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