Thanks for your answers and suggestions. Maybe I should mention that I am not the HW designer of this custom board and it has been working fine for many years in the field, first with the CM1 and then with CM3 and CM3+. I also checked the LAN9514 data sheet and there it states that actually there is no need for an external reset:
[*] "Built-in Power-On-Reset (POR) circuit (Eliminates requirement for external passive or active reset)"
[*] "Assertion of nRESET is not a requirement."
Therefore I assume there is no issue with the HW design. The fact that Ethernet is not working reliable with the CM4S must be some configuration or software issue. The problems described above occur with an older Raspbian OS with Kernel 5.10. When running the latest Raspbian OS Bookworm with Kernel 6.6, the startup issue is gone. However there are some RX errors on the eth0 interface and after some hours the link goes down. So something is still off. But I can't quite put my finger on it.
[*] "Built-in Power-On-Reset (POR) circuit (Eliminates requirement for external passive or active reset)"
[*] "Assertion of nRESET is not a requirement."
Therefore I assume there is no issue with the HW design. The fact that Ethernet is not working reliable with the CM4S must be some configuration or software issue. The problems described above occur with an older Raspbian OS with Kernel 5.10. When running the latest Raspbian OS Bookworm with Kernel 6.6, the startup issue is gone. However there are some RX errors on the eth0 interface and after some hours the link goes down. So something is still off. But I can't quite put my finger on it.
Statistics: Posted by ondwis — Tue Nov 19, 2024 8:03 am