Yes, having a QoS parameter per-subsystem (or even per-device) is very
important for SoCs that have independently controlled powerdomains.
If all devices/subsystems in a particular powerdomain have QoS
parameters that permit, the power state of that powerdomain can be
lowered independently from system-wide power state and power states of
other power domains.
This seems similar to that pm_qos generalization into bus drivers we where
waving our hands at during the collab summit in April? We never did get
into meaningful detail at that time.
--mgross
I think there is definitely a need for QoS parameters per-device. I've
been pondering how to incorporate this concept into runtime_pm. One
idea would be to add pm_qos-like callbacks to struct dev_pm_ops, e.g.
runtime_pm_qos_add/update/remove_requirement(). Requirements would be
passed up the tree to the first parent that cares, usually a bus driver.
Is this similar to what you guys were discussing at the collab summit?
Thanks.
- Bryan
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