Re: [PATCH v2 0/3] Clarify abstract scale usage for power values in Energy Model, EAS and IPA
From: Daniel Lezcano
Date: Thu Oct 15 2020 - 06:22:03 EST
On 15/10/2020 11:00, Lukasz Luba wrote:
[ ... ]
>> There is the SCMI and the DT. Because there are two sources where it is
>> impossible to know if they are using the same units, we are stuck to
>> ensure a consistency for the kernel.
>>
>> The platform should use:
>> - the SCMI only (scaled or real)
>> - the DT only (real)
>> [ - the firmware file only (scaled or real) ]
>>
>
> Do you mean by SCMI - registration using em_dev_register_perf_domain() ?
It was high level description, but yes, I guess it is the case.
>> As it is not possible to know if they are scaled or real, there is no
>> choice except making them mutually exclusive.
>
> So you propose a bit more restriction in registration EM, to not get
> lost in the future. I also have these doubts. Let's consider it and
> maybe agree.
>
> I've recommended Qcom to use em_dev_register_perf_domain() when they
> have this obfuscated power values. Then any developer in the future
> who wants to add EM for a new device on that platform, should use the
> em_dev_register_perf_domain().
>
> In this case the flag in EM that you have proposed makes sense.
> We probably need an argument 'bool abstract_scale' in the
> em_dev_register_perf_domain(..., bool abstract_scale)
> as a source of information.
I was suggesting to add a flag to the em_perf_domain structure giving
the source of the power numbers.
So if the IPA is having the 'sustainable-power' set in DT but the
em_perf_domain is flagged with power number coming from SCMI, then they
will be incompatible, the thermal zone will fail to register.
> We would allow to co-exist em_dev_register_perf_domain(..., false)
> with dev_pm_opp_of_register_em() EM devices.
>
> Is it make sense?
Well, it does not change my opinion. We should assume the energy model
is always milliwatts. If the SoC vendors find a way to get around with
bogoWatts, then good to them and up to them to deal with in the future.
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