I40E_PRTDCB_RPPMC_RX_FIFO_SIZE_MASK
reg &= ~I40E_PRTDCB_RPPMC_RX_FIFO_SIZE_MASK;
reg |= FIELD_PREP(I40E_PRTDCB_RPPMC_RX_FIFO_SIZE_MASK, fifo_size);