Input: Add touchscreen support for Colibri VF50

* 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";

	};

	  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

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

/*

 * Toradex Colibri VF50 Touchscreen driver

 *

 * Copyright 2015 Toradex AG

 *

 * 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/gpio/consumer.h>

#include <linux/iio/consumer.h>

#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>

#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_PULLUP_MIN_DELAY_US	10000

#define COLI_PULLUP_MAX_DELAY_US	11000

#define COLI_TOUCH_NO_OF_AVGS		5

#define COLI_TOUCH_REQ_ADC_CHAN		4

struct vf50_touch_device {

	struct platform_device *pdev;

	struct input_dev *ts_input;

	struct iio_channel *channels;

	struct gpio_desc *gpio_xp;

	struct gpio_desc *gpio_xm;

	struct gpio_desc *gpio_yp;

	struct gpio_desc *gpio_ym;

	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 error;

	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++) {

		error = iio_read_channel_raw(channel, &val);

		if (error < 0) {

			value = error;

			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);

	/* Wait for the pull-up to be stable on high */

	usleep_range(COLI_PULLUP_MIN_DELAY_US, COLI_PULLUP_MAX_DELAY_US);

}

/*

 * 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 = private;

	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

			 * the 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);

		}

		usleep_range(COLI_PULLUP_MIN_DELAY_US,

			     COLI_PULLUP_MAX_DELAY_US);

	}

	/* Report no more touch, re-enable 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);

	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);

	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;

	touchdev->stop_touchscreen = true;

	/* Make sure IRQ is not running past close */

	mb();

	synchronize_irq(touchdev->pen_irq);

	gpiod_set_value(touchdev->gpio_ym, 0);

	pinctrl_pm_select_default_state(dev);

	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 iio_channel *channels = data;

	iio_channel_release_all(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;

	int num_adc_channels;

	int error;

	channels = iio_channel_get_all(dev);

	if (IS_ERR(channels))

		return PTR_ERR(channels);

	error = devm_add_action(dev, vf50_ts_channel_release, channels);

	if (error) {

		iio_channel_release_all(channels);

		dev_err(dev, "Failed to register iio channel release action");

		return error;

	}

	num_adc_channels = 0;

	while (channels[num_adc_channels].indio_dev)

		num_adc_channels++;

	if (num_adc_channels != COLI_TOUCH_REQ_ADC_CHAN) {

		dev_err(dev, "Inadequate ADC channels specified\n");

		return -EINVAL;

	}

	touchdev = devm_kzalloc(dev, sizeof(*touchdev), GFP_KERNEL);

	if (!touchdev)

		return -ENOMEM;

	touchdev->pdev = pdev;

	touchdev->channels = channels;

	error = of_property_read_u32(dev->of_node, "vf50-ts-min-pressure",

				 &touchdev->min_pressure);

	if (error)

		return error;

	input = devm_input_allocate_device(dev);

	if (!input) {

		dev_err(dev, "Failed to allocate TS input device\n");

		return -ENOMEM;

	}

	platform_set_drvdata(pdev, touchdev);

	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) {

		dev_err(dev, "Failed to request IRQ %d: %d\n",

			touchdev->pen_irq, error);

		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,

};

module_platform_driver(vf50_touch_driver);

MODULE_AUTHOR("Sanchayan Maity");

MODULE_DESCRIPTION("Colibri VF50 Touchscreen driver");

MODULE_LICENSE("GPL");

MODULE_VERSION(DRV_VERSION);