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@xxxxx>
Acked-by: Pavel Machek <pavel@xxxxxx>
Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
---
Changes since v5:
- Added Rob Herring's Reviewed-by tag
Changes since v1:
- s/cmd-gpio/cmd-gpios/
- s/ready-gpio/ready-gpios/ in the documentation paragraph
- Remove status = "okay" from the example
.../bindings/misc/olpc,xo1.75-ec.txt | 23 +++++++++++++++++++
1 file changed, 23 insertions(+)
create mode 100644 Documentation/devicetree/bindings/misc/olpc,xo1.75-ec.txt
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
index 000000000000..8c4d649cdd8f
--- /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>;
+ };
+ };
--
2.21.0
