PCIe Devices Sometimes Detected

Hi, this happened on a custom board. A PCIe switch is added downstream from the port of the Jetson Nano. The devices downstream and the PCIe switch itself sometimes would be recognized by linux but sometimes it doesnt. When it does recognize the device, it always has the error of unknown header 7F

Is this board yours or other vendor’s? If yours, first you should check your design based on Design Guide and reference schematic. If other vendor’s, you should check with them first.

This is my own board and yes we have checked with the design guide and reference schematic

It looks like pcb layout quality issue. Have you checked in that way? Also do you have log info?

i see. here are the errors that i managed to get. apologies for it being in image format

Please try to share log as a human readable text file.

Also, please test more pcie devices and see if only specific kind of device would hit error, or every of them would.

Also, tell us what kind of jetpack release you are using. Make sure we are debugging on latest version first.

Hi, currently using jetpack 4.6.2 and cant try other pcie devices as the pcie switch in question is in the carrier board design and could not be swapped out for a different device

Hi all, we are able to solve the issue on our side which is a circuit connection issue. Thanks for all the help and support.

Great, can you share what the error is so that we can take it as a lesson for all?

Sure, we initially connected the wrong upstream and downstream of the PCIe switch connection as well as the reference clock from the Upstream Jetson Nano SOM to the PCIe Switch. Take note on the P and N of the clock signal as we connected them backwards. With the clock connected correctly, we are able to detect all of the devices downstream of the switch and the switch itself. The number of lanes connecting from the Jetson Nano SOM to the PCIe switch only affects the speed of transmission and not the connectivity itself in our case.

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