NRF5340 rpmsg_service RX callback in master (app core) seemingly not triggered via interrupt

[JustinL]

Hi,

Using NRF Connect  1.6.1 on NRF5340 I have modified hci_rpmsg project to add another endpoint for bidirectional calling between app core and net core. 
I have used the rpgmsg_service sample as a guide.

I can send messages from the app core (master) to the net core and all works as expected. 

However, when sending a message from the net core to the app core, the message is not delivered until the app core next sends a message to the net core.
Once app core sends another message all awaiting messages are delivered. This is a problem because I am send the message from net core based on radio notification and latency is important.

It is as if there is no RX interrupt for the app core. I noticed the following relevant commit in Zephyr from August "

"The IPC drivers rpmsg_service and rpmsg_multi_instance are not
explicitly enabling the RX IPM channel when two different devices are
used for TX and RX. While this could be redundant for some IPM drivers,
in some cases the hardware needs to be enabled before using it.

Add the missing calls to ipm_set_enabled() for both the devices."

So I tried patching the rpmsg_backend.c with the change in that commit

err = ipm_set_enabled(ipm_rx_handle, 1);
	if (err != 0) {
		LOG_ERR("Could not enable IPM interrupts and callbacks for RX");
		return err;
	}

But this made no difference. Maybe there is some other interrupt conflict or configuration that I am missing. The prj.conf entries for master and remote are as in the rpmsg_service sample.

Any help in getting messages from the net core to the app core would be great.

Thanks

[Einar Thorsrud]

Hi,

I do not have an immediate suggestion here, but I will try to look into it. Would it be possible to share your firmware where you have implemented the extra endpoint and see this issue?

[JustinL]

Hi,

I can't share my firmware code, but I have tracked down the issue to something relating to the thread calling rpmsg_service_send(). I have been sending the message from a thread I created. However, if I send the message from the main thread then it works as expected.

Here is how I create the thread, maybe there is something incorrect in the priority or options?

        k_thread_create(&notify_data_apply_thread_data, notify_data_apply_thread_stack,
			K_THREAD_STACK_SIZEOF(notify_data_apply_thread_stack), notify_data_apply_thread,
			NULL, NULL, NULL, K_PRIO_COOP(7), 0, K_NO_WAIT);

Thanks,

Justin

[Einar Thorsrud]

Hi Justin,

That seems odd. What does your notify_data_apply_thread look like? Could it be that for some reason it does not call rpmsg_service_send() on a timely manner?