// Surface.java (frameworks\base\core\java\android\view)/*** Sets the intended frame rate for this surface.** <p>On devices that are capable of running the display at different refresh rates,* the system may choose a display refresh rate to better match this surface's frame* rate. Usage of this API won't introduce frame rate throttling, or affect other* aspects of the application's frame production pipeline. However, because the system* may change the display refresh rate, calls to this function may result in changes* to Choreographer callback timings, and changes to the time interval at which the* system releases buffers back to the application.</p>** <p>Note that this only has an effect for surfaces presented on the display. If this* surface is consumed by something other than the system compositor, e.g. a media* codec, this call has no effect.</p>** @param frameRate The intended frame rate of this surface, in frames per second. 0* is a special value that indicates the app will accept the system's choice for the* display frame rate, which is the default behavior if this function isn't* called. The <code>frameRate</code> parameter does <em>not</em> need to be a valid refresh* rate for this device's display - e.g., it's fine to pass 30fps to a device that can only run* the display at 60fps.** @param compatibility The frame rate compatibility of this surface. The* compatibility value may influence the system's choice of display frame rate.* This parameter is ignored when <code>frameRate</code> is 0.** @param changeFrameRateStrategy Whether display refresh rate transitions caused by this* surface should be seamless. A seamless transition is one that doesn't have any visual* interruptions, such as a black screen for a second or two. This parameter is ignored when* <code>frameRate</code> is 0.** @throws IllegalArgumentException If <code>frameRate</code>, <code>compatibility</code> or* <code>changeFrameRateStrategy</code> are invalid.*/public void setFrameRate(@FloatRange(from = 0.0) float frameRate,@FrameRateCompatibility int compatibility,@ChangeFrameRateStrategy int changeFrameRateStrategy) {synchronized (mLock) {checkNotReleasedLocked();int error = nativeSetFrameRate(mNativeObject, frameRate, compatibility,changeFrameRateStrategy);if (error == -EINVAL) {throw new IllegalArgumentException("Invalid argument to Surface.setFrameRate()");} else if (error != 0) {throw new RuntimeException("Failed to set frame rate on Surface");}}}/*** Sets the intended frame rate for this surface. Any switching of refresh rates is* most probably going to be seamless.** @see #setFrameRate(float, int, int)*/public void setFrameRate(@FloatRange(from = 0.0) float frameRate, @FrameRateCompatibility int compatibility) {setFrameRate(frameRate, compatibility, CHANGE_FRAME_RATE_ONLY_IF_SEAMLESS);}

// android_view_Surface.cpp (frameworks\base\core\jni)
static jint nativeSetFrameRate(JNIEnv* env, jclass clazz, jlong nativeObject, jfloat frameRate,jint compatibility, jint changeFrameRateStrategy) {Surface* surface = reinterpret_cast<Surface*>(nativeObject);ANativeWindow* anw = static_cast<ANativeWindow*>(surface);// Our compatibility is a Surface.FRAME_RATE_COMPATIBILITY_* value, and// NATIVE_WINDOW_SET_FRAME_RATE takes an// ANATIVEWINDOW_FRAME_RATE_COMPATIBILITY_* value. The values are identical// though, so no need to explicitly convert.return anw->perform(surface, NATIVE_WINDOW_SET_FRAME_RATE, double(frameRate), compatibility,int(changeFrameRateStrategy));
}

// Surface.cpp (frameworks\native\libs\gui)
int Surface::perform(int operation, va_list args)
{case NATIVE_WINDOW_SET_FRAME_RATE:res = dispatchSetFrameRate(args);break;int Surface::dispatchSetFrameRate(va_list args) {float frameRate = static_cast<float>(va_arg(args, double));int8_t compatibility = static_cast<int8_t>(va_arg(args, int));int8_t changeFrameRateStrategy = static_cast<int8_t>(va_arg(args, int));return setFrameRate(frameRate, compatibility, changeFrameRateStrategy);
}status_t Surface::setFrameRate(float frameRate, int8_t compatibility,int8_t changeFrameRateStrategy) {ATRACE_CALL();ALOGV("Surface::setFrameRate");if (!ValidateFrameRate(frameRate, compatibility, changeFrameRateStrategy,"Surface::setFrameRate")) {return BAD_VALUE;}return composerService()->setFrameRate(mGraphicBufferProducer, frameRate, compatibility,changeFrameRateStrategy);
}

// ISurfaceComposer.cpp (frameworks\native\libs\gui)status_t setFrameRate(const sp<IGraphicBufferProducer>& surface, float frameRate,int8_t compatibility, int8_t changeFrameRateStrategy) override {..status_t err = remote()->transact(BnSurfaceComposer::SET_FRAME_RATE, data, &reply);}
status_t BnSurfaceComposer::onTransact(
...setFrameRate(surface, frameRate, compatibility, changeFrameRateStrategy);// SurfaceFlinger.cpp (miui\frameworks\native\services\surfaceflinger)
status_t SurfaceFlinger::setFrameRate(const sp<IGraphicBufferProducer>& surface, float frameRate,int8_t compatibility, int8_t changeFrameRateStrategy)layer->setFrameRate(Layer::FrameRate(Fps{frameRate}, Layer::FrameRate::convertCompatibility(compatibility), strategy))

1、surfaceflinger layerinfo保存app传递下来的结构体是FrameRatestruct FrameRate {using Seamlessness = scheduler::Seamlessness;Fps rate;FrameRateCompatibility type;Seamlessness seamlessness;
}enum class FrameRateCompatibility {Default, // 图层没有指定任何具体的处理策略Exact, // 图层需要准确的帧速率。如视频类ExactOrMultiple, // 图层需要精确的帧速率（或它的倍数）来呈现内容。 任何其他值都将导致下拉。NoVote, // 图层对刷新率没有任何要求，不考虑显示刷新率
};// The seamlessness requirement of a Layer.
enum class Seamlessness {// Indicates a requirement for a seamless mode switch.OnlySeamless,// Indicates that both seamless and seamed mode switches are allowed.SeamedAndSeamless,// Indicates no preference for seamlessness. For such layers the system will// prefer seamless switches, but also non-seamless switches to the group of the// default config are allowed.Default
};

// SurfaceControl.java (frameworks\base\core\java\android\view)/*** Sets the intended frame rate for this surface. Any switching of refresh rates is* most probably going to be seamless.** @see #setFrameRate(SurfaceControl, float, int, int)*/@NonNullpublic Transaction setFrameRate(@NonNull SurfaceControl sc,@FloatRange(from = 0.0) float frameRate,@Surface.FrameRateCompatibility int compatibility) {return setFrameRate(sc, frameRate, compatibility,Surface.CHANGE_FRAME_RATE_ONLY_IF_SEAMLESS);}

// android_view_SurfaceControl.cpp (frameworks\base\core\jni)
static void nativeSetFrameRate(JNIEnv* env, jclass clazz, jlong transactionObj, jlong nativeObject,jfloat frameRate, jint compatibility, jint changeFrameRateStrategy) {auto transaction = reinterpret_cast<SurfaceComposerClient::Transaction*>(transactionObj);const auto ctrl = reinterpret_cast<SurfaceControl*>(nativeObject);// Our compatibility is a Surface.FRAME_RATE_COMPATIBILITY_* value, and// Transaction::setFrameRate() takes an ANATIVEWINDOW_FRAME_RATE_COMPATIBILITY_* value. The// values are identical though, so no need to convert anything.transaction->setFrameRate(ctrl, frameRate, static_cast<int8_t>(compatibility),static_cast<int8_t>(changeFrameRateStrategy));
}

// SurfaceComposerClient.cpp (frameworks\native\libs\gui)
SurfaceComposerClient::Transaction& SurfaceComposerClient::Transaction::setFrameRate(const sp<SurfaceControl>& sc, float frameRate, int8_t compatibility,int8_t changeFrameRateStrategy) {layer_state_t* s = getLayerState(sc);if (!s) {mStatus = BAD_INDEX;return *this;}// Allow privileged values as well here, those will be ignored by SF if// the caller is not privilegedif (!ValidateFrameRate(frameRate, compatibility, changeFrameRateStrategy,"Transaction::setFrameRate",/*privileged=*/true)) {mStatus = BAD_VALUE;return *this;}s->what |= layer_state_t::eFrameRateChanged;s->frameRate = frameRate;s->frameRateCompatibility = compatibility;s->changeFrameRateStrategy = changeFrameRateStrategy;return *this;
}
// SurfaceFlinger.cpp (frameworks\native\services\surfaceflinger)
applyTransactionStatesetClientStateLockeduint32_t SurfaceFlinger::setClientStateLocked(const FrameTimelineInfo& frameTimelineInfo, const ComposerState& composerState,int64_t desiredPresentTime, bool isAutoTimestamp, int64_t postTime, uint32_t permissions,std::unordered_set<ListenerCallbacks, ListenerCallbacksHash>& outListenerCallbacks) {
...if (what & layer_state_t::eFrameRateChanged) {if (ValidateFrameRate(s.frameRate, s.frameRateCompatibility, s.changeFrameRateStrategy,"SurfaceFlinger::setClientStateLocked", privileged)) {const auto compatibility =Layer::FrameRate::convertCompatibility(s.frameRateCompatibility);const auto strategy =Layer::FrameRate::convertChangeFrameRateStrategy(s.changeFrameRateStrategy);if (layer->setFrameRate(Layer::FrameRate(Fps(s.frameRate), compatibility, strategy))) {flags |= eTraversalNeeded;}}}

// RefreshRatePolicy.java (mframeworks\base\services\core\java\com\android\server\wm)int getPreferredModeId(WindowState w) {// If app is animating, it's not able to control refresh rate because we want the animation// to run in default refresh rate.if (w.isAnimating(TRANSITION | PARENTS)) {return 0;}return w.mAttrs.preferredDisplayModeId;}
// DisplayContent.java (frameworks\base\services\core\java\com\android\server\wm)
会保存到   
private static final class ApplySurfaceChangesTransactionState 的preferredModeIdvoid applySurfaceChangesTransaction() {if (!mWmService.mDisplayFrozen) {mWmService.mDisplayManagerInternal.setDisplayProperties(mDisplayId,mLastHasContent,mTmpApplySurfaceChangesTransactionState.preferredRefreshRate,mTmpApplySurfaceChangesTransactionState.preferredModeId,mTmpApplySurfaceChangesTransactionState.preferredMinRefreshRate,mTmpApplySurfaceChangesTransactionState.preferredMaxRefreshRate,mTmpApplySurfaceChangesTransactionState.preferMinimalPostProcessing,true /* inTraversal, must call performTraversalInTrans... below */);}
// DisplayManagerService.java (frameworks\base\services\core\java\com\android\server\display)public void setDisplayProperties(int displayId, boolean hasContent,float requestedRefreshRate, int requestedMode, float requestedMinRefreshRate,float requestedMaxRefreshRate, boolean requestedMinimalPostProcessing,boolean inTraversal) {setDisplayPropertiesInternal(displayId, hasContent, requestedRefreshRate,requestedMode, requestedMinRefreshRate, requestedMaxRefreshRate,requestedMinimalPostProcessing, inTraversal);}
setDisplayPropertiesInternal
|--> mDisplayModeDirector.getAppRequestObserver().setAppRequest(displayId, requestedModeId, requestedMinRefreshRate, requestedMaxRefreshRate);// DisplayModeDirector.java (frameworks\base\services\core\java\com\android\server\display)public void setAppRequest(int displayId, int modeId, float requestedMinRefreshRateRange,float requestedMaxRefreshRateRange) {synchronized (mLock) {setAppRequestedModeLocked(displayId, modeId);setAppPreferredRefreshRateRangeLocked(displayId, requestedMinRefreshRateRange,requestedMaxRefreshRateRange);}}setAppRequest 最后通过：
updateVoteLocked(displayId, Vote.PRIORITY_APP_REQUEST_REFRESH_RATE_RANGE, vote);
还就是最后调用surfaceflinger的：
setDesiredDisplayModeSpecs // surface的标准API接口