doc/README.nand

   1 NAND FLASH commands and notes
   2
   3 See NOTE below!!!
   4
   5 # (C) Copyright 2003
   6 # Dave Ellis, SIXNET, dge@sixnetio.com
   7 #
   8 # See file CREDITS for list of people who contributed to this
   9 # project.
  10 #
  11 # This program is free software; you can redistribute it and/or
  12 # modify it under the terms of the GNU General Public License as
  13 # published by the Free Software Foundation; either version 2 of
  14 # the License, or (at your option) any later version.
  15 #
  16 # This program is distributed in the hope that it will be useful,
  17 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 # GNU General Public License for more details.
  20 #
  21 # You should have received a copy of the GNU General Public License
  22 # along with this program; if not, write to the Free Software
  23 # Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  24 # MA 02111-1307 USA
  25
  26 Commands:
  27
  28    nand bad
  29       Print a list of all of the bad blocks in the current device.
  30
  31    nand device
  32       Print information about the current NAND device.
  33
  34    nand device num
  35       Make device `num' the current device and print information about it.
  36
  37    nand erase off|partition size
  38    nand erase clean [off|partition size]
  39       Erase `size' bytes starting at offset `off'. Alternatively partition
  40       name can be specified, in this case size will be eventually limited
  41       to not exceed partition size (this behaviour applies also to read
  42       and write commands). Only complete erase blocks can be erased.
  43
  44       If `erase' is specified without an offset or size, the entire flash
  45       is erased. If `erase' is specified with partition but without an
  46       size, the entire partition is erased.
  47
  48       If `clean' is specified, a JFFS2-style clean marker is written to
  49       each block after it is erased.
  50
  51       This command will not erase blocks that are marked bad. There is
  52       a debug option in cmd_nand.c to allow bad blocks to be erased.
  53       Please read the warning there before using it, as blocks marked
  54       bad by the manufacturer must _NEVER_ be erased.
  55
  56    nand info
  57       Print information about all of the NAND devices found.
  58
  59    nand read addr ofs|partition size
  60       Read `size' bytes from `ofs' in NAND flash to `addr'.  Blocks that
  61       are marked bad are skipped.  If a page cannot be read because an
  62       uncorrectable data error is found, the command stops with an error.
  63
  64    nand read.oob addr ofs|partition size
  65       Read `size' bytes from the out-of-band data area corresponding to
  66       `ofs' in NAND flash to `addr'. This is limited to the 16 bytes of
  67       data for one 512-byte page or 2 256-byte pages. There is no check
  68       for bad blocks or ECC errors.
  69
  70    nand write addr ofs|partition size
  71       Write `size' bytes from `addr' to `ofs' in NAND flash.  Blocks that
  72       are marked bad are skipped.  If a page cannot be read because an
  73       uncorrectable data error is found, the command stops with an error.
  74
  75       As JFFS2 skips blocks similarly, this allows writing a JFFS2 image,
  76       as long as the image is short enough to fit even after skipping the
  77       bad blocks.  Compact images, such as those produced by mkfs.jffs2
  78       should work well, but loading an image copied from another flash is
  79       going to be trouble if there are any bad blocks.
  80
  81    nand write.oob addr ofs|partition size
  82       Write `size' bytes from `addr' to the out-of-band data area
  83       corresponding to `ofs' in NAND flash. This is limited to the 16 bytes
  84       of data for one 512-byte page or 2 256-byte pages. There is no check
  85       for bad blocks.
  86
  87 Configuration Options:
  88
  89    CONFIG_CMD_NAND
  90       Enables NAND support and commmands.
  91
  92    CONFIG_MTD_NAND_ECC_JFFS2
  93       Define this if you want the Error Correction Code information in
  94       the out-of-band data to be formatted to match the JFFS2 file system.
  95       CONFIG_MTD_NAND_ECC_YAFFS would be another useful choice for
  96       someone to implement.
  97
  98    CONFIG_SYS_MAX_NAND_DEVICE
  99       The maximum number of NAND devices you want to support.
 100
 101    CONFIG_SYS_NAND_MAX_CHIPS
 102       The maximum number of NAND chips per device to be supported.
 103
 104    CONFIG_SYS_DAVINCI_BROKEN_ECC
 105       Versions of U-Boot <= 1.3.3 and Montavista Linux kernels
 106       generated bogus ECCs on large-page NAND. Both large and small page
 107       NAND ECCs were incompatible with the Linux davinci git tree (since
 108       NAND was integrated in 2.6.24).
 109       Turn this ON if you want backwards compatibility.
 110       Turn this OFF if you want U-Boot and the Linux davinci git kernel
 111       to use the same ECC format.
 112
 113 NOTE:
 114 =====
 115
 116 The current NAND implementation is based on what is in recent
 117 Linux kernels.  The old legacy implementation has been disabled,
 118 and will be removed soon.
 119
 120 If you have board code which used CONFIG_NAND_LEGACY, you'll need
 121 to convert to the current NAND interface for it to continue to work.
 122
 123 The Disk On Chip driver is currently broken and has been for some time.
 124 There is a driver in drivers/mtd/nand, taken from Linux, that works with
 125 the current NAND system but has not yet been adapted to the u-boot
 126 environment.
 127
 128 Additional improvements to the NAND subsystem by Guido Classen, 10-10-2006
 129
 130 JFFS2 related commands:
 131
 132   implement "nand erase clean" and old "nand erase"
 133   using both the new code which is able to skip bad blocks
 134   "nand erase clean" additionally writes JFFS2-cleanmarkers in the oob.
 135
 136 Miscellaneous and testing commands:
 137   "markbad [offset]"
 138   create an artificial bad block (for testing bad block handling)
 139
 140   "scrub [offset length]"
 141   like "erase" but don't skip bad block. Instead erase them.
 142   DANGEROUS!!! Factory set bad blocks will be lost. Use only
 143   to remove artificial bad blocks created with the "markbad" command.
 144
 145
 146 NAND locking command (for chips with active LOCKPRE pin)
 147
 148   "nand lock"
 149   set NAND chip to lock state (all pages locked)
 150
 151   "nand lock tight"
 152   set NAND chip to lock tight state (software can't change locking anymore)
 153
 154   "nand lock status"
 155   displays current locking status of all pages
 156
 157   "nand unlock [offset] [size]"
 158   unlock consecutive area (can be called multiple times for different areas)
 159
 160
 161 I have tested the code with board containing 128MiB NAND large page chips
 162 and 32MiB small page chips.