Orin Nano PCIe Endpoint Mode: Symbolic Link Creation Failure

Issue Overview

Users are experiencing difficulties when attempting to set up the Nvidia Jetson Orin Nano Devkit as a PCIe endpoint. The main symptom reported is the inability to create a symbolic link necessary for configuring the PCIe endpoint mode. Specifically, the command:

ln -s functions/tegra_pcie_dma_epf/func1 controllers/141a0000.pcie-ep/

results in the error message: “ln: failed to create symbolic link ‘controllers/141a0000.pcie-ep/’: No such file or directory.” Users have noted that the controllers directory under /sys/kernel/config/pcie_ep/ is empty, indicating that the expected PCIe endpoint configuration is not being established.

This issue arises during the setup process, particularly after flashing the device using an SD card with the jetson-disk-image-creator tool and Etcher, as per instructions from Nvidia’s documentation. Users have confirmed that booting and other functionalities appear to work correctly, but the symbolic link creation fails consistently. The problem significantly impacts users’ ability to utilize the PCIe capabilities of their devices, limiting their development and application options.

Possible Causes

1. Hardware Limitations: The Jetson Orin Nano does not have a dedicated PCIe slot for endpoint mode configuration, which may lead to confusion regarding its capabilities.
2. Incorrect Documentation: Instructions for creating symbolic links may be applicable only to other models (like Orin AGX) and not specifically for Orin Nano, leading to errors in execution.
3. Module Insertion Issues: Although users reported successful insertion of modules using modprobe, there might be underlying issues preventing proper configuration.
4. Configuration Errors: Misconfigurations during the flashing process could lead to missing directories or files necessary for establishing PCIe endpoints.
5. Driver Issues: Potential incompatibilities or bugs in the driver handling PCIe configurations could lead to failures in creating required links.

Troubleshooting Steps, Solutions & Fixes

1. Verify Hardware Compatibility:

   • Confirm that you are using an appropriate model of the Jetson Orin Nano that supports PCIe endpoint mode.
   • Check if any additional hardware (like an M.2 connector shield) is required for your specific setup.

2. Review Documentation:

   • Revisit Nvidia’s official documentation for PCIe endpoint mode and ensure you are following instructions tailored specifically for the Orin Nano:
     • PCIe Endpoint Mode Documentation

3. Check Directory Structure:

   • Use the command ls /sys/kernel/config/pcie_ep/controllers to verify if any directories exist.
   • If empty, investigate whether the necessary modules are loaded correctly.

4. Module Management:

   • Run modprobe tegra_pcie_dma_epf and check verbose output with modprobe -v --first-time tegra_pcie_dma_epf to ensure no errors occur during module insertion.
   • If errors persist, consider reloading or reinstalling relevant drivers.

5. Alternative Commands:

   • If you encounter issues with creating symbolic links, try manually creating directories first:

     mkdir -p /sys/kernel/config/pcie_ep/controllers/141a0000.pcie-ep/
     ln -s functions/tegra_pcie_dma_epf/func1 /sys/kernel/config/pcie_ep/controllers/141a0000.pcie-ep/
     

6. Consult Community Forums:

   • Engage with community forums such as NVIDIA Developer Forums or Reddit’s r/JetsonNano for additional insights and shared experiences from other users facing similar issues.

7. Consider Software Updates:

   • Ensure that your JetPack version is up to date (preferably JetPack 5.x) as newer versions may contain fixes or improvements related to PCIe configurations.

8. Document Unresolved Issues:

   • Note any persistent problems or areas where additional investigation is needed, such as compatibility with specific hardware setups.

By following these troubleshooting steps and solutions, users can systematically diagnose and potentially resolve issues related to setting up PCIe endpoint mode on their Nvidia Jetson Orin Nano Devkit.