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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
39/*
40 * In order to prevent arbitrary modification of the time register,
41 * when modification of the register,
42 * the "write" bit needs to be written in a certain order.
43 * 1. set WRITE1 bit
44 * 2. set WRITE2 bit
45 * 3. set WRITE3 bit
46 */
47static void sd3078_enable_reg_write(struct regmap *regmap)
48{
49 regmap_update_bits(regmap, SD3078_REG_CTRL2, KEY_WRITE1, KEY_WRITE1);
50 regmap_update_bits(regmap, SD3078_REG_CTRL1, KEY_WRITE2, KEY_WRITE2);
51 regmap_update_bits(regmap, SD3078_REG_CTRL1, KEY_WRITE3, KEY_WRITE3);
52}
53
54#if WRITE_PROTECT_EN
55/*
56 * In order to prevent arbitrary modification of the time register,
57 * we should disable the write function.
58 * when disable write,
59 * the "write" bit needs to be clear in a certain order.
60 * 1. clear WRITE2 bit
61 * 2. clear WRITE3 bit
62 * 3. clear WRITE1 bit
63 */
64static void sd3078_disable_reg_write(struct regmap *regmap)
65{
66 regmap_update_bits(regmap, SD3078_REG_CTRL1, KEY_WRITE2, 0);
67 regmap_update_bits(regmap, SD3078_REG_CTRL1, KEY_WRITE3, 0);
68 regmap_update_bits(regmap, SD3078_REG_CTRL2, KEY_WRITE1, 0);
69}
70#endif
71
72static int sd3078_rtc_read_time(struct device *dev, struct rtc_time *tm)
73{
74 unsigned char hour;
75 unsigned char rtc_data[NUM_TIME_REGS] = {0};
76 struct i2c_client *client = to_i2c_client(dev);
77 struct regmap *regmap = i2c_get_clientdata(client);
78 int ret;
79
80 ret = regmap_bulk_read(regmap, SD3078_REG_SC, rtc_data, NUM_TIME_REGS);
81 if (ret < 0) {
82 dev_err(dev, "reading from RTC failed with err:%d\n", ret);
83 return ret;
84 }
85
86 tm->tm_sec = bcd2bin(rtc_data[SD3078_REG_SC] & 0x7F);
87 tm->tm_min = bcd2bin(rtc_data[SD3078_REG_MN] & 0x7F);
88
89 /*
90 * The sd3078 supports 12/24 hour mode.
91 * When getting time,
92 * we need to convert the 12 hour mode to the 24 hour mode.
93 */
94 hour = rtc_data[SD3078_REG_HR];
95 if (hour & 0x80) /* 24H MODE */
96 tm->tm_hour = bcd2bin(rtc_data[SD3078_REG_HR] & 0x3F);
97 else if (hour & 0x20) /* 12H MODE PM */
98 tm->tm_hour = bcd2bin(rtc_data[SD3078_REG_HR] & 0x1F) + 12;
99 else /* 12H MODE AM */
100 tm->tm_hour = bcd2bin(rtc_data[SD3078_REG_HR] & 0x1F);
101
102 tm->tm_mday = bcd2bin(rtc_data[SD3078_REG_DM] & 0x3F);
103 tm->tm_wday = rtc_data[SD3078_REG_DW] & 0x07;
104 tm->tm_mon = bcd2bin(rtc_data[SD3078_REG_MO] & 0x1F) - 1;
105 tm->tm_year = bcd2bin(rtc_data[SD3078_REG_YR]) + 100;
106
107 return 0;
108}
109
110static int sd3078_rtc_set_time(struct device *dev, struct rtc_time *tm)
111{
112 unsigned char rtc_data[NUM_TIME_REGS];
113 struct i2c_client *client = to_i2c_client(dev);
114 struct regmap *regmap = i2c_get_clientdata(client);
115 int ret;
116
117 rtc_data[SD3078_REG_SC] = bin2bcd(tm->tm_sec);
118 rtc_data[SD3078_REG_MN] = bin2bcd(tm->tm_min);
119 rtc_data[SD3078_REG_HR] = bin2bcd(tm->tm_hour) | 0x80;
120 rtc_data[SD3078_REG_DM] = bin2bcd(tm->tm_mday);
121 rtc_data[SD3078_REG_DW] = tm->tm_wday & 0x07;
122 rtc_data[SD3078_REG_MO] = bin2bcd(tm->tm_mon) + 1;
123 rtc_data[SD3078_REG_YR] = bin2bcd(tm->tm_year - 100);
124
125#if WRITE_PROTECT_EN
126 sd3078_enable_reg_write(regmap);
127#endif
128
129 ret = regmap_bulk_write(regmap, SD3078_REG_SC, rtc_data,
130 NUM_TIME_REGS);
131 if (ret < 0) {
132 dev_err(dev, "writing to RTC failed with err:%d\n", ret);
133 return ret;
134 }
135
136#if WRITE_PROTECT_EN
137 sd3078_disable_reg_write(regmap);
138#endif
139
140 return 0;
141}
142
143static const struct rtc_class_ops sd3078_rtc_ops = {
144 .read_time = sd3078_rtc_read_time,
145 .set_time = sd3078_rtc_set_time,
146};
147
148static const struct regmap_config regmap_config = {
149 .reg_bits = 8,
150 .val_bits = 8,
151 .max_register = 0x11,
152};
153
154static int sd3078_probe(struct i2c_client *client)
155{
156 int ret;
157 struct regmap *regmap;
158 struct rtc_device *rtc;
159
160 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
161 return -ENODEV;
162
163 regmap = devm_regmap_init_i2c(client, &regmap_config);
164 if (IS_ERR(regmap)) {
165 dev_err(&client->dev, "regmap allocation failed\n");
166 return PTR_ERR(regmap);
167 }
168
169 i2c_set_clientdata(client, regmap);
170
171 rtc = devm_rtc_allocate_device(&client->dev);
172 if (IS_ERR(rtc))
173 return PTR_ERR(rtc);
174
175 rtc->ops = &sd3078_rtc_ops;
176 rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
177 rtc->range_max = RTC_TIMESTAMP_END_2099;
178
179 ret = devm_rtc_register_device(rtc);
180 if (ret)
181 return ret;
182
183 sd3078_enable_reg_write(regmap);
184
185 return 0;
186}
187
188static const struct i2c_device_id sd3078_id[] = {
189 { .name = "sd3078" },
190 { }
191};
192MODULE_DEVICE_TABLE(i2c, sd3078_id);
193
194static const __maybe_unused struct of_device_id rtc_dt_match[] = {
195 { .compatible = "whwave,sd3078" },
196 {},
197};
198MODULE_DEVICE_TABLE(of, rtc_dt_match);
199
200static struct i2c_driver sd3078_driver = {
201 .driver = {
202 .name = "sd3078",
203 .of_match_table = of_match_ptr(rtc_dt_match),
204 },
205 .probe = sd3078_probe,
206 .id_table = sd3078_id,
207};
208
209module_i2c_driver(sd3078_driver);
210
211MODULE_AUTHOR("Dianlong Li <[email protected]>");
212MODULE_DESCRIPTION("SD3078 RTC driver");
213MODULE_LICENSE("GPL v2");