rtc: Add driver for Epson RX8111

Epson RX8111 is an RTC with alarm, timer and timestamp functionality.
Add a basic driver with support for only reading/writing time (for now).

Signed-off-by: Waqar Hameed <[e-mail]>
Link: https://lore.kernel.org/r/0c3e[e-mail]
Signed-off-by: Alexandre Belloni <[e-mail]>

drivers/rtc/Kconfig

···
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-rx8010.
 
+config RTC_DRV_RX8111
+	tristate "Epson RX8111"
+	select REGMAP_I2C
+	depends on I2C
+	help
+	  If you say yes here you will get support for the Epson RX8111 RTC.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called rtc-rx8111.
+
 config RTC_DRV_RX8581
 	tristate "Epson RX-8571/RX-8581"
 	select REGMAP_I2C

drivers/rtc/Makefile

···
 obj-$(CONFIG_RTC_DRV_RX6110)	+= rtc-rx6110.o
 obj-$(CONFIG_RTC_DRV_RX8010)	+= rtc-rx8010.o
 obj-$(CONFIG_RTC_DRV_RX8025)	+= rtc-rx8025.o
+obj-$(CONFIG_RTC_DRV_RX8111)	+= rtc-rx8111.o
 obj-$(CONFIG_RTC_DRV_RX8581)	+= rtc-rx8581.o
 obj-$(CONFIG_RTC_DRV_RZN1)	+= rtc-rzn1.o
 obj-$(CONFIG_RTC_DRV_S35390A)	+= rtc-s35390a.o

drivers/rtc/rtc-rx8111.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Driver for Epson RX8111 RTC.
+ *
+ * Copyright (C) 2023 Axis Communications AB
+ */
+
+#include <linux/bcd.h>
+#include <linux/bitfield.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#include <linux/rtc.h>
+
+#define RX8111_REG_SEC			0x10	/* Second counter. */
+#define RX8111_REG_MIN			0x11	/* Minute counter */
+#define RX8111_REG_HOUR			0x12	/* Hour counter. */
+#define RX8111_REG_WEEK			0x13	/* Week day counter. */
+#define RX8111_REG_DAY			0x14	/* Month day counter. */
+#define RX8111_REG_MONTH		0x15	/* Month counter. */
+#define RX8111_REG_YEAR			0x16	/* Year counter. */
+
+#define RX8111_REG_ALARM_MIN		0x17	/* Alarm minute. */
+#define RX8111_REG_ALARM_HOUR		0x18	/* Alarm hour. */
+#define RX8111_REG_ALARM_WEEK_DAY	0x19	/* Alarm week or month day. */
+
+#define RX8111_REG_TIMER_COUNTER0	0x1a	/* Timer counter LSB. */
+#define RX8111_REG_TIMER_COUNTER1	0x1b	/* Timer counter. */
+#define RX8111_REG_TIMER_COUNTER2	0x1c	/* Timer counter MSB. */
+
+#define RX8111_REG_EXT			0x1d	/* Extension register. */
+#define RX8111_REG_FLAG			0x1e	/* Flag register. */
+#define RX8111_REG_CTRL			0x1f	/* Control register. */
+
+#define RX8111_REG_TS_1_1000_SEC	0x20	/* Timestamp 256 or 512 Hz . */
+#define RX8111_REG_TS_1_100_SEC		0x21	/* Timestamp 1 - 128 Hz. */
+#define RX8111_REG_TS_SEC		0x22	/* Timestamp second. */
+#define RX8111_REG_TS_MIN		0x23	/* Timestamp minute. */
+#define RX8111_REG_TS_HOUR		0x24	/* Timestamp hour. */
+#define RX8111_REG_TS_WEEK		0x25	/* Timestamp week day. */
+#define RX8111_REG_TS_DAY		0x26	/* Timestamp month day. */
+#define RX8111_REG_TS_MONTH		0x27	/* Timestamp month. */
+#define RX8111_REG_TS_YEAR		0x28	/* Timestamp year. */
+#define RX8111_REG_TS_STATUS		0x29	/* Timestamp status. */
+
+#define RX8111_REG_EVIN_SETTING		0x2b	/* Timestamp trigger setting. */
+#define RX8111_REG_ALARM_SEC		0x2c	/* Alarm second. */
+#define RX8111_REG_TIMER_CTRL		0x2d	/* Timer control. */
+#define RX8111_REG_TS_CTRL0		0x2e	/* Timestamp control 0. */
+#define RX8111_REG_CMD_TRIGGER		0x2f	/* Timestamp trigger. */
+#define RX8111_REG_PWR_SWITCH_CTRL	0x32	/* Power switch control. */
+#define RX8111_REG_STATUS_MON		0x33	/* Status monitor. */
+#define RX8111_REG_TS_CTRL1		0x34	/* Timestamp control 1. */
+#define RX8111_REG_TS_CTRL2		0x35	/* Timestamp control 2. */
+#define RX8111_REG_TS_CTRL3		0x36	/* Timestamp control 3. */
+
+#define RX8111_FLAG_XST_BIT BIT(0)
+#define RX8111_FLAG_VLF_BIT BIT(1)
+
+#define RX8111_TIME_BUF_SZ (RX8111_REG_YEAR - RX8111_REG_SEC + 1)
+
+enum rx8111_regfield {
+	/* RX8111_REG_EXT. */
+	RX8111_REGF_TSEL0,
+	RX8111_REGF_TSEL1,
+	RX8111_REGF_ETS,
+	RX8111_REGF_WADA,
+	RX8111_REGF_TE,
+	RX8111_REGF_USEL,
+	RX8111_REGF_FSEL0,
+	RX8111_REGF_FSEL1,
+
+	/* RX8111_REG_FLAG. */
+	RX8111_REGF_XST,
+	RX8111_REGF_VLF,
+	RX8111_REGF_EVF,
+	RX8111_REGF_AF,
+	RX8111_REGF_TF,
+	RX8111_REGF_UF,
+	RX8111_REGF_POR,
+
+	/* RX8111_REG_CTRL. */
+	RX8111_REGF_STOP,
+	RX8111_REGF_EIE,
+	RX8111_REGF_AIE,
+	RX8111_REGF_TIE,
+	RX8111_REGF_UIE,
+
+	/* RX8111_REG_PWR_SWITCH_CTRL. */
+	RX8111_REGF_SMPT0,
+	RX8111_REGF_SMPT1,
+	RX8111_REGF_SWSEL0,
+	RX8111_REGF_SWSEL1,
+	RX8111_REGF_INIEN,
+	RX8111_REGF_CHGEN,
+
+	/* Sentinel value. */
+	RX8111_REGF_MAX
+};
+
+static const struct reg_field rx8111_regfields[] = {
+	[RX8111_REGF_TSEL0] = REG_FIELD(RX8111_REG_EXT, 0, 0),
+	[RX8111_REGF_TSEL1] = REG_FIELD(RX8111_REG_EXT, 1, 1),
+	[RX8111_REGF_ETS]   = REG_FIELD(RX8111_REG_EXT, 2, 2),
+	[RX8111_REGF_WADA]  = REG_FIELD(RX8111_REG_EXT, 3, 3),
+	[RX8111_REGF_TE]    = REG_FIELD(RX8111_REG_EXT, 4, 4),
+	[RX8111_REGF_USEL]  = REG_FIELD(RX8111_REG_EXT, 5, 5),
+	[RX8111_REGF_FSEL0] = REG_FIELD(RX8111_REG_EXT, 6, 6),
+	[RX8111_REGF_FSEL1] = REG_FIELD(RX8111_REG_EXT, 7, 7),
+
+	[RX8111_REGF_XST] = REG_FIELD(RX8111_REG_FLAG, 0, 0),
+	[RX8111_REGF_VLF] = REG_FIELD(RX8111_REG_FLAG, 1, 1),
+	[RX8111_REGF_EVF] = REG_FIELD(RX8111_REG_FLAG, 2, 2),
+	[RX8111_REGF_AF]  = REG_FIELD(RX8111_REG_FLAG, 3, 3),
+	[RX8111_REGF_TF]  = REG_FIELD(RX8111_REG_FLAG, 4, 4),
+	[RX8111_REGF_UF]  = REG_FIELD(RX8111_REG_FLAG, 5, 5),
+	[RX8111_REGF_POR] = REG_FIELD(RX8111_REG_FLAG, 7, 7),
+
+	[RX8111_REGF_STOP] = REG_FIELD(RX8111_REG_CTRL, 0, 0),
+	[RX8111_REGF_EIE]  = REG_FIELD(RX8111_REG_CTRL, 2, 2),
+	[RX8111_REGF_AIE]  = REG_FIELD(RX8111_REG_CTRL, 3, 3),
+	[RX8111_REGF_TIE]  = REG_FIELD(RX8111_REG_CTRL, 4, 4),
+	[RX8111_REGF_UIE]  = REG_FIELD(RX8111_REG_CTRL, 5, 5),
+
+	[RX8111_REGF_SMPT0]  = REG_FIELD(RX8111_REG_PWR_SWITCH_CTRL, 0, 0),
+	[RX8111_REGF_SMPT1]  = REG_FIELD(RX8111_REG_PWR_SWITCH_CTRL, 1, 1),
+	[RX8111_REGF_SWSEL0] = REG_FIELD(RX8111_REG_PWR_SWITCH_CTRL, 2, 2),
+	[RX8111_REGF_SWSEL1] = REG_FIELD(RX8111_REG_PWR_SWITCH_CTRL, 3, 3),
+	[RX8111_REGF_INIEN]  = REG_FIELD(RX8111_REG_PWR_SWITCH_CTRL, 6, 6),
+	[RX8111_REGF_CHGEN]  = REG_FIELD(RX8111_REG_PWR_SWITCH_CTRL, 7, 7),
+};
+
+static const struct regmap_config rx8111_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = RX8111_REG_TS_CTRL3,
+};
+
+struct rx8111_data {
+	struct regmap *regmap;
+	struct regmap_field *regfields[RX8111_REGF_MAX];
+	struct device *dev;
+	struct rtc_device *rtc;
+};
+
+static int rx8111_read_vl_flag(struct rx8111_data *data, unsigned int *vlval)
+{
+	int ret;
+
+	ret = regmap_field_read(data->regfields[RX8111_REGF_VLF], vlval);
+	if (ret)
+		dev_dbg(data->dev, "Could not read VL flag (%d)", ret);
+
+	return ret;
+}
+
+static int rx8111_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rx8111_data *data = dev_get_drvdata(dev);
+	u8 buf[RX8111_TIME_BUF_SZ];
+	unsigned int regval;
+	int ret;
+
+	/* Check status. */
+	ret = regmap_read(data->regmap, RX8111_REG_FLAG, &regval);
+	if (ret) {
+		dev_dbg(data->dev, "Could not read flag register (%d)\n", ret);
+		return ret;
+	}
+
+	if (FIELD_GET(RX8111_FLAG_XST_BIT, regval)) {
+		dev_warn(data->dev,
+			 "Crystal oscillation stopped, time is not reliable\n");
+		return -EINVAL;
+	}
+
+	if (FIELD_GET(RX8111_FLAG_VLF_BIT, regval)) {
+		dev_warn(data->dev,
+			 "Low voltage detected, time is not reliable\n");
+		return -EINVAL;
+	}
+
+	ret = regmap_field_read(data->regfields[RX8111_REGF_STOP], &regval);
+	if (ret) {
+		dev_dbg(data->dev, "Could not read clock status (%d)\n", ret);
+		return ret;
+	}
+
+	if (regval) {
+		dev_warn(data->dev, "Clock stopped, time is not reliable\n");
+		return -EINVAL;
+	}
+
+	/* Read time. */
+	ret = regmap_bulk_read(data->regmap, RX8111_REG_SEC, buf,
+			       ARRAY_SIZE(buf));
+	if (ret) {
+		dev_dbg(data->dev, "Could not bulk read time (%d)\n", ret);
+		return ret;
+	}
+
+	tm->tm_sec = bcd2bin(buf[0]);
+	tm->tm_min = bcd2bin(buf[1]);
+	tm->tm_hour = bcd2bin(buf[2]);
+	tm->tm_wday = ffs(buf[3]) - 1;
+	tm->tm_mday = bcd2bin(buf[4]);
+	tm->tm_mon = bcd2bin(buf[5]) - 1;
+	tm->tm_year = bcd2bin(buf[6]) + 100;
+
+	return 0;
+}
+
+static int rx8111_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rx8111_data *data = dev_get_drvdata(dev);
+	u8 buf[RX8111_TIME_BUF_SZ];
+	int ret;
+
+	buf[0] = bin2bcd(tm->tm_sec);
+	buf[1] = bin2bcd(tm->tm_min);
+	buf[2] = bin2bcd(tm->tm_hour);
+	buf[3] = BIT(tm->tm_wday);
+	buf[4] = bin2bcd(tm->tm_mday);
+	buf[5] = bin2bcd(tm->tm_mon + 1);
+	buf[6] = bin2bcd(tm->tm_year - 100);
+
+	ret = regmap_clear_bits(data->regmap, RX8111_REG_FLAG,
+				RX8111_FLAG_XST_BIT | RX8111_FLAG_VLF_BIT);
+	if (ret)
+		return ret;
+
+	/* Stop the clock. */
+	ret = regmap_field_write(data->regfields[RX8111_REGF_STOP], 1);
+	if (ret) {
+		dev_dbg(data->dev, "Could not stop the clock (%d)\n", ret);
+		return ret;
+	}
+
+	/* Set the time. */
+	ret = regmap_bulk_write(data->regmap, RX8111_REG_SEC, buf,
+				ARRAY_SIZE(buf));
+	if (ret) {
+		dev_dbg(data->dev, "Could not bulk write time (%d)\n", ret);
+
+		/*
+		 * We don't bother with trying to start the clock again. We
+		 * check for this in rx8111_read_time() (and thus force user to
+		 * call rx8111_set_time() to try again).
+		 */
+		return ret;
+	}
+
+	/* Start the clock. */
+	ret = regmap_field_write(data->regfields[RX8111_REGF_STOP], 0);
+	if (ret) {
+		dev_dbg(data->dev, "Could not start the clock (%d)\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int rx8111_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
+{
+	struct rx8111_data *data = dev_get_drvdata(dev);
+	unsigned int regval;
+	unsigned int vlval;
+	int ret;
+
+	switch (cmd) {
+	case RTC_VL_READ:
+		ret = rx8111_read_vl_flag(data, &regval);
+		if (ret)
+			return ret;
+
+		vlval = regval ? RTC_VL_DATA_INVALID : 0;
+
+		return put_user(vlval, (typeof(vlval) __user *)arg);
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+
+static const struct rtc_class_ops rx8111_rtc_ops = {
+	.read_time = rx8111_read_time,
+	.set_time = rx8111_set_time,
+	.ioctl = rx8111_ioctl,
+};
+
+static int rx8111_probe(struct i2c_client *client)
+{
+	struct rx8111_data *data;
+	struct rtc_device *rtc;
+	size_t i;
+
+	data = devm_kmalloc(&client->dev, sizeof(*data), GFP_KERNEL);
+	if (!data) {
+		dev_dbg(&client->dev, "Could not allocate device data\n");
+		return -ENOMEM;
+	}
+
+	data->dev = &client->dev;
+	dev_set_drvdata(data->dev, data);
+
+	data->regmap = devm_regmap_init_i2c(client, &rx8111_regmap_config);
+	if (IS_ERR(data->regmap)) {
+		dev_dbg(data->dev, "Could not initialize regmap\n");
+		return PTR_ERR(data->regmap);
+	}
+
+	for (i = 0; i < RX8111_REGF_MAX; ++i) {
+		data->regfields[i] = devm_regmap_field_alloc(
+			data->dev, data->regmap, rx8111_regfields[i]);
+		if (IS_ERR(data->regfields[i])) {
+			dev_dbg(data->dev,
+				"Could not allocate register field %zu\n", i);
+			return PTR_ERR(data->regfields[i]);
+		}
+	}
+
+	rtc = devm_rtc_allocate_device(data->dev);
+	if (IS_ERR(rtc)) {
+		dev_dbg(data->dev, "Could not allocate rtc device\n");
+		return PTR_ERR(rtc);
+	}
+
+	rtc->ops = &rx8111_rtc_ops;
+	rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	rtc->range_max = RTC_TIMESTAMP_END_2099;
+
+	clear_bit(RTC_FEATURE_ALARM, rtc->features);
+
+	return devm_rtc_register_device(rtc);
+}
+
+static const struct of_device_id rx8111_of_match[] = {
+	{
+		.compatible = "epson,rx8111",
+	},
+	{}
+};
+MODULE_DEVICE_TABLE(of, rx8111_of_match);
+
+static struct i2c_driver rx8111_driver = {
+	.driver = {
+		.name = "rtc-rx8111",
+		.of_match_table = rx8111_of_match,
+	},
+	.probe = rx8111_probe,
+};
+module_i2c_driver(rx8111_driver);
+
+MODULE_AUTHOR("Waqar Hameed <[e-mail]>");
+MODULE_DESCRIPTION("Epson RX8111 RTC driver");
+MODULE_LICENSE("GPL");