[PATCH v7] drm/msm/dp: reuse generic HDMI codec implementation

[Dmitry Baryshkov]

On Thu, May 29, 2025 at 10:40:12AM +0800, Xilin Wu wrote:
> On 2025/4/24 01:52:45, Dmitry Baryshkov wrote:
> > From: Dmitry Baryshkov <lumag at kernel.org>
> > 
> > The MSM DisplayPort driver implements several HDMI codec functions
> > in the driver, e.g. it manually manages HDMI codec device registration,
> > returning ELD and plugged_cb support. In order to reduce code
> > duplication reuse drm_hdmi_audio_* helpers and drm_bridge_connector
> > integration.
> > 
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at oss.qualcomm.com>
> > ---
> > A lot of DisplayPort bridges use HDMI Codec in order to provide audio
> > support. Present DRM HDMI Audio support has been written with the HDMI
> > and in particular DRM HDMI Connector framework support, however those
> > audio helpers can be easily reused for DisplayPort drivers too.
> > 
> > Patches by Hermes Wu that targeted implementing HDMI Audio support in
> > the iTE IT6506 driver pointed out the necessity of allowing one to use
> > generic audio helpers for DisplayPort drivers, as otherwise each driver
> > has to manually (and correctly) implement the get_eld() and plugged_cb
> > support.
> > 
> > Implement necessary integration in drm_bridge_connector and provide an
> > example implementation in the msm/dp driver.
> > ---
> > Changes in v7:
> > - Dropped applied patches
> > - Link to v6: https://lore.kernel.org/r/20250314-dp-hdmi-audio-v6-0-dbd228fa73d7@oss.qualcomm.com
> > 
> > Changes in v6:
> > - Added DRM_BRIDGE_OP_DP_AUDIO and separate set of DisplayPort audio
> >    callbacks to the drm_bridge interface (Maxime)
> > - Link to v5: https://lore.kernel.org/r/20250307-dp-hdmi-audio-v5-0-f3be215fdb78@linaro.org
> > 
> > Changes in v5:
> > - Rebased on top of linux-next, also handling HDMI audio piece of the
> >    MSM HDMI driver.
> > - Link to v4: https://lore.kernel.org/r/20250301-dp-hdmi-audio-v4-0-82739daf28cc@linaro.org
> > 
> > Changes in v4:
> > - Rebased on linux-next, adding DRM_BRIDGE_OP_HDMI_AUDIO to Synopsys QP
> >    HDMI driver.
> > - Drop outdated comment regarding subconnector from the commit message.
> > - Link to v3: https://lore.kernel.org/r/20250219-dp-hdmi-audio-v3-0-42900f034b40@linaro.org
> > 
> > Changes in v3:
> > - Dropped DRM_BRIDGE_OP_DisplayPort, added DRM_BRIDGE_OP_HDMI_AUDIO
> >    (Laurent, Maxime)
> > - Dropped the subconnector patch (again)
> > - Link to v2: https://lore.kernel.org/r/20250209-dp-hdmi-audio-v2-0-16db6ebf22ff@linaro.org
> > 
> > Changes in v2:
> > - Added drm_connector_attach_dp_subconnector_property() patches
> > - Link to v1: https://lore.kernel.org/r/20250206-dp-hdmi-audio-v1-0-8aa14a8c0d4d@linaro.org
> > ---
> >   drivers/gpu/drm/msm/Kconfig         |   1 +
> >   drivers/gpu/drm/msm/dp/dp_audio.c   | 131 ++++--------------------------------
> >   drivers/gpu/drm/msm/dp/dp_audio.h   |  27 ++------
> >   drivers/gpu/drm/msm/dp/dp_display.c |  28 ++------
> >   drivers/gpu/drm/msm/dp/dp_display.h |   6 --
> >   drivers/gpu/drm/msm/dp/dp_drm.c     |   8 +++
> >   6 files changed, 31 insertions(+), 170 deletions(-)
> > 
> 
> This change breaks DP audio on the qcs6490 platform, tested on kernel
> next-20250528.

I can not confirm this issue here (though I tested it on a different
hardware). Do you have any patches on top of linux-next?

> 
> [    0.368035] [drm:dpu_kms_hw_init:1173] dpu hardware revision:0x70020000
> [    0.369359] hdmi-audio-codec hdmi-audio-codec.0.auto: hdmi_codec_probe:
> dai_count 0
> [    0.369362] hdmi-audio-codec hdmi-audio-codec.0.auto: hdmi_codec_probe:
> Missing hw_params
> [    0.369364] hdmi-audio-codec hdmi-audio-codec.0.auto: hdmi_codec_probe:
> Invalid parameters
> [    0.369366] hdmi-audio-codec hdmi-audio-codec.0.auto: probe with driver
> hdmi-audio-codec failed with error -22
> [    0.370536] [drm] Initialized msm 1.12.0 for ae01000.display-controller
> on minor 0
> 
> Manually reverting this change solves the problem.

It is suspicious, since dai_count can not be 0. We set
hdmi_audio_max_i2s_playback_channels to 8, which in turn should set the
hdmi_codec_pdata.i2s to 1.

> 
> -- 
> Best regards,
> Xilin Wu <sophon at radxa.com>

-- 
With best wishes
Dmitry