arch/arm/stm32: fix stm32f1xx alarm support

Summary:
stm32: support querying a previously set RTC alarm In the STM32F1xx series

Impact:
When using the stm32f1xx series MCU, the alarm function can be used, but when we enabled the CONFIG_RTC_ALARM configuration, an error was reported due to the inability to find the specific implementation of rdalarm.

Testing:
In our own projects, we have done alarm verification using the STM32F103RE..

arch/arm/src/stm32/stm32_alarm.h

@@ -43,6 +43,14 @@
 
 typedef void (*alarmcb_t)(void);
 
+/* Structure used to pass parameters to query an alarm */
+
+struct alm_rdalarm_s
+{
+  int ar_id;                    /* enum alm_id_e */
+  FAR struct rtc_time *ar_time; /* Argument for storing ALARM RTC time */
+};
+
 /****************************************************************************
  * Public Function Prototypes
  ****************************************************************************/
@@ -90,6 +98,22 @@ int stm32_rtc_setalarm(const struct timespec *tp, alarmcb_t callback);
 
 int stm32_rtc_cancelalarm(void);
 
+/****************************************************************************
+ * Name: stm32_rtc_rdalarm
+ *
+ * Description:
+ *   Query an alarm configured in hardware.
+ *
+ * Input Parameters:
+ *  alminfo - Information about the alarm configuration.
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno on failure
+ *
+ ****************************************************************************/
+
+int stm32_rtc_rdalarm(FAR struct alm_rdalarm_s *alminfo);
+
 #undef EXTERN
 #if defined(__cplusplus)
 }

arch/arm/src/stm32/stm32_rtc_lowerhalf.c

@@ -745,9 +745,16 @@ static int stm32_rdalarm(struct rtc_lowerhalf_s *lower,
   irqstate_t flags;
 
   DEBUGASSERT(lower != NULL && alarminfo != NULL && alarminfo->time != NULL);
+#if defined(CONFIG_STM32_STM32F4XXX) || defined(CONFIG_STM32_STM32L15XX)
   DEBUGASSERT(alarminfo->id == RTC_ALARMA || alarminfo->id == RTC_ALARMB);
 
   if (alarminfo->id == RTC_ALARMA || alarminfo->id == RTC_ALARMB)
+#else
+  DEBUGASSERT(alarminfo->id >= 0 && alarminfo->id < CONFIG_RTC_NALARMS);
+
+  if (alarminfo != NULL && alarminfo->id >= 0 &&
+      alarminfo->id < CONFIG_RTC_NALARMS)
+#endif
     {
       /* Disable pre-emption while we do this so that we don't have to worry
        * about being suspended and working on an old time.

arch/arm/src/stm32/stm32_rtcounter.c

@@ -53,7 +53,10 @@
 #include <stdint.h>
 #include <stdbool.h>
 #include <stdio.h>
+#include <assert.h>
 #include <errno.h>
+#include <debug.h>
+#include <time.h>
 
 #include "arm_internal.h"
 #include "stm32_pwr.h"
@@ -797,3 +800,49 @@ int stm32_rtc_cancelalarm(void)
   return ret;
 }
 #endif
+
+/****************************************************************************
+ * Name: stm32_rtc_rdalarm
+ *
+ * Description:
+ *   Query an alarm configured in hardware.
+ *
+ * Input Parameters:
+ *  alminfo - Information about the alarm configuration.
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno on failure
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_RTC_ALARM
+int stm32_rtc_rdalarm(FAR struct alm_rdalarm_s *alminfo)
+{
+  struct rtc_regvals_s regvals;
+  FAR struct timespec tp;
+  int ret = -EINVAL;
+
+  DEBUGASSERT(alminfo != NULL);
+  DEBUGASSERT(alminfo->ar_id == 0);
+
+  switch (alminfo->ar_id)
+    {
+      case 0:
+        {
+          regvals.cnth = getreg16(STM32_RTC_ALRH);
+          regvals.cntl = getreg16(STM32_RTC_ALRL);
+          tp.tv_sec    = regvals.cnth << 16 | regvals.cntl;
+          memcpy(alminfo->ar_time, (FAR struct tm *)gmtime(&tp.tv_sec),
+                 sizeof(FAR struct tm));
+          ret = OK;
+        }
+        break;
+
+      default:
+        rtcerr("ERROR: Invalid ALARM%d\n", alminfo->ar_id);
+        break;
+    }
+
+  return ret;
+}
+#endif