Hi!

On Fri, Jun 28, 2019 at 12:39:32PM +0200, Andrzej Hajda wrote:
> On 12.06.2019 17:20, Maxime Ripard wrote:
> >> I am not sure if I understand whole discussion here, but I also do not
> >> understand whole edp-connector thing.
> > The context is this one:
> > https://patchwork.freedesktop.org/patch/257352/?series=51182&rev=1
> > https://patchwork.freedesktop.org/patch/283012/?series=56163&rev=1
> > https://patchwork.freedesktop.org/patch/286468/?series=56776&rev=2
> >
> > TL;DR: This bridge is being used on ARM laptops that can come with
> > different eDP panels. Some of these panels require a regulator to be
> > enabled for the panel to work, and this is obviously something that
> > should be in the DT.
> >
> > However, we can't really describe the panel itself, since the vendor
> > uses several of them and just relies on the eDP bus to do its job at
> > retrieving the EDIDs. A generic panel isn't really working either
> > since that would mean having a generic behaviour for all the panels
> > connected to that bus, which isn't there either.
> >
> > The connector allows to expose this nicely.
>
> As VESA presentation says[1] eDP is based on DP but is much more
> flexible, it is up to integrator (!!!) how the connection, power
> up/down, initialization sequence should be performed. Trying to cover
> every such case in edp-connector seems to me similar to panel-simple
> attempt failure. Moreover there is no such thing as physical standard
> eDP connector. Till now I though DT connector should describe physical
> connector on the device, now I am lost, are there some DT bindings
> guidelines about definition of a connector?

This might be semantics but I guess we're in some kind of grey area?

Like, for eDP, if it's soldered I guess we could say that there's no
connector. But what happens if for some other board, that signal is
routed through a ribbon?

You could argue that there's no physical connector in both cases, or
that there's one in both, or one for the ribbon and no connector for
the one soldered in.

> Maybe instead of edp-connector one would introduce integrator's specific
> connector, for example with compatible "olimex,teres-edp-connector"
> which should follow edp abstract connector rules? This will be at least
> consistent with below presentation[1] - eDP requirements depends on
> integrator. Then if olimex has standard way of dealing with panels
> present in olimex/teres platforms the driver would then create
> drm_panel/drm_connector/drm_bridge(?) according to these rules, I guess.
> Anyway it still looks fishy for me :), maybe because I am not
> familiarized with details of these platforms.

That makes sense yes

Maxime

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