[PATCH] spi: spi-imx: fix MX51_ECSPI_* macros when cs > 3

[Kevin Groeneveld <kgroeneveld@lenbrook.com>]

When using gpio based chip select the cs value can go outside the range
0 – 3. The various MX51_ECSPI_* macros did not take this into consideration
resulting in possible corruption of the configuration.

For example for any cs value over 3 the SCLKPHA bits would not be set and
other values in the register possibly corrupted.

One way to fix this is to just mask the cs bits to 2 bits. This still
allows all 4 native chip selects to work as well as gpio chip selects
(which can use any of the 4 chip select configurations).

Signed-off-by: Kevin Groeneveld <kgroeneveld@lenbrook.com>
---
 drivers/spi/spi-imx.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index e4ccd0c329d0..c61c7ac4c70c 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -252,6 +252,18 @@ static bool spi_imx_can_dma(struct spi_controller *controller, struct spi_device
 	return true;
 }
 
+/*
+ * Note the number of natively supported chip selects for MX51 is 4. Some
+ * devices may have less actual SS pins but the register map supports 4. When
+ * using gpio chip selects the cs values passed into the macros below can go
+ * outside the range 0 - 3. We therefore need to limit the cs value to avoid
+ * corrupting bits outside the allocated locations.
+ *
+ * The simplest way to do this is to just mask the cs bits to 2 bits. This
+ * still allows all 4 native chip selects to work as well as gpio chip selects
+ * (which can use any of the 4 chip select configurations).
+ */
+
 #define MX51_ECSPI_CTRL		0x08
 #define MX51_ECSPI_CTRL_ENABLE		(1 <<  0)
 #define MX51_ECSPI_CTRL_XCH		(1 <<  2)
@@ -260,16 +272,16 @@ static bool spi_imx_can_dma(struct spi_controller *controller, struct spi_device
 #define MX51_ECSPI_CTRL_DRCTL(drctl)	((drctl) << 16)
 #define MX51_ECSPI_CTRL_POSTDIV_OFFSET	8
 #define MX51_ECSPI_CTRL_PREDIV_OFFSET	12
-#define MX51_ECSPI_CTRL_CS(cs)		((cs) << 18)
+#define MX51_ECSPI_CTRL_CS(cs)		((cs & 3) << 18)
 #define MX51_ECSPI_CTRL_BL_OFFSET	20
 #define MX51_ECSPI_CTRL_BL_MASK		(0xfff << 20)
 
 #define MX51_ECSPI_CONFIG	0x0c
-#define MX51_ECSPI_CONFIG_SCLKPHA(cs)	(1 << ((cs) +  0))
-#define MX51_ECSPI_CONFIG_SCLKPOL(cs)	(1 << ((cs) +  4))
-#define MX51_ECSPI_CONFIG_SBBCTRL(cs)	(1 << ((cs) +  8))
-#define MX51_ECSPI_CONFIG_SSBPOL(cs)	(1 << ((cs) + 12))
-#define MX51_ECSPI_CONFIG_SCLKCTL(cs)	(1 << ((cs) + 20))
+#define MX51_ECSPI_CONFIG_SCLKPHA(cs)	(1 << ((cs & 3) +  0))
+#define MX51_ECSPI_CONFIG_SCLKPOL(cs)	(1 << ((cs & 3) +  4))
+#define MX51_ECSPI_CONFIG_SBBCTRL(cs)	(1 << ((cs & 3) +  8))
+#define MX51_ECSPI_CONFIG_SSBPOL(cs)	(1 << ((cs & 3) + 12))
+#define MX51_ECSPI_CONFIG_SCLKCTL(cs)	(1 << ((cs & 3) + 20))
 
 #define MX51_ECSPI_INT		0x10
 #define MX51_ECSPI_INT_TEEN		(1 <<  0)
-- 
2.34.1