Hi Maxime,

It seems I have missed your response.

On 12.06.2019 17:20, Maxime Ripard wrote:

quoted

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?

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.

[1]: https://www.vesa.org/wp-content/uploads/2010/12/DisplayPort-DevCon-Presentation-eDP-Dec-2010-v3.pdf

quoted

According to VESA[1] eDP is "Internal display interface" - there is no
external connector for eDP, the way it is connected is integrator's
decision, but it is fixed - ie end user do not plug/unplug it.

I'm not sure if you mean DRM or DT connector here though. In DRM,
we're doing this all the time for panels. I'm literaly typing this
from a laptop that has a screen with an eDP connector.

VESA describes only hardware, but since DT also describes hardware I
guess it should be similar.


Regards

Andrzej

Maxime

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

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