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: %3ph, %4ph\n", "read", &buf[0], &buf[3]);
 190
 191         /* Decode the registers */
 192         time->tm_sec = bcd2bin(buf[DS1305_SEC]);
 193         time->tm_min = bcd2bin(buf[DS1305_MIN]);
 194         time->tm_hour = bcd2hour(buf[DS1305_HOUR]);
 195         time->tm_wday = buf[DS1305_WDAY] - 1;
 196         time->tm_mday = bcd2bin(buf[DS1305_MDAY]);
 197         time->tm_mon = bcd2bin(buf[DS1305_MON]) - 1;
 198         time->tm_year = bcd2bin(buf[DS1305_YEAR]) + 100;
 199
 200         dev_vdbg(dev, "%s secs=%d, mins=%d, "
 201                 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
 202                 "read", time->tm_sec, time->tm_min,
 203                 time->tm_hour, time->tm_mday,
 204                 time->tm_mon, time->tm_year, time->tm_wday);
 205
 206         /* Time may not be set */
 207         return rtc_valid_tm(time);
 208 }
 209
 210 static int ds1305_set_time(struct device *dev, struct rtc_time *time)
 211 {
 212         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 213         u8              buf[1 + DS1305_RTC_LEN];
 214         u8              *bp = buf;
 215
 216         dev_vdbg(dev, "%s secs=%d, mins=%d, "
 217                 "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
 218                 "write", time->tm_sec, time->tm_min,
 219                 time->tm_hour, time->tm_mday,
 220                 time->tm_mon, time->tm_year, time->tm_wday);
 221
 222         /* Write registers starting at the first time/date address. */
 223         *bp++ = DS1305_WRITE | DS1305_SEC;
 224
 225         *bp++ = bin2bcd(time->tm_sec);
 226         *bp++ = bin2bcd(time->tm_min);
 227         *bp++ = hour2bcd(ds1305->hr12, time->tm_hour);
 228         *bp++ = (time->tm_wday < 7) ? (time->tm_wday + 1) : 1;
 229         *bp++ = bin2bcd(time->tm_mday);
 230         *bp++ = bin2bcd(time->tm_mon + 1);
 231         *bp++ = bin2bcd(time->tm_year - 100);
 232
 233         dev_dbg(dev, "%s: %3ph, %4ph\n", "write", &buf[1], &buf[4]);
 234
 235         /* use write-then-read since dma from stack is nonportable */
 236         return spi_write_then_read(ds1305->spi, buf, sizeof(buf),
 237                         NULL, 0);
 238 }
 239
 240 /*
 241  * Get/set of alarm is a bit funky:
 242  *
 243  * - First there's the inherent raciness of getting the (partitioned)
 244  *   status of an alarm that could trigger while we're reading parts
 245  *   of that status.
 246  *
 247  * - Second there's its limited range (we could increase it a bit by
 248  *   relying on WDAY), which means it will easily roll over.
 249  *
 250  * - Third there's the choice of two alarms and alarm signals.
 251  *   Here we use ALM0 and expect that nINT0 (open drain) is used;
 252  *   that's the only real option for DS1306 runtime alarms, and is
 253  *   natural on DS1305.
 254  *
 255  * - Fourth, there's also ALM1, and a second interrupt signal:
 256  *     + On DS1305 ALM1 uses nINT1 (when INTCN=1) else nINT0;
 257  *     + On DS1306 ALM1 only uses INT1 (an active high pulse)
 258  *       and it won't work when VCC1 is active.
 259  *
 260  *   So to be most general, we should probably set both alarms to the
 261  *   same value, letting ALM1 be the wakeup event source on DS1306
 262  *   and handling several wiring options on DS1305.
 263  *
 264  * - Fifth, we support the polled mode (as well as possible; why not?)
 265  *   even when no interrupt line is wired to an IRQ.
 266  */
 267
 268 /*
 269  * Context: caller holds rtc->ops_lock (to protect ds1305->ctrl)
 270  */
 271 static int ds1305_get_alarm(struct device *dev, struct rtc_wkalrm *alm)
 272 {
 273         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 274         struct spi_device *spi = ds1305->spi;
 275         u8              addr;
 276         int             status;
 277         u8              buf[DS1305_ALM_LEN];
 278
 279         /* Refresh control register cache BEFORE reading ALM0 registers,
 280          * since reading alarm registers acks any pending IRQ.  That
 281          * makes returning "pending" status a bit of a lie, but that bit
 282          * of EFI status is at best fragile anyway (given IRQ handlers).
 283          */
 284         addr = DS1305_CONTROL;
 285         status = spi_write_then_read(spi, &addr, sizeof(addr),
 286                         ds1305->ctrl, sizeof(ds1305->ctrl));
 287         if (status < 0)
 288                 return status;
 289
 290         alm->enabled = !!(ds1305->ctrl[0] & DS1305_AEI0);
 291         alm->pending = !!(ds1305->ctrl[1] & DS1305_AEI0);
 292
 293         /* get and check ALM0 registers */
 294         addr = DS1305_ALM0(DS1305_SEC);
 295         status = spi_write_then_read(spi, &addr, sizeof(addr),
 296                         buf, sizeof(buf));
 297         if (status < 0)
 298                 return status;
 299
 300         dev_vdbg(dev, "%s: %02x %02x %02x %02x\n",
 301                 "alm0 read", buf[DS1305_SEC], buf[DS1305_MIN],
 302                 buf[DS1305_HOUR], buf[DS1305_WDAY]);
 303
 304         if ((DS1305_ALM_DISABLE & buf[DS1305_SEC])
 305                         || (DS1305_ALM_DISABLE & buf[DS1305_MIN])
 306                         || (DS1305_ALM_DISABLE & buf[DS1305_HOUR]))
 307                 return -EIO;
 308
 309         /* Stuff these values into alm->time and let RTC framework code
 310          * fill in the rest ... and also handle rollover to tomorrow when
 311          * that's needed.
 312          */
 313         alm->time.tm_sec = bcd2bin(buf[DS1305_SEC]);
 314         alm->time.tm_min = bcd2bin(buf[DS1305_MIN]);
 315         alm->time.tm_hour = bcd2hour(buf[DS1305_HOUR]);
 316
 317         return 0;
 318 }
 319
 320 /*
 321  * Context: caller holds rtc->ops_lock (to protect ds1305->ctrl)
 322  */
 323 static int ds1305_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
 324 {
 325         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 326         struct spi_device *spi = ds1305->spi;
 327         unsigned long   now, later;
 328         struct rtc_time tm;
 329         int             status;
 330         u8              buf[1 + DS1305_ALM_LEN];
 331
 332         /* convert desired alarm to time_t */
 333         status = rtc_tm_to_time(&alm->time, &later);
 334         if (status < 0)
 335                 return status;
 336
 337         /* Read current time as time_t */
 338         status = ds1305_get_time(dev, &tm);
 339         if (status < 0)
 340                 return status;
 341         status = rtc_tm_to_time(&tm, &now);
 342         if (status < 0)
 343                 return status;
 344
 345         /* make sure alarm fires within the next 24 hours */
 346         if (later <= now)
 347                 return -EINVAL;
 348         if ((later - now) > 24 * 60 * 60)
 349                 return -EDOM;
 350
 351         /* disable alarm if needed */
 352         if (ds1305->ctrl[0] & DS1305_AEI0) {
 353                 ds1305->ctrl[0] &= ~DS1305_AEI0;
 354
 355                 buf[0] = DS1305_WRITE | DS1305_CONTROL;
 356                 buf[1] = ds1305->ctrl[0];
 357                 status = spi_write_then_read(ds1305->spi, buf, 2, NULL, 0);
 358                 if (status < 0)
 359                         return status;
 360         }
 361
 362         /* write alarm */
 363         buf[0] = DS1305_WRITE | DS1305_ALM0(DS1305_SEC);
 364         buf[1 + DS1305_SEC] = bin2bcd(alm->time.tm_sec);
 365         buf[1 + DS1305_MIN] = bin2bcd(alm->time.tm_min);
 366         buf[1 + DS1305_HOUR] = hour2bcd(ds1305->hr12, alm->time.tm_hour);
 367         buf[1 + DS1305_WDAY] = DS1305_ALM_DISABLE;
 368
 369         dev_dbg(dev, "%s: %02x %02x %02x %02x\n",
 370                 "alm0 write", buf[1 + DS1305_SEC], buf[1 + DS1305_MIN],
 371                 buf[1 + DS1305_HOUR], buf[1 + DS1305_WDAY]);
 372
 373         status = spi_write_then_read(spi, buf, sizeof(buf), NULL, 0);
 374         if (status < 0)
 375                 return status;
 376
 377         /* enable alarm if requested */
 378         if (alm->enabled) {
 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         }
 385
 386         return status;
 387 }
 388
 389 #ifdef CONFIG_PROC_FS
 390
 391 static int ds1305_proc(struct device *dev, struct seq_file *seq)
 392 {
 393         struct ds1305   *ds1305 = dev_get_drvdata(dev);
 394         char            *diodes = "no";
 395         char            *resistors = "";
 396
 397         /* ctrl[2] is treated as read-only; no locking needed */
 398         if ((ds1305->ctrl[2] & 0xf0) == DS1305_TRICKLE_MAGIC) {
 399                 switch (ds1305->ctrl[2] & 0x0c) {
 400                 case DS1305_TRICKLE_DS2:
 401                         diodes = "2 diodes, ";
 402                         break;
 403                 case DS1305_TRICKLE_DS1:
 404                         diodes = "1 diode, ";
 405                         break;
 406                 default:
 407                         goto done;
 408                 }
 409                 switch (ds1305->ctrl[2] & 0x03) {
 410                 case DS1305_TRICKLE_2K:
 411                         resistors = "2k Ohm";
 412                         break;
 413                 case DS1305_TRICKLE_4K:
 414                         resistors = "4k Ohm";
 415                         break;
 416                 case DS1305_TRICKLE_8K:
 417                         resistors = "8k Ohm";
 418                         break;
 419                 default:
 420                         diodes = "no";
 421                         break;
 422                 }
 423         }
 424
 425 done:
 426         seq_printf(seq, "trickle_charge\t: %s%s\n", diodes, resistors);
 427
 428         return 0;
 429 }
 430
 431 #else
 432 #define ds1305_proc     NULL
 433 #endif
 434
 435 static const struct rtc_class_ops ds1305_ops = {
 436         .read_time      = ds1305_get_time,
 437         .set_time       = ds1305_set_time,
 438         .read_alarm     = ds1305_get_alarm,
 439         .set_alarm      = ds1305_set_alarm,
 440         .proc           = ds1305_proc,
 441         .alarm_irq_enable = ds1305_alarm_irq_enable,
 442 };
 443
 444 static void ds1305_work(struct work_struct *work)
 445 {
 446         struct ds1305   *ds1305 = container_of(work, struct ds1305, work);
 447         struct mutex    *lock = &ds1305->rtc->ops_lock;
 448         struct spi_device *spi = ds1305->spi;
 449         u8              buf[3];
 450         int             status;
 451
 452         /* lock to protect ds1305->ctrl */
 453         mutex_lock(lock);
 454
 455         /* Disable the IRQ, and clear its status ... for now, we "know"
 456          * that if more than one alarm is active, they're in sync.
 457          * Note that reading ALM data registers also clears IRQ status.
 458          */
 459         ds1305->ctrl[0] &= ~(DS1305_AEI1 | DS1305_AEI0);
 460         ds1305->ctrl[1] = 0;
 461
 462         buf[0] = DS1305_WRITE | DS1305_CONTROL;
 463         buf[1] = ds1305->ctrl[0];
 464         buf[2] = 0;
 465
 466         status = spi_write_then_read(spi, buf, sizeof(buf),
 467                         NULL, 0);
 468         if (status < 0)
 469                 dev_dbg(&spi->dev, "clear irq --> %d\n", status);
 470
 471         mutex_unlock(lock);
 472
 473         if (!test_bit(FLAG_EXITING, &ds1305->flags))
 474                 enable_irq(spi->irq);
 475
 476         rtc_update_irq(ds1305->rtc, 1, RTC_AF | RTC_IRQF);
 477 }
 478
 479 /*
 480  * This "real" IRQ handler hands off to a workqueue mostly to allow
 481  * mutex locking for ds1305->ctrl ... unlike I2C, we could issue async
 482  * I/O requests in IRQ context (to clear the IRQ status).
 483  */
 484 static irqreturn_t ds1305_irq(int irq, void *p)
 485 {
 486         struct ds1305           *ds1305 = p;
 487
 488         disable_irq(irq);
 489         schedule_work(&ds1305->work);
 490         return IRQ_HANDLED;
 491 }
 492
 493 /*----------------------------------------------------------------------*/
 494
 495 /*
 496  * Interface for NVRAM
 497  */
 498
 499 static void msg_init(struct spi_message *m, struct spi_transfer *x,
 500                 u8 *addr, size_t count, char *tx, char *rx)
 501 {
 502         spi_message_init(m);
 503         memset(x, 0, 2 * sizeof(*x));
 504
 505         x->tx_buf = addr;
 506         x->len = 1;
 507         spi_message_add_tail(x, m);
 508
 509         x++;
 510
 511         x->tx_buf = tx;
 512         x->rx_buf = rx;
 513         x->len = count;
 514         spi_message_add_tail(x, m);
 515 }
 516
 517 static int ds1305_nvram_read(void *priv, unsigned int off, void *buf,
 518                              size_t count)
 519 {
 520         struct ds1305           *ds1305 = priv;
 521         struct spi_device       *spi = ds1305->spi;
 522         u8                      addr;
 523         struct spi_message      m;
 524         struct spi_transfer     x[2];
 525
 526         addr = DS1305_NVRAM + off;
 527         msg_init(&m, x, &addr, count, NULL, buf);
 528
 529         return spi_sync(spi, &m);
 530 }
 531
 532 static int ds1305_nvram_write(void *priv, unsigned int off, void *buf,
 533                               size_t count)
 534 {
 535         struct ds1305           *ds1305 = priv;
 536         struct spi_device       *spi = ds1305->spi;
 537         u8                      addr;
 538         struct spi_message      m;
 539         struct spi_transfer     x[2];
 540
 541         addr = (DS1305_WRITE | DS1305_NVRAM) + off;
 542         msg_init(&m, x, &addr, count, buf, NULL);
 543
 544         return spi_sync(spi, &m);
 545 }
 546
 547 static struct nvmem_config ds1305_nvmem_cfg = {
 548         .name = "ds1305_nvram",
 549         .word_size = 1,
 550         .stride = 1,
 551         .size = DS1305_NVRAM_LEN,
 552         .reg_read = ds1305_nvram_read,
 553         .reg_write = ds1305_nvram_write,
 554 };
 555
 556 /*----------------------------------------------------------------------*/
 557
 558 /*
 559  * Interface to SPI stack
 560  */
 561
 562 static int ds1305_probe(struct spi_device *spi)
 563 {
 564         struct ds1305                   *ds1305;
 565         int                             status;
 566         u8                              addr, value;
 567         struct ds1305_platform_data     *pdata = dev_get_platdata(&spi->dev);
 568         bool                            write_ctrl = false;
 569
 570         /* Sanity check board setup data.  This may be hooked up
 571          * in 3wire mode, but we don't care.  Note that unless
 572          * there's an inverter in place, this needs SPI_CS_HIGH!
 573          */
 574         if ((spi->bits_per_word && spi->bits_per_word != 8)
 575                         || (spi->max_speed_hz > 2000000)
 576                         || !(spi->mode & SPI_CPHA))
 577                 return -EINVAL;
 578
 579         /* set up driver data */
 580         ds1305 = devm_kzalloc(&spi->dev, sizeof(*ds1305), GFP_KERNEL);
 581         if (!ds1305)
 582                 return -ENOMEM;
 583         ds1305->spi = spi;
 584         spi_set_drvdata(spi, ds1305);
 585
 586         /* read and cache control registers */
 587         addr = DS1305_CONTROL;
 588         status = spi_write_then_read(spi, &addr, sizeof(addr),
 589                         ds1305->ctrl, sizeof(ds1305->ctrl));
 590         if (status < 0) {
 591                 dev_dbg(&spi->dev, "can't %s, %d\n",
 592                                 "read", status);
 593                 return status;
 594         }
 595
 596         dev_dbg(&spi->dev, "ctrl %s: %3ph\n", "read", ds1305->ctrl);
 597
 598         /* Sanity check register values ... partially compensating for the
 599          * fact that SPI has no device handshake.  A pullup on MISO would
 600          * make these tests fail; but not all systems will have one.  If
 601          * some register is neither 0x00 nor 0xff, a chip is likely there.
 602          */
 603         if ((ds1305->ctrl[0] & 0x38) != 0 || (ds1305->ctrl[1] & 0xfc) != 0) {
 604                 dev_dbg(&spi->dev, "RTC chip is not present\n");
 605                 return -ENODEV;
 606         }
 607         if (ds1305->ctrl[2] == 0)
 608                 dev_dbg(&spi->dev, "chip may not be present\n");
 609
 610         /* enable writes if needed ... if we were paranoid it would
 611          * make sense to enable them only when absolutely necessary.
 612          */
 613         if (ds1305->ctrl[0] & DS1305_WP) {
 614                 u8              buf[2];
 615
 616                 ds1305->ctrl[0] &= ~DS1305_WP;
 617
 618                 buf[0] = DS1305_WRITE | DS1305_CONTROL;
 619                 buf[1] = ds1305->ctrl[0];
 620                 status = spi_write_then_read(spi, buf, sizeof(buf), NULL, 0);
 621
 622                 dev_dbg(&spi->dev, "clear WP --> %d\n", status);
 623                 if (status < 0)
 624                         return status;
 625         }
 626
 627         /* on DS1305, maybe start oscillator; like most low power
 628          * oscillators, it may take a second to stabilize
 629          */
 630         if (ds1305->ctrl[0] & DS1305_nEOSC) {
 631                 ds1305->ctrl[0] &= ~DS1305_nEOSC;
 632                 write_ctrl = true;
 633                 dev_warn(&spi->dev, "SET TIME!\n");
 634         }
 635
 636         /* ack any pending IRQs */
 637         if (ds1305->ctrl[1]) {
 638                 ds1305->ctrl[1] = 0;
 639                 write_ctrl = true;
 640         }
 641
 642         /* this may need one-time (re)init */
 643         if (pdata) {
 644                 /* maybe enable trickle charge */
 645                 if (((ds1305->ctrl[2] & 0xf0) != DS1305_TRICKLE_MAGIC)) {
 646                         ds1305->ctrl[2] = DS1305_TRICKLE_MAGIC
 647                                                 | pdata->trickle;
 648                         write_ctrl = true;
 649                 }
 650
 651                 /* on DS1306, configure 1 Hz signal */
 652                 if (pdata->is_ds1306) {
 653                         if (pdata->en_1hz) {
 654                                 if (!(ds1305->ctrl[0] & DS1306_1HZ)) {
 655                                         ds1305->ctrl[0] |= DS1306_1HZ;
 656                                         write_ctrl = true;
 657                                 }
 658                         } else {
 659                                 if (ds1305->ctrl[0] & DS1306_1HZ) {
 660                                         ds1305->ctrl[0] &= ~DS1306_1HZ;
 661                                         write_ctrl = true;
 662                                 }
 663                         }
 664                 }
 665         }
 666
 667         if (write_ctrl) {
 668                 u8              buf[4];
 669
 670                 buf[0] = DS1305_WRITE | DS1305_CONTROL;
 671                 buf[1] = ds1305->ctrl[0];
 672                 buf[2] = ds1305->ctrl[1];
 673                 buf[3] = ds1305->ctrl[2];
 674                 status = spi_write_then_read(spi, buf, sizeof(buf), NULL, 0);
 675                 if (status < 0) {
 676                         dev_dbg(&spi->dev, "can't %s, %d\n",
 677                                         "write", status);
 678                         return status;
 679                 }
 680
 681                 dev_dbg(&spi->dev, "ctrl %s: %3ph\n", "write", ds1305->ctrl);
 682         }
 683
 684         /* see if non-Linux software set up AM/PM mode */
 685         addr = DS1305_HOUR;
 686         status = spi_write_then_read(spi, &addr, sizeof(addr),
 687                                 &value, sizeof(value));
 688         if (status < 0) {
 689                 dev_dbg(&spi->dev, "read HOUR --> %d\n", status);
 690                 return status;
 691         }
 692
 693         ds1305->hr12 = (DS1305_HR_12 & value) != 0;
 694         if (ds1305->hr12)
 695                 dev_dbg(&spi->dev, "AM/PM\n");
 696
 697         /* register RTC ... from here on, ds1305->ctrl needs locking */
 698         ds1305->rtc = devm_rtc_allocate_device(&spi->dev);
 699         if (IS_ERR(ds1305->rtc)) {
 700                 return PTR_ERR(ds1305->rtc);
 701         }
 702
 703         ds1305->rtc->ops = &ds1305_ops;
 704
 705         ds1305_nvmem_cfg.priv = ds1305;
 706         ds1305->rtc->nvmem_config = &ds1305_nvmem_cfg;
 707         ds1305->rtc->nvram_old_abi = true;
 708
 709         status = rtc_register_device(ds1305->rtc);
 710         if (status) {
 711                 dev_dbg(&spi->dev, "register rtc --> %d\n", status);
 712                 return status;
 713         }
 714
 715         /* Maybe set up alarm IRQ; be ready to handle it triggering right
 716          * away.  NOTE that we don't share this.  The signal is active low,
 717          * and we can't ack it before a SPI message delay.  We temporarily
 718          * disable the IRQ until it's acked, which lets us work with more
 719          * IRQ trigger modes (not all IRQ controllers can do falling edge).
 720          */
 721         if (spi->irq) {
 722                 INIT_WORK(&ds1305->work, ds1305_work);
 723                 status = devm_request_irq(&spi->dev, spi->irq, ds1305_irq,
 724                                 0, dev_name(&ds1305->rtc->dev), ds1305);
 725                 if (status < 0) {
 726                         dev_err(&spi->dev, "request_irq %d --> %d\n",
 727                                         spi->irq, status);
 728                 } else {
 729                         device_set_wakeup_capable(&spi->dev, 1);
 730                 }
 731         }
 732
 733         return 0;
 734 }
 735
 736 static int ds1305_remove(struct spi_device *spi)
 737 {
 738         struct ds1305 *ds1305 = spi_get_drvdata(spi);
 739
 740         /* carefully shut down irq and workqueue, if present */
 741         if (spi->irq) {
 742                 set_bit(FLAG_EXITING, &ds1305->flags);
 743                 devm_free_irq(&spi->dev, spi->irq, ds1305);
 744                 cancel_work_sync(&ds1305->work);
 745         }
 746
 747         return 0;
 748 }
 749
 750 static struct spi_driver ds1305_driver = {
 751         .driver.name    = "rtc-ds1305",
 752         .probe          = ds1305_probe,
 753         .remove         = ds1305_remove,
 754         /* REVISIT add suspend/resume */
 755 };
 756
 757 module_spi_driver(ds1305_driver);
 758
 759 MODULE_DESCRIPTION("RTC driver for DS1305 and DS1306 chips");
 760 MODULE_LICENSE("GPL");
 761 MODULE_ALIAS("spi:rtc-ds1305");