RE: [PATCH v2 27/28] libsas: fix sas_find_local_phy(), take phy references

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> 
> On Tue, Dec 27, 2011 at 1:21 AM, Jack Wang <jack_wang@xxxxxxxxx> wrote:
> >>
> >> In the direct-attached case this routine returns the phy on which this
> >> device was first discovered.  Which is broken if we want to support
> >> wide-targets, as this phy reference can become stale even though the
> >> port is still active.
> >>
> >> In the expander-attached case this routine tries to lookup the phy by
> >> scanning the attached sas addresses of the parent expander, and BUG_ONs
> >> if it can't find it.  However since eh and the libsas workqueue run
> >> independently we can still be attempting device recovery via eh after
> >> libsas has recorded the device as detached.  This is even easier to hit
> >> now that eh is blocked while device domain rediscovery takes place, and
> >> that libata is fed more timed out commands increasing the chances that
> >> it will try to recover the ata device.
> >>
> >> Arrange for dev->phy to always point to a last known good phy, it may
be
> >> stale after the port is torn down, but it will catch up for wide port
> >> reconfigurations, and never be NULL.
> >>
> >> Q: How is pm8001_I_T_nexus_reset getting away with not performing reset
> >>    on direct attached sata devices?
> >>
> > [Jack Wang]
> > We found reset may lead to some SATA disks can not be found sometime, in
> > fact no only for direct attached sata devices.
> >
> > I wonder why we always reset the sata device when probe, for pm8001
direct
> > attached sata firmware will report Initial SATA FIS when phy ready.
> >
> 
> We need to get the drive to a known state.  Do these problems still
> happen in your tests with the "wait for ready" checking?  That's
> supposed to allow enough time for the signature fis to be transmitted.
> 
> I'll take a closer look at your libsas fix, because I believe we are
> still seeing failures to rediscover all attached devices even with
> these patches.
> 
> --
> Dan
[Jack Wang] 
I only test sata behind expander, will add lldd_ata_check_ready to have a
test later.



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