[PATCH linux-next v2 05/14] mtd: spi-nor: fix support of Winbond memories

[Cyrille Pitchen <cyrille.pitchen@atmel.com>]

This patch fixes the support of Winbond memories. Indeed, before
performing any Quad SPI command, the Quad Enable (QE) non-volatile bit
MUST be set in the Status Register 2.

According to the w25q16fw datasheet from Winbond:
"When QE=1, the /WP pin becomes IO2 and /HOLD pin becomes IO3."

Quad SPI instructions requires the bidirectional IO2 and IO3 pins.

Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
---
 drivers/mtd/spi-nor/spi-nor.c | 100 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/mtd/spi-nor.h   |   6 +++
 2 files changed, 106 insertions(+)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index 042ac49d6188..f8a4887ca6eb 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -1174,6 +1174,40 @@ static int spansion_quad_enable(struct spi_nor *nor)
 	return 0;
 }
 
+static int winbond_quad_enable(struct spi_nor *nor)
+{
+	int ret;
+	u8 sr2;
+
+	ret = nor->read_reg(nor, SPINOR_OP_RDSR2_WINB, &sr2, 1);
+	if (ret < 0)
+		return ret;
+
+	if (likely(sr2 & SR2_QUAD_EN_WINB))
+		return 0;
+	dev_warn(nor->dev, "Winbond Quad mode disabled, enable it\n");
+
+	write_enable(nor);
+
+	sr2 |= SR2_QUAD_EN_WINB;
+	ret = nor->write_reg(nor, SPINOR_OP_WRSR2_WINB, &sr2, 1);
+	if (ret < 0)
+		return ret;
+
+	if (spi_nor_wait_till_ready(nor))
+		return -EIO;
+
+	ret = nor->read_reg(nor, SPINOR_OP_RDSR2_WINB, &sr2, 1);
+	if (ret < 0)
+		return ret;
+	if (!(sr2 & SR2_QUAD_EN_WINB)) {
+		dev_err(nor->dev, "Winbond Quad bit not set\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int macronix_set_quad_mode(struct spi_nor *nor)
 {
 	int status;
@@ -1234,6 +1268,63 @@ static int macronix_set_single_mode(struct spi_nor *nor)
 	return 0;
 }
 
+static int winbond_set_quad_mode(struct spi_nor *nor)
+{
+	int status;
+
+	/* Check whether the QPI mode is enabled. */
+	if (nor->read_proto == SNOR_PROTO_4_4_4) {
+		/* Since the QPI mode is enabled, the Quad Enabled (QE)
+		 * non-volatile bit is already set.
+		 * If the Fast Read 1-4-4 (0xeb) were used, we should
+		 * take care about the value M7-M0 written during
+		 * dummy/mode cycles to avoid entering the continuous
+		 * read mode by  mistake.
+		 * Also the Fast Read 1-1-4 (0x6b) op code is not
+		 * supported in QPI mode.
+		 * Hence the Fast Read 1-1-1 (0x0b) op code is chosen.
+		 */
+		nor->read_opcode = SPINOR_OP_READ_FAST;
+		return 0;
+	}
+
+	/*
+	 * The QPI mode is disabled but we still need to set the QE bit:
+	 * when QE=1, the /WP pin becomes IO2 and /HOLD pin becomes IO3.
+	 * If the Fast Read 1-4-4 (0xeb) were used, we should take care
+	 * about the value M7-M0 written during dummy/mode cycles to
+	 * avoid entering the continuous read mode by mistake.
+	 * Hence the Fast Read 1-1-4 (0x6b) op code is preferred.
+	 */
+	status = winbond_quad_enable(nor);
+	if (status) {
+		dev_err(nor->dev, "Winbond quad-read nor enabled\n");
+		return status;
+	}
+	nor->read_proto = SNOR_PROTO_1_1_4;
+	nor->read_opcode = SPINOR_OP_READ_1_1_4;
+	return 0;
+}
+
+/*
+ * For both Winbond Dual and Single modes, we don't care about the value of
+ * the Quad Enabled (QE) bit since the memory still replies to Dual or Single
+ * SPI commands.
+ */
+
+static int winbond_set_dual_mode(struct spi_nor *nor)
+{
+	nor->read_proto = SNOR_PROTO_1_1_2;
+	nor->read_opcode = SPINOR_OP_READ_1_1_2;
+	return 0;
+}
+
+static int winbond_set_single_mode(struct spi_nor *nor)
+{
+	nor->read_proto = SNOR_PROTO_1_1_1;
+	return 0;
+}
+
 static int set_quad_mode(struct spi_nor *nor, const struct flash_info *info)
 {
 	int status;
@@ -1242,6 +1333,9 @@ static int set_quad_mode(struct spi_nor *nor, const struct flash_info *info)
 	case SNOR_MFR_MACRONIX:
 		return macronix_set_quad_mode(nor);
 
+	case SNOR_MFR_WINBOND:
+		return winbond_set_quad_mode(nor);
+
 	case SNOR_MFR_MICRON:
 		/* Check whether Micron Quad mode is enabled. */
 		if (nor->read_proto != SNOR_PROTO_4_4_4)
@@ -1271,6 +1365,9 @@ static int set_dual_mode(struct spi_nor *nor, const struct flash_info *info)
 	case SNOR_MFR_MACRONIX:
 		return macronix_set_dual_mode(nor);
 
+	case SNOR_MFR_WINBOND:
+		return winbond_set_dual_mode(nor);
+
 	case SNOR_MFR_MICRON:
 		/* Check whether Micron Dual mode is enabled. */
 		if (nor->read_proto != SNOR_PROTO_2_2_2)
@@ -1292,6 +1389,9 @@ static int set_single_mode(struct spi_nor *nor, const struct flash_info *info)
 	case SNOR_MFR_MACRONIX:
 		return macronix_set_single_mode(nor);
 
+	case SNOR_MFR_WINBOND:
+		return winbond_set_single_mode(nor);
+
 	default:
 		nor->read_proto = SNOR_PROTO_1_1_1;
 		break;
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index 89e3228ec1d0..46343f5a8162 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -75,6 +75,12 @@
 #define SPINOR_OP_EN4B		0xb7	/* Enter 4-byte mode */
 #define SPINOR_OP_EX4B		0xe9	/* Exit 4-byte mode */
 
+/* Used for Winbond flashes only. */
+#define SPINOR_OP_RDSR2_WINB	0x35	/* Read status register 2 */
+#define SPINOR_OP_WRSR2_WINB	0x31	/* Write status register 2 */
+
+#define SR2_QUAD_EN_WINB	BIT(1)	/* Quad Enable bit */
+
 /* Used for Spansion flashes only. */
 #define SPINOR_OP_BRWR		0x17	/* Bank register write */
 
-- 
1.8.2.2