rtc: add driver for RX6110SA real time clock

The RX6110 comes in two different variants: SPI and I2C.
This driver only supports the SPI variant.

If the need ever arises to also support the I2C variant, this driver
could easily be refactored to support both cases.

Reviewed-by: Philipp Zabel <[e-mail]>
Signed-off-by: Steffen Trumtrar <[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-rx4581.
 
+config RTC_DRV_RX6110
+	tristate "Epson RX-6110"
+	select REGMAP_SPI
+	help
+	  If you say yes here you will get support for the Epson RX-6610.
+
+	  This driver can also be built as a module. If so the module
+	  will be called rtc-rx6110.
+
 config RTC_DRV_MCP795
 	tristate "Microchip MCP795"
 	help

drivers/rtc/Makefile

···
 obj-$(CONFIG_RTC_DRV_RV3029C2)	+= rtc-rv3029c2.o
 obj-$(CONFIG_RTC_DRV_RV8803)	+= rtc-rv8803.o
 obj-$(CONFIG_RTC_DRV_RX4581)	+= rtc-rx4581.o
+obj-$(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_RX8581)	+= rtc-rx8581.o

drivers/rtc/rtc-rx6110.c

···
+/*
+ * Driver for the Epson RTC module RX-6110 SA
+ *
+ * Copyright(C) 2015 Pengutronix, Steffen Trumtrar <[e-mail]>
+ * Copyright(C) SEIKO EPSON CORPORATION 2013. All rights reserved.
+ *
+ * This driver software is distributed as is, without any warranty of any kind,
+ * either express or implied as further specified in the GNU Public License.
+ * This software may be used and distributed according to the terms of the GNU
+ * Public License, version 2 as published by the Free Software Foundation.
+ * See the file COPYING in the main directory of this archive for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/bcd.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_gpio.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+#include <linux/spi/spi.h>
+
+/* RX-6110 Register definitions */
+#define RX6110_REG_SEC		0x10
+#define RX6110_REG_MIN		0x11
+#define RX6110_REG_HOUR		0x12
+#define RX6110_REG_WDAY		0x13
+#define RX6110_REG_MDAY		0x14
+#define RX6110_REG_MONTH	0x15
+#define RX6110_REG_YEAR		0x16
+#define RX6110_REG_RES1		0x17
+#define RX6110_REG_ALMIN	0x18
+#define RX6110_REG_ALHOUR	0x19
+#define RX6110_REG_ALWDAY	0x1A
+#define RX6110_REG_TCOUNT0	0x1B
+#define RX6110_REG_TCOUNT1	0x1C
+#define RX6110_REG_EXT		0x1D
+#define RX6110_REG_FLAG		0x1E
+#define RX6110_REG_CTRL		0x1F
+#define RX6110_REG_USER0	0x20
+#define RX6110_REG_USER1	0x21
+#define RX6110_REG_USER2	0x22
+#define RX6110_REG_USER3	0x23
+#define RX6110_REG_USER4	0x24
+#define RX6110_REG_USER5	0x25
+#define RX6110_REG_USER6	0x26
+#define RX6110_REG_USER7	0x27
+#define RX6110_REG_USER8	0x28
+#define RX6110_REG_USER9	0x29
+#define RX6110_REG_USERA	0x2A
+#define RX6110_REG_USERB	0x2B
+#define RX6110_REG_USERC	0x2C
+#define RX6110_REG_USERD	0x2D
+#define RX6110_REG_USERE	0x2E
+#define RX6110_REG_USERF	0x2F
+#define RX6110_REG_RES2		0x30
+#define RX6110_REG_RES3		0x31
+#define RX6110_REG_IRQ		0x32
+
+#define RX6110_BIT_ALARM_EN		BIT(7)
+
+/* Extension Register (1Dh) bit positions */
+#define RX6110_BIT_EXT_TSEL0		BIT(0)
+#define RX6110_BIT_EXT_TSEL1		BIT(1)
+#define RX6110_BIT_EXT_TSEL2		BIT(2)
+#define RX6110_BIT_EXT_WADA		BIT(3)
+#define RX6110_BIT_EXT_TE		BIT(4)
+#define RX6110_BIT_EXT_USEL		BIT(5)
+#define RX6110_BIT_EXT_FSEL0		BIT(6)
+#define RX6110_BIT_EXT_FSEL1		BIT(7)
+
+/* Flag Register (1Eh) bit positions */
+#define RX6110_BIT_FLAG_VLF		BIT(1)
+#define RX6110_BIT_FLAG_AF		BIT(3)
+#define RX6110_BIT_FLAG_TF		BIT(4)
+#define RX6110_BIT_FLAG_UF		BIT(5)
+
+/* Control Register (1Fh) bit positions */
+#define RX6110_BIT_CTRL_TBKE		BIT(0)
+#define RX6110_BIT_CTRL_TBKON		BIT(1)
+#define RX6110_BIT_CTRL_TSTP		BIT(2)
+#define RX6110_BIT_CTRL_AIE		BIT(3)
+#define RX6110_BIT_CTRL_TIE		BIT(4)
+#define RX6110_BIT_CTRL_UIE		BIT(5)
+#define RX6110_BIT_CTRL_STOP		BIT(6)
+#define RX6110_BIT_CTRL_TEST		BIT(7)
+
+enum {
+	RTC_SEC = 0,
+	RTC_MIN,
+	RTC_HOUR,
+	RTC_WDAY,
+	RTC_MDAY,
+	RTC_MONTH,
+	RTC_YEAR,
+	RTC_NR_TIME
+};
+
+#define RX6110_DRIVER_NAME		"rx6110"
+
+struct rx6110_data {
+	struct rtc_device *rtc;
+	struct regmap *regmap;
+};
+
+/**
+ * rx6110_rtc_tm_to_data - convert rtc_time to native time encoding
+ *
+ * @tm: holds date and time
+ * @data: holds the encoding in rx6110 native form
+ */
+static int rx6110_rtc_tm_to_data(struct rtc_time *tm, u8 *data)
+{
+	pr_debug("%s: date %ds %dm %dh %dmd %dm %dy\n", __func__,
+		 tm->tm_sec, tm->tm_min, tm->tm_hour,
+		 tm->tm_mday, tm->tm_mon, tm->tm_year);
+
+	/*
+	 * The year in the RTC is a value between 0 and 99.
+	 * Assume that this represents the current century
+	 * and disregard all other values.
+	 */
+	if (tm->tm_year < 100 || tm->tm_year >= 200)
+		return -EINVAL;
+
+	data[RTC_SEC] = bin2bcd(tm->tm_sec);
+	data[RTC_MIN] = bin2bcd(tm->tm_min);
+	data[RTC_HOUR] = bin2bcd(tm->tm_hour);
+	data[RTC_WDAY] = BIT(bin2bcd(tm->tm_wday));
+	data[RTC_MDAY] = bin2bcd(tm->tm_mday);
+	data[RTC_MONTH] = bin2bcd(tm->tm_mon + 1);
+	data[RTC_YEAR] = bin2bcd(tm->tm_year % 100);
+
+	return 0;
+}
+
+/**
+ * rx6110_data_to_rtc_tm - convert native time encoding to rtc_time
+ *
+ * @data: holds the encoding in rx6110 native form
+ * @tm: holds date and time
+ */
+static int rx6110_data_to_rtc_tm(u8 *data, struct rtc_time *tm)
+{
+	tm->tm_sec = bcd2bin(data[RTC_SEC] & 0x7f);
+	tm->tm_min = bcd2bin(data[RTC_MIN] & 0x7f);
+	/* only 24-hour clock */
+	tm->tm_hour = bcd2bin(data[RTC_HOUR] & 0x3f);
+	tm->tm_wday = ffs(data[RTC_WDAY] & 0x7f);
+	tm->tm_mday = bcd2bin(data[RTC_MDAY] & 0x3f);
+	tm->tm_mon = bcd2bin(data[RTC_MONTH] & 0x1f) - 1;
+	tm->tm_year = bcd2bin(data[RTC_YEAR]) + 100;
+
+	pr_debug("%s: date %ds %dm %dh %dmd %dm %dy\n", __func__,
+		 tm->tm_sec, tm->tm_min, tm->tm_hour,
+		 tm->tm_mday, tm->tm_mon, tm->tm_year);
+
+	/*
+	 * The year in the RTC is a value between 0 and 99.
+	 * Assume that this represents the current century
+	 * and disregard all other values.
+	 */
+	if (tm->tm_year < 100 || tm->tm_year >= 200)
+		return -EINVAL;
+
+	return 0;
+}
+
+/**
+ * rx6110_set_time - set the current time in the rx6110 registers
+ *
+ * @dev: the rtc device in use
+ * @tm: holds date and time
+ *
+ * BUG: The HW assumes every year that is a multiple of 4 to be a leap
+ * year. Next time this is wrong is 2100, which will not be a leap year
+ *
+ * Note: If STOP is not set/cleared, the clock will start when the seconds
+ *       register is written
+ *
+ */
+static int rx6110_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rx6110_data *rx6110 = dev_get_drvdata(dev);
+	u8 data[RTC_NR_TIME];
+	int ret;
+
+	ret = rx6110_rtc_tm_to_data(tm, data);
+	if (ret < 0)
+		return ret;
+
+	/* set STOP bit before changing clock/calendar */
+	ret = regmap_update_bits(rx6110->regmap, RX6110_REG_CTRL,
+				 RX6110_BIT_CTRL_STOP, RX6110_BIT_CTRL_STOP);
+	if (ret)
+		return ret;
+
+	ret = regmap_bulk_write(rx6110->regmap, RX6110_REG_SEC, data,
+				RTC_NR_TIME);
+	if (ret)
+		return ret;
+
+	/* The time in the RTC is valid. Be sure to have VLF cleared. */
+	ret = regmap_update_bits(rx6110->regmap, RX6110_REG_FLAG,
+				 RX6110_BIT_FLAG_VLF, 0);
+	if (ret)
+		return ret;
+
+	/* clear STOP bit after changing clock/calendar */
+	ret = regmap_update_bits(rx6110->regmap, RX6110_REG_CTRL,
+				 RX6110_BIT_CTRL_STOP, 0);
+
+	return ret;
+}
+
+/**
+ * rx6110_get_time - get the current time from the rx6110 registers
+ * @dev: the rtc device in use
+ * @tm: holds date and time
+ */
+static int rx6110_get_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rx6110_data *rx6110 = dev_get_drvdata(dev);
+	u8 data[RTC_NR_TIME];
+	int flags;
+	int ret;
+
+	ret = regmap_read(rx6110->regmap, RX6110_REG_FLAG, &flags);
+	if (ret)
+		return -EINVAL;
+
+	/* check for VLF Flag (set at power-on) */
+	if ((flags & RX6110_BIT_FLAG_VLF)) {
+		dev_warn(dev, "Voltage low, data is invalid.\n");
+		return -EINVAL;
+	}
+
+	/* read registers to date */
+	ret = regmap_bulk_read(rx6110->regmap, RX6110_REG_SEC, data,
+			       RTC_NR_TIME);
+	if (ret)
+		return ret;
+
+	ret = rx6110_data_to_rtc_tm(data, tm);
+	if (ret)
+		return ret;
+
+	dev_dbg(dev, "%s: date %ds %dm %dh %dmd %dm %dy\n", __func__,
+		tm->tm_sec, tm->tm_min, tm->tm_hour,
+		tm->tm_mday, tm->tm_mon, tm->tm_year);
+
+	return rtc_valid_tm(tm);
+}
+
+static const struct reg_sequence rx6110_default_regs[] = {
+	{ RX6110_REG_RES1,   0xB8 },
+	{ RX6110_REG_RES2,   0x00 },
+	{ RX6110_REG_RES3,   0x10 },
+	{ RX6110_REG_IRQ,    0x00 },
+	{ RX6110_REG_ALMIN,  0x00 },
+	{ RX6110_REG_ALHOUR, 0x00 },
+	{ RX6110_REG_ALWDAY, 0x00 },
+};
+
+/**
+ * rx6110_init - initialize the rx6110 registers
+ *
+ * @rx6110: pointer to the rx6110 struct in use
+ *
+ */
+static int rx6110_init(struct rx6110_data *rx6110)
+{
+	struct rtc_device *rtc = rx6110->rtc;
+	int flags;
+	int ret;
+
+	ret = regmap_update_bits(rx6110->regmap, RX6110_REG_EXT,
+				 RX6110_BIT_EXT_TE, 0);
+	if (ret)
+		return ret;
+
+	ret = regmap_register_patch(rx6110->regmap, rx6110_default_regs,
+				    ARRAY_SIZE(rx6110_default_regs));
+	if (ret)
+		return ret;
+
+	ret = regmap_read(rx6110->regmap, RX6110_REG_FLAG, &flags);
+	if (ret)
+		return ret;
+
+	/* check for VLF Flag (set at power-on) */
+	if ((flags & RX6110_BIT_FLAG_VLF))
+		dev_warn(&rtc->dev, "Voltage low, data loss detected.\n");
+
+	/* check for Alarm Flag */
+	if (flags & RX6110_BIT_FLAG_AF)
+		dev_warn(&rtc->dev, "An alarm may have been missed.\n");
+
+	/* check for Periodic Timer Flag */
+	if (flags & RX6110_BIT_FLAG_TF)
+		dev_warn(&rtc->dev, "Periodic timer was detected\n");
+
+	/* check for Update Timer Flag */
+	if (flags & RX6110_BIT_FLAG_UF)
+		dev_warn(&rtc->dev, "Update timer was detected\n");
+
+	/* clear all flags BUT VLF */
+	ret = regmap_update_bits(rx6110->regmap, RX6110_REG_FLAG,
+				 RX6110_BIT_FLAG_AF |
+				 RX6110_BIT_FLAG_UF |
+				 RX6110_BIT_FLAG_TF,
+				 0);
+
+	return ret;
+}
+
+static struct rtc_class_ops rx6110_rtc_ops = {
+	.read_time = rx6110_get_time,
+	.set_time = rx6110_set_time,
+};
+
+static struct regmap_config regmap_spi_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = RX6110_REG_IRQ,
+	.read_flag_mask = 0x80,
+};
+
+/**
+ * rx6110_probe - initialize rtc driver
+ * @spi: pointer to spi device
+ */
+static int rx6110_probe(struct spi_device *spi)
+{
+	struct rx6110_data *rx6110;
+	int err;
+
+	if ((spi->bits_per_word && spi->bits_per_word != 8) ||
+	    (spi->max_speed_hz > 2000000) ||
+	    (spi->mode != (SPI_CS_HIGH | SPI_CPOL | SPI_CPHA))) {
+		dev_warn(&spi->dev, "SPI settings: bits_per_word: %d, max_speed_hz: %d, mode: %xh\n",
+			 spi->bits_per_word, spi->max_speed_hz, spi->mode);
+		dev_warn(&spi->dev, "driving device in an unsupported mode");
+	}
+
+	rx6110 = devm_kzalloc(&spi->dev, sizeof(*rx6110), GFP_KERNEL);
+	if (!rx6110)
+		return -ENOMEM;
+
+	rx6110->regmap = devm_regmap_init_spi(spi, &regmap_spi_config);
+	if (IS_ERR(rx6110->regmap)) {
+		dev_err(&spi->dev, "regmap init failed for rtc rx6110\n");
+		return PTR_ERR(rx6110->regmap);
+	}
+
+	spi_set_drvdata(spi, rx6110);
+
+	rx6110->rtc = devm_rtc_device_register(&spi->dev,
+					       RX6110_DRIVER_NAME,
+					       &rx6110_rtc_ops, THIS_MODULE);
+
+	if (IS_ERR(rx6110->rtc))
+		return PTR_ERR(rx6110->rtc);
+
+	err = rx6110_init(rx6110);
+	if (err)
+		return err;
+
+	rx6110->rtc->max_user_freq = 1;
+
+	return 0;
+}
+
+static int rx6110_remove(struct spi_device *spi)
+{
+	return 0;
+}
+
+static const struct spi_device_id rx6110_id[] = {
+	{ "rx6110", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, rx6110_id);
+
+static struct spi_driver rx6110_driver = {
+	.driver = {
+		.name = RX6110_DRIVER_NAME,
+		.owner = THIS_MODULE,
+	},
+	.probe		= rx6110_probe,
+	.remove		= rx6110_remove,
+	.id_table	= rx6110_id,
+};
+
+module_spi_driver(rx6110_driver);
+
+MODULE_AUTHOR("Val Krutov <[e-mail]>");
+MODULE_DESCRIPTION("RX-6110 SA RTC driver");
+MODULE_LICENSE("GPL");