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Subject[PATCH v3 01/37] mtd: nand: relax ecc.read_page() return value for uncorrectable ECC
Date
The comment for ecc.read_page() requires that it should return
"0 if bitflips uncorrectable".

Actually, drivers could return positive values when uncorrectable
bitflips occur. For example, nand_read_page_swecc() is the case.
If ecc.correct() returns -EBADMSG for the first ECC sector, and
a positive value for the second one, nand_read_page_swecc() returns
a positive max_bitflips and increments ecc_stats.failed for the same
page.

The requirement can be relaxed by tweaking nand_do_read_ops().
Move the max_bitflips calculation below the retry.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Suggested-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---

Changes in v3:
- Newly added

Changes in v2: None

drivers/mtd/nand/nand_base.c | 3 +--
include/linux/mtd/nand.h | 2 +-
2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index e13f959..f828ad7 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -1993,8 +1993,6 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
break;
}

- max_bitflips = max_t(unsigned int, max_bitflips, ret);
-
/* Transfer not aligned data */
if (use_bufpoi) {
if (!NAND_HAS_SUBPAGE_READ(chip) && !oob &&
@@ -2045,6 +2043,7 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
}

buf += bytes;
+ max_bitflips = max_t(unsigned int, max_bitflips, ret);
} else {
memcpy(buf, chip->buffers->databuf + col, bytes);
buf += bytes;
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 9591e0f..69cccd1 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -525,7 +525,7 @@ static inline void nand_hw_control_init(struct nand_hw_control *nfc)
* out-of-band data).
* @read_page: function to read a page according to the ECC generator
* requirements; returns maximum number of bitflips corrected in
- * any single ECC step, 0 if bitflips uncorrectable, -EIO hw error
+ * any single ECC step, -EIO hw error
* @read_subpage: function to read parts of the page covered by ECC;
* returns same as read_page()
* @write_subpage: function to write parts of the page covered by ECC.
--
2.7.4
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