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
26 #define REG_CONTROL3_BLF (1 << 2) /* battery low bit, read-only */
28 #define REG_SECONDS 0x03
29 #define REG_SECONDS_OS (1 << 7)
31 #define REG_MINUTES 0x04
32 #define REG_HOURS 0x05
34 #define REG_WEEKDAYS 0x07
35 #define REG_MONTHS 0x08
36 #define REG_YEARS 0x09
39 struct rtc_device *rtc;
42 static int pcf8523_read(struct i2c_client *client, u8 reg, u8 *valuep)
44 struct i2c_msg msgs[2];
48 msgs[0].addr = client->addr;
50 msgs[0].len = sizeof(reg);
53 msgs[1].addr = client->addr;
54 msgs[1].flags = I2C_M_RD;
55 msgs[1].len = sizeof(value);
58 err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
67 static int pcf8523_write(struct i2c_client *client, u8 reg, u8 value)
69 u8 buffer[2] = { reg, value };
73 msg.addr = client->addr;
75 msg.len = sizeof(buffer);
78 err = i2c_transfer(client->adapter, &msg, 1);
85 static int pcf8523_voltage_low(struct i2c_client *client)
90 err = pcf8523_read(client, REG_CONTROL3, &value);
94 return !!(value & REG_CONTROL3_BLF);
97 static int pcf8523_load_capacitance(struct i2c_client *client)
103 err = pcf8523_read(client, REG_CONTROL1, &value);
108 of_property_read_u32(client->dev.of_node, "quartz-load-femtofarads",
113 dev_warn(&client->dev, "Unknown quartz-load-femtofarads value: %d. Assuming 12500",
117 value |= REG_CONTROL1_CAP_SEL;
120 value &= ~REG_CONTROL1_CAP_SEL;
124 err = pcf8523_write(client, REG_CONTROL1, value);
129 static int pcf8523_set_pm(struct i2c_client *client, u8 pm)
134 err = pcf8523_read(client, REG_CONTROL3, &value);
138 value = (value & ~REG_CONTROL3_PM_MASK) | pm;
140 err = pcf8523_write(client, REG_CONTROL3, value);
147 static int pcf8523_stop_rtc(struct i2c_client *client)
152 err = pcf8523_read(client, REG_CONTROL1, &value);
156 value |= REG_CONTROL1_STOP;
158 err = pcf8523_write(client, REG_CONTROL1, value);
165 static int pcf8523_start_rtc(struct i2c_client *client)
170 err = pcf8523_read(client, REG_CONTROL1, &value);
174 value &= ~REG_CONTROL1_STOP;
176 err = pcf8523_write(client, REG_CONTROL1, value);
183 static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm)
185 struct i2c_client *client = to_i2c_client(dev);
186 u8 start = REG_SECONDS, regs[7];
187 struct i2c_msg msgs[2];
190 err = pcf8523_voltage_low(client);
193 } else if (err > 0) {
194 dev_err(dev, "low voltage detected, time is unreliable\n");
198 msgs[0].addr = client->addr;
201 msgs[0].buf = &start;
203 msgs[1].addr = client->addr;
204 msgs[1].flags = I2C_M_RD;
205 msgs[1].len = sizeof(regs);
208 err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
212 if (regs[0] & REG_SECONDS_OS)
215 tm->tm_sec = bcd2bin(regs[0] & 0x7f);
216 tm->tm_min = bcd2bin(regs[1] & 0x7f);
217 tm->tm_hour = bcd2bin(regs[2] & 0x3f);
218 tm->tm_mday = bcd2bin(regs[3] & 0x3f);
219 tm->tm_wday = regs[4] & 0x7;
220 tm->tm_mon = bcd2bin(regs[5] & 0x1f) - 1;
221 tm->tm_year = bcd2bin(regs[6]) + 100;
223 return rtc_valid_tm(tm);
226 static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm)
228 struct i2c_client *client = to_i2c_client(dev);
234 * The hardware can only store values between 0 and 99 in it's YEAR
235 * register (with 99 overflowing to 0 on increment).
236 * After 2100-02-28 we could start interpreting the year to be in the
237 * interval [2100, 2199], but there is no path to switch in a smooth way
238 * because the chip handles YEAR=0x00 (and the out-of-spec
239 * YEAR=0xa0) as a leap year, but 2100 isn't.
241 if (tm->tm_year < 100 || tm->tm_year >= 200)
244 err = pcf8523_stop_rtc(client);
248 regs[0] = REG_SECONDS;
249 /* This will purposely overwrite REG_SECONDS_OS */
250 regs[1] = bin2bcd(tm->tm_sec);
251 regs[2] = bin2bcd(tm->tm_min);
252 regs[3] = bin2bcd(tm->tm_hour);
253 regs[4] = bin2bcd(tm->tm_mday);
254 regs[5] = tm->tm_wday;
255 regs[6] = bin2bcd(tm->tm_mon + 1);
256 regs[7] = bin2bcd(tm->tm_year - 100);
258 msg.addr = client->addr;
260 msg.len = sizeof(regs);
263 err = i2c_transfer(client->adapter, &msg, 1);
266 * If the time cannot be set, restart the RTC anyway. Note
267 * that errors are ignored if the RTC cannot be started so
268 * that we have a chance to propagate the original error.
270 pcf8523_start_rtc(client);
274 return pcf8523_start_rtc(client);
277 #ifdef CONFIG_RTC_INTF_DEV
278 static int pcf8523_rtc_ioctl(struct device *dev, unsigned int cmd,
281 struct i2c_client *client = to_i2c_client(dev);
286 ret = pcf8523_voltage_low(client);
290 if (copy_to_user((void __user *)arg, &ret, sizeof(int)))
299 #define pcf8523_rtc_ioctl NULL
302 static const struct rtc_class_ops pcf8523_rtc_ops = {
303 .read_time = pcf8523_rtc_read_time,
304 .set_time = pcf8523_rtc_set_time,
305 .ioctl = pcf8523_rtc_ioctl,
308 static int pcf8523_probe(struct i2c_client *client,
309 const struct i2c_device_id *id)
314 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
317 pcf = devm_kzalloc(&client->dev, sizeof(*pcf), GFP_KERNEL);
321 err = pcf8523_load_capacitance(client);
323 dev_warn(&client->dev, "failed to set xtal load capacitance: %d",
326 err = pcf8523_set_pm(client, 0);
330 pcf->rtc = devm_rtc_device_register(&client->dev, DRIVER_NAME,
331 &pcf8523_rtc_ops, THIS_MODULE);
332 if (IS_ERR(pcf->rtc))
333 return PTR_ERR(pcf->rtc);
335 i2c_set_clientdata(client, pcf);
340 static const struct i2c_device_id pcf8523_id[] = {
344 MODULE_DEVICE_TABLE(i2c, pcf8523_id);
347 static const struct of_device_id pcf8523_of_match[] = {
348 { .compatible = "nxp,pcf8523" },
351 MODULE_DEVICE_TABLE(of, pcf8523_of_match);
354 static struct i2c_driver pcf8523_driver = {
357 .of_match_table = of_match_ptr(pcf8523_of_match),
359 .probe = pcf8523_probe,
360 .id_table = pcf8523_id,
362 module_i2c_driver(pcf8523_driver);
364 MODULE_AUTHOR("Thierry Reding <thierry.reding@avionic-design.de>");
365 MODULE_DESCRIPTION("NXP PCF8523 RTC driver");
366 MODULE_LICENSE("GPL v2");