[PATCH v3 3/6] mtd: nand: erase block before marking bad

[Brian Norris <computersforpeace@gmail.com>]

Many NAND flash systems (especially those with MLC NAND) cannot be
reliably written twice in a row. For instance, when marking a bad block,
the block may already have data written to it, and so we should attempt
to erase the block before writing a bad block marker to its OOB region.

We can ignore erase failures, since the block may be bad such that it
cannot be erased properly; we still attempt to write zeros to its spare
area.

Note that the erase must be performed before the BBT is updated, since
otherwise, nand_erase_nand() would not allow us to erase our "bad
block."

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
---
 drivers/mtd/nand/nand_base.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index ead2a12..d5dbe0a 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -397,6 +397,16 @@ static int nand_default_block_markbad(struct mtd_info *mtd, loff_t ofs)
 	BUG_ON((chip->options & NAND_NO_WRITE_OOB) &&
 			!(chip->bbt_options & NAND_BBT_USE_FLASH));
 
+	/* Erase before writing to OOB and before BBT is updated */
+	if (!(chip->options & NAND_NO_WRITE_OOB)) {
+		struct erase_info einfo;
+		memset(&einfo, 0, sizeof(einfo));
+		einfo.mtd = mtd;
+		einfo.addr = ofs;
+		einfo.len = 1 << chip->phys_erase_shift;
+		nand_erase_nand(mtd, &einfo, 0);
+	}
+
 	if (chip->bbt_options & NAND_BBT_SCANLASTPAGE)
 		ofs += mtd->erasesize - mtd->writesize;
 
-- 
1.7.5.4