Input: ad7879 - add device tree support

Add device tree support for the I2C and SPI variant of AD7879(-1).
This allows to specify the touchscreen controller as a I2C client
node or SPI slave device. Most of the options available in platform
data are also available as device tree properties, the only exception
being GPIO capabilities, which can not be activated through device
tree currently.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

1 files changed, 53 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/input/touchscreen/ad7879.txt b/Documentation/devicetree/bindings/input/touchscreen/ad7879.txt
new file mode 100644
index 000000000000..e3f22d23fc8f
--- /dev/null
+++ b/Documentation/devicetree/bindings/input/touchscreen/ad7879.txt
@@ -0,0 +1,53 @@
+* Analog Devices AD7879(-1)/AD7889(-1) touchscreen interface (SPI/I2C)
+
+Required properties:
+- compatible			: for SPI slave, use "adi,ad7879"
+				  for I2C slave, use "adi,ad7879-1"
+- reg				: SPI chipselect/I2C slave address
+				  See spi-bus.txt for more SPI slave properties
+- interrupt-parent		: the phandle for the interrupt controller
+- interrupts			: touch controller interrupt
+- touchscreen-max-pressure	: maximum reported pressure
+- adi,resistance-plate-x	: total resistance of X-plate (for pressure
+				  calculation)
+Optional properties:
+- touchscreen-swapped-x-y	: X and Y axis are swapped (boolean)
+- adi,first-conversion-delay	: 0-12: In 128us steps (starting with 128us)
+				  13  : 2.560ms
+				  14  : 3.584ms
+				  15  : 4.096ms
+				  This property has to be a '/bits/ 8' value
+- adi,acquisition-time		: 0: 2us
+				  1: 4us
+				  2: 8us
+				  3: 16us
+				  This property has to be a '/bits/ 8' value
+- adi,median-filter-size	: 0: disabled
+				  1: 4 measurements
+				  2: 8 measurements
+				  3: 16 measurements
+				  This property has to be a '/bits/ 8' value
+- adi,averaging			: 0: 2 middle values (1 if median disabled)
+				  1: 4 middle values
+				  2: 8 middle values
+				  3: 16 values
+				  This property has to be a '/bits/ 8' value
+- adi,conversion-interval:	: 0    : convert one time only
+				  1-255: 515us + val * 35us (up to 9.440ms)
+				  This property has to be a '/bits/ 8' value
+
+Example:
+
+	ad7879@2c {
+		compatible = "adi,ad7879-1";
+		reg = <0x2c>;
+		interrupt-parent = <&gpio1>;
+		interrupts = <13 IRQ_TYPE_EDGE_FALLING>;
+		touchscreen-max-pressure = <4096>;
+		adi,resistance-plate-x = <120>;
+		adi,first-conversion-delay = /bits/ 8 <3>;
+		adi,acquisition-time = /bits/ 8 <1>;
+		adi,median-filter-size = /bits/ 8 <2>;
+		adi,averaging = /bits/ 8 <1>;
+		adi,conversion-interval = /bits/ 8 <255>;
+	};