On 12/21/2009 03:47 PM, Michael Buesch wrote:
> On Monday 21 December 2009 22:31:10 Larry Finger wrote:
>> Hi,
>>
>> I placed a number of test prints in my system trying to find where a
>> DMA data error might occur. In doing so, I found that 3 slots in the
>> DMA header cache cross a page boundary. Such a situation is allowed on
>> my system, but it might be forbidden on Atom processors. Please try
>> this really ugly hack to see if it makes any difference.
> 
> First thing is that the DMA buffers are allowed to cross any boundary (and
> the header is just a buffer). The boundary requirements only apply to the
> memory holding the descriptors.

That is what we will test for the Atom. I know it doesn't matter for
my CPU, but ...

> Second thing is: How does the patch prevent a boundary crossing?

The number of slots is reduced to the point that the header cache fits
in one page, just as the RX header cache does. As I said, this is
really ugly. If this fixes the problem, then a more elegant fix will
be needed.

Larry
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