linux-kernel - Re: [PATCH] arm64: dts: qcom: sc7180: Set 'polling-delay-passive' for thermal zones back to 250 ms

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Date:   Wed, 11 Nov 2020 14:23:25 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Amit Kucheria <amit.kucheria@...aro.org>,
        Rajeshwari <rkambl@...eaurora.org>,
        Akhil P Oommen <akhilpo@...eaurora.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: dts: qcom: sc7180: Set 'polling-delay-passive' for
 thermal zones back to 250 ms

Hi,

On Wed, Nov 11, 2020 at 12:03 PM Matthias Kaehlcke <mka@...omium.org> wrote:
>
> Commit 22337b91022d ("arm64: dts: qcom: sc7180: Changed polling mode
> in Thermal-zones node") sets both 'polling-delay' and
> 'polling-delay-passive' to zero with the rationale that TSENS interrupts
> are enabled. A TSENS interrupt fires when the temperature of a thermal
> zone reaches a trip point, which makes regular polling below the passive
> trip point temperature unnecessary. However the situation is different
> when passive cooling is active, regular polling is still needed to
> trigger a periodic evaluation of the thermal zone by the thermal governor.
>
> Change 'polling-delay-passive' back to the original value of 250 ms.
> Commit 2315ae70af95 ("arm64: dts: qcom: sc7180: Add gpu cooling
> support") recently changed the value for the GPU thermal zones from
> zero to 100 ms, also set it to 250 ms for uniformity. If some zones
> really need different values these can be changed in dedicated patches.
>
> Fixes: 22337b91022d ("arm64: dts: qcom: sc7180: Changed polling mode in Thermal-zones node")
> Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> ---
>
>  arch/arm64/boot/dts/qcom/sc7180.dtsi | 50 ++++++++++++++--------------
>  1 file changed, 25 insertions(+), 25 deletions(-)

For further context:

https://lore.kernel.org/r/a4be2cf9e51e4f40aae3f9a56989a42f@codeaurora.org
https://lore.kernel.org/r/20201015221920.GA1657396@google.com

I didn't personally go dig through the code, but what's said in those
emails seems reasonable to me.

Reviewed-by: Douglas Anderson <dianders@...omium.org>