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.trimffs addr ofs|partition size
  82       Enabled by the CONFIG_CMD_NAND_TRIMFFS macro. This command will write to
  83       the NAND flash in a manner identical to the 'nand write' command
  84       described above -- with the additional check that all pages at the end
  85       of eraseblocks which contain only 0xff data will not be written to the
  86       NAND flash. This behaviour is required when flashing UBI images
  87       containing UBIFS volumes as per the UBI FAQ[1].
  88
  89       [1] http://www.linux-mtd.infradead.org/doc/ubi.html#L_flasher_algo
  90
  91    nand write.oob addr ofs|partition size
  92       Write `size' bytes from `addr' to the out-of-band data area
  93       corresponding to `ofs' in NAND flash. This is limited to the 16 bytes
  94       of data for one 512-byte page or 2 256-byte pages. There is no check
  95       for bad blocks.
  96
  97    nand read.raw addr ofs|partition
  98       Read page from `ofs' in NAND flash to `addr'. This reads the raw page,
  99       so ECC is avoided and the OOB area is read as well.
 100
 101    nand write.raw addr ofs|partition
 102       Write page from `addr' to `ofs' in NAND flash. This writes the raw page,
 103       so ECC is avoided and the OOB area is written as well, making the whole
 104       page written as-is.
 105
 106 Configuration Options:
 107
 108    CONFIG_CMD_NAND
 109       Enables NAND support and commmands.
 110
 111    CONFIG_MTD_NAND_ECC_JFFS2
 112       Define this if you want the Error Correction Code information in
 113       the out-of-band data to be formatted to match the JFFS2 file system.
 114       CONFIG_MTD_NAND_ECC_YAFFS would be another useful choice for
 115       someone to implement.
 116
 117    CONFIG_SYS_MAX_NAND_DEVICE
 118       The maximum number of NAND devices you want to support.
 119
 120    CONFIG_SYS_NAND_MAX_CHIPS
 121       The maximum number of NAND chips per device to be supported.
 122
 123 NOTE:
 124 =====
 125
 126 The current NAND implementation is based on what is in recent
 127 Linux kernels.  The old legacy implementation has been removed.
 128
 129 If you have board code which used CONFIG_NAND_LEGACY, you'll need
 130 to convert to the current NAND interface for it to continue to work.
 131
 132 The Disk On Chip driver is currently broken and has been for some time.
 133 There is a driver in drivers/mtd/nand, taken from Linux, that works with
 134 the current NAND system but has not yet been adapted to the u-boot
 135 environment.
 136
 137 Additional improvements to the NAND subsystem by Guido Classen, 10-10-2006
 138
 139 JFFS2 related commands:
 140
 141   implement "nand erase clean" and old "nand erase"
 142   using both the new code which is able to skip bad blocks
 143   "nand erase clean" additionally writes JFFS2-cleanmarkers in the oob.
 144
 145 Miscellaneous and testing commands:
 146   "markbad [offset]"
 147   create an artificial bad block (for testing bad block handling)
 148
 149   "scrub [offset length]"
 150   like "erase" but don't skip bad block. Instead erase them.
 151   DANGEROUS!!! Factory set bad blocks will be lost. Use only
 152   to remove artificial bad blocks created with the "markbad" command.
 153
 154
 155 NAND locking command (for chips with active LOCKPRE pin)
 156
 157   "nand lock"
 158   set NAND chip to lock state (all pages locked)
 159
 160   "nand lock tight"
 161   set NAND chip to lock tight state (software can't change locking anymore)
 162
 163   "nand lock status"
 164   displays current locking status of all pages
 165
 166   "nand unlock [offset] [size]"
 167   unlock consecutive area (can be called multiple times for different areas)
 168
 169
 170 I have tested the code with board containing 128MiB NAND large page chips
 171 and 32MiB small page chips.