How does BootROM decide the boot media

Issue Overview

The discussion revolves around the boot process of the Nvidia Jetson Orin Nano Dev board, specifically focusing on how the BootROM determines the boot media (eMMC, SD, NVMe). Users have reported confusion regarding the boot sequence and how UEFI interacts with BootROM to select the appropriate boot device.

Symptoms and Context

• Users are uncertain about which boot media is selected during the initialization process.
• The issue occurs primarily during system setup and when attempting to flash a system image.
• Specific hardware mentioned includes SD cards and NVMe SSDs used for booting.
• The frequency of the issue appears to be consistent among users who are transitioning between different boot media types.
• The impact on user experience includes difficulty in configuring and understanding the boot process, leading to potential misconfigurations or failure to boot.

Relevant Specifications

• The discussion references the R35.2.1 document, which outlines BootROM’s role in initializing boot media.
• Users are utilizing SDK Manager for flashing images onto SD cards.

Possible Causes

• Hardware Incompatibilities: If there are issues with the SD card or NVMe SSD itself, it could lead to failure in recognizing the boot media.

• Software Bugs or Conflicts: There may be bugs within the UEFI firmware that affect how it communicates with BootROM.

• Configuration Errors: Incorrect settings in UEFI or L4T configuration files could lead to improper boot order selection.

• Driver Issues: Outdated or incompatible drivers could prevent proper initialization of certain boot devices.

• User Errors: Misunderstandings about how to configure UEFI settings or flash images correctly can lead to issues.

Troubleshooting Steps, Solutions & Fixes

1. Verify Boot Order Configuration:

   • Access UEFI settings and check the boot order configuration.
   • Refer to "UEFI Adaptation — Boot Order Selection" for detailed instructions on adjusting boot priorities.

2. Check Boot Media Compatibility:

   • Ensure that the SD card or NVMe SSD is compatible with the Jetson Orin Nano Dev board.
   • Perform a physical inspection of the hardware for any visible defects.

3. Flashing System Images:

   • When using SDK Manager, ensure that you are selecting the correct target device and image.
   • Use the command:

     sudo sdkmanager --flash <target_device>
     

   • Confirm that kernel images are correctly flashed into both partition and file system by checking:
     • /boot/Image
     • The corresponding partitions using tools like lsblk.

4. Review Boot Flow Documentation:

   • Consult "Jetson AGX Orin, Orin NX and Orin Nano Boot Flow" for an overview of how BootROM interacts with UEFI during startup.

5. Testing Different Configurations:

   • If transitioning from SD to NVMe, test each configuration separately to isolate potential issues.
   • Use a different SD card or SSD if problems persist.

6. Consult L4T Configuration Documentation:

   • Refer to "Customizing the Default Boot Order in L4TConfiguration.dtbo" for guidance on setting up boot media preferences without needing to change UEFI settings manually.

7. Kernel Image Loading Verification:

   • To determine which kernel image is being loaded, check both /boot directory and partitions during system startup.
   • If loading fails from rootfs, confirm that fallback mechanisms are functioning correctly by observing logs during boot.

8. Preventive Best Practices:

   • Regularly update firmware and drivers to ensure compatibility with new hardware.
   • Maintain backups of configuration files before making changes to UEFI settings.

Unresolved Aspects

• There remains uncertainty regarding where UEFI writes information about the selected boot device and its interaction with BootROM.
• Further investigation may be needed into specific error messages encountered during boot attempts or flashing processes.

By following these steps and solutions, users should be able to diagnose and resolve issues related to BootROM’s selection of boot media on the Nvidia Jetson Orin Nano Dev board effectively.