PCIe lane reversal on C0

Autonomous Machines Jetson & Embedded Systems Jetson AGX Xavier
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1

Hi,

We are designing our carrier board for agx-xavier. We would like to reverse PCIe lanes for C0 used for M.2 M key for SSD, in order to facilitate PCB layout. And we use PCIe in root-complex mode ONLY on Xavier side.

Original: UPHY2 → lane0, UPHY3 → lane1, UPHY4 → lane2, UPHY5 → lane3.
Reverse: UPHY5 → lane0, UPHY4 → lane1, UPHY3 → lane2, UPHY2 → lane3.

Please check my attached screenshot for detail.

pcie_lane_reverse
pcie_lane_reverse1238×538 85.7 KB

  1. Is this PCIe lane reversal supported by PCIe controller on Xavier?
  2. Do I need any software change in Linux device-treee and/or Linux PCIe driver?
  3. Can I do the lane reversal on other multi-lane PCIe controllers: C4 and C5?
  4. Is this PCIe lane reversal independent on the PCIe endpoint/device that is connected with (work for any PCIe endpoint/device)?
  5. Instead of lane reversal, can I do any lane swap in random way within the PCIe controller group? For example, for my C0 case, can I do UPHY3 → lane0, and UPHY2 → lane1 (UPHY4 and PUHY5 unchanged.)? I think the answer is no, but I want to confirm on it.

Regards.

3

Hi,

Any update on this question? This is kind of urgent which is causing issue for our PCB layout.

Regards

4

Hi Nvidia,

I also want to confirm on PCIe Polarity Inversion is supported on Xavier. So, please confirm both “Lane Reversal” and “Polarity Inversion”.

I can find a similar post, but that is for NX. I want confirm on Xavier as well.

Regards.

6

Lane reversal support for of AGX and NX is same.

7

Hi

Thanks for you reply.
Can you confirm on both “Lane Reversal” and “Polarity Inversion”? (not just lane reversal)

Thanks.

8

Yes, Xavier supports both.

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