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

This is based on Linux:

commit e2414f4c20bd4dc62186fbfd7bdec50bce6d2ead
Author: Brian Norris <computersforpeace@gmail.com>
Date:   Mon Feb 6 13:44:00 2012 -0800

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:

 * code accessing the flash 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.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

0 files changed, 0 insertions, 0 deletions