drivers: rtc: rpi_pico: Add support for the Raspberry Pi Pico RTC

This adds the minimal get_time/set_time support for the rp2040 and
enables support by default on the Pico boards. This doesn't support
configuring the clock source or alarm interrupts yet.

Signed-off-by: Andrew Featherstone <andrew.featherstone@gmail.com>

boards/raspberrypi/rpi_pico/rpi_pico-common.dtsi

@@ -24,6 +24,7 @@
 	};
 
 	aliases {
+		rtc = &rtc;
 		watchdog0 = &wdt0;
 	};
 
@@ -133,6 +134,11 @@
 	status = "okay";
 };
 
+&rtc {
+	clocks = <&clocks RPI_PICO_CLKID_CLK_RTC>;
+	status = "okay";
+};
+
 &adc {
 	status = "okay";
 	pinctrl-0 = <&adc_default>;

drivers/rtc/CMakeLists.txt

@@ -19,3 +19,4 @@ zephyr_library_sources_ifdef(CONFIG_RTC_SHELL rtc_shell.c)
 zephyr_library_sources_ifdef(CONFIG_RTC_FAKE rtc_fake.c)
 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)

drivers/rtc/Kconfig

@@ -45,11 +45,12 @@ source "drivers/rtc/Kconfig.am1805"
 source "drivers/rtc/Kconfig.ds1307"
 source "drivers/rtc/Kconfig.emul"
 source "drivers/rtc/Kconfig.fake"
+source "drivers/rtc/Kconfig.mc146818"
 source "drivers/rtc/Kconfig.pcf8523"
 source "drivers/rtc/Kconfig.pcf8563"
-source "drivers/rtc/Kconfig.mc146818"
+source "drivers/rtc/Kconfig.rpi_pico"
 source "drivers/rtc/Kconfig.sam"
-source "drivers/rtc/Kconfig.stm32"
 source "drivers/rtc/Kconfig.smartbond"
+source "drivers/rtc/Kconfig.stm32"
 
 endif # RTC

drivers/rtc/Kconfig.rpi_pico

@@ -0,0 +1,9 @@
+# Copyright (c) 2023 Andrew Featherstone
+# SPDX-License-Identifier: Apache-2.0
+
+config RTC_RPI_PICO
+	bool "Raspberry Pi Pico RTC driver"
+	default y
+	depends on DT_HAS_RASPBERRYPI_PICO_RTC_ENABLED
+	select PICOSDK_USE_RTC
+	depends on RESET

drivers/rtc/rtc_rpi_pico.c

@@ -0,0 +1,112 @@
+/*
+ * Copyright (c) 2024 Andrew Featherstone
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/drivers/clock_control.h>
+#include <zephyr/drivers/rtc.h>
+#include <zephyr/irq.h>
+#include <zephyr/kernel.h>
+#include <zephyr/logging/log.h>
+#include <zephyr/spinlock.h>
+
+#include <hardware/rtc.h>
+
+#define DT_DRV_COMPAT raspberrypi_pico_rtc
+
+#define CLK_DRV DEVICE_DT_GET(DT_INST_CLOCKS_CTLR(0))
+#define CLK_ID  (clock_control_subsys_t) DT_INST_PHA_BY_IDX(0, clocks, 0, clk_id)
+
+/* struct tm start time:   1st, Jan, 1900 */
+#define TM_YEAR_REF 1900
+/* See section 4.8.1 of the RP2040 datasheet. */
+#define RP2040_RTC_YEAR_MAX 4095
+struct rtc_rpi_pico_data {
+	struct k_spinlock lock;
+};
+
+LOG_MODULE_REGISTER(rtc_rpi, CONFIG_RTC_LOG_LEVEL);
+
+static int rtc_rpi_pico_init(const struct device *dev)
+{
+	int ret;
+
+	ret = clock_control_on(CLK_DRV, CLK_ID);
+	if (ret < 0) {
+		return ret;
+	}
+
+	rtc_init();
+	return 0;
+}
+
+static int rtc_rpi_pico_set_time(const struct device *dev, const struct rtc_time *timeptr)
+{
+	struct rtc_rpi_pico_data *data = dev->data;
+	int err = 0;
+
+	if (timeptr->tm_year + TM_YEAR_REF > RP2040_RTC_YEAR_MAX) {
+		return -EINVAL;
+	}
+
+	if (timeptr->tm_wday == -1) {
+		/* day of the week is expected */
+		return -EINVAL;
+	}
+
+	k_spinlock_key_t key = k_spin_lock(&data->lock);
+	datetime_t dt = {
+		.year = timeptr->tm_year + TM_YEAR_REF,
+		.month = timeptr->tm_mon + 1,
+		.day = timeptr->tm_mday,
+		.dotw = timeptr->tm_wday,
+		.hour = timeptr->tm_hour,
+		.min = timeptr->tm_min,
+		.sec = timeptr->tm_sec,
+	};
+	/* Use the validation in the Pico SDK. */
+	if (!rtc_set_datetime(&dt)) {
+		err = -EINVAL;
+	}
+	k_spin_unlock(&data->lock, key);
+
+	return err;
+}
+
+static int rtc_rpi_pico_get_time(const struct device *dev, struct rtc_time *timeptr)
+{
+	struct rtc_rpi_pico_data *data = dev->data;
+	datetime_t dt;
+	int err = 0;
+	k_spinlock_key_t key = k_spin_lock(&data->lock);
+
+	if (!rtc_get_datetime(&dt)) {
+		err = -ENODATA;
+	}
+
+	timeptr->tm_sec = dt.sec;
+	timeptr->tm_min = dt.min;
+	timeptr->tm_hour = dt.hour;
+	timeptr->tm_mday = dt.day;
+	timeptr->tm_mon = dt.month - 1;
+	timeptr->tm_year = dt.year - TM_YEAR_REF;
+	timeptr->tm_wday = dt.dotw;
+	/* unknown values */
+	timeptr->tm_yday = -1;
+	timeptr->tm_isdst = -1;
+	timeptr->tm_nsec = 0;
+	k_spin_unlock(&data->lock, key);
+
+	return err;
+}
+
+static const struct rtc_driver_api rtc_rpi_pico_driver_api = {
+	.set_time = rtc_rpi_pico_set_time,
+	.get_time = rtc_rpi_pico_get_time,
+};
+
+static struct rtc_rpi_pico_data rtc_data;
+
+DEVICE_DT_INST_DEFINE(0, &rtc_rpi_pico_init, NULL, &rtc_data, NULL, POST_KERNEL,
+		      CONFIG_RTC_INIT_PRIORITY, &rtc_rpi_pico_driver_api);

dts/arm/rpi_pico/rp2040.dtsi

@@ -399,6 +399,14 @@
 			resets = <&reset RPI_PICO_RESETS_RESET_PIO1>;
 			status = "disabled";
 		};
+
+		rtc: rtc@4005c000 {
+			compatible = "raspberrypi,pico-rtc";
+			reg = <0x4005c000 DT_SIZE_K(4)>;
+			interrupts = <25 RPI_PICO_DEFAULT_IRQ_PRIORITY>;
+			resets = <&reset RPI_PICO_RESETS_RESET_RTC>;
+			status = "disabled";
+		};
 	};
 
 	pinctrl: pin-controller {

dts/bindings/rtc/raspberrypi,pico-rtc.yaml

@@ -0,0 +1,12 @@
+# Copyright (c) 2024 Andrew Featherstone <andrew.featherstone@gmail.com>
+# SPDX-License-Identifier: Apache-2.0
+
+description: RaspberryPi Pico RTC
+
+compatible: "raspberrypi,pico-rtc"
+
+include: [rtc.yaml, reset-device.yaml]
+
+properties:
+  reg:
+    required: true

modules/hal_rpi_pico/CMakeLists.txt

@@ -113,6 +113,11 @@ if(CONFIG_HAS_RPI_PICO)
   zephyr_include_directories_ifdef(CONFIG_PICOSDK_USE_CLAIM
           ${rp2_common_dir}/hardware_claim/include)
 
+  zephyr_library_sources_ifdef(CONFIG_PICOSDK_USE_RTC
+          ${rp2_common_dir}/hardware_rtc/rtc.c)
+  zephyr_include_directories_ifdef(CONFIG_PICOSDK_USE_RTC
+          ${rp2_common_dir}/hardware_rtc/include)
+
   # Some flash driver functions must be executed from the RAM.
   # Originally pico-sdk places them in the RW data section, so this
   # implementation does the same.

modules/hal_rpi_pico/Kconfig

@@ -49,3 +49,8 @@ config PICOSDK_USE_TIMER
 	bool
 	help
 	  Use the TIMER driver from pico-sdk
+
+config PICOSDK_USE_RTC
+	bool
+	help
+	  Use the RTC driver from pico-sdk