Re: [PATCH 08/13] drm/i915/bdw: poll semaphores

Ville Syrjälä
2014-02-24T13:06:17Z

On Wed, Feb 19, 2014 at 10:19:21PM -0800, Ben Widawsky wrote:
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
> drivers/gpu/drm/i915/intel_ringbuffer.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 3d5dd4a..5f7bee8 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -813,6 +813,7 @@ gen8_ring_sync(struct intel_ring_buffer *waiter,
>
> intel_ring_emit(waiter, MI_SEMAPHORE_WAIT |
> MI_SEMAPHORE_GLOBAL_GTT |
> + MI_SEMAPHORE_POLL |

I discussed this on irc w/ Ben, and I was suggesting we don't need to
poll. Polling apparently can be used as a workaround for certain
hardware issues, but it looks like those issues shouldn't affect us,
for the momemnt at least. So my suggestion was to try w/o polling first
(since there could be some power cost to polling) and add the poll bit
if problems arise.

> MI_SEMAPHORE_SAD_GTE_SDD);
> intel_ring_emit(waiter, seqno);
> intel_ring_emit(waiter,
> --
> 1.9.0

--
Ville Syrjälä
Intel OTC