[PATCH v2 8/8] ubi: Relax the 'no MLC' rule and allow MLCs operating in SLC mode

[Miquel Raynal <miquel.raynal@xxxxxxxxxxx>]

From: Boris Brezillon <bbrezillon@xxxxxxxxxx>

The MTD layer provides an SLC mode (purely software emulation of SLC
behavior) addressing the paired-pages corruption issue, which was the
main reason for refusing attaching MLC NANDs to UBI.

Relax this rule and allow partitions that have the
MTD_EMULATE_SLC_ON_MLC flag set to be attached.

Signed-off-by: Boris Brezillon <bbrezillon@xxxxxxxxxx>
Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
Acked-by: Richard Weinberger <richard@xxxxxx>
---
 drivers/mtd/ubi/build.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 12c02342149c..e85b04e9716b 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -867,8 +867,11 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num,
 	 * Both UBI and UBIFS have been designed for SLC NAND and NOR flashes.
 	 * MLC NAND is different and needs special care, otherwise UBI or UBIFS
 	 * will die soon and you will lose all your data.
+	 * Relax this rule if the partition we're attaching to operates in SLC
+	 * mode.
 	 */
-	if (mtd->type == MTD_MLCNANDFLASH) {
+	if (mtd->type == MTD_MLCNANDFLASH &&
+	    !(mtd->flags & MTD_SLC_ON_MLC_EMULATION)) {
 		pr_err("ubi: refuse attaching mtd%d - MLC NAND is not supported\n",
 			mtd->index);
 		return -EINVAL;
-- 
2.20.1


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