From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937157AbYEBWk4 (ORCPT ); Fri, 2 May 2008 18:40:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932498AbYEBWkr (ORCPT ); Fri, 2 May 2008 18:40:47 -0400 Received: from mail0.lsil.com ([147.145.40.20]:54178 "EHLO mail0.lsil.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759690AbYEBWkr convert rfc822-to-8bit (ORCPT ); Fri, 2 May 2008 18:40:47 -0400 X-MimeOLE: Produced By Microsoft Exchange V6.5 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT Subject: HELP: Is writeq an atomic operation?? Date: Fri, 2 May 2008 16:40:40 -0600 Message-ID: <0631C836DBF79F42B5A60C8C8D4E822901047B2F@NAMAIL2.ad.lsil.com> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: HELP: Is writeq an atomic operation?? thread-index: AcispYybFejKsZY7TdKOeQIP2NgymA== From: "Moore, Eric" To: X-OriginalArrivalTime: 02 May 2008 22:40:41.0288 (UTC) FILETIME=[8CDC2C80:01C8ACA5] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Is a 64bit write to MMIO registers an atomic operation when using the writeq API? My concern is when I send 64bit data via writeq, will it be sent out as two 32 bit writes? If so, is it possible that another CPU be sending the data at the same time. Meaning can I write the 1st 32bit data from CPU-A, meanwhile CPU-B is writing his 32bit data at the same time, and CPU-A didn't complete the full 64bit in one shot. If this could occur, is there an API that I can use to make sure the entire data sent in one atomic operation? Here is a trace from pci express analyzer. I'm sending 0x0800010000000000 to the adress DD1400C0 using writeq. Notice that in the TLP header it sent a 32bit Memory write with data length of two. Trace follows: Link Tra(597) Downstream 2.5(x1) TLP(1992) Mem MWr(32)(10:00000) TC(0) TD(0) _______| EP(0) Attributes(01) Length(2) RequesterID(000:02:0) Tag(8) _______| Address(DD1400C0) 1st BE(1111) Last BE(1111) Data(08000100 00000000) _______| VC ID(0) Explicit ACK(Packet #1195) Metrics # Packets(2) _______| Time Stamp(0003 . 120 181 840 s)