Add support for touchscreen on 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 <[email protected]>

---
 drivers/input/touchscreen/Kconfig           |  12 +
 drivers/input/touchscreen/Makefile          |   1 +
 drivers/input/touchscreen/colibri-vf50-ts.c | 370 ++++++++++++++++++++++++++++
 3 files changed, 383 insertions(+)
 create mode 100644 drivers/input/touchscreen/colibri-vf50-ts.c

drivers/input/touchscreen/Kconfig +0 -0

index 80f6386..28948ca 100644

drivers/input/touchscreen/Kconfig +9 -0

+	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 +1 -0

index 44deea7..93746a0 100644
@@ -84,3 +84,4 @@ 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

drivers/input/touchscreen/colibri-vf50-ts.c new file +12 -0

new file mode 100644
index 0000000..0793fdc
@@ -0,0 +1,370 @@
+/* Copyright 2015 Toradex AG
+ *
+ * Toradex Colibri VF50 Touchscreen driver
+ *
+ * Originally authored by Stefan Agner for 3.0 kernel
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+

drivers/input/touchscreen/colibri-vf50-ts.c new file +12 -0

+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#define DRIVER_NAME "colibri-vf50-ts"
+#define DRV_VERSION "1.0"
+
+#define VF_ADC_MAX ((1 << 12) - 1)
+
+#define COLI_TOUCH_MIN_DELAY_US 1000
+#define COLI_TOUCH_MAX_DELAY_US 2000
+#define COLI_TOUCH_NO_OF_AVGS	5

drivers/input/touchscreen/colibri-vf50-ts.c new file +49 -0

+	int pen_irq;
+	int min_pressure;
+	bool stop_touchscreen;
+};
+
+/*
+ * Enables given plates and measures touch parameters using ADC
+ */
+static int adc_ts_measure(struct iio_channel *channel,
+		  struct gpio_desc *plate_p, struct gpio_desc *plate_m)
+{
+	int i, value = 0, val = 0;
+	int ret;
+
+	gpiod_set_value(plate_p, 1);
+	gpiod_set_value(plate_m, 1);
+
+	usleep_range(COLI_TOUCH_MIN_DELAY_US, COLI_TOUCH_MAX_DELAY_US);
+
+	for (i = 0; i < COLI_TOUCH_NO_OF_AVGS; i++) {
+		ret = iio_read_channel_raw(channel, &val);
+		if (ret < 0) {
+			value = ret;
+			goto error_iio_read;
+		}
+
+		value += val;
+	}
+
+	value /= COLI_TOUCH_NO_OF_AVGS;
+
+error_iio_read:
+	gpiod_set_value(plate_p, 0);
+	gpiod_set_value(plate_m, 0);
+
+	return value;
+}
+
+/*
+ * Enable touch detection using falling edge detection on XM
+ */
+static void vf50_ts_enable_touch_detection(struct vf50_touch_device *vf50_ts)
+{
+	/* Enable plate YM (needs to be strong GND, high active) */
+	gpiod_set_value(vf50_ts->gpio_ym, 1);
+
+	/*
+	 * Let the platform mux to idle state in order to enable
+	 * Pull-Up on GPIO

drivers/input/touchscreen/colibri-vf50-ts.c new file +118 -0

+	struct device *dev = &vf50_ts->pdev->dev;
+	int val_x, val_y, val_z1, val_z2, val_p = 0;
+	bool discard_val_on_start = true;
+
+	/* Disable the touch detection plates */
+	gpiod_set_value(vf50_ts->gpio_ym, 0);
+
+	/* Let the platform mux to default state in order to mux as ADC */
+	pinctrl_pm_select_default_state(dev);
+
+	while (!vf50_ts->stop_touchscreen) {
+		/* X-Direction */
+		val_x = adc_ts_measure(&vf50_ts->channels[0],
+				vf50_ts->gpio_xp, vf50_ts->gpio_xm);
+		if (val_x < 0)
+			break;
+
+		/* Y-Direction */
+		val_y = adc_ts_measure(&vf50_ts->channels[1],
+				vf50_ts->gpio_yp, vf50_ts->gpio_ym);
+		if (val_y < 0)
+			break;
+
+		/*
+		 * Touch pressure
+		 * Measure on XP/YM
+		 */
+		val_z1 = adc_ts_measure(&vf50_ts->channels[2],
+				vf50_ts->gpio_yp, vf50_ts->gpio_xm);
+		if (val_z1 < 0)
+			break;
+		val_z2 = adc_ts_measure(&vf50_ts->channels[3],
+				vf50_ts->gpio_yp, vf50_ts->gpio_xm);
+		if (val_z2 < 0)
+			break;
+
+		/* Validate signal (avoid calculation using noise) */
+		if (val_z1 > 64 && val_x > 64) {
+			/*
+			 * Calculate resistance between the plates
+			 * lower resistance means higher pressure
+			 */
+			int r_x = (1000 * val_x) / VF_ADC_MAX;
+
+			val_p = (r_x * val_z2) / val_z1 - r_x;
+
+		} else {
+			val_p = 2000;
+		}
+
+		val_p = 2000 - val_p;
+		dev_dbg(dev, "Measured values: x: %d, y: %d, z1: %d, z2: %d, "
+			"p: %d\n", val_x, val_y, val_z1, val_z2, val_p);
+
+		/*
+		 * If touch pressure is too low, stop measuring and reenable
+		 * touch detection
+		 */
+		if (val_p < vf50_ts->min_pressure || val_p > 2000)
+			break;
+
+		/*
+		 * The pressure may not be enough for the first x and the
+		 * second y measurement, but, the pressure is ok when the
+		 * driver is doing the third and fourth measurement. To
+		 * take care of this, we drop the first measurement always.
+		 */
+		if (discard_val_on_start) {
+			discard_val_on_start = false;
+		} else {
+			/*
+			 * Report touch position and sleep for
+			 * next measurement
+			 */
+			input_report_abs(vf50_ts->ts_input,
+					ABS_X, VF_ADC_MAX - val_x);
+			input_report_abs(vf50_ts->ts_input,
+					ABS_Y, VF_ADC_MAX - val_y);
+			input_report_abs(vf50_ts->ts_input,
+					ABS_PRESSURE, val_p);
+			input_report_key(vf50_ts->ts_input, BTN_TOUCH, 1);
+			input_sync(vf50_ts->ts_input);
+		}
+
+		msleep(10);
+	}
+
+	/* Report no more touch, reenable touch detection */
+	input_report_abs(vf50_ts->ts_input, ABS_PRESSURE, 0);
+	input_report_key(vf50_ts->ts_input, BTN_TOUCH, 0);
+	input_sync(vf50_ts->ts_input);
+
+	vf50_ts_enable_touch_detection(vf50_ts);
+
+	/* Wait for the pull-up to be stable on high */
+	msleep(10);
+
+	return IRQ_HANDLED;
+}
+
+static int vf50_ts_open(struct input_dev *dev_input)
+{
+	struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
+	struct device *dev = &touchdev->pdev->dev;
+
+	dev_dbg(dev, "Input device %s opened, starting touch detection\n",
+			dev_input->name);
+
+	touchdev->stop_touchscreen = false;
+
+	/* Mux detection before request IRQ, wait for pull-up to settle */
+	vf50_ts_enable_touch_detection(touchdev);
+	msleep(10);
+
+	return 0;
+}
+
+static void vf50_ts_close(struct input_dev *dev_input)

drivers/input/touchscreen/colibri-vf50-ts.c new file +32 -0

+	dev_dbg(dev, "Input device %s closed, disable touch detection\n",
+		dev_input->name);
+}
+
+static int vf50_ts_get_gpiod(struct device *dev,
+	struct gpio_desc **gpio_d, const char *con_id, enum gpiod_flags flags)
+{
+	int error;
+
+	*gpio_d = devm_gpiod_get(dev, con_id, flags);
+	if (IS_ERR(*gpio_d)) {
+		error = PTR_ERR(*gpio_d);
+		dev_err(dev, "Could not get gpio_%s %d\n", con_id, error);
+		return error;
+	}
+
+	return 0;
+}
+
+static void vf50_ts_channel_release(void *data)
+{
+	struct vf50_touch_device *touchdev = data;
+
+	iio_channel_release_all(touchdev->channels);
+}
+
+static int vf50_ts_probe(struct platform_device *pdev)
+{
+	struct input_dev *input;
+	struct iio_channel *channels;
+	struct device *dev = &pdev->dev;
+	struct vf50_touch_device *touchdev;

drivers/input/touchscreen/colibri-vf50-ts.c new file +68 -0

+	}
+
+	platform_set_drvdata(pdev, touchdev);
+
+	touchdev->pdev = pdev;
+	touchdev->channels = channels;
+
+	input->name = DRIVER_NAME;
+	input->id.bustype = BUS_HOST;
+	input->dev.parent = dev;
+	input->open = vf50_ts_open;
+	input->close = vf50_ts_close;
+
+	input_set_capability(input, EV_KEY, BTN_TOUCH);
+	input_set_abs_params(input, ABS_X, 0, VF_ADC_MAX, 0, 0);
+	input_set_abs_params(input, ABS_Y, 0, VF_ADC_MAX, 0, 0);
+	input_set_abs_params(input, ABS_PRESSURE, 0, VF_ADC_MAX, 0, 0);
+
+	touchdev->ts_input = input;
+	input_set_drvdata(input, touchdev);
+	error = input_register_device(input);
+	if (error) {
+		dev_err(dev, "Failed to register input device\n");
+		return error;
+	}
+
+	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xp,
+				"xp", GPIOD_OUT_LOW);
+	if (error)
+		return error;
+
+	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xm,
+				"xm", GPIOD_OUT_LOW);
+	if (error)
+		return error;
+
+	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_yp,
+				"yp", GPIOD_OUT_LOW);
+	if (error)
+		return error;
+
+	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_ym,
+				"ym", GPIOD_OUT_LOW);
+	if (error)
+		return error;
+
+	touchdev->pen_irq = platform_get_irq(pdev, 0);
+	if (touchdev->pen_irq < 0)
+		return touchdev->pen_irq;
+
+	error = devm_request_threaded_irq(dev, touchdev->pen_irq, NULL,
+			vf50_ts_irq_bh, IRQF_ONESHOT,
+			"vf50 touch", touchdev);
+	if (error < 0)
+		return error;
+
+	return 0;
+}
+
+static const struct of_device_id vf50_touch_of_match[] = {
+	{ .compatible = "toradex,vf50-touchscreen", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, vf50_touch_of_match);
+
+static struct platform_driver vf50_touch_driver = {
+	.driver = {
+		.name = "toradex,vf50_touchctrl",

drivers/input/touchscreen/colibri-vf50-ts.c new file +1 -0

+MODULE_VERSION(DRV_VERSION);

Signature · 1 line

2.5.0

This adds device tree binding documentation for the Colibri VF50 touchscreen driver.

Signed-off-by Sanchayan Maity <[email protected]>

---
 .../bindings/input/touchscreen/colibri-vf50-ts.txt | 36 ++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644

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

diff --git a/Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt b/Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt new file mode 100644
index 0000000..e615aa9

Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt new file +1 -0

@@ -0,0 +1,36 @@
+* Toradex Colibri VF50 Touchscreen driver

Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt new file +12 -0

+- 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>;

Add device tree node for touchscreen support on Colibri VF50. The touchscreen functionality on VF50 uses the ADC channels of Vybrid and some GPIOs. Also add pinctrl nodes for proper pinmux.

Signed-off-by Sanchayan Maity <[email protected]>

---
 arch/arm/boot/dts/vf500-colibri-eval-v3.dts |  4 +++
 arch/arm/boot/dts/vf500-colibri.dtsi        | 47 +++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

arch/arm/boot/dts/vf500-colibri-eval-v3.dts +4 -0

index 7fc782c..14c0b00 100644
@@ -15,3 +15,7 @@
 	model = "Toradex Colibri VF50 on Colibri Evaluation Board";
 	compatible = "toradex,vf500-colibri_vf50-on-eval",
 "toradex,vf500-colibri_vf50", "fsl,vf500";
 };
+
+&touchscreen {
+	status = "okay";
+};

arch/arm/boot/dts/vf500-colibri.dtsi +6 -0

index cee34a3..84f091d 100644
@@ -17,4 +17,51 @@
 	memory {
 		reg = <0x80000000 0x8000000>;
 	};
+
+	touchscreen: vf50-touchscreen {
+		compatible = "toradex,vf50-touchscreen";
+		io-channels = <&adc1 0>,<&adc0 0>,
+				<&adc0 1>,<&adc1 2>;
+		xp-gpios = <&gpio0 13 GPIO_ACTIVE_LOW>;

Quoted 44 lines · Sanchayan Maity

Add device tree node for touchscreen support on Colibri VF50. The touchscreen functionality on VF50 uses the ADC channels of Vybrid and some GPIOs. Also add pinctrl nodes for proper pinmux.

Signed-off-by Sanchayan Maity <[email protected]>

---
 arch/arm/boot/dts/vf500-colibri-eval-v3.dts |  4 +++
 arch/arm/boot/dts/vf500-colibri.dtsi        | 47 +++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

arch/arm/boot/dts/vf500-colibri-eval-v3.dts +4 -0

index 7fc782c..14c0b00 100644
@@ -15,3 +15,7 @@
 	model = "Toradex Colibri VF50 on Colibri Evaluation Board";
 	compatible = "toradex,vf500-colibri_vf50-on-eval",
 "toradex,vf500-colibri_vf50", "fsl,vf500";
 };
+
+&touchscreen {
+	status = "okay";
+};

arch/arm/boot/dts/vf500-colibri.dtsi +11 -0

index cee34a3..84f091d 100644
@@ -17,4 +17,51 @@
 	memory {
 		reg = <0x80000000 0x8000000>;
 	};
+
+	touchscreen: vf50-touchscreen {
+		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>;

arch/arm/boot/dts/vf500-colibri.dtsi line 35

Quoted 5 lines

arch/arm/boot/dts/vf500-colibri.dtsi +5 -0

+		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>;

Since this is a touch screen related property, we even would want to have that in the board specific device-tree (vf500-colibri-eval-v3.dts).

Hi Sanchayan,

drivers/input/touchscreen/colibri-vf50-ts.c line 268

Quoted 11 lines · Sanchayan Maity

drivers/input/touchscreen/colibri-vf50-ts.c new file +11 -0

+static int vf50_ts_probe(struct platform_device *pdev)
+{
+	struct input_dev *input;
+	struct iio_channel *channels;
+	struct device *dev = &pdev->dev;
+	struct vf50_touch_device *touchdev;
+	int error;
+
+	channels = iio_channel_get_all(dev);
+	if (IS_ERR(channels))
+		return PTR_ERR(channels);

Hm, we expect here that four channels are returned, however a faulty device tree could contain less. Access to the fourth channel above would lead to a bug.

Can you check the amount of channels returned? The returned list is explicitly terminated with a null entry, you can rely on that. Something similar to hwmon should do the job.
http://lxr.free-electrons.com/source/drivers/hwmon/iio_hwmon.c#L86

Otherwise, Acked-by: Stefan Agner <[email protected]>

--
Stefan

Quoted 19 lines · Sanchayan Maity

This adds device tree binding documentation for the Colibri VF50 touchscreen driver.

Signed-off-by Sanchayan Maity <[email protected]>

---
 .../bindings/input/touchscreen/colibri-vf50-ts.txt | 36 ++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644

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

diff --git a/Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt b/Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt new file mode 100644
index 0000000..e615aa9

Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt new file +1 -0

@@ -0,0 +1,36 @@
+* Toradex Colibri VF50 Touchscreen driver

Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt line 11

Quoted 10 lines

Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt new file +10 -0

+
+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

I like the use of the interrupt interface for the touch detection pin. Maybe you can mention here that this is (typically) a GPIO...

Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt line 14

Quoted 3 lines

Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt new file +3 -0

+- pinctrl-names: "idle", "default", "gpios"
+- pinctrl-0: pinctrl node for idle state gpio pinmux
+- pinctrl-1: pinctrl node for touch detection state pinmux

"touch detection" for default is rather confusing or even wrong. The Idle state is used for pen/touch detection, default is used for X/Y and Pressure measurement (maybe better described as touch measurement).

Quoted 13 lines

Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt new file +12 -0

+- 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>;

Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt line 36

Quoted 10 lines

Documentation/devicetree/bindings/input/touchscreen/colibri-vf50-ts.txt new file +10 -0

+		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";
+	};

Otherwise I agree with 1 and 2:

Acked-by Stefan Agner <[email protected]>

--
Stefan

Hi Sanchayan,

Quoted 4 lines · Sanchayan Maity

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.

Thank you for making changes. I have a few comments still.

Quoted 17 lines

Signed-off-by Sanchayan Maity <[email protected]>

---
 drivers/input/touchscreen/Kconfig           |  12 +
 drivers/input/touchscreen/Makefile          |   1 +
 drivers/input/touchscreen/colibri-vf50-ts.c | 370 ++++++++++++++++++++++++++++
 3 files changed, 383 insertions(+)
 create mode 100644 drivers/input/touchscreen/colibri-vf50-ts.c

drivers/input/touchscreen/Kconfig +0 -0

index 80f6386..28948ca 100644
@@ -1027,4 +1027,16 @@ config TOUCHSCREEN_ZFORCE
 	  To compile this driver as a module, choose M here: the
 	  module will be called zforce_ts.
 

drivers/input/touchscreen/Kconfig config TOUCHSCREEN_ZFORCE · line 1032

Quoted 3 lines

drivers/input/touchscreen/Kconfig +3 -0

+config TOUCHSCREEN_COLIBRI_VF50
+	tristate "Toradex Colibri on board touchscreen driver"
+	depends on GPIOLIB && IIO && VF610_ADC

Can we possibly add "|| COMPILE_TEST" dependency? Will it compile without IIO or VF610_ADC enabled?

Quoted 43 lines

drivers/input/touchscreen/Kconfig +9 -0

+	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 +1 -0

index 44deea7..93746a0 100644
@@ -84,3 +84,4 @@ 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

drivers/input/touchscreen/colibri-vf50-ts.c new file +16 -0

new file mode 100644
index 0000000..0793fdc
@@ -0,0 +1,370 @@
+/* Copyright 2015 Toradex AG
+ *
+ * Toradex Colibri VF50 Touchscreen driver
+ *
+ * Originally authored by Stefan Agner for 3.0 kernel
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/gpio.h>
+#include <linux/iio/consumer.h>

drivers/input/touchscreen/colibri-vf50-ts.c line 22

Quoted 6 lines

drivers/input/touchscreen/colibri-vf50-ts.c new file +6 -0

+#include <linux/iio/types.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pinctrl/consumer.h>

Don't you need gpio/consumer.h?

Quoted 17 lines

drivers/input/touchscreen/colibri-vf50-ts.c new file +16 -0

+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#define DRIVER_NAME "colibri-vf50-ts"
+#define DRV_VERSION "1.0"
+
+#define VF_ADC_MAX ((1 << 12) - 1)
+
+#define COLI_TOUCH_MIN_DELAY_US 1000
+#define COLI_TOUCH_MAX_DELAY_US 2000
+#define COLI_TOUCH_NO_OF_AVGS	5
+
+struct vf50_touch_device {
+	struct platform_device	*pdev;
+	struct input_dev	*ts_input;

drivers/input/touchscreen/colibri-vf50-ts.c line 44

Quoted 6 lines

drivers/input/touchscreen/colibri-vf50-ts.c new file +6 -0

+	struct iio_channel	*channels;
+	struct gpio_desc *gpio_xp;
+	struct gpio_desc *gpio_xm;
+	struct gpio_desc *gpio_yp;
+	struct gpio_desc *gpio_ym;
+	struct gpio_desc *gpio_pen_detect;

I do not see gpio_pen_detect being used anymore.

Quoted 54 lines

drivers/input/touchscreen/colibri-vf50-ts.c new file +53 -0

+	int pen_irq;
+	int min_pressure;
+	bool stop_touchscreen;
+};
+
+/*
+ * Enables given plates and measures touch parameters using ADC
+ */
+static int adc_ts_measure(struct iio_channel *channel,
+		  struct gpio_desc *plate_p, struct gpio_desc *plate_m)
+{
+	int i, value = 0, val = 0;
+	int ret;
+
+	gpiod_set_value(plate_p, 1);
+	gpiod_set_value(plate_m, 1);
+
+	usleep_range(COLI_TOUCH_MIN_DELAY_US, COLI_TOUCH_MAX_DELAY_US);
+
+	for (i = 0; i < COLI_TOUCH_NO_OF_AVGS; i++) {
+		ret = iio_read_channel_raw(channel, &val);
+		if (ret < 0) {
+			value = ret;
+			goto error_iio_read;
+		}
+
+		value += val;
+	}
+
+	value /= COLI_TOUCH_NO_OF_AVGS;
+
+error_iio_read:
+	gpiod_set_value(plate_p, 0);
+	gpiod_set_value(plate_m, 0);
+
+	return value;
+}
+
+/*
+ * Enable touch detection using falling edge detection on XM
+ */
+static void vf50_ts_enable_touch_detection(struct vf50_touch_device *vf50_ts)
+{
+	/* Enable plate YM (needs to be strong GND, high active) */
+	gpiod_set_value(vf50_ts->gpio_ym, 1);
+
+	/*
+	 * Let the platform mux to idle state in order to enable
+	 * Pull-Up on GPIO
+	 */
+	pinctrl_pm_select_idle_state(&vf50_ts->pdev->dev);
+}
+

drivers/input/touchscreen/colibri-vf50-ts.c line 103

Quoted 6 lines

drivers/input/touchscreen/colibri-vf50-ts.c new file +6 -0

+/*
+ * ADC touch screen sampling bottom half irq handler
+ */
+static irqreturn_t vf50_ts_irq_bh(int irq, void *private)
+{
+	struct vf50_touch_device *vf50_ts = (struct vf50_touch_device *)private;

No need to cast from void * pointer.

Quoted 123 lines

drivers/input/touchscreen/colibri-vf50-ts.c new file +122 -0

+	struct device *dev = &vf50_ts->pdev->dev;
+	int val_x, val_y, val_z1, val_z2, val_p = 0;
+	bool discard_val_on_start = true;
+
+	/* Disable the touch detection plates */
+	gpiod_set_value(vf50_ts->gpio_ym, 0);
+
+	/* Let the platform mux to default state in order to mux as ADC */
+	pinctrl_pm_select_default_state(dev);
+
+	while (!vf50_ts->stop_touchscreen) {
+		/* X-Direction */
+		val_x = adc_ts_measure(&vf50_ts->channels[0],
+				vf50_ts->gpio_xp, vf50_ts->gpio_xm);
+		if (val_x < 0)
+			break;
+
+		/* Y-Direction */
+		val_y = adc_ts_measure(&vf50_ts->channels[1],
+				vf50_ts->gpio_yp, vf50_ts->gpio_ym);
+		if (val_y < 0)
+			break;
+
+		/*
+		 * Touch pressure
+		 * Measure on XP/YM
+		 */
+		val_z1 = adc_ts_measure(&vf50_ts->channels[2],
+				vf50_ts->gpio_yp, vf50_ts->gpio_xm);
+		if (val_z1 < 0)
+			break;
+		val_z2 = adc_ts_measure(&vf50_ts->channels[3],
+				vf50_ts->gpio_yp, vf50_ts->gpio_xm);
+		if (val_z2 < 0)
+			break;
+
+		/* Validate signal (avoid calculation using noise) */
+		if (val_z1 > 64 && val_x > 64) {
+			/*
+			 * Calculate resistance between the plates
+			 * lower resistance means higher pressure
+			 */
+			int r_x = (1000 * val_x) / VF_ADC_MAX;
+
+			val_p = (r_x * val_z2) / val_z1 - r_x;
+
+		} else {
+			val_p = 2000;
+		}
+
+		val_p = 2000 - val_p;
+		dev_dbg(dev, "Measured values: x: %d, y: %d, z1: %d, z2: %d, "
+			"p: %d\n", val_x, val_y, val_z1, val_z2, val_p);
+
+		/*
+		 * If touch pressure is too low, stop measuring and reenable
+		 * touch detection
+		 */
+		if (val_p < vf50_ts->min_pressure || val_p > 2000)
+			break;
+
+		/*
+		 * The pressure may not be enough for the first x and the
+		 * second y measurement, but, the pressure is ok when the
+		 * driver is doing the third and fourth measurement. To
+		 * take care of this, we drop the first measurement always.
+		 */
+		if (discard_val_on_start) {
+			discard_val_on_start = false;
+		} else {
+			/*
+			 * Report touch position and sleep for
+			 * next measurement
+			 */
+			input_report_abs(vf50_ts->ts_input,
+					ABS_X, VF_ADC_MAX - val_x);
+			input_report_abs(vf50_ts->ts_input,
+					ABS_Y, VF_ADC_MAX - val_y);
+			input_report_abs(vf50_ts->ts_input,
+					ABS_PRESSURE, val_p);
+			input_report_key(vf50_ts->ts_input, BTN_TOUCH, 1);
+			input_sync(vf50_ts->ts_input);
+		}
+
+		msleep(10);
+	}
+
+	/* Report no more touch, reenable touch detection */
+	input_report_abs(vf50_ts->ts_input, ABS_PRESSURE, 0);
+	input_report_key(vf50_ts->ts_input, BTN_TOUCH, 0);
+	input_sync(vf50_ts->ts_input);
+
+	vf50_ts_enable_touch_detection(vf50_ts);
+
+	/* Wait for the pull-up to be stable on high */
+	msleep(10);
+
+	return IRQ_HANDLED;
+}
+
+static int vf50_ts_open(struct input_dev *dev_input)
+{
+	struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
+	struct device *dev = &touchdev->pdev->dev;
+
+	dev_dbg(dev, "Input device %s opened, starting touch detection\n",
+			dev_input->name);
+
+	touchdev->stop_touchscreen = false;
+
+	/* Mux detection before request IRQ, wait for pull-up to settle */
+	vf50_ts_enable_touch_detection(touchdev);
+	msleep(10);
+
+	return 0;
+}
+
+static void vf50_ts_close(struct input_dev *dev_input)
+{
+	struct vf50_touch_device *touchdev = input_get_drvdata(dev_input);
+	struct device *dev = &touchdev->pdev->dev;
+

drivers/input/touchscreen/colibri-vf50-ts.c line 231

Quoted 6 lines

drivers/input/touchscreen/colibri-vf50-ts.c new file +6 -0

+	touchdev->stop_touchscreen = true;
+
+	/* Make sure IRQ is not running past close */
+	mb();
+	synchronize_irq(touchdev->pen_irq);
+

Should we drive the gpio_ym inactive here? What about pin control?

Quoted 33 lines

drivers/input/touchscreen/colibri-vf50-ts.c new file +32 -0

+	dev_dbg(dev, "Input device %s closed, disable touch detection\n",
+		dev_input->name);
+}
+
+static int vf50_ts_get_gpiod(struct device *dev,
+	struct gpio_desc **gpio_d, const char *con_id, enum gpiod_flags flags)
+{
+	int error;
+
+	*gpio_d = devm_gpiod_get(dev, con_id, flags);
+	if (IS_ERR(*gpio_d)) {
+		error = PTR_ERR(*gpio_d);
+		dev_err(dev, "Could not get gpio_%s %d\n", con_id, error);
+		return error;
+	}
+
+	return 0;
+}
+
+static void vf50_ts_channel_release(void *data)
+{
+	struct vf50_touch_device *touchdev = data;
+
+	iio_channel_release_all(touchdev->channels);
+}
+
+static int vf50_ts_probe(struct platform_device *pdev)
+{
+	struct input_dev *input;
+	struct iio_channel *channels;
+	struct device *dev = &pdev->dev;
+	struct vf50_touch_device *touchdev;

drivers/input/touchscreen/colibri-vf50-ts.c line 273

Quoted 10 lines

drivers/input/touchscreen/colibri-vf50-ts.c new file +10 -0

+	int error;
+
+	channels = iio_channel_get_all(dev);
+	if (IS_ERR(channels))
+		return PTR_ERR(channels);
+
+	touchdev = devm_kzalloc(dev, sizeof(*touchdev), GFP_KERNEL);
+	if (!touchdev) {
+		error = -ENOMEM;
+		return error;

Why not simply

		return -ENOMEM;

here?

Also you are leaking your iio channels here. You need to install the custom action earlier.

drivers/input/touchscreen/colibri-vf50-ts.c line 283

Quoted 11 lines

drivers/input/touchscreen/colibri-vf50-ts.c new file +10 -0

+	}
+
+	error = of_property_read_u32(dev->of_node, "vf50-ts-min-pressure",
+				 &touchdev->min_pressure);
+	if (error)
+		return error;
+
+	error = devm_add_action(dev, vf50_ts_channel_release, channels);
+	if (error) {
+		dev_err(dev, "Failed to register iio channel release action");

You also need

		vf50_ts_channel_release(touchdev);

drivers/input/touchscreen/colibri-vf50-ts.c line 291

Quoted 8 lines

drivers/input/touchscreen/colibri-vf50-ts.c new file +8 -0

+		return error;
+	}
+
+	input = devm_input_allocate_device(dev);
+	if (!input) {
+		dev_err(dev, "Failed to allocate TS input device\n");
+		error = -ENOMEM;
+		return error;

Again simply return error code, no need to assign to the error variable.

Quoted 74 lines

drivers/input/touchscreen/colibri-vf50-ts.c new file +73 -0

+	}
+
+	platform_set_drvdata(pdev, touchdev);
+
+	touchdev->pdev = pdev;
+	touchdev->channels = channels;
+
+	input->name = DRIVER_NAME;
+	input->id.bustype = BUS_HOST;
+	input->dev.parent = dev;
+	input->open = vf50_ts_open;
+	input->close = vf50_ts_close;
+
+	input_set_capability(input, EV_KEY, BTN_TOUCH);
+	input_set_abs_params(input, ABS_X, 0, VF_ADC_MAX, 0, 0);
+	input_set_abs_params(input, ABS_Y, 0, VF_ADC_MAX, 0, 0);
+	input_set_abs_params(input, ABS_PRESSURE, 0, VF_ADC_MAX, 0, 0);
+
+	touchdev->ts_input = input;
+	input_set_drvdata(input, touchdev);
+	error = input_register_device(input);
+	if (error) {
+		dev_err(dev, "Failed to register input device\n");
+		return error;
+	}
+
+	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xp,
+				"xp", GPIOD_OUT_LOW);
+	if (error)
+		return error;
+
+	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_xm,
+				"xm", GPIOD_OUT_LOW);
+	if (error)
+		return error;
+
+	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_yp,
+				"yp", GPIOD_OUT_LOW);
+	if (error)
+		return error;
+
+	error = vf50_ts_get_gpiod(dev, &touchdev->gpio_ym,
+				"ym", GPIOD_OUT_LOW);
+	if (error)
+		return error;
+
+	touchdev->pen_irq = platform_get_irq(pdev, 0);
+	if (touchdev->pen_irq < 0)
+		return touchdev->pen_irq;
+
+	error = devm_request_threaded_irq(dev, touchdev->pen_irq, NULL,
+			vf50_ts_irq_bh, IRQF_ONESHOT,
+			"vf50 touch", touchdev);
+	if (error < 0)
+		return error;
+
+	return 0;
+}
+
+static const struct of_device_id vf50_touch_of_match[] = {
+	{ .compatible = "toradex,vf50-touchscreen", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, vf50_touch_of_match);
+
+static struct platform_driver vf50_touch_driver = {
+	.driver = {
+		.name = "toradex,vf50_touchctrl",
+		.of_match_table = vf50_touch_of_match,
+	},
+	.probe = vf50_ts_probe,
+};
+

drivers/input/touchscreen/colibri-vf50-ts.c line 369

Quoted 5 lines

drivers/input/touchscreen/colibri-vf50-ts.c new file +5 -0

+module_platform_driver(vf50_touch_driver);
+
+MODULE_AUTHOR("Sanchayan Maity");
+MODULE_DESCRIPTION("Colibri VF50 Touchscreen driver");
+MODULE_LICENSE("GPL v2");

Please change it to "GPL" which means GPL v2+ to match license notice at the top.

Quoted 5 lines

drivers/input/touchscreen/colibri-vf50-ts.c new file +1 -0

+MODULE_VERSION(DRV_VERSION);

Signature · 1 line

2.5.0

Thank you.

Signature · 1 line

Dmitry