diff --git a/drv/rcc.c b/drv/rcc.c
index 56adbbc..c229c45 100644
--- a/drv/rcc.c
+++ b/drv/rcc.c
@@ -66,10 +66,16 @@ void rcc_configure_lsi(bool enable)
 
 	//ensure LSI is enabled
 	if (enable) {
-		while (regs->CSR.LSIRDY != 0x1);
+		while (regs->CSR.LSIRDY != 0x1) {}
 	}
 }
 
+void rcc_configure_rtc(bool enable, enum RccRtcClockSrc clock_src)
+{
+	regs->BDCR.RTCSEL = clock_src;
+	regs->BDCR.RTCEN = enable;
+}
+
 void rcc_enable(enum RccAhb ahb_mask, enum RccApb1 apb1_mask,
 		enum RccApb2 apb2_mask)
 {
diff --git a/drv/rcc.h b/drv/rcc.h
index f26ba01..b437ecb 100644
--- a/drv/rcc.h
+++ b/drv/rcc.h
@@ -95,6 +95,13 @@ enum RccApb2 {
 	RCC_APB2_TIM11 = (0x1 << 21),
 };
 
+enum RccRtcClockSrc {
+	RCC_RTC_CLOCK_SRC_NONE = 0x0,
+	RCC_RTC_CLOCK_SRC_LSE  = 0x1,
+	RCC_RTC_CLOCK_SRC_LSI  = 0x2,
+	RCC_RTC_CLOCK_SRC_HSE  = 0x3,
+};
+
 struct RccClocks {
 	uint32_t ahb_freq;
 	uint32_t apb1_freq;
@@ -118,6 +125,8 @@ void rcc_configure(enum RccPreset preset);
  */
 void rcc_configure_lsi(bool enable);
 
+void rcc_configure_rtc(bool enable, enum RccRtcClockSrc clock_src);
+
 /**
  * Enables peripherals on the different buses. The enums values can used as
  * masks to enable multiple peripherals at the same time. Invalid values will be