drm/i915: Mark the addition of the initial-breadcrumb in the request

The initial-breadcrumb is used to mark the end of the awaiting and the
beginning of the user payload. We verify that we do not start the user
payload before all signaler are completed, checking our semaphore setup
by looking for the initial breadcrumb being written too early. We also
want to ensure that we do not add semaphore waits after we have already
closed the semaphore section, an issue for later deferred waits.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200513165937.9508-2-chris@chris-wilson.co.uk

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 32feb2a27dfc..51470e96cdd4 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -1886,7 +1886,7 @@ static void defer_request(struct i915_request *rq, struct list_head * const pl)
 				continue;
 
 			/* No waiter should start before its signaler */
-			GEM_BUG_ON(w->context->timeline->has_initial_breadcrumb &&
+			GEM_BUG_ON(i915_request_has_initial_breadcrumb(w) &&
 				   i915_request_started(w) &&
 				   !i915_request_completed(rq));
 
@@ -3493,6 +3493,7 @@ static int gen8_emit_init_breadcrumb(struct i915_request *rq)
 {
 	u32 *cs;
 
+	GEM_BUG_ON(i915_request_has_initial_breadcrumb(rq));
 	if (!i915_request_timeline(rq)->has_initial_breadcrumb)
 		return 0;
 
@@ -3519,6 +3520,8 @@ static int gen8_emit_init_breadcrumb(struct i915_request *rq)
 	/* Record the updated position of the request's payload */
 	rq->infix = intel_ring_offset(rq, cs);
 
+	__set_bit(I915_FENCE_FLAG_INITIAL_BREADCRUMB, &rq->fence.flags);
+
 	return 0;
 }