SurfaceFlinger: use intended wake up time when calculating next present time

If SurfaceFlinger wakes up too late (due to the main thread being busy)
it may calculate a wrong presentation time as it is based on the wake up time.
Instead, cache the intended wake up time and use it as the base time.

Change-Id: I84c37bd5f164fbdef3151c0898d3cea624cea515
Bug: 154199567
Test: collect systrace for launcher scrolling
diff --git a/services/surfaceflinger/Scheduler/DispSync.cpp b/services/surfaceflinger/Scheduler/DispSync.cpp
index 809a0e5..fc6ccae 100644
--- a/services/surfaceflinger/Scheduler/DispSync.cpp
+++ b/services/surfaceflinger/Scheduler/DispSync.cpp
@@ -768,9 +768,8 @@
     }
 }
 
-nsecs_t DispSync::computeNextRefresh(int periodOffset) const {
+nsecs_t DispSync::computeNextRefresh(int periodOffset, nsecs_t now) const {
     Mutex::Autolock lock(mMutex);
-    nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
     nsecs_t phase = mReferenceTime + mPhase;
     if (mPeriod == 0) {
         return 0;
@@ -837,7 +836,7 @@
     StringAppendF(&result, "current monotonic time: %" PRId64 "\n", now);
 }
 
-nsecs_t DispSync::expectedPresentTime() {
+nsecs_t DispSync::expectedPresentTime(nsecs_t now) {
     // The HWC doesn't currently have a way to report additional latency.
     // Assume that whatever we submit now will appear right after the flip.
     // For a smart panel this might be 1.  This is expressed in frames,
@@ -846,7 +845,7 @@
     const uint32_t hwcLatency = 0;
 
     // Ask DispSync when the next refresh will be (CLOCK_MONOTONIC).
-    return computeNextRefresh(hwcLatency);
+    return computeNextRefresh(hwcLatency, now);
 }
 
 } // namespace impl
diff --git a/services/surfaceflinger/Scheduler/DispSync.h b/services/surfaceflinger/Scheduler/DispSync.h
index 2d9afc9..2faa81c 100644
--- a/services/surfaceflinger/Scheduler/DispSync.h
+++ b/services/surfaceflinger/Scheduler/DispSync.h
@@ -58,9 +58,9 @@
                                       nsecs_t lastCallbackTime) = 0;
     virtual status_t removeEventListener(Callback* callback, nsecs_t* outLastCallback) = 0;
     virtual status_t changePhaseOffset(Callback* callback, nsecs_t phase) = 0;
-    virtual nsecs_t computeNextRefresh(int periodOffset) const = 0;
+    virtual nsecs_t computeNextRefresh(int periodOffset, nsecs_t now) const = 0;
     virtual void setIgnorePresentFences(bool ignore) = 0;
-    virtual nsecs_t expectedPresentTime() = 0;
+    virtual nsecs_t expectedPresentTime(nsecs_t now) = 0;
 
     virtual void dump(std::string& result) const = 0;
 
@@ -167,7 +167,7 @@
     // The periodOffset value can be used to move forward or backward; an
     // offset of zero is the next refresh, -1 is the previous refresh, 1 is
     // the refresh after next. etc.
-    nsecs_t computeNextRefresh(int periodOffset) const override;
+    nsecs_t computeNextRefresh(int periodOffset, nsecs_t now) const override;
 
     // In certain situations the present fences aren't a good indicator of vsync
     // time, e.g. when vr flinger is active, or simply aren't available,
@@ -178,7 +178,7 @@
     void setIgnorePresentFences(bool ignore) override;
 
     // Determine the expected present time when a buffer acquired now will be displayed.
-    nsecs_t expectedPresentTime();
+    nsecs_t expectedPresentTime(nsecs_t now);
 
     // dump appends human-readable debug info to the result string.
     void dump(std::string& result) const override;
diff --git a/services/surfaceflinger/Scheduler/MessageQueue.cpp b/services/surfaceflinger/Scheduler/MessageQueue.cpp
index 005d157..d8a666a 100644
--- a/services/surfaceflinger/Scheduler/MessageQueue.cpp
+++ b/services/surfaceflinger/Scheduler/MessageQueue.cpp
@@ -62,8 +62,9 @@
     }
 }
 
-void MessageQueue::Handler::dispatchInvalidate() {
+void MessageQueue::Handler::dispatchInvalidate(nsecs_t timestamp) {
     if ((android_atomic_or(eventMaskInvalidate, &mEventMask) & eventMaskInvalidate) == 0) {
+        mLastVsyncTime = timestamp;
         mQueue.mLooper->sendMessage(this, Message(MessageQueue::INVALIDATE));
     }
 }
@@ -72,11 +73,11 @@
     switch (message.what) {
         case INVALIDATE:
             android_atomic_and(~eventMaskInvalidate, &mEventMask);
-            mQueue.mFlinger->onMessageReceived(message.what);
+            mQueue.mFlinger->onMessageReceived(message.what, mLastVsyncTime);
             break;
         case REFRESH:
             android_atomic_and(~eventMaskRefresh, &mEventMask);
-            mQueue.mFlinger->onMessageReceived(message.what);
+            mQueue.mFlinger->onMessageReceived(message.what, mLastVsyncTime);
             break;
     }
 }
@@ -151,7 +152,7 @@
     while ((n = DisplayEventReceiver::getEvents(&mEventTube, buffer, 8)) > 0) {
         for (int i = 0; i < n; i++) {
             if (buffer[i].header.type == DisplayEventReceiver::DISPLAY_EVENT_VSYNC) {
-                mHandler->dispatchInvalidate();
+                mHandler->dispatchInvalidate(buffer[i].header.timestamp);
                 break;
             }
         }
diff --git a/services/surfaceflinger/Scheduler/MessageQueue.h b/services/surfaceflinger/Scheduler/MessageQueue.h
index fcfc4aa..dbd5e96 100644
--- a/services/surfaceflinger/Scheduler/MessageQueue.h
+++ b/services/surfaceflinger/Scheduler/MessageQueue.h
@@ -101,12 +101,13 @@
         enum { eventMaskInvalidate = 0x1, eventMaskRefresh = 0x2, eventMaskTransaction = 0x4 };
         MessageQueue& mQueue;
         int32_t mEventMask;
+        std::atomic<nsecs_t> mLastVsyncTime;
 
     public:
         explicit Handler(MessageQueue& queue) : mQueue(queue), mEventMask(0) {}
         virtual void handleMessage(const Message& message);
         void dispatchRefresh();
-        void dispatchInvalidate();
+        void dispatchInvalidate(nsecs_t timestamp);
     };
 
     friend class Handler;
diff --git a/services/surfaceflinger/Scheduler/Scheduler.cpp b/services/surfaceflinger/Scheduler/Scheduler.cpp
index 9a9523f..5abb0d6 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.cpp
+++ b/services/surfaceflinger/Scheduler/Scheduler.cpp
@@ -250,7 +250,7 @@
 }
 
 void Scheduler::getDisplayStatInfo(DisplayStatInfo* stats) {
-    stats->vsyncTime = mPrimaryDispSync->computeNextRefresh(0);
+    stats->vsyncTime = mPrimaryDispSync->computeNextRefresh(0, systemTime());
     stats->vsyncPeriod = mPrimaryDispSync->getPeriod();
 }
 
@@ -378,8 +378,8 @@
     mPrimaryDispSync->setIgnorePresentFences(ignore);
 }
 
-nsecs_t Scheduler::getDispSyncExpectedPresentTime() {
-    return mPrimaryDispSync->expectedPresentTime();
+nsecs_t Scheduler::getDispSyncExpectedPresentTime(nsecs_t now) {
+    return mPrimaryDispSync->expectedPresentTime(now);
 }
 
 void Scheduler::registerLayer(Layer* layer) {
diff --git a/services/surfaceflinger/Scheduler/Scheduler.h b/services/surfaceflinger/Scheduler/Scheduler.h
index 04cc96a..d36b16a 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.h
+++ b/services/surfaceflinger/Scheduler/Scheduler.h
@@ -114,7 +114,7 @@
                          bool* periodFlushed);
     void addPresentFence(const std::shared_ptr<FenceTime>&);
     void setIgnorePresentFences(bool ignore);
-    nsecs_t getDispSyncExpectedPresentTime();
+    nsecs_t getDispSyncExpectedPresentTime(nsecs_t now);
 
     // Layers are registered on creation, and unregistered when the weak reference expires.
     void registerLayer(Layer*);
diff --git a/services/surfaceflinger/Scheduler/VSyncReactor.cpp b/services/surfaceflinger/Scheduler/VSyncReactor.cpp
index 892ae62..2f1faac 100644
--- a/services/surfaceflinger/Scheduler/VSyncReactor.cpp
+++ b/services/surfaceflinger/Scheduler/VSyncReactor.cpp
@@ -221,14 +221,13 @@
     }
 }
 
-nsecs_t VSyncReactor::computeNextRefresh(int periodOffset) const {
-    auto const now = mClock->now();
+nsecs_t VSyncReactor::computeNextRefresh(int periodOffset, nsecs_t now) const {
     auto const currentPeriod = periodOffset ? mTracker->currentPeriod() : 0;
     return mTracker->nextAnticipatedVSyncTimeFrom(now + periodOffset * currentPeriod);
 }
 
-nsecs_t VSyncReactor::expectedPresentTime() {
-    return mTracker->nextAnticipatedVSyncTimeFrom(mClock->now());
+nsecs_t VSyncReactor::expectedPresentTime(nsecs_t now) {
+    return mTracker->nextAnticipatedVSyncTimeFrom(now);
 }
 
 void VSyncReactor::startPeriodTransition(nsecs_t newPeriod) {
diff --git a/services/surfaceflinger/Scheduler/VSyncReactor.h b/services/surfaceflinger/Scheduler/VSyncReactor.h
index 5ee29f8..31ddf5a 100644
--- a/services/surfaceflinger/Scheduler/VSyncReactor.h
+++ b/services/surfaceflinger/Scheduler/VSyncReactor.h
@@ -42,8 +42,8 @@
     bool addPresentFence(const std::shared_ptr<FenceTime>& fence) final;
     void setIgnorePresentFences(bool ignoration) final;
 
-    nsecs_t computeNextRefresh(int periodOffset) const final;
-    nsecs_t expectedPresentTime() final;
+    nsecs_t computeNextRefresh(int periodOffset, nsecs_t now) const final;
+    nsecs_t expectedPresentTime(nsecs_t now) final;
 
     void setPeriod(nsecs_t period) final;
     nsecs_t getPeriod() final;