[Intel-gfx] [PATCH] drm/i915: Set DERRMR around batches required vblank events

[Chris Wilson]

On Thu, 26 Jul 2012 21:30:19 +0100, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> In order for the Display Engine to send messages to the Render Engine,
> that event must be unmasked in the Display Engine Render Response Mask
> Register (DERRMR). By default all events are masked to prevent unwanted
> messages to conserve power, and it is strongly recommended that only
> single events be unmasked at any time. So in order to pipeline the
> register writes around individual batchbuffers, userspace must notify
> the kernel when it requires a vblank event, this patch implements an
> interface to do so with an single (pipe, event) request through the
> execbuffer flags.
> 
> Note that another workaround is required for IVB, in that we must also
> prevent RC6 sleeps whilst waiting upon an event. To do that we also
> pipeline a forcewake into the second MT slot.

Anyone have any criticisms for this patch?
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre