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    SubjectRe: [PATCH] fsl_ifc_nand: fix handing of bit flips in erased nand
    Hi!

    > On Wed, 17 May 2017 14:22:24 +0200
    > Pavel Machek <pavel@ucw.cz> wrote:
    >
    > > If we see unrecoverable ECC error, we need to count number of bitflips
    > > from all-ones and report correctable/uncorrectable according to
    > > that. Otherwise we report ECC failed on erased flash with single bit error.
    > >
    > > Signed-off-by: Pavel Machek <pavel@denx.de>
    > >
    > > @@ -678,6 +648,41 @@ static int fsl_ifc_wait(struct mtd_info *mtd, struct nand_chip *chip)
    > > return nand_fsr | NAND_STATUS_WP;
    > > }
    > >
    > > +/*
    > > + * The controller does not check for bitflips in erased pages,
    > > + * therefore software must check instead.
    > > + */
    > > +static int check_erased_page(struct nand_chip *chip, u8 *buf)
    > > +{
    > > + struct mtd_info *mtd = nand_to_mtd(chip);
    > > + u8 *ecc = chip->oob_poi;
    > > + const int ecc_size = chip->ecc.bytes;
    > > + const int pkt_size = chip->ecc.size;
    > > + int i, res, bitflips = 0;
    > > + struct mtd_oob_region oobregion = { };
    > > +
    > > + mtd_ooblayout_ecc(mtd, 0, &oobregion);
    > > + ecc += oobregion.offset;
    > > +
    > > + for (i = 0; i < chip->ecc.steps; ++i) {
    > > + res = nand_check_erased_ecc_chunk(buf, pkt_size, ecc, ecc_size,
    > > + NULL, 0,
    > > + chip->ecc.strength);
    > > + if (res < 0)
    > > + mtd->ecc_stats.failed++;
    > > + else
    > > + mtd->ecc_stats.corrected += res;
    > > +
    > > + bitflips = max(res, bitflips);
    > > + buf += pkt_size;
    > > + ecc += ecc_size;
    > > + }
    > > +
    > > + mtd_ooblayout_ecc(mtd, 1, &oobregion);
    >
    > Why is this needed?

    It is not, will remove.

    > > @@ -904,6 +922,21 @@ static int fsl_ifc_chip_init(struct fsl_ifc_mtd *priv)
    > > chip->ecc.algo = NAND_ECC_HAMMING;
    > > }
    > >
    > > + {
    > > + struct mtd_oob_region oobregion = { };
    > > +
    > > + mtd_ooblayout_ecc(mtd, 0, &oobregion);
    > > + if (!oobregion.length) {
    > > + dev_err(priv->dev, "No ECC in oobregion?\n");
    > > + return -EINVAL;
    > > + }
    > > + mtd_ooblayout_ecc(mtd, 1, &oobregion);
    > > + if (oobregion.length) {
    > > + dev_err(priv->dev, "Extra data in oobregion?\n");
    > > + return -EINVAL;
    > > + }
    > > + }
    >
    > This clearly doesn't belong in this patch. And if you really want to
    > check that, please create a separate function instead of defining a
    > non-conditional code block inside fsl_ifc_chip_init().

    I am not sure I want to check that. check_erased_page() can only
    handle layout with just one oobregion. If you think check is not
    needed, I'll happily remove the checking.

    Best regards,
    Pavel
    --
    (english) http://www.livejournal.com/~pavelmachek
    (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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