Devices under PCIE packet switch sometimes are not detected after system boots or reboots

Hi,

We designed a carrier board for Xavier NX/Nano/TX2 NX. There’s one M.2 M key connector on it.

Here’s the problem we faced.

Plug an NVME SSD on M key, all 3 SOMs work fine.

Plug a M.2 module with a Pericom packet switch PI7C9X2G303EL and 2 LAN controllers after switch on it, Xavier NX sometimes can’t detect the 2 LAN controllers. However, Nano and TX2 NX work fine.

We found some discussions similar to this problem,
PCIE-HUB chip not being detected on boot occasionally
Jetson xavier nx can't find PCIe Device sometime, can it support rescan?
Xavier NX hardware pcie connect pcie switch pm8561 problem

The solution is to downgrade host PCIE max speed from Gen 4 to Gen 2 or Gen 1. We tried it, and it seems to set Gen 2 can avoid this problem.

Here’s are the questions.

1. Did NVIDIA get the root cause of this problem? To downgrade max speed is just a workaround not a solution.


2. M.2 M key PCIE Gen 3 SSD is supported in our product, so we need to set the speed at Gen 3 or above for better performance. However, setting max speed at Gen 3, we will face the problem that devices after Pericom packet switch can’t be detected problem mentioned in the beginning. Did NVIDIA have solution for this?

Thanks

Wayne.