Re: [Linaro-mm-sig] [RFC 0/2] DMA-mapping & IOMMU - physicallycontiguous allocations
From: Hiroshi Doyu
Date: Tue Oct 16 2012 - 06:28:02 EST
Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote @ Tue, 16 Oct 2012 10:59:28 +0200:
> On Tue, Oct 16, 2012 at 09:04:34AM +0300, Hiroshi Doyu wrote:
> > In addition to those contiguous/discontiguous page allocation, is
> > there any way to _import_ anonymous pages allocated by a process to be
> > used in dma-mapping API later?
> > I'm considering the following scenario, an user process allocates a
> > buffer by malloc() in advance, and then it asks some driver to convert
> > that buffer into IOMMU'able/DMA'able ones later. In this case, pages
> > are discouguous and even they may not be yet allocated at
> > malloc()/mmap().
> That situation is covered. It's the streaming API you're wanting for that.
> dma_map_sg() - but you may need additional cache handling via
> flush_dcache_page() to ensure that your code is safe for all CPU cache
> Remember that pages allocated into userspace will be cacheable, so a cache
> flush is required before they can be DMA'd. Hence the streaming
Is the syscall "cacheflush()" supposed to be the knob for that?
Or is there any other ones to have more precise control, "clean",
"invalidate" and "flush", from userland in generic way?
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