linux/drivers/rtc/rtc-ds1374.c
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   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#include <linux/slab.h>
  28#include <linux/pm.h>
  29
  30#define DS1374_REG_TOD0         0x00 /* Time of Day */
  31#define DS1374_REG_TOD1         0x01
  32#define DS1374_REG_TOD2         0x02
  33#define DS1374_REG_TOD3         0x03
  34#define DS1374_REG_WDALM0       0x04 /* Watchdog/Alarm */
  35#define DS1374_REG_WDALM1       0x05
  36#define DS1374_REG_WDALM2       0x06
  37#define DS1374_REG_CR           0x07 /* Control */
  38#define DS1374_REG_CR_AIE       0x01 /* Alarm Int. Enable */
  39#define DS1374_REG_CR_WDALM     0x20 /* 1=Watchdog, 0=Alarm */
  40#define DS1374_REG_CR_WACE      0x40 /* WD/Alarm counter enable */
  41#define DS1374_REG_SR           0x08 /* Status */
  42#define DS1374_REG_SR_OSF       0x80 /* Oscillator Stop Flag */
  43#define DS1374_REG_SR_AF        0x01 /* Alarm Flag */
  44#define DS1374_REG_TCR          0x09 /* Trickle Charge */
  45
  46static const struct i2c_device_id ds1374_id[] = {
  47        { "ds1374", 0 },
  48        { }
  49};
  50MODULE_DEVICE_TABLE(i2c, ds1374_id);
  51
  52struct ds1374 {
  53        struct i2c_client *client;
  54        struct rtc_device *rtc;
  55        struct work_struct work;
  56
  57        /* The mutex protects alarm operations, and prevents a race
  58         * between the enable_irq() in the workqueue and the free_irq()
  59         * in the remove function.
  60         */
  61        struct mutex mutex;
  62        int exiting;
  63};
  64
  65static struct i2c_driver ds1374_driver;
  66
  67static int ds1374_read_rtc(struct i2c_client *client, u32 *time,
  68                           int reg, int nbytes)
  69{
  70        u8 buf[4];
  71        int ret;
  72        int i;
  73
  74        if (nbytes > 4) {
  75                WARN_ON(1);
  76                return -EINVAL;
  77        }
  78
  79        ret = i2c_smbus_read_i2c_block_data(client, reg, nbytes, buf);
  80
  81        if (ret < 0)
  82                return ret;
  83        if (ret < nbytes)
  84                return -EIO;
  85
  86        for (i = nbytes - 1, *time = 0; i >= 0; i--)
  87                *time = (*time << 8) | buf[i];
  88
  89        return 0;
  90}
  91
  92static int ds1374_write_rtc(struct i2c_client *client, u32 time,
  93                            int reg, int nbytes)
  94{
  95        u8 buf[4];
  96        int i;
  97
  98        if (nbytes > 4) {
  99                WARN_ON(1);
 100                return -EINVAL;
 101        }
 102
 103        for (i = 0; i < nbytes; i++) {
 104                buf[i] = time & 0xff;
 105                time >>= 8;
 106        }
 107
 108        return i2c_smbus_write_i2c_block_data(client, reg, nbytes, buf);
 109}
 110
 111static int ds1374_check_rtc_status(struct i2c_client *client)
 112{
 113        int ret = 0;
 114        int control, stat;
 115
 116        stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
 117        if (stat < 0)
 118                return stat;
 119
 120        if (stat & DS1374_REG_SR_OSF)
 121                dev_warn(&client->dev,
 122                         "oscillator discontinuity flagged, "
 123                         "time unreliable\n");
 124
 125        stat &= ~(DS1374_REG_SR_OSF | DS1374_REG_SR_AF);
 126
 127        ret = i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);
 128        if (ret < 0)
 129                return ret;
 130
 131        /* If the alarm is pending, clear it before requesting
 132         * the interrupt, so an interrupt event isn't reported
 133         * before everything is initialized.
 134         */
 135
 136        control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 137        if (control < 0)
 138                return control;
 139
 140        control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
 141        return i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
 142}
 143
 144static int ds1374_read_time(struct device *dev, struct rtc_time *time)
 145{
 146        struct i2c_client *client = to_i2c_client(dev);
 147        u32 itime;
 148        int ret;
 149
 150        ret = ds1374_read_rtc(client, &itime, DS1374_REG_TOD0, 4);
 151        if (!ret)
 152                rtc_time_to_tm(itime, time);
 153
 154        return ret;
 155}
 156
 157static int ds1374_set_time(struct device *dev, struct rtc_time *time)
 158{
 159        struct i2c_client *client = to_i2c_client(dev);
 160        unsigned long itime;
 161
 162        rtc_tm_to_time(time, &itime);
 163        return ds1374_write_rtc(client, itime, DS1374_REG_TOD0, 4);
 164}
 165
 166/* The ds1374 has a decrementer for an alarm, rather than a comparator.
 167 * If the time of day is changed, then the alarm will need to be
 168 * reset.
 169 */
 170static int ds1374_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 171{
 172        struct i2c_client *client = to_i2c_client(dev);
 173        struct ds1374 *ds1374 = i2c_get_clientdata(client);
 174        u32 now, cur_alarm;
 175        int cr, sr;
 176        int ret = 0;
 177
 178        if (client->irq <= 0)
 179                return -EINVAL;
 180
 181        mutex_lock(&ds1374->mutex);
 182
 183        cr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 184        if (ret < 0)
 185                goto out;
 186
 187        sr = ret = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
 188        if (ret < 0)
 189                goto out;
 190
 191        ret = ds1374_read_rtc(client, &now, DS1374_REG_TOD0, 4);
 192        if (ret)
 193                goto out;
 194
 195        ret = ds1374_read_rtc(client, &cur_alarm, DS1374_REG_WDALM0, 3);
 196        if (ret)
 197                goto out;
 198
 199        rtc_time_to_tm(now + cur_alarm, &alarm->time);
 200        alarm->enabled = !!(cr & DS1374_REG_CR_WACE);
 201        alarm->pending = !!(sr & DS1374_REG_SR_AF);
 202
 203out:
 204        mutex_unlock(&ds1374->mutex);
 205        return ret;
 206}
 207
 208static int ds1374_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 209{
 210        struct i2c_client *client = to_i2c_client(dev);
 211        struct ds1374 *ds1374 = i2c_get_clientdata(client);
 212        struct rtc_time now;
 213        unsigned long new_alarm, itime;
 214        int cr;
 215        int ret = 0;
 216
 217        if (client->irq <= 0)
 218                return -EINVAL;
 219
 220        ret = ds1374_read_time(dev, &now);
 221        if (ret < 0)
 222                return ret;
 223
 224        rtc_tm_to_time(&alarm->time, &new_alarm);
 225        rtc_tm_to_time(&now, &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 (time_before_eq(new_alarm, itime))
 234                new_alarm = 1;
 235        else
 236                new_alarm -= itime;
 237
 238        mutex_lock(&ds1374->mutex);
 239
 240        ret = cr = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 241        if (ret < 0)
 242                goto out;
 243
 244        /* Disable any existing alarm before setting the new one
 245         * (or lack thereof). */
 246        cr &= ~DS1374_REG_CR_WACE;
 247
 248        ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
 249        if (ret < 0)
 250                goto out;
 251
 252        ret = ds1374_write_rtc(client, new_alarm, DS1374_REG_WDALM0, 3);
 253        if (ret)
 254                goto out;
 255
 256        if (alarm->enabled) {
 257                cr |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
 258                cr &= ~DS1374_REG_CR_WDALM;
 259
 260                ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, cr);
 261        }
 262
 263out:
 264        mutex_unlock(&ds1374->mutex);
 265        return ret;
 266}
 267
 268static irqreturn_t ds1374_irq(int irq, void *dev_id)
 269{
 270        struct i2c_client *client = dev_id;
 271        struct ds1374 *ds1374 = i2c_get_clientdata(client);
 272
 273        disable_irq_nosync(irq);
 274        schedule_work(&ds1374->work);
 275        return IRQ_HANDLED;
 276}
 277
 278static void ds1374_work(struct work_struct *work)
 279{
 280        struct ds1374 *ds1374 = container_of(work, struct ds1374, work);
 281        struct i2c_client *client = ds1374->client;
 282        int stat, control;
 283
 284        mutex_lock(&ds1374->mutex);
 285
 286        stat = i2c_smbus_read_byte_data(client, DS1374_REG_SR);
 287        if (stat < 0)
 288                goto unlock;
 289
 290        if (stat & DS1374_REG_SR_AF) {
 291                stat &= ~DS1374_REG_SR_AF;
 292                i2c_smbus_write_byte_data(client, DS1374_REG_SR, stat);
 293
 294                control = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 295                if (control < 0)
 296                        goto out;
 297
 298                control &= ~(DS1374_REG_CR_WACE | DS1374_REG_CR_AIE);
 299                i2c_smbus_write_byte_data(client, DS1374_REG_CR, control);
 300
 301                rtc_update_irq(ds1374->rtc, 1, RTC_AF | RTC_IRQF);
 302        }
 303
 304out:
 305        if (!ds1374->exiting)
 306                enable_irq(client->irq);
 307unlock:
 308        mutex_unlock(&ds1374->mutex);
 309}
 310
 311static int ds1374_alarm_irq_enable(struct device *dev, unsigned int enabled)
 312{
 313        struct i2c_client *client = to_i2c_client(dev);
 314        struct ds1374 *ds1374 = i2c_get_clientdata(client);
 315        int ret;
 316
 317        mutex_lock(&ds1374->mutex);
 318
 319        ret = i2c_smbus_read_byte_data(client, DS1374_REG_CR);
 320        if (ret < 0)
 321                goto out;
 322
 323        if (enabled) {
 324                ret |= DS1374_REG_CR_WACE | DS1374_REG_CR_AIE;
 325                ret &= ~DS1374_REG_CR_WDALM;
 326        } else {
 327                ret &= ~DS1374_REG_CR_WACE;
 328        }
 329        ret = i2c_smbus_write_byte_data(client, DS1374_REG_CR, ret);
 330
 331out:
 332        mutex_unlock(&ds1374->mutex);
 333        return ret;
 334}
 335
 336static const struct rtc_class_ops ds1374_rtc_ops = {
 337        .read_time = ds1374_read_time,
 338        .set_time = ds1374_set_time,
 339        .read_alarm = ds1374_read_alarm,
 340        .set_alarm = ds1374_set_alarm,
 341        .alarm_irq_enable = ds1374_alarm_irq_enable,
 342};
 343
 344static int ds1374_probe(struct i2c_client *client,
 345                        const struct i2c_device_id *id)
 346{
 347        struct ds1374 *ds1374;
 348        int ret;
 349
 350        ds1374 = kzalloc(sizeof(struct ds1374), GFP_KERNEL);
 351        if (!ds1374)
 352                return -ENOMEM;
 353
 354        ds1374->client = client;
 355        i2c_set_clientdata(client, ds1374);
 356
 357        INIT_WORK(&ds1374->work, ds1374_work);
 358        mutex_init(&ds1374->mutex);
 359
 360        ret = ds1374_check_rtc_status(client);
 361        if (ret)
 362                goto out_free;
 363
 364        if (client->irq > 0) {
 365                ret = request_irq(client->irq, ds1374_irq, 0,
 366                                  "ds1374", client);
 367                if (ret) {
 368                        dev_err(&client->dev, "unable to request IRQ\n");
 369                        goto out_free;
 370                }
 371
 372                device_set_wakeup_capable(&client->dev, 1);
 373        }
 374
 375        ds1374->rtc = rtc_device_register(client->name, &client->dev,
 376                                          &ds1374_rtc_ops, THIS_MODULE);
 377        if (IS_ERR(ds1374->rtc)) {
 378                ret = PTR_ERR(ds1374->rtc);
 379                dev_err(&client->dev, "unable to register the class device\n");
 380                goto out_irq;
 381        }
 382
 383        return 0;
 384
 385out_irq:
 386        if (client->irq > 0)
 387                free_irq(client->irq, client);
 388
 389out_free:
 390        kfree(ds1374);
 391        return ret;
 392}
 393
 394static int ds1374_remove(struct i2c_client *client)
 395{
 396        struct ds1374 *ds1374 = i2c_get_clientdata(client);
 397
 398        if (client->irq > 0) {
 399                mutex_lock(&ds1374->mutex);
 400                ds1374->exiting = 1;
 401                mutex_unlock(&ds1374->mutex);
 402
 403                free_irq(client->irq, client);
 404                cancel_work_sync(&ds1374->work);
 405        }
 406
 407        rtc_device_unregister(ds1374->rtc);
 408        kfree(ds1374);
 409        return 0;
 410}
 411
 412#ifdef CONFIG_PM
 413static int ds1374_suspend(struct device *dev)
 414{
 415        struct i2c_client *client = to_i2c_client(dev);
 416
 417        if (client->irq >= 0 && device_may_wakeup(&client->dev))
 418                enable_irq_wake(client->irq);
 419        return 0;
 420}
 421
 422static int ds1374_resume(struct device *dev)
 423{
 424        struct i2c_client *client = to_i2c_client(dev);
 425
 426        if (client->irq >= 0 && device_may_wakeup(&client->dev))
 427                disable_irq_wake(client->irq);
 428        return 0;
 429}
 430
 431static SIMPLE_DEV_PM_OPS(ds1374_pm, ds1374_suspend, ds1374_resume);
 432
 433#define DS1374_PM (&ds1374_pm)
 434#else
 435#define DS1374_PM NULL
 436#endif
 437
 438static struct i2c_driver ds1374_driver = {
 439        .driver = {
 440                .name = "rtc-ds1374",
 441                .owner = THIS_MODULE,
 442                .pm = DS1374_PM,
 443        },
 444        .probe = ds1374_probe,
 445        .remove = ds1374_remove,
 446        .id_table = ds1374_id,
 447};
 448
 449module_i2c_driver(ds1374_driver);
 450
 451MODULE_AUTHOR("Scott Wood <scottwood@freescale.com>");
 452MODULE_DESCRIPTION("Maxim/Dallas DS1374 RTC Driver");
 453MODULE_LICENSE("GPL");
 454
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