Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752423Ab0LHEzt (ORCPT ); Tue, 7 Dec 2010 23:55:49 -0500 Received: from mail-iw0-f172.google.com ([209.85.214.172]:42981 "EHLO mail-iw0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751438Ab0LHEzs (ORCPT ); Tue, 7 Dec 2010 23:55:48 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=lRUpT8hpplqDIqYztv50JAx5GOZ02YC8fFR5sv4jYqAhGsmPp8FN5BNWzQQ/snG0NS dQCHdEWQNjJllFMPe8B9NlaV77XedaFo12hZOQqsPedTiXNCcjLIpT2R1qxk+zilWUzd NfNRCNw80hAgjy6V2ols2crAEqAyQcC3lCndQ= MIME-Version: 1.0 In-Reply-To: <597621.83948.qm@web31707.mail.mud.yahoo.com> References: <712019.56679.qm@web31702.mail.mud.yahoo.com> <4CFEE38E.3020500@gmail.com> <597621.83948.qm@web31707.mail.mud.yahoo.com> Date: Tue, 7 Dec 2010 22:55:47 -0600 Message-ID: Subject: Re: Posted Write onto a PCI end point device using Linux From: Robert Hancock To: Sanka Piyaratna Cc: linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1607 Lines: 46 On Tue, Dec 7, 2010 at 9:57 PM, Sanka Piyaratna wrote: > Hi Robert, > Could you please tell me how I can initiate a posted write towards a PCIe > endpoint with larger than 32 bit payload using Linux? > Thanks and regards, You can try writeq to get a 64-bit payload, but I don't think it's available on all platforms. In particular with a 32-bit CPU, it may not be possible at all. If you need to send bigger payloads then you need to use DMA. > > Sanka Piyaratna > > ________________________________ > From: Robert Hancock > To: Sanka Piyaratna > Cc: linux-kernel@vger.kernel.org > Sent: Wed, 8 December, 2010 12:16:54 PM > Subject: Re: Posted Write onto a PCI end point device using Linux > > On 12/07/2010 05:29 AM, Sanka Piyaratna wrote: >> Hi, >> >> >> I am wondering whether it is possible to issue a posted write using the >> host >> computer's root complex towards an PCI express end point. I have done this >> using >> >> DMA in the past. However, if posted writes are possible that would save a >> lot of >> >> time and effort and would be quicker too. > > Writes from the CPU to PCI memory are always posted. However, the posted > write buffer size is usually quite limited and so this probably will > still cause CPU overhead when writing any significant amount of data > this way. > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/