[PATCH 2/2] drm/scheduler: Add a start_timeout_notify() backend function

[Sharat Masetty <smasetty-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>]

Add an optional backend function op which will let the scheduler clients
know when the timeout got scheduled on the scheduler instance. This will
help drivers with multiple schedulers(one per ring) measure time spent on
the ring accurately, eventually helping with better timeout detection.

Signed-off-by: Sharat Masetty <smasetty@codeaurora.org>
---
Here is an example of how I plan to use this new function callback.

[1] https://patchwork.freedesktop.org/patch/254227/

 drivers/gpu/drm/scheduler/sched_main.c | 7 ++++++-
 include/drm/gpu_scheduler.h            | 6 ++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index c993d10..afd461e 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -192,8 +192,13 @@ bool drm_sched_dependency_optimized(struct dma_fence* fence,
 static void drm_sched_start_timeout(struct drm_gpu_scheduler *sched)
 {
 	if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&
-	    !list_empty(&sched->ring_mirror_list))
+	    !list_empty(&sched->ring_mirror_list)) {
+
 		schedule_delayed_work(&sched->work_tdr, sched->timeout);
+
+		if (sched->ops->start_timeout_notify)
+			sched->ops->start_timeout_notify(sched);
+	}
 }

 /* job_finish is called after hw fence signaled
diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index d87b268..faf28b4 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -239,6 +239,12 @@ struct drm_sched_backend_ops {
          * and it's time to clean it up.
 	 */
 	void (*free_job)(struct drm_sched_job *sched_job);
+
+	/*
+	 * (Optional) Called to let the driver know that a timeout detection
+	 * timer has been started.
+	 */
+	void (*start_timeout_notify)(struct drm_gpu_scheduler *sched);
 };

 /**
--
1.9.1

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