1 // SPDX-License-Identifier: GPL-2.0+
5 * (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
8 * (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
10 * This source code is part of the generic code that can be used
11 * by all the watchdog timer drivers.
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>
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.
25 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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 */
38 #include "watchdog_core.h" /* For watchdog_dev_register/... */
40 static DEFINE_IDA(watchdog_ida);
42 static int stop_on_reboot = -1;
43 module_param(stop_on_reboot, int, 0444);
44 MODULE_PARM_DESC(stop_on_reboot, "Stop watchdogs on reboot (0=keep watching, 1=stop)");
47 * Deferred Registration infrastructure.
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.
55 * The deferred registration infrastructure offer a way for the watchdog
56 * subsystem to register a watchdog properly, even before miscdev is ready.
59 static DEFINE_MUTEX(wtd_deferred_reg_mutex);
60 static LIST_HEAD(wtd_deferred_reg_list);
61 static bool wtd_deferred_reg_done;
63 static void watchdog_deferred_registration_add(struct watchdog_device *wdd)
65 list_add_tail(&wdd->deferred,
66 &wtd_deferred_reg_list);
69 static void watchdog_deferred_registration_del(struct watchdog_device *wdd)
71 struct list_head *p, *n;
72 struct watchdog_device *wdd_tmp;
74 list_for_each_safe(p, n, &wtd_deferred_reg_list) {
75 wdd_tmp = list_entry(p, struct watchdog_device,
78 list_del(&wdd_tmp->deferred);
84 static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
87 * Check that we have valid min and max timeout values, if
88 * not reset them both to 0 (=not used or unknown)
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");
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
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.
111 * A zero is returned on success or -EINVAL if all provided values are out of
114 int watchdog_init_timeout(struct watchdog_device *wdd,
115 unsigned int timeout_parm, struct device *dev)
117 const char *dev_str = wdd->parent ? dev_name(wdd->parent) :
118 (const char *)wdd->info->identity;
122 watchdog_check_min_max_timeout(wdd);
124 /* check the driver supplied value (likely a module parameter) first */
126 if (!watchdog_timeout_invalid(wdd, timeout_parm)) {
127 wdd->timeout = timeout_parm;
130 pr_err("%s: driver supplied timeout (%u) out of range\n",
131 dev_str, timeout_parm);
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)) {
142 pr_err("%s: DT supplied timeout (%u) out of range\n", dev_str, t);
146 if (ret < 0 && wdd->timeout)
147 pr_warn("%s: falling back to default timeout (%u)\n", dev_str,
152 EXPORT_SYMBOL_GPL(watchdog_init_timeout);
154 static int watchdog_reboot_notifier(struct notifier_block *nb,
155 unsigned long code, void *data)
157 struct watchdog_device *wdd;
159 wdd = container_of(nb, struct watchdog_device, reboot_nb);
160 if (code == SYS_DOWN || code == SYS_HALT) {
161 if (watchdog_active(wdd)) {
164 ret = wdd->ops->stop(wdd);
173 static int watchdog_restart_notifier(struct notifier_block *nb,
174 unsigned long action, void *data)
176 struct watchdog_device *wdd = container_of(nb, struct watchdog_device,
181 ret = wdd->ops->restart(wdd, action, data);
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
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
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
202 void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority)
204 wdd->restart_nb.priority = priority;
206 EXPORT_SYMBOL_GPL(watchdog_set_restart_priority);
208 static int __watchdog_register_device(struct watchdog_device *wdd)
212 if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
215 /* Mandatory operations need to be supported */
216 if (!wdd->ops->start || (!wdd->ops->stop && !wdd->max_hw_heartbeat_ms))
219 watchdog_check_min_max_timeout(wdd);
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!
227 /* Use alias for watchdog id if possible */
229 ret = of_alias_get_id(wdd->parent->of_node, "watchdog");
231 id = ida_simple_get(&watchdog_ida, ret,
232 ret + 1, GFP_KERNEL);
236 id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
242 ret = watchdog_dev_register(wdd);
244 ida_simple_remove(&watchdog_ida, id);
245 if (!(id == 0 && ret == -EBUSY))
248 /* Retry in case a legacy watchdog module exists */
249 id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
254 ret = watchdog_dev_register(wdd);
256 ida_simple_remove(&watchdog_ida, id);
261 /* Module parameter to force watchdog policy on reboot. */
262 if (stop_on_reboot != -1) {
264 set_bit(WDOG_STOP_ON_REBOOT, &wdd->status);
266 clear_bit(WDOG_STOP_ON_REBOOT, &wdd->status);
269 if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
271 pr_warn("watchdog%d: stop_on_reboot not supported\n", wdd->id);
273 wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
275 ret = register_reboot_notifier(&wdd->reboot_nb);
277 pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
279 watchdog_dev_unregister(wdd);
280 ida_simple_remove(&watchdog_ida, id);
286 if (wdd->ops->restart) {
287 wdd->restart_nb.notifier_call = watchdog_restart_notifier;
289 ret = register_restart_handler(&wdd->restart_nb);
291 pr_warn("watchdog%d: Cannot register restart handler (%d)\n",
299 * watchdog_register_device() - register a watchdog device
300 * @wdd: watchdog device
302 * Register a watchdog device with the kernel so that the
303 * watchdog timer can be accessed from userspace.
305 * A zero is returned on success and a negative errno code for
309 int watchdog_register_device(struct watchdog_device *wdd)
314 mutex_lock(&wtd_deferred_reg_mutex);
315 if (wtd_deferred_reg_done)
316 ret = __watchdog_register_device(wdd);
318 watchdog_deferred_registration_add(wdd);
319 mutex_unlock(&wtd_deferred_reg_mutex);
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",
330 EXPORT_SYMBOL_GPL(watchdog_register_device);
332 static void __watchdog_unregister_device(struct watchdog_device *wdd)
337 if (wdd->ops->restart)
338 unregister_restart_handler(&wdd->restart_nb);
340 if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))
341 unregister_reboot_notifier(&wdd->reboot_nb);
343 watchdog_dev_unregister(wdd);
344 ida_simple_remove(&watchdog_ida, wdd->id);
348 * watchdog_unregister_device() - unregister a watchdog device
349 * @wdd: watchdog device to unregister
351 * Unregister a watchdog device that was previously successfully
352 * registered with watchdog_register_device().
355 void watchdog_unregister_device(struct watchdog_device *wdd)
357 mutex_lock(&wtd_deferred_reg_mutex);
358 if (wtd_deferred_reg_done)
359 __watchdog_unregister_device(wdd);
361 watchdog_deferred_registration_del(wdd);
362 mutex_unlock(&wtd_deferred_reg_mutex);
365 EXPORT_SYMBOL_GPL(watchdog_unregister_device);
367 static void devm_watchdog_unregister_device(struct device *dev, void *res)
369 watchdog_unregister_device(*(struct watchdog_device **)res);
373 * devm_watchdog_register_device() - resource managed watchdog_register_device()
374 * @dev: device that is registering this watchdog device
375 * @wdd: watchdog device
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.
381 int devm_watchdog_register_device(struct device *dev,
382 struct watchdog_device *wdd)
384 struct watchdog_device **rcwdd;
387 rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd),
392 ret = watchdog_register_device(wdd);
395 devres_add(dev, rcwdd);
402 EXPORT_SYMBOL_GPL(devm_watchdog_register_device);
404 static int __init watchdog_deferred_registration(void)
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;
411 wdd = list_first_entry(&wtd_deferred_reg_list,
412 struct watchdog_device, deferred);
413 list_del(&wdd->deferred);
414 __watchdog_register_device(wdd);
416 mutex_unlock(&wtd_deferred_reg_mutex);
420 static int __init watchdog_init(void)
424 err = watchdog_dev_init();
428 watchdog_deferred_registration();
432 static void __exit watchdog_exit(void)
435 ida_destroy(&watchdog_ida);
438 subsys_initcall_sync(watchdog_init);
439 module_exit(watchdog_exit);
441 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
442 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
443 MODULE_DESCRIPTION("WatchDog Timer Driver Core");
444 MODULE_LICENSE("GPL");