drivers/rtc/rtc-ds1305.c

   1 /*
   2  * rtc-ds1305.c -- driver for DS1305 and DS1306 SPI RTC chips
   3  *
   4  * Copyright (C) 2008 David Brownell
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  */
  11 #include <linux/kernel.h>
  12 #include <linux/init.h>
  13 #include <linux/bcd.h>
  14 #include <linux/rtc.h>
  15 #include <linux/workqueue.h>
  16
  17 #include <linux/spi/spi.h>
  18 #include <linux/spi/ds1305.h>
  19
  20
  21 /*
  22  * Registers ... mask DS1305_WRITE into register address to write,
  23  * otherwise you're reading it.  All non-bitmask values are BCD.
  24  */
  25 #define DS1305_WRITE            0x80
  26
  27
  28 /* RTC date/time ... the main special cases are that we:
  29  *  - Need fancy "hours" encoding in 12hour mode
  30  *  - Don't rely on the "day-of-week" field (or tm_wday)
  31  *  - Are a 21st-century clock (2000 <= year < 2100)
  32  */
  33 #define DS1305_RTC_LEN          7               /* bytes for RTC regs */
  34
  35 #define DS1305_SEC              0x00            /* register addresses */
  36 #define DS1305_MIN              0x01
  37 #define DS1305_HOUR             0x02
  38 #       define DS1305_HR_12             0x40    /* set == 12 hr mode */
  39 #       define DS1305_HR_PM             0x20    /* set == PM (12hr mode) */
  40 #define DS1305_WDAY             0x03
  41 #define DS1305_MDAY             0x04
  42 #define DS1305_MON              0x05
  43 #define DS1305_YEAR             0x06
  44
  45
  46 /* The two alarms have only sec/min/hour/wday fields (ALM_LEN).
  47  * DS1305_ALM_DISABLE disables a match field (some combos are bad).
  48  *
  49  * NOTE that since we don't use WDAY, we limit ourselves to alarms
  50  * only one day into the future (vs potentially up to a week).
  51  *
  52  * NOTE ALSO that while we could generate once-a-second IRQs (UIE), we
  53  * don't currently support them.  We'd either need to do it only when
  54  * no alarm is pending (not the standard model), or to use the second
  55  * alarm (implying that this is a DS1305 not DS1306, *and* that either
  56  * it's wired up a second IRQ we know, or that INTCN is set)
  57  */
  58 #define DS1305_ALM_LEN          4               /* bytes for ALM regs */
  59 #define DS1305_ALM_DISABLE      0x80
  60
  61 #define DS1305_ALM0(r)          (0x07 + (r))    /* register addresses */
  62 #define DS1305_ALM1(r)          (0x0b + (r))
  63
  64
  65 /* three control registers */
  66 #define DS1305_CONTROL_LEN      3               /* bytes of control regs */
  67
  68 #define DS1305_CONTROL          0x0f            /* register addresses */
  69 #       define DS1305_nEOSC             0x80    /* low enables oscillator */
  70 #       define DS1305_WP                0x40    /* write protect */
  71 #       define DS1305_INTCN             0x04    /* clear == only int0 used */
  72 #       define DS1306_1HZ               0x04    /* enable 1Hz output */
  73 #       define DS1305_AEI1              0x02    /* enable ALM1 IRQ */
  74 #       define DS1305_AEI0              0x01    /* enable ALM0 IRQ */
  75 #define DS1305_STATUS           0x10
  76 /* status has just AEIx bits, mirrored as IRQFx */
  77 #define DS1305_TRICKLE          0x11
  78 /* trickle bits are defined in <linux/spi/ds1305.h> */
  79
  80 /* a bunch of NVRAM */
  81 #define DS1305_NVRAM_LEN        96              /* bytes of NVRAM */
  82
  83 #define DS1305_NVRAM            0x20            /* register addresses */
  84
  85
  86 struct ds1305 {
  87         struct spi_device       *spi;
  88         struct rtc_device       *rtc;
  89
  90         struct work_struct      work;
  91
  92         unsigned long           flags;
  93 #define FLAG_EXITING    0
  94
  95         bool                    hr12;
  96         u8                      ctrl[DS1305_CONTROL_LEN];
  97 };
  98
  99
 100 /*----------------------------------------------------------------------*/
 101
 102 /*
 103  * Utilities ...  tolerate 12-hour AM/PM notation in case of non-Linux
 104  * software (like a bootloader) which may require it.
 105  */
 106
 107 static unsigned bcd2hour(u8 bcd)
 108 {
 109         if (bcd & DS1305_HR_12) {
 110                 unsigned        hour = 0;
 111
 112                 bcd &= ~DS1305_HR_12;
 113                 if (bcd & DS1305_HR_PM) {
 114                         hour = 12;
 115                         bcd &= ~DS1305_HR_PM;
 116                 }
 117                 hour += bcd2bin(bcd);
 118                 return hour - 1;
 119         }
 120         return bcd2bin(bcd);
 121 }
 122
 123 static u8 hour2bcd(bool hr12, int hour)
 124 {
 125         if (hr12) {
 126                 hour++;
 127                 if (hour <= 12)
 128                         return DS1305_HR_12 | bin2bcd(hour);
 129                 hour -= 12;
 130                 return DS1305_HR_12 | DS1305_HR_PM | bin2bcd(hour);
 131         }
 132         return bin2bcd(hour);
 133 }
 134
 135 /*----------------------------------------------------------------------*/
 136
 137 /*
 138  * Interface to RTC framework
 139  */
 140
 141 #ifdef CONFIG_RTC_INTF_DEV
 142
 143 /*
 144  * Context: caller holds rtc->ops_lock (to protect ds1305->ctrl)
 145  */
 146 static int ds1305_ioctl(struct device *dev, unsigned cmd, unsigned long arg)
 147 {
 148         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 149         u8              buf[2];
 150         int             status = -ENOIOCTLCMD;
 151
 152         buf[0] = DS1305_WRITE | DS1305_CONTROL;
 153         buf[1] = ds1305->ctrl[0];
 154
 155         switch (cmd) {
 156         case RTC_AIE_OFF:
 157                 status = 0;
 158                 if (!(buf[1] & DS1305_AEI0))
 159                         goto done;
 160                 buf[1] &= ~DS1305_AEI0;
 161                 break;
 162
 163         case RTC_AIE_ON:
 164                 status = 0;
 165                 if (ds1305->ctrl[0] & DS1305_AEI0)
 166                         goto done;
 167                 buf[1] |= DS1305_AEI0;
 168                 break;
 169         }
 170         if (status == 0) {
 171                 status = spi_write_then_read(ds1305->spi, buf, sizeof buf,
 172                                 NULL, 0);
 173                 if (status >= 0)
 174                         ds1305->ctrl[0] = buf[1];
 175         }
 176
 177 done:
 178         return status;
 179 }
 180
 181 #else
 182 #define ds1305_ioctl    NULL
 183 #endif
 184
 185 /*
 186  * Get/set of date and time is pretty normal.
 187  */
 188
 189 static int ds1305_get_time(struct device *dev, struct rtc_time *time)
 190 {
 191         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 192         u8              addr = DS1305_SEC;
 193         u8              buf[DS1305_RTC_LEN];
 194         int             status;
 195
 196         /* Use write-then-read to get all the date/time registers
 197          * since dma from stack is nonportable
 198          */
 199         status = spi_write_then_read(ds1305->spi, &addr, sizeof addr,
 200                         buf, sizeof buf);
 201         if (status < 0)
 202                 return status;
 203
 204         dev_vdbg(dev, "%s: %02x %02x %02x, %02x %02x %02x %02x\n",
 205                 "read", buf[0], buf[1], buf[2], buf[3],
 206                 buf[4], buf[5], buf[6]);
 207
 208         /* Decode the registers */
 209         time->tm_sec = bcd2bin(buf[DS1305_SEC]);
 210         time->tm_min = bcd2bin(buf[DS1305_MIN]);
 211         time->tm_hour = bcd2hour(buf[DS1305_HOUR]);
 212         time->tm_wday = buf[DS1305_WDAY] - 1;
 213         time->tm_mday = bcd2bin(buf[DS1305_MDAY]);
 214         time->tm_mon = bcd2bin(buf[DS1305_MON]) - 1;
 215         time->tm_year = bcd2bin(buf[DS1305_YEAR]) + 100;
 216
 217         dev_vdbg(dev, "%s secs=%d, mins=%d, "
 218                 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
 219                 "read", time->tm_sec, time->tm_min,
 220                 time->tm_hour, time->tm_mday,
 221                 time->tm_mon, time->tm_year, time->tm_wday);
 222
 223         /* Time may not be set */
 224         return rtc_valid_tm(time);
 225 }
 226
 227 static int ds1305_set_time(struct device *dev, struct rtc_time *time)
 228 {
 229         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 230         u8              buf[1 + DS1305_RTC_LEN];
 231         u8              *bp = buf;
 232
 233         dev_vdbg(dev, "%s secs=%d, mins=%d, "
 234                 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
 235                 "write", time->tm_sec, time->tm_min,
 236                 time->tm_hour, time->tm_mday,
 237                 time->tm_mon, time->tm_year, time->tm_wday);
 238
 239         /* Write registers starting at the first time/date address. */
 240         *bp++ = DS1305_WRITE | DS1305_SEC;
 241
 242         *bp++ = bin2bcd(time->tm_sec);
 243         *bp++ = bin2bcd(time->tm_min);
 244         *bp++ = hour2bcd(ds1305->hr12, time->tm_hour);
 245         *bp++ = (time->tm_wday < 7) ? (time->tm_wday + 1) : 1;
 246         *bp++ = bin2bcd(time->tm_mday);
 247         *bp++ = bin2bcd(time->tm_mon + 1);
 248         *bp++ = bin2bcd(time->tm_year - 100);
 249
 250         dev_dbg(dev, "%s: %02x %02x %02x, %02x %02x %02x %02x\n",
 251                 "write", buf[1], buf[2], buf[3],
 252                 buf[4], buf[5], buf[6], buf[7]);
 253
 254         /* use write-then-read since dma from stack is nonportable */
 255         return spi_write_then_read(ds1305->spi, buf, sizeof buf,
 256                         NULL, 0);
 257 }
 258
 259 /*
 260  * Get/set of alarm is a bit funky:
 261  *
 262  * - First there's the inherent raciness of getting the (partitioned)
 263  *   status of an alarm that could trigger while we're reading parts
 264  *   of that status.
 265  *
 266  * - Second there's its limited range (we could increase it a bit by
 267  *   relying on WDAY), which means it will easily roll over.
 268  *
 269  * - Third there's the choice of two alarms and alarm signals.
 270  *   Here we use ALM0 and expect that nINT0 (open drain) is used;
 271  *   that's the only real option for DS1306 runtime alarms, and is
 272  *   natural on DS1305.
 273  *
 274  * - Fourth, there's also ALM1, and a second interrupt signal:
 275  *     + On DS1305 ALM1 uses nINT1 (when INTCN=1) else nINT0;
 276  *     + On DS1306 ALM1 only uses INT1 (an active high pulse)
 277  *       and it won't work when VCC1 is active.
 278  *
 279  *   So to be most general, we should probably set both alarms to the
 280  *   same value, letting ALM1 be the wakeup event source on DS1306
 281  *   and handling several wiring options on DS1305.
 282  *
 283  * - Fifth, we support the polled mode (as well as possible; why not?)
 284  *   even when no interrupt line is wired to an IRQ.
 285  */
 286
 287 /*
 288  * Context: caller holds rtc->ops_lock (to protect ds1305->ctrl)
 289  */
 290 static int ds1305_get_alarm(struct device *dev, struct rtc_wkalrm *alm)
 291 {
 292         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 293         struct spi_device *spi = ds1305->spi;
 294         u8              addr;
 295         int             status;
 296         u8              buf[DS1305_ALM_LEN];
 297
 298         /* Refresh control register cache BEFORE reading ALM0 registers,
 299          * since reading alarm registers acks any pending IRQ.  That
 300          * makes returning "pending" status a bit of a lie, but that bit
 301          * of EFI status is at best fragile anyway (given IRQ handlers).
 302          */
 303         addr = DS1305_CONTROL;
 304         status = spi_write_then_read(spi, &addr, sizeof addr,
 305                         ds1305->ctrl, sizeof ds1305->ctrl);
 306         if (status < 0)
 307                 return status;
 308
 309         alm->enabled = !!(ds1305->ctrl[0] & DS1305_AEI0);
 310         alm->pending = !!(ds1305->ctrl[1] & DS1305_AEI0);
 311
 312         /* get and check ALM0 registers */
 313         addr = DS1305_ALM0(DS1305_SEC);
 314         status = spi_write_then_read(spi, &addr, sizeof addr,
 315                         buf, sizeof buf);
 316         if (status < 0)
 317                 return status;
 318
 319         dev_vdbg(dev, "%s: %02x %02x %02x %02x\n",
 320                 "alm0 read", buf[DS1305_SEC], buf[DS1305_MIN],
 321                 buf[DS1305_HOUR], buf[DS1305_WDAY]);
 322
 323         if ((DS1305_ALM_DISABLE & buf[DS1305_SEC])
 324                         || (DS1305_ALM_DISABLE & buf[DS1305_MIN])
 325                         || (DS1305_ALM_DISABLE & buf[DS1305_HOUR]))
 326                 return -EIO;
 327
 328         /* Stuff these values into alm->time and let RTC framework code
 329          * fill in the rest ... and also handle rollover to tomorrow when
 330          * that's needed.
 331          */
 332         alm->time.tm_sec = bcd2bin(buf[DS1305_SEC]);
 333         alm->time.tm_min = bcd2bin(buf[DS1305_MIN]);
 334         alm->time.tm_hour = bcd2hour(buf[DS1305_HOUR]);
 335         alm->time.tm_mday = -1;
 336         alm->time.tm_mon = -1;
 337         alm->time.tm_year = -1;
 338         /* next three fields are unused by Linux */
 339         alm->time.tm_wday = -1;
 340         alm->time.tm_mday = -1;
 341         alm->time.tm_isdst = -1;
 342
 343         return 0;
 344 }
 345
 346 /*
 347  * Context: caller holds rtc->ops_lock (to protect ds1305->ctrl)
 348  */
 349 static int ds1305_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
 350 {
 351         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 352         struct spi_device *spi = ds1305->spi;
 353         unsigned long   now, later;
 354         struct rtc_time tm;
 355         int             status;
 356         u8              buf[1 + DS1305_ALM_LEN];
 357
 358         /* convert desired alarm to time_t */
 359         status = rtc_tm_to_time(&alm->time, &later);
 360         if (status < 0)
 361                 return status;
 362
 363         /* Read current time as time_t */
 364         status = ds1305_get_time(dev, &tm);
 365         if (status < 0)
 366                 return status;
 367         status = rtc_tm_to_time(&tm, &now);
 368         if (status < 0)
 369                 return status;
 370
 371         /* make sure alarm fires within the next 24 hours */
 372         if (later <= now)
 373                 return -EINVAL;
 374         if ((later - now) > 24 * 60 * 60)
 375                 return -EDOM;
 376
 377         /* disable alarm if needed */
 378         if (ds1305->ctrl[0] & DS1305_AEI0) {
 379                 ds1305->ctrl[0] &= ~DS1305_AEI0;
 380
 381                 buf[0] = DS1305_WRITE | DS1305_CONTROL;
 382                 buf[1] = ds1305->ctrl[0];
 383                 status = spi_write_then_read(ds1305->spi, buf, 2, NULL, 0);
 384                 if (status < 0)
 385                         return status;
 386         }
 387
 388         /* write alarm */
 389         buf[0] = DS1305_WRITE | DS1305_ALM0(DS1305_SEC);
 390         buf[1 + DS1305_SEC] = bin2bcd(alm->time.tm_sec);
 391         buf[1 + DS1305_MIN] = bin2bcd(alm->time.tm_min);
 392         buf[1 + DS1305_HOUR] = hour2bcd(ds1305->hr12, alm->time.tm_hour);
 393         buf[1 + DS1305_WDAY] = DS1305_ALM_DISABLE;
 394
 395         dev_dbg(dev, "%s: %02x %02x %02x %02x\n",
 396                 "alm0 write", buf[1 + DS1305_SEC], buf[1 + DS1305_MIN],
 397                 buf[1 + DS1305_HOUR], buf[1 + DS1305_WDAY]);
 398
 399         status = spi_write_then_read(spi, buf, sizeof buf, NULL, 0);
 400         if (status < 0)
 401                 return status;
 402
 403         /* enable alarm if requested */
 404         if (alm->enabled) {
 405                 ds1305->ctrl[0] |= DS1305_AEI0;
 406
 407                 buf[0] = DS1305_WRITE | DS1305_CONTROL;
 408                 buf[1] = ds1305->ctrl[0];
 409                 status = spi_write_then_read(ds1305->spi, buf, 2, NULL, 0);
 410         }
 411
 412         return status;
 413 }
 414
 415 #ifdef CONFIG_PROC_FS
 416
 417 static int ds1305_proc(struct device *dev, struct seq_file *seq)
 418 {
 419         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 420         char            *diodes = "no";
 421         char            *resistors = "";
 422
 423         /* ctrl[2] is treated as read-only; no locking needed */
 424         if ((ds1305->ctrl[2] & 0xf0) == DS1305_TRICKLE_MAGIC) {
 425                 switch (ds1305->ctrl[2] & 0x0c) {
 426                 case DS1305_TRICKLE_DS2:
 427                         diodes = "2 diodes, ";
 428                         break;
 429                 case DS1305_TRICKLE_DS1:
 430                         diodes = "1 diode, ";
 431                         break;
 432                 default:
 433                         goto done;
 434                 }
 435                 switch (ds1305->ctrl[2] & 0x03) {
 436                 case DS1305_TRICKLE_2K:
 437                         resistors = "2k Ohm";
 438                         break;
 439                 case DS1305_TRICKLE_4K:
 440                         resistors = "4k Ohm";
 441                         break;
 442                 case DS1305_TRICKLE_8K:
 443                         resistors = "8k Ohm";
 444                         break;
 445                 default:
 446                         diodes = "no";
 447                         break;
 448                 }
 449         }
 450
 451 done:
 452         return seq_printf(seq,
 453                         "trickle_charge\t: %s%s\n",
 454                         diodes, resistors);
 455 }
 456
 457 #else
 458 #define ds1305_proc     NULL
 459 #endif
 460
 461 static const struct rtc_class_ops ds1305_ops = {
 462         .ioctl          = ds1305_ioctl,
 463         .read_time      = ds1305_get_time,
 464         .set_time       = ds1305_set_time,
 465         .read_alarm     = ds1305_get_alarm,
 466         .set_alarm      = ds1305_set_alarm,
 467         .proc           = ds1305_proc,
 468 };
 469
 470 static void ds1305_work(struct work_struct *work)
 471 {
 472         struct ds1305   *ds1305 = container_of(work, struct ds1305, work);
 473         struct mutex    *lock = &ds1305->rtc->ops_lock;
 474         struct spi_device *spi = ds1305->spi;
 475         u8              buf[3];
 476         int             status;
 477
 478         /* lock to protect ds1305->ctrl */
 479         mutex_lock(lock);
 480
 481         /* Disable the IRQ, and clear its status ... for now, we "know"
 482          * that if more than one alarm is active, they're in sync.
 483          * Note that reading ALM data registers also clears IRQ status.
 484          */
 485         ds1305->ctrl[0] &= ~(DS1305_AEI1 | DS1305_AEI0);
 486         ds1305->ctrl[1] = 0;
 487
 488         buf[0] = DS1305_WRITE | DS1305_CONTROL;
 489         buf[1] = ds1305->ctrl[0];
 490         buf[2] = 0;
 491
 492         status = spi_write_then_read(spi, buf, sizeof buf,
 493                         NULL, 0);
 494         if (status < 0)
 495                 dev_dbg(&spi->dev, "clear irq --> %d\n", status);
 496
 497         mutex_unlock(lock);
 498
 499         if (!test_bit(FLAG_EXITING, &ds1305->flags))
 500                 enable_irq(spi->irq);
 501
 502         rtc_update_irq(ds1305->rtc, 1, RTC_AF | RTC_IRQF);
 503 }
 504
 505 /*
 506  * This "real" IRQ handler hands off to a workqueue mostly to allow
 507  * mutex locking for ds1305->ctrl ... unlike I2C, we could issue async
 508  * I/O requests in IRQ context (to clear the IRQ status).
 509  */
 510 static irqreturn_t ds1305_irq(int irq, void *p)
 511 {
 512         struct ds1305           *ds1305 = p;
 513
 514         disable_irq(irq);
 515         schedule_work(&ds1305->work);
 516         return IRQ_HANDLED;
 517 }
 518
 519 /*----------------------------------------------------------------------*/
 520
 521 /*
 522  * Interface for NVRAM
 523  */
 524
 525 static void msg_init(struct spi_message *m, struct spi_transfer *x,
 526                 u8 *addr, size_t count, char *tx, char *rx)
 527 {
 528         spi_message_init(m);
 529         memset(x, 0, 2 * sizeof(*x));
 530
 531         x->tx_buf = addr;
 532         x->len = 1;
 533         spi_message_add_tail(x, m);
 534
 535         x++;
 536
 537         x->tx_buf = tx;
 538         x->rx_buf = rx;
 539         x->len = count;
 540         spi_message_add_tail(x, m);
 541 }
 542
 543 static ssize_t
 544 ds1305_nvram_read(struct kobject *kobj, struct bin_attribute *attr,
 545                 char *buf, loff_t off, size_t count)
 546 {
 547         struct spi_device       *spi;
 548         u8                      addr;
 549         struct spi_message      m;
 550         struct spi_transfer     x[2];
 551         int                     status;
 552
 553         spi = container_of(kobj, struct spi_device, dev.kobj);
 554
 555         if (unlikely(off >= DS1305_NVRAM_LEN))
 556                 return 0;
 557         if (count >= DS1305_NVRAM_LEN)
 558                 count = DS1305_NVRAM_LEN;
 559         if ((off + count) > DS1305_NVRAM_LEN)
 560                 count = DS1305_NVRAM_LEN - off;
 561         if (unlikely(!count))
 562                 return count;
 563
 564         addr = DS1305_NVRAM + off;
 565         msg_init(&m, x, &addr, count, NULL, buf);
 566
 567         status = spi_sync(spi, &m);
 568         if (status < 0)
 569                 dev_err(&spi->dev, "nvram %s error %d\n", "read", status);
 570         return (status < 0) ? status : count;
 571 }
 572
 573 static ssize_t
 574 ds1305_nvram_write(struct kobject *kobj, struct bin_attribute *attr,
 575                 char *buf, loff_t off, size_t count)
 576 {
 577         struct spi_device       *spi;
 578         u8                      addr;
 579         struct spi_message      m;
 580         struct spi_transfer     x[2];
 581         int                     status;
 582
 583         spi = container_of(kobj, struct spi_device, dev.kobj);
 584
 585         if (unlikely(off >= DS1305_NVRAM_LEN))
 586                 return -EFBIG;
 587         if (count >= DS1305_NVRAM_LEN)
 588                 count = DS1305_NVRAM_LEN;
 589         if ((off + count) > DS1305_NVRAM_LEN)
 590                 count = DS1305_NVRAM_LEN - off;
 591         if (unlikely(!count))
 592                 return count;
 593
 594         addr = (DS1305_WRITE | DS1305_NVRAM) + off;
 595         msg_init(&m, x, &addr, count, buf, NULL);
 596
 597         status = spi_sync(spi, &m);
 598         if (status < 0)
 599                 dev_err(&spi->dev, "nvram %s error %d\n", "write", status);
 600         return (status < 0) ? status : count;
 601 }
 602
 603 static struct bin_attribute nvram = {
 604         .attr.name      = "nvram",
 605         .attr.mode      = S_IRUGO | S_IWUSR,
 606         .read           = ds1305_nvram_read,
 607         .write          = ds1305_nvram_write,
 608         .size           = DS1305_NVRAM_LEN,
 609 };
 610
 611 /*----------------------------------------------------------------------*/
 612
 613 /*
 614  * Interface to SPI stack
 615  */
 616
 617 static int __devinit ds1305_probe(struct spi_device *spi)
 618 {
 619         struct ds1305                   *ds1305;
 620         int                             status;
 621         u8                              addr, value;
 622         struct ds1305_platform_data     *pdata = spi->dev.platform_data;
 623         bool                            write_ctrl = false;
 624
 625         /* Sanity check board setup data.  This may be hooked up
 626          * in 3wire mode, but we don't care.  Note that unless
 627          * there's an inverter in place, this needs SPI_CS_HIGH!
 628          */
 629         if ((spi->bits_per_word && spi->bits_per_word != 8)
 630                         || (spi->max_speed_hz > 2000000)
 631                         || !(spi->mode & SPI_CPHA))
 632                 return -EINVAL;
 633
 634         /* set up driver data */
 635         ds1305 = kzalloc(sizeof *ds1305, GFP_KERNEL);
 636         if (!ds1305)
 637                 return -ENOMEM;
 638         ds1305->spi = spi;
 639         spi_set_drvdata(spi, ds1305);
 640
 641         /* read and cache control registers */
 642         addr = DS1305_CONTROL;
 643         status = spi_write_then_read(spi, &addr, sizeof addr,
 644                         ds1305->ctrl, sizeof ds1305->ctrl);
 645         if (status < 0) {
 646                 dev_dbg(&spi->dev, "can't %s, %d\n",
 647                                 "read", status);
 648                 goto fail0;
 649         }
 650
 651         dev_dbg(&spi->dev, "ctrl %s: %02x %02x %02x\n",
 652                         "read", ds1305->ctrl[0],
 653                         ds1305->ctrl[1], ds1305->ctrl[2]);
 654
 655         /* Sanity check register values ... partially compensating for the
 656          * fact that SPI has no device handshake.  A pullup on MISO would
 657          * make these tests fail; but not all systems will have one.  If
 658          * some register is neither 0x00 nor 0xff, a chip is likely there.
 659          */
 660         if ((ds1305->ctrl[0] & 0x38) != 0 || (ds1305->ctrl[1] & 0xfc) != 0) {
 661                 dev_dbg(&spi->dev, "RTC chip is not present\n");
 662                 status = -ENODEV;
 663                 goto fail0;
 664         }
 665         if (ds1305->ctrl[2] == 0)
 666                 dev_dbg(&spi->dev, "chip may not be present\n");
 667
 668         /* enable writes if needed ... if we were paranoid it would
 669          * make sense to enable them only when absolutely necessary.
 670          */
 671         if (ds1305->ctrl[0] & DS1305_WP) {
 672                 u8              buf[2];
 673
 674                 ds1305->ctrl[0] &= ~DS1305_WP;
 675
 676                 buf[0] = DS1305_WRITE | DS1305_CONTROL;
 677                 buf[1] = ds1305->ctrl[0];
 678                 status = spi_write_then_read(spi, buf, sizeof buf, NULL, 0);
 679
 680                 dev_dbg(&spi->dev, "clear WP --> %d\n", status);
 681                 if (status < 0)
 682                         goto fail0;
 683         }
 684
 685         /* on DS1305, maybe start oscillator; like most low power
 686          * oscillators, it may take a second to stabilize
 687          */
 688         if (ds1305->ctrl[0] & DS1305_nEOSC) {
 689                 ds1305->ctrl[0] &= ~DS1305_nEOSC;
 690                 write_ctrl = true;
 691                 dev_warn(&spi->dev, "SET TIME!\n");
 692         }
 693
 694         /* ack any pending IRQs */
 695         if (ds1305->ctrl[1]) {
 696                 ds1305->ctrl[1] = 0;
 697                 write_ctrl = true;
 698         }
 699
 700         /* this may need one-time (re)init */
 701         if (pdata) {
 702                 /* maybe enable trickle charge */
 703                 if (((ds1305->ctrl[2] & 0xf0) != DS1305_TRICKLE_MAGIC)) {
 704                         ds1305->ctrl[2] = DS1305_TRICKLE_MAGIC
 705                                                 | pdata->trickle;
 706                         write_ctrl = true;
 707                 }
 708
 709                 /* on DS1306, configure 1 Hz signal */
 710                 if (pdata->is_ds1306) {
 711                         if (pdata->en_1hz) {
 712                                 if (!(ds1305->ctrl[0] & DS1306_1HZ)) {
 713                                         ds1305->ctrl[0] |= DS1306_1HZ;
 714                                         write_ctrl = true;
 715                                 }
 716                         } else {
 717                                 if (ds1305->ctrl[0] & DS1306_1HZ) {
 718                                         ds1305->ctrl[0] &= ~DS1306_1HZ;
 719                                         write_ctrl = true;
 720                                 }
 721                         }
 722                 }
 723         }
 724
 725         if (write_ctrl) {
 726                 u8              buf[4];
 727
 728                 buf[0] = DS1305_WRITE | DS1305_CONTROL;
 729                 buf[1] = ds1305->ctrl[0];
 730                 buf[2] = ds1305->ctrl[1];
 731                 buf[3] = ds1305->ctrl[2];
 732                 status = spi_write_then_read(spi, buf, sizeof buf, NULL, 0);
 733                 if (status < 0) {
 734                         dev_dbg(&spi->dev, "can't %s, %d\n",
 735                                         "write", status);
 736                         goto fail0;
 737                 }
 738
 739                 dev_dbg(&spi->dev, "ctrl %s: %02x %02x %02x\n",
 740                                 "write", ds1305->ctrl[0],
 741                                 ds1305->ctrl[1], ds1305->ctrl[2]);
 742         }
 743
 744         /* see if non-Linux software set up AM/PM mode */
 745         addr = DS1305_HOUR;
 746         status = spi_write_then_read(spi, &addr, sizeof addr,
 747                                 &value, sizeof value);
 748         if (status < 0) {
 749                 dev_dbg(&spi->dev, "read HOUR --> %d\n", status);
 750                 goto fail0;
 751         }
 752
 753         ds1305->hr12 = (DS1305_HR_12 & value) != 0;
 754         if (ds1305->hr12)
 755                 dev_dbg(&spi->dev, "AM/PM\n");
 756
 757         /* register RTC ... from here on, ds1305->ctrl needs locking */
 758         ds1305->rtc = rtc_device_register("ds1305", &spi->dev,
 759                         &ds1305_ops, THIS_MODULE);
 760         if (IS_ERR(ds1305->rtc)) {
 761                 status = PTR_ERR(ds1305->rtc);
 762                 dev_dbg(&spi->dev, "register rtc --> %d\n", status);
 763                 goto fail0;
 764         }
 765
 766         /* Maybe set up alarm IRQ; be ready to handle it triggering right
 767          * away.  NOTE that we don't share this.  The signal is active low,
 768          * and we can't ack it before a SPI message delay.  We temporarily
 769          * disable the IRQ until it's acked, which lets us work with more
 770          * IRQ trigger modes (not all IRQ controllers can do falling edge).
 771          */
 772         if (spi->irq) {
 773                 INIT_WORK(&ds1305->work, ds1305_work);
 774                 status = request_irq(spi->irq, ds1305_irq,
 775                                 0, dev_name(&ds1305->rtc->dev), ds1305);
 776                 if (status < 0) {
 777                         dev_dbg(&spi->dev, "request_irq %d --> %d\n",
 778                                         spi->irq, status);
 779                         goto fail1;
 780                 }
 781
 782                 device_set_wakeup_capable(&spi->dev, 1);
 783         }
 784
 785         /* export NVRAM */
 786         status = sysfs_create_bin_file(&spi->dev.kobj, &nvram);
 787         if (status < 0) {
 788                 dev_dbg(&spi->dev, "register nvram --> %d\n", status);
 789                 goto fail2;
 790         }
 791
 792         return 0;
 793
 794 fail2:
 795         free_irq(spi->irq, ds1305);
 796 fail1:
 797         rtc_device_unregister(ds1305->rtc);
 798 fail0:
 799         kfree(ds1305);
 800         return status;
 801 }
 802
 803 static int __devexit ds1305_remove(struct spi_device *spi)
 804 {
 805         struct ds1305 *ds1305 = spi_get_drvdata(spi);
 806
 807         sysfs_remove_bin_file(&spi->dev.kobj, &nvram);
 808
 809         /* carefully shut down irq and workqueue, if present */
 810         if (spi->irq) {
 811                 set_bit(FLAG_EXITING, &ds1305->flags);
 812                 free_irq(spi->irq, ds1305);
 813                 flush_scheduled_work();
 814         }
 815
 816         rtc_device_unregister(ds1305->rtc);
 817         spi_set_drvdata(spi, NULL);
 818         kfree(ds1305);
 819         return 0;
 820 }
 821
 822 static struct spi_driver ds1305_driver = {
 823         .driver.name    = "rtc-ds1305",
 824         .driver.owner   = THIS_MODULE,
 825         .probe          = ds1305_probe,
 826         .remove         = __devexit_p(ds1305_remove),
 827         /* REVISIT add suspend/resume */
 828 };
 829
 830 static int __init ds1305_init(void)
 831 {
 832         return spi_register_driver(&ds1305_driver);
 833 }
 834 module_init(ds1305_init);
 835
 836 static void __exit ds1305_exit(void)
 837 {
 838         spi_unregister_driver(&ds1305_driver);
 839 }
 840 module_exit(ds1305_exit);
 841
 842 MODULE_DESCRIPTION("RTC driver for DS1305 and DS1306 chips");
 843 MODULE_LICENSE("GPL");
 844 MODULE_ALIAS("spi:rtc-ds1305");