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Linux/drivers/rtc/rtc-pcf8523.c

  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 struct pcf8523 {
 39         struct rtc_device *rtc;
 40 };
 41 
 42 static int pcf8523_read(struct i2c_client *client, u8 reg, u8 *valuep)
 43 {
 44         struct i2c_msg msgs[2];
 45         u8 value = 0;
 46         int err;
 47 
 48         msgs[0].addr = client->addr;
 49         msgs[0].flags = 0;
 50         msgs[0].len = sizeof(reg);
 51         msgs[0].buf = &reg;
 52 
 53         msgs[1].addr = client->addr;
 54         msgs[1].flags = I2C_M_RD;
 55         msgs[1].len = sizeof(value);
 56         msgs[1].buf = &value;
 57 
 58         err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
 59         if (err < 0)
 60                 return err;
 61 
 62         *valuep = value;
 63 
 64         return 0;
 65 }
 66 
 67 static int pcf8523_write(struct i2c_client *client, u8 reg, u8 value)
 68 {
 69         u8 buffer[2] = { reg, value };
 70         struct i2c_msg msg;
 71         int err;
 72 
 73         msg.addr = client->addr;
 74         msg.flags = 0;
 75         msg.len = sizeof(buffer);
 76         msg.buf = buffer;
 77 
 78         err = i2c_transfer(client->adapter, &msg, 1);
 79         if (err < 0)
 80                 return err;
 81 
 82         return 0;
 83 }
 84 
 85 static int pcf8523_select_capacitance(struct i2c_client *client, bool high)
 86 {
 87         u8 value;
 88         int err;
 89 
 90         err = pcf8523_read(client, REG_CONTROL1, &value);
 91         if (err < 0)
 92                 return err;
 93 
 94         if (!high)
 95                 value &= ~REG_CONTROL1_CAP_SEL;
 96         else
 97                 value |= REG_CONTROL1_CAP_SEL;
 98 
 99         err = pcf8523_write(client, REG_CONTROL1, value);
100         if (err < 0)
101                 return err;
102 
103         return err;
104 }
105 
106 static int pcf8523_set_pm(struct i2c_client *client, u8 pm)
107 {
108         u8 value;
109         int err;
110 
111         err = pcf8523_read(client, REG_CONTROL3, &value);
112         if (err < 0)
113                 return err;
114 
115         value = (value & ~REG_CONTROL3_PM_MASK) | pm;
116 
117         err = pcf8523_write(client, REG_CONTROL3, value);
118         if (err < 0)
119                 return err;
120 
121         return 0;
122 }
123 
124 static int pcf8523_stop_rtc(struct i2c_client *client)
125 {
126         u8 value;
127         int err;
128 
129         err = pcf8523_read(client, REG_CONTROL1, &value);
130         if (err < 0)
131                 return err;
132 
133         value |= REG_CONTROL1_STOP;
134 
135         err = pcf8523_write(client, REG_CONTROL1, value);
136         if (err < 0)
137                 return err;
138 
139         return 0;
140 }
141 
142 static int pcf8523_start_rtc(struct i2c_client *client)
143 {
144         u8 value;
145         int err;
146 
147         err = pcf8523_read(client, REG_CONTROL1, &value);
148         if (err < 0)
149                 return err;
150 
151         value &= ~REG_CONTROL1_STOP;
152 
153         err = pcf8523_write(client, REG_CONTROL1, value);
154         if (err < 0)
155                 return err;
156 
157         return 0;
158 }
159 
160 static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm)
161 {
162         struct i2c_client *client = to_i2c_client(dev);
163         u8 start = REG_SECONDS, regs[7];
164         struct i2c_msg msgs[2];
165         int err;
166 
167         msgs[0].addr = client->addr;
168         msgs[0].flags = 0;
169         msgs[0].len = 1;
170         msgs[0].buf = &start;
171 
172         msgs[1].addr = client->addr;
173         msgs[1].flags = I2C_M_RD;
174         msgs[1].len = sizeof(regs);
175         msgs[1].buf = regs;
176 
177         err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
178         if (err < 0)
179                 return err;
180 
181         if (regs[0] & REG_SECONDS_OS) {
182                 /*
183                  * If the oscillator was stopped, try to clear the flag. Upon
184                  * power-up the flag is always set, but if we cannot clear it
185                  * the oscillator isn't running properly for some reason. The
186                  * sensible thing therefore is to return an error, signalling
187                  * that the clock cannot be assumed to be correct.
188                  */
189 
190                 regs[0] &= ~REG_SECONDS_OS;
191 
192                 err = pcf8523_write(client, REG_SECONDS, regs[0]);
193                 if (err < 0)
194                         return err;
195 
196                 err = pcf8523_read(client, REG_SECONDS, &regs[0]);
197                 if (err < 0)
198                         return err;
199 
200                 if (regs[0] & REG_SECONDS_OS)
201                         return -EAGAIN;
202         }
203 
204         tm->tm_sec = bcd2bin(regs[0] & 0x7f);
205         tm->tm_min = bcd2bin(regs[1] & 0x7f);
206         tm->tm_hour = bcd2bin(regs[2] & 0x3f);
207         tm->tm_mday = bcd2bin(regs[3] & 0x3f);
208         tm->tm_wday = regs[4] & 0x7;
209         tm->tm_mon = bcd2bin(regs[5] & 0x1f) - 1;
210         tm->tm_year = bcd2bin(regs[6]) + 100;
211 
212         return rtc_valid_tm(tm);
213 }
214 
215 static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm)
216 {
217         struct i2c_client *client = to_i2c_client(dev);
218         struct i2c_msg msg;
219         u8 regs[8];
220         int err;
221 
222         /*
223          * The hardware can only store values between 0 and 99 in it's YEAR
224          * register (with 99 overflowing to 0 on increment).
225          * After 2100-02-28 we could start interpreting the year to be in the
226          * interval [2100, 2199], but there is no path to switch in a smooth way
227          * because the chip handles YEAR=0x00 (and the out-of-spec
228          * YEAR=0xa0) as a leap year, but 2100 isn't.
229          */
230         if (tm->tm_year < 100 || tm->tm_year >= 200)
231                 return -EINVAL;
232 
233         err = pcf8523_stop_rtc(client);
234         if (err < 0)
235                 return err;
236 
237         regs[0] = REG_SECONDS;
238         regs[1] = bin2bcd(tm->tm_sec);
239         regs[2] = bin2bcd(tm->tm_min);
240         regs[3] = bin2bcd(tm->tm_hour);
241         regs[4] = bin2bcd(tm->tm_mday);
242         regs[5] = tm->tm_wday;
243         regs[6] = bin2bcd(tm->tm_mon + 1);
244         regs[7] = bin2bcd(tm->tm_year - 100);
245 
246         msg.addr = client->addr;
247         msg.flags = 0;
248         msg.len = sizeof(regs);
249         msg.buf = regs;
250 
251         err = i2c_transfer(client->adapter, &msg, 1);
252         if (err < 0) {
253                 /*
254                  * If the time cannot be set, restart the RTC anyway. Note
255                  * that errors are ignored if the RTC cannot be started so
256                  * that we have a chance to propagate the original error.
257                  */
258                 pcf8523_start_rtc(client);
259                 return err;
260         }
261 
262         return pcf8523_start_rtc(client);
263 }
264 
265 #ifdef CONFIG_RTC_INTF_DEV
266 static int pcf8523_rtc_ioctl(struct device *dev, unsigned int cmd,
267                              unsigned long arg)
268 {
269         struct i2c_client *client = to_i2c_client(dev);
270         u8 value;
271         int ret = 0, err;
272 
273         switch (cmd) {
274         case RTC_VL_READ:
275                 err = pcf8523_read(client, REG_CONTROL3, &value);
276                 if (err < 0)
277                         return err;
278 
279                 if (value & REG_CONTROL3_BLF)
280                         ret = 1;
281 
282                 if (copy_to_user((void __user *)arg, &ret, sizeof(int)))
283                         return -EFAULT;
284 
285                 return 0;
286         default:
287                 return -ENOIOCTLCMD;
288         }
289 }
290 #else
291 #define pcf8523_rtc_ioctl NULL
292 #endif
293 
294 static const struct rtc_class_ops pcf8523_rtc_ops = {
295         .read_time = pcf8523_rtc_read_time,
296         .set_time = pcf8523_rtc_set_time,
297         .ioctl = pcf8523_rtc_ioctl,
298 };
299 
300 static int pcf8523_probe(struct i2c_client *client,
301                          const struct i2c_device_id *id)
302 {
303         struct pcf8523 *pcf;
304         int err;
305 
306         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
307                 return -ENODEV;
308 
309         pcf = devm_kzalloc(&client->dev, sizeof(*pcf), GFP_KERNEL);
310         if (!pcf)
311                 return -ENOMEM;
312 
313         err = pcf8523_select_capacitance(client, true);
314         if (err < 0)
315                 return err;
316 
317         err = pcf8523_set_pm(client, 0);
318         if (err < 0)
319                 return err;
320 
321         pcf->rtc = devm_rtc_device_register(&client->dev, DRIVER_NAME,
322                                        &pcf8523_rtc_ops, THIS_MODULE);
323         if (IS_ERR(pcf->rtc))
324                 return PTR_ERR(pcf->rtc);
325 
326         i2c_set_clientdata(client, pcf);
327 
328         return 0;
329 }
330 
331 static const struct i2c_device_id pcf8523_id[] = {
332         { "pcf8523", 0 },
333         { }
334 };
335 MODULE_DEVICE_TABLE(i2c, pcf8523_id);
336 
337 #ifdef CONFIG_OF
338 static const struct of_device_id pcf8523_of_match[] = {
339         { .compatible = "nxp,pcf8523" },
340         { }
341 };
342 MODULE_DEVICE_TABLE(of, pcf8523_of_match);
343 #endif
344 
345 static struct i2c_driver pcf8523_driver = {
346         .driver = {
347                 .name = DRIVER_NAME,
348                 .of_match_table = of_match_ptr(pcf8523_of_match),
349         },
350         .probe = pcf8523_probe,
351         .id_table = pcf8523_id,
352 };
353 module_i2c_driver(pcf8523_driver);
354 
355 MODULE_AUTHOR("Thierry Reding <thierry.reding@avionic-design.de>");
356 MODULE_DESCRIPTION("NXP PCF8523 RTC driver");
357 MODULE_LICENSE("GPL v2");
358 

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