Re: 'Device not ready' issue on mpt2sas since 3.1.10

[Tejun Heo <tj@kernel.org>]

Hello, James.

On Wed, Jul 25, 2012 at 06:19:13PM +0400, James Bottomley wrote:
> > I haven't consulted SAT but it seems like a bug in SAS driver or
> > firmware.  If it's a driver bug, we better fix it there.  If a
> > firmware bug, working around those is one of major roles of drivers,
> > so I think setting allow_restart is fine.
> 
> Actually, I don't think so.  SAT-2 section 8.12.2 does say 
> 
>         if the device is in the stopped state as the result of
>         processing a START STOP UNIT command (see 9.11), then the SATL
>         shall terminate the TEST UNIT READY command with CHECK CONDITION
>         status with the sense key set to NOT READY and the additional
>         sense code of LOGICAL UNIT NOT READY, INITIALIZING COMMAND
>         REQUIRED;
> 
> START STOP UNIT (with START=0) translates to STANDBY IMMEDIATE, and
> that's what hdparm -y issues.  We don't see this in /drivers/ata because
> TEST UNIT READY always returns success.

Urgh... ATA device in standby mode is ready for any command and
definitely doesn't need an "initializing command".  Oh, well...

> So it looks like the mpt2sas SAT is doing the correct thing and we only
> don't see this problem in normal SATA devices because of a bug in the
> libata-scsi SAT.

libata is inconsistent with the standard but I think the standard is
wrong here. :(

Thanks.

-- 
tejun