mtd: nand: gpmi: Fix failure when a erased page has a bitflip at BBM

When erased subpages are read then the BCH decoder returns STATUS_ERASED
if they are all empty, or STATUS_UNCORRECTABLE if there are bitflips.
When there are bitflips, we have to set these bits again to show the
upper layers a completely erased page. When a bitflip happens in the
exact byte where the bad block marker is, then this byte is swapped
with another byte in block_mark_swapping(). The correction code then
detects a bitflip in another subpage and no longer corrects the bitflip
where it really happens.

Correct this behaviour by calling block_mark_swapping() after the
bitflips have been corrected.

In our case UBIFS failed with this bug because it expects erased
pages to be really empty:

UBIFS error (pid 187): ubifs_scan: corrupt empty space at LEB 36:118735
UBIFS error (pid 187): ubifs_scanned_corruption: corruption at LEB 36:118735
UBIFS error (pid 187): ubifs_scanned_corruption: first 8192 bytes from LEB 36:118735
UBIFS error (pid 187): ubifs_scan: LEB 36 scanning failed
UBIFS error (pid 187): do_commit: commit failed, error -117

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Richard Weinberger <richard@nod.at>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
index 50f8d4a..d4d824e 100644 (file)
--- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
+++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
@@ -1067,9 +1067,6 @@ static int gpmi_ecc_read_page(struct mtd_info *mtd, struct nand_chip *chip,
                return ret;
        }
 
-       /* handle the block mark swapping */
-       block_mark_swapping(this, payload_virt, auxiliary_virt);
-
        /* Loop over status bytes, accumulating ECC status. */
        status = auxiliary_virt + nfc_geo->auxiliary_status_offset;
 
@@ -1158,6 +1155,9 @@ static int gpmi_ecc_read_page(struct mtd_info *mtd, struct nand_chip *chip,
                max_bitflips = max_t(unsigned int, max_bitflips, *status);
        }
 
+       /* handle the block mark swapping */
+       block_mark_swapping(this, buf, auxiliary_virt);
+
        if (oob_required) {
                /*
                 * It's time to deliver the OOB bytes. See gpmi_ecc_read_oob()