nrf5340 is unable to trigger rpmsg(ipc) transfer


I have quite demanding SPI device which should send its data over BLE.
Thanks to throughput example i was able to achieve maximum transfer speeds for synthetic tests (without SPI).
Sadly after adding real data input, I noticed that no transfer is executed until I finish my commands. 

Thanks to SystemView I was able to narrow this problem to one part of configuration -> rpmsg.



Green -> spi thread
Yellow -> bt_hci thread
Orange -> ble host TX
Red (small squere in top) - IRQ 58 from probably ipc, but i wasnt able to find it in manual (not listed)
Blue - probably openAmp mailing work queue thread
purple - systemwork queue

SystemView Data Log

Here is repo with configs etc.

Parents Reply
  • Thanks for this reply, but:

    1. I posted URL to my code where you can easily track that I'm not using work queue but separate thread.
    I posted a print screen from Seeger System View, where there is only info about thread
    2. I call there bt_gatt_write_without_response_cb(), which calls bt_gatt_write_without_response_cb(). This calls still blocks thread execution. 
    3. My issues are the same as ones mentioned here, for the same board, for the same situation:
    What's different in my case is that I'm using a `write without response` not notify.
    Fast notifications with nRF5340 and nRF Connect SDK

    4. For this board, if you use BLE stack anywhere, then net CPU is included.
    This converts the project to multicore one and adds a simple rpmsg project for net-core and installs SoftDevice by default on it.
    After that in config you can also see that HCI RPMSG stack is enabled for app core. 
    So every command from app-core to HCI BLE is sent via RPMSG module.
    This module uses RPROC protocol and MBOX module to sync over IPC.
    Sadly, to process this in correct manner, MBOX module is using WORKQUEUE.

    I guess this is the main reason for locks.
    If this issue is true.
    bt_gatt_notify() can block when running on Zephyr workqueue.

    5. nrf52840 has different driver HCI RPC, but there is similar WORKQUEUE implemented to sync with SoftDevice.

  • Hi,
    The issue persists. I was able to partially overcome it, by changing net core BLE Stack implementation in hci_rpmsg_nrf5340dk_nrf5340_cpuapp.conf to:

    # select ll layer

    After this change, I was able to achieve 1,1Mbps of throughput. 
    I still will be fighting with this code to reach 1,4Mbps, but It can be hard to do so.

    According to System View, not much room left for processing.

    If I find something useful, I will post it here.

  • Both nrf52840 and nrf5340 have bigger throughput with Zephyr stack.
    If I replace this with SoftDevice stack, then throughput drops to 500kbps.

     If you're interested I can prepare an example project which will reproduce my case only with two nrf5340 boards, without any SPI device (it can be in loopback).

  • Hello,

    Sorry for the late reply. I was unexpectedly out of office since Thursday.

    That would be great. If I can have a look, reproduce it and run it by our SoftDevice controller, I can ask them whether they have any hints on whether it is the intended workflow, or if this is in fact a bug.

    Best regards,