I have acquired a device that looks similar to USBDM/CF V3.1. I tried to use it with a MCF54415 and GDB.
While I was able to initialize the system and load a program into DRAM there are still too many problems to be usable.
Quite often during initialization there is no response from GDB. I suspect this happens when the CPU is switched from limp mode to full clock speed. But sometimes it works.
When stepping through the code sometimes the target halts/locks up and the debugger does not respond to a break.
Also I have encountered that the CPU does not halt on breakpoints or halts on positions without a breakpoint.
Some of these problems may be caused by a stale instruction cache when it is not flushed after soft breakpoints have been set/cleared. My tests clearly showed that the CPU does not execute the statement that is displayed in the disassembly. Regrettably I couldn't try to flush the cache by hand because the special registers that control the cache are not accessible with GDB.
I suppose that coldfire V4 cores are not really supported by Gdbserver as the target device selection does not show any of them but maybe there are plans to do so?