equal to
2519		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2520
2521		CONFIG_SPL_BSS_START_ADDR
2522		Link address for the BSS within the SPL binary.
2523
2524		CONFIG_SPL_BSS_MAX_SIZE
2525		Maximum size in memory allocated to the SPL BSS.
2526		When defined, the linker checks that the actual memory used
2527		by SPL from __bss_start to __bss_end does not exceed it.
2528		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2529		must not be both defined at the same time.
2530
2531		CONFIG_SPL_STACK
2532		Adress of the start of the stack SPL will use
2533
2534		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2535		When defined, SPL will panic() if the image it has
2536		loaded does not have a signature.
2537		Defining this is useful when code which loads images
2538		in SPL cannot guarantee that absolutely all read errors
2539		will be caught.
2540		An example is the LPC32XX MLC NAND driver, which will
2541		consider that a completely unreadable NAND block is bad,
2542		and thus should be skipped silently.
2543
2544		CONFIG_SPL_RELOC_STACK
2545		Adress of the start of the stack SPL will use after
2546		relocation.  If unspecified, this is equal to
2547		CONFIG_SPL_STACK.
2548
2549		CONFIG_SYS_SPL_MALLOC_START
2550		Starting address of the malloc pool used in SPL.
2551		When this option is set the full malloc is used in SPL and
2552		it is set up by spl_init() and before that, the simple malloc()
2553		can be used if CONFIG_SYS_MALLOC_F is defined.
2554
2555		CONFIG_SYS_SPL_MALLOC_SIZE
2556		The size of the malloc pool used in SPL.
2557
2558		CONFIG_SPL_OS_BOOT
2559		Enable booting directly to an OS from SPL.
2560		See also: doc/README.falcon
2561
2562		CONFIG_SPL_DISPLAY_PRINT
2563		For ARM, enable an optional function to print more information
2564		about the running system.
2565
2566		CONFIG_SPL_INIT_MINIMAL
2567		Arch init code should be built for a very small image
2568
2569		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2570		Partition on the MMC to load U-Boot from when the MMC is being
2571		used in raw mode
2572
2573		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2574		Sector to load kernel uImage from when MMC is being
2575		used in raw mode (for Falcon mode)
2576
2577		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2578		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2579		Sector and number of sectors to load kernel argument
2580		parameters from when MMC is being used in raw mode
2581		(for falcon mode)
2582
2583		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2584		Partition on the MMC to load U-Boot from when the MMC is being
2585		used in fs mode
2586
2587		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2588		Filename to read to load U-Boot when reading from filesystem
2589
2590		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2591		Filename to read to load kernel uImage when reading
2592		from filesystem (for Falcon mode)
2593
2594		CONFIG_SPL_FS_LOAD_ARGS_NAME
2595		Filename to read to load kernel argument parameters
2596		when reading from filesystem (for Falcon mode)
2597
2598		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2599		Set this for NAND SPL on PPC mpc83xx targets, so that
2600		start.S waits for the rest of the SPL to load before
2601		continuing (the hardware starts execution after just
2602		loading the first page rather than the full 4K).
2603
2604		CONFIG_SPL_SKIP_RELOCATE
2605		Avoid SPL relocation
2606
2607		CONFIG_SPL_NAND_BASE
2608		Include nand_base.c in the SPL.  Requires
2609		CONFIG_SPL_NAND_DRIVERS.
2610
2611		CONFIG_SPL_NAND_DRIVERS
2612		SPL uses normal NAND drivers, not minimal drivers.
2613
2614		CONFIG_SPL_NAND_IDENT
2615		SPL uses the chip ID list to identify the NAND flash.
2616		Requires CONFIG_SPL_NAND_BASE.
2617
2618		CONFIG_SPL_NAND_ECC
2619		Include standard software ECC in the SPL
2620
2621		CONFIG_SPL_NAND_SIMPLE
2622		Support for NAND boot using simple NAND drivers that
2623		expose the cmd_ctrl() interface.
2624
2625		CONFIG_SPL_UBI
2626		Support for a lightweight UBI (fastmap) scanner and
2627		loader
2628
2629		CONFIG_SPL_NAND_RAW_ONLY
2630		Support to boot only raw u-boot.bin images. Use this only
2631		if you need to save space.
2632
2633		CONFIG_SPL_COMMON_INIT_DDR
2634		Set for common ddr init with serial presence detect in
2635		SPL binary.
2636
2637		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2638		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2639		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2640		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2641		CONFIG_SYS_NAND_ECCBYTES
2642		Defines the size and behavior of the NAND that SPL uses
2643		to read U-Boot
2644
2645		CONFIG_SPL_NAND_BOOT
2646		Add support NAND boot
2647
2648		CONFIG_SYS_NAND_U_BOOT_OFFS
2649		Location in NAND to read U-Boot from
2650
2651		CONFIG_SYS_NAND_U_BOOT_DST
2652		Location in memory to load U-Boot to
2653
2654		CONFIG_SYS_NAND_U_BOOT_SIZE
2655		Size of image to load
2656
2657		CONFIG_SYS_NAND_U_BOOT_START
2658		Entry point in loaded image to jump to
2659
2660		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2661		Define this if you need to first read the OOB and then the
2662		data. This is used, for example, on davinci platforms.
2663
2664		CONFIG_SPL_RAM_DEVICE
2665		Support for running image already present in ram, in SPL binary
2666
2667		CONFIG_SPL_PAD_TO
2668		Image offset to which the SPL should be padded before appending
2669		the SPL payload. By default, this is defined as
2670		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2671		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2672		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2673
2674		CONFIG_SPL_TARGET
2675		Final target image containing SPL and payload.  Some SPLs
2676		use an arch-specific makefile fragment instead, for
2677		example if more than one image needs to be produced.
2678
2679		CONFIG_SPL_FIT_PRINT
2680		Printing information about a FIT image adds quite a bit of
2681		code to SPL. So this is normally disabled in SPL. Use this
2682		option to re-enable it. This will affect the output of the
2683		bootm command when booting a FIT image.
2684
2685- TPL framework
2686		CONFIG_TPL
2687		Enable building of TPL globally.
2688
2689		CONFIG_TPL_PAD_TO
2690		Image offset to which the TPL should be padded before appending
2691		the TPL payload. By default, this is defined as
2692		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2693		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2694		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2695
2696- Interrupt support (PPC):
2697
2698		There are common interrupt_init() and timer_interrupt()
2699		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2700		for CPU specific initialization. interrupt_init_cpu()
2701		should set decrementer_count to appropriate value. If
2702		CPU resets decrementer automatically after interrupt
2703		(ppc4xx) it should set decrementer_count to zero.
2704		timer_interrupt() calls timer_interrupt_cpu() for CPU
2705		specific handling. If board has watchdog / status_led
2706		/ other_activity_monitor it works automatically from
2707		general timer_interrupt().
2708
2709
2710Board initialization settings:
2711------------------------------
2712
2713During Initialization u-boot calls a number of board specific functions
2714to allow the preparation of board specific prerequisites, e.g. pin setup
2715before drivers are initialized. To enable these callbacks the
2716following configuration macros have to be defined. Currently this is
2717architecture specific, so please check arch/your_architecture/lib/board.c
2718typically in board_init_f() and board_init_r().
2719
2720- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2721- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2722- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2723- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2724
2725Configuration Settings:
2726-----------------------
2727
2728- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2729		Optionally it can be defined to support 64-bit memory commands.
2730
2731- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2732		undefine this when you're short of memory.
2733
2734- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2735		width of the commands listed in the 'help' command output.
2736
2737- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2738		prompt for user input.
2739
2740- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2741
2742- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2743
2744- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2745
2746- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2747		the application (usually a Linux kernel) when it is
2748		booted
2749
2750- CONFIG_SYS_BAUDRATE_TABLE:
2751		List of legal baudrate settings for this board.
2752
2753- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2754		Begin and End addresses of the area used by the
2755		simple memory test.
2756
2757- CONFIG_SYS_MEMTEST_SCRATCH:
2758		Scratch address used by the alternate memory test
2759		You only need to set this if address zero isn't writeable
2760
2761- CONFIG_SYS_MEM_RESERVE_SECURE
2762		Only implemented for ARMv8 for now.
2763		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2764		is substracted from total RAM and won't be reported to OS.
2765		This memory can be used as secure memory. A variable
2766		gd->arch.secure_ram is used to track the location. In systems
2767		the RAM base is not zero, or RAM is divided into banks,
2768		this variable needs to be recalcuated to get the address.
2769
2770- CONFIG_SYS_MEM_TOP_HIDE:
2771		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2772		this specified memory area will get subtracted from the top
2773		(end) of RAM and won't get "touched" at all by U-Boot. By
2774		fixing up gd->ram_size the Linux kernel should gets passed
2775		the now "corrected" memory size and won't touch it either.
2776		This should work for arch/ppc and arch/powerpc. Only Linux
2777		board ports in arch/powerpc with bootwrapper support that
2778		recalculate the memory size from the SDRAM controller setup
2779		will have to get fixed in Linux additionally.
2780
2781		This option can be used as a workaround for the 440EPx/GRx
2782		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2783		be touched.
2784
2785		WARNING: Please make sure that this value is a multiple of
2786		the Linux page size (normally 4k). If this is not the case,
2787		then the end address of the Linux memory will be located at a
2788		non page size aligned address and this could cause major
2789		problems.
2790
2791- CONFIG_SYS_LOADS_BAUD_CHANGE:
2792		Enable temporary baudrate change while serial download
2793
2794- CONFIG_SYS_SDRAM_BASE:
2795		Physical start address of SDRAM. _Must_ be 0 here.
2796
2797- CONFIG_SYS_FLASH_BASE:
2798		Physical start address of Flash memory.
2799
2800- CONFIG_SYS_MONITOR_BASE:
2801		Physical start address of boot monitor code (set by
2802		make config files to be same as the text base address
2803		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2804		CONFIG_SYS_FLASH_BASE when booting from flash.
2805
2806- CONFIG_SYS_MONITOR_LEN:
2807		Size of memory reserved for monitor code, used to
2808		determine _at_compile_time_ (!) if the environment is
2809		embedded within the U-Boot image, or in a separate
2810		flash sector.
2811
2812- CONFIG_SYS_MALLOC_LEN:
2813		Size of DRAM reserved for malloc() use.
2814
2815- CONFIG_SYS_MALLOC_F_LEN
2816		Size of the malloc() pool for use before relocation. If
2817		this is defined, then a very simple malloc() implementation
2818		will become available before relocation. The address is just
2819		below the global data, and the stack is moved down to make
2820		space.
2821
2822		This feature allocates regions with increasing addresses
2823		within the region. calloc() is supported, but realloc()
2824		is not available. free() is supported but does nothing.
2825		The memory will be freed (or in fact just forgotten) when
2826		U-Boot relocates itself.
2827
2828- CONFIG_SYS_MALLOC_SIMPLE
2829		Provides a simple and small malloc() and calloc() for those
2830		boards which do not use the full malloc in SPL (which is
2831		enabled with CONFIG_SYS_SPL_MALLOC_START).
2832
2833- CONFIG_SYS_NONCACHED_MEMORY:
2834		Size of non-cached memory area. This area of memory will be
2835		typically located right below the malloc() area and mapped
2836		uncached in the MMU. This is useful for drivers that would
2837		otherwise require a lot of explicit cache maintenance. For
2838		some drivers it's also impossible to properly maintain the
2839		cache. For example if the regions that need to be flushed
2840		are not a multiple of the cache-line size, *and* padding
2841		cannot be allocated between the regions to align them (i.e.
2842		if the HW requires a contiguous array of regions, and the
2843		size of each region is not cache-aligned), then a flush of
2844		one region may result in overwriting data that hardware has
2845		written to another region in the same cache-line. This can
2846		happen for example in network drivers where descriptors for
2847		buffers are typically smaller than the CPU cache-line (e.g.
2848		16 bytes vs. 32 or 64 bytes).
2849
2850		Non-cached memory is only supported on 32-bit ARM at present.
2851
2852- CONFIG_SYS_BOOTM_LEN:
2853		Normally compressed uImages are limited to an
2854		uncompressed size of 8 MBytes. If this is not enough,
2855		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2856		to adjust this setting to your needs.
2857
2858- CONFIG_SYS_BOOTMAPSZ:
2859		Maximum size of memory mapped by the startup code of
2860		the Linux kernel; all data that must be processed by
2861		the Linux kernel (bd_info, boot arguments, FDT blob if
2862		used) must be put below this limit, unless "bootm_low"
2863		environment variable is defined and non-zero. In such case
2864		all data for the Linux kernel must be between "bootm_low"
2865		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2866		variable "bootm_mapsize" will override the value of
2867		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2868		then the value in "bootm_size" will be used instead.
2869
2870- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2871		Enable initrd_high functionality.  If defined then the
2872		initrd_high feature is enabled and the bootm ramdisk subcommand
2873		is enabled.
2874
2875- CONFIG_SYS_BOOT_GET_CMDLINE:
2876		Enables allocating and saving kernel cmdline in space between
2877		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2878
2879- CONFIG_SYS_BOOT_GET_KBD:
2880		Enables allocating and saving a kernel copy of the bd_info in
2881		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2882
2883- CONFIG_SYS_MAX_FLASH_BANKS:
2884		Max number of Flash memory banks
2885
2886- CONFIG_SYS_MAX_FLASH_SECT:
2887		Max number of sectors on a Flash chip
2888
2889- CONFIG_SYS_FLASH_ERASE_TOUT:
2890		Timeout for Flash erase operations (in ms)
2891
2892- CONFIG_SYS_FLASH_WRITE_TOUT:
2893		Timeout for Flash write operations (in ms)
2894
2895- CONFIG_SYS_FLASH_LOCK_TOUT
2896		Timeout for Flash set sector lock bit operation (in ms)
2897
2898- CONFIG_SYS_FLASH_UNLOCK_TOUT
2899		Timeout for Flash clear lock bits operation (in ms)
2900
2901- CONFIG_SYS_FLASH_PROTECTION
2902		If defined, hardware flash sectors protection is used
2903		instead of U-Boot software protection.
2904
2905- CONFIG_SYS_DIRECT_FLASH_TFTP:
2906
2907		Enable TFTP transfers directly to flash memory;
2908		without this option such a download has to be
2909		performed in two steps: (1) download to RAM, and (2)
2910		copy from RAM to flash.
2911
2912		The two-step approach is usually more reliable, since
2913		you can check if the download worked before you erase
2914		the flash, but in some situations (when system RAM is
2915		too limited to allow for a temporary copy of the
2916		downloaded image) this option may be very useful.
2917
2918- CONFIG_SYS_FLASH_CFI:
2919		Define if the flash driver uses extra elements in the
2920		common flash structure for storing flash geometry.
2921
2922- CONFIG_FLASH_CFI_DRIVER
2923		This option also enables the building of the cfi_flash driver
2924		in the drivers directory
2925
2926- CONFIG_FLASH_CFI_MTD
2927		This option enables the building of the cfi_mtd driver
2928		in the drivers directory. The driver exports CFI flash
2929		to the MTD layer.
2930
2931- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2932		Use buffered writes to flash.
2933
2934- CONFIG_FLASH_SPANSION_S29WS_N
2935		s29ws-n MirrorBit flash has non-standard addresses for buffered
2936		write commands.
2937
2938- CONFIG_SYS_FLASH_QUIET_TEST
2939		If this option is defined, the common CFI flash doesn't
2940		print it's warning upon not recognized FLASH banks. This
2941		is useful, if some of the configured banks are only
2942		optionally available.
2943
2944- CONFIG_FLASH_SHOW_PROGRESS
2945		If defined (must be an integer), print out countdown
2946		digits and dots.  Recommended value: 45 (9..1) for 80
2947		column displays, 15 (3..1) for 40 column displays.
2948
2949- CONFIG_FLASH_VERIFY
2950		If defined, the content of the flash (destination) is compared
2951		against the source after the write operation. An error message
2952		will be printed when the contents are not identical.
2953		Please note that this option is useless in nearly all cases,
2954		since such flash programming errors usually are detected earlier
2955		while unprotecting/erasing/programming. Please only enable
2956		this option if you really know what you are doing.
2957
2958- CONFIG_SYS_RX_ETH_BUFFER:
2959		Defines the number of Ethernet receive buffers. On some
2960		Ethernet controllers it is recommended to set this value
2961		to 8 or even higher (EEPRO100 or 405 EMAC), since all
2962		buffers can be full shortly after enabling the interface
2963		on high Ethernet traffic.
2964		Defaults to 4 if not defined.
2965
2966- CONFIG_ENV_MAX_ENTRIES
2967
2968	Maximum number of entries in the hash table that is used
2969	internally to store the environment settings. The default
2970	setting is supposed to be generous and should work in most
2971	cases. This setting can be used to tune behaviour; see
2972	lib/hashtable.c for details.
2973
2974- CONFIG_ENV_FLAGS_LIST_DEFAULT
2975- CONFIG_ENV_FLAGS_LIST_STATIC
2976	Enable validation of the values given to environment variables when
2977	calling env set.  Variables can be restricted to only decimal,
2978	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2979	the variables can also be restricted to IP address or MAC address.
2980
2981	The format of the list is:
2982		type_attribute = [s|d|x|b|i|m]
2983		access_attribute = [a|r|o|c]
2984		attributes = type_attribute[access_attribute]
2985		entry = variable_name[:attributes]
2986		list = entry[,list]
2987
2988	The type attributes are:
2989		s - String (default)
2990		d - Decimal
2991		x - Hexadecimal
2992		b - Boolean ([1yYtT|0nNfF])
2993		i - IP address
2994		m - MAC address
2995
2996	The access attributes are:
2997		a - Any (default)
2998		r - Read-only
2999		o - Write-once
3000		c - Change-default
3001
3002	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3003		Define this to a list (string) to define the ".flags"
3004		environment variable in the default or embedded environment.
3005
3006	- CONFIG_ENV_FLAGS_LIST_STATIC
3007		Define this to a list (string) to define validation that
3008		should be done if an entry is not found in the ".flags"
3009		environment variable.  To override a setting in the static
3010		list, simply add an entry for the same variable name to the
3011		".flags" variable.
3012
3013	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3014	regular expression. This allows multiple variables to define the same
3015	flags without explicitly listing them for each variable.
3016
3017- CONFIG_ENV_ACCESS_IGNORE_FORCE
3018	If defined, don't allow the -f switch to env set override variable
3019	access flags.
3020
3021- CONFIG_USE_STDINT
3022	If stdint.h is available with your toolchain you can define this
3023	option to enable it. You can provide option 'USE_STDINT=1' when
3024	building U-Boot to enable this.
3025
3026The following definitions that deal with the placement and management
3027of environment data (variable area); in general, we support the
3028following configurations:
3029
3030- CONFIG_BUILD_ENVCRC:
3031
3032	Builds up envcrc with the target environment so that external utils
3033	may easily extract it and embed it in final U-Boot images.
3034
3035BE CAREFUL! The first access to the environment happens quite early
3036in U-Boot initialization (when we try to get the setting of for the
3037console baudrate). You *MUST* have mapped your NVRAM area then, or
3038U-Boot will hang.
3039
3040Please note that even with NVRAM we still use a copy of the
3041environment in RAM: we could work on NVRAM directly, but we want to
3042keep settings there always unmodified except somebody uses "saveenv"
3043to save the current settings.
3044
3045BE CAREFUL! For some special cases, the local device can not use
3046"saveenv" command. For example, the local device will get the
3047environment stored in a remote NOR flash by SRIO or PCIE link,
3048but it can not erase, write this NOR flash by SRIO or PCIE interface.
3049
3050- CONFIG_NAND_ENV_DST
3051
3052	Defines address in RAM to which the nand_spl code should copy the
3053	environment. If redundant environment is used, it will be copied to
3054	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3055
3056Please note that the environment is read-only until the monitor
3057has been relocated to RAM and a RAM copy of the environment has been
3058created; also, when using EEPROM you will have to use env_get_f()
3059until then to read environment variables.
3060
3061The environment is protected by a CRC32 checksum. Before the monitor
3062is relocated into RAM, as a result of a bad CRC you will be working
3063with the compiled-in default environment - *silently*!!! [This is
3064necessary, because the first environment variable we need is the
3065"baudrate" setting for the console - if we have a bad CRC, we don't
3066have any device yet where we could complain.]
3067
3068Note: once the monitor has been relocated, then it will complain if
3069the default environment is used; a new CRC is computed as soon as you
3070use the "saveenv" command to store a valid environment.
3071
3072- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3073		Echo the inverted Ethernet link state to the fault LED.
3074
3075		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3076		      also needs to be defined.
3077
3078- CONFIG_SYS_FAULT_MII_ADDR:
3079		MII address of the PHY to check for the Ethernet link state.
3080
3081- CONFIG_NS16550_MIN_FUNCTIONS:
3082		Define this if you desire to only have use of the NS16550_init
3083		and NS16550_putc functions for the serial driver located at
3084		drivers/serial/ns16550.c.  This option is useful for saving
3085		space for already greatly restricted images, including but not
3086		limited to NAND_SPL configurations.
3087
3088- CONFIG_DISPLAY_BOARDINFO
3089		Display information about the board that U-Boot is running on
3090		when U-Boot starts up. The board function checkboard() is called
3091		to do this.
3092
3093- CONFIG_DISPLAY_BOARDINFO_LATE
3094		Similar to the previous option, but display this information
3095		later, once stdio is running and output goes to the LCD, if
3096		present.
3097
3098- CONFIG_BOARD_SIZE_LIMIT:
3099		Maximum size of the U-Boot image. When defined, the
3100		build system checks that the actual size does not
3101		exceed it.
3102
3103Low Level (hardware related) configuration options:
3104---------------------------------------------------
3105
3106- CONFIG_SYS_CACHELINE_SIZE:
3107		Cache Line Size of the CPU.
3108
3109- CONFIG_SYS_CCSRBAR_DEFAULT:
3110		Default (power-on reset) physical address of CCSR on Freescale
3111		PowerPC SOCs.
3112
3113- CONFIG_SYS_CCSRBAR:
3114		Virtual address of CCSR.  On a 32-bit build, this is typically
3115		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3116
3117- CONFIG_SYS_CCSRBAR_PHYS:
3118		Physical address of CCSR.  CCSR can be relocated to a new
3119		physical address, if desired.  In this case, this macro should
3120		be set to that address.	 Otherwise, it should be set to the
3121		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3122		is typically relocated on 36-bit builds.  It is recommended
3123		that this macro be defined via the _HIGH and _LOW macros:
3124
3125		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3126			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3127
3128- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3129		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3130		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3131		used in assembly code, so it must not contain typecasts or
3132		integer size suffixes (e.g. "ULL").
3133
3134- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3135		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3136		used in assembly code, so it must not contain typecasts or
3137		integer size suffixes (e.g. "ULL").
3138
3139- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3140		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3141		forced to a value that ensures that CCSR is not relocated.
3142
3143- Floppy Disk Support:
3144		CONFIG_SYS_FDC_DRIVE_NUMBER
3145
3146		the default drive number (default value 0)
3147
3148		CONFIG_SYS_ISA_IO_STRIDE
3149
3150		defines the spacing between FDC chipset registers
3151		(default value 1)
3152
3153		CONFIG_SYS_ISA_IO_OFFSET
3154
3155		defines the offset of register from address. It
3156		depends on which part of the data bus is connected to
3157		the FDC chipset. (default value 0)
3158
3159		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3160		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3161		default value.
3162
3163		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3164		fdc_hw_init() is called at the beginning of the FDC
3165		setup. fdc_hw_init() must be provided by the board
3166		source code. It is used to make hardware-dependent
3167		initializations.
3168
3169- CONFIG_IDE_AHB:
3170		Most IDE controllers were designed to be connected with PCI
3171		interface. Only few of them were designed for AHB interface.
3172		When software is doing ATA command and data transfer to
3173		IDE devices through IDE-AHB controller, some additional
3174		registers accessing to these kind of IDE-AHB controller
3175		is required.
3176
3177- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3178		DO NOT CHANGE unless you know exactly what you're
3179		doing! (11-4) [MPC8xx systems only]
3180
3181- CONFIG_SYS_INIT_RAM_ADDR:
3182
3183		Start address of memory area that can be used for
3184		initial data and stack; please note that this must be
3185		writable memory that is working WITHOUT special
3186		initialization, i. e. you CANNOT use normal RAM which
3187		will become available only after programming the
3188		memory controller and running certain initialization
3189		sequences.
3190
3191		U-Boot uses the following memory types:
3192		- MPC8xx: IMMR (internal memory of the CPU)
3193
3194- CONFIG_SYS_GBL_DATA_OFFSET:
3195
3196		Offset of the initial data structure in the memory
3197		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3198		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3199		data is located at the end of the available space
3200		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3201		GENERATED_GBL_DATA_SIZE), and the initial stack is just
3202		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3203		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3204
3205	Note:
3206		On the MPC824X (or other systems that use the data
3207		cache for initial memory) the address chosen for
3208		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3209		point to an otherwise UNUSED address space between
3210		the top of RAM and the start of the PCI space.
3211
3212- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3213
3214- CONFIG_SYS_OR_TIMING_SDRAM:
3215		SDRAM timing
3216
3217- CONFIG_SYS_MAMR_PTA:
3218		periodic timer for refresh
3219
3220- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3221  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3222  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3223  CONFIG_SYS_BR1_PRELIM:
3224		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3225
3226- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3227  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3228  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3229		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3230
3231- CONFIG_PCI_ENUM_ONLY
3232		Only scan through and get the devices on the buses.
3233		Don't do any setup work, presumably because someone or
3234		something has already done it, and we don't need to do it
3235		a second time.	Useful for platforms that are pre-booted
3236		by coreboot or similar.
3237
3238- CONFIG_PCI_INDIRECT_BRIDGE:
3239		Enable support for indirect PCI bridges.
3240
3241- CONFIG_SYS_SRIO:
3242		Chip has SRIO or not
3243
3244- CONFIG_SRIO1:
3245		Board has SRIO 1 port available
3246
3247- CONFIG_SRIO2:
3248		Board has SRIO 2 port available
3249
3250- CONFIG_SRIO_PCIE_BOOT_MASTER
3251		Board can support master function for Boot from SRIO and PCIE
3252
3253- CONFIG_SYS_SRIOn_MEM_VIRT:
3254		Virtual Address of SRIO port 'n' memory region
3255
3256- CONFIG_SYS_SRIOn_MEM_PHYS:
3257		Physical Address of SRIO port 'n' memory region
3258
3259- CONFIG_SYS_SRIOn_MEM_SIZE:
3260		Size of SRIO port 'n' memory region
3261
3262- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3263		Defined to tell the NAND controller that the NAND chip is using
3264		a 16 bit bus.
3265		Not all NAND drivers use this symbol.
3266		Example of drivers that use it:
3267		- drivers/mtd/nand/ndfc.c
3268		- drivers/mtd/nand/mxc_nand.c
3269
3270- CONFIG_SYS_NDFC_EBC0_CFG
3271		Sets the EBC0_CFG register for the NDFC. If not defined
3272		a default value will be used.
3273
3274- CONFIG_SPD_EEPROM
3275		Get DDR timing information from an I2C EEPROM. Common
3276		with pluggable memory modules such as SODIMMs
3277
3278  SPD_EEPROM_ADDRESS
3279		I2C address of the SPD EEPROM
3280
3281- CONFIG_SYS_SPD_BUS_NUM
3282		If SPD EEPROM is on an I2C bus other than the first
3283		one, specify here. Note that the value must resolve
3284		to something your driver can deal with.
3285
3286- CONFIG_SYS_DDR_RAW_TIMING
3287		Get DDR timing information from other than SPD. Common with
3288		soldered DDR chips onboard without SPD. DDR raw timing
3289		parameters are extracted from datasheet and hard-coded into
3290		header files or board specific files.
3291
3292- CONFIG_FSL_DDR_INTERACTIVE
3293		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3294
3295- CONFIG_FSL_DDR_SYNC_REFRESH
3296		Enable sync of refresh for multiple controllers.
3297
3298- CONFIG_FSL_DDR_BIST
3299		Enable built-in memory test for Freescale DDR controllers.
3300
3301- CONFIG_SYS_83XX_DDR_USES_CS0
3302		Only for 83xx systems. If specified, then DDR should
3303		be configured using CS0 and CS1 instead of CS2 and CS3.
3304
3305- CONFIG_RMII
3306		Enable RMII mode for all FECs.
3307		Note that this is a global option, we can't
3308		have one FEC in standard MII mode and another in RMII mode.
3309
3310- CONFIG_CRC32_VERIFY
3311		Add a verify option to the crc32 command.
3312		The syntax is:
3313
3314		=> crc32 -v <address> <count> <crc32>
3315
3316		Where address/count indicate a memory area
3317		and crc32 is the correct crc32 which the
3318		area should have.
3319
3320- CONFIG_LOOPW
3321		Add the "loopw" memory command. This only takes effect if
3322		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3323
3324- CONFIG_MX_CYCLIC
3325		Add the "mdc" and "mwc" memory commands. These are cyclic
3326		"md/mw" commands.
3327		Examples:
3328
3329		=> mdc.b 10 4 500
3330		This command will print 4 bytes (10,11,12,13) each 500 ms.
3331
3332		=> mwc.l 100 12345678 10
3333		This command will write 12345678 to address 100 all 10 ms.
3334
3335		This only takes effect if the memory commands are activated
3336		globally (CONFIG_CMD_MEMORY).
3337
3338- CONFIG_SKIP_LOWLEVEL_INIT
3339		[ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3340		low level initializations (like setting up the memory
3341		controller) are omitted and/or U-Boot does not
3342		relocate itself into RAM.
3343
3344		Normally this variable MUST NOT be defined. The only
3345		exception is when U-Boot is loaded (to RAM) by some
3346		other boot loader or by a debugger which performs
3347		these initializations itself.
3348
3349- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3350		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3351		to be skipped. The normal CP15 init (such as enabling the
3352		instruction cache) is still performed.
3353
3354- CONFIG_SPL_BUILD
3355		Modifies the behaviour of start.S when compiling a loader
3356		that is executed before the actual U-Boot. E.g. when
3357		compiling a NAND SPL.
3358
3359- CONFIG_TPL_BUILD
3360		Modifies the behaviour of start.S  when compiling a loader
3361		that is executed after the SPL and before the actual U-Boot.
3362		It is loaded by the SPL.
3363
3364- CONFIG_SYS_MPC85XX_NO_RESETVEC
3365		Only for 85xx systems. If this variable is specified, the section
3366		.resetvec is not kept and the section .bootpg is placed in the
3367		previous 4k of the .text section.
3368
3369- CONFIG_ARCH_MAP_SYSMEM
3370		Generally U-Boot (and in particular the md command) uses
3371		effective address. It is therefore not necessary to regard
3372		U-Boot address as virtual addresses that need to be translated
3373		to physical addresses. However, sandbox requires this, since
3374		it maintains its own little RAM buffer which contains all
3375		addressable memory. This option causes some memory accesses
3376		to be mapped through map_sysmem() / unmap_sysmem().
3377
3378- CONFIG_X86_RESET_VECTOR
3379		If defined, the x86 reset vector code is included. This is not
3380		needed when U-Boot is running from Coreboot.
3381
3382- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3383		Option to disable subpage write in NAND driver
3384		driver that uses this:
3385		drivers/mtd/nand/davinci_nand.c
3386
3387Freescale QE/FMAN Firmware Support:
3388-----------------------------------
3389
3390The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3391loading of "firmware", which is encoded in the QE firmware binary format.
3392This firmware often needs to be loaded during U-Boot booting, so macros
3393are used to identify the storage device (NOR flash, SPI, etc) and the address
3394within that device.
3395
3396- CONFIG_SYS_FMAN_FW_ADDR
3397	The address in the storage device where the FMAN microcode is located.  The
3398	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3399	is also specified.
3400
3401- CONFIG_SYS_QE_FW_ADDR
3402	The address in the storage device where the QE microcode is located.  The
3403	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3404	is also specified.
3405
3406- CONFIG_SYS_QE_FMAN_FW_LENGTH
3407	The maximum possible size of the firmware.  The firmware binary format
3408	has a field that specifies the actual size of the firmware, but it
3409	might not be possible to read any part of the firmware unless some
3410	local storage is allocated to hold the entire firmware first.
3411
3412- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3413	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3414	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3415	virtual address in NOR flash.
3416
3417- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3418	Specifies that QE/FMAN firmware is located in NAND flash.
3419	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3420
3421- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3422	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3423	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3424
3425- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3426	Specifies that QE/FMAN firmware is located in the remote (master)
3427	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3428	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3429	window->master inbound window->master LAW->the ucode address in
3430	master's memory space.
3431
3432Freescale Layerscape Management Complex Firmware Support:
3433---------------------------------------------------------
3434The Freescale Layerscape Management Complex (MC) supports the loading of
3435"firmware".
3436This firmware often needs to be loaded during U-Boot booting, so macros
3437are used to identify the storage device (NOR flash, SPI, etc) and the address
3438within that device.
3439
3440- CONFIG_FSL_MC_ENET
3441	Enable the MC driver for Layerscape SoCs.
3442
3443Freescale Layerscape Debug Server Support:
3444-------------------------------------------
3445The Freescale Layerscape Debug Server Support supports the loading of
3446"Debug Server firmware" and triggering SP boot-rom.
3447This firmware often needs to be loaded during U-Boot booting.
3448
3449- CONFIG_SYS_MC_RSV_MEM_ALIGN
3450	Define alignment of reserved memory MC requires
3451
3452Reproducible builds
3453-------------------
3454
3455In order to achieve reproducible builds, timestamps used in the U-Boot build
3456process have to be set to a fixed value.
3457
3458This is done using the SOURCE_DATE_EPOCH environment variable.
3459SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3460option for U-Boot or an environment variable in U-Boot.
3461
3462SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3463
3464Building the Software:
3465======================
3466
3467Building U-Boot has been tested in several native build environments
3468and in many different cross environments. Of course we cannot support
3469all possibly existing versions of cross development tools in all
3470(potentially obsolete) versions. In case of tool chain problems we
3471recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3472which is extensively used to build and test U-Boot.
3473
3474If you are not using a native environment, it is assumed that you
3475have GNU cross compiling tools available in your path. In this case,
3476you must set the environment variable CROSS_COMPILE in your shell.
3477Note that no changes to the Makefile or any other source files are
3478necessary. For example using the ELDK on a 4xx CPU, please enter:
3479
3480	$ CROSS_COMPILE=ppc_4xx-
3481	$ export CROSS_COMPILE
3482
3483Note: If you wish to generate Windows versions of the utilities in
3484      the tools directory you can use the MinGW toolchain
3485      (http://www.mingw.org).  Set your HOST tools to the MinGW
3486      toolchain and execute 'make tools'.  For example:
3487
3488       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3489
3490      Binaries such as tools/mkimage.exe will be created which can
3491      be executed on computers running Windows.
3492
3493U-Boot is intended to be simple to build. After installing the
3494sources you must configure U-Boot for one specific board type. This
3495is done by typing:
3496
3497	make NAME_defconfig
3498
3499where "NAME_defconfig" is the name of one of the existing configu-
3500rations; see boards.cfg for supported names.
3501
3502Note: for some board special configuration names may exist; check if
3503      additional information is available from the board vendor; for
3504      instance, the TQM823L systems are available without (standard)
3505      or with LCD support. You can select such additional "features"
3506      when choosing the configuration, i. e.
3507
3508      make TQM823L_defconfig
3509	- will configure for a plain TQM823L, i. e. no LCD support
3510
3511      make TQM823L_LCD_defconfig
3512	- will configure for a TQM823L with U-Boot console on LCD
3513
3514      etc.
3515
3516
3517Finally, type "make all", and you should get some working U-Boot
3518images ready for download to / installation on your system:
3519
3520- "u-boot.bin" is a raw binary image
3521- "u-boot" is an image in ELF binary format
3522- "u-boot.srec" is in Motorola S-Record format
3523
3524By default the build is performed locally and the objects are saved
3525in the source directory. One of the two methods can be used to change
3526this behavior and build U-Boot to some external directory:
3527
35281. Add O= to the make command line invocations:
3529
3530	make O=/tmp/build distclean
3531	make O=/tmp/build NAME_defconfig
3532	make O=/tmp/build all
3533
35342. Set environment variable KBUILD_OUTPUT to point to the desired location:
3535
3536	export KBUILD_OUTPUT=/tmp/build
3537	make distclean
3538	make NAME_defconfig
3539	make all
3540
3541Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3542variable.
3543
3544User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3545setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3546For example to treat all compiler warnings as errors:
3547
3548	make KCFLAGS=-Werror
3549
3550Please be aware that the Makefiles assume you are using GNU make, so
3551for instance on NetBSD you might need to use "gmake" instead of
3552native "make".
3553
3554
3555If the system board that you have is not listed, then you will need
3556to port U-Boot to your hardware platform. To do this, follow these
3557steps:
3558
35591.  Create a new directory to hold your board specific code. Add any
3560    files you need. In your board directory, you will need at least
3561    the "Makefile" and a "<board>.c".
35622.  Create a new configuration file "include/configs/<board>.h" for
3563    your board.
35643.  If you're porting U-Boot to a new CPU, then also create a new
3565    directory to hold your CPU specific code. Add any files you need.
35664.  Run "make <board>_defconfig" with your new name.
35675.  Type "make", and you should get a working "u-boot.srec" file
3568    to be installed on your target system.
35696.  Debug and solve any problems that might arise.
3570    [Of course, this last step is much harder than it sounds.]
3571
3572
3573Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3574==============================================================
3575
3576If you have modified U-Boot sources (for instance added a new board
3577or support for new devices, a new CPU, etc.) you are expected to
3578provide feedback to the other developers. The feedback normally takes
3579the form of a "patch", i. e. a context diff against a certain (latest
3580official or latest in the git repository) version of U-Boot sources.
3581
3582But before you submit such a patch, please verify that your modifi-
3583cation did not break existing code. At least make sure that *ALL* of
3584the supported boards compile WITHOUT ANY compiler warnings. To do so,
3585just run the buildman script (tools/buildman/buildman), which will
3586configure and build U-Boot for ALL supported system. Be warned, this
3587will take a while. Please see the buildman README, or run 'buildman -H'
3588for documentation.
3589
3590
3591See also "U-Boot Porting Guide" below.
3592
3593
3594Monitor Commands - Overview:
3595============================
3596
3597go	- start application at address 'addr'
3598run	- run commands in an environment variable
3599bootm	- boot application image from memory
3600bootp	- boot image via network using BootP/TFTP protocol
3601bootz   - boot zImage from memory
3602tftpboot- boot image via network using TFTP protocol
3603	       and env variables "ipaddr" and "serverip"
3604	       (and eventually "gatewayip")
3605tftpput - upload a file via network using TFTP protocol
3606rarpboot- boot image via network using RARP/TFTP protocol
3607diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3608loads	- load S-Record file over serial line
3609loadb	- load binary file over serial line (kermit mode)
3610md	- memory display
3611mm	- memory modify (auto-incrementing)
3612nm	- memory modify (constant address)
3613mw	- memory write (fill)
3614cp	- memory copy
3615cmp	- memory compare
3616crc32	- checksum calculation
3617i2c	- I2C sub-system
3618sspi	- SPI utility commands
3619base	- print or set address offset
3620printenv- print environment variables
3621setenv	- set environment variables
3622saveenv - save environment variables to persistent storage
3623protect - enable or disable FLASH write protection
3624erase	- erase FLASH memory
3625flinfo	- print FLASH memory information
3626nand	- NAND memory operations (see doc/README.nand)
3627bdinfo	- print Board Info structure
3628iminfo	- print header information for application image
3629coninfo - print console devices and informations
3630ide	- IDE sub-system
3631loop	- infinite loop on address range
3632loopw	- infinite write loop on address range
3633mtest	- simple RAM test
3634icache	- enable or disable instruction cache
3635dcache	- enable or disable data cache
3636reset	- Perform RESET of the CPU
3637echo	- echo args to console
3638version - print monitor version
3639help	- print online help
3640?	- alias for 'help'
3641
3642
3643Monitor Commands - Detailed Description:
3644========================================
3645
3646TODO.
3647
3648For now: just type "help <command>".
3649
3650
3651Environment Variables:
3652======================
3653
3654U-Boot supports user configuration using Environment Variables which
3655can be made persistent by saving to Flash memory.
3656
3657Environment Variables are set using "setenv", printed using
3658"printenv", and saved to Flash using "saveenv". Using "setenv"
3659without a value can be used to delete a variable from the
3660environment. As long as you don't save the environment you are
3661working with an in-memory copy. In case the Flash area containing the
3662environment is erased by accident, a default environment is provided.
3663
3664Some configuration options can be set using Environment Variables.
3665
3666List of environment variables (most likely not complete):
3667
3668  baudrate	- see CONFIG_BAUDRATE
3669
3670  bootdelay	- see CONFIG_BOOTDELAY
3671
3672  bootcmd	- see CONFIG_BOOTCOMMAND
3673
3674  bootargs	- Boot arguments when booting an RTOS image
3675
3676  bootfile	- Name of the image to load with TFTP
3677
3678  bootm_low	- Memory range available for image processing in the bootm
3679		  command can be restricted. This variable is given as
3680		  a hexadecimal number and defines lowest address allowed
3681		  for use by the bootm command. See also "bootm_size"
3682		  environment variable. Address defined by "bootm_low" is
3683		  also the base of the initial memory mapping for the Linux
3684		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3685		  bootm_mapsize.
3686
3687  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3688		  This variable is given as a hexadecimal number and it
3689		  defines the size of the memory region starting at base
3690		  address bootm_low that is accessible by the Linux kernel
3691		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3692		  as the default value if it is defined, and bootm_size is
3693		  used otherwise.
3694
3695  bootm_size	- Memory range available for image processing in the bootm
3696		  command can be restricted. This variable is given as
3697		  a hexadecimal number and defines the size of the region
3698		  allowed for use by the bootm command. See also "bootm_low"
3699		  environment variable.
3700
3701  updatefile	- Location of the software update file on a TFTP server, used
3702		  by the automatic software update feature. Please refer to
3703		  documentation in doc/README.update for more details.
3704
3705  autoload	- if set to "no" (any string beginning with 'n'),
3706		  "bootp" will just load perform a lookup of the
3707		  configuration from the BOOTP server, but not try to
3708		  load any image using TFTP
3709
3710  autostart	- if set to "yes", an image loaded using the "bootp",
3711		  "rarpboot", "tftpboot" or "diskboot" commands will
3712		  be automatically started (by internally calling
3713		  "bootm")
3714
3715		  If set to "no", a standalone image passed to the
3716		  "bootm" command will be copied to the load address
3717		  (and eventually uncompressed), but NOT be started.
3718		  This can be used to load and uncompress arbitrary
3719		  data.
3720
3721  fdt_high	- if set this restricts the maximum address that the
3722		  flattened device tree will be copied into upon boot.
3723		  For example, if you have a system with 1 GB memory
3724		  at physical address 0x10000000, while Linux kernel
3725		  only recognizes the first 704 MB as low memory, you
3726		  may need to set fdt_high as 0x3C000000 to have the
3727		  device tree blob be copied to the maximum address
3728		  of the 704 MB low memory, so that Linux kernel can
3729		  access it during the boot procedure.
3730
3731		  If this is set to the special value 0xFFFFFFFF then
3732		  the fdt will not be copied at all on boot.  For this
3733		  to work it must reside in writable memory, have
3734		  sufficient padding on the end of it for u-boot to
3735		  add the information it needs into it, and the memory
3736		  must be accessible by the kernel.
3737
3738  fdtcontroladdr- if set this is the address of the control flattened
3739		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3740		  defined.
3741
3742  i2cfast	- (PPC405GP|PPC405EP only)
3743		  if set to 'y' configures Linux I2C driver for fast
3744		  mode (400kHZ). This environment variable is used in
3745		  initialization code. So, for changes to be effective
3746		  it must be saved and board must be reset.
3747
3748  initrd_high	- restrict positioning of initrd images:
3749		  If this variable is not set, initrd images will be
3750		  copied to the highest possible address in RAM; this
3751		  is usually what you want since it allows for
3752		  maximum initrd size. If for some reason you want to
3753		  make sure that the initrd image is loaded below the
3754		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3755		  variable to a value of "no" or "off" or "0".
3756		  Alternatively, you can set it to a maximum upper
3757		  address to use (U-Boot will still check that it
3758		  does not overwrite the U-Boot stack and data).
3759
3760		  For instance, when you have a system with 16 MB
3761		  RAM, and want to reserve 4 MB from use by Linux,
3762		  you can do this by adding "mem=12M" to the value of
3763		  the "bootargs" variable. However, now you must make
3764		  sure that the initrd image is placed in the first
3765		  12 MB as well - this can be done with
3766
3767		  setenv initrd_high 00c00000
3768
3769		  If you set initrd_high to 0xFFFFFFFF, this is an
3770		  indication to U-Boot that all addresses are legal
3771		  for the Linux kernel, including addresses in flash
3772		  memory. In this case U-Boot will NOT COPY the
3773		  ramdisk at all. This may be useful to reduce the
3774		  boot time on your system, but requires that this
3775		  feature is supported by your Linux kernel.
3776
3777  ipaddr	- IP address; needed for tftpboot command
3778
3779  loadaddr	- Default load address for commands like "bootp",
3780		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3781
3782  loads_echo	- see CONFIG_LOADS_ECHO
3783
3784  serverip	- TFTP server IP address; needed for tftpboot command
3785
3786  bootretry	- see CONFIG_BOOT_RETRY_TIME
3787
3788  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3789
3790  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3791
3792  ethprime	- controls which interface is used first.
3793
3794  ethact	- controls which interface is currently active.
3795		  For example you can do the following
3796
3797		  => setenv ethact FEC
3798		  => ping 192.168.0.1 # traffic sent on FEC
3799		  => setenv ethact SCC
3800		  => ping 10.0.0.1 # traffic sent on SCC
3801
3802  ethrotate	- When set to "no" U-Boot does not go through all
3803		  available network interfaces.
3804		  It just stays at the currently selected interface.
3805
3806  netretry	- When set to "no" each network operation will
3807		  either succeed or fail without retrying.
3808		  When set to "once" the network operation will
3809		  fail when all the available network interfaces
3810		  are tried once without success.
3811		  Useful on scripts which control the retry operation
3812		  themselves.
3813
3814  npe_ucode	- set load address for the NPE microcode
3815
3816  silent_linux  - If set then Linux will be told to boot silently, by
3817		  changing the console to be empty. If "yes" it will be
3818		  made silent. If "no" it will not be made silent. If
3819		  unset, then it will be made silent if the U-Boot console
3820		  is silent.
3821
3822  tftpsrcp	- If this is set, the value is used for TFTP's
3823		  UDP source port.
3824
3825  tftpdstp	- If this is set, the value is used for TFTP's UDP
3826		  destination port instead of the Well Know Port 69.
3827
3828  tftpblocksize - Block size to use for TFTP transfers; if not set,
3829		  we use the TFTP server's default block size
3830
3831  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3832		  seconds, minimum value is 1000 = 1 second). Defines
3833		  when a packet is considered to be lost so it has to
3834		  be retransmitted. The default is 5000 = 5 seconds.
3835		  Lowering this value may make downloads succeed
3836		  faster in networks with high packet loss rates or
3837		  with unreliable TFTP servers.
3838
3839  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
3840		  unit, minimum value = 0). Defines how many timeouts
3841		  can happen during a single file transfer before that
3842		  transfer is aborted. The default is 10, and 0 means
3843		  'no timeouts allowed'. Increasing this value may help
3844		  downloads succeed with high packet loss rates, or with
3845		  unreliable TFTP servers or client hardware.
3846
3847  vlan		- When set to a value < 4095 the traffic over
3848		  Ethernet is encapsulated/received over 802.1q
3849		  VLAN tagged frames.
3850
3851  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
3852		  Unsigned value, in milliseconds. If not set, the period will
3853		  be either the default (28000), or a value based on
3854		  CONFIG_NET_RETRY_COUNT, if defined. This value has
3855		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3856
3857The following image location variables contain the location of images
3858used in booting. The "Image" column gives the role of the image and is
3859not an environment variable name. The other columns are environment
3860variable names. "File Name" gives the name of the file on a TFTP
3861server, "RAM Address" gives the location in RAM the image will be
3862loaded to, and "Flash Location" gives the image's address in NOR
3863flash or offset in NAND flash.
3864
3865*Note* - these variables don't have to be defined for all boards, some
3866boards currently use other variables for these purposes, and some
3867boards use these variables for other purposes.
3868
3869Image		    File Name	     RAM Address       Flash Location
3870-----		    ---------	     -----------       --------------
3871u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
3872Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
3873device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
3874ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
3875
3876The following environment variables may be used and automatically
3877updated by the network boot commands ("bootp" and "rarpboot"),
3878depending the information provided by your boot server:
3879
3880  bootfile	- see above
3881  dnsip		- IP address of your Domain Name Server
3882  dnsip2	- IP address of your secondary Domain Name Server
3883  gatewayip	- IP address of the Gateway (Router) to use
3884  hostname	- Target hostname
3885  ipaddr	- see above
3886  netmask	- Subnet Mask
3887  rootpath	- Pathname of the root filesystem on the NFS server
3888  serverip	- see above
3889
3890
3891There are two special Environment Variables:
3892
3893  serial#	- contains hardware identification information such
3894		  as type string and/or serial number
3895  ethaddr	- Ethernet address
3896
3897These variables can be set only once (usually during manufacturing of
3898the board). U-Boot refuses to delete or overwrite these variables
3899once they have been set once.
3900
3901
3902Further special Environment Variables:
3903
3904  ver		- Contains the U-Boot version string as printed
3905		  with the "version" command. This variable is
3906		  readonly (see CONFIG_VERSION_VARIABLE).
3907
3908
3909Please note that changes to some configuration parameters may take
3910only effect after the next boot (yes, that's just like Windoze :-).
3911
3912
3913Callback functions for environment variables:
3914---------------------------------------------
3915
3916For some environment variables, the behavior of u-boot needs to change
3917when their values are changed.  This functionality allows functions to
3918be associated with arbitrary variables.  On creation, overwrite, or
3919deletion, the callback will provide the opportunity for some side
3920effect to happen or for the change to be rejected.
3921
3922The callbacks are named and associated with a function using the
3923U_BOOT_ENV_CALLBACK macro in your board or driver code.
3924
3925These callbacks are associated with variables in one of two ways.  The
3926static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3927in the board configuration to a string that defines a list of
3928associations.  The list must be in the following format:
3929
3930	entry = variable_name[:callback_name]
3931	list = entry[,list]
3932
3933If the callback name is not specified, then the callback is deleted.
3934Spaces are also allowed anywhere in the list.
3935
3936Callbacks can also be associated by defining the ".callbacks" variable
3937with the same list format above.  Any association in ".callbacks" will
3938override any association in the static list. You can define
3939CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3940".callbacks" environment variable in the default or embedded environment.
3941
3942If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3943regular expression. This allows multiple variables to be connected to
3944the same callback without explicitly listing them all out.
3945
3946
3947Command Line Parsing:
3948=====================
3949
3950There are two different command line parsers available with U-Boot:
3951the old "simple" one, and the much more powerful "hush" shell:
3952
3953Old, simple command line parser:
3954--------------------------------
3955
3956- supports environment variables (through setenv / saveenv commands)
3957- several commands on one line, separated by ';'
3958- variable substitution using "... ${name} ..." syntax
3959- special characters ('$', ';') can be escaped by prefixing with '\',
3960  for example:
3961	setenv bootcmd bootm \${address}
3962- You can also escape text by enclosing in single apostrophes, for example:
3963	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3964
3965Hush shell:
3966-----------
3967
3968- similar to Bourne shell, with control structures like
3969  if...then...else...fi, for...do...done; while...do...done,
3970  until...do...done, ...
3971- supports environment ("global") variables (through setenv / saveenv
3972  commands) and local shell variables (through standard shell syntax
3973  "name=value"); only environment variables can be used with "run"
3974  command
3975
3976General rules:
3977--------------
3978
3979(1) If a command line (or an environment variable executed by a "run"
3980    command) contains several commands separated by semicolon, and
3981    one of these commands fails, then the remaining commands will be
3982    executed anyway.
3983
3984(2) If you execute several variables with one call to run (i. e.
3985    calling run with a list of variables as arguments), any failing
3986    command will cause "run" to terminate, i. e. the remaining
3987    variables are not executed.
3988
3989Note for Redundant Ethernet Interfaces:
3990=======================================
3991
3992Some boards come with redundant Ethernet interfaces; U-Boot supports
3993such configurations and is capable of automatic selection of a
3994"working" interface when needed. MAC assignment works as follows:
3995
3996Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
3997MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
3998"eth1addr" (=>eth1), "eth2addr", ...
3999
4000If the network interface stores some valid MAC address (for instance
4001in SROM), this is used as default address if there is NO correspon-
4002ding setting in the environment; if the corresponding environment
4003variable is set, this overrides the settings in the card; that means:
4004
4005o If the SROM has a valid MAC address, and there is no address in the
4006  environment, the SROM's address is used.
4007
4008o If there is no valid address in the SROM, and a definition in the
4009  environment exists, then the value from the environment variable is
4010  used.
4011
4012o If both the SROM and the environment contain a MAC address, and
4013  both addresses are the same, this MAC address is used.
4014
4015o If both the SROM and the environment contain a MAC address, and the
4016  addresses differ, the value from the environment is used and a
4017  warning is printed.
4018
4019o If neither SROM nor the environment contain a MAC address, an error
4020  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4021  a random, locally-assigned MAC is used.
4022
4023If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4024will be programmed into hardware as part of the initialization process.	 This
4025may be skipped by setting the appropriate 'ethmacskip' environment variable.
4026The naming convention is as follows:
4027"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4028
4029Image Formats:
4030==============
4031
4032U-Boot is capable of booting (and performing other auxiliary operations on)
4033images in two formats:
4034
4035New uImage format (FIT)
4036-----------------------
4037
4038Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4039to Flattened Device Tree). It allows the use of images with multiple
4040components (several kernels, ramdisks, etc.), with contents protected by
4041SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4042
4043
4044Old uImage format
4045-----------------
4046
4047Old image format is based on binary files which can be basically anything,
4048preceded by a special header; see the definitions in include/image.h for
4049details; basically, the header defines the following image properties:
4050
4051* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4052  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4053  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4054  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4055  INTEGRITY).
4056* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4057  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4058  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4059* Compression Type (uncompressed, gzip, bzip2)
4060* Load Address
4061* Entry Point
4062* Image Name
4063* Image Timestamp
4064
4065The header is marked by a special Magic Number, and both the header
4066and the data portions of the image are secured against corruption by
4067CRC32 checksums.
4068
4069
4070Linux Support:
4071==============
4072
4073Although U-Boot should support any OS or standalone application
4074easily, the main focus has always been on Linux during the design of
4075U-Boot.
4076
4077U-Boot includes many features that so far have been part of some
4078special "boot loader" code within the Linux kernel. Also, any
4079"initrd" images to be used are no longer part of one big Linux image;
4080instead, kernel and "initrd" are separate images. This implementation
4081serves several purposes:
4082
4083- the same features can be used for other OS or standalone
4084  applications (for instance: using compressed images to reduce the
4085  Flash memory footprint)
4086
4087- it becomes much easier to port new Linux kernel versions because
4088  lots of low-level, hardware dependent stuff are done by U-Boot
4089
4090- the same Linux kernel image can now be used with different "initrd"
4091  images; of course this also means that different kernel images can
4092  be run with the same "initrd". This makes testing easier (you don't
4093  have to build a new "zImage.initrd" Linux image when you just
4094  change a file in your "initrd"). Also, a field-upgrade of the
4095  software is easier now.
4096
4097
4098Linux HOWTO:
4099============
4100
4101Porting Linux to U-Boot based systems:
4102---------------------------------------
4103
4104U-Boot cannot save you from doing all the necessary modifications to
4105configure the Linux device drivers for use with your target hardware
4106(no, we don't intend to provide a full virtual machine interface to
4107Linux :-).
4108
4109But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4110
4111Just make sure your machine specific header file (for instance
4112include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4113Information structure as we define in include/asm-<arch>/u-boot.h,
4114and make sure that your definition of IMAP_ADDR uses the same value
4115as your U-Boot configuration in CONFIG_SYS_IMMR.
4116
4117Note that U-Boot now has a driver model, a unified model for drivers.
4118If you are adding a new driver, plumb it into driver model. If there
4119is no uclass available, you are encouraged to create one. See
4120doc/driver-model.
4121
4122
4123Configuring the Linux kernel:
4124-----------------------------
4125
4126No specific requirements for U-Boot. Make sure you have some root
4127device (initial ramdisk, NFS) for your target system.
4128
4129
4130Building a Linux Image:
4131-----------------------
4132
4133With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4134not used. If you use recent kernel source, a new build target
4135"uImage" will exist which automatically builds an image usable by
4136U-Boot. Most older kernels also have support for a "pImage" target,
4137which was introduced for our predecessor project PPCBoot and uses a
4138100% compatible format.
4139
4140Example:
4141
4142	make TQM850L_defconfig
4143	make oldconfig
4144	make dep
4145	make uImage
4146
4147The "uImage" build target uses a special tool (in 'tools/mkimage') to
4148encapsulate a compressed Linux kernel image with header	 information,
4149CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4150
4151* build a standard "vmlinux" kernel image (in ELF binary format):
4152
4153* convert the kernel into a raw binary image:
4154
4155	${CROSS_COMPILE}-objcopy -O binary \
4156				 -R .note -R .comment \
4157				 -S vmlinux linux.bin
4158
4159* compress the binary image:
4160
4161	gzip -9 linux.bin
4162
4163* package compressed binary image for U-Boot:
4164
4165	mkimage -A ppc -O linux -T kernel -C gzip \
4166		-a 0 -e 0 -n "Linux Kernel Image" \
4167		-d linux.bin.gz uImage
4168
4169
4170The "mkimage" tool can also be used to create ramdisk images for use
4171with U-Boot, either separated from the Linux kernel image, or
4172combined into one file. "mkimage" encapsulates the images with a 64
4173byte header containing information about target architecture,
4174operating system, image type, compression method, entry points, time
4175stamp, CRC32 checksums, etc.
4176
4177"mkimage" can be called in two ways: to verify existing images and
4178print the header information, or to build new images.
4179
4180In the first form (with "-l" option) mkimage lists the information
4181contained in the header of an existing U-Boot image; this includes
4182checksum verification:
4183
4184	tools/mkimage -l image
4185	  -l ==> list image header information
4186
4187The second form (with "-d" option) is used to build a U-Boot image
4188from a "data file" which is used as image payload:
4189
4190	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4191		      -n name -d data_file image
4192	  -A ==> set architecture to 'arch'
4193	  -O ==> set operating system to 'os'
4194	  -T ==> set image type to 'type'
4195	  -C ==> set compression type 'comp'
4196	  -a ==> set load address to 'addr' (hex)
4197	  -e ==> set entry point to 'ep' (hex)
4198	  -n ==> set image name to 'name'
4199	  -d ==> use image data from 'datafile'
4200
4201Right now, all Linux kernels for PowerPC systems use the same load
4202address (0x00000000), but the entry point address depends on the
4203kernel version:
4204
4205- 2.2.x kernels have the entry point at 0x0000000C,
4206- 2.3.x and later kernels have the entry point at 0x00000000.
4207
4208So a typical call to build a U-Boot image would read:
4209
4210	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4211	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4212	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4213	> examples/uImage.TQM850L
4214	Image Name:   2.4.4 kernel for TQM850L
4215	Created:      Wed Jul 19 02:34:59 2000
4216	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4217	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4218	Load Address: 0x00000000
4219	Entry Point:  0x00000000
4220
4221To verify the contents of the image (or check for corruption):
4222
4223	-> tools/mkimage -l examples/uImage.TQM850L
4224	Image Name:   2.4.4 kernel for TQM850L
4225	Created:      Wed Jul 19 02:34:59 2000
4226	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4227	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4228	Load Address: 0x00000000
4229	Entry Point:  0x00000000
4230
4231NOTE: for embedded systems where boot time is critical you can trade
4232speed for memory and install an UNCOMPRESSED image instead: this
4233needs more space in Flash, but boots much faster since it does not
4234need to be uncompressed:
4235
4236	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4237	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4238	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4239	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4240	> examples/uImage.TQM850L-uncompressed
4241	Image Name:   2.4.4 kernel for TQM850L
4242	Created:      Wed Jul 19 02:34:59 2000
4243	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4244	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4245	Load Address: 0x00000000
4246	Entry Point:  0x00000000
4247
4248
4249Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4250when your kernel is intended to use an initial ramdisk:
4251
4252	-> tools/mkimage -n 'Simple Ramdisk Image' \
4253	> -A ppc -O linux -T ramdisk -C gzip \
4254	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4255	Image Name:   Simple Ramdisk Image
4256	Created:      Wed Jan 12 14:01:50 2000
4257	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4258	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4259	Load Address: 0x00000000
4260	Entry Point:  0x00000000
4261
4262The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4263option performs the converse operation of the mkimage's second form (the "-d"
4264option). Given an image built by mkimage, the dumpimage extracts a "data file"
4265from the image:
4266
4267	tools/dumpimage -i image -T type -p position data_file
4268	  -i ==> extract from the 'image' a specific 'data_file'
4269	  -T ==> set image type to 'type'
4270	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4271
4272
4273Installing a Linux Image:
4274-------------------------
4275
4276To downloading a U-Boot image over the serial (console) interface,
4277you must convert the image to S-Record format:
4278
4279	objcopy -I binary -O srec examples/image examples/image.srec
4280
4281The 'objcopy' does not understand the information in the U-Boot
4282image header, so the resulting S-Record file will be relative to
4283address 0x00000000. To load it to a given address, you need to
4284specify the target address as 'offset' parameter with the 'loads'
4285command.
4286
4287Example: install the image to address 0x40100000 (which on the
4288TQM8xxL is in the first Flash bank):
4289
4290	=> erase 40100000 401FFFFF
4291
4292	.......... done
4293	Erased 8 sectors
4294
4295	=> loads 40100000
4296	## Ready for S-Record download ...
4297	~>examples/image.srec
4298	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4299	...
4300	15989 15990 15991 15992
4301	[file transfer complete]
4302	[connected]
4303	## Start Addr = 0x00000000
4304
4305
4306You can check the success of the download using the 'iminfo' command;
4307this includes a checksum verification so you can be sure no data
4308corruption happened:
4309
4310	=> imi 40100000
4311
4312	## Checking Image at 40100000 ...
4313	   Image Name:	 2.2.13 for initrd on TQM850L
4314	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4315	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4316	   Load Address: 00000000
4317	   Entry Point:	 0000000c
4318	   Verifying Checksum ... OK
4319
4320
4321Boot Linux:
4322-----------
4323
4324The "bootm" command is used to boot an application that is stored in
4325memory (RAM or Flash). In case of a Linux kernel image, the contents
4326of the "bootargs" environment variable is passed to the kernel as
4327parameters. You can check and modify this variable using the
4328"printenv" and "setenv" commands:
4329
4330
4331	=> printenv bootargs
4332	bootargs=root=/dev/ram
4333
4334	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4335
4336	=> printenv bootargs
4337	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4338
4339	=> bootm 40020000
4340	## Booting Linux kernel at 40020000 ...
4341	   Image Name:	 2.2.13 for NFS on TQM850L
4342	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4343	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4344	   Load Address: 00000000
4345	   Entry Point:	 0000000c
4346	   Verifying Checksum ... OK
4347	   Uncompressing Kernel Image ... OK
4348	Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000
4349	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4350	time_init: decrementer frequency = 187500000/60
4351	Calibrating delay loop... 49.77 BogoMIPS
4352	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4353	...
4354
4355If you want to boot a Linux kernel with initial RAM disk, you pass
4356the memory addresses of both the kernel and the initrd image (PPBCOOT
4357format!) to the "bootm" command:
4358
4359	=> imi 40100000 40200000
4360
4361	## Checking Image at 40100000 ...
4362	   Image Name:	 2.2.13 for initrd on TQM850L
4363	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4364	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4365	   Load Address: 00000000
4366	   Entry Point:	 0000000c
4367	   Verifying Checksum ... OK
4368
4369	## Checking Image at 40200000 ...
4370	   Image Name:	 Simple Ramdisk Image
4371	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4372	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4373	   Load Address: 00000000
4374	   Entry Point:	 00000000
4375	   Verifying Checksum ... OK
4376
4377	=> bootm 40100000 40200000
4378	## Booting Linux kernel at 40100000 ...
4379	   Image Name:	 2.2.13 for initrd on TQM850L
4380	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4381	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4382	   Load Address: 00000000
4383	   Entry Point:	 0000000c
4384	   Verifying Checksum ... OK
4385	   Uncompressing Kernel Image ... OK
4386	## Loading RAMDisk Image at 40200000 ...
4387	   Image Name:	 Simple Ramdisk Image
4388	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4389	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4390	   Load Address: 00000000
4391	   Entry Point:	 00000000
4392	   Verifying Checksum ... OK
4393	   Loading Ramdisk ... OK
4394	Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000
4395	Boot arguments: root=/dev/ram
4396	time_init: decrementer frequency = 187500000/60
4397	Calibrating delay loop... 49.77 BogoMIPS
4398	...
4399	RAMDISK: Compressed image found at block 0
4400	VFS: Mounted root (ext2 filesystem).
4401
4402	bash#
4403
4404Boot Linux and pass a flat device tree:
4405-----------
4406
4407First, U-Boot must be compiled with the appropriate defines. See the section
4408titled "Linux Kernel Interface" above for a more in depth explanation. The
4409following is an example of how to start a kernel and pass an updated
4410flat device tree:
4411
4412=> print oftaddr
4413oftaddr=0x300000
4414=> print oft
4415oft=oftrees/mpc8540ads.dtb
4416=> tftp $oftaddr $oft
4417Speed: 1000, full duplex
4418Using TSEC0 device
4419TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4420Filename 'oftrees/mpc8540ads.dtb'.
4421Load address: 0x300000
4422Loading: #
4423done
4424Bytes transferred = 4106 (100a hex)
4425=> tftp $loadaddr $bootfile
4426Speed: 1000, full duplex
4427Using TSEC0 device
4428TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4429Filename 'uImage'.
4430Load address: 0x200000
4431Loading:############
4432done
4433Bytes transferred = 1029407 (fb51f hex)
4434=> print loadaddr
4435loadaddr=200000
4436=> print oftaddr
4437oftaddr=0x300000
4438=> bootm $loadaddr - $oftaddr
4439## Booting image at 00200000 ...
4440   Image Name:	 Linux-2.6.17-dirty
4441   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4442   Data Size:	 1029343 Bytes = 1005.2 kB
4443   Load Address: 00000000
4444   Entry Point:	 00000000
4445   Verifying Checksum ... OK
4446   Uncompressing Kernel Image ... OK
4447Booting using flat device tree at 0x300000
4448Using MPC85xx ADS machine description
4449Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4450[snip]
4451
4452
4453More About U-Boot Image Types:
4454------------------------------
4455
4456U-Boot supports the following image types:
4457
4458   "Standalone Programs" are directly runnable in the environment
4459	provided by U-Boot; it is expected that (if they behave
4460	well) you can continue to work in U-Boot after return from
4461	the Standalone Program.
4462   "OS Kernel Images" are usually images of some Embedded OS which
4463	will take over control completely. Usually these programs
4464	will install their own set of exception handlers, device
4465	drivers, set up the MMU, etc. - this means, that you cannot
4466	expect to re-enter U-Boot except by resetting the CPU.
4467   "RAMDisk Images" are more or less just data blocks, and their
4468	parameters (address, size) are passed to an OS kernel that is
4469	being started.
4470   "Multi-File Images" contain several images, typically an OS
4471	(Linux) kernel image and one or more data images like
4472	RAMDisks. This construct is useful for instance when you want
4473	to boot over the network using BOOTP etc., where the boot
4474	server provides just a single image file, but you want to get
4475	for instance an OS kernel and a RAMDisk image.
4476
4477	"Multi-File Images" start with a list of image sizes, each
4478	image size (in bytes) specified by an "uint32_t" in network
4479	byte order. This list is terminated by an "(uint32_t)0".
4480	Immediately after the terminating 0 follow the images, one by
4481	one, all aligned on "uint32_t" boundaries (size rounded up to
4482	a multiple of 4 bytes).
4483
4484   "Firmware Images" are binary images containing firmware (like
4485	U-Boot or FPGA images) which usually will be programmed to
4486	flash memory.
4487
4488   "Script files" are command sequences that will be executed by
4489	U-Boot's command interpreter; this feature is especially
4490	useful when you configure U-Boot to use a real shell (hush)
4491	as command interpreter.
4492
4493Booting the Linux zImage:
4494-------------------------
4495
4496On some platforms, it's possible to boot Linux zImage. This is done
4497using the "bootz" command. The syntax of "bootz" command is the same
4498as the syntax of "bootm" command.
4499
4500Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4501kernel with raw initrd images. The syntax is slightly different, the
4502address of the initrd must be augmented by it's size, in the following
4503format: "<initrd addres>:<initrd size>".
4504
4505
4506Standalone HOWTO:
4507=================
4508
4509One of the features of U-Boot is that you can dynamically load and
4510run "standalone" applications, which can use some resources of
4511U-Boot like console I/O functions or interrupt services.
4512
4513Two simple examples are included with the sources:
4514
4515"Hello World" Demo:
4516-------------------
4517
4518'examples/hello_world.c' contains a small "Hello World" Demo
4519application; it is automatically compiled when you build U-Boot.
4520It's configured to run at address 0x00040004, so you can play with it
4521like that:
4522
4523	=> loads
4524	## Ready for S-Record download ...
4525	~>examples/hello_world.srec
4526	1 2 3 4 5 6 7 8 9 10 11 ...
4527	[file transfer complete]
4528	[connected]
4529	## Start Addr = 0x00040004
4530
4531	=> go 40004 Hello World! This is a test.
4532	## Starting application at 0x00040004 ...
4533	Hello World
4534	argc = 7
4535	argv[0] = "40004"
4536	argv[1] = "Hello"
4537	argv[2] = "World!"
4538	argv[3] = "This"
4539	argv[4] = "is"
4540	argv[5] = "a"
4541	argv[6] = "test."
4542	argv[7] = "<NULL>"
4543	Hit any key to exit ...
4544
4545	## Application terminated, rc = 0x0
4546
4547Another example, which demonstrates how to register a CPM interrupt
4548handler with the U-Boot code, can be found in 'examples/timer.c'.
4549Here, a CPM timer is set up to generate an interrupt every second.
4550The interrupt service routine is trivial, just printing a '.'
4551character, but this is just a demo program. The application can be
4552controlled by the following keys:
4553
4554	? - print current values og the CPM Timer registers
4555	b - enable interrupts and start timer
4556	e - stop timer and disable interrupts
4557	q - quit application
4558
4559	=> loads
4560	## Ready for S-Record download ...
4561	~>examples/timer.srec
4562	1 2 3 4 5 6 7 8 9 10 11 ...
4563	[file transfer complete]
4564	[connected]
4565	## Start Addr = 0x00040004
4566
4567	=> go 40004
4568	## Starting application at 0x00040004 ...
4569	TIMERS=0xfff00980
4570	Using timer 1
4571	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4572
4573Hit 'b':
4574	[q, b, e, ?] Set interval 1000000 us
4575	Enabling timer
4576Hit '?':
4577	[q, b, e, ?] ........
4578	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4579Hit '?':
4580	[q, b, e, ?] .
4581	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4582Hit '?':
4583	[q, b, e, ?] .
4584	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4585Hit '?':
4586	[q, b, e, ?] .
4587	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4588Hit 'e':
4589	[q, b, e, ?] ...Stopping timer
4590Hit 'q':
4591	[q, b, e, ?] ## Application terminated, rc = 0x0
4592
4593
4594Minicom warning:
4595================
4596
4597Over time, many people have reported problems when trying to use the
4598"minicom" terminal emulation program for serial download. I (wd)
4599consider minicom to be broken, and recommend not to use it. Under
4600Unix, I recommend to use C-Kermit for general purpose use (and
4601especially for kermit binary protocol download ("loadb" command), and
4602use "cu" for S-Record download ("loads" command).  See
4603http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4604for help with kermit.
4605
4606
4607Nevertheless, if you absolutely want to use it try adding this
4608configuration to your "File transfer protocols" section:
4609
4610	   Name	   Program			Name U/D FullScr IO-Red. Multi
4611	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4612	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4613
4614
4615NetBSD Notes:
4616=============
4617
4618Starting at version 0.9.2, U-Boot supports NetBSD both as host
4619(build U-Boot) and target system (boots NetBSD/mpc8xx).
4620
4621Building requires a cross environment; it is known to work on
4622NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4623need gmake since the Makefiles are not compatible with BSD make).
4624Note that the cross-powerpc package does not install include files;
4625attempting to build U-Boot will fail because <machine/ansi.h> is
4626missing.  This file has to be installed and patched manually:
4627
4628	# cd /usr/pkg/cross/powerpc-netbsd/include
4629	# mkdir powerpc
4630	# ln -s powerpc machine
4631	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4632	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4633
4634Native builds *don't* work due to incompatibilities between native
4635and U-Boot include files.
4636
4637Booting assumes that (the first part of) the image booted is a
4638stage-2 loader which in turn loads and then invokes the kernel
4639proper. Loader sources will eventually appear in the NetBSD source
4640tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4641meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4642
4643
4644Implementation Internals:
4645=========================
4646
4647The following is not intended to be a complete description of every
4648implementation detail. However, it should help to understand the
4649inner workings of U-Boot and make it easier to port it to custom
4650hardware.
4651
4652
4653Initial Stack, Global Data:
4654---------------------------
4655
4656The implementation of U-Boot is complicated by the fact that U-Boot
4657starts running out of ROM (flash memory), usually without access to
4658system RAM (because the memory controller is not initialized yet).
4659This means that we don't have writable Data or BSS segments, and BSS
4660is not initialized as zero. To be able to get a C environment working
4661at all, we have to allocate at least a minimal stack. Implementation
4662options for this are defined and restricted by the CPU used: Some CPU
4663models provide on-chip memory (like the IMMR area on MPC8xx and
4664MPC826x processors), on others (parts of) the data cache can be
4665locked as (mis-) used as memory, etc.
4666
4667	Chris Hallinan posted a good summary of these issues to the
4668	U-Boot mailing list:
4669
4670	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4671	From: "Chris Hallinan" <clh@net1plus.com>
4672	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4673	...
4674
4675	Correct me if I'm wrong, folks, but the way I understand it
4676	is this: Using DCACHE as initial RAM for Stack, etc, does not
4677	require any physical RAM backing up the cache. The cleverness
4678	is that the cache is being used as a temporary supply of
4679	necessary storage before the SDRAM controller is setup. It's
4680	beyond the scope of this list to explain the details, but you
4681	can see how this works by studying the cache architecture and
4682	operation in the architecture and processor-specific manuals.
4683
4684	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4685	is another option for the system designer to use as an
4686	initial stack/RAM area prior to SDRAM being available. Either
4687	option should work for you. Using CS 4 should be fine if your
4688	board designers haven't used it for something that would
4689	cause you grief during the initial boot! It is frequently not
4690	used.
4691
4692	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4693	with your processor/board/system design. The default value
4694	you will find in any recent u-boot distribution in
4695	walnut.h should work for you. I'd set it to a value larger
4696	than your SDRAM module. If you have a 64MB SDRAM module, set
4697	it above 400_0000. Just make sure your board has no resources
4698	that are supposed to respond to that address! That code in
4699	start.S has been around a while and should work as is when
4700	you get the config right.
4701
4702	-Chris Hallinan
4703	DS4.COM, Inc.
4704
4705It is essential to remember this, since it has some impact on the C
4706code for the initialization procedures:
4707
4708* Initialized global data (data segment) is read-only. Do not attempt
4709  to write it.
4710
4711* Do not use any uninitialized global data (or implicitly initialized
4712  as zero data - BSS segment) at all - this is undefined, initiali-
4713  zation is performed later (when relocating to RAM).
4714
4715* Stack space is very limited. Avoid big data buffers or things like
4716  that.
4717
4718Having only the stack as writable memory limits means we cannot use
4719normal global data to share information between the code. But it
4720turned out that the implementation of U-Boot can be greatly
4721simplified by making a global data structure (gd_t) available to all
4722functions. We could pass a pointer to this data as argument to _all_
4723functions, but this would bloat the code. Instead we use a feature of
4724the GCC compiler (Global Register Variables) to share the data: we
4725place a pointer (gd) to the global data into a register which we
4726reserve for this purpose.
4727
4728When choosing a register for such a purpose we are restricted by the
4729relevant  (E)ABI  specifications for the current architecture, and by
4730GCC's implementation.
4731
4732For PowerPC, the following registers have specific use:
4733	R1:	stack pointer
4734	R2:	reserved for system use
4735	R3-R4:	parameter passing and return values
4736	R5-R10: parameter passing
4737	R13:	small data area pointer
4738	R30:	GOT pointer
4739	R31:	frame pointer
4740
4741	(U-Boot also uses R12 as internal GOT pointer. r12
4742	is a volatile register so r12 needs to be reset when
4743	going back and forth between asm and C)
4744
4745    ==> U-Boot will use R2 to hold a pointer to the global data
4746
4747    Note: on PPC, we could use a static initializer (since the
4748    address of the global data structure is known at compile time),
4749    but it turned out that reserving a register results in somewhat
4750    smaller code - although the code savings are not that big (on
4751    average for all boards 752 bytes for the whole U-Boot image,
4752    624 text + 127 data).
4753
4754On ARM, the following registers are used:
4755
4756	R0:	function argument word/integer result
4757	R1-R3:	function argument word
4758	R9:	platform specific
4759	R10:	stack limit (used only if stack checking is enabled)
4760	R11:	argument (frame) pointer
4761	R12:	temporary workspace
4762	R13:	stack pointer
4763	R14:	link register
4764	R15:	program counter
4765
4766    ==> U-Boot will use R9 to hold a pointer to the global data
4767
4768    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4769
4770On Nios II, the ABI is documented here:
4771	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4772
4773    ==> U-Boot will use gp to hold a pointer to the global data
4774
4775    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4776    to access small data sections, so gp is free.
4777
4778On NDS32, the following registers are used:
4779
4780	R0-R1:	argument/return
4781	R2-R5:	argument
4782	R15:	temporary register for assembler
4783	R16:	trampoline register
4784	R28:	frame pointer (FP)
4785	R29:	global pointer (GP)
4786	R30:	link register (LP)
4787	R31:	stack pointer (SP)
4788	PC:	program counter (PC)
4789
4790    ==> U-Boot will use R10 to hold a pointer to the global data
4791
4792NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4793or current versions of GCC may "optimize" the code too much.
4794
4795On RISC-V, the following registers are used:
4796
4797	x0: hard-wired zero (zero)
4798	x1: return address (ra)
4799	x2:	stack pointer (sp)
4800	x3:	global pointer (gp)
4801	x4:	thread pointer (tp)
4802	x5:	link register (t0)
4803	x8:	frame pointer (fp)
4804	x10-x11:	arguments/return values (a0-1)
4805	x12-x17:	arguments (a2-7)
4806	x28-31:	 temporaries (t3-6)
4807	pc:	program counter (pc)
4808
4809    ==> U-Boot will use gp to hold a pointer to the global data
4810
4811Memory Management:
4812------------------
4813
4814U-Boot runs in system state and uses physical addresses, i.e. the
4815MMU is not used either for address mapping nor for memory protection.
4816
4817The available memory is mapped to fixed addresses using the memory
4818controller. In this process, a contiguous block is formed for each
4819memory type (Flash, SDRAM, SRAM), even when it consists of several
4820physical memory banks.
4821
4822U-Boot is installed in the first 128 kB of the first Flash bank (on
4823TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4824booting and sizing and initializing DRAM, the code relocates itself
4825to the upper end of DRAM. Immediately below the U-Boot code some
4826memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4827configuration setting]. Below that, a structure with global Board
4828Info data is placed, followed by the stack (growing downward).
4829
4830Additionally, some exception handler code is copied to the low 8 kB
4831of DRAM (0x00000000 ... 0x00001FFF).
4832
4833So a typical memory configuration with 16 MB of DRAM could look like
4834this:
4835
4836	0x0000 0000	Exception Vector code
4837	      :
4838	0x0000 1FFF
4839	0x0000 2000	Free for Application Use
4840	      :
4841	      :
4842
4843	      :
4844	      :
4845	0x00FB FF20	Monitor Stack (Growing downward)
4846	0x00FB FFAC	Board Info Data and permanent copy of global data
4847	0x00FC 0000	Malloc Arena
4848	      :
4849	0x00FD FFFF
4850	0x00FE 0000	RAM Copy of Monitor Code
4851	...		eventually: LCD or video framebuffer
4852	...		eventually: pRAM (Protected RAM - unchanged by reset)
4853	0x00FF FFFF	[End of RAM]
4854
4855
4856System Initialization:
4857----------------------
4858
4859In the reset configuration, U-Boot starts at the reset entry point
4860(on most PowerPC systems at address 0x00000100). Because of the reset
4861configuration for CS0# this is a mirror of the on board Flash memory.
4862To be able to re-map memory U-Boot then jumps to its link address.
4863To be able to implement the initialization code in C, a (small!)
4864initial stack is set up in the internal Dual Ported RAM (in case CPUs
4865which provide such a feature like), or in a locked part of the data
4866cache. After that, U-Boot initializes the CPU core, the caches and
4867the SIU.
4868
4869Next, all (potentially) available memory banks are mapped using a
4870preliminary mapping. For example, we put them on 512 MB boundaries
4871(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4872on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4873programmed for SDRAM access. Using the temporary configuration, a
4874simple memory test is run that determines the size of the SDRAM
4875banks.
4876
4877When there is more than one SDRAM bank, and the banks are of
4878different size, the largest is mapped first. For equal size, the first
4879bank (CS2#) is mapped first. The first mapping is always for address
48800x00000000, with any additional banks following immediately to create
4881contiguous memory starting from 0.
4882
4883Then, the monitor installs itself at the upper end of the SDRAM area
4884and allocates memory for use by malloc() and for the global Board
4885Info data; also, the exception vector code is copied to the low RAM
4886pages, and the final stack is set up.
4887
4888Only after this relocation will you have a "normal" C environment;
4889until that you are restricted in several ways, mostly because you are
4890running from ROM, and because the code will have to be relocated to a
4891new address in RAM.
4892
4893
4894U-Boot Porting Guide:
4895----------------------
4896
4897[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4898list, October 2002]
4899
4900
4901int main(int argc, char *argv[])
4902{
4903	sighandler_t no_more_time;
4904
4905	signal(SIGALRM, no_more_time);
4906	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4907
4908	if (available_money > available_manpower) {
4909		Pay consultant to port U-Boot;
4910		return 0;
4911	}
4912
4913	Download latest U-Boot source;
4914
4915	Subscribe to u-boot mailing list;
4916
4917	if (clueless)
4918		email("Hi, I am new to U-Boot, how do I get started?");
4919
4920	while (learning) {
4921		Read the README file in the top level directory;
4922		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4923		Read applicable doc/*.README;
4924		Read the source, Luke;
4925		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
4926	}
4927
4928	if (available_money > toLocalCurrency ($2500))
4929		Buy a BDI3000;
4930	else
4931		Add a lot of aggravation and time;
4932
4933	if (a similar board exists) {	/* hopefully... */
4934		cp -a board/<similar> board/<myboard>
4935		cp include/configs/<similar>.h include/configs/<myboard>.h
4936	} else {
4937		Create your own board support subdirectory;
4938		Create your own board include/configs/<myboard>.h file;
4939	}
4940	Edit new board/<myboard> files
4941	Edit new include/configs/<myboard>.h
4942
4943	while (!accepted) {
4944		while (!running) {
4945			do {
4946				Add / modify source code;
4947			} until (compiles);
4948			Debug;
4949			if (clueless)
4950				email("Hi, I am having problems...");
4951		}
4952		Send patch file to the U-Boot email list;
4953		if (reasonable critiques)
4954			Incorporate improvements from email list code review;
4955		else
4956			Defend code as written;
4957	}
4958
4959	return 0;
4960}
4961
4962void no_more_time (int sig)
4963{
4964      hire_a_guru();
4965}
4966
4967
4968Coding Standards:
4969-----------------
4970
4971All contributions to U-Boot should conform to the Linux kernel
4972coding style; see the kernel coding style guide at
4973https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4974script "scripts/Lindent" in your Linux kernel source directory.
4975
4976Source files originating from a different project (for example the
4977MTD subsystem) are generally exempt from these guidelines and are not
4978reformatted to ease subsequent migration to newer versions of those
4979sources.
4980
4981Please note that U-Boot is implemented in C (and to some small parts in
4982Assembler); no C++ is used, so please do not use C++ style comments (//)
4983in your code.
4984
4985Please also stick to the following formatting rules:
4986- remove any trailing white space
4987- use TAB characters for indentation and vertical alignment, not spaces
4988- make sure NOT to use DOS '\r\n' line feeds
4989- do not add more than 2 consecutive empty lines to source files
4990- do not add trailing empty lines to source files
4991
4992Submissions which do not conform to the standards may be returned
4993with a request to reformat the changes.
4994
4995
4996Submitting Patches:
4997-------------------
4998
4999Since the number of patches for U-Boot is growing, we need to
5000establish some rules. Submissions which do not conform to these rules
5001may be rejected, even when they contain important and valuable stuff.
5002
5003Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5004
5005Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5006see https://lists.denx.de/listinfo/u-boot
5007
5008When you send a patch, please include the following information with
5009it:
5010
5011* For bug fixes: a description of the bug and how your patch fixes
5012  this bug. Please try to include a way of demonstrating that the
5013  patch actually fixes something.
5014
5015* For new features: a description of the feature and your
5016  implementation.
5017
5018* A CHANGELOG entry as plaintext (separate from the patch)
5019
5020* For major contributions, add a MAINTAINERS file with your
5021  information and associated file and directory references.
5022
5023* When you add support for a new board, don't forget to add a
5024  maintainer e-mail address to the boards.cfg file, too.
5025
5026* If your patch adds new configuration options, don't forget to
5027  document these in the README file.
5028
5029* The patch itself. If you are using git (which is *strongly*
5030  recommended) you can easily generate the patch using the
5031  "git format-patch". If you then use "git send-email" to send it to
5032  the U-Boot mailing list, you will avoid most of the common problems
5033  with some other mail clients.
5034
5035  If you cannot use git, use "diff -purN OLD NEW". If your version of
5036  diff does not support these options, then get the latest version of
5037  GNU diff.
5038
5039  The current directory when running this command shall be the parent
5040  directory of the U-Boot source tree (i. e. please make sure that
5041  your patch includes sufficient directory information for the
5042  affected files).
5043
5044  We prefer patches as plain text. MIME attachments are discouraged,
5045  and compressed attachments must not be used.
5046
5047* If one logical set of modifications affects or creates several
5048  files, all these changes shall be submitted in a SINGLE patch file.
5049
5050* Changesets that contain different, unrelated modifications shall be
5051  submitted as SEPARATE patches, one patch per changeset.
5052
5053
5054Notes:
5055
5056* Before sending the patch, run the buildman script on your patched
5057  source tree and make sure that no errors or warnings are reported
5058  for any of the boards.
5059
5060* Keep your modifications to the necessary minimum: A patch
5061  containing several unrelated changes or arbitrary reformats will be
5062  returned with a request to re-formatting / split it.
5063
5064* If you modify existing code, make sure that your new code does not
5065  add to the memory footprint of the code ;-) Small is beautiful!
5066  When adding new features, these should compile conditionally only
5067  (using #ifdef), and the resulting code with the new feature
5068  disabled must not need more memory than the old code without your
5069  modification.
5070
5071* Remember that there is a size limit of 100 kB per message on the
5072  u-boot mailing list. Bigger patches will be moderated. If they are
5073  reasonable and not too big, they will be acknowledged. But patches
5074  bigger than the size limit should be avoided.
5075