On 10.04.2017 05:57, Peter Chen wrote:
On Thu, Mar 30, 2017 at 11:29:57AM +0300, Mathias Nyman wrote:
the other way around. First you patch dma_alloc_coherent() to
dma_zalloc_coherent() and that could go in during the -rc and possibly
get a stable tag, since spec requires kernel to zero the memory area.
--
balbi
In fact, it fixes two things at spec, the other thing is the scratchpad
buffer needs to be page_size boundary. I will send these two fixes
first.
If I remember correctly dma_alloc_coherent() takes care of proper alignment
and won't cross the boundary
Sorry to reply late.
The dma_alloc_coherent design is different per platform, and both the
code include/linux/dma-mapping.h and doc Documentation/DMA-API.txt
does not mention boundary and alignment.
DMA-API-HOWTO.txt mentions alignment and boundary:
"dma_alloc_coherent() returns two values: the virtual address which you
can use to access it from the CPU and dma_handle which you pass to the
card.
The CPU virtual address and the DMA address are both
guaranteed to be aligned to the smallest PAGE_SIZE order which
is greater than or equal to the requested size. This invariant
exists (for example) to guarantee that if you allocate a chunk
which is smaller than or equal to 64 kilobytes, the extent of the
buffer you receive will not cross a 64K boundary."
To me it looks like it's taken care of
-Mathias
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