i have very simple project on board stm32f4discovery, it is test microSD card project, code was generate in stm32cubemx version 4.22 (fatfs r0.11) with pack STM32Cube_FW_F4_V1.15.0 for MDK-ARM V5. This project good working.
After upgrade stm32cubemx version 4.23 (fatfs r0.12c) with pack STM32Cube_FW_F4_V1.17.0 function f_mount (mount immediately) or f_open always return FR_NOT_READY.
In hardware there were no changes.
I did update current project after read release_Notes.html for r0.12 and recreate clean project, sdio + fatfs r0.12c not working.
Can't rollback to stm32cubemx 4.22, on st.com just 4.23 version stm32cubemx.