Re: RDMA/cxgb4: Support on-chip SQs

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

On 1/30/2013 3:52 PM, Steve Wise wrote:
>
> On 1/30/2013 3:45 PM, Dan Carpenter 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.
>>>
>> Here is another relevant comment I should have included.
>>
>> commit ae6a5d37725853325a2b3460165fbc5613ce2916
>> Author: Russell King <rmk+kernel-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>
>> Date:   Tue Nov 20 12:17:51 2012 +0000
>>
>>      ASoC: kirkwood-dma: fix use of virt_to_phys()
>>
>>      This is part of a patch found in Rabeeh Khoury's git tree for the
>>      cubox.
>>
>>      You can not use virt_to_phys() on the address returned from
>>      dma_alloc_coherent(); it may not be part of the kernel 
>> direct-mapped
>>      memory.  Fix this to use the DMA address instead.
>>
>>      Signed-off-by: Russell King <rmk+kernel-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>
>>      Signed-off-by: Mark Brown <broonie-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org>
>>
>> I don't know the details though, and I certainly don't know how
>> someone would fix this.  ;)
>>
>
> How do I map the dma address into a physical address suitable for 
> passing to remap_pfn_range()?
>

To clarify, on some systems the dma bus address != the host physical 
address.  So i'm not sure remap_pfn_range() really wants a dma bus address.

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