From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from omx2-ext.sgi.com ([192.48.171.19]:9185 "EHLO omx2.sgi.com") by vger.kernel.org with ESMTP id S266048AbUIWTzI (ORCPT ); Thu, 23 Sep 2004 15:55:08 -0400 Date: Thu, 23 Sep 2004 12:55:01 -0700 From: Jeremy Higdon Subject: Re: [PATCH] I/O space write barrier Message-ID: <20040923195500.GA156548@sgi.com> References: <200409231448.21887.jbarnes@engr.sgi.com> <1095966238.3043.26.camel@mulgrave> <200409231507.26672.jbarnes@engr.sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200409231507.26672.jbarnes@engr.sgi.com> To: Jesse Barnes Cc: James Bottomley , linux-arch@vger.kernel.org List-ID: 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(®->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. Take a look at the 1.56 diffs in the scsi_misc-2.6 tree. jeremy