drm/i915: Introduce concept of per-timeline (context) HWSP

Supplement the per-engine HWSP with a per-timeline HWSP. That is a
per-request pointer through which we can check a local seqno,
abstracting away the presumption of a global seqno. In this first step,
we point each request back into the engine's HWSP so everything
continues to work with the global timeline.

v2: s/i915_request_hwsp/hwsp_seqno/ to emphasis that this is the current
HW value and that we are accessing it via i915_request merely as a
convenience.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190128181812.22804-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_request.c

@@ -182,10 +182,11 @@ static void free_capture_list(struct i915_request *request)
 static void __retire_engine_request(struct intel_engine_cs *engine,
 				    struct i915_request *rq)
 {
-	GEM_TRACE("%s(%s) fence %llx:%lld, global=%d, current %d\n",
+	GEM_TRACE("%s(%s) fence %llx:%lld, global=%d, current %d:%d\n",
 		  __func__, engine->name,
 		  rq->fence.context, rq->fence.seqno,
 		  rq->global_seqno,
+		  hwsp_seqno(rq),
 		  intel_engine_get_seqno(engine));
 
 	GEM_BUG_ON(!i915_request_completed(rq));
@@ -244,10 +245,11 @@ static void i915_request_retire(struct i915_request *request)
 {
 	struct i915_gem_active *active, *next;
 
-	GEM_TRACE("%s fence %llx:%lld, global=%d, current %d\n",
+	GEM_TRACE("%s fence %llx:%lld, global=%d, current %d:%d\n",
 		  request->engine->name,
 		  request->fence.context, request->fence.seqno,
 		  request->global_seqno,
+		  hwsp_seqno(request),
 		  intel_engine_get_seqno(request->engine));
 
 	lockdep_assert_held(&request->i915->drm.struct_mutex);
@@ -307,10 +309,11 @@ void i915_request_retire_upto(struct i915_request *rq)
 	struct intel_ring *ring = rq->ring;
 	struct i915_request *tmp;
 
-	GEM_TRACE("%s fence %llx:%lld, global=%d, current %d\n",
+	GEM_TRACE("%s fence %llx:%lld, global=%d, current %d:%d\n",
 		  rq->engine->name,
 		  rq->fence.context, rq->fence.seqno,
 		  rq->global_seqno,
+		  hwsp_seqno(rq),
 		  intel_engine_get_seqno(rq->engine));
 
 	lockdep_assert_held(&rq->i915->drm.struct_mutex);
@@ -355,10 +358,11 @@ void __i915_request_submit(struct i915_request *request)
 	struct intel_engine_cs *engine = request->engine;
 	u32 seqno;
 
-	GEM_TRACE("%s fence %llx:%lld -> global=%d, current %d\n",
+	GEM_TRACE("%s fence %llx:%lld -> global=%d, current %d:%d\n",
 		  engine->name,
 		  request->fence.context, request->fence.seqno,
 		  engine->timeline.seqno + 1,
+		  hwsp_seqno(request),
 		  intel_engine_get_seqno(engine));
 
 	GEM_BUG_ON(!irqs_disabled());
@@ -405,10 +409,11 @@ void __i915_request_unsubmit(struct i915_request *request)
 {
 	struct intel_engine_cs *engine = request->engine;
 
-	GEM_TRACE("%s fence %llx:%lld <- global=%d, current %d\n",
+	GEM_TRACE("%s fence %llx:%lld <- global=%d, current %d:%d\n",
 		  engine->name,
 		  request->fence.context, request->fence.seqno,
 		  request->global_seqno,
+		  hwsp_seqno(request),
 		  intel_engine_get_seqno(engine));
 
 	GEM_BUG_ON(!irqs_disabled());
@@ -616,6 +621,7 @@ i915_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx)
 	rq->ring = ce->ring;
 	rq->timeline = ce->ring->timeline;
 	GEM_BUG_ON(rq->timeline == &engine->timeline);
+	rq->hwsp_seqno = &engine->status_page.addr[I915_GEM_HWS_INDEX];
 
 	spin_lock_init(&rq->lock);
 	dma_fence_init(&rq->fence,

drivers/gpu/drm/i915/i915_request.h

@@ -130,6 +130,13 @@ struct i915_request {
 	struct i915_sched_node sched;
 	struct i915_dependency dep;
 
+	/*
+	 * A convenience pointer to the current breadcrumb value stored in
+	 * the HW status page (or our timeline's local equivalent). The full
+	 * path would be rq->hw_context->ring->timeline->hwsp_seqno.
+	 */
+	const u32 *hwsp_seqno;
+
 	/**
 	 * GEM sequence number associated with this request on the
 	 * global execution timeline. It is zero when the request is not
@@ -285,11 +292,6 @@ static inline bool i915_request_signaled(const struct i915_request *rq)
 	return test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &rq->fence.flags);
 }
 
-static inline bool intel_engine_has_started(struct intel_engine_cs *engine,
-					    u32 seqno);
-static inline bool intel_engine_has_completed(struct intel_engine_cs *engine,
-					      u32 seqno);
-
 /**
  * Returns true if seq1 is later than seq2.
  */
@@ -298,6 +300,35 @@ static inline bool i915_seqno_passed(u32 seq1, u32 seq2)
 	return (s32)(seq1 - seq2) >= 0;
 }
 
+static inline u32 __hwsp_seqno(const struct i915_request *rq)
+{
+	return READ_ONCE(*rq->hwsp_seqno);
+}
+
+/**
+ * hwsp_seqno - the current breadcrumb value in the HW status page
+ * @rq: the request, to chase the relevant HW status page
+ *
+ * The emphasis in naming here is that hwsp_seqno() is not a property of the
+ * request, but an indication of the current HW state (associated with this
+ * request). Its value will change as the GPU executes more requests.
+ *
+ * Returns the current breadcrumb value in the associated HW status page (or
+ * the local timeline's equivalent) for this request. The request itself
+ * has the associated breadcrumb value of rq->fence.seqno, when the HW
+ * status page has that breadcrumb or later, this request is complete.
+ */
+static inline u32 hwsp_seqno(const struct i915_request *rq)
+{
+	u32 seqno;
+
+	rcu_read_lock(); /* the HWSP may be freed at runtime */
+	seqno = __hwsp_seqno(rq);
+	rcu_read_unlock();
+
+	return seqno;
+}
+
 /**
  * i915_request_started - check if the request has begun being executed
  * @rq: the request
@@ -315,14 +346,14 @@ static inline bool i915_request_started(const struct i915_request *rq)
 	if (!seqno) /* not yet submitted to HW */
 		return false;
 
-	return intel_engine_has_started(rq->engine, seqno);
+	return i915_seqno_passed(hwsp_seqno(rq), seqno - 1);
 }
 
 static inline bool
 __i915_request_completed(const struct i915_request *rq, u32 seqno)
 {
 	GEM_BUG_ON(!seqno);
-	return intel_engine_has_completed(rq->engine, seqno) &&
+	return i915_seqno_passed(hwsp_seqno(rq), seqno) &&
 		seqno == i915_request_global_seqno(rq);
 }
 

drivers/gpu/drm/i915/intel_lrc.c

@@ -446,11 +446,12 @@ static void execlists_submit_ports(struct intel_engine_cs *engine)
 			desc = execlists_update_context(rq);
 			GEM_DEBUG_EXEC(port[n].context_id = upper_32_bits(desc));
 
-			GEM_TRACE("%s in[%d]:  ctx=%d.%d, global=%d (fence %llx:%lld) (current %d), prio=%d\n",
+			GEM_TRACE("%s in[%d]:  ctx=%d.%d, global=%d (fence %llx:%lld) (current %d:%d), prio=%d\n",
 				  engine->name, n,
 				  port[n].context_id, count,
 				  rq->global_seqno,
 				  rq->fence.context, rq->fence.seqno,
+				  hwsp_seqno(rq),
 				  intel_engine_get_seqno(engine),
 				  rq_prio(rq));
 		} else {
@@ -742,11 +743,12 @@ execlists_cancel_port_requests(struct intel_engine_execlists * const execlists)
 	while (num_ports-- && port_isset(port)) {
 		struct i915_request *rq = port_request(port);
 
-		GEM_TRACE("%s:port%u global=%d (fence %llx:%lld), (current %d)\n",
+		GEM_TRACE("%s:port%u global=%d (fence %llx:%lld), (current %d:%d)\n",
 			  rq->engine->name,
 			  (unsigned int)(port - execlists->port),
 			  rq->global_seqno,
 			  rq->fence.context, rq->fence.seqno,
+			  hwsp_seqno(rq),
 			  intel_engine_get_seqno(rq->engine));
 
 		GEM_BUG_ON(!execlists->active);
@@ -970,12 +972,13 @@ static void process_csb(struct intel_engine_cs *engine)
 						EXECLISTS_ACTIVE_USER));
 
 		rq = port_unpack(port, &count);
-		GEM_TRACE("%s out[0]: ctx=%d.%d, global=%d (fence %llx:%lld) (current %d), prio=%d\n",
+		GEM_TRACE("%s out[0]: ctx=%d.%d, global=%d (fence %llx:%lld) (current %d:%d), prio=%d\n",
 			  engine->name,
 			  port->context_id, count,
 			  rq ? rq->global_seqno : 0,
 			  rq ? rq->fence.context : 0,
 			  rq ? rq->fence.seqno : 0,
+			  rq ? hwsp_seqno(rq) : 0,
 			  intel_engine_get_seqno(engine),
 			  rq ? rq_prio(rq) : 0);