[PATCH v2 4/5] mtd: add ECC error accounting for each read request

[Michał Kępień]

Extend struct mtd_req_stats with two new fields holding the number of
corrected bitflips and uncorrectable errors detected during a read
operation.  This is a prerequisite for ultimately passing those counters
to user space, where they can be useful to applications for making
better-informed choices about moving data around.  Maintaining these
counters is also necessary for the value returned by mtdchar's MEMREAD
ioctl to be determined correctly.

Unlike 'max_bitflips' (which is set - in a common code path - to the
return value of a function called while the MTD device's mutex is held),
these counters have to be maintained in each MTD driver which defines
the '_read_oob' callback because the statistics need to be calculated
while the MTD device's mutex is held.

Suggested-by: Boris Brezillon <boris.brezillon at collabora.com>
Signed-off-by: Michał Kępień <kernel at kempniu.pl>
---
 drivers/mtd/devices/docg3.c             |  8 ++++++++
 drivers/mtd/nand/onenand/onenand_base.c | 12 ++++++++++++
 drivers/mtd/nand/raw/nand_base.c        | 10 ++++++++++
 drivers/mtd/nand/spi/core.c             | 10 ++++++++++
 include/linux/mtd/mtd.h                 |  2 ++
 5 files changed, 42 insertions(+)

diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c
index 5b0ae5ddad74..3783ae5c6d23 100644
--- a/drivers/mtd/devices/docg3.c
+++ b/drivers/mtd/devices/docg3.c
@@ -871,6 +871,7 @@ 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;
+	struct mtd_ecc_stats old_stats;
 	int max_bitflips = 0;
 
 	if (buf)
@@ -895,6 +896,7 @@ 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);
+	old_stats = mtd->ecc_stats;
 	while (ret >= 0 && (len > 0 || ooblen > 0)) {
 		calc_block_sector(from - skip, &block0, &block1, &page, &ofs,
 			docg3->reliable);
@@ -966,6 +968,12 @@ static int doc_read_oob(struct mtd_info *mtd, loff_t from,
 	}
 
 out:
+	if (ops->stats) {
+		ops->stats->uncorrectable_errors +=
+			mtd->ecc_stats.failed - old_stats.failed;
+		ops->stats->corrected_bitflips +=
+			mtd->ecc_stats.corrected - old_stats.corrected;
+	}
 	mutex_unlock(&docg3->cascade->lock);
 	return ret;
 err_in_read:
diff --git a/drivers/mtd/nand/onenand/onenand_base.c b/drivers/mtd/nand/onenand/onenand_base.c
index 5810104420a2..f66385faf631 100644
--- a/drivers/mtd/nand/onenand/onenand_base.c
+++ b/drivers/mtd/nand/onenand/onenand_base.c
@@ -1440,6 +1440,7 @@ static int onenand_read_oob(struct mtd_info *mtd, loff_t from,
 			    struct mtd_oob_ops *ops)
 {
 	struct onenand_chip *this = mtd->priv;
+	struct mtd_ecc_stats old_stats;
 	int ret;
 
 	switch (ops->mode) {
@@ -1453,12 +1454,23 @@ static int onenand_read_oob(struct mtd_info *mtd, loff_t from,
 	}
 
 	onenand_get_device(mtd, FL_READING);
+
+	old_stats = mtd->ecc_stats;
+
 	if (ops->datbuf)
 		ret = ONENAND_IS_4KB_PAGE(this) ?
 			onenand_mlc_read_ops_nolock(mtd, from, ops) :
 			onenand_read_ops_nolock(mtd, from, ops);
 	else
 		ret = onenand_read_oob_nolock(mtd, from, ops);
+
+	if (ops->stats) {
+		ops->stats->uncorrectable_errors +=
+			mtd->ecc_stats.failed - old_stats.failed;
+		ops->stats->corrected_bitflips +=
+			mtd->ecc_stats.corrected - old_stats.corrected;
+	}
+
 	onenand_release_device(mtd);
 
 	return ret;
diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index b3a9bc08b4bb..902a88a4caaf 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -3750,6 +3750,7 @@ static int nand_read_oob(struct mtd_info *mtd, loff_t from,
 			 struct mtd_oob_ops *ops)
 {
 	struct nand_chip *chip = mtd_to_nand(mtd);
+	struct mtd_ecc_stats old_stats;
 	int ret;
 
 	ops->retlen = 0;
@@ -3763,11 +3764,20 @@ static int nand_read_oob(struct mtd_info *mtd, loff_t from,
 	if (ret)
 		return ret;
 
+	old_stats = mtd->ecc_stats;
+
 	if (!ops->datbuf)
 		ret = nand_do_read_oob(chip, from, ops);
 	else
 		ret = nand_do_read_ops(chip, from, ops);
 
+	if (ops->stats) {
+		ops->stats->uncorrectable_errors +=
+			mtd->ecc_stats.failed - old_stats.failed;
+		ops->stats->corrected_bitflips +=
+			mtd->ecc_stats.corrected - old_stats.corrected;
+	}
+
 	nand_release_device(chip);
 	return ret;
 }
diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
index 2c8685f1f2fa..5c956c8cae9f 100644
--- a/drivers/mtd/nand/spi/core.c
+++ b/drivers/mtd/nand/spi/core.c
@@ -629,6 +629,7 @@ static int spinand_mtd_read(struct mtd_info *mtd, loff_t from,
 {
 	struct spinand_device *spinand = mtd_to_spinand(mtd);
 	struct nand_device *nand = mtd_to_nanddev(mtd);
+	struct mtd_ecc_stats old_stats;
 	unsigned int max_bitflips = 0;
 	struct nand_io_iter iter;
 	bool disable_ecc = false;
@@ -640,6 +641,8 @@ static int spinand_mtd_read(struct mtd_info *mtd, loff_t from,
 
 	mutex_lock(&spinand->lock);
 
+	old_stats = mtd->ecc_stats;
+
 	nanddev_io_for_each_page(nand, NAND_PAGE_READ, from, ops, &iter) {
 		if (disable_ecc)
 			iter.req.mode = MTD_OPS_RAW;
@@ -662,6 +665,13 @@ static int spinand_mtd_read(struct mtd_info *mtd, loff_t from,
 		ops->oobretlen += iter.req.ooblen;
 	}
 
+	if (ops->stats) {
+		ops->stats->uncorrectable_errors +=
+			mtd->ecc_stats.failed - old_stats.failed;
+		ops->stats->corrected_bitflips +=
+			mtd->ecc_stats.corrected - old_stats.corrected;
+	}
+
 	mutex_unlock(&spinand->lock);
 
 	if (ecc_failed && !ret)
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index f976aabcb378..45a0c20305b0 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -41,6 +41,8 @@ struct mtd_erase_region_info {
 };
 
 struct mtd_req_stats {
+	unsigned int uncorrectable_errors;
+	unsigned int corrected_bitflips;
 	unsigned int max_bitflips;
 };
 
-- 
2.34.1