On 27/02/2019 20:58, Ulf Hansson wrote:

As it's now perfectly possible that a PM domain managed by genpd contains
devices belonging to CPUs, we should start to take into account the
residency values for the idle states during the state selection process.
The residency value specifies the minimum duration of time, the CPU or a
group of CPUs, needs to spend in an idle state to not waste energy entering
it.

To deal with this, let's add a new genpd governor, pm_domain_cpu_gov, that
may be used for a PM domain that have CPU devices attached or if the CPUs
are attached through subdomains.

The new governor computes the minimum expected idle duration time for the
online CPUs being attached to the PM domain and its subdomains. Then in the
state selection process, trying the deepest state first, it verifies that
the idle duration time satisfies the state's residency value.

It should be noted that, when computing the minimum expected idle duration
time, we use the information about the next timer/tick that is stored in
the per CPU variable, cpuidle_devices, for the related CPUs. Future wise,
this deserves to be improved, as there are obviously more reasons to why a
CPU may be woken up from idle.

Cc: Lina Iyer <redacted>
Co-developed-by: Lina Iyer <redacted>
Signed-off-by: Ulf Hansson <redacted>

Acked-by: Daniel Lezcano <redacted>



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