[RFC PATCH] mtd: nand: toshiba: Add support for ->exec_op()

[yoshitake.kobayashi@xxxxxxxxxxxxx (KOBAYASHI Yoshitake)]

This patch is a patch to support TOSHIBA MEMORY CORPORATION BENAND
memory devices.  This use vendor specific command
(TOSHIBA_NAND_CMD_ECC_STATUS) to know the exact bitflips.  However, I
could not test this patch because I do not have a platform that
supports chip-> exec_op.  Therefore, I post this patch as RFC.

As soon as I get a platform that supports chip-> exec_op, I would like
to test and re-post.

Signed-off-by: KOBAYASHI Yoshitake <yoshitake.kobayashi at toshiba.co.jp>
---
 drivers/mtd/nand/raw/nand_toshiba.c | 76 +++++++++++++++++++++++++++++--------
 1 file changed, 61 insertions(+), 15 deletions(-)

diff --git a/drivers/mtd/nand/raw/nand_toshiba.c b/drivers/mtd/nand/raw/nand_toshiba.c
index 6cec923..12218cd 100644
--- a/drivers/mtd/nand/raw/nand_toshiba.c
+++ b/drivers/mtd/nand/raw/nand_toshiba.c
@@ -17,28 +17,74 @@
 
 #include <linux/mtd/rawnand.h>
 
+/* 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
+
 /* Recommended to rewrite for BENAND */
 #define TOSHIBA_NAND_STATUS_REWRITE_RECOMMENDED	BIT(3)
 
+static int toshiba_nand_benand_read_eccstatus_op(struct nand_chip *chip,
+						 u8 *buf)
+{
+	u8 *ecc_status = buf;
+
+	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(instrs);
+
+	/* Drop the DATA_IN instruction if chip->ecc.steps is set to 0. */
+	if (!chip->ecc.steps)
+		op.ninstrs--;
+
+	return nand_exec_op(chip, &op);
+}
+
 static int toshiba_nand_benand_eccstatus(struct mtd_info *mtd,
 					 struct nand_chip *chip)
 {
-	int ret;
+	int ret, i;
 	unsigned int max_bitflips = 0;
-	u8 status;
-
-	/* Check Status */
-	ret = nand_status_op(chip, &status);
-	if (ret)
-		return ret;
-
-	if (status & NAND_STATUS_FAIL) {
-		/* uncorrected */
-		mtd->ecc_stats.failed++;
-	} else if (status & TOSHIBA_NAND_STATUS_REWRITE_RECOMMENDED) {
-		/* corrected */
-		max_bitflips = mtd->bitflip_threshold;
-		mtd->ecc_stats.corrected += max_bitflips;
+	u8 status, bitflips, ecc_status[8];
+
+	if (chip->exec_op) {
+		/* Check ECC Status */
+		ret = toshiba_nand_benand_read_eccstatus_op(chip, ecc_status);
+		if (ret)
+			return ret;
+
+		for (i = 0; i < chip->ecc.steps; i++) {
+			bitflips = (ecc_status[i] &
+				    TOSHIBA_NAND_ECC_STATUS_MASK);
+			if (bitflips == 0x0F) {
+				mtd->ecc_stats.failed++;
+			} else {
+				mtd->ecc_stats.corrected += bitflips;
+				max_bitflips = max_t(unsigned int,
+						     max_bitflips, bitflips);
+			}
+		}
+	} else {
+		/* Check Status */
+		ret = nand_status_op(chip, &status);
+		if (ret)
+			return ret;
+
+		if (status & NAND_STATUS_FAIL) {
+			/* uncorrected */
+			mtd->ecc_stats.failed++;
+		} else if (status & TOSHIBA_NAND_STATUS_REWRITE_RECOMMENDED) {
+			/* corrected */
+			max_bitflips = mtd->bitflip_threshold;
+			mtd->ecc_stats.corrected += max_bitflips;
+		}
 	}
 
 	return max_bitflips;
-- 
2.7.4