commit f34b9be610ce286af224364cb6e69ef6f7697ee9
author Dan Stoza <stoza@google.com> Tue Apr 05 16:45:26 2016 -0700
committer Dan Stoza <stoza@google.com> Thu Apr 07 14:03:02 2016 -0700
tree 0096a8de0b2e5f1747bd6ac9569520230d71652a
parent 90e840f00713bf9c1016c4f2584ef70e0a87ca14

DispSync: Always resync after inactivity

Changes DispSync to enable hardware vsync immediately when new frames
arrive after a period of inactivity.

No matter how hard we try, we can't avoid drifting over time without
being able to detect error based on display retire fences. By enabling
hardware vsync immediately, we avoid having a weird period or phase
offset relative to hardware while we retrain the model. Once the model
has locked, we turn hardware vsync back off to save power (until we
detect drift again).

Bug: 26255070
Change-Id: If4dd17c2d541015c730f47d824359d7cb4b52c3c

services/surfaceflinger/SurfaceFlinger.cpp

diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index ea9fe21..b6c86d3 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -149,6 +149,7 @@
         mLastTransactionTime(0),
         mBootFinished(false),
         mForceFullDamage(false),
+        mPrimaryDispSync("PrimaryDispSync"),
         mPrimaryHWVsyncEnabled(false),
         mHWVsyncAvailable(false),
         mDaltonize(false),
@@ -331,11 +332,12 @@
 class DispSyncSource : public VSyncSource, private DispSync::Callback {
 public:
     DispSyncSource(DispSync* dispSync, nsecs_t phaseOffset, bool traceVsync,
-        const char* label) :
+        const char* name) :
+            mName(name),
             mValue(0),
             mTraceVsync(traceVsync),
-            mVsyncOnLabel(String8::format("VsyncOn-%s", label)),
-            mVsyncEventLabel(String8::format("VSYNC-%s", label)),
+            mVsyncOnLabel(String8::format("VsyncOn-%s", name)),
+            mVsyncEventLabel(String8::format("VSYNC-%s", name)),
             mDispSync(dispSync),
             mCallbackMutex(),
             mCallback(),
@@ -348,7 +350,7 @@
     virtual void setVSyncEnabled(bool enable) {
         Mutex::Autolock lock(mVsyncMutex);
         if (enable) {
-            status_t err = mDispSync->addEventListener(mPhaseOffset,
+            status_t err = mDispSync->addEventListener(mName, mPhaseOffset,
                     static_cast<DispSync::Callback*>(this));
             if (err != NO_ERROR) {
                 ALOGE("error registering vsync callback: %s (%d)",
@@ -399,7 +401,7 @@
         }
 
         // Add a listener with the new offset
-        err = mDispSync->addEventListener(mPhaseOffset,
+        err = mDispSync->addEventListener(mName, mPhaseOffset,
                 static_cast<DispSync::Callback*>(this));
         if (err != NO_ERROR) {
             ALOGE("error registering vsync callback: %s (%d)",
@@ -425,6 +427,8 @@
         }
     }
 
+    const char* const mName;
+
     int mValue;
 
     const bool mTraceVsync;
@@ -455,10 +459,10 @@
         // start the EventThread
         sp<VSyncSource> vsyncSrc = new DispSyncSource(&mPrimaryDispSync,
                 vsyncPhaseOffsetNs, true, "app");
-        mEventThread = new EventThread(vsyncSrc);
+        mEventThread = new EventThread(vsyncSrc, *this);
         sp<VSyncSource> sfVsyncSrc = new DispSyncSource(&mPrimaryDispSync,
                 sfVsyncPhaseOffsetNs, true, "sf");
-        mSFEventThread = new EventThread(sfVsyncSrc);
+        mSFEventThread = new EventThread(sfVsyncSrc, *this);
         mEventQueue.setEventThread(mSFEventThread);
 
         // Get a RenderEngine for the given display / config (can't fail)
@@ -806,6 +810,13 @@
     }
 }
 
+void SurfaceFlinger::resyncWithRateLimit() {
+    static constexpr nsecs_t kIgnoreDelay = ms2ns(500);
+    if (systemTime() - mLastSwapTime > kIgnoreDelay) {
+        resyncToHardwareVsync(true);
+    }
+}
+
 void SurfaceFlinger::onVSyncReceived(int32_t type, nsecs_t timestamp) {
     bool needsHwVsync = false;