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Date:   Wed, 24 Feb 2021 09:12:13 -0800
From:   Matthias Kaehlcke <mka@chromium.org>
To:     Stephen Boyd <swboyd@chromium.org>
Cc:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
        Douglas Anderson <dianders@chromium.org>,
        devicetree@vger.kernel.org
Subject: Re: [PATCH 3/3] arm64: dts: qcom: sc7180: Delete charger thermal
 zone and ADC channel for lazor <= rev3
Message-ID: <YDaI7RZLb0r/MfwM@google.com>
References: <20210219181032.1.I23e12818c4a841ba9c37c60b3ba8cfeeb048285f@changeid>
 <20210219181032.3.Ia4c1022191d09fe8c56a16486b77796b83ffcae4@changeid>
 <161402520418.1254594.7435679604383921403@swboyd.mtv.corp.google.com>
 <YDQWVresOGZGLL6N@google.com>
 <161402672369.1254594.14091287979440332862@swboyd.mtv.corp.google.com>
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On Mon, Feb 22, 2021 at 12:45:23PM -0800, Stephen Boyd wrote:
> 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@chromium.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?

Yes, that would work. I also deleted the ADC/TM nodes to remove the bogus
temperature completely from the system, but one could argue that it does
no harm to keep it as long as it isn't used.