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Subject[PATCH -next v3 2/2] mtd: nand: toshiba: Add support for Toshiba Memory BENAND (Built-in ECC NAND)
Date
This patch enables support for Toshiba Memory BENAND. This checks
internal ECC status in read operation when using BENAND and selecting
ECC mode as on-die.

Signed-off-by: KOBAYASHI Yoshitake <yoshitake.kobayashi@toshiba.co.jp>
---
drivers/mtd/nand/nand_toshiba.c | 89 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 89 insertions(+)

diff --git a/drivers/mtd/nand/nand_toshiba.c b/drivers/mtd/nand/nand_toshiba.c
index c2c141b..35c0ddf 100644
--- a/drivers/mtd/nand/nand_toshiba.c
+++ b/drivers/mtd/nand/nand_toshiba.c
@@ -17,6 +17,91 @@

#include <linux/mtd/rawnand.h>

+/* ECC Status Read Command for BENAND */
+#define TOSHIBA_NAND_CMD_ECC_STATUS 0x7A
+
+/* Recommended to rewrite for BENAND */
+#define TOSHIBA_NAND_STATUS_REWRITE_RECOMMENDED BIT(3)
+
+static int toshiba_nand_benand_status_chk(struct mtd_info *mtd,
+ struct nand_chip *chip)
+{
+ unsigned int max_bitflips = 0;
+ u8 status;
+
+ /* Check Read Status */
+ chip->cmdfunc(mtd, NAND_CMD_STATUS, -1, -1);
+ status = chip->read_byte(mtd);
+
+ /*
+ * TOSHIBA_NAND_CMD_ECC_STATUS is vendor specific command.
+ * Currently we have no way to send arbitrary sequences of
+ * CMD+ADDR+DATA cycles and thus cannot support this custom
+ * TOSHIBA_NAND_CMD_ECC_STATUS operation.
+ * For now, we set max_bitflips mtd->bitflip_threshold.
+ */
+ if (status & NAND_STATUS_FAIL) {
+ /* uncorrectable */
+ mtd->ecc_stats.failed++;
+ } else if (status & TOSHIBA_NAND_STATUS_REWRITE_RECOMMENDED) {
+ /* correctable */
+ max_bitflips = mtd->bitflip_threshold;
+ mtd->ecc_stats.corrected += max_bitflips;
+ }
+
+ return max_bitflips;
+}
+
+static int
+toshiba_nand_read_page_benand(struct mtd_info *mtd,
+ struct nand_chip *chip, uint8_t *buf,
+ int oob_required, int page)
+{
+ nand_read_page_raw(mtd, chip, buf, oob_required, page);
+
+ return toshiba_nand_benand_status_chk(mtd, chip);
+}
+
+static int
+toshiba_nand_read_subpage_benand(struct mtd_info *mtd,
+ struct nand_chip *chip, uint32_t data_offs,
+ uint32_t readlen, uint8_t *bufpoi, int page)
+{
+ uint8_t *p;
+
+ if (data_offs != 0)
+ chip->cmdfunc(mtd, NAND_CMD_RNDOUT, data_offs, -1);
+
+ p = bufpoi + data_offs;
+ chip->read_buf(mtd, p, readlen);
+
+ return toshiba_nand_benand_status_chk(mtd, chip);
+}
+
+static void toshiba_nand_benand_init(struct nand_chip *chip)
+{
+ struct mtd_info *mtd = nand_to_mtd(chip);
+
+ /*
+ * On BENAND, the entire OOB region can be used by the MTD user.
+ * The calculated ECC bytes are stored into other isolated
+ * area which is not accessible to users.
+ * This is why chip->ecc.bytes = 0.
+ */
+ chip->ecc.bytes = 0;
+ chip->ecc.size = 512;
+ chip->ecc.strength = 8;
+ chip->ecc.read_page = toshiba_nand_read_page_benand;
+ chip->ecc.read_subpage = toshiba_nand_read_subpage_benand;
+ chip->ecc.write_page = nand_write_page_raw;
+ chip->ecc.read_page_raw = nand_read_page_raw;
+ chip->ecc.write_page_raw = nand_write_page_raw;
+
+ chip->options |= NAND_SUBPAGE_READ;
+
+ mtd_set_ooblayout(mtd, &nand_ooblayout_lp_ops);
+}
+
static void toshiba_nand_decode_id(struct nand_chip *chip)
{
struct mtd_info *mtd = nand_to_mtd(chip);
@@ -70,6 +155,10 @@ static int toshiba_nand_init(struct nand_chip *chip)
if (nand_is_slc(chip))
chip->bbt_options |= NAND_BBT_SCAN2NDPAGE;

+ if (nand_is_slc(chip) && (chip->id.data[4] & 0x80) /* BENAND */ &&
+ (chip->ecc.mode == NAND_ECC_ON_DIE))
+ toshiba_nand_benand_init(chip);
+
return 0;
}

--
2.7.4

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