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 09:37:30 +0200 Message-ID: <20171020073730.GA12937@lst.de> References: <1507761269-7017-1-git-send-email-jim2101024@gmail.com> <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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jim Quinlan Cc: Christoph Hellwig , Robin Murphy , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Mark Rutland , linux-mips-6z/3iImG2C8G8FEW9MqTrA@public.gmane.org, Florian Fainelli , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.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-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Marek Szyprowski , iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org List-Id: devicetree@vger.kernel.org On Thu, Oct 19, 2017 at 06:47:45PM -0400, Jim Quinlan wrote: > The only way to prevent this is to reserve a single page at the end of > the first memory region of any pair that are adjacent in physical > memory. A hack, yes, but I don't see an easier way out of this. Many > if not most of our boards do not have adjacent regions and would not > need this. dma mappings can be much larger than a single page. For the block world take a look at __blk_segment_map_sg which does the merging of contiguous pages into a single SG segment. You'd have to override BIOVEC_PHYS_MERGEABLE to prevent this from happening in your supported architectures for the block layer. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html