[PATCH linux-next v6 1/8] mtd: spi-nor: read JEDEC ID with multiple I/O protocols

When their quad or dual I/O mode is enabled, Micron and Macronix spi-nor
memories don't reply to the regular Read ID (0x9f) command. Instead they
reply to a new dedicated command Read ID Multiple I/O (0xaf).

If the Read ID (0x9f) command fails (the read ID is all 1's or all 0's),
then the Read ID Multiple I/O (0xaf) is used, first with SPI 4-4-4 protocol
(supported by both Micron and Macronix memories), lately with SPI-2-2-2
protocol (supported only by Micron memories).

Signed-off-by: Cyrille Pitchen <redacted>
---
 drivers/mtd/spi-nor/spi-nor.c | 28 +++++++++++++++++++++++++++-
 include/linux/mtd/spi-nor.h   | 23 +++++++++++++++++++++--
 2 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index f59aedfe1462..80a0db078aaa 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c

@@ -703,8 +703,9 @@ static const struct flash_info spi_nor_ids[] = {

 static const struct flash_info *spi_nor_read_id(struct spi_nor *nor)
 {
-	int			tmp;
+	int			i, tmp;
 	u8			id[SPI_NOR_MAX_ID_LEN];
+	enum spi_protocol	proto[2] = {SPI_PROTO_4_4_4, SPI_PROTO_2_2_2};
 	const struct flash_info	*info;

 	tmp = nor->read_reg(nor, SPINOR_OP_RDID, id, SPI_NOR_MAX_ID_LEN);

@@ -713,6 +714,25 @@ static const struct flash_info *spi_nor_read_id(struct

spi_nor *nor) return ERR_PTR(tmp);
 	}

+	/* Special case for Micron/Macronix qspi nor. */
+	for (i = 0; i < ARRAY_SIZE(proto); ++i) {
+		if (!((id[0] == 0xff && id[1] == 0xff && id[2] == 0xff) ||
+		      (id[0] == 0x00 && id[1] == 0x00 && id[2] == 0x00)))
+			break;
+
+		nor->erase_proto = proto[i];
+		nor->read_proto = proto[i];
+		nor->write_proto = proto[i];
+		nor->reg_proto = proto[i];
+		tmp = nor->read_reg(nor, SPINOR_OP_MIO_RDID,
+				    id, SPI_NOR_MAX_ID_LEN);
+		if (tmp < 0) {
+			dev_dbg(nor->dev,
+				" error %d reading JEDEC ID (MULTI IO)\n", tmp);

+			return ERR_PTR(tmp);
+		}
+	}
+
 	for (tmp = 0; tmp < ARRAY_SIZE(spi_nor_ids) - 1; tmp++) {
 		info = &spi_nor_ids[tmp];
 		if (info->id_len) {