SF: fix a few bugs with FrameTargeter storing N fences

Bug: 267315508
Bug: 354007767
Bug: 308858993
Test: SF unit tests
Flag: com.android.graphics.surfaceflinger.flags.allow_n_vsyncs_in_targeter
Change-Id: Ib603c0fd29a3e4cb2fcd99dca59bbd5bfb55a787
diff --git a/services/surfaceflinger/Scheduler/include/scheduler/FrameTargeter.h b/services/surfaceflinger/Scheduler/include/scheduler/FrameTargeter.h
index 38cb446..2185bb0 100644
--- a/services/surfaceflinger/Scheduler/include/scheduler/FrameTargeter.h
+++ b/services/surfaceflinger/Scheduler/include/scheduler/FrameTargeter.h
@@ -55,15 +55,11 @@
 
     std::optional<TimePoint> earliestPresentTime() const { return mEarliestPresentTime; }
 
-    // The time of the VSYNC that preceded this frame. See `presentFenceForPastVsync` for details.
-    TimePoint pastVsyncTime(Period minFramePeriod) const;
-
-    // Equivalent to `presentFenceForPastVsync` unless running N VSYNCs ahead.
-    const FenceTimePtr& presentFenceForPreviousFrame() const {
-        return mPresentFences.front().fenceTime;
-    }
+    // Equivalent to `expectedSignaledPresentFence` unless running N VSYNCs ahead.
+    const FenceTimePtr& presentFenceForPreviousFrame() const;
 
     bool isFramePending() const { return mFramePending; }
+    bool wouldBackpressureHwc() const { return mWouldBackpressureHwc; }
     bool didMissFrame() const { return mFrameMissed; }
     bool didMissHwcFrame() const { return mHwcFrameMissed && !mGpuFrameMissed; }
     FrameTime lastSignaledFrameTime() const { return mLastSignaledFrameTime; }
@@ -72,7 +68,7 @@
     explicit FrameTarget(const std::string& displayLabel);
     ~FrameTarget() = default;
 
-    bool wouldPresentEarly(Period minFramePeriod) const;
+    bool wouldPresentEarly(Period vsyncPeriod, Period minFramePeriod) const;
 
     // Equivalent to `pastVsyncTime` unless running N VSYNCs ahead.
     TimePoint previousFrameVsyncTime(Period minFramePeriod) const {
@@ -81,8 +77,7 @@
 
     void addFence(sp<Fence> presentFence, FenceTimePtr presentFenceTime,
                   TimePoint expectedPresentTime) {
-        mFenceWithFenceTimes.next() = {std::move(presentFence), presentFenceTime,
-                                       expectedPresentTime};
+        mPresentFences.next() = {std::move(presentFence), presentFenceTime, expectedPresentTime};
     }
 
     VsyncId mVsyncId;
@@ -94,8 +89,9 @@
     TracedOrdinal<bool> mFrameMissed;
     TracedOrdinal<bool> mHwcFrameMissed;
     TracedOrdinal<bool> mGpuFrameMissed;
+    bool mWouldBackpressureHwc = false;
 
-    struct FenceWithFenceTime {
+    struct PresentFence {
         sp<Fence> fence = Fence::NO_FENCE;
         FenceTimePtr fenceTime = FenceTime::NO_FENCE;
         TimePoint expectedPresentTime = TimePoint();
@@ -106,9 +102,10 @@
     // VSYNC of at least one previous frame has not yet passed. In other words, this is NOT the
     // `presentFenceForPreviousFrame` if running N VSYNCs ahead, but the one that should have been
     // signaled by now (unless that frame missed).
-    FenceWithFenceTime presentFenceForPastVsync(Period minFramePeriod) const;
-    std::array<FenceWithFenceTime, 2> mPresentFences;
-    utils::RingBuffer<FenceWithFenceTime, 5> mFenceWithFenceTimes;
+    std::pair<bool /* wouldBackpressure */, PresentFence> expectedSignaledPresentFence(
+            Period vsyncPeriod, Period minFramePeriod) const;
+    std::array<PresentFence, 2> mPresentFencesLegacy;
+    utils::RingBuffer<PresentFence, 5> mPresentFences;
 
     FrameTime mLastSignaledFrameTime;
 
@@ -120,19 +117,6 @@
         static_assert(N > 1);
         return expectedFrameDuration() > (N - 1) * minFramePeriod;
     }
-
-    FenceWithFenceTime pastVsyncTimePtr() const {
-        FenceWithFenceTime pastFenceWithFenceTime;
-        for (size_t i = 0; i < mFenceWithFenceTimes.size(); i++) {
-            const auto& fenceWithFenceTime = mFenceWithFenceTimes[i];
-            // TODO(b/354007767) Fix the below condition to avoid frame drop
-            if (fenceWithFenceTime.expectedPresentTime > mFrameBeginTime) {
-                return pastFenceWithFenceTime;
-            }
-            pastFenceWithFenceTime = fenceWithFenceTime;
-        }
-        return pastFenceWithFenceTime;
-    }
 };
 
 // Computes a display's per-frame metrics about past/upcoming targeting of present deadlines.
@@ -155,7 +139,7 @@
 
     void beginFrame(const BeginFrameArgs&, const IVsyncSource&);
 
-    std::optional<TimePoint> computeEarliestPresentTime(Period minFramePeriod,
+    std::optional<TimePoint> computeEarliestPresentTime(Period vsyncPeriod, Period minFramePeriod,
                                                         Duration hwcMinWorkDuration);
 
     // TODO(b/241285191): Merge with FrameTargeter::endFrame.
diff --git a/services/surfaceflinger/Scheduler/src/FrameTargeter.cpp b/services/surfaceflinger/Scheduler/src/FrameTargeter.cpp
index 1d248fb..21f5949 100644
--- a/services/surfaceflinger/Scheduler/src/FrameTargeter.cpp
+++ b/services/surfaceflinger/Scheduler/src/FrameTargeter.cpp
@@ -18,8 +18,10 @@
 #include <common/trace.h>
 #include <scheduler/FrameTargeter.h>
 #include <scheduler/IVsyncSource.h>
+#include <utils/Log.h>
 
 namespace android::scheduler {
+using namespace std::chrono_literals;
 
 FrameTarget::FrameTarget(const std::string& displayLabel)
       : mFramePending("PrevFramePending " + displayLabel, false),
@@ -27,32 +29,48 @@
         mHwcFrameMissed("PrevHwcFrameMissed " + displayLabel, false),
         mGpuFrameMissed("PrevGpuFrameMissed " + displayLabel, false) {}
 
-TimePoint FrameTarget::pastVsyncTime(Period minFramePeriod) const {
-    // TODO(b/267315508): Generalize to N VSYNCs.
-    const int shift = static_cast<int>(targetsVsyncsAhead<2>(minFramePeriod));
-    return mExpectedPresentTime - Period::fromNs(minFramePeriod.ns() << shift);
-}
-
-FrameTarget::FenceWithFenceTime FrameTarget::presentFenceForPastVsync(Period minFramePeriod) const {
-    if (FlagManager::getInstance().allow_n_vsyncs_in_targeter()) {
-        return pastVsyncTimePtr();
+std::pair<bool /* wouldBackpressure */, FrameTarget::PresentFence>
+FrameTarget::expectedSignaledPresentFence(Period vsyncPeriod, Period minFramePeriod) const {
+    if (!FlagManager::getInstance().allow_n_vsyncs_in_targeter()) {
+        const size_t i = static_cast<size_t>(targetsVsyncsAhead<2>(minFramePeriod));
+        return {true, mPresentFencesLegacy[i]};
     }
-    const size_t i = static_cast<size_t>(targetsVsyncsAhead<2>(minFramePeriod));
-    return mPresentFences[i];
+
+    bool wouldBackpressure = true;
+    auto expectedPresentTime = mExpectedPresentTime;
+    for (size_t i = mPresentFences.size(); i != 0; --i) {
+        const auto& fence = mPresentFences[i - 1];
+
+        if (fence.expectedPresentTime + minFramePeriod < expectedPresentTime - vsyncPeriod / 2) {
+            wouldBackpressure = false;
+        }
+
+        if (fence.expectedPresentTime <= mFrameBeginTime) {
+            return {wouldBackpressure, fence};
+        }
+
+        expectedPresentTime = fence.expectedPresentTime;
+    }
+    return {wouldBackpressure, PresentFence{}};
 }
 
-bool FrameTarget::wouldPresentEarly(Period minFramePeriod) const {
-    // TODO(b/241285475): Since this is called during `composite`, the calls to `targetsVsyncsAhead`
-    // should use `TimePoint::now()` in case of delays since `mFrameBeginTime`.
-
-    // TODO(b/267315508): Generalize to N VSYNCs.
-    const bool allowNVsyncs = FlagManager::getInstance().allow_n_vsyncs_in_targeter();
-    if (!allowNVsyncs && targetsVsyncsAhead<3>(minFramePeriod)) {
+bool FrameTarget::wouldPresentEarly(Period vsyncPeriod, Period minFramePeriod) const {
+    if (targetsVsyncsAhead<3>(minFramePeriod)) {
         return true;
     }
 
-    const auto fence = presentFenceForPastVsync(minFramePeriod).fenceTime;
-    return fence->isValid() && fence->getSignalTime() != Fence::SIGNAL_TIME_PENDING;
+    const auto [wouldBackpressure, fence] =
+            expectedSignaledPresentFence(vsyncPeriod, minFramePeriod);
+    return wouldBackpressure && fence.fenceTime->isValid() &&
+            fence.fenceTime->getSignalTime() != Fence::SIGNAL_TIME_PENDING;
+}
+
+const FenceTimePtr& FrameTarget::presentFenceForPreviousFrame() const {
+    if (FlagManager::getInstance().allow_n_vsyncs_in_targeter()) {
+        return mPresentFences.back().fenceTime;
+    }
+
+    return mPresentFencesLegacy.front().fenceTime;
 }
 
 void FrameTargeter::beginFrame(const BeginFrameArgs& args, const IVsyncSource& vsyncSource) {
@@ -86,27 +104,39 @@
     }
 
     if (!mSupportsExpectedPresentTime) {
-        mEarliestPresentTime = computeEarliestPresentTime(minFramePeriod, args.hwcMinWorkDuration);
+        mEarliestPresentTime =
+                computeEarliestPresentTime(vsyncPeriod, minFramePeriod, args.hwcMinWorkDuration);
     }
 
     SFTRACE_FORMAT("%s %" PRId64 " vsyncIn %.2fms%s", __func__, ftl::to_underlying(args.vsyncId),
                    ticks<std::milli, float>(mExpectedPresentTime - TimePoint::now()),
                    mExpectedPresentTime == args.expectedVsyncTime ? "" : " (adjusted)");
 
-    FenceWithFenceTime pastPresentFence = presentFenceForPastVsync(minFramePeriod);
+    const auto [wouldBackpressure, fence] =
+            expectedSignaledPresentFence(vsyncPeriod, minFramePeriod);
 
     // In cases where the present fence is about to fire, give it a small grace period instead of
     // giving up on the frame.
-    //
-    // TODO(b/280667110): The grace period should depend on `sfWorkDuration` and `vsyncPeriod` being
-    // approximately equal, not whether backpressure propagation is enabled.
-    const int graceTimeForPresentFenceMs = static_cast<int>(
-            mBackpressureGpuComposition || !mCompositionCoverage.test(CompositionCoverage::Gpu));
+    const int graceTimeForPresentFenceMs = [&] {
+        const bool considerBackpressure =
+                mBackpressureGpuComposition || !mCompositionCoverage.test(CompositionCoverage::Gpu);
+
+        if (!FlagManager::getInstance().allow_n_vsyncs_in_targeter()) {
+            return static_cast<int>(considerBackpressure);
+        }
+
+        if (!wouldBackpressure || !considerBackpressure) {
+            return 0;
+        }
+
+        return static_cast<int>((std::abs(fence.expectedPresentTime.ns() - mFrameBeginTime.ns()) <=
+                                 Duration(1ms).ns()));
+    }();
 
     // Pending frames may trigger backpressure propagation.
     const auto& isFencePending = *isFencePendingFuncPtr;
-    mFramePending = pastPresentFence.fenceTime != FenceTime::NO_FENCE &&
-            isFencePending(pastPresentFence.fenceTime, graceTimeForPresentFenceMs);
+    mFramePending = fence.fenceTime != FenceTime::NO_FENCE &&
+            isFencePending(fence.fenceTime, graceTimeForPresentFenceMs);
 
     // A frame is missed if the prior frame is still pending. If no longer pending, then we still
     // count the frame as missed if the predicted present time was further in the past than when the
@@ -114,10 +144,10 @@
     // than a typical frame duration, but should not be so small that it reports reasonable drift as
     // a missed frame.
     mFrameMissed = mFramePending || [&] {
-        const nsecs_t pastPresentTime = pastPresentFence.fenceTime->getSignalTime();
+        const nsecs_t pastPresentTime = fence.fenceTime->getSignalTime();
         if (pastPresentTime < 0) return false;
         mLastSignaledFrameTime = {.signalTime = TimePoint::fromNs(pastPresentTime),
-                                  .expectedPresentTime = pastPresentFence.expectedPresentTime};
+                                  .expectedPresentTime = fence.expectedPresentTime};
         const nsecs_t frameMissedSlop = vsyncPeriod.ns() / 2;
         return lastScheduledPresentTime.ns() < pastPresentTime - frameMissedSlop;
     }();
@@ -128,11 +158,14 @@
     if (mFrameMissed) mFrameMissedCount++;
     if (mHwcFrameMissed) mHwcFrameMissedCount++;
     if (mGpuFrameMissed) mGpuFrameMissedCount++;
+
+    mWouldBackpressureHwc = mFramePending && wouldBackpressure;
 }
 
-std::optional<TimePoint> FrameTargeter::computeEarliestPresentTime(Period minFramePeriod,
+std::optional<TimePoint> FrameTargeter::computeEarliestPresentTime(Period vsyncPeriod,
+                                                                   Period minFramePeriod,
                                                                    Duration hwcMinWorkDuration) {
-    if (wouldPresentEarly(minFramePeriod)) {
+    if (wouldPresentEarly(vsyncPeriod, minFramePeriod)) {
         return previousFrameVsyncTime(minFramePeriod) - hwcMinWorkDuration;
     }
     return {};
@@ -151,8 +184,8 @@
     if (FlagManager::getInstance().allow_n_vsyncs_in_targeter()) {
         addFence(std::move(presentFence), presentFenceTime, mExpectedPresentTime);
     } else {
-        mPresentFences[1] = mPresentFences[0];
-        mPresentFences[0] = {std::move(presentFence), presentFenceTime, mExpectedPresentTime};
+        mPresentFencesLegacy[1] = mPresentFencesLegacy[0];
+        mPresentFencesLegacy[0] = {std::move(presentFence), presentFenceTime, mExpectedPresentTime};
     }
     return presentFenceTime;
 }
diff --git a/services/surfaceflinger/Scheduler/tests/FrameTargeterTest.cpp b/services/surfaceflinger/Scheduler/tests/FrameTargeterTest.cpp
index 190d062..bc73cbb 100644
--- a/services/surfaceflinger/Scheduler/tests/FrameTargeterTest.cpp
+++ b/services/surfaceflinger/Scheduler/tests/FrameTargeterTest.cpp
@@ -53,12 +53,13 @@
 
     const auto& target() const { return mTargeter.target(); }
 
-    bool wouldPresentEarly(Period minFramePeriod) const {
-        return target().wouldPresentEarly(minFramePeriod);
+    bool wouldPresentEarly(Period vsyncPeriod, Period minFramePeriod) const {
+        return target().wouldPresentEarly(vsyncPeriod, minFramePeriod);
     }
 
-    FrameTarget::FenceWithFenceTime presentFenceForPastVsync(Period minFramePeriod) const {
-        return target().presentFenceForPastVsync(minFramePeriod);
+    std::pair<bool /*wouldBackpressure*/, FrameTarget::PresentFence> expectedSignaledPresentFence(
+            Period vsyncPeriod, Period minFramePeriod) const {
+        return target().expectedSignaledPresentFence(vsyncPeriod, minFramePeriod);
     }
 
     struct Frame {
@@ -173,7 +174,6 @@
 }
 
 TEST_F(FrameTargeterTest, recallsPastVsync) {
-    SET_FLAG_FOR_TEST(flags::allow_n_vsyncs_in_targeter, false);
     VsyncId vsyncId{111};
     TimePoint frameBeginTime(1000ms);
     constexpr Fps kRefreshRate = 60_Hz;
@@ -181,16 +181,72 @@
     constexpr Duration kFrameDuration = 13ms;
 
     for (int n = 5; n-- > 0;) {
-        Frame frame(this, vsyncId++, frameBeginTime, kFrameDuration, kRefreshRate, kRefreshRate);
-        const auto fence = frame.end();
+        FenceTimePtr fence;
+        {
+            Frame frame(this, vsyncId++, frameBeginTime, kFrameDuration, kRefreshRate,
+                        kRefreshRate);
+            fence = frame.end();
+        }
 
-        EXPECT_EQ(target().pastVsyncTime(kPeriod), frameBeginTime + kFrameDuration - kPeriod);
-        EXPECT_EQ(presentFenceForPastVsync(kPeriod).fenceTime, fence);
+        Frame frame(this, vsyncId++, frameBeginTime, kFrameDuration, kRefreshRate, kRefreshRate);
+        const auto [wouldBackpressure, presentFence] =
+                expectedSignaledPresentFence(kPeriod, kPeriod);
+        ASSERT_TRUE(wouldBackpressure);
+        EXPECT_EQ(presentFence.fenceTime, fence);
+    }
+}
+
+TEST_F(FrameTargeterTest, wouldBackpressureAfterTime) {
+    SET_FLAG_FOR_TEST(flags::allow_n_vsyncs_in_targeter, true);
+    VsyncId vsyncId{111};
+    TimePoint frameBeginTime(1000ms);
+    constexpr Fps kRefreshRate = 60_Hz;
+    constexpr Period kPeriod = kRefreshRate.getPeriod();
+    constexpr Duration kFrameDuration = 13ms;
+
+    { Frame frame(this, vsyncId++, frameBeginTime, kFrameDuration, kRefreshRate, kRefreshRate); }
+    {
+        Frame frame(this, vsyncId++, frameBeginTime, kFrameDuration, kRefreshRate, kRefreshRate);
+
+        const auto [wouldBackpressure, presentFence] =
+                expectedSignaledPresentFence(kPeriod, kPeriod);
+        EXPECT_TRUE(wouldBackpressure);
+    }
+    {
+        frameBeginTime += kPeriod;
+        Frame frame(this, vsyncId++, frameBeginTime, kFrameDuration, kRefreshRate, kRefreshRate);
+        const auto [wouldBackpressure, presentFence] =
+                expectedSignaledPresentFence(kPeriod, kPeriod);
+        EXPECT_FALSE(wouldBackpressure);
+    }
+}
+
+TEST_F(FrameTargeterTest, wouldBackpressureAfterTimeLegacy) {
+    SET_FLAG_FOR_TEST(flags::allow_n_vsyncs_in_targeter, false);
+    VsyncId vsyncId{111};
+    TimePoint frameBeginTime(1000ms);
+    constexpr Fps kRefreshRate = 60_Hz;
+    constexpr Period kPeriod = kRefreshRate.getPeriod();
+    constexpr Duration kFrameDuration = 13ms;
+
+    { Frame frame(this, vsyncId++, frameBeginTime, kFrameDuration, kRefreshRate, kRefreshRate); }
+    {
+        Frame frame(this, vsyncId++, frameBeginTime, kFrameDuration, kRefreshRate, kRefreshRate);
+
+        const auto [wouldBackpressure, presentFence] =
+                expectedSignaledPresentFence(kPeriod, kPeriod);
+        EXPECT_TRUE(wouldBackpressure);
+    }
+    {
+        frameBeginTime += kPeriod;
+        Frame frame(this, vsyncId++, frameBeginTime, kFrameDuration, kRefreshRate, kRefreshRate);
+        const auto [wouldBackpressure, presentFence] =
+                expectedSignaledPresentFence(kPeriod, kPeriod);
+        EXPECT_TRUE(wouldBackpressure);
     }
 }
 
 TEST_F(FrameTargeterTest, recallsPastVsyncTwoVsyncsAhead) {
-    SET_FLAG_FOR_TEST(flags::allow_n_vsyncs_in_targeter, false);
     VsyncId vsyncId{222};
     TimePoint frameBeginTime(2000ms);
     constexpr Fps kRefreshRate = 120_Hz;
@@ -198,101 +254,66 @@
     constexpr Duration kFrameDuration = 10ms;
 
     FenceTimePtr previousFence = FenceTime::NO_FENCE;
-
+    FenceTimePtr currentFence = FenceTime::NO_FENCE;
     for (int n = 5; n-- > 0;) {
         Frame frame(this, vsyncId++, frameBeginTime, kFrameDuration, kRefreshRate, kRefreshRate);
-        const auto fence = frame.end();
-
-        EXPECT_EQ(target().pastVsyncTime(kPeriod), frameBeginTime + kFrameDuration - 2 * kPeriod);
-        EXPECT_EQ(presentFenceForPastVsync(kPeriod).fenceTime, previousFence);
-
-        previousFence = fence;
+        EXPECT_EQ(expectedSignaledPresentFence(kPeriod, kPeriod).second.fenceTime, previousFence);
+        previousFence = currentFence;
+        currentFence = frame.end();
     }
 }
 
-TEST_F(FrameTargeterTest, recallsPastNVsyncTwoVsyncsAhead) {
+TEST_F(FrameTargeterTest, recallsPastVsyncFiveVsyncsAhead) {
     SET_FLAG_FOR_TEST(flags::allow_n_vsyncs_in_targeter, true);
+
     VsyncId vsyncId{222};
     TimePoint frameBeginTime(2000ms);
     constexpr Fps kRefreshRate = 120_Hz;
     constexpr Period kPeriod = kRefreshRate.getPeriod();
-    constexpr Duration kFrameDuration = 10ms;
+    constexpr Duration kFrameDuration = 40ms;
 
-    FenceTimePtr previousFence = FenceTime::NO_FENCE;
-
+    FenceTimePtr firstFence = FenceTime::NO_FENCE;
     for (int n = 5; n-- > 0;) {
         Frame frame(this, vsyncId++, frameBeginTime, kFrameDuration, kRefreshRate, kRefreshRate);
         const auto fence = frame.end();
-
-        const auto pastVsyncTime = frameBeginTime + kFrameDuration - 2 * kPeriod;
-        EXPECT_EQ(target().pastVsyncTime(kPeriod), pastVsyncTime);
-        EXPECT_EQ(presentFenceForPastVsync(kFrameDuration).fenceTime, previousFence);
-
-        frameBeginTime += kPeriod;
-        previousFence = fence;
+        if (firstFence == FenceTime::NO_FENCE) {
+            firstFence = fence;
+        }
     }
+
+    Frame frame(this, vsyncId++, frameBeginTime, kFrameDuration, kRefreshRate, kRefreshRate);
+    EXPECT_EQ(expectedSignaledPresentFence(kPeriod, kPeriod).second.fenceTime, firstFence);
 }
 
 TEST_F(FrameTargeterTest, recallsPastVsyncTwoVsyncsAheadVrr) {
     SET_FLAG_FOR_TEST(flags::vrr_config, true);
-    SET_FLAG_FOR_TEST(flags::allow_n_vsyncs_in_targeter, false);
 
     VsyncId vsyncId{222};
     TimePoint frameBeginTime(2000ms);
     constexpr Fps kRefreshRate = 120_Hz;
-    constexpr Fps kPeakRefreshRate = 240_Hz;
+    constexpr Fps kVsyncRate = 240_Hz;
     constexpr Period kPeriod = kRefreshRate.getPeriod();
+    constexpr Period kVsyncPeriod = kVsyncRate.getPeriod();
     constexpr Duration kFrameDuration = 10ms;
 
     FenceTimePtr previousFence = FenceTime::NO_FENCE;
-
+    FenceTimePtr currentFence = FenceTime::NO_FENCE;
     for (int n = 5; n-- > 0;) {
-        Frame frame(this, vsyncId++, frameBeginTime, kFrameDuration, kRefreshRate,
-                    kPeakRefreshRate);
-        const auto fence = frame.end();
-
-        EXPECT_EQ(target().pastVsyncTime(kPeriod), frameBeginTime + kFrameDuration - 2 * kPeriod);
-        EXPECT_EQ(presentFenceForPastVsync(kPeriod).fenceTime, previousFence);
-
-        previousFence = fence;
-    }
-}
-
-TEST_F(FrameTargeterTest, recallsPastNVsyncTwoVsyncsAheadVrr) {
-    SET_FLAG_FOR_TEST(flags::vrr_config, true);
-    SET_FLAG_FOR_TEST(flags::allow_n_vsyncs_in_targeter, true);
-
-    VsyncId vsyncId{222};
-    TimePoint frameBeginTime(2000ms);
-    constexpr Fps kRefreshRate = 120_Hz;
-    constexpr Fps kPeakRefreshRate = 240_Hz;
-    constexpr Period kPeriod = kRefreshRate.getPeriod();
-    constexpr Duration kFrameDuration = 10ms;
-
-    FenceTimePtr previousFence = FenceTime::NO_FENCE;
-
-    for (int n = 5; n-- > 0;) {
-        Frame frame(this, vsyncId++, frameBeginTime, kFrameDuration, kRefreshRate,
-                    kPeakRefreshRate);
-        const auto fence = frame.end();
-
-        const auto pastVsyncTime = frameBeginTime + kFrameDuration - 2 * kPeriod;
-        EXPECT_EQ(target().pastVsyncTime(kPeriod), pastVsyncTime);
-        EXPECT_EQ(presentFenceForPastVsync(kFrameDuration).fenceTime, previousFence);
-
-        frameBeginTime += kPeriod;
-        previousFence = fence;
+        Frame frame(this, vsyncId++, frameBeginTime, kFrameDuration, kRefreshRate, kRefreshRate);
+        EXPECT_EQ(expectedSignaledPresentFence(kVsyncPeriod, kPeriod).second.fenceTime,
+                  previousFence);
+        previousFence = currentFence;
+        currentFence = frame.end();
     }
 }
 
 TEST_F(FrameTargeterTest, doesNotDetectEarlyPresentIfNoFence) {
     constexpr Period kPeriod = (60_Hz).getPeriod();
-    EXPECT_EQ(presentFenceForPastVsync(kPeriod).fenceTime, FenceTime::NO_FENCE);
-    EXPECT_FALSE(wouldPresentEarly(kPeriod));
+    EXPECT_EQ(expectedSignaledPresentFence(kPeriod, kPeriod).second.fenceTime, FenceTime::NO_FENCE);
+    EXPECT_FALSE(wouldPresentEarly(kPeriod, kPeriod));
 }
 
 TEST_F(FrameTargeterTest, detectsEarlyPresent) {
-    SET_FLAG_FOR_TEST(flags::allow_n_vsyncs_in_targeter, false);
     VsyncId vsyncId{333};
     TimePoint frameBeginTime(3000ms);
     constexpr Fps kRefreshRate = 60_Hz;
@@ -300,20 +321,24 @@
 
     // The target is not early while past present fences are pending.
     for (int n = 3; n-- > 0;) {
-        const Frame frame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate);
-        EXPECT_FALSE(wouldPresentEarly(kPeriod));
+        {
+            const Frame frame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate);
+        }
+        EXPECT_FALSE(wouldPresentEarly(kPeriod, kPeriod));
         EXPECT_FALSE(target().earliestPresentTime());
     }
 
     // The target is early if the past present fence was signaled.
-    Frame frame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate);
-    const auto fence = frame.end();
-    fence->signalForTest(frameBeginTime.ns());
+    {
+        Frame frame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate);
+        const auto fence = frame.end();
+        fence->signalForTest(frameBeginTime.ns());
+    }
 
     Frame finalFrame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate);
 
     // `finalFrame` would present early, so it has an earliest present time.
-    EXPECT_TRUE(wouldPresentEarly(kPeriod));
+    EXPECT_TRUE(wouldPresentEarly(kPeriod, kPeriod));
     ASSERT_NE(std::nullopt, target().earliestPresentTime());
     EXPECT_EQ(*target().earliestPresentTime(),
               target().expectedPresentTime() - kPeriod - kHwcMinWorkDuration);
@@ -322,7 +347,6 @@
 // Same as `detectsEarlyPresent`, above, but verifies that we do not set an earliest present time
 // when there is expected present time support.
 TEST_F(FrameTargeterWithExpectedPresentSupportTest, detectsEarlyPresent) {
-    SET_FLAG_FOR_TEST(flags::allow_n_vsyncs_in_targeter, false);
     VsyncId vsyncId{333};
     TimePoint frameBeginTime(3000ms);
     constexpr Fps kRefreshRate = 60_Hz;
@@ -330,26 +354,30 @@
 
     // The target is not early while past present fences are pending.
     for (int n = 3; n-- > 0;) {
-        const Frame frame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate);
-        EXPECT_FALSE(wouldPresentEarly(kPeriod));
+        {
+            const Frame frame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate);
+        }
+        EXPECT_FALSE(wouldPresentEarly(kPeriod, kPeriod));
         EXPECT_FALSE(target().earliestPresentTime());
     }
 
     // The target is early if the past present fence was signaled.
-    Frame frame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate);
-    const auto fence = frame.end();
-    fence->signalForTest(frameBeginTime.ns());
+    {
+        Frame frame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate);
+
+        const auto fence = frame.end();
+        fence->signalForTest(frameBeginTime.ns());
+    }
 
     Frame finalFrame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate);
 
     // `finalFrame` would present early, but we have expected present time support, so it has no
     // earliest present time.
-    EXPECT_TRUE(wouldPresentEarly(kPeriod));
+    EXPECT_TRUE(wouldPresentEarly(kPeriod, kPeriod));
     ASSERT_EQ(std::nullopt, target().earliestPresentTime());
 }
 
 TEST_F(FrameTargeterTest, detectsEarlyPresentTwoVsyncsAhead) {
-    SET_FLAG_FOR_TEST(flags::allow_n_vsyncs_in_targeter, false);
     VsyncId vsyncId{444};
     TimePoint frameBeginTime(4000ms);
     constexpr Fps kRefreshRate = 120_Hz;
@@ -357,17 +385,21 @@
 
     // The target is not early while past present fences are pending.
     for (int n = 3; n-- > 0;) {
-        const Frame frame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate);
-        EXPECT_FALSE(wouldPresentEarly(kPeriod));
+        {
+            const Frame frame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate);
+        }
+        EXPECT_FALSE(wouldPresentEarly(kPeriod, kPeriod));
         EXPECT_FALSE(target().earliestPresentTime());
     }
+    {
+        Frame frame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate);
 
-    Frame frame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate);
-    const auto fence = frame.end();
-    fence->signalForTest(frameBeginTime.ns());
+        const auto fence = frame.end();
+        fence->signalForTest(frameBeginTime.ns());
+    }
 
     // The target is two VSYNCs ahead, so the past present fence is still pending.
-    EXPECT_FALSE(wouldPresentEarly(kPeriod));
+    EXPECT_FALSE(wouldPresentEarly(kPeriod, kPeriod));
     EXPECT_FALSE(target().earliestPresentTime());
 
     { const Frame frame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate); }
@@ -375,66 +407,21 @@
     Frame finalFrame(this, vsyncId++, frameBeginTime, 10ms, kRefreshRate, kRefreshRate);
 
     // The target is early if the past present fence was signaled.
-    EXPECT_TRUE(wouldPresentEarly(kPeriod));
+    EXPECT_TRUE(wouldPresentEarly(kPeriod, kPeriod));
     ASSERT_NE(std::nullopt, target().earliestPresentTime());
     EXPECT_EQ(*target().earliestPresentTime(),
               target().expectedPresentTime() - kPeriod - kHwcMinWorkDuration);
 }
 
-TEST_F(FrameTargeterTest, detectsEarlyPresentNVsyncsAhead) {
-    SET_FLAG_FOR_TEST(flags::allow_n_vsyncs_in_targeter, true);
-    VsyncId vsyncId{444};
-    TimePoint frameBeginTime(4000ms);
-    Fps refreshRate = 120_Hz;
-    Period period = refreshRate.getPeriod();
-
-    // The target is not early while past present fences are pending.
-    for (int n = 5; n-- > 0;) {
-        const Frame frame(this, vsyncId++, frameBeginTime, 10ms, refreshRate, refreshRate);
-        EXPECT_FALSE(wouldPresentEarly(period));
-        EXPECT_FALSE(target().earliestPresentTime());
-    }
-
-    Frame frame(this, vsyncId++, frameBeginTime, 10ms, refreshRate, refreshRate);
-    auto fence = frame.end();
-    frameBeginTime += period;
-    fence->signalForTest(frameBeginTime.ns());
-
-    // The target is two VSYNCs ahead, so the past present fence is still pending.
-    EXPECT_FALSE(wouldPresentEarly(period));
-    EXPECT_FALSE(target().earliestPresentTime());
-
-    { const Frame frame(this, vsyncId++, frameBeginTime, 10ms, refreshRate, refreshRate); }
-
-    Frame oneEarlyPresentFrame(this, vsyncId++, frameBeginTime, 10ms, refreshRate, refreshRate);
-    // The target is early if the past present fence was signaled.
-    EXPECT_TRUE(wouldPresentEarly(period));
-    ASSERT_NE(std::nullopt, target().earliestPresentTime());
-    EXPECT_EQ(*target().earliestPresentTime(),
-              target().expectedPresentTime() - period - kHwcMinWorkDuration);
-
-    fence = oneEarlyPresentFrame.end();
-    frameBeginTime += period;
-    fence->signalForTest(frameBeginTime.ns());
-
-    // Change rate to track frame more than 2 vsyncs ahead
-    refreshRate = 144_Hz;
-    period = refreshRate.getPeriod();
-    Frame onePresentEarlyFrame(this, vsyncId++, frameBeginTime, 16ms, refreshRate, refreshRate);
-    // The target is not early as last frame as the past frame is tracked for pending.
-    EXPECT_FALSE(wouldPresentEarly(period));
-}
-
 TEST_F(FrameTargeterTest, detectsEarlyPresentThreeVsyncsAhead) {
-    SET_FLAG_FOR_TEST(flags::allow_n_vsyncs_in_targeter, false);
     TimePoint frameBeginTime(5000ms);
     constexpr Fps kRefreshRate = 144_Hz;
     constexpr Period kPeriod = kRefreshRate.getPeriod();
 
-    const Frame frame(this, VsyncId{555}, frameBeginTime, 16ms, kRefreshRate, kRefreshRate);
+    { const Frame frame(this, VsyncId{555}, frameBeginTime, 16ms, kRefreshRate, kRefreshRate); }
 
     // The target is more than two VSYNCs ahead, but present fences are not tracked that far back.
-    EXPECT_TRUE(wouldPresentEarly(kPeriod));
+    EXPECT_TRUE(wouldPresentEarly(kPeriod, kPeriod));
     EXPECT_TRUE(target().earliestPresentTime());
     EXPECT_EQ(*target().earliestPresentTime(),
               target().expectedPresentTime() - kPeriod - kHwcMinWorkDuration);
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 1d35730..e32202f 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -2623,7 +2623,7 @@
         }
     }
 
-    if (pacesetterFrameTarget.isFramePending()) {
+    if (pacesetterFrameTarget.wouldBackpressureHwc()) {
         if (mBackpressureGpuComposition || pacesetterFrameTarget.didMissHwcFrame()) {
             if (FlagManager::getInstance().vrr_config()) {
                 mScheduler->getVsyncSchedule()->getTracker().onFrameMissed(
@@ -2921,6 +2921,9 @@
         // Now that the current frame has been presented above, PowerAdvisor needs the present time
         // of the previous frame (whose fence is signaled by now) to determine how long the HWC had
         // waited on that fence to retire before presenting.
+        // TODO(b/355238809) `presentFenceForPreviousFrame` might not always be signaled (e.g. on
+        // devices
+        //  where HWC does not block on the previous present fence). Revise this assumtion.
         const auto& previousPresentFence = pacesetterTarget.presentFenceForPreviousFrame();
 
         mPowerAdvisor->setSfPresentTiming(TimePoint::fromNs(previousPresentFence->getSignalTime()),
diff --git a/services/surfaceflinger/Utils/RingBuffer.h b/services/surfaceflinger/Utils/RingBuffer.h
index 198e7b2..215472b 100644
--- a/services/surfaceflinger/Utils/RingBuffer.h
+++ b/services/surfaceflinger/Utils/RingBuffer.h
@@ -43,8 +43,10 @@
     }
 
     T& front() { return (*this)[0]; }
+    const T& front() const { return (*this)[0]; }
 
     T& back() { return (*this)[size() - 1]; }
+    const T& back() const { return (*this)[size() - 1]; }
 
     T& operator[](size_t index) {
         return mBuffer[(static_cast<size_t>(mHead + 1) + index) % mCount];