spi: Add support for specifying 3-wire mode via device tree

This patch allows to specify that a SPI device is connected in 3-wire mode via
device tree.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

2 files changed, 4 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt
index 77a8b0d39b54..296015e3c632 100644
--- a/Documentation/devicetree/bindings/spi/spi-bus.txt
+++ b/Documentation/devicetree/bindings/spi/spi-bus.txt
@@ -53,6 +53,8 @@ contain the following properties.
                 shifted clock phase (CPHA) mode
 - spi-cs-high     - (optional) Empty property indicating device requires
                 chip select active high
+- spi-3wire       - (optional) Empty property indicating device requires
+                    3-wire mode.
 
 If a gpio chipselect is used for the SPI slave the gpio number will be passed
 via the cs_gpio
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index b370d292d19c..2ca5f079ff01 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -861,6 +861,8 @@ static void of_register_spi_devices(struct spi_master *master)
                         spi->mode |= SPI_CPOL;
                 if (of_find_property(nc, "spi-cs-high", NULL))
                         spi->mode |= SPI_CS_HIGH;
+                if (of_find_property(nc, "spi-3wire", NULL))
+                        spi->mode |= SPI_3WIRE;
 
                 /* Device speed */
                 prop = of_get_property(nc, "spi-max-frequency", &len);