Re: SCSI QLA not working on latest *-mm SN2

Jesse Barnes
2004-09-21T16:18:29Z

On Tuesday, September 21, 2004 12:11 pm, James Bottomley wrote:
> On Tue, 2004-09-21 at 12:05, Jesse Barnes wrote:
> > Reading from the closest bridge won't be enough? If not, then dealing
> > with posting in a nice way is simply impossible for some devices. We'd
> > be stuck with udelay().
>
> That's correct. The posted write is held somewhere in one of the
> bridges, but the PCI ordering rules only require it to be ordered with
> other MMIO reads to the *device*; so you only guarantee that the posted
> write is flushed by doing a device read....obviously, there exist
> bridges with looser ideas than this, but we need to follow the PCI
> specs.
>
> udelay() isn't a viable solution because the PCI specs have no upper
> bound on the length of time a write may remain posted.

Well then. Sounds like we're hosed for the qla2xxx case at least. I think we
still need pioflush for the case of writes from different CPUs (described in
the document). Using it *should* make the window pretty small for qla2xxx
type problems too, but we have no guarantee.

Jesse