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

[Tomi Valkeinen]

On 17/09/2020 14:22, Ville Syrjälä wrote:
> 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.

Ok, thanks for the clarifications on this.

> 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).

Is that automatic on i915? I could imagine a gpio-controlled mux doing the isolation, and then we
need some driver controlling the gpio.

I could add the ddc bus the same way as on hdmi-connector.yaml, but perhaps it's better to leave
that for someone with a DP++ board. Afaics, there should be no problems adding this later.

 Tomi

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