drm/i915: unconditionally use mt forcewake on hsw/ivb

Single-threaded forcewake was only used on some early pre-production
ivybridge machines, all the latest ones should use mt forcewake. And
we already assume this in other places of the code (e.g. DERRMR
support in the ddx, or the latest intel_gt_reset patch to reset any
lingering forcewake references left behind by the bios), so don't
bother here, too.
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -4146,35 +4146,12 @@ void intel_gt_init(struct drm_device *dev)
 	if (IS_VALLEYVIEW(dev)) {
 		dev_priv->gt.force_wake_get = vlv_force_wake_get;
 		dev_priv->gt.force_wake_put = vlv_force_wake_put;
-	} else if (INTEL_INFO(dev)->gen >= 6) {
+	} else if (IS_IVYBRIDGE(dev) || IS_HASWELL(dev)) {
+		dev_priv->gt.force_wake_get = __gen6_gt_force_wake_mt_get;
+		dev_priv->gt.force_wake_put = __gen6_gt_force_wake_mt_put;
+	} else if (IS_GEN6(dev)) {
 		dev_priv->gt.force_wake_get = __gen6_gt_force_wake_get;
 		dev_priv->gt.force_wake_put = __gen6_gt_force_wake_put;
-
-		/* IVB configs may use multi-threaded forcewake */
-		if (IS_IVYBRIDGE(dev) || IS_HASWELL(dev)) {
-			u32 ecobus;
-
-			/* A small trick here - if the bios hasn't configured
-			 * MT forcewake, and if the device is in RC6, then
-			 * force_wake_mt_get will not wake the device and the
-			 * ECOBUS read will return zero. Which will be
-			 * (correctly) interpreted by the test below as MT
-			 * forcewake being disabled.
-			 */
-			mutex_lock(&dev->struct_mutex);
-			__gen6_gt_force_wake_mt_get(dev_priv);
-			ecobus = I915_READ_NOTRACE(ECOBUS);
-			__gen6_gt_force_wake_mt_put(dev_priv);
-			mutex_unlock(&dev->struct_mutex);
-
-			if (ecobus & FORCEWAKE_MT_ENABLE) {
-				DRM_DEBUG_KMS("Using MT version of forcewake\n");
-				dev_priv->gt.force_wake_get =
-					__gen6_gt_force_wake_mt_get;
-				dev_priv->gt.force_wake_put =
-					__gen6_gt_force_wake_mt_put;
-			}
-		}
 	}
 }