/*
* drivers/base/power/wakeup.c - System wakeup events framework
*
* Copyright (c) 2010 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc.
*
* This file is released under the GPLv2.
*/
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/capability.h>
#include <linux/suspend.h>
#include <linux/pm.h>
/*
* If set, the suspend/hibernate code will abort transitions to a sleep state
* if wakeup events are registered during or immediately before the transition.
*/
bool events_check_enabled;
/* The counter of registered wakeup events. */
static unsigned long event_count;
/* A preserved old value of event_count. */
static unsigned long saved_event_count;
/* The counter of wakeup events being processed. */
static unsigned long events_in_progress;
static DEFINE_SPINLOCK(events_lock);
/*
* The functions below use the observation that each wakeup event starts a
* period in which the system should not be suspended. The moment this period
* will end depends on how the wakeup event is going to be processed after being
* detected and all of the possible cases can be divided into two distinct
* groups.
*
* First, a wakeup event may be detected by the same functional unit that will
* carry out the entire processing of it and possibly will pass it to user space
* for further processing. In that case the functional unit that has detected
* the event may later "close" the "no suspend" period associated with it
* directly as soon as it has been dealt with. The pair of pm_stay_awake() and
* pm_relax(), balanced with each other, is supposed to be used in such
* situations.
*
* Second, a wakeup event may be detected by one functional unit and processed
* by another one. In that case the unit that has detected it cannot really
* "close" the "no suspend" period associated with it, unless it knows in
* advance what's going to happen to the event during processing. This
* knowledge, however, may not be available to it, so it can simply specify time
* to wait before the system can be suspended and pass it as the second
* argument of pm_wakeup_event().
*/
/**
* pm_stay_awake - Notify the PM core that a wakeup event is being processed.
* @dev: Device the wakeup event is related to.
*
* Notify the PM core of a wakeup event (signaled by @dev) by incrementing the
* counter of wakeup events being processed. If @dev is not NULL, the counter
* of wakeup events related to @dev is incremented too.
*
* Call this function after detecting of a wakeup event if pm_relax() is going
* to be called directly after processing the event (and possibly passing it to
* user space for further processing).
*
* It is safe to call this function from interrupt context.
*/
void pm_stay_awake(struct device *dev)
{
unsigned long flags;
spin_lock_irqsave(&events_lock, flags);
if (dev)
dev->power.wakeup_count++;
events_in_progress++;
spin_unlock_irqrestore(&events_lock, flags);
}
/**
* pm_relax - Notify the PM core that processing of a wakeup event has ended.
*
* Notify the PM core that a wakeup event has been processed by decrementing
* the counter of wakeup events being processed and incrementing the counter
* of registered wakeup events.
*
* Call this function for wakeup events whose processing started with calling
* pm_stay_awake().
*
* It is safe to call it from interrupt context.
*/
void pm_relax(void)
{
unsigned long flags;
spin_lock_irqsave(&events_lock, flags);
if (events_in_progress) {
events_in_progress--;
event_count++;
}
spin_unlock_irqrestore(&events_lock, flags);
}
/**
* pm_wakeup_work_fn - Deferred closing of a wakeup event.
*
* Execute pm_relax() for a wakeup event detected in the past and free the
* work item object used for queuing up the work.
*/
static void pm_wakeup_work_fn(struct work_struct *work)
{
struct delayed_work *dwork = to_delayed_work(work);
pm_relax();
kfree(dwork);
}
/**
* pm_wakeup_event - Notify the PM core of a wakeup event.
* @dev: Device the wakeup event is related to.
* @msec: Anticipated event processing time (in milliseconds).
*
* Notify the PM core of a wakeup event (signaled by @dev) that will take
* approximately @msec milliseconds to be processed by the kernel. Increment
* the counter of wakeup events being processed and queue up a work item
* that will execute pm_relax() for the event after @msec milliseconds. If @dev
* is not NULL, the counter of wakeup events related to @dev is incremented too.
*
* It is safe to call this function from interrupt context.
*/
void pm_wakeup_event(struct device *dev, unsigned int msec)
{
unsigned long flags;
struct delayed_work *dwork;
dwork = msec ? kzalloc(sizeof(*dwork), GFP_ATOMIC) : NULL;
spin_lock_irqsave(&events_lock, flags);
if (dev)
dev->power.wakeup_count++;
if (dwork) {
INIT_DELAYED_WORK(dwork, pm_wakeup_work_fn);
schedule_delayed_work(dwork, msecs_to_jiffies(msec));
events_in_progress++;
} else {
event_count++;
}
spin_unlock_irqrestore(&events_lock, flags);
}
/**
* pm_check_wakeup_events - Check for new wakeup events.
*
* Compare the current number of registered wakeup events with its preserved
* value from the past to check if new wakeup events have been registered since
* the old value was stored. Check if the current number of wakeup events being
* processed is zero.
*/
bool pm_check_wakeup_events(void)
{
unsigned long flags;
bool ret = true;
spin_lock_irqsave(&events_lock, flags);
if (events_check_enabled) {
ret = (event_count == saved_event_count) && !events_in_progress;
events_check_enabled = ret;
}
spin_unlock_irqrestore(&events_lock, flags);
return ret;
}
/**
* pm_get_wakeup_count - Read the number of registered wakeup events.
* @count: Address to store the value at.
*
* Store the number of registered wakeup events at the address in @count. Block
* if the current number of wakeup events being processed is nonzero.
*
* Return false if the wait for the number of wakeup events being processed to
* drop down to zero has been interrupted by a signal (and the current number
* of wakeup events being processed is still nonzero). Otherwise return true.
*/
bool pm_get_wakeup_count(unsigned long *count)
{
bool ret;
spin_lock_irq(&events_lock);
if (capable(CAP_SYS_ADMIN))
events_check_enabled = false;
while (events_in_progress && !signal_pending(current)) {
spin_unlock_irq(&events_lock);
schedule_timeout_interruptible(msecs_to_jiffies(100));
spin_lock_irq(&events_lock);
}
*count = event_count;
ret = !events_in_progress;
spin_unlock_irq(&events_lock);
return ret;
}
/**
* pm_save_wakeup_count - Save the current number of registered wakeup events.
* @count: Value to compare with the current number of registered wakeup events.
*
* If @count is equal to the current number of registered wakeup events and the
* current number of wakeup events being processed is zero, store @count as the
* old number of registered wakeup events to be used by pm_check_wakeup_events()
* and return true. Otherwise return false.
*/
bool pm_save_wakeup_count(unsigned long count)
{
bool ret = false;
spin_lock_irq(&events_lock);
if (count == event_count && !events_in_progress) {
saved_event_count = count;
events_check_enabled = true;
ret = true;
}
spin_unlock_irq(&events_lock);
return ret;
}
