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         unsigned long val;
 230
 231         rc = kstrtoul(buf, 0, &val);
 232         if (rc < 0)
 233                 return rc;
 234
 235         if (!(clientdata->features & M41T80_FEATURE_SQ))
 236                 return -EINVAL;
 237
 238         if (val) {
 239                 if (!is_power_of_2(val))
 240                         return -EINVAL;
 241                 val = ilog2(val);
 242                 if (val == 15)
 243                         val = 1;
 244                 else if (val < 14)
 245                         val = 15 - val;
 246                 else
 247                         return -EINVAL;
 248         }
 249         /* disable SQW, set SQW frequency & re-enable */
 250         almon = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
 251         if (almon < 0)
 252                 return almon;
 253         reg_sqw = M41T80_REG_SQW;
 254         if (clientdata->features & M41T80_FEATURE_SQ_ALT)
 255                 reg_sqw = M41T80_REG_WDAY;
 256         sqw = i2c_smbus_read_byte_data(client, reg_sqw);
 257         if (sqw < 0)
 258                 return sqw;
 259         sqw = (sqw & 0x0f) | (val << 4);
 260
 261         rc = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
 262                                        almon & ~M41T80_ALMON_SQWE);
 263         if (rc < 0)
 264                 return rc;
 265
 266         if (val) {
 267                 rc = i2c_smbus_write_byte_data(client, reg_sqw, sqw);
 268                 if (rc < 0)
 269                         return rc;
 270
 271                 rc = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
 272                                                almon | M41T80_ALMON_SQWE);
 273                 if (rc < 0)
 274                         return rc;
 275         }
 276         return count;
 277 }
 278 static DEVICE_ATTR_RW(sqwfreq);
 279
 280 static struct attribute *attrs[] = {
 281         &dev_attr_flags.attr,
 282         &dev_attr_sqwfreq.attr,
 283         NULL,
 284 };
 285
 286 static struct attribute_group attr_group = {
 287         .attrs = attrs,
 288 };
 289
 290 #ifdef CONFIG_RTC_DRV_M41T80_WDT
 291 /*
 292  *****************************************************************************
 293  *
 294  * Watchdog Driver
 295  *
 296  *****************************************************************************
 297  */
 298 static struct i2c_client *save_client;
 299
 300 /* Default margin */
 301 #define WD_TIMO 60              /* 1..31 seconds */
 302
 303 static int wdt_margin = WD_TIMO;
 304 module_param(wdt_margin, int, 0);
 305 MODULE_PARM_DESC(wdt_margin, "Watchdog timeout in seconds (default 60s)");
 306
 307 static unsigned long wdt_is_open;
 308 static int boot_flag;
 309
 310 /**
 311  *      wdt_ping:
 312  *
 313  *      Reload counter one with the watchdog timeout. We don't bother reloading
 314  *      the cascade counter.
 315  */
 316 static void wdt_ping(void)
 317 {
 318         unsigned char i2c_data[2];
 319         struct i2c_msg msgs1[1] = {
 320                 {
 321                         .addr   = save_client->addr,
 322                         .flags  = 0,
 323                         .len    = 2,
 324                         .buf    = i2c_data,
 325                 },
 326         };
 327         struct m41t80_data *clientdata = i2c_get_clientdata(save_client);
 328
 329         i2c_data[0] = 0x09;             /* watchdog register */
 330
 331         if (wdt_margin > 31)
 332                 i2c_data[1] = (wdt_margin & 0xFC) | 0x83; /* resolution = 4s */
 333         else
 334                 /*
 335                  * WDS = 1 (0x80), mulitplier = WD_TIMO, resolution = 1s (0x02)
 336                  */
 337                 i2c_data[1] = wdt_margin << 2 | 0x82;
 338
 339         /*
 340          * M41T65 has three bits for watchdog resolution.  Don't set bit 7, as
 341          * that would be an invalid resolution.
 342          */
 343         if (clientdata->features & M41T80_FEATURE_WD)
 344                 i2c_data[1] &= ~M41T80_WATCHDOG_RB2;
 345
 346         i2c_transfer(save_client->adapter, msgs1, 1);
 347 }
 348
 349 /**
 350  *      wdt_disable:
 351  *
 352  *      disables watchdog.
 353  */
 354 static void wdt_disable(void)
 355 {
 356         unsigned char i2c_data[2], i2c_buf[0x10];
 357         struct i2c_msg msgs0[2] = {
 358                 {
 359                         .addr   = save_client->addr,
 360                         .flags  = 0,
 361                         .len    = 1,
 362                         .buf    = i2c_data,
 363                 },
 364                 {
 365                         .addr   = save_client->addr,
 366                         .flags  = I2C_M_RD,
 367                         .len    = 1,
 368                         .buf    = i2c_buf,
 369                 },
 370         };
 371         struct i2c_msg msgs1[1] = {
 372                 {
 373                         .addr   = save_client->addr,
 374                         .flags  = 0,
 375                         .len    = 2,
 376                         .buf    = i2c_data,
 377                 },
 378         };
 379
 380         i2c_data[0] = 0x09;
 381         i2c_transfer(save_client->adapter, msgs0, 2);
 382
 383         i2c_data[0] = 0x09;
 384         i2c_data[1] = 0x00;
 385         i2c_transfer(save_client->adapter, msgs1, 1);
 386 }
 387
 388 /**
 389  *      wdt_write:
 390  *      @file: file handle to the watchdog
 391  *      @buf: buffer to write (unused as data does not matter here
 392  *      @count: count of bytes
 393  *      @ppos: pointer to the position to write. No seeks allowed
 394  *
 395  *      A write to a watchdog device is defined as a keepalive signal. Any
 396  *      write of data will do, as we we don't define content meaning.
 397  */
 398 static ssize_t wdt_write(struct file *file, const char __user *buf,
 399                          size_t count, loff_t *ppos)
 400 {
 401         if (count) {
 402                 wdt_ping();
 403                 return 1;
 404         }
 405         return 0;
 406 }
 407
 408 static ssize_t wdt_read(struct file *file, char __user *buf,
 409                         size_t count, loff_t *ppos)
 410 {
 411         return 0;
 412 }
 413
 414 /**
 415  *      wdt_ioctl:
 416  *      @inode: inode of the device
 417  *      @file: file handle to the device
 418  *      @cmd: watchdog command
 419  *      @arg: argument pointer
 420  *
 421  *      The watchdog API defines a common set of functions for all watchdogs
 422  *      according to their available features. We only actually usefully support
 423  *      querying capabilities and current status.
 424  */
 425 static int wdt_ioctl(struct file *file, unsigned int cmd,
 426                      unsigned long arg)
 427 {
 428         int new_margin, rv;
 429         static struct watchdog_info ident = {
 430                 .options = WDIOF_POWERUNDER | WDIOF_KEEPALIVEPING |
 431                         WDIOF_SETTIMEOUT,
 432                 .firmware_version = 1,
 433                 .identity = "M41T80 WTD"
 434         };
 435
 436         switch (cmd) {
 437         case WDIOC_GETSUPPORT:
 438                 return copy_to_user((struct watchdog_info __user *)arg, &ident,
 439                                     sizeof(ident)) ? -EFAULT : 0;
 440
 441         case WDIOC_GETSTATUS:
 442         case WDIOC_GETBOOTSTATUS:
 443                 return put_user(boot_flag, (int __user *)arg);
 444         case WDIOC_KEEPALIVE:
 445                 wdt_ping();
 446                 return 0;
 447         case WDIOC_SETTIMEOUT:
 448                 if (get_user(new_margin, (int __user *)arg))
 449                         return -EFAULT;
 450                 /* Arbitrary, can't find the card's limits */
 451                 if (new_margin < 1 || new_margin > 124)
 452                         return -EINVAL;
 453                 wdt_margin = new_margin;
 454                 wdt_ping();
 455                 /* Fall */
 456         case WDIOC_GETTIMEOUT:
 457                 return put_user(wdt_margin, (int __user *)arg);
 458
 459         case WDIOC_SETOPTIONS:
 460                 if (copy_from_user(&rv, (int __user *)arg, sizeof(int)))
 461                         return -EFAULT;
 462
 463                 if (rv & WDIOS_DISABLECARD) {
 464                         pr_info("disable watchdog\n");
 465                         wdt_disable();
 466                 }
 467
 468                 if (rv & WDIOS_ENABLECARD) {
 469                         pr_info("enable watchdog\n");
 470                         wdt_ping();
 471                 }
 472
 473                 return -EINVAL;
 474         }
 475         return -ENOTTY;
 476 }
 477
 478 static long wdt_unlocked_ioctl(struct file *file, unsigned int cmd,
 479                                unsigned long arg)
 480 {
 481         int ret;
 482
 483         mutex_lock(&m41t80_rtc_mutex);
 484         ret = wdt_ioctl(file, cmd, arg);
 485         mutex_unlock(&m41t80_rtc_mutex);
 486
 487         return ret;
 488 }
 489
 490 /**
 491  *      wdt_open:
 492  *      @inode: inode of device
 493  *      @file: file handle to device
 494  *
 495  */
 496 static int wdt_open(struct inode *inode, struct file *file)
 497 {
 498         if (MINOR(inode->i_rdev) == WATCHDOG_MINOR) {
 499                 mutex_lock(&m41t80_rtc_mutex);
 500                 if (test_and_set_bit(0, &wdt_is_open)) {
 501                         mutex_unlock(&m41t80_rtc_mutex);
 502                         return -EBUSY;
 503                 }
 504                 /*
 505                  *      Activate
 506                  */
 507                 wdt_is_open = 1;
 508                 mutex_unlock(&m41t80_rtc_mutex);
 509                 return nonseekable_open(inode, file);
 510         }
 511         return -ENODEV;
 512 }
 513
 514 /**
 515  *      wdt_close:
 516  *      @inode: inode to board
 517  *      @file: file handle to board
 518  *
 519  */
 520 static int wdt_release(struct inode *inode, struct file *file)
 521 {
 522         if (MINOR(inode->i_rdev) == WATCHDOG_MINOR)
 523                 clear_bit(0, &wdt_is_open);
 524         return 0;
 525 }
 526
 527 /**
 528  *      notify_sys:
 529  *      @this: our notifier block
 530  *      @code: the event being reported
 531  *      @unused: unused
 532  *
 533  *      Our notifier is called on system shutdowns. We want to turn the card
 534  *      off at reboot otherwise the machine will reboot again during memory
 535  *      test or worse yet during the following fsck. This would suck, in fact
 536  *      trust me - if it happens it does suck.
 537  */
 538 static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
 539                           void *unused)
 540 {
 541         if (code == SYS_DOWN || code == SYS_HALT)
 542                 /* Disable Watchdog */
 543                 wdt_disable();
 544         return NOTIFY_DONE;
 545 }
 546
 547 static const struct file_operations wdt_fops = {
 548         .owner  = THIS_MODULE,
 549         .read   = wdt_read,
 550         .unlocked_ioctl = wdt_unlocked_ioctl,
 551         .write  = wdt_write,
 552         .open   = wdt_open,
 553         .release = wdt_release,
 554         .llseek = no_llseek,
 555 };
 556
 557 static struct miscdevice wdt_dev = {
 558         .minor = WATCHDOG_MINOR,
 559         .name = "watchdog",
 560         .fops = &wdt_fops,
 561 };
 562
 563 /*
 564  *      The WDT card needs to learn about soft shutdowns in order to
 565  *      turn the timebomb registers off.
 566  */
 567 static struct notifier_block wdt_notifier = {
 568         .notifier_call = wdt_notify_sys,
 569 };
 570 #endif /* CONFIG_RTC_DRV_M41T80_WDT */
 571
 572 /*
 573  *****************************************************************************
 574  *
 575  *      Driver Interface
 576  *
 577  *****************************************************************************
 578  */
 579
 580 static void m41t80_remove_sysfs_group(void *_dev)
 581 {
 582         struct device *dev = _dev;
 583
 584         sysfs_remove_group(&dev->kobj, &attr_group);
 585 }
 586
 587 static int m41t80_probe(struct i2c_client *client,
 588                         const struct i2c_device_id *id)
 589 {
 590         struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);
 591         int rc = 0;
 592         struct rtc_device *rtc = NULL;
 593         struct rtc_time tm;
 594         struct m41t80_data *clientdata = NULL;
 595
 596         if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_I2C_BLOCK |
 597                                      I2C_FUNC_SMBUS_BYTE_DATA)) {
 598                 dev_err(&adapter->dev, "doesn't support I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_I2C_BLOCK\n");
 599                 return -ENODEV;
 600         }
 601
 602         clientdata = devm_kzalloc(&client->dev, sizeof(*clientdata),
 603                                   GFP_KERNEL);
 604         if (!clientdata)
 605                 return -ENOMEM;
 606
 607         clientdata->features = id->driver_data;
 608         i2c_set_clientdata(client, clientdata);
 609
 610         rtc = devm_rtc_device_register(&client->dev, client->name,
 611                                        &m41t80_rtc_ops, THIS_MODULE);
 612         if (IS_ERR(rtc))
 613                 return PTR_ERR(rtc);
 614
 615         clientdata->rtc = rtc;
 616
 617         /* Make sure HT (Halt Update) bit is cleared */
 618         rc = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_HOUR);
 619
 620         if (rc >= 0 && rc & M41T80_ALHOUR_HT) {
 621                 if (clientdata->features & M41T80_FEATURE_HT) {
 622                         m41t80_get_datetime(client, &tm);
 623                         dev_info(&client->dev, "HT bit was set!\n");
 624                         dev_info(&client->dev,
 625                                  "Power Down at %04i-%02i-%02i %02i:%02i:%02i\n",
 626                                  tm.tm_year + 1900,
 627                                  tm.tm_mon + 1, tm.tm_mday, tm.tm_hour,
 628                                  tm.tm_min, tm.tm_sec);
 629                 }
 630                 rc = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_HOUR,
 631                                                rc & ~M41T80_ALHOUR_HT);
 632         }
 633
 634         if (rc < 0) {
 635                 dev_err(&client->dev, "Can't clear HT bit\n");
 636                 return rc;
 637         }
 638
 639         /* Make sure ST (stop) bit is cleared */
 640         rc = i2c_smbus_read_byte_data(client, M41T80_REG_SEC);
 641
 642         if (rc >= 0 && rc & M41T80_SEC_ST)
 643                 rc = i2c_smbus_write_byte_data(client, M41T80_REG_SEC,
 644                                                rc & ~M41T80_SEC_ST);
 645         if (rc < 0) {
 646                 dev_err(&client->dev, "Can't clear ST bit\n");
 647                 return rc;
 648         }
 649
 650         /* Export sysfs entries */
 651         rc = sysfs_create_group(&(&client->dev)->kobj, &attr_group);
 652         if (rc) {
 653                 dev_err(&client->dev, "Failed to create sysfs group: %d\n", rc);
 654                 return rc;
 655         }
 656
 657         rc = devm_add_action(&client->dev, m41t80_remove_sysfs_group,
 658                              &client->dev);
 659         if (rc) {
 660                 m41t80_remove_sysfs_group(&client->dev);
 661                 dev_err(&client->dev,
 662                         "Failed to add sysfs cleanup action: %d\n", rc);
 663                 return rc;
 664         }
 665
 666 #ifdef CONFIG_RTC_DRV_M41T80_WDT
 667         if (clientdata->features & M41T80_FEATURE_HT) {
 668                 save_client = client;
 669                 rc = misc_register(&wdt_dev);
 670                 if (rc)
 671                         return rc;
 672                 rc = register_reboot_notifier(&wdt_notifier);
 673                 if (rc) {
 674                         misc_deregister(&wdt_dev);
 675                         return rc;
 676                 }
 677         }
 678 #endif
 679         return 0;
 680 }
 681
 682 static int m41t80_remove(struct i2c_client *client)
 683 {
 684 #ifdef CONFIG_RTC_DRV_M41T80_WDT
 685         struct m41t80_data *clientdata = i2c_get_clientdata(client);
 686
 687         if (clientdata->features & M41T80_FEATURE_HT) {
 688                 misc_deregister(&wdt_dev);
 689                 unregister_reboot_notifier(&wdt_notifier);
 690         }
 691 #endif
 692
 693         return 0;
 694 }
 695
 696 static struct i2c_driver m41t80_driver = {
 697         .driver = {
 698                 .name = "rtc-m41t80",
 699         },
 700         .probe = m41t80_probe,
 701         .remove = m41t80_remove,
 702         .id_table = m41t80_id,
 703 };
 704
 705 module_i2c_driver(m41t80_driver);
 706
 707 MODULE_AUTHOR("Alexander Bigga <ab@mycable.de>");
 708 MODULE_DESCRIPTION("ST Microelectronics M41T80 series RTC I2C Client Driver");
 709 MODULE_LICENSE("GPL");