Messages in this thread | | | Date | Thu, 3 Sep 2009 09:36:00 +0100 | From | Russell King - ARM Linux <> | Subject | Re: How to efficiently handle DMA and cache on ARMv7 ? (was "Is get_user_pages() enough to prevent pages from being swapped out ?") |
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On Wed, Sep 02, 2009 at 06:10:44PM +0300, Imre Deak wrote: > To my understanding buffers returned by dma_alloc_*, kmalloc, vmalloc > are ok:
For dma_map_*, the only pages/addresses which are valid to pass are those returned by get_free_pages() or kmalloc. Everything else is not permitted.
Use of vmalloc'd and dma_alloc_* pages with the dma_map_* APIs is invalid use of the DMA API. See the notes in the DMA-mapping.txt document against "dma_map_single".
> For user mappings I think you'd have to do an additional flush for > the direct mapping, while the user mapping is flushed in dma_map_*.
I will not accept a patch which adds flushing of anything other than the kernel direct mapping in the dma_map_* functions, so please find a different approach.
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