stm32: g0b1: RTT doesn't work properly after stop mode

[ycsin]

Describe the bug
The RTT stops working properly after the MCU enter stop mode. I'm on 2.7.1 LTS branch which already has #38561 patch.
It prints garbage after MCU went to sleep, it also missed some lines that would have been printed if UART backend were used:

Apart from this, I believe some of the character (next line?) sent from the log/shell cant be recognized by the RTT viewer for some reason:

WARNING: <Terminal 0>: ANSI CSI SGR parameter 7 not supported.
WARNING: <Terminal 0>: ANSI CSI SGR parameter 7 not supported.
WARNING: <Terminal 0>: ANSI CSI SGR parameter 7 not supported.
WARNING: <Terminal 0>: ANSI CSI SGR parameter 7 not supported.
WARNING: <Terminal 0>: ANSI CSI SGR parameter 7 not supported.

Environment (please complete the following information):

• OS: Windows
• gnuarmemb
• 2.7.1 LTS

prj.conf
I have these extra Kconfig to get the RTT built:

CONFIG_USE_SEGGER_RTT=y
CONFIG_LOG_BACKEND_RTT=y
CONFIG_LOG_BACKEND_UART=n

CONFIG_LOG_BACKEND_RTT_BUFFER=1
CONFIG_SHELL_BACKEND_SERIAL=n
CONFIG_SHELL_BACKEND_RTT=y

shell_rtt.c fails to build without CONFIG_LOG_BACKEND_RTT_BUFFER=1:

C:/Users/yongc/zephyrproject/zephyr/subsys/shell/shell_rtt.c:12:1: note: in expansion of macro 'BUILD_ASSERT'
   12 | BUILD_ASSERT(!(IS_ENABLED(CONFIG_LOG_BACKEND_RTT) &&
      | ^~~~~~~~~~~~

[ycsin]

@erwango @ABOSTM any idea?

[ABOSTM]

At first glance I would say: maybe one of the condition described in #38561 in not respected after wakeup

• one of the DMA is clocked

and sometimes also

• one of the DBGMCU bit STOP/STANDBY/SLEEP is set

@ycsin , could you check that ?

[ycsin]

@ycsin , could you check that ?

Thanks for looking into this.
How should I check this? Break point in the power.c exit post ops?

[ABOSTM]

Anywhere but after wakeup, power.c exit post ops sounds good, but at the end of this function.

[ycsin]

@ycsin , could you check that ?

I added a breakpoint here:

EDIT: so it seems to have satisfied the requirements stated in #38561

[erwango]

@ycsin Did you made any progress on this issue? Is it still valid ?

[ycsin]

@ycsin Did you made any progress on this issue? Is it still valid ?

I've left my previous company and I doubt if anyone (in my previous company) made any progress on this issue, it should still be valid

[erwango]

@ycsin Did you made any progress on this issue? Is it still valid ?

I've left my previous company and I doubt if anyone made any progress on this issue, it should still be valid

Thanks for the head's up.

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