drivers: rtc: maxim,ds3231: RTC driver

This is a squash of all the groundwork needed to
get a functioning driver for the DS3231 with the RTC API.

(cherry picked from commit 2759ada)

Original-Signed-off-by: Gergo Vari <work@gergovari.com>
GitOrigin-RevId: 2759ada
Cr-Build-Id: 8726362737952124785
Cr-Build-Url: https://cr-buildbucket.appspot.com/build/8726362737952124785
Copybot-Job-Name: zephyr-main-copybot-downstream
Change-Id: Idf14862d682179c0c1c50e3a8761c5e62cd97956
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/zephyr/+/6154244
Tested-by: ChromeOS Prod (Robot) <chromeos-ci-prod@chromeos-bot.iam.gserviceaccount.com>
Bot-Commit: ChromeOS Prod (Robot) <chromeos-ci-prod@chromeos-bot.iam.gserviceaccount.com>
Commit-Queue: ChromeOS Prod (Robot) <chromeos-ci-prod@chromeos-bot.iam.gserviceaccount.com>

drivers/mfd/CMakeLists.txt

@@ -20,3 +20,4 @@ zephyr_library_sources_ifdef(CONFIG_MFD_TLE9104 mfd_tle9104.c)
 zephyr_library_sources_ifdef(CONFIG_MFD_ITE_IT8801 mfd_ite_it8801.c)
 zephyr_library_sources_ifdef(CONFIG_MFD_ITE_IT8801_ALTCTRL mfd_it8801_altctrl.c)
 zephyr_library_sources_ifdef(CONFIG_MFD_AW9523B mfd_aw9523b.c)
+zephyr_library_sources_ifdef(CONFIG_MFD_DS3231 mfd_ds3231.c)

drivers/mfd/Kconfig

@@ -23,6 +23,7 @@ source "drivers/mfd/Kconfig.adp5585"
 source "drivers/mfd/Kconfig.axp192"
 source "drivers/mfd/Kconfig.aw9523b"
 source "drivers/mfd/Kconfig.bd8lb600fs"
+source "drivers/mfd/Kconfig.ds3231"
 source "drivers/mfd/Kconfig.max20335"
 source "drivers/mfd/Kconfig.max31790"
 source "drivers/mfd/Kconfig.nct38xx"

drivers/mfd/Kconfig.ds3231

@@ -0,0 +1,10 @@
+# Copyright (c) 2024 Gergo Vari <work@gergovari.com>
+# SPDX-License-Identifier: Apache-2.0
+
+config MFD_DS3231
+	bool "DS3231 multi-function device driver"
+	default y
+	depends on DT_HAS_MAXIM_DS3231_MFD_ENABLED
+	select I2C
+	help
+	  Enable the Maxim DS3231 multi-function device driver

drivers/mfd/mfd_ds3231.c

@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2024 Gergo Vari <work@gergovari.com>
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/drivers/mfd/ds3231.h>
+
+#include <zephyr/kernel.h>
+#include <zephyr/drivers/i2c.h>
+
+#include <zephyr/sys/util.h>
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_REGISTER(mfd_ds3231, CONFIG_MFD_LOG_LEVEL);
+
+#define DT_DRV_COMPAT maxim_ds3231_mfd
+
+struct mfd_ds3231_data {
+	struct k_sem lock;
+	const struct device *dev;
+};
+
+struct mfd_ds3231_conf {
+	struct i2c_dt_spec i2c_bus;
+};
+
+int mfd_ds3231_i2c_get_registers(const struct device *dev, uint8_t start_reg, uint8_t *buf,
+				 const size_t buf_size)
+{
+	struct mfd_ds3231_data *data = dev->data;
+	const struct mfd_ds3231_conf *config = dev->config;
+
+	/* FIXME: bad start_reg/buf_size values break i2c for that run */
+
+	(void)k_sem_take(&data->lock, K_FOREVER);
+	int err = i2c_burst_read_dt(&config->i2c_bus, start_reg, buf, buf_size);
+
+	k_sem_give(&data->lock);
+
+	return err;
+}
+
+int mfd_ds3231_i2c_set_registers(const struct device *dev, uint8_t start_reg, const uint8_t *buf,
+				 const size_t buf_size)
+{
+	struct mfd_ds3231_data *data = dev->data;
+	const struct mfd_ds3231_conf *config = dev->config;
+
+	(void)k_sem_take(&data->lock, K_FOREVER);
+	int err = i2c_burst_write_dt(&config->i2c_bus, start_reg, buf, buf_size);
+
+	k_sem_give(&data->lock);
+
+	return err;
+}
+
+static int mfd_ds3231_init(const struct device *dev)
+{
+	struct mfd_ds3231_data *data = dev->data;
+	const struct mfd_ds3231_conf *config = (struct mfd_ds3231_conf *)(dev->config);
+
+	k_sem_init(&data->lock, 1, 1);
+	if (!i2c_is_ready_dt(&(config->i2c_bus))) {
+		LOG_ERR("I2C bus not ready.");
+		return -ENODEV;
+	}
+	return 0;
+}
+
+#define MFD_DS3231_DEFINE(inst)                                                                    \
+	static const struct mfd_ds3231_conf config##inst = {.i2c_bus =                             \
+								    I2C_DT_SPEC_INST_GET(inst)};   \
+	static struct mfd_ds3231_data data##inst;                                                  \
+	DEVICE_DT_INST_DEFINE(inst, &mfd_ds3231_init, NULL, &data##inst, &config##inst,            \
+			      POST_KERNEL, CONFIG_MFD_INIT_PRIORITY, NULL);
+
+DT_INST_FOREACH_STATUS_OKAY(MFD_DS3231_DEFINE)

drivers/rtc/CMakeLists.txt

@@ -11,6 +11,7 @@ zephyr_library_sources_ifdef(CONFIG_RTC_RV8263 rtc_rv8263.c)
 zephyr_library_sources_ifdef(CONFIG_RTC_AM1805 rtc_am1805.c)
 zephyr_library_sources_ifdef(CONFIG_RTC_AMBIQ rtc_ambiq.c)
 zephyr_library_sources_ifdef(CONFIG_RTC_DS1307 rtc_ds1307.c)
+zephyr_library_sources_ifdef(CONFIG_RTC_DS3231 rtc_ds3231.c)
 zephyr_library_sources_ifdef(CONFIG_USERSPACE rtc_handlers.c)
 zephyr_library_sources_ifdef(CONFIG_RTC_EMUL rtc_emul.c)
 zephyr_library_sources_ifdef(CONFIG_RTC_INFINEON_CAT1 rtc_ifx_cat1.c)

drivers/rtc/Kconfig

@@ -44,6 +44,7 @@ config RTC_SHELL
 source "drivers/rtc/Kconfig.am1805"
 source "drivers/rtc/Kconfig.ambiq"
 source "drivers/rtc/Kconfig.ds1307"
+source "drivers/rtc/Kconfig.ds3231"
 source "drivers/rtc/Kconfig.emul"
 source "drivers/rtc/Kconfig.fake"
 source "drivers/rtc/Kconfig.ifx_cat1"

drivers/rtc/Kconfig.ds3231

@@ -0,0 +1,23 @@
+# Copyright (c) 2024, Gergo Vari <work@gergovari.com>
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+config RTC_DS3231
+	bool "Maxim DS3231 RTC/TCXO"
+	default y
+	depends on DT_HAS_MAXIM_DS3231_MFD_ENABLED
+	depends on DT_HAS_MAXIM_DS3231_RTC_ENABLED
+	select I2C
+	select MFD
+	help
+	  Enable RTC driver based on Maxim DS3231 I2C device.
+
+config RTC_DS3231_INIT_PRIORITY
+	int "DS3231 RTC driver initialization priority"
+	depends on RTC_DS3231
+	default 86
+	help
+	  Initialization priority for the DS3231 RTC driver. It must be
+	  greater than the I2C controller init priority and the mfd driver
+	  init priority.