[PATCH v3 4/6] mtd: spi-nor: spansion: 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. The function supports multi-die package parts that require to
set the Quad Enable bit in each die.

Signed-off-by: Takahiro Kuwano <Takahiro.Kuwano at infineon.com>
---
Changes in v3:
  - Add multi-die package parts support

 drivers/mtd/spi-nor/spansion.c | 58 ++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/drivers/mtd/spi-nor/spansion.c b/drivers/mtd/spi-nor/spansion.c
index 1bce95cb7896..b5b5df4836c6 100644
--- a/drivers/mtd/spi-nor/spansion.c
+++ b/drivers/mtd/spi-nor/spansion.c
@@ -10,6 +10,8 @@
 
 #define SPINOR_OP_RD_ANY_REG			0x65	/* Read any register */
 #define SPINOR_OP_WR_ANY_REG			0x71	/* Write any register */
+#define SPINOR_REG_CYPRESS_CFR1V		0x00800002
+#define SPINOR_REG_CYPRESS_CFR1V_QUAD_EN	BIT(1)	/* Quad Enable */
 #define SPINOR_REG_CYPRESS_CFR2V		0x00800003
 #define SPINOR_REG_CYPRESS_CFR2V_MEMLAT_11_24	0xb
 #define SPINOR_REG_CYPRESS_CFR3V		0x00800004
@@ -121,6 +123,62 @@ static int spansion_write_any_reg(struct spi_nor *nor, u32 reg_addr, u8 reg_val)
 	return ret;
 }
 
+/**
+ * spansion_quad_enable_volatile() - enable Quad I/O mode in volatile register.
+ * @nor:	pointer to a 'struct spi_nor'
+ * @reg_dummy:	number of dummy cycles for register read
+ * @die_size:	size of each die to determine the number of dies
+ *
+ * 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. If users set the Quad Enable
+ * bit in the CFR1 non-volatile in advance (typically by a Flash programmer
+ * before mounting Flash on PCB), the Quad Enable bit in the CFR1 volatile is
+ * also set during Flash power-up. This function supports multi-die package
+ * parts that require to set the Quad Enable bit in each die.
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+static int spansion_quad_enable_volatile(struct spi_nor *nor, u8 reg_dummy,
+					 u32 die_size)
+{
+	int ret;
+	u32 base, reg_addr;
+	u8 cfr1v, cfr1v_written;
+
+	for (base = 0; base < nor->params->size; base += die_size) {
+		reg_addr = base + SPINOR_REG_CYPRESS_CFR1V;
+
+		ret = spansion_read_any_reg(nor, reg_addr, reg_dummy, &cfr1v);
+		if (ret)
+			return ret;
+
+		if (cfr1v & SPINOR_REG_CYPRESS_CFR1V_QUAD_EN)
+			continue;
+
+		/* Update the Quad Enable bit. */
+		cfr1v |= SPINOR_REG_CYPRESS_CFR1V_QUAD_EN;
+
+		ret = spansion_write_any_reg(nor, reg_addr, cfr1v);
+		if (ret)
+			return ret;
+
+		cfr1v_written = cfr1v;
+
+		/* Read back and check it. */
+		ret = spansion_read_any_reg(nor, reg_addr, reg_dummy, &cfr1v);
+		if (ret)
+			return ret;
+
+		if (cfr1v != cfr1v_written) {
+			dev_err(nor->dev, "CFR1: Read back test failed\n");
+			return -EIO;
+		}
+	}
+
+	return 0;
+}
+
 /**
  * spi_nor_cypress_octal_dtr_enable() - Enable octal DTR on Cypress flashes.
  * @nor:		pointer to a 'struct spi_nor'
-- 
2.25.1