[997] in linux-scsi channel archive
Re: Buslogic 445S and iomega jaz drive
daemon@ATHENA.MIT.EDU (Leonard N. Zubkoff)
Fri Nov 22 15:21:59 1996
Date: Fri, 22 Nov 1996 12:18:53 -0800
From: "Leonard N. Zubkoff" <lnz@dandelion.com>
To: groudier@club-internet.fr
CC: dodson@redwood.mza.com, linux-scsi@vger.rutgers.edu
In-reply-to: <Pine.LNX.3.91.961122215205.113A-100000@localhost> (message from
Gerard Roudier on Fri, 22 Nov 1996 22:06:45 +0000 (GMT))
Date: Fri, 22 Nov 1996 22:06:45 +0000 (GMT)
From: Gerard Roudier <groudier@club-internet.fr>
On Thu, 21 Nov 1996, Leonard N. Zubkoff wrote:
> Sounds like the Jaz may have a buggy implementation of tagged queuing. You
> can disable tagged queuing entirely by booting with the command line
> "BusLogic=TQ:Disable", or just for target 4 with "BusLogic=TQ:YYYYN".
It has been reported to me that Jaz devices support tagged commands but
send REJECT messages in some situation, for example while spinning up.
That is a indeed a nasty implementation of tagged queuing, but it seems
not buggy, as we can read in scsi-2 specifications 6.8.2:
Tagged queuing may also be temporarily disabled internal to the SCSI
device during certain initialization periods or to control internal
resource utilization. During these periods the target may elect to
return QUEUE FULL status or it may respond to any queue tag message
with a MESSAGE REJECT message.
I would think both of those conditions should be handled correctly by the host
adapter's firmware. It's not really clear what has actually occurred between
the BT-445S firmware and the Jaz. It's quite possible the BT-445S firmware
gets confused in this situation. The BT-445S is rather long in the tooth now,
shall we say.
BusLogic reports "Abort Tag" to the driver. I donnot know the protocol
between driver and BusLogic controller, but the semantic of "Abort Tag"
seems to me correct.
The message you saw was the driver reporting that the old 3.37 firmware does
not generate the Abort Tag message, and so cannot abort a tagged command. It
had nothing to do with the Jaz returning an Abort Tag itself.
The ncr53c8xx driver does not a lot better than BusLogic one with Jaz
devices. The solution is to disable Tagged Command Queuing too.
I'm going to see if BusLogic has a Jaz around that I can test with more recent
host adapters.
Leonard
