dma_alloc_coherent versus streaming DMA, neither works satisfactory

[arnd@arndb.de (Arnd Bergmann)]

On Thursday 23 April 2015 13:52:34 Mike Looijmans wrote:
> Can anyone here offer some advise on this?
> 

The problem you are experiencing is a direct result of using hardware
without cache-coherency from user space. There is no software workaround
for this: If you want data to be cacheable *and* avoid doing manual cache
flushes each time data is passed between user space and hardware, you have
to use hardware that is cache-coherent.

You mentioned that you are using 'Zynq', which supports cache-coherent
DMA using the 'accelerator coherency port'. If you are able to connect
your device to that port, it should work, otherwise you should consider
using a different platform.

	Arnd