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

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Message-ID: <b98c6196-d3e5-888b-e85e-633deefe1a49@linaro.org>
Date:   Mon, 30 Nov 2020 10:40:37 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     gao yunxiao <gao.yunxiao6@...il.com>,
        Lukasz Luba <lukasz.luba@....com>
Cc:     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

On 30/11/2020 10:03, gao yunxiao wrote:
> 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.

Can you give a pointer to a DT describing your hardware ?



> 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
>>


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