Re: No audio from HDMI (MCP89 / Geforce 320M): Reason: no connected devices detected
Could I please prevail upon you to test a few things so that I better understand your problems and can help others with similar issues better:
Can you please describe how you have your receiver, AV processor, and TV connected together (i.e. what order they're in from PC to TV, what connectors are used, etc.).
Could you please capture the EDID that our driver is seeing, using nvidia-settings as I described above, with the receiver both in "bypass mode" and not, i.e. the original configuration.
I see the following in your kernel log:
hda_intel: Disable MSI for Nvidia chipset
I believe this means that you don't need to add "enable_msi=0" to alsa-base.conf. Can you please try removing this option, rebooting, and see if everything still works fine.
Could you possibly check which combinations of probe_mask=0xffff,0xfff2, the updated asound.conf/HDA-intel.conf, and bypass mode on your receiver you need (try reverting each change individually). It's possible that only 1 or 2 of these things are needed, and the other is a red herring.
Thanks very much for any information at all you can provide!