From 782f2ad37538c8decfbe8cac48f26c593182c358 Mon Sep 17 00:00:00 2001 From: Jamie Gennis Date: Sun, 6 Oct 2013 16:02:02 -0700 Subject: [PATCH] BoardConfig: Add and document vsync phase offset setting Bug: 10624956 Change-Id: I82def5730f9d09396809d4b8cd2ea44829b21f22 --- target/board/generic/BoardConfig.mk | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/target/board/generic/BoardConfig.mk b/target/board/generic/BoardConfig.mk index 3bd4f3107..60decfb3e 100644 --- a/target/board/generic/BoardConfig.mk +++ b/target/board/generic/BoardConfig.mk @@ -45,6 +45,28 @@ BUILD_EMULATOR_OPENGL := true # the GLES renderer disables itself if host GL acceleration isn't available. USE_OPENGL_RENDERER := true +# Set the phase offset of the system's vsync event relative to the hardware +# vsync. The system's vsync event drives Choreographer and SurfaceFlinger's +# rendering. This value is the number of nanoseconds after the hardware vsync +# that the system vsync event will occur. +# +# This phase offset allows adjustment of the minimum latency from application +# wake-up (by Choregographer) time to the time at which the resulting window +# image is displayed. This value may be either positive (after the HW vsync) +# or negative (before the HW vsync). Setting it to 0 will result in a +# minimum latency of two vsync periods because the app and SurfaceFlinger +# will run just after the HW vsync. Setting it to a positive number will +# result in the minimum latency being: +# +# (2 * VSYNC_PERIOD - (vsyncPhaseOffsetNs % VSYNC_PERIOD)) +# +# Note that reducing this latency makes it more likely for the applications +# to not have their window content image ready in time. When this happens +# the latency will end up being an additional vsync period, and animations +# will hiccup. Therefore, this latency should be tuned somewhat +# conservatively (or at least with awareness of the trade-off being made). +VSYNC_EVENT_PHASE_OFFSET_NS := 0 + TARGET_USERIMAGES_USE_EXT4 := true BOARD_SYSTEMIMAGE_PARTITION_SIZE := 576716800 BOARD_USERDATAIMAGE_PARTITION_SIZE := 209715200 -- 2.11.0