linux-kernel - Re: [PATCH v2 09/15] arm64: dts: msm8996: thermal: Add interrupt support

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Date:   Sat, 31 Aug 2019 01:40:10 +0530
From:   Amit Kucheria <amit.kucheria@...aro.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Eduardo Valentin <edubezval@...il.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Marc Gonzalez <marc.w.gonzalez@...e.fr>,
        Brian Masney <masneyb@...tation.org>,
        DTML <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 09/15] arm64: dts: msm8996: thermal: Add interrupt support

On Wed, Aug 28, 2019 at 6:05 AM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Amit Kucheria (2019-08-27 05:14:05)
> > Register upper-lower interrupts for each of the two tsens controllers.
> >
> > Signed-off-by: Amit Kucheria <amit.kucheria@...aro.org>
> > ---
> >  arch/arm64/boot/dts/qcom/msm8996.dtsi | 60 ++++++++++++++-------------
> >  1 file changed, 32 insertions(+), 28 deletions(-)
> >
> > diff --git a/arch/arm64/boot/dts/qcom/msm8996.dtsi b/arch/arm64/boot/dts/qcom/msm8996.dtsi
> > index 96c0a481f454e..bb763b362c162 100644
> > --- a/arch/arm64/boot/dts/qcom/msm8996.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/msm8996.dtsi
> > @@ -175,8 +175,8 @@
> >
> >         thermal-zones {
> >                 cpu0-thermal {
> > -                       polling-delay-passive = <250>;
> > -                       polling-delay = <1000>;
> > +                       polling-delay-passive = <0>;
> > +                       polling-delay = <0>;
>
> Is it really necessary to change the configuration here to be 0 instead
> of some number? Why can't we detect that there's an interrupt and then
> ignore these properties?

AFAICT, the thermal core currently depends on the passive and
polling_delay being set to 0 to avoid setting dispatching polling work
to a workqueue. If we leave the values to set, we'll continue to poll
inspite of an interrupt. See
thermal_core.c:thermal_zone_device_set_polling()

But I agree, the core should detect the presence of an interrupt
property and ignore the polling intervals. I'll see if I can fix this
up later.

Regards,
Amit