AHCI_REG_IS
is = ahci_read(sc, AHCI_REG_IS);
ahci_write(sc, AHCI_REG_IS, ack);
ahci_write(sc, AHCI_REG_IS, ahci_read(sc, AHCI_REG_IS));
ahci_write(sc, AHCI_REG_IS, 1 << port);
ahci_write(sc, AHCI_REG_IS, 1 << port);
ahci_write(sc, AHCI_REG_IS, 1 << port);
ahci_write(sc, AHCI_REG_IS, 1 << port);