aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/char/watchdog/shwdt.c
blob: 1355038f10440e27f4a708eea95694f897edbc0a (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
/*
 * 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 <asm/io.h>
#include <asm/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 seperate 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 unsigned long shwdt_is_open;
static struct watchdog_info sh_wdt_info;
static char shwdt_expect_close;
static struct timer_list timer;
static unsigned long next_heartbeat;

#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;

	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
}

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

	del_timer(&timer);

	csr = sh_wdt_read_csr();
	csr &= ~WTCSR_TME;
	sh_wdt_write_csr(csr);
}

/**
 * 	sh_wdt_keepalive - Keep the Userspace Watchdog Alive
 *
 * 	The Userspace watchdog got a KeepAlive: schedule the next heartbeat.
 */
static void sh_wdt_keepalive(void)
{
	next_heartbeat = jiffies + (heartbeat * HZ);
}

/**
 * 	sh_wdt_set_heartbeat - Set the Userspace Watchdog heartbeat
 *
 * 	Set the Userspace Watchdog heartbeat
 */
static int sh_wdt_set_heartbeat(int t)
{
	if ((t < 1) || (t > 3600)) /* arbitrary upper limit */
		return -EINVAL;

	heartbeat = t;
	return 0;
}

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

/**
 * 	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_ioctl - Query Device
 *
 * 	@inode: inode of 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 int sh_wdt_ioctl(struct inode *inode, 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_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);
		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;
		default:
			return -ENOIOCTLCMD;
	}

	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,
	.ioctl		= sh_wdt_ioctl,
	.open		= sh_wdt_open,
	.release	= sh_wdt_close,
};

static 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);
	}

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

	init_timer(&timer);
	timer.function = sh_wdt_ping;
	timer.data = 0;

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

	rc = misc_register(&sh_wdt_miscdev);
	if (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). Defaults to 0x7.");

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=CONFIG_WATCHDOG_NOWAYOUT)");

module_init(sh_wdt_init);
module_exit(sh_wdt_exit);