Since requests can no longer be generated as a side-effect of
intel_ring_begin(), we know that the seqno will be unchanged during
ring-emission. This predicatablity then means we do not have to check
for the seqno wrapping around whilst emitting the semaphore for
engine->sync_to().

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem.c         | 13 ++-----
 drivers/gpu/drm/i915/intel_ringbuffer.c | 67 ++++++++++++++-------------------
 drivers/gpu/drm/i915/intel_ringbuffer.h |  5 +--
 3 files changed, 33 insertions(+), 52 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 235a3de6e0a0..b0230e7151ce 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2572,22 +2572,15 @@ __i915_gem_object_sync(struct drm_i915_gem_object *obj,
                i915_gem_object_retire_request(obj, from);
        } else {
                int idx = intel_engine_sync_index(from->engine, to->engine);
-               u32 seqno = i915_gem_request_get_seqno(from);
-
-               if (seqno <= from->engine->semaphore.sync_seqno[idx])
+               if (from->fence.seqno <= 
from->engine->semaphore.sync_seqno[idx])
                        return 0;
 
                trace_i915_gem_ring_sync_to(to, from);
-               ret = to->engine->semaphore.sync_to(to, from->engine, seqno);
+               ret = to->engine->semaphore.sync_to(to, from);
                if (ret)
                        return ret;
 
-               /* We use last_read_req because sync_to()
-                * might have just caused seqno wrap under
-                * the radar.
-                */
-               from->engine->semaphore.sync_seqno[idx] =
-                       
i915_gem_request_get_seqno(obj->last_read_req[from->engine->id]);
+               from->engine->semaphore.sync_seqno[idx] = from->fence.seqno;
        }
 
        return 0;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c 
b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 556e9e2c1fec..d37cdb2f9073 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1384,69 +1384,58 @@ static inline bool i915_gem_has_seqno_wrapped(struct 
drm_i915_private *dev_priv,
  */
 
 static int
-gen8_ring_sync(struct drm_i915_gem_request *waiter_req,
-              struct intel_engine_cs *signaller,
-              u32 seqno)
+gen8_ring_sync(struct drm_i915_gem_request *wait,
+              struct drm_i915_gem_request *signal)
 {
-       struct intel_ring *waiter = waiter_req->ring;
-       struct drm_i915_private *dev_priv = waiter_req->i915;
+       struct intel_ring *waiter = wait->ring;
+       struct drm_i915_private *dev_priv = wait->i915;
        int ret;
 
-       ret = intel_ring_begin(waiter_req, 4);
+       ret = intel_ring_begin(wait, 4);
        if (ret)
                return ret;
 
-       intel_ring_emit(waiter, MI_SEMAPHORE_WAIT |
-                               MI_SEMAPHORE_GLOBAL_GTT |
-                               MI_SEMAPHORE_POLL |
-                               MI_SEMAPHORE_SAD_GTE_SDD);
-       intel_ring_emit(waiter, seqno);
        intel_ring_emit(waiter,
-                       lower_32_bits(GEN8_WAIT_OFFSET(waiter_req->engine,
-                                                      signaller->id)));
+                       MI_SEMAPHORE_WAIT |
+                       MI_SEMAPHORE_GLOBAL_GTT |
+                       MI_SEMAPHORE_POLL |
+                       MI_SEMAPHORE_SAD_GTE_SDD);
+       intel_ring_emit(waiter, signal->fence.seqno);
        intel_ring_emit(waiter,
-                       upper_32_bits(GEN8_WAIT_OFFSET(waiter_req->engine,
-                                                      signaller->id)));
+                       lower_32_bits(GEN8_WAIT_OFFSET(wait->engine,
+                                                      signal->engine->id)));
+       intel_ring_emit(waiter,
+                       upper_32_bits(GEN8_WAIT_OFFSET(wait->engine,
+                                                      signal->engine->id)));
        intel_ring_advance(waiter);
        return 0;
 }
 
 static int
-gen6_ring_sync(struct drm_i915_gem_request *waiter_req,
-              struct intel_engine_cs *signaller,
-              u32 seqno)
+gen6_ring_sync(struct drm_i915_gem_request *wait,
+              struct drm_i915_gem_request *signal)
 {
-       struct intel_ring *waiter = waiter_req->ring;
+       struct intel_ring *waiter = wait->ring;
        u32 dw1 = MI_SEMAPHORE_MBOX |
                  MI_SEMAPHORE_COMPARE |
                  MI_SEMAPHORE_REGISTER;
-       u32 wait_mbox = signaller->semaphore.mbox.wait[waiter_req->engine->id];
+       u32 wait_mbox = signal->engine->semaphore.mbox.wait[wait->engine->id];
        int ret;
 
-       /* 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;
-
        WARN_ON(wait_mbox == MI_SEMAPHORE_SYNC_INVALID);
 
-       ret = intel_ring_begin(waiter_req, 4);
+       ret = intel_ring_begin(wait, 4);
        if (ret)
                return ret;
 
-       /* If seqno wrap happened, omit the wait with no-ops */
-       if (likely(!i915_gem_has_seqno_wrapped(waiter_req->i915, seqno))) {
-               intel_ring_emit(waiter, dw1 | wait_mbox);
-               intel_ring_emit(waiter, seqno);
-               intel_ring_emit(waiter, 0);
-               intel_ring_emit(waiter, MI_NOOP);
-       } else {
-               intel_ring_emit(waiter, MI_NOOP);
-               intel_ring_emit(waiter, MI_NOOP);
-               intel_ring_emit(waiter, MI_NOOP);
-               intel_ring_emit(waiter, MI_NOOP);
-       }
+       intel_ring_emit(waiter, dw1 | wait_mbox);
+       /* 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.
+        */
+       intel_ring_emit(waiter, signal->fence.seqno - 1);
+       intel_ring_emit(waiter, 0);
+       intel_ring_emit(waiter, MI_NOOP);
        intel_ring_advance(waiter);
 
        return 0;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h 
b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 8147ce1379fb..fc9c1e453be1 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -283,9 +283,8 @@ struct intel_engine_cs {
                };
 
                /* AKA wait() */
-               int     (*sync_to)(struct drm_i915_gem_request *to_req,
-                                  struct intel_engine_cs *from,
-                                  u32 seqno);
+               int     (*sync_to)(struct drm_i915_gem_request *to,
+                                  struct drm_i915_gem_request *from);
                int     (*signal)(struct drm_i915_gem_request *signaller_req,
                                  /* num_dwords needed by caller */
                                  unsigned int num_dwords);
-- 
2.7.0.rc3

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