1 /*
2 * drivers/char/watchdog/shwdt.c
3 *
4 * Watchdog driver for integrated watchdog in the SuperH processors.
5 *
6 * Copyright (C) 2001, 2002, 2003 Paul Mundt <lethal@linux-sh.org>
7 *
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.
12 *
13 * 14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
14 * Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
15 *
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
19 */
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>
30 #include <linux/fs.h>
31
32 #include <asm/io.h>
33 #include <asm/uaccess.h>
34 #include <asm/watchdog.h>
35
36 #define PFX "shwdt: "
37
38 /*
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
41 * time.
42 *
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
49 * necssary.
50 *
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.
54 *
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.
59 *
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.
64 */
65 static int clock_division_ratio = WTCSR_CKS_4096;
66
67 #define next_ping_period(cks) msecs_to_jiffies(cks - 4)
68
69 static unsigned long shwdt_is_open;
70 static struct watchdog_info sh_wdt_info;
71 static char shwdt_expect_close;
72 static struct timer_list timer;
73 static unsigned long next_heartbeat;
74
75 #define WATCHDOG_HEARTBEAT 30 /* 30 sec default heartbeat */
76 static int heartbeat = WATCHDOG_HEARTBEAT; /* in seconds */
77
78 static int nowayout = WATCHDOG_NOWAYOUT;
79
80 /**
81 * sh_wdt_start - Start the Watchdog
82 *
83 * Starts the watchdog.
84 */
85 static void sh_wdt_start(void)
86 {
87 __u8 csr;
88
89 next_heartbeat = jiffies + (heartbeat * HZ);
90 mod_timer(&timer, next_ping_period(clock_division_ratio));
91
92 csr = sh_wdt_read_csr();
93 csr |= WTCSR_WT | clock_division_ratio;
94 sh_wdt_write_csr(csr);
95
96 sh_wdt_write_cnt(0);
97
98 /*
99 * These processors have a bit of an inconsistent initialization
100 * process.. starting with SH-3, RSTS was moved to WTCSR, and the
101 * RSTCSR register was removed.
102 *
103 * On the SH-2 however, in addition with bits being in different
104 * locations, we must deal with RSTCSR outright..
105 */
106 csr = sh_wdt_read_csr();
107 csr |= WTCSR_TME;
108 csr &= ~WTCSR_RSTS;
109 sh_wdt_write_csr(csr);
110
111 #ifdef CONFIG_CPU_SH2
112 /*
113 * Whoever came up with the RSTCSR semantics must've been smoking
114 * some of the good stuff, since in addition to the WTCSR/WTCNT write
115 * brain-damage, it's managed to fuck things up one step further..
116 *
117 * If we need to clear the WOVF bit, the upper byte has to be 0xa5..
118 * but if we want to touch RSTE or RSTS, the upper byte has to be
119 * 0x5a..
120 */
121 csr = sh_wdt_read_rstcsr();
122 csr &= ~RSTCSR_RSTS;
123 sh_wdt_write_rstcsr(csr);
124 #endif
125 }
126
127 /**
128 * sh_wdt_stop - Stop the Watchdog
129 *
130 * Stops the watchdog.
131 */
132 static void sh_wdt_stop(void)
133 {
134 __u8 csr;
135
136 del_timer(&timer);
137
138 csr = sh_wdt_read_csr();
139 csr &= ~WTCSR_TME;
140 sh_wdt_write_csr(csr);
141 }
142
143 /**
144 * sh_wdt_keepalive - Keep the Userspace Watchdog Alive
145 *
146 * The Userspace watchdog got a KeepAlive: schedule the next heartbeat.
147 */
148 static void sh_wdt_keepalive(void)
149 {
150 next_heartbeat = jiffies + (heartbeat * HZ);
151 }
152
153 /**
154 * sh_wdt_set_heartbeat - Set the Userspace Watchdog heartbeat
155 *
156 * Set the Userspace Watchdog heartbeat
157 */
158 static int sh_wdt_set_heartbeat(int t)
159 {
160 if ((t < 1) || (t > 3600)) /* arbitrary upper limit */
161 return -EINVAL;
162
163 heartbeat = t;
164 return 0;
165 }
166
167 /**
168 * sh_wdt_ping - Ping the Watchdog
169 *
170 * @data: Unused
171 *
172 * Clears overflow bit, resets timer counter.
173 */
174 static void sh_wdt_ping(unsigned long data)
175 {
176 if (time_before(jiffies, next_heartbeat)) {
177 __u8 csr;
178
179 csr = sh_wdt_read_csr();
180 csr &= ~WTCSR_IOVF;
181 sh_wdt_write_csr(csr);
182
183 sh_wdt_write_cnt(0);
184
185 mod_timer(&timer, next_ping_period(clock_division_ratio));
186 } else {
187 printk(KERN_WARNING PFX "Heartbeat lost! Will not ping the watchdog\n");
188 }
189 }
190
191 /**
192 * sh_wdt_open - Open the Device
193 *
194 * @inode: inode of device
195 * @file: file handle of device
196 *
197 * Watchdog device is opened and started.
198 */
199 static int sh_wdt_open(struct inode *inode, struct file *file)
200 {
201 if (test_and_set_bit(0, &shwdt_is_open))
202 return -EBUSY;
203 if (nowayout)
204 __module_get(THIS_MODULE);
205
206 sh_wdt_start();
207
208 return nonseekable_open(inode, file);
209 }
210
211 /**
212 * sh_wdt_close - Close the Device
213 *
214 * @inode: inode of device
215 * @file: file handle of device
216 *
217 * Watchdog device is closed and stopped.
218 */
219 static int sh_wdt_close(struct inode *inode, struct file *file)
220 {
221 if (shwdt_expect_close == 42) {
222 sh_wdt_stop();
223 } else {
224 printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n");
225 sh_wdt_keepalive();
226 }
227
228 clear_bit(0, &shwdt_is_open);
229 shwdt_expect_close = 0;
230
231 return 0;
232 }
233
234 /**
235 * sh_wdt_write - Write to Device
236 *
237 * @file: file handle of device
238 * @buf: buffer to write
239 * @count: length of buffer
240 * @ppos: offset
241 *
242 * Pings the watchdog on write.
243 */
244 static ssize_t sh_wdt_write(struct file *file, const char *buf,
245 size_t count, loff_t *ppos)
246 {
247 if (count) {
248 if (!nowayout) {
249 size_t i;
250
251 shwdt_expect_close = 0;
252
253 for (i = 0; i != count; i++) {
254 char c;
255 if (get_user(c, buf + i))
256 return -EFAULT;
257 if (c == 'V')
258 shwdt_expect_close = 42;
259 }
260 }
261 sh_wdt_keepalive();
262 }
263
264 return count;
265 }
266
267 /**
268 * sh_wdt_ioctl - Query Device
269 *
270 * @inode: inode of device
271 * @file: file handle of device
272 * @cmd: watchdog command
273 * @arg: argument
274 *
275 * Query basic information from the device or ping it, as outlined by the
276 * watchdog API.
277 */
278 static int sh_wdt_ioctl(struct inode *inode, struct file *file,
279 unsigned int cmd, unsigned long arg)
280 {
281 int new_heartbeat;
282 int options, retval = -EINVAL;
283
284 switch (cmd) {
285 case WDIOC_GETSUPPORT:
286 return copy_to_user((struct watchdog_info *)arg,
287 &sh_wdt_info,
288 sizeof(sh_wdt_info)) ? -EFAULT : 0;
289 case WDIOC_GETSTATUS:
290 case WDIOC_GETBOOTSTATUS:
291 return put_user(0, (int *)arg);
292 case WDIOC_KEEPALIVE:
293 sh_wdt_keepalive();
294 return 0;
295 case WDIOC_SETTIMEOUT:
296 if (get_user(new_heartbeat, (int *)arg))
297 return -EFAULT;
298
299 if (sh_wdt_set_heartbeat(new_heartbeat))
300 return -EINVAL;
301
302 sh_wdt_keepalive();
303 /* Fall */
304 case WDIOC_GETTIMEOUT:
305 return put_user(heartbeat, (int *)arg);
306 case WDIOC_SETOPTIONS:
307 if (get_user(options, (int *)arg))
308 return -EFAULT;
309
310 if (options & WDIOS_DISABLECARD) {
311 sh_wdt_stop();
312 retval = 0;
313 }
314
315 if (options & WDIOS_ENABLECARD) {
316 sh_wdt_start();
317 retval = 0;
318 }
319
320 return retval;
321 default:
322 return -ENOIOCTLCMD;
323 }
324
325 return 0;
326 }
327
328 /**
329 * sh_wdt_notify_sys - Notifier Handler
330 *
331 * @this: notifier block
332 * @code: notifier event
333 * @unused: unused
334 *
335 * Handles specific events, such as turning off the watchdog during a
336 * shutdown event.
337 */
338 static int sh_wdt_notify_sys(struct notifier_block *this,
339 unsigned long code, void *unused)
340 {
341 if (code == SYS_DOWN || code == SYS_HALT) {
342 sh_wdt_stop();
343 }
344
345 return NOTIFY_DONE;
346 }
347
348 static struct file_operations sh_wdt_fops = {
349 .owner = THIS_MODULE,
350 .llseek = no_llseek,
351 .write = sh_wdt_write,
352 .ioctl = sh_wdt_ioctl,
353 .open = sh_wdt_open,
354 .release = sh_wdt_close,
355 };
356
357 static struct watchdog_info sh_wdt_info = {
358 .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
359 .firmware_version = 1,
360 .identity = "SH WDT",
361 };
362
363 static struct notifier_block sh_wdt_notifier = {
364 .notifier_call = sh_wdt_notify_sys,
365 };
366
367 static struct miscdevice sh_wdt_miscdev = {
368 .minor = WATCHDOG_MINOR,
369 .name = "watchdog",
370 .fops = &sh_wdt_fops,
371 };
372
373 /**
374 * sh_wdt_init - Initialize module
375 *
376 * Registers the device and notifier handler. Actual device
377 * initialization is handled by sh_wdt_open().
378 */
379 static int __init sh_wdt_init(void)
380 {
381 int rc;
382
383 if ((clock_division_ratio < 0x5) || (clock_division_ratio > 0x7)) {
384 clock_division_ratio = WTCSR_CKS_4096;
385 printk(KERN_INFO PFX "clock_division_ratio value must be 0x5<=x<=0x7, using %d\n",
386 clock_division_ratio);
387 }
388
389 if (sh_wdt_set_heartbeat(heartbeat))
390 {
391 heartbeat = WATCHDOG_HEARTBEAT;
392 printk(KERN_INFO PFX "heartbeat value must be 1<=x<=3600, using %d\n",
393 heartbeat);
394 }
395
396 init_timer(&timer);
397 timer.function = sh_wdt_ping;
398 timer.data = 0;
399
400 rc = register_reboot_notifier(&sh_wdt_notifier);
401 if (rc) {
402 printk(KERN_ERR PFX "Can't register reboot notifier (err=%d)\n", rc);
403 return rc;
404 }
405
406 rc = misc_register(&sh_wdt_miscdev);
407 if (rc) {
408 printk(KERN_ERR PFX "Can't register miscdev on minor=%d (err=%d)\n",
409 sh_wdt_miscdev.minor, rc);
410 unregister_reboot_notifier(&sh_wdt_notifier);
411 return rc;
412 }
413
414 printk(KERN_INFO PFX "initialized. heartbeat=%d sec (nowayout=%d)\n",
415 heartbeat, nowayout);
416
417 return 0;
418 }
419
420 /**
421 * sh_wdt_exit - Deinitialize module
422 *
423 * Unregisters the device and notifier handler. Actual device
424 * deinitialization is handled by sh_wdt_close().
425 */
426 static void __exit sh_wdt_exit(void)
427 {
428 misc_deregister(&sh_wdt_miscdev);
429 unregister_reboot_notifier(&sh_wdt_notifier);
430 }
431
432 MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
433 MODULE_DESCRIPTION("SuperH watchdog driver");
434 MODULE_LICENSE("GPL");
435 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
436
437 module_param(clock_division_ratio, int, 0);
438 MODULE_PARM_DESC(clock_division_ratio, "Clock division ratio. Valid ranges are from 0x5 (1.31ms) to 0x7 (5.25ms). Defaults to 0x7.");
439
440 module_param(heartbeat, int, 0);
441 MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds. (1<=heartbeat<=3600, default=" __MODULE_STRING(WATCHDOG_HEARTBEAT) ")");
442
443 module_param(nowayout, int, 0);
444 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=CONFIG_WATCHDOG_NOWAYOUT)");
445
446 module_init(sh_wdt_init);
447 module_exit(sh_wdt_exit);
448
449
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