[PATCH 1/1 v3] driver:mtd:spi-nor: Add Micron quad I/O support

[Bean Huo 霍斌斌 (beanhuo)]

This patch adds code which enables Quad I/O mode on Micron SPI NOR flashes.

For Micron SPI NOR flash, enabling or disabling quad I/O protocol is controlled 
by EVCR (Enhanced Volatile Configuration Register), Quad I/O protocol bit 7. 
When EVCR bit 7 is reset to 0, the SPI NOR flash will operate in quad I/O mode.

Signed-off-by: bean huo <beanhuo at micron.com>
Acked-by: Marek Vasut <marex at denx.de>
---
 v1-v2:modified to that capture wait_till_ready()
	 return value,if error,directly return its
	 the value.
 v2-v3:directly use the reurning error value of
	 read_reg and write_reg,instead of -EINVAL.

 drivers/mtd/spi-nor/spi-nor.c |   46 +++++++++++++++++++++++++++++++++++++++++
 include/linux/mtd/spi-nor.h   |    6 ++++++
 2 files changed, 52 insertions(+)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c index b5ad6be..486b167 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -878,6 +878,45 @@ static int spansion_quad_enable(struct spi_nor *nor)
 	return 0;
 }
 
+static int micron_quad_enable(struct spi_nor *nor) {
+	int ret, val;
+
+	ret = nor->read_reg(nor, SPINOR_OP_RD_EVCR, &val, 1);
+	if (ret < 0) {
+		dev_err(nor->dev, "error %d reading EVCR\n", ret);
+		return ret;
+	}
+
+	write_enable(nor);
+
+	/* set EVCR ,enable quad I/O */
+	nor->cmd_buf[0] = val & ~EVCR_QUAD_EN_MICRON;
+	ret = nor->write_reg(nor, SPINOR_OP_WD_EVCR, nor->cmd_buf, 1, 0);
+	if (ret < 0) {
+		dev_err(nor->dev,
+			"error while writing EVCR register\n");
+		return ret;
+	}
+
+	ret = wait_till_ready(nor);
+	if (ret)
+		return ret;
+
+	/* read EVCR and check it */
+	ret = nor->read_reg(nor, SPINOR_OP_RD_EVCR, &val, 1);
+	if (ret < 0) {
+		dev_err(nor->dev, "error %d reading EVCR\n", ret);
+		return ret;
+	}
+	if (val & EVCR_QUAD_EN_MICRON) {
+		dev_err(nor->dev, "Micron EVCR Quad bit not clear\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int set_quad_mode(struct spi_nor *nor, u32 jedec_id)  {
 	int status;
@@ -890,6 +929,13 @@ static int set_quad_mode(struct spi_nor *nor, u32 jedec_id)
 			return -EINVAL;
 		}
 		return status;
+	case CFI_MFR_ST:
+		status = micron_quad_enable(nor);
+		if (status) {
+			dev_err(nor->dev, "Micron quad-read not enabled\n");
+			return -EINVAL;
+		}
+		return status;
 	default:
 		status = spansion_quad_enable(nor);
 		if (status) {
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h index 9e6294f..d71b659 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -56,6 +56,10 @@
 /* Used for Spansion flashes only. */
 #define SPINOR_OP_BRWR		0x17	/* Bank register write */
 
+/* Used for Micron flashes only. */
+#define SPINOR_OP_RD_EVCR	0x65	/* Read EVCR register */
+#define SPINOR_OP_WD_EVCR	0x61	/* Write EVCR register */
+
 /* Status Register bits. */
 #define SR_WIP			1	/* Write in progress */
 #define SR_WEL			2	/* Write enable latch */
@@ -67,6 +71,8 @@
 
 #define SR_QUAD_EN_MX		0x40	/* Macronix Quad I/O */
 
+#define EVCR_QUAD_EN_MICRON	0x80	/* Micron Quad I/O */
+
 /* Flag Status Register bits */
 #define FSR_READY		0x80
 
--
1.7.9.5