machzwd.c

Go to the documentation of this file.

/*
 *  MachZ ZF-Logic Watchdog Timer driver for Linux
 *
 *
 *  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.
 *
 *  Author: Fernando Fuganti <[email protected]>
 *
 *  Based on sbc60xxwdt.c by Jakob Oestergaard
 *
 *
 *  We have two timers (wd#1, wd#2) driven by a 32 KHz clock with the
 *  following periods:
 *      wd#1 - 2 seconds;
 *      wd#2 - 7.2 ms;
 *  After the expiration of wd#1, it can generate a NMI, SCI, SMI, or
 *  a system RESET and it starts wd#2 that unconditionally will RESET
 *  the system when the counter reaches zero.
 *
 *  14-Dec-2001 Matt Domsch <[email protected]>
 *      Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
 */

#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>


/* ports */
#define ZF_IOBASE   0x218
#define INDEX       0x218
#define DATA_B      0x219
#define DATA_W      0x21A
#define DATA_D      0x21A

/* indexes */           /* size */
#define ZFL_VERSION 0x02    /* 16   */
#define CONTROL     0x10    /* 16   */
#define STATUS      0x12    /* 8    */
#define COUNTER_1   0x0C    /* 16   */
#define COUNTER_2   0x0E    /* 8    */
#define PULSE_LEN   0x0F    /* 8    */

/* controls */
#define ENABLE_WD1  0x0001
#define ENABLE_WD2  0x0002
#define RESET_WD1   0x0010
#define RESET_WD2   0x0020
#define GEN_SCI     0x0100
#define GEN_NMI     0x0200
#define GEN_SMI     0x0400
#define GEN_RESET   0x0800


/* utilities */

#define WD1 0
#define WD2 1

#define zf_writew(port, data)  { outb(port, INDEX); outw(data, DATA_W); }
#define zf_writeb(port, data)  { outb(port, INDEX); outb(data, DATA_B); }
#define zf_get_ZFL_version()   zf_readw(ZFL_VERSION)


static unsigned short zf_readw(unsigned char port)
{
    outb(port, INDEX);
    return inw(DATA_W);
}


MODULE_AUTHOR("Fernando Fuganti <[email protected]>");
MODULE_DESCRIPTION("MachZ ZF-Logic Watchdog driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);

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) ")");

#define PFX "machzwd"

static const struct watchdog_info zf_info = {
    .options        = WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
    .firmware_version   = 1,
    .identity       = "ZF-Logic watchdog",
};


/*
 * action refers to action taken when watchdog resets
 * 0 = GEN_RESET
 * 1 = GEN_SMI
 * 2 = GEN_NMI
 * 3 = GEN_SCI
 * defaults to GEN_RESET (0)
 */
static int action;
module_param(action, int, 0);
MODULE_PARM_DESC(action, "after watchdog resets, generate: "
                "0 = RESET(*)  1 = SMI  2 = NMI  3 = SCI");

static void zf_ping(unsigned long data);

static int zf_action = GEN_RESET;
static unsigned long zf_is_open;
static char zf_expect_close;
static DEFINE_SPINLOCK(zf_port_lock);
static DEFINE_TIMER(zf_timer, zf_ping, 0, 0);
static unsigned long next_heartbeat;


/* timeout for user land heart beat (10 seconds) */
#define ZF_USER_TIMEO (HZ*10)

/* timeout for hardware watchdog (~500ms) */
#define ZF_HW_TIMEO (HZ/2)

/* number of ticks on WD#1 (driven by a 32KHz clock, 2s) */
#define ZF_CTIMEOUT 0xffff

#ifndef ZF_DEBUG
#define dprintk(format, args...)
#else
#define dprintk(format, args...)                    \
    pr_debug(":%s:%d: " format, __func__, __LINE__ , ## args)
#endif


static inline void zf_set_status(unsigned char new)
{
    zf_writeb(STATUS, new);
}


/* CONTROL register functions */

static inline unsigned short zf_get_control(void)
{
    return zf_readw(CONTROL);
}

static inline void zf_set_control(unsigned short new)
{
    zf_writew(CONTROL, new);
}


/* WD#? counter functions */
/*
 *  Just set counter value
 */

static inline void zf_set_timer(unsigned short new, unsigned char n)
{
    switch (n) {
    case WD1:
        zf_writew(COUNTER_1, new);
    case WD2:
        zf_writeb(COUNTER_2, new > 0xff ? 0xff : new);
    default:
        return;
    }
}

/*
 * stop hardware timer
 */
static void zf_timer_off(void)
{
    unsigned int ctrl_reg = 0;
    unsigned long flags;

    /* stop internal ping */
    del_timer_sync(&zf_timer);

    spin_lock_irqsave(&zf_port_lock, flags);
    /* stop watchdog timer */
    ctrl_reg = zf_get_control();
    ctrl_reg |= (ENABLE_WD1|ENABLE_WD2);    /* disable wd1 and wd2 */
    ctrl_reg &= ~(ENABLE_WD1|ENABLE_WD2);
    zf_set_control(ctrl_reg);
    spin_unlock_irqrestore(&zf_port_lock, flags);

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


/*
 * start hardware timer
 */
static void zf_timer_on(void)
{
    unsigned int ctrl_reg = 0;
    unsigned long flags;

    spin_lock_irqsave(&zf_port_lock, flags);

    zf_writeb(PULSE_LEN, 0xff);

    zf_set_timer(ZF_CTIMEOUT, WD1);

    /* user land ping */
    next_heartbeat = jiffies + ZF_USER_TIMEO;

    /* start the timer for internal ping */
    mod_timer(&zf_timer, jiffies + ZF_HW_TIMEO);

    /* start watchdog timer */
    ctrl_reg = zf_get_control();
    ctrl_reg |= (ENABLE_WD1|zf_action);
    zf_set_control(ctrl_reg);
    spin_unlock_irqrestore(&zf_port_lock, flags);

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


static void zf_ping(unsigned long data)
{
    unsigned int ctrl_reg = 0;
    unsigned long flags;

    zf_writeb(COUNTER_2, 0xff);

    if (time_before(jiffies, next_heartbeat)) {
        dprintk("time_before: %ld\n", next_heartbeat - jiffies);
        /*
         * reset event is activated by transition from 0 to 1 on
         * RESET_WD1 bit and we assume that it is already zero...
         */

        spin_lock_irqsave(&zf_port_lock, flags);
        ctrl_reg = zf_get_control();
        ctrl_reg |= RESET_WD1;
        zf_set_control(ctrl_reg);

        /* ...and nothing changes until here */
        ctrl_reg &= ~(RESET_WD1);
        zf_set_control(ctrl_reg);
        spin_unlock_irqrestore(&zf_port_lock, flags);

        mod_timer(&zf_timer, jiffies + ZF_HW_TIMEO);
    } else
        pr_crit("I will reset your machine\n");
}

static ssize_t zf_write(struct file *file, const char __user *buf, size_t count,
                                loff_t *ppos)
{
    /* See if we got the magic character */
    if (count) {
        /*
         * no need to check for close confirmation
         * no way to disable watchdog ;)
         */
        if (!nowayout) {
            size_t ofs;
            /*
             * note: just in case someone wrote the magic character
             * five months ago...
             */
            zf_expect_close = 0;

            /* now scan */
            for (ofs = 0; ofs != count; ofs++) {
                char c;
                if (get_user(c, buf + ofs))
                    return -EFAULT;
                if (c == 'V') {
                    zf_expect_close = 42;
                    dprintk("zf_expect_close = 42\n");
                }
            }
        }

        /*
         * Well, anyhow someone wrote to us,
         * we should return that favour
         */
        next_heartbeat = jiffies + ZF_USER_TIMEO;
        dprintk("user ping at %ld\n", jiffies);
    }
    return count;
}

static long zf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    void __user *argp = (void __user *)arg;
    int __user *p = argp;
    switch (cmd) {
    case WDIOC_GETSUPPORT:
        if (copy_to_user(argp, &zf_info, sizeof(zf_info)))
            return -EFAULT;
        break;
    case WDIOC_GETSTATUS:
    case WDIOC_GETBOOTSTATUS:
        return put_user(0, p);
    case WDIOC_KEEPALIVE:
        zf_ping(0);
        break;
    default:
        return -ENOTTY;
    }
    return 0;
}

static int zf_open(struct inode *inode, struct file *file)
{
    if (test_and_set_bit(0, &zf_is_open))
        return -EBUSY;
    if (nowayout)
        __module_get(THIS_MODULE);
    zf_timer_on();
    return nonseekable_open(inode, file);
}

static int zf_close(struct inode *inode, struct file *file)
{
    if (zf_expect_close == 42)
        zf_timer_off();
    else {
        del_timer(&zf_timer);
        pr_err("device file closed unexpectedly. Will not stop the WDT!\n");
    }
    clear_bit(0, &zf_is_open);
    zf_expect_close = 0;
    return 0;
}

/*
 * Notifier for system down
 */

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

static const struct file_operations zf_fops = {
    .owner      = THIS_MODULE,
    .llseek     = no_llseek,
    .write      = zf_write,
    .unlocked_ioctl = zf_ioctl,
    .open       = zf_open,
    .release    = zf_close,
};

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


/*
 * The device needs to learn about soft shutdowns in order to
 * turn the timebomb registers off.
 */
static struct notifier_block zf_notifier = {
    .notifier_call = zf_notify_sys,
};

static void __init zf_show_action(int act)
{
    static const char * const str[] = { "RESET", "SMI", "NMI", "SCI" };

    pr_info("Watchdog using action = %s\n", str[act]);
}

static int __init zf_init(void)
{
    int ret;

    pr_info("MachZ ZF-Logic Watchdog driver initializing\n");

    ret = zf_get_ZFL_version();
    if (!ret || ret == 0xffff) {
        pr_warn("no ZF-Logic found\n");
        return -ENODEV;
    }

    if (action <= 3 && action >= 0)
        zf_action = zf_action >> action;
    else
        action = 0;

    zf_show_action(action);

    if (!request_region(ZF_IOBASE, 3, "MachZ ZFL WDT")) {
        pr_err("cannot reserve I/O ports at %d\n", ZF_IOBASE);
        ret = -EBUSY;
        goto no_region;
    }

    ret = register_reboot_notifier(&zf_notifier);
    if (ret) {
        pr_err("can't register reboot notifier (err=%d)\n", ret);
        goto no_reboot;
    }

    ret = misc_register(&zf_miscdev);
    if (ret) {
        pr_err("can't misc_register on minor=%d\n", WATCHDOG_MINOR);
        goto no_misc;
    }

    zf_set_status(0);
    zf_set_control(0);

    return 0;

no_misc:
    unregister_reboot_notifier(&zf_notifier);
no_reboot:
    release_region(ZF_IOBASE, 3);
no_region:
    return ret;
}


static void __exit zf_exit(void)
{
    zf_timer_off();

    misc_deregister(&zf_miscdev);
    unregister_reboot_notifier(&zf_notifier);
    release_region(ZF_IOBASE, 3);
}

module_init(zf_init);
module_exit(zf_exit);