[PATCH v8 10/15] mtd: spi-nor-core: Add support for volatile QE bit

[tkuw584924 at gmail.com]

From: Takahiro Kuwano <Takahiro.Kuwano at 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 at infineon.com>
---
Changes in v8:
  - Define spansion_quad_enable_volatile() under CONFIG_SPI_FLASH_SPANSION
  
Changes in v7:
  - No change
  
Changes in v6:
  - No change

Changes in v5:
  - Fix register address calculation, 'base | offset' -> 'base + offset'

 drivers/mtd/spi/spi-nor-core.c | 55 ++++++++++++++++++++++++++++++++++
 include/linux/mtd/spi-nor.h    |  1 +
 2 files changed, 56 insertions(+)

diff --git a/drivers/mtd/spi/spi-nor-core.c b/drivers/mtd/spi/spi-nor-core.c
index 36c1756576..ac8ebfc4f0 100644
--- a/drivers/mtd/spi/spi-nor-core.c
+++ b/drivers/mtd/spi/spi-nor-core.c
@@ -1561,6 +1561,61 @@ static int macronix_quad_enable(struct spi_nor *nor)
 }
 #endif
 
+#ifdef CONFIG_SPI_FLASH_SPANSION
+/**
+ * spansion_quad_enable_volatile() - enable Quad I/O mode in volatile register.
+ * @nor:	pointer to a 'struct spi_nor'
+ * @addr_base:	base address of register (can be >0 in multi-die parts)
+ * @dummy:	number of dummy cycles for register read
+ *
+ * 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, u32 addr_base,
+					 u8 dummy)
+{
+	u32 addr = addr_base + SPINOR_REG_ADDR_CFR1V;
+
+	u8 cr;
+	int ret;
+
+	/* Check current Quad Enable bit value. */
+	ret = spansion_read_any_reg(nor, addr, dummy, &cr);
+	if (ret < 0) {
+		dev_dbg(nor->dev,
+			"error while reading configuration register\n");
+		return -EINVAL;
+	}
+
+	if (cr & CR_QUAD_EN_SPAN)
+		return 0;
+
+	cr |= CR_QUAD_EN_SPAN;
+
+	write_enable(nor);
+
+	ret = spansion_write_any_reg(nor, addr, cr);
+
+	if (ret < 0) {
+		dev_dbg(nor->dev,
+			"error while writing configuration register\n");
+		return -EINVAL;
+	}
+
+	/* Read back and check it. */
+	ret = spansion_read_any_reg(nor, addr, dummy, &cr);
+	if (ret || !(cr & CR_QUAD_EN_SPAN)) {
+		dev_dbg(nor->dev, "Spansion Quad bit not set\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+#endif
+
 #if defined(CONFIG_SPI_FLASH_SPANSION) || defined(CONFIG_SPI_FLASH_WINBOND)
 /*
  * Write status Register and configuration register with 2 bytes
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index a9b389f2af..de4472da5c 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -123,6 +123,7 @@
 #define SPINOR_OP_CLSR		0x30	/* Clear status register 1 */
 #define SPINOR_OP_RDAR		0x65	/* Read any register */
 #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