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_alias_get_id */
37#include <linux/property.h> /* For device_property_read_u32 */
38#include <linux/suspend.h>
39
40#include "watchdog_core.h" /* For watchdog_dev_register/... */
41
42#define CREATE_TRACE_POINTS
43#include <trace/events/watchdog.h>
44
45static DEFINE_IDA(watchdog_ida);
46
47static int stop_on_reboot = -1;
48module_param(stop_on_reboot, int, 0444);
49MODULE_PARM_DESC(stop_on_reboot, "Stop watchdogs on reboot (0=keep watching, 1=stop)");
50
51/*
52 * Deferred Registration infrastructure.
53 *
54 * Sometimes watchdog drivers needs to be loaded as soon as possible,
55 * for example when it's impossible to disable it. To do so,
56 * raising the initcall level of the watchdog driver is a solution.
57 * But in such case, the miscdev is maybe not ready (subsys_initcall), and
58 * watchdog_core need miscdev to register the watchdog as a char device.
59 *
60 * The deferred registration infrastructure offer a way for the watchdog
61 * subsystem to register a watchdog properly, even before miscdev is ready.
62 */
63
64static DEFINE_MUTEX(wtd_deferred_reg_mutex);
65static LIST_HEAD(wtd_deferred_reg_list);
66static bool wtd_deferred_reg_done;
67
68static void watchdog_deferred_registration_add(struct watchdog_device *wdd)
69{
70 list_add_tail(new: &wdd->deferred,
71 head: &wtd_deferred_reg_list);
72}
73
74static void watchdog_deferred_registration_del(struct watchdog_device *wdd)
75{
76 struct list_head *p, *n;
77 struct watchdog_device *wdd_tmp;
78
79 list_for_each_safe(p, n, &wtd_deferred_reg_list) {
80 wdd_tmp = list_entry(p, struct watchdog_device,
81 deferred);
82 if (wdd_tmp == wdd) {
83 list_del(entry: &wdd_tmp->deferred);
84 break;
85 }
86 }
87}
88
89static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
90{
91 /*
92 * Check that we have valid min and max timeout values, if
93 * not reset them both to 0 (=not used or unknown)
94 */
95 if (!wdd->max_hw_heartbeat_ms && wdd->min_timeout > wdd->max_timeout) {
96 pr_info("Invalid min and max timeout values, resetting to 0!\n");
97 wdd->min_timeout = 0;
98 wdd->max_timeout = 0;
99 }
100}
101
102/**
103 * watchdog_init_timeout() - initialize the timeout field
104 * @wdd: watchdog device
105 * @timeout_parm: timeout module parameter
106 * @dev: Device that stores the timeout-sec property
107 *
108 * Initialize the timeout field of the watchdog_device struct with either the
109 * timeout module parameter (if it is valid value) or the timeout-sec property
110 * (only if it is a valid value and the timeout_parm is out of bounds).
111 * If none of them are valid then we keep the old value (which should normally
112 * be the default timeout value). Note that for the module parameter, '0' means
113 * 'use default' while it is an invalid value for the timeout-sec property.
114 * It should simply be dropped if you want to use the default value then.
115 *
116 * A zero is returned on success or -EINVAL if all provided values are out of
117 * bounds.
118 */
119int watchdog_init_timeout(struct watchdog_device *wdd,
120 unsigned int timeout_parm, struct device *dev)
121{
122 const char *dev_str = wdd->parent ? dev_name(dev: wdd->parent) :
123 (const char *)wdd->info->identity;
124 unsigned int t = 0;
125 int ret = 0;
126
127 watchdog_check_min_max_timeout(wdd);
128
129 /* check the driver supplied value (likely a module parameter) first */
130 if (timeout_parm) {
131 if (!watchdog_timeout_invalid(wdd, t: timeout_parm)) {
132 wdd->timeout = timeout_parm;
133 return 0;
134 }
135 pr_err("%s: driver supplied timeout (%u) out of range\n",
136 dev_str, timeout_parm);
137 ret = -EINVAL;
138 }
139
140 /* try to get the timeout_sec property */
141 if (dev && device_property_read_u32(dev, propname: "timeout-sec", val: &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, err: 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(np: wdd->parent->of_node, stem: "watchdog");
262 if (ret >= 0)
263 id = ida_alloc_range(&watchdog_ida, min: ret, max: ret,
264 GFP_KERNEL);
265 }
266
267 if (id < 0)
268 id = ida_alloc_max(ida: &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, min: 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, addr: &wdd->status);
298 else
299 clear_bit(WDOG_STOP_ON_REBOOT, addr: &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(nb: &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
340static int __watchdog_register_device(struct watchdog_device *wdd)
341{
342 const char *dev_str;
343 int ret;
344
345 ret = ___watchdog_register_device(wdd);
346 if (ret) {
347 dev_str = wdd->parent ? dev_name(dev: wdd->parent) :
348 (const char *)wdd->info->identity;
349 pr_err("%s: failed to register watchdog device (err = %d)\n",
350 dev_str, ret);
351 }
352
353 return ret;
354}
355
356/**
357 * watchdog_register_device() - register a watchdog device
358 * @wdd: watchdog device
359 *
360 * Register a watchdog device with the kernel so that the
361 * watchdog timer can be accessed from userspace.
362 *
363 * A zero is returned on success and a negative errno code for
364 * failure.
365 */
366
367int watchdog_register_device(struct watchdog_device *wdd)
368{
369 int ret = 0;
370
371 mutex_lock(&wtd_deferred_reg_mutex);
372 if (wtd_deferred_reg_done)
373 ret = __watchdog_register_device(wdd);
374 else
375 watchdog_deferred_registration_add(wdd);
376 mutex_unlock(lock: &wtd_deferred_reg_mutex);
377
378 return ret;
379}
380EXPORT_SYMBOL_GPL(watchdog_register_device);
381
382static void __watchdog_unregister_device(struct watchdog_device *wdd)
383{
384 if (wdd == NULL)
385 return;
386
387 if (wdd->ops->restart)
388 unregister_restart_handler(&wdd->restart_nb);
389
390 if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))
391 unregister_reboot_notifier(&wdd->reboot_nb);
392
393 watchdog_dev_unregister(wdd);
394 ida_free(&watchdog_ida, id: wdd->id);
395}
396
397/**
398 * watchdog_unregister_device() - unregister a watchdog device
399 * @wdd: watchdog device to unregister
400 *
401 * Unregister a watchdog device that was previously successfully
402 * registered with watchdog_register_device().
403 */
404
405void watchdog_unregister_device(struct watchdog_device *wdd)
406{
407 mutex_lock(&wtd_deferred_reg_mutex);
408 if (wtd_deferred_reg_done)
409 __watchdog_unregister_device(wdd);
410 else
411 watchdog_deferred_registration_del(wdd);
412 mutex_unlock(lock: &wtd_deferred_reg_mutex);
413}
414
415EXPORT_SYMBOL_GPL(watchdog_unregister_device);
416
417static void devm_watchdog_unregister_device(struct device *dev, void *res)
418{
419 watchdog_unregister_device(*(struct watchdog_device **)res);
420}
421
422/**
423 * devm_watchdog_register_device() - resource managed watchdog_register_device()
424 * @dev: device that is registering this watchdog device
425 * @wdd: watchdog device
426 *
427 * Managed watchdog_register_device(). For watchdog device registered by this
428 * function, watchdog_unregister_device() is automatically called on driver
429 * detach. See watchdog_register_device() for more information.
430 */
431int devm_watchdog_register_device(struct device *dev,
432 struct watchdog_device *wdd)
433{
434 struct watchdog_device **rcwdd;
435 int ret;
436
437 rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd),
438 GFP_KERNEL);
439 if (!rcwdd)
440 return -ENOMEM;
441
442 ret = watchdog_register_device(wdd);
443 if (!ret) {
444 *rcwdd = wdd;
445 devres_add(dev, res: rcwdd);
446 } else {
447 devres_free(res: rcwdd);
448 }
449
450 return ret;
451}
452EXPORT_SYMBOL_GPL(devm_watchdog_register_device);
453
454static int __init watchdog_deferred_registration(void)
455{
456 mutex_lock(&wtd_deferred_reg_mutex);
457 wtd_deferred_reg_done = true;
458 while (!list_empty(head: &wtd_deferred_reg_list)) {
459 struct watchdog_device *wdd;
460
461 wdd = list_first_entry(&wtd_deferred_reg_list,
462 struct watchdog_device, deferred);
463 list_del(entry: &wdd->deferred);
464 __watchdog_register_device(wdd);
465 }
466 mutex_unlock(lock: &wtd_deferred_reg_mutex);
467 return 0;
468}
469
470static int __init watchdog_init(void)
471{
472 int err;
473
474 err = watchdog_dev_init();
475 if (err < 0)
476 return err;
477
478 watchdog_deferred_registration();
479 return 0;
480}
481
482static void __exit watchdog_exit(void)
483{
484 watchdog_dev_exit();
485 ida_destroy(ida: &watchdog_ida);
486}
487
488subsys_initcall_sync(watchdog_init);
489module_exit(watchdog_exit);
490
491MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
492MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
493MODULE_DESCRIPTION("WatchDog Timer Driver Core");
494MODULE_LICENSE("GPL");
495

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source code of linux/drivers/watchdog/watchdog_core.c