[PATCH] mtd: nand: fsl_ifc: fix handing of bit flips in erased pages

Pavel Machek
2017-05-17T20:03:17Z

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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>

diff --git a/drivers/mtd/nand/fsl_ifc_nand.c b/drivers/mtd/nand/fsl_ifc_nand.c
index d1570f5..1c66696 100644
--- a/drivers/mtd/nand/fsl_ifc_nand.c
+++ b/drivers/mtd/nand/fsl_ifc_nand.c
@@ -171,34 +171,6 @@ static void set_addr(struct mtd_info *mtd, int column, int page_addr, int oob)
ifc_nand_ctrl->index += mtd->writesize;
}

-static int is_blank(struct mtd_info *mtd, unsigned int bufnum)
-{
- struct nand_chip *chip = mtd_to_nand(mtd);
- struct fsl_ifc_mtd *priv = nand_get_controller_data(chip);
- u8 __iomem *addr = priv->vbase + bufnum * (mtd->writesize * 2);
- u32 __iomem *mainarea = (u32 __iomem *)addr;
- u8 __iomem *oob = addr + mtd->writesize;
- struct mtd_oob_region oobregion = { };
- int i, section = 0;
-
- for (i = 0; i < mtd->writesize / 4; i++) {
- if (__raw_readl(&mainarea[i]) != 0xffffffff)
- return 0;
- }
-
- mtd_ooblayout_ecc(mtd, section++, &oobregion);
- while (oobregion.length) {
- for (i = 0; i < oobregion.length; i++) {
- if (__raw_readb(&oob[oobregion.offset + i]) != 0xff)
- return 0;
- }
-
- mtd_ooblayout_ecc(mtd, section++, &oobregion);
- }
-
- return 1;
-}
-
/* returns nonzero if entire page is blank */
static int check_read_ecc(struct mtd_info *mtd, struct fsl_ifc_ctrl *ctrl,
u32 *eccstat, unsigned int bufnum)
@@ -274,16 +246,13 @@ static void fsl_ifc_run_command(struct mtd_info *mtd)
if (errors == 15) {
/*
* Uncorrectable error.
- * OK only if the whole page is blank.
+ * We'll check for blank pages later.
*
* We disable ECCER reporting due to...
* erratum IFC-A002770 -- so report it now if we
* see an uncorrectable error in ECCSTAT.
*/
- if (!is_blank(mtd, bufnum))
- ctrl->nand_stat |=
- IFC_NAND_EVTER_STAT_ECCER;
- break;
+ ctrl->nand_stat |= IFC_NAND_EVTER_STAT_ECCER;
}

mtd->ecc_stats.corrected += errors;
@@ -678,6 +648,39 @@ 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;
+ }
+
+ return bitflips;
+}
+
static int fsl_ifc_read_page(struct mtd_info *mtd, struct nand_chip *chip,
uint8_t *buf, int oob_required, int page)
{
@@ -689,11 +695,18 @@ static int fsl_ifc_read_page(struct mtd_info *mtd, struct nand_chip *chip,
if (oob_required)
fsl_ifc_read_buf(mtd, chip->oob_poi, mtd->oobsize);

- if (ctrl->nand_stat & IFC_NAND_EVTER_STAT_ECCER)
- dev_err(priv->dev, "NAND Flash ECC Uncorrectable Error\n");
-
if (ctrl->nand_stat != IFC_NAND_EVTER_STAT_OPC)
mtd->ecc_stats.failed++;
+
+ if (ctrl->nand_stat & IFC_NAND_EVTER_STAT_ECCER) {
+ int res;
+
+ if (!oob_required)
+ fsl_ifc_read_buf(mtd, chip->oob_poi, mtd->oobsize);
+
+ res = check_erased_page(chip, buf);
+ return res;
+ }

return nctrl->max_bitflips;
}