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

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Message-ID: <CAPY8ntDdcOXuWVgx6+cbgX5ct_-MXcE7CWDKgGP57EX6bvBLaw@mail.gmail.com>
Date: Wed, 18 Dec 2024 14:52:04 +0000
From: Dave Stevenson <dave.stevenson@...pberrypi.com>
To: Maxime Ripard <mripard@...nel.org>
Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, Maíra Canal <mcanal@...lia.com>, 
	Raspberry Pi Kernel Maintenance <kernel-list@...pberrypi.com>, Andrzej Hajda <andrzej.hajda@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Jaroslav Kysela <perex@...ex.cz>, 
	Takashi Iwai <tiwai@...e.com>, Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>, 
	Phong LE <ple@...libre.com>, Inki Dae <inki.dae@...sung.com>, 
	Seung-Woo Kim <sw0312.kim@...sung.com>, Kyungmin Park <kyungmin.park@...sung.com>, 
	Krzysztof Kozlowski <krzk@...nel.org>, Alim Akhtar <alim.akhtar@...sung.com>, 
	Russell King <linux@...linux.org.uk>, Chun-Kuang Hu <chunkuang.hu@...nel.org>, 
	Philipp Zabel <p.zabel@...gutronix.de>, Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Sandy Huang <hjc@...k-chips.com>, 
	Heiko Stübner <heiko@...ech.de>, 
	Andy Yan <andy.yan@...k-chips.com>, Alain Volmat <alain.volmat@...s.st.com>, 
	Raphael Gallais-Pou <rgallaispou@...il.com>, Jani Nikula <jani.nikula@...ux.intel.com>, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	linux-sound@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-samsung-soc@...r.kernel.org, linux-mediatek@...ts.infradead.org, 
	linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v7 00/10] drm: add DRM HDMI Codec framework

Hi Maxime & Dmitry

On Wed, 18 Dec 2024 at 07:59, Maxime Ripard <mripard@...nel.org> wrote:
>
> On Wed, Dec 18, 2024 at 07:24:23AM +0200, Dmitry Baryshkov wrote:
> > On Tue, 17 Dec 2024 at 19:21, Maxime Ripard <mripard@...nel.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?

I'm on it.

  Dave

> Maxime