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 12:38:46 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Stephen Boyd <swboyd@...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

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.