Comment 46 for bug 755841

I spent a couple of days trying to understand what could be wrong with the algorithm I described. There could be two things:
1. MI_LOAD_REGISTER_IMM is not allowed (that's why I cannot set DE_LOAD_SL register) and this operation is converted to NOOP.
2. For the same reason, I cannot unmask VBLANK bit in DERRMR register.

I believe that MI_WAIT_FOR_EVENT works properly because it really locks the GPU while waiting for event which never happens (and I get slide-show but without tearing!)
Thus, I think that it may require to modify both user-space driver and kernel driver. But I still haven't found if it is possible to do MI_LOAD_REGISTER_IMM inside the batch buffer (it should be, but I cannot check if it works).
Sorry, I really have not enough time for this because of my main job.
In addition, Chris Wilson has dissapeared unexpectedly, a person who may help.