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 /* 43 * Deferred Registration infrastructure. 44 * 45 * Sometimes watchdog drivers needs to be loaded as soon as possible, 46 * for example when it's impossible to disable it. To do so, 47 * raising the initcall level of the watchdog driver is a solution. 48 * But in such case, the miscdev is maybe not ready (subsys_initcall), and 49 * watchdog_core need miscdev to register the watchdog as a char device. 50 * 51 * The deferred registration infrastructure offer a way for the watchdog 52 * subsystem to register a watchdog properly, even before miscdev is ready. 53 */ 54 55 static DEFINE_MUTEX(wtd_deferred_reg_mutex); 56 static LIST_HEAD(wtd_deferred_reg_list); 57 static bool wtd_deferred_reg_done; 58 59 static void watchdog_deferred_registration_add(struct watchdog_device *wdd) 60 { 61 list_add_tail(&wdd->deferred, 62 &wtd_deferred_reg_list); 63 } 64 65 static void watchdog_deferred_registration_del(struct watchdog_device *wdd) 66 { 67 struct list_head *p, *n; 68 struct watchdog_device *wdd_tmp; 69 70 list_for_each_safe(p, n, &wtd_deferred_reg_list) { 71 wdd_tmp = list_entry(p, struct watchdog_device, 72 deferred); 73 if (wdd_tmp == wdd) { 74 list_del(&wdd_tmp->deferred); 75 break; 76 } 77 } 78 } 79 80 static void watchdog_check_min_max_timeout(struct watchdog_device *wdd) 81 { 82 /* 83 * Check that we have valid min and max timeout values, if 84 * not reset them both to 0 (=not used or unknown) 85 */ 86 if (!wdd->max_hw_heartbeat_ms && wdd->min_timeout > wdd->max_timeout) { 87 pr_info("Invalid min and max timeout values, resetting to 0!\n"); 88 wdd->min_timeout = 0; 89 wdd->max_timeout = 0; 90 } 91 } 92 93 /** 94 * watchdog_init_timeout() - initialize the timeout field 95 * @wdd: watchdog device 96 * @timeout_parm: timeout module parameter 97 * @dev: Device that stores the timeout-sec property 98 * 99 * Initialize the timeout field of the watchdog_device struct with either the 100 * timeout module parameter (if it is valid value) or the timeout-sec property 101 * (only if it is a valid value and the timeout_parm is out of bounds). 102 * If none of them are valid then we keep the old value (which should normally 103 * be the default timeout value). Note that for the module parameter, '0' means 104 * 'use default' while it is an invalid value for the timeout-sec property. 105 * It should simply be dropped if you want to use the default value then. 106 * 107 * A zero is returned on success or -EINVAL if all provided values are out of 108 * bounds. 109 */ 110 int watchdog_init_timeout(struct watchdog_device *wdd, 111 unsigned int timeout_parm, struct device *dev) 112 { 113 const char *dev_str = wdd->parent ? dev_name(wdd->parent) : 114 (const char *)wdd->info->identity; 115 unsigned int t = 0; 116 int ret = 0; 117 118 watchdog_check_min_max_timeout(wdd); 119 120 /* check the driver supplied value (likely a module parameter) first */ 121 if (timeout_parm) { 122 if (!watchdog_timeout_invalid(wdd, timeout_parm)) { 123 wdd->timeout = timeout_parm; 124 return 0; 125 } 126 pr_err("%s: driver supplied timeout (%u) out of range\n", 127 dev_str, timeout_parm); 128 ret = -EINVAL; 129 } 130 131 /* try to get the timeout_sec property */ 132 if (dev && dev->of_node && 133 of_property_read_u32(dev->of_node, "timeout-sec", &t) == 0) { 134 if (t && !watchdog_timeout_invalid(wdd, t)) { 135 wdd->timeout = t; 136 return 0; 137 } 138 pr_err("%s: DT supplied timeout (%u) out of range\n", dev_str, t); 139 ret = -EINVAL; 140 } 141 142 if (ret < 0 && wdd->timeout) 143 pr_warn("%s: falling back to default timeout (%u)\n", dev_str, 144 wdd->timeout); 145 146 return ret; 147 } 148 EXPORT_SYMBOL_GPL(watchdog_init_timeout); 149 150 static int watchdog_reboot_notifier(struct notifier_block *nb, 151 unsigned long code, void *data) 152 { 153 struct watchdog_device *wdd; 154 155 wdd = container_of(nb, struct watchdog_device, reboot_nb); 156 if (code == SYS_DOWN || code == SYS_HALT) { 157 if (watchdog_active(wdd)) { 158 int ret; 159 160 ret = wdd->ops->stop(wdd); 161 if (ret) 162 return NOTIFY_BAD; 163 } 164 } 165 166 return NOTIFY_DONE; 167 } 168 169 static int watchdog_restart_notifier(struct notifier_block *nb, 170 unsigned long action, void *data) 171 { 172 struct watchdog_device *wdd = container_of(nb, struct watchdog_device, 173 restart_nb); 174 175 int ret; 176 177 ret = wdd->ops->restart(wdd, action, data); 178 if (ret) 179 return NOTIFY_BAD; 180 181 return NOTIFY_DONE; 182 } 183 184 /** 185 * watchdog_set_restart_priority - Change priority of restart handler 186 * @wdd: watchdog device 187 * @priority: priority of the restart handler, should follow these guidelines: 188 * 0: use watchdog's restart function as last resort, has limited restart 189 * capabilies 190 * 128: default restart handler, use if no other handler is expected to be 191 * available and/or if restart is sufficient to restart the entire system 192 * 255: preempt all other handlers 193 * 194 * If a wdd->ops->restart function is provided when watchdog_register_device is 195 * called, it will be registered as a restart handler with the priority given 196 * here. 197 */ 198 void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority) 199 { 200 wdd->restart_nb.priority = priority; 201 } 202 EXPORT_SYMBOL_GPL(watchdog_set_restart_priority); 203 204 static int __watchdog_register_device(struct watchdog_device *wdd) 205 { 206 int ret, id = -1; 207 208 if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL) 209 return -EINVAL; 210 211 /* Mandatory operations need to be supported */ 212 if (!wdd->ops->start || (!wdd->ops->stop && !wdd->max_hw_heartbeat_ms)) 213 return -EINVAL; 214 215 watchdog_check_min_max_timeout(wdd); 216 217 /* 218 * Note: now that all watchdog_device data has been verified, we 219 * will not check this anymore in other functions. If data gets 220 * corrupted in a later stage then we expect a kernel panic! 221 */ 222 223 /* Use alias for watchdog id if possible */ 224 if (wdd->parent) { 225 ret = of_alias_get_id(wdd->parent->of_node, "watchdog"); 226 if (ret >= 0) 227 id = ida_simple_get(&watchdog_ida, ret, 228 ret + 1, GFP_KERNEL); 229 } 230 231 if (id < 0) 232 id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL); 233 234 if (id < 0) 235 return id; 236 wdd->id = id; 237 238 ret = watchdog_dev_register(wdd); 239 if (ret) { 240 ida_simple_remove(&watchdog_ida, id); 241 if (!(id == 0 && ret == -EBUSY)) 242 return ret; 243 244 /* Retry in case a legacy watchdog module exists */ 245 id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL); 246 if (id < 0) 247 return id; 248 wdd->id = id; 249 250 ret = watchdog_dev_register(wdd); 251 if (ret) { 252 ida_simple_remove(&watchdog_ida, id); 253 return ret; 254 } 255 } 256 257 if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) { 258 wdd->reboot_nb.notifier_call = watchdog_reboot_notifier; 259 260 ret = register_reboot_notifier(&wdd->reboot_nb); 261 if (ret) { 262 pr_err("watchdog%d: Cannot register reboot notifier (%d)\n", 263 wdd->id, ret); 264 watchdog_dev_unregister(wdd); 265 ida_simple_remove(&watchdog_ida, id); 266 return ret; 267 } 268 } 269 270 if (wdd->ops->restart) { 271 wdd->restart_nb.notifier_call = watchdog_restart_notifier; 272 273 ret = register_restart_handler(&wdd->restart_nb); 274 if (ret) 275 pr_warn("watchdog%d: Cannot register restart handler (%d)\n", 276 wdd->id, ret); 277 } 278 279 return 0; 280 } 281 282 /** 283 * watchdog_register_device() - register a watchdog device 284 * @wdd: watchdog device 285 * 286 * Register a watchdog device with the kernel so that the 287 * watchdog timer can be accessed from userspace. 288 * 289 * A zero is returned on success and a negative errno code for 290 * failure. 291 */ 292 293 int watchdog_register_device(struct watchdog_device *wdd) 294 { 295 const char *dev_str; 296 int ret = 0; 297 298 mutex_lock(&wtd_deferred_reg_mutex); 299 if (wtd_deferred_reg_done) 300 ret = __watchdog_register_device(wdd); 301 else 302 watchdog_deferred_registration_add(wdd); 303 mutex_unlock(&wtd_deferred_reg_mutex); 304 305 if (ret) { 306 dev_str = wdd->parent ? dev_name(wdd->parent) : 307 (const char *)wdd->info->identity; 308 pr_err("%s: failed to register watchdog device (err = %d)\n", 309 dev_str, ret); 310 } 311 312 return ret; 313 } 314 EXPORT_SYMBOL_GPL(watchdog_register_device); 315 316 static void __watchdog_unregister_device(struct watchdog_device *wdd) 317 { 318 if (wdd == NULL) 319 return; 320 321 if (wdd->ops->restart) 322 unregister_restart_handler(&wdd->restart_nb); 323 324 if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) 325 unregister_reboot_notifier(&wdd->reboot_nb); 326 327 watchdog_dev_unregister(wdd); 328 ida_simple_remove(&watchdog_ida, wdd->id); 329 } 330 331 /** 332 * watchdog_unregister_device() - unregister a watchdog device 333 * @wdd: watchdog device to unregister 334 * 335 * Unregister a watchdog device that was previously successfully 336 * registered with watchdog_register_device(). 337 */ 338 339 void watchdog_unregister_device(struct watchdog_device *wdd) 340 { 341 mutex_lock(&wtd_deferred_reg_mutex); 342 if (wtd_deferred_reg_done) 343 __watchdog_unregister_device(wdd); 344 else 345 watchdog_deferred_registration_del(wdd); 346 mutex_unlock(&wtd_deferred_reg_mutex); 347 } 348 349 EXPORT_SYMBOL_GPL(watchdog_unregister_device); 350 351 static void devm_watchdog_unregister_device(struct device *dev, void *res) 352 { 353 watchdog_unregister_device(*(struct watchdog_device **)res); 354 } 355 356 /** 357 * devm_watchdog_register_device() - resource managed watchdog_register_device() 358 * @dev: device that is registering this watchdog device 359 * @wdd: watchdog device 360 * 361 * Managed watchdog_register_device(). For watchdog device registered by this 362 * function, watchdog_unregister_device() is automatically called on driver 363 * detach. See watchdog_register_device() for more information. 364 */ 365 int devm_watchdog_register_device(struct device *dev, 366 struct watchdog_device *wdd) 367 { 368 struct watchdog_device **rcwdd; 369 int ret; 370 371 rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd), 372 GFP_KERNEL); 373 if (!rcwdd) 374 return -ENOMEM; 375 376 ret = watchdog_register_device(wdd); 377 if (!ret) { 378 *rcwdd = wdd; 379 devres_add(dev, rcwdd); 380 } else { 381 devres_free(rcwdd); 382 } 383 384 return ret; 385 } 386 EXPORT_SYMBOL_GPL(devm_watchdog_register_device); 387 388 static int __init watchdog_deferred_registration(void) 389 { 390 mutex_lock(&wtd_deferred_reg_mutex); 391 wtd_deferred_reg_done = true; 392 while (!list_empty(&wtd_deferred_reg_list)) { 393 struct watchdog_device *wdd; 394 395 wdd = list_first_entry(&wtd_deferred_reg_list, 396 struct watchdog_device, deferred); 397 list_del(&wdd->deferred); 398 __watchdog_register_device(wdd); 399 } 400 mutex_unlock(&wtd_deferred_reg_mutex); 401 return 0; 402 } 403 404 static int __init watchdog_init(void) 405 { 406 int err; 407 408 err = watchdog_dev_init(); 409 if (err < 0) 410 return err; 411 412 watchdog_deferred_registration(); 413 return 0; 414 } 415 416 static void __exit watchdog_exit(void) 417 { 418 watchdog_dev_exit(); 419 ida_destroy(&watchdog_ida); 420 } 421 422 subsys_initcall_sync(watchdog_init); 423 module_exit(watchdog_exit); 424 425 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>"); 426 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>"); 427 MODULE_DESCRIPTION("WatchDog Timer Driver Core"); 428 MODULE_LICENSE("GPL"); 429