diff --git a/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/HwcBufferCache.h b/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/HwcBufferCache.h
index 6e9ea6f..b6a4240 100644
--- a/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/HwcBufferCache.h
+++ b/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/HwcBufferCache.h
@@ -83,7 +83,7 @@
     // If the buffer is already in the cache, the buffer is null to optimize away sending HWC the
     // buffer handle.
     //
-    HwcSlotAndBuffer getHwcSlotAndBufferForOverride(const sp<GraphicBuffer>& buffer);
+    HwcSlotAndBuffer getOverrideHwcSlotAndBuffer(const sp<GraphicBuffer>& buffer);
 
     //
     // When a client process discards a buffer, it needs to be purged from the HWC cache.
diff --git a/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/OutputLayerCompositionState.h b/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/OutputLayerCompositionState.h
index 2b383c1..2a5bfae 100644
--- a/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/OutputLayerCompositionState.h
+++ b/services/surfaceflinger/CompositionEngine/include/compositionengine/impl/OutputLayerCompositionState.h
@@ -136,6 +136,9 @@
         // cost of sending reused buffers to the HWC.
         HwcBufferCache hwcBufferCache;
 
+        // The previously-active buffer for this layer.
+        uint32_t activeBufferSlot;
+
         // Set to true when overridden info has been sent to HW composer
         bool stateOverridden = false;
 
diff --git a/services/surfaceflinger/CompositionEngine/include/compositionengine/mock/LayerFE.h b/services/surfaceflinger/CompositionEngine/include/compositionengine/mock/LayerFE.h
index 14922a4..12e063b 100644
--- a/services/surfaceflinger/CompositionEngine/include/compositionengine/mock/LayerFE.h
+++ b/services/surfaceflinger/CompositionEngine/include/compositionengine/mock/LayerFE.h
@@ -36,6 +36,7 @@
     // sp<StrictMock<LayerFE>>::make()
     friend class sp<LayerFE>;
     friend class testing::StrictMock<LayerFE>;
+    friend class testing::NiceMock<LayerFE>;
 
 public:
     virtual ~LayerFE();
diff --git a/services/surfaceflinger/CompositionEngine/src/HwcBufferCache.cpp b/services/surfaceflinger/CompositionEngine/src/HwcBufferCache.cpp
index d64fd57..34ed214 100644
--- a/services/surfaceflinger/CompositionEngine/src/HwcBufferCache.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/HwcBufferCache.cpp
@@ -22,7 +22,7 @@
 namespace android::compositionengine::impl {
 
 HwcBufferCache::HwcBufferCache() {
-    for (uint32_t i = 0; i < kMaxLayerBufferCount; i++) {
+    for (uint32_t i = kMaxLayerBufferCount; i-- > 0;) {
         mFreeSlots.push(i);
     }
 }
@@ -42,7 +42,7 @@
     return {cache(buffer), buffer};
 }
 
-HwcSlotAndBuffer HwcBufferCache::getHwcSlotAndBufferForOverride(const sp<GraphicBuffer>& buffer) {
+HwcSlotAndBuffer HwcBufferCache::getOverrideHwcSlotAndBuffer(const sp<GraphicBuffer>& buffer) {
     if (buffer == mLastOverrideBuffer) {
         return {kOverrideBufferSlot, nullptr};
     }
diff --git a/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp b/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
index a7c24b6..766d7ea 100644
--- a/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
+++ b/services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp
@@ -610,16 +610,26 @@
     }
 }
 
-void OutputLayer::uncacheBuffers(std::vector<uint64_t> const& bufferIdsToUncache) {
+void OutputLayer::uncacheBuffers(const std::vector<uint64_t>& bufferIdsToUncache) {
     auto& state = editState();
     // Skip doing this if there is no HWC interface
     if (!state.hwc) {
         return;
     }
 
-    for (auto bufferId : bufferIdsToUncache) {
-        state.hwc->hwcBufferCache.uncache(bufferId);
-        // TODO(b/258196272): send uncache requests to Composer HAL
+    std::vector<uint32_t> slotsToClear;
+    for (uint64_t bufferId : bufferIdsToUncache) {
+        uint32_t slot = state.hwc->hwcBufferCache.uncache(bufferId);
+        if (slot != UINT32_MAX) {
+            slotsToClear.push_back(slot);
+        }
+    }
+
+    hal::Error error =
+            state.hwc->hwcLayer->setBufferSlotsToClear(slotsToClear, state.hwc->activeBufferSlot);
+    if (error != hal::Error::NONE) {
+        ALOGE("[%s] Failed to clear buffer slots: %s (%d)", getLayerFE().getDebugName(),
+              to_string(error).c_str(), static_cast<int32_t>(error));
     }
 }
 
@@ -637,15 +647,25 @@
 
     HwcSlotAndBuffer hwcSlotAndBuffer;
     sp<Fence> hwcFence;
-    // Override buffers use a special cache slot so that they don't evict client buffers.
-    if (getState().overrideInfo.buffer != nullptr && !skipLayer) {
-        hwcSlotAndBuffer = editState().hwc->hwcBufferCache.getHwcSlotAndBufferForOverride(
-                getState().overrideInfo.buffer->getBuffer());
-        hwcFence = getState().overrideInfo.acquireFence;
-    } else {
-        hwcSlotAndBuffer =
-                editState().hwc->hwcBufferCache.getHwcSlotAndBuffer(outputIndependentState.buffer);
-        hwcFence = outputIndependentState.acquireFence;
+    {
+        // Editing the state only because we update the HWC buffer cache and active buffer.
+        auto& state = editState();
+        // Override buffers use a special cache slot so that they don't evict client buffers.
+        if (state.overrideInfo.buffer != nullptr && !skipLayer) {
+            hwcSlotAndBuffer = state.hwc->hwcBufferCache.getOverrideHwcSlotAndBuffer(
+                    state.overrideInfo.buffer->getBuffer());
+            hwcFence = state.overrideInfo.acquireFence;
+        } else {
+            hwcSlotAndBuffer =
+                    state.hwc->hwcBufferCache.getHwcSlotAndBuffer(outputIndependentState.buffer);
+            hwcFence = outputIndependentState.acquireFence;
+        }
+
+        // Keep track of the active buffer slot, so we can restore it after clearing other buffer
+        // slots.
+        if (hwcSlotAndBuffer.buffer) {
+            state.hwc->activeBufferSlot = hwcSlotAndBuffer.slot;
+        }
     }
 
     if (auto error = hwcLayer->setBuffer(hwcSlotAndBuffer.slot, hwcSlotAndBuffer.buffer, hwcFence);
diff --git a/services/surfaceflinger/CompositionEngine/tests/HwcBufferCacheTest.cpp b/services/surfaceflinger/CompositionEngine/tests/HwcBufferCacheTest.cpp
index cf72e8f..c5fb594 100644
--- a/services/surfaceflinger/CompositionEngine/tests/HwcBufferCacheTest.cpp
+++ b/services/surfaceflinger/CompositionEngine/tests/HwcBufferCacheTest.cpp
@@ -115,20 +115,20 @@
     EXPECT_EQ(cache.uncache(mBuffer2->getId()), UINT32_MAX);
 }
 
-TEST_F(HwcBufferCacheTest, getHwcSlotAndBufferForOverride_whenCached_returnsSameSlotAndNullBuffer) {
+TEST_F(HwcBufferCacheTest, getOverrideHwcSlotAndBuffer_whenCached_returnsSameSlotAndNullBuffer) {
     HwcBufferCache cache;
     sp<GraphicBuffer> outBuffer;
 
-    HwcSlotAndBuffer originalSlotAndBuffer = cache.getHwcSlotAndBufferForOverride(mBuffer1);
+    HwcSlotAndBuffer originalSlotAndBuffer = cache.getOverrideHwcSlotAndBuffer(mBuffer1);
     EXPECT_NE(originalSlotAndBuffer.slot, UINT32_MAX);
     EXPECT_EQ(originalSlotAndBuffer.buffer, mBuffer1);
 
-    HwcSlotAndBuffer finalSlotAndBuffer = cache.getHwcSlotAndBufferForOverride(mBuffer1);
+    HwcSlotAndBuffer finalSlotAndBuffer = cache.getOverrideHwcSlotAndBuffer(mBuffer1);
     EXPECT_EQ(finalSlotAndBuffer.slot, originalSlotAndBuffer.slot);
     EXPECT_EQ(finalSlotAndBuffer.buffer, nullptr);
 }
 
-TEST_F(HwcBufferCacheTest, getHwcSlotAndBufferForOverride_whenSlotsFull_returnsIndependentSlot) {
+TEST_F(HwcBufferCacheTest, getOverrideHwcSlotAndBuffer_whenSlotsFull_returnsIndependentSlot) {
     HwcBufferCache cache;
     sp<GraphicBuffer> outBuffer;
 
@@ -149,7 +149,7 @@
 
     sp<GraphicBuffer> overrideBuffer =
             sp<GraphicBuffer>::make(1u, 1u, HAL_PIXEL_FORMAT_RGBA_8888, 1u, 0u);
-    HwcSlotAndBuffer overrideSlotAndBuffer = cache.getHwcSlotAndBufferForOverride(overrideBuffer);
+    HwcSlotAndBuffer overrideSlotAndBuffer = cache.getOverrideHwcSlotAndBuffer(overrideBuffer);
     // expect us to have a slot number
     EXPECT_NE(overrideSlotAndBuffer.slot, UINT32_MAX);
     // expect this to be the first time we cached the buffer
@@ -173,7 +173,7 @@
     HwcBufferCache cache;
     sp<GraphicBuffer> outBuffer;
 
-    HwcSlotAndBuffer hwcSlotAndBuffer = cache.getHwcSlotAndBufferForOverride(mBuffer1);
+    HwcSlotAndBuffer hwcSlotAndBuffer = cache.getOverrideHwcSlotAndBuffer(mBuffer1);
     ASSERT_NE(hwcSlotAndBuffer.slot, UINT32_MAX);
 
     EXPECT_EQ(cache.uncache(mBuffer1->getId()), hwcSlotAndBuffer.slot);
@@ -184,7 +184,7 @@
     HwcBufferCache cache;
     sp<GraphicBuffer> outBuffer;
 
-    HwcSlotAndBuffer hwcSlotAndBuffer = cache.getHwcSlotAndBufferForOverride(mBuffer1);
+    HwcSlotAndBuffer hwcSlotAndBuffer = cache.getOverrideHwcSlotAndBuffer(mBuffer1);
     ASSERT_NE(hwcSlotAndBuffer.slot, UINT32_MAX);
 
     EXPECT_EQ(cache.uncache(mBuffer2->getId()), UINT32_MAX);
diff --git a/services/surfaceflinger/CompositionEngine/tests/MockHWC2.h b/services/surfaceflinger/CompositionEngine/tests/MockHWC2.h
index d933b94..b0b1a02 100644
--- a/services/surfaceflinger/CompositionEngine/tests/MockHWC2.h
+++ b/services/surfaceflinger/CompositionEngine/tests/MockHWC2.h
@@ -56,6 +56,7 @@
     MOCK_METHOD3(setBuffer,
                  Error(uint32_t, const android::sp<android::GraphicBuffer>&,
                        const android::sp<android::Fence>&));
+    MOCK_METHOD2(setBufferSlotsToClear, Error(const std::vector<uint32_t>&, uint32_t));
     MOCK_METHOD1(setSurfaceDamage, Error(const android::Region&));
     MOCK_METHOD1(setBlendMode, Error(hal::BlendMode));
     MOCK_METHOD1(setColor, Error(aidl::android::hardware::graphics::composer3::Color));
diff --git a/services/surfaceflinger/CompositionEngine/tests/OutputLayerTest.cpp b/services/surfaceflinger/CompositionEngine/tests/OutputLayerTest.cpp
index 03cf292..0edc226 100644
--- a/services/surfaceflinger/CompositionEngine/tests/OutputLayerTest.cpp
+++ b/services/surfaceflinger/CompositionEngine/tests/OutputLayerTest.cpp
@@ -42,6 +42,8 @@
 
 using testing::_;
 using testing::InSequence;
+using testing::Mock;
+using testing::NiceMock;
 using testing::Return;
 using testing::ReturnRef;
 using testing::StrictMock;
@@ -82,13 +84,13 @@
 
 struct OutputLayerTest : public testing::Test {
     struct OutputLayer final : public impl::OutputLayer {
-        OutputLayer(const compositionengine::Output& output, sp<compositionengine::LayerFE> layerFE)
+        OutputLayer(const compositionengine::Output& output, compositionengine::LayerFE& layerFE)
               : mOutput(output), mLayerFE(layerFE) {}
         ~OutputLayer() override = default;
 
         // compositionengine::OutputLayer overrides
         const compositionengine::Output& getOutput() const override { return mOutput; }
-        compositionengine::LayerFE& getLayerFE() const override { return *mLayerFE; }
+        compositionengine::LayerFE& getLayerFE() const override { return mLayerFE; }
         const impl::OutputLayerCompositionState& getState() const override { return mState; }
         impl::OutputLayerCompositionState& editState() override { return mState; }
 
@@ -96,21 +98,22 @@
         void dumpState(std::string& out) const override { mState.dump(out); }
 
         const compositionengine::Output& mOutput;
-        sp<compositionengine::LayerFE> mLayerFE;
+        compositionengine::LayerFE& mLayerFE;
         impl::OutputLayerCompositionState mState;
     };
 
     OutputLayerTest() {
-        EXPECT_CALL(*mLayerFE, getDebugName()).WillRepeatedly(Return("Test LayerFE"));
-        EXPECT_CALL(mOutput, getName()).WillRepeatedly(ReturnRef(kOutputName));
+        ON_CALL(mLayerFE, getDebugName()).WillByDefault(Return("Test LayerFE"));
+        ON_CALL(mOutput, getName()).WillByDefault(ReturnRef(kOutputName));
 
-        EXPECT_CALL(*mLayerFE, getCompositionState()).WillRepeatedly(Return(&mLayerFEState));
-        EXPECT_CALL(mOutput, getState()).WillRepeatedly(ReturnRef(mOutputState));
+        ON_CALL(mLayerFE, getCompositionState()).WillByDefault(Return(&mLayerFEState));
+        ON_CALL(mOutput, getState()).WillByDefault(ReturnRef(mOutputState));
     }
 
-    compositionengine::mock::Output mOutput;
-    sp<StrictMock<compositionengine::mock::LayerFE>> mLayerFE =
-            sp<StrictMock<compositionengine::mock::LayerFE>>::make();
+    NiceMock<compositionengine::mock::Output> mOutput;
+    sp<NiceMock<compositionengine::mock::LayerFE>> mLayerFE_ =
+            sp<NiceMock<compositionengine::mock::LayerFE>>::make();
+    NiceMock<compositionengine::mock::LayerFE>& mLayerFE = *mLayerFE_;
     OutputLayer mOutputLayer{mOutput, mLayerFE};
 
     LayerFECompositionState mLayerFEState;
@@ -530,7 +533,7 @@
 
 struct OutputLayerPartialMockForUpdateCompositionState : public impl::OutputLayer {
     OutputLayerPartialMockForUpdateCompositionState(const compositionengine::Output& output,
-                                                    sp<compositionengine::LayerFE> layerFE)
+                                                    compositionengine::LayerFE& layerFE)
           : mOutput(output), mLayerFE(layerFE) {}
     // Mock everything called by updateCompositionState to simplify testing it.
     MOCK_CONST_METHOD1(calculateOutputSourceCrop, FloatRect(uint32_t));
@@ -539,7 +542,7 @@
 
     // compositionengine::OutputLayer overrides
     const compositionengine::Output& getOutput() const override { return mOutput; }
-    compositionengine::LayerFE& getLayerFE() const override { return *mLayerFE; }
+    compositionengine::LayerFE& getLayerFE() const override { return mLayerFE; }
     const impl::OutputLayerCompositionState& getState() const override { return mState; }
     impl::OutputLayerCompositionState& editState() override { return mState; }
 
@@ -547,7 +550,7 @@
     MOCK_CONST_METHOD1(dumpState, void(std::string&));
 
     const compositionengine::Output& mOutput;
-    sp<compositionengine::LayerFE> mLayerFE;
+    compositionengine::LayerFE& mLayerFE;
     impl::OutputLayerCompositionState mState;
 };
 
@@ -588,7 +591,7 @@
 };
 
 TEST_F(OutputLayerUpdateCompositionStateTest, doesNothingIfNoFECompositionState) {
-    EXPECT_CALL(*mLayerFE, getCompositionState()).WillOnce(Return(nullptr));
+    EXPECT_CALL(mLayerFE, getCompositionState()).WillOnce(Return(nullptr));
 
     mOutputLayer.updateCompositionState(true, false, ui::Transform::RotationFlags::ROT_90);
 }
@@ -833,7 +836,6 @@
         EXPECT_CALL(mDisplayColorProfile, getSupportedPerFrameMetadata())
                 .WillRepeatedly(Return(kSupportedPerFrameMetadata));
     }
-
     // Some tests may need to simulate unsupported HWC calls
     enum class SimulateUnsupported { None, ColorTransform };
 
@@ -952,7 +954,10 @@
 const HdrMetadata OutputLayerWriteStateToHWCTest::kHdrMetadata{{/* LightFlattenable */}, 1029};
 native_handle_t* OutputLayerWriteStateToHWCTest::kSidebandStreamHandle =
         reinterpret_cast<native_handle_t*>(1031);
-const sp<GraphicBuffer> OutputLayerWriteStateToHWCTest::kBuffer;
+const sp<GraphicBuffer> OutputLayerWriteStateToHWCTest::kBuffer =
+        sp<GraphicBuffer>::make(1, 2, PIXEL_FORMAT_RGBA_8888,
+                                AHARDWAREBUFFER_USAGE_CPU_WRITE_OFTEN |
+                                        AHARDWAREBUFFER_USAGE_CPU_READ_OFTEN);
 const sp<GraphicBuffer> OutputLayerWriteStateToHWCTest::kOverrideBuffer =
         sp<GraphicBuffer>::make(4, 5, PIXEL_FORMAT_RGBA_8888,
                                 AHARDWAREBUFFER_USAGE_CPU_WRITE_OFTEN |
@@ -968,7 +973,7 @@
         {4, 5, 6, 7}};
 
 TEST_F(OutputLayerWriteStateToHWCTest, doesNothingIfNoFECompositionState) {
-    EXPECT_CALL(*mLayerFE, getCompositionState()).WillOnce(Return(nullptr));
+    EXPECT_CALL(mLayerFE, getCompositionState()).WillOnce(Return(nullptr));
 
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ true, /*skipLayer*/ false, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
@@ -993,7 +998,7 @@
     expectPerFrameCommonCalls();
 
     expectNoSetCompositionTypeCall();
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillOnce(Return(false));
+    EXPECT_CALL(mLayerFE, hasRoundedCorners()).WillOnce(Return(false));
 
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ true, /*skipLayer*/ false, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
@@ -1018,7 +1023,6 @@
     mLayerFEState.compositionType = Composition::SOLID_COLOR;
 
     expectPerFrameCommonCalls();
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillOnce(Return(false));
 
     // Setting the composition type should happen before setting the color. We
     // check this in this test only by setting up an testing::InSeqeuence
@@ -1038,8 +1042,6 @@
     expectSetSidebandHandleCall();
     expectSetCompositionTypeCall(Composition::SIDEBAND);
 
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillOnce(Return(false));
-
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ false, /*skipLayer*/ false, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
 }
@@ -1051,8 +1053,6 @@
     expectSetHdrMetadataAndBufferCalls();
     expectSetCompositionTypeCall(Composition::CURSOR);
 
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillOnce(Return(false));
-
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ false, /*skipLayer*/ false, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
 }
@@ -1064,8 +1064,6 @@
     expectSetHdrMetadataAndBufferCalls();
     expectSetCompositionTypeCall(Composition::DEVICE);
 
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillOnce(Return(false));
-
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ false, /*skipLayer*/ false, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
 }
@@ -1079,8 +1077,6 @@
     expectSetColorCall();
     expectNoSetCompositionTypeCall();
 
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillOnce(Return(false));
-
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ false, /*skipLayer*/ false, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
 }
@@ -1119,8 +1115,6 @@
     expectGenericLayerMetadataCalls();
     expectSetCompositionTypeCall(Composition::DEVICE);
 
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillOnce(Return(false));
-
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ true, /*skipLayer*/ false, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
 }
@@ -1133,8 +1127,6 @@
     expectSetHdrMetadataAndBufferCalls();
     expectSetCompositionTypeCall(Composition::DEVICE);
 
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillOnce(Return(false));
-
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ false, /*skipLayer*/ false, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
 }
@@ -1149,7 +1141,6 @@
                               kOverrideSurfaceDamage, kOverrideLayerBrightness);
     expectSetHdrMetadataAndBufferCalls();
     expectSetCompositionTypeCall(Composition::DEVICE);
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillRepeatedly(Return(false));
 
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ true, /*skipLayer*/ true, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
@@ -1165,7 +1156,6 @@
                               kOverrideSurfaceDamage, kOverrideLayerBrightness);
     expectSetHdrMetadataAndBufferCalls();
     expectSetCompositionTypeCall(Composition::DEVICE);
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillRepeatedly(Return(false));
 
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ true, /*skipLayer*/ true, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
@@ -1181,7 +1171,6 @@
                               kOverrideSurfaceDamage, kOverrideLayerBrightness);
     expectSetHdrMetadataAndBufferCalls(kOverrideHwcSlot, kOverrideBuffer, kOverrideFence);
     expectSetCompositionTypeCall(Composition::DEVICE);
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillRepeatedly(Return(false));
 
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ true, /*skipLayer*/ false, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
@@ -1197,7 +1186,6 @@
                               kOverrideSurfaceDamage, kOverrideLayerBrightness);
     expectSetHdrMetadataAndBufferCalls(kOverrideHwcSlot, kOverrideBuffer, kOverrideFence);
     expectSetCompositionTypeCall(Composition::DEVICE);
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillRepeatedly(Return(false));
 
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ true, /*skipLayer*/ false, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
@@ -1212,7 +1200,6 @@
                               Region::INVALID_REGION);
     expectSetHdrMetadataAndBufferCalls();
     expectSetCompositionTypeCall(Composition::DEVICE);
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillRepeatedly(Return(false));
 
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ true, /*skipLayer*/ false, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
@@ -1229,7 +1216,6 @@
                               Region::INVALID_REGION);
     expectSetHdrMetadataAndBufferCalls();
     expectSetCompositionTypeCall(Composition::DEVICE);
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillOnce(Return(false));
 
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ true, /*skipLayer*/ false, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
@@ -1247,22 +1233,20 @@
                               Region::INVALID_REGION);
     expectSetHdrMetadataAndBufferCalls();
     expectSetCompositionTypeCall(Composition::CLIENT);
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillRepeatedly(Return(false));
 
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ true, /*skipLayer*/ false, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
 }
 
 TEST_F(OutputLayerWriteStateToHWCTest, peekThroughChangesBlendMode) {
-    auto peekThroughLayerFE = sp<compositionengine::mock::LayerFE>::make();
-    OutputLayer peekThroughLayer{mOutput, peekThroughLayerFE};
+    auto peekThroughLayerFE = sp<NiceMock<compositionengine::mock::LayerFE>>::make();
+    OutputLayer peekThroughLayer{mOutput, *peekThroughLayerFE};
 
     mOutputLayer.mState.overrideInfo.peekThroughLayer = &peekThroughLayer;
 
     expectGeometryCommonCalls(kDisplayFrame, kSourceCrop, kBufferTransform,
                               Hwc2::IComposerClient::BlendMode::PREMULTIPLIED);
     expectPerFrameCommonCalls();
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillOnce(Return(false));
 
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ true, /*skipLayer*/ false, 0,
                                  /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
@@ -1280,7 +1264,6 @@
 TEST_F(OutputLayerWriteStateToHWCTest, zIsOverriddenSetsOverride) {
     expectGeometryCommonCalls();
     expectPerFrameCommonCalls();
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillOnce(Return(false));
 
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ true, /*skipLayer*/ false, 0,
                                  /*zIsOverridden*/ true, /*isPeekingThrough*/
@@ -1291,7 +1274,7 @@
 TEST_F(OutputLayerWriteStateToHWCTest, roundedCornersForceClientComposition) {
     expectGeometryCommonCalls();
     expectPerFrameCommonCalls();
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillOnce(Return(true));
+    EXPECT_CALL(mLayerFE, hasRoundedCorners()).WillOnce(Return(true));
     expectSetCompositionTypeCall(Composition::CLIENT);
 
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ true, /*skipLayer*/ false, 0,
@@ -1303,7 +1286,7 @@
     expectGeometryCommonCalls();
     expectPerFrameCommonCalls();
     expectSetHdrMetadataAndBufferCalls();
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillRepeatedly(Return(true));
+    EXPECT_CALL(mLayerFE, hasRoundedCorners()).WillRepeatedly(Return(true));
     expectSetCompositionTypeCall(Composition::DEVICE);
 
     mLayerFEState.compositionType = Composition::DEVICE;
@@ -1322,7 +1305,6 @@
     expectPerFrameCommonCalls(SimulateUnsupported::None, kDataspace, kOutputSpaceVisibleRegion,
                               kSurfaceDamage, kLayerBrightness, blockingRegion);
     expectSetHdrMetadataAndBufferCalls();
-    EXPECT_CALL(*mLayerFE, hasRoundedCorners()).WillRepeatedly(Return(false));
     expectSetCompositionTypeCall(Composition::DISPLAY_DECORATION);
 
     mOutputLayer.writeStateToHWC(/*includeGeometry*/ true, /*skipLayer*/ false, 0,
@@ -1331,6 +1313,76 @@
 }
 
 /*
+ * OutputLayer::uncacheBuffers
+ */
+struct OutputLayerUncacheBufferTest : public OutputLayerTest {
+    static const sp<GraphicBuffer> kBuffer1;
+    static const sp<GraphicBuffer> kBuffer2;
+    static const sp<Fence> kFence;
+
+    OutputLayerUncacheBufferTest() {
+        auto& outputLayerState = mOutputLayer.editState();
+        outputLayerState.hwc = impl::OutputLayerCompositionState::Hwc(mHwcLayer_);
+
+        mLayerFEState.compositionType = Composition::DEVICE;
+        mLayerFEState.acquireFence = kFence;
+
+        ON_CALL(mOutput, getDisplayColorProfile()).WillByDefault(Return(&mDisplayColorProfile));
+    }
+
+    std::shared_ptr<HWC2::mock::Layer> mHwcLayer_{std::make_shared<NiceMock<HWC2::mock::Layer>>()};
+    HWC2::mock::Layer& mHwcLayer = *mHwcLayer_;
+    NiceMock<mock::DisplayColorProfile> mDisplayColorProfile;
+};
+
+const sp<GraphicBuffer> OutputLayerUncacheBufferTest::kBuffer1 =
+        sp<GraphicBuffer>::make(1, 2, PIXEL_FORMAT_RGBA_8888,
+                                AHARDWAREBUFFER_USAGE_CPU_WRITE_OFTEN |
+                                        AHARDWAREBUFFER_USAGE_CPU_READ_OFTEN);
+const sp<GraphicBuffer> OutputLayerUncacheBufferTest::kBuffer2 =
+        sp<GraphicBuffer>::make(2, 3, PIXEL_FORMAT_RGBA_8888,
+                                AHARDWAREBUFFER_USAGE_CPU_WRITE_OFTEN |
+                                        AHARDWAREBUFFER_USAGE_CPU_READ_OFTEN);
+const sp<Fence> OutputLayerUncacheBufferTest::kFence = sp<Fence>::make();
+
+TEST_F(OutputLayerUncacheBufferTest, canUncacheAndReuseSlot) {
+    // Buffer1 is stored in slot 0
+    mLayerFEState.buffer = kBuffer1;
+    EXPECT_CALL(mHwcLayer, setBuffer(/*slot*/ 0, kBuffer1, kFence));
+    mOutputLayer.writeStateToHWC(/*includeGeometry*/ false, /*skipLayer*/ false, 0,
+                                 /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
+    Mock::VerifyAndClearExpectations(&mHwcLayer);
+
+    // Buffer2 is stored in slot 1
+    mLayerFEState.buffer = kBuffer2;
+    EXPECT_CALL(mHwcLayer, setBuffer(/*slot*/ 1, kBuffer2, kFence));
+    mOutputLayer.writeStateToHWC(/*includeGeometry*/ false, /*skipLayer*/ false, 0,
+                                 /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
+    Mock::VerifyAndClearExpectations(&mHwcLayer);
+
+    // buffer slots are cleared in HWC
+    std::vector<uint32_t> slotsToClear = {0, 1};
+    EXPECT_CALL(mHwcLayer,
+                setBufferSlotsToClear(/*slotsToClear*/ slotsToClear, /*activeBufferSlot*/ 1));
+    mOutputLayer.uncacheBuffers({kBuffer1->getId(), kBuffer2->getId()});
+    Mock::VerifyAndClearExpectations(&mHwcLayer);
+
+    // rather than allocating a new slot, the active buffer slot (slot 1) is reused first to free
+    // the memory as soon as possible
+    mLayerFEState.buffer = kBuffer1;
+    EXPECT_CALL(mHwcLayer, setBuffer(/*slot*/ 1, kBuffer1, kFence));
+    mOutputLayer.writeStateToHWC(/*includeGeometry*/ false, /*skipLayer*/ false, 0,
+                                 /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
+    Mock::VerifyAndClearExpectations(&mHwcLayer);
+
+    // rather than allocating a new slot, slot 0 is reused
+    mLayerFEState.buffer = kBuffer2;
+    EXPECT_CALL(mHwcLayer, setBuffer(/*slot*/ 0, kBuffer2, kFence));
+    mOutputLayer.writeStateToHWC(/*includeGeometry*/ false, /*skipLayer*/ false, 0,
+                                 /*zIsOverridden*/ false, /*isPeekingThrough*/ false);
+}
+
+/*
  * OutputLayer::writeCursorPositionToHWC()
  */
 
@@ -1358,7 +1410,7 @@
 const Rect OutputLayerWriteCursorPositionToHWCTest::kDefaultCursorFrame{1, 2, 3, 4};
 
 TEST_F(OutputLayerWriteCursorPositionToHWCTest, doesNothingIfNoFECompositionState) {
-    EXPECT_CALL(*mLayerFE, getCompositionState()).WillOnce(Return(nullptr));
+    EXPECT_CALL(mLayerFE, getCompositionState()).WillOnce(Return(nullptr));
 
     mOutputLayer.writeCursorPositionToHWC();
 }
diff --git a/services/surfaceflinger/DisplayHardware/AidlComposerHal.cpp b/services/surfaceflinger/DisplayHardware/AidlComposerHal.cpp
index 806df87..d061a99 100644
--- a/services/surfaceflinger/DisplayHardware/AidlComposerHal.cpp
+++ b/services/surfaceflinger/DisplayHardware/AidlComposerHal.cpp
@@ -233,6 +233,17 @@
 
     addReader(translate<Display>(kSingleReaderKey));
 
+    // TODO(b/262041682): When using new API to clear buffer slots, don't allocate this buffer.
+    mClearSlotBuffer = sp<GraphicBuffer>::make(1, 1, PIXEL_FORMAT_RGBX_8888,
+                                               GraphicBuffer::USAGE_HW_COMPOSER |
+                                                       GraphicBuffer::USAGE_SW_READ_OFTEN |
+                                                       GraphicBuffer::USAGE_SW_WRITE_OFTEN,
+                                               "AidlComposer");
+    if (!mClearSlotBuffer || mClearSlotBuffer->initCheck() != ::android::OK) {
+        LOG_ALWAYS_FATAL("Failed to allocate a buffer for clearing layer buffer slots");
+        return;
+    }
+
     ALOGI("Loaded AIDL composer3 HAL service");
 }
 
@@ -814,6 +825,42 @@
     return error;
 }
 
+Error AidlComposer::setLayerBufferSlotsToClear(Display display, Layer layer,
+                                               const std::vector<uint32_t>& slotsToClear,
+                                               uint32_t activeBufferSlot) {
+    if (slotsToClear.empty()) {
+        return Error::NONE;
+    }
+
+    Error error = Error::NONE;
+    mMutex.lock_shared();
+    if (auto writer = getWriter(display)) {
+        // Backwards compatible way of clearing buffer slots is tricky...
+        for (uint32_t slot : slotsToClear) {
+            // Don't clear the active buffer slot because we need to restore the active buffer
+            // after clearing the requested buffer slots with a placeholder buffer.
+            if (slot != activeBufferSlot) {
+                writer->get().setLayerBufferWithNewCommand(translate<int64_t>(display),
+                                                           translate<int64_t>(layer), slot,
+                                                           mClearSlotBuffer->handle, /*fence*/ -1);
+            }
+        }
+        // Since we clear buffers by setting them to a placeholder buffer, we want to make
+        // sure that the last setLayerBuffer command is sent with the currently active
+        // buffer, not the placeholder buffer, so that there is no perceptual change when
+        // buffers are discarded.
+        writer->get().setLayerBufferWithNewCommand(translate<int64_t>(display),
+                                                   translate<int64_t>(layer), activeBufferSlot,
+                                                   // The active buffer is still cached in
+                                                   // its slot and doesn't need a fence.
+                                                   /*buffer*/ nullptr, /*fence*/ -1);
+    } else {
+        error = Error::BAD_DISPLAY;
+    }
+    mMutex.unlock_shared();
+    return error;
+}
+
 Error AidlComposer::setLayerSurfaceDamage(Display display, Layer layer,
                                           const std::vector<IComposerClient::Rect>& damage) {
     Error error = Error::NONE;
diff --git a/services/surfaceflinger/DisplayHardware/AidlComposerHal.h b/services/surfaceflinger/DisplayHardware/AidlComposerHal.h
index 2a043fd..9a7ade7 100644
--- a/services/surfaceflinger/DisplayHardware/AidlComposerHal.h
+++ b/services/surfaceflinger/DisplayHardware/AidlComposerHal.h
@@ -143,6 +143,9 @@
     /* see setClientTarget for the purpose of slot */
     Error setLayerBuffer(Display display, Layer layer, uint32_t slot,
                          const sp<GraphicBuffer>& buffer, int acquireFence) override;
+    Error setLayerBufferSlotsToClear(Display display, Layer layer,
+                                     const std::vector<uint32_t>& slotsToClear,
+                                     uint32_t activeBufferSlot) override;
     Error setLayerSurfaceDamage(Display display, Layer layer,
                                 const std::vector<IComposerClient::Rect>& damage) override;
     Error setLayerBlendMode(Display display, Layer layer, IComposerClient::BlendMode mode) override;
@@ -280,6 +283,9 @@
     // threading annotations.
     ftl::SharedMutex mMutex;
 
+    // Buffer slots for layers are cleared by setting the slot buffer to this buffer.
+    sp<GraphicBuffer> mClearSlotBuffer;
+
     // Aidl interface
     using AidlIComposer = aidl::android::hardware::graphics::composer3::IComposer;
     using AidlIComposerClient = aidl::android::hardware::graphics::composer3::IComposerClient;
diff --git a/services/surfaceflinger/DisplayHardware/ComposerHal.h b/services/surfaceflinger/DisplayHardware/ComposerHal.h
index ec23935..1c2b8b5 100644
--- a/services/surfaceflinger/DisplayHardware/ComposerHal.h
+++ b/services/surfaceflinger/DisplayHardware/ComposerHal.h
@@ -179,6 +179,9 @@
     /* see setClientTarget for the purpose of slot */
     virtual Error setLayerBuffer(Display display, Layer layer, uint32_t slot,
                                  const sp<GraphicBuffer>& buffer, int acquireFence) = 0;
+    virtual Error setLayerBufferSlotsToClear(Display display, Layer layer,
+                                             const std::vector<uint32_t>& slotsToClear,
+                                             uint32_t activeBufferSlot) = 0;
     virtual Error setLayerSurfaceDamage(Display display, Layer layer,
                                         const std::vector<IComposerClient::Rect>& damage) = 0;
     virtual Error setLayerBlendMode(Display display, Layer layer,
diff --git a/services/surfaceflinger/DisplayHardware/HWC2.cpp b/services/surfaceflinger/DisplayHardware/HWC2.cpp
index d0126d0..6738f00 100644
--- a/services/surfaceflinger/DisplayHardware/HWC2.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWC2.cpp
@@ -717,6 +717,16 @@
     return static_cast<Error>(intError);
 }
 
+Error Layer::setBufferSlotsToClear(const std::vector<uint32_t>& slotsToClear,
+                                   uint32_t activeBufferSlot) {
+    if (CC_UNLIKELY(!mDisplay)) {
+        return Error::BAD_DISPLAY;
+    }
+    auto intError = mComposer.setLayerBufferSlotsToClear(mDisplay->getId(), mId, slotsToClear,
+                                                         activeBufferSlot);
+    return static_cast<Error>(intError);
+}
+
 Error Layer::setSurfaceDamage(const Region& damage)
 {
     if (CC_UNLIKELY(!mDisplay)) {
diff --git a/services/surfaceflinger/DisplayHardware/HWC2.h b/services/surfaceflinger/DisplayHardware/HWC2.h
index 4971d19..c1c7070 100644
--- a/services/surfaceflinger/DisplayHardware/HWC2.h
+++ b/services/surfaceflinger/DisplayHardware/HWC2.h
@@ -310,6 +310,8 @@
     [[nodiscard]] virtual hal::Error setBuffer(uint32_t slot,
                                                const android::sp<android::GraphicBuffer>& buffer,
                                                const android::sp<android::Fence>& acquireFence) = 0;
+    [[nodiscard]] virtual hal::Error setBufferSlotsToClear(
+            const std::vector<uint32_t>& slotsToClear, uint32_t activeBufferSlot) = 0;
     [[nodiscard]] virtual hal::Error setSurfaceDamage(const android::Region& damage) = 0;
 
     [[nodiscard]] virtual hal::Error setBlendMode(hal::BlendMode mode) = 0;
@@ -360,6 +362,8 @@
     hal::Error setCursorPosition(int32_t x, int32_t y) override;
     hal::Error setBuffer(uint32_t slot, const android::sp<android::GraphicBuffer>& buffer,
                          const android::sp<android::Fence>& acquireFence) override;
+    hal::Error setBufferSlotsToClear(const std::vector<uint32_t>& slotsToClear,
+                                     uint32_t activeBufferSlot) override;
     hal::Error setSurfaceDamage(const android::Region& damage) override;
 
     hal::Error setBlendMode(hal::BlendMode mode) override;
diff --git a/services/surfaceflinger/DisplayHardware/HidlComposerHal.cpp b/services/surfaceflinger/DisplayHardware/HidlComposerHal.cpp
index b607df0..c9e1e79 100644
--- a/services/surfaceflinger/DisplayHardware/HidlComposerHal.cpp
+++ b/services/surfaceflinger/DisplayHardware/HidlComposerHal.cpp
@@ -186,9 +186,22 @@
     return out;
 }
 
+sp<GraphicBuffer> allocateClearSlotBuffer() {
+    sp<GraphicBuffer> buffer = sp<GraphicBuffer>::make(1, 1, PIXEL_FORMAT_RGBX_8888,
+                                                       GraphicBuffer::USAGE_HW_COMPOSER |
+                                                               GraphicBuffer::USAGE_SW_READ_OFTEN |
+                                                               GraphicBuffer::USAGE_SW_WRITE_OFTEN,
+                                                       "HidlComposer");
+    if (!buffer || buffer->initCheck() != ::android::OK) {
+        return nullptr;
+    }
+    return std::move(buffer);
+}
+
 } // anonymous namespace
 
-HidlComposer::HidlComposer(const std::string& serviceName) : mWriter(kWriterInitialSize) {
+HidlComposer::HidlComposer(const std::string& serviceName)
+      : mClearSlotBuffer(allocateClearSlotBuffer()), mWriter(kWriterInitialSize) {
     mComposer = V2_1::IComposer::getService(serviceName);
 
     if (mComposer == nullptr) {
@@ -230,6 +243,11 @@
     if (mClient == nullptr) {
         LOG_ALWAYS_FATAL("failed to create composer client");
     }
+
+    if (!mClearSlotBuffer) {
+        LOG_ALWAYS_FATAL("Failed to allocate a buffer for clearing layer buffer slots");
+        return;
+    }
 }
 
 bool HidlComposer::isSupported(OptionalFeature feature) const {
@@ -694,6 +712,32 @@
     return Error::NONE;
 }
 
+Error HidlComposer::setLayerBufferSlotsToClear(Display display, Layer layer,
+                                               const std::vector<uint32_t>& slotsToClear,
+                                               uint32_t activeBufferSlot) {
+    if (slotsToClear.empty()) {
+        return Error::NONE;
+    }
+    // Backwards compatible way of clearing buffer is to set the layer buffer with a placeholder
+    // buffer, using the slot that needs to cleared... tricky.
+    for (uint32_t slot : slotsToClear) {
+        // Don't clear the active buffer slot because we need to restore the active buffer after
+        // setting the requested buffer slots with a placeholder buffer.
+        if (slot != activeBufferSlot) {
+            mWriter.selectDisplay(display);
+            mWriter.selectLayer(layer);
+            mWriter.setLayerBuffer(slot, mClearSlotBuffer->handle, /*fence*/ -1);
+        }
+    }
+    // Since we clear buffers by setting them to a placeholder buffer, we want to make sure that the
+    // last setLayerBuffer command is sent with the currently active buffer, not the placeholder
+    // buffer, so that there is no perceptual change.
+    mWriter.selectDisplay(display);
+    mWriter.selectLayer(layer);
+    mWriter.setLayerBuffer(activeBufferSlot, /*buffer*/ nullptr, /*fence*/ -1);
+    return Error::NONE;
+}
+
 Error HidlComposer::setLayerSurfaceDamage(Display display, Layer layer,
                                           const std::vector<IComposerClient::Rect>& damage) {
     mWriter.selectDisplay(display);
diff --git a/services/surfaceflinger/DisplayHardware/HidlComposerHal.h b/services/surfaceflinger/DisplayHardware/HidlComposerHal.h
index 3602bbb..921add5 100644
--- a/services/surfaceflinger/DisplayHardware/HidlComposerHal.h
+++ b/services/surfaceflinger/DisplayHardware/HidlComposerHal.h
@@ -248,6 +248,9 @@
     /* see setClientTarget for the purpose of slot */
     Error setLayerBuffer(Display display, Layer layer, uint32_t slot,
                          const sp<GraphicBuffer>& buffer, int acquireFence) override;
+    Error setLayerBufferSlotsToClear(Display display, Layer layer,
+                                     const std::vector<uint32_t>& slotsToClear,
+                                     uint32_t activeBufferSlot) override;
     Error setLayerSurfaceDamage(Display display, Layer layer,
                                 const std::vector<IComposerClient::Rect>& damage) override;
     Error setLayerBlendMode(Display display, Layer layer, IComposerClient::BlendMode mode) override;
@@ -362,6 +365,9 @@
     sp<V2_3::IComposerClient> mClient_2_3;
     sp<IComposerClient> mClient_2_4;
 
+    // Buffer slots for layers are cleared by setting the slot buffer to this buffer.
+    sp<GraphicBuffer> mClearSlotBuffer;
+
     // 64KiB minus a small space for metadata such as read/write pointers
     static constexpr size_t kWriterInitialSize = 64 * 1024 / sizeof(uint32_t) - 16;
     // Max number of buffers that may be cached for a given layer
diff --git a/services/surfaceflinger/tests/unittests/mock/DisplayHardware/MockComposer.h b/services/surfaceflinger/tests/unittests/mock/DisplayHardware/MockComposer.h
index 836e3a4..2f16b7b 100644
--- a/services/surfaceflinger/tests/unittests/mock/DisplayHardware/MockComposer.h
+++ b/services/surfaceflinger/tests/unittests/mock/DisplayHardware/MockComposer.h
@@ -98,6 +98,8 @@
                  Error(Display, nsecs_t, uint32_t*, uint32_t*, int*, uint32_t*));
     MOCK_METHOD4(setCursorPosition, Error(Display, Layer, int32_t, int32_t));
     MOCK_METHOD5(setLayerBuffer, Error(Display, Layer, uint32_t, const sp<GraphicBuffer>&, int));
+    MOCK_METHOD4(setLayerBufferSlotsToClear,
+                 Error(Display, Layer, const std::vector<uint32_t>&, uint32_t));
     MOCK_METHOD3(setLayerSurfaceDamage,
                  Error(Display, Layer, const std::vector<IComposerClient::Rect>&));
     MOCK_METHOD3(setLayerBlendMode, Error(Display, Layer, IComposerClient::BlendMode));