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 14:05:44 -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 2:01 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Doug Anderson (2022-05-20 13:39:21)
> > On Fri, May 20, 2022 at 1:38 PM Stephen Boyd <swboyd@...omium.org> wrote:
> > >
> > > Quoting Judy Hsiao (2022-05-20 09:10:02)
> > > > +};
> > > > +
> > > > +&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?
>
> Ok makes sense. Even for an open drain signal it would be an "input" so
> that rule still applies?

I think open drain is mostly used for bidirectional signals, like i2c
lines. In that case then you're right, you can have a drive-strength
and a pull. ...I thought i2s was not bidirectoinal and not open-drain,
but I certainly could be wrong.

-Doug