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Commit a5bef810 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
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PM / Domains: Rework default device stop governor function, v2 



The existing default device stop governor function for PM domains,
default_stop_ok(), is supposed to check whether or not the device's
PM QoS latency constraint will be violated if the device is stopped
by pm_genpd_runtime_suspend().  However, the computations carried out
by it don't reflect the definition of the PM QoS latency constrait in
Documentation/ABI/testing/sysfs-devices-power.

Make default_stop_ok() follow the definition of the PM QoS latency
constrait.  In particular, make it take the device's start and stop
latencies correctly.

Add a new field, effective_constraint_ns, to struct gpd_timing_data
and use it to store the difference between the device's PM QoS
constraint and its resume latency for use by the device's parent
(the effective_constraint_ns values for the children are used for
computing the parent's one along with its PM QoS constraint).

Remove the break_even_ns field from struct gpd_timing_data, because
it's not used any more.

Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
parent 69964ea4

drivers/base/power/domain.c

+1 −0
Original line number Diff line number Diff line
@@ -506,6 +506,7 @@ static int pm_genpd_runtime_suspend(struct device *dev) 
	if (dev_gpd_data(dev)->always_on)

		return -EBUSY;



	dev_gpd_data(dev)->td.effective_constraint_ns = -1;

	stop_ok = genpd->gov ? genpd->gov->stop_ok : NULL;

	if (stop_ok && !stop_ok(dev))

		return -EBUSY;

drivers/base/power/domain_governor.c

+49 −4
Original line number Diff line number Diff line
@@ -14,6 +14,31 @@ 


#ifdef CONFIG_PM_RUNTIME



static int dev_update_qos_constraint(struct device *dev, void *data)

{

	s64 *constraint_ns_p = data;

	s32 constraint_ns = -1;



	if (dev->power.subsys_data && dev->power.subsys_data->domain_data)

		constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;



	if (constraint_ns < 0) {

		constraint_ns = dev_pm_qos_read_value(dev);

		constraint_ns *= NSEC_PER_USEC;

	}

	if (constraint_ns == 0)

		return 0;



	/*

	 * constraint_ns cannot be negative here, because the device has been

	 * suspended.

	 */

	if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0)

		*constraint_ns_p = constraint_ns;



	return 0;

}



/**

 * default_stop_ok - Default PM domain governor routine for stopping devices.

 * @dev: Device to check.
@@ -21,14 +46,34 @@ 
bool default_stop_ok(struct device *dev)

{

	struct gpd_timing_data *td = &dev_gpd_data(dev)->td;

	s64 constraint_ns;



	dev_dbg(dev, "%s()\n", __func__);



	if (dev->power.max_time_suspended_ns < 0 || td->break_even_ns == 0)

		return true;

	constraint_ns = dev_pm_qos_read_value(dev);

	if (constraint_ns < 0)

		return false;



	constraint_ns *= NSEC_PER_USEC;

	/*

	 * We can walk the children without any additional locking, because

	 * they all have been suspended at this point.

	 */

	if (!dev->power.ignore_children)

		device_for_each_child(dev, &constraint_ns,

				      dev_update_qos_constraint);



	return td->stop_latency_ns + td->start_latency_ns < td->break_even_ns

		&& td->break_even_ns < dev->power.max_time_suspended_ns;

	if (constraint_ns > 0) {

		constraint_ns -= td->start_latency_ns;

		if (constraint_ns == 0)

			return false;

	}

	td->effective_constraint_ns = constraint_ns;

	/*

	 * The children have been suspended already, so we don't need to take

	 * their stop latencies into account here.

	 */

	return constraint_ns > td->stop_latency_ns || constraint_ns == 0;

}



/**

include/linux/pm_domain.h

+1 −1
Original line number Diff line number Diff line
@@ -93,7 +93,7 @@ struct gpd_timing_data { 
	s64 start_latency_ns;

	s64 save_state_latency_ns;

	s64 restore_state_latency_ns;

	s64 break_even_ns;

	s64 effective_constraint_ns;

};



struct generic_pm_domain_data {