drm/i915: Add early exit to execbuff_final() if insufficient ring space

One of the major purposes of the GPU scheduler is to avoid stalling
the CPU when the GPU is busy and unable to accept more work. This
change adds support to the ring submission code to allow a ring space
check to be performed before attempting to submit a batch buffer to
the hardware. If insufficient space is available then the scheduler
can go away and come back later, letting the CPU get on with other
work, rather than stalling and waiting for the hardware to catch up.

v3: Updated to use locally cached request pointer.

v4: Line wrapped some comments differently to keep the style checker
happy. Downgraded a BUG_ON to a WARN_ON as the latter is preferred.

Removed some obsolete, commented out code.

v6: Updated to newer nightly (lots of ring -> engine renaming).

Updated to use 'to_i915()' instead of dev_private. [review feedback
from Joonas Lahtinen]

For: VIZ-1587
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>

0 files changed, 0 insertions, 0 deletions