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

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=07604686e808cd93d352172806a7828860f048f5
Commit:     07604686e808cd93d352172806a7828860f048f5
Parent:     f107d7a43923a83d837b3ea3c7b7de58cd014bbd
Author:     Masahiro Yamada <yamada.masahiro at socionext.com>
AuthorDate: Thu Mar 30 15:45:47 2017 +0900
Committer:  Boris Brezillon <boris.brezillon at free-electrons.com>
CommitDate: Tue Apr 25 14:18:31 2017 +0200

    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 at socionext.com>
    Suggested-by: Boris Brezillon <boris.brezillon at free-electrons.com>
    Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>
---
 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 36258e6..de6c804 100644
--- 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 4065793..9e0c93c 100644
--- 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.