Problem with enabling uartb serial@3110000 as a serial port

Issue Overview

Users are experiencing issues with enabling the uartb serial@3110000 on the Nvidia Jetson Orin Nano Dev board while using L4T 36.3. The main symptoms include:

• The expected mapping of /dev/ttyTHS1 to uartb@3110000 is not occurring. Instead, the system maps it to /dev/ttyS0, which exhibits abnormal behavior.
• During the setup, users have enabled uartb serial@3110000 in the device tree but are not seeing the expected results in the device messages (dmesg).
• The issue arises consistently across different setups and configurations, particularly when using custom carrier boards.
• The problem significantly impacts user experience, especially for applications relying on serial communication, such as Bluetooth devices.

The context of this problem typically occurs during the initial configuration of the custom carrier board or when attempting to connect peripheral devices that rely on UART communication.

Possible Causes

Several potential causes for the issue have been identified:

• Hardware Incompatibilities: Differences in hardware configurations between versions JP5 and JP6 of the carrier board may lead to incorrect mappings.

• Device Tree Configuration Errors: Incorrect entries in the device tree can result in improper driver assignments, causing /dev/ttyS0 to be used instead of /dev/ttyTHS1.

• Driver Issues: The system may be using the 8250 serial driver instead of the Tegra High-Speed (THS) driver, which could lead to abnormal behavior with /dev/ttyS0.

• Software Bugs or Conflicts: Variations between different L4T versions (e.g., 35.5 vs. 36.3) may introduce bugs that affect UART functionality.

• User Misconfigurations: Incorrect modifications made by users when editing the device tree might lead to unintended consequences.

Troubleshooting Steps, Solutions & Fixes

To address the issue with enabling uartb serial@3110000, follow these troubleshooting steps and potential solutions:

1. Check Device Tree Configuration:

   • Review your device tree source (DTS) file for correct alias mappings.
   • Ensure that serial@3110000 is correctly defined in your DTS file:

     aliases {
         ...
         serial1 = "/bus@0/serial@3110000";
         ...
     }
     

2. Modify Compatibility String:

   • Change the compatibility string for serial@3110000 to use the Tegra High-Speed UART driver:

     serial@3110000 {
         ...
         compatible = "nvidia,tegra194-hsuart";
         ...
     }
     

3. Use Correct Driver:

   • If your Bluetooth device is not functioning properly with /dev/ttyS0, try switching to use /dev/ttyTHS1 by ensuring that your configuration forces the use of the THS driver.

4. Test with Different L4T Versions:

   • If you are facing issues with L4T 36.3, consider testing your setup with L4T 35.5 where users have reported successful operation of Bluetooth devices.

5. Gather System Information:

   • Use terminal commands to check current mappings and configurations:

     dmesg | grep tty
     ls /dev/tty*
     

6. Consult Documentation and Community Resources:

   • Review Nvidia’s official documentation for any updates on device tree configurations and driver compatibility.
   • Engage with community forums for insights from other users who have faced similar issues.

7. Best Practices for Future Configurations:

   • Always back up your device tree files before making changes.
   • Document any changes made to configurations for easier troubleshooting in the future.

8. Unresolved Issues:

   • Users may need further assistance if modifications do not resolve their issues. Engaging with Nvidia support or community forums may provide additional insights or solutions.

By following these steps and recommendations, users can effectively troubleshoot and potentially resolve issues related to enabling uartb serial@3110000 on their Nvidia Jetson Orin Nano Dev board.