linux/drivers/watchdog/watchdog_core.c
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   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
  40static DEFINE_IDA(watchdog_ida);
  41
  42static int stop_on_reboot = -1;
  43module_param(stop_on_reboot, int, 0444);
  44MODULE_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
  59static DEFINE_MUTEX(wtd_deferred_reg_mutex);
  60static LIST_HEAD(wtd_deferred_reg_list);
  61static bool wtd_deferred_reg_done;
  62
  63static void watchdog_deferred_registration_add(struct watchdog_device *wdd)
  64{
  65        list_add_tail(&wdd->deferred,
  66                      &wtd_deferred_reg_list);
  67}
  68
  69static 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
  84static 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 */
 114int 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}
 152EXPORT_SYMBOL_GPL(watchdog_init_timeout);
 153
 154static 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) || watchdog_hw_running(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
 173static 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 */
 202void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority)
 203{
 204        wdd->restart_nb.priority = priority;
 205}
 206EXPORT_SYMBOL_GPL(watchdog_set_restart_priority);
 207
 208static 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                if (!wdd->ops->stop)
 271                        pr_warn("watchdog%d: stop_on_reboot not supported\n", wdd->id);
 272                else {
 273                        wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;
 274
 275                        ret = register_reboot_notifier(&wdd->reboot_nb);
 276                        if (ret) {
 277                                pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
 278                                        wdd->id, ret);
 279                                watchdog_dev_unregister(wdd);
 280                                ida_simple_remove(&watchdog_ida, id);
 281                                return ret;
 282                        }
 283                }
 284        }
 285
 286        if (wdd->ops->restart) {
 287                wdd->restart_nb.notifier_call = watchdog_restart_notifier;
 288
 289                ret = register_restart_handler(&wdd->restart_nb);
 290                if (ret)
 291                        pr_warn("watchdog%d: Cannot register restart handler (%d)\n",
 292                                wdd->id, ret);
 293        }
 294
 295        return 0;
 296}
 297
 298/**
 299 * watchdog_register_device() - register a watchdog device
 300 * @wdd: watchdog device
 301 *
 302 * Register a watchdog device with the kernel so that the
 303 * watchdog timer can be accessed from userspace.
 304 *
 305 * A zero is returned on success and a negative errno code for
 306 * failure.
 307 */
 308
 309int watchdog_register_device(struct watchdog_device *wdd)
 310{
 311        const char *dev_str;
 312        int ret = 0;
 313
 314        mutex_lock(&wtd_deferred_reg_mutex);
 315        if (wtd_deferred_reg_done)
 316                ret = __watchdog_register_device(wdd);
 317        else
 318                watchdog_deferred_registration_add(wdd);
 319        mutex_unlock(&wtd_deferred_reg_mutex);
 320
 321        if (ret) {
 322                dev_str = wdd->parent ? dev_name(wdd->parent) :
 323                          (const char *)wdd->info->identity;
 324                pr_err("%s: failed to register watchdog device (err = %d)\n",
 325                        dev_str, ret);
 326        }
 327
 328        return ret;
 329}
 330EXPORT_SYMBOL_GPL(watchdog_register_device);
 331
 332static void __watchdog_unregister_device(struct watchdog_device *wdd)
 333{
 334        if (wdd == NULL)
 335                return;
 336
 337        if (wdd->ops->restart)
 338                unregister_restart_handler(&wdd->restart_nb);
 339
 340        if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))
 341                unregister_reboot_notifier(&wdd->reboot_nb);
 342
 343        watchdog_dev_unregister(wdd);
 344        ida_simple_remove(&watchdog_ida, wdd->id);
 345}
 346
 347/**
 348 * watchdog_unregister_device() - unregister a watchdog device
 349 * @wdd: watchdog device to unregister
 350 *
 351 * Unregister a watchdog device that was previously successfully
 352 * registered with watchdog_register_device().
 353 */
 354
 355void watchdog_unregister_device(struct watchdog_device *wdd)
 356{
 357        mutex_lock(&wtd_deferred_reg_mutex);
 358        if (wtd_deferred_reg_done)
 359                __watchdog_unregister_device(wdd);
 360        else
 361                watchdog_deferred_registration_del(wdd);
 362        mutex_unlock(&wtd_deferred_reg_mutex);
 363}
 364
 365EXPORT_SYMBOL_GPL(watchdog_unregister_device);
 366
 367static void devm_watchdog_unregister_device(struct device *dev, void *res)
 368{
 369        watchdog_unregister_device(*(struct watchdog_device **)res);
 370}
 371
 372/**
 373 * devm_watchdog_register_device() - resource managed watchdog_register_device()
 374 * @dev: device that is registering this watchdog device
 375 * @wdd: watchdog device
 376 *
 377 * Managed watchdog_register_device(). For watchdog device registered by this
 378 * function,  watchdog_unregister_device() is automatically called on driver
 379 * detach. See watchdog_register_device() for more information.
 380 */
 381int devm_watchdog_register_device(struct device *dev,
 382                                struct watchdog_device *wdd)
 383{
 384        struct watchdog_device **rcwdd;
 385        int ret;
 386
 387        rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd),
 388                             GFP_KERNEL);
 389        if (!rcwdd)
 390                return -ENOMEM;
 391
 392        ret = watchdog_register_device(wdd);
 393        if (!ret) {
 394                *rcwdd = wdd;
 395                devres_add(dev, rcwdd);
 396        } else {
 397                devres_free(rcwdd);
 398        }
 399
 400        return ret;
 401}
 402EXPORT_SYMBOL_GPL(devm_watchdog_register_device);
 403
 404static int __init watchdog_deferred_registration(void)
 405{
 406        mutex_lock(&wtd_deferred_reg_mutex);
 407        wtd_deferred_reg_done = true;
 408        while (!list_empty(&wtd_deferred_reg_list)) {
 409                struct watchdog_device *wdd;
 410
 411                wdd = list_first_entry(&wtd_deferred_reg_list,
 412                                       struct watchdog_device, deferred);
 413                list_del(&wdd->deferred);
 414                __watchdog_register_device(wdd);
 415        }
 416        mutex_unlock(&wtd_deferred_reg_mutex);
 417        return 0;
 418}
 419
 420static int __init watchdog_init(void)
 421{
 422        int err;
 423
 424        err = watchdog_dev_init();
 425        if (err < 0)
 426                return err;
 427
 428        watchdog_deferred_registration();
 429        return 0;
 430}
 431
 432static void __exit watchdog_exit(void)
 433{
 434        watchdog_dev_exit();
 435        ida_destroy(&watchdog_ida);
 436}
 437
 438subsys_initcall_sync(watchdog_init);
 439module_exit(watchdog_exit);
 440
 441MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
 442MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
 443MODULE_DESCRIPTION("WatchDog Timer Driver Core");
 444MODULE_LICENSE("GPL");
 445