xref: /linux/drivers/rtc/rtc-at91sam9.c (revision 8e07e0e3964ca4e23ce7b68e2096fe660a888942) 
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * "RTT as Real Time Clock" driver for AT91SAM9 SoC family
4  *
5  * (C) 2007 Michel Benoit
6  *
7  * Based on rtc-at91rm9200.c by Rick Bronson
8  */
9 
10 #include <linux/clk.h>
11 #include <linux/interrupt.h>
12 #include <linux/ioctl.h>
13 #include <linux/io.h>
14 #include <linux/kernel.h>
15 #include <linux/mfd/syscon.h>
16 #include <linux/module.h>
17 #include <linux/of.h>
18 #include <linux/platform_device.h>
19 #include <linux/regmap.h>
20 #include <linux/rtc.h>
21 #include <linux/slab.h>
22 #include <linux/suspend.h>
23 #include <linux/time.h>
24 
25 /*
26  * This driver uses two configurable hardware resources that live in the
27  * AT91SAM9 backup power domain (intended to be powered at all times)
28  * to implement the Real Time Clock interfaces
29  *
30  *  - A "Real-time Timer" (RTT) counts up in seconds from a base time.
31  *    We can't assign the counter value (CRTV) ... but we can reset it.
32  *
33  *  - One of the "General Purpose Backup Registers" (GPBRs) holds the
34  *    base time, normally an offset from the beginning of the POSIX
35  *    epoch (1970-Jan-1 00:00:00 UTC).  Some systems also include the
36  *    local timezone's offset.
37  *
38  * The RTC's value is the RTT counter plus that offset.  The RTC's alarm
39  * is likewise a base (ALMV) plus that offset.
40  *
41  * Not all RTTs will be used as RTCs; some systems have multiple RTTs to
42  * choose from, or a "real" RTC module.  All systems have multiple GPBR
43  * registers available, likewise usable for more than "RTC" support.
44  */
45 
46 #define AT91_RTT_MR		0x00		/* Real-time Mode Register */
47 #define AT91_RTT_RTPRES		(0xffff << 0)	/* Timer Prescaler Value */
48 #define AT91_RTT_ALMIEN		BIT(16)		/* Alarm Interrupt Enable */
49 #define AT91_RTT_RTTINCIEN	BIT(17)		/* Increment Interrupt Enable */
50 #define AT91_RTT_RTTRST		BIT(18)		/* Timer Restart */
51 
52 #define AT91_RTT_AR		0x04		/* Real-time Alarm Register */
53 #define AT91_RTT_ALMV		(0xffffffff)	/* Alarm Value */
54 
55 #define AT91_RTT_VR		0x08		/* Real-time Value Register */
56 #define AT91_RTT_CRTV		(0xffffffff)	/* Current Real-time Value */
57 
58 #define AT91_RTT_SR		0x0c		/* Real-time Status Register */
59 #define AT91_RTT_ALMS		BIT(0)		/* Alarm Status */
60 #define AT91_RTT_RTTINC		BIT(1)		/* Timer Increment */
61 
62 /*
63  * We store ALARM_DISABLED in ALMV to record that no alarm is set.
64  * It's also the reset value for that field.
65  */
66 #define ALARM_DISABLED	((u32)~0)
67 
68 struct sam9_rtc {
69 	void __iomem		*rtt;
70 	struct rtc_device	*rtcdev;
71 	u32			imr;
72 	struct regmap		*gpbr;
73 	unsigned int		gpbr_offset;
74 	int			irq;
75 	struct clk		*sclk;
76 	bool			suspended;
77 	unsigned long		events;
78 	spinlock_t		lock;
79 };
80 
81 #define rtt_readl(rtc, field) \
82 	readl((rtc)->rtt + AT91_RTT_ ## field)
83 #define rtt_writel(rtc, field, val) \
84 	writel((val), (rtc)->rtt + AT91_RTT_ ## field)
85 
86 static inline unsigned int gpbr_readl(struct sam9_rtc *rtc)
87 {
88 	unsigned int val;
89 
90 	regmap_read(rtc->gpbr, rtc->gpbr_offset, &val);
91 
92 	return val;
93 }
94 
95 static inline void gpbr_writel(struct sam9_rtc *rtc, unsigned int val)
96 {
97 	regmap_write(rtc->gpbr, rtc->gpbr_offset, val);
98 }
99 
100 /*
101  * Read current time and date in RTC
102  */
103 static int at91_rtc_readtime(struct device *dev, struct rtc_time *tm)
104 {
105 	struct sam9_rtc *rtc = dev_get_drvdata(dev);
106 	u32 secs, secs2;
107 	u32 offset;
108 
109 	/* read current time offset */
110 	offset = gpbr_readl(rtc);
111 	if (offset == 0)
112 		return -EILSEQ;
113 
114 	/* reread the counter to help sync the two clock domains */
115 	secs = rtt_readl(rtc, VR);
116 	secs2 = rtt_readl(rtc, VR);
117 	if (secs != secs2)
118 		secs = rtt_readl(rtc, VR);
119 
120 	rtc_time64_to_tm(offset + secs, tm);
121 
122 	dev_dbg(dev, "%s: %ptR\n", __func__, tm);
123 
124 	return 0;
125 }
126 
127 /*
128  * Set current time and date in RTC
129  */
130 static int at91_rtc_settime(struct device *dev, struct rtc_time *tm)
131 {
132 	struct sam9_rtc *rtc = dev_get_drvdata(dev);
133 	u32 offset, alarm, mr;
134 	unsigned long secs;
135 
136 	dev_dbg(dev, "%s: %ptR\n", __func__, tm);
137 
138 	secs = rtc_tm_to_time64(tm);
139 
140 	mr = rtt_readl(rtc, MR);
141 
142 	/* disable interrupts */
143 	rtt_writel(rtc, MR, mr & ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN));
144 
145 	/* read current time offset */
146 	offset = gpbr_readl(rtc);
147 
148 	/* store the new base time in a battery backup register */
149 	secs += 1;
150 	gpbr_writel(rtc, secs);
151 
152 	/* adjust the alarm time for the new base */
153 	alarm = rtt_readl(rtc, AR);
154 	if (alarm != ALARM_DISABLED) {
155 		if (offset > secs) {
156 			/* time jumped backwards, increase time until alarm */
157 			alarm += (offset - secs);
158 		} else if ((alarm + offset) > secs) {
159 			/* time jumped forwards, decrease time until alarm */
160 			alarm -= (secs - offset);
161 		} else {
162 			/* time jumped past the alarm, disable alarm */
163 			alarm = ALARM_DISABLED;
164 			mr &= ~AT91_RTT_ALMIEN;
165 		}
166 		rtt_writel(rtc, AR, alarm);
167 	}
168 
169 	/* reset the timer, and re-enable interrupts */
170 	rtt_writel(rtc, MR, mr | AT91_RTT_RTTRST);
171 
172 	return 0;
173 }
174 
175 static int at91_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
176 {
177 	struct sam9_rtc *rtc = dev_get_drvdata(dev);
178 	struct rtc_time *tm = &alrm->time;
179 	u32 alarm = rtt_readl(rtc, AR);
180 	u32 offset;
181 
182 	offset = gpbr_readl(rtc);
183 	if (offset == 0)
184 		return -EILSEQ;
185 
186 	memset(alrm, 0, sizeof(*alrm));
187 	if (alarm != ALARM_DISABLED) {
188 		rtc_time64_to_tm(offset + alarm, tm);
189 
190 		dev_dbg(dev, "%s: %ptR\n", __func__, tm);
191 
192 		if (rtt_readl(rtc, MR) & AT91_RTT_ALMIEN)
193 			alrm->enabled = 1;
194 	}
195 
196 	return 0;
197 }
198 
199 static int at91_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
200 {
201 	struct sam9_rtc *rtc = dev_get_drvdata(dev);
202 	struct rtc_time *tm = &alrm->time;
203 	unsigned long secs;
204 	u32 offset;
205 	u32 mr;
206 
207 	secs = rtc_tm_to_time64(tm);
208 
209 	offset = gpbr_readl(rtc);
210 	if (offset == 0) {
211 		/* time is not set */
212 		return -EILSEQ;
213 	}
214 	mr = rtt_readl(rtc, MR);
215 	rtt_writel(rtc, MR, mr & ~AT91_RTT_ALMIEN);
216 
217 	/* alarm in the past? finish and leave disabled */
218 	if (secs <= offset) {
219 		rtt_writel(rtc, AR, ALARM_DISABLED);
220 		return 0;
221 	}
222 
223 	/* else set alarm and maybe enable it */
224 	rtt_writel(rtc, AR, secs - offset);
225 	if (alrm->enabled)
226 		rtt_writel(rtc, MR, mr | AT91_RTT_ALMIEN);
227 
228 	dev_dbg(dev, "%s: %ptR\n", __func__, tm);
229 
230 	return 0;
231 }
232 
233 static int at91_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
234 {
235 	struct sam9_rtc *rtc = dev_get_drvdata(dev);
236 	u32 mr = rtt_readl(rtc, MR);
237 
238 	dev_dbg(dev, "alarm_irq_enable: enabled=%08x, mr %08x\n", enabled, mr);
239 	if (enabled)
240 		rtt_writel(rtc, MR, mr | AT91_RTT_ALMIEN);
241 	else
242 		rtt_writel(rtc, MR, mr & ~AT91_RTT_ALMIEN);
243 	return 0;
244 }
245 
246 /*
247  * Provide additional RTC information in /proc/driver/rtc
248  */
249 static int at91_rtc_proc(struct device *dev, struct seq_file *seq)
250 {
251 	struct sam9_rtc *rtc = dev_get_drvdata(dev);
252 	u32 mr = rtt_readl(rtc, MR);
253 
254 	seq_printf(seq, "update_IRQ\t: %s\n",
255 		   (mr & AT91_RTT_RTTINCIEN) ? "yes" : "no");
256 	return 0;
257 }
258 
259 static irqreturn_t at91_rtc_cache_events(struct sam9_rtc *rtc)
260 {
261 	u32 sr, mr;
262 
263 	/* Shared interrupt may be for another device.  Note: reading
264 	 * SR clears it, so we must only read it in this irq handler!
265 	 */
266 	mr = rtt_readl(rtc, MR) & (AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
267 	sr = rtt_readl(rtc, SR) & (mr >> 16);
268 	if (!sr)
269 		return IRQ_NONE;
270 
271 	/* alarm status */
272 	if (sr & AT91_RTT_ALMS)
273 		rtc->events |= (RTC_AF | RTC_IRQF);
274 
275 	/* timer update/increment */
276 	if (sr & AT91_RTT_RTTINC)
277 		rtc->events |= (RTC_UF | RTC_IRQF);
278 
279 	return IRQ_HANDLED;
280 }
281 
282 static void at91_rtc_flush_events(struct sam9_rtc *rtc)
283 {
284 	if (!rtc->events)
285 		return;
286 
287 	rtc_update_irq(rtc->rtcdev, 1, rtc->events);
288 	rtc->events = 0;
289 
290 	pr_debug("%s: num=%ld, events=0x%02lx\n", __func__,
291 		 rtc->events >> 8, rtc->events & 0x000000FF);
292 }
293 
294 /*
295  * IRQ handler for the RTC
296  */
297 static irqreturn_t at91_rtc_interrupt(int irq, void *_rtc)
298 {
299 	struct sam9_rtc *rtc = _rtc;
300 	int ret;
301 
302 	spin_lock(&rtc->lock);
303 
304 	ret = at91_rtc_cache_events(rtc);
305 
306 	/* We're called in suspended state */
307 	if (rtc->suspended) {
308 		/* Mask irqs coming from this peripheral */
309 		rtt_writel(rtc, MR,
310 			   rtt_readl(rtc, MR) &
311 			   ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN));
312 		/* Trigger a system wakeup */
313 		pm_system_wakeup();
314 	} else {
315 		at91_rtc_flush_events(rtc);
316 	}
317 
318 	spin_unlock(&rtc->lock);
319 
320 	return ret;
321 }
322 
323 static const struct rtc_class_ops at91_rtc_ops = {
324 	.read_time	= at91_rtc_readtime,
325 	.set_time	= at91_rtc_settime,
326 	.read_alarm	= at91_rtc_readalarm,
327 	.set_alarm	= at91_rtc_setalarm,
328 	.proc		= at91_rtc_proc,
329 	.alarm_irq_enable = at91_rtc_alarm_irq_enable,
330 };
331 
332 /*
333  * Initialize and install RTC driver
334  */
335 static int at91_rtc_probe(struct platform_device *pdev)
336 {
337 	struct sam9_rtc	*rtc;
338 	int		ret, irq;
339 	u32		mr;
340 	unsigned int	sclk_rate;
341 	struct of_phandle_args args;
342 
343 	irq = platform_get_irq(pdev, 0);
344 	if (irq < 0)
345 		return irq;
346 
347 	rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
348 	if (!rtc)
349 		return -ENOMEM;
350 
351 	spin_lock_init(&rtc->lock);
352 	rtc->irq = irq;
353 
354 	/* platform setup code should have handled this; sigh */
355 	if (!device_can_wakeup(&pdev->dev))
356 		device_init_wakeup(&pdev->dev, 1);
357 
358 	platform_set_drvdata(pdev, rtc);
359 
360 	rtc->rtt = devm_platform_ioremap_resource(pdev, 0);
361 	if (IS_ERR(rtc->rtt))
362 		return PTR_ERR(rtc->rtt);
363 
364 	ret = of_parse_phandle_with_fixed_args(pdev->dev.of_node,
365 					       "atmel,rtt-rtc-time-reg", 1, 0,
366 					       &args);
367 	if (ret)
368 		return ret;
369 
370 	rtc->gpbr = syscon_node_to_regmap(args.np);
371 	rtc->gpbr_offset = args.args[0];
372 	if (IS_ERR(rtc->gpbr)) {
373 		dev_err(&pdev->dev, "failed to retrieve gpbr regmap, aborting.\n");
374 		return -ENOMEM;
375 	}
376 
377 	rtc->sclk = devm_clk_get(&pdev->dev, NULL);
378 	if (IS_ERR(rtc->sclk))
379 		return PTR_ERR(rtc->sclk);
380 
381 	ret = clk_prepare_enable(rtc->sclk);
382 	if (ret) {
383 		dev_err(&pdev->dev, "Could not enable slow clock\n");
384 		return ret;
385 	}
386 
387 	sclk_rate = clk_get_rate(rtc->sclk);
388 	if (!sclk_rate || sclk_rate > AT91_RTT_RTPRES) {
389 		dev_err(&pdev->dev, "Invalid slow clock rate\n");
390 		ret = -EINVAL;
391 		goto err_clk;
392 	}
393 
394 	mr = rtt_readl(rtc, MR);
395 
396 	/* unless RTT is counting at 1 Hz, re-initialize it */
397 	if ((mr & AT91_RTT_RTPRES) != sclk_rate) {
398 		mr = AT91_RTT_RTTRST | (sclk_rate & AT91_RTT_RTPRES);
399 		gpbr_writel(rtc, 0);
400 	}
401 
402 	/* disable all interrupts (same as on shutdown path) */
403 	mr &= ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
404 	rtt_writel(rtc, MR, mr);
405 
406 	rtc->rtcdev = devm_rtc_allocate_device(&pdev->dev);
407 	if (IS_ERR(rtc->rtcdev)) {
408 		ret = PTR_ERR(rtc->rtcdev);
409 		goto err_clk;
410 	}
411 
412 	rtc->rtcdev->ops = &at91_rtc_ops;
413 	rtc->rtcdev->range_max = U32_MAX;
414 
415 	/* register irq handler after we know what name we'll use */
416 	ret = devm_request_irq(&pdev->dev, rtc->irq, at91_rtc_interrupt,
417 			       IRQF_SHARED | IRQF_COND_SUSPEND,
418 			       dev_name(&rtc->rtcdev->dev), rtc);
419 	if (ret) {
420 		dev_dbg(&pdev->dev, "can't share IRQ %d?\n", rtc->irq);
421 		goto err_clk;
422 	}
423 
424 	/* NOTE:  sam9260 rev A silicon has a ROM bug which resets the
425 	 * RTT on at least some reboots.  If you have that chip, you must
426 	 * initialize the time from some external source like a GPS, wall
427 	 * clock, discrete RTC, etc
428 	 */
429 
430 	if (gpbr_readl(rtc) == 0)
431 		dev_warn(&pdev->dev, "%s: SET TIME!\n",
432 			 dev_name(&rtc->rtcdev->dev));
433 
434 	return devm_rtc_register_device(rtc->rtcdev);
435 
436 err_clk:
437 	clk_disable_unprepare(rtc->sclk);
438 
439 	return ret;
440 }
441 
442 /*
443  * Disable and remove the RTC driver
444  */
445 static void at91_rtc_remove(struct platform_device *pdev)
446 {
447 	struct sam9_rtc	*rtc = platform_get_drvdata(pdev);
448 	u32		mr = rtt_readl(rtc, MR);
449 
450 	/* disable all interrupts */
451 	rtt_writel(rtc, MR, mr & ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN));
452 
453 	clk_disable_unprepare(rtc->sclk);
454 }
455 
456 static void at91_rtc_shutdown(struct platform_device *pdev)
457 {
458 	struct sam9_rtc	*rtc = platform_get_drvdata(pdev);
459 	u32		mr = rtt_readl(rtc, MR);
460 
461 	rtc->imr = mr & (AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
462 	rtt_writel(rtc, MR, mr & ~rtc->imr);
463 }
464 
465 #ifdef CONFIG_PM_SLEEP
466 
467 /* AT91SAM9 RTC Power management control */
468 
469 static int at91_rtc_suspend(struct device *dev)
470 {
471 	struct sam9_rtc	*rtc = dev_get_drvdata(dev);
472 	u32		mr = rtt_readl(rtc, MR);
473 
474 	/*
475 	 * This IRQ is shared with DBGU and other hardware which isn't
476 	 * necessarily a wakeup event source.
477 	 */
478 	rtc->imr = mr & (AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN);
479 	if (rtc->imr) {
480 		if (device_may_wakeup(dev) && (mr & AT91_RTT_ALMIEN)) {
481 			unsigned long flags;
482 
483 			enable_irq_wake(rtc->irq);
484 			spin_lock_irqsave(&rtc->lock, flags);
485 			rtc->suspended = true;
486 			spin_unlock_irqrestore(&rtc->lock, flags);
487 			/* don't let RTTINC cause wakeups */
488 			if (mr & AT91_RTT_RTTINCIEN)
489 				rtt_writel(rtc, MR, mr & ~AT91_RTT_RTTINCIEN);
490 		} else {
491 			rtt_writel(rtc, MR, mr & ~rtc->imr);
492 		}
493 	}
494 
495 	return 0;
496 }
497 
498 static int at91_rtc_resume(struct device *dev)
499 {
500 	struct sam9_rtc	*rtc = dev_get_drvdata(dev);
501 	u32		mr;
502 
503 	if (rtc->imr) {
504 		unsigned long flags;
505 
506 		if (device_may_wakeup(dev))
507 			disable_irq_wake(rtc->irq);
508 		mr = rtt_readl(rtc, MR);
509 		rtt_writel(rtc, MR, mr | rtc->imr);
510 
511 		spin_lock_irqsave(&rtc->lock, flags);
512 		rtc->suspended = false;
513 		at91_rtc_cache_events(rtc);
514 		at91_rtc_flush_events(rtc);
515 		spin_unlock_irqrestore(&rtc->lock, flags);
516 	}
517 
518 	return 0;
519 }
520 #endif
521 
522 static SIMPLE_DEV_PM_OPS(at91_rtc_pm_ops, at91_rtc_suspend, at91_rtc_resume);
523 
524 static const struct of_device_id at91_rtc_dt_ids[] = {
525 	{ .compatible = "atmel,at91sam9260-rtt" },
526 	{ /* sentinel */ }
527 };
528 MODULE_DEVICE_TABLE(of, at91_rtc_dt_ids);
529 
530 static struct platform_driver at91_rtc_driver = {
531 	.probe		= at91_rtc_probe,
532 	.remove_new	= at91_rtc_remove,
533 	.shutdown	= at91_rtc_shutdown,
534 	.driver		= {
535 		.name	= "rtc-at91sam9",
536 		.pm	= &at91_rtc_pm_ops,
537 		.of_match_table = at91_rtc_dt_ids,
538 	},
539 };
540 
541 module_platform_driver(at91_rtc_driver);
542 
543 MODULE_AUTHOR("Michel Benoit");
544 MODULE_DESCRIPTION("RTC driver for Atmel AT91SAM9x");
545 MODULE_LICENSE("GPL");
546