linux-kernel - Re: [PATCH 3/3] arm64: dts: qcom: sc7180: Delete charger thermal zone and ADC channel for lazor <= rev3

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Date:   Mon, 22 Feb 2021 12:45:23 -0800
From:   Stephen Boyd <swboyd@...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>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 3/3] arm64: dts: qcom: sc7180: Delete charger thermal zone and ADC channel for lazor <= rev3

Quoting Matthias Kaehlcke (2021-02-22 12:38:46)
> On Mon, Feb 22, 2021 at 12:20:04PM -0800, Stephen Boyd wrote:
> > Quoting Matthias Kaehlcke (2021-02-19 18:10:59)
> > > Lazor rev3 and older are stuffed with a 47k NTC as thermistor for
> > > the charger temperature which currently isn't supported by the
> > > PM6150 ADC driver. Delete the charger thermal zone and ADC channel
> > > to avoid the use of bogus temperature values.
> > > 
> > > Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> > > ---
> > > 
> > >  arch/arm64/boot/dts/qcom/sc7180-trogdor-lazor-r0.dts | 9 +++++++++
> > >  arch/arm64/boot/dts/qcom/sc7180-trogdor-lazor-r1.dts | 9 +++++++++
> > >  arch/arm64/boot/dts/qcom/sc7180-trogdor-lazor-r3.dts | 9 +++++++++
> > >  3 files changed, 27 insertions(+)
> > > 
> > > diff --git a/arch/arm64/boot/dts/qcom/sc7180-trogdor-lazor-r0.dts b/arch/arm64/boot/dts/qcom/sc7180-trogdor-lazor-r0.dts
> > > index 30e3e769d2b4..0974dbd424e1 100644
> > > --- a/arch/arm64/boot/dts/qcom/sc7180-trogdor-lazor-r0.dts
> > > +++ b/arch/arm64/boot/dts/qcom/sc7180-trogdor-lazor-r0.dts
> > > @@ -14,6 +14,15 @@ / {
> > >         compatible = "google,lazor-rev0", "qcom,sc7180";
> > >  };
> > >  
> > > +/*
> > > + * rev <= 3 are stuffed with a 47k NTC as charger thermistor which is currently
> > > + * not supported by the PM6150 ADC driver. Delete the thermal zone and ADC
> > > + * channel to avoid the use of bogus temperature values.
> > > + */
> > > +/delete-node/ &charger_thermal;
> > > +/delete-node/ &pm6150_adc_charger_thm;
> > > +/delete-node/ &pm6150_adc_tm_charger_thm;
> > 
> > Can we disable pm6150_adc_tm instead on <= rev3 boards? It would be the
> > same number of lines, but is simpler to reason about disabled nodes vs.
> > deleted nodes usually.
> 
> For Lazor theoretically this could be done since it doesn't use other ADC
> channels, however it won't work for other trogdor devices that will be
> upstreamed eventually. Some of these boards have the same problem, however
> they have other thermistors connected to the ADC. One could argue that it's
> preferable to do things in a uniform way, but I'm open to do it either way
> for Lazor.
> 

I see. Can the thermal-zone be disabled then vs. deleting three nodes? I
think the thermal driver uses for_each_available_child_of_node() so that
would work?