I am using B-L475E-IOT01A. I am wondering that MSI can be changed on the fly when it used as system clock source.
In `HAL_RCC_OscConfig` from STM32L4Cube drivers code, it looks like ok. But I didn't find any relative information from l47xxx manual. The manual only specifies that MSIRGSEL can be modified when MSION is 0 or when MSIRDY is 1. Not allow changing it when MSION is 1 and MSIRDY is 0.