DSI (DataStorage exception) when enabling address translation

Hello,

We are trying to bring up a new HW based on the MPC8347e.
I did create new board and config files and programmed u-boot in the flash.

As I have no u-boot prompt on the serial console, I did connect a BDI and try to debug u-boot via remote GDB.

When stepping in early u-boot (start.S) I get a SIGSTOP. Here is the GDB output:

in_flash () at start.S:188
188 sync
204 bl enable_addr_trans
enable_addr_trans () at start.S:750

750             mfmsr   r5
751             ori     r5, r5, (MSR_IR | MSR_DR)
752             mtmsr   r5

Program received signal SIGSTOP, Stopped (signal). 0x000003fc in DataStorage () at start.S:253
253 STD_EXCEPTION(0x300, DataStorage, UnknownException)

What can cause a DSI? What should I check?

Thanks,
Greg