[v1,9/9] rtc: Add Nuvoton NCT6694 RTC support

diff --git a/MAINTAINERS b/MAINTAINERS
index 4d5a5eded3b9..8de90bda8b5e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -16445,6 +16445,7 @@  F:	drivers/i2c/busses/i2c-nct6694.c
 F:	drivers/mfd/nct6694.c
 F:	drivers/net/can/nct6694_canfd.c
 F:	drivers/pwm/pwm-nct6694.c
+F:	drivers/rtc/rtc-nct6694.c
 F:	drivers/watchdog/nct6694_wdt.c
 F:	include/linux/mfd/nct6694.h
 
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 66eb1122248b..240c496d95f7 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -406,6 +406,16 @@  config RTC_DRV_NCT3018Y
 	   This driver can also be built as a module, if so, the module will be
 	   called "rtc-nct3018y".
 
+config RTC_DRV_NCT6694
+	tristate "Nuvoton NCT6694 RTC support"
+	depends on MFD_NCT6694
+	help
+	If you say yes to this option, support will be included for Nuvoton
+	NCT6694, a USB device to RTC.
+
+	This driver can also be built as a module. If so, the module
+	will be called rtc-nct6694.
+
 config RTC_DRV_RK808
 	tristate "Rockchip RK805/RK808/RK809/RK817/RK818 RTC"
 	depends on MFD_RK8XX
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index f62340ecc534..64443d26bb5b 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -116,6 +116,7 @@  obj-$(CONFIG_RTC_DRV_MXC)	+= rtc-mxc.o
 obj-$(CONFIG_RTC_DRV_MXC_V2)	+= rtc-mxc_v2.o
 obj-$(CONFIG_RTC_DRV_GAMECUBE)	+= rtc-gamecube.o
 obj-$(CONFIG_RTC_DRV_NCT3018Y)	+= rtc-nct3018y.o
+obj-$(CONFIG_RTC_DRV_NCT6694)	+= rtc-nct6694.o
 obj-$(CONFIG_RTC_DRV_NTXEC)	+= rtc-ntxec.o
 obj-$(CONFIG_RTC_DRV_OMAP)	+= rtc-omap.o
 obj-$(CONFIG_RTC_DRV_OPAL)	+= rtc-opal.o
diff --git a/drivers/rtc/rtc-nct6694.c b/drivers/rtc/rtc-nct6694.c
new file mode 100644
index 000000000000..622bb9fbe6f6
--- /dev/null
+++ b/drivers/rtc/rtc-nct6694.c
@@ -0,0 +1,276 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Nuvoton NCT6694 RTC driver based on USB interface.
+ *
+ * Copyright (C) 2024 Nuvoton Technology Corp.
+ */
+
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/rtc.h>
+#include <linux/bcd.h>
+#include <linux/platform_device.h>
+#include <linux/mfd/nct6694.h>
+
+#define DRVNAME "nct6694-rtc"
+
+/* Host interface */
+#define REQUEST_RTC_MOD		0x08
+
+/* Message Channel */
+/* Command 00h */
+#define REQUEST_RTC_CMD0_LEN	0x07
+#define REQUEST_RTC_CMD0_OFFSET	0x0000	/* OFFSET = SEL|CMD */
+#define RTC_SEC_IDX		0x00
+#define RTC_MIN_IDX		0x01
+#define RTC_HOUR_IDX		0x02
+#define RTC_WEEK_IDX		0x03
+#define RTC_DAY_IDX		0x04
+#define RTC_MONTH_IDX		0x05
+#define RTC_YEAR_IDX		0x06
+/* Command 01h */
+#define REQUEST_RTC_CMD1_LEN	0x05
+#define REQUEST_RTC_CMD1_OFFSET	0x0001	/* OFFSET = SEL|CMD */
+#define RTC_ALRM_EN_IDX		0x03
+#define RTC_ALRM_PEND_IDX	0x04
+/* Command 02h */
+#define REQUEST_RTC_CMD2_LEN	0x02
+#define REQUEST_RTC_CMD2_OFFSET	0x0002	/* OFFSET = SEL|CMD */
+#define RTC_IRQ_EN_IDX		0x00
+#define RTC_IRQ_PEND_IDX	0x01
+
+#define RTC_IRQ_EN		(BIT(0) | BIT(5))
+#define RTC_IRQ_INT_EN		BIT(0)	/* Transmit a USB INT-in when RTC alarm */
+#define RTC_IRQ_GPO_EN		BIT(5)	/* Trigger a GPO Low Pulse when RTC alarm */
+#define RTC_IRQ_STS		BIT(0)	/* Write 1 clear IRQ status */
+
+struct nct6694_rtc_data {
+	struct nct6694 *nct6694;
+	struct rtc_device *rtc;
+	struct work_struct alarm_work;
+};
+
+static int nct6694_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct nct6694_rtc_data *data = dev_get_drvdata(dev);
+	unsigned char buf[REQUEST_RTC_CMD0_LEN];
+	int ret;
+
+	ret = nct6694_read_msg(data->nct6694, REQUEST_RTC_MOD,
+			       REQUEST_RTC_CMD0_OFFSET, REQUEST_RTC_CMD0_LEN,
+			       0, REQUEST_RTC_CMD0_LEN, buf);
+	if (ret) {
+		pr_err("%s: Failed to get rtc device!\n", __func__);
+		return -EIO;
+	}
+
+	tm->tm_sec = bcd2bin(buf[RTC_SEC_IDX]);		/* tm_sec expect 0 ~ 59 */
+	tm->tm_min = bcd2bin(buf[RTC_MIN_IDX]);		/* tm_min expect 0 ~ 59 */
+	tm->tm_hour = bcd2bin(buf[RTC_HOUR_IDX]);	/* tm_hour expect 0 ~ 23 */
+	tm->tm_wday = bcd2bin(buf[RTC_WEEK_IDX]) - 1;	/* tm_wday expect 0 ~ 6 */
+	tm->tm_mday = bcd2bin(buf[RTC_DAY_IDX]);	/* tm_mday expect 1 ~ 31 */
+	tm->tm_mon = bcd2bin(buf[RTC_MONTH_IDX]) - 1;	/* tm_month expect 0 ~ 11 */
+	tm->tm_year = bcd2bin(buf[RTC_YEAR_IDX]) + 100;	/* tm_year expect since 1900 */
+
+	return ret;
+}
+
+static int nct6694_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct nct6694_rtc_data *data = dev_get_drvdata(dev);
+	unsigned char buf[REQUEST_RTC_CMD0_LEN];
+	int ret;
+
+	buf[RTC_SEC_IDX] = bin2bcd(tm->tm_sec);
+	buf[RTC_MIN_IDX] = bin2bcd(tm->tm_min);
+	buf[RTC_HOUR_IDX] = bin2bcd(tm->tm_hour);
+	buf[RTC_WEEK_IDX] = bin2bcd(tm->tm_wday + 1);
+	buf[RTC_DAY_IDX] = bin2bcd(tm->tm_mday);
+	buf[RTC_MONTH_IDX] = bin2bcd(tm->tm_mon + 1);
+	buf[RTC_YEAR_IDX] = bin2bcd(tm->tm_year - 100);
+
+	ret = nct6694_write_msg(data->nct6694, REQUEST_RTC_MOD,
+				REQUEST_RTC_CMD0_OFFSET, REQUEST_RTC_CMD0_LEN,
+				buf);
+	if (ret) {
+		pr_err("%s: Failed to set rtc device!\n", __func__);
+		return -EIO;
+	}
+
+	return ret;
+}
+
+static int nct6694_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct nct6694_rtc_data *data = dev_get_drvdata(dev);
+	unsigned char buf[REQUEST_RTC_CMD1_LEN];
+	int ret;
+
+	ret = nct6694_read_msg(data->nct6694, REQUEST_RTC_MOD,
+			       REQUEST_RTC_CMD1_OFFSET, REQUEST_RTC_CMD1_LEN,
+			       0, REQUEST_RTC_CMD1_LEN, buf);
+	if (ret) {
+		pr_err("%s: Failed to get rtc device!\n", __func__);
+		return -EIO;
+	}
+
+	alrm->time.tm_sec = bcd2bin(buf[RTC_SEC_IDX]);
+	alrm->time.tm_min = bcd2bin(buf[RTC_MIN_IDX]);
+	alrm->time.tm_hour = bcd2bin(buf[RTC_HOUR_IDX]);
+
+	alrm->enabled = buf[RTC_ALRM_EN_IDX];
+	alrm->pending = buf[RTC_ALRM_PEND_IDX];
+
+	return ret;
+}
+
+static int nct6694_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct nct6694_rtc_data *data = dev_get_drvdata(dev);
+	unsigned char buf[REQUEST_RTC_CMD1_LEN];
+	int ret;
+
+	buf[RTC_SEC_IDX] = bin2bcd(alrm->time.tm_sec);
+	buf[RTC_MIN_IDX] = bin2bcd(alrm->time.tm_min);
+	buf[RTC_HOUR_IDX] = bin2bcd(alrm->time.tm_hour);
+	buf[RTC_ALRM_EN_IDX] = alrm->enabled ? RTC_IRQ_EN : 0;
+	buf[RTC_ALRM_PEND_IDX] = 0;
+
+	ret = nct6694_write_msg(data->nct6694, REQUEST_RTC_MOD,
+				REQUEST_RTC_CMD1_OFFSET, REQUEST_RTC_CMD1_LEN,
+				buf);
+	if (ret) {
+		pr_err("%s: Failed to set rtc device!\n", __func__);
+		return -EIO;
+	}
+
+	return ret;
+}
+
+static int nct6694_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct nct6694_rtc_data *data = dev_get_drvdata(dev);
+	unsigned char buf[REQUEST_RTC_CMD2_LEN] = {0};
+	int ret;
+
+	if (enabled)
+		buf[RTC_IRQ_EN_IDX] |= RTC_IRQ_EN;
+	else
+		buf[RTC_IRQ_EN_IDX] &= ~RTC_IRQ_EN;
+
+	ret = nct6694_write_msg(data->nct6694, REQUEST_RTC_MOD,
+				REQUEST_RTC_CMD2_OFFSET, REQUEST_RTC_CMD2_LEN,
+				buf);
+	if (ret) {
+		pr_err("%s: Failed to set rtc device!\n", __func__);
+		return -EIO;
+	}
+
+	return ret;
+}
+
+static const struct rtc_class_ops nct6694_rtc_ops = {
+	.read_time = nct6694_rtc_read_time,
+	.set_time = nct6694_rtc_set_time,
+	.read_alarm = nct6694_rtc_read_alarm,
+	.set_alarm = nct6694_rtc_set_alarm,
+	.alarm_irq_enable = nct6694_rtc_alarm_irq_enable,
+};
+
+static void nct6694_rtc_alarm(struct work_struct *work)
+{
+	struct nct6694_rtc_data *data;
+	unsigned char buf[REQUEST_RTC_CMD2_LEN] = {0};
+
+	data = container_of(work, struct nct6694_rtc_data, alarm_work);
+
+	pr_info("%s: Got RTC alarm!\n", __func__);
+	buf[RTC_IRQ_EN_IDX] = RTC_IRQ_EN;
+	buf[RTC_IRQ_PEND_IDX] = RTC_IRQ_STS;
+	nct6694_write_msg(data->nct6694, REQUEST_RTC_MOD,
+			  REQUEST_RTC_CMD2_OFFSET,
+			  REQUEST_RTC_CMD2_LEN, buf);
+}
+
+static void nct6694_rtc_handler(void *private_data)
+{
+	struct nct6694_rtc_data *data = private_data;
+	struct nct6694 *nct6694 = data->nct6694;
+
+	queue_work(nct6694->async_workqueue, &data->alarm_work);
+}
+
+static int nct6694_rtc_probe(struct platform_device *pdev)
+{
+	struct nct6694_rtc_data *data;
+	struct nct6694 *nct6694 = dev_get_drvdata(pdev->dev.parent);
+	int ret;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(data->rtc))
+		return PTR_ERR(data->rtc);
+
+	data->nct6694 = nct6694;
+	data->rtc->ops = &nct6694_rtc_ops;
+	data->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	data->rtc->range_max = RTC_TIMESTAMP_END_2099;
+
+	INIT_WORK(&data->alarm_work, nct6694_rtc_alarm);
+
+	ret = nct6694_register_handler(nct6694, RTC_IRQ_STATUS,
+				       nct6694_rtc_handler, data);
+	if (ret) {
+		dev_err(&pdev->dev, "%s:  Failed to register handler: %pe\n",
+			__func__, ERR_PTR(ret));
+		return ret;
+	}
+
+	device_set_wakeup_capable(&pdev->dev, 1);
+
+	platform_set_drvdata(pdev, data);
+
+	/* Register rtc device to RTC framework */
+	ret = devm_rtc_register_device(data->rtc);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to register rtc device!\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static struct platform_driver nct6694_rtc_driver = {
+	.driver = {
+		.name	= DRVNAME,
+	},
+	.probe		= nct6694_rtc_probe,
+};
+
+static int __init nct6694_init(void)
+{
+	int err;
+
+	err = platform_driver_register(&nct6694_rtc_driver);
+	if (!err) {
+		if (err)
+			platform_driver_unregister(&nct6694_rtc_driver);
+	}
+
+	return err;
+}
+subsys_initcall(nct6694_init);
+
+static void __exit nct6694_exit(void)
+{
+	platform_driver_unregister(&nct6694_rtc_driver);
+}
+module_exit(nct6694_exit);
+
+MODULE_DESCRIPTION("USB-RTC driver for NCT6694");
+MODULE_AUTHOR("Ming Yu <tmyu0@nuvoton.com>");
+MODULE_LICENSE("GPL");