OHCI1394_IsoRecvIntEventClear
reg_write(ohci, OHCI1394_IsoRecvIntEventClear, 0xffffffff);
iso_event = reg_read(ohci, OHCI1394_IsoRecvIntEventClear);
reg_write(ohci, OHCI1394_IsoRecvIntEventClear, iso_event);
reg_write(ohci, OHCI1394_IsoRecvIntEventClear, 1 << index);