AM3358: RemoteProc RPMsg with large payload [Meta TI]

Jeff Kaleshi

Part Number: AM3358

Hello,

I’m currently in the process of looking for a new remote processor communication framework (for the AM3358 and AM6254), previously using uio and a shared buffer. I would like to switch to RemoteProc and RPMsg, but have a few questions based on our use-case (updating a display buffer of 7860 bytes @25HZ).

Questions:

RPMsg payloads have a max size of 496 and max buffer size of 512. What is the recommended approach for transferring large chunks of data between the PRU and the Host?
If I allocate a shared buffer (12K shared buffer between the PRU and host) will this affect RPMsg ability to send messages?

over 3 years ago

0 Nick Saulnier over 2 years ago

TI__Guru** 100980 points

Hello Jeff,

Apologies for the delayed response, I lost your thread over my summer vacation.

I do not recommend using RPMsg packets themselves to transfer large quantities of data. RPMsg can be used as a notification service between cores alongside shared memory. Over the next couple of weeks, we are actually working on publishing a shared memory example that uses RPMsg to notify between Linux A53 and remote R5F and M4F cores. Let me know if you want me to point to the git repos when they go live, or if you need the information sooner and just want to see a rough draft of the code. I would expect things to be very similar from the Linux side when communicating with the PRU cores, but the PRU firmware project will obviously look pretty different from the R5F / M4F projects.

The fastest way to notify would be to use interrupts instead of RPMsg. At this point TI does not provide an example of exposing interrupts up to userspace, but other customers have implemented that outside of UIO.

Regards,

Nick

0 Jeff Kaleshi over 2 years ago

Prodigy 20 points

Hi Nick,

Are you able to share the sample code and any resources you have for the shared memory example?

Thanks,

Jeff Kaleshi

0 Nick Saulnier over 2 years ago in reply to Jeff Kaleshi

TI__Guru** 100980 points

Hello Jeff,

I talked with the developers and they said they'll start the process of making the git repo with the R5F / M4F shared memory example public. Please ping the thread if I have not provided an update by the middle of next week.

Regards,

Nick

0 Jeff Kaleshi over 2 years ago in reply to Nick Saulnier

Prodigy 20 points

Hey Nick,

Any updates?

0 Nick Saulnier over 2 years ago in reply to Jeff Kaleshi

TI__Guru** 100980 points

Hello Jeff,

Thanks for the ping. It looks like it is gunna be a few more weeks before the repo goes public, so I am going to just grab some files from the git repo and post them here within the next couple of days so you don't have to wait that long.

I'm signing off of work for the day. Please keep me honest and ping again if I haven't posted files by Friday.

Regards,

Nick

0 Nick Saulnier over 2 years ago in reply to Nick Saulnier

TI__Guru** 100980 points

Hello Jeff,

Shoot, looks like this fell through the cracks. I apologize.

The example is now live here:
https://git.ti.com/cgit/rpmsg/rpmsg_char_zerocopy/

There's another PRU customer who is looking at doing something similar to yall (on AM64x which has PRU_ICSSG, but the concept should be the same). They posted about it here: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1169066/sk-am64-follow-up-question-how-to-read-write-data-with-the-pru_icssg-xfr2vbus-hardware-accelerator/4402839#4402839

Regards,

Nick

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AM3358: RemoteProc RPMsg with large payload [Meta TI]