linux-kernel - Re: [v2 1/3] arm64: dts: qcom: sc7280: herobrine: Add pinconf settings for mi2s1

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Date:   Fri, 20 May 2022 13:39:21 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Andy Gross <agross@...nel.org>,
        Judy Hsiao <judyhsiao@...omium.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Srini Kandagatla <srinivas.kandagatla@...aro.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Jimmy Cheng-Yi Chiang <cychiang@...gle.com>,
        Judy Hsiao <judyhsiao@...gle.com>,
        Tzung-Bi Shih <tzungbi@...omium.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [v2 1/3] arm64: dts: qcom: sc7280: herobrine: Add pinconf
 settings for mi2s1

Hi,

On Fri, May 20, 2022 at 1:38 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Judy Hsiao (2022-05-20 09:10:02)
> > 1. Add drive strength property for mi2s1 on sc7280 based platforms.
> > 2. Disbale the pull-up mi2s1_data0, mi2s1_sclk.
>
> s/Disbale/Disable/
>
> The commit text is a list of things done but no reason why they're done.
> I'd appreciate more freeform text with a blurb why a drive strength is
> chosen and why pulls are disabled.
>
> > Signed-off-by: Judy Hsiao <judyhsiao@...omium.org>
> > ---
> >  arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi b/arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi
> > index 9cb1bc8ed6b5..6d8744e130b0 100644
> > --- a/arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/sc7280-herobrine.dtsi
> > @@ -612,6 +612,20 @@ &dp_hot_plug_det {
> >         bias-disable;
> >  };
> >
> > +&mi2s1_data0 {
> > +       drive-strength = <6>;
> > +       bias-disable;
>
> Is there an external pull on this line?
>
> > +};
> > +
> > +&mi2s1_sclk {
> > +       drive-strength = <6>;
> > +       bias-disable;
>
> Is there an external pull on this line? If so please add that details as
> a comment like we do for other external pulls.

Actually, I think they are output lines, which is why they have a
drive-strength. I think for output lines we don't usually comment
about why we're disabling the pulls, only for input lines?

-Doug