linux-kernel - Re: [PATCH v1 03/10] ARM: tegra: acer-a500: Bump thermal trips by 10C

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Message-ID: <1abadc69-1dd1-5939-c089-37a84be4781b@linaro.org>
Date:   Sun, 13 Jun 2021 20:19:32 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Dmitry Osipenko <digetx@...il.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Agneli <poczt@...tonmail.ch>, Paul Fertser <fercerpav@...il.com>,
        Svyatoslav Ryhel <clamor95@...il.com>,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 03/10] ARM: tegra: acer-a500: Bump thermal trips by 10C

On 13/06/2021 02:25, Dmitry Osipenko wrote:

[ ... ]

>> You should set the trip points close to the functioning boundary
>> temperature given in the hardware specification whatever the resulting
>> heating effect is on the device.
>>
>> The thermal zone is there to protect the silicon and the system from a
>> wild reboot.
>>
>> If the Nexus 7 is too hot after the changes, then you may act on the
>> sources of the heat. For instance, set the the highest OPP to turbo or
>> remove it, or, if there is one, change the thermal daemon to reduce the
>> overall power consumption.
>> In case you are interested in: https://lwn.net/Articles/839318/
> 
> The DTPM is a very interesting approach. For now Tegra still misses some
> basics in mainline kernel which have a higher priority, so I think it
> should be good enough to perform the in-kernel thermal management for
> the starter. We may consider a more complex solutions later on if will
> be necessary.
> 
> What I'm currently thinking to do is:
> 
> 1. Set up the trips of SoC/CPU core thermal zones in accordance to the
> silicon limits.
> 
> 2. Set up the skin trips in accordance to the device limits.
> 
> The breached skin trips will cause a mild throttling, while the SoC/CPU
> trips will be allowed to cause the severe throttling. Does this sound
> good to you?

The skin temperature must be managed from userspace. The kernel is
unable to do a smart thermal management given different thermal zones
but if the goal is to go forward and prevent the tablet to be hot
temporarily until the other hardware support is there, I think it is
acceptable.


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