Re: [PATCHv2] dt-bindings: dp-connector: add binding for DisplayPort connector

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Sep 17, 2020 at 08:52:10AM +0300, Tomi Valkeinen wrote:
> Add binding for DisplayPort connector. A few notes:
> 
> * Similar to hdmi-connector, it has hpd-gpios as an optional property,
>   as the HPD could also be handled by, e.g., the DP bridge.
> 
> * dp-pwr-supply, which provides 3.3V on DP_PWR pin, is optional, as it
>   is not strictly required: standard DP cables do not even have the pin
>   connected.
> 
> * Connector type. Full size and mini connectors are identical except for
>   the connector size and form, so I believe there is no functional need
>   for this property. But similar to 'label' property, it might be used
>   to present information about the connector to the userspace.
> 
> * No eDP. There's really no "eDP connector", as it's always a custom
>   made connection between the DP and the DP panel. So possibly there is
>   no need for edp-connector binding, but even if there is, I don't want
>   to guess what it could look like, and could it be part of the
>   dp-connector binding.
> 
> * No DP++. I'm not familiar with DP++, but I think it's all handled by
>   the DP bridge, and does not need any new properties to the dp-connector.

You might need an i2c bus for this. It's up to the source device
to either hook up just AUX CH, or both AUX CH and DDC to a DP++
connector. If just AUX CH is wired up you are limited to using
only type2 DP dual mode adapters, whereas if you also have DDC
the crappier type1 adapters will also work.

I guess it's possible some bridges might handle all that for you.
But eg. on i915 we always set up both AUX CH and DDC, and some
extra circuitry on the board will isolate one or the other
depending on what kind of dongle/cable gets plugged in
(identified via the CONFIG pins).

-- 
Ville Syrjälä
Intel