Re: [PATCH v3] ad7877: keep dma rx buffers in seperate cache lines

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Mike Frysinger wrote:
On Tue, May 11, 2010 at 16:38, Pekka Enberg wrote:
Mike Frysinger wrote:
that is a question for David/Grant.  i'm not the SPI core maintainer,
i'm merely watching over some SPI drivers.  however, this answer also
doesnt sound like it's thinking big enough because what you're
proposing isnt specific to the SPI bus -- any time a DMA safe buffer
is needed dynamically, this function could be used.
Well, we have dma_alloc_coherent(), shouldn't you be using that instead?

my understanding is that dma_alloc_coherent() gives you a buffer that
is always coherent.  the SPI layers take care of flushing and such on
the fly which means allocating coherent memory is overkill and bad for
performance.

OK, I'm out of my expert area here but if dma_alloc_coherent() doesn't work for you, you should probably extend the DMA API, not kmalloc().

			Pekka
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