2 files changed, 37 insertions, 0 deletions
diff --git a/os/hal/platforms/STM32F4xx/hal_lld.c b/os/hal/platforms/STM32F4xx/hal_lld.c
index faf480333..d99661799 100644
--- a/os/hal/platforms/STM32F4xx/hal_lld.c
+++ b/os/hal/platforms/STM32F4xx/hal_lld.c
@@ -45,12 +45,15 @@
 
 /**
  * @brief   Initializes the backup domain.
+ * @note    WARNING! Changing clock source impossible without resetting
+ *          of the whole BKP domain.
  */
 static void hal_lld_backup_domain_init(void) {
 
   /* Backup domain access enabled and left open.*/
   PWR->CR |= PWR_CR_DBP;
 
+#if HAL_USE_RTC
   /* Reset BKP domain if different clock source selected.*/
   if ((RCC->BDCR & STM32_RTCSEL_MASK) != STM32_RTCSEL) {
     /* Backup domain reset.*/
@@ -76,6 +79,17 @@ static void hal_lld_backup_domain_init(void) {
     RCC->BDCR |= RCC_BDCR_RTCEN;
   }
 #endif /* STM32_RTCSEL != STM32_RTCSEL_NOCLOCK */
+#endif /* HAL_USE_RTC */
+
+#if HAL_USE_BKPSRAM
+  rccEnableBKPSRAM(false);
+
+  PWR->CSR |= PWR_CSR_BRE;
+  while ((PWR->CSR & PWR_CSR_BRR) == 0)
+    ;                                /* Waits until the regulator is stable */
+#else
+  PWR->CSR &= ~PWR_CSR_BRE;
+#endif /* HAL_USE_BKPSRAM */
 }
 
 /*===========================================================================*/
diff --git a/os/hal/platforms/STM32F4xx/stm32_rcc.h b/os/hal/platforms/STM32F4xx/stm32_rcc.h
index d87bc2ab2..b429d7bcd 100644
--- a/os/hal/platforms/STM32F4xx/stm32_rcc.h
+++ b/os/hal/platforms/STM32F4xx/stm32_rcc.h
@@ -387,6 +387,29 @@
 /** @} */
 
 /**
+ * @name    BKPSRAM specific RCC operations
+ * @{
+ */
+/**
+ * @brief   Enables the BKPSRAM peripheral clock.
+ *
+ * @param[in] lp        low power enable flag
+ *
+ * @api
+ */
+#define rccEnableBKPSRAM(lp) rccEnableAHB1(RCC_AHB1ENR_BKPSRAMEN, lp)
+
+/**
+ * @brief   Disables the BKPSRAM peripheral clock.
+ *
+ * @param[in] lp        low power enable flag
+ *
+ * @api
+ */
+#define rccDisableBKPSRAM(lp) rccDisableAHB1(RCC_AHB1ENR_BKPSRAMEN, lp)
+/** @} */
+
+/**
  * @name    PWR interface specific RCC operations
  * @{
  */