PM / Runtime: Use device PM QoS constraints (v2)

Make the runtime PM core use device PM QoS constraints to check if
it is allowed to suspend a given device, so that an error code is
returned if the device's own PM QoS constraint is negative or one of
its children has already been suspended for too long.  If this is
not the case, the maximum estimated time the device is allowed to be
suspended, computed as the minimum of the device's PM QoS constraint
and the PM QoS constraints of its children (reduced by the difference
between the current time and their suspend times) is stored in a new
device's PM field power.max_time_suspended_ns that can be used by
the device's subsystem or PM domain to decide whether or not to put
the device into lower-power (and presumably higher-latency) states
later (if the constraint is 0, which means "no constraint", the
power.max_time_suspended_ns is set to -1).

Additionally, the time of execution of the subsystem-level
.runtime_suspend() callback for the device is recorded in the new
power.suspend_time field for later use by the device's subsystem or
PM domain along with power.max_time_suspended_ns (it also is used
by the core code when the device's parent is suspended).

Introduce a new helper function,
pm_runtime_update_max_time_suspended(), allowing subsystems and PM
domains (or device drivers) to update the power.max_time_suspended_ns
field, for example after changing the power state of a suspended
device.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h
index d3085e72a0ee..609daae7a014 100644
--- a/include/linux/pm_runtime.h
+++ b/include/linux/pm_runtime.h
@@ -45,6 +45,8 @@ extern void pm_runtime_irq_safe(struct device *dev);
 extern void __pm_runtime_use_autosuspend(struct device *dev, bool use);
 extern void pm_runtime_set_autosuspend_delay(struct device *dev, int delay);
 extern unsigned long pm_runtime_autosuspend_expiration(struct device *dev);
+extern void pm_runtime_update_max_time_suspended(struct device *dev,
+						 s64 delta_ns);
 
 static inline bool pm_children_suspended(struct device *dev)
 {
@@ -148,6 +150,9 @@ static inline void pm_runtime_set_autosuspend_delay(struct device *dev,
 static inline unsigned long pm_runtime_autosuspend_expiration(
 				struct device *dev) { return 0; }
 
+static inline void pm_runtime_update_max_time_suspended(struct device *dev,
+							s64 delta_ns) {}
+
 #endif /* !CONFIG_PM_RUNTIME */
 
 static inline int pm_runtime_idle(struct device *dev)