drm/i915/skl: Implement WaDisableSDEUnitClockGating:skl

Reviewed-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -68,6 +68,14 @@
 
 static void gen9_init_clock_gating(struct drm_device *dev)
 {
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	/*
+	 * WaDisableSDEUnitClockGating:skl
+	 * This seems to be a pre-production w/a.
+	 */
+	I915_WRITE(GEN8_UCGCTL6, I915_READ(GEN8_UCGCTL6) |
+		   GEN8_SDEUNIT_CLOCK_GATE_DISABLE);
 }
 
 static void i8xx_disable_fbc(struct drm_device *dev)