// SPDX-License-Identifier: GPL-2.0+
/*
 *      Driver for the MTX-1 Watchdog.
 *
 *      (C) Copyright 2005 4G Systems <info@4g-systems.biz>,
 *                                                      All Rights Reserved.
 *                              http://www.4g-systems.biz
 *
 *      (C) Copyright 2007 OpenWrt.org, Florian Fainelli <florian@openwrt.org>
 *      (c) Copyright 2005    4G Systems <info@4g-systems.biz>
 *
 *      Release 0.01.
 *      Author: Michael Stickel  michael.stickel@4g-systems.biz
 *
 *      Release 0.02.
 *      Author: Florian Fainelli florian@openwrt.org
 *              use the Linux watchdog/timer APIs
 *
 *      The Watchdog is configured to reset the MTX-1
 *      if it is not triggered for 100 seconds.
 *      It should not be triggered more often than 1.6 seconds.
 *
 *      A timer triggers the watchdog every 5 seconds, until
 *      it is opened for the first time. After the first open
 *      it MUST be triggered every 2..95 seconds.
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
#include <linux/ioport.h>
#include <linux/timer.h>
#include <linux/completion.h>
#include <linux/jiffies.h>
#include <linux/watchdog.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/uaccess.h>
#include <linux/gpio/consumer.h>

#define MTX1_WDT_INTERVAL       (5 * HZ)

static int ticks = 100 * HZ;

static struct {
        struct completion stop;
        spinlock_t lock;
        int running;
        struct timer_list timer;
        int queue;
        int default_ticks;
        unsigned long inuse;
        struct gpio_desc *gpiod;
        unsigned int gstate;
} mtx1_wdt_device;

static void mtx1_wdt_trigger(struct timer_list *unused)
{
        spin_lock(&mtx1_wdt_device.lock);
        if (mtx1_wdt_device.running)
                ticks--;

        /* toggle wdt gpio */
        mtx1_wdt_device.gstate = !mtx1_wdt_device.gstate;
        gpiod_set_value(mtx1_wdt_device.gpiod, mtx1_wdt_device.gstate);

        if (mtx1_wdt_device.queue && ticks)
                mod_timer(&mtx1_wdt_device.timer, jiffies + MTX1_WDT_INTERVAL);
        else
                complete(&mtx1_wdt_device.stop);
        spin_unlock(&mtx1_wdt_device.lock);
}

static void mtx1_wdt_reset(void)
{
        ticks = mtx1_wdt_device.default_ticks;
}


static void mtx1_wdt_start(void)
{
        unsigned long flags;

        spin_lock_irqsave(&mtx1_wdt_device.lock, flags);
        if (!mtx1_wdt_device.queue) {
                mtx1_wdt_device.queue = 1;
                mtx1_wdt_device.gstate = 1;
                gpiod_set_value(mtx1_wdt_device.gpiod, 1);
                mod_timer(&mtx1_wdt_device.timer, jiffies + MTX1_WDT_INTERVAL);
        }
        mtx1_wdt_device.running++;
        spin_unlock_irqrestore(&mtx1_wdt_device.lock, flags);
}

static int mtx1_wdt_stop(void)
{
        unsigned long flags;

        spin_lock_irqsave(&mtx1_wdt_device.lock, flags);
        if (mtx1_wdt_device.queue) {
                mtx1_wdt_device.queue = 0;
                mtx1_wdt_device.gstate = 0;
                gpiod_set_value(mtx1_wdt_device.gpiod, 0);
        }
        ticks = mtx1_wdt_device.default_ticks;
        spin_unlock_irqrestore(&mtx1_wdt_device.lock, flags);
        return 0;
}

/* Filesystem functions */

static int mtx1_wdt_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(0, &mtx1_wdt_device.inuse))
                return -EBUSY;
        return stream_open(inode, file);
}


static int mtx1_wdt_release(struct inode *inode, struct file *file)
{
        clear_bit(0, &mtx1_wdt_device.inuse);
        return 0;
}

static long mtx1_wdt_ioctl(struct file *file, unsigned int cmd,
                                                        unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        int __user *p = (int __user *)argp;
        unsigned int value;
        static const struct watchdog_info ident = {
                .options = WDIOF_CARDRESET,
                .identity = "MTX-1 WDT",
        };

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                if (copy_to_user(argp, &ident, sizeof(ident)))
                        return -EFAULT;
                break;
        case WDIOC_GETSTATUS:
        case WDIOC_GETBOOTSTATUS:
                put_user(0, p);
                break;
        case WDIOC_SETOPTIONS:
                if (get_user(value, p))
                        return -EFAULT;
                if (value & WDIOS_ENABLECARD)
                        mtx1_wdt_start();
                else if (value & WDIOS_DISABLECARD)
                        mtx1_wdt_stop();
                else
                        return -EINVAL;
                return 0;
        case WDIOC_KEEPALIVE:
                mtx1_wdt_reset();
                break;
        default:
                return -ENOTTY;
        }
        return 0;
}


static ssize_t mtx1_wdt_write(struct file *file, const char *buf,
                                                size_t count, loff_t *ppos)
{
        if (!count)
                return -EIO;
        mtx1_wdt_reset();
        return count;
}

static const struct file_operations mtx1_wdt_fops = {
        .owner          = THIS_MODULE,
        .unlocked_ioctl = mtx1_wdt_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = mtx1_wdt_open,
        .write          = mtx1_wdt_write,
        .release        = mtx1_wdt_release,
};


static struct miscdevice mtx1_wdt_misc = {
        .minor  = WATCHDOG_MINOR,
        .name   = "watchdog",
        .fops   = &mtx1_wdt_fops,
};


static int mtx1_wdt_probe(struct platform_device *pdev)
{
        int ret;

        mtx1_wdt_device.gpiod = devm_gpiod_get(&pdev->dev,
                                               NULL, GPIOD_OUT_HIGH);
        if (IS_ERR(mtx1_wdt_device.gpiod)) {
                dev_err(&pdev->dev, "failed to request gpio");
                return PTR_ERR(mtx1_wdt_device.gpiod);
        }

        spin_lock_init(&mtx1_wdt_device.lock);
        init_completion(&mtx1_wdt_device.stop);
        mtx1_wdt_device.queue = 0;
        clear_bit(0, &mtx1_wdt_device.inuse);
        timer_setup(&mtx1_wdt_device.timer, mtx1_wdt_trigger, 0);
        mtx1_wdt_device.default_ticks = ticks;

        ret = misc_register(&mtx1_wdt_misc);
        if (ret < 0) {
                dev_err(&pdev->dev, "failed to register\n");
                return ret;
        }
        mtx1_wdt_start();
        dev_info(&pdev->dev, "MTX-1 Watchdog driver\n");
        return 0;
}

static void mtx1_wdt_remove(struct platform_device *pdev)
{
        /* FIXME: do we need to lock this test ? */
        if (mtx1_wdt_device.queue) {
                mtx1_wdt_device.queue = 0;
                wait_for_completion(&mtx1_wdt_device.stop);
        }

        misc_deregister(&mtx1_wdt_misc);
}

static struct platform_driver mtx1_wdt_driver = {
        .probe = mtx1_wdt_probe,
        .remove = mtx1_wdt_remove,
        .driver.name = "mtx1-wdt",
};

module_platform_driver(mtx1_wdt_driver);

MODULE_AUTHOR("Michael Stickel, Florian Fainelli");
MODULE_DESCRIPTION("Driver for the MTX-1 watchdog");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:mtx1-wdt");