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 #define REG_OFFSET   0x0e
  39 #define REG_OFFSET_MODE BIT(7)
  40
  41 struct pcf8523 {
  42         struct rtc_device *rtc;
  43 };
  44
  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 = &reg;
  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
  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
  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
 100 static int pcf8523_select_capacitance(struct i2c_client *client, bool high)
 101 {
 102         u8 value;
 103         int err;
 104
 105         err = pcf8523_read(client, REG_CONTROL1, &value);
 106         if (err < 0)
 107                 return err;
 108
 109         if (!high)
 110                 value &= ~REG_CONTROL1_CAP_SEL;
 111         else
 112                 value |= REG_CONTROL1_CAP_SEL;
 113
 114         err = pcf8523_write(client, REG_CONTROL1, value);
 115         if (err < 0)
 116                 return err;
 117
 118         return err;
 119 }
 120
 121 static int pcf8523_set_pm(struct i2c_client *client, u8 pm)
 122 {
 123         u8 value;
 124         int err;
 125
 126         err = pcf8523_read(client, REG_CONTROL3, &value);
 127         if (err < 0)
 128                 return err;
 129
 130         value = (value & ~REG_CONTROL3_PM_MASK) | pm;
 131
 132         err = pcf8523_write(client, REG_CONTROL3, value);
 133         if (err < 0)
 134                 return err;
 135
 136         return 0;
 137 }
 138
 139 static int pcf8523_stop_rtc(struct i2c_client *client)
 140 {
 141         u8 value;
 142         int err;
 143
 144         err = pcf8523_read(client, REG_CONTROL1, &value);
 145         if (err < 0)
 146                 return err;
 147
 148         value |= REG_CONTROL1_STOP;
 149
 150         err = pcf8523_write(client, REG_CONTROL1, value);
 151         if (err < 0)
 152                 return err;
 153
 154         return 0;
 155 }
 156
 157 static int pcf8523_start_rtc(struct i2c_client *client)
 158 {
 159         u8 value;
 160         int err;
 161
 162         err = pcf8523_read(client, REG_CONTROL1, &value);
 163         if (err < 0)
 164                 return err;
 165
 166         value &= ~REG_CONTROL1_STOP;
 167
 168         err = pcf8523_write(client, REG_CONTROL1, value);
 169         if (err < 0)
 170                 return err;
 171
 172         return 0;
 173 }
 174
 175 static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm)
 176 {
 177         struct i2c_client *client = to_i2c_client(dev);
 178         u8 start = REG_SECONDS, regs[7];
 179         struct i2c_msg msgs[2];
 180         int err;
 181
 182         err = pcf8523_voltage_low(client);
 183         if (err < 0) {
 184                 return err;
 185         } else if (err > 0) {
 186                 dev_err(dev, "low voltage detected, time is unreliable\n");
 187                 return -EINVAL;
 188         }
 189
 190         msgs[0].addr = client->addr;
 191         msgs[0].flags = 0;
 192         msgs[0].len = 1;
 193         msgs[0].buf = &start;
 194
 195         msgs[1].addr = client->addr;
 196         msgs[1].flags = I2C_M_RD;
 197         msgs[1].len = sizeof(regs);
 198         msgs[1].buf = regs;
 199
 200         err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
 201         if (err < 0)
 202                 return err;
 203
 204         if (regs[0] & REG_SECONDS_OS)
 205                 return -EINVAL;
 206
 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;
 214
 215         return 0;
 216 }
 217
 218 static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm)
 219 {
 220         struct i2c_client *client = to_i2c_client(dev);
 221         struct i2c_msg msg;
 222         u8 regs[8];
 223         int err;
 224
 225         /*
 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.
 232          */
 233         if (tm->tm_year < 100 || tm->tm_year >= 200)
 234                 return -EINVAL;
 235
 236         err = pcf8523_stop_rtc(client);
 237         if (err < 0)
 238                 return err;
 239
 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);
 249
 250         msg.addr = client->addr;
 251         msg.flags = 0;
 252         msg.len = sizeof(regs);
 253         msg.buf = regs;
 254
 255         err = i2c_transfer(client->adapter, &msg, 1);
 256         if (err < 0) {
 257                 /*
 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.
 261                  */
 262                 pcf8523_start_rtc(client);
 263                 return err;
 264         }
 265
 266         return pcf8523_start_rtc(client);
 267 }
 268
 269 #ifdef CONFIG_RTC_INTF_DEV
 270 static int pcf8523_rtc_ioctl(struct device *dev, unsigned int cmd,
 271                              unsigned long arg)
 272 {
 273         struct i2c_client *client = to_i2c_client(dev);
 274         int ret;
 275
 276         switch (cmd) {
 277         case RTC_VL_READ:
 278                 ret = pcf8523_voltage_low(client);
 279                 if (ret < 0)
 280                         return ret;
 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 int pcf8523_rtc_read_offset(struct device *dev, long *offset)
 295 {
 296         struct i2c_client *client = to_i2c_client(dev);
 297         int err;
 298         u8 value;
 299         s8 val;
 300
 301         err = pcf8523_read(client, REG_OFFSET, &value);
 302         if (err < 0)
 303                 return err;
 304
 305         /* sign extend the 7-bit offset value */
 306         val = value << 1;
 307         *offset = (value & REG_OFFSET_MODE ? 4069 : 4340) * (val >> 1);
 308
 309         return 0;
 310 }
 311
 312 static int pcf8523_rtc_set_offset(struct device *dev, long offset)
 313 {
 314         struct i2c_client *client = to_i2c_client(dev);
 315         long reg_m0, reg_m1;
 316         u8 value;
 317
 318         reg_m0 = clamp(DIV_ROUND_CLOSEST(offset, 4340), -64L, 63L);
 319         reg_m1 = clamp(DIV_ROUND_CLOSEST(offset, 4069), -64L, 63L);
 320
 321         if (abs(reg_m0 * 4340 - offset) < abs(reg_m1 * 4069 - offset))
 322                 value = reg_m0 & 0x7f;
 323         else
 324                 value = (reg_m1 & 0x7f) | REG_OFFSET_MODE;
 325
 326         return pcf8523_write(client, REG_OFFSET, value);
 327 }
 328
 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,
 335 };
 336
 337 static int pcf8523_probe(struct i2c_client *client,
 338                          const struct i2c_device_id *id)
 339 {
 340         struct pcf8523 *pcf;
 341         int err;
 342
 343         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 344                 return -ENODEV;
 345
 346         pcf = devm_kzalloc(&client->dev, sizeof(*pcf), GFP_KERNEL);
 347         if (!pcf)
 348                 return -ENOMEM;
 349
 350         err = pcf8523_select_capacitance(client, true);
 351         if (err < 0)
 352                 return err;
 353
 354         err = pcf8523_set_pm(client, 0);
 355         if (err < 0)
 356                 return err;
 357
 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);
 362
 363         i2c_set_clientdata(client, pcf);
 364
 365         return 0;
 366 }
 367
 368 static const struct i2c_device_id pcf8523_id[] = {
 369         { "pcf8523", 0 },
 370         { }
 371 };
 372 MODULE_DEVICE_TABLE(i2c, pcf8523_id);
 373
 374 #ifdef CONFIG_OF
 375 static const struct of_device_id pcf8523_of_match[] = {
 376         { .compatible = "nxp,pcf8523" },
 377         { }
 378 };
 379 MODULE_DEVICE_TABLE(of, pcf8523_of_match);
 380 #endif
 381
 382 static struct i2c_driver pcf8523_driver = {
 383         .driver = {
 384                 .name = DRIVER_NAME,
 385                 .of_match_table = of_match_ptr(pcf8523_of_match),
 386         },
 387         .probe = pcf8523_probe,
 388         .id_table = pcf8523_id,
 389 };
 390 module_i2c_driver(pcf8523_driver);
 391
 392 MODULE_AUTHOR("Thierry Reding <thierry.reding@avionic-design.de>");
 393 MODULE_DESCRIPTION("NXP PCF8523 RTC driver");
 394 MODULE_LICENSE("GPL v2");