drm/i915: hide (seqno-1) in ringbuffer code

Waiting for seqno-1 in our object synchronization code is an
implementation detail given how we've decided to do the waits within the
rest of our code.

Requested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ben Widawsky <benjamin.widawsky@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

2 files changed, 7 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 0115b12df573..71934dd0ee43 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2002,7 +2002,7 @@ i915_gem_object_sync(struct drm_i915_gem_object *obj,
         }
 
 
-        ret = to->sync_to(to, from, seqno - 1);
+        ret = to->sync_to(to, from, seqno);
         if (!ret)
                 from->sync_seqno[idx] = seqno;
 
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index dfdb613752c5..467b3319e4bd 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -482,6 +482,12 @@ intel_ring_sync(struct intel_ring_buffer *waiter,
                   MI_SEMAPHORE_COMPARE |
                   MI_SEMAPHORE_REGISTER;
 
+        /* Throughout all of the GEM code, seqno passed implies our current
+         * seqno is >= the last seqno executed. However for hardware the
+         * comparison is strictly greater than.
+         */
+        seqno -= 1;
+
         ret = intel_ring_begin(waiter, 4);
         if (ret)
                 return ret;