class.c

  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
 23static DEFINE_IDA(rtc_ida);
 24
 25static void rtc_device_release(struct device *dev)
 26{
 27	struct rtc_device *rtc = to_rtc_device(dev);
 28	struct timerqueue_head *head = &rtc->timerqueue;
 29	struct timerqueue_node *node;
 30
 31	mutex_lock(&rtc->ops_lock);
 32	while ((node = timerqueue_getnext(head)))
 33		timerqueue_del(head, node);
 34	mutex_unlock(&rtc->ops_lock);
 35
 36	cancel_work_sync(&rtc->irqwork);
 37
 38	ida_free(&rtc_ida, rtc->id);
 39	mutex_destroy(&rtc->ops_lock);
 40	kfree(rtc);
 41}
 42
 43#ifdef CONFIG_RTC_HCTOSYS_DEVICE
 44/* Result of the last RTC to system clock attempt. */
 45int rtc_hctosys_ret = -ENODEV;
 46
 47/* IMPORTANT: the RTC only stores whole seconds. It is arbitrary
 48 * whether it stores the most close value or the value with partial
 49 * seconds truncated. However, it is important that we use it to store
 50 * the truncated value. This is because otherwise it is necessary,
 51 * in an rtc sync function, to read both xtime.tv_sec and
 52 * xtime.tv_nsec. On some processors (i.e. ARM), an atomic read
 53 * of >32bits is not possible. So storing the most close value would
 54 * slow down the sync API. So here we have the truncated value and
 55 * the best guess is to add 0.5s.
 56 */
 57
 58static void rtc_hctosys(struct rtc_device *rtc)
 59{
 60	int err;
 61	struct rtc_time tm;
 62	struct timespec64 tv64 = {
 63		.tv_nsec = NSEC_PER_SEC >> 1,
 64	};
 65
 66	err = rtc_read_time(rtc, &tm);
 67	if (err) {
 68		dev_err(rtc->dev.parent,
 69			"hctosys: unable to read the hardware clock\n");
 70		goto err_read;
 71	}
 72
 73	tv64.tv_sec = rtc_tm_to_time64(&tm);
 74
 75#if BITS_PER_LONG == 32
 76	if (tv64.tv_sec > INT_MAX) {
 77		err = -ERANGE;
 78		goto err_read;
 79	}
 80#endif
 81
 82	err = do_settimeofday64(&tv64);
 83
 84	dev_info(rtc->dev.parent, "setting system clock to %ptR UTC (%lld)\n",
 85		 &tm, (long long)tv64.tv_sec);
 86
 87err_read:
 88	rtc_hctosys_ret = err;
 89}
 90#endif
 91
 92#if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
 93/*
 94 * On suspend(), measure the delta between one RTC and the
 95 * system's wall clock; restore it on resume().
 96 */
 97
 98static struct timespec64 old_rtc, old_system, old_delta;
 99
100static int rtc_suspend(struct device *dev)
101{
102	struct rtc_device	*rtc = to_rtc_device(dev);
103	struct rtc_time		tm;
104	struct timespec64	delta, delta_delta;
105	int err;
106
107	if (timekeeping_rtc_skipsuspend())
108		return 0;
109
110	if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
111		return 0;
112
113	/* snapshot the current RTC and system time at suspend*/
114	err = rtc_read_time(rtc, &tm);
115	if (err < 0) {
116		pr_debug("%s:  fail to read rtc time\n", dev_name(&rtc->dev));
117		return 0;
118	}
119
120	ktime_get_real_ts64(&old_system);
121	old_rtc.tv_sec = rtc_tm_to_time64(&tm);
122
123	/*
124	 * To avoid drift caused by repeated suspend/resumes,
125	 * which each can add ~1 second drift error,
126	 * try to compensate so the difference in system time
127	 * and rtc time stays close to constant.
128	 */
129	delta = timespec64_sub(old_system, old_rtc);
130	delta_delta = timespec64_sub(delta, old_delta);
131	if (delta_delta.tv_sec < -2 || delta_delta.tv_sec >= 2) {
132		/*
133		 * if delta_delta is too large, assume time correction
134		 * has occurred and set old_delta to the current delta.
135		 */
136		old_delta = delta;
137	} else {
138		/* Otherwise try to adjust old_system to compensate */
139		old_system = timespec64_sub(old_system, delta_delta);
140	}
141
142	return 0;
143}
144
145static int rtc_resume(struct device *dev)
146{
147	struct rtc_device	*rtc = to_rtc_device(dev);
148	struct rtc_time		tm;
149	struct timespec64	new_system, new_rtc;
150	struct timespec64	sleep_time;
151	int err;
152
153	if (timekeeping_rtc_skipresume())
154		return 0;
155
156	rtc_hctosys_ret = -ENODEV;
157	if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
158		return 0;
159
160	/* snapshot the current rtc and system time at resume */
161	ktime_get_real_ts64(&new_system);
162	err = rtc_read_time(rtc, &tm);
163	if (err < 0) {
164		pr_debug("%s:  fail to read rtc time\n", dev_name(&rtc->dev));
165		return 0;
166	}
167
168	new_rtc.tv_sec = rtc_tm_to_time64(&tm);
169	new_rtc.tv_nsec = 0;
170
171	if (new_rtc.tv_sec < old_rtc.tv_sec) {
172		pr_debug("%s:  time travel!\n", dev_name(&rtc->dev));
173		return 0;
174	}
175
176	/* calculate the RTC time delta (sleep time)*/
177	sleep_time = timespec64_sub(new_rtc, old_rtc);
178
179	/*
180	 * Since these RTC suspend/resume handlers are not called
181	 * at the very end of suspend or the start of resume,
182	 * some run-time may pass on either sides of the sleep time
183	 * so subtract kernel run-time between rtc_suspend to rtc_resume
184	 * to keep things accurate.
185	 */
186	sleep_time = timespec64_sub(sleep_time,
187				    timespec64_sub(new_system, old_system));
188
189	if (sleep_time.tv_sec >= 0)
190		timekeeping_inject_sleeptime64(&sleep_time);
191	rtc_hctosys_ret = 0;
192	return 0;
193}
194
195static SIMPLE_DEV_PM_OPS(rtc_class_dev_pm_ops, rtc_suspend, rtc_resume);
196#define RTC_CLASS_DEV_PM_OPS	(&rtc_class_dev_pm_ops)
197#else
198#define RTC_CLASS_DEV_PM_OPS	NULL
199#endif
200
201const struct class rtc_class = {
202	.name = "rtc",
203	.pm = RTC_CLASS_DEV_PM_OPS,
204};
205
206/* Ensure the caller will set the id before releasing the device */
207static struct rtc_device *rtc_allocate_device(void)
208{
209	struct rtc_device *rtc;
210
211	rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
212	if (!rtc)
213		return NULL;
214
215	device_initialize(&rtc->dev);
216
217	/*
218	 * Drivers can revise this default after allocating the device.
219	 * The default is what most RTCs do: Increment seconds exactly one
220	 * second after the write happened. This adds a default transport
221	 * time of 5ms which is at least halfways close to reality.
222	 */
223	rtc->set_offset_nsec = NSEC_PER_SEC + 5 * NSEC_PER_MSEC;
224
225	rtc->irq_freq = 1;
226	rtc->max_user_freq = 64;
227	rtc->dev.class = &rtc_class;
228	rtc->dev.groups = rtc_get_dev_attribute_groups();
229	rtc->dev.release = rtc_device_release;
230
231	mutex_init(&rtc->ops_lock);
232	spin_lock_init(&rtc->irq_lock);
233	init_waitqueue_head(&rtc->irq_queue);
234
235	/* Init timerqueue */
236	timerqueue_init_head(&rtc->timerqueue);
237	INIT_WORK(&rtc->irqwork, rtc_timer_do_work);
238	/* Init aie timer */
239	rtc_timer_init(&rtc->aie_timer, rtc_aie_update_irq, rtc);
240	/* Init uie timer */
241	rtc_timer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, rtc);
242	/* Init pie timer */
243	hrtimer_setup(&rtc->pie_timer, rtc_pie_update_irq, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
244	rtc->pie_enabled = 0;
245
246	set_bit(RTC_FEATURE_ALARM, rtc->features);
247	set_bit(RTC_FEATURE_UPDATE_INTERRUPT, rtc->features);
248
249	return rtc;
250}
251
252static int rtc_device_get_id(struct device *dev)
253{
254	int of_id = -1, id = -1;
255
256	if (dev->of_node)
257		of_id = of_alias_get_id(dev->of_node, "rtc");
258	else if (dev->parent && dev->parent->of_node)
259		of_id = of_alias_get_id(dev->parent->of_node, "rtc");
260
261	if (of_id >= 0) {
262		id = ida_alloc_range(&rtc_ida, of_id, of_id, GFP_KERNEL);
263		if (id < 0)
264			dev_warn(dev, "/aliases ID %d not available\n", of_id);
265	}
266
267	if (id < 0)
268		id = ida_alloc(&rtc_ida, GFP_KERNEL);
269
270	return id;
271}
272
273static void rtc_device_get_offset(struct rtc_device *rtc)
274{
275	time64_t range_secs;
276	u32 start_year;
277	int ret;
278
279	/*
280	 * If RTC driver did not implement the range of RTC hardware device,
281	 * then we can not expand the RTC range by adding or subtracting one
282	 * offset.
283	 */
284	if (rtc->range_min == rtc->range_max)
285		return;
286
287	ret = device_property_read_u32(rtc->dev.parent, "start-year",
288				       &start_year);
289	if (!ret) {
290		rtc->start_secs = mktime64(start_year, 1, 1, 0, 0, 0);
291		rtc->set_start_time = true;
292	}
293
294	/*
295	 * If user did not implement the start time for RTC driver, then no
296	 * need to expand the RTC range.
297	 */
298	if (!rtc->set_start_time)
299		return;
300
301	range_secs = rtc->range_max - rtc->range_min + 1;
302
303	/*
304	 * If the start_secs is larger than the maximum seconds (rtc->range_max)
305	 * supported by RTC hardware or the maximum seconds of new expanded
306	 * range (start_secs + rtc->range_max - rtc->range_min) is less than
307	 * rtc->range_min, which means the minimum seconds (rtc->range_min) of
308	 * RTC hardware will be mapped to start_secs by adding one offset, so
309	 * the offset seconds calculation formula should be:
310	 * rtc->offset_secs = rtc->start_secs - rtc->range_min;
311	 *
312	 * If the start_secs is larger than the minimum seconds (rtc->range_min)
313	 * supported by RTC hardware, then there is one region is overlapped
314	 * between the original RTC hardware range and the new expanded range,
315	 * and this overlapped region do not need to be mapped into the new
316	 * expanded range due to it is valid for RTC device. So the minimum
317	 * seconds of RTC hardware (rtc->range_min) should be mapped to
318	 * rtc->range_max + 1, then the offset seconds formula should be:
319	 * rtc->offset_secs = rtc->range_max - rtc->range_min + 1;
320	 *
321	 * If the start_secs is less than the minimum seconds (rtc->range_min),
322	 * which is similar to case 2. So the start_secs should be mapped to
323	 * start_secs + rtc->range_max - rtc->range_min + 1, then the
324	 * offset seconds formula should be:
325	 * rtc->offset_secs = -(rtc->range_max - rtc->range_min + 1);
326	 *
327	 * Otherwise the offset seconds should be 0.
328	 */
329	if ((rtc->start_secs >= 0 && rtc->start_secs > rtc->range_max) ||
330	    rtc->start_secs + range_secs - 1 < rtc->range_min)
331		rtc->offset_secs = rtc->start_secs - rtc->range_min;
332	else if (rtc->start_secs > rtc->range_min)
333		rtc->offset_secs = range_secs;
334	else if (rtc->start_secs < rtc->range_min)
335		rtc->offset_secs = -range_secs;
336	else
337		rtc->offset_secs = 0;
338}
339
340static void devm_rtc_unregister_device(void *data)
341{
342	struct rtc_device *rtc = data;
343
344	mutex_lock(&rtc->ops_lock);
345	/*
346	 * Remove innards of this RTC, then disable it, before
347	 * letting any rtc_class_open() users access it again
348	 */
349	rtc_proc_del_device(rtc);
350	if (!test_bit(RTC_NO_CDEV, &rtc->flags))
351		cdev_device_del(&rtc->char_dev, &rtc->dev);
352	rtc->ops = NULL;
353	mutex_unlock(&rtc->ops_lock);
354}
355
356static void devm_rtc_release_device(void *res)
357{
358	struct rtc_device *rtc = res;
359
360	put_device(&rtc->dev);
361}
362
363struct rtc_device *devm_rtc_allocate_device(struct device *dev)
364{
365	struct rtc_device *rtc;
366	int id, err;
367
368	id = rtc_device_get_id(dev);
369	if (id < 0)
370		return ERR_PTR(id);
371
372	rtc = rtc_allocate_device();
373	if (!rtc) {
374		ida_free(&rtc_ida, id);
375		return ERR_PTR(-ENOMEM);
376	}
377
378	rtc->id = id;
379	rtc->dev.parent = dev;
380	err = devm_add_action_or_reset(dev, devm_rtc_release_device, rtc);
381	if (err)
382		return ERR_PTR(err);
383
384	err = dev_set_name(&rtc->dev, "rtc%d", id);
385	if (err)
386		return ERR_PTR(err);
387
388	return rtc;
389}
390EXPORT_SYMBOL_GPL(devm_rtc_allocate_device);
391
392int __devm_rtc_register_device(struct module *owner, struct rtc_device *rtc)
393{
394	struct rtc_wkalrm alrm;
395	int err;
396
397	if (!rtc->ops) {
398		dev_dbg(&rtc->dev, "no ops set\n");
399		return -EINVAL;
400	}
401
402	if (!rtc->ops->set_alarm)
403		clear_bit(RTC_FEATURE_ALARM, rtc->features);
404
405	if (rtc->ops->set_offset)
406		set_bit(RTC_FEATURE_CORRECTION, rtc->features);
407
408	rtc->owner = owner;
409	rtc_device_get_offset(rtc);
410
411	/* Check to see if there is an ALARM already set in hw */
412	err = __rtc_read_alarm(rtc, &alrm);
413	if (!err && !rtc_valid_tm(&alrm.time))
414		rtc_initialize_alarm(rtc, &alrm);
415
416	rtc_dev_prepare(rtc);
417
418	err = cdev_device_add(&rtc->char_dev, &rtc->dev);
419	if (err) {
420		set_bit(RTC_NO_CDEV, &rtc->flags);
421		dev_warn(rtc->dev.parent, "failed to add char device %d:%d\n",
422			 MAJOR(rtc->dev.devt), rtc->id);
423	} else {
424		dev_dbg(rtc->dev.parent, "char device (%d:%d)\n",
425			MAJOR(rtc->dev.devt), rtc->id);
426	}
427
428	rtc_proc_add_device(rtc);
429
430	dev_info(rtc->dev.parent, "registered as %s\n",
431		 dev_name(&rtc->dev));
432
433#ifdef CONFIG_RTC_HCTOSYS_DEVICE
434	if (!strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE))
435		rtc_hctosys(rtc);
436#endif
437
438	return devm_add_action_or_reset(rtc->dev.parent,
439					devm_rtc_unregister_device, rtc);
440}
441EXPORT_SYMBOL_GPL(__devm_rtc_register_device);
442
443/**
444 * devm_rtc_device_register - resource managed rtc_device_register()
445 * @dev: the device to register
446 * @name: the name of the device (unused)
447 * @ops: the rtc operations structure
448 * @owner: the module owner
449 *
450 * @return a struct rtc on success, or an ERR_PTR on error
451 *
452 * Managed rtc_device_register(). The rtc_device returned from this function
453 * are automatically freed on driver detach.
454 * This function is deprecated, use devm_rtc_allocate_device and
455 * rtc_register_device instead
456 */
457struct rtc_device *devm_rtc_device_register(struct device *dev,
458					    const char *name,
459					    const struct rtc_class_ops *ops,
460					    struct module *owner)
461{
462	struct rtc_device *rtc;
463	int err;
464
465	rtc = devm_rtc_allocate_device(dev);
466	if (IS_ERR(rtc))
467		return rtc;
468
469	rtc->ops = ops;
470
471	err = __devm_rtc_register_device(owner, rtc);
472	if (err)
473		return ERR_PTR(err);
474
475	return rtc;
476}
477EXPORT_SYMBOL_GPL(devm_rtc_device_register);
478
479static int __init rtc_init(void)
480{
481	int err;
482
483	err = class_register(&rtc_class);
484	if (err)
485		return err;
486
487	rtc_dev_init();
488
489	return 0;
490}
491subsys_initcall(rtc_init);