Device tree overlay help for SPI <> CAN driver

Issue Overview

Users are experiencing issues while configuring a device tree overlay for the TCAN4X5X module on the Nvidia Jetson Orin Nano development kit. The problems arise during the compilation of the device tree source (DTS) file using the config-by-hardware.py tool. The specific symptoms include:

• Compilation Warnings: Users receive multiple warnings during compilation, such as:

  • Incorrect #address-cells and #size-cells for the SPI bus.
  • Failed prerequisite warnings related to the spi_bus_bridge.

• Non-Configured SPI Pins: After rebooting, the expected SPI pins are not configured, despite updates to the extlinux.conf file.

• Additional Errors on Decompilation: When users decompile the generated device tree blob (DTBO) back to a DTS file, they encounter further warnings, including issues with unit names and invalid property sizes.

The context of these issues primarily occurs during setup and configuration of the TCAN4X5X module, and users report that they are using JetPack version 5.1.1 with L4T 35.3.1 on the Orin Nano devkit.

Possible Causes

Several potential causes could lead to the observed problems:

• Incorrect Device Tree Configuration: The warnings regarding #address-cells and #size-cells suggest that there may be misconfigurations in how these properties are defined in the device tree overlay.

• Compatibility Issues: The TCAN4X5X module may not be fully compatible with the current kernel or JetPack version being used, leading to incomplete or incorrect initialization.

• Driver Issues: There may be missing or improperly configured kernel modules required for proper communication with the TCAN4X5X module.

• Decompilation Errors: The process of decompiling and recompiling the device tree may introduce errors if not handled correctly, particularly if properties like phandle are not generated properly during compilation.

• User Errors: Misconfigurations in the DTS file or incorrect usage of tools could also contribute to these issues.

Troubleshooting Steps, Solutions & Fixes

To address these issues effectively, follow these comprehensive troubleshooting steps:

1. Verify Device Tree Syntax:

   • Ensure that your device tree overlay syntax adheres to Nvidia’s guidelines. Check for correct definitions of #address-cells and #size-cells.
   • Example correction:

     #address-cells = <1>;
     #size-cells = <0>;
     

2. Check Compatibility:

   • Confirm that you are using a compatible version of JetPack and L4T for your hardware setup. Refer to Nvidia’s documentation for compatibility matrices.

3. Rebuild Device Tree Blob:

   • Instead of simply decompiling and recompiling your DTS file, follow these steps to ensure proper building:
     • Sync your changes with the kernel.
     • Build the kernel image and DTB using appropriate commands as outlined in Nvidia’s Kernel Customization guide.
     • Example command:

       sudo ./build.sh
       

4. Enable Required Kernel Configurations:

   • Ensure that any required kernel configurations for TCAN4X5X support are enabled. This may involve modifying configuration files in your kernel source directory.

5. Update extlinux.conf:

   • Double-check that your extlinux.conf file correctly points to the newly built DTBO file. Any discrepancies can prevent proper loading at boot time.

6. Test with Known Good Configurations:

   • If available, test with a known working configuration from similar setups (e.g., MCP2515 module) as a reference point.

7. Consult Vendor Documentation:

   • Reach out to your hardware vendor for specific porting guides or additional support documentation related to the TCAN4X5X module.

8. Review Community Resources:

   • Explore relevant forum threads or community discussions where similar issues have been resolved. For example, check discussions on MCP2515 for insights on SPI-CAN modules.

9. Log and Monitor Outputs:

   • Use logging tools to capture outputs during boot and runtime to identify any further errors or misconfigurations.
   • Example command for logging:

     dmesg | grep spi
     

10. Future Prevention:

    • Maintain updated documentation of your configurations and changes made during setup to facilitate troubleshooting in future projects.
    • Regularly check for updates from Nvidia regarding JetPack and L4T versions that may impact device compatibility.

By following these steps systematically, users should be able to diagnose and resolve issues related to configuring the TCAN4X5X module on their Nvidia Jetson Orin Nano development kit effectively.