1 /*
2 * Copyright (C) 2012 Avionic Design GmbH
3 *
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.
7 */
8
9 #include <linux/bcd.h>
10 #include <linux/i2c.h>
11 #include <linux/module.h>
12 #include <linux/rtc.h>
13 #include <linux/of.h>
14
15 #define DRIVER_NAME "rtc-pcf8523"
16
17 #define REG_CONTROL1 0x00
18 #define REG_CONTROL1_CAP_SEL (1 << 7)
19 #define REG_CONTROL1_STOP (1 << 5)
20
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 */
27
28 #define REG_SECONDS 0x03
29 #define REG_SECONDS_OS (1 << 7)
30
31 #define REG_MINUTES 0x04
32 #define REG_HOURS 0x05
33 #define REG_DAYS 0x06
34 #define REG_WEEKDAYS 0x07
35 #define REG_MONTHS 0x08
36 #define REG_YEARS 0x09
37
38 #define REG_OFFSET 0x0e
39 #define REG_OFFSET_MODE BIT(7)
40
41 struct pcf8523 {
42 struct rtc_device *rtc;
43 };
44
pcf8523_read(struct i2c_client * client,u8 reg,u8 * valuep)45 static int pcf8523_read(struct i2c_client *client, u8 reg, u8 *valuep)
46 {
47 struct i2c_msg msgs[2];
48 u8 value = 0;
49 int err;
50
51 msgs[0].addr = client->addr;
52 msgs[0].flags = 0;
53 msgs[0].len = sizeof(reg);
54 msgs[0].buf = ®
55
56 msgs[1].addr = client->addr;
57 msgs[1].flags = I2C_M_RD;
58 msgs[1].len = sizeof(value);
59 msgs[1].buf = &value;
60
61 err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
62 if (err < 0)
63 return err;
64
65 *valuep = value;
66
67 return 0;
68 }
69
pcf8523_write(struct i2c_client * client,u8 reg,u8 value)70 static int pcf8523_write(struct i2c_client *client, u8 reg, u8 value)
71 {
72 u8 buffer[2] = { reg, value };
73 struct i2c_msg msg;
74 int err;
75
76 msg.addr = client->addr;
77 msg.flags = 0;
78 msg.len = sizeof(buffer);
79 msg.buf = buffer;
80
81 err = i2c_transfer(client->adapter, &msg, 1);
82 if (err < 0)
83 return err;
84
85 return 0;
86 }
87
pcf8523_voltage_low(struct i2c_client * client)88 static int pcf8523_voltage_low(struct i2c_client *client)
89 {
90 u8 value;
91 int err;
92
93 err = pcf8523_read(client, REG_CONTROL3, &value);
94 if (err < 0)
95 return err;
96
97 return !!(value & REG_CONTROL3_BLF);
98 }
99
pcf8523_load_capacitance(struct i2c_client * client)100 static int pcf8523_load_capacitance(struct i2c_client *client)
101 {
102 u32 load;
103 u8 value;
104 int err;
105
106 err = pcf8523_read(client, REG_CONTROL1, &value);
107 if (err < 0)
108 return err;
109
110 load = 12500;
111 of_property_read_u32(client->dev.of_node, "quartz-load-femtofarads",
112 &load);
113
114 switch (load) {
115 default:
116 dev_warn(&client->dev, "Unknown quartz-load-femtofarads value: %d. Assuming 12500",
117 load);
118 /* fall through */
119 case 12500:
120 value |= REG_CONTROL1_CAP_SEL;
121 break;
122 case 7000:
123 value &= ~REG_CONTROL1_CAP_SEL;
124 break;
125 }
126
127 err = pcf8523_write(client, REG_CONTROL1, value);
128
129 return err;
130 }
131
pcf8523_set_pm(struct i2c_client * client,u8 pm)132 static int pcf8523_set_pm(struct i2c_client *client, u8 pm)
133 {
134 u8 value;
135 int err;
136
137 err = pcf8523_read(client, REG_CONTROL3, &value);
138 if (err < 0)
139 return err;
140
141 value = (value & ~REG_CONTROL3_PM_MASK) | pm;
142
143 err = pcf8523_write(client, REG_CONTROL3, value);
144 if (err < 0)
145 return err;
146
147 return 0;
148 }
149
pcf8523_stop_rtc(struct i2c_client * client)150 static int pcf8523_stop_rtc(struct i2c_client *client)
151 {
152 u8 value;
153 int err;
154
155 err = pcf8523_read(client, REG_CONTROL1, &value);
156 if (err < 0)
157 return err;
158
159 value |= REG_CONTROL1_STOP;
160
161 err = pcf8523_write(client, REG_CONTROL1, value);
162 if (err < 0)
163 return err;
164
165 return 0;
166 }
167
pcf8523_start_rtc(struct i2c_client * client)168 static int pcf8523_start_rtc(struct i2c_client *client)
169 {
170 u8 value;
171 int err;
172
173 err = pcf8523_read(client, REG_CONTROL1, &value);
174 if (err < 0)
175 return err;
176
177 value &= ~REG_CONTROL1_STOP;
178
179 err = pcf8523_write(client, REG_CONTROL1, value);
180 if (err < 0)
181 return err;
182
183 return 0;
184 }
185
pcf8523_rtc_read_time(struct device * dev,struct rtc_time * tm)186 static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm)
187 {
188 struct i2c_client *client = to_i2c_client(dev);
189 u8 start = REG_SECONDS, regs[7];
190 struct i2c_msg msgs[2];
191 int err;
192
193 err = pcf8523_voltage_low(client);
194 if (err < 0) {
195 return err;
196 } else if (err > 0) {
197 dev_err(dev, "low voltage detected, time is unreliable\n");
198 return -EINVAL;
199 }
200
201 msgs[0].addr = client->addr;
202 msgs[0].flags = 0;
203 msgs[0].len = 1;
204 msgs[0].buf = &start;
205
206 msgs[1].addr = client->addr;
207 msgs[1].flags = I2C_M_RD;
208 msgs[1].len = sizeof(regs);
209 msgs[1].buf = regs;
210
211 err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
212 if (err < 0)
213 return err;
214
215 if (regs[0] & REG_SECONDS_OS)
216 return -EINVAL;
217
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;
225
226 return 0;
227 }
228
pcf8523_rtc_set_time(struct device * dev,struct rtc_time * tm)229 static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm)
230 {
231 struct i2c_client *client = to_i2c_client(dev);
232 struct i2c_msg msg;
233 u8 regs[8];
234 int err;
235
236 /*
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.
243 */
244 if (tm->tm_year < 100 || tm->tm_year >= 200)
245 return -EINVAL;
246
247 err = pcf8523_stop_rtc(client);
248 if (err < 0)
249 return err;
250
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);
260
261 msg.addr = client->addr;
262 msg.flags = 0;
263 msg.len = sizeof(regs);
264 msg.buf = regs;
265
266 err = i2c_transfer(client->adapter, &msg, 1);
267 if (err < 0) {
268 /*
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.
272 */
273 pcf8523_start_rtc(client);
274 return err;
275 }
276
277 return pcf8523_start_rtc(client);
278 }
279
280 #ifdef CONFIG_RTC_INTF_DEV
pcf8523_rtc_ioctl(struct device * dev,unsigned int cmd,unsigned long arg)281 static int pcf8523_rtc_ioctl(struct device *dev, unsigned int cmd,
282 unsigned long arg)
283 {
284 struct i2c_client *client = to_i2c_client(dev);
285 int ret;
286
287 switch (cmd) {
288 case RTC_VL_READ:
289 ret = pcf8523_voltage_low(client);
290 if (ret < 0)
291 return ret;
292
293 if (copy_to_user((void __user *)arg, &ret, sizeof(int)))
294 return -EFAULT;
295
296 return 0;
297 default:
298 return -ENOIOCTLCMD;
299 }
300 }
301 #else
302 #define pcf8523_rtc_ioctl NULL
303 #endif
304
pcf8523_rtc_read_offset(struct device * dev,long * offset)305 static int pcf8523_rtc_read_offset(struct device *dev, long *offset)
306 {
307 struct i2c_client *client = to_i2c_client(dev);
308 int err;
309 u8 value;
310 s8 val;
311
312 err = pcf8523_read(client, REG_OFFSET, &value);
313 if (err < 0)
314 return err;
315
316 /* sign extend the 7-bit offset value */
317 val = value << 1;
318 *offset = (value & REG_OFFSET_MODE ? 4069 : 4340) * (val >> 1);
319
320 return 0;
321 }
322
pcf8523_rtc_set_offset(struct device * dev,long offset)323 static int pcf8523_rtc_set_offset(struct device *dev, long offset)
324 {
325 struct i2c_client *client = to_i2c_client(dev);
326 long reg_m0, reg_m1;
327 u8 value;
328
329 reg_m0 = clamp(DIV_ROUND_CLOSEST(offset, 4340), -64L, 63L);
330 reg_m1 = clamp(DIV_ROUND_CLOSEST(offset, 4069), -64L, 63L);
331
332 if (abs(reg_m0 * 4340 - offset) < abs(reg_m1 * 4069 - offset))
333 value = reg_m0 & 0x7f;
334 else
335 value = (reg_m1 & 0x7f) | REG_OFFSET_MODE;
336
337 return pcf8523_write(client, REG_OFFSET, value);
338 }
339
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,
346 };
347
pcf8523_probe(struct i2c_client * client,const struct i2c_device_id * id)348 static int pcf8523_probe(struct i2c_client *client,
349 const struct i2c_device_id *id)
350 {
351 struct pcf8523 *pcf;
352 int err;
353
354 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
355 return -ENODEV;
356
357 pcf = devm_kzalloc(&client->dev, sizeof(*pcf), GFP_KERNEL);
358 if (!pcf)
359 return -ENOMEM;
360
361 err = pcf8523_load_capacitance(client);
362 if (err < 0)
363 dev_warn(&client->dev, "failed to set xtal load capacitance: %d",
364 err);
365
366 err = pcf8523_set_pm(client, 0);
367 if (err < 0)
368 return err;
369
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);
374
375 i2c_set_clientdata(client, pcf);
376
377 return 0;
378 }
379
380 static const struct i2c_device_id pcf8523_id[] = {
381 { "pcf8523", 0 },
382 { }
383 };
384 MODULE_DEVICE_TABLE(i2c, pcf8523_id);
385
386 #ifdef CONFIG_OF
387 static const struct of_device_id pcf8523_of_match[] = {
388 { .compatible = "nxp,pcf8523" },
389 { }
390 };
391 MODULE_DEVICE_TABLE(of, pcf8523_of_match);
392 #endif
393
394 static struct i2c_driver pcf8523_driver = {
395 .driver = {
396 .name = DRIVER_NAME,
397 .of_match_table = of_match_ptr(pcf8523_of_match),
398 },
399 .probe = pcf8523_probe,
400 .id_table = pcf8523_id,
401 };
402 module_i2c_driver(pcf8523_driver);
403
404 MODULE_AUTHOR("Thierry Reding <thierry.reding@avionic-design.de>");
405 MODULE_DESCRIPTION("NXP PCF8523 RTC driver");
406 MODULE_LICENSE("GPL v2");
407