FSL_XCVR_FIFO_WMK_TX
val |= FSL_XCVR_EXT_CTRL_TX_FWM(FSL_XCVR_FIFO_WMK_TX);
#define FSL_XCVR_MAXBURST_TX (FSL_XCVR_FIFO_WMK_TX >> 2) /* 16 */