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