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SubjectRe: RFC non barrier versions of dma_map functions
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On Mon, 04 Jan 2010 15:28:33 -0800
Abhijeet Dharmapurikar <adharmap@codeaurora.org> wrote:

> This is a request for extending the DMA api for efficient handling of
> multiple buffers or scatter gather mapping/unmapping operations.
>
> I am based on an ARMv7 device and we have a situation where we need
> to dma map multiple cached buffers for a single dma transaction.
>
> The current DMA api suggests the use of dma_map_single/
> dma_unmap_single for cache consistency. On ARMv7 it performs the
> necessary cache-operations and calls data sync barrier instruction
> (DSB). In our case we would be executing multiple DSB instructions
> before starting the dma operation - we need memory to be consistent
> only after we map the last buffer.

dma_map_sg? dma_map_sg requires the buffers to be consistent only
after it maps the last buffer, I think (I guess that you mean
'consistent' buffer is 'DMA ready' wrt cache).


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