sk.syed2 wrote:

quoted

I have looked at the code for dma_alloc_coherent etc and it seems to me that
it's returning null because there isn't the space available to allocate the
requested memory.

You might have to increase the consistent(or dma) memory size. In
recent kernels its defined by  CONSISTENT_DMA_SIZE
(ach/arm/include/asm/memory.h). Which kernel version are you using?
You might have to override this value to match your needs. Are there
any other drivers that allocate using dma_alloc_coherent?

Oh, awesome! This was it, I'm using kernel version 2.6.37 and changing 
CONSISTENT_DMA_SIZE for arm has allowed me to allocate enough memory 
using dma_alloc_coherent so I can use the original code which I had 
working on x86.

Is there any reason why this isn't a kconfig option?

Thanks for the help.

Phil