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Subject: Re: [PATCH v2 47/48] ARM: tegra: ventana: Support CPU voltage scaling
 and thermal throttling
To:     Daniel Lezcano <daniel.lezcano@linaro.org>,
        Thierry Reding <thierry.reding@gmail.com>,
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        Krzysztof Kozlowski <krzk@kernel.org>,
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        Peter De Schrijver <pdeschrijver@nvidia.com>,
        Viresh Kumar <vireshk@kernel.org>,
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From:   Dmitry Osipenko <digetx@gmail.com>
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Date:   Thu, 17 Dec 2020 23:28:56 +0300
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17.12.2020 22:36, Daniel Lezcano пишет:
>>>> +					type = "critical";
>>>> +				};
>>>> +			};
>>>> +
>>>> +			cooling-maps {
>>>> +				map0 {
>>>> +					trip = <&trip0>;
>>>> +					cooling-device = <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
>>> You should add all CPUs here.
>>
>> All CPU cores are coupled on Tegra in regards to CPUFreq, hence I think
>> it won't make any difference if secondary CPU cores will be added here,
>> isn't it?
> The explanation is in the description of commit ef4734500407ce4d

I think that really only makes sense if CPU cores have independent clock
rate management. IIRC, I actually made some research about this in the
past and intentionally removed the secondary cores from the
cooling-device since they didn't make any difference for a coupled CPU
cores.

That commit also says:

"But as soon as this CPU ordering changes and any other CPU is used to
bring up the cooling device, we will start seeing failures."

I don't quite understand to what "failures" that commit referrers. I
tried to change the cpu0 to cpu1 in the cooling-device and don't see any
failures. Could you please clarify this?

In general it should be fine to add all the cores to the cooling-device
and I'll do it in v3, but I want to make it clear why this is needed.