drm/scheduler: Add job dependency trace.

During debug sessions I encountered a need to trace
back a job dependecy a few steps back to the first failing
job. This trace helpped me a lot.
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/scheduler/gpu_scheduler.c

@@ -522,9 +522,13 @@ drm_sched_entity_pop_job(struct drm_sched_entity *entity)
 
 	sched_job->sched = sched;
 	sched_job->s_fence->sched = sched;
-	while ((entity->dependency = sched->ops->dependency(sched_job, entity)))
-		if (drm_sched_entity_add_dependency_cb(entity))
+	while ((entity->dependency = sched->ops->dependency(sched_job, entity))) {
+		if (drm_sched_entity_add_dependency_cb(entity)) {
+
+			trace_drm_sched_job_wait_dep(sched_job, entity->dependency);
 			return NULL;
+		}
+	}
 
 	/* skip jobs from entity that marked guilty */
 	if (entity->guilty && atomic_read(entity->guilty))

drivers/gpu/drm/scheduler/gpu_scheduler_trace.h

@@ -74,6 +74,30 @@ TRACE_EVENT(drm_sched_process_job,
 	    TP_printk("fence=%p signaled", __entry->fence)
 );
 
+TRACE_EVENT(drm_sched_job_wait_dep,
+	    TP_PROTO(struct drm_sched_job *sched_job, struct dma_fence *fence),
+	    TP_ARGS(sched_job, fence),
+	    TP_STRUCT__entry(
+			     __field(const char *,name)
+			     __field(uint64_t, id)
+			     __field(struct dma_fence *, fence)
+			     __field(uint64_t, ctx)
+			     __field(unsigned, seqno)
+			     ),
+
+	    TP_fast_assign(
+			   __entry->name = sched_job->sched->name;
+			   __entry->id = sched_job->id;
+			   __entry->fence = fence;
+			   __entry->ctx = fence->context;
+			   __entry->seqno = fence->seqno;
+			   ),
+	    TP_printk("job ring=%s, id=%llu, depends fence=%p, context=%llu, seq=%u",
+		      __entry->name, __entry->id,
+		      __entry->fence, __entry->ctx,
+		      __entry->seqno)
+);
+
 #endif
 
 /* This part must be outside protection */