linux-kernel - Re: [PATCH 2/3] arm64: dts: qcom: pm8998: Add adc node

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Message-ID: <20180906203615.GD22824@google.com>
Date:   Thu, 6 Sep 2018 13:36:15 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "open list:ARM/QUALCOMM SUPPORT" <linux-soc@...r.kernel.org>,
        devicetree@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Siddartha Mohanadoss <smohanad@...eaurora.org>,
        Jonathan Cameron <jic23@...nel.org>
Subject: Re: [PATCH 2/3] arm64: dts: qcom: pm8998: Add adc node

On Thu, Sep 06, 2018 at 11:34:32AM -0700, Doug Anderson wrote:
> Hi,
> 
> On Mon, Aug 27, 2018 at 10:10 AM, Matthias Kaehlcke <mka@...omium.org> wrote:
> > On Fri, Aug 10, 2018 at 05:09:17PM -0700, Doug Anderson wrote:
> >> Hi,
> >>
> >> On Wed, Aug 8, 2018 at 12:13 PM, Matthias Kaehlcke <mka@...omium.org> wrote:
> >> > This adds the adc node to pm8998 based on the examples in the
> >> > bindings. It also fixes the order of the included headers.
> >> >
> >> > Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> >> > ---
> >> >  arch/arm64/boot/dts/qcom/pm8998.dtsi | 13 ++++++++++++-
> >> >  1 file changed, 12 insertions(+), 1 deletion(-)
> >> >
> >> > diff --git a/arch/arm64/boot/dts/qcom/pm8998.dtsi b/arch/arm64/boot/dts/qcom/pm8998.dtsi
> >> > index 92bed1e7d4bb..f70f6101bceb 100644
> >> > --- a/arch/arm64/boot/dts/qcom/pm8998.dtsi
> >> > +++ b/arch/arm64/boot/dts/qcom/pm8998.dtsi
> >> > @@ -1,8 +1,9 @@
> >> >  // SPDX-License-Identifier: (GPL-2.0+ OR MIT)
> >> >  /* Copyright 2018 Google LLC. */
> >> >
> >> > -#include <dt-bindings/spmi/spmi.h>
> >> > +#include <dt-bindings/iio/qcom,spmi-vadc.h>
> >> >  #include <dt-bindings/interrupt-controller/irq.h>
> >> > +#include <dt-bindings/spmi/spmi.h>
> >> >
> >> >  &spmi_bus {
> >> >         pm8998_lsid0: pmic@0 {
> >> > @@ -11,6 +12,16 @@
> >> >                 #address-cells = <1>;
> >> >                 #size-cells = <0>;
> >> >
> >> > +               pm8998_adc: adc@...0 {
> >> > +                       compatible = "qcom,spmi-adc-rev2";
> >> > +                       reg = <0x3100>;
> >> > +                       interrupts = <0x0 0x31 0x0 IRQ_TYPE_EDGE_RISING>;
> >> > +                       #address-cells = <1>;
> >> > +                       #size-cells = <0>;
> >> > +                       #io-channel-cells = <1>;
> >> > +                       io-channel-ranges;
> >> > +               };
> >>
> >> I'm a little confused about what the "io-channel-ranges" does here.
> >> The documentation isn't clear at all to me for it.  If I'm reading it
> >> right it's also supposed to be for iio-consumers, but you're using it
> >> in a provider.  I see you copied this from the example.  Maybe the
> >> example is wrong?  ...or I'm just confused...
> >
> > Yes, I copied it from the example, its use here is also not clear to
> > me, other ADC providers like adc@...c0000 in exynos3250.dtsi or
> > adc@...a6000 in bcm-cygnus.dtsi also specify it ...
> >
> > Siddartha/Jonathan, could you help to clarify if "io-channel-ranges"
> > should really be specified here as the DT example suggests?
> 
> Does everything work if you just remove the "io-channel-ranges"?

Yes, the ADC channels are still available within the kernel and
through sysfs and provide reasonable values.

> We could remove it and always add it back in later if someone could
> explain what it's for or if we find a reason why it was needed?  ...or
> we have any other ideas for how to get this resolved?  :(

Sounds good, I'll respin with 'io-channel-ranges' removed.