linux-kernel - Re: [PATCH v1] arm64: dts: sdm845: enable tsens thermal zones

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Message-ID: <20180829181216.GD10879@google.com>
Date:   Wed, 29 Aug 2018 11:12:16 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     Amit Kucheria <amit.kucheria@...aro.org>,
        linux-kernel@...r.kernel.org, rnayak@...eaurora.org,
        linux-arm-msm@...r.kernel.org, bjorn.andersson@...aro.org,
        andy.gross@...aro.org, dianders@...omium.org, edubezval@...il.com,
        David Brown <david.brown@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>, linux-soc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Taniya Das <tdas@...eaurora.org>
Subject: Re: [PATCH v1] arm64: dts: sdm845: enable tsens thermal zones

On Wed, Aug 29, 2018 at 11:39:12AM +0200, Daniel Lezcano wrote:
> On 18/07/2018 09:49, Amit Kucheria wrote:
> > One thermal zone per cpu is defined
> 
> The thermal zones are very close, especially when the CPUs belong to the
> same 'cluster'. Very likely the temperature will propagate from one core
> to another core, so when one core reaches the trip0, there is good
> chance the other cores will be close and cross the trip0 threshold too.
> 
> Having multiple thermal zones, one per CPU, may trigger an interrupts
> storm with the passive polling timer delay.
> 
> Does this board have a cooling device per CPU also ?

The cpufreq driver is still under development:
https://lore.kernel.org/patchwork/patch/966833/ . It currently doesn't
register cooling devices, but since CPUs from a 'cluster' use the same
cpufreq policy I think there will be one cooling device per 'cluster'.