1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Real Time Clock (RTC) Driver for sd3078
4 * Copyright (C) 2018 Zoro Li
5 */
6
7#include <linux/bcd.h>
8#include <linux/i2c.h>
9#include <linux/module.h>
10#include <linux/regmap.h>
11#include <linux/rtc.h>
12#include <linux/slab.h>
13
14#define SD3078_REG_SC 0x00
15#define SD3078_REG_MN 0x01
16#define SD3078_REG_HR 0x02
17#define SD3078_REG_DW 0x03
18#define SD3078_REG_DM 0x04
19#define SD3078_REG_MO 0x05
20#define SD3078_REG_YR 0x06
21
22#define SD3078_REG_CTRL1 0x0f
23#define SD3078_REG_CTRL2 0x10
24#define SD3078_REG_CTRL3 0x11
25
26#define KEY_WRITE1 0x80
27#define KEY_WRITE2 0x04
28#define KEY_WRITE3 0x80
29
30#define NUM_TIME_REGS (SD3078_REG_YR - SD3078_REG_SC + 1)
31
32/*
33 * The sd3078 has write protection
34 * and we can choose whether or not to use it.
35 * Write protection is turned off by default.
36 */
37#define WRITE_PROTECT_EN 0
38
39struct sd3078 {
40 struct rtc_device *rtc;
41 struct regmap *regmap;
42};
43
44/*
45 * In order to prevent arbitrary modification of the time register,
46 * when modification of the register,
47 * the "write" bit needs to be written in a certain order.
48 * 1. set WRITE1 bit
49 * 2. set WRITE2 bit
50 * 3. set WRITE3 bit
51 */
52static void sd3078_enable_reg_write(struct sd3078 *sd3078)
53{
54 regmap_update_bits(map: sd3078->regmap, SD3078_REG_CTRL2,
55 KEY_WRITE1, KEY_WRITE1);
56 regmap_update_bits(map: sd3078->regmap, SD3078_REG_CTRL1,
57 KEY_WRITE2, KEY_WRITE2);
58 regmap_update_bits(map: sd3078->regmap, SD3078_REG_CTRL1,
59 KEY_WRITE3, KEY_WRITE3);
60}
61
62#if WRITE_PROTECT_EN
63/*
64 * In order to prevent arbitrary modification of the time register,
65 * we should disable the write function.
66 * when disable write,
67 * the "write" bit needs to be clear in a certain order.
68 * 1. clear WRITE2 bit
69 * 2. clear WRITE3 bit
70 * 3. clear WRITE1 bit
71 */
72static void sd3078_disable_reg_write(struct sd3078 *sd3078)
73{
74 regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL1,
75 KEY_WRITE2, 0);
76 regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL1,
77 KEY_WRITE3, 0);
78 regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL2,
79 KEY_WRITE1, 0);
80}
81#endif
82
83static int sd3078_rtc_read_time(struct device *dev, struct rtc_time *tm)
84{
85 unsigned char hour;
86 unsigned char rtc_data[NUM_TIME_REGS] = {0};
87 struct i2c_client *client = to_i2c_client(dev);
88 struct sd3078 *sd3078 = i2c_get_clientdata(client);
89 int ret;
90
91 ret = regmap_bulk_read(map: sd3078->regmap, SD3078_REG_SC, val: rtc_data,
92 NUM_TIME_REGS);
93 if (ret < 0) {
94 dev_err(dev, "reading from RTC failed with err:%d\n", ret);
95 return ret;
96 }
97
98 tm->tm_sec = bcd2bin(rtc_data[SD3078_REG_SC] & 0x7F);
99 tm->tm_min = bcd2bin(rtc_data[SD3078_REG_MN] & 0x7F);
100
101 /*
102 * The sd3078 supports 12/24 hour mode.
103 * When getting time,
104 * we need to convert the 12 hour mode to the 24 hour mode.
105 */
106 hour = rtc_data[SD3078_REG_HR];
107 if (hour & 0x80) /* 24H MODE */
108 tm->tm_hour = bcd2bin(rtc_data[SD3078_REG_HR] & 0x3F);
109 else if (hour & 0x20) /* 12H MODE PM */
110 tm->tm_hour = bcd2bin(rtc_data[SD3078_REG_HR] & 0x1F) + 12;
111 else /* 12H MODE AM */
112 tm->tm_hour = bcd2bin(rtc_data[SD3078_REG_HR] & 0x1F);
113
114 tm->tm_mday = bcd2bin(rtc_data[SD3078_REG_DM] & 0x3F);
115 tm->tm_wday = rtc_data[SD3078_REG_DW] & 0x07;
116 tm->tm_mon = bcd2bin(rtc_data[SD3078_REG_MO] & 0x1F) - 1;
117 tm->tm_year = bcd2bin(rtc_data[SD3078_REG_YR]) + 100;
118
119 return 0;
120}
121
122static int sd3078_rtc_set_time(struct device *dev, struct rtc_time *tm)
123{
124 unsigned char rtc_data[NUM_TIME_REGS];
125 struct i2c_client *client = to_i2c_client(dev);
126 struct sd3078 *sd3078 = i2c_get_clientdata(client);
127 int ret;
128
129 rtc_data[SD3078_REG_SC] = bin2bcd(tm->tm_sec);
130 rtc_data[SD3078_REG_MN] = bin2bcd(tm->tm_min);
131 rtc_data[SD3078_REG_HR] = bin2bcd(tm->tm_hour) | 0x80;
132 rtc_data[SD3078_REG_DM] = bin2bcd(tm->tm_mday);
133 rtc_data[SD3078_REG_DW] = tm->tm_wday & 0x07;
134 rtc_data[SD3078_REG_MO] = bin2bcd(tm->tm_mon) + 1;
135 rtc_data[SD3078_REG_YR] = bin2bcd(tm->tm_year - 100);
136
137#if WRITE_PROTECT_EN
138 sd3078_enable_reg_write(sd3078);
139#endif
140
141 ret = regmap_bulk_write(map: sd3078->regmap, SD3078_REG_SC, val: rtc_data,
142 NUM_TIME_REGS);
143 if (ret < 0) {
144 dev_err(dev, "writing to RTC failed with err:%d\n", ret);
145 return ret;
146 }
147
148#if WRITE_PROTECT_EN
149 sd3078_disable_reg_write(sd3078);
150#endif
151
152 return 0;
153}
154
155static const struct rtc_class_ops sd3078_rtc_ops = {
156 .read_time = sd3078_rtc_read_time,
157 .set_time = sd3078_rtc_set_time,
158};
159
160static const struct regmap_config regmap_config = {
161 .reg_bits = 8,
162 .val_bits = 8,
163 .max_register = 0x11,
164};
165
166static int sd3078_probe(struct i2c_client *client)
167{
168 int ret;
169 struct sd3078 *sd3078;
170
171 if (!i2c_check_functionality(adap: client->adapter, I2C_FUNC_I2C))
172 return -ENODEV;
173
174 sd3078 = devm_kzalloc(dev: &client->dev, size: sizeof(*sd3078), GFP_KERNEL);
175 if (!sd3078)
176 return -ENOMEM;
177
178 sd3078->regmap = devm_regmap_init_i2c(client, &regmap_config);
179 if (IS_ERR(ptr: sd3078->regmap)) {
180 dev_err(&client->dev, "regmap allocation failed\n");
181 return PTR_ERR(ptr: sd3078->regmap);
182 }
183
184 i2c_set_clientdata(client, data: sd3078);
185
186 sd3078->rtc = devm_rtc_allocate_device(dev: &client->dev);
187 if (IS_ERR(ptr: sd3078->rtc))
188 return PTR_ERR(ptr: sd3078->rtc);
189
190 sd3078->rtc->ops = &sd3078_rtc_ops;
191 sd3078->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
192 sd3078->rtc->range_max = RTC_TIMESTAMP_END_2099;
193
194 ret = devm_rtc_register_device(sd3078->rtc);
195 if (ret)
196 return ret;
197
198 sd3078_enable_reg_write(sd3078);
199
200 return 0;
201}
202
203static const struct i2c_device_id sd3078_id[] = {
204 {"sd3078", 0},
205 { }
206};
207MODULE_DEVICE_TABLE(i2c, sd3078_id);
208
209static const __maybe_unused struct of_device_id rtc_dt_match[] = {
210 { .compatible = "whwave,sd3078" },
211 {},
212};
213MODULE_DEVICE_TABLE(of, rtc_dt_match);
214
215static struct i2c_driver sd3078_driver = {
216 .driver = {
217 .name = "sd3078",
218 .of_match_table = of_match_ptr(rtc_dt_match),
219 },
220 .probe = sd3078_probe,
221 .id_table = sd3078_id,
222};
223
224module_i2c_driver(sd3078_driver);
225
226MODULE_AUTHOR("Dianlong Li <long17.cool@163.com>");
227MODULE_DESCRIPTION("SD3078 RTC driver");
228MODULE_LICENSE("GPL v2");
229

source code of linux/drivers/rtc/rtc-sd3078.c