Re: [PATCH] fsldma: use PCI Read Multiple command
- From: Timur Tabi <timur@xxxxxxxxxxxxx>
- Date: Mon, 27 Apr 2009 09:31:12 -0500
On Mon, Apr 27, 2009 at 4:09 AM, Liu Dave-R63238 <DaveLiu@xxxxxxxxxxxxx> wrote:
You are assuming the PCI memory space is prefetchable( no side effect)
for DMA.
Is it possible that DMA is from non-prefetchable memory space?
This should be a safe assumption for this driver. Remember, this
driver just does offload memcpy, from one region to another. So the
PCI memory that you are reading from should be just a buffer of data,
and there should be side-effect of reading it.
However, I would like to see a comment at the top of the file warning
people that copying from PCI memory will result in prefetched reads.
--
Timur Tabi
Linux kernel developer at Freescale
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