STM32 RTC

modulename: rtc-stm32.ko

configname: CONFIG_RTC_DRV_STM32

Linux Kernel Configuration
└─>Device Drivers
└─>Real Time Clock
└─>Device Tree and Open Firmware support
└─>Pin controllers
└─>STM32 RTC
In linux kernel since version 3.10 (release Date: 2013-06-30)  
If you say yes here you get support for the STM32 On-Chip
Real Time Clock.

This driver can also be built as a module, if so, the module
will be called "rtc-stm32".

source code:
drivers/rtc/rtc-stm32.c