xref: /openbmc/linux/drivers/rtc/class.c (revision e7f127b2)
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 
26 static void rtc_device_release(struct device *dev)
27 {
28 	struct rtc_device *rtc = to_rtc_device(dev);
29 
30 	ida_simple_remove(&rtc_ida, rtc->id);
31 	mutex_destroy(&rtc->ops_lock);
32 	kfree(rtc);
33 }
34 
35 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
36 /* Result of the last RTC to system clock attempt. */
37 int rtc_hctosys_ret = -ENODEV;
38 
39 /* IMPORTANT: the RTC only stores whole seconds. It is arbitrary
40  * whether it stores the most close value or the value with partial
41  * seconds truncated. However, it is important that we use it to store
42  * the truncated value. This is because otherwise it is necessary,
43  * in an rtc sync function, to read both xtime.tv_sec and
44  * xtime.tv_nsec. On some processors (i.e. ARM), an atomic read
45  * of >32bits is not possible. So storing the most close value would
46  * slow down the sync API. So here we have the truncated value and
47  * the best guess is to add 0.5s.
48  */
49 
50 static void rtc_hctosys(struct rtc_device *rtc)
51 {
52 	int err;
53 	struct rtc_time tm;
54 	struct timespec64 tv64 = {
55 		.tv_nsec = NSEC_PER_SEC >> 1,
56 	};
57 
58 	err = rtc_read_time(rtc, &tm);
59 	if (err) {
60 		dev_err(rtc->dev.parent,
61 			"hctosys: unable to read the hardware clock\n");
62 		goto err_read;
63 	}
64 
65 	tv64.tv_sec = rtc_tm_to_time64(&tm);
66 
67 #if BITS_PER_LONG == 32
68 	if (tv64.tv_sec > INT_MAX) {
69 		err = -ERANGE;
70 		goto err_read;
71 	}
72 #endif
73 
74 	err = do_settimeofday64(&tv64);
75 
76 	dev_info(rtc->dev.parent, "setting system clock to %ptR UTC (%lld)\n",
77 		 &tm, (long long)tv64.tv_sec);
78 
79 err_read:
80 	rtc_hctosys_ret = err;
81 }
82 #endif
83 
84 #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
85 /*
86  * On suspend(), measure the delta between one RTC and the
87  * system's wall clock; restore it on resume().
88  */
89 
90 static struct timespec64 old_rtc, old_system, old_delta;
91 
92 static int rtc_suspend(struct device *dev)
93 {
94 	struct rtc_device	*rtc = to_rtc_device(dev);
95 	struct rtc_time		tm;
96 	struct timespec64	delta, delta_delta;
97 	int err;
98 
99 	if (timekeeping_rtc_skipsuspend())
100 		return 0;
101 
102 	if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
103 		return 0;
104 
105 	/* snapshot the current RTC and system time at suspend*/
106 	err = rtc_read_time(rtc, &tm);
107 	if (err < 0) {
108 		pr_debug("%s:  fail to read rtc time\n", dev_name(&rtc->dev));
109 		return 0;
110 	}
111 
112 	ktime_get_real_ts64(&old_system);
113 	old_rtc.tv_sec = rtc_tm_to_time64(&tm);
114 
115 	/*
116 	 * To avoid drift caused by repeated suspend/resumes,
117 	 * which each can add ~1 second drift error,
118 	 * try to compensate so the difference in system time
119 	 * and rtc time stays close to constant.
120 	 */
121 	delta = timespec64_sub(old_system, old_rtc);
122 	delta_delta = timespec64_sub(delta, old_delta);
123 	if (delta_delta.tv_sec < -2 || delta_delta.tv_sec >= 2) {
124 		/*
125 		 * if delta_delta is too large, assume time correction
126 		 * has occurred and set old_delta to the current delta.
127 		 */
128 		old_delta = delta;
129 	} else {
130 		/* Otherwise try to adjust old_system to compensate */
131 		old_system = timespec64_sub(old_system, delta_delta);
132 	}
133 
134 	return 0;
135 }
136 
137 static int rtc_resume(struct device *dev)
138 {
139 	struct rtc_device	*rtc = to_rtc_device(dev);
140 	struct rtc_time		tm;
141 	struct timespec64	new_system, new_rtc;
142 	struct timespec64	sleep_time;
143 	int err;
144 
145 	if (timekeeping_rtc_skipresume())
146 		return 0;
147 
148 	rtc_hctosys_ret = -ENODEV;
149 	if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
150 		return 0;
151 
152 	/* snapshot the current rtc and system time at resume */
153 	ktime_get_real_ts64(&new_system);
154 	err = rtc_read_time(rtc, &tm);
155 	if (err < 0) {
156 		pr_debug("%s:  fail to read rtc time\n", dev_name(&rtc->dev));
157 		return 0;
158 	}
159 
160 	new_rtc.tv_sec = rtc_tm_to_time64(&tm);
161 	new_rtc.tv_nsec = 0;
162 
163 	if (new_rtc.tv_sec < old_rtc.tv_sec) {
164 		pr_debug("%s:  time travel!\n", dev_name(&rtc->dev));
165 		return 0;
166 	}
167 
168 	/* calculate the RTC time delta (sleep time)*/
169 	sleep_time = timespec64_sub(new_rtc, old_rtc);
170 
171 	/*
172 	 * Since these RTC suspend/resume handlers are not called
173 	 * at the very end of suspend or the start of resume,
174 	 * some run-time may pass on either sides of the sleep time
175 	 * so subtract kernel run-time between rtc_suspend to rtc_resume
176 	 * to keep things accurate.
177 	 */
178 	sleep_time = timespec64_sub(sleep_time,
179 				    timespec64_sub(new_system, old_system));
180 
181 	if (sleep_time.tv_sec >= 0)
182 		timekeeping_inject_sleeptime64(&sleep_time);
183 	rtc_hctosys_ret = 0;
184 	return 0;
185 }
186 
187 static SIMPLE_DEV_PM_OPS(rtc_class_dev_pm_ops, rtc_suspend, rtc_resume);
188 #define RTC_CLASS_DEV_PM_OPS	(&rtc_class_dev_pm_ops)
189 #else
190 #define RTC_CLASS_DEV_PM_OPS	NULL
191 #endif
192 
193 /* Ensure the caller will set the id before releasing the device */
194 static struct rtc_device *rtc_allocate_device(void)
195 {
196 	struct rtc_device *rtc;
197 
198 	rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
199 	if (!rtc)
200 		return NULL;
201 
202 	device_initialize(&rtc->dev);
203 
204 	/*
205 	 * Drivers can revise this default after allocating the device.
206 	 * The default is what most RTCs do: Increment seconds exactly one
207 	 * second after the write happened. This adds a default transport
208 	 * time of 5ms which is at least halfways close to reality.
209 	 */
210 	rtc->set_offset_nsec = NSEC_PER_SEC + 5 * NSEC_PER_MSEC;
211 
212 	rtc->irq_freq = 1;
213 	rtc->max_user_freq = 64;
214 	rtc->dev.class = rtc_class;
215 	rtc->dev.groups = rtc_get_dev_attribute_groups();
216 	rtc->dev.release = rtc_device_release;
217 
218 	mutex_init(&rtc->ops_lock);
219 	spin_lock_init(&rtc->irq_lock);
220 	init_waitqueue_head(&rtc->irq_queue);
221 
222 	/* Init timerqueue */
223 	timerqueue_init_head(&rtc->timerqueue);
224 	INIT_WORK(&rtc->irqwork, rtc_timer_do_work);
225 	/* Init aie timer */
226 	rtc_timer_init(&rtc->aie_timer, rtc_aie_update_irq, rtc);
227 	/* Init uie timer */
228 	rtc_timer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, rtc);
229 	/* Init pie timer */
230 	hrtimer_init(&rtc->pie_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
231 	rtc->pie_timer.function = rtc_pie_update_irq;
232 	rtc->pie_enabled = 0;
233 
234 	set_bit(RTC_FEATURE_ALARM, rtc->features);
235 	set_bit(RTC_FEATURE_UPDATE_INTERRUPT, rtc->features);
236 
237 	return rtc;
238 }
239 
240 static int rtc_device_get_id(struct device *dev)
241 {
242 	int of_id = -1, id = -1;
243 
244 	if (dev->of_node)
245 		of_id = of_alias_get_id(dev->of_node, "rtc");
246 	else if (dev->parent && dev->parent->of_node)
247 		of_id = of_alias_get_id(dev->parent->of_node, "rtc");
248 
249 	if (of_id >= 0) {
250 		id = ida_simple_get(&rtc_ida, of_id, of_id + 1, GFP_KERNEL);
251 		if (id < 0)
252 			dev_warn(dev, "/aliases ID %d not available\n", of_id);
253 	}
254 
255 	if (id < 0)
256 		id = ida_simple_get(&rtc_ida, 0, 0, GFP_KERNEL);
257 
258 	return id;
259 }
260 
261 static void rtc_device_get_offset(struct rtc_device *rtc)
262 {
263 	time64_t range_secs;
264 	u32 start_year;
265 	int ret;
266 
267 	/*
268 	 * If RTC driver did not implement the range of RTC hardware device,
269 	 * then we can not expand the RTC range by adding or subtracting one
270 	 * offset.
271 	 */
272 	if (rtc->range_min == rtc->range_max)
273 		return;
274 
275 	ret = device_property_read_u32(rtc->dev.parent, "start-year",
276 				       &start_year);
277 	if (!ret) {
278 		rtc->start_secs = mktime64(start_year, 1, 1, 0, 0, 0);
279 		rtc->set_start_time = true;
280 	}
281 
282 	/*
283 	 * If user did not implement the start time for RTC driver, then no
284 	 * need to expand the RTC range.
285 	 */
286 	if (!rtc->set_start_time)
287 		return;
288 
289 	range_secs = rtc->range_max - rtc->range_min + 1;
290 
291 	/*
292 	 * If the start_secs is larger than the maximum seconds (rtc->range_max)
293 	 * supported by RTC hardware or the maximum seconds of new expanded
294 	 * range (start_secs + rtc->range_max - rtc->range_min) is less than
295 	 * rtc->range_min, which means the minimum seconds (rtc->range_min) of
296 	 * RTC hardware will be mapped to start_secs by adding one offset, so
297 	 * the offset seconds calculation formula should be:
298 	 * rtc->offset_secs = rtc->start_secs - rtc->range_min;
299 	 *
300 	 * If the start_secs is larger than the minimum seconds (rtc->range_min)
301 	 * supported by RTC hardware, then there is one region is overlapped
302 	 * between the original RTC hardware range and the new expanded range,
303 	 * and this overlapped region do not need to be mapped into the new
304 	 * expanded range due to it is valid for RTC device. So the minimum
305 	 * seconds of RTC hardware (rtc->range_min) should be mapped to
306 	 * rtc->range_max + 1, then the offset seconds formula should be:
307 	 * rtc->offset_secs = rtc->range_max - rtc->range_min + 1;
308 	 *
309 	 * If the start_secs is less than the minimum seconds (rtc->range_min),
310 	 * which is similar to case 2. So the start_secs should be mapped to
311 	 * start_secs + rtc->range_max - rtc->range_min + 1, then the
312 	 * offset seconds formula should be:
313 	 * rtc->offset_secs = -(rtc->range_max - rtc->range_min + 1);
314 	 *
315 	 * Otherwise the offset seconds should be 0.
316 	 */
317 	if (rtc->start_secs > rtc->range_max ||
318 	    rtc->start_secs + range_secs - 1 < rtc->range_min)
319 		rtc->offset_secs = rtc->start_secs - rtc->range_min;
320 	else if (rtc->start_secs > rtc->range_min)
321 		rtc->offset_secs = range_secs;
322 	else if (rtc->start_secs < rtc->range_min)
323 		rtc->offset_secs = -range_secs;
324 	else
325 		rtc->offset_secs = 0;
326 }
327 
328 static void devm_rtc_unregister_device(void *data)
329 {
330 	struct rtc_device *rtc = data;
331 
332 	mutex_lock(&rtc->ops_lock);
333 	/*
334 	 * Remove innards of this RTC, then disable it, before
335 	 * letting any rtc_class_open() users access it again
336 	 */
337 	rtc_proc_del_device(rtc);
338 	if (!test_bit(RTC_NO_CDEV, &rtc->flags))
339 		cdev_device_del(&rtc->char_dev, &rtc->dev);
340 	rtc->ops = NULL;
341 	mutex_unlock(&rtc->ops_lock);
342 }
343 
344 static void devm_rtc_release_device(void *res)
345 {
346 	struct rtc_device *rtc = res;
347 
348 	put_device(&rtc->dev);
349 }
350 
351 struct rtc_device *devm_rtc_allocate_device(struct device *dev)
352 {
353 	struct rtc_device *rtc;
354 	int id, err;
355 
356 	id = rtc_device_get_id(dev);
357 	if (id < 0)
358 		return ERR_PTR(id);
359 
360 	rtc = rtc_allocate_device();
361 	if (!rtc) {
362 		ida_simple_remove(&rtc_ida, id);
363 		return ERR_PTR(-ENOMEM);
364 	}
365 
366 	rtc->id = id;
367 	rtc->dev.parent = dev;
368 	err = dev_set_name(&rtc->dev, "rtc%d", id);
369 	if (err)
370 		return ERR_PTR(err);
371 
372 	err = devm_add_action_or_reset(dev, devm_rtc_release_device, rtc);
373 	if (err)
374 		return ERR_PTR(err);
375 
376 	return rtc;
377 }
378 EXPORT_SYMBOL_GPL(devm_rtc_allocate_device);
379 
380 int __devm_rtc_register_device(struct module *owner, struct rtc_device *rtc)
381 {
382 	struct rtc_wkalrm alrm;
383 	int err;
384 
385 	if (!rtc->ops) {
386 		dev_dbg(&rtc->dev, "no ops set\n");
387 		return -EINVAL;
388 	}
389 
390 	if (!rtc->ops->set_alarm)
391 		clear_bit(RTC_FEATURE_ALARM, rtc->features);
392 
393 	if (rtc->uie_unsupported)
394 		clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, rtc->features);
395 
396 	if (rtc->ops->set_offset)
397 		set_bit(RTC_FEATURE_CORRECTION, rtc->features);
398 
399 	rtc->owner = owner;
400 	rtc_device_get_offset(rtc);
401 
402 	/* Check to see if there is an ALARM already set in hw */
403 	err = __rtc_read_alarm(rtc, &alrm);
404 	if (!err && !rtc_valid_tm(&alrm.time))
405 		rtc_initialize_alarm(rtc, &alrm);
406 
407 	rtc_dev_prepare(rtc);
408 
409 	err = cdev_device_add(&rtc->char_dev, &rtc->dev);
410 	if (err) {
411 		set_bit(RTC_NO_CDEV, &rtc->flags);
412 		dev_warn(rtc->dev.parent, "failed to add char device %d:%d\n",
413 			 MAJOR(rtc->dev.devt), rtc->id);
414 	} else {
415 		dev_dbg(rtc->dev.parent, "char device (%d:%d)\n",
416 			MAJOR(rtc->dev.devt), rtc->id);
417 	}
418 
419 	rtc_proc_add_device(rtc);
420 
421 	dev_info(rtc->dev.parent, "registered as %s\n",
422 		 dev_name(&rtc->dev));
423 
424 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
425 	if (!strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE))
426 		rtc_hctosys(rtc);
427 #endif
428 
429 	return devm_add_action_or_reset(rtc->dev.parent,
430 					devm_rtc_unregister_device, rtc);
431 }
432 EXPORT_SYMBOL_GPL(__devm_rtc_register_device);
433 
434 /**
435  * devm_rtc_device_register - resource managed rtc_device_register()
436  * @dev: the device to register
437  * @name: the name of the device (unused)
438  * @ops: the rtc operations structure
439  * @owner: the module owner
440  *
441  * @return a struct rtc on success, or an ERR_PTR on error
442  *
443  * Managed rtc_device_register(). The rtc_device returned from this function
444  * are automatically freed on driver detach.
445  * This function is deprecated, use devm_rtc_allocate_device and
446  * rtc_register_device instead
447  */
448 struct rtc_device *devm_rtc_device_register(struct device *dev,
449 					    const char *name,
450 					    const struct rtc_class_ops *ops,
451 					    struct module *owner)
452 {
453 	struct rtc_device *rtc;
454 	int err;
455 
456 	rtc = devm_rtc_allocate_device(dev);
457 	if (IS_ERR(rtc))
458 		return rtc;
459 
460 	rtc->ops = ops;
461 
462 	err = __devm_rtc_register_device(owner, rtc);
463 	if (err)
464 		return ERR_PTR(err);
465 
466 	return rtc;
467 }
468 EXPORT_SYMBOL_GPL(devm_rtc_device_register);
469 
470 static int __init rtc_init(void)
471 {
472 	rtc_class = class_create(THIS_MODULE, "rtc");
473 	if (IS_ERR(rtc_class)) {
474 		pr_err("couldn't create class\n");
475 		return PTR_ERR(rtc_class);
476 	}
477 	rtc_class->pm = RTC_CLASS_DEV_PM_OPS;
478 	rtc_dev_init();
479 	return 0;
480 }
481 subsys_initcall(rtc_init);
482