drm/i915: Wait first for submission, before waiting for request completion

In future patches, we will no longer be able to wait on a static global
seqno and instead have to break our wait up into phases. First we wait
for the global seqno assignment (upon submission to hardware), and once
submitted we wait for the hardware to complete.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161028125858.23563-25-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem_request.c

@@ -789,6 +789,49 @@ bool __i915_spin_request(const struct drm_i915_gem_request *req,
 	return false;
 }
 
+static long
+__i915_request_wait_for_submit(struct drm_i915_gem_request *request,
+			       unsigned int flags,
+			       long timeout)
+{
+	const int state = flags & I915_WAIT_INTERRUPTIBLE ?
+		TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE;
+	wait_queue_head_t *q = &request->i915->gpu_error.wait_queue;
+	DEFINE_WAIT(reset);
+	DEFINE_WAIT(wait);
+
+	if (flags & I915_WAIT_LOCKED)
+		add_wait_queue(q, &reset);
+
+	do {
+		prepare_to_wait(&request->submit.wait, &wait, state);
+
+		if (i915_sw_fence_done(&request->submit))
+			break;
+
+		if (flags & I915_WAIT_LOCKED &&
+		    i915_reset_in_progress(&request->i915->gpu_error)) {
+			__set_current_state(TASK_RUNNING);
+			i915_reset(request->i915);
+			reset_wait_queue(q, &reset);
+			continue;
+		}
+
+		if (signal_pending_state(state, current)) {
+			timeout = -ERESTARTSYS;
+			break;
+		}
+
+		timeout = io_schedule_timeout(timeout);
+	} while (timeout);
+	finish_wait(&request->submit.wait, &wait);
+
+	if (flags & I915_WAIT_LOCKED)
+		remove_wait_queue(q, &reset);
+
+	return timeout;
+}
+
 /**
  * i915_wait_request - wait until execution of request has finished
  * @req: the request to wait upon
@@ -833,6 +876,14 @@ long i915_wait_request(struct drm_i915_gem_request *req,
 
 	trace_i915_gem_request_wait_begin(req);
 
+	if (!i915_sw_fence_done(&req->submit)) {
+		timeout = __i915_request_wait_for_submit(req, flags, timeout);
+		if (timeout < 0)
+			goto complete;
+
+		GEM_BUG_ON(!i915_sw_fence_done(&req->submit));
+	}
+
 	/* Optimistic short spin before touching IRQs */
 	if (i915_spin_request(req, state, 5))
 		goto complete;