rtc-sd3078.c

  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	{ "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 <long17.cool@163.com>");
212MODULE_DESCRIPTION("SD3078 RTC driver");
213MODULE_LICENSE("GPL v2");