mtd: nand: use nand_check_erased_ecc_chunk in default ECC read functions

The default NAND read functions are relying on the underlying controller
driver to correct bitflips, but some of those controllers cannot properly
fix bitflips in erased pages.
Check for bitflips in erased pages in default core functions if the driver
delegated the this check by setting the NAND_ECC_GENERIC_ERASED_CHECK flag.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Tested-by: Franklin S Cooper Jr. <fcooper@ti.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

1 files changed, 46 insertions, 7 deletions

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 50514f2501bb..f2c8ff398d6c 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -1426,6 +1426,16 @@ static int nand_read_subpage(struct mtd_info *mtd, struct nand_chip *chip,
 
 		stat = chip->ecc.correct(mtd, p,
 			&chip->buffers->ecccode[i], &chip->buffers->ecccalc[i]);
+		if (stat == -EBADMSG &&
+		    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
+			/* check for empty pages with bitflips */
+			stat = nand_check_erased_ecc_chunk(p, chip->ecc.size,
+						&chip->buffers->ecccode[i],
+						chip->ecc.bytes,
+						NULL, 0,
+						chip->ecc.strength);
+		}
+
 		if (stat < 0) {
 			mtd->ecc_stats.failed++;
 		} else {
@@ -1475,6 +1485,15 @@ static int nand_read_page_hwecc(struct mtd_info *mtd, struct nand_chip *chip,
 		int stat;
 
 		stat = chip->ecc.correct(mtd, p, &ecc_code[i], &ecc_calc[i]);
+		if (stat == -EBADMSG &&
+		    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
+			/* check for empty pages with bitflips */
+			stat = nand_check_erased_ecc_chunk(p, eccsize,
+						&ecc_code[i], eccbytes,
+						NULL, 0,
+						chip->ecc.strength);
+		}
+
 		if (stat < 0) {
 			mtd->ecc_stats.failed++;
 		} else {
@@ -1527,6 +1546,15 @@ static int nand_read_page_hwecc_oob_first(struct mtd_info *mtd,
 		chip->ecc.calculate(mtd, p, &ecc_calc[i]);
 
 		stat = chip->ecc.correct(mtd, p, &ecc_code[i], NULL);
+		if (stat == -EBADMSG &&
+		    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
+			/* check for empty pages with bitflips */
+			stat = nand_check_erased_ecc_chunk(p, eccsize,
+						&ecc_code[i], eccbytes,
+						NULL, 0,
+						chip->ecc.strength);
+		}
+
 		if (stat < 0) {
 			mtd->ecc_stats.failed++;
 		} else {
@@ -1554,6 +1582,7 @@ static int nand_read_page_syndrome(struct mtd_info *mtd, struct nand_chip *chip,
 	int i, eccsize = chip->ecc.size;
 	int eccbytes = chip->ecc.bytes;
 	int eccsteps = chip->ecc.steps;
+	int eccpadbytes = eccbytes + chip->ecc.prepad + chip->ecc.postpad;
 	uint8_t *p = buf;
 	uint8_t *oob = chip->oob_poi;
 	unsigned int max_bitflips = 0;
@@ -1573,19 +1602,29 @@ static int nand_read_page_syndrome(struct mtd_info *mtd, struct nand_chip *chip,
 		chip->read_buf(mtd, oob, eccbytes);
 		stat = chip->ecc.correct(mtd, p, oob, NULL);
 
-		if (stat < 0) {
-			mtd->ecc_stats.failed++;
-		} else {
-			mtd->ecc_stats.corrected += stat;
-			max_bitflips = max_t(unsigned int, max_bitflips, stat);
-		}
-
 		oob += eccbytes;
 
 		if (chip->ecc.postpad) {
 			chip->read_buf(mtd, oob, chip->ecc.postpad);
 			oob += chip->ecc.postpad;
 		}
+
+		if (stat == -EBADMSG &&
+		    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
+			/* check for empty pages with bitflips */
+			stat = nand_check_erased_ecc_chunk(p, chip->ecc.size,
+							   oob - eccpadbytes,
+							   eccpadbytes,
+							   NULL, 0,
+							   chip->ecc.strength);
+		}
+
+		if (stat < 0) {
+			mtd->ecc_stats.failed++;
+		} else {
+			mtd->ecc_stats.corrected += stat;
+			max_bitflips = max_t(unsigned int, max_bitflips, stat);
+		}
 	}
 
 	/* Calculate remaining oob bytes */