Merge "[SurfaceFlinger] Exclude first vsync duration from period calculation" into qt-r1-dev

        nsecs_t durationSum = 0;

        nsecs_t minDuration = INT64_MAX;

        nsecs_t maxDuration = 0;

        for (size_t i = 1; i < mNumResyncSamples; i++) {

        // We skip the first 2 samples because the first vsync duration on some

        // devices may be much more inaccurate than on other devices, e.g. due

        // to delays in ramping up from a power collapse. By doing so this

        // actually increases the accuracy of the DispSync model even though

        // we're effectively relying on fewer sample points.

        static constexpr size_t numSamplesSkipped = 2;

        for (size_t i = numSamplesSkipped; i < mNumResyncSamples; i++) {

            size_t idx = (mFirstResyncSample + i) % MAX_RESYNC_SAMPLES;

            size_t prev = (idx + MAX_RESYNC_SAMPLES - 1) % MAX_RESYNC_SAMPLES;

            nsecs_t duration = mResyncSamples[idx] - mResyncSamples[prev];

        // Exclude the min and max from the average

        durationSum -= minDuration + maxDuration;

        mPeriod = durationSum / (mNumResyncSamples - 3);

        mPeriod = durationSum / (mNumResyncSamples - numSamplesSkipped - 2);

        ALOGV("[%s] mPeriod = %" PRId64, mName, ns2us(mPeriod));

        double sampleAvgX = 0;

        double sampleAvgY = 0;

        double scale = 2.0 * M_PI / double(mPeriod);

        // Intentionally skip the first sample

        for (size_t i = 1; i < mNumResyncSamples; i++) {

        for (size_t i = numSamplesSkipped; i < mNumResyncSamples; i++) {

            size_t idx = (mFirstResyncSample + i) % MAX_RESYNC_SAMPLES;

            nsecs_t sample = mResyncSamples[idx] - mReferenceTime;

            double samplePhase = double(sample % mPeriod) * scale;

            sampleAvgY += sin(samplePhase);

        }

        sampleAvgX /= double(mNumResyncSamples - 1);

        sampleAvgY /= double(mNumResyncSamples - 1);

        sampleAvgX /= double(mNumResyncSamples - numSamplesSkipped);

        sampleAvgY /= double(mNumResyncSamples - numSamplesSkipped);

        mPhase = nsecs_t(atan2(sampleAvgY, sampleAvgX) / scale);