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 40 static DEFINE_IDA(watchdog_ida); 41 42 static int stop_on_reboot = -1; 43 module_param(stop_on_reboot, int, 0444); 44 MODULE_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 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 void watchdog_deferred_registration_add(struct watchdog_device *wdd) 64 { 65 list_add_tail(&wdd->deferred, 66 &wtd_deferred_reg_list); 67 } 68 69 static 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 84 static 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 */ 114 int 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 } 152 EXPORT_SYMBOL_GPL(watchdog_init_timeout); 153 154 static 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 } 172 173 static 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 */ 202 void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority) 203 { 204 wdd->restart_nb.priority = priority; 205 } 206 EXPORT_SYMBOL_GPL(watchdog_set_restart_priority); 207 208 static 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 if (!wdd->ops->stop) 271 pr_warn("watchdog%d: stop_on_reboot not supported\n", wdd->id); 272 else { 273 wdd->reboot_nb.notifier_call = watchdog_reboot_notifier; 274 275 ret = register_reboot_notifier(&wdd->reboot_nb); 276 if (ret) { 277 pr_err("watchdog%d: Cannot register reboot notifier (%d)\n", 278 wdd->id, ret); 279 watchdog_dev_unregister(wdd); 280 ida_simple_remove(&watchdog_ida, id); 281 return ret; 282 } 283 } 284 } 285 286 if (wdd->ops->restart) { 287 wdd->restart_nb.notifier_call = watchdog_restart_notifier; 288 289 ret = register_restart_handler(&wdd->restart_nb); 290 if (ret) 291 pr_warn("watchdog%d: Cannot register restart handler (%d)\n", 292 wdd->id, ret); 293 } 294 295 return 0; 296 } 297 298 /** 299 * watchdog_register_device() - register a watchdog device 300 * @wdd: watchdog device 301 * 302 * Register a watchdog device with the kernel so that the 303 * watchdog timer can be accessed from userspace. 304 * 305 * A zero is returned on success and a negative errno code for 306 * failure. 307 */ 308 309 int watchdog_register_device(struct watchdog_device *wdd) 310 { 311 const char *dev_str; 312 int ret = 0; 313 314 mutex_lock(&wtd_deferred_reg_mutex); 315 if (wtd_deferred_reg_done) 316 ret = __watchdog_register_device(wdd); 317 else 318 watchdog_deferred_registration_add(wdd); 319 mutex_unlock(&wtd_deferred_reg_mutex); 320 321 if (ret) { 322 dev_str = wdd->parent ? dev_name(wdd->parent) : 323 (const char *)wdd->info->identity; 324 pr_err("%s: failed to register watchdog device (err = %d)\n", 325 dev_str, ret); 326 } 327 328 return ret; 329 } 330 EXPORT_SYMBOL_GPL(watchdog_register_device); 331 332 static void __watchdog_unregister_device(struct watchdog_device *wdd) 333 { 334 if (wdd == NULL) 335 return; 336 337 if (wdd->ops->restart) 338 unregister_restart_handler(&wdd->restart_nb); 339 340 if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) 341 unregister_reboot_notifier(&wdd->reboot_nb); 342 343 watchdog_dev_unregister(wdd); 344 ida_simple_remove(&watchdog_ida, wdd->id); 345 } 346 347 /** 348 * watchdog_unregister_device() - unregister a watchdog device 349 * @wdd: watchdog device to unregister 350 * 351 * Unregister a watchdog device that was previously successfully 352 * registered with watchdog_register_device(). 353 */ 354 355 void watchdog_unregister_device(struct watchdog_device *wdd) 356 { 357 mutex_lock(&wtd_deferred_reg_mutex); 358 if (wtd_deferred_reg_done) 359 __watchdog_unregister_device(wdd); 360 else 361 watchdog_deferred_registration_del(wdd); 362 mutex_unlock(&wtd_deferred_reg_mutex); 363 } 364 365 EXPORT_SYMBOL_GPL(watchdog_unregister_device); 366 367 static void devm_watchdog_unregister_device(struct device *dev, void *res) 368 { 369 watchdog_unregister_device(*(struct watchdog_device **)res); 370 } 371 372 /** 373 * devm_watchdog_register_device() - resource managed watchdog_register_device() 374 * @dev: device that is registering this watchdog device 375 * @wdd: watchdog device 376 * 377 * Managed watchdog_register_device(). For watchdog device registered by this 378 * function, watchdog_unregister_device() is automatically called on driver 379 * detach. See watchdog_register_device() for more information. 380 */ 381 int devm_watchdog_register_device(struct device *dev, 382 struct watchdog_device *wdd) 383 { 384 struct watchdog_device **rcwdd; 385 int ret; 386 387 rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd), 388 GFP_KERNEL); 389 if (!rcwdd) 390 return -ENOMEM; 391 392 ret = watchdog_register_device(wdd); 393 if (!ret) { 394 *rcwdd = wdd; 395 devres_add(dev, rcwdd); 396 } else { 397 devres_free(rcwdd); 398 } 399 400 return ret; 401 } 402 EXPORT_SYMBOL_GPL(devm_watchdog_register_device); 403 404 static int __init watchdog_deferred_registration(void) 405 { 406 mutex_lock(&wtd_deferred_reg_mutex); 407 wtd_deferred_reg_done = true; 408 while (!list_empty(&wtd_deferred_reg_list)) { 409 struct watchdog_device *wdd; 410 411 wdd = list_first_entry(&wtd_deferred_reg_list, 412 struct watchdog_device, deferred); 413 list_del(&wdd->deferred); 414 __watchdog_register_device(wdd); 415 } 416 mutex_unlock(&wtd_deferred_reg_mutex); 417 return 0; 418 } 419 420 static int __init watchdog_init(void) 421 { 422 int err; 423 424 err = watchdog_dev_init(); 425 if (err < 0) 426 return err; 427 428 watchdog_deferred_registration(); 429 return 0; 430 } 431 432 static void __exit watchdog_exit(void) 433 { 434 watchdog_dev_exit(); 435 ida_destroy(&watchdog_ida); 436 } 437 438 subsys_initcall_sync(watchdog_init); 439 module_exit(watchdog_exit); 440 441 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>"); 442 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>"); 443 MODULE_DESCRIPTION("WatchDog Timer Driver Core"); 444 MODULE_LICENSE("GPL"); 445