// SPDX-License-Identifier: GPL-2.0+
/*
* watchdog_core.c
*
* (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
* All Rights Reserved.
*
* (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
*
* This source code is part of the generic code that can be used
* by all the watchdog timer drivers.
*
* Based on source code of the following authors:
* Matt Domsch <Matt_Domsch@dell.com>,
* Rob Radez <rob@osinvestor.com>,
* Rusty Lynch <rusty@linux.co.intel.com>
* Satyam Sharma <satyam@infradead.org>
* Randy Dunlap <randy.dunlap@oracle.com>
*
* Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
* admit liability nor provide warranty for any of this software.
* This material is provided "AS-IS" and at no charge.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h> /* For EXPORT_SYMBOL/module stuff/... */
#include <linux/types.h> /* For standard types */
#include <linux/errno.h> /* For the -ENODEV/... values */
#include <linux/kernel.h> /* For printk/panic/... */
#include <linux/reboot.h> /* For restart handler */
#include <linux/watchdog.h> /* For watchdog specific items */
#include <linux/init.h> /* For __init/__exit/... */
#include <linux/idr.h> /* For ida_* macros */
#include <linux/err.h> /* For IS_ERR macros */
#include <linux/of.h> /* For of_get_timeout_sec */
#include "watchdog_core.h" /* For watchdog_dev_register/... */
static DEFINE_IDA(watchdog_ida);
/*
* Deferred Registration infrastructure.
*
* Sometimes watchdog drivers needs to be loaded as soon as possible,
* for example when it's impossible to disable it. To do so,
* raising the initcall level of the watchdog driver is a solution.
* But in such case, the miscdev is maybe not ready (subsys_initcall), and
* watchdog_core need miscdev to register the watchdog as a char device.
*
* The deferred registration infrastructure offer a way for the watchdog
* subsystem to register a watchdog properly, even before miscdev is ready.
*/
static DEFINE_MUTEX(wtd_deferred_reg_mutex);
static LIST_HEAD(wtd_deferred_reg_list);
static bool wtd_deferred_reg_done;
static void watchdog_deferred_registration_add(struct watchdog_device *wdd)
{
list_add_tail(&wdd->deferred,
&wtd_deferred_reg_list);
}
static void watchdog_deferred_registration_del(struct watchdog_device *wdd)
{
struct list_head *p, *n;
struct watchdog_device *wdd_tmp;
list_for_each_safe(p, n, &wtd_deferred_reg_list) {
wdd_tmp = list_entry(p, struct watchdog_device,
deferred);
if (wdd_tmp == wdd) {
list_del(&wdd_tmp->deferred);
break;
}
}
}
static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
{
/*
* Check that we have valid min and max timeout values, if
* not reset them both to 0 (=not used or unknown)
*/
if (!wdd->max_hw_heartbeat_ms && wdd->min_timeout > wdd->max_timeout) {
pr_info("Invalid min and max timeout values, resetting to 0!\n");
wdd->min_timeout = 0;
wdd->max_timeout = 0;
}
}
/**
* watchdog_init_timeout() - initialize the timeout field
* @wdd: watchdog device
* @timeout_parm: timeout module parameter
* @dev: Device that stores the timeout-sec property
*
* Initialize the timeout field of the watchdog_device struct with either the
* timeout module parameter (if it is valid value) or the timeout-sec property
* (only if it is a valid value and the timeout_parm is out of bounds).
* If none of them are valid then we keep the old value (which should normally
* be the default timeout value). Note that for the module parameter, '0' means
* 'use default' while it is an invalid value for the timeout-sec property.
* It should simply be dropped if you want to use the default value then.
*
* A zero is returned on success or -EINVAL if all provided values are out of
* bounds.
*/
int watchdog_init_timeout(struct watchdog_device *wdd,
unsigned int timeout_parm, struct device *dev)
{
const char *dev_str = wdd->parent ? dev_name(wdd->parent) :
(const char *)wdd->info->identity;
unsigned int t = 0;
int ret = 0;
watchdog_check_min_max_timeout(wdd);
/* check the driver supplied value (likely a module parameter) first */
if (timeout_parm) {
if (!watchdog_timeout_invalid(wdd, timeout_parm)) {
wdd->timeout = timeout_parm;
return 0;
}
pr_err("%s: driver supplied timeout (%u) out of range\n",
dev_str, timeout_parm);
ret = -EINVAL;
}
/* try to get the timeout_sec property */
if (dev && dev->of_node &&
of_property_read_u32(dev->of_node, "timeout-sec", &t) == 0) {
if (t && !watchdog_timeout_invalid(wdd, t)) {
wdd->timeout = t;
return 0;
}
pr_err("%s: DT supplied timeout (%u) out of range\n", dev_str, t);
ret = -EINVAL;
}
if (ret < 0 && wdd->timeout)
pr_warn("%s: falling back to default timeout (%u)\n", dev_str,
wdd->timeout);
return ret;
}
EXPORT_SYMBOL_GPL(watchdog_init_timeout);
static int watchdog_restart_notifier(struct notifier_block *nb,
unsigned long action, void *data)
{
struct watchdog_device *wdd = container_of(nb, struct watchdog_device,
restart_nb);
int ret;
ret = wdd->ops->restart(wdd, action, data);
if (ret)
return NOTIFY_BAD;
return NOTIFY_DONE;
}
/**
* watchdog_set_restart_priority - Change priority of restart handler
* @wdd: watchdog device
* @priority: priority of the restart handler, should follow these guidelines:
* 0: use watchdog's restart function as last resort, has limited restart
* capabilies
* 128: default restart handler, use if no other handler is expected to be
* available and/or if restart is sufficient to restart the entire system
* 255: preempt all other handlers
*
* If a wdd->ops->restart function is provided when watchdog_register_device is
* called, it will be registered as a restart handler with the priority given
* here.
*/
void watchdog_set_restart_priority(struct watchdog_device *wdd, int priority)
{
wdd->restart_nb.priority = priority;
}
EXPORT_SYMBOL_GPL(watchdog_set_restart_priority);
static int __watchdog_register_device(struct watchdog_device *wdd)
{
int ret, id = -1;
if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
return -EINVAL;
/* Mandatory operations need to be supported */
if (!wdd->ops->start || (!wdd->ops->stop && !wdd->max_hw_heartbeat_ms))
return -EINVAL;
watchdog_check_min_max_timeout(wdd);
/*
* Note: now that all watchdog_device data has been verified, we
* will not check this anymore in other functions. If data gets
* corrupted in a later stage then we expect a kernel panic!
*/
/* Use alias for watchdog id if possible */
if (wdd->parent) {
ret = of_alias_get_id(wdd->parent->of_node, "watchdog");
if (ret >= 0)
id = ida_simple_get(&watchdog_ida, ret,
ret + 1, GFP_KERNEL);
}
if (id < 0)
id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
if (id < 0)
return id;
wdd->id = id;
ret = watchdog_dev_register(wdd);
if (ret) {
ida_simple_remove(&watchdog_ida, id);
if (!(id == 0 && ret == -EBUSY))
return ret;
/* Retry in case a legacy watchdog module exists */
id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
if (id < 0)
return id;
wdd->id = id;
ret = watchdog_dev_register(wdd);
if (ret) {
ida_simple_remove(&watchdog_ida, id);
return ret;
}
}
if (wdd->ops->restart) {
wdd->restart_nb.notifier_call = watchdog_restart_notifier;
ret = register_restart_handler(&wdd->restart_nb);
if (ret)
pr_warn("watchdog%d: Cannot register restart handler (%d)\n",
wdd->id, ret);
}
return 0;
}
/**
* watchdog_register_device() - register a watchdog device
* @wdd: watchdog device
*
* Register a watchdog device with the kernel so that the
* watchdog timer can be accessed from userspace.
*
* A zero is returned on success and a negative errno code for
* failure.
*/
int watchdog_register_device(struct watchdog_device *wdd)
{
const char *dev_str;
int ret = 0;
mutex_lock(&wtd_deferred_reg_mutex);
if (wtd_deferred_reg_done)
ret = __watchdog_register_device(wdd);
else
watchdog_deferred_registration_add(wdd);
mutex_unlock(&wtd_deferred_reg_mutex);
if (ret) {
dev_str = wdd->parent ? dev_name(wdd->parent) :
(const char *)wdd->info->identity;
pr_err("%s: failed to register watchdog device (err = %d)\n",
dev_str, ret);
}
return ret;
}
EXPORT_SYMBOL_GPL(watchdog_register_device);
static void __watchdog_unregister_device(struct watchdog_device *wdd)
{
if (wdd == NULL)
return;
if (wdd->ops->restart)
unregister_restart_handler(&wdd->restart_nb);
watchdog_dev_unregister(wdd);
ida_simple_remove(&watchdog_ida, wdd->id);
}
/**
* watchdog_unregister_device() - unregister a watchdog device
* @wdd: watchdog device to unregister
*
* Unregister a watchdog device that was previously successfully
* registered with watchdog_register_device().
*/
void watchdog_unregister_device(struct watchdog_device *wdd)
{
mutex_lock(&wtd_deferred_reg_mutex);
if (wtd_deferred_reg_done)
__watchdog_unregister_device(wdd);
else
watchdog_deferred_registration_del(wdd);
mutex_unlock(&wtd_deferred_reg_mutex);
}
EXPORT_SYMBOL_GPL(watchdog_unregister_device);
static void devm_watchdog_unregister_device(struct device *dev, void *res)
{
watchdog_unregister_device(*(struct watchdog_device **)res);
}
/**
* devm_watchdog_register_device() - resource managed watchdog_register_device()
* @dev: device that is registering this watchdog device
* @wdd: watchdog device
*
* Managed watchdog_register_device(). For watchdog device registered by this
* function, watchdog_unregister_device() is automatically called on driver
* detach. See watchdog_register_device() for more information.
*/
int devm_watchdog_register_device(struct device *dev,
struct watchdog_device *wdd)
{
struct watchdog_device **rcwdd;
int ret;
rcwdd = devres_alloc(devm_watchdog_unregister_device, sizeof(*rcwdd),
GFP_KERNEL);
if (!rcwdd)
return -ENOMEM;
ret = watchdog_register_device(wdd);
if (!ret) {
*rcwdd = wdd;
devres_add(dev, rcwdd);
} else {
devres_free(rcwdd);
}
return ret;
}
EXPORT_SYMBOL_GPL(devm_watchdog_register_device);
static int __init watchdog_deferred_registration(void)
{
mutex_lock(&wtd_deferred_reg_mutex);
wtd_deferred_reg_done = true;
while (!list_empty(&wtd_deferred_reg_list)) {
struct watchdog_device *wdd;
wdd = list_first_entry(&wtd_deferred_reg_list,
struct watchdog_device, deferred);
list_del(&wdd->deferred);
__watchdog_register_device(wdd);
}
mutex_unlock(&wtd_deferred_reg_mutex);
return 0;
}
static int __init watchdog_init(void)
{
int err;
err = watchdog_dev_init();
if (err < 0)
return err;
watchdog_deferred_registration();
return 0;
}
static void __exit watchdog_exit(void)
{
watchdog_dev_exit();
ida_destroy(&watchdog_ida);
}
subsys_initcall_sync(watchdog_init);
module_exit(watchdog_exit);
MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
MODULE_DESCRIPTION("WatchDog Timer Driver Core");
MODULE_LICENSE("GPL");
