[PATCH] mtd: spi-nor: Check that BP bits are set properly

[Aaron Sierra]

Previously, the lock and unlock functions returned success even if the
BP bits were not actually updated in the status register due to
hardware write protection. Introduce write_sr_and_check() to write and
read back the status register to ensure the desired BP bits are
actually set as requested.

Signed-off-by: Joe Schultz <jschultz at xes-inc.com>
Signed-off-by: Aaron Sierra <asierra at xes-inc.com>
---
 drivers/mtd/spi-nor/spi-nor.c | 39 +++++++++++++++++++++++++++------------
 1 file changed, 27 insertions(+), 12 deletions(-)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index 19c00072..8a87bd1 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -550,6 +550,31 @@ static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
 	return ret;
 }
 
+/* Write status register and ensure bits in mask match written values */
+static int write_sr_and_check(struct spi_nor *nor, u8 new, u8 mask)
+{
+	int ret;
+
+	ret = spi_nor_wait_till_ready(nor);
+	if (ret)
+		return ret;
+
+	write_enable(nor);
+	ret = write_sr(nor, new);
+	if (ret)
+		return ret;
+
+	ret = spi_nor_wait_till_ready(nor);
+	if (ret)
+		return ret;
+
+	ret = read_sr(nor);
+	if (ret < 0)
+		return ret;
+
+	return ((ret & mask) != (new & mask)) ? -EIO : 0;
+}
+
 static void stm_get_locked_range(struct spi_nor *nor, u8 sr, loff_t *ofs,
 				 uint64_t *len)
 {
@@ -648,7 +673,6 @@ static int stm_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
 	loff_t lock_len;
 	bool can_be_top = true, can_be_bottom = nor->flags & SNOR_F_HAS_SR_TB;
 	bool use_top;
-	int ret;
 
 	status_old = read_sr(nor);
 	if (status_old < 0)
@@ -712,11 +736,7 @@ static int stm_lock(struct spi_nor *nor, loff_t ofs, uint64_t len)
 	if ((status_new & mask) < (status_old & mask))
 		return -EINVAL;
 
-	write_enable(nor);
-	ret = write_sr(nor, status_new);
-	if (ret)
-		return ret;
-	return spi_nor_wait_till_ready(nor);
+	return write_sr_and_check(nor, status_new, mask);
 }
 
 /*
@@ -733,7 +753,6 @@ static int stm_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len)
 	loff_t lock_len;
 	bool can_be_top = true, can_be_bottom = nor->flags & SNOR_F_HAS_SR_TB;
 	bool use_top;
-	int ret;
 
 	status_old = read_sr(nor);
 	if (status_old < 0)
@@ -800,11 +819,7 @@ static int stm_unlock(struct spi_nor *nor, loff_t ofs, uint64_t len)
 	if ((status_new & mask) > (status_old & mask))
 		return -EINVAL;
 
-	write_enable(nor);
-	ret = write_sr(nor, status_new);
-	if (ret)
-		return ret;
-	return spi_nor_wait_till_ready(nor);
+	return write_sr_and_check(nor, status_new, mask);
 }
 
 /*
-- 
2.7.4