Re: [PATCH v5 4/7] drivers: dma-coherent: Introduce default DMA pool

From	Christoph Hellwig <hch@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v5 4/7] drivers: dma-coherent: Introduce default DMA pool
Date	2017-06-26 11:50 +0200
Message-ID	<tWyOC-EC-7@gated-at.bofh.it> (permalink)
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On Thu, Jun 22, 2017 at 02:18:48PM +0100, Vladimir Murzin wrote:
> It is how it has been started [1] - defining memory which is not cacheable
> (i.e. suitable for coherent allocations) and building custom allocator on top
> of it, like it was done for c6x and blackfin. The annoying thing was that we
> needed to advertise such memory via command line parameter plus some "mem="
> adjustment to hide coherent memory from buddy allocator. So it was suggested
> to use reserved memory and this makes things look much better, but on the
> other hand require changes on dts side to "bind" devices with reserved memory
> - default DMA pool removes such drawback.

I like the idea in general, I'm just worried about the overlap with the
per-device coherent memory, especially when we have slight semantic
mismatches like the one about the physical (or rather dma) address
earlier.

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Re: [PATCH v5 4/7] drivers: dma-coherent: Introduce default DMA pool Christoph Hellwig <hch@infradead.org> - 2017-06-20 15:50 +0200
  Re: [PATCH v5 4/7] drivers: dma-coherent: Introduce default DMA pool Robin Murphy <robin.murphy@arm.com> - 2017-06-20 16:30 +0200
    Re: [PATCH v5 4/7] drivers: dma-coherent: Introduce default DMA pool Christoph Hellwig <hch@infradead.org> - 2017-06-26 11:50 +0200
      Re: [PATCH v5 4/7] drivers: dma-coherent: Introduce default DMA pool Vladimir Murzin <vladimir.murzin@arm.com> - 2017-06-26 16:10 +0200
      Re: [PATCH v5 4/7] drivers: dma-coherent: Introduce default DMA pool Robin Murphy <robin.murphy@arm.com> - 2017-06-27 16:40 +0200
        Re: [PATCH v5 4/7] drivers: dma-coherent: Introduce default DMA pool Christoph Hellwig <hch@infradead.org> - 2017-06-27 17:30 +0200
  Re: [PATCH v5 4/7] drivers: dma-coherent: Introduce default DMA pool Vladimir Murzin <vladimir.murzin@arm.com> - 2017-06-22 15:20 +0200
    Re: [PATCH v5 4/7] drivers: dma-coherent: Introduce default DMA pool Christoph Hellwig <hch@infradead.org> - 2017-06-26 11:50 +0200

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