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。
首先,什么是深度睡眠(Deep Sleep)?
Android进入Deep Sleep后,关闭屏幕、关闭CPU的电源,保持RAM的电源(激活状态)。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)。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。STR指的是深度睡眠时的状态,但STR不等于深度睡眠。
DeepSleep或STR,需要内核配合实现。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。
感觉这种方式,跟snapshot快启动有点类似。不过是两个概念上的事情了。
下面摘自Android官网对这种状态的介绍。
也称为“挂起到 RAM”(S2R 或 STR)。将 SoC 置于 S3 电源模式,CPU 断电而 RAM 仍通电。
VMCU 应将 SoC 置于“深度睡眠”状态,并断开应用处理器的电源。然后,AAOS 将进入“挂起到 RAM”状态,但不执行任何代码。
整套深度睡眠的实现,涉及的主要模块(这里指单Android系统。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、以太方式)
- CarPowerManagerService(CPMS): 实现Android侧的电源控制,应用电源策略。
- 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。启动深度睡眠后,VMCU 会通过 VHAL 向 CPMS 发送通知。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。
CPM 在应用/服务与 CPMS 之间进行协调。在 CPM 的 onStateChanged() 方法中,同步调用应用/服务的
onStateChanged() 方法。大多数应用和服务需要完成其准备后才能从该调用返回。特权服务可以在为
PRE_SHUTDOWN_PREPARE、SUSPEND_ENTER 和 POST_SUSPEND_ENTER
返回后,异步继续关闭准备。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()。请注意,SHUTDOWN_PREPARE 不允许异步准备。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。
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。CPMS 还会调用其挂起方法以挂起内核。
下面的图,是Android官网对于深度睡眠的时序图。这里贴在这里。后面会根据源码,分析并画一个跟代码对应的时序图。
CPMS深度睡眠代码实现
- 到这里,我们开始分析CPMS的实现。代码基于Android11
首先,VMCU请求挂起。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。一路通知给CPMS进行状态处理。
- packages/services/Car/service/src/com/android/car/hal/VehicleHal.java
public void onPropertyEvent(ArrayList<VehiclePropValue> propValues) {
// 省略
for (HalServiceBase s : 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
@Override
public void onHalEvents(List<VehiclePropValue> values) {
// 省略
dispatchEvents(values, listener);
}
private void dispatchEvents(List<VehiclePropValue> values, PowerEventListener listener) {
for (VehiclePropValue v : values) {
switch (v.prop) {
case AP_POWER_STATE_REPORT:
// Ignore this property event. It was generated inside of CarService.
break;
case AP_POWER_STATE_REQ:
int state = v.value.int32Values.get(VehicleApPowerStateReqIndex.STATE);
int param = 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(new PowerState(state, param));
break;
case DISPLAY_BRIGHTNESS:
{
// 省略
}
break;
}
}
}
- packages/services/Car/service/src/com/android/car/CarPowerManagementService.java
@Override
public void onApPowerStateChange(PowerState state) {
synchronized (mLock) {
mPendingPowerStates.addFirst(new CpmsState(state));
mLock.notify();
}
mHandler.handlePowerStateChange();
}
private void handlePowerStateChange() {
Message msg = obtainMessage(MSG_POWER_STATE_CHANGE);
sendMessage(msg);
}
@Override
public void handleMessage(Message msg) {
CarPowerManagementService service = mService.get();
if (service == null) {
Slog.i(TAG, "handleMessage null service");
return;
}
switch (msg.what) {
case MSG_POWER_STATE_CHANGE:
// 开始处理
// service是doHandlePowerStateChange对象
service.doHandlePowerStateChange();
break;
// 省略
}
}
private void doHandlePowerStateChange() {
// 省略了
mCurrentState = state;
switch (state.mState) {
case CpmsState.WAIT_FOR_VHAL:
handleWaitForVhal(state);
break;
case CpmsState.ON:
handleOn();
break;
case CpmsState.SHUTDOWN_PREPARE:
// 处理SHUTDOWN_PREPARE
handleShutdownPrepare(state);
break;
// 省略
default:
// Illegal state
// TODO: Throw exception?
break;
}
}
CarPowerManagementService开始处理SHUTDOWN_PREPARE。主要是关闭VR交互、关闭屏幕。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
private void handleShutdownPrepare(CpmsState newState) {
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();
}
private void doHandlePreprocessing() {
int intervalMs;
int pollingCount;
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。
}
Slog.i(TAG, "processing before shutdown expected for: "
+ mShutdownPrepareTimeMs + " ms, adding polling:" + pollingCount);
// 启动超时任务,定期检查。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。
// 如果超时还没完成,强制走DeepSleep流程。
synchronized (mLock) {
mProcessingStartTime = SystemClock.elapsedRealtime();
releaseTimerLocked();
mTimer = new Timer();
mTimerActive = true;
mTimer.scheduleAtFixedRate(
new ShutdownProcessingTimerTask(pollingCount),
0 /*delay*/,
intervalMs);
}
if (mSwitchGuestUserBeforeSleep) {
switchToNewGuestIfNecessary();
}
}
// 超时处理Task
private class ShutdownProcessingTimerTask extends TimerTask {
private final int mExpirationCount;
private int mCurrentCount;
private ShutdownProcessingTimerTask(int expirationCount) {
mExpirationCount = expirationCount;
mCurrentCount = 0;
}
@Override
public void run() {
synchronized (mLock) {
if (!mTimerActive) {
// Ignore timer expiration since we got cancelled
return;
}
mCurrentCount++;
if (mCurrentCount > mExpirationCount) {
// 超时处理。给Vehicle HAL通知DEEP_SLEEP_ENTRY,告知可以开始进入深入睡眠状态。
PowerHandler handler;
releaseTimerLocked();
handler = mHandler;
handler.handleProcessingComplete();
} else {
// 定期通过PowerServiceHAL向Vehicle HAL发送延时通知。
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。那么CPMS,就会通过PowerserviceHAL告知 VehicleHAL “DEEP_SLEEP_ENTRY”状态。下面是CarPowerStateListenerWithCompletion的一个例子。
mCarPowerManager.setListenerWithCompletion(mCarPowerStateListener);
private final CarPowerStateListenerWithCompletion mCarPowerStateListener =
new CarPowerStateListenerWithCompletion() {
@Override
public void onStateChanged(int state, 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。
@Override
public void finished(ICarPowerStateListener listener) {
ICarImpl.assertPermission(mContext, Car.PERMISSION_CAR_POWER);
ICarImpl.assertCallingFromSystemProcessOrSelf();
finishedImpl(listener.asBinder());
}
private void finishedImpl(IBinder binder) {
boolean allAreComplete;
synchronized (mLock) {
mListenersWeAreWaitingFor.remove(binder);
allAreComplete = mListenersWeAreWaitingFor.isEmpty();
}
// 所有Listener处理完成了。
if (allAreComplete) {
signalComplete();
}
}
private void signalComplete() {
if (mCurrentState.mState == CpmsState.SHUTDOWN_PREPARE
|| mCurrentState.mState == CpmsState.SIMULATE_SLEEP) {
PowerHandler powerHandler;
// 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();
}
}
private void handleProcessingComplete() {
removeMessages(MSG_PROCESSING_COMPLETE);
Message msg = obtainMessage(MSG_PROCESSING_COMPLETE);
sendMessage(msg);
}
@Override
public void handleMessage(Message msg) {
CarPowerManagementService service = mService.get();
if (service == null) {
Slog.i(TAG, "handleMessage null service");
return;
}
switch (msg.what) {
case MSG_POWER_STATE_CHANGE:
service.doHandlePowerStateChange();
break;
case MSG_DISPLAY_BRIGHTNESS_CHANGE:
service.doHandleDisplayBrightnessChange(msg.arg1);
break;
case MSG_MAIN_DISPLAY_STATE_CHANGE:
service.doHandleMainDisplayStateChange((Boolean) msg.obj);
break;
case MSG_PROCESSING_COMPLETE:
// 走这里
service.doHandleProcessingComplete();
break;
}
}
private void doHandleProcessingComplete() {
int listenerState;
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。
// 默认状态,走SUSPEND_ENTER
listenerState = 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);
}
private void onApPowerStateChange(int apState, int carPowerStateListenerState) {
CpmsState newState = new CpmsState(apState, carPowerStateListenerState);
synchronized (mLock) {
mPendingPowerStates.addFirst(newState);
mLock.notify();
}
// 用 handler线程处理。下面省略了中间流程,最终调用的是doHandlePowerStateChange
mHandler.handlePowerStateChange();
}
private void doHandlePowerStateChange() {
mCurrentState = state;
switch (state.mState) {
// 省略
case CpmsState.WAIT_FOR_FINISH:
// 走这里
handleWaitForFinish(state);
break;
// 省略
default:
// Illegal state
// TODO: Throw exception?
break;
}
}
private void handleWaitForFinish(CpmsState state) {
// 通知给CPMS的监听者当前状态
sendPowerManagerEvent(state.mCarPowerStateListenerState);
int wakeupSec;
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) {
case CarPowerStateListener.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。
mHal.sendSleepEntry(wakeupSec);
break;
case CarPowerStateListener.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。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)。消息通知流程,跟上面的onPropertyEvent一致,这部分下面就省略了。文章来源:https://www.toymoban.com/news/detail-743335.html
- packages/services/Car/service/src/com/android/car/CarPowerManagementService.java
private void doHandlePowerStateChange() {
mCurrentState = state;
switch (state.mState) {
// 省略
case CpmsState.SUSPEND:
// Received FINISH from VHAL
// 走这里
handleFinish();
break;
default:
// Illegal state
// TODO: Throw exception?
break;
}
}
private void handleFinish() {
// 省略
// 关闭Voice
setVoiceInteractionDisabled(true);
// To make Kernel implementation simpler when going into sleep.
disableWifi();
if (mustShutDown) {
// shutdown HU
mSystemInterface.shutdown();
} else {
// 处理深入睡眠
doHandleDeepSleep(simulatedMode);
}
mShutdownOnNextSuspend = false;
}
private void doHandleDeepSleep(boolean simulatedMode) {
// 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();
}
int nextListenerState;
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。
// 挂成功的情况下面,下面的代码就不会走了(CPU都没电了)。
// 之后的代码,就是CPU上电后的恢复流程了。
// 可以看出恢复前,要刷新一下屏幕亮度。然后走WAIT_FOR_VHAL状态。
boolean sleepSucceeded = 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 resumed
nextListenerState = 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。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。下面是上面代码的时序图,供参考。文章来源地址https://www.toymoban.com/news/detail-743335.html
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