drivers/watchdog/watchdog_core.c

   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 static int stop_on_reboot = -1;
  43 module_param(stop_on_reboot, int, 0444);
  44 MODULE_PARM_DESC(stop_on_reboot, "Stop watchdogs on reboot (0=keep watching, 1=stop)");
  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 void watchdog_deferred_registration_add(struct watchdog_device *wdd)
  64 {
  65         list_add_tail(&wdd->deferred,
  66                       &wtd_deferred_reg_list);
  67 }
  68
  69 static void watchdog_deferred_registration_del(struct watchdog_device *wdd)
  70 {
  71         struct list_head *p, *n;
  72         struct watchdog_device *wdd_tmp;
  73
  74         list_for_each_safe(p, n, &wtd_deferred_reg_list) {
  75                 wdd_tmp = list_entry(p, struct watchdog_device,
  76                                      deferred);
  77                 if (wdd_tmp == wdd) {
  78                         list_del(&wdd_tmp->deferred);
  79                         break;
  80                 }
  81         }
  82 }
  83
  84 static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
  85 {
  86         /*
  87          * Check that we have valid min and max timeout values, if
  88          * not reset them both to 0 (=not used or unknown)
  89          */
  90         if (!wdd->max_hw_heartbeat_ms && wdd->min_timeout > wdd->max_timeout) {
  91                 pr_info("Invalid min and max timeout values, resetting to 0!\n");
  92                 wdd->min_timeout = 0;
  93                 wdd->max_timeout = 0;
  94         }
  95 }
  96
  97 /**
  98  * watchdog_init_timeout() - initialize the timeout field
  99  * @wdd: watchdog device
 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). Note that for the module parameter, '0' means
 108  * 'use default' while it is an invalid value for the timeout-sec property.
 109  * It should simply be dropped if you want to use the default value then.
 110  *
 111  * A zero is returned on success or -EINVAL if all provided values are out of
 112  * bounds.
 113  */
 114 int watchdog_init_timeout(struct watchdog_device *wdd,
 115                                 unsigned int timeout_parm, struct device *dev)
 116 {
 117         const char *dev_str = wdd->parent ? dev_name(wdd->parent) :
 118                               (const char *)wdd->info->identity;
 119         unsigned int t = 0;
 120         int ret = 0;
 121
 122         watchdog_check_min_max_timeout(wdd);
 123
 124         /* check the driver supplied value (likely a module parameter) first */
 125         if (timeout_parm) {
 126                 if (!watchdog_timeout_invalid(wdd, timeout_parm)) {
 127                         wdd->timeout = timeout_parm;
 128                         return 0;
 129                 }
 130                 pr_err("%s: driver supplied timeout (%u) out of range\n",
 131                         dev_str, timeout_parm);
 132                 ret = -EINVAL;
 133         }
 134
 135         /* try to get the timeout_sec property */
 136         if (dev && dev->of_node &&
 137             of_property_read_u32(dev->of_node, "timeout-sec", &t) == 0) {
 138                 if (t && !watchdog_timeout_invalid(wdd, t)) {
 139                         wdd->timeout = t;
 140                         return 0;
 141                 }
 142                 pr_err("%s: DT supplied timeout (%u) out of range\n", dev_str, t);
 143                 ret = -EINVAL;
 144         }
 145
 146         if (ret < 0 && wdd->timeout)
 147                 pr_warn("%s: falling back to default timeout (%u)\n", dev_str,
 148                         wdd->timeout);
 149
 150         return ret;
 151 }
 152 EXPORT_SYMBOL_GPL(watchdog_init_timeout);
 153
 154 static int watchdog_reboot_notifier(struct notifier_block *nb,
 155                                     unsigned long code, void *data)
 156 {
 157         struct watchdog_device *wdd;
 158
 159         wdd = container_of(nb, struct watchdog_device, reboot_nb);
 160         if (code == SYS_DOWN || code == SYS_HALT) {
 161                 if (watchdog_active(wdd)) {
 162                         int ret;
 163
 164                         ret = wdd->ops->stop(wdd);
 165                         if (ret)
 166                                 return NOTIFY_BAD;
 167                 }
 168         }
 169
 170         return NOTIFY_DONE;
 171 }
 172
 173 static int watchdog_restart_notifier(struct notifier_block *nb,
 174                                      unsigned long action, void *data)
 175 {
 176         struct watchdog_device *wdd = container_of(nb, struct watchdog_device,
 177                                                    restart_nb);
 178
 179         int ret;
 180
 181         ret = wdd->ops->restart(wdd, action, data);
 182         if (ret)
 183                 return NOTIFY_BAD;
 184
 185         return NOTIFY_DONE;
 186 }
 187
 188 /**
 189  * watchdog_set_restart_priority - Change priority of restart handler
 190  * @wdd: watchdog device
 191  * @priority: priority of the restart handler, should follow these guidelines:
 192  *   0:   use watchdog's restart function as last resort, has limited restart
 193  *        capabilies
 194  *   128: default restart handler, use if no other handler is expected to be
 195  *        available and/or if restart is sufficient to restart the entire system
 196  *   255: preempt all other handlers
 197  *
 198  * If a wdd->ops->restart function is provided when watchdog_register_device is
 199  * called, it will be registered as a restart handler with the priority given
 200  * here.
 201  */
 202 void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority)
 203 {
 204         wdd->restart_nb.priority = priority;
 205 }
 206 EXPORT_SYMBOL_GPL(watchdog_set_restart_priority);
 207
 208 static int __watchdog_register_device(struct watchdog_device *wdd)
 209 {
 210         int ret, id = -1;
 211
 212         if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
 213                 return -EINVAL;
 214
 215         /* Mandatory operations need to be supported */
 216         if (!wdd->ops->start || (!wdd->ops->stop && !wdd->max_hw_heartbeat_ms))
 217                 return -EINVAL;
 218
 219         watchdog_check_min_max_timeout(wdd);
 220
 221         /*
 222          * Note: now that all watchdog_device data has been verified, we
 223          * will not check this anymore in other functions. If data gets
 224          * corrupted in a later stage then we expect a kernel panic!
 225          */
 226
 227         /* Use alias for watchdog id if possible */
 228         if (wdd->parent) {
 229                 ret = of_alias_get_id(wdd->parent->of_node, "watchdog");
 230                 if (ret >= 0)
 231                         id = ida_simple_get(&watchdog_ida, ret,
 232                                             ret + 1, GFP_KERNEL);
 233         }
 234
 235         if (id < 0)
 236                 id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
 237
 238         if (id < 0)
 239                 return id;
 240         wdd->id = id;
 241
 242         ret = watchdog_dev_register(wdd);
 243         if (ret) {
 244                 ida_simple_remove(&watchdog_ida, id);
 245                 if (!(id == 0 && ret == -EBUSY))
 246                         return ret;
 247
 248                 /* Retry in case a legacy watchdog module exists */
 249                 id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
 250                 if (id < 0)
 251                         return id;
 252                 wdd->id = id;
 253
 254                 ret = watchdog_dev_register(wdd);
 255                 if (ret) {
 256                         ida_simple_remove(&watchdog_ida, id);
 257                         return ret;
 258                 }
 259         }
 260
 261         /* Module parameter to force watchdog policy on reboot. */
 262         if (stop_on_reboot != -1) {
 263                 if (stop_on_reboot)
 264                         set_bit(WDOG_STOP_ON_REBOOT, &wdd->status);
 265                 else
 266                         clear_bit(WDOG_STOP_ON_REBOOT, &wdd->status);
 267         }
 268
 269         if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
 270                 wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
 271
 272                 ret = register_reboot_notifier(&wdd->reboot_nb);
 273                 if (ret) {
 274                         pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
 275                                wdd->id, ret);
 276                         watchdog_dev_unregister(wdd);
 277                         ida_simple_remove(&watchdog_ida, id);
 278                         return ret;
 279                 }
 280         }
 281
 282         if (wdd->ops->restart) {
 283                 wdd->restart_nb.notifier_call = watchdog_restart_notifier;
 284
 285                 ret = register_restart_handler(&wdd->restart_nb);
 286                 if (ret)
 287                         pr_warn("watchdog%d: Cannot register restart handler (%d)\n",
 288                                 wdd->id, ret);
 289         }
 290
 291         return 0;
 292 }
 293
 294 /**
 295  * watchdog_register_device() - register a watchdog device
 296  * @wdd: watchdog device
 297  *
 298  * Register a watchdog device with the kernel so that the
 299  * watchdog timer can be accessed from userspace.
 300  *
 301  * A zero is returned on success and a negative errno code for
 302  * failure.
 303  */
 304
 305 int watchdog_register_device(struct watchdog_device *wdd)
 306 {
 307         const char *dev_str;
 308         int ret = 0;
 309
 310         mutex_lock(&wtd_deferred_reg_mutex);
 311         if (wtd_deferred_reg_done)
 312                 ret = __watchdog_register_device(wdd);
 313         else
 314                 watchdog_deferred_registration_add(wdd);
 315         mutex_unlock(&wtd_deferred_reg_mutex);
 316
 317         if (ret) {
 318                 dev_str = wdd->parent ? dev_name(wdd->parent) :
 319                           (const char *)wdd->info->identity;
 320                 pr_err("%s: failed to register watchdog device (err = %d)\n",
 321                         dev_str, ret);
 322         }
 323
 324         return ret;
 325 }
 326 EXPORT_SYMBOL_GPL(watchdog_register_device);
 327
 328 static void __watchdog_unregister_device(struct watchdog_device *wdd)
 329 {
 330         if (wdd == NULL)
 331                 return;
 332
 333         if (wdd->ops->restart)
 334                 unregister_restart_handler(&wdd->restart_nb);
 335
 336         if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))
 337                 unregister_reboot_notifier(&wdd->reboot_nb);
 338
 339         watchdog_dev_unregister(wdd);
 340         ida_simple_remove(&watchdog_ida, wdd->id);
 341 }
 342
 343 /**
 344  * watchdog_unregister_device() - unregister a watchdog device
 345  * @wdd: watchdog device to unregister
 346  *
 347  * Unregister a watchdog device that was previously successfully
 348  * registered with watchdog_register_device().
 349  */
 350
 351 void watchdog_unregister_device(struct watchdog_device *wdd)
 352 {
 353         mutex_lock(&wtd_deferred_reg_mutex);
 354         if (wtd_deferred_reg_done)
 355                 __watchdog_unregister_device(wdd);
 356         else
 357                 watchdog_deferred_registration_del(wdd);
 358         mutex_unlock(&wtd_deferred_reg_mutex);
 359 }
 360
 361 EXPORT_SYMBOL_GPL(watchdog_unregister_device);
 362
 363 static void devm_watchdog_unregister_device(struct device *dev, void *res)
 364 {
 365         watchdog_unregister_device(*(struct watchdog_device **)res);
 366 }
 367
 368 /**
 369  * devm_watchdog_register_device() - resource managed watchdog_register_device()
 370  * @dev: device that is registering this watchdog device
 371  * @wdd: watchdog device
 372  *
 373  * Managed watchdog_register_device(). For watchdog device registered by this
 374  * function,  watchdog_unregister_device() is automatically called on driver
 375  * detach. See watchdog_register_device() for more information.
 376  */
 377 int devm_watchdog_register_device(struct device *dev,
 378                                 struct watchdog_device *wdd)
 379 {
 380         struct watchdog_device **rcwdd;
 381         int ret;
 382
 383         rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd),
 384                              GFP_KERNEL);
 385         if (!rcwdd)
 386                 return -ENOMEM;
 387
 388         ret = watchdog_register_device(wdd);
 389         if (!ret) {
 390                 *rcwdd = wdd;
 391                 devres_add(dev, rcwdd);
 392         } else {
 393                 devres_free(rcwdd);
 394         }
 395
 396         return ret;
 397 }
 398 EXPORT_SYMBOL_GPL(devm_watchdog_register_device);
 399
 400 static int __init watchdog_deferred_registration(void)
 401 {
 402         mutex_lock(&wtd_deferred_reg_mutex);
 403         wtd_deferred_reg_done = true;
 404         while (!list_empty(&wtd_deferred_reg_list)) {
 405                 struct watchdog_device *wdd;
 406
 407                 wdd = list_first_entry(&wtd_deferred_reg_list,
 408                                        struct watchdog_device, deferred);
 409                 list_del(&wdd->deferred);
 410                 __watchdog_register_device(wdd);
 411         }
 412         mutex_unlock(&wtd_deferred_reg_mutex);
 413         return 0;
 414 }
 415
 416 static int __init watchdog_init(void)
 417 {
 418         int err;
 419
 420         err = watchdog_dev_init();
 421         if (err < 0)
 422                 return err;
 423
 424         watchdog_deferred_registration();
 425         return 0;
 426 }
 427
 428 static void __exit watchdog_exit(void)
 429 {
 430         watchdog_dev_exit();
 431         ida_destroy(&watchdog_ida);
 432 }
 433
 434 subsys_initcall_sync(watchdog_init);
 435 module_exit(watchdog_exit);
 436
 437 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
 438 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
 439 MODULE_DESCRIPTION("WatchDog Timer Driver Core");
 440 MODULE_LICENSE("GPL");