drm/i915/bxt: Add WaForceContextSaveRestoreNonCoherent

Note that we also need this for skl.
Signed-off-by: Nick Hoath <nicholas.hoath@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
[danvet: Note that we also need this for skl, requested by Imre.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -1057,6 +1057,10 @@ static int bxt_init_workarounds(struct intel_engine_cs *ring)
 			GEN7_SBE_SS_CACHE_DISPATCH_PORT_SHARING_DISABLE);
 	}
 
+	/* WaForceContextSaveRestoreNonCoherent:bxt */
+	WA_SET_BIT_MASKED(HDC_CHICKEN0,
+			  HDC_FORCE_CONTEXT_SAVE_RESTORE_NON_COHERENT);
+
 	return 0;
 }