Improve heuristics for detecting wireless chargers.
On some devices, we need to apply heuristics to determine whether
the device is docked on a wireless charger because the charging
circuits do not provide sufficient information to know whether
the device is on the charger unless it is actually receiving
power.
The previous heuristics only considered the battery level to
suppress spurious dock signals.
The new heuristics also take into account whether the device
appears to have moved from its previous position on the dock.
Bug: 7744185
Change-Id: I5ba885dac25b37840b6db46b8a0f30968a06776c
diff --git a/services/java/com/android/server/power/DisplayPowerController.java b/services/java/com/android/server/power/DisplayPowerController.java
index 724e126..b5010f2 100644
--- a/services/java/com/android/server/power/DisplayPowerController.java
+++ b/services/java/com/android/server/power/DisplayPowerController.java
@@ -344,7 +344,7 @@
* Creates the display power controller.
*/
public DisplayPowerController(Looper looper, Context context, Notifier notifier,
- LightsService lights, TwilightService twilight,
+ LightsService lights, TwilightService twilight, SensorManager sensorManager,
DisplayManagerService displayManager,
DisplayBlanker displayBlanker,
Callbacks callbacks, Handler callbackHandler) {
@@ -356,7 +356,7 @@
mLights = lights;
mTwilight = twilight;
- mSensorManager = new SystemSensorManager(mHandler.getLooper());
+ mSensorManager = sensorManager;
mDisplayManager = displayManager;
final Resources resources = context.getResources();
diff --git a/services/java/com/android/server/power/PowerManagerService.java b/services/java/com/android/server/power/PowerManagerService.java
index 5a5d910..546f22e 100644
--- a/services/java/com/android/server/power/PowerManagerService.java
+++ b/services/java/com/android/server/power/PowerManagerService.java
@@ -35,6 +35,8 @@
import android.content.pm.PackageManager;
import android.content.res.Resources;
import android.database.ContentObserver;
+import android.hardware.SensorManager;
+import android.hardware.SystemSensorManager;
import android.net.Uri;
import android.os.BatteryManager;
import android.os.Binder;
@@ -153,11 +155,6 @@
// Otherwise the user won't get much screen on time before dimming occurs.
private static final float MAXIMUM_SCREEN_DIM_RATIO = 0.2f;
- // Upper bound on the battery charge percentage in order to consider turning
- // the screen on when the device starts charging wirelessly.
- // See point of use for more details.
- private static final int WIRELESS_CHARGER_TURN_ON_BATTERY_LEVEL_LIMIT = 95;
-
// The name of the boot animation service in init.rc.
private static final String BOOT_ANIMATION_SERVICE = "bootanim";
@@ -179,6 +176,7 @@
private WindowManagerPolicy mPolicy;
private Notifier mNotifier;
private DisplayPowerController mDisplayPowerController;
+ private WirelessChargerDetector mWirelessChargerDetector;
private SettingsObserver mSettingsObserver;
private DreamManagerService mDreamManager;
private LightsService.Light mAttentionLight;
@@ -423,6 +421,8 @@
mScreenBrightnessSettingMaximum = pm.getMaximumScreenBrightnessSetting();
mScreenBrightnessSettingDefault = pm.getDefaultScreenBrightnessSetting();
+ SensorManager sensorManager = new SystemSensorManager(mHandler.getLooper());
+
// The notifier runs on the system server's main looper so as not to interfere
// with the animations and other critical functions of the power manager.
mNotifier = new Notifier(Looper.getMainLooper(), mContext, mBatteryStats,
@@ -430,11 +430,14 @@
mScreenOnBlocker, mPolicy);
// The display power controller runs on the power manager service's
- // own handler thread.
+ // own handler thread to ensure timely operation.
mDisplayPowerController = new DisplayPowerController(mHandler.getLooper(),
- mContext, mNotifier, mLightsService, twilight, mDisplayManagerService,
- mDisplayBlanker, mDisplayPowerControllerCallbacks, mHandler);
+ mContext, mNotifier, mLightsService, twilight, sensorManager,
+ mDisplayManagerService, mDisplayBlanker,
+ mDisplayPowerControllerCallbacks, mHandler);
+ mWirelessChargerDetector = new WirelessChargerDetector(sensorManager,
+ createSuspendBlockerLocked("PowerManagerService.WirelessChargerDetector"));
mSettingsObserver = new SettingsObserver(mHandler);
mAttentionLight = mLightsService.getLight(LightsService.LIGHT_ID_ATTENTION);
@@ -1139,65 +1142,51 @@
if (wasPowered != mIsPowered || oldPlugType != mPlugType) {
mDirty |= DIRTY_IS_POWERED;
+ // Update wireless dock detection state.
+ final boolean dockedOnWirelessCharger = mWirelessChargerDetector.update(
+ mIsPowered, mPlugType, mBatteryLevel);
+
// Treat plugging and unplugging the devices as a user activity.
// Users find it disconcerting when they plug or unplug the device
// and it shuts off right away.
// Some devices also wake the device when plugged or unplugged because
// they don't have a charging LED.
final long now = SystemClock.uptimeMillis();
- if (shouldWakeUpWhenPluggedOrUnpluggedLocked(wasPowered, oldPlugType)) {
+ if (shouldWakeUpWhenPluggedOrUnpluggedLocked(wasPowered, oldPlugType,
+ dockedOnWirelessCharger)) {
wakeUpNoUpdateLocked(now);
}
userActivityNoUpdateLocked(
now, PowerManager.USER_ACTIVITY_EVENT_OTHER, 0, Process.SYSTEM_UID);
// Tell the notifier whether wireless charging has started so that
- // it can provide feedback to the user. Refer to
- // shouldWakeUpWhenPluggedOrUnpluggedLocked for justification of the
- // heuristics used here.
- if (!wasPowered && mIsPowered
- && mPlugType == BatteryManager.BATTERY_PLUGGED_WIRELESS
- && mBatteryLevel < WIRELESS_CHARGER_TURN_ON_BATTERY_LEVEL_LIMIT) {
+ // it can provide feedback to the user.
+ if (dockedOnWirelessCharger) {
mNotifier.onWirelessChargingStarted();
}
}
}
}
- private boolean shouldWakeUpWhenPluggedOrUnpluggedLocked(boolean wasPowered, int oldPlugType) {
+ private boolean shouldWakeUpWhenPluggedOrUnpluggedLocked(
+ boolean wasPowered, int oldPlugType, boolean dockedOnWirelessCharger) {
// Don't wake when powered unless configured to do so.
if (!mWakeUpWhenPluggedOrUnpluggedConfig) {
return false;
}
- // FIXME: Need more accurate detection of wireless chargers.
- //
- // We are unable to accurately detect whether the device is resting on the
- // charger unless it is actually receiving power. This causes us some grief
- // because the device might not appear to be plugged into the wireless charger
- // unless it actually charging.
- //
- // To avoid spuriously waking the screen, we apply a special policy to
- // wireless chargers.
- //
- // 1. Don't wake the device when unplugged from wireless charger because
- // it might be that the device is still resting on the wireless charger
- // but is not receiving power anymore because the battery is full.
- //
- // 2. Don't wake the device when plugged into a wireless charger if the
- // battery already appears to be mostly full. This situation may indicate
- // that the device was resting on the charger the whole time and simply
- // wasn't receiving power because the battery was full. We can't tell
- // whether the device was just placed on the charger or whether it has
- // been there for half of the night slowly discharging until it hit
- // the point where it needed to start charging again.
+ // Don't wake when undocked from wireless charger.
+ // See WirelessChargerDetector for justification.
if (wasPowered && !mIsPowered
&& oldPlugType == BatteryManager.BATTERY_PLUGGED_WIRELESS) {
return false;
}
+
+ // Don't wake when docked on wireless charger unless we are certain of it.
+ // See WirelessChargerDetector for justification.
if (!wasPowered && mIsPowered
&& mPlugType == BatteryManager.BATTERY_PLUGGED_WIRELESS
- && mBatteryLevel >= WIRELESS_CHARGER_TURN_ON_BATTERY_LEVEL_LIMIT) {
+ && !dockedOnWirelessCharger) {
return false;
}
@@ -2183,6 +2172,7 @@
pw.println("POWER MANAGER (dumpsys power)\n");
final DisplayPowerController dpc;
+ final WirelessChargerDetector wcd;
synchronized (mLock) {
pw.println("Power Manager State:");
pw.println(" mDirty=0x" + Integer.toHexString(mDirty));
@@ -2264,11 +2254,16 @@
pw.println("Display Blanker: " + mDisplayBlanker);
dpc = mDisplayPowerController;
+ wcd = mWirelessChargerDetector;
}
if (dpc != null) {
dpc.dump(pw);
}
+
+ if (wcd != null) {
+ wcd.dump(pw);
+ }
}
private SuspendBlocker createSuspendBlockerLocked(String name) {
diff --git a/services/java/com/android/server/power/WirelessChargerDetector.java b/services/java/com/android/server/power/WirelessChargerDetector.java
new file mode 100644
index 0000000..ac6dc3e
--- /dev/null
+++ b/services/java/com/android/server/power/WirelessChargerDetector.java
@@ -0,0 +1,320 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.power;
+
+import android.hardware.Sensor;
+import android.hardware.SensorEvent;
+import android.hardware.SensorEventListener;
+import android.hardware.SensorManager;
+import android.os.BatteryManager;
+import android.util.Slog;
+
+import java.io.PrintWriter;
+
+/**
+ * Implements heuristics to detect docking or undocking from a wireless charger.
+ * <p>
+ * Some devices have wireless charging circuits that are unable to detect when the
+ * device is resting on a wireless charger except when the device is actually
+ * receiving power from the charger. The device may stop receiving power
+ * if the battery is already nearly full or if it is too hot. As a result, we cannot
+ * always rely on the battery service wireless plug signal to accurately indicate
+ * whether the device has been docked or undocked from a wireless charger.
+ * </p><p>
+ * This is a problem because the power manager typically wakes up the screen and
+ * plays a tone when the device is docked in a wireless charger. It is important
+ * for the system to suppress spurious docking and undocking signals because they
+ * can be intrusive for the user (especially if they cause a tone to be played
+ * late at night for no apparent reason).
+ * </p><p>
+ * To avoid spurious signals, we apply some special policies to wireless chargers.
+ * </p><p>
+ * 1. Don't wake the device when undocked from the wireless charger because
+ * it might be that the device is still resting on the wireless charger
+ * but is not receiving power anymore because the battery is full.
+ * Ideally we would wake the device if we could be certain that the user had
+ * picked it up from the wireless charger but due to hardware limitations we
+ * must be more conservative.
+ * </p><p>
+ * 2. Don't wake the device when docked on a wireless charger if the
+ * battery already appears to be mostly full. This situation may indicate
+ * that the device was resting on the charger the whole time and simply
+ * wasn't receiving power because the battery was already full. We can't tell
+ * whether the device was just placed on the charger or whether it has
+ * been there for half of the night slowly discharging until it reached
+ * the point where it needed to start charging again. So we suppress docking
+ * signals that occur when the battery level is above a given threshold.
+ * </p><p>
+ * 3. Don't wake the device when docked on a wireless charger if it does
+ * not appear to have moved since it was last undocked because it may
+ * be that the prior undocking signal was spurious. We use the gravity
+ * sensor to detect this case.
+ * </p>
+ */
+final class WirelessChargerDetector {
+ private static final String TAG = "WirelessChargerDetector";
+ private static final boolean DEBUG = false;
+
+ // Number of nanoseconds per millisecond.
+ private static final long NANOS_PER_MS = 1000000;
+
+ // The minimum amount of time to spend watching the sensor before making
+ // a determination of whether movement occurred.
+ private static final long SETTLE_TIME_NANOS = 500 * NANOS_PER_MS;
+
+ // The minimum number of samples that must be collected.
+ private static final int MIN_SAMPLES = 3;
+
+ // Upper bound on the battery charge percentage in order to consider turning
+ // the screen on when the device starts charging wirelessly.
+ private static final int WIRELESS_CHARGER_TURN_ON_BATTERY_LEVEL_LIMIT = 95;
+
+ // To detect movement, we compute the angle between the gravity vector
+ // at rest and the current gravity vector. This field specifies the
+ // cosine of the maximum angle variance that we tolerate while at rest.
+ private static final double MOVEMENT_ANGLE_COS_THRESHOLD = Math.cos(5 * Math.PI / 180);
+
+ // Sanity thresholds for the gravity vector.
+ private static final double MIN_GRAVITY = SensorManager.GRAVITY_EARTH - 1.0f;
+ private static final double MAX_GRAVITY = SensorManager.GRAVITY_EARTH + 1.0f;
+
+ private final Object mLock = new Object();
+
+ private final SensorManager mSensorManager;
+ private final SuspendBlocker mSuspendBlocker;
+
+ // The gravity sensor, or null if none.
+ private Sensor mGravitySensor;
+
+ // Previously observed wireless power state.
+ private boolean mPoweredWirelessly;
+
+ // True if the device is thought to be at rest on a wireless charger.
+ private boolean mAtRest;
+
+ // The gravity vector most recently observed while at rest.
+ private float mRestX, mRestY, mRestZ;
+
+ /* These properties are only meaningful while detection is in progress. */
+
+ // True if detection is in progress.
+ // The suspend blocker is held while this is the case.
+ private boolean mDetectionInProgress;
+
+ // True if the rest position should be updated if at rest.
+ // Otherwise, the current rest position is simply checked and cleared if movement
+ // is detected but no new rest position is stored.
+ private boolean mMustUpdateRestPosition;
+
+ // The total number of samples collected.
+ private int mTotalSamples;
+
+ // The number of samples collected that showed evidence of not being at rest.
+ private int mMovingSamples;
+
+ // The time and value of the first sample that was collected.
+ private long mFirstSampleTime;
+ private float mFirstSampleX, mFirstSampleY, mFirstSampleZ;
+
+ public WirelessChargerDetector(SensorManager sensorManager,
+ SuspendBlocker suspendBlocker) {
+ mSensorManager = sensorManager;
+ mSuspendBlocker = suspendBlocker;
+
+ mGravitySensor = sensorManager.getDefaultSensor(Sensor.TYPE_GRAVITY);
+ }
+
+ public void dump(PrintWriter pw) {
+ synchronized (mLock) {
+ pw.println();
+ pw.println("Wireless Charger Detector State:");
+ pw.println(" mGravitySensor=" + mGravitySensor);
+ pw.println(" mPoweredWirelessly=" + mPoweredWirelessly);
+ pw.println(" mAtRest=" + mAtRest);
+ pw.println(" mRestX=" + mRestX + ", mRestY=" + mRestY + ", mRestZ=" + mRestZ);
+ pw.println(" mDetectionInProgress=" + mDetectionInProgress);
+ pw.println(" mMustUpdateRestPosition=" + mMustUpdateRestPosition);
+ pw.println(" mTotalSamples=" + mTotalSamples);
+ pw.println(" mMovingSamples=" + mMovingSamples);
+ pw.println(" mFirstSampleTime=" + mFirstSampleTime);
+ pw.println(" mFirstSampleX=" + mFirstSampleX
+ + ", mFirstSampleY=" + mFirstSampleY + ", mFirstSampleZ=" + mFirstSampleZ);
+ }
+ }
+
+ /**
+ * Updates the charging state and returns true if docking was detected.
+ *
+ * @param isPowered True if the device is powered.
+ * @param plugType The current plug type.
+ * @param batteryLevel The current battery level.
+ * @return True if the device is determined to have just been docked on a wireless
+ * charger, after suppressing spurious docking or undocking signals.
+ */
+ public boolean update(boolean isPowered, int plugType, int batteryLevel) {
+ synchronized (mLock) {
+ final boolean wasPoweredWirelessly = mPoweredWirelessly;
+
+ if (isPowered && plugType == BatteryManager.BATTERY_PLUGGED_WIRELESS) {
+ // The device is receiving power from the wireless charger.
+ // Update the rest position asynchronously.
+ mPoweredWirelessly = true;
+ mMustUpdateRestPosition = true;
+ startDetectionLocked();
+ } else {
+ // The device may or may not be on the wireless charger depending on whether
+ // the unplug signal that we received was spurious.
+ mPoweredWirelessly = false;
+ if (mAtRest) {
+ if (plugType != 0 && plugType != BatteryManager.BATTERY_PLUGGED_WIRELESS) {
+ // The device was plugged into a new non-wireless power source.
+ // It's safe to assume that it is no longer on the wireless charger.
+ mMustUpdateRestPosition = false;
+ clearAtRestLocked();
+ } else {
+ // The device may still be on the wireless charger but we don't know.
+ // Check whether the device has remained at rest on the charger
+ // so that we will know to ignore the next wireless plug event
+ // if needed.
+ startDetectionLocked();
+ }
+ }
+ }
+
+ // Report that the device has been docked only if the device just started
+ // receiving power wirelessly, has a high enough battery level that we
+ // can be assured that charging was not delayed due to the battery previously
+ // having been full, and the device is not known to already be at rest
+ // on the wireless charger from earlier.
+ return mPoweredWirelessly && !wasPoweredWirelessly
+ && batteryLevel < WIRELESS_CHARGER_TURN_ON_BATTERY_LEVEL_LIMIT
+ && !mAtRest;
+ }
+ }
+
+ private void startDetectionLocked() {
+ if (!mDetectionInProgress && mGravitySensor != null) {
+ if (mSensorManager.registerListener(mListener, mGravitySensor,
+ SensorManager.SENSOR_DELAY_UI)) {
+ mSuspendBlocker.acquire();
+ mDetectionInProgress = true;
+ mTotalSamples = 0;
+ mMovingSamples = 0;
+ }
+ }
+ }
+
+ private void processSample(long timeNanos, float x, float y, float z) {
+ synchronized (mLock) {
+ if (!mDetectionInProgress) {
+ return;
+ }
+
+ mTotalSamples += 1;
+ if (mTotalSamples == 1) {
+ // Save information about the first sample collected.
+ mFirstSampleTime = timeNanos;
+ mFirstSampleX = x;
+ mFirstSampleY = y;
+ mFirstSampleZ = z;
+ } else {
+ // Determine whether movement has occurred relative to the first sample.
+ if (hasMoved(mFirstSampleX, mFirstSampleY, mFirstSampleZ, x, y, z)) {
+ mMovingSamples += 1;
+ }
+ }
+
+ // Clear the at rest flag if movement has occurred relative to the rest sample.
+ if (mAtRest && hasMoved(mRestX, mRestY, mRestZ, x, y, z)) {
+ if (DEBUG) {
+ Slog.d(TAG, "No longer at rest: "
+ + "mRestX=" + mRestX + ", mRestY=" + mRestY + ", mRestZ=" + mRestZ
+ + ", x=" + x + ", y=" + y + ", z=" + z);
+ }
+ clearAtRestLocked();
+ }
+
+ // Save the result when done.
+ if (timeNanos - mFirstSampleTime >= SETTLE_TIME_NANOS
+ && mTotalSamples >= MIN_SAMPLES) {
+ mSensorManager.unregisterListener(mListener);
+ if (mMustUpdateRestPosition) {
+ if (mMovingSamples == 0) {
+ mAtRest = true;
+ mRestX = x;
+ mRestY = y;
+ mRestZ = z;
+ } else {
+ clearAtRestLocked();
+ }
+ mMustUpdateRestPosition = false;
+ }
+ mDetectionInProgress = false;
+ mSuspendBlocker.release();
+
+ if (DEBUG) {
+ Slog.d(TAG, "New state: mAtRest=" + mAtRest
+ + ", mRestX=" + mRestX + ", mRestY=" + mRestY + ", mRestZ=" + mRestZ
+ + ", mTotalSamples=" + mTotalSamples
+ + ", mMovingSamples=" + mMovingSamples);
+ }
+ }
+ }
+ }
+
+ private void clearAtRestLocked() {
+ mAtRest = false;
+ mRestX = 0;
+ mRestY = 0;
+ mRestZ = 0;
+ }
+
+ private static boolean hasMoved(float x1, float y1, float z1,
+ float x2, float y2, float z2) {
+ final double dotProduct = (x1 * x2) + (y1 * y2) + (z1 * z2);
+ final double mag1 = Math.sqrt((x1 * x1) + (y1 * y1) + (z1 * z1));
+ final double mag2 = Math.sqrt((x2 * x2) + (y2 * y2) + (z2 * z2));
+ if (mag1 < MIN_GRAVITY || mag1 > MAX_GRAVITY
+ || mag2 < MIN_GRAVITY || mag2 > MAX_GRAVITY) {
+ if (DEBUG) {
+ Slog.d(TAG, "Weird gravity vector: mag1=" + mag1 + ", mag2=" + mag2);
+ }
+ return true;
+ }
+ final boolean moved = (dotProduct < mag1 * mag2 * MOVEMENT_ANGLE_COS_THRESHOLD);
+ if (DEBUG) {
+ Slog.d(TAG, "Check: moved=" + moved
+ + ", x1=" + x1 + ", y1=" + y1 + ", z1=" + z1
+ + ", x2=" + x2 + ", y2=" + y2 + ", z2=" + z2
+ + ", angle=" + (Math.acos(dotProduct / mag1 / mag2) * 180 / Math.PI)
+ + ", dotProduct=" + dotProduct
+ + ", mag1=" + mag1 + ", mag2=" + mag2);
+ }
+ return moved;
+ }
+
+ private final SensorEventListener mListener = new SensorEventListener() {
+ @Override
+ public void onSensorChanged(SensorEvent event) {
+ processSample(event.timestamp, event.values[0], event.values[1], event.values[2]);
+ }
+
+ @Override
+ public void onAccuracyChanged(Sensor sensor, int accuracy) {
+ }
+ };
+}