[PATCH v3 3/7] mtd: spi-nor: Add support for volatile QE bit

[tkuw584924 at gmail.com <tkuw584924@gmail.com>]

From: Takahiro Kuwano <Takahiro.Kuwano@infineon.com>

Some of Spansion/Cypress chips support volatile version of configuration
registers and it is recommended to update volatile registers in the field
application due to a risk of the non-volatile registers corruption by
power interrupt. This patch adds a function to set Quad Enable bit in
CFR1 volatile. 

Signed-off-by: Takahiro Kuwano <Takahiro.Kuwano@infineon.com>
---
 drivers/mtd/spi/spi-nor-core.c | 54 +++++++++++++++++++++++++++++
 drivers/mtd/spi/spi-nor-tiny.c | 63 ++++++++++++++++++++++++++++++++++
 include/linux/mtd/spi-nor.h    |  2 ++
 3 files changed, 119 insertions(+)

diff --git a/drivers/mtd/spi/spi-nor-core.c b/drivers/mtd/spi/spi-nor-core.c
index 34c15f1561..9a271841ab 100644
--- a/drivers/mtd/spi/spi-nor-core.c
+++ b/drivers/mtd/spi/spi-nor-core.c
@@ -1551,6 +1551,60 @@ static int spansion_read_cr_quad_enable(struct spi_nor *nor)
 	return 0;
 }
 
+/**
+ * spansion_quad_enable_volatile() - enable Quad I/O mode in volatile register.
+ * @nor:	pointer to a 'struct spi_nor'
+ *
+ * It is recommended to update volatile registers in the field application due
+ * to a risk of the non-volatile registers corruption by power interrupt. This
+ * function sets Quad Enable bit in CFR1 volatile.
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+static int spansion_quad_enable_volatile(struct spi_nor *nor)
+{
+	struct spi_mem_op op =
+			SPI_MEM_OP(SPI_MEM_OP_CMD(SPINOR_OP_WRAR, 1),
+				   SPI_MEM_OP_ADDR(nor->addr_width,
+						   SPINOR_REG_ADDR_CFR1V, 1),
+				   SPI_MEM_OP_NO_DUMMY,
+				   SPI_MEM_OP_DATA_OUT(1, NULL, 1));
+	u8 cr;
+	int ret;
+
+	/* Check current Quad Enable bit value. */
+	ret = read_cr(nor);
+	if (ret < 0) {
+		dev_dbg(nor->dev,
+			"error while reading configuration register\n");
+		return -EINVAL;
+	}
+
+	if (ret & CR_QUAD_EN_SPAN)
+		return 0;
+
+	cr = ret | CR_QUAD_EN_SPAN;
+
+	write_enable(nor);
+
+	ret = spi_nor_read_write_reg(nor, &op, &cr);
+
+	if (ret < 0) {
+		dev_dbg(nor->dev,
+			"error while writing configuration register\n");
+		return -EINVAL;
+	}
+
+	/* Read back and check it. */
+	ret = read_cr(nor);
+	if (!(ret > 0 && (ret & CR_QUAD_EN_SPAN))) {
+		dev_dbg(nor->dev, "Spansion Quad bit not set\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 #if CONFIG_IS_ENABLED(SPI_FLASH_SFDP_SUPPORT)
 /**
  * spansion_no_read_cr_quad_enable() - set QE bit in Configuration Register.
diff --git a/drivers/mtd/spi/spi-nor-tiny.c b/drivers/mtd/spi/spi-nor-tiny.c
index 5cc2b7d996..1326f028a6 100644
--- a/drivers/mtd/spi/spi-nor-tiny.c
+++ b/drivers/mtd/spi/spi-nor-tiny.c
@@ -555,6 +555,69 @@ static int spansion_read_cr_quad_enable(struct spi_nor *nor)
 }
 #endif /* CONFIG_SPI_FLASH_SPANSION */
 
+#ifdef CONFIG_SPI_FLASH_SPANSION
+/**
+ * spansion_quad_enable_volatile() - enable Quad I/O mode in volatile register.
+ * @nor:	pointer to a 'struct spi_nor'
+ *
+ * It is recommended to update volatile registers in the field application due
+ * to a risk of the non-volatile registers corruption by power interrupt. This
+ * function sets Quad Enable bit in CFR1 volatile.
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+static int spansion_quad_enable_volatile(struct spi_nor *nor)
+{
+	struct spi_mem_op op =
+			SPI_MEM_OP(SPI_MEM_OP_CMD(SPINOR_OP_WRAR, 1),
+				   SPI_MEM_OP_ADDR(4, SPINOR_REG_ADDR_CFR1V, 1),
+				   SPI_MEM_OP_NO_DUMMY,
+				   SPI_MEM_OP_DATA_OUT(1, NULL, 1));
+	u8 cr;
+	int ret;
+
+	/* Check current Quad Enable bit value. */
+	ret = read_cr(nor);
+	if (ret < 0) {
+		dev_dbg(nor->dev,
+			"error while reading configuration register\n");
+		return -EINVAL;
+	}
+
+	if (ret & CR_QUAD_EN_SPAN)
+		return 0;
+
+	cr = ret | CR_QUAD_EN_SPAN;
+
+	/* Use 4-byte address for WRAR */
+	ret = spi_nor_write_reg(nor, SPINOR_OP_EN4B, NULL, 0);
+	if (ret < 0) {
+		dev_dbg(nor->dev,
+			"error while enabling 4-byte address\n");
+		return ret;
+	}
+
+	write_enable(nor);
+
+	ret = spi_nor_read_write_reg(nor, &op, &cr);
+
+	if (ret < 0) {
+		dev_dbg(nor->dev,
+			"error while writing configuration register\n");
+		return -EINVAL;
+	}
+
+	/* Read back and check it. */
+	ret = read_cr(nor);
+	if (!(ret > 0 && (ret & CR_QUAD_EN_SPAN))) {
+		dev_dbg(nor->dev, "Spansion Quad bit not set\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+#endif
+
 static void
 spi_nor_set_read_settings(struct spi_nor_read_command *read,
 			  u8 num_mode_clocks,
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index 89e7a4fdcd..9fb4c8521d 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -121,6 +121,8 @@
 #define SPINOR_OP_BRWR		0x17	/* Bank register write */
 #define SPINOR_OP_BRRD		0x16	/* Bank register read */
 #define SPINOR_OP_CLSR		0x30	/* Clear status register 1 */
+#define SPINOR_OP_WRAR		0x71	/* Write any register */
+#define SPINOR_REG_ADDR_CFR1V	0x00800002
 
 /* Used for Micron flashes only. */
 #define SPINOR_OP_RD_EVCR      0x65    /* Read EVCR register */
-- 
2.25.1