GPIO Control During Shutdown on Nvidia Jetson Orin Nano Dev Board

Issue Overview

Users have reported challenges in controlling GPIO pins during the shutdown process of the Nvidia Jetson Orin Nano Dev board. The primary symptoms include:

• Inability to Set GPIO State: Users are unable to pulse a GPIO pin high as part of the shutdown sequence, which is crucial for certain battery-powered applications.

• Context of the Issue: This problem arises specifically when attempting to unlatch a microcontroller-based module that powers the Jetson from a battery upon a button press. The need for GPIO control during shutdown is essential for proper power management.

• User Experience Impact: The inability to control GPIO pins during shutdown can lead to improper power management, potentially causing devices to remain powered on unintentionally or requiring manual intervention.

• Hardware and Software Specifications: Users are familiar with setting initial pinmux states and controlling GPIO through sysfs and other libraries in userspace, indicating a moderate level of experience with the hardware.

• Frequency of the Issue: This appears to be a common concern among users working on similar battery-powered projects, suggesting it may not be an isolated incident.

Possible Causes

The following potential causes have been identified for the inability to control GPIO during shutdown:

• Hardware Limitations: The design of the Orin Nano may not support GPIO manipulation during the shutdown process due to hardware constraints.

• Software Bugs or Conflicts: There may be bugs in the kernel or conflicts within the GPIO driver that prevent proper interaction during shutdown.

• Configuration Errors: Incorrect configurations in pinmux settings or sysfs may lead to issues when attempting to control GPIOs at shutdown.

• Driver Issues: The specific implementation of the gpio-tegra186 driver may not allow for GPIO state changes once the device begins its shutdown sequence.

• Environmental Factors: Power supply fluctuations or temperature variations could affect GPIO behavior during critical operations like shutdown.

• User Errors or Misconfigurations: Users might not be utilizing the correct methods or scripts to interact with GPIOs at the right time during the shutdown process.

Troubleshooting Steps, Solutions & Fixes

To address the issue of controlling GPIO during shutdown, users can follow these troubleshooting steps and potential solutions:

1. Script Creation:

   • Write a script that toggles the desired power key GPIO during the shutdown process. This script should be executed as part of system shutdown procedures.
   • Example command to create a script:

     sudo nano /etc/systemd/system/gpio_shutdown.service
     

   • Add the following content to toggle GPIO:

     [Unit]
     Description=Toggle GPIO on Shutdown
     DefaultDependencies=no
     Before=shutdown.target
     
     [Service]
     Type=oneshot
     ExecStart=/usr/bin/gpio_command_here
     
     [Install]
     WantedBy=halt.target reboot.target
     

2. Debugging Shutdown Process:

   • Determine at what point during the shutdown process GPIO can no longer be interacted with. This can be done by logging messages at various points in your custom script.

3. Review Kernel Documentation:

   • Examine Linux kernel documentation related to device_shutdown and machine_power_off functions. Understanding these processes will provide insight into when GPIO control is lost.

4. Driver Inspection:

   • Check the gpio-tegra186 driver source code located at kernel/kernel-5.10/drivers/gpio/gpio-tegra186.c to identify when GPIO interactions are disabled.
   • Look for function calls related to device shutdown and their impact on GPIO states.

5. Utilize SYS_RST_N Pin:

   • Investigate whether SYS_RST_N goes high on shutdown or if there are any accessible pins that change state upon successful shutdown. This could serve as an alternative method for managing power without relying on GPIO control.

6. Consult Product Design Guide:

   • Refer to Nvidia’s product design guide for detailed information regarding power down sequences and accessible pins during shutdown. This documentation may provide critical insights into expected behavior.

7. Best Practices for Future Prevention:

   • Ensure all scripts and configurations are thoroughly tested in various scenarios before deployment.
   • Regularly check for firmware updates or patches that address known issues with GPIO control during system events.

By following these steps, users should be able to diagnose and potentially resolve issues related to GPIO control during the shutdown process on their Nvidia Jetson Orin Nano Dev boards.