/*
 * 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);