[Intel-gfx] [PATCH 1/3] uxa: Don't emit PIPE_CONTROLs in an empty batch.

[Chris Wilson]

On Thu, Mar 06, 2014 at 01:12:30PM -0800, Kenneth Graunke wrote:
> The first call to BEGIN_BATCH or BEGIN_BATCH_BLT will set current_batch
> to RENDER_BATCH or BLT_BATCH.  If it's zero, that means the batch is
> empty, so there's no point in flushing.
> 
> Previously, we would just go ahead and do a RENDER_RING flush, though
> more by accident than intentional design.

It was intentional. One code path required us to emit an empty batch -
except that we don't allow such and so had to emit a flush instead.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre