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  * @wdd: watchdog device
 101  * @timeout_parm: timeout module parameter
 102  * @dev: Device that stores the timeout-sec property
 103  *
 104  * Initialize the timeout field of the watchdog_device struct with either the
 105  * timeout module parameter (if it is valid value) or the timeout-sec property
 106  * (only if it is a valid value and the timeout_parm is out of bounds).
 107  * If none of them are valid then we keep the old value (which should normally
 108  * be the default timeout value).
 109  *
 110  * A zero is returned on success and -EINVAL for failure.
 111  */
 112 int watchdog_init_timeout(struct watchdog_device *wdd,
 113                                 unsigned int timeout_parm, struct device *dev)
 114 {
 115         unsigned int t = 0;
 116         int ret = 0;
 117
 118         watchdog_check_min_max_timeout(wdd);
 119
 120         /* try to get the timeout module parameter first */
 121         if (!watchdog_timeout_invalid(wdd, timeout_parm) && timeout_parm) {
 122                 wdd->timeout = timeout_parm;
 123                 return ret;
 124         }
 125         if (timeout_parm)
 126                 ret = -EINVAL;
 127
 128         /* try to get the timeout_sec property */
 129         if (dev == NULL || dev->of_node == NULL)
 130                 return ret;
 131         of_property_read_u32(dev->of_node, "timeout-sec", &t);
 132         if (!watchdog_timeout_invalid(wdd, t) && t)
 133                 wdd->timeout = t;
 134         else
 135                 ret = -EINVAL;
 136
 137         return ret;
 138 }
 139 EXPORT_SYMBOL_GPL(watchdog_init_timeout);
 140
 141 static int watchdog_restart_notifier(struct notifier_block *nb,
 142                                      unsigned long action, void *data)
 143 {
 144         struct watchdog_device *wdd = container_of(nb, struct watchdog_device,
 145                                                    restart_nb);
 146
 147         int ret;
 148
 149         ret = wdd->ops->restart(wdd, action, data);
 150         if (ret)
 151                 return NOTIFY_BAD;
 152
 153         return NOTIFY_DONE;
 154 }
 155
 156 /**
 157  * watchdog_set_restart_priority - Change priority of restart handler
 158  * @wdd: watchdog device
 159  * @priority: priority of the restart handler, should follow these guidelines:
 160  *   0:   use watchdog's restart function as last resort, has limited restart
 161  *        capabilies
 162  *   128: default restart handler, use if no other handler is expected to be
 163  *        available and/or if restart is sufficient to restart the entire system
 164  *   255: preempt all other handlers
 165  *
 166  * If a wdd->ops->restart function is provided when watchdog_register_device is
 167  * called, it will be registered as a restart handler with the priority given
 168  * here.
 169  */
 170 void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority)
 171 {
 172         wdd->restart_nb.priority = priority;
 173 }
 174 EXPORT_SYMBOL_GPL(watchdog_set_restart_priority);
 175
 176 static int __watchdog_register_device(struct watchdog_device *wdd)
 177 {
 178         int ret, id = -1;
 179
 180         if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
 181                 return -EINVAL;
 182
 183         /* Mandatory operations need to be supported */
 184         if (!wdd->ops->start || (!wdd->ops->stop && !wdd->max_hw_heartbeat_ms))
 185                 return -EINVAL;
 186
 187         watchdog_check_min_max_timeout(wdd);
 188
 189         /*
 190          * Note: now that all watchdog_device data has been verified, we
 191          * will not check this anymore in other functions. If data gets
 192          * corrupted in a later stage then we expect a kernel panic!
 193          */
 194
 195         /* Use alias for watchdog id if possible */
 196         if (wdd->parent) {
 197                 ret = of_alias_get_id(wdd->parent->of_node, "watchdog");
 198                 if (ret >= 0)
 199                         id = ida_simple_get(&watchdog_ida, ret,
 200                                             ret + 1, GFP_KERNEL);
 201         }
 202
 203         if (id < 0)
 204                 id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
 205
 206         if (id < 0)
 207                 return id;
 208         wdd->id = id;
 209
 210         ret = watchdog_dev_register(wdd);
 211         if (ret) {
 212                 ida_simple_remove(&watchdog_ida, id);
 213                 if (!(id == 0 && ret == -EBUSY))
 214                         return ret;
 215
 216                 /* Retry in case a legacy watchdog module exists */
 217                 id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
 218                 if (id < 0)
 219                         return id;
 220                 wdd->id = id;
 221
 222                 ret = watchdog_dev_register(wdd);
 223                 if (ret) {
 224                         ida_simple_remove(&watchdog_ida, id);
 225                         return ret;
 226                 }
 227         }
 228
 229         if (wdd->ops->restart) {
 230                 wdd->restart_nb.notifier_call = watchdog_restart_notifier;
 231
 232                 ret = register_restart_handler(&wdd->restart_nb);
 233                 if (ret)
 234                         pr_warn("watchdog%d: Cannot register restart handler (%d)\n",
 235                                 wdd->id, ret);
 236         }
 237
 238         return 0;
 239 }
 240
 241 /**
 242  * watchdog_register_device() - register a watchdog device
 243  * @wdd: watchdog device
 244  *
 245  * Register a watchdog device with the kernel so that the
 246  * watchdog timer can be accessed from userspace.
 247  *
 248  * A zero is returned on success and a negative errno code for
 249  * failure.
 250  */
 251
 252 int watchdog_register_device(struct watchdog_device *wdd)
 253 {
 254         int ret;
 255
 256         mutex_lock(&wtd_deferred_reg_mutex);
 257         if (wtd_deferred_reg_done)
 258                 ret = __watchdog_register_device(wdd);
 259         else
 260                 ret = watchdog_deferred_registration_add(wdd);
 261         mutex_unlock(&wtd_deferred_reg_mutex);
 262         return ret;
 263 }
 264 EXPORT_SYMBOL_GPL(watchdog_register_device);
 265
 266 static void __watchdog_unregister_device(struct watchdog_device *wdd)
 267 {
 268         if (wdd == NULL)
 269                 return;
 270
 271         if (wdd->ops->restart)
 272                 unregister_restart_handler(&wdd->restart_nb);
 273
 274         watchdog_dev_unregister(wdd);
 275         ida_simple_remove(&watchdog_ida, wdd->id);
 276 }
 277
 278 /**
 279  * watchdog_unregister_device() - unregister a watchdog device
 280  * @wdd: watchdog device to unregister
 281  *
 282  * Unregister a watchdog device that was previously successfully
 283  * registered with watchdog_register_device().
 284  */
 285
 286 void watchdog_unregister_device(struct watchdog_device *wdd)
 287 {
 288         mutex_lock(&wtd_deferred_reg_mutex);
 289         if (wtd_deferred_reg_done)
 290                 __watchdog_unregister_device(wdd);
 291         else
 292                 watchdog_deferred_registration_del(wdd);
 293         mutex_unlock(&wtd_deferred_reg_mutex);
 294 }
 295
 296 EXPORT_SYMBOL_GPL(watchdog_unregister_device);
 297
 298 static void devm_watchdog_unregister_device(struct device *dev, void *res)
 299 {
 300         watchdog_unregister_device(*(struct watchdog_device **)res);
 301 }
 302
 303 /**
 304  * devm_watchdog_register_device() - resource managed watchdog_register_device()
 305  * @dev: device that is registering this watchdog device
 306  * @wdd: watchdog device
 307  *
 308  * Managed watchdog_register_device(). For watchdog device registered by this
 309  * function,  watchdog_unregister_device() is automatically called on driver
 310  * detach. See watchdog_register_device() for more information.
 311  */
 312 int devm_watchdog_register_device(struct device *dev,
 313                                 struct watchdog_device *wdd)
 314 {
 315         struct watchdog_device **rcwdd;
 316         int ret;
 317
 318         rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd),
 319                              GFP_KERNEL);
 320         if (!rcwdd)
 321                 return -ENOMEM;
 322
 323         ret = watchdog_register_device(wdd);
 324         if (!ret) {
 325                 *rcwdd = wdd;
 326                 devres_add(dev, rcwdd);
 327         } else {
 328                 devres_free(rcwdd);
 329         }
 330
 331         return ret;
 332 }
 333 EXPORT_SYMBOL_GPL(devm_watchdog_register_device);
 334
 335 static int __init watchdog_deferred_registration(void)
 336 {
 337         mutex_lock(&wtd_deferred_reg_mutex);
 338         wtd_deferred_reg_done = true;
 339         while (!list_empty(&wtd_deferred_reg_list)) {
 340                 struct watchdog_device *wdd;
 341
 342                 wdd = list_first_entry(&wtd_deferred_reg_list,
 343                                        struct watchdog_device, deferred);
 344                 list_del(&wdd->deferred);
 345                 __watchdog_register_device(wdd);
 346         }
 347         mutex_unlock(&wtd_deferred_reg_mutex);
 348         return 0;
 349 }
 350
 351 static int __init watchdog_init(void)
 352 {
 353         int err;
 354
 355         err = watchdog_dev_init();
 356         if (err < 0)
 357                 return err;
 358
 359         watchdog_deferred_registration();
 360         return 0;
 361 }
 362
 363 static void __exit watchdog_exit(void)
 364 {
 365         watchdog_dev_exit();
 366         ida_destroy(&watchdog_ida);
 367 }
 368
 369 subsys_initcall_sync(watchdog_init);
 370 module_exit(watchdog_exit);
 371
 372 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
 373 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
 374 MODULE_DESCRIPTION("WatchDog Timer Driver Core");
 375 MODULE_LICENSE("GPL");