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_select_capacitance(struct i2c_client *client, bool high)
  89 {
  90         u8 value;
  91         int err;
  92
  93         err = pcf8523_read(client, REG_CONTROL1, &value);
  94         if (err < 0)
  95                 return err;
  96
  97         if (!high)
  98                 value &= ~REG_CONTROL1_CAP_SEL;
  99         else
 100                 value |= REG_CONTROL1_CAP_SEL;
 101
 102         err = pcf8523_write(client, REG_CONTROL1, value);
 103         if (err < 0)
 104                 return err;
 105
 106         return err;
 107 }
 108
 109 static int pcf8523_set_pm(struct i2c_client *client, u8 pm)
 110 {
 111         u8 value;
 112         int err;
 113
 114         err = pcf8523_read(client, REG_CONTROL3, &value);
 115         if (err < 0)
 116                 return err;
 117
 118         value = (value & ~REG_CONTROL3_PM_MASK) | pm;
 119
 120         err = pcf8523_write(client, REG_CONTROL3, value);
 121         if (err < 0)
 122                 return err;
 123
 124         return 0;
 125 }
 126
 127 static int pcf8523_stop_rtc(struct i2c_client *client)
 128 {
 129         u8 value;
 130         int err;
 131
 132         err = pcf8523_read(client, REG_CONTROL1, &value);
 133         if (err < 0)
 134                 return err;
 135
 136         value |= REG_CONTROL1_STOP;
 137
 138         err = pcf8523_write(client, REG_CONTROL1, value);
 139         if (err < 0)
 140                 return err;
 141
 142         return 0;
 143 }
 144
 145 static int pcf8523_start_rtc(struct i2c_client *client)
 146 {
 147         u8 value;
 148         int err;
 149
 150         err = pcf8523_read(client, REG_CONTROL1, &value);
 151         if (err < 0)
 152                 return err;
 153
 154         value &= ~REG_CONTROL1_STOP;
 155
 156         err = pcf8523_write(client, REG_CONTROL1, value);
 157         if (err < 0)
 158                 return err;
 159
 160         return 0;
 161 }
 162
 163 static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm)
 164 {
 165         struct i2c_client *client = to_i2c_client(dev);
 166         u8 start = REG_SECONDS, regs[7];
 167         struct i2c_msg msgs[2];
 168         int err;
 169
 170         msgs[0].addr = client->addr;
 171         msgs[0].flags = 0;
 172         msgs[0].len = 1;
 173         msgs[0].buf = &start;
 174
 175         msgs[1].addr = client->addr;
 176         msgs[1].flags = I2C_M_RD;
 177         msgs[1].len = sizeof(regs);
 178         msgs[1].buf = regs;
 179
 180         err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
 181         if (err < 0)
 182                 return err;
 183
 184         if (regs[0] & REG_SECONDS_OS)
 185                 return -EINVAL;
 186
 187         tm->tm_sec = bcd2bin(regs[0] & 0x7f);
 188         tm->tm_min = bcd2bin(regs[1] & 0x7f);
 189         tm->tm_hour = bcd2bin(regs[2] & 0x3f);
 190         tm->tm_mday = bcd2bin(regs[3] & 0x3f);
 191         tm->tm_wday = regs[4] & 0x7;
 192         tm->tm_mon = bcd2bin(regs[5] & 0x1f) - 1;
 193         tm->tm_year = bcd2bin(regs[6]) + 100;
 194
 195         return 0;
 196 }
 197
 198 static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm)
 199 {
 200         struct i2c_client *client = to_i2c_client(dev);
 201         struct i2c_msg msg;
 202         u8 regs[8];
 203         int err;
 204
 205         /*
 206          * The hardware can only store values between 0 and 99 in it's YEAR
 207          * register (with 99 overflowing to 0 on increment).
 208          * After 2100-02-28 we could start interpreting the year to be in the
 209          * interval [2100, 2199], but there is no path to switch in a smooth way
 210          * because the chip handles YEAR=0x00 (and the out-of-spec
 211          * YEAR=0xa0) as a leap year, but 2100 isn't.
 212          */
 213         if (tm->tm_year < 100 || tm->tm_year >= 200)
 214                 return -EINVAL;
 215
 216         err = pcf8523_stop_rtc(client);
 217         if (err < 0)
 218                 return err;
 219
 220         regs[0] = REG_SECONDS;
 221         /* This will purposely overwrite REG_SECONDS_OS */
 222         regs[1] = bin2bcd(tm->tm_sec);
 223         regs[2] = bin2bcd(tm->tm_min);
 224         regs[3] = bin2bcd(tm->tm_hour);
 225         regs[4] = bin2bcd(tm->tm_mday);
 226         regs[5] = tm->tm_wday;
 227         regs[6] = bin2bcd(tm->tm_mon + 1);
 228         regs[7] = bin2bcd(tm->tm_year - 100);
 229
 230         msg.addr = client->addr;
 231         msg.flags = 0;
 232         msg.len = sizeof(regs);
 233         msg.buf = regs;
 234
 235         err = i2c_transfer(client->adapter, &msg, 1);
 236         if (err < 0) {
 237                 /*
 238                  * If the time cannot be set, restart the RTC anyway. Note
 239                  * that errors are ignored if the RTC cannot be started so
 240                  * that we have a chance to propagate the original error.
 241                  */
 242                 pcf8523_start_rtc(client);
 243                 return err;
 244         }
 245
 246         return pcf8523_start_rtc(client);
 247 }
 248
 249 #ifdef CONFIG_RTC_INTF_DEV
 250 static int pcf8523_rtc_ioctl(struct device *dev, unsigned int cmd,
 251                              unsigned long arg)
 252 {
 253         struct i2c_client *client = to_i2c_client(dev);
 254         u8 value;
 255         int ret = 0, err;
 256
 257         switch (cmd) {
 258         case RTC_VL_READ:
 259                 err = pcf8523_read(client, REG_CONTROL3, &value);
 260                 if (err < 0)
 261                         return err;
 262
 263                 if (value & REG_CONTROL3_BLF)
 264                         ret = 1;
 265
 266                 if (copy_to_user((void __user *)arg, &ret, sizeof(int)))
 267                         return -EFAULT;
 268
 269                 return 0;
 270         default:
 271                 return -ENOIOCTLCMD;
 272         }
 273 }
 274 #else
 275 #define pcf8523_rtc_ioctl NULL
 276 #endif
 277
 278 static int pcf8523_rtc_read_offset(struct device *dev, long *offset)
 279 {
 280         struct i2c_client *client = to_i2c_client(dev);
 281         int err;
 282         u8 value;
 283         s8 val;
 284
 285         err = pcf8523_read(client, REG_OFFSET, &value);
 286         if (err < 0)
 287                 return err;
 288
 289         /* sign extend the 7-bit offset value */
 290         val = value << 1;
 291         *offset = (value & REG_OFFSET_MODE ? 4069 : 4340) * (val >> 1);
 292
 293         return 0;
 294 }
 295
 296 static int pcf8523_rtc_set_offset(struct device *dev, long offset)
 297 {
 298         struct i2c_client *client = to_i2c_client(dev);
 299         long reg_m0, reg_m1;
 300         u8 value;
 301
 302         reg_m0 = clamp(DIV_ROUND_CLOSEST(offset, 4340), -64L, 63L);
 303         reg_m1 = clamp(DIV_ROUND_CLOSEST(offset, 4069), -64L, 63L);
 304
 305         if (abs(reg_m0 * 4340 - offset) < abs(reg_m1 * 4069 - offset))
 306                 value = reg_m0 & 0x7f;
 307         else
 308                 value = (reg_m1 & 0x7f) | REG_OFFSET_MODE;
 309
 310         return pcf8523_write(client, REG_OFFSET, value);
 311 }
 312
 313 static const struct rtc_class_ops pcf8523_rtc_ops = {
 314         .read_time = pcf8523_rtc_read_time,
 315         .set_time = pcf8523_rtc_set_time,
 316         .ioctl = pcf8523_rtc_ioctl,
 317         .read_offset = pcf8523_rtc_read_offset,
 318         .set_offset = pcf8523_rtc_set_offset,
 319 };
 320
 321 static int pcf8523_probe(struct i2c_client *client,
 322                          const struct i2c_device_id *id)
 323 {
 324         struct pcf8523 *pcf;
 325         int err;
 326
 327         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 328                 return -ENODEV;
 329
 330         pcf = devm_kzalloc(&client->dev, sizeof(*pcf), GFP_KERNEL);
 331         if (!pcf)
 332                 return -ENOMEM;
 333
 334         err = pcf8523_select_capacitance(client, true);
 335         if (err < 0)
 336                 return err;
 337
 338         err = pcf8523_set_pm(client, 0);
 339         if (err < 0)
 340                 return err;
 341
 342         pcf->rtc = devm_rtc_device_register(&client->dev, DRIVER_NAME,
 343                                        &pcf8523_rtc_ops, THIS_MODULE);
 344         if (IS_ERR(pcf->rtc))
 345                 return PTR_ERR(pcf->rtc);
 346
 347         i2c_set_clientdata(client, pcf);
 348
 349         return 0;
 350 }
 351
 352 static const struct i2c_device_id pcf8523_id[] = {
 353         { "pcf8523", 0 },
 354         { }
 355 };
 356 MODULE_DEVICE_TABLE(i2c, pcf8523_id);
 357
 358 #ifdef CONFIG_OF
 359 static const struct of_device_id pcf8523_of_match[] = {
 360         { .compatible = "nxp,pcf8523" },
 361         { }
 362 };
 363 MODULE_DEVICE_TABLE(of, pcf8523_of_match);
 364 #endif
 365
 366 static struct i2c_driver pcf8523_driver = {
 367         .driver = {
 368                 .name = DRIVER_NAME,
 369                 .of_match_table = of_match_ptr(pcf8523_of_match),
 370         },
 371         .probe = pcf8523_probe,
 372         .id_table = pcf8523_id,
 373 };
 374 module_i2c_driver(pcf8523_driver);
 375
 376 MODULE_AUTHOR("Thierry Reding <thierry.reding@avionic-design.de>");
 377 MODULE_DESCRIPTION("NXP PCF8523 RTC driver");
 378 MODULE_LICENSE("GPL v2");