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author | Ezequiel Garcia <ezequiel.garcia@free-electrons.com> | 2014-05-14 14:58:06 -0300 |
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committer | Brian Norris <computersforpeace@gmail.com> | 2014-05-21 12:55:08 -0700 |
commit | 67a9ad9b8a6f6ea76ef8fc484ae49970d72d5534 (patch) | |
tree | c1678fc73873ba2bdbb8dffb15f4749923f91e4d | |
parent | edf02fb248022c13b2c86f08177b99ce619e693a (diff) | |
download | op-kernel-dev-67a9ad9b8a6f6ea76ef8fc484ae49970d72d5534.zip op-kernel-dev-67a9ad9b8a6f6ea76ef8fc484ae49970d72d5534.tar.gz |
mtd: nand: Warn the user if the selected ECC strength is too weak
This commit makes use of the chip->ecc_strength_ds and chip->ecc_step_ds which
contain the datasheet minimum requested ECC strength to produce a noisy warning
if the configured ECC strength is weaker.
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
-rw-r--r-- | drivers/mtd/nand/nand_base.c | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c index 0c1593b..41167e9 100644 --- a/drivers/mtd/nand/nand_base.c +++ b/drivers/mtd/nand/nand_base.c @@ -3794,6 +3794,39 @@ int nand_scan_ident(struct mtd_info *mtd, int maxchips, } EXPORT_SYMBOL(nand_scan_ident); +/* + * Check if the chip configuration meet the datasheet requirements. + + * If our configuration corrects A bits per B bytes and the minimum + * required correction level is X bits per Y bytes, then we must ensure + * both of the following are true: + * + * (1) A / B >= X / Y + * (2) A >= X + * + * Requirement (1) ensures we can correct for the required bitflip density. + * Requirement (2) ensures we can correct even when all bitflips are clumped + * in the same sector. + */ +static bool nand_ecc_strength_good(struct mtd_info *mtd) +{ + struct nand_chip *chip = mtd->priv; + struct nand_ecc_ctrl *ecc = &chip->ecc; + int corr, ds_corr; + + if (ecc->size == 0 || chip->ecc_step_ds == 0) + /* Not enough information */ + return true; + + /* + * We get the number of corrected bits per page to compare + * the correction density. + */ + corr = (mtd->writesize * ecc->strength) / ecc->size; + ds_corr = (mtd->writesize * chip->ecc_strength_ds) / chip->ecc_step_ds; + + return corr >= ds_corr && ecc->strength >= chip->ecc_strength_ds; +} /** * nand_scan_tail - [NAND Interface] Scan for the NAND device @@ -4014,6 +4047,9 @@ int nand_scan_tail(struct mtd_info *mtd) ecc->layout->oobavail += ecc->layout->oobfree[i].length; mtd->oobavail = ecc->layout->oobavail; + /* ECC sanity check: warn noisily if it's too weak */ + WARN_ON(!nand_ecc_strength_good(mtd)); + /* * Set the number of read / write steps for one page depending on ECC * mode. |