PowerManagerService之亮屏流程示例分析

// PowerManagerService.java
@Override // Binder call
public void wakeUp(long eventTime, @WakeReason int reason, String details,
        String opPackageName) {
    // ...
    try {
        // 只能唤醒 default display group 下的显示屏
        wakeDisplayGroup(Display.DEFAULT_DISPLAY_GROUP, eventTime, reason, details, uid,
                opPackageName, uid);
    } finally {
        Binder.restoreCallingIdentity(ident);
    }
}  
private void wakeDisplayGroup(int groupId, long eventTime, @WakeReason int reason,
        String details, int uid, String opPackageName, int opUid) {
    synchronized (mLock) {
        // 1. 更新 wakefulness 为 WAKEFULNESS_AWAKE
        // 包括更新 PowerManagerService 和 DisplayGroupPowerStateMapper 的 wakefulness
        if (wakeDisplayGroupNoUpdateLocked(groupId, eventTime, reason, details, uid,
                opPackageName, opUid)) {
            // 2. 更新电源状态
            updatePowerStateLocked();
        }
    }
} 

private boolean wakeDisplayGroupNoUpdateLocked(int groupId, long eventTime,
        @WakeReason int reason, String details, int uid, String opPackageName, int opUid) {
    // ...
    try {
        // ...
        // 设置 wakefulness 为 WAKEFULNESS_AWAKE
        setWakefulnessLocked(groupId, WAKEFULNESS_AWAKE, eventTime, uid, reason, opUid,
                opPackageName, details);
        // 更新分组显示屏的信息
        mDisplayGroupPowerStateMapper.setLastPowerOnTimeLocked(groupId, eventTime);
        mDisplayGroupPowerStateMapper.setPoweringOnLocked(groupId, true);
    } 
    return true;
}
void setWakefulnessLocked(int groupId, int wakefulness, long eventTime, int uid, int reason,
        int opUid, String opPackageName, String details) {
    // 1. 更新 DisplayGroupPowerStateMapper 的 wakefulness
    if (mDisplayGroupPowerStateMapper.setWakefulnessLocked(groupId, wakefulness)) {
        // display group wakefulness 改变了
        mDirty |= DIRTY_DISPLAY_GROUP_WAKEFULNESS;
        // 2. 更新 PMS 的 wakefulness
        // 注意第一个参数取所有 display group 的最大的 wakefulness，优先级如下
        //  PowerManagerInternal#WAKEFULNESS_AWAKE
        //  PowerManagerInternal#WAKEFULNESS_DREAMING
        //  PowerManagerInternal#WAKEFULNESS_DOZING
        //  PowerManagerInternal#WAKEFULNESS_ASLEEP
        // TODO: 为何 PMS 的 wakefulness 要设置为所有 display group 的最大的 wakefulness ?
        setGlobalWakefulnessLocked(mDisplayGroupPowerStateMapper.getGlobalWakefulnessLocked(),
                eventTime, reason, uid, opUid, opPackageName, details);
        if (wakefulness == WAKEFULNESS_AWAKE) {
            // Kick user activity to prevent newly awake group from timing out instantly.
            // 3. 保存用户行为的时间
            userActivityNoUpdateLocked(
                    groupId, eventTime, PowerManager.USER_ACTIVITY_EVENT_OTHER, 0, uid);
        }
    }
}    

// PowerManagerService.java
private void setGlobalWakefulnessLocked(int wakefulness, long eventTime, int reason, int uid,
        int opUid, String opPackageName, String details) {
    if (getWakefulnessLocked() == wakefulness) {
        return;
    }
    // Phase 1: Handle pre-wakefulness change bookkeeping.
    final String traceMethodName;
    switch (wakefulness) {
        // ...
        case WAKEFULNESS_AWAKE:
            // 保存唤醒设备的时间
            // 这个时间，后面在更新用户行为的时候会用到
            mLastWakeTime = eventTime;
            mLastWakeReason = reason;
            break;
        // ...
    }
    try {
        // Phase 2: Handle wakefulness change and bookkeeping.
        // Under lock, invalidate before set ensures caches won't return stale values.
        mInjector.invalidateIsInteractiveCaches();
        // 更新 PMS 的 wakefulness 相关变量
        mWakefulnessRaw = wakefulness;
        mWakefulnessChanging = true;
        // mDirty 设置 DIRTY_WAKEFULNESS，表示 PMS 的 wakefulness 改变了
        mDirty |= DIRTY_WAKEFULNESS;
        mDozeStartInProgress &= (getWakefulnessLocked() == WAKEFULNESS_DOZING);
        // 通知其它组件，wakefulness改变 或者 交互状态改变
        if (mNotifier != null) {
            mNotifier.onWakefulnessChangeStarted(wakefulness, reason, eventTime);
        }
        mAttentionDetector.onWakefulnessChangeStarted(wakefulness);
        // Phase 3: Handle post-wakefulness change bookkeeping.
        switch (wakefulness) {
            case WAKEFULNESS_AWAKE:
                // 记录并检测是否有权限
                mNotifier.onWakeUp(reason, details, uid, opPackageName, opUid);
                if (sQuiescent) {
                    mDirty |= DIRTY_QUIESCENT;
                }
                break;
            // ...
        }
    } finally {
        Trace.traceEnd(Trace.TRACE_TAG_POWER);
    }
}

// Notifier.java
public void onWakefulnessChangeStarted(final int wakefulness, int reason, long eventTime) {
    // 判断新的 wakefulness 是否是交互状态
    // WAKEFULNESS_AWAKE 是可交互状态
    final boolean interactive = PowerManagerInternal.isInteractive(wakefulness);
    // 1. 通知 AMS wakefulness 改变了
    mHandler.post(new Runnable() {
        @Override
        public void run() {
            mActivityManagerInternal.onWakefulnessChanged(wakefulness);
        }
    });
    // 2. 处理交互状态改变
    // Handle any early interactive state changes.
    // Finish pending incomplete ones from a previous cycle.
    // 处理早期交互状态改变
    if (mInteractive != interactive) {
        // Finish up late behaviors if needed.
        // mInteractiveChanging 为 true，表示上一次的处理流程还没有执行完
        // 这里会先执行上一次的流程
        if (mInteractiveChanging) {
            handleLateInteractiveChange();
        }
        // 2.1 更新系统组件的交互状态
        // Start input as soon as we start waking up or going to sleep.
        mInputManagerInternal.setInteractive(interactive);
        mInputMethodManagerInternal.setInteractive(interactive);
        // ...
        // Handle early behaviors.
        // 2.2 更新关于交互状态的变量
        mInteractive = interactive;
        mInteractiveChangeReason = reason;
        mInteractiveChangeStartTime = eventTime;
        // 交互状态正在改变
        mInteractiveChanging = true;
        // 2.3 处理早期的交互状态改变任务
        handleEarlyInteractiveChange();
    }
}
private void handleEarlyInteractiveChange() {
    synchronized (mLock) {
        if (mInteractive) {
            // 通知 PhoneWindowManager，PhoneWindowManager再通知 SystemUI keyguard
            mHandler.post(() -> mPolicy.startedWakingUp(mInteractiveChangeReason));
            // 发送亮屏广播
            mPendingInteractiveState = INTERACTIVE_STATE_AWAKE;
            mPendingWakeUpBroadcast = true;
            updatePendingBroadcastLocked();
        } else {
            // ...
        }
    }
}    

// PowerManagerService.java
private boolean userActivityNoUpdateLocked(int groupId, long eventTime, int event, int flags,
        int uid) {
    if (eventTime < mLastSleepTime || eventTime < mLastWakeTime || !mSystemReady) {
        return false;
    }
    Trace.traceBegin(Trace.TRACE_TAG_POWER, "userActivity");
    try {
        if (eventTime > mLastInteractivePowerHintTime) {
            setPowerBoostInternal(Boost.INTERACTION, 0);
            mLastInteractivePowerHintTime = eventTime;
        }
        // 1. 通知系统组件，有用户行为发生
        mNotifier.onUserActivity(event, uid);
        mAttentionDetector.onUserActivity(eventTime, event);
        if (mUserInactiveOverrideFromWindowManager) {
            mUserInactiveOverrideFromWindowManager = false;
            mOverriddenTimeout = -1;
        }
        final int wakefulness = mDisplayGroupPowerStateMapper.getWakefulnessLocked(groupId);
        if (wakefulness == WAKEFULNESS_ASLEEP
                || wakefulness == WAKEFULNESS_DOZING
                || (flags & PowerManager.USER_ACTIVITY_FLAG_INDIRECT) != 0) {
            return false;
        }
        maybeUpdateForegroundProfileLastActivityLocked(eventTime);
        if ((flags & PowerManager.USER_ACTIVITY_FLAG_NO_CHANGE_LIGHTS) != 0) {
            // 这里处理延长亮屏的时间的逻辑 ...
        } else {
            if (eventTime > mDisplayGroupPowerStateMapper.getLastUserActivityTimeLocked(
                    groupId)) {
                // 2. 保存用户活动时间
                mDisplayGroupPowerStateMapper.setLastUserActivityTimeLocked(groupId, eventTime);
                // 3. mDirty 设置 DIRTY_USER_ACTIVITY 标志位，
                // 表示用户活动有更新
                mDirty |= DIRTY_USER_ACTIVITY;
                if (event == PowerManager.USER_ACTIVITY_EVENT_BUTTON) {
                    mDirty |= DIRTY_QUIESCENT;
                }
                return true;
            }
        }
    } finally {
        Trace.traceEnd(Trace.TRACE_TAG_POWER);
    }
    return false;
}

    private void sendUserActivity(int event) {
        synchronized (mLock) {
            if (!mUserActivityPending) {
                return;
            }
            mUserActivityPending = false;
        }
        // 这里暂时不知道做了什么
        TelephonyManager tm = mContext.getSystemService(TelephonyManager.class);
        tm.notifyUserActivity();
        // PhoneWindowManger 会通知 SystemUI
        mPolicy.userActivity();
        // 如果 FaceDownDetector 正在执行翻转灭屏任务，此时有用户行为，取消这个任务
        mFaceDownDetector.userActivity(event);
    }

// PowerManagerService.java
private void updatePowerStateLocked() {
    if (!mSystemReady || mDirty == 0) {
        return;
    }
    // 注意这里的技术，线程可以判断是否获取了某个锁
    if (!Thread.holdsLock(mLock)) {
        Slog.wtf(TAG, "Power manager lock was not held when calling updatePowerStateLocked");
    }
    Trace.traceBegin(Trace.TRACE_TAG_POWER, "updatePowerState");
    try {
        // Phase 0: Basic state updates.
        // 省电模式功能
        updateIsPoweredLocked(mDirty);
        // 设置中"充电常亮功能"
        updateStayOnLocked(mDirty);
        // 亮度增加功能
        updateScreenBrightnessBoostLocked(mDirty);
        // Phase 1: Update wakefulness.
        // Loop because the wake lock and user activity computations are influenced
        // by changes in wakefulness.
        final long now = mClock.uptimeMillis();
        int dirtyPhase2 = 0;
        for (;;) {
            int dirtyPhase1 = mDirty;
            dirtyPhase2 |= dirtyPhase1;
            mDirty = 0;
            // 把所有的唤醒锁归纳到 mWakeLockSummary
            updateWakeLockSummaryLocked(dirtyPhase1);
            // 1. 更新用户行为
            updateUserActivitySummaryLocked(now, dirtyPhase1);
            updateAttentiveStateLocked(now, dirtyPhase1);
            // 决定是否进入休眠/dream/doze状态
            // 如果进入某一种状态，会更新 wakefulness，因此这里要通过循环再来更新上面的东西
            if (!updateWakefulnessLocked(dirtyPhase1)) {
                break;
            }
        }
        // Phase 2: Lock profiles that became inactive/not kept awake.
        updateProfilesLocked(now);
        // Phase 3: Update display power state.
        // 2. 更新显示屏的电源状态
        final boolean displayBecameReady = updateDisplayPowerStateLocked(dirtyPhase2);
        // Phase 4: Update dream state (depends on display ready signal).
        updateDreamLocked(dirtyPhase2, displayBecameReady);
        // Phase 5: Send notifications, if needed.
        finishWakefulnessChangeIfNeededLocked();
        // Phase 6: Update suspend blocker.
        // Because we might release the last suspend blocker here, we need to make sure
        // we finished everything else first!
        updateSuspendBlockerLocked();
    } finally {
        Trace.traceEnd(Trace.TRACE_TAG_POWER);
    }
}

// PowerManagerService.java
private void updateUserActivitySummaryLocked(long now, int dirty) {
    // Update the status of the user activity timeout timer.
    if ((dirty & (DIRTY_DISPLAY_GROUP_WAKEFULNESS | DIRTY_WAKE_LOCKS
            | DIRTY_USER_ACTIVITY | DIRTY_WAKEFULNESS | DIRTY_SETTINGS)) == 0) {
        return;
    }
    mHandler.removeMessages(MSG_USER_ACTIVITY_TIMEOUT);
    // 默认为 -1
    final long attentiveTimeout = getAttentiveTimeoutLocked();
    // 休眠超时时间，默认为 -1
    final long sleepTimeout = getSleepTimeoutLocked(attentiveTimeout);
    // 屏幕超时时间
    long screenOffTimeout = getScreenOffTimeoutLocked(sleepTimeout,
            attentiveTimeout);
    // dim duration = 20 % screen off timeout
    final long screenDimDuration = getScreenDimDurationLocked(screenOffTimeout);
    screenOffTimeout =
            getScreenOffTimeoutWithFaceDownLocked(screenOffTimeout, screenDimDuration);
    final boolean userInactiveOverride = mUserInactiveOverrideFromWindowManager;
    long nextTimeout = -1;
    boolean hasUserActivitySummary = false;
    // 遍历 display group id
    for (int groupId : mDisplayGroupPowerStateMapper.getDisplayGroupIdsLocked()) {
        int groupUserActivitySummary = 0;
        long groupNextTimeout = 0;
        // 注意，休眠状态是无法决定用户行为的
        if (mDisplayGroupPowerStateMapper.getWakefulnessLocked(groupId) != WAKEFULNESS_ASLEEP) {
            final long lastUserActivityTime =
                    mDisplayGroupPowerStateMapper.getLastUserActivityTimeLocked(groupId);
            final long lastUserActivityTimeNoChangeLights =
                    mDisplayGroupPowerStateMapper.getLastUserActivityTimeNoChangeLightsLocked(
                            groupId);
            // 1. 获取用户行为与超时时间
            // 上一次用户行为的时间 >= 上一次唤醒屏幕的时间
            if (lastUserActivityTime >= mLastWakeTime) {
                groupNextTimeout = lastUserActivityTime + screenOffTimeout - screenDimDuration;
                if (now < groupNextTimeout) { // 没有到 dim 时间
                    groupUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT;
                } else {
                    groupNextTimeout = lastUserActivityTime + screenOffTimeout;
                    if (now < groupNextTimeout) { // 处于 dim 时间段
                        groupUserActivitySummary = USER_ACTIVITY_SCREEN_DIM;
                    }
                }
            }
            // 超时了，但是由于释放了某一个锁，需要延长亮屏时间
            if (groupUserActivitySummary == 0
                    && lastUserActivityTimeNoChangeLights >= mLastWakeTime) {
                // ...
            }
            // 一般的超时情况，
            if (groupUserActivitySummary == 0) {
                // ...
            }
            // PhoneWindowManager 处理 KeyEvent.KEYCODE_SOFT_SLEEP 时，userInactiveOverride 为 true
            // KeyEvent.KEYCODE_SOFT_SLEEP 这个软件的休眠按键 ？
            if (groupUserActivitySummary != USER_ACTIVITY_SCREEN_DREAM
                    && userInactiveOverride) {
                // ...
            }
            // 用户行为是点亮屏幕，并且WakeLock没有保持屏幕常亮，用AttentionDetector再次计算屏幕超时时间
            if ((groupUserActivitySummary & USER_ACTIVITY_SCREEN_BRIGHT) != 0
                    && (mDisplayGroupPowerStateMapper.getWakeLockSummaryLocked(groupId)
                    & WAKE_LOCK_STAY_AWAKE) == 0) {
                // ...
            }
            hasUserActivitySummary |= groupUserActivitySummary != 0;
            if (nextTimeout == -1) {
                nextTimeout = groupNextTimeout;
            } else if (groupNextTimeout != -1) {
                // 这里表示 nextTimeout != -1 的情况，也说明有多个 display group 的情况
                // 从这里可以看出，多个 display group 的超时时间是相同的
                nextTimeout = Math.min(nextTimeout, groupNextTimeout);
            }
        }
        // 2. DisplayGroupPowerStateMapper 保存用户行为
        mDisplayGroupPowerStateMapper.setUserActivitySummaryLocked(groupId,
                groupUserActivitySummary);
        }
    } // 遍历 display group id 结束
    final long nextProfileTimeout = getNextProfileTimeoutLocked(now);
    if (nextProfileTimeout > 0) {
        nextTimeout = Math.min(nextTimeout, nextProfileTimeout);
    }
    // 3. 定时更新电源状态
    // 这一步决定自动灭屏
    if (hasUserActivitySummary && nextTimeout >= 0) {
        scheduleUserInactivityTimeout(nextTimeout);
    }
}

// PowerManagerService.java
private boolean updateDisplayPowerStateLocked(int dirty) {
    final boolean oldDisplayReady = mDisplayGroupPowerStateMapper.areAllDisplaysReadyLocked();
    if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_USER_ACTIVITY | DIRTY_WAKEFULNESS
            | DIRTY_ACTUAL_DISPLAY_POWER_STATE_UPDATED | DIRTY_BOOT_COMPLETED
            | DIRTY_SETTINGS | DIRTY_SCREEN_BRIGHTNESS_BOOST | DIRTY_VR_MODE_CHANGED |
            DIRTY_QUIESCENT | DIRTY_DISPLAY_GROUP_WAKEFULNESS)) != 0) {
        if ((dirty & DIRTY_QUIESCENT) != 0) {
            // ...
        }
        // 遍历 display group
        for (final int groupId : mDisplayGroupPowerStateMapper.getDisplayGroupIdsLocked()) {
            // 1. 获取 display group 的请求
            final DisplayPowerRequest displayPowerRequest =
                    mDisplayGroupPowerStateMapper.getPowerRequestLocked(groupId);
            // 2. 更新请求的各种参数
            // 更新请求的策略参数，所谓的策略，就是亮屏，还是灭屏，或者使屏幕变暗，等等
            displayPowerRequest.policy = getDesiredScreenPolicyLocked(groupId);
            // ...省略更新其它请求参数的过程...
            // 3. 向 DisplayManagerService 发起请求
            // 如果此次请求与上一次的请求不同，那么这个请求的处理是一个异步处理过程，此时返回 false。
            // 否则，不用处理，直接返回 true。
            final boolean ready = mDisplayManagerInternal.requestPowerState(groupId,
                    displayPowerRequest, mRequestWaitForNegativeProximity);
            // 更新 DisplayGroupPowerStateMapper 的 ready 状态
            final boolean displayReadyStateChanged =
                    mDisplayGroupPowerStateMapper.setDisplayGroupReadyLocked(groupId, ready);
            // 如果异步请求处理完毕，DMS 会回调通知 PMS，PMS 再更新状态走到这里
            // 如果点亮屏幕时间过长，那么用log记录下来
            final boolean poweringOn =
                    mDisplayGroupPowerStateMapper.isPoweringOnLocked(groupId);
            if (ready && displayReadyStateChanged && poweringOn
                    && mDisplayGroupPowerStateMapper.getWakefulnessLocked(
                    groupId) == WAKEFULNESS_AWAKE) {
                mDisplayGroupPowerStateMapper.setPoweringOnLocked(groupId, false);
                Trace.asyncTraceEnd(Trace.TRACE_TAG_POWER, TRACE_SCREEN_ON, groupId);
                final int latencyMs = (int) (mClock.uptimeMillis()
                        - mDisplayGroupPowerStateMapper.getLastPowerOnTimeLocked(groupId));
                if (latencyMs >= SCREEN_ON_LATENCY_WARNING_MS) {
                    Slog.w(TAG, "Screen on took " + latencyMs + " ms");
                }
            }
        }
        mRequestWaitForNegativeProximity = false;
    }
    // 返回值表示是否从非ready状态变为ready状态
    return mDisplayGroupPowerStateMapper.areAllDisplaysReadyLocked() && !oldDisplayReady;
}

// PowerManagerService.java
 int getDesiredScreenPolicyLocked(int groupId) {
    final int wakefulness = mDisplayGroupPowerStateMapper.getWakefulnessLocked(groupId);
    final int wakeLockSummary = mDisplayGroupPowerStateMapper.getWakeLockSummaryLocked(groupId);
    if (wakefulness == WAKEFULNESS_ASLEEP || sQuiescent) {
        return DisplayPowerRequest.POLICY_OFF;
    } else if (wakefulness == WAKEFULNESS_DOZING) {
        // ...
    }
    if (mIsVrModeEnabled) {
        return DisplayPowerRequest.POLICY_VR;
    }
    // 由于此时的 UserActivity 为 USER_ACTIVITY_SCREEN_BRIGHT，因此策略为 DisplayPowerRequest.POLICY_BRIGHT
    if ((wakeLockSummary & WAKE_LOCK_SCREEN_BRIGHT) != 0
            || !mBootCompleted
            || (mDisplayGroupPowerStateMapper.getUserActivitySummaryLocked(groupId)
            & USER_ACTIVITY_SCREEN_BRIGHT) != 0
            || mScreenBrightnessBoostInProgress) {
        return DisplayPowerRequest.POLICY_BRIGHT;
    }
    return DisplayPowerRequest.POLICY_DIM;
}

// PowerManagerService.java
public void systemReady(IAppOpsService appOps) {
    synchronized (mLock) {
        mDisplayManagerInternal.initPowerManagement(
                mDisplayPowerCallbacks, mHandler, sensorManager);                 
    }
}
private final DisplayManagerInternal.DisplayPowerCallbacks mDisplayPowerCallbacks =
        new DisplayManagerInternal.DisplayPowerCallbacks() {
    @Override
    public void onStateChanged() {
        synchronized (mLock) {
            // 表示屏幕状态更新了
            mDirty |= DIRTY_ACTUAL_DISPLAY_POWER_STATE_UPDATED;
            updatePowerStateLocked();
        }
    }
}    

// PowerManagerService.java
private void finishWakefulnessChangeIfNeededLocked() {
    // 注意，其中一个条件就是所有 display group 要 ready
    if (mWakefulnessChanging && mDisplayGroupPowerStateMapper.areAllDisplaysReadyLocked()) {
        // ...
        // 显示屏 ready 了， PMS 的 wakefulness 改变的工作才算处理完
        mWakefulnessChanging = false;
        // Notier 通知 wakefulness 的改变已经完成
        mNotifier.onWakefulnessChangeFinished();
    }
}

// Notifier.java
public void onWakefulnessChangeFinished() {
    if (mInteractiveChanging) {
        mInteractiveChanging = false;
        // 处理交互状态的后期任务
        handleLateInteractiveChange();
    }
}
private void handleLateInteractiveChange() {
    synchronized (mLock) {
        final int interactiveChangeLatency =
                (int) (SystemClock.uptimeMillis() - mInteractiveChangeStartTime);
        if (mInteractive) {
            // Finished waking up...
            mHandler.post(() -> {
                // 通知 PhoneWindowManager 完成设备唤醒工作
                mPolicy.finishedWakingUp(mInteractiveChangeReason);
            });
        } else {
            // ...
        }
    }
}