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 * @wdd: watchdog device 101 * @timeout_parm: timeout module parameter 102 * @dev: Device that stores the timeout-sec property 103 * 104 * Initialize the timeout field of the watchdog_device struct with either the 105 * timeout module parameter (if it is valid value) or the timeout-sec property 106 * (only if it is a valid value and the timeout_parm is out of bounds). 107 * If none of them are valid then we keep the old value (which should normally 108 * be the default timeout value). 109 * 110 * A zero is returned on success and -EINVAL for failure. 111 */ 112 int watchdog_init_timeout(struct watchdog_device *wdd, 113 unsigned int timeout_parm, struct device *dev) 114 { 115 unsigned int t = 0; 116 int ret = 0; 117 118 watchdog_check_min_max_timeout(wdd); 119 120 /* try to get the timeout module parameter first */ 121 if (!watchdog_timeout_invalid(wdd, timeout_parm) && timeout_parm) { 122 wdd->timeout = timeout_parm; 123 return ret; 124 } 125 if (timeout_parm) 126 ret = -EINVAL; 127 128 /* try to get the timeout_sec property */ 129 if (dev == NULL || dev->of_node == NULL) 130 return ret; 131 of_property_read_u32(dev->of_node, "timeout-sec", &t); 132 if (!watchdog_timeout_invalid(wdd, t) && t) 133 wdd->timeout = t; 134 else 135 ret = -EINVAL; 136 137 return ret; 138 } 139 EXPORT_SYMBOL_GPL(watchdog_init_timeout); 140 141 static int watchdog_restart_notifier(struct notifier_block *nb, 142 unsigned long action, void *data) 143 { 144 struct watchdog_device *wdd = container_of(nb, struct watchdog_device, 145 restart_nb); 146 147 int ret; 148 149 ret = wdd->ops->restart(wdd, action, data); 150 if (ret) 151 return NOTIFY_BAD; 152 153 return NOTIFY_DONE; 154 } 155 156 /** 157 * watchdog_set_restart_priority - Change priority of restart handler 158 * @wdd: watchdog device 159 * @priority: priority of the restart handler, should follow these guidelines: 160 * 0: use watchdog's restart function as last resort, has limited restart 161 * capabilies 162 * 128: default restart handler, use if no other handler is expected to be 163 * available and/or if restart is sufficient to restart the entire system 164 * 255: preempt all other handlers 165 * 166 * If a wdd->ops->restart function is provided when watchdog_register_device is 167 * called, it will be registered as a restart handler with the priority given 168 * here. 169 */ 170 void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority) 171 { 172 wdd->restart_nb.priority = priority; 173 } 174 EXPORT_SYMBOL_GPL(watchdog_set_restart_priority); 175 176 static int __watchdog_register_device(struct watchdog_device *wdd) 177 { 178 int ret, id = -1; 179 180 if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL) 181 return -EINVAL; 182 183 /* Mandatory operations need to be supported */ 184 if (!wdd->ops->start || (!wdd->ops->stop && !wdd->max_hw_heartbeat_ms)) 185 return -EINVAL; 186 187 watchdog_check_min_max_timeout(wdd); 188 189 /* 190 * Note: now that all watchdog_device data has been verified, we 191 * will not check this anymore in other functions. If data gets 192 * corrupted in a later stage then we expect a kernel panic! 193 */ 194 195 /* Use alias for watchdog id if possible */ 196 if (wdd->parent) { 197 ret = of_alias_get_id(wdd->parent->of_node, "watchdog"); 198 if (ret >= 0) 199 id = ida_simple_get(&watchdog_ida, ret, 200 ret + 1, GFP_KERNEL); 201 } 202 203 if (id < 0) 204 id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL); 205 206 if (id < 0) 207 return id; 208 wdd->id = id; 209 210 ret = watchdog_dev_register(wdd); 211 if (ret) { 212 ida_simple_remove(&watchdog_ida, id); 213 if (!(id == 0 && ret == -EBUSY)) 214 return ret; 215 216 /* Retry in case a legacy watchdog module exists */ 217 id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL); 218 if (id < 0) 219 return id; 220 wdd->id = id; 221 222 ret = watchdog_dev_register(wdd); 223 if (ret) { 224 ida_simple_remove(&watchdog_ida, id); 225 return ret; 226 } 227 } 228 229 if (wdd->ops->restart) { 230 wdd->restart_nb.notifier_call = watchdog_restart_notifier; 231 232 ret = register_restart_handler(&wdd->restart_nb); 233 if (ret) 234 pr_warn("watchdog%d: Cannot register restart handler (%d)\n", 235 wdd->id, ret); 236 } 237 238 return 0; 239 } 240 241 /** 242 * watchdog_register_device() - register a watchdog device 243 * @wdd: watchdog device 244 * 245 * Register a watchdog device with the kernel so that the 246 * watchdog timer can be accessed from userspace. 247 * 248 * A zero is returned on success and a negative errno code for 249 * failure. 250 */ 251 252 int watchdog_register_device(struct watchdog_device *wdd) 253 { 254 int ret; 255 256 mutex_lock(&wtd_deferred_reg_mutex); 257 if (wtd_deferred_reg_done) 258 ret = __watchdog_register_device(wdd); 259 else 260 ret = watchdog_deferred_registration_add(wdd); 261 mutex_unlock(&wtd_deferred_reg_mutex); 262 return ret; 263 } 264 EXPORT_SYMBOL_GPL(watchdog_register_device); 265 266 static void __watchdog_unregister_device(struct watchdog_device *wdd) 267 { 268 if (wdd == NULL) 269 return; 270 271 if (wdd->ops->restart) 272 unregister_restart_handler(&wdd->restart_nb); 273 274 watchdog_dev_unregister(wdd); 275 ida_simple_remove(&watchdog_ida, wdd->id); 276 } 277 278 /** 279 * watchdog_unregister_device() - unregister a watchdog device 280 * @wdd: watchdog device to unregister 281 * 282 * Unregister a watchdog device that was previously successfully 283 * registered with watchdog_register_device(). 284 */ 285 286 void watchdog_unregister_device(struct watchdog_device *wdd) 287 { 288 mutex_lock(&wtd_deferred_reg_mutex); 289 if (wtd_deferred_reg_done) 290 __watchdog_unregister_device(wdd); 291 else 292 watchdog_deferred_registration_del(wdd); 293 mutex_unlock(&wtd_deferred_reg_mutex); 294 } 295 296 EXPORT_SYMBOL_GPL(watchdog_unregister_device); 297 298 static void devm_watchdog_unregister_device(struct device *dev, void *res) 299 { 300 watchdog_unregister_device(*(struct watchdog_device **)res); 301 } 302 303 /** 304 * devm_watchdog_register_device() - resource managed watchdog_register_device() 305 * @dev: device that is registering this watchdog device 306 * @wdd: watchdog device 307 * 308 * Managed watchdog_register_device(). For watchdog device registered by this 309 * function, watchdog_unregister_device() is automatically called on driver 310 * detach. See watchdog_register_device() for more information. 311 */ 312 int devm_watchdog_register_device(struct device *dev, 313 struct watchdog_device *wdd) 314 { 315 struct watchdog_device **rcwdd; 316 int ret; 317 318 rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd), 319 GFP_KERNEL); 320 if (!rcwdd) 321 return -ENOMEM; 322 323 ret = watchdog_register_device(wdd); 324 if (!ret) { 325 *rcwdd = wdd; 326 devres_add(dev, rcwdd); 327 } else { 328 devres_free(rcwdd); 329 } 330 331 return ret; 332 } 333 EXPORT_SYMBOL_GPL(devm_watchdog_register_device); 334 335 static int __init watchdog_deferred_registration(void) 336 { 337 mutex_lock(&wtd_deferred_reg_mutex); 338 wtd_deferred_reg_done = true; 339 while (!list_empty(&wtd_deferred_reg_list)) { 340 struct watchdog_device *wdd; 341 342 wdd = list_first_entry(&wtd_deferred_reg_list, 343 struct watchdog_device, deferred); 344 list_del(&wdd->deferred); 345 __watchdog_register_device(wdd); 346 } 347 mutex_unlock(&wtd_deferred_reg_mutex); 348 return 0; 349 } 350 351 static int __init watchdog_init(void) 352 { 353 int err; 354 355 err = watchdog_dev_init(); 356 if (err < 0) 357 return err; 358 359 watchdog_deferred_registration(); 360 return 0; 361 } 362 363 static void __exit watchdog_exit(void) 364 { 365 watchdog_dev_exit(); 366 ida_destroy(&watchdog_ida); 367 } 368 369 subsys_initcall_sync(watchdog_init); 370 module_exit(watchdog_exit); 371 372 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>"); 373 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>"); 374 MODULE_DESCRIPTION("WatchDog Timer Driver Core"); 375 MODULE_LICENSE("GPL"); 376