Blackfin: on-chip RTC controller driver
[linux-2.6.git] / 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");