Unexpectedly dma_ops is NULL in struct device

Hello,

I tried to use Switchtec NTB on PowerPC platform and faced a strange behaviour. In ntb_hw_switchtec module's initialization section the "struct device" has uninitialized field dma_ops (NULL). Meanwhile the same NTB hardware on x86 platform get correct dma_ops in this driver. It looks like on lower layer "struct device" init differs between x86 and powerpc.
This issue makes functions dma_set_mask() and dma_set_coherent_mask() and dma_alloc_coherent() fail in ntb_hw_switchtec. And the driver can't start on powerpc.

Can anybody help to trace this issue? 
Thanks in advance.

Best regards, 
Alexander

On 15/11/18 03:05 AM, Alexander Fomichev wrote:

This issue makes functions dma_set_mask() and dma_set_coherent_mask() and dma_alloc_coherent() fail in ntb_hw_switchtec. And the driver can't start on powerpc.

I don't know a lot about powerpc in this area, but a quick peek shows
that dma_set_mask() does some platform specific stuff so it would
definitely help if you can let us know more about your hardware.

On one platform I looked at, it seems that dma_set_mask() sets the
dma_ops for the device, so the fact that it is NULL at that point is not
likely the issue. It's probably some platform specific bug that's
causing this.

Logan