Commit 75e94645 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

PM / core: Direct DPM_FLAG_SMART_SUSPEND optimization 



Make the PM core avoid invoking the "late" and "noirq" system-wide
suspend (or analogous) callbacks provided by device drivers directly
for devices with DPM_FLAG_SMART_SUSPEND set that are in runtime
suspend during the "late" and "noirq" phases of system-wide suspend
(or analogous) transitions.  That is only done for devices without
any middle-layer "late" and "noirq" suspend callbacks (to avoid
confusing the middle layer if there is one).

The underlying observation is that runtime PM is disabled for devices
during the "late" and "noirq" system-wide suspend phases, so if they
remain in runtime suspend from the "late" phase forward, it doesn't
make sense to invoke the "late" and "noirq" callbacks provided by
the drivers for them (arguably, the device is already suspended and
in the right state).  Thus, if the remaining driver suspend callbacks
are to be invoked directly by the core, they can be skipped.

This change really makes it possible for, say, platform device
drivers to re-use runtime PM suspend and resume callbacks by
pointing ->suspend_late and ->resume_early, respectively (and
possibly the analogous hibernation-related callback pointers too),
to them without adding any extra "is the device already suspended?"
type of checks to the callback routines, as long as they will be
invoked directly by the core.

Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 4fa3061a

Documentation/driver-api/pm/devices.rst

+10 −8
Original line number Diff line number Diff line
@@ -777,14 +777,16 @@ The driver can indicate that by setting ``DPM_FLAG_SMART_SUSPEND`` in 
runtime suspend at the beginning of the ``suspend_late`` phase of system-wide

suspend (or in the ``poweroff_late`` phase of hibernation), when runtime PM

has been disabled for it, under the assumption that its state should not change

after that point until the system-wide transition is over.  If that happens, the

driver's system-wide resume callbacks, if present, may still be invoked during

the subsequent system-wide resume transition and the device's runtime power

management status may be set to "active" before enabling runtime PM for it,

so the driver must be prepared to cope with the invocation of its system-wide

resume callbacks back-to-back with its ``->runtime_suspend`` one (without the

intervening ``->runtime_resume`` and so on) and the final state of the device

must reflect the "active" status for runtime PM in that case.

after that point until the system-wide transition is over (the PM core itself

does that for devices whose "noirq", "late" and "early" system-wide PM callbacks

are executed directly by it).  If that happens, the driver's system-wide resume

callbacks, if present, may still be invoked during the subsequent system-wide

resume transition and the device's runtime power management status may be set

to "active" before enabling runtime PM for it, so the driver must be prepared to

cope with the invocation of its system-wide resume callbacks back-to-back with

its ``->runtime_suspend`` one (without the intervening ``->runtime_resume`` and

so on) and the final state of the device must reflect the "active" runtime PM

status in that case.



During system-wide resume from a sleep state it's easiest to put devices into

the full-power state, as explained in :file:`Documentation/power/runtime_pm.txt`.

drivers/base/power/main.c

+78 −7
Original line number Diff line number Diff line
@@ -539,6 +539,24 @@ void dev_pm_skip_next_resume_phases(struct device *dev) 
	dev->power.is_suspended = false;

}



/**

 * suspend_event - Return a "suspend" message for given "resume" one.

 * @resume_msg: PM message representing a system-wide resume transition.

 */

static pm_message_t suspend_event(pm_message_t resume_msg)

{

	switch (resume_msg.event) {

	case PM_EVENT_RESUME:

		return PMSG_SUSPEND;

	case PM_EVENT_THAW:

	case PM_EVENT_RESTORE:

		return PMSG_FREEZE;

	case PM_EVENT_RECOVER:

		return PMSG_HIBERNATE;

	}

	return PMSG_ON;

}



/**

 * dev_pm_may_skip_resume - System-wide device resume optimization check.

 * @dev: Target device.
@@ -580,6 +598,14 @@ static pm_callback_t dpm_subsys_resume_noirq_cb(struct device *dev, 
	return callback;

}



static pm_callback_t dpm_subsys_suspend_noirq_cb(struct device *dev,

						 pm_message_t state,

						 const char **info_p);



static pm_callback_t dpm_subsys_suspend_late_cb(struct device *dev,

						pm_message_t state,

						const char **info_p);



/**

 * device_resume_noirq - Execute a "noirq resume" callback for given device.

 * @dev: Device to handle.
@@ -607,13 +633,40 @@ static int device_resume_noirq(struct device *dev, pm_message_t state, bool asyn 
	dpm_wait_for_superior(dev, async);



	callback = dpm_subsys_resume_noirq_cb(dev, state, &info);

	if (callback)

		goto Run;



	if (!callback && dev->driver && dev->driver->pm) {

	if (dev_pm_smart_suspend_and_suspended(dev)) {

		pm_message_t suspend_msg = suspend_event(state);



		/*

		 * If "freeze" callbacks have been skipped during a transition

		 * related to hibernation, the subsequent "thaw" callbacks must

		 * be skipped too or bad things may happen.  Otherwise, resume

		 * callbacks are going to be run for the device, so its runtime

		 * PM status must be changed to reflect the new state after the

		 * transition under way.

		 */

		if (!dpm_subsys_suspend_late_cb(dev, suspend_msg, NULL) &&

		    !dpm_subsys_suspend_noirq_cb(dev, suspend_msg, NULL)) {

			if (state.event == PM_EVENT_THAW) {

				dev_pm_skip_next_resume_phases(dev);

				goto Skip;

			} else {

				pm_runtime_set_active(dev);

			}

		}

	}



	if (dev->driver && dev->driver->pm) {

		info = "noirq driver ";

		callback = pm_noirq_op(dev->driver->pm, state);

	}



Run:

	error = dpm_run_callback(callback, dev, state, info);



Skip:

	dev->power.is_noirq_suspended = false;



	if (dev_pm_may_skip_resume(dev)) {
@@ -1223,18 +1276,26 @@ static int __device_suspend_noirq(struct device *dev, pm_message_t state, bool a 
		goto Complete;



	callback = dpm_subsys_suspend_noirq_cb(dev, state, &info);

	if (callback)

		goto Run;



	if (!callback && dev->driver && dev->driver->pm) {

	if (dev_pm_smart_suspend_and_suspended(dev) &&

	    !dpm_subsys_suspend_late_cb(dev, state, NULL))

		goto Skip;



	if (dev->driver && dev->driver->pm) {

		info = "noirq driver ";

		callback = pm_noirq_op(dev->driver->pm, state);

	}



Run:

	error = dpm_run_callback(callback, dev, state, info);

	if (error) {

		async_error = error;

		goto Complete;

	}



Skip:

	dev->power.is_noirq_suspended = true;



	if (dev_pm_test_driver_flags(dev, DPM_FLAG_LEAVE_SUSPENDED)) {
@@ -1419,17 +1480,27 @@ static int __device_suspend_late(struct device *dev, pm_message_t state, bool as 
		goto Complete;



	callback = dpm_subsys_suspend_late_cb(dev, state, &info);

	if (callback)

		goto Run;



	if (!callback && dev->driver && dev->driver->pm) {

	if (dev_pm_smart_suspend_and_suspended(dev) &&

	    !dpm_subsys_suspend_noirq_cb(dev, state, NULL))

		goto Skip;



	if (dev->driver && dev->driver->pm) {

		info = "late driver ";

		callback = pm_late_early_op(dev->driver->pm, state);

	}



Run:

	error = dpm_run_callback(callback, dev, state, info);

	if (!error)

		dev->power.is_late_suspended = true;

	else

	if (error) {

		async_error = error;

		goto Complete;

	}



Skip:

	dev->power.is_late_suspended = true;



Complete:

	TRACE_SUSPEND(error);

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