I've got a GT240 NVidia card and PCM HDMI audio is limited to two channels with kernel 2.6.37. Other NVidia cards are probably affected as well. Reverting http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=53d7d69d8ffdfa60c5b66cc2e9ee0774aaaef5c0 make things going back to normal.
Fixed in sound git tree. The patch is attached below.
Created attachment 46852 [details] Fix patch
Handled-By : Takashi Iwai <tiwai@suse.de> Patch : https://bugzilla.kernel.org/attachment.cgi?id=46852
merged for .38-rc5: commit 11839aed21881d7edd65dd79f22a8eb18426f672 Author: Takashi Iwai <tiwai@suse.de> Date: Tue Feb 8 17:25:49 2011 +0100 ALSA: hda - Fix missing CA initialization for HDMI/DP
Any chance this issue was re-introduced? I'm running Ubuntu 13.10 and after latest updates I no longer get 5.1 sound only 2 channel. I've swapped hardware to confirm it is not the card. Changed drivers etc nothing seems to work. How do go about confirm if this is the same issue or a new bug? Thanks Andrew