Connecting and debuging STM32MP157F with M4 core

[Bennny]

Hi.

I'm trying to develop some SW on the M4 core of STM32MP157FAD1 on custom board with custom Linux.
After 2 days of fighting I'm finally able to run the tty echo example on it.

But I still struggle with connection to the board.

1. Why CubeIDE Debugger requires Serial port?
   We have the SSH accessible through the USB ETH over IP, that should be enough.
2. The Debugger resolve wrongly IP of the board:
   We have pppd interface in the Linux. The debugger wrongly detects it's IP as the debugger IP.
   It results with this error:
   
   I'm also getting this error in console, it looks like the script/commands are interpreted wrongly:
   
3. I'm still not able to get the ST-Link to work. It always ends with this error:
   

Thank you

P.S.

For others who also struggle to get it to work, check your device tree, CubeMX doesn't generate proper mbox m4_rproc. Add to end of the dts to the user section this:

&m4_rproc {
	mboxes = <&ipcc 0>, <&ipcc 1>, <&ipcc 2>, <&ipcc 3>;
	mbox-names = "vq0", "vq1", "shutdown", "detach";
};

 To have the trace0 interface, you must add define for build preprocessor __LOG_TRACE_IO_

[Bennny]

Some update:
I was finally able to get the st-link debugger to work on a custom board. What I found, SWO pin is also needed (I had connected only SW data and clock).
I also had to add manual routing to my notebook to be able to work with the wrong IP address (I didn't find any way how to fix this, it's obvious bug in the debugger).

But I have one more question. If I want to debug e.g. initialization part of the code (start of the main loop before while(1)), I'm not able to do that.
When I place breakpoint here, it never stops on it (because program is already after this BP). When I do terminate and relaunch, it loads the whole program again like running the debugger for the first time! So the debugger connects again after some time of the program run (which is long time after the breakpoint).
Is there any way how to overcome this or is it another bug?