aboutsummaryrefslogtreecommitdiff
path: root/drivers/rtc/rtc-bfin.c
blob: 535a5f9338d026ec8f433fb4960dc7227728ddf6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
/*
 * Blackfin On-Chip Real Time Clock Driver
 *  Supports BF51x/BF52x/BF53[123]/BF53[467]/BF54x
 *
 * Copyright 2004-2010 Analog Devices Inc.
 *
 * Enter bugs at http://blackfin.uclinux.org/
 *
 * Licensed under the GPL-2 or later.
 */

/* The biggest issue we deal with in this driver is that register writes are
 * synced to the RTC frequency of 1Hz.  So if you write to a register and
 * attempt to write again before the first write has completed, the new write
 * is simply discarded.  This can easily be troublesome if userspace disables
 * one event (say periodic) and then right after enables an event (say alarm).
 * Since all events are maintained in the same interrupt mask register, if
 * we wrote to it to disable the first event and then wrote to it again to
 * enable the second event, that second event would not be enabled as the
 * write would be discarded and things quickly fall apart.
 *
 * To keep this delay from significantly degrading performance (we, in theory,
 * would have to sleep for up to 1 second every time we wanted to write a
 * register), we only check the write pending status before we start to issue
 * a new write.  We bank on the idea that it doesn't matter when the sync
 * happens so long as we don't attempt another write before it does.  The only
 * time userspace would take this penalty is when they try and do multiple
 * operations right after another ... but in this case, they need to take the
 * sync penalty, so we should be OK.
 *
 * Also note that the RTC_ISTAT register does not suffer this penalty; its
 * writes to clear status registers complete immediately.
 */

/* It may seem odd that there is no SWCNT code in here (which would be exposed
 * via the periodic interrupt event, or PIE).  Since the Blackfin RTC peripheral
 * runs in units of seconds (N/HZ) but the Linux framework runs in units of HZ
 * (2^N HZ), there is no point in keeping code that only provides 1 HZ PIEs.
 * The same exact behavior can be accomplished by using the update interrupt
 * event (UIE).  Maybe down the line the RTC peripheral will suck less in which
 * case we can re-introduce PIE support.
 */

#include <linux/bcd.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/seq_file.h>
#include <linux/slab.h>

#include <asm/blackfin.h>

#define dev_dbg_stamp(dev) dev_dbg(dev, "%s:%i: here i am\n", __func__, __LINE__)

struct bfin_rtc {
	struct rtc_device *rtc_dev;
	struct rtc_time rtc_alarm;
	u16 rtc_wrote_regs;
};

/* Bit values for the ISTAT / ICTL registers */
#define RTC_ISTAT_WRITE_COMPLETE  0x8000
#define RTC_ISTAT_WRITE_PENDING   0x4000
#define RTC_ISTAT_ALARM_DAY       0x0040
#define RTC_ISTAT_24HR            0x0020
#define RTC_ISTAT_HOUR            0x0010
#define RTC_ISTAT_MIN             0x0008
#define RTC_ISTAT_SEC             0x0004
#define RTC_ISTAT_ALARM           0x0002
#define RTC_ISTAT_STOPWATCH       0x0001

/* Shift values for RTC_STAT register */
#define DAY_BITS_OFF    17
#define HOUR_BITS_OFF   12
#define MIN_BITS_OFF    6
#define SEC_BITS_OFF    0

/* Some helper functions to convert between the common RTC notion of time
 * and the internal Blackfin notion that is encoded in 32bits.
 */
static inline u32 rtc_time_to_bfin(unsigned long now)
{
	u32 sec  = (now % 60);
	u32 min  = (now % (60 * 60)) / 60;
	u32 hour = (now % (60 * 60 * 24)) / (60 * 60);
	u32 days = (now / (60 * 60 * 24));
	return (sec  << SEC_BITS_OFF) +
	       (min  << MIN_BITS_OFF) +
	       (hour << HOUR_BITS_OFF) +
	       (days << DAY_BITS_OFF);
}
static inline unsigned long rtc_bfin_to_time(u32 rtc_bfin)
{
	return (((rtc_bfin >> SEC_BITS_OFF)  & 0x003F)) +
	       (((rtc_bfin >> MIN_BITS_OFF)  & 0x003F) * 60) +
	       (((rtc_bfin >> HOUR_BITS_OFF) & 0x001F) * 60 * 60) +
	       (((rtc_bfin >> DAY_BITS_OFF)  & 0x7FFF) * 60 * 60 * 24);
}
static inline void rtc_bfin_to_tm(u32 rtc_bfin, struct rtc_time *tm)
{
	rtc_time_to_tm(rtc_bfin_to_time(rtc_bfin), tm);
}

/**
 *	bfin_rtc_sync_pending - make sure pending writes have complete
 *
 * Wait for the previous write to a RTC register to complete.
 * Unfortunately, we can't sleep here as that introduces a race condition when
 * turning on interrupt events.  Consider this:
 *  - process sets alarm
 *  - process enables alarm
 *  - process sleeps while waiting for rtc write to sync
 *  - interrupt fires while process is sleeping
 *  - interrupt acks the event by writing to ISTAT
 *  - interrupt sets the WRITE PENDING bit
 *  - interrupt handler finishes
 *  - process wakes up, sees WRITE PENDING bit set, goes to sleep
 *  - interrupt fires while process is sleeping
 * If anyone can point out the obvious solution here, i'm listening :).  This
 * shouldn't be an issue on an SMP or preempt system as this function should
 * only be called with the rtc lock held.
 *
 * Other options:
 *  - disable PREN so the sync happens at 32.768kHZ ... but this changes the
 *    inc rate for all RTC registers from 1HZ to 32.768kHZ ...
 *  - use the write complete IRQ
 */
/*
static void bfin_rtc_sync_pending_polled(void)
{
	while (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_COMPLETE))
		if (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_PENDING))
			break;
	bfin_write_RTC_ISTAT(RTC_ISTAT_WRITE_COMPLETE);
}
*/
static DECLARE_COMPLETION(bfin_write_complete);
static void bfin_rtc_sync_pending(struct device *dev)
{
	dev_dbg_stamp(dev);
	while (bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_PENDING)
		wait_for_completion_timeout(&bfin_write_complete, HZ * 5);
	dev_dbg_stamp(dev);
}

/**
 *	bfin_rtc_reset - set RTC to sane/known state
 *
 * Initialize the RTC.  Enable pre-scaler to scale RTC clock
 * to 1Hz and clear interrupt/status registers.
 */
static void bfin_rtc_reset(struct device *dev, u16 rtc_ictl)
{
	struct bfin_rtc *rtc = dev_get_drvdata(dev);
	dev_dbg_stamp(dev);
	bfin_rtc_sync_pending(dev);
	bfin_write_RTC_PREN(0x1);
	bfin_write_RTC_ICTL(rtc_ictl);
	bfin_write_RTC_ALARM(0);
	bfin_write_RTC_ISTAT(0xFFFF);
	rtc->rtc_wrote_regs = 0;
}

/**
 *	bfin_rtc_interrupt - handle interrupt from RTC
 *
 * Since we handle all RTC events here, we have to make sure the requested
 * interrupt is enabled (in RTC_ICTL) as the event status register (RTC_ISTAT)
 * always gets updated regardless of the interrupt being enabled.  So when one
 * even we care about (e.g. stopwatch) goes off, we don't want to turn around
 * and say that other events have happened as well (e.g. second).  We do not
 * have to worry about pending writes to the RTC_ICTL register as interrupts
 * only fire if they are enabled in the RTC_ICTL register.
 */
static irqreturn_t bfin_rtc_interrupt(int irq, void *dev_id)
{
	struct device *dev = dev_id;
	struct bfin_rtc *rtc = dev_get_drvdata(dev);
	unsigned long events = 0;
	bool write_complete = false;
	u16 rtc_istat, rtc_istat_clear, rtc_ictl, bits;

	dev_dbg_stamp(dev);

	rtc_istat = bfin_read_RTC_ISTAT();
	rtc_ictl = bfin_read_RTC_ICTL();
	rtc_istat_clear = 0;

	bits = RTC_ISTAT_WRITE_COMPLETE;
	if (rtc_istat & bits) {
		rtc_istat_clear |= bits;
		write_complete = true;
		complete(&bfin_write_complete);
	}

	bits = (RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY);
	if (rtc_ictl & bits) {
		if (rtc_istat & bits) {
			rtc_istat_clear |= bits;
			events |= RTC_AF | RTC_IRQF;
		}
	}

	bits = RTC_ISTAT_SEC;
	if (rtc_ictl & bits) {
		if (rtc_istat & bits) {
			rtc_istat_clear |= bits;
			events |= RTC_UF | RTC_IRQF;
		}
	}

	if (events)
		rtc_update_irq(rtc->rtc_dev, 1, events);

	if (write_complete || events) {
		bfin_write_RTC_ISTAT(rtc_istat_clear);
		return IRQ_HANDLED;
	} else
		return IRQ_NONE;
}

static void bfin_rtc_int_set(u16 rtc_int)
{
	bfin_write_RTC_ISTAT(rtc_int);
	bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() | rtc_int);
}
static void bfin_rtc_int_clear(u16 rtc_int)
{
	bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() & rtc_int);
}
static void bfin_rtc_int_set_alarm(struct bfin_rtc *rtc)
{
	/* Blackfin has different bits for whether the alarm is
	 * more than 24 hours away.
	 */
	bfin_rtc_int_set(rtc->rtc_alarm.tm_yday == -1 ? RTC_ISTAT_ALARM : RTC_ISTAT_ALARM_DAY);
}

static int bfin_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
	struct bfin_rtc *rtc = dev_get_drvdata(dev);

	dev_dbg_stamp(dev);
	if (enabled)
		bfin_rtc_int_set_alarm(rtc);
	else
		bfin_rtc_int_clear(~(RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY));

	return 0;
}

static int bfin_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	struct bfin_rtc *rtc = dev_get_drvdata(dev);

	dev_dbg_stamp(dev);

	if (rtc->rtc_wrote_regs & 0x1)
		bfin_rtc_sync_pending(dev);

	rtc_bfin_to_tm(bfin_read_RTC_STAT(), tm);

	return 0;
}

static int bfin_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
	struct bfin_rtc *rtc = dev_get_drvdata(dev);
	int ret;
	unsigned long now;

	dev_dbg_stamp(dev);

	ret = rtc_tm_to_time(tm, &now);
	if (ret == 0) {
		if (rtc->rtc_wrote_regs & 0x1)
			bfin_rtc_sync_pending(dev);
		bfin_write_RTC_STAT(rtc_time_to_bfin(now));
		rtc->rtc_wrote_regs = 0x1;
	}

	return ret;
}

static int bfin_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct bfin_rtc *rtc = dev_get_drvdata(dev);
	dev_dbg_stamp(dev);
	alrm->time = rtc->rtc_alarm;
	bfin_rtc_sync_pending(dev);
	alrm->enabled = !!(bfin_read_RTC_ICTL() & (RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY));
	return 0;
}

static int bfin_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
	struct bfin_rtc *rtc = dev_get_drvdata(dev);
	unsigned long rtc_alarm;

	dev_dbg_stamp(dev);

	if (rtc_tm_to_time(&alrm->time, &rtc_alarm))
		return -EINVAL;

	rtc->rtc_alarm = alrm->time;

	bfin_rtc_sync_pending(dev);
	bfin_write_RTC_ALARM(rtc_time_to_bfin(rtc_alarm));
	if (alrm->enabled)
		bfin_rtc_int_set_alarm(rtc);

	return 0;
}

static int bfin_rtc_proc(struct device *dev, struct seq_file *seq)
{
#define yesno(x) ((x) ? "yes" : "no")
	u16 ictl = bfin_read_RTC_ICTL();
	dev_dbg_stamp(dev);
	seq_printf(seq,
		"alarm_IRQ\t: %s\n"
		"wkalarm_IRQ\t: %s\n"
		"seconds_IRQ\t: %s\n",
		yesno(ictl & RTC_ISTAT_ALARM),
		yesno(ictl & RTC_ISTAT_ALARM_DAY),
		yesno(ictl & RTC_ISTAT_SEC));
	return 0;
#undef yesno
}

static struct rtc_class_ops bfin_rtc_ops = {
	.read_time     = bfin_rtc_read_time,
	.set_time      = bfin_rtc_set_time,
	.read_alarm    = bfin_rtc_read_alarm,
	.set_alarm     = bfin_rtc_set_alarm,
	.proc          = bfin_rtc_proc,
	.alarm_irq_enable = bfin_rtc_alarm_irq_enable,
};

static int bfin_rtc_probe(struct platform_device *pdev)
{
	struct bfin_rtc *rtc;
	struct device *dev = &pdev->dev;
	int ret;
	unsigned long timeout = jiffies + HZ;

	dev_dbg_stamp(dev);

	/* Allocate memory for our RTC struct */
	rtc = devm_kzalloc(dev, sizeof(*rtc), GFP_KERNEL);
	if (unlikely(!rtc))
		return -ENOMEM;
	platform_set_drvdata(pdev, rtc);
	device_init_wakeup(dev, 1);

	/* Register our RTC with the RTC framework */
	rtc->rtc_dev = devm_rtc_device_register(dev, pdev->name, &bfin_rtc_ops,
						THIS_MODULE);
	if (IS_ERR(rtc->rtc_dev))
		return PTR_ERR(rtc->rtc_dev);

	/* Grab the IRQ and init the hardware */
	ret = devm_request_irq(dev, IRQ_RTC, bfin_rtc_interrupt, 0,
				pdev->name, dev);
	if (unlikely(ret))
		dev_err(&pdev->dev,
			"unable to request IRQ; alarm won't work, "
			"and writes will be delayed\n");

	/* sometimes the bootloader touched things, but the write complete was not
	 * enabled, so let's just do a quick timeout here since the IRQ will not fire ...
	 */
	while (bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_PENDING)
		if (time_after(jiffies, timeout))
			break;
	bfin_rtc_reset(dev, RTC_ISTAT_WRITE_COMPLETE);
	bfin_write_RTC_SWCNT(0);

	return 0;
}

static int bfin_rtc_remove(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;

	bfin_rtc_reset(dev, 0);

	return 0;
}

#ifdef CONFIG_PM_SLEEP
static int bfin_rtc_suspend(struct device *dev)
{
	dev_dbg_stamp(dev);

	if (device_may_wakeup(dev)) {
		enable_irq_wake(IRQ_RTC);
		bfin_rtc_sync_pending(dev);
	} else
		bfin_rtc_int_clear(0);

	return 0;
}

static int bfin_rtc_resume(struct device *dev)
{
	dev_dbg_stamp(dev);

	if (device_may_wakeup(dev))
		disable_irq_wake(IRQ_RTC);

	/*
	 * Since only some of the RTC bits are maintained externally in the
	 * Vbat domain, we need to wait for the RTC MMRs to be synced into
	 * the core after waking up.  This happens every RTC 1HZ.  Once that
	 * has happened, we can go ahead and re-enable the important write
	 * complete interrupt event.
	 */
	while (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_SEC))
		continue;
	bfin_rtc_int_set(RTC_ISTAT_WRITE_COMPLETE);

	return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(bfin_rtc_pm_ops, bfin_rtc_suspend, bfin_rtc_resume);

static struct platform_driver bfin_rtc_driver = {
	.driver		= {
		.name	= "rtc-bfin",
		.pm	= &bfin_rtc_pm_ops,
	},
	.probe		= bfin_rtc_probe,
	.remove		= bfin_rtc_remove,
};

module_platform_driver(bfin_rtc_driver);

MODULE_DESCRIPTION("Blackfin On-Chip Real Time Clock Driver");
MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:rtc-bfin");