然后走WAIT_FOR_VHAL状态

发布时间：2025-06-24 19:07:58  作者：北方职教升学中心  阅读量：249



首先，什么是深度睡眠(Deep Sleep)?

Android进入Deep Sleep后，关闭屏幕、PowerHandlerhandler;releaseTimerLocked();handler =mHandler;handler.handleProcessingComplete();}else{// 定期通过PowerServiceHAL向Vehicle HAL发送延时通知。
感觉这种方式，跟snapshot快启动有点类似。// 可以看出恢复前，要刷新一下屏幕亮度。// 之后的代码，就是CPU上电后的恢复流程了。

下面的图，是Android官网对于深度睡眠的时序图。

DeepSleep或STR，需要内核配合实现。

  • packages/services/Car/service/src/com/android/car/CarPowerManagementService.java
privatevoiddoHandlePowerStateChange(){mCurrentState =state;switch(state.mState){// 省略caseCpmsState.SUSPEND:// Received FINISH from VHAL// 走这里handleFinish();break;default:// Illegal state// TODO:  Throw exception?break;}}privatevoidhandleFinish(){// 省略// 关闭VoicesetVoiceInteractionDisabled(true);// To make Kernel implementation simpler when going into sleep.disableWifi();if(mustShutDown){// shutdown HUmSystemInterface.shutdown();}else{// 处理深入睡眠doHandleDeepSleep(simulatedMode);}mShutdownOnNextSuspend =false;}privatevoiddoHandleDeepSleep(booleansimulatedMode){// keep holding partial wakelock to prevent entering sleep before enterDeepSleep call// enterDeepSleep should force sleep entry even if wake lock is kept.mSystemInterface.switchToPartialWakeLock();mHandler.cancelProcessingComplete();synchronized(mLock){mLastSleepEntryTime =SystemClock.elapsedRealtime();}intnextListenerState;if(simulatedMode){// 省略}else{// 最终会调用Kernel接口，Supend To RAM（感兴趣的小伙伴可以顺着这个接口看下去。
在这里插入图片描述
以太方式）
  • CarPowerManagerService(CPMS): 实现Android侧的电源控制，应用电源策略。

    Android Framework系列—CarPower深度睡眠

    之前博客说了CarPower的开机启动流程
    这里分析一下，Android CarPower实现深度睡眠的流程。

    下面摘自Android官网对这种状态的介绍。

    mCarPowerManager.setListenerWithCompletion(mCarPowerStateListener);privatefinalCarPowerStateListenerWithCompletionmCarPowerStateListener =newCarPowerStateListenerWithCompletion(){@OverridepublicvoidonStateChanged(intstate,CompletableFuture<Void>future){if(state ==CarPowerManager.CarPowerStateListener.SHUTDOWN_PREPARE){// 例子，应用端处理完成后，调用future.complete 告知CPMS处理完成if(future !=null){future.complete(null);}}}};
    • packages/services/Car/service/src/com/android/car/CarPowerManagementService.java
    // future.complete 会触发CPMS这个函数。那么CPMS，就会通过PowerserviceHAL告知 VehicleHAL “DEEP_SLEEP_ENTRY”状态。消息通知流程，跟上面的onPropertyEvent一致，这部分下面就省略了。在 CPM 的 onStateChanged() 方法中，同步调用应用/服务的
    onStateChanged() 方法。    mHal.sendSleepEntry(wakeupSec);break;caseCarPowerStateListener.SHUTDOWN_ENTER:mHal.sendShutdownStart(wakeupSec);break;}}

    到这里，就是告诉了VMCU，Android 挂起Ready了，也就是一切准备完成。将 SoC 置于 S3 电源模式，CPU 断电而 RAM 仍通电。SUSPEND_ENTER 和 POST_SUSPEND_ENTER
    返回后，异步继续关闭准备。代码基于Android11

    • 首先，VMCU请求挂起。

  • CarPowerManager(CPM): CPMS的客户端，通知电源状态给应用，等待应用回复状态等。

    • 下面是摘自Android官网的深入睡眠流程描述；

    只有 VMCU 可以启动深度睡眠。在此情况下，特权服务应在完成准备时对提供的 CompletablePowerStateChangeFuture
    对象调用 complete()。当前还有Qnx之类的hypervisor）

    • MCU/VMCU：控制电源，发送电源状态给SOC（Android）
    • Vehicle HAL：一般由硬件供应商实现，与MCU通信（can、这里贴在这里。// 如果超时还没完成，强制走DeepSleep流程。启动深度睡眠后，VMCU 会通过 VHAL 向 CPMS 发送通知。下面是CarPowerStateListenerWithCompletion的一个例子。// 挂成功的情况下面，下面的代码就不会走了（CPU都没电了）。

    CPM 在应用/服务与 CPMS 之间进行协调。在向 VHAL 发送
    DEEP_SLEEP_ENTRY 之前，CPMS 会定期向 VHAL 发送推迟关闭的请求。@Overridepublicvoidfinished(ICarPowerStateListenerlistener){ICarImpl.assertPermission(mContext,Car.PERMISSION_CAR_POWER);ICarImpl.assertCallingFromSystemProcessOrSelf();finishedImpl(listener.asBinder());}privatevoidfinishedImpl(IBinderbinder){booleanallAreComplete;synchronized(mLock){mListenersWeAreWaitingFor.remove(binder);allAreComplete =mListenersWeAreWaitingFor.isEmpty();}// 所有Listener处理完成了。mHal.sendShutdownPostpone(SHUTDOWN_EXTEND_MAX_MS);}}}}

    这里假设走正常的处理了，即所有客户端（CarPowerStateListenerWithCompletion）期限内完成了处理。当然深度睡眠，还有一种方式是挂起到硬盘（Suspend-to-Disk），不过目前主要用的是STR。

    当所有 CPM 对象完成关闭准备后，CPMS 会向 VHAL 发送 AP_POWER_STATE_REPORT，VHAL 随后通知
    VMCU，告知它 AP 已准备好挂起。Vehicle HAL （Hal层的nativeservice）发送“AP_POWER_STATE_REQ(SHUTDOWN_PREPARE)”， 这样CarService中的 VehicleHal（Client端 ）就收到了这个通知。深度睡眠会进行Suspend-to-RAM挂起到内存（做车载的经常会听到的STR）。

    整套深度睡眠的实现，涉及的主要模块（这里指单Android系统。后面会根据源码，分析并画一个跟代码对应的时序图。synchronized(mLock){mProcessingStartTime =SystemClock.elapsedRealtime();releaseTimerLocked();mTimer =newTimer();mTimerActive =true;mTimer.scheduleAtFixedRate(newShutdownProcessingTimerTask(pollingCount),0/*delay*/,intervalMs);}if(mSwitchGuestUserBeforeSleep){switchToNewGuestIfNecessary();}}// 超时处理TaskprivateclassShutdownProcessingTimerTaskextendsTimerTask{privatefinalintmExpirationCount;privateintmCurrentCount;privateShutdownProcessingTimerTask(intexpirationCount){mExpirationCount =expirationCount;mCurrentCount =0;}@Overridepublicvoidrun(){synchronized(mLock){if(!mTimerActive){// Ignore timer expiration since we got cancelledreturn;}mCurrentCount++;if(mCurrentCount >mExpirationCount){// 超时处理。
    Android官网深入睡眠流程

    CPMS深度睡眠代码实现

    • 到这里，我们开始分析CPMS的实现。// 默认状态，走SUSPEND_ENTERlistenerState =mShutdownOnFinish ?CarPowerStateListener.SHUTDOWN_ENTER:CarPowerStateListener.SUSPEND_ENTER;}// 处理状态变化（这个函数是两参的，并且是private的）onApPowerStateChange(CpmsState.WAIT_FOR_FINISH,listenerState);}privatevoidonApPowerStateChange(intapState,intcarPowerStateListenerState){CpmsStatenewState =newCpmsState(apState,carPowerStateListenerState);synchronized(mLock){mPendingPowerStates.addFirst(newState);mLock.notify();}// 用 handler线程处理。booleansleepSucceeded =suspendWithRetries();if(!sleepSucceeded){// Suspend failed and we shut down instead.// We either won't get here at all or we will power off very soon.return;}// We suspended and have now resumednextListenerState =CarPowerStateListener.SUSPEND_EXIT;}synchronized(mLock){mIsResuming =true;// Any wakeup time from before is no longer valid.mNextWakeupSec =0;}Slog.i(TAG,"Resuming after suspending");mSystemInterface.refreshDisplayBrightness();onApPowerStateChange(CpmsState.WAIT_FOR_VHAL,nextListenerState);}

      综上是Android CarPower的深入睡眠睡眠主要流程，实际开发过程中。给Vehicle HAL通知DEEP_SLEEP_ENTRY，告知可以开始进入深入睡眠状态。STR指的是深度睡眠时的状态，但STR不等于深度睡眠。然后走WAIT_FOR_VHAL状态。那些使用 CarPowerStateListenerWithCompletion//（带有future，告知CPMS自己是否处理完了）的应用端是否处理完毕。根据业务进行扩展，一般会添加一个跟CPMS平行，或者基于它的新的电源模块。然后MCU就会发送AP_POWER_STATE_REQ(FINISHED)，告知Android侧调用Linux内核的实现，把自己挂起来（Supend）。

      也称为“挂起到 RAM”（S2R 或 STR）。

      • packages/services/Car/service/src/com/android/car/hal/VehicleHal.java
      publicvoidonPropertyEvent(ArrayList<VehiclePropValue>propValues){// 省略for(HalServiceBases :mServicesToDispatch){//  通知给监听者s.onHalEvents(s.getDispatchList());s.getDispatchList().clear();}mServicesToDispatch.clear();}
      • packages/services/Car/service/src/com/android/car/hal/PowerHalService.java
      @OverridepublicvoidonHalEvents(List<VehiclePropValue>values){// 省略dispatchEvents(values,listener);}privatevoiddispatchEvents(List<VehiclePropValue>values,PowerEventListenerlistener){for(VehiclePropValuev :values){switch(v.prop){caseAP_POWER_STATE_REPORT:// Ignore this property event. It was generated inside of CarService.break;caseAP_POWER_STATE_REQ:intstate =v.value.int32Values.get(VehicleApPowerStateReqIndex.STATE);intparam =v.value.int32Values.get(VehicleApPowerStateReqIndex.ADDITIONAL);Log.i(CarLog.TAG_POWER,"Received AP_POWER_STATE_REQ="+powerStateReqName(state)+" param="+param);// 通知状态给CPMS对象// AP_POWER_STATE_REQ(SHUTDOWN_PREPARE, CAN_SLEEP)listener.onApPowerStateChange(newPowerState(state,param));break;caseDISPLAY_BRIGHTNESS:{// 省略}break;}}}
      • packages/services/Car/service/src/com/android/car/CarPowerManagementService.java
      @OverridepublicvoidonApPowerStateChange(PowerStatestate){synchronized(mLock){mPendingPowerStates.addFirst(newCpmsState(state));mLock.notify();}mHandler.handlePowerStateChange();}privatevoidhandlePowerStateChange(){Messagemsg =obtainMessage(MSG_POWER_STATE_CHANGE);sendMessage(msg);}@OverridepublicvoidhandleMessage(Messagemsg){CarPowerManagementServiceservice =mService.get();if(service ==null){Slog.i(TAG,"handleMessage null service");return;}switch(msg.what){caseMSG_POWER_STATE_CHANGE:// 开始处理//  service是doHandlePowerStateChange对象service.doHandlePowerStateChange();break;// 省略}}privatevoiddoHandlePowerStateChange(){// 省略了mCurrentState =state;switch(state.mState){caseCpmsState.WAIT_FOR_VHAL:handleWaitForVhal(state);break;caseCpmsState.ON:handleOn();break;caseCpmsState.SHUTDOWN_PREPARE:// 处理SHUTDOWN_PREPAREhandleShutdownPrepare(state);break;// 省略default:// Illegal state// TODO:  Throw exception?break;}}

      CarPowerManagementService开始处理SHUTDOWN_PREPARE。通过这种技术，车载系统可以进入低能耗模式，同时又可以再用户需要时实现快速(非常快，因为从内存中恢复状态）的启动。一路通知给CPMS进行状态处理。特权服务可以在为
      PRE_SHUTDOWN_PREPARE、

      VMCU 应将 SoC 置于“深度睡眠”状态，并断开应用处理器的电源。CPMS 通过使用由 CPM 提供的新状态 ID 调用 onStateChanged() 方法，将状态更改为“关闭准备”并向所有观察者（监控 CPMS 的应用和服务）广播此状态转换。请注意，SHUTDOWN_PREPARE 不允许异步准备。if(allAreComplete){signalComplete();}}privatevoidsignalComplete(){if(mCurrentState.mState ==CpmsState.SHUTDOWN_PREPARE||mCurrentState.mState ==CpmsState.SIMULATE_SLEEP){PowerHandlerpowerHandler;// All apps are ready to shutdown/suspend.synchronized(mLock){if(!mShutdownOnFinish){if(mLastSleepEntryTime >mProcessingStartTime &&mLastSleepEntryTime <SystemClock.elapsedRealtime()){Slog.i(TAG,"signalComplete: Already slept!");return;}}powerHandler =mHandler;}Slog.i(TAG,"Apps are finished, call handleProcessingComplete()");powerHandler.handleProcessingComplete();}}privatevoidhandleProcessingComplete(){removeMessages(MSG_PROCESSING_COMPLETE);Messagemsg =obtainMessage(MSG_PROCESSING_COMPLETE);sendMessage(msg);}@OverridepublicvoidhandleMessage(Messagemsg){CarPowerManagementServiceservice =mService.get();if(service ==null){Slog.i(TAG,"handleMessage null service");return;}switch(msg.what){caseMSG_POWER_STATE_CHANGE:service.doHandlePowerStateChange();break;caseMSG_DISPLAY_BRIGHTNESS_CHANGE:service.doHandleDisplayBrightnessChange(msg.arg1);break;caseMSG_MAIN_DISPLAY_STATE_CHANGE:service.doHandleMainDisplayStateChange((Boolean)msg.obj);break;caseMSG_PROCESSING_COMPLETE:// 走这里service.doHandleProcessingComplete();break;}}privatevoiddoHandleProcessingComplete(){intlistenerState;synchronized(mLock){releaseTimerLocked();if(!mShutdownOnFinish &&mLastSleepEntryTime >mProcessingStartTime){// entered sleep after processing start. So this could be duplicate request.Slog.w(TAG,"Duplicate sleep entry request, ignore");return;}// 可以设置关机，即不进入挂起。主要是关闭VR交互、关闭屏幕。下面是上面代码的时序图，供参考。关闭CPU的电源，保持RAM的电源（激活状态）。}Slog.i(TAG,"processing before shutdown expected for: "+mShutdownPrepareTimeMs +" ms, adding polling:"+pollingCount);// 启动超时任务，定期检查。大多数应用和服务需要完成其准备后才能从该调用返回。下面省略了中间流程，最终调用的是doHandlePowerStateChangemHandler.handlePowerStateChange();}privatevoiddoHandlePowerStateChange(){mCurrentState =state;switch(state.mState){// 省略caseCpmsState.WAIT_FOR_FINISH:// 走这里handleWaitForFinish(state);break;// 省略default:// Illegal state// TODO: Throw exception?break;}}privatevoidhandleWaitForFinish(CpmsStatestate){// 通知给CPMS的监听者当前状态sendPowerManagerEvent(state.mCarPowerStateListenerState);intwakeupSec;synchronized(mLock){// If we're shutting down immediately, don't schedule// a wakeup time.// 可以设置，进入休眠状态后的唤醒时间（默认是不设置的），0表示一直Sleep（除非VMCU主动唤起）wakeupSec =mGarageModeShouldExitImmediately ?0:mNextWakeupSec;}switch(state.mCarPowerStateListenerState){caseCarPowerStateListener.SUSPEND_ENTER:// // 给Vehicle HAL发送状态// 发送的是DEEP_SLEEP_ENTRY，告知可以进入休眠状态了。CPMS 还会调用其挂起方法以挂起内核。不过是两个概念上的事情了。通知状态给CPMS的客户端，启动超时等待客户端处理完成（使用****CarPowerStateListenerWithCompletion的客户端）

      • packages/services/Car/service/src/com/android/car/CarPowerManagementService.java
      privatevoidhandleShutdownPrepare(CpmsStatenewState){setVoiceInteractionDisabled(true);mSystemInterface.setDisplayState(false);// Shutdown on finish if the system doesn't support deep sleep or doesn't allow it.// 通知状态给客户端sendPowerManagerEvent(CarPowerStateListener.SHUTDOWN_PREPARE);mHal.sendShutdownPrepare();doHandlePreprocessing();}privatevoiddoHandlePreprocessing(){intintervalMs;intpollingCount;synchronized(mLock){intervalMs =mShutdownPollingIntervalMs;pollingCount =(mShutdownPrepareTimeMs /mShutdownPollingIntervalMs)+1;}if(Build.IS_USERDEBUG||Build.IS_ENG){// 这里省略了，主要是可以通过属性，修改超时时间。然后，AAOS 将进入“挂起到 RAM”状态，但不执行任何代码。