surfaceflinger: signalRefresh after boot animation starts

Assume BootStage::BOOTLOADER initially.  Switch to
BootStage::BOOTANIMATION on first buffer latch and switch to
BootStage::FINISHED after bootFinished is called.

Do not invoke signalRefresh when in BootStage::BOOTLOADER.  We do
not want to replace bootloader splash by a blank screen.  This saves
HWC from workarounds that may or may not work reliably.

Bug: 79434305
Bug: 110772452
Test: reboot and observe
Change-Id: I9e892e629303177431acd2cfe23f0f984ca6866e
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 32c313b..488bc20 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -223,6 +223,7 @@
         mVisibleRegionsDirty(false),
         mGeometryInvalid(false),
         mAnimCompositionPending(false),
+        mBootStage(BootStage::BOOTLOADER),
         mDebugRegion(0),
         mDebugDDMS(0),
         mDebugDisableHWC(0),
@@ -231,7 +232,6 @@
         mLastSwapBufferTime(0),
         mDebugInTransaction(0),
         mLastTransactionTime(0),
-        mBootFinished(false),
         mForceFullDamage(false),
         mPrimaryDispSync("PrimaryDispSync"),
         mPrimaryHWVsyncEnabled(false),
@@ -498,7 +498,10 @@
     LOG_EVENT_LONG(LOGTAG_SF_STOP_BOOTANIM,
                    ns2ms(systemTime(SYSTEM_TIME_MONOTONIC)));
 
-    postMessageAsync(new LambdaMessage([this] { readPersistentProperties(); }));
+    postMessageAsync(new LambdaMessage([this] {
+        readPersistentProperties();
+        mBootStage = BootStage::FINISHED;
+    }));
 }
 
 uint32_t SurfaceFlinger::getNewTexture() {
@@ -1478,7 +1481,7 @@
             bool refreshNeeded = handleMessageTransaction();
             refreshNeeded |= handleMessageInvalidate();
             refreshNeeded |= mRepaintEverything;
-            if (refreshNeeded) {
+            if (refreshNeeded && CC_LIKELY(mBootStage != BootStage::BOOTLOADER)) {
                 // Signal a refresh if a transaction modified the window state,
                 // a new buffer was latched, or if HWC has requested a full
                 // repaint
@@ -2835,6 +2838,12 @@
         signalLayerUpdate();
     }
 
+    // enter boot animation on first buffer latch
+    if (CC_UNLIKELY(mBootStage == BootStage::BOOTLOADER && newDataLatched)) {
+        ALOGI("Enter boot animation");
+        mBootStage = BootStage::BOOTANIMATION;
+    }
+
     // Only continue with the refresh if there is actually new work to do
     return !mLayersWithQueuedFrames.empty() && newDataLatched;
 }