Android电源管理系列之PowerManagerService(一)

 

PowerManagerService 提供Android系统的电源管理服务，主要功能是控制系统待机状态，屏幕显示，亮度调节，光线/距离传感器的控制等。

相关代码在以下文件中

frameworks/base/services/java/com/android/server/SystemServer.java frameworks/base/core/java/android/os/PowerManager.java frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java frameworks/base/services/core/jni/com_android_server_power_PowerManagerService.cpp frameworks/base/core/java/android/os/PowerManagerInternal.java frameworks/base/services/core/java/com/android/server/power/Notifier.java device/qcom/common/power/power.c system/core/libsuspend/autosuspend.c hardware/libhardware_legacy/power/power.c

初始化流程

跟其他系统服务一样，PowerManagerService也是继承于SystemService并通过SystemServer启动。
SystemServer
frameworks/base/services/java/com/android/server/SystemServer.java

private void startBootstrapServices() {  ......  mPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class);  ...... }

PowerManagerService
frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

public final class PowerManagerService extends SystemService        implements Watchdog.Monitor {    ...... }

在SystemServer的startBootstrapServices中，通过SystemServiceManager.startService启动了PowerManagerService，下面首先来看PowerManagerService构造方法。
frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

public PowerManagerService(Context context) {    super(context);    // mContext赋值为SystemContext    mContext = context;    // 创建消息处理线程并启动，创建关联消息处理线程的handler对象    mHandlerThread = new ServiceThread(TAG,            Process.THREAD_PRIORITY_DISPLAY, false /*allowIo*/);    mHandlerThread.start();    mHandler = new PowerManagerHandler(mHandlerThread.getLooper());    qcNsrmPowExt = new QCNsrmPowerExtension(this);    synchronized (mLock) {        // 创建"PowerManagerService.WakeLocks"的SuspendBlocker        mWakeLockSuspendBlocker = createSuspendBlockerLocked("PowerManagerService.WakeLocks");        // 创建"PowerManagerService.Display"的SuspendBlocker        mDisplaySuspendBlocker = createSuspendBlockerLocked("PowerManagerService.Display");        // 请求DisplaySuspendBlocker，禁止系统进入休眠        mDisplaySuspendBlocker.acquire();        mHoldingDisplaySuspendBlocker = true;        mHalAutoSuspendModeEnabled = false;        mHalInteractiveModeEnabled = true;        // 设置mWakefulness为唤醒状态        mWakefulness = WAKEFULNESS_AWAKE;        // 进入到native层初始化        nativeInit();        nativeSetAutoSuspend(false);        nativeSetInteractive(true);        nativeSetFeature(POWER_FEATURE_DOUBLE_TAP_TO_WAKE, 0);    } }

PowerManagerService构造函数中首先创建了处理消息的进程及对应的handler对象以进行消息处理，然后创建SuspendBlocker对象，用于WakeLocks与Display，并设置mWakefulness的初始状态为WAKEFULNESS_AWAKE，最后进入到native层初始化。下面先看一下关于mWakefulness的定义。

>>> frameworks/base/core/java/android/os/PowerManagerInternal.java/** * 设备处于休眠状态，只能被wakeUp()唤醒． */public static final int WAKEFULNESS_ASLEEP = 0;/** * 设备处于正常工作(fully awake)状态． */public static final int WAKEFULNESS_AWAKE = 1;/** * 设备处于播放屏保状态． */public static final int WAKEFULNESS_DREAMING = 2;/** * 设备处于doze状态，只有低耗电的屏保可以运行，其他应用被挂起． */public static final int WAKEFULNESS_DOZING = 3;

继续回到PowerManagerService构造函数的native初始化中，首先来看nativeInit的实现。
frameworks/base/services/core/jni/com_android_server_power_PowerManagerService.cpp

static const JNINativeMethod gPowerManagerServiceMethods[] = {    /* name, signature, funcPtr */    { "nativeInit", "()V",            (void*) nativeInit },    { "nativeAcquireSuspendBlocker", "(Ljava/lang/String;)V",            (void*) nativeAcquireSuspendBlocker },    { "nativeReleaseSuspendBlocker", "(Ljava/lang/String;)V",            (void*) nativeReleaseSuspendBlocker },    { "nativeSetInteractive", "(Z)V",            (void*) nativeSetInteractive },    { "nativeSetAutoSuspend", "(Z)V",            (void*) nativeSetAutoSuspend },    { "nativeSendPowerHint", "(II)V",            (void*) nativeSendPowerHint },    { "nativeSetFeature", "(II)V",            (void*) nativeSetFeature }, };

PowerManagerService中的native方法定义如上，nativeInit即调用nativeInit()。
frameworks/base/services/core/jni/com_android_server_power_PowerManagerService.cpp

static void nativeInit(JNIEnv* env, jobject obj) {    // 创建一个全局对象，引用PMS    gPowerManagerServiceObj = env->NewGlobalRef(obj);    // 利用hw_get_module加载power模块    status_t err = hw_get_module(POWER_HARDWARE_MODULE_ID,            (hw_module_t const**)&gPowerModule);    if (!err) {        gPowerModule->init(gPowerModule);    } else {        ALOGE("Couldn't load %s module (%s)", POWER_HARDWARE_MODULE_ID, strerror(-err));    } }

nativeInit的主要任务时装载power模块，该模块由厂商实现，以高通为例，如下。
device/qcom/common/power/power.c

tatic struct hw_module_methods_t power_module_methods = {    .open = NULL, };struct power_module HAL_MODULE_INFO_SYM = {    .common = {        .tag = HARDWARE_MODULE_TAG,        .module_api_version = POWER_MODULE_API_VERSION_0_2,        .hal_api_version = HARDWARE_HAL_API_VERSION,        .id = POWER_HARDWARE_MODULE_ID,        .name = "QCOM Power HAL",        .author = "Qualcomm",        .methods = &power_module_methods,    },    .init = power_init,    .powerHint = power_hint,    .setInteractive = set_interactive, };

power_module中实现了init，powerHint，setInteractive，nativeInit最终调用到HAL power模块的power_init具体实现中。接着看native初始化nativeSetAutoSuspend的实现。

frameworks/base/services/core/jni/com_android_server_power_PowerManagerService.cpp

static void nativeSetAutoSuspend(JNIEnv* /* env */, jclass /* clazz */, jboolean enable) {    if (enable) {        ALOGD_IF_SLOW(100, "Excessive delay in autosuspend_enable() while turning screen off");        autosuspend_enable();    } else {        ALOGD_IF_SLOW(100, "Excessive delay in autosuspend_disable() while turning screen on");        autosuspend_disable();    } }

system/core/libsuspend/autosuspend.c

int autosuspend_disable(void){    int ret;    ret = autosuspend_init();    if (ret) {        return ret;    }    ALOGV("autosuspend_disable\n");    if (!autosuspend_enabled) {        return 0;    }    ret = autosuspend_ops->disable();    if (ret) {        return ret;    }    autosuspend_enabled = false;    return 0; }

nativeSetAutoSuspend最终调用到libsuspend(参考Android电源管理系列之libsuspend)的autosuspend_disable禁止系统休眠。继续看native初始化nativeSetInteractive，nativeSetFeature的实现
frameworks/base/services/core/jni/com_android_server_power_PowerManagerService.cpp

static void nativeSetInteractive(JNIEnv* /* env */, jclass /* clazz */, jboolean enable) {    if (gPowerModule) {        if (enable) {            ALOGD_IF_SLOW(20, "Excessive delay in setInteractive(true) while turning screen on");            gPowerModule->setInteractive(gPowerModule, true);        } else {            ALOGD_IF_SLOW(20, "Excessive delay in setInteractive(false) while turning screen off");            gPowerModule->setInteractive(gPowerModule, false);        }    } }static void nativeSetFeature(JNIEnv *env, jclass clazz, jint featureId, jint data) {    int data_param = data;    if (gPowerModule && gPowerModule->setFeature) {        gPowerModule->setFeature(gPowerModule, (feature_t)featureId, data_param);    } }

同nativeInit一样，最终都是调用到HAL power模块的具体实现中。以上是构造函数的分析流程，下面继续看PowerManagerService在系统启动过程中回调onStart()，onBootPhase()，systemReady()的实现。
frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

public void onStart() {    publishBinderService(Context.POWER_SERVICE, new BinderService());    publishLocalService(PowerManagerInternal.class, new LocalService());    Watchdog.getInstance().addMonitor(this);    Watchdog.getInstance().addThread(mHandler); }private final class BinderService extends IPowerManager.Stub ｛    ...... ｝private final class LocalService extends PowerManagerInternal {    ...... }

onStart()中发布了BinderService，LocalService分别供其他进程，进程内其他服务调用，并将PowerManagerService加入到Watchdog监控中。

frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

public void onBootPhase(int phase) {    synchronized (mLock) {        if (phase == PHASE_THIRD_PARTY_APPS_CAN_START) {            ......        } else if (phase == PHASE_BOOT_COMPLETED) {            final long now = SystemClock.uptimeMillis();            // 设置mBootCompleted状态            mBootCompleted = true;            mDirty |= DIRTY_BOOT_COMPLETED;            // 更新userActivity及PowerState，后面分析            userActivityNoUpdateLocked(                    now, PowerManager.USER_ACTIVITY_EVENT_OTHER, 0, Process.SYSTEM_UID);            updatePowerStateLocked();            // 执行mBootCompletedRunnables中的runnable方法            if (!ArrayUtils.isEmpty(mBootCompletedRunnables)) {                Slog.d(TAG, "Posting " + mBootCompletedRunnables.length + " delayed runnables");                for (Runnable r : mBootCompletedRunnables) {                    BackgroundThread.getHandler().post(r);                }            }            mBootCompletedRunnables = null;        }    } }

onBootPhase中主要设置mBootCompleted状态，更新PowerState状态，并执行mBootCompletedRunnables中的runnables方法(低电量模式会设置)。
frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

public void systemReady(IAppOpsService appOps) {    synchronized (mLock) {        mSystemReady = true;        // 获取AppOpsService        mAppOps = appOps;        // 获取DreamManager        mDreamManager = getLocalService(DreamManagerInternal.class);        // 获取DisplayManagerService        mDisplayManagerInternal = getLocalService(DisplayManagerInternal.class);        mPolicy = getLocalService(WindowManagerPolicy.class);        // 获取mBatteryService        mBatteryManagerInternal = getLocalService(BatteryManagerInternal.class);        PowerManager pm = (PowerManager) mContext.getSystemService(Context.POWER_SERVICE);        // 获取屏幕默认，最大，最小亮度        mScreenBrightnessSettingMinimum = pm.getMinimumScreenBrightnessSetting();        mScreenBrightnessSettingMaximum = pm.getMaximumScreenBrightnessSetting();        mScreenBrightnessSettingDefault = pm.getDefaultScreenBrightnessSetting();        // 获取SensorManager        SensorManager sensorManager = new SystemSensorManager(mContext, mHandler.getLooper());        mBatteryStats = BatteryStatsService.getService();        // 创建Notifier对象，用于广播power state的变化        mNotifier = new Notifier(Looper.getMainLooper(), mContext, mBatteryStats,                mAppOps, createSuspendBlockerLocked("PowerManagerService.Broadcasts"),                mPolicy);        // 无线充电检测        mWirelessChargerDetector = new WirelessChargerDetector(sensorManager,                createSuspendBlockerLocked("PowerManagerService.WirelessChargerDetector"),                mHandler);        // 监听设置的变化        mSettingsObserver = new SettingsObserver(mHandler);        mLightsManager = getLocalService(LightsManager.class);        mAttentionLight = mLightsManager.getLight(LightsManager.LIGHT_ID_ATTENTION);        // Initialize display power management.        mDisplayManagerInternal.initPowerManagement(                mDisplayPowerCallbacks, mHandler, sensorManager);        // Register for settings changes.        final ContentResolver resolver = mContext.getContentResolver();        resolver.registerContentObserver(Settings.Secure.getUriFor(                Settings.Secure.SCREENSAVER_ENABLED),        ......        IVrManager vrManager =                (IVrManager) getBinderService(VrManagerService.VR_MANAGER_BINDER_SERVICE);        try {            vrManager.registerListener(mVrStateCallbacks);        } catch (RemoteException e) {            Slog.e(TAG, "Failed to register VR mode state listener: " + e);        }        // 读取配置        readConfigurationLocked();        updateSettingsLocked();        mDirty |= DIRTY_BATTERY_STATE;        updatePowerStateLocked();    }    // Register for broadcasts from other components of the system.    IntentFilter filter = new IntentFilter();    filter.addAction(Intent.ACTION_BATTERY_CHANGED);    filter.setPriority(IntentFilter.SYSTEM_HIGH_PRIORITY);    mContext.registerReceiver(new BatteryReceiver(), filter, null, mHandler);    filter = new IntentFilter();    filter.addAction(Intent.ACTION_DREAMING_STARTED);    filter.addAction(Intent.ACTION_DREAMING_STOPPED);    mContext.registerReceiver(new DreamReceiver(), filter, null, mHandler);    filter = new IntentFilter();    filter.addAction(Intent.ACTION_USER_SWITCHED);    mContext.registerReceiver(new UserSwitchedReceiver(), filter, null, mHandler);    filter = new IntentFilter();    filter.addAction(Intent.ACTION_DOCK_EVENT);    mContext.registerReceiver(new DockReceiver(), filter, null, mHandler); }

userActivity
userActivity是定义在PowerManager中的SystemApi，用户向PowerManagerService报告用户活动，以更新PowerManagerService内部时间/状态值，推迟系统休眠的时间。下面首先来看userActivity的定义。

frameworks/base/core/java/android/os/PowerManager.java

/** * User activity event type: Unspecified event type. */public static final int USER_ACTIVITY_EVENT_OTHER = 0;/** * User activity event type: Button or key pressed or released. */public static final int USER_ACTIVITY_EVENT_BUTTON = 1;/** * User activity event type: Touch down, move or up. */public static final int USER_ACTIVITY_EVENT_TOUCH = 2;/** * User activity event type: Accessibility taking action on behalf of user. */public static final int USER_ACTIVITY_EVENT_ACCESSIBILITY = 3;@SystemApipublic void userActivity(long when, int event, int flags) {    try {        mService.userActivity(when, event, flags);    } catch (RemoteException e) {        throw e.rethrowFromSystemServer();    } }

frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

private final class BinderService extends IPowerManager.Stub {  ......  public void userActivity(long eventTime, int event, int flags) {      final long now = SystemClock.uptimeMillis();      ......      if (eventTime > now) {          throw new IllegalArgumentException("event time must not be in the future");      }      final int uid = Binder.getCallingUid();      final long ident = Binder.clearCallingIdentity();      try {          userActivityInternal(eventTime, event, flags, uid);      } finally {          Binder.restoreCallingIdentity(ident);      }  }  ...... }

PowerManager中userActivity请求调用服务端PowerManagerService BinderService的userActivity，即调用内部方法userActivityInternal。

frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

private void userActivityInternal(long eventTime, int event, int flags, int uid) {    synchronized (mLock) {        if (userActivityNoUpdateLocked(eventTime, event, flags, uid)) {            updatePowerStateLocked();        }    } }

userActivityInternal中首先调用userActivityNoUpdateLocked更新相关数据及状态(***NoUpdateLocked仅仅更新内部状态并不采取任何操作)，然后调用updatePowerStateLocked更新所有PowerState，下面分析userActivityNoUpdateLocked的实现，updatePowerStateLocked是PowerManagerService的核心方法，在最后进行分析。

frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

private boolean userActivityNoUpdateLocked(long eventTime, int event, int flags, int uid) {    // 如果发生时间是上一次休眠或唤醒前，或当前没有开机完成到systemReady，不采取操作直接返回    if (eventTime < mLastSleepTime || eventTime < mLastWakeTime            || !mBootCompleted || !mSystemReady) {        return false;    }    try {        // 更新mLastInteractivePowerHintTime时间        if (eventTime > mLastInteractivePowerHintTime) {            powerHintInternal(POWER_HINT_INTERACTION, 0);            mLastInteractivePowerHintTime = eventTime;        }        // 通过mNotifier通知BatteryStats UserActivity事件        mNotifier.onUserActivity(event, uid);        if (mUserInactiveOverrideFromWindowManager) {            mUserInactiveOverrideFromWindowManager = false;            mOverriddenTimeout = -1;        }        // 如果系统处于休眠状态，不进行处理        if (mWakefulness == WAKEFULNESS_ASLEEP                || mWakefulness == WAKEFULNESS_DOZING                || (flags & PowerManager.USER_ACTIVITY_FLAG_INDIRECT) != 0) {            return false;        }        // 根据flag是否在已变暗的情况下是否重启活动超时更新mLastUserActivityTimeNoChangeLights或mLastUserActivityTime        // 并且设置mDirty DIRTY_USER_ACTIVITY        if ((flags & PowerManager.USER_ACTIVITY_FLAG_NO_CHANGE_LIGHTS) != 0) {            if (eventTime > mLastUserActivityTimeNoChangeLights                    && eventTime > mLastUserActivityTime) {                mLastUserActivityTimeNoChangeLights = eventTime;                mDirty |= DIRTY_USER_ACTIVITY;                return true;            }        } else {            if (eventTime > mLastUserActivityTime) {                mLastUserActivityTime = eventTime;                mDirty |= DIRTY_USER_ACTIVITY;                return true;            }        }    } finally {        Trace.traceEnd(Trace.TRACE_TAG_POWER);    }    return false; }

gotoSleep
gotoSleep在PowerManager中的定义如下：
frameworks/base/core/java/android/os/PowerManager.java

public void goToSleep(long time) {    goToSleep(time, GO_TO_SLEEP_REASON_APPLICATION, 0); }public void goToSleep(long time, int reason, int flags) {    try {        mService.goToSleep(time, reason, flags);    } catch (RemoteException e) {        throw e.rethrowFromSystemServer();    } }

与userActivity一样，gotoSleep最终将调用到goToSleepInternal。
frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

private final class BinderService extends IPowerManager.Stub {  ......  public void goToSleep(long eventTime, int reason, int flags) {      if (eventTime > SystemClock.uptimeMillis()) {          throw new IllegalArgumentException("event time must not be in the future");      }      mContext.enforceCallingOrSelfPermission(              android.Manifest.permission.DEVICE_POWER, null);      final int uid = Binder.getCallingUid();      final long ident = Binder.clearCallingIdentity();      try {          goToSleepInternal(eventTime, reason, flags, uid);      } finally {          Binder.restoreCallingIdentity(ident);      }  }  ...... }private void goToSleepInternal(long eventTime, int reason, int flags, int uid) {    synchronized (mLock) {        if (goToSleepNoUpdateLocked(eventTime, reason, flags, uid)) {            updatePowerStateLocked();        }    } }

goToSleepInternal中将执行goToSleepNoUpdateLocked更新内部状态，同样在updatePowerStateLocked中更新PowerState的操作。
frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java

private boolean goToSleepNoUpdateLocked(long eventTime, int reason, int flags, int uid) {    // 当不处于awake状态或未开机systemReady，不处理    if (eventTime < mLastWakeTime            || mWakefulness == WAKEFULNESS_ASLEEP            || mWakefulness == WAKEFULNESS_DOZING            || !mBootCompleted || !mSystemReady) {        return false;    }    try {        ......        // 更新mLastSleepTime时间，设置DIRTY_WAKEFULNESS标志位        mLastSleepTime = eventTime;        mSandmanSummoned = true;        setWakefulnessLocked(WAKEFULNESS_DOZING, reason);        // Report the number of wake locks that will be cleared by going to sleep.        int numWakeLocksCleared = 0;        final int numWakeLocks = mWakeLocks.size();        for (int i = 0; i < numWakeLocks; i++) {            final WakeLock wakeLock = mWakeLocks.get(i);            switch (wakeLock.mFlags & PowerManager.WAKE_LOCK_LEVEL_MASK) {                case PowerManager.FULL_WAKE_LOCK:                case PowerManager.SCREEN_BRIGHT_WAKE_LOCK:                case PowerManager.SCREEN_DIM_WAKE_LOCK:                    numWakeLocksCleared += 1;                    break;            }        }        // Skip dozing if requested.        if ((flags & PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE) != 0) {            reallyGoToSleepNoUpdateLocked(eventTime, uid);        }    } finally {        Trace.traceEnd(Trace.TRACE_TAG_POWER);    }    return true; }

goToSleepNoUpdateLocked中更新mLastSleepTime，mWakefulness，mDirty状态。