// SPDX-License-Identifier: GPL-2.0
/*
 * kernel/power/wakelock.c
 *
 * User space wakeup sources support.
 *
 * Copyright (C) 2012 Rafael J. Wysocki <rjw@sisk.pl>
 *
 * This code is based on the analogous interface allowing user space to
 * manipulate wakelocks on Android.
 */

#include <linux/capability.h>
#include <linux/ctype.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/hrtimer.h>
#include <linux/list.h>
#include <linux/rbtree.h>
#include <linux/slab.h>
#include <linux/workqueue.h>

#include "power.h"

static DEFINE_MUTEX(wakelocks_lock);

struct wakelock {
        char                    *name;
        struct rb_node          node;
        struct wakeup_source    *ws;
#ifdef CONFIG_PM_WAKELOCKS_GC
        struct list_head        lru;
#endif
};

static struct rb_root wakelocks_tree = RB_ROOT;

ssize_t pm_show_wakelocks(char *buf, bool show_active)
{
        struct rb_node *node;
        struct wakelock *wl;
        int len = 0;

        mutex_lock(&wakelocks_lock);

        for (node = rb_first(&wakelocks_tree); node; node = rb_next(node)) {
                wl = rb_entry(node, struct wakelock, node);
                if (wl->ws->active == show_active)
                        len += sysfs_emit_at(buf, len, "%s ", wl->name);
        }

        if (len > 0)
                --len;

        len += sysfs_emit_at(buf, len, "\n");

        mutex_unlock(&wakelocks_lock);
        return len;
}

#if CONFIG_PM_WAKELOCKS_LIMIT > 0
static unsigned int number_of_wakelocks;

static inline bool wakelocks_limit_exceeded(void)
{
        return number_of_wakelocks > CONFIG_PM_WAKELOCKS_LIMIT;
}

static inline void increment_wakelocks_number(void)
{
        number_of_wakelocks++;
}

static inline void decrement_wakelocks_number(void)
{
        number_of_wakelocks--;
}
#else /* CONFIG_PM_WAKELOCKS_LIMIT = 0 */
static inline bool wakelocks_limit_exceeded(void) { return false; }
static inline void increment_wakelocks_number(void) {}
static inline void decrement_wakelocks_number(void) {}
#endif /* CONFIG_PM_WAKELOCKS_LIMIT */

#ifdef CONFIG_PM_WAKELOCKS_GC
#define WL_GC_COUNT_MAX 100
#define WL_GC_TIME_SEC  300

static void __wakelocks_gc(struct work_struct *work);
static LIST_HEAD(wakelocks_lru_list);
static DECLARE_WORK(wakelock_work, __wakelocks_gc);
static unsigned int wakelocks_gc_count;

static inline void wakelocks_lru_add(struct wakelock *wl)
{
        list_add(&wl->lru, &wakelocks_lru_list);
}

static inline void wakelocks_lru_most_recent(struct wakelock *wl)
{
        list_move(&wl->lru, &wakelocks_lru_list);
}

static void __wakelocks_gc(struct work_struct *work)
{
        struct wakelock *wl, *aux;
        ktime_t now;

        mutex_lock(&wakelocks_lock);

        now = ktime_get();
        list_for_each_entry_safe_reverse(wl, aux, &wakelocks_lru_list, lru) {
                u64 idle_time_ns;
                bool active;

                spin_lock_irq(&wl->ws->lock);
                idle_time_ns = ktime_to_ns(ktime_sub(now, wl->ws->last_time));
                active = wl->ws->active;
                spin_unlock_irq(&wl->ws->lock);

                if (idle_time_ns < ((u64)WL_GC_TIME_SEC * NSEC_PER_SEC))
                        break;

                if (!active) {
                        wakeup_source_unregister(wl->ws);
                        rb_erase(&wl->node, &wakelocks_tree);
                        list_del(&wl->lru);
                        kfree(wl->name);
                        kfree(wl);
                        decrement_wakelocks_number();
                }
        }
        wakelocks_gc_count = 0;

        mutex_unlock(&wakelocks_lock);
}

static void wakelocks_gc(void)
{
        if (++wakelocks_gc_count <= WL_GC_COUNT_MAX)
                return;

        schedule_work(&wakelock_work);
}
#else /* !CONFIG_PM_WAKELOCKS_GC */
static inline void wakelocks_lru_add(struct wakelock *wl) {}
static inline void wakelocks_lru_most_recent(struct wakelock *wl) {}
static inline void wakelocks_gc(void) {}
#endif /* !CONFIG_PM_WAKELOCKS_GC */

static struct wakelock *wakelock_lookup_add(const char *name, size_t len,
                                            bool add_if_not_found)
{
        struct rb_node **node = &wakelocks_tree.rb_node;
        struct rb_node *parent = *node;
        struct wakelock *wl;

        while (*node) {
                int diff;

                parent = *node;
                wl = rb_entry(*node, struct wakelock, node);
                diff = strncmp(name, wl->name, len);
                if (diff == 0) {
                        if (wl->name[len])
                                diff = -1;
                        else
                                return wl;
                }
                if (diff < 0)
                        node = &(*node)->rb_left;
                else
                        node = &(*node)->rb_right;
        }
        if (!add_if_not_found)
                return ERR_PTR(-EINVAL);

        if (wakelocks_limit_exceeded())
                return ERR_PTR(-ENOSPC);

        /* Not found, we have to add a new one. */
        wl = kzalloc_obj(*wl);
        if (!wl)
                return ERR_PTR(-ENOMEM);

        wl->name = kstrndup(name, len, GFP_KERNEL);
        if (!wl->name) {
                kfree(wl);
                return ERR_PTR(-ENOMEM);
        }

        wl->ws = wakeup_source_register(NULL, wl->name);
        if (!wl->ws) {
                kfree(wl->name);
                kfree(wl);
                return ERR_PTR(-ENOMEM);
        }
        wl->ws->last_time = ktime_get();

        rb_link_node(&wl->node, parent, node);
        rb_insert_color(&wl->node, &wakelocks_tree);
        wakelocks_lru_add(wl);
        increment_wakelocks_number();
        return wl;
}

int pm_wake_lock(const char *buf)
{
        const char *str = buf;
        struct wakelock *wl;
        u64 timeout_ns = 0;
        size_t len;
        int ret = 0;

        if (!capable(CAP_BLOCK_SUSPEND))
                return -EPERM;

        while (*str && !isspace(*str))
                str++;

        len = str - buf;
        if (!len)
                return -EINVAL;

        if (*str && *str != '\n') {
                /* Find out if there's a valid timeout string appended. */
                ret = kstrtou64(skip_spaces(str), 10, &timeout_ns);
                if (ret)
                        return -EINVAL;
        }

        mutex_lock(&wakelocks_lock);

        wl = wakelock_lookup_add(buf, len, true);
        if (IS_ERR(wl)) {
                ret = PTR_ERR(wl);
                goto out;
        }
        if (timeout_ns) {
                u64 timeout_ms = timeout_ns + NSEC_PER_MSEC - 1;

                do_div(timeout_ms, NSEC_PER_MSEC);
                __pm_wakeup_event(wl->ws, timeout_ms);
        } else {
                __pm_stay_awake(wl->ws);
        }

        wakelocks_lru_most_recent(wl);

 out:
        mutex_unlock(&wakelocks_lock);
        return ret;
}

int pm_wake_unlock(const char *buf)
{
        struct wakelock *wl;
        size_t len;
        int ret = 0;

        if (!capable(CAP_BLOCK_SUSPEND))
                return -EPERM;

        len = strlen(buf);
        if (!len)
                return -EINVAL;

        if (buf[len-1] == '\n')
                len--;

        if (!len)
                return -EINVAL;

        mutex_lock(&wakelocks_lock);

        wl = wakelock_lookup_add(buf, len, false);
        if (IS_ERR(wl)) {
                ret = PTR_ERR(wl);
                goto out;
        }
        __pm_relax(wl->ws);

        wakelocks_lru_most_recent(wl);
        wakelocks_gc();

 out:
        mutex_unlock(&wakelocks_lock);
        return ret;
}