xref: /openbmc/linux/drivers/rtc/rtc-at91sam9.c (revision 9ac8d3fb)
1 /*
2  * "RTT as Real Time Clock" driver for AT91SAM9 SoC family
3  *
4  * (C) 2007 Michel Benoit
5  *
6  * Based on rtc-at91rm9200.c by Rick Bronson
7  *
8  * This program is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU General Public License
10  * as published by the Free Software Foundation; either version
11  * 2 of the License, or (at your option) any later version.
12  */
13 
14 #include <linux/module.h>
15 #include <linux/kernel.h>
16 #include <linux/platform_device.h>
17 #include <linux/time.h>
18 #include <linux/rtc.h>
19 #include <linux/interrupt.h>
20 #include <linux/ioctl.h>
21 
22 #include <mach/board.h>
23 #include <mach/at91_rtt.h>
24 
25 
26 /*
27  * This driver uses two configurable hardware resources that live in the
28  * AT91SAM9 backup power domain (intended to be powered at all times)
29  * to implement the Real Time Clock interfaces
30  *
31  *  - A "Real-time Timer" (RTT) counts up in seconds from a base time.
32  *    We can't assign the counter value (CRTV) ... but we can reset it.
33  *
34  *  - One of the "General Purpose Backup Registers" (GPBRs) holds the
35  *    base time, normally an offset from the beginning of the POSIX
36  *    epoch (1970-Jan-1 00:00:00 UTC).  Some systems also include the
37  *    local timezone's offset.
38  *
39  * The RTC's value is the RTT counter plus that offset.  The RTC's alarm
40  * is likewise a base (ALMV) plus that offset.
41  *
42  * Not all RTTs will be used as RTCs; some systems have multiple RTTs to
43  * choose from, or a "real" RTC module.  All systems have multiple GPBR
44  * registers available, likewise usable for more than "RTC" support.
45  */
46 
47 /*
48  * We store ALARM_DISABLED in ALMV to record that no alarm is set.
49  * It's also the reset value for that field.
50  */
51 #define ALARM_DISABLED	((u32)~0)
52 
53 
54 struct sam9_rtc {
55 	void __iomem		*rtt;
56 	struct rtc_device	*rtcdev;
57 	u32			imr;
58 };
59 
60 #define rtt_readl(rtc, field) \
61 	__raw_readl((rtc)->rtt + AT91_RTT_ ## field)
62 #define rtt_writel(rtc, field, val) \
63 	__raw_writel((val), (rtc)->rtt + AT91_RTT_ ## field)
64 
65 #define gpbr_readl(rtc) \
66 	at91_sys_read(AT91_GPBR + 4 * CONFIG_RTC_DRV_AT91SAM9_GPBR)
67 #define gpbr_writel(rtc, val) \
68 	at91_sys_write(AT91_GPBR + 4 * CONFIG_RTC_DRV_AT91SAM9_GPBR, (val))
69 
70 /*
71  * Read current time and date in RTC
72  */
73 static int at91_rtc_readtime(struct device *dev, struct rtc_time *tm)
74 {
75 	struct sam9_rtc *rtc = dev_get_drvdata(dev);
76 	u32 secs, secs2;
77 	u32 offset;
78 
79 	/* read current time offset */
80 	offset = gpbr_readl(rtc);
81 	if (offset == 0)
82 		return -EILSEQ;
83 
84 	/* reread the counter to help sync the two clock domains */
85 	secs = rtt_readl(rtc, VR);
86 	secs2 = rtt_readl(rtc, VR);
87 	if (secs != secs2)
88 		secs = rtt_readl(rtc, VR);
89 
90 	rtc_time_to_tm(offset + secs, tm);
91 
92 	dev_dbg(dev, "%s: %4d-%02d-%02d %02d:%02d:%02d\n", "readtime",
93 		1900 + tm->tm_year, tm->tm_mon, tm->tm_mday,
94 		tm->tm_hour, tm->tm_min, tm->tm_sec);
95 
96 	return 0;
97 }
98 
99 /*
100  * Set current time and date in RTC
101  */
102 static int at91_rtc_settime(struct device *dev, struct rtc_time *tm)
103 {
104 	struct sam9_rtc *rtc = dev_get_drvdata(dev);
105 	int err;
106 	u32 offset, alarm, mr;
107 	unsigned long secs;
108 
109 	dev_dbg(dev, "%s: %4d-%02d-%02d %02d:%02d:%02d\n", "settime",
110 		1900 + tm->tm_year, tm->tm_mon, tm->tm_mday,
111 		tm->tm_hour, tm->tm_min, tm->tm_sec);
112 
113 	err = rtc_tm_to_time(tm, &secs);
114 	if (err != 0)
115 		return err;
116 
117 	mr = rtt_readl(rtc, MR);
118 
119 	/* disable interrupts */
120 	rtt_writel(rtc, MR, mr & ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN));
121 
122 	/* read current time offset */
123 	offset = gpbr_readl(rtc);
124 
125 	/* store the new base time in a battery backup register */
126 	secs += 1;
127 	gpbr_writel(rtc, secs);
128 
129 	/* adjust the alarm time for the new base */
130 	alarm = rtt_readl(rtc, AR);
131 	if (alarm != ALARM_DISABLED) {
132 		if (offset > secs) {
133 			/* time jumped backwards, increase time until alarm */
134 			alarm += (offset - secs);
135 		} else if ((alarm + offset) > secs) {
136 			/* time jumped forwards, decrease time until alarm */
137 			alarm -= (secs - offset);
138 		} else {
139 			/* time jumped past the alarm, disable alarm */
140 			alarm = ALARM_DISABLED;
141 			mr &= ~AT91_RTT_ALMIEN;
142 		}
143 		rtt_writel(rtc, AR, alarm);
144 	}
145 
146 	/* reset the timer, and re-enable interrupts */
147 	rtt_writel(rtc, MR, mr | AT91_RTT_RTTRST);
148 
149 	return 0;
150 }
151 
152 static int at91_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
153 {
154 	struct sam9_rtc *rtc = dev_get_drvdata(dev);
155 	struct rtc_time *tm = &alrm->time;
156 	u32 alarm = rtt_readl(rtc, AR);
157 	u32 offset;
158 
159 	offset = gpbr_readl(rtc);
160 	if (offset == 0)
161 		return -EILSEQ;
162 
163 	memset(alrm, 0, sizeof(alrm));
164 	if (alarm != ALARM_DISABLED && offset != 0) {
165 		rtc_time_to_tm(offset + alarm, tm);
166 
167 		dev_dbg(dev, "%s: %4d-%02d-%02d %02d:%02d:%02d\n", "readalarm",
168 			1900 + tm->tm_year, tm->tm_mon, tm->tm_mday,
169 			tm->tm_hour, tm->tm_min, tm->tm_sec);
170 
171 		if (rtt_readl(rtc, MR) & AT91_RTT_ALMIEN)
172 			alrm->enabled = 1;
173 	}
174 
175 	return 0;
176 }
177 
178 static int at91_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
179 {
180 	struct sam9_rtc *rtc = dev_get_drvdata(dev);
181 	struct rtc_time *tm = &alrm->time;
182 	unsigned long secs;
183 	u32 offset;
184 	u32 mr;
185 	int err;
186 
187 	err = rtc_tm_to_time(tm, &secs);
188 	if (err != 0)
189 		return err;
190 
191 	offset = gpbr_readl(rtc);
192 	if (offset == 0) {
193 		/* time is not set */
194 		return -EILSEQ;
195 	}
196 	mr = rtt_readl(rtc, MR);
197 	rtt_writel(rtc, MR, mr & ~AT91_RTT_ALMIEN);
198 
199 	/* alarm in the past? finish and leave disabled */
200 	if (secs <= offset) {
201 		rtt_writel(rtc, AR, ALARM_DISABLED);
202 		return 0;
203 	}
204 
205 	/* else set alarm and maybe enable it */
206 	rtt_writel(rtc, AR, secs - offset);
207 	if (alrm->enabled)
208 		rtt_writel(rtc, MR, mr | AT91_RTT_ALMIEN);
209 
210 	dev_dbg(dev, "%s: %4d-%02d-%02d %02d:%02d:%02d\n", "setalarm",
211 		tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_hour,
212 		tm->tm_min, tm->tm_sec);
213 
214 	return 0;
215 }
216 
217 /*
218  * Handle commands from user-space
219  */
220 static int at91_rtc_ioctl(struct device *dev, unsigned int cmd,
221 			unsigned long arg)
222 {
223 	struct sam9_rtc *rtc = dev_get_drvdata(dev);
224 	int ret = 0;
225 	u32 mr = rtt_readl(rtc, MR);
226 
227 	dev_dbg(dev, "ioctl: cmd=%08x, arg=%08lx, mr %08x\n", cmd, arg, mr);
228 
229 	switch (cmd) {
230 	case RTC_AIE_OFF:		/* alarm off */
231 		rtt_writel(rtc, MR, mr & ~AT91_RTT_ALMIEN);
232 		break;
233 	case RTC_AIE_ON:		/* alarm on */
234 		rtt_writel(rtc, MR, mr | AT91_RTT_ALMIEN);
235 		break;
236 	case RTC_UIE_OFF:		/* update off */
237 		rtt_writel(rtc, MR, mr & ~AT91_RTT_RTTINCIEN);
238 		break;
239 	case RTC_UIE_ON:		/* update on */
240 		rtt_writel(rtc, MR, mr | AT91_RTT_RTTINCIEN);
241 		break;
242 	default:
243 		ret = -ENOIOCTLCMD;
244 		break;
245 	}
246 
247 	return ret;
248 }
249 
250 /*
251  * Provide additional RTC information in /proc/driver/rtc
252  */
253 static int at91_rtc_proc(struct device *dev, struct seq_file *seq)
254 {
255 	struct sam9_rtc *rtc = dev_get_drvdata(dev);
256 	u32 mr = mr = rtt_readl(rtc, MR);
257 
258 	seq_printf(seq, "update_IRQ\t: %s\n",
259 			(mr & AT91_RTT_RTTINCIEN) ? "yes" : "no");
260 	return 0;
261 }
262 
263 /*
264  * IRQ handler for the RTC
265  */
266 static irqreturn_t at91_rtc_interrupt(int irq, void *_rtc)
267 {
268 	struct sam9_rtc *rtc = _rtc;
269 	u32 sr, mr;
270 	unsigned long events = 0;
271 
272 	/* Shared interrupt may be for another device.  Note: reading
273 	 * SR clears it, so we must only read it in this irq handler!
274 	 */
275 	mr = rtt_readl(rtc, MR) & (AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
276 	sr = rtt_readl(rtc, SR) & (mr >> 16);
277 	if (!sr)
278 		return IRQ_NONE;
279 
280 	/* alarm status */
281 	if (sr & AT91_RTT_ALMS)
282 		events |= (RTC_AF | RTC_IRQF);
283 
284 	/* timer update/increment */
285 	if (sr & AT91_RTT_RTTINC)
286 		events |= (RTC_UF | RTC_IRQF);
287 
288 	rtc_update_irq(rtc->rtcdev, 1, events);
289 
290 	pr_debug("%s: num=%ld, events=0x%02lx\n", __func__,
291 		events >> 8, events & 0x000000FF);
292 
293 	return IRQ_HANDLED;
294 }
295 
296 static const struct rtc_class_ops at91_rtc_ops = {
297 	.ioctl		= at91_rtc_ioctl,
298 	.read_time	= at91_rtc_readtime,
299 	.set_time	= at91_rtc_settime,
300 	.read_alarm	= at91_rtc_readalarm,
301 	.set_alarm	= at91_rtc_setalarm,
302 	.proc		= at91_rtc_proc,
303 };
304 
305 /*
306  * Initialize and install RTC driver
307  */
308 static int __init at91_rtc_probe(struct platform_device *pdev)
309 {
310 	struct resource	*r;
311 	struct sam9_rtc	*rtc;
312 	int		ret;
313 	u32		mr;
314 
315 	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
316 	if (!r)
317 		return -ENODEV;
318 
319 	rtc = kzalloc(sizeof *rtc, GFP_KERNEL);
320 	if (!rtc)
321 		return -ENOMEM;
322 
323 	/* platform setup code should have handled this; sigh */
324 	if (!device_can_wakeup(&pdev->dev))
325 		device_init_wakeup(&pdev->dev, 1);
326 
327 	platform_set_drvdata(pdev, rtc);
328 	rtc->rtt = (void __force __iomem *) (AT91_VA_BASE_SYS - AT91_BASE_SYS);
329 	rtc->rtt += r->start;
330 
331 	mr = rtt_readl(rtc, MR);
332 
333 	/* unless RTT is counting at 1 Hz, re-initialize it */
334 	if ((mr & AT91_RTT_RTPRES) != AT91_SLOW_CLOCK) {
335 		mr = AT91_RTT_RTTRST | (AT91_SLOW_CLOCK & AT91_RTT_RTPRES);
336 		gpbr_writel(rtc, 0);
337 	}
338 
339 	/* disable all interrupts (same as on shutdown path) */
340 	mr &= ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
341 	rtt_writel(rtc, MR, mr);
342 
343 	rtc->rtcdev = rtc_device_register(pdev->name, &pdev->dev,
344 				&at91_rtc_ops, THIS_MODULE);
345 	if (IS_ERR(rtc->rtcdev)) {
346 		ret = PTR_ERR(rtc->rtcdev);
347 		goto fail;
348 	}
349 
350 	/* register irq handler after we know what name we'll use */
351 	ret = request_irq(AT91_ID_SYS, at91_rtc_interrupt,
352 				IRQF_DISABLED | IRQF_SHARED,
353 				rtc->rtcdev->dev.bus_id, rtc);
354 	if (ret) {
355 		dev_dbg(&pdev->dev, "can't share IRQ %d?\n", AT91_ID_SYS);
356 		rtc_device_unregister(rtc->rtcdev);
357 		goto fail;
358 	}
359 
360 	/* NOTE:  sam9260 rev A silicon has a ROM bug which resets the
361 	 * RTT on at least some reboots.  If you have that chip, you must
362 	 * initialize the time from some external source like a GPS, wall
363 	 * clock, discrete RTC, etc
364 	 */
365 
366 	if (gpbr_readl(rtc) == 0)
367 		dev_warn(&pdev->dev, "%s: SET TIME!\n",
368 				rtc->rtcdev->dev.bus_id);
369 
370 	return 0;
371 
372 fail:
373 	platform_set_drvdata(pdev, NULL);
374 	kfree(rtc);
375 	return ret;
376 }
377 
378 /*
379  * Disable and remove the RTC driver
380  */
381 static int __exit at91_rtc_remove(struct platform_device *pdev)
382 {
383 	struct sam9_rtc	*rtc = platform_get_drvdata(pdev);
384 	u32		mr = rtt_readl(rtc, MR);
385 
386 	/* disable all interrupts */
387 	rtt_writel(rtc, MR, mr & ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN));
388 	free_irq(AT91_ID_SYS, rtc);
389 
390 	rtc_device_unregister(rtc->rtcdev);
391 
392 	platform_set_drvdata(pdev, NULL);
393 	kfree(rtc);
394 	return 0;
395 }
396 
397 static void at91_rtc_shutdown(struct platform_device *pdev)
398 {
399 	struct sam9_rtc	*rtc = platform_get_drvdata(pdev);
400 	u32		mr = rtt_readl(rtc, MR);
401 
402 	rtc->imr = mr & (AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
403 	rtt_writel(rtc, MR, mr & ~rtc->imr);
404 }
405 
406 #ifdef CONFIG_PM
407 
408 /* AT91SAM9 RTC Power management control */
409 
410 static int at91_rtc_suspend(struct platform_device *pdev,
411 					pm_message_t state)
412 {
413 	struct sam9_rtc	*rtc = platform_get_drvdata(pdev);
414 	u32		mr = rtt_readl(rtc, MR);
415 
416 	/*
417 	 * This IRQ is shared with DBGU and other hardware which isn't
418 	 * necessarily a wakeup event source.
419 	 */
420 	rtc->imr = mr & (AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
421 	if (rtc->imr) {
422 		if (device_may_wakeup(&pdev->dev) && (mr & AT91_RTT_ALMIEN)) {
423 			enable_irq_wake(AT91_ID_SYS);
424 			/* don't let RTTINC cause wakeups */
425 			if (mr & AT91_RTT_RTTINCIEN)
426 				rtt_writel(rtc, MR, mr & ~AT91_RTT_RTTINCIEN);
427 		} else
428 			rtt_writel(rtc, MR, mr & ~rtc->imr);
429 	}
430 
431 	return 0;
432 }
433 
434 static int at91_rtc_resume(struct platform_device *pdev)
435 {
436 	struct sam9_rtc	*rtc = platform_get_drvdata(pdev);
437 	u32		mr;
438 
439 	if (rtc->imr) {
440 		if (device_may_wakeup(&pdev->dev))
441 			disable_irq_wake(AT91_ID_SYS);
442 		mr = rtt_readl(rtc, MR);
443 		rtt_writel(rtc, MR, mr | rtc->imr);
444 	}
445 
446 	return 0;
447 }
448 #else
449 #define at91_rtc_suspend	NULL
450 #define at91_rtc_resume		NULL
451 #endif
452 
453 static struct platform_driver at91_rtc_driver = {
454 	.driver.name	= "rtc-at91sam9",
455 	.driver.owner	= THIS_MODULE,
456 	.remove		= __exit_p(at91_rtc_remove),
457 	.shutdown	= at91_rtc_shutdown,
458 	.suspend	= at91_rtc_suspend,
459 	.resume		= at91_rtc_resume,
460 };
461 
462 /* Chips can have more than one RTT module, and they can be used for more
463  * than just RTCs.  So we can't just register as "the" RTT driver.
464  *
465  * A normal approach in such cases is to create a library to allocate and
466  * free the modules.  Here we just use bus_find_device() as like such a
467  * library, binding directly ... no runtime "library" footprint is needed.
468  */
469 static int __init at91_rtc_match(struct device *dev, void *v)
470 {
471 	struct platform_device *pdev = to_platform_device(dev);
472 	int ret;
473 
474 	/* continue searching if this isn't the RTT we need */
475 	if (strcmp("at91_rtt", pdev->name) != 0
476 			|| pdev->id != CONFIG_RTC_DRV_AT91SAM9_RTT)
477 		goto fail;
478 
479 	/* else we found it ... but fail unless we can bind to the RTC driver */
480 	if (dev->driver) {
481 		dev_dbg(dev, "busy, can't use as RTC!\n");
482 		goto fail;
483 	}
484 	dev->driver = &at91_rtc_driver.driver;
485 	if (device_attach(dev) == 0) {
486 		dev_dbg(dev, "can't attach RTC!\n");
487 		goto fail;
488 	}
489 	ret = at91_rtc_probe(pdev);
490 	if (ret == 0)
491 		return true;
492 
493 	dev_dbg(dev, "RTC probe err %d!\n", ret);
494 fail:
495 	return false;
496 }
497 
498 static int __init at91_rtc_init(void)
499 {
500 	int status;
501 	struct device *rtc;
502 
503 	status = platform_driver_register(&at91_rtc_driver);
504 	if (status)
505 		return status;
506 	rtc = bus_find_device(&platform_bus_type, NULL,
507 			NULL, at91_rtc_match);
508 	if (!rtc)
509 		platform_driver_unregister(&at91_rtc_driver);
510 	return rtc ? 0 : -ENODEV;
511 }
512 module_init(at91_rtc_init);
513 
514 static void __exit at91_rtc_exit(void)
515 {
516 	platform_driver_unregister(&at91_rtc_driver);
517 }
518 module_exit(at91_rtc_exit);
519 
520 
521 MODULE_AUTHOR("Michel Benoit");
522 MODULE_DESCRIPTION("RTC driver for Atmel AT91SAM9x");
523 MODULE_LICENSE("GPL");
524