Stm32 chibios register documentation

where can we find a proper documentation on the stm32 register configuration under chibios HAL. Reading the code without a ref doc nor tutorial nor example code is quite cumbersome.

Not sure what are you referring to as “register configuration”? ChibiOS is a bit lacking, to put it mildly, when it comes to documentation, but this may help at least somewhat: ChibiOS/HAL: Introduction