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). Note that for the module parameter, '0' means 109 * 'use default' while it is an invalid value for the timeout-sec property. 110 * It should simply be dropped if you want to use the default value then. 111 * 112 * A zero is returned on success or -EINVAL if all provided values are out of 113 * bounds. 114 */ 115 int watchdog_init_timeout(struct watchdog_device *wdd, 116 unsigned int timeout_parm, struct device *dev) 117 { 118 const char *dev_str = wdd->parent ? dev_name(wdd->parent) : 119 (const char *)wdd->info->identity; 120 unsigned int t = 0; 121 int ret = 0; 122 123 watchdog_check_min_max_timeout(wdd); 124 125 /* check the driver supplied value (likely a module parameter) first */ 126 if (timeout_parm) { 127 if (!watchdog_timeout_invalid(wdd, timeout_parm)) { 128 wdd->timeout = timeout_parm; 129 return 0; 130 } 131 pr_err("%s: driver supplied timeout (%u) out of range\n", 132 dev_str, timeout_parm); 133 ret = -EINVAL; 134 } 135 136 /* try to get the timeout_sec property */ 137 if (dev && dev->of_node && 138 of_property_read_u32(dev->of_node, "timeout-sec", &t) == 0) { 139 if (t && !watchdog_timeout_invalid(wdd, t)) { 140 wdd->timeout = t; 141 return 0; 142 } 143 pr_err("%s: DT supplied timeout (%u) out of range\n", dev_str, t); 144 ret = -EINVAL; 145 } 146 147 if (ret < 0 && wdd->timeout) 148 pr_warn("%s: falling back to default timeout (%u)\n", dev_str, 149 wdd->timeout); 150 151 return ret; 152 } 153 EXPORT_SYMBOL_GPL(watchdog_init_timeout); 154 155 static int watchdog_restart_notifier(struct notifier_block *nb, 156 unsigned long action, void *data) 157 { 158 struct watchdog_device *wdd = container_of(nb, struct watchdog_device, 159 restart_nb); 160 161 int ret; 162 163 ret = wdd->ops->restart(wdd, action, data); 164 if (ret) 165 return NOTIFY_BAD; 166 167 return NOTIFY_DONE; 168 } 169 170 /** 171 * watchdog_set_restart_priority - Change priority of restart handler 172 * @wdd: watchdog device 173 * @priority: priority of the restart handler, should follow these guidelines: 174 * 0: use watchdog's restart function as last resort, has limited restart 175 * capabilies 176 * 128: default restart handler, use if no other handler is expected to be 177 * available and/or if restart is sufficient to restart the entire system 178 * 255: preempt all other handlers 179 * 180 * If a wdd->ops->restart function is provided when watchdog_register_device is 181 * called, it will be registered as a restart handler with the priority given 182 * here. 183 */ 184 void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority) 185 { 186 wdd->restart_nb.priority = priority; 187 } 188 EXPORT_SYMBOL_GPL(watchdog_set_restart_priority); 189 190 static int __watchdog_register_device(struct watchdog_device *wdd) 191 { 192 int ret, id = -1; 193 194 if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL) 195 return -EINVAL; 196 197 /* Mandatory operations need to be supported */ 198 if (!wdd->ops->start || (!wdd->ops->stop && !wdd->max_hw_heartbeat_ms)) 199 return -EINVAL; 200 201 watchdog_check_min_max_timeout(wdd); 202 203 /* 204 * Note: now that all watchdog_device data has been verified, we 205 * will not check this anymore in other functions. If data gets 206 * corrupted in a later stage then we expect a kernel panic! 207 */ 208 209 /* Use alias for watchdog id if possible */ 210 if (wdd->parent) { 211 ret = of_alias_get_id(wdd->parent->of_node, "watchdog"); 212 if (ret >= 0) 213 id = ida_simple_get(&watchdog_ida, ret, 214 ret + 1, GFP_KERNEL); 215 } 216 217 if (id < 0) 218 id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL); 219 220 if (id < 0) 221 return id; 222 wdd->id = id; 223 224 ret = watchdog_dev_register(wdd); 225 if (ret) { 226 ida_simple_remove(&watchdog_ida, id); 227 if (!(id == 0 && ret == -EBUSY)) 228 return ret; 229 230 /* Retry in case a legacy watchdog module exists */ 231 id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL); 232 if (id < 0) 233 return id; 234 wdd->id = id; 235 236 ret = watchdog_dev_register(wdd); 237 if (ret) { 238 ida_simple_remove(&watchdog_ida, id); 239 return ret; 240 } 241 } 242 243 if (wdd->ops->restart) { 244 wdd->restart_nb.notifier_call = watchdog_restart_notifier; 245 246 ret = register_restart_handler(&wdd->restart_nb); 247 if (ret) 248 pr_warn("watchdog%d: Cannot register restart handler (%d)\n", 249 wdd->id, ret); 250 } 251 252 return 0; 253 } 254 255 /** 256 * watchdog_register_device() - register a watchdog device 257 * @wdd: watchdog device 258 * 259 * Register a watchdog device with the kernel so that the 260 * watchdog timer can be accessed from userspace. 261 * 262 * A zero is returned on success and a negative errno code for 263 * failure. 264 */ 265 266 int watchdog_register_device(struct watchdog_device *wdd) 267 { 268 int ret; 269 270 mutex_lock(&wtd_deferred_reg_mutex); 271 if (wtd_deferred_reg_done) 272 ret = __watchdog_register_device(wdd); 273 else 274 ret = watchdog_deferred_registration_add(wdd); 275 mutex_unlock(&wtd_deferred_reg_mutex); 276 return ret; 277 } 278 EXPORT_SYMBOL_GPL(watchdog_register_device); 279 280 static void __watchdog_unregister_device(struct watchdog_device *wdd) 281 { 282 if (wdd == NULL) 283 return; 284 285 if (wdd->ops->restart) 286 unregister_restart_handler(&wdd->restart_nb); 287 288 watchdog_dev_unregister(wdd); 289 ida_simple_remove(&watchdog_ida, wdd->id); 290 } 291 292 /** 293 * watchdog_unregister_device() - unregister a watchdog device 294 * @wdd: watchdog device to unregister 295 * 296 * Unregister a watchdog device that was previously successfully 297 * registered with watchdog_register_device(). 298 */ 299 300 void watchdog_unregister_device(struct watchdog_device *wdd) 301 { 302 mutex_lock(&wtd_deferred_reg_mutex); 303 if (wtd_deferred_reg_done) 304 __watchdog_unregister_device(wdd); 305 else 306 watchdog_deferred_registration_del(wdd); 307 mutex_unlock(&wtd_deferred_reg_mutex); 308 } 309 310 EXPORT_SYMBOL_GPL(watchdog_unregister_device); 311 312 static void devm_watchdog_unregister_device(struct device *dev, void *res) 313 { 314 watchdog_unregister_device(*(struct watchdog_device **)res); 315 } 316 317 /** 318 * devm_watchdog_register_device() - resource managed watchdog_register_device() 319 * @dev: device that is registering this watchdog device 320 * @wdd: watchdog device 321 * 322 * Managed watchdog_register_device(). For watchdog device registered by this 323 * function, watchdog_unregister_device() is automatically called on driver 324 * detach. See watchdog_register_device() for more information. 325 */ 326 int devm_watchdog_register_device(struct device *dev, 327 struct watchdog_device *wdd) 328 { 329 struct watchdog_device **rcwdd; 330 int ret; 331 332 rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd), 333 GFP_KERNEL); 334 if (!rcwdd) 335 return -ENOMEM; 336 337 ret = watchdog_register_device(wdd); 338 if (!ret) { 339 *rcwdd = wdd; 340 devres_add(dev, rcwdd); 341 } else { 342 devres_free(rcwdd); 343 } 344 345 return ret; 346 } 347 EXPORT_SYMBOL_GPL(devm_watchdog_register_device); 348 349 static int __init watchdog_deferred_registration(void) 350 { 351 mutex_lock(&wtd_deferred_reg_mutex); 352 wtd_deferred_reg_done = true; 353 while (!list_empty(&wtd_deferred_reg_list)) { 354 struct watchdog_device *wdd; 355 356 wdd = list_first_entry(&wtd_deferred_reg_list, 357 struct watchdog_device, deferred); 358 list_del(&wdd->deferred); 359 __watchdog_register_device(wdd); 360 } 361 mutex_unlock(&wtd_deferred_reg_mutex); 362 return 0; 363 } 364 365 static int __init watchdog_init(void) 366 { 367 int err; 368 369 err = watchdog_dev_init(); 370 if (err < 0) 371 return err; 372 373 watchdog_deferred_registration(); 374 return 0; 375 } 376 377 static void __exit watchdog_exit(void) 378 { 379 watchdog_dev_exit(); 380 ida_destroy(&watchdog_ida); 381 } 382 383 subsys_initcall_sync(watchdog_init); 384 module_exit(watchdog_exit); 385 386 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>"); 387 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>"); 388 MODULE_DESCRIPTION("WatchDog Timer Driver Core"); 389 MODULE_LICENSE("GPL"); 390