2 * drivers/char/watchdog/shwdt.c
4 * Watchdog driver for integrated watchdog in the SuperH processors.
6 * Copyright (C) 2001, 2002, 2003 Paul Mundt <lethal@linux-sh.org>
8 * This program is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License as published by the
10 * Free Software Foundation; either version 2 of the License, or (at your
11 * option) any later version.
13 * 14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
14 * Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
16 * 19-Apr-2002 Rob Radez <rob@osinvestor.com>
17 * Added expect close support, made emulated timeout runtime changeable
18 * general cleanups, add some ioctls
20 #include <linux/config.h>
21 #include <linux/module.h>
22 #include <linux/moduleparam.h>
23 #include <linux/init.h>
24 #include <linux/types.h>
25 #include <linux/miscdevice.h>
26 #include <linux/watchdog.h>
27 #include <linux/reboot.h>
28 #include <linux/notifier.h>
29 #include <linux/ioport.h>
33 #include <asm/uaccess.h>
34 #include <asm/watchdog.h>
39 * Default clock division ratio is 5.25 msecs. For an additional table of
40 * values, consult the asm-sh/watchdog.h. Overload this at module load
43 * In order for this to work reliably we need to have HZ set to 1000 or
44 * something quite higher than 100 (or we need a proper high-res timer
45 * implementation that will deal with this properly), otherwise the 10ms
46 * resolution of a jiffy is enough to trigger the overflow. For things like
47 * the SH-4 and SH-5, this isn't necessarily that big of a problem, though
48 * for the SH-2 and SH-3, this isn't recommended unless the WDT is absolutely
51 * As a result of this timing problem, the only modes that are particularly
52 * feasible are the 4096 and the 2048 divisors, which yeild 5.25 and 2.62ms
53 * overflow periods respectively.
55 * Also, since we can't really expect userspace to be responsive enough
56 * before the overflow happens, we maintain two seperate timers .. One in
57 * the kernel for clearing out WOVF every 2ms or so (again, this depends on
58 * HZ == 1000), and another for monitoring userspace writes to the WDT device.
60 * As such, we currently use a configurable heartbeat interval which defaults
61 * to 30s. In this case, the userspace daemon is only responsible for periodic
62 * writes to the device before the next heartbeat is scheduled. If the daemon
63 * misses its deadline, the kernel timer will allow the WDT to overflow.
65 static int clock_division_ratio = WTCSR_CKS_4096;
67 #define msecs_to_jiffies(msecs) (jiffies + (HZ * msecs + 9999) / 10000)
68 #define next_ping_period(cks) msecs_to_jiffies(cks - 4)
70 static unsigned long shwdt_is_open;
71 static struct watchdog_info sh_wdt_info;
72 static char shwdt_expect_close;
73 static struct timer_list timer;
74 static unsigned long next_heartbeat;
76 #define WATCHDOG_HEARTBEAT 30 /* 30 sec default heartbeat */
77 static int heartbeat = WATCHDOG_HEARTBEAT; /* in seconds */
79 #ifdef CONFIG_WATCHDOG_NOWAYOUT
80 static int nowayout = 1;
82 static int nowayout = 0;
86 * sh_wdt_start - Start the Watchdog
88 * Starts the watchdog.
90 static void sh_wdt_start(void)
94 next_heartbeat = jiffies + (heartbeat * HZ);
95 mod_timer(&timer, next_ping_period(clock_division_ratio));
97 csr = sh_wdt_read_csr();
98 csr |= WTCSR_WT | clock_division_ratio;
99 sh_wdt_write_csr(csr);
104 * These processors have a bit of an inconsistent initialization
105 * process.. starting with SH-3, RSTS was moved to WTCSR, and the
106 * RSTCSR register was removed.
108 * On the SH-2 however, in addition with bits being in different
109 * locations, we must deal with RSTCSR outright..
111 csr = sh_wdt_read_csr();
114 sh_wdt_write_csr(csr);
116 #ifdef CONFIG_CPU_SH2
118 * Whoever came up with the RSTCSR semantics must've been smoking
119 * some of the good stuff, since in addition to the WTCSR/WTCNT write
120 * brain-damage, it's managed to fuck things up one step further..
122 * If we need to clear the WOVF bit, the upper byte has to be 0xa5..
123 * but if we want to touch RSTE or RSTS, the upper byte has to be
126 csr = sh_wdt_read_rstcsr();
128 sh_wdt_write_rstcsr(csr);
133 * sh_wdt_stop - Stop the Watchdog
135 * Stops the watchdog.
137 static void sh_wdt_stop(void)
143 csr = sh_wdt_read_csr();
145 sh_wdt_write_csr(csr);
149 * sh_wdt_keepalive - Keep the Userspace Watchdog Alive
151 * The Userspace watchdog got a KeepAlive: schedule the next heartbeat.
153 static void sh_wdt_keepalive(void)
155 next_heartbeat = jiffies + (heartbeat * HZ);
159 * sh_wdt_set_heartbeat - Set the Userspace Watchdog heartbeat
161 * Set the Userspace Watchdog heartbeat
163 static int sh_wdt_set_heartbeat(int t)
165 if ((t < 1) || (t > 3600)) /* arbitrary upper limit */
173 * sh_wdt_ping - Ping the Watchdog
177 * Clears overflow bit, resets timer counter.
179 static void sh_wdt_ping(unsigned long data)
181 if (time_before(jiffies, next_heartbeat)) {
184 csr = sh_wdt_read_csr();
186 sh_wdt_write_csr(csr);
190 mod_timer(&timer, next_ping_period(clock_division_ratio));
192 printk(KERN_WARNING PFX "Heartbeat lost! Will not ping the watchdog\n");
197 * sh_wdt_open - Open the Device
199 * @inode: inode of device
200 * @file: file handle of device
202 * Watchdog device is opened and started.
204 static int sh_wdt_open(struct inode *inode, struct file *file)
206 if (test_and_set_bit(0, &shwdt_is_open))
209 __module_get(THIS_MODULE);
217 * sh_wdt_close - Close the Device
219 * @inode: inode of device
220 * @file: file handle of device
222 * Watchdog device is closed and stopped.
224 static int sh_wdt_close(struct inode *inode, struct file *file)
226 if (shwdt_expect_close == 42) {
229 printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n");
233 clear_bit(0, &shwdt_is_open);
234 shwdt_expect_close = 0;
240 * sh_wdt_write - Write to Device
242 * @file: file handle of device
243 * @buf: buffer to write
244 * @count: length of buffer
247 * Pings the watchdog on write.
249 static ssize_t sh_wdt_write(struct file *file, const char *buf,
250 size_t count, loff_t *ppos)
252 /* Can't seek (pwrite) on this device */
253 if (ppos != &file->f_pos)
260 shwdt_expect_close = 0;
262 for (i = 0; i != count; i++) {
264 if (get_user(c, buf + i))
267 shwdt_expect_close = 42;
277 * sh_wdt_ioctl - Query Device
279 * @inode: inode of device
280 * @file: file handle of device
281 * @cmd: watchdog command
284 * Query basic information from the device or ping it, as outlined by the
287 static int sh_wdt_ioctl(struct inode *inode, struct file *file,
288 unsigned int cmd, unsigned long arg)
291 int options, retval = -EINVAL;
294 case WDIOC_GETSUPPORT:
295 return copy_to_user((struct watchdog_info *)arg,
297 sizeof(sh_wdt_info)) ? -EFAULT : 0;
298 case WDIOC_GETSTATUS:
299 case WDIOC_GETBOOTSTATUS:
300 return put_user(0, (int *)arg);
301 case WDIOC_KEEPALIVE:
304 case WDIOC_SETTIMEOUT:
305 if (get_user(new_heartbeat, (int *)arg))
308 if (sh_wdt_set_heartbeat(new_heartbeat))
313 case WDIOC_GETTIMEOUT:
314 return put_user(heartbeat, (int *)arg);
315 case WDIOC_SETOPTIONS:
316 if (get_user(options, (int *)arg))
319 if (options & WDIOS_DISABLECARD) {
324 if (options & WDIOS_ENABLECARD) {
338 * sh_wdt_notify_sys - Notifier Handler
340 * @this: notifier block
341 * @code: notifier event
344 * Handles specific events, such as turning off the watchdog during a
347 static int sh_wdt_notify_sys(struct notifier_block *this,
348 unsigned long code, void *unused)
350 if (code == SYS_DOWN || code == SYS_HALT) {
357 static struct file_operations sh_wdt_fops = {
358 .owner = THIS_MODULE,
360 .write = sh_wdt_write,
361 .ioctl = sh_wdt_ioctl,
363 .release = sh_wdt_close,
366 static struct watchdog_info sh_wdt_info = {
367 .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
368 .firmware_version = 1,
369 .identity = "SH WDT",
372 static struct notifier_block sh_wdt_notifier = {
373 .notifier_call = sh_wdt_notify_sys,
376 static struct miscdevice sh_wdt_miscdev = {
377 .minor = WATCHDOG_MINOR,
379 .fops = &sh_wdt_fops,
383 * sh_wdt_init - Initialize module
385 * Registers the device and notifier handler. Actual device
386 * initialization is handled by sh_wdt_open().
388 static int __init sh_wdt_init(void)
392 if ((clock_division_ratio < 0x5) || (clock_division_ratio > 0x7)) {
393 clock_division_ratio = WTCSR_CKS_4096;
394 printk(KERN_INFO PFX "clock_division_ratio value must be 0x5<=x<=0x7, using %d\n",
395 clock_division_ratio);
398 if (sh_wdt_set_heartbeat(heartbeat))
400 heartbeat = WATCHDOG_HEARTBEAT;
401 printk(KERN_INFO PFX "heartbeat value must be 1<=x<=3600, using %d\n",
406 timer.function = sh_wdt_ping;
409 rc = register_reboot_notifier(&sh_wdt_notifier);
411 printk(KERN_ERR PFX "Can't register reboot notifier (err=%d)\n", rc);
415 rc = misc_register(&sh_wdt_miscdev);
417 printk(KERN_ERR PFX "Can't register miscdev on minor=%d (err=%d)\n",
418 sh_wdt_miscdev.minor, rc);
419 unregister_reboot_notifier(&sh_wdt_notifier);
423 printk(KERN_INFO PFX "initialized. heartbeat=%d sec (nowayout=%d)\n",
424 heartbeat, nowayout);
430 * sh_wdt_exit - Deinitialize module
432 * Unregisters the device and notifier handler. Actual device
433 * deinitialization is handled by sh_wdt_close().
435 static void __exit sh_wdt_exit(void)
437 misc_deregister(&sh_wdt_miscdev);
438 unregister_reboot_notifier(&sh_wdt_notifier);
441 MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
442 MODULE_DESCRIPTION("SuperH watchdog driver");
443 MODULE_LICENSE("GPL");
444 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
446 module_param(clock_division_ratio, int, 0);
447 MODULE_PARM_DESC(clock_division_ratio, "Clock division ratio. Valid ranges are from 0x5 (1.31ms) to 0x7 (5.25ms). Defaults to 0x7.");
449 module_param(heartbeat, int, 0);
450 MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds. (1<=heartbeat<=3600, default=" __MODULE_STRING(WATCHDOG_HEARTBEAT) ")");
452 module_param(nowayout, int, 0);
453 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=CONFIG_WATCHDOG_NOWAYOUT)");
455 module_init(sh_wdt_init);
456 module_exit(sh_wdt_exit);