[PATCH v3 2/6] mtd: nand: write bad block marker by default even with BBT

[Brian Norris]

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bad blocks are marked over time, the OOB markers become out of date and
the flash-based table becomes the only source of current bad block
information. This can be a 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

In an attempt 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.

Theoretically, the bad block table and the OOB markers can still get out
of sync if the system experiences a power cut between writing the BBT to
flash and writing the OOB marker to a newly-marked bad block. However,
this is a relatively unlikely event, as new bad blocks shouldn't appear
frequently.

Note that this is a change from the previous default flash-based BBT
behavior. To restore old behavior (and to generally prevent writing to
OOB area), use the NAND_NO_WRITE_OOB options (in combination with
NAND_BBT_USE_FLASH and NAND_BBT_NO_OOB).

Signed-off-by: Brian Norris <computersforpeace at gmail.com>
---
 drivers/mtd/nand/nand_base.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index b9dbf0c..ead2a12 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -392,7 +392,10 @@ static int nand_default_block_markbad(struct mtd_info *mtd, loff_t ofs)
 {
 	struct nand_chip *chip = mtd->priv;
 	uint8_t buf[2] = { 0, 0 };
-	int block, ret, i = 0;
+	int block, ret = 0, i = 0;
+
+	BUG_ON((chip->options & NAND_NO_WRITE_OOB) &&
+			!(chip->bbt_options & NAND_BBT_USE_FLASH));
 
 	if (chip->bbt_options & NAND_BBT_SCANLASTPAGE)
 		ofs += mtd->erasesize - mtd->writesize;
@@ -405,7 +408,9 @@ static int nand_default_block_markbad(struct mtd_info *mtd, loff_t ofs)
 	/* Do we have a flash based bad block table? */
 	if (chip->bbt_options & NAND_BBT_USE_FLASH)
 		ret = nand_update_bbt(mtd, ofs);
-	else {
+
+	/* Write bad block marker to OOB */
+	if (!(chip->options & NAND_NO_WRITE_OOB)) {
 		struct mtd_oob_ops ops;
 
 		nand_get_device(chip, mtd, FL_WRITING);
-- 
1.7.5.4