Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757529Ab1D2WzW (ORCPT ); Fri, 29 Apr 2011 18:55:22 -0400 Received: from gate.crashing.org ([63.228.1.57]:36613 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753363Ab1D2WzU (ORCPT ); Fri, 29 Apr 2011 18:55:20 -0400 Subject: Re: [Linaro-mm-sig] [RFC] ARM DMA mapping TODO, v1 From: Benjamin Herrenschmidt To: Jerome Glisse Cc: Thomas Hellstrom , Russell King - ARM Linux , Arnd Bergmann , linux-kernel@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-arm-kernel@lists.infradead.org In-Reply-To: References: <201104212129.17013.arnd@arndb.de> <20110428093039.GU17290@n2100.arm.linux.org.uk> <1304024836.2513.198.camel@pasglop> <201104291326.25634.arnd@arndb.de> <4DBAA9B4.3070306@vmware.com> Content-Type: text/plain; charset="UTF-8" Date: Sat, 30 Apr 2011 08:55:06 +1000 Message-ID: <1304117706.2513.269.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1190 Lines: 26 On Fri, 2011-04-29 at 09:34 -0400, Jerome Glisse wrote: > > Radeon memory controller can do non snooped pci transaction, as far as > i have tested most of the x86 pci bridge don't try to be coherent then > ie they don't analyze pci dma and ask for cpu flush they just perform > the request (and i guess it's what all bridge will do), so it endup > being noncoherent. I haven't done any benchmark of how faster it's for > the GPU when it's not snooping but i guess it can give 50% boost as it > likely drastictly reduce pci transaction overhead. > > I am talking here about device that you plug into any pci or pcie > slot, so it's not igp integrated into northbridge or into the cpu. Right, the card has nothing to do with the snooping process, it's purely a feature of the bridge, based on a flag optionally set by the card. As I said earlier, bridges have the freedom to ignore it, which we do on ppc, so that's a non issue. Cheers, Ben. -- 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/