drm/i915: Reserve some priority bits for internal use

In the next few patches, we will want to give a small priority boost to
some requests/queues but not so much that we perturb the user controlled
order. As such we will shift the user priority bits higher leaving
ourselves a few low priority bits for our internal bumping.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181001123204.23982-3-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_scheduler.h

@@ -19,6 +19,12 @@ enum {
 	I915_PRIORITY_INVALID = INT_MIN
 };
 
+#define I915_USER_PRIORITY_SHIFT 0
+#define I915_USER_PRIORITY(x) ((x) << I915_USER_PRIORITY_SHIFT)
+
+#define I915_PRIORITY_COUNT BIT(I915_USER_PRIORITY_SHIFT)
+#define I915_PRIORITY_MASK (I915_PRIORITY_COUNT - 1)
+
 struct i915_sched_attr {
 	/**
 	 * @priority: execution and service priority