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

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>
Reported-by: Darwin Dingel <Darwin.Dingel@alliedtelesis.co.nz>
Acked-by: Darwin Dingel <Darwin.Dingel@alliedtelesis.co.nz>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

diff --git a/drivers/mtd/nand/fsl_ifc_nand.c b/drivers/mtd/nand/fsl_ifc_nand.c
index 89e14daeaba697f5559fcaa7c6d30cc013c126c1..d1c4538f870f95a1787bc4ef7e7e9872ff18f951 100644 (file)
--- 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 +246,14 @@ 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;
+                               continue;
                        }
 
                        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)
 {
@@ -689,8 +692,12 @@ 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_ECCER) {
+               if (!oob_required)
+                       fsl_ifc_read_buf(mtd, chip->oob_poi, mtd->oobsize);
+
+               return check_erased_page(chip, buf);
+       }
 
        if (ctrl->nand_stat != IFC_NAND_EVTER_STAT_OPC)
                mtd->ecc_stats.failed++;