2.10.13. IPC Example#
There are many different ways to implement Inter-Processor Communication (IPC) between Linux and remote cores. The Processor SDK for Linux includes an RPMsg IPC example in the default filesystem. RPMsg allows Linux to send and receive 512-Byte messages to and from remote cores.
For more information about the Linux side of RPMsg, reference the Processor SDK Linux Documentation, section “IPC for AM62x”.
For more information about the remote core side of RPMsg, reference the MCU+ SDK Documentation, sections:
“Developer Guides” > “Understanding inter-processor communication (IPC)”
“SOC Peripheral Drivers” > “IPC RPMessage”
“Examples and Demos” > “SOC and Board Peripheral Drivers” > “IPC RP Message Linux Echo”.
2.10.13.1. Load the Example IPC Binaries#
Check to see if the remote core soft links point to the ipc_echo binaries.
On the below board, the M4F core loaded the ipc_echo firmware. That means the Linux RPMsg example will work out-of-the-box with the M4F core.
root@am62xx-evm:/opt/ltp# ls -l /lib/firmware
...
lrwxrwxrwx 1 root root 72 May 21 2022 am62-mcu-m4f0_0-fw -> /lib/firmware/pdk-ipc/ipc_echo_baremetal_test_mcu2_0_release_strip.xer5f
If needed, follow the steps at Booting Remote Cores from the Linux Console or User Space to update the remote core soft links to point to the ipc_echo binaries in /lib/firmware/pdk-ipc. Reboot the board in order to load new binaries onto the remote cores.
2.10.13.2. Run the IPC Echo Example#
An RPMsg user space example is prebuilt and included in the default root filesystem (rootfs) under /usr/bin/rpmsg_char_simple. Steps for building the user space example, as well as building a kernel module example, are covered in a later section dev_remote_core_ipc.
Usage: rpmsg_char_simple [-r <rproc_id>] [-n <num_msgs>] [-d <rpmsg_dev_name] [-p <remote_endpt]
Defaults: rproc_id: 0 num_msgs: 100 rpmsg_dev_name: NULL remote_endpt: 14
All remote processor IDs (rproc_id) are defined in rproc_id.h
The below table lists the device enumerations as defined in the rpmsg_char_library. The table also specifies whether an Enumeration ID is valid on AM62x.
rproc_id |
Enumeration ID |
Device Name |
Valid |
Description |
|---|---|---|---|---|
9 |
M4F_MCU0_0 |
5000000.m4f |
Yes |
M4F core in MCU Domain |
For example, to test IPC with M4F_MCU0_0 (5000000.m4f) after an ipc_echo binary was loaded into the remote core:
root@am62xx-evm:~# rpmsg_char_simple -r 9 -n 3
Created endpt device rpmsg-char-2-1027, fd = 3 port = 1025
Exchanging 3 messages with rpmsg device ti.ipc4.ping-pong on rproc id 9 ...
Sending message #0: hello there 0!
Receiving message #0: hello there 0!
Sending message #1: hello there 1!
Receiving message #1: hello there 1!
Sending message #2: hello there 2!
Receiving message #2: hello there 2!
Communicated 3 messages successfully on rpmsg-char-2-1027
TEST STATUS: PASSED