NAND FLASH commands and notes

See NOTE below!!!

# (C) Copyright 2003
# Dave Ellis, SIXNET, dge@sixnetio.com
#
# See file CREDITS for list of people who contributed to this
# project.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License as
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# GNU General Public License for more details.
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Commands:

   nand bad
      Print a list of all of the bad blocks in the current device.

   nand device
      Print information about the current NAND device.

   nand device num
      Make device `num' the current device and print information about it.

   nand erase off|partition size
   nand erase clean [off|partition size]
      Erase `size' bytes starting at offset `off'. Alternatively partition
      name can be specified, in this case size will be eventually limited
      to not exceed partition size (this behaviour applies also to read
      and write commands). Only complete erase blocks can be erased.

      If `erase' is specified without an offset or size, the entire flash
      is erased. If `erase' is specified with partition but without an
      size, the entire partition is erased.

      If `clean' is specified, a JFFS2-style clean marker is written to
      each block after it is erased.

      This command will not erase blocks that are marked bad. There is
      a debug option in cmd_nand.c to allow bad blocks to be erased.
      Please read the warning there before using it, as blocks marked
      bad by the manufacturer must _NEVER_ be erased.

   nand info
      Print information about all of the NAND devices found.

   nand read addr ofs|partition size
      Read `size' bytes from `ofs' in NAND flash to `addr'.  Blocks that
      are marked bad are skipped.  If a page cannot be read because an
      uncorrectable data error is found, the command stops with an error.

   nand read.oob addr ofs|partition size
      Read `size' bytes from the out-of-band data area corresponding to
      `ofs' in NAND flash to `addr'. This is limited to the 16 bytes of
      data for one 512-byte page or 2 256-byte pages. There is no check
      for bad blocks or ECC errors.

   nand write addr ofs|partition size
      Write `size' bytes from `addr' to `ofs' in NAND flash.  Blocks that
      are marked bad are skipped.  If a page cannot be read because an
      uncorrectable data error is found, the command stops with an error.

      As JFFS2 skips blocks similarly, this allows writing a JFFS2 image,
      as long as the image is short enough to fit even after skipping the
      bad blocks.  Compact images, such as those produced by mkfs.jffs2
      should work well, but loading an image copied from another flash is
      going to be trouble if there are any bad blocks.

   nand write.oob addr ofs|partition size
      Write `size' bytes from `addr' to the out-of-band data area
      corresponding to `ofs' in NAND flash. This is limited to the 16 bytes
      of data for one 512-byte page or 2 256-byte pages. There is no check
      for bad blocks.

Configuration Options:

   CONFIG_CMD_NAND
      Enables NAND support and commmands.

   CONFIG_MTD_NAND_ECC_JFFS2
      Define this if you want the Error Correction Code information in
      the out-of-band data to be formatted to match the JFFS2 file system.
      CONFIG_MTD_NAND_ECC_YAFFS would be another useful choice for
      someone to implement.

   CONFIG_SYS_MAX_NAND_DEVICE
      The maximum number of NAND devices you want to support.

   CONFIG_SYS_NAND_MAX_CHIPS
      The maximum number of NAND chips per device to be supported.

   CONFIG_SYS_DAVINCI_BROKEN_ECC
      Versions of U-Boot <= 1.3.3 and Montavista Linux kernels
      generated bogus ECCs on large-page NAND. Both large and small page
      NAND ECCs were incompatible with the Linux davinci git tree (since
      NAND was integrated in 2.6.24).
      Turn this ON if you want backwards compatibility.
      Turn this OFF if you want U-Boot and the Linux davinci git kernel
      to use the same ECC format.

NOTE:
=====

The current NAND implementation is based on what is in recent
Linux kernels.  The old legacy implementation has been disabled,
and will be removed soon.

If you have board code which used CONFIG_NAND_LEGACY, you'll need
to convert to the current NAND interface for it to continue to work.

The Disk On Chip driver is currently broken and has been for some time.
There is a driver in drivers/mtd/nand, taken from Linux, that works with
the current NAND system but has not yet been adapted to the u-boot
environment.

Additional improvements to the NAND subsystem by Guido Classen, 10-10-2006

JFFS2 related commands:

  implement "nand erase clean" and old "nand erase"
  using both the new code which is able to skip bad blocks
  "nand erase clean" additionally writes JFFS2-cleanmarkers in the oob.

Miscellaneous and testing commands:
  "markbad [offset]"
  create an artificial bad block (for testing bad block handling)

  "scrub [offset length]"
  like "erase" but don't skip bad block. Instead erase them.
  DANGEROUS!!! Factory set bad blocks will be lost. Use only
  to remove artificial bad blocks created with the "markbad" command.


NAND locking command (for chips with active LOCKPRE pin)

  "nand lock"
  set NAND chip to lock state (all pages locked)

  "nand lock tight"
  set NAND chip to lock tight state (software can't change locking anymore)

  "nand lock status"
  displays current locking status of all pages

  "nand unlock [offset] [size]"
  unlock consecutive area (can be called multiple times for different areas)


I have tested the code with board containing 128MiB NAND large page chips
and 32MiB small page chips.
