// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      W83877F Computer Watchdog Timer driver
 *
 *      Based on acquirewdt.c by Alan Cox,
 *           and sbc60xxwdt.c by Jakob Oestergaard <jakob@unthought.net>
 *
 *      The authors do NOT admit liability nor provide warranty for
 *      any of this software. This material is provided "AS-IS" in
 *      the hope that it may be useful for others.
 *
 *      (c) Copyright 2001    Scott Jennings <linuxdrivers@oro.net>
 *
 *           4/19 - 2001      [Initial revision]
 *           9/27 - 2001      Added spinlocking
 *           4/12 - 2002      [rob@osinvestor.com] Eliminate extra comments
 *                            Eliminate fop_read
 *                            Eliminate extra spin_unlock
 *                            Added KERN_* tags to printks
 *                            add CONFIG_WATCHDOG_NOWAYOUT support
 *                            fix possible wdt_is_open race
 *                            changed watchdog_info to correctly reflect what
 *                            the driver offers
 *                            added WDIOC_GETSTATUS, WDIOC_GETBOOTSTATUS,
 *                            WDIOC_SETTIMEOUT,
 *                            WDIOC_GETTIMEOUT, and WDIOC_SETOPTIONS ioctls
 *           09/8 - 2003      [wim@iguana.be] cleanup of trailing spaces
 *                            added extra printk's for startup problems
 *                            use module_param
 *                            made timeout (the emulated heartbeat) a
 *                            module_param
 *                            made the keepalive ping an internal subroutine
 *
 *  This WDT driver is different from most other Linux WDT
 *  drivers in that the driver will ping the watchdog by itself,
 *  because this particular WDT has a very short timeout (1.6
 *  seconds) and it would be insane to count on any userspace
 *  daemon always getting scheduled within that time frame.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/jiffies.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/ioport.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/uaccess.h>

#define OUR_NAME "w83877f_wdt"

#define ENABLE_W83877F_PORT 0x3F0
#define ENABLE_W83877F 0x87
#define DISABLE_W83877F 0xAA
#define WDT_PING 0x443
#define WDT_REGISTER 0x14
#define WDT_ENABLE 0x9C
#define WDT_DISABLE 0x8C

/*
 * The W83877F seems to be fixed at 1.6s timeout (at least on the
 * EMACS PC-104 board I'm using). If we reset the watchdog every
 * ~250ms we should be safe.  */

#define WDT_INTERVAL (HZ/4+1)

/*
 * We must not require too good response from the userspace daemon.
 * Here we require the userspace daemon to send us a heartbeat
 * char to /dev/watchdog every 30 seconds.
 */

#define WATCHDOG_TIMEOUT 30            /* 30 sec default timeout */
/* in seconds, will be multiplied by HZ to get seconds to wait for a ping */
static int timeout = WATCHDOG_TIMEOUT;
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
        "Watchdog timeout in seconds. (1<=timeout<=3600, default="
                                __MODULE_STRING(WATCHDOG_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 wdt_timer_ping(struct timer_list *);
static DEFINE_TIMER(timer, wdt_timer_ping);
static unsigned long next_heartbeat;
static unsigned long wdt_is_open;
static char wdt_expect_close;
static DEFINE_SPINLOCK(wdt_spinlock);

/*
 *      Whack the dog
 */

static void wdt_timer_ping(struct timer_list *unused)
{
        /* If we got a heartbeat pulse within the WDT_US_INTERVAL
         * we agree to ping the WDT
         */
        if (time_before(jiffies, next_heartbeat)) {
                /* Ping the WDT */
                spin_lock(&wdt_spinlock);

                /* Ping the WDT by reading from WDT_PING */
                inb_p(WDT_PING);

                /* Re-set the timer interval */
                mod_timer(&timer, jiffies + WDT_INTERVAL);

                spin_unlock(&wdt_spinlock);

        } else
                pr_warn("Heartbeat lost! Will not ping the watchdog\n");
}

/*
 * Utility routines
 */

static void wdt_change(int writeval)
{
        unsigned long flags;
        spin_lock_irqsave(&wdt_spinlock, flags);

        /* buy some time */
        inb_p(WDT_PING);

        /* make W83877F available */
        outb_p(ENABLE_W83877F,  ENABLE_W83877F_PORT);
        outb_p(ENABLE_W83877F,  ENABLE_W83877F_PORT);

        /* enable watchdog */
        outb_p(WDT_REGISTER,    ENABLE_W83877F_PORT);
        outb_p(writeval,        ENABLE_W83877F_PORT+1);

        /* lock the W8387FF away */
        outb_p(DISABLE_W83877F, ENABLE_W83877F_PORT);

        spin_unlock_irqrestore(&wdt_spinlock, flags);
}

static void wdt_startup(void)
{
        next_heartbeat = jiffies + (timeout * HZ);

        /* Start the timer */
        mod_timer(&timer, jiffies + WDT_INTERVAL);

        wdt_change(WDT_ENABLE);

        pr_info("Watchdog timer is now enabled\n");
}

static void wdt_turnoff(void)
{
        /* Stop the timer */
        timer_delete_sync(&timer);

        wdt_change(WDT_DISABLE);

        pr_info("Watchdog timer is now disabled...\n");
}

static void wdt_keepalive(void)
{
        /* user land ping */
        next_heartbeat = jiffies + (timeout * HZ);
}

/*
 * /dev/watchdog handling
 */

static ssize_t fop_write(struct file *file, const char __user *buf,
                                                size_t count, loff_t *ppos)
{
        /* See if we got the magic character 'V' and reload the timer */
        if (count) {
                if (!nowayout) {
                        size_t ofs;

                        /* note: just in case someone wrote the magic
                           character five months ago... */
                        wdt_expect_close = 0;

                        /* scan to see whether or not we got the
                           magic character */
                        for (ofs = 0; ofs != count; ofs++) {
                                char c;
                                if (get_user(c, buf + ofs))
                                        return -EFAULT;
                                if (c == 'V')
                                        wdt_expect_close = 42;
                        }
                }

                /* someone wrote to us, we should restart timer */
                wdt_keepalive();
        }
        return count;
}

static int fop_open(struct inode *inode, struct file *file)
{
        /* Just in case we're already talking to someone... */
        if (test_and_set_bit(0, &wdt_is_open))
                return -EBUSY;

        /* Good, fire up the show */
        wdt_startup();
        return stream_open(inode, file);
}

static int fop_close(struct inode *inode, struct file *file)
{
        if (wdt_expect_close == 42)
                wdt_turnoff();
        else {
                timer_delete(&timer);
                pr_crit("device file closed unexpectedly. Will not stop the WDT!\n");
        }
        clear_bit(0, &wdt_is_open);
        wdt_expect_close = 0;
        return 0;
}

static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        int __user *p = argp;
        static const struct watchdog_info ident = {
                .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT
                                                        | WDIOF_MAGICCLOSE,
                .firmware_version = 1,
                .identity = "W83877F",
        };

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
        case WDIOC_GETSTATUS:
        case WDIOC_GETBOOTSTATUS:
                return put_user(0, p);
        case WDIOC_SETOPTIONS:
        {
                int new_options, retval = -EINVAL;

                if (get_user(new_options, p))
                        return -EFAULT;

                if (new_options & WDIOS_DISABLECARD) {
                        wdt_turnoff();
                        retval = 0;
                }

                if (new_options & WDIOS_ENABLECARD) {
                        wdt_startup();
                        retval = 0;
                }

                return retval;
        }
        case WDIOC_KEEPALIVE:
                wdt_keepalive();
                return 0;
        case WDIOC_SETTIMEOUT:
        {
                int new_timeout;

                if (get_user(new_timeout, p))
                        return -EFAULT;

                /* arbitrary upper limit */
                if (new_timeout < 1 || new_timeout > 3600)
                        return -EINVAL;

                timeout = new_timeout;
                wdt_keepalive();
        }
                fallthrough;
        case WDIOC_GETTIMEOUT:
                return put_user(timeout, p);
        default:
                return -ENOTTY;
        }
}

static const struct file_operations wdt_fops = {
        .owner          = THIS_MODULE,
        .write          = fop_write,
        .open           = fop_open,
        .release        = fop_close,
        .unlocked_ioctl = fop_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
};

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

/*
 *      Notifier for system down
 */

static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
        void *unused)
{
        if (code == SYS_DOWN || code == SYS_HALT)
                wdt_turnoff();
        return NOTIFY_DONE;
}

/*
 *      The WDT needs to learn about soft shutdowns in order to
 *      turn the timebomb registers off.
 */

static struct notifier_block wdt_notifier = {
        .notifier_call = wdt_notify_sys,
};

static void __exit w83877f_wdt_unload(void)
{
        wdt_turnoff();

        /* Deregister */
        misc_deregister(&wdt_miscdev);

        unregister_reboot_notifier(&wdt_notifier);
        release_region(WDT_PING, 1);
        release_region(ENABLE_W83877F_PORT, 2);
}

static int __init w83877f_wdt_init(void)
{
        int rc = -EBUSY;

        if (timeout < 1 || timeout > 3600) { /* arbitrary upper limit */
                timeout = WATCHDOG_TIMEOUT;
                pr_info("timeout value must be 1 <= x <= 3600, using %d\n",
                        timeout);
        }

        if (!request_region(ENABLE_W83877F_PORT, 2, "W83877F WDT")) {
                pr_err("I/O address 0x%04x already in use\n",
                       ENABLE_W83877F_PORT);
                rc = -EIO;
                goto err_out;
        }

        if (!request_region(WDT_PING, 1, "W8387FF WDT")) {
                pr_err("I/O address 0x%04x already in use\n", WDT_PING);
                rc = -EIO;
                goto err_out_region1;
        }

        rc = register_reboot_notifier(&wdt_notifier);
        if (rc) {
                pr_err("cannot register reboot notifier (err=%d)\n", rc);
                goto err_out_region2;
        }

        rc = misc_register(&wdt_miscdev);
        if (rc) {
                pr_err("cannot register miscdev on minor=%d (err=%d)\n",
                       wdt_miscdev.minor, rc);
                goto err_out_reboot;
        }

        pr_info("WDT driver for W83877F initialised. timeout=%d sec (nowayout=%d)\n",
                timeout, nowayout);

        return 0;

err_out_reboot:
        unregister_reboot_notifier(&wdt_notifier);
err_out_region2:
        release_region(WDT_PING, 1);
err_out_region1:
        release_region(ENABLE_W83877F_PORT, 2);
err_out:
        return rc;
}

module_init(w83877f_wdt_init);
module_exit(w83877f_wdt_unload);

MODULE_AUTHOR("Scott and Bill Jennings");
MODULE_DESCRIPTION("Driver for watchdog timer in w83877f chip");
MODULE_LICENSE("GPL");