Input: Add touchscreen support for Colibri VF50

The Colibri Vybrid VF50 module supports 4-wire touchscreens using
FETs and ADC inputs. This driver uses the IIO consumer interface
and relies on the vf610_adc driver based on the IIO framework.

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt

@@ -0,0 +1,36 @@
+* Toradex Colibri VF50 Touchscreen driver
+
+Required Properties:
+- compatible must be toradex,vf50-touchscreen
+- io-channels: adc channels being used by the Colibri VF50 module
+- xp-gpios: FET gate driver for input of X+
+- xm-gpios: FET gate driver for input of X-
+- yp-gpios: FET gate driver for input of Y+
+- ym-gpios: FET gate driver for input of Y-
+- interrupt-parent: phandle for the interrupt controller
+- interrupts: pen irq interrupt for touch detection
+- pinctrl-names: "idle", "default", "gpios"
+- pinctrl-0: pinctrl node for pen/touch detection state pinmux
+- pinctrl-1: pinctrl node for X/Y and pressure measurement (ADC) state pinmux
+- pinctrl-2: pinctrl node for gpios functioning as FET gate drivers
+- vf50-ts-min-pressure: pressure level at which to stop measuring X/Y values
+
+Example:
+
+	touchctrl: vf50_touchctrl {
+		compatible = "toradex,vf50-touchscreen";
+		io-channels = <&adc1 0>,<&adc0 0>,
+				<&adc0 1>,<&adc1 2>;
+		xp-gpios = <&gpio0 13 GPIO_ACTIVE_LOW>;
+		xm-gpios = <&gpio2 29 GPIO_ACTIVE_HIGH>;
+		yp-gpios = <&gpio0 12 GPIO_ACTIVE_LOW>;
+		ym-gpios = <&gpio0 4 GPIO_ACTIVE_HIGH>;
+		interrupt-parent = <&gpio0>;
+		interrupts = <8 IRQ_TYPE_LEVEL_LOW>;
+		pinctrl-names = "idle","default","gpios";
+		pinctrl-0 = <&pinctrl_touchctrl_idle>;
+		pinctrl-1 = <&pinctrl_touchctrl_default>;
+		pinctrl-2 = <&pinctrl_touchctrl_gpios>;
+		vf50-ts-min-pressure = <200>;
+		status = "disabled";
+	};

drivers/input/touchscreen/Kconfig

@@ -1040,4 +1040,16 @@ config TOUCHSCREEN_ZFORCE
 	  To compile this driver as a module, choose M here: the
 	  module will be called zforce_ts.
 
+config TOUCHSCREEN_COLIBRI_VF50
+	tristate "Toradex Colibri on board touchscreen driver"
+	depends on GPIOLIB && IIO && VF610_ADC
+	help
+	  Say Y here if you have a Colibri VF50 and plan to use
+	  the on-board provided 4-wire touchscreen driver.
+
+	  If unsure, say N.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called colibri_vf50_ts.
+
 endif

drivers/input/touchscreen/Makefile

@@ -85,3 +85,4 @@ obj-$(CONFIG_TOUCHSCREEN_W90X900)	+= w90p910_ts.o
 obj-$(CONFIG_TOUCHSCREEN_SX8654)	+= sx8654.o
 obj-$(CONFIG_TOUCHSCREEN_TPS6507X)	+= tps6507x-ts.o
 obj-$(CONFIG_TOUCHSCREEN_ZFORCE)	+= zforce_ts.o
+obj-$(CONFIG_TOUCHSCREEN_COLIBRI_VF50)	+= colibri-vf50-ts.o