From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mms1.broadcom.com ([216.31.210.17]) by canuck.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1QZtbL-0008AN-CU for linux-mtd@lists.infradead.org; Thu, 23 Jun 2011 23:46:24 +0000 From: "Brian Norris" To: "Artem Bityutskiy" Subject: [PATCH] mtd: nand: handle ECC errors in OOB Date: Thu, 23 Jun 2011 16:45:24 -0700 Message-ID: <1308872724-6196-1-git-send-email-computersforpeace@gmail.com> MIME-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Jim Quinlan , linux-mtd@lists.infradead.org, Brian Norris , David Woodhouse , Kevin Cernekee List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 --- drivers/mtd/mtdchar.c | 15 +++++++++++++++ drivers/mtd/nand/nand_base.c | 9 ++++++++- 2 files changed, 23 insertions(+), 1 deletions(-) diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c index 3f92731..8a45525 100644 --- a/drivers/mtd/mtdchar.c +++ b/drivers/mtd/mtdchar.c @@ -472,6 +472,21 @@ 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; } diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c index a46e9bb..f0ba2da 100644 --- a/drivers/mtd/nand/nand_base.c +++ b/drivers/mtd/nand/nand_base.c @@ -1761,6 +1761,7 @@ 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; @@ -1769,6 +1770,8 @@ 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 @@ -1838,7 +1841,11 @@ 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; } /** -- 1.7.0.4