[3.11.y.z extended stable] Patch "mtd: nand: omap: fix BCHx ecc.correct to return detected bit-flips in erased-page" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

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

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From babca84d1ef44d42409a4189f4f68bad3e9c2d53 Mon Sep 17 00:00:00 2001
From: pekon gupta <pekon at ti.com>
Date: Thu, 20 Mar 2014 18:49:58 +0530
Subject: mtd: nand: omap: fix BCHx ecc.correct to return detected bit-flips in
 erased-page

commit f306e8c3b667632952f1a4a74ffb910bbc06255f upstream.

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 at gmail.com>
Signed-off-by: Pekon Gupta <pekon at ti.com>
Signed-off-by: Brian Norris <computersforpeace at gmail.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/mtd/nand/omap2.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
index 81b80af55872..8c4eb287bbdb 100644
--- a/drivers/mtd/nand/omap2.c
+++ b/drivers/mtd/nand/omap2.c
@@ -1463,7 +1463,7 @@ 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);
--
1.9.1