From 240181fd0ffa69cac08d6b06c94e843707370f5f Mon Sep 17 00:00:00 2001 From: Brian Norris Date: Mon, 12 Jan 2015 12:51:29 -0800 Subject: [PATCH] mtd: nand: default bitflip-reporting threshold to 75% of correction strength The MTD API reports -EUCLEAN only if the maximum number of bitflips found in any ECC block exceeds a certain threshold. This is done to avoid excessive -EUCLEAN reports to MTD users, which may induce additional scrubbing of data, even when the ECC algorithm in use is perfectly capable of handling the bitflips. This threshold can be controlled by user-space (via sysfs), to allow users to determine what they are willing to tolerate in their application. But it still helps to have sane defaults. In recent discussion [1], it was pointed out that our default threshold is equal to the correction strength. That means that we won't actually report any -EUCLEAN (i.e., "bitflips were corrected") errors until there are almost too many to handle. It was determined that 3/4 of the correction strength is probably a better default. [1] http://lists.infradead.org/pipermail/linux-mtd/2015-January/057259.html Signed-off-by: Brian Norris Acked-by: Huang Shijie --- drivers/mtd/nand/nand_base.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c index 816b5c1fd416..3f24b587304f 100644 --- a/drivers/mtd/nand/nand_base.c +++ b/drivers/mtd/nand/nand_base.c @@ -4171,7 +4171,7 @@ int nand_scan_tail(struct mtd_info *mtd) * properly set. */ if (!mtd->bitflip_threshold) - mtd->bitflip_threshold = mtd->ecc_strength; + mtd->bitflip_threshold = DIV_ROUND_UP(mtd->ecc_strength * 3, 4); /* Check, if we should skip the bad block table scan */ if (chip->options & NAND_SKIP_BBTSCAN) -- 2.20.1