SuperSpeed USB storage device not detected on X8 (Bottom) in combination with Apalis iMX8QM

Technical Support
, ,
1

Setup:

  • Apalis iMX8QM 4GB IT
  • Ixora Carrier Board V1.1D
  • Apalis-iMX8_Reference-Minimal-Image-Tezi_7.2.0+build.5

and

  • Apalis iMX6Q 1GB
  • Ixora Carrier Board V1.1D
  • Apalis-iMX6_Reference-Minimal-Image-upstream-Tezi_7.2.0+build.5

Issue:
When using a Apalis iMX8QM board in combination with a Ixora v1.1D carrier board, then a SuperSpeed USB storage device is:

  • “Detected” on “X8 Top” port as “super speed” device
  • “Not detected” on the “X8 Bottom” port

This is contrast to a similar setup with an Apalis iMX6Q board.
In this case, the USB storage device is detected on both X8 ports (as “high-speed” device, which is expected).

I would expect that for the Apalis iMX8QM board the storage device would also be detected as “high-speed” device when using the “X8 Bottom port”.
Note that other old non-SuperSpeed storage devices are actually detected on the X8 Bottom port when using the iMX8QM board.

Question:
Can the iMX8QM board be configured (using a device tree overlay??) such that a SuperSpeed storage device is also detected when using the “X8 bottom” port similar to the iMX6Q board?

  • If yes, please explain how?
  • If not, please what is the difference between the boards that causes this difference in behavior.
2

Hi, I’m the Toradex AI Assistant.

I might make mistakes. Our support team will step in if needed. If I answered your question, please tick the “Solution” checkbox. For follow-up questions to me, please use @ToradexAI in your post.

Did you like my answer? :+1: :-1:

Hello and thank you for your detailed description of your setup and issue.

What you are observing is related to the hardware design of the Ixora carrier board in conjunction with the different capabilities of the Apalis iMX8QM and iMX6Q modules.

Key Points

  • Ixora Carrier Board USB Ports:
    The X8 connector on the Ixora board has two USB ports:

  • Module USB Support:

    • iMX6Q: Supports up to USB 2.0 (High Speed). Thus, when you connect any USB device (including SuperSpeed devices), the device falls back to High Speed and is detected on both X8 Top and Bottom.
    • iMX8QM: Supports USB 3.0 (SuperSpeed) on the Top port. The Bottom port, while available, is still only USB 2.0 due to hardware design. SuperSpeed devices might not properly fall back to High Speed on this port, particularly if they’re strictly looking for SuperSpeed negotiation or the controller’s initialization on iMX8QM differs from that of iMX6Q.

  • Device Tree/Overlay Configuration:
    Device tree overlays are useful for configuring software aspects like enabling/disabling ports or tweaking pin control, but they cannot overcome hardware limitations or differences in how the SoC and PHY interact with the board’s routing (Device Tree Overlays Overview).

Why the Difference?

  • The iMX8QM uses a different USB controller and PHY, which enforces SuperSpeed operation on the X8 Top and may not support proper fallback to High Speed for SuperSpeed devices on the X8 Bottom, especially if the port is not physically routed for SuperSpeed signaling.
  • The iMX6Q only supports up to USB 2.0, ensuring all devices, even SuperSpeed-capable ones, are seen as High Speed on both ports.

Conclusion

  • You cannot configure the iMX8QM through a device tree overlay (or any software means) to make the X8 Bottom port behave like the iMX6Q.
  • The X8 Bottom port on Ixora is physically a USB 2.0-only port; detection of some SuperSpeed devices as High Speed on iMX6Q is due to that module’s limited controller, not a difference you can reproduce on iMX8QM through configuration.
  • For reliable SuperSpeed USB storage device operation with the Apalis iMX8QM, you must use the X8 Top port. The X8 Bottom port is best used for USB 2.0 devices.

For further details on the Ixora board USB implementation and limitations, please refer to the official documentation:

Best regards,
Toradex AI Assistant.

3

Since the i.MX 8 features only one USB port with SuperSpeed signals, the USB 3.0 functionality is only available on the USB_H4 port of the Apalis form factor. The USB_O1 port (which is routed to the “X8" Bottom half ) does not feature the SuperSpeed signals. Only USB High-Speed is available there. Please refer to the chapter 5.5 USB of Apalis iMX8 datasheet for details.

4

Ok thank you for explanation.