linux-kernel - Re: [RFC PATCH v3 4/5] arm64: dts: mediatek: mt8173-elm-hana: Mark touchscreens and trackpads as fail

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Message-ID: <CAGXv+5G5fFTv8zn=YamSdccjuYemE5oKBqjb8CSyGzu9aMJ0eg@mail.gmail.com>
Date:   Wed, 6 Dec 2023 10:55:44 +0800
From:   Chen-Yu Tsai <wenst@...omium.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     Doug Anderson <dianders@...omium.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Wolfram Sang <wsa@...nel.org>,
        Benson Leung <bleung@...omium.org>,
        Tzung-Bi Shih <tzungbi@...nel.org>,
        chrome-platform@...ts.linux.dev, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Johan Hovold <johan@...nel.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        andriy.shevchenko@...ux.intel.com, Jiri Kosina <jikos@...nel.org>,
        linus.walleij@...aro.org, broonie@...nel.org,
        gregkh@...uxfoundation.org, hdegoede@...hat.com,
        james.clark@....com, james@...iv.tech, keescook@...omium.org,
        rafael@...nel.org, tglx@...utronix.de,
        Jeff LaBundy <jeff@...undy.com>, linux-input@...r.kernel.org,
        linux-i2c@...r.kernel.org
Subject: Re: [RFC PATCH v3 4/5] arm64: dts: mediatek: mt8173-elm-hana: Mark
 touchscreens and trackpads as fail

On Tue, Dec 5, 2023 at 6:22 PM AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com> wrote:
>
> Il 04/12/23 17:50, Doug Anderson ha scritto:
> > Hi,
> >
> > On Sun, Dec 3, 2023 at 10:59 PM Chen-Yu Tsai <wenst@...omium.org> wrote:
> >>
> >> On Sat, Dec 2, 2023 at 8:58 AM Doug Anderson <dianders@...omium.org> wrote:
> >>>
> >>> Hi,
> >>>
> >>> On Tue, Nov 28, 2023 at 12:45 AM Chen-Yu Tsai <wenst@...omium.org> wrote:
> >>>>
> >>>> @@ -44,6 +46,7 @@ trackpad2: trackpad@2c {
> >>>>                  reg = <0x2c>;
> >>>>                  hid-descr-addr = <0x0020>;
> >>>>                  wakeup-source;
> >>>> +               status = "fail-needs-probe";
> >>>
> >>> While doing this, you could also remove the hack where the trackpad
> >>> IRQ pinctrl is listed under i2c4.
> >>
> >> Sure. I do think we can do away with it though. According to at least one
> >> schematic, the interrupt line has pull-ups on both sides of the voltage
> >> shifter.
> >>
> >> BTW, The touchscreen doesn't have pinctrl entries. This has pull-ups on
> >> both sides of the voltage shifter as well.
> >
> > I dunno if the convention is different on Mediatek boards, but at
> > least on boards I've been involved with in the past we've always put
> > pinctrl entries just to make things explicit. This meant that we
> > didn't rely on the firmware/bootrom/defaults to leave pulls in any
> > particular state. ...otherwise those external pull-ups could be
> > fighting with internal pull-downs, right?
> >
>
> MediaTek boards aren't special and there's no good reason for those to rely on
> firmware/bootrom/defaults - so there is no good reason to avoid declaring any
> relevant pinctrl entry.

I think this should be migrated to use the proper GPIO bindings: the
GPIO_PULL_UP / GPIO_PULL_DOWN / GPIO_BIAS_DISABLE flags.

But that's a different discussion.

ChenYu