dt-bindings: olpc,xo1.75-ec: Add OLPC XO-1.75 EC bindings

The OLPC XO-1.75 Embedded Controller is a SPI master that uses extra
signals for handshaking. It needs to know when is the slave (Linux)
side's TX FIFO ready for transfer (the ready-gpio signal on the SPI
controller node) and when does it wish to respond with a command (the
cmd-gpio property).

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Acked-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

diff --git a/Documentation/devicetree/bindings/misc/olpc,xo1.75-ec.txt b/Documentation/devicetree/bindings/misc/olpc,xo1.75-ec.txt
new file mode 100644 (file)
index 0000000..8c4d649
--- /dev/null
+++ b/Documentation/devicetree/bindings/misc/olpc,xo1.75-ec.txt
@@ -0,0 +1,23 @@
+OLPC XO-1.75 Embedded Controller
+
+Required properties:
+- compatible: Should be "olpc,xo1.75-ec".
+- cmd-gpios: gpio specifier of the CMD pin
+
+The embedded controller requires the SPI controller driver to signal readiness
+to receive a transfer (that is, when TX FIFO contains the response data) by
+strobing the ACK pin with the ready signal. See the "ready-gpios" property of the
+SSP binding as documented in:
+<Documentation/devicetree/bindings/spi/spi-pxa2xx.txt>.
+
+Example:
+       &ssp3 {
+               spi-slave;
+               ready-gpios = <&gpio 125 GPIO_ACTIVE_HIGH>;
+
+               slave {
+                       compatible = "olpc,xo1.75-ec";
+                       spi-cpha;
+                       cmd-gpios = <&gpio 155 GPIO_ACTIVE_HIGH>;
+               };
+       };