On 10/30/2015 10:09 AM, Joerg Roedel wrote:
On Fri, Oct 30, 2015 at 09:17:52AM +0800, Daniel Kurtz wrote:
Hmm, I thought the DMA API maps a (possibly) non-contiguous set of
memory pages into a contiguous block in device memory address space.
This would allow passing a dma mapped buffer to device dma using just
a device address and length.
If you are speaking of the dma_map_sg interface, than there is absolutly
no guarantee from the API side that the buffers you pass in will end up
mapped contiguously.
IOMMU drivers handle this differently, and when there is no IOMMU at all
there is also no way to map these buffers together.
That is what CMA is for ya know. It makes it physically contiguous.
Mark
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