// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Toradex Colibri VF50 Touchscreen driver
 *
 * Copyright 2015 Toradex AG
 *
 * Originally authored by Stefan Agner for 3.0 kernel
 */

#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/of.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 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;
        }

        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");