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From:   Amit Kucheria <amit.kucheria@linaro.org>
Date:   Fri, 11 Jan 2019 01:15:09 +0530
Message-ID: <CAHLCerM+p+GkVsR_WuC0xF1oFvj=8cZ+OmU=pMssfZGGs-eS7w@mail.gmail.com>
Subject: Re: [PATCH v1 6/7] arm64: dts: sdm845: Increase alert trip point to
 95 degrees
To:     Matthias Kaehlcke <mka@chromium.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Eduardo Valentin <edubezval@gmail.com>,
        Andy Gross <andy.gross@linaro.org>,
        Taniya Das <tdas@codeaurora.org>,
        Stephen Boyd <swboyd@chromium.org>,
        Douglas Anderson <dianders@chromium.org>,
        David Brown <david.brown@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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On Thu, Jan 10, 2019 at 7:45 AM Matthias Kaehlcke <mka@chromium.org> wrote:
>
> On Wed, Jan 09, 2019 at 05:15:33PM -0800, Matthias Kaehlcke wrote:
> > Hi Amit,
> >
> > On Thu, Jan 10, 2019 at 05:30:55AM +0530, Amit Kucheria wrote:
> > > 75 degrees is too aggressive for throttling the CPU. After speaking to
> > > Qualcomm engineers, increase it to 95 degrees.
> > >
> > > Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
> > > ---
> > >  arch/arm64/boot/dts/qcom/sdm845.dtsi | 16 ++++++++--------
> > >  1 file changed, 8 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/arch/arm64/boot/dts/qcom/sdm845.dtsi b/arch/arm64/boot/dts/qcom/sdm845.dtsi
> > > index c27cbd3bcb0a..29e823b0caf4 100644
> > > --- a/arch/arm64/boot/dts/qcom/sdm845.dtsi
> > > +++ b/arch/arm64/boot/dts/qcom/sdm845.dtsi
> > > @@ -1692,7 +1692,7 @@
> > >
> > >                     trips {
> > >                             cpu_alert0: trip0 {
> > > -                                   temperature = <75000>;
> > > +                                   temperature = <95000>;
> > >                                     hysteresis = <2000>;
> > >                                     type = "passive";
> > >                             };
> > > @@ -1713,7 +1713,7 @@
> > >
> > >                     trips {
> > >                             cpu_alert1: trip0 {
> > > -                                   temperature = <75000>;
> > > +                                   temperature = <95000>;
> > >                                     hysteresis = <2000>;
> > >                                     type = "passive";
> > >                             };
> > > @@ -1734,7 +1734,7 @@
> > >
> > >                     trips {
> > >                             cpu_alert2: trip0 {
> > > -                                   temperature = <75000>;
> > > +                                   temperature = <95000>;
> > >                                     hysteresis = <2000>;
> > >                                     type = "passive";
> > >                             };
> > > @@ -1755,7 +1755,7 @@
> > >
> > >                     trips {
> > >                             cpu_alert3: trip0 {
> > > -                                   temperature = <75000>;
> > > +                                   temperature = <95000>;
> > >                                     hysteresis = <2000>;
> > >                                     type = "passive";
> > >                             };
> > > @@ -1776,7 +1776,7 @@
> > >
> > >                     trips {
> > >                             cpu_alert4: trip0 {
> > > -                                   temperature = <75000>;
> > > +                                   temperature = <95000>;
> > >                                     hysteresis = <2000>;
> > >                                     type = "passive";
> > >                             };
> > > @@ -1797,7 +1797,7 @@
> > >
> > >                     trips {
> > >                             cpu_alert5: trip0 {
> > > -                                   temperature = <75000>;
> > > +                                   temperature = <95000>;
> > >                                     hysteresis = <2000>;
> > >                                     type = "passive";
> > >                             };
> > > @@ -1818,7 +1818,7 @@
> > >
> > >                     trips {
> > >                             cpu_alert6: trip0 {
> > > -                                   temperature = <75000>;
> > > +                                   temperature = <95000>;
> > >                                     hysteresis = <2000>;
> > >                                     type = "passive";
> > >                             };
> > > @@ -1839,7 +1839,7 @@
> > >
> > >                     trips {
> > >                             cpu_alert7: trip0 {
> > > -                                   temperature = <75000>;
> > > +                                   temperature = <95000>;
> > >                                     hysteresis = <2000>;
> > >                                     type = "passive";
> > >                             };
> >
> > The change itself looks good to me, however I wonder if it would be
> > worth to eliminate redundancy and merge the current 8 thermal zones
> > into 2, one for the Silver and one for the Gold cluster (as done by
> > http://crrev.com/c/1381752). There is a single cooling device for
> > each cluster, so it's not clear to me if there is any gain from having
> > a separate thermal zone for each CPU. If it is important to monitor
> > the temperatures of the individual cores this can still be done by
> > configuring the thermal zone of the cluster with multiple thermal
> > sensors.
>
> I see your idea is to have a cooling device per CPU ("arm64: dts:
> sdm845: wireup the thermal trip points to cpufreq" /
> https://lore.kernel.org/patchwork/patch/1030742/), however that
> doesn't work as intended. Only two cpufreq 'devices' are created,
> one for CPU0 and one for CPU4. In consequence cpufreq->ready() only
> runs for these cores and only two cooling devices are
> registered. Since the cores of a cluster all run at the same
> frequency I also doubt if having multiple cooling devices would
> bring any benefits.

I actually only intended for two cooling devices - one for each
frequency domain. I'll clarify it better in the patch description.