commit bf711ebeb6931f5b2094ac4ab4fe710b9dbebbe3
author Drew Davenport <ddavenport@google.com> Wed Feb 19 09:41:20 2025 -0700
committer Drew Davenport <ddavenport@google.com> Fri Feb 21 10:51:42 2025 -0700
tree 1ac7ca1ca7d552ac19b39aa926b35291bd5234e7
parent 35a395720a4d567e1aaf1749963088d9829ef8b8

drm_hwcomposer: Avoid resetting vsync timestamp

last_timestamp_ tracks the most recent timestamp from a vblank event. Do
not reset it when toggling vsync tracking on/off. This allows for
GetPhasedVSync to calculate a more precise approximation of the next
vsync relative to the current time, even if a vsync hasn't happened for
a while.

Reset last_timestamp_ when the vsync period changes, since the phased
vsync calculation is based on the current vsync.

Also change last_timestamp_ to std::optional type.

Change-Id: I101b36f87d6ba8197c321c83ac0bc230fba9cf7e
Signed-off-by: Drew Davenport <ddavenport@google.com>

hwc2_device/HwcDisplay.cpp

diff --git a/hwc2_device/HwcDisplay.cpp b/hwc2_device/HwcDisplay.cpp
index 121f04f..977ab1a 100644
--- a/hwc2_device/HwcDisplay.cpp
+++ b/hwc2_device/HwcDisplay.cpp
@@ -822,7 +822,6 @@
   }
 
   if (new_vsync_period_ns) {
-    vsync_worker_->SetVsyncPeriodNs(new_vsync_period_ns.value());
     staged_mode_config_id_.reset();
 
     vsync_worker_->SetVsyncTimestampTracking(false);
@@ -832,6 +831,7 @@
                                                       last_vsync_ts +
                                                           prev_vperiod_ns);
     }
+    vsync_worker_->SetVsyncPeriodNs(new_vsync_period_ns.value());
   }
 
   return HWC2::Error::None;