drm: Use vblank time from page flip handler

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
 

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;
 }
 

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;
 }

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 );