[PATCH v1] drm/bridge: simple-bridge: Add support for TI TDP158

[Arnaud Vrac]

On 28/05/2024 11:17, Maxime Ripard wrote:
> On Tue, May 28, 2024 at 10:05:50AM GMT, Arnaud Vrac wrote:
>> On 28/05/2024 09:43, Maxime Ripard wrote:
>>> Hi,
>>>
>>> On Mon, May 27, 2024 at 06:03:56PM GMT, Marc Gonzalez wrote:
>>>> From: Arnaud Vrac <avrac at freebox.fr>
>>>>
>>>> The TI TDP158 is an AC-Coupled HDMI signal to TMDS Redriver supporting
>>>> DVI 1.0 and HDMI 1.4b and 2.0b output signals.
>>>>
>>>> Since it's an I2C-programmable bridge, it could have a proper driver,
>>>> but the default settings work fine, thus simple bridge is sufficient.
>>>
>>> No it doesn't. That bridge supports HDMI 2.0 which means you'll need to
>>> change the TMDS clock ratio when programming a TMDS character rate
>>> higher than 340MHz. And you'll need hotplug support to deal with it
>>> properly too.
>>>
>>> So sorry, you need a real driver there.
>>
>> Hello, this is an HDMI redriver, which simply cleans up the HDMI
>> signal, so no programming is needed to support HDMI 2.0.
> 
> I mean, if I'm to trust the datasheet, it is more complicated than that.
> It snoops the DDC bus so it can update the TMDS clock ratio bit if it's
> sent on its input side, but that wouldn't happen with DP for example.
> 

That's a use case we can't test and will never use as a device integrator, unfortunately.

To support our simple HDMI redriver use case, would it be ok to write a driver just handling power up with documented bindings with the chip default settings ? Someone with an actual need for more specific setups could then implement the additional code needed to support that. The bindings could be extended without breaking compatibility.

Regards,
-Arnaud