Can PCIe controller C7 be used for endpoint operation on Nvidia Jetson Orin Nano?

Issue Overview

Users of the Nvidia Jetson Orin Nano development board are experiencing confusion regarding the capabilities of the PCIe controller C7. The main concern is whether this controller can be used for endpoint operation or if it is limited to root port operation only. This issue arises from conflicting information found in different Nvidia documentation:

1. The Orin Nano/NX Product Design Guide (Table 7-3) states that PCIe controller C7 only supports root port operation.
2. The Orin Technical Reference Manual and the AGX Orin Series Design Guide (Table 7-4) indicate that C7 is a dual-mode controller, implying it can function as both root port and endpoint.

This discrepancy has led to uncertainty among developers and system integrators working with the Jetson Orin Nano platform, potentially affecting their design decisions and implementation strategies.

Possible Causes

1. Documentation Inconsistency: The conflicting information in different Nvidia documents could be due to:

   • Outdated information in one of the guides
   • Errors in documentation
   • Differences in hardware capabilities between Orin Nano/NX and AGX Orin Series

2. Hardware Limitations: The Orin Nano/NX module might have specific hardware constraints that limit the functionality of the C7 controller, despite the controller itself being capable of dual-mode operation.

3. Design Choices: Nvidia may have intentionally limited the C7 controller’s functionality on the Orin Nano/NX for reasons such as:

   • Power efficiency
   • Simplifying the module design
   • Differentiating between product lines

4. Firmware or Software Restrictions: The limitation could be imposed by firmware or software, rather than being a hardware constraint.

Troubleshooting Steps, Solutions & Fixes

1. Confirm Current Status:

   • An Nvidia embedded team member has confirmed that the module design is not architected to support Endpoint operation on C7.
   • Only the C4 controller supports Endpoint operation, and this is achieved via a mux on the module that selects between PCIe CLOCK Out or REFCLK In.

2. Use C4 for Endpoint Operation:

   • If your design requires PCIe Endpoint functionality, use the C4 controller instead of C7.
   • When configuring C4 for Endpoint operation, ensure the mux is correctly set to select REFCLK In.

3. Design Considerations:

   • Plan your PCIe connections around C7 being a root port only.
   • If you need multiple Endpoint capable controllers, consider using a different Jetson module that offers this capability.

4. Documentation Clarification:

   • Refer to the Orin Nano/NX Product Design Guide as the authoritative source for this specific module.
   • Be aware that information in the Orin Technical Reference Manual and AGX Orin Series Design Guide may not apply directly to the Nano/NX modules.

5. Stay Updated:

   • Regularly check for updates to the Jetson Orin Nano documentation.
   • Subscribe to Nvidia Developer forums or newsletters for any announcements regarding firmware updates that might change PCIe controller functionality.

6. Seek Official Support:

   • If your project critically depends on C7 Endpoint functionality, contact Nvidia support directly for the most up-to-date information and potential workarounds.
   • Provide them with your specific use case to see if there are alternative solutions within the Jetson ecosystem.

7. Community Resources:

   • Engage with the Jetson developer community through forums and social media.
   • Share your experiences and workarounds, as other developers might have found creative solutions to similar limitations.

By following these steps and understanding the current limitations, developers can make informed decisions about their Jetson Orin Nano implementations and effectively utilize the available PCIe resources.