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From: David Miller <davem@davemloft.net>
Subject: Re: Hang: 2.6.32.4 sky2/DMAR
Date: Wed, 27 Jan 2010 15:54:23 -0800 (PST)
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From: Stephen Hemminger <shemminger@vyatta.com>
Date: Wed, 27 Jan 2010 09:45:31 -0800

> Setting it to 1 causes driver to never go through the dma_sync_single/memcpy
> path.  Perhaps the code for DMAR doesn't do dma_sync_single_for_cpu
> properly, or the value passed to sync_single_for_cpu doesn't account for
> all the overhead of padding and/or ether header.

For the millionth time...

DMAR does not implement any of the DMA SYNC operations, they are set
to NULL in the dma ops vector, and thus are NOPs.