73 lines
3.3 KiB
Plaintext
73 lines
3.3 KiB
Plaintext
# $NetBSD: README.seagate,v 1.3 2003/05/03 18:11:25 wiz Exp $
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The hardware:
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The ST01/02, and Future Domain 950 are very simple SCSI controllers. They are
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not busmastering, so the processor must do all transfers a la IDE. They support
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blind transfer by adding wait states (up to a certain limit). Interrupt is
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generated for reconnect and parity errors (maybe also for some other events).
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The card consists of one command port that writes to scsi control lines, reads
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status lines, and a data port that read/writes to the 8 data lines. The address
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decoding gives both data and control ports large memory areas to a single
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port. This is used by the code.
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The ST01/02 differs from the FD950 in memory address location and SCSI id.
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Probing for the card:
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A card is recognized by comparing the BIOS signature with known signatures. A
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new card may not be recognized if the BIOS signature has changed. Please send
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new signatures to me.
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Driver function:
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A scsi command is sent to scsi_cmd function. The command is either placed in
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the queue or an retryable message is returned. The routine may wait for
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completion of the command depending on the supplied flags. A timer is started
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for every command placed in the queue. The commands are added in the order they
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are received. There is a possiblity to make all REQUEST SENSE commands be
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queued before all other commands, but I dont think it is a good thing (Linux
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do however use this).
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The card is mostly controlled by the sea_main function. It is called by
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scsi_cmd, the interrupt routine, and the timeout routine. The sea_main routine
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runs as long there are something to do (transfer data, issue queued commands,
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and handle reconnected commands).
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The data transfers may be done in two different ways: Blind and polled
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transfers. They differ in the way the driver does it handshaking with the
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target. During a blind transfer, the driver code blindly transfers a block
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of data without checking for changed phase. During polled transfers, the
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phase is checked between every character transfered. The polled transfers
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are always used for status information and command transfers.
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Because the card does not use DMA in any way, there is no need to handle
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physical addresses. There is no problem with the isa-bus address limit of
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16MB, making bounce-buffers unnecessary.
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The data structures:
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Every card has a sea_softc structure keeping the queues of commands waiting to
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be issued, and commands currently disconnected. The type of card (Seagate or
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Future Domain), data and control port addresses, scsi id, busy flags for all
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possible targets, and interrupt vector for the card.
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Every scsi command to be issued are stored in a sea_scb structure. It contains
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a flag describing status/error of the command, current data buffer position,
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and number of bytes remaining to be transfered.
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PROBLEMS
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I have had problems getting the ST02 boot using the boot floppies. I think it
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is some problem with BIOS calls not working. It is unfortunately impossible to
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disconnect the ST02 floppy controller.
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I have had problem to get the driver talk to a 40 MB Seagate disk. I dont have
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access to it any more, so I can't do any more checks on that.
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NOTE: The ST02 creates its own description of the disk attached. This is not
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the same as the disk says. This translation problem may cause problems when
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sharing a disk between both DOS and BSD. It is however not impossible.
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