linux-kernel - Re: [PATCH v2 1/6] dt-bindings: drm/panel-simple: Introduce generic eDP panels

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Message-ID: <CAD=FV=U63qGf+RTOe=X+BYK06OuJM5N5Vy6zcA8+7ka1CFLwcg@mail.gmail.com>
Date:   Mon, 9 Aug 2021 15:20:43 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Daniel Vetter <daniel@...ll.ch>,
        Thierry Reding <thierry.reding@...il.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Sam Ravnborg <sam@...nborg.org>,
        David Airlie <airlied@...ux.ie>,
        Linus W <linus.walleij@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Steev Klimaszewski <steev@...i.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH v2 1/6] dt-bindings: drm/panel-simple: Introduce generic
 eDP panels

Hi,

On Mon, Aug 2, 2021 at 6:39 AM Rob Herring <robh@...nel.org> wrote:
>
> On Fri, 30 Jul 2021 14:26:20 -0700, Douglas Anderson wrote:
> > eDP panels generally contain almost everything needed to control them
> > in their EDID. This comes from their DP heritage were a computer needs
> > to be able to properly control pretty much any DP display that's
> > plugged into it.
> >
> > The one big issue with eDP panels and the reason that we need a panel
> > driver for them is that the power sequencing can be different per
> > panel.
> >
> > While it is true that eDP panel sequencing can be arbitrarily complex,
> > in practice it turns out that many eDP panels are compatible with just
> > some slightly different delays. See the contents of the bindings file
> > introduced in this patch for some details.
> >
> > The fact that eDP panels are 99% probable and that the power
> > sequencing (especially power up) can be compatible between many panels
> > means that there's a constant desire to plug multiple different panels
> > into the same board. This could be for second sourcing purposes or to
> > support multiple SKUs (maybe a 11" and a 13", for instance).
> >
> > As discussed [1], it should be OK to support this by adding two
> > properties to the device tree to specify the delays needed for
> > powering up the panel the first time. We'll create a new "edp-panel"
> > bindings file and define the two delays that might need to be
> > specified. NOTE: in the vast majority of the cases (HPD is hooked up
> > and isn't glitchy or is debounced) even these delays aren't needed.
> >
> > [1] https://lore.kernel.org/r/CAD=FV=VZYOMPwQZzWdhJGh5cjJWw_EcM-wQVEivZ-bdGXjPrEQ@mail.gmail.com
> >
> > Signed-off-by: Douglas Anderson <dianders@...omium.org>
> > ---
> >
> > Changes in v2:
> > - No longer allow fallback to panel-simple.
> > - Add "-ms" suffix to delays.
> >
> >  .../bindings/display/panel/panel-edp.yaml     | 188 ++++++++++++++++++
> >  1 file changed, 188 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/display/panel/panel-edp.yaml
> >
>
> My bot found errors running 'make DT_CHECKER_FLAGS=-m dt_binding_check'
> on your patch (DT_CHECKER_FLAGS is new in v5.13):
>
> yamllint warnings/errors:
>
> dtschema/dtc warnings/errors:
> /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/display/panel/panel-edp.example.dt.yaml: bridge@2d: 'aux-bus' does not match any of the regexes: 'pinctrl-[0-9]+'
>         From schema: /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml
> \ndoc reference errors (make refcheckdocs):
>
> See https://patchwork.ozlabs.org/patch/1511822
>
> This check can fail if there are any dependencies. The base for a patch
> series is generally the most recent rc1.

I think it's a dependency problem. No hits here:

git grep aux-bus v5.14-rc5 -- Documentation/devicetree/bindings/

...but I get hits against "linuxnext". Rob: I'm hoping that this can
still be in your queue for review even with the bot warning. Thanks!
:-)

-Doug