samples: ipc: openamp_rsc_table fails on NXP i.MX8QM and i.MX8QXP ADSP

[iuliana-prodan]

Describe the bug
The sample samples/subsys/ipc/openamp_rsc_table fails on NXP i.MX8QM and i.MX8QXP ADSP.

More exactly the board names are:

• imx8qm_mek/mimx8qm6/adsp
• imx8qxp_mek/mimx8qx6/adsp

To Reproduce

1. Compile the sample like:
   west build -p -b imx8qm_mek/mimx8qm6/adsp -S nxp-openamp-imx8-adsp -s samples/subsys/ipc/openamp_rsc_table/
2. Copy the firmware on target, in /lib/firmware.
3. Load the firmware with remoteproc from Linux:

Expected behavior
No error should appear when loading and starting the firmware on the DSP core.

Impact
Sample doesn't work

Logs and console output

root@imx8qmmek:~# echo -n zephyr_openamp_rsc_table.elf > /sys/class/remoteproc/remoteproc2/firmware
root@imx8qmmek:~# echo start > /sys/class/remoteproc/remoteproc2/state
root@imx8qmmek:~# dmesg | tail
[  151.002661] remoteproc remoteproc2: powering up imx-dsp-rproc
[  151.005249] remoteproc remoteproc2: Booting fw image zephyr_openamp_rsc_table.elf, size 1866036
[  151.018705] rproc-virtio rproc-virtio.1.auto: assigned reserved memory node vdev0buffer@94300000
[  151.122407] imx-dsp-rproc 556e8000.dsp: imx_dsp_rproc_kick: failed (0, err:-62)
[  151.122427] virtio_rpmsg_bus virtio0: rpmsg host is online
[  151.122593] rproc-virtio rproc-virtio.1.auto: registered virtio0 (type 7)
[  151.122607] remoteproc remoteproc2: remote processor imx-dsp-rproc is now up

Environment (please complete the following information):

• OS: Linux 6.6
• Toolchain - zephyr-sdk-0.16.9-rc2
• Commit SHA: Zephyr main - commit 829c03bcdca378fa2fa55484d16a190d379f754c

Additional context
If the CONFIG_SHELL is disabled the sample works.

[iuliana-prodan]

A workaround was sent for review: #79428

[pdgendt]

What is the difference between /dev/ttyRPMSG0 and /dev/ttyRPMSG1 technically? The shell implementation is based on this sample using a tty.

[iuliana-prodan]

What is the difference between /dev/ttyRPMSG0 and /dev/ttyRPMSG1 technically? The shell implementation is based on this sample using a tty.

@pdgendt they are ~identical. But this issue has nothing to do with Linux.
The problem is in Zephyr.
Even if I don't enable the rpmsg_tty from openamp_rsc_table the fw still doesn't load if CONFIG_SHELL is y.

IMO this should be enabled per board, not in prj.conf. I'm not sure if this was tested on all supported platforms when introduced.

I didn't had time to find the exact root cause for this, yet.
But what doesn't this rpmsg shell do? It has any specific requirements?

[pdgendt]

The rpmsg shell creates a second tty endpoint which can be used to open like a serial console. I only have i.MX8MP to test with unfortunately. But it should be as generic as the other tty endpoint used in the sample.

[iuliana-prodan]

The rpmsg shell creates a second tty endpoint which can be used to open like a serial console. I only have i.MX8MP to test with unfortunately. But it should be as generic as the other tty endpoint used in the sample.

Yes, on 8MP is working with CONFIG_SHELL=y
The difference between the 8MP and 8QM is the UART which for 8QM is interrupt driven. Any idea why would this impact the rpmsg backend?

[pdgendt]

It doesn't use UART, but a mailbox? The serial part is fully emulated on linux side?

CC @arnopo

[arnopo]

It doesn't use UART, but a mailbox? The serial part is fully emulated on linux side?

CC @arnopo

Perhaps there is a conflict between the UART shell and the RPMSG Shell?
does board support the Zephyr shell on UART? An in such case, can we have both enabled?