AHCI_P_FB
AHCI_READ(sc, AHCI_P_FB(chp->ch_channel)),
AHCI_READ(sc, AHCI_P_FB(chp->ch_channel)),
AHCI_READ(sc, AHCI_P_FB(chp->ch_channel)),
AHCI_WRITE(sc, AHCI_P_FB(i), BUS_ADDR_LO32(achp->ahcic_bus_rfis));