drivers/watchdog/shwdt.c - kernel/prism - Git at Google

 /*
  * drivers/char/watchdog/shwdt.c
  *
  * Watchdog driver for integrated watchdog in the SuperH processors.
  *
  * Copyright (C) 2001, 2002, 2003 Paul Mundt <lethal@linux-sh.org>
  *
  * 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.
  *
  * 14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
  *     Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
  *
  * 19-Apr-2002 Rob Radez <rob@osinvestor.com>
  *     Added expect close support, made emulated timeout runtime changeable
  *     general cleanups, add some ioctls
  */
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/init.h>
 #include <linux/types.h>
 #include <linux/miscdevice.h>
 #include <linux/watchdog.h>
 #include <linux/reboot.h>
 #include <linux/notifier.h>
 #include <linux/ioport.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/io.h>
 #include <linux/uaccess.h>
 #include <asm/watchdog.h>

 #define PFX "shwdt: "

 /*
  * Default clock division ratio is 5.25 msecs. For an additional table of
  * values, consult the asm-sh/watchdog.h. Overload this at module load
  * time.
  *
  * In order for this to work reliably we need to have HZ set to 1000 or
  * something quite higher than 100 (or we need a proper high-res timer
  * implementation that will deal with this properly), otherwise the 10ms
  * resolution of a jiffy is enough to trigger the overflow. For things like
  * the SH-4 and SH-5, this isn't necessarily that big of a problem, though
  * for the SH-2 and SH-3, this isn't recommended unless the WDT is absolutely
  * necssary.
  *
  * As a result of this timing problem, the only modes that are particularly
  * feasible are the 4096 and the 2048 divisors, which yeild 5.25 and 2.62ms
  * overflow periods respectively.
  *
  * Also, since we can't really expect userspace to be responsive enough
  * before the overflow happens, we maintain two separate timers .. One in
  * the kernel for clearing out WOVF every 2ms or so (again, this depends on
  * HZ == 1000), and another for monitoring userspace writes to the WDT device.
  *
  * As such, we currently use a configurable heartbeat interval which defaults
  * to 30s. In this case, the userspace daemon is only responsible for periodic
  * writes to the device before the next heartbeat is scheduled. If the daemon
  * misses its deadline, the kernel timer will allow the WDT to overflow.
  */
 static int clock_division_ratio = WTCSR_CKS_4096;

 #define next_ping_period(cks)	msecs_to_jiffies(cks - 4)

 static void sh_wdt_ping(unsigned long data);

 static unsigned long shwdt_is_open;
 static const struct watchdog_info sh_wdt_info;
 static char shwdt_expect_close;
 static DEFINE_TIMER(timer, sh_wdt_ping, 0, 0);
 static unsigned long next_heartbeat;
 static DEFINE_SPINLOCK(shwdt_lock);

 #define WATCHDOG_HEARTBEAT 30			/* 30 sec default heartbeat */
 static int heartbeat = WATCHDOG_HEARTBEAT;	/* in seconds */

 static int nowayout = WATCHDOG_NOWAYOUT;

 /**
  * 	sh_wdt_start - Start the Watchdog
  *
  * 	Starts the watchdog.
  */
 static void sh_wdt_start(void)
 {
 	__u8 csr;
 	unsigned long flags;

 	spin_lock_irqsave(&shwdt_lock, flags);

 	next_heartbeat = jiffies + (heartbeat * HZ);
 	mod_timer(&timer, next_ping_period(clock_division_ratio));

 	csr = sh_wdt_read_csr();
 	csr |= WTCSR_WT | clock_division_ratio;
 	sh_wdt_write_csr(csr);

 	sh_wdt_write_cnt(0);

 	/*
 	 * These processors have a bit of an inconsistent initialization
 	 * process.. starting with SH-3, RSTS was moved to WTCSR, and the
 	 * RSTCSR register was removed.
 	 *
 	 * On the SH-2 however, in addition with bits being in different
 	 * locations, we must deal with RSTCSR outright..
 	 */
 	csr = sh_wdt_read_csr();
 	csr |= WTCSR_TME;
 	csr &= ~WTCSR_RSTS;
 	sh_wdt_write_csr(csr);

 #ifdef CONFIG_CPU_SH2
 	/*
 	 * Whoever came up with the RSTCSR semantics must've been smoking
 	 * some of the good stuff, since in addition to the WTCSR/WTCNT write
 	 * brain-damage, it's managed to fuck things up one step further..
 	 *
 	 * If we need to clear the WOVF bit, the upper byte has to be 0xa5..
 	 * but if we want to touch RSTE or RSTS, the upper byte has to be
 	 * 0x5a..
 	 */
 	csr = sh_wdt_read_rstcsr();
 	csr &= ~RSTCSR_RSTS;
 	sh_wdt_write_rstcsr(csr);
 #endif
 	spin_unlock_irqrestore(&shwdt_lock, flags);
 }

 /**
  * 	sh_wdt_stop - Stop the Watchdog
  * 	Stops the watchdog.
  */
 static void sh_wdt_stop(void)
 {
 	__u8 csr;
 	unsigned long flags;

 	spin_lock_irqsave(&shwdt_lock, flags);

 	del_timer(&timer);

 	csr = sh_wdt_read_csr();
 	csr &= ~WTCSR_TME;
 	sh_wdt_write_csr(csr);
 	spin_unlock_irqrestore(&shwdt_lock, flags);
 }

 /**
  * 	sh_wdt_keepalive - Keep the Userspace Watchdog Alive
  * 	The Userspace watchdog got a KeepAlive: schedule the next heartbeat.
  */
 static inline void sh_wdt_keepalive(void)
 {
 	unsigned long flags;

 	spin_lock_irqsave(&shwdt_lock, flags);
 	next_heartbeat = jiffies + (heartbeat * HZ);
 	spin_unlock_irqrestore(&shwdt_lock, flags);
 }

 /**
  * 	sh_wdt_set_heartbeat - Set the Userspace Watchdog heartbeat
  * 	Set the Userspace Watchdog heartbeat
  */
 static int sh_wdt_set_heartbeat(int t)
 {
 	unsigned long flags;

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

 	spin_lock_irqsave(&shwdt_lock, flags);
 	heartbeat = t;
 	spin_unlock_irqrestore(&shwdt_lock, flags);
 	return 0;
 }

 /**
  * 	sh_wdt_ping - Ping the Watchdog
  *	@data: Unused
  *
  * 	Clears overflow bit, resets timer counter.
  */
 static void sh_wdt_ping(unsigned long data)
 {
 	unsigned long flags;

 	spin_lock_irqsave(&shwdt_lock, flags);
 	if (time_before(jiffies, next_heartbeat)) {
 		__u8 csr;

 		csr = sh_wdt_read_csr();
 		csr &= ~WTCSR_IOVF;
 		sh_wdt_write_csr(csr);

 		sh_wdt_write_cnt(0);

 		mod_timer(&timer, next_ping_period(clock_division_ratio));
 	} else
 		printk(KERN_WARNING PFX "Heartbeat lost! Will not ping "
 		       "the watchdog\n");
 	spin_unlock_irqrestore(&shwdt_lock, flags);
 }

 /**
  * 	sh_wdt_open - Open the Device
  * 	@inode: inode of device
  * 	@file: file handle of device
  *
  * 	Watchdog device is opened and started.
  */
 static int sh_wdt_open(struct inode *inode, struct file *file)
 {
 	if (test_and_set_bit(0, &shwdt_is_open))
 		return -EBUSY;
 	if (nowayout)
 		__module_get(THIS_MODULE);

 	sh_wdt_start();

 	return nonseekable_open(inode, file);
 }

 /**
  * 	sh_wdt_close - Close the Device
  * 	@inode: inode of device
  * 	@file: file handle of device
  *
  * 	Watchdog device is closed and stopped.
  */
 static int sh_wdt_close(struct inode *inode, struct file *file)
 {
 	if (shwdt_expect_close == 42) {
 		sh_wdt_stop();
 	} else {
 		printk(KERN_CRIT PFX "Unexpected close, not "
 		       "stopping watchdog!\n");
 		sh_wdt_keepalive();
 	}

 	clear_bit(0, &shwdt_is_open);
 	shwdt_expect_close = 0;

 	return 0;
 }

 /**
  * 	sh_wdt_write - Write to Device
  * 	@file: file handle of device
  * 	@buf: buffer to write
  * 	@count: length of buffer
  * 	@ppos: offset
  *
  * 	Pings the watchdog on write.
  */
 static ssize_t sh_wdt_write(struct file *file, const char *buf,
 			    size_t count, loff_t *ppos)
 {
 	if (count) {
 		if (!nowayout) {
 			size_t i;

 			shwdt_expect_close = 0;

 			for (i = 0; i != count; i++) {
 				char c;
 				if (get_user(c, buf + i))
 					return -EFAULT;
 				if (c == 'V')
 					shwdt_expect_close = 42;
 			}
 		}
 		sh_wdt_keepalive();
 	}

 	return count;
 }

 /**
  * 	sh_wdt_mmap - map WDT/CPG registers into userspace
  * 	@file: file structure for the device
  * 	@vma: VMA to map the registers into
  *
  * 	A simple mmap() implementation for the corner cases where the counter
  * 	needs to be mapped in userspace directly. Due to the relatively small
  * 	size of the area, neighbouring registers not necessarily tied to the
  * 	CPG will also be accessible through the register page, so this remains
  * 	configurable for users that really know what they're doing.
  *
  *	Additionaly, the register page maps in the CPG register base relative
  *	to the nearest page-aligned boundary, which requires that userspace do
  *	the appropriate CPU subtype math for calculating the page offset for
  *	the counter value.
  */
 static int sh_wdt_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	int ret = -ENOSYS;

 #ifdef CONFIG_SH_WDT_MMAP
 	unsigned long addr;

 	/* Only support the simple cases where we map in a register page. */
 	if (((vma->vm_end - vma->vm_start) != PAGE_SIZE) || vma->vm_pgoff)
 		return -EINVAL;

 	/*
 	 * Pick WTCNT as the start, it's usually the first register after the
 	 * FRQCR, and neither one are generally page-aligned out of the box.
 	 */
 	addr = WTCNT & ~(PAGE_SIZE - 1);

 	vma->vm_flags |= VM_IO;
 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

 	if (io_remap_pfn_range(vma, vma->vm_start, addr >> PAGE_SHIFT,
 			       PAGE_SIZE, vma->vm_page_prot)) {
 		printk(KERN_ERR PFX "%s: io_remap_pfn_range failed\n",
 		       __func__);
 		return -EAGAIN;
 	}

 	ret = 0;
 #endif

 	return ret;
 }

 /**
  * 	sh_wdt_ioctl - Query Device
  * 	@file: file handle of device
  * 	@cmd: watchdog command
  * 	@arg: argument
  *
  * 	Query basic information from the device or ping it, as outlined by the
  * 	watchdog API.
  */
 static long sh_wdt_ioctl(struct file *file, unsigned int cmd,
 							unsigned long arg)
 {
 	int new_heartbeat;
 	int options, retval = -EINVAL;

 	switch (cmd) {
 	case WDIOC_GETSUPPORT:
 		return copy_to_user((struct watchdog_info *)arg,
 			  &sh_wdt_info, sizeof(sh_wdt_info)) ? -EFAULT : 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) {
 			sh_wdt_stop();
 			retval = 0;
 		}

 		if (options & WDIOS_ENABLECARD) {
 			sh_wdt_start();
 			retval = 0;
 		}

 		return retval;
 	case WDIOC_KEEPALIVE:
 		sh_wdt_keepalive();
 		return 0;
 	case WDIOC_SETTIMEOUT:
 		if (get_user(new_heartbeat, (int *)arg))
 			return -EFAULT;

 		if (sh_wdt_set_heartbeat(new_heartbeat))
 			return -EINVAL;

 		sh_wdt_keepalive();
 		/* Fall */
 	case WDIOC_GETTIMEOUT:
 		return put_user(heartbeat, (int *)arg);
 	default:
 		return -ENOTTY;
 	}
 	return 0;
 }

 /**
  * 	sh_wdt_notify_sys - Notifier Handler
  * 	@this: notifier block
  * 	@code: notifier event
  * 	@unused: unused
  *
  * 	Handles specific events, such as turning off the watchdog during a
  * 	shutdown event.
  */
 static int sh_wdt_notify_sys(struct notifier_block *this,
 			     unsigned long code, void *unused)
 {
 	if (code == SYS_DOWN || code == SYS_HALT)
 		sh_wdt_stop();

 	return NOTIFY_DONE;
 }

 static const struct file_operations sh_wdt_fops = {
 	.owner		= THIS_MODULE,
 	.llseek		= no_llseek,
 	.write		= sh_wdt_write,
 	.unlocked_ioctl	= sh_wdt_ioctl,
 	.open		= sh_wdt_open,
 	.release	= sh_wdt_close,
 	.mmap		= sh_wdt_mmap,
 };

 static const struct watchdog_info sh_wdt_info = {
 	.options		= WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
 				  WDIOF_MAGICCLOSE,
 	.firmware_version	= 1,
 	.identity		= "SH WDT",
 };

 static struct notifier_block sh_wdt_notifier = {
 	.notifier_call		= sh_wdt_notify_sys,
 };

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

 /**
  * 	sh_wdt_init - Initialize module
  * 	Registers the device and notifier handler. Actual device
  * 	initialization is handled by sh_wdt_open().
  */
 static int __init sh_wdt_init(void)
 {
 	int rc;

 	if (clock_division_ratio < 0x5 || clock_division_ratio > 0x7) {
 		clock_division_ratio = WTCSR_CKS_4096;
 		printk(KERN_INFO PFX
 		  "clock_division_ratio value must be 0x5<=x<=0x7, using %d\n",
 				clock_division_ratio);
 	}

 	rc = sh_wdt_set_heartbeat(heartbeat);
 	if (unlikely(rc)) {
 		heartbeat = WATCHDOG_HEARTBEAT;
 		printk(KERN_INFO PFX
 			"heartbeat value must be 1<=x<=3600, using %d\n",
 								heartbeat);
 	}

 	rc = register_reboot_notifier(&sh_wdt_notifier);
 	if (unlikely(rc)) {
 		printk(KERN_ERR PFX
 			"Can't register reboot notifier (err=%d)\n", rc);
 		return rc;
 	}

 	rc = misc_register(&sh_wdt_miscdev);
 	if (unlikely(rc)) {
 		printk(KERN_ERR PFX
 			"Can't register miscdev on minor=%d (err=%d)\n",
 						sh_wdt_miscdev.minor, rc);
 		unregister_reboot_notifier(&sh_wdt_notifier);
 		return rc;
 	}

 	printk(KERN_INFO PFX "initialized. heartbeat=%d sec (nowayout=%d)\n",
 		heartbeat, nowayout);

 	return 0;
 }

 /**
  * 	sh_wdt_exit - Deinitialize module
  * 	Unregisters the device and notifier handler. Actual device
  * 	deinitialization is handled by sh_wdt_close().
  */
 static void __exit sh_wdt_exit(void)
 {
 	misc_deregister(&sh_wdt_miscdev);
 	unregister_reboot_notifier(&sh_wdt_notifier);
 }

 MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
 MODULE_DESCRIPTION("SuperH watchdog driver");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);

 module_param(clock_division_ratio, int, 0);
 MODULE_PARM_DESC(clock_division_ratio,
 	"Clock division ratio. Valid ranges are from 0x5 (1.31ms) "
 	"to 0x7 (5.25ms). (default=" __MODULE_STRING(clock_division_ratio) ")");

 module_param(heartbeat, int, 0);
 MODULE_PARM_DESC(heartbeat,
 	"Watchdog heartbeat in seconds. (1 <= heartbeat <= 3600, default="
 				__MODULE_STRING(WATCHDOG_HEARTBEAT) ")");

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

 module_init(sh_wdt_init);
 module_exit(sh_wdt_exit);
	/*
	* drivers/char/watchdog/shwdt.c
	*
	* Watchdog driver for integrated watchdog in the SuperH processors.
	*
	* Copyright (C) 2001, 2002, 2003 Paul Mundt <lethal@linux-sh.org>
	*
	* 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.
	*
	* 14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
	* Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
	*
	* 19-Apr-2002 Rob Radez <rob@osinvestor.com>
	* Added expect close support, made emulated timeout runtime changeable
	* general cleanups, add some ioctls
	*/
	#include <linux/module.h>
	#include <linux/moduleparam.h>
	#include <linux/init.h>
	#include <linux/types.h>
	#include <linux/miscdevice.h>
	#include <linux/watchdog.h>
	#include <linux/reboot.h>
	#include <linux/notifier.h>
	#include <linux/ioport.h>
	#include <linux/fs.h>
	#include <linux/mm.h>
	#include <linux/io.h>
	#include <linux/uaccess.h>
	#include <asm/watchdog.h>

	#define PFX "shwdt: "

	/*
	* Default clock division ratio is 5.25 msecs. For an additional table of
	* values, consult the asm-sh/watchdog.h. Overload this at module load
	* time.
	*
	* In order for this to work reliably we need to have HZ set to 1000 or
	* something quite higher than 100 (or we need a proper high-res timer
	* implementation that will deal with this properly), otherwise the 10ms
	* resolution of a jiffy is enough to trigger the overflow. For things like
	* the SH-4 and SH-5, this isn't necessarily that big of a problem, though
	* for the SH-2 and SH-3, this isn't recommended unless the WDT is absolutely
	* necssary.
	*
	* As a result of this timing problem, the only modes that are particularly
	* feasible are the 4096 and the 2048 divisors, which yeild 5.25 and 2.62ms
	* overflow periods respectively.
	*
	* Also, since we can't really expect userspace to be responsive enough
	* before the overflow happens, we maintain two separate timers .. One in
	* the kernel for clearing out WOVF every 2ms or so (again, this depends on
	* HZ == 1000), and another for monitoring userspace writes to the WDT device.
	*
	* As such, we currently use a configurable heartbeat interval which defaults
	* to 30s. In this case, the userspace daemon is only responsible for periodic
	* writes to the device before the next heartbeat is scheduled. If the daemon
	* misses its deadline, the kernel timer will allow the WDT to overflow.
	*/
	static int clock_division_ratio = WTCSR_CKS_4096;

	#define next_ping_period(cks) msecs_to_jiffies(cks - 4)

	static void sh_wdt_ping(unsigned long data);

	static unsigned long shwdt_is_open;
	static const struct watchdog_info sh_wdt_info;
	static char shwdt_expect_close;
	static DEFINE_TIMER(timer, sh_wdt_ping, 0, 0);
	static unsigned long next_heartbeat;
	static DEFINE_SPINLOCK(shwdt_lock);

	#define WATCHDOG_HEARTBEAT 30 /* 30 sec default heartbeat */
	static int heartbeat = WATCHDOG_HEARTBEAT; /* in seconds */

	static int nowayout = WATCHDOG_NOWAYOUT;

	/**
	* sh_wdt_start - Start the Watchdog
	*
	* Starts the watchdog.
	*/
	static void sh_wdt_start(void)
	{
	__u8 csr;
	unsigned long flags;

	spin_lock_irqsave(&shwdt_lock, flags);

	next_heartbeat = jiffies + (heartbeat * HZ);
	mod_timer(&timer, next_ping_period(clock_division_ratio));

	csr = sh_wdt_read_csr();
	csr \|= WTCSR_WT \| clock_division_ratio;
	sh_wdt_write_csr(csr);

	sh_wdt_write_cnt(0);

	/*
	* These processors have a bit of an inconsistent initialization
	* process.. starting with SH-3, RSTS was moved to WTCSR, and the
	* RSTCSR register was removed.
	*
	* On the SH-2 however, in addition with bits being in different
	* locations, we must deal with RSTCSR outright..
	*/
	csr = sh_wdt_read_csr();
	csr \|= WTCSR_TME;
	csr &= ~WTCSR_RSTS;
	sh_wdt_write_csr(csr);

	#ifdef CONFIG_CPU_SH2
	/*
	* Whoever came up with the RSTCSR semantics must've been smoking
	* some of the good stuff, since in addition to the WTCSR/WTCNT write
	* brain-damage, it's managed to fuck things up one step further..
	*
	* If we need to clear the WOVF bit, the upper byte has to be 0xa5..
	* but if we want to touch RSTE or RSTS, the upper byte has to be
	* 0x5a..
	*/
	csr = sh_wdt_read_rstcsr();
	csr &= ~RSTCSR_RSTS;
	sh_wdt_write_rstcsr(csr);
	#endif
	spin_unlock_irqrestore(&shwdt_lock, flags);
	}

	/**
	* sh_wdt_stop - Stop the Watchdog
	* Stops the watchdog.
	*/
	static void sh_wdt_stop(void)
	{
	__u8 csr;
	unsigned long flags;

	spin_lock_irqsave(&shwdt_lock, flags);

	del_timer(&timer);

	csr = sh_wdt_read_csr();
	csr &= ~WTCSR_TME;
	sh_wdt_write_csr(csr);
	spin_unlock_irqrestore(&shwdt_lock, flags);
	}

	/**
	* sh_wdt_keepalive - Keep the Userspace Watchdog Alive
	* The Userspace watchdog got a KeepAlive: schedule the next heartbeat.
	*/
	static inline void sh_wdt_keepalive(void)
	{
	unsigned long flags;

	spin_lock_irqsave(&shwdt_lock, flags);
	next_heartbeat = jiffies + (heartbeat * HZ);
	spin_unlock_irqrestore(&shwdt_lock, flags);
	}

	/**
	* sh_wdt_set_heartbeat - Set the Userspace Watchdog heartbeat
	* Set the Userspace Watchdog heartbeat
	*/
	static int sh_wdt_set_heartbeat(int t)
	{
	unsigned long flags;

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

	spin_lock_irqsave(&shwdt_lock, flags);
	heartbeat = t;
	spin_unlock_irqrestore(&shwdt_lock, flags);
	return 0;
	}

	/**
	* sh_wdt_ping - Ping the Watchdog
	* @data: Unused
	*
	* Clears overflow bit, resets timer counter.
	*/
	static void sh_wdt_ping(unsigned long data)
	{
	unsigned long flags;

	spin_lock_irqsave(&shwdt_lock, flags);
	if (time_before(jiffies, next_heartbeat)) {
	__u8 csr;

	csr = sh_wdt_read_csr();
	csr &= ~WTCSR_IOVF;
	sh_wdt_write_csr(csr);

	sh_wdt_write_cnt(0);

	mod_timer(&timer, next_ping_period(clock_division_ratio));
	} else
	printk(KERN_WARNING PFX "Heartbeat lost! Will not ping "
	"the watchdog\n");
	spin_unlock_irqrestore(&shwdt_lock, flags);
	}

	/**
	* sh_wdt_open - Open the Device
	* @inode: inode of device
	* @file: file handle of device
	*
	* Watchdog device is opened and started.
	*/
	static int sh_wdt_open(struct inode inode, struct file file)
	{
	if (test_and_set_bit(0, &shwdt_is_open))
	return -EBUSY;
	if (nowayout)
	__module_get(THIS_MODULE);

	sh_wdt_start();

	return nonseekable_open(inode, file);
	}

	/**
	* sh_wdt_close - Close the Device
	* @inode: inode of device
	* @file: file handle of device
	*
	* Watchdog device is closed and stopped.
	*/
	static int sh_wdt_close(struct inode inode, struct file file)
	{
	if (shwdt_expect_close == 42) {
	sh_wdt_stop();
	} else {
	printk(KERN_CRIT PFX "Unexpected close, not "
	"stopping watchdog!\n");
	sh_wdt_keepalive();
	}

	clear_bit(0, &shwdt_is_open);
	shwdt_expect_close = 0;

	return 0;
	}

	/**
	* sh_wdt_write - Write to Device
	* @file: file handle of device
	* @buf: buffer to write
	* @count: length of buffer
	* @ppos: offset
	*
	* Pings the watchdog on write.
	*/
	static ssize_t sh_wdt_write(struct file file, const char buf,
	size_t count, loff_t *ppos)
	{
	if (count) {
	if (!nowayout) {
	size_t i;

	shwdt_expect_close = 0;

	for (i = 0; i != count; i++) {
	char c;
	if (get_user(c, buf + i))
	return -EFAULT;
	if (c == 'V')
	shwdt_expect_close = 42;
	}
	}
	sh_wdt_keepalive();
	}

	return count;
	}

	/**
	* sh_wdt_mmap - map WDT/CPG registers into userspace
	* @file: file structure for the device
	* @vma: VMA to map the registers into
	*
	* A simple mmap() implementation for the corner cases where the counter
	* needs to be mapped in userspace directly. Due to the relatively small
	* size of the area, neighbouring registers not necessarily tied to the
	* CPG will also be accessible through the register page, so this remains
	* configurable for users that really know what they're doing.
	*
	* Additionaly, the register page maps in the CPG register base relative
	* to the nearest page-aligned boundary, which requires that userspace do
	* the appropriate CPU subtype math for calculating the page offset for
	* the counter value.
	*/
	static int sh_wdt_mmap(struct file file, struct vm_area_struct vma)
	{
	int ret = -ENOSYS;

	#ifdef CONFIG_SH_WDT_MMAP
	unsigned long addr;

	/* Only support the simple cases where we map in a register page. */
	if (((vma->vm_end - vma->vm_start) != PAGE_SIZE) \|\| vma->vm_pgoff)
	return -EINVAL;

	/*
	* Pick WTCNT as the start, it's usually the first register after the
	* FRQCR, and neither one are generally page-aligned out of the box.
	*/
	addr = WTCNT & ~(PAGE_SIZE - 1);

	vma->vm_flags \|= VM_IO;
	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

	if (io_remap_pfn_range(vma, vma->vm_start, addr >> PAGE_SHIFT,
	PAGE_SIZE, vma->vm_page_prot)) {
	printk(KERN_ERR PFX "%s: io_remap_pfn_range failed\n",
	__func__);
	return -EAGAIN;
	}

	ret = 0;
	#endif

	return ret;
	}

	/**
	* sh_wdt_ioctl - Query Device
	* @file: file handle of device
	* @cmd: watchdog command
	* @arg: argument
	*
	* Query basic information from the device or ping it, as outlined by the
	* watchdog API.
	*/
	static long sh_wdt_ioctl(struct file *file, unsigned int cmd,
	unsigned long arg)
	{
	int new_heartbeat;
	int options, retval = -EINVAL;

	switch (cmd) {
	case WDIOC_GETSUPPORT:
	return copy_to_user((struct watchdog_info *)arg,
	&sh_wdt_info, sizeof(sh_wdt_info)) ? -EFAULT : 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) {
	sh_wdt_stop();
	retval = 0;
	}

	if (options & WDIOS_ENABLECARD) {
	sh_wdt_start();
	retval = 0;
	}

	return retval;
	case WDIOC_KEEPALIVE:
	sh_wdt_keepalive();
	return 0;
	case WDIOC_SETTIMEOUT:
	if (get_user(new_heartbeat, (int *)arg))
	return -EFAULT;

	if (sh_wdt_set_heartbeat(new_heartbeat))
	return -EINVAL;

	sh_wdt_keepalive();
	/* Fall */
	case WDIOC_GETTIMEOUT:
	return put_user(heartbeat, (int *)arg);
	default:
	return -ENOTTY;
	}
	return 0;
	}

	/**
	* sh_wdt_notify_sys - Notifier Handler
	* @this: notifier block
	* @code: notifier event
	* @unused: unused
	*
	* Handles specific events, such as turning off the watchdog during a
	* shutdown event.
	*/
	static int sh_wdt_notify_sys(struct notifier_block *this,
	unsigned long code, void *unused)
	{
	if (code == SYS_DOWN \|\| code == SYS_HALT)
	sh_wdt_stop();

	return NOTIFY_DONE;
	}

	static const struct file_operations sh_wdt_fops = {
	.owner = THIS_MODULE,
	.llseek = no_llseek,
	.write = sh_wdt_write,
	.unlocked_ioctl = sh_wdt_ioctl,
	.open = sh_wdt_open,
	.release = sh_wdt_close,
	.mmap = sh_wdt_mmap,
	};

	static const struct watchdog_info sh_wdt_info = {
	.options = WDIOF_KEEPALIVEPING \| WDIOF_SETTIMEOUT \|
	WDIOF_MAGICCLOSE,
	.firmware_version = 1,
	.identity = "SH WDT",
	};

	static struct notifier_block sh_wdt_notifier = {
	.notifier_call = sh_wdt_notify_sys,
	};

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

	/**
	* sh_wdt_init - Initialize module
	* Registers the device and notifier handler. Actual device
	* initialization is handled by sh_wdt_open().
	*/
	static int __init sh_wdt_init(void)
	{
	int rc;

	if (clock_division_ratio < 0x5 \|\| clock_division_ratio > 0x7) {
	clock_division_ratio = WTCSR_CKS_4096;
	printk(KERN_INFO PFX
	"clock_division_ratio value must be 0x5<=x<=0x7, using %d\n",
	clock_division_ratio);
	}

	rc = sh_wdt_set_heartbeat(heartbeat);
	if (unlikely(rc)) {
	heartbeat = WATCHDOG_HEARTBEAT;
	printk(KERN_INFO PFX
	"heartbeat value must be 1<=x<=3600, using %d\n",
	heartbeat);
	}

	rc = register_reboot_notifier(&sh_wdt_notifier);
	if (unlikely(rc)) {
	printk(KERN_ERR PFX
	"Can't register reboot notifier (err=%d)\n", rc);
	return rc;
	}

	rc = misc_register(&sh_wdt_miscdev);
	if (unlikely(rc)) {
	printk(KERN_ERR PFX
	"Can't register miscdev on minor=%d (err=%d)\n",
	sh_wdt_miscdev.minor, rc);
	unregister_reboot_notifier(&sh_wdt_notifier);
	return rc;
	}

	printk(KERN_INFO PFX "initialized. heartbeat=%d sec (nowayout=%d)\n",
	heartbeat, nowayout);

	return 0;
	}

	/**
	* sh_wdt_exit - Deinitialize module
	* Unregisters the device and notifier handler. Actual device
	* deinitialization is handled by sh_wdt_close().
	*/
	static void __exit sh_wdt_exit(void)
	{
	misc_deregister(&sh_wdt_miscdev);
	unregister_reboot_notifier(&sh_wdt_notifier);
	}

	MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
	MODULE_DESCRIPTION("SuperH watchdog driver");
	MODULE_LICENSE("GPL");
	MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);

	module_param(clock_division_ratio, int, 0);
	MODULE_PARM_DESC(clock_division_ratio,
	"Clock division ratio. Valid ranges are from 0x5 (1.31ms) "
	"to 0x7 (5.25ms). (default=" __MODULE_STRING(clock_division_ratio) ")");

	module_param(heartbeat, int, 0);
	MODULE_PARM_DESC(heartbeat,
	"Watchdog heartbeat in seconds. (1 <= heartbeat <= 3600, default="
	__MODULE_STRING(WATCHDOG_HEARTBEAT) ")");

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

	module_init(sh_wdt_init);
	module_exit(sh_wdt_exit);