Northern Islands HDMI audio support

Good news Northern Islands users!

Today Linus pulled Dave's drm-fixes tree with one (interesting?) patch from me:
drm/radeon: enable HDMI on DCE5 (AKA NI excluding Aruba)

Unless something really bad happens, starting with kernel 3.5-rc4 you will have NI HDMI audio support in radeon KMS driver :)

Patch is really trivial, it just enables existing Evergreen code for Northern Islands cards. HDMI is almost the same between that two families, so nothing special was needed.

Kernel 3.5 also contains a lot of code rewritten thanks to the info recently released by AMD. It should stabilize HDMI support and hopefully will allow enabling it by default in the near future.

I wish to say here "thanks" once again to the AMD. They donated me with Northern Islands card that allowed me to test the code, fix minor issues and finally enable HDMI support for it. Thanks AMD!

Unfortunately I've also some bad news :( Southern Islands while having (almost?) the same HDMI engines have at the same time different audio engine. I've spent 2 full days analyzing and hacking GPU registers without any success. Enabling HDMI mode works just fine, but audio doesn't play. I'm afraid just watching GPU registers won't allow us to RE audio support. We may need specs which personally I don't expect to see anytime soon, or alternatively we may need some hack to dump MMIO operations done by fglrx.