[996] in linux-scsi channel archive
Re: Buslogic 445S and iomega jaz drive
daemon@ATHENA.MIT.EDU (Gerard Roudier)
Fri Nov 22 15:10:35 1996
Date: Fri, 22 Nov 1996 22:06:45 +0000 (GMT)
From: Gerard Roudier <groudier@club-internet.fr>
To: "Leonard N. Zubkoff" <lnz@dandelion.com>
cc: dodson@redwood.mza.com, linux-scsi@vger.rutgers.edu
In-Reply-To: <199611220744.XAA06512@dandelion.com>
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.
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 ncr53c8xx driver does not a lot better than BusLogic one with Jaz
devices. The solution is to disable Tagged Command Queuing too.
Gerard.
