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/module.h>
21 #include <linux/moduleparam.h>
22 #include <linux/init.h>
23 #include <linux/types.h>
24 #include <linux/miscdevice.h>
25 #include <linux/watchdog.h>
26 #include <linux/reboot.h>
27 #include <linux/notifier.h>
28 #include <linux/ioport.h>
32 #include <asm/uaccess.h>
33 #include <asm/watchdog.h>
38 * Default clock division ratio is 5.25 msecs. For an additional table of
39 * values, consult the asm-sh/watchdog.h. Overload this at module load
42 * In order for this to work reliably we need to have HZ set to 1000 or
43 * something quite higher than 100 (or we need a proper high-res timer
44 * implementation that will deal with this properly), otherwise the 10ms
45 * resolution of a jiffy is enough to trigger the overflow. For things like
46 * the SH-4 and SH-5, this isn't necessarily that big of a problem, though
47 * for the SH-2 and SH-3, this isn't recommended unless the WDT is absolutely
50 * As a result of this timing problem, the only modes that are particularly
51 * feasible are the 4096 and the 2048 divisors, which yeild 5.25 and 2.62ms
52 * overflow periods respectively.
54 * Also, since we can't really expect userspace to be responsive enough
55 * before the overflow happens, we maintain two seperate timers .. One in
56 * the kernel for clearing out WOVF every 2ms or so (again, this depends on
57 * HZ == 1000), and another for monitoring userspace writes to the WDT device.
59 * As such, we currently use a configurable heartbeat interval which defaults
60 * to 30s. In this case, the userspace daemon is only responsible for periodic
61 * writes to the device before the next heartbeat is scheduled. If the daemon
62 * misses its deadline, the kernel timer will allow the WDT to overflow.
64 static int clock_division_ratio
= WTCSR_CKS_4096
;
66 #define next_ping_period(cks) msecs_to_jiffies(cks - 4)
68 static unsigned long shwdt_is_open
;
69 static struct watchdog_info sh_wdt_info
;
70 static char shwdt_expect_close
;
71 static struct timer_list timer
;
72 static unsigned long next_heartbeat
;
74 #define WATCHDOG_HEARTBEAT 30 /* 30 sec default heartbeat */
75 static int heartbeat
= WATCHDOG_HEARTBEAT
; /* in seconds */
77 static int nowayout
= WATCHDOG_NOWAYOUT
;
80 * sh_wdt_start - Start the Watchdog
82 * Starts the watchdog.
84 static void sh_wdt_start(void)
88 next_heartbeat
= jiffies
+ (heartbeat
* HZ
);
89 mod_timer(&timer
, next_ping_period(clock_division_ratio
));
91 csr
= sh_wdt_read_csr();
92 csr
|= WTCSR_WT
| clock_division_ratio
;
93 sh_wdt_write_csr(csr
);
98 * These processors have a bit of an inconsistent initialization
99 * process.. starting with SH-3, RSTS was moved to WTCSR, and the
100 * RSTCSR register was removed.
102 * On the SH-2 however, in addition with bits being in different
103 * locations, we must deal with RSTCSR outright..
105 csr
= sh_wdt_read_csr();
108 sh_wdt_write_csr(csr
);
110 #ifdef CONFIG_CPU_SH2
112 * Whoever came up with the RSTCSR semantics must've been smoking
113 * some of the good stuff, since in addition to the WTCSR/WTCNT write
114 * brain-damage, it's managed to fuck things up one step further..
116 * If we need to clear the WOVF bit, the upper byte has to be 0xa5..
117 * but if we want to touch RSTE or RSTS, the upper byte has to be
120 csr
= sh_wdt_read_rstcsr();
122 sh_wdt_write_rstcsr(csr
);
127 * sh_wdt_stop - Stop the Watchdog
129 * Stops the watchdog.
131 static void sh_wdt_stop(void)
137 csr
= sh_wdt_read_csr();
139 sh_wdt_write_csr(csr
);
143 * sh_wdt_keepalive - Keep the Userspace Watchdog Alive
145 * The Userspace watchdog got a KeepAlive: schedule the next heartbeat.
147 static void sh_wdt_keepalive(void)
149 next_heartbeat
= jiffies
+ (heartbeat
* HZ
);
153 * sh_wdt_set_heartbeat - Set the Userspace Watchdog heartbeat
155 * Set the Userspace Watchdog heartbeat
157 static int sh_wdt_set_heartbeat(int t
)
159 if ((t
< 1) || (t
> 3600)) /* arbitrary upper limit */
167 * sh_wdt_ping - Ping the Watchdog
171 * Clears overflow bit, resets timer counter.
173 static void sh_wdt_ping(unsigned long data
)
175 if (time_before(jiffies
, next_heartbeat
)) {
178 csr
= sh_wdt_read_csr();
180 sh_wdt_write_csr(csr
);
184 mod_timer(&timer
, next_ping_period(clock_division_ratio
));
186 printk(KERN_WARNING PFX
"Heartbeat lost! Will not ping the watchdog\n");
191 * sh_wdt_open - Open the Device
193 * @inode: inode of device
194 * @file: file handle of device
196 * Watchdog device is opened and started.
198 static int sh_wdt_open(struct inode
*inode
, struct file
*file
)
200 if (test_and_set_bit(0, &shwdt_is_open
))
203 __module_get(THIS_MODULE
);
207 return nonseekable_open(inode
, file
);
211 * sh_wdt_close - Close the Device
213 * @inode: inode of device
214 * @file: file handle of device
216 * Watchdog device is closed and stopped.
218 static int sh_wdt_close(struct inode
*inode
, struct file
*file
)
220 if (shwdt_expect_close
== 42) {
223 printk(KERN_CRIT PFX
"Unexpected close, not stopping watchdog!\n");
227 clear_bit(0, &shwdt_is_open
);
228 shwdt_expect_close
= 0;
234 * sh_wdt_write - Write to Device
236 * @file: file handle of device
237 * @buf: buffer to write
238 * @count: length of buffer
241 * Pings the watchdog on write.
243 static ssize_t
sh_wdt_write(struct file
*file
, const char *buf
,
244 size_t count
, loff_t
*ppos
)
250 shwdt_expect_close
= 0;
252 for (i
= 0; i
!= count
; i
++) {
254 if (get_user(c
, buf
+ i
))
257 shwdt_expect_close
= 42;
267 * sh_wdt_ioctl - Query Device
269 * @inode: inode of device
270 * @file: file handle of device
271 * @cmd: watchdog command
274 * Query basic information from the device or ping it, as outlined by the
277 static int sh_wdt_ioctl(struct inode
*inode
, struct file
*file
,
278 unsigned int cmd
, unsigned long arg
)
281 int options
, retval
= -EINVAL
;
284 case WDIOC_GETSUPPORT
:
285 return copy_to_user((struct watchdog_info
*)arg
,
287 sizeof(sh_wdt_info
)) ? -EFAULT
: 0;
288 case WDIOC_GETSTATUS
:
289 case WDIOC_GETBOOTSTATUS
:
290 return put_user(0, (int *)arg
);
291 case WDIOC_KEEPALIVE
:
294 case WDIOC_SETTIMEOUT
:
295 if (get_user(new_heartbeat
, (int *)arg
))
298 if (sh_wdt_set_heartbeat(new_heartbeat
))
303 case WDIOC_GETTIMEOUT
:
304 return put_user(heartbeat
, (int *)arg
);
305 case WDIOC_SETOPTIONS
:
306 if (get_user(options
, (int *)arg
))
309 if (options
& WDIOS_DISABLECARD
) {
314 if (options
& WDIOS_ENABLECARD
) {
328 * sh_wdt_notify_sys - Notifier Handler
330 * @this: notifier block
331 * @code: notifier event
334 * Handles specific events, such as turning off the watchdog during a
337 static int sh_wdt_notify_sys(struct notifier_block
*this,
338 unsigned long code
, void *unused
)
340 if (code
== SYS_DOWN
|| code
== SYS_HALT
) {
347 static struct file_operations sh_wdt_fops
= {
348 .owner
= THIS_MODULE
,
350 .write
= sh_wdt_write
,
351 .ioctl
= sh_wdt_ioctl
,
353 .release
= sh_wdt_close
,
356 static struct watchdog_info sh_wdt_info
= {
357 .options
= WDIOF_KEEPALIVEPING
| WDIOF_SETTIMEOUT
| WDIOF_MAGICCLOSE
,
358 .firmware_version
= 1,
359 .identity
= "SH WDT",
362 static struct notifier_block sh_wdt_notifier
= {
363 .notifier_call
= sh_wdt_notify_sys
,
366 static struct miscdevice sh_wdt_miscdev
= {
367 .minor
= WATCHDOG_MINOR
,
369 .fops
= &sh_wdt_fops
,
373 * sh_wdt_init - Initialize module
375 * Registers the device and notifier handler. Actual device
376 * initialization is handled by sh_wdt_open().
378 static int __init
sh_wdt_init(void)
382 if ((clock_division_ratio
< 0x5) || (clock_division_ratio
> 0x7)) {
383 clock_division_ratio
= WTCSR_CKS_4096
;
384 printk(KERN_INFO PFX
"clock_division_ratio value must be 0x5<=x<=0x7, using %d\n",
385 clock_division_ratio
);
388 if (sh_wdt_set_heartbeat(heartbeat
))
390 heartbeat
= WATCHDOG_HEARTBEAT
;
391 printk(KERN_INFO PFX
"heartbeat value must be 1<=x<=3600, using %d\n",
396 timer
.function
= sh_wdt_ping
;
399 rc
= register_reboot_notifier(&sh_wdt_notifier
);
401 printk(KERN_ERR PFX
"Can't register reboot notifier (err=%d)\n", rc
);
405 rc
= misc_register(&sh_wdt_miscdev
);
407 printk(KERN_ERR PFX
"Can't register miscdev on minor=%d (err=%d)\n",
408 sh_wdt_miscdev
.minor
, rc
);
409 unregister_reboot_notifier(&sh_wdt_notifier
);
413 printk(KERN_INFO PFX
"initialized. heartbeat=%d sec (nowayout=%d)\n",
414 heartbeat
, nowayout
);
420 * sh_wdt_exit - Deinitialize module
422 * Unregisters the device and notifier handler. Actual device
423 * deinitialization is handled by sh_wdt_close().
425 static void __exit
sh_wdt_exit(void)
427 misc_deregister(&sh_wdt_miscdev
);
428 unregister_reboot_notifier(&sh_wdt_notifier
);
431 MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
432 MODULE_DESCRIPTION("SuperH watchdog driver");
433 MODULE_LICENSE("GPL");
434 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR
);
436 module_param(clock_division_ratio
, int, 0);
437 MODULE_PARM_DESC(clock_division_ratio
, "Clock division ratio. Valid ranges are from 0x5 (1.31ms) to 0x7 (5.25ms). Defaults to 0x7.");
439 module_param(heartbeat
, int, 0);
440 MODULE_PARM_DESC(heartbeat
, "Watchdog heartbeat in seconds. (1<=heartbeat<=3600, default=" __MODULE_STRING(WATCHDOG_HEARTBEAT
) ")");
442 module_param(nowayout
, int, 0);
443 MODULE_PARM_DESC(nowayout
, "Watchdog cannot be stopped once started (default=CONFIG_WATCHDOG_NOWAYOUT)");
445 module_init(sh_wdt_init
);
446 module_exit(sh_wdt_exit
);