[4028] in linux-scsi channel archive
Re: SCSI Timeout on AIC7xxx when PPA is active.
daemon@ATHENA.MIT.EDU (David Campbell)
Thu May 28 19:23:43 1998
From: "David Campbell" <campbell@gear.torque.net>
To: Mark Garlanger <garlangr@cyberramp.net>
Date: Fri, 29 May 1998 07:21:12 +0000
CC: linux-scsi@vger.rutgers.edu
In-reply-to: <356D5187.48973FDF@cyberramp.net>
> Date: Thu, 28 May 1998 06:59:03 -0500
> From: Mark Garlanger <garlangr@cyberramp.net>
> To: David Campbell <campbell@gear.torque.net>
> Cc: linux-parport@torque.net, linux-scsi@vger.rutgers.edu
> Subject: Re: SCSI Timeout on AIC7xxx when PPA is active.
*snip*
> 1) Zip drive unplugged but driver still in the kernel
*snip*
SMP => OK
!SMP => OK (??)
> 2) Zip drive plugged in, turned on but no disk in drive
*snip*
SMP => Crash
!SMP => ????
> 3) Zip drive plugged in, turned on but with a disk in drive
*snip*
SMP => Crash
!SMP => ????
*light bulb over head*
The problem may reside in the the AIC7xxx driver. When *any* low level
driver completes a command then the mid-level driver checks *all* low
level drivers to see if they can accept another command.
Perhaps when ppa returns from a command it sees that the AIC7xxx is free
(incorrectly) and sends it a SCSI command which jams the queue (this
would fit the symptoms).
Another posibility is that ppa calls the completion function in an
interrupt (OK - software interrupt. tq_timer to be exact). The AIC7xxx may
receive its next instruction in this state and do something strange with
it.
I will take a quick peek at the AIC code, don't expect any miracles.
David Campbell
=======================================================
campbell@torque.net
"All parallel ports are equal - Some are more equal than others"
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