Syntax error when compiling device tree usb-otg modification

Issue Overview

Users are encountering a syntax error while attempting to compile a modified device tree for the Nvidia Jetson Orin Nano Dev board. The issue arises specifically during the process of modifying the device tree to enable OTG (On-The-Go) mode for a custom carrier board equipped with a micro USB port.

Symptoms and Context

• Error Message: The user receives an error indicating a syntax issue at line 3717 of their modified .dts file. The specific error is:

  Error: temp.dts:3717.26-27 syntax error
  FATAL ERROR: Unable to parse input tree
  

• Modification Process: The user is following these steps:

  • Decompiling the existing .dtb file into a .dts format.
  • Modifying the .dts file to include OTG settings.
  • Attempting to recompile the modified .dts back into a .dtb format.

• Environment:

  • Hardware: Jetson Orin Nano (8GB)
  • Software: Jetpack 6.0 (rev. 1)

• Frequency: This issue appears consistently when following the outlined modification steps.

• Impact: The inability to compile the device tree prevents users from enabling OTG functionality, which may hinder development and testing of applications that rely on USB connectivity.

Possible Causes

• Macro Usage: The use of macros like TEGRA234_MAIN_GPIO in the modified device tree may not be supported by the Device Tree Compiler (DTC). Macros can only be utilized when building from the kernel source, leading to compilation errors when attempting to use them in a standalone .dts file.

• Syntax Errors: Errors in formatting or syntax within the .dts file can lead to parsing failures. This includes incorrect usage of properties or missing required fields.

• Version Compatibility: Differences between Jetpack versions (e.g., R36.2 vs. R36.3) may introduce changes that affect how device trees are compiled or structured.

Troubleshooting Steps, Solutions & Fixes

1. Verify Jetpack Version:

   • Run the command:

     cat /etc/nv_tegra_release
     

   • Ensure compatibility with instructions and modifications relevant to your version.

2. Replace Macros with Raw Values:

   • If possible, replace macro definitions like TEGRA234_MAIN_GPIO(Z, 1) with their corresponding raw hexadecimal values. This avoids the need for kernel rebuilding.
   • Check other nodes in the device tree for examples of raw values used in similar contexts.

3. Rebuild Kernel Image/Dtb:

   • If macro usage is necessary, download the kernel source and modify the device tree there before rebuilding the kernel image and device tree blob (dtb).
   • Follow these steps:
     • Download and extract the kernel source.
     • Modify the device tree in the source.
     • Rebuild using appropriate commands (e.g., make).

4. Consult Documentation:

   • Refer to Nvidia’s official documentation on modifying device trees and compiling them for specific guidance related to your Jetpack version.

5. Testing Different Configurations:

   • Test with different configurations or revert any recent changes to isolate whether specific modifications are causing issues.

6. Community Support:

   • Engage with community forums or Nvidia support channels if issues persist after following these steps.

Example Commands

To decompile and recompile using DTC, use:

sudo dtc tegra234-p3768-0000+p3767-0003-nv.dtb -o temp.dts

To compile back:

sudo dtc temp.dts -o tegra234-p3768-0000+p3767-0003-mod-nv.dtb

Best Practices

• Always back up original device tree files before making modifications.

• Validate syntax using tools like dtc before recompiling to catch errors early.

By following these troubleshooting steps, users should be able to resolve syntax errors encountered during device tree modifications on the Nvidia Jetson Orin Nano Dev board. Further investigation may be required for unresolved aspects, particularly concerning macro definitions and their usage in modified files.