xref: /openbmc/linux/drivers/rtc/class.c (revision 1aaba11d)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * RTC subsystem, base class
4  *
5  * Copyright (C) 2005 Tower Technologies
6  * Author: Alessandro Zummo <a.zummo@towertech.it>
7  *
8  * class skeleton from drivers/hwmon/hwmon.c
9  */
10 
11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12 
13 #include <linux/module.h>
14 #include <linux/of.h>
15 #include <linux/rtc.h>
16 #include <linux/kdev_t.h>
17 #include <linux/idr.h>
18 #include <linux/slab.h>
19 #include <linux/workqueue.h>
20 
21 #include "rtc-core.h"
22 
23 static DEFINE_IDA(rtc_ida);
24 struct class *rtc_class;
25 
rtc_device_release(struct device * dev)26 static void rtc_device_release(struct device *dev)
27 {
28 	struct rtc_device *rtc = to_rtc_device(dev);
29 	struct timerqueue_head *head = &rtc->timerqueue;
30 	struct timerqueue_node *node;
31 
32 	mutex_lock(&rtc->ops_lock);
33 	while ((node = timerqueue_getnext(head)))
34 		timerqueue_del(head, node);
35 	mutex_unlock(&rtc->ops_lock);
36 
37 	cancel_work_sync(&rtc->irqwork);
38 
39 	ida_free(&rtc_ida, rtc->id);
40 	mutex_destroy(&rtc->ops_lock);
41 	kfree(rtc);
42 }
43 
44 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
45 /* Result of the last RTC to system clock attempt. */
46 int rtc_hctosys_ret = -ENODEV;
47 
48 /* IMPORTANT: the RTC only stores whole seconds. It is arbitrary
49  * whether it stores the most close value or the value with partial
50  * seconds truncated. However, it is important that we use it to store
51  * the truncated value. This is because otherwise it is necessary,
52  * in an rtc sync function, to read both xtime.tv_sec and
53  * xtime.tv_nsec. On some processors (i.e. ARM), an atomic read
54  * of >32bits is not possible. So storing the most close value would
55  * slow down the sync API. So here we have the truncated value and
56  * the best guess is to add 0.5s.
57  */
58 
rtc_hctosys(struct rtc_device * rtc)59 static void rtc_hctosys(struct rtc_device *rtc)
60 {
61 	int err;
62 	struct rtc_time tm;
63 	struct timespec64 tv64 = {
64 		.tv_nsec = NSEC_PER_SEC >> 1,
65 	};
66 
67 	err = rtc_read_time(rtc, &tm);
68 	if (err) {
69 		dev_err(rtc->dev.parent,
70 			"hctosys: unable to read the hardware clock\n");
71 		goto err_read;
72 	}
73 
74 	tv64.tv_sec = rtc_tm_to_time64(&tm);
75 
76 #if BITS_PER_LONG == 32
77 	if (tv64.tv_sec > INT_MAX) {
78 		err = -ERANGE;
79 		goto err_read;
80 	}
81 #endif
82 
83 	err = do_settimeofday64(&tv64);
84 
85 	dev_info(rtc->dev.parent, "setting system clock to %ptR UTC (%lld)\n",
86 		 &tm, (long long)tv64.tv_sec);
87 
88 err_read:
89 	rtc_hctosys_ret = err;
90 }
91 #endif
92 
93 #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
94 /*
95  * On suspend(), measure the delta between one RTC and the
96  * system's wall clock; restore it on resume().
97  */
98 
99 static struct timespec64 old_rtc, old_system, old_delta;
100 
rtc_suspend(struct device * dev)101 static int rtc_suspend(struct device *dev)
102 {
103 	struct rtc_device	*rtc = to_rtc_device(dev);
104 	struct rtc_time		tm;
105 	struct timespec64	delta, delta_delta;
106 	int err;
107 
108 	if (timekeeping_rtc_skipsuspend())
109 		return 0;
110 
111 	if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
112 		return 0;
113 
114 	/* snapshot the current RTC and system time at suspend*/
115 	err = rtc_read_time(rtc, &tm);
116 	if (err < 0) {
117 		pr_debug("%s:  fail to read rtc time\n", dev_name(&rtc->dev));
118 		return 0;
119 	}
120 
121 	ktime_get_real_ts64(&old_system);
122 	old_rtc.tv_sec = rtc_tm_to_time64(&tm);
123 
124 	/*
125 	 * To avoid drift caused by repeated suspend/resumes,
126 	 * which each can add ~1 second drift error,
127 	 * try to compensate so the difference in system time
128 	 * and rtc time stays close to constant.
129 	 */
130 	delta = timespec64_sub(old_system, old_rtc);
131 	delta_delta = timespec64_sub(delta, old_delta);
132 	if (delta_delta.tv_sec < -2 || delta_delta.tv_sec >= 2) {
133 		/*
134 		 * if delta_delta is too large, assume time correction
135 		 * has occurred and set old_delta to the current delta.
136 		 */
137 		old_delta = delta;
138 	} else {
139 		/* Otherwise try to adjust old_system to compensate */
140 		old_system = timespec64_sub(old_system, delta_delta);
141 	}
142 
143 	return 0;
144 }
145 
rtc_resume(struct device * dev)146 static int rtc_resume(struct device *dev)
147 {
148 	struct rtc_device	*rtc = to_rtc_device(dev);
149 	struct rtc_time		tm;
150 	struct timespec64	new_system, new_rtc;
151 	struct timespec64	sleep_time;
152 	int err;
153 
154 	if (timekeeping_rtc_skipresume())
155 		return 0;
156 
157 	rtc_hctosys_ret = -ENODEV;
158 	if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
159 		return 0;
160 
161 	/* snapshot the current rtc and system time at resume */
162 	ktime_get_real_ts64(&new_system);
163 	err = rtc_read_time(rtc, &tm);
164 	if (err < 0) {
165 		pr_debug("%s:  fail to read rtc time\n", dev_name(&rtc->dev));
166 		return 0;
167 	}
168 
169 	new_rtc.tv_sec = rtc_tm_to_time64(&tm);
170 	new_rtc.tv_nsec = 0;
171 
172 	if (new_rtc.tv_sec < old_rtc.tv_sec) {
173 		pr_debug("%s:  time travel!\n", dev_name(&rtc->dev));
174 		return 0;
175 	}
176 
177 	/* calculate the RTC time delta (sleep time)*/
178 	sleep_time = timespec64_sub(new_rtc, old_rtc);
179 
180 	/*
181 	 * Since these RTC suspend/resume handlers are not called
182 	 * at the very end of suspend or the start of resume,
183 	 * some run-time may pass on either sides of the sleep time
184 	 * so subtract kernel run-time between rtc_suspend to rtc_resume
185 	 * to keep things accurate.
186 	 */
187 	sleep_time = timespec64_sub(sleep_time,
188 				    timespec64_sub(new_system, old_system));
189 
190 	if (sleep_time.tv_sec >= 0)
191 		timekeeping_inject_sleeptime64(&sleep_time);
192 	rtc_hctosys_ret = 0;
193 	return 0;
194 }
195 
196 static SIMPLE_DEV_PM_OPS(rtc_class_dev_pm_ops, rtc_suspend, rtc_resume);
197 #define RTC_CLASS_DEV_PM_OPS	(&rtc_class_dev_pm_ops)
198 #else
199 #define RTC_CLASS_DEV_PM_OPS	NULL
200 #endif
201 
202 /* Ensure the caller will set the id before releasing the device */
rtc_allocate_device(void)203 static struct rtc_device *rtc_allocate_device(void)
204 {
205 	struct rtc_device *rtc;
206 
207 	rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
208 	if (!rtc)
209 		return NULL;
210 
211 	device_initialize(&rtc->dev);
212 
213 	/*
214 	 * Drivers can revise this default after allocating the device.
215 	 * The default is what most RTCs do: Increment seconds exactly one
216 	 * second after the write happened. This adds a default transport
217 	 * time of 5ms which is at least halfways close to reality.
218 	 */
219 	rtc->set_offset_nsec = NSEC_PER_SEC + 5 * NSEC_PER_MSEC;
220 
221 	rtc->irq_freq = 1;
222 	rtc->max_user_freq = 64;
223 	rtc->dev.class = rtc_class;
224 	rtc->dev.groups = rtc_get_dev_attribute_groups();
225 	rtc->dev.release = rtc_device_release;
226 
227 	mutex_init(&rtc->ops_lock);
228 	spin_lock_init(&rtc->irq_lock);
229 	init_waitqueue_head(&rtc->irq_queue);
230 
231 	/* Init timerqueue */
232 	timerqueue_init_head(&rtc->timerqueue);
233 	INIT_WORK(&rtc->irqwork, rtc_timer_do_work);
234 	/* Init aie timer */
235 	rtc_timer_init(&rtc->aie_timer, rtc_aie_update_irq, rtc);
236 	/* Init uie timer */
237 	rtc_timer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, rtc);
238 	/* Init pie timer */
239 	hrtimer_init(&rtc->pie_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
240 	rtc->pie_timer.function = rtc_pie_update_irq;
241 	rtc->pie_enabled = 0;
242 
243 	set_bit(RTC_FEATURE_ALARM, rtc->features);
244 	set_bit(RTC_FEATURE_UPDATE_INTERRUPT, rtc->features);
245 
246 	return rtc;
247 }
248 
rtc_device_get_id(struct device * dev)249 static int rtc_device_get_id(struct device *dev)
250 {
251 	int of_id = -1, id = -1;
252 
253 	if (dev->of_node)
254 		of_id = of_alias_get_id(dev->of_node, "rtc");
255 	else if (dev->parent && dev->parent->of_node)
256 		of_id = of_alias_get_id(dev->parent->of_node, "rtc");
257 
258 	if (of_id >= 0) {
259 		id = ida_simple_get(&rtc_ida, of_id, of_id + 1, GFP_KERNEL);
260 		if (id < 0)
261 			dev_warn(dev, "/aliases ID %d not available\n", of_id);
262 	}
263 
264 	if (id < 0)
265 		id = ida_alloc(&rtc_ida, GFP_KERNEL);
266 
267 	return id;
268 }
269 
rtc_device_get_offset(struct rtc_device * rtc)270 static void rtc_device_get_offset(struct rtc_device *rtc)
271 {
272 	time64_t range_secs;
273 	u32 start_year;
274 	int ret;
275 
276 	/*
277 	 * If RTC driver did not implement the range of RTC hardware device,
278 	 * then we can not expand the RTC range by adding or subtracting one
279 	 * offset.
280 	 */
281 	if (rtc->range_min == rtc->range_max)
282 		return;
283 
284 	ret = device_property_read_u32(rtc->dev.parent, "start-year",
285 				       &start_year);
286 	if (!ret) {
287 		rtc->start_secs = mktime64(start_year, 1, 1, 0, 0, 0);
288 		rtc->set_start_time = true;
289 	}
290 
291 	/*
292 	 * If user did not implement the start time for RTC driver, then no
293 	 * need to expand the RTC range.
294 	 */
295 	if (!rtc->set_start_time)
296 		return;
297 
298 	range_secs = rtc->range_max - rtc->range_min + 1;
299 
300 	/*
301 	 * If the start_secs is larger than the maximum seconds (rtc->range_max)
302 	 * supported by RTC hardware or the maximum seconds of new expanded
303 	 * range (start_secs + rtc->range_max - rtc->range_min) is less than
304 	 * rtc->range_min, which means the minimum seconds (rtc->range_min) of
305 	 * RTC hardware will be mapped to start_secs by adding one offset, so
306 	 * the offset seconds calculation formula should be:
307 	 * rtc->offset_secs = rtc->start_secs - rtc->range_min;
308 	 *
309 	 * If the start_secs is larger than the minimum seconds (rtc->range_min)
310 	 * supported by RTC hardware, then there is one region is overlapped
311 	 * between the original RTC hardware range and the new expanded range,
312 	 * and this overlapped region do not need to be mapped into the new
313 	 * expanded range due to it is valid for RTC device. So the minimum
314 	 * seconds of RTC hardware (rtc->range_min) should be mapped to
315 	 * rtc->range_max + 1, then the offset seconds formula should be:
316 	 * rtc->offset_secs = rtc->range_max - rtc->range_min + 1;
317 	 *
318 	 * If the start_secs is less than the minimum seconds (rtc->range_min),
319 	 * which is similar to case 2. So the start_secs should be mapped to
320 	 * start_secs + rtc->range_max - rtc->range_min + 1, then the
321 	 * offset seconds formula should be:
322 	 * rtc->offset_secs = -(rtc->range_max - rtc->range_min + 1);
323 	 *
324 	 * Otherwise the offset seconds should be 0.
325 	 */
326 	if (rtc->start_secs > rtc->range_max ||
327 	    rtc->start_secs + range_secs - 1 < rtc->range_min)
328 		rtc->offset_secs = rtc->start_secs - rtc->range_min;
329 	else if (rtc->start_secs > rtc->range_min)
330 		rtc->offset_secs = range_secs;
331 	else if (rtc->start_secs < rtc->range_min)
332 		rtc->offset_secs = -range_secs;
333 	else
334 		rtc->offset_secs = 0;
335 }
336 
devm_rtc_unregister_device(void * data)337 static void devm_rtc_unregister_device(void *data)
338 {
339 	struct rtc_device *rtc = data;
340 
341 	mutex_lock(&rtc->ops_lock);
342 	/*
343 	 * Remove innards of this RTC, then disable it, before
344 	 * letting any rtc_class_open() users access it again
345 	 */
346 	rtc_proc_del_device(rtc);
347 	if (!test_bit(RTC_NO_CDEV, &rtc->flags))
348 		cdev_device_del(&rtc->char_dev, &rtc->dev);
349 	rtc->ops = NULL;
350 	mutex_unlock(&rtc->ops_lock);
351 }
352 
devm_rtc_release_device(void * res)353 static void devm_rtc_release_device(void *res)
354 {
355 	struct rtc_device *rtc = res;
356 
357 	put_device(&rtc->dev);
358 }
359 
devm_rtc_allocate_device(struct device * dev)360 struct rtc_device *devm_rtc_allocate_device(struct device *dev)
361 {
362 	struct rtc_device *rtc;
363 	int id, err;
364 
365 	id = rtc_device_get_id(dev);
366 	if (id < 0)
367 		return ERR_PTR(id);
368 
369 	rtc = rtc_allocate_device();
370 	if (!rtc) {
371 		ida_free(&rtc_ida, id);
372 		return ERR_PTR(-ENOMEM);
373 	}
374 
375 	rtc->id = id;
376 	rtc->dev.parent = dev;
377 	err = devm_add_action_or_reset(dev, devm_rtc_release_device, rtc);
378 	if (err)
379 		return ERR_PTR(err);
380 
381 	err = dev_set_name(&rtc->dev, "rtc%d", id);
382 	if (err)
383 		return ERR_PTR(err);
384 
385 	return rtc;
386 }
387 EXPORT_SYMBOL_GPL(devm_rtc_allocate_device);
388 
__devm_rtc_register_device(struct module * owner,struct rtc_device * rtc)389 int __devm_rtc_register_device(struct module *owner, struct rtc_device *rtc)
390 {
391 	struct rtc_wkalrm alrm;
392 	int err;
393 
394 	if (!rtc->ops) {
395 		dev_dbg(&rtc->dev, "no ops set\n");
396 		return -EINVAL;
397 	}
398 
399 	if (!rtc->ops->set_alarm)
400 		clear_bit(RTC_FEATURE_ALARM, rtc->features);
401 
402 	if (rtc->ops->set_offset)
403 		set_bit(RTC_FEATURE_CORRECTION, rtc->features);
404 
405 	rtc->owner = owner;
406 	rtc_device_get_offset(rtc);
407 
408 	/* Check to see if there is an ALARM already set in hw */
409 	err = __rtc_read_alarm(rtc, &alrm);
410 	if (!err && !rtc_valid_tm(&alrm.time))
411 		rtc_initialize_alarm(rtc, &alrm);
412 
413 	rtc_dev_prepare(rtc);
414 
415 	err = cdev_device_add(&rtc->char_dev, &rtc->dev);
416 	if (err) {
417 		set_bit(RTC_NO_CDEV, &rtc->flags);
418 		dev_warn(rtc->dev.parent, "failed to add char device %d:%d\n",
419 			 MAJOR(rtc->dev.devt), rtc->id);
420 	} else {
421 		dev_dbg(rtc->dev.parent, "char device (%d:%d)\n",
422 			MAJOR(rtc->dev.devt), rtc->id);
423 	}
424 
425 	rtc_proc_add_device(rtc);
426 
427 	dev_info(rtc->dev.parent, "registered as %s\n",
428 		 dev_name(&rtc->dev));
429 
430 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
431 	if (!strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE))
432 		rtc_hctosys(rtc);
433 #endif
434 
435 	return devm_add_action_or_reset(rtc->dev.parent,
436 					devm_rtc_unregister_device, rtc);
437 }
438 EXPORT_SYMBOL_GPL(__devm_rtc_register_device);
439 
440 /**
441  * devm_rtc_device_register - resource managed rtc_device_register()
442  * @dev: the device to register
443  * @name: the name of the device (unused)
444  * @ops: the rtc operations structure
445  * @owner: the module owner
446  *
447  * @return a struct rtc on success, or an ERR_PTR on error
448  *
449  * Managed rtc_device_register(). The rtc_device returned from this function
450  * are automatically freed on driver detach.
451  * This function is deprecated, use devm_rtc_allocate_device and
452  * rtc_register_device instead
453  */
devm_rtc_device_register(struct device * dev,const char * name,const struct rtc_class_ops * ops,struct module * owner)454 struct rtc_device *devm_rtc_device_register(struct device *dev,
455 					    const char *name,
456 					    const struct rtc_class_ops *ops,
457 					    struct module *owner)
458 {
459 	struct rtc_device *rtc;
460 	int err;
461 
462 	rtc = devm_rtc_allocate_device(dev);
463 	if (IS_ERR(rtc))
464 		return rtc;
465 
466 	rtc->ops = ops;
467 
468 	err = __devm_rtc_register_device(owner, rtc);
469 	if (err)
470 		return ERR_PTR(err);
471 
472 	return rtc;
473 }
474 EXPORT_SYMBOL_GPL(devm_rtc_device_register);
475 
rtc_init(void)476 static int __init rtc_init(void)
477 {
478 	rtc_class = class_create("rtc");
479 	if (IS_ERR(rtc_class)) {
480 		pr_err("couldn't create class\n");
481 		return PTR_ERR(rtc_class);
482 	}
483 	rtc_class->pm = RTC_CLASS_DEV_PM_OPS;
484 	rtc_dev_init();
485 	return 0;
486 }
487 subsys_initcall(rtc_init);
488