[PATCH v2 3/3] mtd: spi-nor: Add clear flag status register support

[Jagan Teki <jteki@openedev.com>]

The clear flag status register operation is required by Micron
SPI-NOR chips, which support FSR. And if error bits of FSR
have been set like protection, voltage, erase, and program,
it must be cleared by executing clear FSR operation.

Signed-off-by: Jagan Teki <jteki@openedev.com>
Cc: Hou Zhiqiang <B48286@freescale.com>
Cc: Mingkai.Hu <Mingkai.Hu@freescale.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Brian Norris <computersforpeace@gmail.com>
---
Changes for v2:
	- Write cfsr instead of reading it.
	- Return -EINVAL instead of -1

 drivers/mtd/spi-nor/spi-nor.c | 23 +++++++++++++++++++----
 include/linux/mtd/spi-nor.h   |  9 +++++++++
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index f954d03..0a77061 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -163,6 +163,18 @@ static inline int write_disable(struct spi_nor *nor)
 	return nor->write_reg(nor, SPINOR_OP_WRDI, NULL, 0);
 }
 
+/*
+ * The clear flag status register operation is required by Micron
+ * SPI-NOR chips, which support FSR. And if error bits of FSR
+ * have been set like protection, voltage, erase, and program,
+ * it must be cleared by executing clear FSR operation.
+ * Returns negative if error occurred.
+ */
+static inline int write_cfsr(struct spi_nor *nor)
+{
+	return nor->write_reg(nor, SPINOR_OP_WRCFSR, NULL, 0);
+}
+
 static inline struct spi_nor *mtd_to_spi_nor(struct mtd_info *mtd)
 {
 	return mtd->priv;
@@ -209,10 +221,13 @@ static inline int spi_nor_sr_ready(struct spi_nor *nor)
 static inline int spi_nor_fsr_ready(struct spi_nor *nor)
 {
 	int fsr = read_fsr(nor);
-	if (fsr < 0)
-		return fsr;
-	else
-		return fsr & FSR_READY;
+	if (fsr & FSR_ERR_MASK) {
+		pr_err("flag status(0x%x) error occured\n", fsr);
+		write_cfsr(nor);
+		return -EINVAL;
+	}
+
+	return fsr & FSR_READY;
 }
 
 static int spi_nor_ready(struct spi_nor *nor)
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index c5a58c4..0288081 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -35,6 +35,7 @@
 #define SPINOR_OP_RDID		0x9f	/* Read JEDEC ID */
 #define SPINOR_OP_RDCR		0x35	/* Read configuration register */
 #define SPINOR_OP_RDFSR		0x70	/* Read flag status register */
+#define SPINOR_OP_WRCFSR	0x50	/* Write clear flag status register */
 
 /* 4-byte address opcodes - used on Spansion and some Macronix flashes. */
 #define SPINOR_OP_READ4		0x13	/* Read data bytes (low frequency) */
@@ -74,6 +75,14 @@
 /* Enhanced Volatile Configuration Register bits */
 #define EVCR_QUAD_EN_MICRON    0x80    /* Micron Quad I/O */
 
+/* Flag Status Register Error bits */
+#define FSR_ERR_PROT		0x2	/* Protection */
+#define FSR_ERR_VOLT		0x8	/* Voltage on Vpp */
+#define FSR_ERR_PROG		0x10	/* Program operation */
+#define FSR_ERR_ERASE		0x20	/* Erase operation */
+#define FSR_ERR_MASK		(FSR_ERR_PROT | FSR_ERR_VOLT | \
+				FSR_ERR_PROG | FSR_ERR_ERASE)
+
 /* Flag Status Register bits */
 #define FSR_READY		0x80
 
-- 
1.9.1