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

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=fdf2e821052958a114618a95ab18a300d0b080cb
Commit:     fdf2e821052958a114618a95ab18a300d0b080cb
Parent:     50c4c4e268a2d7a3e58ebb698ac74da0de40ae36
Author:     Sascha Hauer <s.hauer at pengutronix.de>
AuthorDate: Tue Dec 5 11:51:40 2017 +0100
Committer:  Richard Weinberger <richard at nod.at>
CommitDate: Fri Dec 15 22:26:15 2017 +0100

    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 at pengutronix.de>
    Reviewed-by: Richard Weinberger <richard at nod.at>
    Acked-by: Boris Brezillon <boris.brezillon at free-electrons.com>
    Signed-off-by: Richard Weinberger <richard at nod.at>
---
 drivers/mtd/nand/gpmi-nand/gpmi-nand.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
index 50f8d4a1b983..d4d824ef64e9 100644
--- 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()