mtd: nand: relax ecc.read_page() return value for uncorrectable ECC

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>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 36258e69a3897b085fb94029df6cabde3f9d4354..de6c8045c85b66939e86c15601a97304b037abb6 100644 (file)
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -1993,8 +1993,6 @@ read_retry:
                                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 @@ read_retry:
                        }
 
                        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 40657939797c4170f19e64ac98eb06ee04830f7a..9e0c93c44bef613100f12bde08145ab88fd2b69e 100644 (file)
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -516,7 +516,7 @@ 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.