Re: fsl_ifc_nand: are blank pages protected by ECC?

Pavel Machek
2017-04-21T13:37:26Z

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Hi!

> (Added driver author to the cc list, maybe he can help).

> > > UBIFS complains:
> > >
> > > UBIFS error (pid 931): ubifs_scan: corrupt empty space at LEB 282:252630
> > > UBIFS error (pid 931): ubifs_scanned_corruption: corruption at LEB 282:252630
> > > UBIFS error (pid 931): ubifs_scanned_corruption: first 1322 bytes from LEB 282:252630
> > > UBIFS error (pid 931): ubifs_scan: LEB 282 scanning failed
...
> > > is_blank() checks for all 0xff's, so single-bit 0xfe in the data will
> > > result in_blank() == 0 and uncorrectable error being signaled.
> > >
> > > Should the driver be modified somehow?
> >
> > Yep, nand_check_erased_ecc_chunk() [1] is here to help you check this
> > case, unfortunately, it's not directly applicable here, because this

Maybe I figured it out. Unfortunately, it is only compile tested. Does
it look approximately right?

Thanks,
Pavel

--- a/drivers/mtd/nand/fsl_ifc_nand.c
+++ b/drivers/mtd/nand/fsl_ifc_nand.c
@@ -171,32 +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;
-
- i = nand_check_erased_buf(&mainarea[i], mtd->writesize, 0);
- if (i)
- return 0;
-
- mtd_ooblayout_ecc(mtd, section++, &oobregion);
- while (oobregion.length) {
- i = nand_check_erased_buf(&oob[oobregion.offset], oobregion.length, 0);
- if (i)
- 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)
@@ -272,16 +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;
+ printk("NAND flash read: error but continuing.\n");
}

mtd->ecc_stats.corrected += errors;
@@ -676,6 +648,40 @@ 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++;
+
+ bitflips = max(res, bitflips);
+ buf += pkt_size;
+ ecc += ecc_size;
+ }
+
+ mtd_ooblayout_ecc(mtd, 1, &oobregion);
+ BUG_ON(oobregion.length);
+
+ return bitflips;
+}
+
static int fsl_ifc_read_page(struct mtd_info *mtd, struct nand_chip *chip,
uint8_t *buf, int oob_required, int page)
{
@@ -687,11 +693,23 @@ 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);
+
+ printk("NAND flash: have error (%d)\n", nctrl->max_bitflips);
+ res = check_erased_page(chip, buf);
+ printk("NAND flash: but erased page says %d\n", res);
+
+ dev_err(priv->dev, "NAND Flash ECC Uncorrectable Error or erased page\n");
+ return res;
+ }
+

return nctrl->max_bitflips;
}