Tagged Queueing and Dque Bit

Klaus Steinberger Klaus.Steinberger at Physik.Uni-Muenchen.DE
Tue Jan 6 03:24:02 PST 1998


I have now some boxes running Linux 2.0.33 (aic driver version 4.1.1/3.2.1).
I now have tagged queueing enabled as suggested and it works rock solid.

But with one box it didn't work, until I figured out that the drive
claims to have tagged queueing, but has the Dque bit set to one 
in the control mode page (Dque inhibits tagged queueing).

The driver did time outs and gave me error messages that there is no
active SCB for this drive.

Attached devices: 
Host: scsi0 Channel: 00 Id: 01 Lun: 00
  Vendor: SGI      Model: IBMDSAS-3540     Rev: S47K
  Type:   Direct-Access                    ANSI SCSI revision: 02

After I figured out the Dque bit, and reset it to zero, it worked flawlessly
with tagged queueing enabled.

So I would suggest, that the driver should check also the Control Mode
Page (if available), and should honor the Dque bit (fall back to not use 
tagged queueing if Dque is set).

Klaus Steinberger               Beschleunigerlabor der TU und LMU Muenchen
Phone: (+49 89)289 14287        Hochschulgelaende, D-85748 Garching, Germany
FAX:   (+49 89)289 14280        EMail: Klaus.Steinberger at Physik.Uni-Muenchen.DE
URL: http://www.bl.physik.tu-muenchen.de/~k2/
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