Comment 34 for bug 1243261

Retesting with latest drm-intel-nightly from http://cgit.freedesktop.org/~danvet/drm-intel/ might be worth a shot, we've recently fixed a few things for audio-over-hdmi.

Otherwise I'd report this on the kernel bugzillal (bugs.kernel.org) against alsa sound drivers. Since it works with other sound modules there's a good chance it's a kernel issue.