[PATCH v11 7/7] rtc: Add Nuvoton NCT6694 RTC support

a0282524688
2025-05-20T02:04:39Z

This driver supports RTC functionality for NCT6694 MFD device
based on USB interface.

Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Ming Yu <tmyu0@nuvoton.com>
---

Changes since version 10:

Changes since version 9:
- Add devm_add_action_or_reset() to dispose irq mapping

Changes since version 8:
- Modify the signed-off-by with my work address
- Add irq_dispose_mapping() in the error handling path and in the remove
function

Changes since version 7:

Changes since version 6:

Changes since version 5:
- Modify the module name and the driver name consistently

Changes since version 4:
- Modify arguments in read/write function to a pointer to cmd_header
- Modify all callers that call the read/write function

Changes since version 3:
- Modify array buffer to structure
- Fix defines and comments
- Drop private mutex and use rtc core lock
- Modify device_set_wakeup_capable() to device_init_wakeup()

Changes since version 2:
- Add MODULE_ALIAS()

Changes since version 1:
- Add each driver's command structure
- Fix platform driver registration
- Drop unnecessary logs
- Fix overwrite error return values
- Modify to use dev_err_probe API

MAINTAINERS | 1 +
drivers/rtc/Kconfig | 10 ++
drivers/rtc/Makefile | 1 +
drivers/rtc/rtc-nct6694.c | 297 ++++++++++++++++++++++++++++++++++++++
4 files changed, 309 insertions(+)
create mode 100644 drivers/rtc/rtc-nct6694.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 661646cab68f..91ea3eafc533 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17459,6 +17459,7 @@ F: drivers/hwmon/nct6694-hwmon.c
F: drivers/i2c/busses/i2c-nct6694.c
F: drivers/mfd/nct6694.c
F: drivers/net/can/usb/nct6694_canfd.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 838bdc138ffe..d8662b5d1e47 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -416,6 +416,16 @@ 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 31473b3276d9..da091d66e2d7 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -118,6 +118,7 @@ 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..35401a0d9cf5
--- /dev/null
+++ b/drivers/rtc/rtc-nct6694.c
@@ -0,0 +1,297 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Nuvoton NCT6694 RTC driver based on USB interface.
+ *
+ * Copyright (C) 2025 Nuvoton Technology Corp.
+ */
+
+#include <linux/bcd.h>
+#include <linux/irqdomain.h>
+#include <linux/kernel.h>
+#include <linux/mfd/nct6694.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/slab.h>
+
+/*
+ * USB command module type for NCT6694 RTC controller.
+ * This defines the module type used for communication with the NCT6694
+ * RTC controller over the USB interface.
+ */
+#define NCT6694_RTC_MOD 0x08
+
+/* Command 00h - RTC Time */
+#define NCT6694_RTC_TIME 0x0000
+#define NCT6694_RTC_TIME_SEL 0x00
+
+/* Command 01h - RTC Alarm */
+#define NCT6694_RTC_ALARM 0x01
+#define NCT6694_RTC_ALARM_SEL 0x00
+
+/* Command 02h - RTC Status */
+#define NCT6694_RTC_STATUS 0x02
+#define NCT6694_RTC_STATUS_SEL 0x00
+
+#define NCT6694_RTC_IRQ_INT_EN BIT(0) /* Transmit a USB INT-in when RTC alarm */
+#define NCT6694_RTC_IRQ_GPO_EN BIT(5) /* Trigger a GPO Low Pulse when RTC alarm */
+
+#define NCT6694_RTC_IRQ_EN (NCT6694_RTC_IRQ_INT_EN | NCT6694_RTC_IRQ_GPO_EN)
+#define NCT6694_RTC_IRQ_STS BIT(0) /* Write 1 clear IRQ status */
+
+struct __packed nct6694_rtc_time {
+ u8 sec;
+ u8 min;
+ u8 hour;
+ u8 week;
+ u8 day;
+ u8 month;
+ u8 year;
+};
+
+struct __packed nct6694_rtc_alarm {
+ u8 sec;
+ u8 min;
+ u8 hour;
+ u8 alarm_en;
+ u8 alarm_pend;
+};
+
+struct __packed nct6694_rtc_status {
+ u8 irq_en;
+ u8 irq_pend;
+};
+
+union __packed nct6694_rtc_msg {
+ struct nct6694_rtc_time time;
+ struct nct6694_rtc_alarm alarm;
+ struct nct6694_rtc_status sts;
+};
+
+struct nct6694_rtc_data {
+ struct nct6694 *nct6694;
+ struct rtc_device *rtc;
+ union nct6694_rtc_msg *msg;
+ int irq;
+};
+
+static int nct6694_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+ struct nct6694_rtc_data *data = dev_get_drvdata(dev);
+ struct nct6694_rtc_time *time = &data->msg->time;
+ static const struct nct6694_cmd_header cmd_hd = {
+ .mod = NCT6694_RTC_MOD,
+ .cmd = NCT6694_RTC_TIME,
+ .sel = NCT6694_RTC_TIME_SEL,
+ .len = cpu_to_le16(sizeof(*time))
+ };
+ int ret;
+
+ ret = nct6694_read_msg(data->nct6694, &cmd_hd, time);
+ if (ret)
+ return ret;
+
+ tm->tm_sec = bcd2bin(time->sec); /* tm_sec expect 0 ~ 59 */
+ tm->tm_min = bcd2bin(time->min); /* tm_min expect 0 ~ 59 */
+ tm->tm_hour = bcd2bin(time->hour); /* tm_hour expect 0 ~ 23 */
+ tm->tm_wday = bcd2bin(time->week) - 1; /* tm_wday expect 0 ~ 6 */
+ tm->tm_mday = bcd2bin(time->day); /* tm_mday expect 1 ~ 31 */
+ tm->tm_mon = bcd2bin(time->month) - 1; /* tm_month expect 0 ~ 11 */
+ tm->tm_year = bcd2bin(time->year) + 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);
+ struct nct6694_rtc_time *time = &data->msg->time;
+ static const struct nct6694_cmd_header cmd_hd = {
+ .mod = NCT6694_RTC_MOD,
+ .cmd = NCT6694_RTC_TIME,
+ .sel = NCT6694_RTC_TIME_SEL,
+ .len = cpu_to_le16(sizeof(*time))
+ };
+
+ time->sec = bin2bcd(tm->tm_sec);
+ time->min = bin2bcd(tm->tm_min);
+ time->hour = bin2bcd(tm->tm_hour);
+ time->week = bin2bcd(tm->tm_wday + 1);
+ time->day = bin2bcd(tm->tm_mday);
+ time->month = bin2bcd(tm->tm_mon + 1);
+ time->year = bin2bcd(tm->tm_year - 100);
+
+ return nct6694_write_msg(data->nct6694, &cmd_hd, time);
+}
+
+static int nct6694_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+ struct nct6694_rtc_data *data = dev_get_drvdata(dev);
+ struct nct6694_rtc_alarm *alarm = &data->msg->alarm;
+ static const struct nct6694_cmd_header cmd_hd = {
+ .mod = NCT6694_RTC_MOD,
+ .cmd = NCT6694_RTC_ALARM,
+ .sel = NCT6694_RTC_ALARM_SEL,
+ .len = cpu_to_le16(sizeof(*alarm))
+ };
+ int ret;
+
+ ret = nct6694_read_msg(data->nct6694, &cmd_hd, alarm);
+ if (ret)
+ return ret;
+
+ alrm->time.tm_sec = bcd2bin(alarm->sec);
+ alrm->time.tm_min = bcd2bin(alarm->min);
+ alrm->time.tm_hour = bcd2bin(alarm->hour);
+ alrm->enabled = alarm->alarm_en;
+ alrm->pending = alarm->alarm_pend;
+
+ return ret;
+}
+
+static int nct6694_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+ struct nct6694_rtc_data *data = dev_get_drvdata(dev);
+ struct nct6694_rtc_alarm *alarm = &data->msg->alarm;
+ static const struct nct6694_cmd_header cmd_hd = {
+ .mod = NCT6694_RTC_MOD,
+ .cmd = NCT6694_RTC_ALARM,
+ .sel = NCT6694_RTC_ALARM_SEL,
+ .len = cpu_to_le16(sizeof(*alarm))
+ };
+
+ alarm->sec = bin2bcd(alrm->time.tm_sec);
+ alarm->min = bin2bcd(alrm->time.tm_min);
+ alarm->hour = bin2bcd(alrm->time.tm_hour);
+ alarm->alarm_en = alrm->enabled ? NCT6694_RTC_IRQ_EN : 0;
+ alarm->alarm_pend = 0;
+
+ return nct6694_write_msg(data->nct6694, &cmd_hd, alarm);
+}
+
+static int nct6694_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+ struct nct6694_rtc_data *data = dev_get_drvdata(dev);
+ struct nct6694_rtc_status *sts = &data->msg->sts;
+ static const struct nct6694_cmd_header cmd_hd = {
+ .mod = NCT6694_RTC_MOD,
+ .cmd = NCT6694_RTC_STATUS,
+ .sel = NCT6694_RTC_STATUS_SEL,
+ .len = cpu_to_le16(sizeof(*sts))
+ };
+
+ if (enabled)
+ sts->irq_en |= NCT6694_RTC_IRQ_EN;
+ else
+ sts->irq_en &= ~NCT6694_RTC_IRQ_EN;
+
+ sts->irq_pend = 0;
+
+ return nct6694_write_msg(data->nct6694, &cmd_hd, sts);
+}
+
+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 irqreturn_t nct6694_irq(int irq, void *dev_id)
+{
+ struct nct6694_rtc_data *data = dev_id;
+ struct nct6694_rtc_status *sts = &data->msg->sts;
+ static const struct nct6694_cmd_header cmd_hd = {
+ .mod = NCT6694_RTC_MOD,
+ .cmd = NCT6694_RTC_STATUS,
+ .sel = NCT6694_RTC_STATUS_SEL,
+ .len = cpu_to_le16(sizeof(*sts))
+ };
+ int ret;
+
+ rtc_lock(data->rtc);
+
+ sts->irq_en = NCT6694_RTC_IRQ_EN;
+ sts->irq_pend = NCT6694_RTC_IRQ_STS;
+ ret = nct6694_write_msg(data->nct6694, &cmd_hd, sts);
+ if (ret) {
+ rtc_unlock(data->rtc);
+ return IRQ_NONE;
+ }
+
+ rtc_update_irq(data->rtc, 1, RTC_IRQF | RTC_AF);
+
+ rtc_unlock(data->rtc);
+
+ return IRQ_HANDLED;
+}
+
+static void nct6694_irq_dispose_mapping(void *d)
+{
+ struct nct6694_rtc_data *data = d;
+
+ irq_dispose_mapping(data->irq);
+}
+
+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->msg = devm_kzalloc(&pdev->dev, sizeof(union nct6694_rtc_msg),
+ GFP_KERNEL);
+ if (!data->msg)
+ return -ENOMEM;
+
+ data->irq = irq_create_mapping(nct6694->domain, NCT6694_IRQ_RTC);
+ if (!data->irq)
+ return -EINVAL;
+
+ ret = devm_add_action_or_reset(&pdev->dev, nct6694_irq_dispose_mapping,
+ data);
+ if (ret)
+ return ret;
+
+ ret = devm_device_init_wakeup(&pdev->dev);
+ if (ret)
+ return dev_err_probe(&pdev->dev, ret, "Failed to init wakeup\n");
+
+ 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;
+
+ platform_set_drvdata(pdev, data);
+
+ ret = devm_request_threaded_irq(&pdev->dev, data->irq, NULL,
+ nct6694_irq, IRQF_ONESHOT,
+ "rtc-nct6694", data);
+ if (ret < 0)
+ return dev_err_probe(&pdev->dev, ret, "Failed to request irq\n");
+
+ return devm_rtc_register_device(data->rtc);
+}
+
+static struct platform_driver nct6694_rtc_driver = {
+ .driver = {
+ .name = "nct6694-rtc",
+ },
+ .probe = nct6694_rtc_probe,
+};
+
+module_platform_driver(nct6694_rtc_driver);
+
+MODULE_DESCRIPTION("USB-RTC driver for NCT6694");
+MODULE_AUTHOR("Ming Yu <tmyu0@nuvoton.com>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:nct6694-rtc");
--
2.34.1