// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      60xx Single Board Computer Watchdog Timer driver for Linux 2.2.x
 *
 *      Based on acquirewdt.c by Alan Cox.
 *
 *      The author does 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 2000    Jakob Oestergaard <jakob@unthought.net>
 *
 *           12/4 - 2000      [Initial revision]
 *           25/4 - 2000      Added /dev/watchdog support
 *           09/5 - 2001      [smj@oro.net] fixed fop_write to "return 1"
 *                                      on success
 *           12/4 - 2002      [rob@osinvestor.com] eliminate fop_read
 *                            fix possible wdt_is_open race
 *                            add CONFIG_WATCHDOG_NOWAYOUT support
 *                            remove lock_kernel/unlock_kernel pairs
 *                            added KERN_* to printk's
 *                            got rid of extraneous comments
 *                            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
 *                            use module_param
 *                            made timeout (the emulated heartbeat) a
 *                            module_param
 *                            made the keepalive ping an internal subroutine
 *                            made wdt_stop and wdt_start module params
 *                            added extra printk's for startup problems
 *                            added MODULE_AUTHOR and MODULE_DESCRIPTION info
 *
 *  This WDT driver is different from the other Linux WDT
 *  drivers in the following ways:
 *  *)  The driver will ping the watchdog by itself, because this
 *      particular WDT has a very short timeout (one second) 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 "sbc60xxwdt"
#define PFX OUR_NAME ": "

/*
 * You must set these - The driver cannot probe for the settings
 */

static int wdt_stop = 0x45;
module_param(wdt_stop, int, 0);
MODULE_PARM_DESC(wdt_stop, "SBC60xx WDT 'stop' io port (default 0x45)");

static int wdt_start = 0x443;
module_param(wdt_start, int, 0);
MODULE_PARM_DESC(wdt_start, "SBC60xx WDT 'start' io port (default 0x443)");

/*
 * The 60xx board can use watchdog timeout values from one second
 * to several minutes.  The default is one second, so 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.
 * If the daemon pulses us every 25 seconds, we can still afford
 * a 5 second scheduling delay on the (high priority) daemon. That
 * should be sufficient for a box under any load.
 */

#define WATCHDOG_TIMEOUT 30             /* 30 sec default timeout */
static int timeout = WATCHDOG_TIMEOUT;  /* in seconds, multiplied by HZ to
                                           get seconds to wait for a ping */
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;

/*
 *      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 by reading from wdt_start */
                inb_p(wdt_start);
                /* Re-set the timer interval */
                mod_timer(&timer, jiffies + WDT_INTERVAL);
        } else
                pr_warn("Heartbeat lost! Will not ping the watchdog\n");
}

/*
 * Utility routines
 */

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

        /* Start the timer */
        mod_timer(&timer, jiffies + WDT_INTERVAL);
        pr_info("Watchdog timer is now enabled\n");
}

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

                /* Well, anyhow someone wrote to us, we should
                   return that favour */
                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;

        if (nowayout)
                __module_get(THIS_MODULE);

        /* 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 = "SBC60xx",
        };

        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 sbc60xxwdt_unload(void)
{
        wdt_turnoff();

        /* Deregister */
        misc_deregister(&wdt_miscdev);

        unregister_reboot_notifier(&wdt_notifier);
        if ((wdt_stop != 0x45) && (wdt_stop != wdt_start))
                release_region(wdt_stop, 1);
        release_region(wdt_start, 1);
}

static int __init sbc60xxwdt_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(wdt_start, 1, "SBC 60XX WDT")) {
                pr_err("I/O address 0x%04x already in use\n", wdt_start);
                rc = -EIO;
                goto err_out;
        }

        /* We cannot reserve 0x45 - the kernel already has! */
        if (wdt_stop != 0x45 && wdt_stop != wdt_start) {
                if (!request_region(wdt_stop, 1, "SBC 60XX WDT")) {
                        pr_err("I/O address 0x%04x already in use\n", wdt_stop);
                        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 60XX single board computer initialised. timeout=%d sec (nowayout=%d)\n",
                timeout, nowayout);

        return 0;

err_out_reboot:
        unregister_reboot_notifier(&wdt_notifier);
err_out_region2:
        if (wdt_stop != 0x45 && wdt_stop != wdt_start)
                release_region(wdt_stop, 1);
err_out_region1:
        release_region(wdt_start, 1);
err_out:
        return rc;
}

module_init(sbc60xxwdt_init);
module_exit(sbc60xxwdt_unload);

MODULE_AUTHOR("Jakob Oestergaard <jakob@unthought.net>");
MODULE_DESCRIPTION("60xx Single Board Computer Watchdog Timer driver");
MODULE_LICENSE("GPL");