[PATCH v3 4/6] mtd: nand: gpmi: correct bitflip for erased NAND page

[Han Xu]

i.MX6QP and i.MX7D BCH module integrated a new feature to detect the
bitflip number for erased NAND page. So for these two platform, set the
erase threshold to ecc_strength and if bitflip detected, GPMI driver
will correct the data to all 0xFF.

Signed-off-by: Han Xu <han.xu@xxxxxxx>
---
 drivers/mtd/nand/gpmi-nand/bch-regs.h  | 10 +++++++++
 drivers/mtd/nand/gpmi-nand/gpmi-lib.c  |  5 +++++
 drivers/mtd/nand/gpmi-nand/gpmi-nand.c | 37 +++++++++++++++++++++++++++++++---
 3 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/nand/gpmi-nand/bch-regs.h b/drivers/mtd/nand/gpmi-nand/bch-regs.h
index 228142c..2c44b88 100644
--- a/drivers/mtd/nand/gpmi-nand/bch-regs.h
+++ b/drivers/mtd/nand/gpmi-nand/bch-regs.h
@@ -30,7 +30,13 @@
 #define BM_BCH_CTRL_COMPLETE_IRQ		(1 << 0)
 
 #define HW_BCH_STATUS0				0x00000010
+
 #define HW_BCH_MODE				0x00000020
+#define BP_BCH_MODE_ERASE_THRESHOLD		0
+#define BM_BCH_MODE_ERASE_THRESHOLD	(0xff << BP_BCH_MODE_ERASE_THRESHOLD)
+#define BF_BCH_MODE_ERASE_THRESHOLD(v)		\
+	(((v) << BP_BCH_MODE_ERASE_THRESHOLD) & BM_BCH_MODE_ERASE_THRESHOLD)
+
 #define HW_BCH_ENCODEPTR			0x00000030
 #define HW_BCH_DATAPTR				0x00000040
 #define HW_BCH_METAPTR				0x00000050
@@ -125,4 +131,8 @@
 	)
 
 #define HW_BCH_VERSION				0x00000160
+#define HW_BCH_DEBUG1				0x00000170
+#define BP_BCH_DEBUG1_ERASED_ZERO_COUNT	0
+#define BM_BCH_DEBUG1_ERASED_ZERO_COUNT		\
+		(0x1ff << BP_BCH_DEBUG1_ERASED_ZERO_COUNT)
 #endif
diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c
index 358ff5d..0b5666a 100644
--- a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c
+++ b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c
@@ -298,6 +298,11 @@ int bch_set_geometry(struct gpmi_nand_data *this)
 			| BF_BCH_FLASH0LAYOUT1_DATAN_SIZE(block_size, this),
 			r->bch_regs + HW_BCH_FLASH0LAYOUT1);
 
+	/* Set erase threshold to ecc_strength for mx6qp and mx7 */
+	if (GPMI_IS_MX6QP(this) || GPMI_IS_MX7(this))
+		writel(BF_BCH_MODE_ERASE_THRESHOLD(ecc_strength),
+			r->bch_regs + HW_BCH_MODE);
+
 	/* Set *all* chip selects to use layout 0. */
 	writel(0, r->bch_regs + HW_BCH_LAYOUTSELECT);
 
diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
index aedaff3..db8e546 100644
--- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
+++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
@@ -1043,11 +1043,12 @@ static int gpmi_ecc_read_page(struct mtd_info *mtd, struct nand_chip *chip,
 {
 	struct gpmi_nand_data *this = nand_get_controller_data(chip);
 	struct bch_geometry *nfc_geo = &this->bch_geometry;
+	void __iomem *bch_regs = this->resources.bch_regs;
 	void          *payload_virt;
 	dma_addr_t    payload_phys;
 	void          *auxiliary_virt;
 	dma_addr_t    auxiliary_phys;
-	unsigned int  i;
+	unsigned int  i, j;
 	unsigned char *status;
 	unsigned int  max_bitflips = 0;
 	int           ret;
@@ -1087,9 +1088,14 @@ static int gpmi_ecc_read_page(struct mtd_info *mtd, struct nand_chip *chip,
 			   nfc_geo->payload_size,
 			   payload_virt, payload_phys);
 
-	for (i = 0; i < nfc_geo->ecc_chunk_count; i++, status++) {
-		if ((*status == STATUS_GOOD) || (*status == STATUS_ERASED))
+	for (i = 0, j = 0; i < nfc_geo->ecc_chunk_count; i++, status++) {
+		if (*status == STATUS_GOOD)
+			continue;
+		if (*status == STATUS_ERASED) {
+			/* count the number of erased chunks */
+			j++;
 			continue;
+		}
 
 		if (*status == STATUS_UNCORRECTABLE) {
 			int eccbits = nfc_geo->ecc_strength * nfc_geo->gf_len;
@@ -1098,6 +1104,12 @@ static int gpmi_ecc_read_page(struct mtd_info *mtd, struct nand_chip *chip,
 			int eccbytes;
 			int flips;
 
+			/* shortcut for i.MX7 and i.MX6QP */
+			if (GPMI_IS_MX6QP(this) || GPMI_IS_MX7(this)) {
+				mtd->ecc_stats.failed++;
+				continue;
+			}
+
 			/* Read ECC bytes into our internal raw_buffer */
 			offset = nfc_geo->metadata_size * 8;
 			offset += ((8 * nfc_geo->ecc_chunk_size) + eccbits) * (i + 1);
@@ -1167,6 +1179,25 @@ static int gpmi_ecc_read_page(struct mtd_info *mtd, struct nand_chip *chip,
 		max_bitflips = max_t(unsigned int, max_bitflips, *status);
 	}
 
+	/*
+	 * i.MX6QP and i.MX7 have dedicate register to check bitflips in the
+	 * page, while it cannot tell in which chunk bitflips locate, memset
+	 * all the data if bitflips exist and all chunks are erased.
+	 */
+	if (j == nfc_geo->ecc_chunk_count &&
+		(GPMI_IS_MX6QP(this) || GPMI_IS_MX7(this))) {
+		int flips;
+
+		flips = readl(bch_regs + HW_BCH_DEBUG1);
+		if (flips) {
+			max_bitflips = max_t(unsigned int, max_bitflips,
+					flips);
+			memset(buf, ~0, nfc_geo->payload_size);
+			memset(chip->oob_poi, ~0, mtd->oobsize);
+			mtd->ecc_stats.corrected += flips;
+		}
+	}
+
 	if (oob_required) {
 		/*
 		 * It's time to deliver the OOB bytes. See gpmi_ecc_read_oob()
-- 
1.9.1