Re: [PATCH] I/O space write barrier

[Jesse Barnes <jbarnes@engr.sgi.com>]

On Thursday, September 23, 2004 3:55 pm, Jeremy Higdon wrote:
> On Thu, Sep 23, 2004 at 03:07:26PM -0400, Jesse Barnes wrote:
> > On Thursday, September 23, 2004 3:03 pm, James Bottomley wrote:
> > > On Thu, 2004-09-23 at 14:48, Jesse Barnes wrote:
> > > > - RD_REG_WORD(&reg->ictrl); /* PCI Posted Write flush */
> > > > + mmiowb(); /* make sure this write arrives before any others */
> > >
> > > What's going on here?  In your docs you say this mmiowb() is explicitly
> > > to prevent write ordering problems and doesn't affect posting.  However
> > > in this patch you're using it to replace a posting flush read.
> >
> > Jeremy was the one that added these, I think the comment is misleading
> > and only ordering was intended.  If that's not the case I'll drop this
> > bit.
>
> No, I didn't add those.  In fact, I thought them to be unnecessary.  Jes
> added them, I believe.  I added the reads after the writes of
> req_ring_index to mailbox4.  Since at the time we did not have a write
> ordering function, I had to use the heavy weight flush.

Ok, sorry for the misattribution :).  At any rate, I've already dropped that 
bit.

Jesse