Re: [RFC][PATCH v0.1 3/6] PM: EM: Add special case to em_dev_register_perf_domain()

[Dietmar Eggemann]

On 08/11/2024 17:38, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> 
> Allow em_dev_register_perf_domain() to register a cost-only stub
> perf domain with one-element states table if the .active_power()
> callback is not provided.
> 
> Subsequently, this will be used by the intel_pstate driver to register
> stub perf domains for CPUs on hybrid systems.

Looks like a 'stub' PD only distinguish itself from a normal PD by not
checking that all CPU in that PD have the same CPU capacity value?

I assume you do this since the Performance Cores (CPUs) can have
different CPU capacity values due to slightly different 'itmt prio' values?

So strictly speaking such a Intel hybrid machine would be tri-gear
system to fit the definition of a PD.

I thought initially by reading the word 'stub' that you only setup a
part of the default EM infrastructure.

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