Date:   Wed, 12 Jun 2019 17:34:23 +0200
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Torsten Duwe <duwe@....de>
Cc:     Harald Geyer <harald@...ib.org>,
        Vasily Khoruzhick <anarsoul@...il.com>,
        Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Icenowy Zheng <icenowy@...c.io>,
        Sean Paul <seanpaul@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        devicetree <devicetree@...r.kernel.org>,
        arm-linux <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 7/7] arm64: dts: allwinner: a64: enable ANX6345 bridge
 on Teres-I

On Fri, Jun 07, 2019 at 11:40:30AM +0200, Torsten Duwe wrote:
> On Fri, Jun 07, 2019 at 08:28:02AM +0200, Maxime Ripard wrote:
> > On Thu, Jun 06, 2019 at 03:59:27PM +0200, Harald Geyer wrote:
> > >
> > > If think valid compatible properties would be:
> > > compatible = "innolux,n116bge", "simple-panel";
> > > compatible = "edp-connector", "simple-panel";
> >
> > A connector isn't a panel.
> >
> > > compatible = "innolux,n116bge", "edp-connector", "simple-panel";
> >
> > And the innolux,n116bge is certainly not a connector either.
> >
> > > compatible = "edp-connector", "innolux,n116bge", "simple-panel";
> > >
> > > I can't make up my mind which one I prefere. However neither of these
> > > variants requires actually implmenting an edp-connector driver.
> >
> > No-one asked to do an edp-connector driver. You should use it in your
> > DT, but if you want to have some code in your driver that parses the
> > DT directly, I'm totally fine with that.
>
> I must admit I fail to understand what that extra node would be good for.
> Logically, the eDP far side is connected to the well-known n116bge.
> Inside the laptop case it might as well be a flat ribbon cable or
> soldered directly.
> In good intention, that's all I wanted to express in the DT. I don't
> know whether the relevant mechanical dimensions of the panel and the
> connector are standardised, so whether one could in theory assemble it
> with a different panel than the one it came with.

Because the panel that comes with the Teres-I is always the
same. However, that's not true for all the devices out there using the
bridge, starting with the pinebook.

> OTOH, as I checked during the discussion with anarsoul, the panel's
> supply voltage is permanently connected to the main 3.3V rail.

Again, that may be the case on the Teres-I, but not necessarily on
other boards.

> We already agreed that the eDP output port must not neccessarily be
> specified, this setup is a good example why: because the panel is
> always powered, the anx6345 can always pull valid EDID data from it
> so at this stage there's no need for any OS driver to reach beyond
> the bridge. IIRC even the backlight got switched off for the blank
> screen without.

That's not really the outcome of the discussion we had here though:
https://patchwork.freedesktop.org/patch/305035/

> All I wanted to say is that "there's usually an n116bge behind it";
> but this is mostly redundant.
>
> So, shall we just drop the output port specification (along with the
> panel node) in order to get one step further?

Depending on the outcome of the discussion above, yes or no :)

Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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