XGMAC_FIFO_MIN_ALLOC
BUILD_BUG_ON_NOT_POWER_OF_2(XGMAC_FIFO_MIN_ALLOC);
fifo[i] = (XGMAC_FIFO_MIN_ALLOC / XGMAC_FIFO_UNIT) - 1;
fifo_size -= XGMAC_FIFO_MIN_ALLOC;