W5300_S0_RX_FIFO
fifo = w5300_read(priv, W5300_S0_RX_FIFO);
fifo = w5300_read(priv, W5300_S0_RX_FIFO);
fifo = w5300_read(priv, W5300_S0_RX_FIFO);
case W5300_S0_RX_FIFO: /* cannot read RX_FIFO */
rx_len = w5300_read(priv, W5300_S0_RX_FIFO);
w5300_read(priv, W5300_S0_RX_FIFO);