drm: Add high-precision time to vblank trace event

Store the timestamp of the current vblank in the new field 'time' of the
vblank trace event. If the timestamp is calculated by a driver that
supports high-precision vblank timing, set the field 'high-prec' to
'true'.

User space can now access actual hardware vblank times via the tracing
infrastructure. Tracing applications (such as GPUVis, see [0] for
related discussion), can use the newly added information to conduct a
more accurate analysis of display timing.

v2 Fix author name (missing last name)

[0] https://github.com/mikesart/gpuvis/issues/30Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Heinrich Fink <heinrich.fink@daqri.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190902142412.27846-2-heinrich.fink@daqri.com

drivers/gpu/drm/drm_trace.h

@@ -13,17 +13,23 @@ struct drm_file;
 #define TRACE_INCLUDE_FILE drm_trace
 
 TRACE_EVENT(drm_vblank_event,
-	    TP_PROTO(int crtc, unsigned int seq),
-	    TP_ARGS(crtc, seq),
+	    TP_PROTO(int crtc, unsigned int seq, ktime_t time, bool high_prec),
+	    TP_ARGS(crtc, seq, time, high_prec),
 	    TP_STRUCT__entry(
 		    __field(int, crtc)
 		    __field(unsigned int, seq)
+		    __field(ktime_t, time)
+		    __field(bool, high_prec)
 		    ),
 	    TP_fast_assign(
 		    __entry->crtc = crtc;
 		    __entry->seq = seq;
-		    ),
-	    TP_printk("crtc=%d, seq=%u", __entry->crtc, __entry->seq)
+		    __entry->time = time;
+		    __entry->high_prec = high_prec;
+			),
+	    TP_printk("crtc=%d, seq=%u, time=%lld, high-prec=%s",
+			__entry->crtc, __entry->seq, __entry->time,
+			__entry->high_prec ? "true" : "false")
 );
 
 TRACE_EVENT(drm_vblank_event_queued,

drivers/gpu/drm/drm_vblank.c

@@ -1731,7 +1731,8 @@ static void drm_handle_vblank_events(struct drm_device *dev, unsigned int pipe)
 		send_vblank_event(dev, e, seq, now);
 	}
 
-	trace_drm_vblank_event(pipe, seq);
+	trace_drm_vblank_event(pipe, seq, now,
+			dev->driver->get_vblank_timestamp != NULL);
 }
 
 /**