drm/i915: Add intel_ring_handle_seqno wrap

If there are pre-wrap values in semaphore-mbox registers after wrap,
syncing against some after-wrap request will complete immediately.
Fix this by emitting ring commands to set mbox registers to zero
when the wrap happens.

v2: Use __intel_ring_begin to emit ring commands, from
Chris Wilson.

Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
[danvet: Add a small comment to handle_seqno_wrap.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

3 files changed, 27 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index cb941448c2bc..02d315164aa9 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1952,6 +1952,10 @@ i915_gem_handle_seqno_wrap(struct drm_device *dev)
 
         i915_gem_retire_requests(dev);
         for_each_ring(ring, dev_priv, i) {
+                ret = intel_ring_handle_seqno_wrap(ring);
+                if (ret)
+                        return ret;
+
                 for (j = 0; j < ARRAY_SIZE(ring->sync_seqno); j++)
                         ring->sync_seqno[j] = 0;
         }
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 01a660a7c167..0d03dc649c5e 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1402,6 +1402,28 @@ int intel_ring_begin(struct intel_ring_buffer *ring,
         return __intel_ring_begin(ring, num_dwords * sizeof(uint32_t));
 }
 
+int intel_ring_handle_seqno_wrap(struct intel_ring_buffer *ring)
+{
+        int ret;
+
+        BUG_ON(ring->outstanding_lazy_request);
+
+        if (INTEL_INFO(ring->dev)->gen < 6)
+                return 0;
+
+        ret = __intel_ring_begin(ring, 6 * sizeof(uint32_t));
+        if (ret)
+                return ret;
+
+        /* Leaving a stale, pre-wrap seqno behind in the mboxes will result in
+         * post-wrap semaphore waits completing immediately. Clear them. */
+        update_mboxes(ring, ring->signal_mbox[0]);
+        update_mboxes(ring, ring->signal_mbox[1]);
+        intel_ring_advance(ring);
+
+        return 0;
+}
+
 void intel_ring_advance(struct intel_ring_buffer *ring)
 {
         struct drm_i915_private *dev_priv = ring->dev->dev_private;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index d4b7416fa1b0..b4a533e53fd1 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -196,7 +196,7 @@ static inline void intel_ring_emit(struct intel_ring_buffer *ring,
 }
 void intel_ring_advance(struct intel_ring_buffer *ring);
 int __must_check intel_ring_idle(struct intel_ring_buffer *ring);
-
+int __must_check intel_ring_handle_seqno_wrap(struct intel_ring_buffer *ring);
 int intel_ring_flush_all_caches(struct intel_ring_buffer *ring);
 int intel_ring_invalidate_all_caches(struct intel_ring_buffer *ring);