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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>
This commit is contained in:
Ezequiel Garcia 2014-05-14 14:58:06 -03:00 committed by Brian Norris
parent edf02fb248
commit 67a9ad9b8a
1 changed files with 36 additions and 0 deletions
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36
drivers/mtd/nand/nand_base.c
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@ -3794,6 +3794,39 @@ int nand_scan_ident(struct mtd_info *mtd, int maxchips,
} }
EXPORT_SYMBOL(nand_scan_ident); 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 * 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; ecc->layout->oobavail += ecc->layout->oobfree[i].length;
mtd->oobavail = ecc->layout->oobavail; 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 * Set the number of read / write steps for one page depending on ECC
* mode. * mode.