rtc-sd2405al.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * RTC driver for the SD2405AL Real-Time Clock
  4 *
  5 * Datasheet:
  6 * https://image.dfrobot.com/image/data/TOY0021/SD2405AL%20datasheet%20(Angelo%20v0.1).pdf
  7 *
  8 * I2C slave address: 0x32
  9 *
 10 * Copyright (C) 2024-2025 Tóth János <gomba007@gmail.com>
 11 */
 12
 13#include <linux/bcd.h>
 14#include <linux/i2c.h>
 15#include <linux/regmap.h>
 16#include <linux/rtc.h>
 17
 18/* Real time clock registers */
 19#define SD2405AL_REG_T_SEC	0x00
 20#define SD2405AL_REG_T_MIN	0x01
 21#define SD2405AL_REG_T_HOUR	0x02
 22#	define SD2405AL_BIT_12H_PM	BIT(5)
 23#	define SD2405AL_BIT_24H		BIT(7)
 24#define SD2405AL_REG_T_WEEK	0x03
 25#define SD2405AL_REG_T_DAY	0x04
 26#define SD2405AL_REG_T_MON	0x05
 27#define SD2405AL_REG_T_YEAR	0x06
 28
 29#define SD2405AL_NUM_T_REGS	(SD2405AL_REG_T_YEAR - SD2405AL_REG_T_SEC + 1)
 30
 31/* Control registers */
 32#define SD2405AL_REG_CTR1	0x0F
 33#	define SD2405AL_BIT_WRTC2	BIT(2)
 34#	define SD2405AL_BIT_WRTC3	BIT(7)
 35#define SD2405AL_REG_CTR2	0x10
 36#	define SD2405AL_BIT_WRTC1	BIT(7)
 37#define SD2405AL_REG_CTR3	0x11
 38#define SD2405AL_REG_TTF	0x12
 39#define SD2405AL_REG_CNTDWN	0x13
 40
 41/* General RAM */
 42#define SD2405AL_REG_M_START	0x14
 43#define SD2405AL_REG_M_END	0x1F
 44
 45struct sd2405al {
 46	struct device		*dev;
 47	struct regmap		*regmap;
 48};
 49
 50static int sd2405al_enable_reg_write(struct sd2405al *sd2405al)
 51{
 52	int ret;
 53
 54	/* order of writes is important */
 55	ret = regmap_update_bits(sd2405al->regmap, SD2405AL_REG_CTR2,
 56				 SD2405AL_BIT_WRTC1, SD2405AL_BIT_WRTC1);
 57	if (ret < 0)
 58		return ret;
 59
 60	ret = regmap_update_bits(sd2405al->regmap, SD2405AL_REG_CTR1,
 61				 SD2405AL_BIT_WRTC2 | SD2405AL_BIT_WRTC3,
 62				 SD2405AL_BIT_WRTC2 | SD2405AL_BIT_WRTC3);
 63	if (ret < 0)
 64		return ret;
 65
 66	return 0;
 67}
 68
 69static int sd2405al_disable_reg_write(struct sd2405al *sd2405al)
 70{
 71	int ret;
 72
 73	/* order of writes is important */
 74	ret = regmap_update_bits(sd2405al->regmap, SD2405AL_REG_CTR1,
 75				 SD2405AL_BIT_WRTC2 | SD2405AL_BIT_WRTC3, 0x00);
 76	if (ret < 0)
 77		return ret;
 78
 79	ret = regmap_update_bits(sd2405al->regmap, SD2405AL_REG_CTR2,
 80				 SD2405AL_BIT_WRTC1, 0x00);
 81	if (ret < 0)
 82		return ret;
 83
 84	return 0;
 85}
 86
 87static int sd2405al_read_time(struct device *dev, struct rtc_time *time)
 88{
 89	u8 data[SD2405AL_NUM_T_REGS] = { 0 };
 90	struct sd2405al *sd2405al = dev_get_drvdata(dev);
 91	int ret;
 92
 93	ret = regmap_bulk_read(sd2405al->regmap, SD2405AL_REG_T_SEC, data,
 94			       SD2405AL_NUM_T_REGS);
 95	if (ret < 0)
 96		return ret;
 97
 98	time->tm_sec = bcd2bin(data[SD2405AL_REG_T_SEC] & 0x7F);
 99	time->tm_min = bcd2bin(data[SD2405AL_REG_T_MIN] & 0x7F);
100
101	if (data[SD2405AL_REG_T_HOUR] & SD2405AL_BIT_24H)
102		time->tm_hour = bcd2bin(data[SD2405AL_REG_T_HOUR] & 0x3F);
103	else
104		if (data[SD2405AL_REG_T_HOUR] & SD2405AL_BIT_12H_PM)
105			time->tm_hour = bcd2bin(data[SD2405AL_REG_T_HOUR]
106						& 0x1F) + 12;
107		else /* 12 hour mode, AM */
108			time->tm_hour = bcd2bin(data[SD2405AL_REG_T_HOUR]
109						& 0x1F);
110
111	time->tm_wday = bcd2bin(data[SD2405AL_REG_T_WEEK] & 0x07);
112	time->tm_mday = bcd2bin(data[SD2405AL_REG_T_DAY] & 0x3F);
113	time->tm_mon = bcd2bin(data[SD2405AL_REG_T_MON] & 0x1F) - 1;
114	time->tm_year = bcd2bin(data[SD2405AL_REG_T_YEAR]) + 100;
115
116	dev_dbg(sd2405al->dev, "read time: %ptR (%d)\n", time, time->tm_wday);
117
118	return 0;
119}
120
121static int sd2405al_set_time(struct device *dev, struct rtc_time *time)
122{
123	u8 data[SD2405AL_NUM_T_REGS];
124	struct sd2405al *sd2405al = dev_get_drvdata(dev);
125	int ret;
126
127	data[SD2405AL_REG_T_SEC] = bin2bcd(time->tm_sec);
128	data[SD2405AL_REG_T_MIN] = bin2bcd(time->tm_min);
129	data[SD2405AL_REG_T_HOUR] = bin2bcd(time->tm_hour) | SD2405AL_BIT_24H;
130	data[SD2405AL_REG_T_DAY] = bin2bcd(time->tm_mday);
131	data[SD2405AL_REG_T_WEEK] = bin2bcd(time->tm_wday);
132	data[SD2405AL_REG_T_MON] = bin2bcd(time->tm_mon) + 1;
133	data[SD2405AL_REG_T_YEAR] = bin2bcd(time->tm_year - 100);
134
135	ret = sd2405al_enable_reg_write(sd2405al);
136	if (ret < 0)
137		return ret;
138
139	ret = regmap_bulk_write(sd2405al->regmap, SD2405AL_REG_T_SEC, data,
140				SD2405AL_NUM_T_REGS);
141	if (ret < 0)
142		return ret;
143
144	ret = regmap_write(sd2405al->regmap, SD2405AL_REG_TTF, 0x00);
145	if (ret < 0)
146		return ret;
147
148	ret = sd2405al_disable_reg_write(sd2405al);
149	if (ret < 0)
150		return ret;
151
152	dev_dbg(sd2405al->dev, "set time: %ptR (%d)\n", time, time->tm_wday);
153
154	return 0;
155}
156
157static const struct rtc_class_ops sd2405al_rtc_ops = {
158	.read_time = sd2405al_read_time,
159	.set_time = sd2405al_set_time,
160};
161
162static const struct regmap_config sd2405al_regmap_conf = {
163	.reg_bits = 8,
164	.val_bits = 8,
165	.max_register = SD2405AL_REG_M_END,
166};
167
168static int sd2405al_probe(struct i2c_client *client)
169{
170	struct sd2405al *sd2405al;
171	struct rtc_device *rtc;
172	int ret;
173
174	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
175		return -ENODEV;
176
177	sd2405al = devm_kzalloc(&client->dev, sizeof(*sd2405al), GFP_KERNEL);
178	if (!sd2405al)
179		return -ENOMEM;
180
181	sd2405al->dev = &client->dev;
182
183	sd2405al->regmap = devm_regmap_init_i2c(client, &sd2405al_regmap_conf);
184	if (IS_ERR(sd2405al->regmap))
185		return PTR_ERR(sd2405al->regmap);
186
187	rtc = devm_rtc_allocate_device(&client->dev);
188	if (IS_ERR(rtc))
189		return PTR_ERR(rtc);
190
191	rtc->ops = &sd2405al_rtc_ops;
192	rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
193	rtc->range_max = RTC_TIMESTAMP_END_2099;
194
195	dev_set_drvdata(&client->dev, sd2405al);
196
197	ret = devm_rtc_register_device(rtc);
198	if (ret < 0)
199		return ret;
200
201	return 0;
202}
203
204static const struct i2c_device_id sd2405al_id[] = {
205	{ "sd2405al" },
206	{ /* sentinel */ }
207};
208MODULE_DEVICE_TABLE(i2c, sd2405al_id);
209
210static const __maybe_unused struct of_device_id sd2405al_of_match[] = {
211	{ .compatible = "dfrobot,sd2405al" },
212	{ /* sentinel */ }
213};
214MODULE_DEVICE_TABLE(of, sd2405al_of_match);
215
216static struct i2c_driver sd2405al_driver = {
217	.driver = {
218		.name = "sd2405al",
219		.of_match_table = of_match_ptr(sd2405al_of_match),
220	},
221	.probe = sd2405al_probe,
222	.id_table = sd2405al_id,
223};
224
225module_i2c_driver(sd2405al_driver);
226
227MODULE_AUTHOR("Tóth János <gomba007@gmail.com>");
228MODULE_LICENSE("GPL");
229MODULE_DESCRIPTION("SD2405AL RTC driver");