[Intel-gfx] HDMI problems when using a A/V receiver

[linux at clnt.de]

some minor update:
it looks like as soon as kms get's activated during boot there is no
picture anymore when the A/V-receiver is between PC and TV (or a
projector which I connected for testing but which has the same
behaviour...).
According to OSD of the projector the PC generates 1280x720 (which
sounds correct) and audio via HDMI is also working fine but the image is
just black...
For testing I disabled kms with the effect that the console is working
fine. But X is longer working since the intel x-server requires kms.
When I reload the i915-module with modeset=1 and start X there is no
picture anymore... (again: PC directly connected to TV or projector is
working fine).
Any idea is highly welcome...
Best regards,
Joerg