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/reboot.h>	/* For restart handler */
36 #include <linux/watchdog.h>	/* For watchdog specific items */
37 #include <linux/init.h>		/* For __init/__exit/... */
38 #include <linux/idr.h>		/* For ida_* macros */
39 #include <linux/err.h>		/* For IS_ERR macros */
40 #include <linux/of.h>		/* For of_get_timeout_sec */
41 
42 #include "watchdog_core.h"	/* For watchdog_dev_register/... */
43 
44 static DEFINE_IDA(watchdog_ida);
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 
59 static DEFINE_MUTEX(wtd_deferred_reg_mutex);
60 static LIST_HEAD(wtd_deferred_reg_list);
61 static bool wtd_deferred_reg_done;
62 
63 static int watchdog_deferred_registration_add(struct watchdog_device *wdd)
64 {
65 	list_add_tail(&wdd->deferred,
66 		      &wtd_deferred_reg_list);
67 	return 0;
68 }
69 
70 static void watchdog_deferred_registration_del(struct watchdog_device *wdd)
71 {
72 	struct list_head *p, *n;
73 	struct watchdog_device *wdd_tmp;
74 
75 	list_for_each_safe(p, n, &wtd_deferred_reg_list) {
76 		wdd_tmp = list_entry(p, struct watchdog_device,
77 				     deferred);
78 		if (wdd_tmp == wdd) {
79 			list_del(&wdd_tmp->deferred);
80 			break;
81 		}
82 	}
83 }
84 
85 static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
86 {
87 	/*
88 	 * Check that we have valid min and max timeout values, if
89 	 * not reset them both to 0 (=not used or unknown)
90 	 */
91 	if (!wdd->max_hw_heartbeat_ms && wdd->min_timeout > wdd->max_timeout) {
92 		pr_info("Invalid min and max timeout values, resetting to 0!\n");
93 		wdd->min_timeout = 0;
94 		wdd->max_timeout = 0;
95 	}
96 }
97 
98 /**
99  * watchdog_init_timeout() - initialize the timeout field
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).
108  *
109  * A zero is returned on success and -EINVAL for failure.
110  */
111 int watchdog_init_timeout(struct watchdog_device *wdd,
112 				unsigned int timeout_parm, struct device *dev)
113 {
114 	unsigned int t = 0;
115 	int ret = 0;
116 
117 	watchdog_check_min_max_timeout(wdd);
118 
119 	/* try to get the timeout module parameter first */
120 	if (!watchdog_timeout_invalid(wdd, timeout_parm) && timeout_parm) {
121 		wdd->timeout = timeout_parm;
122 		return ret;
123 	}
124 	if (timeout_parm)
125 		ret = -EINVAL;
126 
127 	/* try to get the timeout_sec property */
128 	if (dev == NULL || dev->of_node == NULL)
129 		return ret;
130 	of_property_read_u32(dev->of_node, "timeout-sec", &t);
131 	if (!watchdog_timeout_invalid(wdd, t) && t)
132 		wdd->timeout = t;
133 	else
134 		ret = -EINVAL;
135 
136 	return ret;
137 }
138 EXPORT_SYMBOL_GPL(watchdog_init_timeout);
139 
140 static int watchdog_restart_notifier(struct notifier_block *nb,
141 				     unsigned long action, void *data)
142 {
143 	struct watchdog_device *wdd = container_of(nb, struct watchdog_device,
144 						   restart_nb);
145 
146 	int ret;
147 
148 	ret = wdd->ops->restart(wdd, action, data);
149 	if (ret)
150 		return NOTIFY_BAD;
151 
152 	return NOTIFY_DONE;
153 }
154 
155 /**
156  * watchdog_set_restart_priority - Change priority of restart handler
157  * @wdd: watchdog device
158  * @priority: priority of the restart handler, should follow these guidelines:
159  *   0:   use watchdog's restart function as last resort, has limited restart
160  *        capabilies
161  *   128: default restart handler, use if no other handler is expected to be
162  *        available and/or if restart is sufficient to restart the entire system
163  *   255: preempt all other handlers
164  *
165  * If a wdd->ops->restart function is provided when watchdog_register_device is
166  * called, it will be registered as a restart handler with the priority given
167  * here.
168  */
169 void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority)
170 {
171 	wdd->restart_nb.priority = priority;
172 }
173 EXPORT_SYMBOL_GPL(watchdog_set_restart_priority);
174 
175 static int __watchdog_register_device(struct watchdog_device *wdd)
176 {
177 	int ret, id = -1;
178 
179 	if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
180 		return -EINVAL;
181 
182 	/* Mandatory operations need to be supported */
183 	if (!wdd->ops->start || (!wdd->ops->stop && !wdd->max_hw_heartbeat_ms))
184 		return -EINVAL;
185 
186 	watchdog_check_min_max_timeout(wdd);
187 
188 	/*
189 	 * Note: now that all watchdog_device data has been verified, we
190 	 * will not check this anymore in other functions. If data gets
191 	 * corrupted in a later stage then we expect a kernel panic!
192 	 */
193 
194 	/* Use alias for watchdog id if possible */
195 	if (wdd->parent) {
196 		ret = of_alias_get_id(wdd->parent->of_node, "watchdog");
197 		if (ret >= 0)
198 			id = ida_simple_get(&watchdog_ida, ret,
199 					    ret + 1, GFP_KERNEL);
200 	}
201 
202 	if (id < 0)
203 		id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
204 
205 	if (id < 0)
206 		return id;
207 	wdd->id = id;
208 
209 	ret = watchdog_dev_register(wdd);
210 	if (ret) {
211 		ida_simple_remove(&watchdog_ida, id);
212 		if (!(id == 0 && ret == -EBUSY))
213 			return ret;
214 
215 		/* Retry in case a legacy watchdog module exists */
216 		id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
217 		if (id < 0)
218 			return id;
219 		wdd->id = id;
220 
221 		ret = watchdog_dev_register(wdd);
222 		if (ret) {
223 			ida_simple_remove(&watchdog_ida, id);
224 			return ret;
225 		}
226 	}
227 
228 	if (wdd->ops->restart) {
229 		wdd->restart_nb.notifier_call = watchdog_restart_notifier;
230 
231 		ret = register_restart_handler(&wdd->restart_nb);
232 		if (ret)
233 			pr_warn("watchdog%d: Cannot register restart handler (%d)\n",
234 				wdd->id, ret);
235 	}
236 
237 	return 0;
238 }
239 
240 /**
241  * watchdog_register_device() - register a watchdog device
242  * @wdd: watchdog device
243  *
244  * Register a watchdog device with the kernel so that the
245  * watchdog timer can be accessed from userspace.
246  *
247  * A zero is returned on success and a negative errno code for
248  * failure.
249  */
250 
251 int watchdog_register_device(struct watchdog_device *wdd)
252 {
253 	int ret;
254 
255 	mutex_lock(&wtd_deferred_reg_mutex);
256 	if (wtd_deferred_reg_done)
257 		ret = __watchdog_register_device(wdd);
258 	else
259 		ret = watchdog_deferred_registration_add(wdd);
260 	mutex_unlock(&wtd_deferred_reg_mutex);
261 	return ret;
262 }
263 EXPORT_SYMBOL_GPL(watchdog_register_device);
264 
265 static void __watchdog_unregister_device(struct watchdog_device *wdd)
266 {
267 	if (wdd == NULL)
268 		return;
269 
270 	if (wdd->ops->restart)
271 		unregister_restart_handler(&wdd->restart_nb);
272 
273 	watchdog_dev_unregister(wdd);
274 	ida_simple_remove(&watchdog_ida, wdd->id);
275 }
276 
277 /**
278  * watchdog_unregister_device() - unregister a watchdog device
279  * @wdd: watchdog device to unregister
280  *
281  * Unregister a watchdog device that was previously successfully
282  * registered with watchdog_register_device().
283  */
284 
285 void watchdog_unregister_device(struct watchdog_device *wdd)
286 {
287 	mutex_lock(&wtd_deferred_reg_mutex);
288 	if (wtd_deferred_reg_done)
289 		__watchdog_unregister_device(wdd);
290 	else
291 		watchdog_deferred_registration_del(wdd);
292 	mutex_unlock(&wtd_deferred_reg_mutex);
293 }
294 
295 EXPORT_SYMBOL_GPL(watchdog_unregister_device);
296 
297 static void devm_watchdog_unregister_device(struct device *dev, void *res)
298 {
299 	watchdog_unregister_device(*(struct watchdog_device **)res);
300 }
301 
302 /**
303  * devm_watchdog_register_device() - resource managed watchdog_register_device()
304  * @dev: device that is registering this watchdog device
305  * @wdd: watchdog device
306  *
307  * Managed watchdog_register_device(). For watchdog device registered by this
308  * function,  watchdog_unregister_device() is automatically called on driver
309  * detach. See watchdog_register_device() for more information.
310  */
311 int devm_watchdog_register_device(struct device *dev,
312 				struct watchdog_device *wdd)
313 {
314 	struct watchdog_device **rcwdd;
315 	int ret;
316 
317 	rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd),
318 			     GFP_KERNEL);
319 	if (!rcwdd)
320 		return -ENOMEM;
321 
322 	ret = watchdog_register_device(wdd);
323 	if (!ret) {
324 		*rcwdd = wdd;
325 		devres_add(dev, rcwdd);
326 	} else {
327 		devres_free(rcwdd);
328 	}
329 
330 	return ret;
331 }
332 EXPORT_SYMBOL_GPL(devm_watchdog_register_device);
333 
334 static int __init watchdog_deferred_registration(void)
335 {
336 	mutex_lock(&wtd_deferred_reg_mutex);
337 	wtd_deferred_reg_done = true;
338 	while (!list_empty(&wtd_deferred_reg_list)) {
339 		struct watchdog_device *wdd;
340 
341 		wdd = list_first_entry(&wtd_deferred_reg_list,
342 				       struct watchdog_device, deferred);
343 		list_del(&wdd->deferred);
344 		__watchdog_register_device(wdd);
345 	}
346 	mutex_unlock(&wtd_deferred_reg_mutex);
347 	return 0;
348 }
349 
350 static int __init watchdog_init(void)
351 {
352 	int err;
353 
354 	err = watchdog_dev_init();
355 	if (err < 0)
356 		return err;
357 
358 	watchdog_deferred_registration();
359 	return 0;
360 }
361 
362 static void __exit watchdog_exit(void)
363 {
364 	watchdog_dev_exit();
365 	ida_destroy(&watchdog_ida);
366 }
367 
368 subsys_initcall_sync(watchdog_init);
369 module_exit(watchdog_exit);
370 
371 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
372 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
373 MODULE_DESCRIPTION("WatchDog Timer Driver Core");
374 MODULE_LICENSE("GPL");
375