AT91SAM9 RTT as RTC

modulename: rtc-at91sam9.ko

configname: CONFIG_RTC_DRV_AT91SAM9

Linux Kernel Configuration
└─>Device Drivers
└─>Real Time Clock
└─>AT91SAM9 RTT as RTC
In linux kernel since version 2.6.25 (release Date: 2008-04-16)  
Some AT91SAM9 SoCs provide an RTT (Real Time Timer) block which
can be used as an RTC thanks to the backup power supply (e.g. a
small coin cell battery) which keeps this block and the GPBR
(General Purpose Backup Registers) block powered when the device
is shutdown.
Some AT91SAM9 SoCs provide a real RTC block, on those ones you'd
probably want to use the real RTC block instead of the "RTT as an
RTC" driver.

source code: