Re: [PATCH v7 00/10] drm: add DRM HDMI Codec framework

[Maxime Ripard <mripard@kernel.org>]

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On Wed, Dec 18, 2024 at 07:24:23AM +0200, Dmitry Baryshkov wrote:
> On Tue, 17 Dec 2024 at 19:21, Maxime Ripard <mripard@kernel.org> wrote:
> > On Tue, Dec 17, 2024 at 02:40:22AM +0200, Dmitry Baryshkov wrote:
> > > While porting lt9611 DSI-to-HDMI bridge driver to use HDMI Connector
> > > framework, I stumbled upon an issue while handling the Audio InfoFrames.
> > > The HDMI codec callbacks weren't receiving the drm_atomic_state, so
> > > there was no simple way to get the drm_connector that stayed at the end
> > > of the bridge chain. At the same point the drm_hdmi_connector functions
> > > expected to get drm_connector instance.
> > >
> > > While looking for a way to solve the issue, I stumbled upon several
> > > deficiencies in existing hdmi_codec_ops implementations. Only few of the
> > > implementations were able to handle codec's 'plugged' callback. One
> > > third of the drivers didn't implement the get_eld() callback.
> > >
> > > Most of the issues can be solved if drm_connector handles
> > > hdmi-audio-codec on its own, delegating functionality to the actual
> > > implementation, be it a driver that implements drm_connector or
> > > drm_bridge.
> > >
> > > Implement such high-level framework, adding proper support for Audio
> > > InfoFrame generation to the LT9611 driver.
> > >
> > > Several design decisions to be kept in mind:
> > >
> > > - drm_connector_hdmi_codec is kept as simple as possible. It implements
> > >   generic functionality (ELD, hotplug, registration).
> > >
> > > - drm_hdmi_connector sets up HDMI codec device if the connector
> > >   is setup correspondingly (either I2S or S/PDIF is marked as
> > >   supported).
> > >
> > > - drm_bridge_connector provides a way to link HDMI audio codec
> > >   funcionality in the drm_bridge with the drm_connector_hdmi_codec
> > >   framework.
> > >
> > > - It might be worth reverting the no_i2s_capture / no_spdif_capture
> > >   bits. Only TDA889x driver sets them, while it's safe to assume that
> > >   most of HDMI / DP devices do not support ARC / capture. I think the
> > >   drivers should opt-in capture support rather than having to opt-out of
> > >   it.
> >
> > Sorry if this isn't clear to me and I'm quite late to the party, but did
> > you test this on vc4 with both a pi3 and pi4, or was it just compile
> > tested?
> 
> LT9611 is actually tested, VC4 is only compile-tested. Should I put an RFT tag?

Yeah, we definitely need to test it on the pi3 (polling-based) and the
pi4 (irq-based) at least.

Dave, Maira, could you give it a try?

Maxime

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