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Commit 67a9ad9b authored by Ezequiel Garcia's avatar Ezequiel Garcia Committed by Brian Norris
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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: default avatarEzequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: default avatarBrian Norris <computersforpeace@gmail.com>
parent edf02fb2

drivers/mtd/nand/nand_base.c

+36 −0
Original line number Diff line number Diff line
@@ -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.