VLV_REF_DW13
reg_val = vlv_dpio_read(dev_priv, pipe, VLV_REF_DW13);
vlv_dpio_write(dev_priv, pipe, VLV_REF_DW13, reg_val);
reg_val = vlv_dpio_read(dev_priv, pipe, VLV_REF_DW13);
vlv_dpio_write(dev_priv, pipe, VLV_REF_DW13, reg_val);