debugging M4 in STM32H7 Dual Core

Hello,

I'm currently working with a STM32H757XI EVAL board, STM32CubeIDE 1.3.1 toolchain.

I'm following AN5361 but without success.

I tried different things like replacing

 /* Wait until CPU2 boots and enters in stop mode or timeout*/
// timeout = 0xFFFF;
// while((__HAL_RCC_GET_FLAG(RCC_FLAG_D2CKRDY) != RESET) && (timeout-- > 0));
// if ( timeout < 0 )
// {
// Error_Handler();
// }
while(__HAL_RCC_GET_FLAG(RCC_FLAG_D2CKRDY) != RESET)
{
	 asm("nop");
}

as described here.

Debug session for M7 goes fine, but when I try to connect to the M4, the ST links gdb server reports that the device can't be identified.

I think there is an underlying issue there: I have some code blinking LED1 from M7 and LED2 from M4 but I think the M7 gets stuck is waiting for n RCC_FLAG_D2CKRDY.

What situation can make the M4 not to rise the flag RCC_FLAG_D2CKRDY?

Do you have experience on that?

Another information: When I program the M4 using STM32Programmer I can see the LED2 blinking, but when I reset the board, it's not working anymore. So I suspect the bootup process or some OB? are wrong.

I used the examples from ST so it would be great if you give me a hand.

Thanks.