[PATCH v4] mtd: rawnand: toshiba: Support reading the number of bitflips for BENAND (Built-in ECC NAND)

[Yoshio Furuyama <ytc-mb-yfuruyama7@kioxia.com>]

Add support vendor specific commands for KIOXIA CORPORATION BENAND.
The actual bitflips number can be retrieved by this command.

Signed-off-by: Yoshio Furuyama <ytc-mb-yfuruyama7@kioxia.com>
---
changelog[v4]:Change title and message.
              Define "max ecc steps for BENAND".
changelog[v3]:Tested version.
original patch:"[RFC,v2] mtd: nand: toshiba: Add support for ->exec_op()".

 drivers/mtd/nand/raw/nand_toshiba.c | 58 +++++++++++++++++++++++++++++++++++--
 1 file changed, 56 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/raw/nand_toshiba.c b/drivers/mtd/nand/raw/nand_toshiba.c
index 9c03fbb..f3dcd69 100644
--- a/drivers/mtd/nand/raw/nand_toshiba.c
+++ b/drivers/mtd/nand/raw/nand_toshiba.c
@@ -14,14 +14,68 @@
 /* Recommended to rewrite for BENAND */
 #define TOSHIBA_NAND_STATUS_REWRITE_RECOMMENDED	BIT(3)
 
+/* ECC Status Read Command for BENAND */
+#define TOSHIBA_NAND_CMD_ECC_STATUS_READ	0x7A
+
+/* ECC Status Mask for BENAND */
+#define TOSHIBA_NAND_ECC_STATUS_MASK		0x0F
+
+/* Uncorrectable Error for BENAND */
+#define TOSHIBA_NAND_ECC_STATUS_UNCORR		0x0F
+
+/* Max ECC Steps for BENAND */
+#define TOSHIBA_NAND_MAX_ECC_STEPS		8
+
+static int toshiba_nand_benand_read_eccstatus_op(struct nand_chip *chip,
+						 u8 *buf)
+{
+	u8 *ecc_status = buf;
+
+	if (nand_has_exec_op(chip)) {
+		const struct nand_sdr_timings *sdr =
+			nand_get_sdr_timings(&chip->data_interface);
+		struct nand_op_instr instrs[] = {
+			NAND_OP_CMD(TOSHIBA_NAND_CMD_ECC_STATUS_READ,
+				    PSEC_TO_NSEC(sdr->tADL_min)),
+			NAND_OP_8BIT_DATA_IN(chip->ecc.steps, ecc_status, 0),
+		};
+		struct nand_operation op = NAND_OPERATION(chip->cur_cs, instrs);
+
+		return nand_exec_op(chip, &op);
+	}
+
+	return -ENOTSUPP;
+}
+
 static int toshiba_nand_benand_eccstatus(struct nand_chip *chip)
 {
 	struct mtd_info *mtd = nand_to_mtd(chip);
 	int ret;
 	unsigned int max_bitflips = 0;
-	u8 status;
+	u8 status, ecc_status[TOSHIBA_NAND_MAX_ECC_STEPS];
 
 	/* Check Status */
+	ret = toshiba_nand_benand_read_eccstatus_op(chip, ecc_status);
+	if (!ret) {
+		unsigned int i, bitflips = 0;
+
+		for (i = 0; i < chip->ecc.steps; i++) {
+			bitflips = ecc_status[i] & TOSHIBA_NAND_ECC_STATUS_MASK;
+			if (bitflips == TOSHIBA_NAND_ECC_STATUS_UNCORR) {
+				mtd->ecc_stats.failed++;
+			} else {
+				mtd->ecc_stats.corrected += bitflips;
+				max_bitflips = max(max_bitflips, bitflips);
+			}
+		}
+
+		return max_bitflips;
+	}
+
+	/*
+	 * Fallback to regular status check if
+	 * toshiba_nand_benand_read_eccstatus_op() failed.
+	 */
 	ret = nand_status_op(chip, &status);
 	if (ret)
 		return ret;
@@ -108,7 +162,7 @@ static void toshiba_nand_decode_id(struct nand_chip *chip)
 	 */
 	if (chip->id.len >= 6 && nand_is_slc(chip) &&
 	    (chip->id.data[5] & 0x7) == 0x6 /* 24nm */ &&
-	    !(chip->id.data[4] & 0x80) /* !BENAND */) {
+	    !(chip->id.data[4] & TOSHIBA_NAND_ID4_IS_BENAND) /* !BENAND */) {
 		memorg->oobsize = 32 * memorg->pagesize >> 9;
 		mtd->oobsize = memorg->oobsize;
 	}
-- 
1.9.1


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