PROCESSOR-SDK-AM62X: Linux ARM to PRU RPMsg communication

Hello Daisuke-san,

Links to existing documentation

You can find the link to the PRU Getting Started Labs (different from the Hands-on Labs) in your previous thread:
https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1480168/processor-sdk-am62x-how-to-toggle-gpio-pin-by-pru-with-mcu-sdk/5684276#5684276

It looks like I already covered your question about PRU academy on that other thread earlier today:
https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1480168/processor-sdk-am62x-how-to-toggle-gpio-pin-by-pru-with-mcu-sdk/5712389#5712389

The concepts in the RPMsg Quick Start Guide that applied to earlier devices also applies to AM62x, but it looks like the details are out of date:
https://software-dl.ti.com/processor-sdk-linux/esd/AM62X/10_01_10_04/exports/docs/linux/Foundational_Components/PRU-ICSS/RPMsg_Quick_Start_Guide.html#booting-the-board-and-testing-rpmsg

Let's do the demo together 

It will probably be fastest for me to show instead of telling. Here's me running the RPMsg demo on the latest AM62x RT Linux SDK 10.1

am62xx-evm login: root
root@am62xx-evm:~# uname -a
Linux am62xx-evm 6.6.58-rt45-ti-rt-01780-gc79d7ef3a56f-dirty #1 SMP PREEMPT_RT Wed Nov 27 14:15:26 UTC 2024 aarch64 GNU/Linux

// remoteprocX association can change each boot
// that means you should check the name to figure out which
// remoteprocX is associated with which core
root@am62xx-evm:~# head /sys/class/remoteproc/remoteproc*/name
==> /sys/class/remoteproc/remoteproc0/name <==
5000000.m4fss

==> /sys/class/remoteproc/remoteproc1/name <==
78000000.r5f

==> /sys/class/remoteproc/remoteproc2/name <==
30074000.pru

==> /sys/class/remoteproc/remoteproc3/name <==
30078000.pru

// what happened during Linux boot?
root@am62xx-evm:~# dmesg | grep remoteproc
[   21.556333] k3-m4-rproc 5000000.m4fss: configured M4 for remoteproc mode
[   21.562085] remoteproc remoteproc0: 5000000.m4fss is available
[   21.578014] remoteproc remoteproc0: powering up 5000000.m4fss
[   21.578052] remoteproc remoteproc0: Booting fw image am62-mcu-m4f0_0-fw, size 55100
[   21.601408] remoteproc remoteproc0: remote processor 5000000.m4fss is now up
[   21.807209] remoteproc remoteproc1: 78000000.r5f is available
[   21.807354] remoteproc remoteproc1: attaching to 78000000.r5f
[   21.825583] remoteproc remoteproc1: remote processor 78000000.r5f is now attached
[   22.512695] remoteproc remoteproc2: 30074000.pru is available
[   22.525854] remoteproc remoteproc3: 30078000.pru is available

// we expect the cores to be off based on the Linux boot. Is that true?
root@am62xx-evm:~# cat /sys/class/remoteproc/remoteproc2/state
offline
root@am62xx-evm:~# cat /sys/class/remoteproc/remoteproc3/state
offline

// is the RPMsg firmware on the filesystem?
root@am62xx-evm:~# ls /lib/firmware/pru/PRU_
PRU_Halt.out                   PRU_RPMsg_Echo_Interrupt0.out  PRU_RPMsg_Echo_Interrupt1.out

// is the remoteproc firmware already pointing to the RPMsg example?
root@am62xx-evm:~# cat /sys/class/remoteproc/remoteproc2/firmware
am62x-pru0-fw
root@am62xx-evm:~# cat /sys/class/remoteproc/remoteproc3/firmware
am62x-pru1-fw

root@am62xx-evm:~# ls -al /lib/firmware/
total 25460
drwxr-xr-x  6 root root    4096 Mar  9  2018 .
drwxr-xr-x 81 root root   61440 Mar  9  2018 ..
-rw-r--r--  1 root root    2040 Mar  9  2018 LICENCE.ibt_firmware
-rw-r--r--  1 root root    2046 Mar  9  2018 LICENCE.iwlwifi_firmware
lrwxrwxrwx  1 root root      72 Mar  9  2018 am62-mcu-m4f0_0-fw -> /usr/lib/firmware/ti-ipc/am62xx/ipc_echo_test_mcu2_0_release_strip.xer5f
lrwxrwxrwx  1 root root      79 Mar  9  2018 am62-mcu-m4f0_0-fw-sec -> /usr/lib/firmware/ti-ipc/am62xx/ipc_echo_test_mcu2_0_release_strip.xer5f.signed
lrwxrwxrwx  1 root root      51 Mar  9  2018 am62x-pru0-fw -> /usr/lib/firmware/pru/PRU_RPMsg_Echo_Interrupt0.out
lrwxrwxrwx  1 root root      51 Mar  9  2018 am62x-pru1-fw -> /usr/lib/firmware/pru/PRU_RPMsg_Echo_Interrupt1.out
..

// start the PRU cores
root@am62xx-evm:~# echo start > /sys/class/remoteproc/remoteproc2/state
[ 4875.923209] remoteproc remoteproc2: powering up 30074000.pru
[ 4875.926398] remoteproc remoteproc2: Booting fw image am62x-pru0-fw, size 81504
[ 4875.945016] virtio_rpmsg_bus virtio2: rpmsg host is online
[ 4875.945063] virtio_rpmsg_bus virtio2: creating channel rpmsg-pru addr 0x1e
[ 4875.945337] rproc-virtio rproc-virtio.5.auto: registered virtio2 (type 7)
[ 4875.945351] remoteproc remoteproc2: remote processor 30074000.pru is now up
[ 4875.964989] rpmsg_pru virtio2.rpmsg-pru.-1.30: new rpmsg_pru device: /dev/rpmsg_pru30
root@am62xx-evm:~# echo start > /sys/class/remoteproc/remoteproc3/state
[ 4880.992188] remoteproc remoteproc3: powering up 30078000.pru
[ 4880.995432] remoteproc remoteproc3: Booting fw image am62x-pru1-fw, size 81504
[ 4881.014935] virtio_rpmsg_bus virtio3: rpmsg host is online
[ 4881.014978] virtio_rpmsg_bus virtio3: creating channel rpmsg-pru addr 0x1f
[ 4881.015195] rproc-virtio rproc-virtio.6.auto: registered virtio3 (type 7)
[ 4881.015209] remoteproc remoteproc3: remote processor 30078000.pru is now up
[ 4881.015821] rpmsg_pru virtio3.rpmsg-pru.-1.31: new rpmsg_pru device: /dev/rpmsg_pru31

// run the test
root@am62xx-evm:~# ls /dev/ | grep pru
rpmsg_pru30
rpmsg_pru31
root@am62xx-evm:~# echo "test1" > /dev/rpmsg_pru30
root@am62xx-evm:~# echo "test2" > /dev/rpmsg_pru31
root@am62xx-evm:~# cat /dev/rpmsg_pru30
test1
^C
root@am62xx-evm:~# cat /dev/rpmsg_pru31
test2
^C

Regards,

Nick

Hello Daisuke-san,

Please take another look at the code block in my previous response. You will see where the prebuilt PRU_RPMsg_Echo_Interrupt binaries are in the default Linux filesystem that comes with the Linux SDK.

Alternatively, you can find the source code in the PRU Software Support Package (PSSP) here:
https://git.ti.com/cgit/pru-software-support-package/pru-software-support-package/tree/examples/am62x

Regards,

Nick