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From: Dmitry Osipenko <digetx@gmail.com>
To: Peter Geis <pgwipeout@gmail.com>
Cc: Rob Herring <robh+dt@kernel.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Matt Merhar <mattmerhar@protonmail.com>,
	Stephen Warren <swarren@wwwdotorg.org>,
	Bob Ham <rah@settrans.net>, Leonardo Bras <leobras.c@gmail.com>,
	Michael Brougham <jusplainmike@gmail.com>,
	linux-tegra@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 1/3] ARM: tegra: Add device-tree for Ouya
Date: Mon, 5 Oct 2020 17:29:51 +0300	[thread overview]
Message-ID: <6f5fad13-d570-a923-ff40-45071709c296@gmail.com> (raw)
In-Reply-To: <CAMdYzYoKYzTsdWd=99LbwJ4-dG1WOJLo=hxsu_h=Hwrtybiw9A@mail.gmail.com>

05.10.2020 17:22, Peter Geis пишет:
> On Mon, Oct 5, 2020 at 10:02 AM Dmitry Osipenko <digetx@gmail.com> wrote:
>>
>> 04.10.2020 16:31, Peter Geis пишет:
>>> +     thermal-zones {
>>> +             cpu_thermal: cpu-thermal {
>>> +                     polling-delay = <5000>;
>>> +                     polling-delay-passive = <5000>;
>>> +
>>> +                     thermal-sensors = <&cpu_temp 1>;
>>> +
>>> +                     trips {
>>> +                             cpu_alert0: cpu-alert0 {
>>> +                                     temperature = <50000>;
>>> +                                     hysteresis = <10000>;
>>
>> Hello, Peter!
>>
>> A day ago I was tuning thermal zones for Nexus 7 because found that the
>> current variant is a bit too unpractical. In particular temperature
>> hysteresis should be small, otherwise cpufreq could get throttled
>> enormously to the point that device becomes unusable. This is an
>> active-cooling zone, but it looks to me that hysteresis is a bit too
>> high and should make Ouya much noisier than it could be.
>>
>> I suggest to try to set hysteresis to 0.2C here, i.e. hysteresis = <200>.
>>
>> I also suggest to bump the temperature threshold to 55C in order to
>> ignore temporal temperature spikes because CPU temp should be about 40C
>> during idle and then it may raise quickly for a brief moments during
>> average usage.
> 
> Good Morning,
> 
> The Ouya has a rather large heatsink with poor conductivity and a
> single stage fan.
> The fan is not terribly loud, as it runs at a rather low rpm.
> The temperature at the cpu tends to be much higher than observed at
> the heatsink.
> I've found that a low hysteresis value leads to a situation where the
> fan is constantly toggling on and off.
> I actually burned out the power transistor driving the fan on my first
> Ouya this way.
> The high hysteresis value provides a good balance of fan on/off time
> under most loads.
> The temperature threshold was chosen for this as well.
> 
>>
>>> +                                     type = "active";
>>> +                             };
>>> +                             cpu_alert1: cpu-alert1 {
>>> +                                     temperature = <70000>;
>>> +                                     hysteresis = <5000>;
>>> +                                     type = "passive";
>>> +                             };
>>
>> And here to 0.2C as well.
> 
> This value was chosen to protect the CPU in case of fan failure.
> Again, with the large heatsink and poor conductivity we need to
> maintain throttling for longer.
> Otherwise the cpu temp will overshoot and risk thermal shutdown before
> throttling can prevent it.

Alright! Then I don't have any more comments for now, thanks :)

  reply	other threads:[~2020-10-05 14:29 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-04 13:31 [PATCH v3 0/3] Support NVIDIA Tegra-based Ouya game console Peter Geis
2020-10-04 13:31 ` [PATCH v3 1/3] ARM: tegra: Add device-tree for Ouya Peter Geis
2020-10-05 14:02   ` Dmitry Osipenko
2020-10-05 14:22     ` Peter Geis
2020-10-05 14:29       ` Dmitry Osipenko [this message]
2020-10-05 14:29   ` Dmitry Osipenko
2020-10-04 13:31 ` [PATCH v3 2/3] dt-bindings: Add vendor prefix for Ouya Inc Peter Geis
2020-10-05 14:32   ` Dmitry Osipenko
2020-10-04 13:31 ` [PATCH v3 3/3] dt-bindings: ARM: tegra: Add Ouya game console Peter Geis
2020-10-05 14:32   ` Dmitry Osipenko
2020-10-05 15:47 ` [PATCH v3 0/3] Support NVIDIA Tegra-based " Thierry Reding
2020-10-07  7:22 ` Stefan Agner
2020-10-07 13:36   ` Bob Ham
2020-10-07 13:53     ` Dmitry Osipenko
2020-10-07 14:01       ` Dmitry Osipenko
2020-10-07 16:08       ` Stephen Warren
2020-10-07 17:18         ` Peter Geis
2020-10-08  5:05         ` Dmitry Osipenko
2020-11-10 17:42 ` Thierry Reding

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