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 static const struct i2c_device_id ds1374_id[] = {
  45         { "rtc-ds1374", 0 },
  46         { }
  47 };
  48 MODULE_DEVICE_TABLE(i2c, ds1374_id);
  49
  50 struct ds1374 {
  51         struct i2c_client *client;
  52         struct rtc_device *rtc;
  53         struct work_struct work;
  54
  55         /* The mutex protects alarm operations, and prevents a race
  56          * between the enable_irq() in the workqueue and the free_irq()
  57          * in the remove function.
  58          */
  59         struct mutex mutex;
  60         int exiting;
  61 };
  62
  63 static struct i2c_driver ds1374_driver;
  64
  65 static int ds1374_read_rtc(struct i2c_client *client, u32 *time,
  66                            int reg, int nbytes)
  67 {
  68         u8 buf[4];
  69         int ret;
  70         int i;
  71
  72         if (nbytes > 4) {
  73                 WARN_ON(1);
  74                 return -EINVAL;
  75         }
  76
  77         ret = i2c_smbus_read_i2c_block_data(client, reg, nbytes, buf);
  78
  79         if (ret < 0)
  80                 return ret;
  81         if (ret < nbytes)
  82                 return -EIO;
  83
  84         for (i = nbytes - 1, *time = 0; i >= 0; i--)
  85                 *time = (*time << 8) | buf[i];
  86
  87         return 0;
  88 }
  89
  90 static int ds1374_write_rtc(struct i2c_client *client, u32 time,
  91                             int reg, int nbytes)
  92 {
  93         u8 buf[4];
  94         int i;
  95
  96         if (nbytes > 4) {
  97                 WARN_ON(1);
  98                 return -EINVAL;
  99         }
 100
 101         for (i = 0; i < nbytes; i++) {
 102                 buf[i] = time & 0xff;
 103                 time >>= 8;
 104         }
 105
 106         return i2c_smbus_write_i2c_block_data(client, reg, nbytes, buf);
 107 }
 108
 109 static int ds1374_check_rtc_status(struct i2c_client *client)
 110 {
 111         int ret = 0;
 112         int control, stat;
 113
 114         stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
 115         if (stat < 0)
 116                 return stat;
 117
 118         if (stat & DS1374_REG_SR_OSF)
 119                 dev_warn(&client->dev,
 120                          "oscillator discontinuity flagged, "
 121                          "time unreliable\n");
 122
 123         stat &= ~(DS1374_REG_SR_OSF | DS1374_REG_SR_AF);
 124
 125         ret = i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);
 126         if (ret < 0)
 127                 return ret;
 128
 129         /* If the alarm is pending, clear it before requesting
 130          * the interrupt, so an interrupt event isn't reported
 131          * before everything is initialized.
 132          */
 133
 134         control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 135         if (control < 0)
 136                 return control;
 137
 138         control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
 139         return i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
 140 }
 141
 142 static int ds1374_read_time(struct device *dev, struct rtc_time *time)
 143 {
 144         struct i2c_client *client = to_i2c_client(dev);
 145         u32 itime;
 146         int ret;
 147
 148         ret = ds1374_read_rtc(client, &itime, DS1374_REG_TOD0, 4);
 149         if (!ret)
 150                 rtc_time_to_tm(itime, time);
 151
 152         return ret;
 153 }
 154
 155 static int ds1374_set_time(struct device *dev, struct rtc_time *time)
 156 {
 157         struct i2c_client *client = to_i2c_client(dev);
 158         unsigned long itime;
 159
 160         rtc_tm_to_time(time, &itime);
 161         return ds1374_write_rtc(client, itime, DS1374_REG_TOD0, 4);
 162 }
 163
 164 /* The ds1374 has a decrementer for an alarm, rather than a comparator.
 165  * If the time of day is changed, then the alarm will need to be
 166  * reset.
 167  */
 168 static int ds1374_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 169 {
 170         struct i2c_client *client = to_i2c_client(dev);
 171         struct ds1374 *ds1374 = i2c_get_clientdata(client);
 172         u32 now, cur_alarm;
 173         int cr, sr;
 174         int ret = 0;
 175
 176         if (client->irq < 0)
 177                 return -EINVAL;
 178
 179         mutex_lock(&ds1374->mutex);
 180
 181         cr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 182         if (ret < 0)
 183                 goto out;
 184
 185         sr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
 186         if (ret < 0)
 187                 goto out;
 188
 189         ret = ds1374_read_rtc(client, &now, DS1374_REG_TOD0, 4);
 190         if (ret)
 191                 goto out;
 192
 193         ret = ds1374_read_rtc(client, &cur_alarm, DS1374_REG_WDALM0, 3);
 194         if (ret)
 195                 goto out;
 196
 197         rtc_time_to_tm(now + cur_alarm, &alarm->time);
 198         alarm->enabled = !!(cr & DS1374_REG_CR_WACE);
 199         alarm->pending = !!(sr & DS1374_REG_SR_AF);
 200
 201 out:
 202         mutex_unlock(&ds1374->mutex);
 203         return ret;
 204 }
 205
 206 static int ds1374_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 207 {
 208         struct i2c_client *client = to_i2c_client(dev);
 209         struct ds1374 *ds1374 = i2c_get_clientdata(client);
 210         struct rtc_time now;
 211         unsigned long new_alarm, itime;
 212         int cr;
 213         int ret = 0;
 214
 215         if (client->irq < 0)
 216                 return -EINVAL;
 217
 218         ret = ds1374_read_time(dev, &now);
 219         if (ret < 0)
 220                 return ret;
 221
 222         rtc_tm_to_time(&alarm->time, &new_alarm);
 223         rtc_tm_to_time(&now, &itime);
 224
 225         new_alarm -= itime;
 226
 227         /* This can happen due to races, in addition to dates that are
 228          * truly in the past.  To avoid requiring the caller to check for
 229          * races, dates in the past are assumed to be in the recent past
 230          * (i.e. not something that we'd rather the caller know about via
 231          * an error), and the alarm is set to go off as soon as possible.
 232          */
 233         if (new_alarm <= 0)
 234                 new_alarm = 1;
 235
 236         mutex_lock(&ds1374->mutex);
 237
 238         ret = cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 239         if (ret < 0)
 240                 goto out;
 241
 242         /* Disable any existing alarm before setting the new one
 243          * (or lack thereof). */
 244         cr &= ~DS1374_REG_CR_WACE;
 245
 246         ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
 247         if (ret < 0)
 248                 goto out;
 249
 250         ret = ds1374_write_rtc(client, new_alarm, DS1374_REG_WDALM0, 3);
 251         if (ret)
 252                 goto out;
 253
 254         if (alarm->enabled) {
 255                 cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
 256                 cr &= ~DS1374_REG_CR_WDALM;
 257
 258                 ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
 259         }
 260
 261 out:
 262         mutex_unlock(&ds1374->mutex);
 263         return ret;
 264 }
 265
 266 static irqreturn_t ds1374_irq(int irq, void *dev_id)
 267 {
 268         struct i2c_client *client = dev_id;
 269         struct ds1374 *ds1374 = i2c_get_clientdata(client);
 270
 271         disable_irq_nosync(irq);
 272         schedule_work(&ds1374->work);
 273         return IRQ_HANDLED;
 274 }
 275
 276 static void ds1374_work(struct work_struct *work)
 277 {
 278         struct ds1374 *ds1374 = container_of(work, struct ds1374, work);
 279         struct i2c_client *client = ds1374->client;
 280         int stat, control;
 281
 282         mutex_lock(&ds1374->mutex);
 283
 284         stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
 285         if (stat < 0)
 286                 return;
 287
 288         if (stat & DS1374_REG_SR_AF) {
 289                 stat &= ~DS1374_REG_SR_AF;
 290                 i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);
 291
 292                 control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 293                 if (control < 0)
 294                         goto out;
 295
 296                 control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
 297                 i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
 298
 299                 /* rtc_update_irq() assumes that it is called
 300                  * from IRQ-disabled context.
 301                  */
 302                 local_irq_disable();
 303                 rtc_update_irq(ds1374->rtc, 1, RTC_AF | RTC_IRQF);
 304                 local_irq_enable();
 305         }
 306
 307 out:
 308         if (!ds1374->exiting)
 309                 enable_irq(client->irq);
 310
 311         mutex_unlock(&ds1374->mutex);
 312 }
 313
 314 static int ds1374_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
 315 {
 316         struct i2c_client *client = to_i2c_client(dev);
 317         struct ds1374 *ds1374 = i2c_get_clientdata(client);
 318         int ret = -ENOIOCTLCMD;
 319
 320         mutex_lock(&ds1374->mutex);
 321
 322         switch (cmd) {
 323         case RTC_AIE_OFF:
 324                 ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 325                 if (ret < 0)
 326                         goto out;
 327
 328                 ret &= ~DS1374_REG_CR_WACE;
 329
 330                 ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);
 331                 if (ret < 0)
 332                         goto out;
 333
 334                 break;
 335
 336         case RTC_AIE_ON:
 337                 ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 338                 if (ret < 0)
 339                         goto out;
 340
 341                 ret |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
 342                 ret &= ~DS1374_REG_CR_WDALM;
 343
 344                 ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);
 345                 if (ret < 0)
 346                         goto out;
 347
 348                 break;
 349         }
 350
 351 out:
 352         mutex_unlock(&ds1374->mutex);
 353         return ret;
 354 }
 355
 356 static const struct rtc_class_ops ds1374_rtc_ops = {
 357         .read_time = ds1374_read_time,
 358         .set_time = ds1374_set_time,
 359         .read_alarm = ds1374_read_alarm,
 360         .set_alarm = ds1374_set_alarm,
 361         .ioctl = ds1374_ioctl,
 362 };
 363
 364 static int ds1374_probe(struct i2c_client *client,
 365                         const struct i2c_device_id *id)
 366 {
 367         struct ds1374 *ds1374;
 368         int ret;
 369
 370         ds1374 = kzalloc(sizeof(struct ds1374), GFP_KERNEL);
 371         if (!ds1374)
 372                 return -ENOMEM;
 373
 374         ds1374->client = client;
 375         i2c_set_clientdata(client, ds1374);
 376
 377         INIT_WORK(&ds1374->work, ds1374_work);
 378         mutex_init(&ds1374->mutex);
 379
 380         ret = ds1374_check_rtc_status(client);
 381         if (ret)
 382                 goto out_free;
 383
 384         if (client->irq >= 0) {
 385                 ret = request_irq(client->irq, ds1374_irq, 0,
 386                                   "ds1374", client);
 387                 if (ret) {
 388                         dev_err(&client->dev, "unable to request IRQ\n");
 389                         goto out_free;
 390                 }
 391         }
 392
 393         ds1374->rtc = rtc_device_register(client->name, &client->dev,
 394                                           &ds1374_rtc_ops, THIS_MODULE);
 395         if (IS_ERR(ds1374->rtc)) {
 396                 ret = PTR_ERR(ds1374->rtc);
 397                 dev_err(&client->dev, "unable to register the class device\n");
 398                 goto out_irq;
 399         }
 400
 401         return 0;
 402
 403 out_irq:
 404         if (client->irq >= 0)
 405                 free_irq(client->irq, client);
 406
 407 out_free:
 408         i2c_set_clientdata(client, NULL);
 409         kfree(ds1374);
 410         return ret;
 411 }
 412
 413 static int __devexit ds1374_remove(struct i2c_client *client)
 414 {
 415         struct ds1374 *ds1374 = i2c_get_clientdata(client);
 416
 417         if (client->irq >= 0) {
 418                 mutex_lock(&ds1374->mutex);
 419                 ds1374->exiting = 1;
 420                 mutex_unlock(&ds1374->mutex);
 421
 422                 free_irq(client->irq, client);
 423                 flush_scheduled_work();
 424         }
 425
 426         rtc_device_unregister(ds1374->rtc);
 427         i2c_set_clientdata(client, NULL);
 428         kfree(ds1374);
 429         return 0;
 430 }
 431
 432 static struct i2c_driver ds1374_driver = {
 433         .driver = {
 434                 .name = "rtc-ds1374",
 435                 .owner = THIS_MODULE,
 436         },
 437         .probe = ds1374_probe,
 438         .remove = __devexit_p(ds1374_remove),
 439         .id_table = ds1374_id,
 440 };
 441
 442 static int __init ds1374_init(void)
 443 {
 444         return i2c_add_driver(&ds1374_driver);
 445 }
 446
 447 static void __exit ds1374_exit(void)
 448 {
 449         i2c_del_driver(&ds1374_driver);
 450 }
 451
 452 module_init(ds1374_init);
 453 module_exit(ds1374_exit);
 454
 455 MODULE_AUTHOR("Scott Wood <scottwood@freescale.com>");
 456 MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC Driver");
 457 MODULE_LICENSE("GPL");