Re: [PATCH RESEND v2 08/12] dt-bindings: add binding for generic eDP panel

Thierry Reding
2019-02-04T16:27:19Z

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On Mon, Feb 04, 2019 at 08:11:05AM -0800, Vasily Khoruzhick wrote:
> On Mon, Feb 4, 2019 at 12:24 AM Thierry Reding <thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > >
> > > Pinebook used several 768p panels that have slightly different timings
> > > and recent batch uses 1080p panel.
> > >
> > > What panel descriptor should I use as fallback?
> >
> > You don't use panel descriptors as fallback. The simple-panel driver
> > will bind to a panel device and use the corresponding descriptor. If
> > your device tree contains the correct information, the descriptor is
> > correct for the panel you have.
> >
> > In other words you need to ensure that you have the correct panel in
> > device tree for the board that you're using. This is exactly the same
> > thing as for other devices.
> >
> > One way to to this is to have separate device trees for each variant
> > of the board that you want to support. Another variant may be to have
> > a common device tree and then have some early firmware update the DTB
> > with the correct panel information.
>
> That defeats the purpose of using eDP panels. Panel can identify
> itself and report what timings it supports.
>
> If we use separate DTBs then users will have to figure out what panel
> is installed in their hardware and use appropriate software image -
> that's something I'd like to avoid.
>
> I can add a descriptor for something like "pinebook eDP panel" if it
> works for you, but it won't have any display timings in it.

I'd like to point you to this:

http://sietch-tagr.blogspot.com/2016/04/display-panels-are-not-special.html

it addresses some of your questions. Hopefully that will also help you
understand that this isn't only about display timings.

Thierry