mtd: support writing OOB without ECC
This fixes issues with `nandwrite -n -o' and the MEMWRITEOOB[64] ioctls
on hardware that writes ECC when writing OOB. The problem arises as
follows: `nandwrite -n' can write page data to flash without applying
ECC, but when used with the `-o' option, ECC is applied (incorrectly),
contrary to the `--noecc' option.
I found that this is the case because my hardware computes and writes
ECC data to flash upon either OOB write or page write. Thus, to support
a proper "no ECC" write, my driver must know when we're performing a raw
OOB write vs. a normal ECC OOB write. However, MTD does not pass any raw
mode information to the write_oob functions. This patch addresses the
problems by:
1) Passing MTD_OOB_RAW down to lower layers, instead of just defaulting
to MTD_OOB_PLACE
2) Handling MTD_OOB_RAW within the NAND layer's `nand_do_write_oob'
3) Adding a new (replaceable) function pointer in struct ecc_ctrl; this
function should support writing OOB without ECC data. Current
hardware often can use the same OOB write function when writing
either with or without ECC
This was tested with nandsim as well as on actual SLC NAND.
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Cc: Jim Quinlan <jim2101024@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@intel.com>
diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
index b206254..bcb7f05 100644
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -391,6 +391,7 @@
uint64_t start, uint32_t length, void __user *ptr,
uint32_t __user *retp)
{
+ struct mtd_file_info *mfi = file->private_data;
struct mtd_oob_ops ops;
uint32_t retlen;
int ret = 0;
@@ -412,7 +413,7 @@
ops.ooblen = length;
ops.ooboffs = start & (mtd->writesize - 1);
ops.datbuf = NULL;
- ops.mode = MTD_OOB_PLACE;
+ ops.mode = (mfi->mode == MTD_MODE_RAW) ? MTD_OOB_RAW : MTD_OOB_PLACE;
if (ops.ooboffs && ops.ooblen > (mtd->oobsize - ops.ooboffs))
return -EINVAL;
diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 7f2691f..b61a7c7 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -2404,7 +2404,11 @@
chip->pagebuf = -1;
nand_fill_oob(mtd, ops->oobbuf, ops->ooblen, ops);
- status = chip->ecc.write_oob(mtd, chip, page & chip->pagemask);
+
+ if (ops->mode == MTD_OOB_RAW)
+ status = chip->ecc.write_oob_raw(mtd, chip, page & chip->pagemask);
+ else
+ status = chip->ecc.write_oob(mtd, chip, page & chip->pagemask);
if (status)
return status;
@@ -3380,6 +3384,10 @@
BUG();
}
+ /* For many systems, the standard OOB write also works for raw */
+ if (!chip->ecc.write_oob_raw)
+ chip->ecc.write_oob_raw = chip->ecc.write_oob;
+
/*
* The number of bytes available for a client to place data into
* the out of band area.
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 85fef68..5f3fdd9 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -340,6 +340,7 @@
* @read_subpage: function to read parts of the page covered by ECC.
* @write_page: function to write a page according to the ECC generator
* requirements.
+ * @write_oob_raw: function to write chip OOB data without ECC
* @read_oob: function to read chip OOB data
* @write_oob: function to write chip OOB data
*/
@@ -368,6 +369,8 @@
uint32_t offs, uint32_t len, uint8_t *buf);
void (*write_page)(struct mtd_info *mtd, struct nand_chip *chip,
const uint8_t *buf);
+ int (*write_oob_raw)(struct mtd_info *mtd, struct nand_chip *chip,
+ int page);
int (*read_oob)(struct mtd_info *mtd, struct nand_chip *chip, int page,
int sndcmd);
int (*write_oob)(struct mtd_info *mtd, struct nand_chip *chip,