nand: fix wrong default oob layout for small pages using soft ecc

[Linux-MTD Mailing List]

Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=f7f8c1756e9a5f1258a7cc6b663f8451b724900f
Commit:     f7f8c1756e9a5f1258a7cc6b663f8451b724900f
Parent:     3aa0907675a38498d8f2d343e94207ad28a117cf
Author:     Miquel Raynal <miquel.raynal at free-electrons.com>
AuthorDate: Wed Jul 5 08:51:09 2017 +0200
Committer:  Boris Brezillon <boris.brezillon at free-electrons.com>
CommitDate: Wed Aug 2 10:26:26 2017 +0200

    nand: fix wrong default oob layout for small pages using soft ecc
    
    When using soft ecc, if no ooblayout is given, the core automatically
    uses one of the nand_ooblayout_{sp,lp}*() functions to determine the
    layout inside the out of band data.
    
    Until kernel version 4.6, struct nand_ecclayout was used for that
    purpose. During the migration from 4.6 to 4.7, an error shown up in the
    small page layout, in the case oob section is only 8 bytes long.
    
    The layout was using three bytes (0, 1, 2) for ecc, two bytes (3, 4)
    as free bytes, one byte (5) for bad block marker and finally
    two bytes (6, 7) as free bytes, as shown there:
    
    [linux-4.6] drivers/mtd/nand/nand_base.c:52
    static struct nand_ecclayout nand_oob_8 = {
            .eccbytes = 3,
            .eccpos = {0, 1, 2},
            .oobfree = {
                    {.offset = 3,
                     .length = 2},
                    {.offset = 6,
                     .length = 2} }
    };
    
    This fixes the current implementation which is incoherent. It
    references bit 3 at the same time as an ecc byte and a free byte.
    
    Furthermore, it is clear with the previous implementation that there
    is only one ecc section with 8 bytes oob sections. We shall return
    -ERANGE in the nand_ooblayout_ecc_sp() function when asked for the
    second section.
    
    Signed-off-by: Miquel Raynal <miquel.raynal at free-electrons.com>
    Fixes: 41b207a70d3a ("mtd: nand: implement the default mtd_ooblayout_ops")
    Cc: <stable at vger.kernel.org>
    Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>
---
 drivers/mtd/nand/nand_base.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 5fa5ddc..7b3826b 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -65,8 +65,14 @@ static int nand_ooblayout_ecc_sp(struct mtd_info *mtd, int section,
 
 	if (!section) {
 		oobregion->offset = 0;
-		oobregion->length = 4;
+		if (mtd->oobsize == 16)
+			oobregion->length = 4;
+		else
+			oobregion->length = 3;
 	} else {
+		if (mtd->oobsize == 8)
+			return -ERANGE;
+
 		oobregion->offset = 6;
 		oobregion->length = ecc->total - 4;
 	}