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

[Maxime Ripard]

On Tue, May 28, 2024 at 01:39:52PM GMT, Arnaud Vrac wrote:
> 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.

Sure, that's what I meant. We need to make sure the binding is
extensible enough / take all the possibilities into account, but the
driver can definitely be minimal.

Maxime
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