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#define CREATE_TRACE_POINTS
42#include <trace/events/watchdog.h>
43
44static DEFINE_IDA(watchdog_ida);
45
46static int stop_on_reboot = -1;
47module_param(stop_on_reboot, int, 0444);
48MODULE_PARM_DESC(stop_on_reboot, "Stop watchdogs on reboot (0=keep watching, 1=stop)");
49
50/*
51 * Deferred Registration infrastructure.
52 *
53 * Sometimes watchdog drivers needs to be loaded as soon as possible,
54 * for example when it's impossible to disable it. To do so,
55 * raising the initcall level of the watchdog driver is a solution.
56 * But in such case, the miscdev is maybe not ready (subsys_initcall), and
57 * watchdog_core need miscdev to register the watchdog as a char device.
58 *
59 * The deferred registration infrastructure offer a way for the watchdog
60 * subsystem to register a watchdog properly, even before miscdev is ready.
61 */
62
63static DEFINE_MUTEX(wtd_deferred_reg_mutex);
64static LIST_HEAD(wtd_deferred_reg_list);
65static bool wtd_deferred_reg_done;
66
67static void watchdog_deferred_registration_add(struct watchdog_device *wdd)
68{
69	list_add_tail(&wdd->deferred,
70		      &wtd_deferred_reg_list);
71}
72
73static void watchdog_deferred_registration_del(struct watchdog_device *wdd)
74{
75	struct list_head *p, *n;
76	struct watchdog_device *wdd_tmp;
77
78	list_for_each_safe(p, n, &wtd_deferred_reg_list) {
79		wdd_tmp = list_entry(p, struct watchdog_device,
80				     deferred);
81		if (wdd_tmp == wdd) {
82			list_del(&wdd_tmp->deferred);
83			break;
84		}
85	}
86}
87
88static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
89{
90	/*
91	 * Check that we have valid min and max timeout values, if
92	 * not reset them both to 0 (=not used or unknown)
93	 */
94	if (!wdd->max_hw_heartbeat_ms && wdd->min_timeout > wdd->max_timeout) {
95		pr_info("Invalid min and max timeout values, resetting to 0!\n");
96		wdd->min_timeout = 0;
97		wdd->max_timeout = 0;
98	}
99}
100
101/**
102 * watchdog_init_timeout() - initialize the timeout field
103 * @wdd: watchdog device
104 * @timeout_parm: timeout module parameter
105 * @dev: Device that stores the timeout-sec property
106 *
107 * Initialize the timeout field of the watchdog_device struct with either the
108 * timeout module parameter (if it is valid value) or the timeout-sec property
109 * (only if it is a valid value and the timeout_parm is out of bounds).
110 * If none of them are valid then we keep the old value (which should normally
111 * be the default timeout value). Note that for the module parameter, '0' means
112 * 'use default' while it is an invalid value for the timeout-sec property.
113 * It should simply be dropped if you want to use the default value then.
114 *
115 * A zero is returned on success or -EINVAL if all provided values are out of
116 * bounds.
117 */
118int watchdog_init_timeout(struct watchdog_device *wdd,
119				unsigned int timeout_parm, struct device *dev)
120{
121	const char *dev_str = wdd->parent ? dev_name(wdd->parent) :
122			      (const char *)wdd->info->identity;
123	unsigned int t = 0;
124	int ret = 0;
125
126	watchdog_check_min_max_timeout(wdd);
127
128	/* check the driver supplied value (likely a module parameter) first */
129	if (timeout_parm) {
130		if (!watchdog_timeout_invalid(wdd, timeout_parm)) {
131			wdd->timeout = timeout_parm;
132			return 0;
133		}
134		pr_err("%s: driver supplied timeout (%u) out of range\n",
135			dev_str, timeout_parm);
136		ret = -EINVAL;
137	}
138
139	/* try to get the timeout_sec property */
140	if (dev && dev->of_node &&
141	    of_property_read_u32(dev->of_node, "timeout-sec", &t) == 0) {
142		if (t && !watchdog_timeout_invalid(wdd, t)) {
143			wdd->timeout = t;
144			return 0;
145		}
146		pr_err("%s: DT supplied timeout (%u) out of range\n", dev_str, t);
147		ret = -EINVAL;
148	}
149
150	if (ret < 0 && wdd->timeout)
151		pr_warn("%s: falling back to default timeout (%u)\n", dev_str,
152			wdd->timeout);
153
154	return ret;
155}
156EXPORT_SYMBOL_GPL(watchdog_init_timeout);
157
158static int watchdog_reboot_notifier(struct notifier_block *nb,
159				    unsigned long code, void *data)
160{
161	struct watchdog_device *wdd;
162
163	wdd = container_of(nb, struct watchdog_device, reboot_nb);
164	if (code == SYS_DOWN || code == SYS_HALT || code == SYS_POWER_OFF) {
165		if (watchdog_hw_running(wdd)) {
166			int ret;
167
168			ret = wdd->ops->stop(wdd);
169			trace_watchdog_stop(wdd, ret);
170			if (ret)
171				return NOTIFY_BAD;
172		}
173	}
174
175	return NOTIFY_DONE;
176}
177
178static int watchdog_restart_notifier(struct notifier_block *nb,
179				     unsigned long action, void *data)
180{
181	struct watchdog_device *wdd = container_of(nb, struct watchdog_device,
182						   restart_nb);
183
184	int ret;
185
186	ret = wdd->ops->restart(wdd, action, data);
187	if (ret)
188		return NOTIFY_BAD;
189
190	return NOTIFY_DONE;
191}
192
193static int watchdog_pm_notifier(struct notifier_block *nb, unsigned long mode,
194				void *data)
195{
196	struct watchdog_device *wdd;
197	int ret = 0;
198
199	wdd = container_of(nb, struct watchdog_device, pm_nb);
200
201	switch (mode) {
202	case PM_HIBERNATION_PREPARE:
203	case PM_RESTORE_PREPARE:
204	case PM_SUSPEND_PREPARE:
205		ret = watchdog_dev_suspend(wdd);
206		break;
207	case PM_POST_HIBERNATION:
208	case PM_POST_RESTORE:
209	case PM_POST_SUSPEND:
210		ret = watchdog_dev_resume(wdd);
211		break;
212	}
213
214	if (ret)
215		return NOTIFY_BAD;
216
217	return NOTIFY_DONE;
218}
219
220/**
221 * watchdog_set_restart_priority - Change priority of restart handler
222 * @wdd: watchdog device
223 * @priority: priority of the restart handler, should follow these guidelines:
224 *   0:   use watchdog's restart function as last resort, has limited restart
225 *        capabilies
226 *   128: default restart handler, use if no other handler is expected to be
227 *        available and/or if restart is sufficient to restart the entire system
228 *   255: preempt all other handlers
229 *
230 * If a wdd->ops->restart function is provided when watchdog_register_device is
231 * called, it will be registered as a restart handler with the priority given
232 * here.
233 */
234void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority)
235{
236	wdd->restart_nb.priority = priority;
237}
238EXPORT_SYMBOL_GPL(watchdog_set_restart_priority);
239
240static int __watchdog_register_device(struct watchdog_device *wdd)
241{
242	int ret, id = -1;
243
244	if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
245		return -EINVAL;
246
247	/* Mandatory operations need to be supported */
248	if (!wdd->ops->start || (!wdd->ops->stop && !wdd->max_hw_heartbeat_ms))
249		return -EINVAL;
250
251	watchdog_check_min_max_timeout(wdd);
252
253	/*
254	 * Note: now that all watchdog_device data has been verified, we
255	 * will not check this anymore in other functions. If data gets
256	 * corrupted in a later stage then we expect a kernel panic!
257	 */
258
259	/* Use alias for watchdog id if possible */
260	if (wdd->parent) {
261		ret = of_alias_get_id(wdd->parent->of_node, "watchdog");
262		if (ret >= 0)
263			id = ida_alloc_range(&watchdog_ida, ret, ret,
264					     GFP_KERNEL);
265	}
266
267	if (id < 0)
268		id = ida_alloc_max(&watchdog_ida, MAX_DOGS - 1, GFP_KERNEL);
269
270	if (id < 0)
271		return id;
272	wdd->id = id;
273
274	ret = watchdog_dev_register(wdd);
275	if (ret) {
276		ida_free(&watchdog_ida, id);
277		if (!(id == 0 && ret == -EBUSY))
278			return ret;
279
280		/* Retry in case a legacy watchdog module exists */
281		id = ida_alloc_range(&watchdog_ida, 1, MAX_DOGS - 1,
282				     GFP_KERNEL);
283		if (id < 0)
284			return id;
285		wdd->id = id;
286
287		ret = watchdog_dev_register(wdd);
288		if (ret) {
289			ida_free(&watchdog_ida, id);
290			return ret;
291		}
292	}
293
294	/* Module parameter to force watchdog policy on reboot. */
295	if (stop_on_reboot != -1) {
296		if (stop_on_reboot)
297			set_bit(WDOG_STOP_ON_REBOOT, &wdd->status);
298		else
299			clear_bit(WDOG_STOP_ON_REBOOT, &wdd->status);
300	}
301
302	if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
303		if (!wdd->ops->stop)
304			pr_warn("watchdog%d: stop_on_reboot not supported\n", wdd->id);
305		else {
306			wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
307
308			ret = register_reboot_notifier(&wdd->reboot_nb);
309			if (ret) {
310				pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
311					wdd->id, ret);
312				watchdog_dev_unregister(wdd);
313				ida_free(&watchdog_ida, id);
314				return ret;
315			}
316		}
317	}
318
319	if (wdd->ops->restart) {
320		wdd->restart_nb.notifier_call = watchdog_restart_notifier;
321
322		ret = register_restart_handler(&wdd->restart_nb);
323		if (ret)
324			pr_warn("watchdog%d: Cannot register restart handler (%d)\n",
325				wdd->id, ret);
326	}
327
328	if (test_bit(WDOG_NO_PING_ON_SUSPEND, &wdd->status)) {
329		wdd->pm_nb.notifier_call = watchdog_pm_notifier;
330
331		ret = register_pm_notifier(&wdd->pm_nb);
332		if (ret)
333			pr_warn("watchdog%d: Cannot register pm handler (%d)\n",
334				wdd->id, ret);
335	}
336
337	return 0;
338}
339
340/**
341 * watchdog_register_device() - register a watchdog device
342 * @wdd: watchdog device
343 *
344 * Register a watchdog device with the kernel so that the
345 * watchdog timer can be accessed from userspace.
346 *
347 * A zero is returned on success and a negative errno code for
348 * failure.
349 */
350
351int watchdog_register_device(struct watchdog_device *wdd)
352{
353	const char *dev_str;
354	int ret = 0;
355
356	mutex_lock(&wtd_deferred_reg_mutex);
357	if (wtd_deferred_reg_done)
358		ret = __watchdog_register_device(wdd);
359	else
360		watchdog_deferred_registration_add(wdd);
361	mutex_unlock(&wtd_deferred_reg_mutex);
362
363	if (ret) {
364		dev_str = wdd->parent ? dev_name(wdd->parent) :
365			  (const char *)wdd->info->identity;
366		pr_err("%s: failed to register watchdog device (err = %d)\n",
367			dev_str, ret);
368	}
369
370	return ret;
371}
372EXPORT_SYMBOL_GPL(watchdog_register_device);
373
374static void __watchdog_unregister_device(struct watchdog_device *wdd)
375{
376	if (wdd == NULL)
377		return;
378
379	if (wdd->ops->restart)
380		unregister_restart_handler(&wdd->restart_nb);
381
382	if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))
383		unregister_reboot_notifier(&wdd->reboot_nb);
384
385	watchdog_dev_unregister(wdd);
386	ida_free(&watchdog_ida, wdd->id);
387}
388
389/**
390 * watchdog_unregister_device() - unregister a watchdog device
391 * @wdd: watchdog device to unregister
392 *
393 * Unregister a watchdog device that was previously successfully
394 * registered with watchdog_register_device().
395 */
396
397void watchdog_unregister_device(struct watchdog_device *wdd)
398{
399	mutex_lock(&wtd_deferred_reg_mutex);
400	if (wtd_deferred_reg_done)
401		__watchdog_unregister_device(wdd);
402	else
403		watchdog_deferred_registration_del(wdd);
404	mutex_unlock(&wtd_deferred_reg_mutex);
405}
406
407EXPORT_SYMBOL_GPL(watchdog_unregister_device);
408
409static void devm_watchdog_unregister_device(struct device *dev, void *res)
410{
411	watchdog_unregister_device(*(struct watchdog_device **)res);
412}
413
414/**
415 * devm_watchdog_register_device() - resource managed watchdog_register_device()
416 * @dev: device that is registering this watchdog device
417 * @wdd: watchdog device
418 *
419 * Managed watchdog_register_device(). For watchdog device registered by this
420 * function,  watchdog_unregister_device() is automatically called on driver
421 * detach. See watchdog_register_device() for more information.
422 */
423int devm_watchdog_register_device(struct device *dev,
424				struct watchdog_device *wdd)
425{
426	struct watchdog_device **rcwdd;
427	int ret;
428
429	rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd),
430			     GFP_KERNEL);
431	if (!rcwdd)
432		return -ENOMEM;
433
434	ret = watchdog_register_device(wdd);
435	if (!ret) {
436		*rcwdd = wdd;
437		devres_add(dev, rcwdd);
438	} else {
439		devres_free(rcwdd);
440	}
441
442	return ret;
443}
444EXPORT_SYMBOL_GPL(devm_watchdog_register_device);
445
446static int __init watchdog_deferred_registration(void)
447{
448	mutex_lock(&wtd_deferred_reg_mutex);
449	wtd_deferred_reg_done = true;
450	while (!list_empty(&wtd_deferred_reg_list)) {
451		struct watchdog_device *wdd;
452
453		wdd = list_first_entry(&wtd_deferred_reg_list,
454				       struct watchdog_device, deferred);
455		list_del(&wdd->deferred);
456		__watchdog_register_device(wdd);
457	}
458	mutex_unlock(&wtd_deferred_reg_mutex);
459	return 0;
460}
461
462static int __init watchdog_init(void)
463{
464	int err;
465
466	err = watchdog_dev_init();
467	if (err < 0)
468		return err;
469
470	watchdog_deferred_registration();
471	return 0;
472}
473
474static void __exit watchdog_exit(void)
475{
476	watchdog_dev_exit();
477	ida_destroy(&watchdog_ida);
478}
479
480subsys_initcall_sync(watchdog_init);
481module_exit(watchdog_exit);
482
483MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
484MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
485MODULE_DESCRIPTION("WatchDog Timer Driver Core");
486MODULE_LICENSE("GPL");
487