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
  # published by the Free Software Foundation; either version 2 of
  # the License, or (at your option) any later version.
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  # This program is distributed in the hope that it will be useful,
  # but WITHOUT ANY WARRANTY; without even the implied warranty of
  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  # GNU General Public License for more details.
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  # You should have received a copy of the GNU General Public License
  # along with this program; if not, write to the Free Software
  # Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  # MA 02111-1307 USA
  
  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.trimffs addr ofs|partition size
        Enabled by the CONFIG_CMD_NAND_TRIMFFS macro. This command will write to
        the NAND flash in a manner identical to the 'nand write' command
        described above -- with the additional check that all pages at the end
        of eraseblocks which contain only 0xff data will not be written to the
        NAND flash. This behaviour is required when flashing UBI images
        containing UBIFS volumes as per the UBI FAQ[1].
  
        [1] http://www.linux-mtd.infradead.org/doc/ubi.html#L_flasher_algo

     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.

  NOTE:
  =====

  The current NAND implementation is based on what is in recent

  Linux kernels.  The old legacy implementation has been removed.

  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.