Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755855Ab0LHPXH (ORCPT ); Wed, 8 Dec 2010 10:23:07 -0500 Received: from mail-gx0-f180.google.com ([209.85.161.180]:51447 "EHLO mail-gx0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755285Ab0LHPXF convert rfc822-to-8bit (ORCPT ); Wed, 8 Dec 2010 10:23:05 -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:content-transfer-encoding; b=wjsyOkr/F1xvVJ/fOGkQ9pvnDUED81VoPCGQ9Mj/oK3iIL+MM/dQqX8RwxXkw1o98o fqxUqRV5yglUSsYqItgtwKFex7jbOfCAyIL8tax4ZXJk9qKHi34Stl6UFvba8iPsIPnc f3BdccIkkSOcncObuKGB1vpcj5UEI61cDbPIM= MIME-Version: 1.0 In-Reply-To: <241570.15232.qm@web31708.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> <241570.15232.qm@web31708.mail.mud.yahoo.com> Date: Wed, 8 Dec 2010 09:23:04 -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 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2253 Lines: 71 On Wed, Dec 8, 2010 at 12:05 AM, Sanka Piyaratna wrote: > Thanks for that Robert. When you say DMA, this has to be implemented at the > endpoint device doesn't it? There is no DMA mode on the CPU for doing this is > there? No, there's not (on typical hardware, anyway). > > ?Sanka Piyaratna > > > > > ________________________________ > From: Robert Hancock > To: Sanka Piyaratna > Cc: linux-kernel@vger.kernel.org > Sent: Wed, 8 December, 2010 3:25:47 PM > Subject: Re: Posted Write onto a PCI end point device using Linux > > 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/