drivers/rtc/rtc-bfin.c

   1 /*
   2  * Blackfin On-Chip Real Time Clock Driver
   3  *  Supports BF531/BF532/BF533/BF534/BF536/BF537
   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 stored 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 static void rtc_bfin_sync_pending(void)
 117 {
 118         stampit();
 119         while (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_COMPLETE)) {
 120                 if (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_PENDING))
 121                         break;
 122         }
 123         bfin_write_RTC_ISTAT(RTC_ISTAT_WRITE_COMPLETE);
 124 }
 125
 126 static void rtc_bfin_reset(struct bfin_rtc *rtc)
 127 {
 128         /* Initialize the RTC. Enable pre-scaler to scale RTC clock
 129          * to 1Hz and clear interrupt/status registers. */
 130         spin_lock_irq(&rtc->lock);
 131         rtc_bfin_sync_pending();
 132         bfin_write_RTC_PREN(0x1);
 133         bfin_write_RTC_ICTL(0);
 134         bfin_write_RTC_SWCNT(0);
 135         bfin_write_RTC_ALARM(0);
 136         bfin_write_RTC_ISTAT(0xFFFF);
 137         spin_unlock_irq(&rtc->lock);
 138 }
 139
 140 static irqreturn_t bfin_rtc_interrupt(int irq, void *dev_id)
 141 {
 142         struct platform_device *pdev = to_platform_device(dev_id);
 143         struct bfin_rtc *rtc = platform_get_drvdata(pdev);
 144         unsigned long events = 0;
 145         u16 rtc_istat;
 146
 147         stampit();
 148
 149         spin_lock_irq(&rtc->lock);
 150
 151         rtc_istat = bfin_read_RTC_ISTAT();
 152
 153         if (rtc_istat & (RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY)) {
 154                 bfin_write_RTC_ISTAT(RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY);
 155                 events |= RTC_AF | RTC_IRQF;
 156         }
 157
 158         if (rtc_istat & RTC_ISTAT_STOPWATCH) {
 159                 bfin_write_RTC_ISTAT(RTC_ISTAT_STOPWATCH);
 160                 events |= RTC_PF | RTC_IRQF;
 161                 bfin_write_RTC_SWCNT(rtc->rtc_dev->irq_freq);
 162         }
 163
 164         if (rtc_istat & RTC_ISTAT_SEC) {
 165                 bfin_write_RTC_ISTAT(RTC_ISTAT_SEC);
 166                 events |= RTC_UF | RTC_IRQF;
 167         }
 168
 169         rtc_update_irq(rtc->rtc_dev, 1, events);
 170
 171         spin_unlock_irq(&rtc->lock);
 172
 173         return IRQ_HANDLED;
 174 }
 175
 176 static int bfin_rtc_open(struct device *dev)
 177 {
 178         struct bfin_rtc *rtc = dev_get_drvdata(dev);
 179         int ret;
 180
 181         stampit();
 182
 183         ret = request_irq(IRQ_RTC, bfin_rtc_interrupt, IRQF_DISABLED, "rtc-bfin", dev);
 184         if (unlikely(ret)) {
 185                 dev_err(dev, "request RTC IRQ failed with %d\n", ret);
 186                 return ret;
 187         }
 188
 189         rtc_bfin_reset(rtc);
 190
 191         return ret;
 192 }
 193
 194 static void bfin_rtc_release(struct device *dev)
 195 {
 196         struct bfin_rtc *rtc = dev_get_drvdata(dev);
 197         stampit();
 198         rtc_bfin_reset(rtc);
 199         free_irq(IRQ_RTC, dev);
 200 }
 201
 202 static int bfin_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
 203 {
 204         struct bfin_rtc *rtc = dev_get_drvdata(dev);
 205
 206         stampit();
 207
 208         switch (cmd) {
 209         case RTC_PIE_ON:
 210                 stampit();
 211                 spin_lock_irq(&rtc->lock);
 212                 rtc_bfin_sync_pending();
 213                 bfin_write_RTC_ISTAT(RTC_ISTAT_STOPWATCH);
 214                 bfin_write_RTC_SWCNT(rtc->rtc_dev->irq_freq);
 215                 bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() | RTC_ISTAT_STOPWATCH);
 216                 spin_unlock_irq(&rtc->lock);
 217                 return 0;
 218         case RTC_PIE_OFF:
 219                 stampit();
 220                 spin_lock_irq(&rtc->lock);
 221                 rtc_bfin_sync_pending();
 222                 bfin_write_RTC_SWCNT(0);
 223                 bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() & ~RTC_ISTAT_STOPWATCH);
 224                 spin_unlock_irq(&rtc->lock);
 225                 return 0;
 226
 227         case RTC_UIE_ON:
 228                 stampit();
 229                 spin_lock_irq(&rtc->lock);
 230                 rtc_bfin_sync_pending();
 231                 bfin_write_RTC_ISTAT(RTC_ISTAT_SEC);
 232                 bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() | RTC_ISTAT_SEC);
 233                 spin_unlock_irq(&rtc->lock);
 234                 return 0;
 235         case RTC_UIE_OFF:
 236                 stampit();
 237                 spin_lock_irq(&rtc->lock);
 238                 rtc_bfin_sync_pending();
 239                 bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() & ~RTC_ISTAT_SEC);
 240                 spin_unlock_irq(&rtc->lock);
 241                 return 0;
 242
 243         case RTC_AIE_ON: {
 244                 unsigned long rtc_alarm;
 245                 u16 which_alarm;
 246                 int ret = 0;
 247
 248                 stampit();
 249
 250                 spin_lock_irq(&rtc->lock);
 251
 252                 rtc_bfin_sync_pending();
 253                 if (rtc->rtc_alarm.tm_yday == -1) {
 254                         struct rtc_time now;
 255                         rtc_bfin_to_tm(bfin_read_RTC_STAT(), &now);
 256                         now.tm_sec = rtc->rtc_alarm.tm_sec;
 257                         now.tm_min = rtc->rtc_alarm.tm_min;
 258                         now.tm_hour = rtc->rtc_alarm.tm_hour;
 259                         ret = rtc_tm_to_time(&now, &rtc_alarm);
 260                         which_alarm = RTC_ISTAT_ALARM;
 261                 } else {
 262                         ret = rtc_tm_to_time(&rtc->rtc_alarm, &rtc_alarm);
 263                         which_alarm = RTC_ISTAT_ALARM_DAY;
 264                 }
 265                 if (ret == 0) {
 266                         bfin_write_RTC_ISTAT(which_alarm);
 267                         bfin_write_RTC_ALARM(rtc_time_to_bfin(rtc_alarm));
 268                         bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() | which_alarm);
 269                 }
 270
 271                 spin_unlock_irq(&rtc->lock);
 272
 273                 return ret;
 274         }
 275         case RTC_AIE_OFF:
 276                 stampit();
 277                 spin_lock_irq(&rtc->lock);
 278                 rtc_bfin_sync_pending();
 279                 bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() & ~(RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY));
 280                 spin_unlock_irq(&rtc->lock);
 281                 return 0;
 282         }
 283
 284         return -ENOIOCTLCMD;
 285 }
 286
 287 static int bfin_rtc_read_time(struct device *dev, struct rtc_time *tm)
 288 {
 289         struct bfin_rtc *rtc = dev_get_drvdata(dev);
 290
 291         stampit();
 292
 293         spin_lock_irq(&rtc->lock);
 294         rtc_bfin_sync_pending();
 295         rtc_bfin_to_tm(bfin_read_RTC_STAT(), tm);
 296         spin_unlock_irq(&rtc->lock);
 297
 298         return 0;
 299 }
 300
 301 static int bfin_rtc_set_time(struct device *dev, struct rtc_time *tm)
 302 {
 303         struct bfin_rtc *rtc = dev_get_drvdata(dev);
 304         int ret;
 305         unsigned long now;
 306
 307         stampit();
 308
 309         spin_lock_irq(&rtc->lock);
 310
 311         ret = rtc_tm_to_time(tm, &now);
 312         if (ret == 0) {
 313                 rtc_bfin_sync_pending();
 314                 bfin_write_RTC_STAT(rtc_time_to_bfin(now));
 315         }
 316
 317         spin_unlock_irq(&rtc->lock);
 318
 319         return ret;
 320 }
 321
 322 static int bfin_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 323 {
 324         struct bfin_rtc *rtc = dev_get_drvdata(dev);
 325         stampit();
 326         memcpy(&alrm->time, &rtc->rtc_alarm, sizeof(struct rtc_time));
 327         alrm->pending = !!(bfin_read_RTC_ICTL() & (RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY));
 328         return 0;
 329 }
 330
 331 static int bfin_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 332 {
 333         struct bfin_rtc *rtc = dev_get_drvdata(dev);
 334         stampit();
 335         memcpy(&rtc->rtc_alarm, &alrm->time, sizeof(struct rtc_time));
 336         return 0;
 337 }
 338
 339 static int bfin_rtc_proc(struct device *dev, struct seq_file *seq)
 340 {
 341 #define yesno(x) (x ? "yes" : "no")
 342         u16 ictl = bfin_read_RTC_ICTL();
 343         stampit();
 344         seq_printf(seq, "alarm_IRQ\t: %s\n", yesno(ictl & RTC_ISTAT_ALARM));
 345         seq_printf(seq, "wkalarm_IRQ\t: %s\n", yesno(ictl & RTC_ISTAT_ALARM_DAY));
 346         seq_printf(seq, "seconds_IRQ\t: %s\n", yesno(ictl & RTC_ISTAT_SEC));
 347         seq_printf(seq, "periodic_IRQ\t: %s\n", yesno(ictl & RTC_ISTAT_STOPWATCH));
 348 #ifdef DEBUG
 349         seq_printf(seq, "RTC_STAT\t: 0x%08X\n", bfin_read_RTC_STAT());
 350         seq_printf(seq, "RTC_ICTL\t: 0x%04X\n", bfin_read_RTC_ICTL());
 351         seq_printf(seq, "RTC_ISTAT\t: 0x%04X\n", bfin_read_RTC_ISTAT());
 352         seq_printf(seq, "RTC_SWCNT\t: 0x%04X\n", bfin_read_RTC_SWCNT());
 353         seq_printf(seq, "RTC_ALARM\t: 0x%08X\n", bfin_read_RTC_ALARM());
 354         seq_printf(seq, "RTC_PREN\t: 0x%04X\n", bfin_read_RTC_PREN());
 355 #endif
 356         return 0;
 357 }
 358
 359 static int bfin_irq_set_freq(struct device *dev, int freq)
 360 {
 361         struct bfin_rtc *rtc = dev_get_drvdata(dev);
 362         stampit();
 363         rtc->rtc_dev->irq_freq = freq;
 364         return 0;
 365 }
 366
 367 static struct rtc_class_ops bfin_rtc_ops = {
 368         .open          = bfin_rtc_open,
 369         .release       = bfin_rtc_release,
 370         .ioctl         = bfin_rtc_ioctl,
 371         .read_time     = bfin_rtc_read_time,
 372         .set_time      = bfin_rtc_set_time,
 373         .read_alarm    = bfin_rtc_read_alarm,
 374         .set_alarm     = bfin_rtc_set_alarm,
 375         .proc          = bfin_rtc_proc,
 376         .irq_set_freq  = bfin_irq_set_freq,
 377 };
 378
 379 static int __devinit bfin_rtc_probe(struct platform_device *pdev)
 380 {
 381         struct bfin_rtc *rtc;
 382         int ret = 0;
 383
 384         stampit();
 385
 386         rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
 387         if (unlikely(!rtc))
 388                 return -ENOMEM;
 389
 390         spin_lock_init(&rtc->lock);
 391
 392         rtc->rtc_dev = rtc_device_register(pdev->name, &pdev->dev, &bfin_rtc_ops, THIS_MODULE);
 393         if (unlikely(IS_ERR(rtc))) {
 394                 ret = PTR_ERR(rtc->rtc_dev);
 395                 goto err;
 396         }
 397         rtc->rtc_dev->irq_freq = 0;
 398         rtc->rtc_dev->max_user_freq = (2 << 16); /* stopwatch is an unsigned 16 bit reg */
 399
 400         platform_set_drvdata(pdev, rtc);
 401
 402         return 0;
 403
 404 err:
 405         kfree(rtc);
 406         return ret;
 407 }
 408
 409 static int __devexit bfin_rtc_remove(struct platform_device *pdev)
 410 {
 411         struct bfin_rtc *rtc = platform_get_drvdata(pdev);
 412
 413         rtc_device_unregister(rtc->rtc_dev);
 414         platform_set_drvdata(pdev, NULL);
 415         kfree(rtc);
 416
 417         return 0;
 418 }
 419
 420 static struct platform_driver bfin_rtc_driver = {
 421         .driver         = {
 422                 .name   = "rtc-bfin",
 423                 .owner  = THIS_MODULE,
 424         },
 425         .probe          = bfin_rtc_probe,
 426         .remove         = __devexit_p(bfin_rtc_remove),
 427 };
 428
 429 static int __init bfin_rtc_init(void)
 430 {
 431         stampit();
 432         return platform_driver_register(&bfin_rtc_driver);
 433 }
 434
 435 static void __exit bfin_rtc_exit(void)
 436 {
 437         platform_driver_unregister(&bfin_rtc_driver);
 438 }
 439
 440 module_init(bfin_rtc_init);
 441 module_exit(bfin_rtc_exit);
 442
 443 MODULE_DESCRIPTION("Blackfin On-Chip Real Time Clock Driver");
 444 MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
 445 MODULE_LICENSE("GPL");