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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@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.
 *
 */

#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 <asm/io.h>
#include <asm/uaccess.h>
#include <asm/system.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, will be 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 int nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, int, 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 {
		printk(KERN_WARNING PFX "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);
	printk(KERN_INFO PFX "Watchdog timer is now enabled.\n");
}

static void wdt_turnoff(void)
{
	/* Stop the timer */
	del_timer(&timer);
	inb_p(wdt_stop);
	printk(KERN_INFO PFX "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);
		printk(KERN_CRIT PFX "device file closed unexpectedly. Will not stop the WDT!\n");
	}
	clear_bit(0, &wdt_is_open);
	wdt_expect_close = 0;
	return 0;
}

static int fop_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
	unsigned long arg)
{
	void __user *argp = (void __user *)arg;
	int __user *p = argp;
	static struct watchdog_info ident=
	{
		.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
		.firmware_version = 1,
		.identity = "SBC60xx",
	};

	switch(cmd)
	{
		default:
			return -ENOTTY;
		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_KEEPALIVE:
			wdt_keepalive();
			return 0;
		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_SETTIMEOUT:
		{
			int new_timeout;

			if(get_user(new_timeout, p))
				return -EFAULT;

			if(new_timeout < 1 || new_timeout > 3600) /* arbitrary upper limit */
				return -EINVAL;

			timeout = new_timeout;
			wdt_keepalive();
			/* Fall through */
		}
		case WDIOC_GETTIMEOUT:
			return put_user(timeout, p);
	}
}

static const struct file_operations wdt_fops = {
	.owner		= THIS_MODULE,
	.llseek		= no_llseek,
	.write		= fop_write,
	.open		= fop_open,
	.release	= fop_close,
	.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;
		printk(KERN_INFO PFX "timeout value must be 1<=x<=3600, using %d\n",
			timeout);
 	}

	if (!request_region(wdt_start, 1, "SBC 60XX WDT"))
	{
		printk(KERN_ERR PFX "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"))
		{
			printk(KERN_ERR PFX "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)
	{
		printk(KERN_ERR PFX "cannot register reboot notifier (err=%d)\n",
			rc);
		goto err_out_region2;
	}

	rc = misc_register(&wdt_miscdev);
	if (rc)
	{
		printk(KERN_ERR PFX "cannot register miscdev on minor=%d (err=%d)\n",
			wdt_miscdev.minor, rc);
		goto err_out_reboot;
	}

	printk(KERN_INFO PFX "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");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);