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Commit c734d95c authored by Haixia Shi's avatar Haixia Shi
Browse files

DispSync: workaround HH hardware vsync issue 

The HWC of HH seems to have a bug where it fails to generate vsync events upon
the first eventControl call to turn on HWC_EVENT_VSYNC.

The workaround is for DispSync to detect when it has received no resync samples
after many presents, and return false so that SF will disable HW vsync and
re-enable it in the next present. This gets the HWC of HH out of the bad state.

Bug:25845510
TEST=reboot HH then immediately capture systrace while scrolling all apps

Change-Id: Ie034c113d94ea53068eef75b8eac39a32788666a
parent e0c44ed2

services/surfaceflinger/DispSync.cpp

+11 −0
Original line number Diff line number Diff line
@@ -322,6 +322,7 @@ void DispSync::reset() { 
    mNumResyncSamples = 0;

    mFirstResyncSample = 0;

    mNumResyncSamplesSincePresent = 0;

    mNumPresentWithoutResyncSamples = 0;

    resetErrorLocked();

}
@@ -346,6 +347,15 @@ bool DispSync::addPresentFence(const sp<Fence>& fence) { 


    updateErrorLocked();



    // This is a workaround for b/25845510.

    // If we have no resync samples after many presents, something is wrong with

    // HW vsync. Tell SF to disable HW vsync now and re-enable it next time.

    if (mNumResyncSamples == 0 &&

        mNumPresentWithoutResyncSamples++ > MAX_PRESENT_WITHOUT_RESYNC_SAMPLES) {

        mNumPresentWithoutResyncSamples = 0;

        return false;

    }



    return !mModelUpdated || mError > kErrorThreshold;

}
@@ -354,6 +364,7 @@ void DispSync::beginResync() { 


    mModelUpdated = false;

    mNumResyncSamples = 0;

    mNumPresentWithoutResyncSamples = 0;

}



bool DispSync::addResyncSample(nsecs_t timestamp) {

services/surfaceflinger/DispSync.h

+2 −0
Original line number Diff line number Diff line
@@ -140,6 +140,7 @@ private: 
    enum { MIN_RESYNC_SAMPLES_FOR_UPDATE = 3 };

    enum { NUM_PRESENT_SAMPLES = 8 };

    enum { MAX_RESYNC_SAMPLES_WITHOUT_PRESENT = 4 };

    enum { MAX_PRESENT_WITHOUT_RESYNC_SAMPLES = 8 };



    // mPeriod is the computed period of the modeled vsync events in

    // nanoseconds.
@@ -168,6 +169,7 @@ private: 
    size_t mFirstResyncSample;

    size_t mNumResyncSamples;

    int mNumResyncSamplesSincePresent;

    int mNumPresentWithoutResyncSamples;



    // These member variables store information about the present fences used

    // to validate the currently computed model.