linux-kernel - Re: [PATCH 1/3] arm64: defconfig: Enable CONFIG_ENERGY

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Date:   Thu, 28 Mar 2019 17:42:36 +0000
From:   Quentin Perret <quentin.perret@....com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     edubezval@...il.com, rui.zhang@...el.com, javi.merino@...nel.org,
        viresh.kumar@...aro.org, amit.kachhap@...il.com, rjw@...ysocki.net,
        will.deacon@....com, catalin.marinas@....com,
        dietmar.eggemann@....com, ionela.voinescu@....com,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/3] arm64: defconfig: Enable CONFIG_ENERGY_MODEL

Hi Daniel,

On Thursday 28 Mar 2019 at 18:27:49 (+0100), Daniel Lezcano wrote:
> On 28/03/2019 11:22, Quentin Perret wrote:
> >> diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
> >> index 2d9c39033c1a..3c09bdaaefd3 100644
> >> --- a/arch/arm64/configs/defconfig
> >> +++ b/arch/arm64/configs/defconfig
> >> @@ -97,6 +97,7 @@ CONFIG_XEN=y
> >>  CONFIG_COMPAT=y
> >>  CONFIG_HIBERNATION=y
> >>  CONFIG_WQ_POWER_EFFICIENT_DEFAULT=y
> >> +CONFIG_ENERGY_MODEL=n
> > 
> > Hmm, sorry I turned this to '=n' for testing and forgot to update the
> > patch. This obviously should be '=y' ...
> 
> I did a test without the ENERGY_MODEL config option set, dhrystone and
> the power_allocator policy on the hikey. The board did not mitigate well
> and ended up rebooting.

OK ... And is the same thing happening if you just run mainline w/o the
dynamic-power-coefficient binding set for example ? The result _should_
be the same. If not, then perhaps I missed something. I'll try to
reproduce on my end. Just to be sure, when you say hikey, you mean
hikey960 ? Or 620 ? In any case, thanks for testing :-)

> May be the cpu cooling Kconfig option should add
> a SELECT or a DEPENDS on ENERGY_MODEL ?

Right, I've been wondering the same thing. I'm not a big fan of 'select'
because enabling ENERGY_MODEL automatically for the thermal stuff will
also happen to enable other things (EAS) without the user knowing. So
I'd rather keep the ENERGY_MODEL option explicit.

But perhaps having THERMAL_GOV_POWER_ALLOCATOR 'depend on ENERGY_MODEL'
could work. It's just that there is no _strong_ dependency, the IPA code
isn't supposed to crash even if there is no EM ...

Thanks,
Quentin