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>
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@ -3794,6 +3794,39 @@ int nand_scan_ident(struct mtd_info *mtd, int maxchips,
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}
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EXPORT_SYMBOL(nand_scan_ident);
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/*
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* Check if the chip configuration meet the datasheet requirements.
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* If our configuration corrects A bits per B bytes and the minimum
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* required correction level is X bits per Y bytes, then we must ensure
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* both of the following are true:
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*
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* (1) A / B >= X / Y
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* (2) A >= X
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*
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* Requirement (1) ensures we can correct for the required bitflip density.
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* Requirement (2) ensures we can correct even when all bitflips are clumped
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* in the same sector.
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*/
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static bool nand_ecc_strength_good(struct mtd_info *mtd)
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{
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struct nand_chip *chip = mtd->priv;
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struct nand_ecc_ctrl *ecc = &chip->ecc;
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int corr, ds_corr;
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if (ecc->size == 0 || chip->ecc_step_ds == 0)
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/* Not enough information */
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return true;
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/*
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* We get the number of corrected bits per page to compare
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* the correction density.
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*/
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corr = (mtd->writesize * ecc->strength) / ecc->size;
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ds_corr = (mtd->writesize * chip->ecc_strength_ds) / chip->ecc_step_ds;
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return corr >= ds_corr && ecc->strength >= chip->ecc_strength_ds;
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}
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/**
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* nand_scan_tail - [NAND Interface] Scan for the NAND device
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@ -4014,6 +4047,9 @@ int nand_scan_tail(struct mtd_info *mtd)
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ecc->layout->oobavail += ecc->layout->oobfree[i].length;
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mtd->oobavail = ecc->layout->oobavail;
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/* ECC sanity check: warn noisily if it's too weak */
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WARN_ON(!nand_ecc_strength_good(mtd));
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/*
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* Set the number of read / write steps for one page depending on ECC
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* mode.
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