Agilex 5 EMAC to EMAC : Driver error

The fact that gmac2 works, while gmac0/gmac1 fail with identical setup, strongly suggests-> The reset lines for EMAC0 and EMAC1 are not wired or released correctly in the FPGA handoff.

The Linux kernel attempts to reset the DMA via

resets = <&rst EMAC0_RESET>, <&rst EMAC0_OCP_RESET>;

But these don't actually trigger a reset, leave the DMA in a bad state.

Try a simple test, comment out the resets for gmac0:

// resets = <&rst EMAC0_RESET>, <&rst EMAC0_OCP_RESET>;

// reset-names = "stmmaceth", "stmmaceth-ocp";

Recompile and reboot. If this makes the error go away (or lets the DMA at least initialize), the reset was the issue.