sbc60xxwdt.c

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/*
 *  60xx Single Board Computer Watchdog Timer driver for Linux 2.2.x
 *
 *  Based on acquirewdt.c by Alan Cox.
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 *
 *  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 <[email protected]>
 *
 *           12/4 - 2000      [Initial revision]
 *           25/4 - 2000      Added /dev/watchdog support
 *           09/5 - 2001      [[email protected]] fixed fop_write to "return 1"
 *                  on success
 *           12/4 - 2002      [[email protected]] 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      [[email protected]] 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(unsigned long);
static DEFINE_TIMER(timer, wdt_timer_ping, 0, 0);
static unsigned long next_heartbeat;
static unsigned long wdt_is_open;
static char wdt_expect_close;

/*
 *  Whack the dog
 */

static void wdt_timer_ping(unsigned long data)
{
    /* 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 */
    del_timer(&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 nonseekable_open(inode, file);
}

static int fop_close(struct inode *inode, struct file *file)
{
    if (wdt_expect_close == 42)
        wdt_turnoff();
    else {
        del_timer(&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();
        /* Fall through */
    }
    case WDIOC_GETTIMEOUT:
        return put_user(timeout, p);
    default:
        return -ENOTTY;
    }
}

static const struct file_operations wdt_fops = {
    .owner      = THIS_MODULE,
    .llseek     = no_llseek,
    .write      = fop_write,
    .open       = fop_open,
    .release    = fop_close,
    .unlocked_ioctl = fop_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 <[email protected]>");
MODULE_DESCRIPTION("60xx Single Board Computer Watchdog Timer driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);