Re: RDMA/cxgb4: Support on-chip SQs

[Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>]

On 1/30/2013 3:44 PM, Jason Gunthorpe wrote:
> On Wed, Jan 30, 2013 at 03:36:48PM -0600, Steve Wise wrote:
>> I wonder, then, what the correct service is to get the cpu physical
>> address from a kernel virtual address returned from
>> dma_alloc_coherent()?  I think this is correct as-is, since I think
>> dma_alloc_coherent() falls under the "directly mapped" addresses in
>> the virt_to_phys() prototype comment.
> DMA-API.txt says:
>
>   This routine allocates a region of <size> bytes of consistent memory.
>   It also returns a <dma_handle> which may be cast to an unsigned
>   integer the same width as the bus and used as the physical address
>   base of the region.
>
> So instead of virt_to_phys you should use dma_addr??

I don't think so.  The result of virt_to_phys() is used in 
remap_pfn_range() to map this memory into user space...  The dma_addr is 
give to HW for DMA operations.

> I think the note about 'directly mapped' refers to things the arch
> setups during early boot, not dma_alloc stuff.
>
> Jason

--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html