AHCI_IS
AHCI_READ(sc, AHCI_GHC), AHCI_READ(sc, AHCI_IS),
AHCI_READ(sc, AHCI_GHC), AHCI_READ(sc, AHCI_IS),
AHCI_READ(sc, AHCI_GHC), AHCI_READ(sc, AHCI_IS),
AHCI_WRITE(sc, AHCI_IS, AHCI_READ(sc, AHCI_IS));
while ((is = AHCI_READ(sc, AHCI_IS))) {
AHCI_WRITE(sc, AHCI_IS, is);
AHCI_WRITE(sc, AHCI_IS, 1U << chp->ch_channel);