drm/i915: Don't emit semaphore wait if wrap happened
If wrap just happened we need to prevent emitting waits for
pre wrap values. Detect this and emit no-ops instead.
v2: Use olr > seqno to detect wrap instead of *seqno == 0
as suggested by Chris Wilson.
v3: Use last used seqno to detect the wraparound. From
Chris Wilson
v4: Fixed unnecessary last_seqno assigment
References: https://bugs.freedesktop.org/show_bug.cgi?id=57967
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 0d03dc6..69bbe7b 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -596,6 +596,13 @@
return 0;
}
+static inline bool i915_gem_has_seqno_wrapped(struct drm_device *dev,
+ u32 seqno)
+{
+ struct drm_i915_private *dev_priv = dev->dev_private;
+ return dev_priv->last_seqno < seqno;
+}
+
/**
* intel_ring_sync - sync the waiter to the signaller on seqno
*
@@ -626,11 +633,20 @@
if (ret)
return ret;
- intel_ring_emit(waiter,
- dw1 | signaller->semaphore_register[waiter->id]);
- intel_ring_emit(waiter, seqno);
- intel_ring_emit(waiter, 0);
- intel_ring_emit(waiter, MI_NOOP);
+ /* If seqno wrap happened, omit the wait with no-ops */
+ if (likely(!i915_gem_has_seqno_wrapped(waiter->dev, seqno))) {
+ intel_ring_emit(waiter,
+ dw1 |
+ signaller->semaphore_register[waiter->id]);
+ 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_advance(waiter);
return 0;