drm/radeon: HDMI broken on non-default resolutions by 1c3439f: update modesetting

[Matthijs Kooijman]

Hi folks,

I'm using some evergreen systems with HDMI output, which got broken by a
recent commit. In commit 1c3439f (drm/radeon/hdmi: update modesetting),
the HDMI_ACR_SOURCE bit is set in the HDMI_ACR_PACKET_CONTROL register.

However, setting this bit breaks my HDMI audio when a non-default
resolution is used. This problem only occurs on some TV's (it's broken
on a Philips, Sharp and Sony TV and seems to be working on a few LG
TV's).

On the Sony, there are short pulses of distorted audio (couple of
hundred ms audio, then half a second or so silence, then some audio
again, etc.). On the Philips and Shart TV's, the audio is completely
muted.

It seems setting this bit causes the audio infoframe timings to be
controlled by software instead. I suspect that the timings are not
properly (re)calculated when a non-default resolution is used, causing
the audio to break.

Alex Deucher mentioned on IRC that the proper timing code needs to be
ported over. I might have a look at that, if I can find enough time and
understanding, but that might take a while. Would it make sense to
disable this particular bit for the time being, to make audio working
again? Is there any particular reason to not keep the bit disabled and
let the timings be determined by the hardware in any case?

Gr.

Matthijs
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