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