autosleep.c

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/*
 * kernel/power/autosleep.c
 *
 * Opportunistic sleep support.
 *
 * Copyright (C) 2012 Rafael J. Wysocki <[email protected]>
 */

#include <linux/device.h>
#include <linux/mutex.h>
#include <linux/pm_wakeup.h>

#include "power.h"

static suspend_state_t autosleep_state;
static struct workqueue_struct *autosleep_wq;
/*
 * Note: it is only safe to mutex_lock(&autosleep_lock) if a wakeup_source
 * is active, otherwise a deadlock with try_to_suspend() is possible.
 * Alternatively mutex_lock_interruptible() can be used.  This will then fail
 * if an auto_sleep cycle tries to freeze processes.
 */
static DEFINE_MUTEX(autosleep_lock);
static struct wakeup_source *autosleep_ws;

static void try_to_suspend(struct work_struct *work)
{
    unsigned int initial_count, final_count;

    if (!pm_get_wakeup_count(&initial_count, true))
        goto out;

    mutex_lock(&autosleep_lock);

    if (!pm_save_wakeup_count(initial_count)) {
        mutex_unlock(&autosleep_lock);
        goto out;
    }

    if (autosleep_state == PM_SUSPEND_ON) {
        mutex_unlock(&autosleep_lock);
        return;
    }
    if (autosleep_state >= PM_SUSPEND_MAX)
        hibernate();
    else
        pm_suspend(autosleep_state);

    mutex_unlock(&autosleep_lock);

    if (!pm_get_wakeup_count(&final_count, false))
        goto out;

    /*
     * If the wakeup occured for an unknown reason, wait to prevent the
     * system from trying to suspend and waking up in a tight loop.
     */
    if (final_count == initial_count)
        schedule_timeout_uninterruptible(HZ / 2);

 out:
    queue_up_suspend_work();
}

static DECLARE_WORK(suspend_work, try_to_suspend);

void queue_up_suspend_work(void)
{
    if (!work_pending(&suspend_work) && autosleep_state > PM_SUSPEND_ON)
        queue_work(autosleep_wq, &suspend_work);
}

suspend_state_t pm_autosleep_state(void)
{
    return autosleep_state;
}

int pm_autosleep_lock(void)
{
    return mutex_lock_interruptible(&autosleep_lock);
}

void pm_autosleep_unlock(void)
{
    mutex_unlock(&autosleep_lock);
}

int pm_autosleep_set_state(suspend_state_t state)
{

#ifndef CONFIG_HIBERNATION
    if (state >= PM_SUSPEND_MAX)
        return -EINVAL;
#endif

    __pm_stay_awake(autosleep_ws);

    mutex_lock(&autosleep_lock);

    autosleep_state = state;

    __pm_relax(autosleep_ws);

    if (state > PM_SUSPEND_ON) {
        pm_wakep_autosleep_enabled(true);
        queue_up_suspend_work();
    } else {
        pm_wakep_autosleep_enabled(false);
    }

    mutex_unlock(&autosleep_lock);
    return 0;
}

int __init pm_autosleep_init(void)
{
    autosleep_ws = wakeup_source_register("autosleep");
    if (!autosleep_ws)
        return -ENOMEM;

    autosleep_wq = alloc_ordered_workqueue("autosleep", 0);
    if (autosleep_wq)
        return 0;

    wakeup_source_unregister(autosleep_ws);
    return -ENOMEM;
}