E1000_FCRTL_XONE
E1000_WRITE_REG(hw, FCRTL, (hw->fc_low_water | E1000_FCRTL_XONE));
E1000_WRITE_REG(hw, FCRTL, (FC_DEFAULT_LO_THRESH | E1000_FCRTL_XONE));
fcrtl |= E1000_FCRTL_XONE;