HWC2: Add properties to revert latching changes

Adds two properties:

debug.sf.latch_unsignaled - This causes SurfaceFlinger to latch
  buffers even if their fences haven't signaled
debug.sf.disable_backpressure - This causes SurfaceFlinger to skip
  propagating backpressure back to apps by not running when it
  detects that a prior composition missed hardware vsync

Bug: 30216498
Change-Id: Idd70f472ec567a4bc03352f30f201f434cf5d660

1 files changed, 5 insertions, 1 deletions

diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index f298399ac5..8baf28c1c9 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -179,6 +179,10 @@ SurfaceFlinger::SurfaceFlinger()
     }
     ALOGI_IF(mDebugRegion, "showupdates enabled");
     ALOGI_IF(mDebugDDMS, "DDMS debugging enabled");
+
+    property_get("debug.sf.disable_backpressure", value, "0");
+    mPropagateBackpressure = !atoi(value);
+    ALOGI_IF(!mPropagateBackpressure, "Disabling backpressure propagation");
 }
 
 void SurfaceFlinger::onFirstRef()
@@ -924,7 +928,7 @@ void SurfaceFlinger::onMessageReceived(int32_t what) {
                     mPreviousPresentFence != Fence::NO_FENCE &&
                     mPreviousPresentFence->getSignalTime() == INT64_MAX;
             ATRACE_INT("FrameMissed", static_cast<int>(frameMissed));
-            if (frameMissed) {
+            if (mPropagateBackpressure && frameMissed) {
                 signalLayerUpdate();
                 break;
             }