git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@3783 35acf78f-673a-0410-8e92-d51de3d6d3f4

os/hal/platforms/STM32/RTCv1/rtc_lld.c

@@ -87,7 +87,7 @@ static void rtc_lld_serve_interrupt(RTCDriver *rtcp) {
 static void rtc_lld_wait_write(void) {
 
   /* Waits registers write completion.*/
-  while (!(RTC->CRL & RTC_CRL_RTOFF))
+  while ((RTC->CRL & RTC_CRL_RTOFF) == 0)
     ;
 }
 
@@ -122,50 +122,6 @@ CH_IRQ_HANDLER(RTC_IRQHandler) {
  * @notapi
  */
 void rtc_lld_init(void){
-  uint32_t preload;
-
-  rccEnableBKPInterface(FALSE);
-
-  /* Enables access to BKP registers.*/
-  PWR->CR |= PWR_CR_DBP;
-
-  /* If the RTC is not enabled then performs a reset of the backup domain.*/
-  if (!(RCC->BDCR & RCC_BDCR_RTCEN)) {
-    RCC->BDCR = RCC_BDCR_BDRST;
-    RCC->BDCR = 0;
-  }
-
-#if STM32_RTC == STM32_RTC_LSE
-#define RTC_CLK   STM32_LSECLK
-  if (!(RCC->BDCR & RCC_BDCR_LSEON)) {
-    RCC->BDCR |= RCC_BDCR_LSEON;
-    while (!(RCC->BDCR & RCC_BDCR_LSERDY))
-      ;
-  }
-  preload = STM32_LSECLK - 1;
-#elif STM32_RTC == STM32_RTC_LSI
-#define RTC_CLK   STM32_LSICLK
-  /* TODO: Move the LSI clock initialization in the HAL low level driver.*/
-  RCC->CSR |= RCC_CSR_LSION;
-  while (!(RCC->CSR & RCC_CSR_LSIRDY))
-    ;
-  /* According to errata sheet we must wait additional 100 uS for
-     stabilization.
-     TODO: Change this code, software loops are not reliable.*/
-  volatile uint32_t tmo = (STM32_SYSCLK / 1000000) * 100;
-  while (tmo--)
-    ;
-  preload = STM32_LSICLK - 1;
-#elif STM32_RTC == STM32_RTC_HSE
-#define RTC_CLK   (STM32_HSECLK / 128)
-  preload = (STM32_HSECLK / 128) - 1;
-#endif
-
-  /* Selects clock source (previously enabled and stabilized).*/
-  RCC->BDCR = (RCC->BDCR & ~RCC_BDCR_RTCSEL) | STM32_RTC;
-
-  /* RTC enabled regardless its previous status.*/
-  RCC->BDCR |= RCC_BDCR_RTCEN;
 
   /* Ensure that RTC_CNT and RTC_DIV contain actual values after enabling
      clocking on APB1, because these values only update when APB1
@@ -175,15 +131,15 @@ void rtc_lld_init(void){
     ;
 
   /* Write preload register only if its value differs.*/
-  if (preload != ((((uint32_t)(RTC->PRLH)) << 16) + (uint32_t)RTC->PRLL)) {
+  if (STM32_RTCCLK != (((uint32_t)(RTC->PRLH)) << 16) +
-
+                       ((uint32_t)RTC->PRLL) + 1) {
-    rtc_lld_wait_write();
 
     /* Enters configuration mode and writes PRLx registers then leaves the
        configuration mode.*/
+    rtc_lld_wait_write();
     RTC->CRL |= RTC_CRL_CNF;
-    RTC->PRLH = (uint16_t)(preload >> 16);
+    RTC->PRLH = (uint16_t)((STM32_RTCCLK - 1) >> 16);
-    RTC->PRLL = (uint16_t)(preload & 0xFFFF);
+    RTC->PRLL = (uint16_t)((STM32_RTCCLK - 1) & 0xFFFF);
     RTC->CRL &= ~RTC_CRL_CNF;
   }
 
@@ -209,7 +165,6 @@ void rtc_lld_set_time(RTCDriver *rtcp, const RTCTime *timespec) {
   (void)rtcp;
 
   rtc_lld_wait_write();
-
   RTC->CRL |= RTC_CRL_CNF;
   RTC->CNTH = (uint16_t)(timespec->tv_sec >> 16);
   RTC->CNTL = (uint16_t)(timespec->tv_sec & 0xFFFF);
@@ -229,17 +184,15 @@ void rtc_lld_get_time(RTCDriver *rtcp, RTCTime *timespec) {
 
   uint32_t time_frac;
 
-READ_REGISTERS:
+  /* The read is repeated until we are able to do it twice and obtain the
-  timespec->tv_sec = ((uint32_t)(RTC->CNTH) << 16) + RTC->CNTL;
+     same result.*/
-  time_frac = (((uint32_t)RTC->DIVH) << 16) + (uint32_t)RTC->DIVL;
+  do {
+    timespec->tv_sec = ((uint32_t)(RTC->CNTH) << 16) + RTC->CNTL;
+    time_frac = (((uint32_t)RTC->DIVH) << 16) + (uint32_t)RTC->DIVL;
+  } while ((timespec->tv_sec) != (((uint32_t)(RTC->CNTH) << 16) + RTC->CNTL));
 
-  /* If second counter updated between reading of integer and fractional parts
+  timespec->tv_msec = (uint16_t)(((STM32_RTCCLK - 1 - time_frac) * 1000) /
-   * we must reread both values. */
+                                 STM32_RTCCLK);
-  if((timespec->tv_sec) != (((uint32_t)(RTC->CNTH) << 16) + RTC->CNTL)){
-    goto READ_REGISTERS;
-  }
-
-  timespec->tv_msec = (uint16_t)(((RTC_CLK - 1 - time_frac) * 1000) / RTC_CLK);
 }
 
 /**
@@ -260,10 +213,10 @@ void rtc_lld_set_alarm(RTCDriver *rtcp,
   (void)rtcp;
   (void)alarm;
 
-  rtc_lld_wait_write();
 
   /* Enters configuration mode and writes ALRHx registers then leaves the
      configuration mode.*/
+  rtc_lld_wait_write();
   RTC->CRL |= RTC_CRL_CNF;
   if (alarmspec != NULL) {
     RTC->ALRH = (uint16_t)(alarmspec->tv_sec >> 16);
@@ -315,17 +268,14 @@ void rtc_lld_set_callback(RTCDriver *rtcp, rtccb_t callback) {
     rtcp->callback = callback;
 
     /* Interrupts are enabled only after setting up the callback, this
-     way there is no need to check for the NULL callback pointer inside
+       way there is no need to check for the NULL callback pointer inside
-     the IRQ handler.*/
+       the IRQ handler.*/
-    rtc_lld_wait_write();
     RTC->CRL &= ~(RTC_CRL_OWF | RTC_CRL_ALRF | RTC_CRL_SECF);
-    rtc_lld_wait_write();
     nvicEnableVector(RTC_IRQn, CORTEX_PRIORITY_MASK(STM32_RTC_IRQ_PRIORITY));
     RTC->CRH |= RTC_CRH_OWIE | RTC_CRH_ALRIE | RTC_CRH_SECIE;
   }
   else {
     nvicDisableVector(RTC_IRQn);
-    rtc_lld_wait_write();
     RTC->CRL = 0;
     RTC->CRH = 0;
   }

os/hal/platforms/STM32/RTCv1/rtc_lld.h

@@ -61,9 +61,8 @@
 #error "RTC not present in the selected device"
 #endif
 
-#if !(STM32_RTC == STM32_RTC_LSE) && !(STM32_RTC == STM32_RTC_LSI) &&       \
+#if STM32_RTCCLK == 0
-    !(STM32_RTC == STM32_RTC_HSE)
+#error "RTC clock not enabled"
-#error "invalid source selected for RTC clock"
 #endif
 
 /*===========================================================================*/

os/hal/platforms/STM32F1xx/hal_lld.c

@@ -41,6 +41,47 @@
 /* Driver local functions.                                                   */
 /*===========================================================================*/
 
+/**
+ * @brief   Initializes the backup domain.
+ */
+static void hal_lld_backup_domain_init(void) {
+
+  /* Backup domain access enabled during initialization.*/
+  PWR->CR |= PWR_CR_DBP;
+
+  /* RTC clock initialization.*/
+#if STM32_RTCSEL == STM32_RTCSEL_NOCLOCK
+  /* RTC clock not required, backup domain reset as initialization.*/
+  RCC->BDCR = RCC_BDCR_BDRST;
+  RCC->BDCR = 0;
+#else /* STM32_RTCSEL != STM32_RTCSEL_NOCLOCK */
+  /* If the backup domain hasn't been initialized yet then proceed with
+     initialization.*/
+  if (!(RCC->BDCR & RCC_BDCR_LSEON)) {
+    /* Backup domain reset.*/
+    RCC->BDCR = RCC_BDCR_BDRST;
+    RCC->BDCR = 0;
+
+    /* If enabled then the LSE is started.*/
+#if STM32_LSE_ENABLED
+    RCC->BDCR |= RCC_BDCR_LSEON;
+    while ((RCC->BDCR & RCC_BDCR_LSERDY) == 0)
+      ;                                     /* Waits until LSE is stable.   */
+#endif
+
+    /* Selects clock source.*/
+    RCC->BDCR = (RCC->BDCR & ~RCC_BDCR_RTCSEL) | STM32_RTCSEL;
+
+    /* RTC enabled regardless its previous status, this will also prevent
+       successive initializations.*/
+    RCC->BDCR |= RCC_BDCR_RTCEN;
+  }
+#endif /* STM32_RTCSEL != STM32_RTCSEL_NOCLOCK */
+
+  /*  Backup domain access disabled for operations safety.*/
+  PWR->CR &= ~PWR_CR_DBP;
+}
+
 /*===========================================================================*/
 /* Driver interrupt handlers.                                                */
 /*===========================================================================*/
@@ -70,13 +111,19 @@ void hal_lld_init(void) {
   /* DWT cycle counter enable.*/
   DWT_CTRL |= DWT_CTRL_CYCCNTENA;
 
+  /* PWR and BD clocks enabled.*/
+  rccEnablePWRInterface(FALSE);
+  rccEnableBKPInterface(FALSE);
+
+  /* Initializes the backup domain.*/
+  hal_lld_backup_domain_init();
+
 #if defined(STM32_DMA_REQUIRED)
   dmaInit();
 #endif
 
   /* Programmable voltage detector enable.*/
 #if STM32_PVD_ENABLE
-  rccEnablePWRInterface(FALSE);
   PWR->CR |= PWR_CR_PVDE | (STM32_PLS & STM32_PLS_MASK);
 #endif /* STM32_PVD_ENABLE */
 }
@@ -122,15 +169,6 @@ void stm32_clock_init(void) {
     ;                                       /* Waits until LSI is stable.   */
 #endif
 
-#if STM32_LSE_ENABLED
-  /* LSE activation, have to unlock the register.*/
-  PWR->CR |= PWR_CR_DBP;
-  RCC->BDCR |= RCC_BDCR_LSEON;
-  while ((RCC->BDCR & RCC_BDCR_LSERDY) == 0)
-    ;                                       /* Waits until LSE is stable.   */
-  PWR->CR &= ~PWR_CR_DBP;
-#endif
-
 #if STM32_ACTIVATE_PLL
   /* PLL activation.*/
   RCC->CFGR |= STM32_PLLMUL | STM32_PLLXTPRE | STM32_PLLSRC;
@@ -193,15 +231,6 @@ void stm32_clock_init(void) {
     ;                                       /* Waits until LSI is stable.   */
 #endif
 
-#if STM32_LSE_ENABLED
-  /* LSE activation, have to unlock the register.*/
-  PWR->CR |= PWR_CR_DBP;
-  RCC->BDCR |= RCC_BDCR_LSEON;
-  while ((RCC->BDCR & RCC_BDCR_LSERDY) == 0)
-    ;                                       /* Waits until LSE is stable.   */
-  PWR->CR &= ~PWR_CR_DBP;
-#endif
-
   /* Settings of various dividers and multipliers in CFGR2.*/
   RCC->CFGR2 = STM32_PLL3MUL | STM32_PLL2MUL | STM32_PREDIV2 |
                STM32_PREDIV1 | STM32_PREDIV1SRC;

os/hal/platforms/STM32F1xx/hal_lld_f100.h

@@ -648,8 +648,9 @@
 #error "HSI not enabled, required by STM32_SW and STM32_PLLSRC"
 #endif
 
-#if (STM32_MCOSEL == STM32_MCOSEL_HSI) ||                                         \
+#if (STM32_MCOSEL == STM32_MCOSEL_HSI) ||                                   \
-    ((STM32_MCOSEL == STM32_MCOSEL_PLLDIV2) && (STM32_PLLSRC == STM32_PLLSRC_HSI))
+    ((STM32_MCOSEL == STM32_MCOSEL_PLLDIV2) &&                              \
+     (STM32_PLLSRC == STM32_PLLSRC_HSI))
 #error "HSI not enabled, required by STM32_MCOSEL"
 #endif
 
@@ -870,6 +871,21 @@
 #error "STM32_PCLK2 exceeding maximum frequency (STM32_PCLK2_MAX)"
 #endif
 
+/**
+ * @brief   RTC clock.
+ */
+#if (STM32_RTCSEL == STM32_RTCSEL_LSE) || defined(__DOXYGEN__)
+#define STM32_RTCCLK                STM32_LSECLK
+#elif STM32_RTCSEL == STM32_RTCSEL_LSI
+#define STM32_RTCCLK                STM32_LSICLK
+#elif STM32_RTCSEL == STM32_RTCSEL_HSEDIV
+#define STM32_RTCCLK                (STM32_HSECLK / 128)
+#elif STM32_RTCSEL == STM32_RTCSEL_NOCLOCK
+#define STM32_RTCCLK                0
+#else
+#error "invalid source selected for RTC clock"
+#endif
+
 /**
  * @brief   ADC frequency.
  */

os/hal/platforms/STM32F1xx/hal_lld_f103.h

@@ -981,8 +981,9 @@
 #error "HSI not enabled, required by STM32_SW and STM32_PLLSRC"
 #endif
 
-#if (STM32_MCOSEL == STM32_MCOSEL_HSI) ||                                         \
+#if (STM32_MCOSEL == STM32_MCOSEL_HSI) ||                                   \
-    ((STM32_MCOSEL == STM32_MCOSEL_PLLDIV2) && (STM32_PLLSRC == STM32_PLLSRC_HSI))
+    ((STM32_MCOSEL == STM32_MCOSEL_PLLDIV2) &&                              \
+     (STM32_PLLSRC == STM32_PLLSRC_HSI))
 #error "HSI not enabled, required by STM32_MCOSEL"
 #endif
 
@@ -1204,6 +1205,21 @@
 #error "STM32_PCLK2 exceeding maximum frequency (STM32_PCLK2_MAX)"
 #endif
 
+/**
+ * @brief   RTC clock.
+ */
+#if (STM32_RTCSEL == STM32_RTCSEL_LSE) || defined(__DOXYGEN__)
+#define STM32_RTCCLK                STM32_LSECLK
+#elif STM32_RTCSEL == STM32_RTCSEL_LSI
+#define STM32_RTCCLK                STM32_LSICLK
+#elif STM32_RTCSEL == STM32_RTCSEL_HSEDIV
+#define STM32_RTCCLK                (STM32_HSECLK / 128)
+#elif STM32_RTCSEL == STM32_RTCSEL_NOCLOCK
+#define STM32_RTCCLK                0
+#else
+#error "invalid source selected for RTC clock"
+#endif
+
 /**
  * @brief   ADC frequency.
  */

os/hal/platforms/STM32F1xx/hal_lld_f105_f107.h

@@ -596,8 +596,9 @@
 #error "HSI not enabled, required by STM32_SW and STM32_PLLSRC"
 #endif
 
-#if (STM32_MCOSEL == STM32_MCOSEL_HSI) ||                                         \
+#if (STM32_MCOSEL == STM32_MCOSEL_HSI) ||                                   \
-    ((STM32_MCOSEL == STM32_MCOSEL_PLLDIV2) && (STM32_PLLSRC == STM32_PLLSRC_HSI))
+    ((STM32_MCOSEL == STM32_MCOSEL_PLLDIV2) &&                              \
+     (STM32_PLLSRC == STM32_PLLSRC_HSI))
 #error "HSI not enabled, required by STM32_MCOSEL"
 #endif
 
@@ -956,6 +957,21 @@
 #error "STM32_PCLK2 exceeding maximum frequency (STM32_PCLK2_MAX)"
 #endif
 
+/**
+ * @brief   RTC clock.
+ */
+#if (STM32_RTCSEL == STM32_RTCSEL_LSE) || defined(__DOXYGEN__)
+#define STM32_RTCCLK                STM32_LSECLK
+#elif STM32_RTCSEL == STM32_RTCSEL_LSI
+#define STM32_RTCCLK                STM32_LSICLK
+#elif STM32_RTCSEL == STM32_RTCSEL_HSEDIV
+#define STM32_RTCCLK                (STM32_HSECLK / 128)
+#elif STM32_RTCSEL == STM32_RTCSEL_NOCLOCK
+#define STM32_RTCCLK                0
+#else
+#error "invalid source selected for RTC clock"
+#endif
+
 /**
  * @brief   ADC frequency.
  */

os/hal/platforms/STM32F2xx/hal_lld.c

@@ -41,6 +41,47 @@
 /* Driver local functions.                                                   */
 /*===========================================================================*/
 
+/**
+ * @brief   Initializes the backup domain.
+ */
+static void hal_lld_backup_domain_init(void) {
+
+  /* Backup domain access enabled during initialization.*/
+  PWR->CR |= PWR_CR_DBP;
+
+  /* RTC clock initialization.*/
+#if STM32_RTCSEL == STM32_RTCSEL_NOCLOCK
+  /* RTC clock not required, backup domain reset as initialization.*/
+  RCC->BDCR = RCC_BDCR_BDRST;
+  RCC->BDCR = 0;
+#else /* STM32_RTCSEL != STM32_RTCSEL_NOCLOCK */
+  /* If the backup domain hasn't been initialized yet then proceed with
+     initialization.*/
+  if (!(RCC->BDCR & RCC_BDCR_LSEON)) {
+    /* Backup domain reset.*/
+    RCC->BDCR = RCC_BDCR_BDRST;
+    RCC->BDCR = 0;
+
+    /* If enabled then the LSE is started.*/
+#if STM32_LSE_ENABLED
+    RCC->BDCR |= RCC_BDCR_LSEON;
+    while ((RCC->BDCR & RCC_BDCR_LSERDY) == 0)
+      ;                                     /* Waits until LSE is stable.   */
+#endif
+
+    /* Selects clock source.*/
+    RCC->BDCR = (RCC->BDCR & ~RCC_BDCR_RTCSEL) | STM32_RTCSEL;
+
+    /* RTC enabled regardless its previous status, this will also prevent
+       successive initializations.*/
+    RCC->BDCR |= RCC_BDCR_RTCEN;
+  }
+#endif /* STM32_RTCSEL != STM32_RTCSEL_NOCLOCK */
+
+  /*  Backup domain access disabled for operations safety.*/
+  PWR->CR &= ~PWR_CR_DBP;
+}
+
 /*===========================================================================*/
 /* Driver interrupt handlers.                                                */
 /*===========================================================================*/
@@ -74,13 +115,18 @@ void hal_lld_init(void) {
   /* DWT cycle counter enable.*/
   DWT_CTRL |= DWT_CTRL_CYCCNTENA;
 
+  /* PWR clock enabled.*/
+  rccEnablePWRInterface(FALSE);
+
+  /* Initializes the backup domain.*/
+  hal_lld_backup_domain_init();
+
 #if defined(STM32_DMA_REQUIRED)
   dmaInit();
 #endif
 
   /* Programmable voltage detector enable.*/
 #if STM32_PVD_ENABLE
-  rccEnablePWRInterface(FALSE);
   PWR->CR |= PWR_CR_PVDE | (STM32_PLS & STM32_PLS_MASK);
 #endif /* STM32_PVD_ENABLE */
 }

os/hal/platforms/STM32F2xx/hal_lld.h

@@ -1229,16 +1229,6 @@
 #error "invalid STM32_MCO2PRE value specified"
 #endif
 
-/**
- * @brief   HSE divider toward RTC clock.
- */
-#if ((STM32_RTCPRE_VALUE >= 2) && (STM32_RTCPRE_VALUE <= 31))  ||           \
-    defined(__DOXYGEN__)
-#define STM32_HSEDIVCLK             (STM32_HSECLK / STM32_RTCPRE_VALUE)
-#else
-#error "invalid STM32_RTCPRE value specified"
-#endif
-
 /**
  * @brief   RTC HSE divider setting.
  */
@@ -1249,6 +1239,16 @@
 #error "invalid STM32_RTCPRE value specified"
 #endif
 
+/**
+ * @brief   HSE divider toward RTC clock.
+ */
+#if ((STM32_RTCPRE_VALUE >= 2) && (STM32_RTCPRE_VALUE <= 31))  ||           \
+    defined(__DOXYGEN__)
+#define STM32_HSEDIVCLK             (STM32_HSECLK / STM32_RTCPRE_VALUE)
+#else
+#error "invalid STM32_RTCPRE value specified"
+#endif
+
 /**
  * @brief   RTC clock.
  */

os/hal/platforms/STM32F4xx/hal_lld.c

@@ -41,6 +41,47 @@
 /* Driver local functions.                                                   */
 /*===========================================================================*/
 
+/**
+ * @brief   Initializes the backup domain.
+ */
+static void hal_lld_backup_domain_init(void) {
+
+  /* Backup domain access enabled during initialization.*/
+  PWR->CR |= PWR_CR_DBP;
+
+  /* RTC clock initialization.*/
+#if STM32_RTCSEL == STM32_RTCSEL_NOCLOCK
+  /* RTC clock not required, backup domain reset as initialization.*/
+  RCC->BDCR = RCC_BDCR_BDRST;
+  RCC->BDCR = 0;
+#else /* STM32_RTCSEL != STM32_RTCSEL_NOCLOCK */
+  /* If the backup domain hasn't been initialized yet then proceed with
+     initialization.*/
+  if (!(RCC->BDCR & RCC_BDCR_LSEON)) {
+    /* Backup domain reset.*/
+    RCC->BDCR = RCC_BDCR_BDRST;
+    RCC->BDCR = 0;
+
+    /* If enabled then the LSE is started.*/
+#if STM32_LSE_ENABLED
+    RCC->BDCR |= RCC_BDCR_LSEON;
+    while ((RCC->BDCR & RCC_BDCR_LSERDY) == 0)
+      ;                                     /* Waits until LSE is stable.   */
+#endif
+
+    /* Selects clock source.*/
+    RCC->BDCR = (RCC->BDCR & ~RCC_BDCR_RTCSEL) | STM32_RTCSEL;
+
+    /* RTC enabled regardless its previous status, this will also prevent
+       successive initializations.*/
+    RCC->BDCR |= RCC_BDCR_RTCEN;
+  }
+#endif /* STM32_RTCSEL != STM32_RTCSEL_NOCLOCK */
+
+  /*  Backup domain access disabled for operations safety.*/
+  PWR->CR &= ~PWR_CR_DBP;
+}
+
 /*===========================================================================*/
 /* Driver interrupt handlers.                                                */
 /*===========================================================================*/
@@ -74,13 +115,18 @@ void hal_lld_init(void) {
   /* DWT cycle counter enable.*/
   DWT_CTRL |= DWT_CTRL_CYCCNTENA;
 
+  /* PWR clock enabled.*/
+  rccEnablePWRInterface(FALSE);
+
+  /* Initializes the backup domain.*/
+  hal_lld_backup_domain_init();
+
 #if defined(STM32_DMA_REQUIRED)
   dmaInit();
 #endif
 
   /* Programmable voltage detector enable.*/
 #if STM32_PVD_ENABLE
-  rccEnablePWRInterface(FALSE);
   PWR->CR |= PWR_CR_PVDE | (STM32_PLS & STM32_PLS_MASK);
 #endif /* STM32_PVD_ENABLE */
 }

os/hal/platforms/STM32F4xx/hal_lld.h

@@ -1249,16 +1249,6 @@
 #error "invalid STM32_MCO2PRE value specified"
 #endif
 
-/**
- * @brief   HSE divider toward RTC clock.
- */
-#if ((STM32_RTCPRE_VALUE >= 2) && (STM32_RTCPRE_VALUE <= 31))  ||           \
-    defined(__DOXYGEN__)
-#define STM32_HSEDIVCLK             (STM32_HSECLK / STM32_RTCPRE_VALUE)
-#else
-#error "invalid STM32_RTCPRE value specified"
-#endif
-
 /**
  * @brief   RTC HSE divider setting.
  */
@@ -1269,6 +1259,16 @@
 #error "invalid STM32_RTCPRE value specified"
 #endif
 
+/**
+ * @brief   HSE divider toward RTC clock.
+ */
+#if ((STM32_RTCPRE_VALUE >= 2) && (STM32_RTCPRE_VALUE <= 31))  ||           \
+    defined(__DOXYGEN__)
+#define STM32_HSEDIVCLK             (STM32_HSECLK / STM32_RTCPRE_VALUE)
+#else
+#error "invalid STM32_RTCPRE value specified"
+#endif
+
 /**
  * @brief   RTC clock.
  */
@@ -1284,6 +1284,16 @@
 #error "invalid STM32_RTCSEL value specified"
 #endif
 
+/**
+ * @brief   RTC HSE divider setting.
+ */
+#if ((STM32_RTCPRE_VALUE >= 2) && (STM32_RTCPRE_VALUE <= 31)) ||            \
+    defined(__DOXYGEN__)
+#define STM32_RTCPRE                (STM32_RTCPRE_VALUE << 16)
+#else
+#error "invalid STM32_RTCPRE value specified"
+#endif
+
 /**
  * @brief   48MHz frequency.
  */

os/hal/platforms/STM32L1xx/hal_lld.c

@@ -41,6 +41,47 @@
 /* Driver local functions.                                                   */
 /*===========================================================================*/
 
+/**
+ * @brief   Initializes the backup domain.
+ */
+static void hal_lld_backup_domain_init(void) {
+
+  /* Backup domain access enabled during initialization.*/
+  PWR->CR |= PWR_CR_DBP;
+
+  /* RTC clock initialization.*/
+#if STM32_RTCSEL == STM32_RTCSEL_NOCLOCK
+  /* RTC clock not required, backup domain reset as initialization.*/
+  RCC->BDCR = RCC_BDCR_BDRST;
+  RCC->BDCR = 0;
+#else /* STM32_RTCSEL != STM32_RTCSEL_NOCLOCK */
+  /* If the backup domain hasn't been initialized yet then proceed with
+     initialization.*/
+  if (!(RCC->BDCR & RCC_BDCR_LSEON)) {
+    /* Backup domain reset.*/
+    RCC->BDCR = RCC_BDCR_BDRST;
+    RCC->BDCR = 0;
+
+    /* If enabled then the LSE is started.*/
+#if STM32_LSE_ENABLED
+    RCC->BDCR |= RCC_BDCR_LSEON;
+    while ((RCC->BDCR & RCC_BDCR_LSERDY) == 0)
+      ;                                     /* Waits until LSE is stable.   */
+#endif
+
+    /* Selects clock source.*/
+    RCC->BDCR = (RCC->BDCR & ~RCC_BDCR_RTCSEL) | STM32_RTCSEL;
+
+    /* RTC enabled regardless its previous status, this will also prevent
+       successive initializations.*/
+    RCC->BDCR |= RCC_BDCR_RTCEN;
+  }
+#endif /* STM32_RTCSEL != STM32_RTCSEL_NOCLOCK */
+
+  /*  Backup domain access disabled for operations safety.*/
+  PWR->CR &= ~PWR_CR_DBP;
+}
+
 /*===========================================================================*/
 /* Driver interrupt handlers.                                                */
 /*===========================================================================*/
@@ -71,13 +112,18 @@ void hal_lld_init(void) {
   /* DWT cycle counter enable.*/
   DWT_CTRL |= DWT_CTRL_CYCCNTENA;
 
+  /* PWR clock enabled.*/
+  rccEnablePWRInterface(FALSE);
+
+  /* Initializes the backup domain.*/
+  hal_lld_backup_domain_init();
+
 #if defined(STM32_DMA_REQUIRED)
   dmaInit();
 #endif
 
   /* Programmable voltage detector enable.*/
 #if STM32_PVD_ENABLE
-  rccEnablePWRInterface(FALSE);
   PWR->CR |= PWR_CR_PVDE | (STM32_PLS & STM32_PLS_MASK);
 #endif /* STM32_PVD_ENABLE */
 }

os/kernel/include/chthreads.h

@@ -125,7 +125,7 @@ struct Thread {
 #if CH_DBG_THREADS_PROFILING || defined(__DOXYGEN__)
   /**
    * @brief Thread consumed time in ticks.
-   * @note This field can overflow.
+   * @note  This field can overflow.
    */
   volatile systime_t    p_time;
 #endif