drivers/rtc/rtc-ds1374.c

   1 /*
   2  * RTC client/driver for the Maxim/Dallas DS1374 Real-Time Clock over I2C
   3  *
   4  * Based on code by Randy Vinson <rvinson@mvista.com>,
   5  * which was based on the m41t00.c by Mark Greer <mgreer@mvista.com>.
   6  *
   7  * Copyright (C) 2006-2007 Freescale Semiconductor
   8  *
   9  * 2005 (c) MontaVista Software, Inc. This file is licensed under
  10  * the terms of the GNU General Public License version 2. This program
  11  * is licensed "as is" without any warranty of any kind, whether express
  12  * or implied.
  13  */
  14 /*
  15  * It would be more efficient to use i2c msgs/i2c_transfer directly but, as
  16  * recommened in .../Documentation/i2c/writing-clients section
  17  * "Sending and receiving", using SMBus level communication is preferred.
  18  */
  19
  20 #include <linux/kernel.h>
  21 #include <linux/module.h>
  22 #include <linux/interrupt.h>
  23 #include <linux/i2c.h>
  24 #include <linux/rtc.h>
  25 #include <linux/bcd.h>
  26 #include <linux/workqueue.h>
  27
  28 #define DS1374_REG_TOD0         0x00 /* Time of Day */
  29 #define DS1374_REG_TOD1         0x01
  30 #define DS1374_REG_TOD2         0x02
  31 #define DS1374_REG_TOD3         0x03
  32 #define DS1374_REG_WDALM0       0x04 /* Watchdog/Alarm */
  33 #define DS1374_REG_WDALM1       0x05
  34 #define DS1374_REG_WDALM2       0x06
  35 #define DS1374_REG_CR           0x07 /* Control */
  36 #define DS1374_REG_CR_AIE       0x01 /* Alarm Int. Enable */
  37 #define DS1374_REG_CR_WDALM     0x20 /* 1=Watchdog, 0=Alarm */
  38 #define DS1374_REG_CR_WACE      0x40 /* WD/Alarm counter enable */
  39 #define DS1374_REG_SR           0x08 /* Status */
  40 #define DS1374_REG_SR_OSF       0x80 /* Oscillator Stop Flag */
  41 #define DS1374_REG_SR_AF        0x01 /* Alarm Flag */
  42 #define DS1374_REG_TCR          0x09 /* Trickle Charge */
  43
  44 struct ds1374 {
  45         struct i2c_client *client;
  46         struct rtc_device *rtc;
  47         struct work_struct work;
  48
  49         /* The mutex protects alarm operations, and prevents a race
  50          * between the enable_irq() in the workqueue and the free_irq()
  51          * in the remove function.
  52          */
  53         struct mutex mutex;
  54         int exiting;
  55 };
  56
  57 static struct i2c_driver ds1374_driver;
  58
  59 static int ds1374_read_rtc(struct i2c_client *client, u32 *time,
  60                            int reg, int nbytes)
  61 {
  62         u8 buf[4];
  63         int ret;
  64         int i;
  65
  66         if (nbytes > 4) {
  67                 WARN_ON(1);
  68                 return -EINVAL;
  69         }
  70
  71         ret = i2c_smbus_read_i2c_block_data(client, reg, nbytes, buf);
  72
  73         if (ret < 0)
  74                 return ret;
  75         if (ret < nbytes)
  76                 return -EIO;
  77
  78         for (i = nbytes - 1, *time = 0; i >= 0; i--)
  79                 *time = (*time << 8) | buf[i];
  80
  81         return 0;
  82 }
  83
  84 static int ds1374_write_rtc(struct i2c_client *client, u32 time,
  85                             int reg, int nbytes)
  86 {
  87         u8 buf[4];
  88         int i;
  89
  90         if (nbytes > 4) {
  91                 WARN_ON(1);
  92                 return -EINVAL;
  93         }
  94
  95         for (i = 0; i < nbytes; i++) {
  96                 buf[i] = time & 0xff;
  97                 time >>= 8;
  98         }
  99
 100         return i2c_smbus_write_i2c_block_data(client, reg, nbytes, buf);
 101 }
 102
 103 static int ds1374_check_rtc_status(struct i2c_client *client)
 104 {
 105         int ret = 0;
 106         int control, stat;
 107
 108         stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
 109         if (stat < 0)
 110                 return stat;
 111
 112         if (stat & DS1374_REG_SR_OSF)
 113                 dev_warn(&client->dev,
 114                          "oscillator discontinuity flagged, "
 115                          "time unreliable\n");
 116
 117         stat &= ~(DS1374_REG_SR_OSF | DS1374_REG_SR_AF);
 118
 119         ret = i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);
 120         if (ret < 0)
 121                 return ret;
 122
 123         /* If the alarm is pending, clear it before requesting
 124          * the interrupt, so an interrupt event isn't reported
 125          * before everything is initialized.
 126          */
 127
 128         control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 129         if (control < 0)
 130                 return control;
 131
 132         control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
 133         return i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
 134 }
 135
 136 static int ds1374_read_time(struct device *dev, struct rtc_time *time)
 137 {
 138         struct i2c_client *client = to_i2c_client(dev);
 139         u32 itime;
 140         int ret;
 141
 142         ret = ds1374_read_rtc(client, &itime, DS1374_REG_TOD0, 4);
 143         if (!ret)
 144                 rtc_time_to_tm(itime, time);
 145
 146         return ret;
 147 }
 148
 149 static int ds1374_set_time(struct device *dev, struct rtc_time *time)
 150 {
 151         struct i2c_client *client = to_i2c_client(dev);
 152         unsigned long itime;
 153
 154         rtc_tm_to_time(time, &itime);
 155         return ds1374_write_rtc(client, itime, DS1374_REG_TOD0, 4);
 156 }
 157
 158 /* The ds1374 has a decrementer for an alarm, rather than a comparator.
 159  * If the time of day is changed, then the alarm will need to be
 160  * reset.
 161  */
 162 static int ds1374_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 163 {
 164         struct i2c_client *client = to_i2c_client(dev);
 165         struct ds1374 *ds1374 = i2c_get_clientdata(client);
 166         u32 now, cur_alarm;
 167         int cr, sr;
 168         int ret = 0;
 169
 170         if (client->irq < 0)
 171                 return -EINVAL;
 172
 173         mutex_lock(&ds1374->mutex);
 174
 175         cr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 176         if (ret < 0)
 177                 goto out;
 178
 179         sr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
 180         if (ret < 0)
 181                 goto out;
 182
 183         ret = ds1374_read_rtc(client, &now, DS1374_REG_TOD0, 4);
 184         if (ret)
 185                 goto out;
 186
 187         ret = ds1374_read_rtc(client, &cur_alarm, DS1374_REG_WDALM0, 3);
 188         if (ret)
 189                 goto out;
 190
 191         rtc_time_to_tm(now + cur_alarm, &alarm->time);
 192         alarm->enabled = !!(cr & DS1374_REG_CR_WACE);
 193         alarm->pending = !!(sr & DS1374_REG_SR_AF);
 194
 195 out:
 196         mutex_unlock(&ds1374->mutex);
 197         return ret;
 198 }
 199
 200 static int ds1374_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 201 {
 202         struct i2c_client *client = to_i2c_client(dev);
 203         struct ds1374 *ds1374 = i2c_get_clientdata(client);
 204         struct rtc_time now;
 205         unsigned long new_alarm, itime;
 206         int cr;
 207         int ret = 0;
 208
 209         if (client->irq < 0)
 210                 return -EINVAL;
 211
 212         ret = ds1374_read_time(dev, &now);
 213         if (ret < 0)
 214                 return ret;
 215
 216         rtc_tm_to_time(&alarm->time, &new_alarm);
 217         rtc_tm_to_time(&now, &itime);
 218
 219         new_alarm -= itime;
 220
 221         /* This can happen due to races, in addition to dates that are
 222          * truly in the past.  To avoid requiring the caller to check for
 223          * races, dates in the past are assumed to be in the recent past
 224          * (i.e. not something that we'd rather the caller know about via
 225          * an error), and the alarm is set to go off as soon as possible.
 226          */
 227         if (new_alarm <= 0)
 228                 new_alarm = 1;
 229
 230         mutex_lock(&ds1374->mutex);
 231
 232         ret = cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 233         if (ret < 0)
 234                 goto out;
 235
 236         /* Disable any existing alarm before setting the new one
 237          * (or lack thereof). */
 238         cr &= ~DS1374_REG_CR_WACE;
 239
 240         ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
 241         if (ret < 0)
 242                 goto out;
 243
 244         ret = ds1374_write_rtc(client, new_alarm, DS1374_REG_WDALM0, 3);
 245         if (ret)
 246                 goto out;
 247
 248         if (alarm->enabled) {
 249                 cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
 250                 cr &= ~DS1374_REG_CR_WDALM;
 251
 252                 ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
 253         }
 254
 255 out:
 256         mutex_unlock(&ds1374->mutex);
 257         return ret;
 258 }
 259
 260 static irqreturn_t ds1374_irq(int irq, void *dev_id)
 261 {
 262         struct i2c_client *client = dev_id;
 263         struct ds1374 *ds1374 = i2c_get_clientdata(client);
 264
 265         disable_irq_nosync(irq);
 266         schedule_work(&ds1374->work);
 267         return IRQ_HANDLED;
 268 }
 269
 270 static void ds1374_work(struct work_struct *work)
 271 {
 272         struct ds1374 *ds1374 = container_of(work, struct ds1374, work);
 273         struct i2c_client *client = ds1374->client;
 274         int stat, control;
 275
 276         mutex_lock(&ds1374->mutex);
 277
 278         stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
 279         if (stat < 0)
 280                 return;
 281
 282         if (stat & DS1374_REG_SR_AF) {
 283                 stat &= ~DS1374_REG_SR_AF;
 284                 i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);
 285
 286                 control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 287                 if (control < 0)
 288                         goto out;
 289
 290                 control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
 291                 i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
 292
 293                 /* rtc_update_irq() assumes that it is called
 294                  * from IRQ-disabled context.
 295                  */
 296                 local_irq_disable();
 297                 rtc_update_irq(ds1374->rtc, 1, RTC_AF | RTC_IRQF);
 298                 local_irq_enable();
 299         }
 300
 301 out:
 302         if (!ds1374->exiting)
 303                 enable_irq(client->irq);
 304
 305         mutex_unlock(&ds1374->mutex);
 306 }
 307
 308 static int ds1374_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
 309 {
 310         struct i2c_client *client = to_i2c_client(dev);
 311         struct ds1374 *ds1374 = i2c_get_clientdata(client);
 312         int ret = -ENOIOCTLCMD;
 313
 314         mutex_lock(&ds1374->mutex);
 315
 316         switch (cmd) {
 317         case RTC_AIE_OFF:
 318                 ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 319                 if (ret < 0)
 320                         goto out;
 321
 322                 ret &= ~DS1374_REG_CR_WACE;
 323
 324                 ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);
 325                 if (ret < 0)
 326                         goto out;
 327
 328                 break;
 329
 330         case RTC_AIE_ON:
 331                 ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 332                 if (ret < 0)
 333                         goto out;
 334
 335                 ret |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
 336                 ret &= ~DS1374_REG_CR_WDALM;
 337
 338                 ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);
 339                 if (ret < 0)
 340                         goto out;
 341
 342                 break;
 343         }
 344
 345 out:
 346         mutex_unlock(&ds1374->mutex);
 347         return ret;
 348 }
 349
 350 static const struct rtc_class_ops ds1374_rtc_ops = {
 351         .read_time = ds1374_read_time,
 352         .set_time = ds1374_set_time,
 353         .read_alarm = ds1374_read_alarm,
 354         .set_alarm = ds1374_set_alarm,
 355         .ioctl = ds1374_ioctl,
 356 };
 357
 358 static int ds1374_probe(struct i2c_client *client)
 359 {
 360         struct ds1374 *ds1374;
 361         int ret;
 362
 363         ds1374 = kzalloc(sizeof(struct ds1374), GFP_KERNEL);
 364         if (!ds1374)
 365                 return -ENOMEM;
 366
 367         ds1374->client = client;
 368         i2c_set_clientdata(client, ds1374);
 369
 370         INIT_WORK(&ds1374->work, ds1374_work);
 371         mutex_init(&ds1374->mutex);
 372
 373         ret = ds1374_check_rtc_status(client);
 374         if (ret)
 375                 goto out_free;
 376
 377         if (client->irq >= 0) {
 378                 ret = request_irq(client->irq, ds1374_irq, 0,
 379                                   "ds1374", client);
 380                 if (ret) {
 381                         dev_err(&client->dev, "unable to request IRQ\n");
 382                         goto out_free;
 383                 }
 384         }
 385
 386         ds1374->rtc = rtc_device_register(client->name, &client->dev,
 387                                           &ds1374_rtc_ops, THIS_MODULE);
 388         if (IS_ERR(ds1374->rtc)) {
 389                 ret = PTR_ERR(ds1374->rtc);
 390                 dev_err(&client->dev, "unable to register the class device\n");
 391                 goto out_irq;
 392         }
 393
 394         return 0;
 395
 396 out_irq:
 397         if (client->irq >= 0)
 398                 free_irq(client->irq, client);
 399
 400 out_free:
 401         i2c_set_clientdata(client, NULL);
 402         kfree(ds1374);
 403         return ret;
 404 }
 405
 406 static int __devexit ds1374_remove(struct i2c_client *client)
 407 {
 408         struct ds1374 *ds1374 = i2c_get_clientdata(client);
 409
 410         if (client->irq >= 0) {
 411                 mutex_lock(&ds1374->mutex);
 412                 ds1374->exiting = 1;
 413                 mutex_unlock(&ds1374->mutex);
 414
 415                 free_irq(client->irq, client);
 416                 flush_scheduled_work();
 417         }
 418
 419         rtc_device_unregister(ds1374->rtc);
 420         i2c_set_clientdata(client, NULL);
 421         kfree(ds1374);
 422         return 0;
 423 }
 424
 425 static struct i2c_driver ds1374_driver = {
 426         .driver = {
 427                 .name = "rtc-ds1374",
 428                 .owner = THIS_MODULE,
 429         },
 430         .probe = ds1374_probe,
 431         .remove = __devexit_p(ds1374_remove),
 432 };
 433
 434 static int __init ds1374_init(void)
 435 {
 436         return i2c_add_driver(&ds1374_driver);
 437 }
 438
 439 static void __exit ds1374_exit(void)
 440 {
 441         i2c_del_driver(&ds1374_driver);
 442 }
 443
 444 module_init(ds1374_init);
 445 module_exit(ds1374_exit);
 446
 447 MODULE_AUTHOR("Scott Wood <scottwood@freescale.com>");
 448 MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC Driver");
 449 MODULE_LICENSE("GPL");