From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: SCSI QLA not working on latest *-mm SN2 Date: 21 Sep 2004 12:11:10 -0400 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <1095783077.2467.145.camel@mulgrave> References: <20040917183029.GW642@parcelfarce.linux.theplanet.co.uk> <200409211158.25122.jbarnes@engr.sgi.com> <20040921160119.GB642@parcelfarce.linux.theplanet.co.uk> <200409211205.22575.jbarnes@engr.sgi.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from stat16.steeleye.com ([209.192.50.48]:64703 "EHLO hancock.sc.steeleye.com") by vger.kernel.org with ESMTP id S267748AbUIUQLz (ORCPT ); Tue, 21 Sep 2004 12:11:55 -0400 In-Reply-To: <200409211205.22575.jbarnes@engr.sgi.com> List-Id: linux-scsi@vger.kernel.org To: Jesse Barnes Cc: Matthew Wilcox , Grant Grundler , Andrew Vasquez , pj@sgi.com, SCSI Mailing List , mdr@cthulhu.engr.sgi.com, jeremy@cthulhu.engr.sgi.com, djh@cthulhu.engr.sgi.com, Andrew Morton 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. James