drm/i915: Bump GT idling delay to 2 jiffies

In monitoring a transcode pipeline that is latency sensitive (it waits
between submitting frames, and each frame requires work on rcs/vcs/vecs
engines), it is found that it took longer than a single jiffy for it to
sustain its workload. Allowing an extra jiffy headroom for the userspace
prevents us from prematurely parking and having to exit powersaving
immediately.

Link: https://gitlab.freedesktop.org/drm/intel/-/issues/6284
Signed-off-by: Chris Wilson <[email protected]>
Signed-off-by: Karolina Drobnik <[email protected]>
Reviewed-by: Rodrigo Vivi <[email protected]>
Reviewed-by: Andi Shyti <[email protected]>
Signed-off-by: Rodrigo Vivi <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/e37911ec087a9ce50630d6faf61fa2c0d5f96d44.1657289332.git.karolina.drobnik@intel.com

Author: ickle

drivers/gpu/drm/i915/i915_active.c

@@ -974,7 +974,7 @@ void i915_active_acquire_barrier(struct i915_active *ref)
 
 		GEM_BUG_ON(!intel_engine_pm_is_awake(engine));
 		llist_add(barrier_to_ll(node), &engine->barrier_tasks);
-		intel_engine_pm_put_delay(engine, 1);
+		intel_engine_pm_put_delay(engine, 2);
 	}
 }