From 24e412446dc0cc2e95037a6afd5db6df9715fac8 Mon Sep 17 00:00:00 2001
From: Steins7 <steinsset@gmail.com>
Date: Sun, 4 Aug 2024 20:04:09 +0200
Subject: [PATCH] Implement bkp's rtc alarm configuration

Since the alarm must be set each time it is to be used, a separated
function is a better fit
---
 drv/bkp.c | 25 ++++++++++++++++++++++---
 drv/bkp.h | 15 ++++++++++++---
 2 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/drv/bkp.c b/drv/bkp.c
index c6b93a4..69630b9 100644
--- a/drv/bkp.c
+++ b/drv/bkp.c
@@ -33,7 +33,7 @@ static BkpRtcCallback rtc_callback;
 //--public functions------------------------------------------------------------
 
 void bkp_configure_rtc(uint32_t period_ms, enum BkpRtcClockSrc clock_src,
-		enum BkpRtcIrq irq_mask, uint32_t alarm_tick, BkpRtcCallback callback)
+		enum BkpRtcIrq irq_mask, BkpRtcCallback callback)
 {
 	rcc_enable(RCC_AHB_NONE, RCC_APB1_BKP, RCC_APB2_NONE);
 
@@ -55,8 +55,6 @@ void bkp_configure_rtc(uint32_t period_ms, enum BkpRtcClockSrc clock_src,
 	//configure core registers
 	rtc_regs->PRLH.PRL = prescaler >> 16;
 	rtc_regs->PRLL.PRL = prescaler;
-	rtc_regs->ALRH.RTC_ALR = alarm_tick >> 16;
-	rtc_regs->ALRL.RTC_ALR = alarm_tick;
 
 	//apply irq config
 	rtc_regs->CRH.word |= irq_mask & 0x7;
@@ -73,6 +71,27 @@ void bkp_configure_rtc(uint32_t period_ms, enum BkpRtcClockSrc clock_src,
 	}
 }
 
+void bkp_set_rtc_alam(uint32_t offset)
+{
+	uint32_t alarm = bkp_read_rtc() + offset;
+
+	//wait for last operation to finish
+	while (rtc_regs->CRL.RTOFF != 1) {}
+
+	//enable core configuration
+	rtc_regs->CRL.CNF = 1;
+
+	//write alarm value
+	rtc_regs->ALRH.RTC_ALR = alarm >> 16;
+	rtc_regs->ALRL.RTC_ALR = alarm;
+
+	//disable/apply core configuration
+	rtc_regs->CRL.CNF = 0;
+
+	//wait for last operation to finish
+	while (rtc_regs->CRL.RTOFF != 1) {}
+}
+
 uint32_t bkp_read_rtc(void)
 {
 	//wait for core registers to be synchronized, immediate most of the time
diff --git a/drv/bkp.h b/drv/bkp.h
index b78994e..28da3f8 100644
--- a/drv/bkp.h
+++ b/drv/bkp.h
@@ -63,14 +63,23 @@ typedef void (*BkpRtcCallback)(enum BkpRtcIrq src);
  * Clocks must be enabled prior to calling this function
  *
  * Mulitple IRQs can be enabled and redirected to single callback. The alarm
- * IRQ, triggered at the specified tick value can be rerouted to an exti line
- * for wakeup from stanby, in wich case it doesn't need to be enabled here.
+ * IRQ, triggered at the tick value specified by bkp_set_rtc_alam() can be
+ * rerouted to an exti line for wakeup from stop and standby, in wich case it
+ * doesn't need to be enabled here.
  *
  * Ensure backup domain writes are enabled (see pwr_configure_bkp_write()) while
  * calling this function
  */
 void bkp_configure_rtc(uint32_t period_ms, enum BkpRtcClockSrc clock_src,
-		enum BkpRtcIrq irq_mask, uint32_t alarm_tick, BkpRtcCallback callback);
+		enum BkpRtcIrq irq_mask, BkpRtcCallback callback);
+
+/**
+ * Configure the alarm to trigger after the specified time in ticks, which can
+ * be viewed as an offset to the current time value. This offset is only precise
+ * to the tick and thus if the tick changes right after this function is
+ * called, the observed offset will be close to 1 tick short
+ */
+void bkp_set_rtc_alam(uint32_t offset);
 
 /**
  * Returns the current counter value of the RTC