Zephyr 4.1: STM32U5 USART2 fails to suspend when CONFIG_POWER_DOMAIN is enabled

[zafersn]

I'm working with Zephyr 4.1 on an STM32u575, and using runtime power management (CONFIG_PM_DEVICE_RUNTIME=y) successfully to suspend/resume USART2.

However, when I enable:

CONFIG_PM_DEVICE_POWER_DOMAIN=y
CONFIG_POWER_DOMAIN=y

USART2 can no longer suspend. It remains always active.

Am I missing something here?

Steps to Reproduce:

1. Get echo bot sample.
2. as The configs below:

CONFIG_SERIAL=y
CONFIG_UART_INTERRUPT_DRIVEN=y
CONFIG_PM_DEVICE=y
CONFIG_PM_DEVICE_RUNTIME=y
CONFIG_PM_DEVICE_POWER_DOMAIN=y
CONFIG_POWER_DOMAIN=y