Tagged Queueing and Dque Bit

[Steven N. Hirsch]

On Tue, 6 Jan 1998, Klaus Steinberger wrote:

> 
> Hello,
> 
> 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.

Aha!!  Thanks for the hint.  I've been doing battle with an IBM S4W drive
which blows up on boot with the same messages you mention...  I'll give
this solution a try.


> 
> 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).
> 

I'd second that.

Steve