1// SPDX-License-Identifier: GPL-2.0-only
  2/* rtc-ds1347.c
  3 *
  4 * Driver for Dallas Semiconductor DS1347 Low Current, SPI Compatible
  5 * Real Time Clock
  6 *
  7 * Author : Raghavendra Chandra Ganiga <ravi23ganiga@gmail.com>
  8 */
  9
 10#include <linux/init.h>
 11#include <linux/module.h>
 12#include <linux/device.h>
 13#include <linux/platform_device.h>
 14#include <linux/rtc.h>
 15#include <linux/spi/spi.h>
 16#include <linux/bcd.h>
 17#include <linux/regmap.h>
 18
 19/* Registers in ds1347 rtc */
 20
 21#define DS1347_SECONDS_REG	0x01
 22#define DS1347_MINUTES_REG	0x03
 23#define DS1347_HOURS_REG	0x05
 24#define DS1347_DATE_REG		0x07
 25#define DS1347_MONTH_REG	0x09
 26#define DS1347_DAY_REG		0x0B
 27#define DS1347_YEAR_REG		0x0D
 28#define DS1347_CONTROL_REG	0x0F
 29#define DS1347_CENTURY_REG	0x13
 30#define DS1347_STATUS_REG	0x17
 31#define DS1347_CLOCK_BURST	0x3F
 32
 33#define DS1347_WP_BIT		BIT(7)
 34
 35#define DS1347_NEOSC_BIT	BIT(7)
 36#define DS1347_OSF_BIT		BIT(2)
 37
 38static const struct regmap_range ds1347_ranges[] = {
 39	{
 40		.range_min = DS1347_SECONDS_REG,
 41		.range_max = DS1347_STATUS_REG,
 42	},
 43};
 44
 45static const struct regmap_access_table ds1347_access_table = {
 46	.yes_ranges = ds1347_ranges,
 47	.n_yes_ranges = ARRAY_SIZE(ds1347_ranges),
 48};
 49
 50static int ds1347_read_time(struct device *dev, struct rtc_time *dt)
 51{
 52	struct regmap *map = dev_get_drvdata(dev);
 53	unsigned int status, century, secs;
 54	unsigned char buf[8];
 55	int err;
 56
 57	err = regmap_read(map, DS1347_STATUS_REG, &status);
 58	if (err)
 59		return err;
 60
 61	if (status & DS1347_OSF_BIT)
 62		return -EINVAL;
 63
 64	do {
 65		err = regmap_bulk_read(map, DS1347_CLOCK_BURST, buf, 8);
 66		if (err)
 67			return err;
 68
 69		err = regmap_read(map, DS1347_CENTURY_REG, &century);
 70		if (err)
 71			return err;
 72
 73		err = regmap_read(map, DS1347_SECONDS_REG, &secs);
 74		if (err)
 75			return err;
 76	} while (buf[0] != secs);
 77
 78	dt->tm_sec = bcd2bin(buf[0]);
 79	dt->tm_min = bcd2bin(buf[1] & 0x7f);
 80	dt->tm_hour = bcd2bin(buf[2] & 0x3F);
 81	dt->tm_mday = bcd2bin(buf[3]);
 82	dt->tm_mon = bcd2bin(buf[4]) - 1;
 83	dt->tm_wday = bcd2bin(buf[5]) - 1;
 84	dt->tm_year = (bcd2bin(century) * 100) + bcd2bin(buf[6]) - 1900;
 85
 86	return 0;
 87}
 88
 89static int ds1347_set_time(struct device *dev, struct rtc_time *dt)
 90{
 91	struct regmap *map = dev_get_drvdata(dev);
 92	unsigned int century;
 93	unsigned char buf[8];
 94	int err;
 95
 96	err = regmap_update_bits(map, DS1347_STATUS_REG,
 97				 DS1347_NEOSC_BIT, DS1347_NEOSC_BIT);
 98	if (err)
 99		return err;
100
101	buf[0] = bin2bcd(dt->tm_sec);
102	buf[1] = bin2bcd(dt->tm_min);
103	buf[2] = (bin2bcd(dt->tm_hour) & 0x3F);
104	buf[3] = bin2bcd(dt->tm_mday);
105	buf[4] = bin2bcd(dt->tm_mon + 1);
106	buf[5] = bin2bcd(dt->tm_wday + 1);
107	buf[6] = bin2bcd(dt->tm_year % 100);
108	buf[7] = bin2bcd(0x00);
109
110	err = regmap_bulk_write(map, DS1347_CLOCK_BURST, buf, 8);
111	if (err)
112		return err;
113
114	century = (dt->tm_year / 100) + 19;
115	err = regmap_write(map, DS1347_CENTURY_REG, bin2bcd(century));
116	if (err)
117		return err;
118
119	return regmap_update_bits(map, DS1347_STATUS_REG,
120				  DS1347_NEOSC_BIT | DS1347_OSF_BIT, 0);
121}
122
123static const struct rtc_class_ops ds1347_rtc_ops = {
124	.read_time = ds1347_read_time,
125	.set_time = ds1347_set_time,
126};
127
128static int ds1347_probe(struct spi_device *spi)
129{
130	struct rtc_device *rtc;
131	struct regmap_config config;
132	struct regmap *map;
133	int err;
134
135	memset(&config, 0, sizeof(config));
136	config.reg_bits = 8;
137	config.val_bits = 8;
138	config.read_flag_mask = 0x80;
139	config.max_register = 0x3F;
140	config.wr_table = &ds1347_access_table;
141
142	/* spi setup with ds1347 in mode 3 and bits per word as 8 */
143	spi->mode = SPI_MODE_3;
144	spi->bits_per_word = 8;
145	spi_setup(spi);
146
147	map = devm_regmap_init_spi(spi, &config);
148
149	if (IS_ERR(map)) {
150		dev_err(&spi->dev, "ds1347 regmap init spi failed\n");
151		return PTR_ERR(map);
152	}
153
154	spi_set_drvdata(spi, map);
155
156	/* Disable the write protect of rtc */
157	err = regmap_update_bits(map, DS1347_CONTROL_REG, DS1347_WP_BIT, 0);
158	if (err)
159		return err;
160
161	rtc = devm_rtc_allocate_device(&spi->dev);
162	if (IS_ERR(rtc))
163		return PTR_ERR(rtc);
164
165	rtc->ops = &ds1347_rtc_ops;
166	rtc->range_min = RTC_TIMESTAMP_BEGIN_0000;
167	rtc->range_max = RTC_TIMESTAMP_END_9999;
168
169	return devm_rtc_register_device(rtc);
170}
171
172static struct spi_driver ds1347_driver = {
173	.driver = {
174		.name = "ds1347",
175	},
176	.probe = ds1347_probe,
177};
178
179module_spi_driver(ds1347_driver);
180
181MODULE_DESCRIPTION("DS1347 SPI RTC DRIVER");
182MODULE_AUTHOR("Raghavendra C Ganiga <ravi23ganiga@gmail.com>");
183MODULE_LICENSE("GPL v2");