(In reply to comment #31)
> Created attachment 85989 [details] [review] [review]
> testing patch
> 
> Try this patch independent from any other patches.  It forces the engine and
> memory clocks of all performance levels within a power state to the lowest
> level.  If it works, then try and comment out either the sclk part or the
> mclk part and see if either helps.  That should help us narrow down whether
> it's a mclk problem or an sclk problem.

Running with the patch works fine over a vanilla kernel 3.12-rc1. The following
works also fine:
//    if (pl->sclk > 25000)
//        pl->sclk = 25000;
    if (pl->mclk > 15000)
        pl->mclk = 15000;
Which means sclk is working properly.

However, the opposite results in a blank screen before I can even get at the
login screen. It seems mclk is the problematic part.