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From: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
To: Jim Quinlan <jim2101024-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>,
	Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>,
	linux-mips-6z/3iImG2C8G8FEW9MqTrA@public.gmane.org,
	Florian Fainelli
	<f.fainelli-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-pci <linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Kevin Cernekee <cernekee-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>,
	Ralf Baechle <ralf-6z/3iImG2C8G8FEW9MqTrA@public.gmane.org>,
	Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	bcm-kernel-feedback-list
	<bcm-kernel-feedback-list-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>,
	Gregory Fong
	<gregory.0xf0-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Catalin Marinas <catalin.marinas-5wv7dgnIgG8@public.gmane.org>,
	Bjorn Helgaas <bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	Brian Norris
	<computersforpeace-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	Marek Szyprowski
	<m.szyprowski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>,
	iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
Subject: Re: [PATCH 5/9] PCI: host: brcmstb: add dma-ranges for inbound traffic
Date: Fri, 20 Oct 2017 09:37:30 +0200	[thread overview]
Message-ID: <20171020073730.GA12937@lst.de> (raw)
In-Reply-To: <CANCKTBuaTD29My77QfOeUmtZfLAmmJXUYe6QvBW+uoH2Kb+tAQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.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.
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  parent reply	other threads:[~2017-10-20  7:37 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1507761269-7017-1-git-send-email-jim2101024@gmail.com>
     [not found] ` <1507761269-7017-6-git-send-email-jim2101024@gmail.com>
     [not found]   ` <1507761269-7017-6-git-send-email-jim2101024-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-10-12 18:04     ` [PATCH 5/9] PCI: host: brcmstb: add dma-ranges for inbound traffic Robin Murphy
2017-10-12 21:43       ` Jim Quinlan
2017-10-17  8:14       ` Christoph Hellwig
2017-10-17 16:11         ` Jim Quinlan
     [not found]           ` <CANCKTBsCB+x2XgrND9AhRtxPkCXfps1nA+YymkZjKHOUZfjSHQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-18  6:53             ` Christoph Hellwig
     [not found]               ` <20171018065316.GA11183-jcswGhMUV9g@public.gmane.org>
2017-10-18 14:41                 ` Jim Quinlan
     [not found]                   ` <CANCKTBv+yiCNsrnx3m+W9wPqC4NdKPZ2p=zLtSa8fX6v1rPcYQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-19  9:16                     ` Christoph Hellwig
2017-10-19 22:47                       ` Jim Quinlan
     [not found]                         ` <CANCKTBuaTD29My77QfOeUmtZfLAmmJXUYe6QvBW+uoH2Kb+tAQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-20  7:37                           ` Christoph Hellwig [this message]
     [not found]                             ` <20171020073730.GA12937-jcswGhMUV9g@public.gmane.org>
2017-10-20 14:41                               ` Jim Quinlan
2017-10-20 14:57                                 ` Christoph Hellwig
2017-10-20 15:27                                   ` Jim Quinlan
2017-10-20 16:17                                     ` Christoph Hellwig
     [not found]                                     ` <CANCKTBtxp9gSdndKAZ7xGA+VozQsn2PX_-9P8A22_5Matbb7-w-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-23  9:06                                       ` David Laight
     [not found]                                         ` <063D6719AE5E284EB5DD2968C1650D6DD009F05A-VkEWCZq2GCInGFn1LkZF6NBPR1lH4CV8@public.gmane.org>
2017-10-24 18:08                                           ` Jim Quinlan
2017-10-25  9:36                                             ` David Laight

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