// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      IndyDog 0.3     A Hardware Watchdog Device for SGI IP22
 *
 *      (c) Copyright 2002 Guido Guenther <agx@sigxcpu.org>,
 *                                              All Rights Reserved.
 *
 *      based on softdog.c by Alan Cox <alan@lxorguk.ukuu.org.uk>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/uaccess.h>
#include <asm/sgi/mc.h>

static unsigned long indydog_alive;
static DEFINE_SPINLOCK(indydog_lock);

#define WATCHDOG_TIMEOUT 30             /* 30 sec default timeout */

static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout,
                "Watchdog cannot be stopped once started (default="
                                __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

static void indydog_start(void)
{
        spin_lock(&indydog_lock);
        sgimc->cpuctrl0 |= SGIMC_CCTRL0_WDOG;
        spin_unlock(&indydog_lock);
}

static void indydog_stop(void)
{
        spin_lock(&indydog_lock);
        sgimc->cpuctrl0 &= ~SGIMC_CCTRL0_WDOG;
        spin_unlock(&indydog_lock);

        pr_info("Stopped watchdog timer\n");
}

static void indydog_ping(void)
{
        sgimc->watchdogt = 0;
}

/*
 *      Allow only one person to hold it open
 */
static int indydog_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(0, &indydog_alive))
                return -EBUSY;

        if (nowayout)
                __module_get(THIS_MODULE);

        /* Activate timer */
        indydog_start();
        indydog_ping();

        pr_info("Started watchdog timer\n");

        return stream_open(inode, file);
}

static int indydog_release(struct inode *inode, struct file *file)
{
        /* Shut off the timer.
         * Lock it in if it's a module and we defined ...NOWAYOUT */
        if (!nowayout)
                indydog_stop();         /* Turn the WDT off */
        clear_bit(0, &indydog_alive);
        return 0;
}

static ssize_t indydog_write(struct file *file, const char *data,
                                                size_t len, loff_t *ppos)
{
        /* Refresh the timer. */
        if (len)
                indydog_ping();
        return len;
}

static long indydog_ioctl(struct file *file, unsigned int cmd,
                                                        unsigned long arg)
{
        int options, retval = -EINVAL;
        static const struct watchdog_info ident = {
                .options                = WDIOF_KEEPALIVEPING,
                .firmware_version       = 0,
                .identity               = "Hardware Watchdog for SGI IP22",
        };

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                if (copy_to_user((struct watchdog_info *)arg,
                                 &ident, sizeof(ident)))
                        return -EFAULT;
                return 0;
        case WDIOC_GETSTATUS:
        case WDIOC_GETBOOTSTATUS:
                return put_user(0, (int *)arg);
        case WDIOC_SETOPTIONS:
        {
                if (get_user(options, (int *)arg))
                        return -EFAULT;
                if (options & WDIOS_DISABLECARD) {
                        indydog_stop();
                        retval = 0;
                }
                if (options & WDIOS_ENABLECARD) {
                        indydog_start();
                        retval = 0;
                }
                return retval;
        }
        case WDIOC_KEEPALIVE:
                indydog_ping();
                return 0;
        case WDIOC_GETTIMEOUT:
                return put_user(WATCHDOG_TIMEOUT, (int *)arg);
        default:
                return -ENOTTY;
        }
}

static int indydog_notify_sys(struct notifier_block *this,
                                        unsigned long code, void *unused)
{
        if (code == SYS_DOWN || code == SYS_HALT)
                indydog_stop();         /* Turn the WDT off */

        return NOTIFY_DONE;
}

static const struct file_operations indydog_fops = {
        .owner          = THIS_MODULE,
        .write          = indydog_write,
        .unlocked_ioctl = indydog_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = indydog_open,
        .release        = indydog_release,
};

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

static struct notifier_block indydog_notifier = {
        .notifier_call = indydog_notify_sys,
};

static int __init watchdog_init(void)
{
        int ret;

        ret = register_reboot_notifier(&indydog_notifier);
        if (ret) {
                pr_err("cannot register reboot notifier (err=%d)\n", ret);
                return ret;
        }

        ret = misc_register(&indydog_miscdev);
        if (ret) {
                pr_err("cannot register miscdev on minor=%d (err=%d)\n",
                       WATCHDOG_MINOR, ret);
                unregister_reboot_notifier(&indydog_notifier);
                return ret;
        }

        pr_info("Hardware Watchdog Timer for SGI IP22: 0.3\n");

        return 0;
}

static void __exit watchdog_exit(void)
{
        misc_deregister(&indydog_miscdev);
        unregister_reboot_notifier(&indydog_notifier);
}

module_init(watchdog_init);
module_exit(watchdog_exit);

MODULE_AUTHOR("Guido Guenther <agx@sigxcpu.org>");
MODULE_DESCRIPTION("Hardware Watchdog Device for SGI IP22");
MODULE_LICENSE("GPL");