On Tue, 15 Nov 2005, Anton Blanchard wrote:
> TSO fixes
> - fix rare early completion when using TSO
> - extra descriptor for the sentinel descriptor
Is this the same bug as e1000? The extra DMA descriptor is going to be
costly, especially on 10Gb. Would the e1000_unmap_and_free_tx_resource
trick used in e1000 work instead?
Unfortunately, yes, the same bug as e1000. Both drivers absolutely need
this fix to make the hardware work okay with TSO. If we do not we risk
having really really bad bugs due to memory corruption.
(Actually I noticed we are still adding sentinel descriptors in e1000
even now we are doing the e1000_unmap_and_free_tx_resource trick, could
we remove it?)
We can't, because most of these issues involve the hardware going off and
doing something bad, we have to *tweak* the hardware into the right state
with an extra descriptor. Yuck, but there aren't many software
workarounds for these hw problems.
Jesse
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