mtd: nand: brcmnand: fix mtd corrected bits stat

Currently we attempt to get the amount of flipped bits from a hardware
location which is reset on every subpage. Instead obtain total flipped
bits stat from hardware accumulator. In addition identify the correct
maximum subpage corrected bits.

Signed-off-by: David Regan <dregan@broadcom.com>
Reviewed-by: William Zhang <william.zhang@broadcom.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Author: David Regan

drivers/mtd/nand/raw/brcmnand/brcmnand.c

@@ -360,6 +360,7 @@ enum brcmnand_reg {
 	BRCMNAND_CORR_THRESHOLD_EXT,
 	BRCMNAND_UNCORR_COUNT,
 	BRCMNAND_CORR_COUNT,
+	BRCMNAND_READ_ERROR_COUNT,
 	BRCMNAND_CORR_EXT_ADDR,
 	BRCMNAND_CORR_ADDR,
 	BRCMNAND_UNCORR_EXT_ADDR,
@@ -390,6 +391,7 @@ static const u16 brcmnand_regs_v21[] = {
 	[BRCMNAND_CORR_THRESHOLD_EXT]	=     0,
 	[BRCMNAND_UNCORR_COUNT]		=     0,
 	[BRCMNAND_CORR_COUNT]		=     0,
+	[BRCMNAND_READ_ERROR_COUNT]	=     0,
 	[BRCMNAND_CORR_EXT_ADDR]	=  0x60,
 	[BRCMNAND_CORR_ADDR]		=  0x64,
 	[BRCMNAND_UNCORR_EXT_ADDR]	=  0x68,
@@ -420,6 +422,7 @@ static const u16 brcmnand_regs_v33[] = {
 	[BRCMNAND_CORR_THRESHOLD_EXT]	=     0,
 	[BRCMNAND_UNCORR_COUNT]		=     0,
 	[BRCMNAND_CORR_COUNT]		=     0,
+	[BRCMNAND_READ_ERROR_COUNT]	=  0x80,
 	[BRCMNAND_CORR_EXT_ADDR]	=  0x70,
 	[BRCMNAND_CORR_ADDR]		=  0x74,
 	[BRCMNAND_UNCORR_EXT_ADDR]	=  0x78,
@@ -450,6 +453,7 @@ static const u16 brcmnand_regs_v50[] = {
 	[BRCMNAND_CORR_THRESHOLD_EXT]	=     0,
 	[BRCMNAND_UNCORR_COUNT]		=     0,
 	[BRCMNAND_CORR_COUNT]		=     0,
+	[BRCMNAND_READ_ERROR_COUNT]	=  0x80,
 	[BRCMNAND_CORR_EXT_ADDR]	=  0x70,
 	[BRCMNAND_CORR_ADDR]		=  0x74,
 	[BRCMNAND_UNCORR_EXT_ADDR]	=  0x78,
@@ -480,6 +484,7 @@ static const u16 brcmnand_regs_v60[] = {
 	[BRCMNAND_CORR_THRESHOLD_EXT]	=  0xc4,
 	[BRCMNAND_UNCORR_COUNT]		=  0xfc,
 	[BRCMNAND_CORR_COUNT]		= 0x100,
+	[BRCMNAND_READ_ERROR_COUNT]	= 0x104,
 	[BRCMNAND_CORR_EXT_ADDR]	= 0x10c,
 	[BRCMNAND_CORR_ADDR]		= 0x110,
 	[BRCMNAND_UNCORR_EXT_ADDR]	= 0x114,
@@ -510,6 +515,7 @@ static const u16 brcmnand_regs_v71[] = {
 	[BRCMNAND_CORR_THRESHOLD_EXT]	=  0xe0,
 	[BRCMNAND_UNCORR_COUNT]		=  0xfc,
 	[BRCMNAND_CORR_COUNT]		= 0x100,
+	[BRCMNAND_READ_ERROR_COUNT]	= 0x104,
 	[BRCMNAND_CORR_EXT_ADDR]	= 0x10c,
 	[BRCMNAND_CORR_ADDR]		= 0x110,
 	[BRCMNAND_UNCORR_EXT_ADDR]	= 0x114,
@@ -540,6 +546,7 @@ static const u16 brcmnand_regs_v72[] = {
 	[BRCMNAND_CORR_THRESHOLD_EXT]	=  0xe0,
 	[BRCMNAND_UNCORR_COUNT]		=  0xfc,
 	[BRCMNAND_CORR_COUNT]		= 0x100,
+	[BRCMNAND_READ_ERROR_COUNT]	= 0x104,
 	[BRCMNAND_CORR_EXT_ADDR]	= 0x10c,
 	[BRCMNAND_CORR_ADDR]		= 0x110,
 	[BRCMNAND_UNCORR_EXT_ADDR]	= 0x114,
@@ -960,11 +967,11 @@ static inline u16 brcmnand_cs_offset(struct brcmnand_controller *ctrl, int cs,
 	return offs_cs0 + cs * ctrl->reg_spacing + cs_offs;
 }
 
-static inline u32 brcmnand_count_corrected(struct brcmnand_controller *ctrl)
+static inline u32 brcmnand_corr_total(struct brcmnand_controller *ctrl)
 {
-	if (ctrl->nand_version < 0x0600)
-		return 1;
-	return brcmnand_read_reg(ctrl, BRCMNAND_CORR_COUNT);
+	if (ctrl->nand_version < 0x400)
+		return 0;
+	return brcmnand_read_reg(ctrl, BRCMNAND_READ_ERROR_COUNT);
 }
 
 static void brcmnand_wr_corr_thresh(struct brcmnand_host *host, u8 val)
@@ -2067,15 +2074,20 @@ static int brcmnand_dma_trans(struct brcmnand_host *host, u64 addr, u32 *buf,
  */
 static int brcmnand_read_by_pio(struct mtd_info *mtd, struct nand_chip *chip,
 				u64 addr, unsigned int trans, u32 *buf,
-				u8 *oob, u64 *err_addr)
+				u8 *oob, u64 *err_addr, unsigned int *corr)
 {
 	struct brcmnand_host *host = nand_get_controller_data(chip);
 	struct brcmnand_controller *ctrl = host->ctrl;
 	int i, ret = 0;
+	unsigned int prev_corr;
+
+	if (corr)
+		*corr = 0;
 
 	brcmnand_clear_ecc_addr(ctrl);
 
 	for (i = 0; i < trans; i++, addr += FC_BYTES) {
+		prev_corr = brcmnand_corr_total(ctrl);
 		brcmnand_set_cmd_addr(mtd, addr);
 		/* SPARE_AREA_READ does not use ECC, so just use PAGE_READ */
 		brcmnand_send_cmd(host, CMD_PAGE_READ);
@@ -2100,13 +2112,16 @@ static int brcmnand_read_by_pio(struct mtd_info *mtd, struct nand_chip *chip,
 
 			if (*err_addr)
 				ret = -EBADMSG;
-		}
+			else {
+				*err_addr = brcmnand_get_correcc_addr(ctrl);
 
-		if (!ret) {
-			*err_addr = brcmnand_get_correcc_addr(ctrl);
+				if (*err_addr) {
+					ret = -EUCLEAN;
 
-			if (*err_addr)
-				ret = -EUCLEAN;
+					if (corr && (brcmnand_corr_total(ctrl) - prev_corr) > *corr)
+						*corr = brcmnand_corr_total(ctrl) - prev_corr;
+				}
+			}
 		}
 	}
 
@@ -2174,6 +2189,8 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
 	int err;
 	bool retry = true;
 	bool edu_err = false;
+	unsigned int corrected = 0; /* max corrected bits per subpage */
+	unsigned int prev_tot = brcmnand_corr_total(ctrl);
 
 	dev_dbg(ctrl->dev, "read %llx -> %p\n", (unsigned long long)addr, buf);
 
@@ -2201,9 +2218,11 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
 			memset(oob, 0x99, mtd->oobsize);
 
 		err = brcmnand_read_by_pio(mtd, chip, addr, trans, buf,
-					       oob, &err_addr);
+					   oob, &err_addr, &corrected);
 	}
 
+	mtd->ecc_stats.corrected += brcmnand_corr_total(ctrl) - prev_tot;
+
 	if (mtd_is_eccerr(err)) {
 		/*
 		 * On controller version and 7.0, 7.1 , DMA read after a
@@ -2241,16 +2260,20 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
 	}
 
 	if (mtd_is_bitflip(err)) {
-		unsigned int corrected = brcmnand_count_corrected(ctrl);
-
 		/* in case of EDU correctable error we read again using PIO */
 		if (edu_err)
 			err = brcmnand_read_by_pio(mtd, chip, addr, trans, buf,
-						   oob, &err_addr);
+						   oob, &err_addr, &corrected);
 
 		dev_dbg(ctrl->dev, "corrected error at 0x%llx\n",
 			(unsigned long long)err_addr);
-		mtd->ecc_stats.corrected += corrected;
+		/*
+		 * if flipped bits accumulator is not supported but we detected
+		 * a correction, increase stat by 1 to match previous behavior.
+		 */
+		if (brcmnand_corr_total(ctrl) == prev_tot)
+			mtd->ecc_stats.corrected++;
+
 		/* Always exceed the software-imposed threshold */
 		return max(mtd->bitflip_threshold, corrected);
 	}