drivers/watchdog/sc520_wdt.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *	AMD Elan SC520 processor Watchdog Timer driver
  *
  *	Based on acquirewdt.c by Alan Cox,
  *	     and sbc60xxwdt.c by Jakob Oestergaard <jakob@unthought.net>
  *
  *	The authors do 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 2001    Scott Jennings <linuxdrivers@oro.net>
  *           9/27 - 2001      [Initial release]
  *
  *	Additional fixes Alan Cox
  *	-	Fixed formatting
  *	-	Removed debug printks
  *	-	Fixed SMP built kernel deadlock
  *	-	Switched to private locks not lock_kernel
  *	-	Used ioremap/writew/readw
  *	-	Added NOWAYOUT support
  *	4/12 - 2002 Changes by Rob Radez <rob@osinvestor.com>
  *	-	Change comments
  *	-	Eliminate fop_llseek
  *	-	Change CONFIG_WATCHDOG_NOWAYOUT semantics
  *	-	Add KERN_* tags to printks
  *	-	fix possible wdt_is_open race
  *	-	Report proper capabilities in watchdog_info
  *	-	Add WDIOC_{GETSTATUS, GETBOOTSTATUS, SETTIMEOUT,
  *		GETTIMEOUT, SETOPTIONS} ioctls
  *	09/8 - 2003 Changes by Wim Van Sebroeck <wim@iguana.be>
  *	-	cleanup of trailing spaces
  *	-	added extra printk's for startup problems
  *	-	use module_param
  *	-	made timeout (the emulated heartbeat) a module_param
  *	-	made the keepalive ping an internal subroutine
  *	3/27 - 2004 Changes by Sean Young <sean@mess.org>
  *	-	set MMCR_BASE to 0xfffef000
  *	-	CBAR does not need to be read
  *	-	removed debugging printks
  *
  *  This WDT driver is different from most other Linux WDT
  *  drivers in that the driver will ping the watchdog by itself,
  *  because this particular WDT has a very short timeout (1.6
  *  seconds) and it would be insane to count on any userspace
  *  daemon always getting scheduled within that time frame.
  *
  *  This driver uses memory mapped IO, and spinlock.
  */

 #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/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/jiffies.h>
 #include <linux/io.h>
 #include <linux/uaccess.h>


 /*
  * The AMD Elan SC520 timeout value is 492us times a power of 2 (0-7)
  *
  *   0: 492us    2: 1.01s    4: 4.03s   6: 16.22s
  *   1: 503ms    3: 2.01s    5: 8.05s   7: 32.21s
  *
  * We will program the SC520 watchdog for a timeout of 2.01s.
  * 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.
  */

 #define WATCHDOG_TIMEOUT 30		/* 30 sec default timeout */
 /* in seconds, will be multiplied by HZ to get seconds to wait for a ping */
 static int timeout = WATCHDOG_TIMEOUT;
 module_param(timeout, int, 0);
 MODULE_PARM_DESC(timeout,
 	"Watchdog timeout in seconds. (1 <= timeout <= 3600, default="
 				__MODULE_STRING(WATCHDOG_TIMEOUT) ")");

 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) ")");

 /*
  * AMD Elan SC520 - Watchdog Timer Registers
  */
 #define MMCR_BASE	0xfffef000	/* The default base address */
 #define OFFS_WDTMRCTL	0xCB0	/* Watchdog Timer Control Register */

 /* WDT Control Register bit definitions */
 #define WDT_EXP_SEL_01	0x0001	/* [01] Time-out = 496 us (with 33 Mhz clk). */
 #define WDT_EXP_SEL_02	0x0002	/* [02] Time-out = 508 ms (with 33 Mhz clk). */
 #define WDT_EXP_SEL_03	0x0004	/* [03] Time-out = 1.02 s (with 33 Mhz clk). */
 #define WDT_EXP_SEL_04	0x0008	/* [04] Time-out = 2.03 s (with 33 Mhz clk). */
 #define WDT_EXP_SEL_05	0x0010	/* [05] Time-out = 4.07 s (with 33 Mhz clk). */
 #define WDT_EXP_SEL_06	0x0020	/* [06] Time-out = 8.13 s (with 33 Mhz clk). */
 #define WDT_EXP_SEL_07	0x0040	/* [07] Time-out = 16.27s (with 33 Mhz clk). */
 #define WDT_EXP_SEL_08	0x0080	/* [08] Time-out = 32.54s (with 33 Mhz clk). */
 #define WDT_IRQ_FLG	0x1000	/* [12] Interrupt Request Flag */
 #define WDT_WRST_ENB	0x4000	/* [14] Watchdog Timer Reset Enable */
 #define WDT_ENB		0x8000	/* [15] Watchdog Timer Enable */

 static __u16 __iomem *wdtmrctl;

 static void wdt_timer_ping(struct timer_list *);
 static DEFINE_TIMER(timer, wdt_timer_ping);
 static unsigned long next_heartbeat;
 static unsigned long wdt_is_open;
 static char wdt_expect_close;
 static DEFINE_SPINLOCK(wdt_spinlock);

 /*
  *	Whack the dog
  */

 static void wdt_timer_ping(struct timer_list *unused)
 {
 	/* 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 */
 		spin_lock(&wdt_spinlock);
 		writew(0xAAAA, wdtmrctl);
 		writew(0x5555, wdtmrctl);
 		spin_unlock(&wdt_spinlock);

 		/* Re-set the timer interval */
 		mod_timer(&timer, jiffies + WDT_INTERVAL);
 	} else
 		pr_warn("Heartbeat lost! Will not ping the watchdog\n");
 }

 /*
  *	Utility routines
  */

 static void wdt_config(int writeval)
 {
 	unsigned long flags;

 	/* buy some time (ping) */
 	spin_lock_irqsave(&wdt_spinlock, flags);
 	readw(wdtmrctl);	/* ensure write synchronization */
 	writew(0xAAAA, wdtmrctl);
 	writew(0x5555, wdtmrctl);
 	/* unlock WDT = make WDT configuration register writable one time */
 	writew(0x3333, wdtmrctl);
 	writew(0xCCCC, wdtmrctl);
 	/* write WDT configuration register */
 	writew(writeval, wdtmrctl);
 	spin_unlock_irqrestore(&wdt_spinlock, flags);
 }

 static int wdt_startup(void)
 {
 	next_heartbeat = jiffies + (timeout * HZ);

 	/* Start the timer */
 	mod_timer(&timer, jiffies + WDT_INTERVAL);

 	/* Start the watchdog */
 	wdt_config(WDT_ENB | WDT_WRST_ENB | WDT_EXP_SEL_04);

 	pr_info("Watchdog timer is now enabled\n");
 	return 0;
 }

 static int wdt_turnoff(void)
 {
 	/* Stop the timer */
 	del_timer_sync(&timer);

 	/* Stop the watchdog */
 	wdt_config(0);

 	pr_info("Watchdog timer is now disabled...\n");
 	return 0;
 }

 static int wdt_keepalive(void)
 {
 	/* user land ping */
 	next_heartbeat = jiffies + (timeout * HZ);
 	return 0;
 }

 static int wdt_set_heartbeat(int t)
 {
 	if ((t < 1) || (t > 3600))	/* arbitrary upper limit */
 		return -EINVAL;

 	timeout = t;
 	return 0;
 }

 /*
  *	/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;

 			/* now scan */
 			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 stream_open(inode, file);
 }

 static int fop_close(struct inode *inode, struct file *file)
 {
 	if (wdt_expect_close == 42)
 		wdt_turnoff();
 	else {
 		pr_crit("Unexpected close, not stopping watchdog!\n");
 		wdt_keepalive();
 	}
 	clear_bit(0, &wdt_is_open);
 	wdt_expect_close = 0;
 	return 0;
 }

 static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	void __user *argp = (void __user *)arg;
 	int __user *p = argp;
 	static const struct watchdog_info ident = {
 		.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT
 							| WDIOF_MAGICCLOSE,
 		.firmware_version = 1,
 		.identity = "SC520",
 	};

 	switch (cmd) {
 	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_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_KEEPALIVE:
 		wdt_keepalive();
 		return 0;
 	case WDIOC_SETTIMEOUT:
 	{
 		int new_timeout;

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

 		if (wdt_set_heartbeat(new_timeout))
 			return -EINVAL;

 		wdt_keepalive();
 	}
 		fallthrough;
 	case WDIOC_GETTIMEOUT:
 		return put_user(timeout, p);
 	default:
 		return -ENOTTY;
 	}
 }

 static const struct file_operations wdt_fops = {
 	.owner		= THIS_MODULE,
 	.write		= fop_write,
 	.open		= fop_open,
 	.release	= fop_close,
 	.unlocked_ioctl	= fop_ioctl,
 	.compat_ioctl	= compat_ptr_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 sc520_wdt_unload(void)
 {
 	if (!nowayout)
 		wdt_turnoff();

 	/* Deregister */
 	misc_deregister(&wdt_miscdev);
 	unregister_reboot_notifier(&wdt_notifier);
 	iounmap(wdtmrctl);
 }

 static int __init sc520_wdt_init(void)
 {
 	int rc = -EBUSY;

 	/* Check that the timeout value is within it's range ;
 	   if not reset to the default */
 	if (wdt_set_heartbeat(timeout)) {
 		wdt_set_heartbeat(WATCHDOG_TIMEOUT);
 		pr_info("timeout value must be 1 <= timeout <= 3600, using %d\n",
 			WATCHDOG_TIMEOUT);
 	}

 	wdtmrctl = ioremap(MMCR_BASE + OFFS_WDTMRCTL, 2);
 	if (!wdtmrctl) {
 		pr_err("Unable to remap memory\n");
 		rc = -ENOMEM;
 		goto err_out_region2;
 	}

 	rc = register_reboot_notifier(&wdt_notifier);
 	if (rc) {
 		pr_err("cannot register reboot notifier (err=%d)\n", rc);
 		goto err_out_ioremap;
 	}

 	rc = misc_register(&wdt_miscdev);
 	if (rc) {
 		pr_err("cannot register miscdev on minor=%d (err=%d)\n",
 		       WATCHDOG_MINOR, rc);
 		goto err_out_notifier;
 	}

 	pr_info("WDT driver for SC520 initialised. timeout=%d sec (nowayout=%d)\n",
 		timeout, nowayout);

 	return 0;

 err_out_notifier:
 	unregister_reboot_notifier(&wdt_notifier);
 err_out_ioremap:
 	iounmap(wdtmrctl);
 err_out_region2:
 	return rc;
 }

 module_init(sc520_wdt_init);
 module_exit(sc520_wdt_unload);

 MODULE_AUTHOR("Scott and Bill Jennings");
 MODULE_DESCRIPTION(
 	"Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* AMD Elan SC520 processor Watchdog Timer driver
	*
	* Based on acquirewdt.c by Alan Cox,
	* and sbc60xxwdt.c by Jakob Oestergaard <jakob@unthought.net>
	*
	* The authors do 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 2001 Scott Jennings <linuxdrivers@oro.net>
	* 9/27 - 2001 [Initial release]
	*
	* Additional fixes Alan Cox
	* - Fixed formatting
	* - Removed debug printks
	* - Fixed SMP built kernel deadlock
	* - Switched to private locks not lock_kernel
	* - Used ioremap/writew/readw
	* - Added NOWAYOUT support
	* 4/12 - 2002 Changes by Rob Radez <rob@osinvestor.com>
	* - Change comments
	* - Eliminate fop_llseek
	* - Change CONFIG_WATCHDOG_NOWAYOUT semantics
	* - Add KERN_* tags to printks
	* - fix possible wdt_is_open race
	* - Report proper capabilities in watchdog_info
	* - Add WDIOC_{GETSTATUS, GETBOOTSTATUS, SETTIMEOUT,
	* GETTIMEOUT, SETOPTIONS} ioctls
	* 09/8 - 2003 Changes by Wim Van Sebroeck <wim@iguana.be>
	* - cleanup of trailing spaces
	* - added extra printk's for startup problems
	* - use module_param
	* - made timeout (the emulated heartbeat) a module_param
	* - made the keepalive ping an internal subroutine
	* 3/27 - 2004 Changes by Sean Young <sean@mess.org>
	* - set MMCR_BASE to 0xfffef000
	* - CBAR does not need to be read
	* - removed debugging printks
	*
	* This WDT driver is different from most other Linux WDT
	* drivers in that the driver will ping the watchdog by itself,
	* because this particular WDT has a very short timeout (1.6
	* seconds) and it would be insane to count on any userspace
	* daemon always getting scheduled within that time frame.
	*
	* This driver uses memory mapped IO, and spinlock.
	*/

	#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/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/jiffies.h>
	#include <linux/io.h>
	#include <linux/uaccess.h>


	/*
	* The AMD Elan SC520 timeout value is 492us times a power of 2 (0-7)
	*
	* 0: 492us 2: 1.01s 4: 4.03s 6: 16.22s
	* 1: 503ms 3: 2.01s 5: 8.05s 7: 32.21s
	*
	* We will program the SC520 watchdog for a timeout of 2.01s.
	* 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.
	*/

	#define WATCHDOG_TIMEOUT 30 /* 30 sec default timeout */
	/* in seconds, will be multiplied by HZ to get seconds to wait for a ping */
	static int timeout = WATCHDOG_TIMEOUT;
	module_param(timeout, int, 0);
	MODULE_PARM_DESC(timeout,
	"Watchdog timeout in seconds. (1 <= timeout <= 3600, default="
	__MODULE_STRING(WATCHDOG_TIMEOUT) ")");

	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) ")");

	/*
	* AMD Elan SC520 - Watchdog Timer Registers
	*/
	#define MMCR_BASE 0xfffef000 /* The default base address */
	#define OFFS_WDTMRCTL 0xCB0 /* Watchdog Timer Control Register */

	/* WDT Control Register bit definitions */
	#define WDT_EXP_SEL_01 0x0001 /* [01] Time-out = 496 us (with 33 Mhz clk). */
	#define WDT_EXP_SEL_02 0x0002 /* [02] Time-out = 508 ms (with 33 Mhz clk). */
	#define WDT_EXP_SEL_03 0x0004 /* [03] Time-out = 1.02 s (with 33 Mhz clk). */
	#define WDT_EXP_SEL_04 0x0008 /* [04] Time-out = 2.03 s (with 33 Mhz clk). */
	#define WDT_EXP_SEL_05 0x0010 /* [05] Time-out = 4.07 s (with 33 Mhz clk). */
	#define WDT_EXP_SEL_06 0x0020 /* [06] Time-out = 8.13 s (with 33 Mhz clk). */
	#define WDT_EXP_SEL_07 0x0040 /* [07] Time-out = 16.27s (with 33 Mhz clk). */
	#define WDT_EXP_SEL_08 0x0080 /* [08] Time-out = 32.54s (with 33 Mhz clk). */
	#define WDT_IRQ_FLG 0x1000 /* [12] Interrupt Request Flag */
	#define WDT_WRST_ENB 0x4000 /* [14] Watchdog Timer Reset Enable */
	#define WDT_ENB 0x8000 /* [15] Watchdog Timer Enable */

	static __u16 __iomem *wdtmrctl;

	static void wdt_timer_ping(struct timer_list *);
	static DEFINE_TIMER(timer, wdt_timer_ping);
	static unsigned long next_heartbeat;
	static unsigned long wdt_is_open;
	static char wdt_expect_close;
	static DEFINE_SPINLOCK(wdt_spinlock);

	/*
	* Whack the dog
	*/

	static void wdt_timer_ping(struct timer_list *unused)
	{
	/* 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 */
	spin_lock(&wdt_spinlock);
	writew(0xAAAA, wdtmrctl);
	writew(0x5555, wdtmrctl);
	spin_unlock(&wdt_spinlock);

	/* Re-set the timer interval */
	mod_timer(&timer, jiffies + WDT_INTERVAL);
	} else
	pr_warn("Heartbeat lost! Will not ping the watchdog\n");
	}

	/*
	* Utility routines
	*/

	static void wdt_config(int writeval)
	{
	unsigned long flags;

	/* buy some time (ping) */
	spin_lock_irqsave(&wdt_spinlock, flags);
	readw(wdtmrctl); /* ensure write synchronization */
	writew(0xAAAA, wdtmrctl);
	writew(0x5555, wdtmrctl);
	/* unlock WDT = make WDT configuration register writable one time */
	writew(0x3333, wdtmrctl);
	writew(0xCCCC, wdtmrctl);
	/* write WDT configuration register */
	writew(writeval, wdtmrctl);
	spin_unlock_irqrestore(&wdt_spinlock, flags);
	}

	static int wdt_startup(void)
	{
	next_heartbeat = jiffies + (timeout * HZ);

	/* Start the timer */
	mod_timer(&timer, jiffies + WDT_INTERVAL);

	/* Start the watchdog */
	wdt_config(WDT_ENB \| WDT_WRST_ENB \| WDT_EXP_SEL_04);

	pr_info("Watchdog timer is now enabled\n");
	return 0;
	}

	static int wdt_turnoff(void)
	{
	/* Stop the timer */
	del_timer_sync(&timer);

	/* Stop the watchdog */
	wdt_config(0);

	pr_info("Watchdog timer is now disabled...\n");
	return 0;
	}

	static int wdt_keepalive(void)
	{
	/* user land ping */
	next_heartbeat = jiffies + (timeout * HZ);
	return 0;
	}

	static int wdt_set_heartbeat(int t)
	{
	if ((t < 1) \|\| (t > 3600)) /* arbitrary upper limit */
	return -EINVAL;

	timeout = t;
	return 0;
	}

	/*
	* /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;

	/* now scan */
	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 stream_open(inode, file);
	}

	static int fop_close(struct inode inode, struct file file)
	{
	if (wdt_expect_close == 42)
	wdt_turnoff();
	else {
	pr_crit("Unexpected close, not stopping watchdog!\n");
	wdt_keepalive();
	}
	clear_bit(0, &wdt_is_open);
	wdt_expect_close = 0;
	return 0;
	}

	static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
	{
	void __user argp = (void __user )arg;
	int __user *p = argp;
	static const struct watchdog_info ident = {
	.options = WDIOF_KEEPALIVEPING \| WDIOF_SETTIMEOUT
	\| WDIOF_MAGICCLOSE,
	.firmware_version = 1,
	.identity = "SC520",
	};

	switch (cmd) {
	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_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_KEEPALIVE:
	wdt_keepalive();
	return 0;
	case WDIOC_SETTIMEOUT:
	{
	int new_timeout;

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

	if (wdt_set_heartbeat(new_timeout))
	return -EINVAL;

	wdt_keepalive();
	}
	fallthrough;
	case WDIOC_GETTIMEOUT:
	return put_user(timeout, p);
	default:
	return -ENOTTY;
	}
	}

	static const struct file_operations wdt_fops = {
	.owner = THIS_MODULE,
	.write = fop_write,
	.open = fop_open,
	.release = fop_close,
	.unlocked_ioctl = fop_ioctl,
	.compat_ioctl = compat_ptr_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 sc520_wdt_unload(void)
	{
	if (!nowayout)
	wdt_turnoff();

	/* Deregister */
	misc_deregister(&wdt_miscdev);
	unregister_reboot_notifier(&wdt_notifier);
	iounmap(wdtmrctl);
	}

	static int __init sc520_wdt_init(void)
	{
	int rc = -EBUSY;

	/* Check that the timeout value is within it's range ;
	if not reset to the default */
	if (wdt_set_heartbeat(timeout)) {
	wdt_set_heartbeat(WATCHDOG_TIMEOUT);
	pr_info("timeout value must be 1 <= timeout <= 3600, using %d\n",
	WATCHDOG_TIMEOUT);
	}

	wdtmrctl = ioremap(MMCR_BASE + OFFS_WDTMRCTL, 2);
	if (!wdtmrctl) {
	pr_err("Unable to remap memory\n");
	rc = -ENOMEM;
	goto err_out_region2;
	}

	rc = register_reboot_notifier(&wdt_notifier);
	if (rc) {
	pr_err("cannot register reboot notifier (err=%d)\n", rc);
	goto err_out_ioremap;
	}

	rc = misc_register(&wdt_miscdev);
	if (rc) {
	pr_err("cannot register miscdev on minor=%d (err=%d)\n",
	WATCHDOG_MINOR, rc);
	goto err_out_notifier;
	}

	pr_info("WDT driver for SC520 initialised. timeout=%d sec (nowayout=%d)\n",
	timeout, nowayout);

	return 0;

	err_out_notifier:
	unregister_reboot_notifier(&wdt_notifier);
	err_out_ioremap:
	iounmap(wdtmrctl);
	err_out_region2:
	return rc;
	}

	module_init(sc520_wdt_init);
	module_exit(sc520_wdt_unload);

	MODULE_AUTHOR("Scott and Bill Jennings");
	MODULE_DESCRIPTION(
	"Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor");
	MODULE_LICENSE("GPL");