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");