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_load_capacitance(struct i2c_client *client)
106 err = pcf8523_read(client, REG_CONTROL1, &value);
111 of_property_read_u32(client->dev.of_node, "quartz-load-femtofarads",
116 dev_warn(&client->dev, "Unknown quartz-load-femtofarads value: %d. Assuming 12500",
120 value |= REG_CONTROL1_CAP_SEL;
123 value &= ~REG_CONTROL1_CAP_SEL;
127 err = pcf8523_write(client, REG_CONTROL1, value);
132 static int pcf8523_set_pm(struct i2c_client *client, u8 pm)
137 err = pcf8523_read(client, REG_CONTROL3, &value);
141 value = (value & ~REG_CONTROL3_PM_MASK) | pm;
143 err = pcf8523_write(client, REG_CONTROL3, value);
150 static int pcf8523_stop_rtc(struct i2c_client *client)
155 err = pcf8523_read(client, REG_CONTROL1, &value);
159 value |= REG_CONTROL1_STOP;
161 err = pcf8523_write(client, REG_CONTROL1, value);
168 static int pcf8523_start_rtc(struct i2c_client *client)
173 err = pcf8523_read(client, REG_CONTROL1, &value);
177 value &= ~REG_CONTROL1_STOP;
179 err = pcf8523_write(client, REG_CONTROL1, value);
186 static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm)
188 struct i2c_client *client = to_i2c_client(dev);
189 u8 start = REG_SECONDS, regs[7];
190 struct i2c_msg msgs[2];
193 err = pcf8523_voltage_low(client);
196 } else if (err > 0) {
197 dev_err(dev, "low voltage detected, time is unreliable\n");
201 msgs[0].addr = client->addr;
204 msgs[0].buf = &start;
206 msgs[1].addr = client->addr;
207 msgs[1].flags = I2C_M_RD;
208 msgs[1].len = sizeof(regs);
211 err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
215 if (regs[0] & REG_SECONDS_OS)
218 tm->tm_sec = bcd2bin(regs[0] & 0x7f);
219 tm->tm_min = bcd2bin(regs[1] & 0x7f);
220 tm->tm_hour = bcd2bin(regs[2] & 0x3f);
221 tm->tm_mday = bcd2bin(regs[3] & 0x3f);
222 tm->tm_wday = regs[4] & 0x7;
223 tm->tm_mon = bcd2bin(regs[5] & 0x1f) - 1;
224 tm->tm_year = bcd2bin(regs[6]) + 100;
229 static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm)
231 struct i2c_client *client = to_i2c_client(dev);
237 * The hardware can only store values between 0 and 99 in it's YEAR
238 * register (with 99 overflowing to 0 on increment).
239 * After 2100-02-28 we could start interpreting the year to be in the
240 * interval [2100, 2199], but there is no path to switch in a smooth way
241 * because the chip handles YEAR=0x00 (and the out-of-spec
242 * YEAR=0xa0) as a leap year, but 2100 isn't.
244 if (tm->tm_year < 100 || tm->tm_year >= 200)
247 err = pcf8523_stop_rtc(client);
251 regs[0] = REG_SECONDS;
252 /* This will purposely overwrite REG_SECONDS_OS */
253 regs[1] = bin2bcd(tm->tm_sec);
254 regs[2] = bin2bcd(tm->tm_min);
255 regs[3] = bin2bcd(tm->tm_hour);
256 regs[4] = bin2bcd(tm->tm_mday);
257 regs[5] = tm->tm_wday;
258 regs[6] = bin2bcd(tm->tm_mon + 1);
259 regs[7] = bin2bcd(tm->tm_year - 100);
261 msg.addr = client->addr;
263 msg.len = sizeof(regs);
266 err = i2c_transfer(client->adapter, &msg, 1);
269 * If the time cannot be set, restart the RTC anyway. Note
270 * that errors are ignored if the RTC cannot be started so
271 * that we have a chance to propagate the original error.
273 pcf8523_start_rtc(client);
277 return pcf8523_start_rtc(client);
280 #ifdef CONFIG_RTC_INTF_DEV
281 static int pcf8523_rtc_ioctl(struct device *dev, unsigned int cmd,
284 struct i2c_client *client = to_i2c_client(dev);
289 ret = pcf8523_voltage_low(client);
293 if (copy_to_user((void __user *)arg, &ret, sizeof(int)))
302 #define pcf8523_rtc_ioctl NULL
305 static int pcf8523_rtc_read_offset(struct device *dev, long *offset)
307 struct i2c_client *client = to_i2c_client(dev);
312 err = pcf8523_read(client, REG_OFFSET, &value);
316 /* sign extend the 7-bit offset value */
318 *offset = (value & REG_OFFSET_MODE ? 4069 : 4340) * (val >> 1);
323 static int pcf8523_rtc_set_offset(struct device *dev, long offset)
325 struct i2c_client *client = to_i2c_client(dev);
329 reg_m0 = clamp(DIV_ROUND_CLOSEST(offset, 4340), -64L, 63L);
330 reg_m1 = clamp(DIV_ROUND_CLOSEST(offset, 4069), -64L, 63L);
332 if (abs(reg_m0 * 4340 - offset) < abs(reg_m1 * 4069 - offset))
333 value = reg_m0 & 0x7f;
335 value = (reg_m1 & 0x7f) | REG_OFFSET_MODE;
337 return pcf8523_write(client, REG_OFFSET, value);
340 static const struct rtc_class_ops pcf8523_rtc_ops = {
341 .read_time = pcf8523_rtc_read_time,
342 .set_time = pcf8523_rtc_set_time,
343 .ioctl = pcf8523_rtc_ioctl,
344 .read_offset = pcf8523_rtc_read_offset,
345 .set_offset = pcf8523_rtc_set_offset,
348 static int pcf8523_probe(struct i2c_client *client,
349 const struct i2c_device_id *id)
354 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
357 pcf = devm_kzalloc(&client->dev, sizeof(*pcf), GFP_KERNEL);
361 err = pcf8523_load_capacitance(client);
363 dev_warn(&client->dev, "failed to set xtal load capacitance: %d",
366 err = pcf8523_set_pm(client, 0);
370 pcf->rtc = devm_rtc_device_register(&client->dev, DRIVER_NAME,
371 &pcf8523_rtc_ops, THIS_MODULE);
372 if (IS_ERR(pcf->rtc))
373 return PTR_ERR(pcf->rtc);
375 i2c_set_clientdata(client, pcf);
380 static const struct i2c_device_id pcf8523_id[] = {
384 MODULE_DEVICE_TABLE(i2c, pcf8523_id);
387 static const struct of_device_id pcf8523_of_match[] = {
388 { .compatible = "nxp,pcf8523" },
391 MODULE_DEVICE_TABLE(of, pcf8523_of_match);
394 static struct i2c_driver pcf8523_driver = {
397 .of_match_table = of_match_ptr(pcf8523_of_match),
399 .probe = pcf8523_probe,
400 .id_table = pcf8523_id,
402 module_i2c_driver(pcf8523_driver);
404 MODULE_AUTHOR("Thierry Reding <thierry.reding@avionic-design.de>");
405 MODULE_DESCRIPTION("NXP PCF8523 RTC driver");
406 MODULE_LICENSE("GPL v2");