drm/i915/perf: disable NOA logic when not used

We already do it on Haswell and the documentation says it saves power.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170803165812.2373-5-lionel.g.landwerlin@intel.com

drivers/gpu/drm/i915/i915_perf.c

@@ -1827,6 +1827,10 @@ static void gen8_disable_metric_set(struct drm_i915_private *dev_priv)
 {
 	/* Reset all contexts' slices/subslices configurations. */
 	gen8_configure_all_contexts(dev_priv, NULL, false);
+
+	I915_WRITE(GDT_CHICKEN_BITS, (I915_READ(GDT_CHICKEN_BITS) &
+				      ~GT_NOA_ENABLE));
+
 }
 
 static void gen7_oa_enable(struct drm_i915_private *dev_priv)