of/spi: Support specifying chip select as active high via device tree

The patch allows to specify that an SPI device needs an active high chip
select.

Signed-off-by: Wolfgang Ocker <weo@reccoware.de>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

2 files changed, 4 insertions, 0 deletions

diff --git a/Documentation/powerpc/booting-without-of.txt b/Documentation/powerpc/booting-without-of.txt
index de4063cb4fdc..02ea9a971b8e 100644
--- a/Documentation/powerpc/booting-without-of.txt
+++ b/Documentation/powerpc/booting-without-of.txt
@@ -1917,6 +1917,8 @@ platforms are moved over to use the flattened-device-tree model.
                         inverse clock polarity (CPOL) mode
     - spi-cpha        - (optional) Empty property indicating device requires
                         shifted clock phase (CPHA) mode
+    - spi-cs-high     - (optional) Empty property indicating device requires
+                        chip select active high
 
     SPI example for an MPC5200 SPI bus:
                 spi@f00 {
diff --git a/drivers/of/of_spi.c b/drivers/of/of_spi.c
index b01eec026f68..bed0ed6dcdc1 100644
--- a/drivers/of/of_spi.c
+++ b/drivers/of/of_spi.c
@@ -61,6 +61,8 @@ void of_register_spi_devices(struct spi_master *master, struct device_node *np)
                         spi->mode |= SPI_CPHA;
                 if (of_find_property(nc, "spi-cpol", NULL))
                         spi->mode |= SPI_CPOL;
+                if (of_find_property(nc, "spi-cs-high", NULL))
+                        spi->mode |= SPI_CS_HIGH;
 
                 /* Device speed */
                 prop = of_get_property(nc, "spi-max-frequency", &len);