linux-kernel - Re: [RFC 1/2] dt-bindings: thermal: sprd: Add virtual thermal documentation

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Message-ID: <CANO_MS+n6CTom-o7Hs4dKtPf-2uih5R7_8BnU_b4Jv8g1a5dkg@mail.gmail.com>
Date:   Mon, 30 Nov 2020 17:03:43 +0800
From:   gao yunxiao <gao.yunxiao6@...il.com>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>, rui.zhang@...el.com,
        amitk@...nel.org, robh+dt@...nel.org, javi.merino@...nel.org,
        linux-pm@...r.kernel.org, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        orsonzhai@...il.com, zhang.lyra@...il.com,
        "jeson.gao" <jeson.gao@...soc.com>
Subject: Re: [RFC 1/2] dt-bindings: thermal: sprd: Add virtual thermal documentation

Hi Daniel

Thank you for your the new information

I have a question trouble to you
We should choose which per-core thermal zone as the IPA's input
reference temperature in the current kernel version? thank you.

On 27/11/2020, Lukasz Luba <lukasz.luba@....com> wrote:
>
>
> On 11/27/20 1:26 PM, Daniel Lezcano wrote:
>>
>> Hi Lukasz,
>>
>> On 27/11/2020 10:27, Lukasz Luba wrote:
>>>
>>>
>>> On 11/27/20 8:35 AM, gao.yunxiao6@...il.com wrote:
>>>> From: "jeson.gao" <jeson.gao@...soc.com>
>>>>
>>>> virtual thermal node definition description in dts file
>>>>
>>>> Signed-off-by: jeson.gao <jeson.gao@...soc.com>
>>>> ---
>>
>> [ ... ]
>>
>>> It's coming back. There were attempts to solve this problem.
>>> Javi tried to solved this using hierarchical thermal zones [1].
>>> It was even agreed (IIRC during LPC) but couldn't continue. Then Eduardo
>>> was going to continue this (last message at [3]). Unfortunately,
>>> development stopped.
>>>
>>> I also have out-of-tree similar implementation for my Odroid-xu4,
>>> which does no have an 'SoC' sensor, but have CPU sensors and needs
>>> some aggregation function to get temperature.
>>>
>>> I can pick up Javi's patches and continue 'hierarchical thermal zones'
>>> approach.
>>>
>>> Javi, Daniel, Rui what do you think?
>>
>> I already worked on the hierarchical thermal zones and my opinion is
>> that fits not really well.
>>
>> We want to define a new feature because the thermal framework is built
>> on the 1:1 relationship between a governor and a thermal zone.
>>
>> Practically speaking, we want to mitigate two thermal zones from one
>> governor, especially here the IPA governor.
>>
>> The DTPM framework is being implemented to solve that by providing an
>> automatic power rebalancing between the power manageable capable devices.
>>
>> In our case, the IPA would stick on the 'sustainable-power' resulting on
>> the aggregation of the two performance domains and set the power limit
>> on the parent node. The automatic power rebalancing will ensure maximum
>> throughput between the two performance domains instead of capping the
>> whole.
>>
>>
>
> Make sense. Thank you for sharing valuable opinion.
>
> Regards,
> Lukasz
>