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-rw-r--r--Documentation/devicetree/bindings/spi/spi-bus.txt25
1 files changed, 25 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt
index e782add..296015e 100644
--- a/Documentation/devicetree/bindings/spi/spi-bus.txt
+++ b/Documentation/devicetree/bindings/spi/spi-bus.txt
@@ -12,6 +12,7 @@ The SPI master node requires the following properties:
- #size-cells - should be zero.
- compatible - name of SPI bus controller following generic names
recommended practice.
+- cs-gpios - (optional) gpios chip select.
No other properties are required in the SPI bus node. It is assumed
that a driver for an SPI bus device will understand that it is an SPI bus.
However, the binding does not attempt to define the specific method for
@@ -21,6 +22,25 @@ assumption that board specific platform code will be used to manage
chip selects. Individual drivers can define additional properties to
support describing the chip select layout.
+Optional property:
+- num-cs : total number of chipselects
+
+If cs-gpios is used the number of chip select will automatically increased
+with max(cs-gpios > hw cs)
+
+So if for example the controller has 2 CS lines, and the cs-gpios
+property looks like this:
+
+cs-gpios = <&gpio1 0 0> <0> <&gpio1 1 0> <&gpio1 2 0>;
+
+Then it should be configured so that num_chipselect = 4 with the
+following mapping:
+
+cs0 : &gpio1 0 0
+cs1 : native
+cs2 : &gpio1 1 0
+cs3 : &gpio1 2 0
+
SPI slave nodes must be children of the SPI master node and can
contain the following properties.
- reg - (required) chip select address of device.
@@ -33,6 +53,11 @@ 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
SPI example for an MPC5200 SPI bus:
spi@f00 {