drm/i915: Identify active requests

To allow requests to forgo a common execution timeline, one question we
need to be able to answer is "is this request running?". To track
whether a request has started on HW, we can emit a breadcrumb at the
beginning of the request and check its timeline's HWSP to see if the
breadcrumb has advanced past the start of this request. (This is in
contrast to the global timeline where we need only ask if we are on the
global timeline and if the timeline has advanced past the end of the
previous request.)

There is still confusion from a preempted request, which has already
started but relinquished the HW to a high priority request. For the
common case, this discrepancy should be negligible. However, for
identification of hung requests, knowing which one was running at the
time of the hang will be much more important.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190129185452.20989-2-chris@chris-wilson.co.uk

1 files changed, 5 insertions, 5 deletions

diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 4d58770e6a8c..7db15b7b3de8 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -333,7 +333,7 @@ void i915_request_retire_upto(struct i915_request *rq)
 
 static u32 timeline_get_seqno(struct i915_timeline *tl)
 {
-	return ++tl->seqno;
+	return tl->seqno += 1 + tl->has_initial_breadcrumb;
 }
 
 static void move_to_timeline(struct i915_request *request,
@@ -382,8 +382,8 @@ void __i915_request_submit(struct i915_request *request)
 		intel_engine_enable_signaling(request, false);
 	spin_unlock(&request->lock);
 
-	engine->emit_breadcrumb(request,
-				request->ring->vaddr + request->postfix);
+	engine->emit_fini_breadcrumb(request,
+				     request->ring->vaddr + request->postfix);
 
 	/* Transfer from per-context onto the global per-engine timeline */
 	move_to_timeline(request, &engine->timeline);
@@ -657,7 +657,7 @@ i915_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx)
 	 * around inside i915_request_add() there is sufficient space at
 	 * the beginning of the ring as well.
 	 */
-	rq->reserved_space = 2 * engine->emit_breadcrumb_dw * sizeof(u32);
+	rq->reserved_space = 2 * engine->emit_fini_breadcrumb_dw * sizeof(u32);
 
 	/*
 	 * Record the position of the start of the request so that
@@ -908,7 +908,7 @@ void i915_request_add(struct i915_request *request)
 	 * GPU processing the request, we never over-estimate the
 	 * position of the ring's HEAD.
 	 */
-	cs = intel_ring_begin(request, engine->emit_breadcrumb_dw);
+	cs = intel_ring_begin(request, engine->emit_fini_breadcrumb_dw);
 	GEM_BUG_ON(IS_ERR(cs));
 	request->postfix = intel_ring_offset(request, cs);