indydog.c

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/*
 *  IndyDog 0.3 A Hardware Watchdog Device for SGI IP22
 *
 *  (c) Copyright 2002 Guido Guenther <[email protected]>,
 *                      All Rights Reserved.
 *
 *  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.
 *
 *  based on softdog.c by Alan Cox <[email protected]>
 */

#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)
{
    u32 mc_ctrl0;

    spin_lock(&indydog_lock);
    mc_ctrl0 = sgimc->cpuctrl0;
    mc_ctrl0 = sgimc->cpuctrl0 | SGIMC_CCTRL0_WDOG;
    sgimc->cpuctrl0 = mc_ctrl0;
    spin_unlock(&indydog_lock);
}

static void indydog_stop(void)
{
    u32 mc_ctrl0;

    spin_lock(&indydog_lock);

    mc_ctrl0 = sgimc->cpuctrl0;
    mc_ctrl0 &= ~SGIMC_CCTRL0_WDOG;
    sgimc->cpuctrl0 = mc_ctrl0;
    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 nonseekable_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,
    .llseek     = no_llseek,
    .write      = indydog_write,
    .unlocked_ioctl = indydog_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 <[email protected]>");
MODULE_DESCRIPTION("Hardware Watchdog Device for SGI IP22");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);