linux-toradex.git/include/linux/mtd/bbm.h, branch v3.4.73

mtd: nand: write BBM to OOB even with flash-based BBT

2012-03-26T23:27:02+00:00

Currently, the flash-based BBT implementation writes bad block data only
to its flash-based table and not to the OOB marker area. Then, as new bad
blocks are marked over time, the OOB markers become incomplete and the
flash-based table becomes the only source of current bad block
information. This becomes an obvious problem when, for example:

 * bootloader cannot read the flash-based BBT format
 * BBT is corrupted and the flash must be rescanned for bad
   blocks; we want to remember bad blocks that were marked from Linux

So to keep the bad block markers in sync with the flash-based BBT, this
patch changes the default so that we write bad block markers to the proper
OOB area on each block in addition to flash-based BBT. Comments are
updated, expanded, and/or relocated as necessary.

The new flash-based BBT procedure for marking bad blocks:
 (1) erase the affected block, to allow OOB marker to be written cleanly
 (2) update in-memory BBT
 (3) write bad block marker to OOB area of affected block
 (4) update flash-based BBT
Note that we retain the first error encountered in (3) or (4), finish the
procedures, and dump the error in the end.

This should handle power cuts gracefully enough. (1) and (2) are mostly
harmless (note that (1) will not erase an already-recognized bad block).
The OOB and BBT may be "out of sync" if we experience power loss bewteen
(3) and (4), but we can reasonably expect that on next boot, subsequent
I/O operations will discover that the block should be marked bad again,
thus re-syncing the OOB and BBT.

Note that this is a change from the previous default flash-based BBT
behavior. If your system cannot support writing bad block markers to OOB,
use the new NAND_BBT_NO_OOB_BBM option (in combination with
NAND_BBT_USE_FLASH and NAND_BBT_NO_OOB).

Signed-off-by: Brian Norris 
Signed-off-by: Artem Bityutskiy 
Signed-off-by: David Woodhouse

mtd: nand: improve comment on NAND_BBT_DYNAMIC_STRUCT

2011-09-11T12:01:57+00:00

In an attempt to improve the documentation of the BBT code, I am expanding
the comments I left in commit:
    58373ff0afff4cc8ac40608872995f4d87eb72ec
    mtd: nand: more BB Detection refactoring and dynamic scan options

Signed-off-by: Brian Norris 
Signed-off-by: Artem Bityutskiy

mtd: nand: renumber the reorganized flags in nand.h / bbm.h

2011-09-11T12:01:56+00:00

After several steps of rearrangement and consolidation, it is probably
worth re-sequencing the numbers on some of our affected flags in nand.h
and bbm.h.

Signed-off-by: Brian Norris 
Signed-off-by: Artem Bityutskiy

mtd: nand: rename CREATE_EMPTY bbt flag with proper prefix

2011-09-11T12:01:56+00:00

According to our new prefix rules, we should rename NAND_CREATE_EMPTY_BBT
with a NAND_BBT prefix, i.e., NAND_BBT_CREATE_EMPTY.

Signed-off-by: Brian Norris 
Signed-off-by: Artem Bityutskiy

mtd: nand: move NAND_CREATE_EMPTY_BBT flag

2011-09-11T12:01:56+00:00

The NAND_CREATE_EMPTY_BBT flag was added by commit:
  453281a973c10bce941b240d1c654d536623b16b
  mtd: nand: introduce NAND_CREATE_EMPTY_BBT
This flag is not used within the kernel and not explained well, so I
took the liberty to edit its comments.

Also, this is a BBT-related flag (and closely tied with NAND_BBT_CREATE)
so I'm moving it to bbm.h next to NAND_BBT_CREATE, thus requiring that
we use the flag in nand_chip.bbt_options, *not* in nand_chip.options.

Signed-off-by: Brian Norris 
Signed-off-by: Artem Bityutskiy

mtd: nand: rename NAND_USE_FLASH_BBT

2011-09-11T12:01:56+00:00

Recall the recently added prefix requirements:
 * "NAND_" for flags in nand.h, used in nand_chip.options
 * "NAND_BBT_" for flags in bbm.h, used in nand_chip.bbt_options
        or in nand_bbt_descr.options

Thus, I am changing NAND_USE_FLASH_BBT to NAND_BBT_USE_FLASH.

Again, this flag is found in bbm.h and so should NOT be used in the
"nand_chip.options" field.

Signed-off-by: Brian Norris 
Signed-off-by: Artem Bityutskiy

mtd: nand: consolidate redundant flash-based BBT flags

2011-09-11T12:01:56+00:00

This patch works with the following three flags from two headers (nand.h
and bbm.h):
  (1) NAND_USE_FLASH_BBT (nand.h)
  (2) NAND_USE_FLASH_BBT_NO_OOB (nand.h)
  (3) NAND_BBT_NO_OOB (bbm.h)

These flags are all related and interdependent, yet they were in
different headers. Flag (2) is simply the combination of (1) and (3) and
can be eliminated.

This patch accomplishes the following:
  * eliminate NAND_USE_FLASH_BBT_NO_OOB (i.e., flag (2))
  * move NAND_USE_FLASH_BBT (i.e., flag (1)) to bbm.h

It's important to note that because (1) and (3) are now both found in
bbm.h, they should NOT be used in the "nand_chip.options" field.

I removed a small section from the mtdnand DocBook because it referes to
NAND_USE_FLASH_BBT in nand.h, which has been moved to bbm.h.

Signed-off-by: Brian Norris 
Signed-off-by: Artem Bityutskiy

mtd: nand: remove NAND_BBT_SCANBYTE1AND6 option

2011-09-11T12:01:46+00:00

This patch reverts most of:
    commit 58373ff0afff4cc8ac40608872995f4d87eb72ec
    mtd: nand: more BB Detection refactoring and dynamic scan options

According to the discussion at:
    http://lists.infradead.org/pipermail/linux-mtd/2011-May/035696.html
the NAND_BBT_SCANBYTE1AND6 flag, although technically valid, can break
some existing ECC layouts that use the 6th byte in the OOB for ECC data.
Furthermore, we apparently do not need to scan both bytes 1 and 6 in
the OOB region of the devices under consideration; instead, we only need
to scan one or the other.

Thus, the NAND_BBT_SCANBYTE1AND6 flag is at best unnecessary and at
worst a regression.

Signed-off-by: Brian Norris 
Signed-off-by: Artem Bityutskiy

mtd: nand: introduce NAND_CREATE_EMPTY_BBT

2010-10-24T23:54:37+00:00

it will create an empty BBT table without considering vendor's BBT
information. Vendor's information may be unavailable if the NAND
controller has a different DATA & OOB layout or this information may be
allready purged.

Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: David Woodhouse

mtd: nand: add support for BBT without OOB

2010-10-24T23:53:48+00:00

The first (sixt) byte in the OOB area contains vendor's bad block
information. During identification of the NAND chip this information is
collected by scanning the complete chip.
The option NAND_USE_FLASH_BBT is used to store this information in a sector so
we don't have to scan the complete flash. Unfortunately the code stores
a marker in order to recognize the BBT in the OOB area. This will fail
if the OOB area is completely used for ECC.
This patch introduces the option NAND_USE_FLASH_BBT_NO_OOB which has to be
used with NAND_USE_FLASH_BBT. It will then store BBT on flash without
touching the OOB area. The BBT format on flash remains same except the
first page starts with the recognition pattern followed by the version byte.
This change was tested in nandsim and it looks good so far :)

Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: David Woodhouse