Improve STM reset reason

This causes safe mode to skip the wait for reset when waking up
from an alarm. (It also means we don't flash the LED for it.)

Author: tannewt

ports/stm/common-hal/alarm/__init__.c

@@ -64,7 +64,7 @@ void alarm_set_wakeup_reason(stm_sleep_source_t reason) {
     true_deep_wake_reason = reason;
 }
 
-STATIC stm_sleep_source_t _get_wakeup_cause(void) {
+stm_sleep_source_t alarm_get_wakeup_cause(void) {
     // If in light/fake sleep, check modules
     if (alarm_pin_pinalarm_woke_us_up()) {
         return STM_WAKEUP_GPIO;
@@ -73,18 +73,18 @@ STATIC stm_sleep_source_t _get_wakeup_cause(void) {
         return STM_WAKEUP_RTC;
     }
     // Check to see if we woke from deep sleep (reason set in port_init)
-    if (true_deep_wake_reason) {
+    if (true_deep_wake_reason != STM_WAKEUP_UNDEF) {
         return true_deep_wake_reason;
     }
     return STM_WAKEUP_UNDEF;
 }
 
 bool common_hal_alarm_woken_from_sleep(void) {
-    return _get_wakeup_cause() != STM_WAKEUP_UNDEF;
+    return alarm_get_wakeup_cause() != STM_WAKEUP_UNDEF;
 }
 
 STATIC mp_obj_t _get_wake_alarm(size_t n_alarms, const mp_obj_t *alarms) {
-    stm_sleep_source_t cause = _get_wakeup_cause();
+    stm_sleep_source_t cause = alarm_get_wakeup_cause();
     switch (cause) {
         case STM_WAKEUP_RTC: {
             return alarm_time_timealarm_get_wakeup_alarm(n_alarms, alarms);
@@ -156,6 +156,7 @@ void common_hal_alarm_set_deep_sleep_alarms(size_t n_alarms, const mp_obj_t *ala
 }
 
 void NORETURN common_hal_alarm_enter_deep_sleep(void) {
+    alarm_set_wakeup_reason(STM_WAKEUP_UNDEF);
     alarm_pin_pinalarm_prepare_for_deep_sleep();
     alarm_time_timealarm_prepare_for_deep_sleep();
     port_disable_tick();
@@ -182,6 +183,8 @@ void common_hal_alarm_pretending_deep_sleep(void) {
     GPIO_InitStruct.Pull = GPIO_PULLDOWN;
     HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
 
+    alarm_set_wakeup_reason(STM_WAKEUP_UNDEF);
+
     port_idle_until_interrupt();
 }
 

ports/stm/common-hal/alarm/__init__.h

@@ -40,6 +40,7 @@ typedef enum {
 #define STM_ALARM_FLAG      (RTC->BKP0R)
 
 extern void alarm_set_wakeup_reason(stm_sleep_source_t reason);
+stm_sleep_source_t alarm_get_wakeup_cause(void);
 extern void alarm_reset(void);
 
 #endif // MICROPY_INCLUDED_STM32_COMMON_HAL_ALARM__INIT__H

ports/stm/common-hal/microcontroller/Processor.c

@@ -27,6 +27,9 @@
 #include <math.h>
 #include "py/runtime.h"
 
+#if CIRCUITPY_ALARM
+#include "common-hal/alarm/__init__.h"
+#endif
 #include "common-hal/microcontroller/Processor.h"
 #include "shared-bindings/microcontroller/ResetReason.h"
 #include "supervisor/shared/translate.h"
@@ -143,5 +146,10 @@ void common_hal_mcu_processor_get_uid(uint8_t raw_id[]) {
 }
 
 mcu_reset_reason_t common_hal_mcu_processor_get_reset_reason(void) {
+    #if CIRCUITPY_ALARM
+    if (alarm_get_wakeup_cause() != STM_WAKEUP_UNDEF) {
+        return RESET_REASON_DEEP_SLEEP_ALARM;
+    }
+    #endif
     return RESET_REASON_UNKNOWN;
 }