2x Ethernets with Jetson Nano and Custom Board // IOMMU Problem

Hello together,

We have developed a custom board that is compatible with the Jetson Nano, Xavier NX and TX2 NX. There is a PCIE switch on the board and a 1GBit PHY (RTL8111E) behind it.

This is identical to the internal PHY of the Jetson Nano, so they also load the same driver (r8168). We have adjusted the file r8168_n.c so that we don’t create the same kernel object twice, which led to a kernel panic. We also do not have an EEPROM for our PCIE-1Gbit-Phy, so we use the random_mac() function. (r8168_n_custom.c.txt attached). We didn’t change anything in the device tree regarding the ethernet phy.

We currently have the following problem:

When we boot with the Ethernet PHY 1 (Jetson internal) and the Ethernet cable plugged in, we do not get kernel panics, the Ethernet PHY 1 & 2 have a valid MAC address and when we plug the Ethernet cable into the Ethernet PHY 2 (External PHY), the interface gets an IP address and can communicate on the network. → Works as designed (dmesg_works.txt)

When we boot with the Ethernet PHY 2 (Jetson External) and the Ethernet cable plugged in, we get a kernel panic after switching the link UP. Most of the time the Linux boots and gets slower and slower (because of the kernel panic flushing) until it crashes - (syslog_failed.txt output attached). If Ubuntu boots and then you unplug the LAN cable, it also goes straight into a kernel panic and the system freezes.

I would be grateful for any tips!

Thank you and have a nice evening,

Saber

r8168_n_custom.c.txt (1.0 MB)
dmesg_works.txt (72.4 KB)
syslog_failed.txt (744.4 KB)