From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 5/9] PCI: host: brcmstb: add dma-ranges for inbound traffic Date: Fri, 20 Oct 2017 16:57:52 +0200 Message-ID: <20171020145752.GA4694@lst.de> References: <1507761269-7017-6-git-send-email-jim2101024@gmail.com> <589c04cb-061b-a453-3188-79324a02388e@arm.com> <20171017081422.GA19475@lst.de> <20171018065316.GA11183@lst.de> <20171019091644.GA14983@lst.de> <20171020073730.GA12937@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-pci-owner@vger.kernel.org To: Jim Quinlan Cc: Christoph Hellwig , Robin Murphy , linux-kernel@vger.kernel.org, Mark Rutland , Linux-MIPS , Florian Fainelli , devicetree@vger.kernel.org, linux-pci , Kevin Cernekee , Will Deacon , Ralf Baechle , Rob Herring , bcm-kernel-feedback-list , Gregory Fong , Catalin Marinas , Bjorn Helgaas , Brian Norris , linux-arm-kernel@lists.infradead.org, Marek Szyprowski , iommu@lists.linux-foun List-Id: iommu@lists.linux-foundation.org On Fri, Oct 20, 2017 at 10:41:56AM -0400, Jim Quinlan wrote: > I am not sure I understand your comment -- the size of the request > shouldn't be a factor. Let's look at your example of the DMA request > of 3fffff00 to 4000000f (physical memory). Lets say it is for 15 > pages. If we block out the last page [0x3ffff000..0x3fffffff] from > what is available, there is no 15 page span that can happen across the > 0x40000000 boundary. For SG, there can be no merge that connects a > page from one region to another region. Can you give an example of > the scenario you are thinking of? What prevents a merge from say the regions of 0....3fffffff and 40000000....7fffffff? From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Fri, 20 Oct 2017 16:58:02 +0200 (CEST) Received: from verein.lst.de ([213.95.11.211]:39132 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S23992181AbdJTO5zYSI6Q (ORCPT ); Fri, 20 Oct 2017 16:57:55 +0200 Received: by newverein.lst.de (Postfix, from userid 2407) id 823FB7FC80; Fri, 20 Oct 2017 16:57:52 +0200 (CEST) Date: Fri, 20 Oct 2017 16:57:52 +0200 From: Christoph Hellwig To: Jim Quinlan Cc: Christoph Hellwig , Robin Murphy , linux-kernel@vger.kernel.org, Mark Rutland , Linux-MIPS , Florian Fainelli , devicetree@vger.kernel.org, linux-pci , Kevin Cernekee , Will Deacon , Ralf Baechle , Rob Herring , bcm-kernel-feedback-list , Gregory Fong , Catalin Marinas , Bjorn Helgaas , Brian Norris , linux-arm-kernel@lists.infradead.org, Marek Szyprowski , iommu@lists.linux-foundation.org Subject: Re: [PATCH 5/9] PCI: host: brcmstb: add dma-ranges for inbound traffic Message-ID: <20171020145752.GA4694@lst.de> References: <1507761269-7017-6-git-send-email-jim2101024@gmail.com> <589c04cb-061b-a453-3188-79324a02388e@arm.com> <20171017081422.GA19475@lst.de> <20171018065316.GA11183@lst.de> <20171019091644.GA14983@lst.de> <20171020073730.GA12937@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 60507 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: hch@lst.de Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips On Fri, Oct 20, 2017 at 10:41:56AM -0400, Jim Quinlan wrote: > I am not sure I understand your comment -- the size of the request > shouldn't be a factor. Let's look at your example of the DMA request > of 3fffff00 to 4000000f (physical memory). Lets say it is for 15 > pages. If we block out the last page [0x3ffff000..0x3fffffff] from > what is available, there is no 15 page span that can happen across the > 0x40000000 boundary. For SG, there can be no merge that connects a > page from one region to another region. Can you give an example of > the scenario you are thinking of? What prevents a merge from say the regions of 0....3fffffff and 40000000....7fffffff? From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: Date: Fri, 20 Oct 2017 16:57:52 +0200 From: Christoph Hellwig To: Jim Quinlan Subject: Re: [PATCH 5/9] PCI: host: brcmstb: add dma-ranges for inbound traffic Message-ID: <20171020145752.GA4694@lst.de> References: <1507761269-7017-6-git-send-email-jim2101024@gmail.com> <589c04cb-061b-a453-3188-79324a02388e@arm.com> <20171017081422.GA19475@lst.de> <20171018065316.GA11183@lst.de> <20171019091644.GA14983@lst.de> <20171020073730.GA12937@lst.de> MIME-Version: 1.0 In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Linux-MIPS , Florian Fainelli , devicetree@vger.kernel.org, linux-pci , Kevin Cernekee , Will Deacon , linux-kernel@vger.kernel.org, Ralf Baechle , iommu@lists.linux-foundation.org, Rob Herring , bcm-kernel-feedback-list , Gregory Fong , Catalin Marinas , Bjorn Helgaas , Brian Norris , Robin Murphy , Christoph Hellwig , linux-arm-kernel@lists.infradead.org, Marek Szyprowski Content-Type: text/plain; charset="us-ascii" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+bjorn=helgaas.com@lists.infradead.org List-ID: On Fri, Oct 20, 2017 at 10:41:56AM -0400, Jim Quinlan wrote: > I am not sure I understand your comment -- the size of the request > shouldn't be a factor. Let's look at your example of the DMA request > of 3fffff00 to 4000000f (physical memory). Lets say it is for 15 > pages. If we block out the last page [0x3ffff000..0x3fffffff] from > what is available, there is no 15 page span that can happen across the > 0x40000000 boundary. For SG, there can be no merge that connects a > page from one region to another region. Can you give an example of > the scenario you are thinking of? What prevents a merge from say the regions of 0....3fffffff and 40000000....7fffffff? _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel From mboxrd@z Thu Jan 1 00:00:00 1970 From: hch@lst.de (Christoph Hellwig) Date: Fri, 20 Oct 2017 16:57:52 +0200 Subject: [PATCH 5/9] PCI: host: brcmstb: add dma-ranges for inbound traffic In-Reply-To: References: <1507761269-7017-6-git-send-email-jim2101024@gmail.com> <589c04cb-061b-a453-3188-79324a02388e@arm.com> <20171017081422.GA19475@lst.de> <20171018065316.GA11183@lst.de> <20171019091644.GA14983@lst.de> <20171020073730.GA12937@lst.de> Message-ID: <20171020145752.GA4694@lst.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Oct 20, 2017 at 10:41:56AM -0400, Jim Quinlan wrote: > I am not sure I understand your comment -- the size of the request > shouldn't be a factor. Let's look at your example of the DMA request > of 3fffff00 to 4000000f (physical memory). Lets say it is for 15 > pages. If we block out the last page [0x3ffff000..0x3fffffff] from > what is available, there is no 15 page span that can happen across the > 0x40000000 boundary. For SG, there can be no merge that connects a > page from one region to another region. Can you give an example of > the scenario you are thinking of? What prevents a merge from say the regions of 0....3fffffff and 40000000....7fffffff?