drivers/watchdog/watchdog_core.c

   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  * @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 void devm_watchdog_unregister_device(struct device *dev, void *res)
 333 {
 334         watchdog_unregister_device(*(struct watchdog_device **)res);
 335 }
 336
 337 /**
 338  * devm_watchdog_register_device() - resource managed watchdog_register_device()
 339  * @dev: device that is registering this watchdog device
 340  * @wdd: watchdog device
 341  *
 342  * Managed watchdog_register_device(). For watchdog device registered by this
 343  * function,  watchdog_unregister_device() is automatically called on driver
 344  * detach. See watchdog_register_device() for more information.
 345  */
 346 int devm_watchdog_register_device(struct device *dev,
 347                                 struct watchdog_device *wdd)
 348 {
 349         struct watchdog_device **rcwdd;
 350         int ret;
 351
 352         rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd),
 353                              GFP_KERNEL);
 354         if (!rcwdd)
 355                 return -ENOMEM;
 356
 357         ret = watchdog_register_device(wdd);
 358         if (!ret) {
 359                 *rcwdd = wdd;
 360                 devres_add(dev, rcwdd);
 361         } else {
 362                 devres_free(rcwdd);
 363         }
 364
 365         return ret;
 366 }
 367 EXPORT_SYMBOL_GPL(devm_watchdog_register_device);
 368
 369 static int __init watchdog_deferred_registration(void)
 370 {
 371         mutex_lock(&wtd_deferred_reg_mutex);
 372         wtd_deferred_reg_done = true;
 373         while (!list_empty(&wtd_deferred_reg_list)) {
 374                 struct watchdog_device *wdd;
 375
 376                 wdd = list_first_entry(&wtd_deferred_reg_list,
 377                                        struct watchdog_device, deferred);
 378                 list_del(&wdd->deferred);
 379                 __watchdog_register_device(wdd);
 380         }
 381         mutex_unlock(&wtd_deferred_reg_mutex);
 382         return 0;
 383 }
 384
 385 static int __init watchdog_init(void)
 386 {
 387         int err;
 388
 389         err = watchdog_dev_init();
 390         if (err < 0)
 391                 return err;
 392
 393         watchdog_deferred_registration();
 394         return 0;
 395 }
 396
 397 static void __exit watchdog_exit(void)
 398 {
 399         watchdog_dev_exit();
 400         ida_destroy(&watchdog_ida);
 401 }
 402
 403 subsys_initcall_sync(watchdog_init);
 404 module_exit(watchdog_exit);
 405
 406 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
 407 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
 408 MODULE_DESCRIPTION("WatchDog Timer Driver Core");
 409 MODULE_LICENSE("GPL");