Shared memory between remote processors

Shared memory between remote processors

[Michele Rodolfi]

Hi all,
I'm trying to set up a shared memory region for image transfers
between processors.
Since the rpmsg buffer isn't large enough to contain a whole image, I
would like to put the image into a shared memory buffer then send the
physical address of this buffer to the remote processor using rpmsg.
I'm trying to understand how to do so with the functionalities
provided by remoteproc. Has anyone done this before?
The remoteproc driver supports the request for allocation of a
physically contiguous memory region via resource table. Could this be
a solution?

Thanks
Michele

Re: Shared memory between remote processors

[Bjorn Andersson]

On Mon 10 Apr 02:00 PDT 2017, Michele Rodolfi wrote:

> Hi all,
> I'm trying to set up a shared memory region for image transfers
> between processors.
> Since the rpmsg buffer isn't large enough to contain a whole image, I
> would like to put the image into a shared memory buffer then send the
> physical address of this buffer to the remote processor using rpmsg.
> I'm trying to understand how to do so with the functionalities
> provided by remoteproc. Has anyone done this before?
> The remoteproc driver supports the request for allocation of a
> physically contiguous memory region via resource table. Could this be
> a solution?
> 

Specifying a carveout region in your resource table and use that for
your shared buffers sounds plausable, but today we do not have a
mechanism for a rpmsg client driver to acquire a handle to an arbitrary
carveout from a potential parenting remoteproc instance.

This is something that has been discussed, but I have not seem any good
suggestions on how to link the two pieces together.


But as it sounds like you're going to have a "control protocol" running
ontop of rpmsg to provide the remote firmware with buffers to operate on
I would suggest that you allocate the buffers (e.g. using
dma_alloc_coherent()) in the context of that implementation, rather than
tying them to remoteproc.

Regards,
Bjorn