In order to accommodate the requirements of re-enabling FBC after
page-flipping, but to avoid doing so and incurring the cost of a wait
for vblank in the middle of a page-flip sequence, we defer the actual
enablement by 50ms. If any request to disable FBC arrive within that
interval, the enablement is cancelled and we are saved from blocking on
the wait.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NKeith Packard <keithp@keithp.com>