Variable refresh rate for virtual display

Allow virtual display to request a refresh rate, so it can be different
from VSYNC frequencies. SurfaceFlinger drops frames for the
corresponding virtual display based on the refresh rate.

Bug: 241286579
Test: atest libgui_test libsurfaceflinger_unittest SurfaceFlinger_test
Change-Id: I4fba0e553618bb4c7333514b16206ae4277acf72
diff --git a/libs/gui/SurfaceComposerClient.cpp b/libs/gui/SurfaceComposerClient.cpp
index cf9828b..9092f5f 100644
--- a/libs/gui/SurfaceComposerClient.cpp
+++ b/libs/gui/SurfaceComposerClient.cpp
@@ -1182,12 +1182,14 @@
 }
 // ---------------------------------------------------------------------------
 
-sp<IBinder> SurfaceComposerClient::createDisplay(const String8& displayName, bool secure) {
+sp<IBinder> SurfaceComposerClient::createDisplay(const String8& displayName, bool secure,
+                                                 float requestedRefereshRate) {
     sp<IBinder> display = nullptr;
     binder::Status status =
             ComposerServiceAIDL::getComposerService()->createDisplay(std::string(
                                                                              displayName.string()),
-                                                                     secure, &display);
+                                                                     secure, requestedRefereshRate,
+                                                                     &display);
     return status.isOk() ? display : nullptr;
 }
 
diff --git a/libs/gui/aidl/android/gui/ISurfaceComposer.aidl b/libs/gui/aidl/android/gui/ISurfaceComposer.aidl
index c08a7c6..597749a 100644
--- a/libs/gui/aidl/android/gui/ISurfaceComposer.aidl
+++ b/libs/gui/aidl/android/gui/ISurfaceComposer.aidl
@@ -79,9 +79,21 @@
 
     /**
      * Create a virtual display
+     *
+     * displayName
+     *     The name of the virtual display
+     * secure
+     *     Whether this virtual display is secure
+     * requestedRefreshRate
+     *     The refresh rate, frames per second, to request on the virtual display.
+     *     This is just a request, the actual rate may be adjusted to align well
+     *     with physical displays running concurrently. If 0 is specified, the
+     *     virtual display is refreshed at the physical display refresh rate.
+     *
      * requires ACCESS_SURFACE_FLINGER permission.
      */
-    @nullable IBinder createDisplay(@utf8InCpp String displayName, boolean secure);
+    @nullable IBinder createDisplay(@utf8InCpp String displayName, boolean secure,
+            float requestedRefreshRate);
 
     /**
      * Destroy a virtual display
diff --git a/libs/gui/fuzzer/libgui_fuzzer_utils.h b/libs/gui/fuzzer/libgui_fuzzer_utils.h
index 685bd92..14a0e39 100644
--- a/libs/gui/fuzzer/libgui_fuzzer_utils.h
+++ b/libs/gui/fuzzer/libgui_fuzzer_utils.h
@@ -67,7 +67,7 @@
                  sp<gui::IDisplayEventConnection>*),
                 (override));
     MOCK_METHOD(binder::Status, createConnection, (sp<gui::ISurfaceComposerClient>*), (override));
-    MOCK_METHOD(binder::Status, createDisplay, (const std::string&, bool, sp<IBinder>*),
+    MOCK_METHOD(binder::Status, createDisplay, (const std::string&, bool, float, sp<IBinder>*),
                 (override));
     MOCK_METHOD(binder::Status, destroyDisplay, (const sp<IBinder>&), (override));
     MOCK_METHOD(binder::Status, getPhysicalDisplayIds, (std::vector<int64_t>*), (override));
diff --git a/libs/gui/include/gui/SurfaceComposerClient.h b/libs/gui/include/gui/SurfaceComposerClient.h
index c5f59c8..45f4dbe 100644
--- a/libs/gui/include/gui/SurfaceComposerClient.h
+++ b/libs/gui/include/gui/SurfaceComposerClient.h
@@ -355,7 +355,8 @@
     sp<SurfaceControl> mirrorDisplay(DisplayId displayId);
 
     //! Create a virtual display
-    static sp<IBinder> createDisplay(const String8& displayName, bool secure);
+    static sp<IBinder> createDisplay(const String8& displayName, bool secure,
+                                     float requestedRefereshRate = 0);
 
     //! Destroy a virtual display
     static void destroyDisplay(const sp<IBinder>& display);
diff --git a/libs/gui/tests/Surface_test.cpp b/libs/gui/tests/Surface_test.cpp
index 32d60cd..9b2bf7f 100644
--- a/libs/gui/tests/Surface_test.cpp
+++ b/libs/gui/tests/Surface_test.cpp
@@ -736,6 +736,7 @@
     }
 
     binder::Status createDisplay(const std::string& /*displayName*/, bool /*secure*/,
+                                 float /*requestedRefreshRate*/,
                                  sp<IBinder>* /*outDisplay*/) override {
         return binder::Status::ok();
     }
diff --git a/services/surfaceflinger/DisplayDevice.cpp b/services/surfaceflinger/DisplayDevice.cpp
index c61f7d8..ba8b6cf 100644
--- a/services/surfaceflinger/DisplayDevice.cpp
+++ b/services/surfaceflinger/DisplayDevice.cpp
@@ -71,6 +71,7 @@
         mRenderFrameRateFPSTrace("RenderRateFPS -" + to_string(getId())),
         mPhysicalOrientation(args.physicalOrientation),
         mIsPrimary(args.isPrimary),
+        mRequestedRefreshRate(args.requestedRefreshRate),
         mRefreshRateSelector(std::move(args.refreshRateSelector)) {
     mCompositionDisplay->editState().isSecure = args.isSecure;
     mCompositionDisplay->createRenderSurface(
@@ -513,6 +514,23 @@
     mDesiredActiveModeChanged = false;
 }
 
+void DisplayDevice::adjustRefreshRate(Fps leaderDisplayRefreshRate) {
+    using fps_approx_ops::operator==;
+    if (mRequestedRefreshRate == 0_Hz) {
+        return;
+    }
+
+    using fps_approx_ops::operator>;
+    if (mRequestedRefreshRate > leaderDisplayRefreshRate) {
+        mAdjustedRefreshRate = leaderDisplayRefreshRate;
+        return;
+    }
+
+    unsigned divisor = static_cast<unsigned>(
+            std::round(leaderDisplayRefreshRate.getValue() / mRequestedRefreshRate.getValue()));
+    mAdjustedRefreshRate = leaderDisplayRefreshRate / divisor;
+}
+
 std::atomic<int32_t> DisplayDeviceState::sNextSequenceId(1);
 
 }  // namespace android
diff --git a/services/surfaceflinger/DisplayDevice.h b/services/surfaceflinger/DisplayDevice.h
index 370bd66..59f7a30 100644
--- a/services/surfaceflinger/DisplayDevice.h
+++ b/services/surfaceflinger/DisplayDevice.h
@@ -245,6 +245,12 @@
 
     nsecs_t getVsyncPeriodFromHWC() const;
 
+    Fps getAdjustedRefreshRate() const { return mAdjustedRefreshRate; }
+
+    // Round the requested refresh rate to match a divisor of the leader
+    // display's refresh rate. Only supported for virtual displays.
+    void adjustRefreshRate(Fps leaderDisplayRefreshRate);
+
     // release HWC resources (if any) for removable displays
     void disconnect();
 
@@ -279,6 +285,15 @@
 
     uint32_t mFlags = 0;
 
+    // Requested refresh rate in fps, supported only for virtual displays.
+    // when this value is non zero, SurfaceFlinger will try to drop frames
+    // for virtual displays to match this requested refresh rate.
+    const Fps mRequestedRefreshRate;
+
+    // Adjusted refresh rate, rounded to match a divisor of the leader
+    // display's refresh rate. Only supported for virtual displays.
+    Fps mAdjustedRefreshRate = 0_Hz;
+
     std::vector<ui::Hdr> mOverrideHdrTypes;
 
     std::shared_ptr<scheduler::RefreshRateSelector> mRefreshRateSelector;
@@ -316,6 +331,8 @@
     uint32_t height = 0;
     std::string displayName;
     bool isSecure = false;
+    // Refer to DisplayDevice::mRequestedRefreshRate, for virtual display only
+    Fps requestedRefreshRate;
 
 private:
     static std::atomic<int32_t> sNextSequenceId;
@@ -345,6 +362,8 @@
     std::optional<hardware::graphics::composer::hal::PowerMode> initialPowerMode;
     bool isPrimary{false};
     DisplayModeId activeModeId;
+    // Refer to DisplayDevice::mRequestedRefreshRate, for virtual display only
+    Fps requestedRefreshRate;
 };
 
 } // namespace android
diff --git a/services/surfaceflinger/Scheduler/Scheduler.cpp b/services/surfaceflinger/Scheduler/Scheduler.cpp
index 1fc1519..fa95685 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.cpp
+++ b/services/surfaceflinger/Scheduler/Scheduler.cpp
@@ -166,6 +166,10 @@
     return mVsyncSchedule->getTracker().isVSyncInPhase(expectedVsyncTimestamp.ns(), *frameRate);
 }
 
+bool Scheduler::isVsyncInPhase(TimePoint timePoint, const Fps frameRate) const {
+    return mVsyncSchedule->getTracker().isVSyncInPhase(timePoint.ns(), frameRate);
+}
+
 impl::EventThread::ThrottleVsyncCallback Scheduler::makeThrottleVsyncCallback() const {
     return [this](nsecs_t expectedVsyncTimestamp, uid_t uid) {
         return !isVsyncValid(TimePoint::fromNs(expectedVsyncTimestamp), uid);
diff --git a/services/surfaceflinger/Scheduler/Scheduler.h b/services/surfaceflinger/Scheduler/Scheduler.h
index ef7d0cf..e822448 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.h
+++ b/services/surfaceflinger/Scheduler/Scheduler.h
@@ -231,6 +231,9 @@
     // for a given uid
     bool isVsyncValid(TimePoint expectedVsyncTimestamp, uid_t uid) const;
 
+    // Checks if a vsync timestamp is in phase for a frame rate
+    bool isVsyncInPhase(TimePoint timePoint, const Fps frameRate) const;
+
     void dump(utils::Dumper&) const;
     void dump(ConnectionHandle, std::string&) const;
     void dumpVsync(std::string&) const;
@@ -262,6 +265,10 @@
         return leaderSelectorPtr()->getActiveMode().fps.getPeriod();
     }
 
+    Fps getLeaderRefreshRate() const EXCLUDES(mDisplayLock) {
+        return leaderSelectorPtr()->getActiveMode().fps;
+    }
+
     // Returns the framerate of the layer with the given sequence ID
     float getLayerFramerate(nsecs_t now, int32_t id) const {
         return mLayerHistory.getLayerFramerate(now, id);
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 7d0dc93..fe4ae02 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -512,7 +512,8 @@
     mScheduler->run();
 }
 
-sp<IBinder> SurfaceFlinger::createDisplay(const String8& displayName, bool secure) {
+sp<IBinder> SurfaceFlinger::createDisplay(const String8& displayName, bool secure,
+                                          float requestedRefreshRate) {
     // onTransact already checks for some permissions, but adding an additional check here.
     // This is to ensure that only system and graphics can request to create a secure
     // display. Secure displays can show secure content so we add an additional restriction on it.
@@ -543,6 +544,7 @@
     DisplayDeviceState state;
     state.isSecure = secure;
     state.displayName = displayName;
+    state.requestedRefreshRate = Fps::fromValue(requestedRefreshRate);
     mCurrentState.displays.add(token, state);
     return token;
 }
@@ -2343,7 +2345,15 @@
     refreshArgs.outputs.reserve(displays.size());
     std::vector<DisplayId> displayIds;
     for (const auto& [_, display] : displays) {
-        refreshArgs.outputs.push_back(display->getCompositionDisplay());
+        bool dropFrame = false;
+        if (display->isVirtual()) {
+            Fps refreshRate = display->getAdjustedRefreshRate();
+            using fps_approx_ops::operator>;
+            dropFrame = (refreshRate > 0_Hz) && !mScheduler->isVsyncInPhase(frameTime, refreshRate);
+        }
+        if (!dropFrame) {
+            refreshArgs.outputs.push_back(display->getCompositionDisplay());
+        }
         displayIds.push_back(display->getId());
     }
     mPowerAdvisor->setDisplays(displayIds);
@@ -3082,6 +3092,8 @@
     creationArgs.initialPowerMode =
             state.isVirtual() ? std::make_optional(hal::PowerMode::ON) : std::nullopt;
 
+    creationArgs.requestedRefreshRate = state.requestedRefreshRate;
+
     sp<DisplayDevice> display = getFactory().createDisplayDevice(creationArgs);
 
     nativeWindowSurface->preallocateBuffers();
@@ -3198,6 +3210,10 @@
         dispatchDisplayHotplugEvent(displayId, true);
     }
 
+    if (display->isVirtual()) {
+        display->adjustRefreshRate(mScheduler->getLeaderRefreshRate());
+    }
+
     mDisplays.try_emplace(displayToken, std::move(display));
 }
 
@@ -7448,13 +7464,14 @@
 }
 
 binder::Status SurfaceComposerAIDL::createDisplay(const std::string& displayName, bool secure,
+                                                  float requestedRefreshRate,
                                                   sp<IBinder>* outDisplay) {
     status_t status = checkAccessPermission();
     if (status != OK) {
         return binderStatusFromStatusT(status);
     }
     String8 displayName8 = String8::format("%s", displayName.c_str());
-    *outDisplay = mFlinger->createDisplay(displayName8, secure);
+    *outDisplay = mFlinger->createDisplay(displayName8, secure, requestedRefreshRate);
     return binder::Status::ok();
 }
 
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 207dfe2..170af48 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -483,7 +483,8 @@
             EXCLUDES(mStateLock);
 
     // Implements ISurfaceComposer
-    sp<IBinder> createDisplay(const String8& displayName, bool secure);
+    sp<IBinder> createDisplay(const String8& displayName, bool secure,
+                              float requestedRefreshRate = 0);
     void destroyDisplay(const sp<IBinder>& displayToken);
     std::vector<PhysicalDisplayId> getPhysicalDisplayIds() const EXCLUDES(mStateLock) {
         Mutex::Autolock lock(mStateLock);
@@ -1403,7 +1404,7 @@
             sp<gui::IDisplayEventConnection>* outConnection) override;
     binder::Status createConnection(sp<gui::ISurfaceComposerClient>* outClient) override;
     binder::Status createDisplay(const std::string& displayName, bool secure,
-                                 sp<IBinder>* outDisplay) override;
+                                 float requestedRefreshRate, sp<IBinder>* outDisplay) override;
     binder::Status destroyDisplay(const sp<IBinder>& display) override;
     binder::Status getPhysicalDisplayIds(std::vector<int64_t>* outDisplayIds) override;
     binder::Status getPhysicalDisplayToken(int64_t displayId, sp<IBinder>* outDisplay) override;