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/slab.h>
  15 #include <linux/rtc.h>
  16 #include <linux/workqueue.h>
  17
  18 #include <linux/spi/spi.h>
  19 #include <linux/spi/ds1305.h>
  20 #include <linux/module.h>
  21
  22
  23 /*
  24  * Registers ... mask DS1305_WRITE into register address to write,
  25  * otherwise you're reading it.  All non-bitmask values are BCD.
  26  */
  27 #define DS1305_WRITE            0x80
  28
  29
  30 /* RTC date/time ... the main special cases are that we:
  31  *  - Need fancy "hours" encoding in 12hour mode
  32  *  - Don't rely on the "day-of-week" field (or tm_wday)
  33  *  - Are a 21st-century clock (2000 <= year < 2100)
  34  */
  35 #define DS1305_RTC_LEN          7               /* bytes for RTC regs */
  36
  37 #define DS1305_SEC              0x00            /* register addresses */
  38 #define DS1305_MIN              0x01
  39 #define DS1305_HOUR             0x02
  40 #       define DS1305_HR_12             0x40    /* set == 12 hr mode */
  41 #       define DS1305_HR_PM             0x20    /* set == PM (12hr mode) */
  42 #define DS1305_WDAY             0x03
  43 #define DS1305_MDAY             0x04
  44 #define DS1305_MON              0x05
  45 #define DS1305_YEAR             0x06
  46
  47
  48 /* The two alarms have only sec/min/hour/wday fields (ALM_LEN).
  49  * DS1305_ALM_DISABLE disables a match field (some combos are bad).
  50  *
  51  * NOTE that since we don't use WDAY, we limit ourselves to alarms
  52  * only one day into the future (vs potentially up to a week).
  53  *
  54  * NOTE ALSO that while we could generate once-a-second IRQs (UIE), we
  55  * don't currently support them.  We'd either need to do it only when
  56  * no alarm is pending (not the standard model), or to use the second
  57  * alarm (implying that this is a DS1305 not DS1306, *and* that either
  58  * it's wired up a second IRQ we know, or that INTCN is set)
  59  */
  60 #define DS1305_ALM_LEN          4               /* bytes for ALM regs */
  61 #define DS1305_ALM_DISABLE      0x80
  62
  63 #define DS1305_ALM0(r)          (0x07 + (r))    /* register addresses */
  64 #define DS1305_ALM1(r)          (0x0b + (r))
  65
  66
  67 /* three control registers */
  68 #define DS1305_CONTROL_LEN      3               /* bytes of control regs */
  69
  70 #define DS1305_CONTROL          0x0f            /* register addresses */
  71 #       define DS1305_nEOSC             0x80    /* low enables oscillator */
  72 #       define DS1305_WP                0x40    /* write protect */
  73 #       define DS1305_INTCN             0x04    /* clear == only int0 used */
  74 #       define DS1306_1HZ               0x04    /* enable 1Hz output */
  75 #       define DS1305_AEI1              0x02    /* enable ALM1 IRQ */
  76 #       define DS1305_AEI0              0x01    /* enable ALM0 IRQ */
  77 #define DS1305_STATUS           0x10
  78 /* status has just AEIx bits, mirrored as IRQFx */
  79 #define DS1305_TRICKLE          0x11
  80 /* trickle bits are defined in <linux/spi/ds1305.h> */
  81
  82 /* a bunch of NVRAM */
  83 #define DS1305_NVRAM_LEN        96              /* bytes of NVRAM */
  84
  85 #define DS1305_NVRAM            0x20            /* register addresses */
  86
  87
  88 struct ds1305 {
  89         struct spi_device       *spi;
  90         struct rtc_device       *rtc;
  91
  92         struct work_struct      work;
  93
  94         unsigned long           flags;
  95 #define FLAG_EXITING    0
  96
  97         bool                    hr12;
  98         u8                      ctrl[DS1305_CONTROL_LEN];
  99 };
 100
 101
 102 /*----------------------------------------------------------------------*/
 103
 104 /*
 105  * Utilities ...  tolerate 12-hour AM/PM notation in case of non-Linux
 106  * software (like a bootloader) which may require it.
 107  */
 108
 109 static unsigned bcd2hour(u8 bcd)
 110 {
 111         if (bcd & DS1305_HR_12) {
 112                 unsigned        hour = 0;
 113
 114                 bcd &= ~DS1305_HR_12;
 115                 if (bcd & DS1305_HR_PM) {
 116                         hour = 12;
 117                         bcd &= ~DS1305_HR_PM;
 118                 }
 119                 hour += bcd2bin(bcd);
 120                 return hour - 1;
 121         }
 122         return bcd2bin(bcd);
 123 }
 124
 125 static u8 hour2bcd(bool hr12, int hour)
 126 {
 127         if (hr12) {
 128                 hour++;
 129                 if (hour <= 12)
 130                         return DS1305_HR_12 | bin2bcd(hour);
 131                 hour -= 12;
 132                 return DS1305_HR_12 | DS1305_HR_PM | bin2bcd(hour);
 133         }
 134         return bin2bcd(hour);
 135 }
 136
 137 /*----------------------------------------------------------------------*/
 138
 139 /*
 140  * Interface to RTC framework
 141  */
 142
 143 static int ds1305_alarm_irq_enable(struct device *dev, unsigned int enabled)
 144 {
 145         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 146         u8              buf[2];
 147         long            err = -EINVAL;
 148
 149         buf[0] = DS1305_WRITE | DS1305_CONTROL;
 150         buf[1] = ds1305->ctrl[0];
 151
 152         if (enabled) {
 153                 if (ds1305->ctrl[0] & DS1305_AEI0)
 154                         goto done;
 155                 buf[1] |= DS1305_AEI0;
 156         } else {
 157                 if (!(buf[1] & DS1305_AEI0))
 158                         goto done;
 159                 buf[1] &= ~DS1305_AEI0;
 160         }
 161         err = spi_write_then_read(ds1305->spi, buf, sizeof buf, NULL, 0);
 162         if (err >= 0)
 163                 ds1305->ctrl[0] = buf[1];
 164 done:
 165         return err;
 166
 167 }
 168
 169
 170 /*
 171  * Get/set of date and time is pretty normal.
 172  */
 173
 174 static int ds1305_get_time(struct device *dev, struct rtc_time *time)
 175 {
 176         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 177         u8              addr = DS1305_SEC;
 178         u8              buf[DS1305_RTC_LEN];
 179         int             status;
 180
 181         /* Use write-then-read to get all the date/time registers
 182          * since dma from stack is nonportable
 183          */
 184         status = spi_write_then_read(ds1305->spi, &addr, sizeof addr,
 185                         buf, sizeof buf);
 186         if (status < 0)
 187                 return status;
 188
 189         dev_vdbg(dev, "%s: %02x %02x %02x, %02x %02x %02x %02x\n",
 190                 "read", buf[0], buf[1], buf[2], buf[3],
 191                 buf[4], buf[5], buf[6]);
 192
 193         /* Decode the registers */
 194         time->tm_sec = bcd2bin(buf[DS1305_SEC]);
 195         time->tm_min = bcd2bin(buf[DS1305_MIN]);
 196         time->tm_hour = bcd2hour(buf[DS1305_HOUR]);
 197         time->tm_wday = buf[DS1305_WDAY] - 1;
 198         time->tm_mday = bcd2bin(buf[DS1305_MDAY]);
 199         time->tm_mon = bcd2bin(buf[DS1305_MON]) - 1;
 200         time->tm_year = bcd2bin(buf[DS1305_YEAR]) + 100;
 201
 202         dev_vdbg(dev, "%s secs=%d, mins=%d, "
 203                 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
 204                 "read", time->tm_sec, time->tm_min,
 205                 time->tm_hour, time->tm_mday,
 206                 time->tm_mon, time->tm_year, time->tm_wday);
 207
 208         /* Time may not be set */
 209         return rtc_valid_tm(time);
 210 }
 211
 212 static int ds1305_set_time(struct device *dev, struct rtc_time *time)
 213 {
 214         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 215         u8              buf[1 + DS1305_RTC_LEN];
 216         u8              *bp = buf;
 217
 218         dev_vdbg(dev, "%s secs=%d, mins=%d, "
 219                 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
 220                 "write", time->tm_sec, time->tm_min,
 221                 time->tm_hour, time->tm_mday,
 222                 time->tm_mon, time->tm_year, time->tm_wday);
 223
 224         /* Write registers starting at the first time/date address. */
 225         *bp++ = DS1305_WRITE | DS1305_SEC;
 226
 227         *bp++ = bin2bcd(time->tm_sec);
 228         *bp++ = bin2bcd(time->tm_min);
 229         *bp++ = hour2bcd(ds1305->hr12, time->tm_hour);
 230         *bp++ = (time->tm_wday < 7) ? (time->tm_wday + 1) : 1;
 231         *bp++ = bin2bcd(time->tm_mday);
 232         *bp++ = bin2bcd(time->tm_mon + 1);
 233         *bp++ = bin2bcd(time->tm_year - 100);
 234
 235         dev_dbg(dev, "%s: %02x %02x %02x, %02x %02x %02x %02x\n",
 236                 "write", buf[1], buf[2], buf[3],
 237                 buf[4], buf[5], buf[6], buf[7]);
 238
 239         /* use write-then-read since dma from stack is nonportable */
 240         return spi_write_then_read(ds1305->spi, buf, sizeof buf,
 241                         NULL, 0);
 242 }
 243
 244 /*
 245  * Get/set of alarm is a bit funky:
 246  *
 247  * - First there's the inherent raciness of getting the (partitioned)
 248  *   status of an alarm that could trigger while we're reading parts
 249  *   of that status.
 250  *
 251  * - Second there's its limited range (we could increase it a bit by
 252  *   relying on WDAY), which means it will easily roll over.
 253  *
 254  * - Third there's the choice of two alarms and alarm signals.
 255  *   Here we use ALM0 and expect that nINT0 (open drain) is used;
 256  *   that's the only real option for DS1306 runtime alarms, and is
 257  *   natural on DS1305.
 258  *
 259  * - Fourth, there's also ALM1, and a second interrupt signal:
 260  *     + On DS1305 ALM1 uses nINT1 (when INTCN=1) else nINT0;
 261  *     + On DS1306 ALM1 only uses INT1 (an active high pulse)
 262  *       and it won't work when VCC1 is active.
 263  *
 264  *   So to be most general, we should probably set both alarms to the
 265  *   same value, letting ALM1 be the wakeup event source on DS1306
 266  *   and handling several wiring options on DS1305.
 267  *
 268  * - Fifth, we support the polled mode (as well as possible; why not?)
 269  *   even when no interrupt line is wired to an IRQ.
 270  */
 271
 272 /*
 273  * Context: caller holds rtc->ops_lock (to protect ds1305->ctrl)
 274  */
 275 static int ds1305_get_alarm(struct device *dev, struct rtc_wkalrm *alm)
 276 {
 277         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 278         struct spi_device *spi = ds1305->spi;
 279         u8              addr;
 280         int             status;
 281         u8              buf[DS1305_ALM_LEN];
 282
 283         /* Refresh control register cache BEFORE reading ALM0 registers,
 284          * since reading alarm registers acks any pending IRQ.  That
 285          * makes returning "pending" status a bit of a lie, but that bit
 286          * of EFI status is at best fragile anyway (given IRQ handlers).
 287          */
 288         addr = DS1305_CONTROL;
 289         status = spi_write_then_read(spi, &addr, sizeof addr,
 290                         ds1305->ctrl, sizeof ds1305->ctrl);
 291         if (status < 0)
 292                 return status;
 293
 294         alm->enabled = !!(ds1305->ctrl[0] & DS1305_AEI0);
 295         alm->pending = !!(ds1305->ctrl[1] & DS1305_AEI0);
 296
 297         /* get and check ALM0 registers */
 298         addr = DS1305_ALM0(DS1305_SEC);
 299         status = spi_write_then_read(spi, &addr, sizeof addr,
 300                         buf, sizeof buf);
 301         if (status < 0)
 302                 return status;
 303
 304         dev_vdbg(dev, "%s: %02x %02x %02x %02x\n",
 305                 "alm0 read", buf[DS1305_SEC], buf[DS1305_MIN],
 306                 buf[DS1305_HOUR], buf[DS1305_WDAY]);
 307
 308         if ((DS1305_ALM_DISABLE & buf[DS1305_SEC])
 309                         || (DS1305_ALM_DISABLE & buf[DS1305_MIN])
 310                         || (DS1305_ALM_DISABLE & buf[DS1305_HOUR]))
 311                 return -EIO;
 312
 313         /* Stuff these values into alm->time and let RTC framework code
 314          * fill in the rest ... and also handle rollover to tomorrow when
 315          * that's needed.
 316          */
 317         alm->time.tm_sec = bcd2bin(buf[DS1305_SEC]);
 318         alm->time.tm_min = bcd2bin(buf[DS1305_MIN]);
 319         alm->time.tm_hour = bcd2hour(buf[DS1305_HOUR]);
 320         alm->time.tm_mday = -1;
 321         alm->time.tm_mon = -1;
 322         alm->time.tm_year = -1;
 323         /* next three fields are unused by Linux */
 324         alm->time.tm_wday = -1;
 325         alm->time.tm_mday = -1;
 326         alm->time.tm_isdst = -1;
 327
 328         return 0;
 329 }
 330
 331 /*
 332  * Context: caller holds rtc->ops_lock (to protect ds1305->ctrl)
 333  */
 334 static int ds1305_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
 335 {
 336         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 337         struct spi_device *spi = ds1305->spi;
 338         unsigned long   now, later;
 339         struct rtc_time tm;
 340         int             status;
 341         u8              buf[1 + DS1305_ALM_LEN];
 342
 343         /* convert desired alarm to time_t */
 344         status = rtc_tm_to_time(&alm->time, &later);
 345         if (status < 0)
 346                 return status;
 347
 348         /* Read current time as time_t */
 349         status = ds1305_get_time(dev, &tm);
 350         if (status < 0)
 351                 return status;
 352         status = rtc_tm_to_time(&tm, &now);
 353         if (status < 0)
 354                 return status;
 355
 356         /* make sure alarm fires within the next 24 hours */
 357         if (later <= now)
 358                 return -EINVAL;
 359         if ((later - now) > 24 * 60 * 60)
 360                 return -EDOM;
 361
 362         /* disable alarm if needed */
 363         if (ds1305->ctrl[0] & DS1305_AEI0) {
 364                 ds1305->ctrl[0] &= ~DS1305_AEI0;
 365
 366                 buf[0] = DS1305_WRITE | DS1305_CONTROL;
 367                 buf[1] = ds1305->ctrl[0];
 368                 status = spi_write_then_read(ds1305->spi, buf, 2, NULL, 0);
 369                 if (status < 0)
 370                         return status;
 371         }
 372
 373         /* write alarm */
 374         buf[0] = DS1305_WRITE | DS1305_ALM0(DS1305_SEC);
 375         buf[1 + DS1305_SEC] = bin2bcd(alm->time.tm_sec);
 376         buf[1 + DS1305_MIN] = bin2bcd(alm->time.tm_min);
 377         buf[1 + DS1305_HOUR] = hour2bcd(ds1305->hr12, alm->time.tm_hour);
 378         buf[1 + DS1305_WDAY] = DS1305_ALM_DISABLE;
 379
 380         dev_dbg(dev, "%s: %02x %02x %02x %02x\n",
 381                 "alm0 write", buf[1 + DS1305_SEC], buf[1 + DS1305_MIN],
 382                 buf[1 + DS1305_HOUR], buf[1 + DS1305_WDAY]);
 383
 384         status = spi_write_then_read(spi, buf, sizeof buf, NULL, 0);
 385         if (status < 0)
 386                 return status;
 387
 388         /* enable alarm if requested */
 389         if (alm->enabled) {
 390                 ds1305->ctrl[0] |= DS1305_AEI0;
 391
 392                 buf[0] = DS1305_WRITE | DS1305_CONTROL;
 393                 buf[1] = ds1305->ctrl[0];
 394                 status = spi_write_then_read(ds1305->spi, buf, 2, NULL, 0);
 395         }
 396
 397         return status;
 398 }
 399
 400 #ifdef CONFIG_PROC_FS
 401
 402 static int ds1305_proc(struct device *dev, struct seq_file *seq)
 403 {
 404         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 405         char            *diodes = "no";
 406         char            *resistors = "";
 407
 408         /* ctrl[2] is treated as read-only; no locking needed */
 409         if ((ds1305->ctrl[2] & 0xf0) == DS1305_TRICKLE_MAGIC) {
 410                 switch (ds1305->ctrl[2] & 0x0c) {
 411                 case DS1305_TRICKLE_DS2:
 412                         diodes = "2 diodes, ";
 413                         break;
 414                 case DS1305_TRICKLE_DS1:
 415                         diodes = "1 diode, ";
 416                         break;
 417                 default:
 418                         goto done;
 419                 }
 420                 switch (ds1305->ctrl[2] & 0x03) {
 421                 case DS1305_TRICKLE_2K:
 422                         resistors = "2k Ohm";
 423                         break;
 424                 case DS1305_TRICKLE_4K:
 425                         resistors = "4k Ohm";
 426                         break;
 427                 case DS1305_TRICKLE_8K:
 428                         resistors = "8k Ohm";
 429                         break;
 430                 default:
 431                         diodes = "no";
 432                         break;
 433                 }
 434         }
 435
 436 done:
 437         return seq_printf(seq,
 438                         "trickle_charge\t: %s%s\n",
 439                         diodes, resistors);
 440 }
 441
 442 #else
 443 #define ds1305_proc     NULL
 444 #endif
 445
 446 static const struct rtc_class_ops ds1305_ops = {
 447         .read_time      = ds1305_get_time,
 448         .set_time       = ds1305_set_time,
 449         .read_alarm     = ds1305_get_alarm,
 450         .set_alarm      = ds1305_set_alarm,
 451         .proc           = ds1305_proc,
 452         .alarm_irq_enable = ds1305_alarm_irq_enable,
 453 };
 454
 455 static void ds1305_work(struct work_struct *work)
 456 {
 457         struct ds1305   *ds1305 = container_of(work, struct ds1305, work);
 458         struct mutex    *lock = &ds1305->rtc->ops_lock;
 459         struct spi_device *spi = ds1305->spi;
 460         u8              buf[3];
 461         int             status;
 462
 463         /* lock to protect ds1305->ctrl */
 464         mutex_lock(lock);
 465
 466         /* Disable the IRQ, and clear its status ... for now, we "know"
 467          * that if more than one alarm is active, they're in sync.
 468          * Note that reading ALM data registers also clears IRQ status.
 469          */
 470         ds1305->ctrl[0] &= ~(DS1305_AEI1 | DS1305_AEI0);
 471         ds1305->ctrl[1] = 0;
 472
 473         buf[0] = DS1305_WRITE | DS1305_CONTROL;
 474         buf[1] = ds1305->ctrl[0];
 475         buf[2] = 0;
 476
 477         status = spi_write_then_read(spi, buf, sizeof buf,
 478                         NULL, 0);
 479         if (status < 0)
 480                 dev_dbg(&spi->dev, "clear irq --> %d\n", status);
 481
 482         mutex_unlock(lock);
 483
 484         if (!test_bit(FLAG_EXITING, &ds1305->flags))
 485                 enable_irq(spi->irq);
 486
 487         rtc_update_irq(ds1305->rtc, 1, RTC_AF | RTC_IRQF);
 488 }
 489
 490 /*
 491  * This "real" IRQ handler hands off to a workqueue mostly to allow
 492  * mutex locking for ds1305->ctrl ... unlike I2C, we could issue async
 493  * I/O requests in IRQ context (to clear the IRQ status).
 494  */
 495 static irqreturn_t ds1305_irq(int irq, void *p)
 496 {
 497         struct ds1305           *ds1305 = p;
 498
 499         disable_irq(irq);
 500         schedule_work(&ds1305->work);
 501         return IRQ_HANDLED;
 502 }
 503
 504 /*----------------------------------------------------------------------*/
 505
 506 /*
 507  * Interface for NVRAM
 508  */
 509
 510 static void msg_init(struct spi_message *m, struct spi_transfer *x,
 511                 u8 *addr, size_t count, char *tx, char *rx)
 512 {
 513         spi_message_init(m);
 514         memset(x, 0, 2 * sizeof(*x));
 515
 516         x->tx_buf = addr;
 517         x->len = 1;
 518         spi_message_add_tail(x, m);
 519
 520         x++;
 521
 522         x->tx_buf = tx;
 523         x->rx_buf = rx;
 524         x->len = count;
 525         spi_message_add_tail(x, m);
 526 }
 527
 528 static ssize_t
 529 ds1305_nvram_read(struct file *filp, struct kobject *kobj,
 530                 struct bin_attribute *attr,
 531                 char *buf, loff_t off, size_t count)
 532 {
 533         struct spi_device       *spi;
 534         u8                      addr;
 535         struct spi_message      m;
 536         struct spi_transfer     x[2];
 537         int                     status;
 538
 539         spi = container_of(kobj, struct spi_device, dev.kobj);
 540
 541         if (unlikely(off >= DS1305_NVRAM_LEN))
 542                 return 0;
 543         if (count >= DS1305_NVRAM_LEN)
 544                 count = DS1305_NVRAM_LEN;
 545         if ((off + count) > DS1305_NVRAM_LEN)
 546                 count = DS1305_NVRAM_LEN - off;
 547         if (unlikely(!count))
 548                 return count;
 549
 550         addr = DS1305_NVRAM + off;
 551         msg_init(&m, x, &addr, count, NULL, buf);
 552
 553         status = spi_sync(spi, &m);
 554         if (status < 0)
 555                 dev_err(&spi->dev, "nvram %s error %d\n", "read", status);
 556         return (status < 0) ? status : count;
 557 }
 558
 559 static ssize_t
 560 ds1305_nvram_write(struct file *filp, struct kobject *kobj,
 561                 struct bin_attribute *attr,
 562                 char *buf, loff_t off, size_t count)
 563 {
 564         struct spi_device       *spi;
 565         u8                      addr;
 566         struct spi_message      m;
 567         struct spi_transfer     x[2];
 568         int                     status;
 569
 570         spi = container_of(kobj, struct spi_device, dev.kobj);
 571
 572         if (unlikely(off >= DS1305_NVRAM_LEN))
 573                 return -EFBIG;
 574         if (count >= DS1305_NVRAM_LEN)
 575                 count = DS1305_NVRAM_LEN;
 576         if ((off + count) > DS1305_NVRAM_LEN)
 577                 count = DS1305_NVRAM_LEN - off;
 578         if (unlikely(!count))
 579                 return count;
 580
 581         addr = (DS1305_WRITE | DS1305_NVRAM) + off;
 582         msg_init(&m, x, &addr, count, buf, NULL);
 583
 584         status = spi_sync(spi, &m);
 585         if (status < 0)
 586                 dev_err(&spi->dev, "nvram %s error %d\n", "write", status);
 587         return (status < 0) ? status : count;
 588 }
 589
 590 static struct bin_attribute nvram = {
 591         .attr.name      = "nvram",
 592         .attr.mode      = S_IRUGO | S_IWUSR,
 593         .read           = ds1305_nvram_read,
 594         .write          = ds1305_nvram_write,
 595         .size           = DS1305_NVRAM_LEN,
 596 };
 597
 598 /*----------------------------------------------------------------------*/
 599
 600 /*
 601  * Interface to SPI stack
 602  */
 603
 604 static int __devinit ds1305_probe(struct spi_device *spi)
 605 {
 606         struct ds1305                   *ds1305;
 607         int                             status;
 608         u8                              addr, value;
 609         struct ds1305_platform_data     *pdata = spi->dev.platform_data;
 610         bool                            write_ctrl = false;
 611
 612         /* Sanity check board setup data.  This may be hooked up
 613          * in 3wire mode, but we don't care.  Note that unless
 614          * there's an inverter in place, this needs SPI_CS_HIGH!
 615          */
 616         if ((spi->bits_per_word && spi->bits_per_word != 8)
 617                         || (spi->max_speed_hz > 2000000)
 618                         || !(spi->mode & SPI_CPHA))
 619                 return -EINVAL;
 620
 621         /* set up driver data */
 622         ds1305 = kzalloc(sizeof *ds1305, GFP_KERNEL);
 623         if (!ds1305)
 624                 return -ENOMEM;
 625         ds1305->spi = spi;
 626         spi_set_drvdata(spi, ds1305);
 627
 628         /* read and cache control registers */
 629         addr = DS1305_CONTROL;
 630         status = spi_write_then_read(spi, &addr, sizeof addr,
 631                         ds1305->ctrl, sizeof ds1305->ctrl);
 632         if (status < 0) {
 633                 dev_dbg(&spi->dev, "can't %s, %d\n",
 634                                 "read", status);
 635                 goto fail0;
 636         }
 637
 638         dev_dbg(&spi->dev, "ctrl %s: %02x %02x %02x\n",
 639                         "read", ds1305->ctrl[0],
 640                         ds1305->ctrl[1], ds1305->ctrl[2]);
 641
 642         /* Sanity check register values ... partially compensating for the
 643          * fact that SPI has no device handshake.  A pullup on MISO would
 644          * make these tests fail; but not all systems will have one.  If
 645          * some register is neither 0x00 nor 0xff, a chip is likely there.
 646          */
 647         if ((ds1305->ctrl[0] & 0x38) != 0 || (ds1305->ctrl[1] & 0xfc) != 0) {
 648                 dev_dbg(&spi->dev, "RTC chip is not present\n");
 649                 status = -ENODEV;
 650                 goto fail0;
 651         }
 652         if (ds1305->ctrl[2] == 0)
 653                 dev_dbg(&spi->dev, "chip may not be present\n");
 654
 655         /* enable writes if needed ... if we were paranoid it would
 656          * make sense to enable them only when absolutely necessary.
 657          */
 658         if (ds1305->ctrl[0] & DS1305_WP) {
 659                 u8              buf[2];
 660
 661                 ds1305->ctrl[0] &= ~DS1305_WP;
 662
 663                 buf[0] = DS1305_WRITE | DS1305_CONTROL;
 664                 buf[1] = ds1305->ctrl[0];
 665                 status = spi_write_then_read(spi, buf, sizeof buf, NULL, 0);
 666
 667                 dev_dbg(&spi->dev, "clear WP --> %d\n", status);
 668                 if (status < 0)
 669                         goto fail0;
 670         }
 671
 672         /* on DS1305, maybe start oscillator; like most low power
 673          * oscillators, it may take a second to stabilize
 674          */
 675         if (ds1305->ctrl[0] & DS1305_nEOSC) {
 676                 ds1305->ctrl[0] &= ~DS1305_nEOSC;
 677                 write_ctrl = true;
 678                 dev_warn(&spi->dev, "SET TIME!\n");
 679         }
 680
 681         /* ack any pending IRQs */
 682         if (ds1305->ctrl[1]) {
 683                 ds1305->ctrl[1] = 0;
 684                 write_ctrl = true;
 685         }
 686
 687         /* this may need one-time (re)init */
 688         if (pdata) {
 689                 /* maybe enable trickle charge */
 690                 if (((ds1305->ctrl[2] & 0xf0) != DS1305_TRICKLE_MAGIC)) {
 691                         ds1305->ctrl[2] = DS1305_TRICKLE_MAGIC
 692                                                 | pdata->trickle;
 693                         write_ctrl = true;
 694                 }
 695
 696                 /* on DS1306, configure 1 Hz signal */
 697                 if (pdata->is_ds1306) {
 698                         if (pdata->en_1hz) {
 699                                 if (!(ds1305->ctrl[0] & DS1306_1HZ)) {
 700                                         ds1305->ctrl[0] |= DS1306_1HZ;
 701                                         write_ctrl = true;
 702                                 }
 703                         } else {
 704                                 if (ds1305->ctrl[0] & DS1306_1HZ) {
 705                                         ds1305->ctrl[0] &= ~DS1306_1HZ;
 706                                         write_ctrl = true;
 707                                 }
 708                         }
 709                 }
 710         }
 711
 712         if (write_ctrl) {
 713                 u8              buf[4];
 714
 715                 buf[0] = DS1305_WRITE | DS1305_CONTROL;
 716                 buf[1] = ds1305->ctrl[0];
 717                 buf[2] = ds1305->ctrl[1];
 718                 buf[3] = ds1305->ctrl[2];
 719                 status = spi_write_then_read(spi, buf, sizeof buf, NULL, 0);
 720                 if (status < 0) {
 721                         dev_dbg(&spi->dev, "can't %s, %d\n",
 722                                         "write", status);
 723                         goto fail0;
 724                 }
 725
 726                 dev_dbg(&spi->dev, "ctrl %s: %02x %02x %02x\n",
 727                                 "write", ds1305->ctrl[0],
 728                                 ds1305->ctrl[1], ds1305->ctrl[2]);
 729         }
 730
 731         /* see if non-Linux software set up AM/PM mode */
 732         addr = DS1305_HOUR;
 733         status = spi_write_then_read(spi, &addr, sizeof addr,
 734                                 &value, sizeof value);
 735         if (status < 0) {
 736                 dev_dbg(&spi->dev, "read HOUR --> %d\n", status);
 737                 goto fail0;
 738         }
 739
 740         ds1305->hr12 = (DS1305_HR_12 & value) != 0;
 741         if (ds1305->hr12)
 742                 dev_dbg(&spi->dev, "AM/PM\n");
 743
 744         /* register RTC ... from here on, ds1305->ctrl needs locking */
 745         ds1305->rtc = rtc_device_register("ds1305", &spi->dev,
 746                         &ds1305_ops, THIS_MODULE);
 747         if (IS_ERR(ds1305->rtc)) {
 748                 status = PTR_ERR(ds1305->rtc);
 749                 dev_dbg(&spi->dev, "register rtc --> %d\n", status);
 750                 goto fail0;
 751         }
 752
 753         /* Maybe set up alarm IRQ; be ready to handle it triggering right
 754          * away.  NOTE that we don't share this.  The signal is active low,
 755          * and we can't ack it before a SPI message delay.  We temporarily
 756          * disable the IRQ until it's acked, which lets us work with more
 757          * IRQ trigger modes (not all IRQ controllers can do falling edge).
 758          */
 759         if (spi->irq) {
 760                 INIT_WORK(&ds1305->work, ds1305_work);
 761                 status = request_irq(spi->irq, ds1305_irq,
 762                                 0, dev_name(&ds1305->rtc->dev), ds1305);
 763                 if (status < 0) {
 764                         dev_dbg(&spi->dev, "request_irq %d --> %d\n",
 765                                         spi->irq, status);
 766                         goto fail1;
 767                 }
 768
 769                 device_set_wakeup_capable(&spi->dev, 1);
 770         }
 771
 772         /* export NVRAM */
 773         status = sysfs_create_bin_file(&spi->dev.kobj, &nvram);
 774         if (status < 0) {
 775                 dev_dbg(&spi->dev, "register nvram --> %d\n", status);
 776                 goto fail2;
 777         }
 778
 779         return 0;
 780
 781 fail2:
 782         free_irq(spi->irq, ds1305);
 783 fail1:
 784         rtc_device_unregister(ds1305->rtc);
 785 fail0:
 786         kfree(ds1305);
 787         return status;
 788 }
 789
 790 static int __devexit ds1305_remove(struct spi_device *spi)
 791 {
 792         struct ds1305 *ds1305 = spi_get_drvdata(spi);
 793
 794         sysfs_remove_bin_file(&spi->dev.kobj, &nvram);
 795
 796         /* carefully shut down irq and workqueue, if present */
 797         if (spi->irq) {
 798                 set_bit(FLAG_EXITING, &ds1305->flags);
 799                 free_irq(spi->irq, ds1305);
 800                 cancel_work_sync(&ds1305->work);
 801         }
 802
 803         rtc_device_unregister(ds1305->rtc);
 804         spi_set_drvdata(spi, NULL);
 805         kfree(ds1305);
 806         return 0;
 807 }
 808
 809 static struct spi_driver ds1305_driver = {
 810         .driver.name    = "rtc-ds1305",
 811         .driver.owner   = THIS_MODULE,
 812         .probe          = ds1305_probe,
 813         .remove         = __devexit_p(ds1305_remove),
 814         /* REVISIT add suspend/resume */
 815 };
 816
 817 static int __init ds1305_init(void)
 818 {
 819         return spi_register_driver(&ds1305_driver);
 820 }
 821 module_init(ds1305_init);
 822
 823 static void __exit ds1305_exit(void)
 824 {
 825         spi_unregister_driver(&ds1305_driver);
 826 }
 827 module_exit(ds1305_exit);
 828
 829 MODULE_DESCRIPTION("RTC driver for DS1305 and DS1306 chips");
 830 MODULE_LICENSE("GPL");
 831 MODULE_ALIAS("spi:rtc-ds1305");