/*
 *      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>
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 *
 *      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 int watchdog_deferred_registration_add(struct watchdog_device *wdd)
{
        list_add_tail(&wdd->deferred,
                      &wtd_deferred_reg_list);
        return 0;
}

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->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
 * @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).
 *
 * A zero is returned on success and -EINVAL for failure.
 */
int watchdog_init_timeout(struct watchdog_device *wdd,
                                unsigned int timeout_parm, struct device *dev)
{
        unsigned int t = 0;
        int ret = 0;

        watchdog_check_min_max_timeout(wdd);

        /* try to get the timeout module parameter first */
        if (!watchdog_timeout_invalid(wdd, timeout_parm) && timeout_parm) {
                wdd->timeout = timeout_parm;
                return ret;
        }
        if (timeout_parm)
                ret = -EINVAL;

        /* try to get the timeout_sec property */
        if (dev == NULL || dev->of_node == NULL)
                return ret;
        of_property_read_u32(dev->of_node, "timeout-sec", &t);
        if (!watchdog_timeout_invalid(wdd, t) && t)
                wdd->timeout = t;
        else
                ret = -EINVAL;

        return ret;
}
EXPORT_SYMBOL_GPL(watchdog_init_timeout);

static int watchdog_reboot_notifier(struct notifier_block *nb,
                                    unsigned long code, void *data)
{
        struct watchdog_device *wdd = container_of(nb, struct watchdog_device,
                                                   reboot_nb);

        if (code == SYS_DOWN || code == SYS_HALT) {
                if (watchdog_active(wdd)) {
                        int ret;

                        ret = wdd->ops->stop(wdd);
                        if (ret)
                                return NOTIFY_BAD;
                }
        }

        return NOTIFY_DONE;
}

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 (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) {
                wdd->reboot_nb.notifier_call = watchdog_reboot_notifier;

                ret = register_reboot_notifier(&wdd->reboot_nb);
                if (ret) {
                        pr_err("watchdog%d: Cannot register reboot notifier (%d)\n",
                               wdd->id, ret);
                        watchdog_dev_unregister(wdd);
                        ida_simple_remove(&watchdog_ida, wdd->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)
{
        int ret;

        mutex_lock(&wtd_deferred_reg_mutex);
        if (wtd_deferred_reg_done)
                ret = __watchdog_register_device(wdd);
        else
                ret = watchdog_deferred_registration_add(wdd);
        mutex_unlock(&wtd_deferred_reg_mutex);
        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);

        if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status))
                unregister_reboot_notifier(&wdd->reboot_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 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");