From a659fef806759c633d44b12a2a9dbe3c3b92a792 Mon Sep 17 00:00:00 2001
From: Joshua Ashton <joshua@froggi.es>
Date: Tue, 25 Jan 2022 14:35:55 +0000
Subject: [PATCH] drm: Use vblank time from page flip handler

---
 src/drm.cpp           | 4 +++-
 src/steamcompmgr.cpp  | 3 ++-
 src/vblankmanager.cpp | 4 ++--
 src/vblankmanager.hpp | 2 +-
 4 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/drm.cpp b/src/drm.cpp
index 90a078c..58a8a48 100644
--- a/src/drm.cpp
+++ b/src/drm.cpp
@@ -188,7 +188,9 @@ static void page_flip_handler(int fd, unsigned int frame, unsigned int sec, unsi
 	if ( g_DRM.crtc->id != crtc_id )
 		return;
 
-	vblank_mark_possible_vblank();
+	// This is the last vblank time
+	uint64_t vblanktime = sec * 1'000'000'000lu + usec * 1'000lu;
+	vblank_mark_possible_vblank(vblanktime);
 
 	// TODO: get the fbids_queued instance from data if we ever have more than one in flight
 
diff --git a/src/steamcompmgr.cpp b/src/steamcompmgr.cpp
index eb7f9ce..bf876a5 100644
--- a/src/steamcompmgr.cpp
+++ b/src/steamcompmgr.cpp
@@ -494,7 +494,8 @@ static inline void stats_printf( const char* format, ...)
 uint64_t get_time_in_nanos()
 {
 	timespec ts;
-	clock_gettime(CLOCK_MONOTONIC_RAW, &ts);
+	// Kernel reports page flips with CLOCK_MONOTONIC.
+	clock_gettime(CLOCK_MONOTONIC, &ts);
 	return ts.tv_sec * 1'000'000'000ul + ts.tv_nsec;
 }
 
diff --git a/src/vblankmanager.cpp b/src/vblankmanager.cpp
index 8ee15e0..889abb8 100644
--- a/src/vblankmanager.cpp
+++ b/src/vblankmanager.cpp
@@ -77,7 +77,7 @@ int vblank_init( void )
 	return g_vblankPipe[ 0 ];
 }
 
-void vblank_mark_possible_vblank( void )
+void vblank_mark_possible_vblank( uint64_t nanos )
 {
-	g_lastVblank = get_time_in_nanos();
+	g_lastVblank = nanos;
 }
diff --git a/src/vblankmanager.hpp b/src/vblankmanager.hpp
index 9ad0a9f..ec0eaf1 100644
--- a/src/vblankmanager.hpp
+++ b/src/vblankmanager.hpp
@@ -2,4 +2,4 @@
 
 int vblank_init( void );
 
-void vblank_mark_possible_vblank( void );
+void vblank_mark_possible_vblank( uint64_t nanos );