Received: with ECARTIS (v1.0.0; list netdev); Thu, 07 Jul 2005 20:09:49 -0700 (PDT) Received: from mail.dvmed.net (mail.dvmed.net [216.237.124.58]) by oss.sgi.com (8.12.10/8.12.10/SuSE Linux 0.7) with ESMTP id j6839kH9016488 for ; Thu, 7 Jul 2005 20:09:46 -0700 Received: from cpe-065-184-065-144.nc.res.rr.com ([65.184.65.144] helo=[10.10.10.88]) by mail.dvmed.net with esmtpsa (Exim 4.51 #1 (Red Hat Linux)) id 1DqjDi-0006qK-0i; Fri, 08 Jul 2005 03:08:07 +0000 Message-ID: <42CDEE12.5030100@pobox.com> Date: Thu, 07 Jul 2005 23:08:02 -0400 From: Jeff Garzik User-Agent: Mozilla Thunderbird 1.0.2-6 (X11/20050513) X-Accept-Language: en-us, en MIME-Version: 1.0 To: "David S. Miller" , raghavendra.koushik@neterion.com CC: akepner@sgi.com, netdev@oss.sgi.com, netdev@vger.kernel.org, ravinandan.arakali@neterion.com, leonid.grossman@neterion.com, rapuru.sriram@neterion.com Subject: Re: [PATCH 2.6.12.1 5/12] S2io: Performance improvements References: <200507080106.j6816NKP022996@guinness.s2io.com> <20050707.200034.74747399.davem@davemloft.net> In-Reply-To: <20050707.200034.74747399.davem@davemloft.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-archive-position: 2696 X-ecartis-version: Ecartis v1.0.0 Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com X-original-sender: jgarzik@pobox.com Precedence: bulk X-list: netdev Content-Length: 513 Lines: 17 David S. Miller wrote: > If you need a PIO to complete in a specific order, you > have to read it back. If you need PIO operations to occur Correct. A PCI read is the only way to ensure that all the CPU/PCI bridge buffers are flushed to the device. Whenever Arjan and I complain about "PCI posting" problems, we are indicating a need for additional readl() calls to ensure ordering/flushing. Delaying immediately after a writel() is a classic PCI posting mistake. Assuming ordering is another. Jeff