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mtd: nand: handle ECC errors in OOB

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While the standard NAND OOB functions do not do ECC on the spare area,
it is possible for a driver to supply its own OOB ECC functions (e.g., HW
ECC). nand_do_read_oob should act like nand_do_read_ops in checking the
ECC stats and returning -EBADMSG or -EUCLEAN on uncorrectable errors or
correctable bitflips, respectively. These error codes could be used in
flash-based BBT code or in YAFFS, for example.

Doing this, however, messes with the behavior of mtd_do_readoob. Now,
mtd_do_readoob should check whether we had -EUCLEAN or -EBADMSG errors
and discard those as "non-fatal" so that the ioctls can still succeed
with (possibly uncorrected) data.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This commit is contained in:
Brian Norris 2011-06-23 16:45:24 -07:00 committed by Artem Bityutskiy
parent d6137badef
commit 041e4575f0
2 changed files with 23 additions and 1 deletions
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15
drivers/mtd/mtdchar.c
View file

@ -473,6 +473,21 @@ static int mtd_do_readoob(struct mtd_info *mtd, uint64_t start,
ret = -EFAULT;
kfree(ops.oobbuf);
/*
* NAND returns -EBADMSG on ECC errors, but it returns the OOB
* data. For our userspace tools it is important to dump areas
* with ECC errors!
* For kernel internal usage it also might return -EUCLEAN
* to signal the caller that a bitflip has occured and has
* been corrected by the ECC algorithm.
*
* Note: most NAND ECC algorithms do not calculate ECC
* for the OOB area.
*/
if (ret == -EUCLEAN || ret == -EBADMSG)
return 0;
return ret;
}

9
drivers/mtd/nand/nand_base.c
View file

@ -1750,6 +1750,7 @@ static int nand_do_read_oob(struct mtd_info *mtd, loff_t from,
{
int page, realpage, chipnr, sndcmd = 1;
struct nand_chip *chip = mtd->priv;
struct mtd_ecc_stats stats;
int blkcheck = (1 << (chip->phys_erase_shift - chip->page_shift)) - 1;
int readlen = ops->ooblen;
int len;
@ -1758,6 +1759,8 @@ static int nand_do_read_oob(struct mtd_info *mtd, loff_t from,
DEBUG(MTD_DEBUG_LEVEL3, "%s: from = 0x%08Lx, len = %i\n",
__func__, (unsigned long long)from, readlen);
stats = mtd->ecc_stats;
if (ops->mode == MTD_OOB_AUTO)
len = chip->ecc.layout->oobavail;
else
@ -1828,7 +1831,11 @@ static int nand_do_read_oob(struct mtd_info *mtd, loff_t from,
}
ops->oobretlen = ops->ooblen;
return 0;
if (mtd->ecc_stats.failed - stats.failed)
return -EBADMSG;
return mtd->ecc_stats.corrected - stats.corrected ? -EUCLEAN : 0;
}
/**