at91_wdt.c

/*
 * Watchdog driver for Atmel AT91RM9200 (Thunder)
 *
 *  Copyright (C) 2003 SAN People (Pty) Ltd
 *
 * 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.
 */

#include <linux/config.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/watchdog.h>
#include <asm/bitops.h>
#include <asm/uaccess.h>


#define WDT_DEFAULT_TIME	5	/* 5 seconds */
#define WDT_MAX_TIME		256	/* 256 seconds */

static int wdt_time = WDT_DEFAULT_TIME;
static int nowayout = WATCHDOG_NOWAYOUT;

module_param(wdt_time, int, 0);
MODULE_PARM_DESC(wdt_time, "Watchdog time in seconds. (default="__MODULE_STRING(WDT_DEFAULT_TIME) ")");

module_param(nowayout, int, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");


static unsigned long at91wdt_busy;

/* ......................................................................... */

/*
 * Disable the watchdog.
 */
static void inline at91_wdt_stop(void)
{
	at91_sys_write(AT91_ST_WDMR, AT91_ST_EXTEN);
}

/*
 * Enable and reset the watchdog.
 */
static void inline at91_wdt_start(void)
{
	at91_sys_write(AT91_ST_WDMR, AT91_ST_EXTEN | AT91_ST_RSTEN | (((65536 * wdt_time) >> 8) & AT91_ST_WDV));
	at91_sys_write(AT91_ST_CR, AT91_ST_WDRST);
}

/*
 * Reload the watchdog timer.  (ie, pat the watchdog)
 */
static void inline at91_wdt_reload(void)
{
	at91_sys_write(AT91_ST_CR, AT91_ST_WDRST);
}

/* ......................................................................... */

/*
 * Watchdog device is opened, and watchdog starts running.
 */
static int at91_wdt_open(struct inode *inode, struct file *file)
{
	if (test_and_set_bit(0, &at91wdt_busy))
		return -EBUSY;

	at91_wdt_start();
	return nonseekable_open(inode, file);
}

/*
 * Close the watchdog device.
 * If CONFIG_WATCHDOG_NOWAYOUT is NOT defined then the watchdog is also
 *  disabled.
 */
static int at91_wdt_close(struct inode *inode, struct file *file)
{
	if (!nowayout)
		at91_wdt_stop();	/* Disable the watchdog when file is closed */

	clear_bit(0, &at91wdt_busy);
	return 0;
}

/*
 * Change the watchdog time interval.
 */
static int at91_wdt_settimeout(int new_time)
{
	/*
	 * All counting occurs at SLOW_CLOCK / 128 = 0.256 Hz
	 *
	 * Since WDV is a 16-bit counter, the maximum period is
	 * 65536 / 0.256 = 256 seconds.
	 */
	if ((new_time <= 0) || (new_time > WDT_MAX_TIME))
		return -EINVAL;

	/* Set new watchdog time. It will be used when at91_wdt_start() is called. */
	wdt_time = new_time;
	return 0;
}

static struct watchdog_info at91_wdt_info = {
	.identity	= "at91 watchdog",
	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
};

/*
 * Handle commands from user-space.
 */
static int at91_wdt_ioctl(struct inode *inode, struct file *file,
		unsigned int cmd, unsigned long arg)
{
	void __user *argp = (void __user *)arg;
	int __user *p = argp;
	int new_value;

	switch(cmd) {
		case WDIOC_KEEPALIVE:
			at91_wdt_reload();	/* pat the watchdog */
			return 0;

		case WDIOC_GETSUPPORT:
			return copy_to_user(argp, &at91_wdt_info, sizeof(at91_wdt_info)) ? -EFAULT : 0;

		case WDIOC_SETTIMEOUT:
			if (get_user(new_value, p))
				return -EFAULT;
				
			if (at91_wdt_settimeout(new_value))
				return -EINVAL;

			/* Enable new time value */
			at91_wdt_start();

			/* Return current value */
			return put_user(wdt_time, p);

		case WDIOC_GETTIMEOUT:
			return put_user(wdt_time, p);

		case WDIOC_GETSTATUS:
		case WDIOC_GETBOOTSTATUS:
			return put_user(0, p);

		case WDIOC_SETOPTIONS:
			if (get_user(new_value, p))
				return -EFAULT;

			if (new_value & WDIOS_DISABLECARD)
				at91_wdt_stop();
			if (new_value & WDIOS_ENABLECARD)
				at91_wdt_start();
			return 0;

		default:
			return -ENOIOCTLCMD;
	}
}

/*
 * Pat the watchdog whenever device is written to.
 */
static ssize_t at91_wdt_write(struct file *file, const char *data, size_t len, loff_t *ppos)
{
	at91_wdt_reload();		/* pat the watchdog */
	return len;
}

/* ......................................................................... */

static struct file_operations at91wdt_fops = {
	.owner		= THIS_MODULE,
	.llseek		= no_llseek,
	.ioctl		= at91_wdt_ioctl,
	.open		= at91_wdt_open,
	.release	= at91_wdt_close,
	.write		= at91_wdt_write,
};

static struct miscdevice at91wdt_miscdev = {
	.minor		= WATCHDOG_MINOR,
	.name		= "watchdog",
	.fops		= &at91wdt_fops,
};

static int __init at91_wdt_init(void)
{
	int res;

	/* Check that the heartbeat value is within range; if not reset to the default */
	if (at91_wdt_settimeout(wdt_time)) {
		at91_wdt_settimeout(WDT_DEFAULT_TIME);
		printk(KERN_INFO "at91_wdt: wdt_time value must be 1 <= wdt_time <= 256, using %d\n", wdt_time);
	}

	res = misc_register(&at91wdt_miscdev);
	if (res)
		return res;

	printk("AT91 Watchdog Timer enabled (%d seconds, nowayout=%d)\n", wdt_time, nowayout);
	return 0;
}

static void __exit at91_wdt_exit(void)
{
	misc_deregister(&at91wdt_miscdev);
}

module_init(at91_wdt_init);
module_exit(at91_wdt_exit);

MODULE_AUTHOR("Andrew Victor");
MODULE_DESCRIPTION("Watchdog driver for Atmel AT91RM9200");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);