Commit a5bef810 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki

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
......@@ -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;
......
......@@ -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;
}
/**
......
......@@ -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 {
......
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