1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  *	watchdog_core.c
4  *
5  *	(c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
6  *						All Rights Reserved.
7  *
8  *	(c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
9  *
10  *	This source code is part of the generic code that can be used
11  *	by all the watchdog timer drivers.
12  *
13  *	Based on source code of the following authors:
14  *	  Matt Domsch <Matt_Domsch@dell.com>,
15  *	  Rob Radez <rob@osinvestor.com>,
16  *	  Rusty Lynch <rusty@linux.co.intel.com>
17  *	  Satyam Sharma <satyam@infradead.org>
18  *	  Randy Dunlap <randy.dunlap@oracle.com>
19  *
20  *	Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
21  *	admit liability nor provide warranty for any of this software.
22  *	This material is provided "AS-IS" and at no charge.
23  */
24 
25 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
26 
27 #include <linux/module.h>	/* For EXPORT_SYMBOL/module stuff/... */
28 #include <linux/types.h>	/* For standard types */
29 #include <linux/errno.h>	/* For the -ENODEV/... values */
30 #include <linux/kernel.h>	/* For printk/panic/... */
31 #include <linux/reboot.h>	/* For restart handler */
32 #include <linux/watchdog.h>	/* For watchdog specific items */
33 #include <linux/init.h>		/* For __init/__exit/... */
34 #include <linux/idr.h>		/* For ida_* macros */
35 #include <linux/err.h>		/* For IS_ERR macros */
36 #include <linux/of.h>		/* For of_get_timeout_sec */
37 #include <linux/suspend.h>
38 
39 #include "watchdog_core.h"	/* For watchdog_dev_register/... */
40 
41 static DEFINE_IDA(watchdog_ida);
42 
43 static int stop_on_reboot = -1;
44 module_param(stop_on_reboot, int, 0444);
45 MODULE_PARM_DESC(stop_on_reboot, "Stop watchdogs on reboot (0=keep watching, 1=stop)");
46 
47 /*
48  * Deferred Registration infrastructure.
49  *
50  * Sometimes watchdog drivers needs to be loaded as soon as possible,
51  * for example when it's impossible to disable it. To do so,
52  * raising the initcall level of the watchdog driver is a solution.
53  * But in such case, the miscdev is maybe not ready (subsys_initcall), and
54  * watchdog_core need miscdev to register the watchdog as a char device.
55  *
56  * The deferred registration infrastructure offer a way for the watchdog
57  * subsystem to register a watchdog properly, even before miscdev is ready.
58  */
59 
60 static DEFINE_MUTEX(wtd_deferred_reg_mutex);
61 static LIST_HEAD(wtd_deferred_reg_list);
62 static bool wtd_deferred_reg_done;
63 
64 static void watchdog_deferred_registration_add(struct watchdog_device *wdd)
65 {
66 	list_add_tail(&wdd->deferred,
67 		      &wtd_deferred_reg_list);
68 }
69 
70 static void watchdog_deferred_registration_del(struct watchdog_device *wdd)
71 {
72 	struct list_head *p, *n;
73 	struct watchdog_device *wdd_tmp;
74 
75 	list_for_each_safe(p, n, &wtd_deferred_reg_list) {
76 		wdd_tmp = list_entry(p, struct watchdog_device,
77 				     deferred);
78 		if (wdd_tmp == wdd) {
79 			list_del(&wdd_tmp->deferred);
80 			break;
81 		}
82 	}
83 }
84 
85 static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
86 {
87 	/*
88 	 * Check that we have valid min and max timeout values, if
89 	 * not reset them both to 0 (=not used or unknown)
90 	 */
91 	if (!wdd->max_hw_heartbeat_ms && wdd->min_timeout > wdd->max_timeout) {
92 		pr_info("Invalid min and max timeout values, resetting to 0!\n");
93 		wdd->min_timeout = 0;
94 		wdd->max_timeout = 0;
95 	}
96 }
97 
98 /**
99  * watchdog_init_timeout() - initialize the timeout field
100  * @wdd: watchdog device
101  * @timeout_parm: timeout module parameter
102  * @dev: Device that stores the timeout-sec property
103  *
104  * Initialize the timeout field of the watchdog_device struct with either the
105  * timeout module parameter (if it is valid value) or the timeout-sec property
106  * (only if it is a valid value and the timeout_parm is out of bounds).
107  * If none of them are valid then we keep the old value (which should normally
108  * be the default timeout value). Note that for the module parameter, '0' means
109  * 'use default' while it is an invalid value for the timeout-sec property.
110  * It should simply be dropped if you want to use the default value then.
111  *
112  * A zero is returned on success or -EINVAL if all provided values are out of
113  * bounds.
114  */
115 int watchdog_init_timeout(struct watchdog_device *wdd,
116 				unsigned int timeout_parm, struct device *dev)
117 {
118 	const char *dev_str = wdd->parent ? dev_name(wdd->parent) :
119 			      (const char *)wdd->info->identity;
120 	unsigned int t = 0;
121 	int ret = 0;
122 
123 	watchdog_check_min_max_timeout(wdd);
124 
125 	/* check the driver supplied value (likely a module parameter) first */
126 	if (timeout_parm) {
127 		if (!watchdog_timeout_invalid(wdd, timeout_parm)) {
128 			wdd->timeout = timeout_parm;
129 			return 0;
130 		}
131 		pr_err("%s: driver supplied timeout (%u) out of range\n",
132 			dev_str, timeout_parm);
133 		ret = -EINVAL;
134 	}
135 
136 	/* try to get the timeout_sec property */
137 	if (dev && dev->of_node &&
138 	    of_property_read_u32(dev->of_node, "timeout-sec", &t) == 0) {
139 		if (t && !watchdog_timeout_invalid(wdd, t)) {
140 			wdd->timeout = t;
141 			return 0;
142 		}
143 		pr_err("%s: DT supplied timeout (%u) out of range\n", dev_str, t);
144 		ret = -EINVAL;
145 	}
146 
147 	if (ret < 0 && wdd->timeout)
148 		pr_warn("%s: falling back to default timeout (%u)\n", dev_str,
149 			wdd->timeout);
150 
151 	return ret;
152 }
153 EXPORT_SYMBOL_GPL(watchdog_init_timeout);
154 
155 static int watchdog_reboot_notifier(struct notifier_block *nb,
156 				    unsigned long code, void *data)
157 {
158 	struct watchdog_device *wdd;
159 
160 	wdd = container_of(nb, struct watchdog_device, reboot_nb);
161 	if (code == SYS_DOWN || code == SYS_HALT) {
162 		if (watchdog_active(wdd) || watchdog_hw_running(wdd)) {
163 			int ret;
164 
165 			ret = wdd->ops->stop(wdd);
166 			if (ret)
167 				return NOTIFY_BAD;
168 		}
169 	}
170 
171 	return NOTIFY_DONE;
172 }
173 
174 static int watchdog_restart_notifier(struct notifier_block *nb,
175 				     unsigned long action, void *data)
176 {
177 	struct watchdog_device *wdd = container_of(nb, struct watchdog_device,
178 						   restart_nb);
179 
180 	int ret;
181 
182 	ret = wdd->ops->restart(wdd, action, data);
183 	if (ret)
184 		return NOTIFY_BAD;
185 
186 	return NOTIFY_DONE;
187 }
188 
189 static int watchdog_pm_notifier(struct notifier_block *nb, unsigned long mode,
190 				void *data)
191 {
192 	struct watchdog_device *wdd;
193 	int ret = 0;
194 
195 	wdd = container_of(nb, struct watchdog_device, pm_nb);
196 
197 	switch (mode) {
198 	case PM_HIBERNATION_PREPARE:
199 	case PM_RESTORE_PREPARE:
200 	case PM_SUSPEND_PREPARE:
201 		ret = watchdog_dev_suspend(wdd);
202 		break;
203 	case PM_POST_HIBERNATION:
204 	case PM_POST_RESTORE:
205 	case PM_POST_SUSPEND:
206 		ret = watchdog_dev_resume(wdd);
207 		break;
208 	}
209 
210 	if (ret)
211 		return NOTIFY_BAD;
212 
213 	return NOTIFY_DONE;
214 }
215 
216 /**
217  * watchdog_set_restart_priority - Change priority of restart handler
218  * @wdd: watchdog device
219  * @priority: priority of the restart handler, should follow these guidelines:
220  *   0:   use watchdog's restart function as last resort, has limited restart
221  *        capabilies
222  *   128: default restart handler, use if no other handler is expected to be
223  *        available and/or if restart is sufficient to restart the entire system
224  *   255: preempt all other handlers
225  *
226  * If a wdd->ops->restart function is provided when watchdog_register_device is
227  * called, it will be registered as a restart handler with the priority given
228  * here.
229  */
230 void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority)
231 {
232 	wdd->restart_nb.priority = priority;
233 }
234 EXPORT_SYMBOL_GPL(watchdog_set_restart_priority);
235 
236 static int __watchdog_register_device(struct watchdog_device *wdd)
237 {
238 	int ret, id = -1;
239 
240 	if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
241 		return -EINVAL;
242 
243 	/* Mandatory operations need to be supported */
244 	if (!wdd->ops->start || (!wdd->ops->stop && !wdd->max_hw_heartbeat_ms))
245 		return -EINVAL;
246 
247 	watchdog_check_min_max_timeout(wdd);
248 
249 	/*
250 	 * Note: now that all watchdog_device data has been verified, we
251 	 * will not check this anymore in other functions. If data gets
252 	 * corrupted in a later stage then we expect a kernel panic!
253 	 */
254 
255 	/* Use alias for watchdog id if possible */
256 	if (wdd->parent) {
257 		ret = of_alias_get_id(wdd->parent->of_node, "watchdog");
258 		if (ret >= 0)
259 			id = ida_simple_get(&watchdog_ida, ret,
260 					    ret + 1, GFP_KERNEL);
261 	}
262 
263 	if (id < 0)
264 		id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
265 
266 	if (id < 0)
267 		return id;
268 	wdd->id = id;
269 
270 	ret = watchdog_dev_register(wdd);
271 	if (ret) {
272 		ida_simple_remove(&watchdog_ida, id);
273 		if (!(id == 0 && ret == -EBUSY))
274 			return ret;
275 
276 		/* Retry in case a legacy watchdog module exists */
277 		id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
278 		if (id < 0)
279 			return id;
280 		wdd->id = id;
281 
282 		ret = watchdog_dev_register(wdd);
283 		if (ret) {
284 			ida_simple_remove(&watchdog_ida, id);
285 			return ret;
286 		}
287 	}
288 
289 	/* Module parameter to force watchdog policy on reboot. */
290 	if (stop_on_reboot != -1) {
291 		if (stop_on_reboot)
292 			set_bit(WDOG_STOP_ON_REBOOT, &wdd->status);
293 		else
294 			clear_bit(WDOG_STOP_ON_REBOOT, &wdd->status);
295 	}
296 
297 	if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
298 		if (!wdd->ops->stop)
299 			pr_warn("watchdog%d: stop_on_reboot not supported\n", wdd->id);
300 		else {
301 			wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
302 
303 			ret = register_reboot_notifier(&wdd->reboot_nb);
304 			if (ret) {
305 				pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
306 					wdd->id, ret);
307 				watchdog_dev_unregister(wdd);
308 				ida_simple_remove(&watchdog_ida, id);
309 				return ret;
310 			}
311 		}
312 	}
313 
314 	if (wdd->ops->restart) {
315 		wdd->restart_nb.notifier_call = watchdog_restart_notifier;
316 
317 		ret = register_restart_handler(&wdd->restart_nb);
318 		if (ret)
319 			pr_warn("watchdog%d: Cannot register restart handler (%d)\n",
320 				wdd->id, ret);
321 	}
322 
323 	if (test_bit(WDOG_NO_PING_ON_SUSPEND, &wdd->status)) {
324 		wdd->pm_nb.notifier_call = watchdog_pm_notifier;
325 
326 		ret = register_pm_notifier(&wdd->pm_nb);
327 		if (ret)
328 			pr_warn("watchdog%d: Cannot register pm handler (%d)\n",
329 				wdd->id, ret);
330 	}
331 
332 	return 0;
333 }
334 
335 /**
336  * watchdog_register_device() - register a watchdog device
337  * @wdd: watchdog device
338  *
339  * Register a watchdog device with the kernel so that the
340  * watchdog timer can be accessed from userspace.
341  *
342  * A zero is returned on success and a negative errno code for
343  * failure.
344  */
345 
346 int watchdog_register_device(struct watchdog_device *wdd)
347 {
348 	const char *dev_str;
349 	int ret = 0;
350 
351 	mutex_lock(&wtd_deferred_reg_mutex);
352 	if (wtd_deferred_reg_done)
353 		ret = __watchdog_register_device(wdd);
354 	else
355 		watchdog_deferred_registration_add(wdd);
356 	mutex_unlock(&wtd_deferred_reg_mutex);
357 
358 	if (ret) {
359 		dev_str = wdd->parent ? dev_name(wdd->parent) :
360 			  (const char *)wdd->info->identity;
361 		pr_err("%s: failed to register watchdog device (err = %d)\n",
362 			dev_str, ret);
363 	}
364 
365 	return ret;
366 }
367 EXPORT_SYMBOL_GPL(watchdog_register_device);
368 
369 static void __watchdog_unregister_device(struct watchdog_device *wdd)
370 {
371 	if (wdd == NULL)
372 		return;
373 
374 	if (wdd->ops->restart)
375 		unregister_restart_handler(&wdd->restart_nb);
376 
377 	if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))
378 		unregister_reboot_notifier(&wdd->reboot_nb);
379 
380 	watchdog_dev_unregister(wdd);
381 	ida_simple_remove(&watchdog_ida, wdd->id);
382 }
383 
384 /**
385  * watchdog_unregister_device() - unregister a watchdog device
386  * @wdd: watchdog device to unregister
387  *
388  * Unregister a watchdog device that was previously successfully
389  * registered with watchdog_register_device().
390  */
391 
392 void watchdog_unregister_device(struct watchdog_device *wdd)
393 {
394 	mutex_lock(&wtd_deferred_reg_mutex);
395 	if (wtd_deferred_reg_done)
396 		__watchdog_unregister_device(wdd);
397 	else
398 		watchdog_deferred_registration_del(wdd);
399 	mutex_unlock(&wtd_deferred_reg_mutex);
400 }
401 
402 EXPORT_SYMBOL_GPL(watchdog_unregister_device);
403 
404 static void devm_watchdog_unregister_device(struct device *dev, void *res)
405 {
406 	watchdog_unregister_device(*(struct watchdog_device **)res);
407 }
408 
409 /**
410  * devm_watchdog_register_device() - resource managed watchdog_register_device()
411  * @dev: device that is registering this watchdog device
412  * @wdd: watchdog device
413  *
414  * Managed watchdog_register_device(). For watchdog device registered by this
415  * function,  watchdog_unregister_device() is automatically called on driver
416  * detach. See watchdog_register_device() for more information.
417  */
418 int devm_watchdog_register_device(struct device *dev,
419 				struct watchdog_device *wdd)
420 {
421 	struct watchdog_device **rcwdd;
422 	int ret;
423 
424 	rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd),
425 			     GFP_KERNEL);
426 	if (!rcwdd)
427 		return -ENOMEM;
428 
429 	ret = watchdog_register_device(wdd);
430 	if (!ret) {
431 		*rcwdd = wdd;
432 		devres_add(dev, rcwdd);
433 	} else {
434 		devres_free(rcwdd);
435 	}
436 
437 	return ret;
438 }
439 EXPORT_SYMBOL_GPL(devm_watchdog_register_device);
440 
441 static int __init watchdog_deferred_registration(void)
442 {
443 	mutex_lock(&wtd_deferred_reg_mutex);
444 	wtd_deferred_reg_done = true;
445 	while (!list_empty(&wtd_deferred_reg_list)) {
446 		struct watchdog_device *wdd;
447 
448 		wdd = list_first_entry(&wtd_deferred_reg_list,
449 				       struct watchdog_device, deferred);
450 		list_del(&wdd->deferred);
451 		__watchdog_register_device(wdd);
452 	}
453 	mutex_unlock(&wtd_deferred_reg_mutex);
454 	return 0;
455 }
456 
457 static int __init watchdog_init(void)
458 {
459 	int err;
460 
461 	err = watchdog_dev_init();
462 	if (err < 0)
463 		return err;
464 
465 	watchdog_deferred_registration();
466 	return 0;
467 }
468 
469 static void __exit watchdog_exit(void)
470 {
471 	watchdog_dev_exit();
472 	ida_destroy(&watchdog_ida);
473 }
474 
475 subsys_initcall_sync(watchdog_init);
476 module_exit(watchdog_exit);
477 
478 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
479 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
480 MODULE_DESCRIPTION("WatchDog Timer Driver Core");
481 MODULE_LICENSE("GPL");
482