drm/i915: Remove local timeline var from submit/unsubmit

Both request_submit and request_unsubmit deal with transferring the
request from the client's timeline onto the execution timeline and back
again. As both functions deal with a pair of timeline's, using a
shorthand for just one of them is slightly confusing, especially as the
different functions use the shorthand for the alternate timeline.
Instead, use the full version of each timeline so it should be easier to
keep track of the transfer between the request/client and the engine.

v2: Refactor the common lock+list_move
v3: Be clear we require the other timeline list to be locked as well.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180322131034.6036-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_request.c

@@ -492,10 +492,20 @@ static u32 timeline_get_seqno(struct intel_timeline *tl)
 	return ++tl->seqno;
 }
 
+static void move_to_timeline(struct i915_request *request,
+			     struct intel_timeline *timeline)
+{
+	GEM_BUG_ON(request->timeline == request->engine->timeline);
+	lockdep_assert_held(&request->engine->timeline->lock);
+
+	spin_lock(&request->timeline->lock);
+	list_move_tail(&request->link, &timeline->requests);
+	spin_unlock(&request->timeline->lock);
+}
+
 void __i915_request_submit(struct i915_request *request)
 {
 	struct intel_engine_cs *engine = request->engine;
-	struct intel_timeline *timeline;
 	u32 seqno;
 
 	GEM_TRACE("%s fence %llx:%d -> global_seqno %d\n",
@@ -506,12 +516,9 @@ void __i915_request_submit(struct i915_request *request)
 	GEM_BUG_ON(!irqs_disabled());
 	lockdep_assert_held(&engine->timeline->lock);
 
-	/* Transfer from per-context onto the global per-engine timeline */
-	timeline = engine->timeline;
-	GEM_BUG_ON(timeline == request->timeline);
 	GEM_BUG_ON(request->global_seqno);
 
-	seqno = timeline_get_seqno(timeline);
+	seqno = timeline_get_seqno(engine->timeline);
 	GEM_BUG_ON(!seqno);
 	GEM_BUG_ON(i915_seqno_passed(intel_engine_get_seqno(engine), seqno));
 
@@ -525,9 +532,8 @@ void __i915_request_submit(struct i915_request *request)
 	engine->emit_breadcrumb(request,
 				request->ring->vaddr + request->postfix);
 
-	spin_lock(&request->timeline->lock);
-	list_move_tail(&request->link, &timeline->requests);
-	spin_unlock(&request->timeline->lock);
+	/* Transfer from per-context onto the global per-engine timeline */
+	move_to_timeline(request, engine->timeline);
 
 	trace_i915_request_execute(request);
 
@@ -550,7 +556,6 @@ void i915_request_submit(struct i915_request *request)
 void __i915_request_unsubmit(struct i915_request *request)
 {
 	struct intel_engine_cs *engine = request->engine;
-	struct intel_timeline *timeline;
 
 	GEM_TRACE("%s fence %llx:%d <- global_seqno %d\n",
 		  request->engine->name,
@@ -578,12 +583,7 @@ void __i915_request_unsubmit(struct i915_request *request)
 	spin_unlock(&request->lock);
 
 	/* Transfer back from the global per-engine timeline to per-context */
-	timeline = request->timeline;
-	GEM_BUG_ON(timeline == engine->timeline);
-
-	spin_lock(&timeline->lock);
-	list_move(&request->link, &timeline->requests);
-	spin_unlock(&timeline->lock);
+	move_to_timeline(request, request->timeline);
 
 	/*
 	 * We don't need to wake_up any waiters on request->execute, they