1/*
  2 * kernel/power/autosleep.c
  3 *
  4 * Opportunistic sleep support.
  5 *
  6 * Copyright (C) 2012 Rafael J. Wysocki <rjw@sisk.pl>
  7 */
  8
  9#include <linux/device.h>
 10#include <linux/mutex.h>
 11#include <linux/pm_wakeup.h>
 12
 13#include "power.h"
 14
 15static suspend_state_t autosleep_state;
 16static struct workqueue_struct *autosleep_wq;
 17/*
 18 * Note: it is only safe to mutex_lock(&autosleep_lock) if a wakeup_source
 19 * is active, otherwise a deadlock with try_to_suspend() is possible.
 20 * Alternatively mutex_lock_interruptible() can be used.  This will then fail
 21 * if an auto_sleep cycle tries to freeze processes.
 22 */
 23static DEFINE_MUTEX(autosleep_lock);
 24static struct wakeup_source *autosleep_ws;
 25
 26static void try_to_suspend(struct work_struct *work)
 27{
 28	unsigned int initial_count, final_count;
 29
 30	if (!pm_get_wakeup_count(&initial_count, true))
 31		goto out;
 32
 33	mutex_lock(&autosleep_lock);
 34
 35	if (!pm_save_wakeup_count(initial_count)) {
 36		mutex_unlock(&autosleep_lock);
 37		goto out;
 38	}
 39
 40	if (autosleep_state == PM_SUSPEND_ON) {
 41		mutex_unlock(&autosleep_lock);
 42		return;
 43	}
 44	if (autosleep_state >= PM_SUSPEND_MAX)
 45		hibernate();
 46	else
 47		pm_suspend(autosleep_state);
 48
 49	mutex_unlock(&autosleep_lock);
 50
 51	if (!pm_get_wakeup_count(&final_count, false))
 52		goto out;
 53
 54	/*
 55	 * If the wakeup occured for an unknown reason, wait to prevent the
 56	 * system from trying to suspend and waking up in a tight loop.
 57	 */
 58	if (final_count == initial_count)
 59		schedule_timeout_uninterruptible(HZ / 2);
 60
 61 out:
 62	queue_up_suspend_work();
 63}
 64
 65static DECLARE_WORK(suspend_work, try_to_suspend);
 66
 67void queue_up_suspend_work(void)
 68{
 69	if (!work_pending(&suspend_work) && autosleep_state > PM_SUSPEND_ON)
 70		queue_work(autosleep_wq, &suspend_work);
 71}
 72
 73suspend_state_t pm_autosleep_state(void)
 74{
 75	return autosleep_state;
 76}
 77
 78int pm_autosleep_lock(void)
 79{
 80	return mutex_lock_interruptible(&autosleep_lock);
 81}
 82
 83void pm_autosleep_unlock(void)
 84{
 85	mutex_unlock(&autosleep_lock);
 86}
 87
 88int pm_autosleep_set_state(suspend_state_t state)
 89{
 90
 91#ifndef CONFIG_HIBERNATION
 92	if (state >= PM_SUSPEND_MAX)
 93		return -EINVAL;
 94#endif
 95
 96	__pm_stay_awake(autosleep_ws);
 97
 98	mutex_lock(&autosleep_lock);
 99
100	autosleep_state = state;
101
102	__pm_relax(autosleep_ws);
103
104	if (state > PM_SUSPEND_ON) {
105		pm_wakep_autosleep_enabled(true);
106		queue_up_suspend_work();
107	} else {
108		pm_wakep_autosleep_enabled(false);
109	}
110
111	mutex_unlock(&autosleep_lock);
112	return 0;
113}
114
115int __init pm_autosleep_init(void)
116{
117	autosleep_ws = wakeup_source_register("autosleep");
118	if (!autosleep_ws)
119		return -ENOMEM;
120
121	autosleep_wq = alloc_ordered_workqueue("autosleep", 0);
122	if (autosleep_wq)
123		return 0;
124
125	wakeup_source_unregister(autosleep_ws);
126	return -ENOMEM;
127}