2 * Copyright (C) 2012 Avionic Design GmbH
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
10 #include <linux/i2c.h>
11 #include <linux/module.h>
12 #include <linux/rtc.h>
15 #define DRIVER_NAME "rtc-pcf8523"
17 #define REG_CONTROL1 0x00
18 #define REG_CONTROL1_CAP_SEL (1 << 7)
19 #define REG_CONTROL1_STOP (1 << 5)
21 #define REG_CONTROL3 0x02
22 #define REG_CONTROL3_PM_BLD (1 << 7) /* battery low detection disabled */
23 #define REG_CONTROL3_PM_VDD (1 << 6) /* switch-over disabled */
24 #define REG_CONTROL3_PM_DSM (1 << 5) /* direct switching mode */
25 #define REG_CONTROL3_PM_MASK 0xe0
27 #define REG_SECONDS 0x03
28 #define REG_SECONDS_OS (1 << 7)
30 #define REG_MINUTES 0x04
31 #define REG_HOURS 0x05
33 #define REG_WEEKDAYS 0x07
34 #define REG_MONTHS 0x08
35 #define REG_YEARS 0x09
38 struct rtc_device *rtc;
41 static int pcf8523_read(struct i2c_client *client, u8 reg, u8 *valuep)
43 struct i2c_msg msgs[2];
47 msgs[0].addr = client->addr;
49 msgs[0].len = sizeof(reg);
52 msgs[1].addr = client->addr;
53 msgs[1].flags = I2C_M_RD;
54 msgs[1].len = sizeof(value);
57 err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
66 static int pcf8523_write(struct i2c_client *client, u8 reg, u8 value)
68 u8 buffer[2] = { reg, value };
72 msg.addr = client->addr;
74 msg.len = sizeof(buffer);
77 err = i2c_transfer(client->adapter, &msg, 1);
84 static int pcf8523_select_capacitance(struct i2c_client *client, bool high)
89 err = pcf8523_read(client, REG_CONTROL1, &value);
94 value &= ~REG_CONTROL1_CAP_SEL;
96 value |= REG_CONTROL1_CAP_SEL;
98 err = pcf8523_write(client, REG_CONTROL1, value);
105 static int pcf8523_set_pm(struct i2c_client *client, u8 pm)
110 err = pcf8523_read(client, REG_CONTROL3, &value);
114 value = (value & ~REG_CONTROL3_PM_MASK) | pm;
116 err = pcf8523_write(client, REG_CONTROL3, value);
123 static int pcf8523_stop_rtc(struct i2c_client *client)
128 err = pcf8523_read(client, REG_CONTROL1, &value);
132 value |= REG_CONTROL1_STOP;
134 err = pcf8523_write(client, REG_CONTROL1, value);
141 static int pcf8523_start_rtc(struct i2c_client *client)
146 err = pcf8523_read(client, REG_CONTROL1, &value);
150 value &= ~REG_CONTROL1_STOP;
152 err = pcf8523_write(client, REG_CONTROL1, value);
159 static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm)
161 struct i2c_client *client = to_i2c_client(dev);
162 u8 start = REG_SECONDS, regs[7];
163 struct i2c_msg msgs[2];
166 msgs[0].addr = client->addr;
169 msgs[0].buf = &start;
171 msgs[1].addr = client->addr;
172 msgs[1].flags = I2C_M_RD;
173 msgs[1].len = sizeof(regs);
176 err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
180 if (regs[0] & REG_SECONDS_OS) {
182 * If the oscillator was stopped, try to clear the flag. Upon
183 * power-up the flag is always set, but if we cannot clear it
184 * the oscillator isn't running properly for some reason. The
185 * sensible thing therefore is to return an error, signalling
186 * that the clock cannot be assumed to be correct.
189 regs[0] &= ~REG_SECONDS_OS;
191 err = pcf8523_write(client, REG_SECONDS, regs[0]);
195 err = pcf8523_read(client, REG_SECONDS, ®s[0]);
199 if (regs[0] & REG_SECONDS_OS)
203 tm->tm_sec = bcd2bin(regs[0] & 0x7f);
204 tm->tm_min = bcd2bin(regs[1] & 0x7f);
205 tm->tm_hour = bcd2bin(regs[2] & 0x3f);
206 tm->tm_mday = bcd2bin(regs[3] & 0x3f);
207 tm->tm_wday = regs[4] & 0x7;
208 tm->tm_mon = bcd2bin(regs[5] & 0x1f);
209 tm->tm_year = bcd2bin(regs[6]) + 100;
211 return rtc_valid_tm(tm);
214 static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm)
216 struct i2c_client *client = to_i2c_client(dev);
221 err = pcf8523_stop_rtc(client);
225 regs[0] = REG_SECONDS;
226 regs[1] = bin2bcd(tm->tm_sec);
227 regs[2] = bin2bcd(tm->tm_min);
228 regs[3] = bin2bcd(tm->tm_hour);
229 regs[4] = bin2bcd(tm->tm_mday);
230 regs[5] = tm->tm_wday;
231 regs[6] = bin2bcd(tm->tm_mon);
232 regs[7] = bin2bcd(tm->tm_year - 100);
234 msg.addr = client->addr;
236 msg.len = sizeof(regs);
239 err = i2c_transfer(client->adapter, &msg, 1);
242 * If the time cannot be set, restart the RTC anyway. Note
243 * that errors are ignored if the RTC cannot be started so
244 * that we have a chance to propagate the original error.
246 pcf8523_start_rtc(client);
250 return pcf8523_start_rtc(client);
253 static const struct rtc_class_ops pcf8523_rtc_ops = {
254 .read_time = pcf8523_rtc_read_time,
255 .set_time = pcf8523_rtc_set_time,
258 static int pcf8523_probe(struct i2c_client *client,
259 const struct i2c_device_id *id)
264 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
267 pcf = devm_kzalloc(&client->dev, sizeof(*pcf), GFP_KERNEL);
271 err = pcf8523_select_capacitance(client, true);
275 err = pcf8523_set_pm(client, 0);
279 pcf->rtc = rtc_device_register(DRIVER_NAME, &client->dev,
280 &pcf8523_rtc_ops, THIS_MODULE);
281 if (IS_ERR(pcf->rtc))
282 return PTR_ERR(pcf->rtc);
284 i2c_set_clientdata(client, pcf);
289 static int pcf8523_remove(struct i2c_client *client)
291 struct pcf8523 *pcf = i2c_get_clientdata(client);
293 rtc_device_unregister(pcf->rtc);
298 static const struct i2c_device_id pcf8523_id[] = {
302 MODULE_DEVICE_TABLE(i2c, pcf8523_id);
305 static const struct of_device_id pcf8523_of_match[] = {
306 { .compatible = "nxp,pcf8523" },
309 MODULE_DEVICE_TABLE(of, pcf8523_of_match);
312 static struct i2c_driver pcf8523_driver = {
315 .owner = THIS_MODULE,
316 .of_match_table = of_match_ptr(pcf8523_of_match),
318 .probe = pcf8523_probe,
319 .remove = pcf8523_remove,
320 .id_table = pcf8523_id,
322 module_i2c_driver(pcf8523_driver);
324 MODULE_AUTHOR("Thierry Reding <thierry.reding@avionic-design.de>");
325 MODULE_DESCRIPTION("NXP PCF8523 RTC driver");
326 MODULE_LICENSE("GPL v2");