drivers: counter: stm32: Disable BYPSHAD in init

Disable the shadow registers bypass in init function before RTC
deinitialisation to avoid infinite loop as the bit cases the RSF bit
to be kept in 0. The systick is not working in PRE_KERNEL_1 so it will
never timeout.

Signed-off-by: Tomáš Juřena <[email protected]>

Author: jurenat

drivers/counter/counter_ll_stm32_rtc.c

@@ -590,6 +590,18 @@ static int rtc_stm32_init(const struct device *dev)
 	z_stm32_hsem_unlock(CFG_HW_RCC_SEMID);
 
 #if !defined(CONFIG_COUNTER_RTC_STM32_SAVE_VALUE_BETWEEN_RESETS)
+
+/* STM32C0 LL driver does not clear the CR register in LL_RTC_DeInit so it will loop forever waiting
+ * for a flag that will never be set when shadow registers are bypassed (BYPSHAD enabled).
+ */
+#if defined(RTC_CR_BYPSHAD) && defined(CONFIG_SOC_SERIES_STM32C0X)
+	if (LL_RTC_IsShadowRegBypassEnabled(RTC)) {
+		LL_RTC_DisableWriteProtection(RTC);
+		LL_RTC_DisableShadowRegBypass(RTC);
+		LL_RTC_EnableWriteProtection(RTC);
+	}
+#endif /* defined(RTC_CR_BYPSHAD) && defined(CONFIG_SOC_SERIES_STM32C0X) */
+
 	if (LL_RTC_DeInit(RTC) != SUCCESS) {
 		goto out_disable_bkup_access;
 	}