Commit 041e4575 authored by Brian Norris's avatar Brian Norris Committed by Artem Bityutskiy
Browse files

mtd: nand: handle ECC errors in OOB 



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: default avatarBrian Norris <computersforpeace@gmail.com>
Signed-off-by: default avatarArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
parent d6137bad

drivers/mtd/mtdchar.c

+15 −0
Original line number Diff line number Diff line
@@ -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;

}

drivers/mtd/nand/nand_base.c

+8 −1
Original line number Diff line number Diff line
@@ -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;

}



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