diff --git a/services/surfaceflinger/tests/unittests/Android.bp b/services/surfaceflinger/tests/unittests/Android.bp
index 3dc6d8b..af635f9 100644
--- a/services/surfaceflinger/tests/unittests/Android.bp
+++ b/services/surfaceflinger/tests/unittests/Android.bp
@@ -71,6 +71,7 @@
         "MessageQueueTest.cpp",
         "SurfaceFlinger_CreateDisplayTest.cpp",
         "SurfaceFlinger_DestroyDisplayTest.cpp",
+        "SurfaceFlinger_DisplayModeSwitching.cpp",
         "SurfaceFlinger_DisplayTransactionCommitTest.cpp",
         "SurfaceFlinger_GetDisplayNativePrimariesTest.cpp",
         "SurfaceFlinger_HotplugTest.cpp",
diff --git a/services/surfaceflinger/tests/unittests/SurfaceFlinger_DisplayModeSwitching.cpp b/services/surfaceflinger/tests/unittests/SurfaceFlinger_DisplayModeSwitching.cpp
new file mode 100644
index 0000000..025edc2
--- /dev/null
+++ b/services/surfaceflinger/tests/unittests/SurfaceFlinger_DisplayModeSwitching.cpp
@@ -0,0 +1,295 @@
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "mock/MockEventThread.h"
+#undef LOG_TAG
+#define LOG_TAG "LibSurfaceFlingerUnittests"
+
+#include "DisplayTransactionTestHelpers.h"
+
+#include "Fps.h"
+
+namespace android {
+namespace {
+
+using android::hardware::graphics::composer::V2_4::Error;
+using android::hardware::graphics::composer::V2_4::VsyncPeriodChangeTimeline;
+
+class DisplayModeSwitchingTest : public DisplayTransactionTest {
+public:
+    void SetUp() override {
+        injectFakeBufferQueueFactory();
+        injectFakeNativeWindowSurfaceFactory();
+
+        PrimaryDisplayVariant::setupHwcHotplugCallExpectations(this);
+        PrimaryDisplayVariant::setupFramebufferConsumerBufferQueueCallExpectations(this);
+        PrimaryDisplayVariant::setupFramebufferProducerBufferQueueCallExpectations(this);
+        PrimaryDisplayVariant::setupNativeWindowSurfaceCreationCallExpectations(this);
+        PrimaryDisplayVariant::setupHwcGetActiveConfigCallExpectations(this);
+
+        mFlinger.onComposerHalHotplug(PrimaryDisplayVariant::HWC_DISPLAY_ID, Connection::CONNECTED);
+
+        mDisplay = PrimaryDisplayVariant::makeFakeExistingDisplayInjector(this)
+                           .setSupportedModes({kDisplayMode60, kDisplayMode90, kDisplayMode120,
+                                               kDisplayMode90DifferentResolution})
+                           .setActiveMode(kDisplayModeId60)
+                           .inject();
+
+        setupScheduler();
+
+        // isVsyncPeriodSwitchSupported should return true, otherwise the SF's HWC proxy
+        // will call setActiveConfig instead of setActiveConfigWithConstraints.
+        ON_CALL(*mComposer, isVsyncPeriodSwitchSupported()).WillByDefault(Return(true));
+    }
+
+protected:
+    void setupScheduler();
+    void testChangeRefreshRate(bool isDisplayActive, bool isRefreshRequired);
+
+    sp<DisplayDevice> mDisplay;
+    mock::EventThread* mAppEventThread;
+
+    const DisplayModeId kDisplayModeId60 = DisplayModeId(0);
+    const DisplayModePtr kDisplayMode60 =
+            DisplayMode::Builder(hal::HWConfigId(kDisplayModeId60.value()))
+                    .setId(kDisplayModeId60)
+                    .setPhysicalDisplayId(PrimaryDisplayVariant::DISPLAY_ID::get())
+                    .setVsyncPeriod((60_Hz).getPeriodNsecs())
+                    .setGroup(0)
+                    .setHeight(1000)
+                    .setWidth(1000)
+                    .build();
+
+    const DisplayModeId kDisplayModeId90 = DisplayModeId(1);
+    const DisplayModePtr kDisplayMode90 =
+            DisplayMode::Builder(hal::HWConfigId(kDisplayModeId90.value()))
+                    .setId(kDisplayModeId90)
+                    .setPhysicalDisplayId(PrimaryDisplayVariant::DISPLAY_ID::get())
+                    .setVsyncPeriod((90_Hz).getPeriodNsecs())
+                    .setGroup(1)
+                    .setHeight(1000)
+                    .setWidth(1000)
+                    .build();
+
+    const DisplayModeId kDisplayModeId120 = DisplayModeId(2);
+    const DisplayModePtr kDisplayMode120 =
+            DisplayMode::Builder(hal::HWConfigId(kDisplayModeId120.value()))
+                    .setId(kDisplayModeId120)
+                    .setPhysicalDisplayId(PrimaryDisplayVariant::DISPLAY_ID::get())
+                    .setVsyncPeriod((120_Hz).getPeriodNsecs())
+                    .setGroup(2)
+                    .setHeight(1000)
+                    .setWidth(1000)
+                    .build();
+
+    const DisplayModeId kDisplayModeId90DifferentResolution = DisplayModeId(3);
+    const DisplayModePtr kDisplayMode90DifferentResolution =
+            DisplayMode::Builder(hal::HWConfigId(kDisplayModeId90DifferentResolution.value()))
+                    .setId(kDisplayModeId90DifferentResolution)
+                    .setPhysicalDisplayId(PrimaryDisplayVariant::DISPLAY_ID::get())
+                    .setVsyncPeriod((90_Hz).getPeriodNsecs())
+                    .setGroup(3)
+                    .setHeight(2000)
+                    .setWidth(2000)
+                    .build();
+};
+
+void DisplayModeSwitchingTest::setupScheduler() {
+    auto eventThread = std::make_unique<mock::EventThread>();
+    mAppEventThread = eventThread.get();
+    auto sfEventThread = std::make_unique<mock::EventThread>();
+
+    EXPECT_CALL(*eventThread, registerDisplayEventConnection(_));
+    EXPECT_CALL(*eventThread, createEventConnection(_, _))
+            .WillOnce(Return(new EventThreadConnection(eventThread.get(), /*callingUid=*/0,
+                                                       ResyncCallback())));
+
+    EXPECT_CALL(*sfEventThread, registerDisplayEventConnection(_));
+    EXPECT_CALL(*sfEventThread, createEventConnection(_, _))
+            .WillOnce(Return(new EventThreadConnection(sfEventThread.get(), /*callingUid=*/0,
+                                                       ResyncCallback())));
+
+    auto vsyncController = std::make_unique<mock::VsyncController>();
+    auto vsyncTracker = std::make_unique<mock::VSyncTracker>();
+
+    EXPECT_CALL(*vsyncTracker, nextAnticipatedVSyncTimeFrom(_)).WillRepeatedly(Return(0));
+    EXPECT_CALL(*vsyncTracker, currentPeriod())
+            .WillRepeatedly(
+                    Return(TestableSurfaceFlinger::FakeHwcDisplayInjector::DEFAULT_VSYNC_PERIOD));
+    EXPECT_CALL(*vsyncTracker, nextAnticipatedVSyncTimeFrom(_)).WillRepeatedly(Return(0));
+    mFlinger.setupScheduler(std::move(vsyncController), std::move(vsyncTracker),
+                            std::move(eventThread), std::move(sfEventThread), /*callback*/ nullptr,
+                            /*hasMultipleModes*/ true);
+}
+
+TEST_F(DisplayModeSwitchingTest, changeRefreshRate_OnActiveDisplay_WithRefreshRequired) {
+    ASSERT_FALSE(mDisplay->getDesiredActiveMode().has_value());
+    ASSERT_EQ(mDisplay->getActiveMode()->getId(), kDisplayModeId60);
+
+    mFlinger.onActiveDisplayChanged(mDisplay);
+
+    mFlinger.setDesiredDisplayModeSpecs(mDisplay->getDisplayToken().promote(),
+                                        kDisplayModeId90.value(), false, 0.f, 120.f, 0.f, 120.f);
+
+    ASSERT_TRUE(mDisplay->getDesiredActiveMode().has_value());
+    ASSERT_EQ(mDisplay->getDesiredActiveMode()->mode->getId(), kDisplayModeId90);
+    ASSERT_EQ(mDisplay->getActiveMode()->getId(), kDisplayModeId60);
+
+    // Verify that next commit will call setActiveConfigWithConstraints in HWC
+    const VsyncPeriodChangeTimeline timeline{.refreshRequired = true};
+    EXPECT_CALL(*mComposer,
+                setActiveConfigWithConstraints(PrimaryDisplayVariant::HWC_DISPLAY_ID,
+                                               hal::HWConfigId(kDisplayModeId90.value()), _, _))
+            .WillOnce(DoAll(SetArgPointee<3>(timeline), Return(Error::NONE)));
+
+    mFlinger.commit();
+
+    Mock::VerifyAndClearExpectations(mComposer);
+    ASSERT_TRUE(mDisplay->getDesiredActiveMode().has_value());
+    ASSERT_EQ(mDisplay->getActiveMode()->getId(), kDisplayModeId60);
+
+    // Verify that the next commit will complete the mode change and send
+    // a onModeChanged event to the framework.
+
+    EXPECT_CALL(*mAppEventThread, onModeChanged(kDisplayMode90));
+    mFlinger.commit();
+    Mock::VerifyAndClearExpectations(mAppEventThread);
+
+    ASSERT_FALSE(mDisplay->getDesiredActiveMode().has_value());
+    ASSERT_EQ(mDisplay->getActiveMode()->getId(), kDisplayModeId90);
+}
+
+TEST_F(DisplayModeSwitchingTest, changeRefreshRate_OnActiveDisplay_WithoutRefreshRequired) {
+    ASSERT_FALSE(mDisplay->getDesiredActiveMode().has_value());
+
+    mFlinger.onActiveDisplayChanged(mDisplay);
+
+    mFlinger.setDesiredDisplayModeSpecs(mDisplay->getDisplayToken().promote(),
+                                        kDisplayModeId90.value(), true, 0.f, 120.f, 0.f, 120.f);
+
+    ASSERT_TRUE(mDisplay->getDesiredActiveMode().has_value());
+    ASSERT_EQ(mDisplay->getDesiredActiveMode()->mode->getId(), kDisplayModeId90);
+    ASSERT_EQ(mDisplay->getActiveMode()->getId(), kDisplayModeId60);
+
+    // Verify that next commit will call setActiveConfigWithConstraints in HWC
+    // and complete the mode change.
+    const VsyncPeriodChangeTimeline timeline{.refreshRequired = false};
+    EXPECT_CALL(*mComposer,
+                setActiveConfigWithConstraints(PrimaryDisplayVariant::HWC_DISPLAY_ID,
+                                               hal::HWConfigId(kDisplayModeId90.value()), _, _))
+            .WillOnce(DoAll(SetArgPointee<3>(timeline), Return(Error::NONE)));
+
+    EXPECT_CALL(*mAppEventThread, onModeChanged(kDisplayMode90));
+
+    mFlinger.commit();
+
+    ASSERT_FALSE(mDisplay->getDesiredActiveMode().has_value());
+    ASSERT_EQ(mDisplay->getActiveMode()->getId(), kDisplayModeId90);
+}
+
+TEST_F(DisplayModeSwitchingTest, twoConsecutiveSetDesiredDisplayModeSpecs) {
+    // Test that if we call setDesiredDisplayModeSpecs while a previous mode change
+    // is still being processed the later call will be respected.
+
+    ASSERT_FALSE(mDisplay->getDesiredActiveMode().has_value());
+    ASSERT_EQ(mDisplay->getActiveMode()->getId(), kDisplayModeId60);
+
+    mFlinger.onActiveDisplayChanged(mDisplay);
+
+    mFlinger.setDesiredDisplayModeSpecs(mDisplay->getDisplayToken().promote(),
+                                        kDisplayModeId90.value(), false, 0.f, 120.f, 0.f, 120.f);
+
+    const VsyncPeriodChangeTimeline timeline{.refreshRequired = true};
+    EXPECT_CALL(*mComposer,
+                setActiveConfigWithConstraints(PrimaryDisplayVariant::HWC_DISPLAY_ID,
+                                               hal::HWConfigId(kDisplayModeId90.value()), _, _))
+            .WillOnce(DoAll(SetArgPointee<3>(timeline), Return(Error::NONE)));
+
+    mFlinger.commit();
+
+    mFlinger.setDesiredDisplayModeSpecs(mDisplay->getDisplayToken().promote(),
+                                        kDisplayModeId120.value(), false, 0.f, 180.f, 0.f, 180.f);
+
+    ASSERT_TRUE(mDisplay->getDesiredActiveMode().has_value());
+    ASSERT_EQ(mDisplay->getDesiredActiveMode()->mode->getId(), kDisplayModeId120);
+
+    EXPECT_CALL(*mComposer,
+                setActiveConfigWithConstraints(PrimaryDisplayVariant::HWC_DISPLAY_ID,
+                                               hal::HWConfigId(kDisplayModeId120.value()), _, _))
+            .WillOnce(DoAll(SetArgPointee<3>(timeline), Return(Error::NONE)));
+
+    mFlinger.commit();
+
+    ASSERT_TRUE(mDisplay->getDesiredActiveMode().has_value());
+    ASSERT_EQ(mDisplay->getDesiredActiveMode()->mode->getId(), kDisplayModeId120);
+
+    mFlinger.commit();
+
+    ASSERT_FALSE(mDisplay->getDesiredActiveMode().has_value());
+    ASSERT_EQ(mDisplay->getActiveMode()->getId(), kDisplayModeId120);
+}
+
+TEST_F(DisplayModeSwitchingTest, changeResolution_OnActiveDisplay_WithoutRefreshRequired) {
+    ASSERT_FALSE(mDisplay->getDesiredActiveMode().has_value());
+    ASSERT_EQ(mDisplay->getActiveMode()->getId(), kDisplayModeId60);
+
+    mFlinger.onActiveDisplayChanged(mDisplay);
+
+    mFlinger.setDesiredDisplayModeSpecs(mDisplay->getDisplayToken().promote(),
+                                        kDisplayModeId90DifferentResolution.value(), false, 0.f,
+                                        120.f, 0.f, 120.f);
+
+    ASSERT_TRUE(mDisplay->getDesiredActiveMode().has_value());
+    ASSERT_EQ(mDisplay->getDesiredActiveMode()->mode->getId(), kDisplayModeId90DifferentResolution);
+    ASSERT_EQ(mDisplay->getActiveMode()->getId(), kDisplayModeId60);
+
+    // Verify that next commit will call setActiveConfigWithConstraints in HWC
+    // and complete the mode change.
+    const VsyncPeriodChangeTimeline timeline{.refreshRequired = false};
+    EXPECT_CALL(*mComposer,
+                setActiveConfigWithConstraints(PrimaryDisplayVariant::HWC_DISPLAY_ID,
+                                               hal::HWConfigId(
+                                                       kDisplayModeId90DifferentResolution.value()),
+                                               _, _))
+            .WillOnce(DoAll(SetArgPointee<3>(timeline), Return(Error::NONE)));
+
+    EXPECT_CALL(*mAppEventThread, onHotplugReceived(mDisplay->getPhysicalId(), true));
+
+    // Misc expecations. We don't need to enforce these method calls, but since the helper methods
+    // already set expectations we should add new ones here, otherwise the test will fail.
+    EXPECT_CALL(*mConsumer, setDefaultBufferSize(2000, 2000)).WillOnce(Return(NO_ERROR));
+    EXPECT_CALL(*mConsumer, consumerConnect(_, false)).WillOnce(Return(NO_ERROR));
+    EXPECT_CALL(*mComposer, setClientTargetSlotCount(_)).WillOnce(Return(hal::Error::NONE));
+
+    // Create a new native surface to be used by the recreated display.
+    mNativeWindowSurface = nullptr;
+    injectFakeNativeWindowSurfaceFactory();
+    PrimaryDisplayVariant::setupNativeWindowSurfaceCreationCallExpectations(this);
+
+    const auto displayToken = mDisplay->getDisplayToken().promote();
+
+    mFlinger.commit();
+
+    // The DisplayDevice will be destroyed and recreated,
+    // so we need to update with the new instance.
+    mDisplay = mFlinger.getDisplay(displayToken);
+
+    ASSERT_FALSE(mDisplay->getDesiredActiveMode().has_value());
+    ASSERT_EQ(mDisplay->getActiveMode()->getId(), kDisplayModeId90DifferentResolution);
+}
+
+} // namespace
+} // namespace android
diff --git a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
index 4c5789e..6ce72a8 100644
--- a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
+++ b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
@@ -24,6 +24,7 @@
 #include <compositionengine/impl/OutputLayerCompositionState.h>
 #include <compositionengine/mock/DisplaySurface.h>
 #include <gui/ScreenCaptureResults.h>
+#include <algorithm>
 
 #include "BufferQueueLayer.h"
 #include "BufferStateLayer.h"
@@ -305,6 +306,11 @@
         return mFlinger->destroyDisplay(displayToken);
     }
 
+    auto getDisplay(const sp<IBinder>& displayToken) {
+        Mutex::Autolock lock(mFlinger->mStateLock);
+        return mFlinger->getDisplayDeviceLocked(displayToken);
+    }
+
     void enableHalVirtualDisplays(bool enable) { mFlinger->enableHalVirtualDisplays(enable); }
 
     auto setupNewDisplayDeviceInternal(
@@ -393,6 +399,21 @@
         return SurfaceFlinger::calculateMaxAcquiredBufferCount(refreshRate, presentLatency);
     }
 
+    auto setDesiredDisplayModeSpecs(const sp<IBinder>& displayToken, ui::DisplayModeId defaultMode,
+                                    bool allowGroupSwitching, float primaryRefreshRateMin,
+                                    float primaryRefreshRateMax, float appRequestRefreshRateMin,
+                                    float appRequestRefreshRateMax) {
+        return mFlinger->setDesiredDisplayModeSpecs(displayToken, defaultMode, allowGroupSwitching,
+                                                    primaryRefreshRateMin, primaryRefreshRateMax,
+                                                    appRequestRefreshRateMin,
+                                                    appRequestRefreshRateMax);
+    }
+
+    void onActiveDisplayChanged(const sp<DisplayDevice>& activeDisplay) {
+        Mutex::Autolock lock(mFlinger->mStateLock);
+        mFlinger->onActiveDisplayChangedLocked(activeDisplay);
+    }
+
     /* ------------------------------------------------------------------------
      * Read-only access to private data to assert post-conditions.
      */
@@ -480,7 +501,7 @@
         static constexpr hal::HWDisplayId DEFAULT_HWC_DISPLAY_ID = 1000;
         static constexpr int32_t DEFAULT_WIDTH = 1920;
         static constexpr int32_t DEFAULT_HEIGHT = 1280;
-        static constexpr int32_t DEFAULT_VSYNC_PERIOD = 16'666'666;
+        static constexpr int32_t DEFAULT_VSYNC_PERIOD = 16'666'667;
         static constexpr int32_t DEFAULT_CONFIG_GROUP = 7;
         static constexpr int32_t DEFAULT_DPI = 320;
         static constexpr hal::HWConfigId DEFAULT_ACTIVE_CONFIG = 0;
@@ -634,10 +655,10 @@
             mCreationArgs.connectionType = connectionType;
             mCreationArgs.isPrimary = isPrimary;
 
-            mActiveModeId = DisplayModeId(0);
+            mCreationArgs.activeModeId = DisplayModeId(0);
             DisplayModePtr activeMode =
                     DisplayMode::Builder(FakeHwcDisplayInjector::DEFAULT_ACTIVE_CONFIG)
-                            .setId(mActiveModeId)
+                            .setId(mCreationArgs.activeModeId)
                             .setPhysicalDisplayId(PhysicalDisplayId::fromPort(0))
                             .setWidth(FakeHwcDisplayInjector::DEFAULT_WIDTH)
                             .setHeight(FakeHwcDisplayInjector::DEFAULT_HEIGHT)
@@ -673,7 +694,7 @@
         auto& mutableDisplayDevice() { return mFlinger.mutableDisplays()[mDisplayToken]; }
 
         auto& setActiveMode(DisplayModeId mode) {
-            mActiveModeId = mode;
+            mCreationArgs.activeModeId = mode;
             return *this;
         }
 
@@ -728,14 +749,29 @@
                 const auto physicalId = PhysicalDisplayId::tryCast(*displayId);
                 LOG_ALWAYS_FATAL_IF(!physicalId);
                 LOG_ALWAYS_FATAL_IF(!mHwcDisplayId);
-                state.physical = {.id = *physicalId, .type = *type, .hwcDisplayId = *mHwcDisplayId};
+
+                const DisplayModePtr activeModePtr =
+                        *std::find_if(mCreationArgs.supportedModes.begin(),
+                                      mCreationArgs.supportedModes.end(), [&](DisplayModePtr mode) {
+                                          return mode->getId() == mCreationArgs.activeModeId;
+                                      });
+                state.physical = {.id = *physicalId,
+                                  .type = *type,
+                                  .hwcDisplayId = *mHwcDisplayId,
+                                  .deviceProductInfo = {},
+                                  .supportedModes = mCreationArgs.supportedModes,
+                                  .activeMode = activeModePtr};
             }
 
             state.isSecure = mCreationArgs.isSecure;
 
+            mCreationArgs.refreshRateConfigs =
+                    std::make_shared<scheduler::RefreshRateConfigs>(mCreationArgs.supportedModes,
+                                                                    mCreationArgs.activeModeId);
+
             sp<DisplayDevice> device = new DisplayDevice(mCreationArgs);
             if (!device->isVirtual()) {
-                device->setActiveMode(mActiveModeId);
+                device->setActiveMode(mCreationArgs.activeModeId);
             }
             mFlinger.mutableDisplays().emplace(mDisplayToken, device);
             mFlinger.mutableCurrentState().displays.add(mDisplayToken, state);
@@ -753,7 +789,6 @@
         sp<BBinder> mDisplayToken = new BBinder();
         DisplayDeviceCreationArgs mCreationArgs;
         const std::optional<hal::HWDisplayId> mHwcDisplayId;
-        DisplayModeId mActiveModeId;
     };
 
 private: