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_restart_notifier(struct notifier_block *nb, 151 unsigned long action, void *data) 152 { 153 struct watchdog_device *wdd = container_of(nb, struct watchdog_device, 154 restart_nb); 155 156 int ret; 157 158 ret = wdd->ops->restart(wdd, action, data); 159 if (ret) 160 return NOTIFY_BAD; 161 162 return NOTIFY_DONE; 163 } 164 165 /** 166 * watchdog_set_restart_priority - Change priority of restart handler 167 * @wdd: watchdog device 168 * @priority: priority of the restart handler, should follow these guidelines: 169 * 0: use watchdog's restart function as last resort, has limited restart 170 * capabilies 171 * 128: default restart handler, use if no other handler is expected to be 172 * available and/or if restart is sufficient to restart the entire system 173 * 255: preempt all other handlers 174 * 175 * If a wdd->ops->restart function is provided when watchdog_register_device is 176 * called, it will be registered as a restart handler with the priority given 177 * here. 178 */ 179 void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority) 180 { 181 wdd->restart_nb.priority = priority; 182 } 183 EXPORT_SYMBOL_GPL(watchdog_set_restart_priority); 184 185 static int __watchdog_register_device(struct watchdog_device *wdd) 186 { 187 int ret, id = -1; 188 189 if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL) 190 return -EINVAL; 191 192 /* Mandatory operations need to be supported */ 193 if (!wdd->ops->start || (!wdd->ops->stop && !wdd->max_hw_heartbeat_ms)) 194 return -EINVAL; 195 196 watchdog_check_min_max_timeout(wdd); 197 198 /* 199 * Note: now that all watchdog_device data has been verified, we 200 * will not check this anymore in other functions. If data gets 201 * corrupted in a later stage then we expect a kernel panic! 202 */ 203 204 /* Use alias for watchdog id if possible */ 205 if (wdd->parent) { 206 ret = of_alias_get_id(wdd->parent->of_node, "watchdog"); 207 if (ret >= 0) 208 id = ida_simple_get(&watchdog_ida, ret, 209 ret + 1, GFP_KERNEL); 210 } 211 212 if (id < 0) 213 id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL); 214 215 if (id < 0) 216 return id; 217 wdd->id = id; 218 219 ret = watchdog_dev_register(wdd); 220 if (ret) { 221 ida_simple_remove(&watchdog_ida, id); 222 if (!(id == 0 && ret == -EBUSY)) 223 return ret; 224 225 /* Retry in case a legacy watchdog module exists */ 226 id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL); 227 if (id < 0) 228 return id; 229 wdd->id = id; 230 231 ret = watchdog_dev_register(wdd); 232 if (ret) { 233 ida_simple_remove(&watchdog_ida, id); 234 return ret; 235 } 236 } 237 238 if (wdd->ops->restart) { 239 wdd->restart_nb.notifier_call = watchdog_restart_notifier; 240 241 ret = register_restart_handler(&wdd->restart_nb); 242 if (ret) 243 pr_warn("watchdog%d: Cannot register restart handler (%d)\n", 244 wdd->id, ret); 245 } 246 247 return 0; 248 } 249 250 /** 251 * watchdog_register_device() - register a watchdog device 252 * @wdd: watchdog device 253 * 254 * Register a watchdog device with the kernel so that the 255 * watchdog timer can be accessed from userspace. 256 * 257 * A zero is returned on success and a negative errno code for 258 * failure. 259 */ 260 261 int watchdog_register_device(struct watchdog_device *wdd) 262 { 263 const char *dev_str; 264 int ret = 0; 265 266 mutex_lock(&wtd_deferred_reg_mutex); 267 if (wtd_deferred_reg_done) 268 ret = __watchdog_register_device(wdd); 269 else 270 watchdog_deferred_registration_add(wdd); 271 mutex_unlock(&wtd_deferred_reg_mutex); 272 273 if (ret) { 274 dev_str = wdd->parent ? dev_name(wdd->parent) : 275 (const char *)wdd->info->identity; 276 pr_err("%s: failed to register watchdog device (err = %d)\n", 277 dev_str, ret); 278 } 279 280 return ret; 281 } 282 EXPORT_SYMBOL_GPL(watchdog_register_device); 283 284 static void __watchdog_unregister_device(struct watchdog_device *wdd) 285 { 286 if (wdd == NULL) 287 return; 288 289 if (wdd->ops->restart) 290 unregister_restart_handler(&wdd->restart_nb); 291 292 watchdog_dev_unregister(wdd); 293 ida_simple_remove(&watchdog_ida, wdd->id); 294 } 295 296 /** 297 * watchdog_unregister_device() - unregister a watchdog device 298 * @wdd: watchdog device to unregister 299 * 300 * Unregister a watchdog device that was previously successfully 301 * registered with watchdog_register_device(). 302 */ 303 304 void watchdog_unregister_device(struct watchdog_device *wdd) 305 { 306 mutex_lock(&wtd_deferred_reg_mutex); 307 if (wtd_deferred_reg_done) 308 __watchdog_unregister_device(wdd); 309 else 310 watchdog_deferred_registration_del(wdd); 311 mutex_unlock(&wtd_deferred_reg_mutex); 312 } 313 314 EXPORT_SYMBOL_GPL(watchdog_unregister_device); 315 316 static void devm_watchdog_unregister_device(struct device *dev, void *res) 317 { 318 watchdog_unregister_device(*(struct watchdog_device **)res); 319 } 320 321 /** 322 * devm_watchdog_register_device() - resource managed watchdog_register_device() 323 * @dev: device that is registering this watchdog device 324 * @wdd: watchdog device 325 * 326 * Managed watchdog_register_device(). For watchdog device registered by this 327 * function, watchdog_unregister_device() is automatically called on driver 328 * detach. See watchdog_register_device() for more information. 329 */ 330 int devm_watchdog_register_device(struct device *dev, 331 struct watchdog_device *wdd) 332 { 333 struct watchdog_device **rcwdd; 334 int ret; 335 336 rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd), 337 GFP_KERNEL); 338 if (!rcwdd) 339 return -ENOMEM; 340 341 ret = watchdog_register_device(wdd); 342 if (!ret) { 343 *rcwdd = wdd; 344 devres_add(dev, rcwdd); 345 } else { 346 devres_free(rcwdd); 347 } 348 349 return ret; 350 } 351 EXPORT_SYMBOL_GPL(devm_watchdog_register_device); 352 353 static int __init watchdog_deferred_registration(void) 354 { 355 mutex_lock(&wtd_deferred_reg_mutex); 356 wtd_deferred_reg_done = true; 357 while (!list_empty(&wtd_deferred_reg_list)) { 358 struct watchdog_device *wdd; 359 360 wdd = list_first_entry(&wtd_deferred_reg_list, 361 struct watchdog_device, deferred); 362 list_del(&wdd->deferred); 363 __watchdog_register_device(wdd); 364 } 365 mutex_unlock(&wtd_deferred_reg_mutex); 366 return 0; 367 } 368 369 static int __init watchdog_init(void) 370 { 371 int err; 372 373 err = watchdog_dev_init(); 374 if (err < 0) 375 return err; 376 377 watchdog_deferred_registration(); 378 return 0; 379 } 380 381 static void __exit watchdog_exit(void) 382 { 383 watchdog_dev_exit(); 384 ida_destroy(&watchdog_ida); 385 } 386 387 subsys_initcall_sync(watchdog_init); 388 module_exit(watchdog_exit); 389 390 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>"); 391 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>"); 392 MODULE_DESCRIPTION("WatchDog Timer Driver Core"); 393 MODULE_LICENSE("GPL"); 394