drm/i915/bdw: Implement WaSwitchSolVfFArbitrationPriority

GEN8 also needs this workaround.
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
[danvet: Add a generic comment that we need to recheck all these w/a.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -5188,6 +5188,12 @@ static void gen8_init_clock_gating(struct drm_device *dev)
 	I915_WRITE(WM3_LP_ILK, 0);
 	I915_WRITE(WM2_LP_ILK, 0);
 	I915_WRITE(WM1_LP_ILK, 0);
+
+	/* FIXME(BDW): Check all the w/a, some might only apply to
+	 * pre-production hw. */
+
+	/* WaSwitchSolVfFArbitrationPriority */
+	I915_WRITE(GAM_ECOCHK, I915_READ(GAM_ECOCHK) | HSW_ECOCHK_ARB_PRIO_SOL);
 }
 
 static void haswell_init_clock_gating(struct drm_device *dev)