Use RTC to generate tick events

src/fw/drivers/rtc.h

@@ -100,6 +100,22 @@ RtcTicks rtc_alarm_get_elapsed_ticks(void);
 //!     us from going into stop mode before we're ready to wake up from it.
 bool rtc_alarm_is_initialized(void);
 
+// RTC Wake-up
+///////////////////////////////////////////////////////////////////////////////
+
+//! RTC second tick callback.
+typedef void (*RtcSecondTickCallback)(void *ctx);
+
+//! Configures the RTC to fire the given callback on every second tick.
+//!
+//! @note Callback happens in ISR context.
+//!
+//! @param callback Callback to call every time RTC increases 1 second.
+//! @param ctx Context to pass to the callback when called.
+void rtc_second_tick_subscribe(RtcSecondTickCallback callback, void *ctx);
+
+//! Unsubscribes from the RTC second tick.
+void rtc_second_tick_unsubscribe(void);
 
 // Utility Functions
 ///////////////////////////////////////////////////////////////////////////////

src/fw/drivers/rtc/sf32lb.c

@@ -81,6 +81,17 @@ static RTC_HandleTypeDef RTC_Handler = {
 
 static bool s_initialized = false;
 
+static RtcSecondTickCallback s_second_tick_callback = NULL;
+static void *s_second_tick_callback_ctx = NULL;
+
+void RTC_IRQHandler(void) {
+  HAL_RTC_IRQHandler(&RTC_Handler);
+}
+
+void HAL_RTC_AlarmAEventCallback(RTC_HandleTypeDef *hrtc) {
+  s_second_tick_callback(s_second_tick_callback_ctx);
+}
+
 #ifndef SF32LB52_USE_LXT
 static uint32_t prv_rtc_get_lpcycle() {
   uint32_t value;
@@ -204,6 +215,9 @@ void rtc_init(void) {
   prv_rtc_reconfig();
 #endif
 
+  HAL_HPAON_EnableWakeupSrc(HPAON_WAKEUP_SRC_RTC, AON_PIN_MODE_HIGH);
+  HAL_NVIC_SetPriority(RTC_IRQn, 5, 0);
+
   s_initialized = true;
 }
 
@@ -477,3 +491,27 @@ void rtc_calibrate_frequency(uint32_t frequency) {
   PBL_ASSERTN(success);
 #endif
 }
+
+void rtc_second_tick_subscribe(RtcSecondTickCallback callback, void *ctx) {
+  PBL_ASSERTN(s_second_tick_callback == NULL);
+
+  s_second_tick_callback = callback;
+  s_second_tick_callback_ctx = ctx;
+
+  RTC_AlarmTypeDef alarm = {
+    // Mask all fields, and subsecond mask to 8-bit (covers DIV_B=256)
+    .AlarmMask = RTC_ALRMDR_MSKWD | RTC_ALRMDR_MSKM | RTC_ALRMDR_MSKD |
+                 RTC_ALRMDR_MSKH | RTC_ALRMDR_MSKMN | RTC_ALRMDR_MSKS |
+                 (8U << RTC_ALRMDR_MSKSS_Pos),
+    .AlarmSubSecondMask = RTC_ALARMSUBSECONDMASK_ALL,
+  };
+  HAL_RTC_SetAlarm(&RTC_Handler, &alarm, RTC_FORMAT_BIN);
+}
+
+void rtc_second_tick_unsubscribe(void) {
+  PBL_ASSERTN(s_second_tick_callback != NULL);
+
+  HAL_RTC_DeactivateAlarm(&RTC_Handler);
+
+  s_second_tick_callback = NULL;
+}

src/fw/services/common/tick_timer.c

@@ -10,6 +10,11 @@
 #include "system/logging.h"
 #include "system/passert.h"
 
+// FIXME: Move to Kconfig
+#ifdef MICRO_FAMILY_SF32LB52
+#define USE_RTC_SECOND_TICK
+#endif
+
 static uint16_t s_num_subscribers;
 
 static void timer_tick_event_publisher(void* data) {
@@ -18,18 +23,28 @@ static void timer_tick_event_publisher(void* data) {
     .clock_tick.tick_time = rtc_get_time(),
   };
 
+#ifdef USE_RTC_SECOND_TICK
+  event_put_isr(&e);
+#else
   event_put(&e);
+#endif
 }
 
+#ifndef USE_RTC_SECOND_TICK
 static RegularTimerInfo s_tick_timer_info = {
   .cb = &timer_tick_event_publisher
 };
+#endif
 
 void tick_timer_add_subscriber(PebbleTask task) {
   ++s_num_subscribers;
   if (s_num_subscribers == 1) {
     PBL_LOG_DBG("starting tick timer");
+#ifdef USE_RTC_SECOND_TICK
+    rtc_second_tick_subscribe(timer_tick_event_publisher, NULL);
+#else
     regular_timer_add_seconds_callback(&s_tick_timer_info);
+#endif
   }
 }
 
@@ -38,6 +53,10 @@ void tick_timer_remove_subscriber(PebbleTask task) {
   --s_num_subscribers;
   if (s_num_subscribers == 0) {
     PBL_LOG_DBG("stopping tick timer");
+#ifdef USE_RTC_SECOND_TICK
+    rtc_second_tick_unsubscribe();
+#else
     regular_timer_remove_callback(&s_tick_timer_info);
+#endif
   }
 }