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
38 #define REG_OFFSET 0x0e
39 #define REG_OFFSET_MODE BIT(7)
42 struct rtc_device *rtc;
45 static int pcf8523_read(struct i2c_client *client, u8 reg, u8 *valuep)
47 struct i2c_msg msgs[2];
51 msgs[0].addr = client->addr;
53 msgs[0].len = sizeof(reg);
56 msgs[1].addr = client->addr;
57 msgs[1].flags = I2C_M_RD;
58 msgs[1].len = sizeof(value);
61 err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
70 static int pcf8523_write(struct i2c_client *client, u8 reg, u8 value)
72 u8 buffer[2] = { reg, value };
76 msg.addr = client->addr;
78 msg.len = sizeof(buffer);
81 err = i2c_transfer(client->adapter, &msg, 1);
88 static int pcf8523_voltage_low(struct i2c_client *client)
93 err = pcf8523_read(client, REG_CONTROL3, &value);
97 return !!(value & REG_CONTROL3_BLF);
100 static int pcf8523_select_capacitance(struct i2c_client *client, bool high)
105 err = pcf8523_read(client, REG_CONTROL1, &value);
110 value &= ~REG_CONTROL1_CAP_SEL;
112 value |= REG_CONTROL1_CAP_SEL;
114 err = pcf8523_write(client, REG_CONTROL1, value);
121 static int pcf8523_set_pm(struct i2c_client *client, u8 pm)
126 err = pcf8523_read(client, REG_CONTROL3, &value);
130 value = (value & ~REG_CONTROL3_PM_MASK) | pm;
132 err = pcf8523_write(client, REG_CONTROL3, value);
139 static int pcf8523_stop_rtc(struct i2c_client *client)
144 err = pcf8523_read(client, REG_CONTROL1, &value);
148 value |= REG_CONTROL1_STOP;
150 err = pcf8523_write(client, REG_CONTROL1, value);
157 static int pcf8523_start_rtc(struct i2c_client *client)
162 err = pcf8523_read(client, REG_CONTROL1, &value);
166 value &= ~REG_CONTROL1_STOP;
168 err = pcf8523_write(client, REG_CONTROL1, value);
175 static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm)
177 struct i2c_client *client = to_i2c_client(dev);
178 u8 start = REG_SECONDS, regs[7];
179 struct i2c_msg msgs[2];
182 err = pcf8523_voltage_low(client);
185 } else if (err > 0) {
186 dev_err(dev, "low voltage detected, time is unreliable\n");
190 msgs[0].addr = client->addr;
193 msgs[0].buf = &start;
195 msgs[1].addr = client->addr;
196 msgs[1].flags = I2C_M_RD;
197 msgs[1].len = sizeof(regs);
200 err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
204 if (regs[0] & REG_SECONDS_OS)
207 tm->tm_sec = bcd2bin(regs[0] & 0x7f);
208 tm->tm_min = bcd2bin(regs[1] & 0x7f);
209 tm->tm_hour = bcd2bin(regs[2] & 0x3f);
210 tm->tm_mday = bcd2bin(regs[3] & 0x3f);
211 tm->tm_wday = regs[4] & 0x7;
212 tm->tm_mon = bcd2bin(regs[5] & 0x1f) - 1;
213 tm->tm_year = bcd2bin(regs[6]) + 100;
218 static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm)
220 struct i2c_client *client = to_i2c_client(dev);
226 * The hardware can only store values between 0 and 99 in it's YEAR
227 * register (with 99 overflowing to 0 on increment).
228 * After 2100-02-28 we could start interpreting the year to be in the
229 * interval [2100, 2199], but there is no path to switch in a smooth way
230 * because the chip handles YEAR=0x00 (and the out-of-spec
231 * YEAR=0xa0) as a leap year, but 2100 isn't.
233 if (tm->tm_year < 100 || tm->tm_year >= 200)
236 err = pcf8523_stop_rtc(client);
240 regs[0] = REG_SECONDS;
241 /* This will purposely overwrite REG_SECONDS_OS */
242 regs[1] = bin2bcd(tm->tm_sec);
243 regs[2] = bin2bcd(tm->tm_min);
244 regs[3] = bin2bcd(tm->tm_hour);
245 regs[4] = bin2bcd(tm->tm_mday);
246 regs[5] = tm->tm_wday;
247 regs[6] = bin2bcd(tm->tm_mon + 1);
248 regs[7] = bin2bcd(tm->tm_year - 100);
250 msg.addr = client->addr;
252 msg.len = sizeof(regs);
255 err = i2c_transfer(client->adapter, &msg, 1);
258 * If the time cannot be set, restart the RTC anyway. Note
259 * that errors are ignored if the RTC cannot be started so
260 * that we have a chance to propagate the original error.
262 pcf8523_start_rtc(client);
266 return pcf8523_start_rtc(client);
269 #ifdef CONFIG_RTC_INTF_DEV
270 static int pcf8523_rtc_ioctl(struct device *dev, unsigned int cmd,
273 struct i2c_client *client = to_i2c_client(dev);
278 ret = pcf8523_voltage_low(client);
282 if (copy_to_user((void __user *)arg, &ret, sizeof(int)))
291 #define pcf8523_rtc_ioctl NULL
294 static int pcf8523_rtc_read_offset(struct device *dev, long *offset)
296 struct i2c_client *client = to_i2c_client(dev);
301 err = pcf8523_read(client, REG_OFFSET, &value);
305 /* sign extend the 7-bit offset value */
307 *offset = (value & REG_OFFSET_MODE ? 4069 : 4340) * (val >> 1);
312 static int pcf8523_rtc_set_offset(struct device *dev, long offset)
314 struct i2c_client *client = to_i2c_client(dev);
318 reg_m0 = clamp(DIV_ROUND_CLOSEST(offset, 4340), -64L, 63L);
319 reg_m1 = clamp(DIV_ROUND_CLOSEST(offset, 4069), -64L, 63L);
321 if (abs(reg_m0 * 4340 - offset) < abs(reg_m1 * 4069 - offset))
322 value = reg_m0 & 0x7f;
324 value = (reg_m1 & 0x7f) | REG_OFFSET_MODE;
326 return pcf8523_write(client, REG_OFFSET, value);
329 static const struct rtc_class_ops pcf8523_rtc_ops = {
330 .read_time = pcf8523_rtc_read_time,
331 .set_time = pcf8523_rtc_set_time,
332 .ioctl = pcf8523_rtc_ioctl,
333 .read_offset = pcf8523_rtc_read_offset,
334 .set_offset = pcf8523_rtc_set_offset,
337 static int pcf8523_probe(struct i2c_client *client,
338 const struct i2c_device_id *id)
343 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
346 pcf = devm_kzalloc(&client->dev, sizeof(*pcf), GFP_KERNEL);
350 err = pcf8523_select_capacitance(client, true);
354 err = pcf8523_set_pm(client, 0);
358 pcf->rtc = devm_rtc_device_register(&client->dev, DRIVER_NAME,
359 &pcf8523_rtc_ops, THIS_MODULE);
360 if (IS_ERR(pcf->rtc))
361 return PTR_ERR(pcf->rtc);
363 i2c_set_clientdata(client, pcf);
368 static const struct i2c_device_id pcf8523_id[] = {
372 MODULE_DEVICE_TABLE(i2c, pcf8523_id);
375 static const struct of_device_id pcf8523_of_match[] = {
376 { .compatible = "nxp,pcf8523" },
379 MODULE_DEVICE_TABLE(of, pcf8523_of_match);
382 static struct i2c_driver pcf8523_driver = {
385 .of_match_table = of_match_ptr(pcf8523_of_match),
387 .probe = pcf8523_probe,
388 .id_table = pcf8523_id,
390 module_i2c_driver(pcf8523_driver);
392 MODULE_AUTHOR("Thierry Reding <thierry.reding@avionic-design.de>");
393 MODULE_DESCRIPTION("NXP PCF8523 RTC driver");
394 MODULE_LICENSE("GPL v2");