mtd: nand: omap: fix BCHx ecc.correct to return detected bit-flips in erased-page

fixes: commit 62116e5171e00f85a8d53f76e45b84423c89ff34
       mtd: nand: omap2: Support for hardware BCH error correction.

In omap_elm_correct_data(), if bitflip_count in an erased-page is within the
correctable limit (< ecc.strength), then it is not indicated back to the caller
ecc->read_page().

This mis-guides upper layers like MTD and UBIFS layer to assume erased-page as
perfectly clean and use it for writing even if actual bitflip_count was
dangerously high (bitflip_count > mtd->bitflip_threshold).

This patch fixes this above issue, by returning 'stats' to caller
ecc->read_page() under all scenarios.

Reported-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Pekon Gupta <pekon@ti.com>
Cc: <stable@vger.kernel.org> # 3.9.x+
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
index 1b800bc..10c319e 100644 (file)
--- a/drivers/mtd/nand/omap2.c
+++ b/drivers/mtd/nand/omap2.c
@@ -1382,7 +1382,7 @@ static int omap_elm_correct_data(struct mtd_info *mtd, u_char *data,
 
        /* Check if any error reported */
        if (!is_error_reported)
-               return 0;
+               return stat;
 
        /* Decode BCH error using ELM module */
        elm_decode_bch_error_page(info->elm_dev, ecc_vec, err_vec);