Comment # 15 on bug 1129027 from Takashi Iwai

A good catch!  This is likely the cause, indeed.

Although the upstream developer claims that it should be fixed in X modesetting
driver side, I find it's safer to revert the commit for now to make things
working, at least.

I'm building a test kernel in OBS home:tiwai:bsc1129027 repo.  Could you give
it a try once when the build finishes?