Messages in this thread | | | Date | Fri, 20 Oct 2017 09:37:30 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH 5/9] PCI: host: brcmstb: add dma-ranges for inbound traffic |
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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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