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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 <[email protected]>
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 { .name = "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 <[email protected]>");
228MODULE_LICENSE("GPL");
229MODULE_DESCRIPTION("SD2405AL RTC driver");