// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * PING: ultrasonic sensor for distance measuring by using only one GPIOs
 *
 * Copyright (c) 2019 Andreas Klinger <ak@it-klinger.de>
 *
 * For details about the devices see:
 * http://parallax.com/sites/default/files/downloads/28041-LaserPING-2m-Rangefinder-Guide.pdf
 * http://parallax.com/sites/default/files/downloads/28015-PING-Documentation-v1.6.pdf
 *
 * the measurement cycle as timing diagram looks like:
 *
 * GPIO      ___              ________________________
 * ping:  __/   \____________/                        \________________
 *          ^   ^            ^                        ^
 *          |<->|            interrupt                interrupt
 *         udelay(5)         (ts_rising)              (ts_falling)
 *                           |<---------------------->|
 *                           .  pulse time measured   .
 *                           .  --> one round trip of ultra sonic waves
 * ultra                     .                        .
 * sonic            _   _   _.                        .
 * burst: _________/ \_/ \_/ \_________________________________________
 *                                                    .
 * ultra                                              .
 * sonic                                     _   _   _.
 * echo:  __________________________________/ \_/ \_/ \________________
 */
#include <linux/err.h>
#include <linux/gpio/consumer.h>
#include <linux/kernel.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>

struct ping_cfg {
        unsigned long   trigger_pulse_us;       /* length of trigger pulse */
        int             laserping_error;        /* support error code in */
                                                /*   pulse width of laser */
                                                /*   ping sensors */
        s64             timeout_ns;             /* timeout in ns */
};

struct ping_data {
        struct device           *dev;
        struct gpio_desc        *gpiod_ping;
        struct mutex            lock;
        int                     irqnr;
        ktime_t                 ts_rising;
        ktime_t                 ts_falling;
        struct completion       rising;
        struct completion       falling;
        const struct ping_cfg   *cfg;
};

static const struct ping_cfg pa_ping_cfg = {
        .trigger_pulse_us       = 5,
        .laserping_error        = 0,
        .timeout_ns             = 18500000,     /* 3 meters */
};

static const struct ping_cfg pa_laser_ping_cfg = {
        .trigger_pulse_us       = 5,
        .laserping_error        = 1,
        .timeout_ns             = 15500000,     /* 2 meters plus error codes */
};

static irqreturn_t ping_handle_irq(int irq, void *dev_id)
{
        struct iio_dev *indio_dev = dev_id;
        struct ping_data *data = iio_priv(indio_dev);
        ktime_t now = ktime_get();

        if (gpiod_get_value(data->gpiod_ping)) {
                data->ts_rising = now;
                complete(&data->rising);
        } else {
                data->ts_falling = now;
                complete(&data->falling);
        }

        return IRQ_HANDLED;
}

static int ping_read(struct iio_dev *indio_dev)
{
        struct ping_data *data = iio_priv(indio_dev);
        int ret;
        ktime_t ktime_dt;
        s64 dt_ns;
        u32 time_ns, distance_mm;
        struct platform_device *pdev = to_platform_device(data->dev);

        /*
         * just one read-echo-cycle can take place at a time
         * ==> lock against concurrent reading calls
         */
        mutex_lock(&data->lock);

        reinit_completion(&data->rising);
        reinit_completion(&data->falling);

        gpiod_set_value(data->gpiod_ping, 1);
        udelay(data->cfg->trigger_pulse_us);
        gpiod_set_value(data->gpiod_ping, 0);

        ret = gpiod_direction_input(data->gpiod_ping);
        if (ret < 0) {
                mutex_unlock(&data->lock);
                return ret;
        }

        data->irqnr = gpiod_to_irq(data->gpiod_ping);
        if (data->irqnr < 0) {
                dev_err(data->dev, "gpiod_to_irq: %d\n", data->irqnr);
                mutex_unlock(&data->lock);
                return data->irqnr;
        }

        ret = request_irq(data->irqnr, ping_handle_irq,
                                IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
                                                        pdev->name, indio_dev);
        if (ret < 0) {
                dev_err(data->dev, "request_irq: %d\n", ret);
                mutex_unlock(&data->lock);
                return ret;
        }

        /* it should not take more than 20 ms until echo is rising */
        ret = wait_for_completion_killable_timeout(&data->rising, HZ/50);
        if (ret < 0)
                goto err_reset_direction;
        else if (ret == 0) {
                ret = -ETIMEDOUT;
                goto err_reset_direction;
        }

        /* it cannot take more than 50 ms until echo is falling */
        ret = wait_for_completion_killable_timeout(&data->falling, HZ/20);
        if (ret < 0)
                goto err_reset_direction;
        else if (ret == 0) {
                ret = -ETIMEDOUT;
                goto err_reset_direction;
        }

        ktime_dt = ktime_sub(data->ts_falling, data->ts_rising);

        free_irq(data->irqnr, indio_dev);

        ret = gpiod_direction_output(data->gpiod_ping, GPIOD_OUT_LOW);
        if (ret < 0) {
                mutex_unlock(&data->lock);
                return ret;
        }

        mutex_unlock(&data->lock);

        dt_ns = ktime_to_ns(ktime_dt);
        if (dt_ns > data->cfg->timeout_ns) {
                dev_dbg(data->dev, "distance out of range: dt=%lldns\n",
                                                                dt_ns);
                return -EIO;
        }

        time_ns = dt_ns;

        /*
         * read error code of laser ping sensor and give users chance to
         * figure out error by using dynamic debugging
         */
        if (data->cfg->laserping_error) {
                if ((time_ns > 12500000) && (time_ns <= 13500000)) {
                        dev_dbg(data->dev, "target too close or to far\n");
                        return -EIO;
                }
                if ((time_ns > 13500000) && (time_ns <= 14500000)) {
                        dev_dbg(data->dev, "internal sensor error\n");
                        return -EIO;
                }
                if ((time_ns > 14500000) && (time_ns <= 15500000)) {
                        dev_dbg(data->dev, "internal sensor timeout\n");
                        return -EIO;
                }
        }

        /*
         * the speed as function of the temperature is approximately:
         *
         * speed = 331,5 + 0,6 * Temp
         *   with Temp in °C
         *   and speed in m/s
         *
         * use 343,5 m/s as ultrasonic speed at 20 °C here in absence of the
         * temperature
         *
         * therefore:
         *             time     343,5     time * 232
         * distance = ------ * ------- = ------------
         *             10^6         2        1350800
         *   with time in ns
         *   and distance in mm (one way)
         *
         * because we limit to 3 meters the multiplication with 232 just
         * fits into 32 bit
         */
        distance_mm = time_ns * 232 / 1350800;

        return distance_mm;

err_reset_direction:
        free_irq(data->irqnr, indio_dev);
        mutex_unlock(&data->lock);

        if (gpiod_direction_output(data->gpiod_ping, GPIOD_OUT_LOW))
                dev_dbg(data->dev, "error in gpiod_direction_output\n");
        return ret;
}

static int ping_read_raw(struct iio_dev *indio_dev,
                            struct iio_chan_spec const *channel, int *val,
                            int *val2, long info)
{
        int ret;

        if (channel->type != IIO_DISTANCE)
                return -EINVAL;

        switch (info) {
        case IIO_CHAN_INFO_RAW:
                ret = ping_read(indio_dev);
                if (ret < 0)
                        return ret;
                *val = ret;
                return IIO_VAL_INT;
        case IIO_CHAN_INFO_SCALE:
                /*
                 * maximum resolution in datasheet is 1 mm
                 * 1 LSB is 1 mm
                 */
                *val = 0;
                *val2 = 1000;
                return IIO_VAL_INT_PLUS_MICRO;
        default:
                return -EINVAL;
        }
}

static const struct iio_info ping_iio_info = {
        .read_raw               = ping_read_raw,
};

static const struct iio_chan_spec ping_chan_spec[] = {
        {
                .type = IIO_DISTANCE,
                .info_mask_separate =
                                BIT(IIO_CHAN_INFO_RAW) |
                                BIT(IIO_CHAN_INFO_SCALE),
        },
};

static const struct of_device_id of_ping_match[] = {
        { .compatible = "parallax,ping", .data = &pa_ping_cfg },
        { .compatible = "parallax,laserping", .data = &pa_laser_ping_cfg },
        { }
};

MODULE_DEVICE_TABLE(of, of_ping_match);

static int ping_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct ping_data *data;
        struct iio_dev *indio_dev;

        indio_dev = devm_iio_device_alloc(dev, sizeof(struct ping_data));
        if (!indio_dev)
                return -ENOMEM;

        data = iio_priv(indio_dev);
        data->dev = dev;
        data->cfg = device_get_match_data(dev);

        mutex_init(&data->lock);
        init_completion(&data->rising);
        init_completion(&data->falling);

        data->gpiod_ping = devm_gpiod_get(dev, "ping", GPIOD_OUT_LOW);
        if (IS_ERR(data->gpiod_ping)) {
                dev_err(dev, "failed to get ping-gpios: err=%ld\n",
                                                PTR_ERR(data->gpiod_ping));
                return PTR_ERR(data->gpiod_ping);
        }

        if (gpiod_cansleep(data->gpiod_ping)) {
                dev_err(data->dev, "cansleep-GPIOs not supported\n");
                return -ENODEV;
        }

        platform_set_drvdata(pdev, indio_dev);

        indio_dev->name = "ping";
        indio_dev->info = &ping_iio_info;
        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->channels = ping_chan_spec;
        indio_dev->num_channels = ARRAY_SIZE(ping_chan_spec);

        return devm_iio_device_register(dev, indio_dev);
}

static struct platform_driver ping_driver = {
        .probe          = ping_probe,
        .driver         = {
                .name           = "ping-gpio",
                .of_match_table = of_ping_match,
        },
};

module_platform_driver(ping_driver);

MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");
MODULE_DESCRIPTION("PING sensors for distance measuring using one GPIOs");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:ping");