XGBE_TSTAMP_SSINC
XGMAC_IOWRITE_BITS(pdata, MAC_SSIR, SSINC, XGBE_TSTAMP_SSINC);
#define XGBE_PTP_ACT_CLK_FREQ (NSEC_PER_SEC / XGBE_TSTAMP_SSINC)