svn commit: r209026 - in head/sys/ia64: ia64 include

Scott Long scottl at
Fri Jun 11 18:36:20 UTC 2010

On Jun 11, 2010, at 12:30 PM, Pyun YongHyeon wrote:
> On Fri, Jun 11, 2010 at 02:20:46PM -0400, John Baldwin wrote:
>>>>>> I'm not clear why you even need bounce buffers for RX.  The chip 
>> supports 64bit addresses with no boundary or alignment restrictions.
>>>>> Some controllers have 4G boundary bug so bge(4) restricts dma
>>>>> address space.
>>>> That limitation should be reflected in the boundary attribute of the tag, 
>> not the lowaddr/highaddr attributes.
>>> Yes, but that needed more code. And I don't have these buggy
>>> controllers so I chose more simple way that would work even though
>>> it may be inefficient.
>> You can just use a 2GB boundary as a workaround.  Look at what the twa(4) 
>> driver does to enforce a 4GB boundary for an example.
> I vaguely remember the problem was DMA memory allocated with
> bus_dmamem_alloc(9) does not honor boundary argument so bge(4) had
> to ensure the allocated memory is within 4GB.

That might be true, in which case you should set the restriction on the child tags that need it, not the parent tag.


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