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1/*
2 * watchdog_core.c
3 *
4 * (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
5 * All Rights Reserved.
6 *
7 * (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
8 *
9 * This source code is part of the generic code that can be used
10 * by all the watchdog timer drivers.
11 *
12 * Based on source code of the following authors:
13 * Matt Domsch <Matt_Domsch@dell.com>,
14 * Rob Radez <rob@osinvestor.com>,
15 * Rusty Lynch <rusty@linux.co.intel.com>
16 * Satyam Sharma <satyam@infradead.org>
17 * Randy Dunlap <randy.dunlap@oracle.com>
18 *
19 * This program is free software; you can redistribute it and/or
20 * modify it under the terms of the GNU General Public License
21 * as published by the Free Software Foundation; either version
22 * 2 of the License, or (at your option) any later version.
23 *
24 * Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
25 * admit liability nor provide warranty for any of this software.
26 * This material is provided "AS-IS" and at no charge.
27 */
28
29#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
30
31#include <linux/module.h> /* For EXPORT_SYMBOL/module stuff/... */
32#include <linux/types.h> /* For standard types */
33#include <linux/errno.h> /* For the -ENODEV/... values */
34#include <linux/kernel.h> /* For printk/panic/... */
35#include <linux/watchdog.h> /* For watchdog specific items */
36#include <linux/init.h> /* For __init/__exit/... */
37
38#include "watchdog_dev.h" /* For watchdog_dev_register/... */
39
40/**
41 * watchdog_register_device() - register a watchdog device
42 * @wdd: watchdog device
43 *
44 * Register a watchdog device with the kernel so that the
45 * watchdog timer can be accessed from userspace.
46 *
47 * A zero is returned on success and a negative errno code for
48 * failure.
49 */
50int watchdog_register_device(struct watchdog_device *wdd)
51{
52 int ret;
53
54 if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
55 return -EINVAL;
56
57 /* Mandatory operations need to be supported */
58 if (wdd->ops->start == NULL || wdd->ops->stop == NULL)
59 return -EINVAL;
60
61 /*
62 * Check that we have valid min and max timeout values, if
63 * not reset them both to 0 (=not used or unknown)
64 */
65 if (wdd->min_timeout > wdd->max_timeout) {
66 pr_info("Invalid min and max timeout values, resetting to 0!\n");
67 wdd->min_timeout = 0;
68 wdd->max_timeout = 0;
69 }
70
71 /*
72 * Note: now that all watchdog_device data has been verified, we
73 * will not check this anymore in other functions. If data gets
74 * corrupted in a later stage then we expect a kernel panic!
75 */
76
77 /* We only support 1 watchdog device via the /dev/watchdog interface */
78 ret = watchdog_dev_register(wdd);
79 if (ret) {
80 pr_err("error registering /dev/watchdog (err=%d).\n", ret);
81 return ret;
82 }
83
84 return 0;
85}
86EXPORT_SYMBOL_GPL(watchdog_register_device);
87
88/**
89 * watchdog_unregister_device() - unregister a watchdog device
90 * @wdd: watchdog device to unregister
91 *
92 * Unregister a watchdog device that was previously successfully
93 * registered with watchdog_register_device().
94 */
95void watchdog_unregister_device(struct watchdog_device *wdd)
96{
97 int ret;
98
99 if (wdd == NULL)
100 return;
101
102 ret = watchdog_dev_unregister(wdd);
103 if (ret)
104 pr_err("error unregistering /dev/watchdog (err=%d).\n", ret);
105}
106EXPORT_SYMBOL_GPL(watchdog_unregister_device);
107
108MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
109MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
110MODULE_DESCRIPTION("WatchDog Timer Driver Core");
111MODULE_LICENSE("GPL");
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 wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
271
272 ret = register_reboot_notifier(&wdd->reboot_nb);
273 if (ret) {
274 pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
275 wdd->id, ret);
276 watchdog_dev_unregister(wdd);
277 ida_simple_remove(&watchdog_ida, id);
278 return ret;
279 }
280 }
281
282 if (wdd->ops->restart) {
283 wdd->restart_nb.notifier_call = watchdog_restart_notifier;
284
285 ret = register_restart_handler(&wdd->restart_nb);
286 if (ret)
287 pr_warn("watchdog%d: Cannot register restart handler (%d)\n",
288 wdd->id, ret);
289 }
290
291 return 0;
292}
293
294/**
295 * watchdog_register_device() - register a watchdog device
296 * @wdd: watchdog device
297 *
298 * Register a watchdog device with the kernel so that the
299 * watchdog timer can be accessed from userspace.
300 *
301 * A zero is returned on success and a negative errno code for
302 * failure.
303 */
304
305int watchdog_register_device(struct watchdog_device *wdd)
306{
307 const char *dev_str;
308 int ret = 0;
309
310 mutex_lock(&wtd_deferred_reg_mutex);
311 if (wtd_deferred_reg_done)
312 ret = __watchdog_register_device(wdd);
313 else
314 watchdog_deferred_registration_add(wdd);
315 mutex_unlock(&wtd_deferred_reg_mutex);
316
317 if (ret) {
318 dev_str = wdd->parent ? dev_name(wdd->parent) :
319 (const char *)wdd->info->identity;
320 pr_err("%s: failed to register watchdog device (err = %d)\n",
321 dev_str, ret);
322 }
323
324 return ret;
325}
326EXPORT_SYMBOL_GPL(watchdog_register_device);
327
328static void __watchdog_unregister_device(struct watchdog_device *wdd)
329{
330 if (wdd == NULL)
331 return;
332
333 if (wdd->ops->restart)
334 unregister_restart_handler(&wdd->restart_nb);
335
336 if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))
337 unregister_reboot_notifier(&wdd->reboot_nb);
338
339 watchdog_dev_unregister(wdd);
340 ida_simple_remove(&watchdog_ida, wdd->id);
341}
342
343/**
344 * watchdog_unregister_device() - unregister a watchdog device
345 * @wdd: watchdog device to unregister
346 *
347 * Unregister a watchdog device that was previously successfully
348 * registered with watchdog_register_device().
349 */
350
351void watchdog_unregister_device(struct watchdog_device *wdd)
352{
353 mutex_lock(&wtd_deferred_reg_mutex);
354 if (wtd_deferred_reg_done)
355 __watchdog_unregister_device(wdd);
356 else
357 watchdog_deferred_registration_del(wdd);
358 mutex_unlock(&wtd_deferred_reg_mutex);
359}
360
361EXPORT_SYMBOL_GPL(watchdog_unregister_device);
362
363static void devm_watchdog_unregister_device(struct device *dev, void *res)
364{
365 watchdog_unregister_device(*(struct watchdog_device **)res);
366}
367
368/**
369 * devm_watchdog_register_device() - resource managed watchdog_register_device()
370 * @dev: device that is registering this watchdog device
371 * @wdd: watchdog device
372 *
373 * Managed watchdog_register_device(). For watchdog device registered by this
374 * function, watchdog_unregister_device() is automatically called on driver
375 * detach. See watchdog_register_device() for more information.
376 */
377int devm_watchdog_register_device(struct device *dev,
378 struct watchdog_device *wdd)
379{
380 struct watchdog_device **rcwdd;
381 int ret;
382
383 rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd),
384 GFP_KERNEL);
385 if (!rcwdd)
386 return -ENOMEM;
387
388 ret = watchdog_register_device(wdd);
389 if (!ret) {
390 *rcwdd = wdd;
391 devres_add(dev, rcwdd);
392 } else {
393 devres_free(rcwdd);
394 }
395
396 return ret;
397}
398EXPORT_SYMBOL_GPL(devm_watchdog_register_device);
399
400static int __init watchdog_deferred_registration(void)
401{
402 mutex_lock(&wtd_deferred_reg_mutex);
403 wtd_deferred_reg_done = true;
404 while (!list_empty(&wtd_deferred_reg_list)) {
405 struct watchdog_device *wdd;
406
407 wdd = list_first_entry(&wtd_deferred_reg_list,
408 struct watchdog_device, deferred);
409 list_del(&wdd->deferred);
410 __watchdog_register_device(wdd);
411 }
412 mutex_unlock(&wtd_deferred_reg_mutex);
413 return 0;
414}
415
416static int __init watchdog_init(void)
417{
418 int err;
419
420 err = watchdog_dev_init();
421 if (err < 0)
422 return err;
423
424 watchdog_deferred_registration();
425 return 0;
426}
427
428static void __exit watchdog_exit(void)
429{
430 watchdog_dev_exit();
431 ida_destroy(&watchdog_ida);
432}
433
434subsys_initcall_sync(watchdog_init);
435module_exit(watchdog_exit);
436
437MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
438MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
439MODULE_DESCRIPTION("WatchDog Timer Driver Core");
440MODULE_LICENSE("GPL");