PCIe Swapping Issues

[ngoctuan280598]

I’m currently designing a circuit related to Jetson Thor, and I have some questions regarding PCIe.

1. Automatic P/N swapping within a pair of different pins requires rewriting the driver.

2. If I use a 4-lane PCIe port and only swap the P/N of two different pin pairs within the four lanes, will there be any problems? (e.g., Lane 1: PN, Lane 2: NP, Lane 3: NP, Lane 4: PN)

3. Regarding swapping between lanes, for example, a 4-lane PCIe port: tx1 tx2 tx3 tx4 <=> 4<->1, 3<->2… will there be any issues?

[ChrisB_NV]

I am checking on this with the team.

[ChrisB_NV]

@ngoctuan280598

1. Automatic P/N swapping within a pair of different pins requires rewriting the driver.

This is automatic, no configuration change needed.

@ngoctuan280598

2. If I use a 4-lane PCIe port and only swap the P/N of two different pin pairs within the four lanes, will there be any problems? (e.g., Lane 1: PN, Lane 2: NP, Lane 3: NP, Lane 4: PN)

This is allowed.

@ngoctuan280598

3. Regarding swapping between lanes, for example, a 4-lane PCIe port: tx1 tx2 tx3 tx4 <=> 4<->1, 3<->2… will there be any issues?

As mentioned in the Design Guide, lane reversal is allowed, as in 0→3, 1→2, 2→1, 3→0.

But remapping is not supported, for example 0→1, 1→ 3, 2→0, 3→2.