f4 RTC: fixup

Author: dron0gus

firmware/hw_layer/ports/stm32/stm32f4/hw_ports.mk

@@ -2,7 +2,8 @@ HW_LAYER_PORT = $(PROJECT_DIR)/hw_layer/ports/stm32/stm32f4/stm32f4xx_hal_flash.
 				$(PROJECT_DIR)/hw_layer/ports/stm32/stm32f4/stm32f4xx_hal_flash_ex.c
 
 HW_LAYER_PORT_CPP += $(PROJECT_DIR)/hw_layer/ports/stm32/stm32f4/mpu_util.cpp \
-					$(PROJECT_DIR)/hw_layer/ports/stm32/stm32_adc_v2.cpp
+					$(PROJECT_DIR)/hw_layer/ports/stm32/stm32_adc_v2.cpp \
+					$(PROJECT_DIR)/hw_layer/ports/stm32/stm32f4/stm32f4xx_rtc.cpp
 
 MCU = cortex-m4
 USE_FPU = hard

firmware/hw_layer/ports/stm32/stm32f4/stm32f4xx_rtc.cpp

@@ -0,0 +1,79 @@
+/**
+ * @file stm32f7xx_rtc.cpp
+ * @brief Real Time Clock STM32F7xx switched from LSE to LSI
+ *
+ * @date Jan 8, 2025
+ * @author Andrey Gusakov
+ */
+
+#include "pch.h"
+
+#if HAL_USE_RTC
+
+/* switch to LSE clock if ECU previously falledback to LSI clock.
+ * This will preserve current time and set it back to RTC after reinit
+ * On STM32 change of RTC source clock can be done only through reset of whole backup domain
+ * This reset does no affect backup ram */
+void hal_lld_rtc_fixup(void)
+{
+#if (STM32_RTCSEL == STM32_RTCSEL_LSE)
+	// we need some more time than defined in RUSEFI_STM32_LSE_WAIT_MAX
+	// this is safe as we check that LSE is runnig before reseting BKP domain (stopping LSE)
+	// After that we are starting LSE again and waiting for LSERDY.
+	int timeout = 1000000000;
+	if ((RCC->BDCR & STM32_RTCSEL_MASK) == STM32_RTCSEL) {
+		// Backup domain is already driven by expected clock
+		return;
+	}
+	if ((RCC->BDCR & RCC_BDCR_LSERDY) == 0) {
+		// LSE is failed to start
+		efiPrintf("LSE in not ready");
+		return;
+	}
+
+	efiPrintf("Switching RTC to LSE clock");
+
+	// Get current time
+	RTCDateTime timespec;
+	rtcGetTime(&RTCD1, &timespec);
+
+	// Reset BKP domain
+	// The BKPSRAM is not affected by this reset
+	// This will also reset LSEON
+	RCC->BDCR |= RCC_BDCR_BDRST;
+	RCC->BDCR &= ~RCC_BDCR_BDRST;
+
+#if defined(STM32_LSE_BYPASS)
+	// LSE Bypass.
+	RCC->BDCR |= RCC_BDCR_LSEON | RCC_BDCR_LSEBYP;
+#else
+	// No LSE Bypass.
+	RCC->BDCR |= RCC_BDCR_LSEON;
+#endif
+	// Waits until LSE is stable or times out.
+	while (((RCC->BDCR & RCC_BDCR_LSERDY) == 0) && (timeout--)) {
+		//this is executed when RTOS is not ready
+		//chThdSleepMilliseconds(1);
+	}
+
+	// Lets check again
+	if (RCC->BDCR & RCC_BDCR_LSERDY) {
+		RCC->BDCR |= STM32_RTCSEL;
+	} else {
+		// LSE is failed to start
+		efiPrintf("LSE in not ready after restart attemp");
+		// Keep initing
+		RCC->BDCR |= RUSEFI_STM32_LSE_WAIT_MAX_RTCSEL;
+	}
+
+  /* RTC clock enabled.*/
+  RCC->BDCR |= RCC_BDCR_RTCEN;
+
+	// init RTC again
+	rtcInit();
+	// Set previously saved time
+	rtcSetTime(&RTCD1, &timespec);
+#endif
+}
+
+#endif //HAL_USE_RTC