8 files changed, 51 insertions, 19 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-mtd b/Documentation/ABI/testing/sysfs-class-mtd
index 78835080856a..db1ad7e34fc3 100644
--- a/Documentation/ABI/testing/sysfs-class-mtd
+++ b/Documentation/ABI/testing/sysfs-class-mtd
@@ -167,7 +167,10 @@ Description:
                 block degradation, but high enough to avoid the consequences of
                 a persistent return value of -EUCLEAN on devices where sticky
                 bitflips occur.  Note that if bitflip_threshold exceeds
-                ecc_strength, -EUCLEAN is never returned by the read functions.
+                ecc_strength, -EUCLEAN is never returned by mtd_read().
+                Conversely, if bitflip_threshold is zero, -EUCLEAN is always
+                returned, absent a hard error.
 
                 This is generally applicable only to NAND flash devices with ECC
-                capability.  It is ignored on devices lacking ECC capability.
+                capability.  It is ignored on devices lacking ECC capability;
+                i.e., devices for which ecc_strength is zero.
diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c
index 8272c02668d6..65d22a0439c6 100644
--- a/drivers/mtd/devices/docg3.c
+++ b/drivers/mtd/devices/docg3.c
@@ -850,6 +850,7 @@ static int doc_read_oob(struct mtd_info *mtd, loff_t from,
         u8 *buf = ops->datbuf;
         size_t len, ooblen, nbdata, nboob;
         u8 hwecc[DOC_ECC_BCH_SIZE], eccconf1;
+        int max_bitflips = 0;
 
         if (buf)
                 len = ops->len;
@@ -876,7 +877,7 @@ static int doc_read_oob(struct mtd_info *mtd, loff_t from,
         ret = 0;
         skip = from % DOC_LAYOUT_PAGE_SIZE;
         mutex_lock(&docg3->cascade->lock);
-        while (!ret && (len > 0 || ooblen > 0)) {
+        while (ret >= 0 && (len > 0 || ooblen > 0)) {
                 calc_block_sector(from - skip, &block0, &block1, &page, &ofs,
                         docg3->reliable);
                 nbdata = min_t(size_t, len, DOC_LAYOUT_PAGE_SIZE - skip);
@@ -936,7 +937,8 @@ static int doc_read_oob(struct mtd_info *mtd, loff_t from,
                         }
                         if (ret > 0) {
                                 mtd->ecc_stats.corrected += ret;
-                                ret = -EUCLEAN;
+                                max_bitflips = max(max_bitflips, ret);
+                                ret = max_bitflips;
                         }
                 }
 
diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 6a7cba1e24e6..575730744fdb 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -800,12 +800,24 @@ EXPORT_SYMBOL_GPL(mtd_get_unmapped_area);
 int mtd_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
              u_char *buf)
 {
+        int ret_code;
         *retlen = 0;
         if (from < 0 || from > mtd->size || len > mtd->size - from)
                 return -EINVAL;
         if (!len)
                 return 0;
-        return mtd->_read(mtd, from, len, retlen, buf);
+
+        /*
+         * In the absence of an error, drivers return a non-negative integer
+         * representing the maximum number of bitflips that were corrected on
+         * any one ecc region (if applicable; zero otherwise).
+         */
+        ret_code = mtd->_read(mtd, from, len, retlen, buf);
+        if (unlikely(ret_code < 0))
+                return ret_code;
+        if (mtd->ecc_strength == 0)
+                return 0;       /* device lacks ecc */
+        return ret_code >= mtd->bitflip_threshold ? -EUCLEAN : 0;
 }
 EXPORT_SYMBOL_GPL(mtd_read);
 
diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
index ec75d44e0253..d518e4db8a0b 100644
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -67,12 +67,12 @@ static int part_read(struct mtd_info *mtd, loff_t from, size_t len,
         stats = part->master->ecc_stats;
         res = part->master->_read(part->master, from + part->offset, len,
                                   retlen, buf);
-        if (unlikely(res)) {
-                if (mtd_is_bitflip(res))
-                        mtd->ecc_stats.corrected += part->master->ecc_stats.corrected - stats.corrected;
-                if (mtd_is_eccerr(res))
-                        mtd->ecc_stats.failed += part->master->ecc_stats.failed - stats.failed;
-        }
+        if (unlikely(mtd_is_eccerr(res)))
+                mtd->ecc_stats.failed +=
+                        part->master->ecc_stats.failed - stats.failed;
+        else
+                mtd->ecc_stats.corrected +=
+                        part->master->ecc_stats.corrected - stats.corrected;
         return res;
 }
 
diff --git a/drivers/mtd/nand/alauda.c b/drivers/mtd/nand/alauda.c
index 4f20e1d8bef1..60a0dfdb0808 100644
--- a/drivers/mtd/nand/alauda.c
+++ b/drivers/mtd/nand/alauda.c
@@ -414,7 +414,7 @@ static int alauda_bounce_read(struct mtd_info *mtd, loff_t from, size_t len,
         }
         err = 0;
         if (corrected)
-                err = -EUCLEAN;
+                err = 1;        /* return max_bitflips per ecc step */
         if (uncorrected)
                 err = -EBADMSG;
 out:
@@ -446,7 +446,7 @@ static int alauda_read(struct mtd_info *mtd, loff_t from, size_t len,
         }
         err = 0;
         if (corrected)
-                err = -EUCLEAN;
+                err = 1;        /* return max_bitflips per ecc step */
         if (uncorrected)
                 err = -EBADMSG;
         return err;
diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 9f5d339a3610..640f1f8159e8 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -1486,6 +1486,7 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
                 mtd->oobavail : mtd->oobsize;
 
         uint8_t *bufpoi, *oob, *buf;
+        unsigned int max_bitflips = 0;
 
         stats = mtd->ecc_stats;
 
@@ -1513,7 +1514,10 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
                                 sndcmd = 0;
                         }
 
-                        /* Now read the page into the buffer */
+                        /*
+                         * Now read the page into the buffer.  Absent an error,
+                         * the read methods return max bitflips per ecc step.
+                         */
                         if (unlikely(ops->mode == MTD_OPS_RAW))
                                 ret = chip->ecc.read_page_raw(mtd, chip,
                                                               bufpoi, page);
@@ -1530,15 +1534,19 @@ 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 (!aligned) {
                                 if (!NAND_SUBPAGE_READ(chip) && !oob &&
                                     !(mtd->ecc_stats.failed - stats.failed) &&
-                                    (ops->mode != MTD_OPS_RAW))
+                                    (ops->mode != MTD_OPS_RAW)) {
                                         chip->pagebuf = realpage;
-                                else
+                                        chip->pagebuf_bitflips = ret;
+                                } else {
                                         /* Invalidate page cache */
                                         chip->pagebuf = -1;
+                                }
                                 memcpy(buf, chip->buffers->databuf + col, bytes);
                         }
 
@@ -1571,6 +1579,8 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
                 } else {
                         memcpy(buf, chip->buffers->databuf + col, bytes);
                         buf += bytes;
+                        max_bitflips = max_t(unsigned int, max_bitflips,
+                                             chip->pagebuf_bitflips);
                 }
 
                 readlen -= bytes;
@@ -1609,7 +1619,7 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
         if (mtd->ecc_stats.failed - stats.failed)
                 return -EBADMSG;
 
-        return  mtd->ecc_stats.corrected - stats.corrected ? -EUCLEAN : 0;
+        return max_bitflips;
 }
 
 /**
diff --git a/drivers/mtd/onenand/onenand_base.c b/drivers/mtd/onenand/onenand_base.c
index b3ce12ef359e..7153e0d27101 100644
--- a/drivers/mtd/onenand/onenand_base.c
+++ b/drivers/mtd/onenand/onenand_base.c
@@ -1201,7 +1201,8 @@ static int onenand_mlc_read_ops_nolock(struct mtd_info *mtd, loff_t from,
         if (mtd->ecc_stats.failed - stats.failed)
                 return -EBADMSG;
 
-        return mtd->ecc_stats.corrected - stats.corrected ? -EUCLEAN : 0;
+        /* return max bitflips per ecc step; ONENANDs correct 1 bit only */
+        return mtd->ecc_stats.corrected != stats.corrected ? 1 : 0;
 }
 
 /**
@@ -1333,7 +1334,8 @@ static int onenand_read_ops_nolock(struct mtd_info *mtd, loff_t from,
         if (mtd->ecc_stats.failed - stats.failed)
                 return -EBADMSG;
 
-        return mtd->ecc_stats.corrected - stats.corrected ? -EUCLEAN : 0;
+        /* return max bitflips per ecc step; ONENANDs correct 1 bit only */
+        return mtd->ecc_stats.corrected != stats.corrected ? 1 : 0;
 }
 
 /**
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 1482340d3d9f..2829e8be3a62 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -459,6 +459,8 @@ struct nand_buffers {
  * @pagemask:           [INTERN] page number mask = number of (pages / chip) - 1
  * @pagebuf:            [INTERN] holds the pagenumber which is currently in
  *                      data_buf.
+ * @pagebuf_bitflips:   [INTERN] holds the bitflip count for the page which is
+ *                      currently in data_buf.
  * @subpagesize:        [INTERN] holds the subpagesize
  * @onfi_version:       [INTERN] holds the chip ONFI version (BCD encoded),
  *                      non 0 if ONFI supported.
@@ -519,6 +521,7 @@ struct nand_chip {
         uint64_t chipsize;
         int pagemask;
         int pagebuf;
+        unsigned int pagebuf_bitflips;
         int subpagesize;
         uint8_t cellinfo;
         int badblockpos;