// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * pps-gpio.c -- PPS client driver using GPIO
 *
 * Copyright (C) 2010 Ricardo Martins <rasm@fe.up.pt>
 * Copyright (C) 2011 James Nuss <jamesnuss@nanometrics.ca>
 */

#define PPS_GPIO_NAME "pps-gpio"
#define pr_fmt(fmt) PPS_GPIO_NAME ": " fmt

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/pps_kernel.h>
#include <linux/gpio/consumer.h>
#include <linux/list.h>
#include <linux/property.h>
#include <linux/timer.h>
#include <linux/jiffies.h>

/* Info for each registered platform device */
struct pps_gpio_device_data {
        int irq;                        /* IRQ used as PPS source */
        struct pps_device *pps;         /* PPS source device */
        struct pps_source_info info;    /* PPS source information */
        struct gpio_desc *gpio_pin;     /* GPIO port descriptors */
        struct gpio_desc *echo_pin;
        struct timer_list echo_timer;   /* timer to reset echo active state */
        bool assert_falling_edge;
        bool capture_clear;
        unsigned int echo_active_ms;    /* PPS echo active duration */
        unsigned long echo_timeout;     /* timer timeout value in jiffies */
};

/*
 * Report the PPS event
 */

static irqreturn_t pps_gpio_irq_handler(int irq, void *data)
{
        const struct pps_gpio_device_data *info;
        struct pps_event_time ts;
        int rising_edge;

        /* Get the time stamp first */
        pps_get_ts(&ts);

        info = data;

        /* Small trick to bypass the check on edge's direction when capture_clear is unset */
        rising_edge = info->capture_clear ?
                      gpiod_get_value(info->gpio_pin) : !info->assert_falling_edge;
        if ((rising_edge && !info->assert_falling_edge) ||
                        (!rising_edge && info->assert_falling_edge))
                pps_event(info->pps, &ts, PPS_CAPTUREASSERT, data);
        else if (info->capture_clear &&
                        ((rising_edge && info->assert_falling_edge) ||
                        (!rising_edge && !info->assert_falling_edge)))
                pps_event(info->pps, &ts, PPS_CAPTURECLEAR, data);
        else
                dev_warn_ratelimited(&info->pps->dev, "IRQ did not trigger any PPS event\n");

        return IRQ_HANDLED;
}

/* This function will only be called when an ECHO GPIO is defined */
static void pps_gpio_echo(struct pps_device *pps, int event, void *data)
{
        /* add_timer() needs to write into info->echo_timer */
        struct pps_gpio_device_data *info = data;

        switch (event) {
        case PPS_CAPTUREASSERT:
                if (pps->params.mode & PPS_ECHOASSERT)
                        gpiod_set_value(info->echo_pin, 1);
                break;

        case PPS_CAPTURECLEAR:
                if (pps->params.mode & PPS_ECHOCLEAR)
                        gpiod_set_value(info->echo_pin, 1);
                break;
        }

        /* fire the timer */
        if (info->pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) {
                info->echo_timer.expires = jiffies + info->echo_timeout;
                add_timer(&info->echo_timer);
        }
}

/* Timer callback to reset the echo pin to the inactive state */
static void pps_gpio_echo_timer_callback(struct timer_list *t)
{
        const struct pps_gpio_device_data *info;

        info = timer_container_of(info, t, echo_timer);

        gpiod_set_value(info->echo_pin, 0);
}

static int pps_gpio_setup(struct device *dev)
{
        struct pps_gpio_device_data *data = dev_get_drvdata(dev);
        int ret;
        u32 value;

        data->gpio_pin = devm_gpiod_get(dev, NULL, GPIOD_IN);
        if (IS_ERR(data->gpio_pin))
                return dev_err_probe(dev, PTR_ERR(data->gpio_pin),
                                     "failed to request PPS GPIO\n");

        data->assert_falling_edge =
                device_property_read_bool(dev, "assert-falling-edge");

        data->echo_pin = devm_gpiod_get_optional(dev, "echo", GPIOD_OUT_LOW);
        if (IS_ERR(data->echo_pin))
                return dev_err_probe(dev, PTR_ERR(data->echo_pin),
                                     "failed to request ECHO GPIO\n");

        if (!data->echo_pin)
                return 0;

        ret = device_property_read_u32(dev, "echo-active-ms", &value);
        if (ret) {
                dev_err(dev, "failed to get echo-active-ms from FW\n");
                return ret;
        }

        /* sanity check on echo_active_ms */
        if (!value || value > 999) {
                dev_err(dev, "echo-active-ms: %u - bad value from FW\n", value);
                return -EINVAL;
        }

        data->echo_active_ms = value;

        return 0;
}

static unsigned long
get_irqf_trigger_flags(const struct pps_gpio_device_data *data)
{
        unsigned long flags = data->assert_falling_edge ?
                IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;

        if (data->capture_clear) {
                flags |= ((flags & IRQF_TRIGGER_RISING) ?
                                IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING);
        }

        return flags;
}

static int pps_gpio_probe(struct platform_device *pdev)
{
        struct pps_gpio_device_data *data;
        struct device *dev = &pdev->dev;
        int ret;
        int pps_default_params;

        /* allocate space for device info */
        data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        dev_set_drvdata(dev, data);

        /* GPIO setup */
        ret = pps_gpio_setup(dev);
        if (ret)
                return ret;

        /* IRQ setup */
        ret = gpiod_to_irq(data->gpio_pin);
        if (ret < 0) {
                dev_err(dev, "failed to map GPIO to IRQ: %d\n", ret);
                return -EINVAL;
        }
        data->irq = ret;

        /* initialize PPS specific parts of the bookkeeping data structure. */
        data->info.mode = PPS_CAPTUREASSERT | PPS_OFFSETASSERT |
                PPS_ECHOASSERT | PPS_CANWAIT | PPS_TSFMT_TSPEC;
        if (data->capture_clear)
                data->info.mode |= PPS_CAPTURECLEAR | PPS_OFFSETCLEAR |
                        PPS_ECHOCLEAR;
        data->info.owner = THIS_MODULE;
        snprintf(data->info.name, PPS_MAX_NAME_LEN - 1, "%s.%d",
                 pdev->name, pdev->id);
        if (data->echo_pin) {
                data->info.echo = pps_gpio_echo;
                data->echo_timeout = msecs_to_jiffies(data->echo_active_ms);
                timer_setup(&data->echo_timer, pps_gpio_echo_timer_callback, 0);
        }

        /* register PPS source */
        pps_default_params = PPS_CAPTUREASSERT | PPS_OFFSETASSERT;
        if (data->capture_clear)
                pps_default_params |= PPS_CAPTURECLEAR | PPS_OFFSETCLEAR;
        data->pps = pps_register_source(&data->info, pps_default_params);
        if (IS_ERR(data->pps)) {
                dev_err(dev, "failed to register IRQ %d as PPS source\n",
                        data->irq);
                return PTR_ERR(data->pps);
        }

        /* register IRQ interrupt handler */
        ret = request_irq(data->irq, pps_gpio_irq_handler,
                          get_irqf_trigger_flags(data), data->info.name, data);
        if (ret) {
                pps_unregister_source(data->pps);
                dev_err(dev, "failed to acquire IRQ %d\n", data->irq);
                return -EINVAL;
        }

        dev_dbg(&data->pps->dev, "Registered IRQ %d as PPS source\n",
                data->irq);

        return 0;
}

static void pps_gpio_remove(struct platform_device *pdev)
{
        struct pps_gpio_device_data *data = platform_get_drvdata(pdev);

        free_irq(data->irq, data);
        pps_unregister_source(data->pps);
        timer_delete_sync(&data->echo_timer);
        /* reset echo pin in any case */
        gpiod_set_value(data->echo_pin, 0);
        dev_info(&pdev->dev, "removed IRQ %d as PPS source\n", data->irq);
}

static const struct of_device_id pps_gpio_dt_ids[] = {
        { .compatible = "pps-gpio", },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, pps_gpio_dt_ids);

static struct platform_driver pps_gpio_driver = {
        .probe          = pps_gpio_probe,
        .remove         = pps_gpio_remove,
        .driver         = {
                .name   = PPS_GPIO_NAME,
                .of_match_table = pps_gpio_dt_ids,
        },
};

module_platform_driver(pps_gpio_driver);
MODULE_AUTHOR("Ricardo Martins <rasm@fe.up.pt>");
MODULE_AUTHOR("James Nuss <jamesnuss@nanometrics.ca>");
MODULE_DESCRIPTION("Use GPIO pin as PPS source");
MODULE_LICENSE("GPL");
MODULE_VERSION("1.2.0");