drivers/rtc/rtc-sd3078.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Real Time Clock (RTC) Driver for sd3078
0004  * Copyright (C) 2018 Zoro Li
0005  */
0006
0007 #include <linux/bcd.h>
0008 #include <linux/i2c.h>
0009 #include <linux/module.h>
0010 #include <linux/regmap.h>
0011 #include <linux/rtc.h>
0012 #include <linux/slab.h>
0013
0014 #define SD3078_REG_SC           0x00
0015 #define SD3078_REG_MN           0x01
0016 #define SD3078_REG_HR           0x02
0017 #define SD3078_REG_DW           0x03
0018 #define SD3078_REG_DM           0x04
0019 #define SD3078_REG_MO           0x05
0020 #define SD3078_REG_YR           0x06
0021
0022 #define SD3078_REG_CTRL1        0x0f
0023 #define SD3078_REG_CTRL2        0x10
0024 #define SD3078_REG_CTRL3        0x11
0025
0026 #define KEY_WRITE1      0x80
0027 #define KEY_WRITE2      0x04
0028 #define KEY_WRITE3      0x80
0029
0030 #define NUM_TIME_REGS   (SD3078_REG_YR - SD3078_REG_SC + 1)
0031
0032 /*
0033  * The sd3078 has write protection
0034  * and we can choose whether or not to use it.
0035  * Write protection is turned off by default.
0036  */
0037 #define WRITE_PROTECT_EN    0
0038
0039 struct sd3078 {
0040     struct rtc_device   *rtc;
0041     struct regmap       *regmap;
0042 };
0043
0044 /*
0045  * In order to prevent arbitrary modification of the time register,
0046  * when modification of the register,
0047  * the "write" bit needs to be written in a certain order.
0048  * 1. set WRITE1 bit
0049  * 2. set WRITE2 bit
0050  * 3. set WRITE3 bit
0051  */
0052 static void sd3078_enable_reg_write(struct sd3078 *sd3078)
0053 {
0054     regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL2,
0055                KEY_WRITE1, KEY_WRITE1);
0056     regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL1,
0057                KEY_WRITE2, KEY_WRITE2);
0058     regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL1,
0059                KEY_WRITE3, KEY_WRITE3);
0060 }
0061
0062 #if WRITE_PROTECT_EN
0063 /*
0064  * In order to prevent arbitrary modification of the time register,
0065  * we should disable the write function.
0066  * when disable write,
0067  * the "write" bit needs to be clear in a certain order.
0068  * 1. clear WRITE2 bit
0069  * 2. clear WRITE3 bit
0070  * 3. clear WRITE1 bit
0071  */
0072 static void sd3078_disable_reg_write(struct sd3078 *sd3078)
0073 {
0074     regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL1,
0075                KEY_WRITE2, 0);
0076     regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL1,
0077                KEY_WRITE3, 0);
0078     regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL2,
0079                KEY_WRITE1, 0);
0080 }
0081 #endif
0082
0083 static int sd3078_rtc_read_time(struct device *dev, struct rtc_time *tm)
0084 {
0085     unsigned char hour;
0086     unsigned char rtc_data[NUM_TIME_REGS] = {0};
0087     struct i2c_client *client = to_i2c_client(dev);
0088     struct sd3078 *sd3078 = i2c_get_clientdata(client);
0089     int ret;
0090
0091     ret = regmap_bulk_read(sd3078->regmap, SD3078_REG_SC, rtc_data,
0092                    NUM_TIME_REGS);
0093     if (ret < 0) {
0094         dev_err(dev, "reading from RTC failed with err:%d\n", ret);
0095         return ret;
0096     }
0097
0098     tm->tm_sec  = bcd2bin(rtc_data[SD3078_REG_SC] & 0x7F);
0099     tm->tm_min  = bcd2bin(rtc_data[SD3078_REG_MN] & 0x7F);
0100
0101     /*
0102      * The sd3078 supports 12/24 hour mode.
0103      * When getting time,
0104      * we need to convert the 12 hour mode to the 24 hour mode.
0105      */
0106     hour = rtc_data[SD3078_REG_HR];
0107     if (hour & 0x80) /* 24H MODE */
0108         tm->tm_hour = bcd2bin(rtc_data[SD3078_REG_HR] & 0x3F);
0109     else if (hour & 0x20) /* 12H MODE PM */
0110         tm->tm_hour = bcd2bin(rtc_data[SD3078_REG_HR] & 0x1F) + 12;
0111     else /* 12H MODE AM */
0112         tm->tm_hour = bcd2bin(rtc_data[SD3078_REG_HR] & 0x1F);
0113
0114     tm->tm_mday = bcd2bin(rtc_data[SD3078_REG_DM] & 0x3F);
0115     tm->tm_wday = rtc_data[SD3078_REG_DW] & 0x07;
0116     tm->tm_mon  = bcd2bin(rtc_data[SD3078_REG_MO] & 0x1F) - 1;
0117     tm->tm_year = bcd2bin(rtc_data[SD3078_REG_YR]) + 100;
0118
0119     return 0;
0120 }
0121
0122 static int sd3078_rtc_set_time(struct device *dev, struct rtc_time *tm)
0123 {
0124     unsigned char rtc_data[NUM_TIME_REGS];
0125     struct i2c_client *client = to_i2c_client(dev);
0126     struct sd3078 *sd3078 = i2c_get_clientdata(client);
0127     int ret;
0128
0129     rtc_data[SD3078_REG_SC] = bin2bcd(tm->tm_sec);
0130     rtc_data[SD3078_REG_MN] = bin2bcd(tm->tm_min);
0131     rtc_data[SD3078_REG_HR] = bin2bcd(tm->tm_hour) | 0x80;
0132     rtc_data[SD3078_REG_DM] = bin2bcd(tm->tm_mday);
0133     rtc_data[SD3078_REG_DW] = tm->tm_wday & 0x07;
0134     rtc_data[SD3078_REG_MO] = bin2bcd(tm->tm_mon) + 1;
0135     rtc_data[SD3078_REG_YR] = bin2bcd(tm->tm_year - 100);
0136
0137 #if WRITE_PROTECT_EN
0138     sd3078_enable_reg_write(sd3078);
0139 #endif
0140
0141     ret = regmap_bulk_write(sd3078->regmap, SD3078_REG_SC, rtc_data,
0142                 NUM_TIME_REGS);
0143     if (ret < 0) {
0144         dev_err(dev, "writing to RTC failed with err:%d\n", ret);
0145         return ret;
0146     }
0147
0148 #if WRITE_PROTECT_EN
0149     sd3078_disable_reg_write(sd3078);
0150 #endif
0151
0152     return 0;
0153 }
0154
0155 static const struct rtc_class_ops sd3078_rtc_ops = {
0156     .read_time  = sd3078_rtc_read_time,
0157     .set_time   = sd3078_rtc_set_time,
0158 };
0159
0160 static const struct regmap_config regmap_config = {
0161     .reg_bits = 8,
0162     .val_bits = 8,
0163     .max_register = 0x11,
0164 };
0165
0166 static int sd3078_probe(struct i2c_client *client)
0167 {
0168     int ret;
0169     struct sd3078 *sd3078;
0170
0171     if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
0172         return -ENODEV;
0173
0174     sd3078 = devm_kzalloc(&client->dev, sizeof(*sd3078), GFP_KERNEL);
0175     if (!sd3078)
0176         return -ENOMEM;
0177
0178     sd3078->regmap = devm_regmap_init_i2c(client, &regmap_config);
0179     if (IS_ERR(sd3078->regmap)) {
0180         dev_err(&client->dev, "regmap allocation failed\n");
0181         return PTR_ERR(sd3078->regmap);
0182     }
0183
0184     i2c_set_clientdata(client, sd3078);
0185
0186     sd3078->rtc = devm_rtc_allocate_device(&client->dev);
0187     if (IS_ERR(sd3078->rtc))
0188         return PTR_ERR(sd3078->rtc);
0189
0190     sd3078->rtc->ops = &sd3078_rtc_ops;
0191     sd3078->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
0192     sd3078->rtc->range_max = RTC_TIMESTAMP_END_2099;
0193
0194     ret = devm_rtc_register_device(sd3078->rtc);
0195     if (ret)
0196         return ret;
0197
0198     sd3078_enable_reg_write(sd3078);
0199
0200     return 0;
0201 }
0202
0203 static const struct i2c_device_id sd3078_id[] = {
0204     {"sd3078", 0},
0205     { }
0206 };
0207 MODULE_DEVICE_TABLE(i2c, sd3078_id);
0208
0209 static const __maybe_unused struct of_device_id rtc_dt_match[] = {
0210     { .compatible = "whwave,sd3078" },
0211     {},
0212 };
0213 MODULE_DEVICE_TABLE(of, rtc_dt_match);
0214
0215 static struct i2c_driver sd3078_driver = {
0216     .driver     = {
0217         .name   = "sd3078",
0218         .of_match_table = of_match_ptr(rtc_dt_match),
0219     },
0220     .probe_new  = sd3078_probe,
0221     .id_table   = sd3078_id,
0222 };
0223
0224 module_i2c_driver(sd3078_driver);
0225
0226 MODULE_AUTHOR("Dianlong Li <long17.cool@163.com>");
0227 MODULE_DESCRIPTION("SD3078 RTC driver");
0228 MODULE_LICENSE("GPL v2");