Mbox Driver Test Failure On Mimxrt700_evk: Unknown Error

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Mbox Driver Test Failure on mimxrt700_evk: Unknown Error

Hey guys! Today, we're diving into a tricky issue encountered in the Zephyr RTOS where the mbox driver sample test is failing on the mimxrt700_evk/mimxrt798s/cm33_cpu0 platform. This problem surfaces as an "Unknown Error," which can be pretty frustrating to debug. Let's break down the issue, explore the context, and figure out potential solutions.

Understanding the Bug

The Issue

The core problem is that the sample.drivers.mbox test is failing specifically on the v4.3.0-rc2 version of Zephyr OS when running on the mimxrt700_evk/mimxrt798s/cm33_cpu0 board. The error message is simply "Unknown Error," which doesn't give us much to go on initially. To reproduce this, you can use the provided twister commands, which are designed to automate testing within the Zephyr environment. Here are the commands:

scripts/twister -p mimxrt700_evk/mimxrt798s/cm33_cpu0  -T samples/drivers/mbox -s sample.drivers.mbox

Or, alternatively:

# west twister -p mimxrt700_evk/mimxrt798s/cm33_cpu0 -T samples/drivers/mbox -s sample.drivers.mbox

When these commands are executed, the expectation is that the test should pass. However, in this case, it results in the dreaded "Unknown Error."

Impact

While the exact impact isn't explicitly stated, a failing driver test can indicate potential instability or malfunction in the inter-processor communication mechanisms provided by the Mbox driver. This could affect any functionality that relies on this driver for message passing between different cores or components within the system. In simpler terms, if the mbox driver isn't working correctly, different parts of your system might not be able to talk to each other properly.

Reproducing the Error

To get our hands dirty and reproduce this error, you'll need a Zephyr development environment set up. Here’s a breakdown of the steps:

  1. Set up Zephyr Environment: If you haven't already, you'll need to set up the Zephyr SDK and environment. Follow the official Zephyr documentation for this, as it involves installing the necessary tools and configuring your system.

  2. Clone the Zephyr Repository: Make sure you have the Zephyr repository cloned locally. You can do this using Git:

    git clone https://github.com/zephyrproject-rtos/zephyr.git
cd zephyr

  3. Checkout the Specific Version: Since the issue was observed on v4.3.0-rc2, it’s a good idea to checkout that specific tag:

    git checkout v4.3.0-rc2

  4. Run the Twister Command: Now, you can use the twister command to run the test:

    scripts/twister -p mimxrt700_evk/mimxrt798s/cm33_cpu0 -T samples/drivers/mbox -s sample.drivers.mbox

    or using west:

    west twister -p mimxrt700_evk/mimxrt798s/cm33_cpu0 -T samples/drivers/mbox -s sample.drivers.mbox

  5. Observe the Error: If the issue is present, you should see the "Unknown Error" in the output.

Analyzing the Logs and Console Output

The provided logs give us some clues, though the "Unknown Error" itself is quite generic. Let's dissect the logs:

[00:00:00.001,191] <err> memc_mcux_xspi: XSPI_SetDeviceConfig failed with status 10808
[00:00:00.001,857] <inf> nxp_pca9422: mfd_pca9422_work_handler: sub_int[0]=0x80,  [1]=0x0
[00:00:00.001,863] <inf> nxp_pca9422: mfd_pca9422_work_handler: sub_mask[0]=0x7f, [1]=0xff
*** Booting Zephyr OS build v4.3.0-rc2 ***
WARNING: Using a potentially insecure PSA ITS encryption key provider.
[00:00:00.003,025] <wrn> secure_storage: Using a potentially insecure PSA ITS encryption key provider.
[00:00:00.003,038] <inf> psa_its: PSA ITS sample started.*** Booting Zephyr OS build v4.3.0-rc2 ***
Hello from HOST - mimxrt700_evk/mimxrt798s/cm33_cpu0
Maximum RX channels: 4
Maximum bytes of data in the TX message: 4
Maximum TX channels: 4
Ping (on channel 1)
Ping (on channel 1)
Ping (on channel 1)
Ping (on channel 1)
Ping (on channel 1)
Ping (on channel 1)
*** Booting Zephyr OS build v4.3.0-rc2 ***
Hello from HOST - mimxrt700_evk/mimxrt798s/cm33_cpu0
Maximum RX channels: 4
Maximum bytes of data in the TX message: 4
Maximum TX channels: 4
  1. XSPI Configuration Failure: The first error memc_mcux_xspi: XSPI_SetDeviceConfig failed with status 10808 suggests an issue with the XSPI (Serial Peripheral Interface) configuration. XSPI is often used for external memory access, so this could be a critical issue.
  2. PCA9422 Information: The nxp_pca9422 messages relate to a power management IC (PCA9422) from NXP. These messages seem informational but could indicate power-related issues if there are further errors associated with them.
  3. PSA ITS Warning: The warning about a potentially insecure PSA ITS encryption key provider is important for security considerations but might not be directly related to the mbox driver failure. PSA ITS (Platform Security Architecture Identity and Trust Services) is a security framework, and this warning suggests a default or insecure key is being used.
  4. Mbox Driver Output: The "Hello from HOST" and channel information messages indicate that the mbox driver is initializing. The repeated "Ping (on channel 1)" messages suggest that the test is attempting to send messages over the mbox channel. The fact that it gets this far suggests the basic driver initialization is working, but something goes wrong during the message exchange.

Potential Causes

Given the logs and the nature of the error, here are some potential causes:

  1. XSPI Configuration Issue: The failure of XSPI_SetDeviceConfig could be a root cause. If the external memory isn't configured correctly, it could lead to crashes or unexpected behavior when the system tries to use it.
  2. Clocking or Timing Problems: Incorrect clock configurations or timing issues can cause communication failures, especially in peripheral drivers like mbox that rely on precise timing.
  3. Resource Conflicts: There might be a resource conflict, such as an interrupt or memory region, that is causing the driver to fail.
  4. Driver Bug: It’s always possible that there’s a bug in the mbox driver itself, especially in a release candidate version.
  5. Hardware Issue: Although less likely, a hardware problem on the mimxrt700_evk board could also be the cause.

Steps to Debug and Fix

Okay, so we've got a good understanding of the problem. Now, let's talk about how to debug and potentially fix this issue. Here’s a structured approach:

  1. Investigate XSPI Configuration:

    • Check Device Tree: Examine the device tree configuration for the mimxrt700_evk to ensure that the XSPI settings are correct. Look for any discrepancies in clock settings, memory regions, or other parameters.
    • Review XSPI Driver Code: Dive into the memc_mcux_xspi driver code to understand what XSPI_SetDeviceConfig does and what could cause it to fail. Pay attention to the error code 10808, which might provide a specific clue within the driver.

  2. Check Clock Configurations:

    • Verify Clock Settings: Ensure that the clock settings for the XSPI and the mbox driver are correctly configured. Incorrect clock speeds can lead to communication errors.
    • Look for Clock Tree Issues: Investigate the clock tree configuration in the device tree and board files to see if there are any misconfigurations.

  3. Examine Resource Usage:

    • Check Interrupts: Verify that there are no interrupt conflicts between the mbox driver and other peripherals. Use the Zephyr interrupt management APIs to inspect interrupt usage.
    • Memory Regions: Ensure that the memory regions used by the mbox driver do not overlap with other memory regions.

  4. Debug the Mbox Driver:

    • Add Debug Prints: Insert debug print statements in the mbox driver code to trace the execution flow and identify where the error occurs. Focus on the message sending and receiving functions.
    • Use a Debugger: Attach a debugger (like GDB) to the Zephyr application and step through the code to examine the state of the system when the error occurs.

  5. Test Hardware:

    • Try Another Board: If possible, try running the same test on another mimxrt700_evk board to rule out a hardware issue.

  6. Consult Zephyr Community:

    • Zephyr Project Resources: Post your findings and questions on the Zephyr project mailing list or issue tracker. The community can provide valuable insights and help.

Environment Details

  • OS: Linux
  • Toolchain: Zephyr SDK
  • Commit SHA or Version Used: v4.3.0-rc2

Conclusion

The "Unknown Error" in the mbox driver test on mimxrt700_evk is a classic example of a tricky embedded systems bug. By systematically analyzing the logs, understanding the system configuration, and employing debugging techniques, we can narrow down the cause and hopefully find a solution. Remember, guys, debugging is a process of elimination and exploration. Keep digging, and you'll get there! If you encounter similar issues, following these steps should give you a solid starting point for troubleshooting. Good luck, and happy debugging!