drivers/rtc/rtc-m41t80.c

   1 /*
   2  * I2C client/driver for the ST M41T80 family of i2c rtc chips.
   3  *
   4  * Author: Alexander Bigga <ab@mycable.de>
   5  *
   6  * Based on m41t00.c by Mark A. Greer <mgreer@mvista.com>
   7  *
   8  * 2006 (c) mycable GmbH
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License version 2 as
  12  * published by the Free Software Foundation.
  13  *
  14  */
  15
  16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  17
  18 #include <linux/bcd.h>
  19 #include <linux/i2c.h>
  20 #include <linux/init.h>
  21 #include <linux/kernel.h>
  22 #include <linux/module.h>
  23 #include <linux/rtc.h>
  24 #include <linux/slab.h>
  25 #include <linux/mutex.h>
  26 #include <linux/string.h>
  27 #ifdef CONFIG_RTC_DRV_M41T80_WDT
  28 #include <linux/fs.h>
  29 #include <linux/ioctl.h>
  30 #include <linux/miscdevice.h>
  31 #include <linux/reboot.h>
  32 #include <linux/watchdog.h>
  33 #endif
  34
  35 #define M41T80_REG_SSEC         0x00
  36 #define M41T80_REG_SEC          0x01
  37 #define M41T80_REG_MIN          0x02
  38 #define M41T80_REG_HOUR         0x03
  39 #define M41T80_REG_WDAY         0x04
  40 #define M41T80_REG_DAY          0x05
  41 #define M41T80_REG_MON          0x06
  42 #define M41T80_REG_YEAR         0x07
  43 #define M41T80_REG_ALARM_MON    0x0a
  44 #define M41T80_REG_ALARM_DAY    0x0b
  45 #define M41T80_REG_ALARM_HOUR   0x0c
  46 #define M41T80_REG_ALARM_MIN    0x0d
  47 #define M41T80_REG_ALARM_SEC    0x0e
  48 #define M41T80_REG_FLAGS        0x0f
  49 #define M41T80_REG_SQW          0x13
  50
  51 #define M41T80_DATETIME_REG_SIZE        (M41T80_REG_YEAR + 1)
  52 #define M41T80_ALARM_REG_SIZE   \
  53         (M41T80_REG_ALARM_SEC + 1 - M41T80_REG_ALARM_MON)
  54
  55 #define M41T80_SEC_ST           BIT(7)  /* ST: Stop Bit */
  56 #define M41T80_ALMON_AFE        BIT(7)  /* AFE: AF Enable Bit */
  57 #define M41T80_ALMON_SQWE       BIT(6)  /* SQWE: SQW Enable Bit */
  58 #define M41T80_ALHOUR_HT        BIT(6)  /* HT: Halt Update Bit */
  59 #define M41T80_FLAGS_AF         BIT(6)  /* AF: Alarm Flag Bit */
  60 #define M41T80_FLAGS_BATT_LOW   BIT(4)  /* BL: Battery Low Bit */
  61 #define M41T80_WATCHDOG_RB2     BIT(7)  /* RB: Watchdog resolution */
  62 #define M41T80_WATCHDOG_RB1     BIT(1)  /* RB: Watchdog resolution */
  63 #define M41T80_WATCHDOG_RB0     BIT(0)  /* RB: Watchdog resolution */
  64
  65 #define M41T80_FEATURE_HT       BIT(0)  /* Halt feature */
  66 #define M41T80_FEATURE_BL       BIT(1)  /* Battery low indicator */
  67 #define M41T80_FEATURE_SQ       BIT(2)  /* Squarewave feature */
  68 #define M41T80_FEATURE_WD       BIT(3)  /* Extra watchdog resolution */
  69 #define M41T80_FEATURE_SQ_ALT   BIT(4)  /* RSx bits are in reg 4 */
  70
  71 static DEFINE_MUTEX(m41t80_rtc_mutex);
  72 static const struct i2c_device_id m41t80_id[] = {
  73         { "m41t62", M41T80_FEATURE_SQ | M41T80_FEATURE_SQ_ALT },
  74         { "m41t65", M41T80_FEATURE_HT | M41T80_FEATURE_WD },
  75         { "m41t80", M41T80_FEATURE_SQ },
  76         { "m41t81", M41T80_FEATURE_HT | M41T80_FEATURE_SQ},
  77         { "m41t81s", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
  78         { "m41t82", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
  79         { "m41t83", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
  80         { "m41st84", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
  81         { "m41st85", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
  82         { "m41st87", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
  83         { "rv4162", M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT },
  84         { }
  85 };
  86 MODULE_DEVICE_TABLE(i2c, m41t80_id);
  87
  88 struct m41t80_data {
  89         u8 features;
  90         struct rtc_device *rtc;
  91 };
  92
  93 static int m41t80_get_datetime(struct i2c_client *client,
  94                                struct rtc_time *tm)
  95 {
  96         unsigned char buf[8];
  97         int err;
  98
  99         err = i2c_smbus_read_i2c_block_data(client, M41T80_REG_SSEC,
 100                                             sizeof(buf), buf);
 101         if (err < 0) {
 102                 dev_err(&client->dev, "Unable to read date\n");
 103                 return -EIO;
 104         }
 105
 106         tm->tm_sec = bcd2bin(buf[M41T80_REG_SEC] & 0x7f);
 107         tm->tm_min = bcd2bin(buf[M41T80_REG_MIN] & 0x7f);
 108         tm->tm_hour = bcd2bin(buf[M41T80_REG_HOUR] & 0x3f);
 109         tm->tm_mday = bcd2bin(buf[M41T80_REG_DAY] & 0x3f);
 110         tm->tm_wday = buf[M41T80_REG_WDAY] & 0x07;
 111         tm->tm_mon = bcd2bin(buf[M41T80_REG_MON] & 0x1f) - 1;
 112
 113         /* assume 20YY not 19YY, and ignore the Century Bit */
 114         tm->tm_year = bcd2bin(buf[M41T80_REG_YEAR]) + 100;
 115         return rtc_valid_tm(tm);
 116 }
 117
 118 /* Sets the given date and time to the real time clock. */
 119 static int m41t80_set_datetime(struct i2c_client *client, struct rtc_time *tm)
 120 {
 121         unsigned char buf[8];
 122         int err;
 123
 124         if (tm->tm_year < 100 || tm->tm_year > 199)
 125                 return -EINVAL;
 126
 127         buf[M41T80_REG_SSEC] = 0;
 128         buf[M41T80_REG_SEC] = bin2bcd(tm->tm_sec);
 129         buf[M41T80_REG_MIN] = bin2bcd(tm->tm_min);
 130         buf[M41T80_REG_HOUR] = bin2bcd(tm->tm_hour);
 131         buf[M41T80_REG_DAY] = bin2bcd(tm->tm_mday);
 132         buf[M41T80_REG_MON] = bin2bcd(tm->tm_mon + 1);
 133         buf[M41T80_REG_YEAR] = bin2bcd(tm->tm_year - 100);
 134         buf[M41T80_REG_WDAY] = tm->tm_wday;
 135
 136         err = i2c_smbus_write_i2c_block_data(client, M41T80_REG_SSEC,
 137                                              sizeof(buf), buf);
 138         if (err < 0) {
 139                 dev_err(&client->dev, "Unable to write to date registers\n");
 140                 return err;
 141         }
 142
 143         return err;
 144 }
 145
 146 static int m41t80_rtc_proc(struct device *dev, struct seq_file *seq)
 147 {
 148         struct i2c_client *client = to_i2c_client(dev);
 149         struct m41t80_data *clientdata = i2c_get_clientdata(client);
 150         u8 reg;
 151
 152         if (clientdata->features & M41T80_FEATURE_BL) {
 153                 reg = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
 154                 seq_printf(seq, "battery\t\t: %s\n",
 155                            (reg & M41T80_FLAGS_BATT_LOW) ? "exhausted" : "ok");
 156         }
 157         return 0;
 158 }
 159
 160 static int m41t80_rtc_read_time(struct device *dev, struct rtc_time *tm)
 161 {
 162         return m41t80_get_datetime(to_i2c_client(dev), tm);
 163 }
 164
 165 static int m41t80_rtc_set_time(struct device *dev, struct rtc_time *tm)
 166 {
 167         return m41t80_set_datetime(to_i2c_client(dev), tm);
 168 }
 169
 170 /*
 171  * XXX - m41t80 alarm functionality is reported broken.
 172  * until it is fixed, don't register alarm functions.
 173  */
 174 static struct rtc_class_ops m41t80_rtc_ops = {
 175         .read_time = m41t80_rtc_read_time,
 176         .set_time = m41t80_rtc_set_time,
 177         .proc = m41t80_rtc_proc,
 178 };
 179
 180 static ssize_t flags_show(struct device *dev,
 181                           struct device_attribute *attr, char *buf)
 182 {
 183         struct i2c_client *client = to_i2c_client(dev);
 184         int val;
 185
 186         val = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
 187         if (val < 0)
 188                 return val;
 189         return sprintf(buf, "%#x\n", val);
 190 }
 191 static DEVICE_ATTR_RO(flags);
 192
 193 static ssize_t sqwfreq_show(struct device *dev,
 194                             struct device_attribute *attr, char *buf)
 195 {
 196         struct i2c_client *client = to_i2c_client(dev);
 197         struct m41t80_data *clientdata = i2c_get_clientdata(client);
 198         int val, reg_sqw;
 199
 200         if (!(clientdata->features & M41T80_FEATURE_SQ))
 201                 return -EINVAL;
 202
 203         reg_sqw = M41T80_REG_SQW;
 204         if (clientdata->features & M41T80_FEATURE_SQ_ALT)
 205                 reg_sqw = M41T80_REG_WDAY;
 206         val = i2c_smbus_read_byte_data(client, reg_sqw);
 207         if (val < 0)
 208                 return val;
 209         val = (val >> 4) & 0xf;
 210         switch (val) {
 211         case 0:
 212                 break;
 213         case 1:
 214                 val = 32768;
 215                 break;
 216         default:
 217                 val = 32768 >> val;
 218         }
 219         return sprintf(buf, "%d\n", val);
 220 }
 221
 222 static ssize_t sqwfreq_store(struct device *dev,
 223                              struct device_attribute *attr,
 224                              const char *buf, size_t count)
 225 {
 226         struct i2c_client *client = to_i2c_client(dev);
 227         struct m41t80_data *clientdata = i2c_get_clientdata(client);
 228         int almon, sqw, reg_sqw, rc;
 229         int val = simple_strtoul(buf, NULL, 0);
 230
 231         if (!(clientdata->features & M41T80_FEATURE_SQ))
 232                 return -EINVAL;
 233
 234         if (val) {
 235                 if (!is_power_of_2(val))
 236                         return -EINVAL;
 237                 val = ilog2(val);
 238                 if (val == 15)
 239                         val = 1;
 240                 else if (val < 14)
 241                         val = 15 - val;
 242                 else
 243                         return -EINVAL;
 244         }
 245         /* disable SQW, set SQW frequency & re-enable */
 246         almon = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
 247         if (almon < 0)
 248                 return almon;
 249         reg_sqw = M41T80_REG_SQW;
 250         if (clientdata->features & M41T80_FEATURE_SQ_ALT)
 251                 reg_sqw = M41T80_REG_WDAY;
 252         sqw = i2c_smbus_read_byte_data(client, reg_sqw);
 253         if (sqw < 0)
 254                 return sqw;
 255         sqw = (sqw & 0x0f) | (val << 4);
 256
 257         rc = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
 258                                       almon & ~M41T80_ALMON_SQWE);
 259         if (rc < 0)
 260                 return rc;
 261
 262         if (val) {
 263                 rc = i2c_smbus_write_byte_data(client, reg_sqw, sqw);
 264                 if (rc < 0)
 265                         return rc;
 266
 267                 rc = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
 268                                              almon | M41T80_ALMON_SQWE);
 269                 if (rc <0)
 270                         return rc;
 271         }
 272         return count;
 273 }
 274 static DEVICE_ATTR_RW(sqwfreq);
 275
 276 static struct attribute *attrs[] = {
 277         &dev_attr_flags.attr,
 278         &dev_attr_sqwfreq.attr,
 279         NULL,
 280 };
 281 static struct attribute_group attr_group = {
 282         .attrs = attrs,
 283 };
 284
 285 #ifdef CONFIG_RTC_DRV_M41T80_WDT
 286 /*
 287  *****************************************************************************
 288  *
 289  * Watchdog Driver
 290  *
 291  *****************************************************************************
 292  */
 293 static struct i2c_client *save_client;
 294
 295 /* Default margin */
 296 #define WD_TIMO 60              /* 1..31 seconds */
 297
 298 static int wdt_margin = WD_TIMO;
 299 module_param(wdt_margin, int, 0);
 300 MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default 60s)");
 301
 302 static unsigned long wdt_is_open;
 303 static int boot_flag;
 304
 305 /**
 306  *      wdt_ping:
 307  *
 308  *      Reload counter one with the watchdog timeout. We don't bother reloading
 309  *      the cascade counter.
 310  */
 311 static void wdt_ping(void)
 312 {
 313         unsigned char i2c_data[2];
 314         struct i2c_msg msgs1[1] = {
 315                 {
 316                         .addr   = save_client->addr,
 317                         .flags  = 0,
 318                         .len    = 2,
 319                         .buf    = i2c_data,
 320                 },
 321         };
 322         struct m41t80_data *clientdata = i2c_get_clientdata(save_client);
 323
 324         i2c_data[0] = 0x09;             /* watchdog register */
 325
 326         if (wdt_margin > 31)
 327                 i2c_data[1] = (wdt_margin & 0xFC) | 0x83; /* resolution = 4s */
 328         else
 329                 /*
 330                  * WDS = 1 (0x80), mulitplier = WD_TIMO, resolution = 1s (0x02)
 331                  */
 332                 i2c_data[1] = wdt_margin<<2 | 0x82;
 333
 334         /*
 335          * M41T65 has three bits for watchdog resolution.  Don't set bit 7, as
 336          * that would be an invalid resolution.
 337          */
 338         if (clientdata->features & M41T80_FEATURE_WD)
 339                 i2c_data[1] &= ~M41T80_WATCHDOG_RB2;
 340
 341         i2c_transfer(save_client->adapter, msgs1, 1);
 342 }
 343
 344 /**
 345  *      wdt_disable:
 346  *
 347  *      disables watchdog.
 348  */
 349 static void wdt_disable(void)
 350 {
 351         unsigned char i2c_data[2], i2c_buf[0x10];
 352         struct i2c_msg msgs0[2] = {
 353                 {
 354                         .addr   = save_client->addr,
 355                         .flags  = 0,
 356                         .len    = 1,
 357                         .buf    = i2c_data,
 358                 },
 359                 {
 360                         .addr   = save_client->addr,
 361                         .flags  = I2C_M_RD,
 362                         .len    = 1,
 363                         .buf    = i2c_buf,
 364                 },
 365         };
 366         struct i2c_msg msgs1[1] = {
 367                 {
 368                         .addr   = save_client->addr,
 369                         .flags  = 0,
 370                         .len    = 2,
 371                         .buf    = i2c_data,
 372                 },
 373         };
 374
 375         i2c_data[0] = 0x09;
 376         i2c_transfer(save_client->adapter, msgs0, 2);
 377
 378         i2c_data[0] = 0x09;
 379         i2c_data[1] = 0x00;
 380         i2c_transfer(save_client->adapter, msgs1, 1);
 381 }
 382
 383 /**
 384  *      wdt_write:
 385  *      @file: file handle to the watchdog
 386  *      @buf: buffer to write (unused as data does not matter here
 387  *      @count: count of bytes
 388  *      @ppos: pointer to the position to write. No seeks allowed
 389  *
 390  *      A write to a watchdog device is defined as a keepalive signal. Any
 391  *      write of data will do, as we we don't define content meaning.
 392  */
 393 static ssize_t wdt_write(struct file *file, const char __user *buf,
 394                          size_t count, loff_t *ppos)
 395 {
 396         if (count) {
 397                 wdt_ping();
 398                 return 1;
 399         }
 400         return 0;
 401 }
 402
 403 static ssize_t wdt_read(struct file *file, char __user *buf,
 404                         size_t count, loff_t *ppos)
 405 {
 406         return 0;
 407 }
 408
 409 /**
 410  *      wdt_ioctl:
 411  *      @inode: inode of the device
 412  *      @file: file handle to the device
 413  *      @cmd: watchdog command
 414  *      @arg: argument pointer
 415  *
 416  *      The watchdog API defines a common set of functions for all watchdogs
 417  *      according to their available features. We only actually usefully support
 418  *      querying capabilities and current status.
 419  */
 420 static int wdt_ioctl(struct file *file, unsigned int cmd,
 421                      unsigned long arg)
 422 {
 423         int new_margin, rv;
 424         static struct watchdog_info ident = {
 425                 .options = WDIOF_POWERUNDER | WDIOF_KEEPALIVEPING |
 426                         WDIOF_SETTIMEOUT,
 427                 .firmware_version = 1,
 428                 .identity = "M41T80 WTD"
 429         };
 430
 431         switch (cmd) {
 432         case WDIOC_GETSUPPORT:
 433                 return copy_to_user((struct watchdog_info __user *)arg, &ident,
 434                                     sizeof(ident)) ? -EFAULT : 0;
 435
 436         case WDIOC_GETSTATUS:
 437         case WDIOC_GETBOOTSTATUS:
 438                 return put_user(boot_flag, (int __user *)arg);
 439         case WDIOC_KEEPALIVE:
 440                 wdt_ping();
 441                 return 0;
 442         case WDIOC_SETTIMEOUT:
 443                 if (get_user(new_margin, (int __user *)arg))
 444                         return -EFAULT;
 445                 /* Arbitrary, can't find the card's limits */
 446                 if (new_margin < 1 || new_margin > 124)
 447                         return -EINVAL;
 448                 wdt_margin = new_margin;
 449                 wdt_ping();
 450                 /* Fall */
 451         case WDIOC_GETTIMEOUT:
 452                 return put_user(wdt_margin, (int __user *)arg);
 453
 454         case WDIOC_SETOPTIONS:
 455                 if (copy_from_user(&rv, (int __user *)arg, sizeof(int)))
 456                         return -EFAULT;
 457
 458                 if (rv & WDIOS_DISABLECARD) {
 459                         pr_info("disable watchdog\n");
 460                         wdt_disable();
 461                 }
 462
 463                 if (rv & WDIOS_ENABLECARD) {
 464                         pr_info("enable watchdog\n");
 465                         wdt_ping();
 466                 }
 467
 468                 return -EINVAL;
 469         }
 470         return -ENOTTY;
 471 }
 472
 473 static long wdt_unlocked_ioctl(struct file *file, unsigned int cmd,
 474                                unsigned long arg)
 475 {
 476         int ret;
 477
 478         mutex_lock(&m41t80_rtc_mutex);
 479         ret = wdt_ioctl(file, cmd, arg);
 480         mutex_unlock(&m41t80_rtc_mutex);
 481
 482         return ret;
 483 }
 484
 485 /**
 486  *      wdt_open:
 487  *      @inode: inode of device
 488  *      @file: file handle to device
 489  *
 490  */
 491 static int wdt_open(struct inode *inode, struct file *file)
 492 {
 493         if (MINOR(inode->i_rdev) == WATCHDOG_MINOR) {
 494                 mutex_lock(&m41t80_rtc_mutex);
 495                 if (test_and_set_bit(0, &wdt_is_open)) {
 496                         mutex_unlock(&m41t80_rtc_mutex);
 497                         return -EBUSY;
 498                 }
 499                 /*
 500                  *      Activate
 501                  */
 502                 wdt_is_open = 1;
 503                 mutex_unlock(&m41t80_rtc_mutex);
 504                 return nonseekable_open(inode, file);
 505         }
 506         return -ENODEV;
 507 }
 508
 509 /**
 510  *      wdt_close:
 511  *      @inode: inode to board
 512  *      @file: file handle to board
 513  *
 514  */
 515 static int wdt_release(struct inode *inode, struct file *file)
 516 {
 517         if (MINOR(inode->i_rdev) == WATCHDOG_MINOR)
 518                 clear_bit(0, &wdt_is_open);
 519         return 0;
 520 }
 521
 522 /**
 523  *      notify_sys:
 524  *      @this: our notifier block
 525  *      @code: the event being reported
 526  *      @unused: unused
 527  *
 528  *      Our notifier is called on system shutdowns. We want to turn the card
 529  *      off at reboot otherwise the machine will reboot again during memory
 530  *      test or worse yet during the following fsck. This would suck, in fact
 531  *      trust me - if it happens it does suck.
 532  */
 533 static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
 534                           void *unused)
 535 {
 536         if (code == SYS_DOWN || code == SYS_HALT)
 537                 /* Disable Watchdog */
 538                 wdt_disable();
 539         return NOTIFY_DONE;
 540 }
 541
 542 static const struct file_operations wdt_fops = {
 543         .owner  = THIS_MODULE,
 544         .read   = wdt_read,
 545         .unlocked_ioctl = wdt_unlocked_ioctl,
 546         .write  = wdt_write,
 547         .open   = wdt_open,
 548         .release = wdt_release,
 549         .llseek = no_llseek,
 550 };
 551
 552 static struct miscdevice wdt_dev = {
 553         .minor = WATCHDOG_MINOR,
 554         .name = "watchdog",
 555         .fops = &wdt_fops,
 556 };
 557
 558 /*
 559  *      The WDT card needs to learn about soft shutdowns in order to
 560  *      turn the timebomb registers off.
 561  */
 562 static struct notifier_block wdt_notifier = {
 563         .notifier_call = wdt_notify_sys,
 564 };
 565 #endif /* CONFIG_RTC_DRV_M41T80_WDT */
 566
 567 /*
 568  *****************************************************************************
 569  *
 570  *      Driver Interface
 571  *
 572  *****************************************************************************
 573  */
 574
 575 static void m41t80_remove_sysfs_group(void *_dev)
 576 {
 577         struct device *dev = _dev;
 578
 579         sysfs_remove_group(&dev->kobj, &attr_group);
 580 }
 581
 582 static int m41t80_probe(struct i2c_client *client,
 583                         const struct i2c_device_id *id)
 584 {
 585         struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);
 586         int rc = 0;
 587         struct rtc_device *rtc = NULL;
 588         struct rtc_time tm;
 589         struct m41t80_data *clientdata = NULL;
 590
 591         if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_I2C_BLOCK |
 592                                      I2C_FUNC_SMBUS_BYTE_DATA)) {
 593                 dev_err(&adapter->dev, "doesn't support I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_I2C_BLOCK\n");
 594                 return -ENODEV;
 595         }
 596
 597         clientdata = devm_kzalloc(&client->dev, sizeof(*clientdata),
 598                                 GFP_KERNEL);
 599         if (!clientdata)
 600                 return -ENOMEM;
 601
 602         clientdata->features = id->driver_data;
 603         i2c_set_clientdata(client, clientdata);
 604
 605         rtc = devm_rtc_device_register(&client->dev, client->name,
 606                                         &m41t80_rtc_ops, THIS_MODULE);
 607         if (IS_ERR(rtc))
 608                 return PTR_ERR(rtc);
 609
 610         clientdata->rtc = rtc;
 611
 612         /* Make sure HT (Halt Update) bit is cleared */
 613         rc = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_HOUR);
 614
 615         if (rc >= 0 && rc & M41T80_ALHOUR_HT) {
 616                 if (clientdata->features & M41T80_FEATURE_HT) {
 617                         m41t80_get_datetime(client, &tm);
 618                         dev_info(&client->dev, "HT bit was set!\n");
 619                         dev_info(&client->dev,
 620                                  "Power Down at "
 621                                  "%04i-%02i-%02i %02i:%02i:%02i\n",
 622                                  tm.tm_year + 1900,
 623                                  tm.tm_mon + 1, tm.tm_mday, tm.tm_hour,
 624                                  tm.tm_min, tm.tm_sec);
 625                 }
 626                 rc = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_HOUR,
 627                                               rc & ~M41T80_ALHOUR_HT);
 628         }
 629
 630         if (rc < 0) {
 631                 dev_err(&client->dev, "Can't clear HT bit\n");
 632                 return rc;
 633         }
 634
 635         /* Make sure ST (stop) bit is cleared */
 636         rc = i2c_smbus_read_byte_data(client, M41T80_REG_SEC);
 637
 638         if (rc >= 0 && rc & M41T80_SEC_ST)
 639                 rc = i2c_smbus_write_byte_data(client, M41T80_REG_SEC,
 640                                               rc & ~M41T80_SEC_ST);
 641         if (rc < 0) {
 642                 dev_err(&client->dev, "Can't clear ST bit\n");
 643                 return rc;
 644         }
 645
 646         /* Export sysfs entries */
 647         rc = sysfs_create_group(&(&client->dev)->kobj, &attr_group);
 648         if (rc) {
 649                 dev_err(&client->dev, "Failed to create sysfs group: %d\n", rc);
 650                 return rc;
 651         }
 652
 653         rc = devm_add_action(&client->dev, m41t80_remove_sysfs_group,
 654                              &client->dev);
 655         if (rc) {
 656                 m41t80_remove_sysfs_group(&client->dev);
 657                 dev_err(&client->dev,
 658                         "Failed to add sysfs cleanup action: %d\n", rc);
 659                 return rc;
 660         }
 661
 662 #ifdef CONFIG_RTC_DRV_M41T80_WDT
 663         if (clientdata->features & M41T80_FEATURE_HT) {
 664                 save_client = client;
 665                 rc = misc_register(&wdt_dev);
 666                 if (rc)
 667                         return rc;
 668                 rc = register_reboot_notifier(&wdt_notifier);
 669                 if (rc) {
 670                         misc_deregister(&wdt_dev);
 671                         return rc;
 672                 }
 673         }
 674 #endif
 675         return 0;
 676 }
 677
 678 static int m41t80_remove(struct i2c_client *client)
 679 {
 680 #ifdef CONFIG_RTC_DRV_M41T80_WDT
 681         struct m41t80_data *clientdata = i2c_get_clientdata(client);
 682
 683         if (clientdata->features & M41T80_FEATURE_HT) {
 684                 misc_deregister(&wdt_dev);
 685                 unregister_reboot_notifier(&wdt_notifier);
 686         }
 687 #endif
 688
 689         return 0;
 690 }
 691
 692 static struct i2c_driver m41t80_driver = {
 693         .driver = {
 694                 .name = "rtc-m41t80",
 695         },
 696         .probe = m41t80_probe,
 697         .remove = m41t80_remove,
 698         .id_table = m41t80_id,
 699 };
 700
 701 module_i2c_driver(m41t80_driver);
 702
 703 MODULE_AUTHOR("Alexander Bigga <ab@mycable.de>");
 704 MODULE_DESCRIPTION("ST Microelectronics M41T80 series RTC I2C Client Driver");
 705 MODULE_LICENSE("GPL");