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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 <jakob@ostenfeld.dk>

 *

 *           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

 *

 *

 *  Theory of operation:

 *  A Watchdog Timer (WDT) is a hardware circuit that can

 *  reset the computer system in case of a software fault.

 *  You probably knew that already.

 *

 *  Usually a userspace daemon will notify the kernel WDT driver

 *  via the /proc/watchdog special device file that userspace is

 *  still alive, at regular intervals.  When such a notification

 *  occurs, the driver will usually tell the hardware watchdog

 *  that everything is in order, and that the watchdog should wait

 *  for yet another little while to reset the system.

 *  If userspace fails (RAM error, kernel bug, whatever), the

 *  notifications cease to occur, and the hardware watchdog will

 *  reset the system (causing a reboot) after the timeout occurs.

 *

 *  This WDT driver is different from the other Linux WDT

 *  drivers in several 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.

 *  *)  This driver expects the userspace daemon to send a specific

 *      character code ('V') to /dev/watchdog before closing the

 *      /dev/watchdog file.  If the userspace daemon closes the file

 *      without sending this special character, the driver will assume

 *      that the daemon (and userspace in general) died, and will

 *      stop pinging the WDT without disabling it first.  This will

 *      cause a reboot.

 *

 *  Why `V' ?  Well, `V' is the character in ASCII for the value 86,

 *  and we all know that 86 is _the_ most random number in the universe.

 *  Therefore it is the letter that has the slightest chance of occuring

 *  by chance, when the system becomes corrupted.

 *

 */

#include <linux/module.h>

#include <linux/version.h>

#include <linux/types.h>

#include <linux/errno.h>

#include <linux/kernel.h>

#include <linux/timer.h>

#include <linux/sched.h>

#include <linux/miscdevice.h>

#include <linux/watchdog.h>

#include <linux/slab.h>

#include <linux/ioport.h>

#include <linux/fcntl.h>

#include <linux/smp_lock.h>

#include <asm/io.h>

#include <asm/uaccess.h>

#include <asm/system.h>

#include <linux/notifier.h>

#include <linux/reboot.h>

#include <linux/init.h>

#define OUR_NAME "sbc60xxwdt"

/*

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

 */

#define WDT_STOP 0x45

#define WDT_START 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 10 seconds.

 * If the daemon pulses us every 5 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 WDT_HEARTBEAT (HZ * 10)

static void wdt_timer_ping(unsigned long);

static struct timer_list timer;

static unsigned long next_heartbeat;

static int wdt_is_open;

static int 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 */

                timer.expires = jiffies + WDT_INTERVAL;

                add_timer(&timer);

        } else {

                printk(OUR_NAME ": Heartbeat lost! Will not ping the watchdog\n");

        }

}

/*

 * Utility routines

 */

static void wdt_startup(void)

{

        next_heartbeat = jiffies + WDT_HEARTBEAT;

        /* Start the timer */

        timer.expires = jiffies + WDT_INTERVAL;

        add_timer(&timer);

        printk(OUR_NAME ": Watchdog timer is now enabled.\n");

}

static void wdt_turnoff(void)

{

        /* Stop the timer */

        del_timer(&timer);

        inb_p(WDT_STOP);

        printk(OUR_NAME ": Watchdog timer is now disabled...\n");

}

/*

 * /dev/watchdog handling

 */

static ssize_t fop_write(struct file * file, const char * buf, size_t count, loff_t * ppos)

{

        /* We can't seek */

        if(ppos != &file->f_pos)

                return -ESPIPE;

        /* See if we got the magic character */

        if(count)

        {

                size_t ofs;

                /* note: just in case someone wrote the magic character

                 * five months ago... */

                wdt_expect_close = 0;

                /* now scan */

                for(ofs = 0; ofs != count; ofs++)

                {

                        char c;

                        if(get_user(c, buf+ofs))

                                return -EFAULT;

                        if(c == 'V')

                                wdt_expect_close = 1;

                }

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

                next_heartbeat = jiffies + WDT_HEARTBEAT;

                return 1;

        }

        return 0;

}

static ssize_t fop_read(struct file * file, char * buf, size_t count, loff_t * ppos)

{

        /* No can do */

        return -EINVAL;

}

static int fop_open(struct inode * inode, struct file * file)

{

        switch(MINOR(inode->i_rdev))

        {

                case WATCHDOG_MINOR:

                        /* Just in case we're already talking to someone... */

                        if(wdt_is_open)

                                return -EBUSY;

                        /* Good, fire up the show */

                        wdt_is_open = 1;

                        wdt_startup();

                        return 0;

                default:

                        return -ENODEV;

        }

}

static int fop_close(struct inode * inode, struct file * file)

{

        lock_kernel();

        if(MINOR(inode->i_rdev) == WATCHDOG_MINOR)

        {

                if(wdt_expect_close)

                        wdt_turnoff();

                else {

                        del_timer(&timer);

                        printk(OUR_NAME ": device file closed unexpectedly. Will not stop the WDT!\n");

                }

        }

        wdt_is_open = 0;

        unlock_kernel();

        return 0;

}

static int fop_ioctl(struct inode *inode, struct file *file, unsigned int cmd,

        unsigned long arg)

{

        static struct watchdog_info ident=

        {

                WDIOF_MAGICCLOSE,

                1,

                "SB60xx"

        };

        switch(cmd)

        {

                default:

                        return -ENOTTY;

                case WDIOC_GETSUPPORT:

                        return copy_to_user((struct watchdog_info *)arg, &ident, sizeof(ident))?-EFAULT:0;

                case WDIOC_KEEPALIVE:

                        next_heartbeat = jiffies + WDT_HEARTBEAT;

                        return 0;

        }

}

static struct file_operations wdt_fops = {

        owner:          THIS_MODULE,

        llseek:         no_llseek,

        read:           fop_read,

        write:          fop_write,

        open:           fop_open,

        release:        fop_close,

        ioctl:          fop_ioctl

};

static struct miscdevice wdt_miscdev = {

        WATCHDOG_MINOR,

        "watchdog",

        &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=

{

        wdt_notify_sys,

        0,

};

static void __exit sbc60xxwdt_unload(void)

{

        wdt_turnoff();

        /* Deregister */

        misc_deregister(&wdt_miscdev);

        unregister_reboot_notifier(&wdt_notifier);

        release_region(WDT_START,1);

//      release_region(WDT_STOP,1);

}

static int __init sbc60xxwdt_init(void)

{

        int rc = -EBUSY;

//      We cannot reserve 0x45 - the kernel already has!

//      if (!request_region(WDT_STOP, 1, "SBC 60XX WDT"))

//              goto err_out;

        if (!request_region(WDT_START, 1, "SBC 60XX WDT"))

                goto err_out_region1;

        init_timer(&timer);

        timer.function = wdt_timer_ping;

        timer.data = 0;

        rc = misc_register(&wdt_miscdev);

        if (rc)

                goto err_out_region2;

        rc = register_reboot_notifier(&wdt_notifier);

        if (rc)

                goto err_out_miscdev;

        printk(KERN_INFO OUR_NAME ": WDT driver for 60XX single board computer initialised.\n");

        return 0;

err_out_miscdev:

        misc_deregister(&wdt_miscdev);

err_out_region2:

        release_region(WDT_START,1);

err_out_region1:

        release_region(WDT_STOP,1);

/* err_out: */

        return rc;

}

module_init(sbc60xxwdt_init);

module_exit(sbc60xxwdt_unload);

MODULE_LICENSE("GPL");

EXPORT_NO_SYMBOLS;