drm/i915: Squelch nop wait-for-idle trace

If the system is already idle, omit the GEM_TRACE saying we are about to
wait for idle. It looks confusing in the logs to see a continual stream
of wait-for-idle, as one immediately assumes it is stuck in a loop.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Stuart Summers <stuart.summers@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190723091218.5886-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.c

@@ -951,15 +951,15 @@ wait_for_timelines(struct drm_i915_private *i915,
 int i915_gem_wait_for_idle(struct drm_i915_private *i915,
 			   unsigned int flags, long timeout)
 {
+	/* If the device is asleep, we have no requests outstanding */
+	if (!READ_ONCE(i915->gt.awake))
+		return 0;
+
 	GEM_TRACE("flags=%x (%s), timeout=%ld%s, awake?=%s\n",
 		  flags, flags & I915_WAIT_LOCKED ? "locked" : "unlocked",
 		  timeout, timeout == MAX_SCHEDULE_TIMEOUT ? " (forever)" : "",
 		  yesno(i915->gt.awake));
 
-	/* If the device is asleep, we have no requests outstanding */
-	if (!READ_ONCE(i915->gt.awake))
-		return 0;
-
 	timeout = wait_for_timelines(i915, flags, timeout);
 	if (timeout < 0)
 		return timeout;