Android電源管理系列之PowerManagerService(一)

摘要： PowerManagerService提供Android系統的電源管理服務，主要功能是控制系統待機狀態，螢幕顯示，亮度調節，光線/距離感測器的控制等。 相關程式碼在以下檔案中： frameworks/base/services/java/com/android/...

PowerManagerService提供Android系統的電源管理服務，主要功能是控制系統待機狀態，螢幕顯示，亮度調節，光線/距離感測器的控制等。

相關程式碼在以下檔案中：

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

跟其他系統服務一樣，PowerManagerService也是繼承於SystemService並通過SystemServer啟動。

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，通過SystemServiceManager.startService啟動了PowerManagerService，下面首先來看PowerManagerService構造方法。

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

public PowerManagerService(Context context) {
super(context);
// mContext賦值為SystemContext
mContext = context;
// 建立訊息處理執行緒並啟動，建立關聯訊息處理執行緒的handler物件
mHandlerThread = new ServiceThread(TAG,
Process.THREAD_PRIORITY_DISPLAY, false /*allowIo*/);
mHandlerThread.start();
mHandler = new PowerManagerHandler(mHandlerThread.getLooper());
qcNsrmPowExt = new QCNsrmPowerExtension(this);
synchronized (mLock) {
// 建立"PowerManagerService.WakeLocks"的SuspendBlocker
mWakeLockSuspendBlocker = createSuspendBlockerLocked("PowerManagerService.WakeLocks");
// 建立"PowerManagerService.Display"的SuspendBlocker
mDisplaySuspendBlocker = createSuspendBlockerLocked("PowerManagerService.Display");
// 請求DisplaySuspendBlocker，禁止系統進入休眠
mDisplaySuspendBlocker.acquire();
mHoldingDisplaySuspendBlocker = true;
mHalAutoSuspendModeEnabled = false;
mHalInteractiveModeEnabled = true;
// 設定mWakefulness為喚醒狀態
mWakefulness = WAKEFULNESS_AWAKE;
// 進入到native層初始化
nativeInit();
nativeSetAutoSuspend(false);
nativeSetInteractive(true);
nativeSetFeature(POWER_FEATURE_DOUBLE_TAP_TO_WAKE, 0);
}
}

PowerManagerService建構函式中首先建立了處理訊息的程序及對應的handler物件以進行訊息處理，然後建立SuspendBlocker物件，用於WakeLocks與Display，並設定mWakefulness的初始狀態為WAKEFULNESS_AWAKE，最後進入到native層初始化。下面先看一下關於mWakefulness的定義。

>>> frameworks/base/core/java/android/os/PowerManagerInternal.java

/**
 * 裝置處於休眠狀態，只能被wakeUp()喚醒．
 */
public static final int WAKEFULNESS_ASLEEP = 0;

/**
 * 裝置處於正常工作(fully awake)狀態．
 */
public static final int WAKEFULNESS_AWAKE = 1;

/**
 * 裝置處於播放屏保狀態．
 */
public static final int WAKEFULNESS_DREAMING = 2;

/**
 * 裝置處於doze狀態，只有低耗電的屏保可以執行，其他應用被掛起．
 */
public static final int WAKEFULNESS_DOZING = 3;

繼續回到PowerManagerService建構函式的native初始化中，首先來看nativeInit的實現。

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方法定義如上，nativeInit即呼叫nativeInit()。

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

static void nativeInit(JNIEnv* env, jobject obj) {
// 建立一個全域性物件，引用PMS
gPowerManagerServiceObj = env->NewGlobalRef(obj);
// 利用hw_get_module載入power模組
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的主要任務時裝載power模組，該模組由廠商實現，以高通為例，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中實現了init，powerHint，setInteractive，nativeInit最終呼叫到HAL power模組的power_init具體實現中。接著看native初始化nativeSetAutoSuspend的實現。

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最終呼叫到libsuspend(參考Android電源管理系列之libsuspend)的autosuspend_disable禁止系統休眠。繼續看native初始化nativeSetInteractive，nativeSetFeature的實現

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一樣，最終都是呼叫到HAL power模組的具體實現中。以上是建構函式的分析流程，下面繼續看PowerManagerService在系統啟動過程中回撥onStart()，onBootPhase()，systemReady()的實現。

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()中釋出了BinderService，LocalService分別供其他程序，程序內其他服務呼叫，並將PowerManagerService加入到Watchdog監控中。

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();
// 設定mBootCompleted狀態
mBootCompleted = true;
mDirty |= DIRTY_BOOT_COMPLETED;
// 更新userActivity及PowerState，後面分析
userActivityNoUpdateLocked(
now, PowerManager.USER_ACTIVITY_EVENT_OTHER, 0, Process.SYSTEM_UID);
updatePowerStateLocked();
// 執行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中主要設定mBootCompleted狀態，更新PowerState狀態，並執行mBootCompletedRunnables中的runnables方法(低電量模式會設定)。

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

public void systemReady(IAppOpsService appOps) {
synchronized (mLock) {
mSystemReady = true;
// 獲取AppOpsService
mAppOps = appOps;
// 獲取DreamManager
mDreamManager = getLocalService(DreamManagerInternal.class);
// 獲取DisplayManagerService
mDisplayManagerInternal = getLocalService(DisplayManagerInternal.class);
mPolicy = getLocalService(WindowManagerPolicy.class);
// 獲取mBatteryService
mBatteryManagerInternal = getLocalService(BatteryManagerInternal.class);

PowerManager pm = (PowerManager) mContext.getSystemService(Context.POWER_SERVICE);
// 獲取螢幕預設，最大，最小亮度
mScreenBrightnessSettingMinimum = pm.getMinimumScreenBrightnessSetting();
mScreenBrightnessSettingMaximum = pm.getMaximumScreenBrightnessSetting();
mScreenBrightnessSettingDefault = pm.getDefaultScreenBrightnessSetting();
// 獲取SensorManager
SensorManager sensorManager = new SystemSensorManager(mContext, mHandler.getLooper());

mBatteryStats = BatteryStatsService.getService();
// 建立Notifier物件，用於廣播power state的變化
mNotifier = new Notifier(Looper.getMainLooper(), mContext, mBatteryStats,
mAppOps, createSuspendBlockerLocked("PowerManagerService.Broadcasts"),
mPolicy);
// 無線充電檢測
mWirelessChargerDetector = new WirelessChargerDetector(sensorManager,
createSuspendBlockerLocked("PowerManagerService.WirelessChargerDetector"),
mHandler);
// 監聽設定的變化
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);
}
// 讀取配置
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是定義在PowerManager中的SystemApi，使用者向PowerManagerService報告使用者活動，以更新PowerManagerService內部時間/狀態值，推遲系統休眠的時間。下面首先來看userActivity的定義。

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;

@SystemApi
public 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請求呼叫服務端PowerManagerService BinderService的userActivity，即呼叫內部方法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中首先呼叫userActivityNoUpdateLocked更新相關資料及狀態(***NoUpdateLocked僅僅更新內部狀態並不採取任何操作)，然後呼叫updatePowerStateLocked更新所有PowerState，下面分析userActivityNoUpdateLocked的實現，updatePowerStateLocked是PowerManagerService的核心方法，在最後進行分析。

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

private boolean userActivityNoUpdateLocked(long eventTime, int event, int flags, int uid) {
// 如果發生時間是上一次休眠或喚醒前，或當前沒有開機完成到systemReady，不採取操作直接返回
if (eventTime < mLastSleepTime || eventTime < mLastWakeTime
|| !mBootCompleted || !mSystemReady) {
return false;
}

try {
// 更新mLastInteractivePowerHintTime時間
if (eventTime > mLastInteractivePowerHintTime) {
powerHintInternal(POWER_HINT_INTERACTION, 0);
mLastInteractivePowerHintTime = eventTime;
}

// 通過mNotifier通知BatteryStats UserActivity事件
mNotifier.onUserActivity(event, uid);

if (mUserInactiveOverrideFromWindowManager) {
mUserInactiveOverrideFromWindowManager = false;
mOverriddenTimeout = -1;
}

// 如果系統處於休眠狀態，不進行處理
if (mWakefulness == WAKEFULNESS_ASLEEP
|| mWakefulness == WAKEFULNESS_DOZING
|| (flags & PowerManager.USER_ACTIVITY_FLAG_INDIRECT) != 0) {
return false;
}

// 根據flag是否在已變暗的情況下是否重啟活動超時更新mLastUserActivityTimeNoChangeLights或mLastUserActivityTime
// 並且設定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中的定義如下：

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();
}
}

與userActivity一樣，gotoSleep最終將呼叫到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中將執行goToSleepNoUpdateLocked更新內部狀態，同樣在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) {
// 當不處於awake狀態或未開機systemReady，不處理
if (eventTime < mLastWakeTime
|| mWakefulness == WAKEFULNESS_ASLEEP
|| mWakefulness == WAKEFULNESS_DOZING
|| !mBootCompleted || !mSystemReady) {
return false;
}

try {
......
// 更新mLastSleepTime時間，設定DIRTY_WAKEFULNESS標誌位
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狀態。

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