64 lines
2.2 KiB
Diff
64 lines
2.2 KiB
Diff
From 67a9ad9b8a6f6ea76ef8fc484ae49970d72d5534 Mon Sep 17 00:00:00 2001
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From: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
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Date: Wed, 14 May 2014 14:58:06 -0300
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Subject: mtd: nand: Warn the user if the selected ECC strength is too weak
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This commit makes use of the chip->ecc_strength_ds and chip->ecc_step_ds which
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contain the datasheet minimum requested ECC strength to produce a noisy warning
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if the configured ECC strength is weaker.
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Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
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Signed-off-by: Brian Norris <computersforpeace@gmail.com>
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--- a/drivers/mtd/nand/nand_base.c
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+++ b/drivers/mtd/nand/nand_base.c
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@@ -3682,6 +3682,39 @@ int nand_scan_ident(struct mtd_info *mtd
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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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+
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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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+
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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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+ /*
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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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+
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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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@@ -3891,6 +3924,9 @@ 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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/*
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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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