Re: [PATCH] firewire: fw-ohci: sync AT dma buffer before use
From: Stefan Richter
Date: Wed Mar 12 2008 - 19:25:26 EST
David Moore wrote:
1. The dma_sync should probably be done before the context_append
because the controller could in theory start reading the data as soon as
context_append is called right?
Yes, but its syncing is superfluous anyway, as mentioned in the other
post. *If* it is doing something for Jarod's setup, then only because
of side effects like memory barrier properties.
2. As an optimization, we should attempt to allocate the payload in the
lower 32-bits of physical memory, to prevent extra memcopies on x86_64.
I think this can be done by adding GFP_DMA32 to kmalloc where the
payload was allocated in fw-cdev.c. There might be other places where
we would benefit from GFP_DMA32 also. Of course, these optimizations
are probably better saved for another patch.
I think so too. GFP_DMA32 would be appropriate on machines with
"software IOMMU" alias swiotlb.
Does GFP_DMA32 have adverse affects on machines with a real IOMMU?
--
Stefan Richter
-=====-==--- --== -==--
http://arcgraph.de/sr/
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