drm/amd/display: Add refresh rate trace

When we have to debug VRR issues, we usually want to know the current
refresh rate; for this reason, it is handy to have a way to check in
real-time the refresh rate value. This commit introduces a kernel trace
that can provide such information.
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Acked-by: Anson Jacob <Anson.Jacob@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -460,6 +460,9 @@ static void dm_vupdate_high_irq(void *interrupt_params)
 	struct common_irq_params *irq_params = interrupt_params;
 	struct amdgpu_device *adev = irq_params->adev;
 	struct amdgpu_crtc *acrtc;
+	struct drm_device *drm_dev;
+	struct drm_vblank_crtc *vblank;
+	ktime_t frame_duration_ns, previous_timestamp;
 	unsigned long flags;
 	int vrr_active;
 
@@ -467,6 +470,17 @@ static void dm_vupdate_high_irq(void *interrupt_params)
 
 	if (acrtc) {
 		vrr_active = amdgpu_dm_vrr_active_irq(acrtc);
+		drm_dev = acrtc->base.dev;
+		vblank = &drm_dev->vblank[acrtc->base.index];
+		previous_timestamp = atomic64_read(&irq_params->previous_timestamp);
+		frame_duration_ns = vblank->time - previous_timestamp;
+
+		if (frame_duration_ns > 0) {
+			trace_amdgpu_refresh_rate_track(acrtc->base.index,
+						frame_duration_ns,
+						ktime_divns(NSEC_PER_SEC, frame_duration_ns));
+			atomic64_set(&irq_params->previous_timestamp, vblank->time);
+		}
 
 		DRM_DEBUG_VBL("crtc:%d, vupdate-vrr:%d\n",
 			      acrtc->crtc_id,

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h

@@ -66,6 +66,7 @@ struct dc_plane_state;
 struct common_irq_params {
 	struct amdgpu_device *adev;
 	enum dc_irq_source irq_src;
+	atomic64_t previous_timestamp;
 };
 
 /**

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_trace.h

@@ -618,6 +618,25 @@ TRACE_EVENT(amdgpu_dmub_trace_high_irq,
 		  __entry->param0, __entry->param1)
 );
 
+TRACE_EVENT(amdgpu_refresh_rate_track,
+	TP_PROTO(int crtc_index, ktime_t refresh_rate_ns, uint32_t refresh_rate_hz),
+	TP_ARGS(crtc_index, refresh_rate_ns, refresh_rate_hz),
+	TP_STRUCT__entry(
+		__field(int, crtc_index)
+		__field(ktime_t, refresh_rate_ns)
+		__field(uint32_t, refresh_rate_hz)
+		),
+	TP_fast_assign(
+		__entry->crtc_index = crtc_index;
+		__entry->refresh_rate_ns = refresh_rate_ns;
+		__entry->refresh_rate_hz = refresh_rate_hz;
+	),
+	TP_printk("crtc_index=%d refresh_rate=%dHz (%lld)",
+		  __entry->crtc_index,
+		  __entry->refresh_rate_hz,
+		  __entry->refresh_rate_ns)
+);
+
 #endif /* _AMDGPU_DM_TRACE_H_ */
 
 #undef TRACE_INCLUDE_PATH