[PATCH 1/1] mtd: fsl-quadspi: Add mutex for accessing different SPI-NOR devices

[Alexander Stein]

Access is only serialized for each NOR device in spi_nor_lock_and_prep(),
but not for the QSPI device.
We must ensure only one NOR device is accessed as each call to
fsl_qspi_set_base_addr (in fsl_qspi_prep) will affect the effective flash
address.
This can simply be achieved by using a mutex in prepare/unprepare
callbacks.

Signed-off-by: Alexander Stein <alexander.stein at systec-electronic.com>
---
This problem can simply be trigged by doing a hexdump on /dev/mtdblock0
(256 kiB) and /dev/mtdblock3 (64MiB), in my case.

$ hexdump -C /dev/mtdblock3 # doing a long taking access.
$ hexdump -C /dev/mtdblock0 # in the meanwhile will show data from mtdblock3

 drivers/mtd/spi-nor/fsl-quadspi.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/mtd/spi-nor/fsl-quadspi.c b/drivers/mtd/spi-nor/fsl-quadspi.c
index 5d2df50..a48495a 100644
--- a/drivers/mtd/spi-nor/fsl-quadspi.c
+++ b/drivers/mtd/spi-nor/fsl-quadspi.c
@@ -226,6 +226,7 @@ struct fsl_qspi {
 	u32 memmap_phy;
 	struct clk *clk, *clk_en;
 	struct device *dev;
+	struct mutex lock; /* to serialize access to different mtd partitions */
 	struct completion c;
 	struct fsl_qspi_devtype_data *devtype_data;
 	u32 nor_size;
@@ -771,6 +772,8 @@ static int fsl_qspi_prep(struct spi_nor *nor, enum spi_nor_ops ops)
 		return ret;
 	}
 
+	mutex_lock(&q->lock);
+
 	fsl_qspi_set_base_addr(q, nor);
 	return 0;
 }
@@ -779,6 +782,8 @@ static void fsl_qspi_unprep(struct spi_nor *nor, enum spi_nor_ops ops)
 {
 	struct fsl_qspi *q = nor->priv;
 
+	mutex_unlock(&q->lock);
+
 	clk_disable(q->clk);
 	clk_disable(q->clk_en);
 }
@@ -856,6 +861,7 @@ static int fsl_qspi_probe(struct platform_device *pdev)
 	q->dev = dev;
 	q->devtype_data = (struct fsl_qspi_devtype_data *)of_id->data;
 	platform_set_drvdata(pdev, q);
+	mutex_init(&q->lock);
 
 	ret = fsl_qspi_nor_setup(q);
 	if (ret)
-- 
2.3.6