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->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_reboot_notifier(struct notifier_block *nb, 141 unsigned long code, void *data) 142 { 143 struct watchdog_device *wdd = container_of(nb, struct watchdog_device, 144 reboot_nb); 145 146 if (code == SYS_DOWN || code == SYS_HALT) { 147 if (watchdog_active(wdd)) { 148 int ret; 149 150 ret = wdd->ops->stop(wdd); 151 if (ret) 152 return NOTIFY_BAD; 153 } 154 } 155 156 return NOTIFY_DONE; 157 } 158 159 static int watchdog_restart_notifier(struct notifier_block *nb, 160 unsigned long action, void *data) 161 { 162 struct watchdog_device *wdd = container_of(nb, struct watchdog_device, 163 restart_nb); 164 165 int ret; 166 167 ret = wdd->ops->restart(wdd, action, data); 168 if (ret) 169 return NOTIFY_BAD; 170 171 return NOTIFY_DONE; 172 } 173 174 /** 175 * watchdog_set_restart_priority - Change priority of restart handler 176 * @wdd: watchdog device 177 * @priority: priority of the restart handler, should follow these guidelines: 178 * 0: use watchdog's restart function as last resort, has limited restart 179 * capabilies 180 * 128: default restart handler, use if no other handler is expected to be 181 * available and/or if restart is sufficient to restart the entire system 182 * 255: preempt all other handlers 183 * 184 * If a wdd->ops->restart function is provided when watchdog_register_device is 185 * called, it will be registered as a restart handler with the priority given 186 * here. 187 */ 188 void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority) 189 { 190 wdd->restart_nb.priority = priority; 191 } 192 EXPORT_SYMBOL_GPL(watchdog_set_restart_priority); 193 194 static int __watchdog_register_device(struct watchdog_device *wdd) 195 { 196 int ret, id = -1; 197 198 if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL) 199 return -EINVAL; 200 201 /* Mandatory operations need to be supported */ 202 if (!wdd->ops->start || (!wdd->ops->stop && !wdd->max_hw_heartbeat_ms)) 203 return -EINVAL; 204 205 watchdog_check_min_max_timeout(wdd); 206 207 /* 208 * Note: now that all watchdog_device data has been verified, we 209 * will not check this anymore in other functions. If data gets 210 * corrupted in a later stage then we expect a kernel panic! 211 */ 212 213 /* Use alias for watchdog id if possible */ 214 if (wdd->parent) { 215 ret = of_alias_get_id(wdd->parent->of_node, "watchdog"); 216 if (ret >= 0) 217 id = ida_simple_get(&watchdog_ida, ret, 218 ret + 1, GFP_KERNEL); 219 } 220 221 if (id < 0) 222 id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL); 223 224 if (id < 0) 225 return id; 226 wdd->id = id; 227 228 ret = watchdog_dev_register(wdd); 229 if (ret) { 230 ida_simple_remove(&watchdog_ida, id); 231 if (!(id == 0 && ret == -EBUSY)) 232 return ret; 233 234 /* Retry in case a legacy watchdog module exists */ 235 id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL); 236 if (id < 0) 237 return id; 238 wdd->id = id; 239 240 ret = watchdog_dev_register(wdd); 241 if (ret) { 242 ida_simple_remove(&watchdog_ida, id); 243 return ret; 244 } 245 } 246 247 if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) { 248 wdd->reboot_nb.notifier_call = watchdog_reboot_notifier; 249 250 ret = register_reboot_notifier(&wdd->reboot_nb); 251 if (ret) { 252 pr_err("watchdog%d: Cannot register reboot notifier (%d)\n", 253 wdd->id, ret); 254 watchdog_dev_unregister(wdd); 255 ida_simple_remove(&watchdog_ida, wdd->id); 256 return ret; 257 } 258 } 259 260 if (wdd->ops->restart) { 261 wdd->restart_nb.notifier_call = watchdog_restart_notifier; 262 263 ret = register_restart_handler(&wdd->restart_nb); 264 if (ret) 265 pr_warn("watchdog%d: Cannot register restart handler (%d)\n", 266 wdd->id, ret); 267 } 268 269 return 0; 270 } 271 272 /** 273 * watchdog_register_device() - register a watchdog device 274 * @wdd: watchdog device 275 * 276 * Register a watchdog device with the kernel so that the 277 * watchdog timer can be accessed from userspace. 278 * 279 * A zero is returned on success and a negative errno code for 280 * failure. 281 */ 282 283 int watchdog_register_device(struct watchdog_device *wdd) 284 { 285 int ret; 286 287 mutex_lock(&wtd_deferred_reg_mutex); 288 if (wtd_deferred_reg_done) 289 ret = __watchdog_register_device(wdd); 290 else 291 ret = watchdog_deferred_registration_add(wdd); 292 mutex_unlock(&wtd_deferred_reg_mutex); 293 return ret; 294 } 295 EXPORT_SYMBOL_GPL(watchdog_register_device); 296 297 static void __watchdog_unregister_device(struct watchdog_device *wdd) 298 { 299 if (wdd == NULL) 300 return; 301 302 if (wdd->ops->restart) 303 unregister_restart_handler(&wdd->restart_nb); 304 305 if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) 306 unregister_reboot_notifier(&wdd->reboot_nb); 307 308 watchdog_dev_unregister(wdd); 309 ida_simple_remove(&watchdog_ida, wdd->id); 310 } 311 312 /** 313 * watchdog_unregister_device() - unregister a watchdog device 314 * @wdd: watchdog device to unregister 315 * 316 * Unregister a watchdog device that was previously successfully 317 * registered with watchdog_register_device(). 318 */ 319 320 void watchdog_unregister_device(struct watchdog_device *wdd) 321 { 322 mutex_lock(&wtd_deferred_reg_mutex); 323 if (wtd_deferred_reg_done) 324 __watchdog_unregister_device(wdd); 325 else 326 watchdog_deferred_registration_del(wdd); 327 mutex_unlock(&wtd_deferred_reg_mutex); 328 } 329 330 EXPORT_SYMBOL_GPL(watchdog_unregister_device); 331 332 static int __init watchdog_deferred_registration(void) 333 { 334 mutex_lock(&wtd_deferred_reg_mutex); 335 wtd_deferred_reg_done = true; 336 while (!list_empty(&wtd_deferred_reg_list)) { 337 struct watchdog_device *wdd; 338 339 wdd = list_first_entry(&wtd_deferred_reg_list, 340 struct watchdog_device, deferred); 341 list_del(&wdd->deferred); 342 __watchdog_register_device(wdd); 343 } 344 mutex_unlock(&wtd_deferred_reg_mutex); 345 return 0; 346 } 347 348 static int __init watchdog_init(void) 349 { 350 int err; 351 352 err = watchdog_dev_init(); 353 if (err < 0) 354 return err; 355 356 watchdog_deferred_registration(); 357 return 0; 358 } 359 360 static void __exit watchdog_exit(void) 361 { 362 watchdog_dev_exit(); 363 ida_destroy(&watchdog_ida); 364 } 365 366 subsys_initcall_sync(watchdog_init); 367 module_exit(watchdog_exit); 368 369 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>"); 370 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>"); 371 MODULE_DESCRIPTION("WatchDog Timer Driver Core"); 372 MODULE_LICENSE("GPL"); 373