On Wed, 14 Nov 2012 09:15:14 +0000
Chris Wilson <chris at chris-wilson.co.uk> wrote:
> The bspec was recently updated to remove the ability to update the
> semaphore using the MI_SEMAPHORE_BOX command, the ability to wait upon
> the semaphore value remained. Instead the advice is to update the
> register using the MI_LOAD_REGISTER_IMM command. In cursory testing,
> semaphores continue to function - the question is whether this fixes
> some of the deadlocks where the semaphore registers contained stale
> values?
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Daniel J Blueman <daniel at quora.org>
Reviewed-by: Ben Widawsky <ben at bwidawsk.net>
> ---
> drivers/gpu/drm/i915/intel_ringbuffer.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index ee4abc5..dd2e7db 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -554,12 +554,9 @@ update_mboxes(struct intel_ring_buffer *ring,
> u32 seqno,
> u32 mmio_offset)
> {
> - intel_ring_emit(ring, MI_SEMAPHORE_MBOX |
> - MI_SEMAPHORE_GLOBAL_GTT |
> - MI_SEMAPHORE_REGISTER |
> - MI_SEMAPHORE_UPDATE);
> - intel_ring_emit(ring, seqno);
> + intel_ring_emit(ring, MI_LOAD_REGISTER_IMM(1));
> intel_ring_emit(ring, mmio_offset);
> + intel_ring_emit(ring, seqno);
> }
>
> /**
--
Ben Widawsky, Intel Open Source Technology Center
