1# $NetBSD: README.seagate,v 1.2 1998/01/05 07:31:07 perry Exp $ 2 3The hardware: 4 5The ST01/02, and Future Domain 950 are very simple SCSI controllers. They are 6not busmastering, so the processor must do all transfers a la IDE. They support 7blind transfer by adding wait states (up to a certain limit). Interrupt is 8generated for reconnect and parity errors (maybe also for some other events). 9 10The card consists of one command port that writes to scsi control lines, reads 11status lines, and a data port that read/writes to the 8 data lines. The address 12decoding gives both data and control ports large memory areas to a single 13port. This is used by the code. 14 15The ST01/02 differs from the FD950 in memory address location and SCSI id. 16 17Probing for the card: 18 19A card is recognized by comparing the BIOS signature with known signatures. A 20new card may not be recognized if the BIOS signature has changed. Please send 21new signatures to me. 22 23Driver function: 24 25A scsi command is sent to scsi_cmd function. The command is either placed in 26the queue or an retryable message is returned. The routine may wait for 27completion of the command depending on the supplied flags. A timer is started 28for every command placed in the queue. The commands are added in the order they 29are received. There is a possiblity to make all REQUEST SENSE commands be 30queued before all other commands, but I dont think it is a good thing (Linux 31do however use this). 32 33The card is mostly controlled by the sea_main function. It is called by 34scsi_cmd, the interrupt routine, and the timeout routine. The sea_main routine 35runs as long there are something to do (transfer data, issue queued commands, 36and handle reconnected commands). 37 38The data transfers may be done in two different ways: Blind and polled 39transfers. They differ in the way the driver does it handshaking with the 40target. During a blind transfer, the driver code blindly transfers a block 41of data without checking for changed phase. During polled transfers, the 42phase is checked between every character transfered. The polled transfers 43are always used for status information and command transfers. 44 45Because the card does not use dma in any way, there is no need to handle 46physical addresses. There is no problem with the isa-bus address limit of 4716MB, making bounce-buffers unnecessary. 48 49The data structures: 50 51Every card has a sea_softc structure keeping the queues of commands waiting to 52be issued, and commands currently disconnected. The type of card (Seagate or 53Future Domain), data and control port addresses, scsi id, busy flags for all 54possible targets, and interrupt vector for the card. 55 56Every scsi command to be issued are stored in a sea_scb structure. It contains 57a flag describing status/error of the command, current data buffer position, 58and number of bytes remaining to be transfered. 59 60 61PROBLEMS 62 63I have had problems getting the ST02 boot using the boot floppies. I think it 64is some problem with BIOS calls not working. It is unfortunately impossible to 65disconnect the ST02 floppy controller. 66 67I have had problem to get the driver talk to a 40 MB Seagate disk. I dont have 68access to it any more, so I can't do any more checks on that. 69 70NOTE: The ST02 creates its own description of the disk attached. This is not 71the same as the disk says. This translation problem may cause problems when 72sharing a disk between both DOS and BSD. It is however not impossible. 73