Merge "[sf] only update the last latch time if the layer has a buffer" into udc-dev

3 files changed, 13 insertions, 2 deletions

diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 433606a732..ded607eb49 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -3037,6 +3037,10 @@ bool Layer::setBuffer(std::shared_ptr<renderengine::ExternalTexture>& buffer,
                                       mLastClientCompositionFence);
             mLastClientCompositionFence = nullptr;
         }
+    } else {
+        // if we are latching a buffer for the first time then clear the mLastLatchTime since
+        // we don't want to incorrectly classify a frame if we miss the desired present time.
+        updateLastLatchTime(0);
     }
 
     mDrawingState.producerId = bufferData.producerId;
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index 4309aca22c..a0ab4cdb75 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -852,6 +852,7 @@ public:
                                    const sp<GraphicBuffer>& buffer, uint64_t framenumber,
                                    const sp<Fence>& releaseFence);
     bool setFrameRateForLayerTree(FrameRate);
+    bool hasBuffer() const { return mBufferInfo.mBuffer != nullptr; }
 
 protected:
     // For unit tests
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index f0f163211b..31ce30b41d 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -3954,8 +3954,14 @@ bool SurfaceFlinger::latchBuffers() {
             mLayersWithQueuedFrames.emplace(sp<Layer>::fromExisting(layer));
         } else {
             layer->useEmptyDamage();
-            // If the layer has frames we will update the latch time when latching the buffer.
-            layer->updateLastLatchTime(latchTime);
+            if (!layer->hasBuffer()) {
+                // The last latch time is used to classify a missed frame as buffer stuffing
+                // instead of a missed frame. This is used to identify scenarios where we
+                // could not latch a buffer or apply a transaction due to backpressure.
+                // We only update the latch time for buffer less layers here, the latch time
+                // is updated for buffer layers when the buffer is latched.
+                layer->updateLastLatchTime(latchTime);
+            }
         }
     });
     mForceTransactionDisplayChange = false;