Kernel Modules Not Found in Directory /lib/modules/5.10.192-tegra

Issue Overview

Users are experiencing issues with missing kernel modules, specifically the mcp251xfd.ko file, after building and flashing the Nvidia Jetson Orin Nano Dev board. The problem arises during the boot process of Ubuntu, where users cannot locate the necessary kernel module in the /lib/modules/5.10.192-tegra directory. This issue typically occurs after users attempt to build custom kernel modules for their carrier boards and replace the kernel supplements file (kernel_supplements.tbz2) with their own version.

Symptoms:

• The mcp251xfd.ko file is absent from the expected directory.
• Users are unsure if they need to manually copy the module to the root filesystem (rootfs).

Context:

• Occurs post-flashing when users boot into Ubuntu.
• Users have followed specific commands to build and archive kernel modules but fail to see them in the expected location.

Hardware/Software Specifications:

• Kernel version: 5.10.192-tegra.
• Custom carrier boards are being utilized.
• Users are employing Nvidia’s flashing tools (apply_binaries.sh and l4t_initrd_flash.sh).

Frequency:

This issue appears to be consistent among users who are building custom kernel modules for their boards.

Impact:

The inability to locate the required kernel module can significantly hinder development efforts, affecting functionality and performance of applications that rely on this module.

Possible Causes

1. Hardware Incompatibilities or Defects: Custom carrier boards may not fully support all features of the Jetson Orin Nano, leading to missing modules.
2. Software Bugs or Conflicts: There may be bugs in the kernel or conflicts with existing modules that prevent proper loading.
3. Configuration Errors: Incorrect configurations during module compilation or flashing processes could lead to missing files.
4. Driver Issues: Outdated or incompatible drivers may prevent proper recognition of newly built modules.
5. Environmental Factors: Power supply issues or overheating could affect the flashing process and subsequent module availability.
6. User Errors or Misconfigurations: Users may not be following the correct procedures for building or copying modules, leading to errors.

Troubleshooting Steps, Solutions & Fixes

1. Verify Module Presence Before Flashing:

   • Ensure that the mcp251xfd.ko file is present in the root filesystem before executing the flash command.
   • If absent, manually copy it to rootfs using:

     sudo cp /path/to/mcp251xfd.ko /path/to/rootfs/lib/modules/5.10.192-tegra/
     

2. Rebuild Kernel Module:

   • Confirm that you have correctly built the kernel module by following these steps:

     cd Linux_for_Tegra/source/public/modules_out
     tar --owner root --group root -cjf kernel_supplements.tbz2 lib/modules
     cp ./kernel_supplements.tbz2 ../../../kernel/kernel_supplements.tbz2
     

3. Reflash Using Correct Commands:

   • Use the following commands to ensure proper flashing:

     sudo ./apply_binaries.sh
     sudo ./tools/kernel_flash/l4t_initrd_flash.sh --external-device nvme0n1p1 \
       -c tools/kernel_flash/flash_l4t_external.xml -p "-c bootloader/t186ref/cfg/flash_t234_qspi.xml" \
       --showlogs --network usb0 jetson-orin-nano-devkit internal
     

4. Check Logs for Errors:

   • After flashing, check system logs for any errors related to module loading:

     dmesg | grep mcp251xfd
     

5. Update Drivers and Firmware:

   • Ensure that all drivers are up-to-date and compatible with your current kernel version.

6. Consult Documentation:

   • Refer to Nvidia’s official documentation for any updates on kernel module management and troubleshooting steps specific to Jetson Orin Nano.

7. Community Support:

   • Engage with community forums for additional insights and solutions from other users who may have faced similar issues.

8. Best Practices for Future Development:

   • Always back up existing configurations before making changes.
   • Document any changes made during development for future reference.

By following these steps, users can effectively troubleshoot and resolve issues related to missing kernel modules on their Nvidia Jetson Orin Nano Dev board, ensuring a smoother development experience moving forward.