drivers: rtc: add hwclock

The hwclock is selected using the chosen node "zephyr,rtc". It
will automatically set the system real-time clock on boot if the
RTCs time is valid.

Signed-off-by: Bjarki Arge Andreasen <[email protected]>

Author: bjarki-andreasen

drivers/rtc/CMakeLists.txt

@@ -21,3 +21,4 @@ zephyr_library_sources_ifdef(CONFIG_RTC_SMARTBOND rtc_smartbond.c)
 zephyr_library_sources_ifdef(CONFIG_RTC_ATMEL_SAM rtc_sam.c)
 zephyr_library_sources_ifdef(CONFIG_RTC_RPI_PICO rtc_rpi_pico.c)
 zephyr_library_sources_ifdef(CONFIG_RTC_NUMAKER rtc_numaker.c)
+zephyr_library_sources_ifdef(CONFIG_RTC_HWCLOCK rtc_hwclock.c)

drivers/rtc/Kconfig

@@ -53,5 +53,6 @@ source "drivers/rtc/Kconfig.sam"
 source "drivers/rtc/Kconfig.smartbond"
 source "drivers/rtc/Kconfig.stm32"
 source "drivers/rtc/Kconfig.numaker"
+source "drivers/rtc/Kconfig.hwclock"
 
 endif # RTC

drivers/rtc/Kconfig.hwclock

@@ -0,0 +1,25 @@
+# Copyright (c) 2024 Bjarki Arge Andreasen
+# SPDX-License-Identifier: Apache-2.0
+
+DT_CHOSEN_RTC := zephyr,rtc
+
+config RTC_HWCLOCK
+	bool "Hardware clock"
+	default y
+	depends on $(dt_chosen_enabled,$(DT_CHOSEN_RTC))
+	depends on SYS_REALTIME
+	help
+	  The hardware clock is used to set the system
+	  real-time clock on boot.
+
+if RTC_HWCLOCK
+
+config RTC_HWCLOCK_INIT_PRIORITY
+	int "Initialization priority of hardware clock"
+	default 51
+	help
+	  The initialization priority of the hardware clock
+	  must be higher than the initialization priority of
+	  the chosen RTC device driver.
+
+endif # RTC_HWCLOCK

drivers/rtc/rtc_hwclock.c

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2024 Bjarki Arge Andreasen
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/init.h>
+#include <zephyr/drivers/rtc.h>
+#include <zephyr/sys/realtime.h>
+
+BUILD_ASSERT(
+	CONFIG_RTC_HWCLOCK_INIT_PRIORITY > CONFIG_RTC_INIT_PRIORITY,
+	"Hardware clock init prio must be higher than the RTC device driver"
+);
+
+static const struct device *rtc = DEVICE_DT_GET(DT_CHOSEN(zephyr_rtc));
+
+static const struct sys_datetime *rtc_time_to_sys_datetime(const struct rtc_time *timeptr)
+{
+	return (const struct sys_datetime *)timeptr;
+}
+
+static int rtc_hwclock_init(void)
+{
+	int ret;
+	struct rtc_time rtctime;
+	const struct sys_datetime *datetime;
+
+	if (!device_is_ready(rtc)) {
+		return -ENODEV;
+	}
+
+	ret = rtc_get_time(rtc, &rtctime);
+	if (ret == -ENODATA) {
+		return 0;
+	} else if (ret < 0) {
+		return ret;
+	}
+
+	datetime = rtc_time_to_sys_datetime(&rtctime);
+	return sys_realtime_set_datetime(datetime);
+}
+
+SYS_INIT(rtc_hwclock_init, POST_KERNEL, CONFIG_RTC_HWCLOCK_INIT_PRIORITY);