From 38196344691ad32b7f80bb44489c069ceaecb1ec Mon Sep 17 00:00:00 2001
From: Peter Hinch <peter@hinch.me.uk>
Date: Tue, 27 Oct 2015 10:55:47 +0000
Subject: [PATCH] stmhal: Make RTC init skip startup if LTE is already enabled
and ready.
This prevents the loss of RTC time when exiting from standby mode, since
the RTC is paused while it is being re-inited and this loses about 120ms.
Thanks to @chuckbook for the patch.
---
stmhal/rtc.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/stmhal/rtc.c b/stmhal/rtc.c
index 6bed3d1e6..1d349a6e9 100644
--- a/stmhal/rtc.c
+++ b/stmhal/rtc.c
@@ -178,6 +178,17 @@ void rtc_init(void) {
RTCHandle.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
RTCHandle.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
+ // if LTE enabled & ready --> no need to (re-)init RTC
+ if ((RCC->BDCR & (RCC_BDCR_LSEON | RCC_BDCR_LSERDY)) == (RCC_BDCR_LSEON | RCC_BDCR_LSERDY)) {
+ // remove Backup Domain write protection
+ PWR->CR |= PWR_CR_DBP;
+ // Clear source Reset Flag
+ __HAL_RCC_CLEAR_RESET_FLAGS();
+ // provide some status information
+ rtc_info |= 0x40000 | (RCC->BDCR & 7) | (RCC->CSR & 3) << 8;
+ return;
+ }
+
mp_uint_t tick = HAL_GetTick();
if (HAL_RTC_Init(&RTCHandle) != HAL_OK) {
--
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