drivers/rtc/rtc-bfin.c

   1 /*
   2  * Blackfin On-Chip Real Time Clock Driver
   3  *  Supports BF53[123]/BF53[467]/BF54[2489]
   4  *
   5  * Copyright 2004-2007 Analog Devices Inc.
   6  *
   7  * Enter bugs at http://blackfin.uclinux.org/
   8  *
   9  * Licensed under the GPL-2 or later.
  10  */
  11
  12 /* The biggest issue we deal with in this driver is that register writes are
  13  * synced to the RTC frequency of 1Hz.  So if you write to a register and
  14  * attempt to write again before the first write has completed, the new write
  15  * is simply discarded.  This can easily be troublesome if userspace disables
  16  * one event (say periodic) and then right after enables an event (say alarm).
  17  * Since all events are maintained in the same interrupt mask register, if
  18  * we wrote to it to disable the first event and then wrote to it again to
  19  * enable the second event, that second event would not be enabled as the
  20  * write would be discarded and things quickly fall apart.
  21  *
  22  * To keep this delay from significantly degrading performance (we, in theory,
  23  * would have to sleep for up to 1 second everytime we wanted to write a
  24  * register), we only check the write pending status before we start to issue
  25  * a new write.  We bank on the idea that it doesnt matter when the sync
  26  * happens so long as we don't attempt another write before it does.  The only
  27  * time userspace would take this penalty is when they try and do multiple
  28  * operations right after another ... but in this case, they need to take the
  29  * sync penalty, so we should be OK.
  30  *
  31  * Also note that the RTC_ISTAT register does not suffer this penalty; its
  32  * writes to clear status registers complete immediately.
  33  */
  34
  35 #include <linux/module.h>
  36 #include <linux/kernel.h>
  37 #include <linux/bcd.h>
  38 #include <linux/rtc.h>
  39 #include <linux/init.h>
  40 #include <linux/platform_device.h>
  41 #include <linux/seq_file.h>
  42 #include <linux/interrupt.h>
  43 #include <linux/spinlock.h>
  44 #include <linux/delay.h>
  45
  46 #include <asm/blackfin.h>
  47
  48 #define stamp(fmt, args...) pr_debug("%s:%i: " fmt "\n", __FUNCTION__, __LINE__, ## args)
  49 #define stampit() stamp("here i am")
  50
  51 struct bfin_rtc {
  52         struct rtc_device *rtc_dev;
  53         struct rtc_time rtc_alarm;
  54         spinlock_t lock;
  55 };
  56
  57 /* Bit values for the ISTAT / ICTL registers */
  58 #define RTC_ISTAT_WRITE_COMPLETE  0x8000
  59 #define RTC_ISTAT_WRITE_PENDING   0x4000
  60 #define RTC_ISTAT_ALARM_DAY       0x0040
  61 #define RTC_ISTAT_24HR            0x0020
  62 #define RTC_ISTAT_HOUR            0x0010
  63 #define RTC_ISTAT_MIN             0x0008
  64 #define RTC_ISTAT_SEC             0x0004
  65 #define RTC_ISTAT_ALARM           0x0002
  66 #define RTC_ISTAT_STOPWATCH       0x0001
  67
  68 /* Shift values for RTC_STAT register */
  69 #define DAY_BITS_OFF    17
  70 #define HOUR_BITS_OFF   12
  71 #define MIN_BITS_OFF    6
  72 #define SEC_BITS_OFF    0
  73
  74 /* Some helper functions to convert between the common RTC notion of time
  75  * and the internal Blackfin notion that is encoded in 32bits.
  76  */
  77 static inline u32 rtc_time_to_bfin(unsigned long now)
  78 {
  79         u32 sec  = (now % 60);
  80         u32 min  = (now % (60 * 60)) / 60;
  81         u32 hour = (now % (60 * 60 * 24)) / (60 * 60);
  82         u32 days = (now / (60 * 60 * 24));
  83         return (sec  << SEC_BITS_OFF) +
  84                (min  << MIN_BITS_OFF) +
  85                (hour << HOUR_BITS_OFF) +
  86                (days << DAY_BITS_OFF);
  87 }
  88 static inline unsigned long rtc_bfin_to_time(u32 rtc_bfin)
  89 {
  90         return (((rtc_bfin >> SEC_BITS_OFF)  & 0x003F)) +
  91                (((rtc_bfin >> MIN_BITS_OFF)  & 0x003F) * 60) +
  92                (((rtc_bfin >> HOUR_BITS_OFF) & 0x001F) * 60 * 60) +
  93                (((rtc_bfin >> DAY_BITS_OFF)  & 0x7FFF) * 60 * 60 * 24);
  94 }
  95 static inline void rtc_bfin_to_tm(u32 rtc_bfin, struct rtc_time *tm)
  96 {
  97         rtc_time_to_tm(rtc_bfin_to_time(rtc_bfin), tm);
  98 }
  99
 100 /* Wait for the previous write to a RTC register to complete.
 101  * Unfortunately, we can't sleep here as that introduces a race condition when
 102  * turning on interrupt events.  Consider this:
 103  *  - process sets alarm
 104  *  - process enables alarm
 105  *  - process sleeps while waiting for rtc write to sync
 106  *  - interrupt fires while process is sleeping
 107  *  - interrupt acks the event by writing to ISTAT
 108  *  - interrupt sets the WRITE PENDING bit
 109  *  - interrupt handler finishes
 110  *  - process wakes up, sees WRITE PENDING bit set, goes to sleep
 111  *  - interrupt fires while process is sleeping
 112  * If anyone can point out the obvious solution here, i'm listening :).  This
 113  * shouldn't be an issue on an SMP or preempt system as this function should
 114  * only be called with the rtc lock held.
 115  *
 116  * Other options:
 117  *  - disable PREN so the sync happens at 32.768kHZ ... but this changes the
 118  *    inc rate for all RTC registers from 1HZ to 32.768kHZ ...
 119  *  - use the write complete IRQ
 120  */
 121 static void rtc_bfin_sync_pending(void)
 122 {
 123         stampit();
 124         while (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_COMPLETE)) {
 125                 if (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_PENDING))
 126                         break;
 127         }
 128         bfin_write_RTC_ISTAT(RTC_ISTAT_WRITE_COMPLETE);
 129 }
 130
 131 static void rtc_bfin_reset(struct bfin_rtc *rtc)
 132 {
 133         /* Initialize the RTC. Enable pre-scaler to scale RTC clock
 134          * to 1Hz and clear interrupt/status registers. */
 135         spin_lock_irq(&rtc->lock);
 136         rtc_bfin_sync_pending();
 137         bfin_write_RTC_PREN(0x1);
 138         bfin_write_RTC_ICTL(0);
 139         bfin_write_RTC_SWCNT(0);
 140         bfin_write_RTC_ALARM(0);
 141         bfin_write_RTC_ISTAT(0xFFFF);
 142         spin_unlock_irq(&rtc->lock);
 143 }
 144
 145 static irqreturn_t bfin_rtc_interrupt(int irq, void *dev_id)
 146 {
 147         struct platform_device *pdev = to_platform_device(dev_id);
 148         struct bfin_rtc *rtc = platform_get_drvdata(pdev);
 149         unsigned long events = 0;
 150         u16 rtc_istat;
 151
 152         stampit();
 153
 154         spin_lock_irq(&rtc->lock);
 155
 156         rtc_istat = bfin_read_RTC_ISTAT();
 157
 158         if (rtc_istat & (RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY)) {
 159                 bfin_write_RTC_ISTAT(RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY);
 160                 events |= RTC_AF | RTC_IRQF;
 161         }
 162
 163         if (rtc_istat & RTC_ISTAT_STOPWATCH) {
 164                 bfin_write_RTC_ISTAT(RTC_ISTAT_STOPWATCH);
 165                 events |= RTC_PF | RTC_IRQF;
 166                 bfin_write_RTC_SWCNT(rtc->rtc_dev->irq_freq);
 167         }
 168
 169         if (rtc_istat & RTC_ISTAT_SEC) {
 170                 bfin_write_RTC_ISTAT(RTC_ISTAT_SEC);
 171                 events |= RTC_UF | RTC_IRQF;
 172         }
 173
 174         rtc_update_irq(rtc->rtc_dev, 1, events);
 175
 176         spin_unlock_irq(&rtc->lock);
 177
 178         return IRQ_HANDLED;
 179 }
 180
 181 static int bfin_rtc_open(struct device *dev)
 182 {
 183         struct bfin_rtc *rtc = dev_get_drvdata(dev);
 184         int ret;
 185
 186         stampit();
 187
 188         ret = request_irq(IRQ_RTC, bfin_rtc_interrupt, IRQF_DISABLED, "rtc-bfin", dev);
 189         if (unlikely(ret)) {
 190                 dev_err(dev, "request RTC IRQ failed with %d\n", ret);
 191                 return ret;
 192         }
 193
 194         rtc_bfin_reset(rtc);
 195
 196         return ret;
 197 }
 198
 199 static void bfin_rtc_release(struct device *dev)
 200 {
 201         struct bfin_rtc *rtc = dev_get_drvdata(dev);
 202         stampit();
 203         rtc_bfin_reset(rtc);
 204         free_irq(IRQ_RTC, dev);
 205 }
 206
 207 static int bfin_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
 208 {
 209         struct bfin_rtc *rtc = dev_get_drvdata(dev);
 210
 211         stampit();
 212
 213         switch (cmd) {
 214         case RTC_PIE_ON:
 215                 stampit();
 216                 spin_lock_irq(&rtc->lock);
 217                 rtc_bfin_sync_pending();
 218                 bfin_write_RTC_ISTAT(RTC_ISTAT_STOPWATCH);
 219                 bfin_write_RTC_SWCNT(rtc->rtc_dev->irq_freq);
 220                 bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() | RTC_ISTAT_STOPWATCH);
 221                 spin_unlock_irq(&rtc->lock);
 222                 return 0;
 223         case RTC_PIE_OFF:
 224                 stampit();
 225                 spin_lock_irq(&rtc->lock);
 226                 rtc_bfin_sync_pending();
 227                 bfin_write_RTC_SWCNT(0);
 228                 bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() & ~RTC_ISTAT_STOPWATCH);
 229                 spin_unlock_irq(&rtc->lock);
 230                 return 0;
 231
 232         case RTC_UIE_ON:
 233                 stampit();
 234                 spin_lock_irq(&rtc->lock);
 235                 rtc_bfin_sync_pending();
 236                 bfin_write_RTC_ISTAT(RTC_ISTAT_SEC);
 237                 bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() | RTC_ISTAT_SEC);
 238                 spin_unlock_irq(&rtc->lock);
 239                 return 0;
 240         case RTC_UIE_OFF:
 241                 stampit();
 242                 spin_lock_irq(&rtc->lock);
 243                 rtc_bfin_sync_pending();
 244                 bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() & ~RTC_ISTAT_SEC);
 245                 spin_unlock_irq(&rtc->lock);
 246                 return 0;
 247
 248         case RTC_AIE_ON: {
 249                 unsigned long rtc_alarm;
 250                 u16 which_alarm;
 251                 int ret = 0;
 252
 253                 stampit();
 254
 255                 spin_lock_irq(&rtc->lock);
 256
 257                 rtc_bfin_sync_pending();
 258                 if (rtc->rtc_alarm.tm_yday == -1) {
 259                         struct rtc_time now;
 260                         rtc_bfin_to_tm(bfin_read_RTC_STAT(), &now);
 261                         now.tm_sec = rtc->rtc_alarm.tm_sec;
 262                         now.tm_min = rtc->rtc_alarm.tm_min;
 263                         now.tm_hour = rtc->rtc_alarm.tm_hour;
 264                         ret = rtc_tm_to_time(&now, &rtc_alarm);
 265                         which_alarm = RTC_ISTAT_ALARM;
 266                 } else {
 267                         ret = rtc_tm_to_time(&rtc->rtc_alarm, &rtc_alarm);
 268                         which_alarm = RTC_ISTAT_ALARM_DAY;
 269                 }
 270                 if (ret == 0) {
 271                         bfin_write_RTC_ISTAT(which_alarm);
 272                         bfin_write_RTC_ALARM(rtc_time_to_bfin(rtc_alarm));
 273                         bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() | which_alarm);
 274                 }
 275
 276                 spin_unlock_irq(&rtc->lock);
 277
 278                 return ret;
 279         }
 280         case RTC_AIE_OFF:
 281                 stampit();
 282                 spin_lock_irq(&rtc->lock);
 283                 rtc_bfin_sync_pending();
 284                 bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() & ~(RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY));
 285                 spin_unlock_irq(&rtc->lock);
 286                 return 0;
 287         }
 288
 289         return -ENOIOCTLCMD;
 290 }
 291
 292 static int bfin_rtc_read_time(struct device *dev, struct rtc_time *tm)
 293 {
 294         struct bfin_rtc *rtc = dev_get_drvdata(dev);
 295
 296         stampit();
 297
 298         spin_lock_irq(&rtc->lock);
 299         rtc_bfin_sync_pending();
 300         rtc_bfin_to_tm(bfin_read_RTC_STAT(), tm);
 301         spin_unlock_irq(&rtc->lock);
 302
 303         return 0;
 304 }
 305
 306 static int bfin_rtc_set_time(struct device *dev, struct rtc_time *tm)
 307 {
 308         struct bfin_rtc *rtc = dev_get_drvdata(dev);
 309         int ret;
 310         unsigned long now;
 311
 312         stampit();
 313
 314         spin_lock_irq(&rtc->lock);
 315
 316         ret = rtc_tm_to_time(tm, &now);
 317         if (ret == 0) {
 318                 rtc_bfin_sync_pending();
 319                 bfin_write_RTC_STAT(rtc_time_to_bfin(now));
 320         }
 321
 322         spin_unlock_irq(&rtc->lock);
 323
 324         return ret;
 325 }
 326
 327 static int bfin_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 328 {
 329         struct bfin_rtc *rtc = dev_get_drvdata(dev);
 330         stampit();
 331         memcpy(&alrm->time, &rtc->rtc_alarm, sizeof(struct rtc_time));
 332         alrm->pending = !!(bfin_read_RTC_ICTL() & (RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY));
 333         return 0;
 334 }
 335
 336 static int bfin_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 337 {
 338         struct bfin_rtc *rtc = dev_get_drvdata(dev);
 339         stampit();
 340         memcpy(&rtc->rtc_alarm, &alrm->time, sizeof(struct rtc_time));
 341         return 0;
 342 }
 343
 344 static int bfin_rtc_proc(struct device *dev, struct seq_file *seq)
 345 {
 346 #define yesno(x) (x ? "yes" : "no")
 347         u16 ictl = bfin_read_RTC_ICTL();
 348         stampit();
 349         seq_printf(seq, "alarm_IRQ\t: %s\n", yesno(ictl & RTC_ISTAT_ALARM));
 350         seq_printf(seq, "wkalarm_IRQ\t: %s\n", yesno(ictl & RTC_ISTAT_ALARM_DAY));
 351         seq_printf(seq, "seconds_IRQ\t: %s\n", yesno(ictl & RTC_ISTAT_SEC));
 352         seq_printf(seq, "periodic_IRQ\t: %s\n", yesno(ictl & RTC_ISTAT_STOPWATCH));
 353 #ifdef DEBUG
 354         seq_printf(seq, "RTC_STAT\t: 0x%08X\n", bfin_read_RTC_STAT());
 355         seq_printf(seq, "RTC_ICTL\t: 0x%04X\n", bfin_read_RTC_ICTL());
 356         seq_printf(seq, "RTC_ISTAT\t: 0x%04X\n", bfin_read_RTC_ISTAT());
 357         seq_printf(seq, "RTC_SWCNT\t: 0x%04X\n", bfin_read_RTC_SWCNT());
 358         seq_printf(seq, "RTC_ALARM\t: 0x%08X\n", bfin_read_RTC_ALARM());
 359         seq_printf(seq, "RTC_PREN\t: 0x%04X\n", bfin_read_RTC_PREN());
 360 #endif
 361         return 0;
 362 }
 363
 364 /**
 365  *      bfin_irq_set_freq - make sure hardware supports requested freq
 366  *      @dev: pointer to RTC device structure
 367  *      @freq: requested frequency rate
 368  *
 369  *      The Blackfin RTC can only generate periodic events at 1 per
 370  *      second (1 Hz), so reject any attempt at changing it.
 371  */
 372 static int bfin_irq_set_freq(struct device *dev, int freq)
 373 {
 374         stampit();
 375         return -ENOTTY;
 376 }
 377
 378 static struct rtc_class_ops bfin_rtc_ops = {
 379         .open          = bfin_rtc_open,
 380         .release       = bfin_rtc_release,
 381         .ioctl         = bfin_rtc_ioctl,
 382         .read_time     = bfin_rtc_read_time,
 383         .set_time      = bfin_rtc_set_time,
 384         .read_alarm    = bfin_rtc_read_alarm,
 385         .set_alarm     = bfin_rtc_set_alarm,
 386         .proc          = bfin_rtc_proc,
 387         .irq_set_freq  = bfin_irq_set_freq,
 388 };
 389
 390 static int __devinit bfin_rtc_probe(struct platform_device *pdev)
 391 {
 392         struct bfin_rtc *rtc;
 393         int ret = 0;
 394
 395         stampit();
 396
 397         rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
 398         if (unlikely(!rtc))
 399                 return -ENOMEM;
 400
 401         spin_lock_init(&rtc->lock);
 402
 403         rtc->rtc_dev = rtc_device_register(pdev->name, &pdev->dev, &bfin_rtc_ops, THIS_MODULE);
 404         if (unlikely(IS_ERR(rtc))) {
 405                 ret = PTR_ERR(rtc->rtc_dev);
 406                 goto err;
 407         }
 408         rtc->rtc_dev->irq_freq = 1;
 409
 410         platform_set_drvdata(pdev, rtc);
 411
 412         return 0;
 413
 414  err:
 415         kfree(rtc);
 416         return ret;
 417 }
 418
 419 static int __devexit bfin_rtc_remove(struct platform_device *pdev)
 420 {
 421         struct bfin_rtc *rtc = platform_get_drvdata(pdev);
 422
 423         rtc_device_unregister(rtc->rtc_dev);
 424         platform_set_drvdata(pdev, NULL);
 425         kfree(rtc);
 426
 427         return 0;
 428 }
 429
 430 static struct platform_driver bfin_rtc_driver = {
 431         .driver         = {
 432                 .name   = "rtc-bfin",
 433                 .owner  = THIS_MODULE,
 434         },
 435         .probe          = bfin_rtc_probe,
 436         .remove         = __devexit_p(bfin_rtc_remove),
 437 };
 438
 439 static int __init bfin_rtc_init(void)
 440 {
 441         stampit();
 442         return platform_driver_register(&bfin_rtc_driver);
 443 }
 444
 445 static void __exit bfin_rtc_exit(void)
 446 {
 447         platform_driver_unregister(&bfin_rtc_driver);
 448 }
 449
 450 module_init(bfin_rtc_init);
 451 module_exit(bfin_rtc_exit);
 452
 453 MODULE_DESCRIPTION("Blackfin On-Chip Real Time Clock Driver");
 454 MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
 455 MODULE_LICENSE("GPL");