Initialize screen state earlier in the boot process.

The system depends on receiving reliable vsync signals from
surface flinger during the boot process.  If it doesn't get them
because the screen is off then a hang may occur.

This isn't a problem when surface flinger manages the screen
blanking itself but it is a problem for devices that still
rely on early-suspend.  When early-suspend is involved, the
screen may be off without surface flinger knowing.  This is a
problem because surface flinger will only synthesize fake
vsyncs when it knows the screen is off, otherwise relying
on the hardware to generate vsync signals itself.  Unfortunately,
the hardware won't generate vsync signals if the screen was
turned off by early-suspend, so we have a problem.

Bug: 6975688
Change-Id: Iaf4527f716bf4ea72cc3e6fdaf060855697b02f2

2 files changed, 16 insertions, 3 deletions

diff --git a/services/java/com/android/server/power/DisplayPowerState.java b/services/java/com/android/server/power/DisplayPowerState.java
index 64a0462c3aea..3524a08efd6a 100644
--- a/services/java/com/android/server/power/DisplayPowerState.java
+++ b/services/java/com/android/server/power/DisplayPowerState.java
@@ -49,8 +49,6 @@ final class DisplayPowerState {
     private static final int DIRTY_ELECTRON_BEAM = 1 << 1;
     private static final int DIRTY_BRIGHTNESS = 1 << 2;
 
-    private static final int DIRTY_ALL = 0xffffffff;
-
     private final Choreographer mChoreographer;
     private final ElectronBeam mElectronBeam;
     private final PhotonicModulator mScreenBrightnessModulator;
@@ -68,10 +66,16 @@ final class DisplayPowerState {
         mElectronBeam = electronBean;
         mScreenBrightnessModulator = screenBrightnessModulator;
 
+        // At boot time, we know that the screen is on and the electron beam
+        // animation is not playing.  We don't know the screen's brightness though,
+        // so prepare to set it to a known state when the state is next applied.
+        // Although we set the brightness to full on here, the display power controller
+        // will reset the brightness to a new level immediately before the changes
+        // actually have a chance to be applied.
         mScreenOn = true;
         mElectronBeamLevel = 1.0f;
         mScreenBrightness = PowerManager.BRIGHTNESS_ON;
-        invalidate(DIRTY_ALL);
+        invalidate(DIRTY_BRIGHTNESS);
     }
 
     public static final FloatProperty<DisplayPowerState> ELECTRON_BEAM_LEVEL =
diff --git a/services/java/com/android/server/power/PowerManagerService.java b/services/java/com/android/server/power/PowerManagerService.java
index 9f2b247d3106..dc900ca57b18 100644
--- a/services/java/com/android/server/power/PowerManagerService.java
+++ b/services/java/com/android/server/power/PowerManagerService.java
@@ -296,6 +296,7 @@ public final class PowerManagerService extends IPowerManager.Stub
         }
 
         nativeInit();
+        nativeSetPowerState(true, true);
     }
 
     /**
@@ -305,6 +306,14 @@ public final class PowerManagerService extends IPowerManager.Stub
     public void init(Context context, LightsService ls,
             ActivityManagerService am, BatteryService bs, IBatteryStats bss,
             DisplayManagerService dm) {
+        // Forcibly turn the screen on at boot so that it is in a known power state.
+        // We do this in init() rather than in the constructor because setting the
+        // screen state requires a call into surface flinger which then needs to call back
+        // into the activity manager to check permissions.  Unfortunately the
+        // activity manager is not running when the constructor is called, so we
+        // have to defer setting the screen state until this point.
+        nativeSetScreenState(true);
+
         mContext = context;
         mLightsService = ls;
         mBatteryService = bs;