ALC_SRAM_RX_FIFO_LEN
CSR_READ_4(sc, ALC_SRAM_RX_FIFO_LEN) * 8);
CSR_WRITE_4(sc, ALC_SRAM_RX_FIFO_LEN, 0x000002A0);
reg = CSR_READ_4(sc, ALC_SRAM_RX_FIFO_LEN);
reg = CSR_READ_4(sc, ALC_SRAM_RX_FIFO_LEN);