1 // SPDX-License-Identifier: GPL-2.0
3 * RTC subsystem, base class
5 * Copyright (C) 2005 Tower Technologies
6 * Author: Alessandro Zummo <a.zummo@towertech.it>
8 * class skeleton from drivers/hwmon/hwmon.c
11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13 #include <linux/module.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>
23 static DEFINE_IDA(rtc_ida);
24 struct class *rtc_class;
26 static void rtc_device_release(struct device *dev)
28 struct rtc_device *rtc = to_rtc_device(dev);
29 struct timerqueue_head *head = &rtc->timerqueue;
30 struct timerqueue_node *node;
32 mutex_lock(&rtc->ops_lock);
33 while ((node = timerqueue_getnext(head)))
34 timerqueue_del(head, node);
35 mutex_unlock(&rtc->ops_lock);
37 cancel_work_sync(&rtc->irqwork);
39 ida_simple_remove(&rtc_ida, rtc->id);
43 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
44 /* Result of the last RTC to system clock attempt. */
45 int rtc_hctosys_ret = -ENODEV;
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.
58 static void rtc_hctosys(struct rtc_device *rtc)
62 struct timespec64 tv64 = {
63 .tv_nsec = NSEC_PER_SEC >> 1,
66 err = rtc_read_time(rtc, &tm);
68 dev_err(rtc->dev.parent,
69 "hctosys: unable to read the hardware clock\n");
73 tv64.tv_sec = rtc_tm_to_time64(&tm);
75 #if BITS_PER_LONG == 32
76 if (tv64.tv_sec > INT_MAX) {
82 err = do_settimeofday64(&tv64);
84 dev_info(rtc->dev.parent, "setting system clock to %ptR UTC (%lld)\n",
85 &tm, (long long)tv64.tv_sec);
88 rtc_hctosys_ret = err;
92 #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
94 * On suspend(), measure the delta between one RTC and the
95 * system's wall clock; restore it on resume().
98 static struct timespec64 old_rtc, old_system, old_delta;
100 static int rtc_suspend(struct device *dev)
102 struct rtc_device *rtc = to_rtc_device(dev);
104 struct timespec64 delta, delta_delta;
107 if (timekeeping_rtc_skipsuspend())
110 if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
113 /* snapshot the current RTC and system time at suspend*/
114 err = rtc_read_time(rtc, &tm);
116 pr_debug("%s: fail to read rtc time\n", dev_name(&rtc->dev));
120 ktime_get_real_ts64(&old_system);
121 old_rtc.tv_sec = rtc_tm_to_time64(&tm);
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.
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) {
133 * if delta_delta is too large, assume time correction
134 * has occurred and set old_delta to the current delta.
138 /* Otherwise try to adjust old_system to compensate */
139 old_system = timespec64_sub(old_system, delta_delta);
145 static int rtc_resume(struct device *dev)
147 struct rtc_device *rtc = to_rtc_device(dev);
149 struct timespec64 new_system, new_rtc;
150 struct timespec64 sleep_time;
153 if (timekeeping_rtc_skipresume())
156 rtc_hctosys_ret = -ENODEV;
157 if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
160 /* snapshot the current rtc and system time at resume */
161 ktime_get_real_ts64(&new_system);
162 err = rtc_read_time(rtc, &tm);
164 pr_debug("%s: fail to read rtc time\n", dev_name(&rtc->dev));
168 new_rtc.tv_sec = rtc_tm_to_time64(&tm);
171 if (new_rtc.tv_sec < old_rtc.tv_sec) {
172 pr_debug("%s: time travel!\n", dev_name(&rtc->dev));
176 /* calculate the RTC time delta (sleep time)*/
177 sleep_time = timespec64_sub(new_rtc, old_rtc);
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.
186 sleep_time = timespec64_sub(sleep_time,
187 timespec64_sub(new_system, old_system));
189 if (sleep_time.tv_sec >= 0)
190 timekeeping_inject_sleeptime64(&sleep_time);
195 static 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)
198 #define RTC_CLASS_DEV_PM_OPS NULL
201 /* Ensure the caller will set the id before releasing the device */
202 static struct rtc_device *rtc_allocate_device(void)
204 struct rtc_device *rtc;
206 rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
210 device_initialize(&rtc->dev);
212 /* Drivers can revise this default after allocating the device. */
213 rtc->set_offset_nsec = NSEC_PER_SEC / 2;
216 rtc->max_user_freq = 64;
217 rtc->dev.class = rtc_class;
218 rtc->dev.groups = rtc_get_dev_attribute_groups();
219 rtc->dev.release = rtc_device_release;
221 mutex_init(&rtc->ops_lock);
222 spin_lock_init(&rtc->irq_lock);
223 init_waitqueue_head(&rtc->irq_queue);
225 /* Init timerqueue */
226 timerqueue_init_head(&rtc->timerqueue);
227 INIT_WORK(&rtc->irqwork, rtc_timer_do_work);
229 rtc_timer_init(&rtc->aie_timer, rtc_aie_update_irq, rtc);
231 rtc_timer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, rtc);
233 hrtimer_init(&rtc->pie_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
234 rtc->pie_timer.function = rtc_pie_update_irq;
235 rtc->pie_enabled = 0;
240 static int rtc_device_get_id(struct device *dev)
242 int of_id = -1, id = -1;
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");
250 id = ida_simple_get(&rtc_ida, of_id, of_id + 1, GFP_KERNEL);
252 dev_warn(dev, "/aliases ID %d not available\n", of_id);
256 id = ida_simple_get(&rtc_ida, 0, 0, GFP_KERNEL);
261 static void rtc_device_get_offset(struct rtc_device *rtc)
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
272 if (rtc->range_min == rtc->range_max)
275 ret = device_property_read_u32(rtc->dev.parent, "start-year",
278 rtc->start_secs = mktime64(start_year, 1, 1, 0, 0, 0);
279 rtc->set_start_time = true;
283 * If user did not implement the start time for RTC driver, then no
284 * need to expand the RTC range.
286 if (!rtc->set_start_time)
289 range_secs = rtc->range_max - rtc->range_min + 1;
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;
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;
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);
315 * Otherwise the offset seconds should be 0.
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;
325 rtc->offset_secs = 0;
329 * rtc_device_unregister - removes the previously registered RTC class device
331 * @rtc: the RTC class device to destroy
333 static void rtc_device_unregister(struct rtc_device *rtc)
335 mutex_lock(&rtc->ops_lock);
337 * Remove innards of this RTC, then disable it, before
338 * letting any rtc_class_open() users access it again
340 rtc_proc_del_device(rtc);
341 cdev_device_del(&rtc->char_dev, &rtc->dev);
343 mutex_unlock(&rtc->ops_lock);
344 put_device(&rtc->dev);
347 static void devm_rtc_release_device(struct device *dev, void *res)
349 struct rtc_device *rtc = *(struct rtc_device **)res;
351 rtc_nvmem_unregister(rtc);
354 rtc_device_unregister(rtc);
356 put_device(&rtc->dev);
359 struct rtc_device *devm_rtc_allocate_device(struct device *dev)
361 struct rtc_device **ptr, *rtc;
364 id = rtc_device_get_id(dev);
368 ptr = devres_alloc(devm_rtc_release_device, sizeof(*ptr), GFP_KERNEL);
374 rtc = rtc_allocate_device();
381 devres_add(dev, ptr);
384 rtc->dev.parent = dev;
385 dev_set_name(&rtc->dev, "rtc%d", id);
392 ida_simple_remove(&rtc_ida, id);
395 EXPORT_SYMBOL_GPL(devm_rtc_allocate_device);
397 int __rtc_register_device(struct module *owner, struct rtc_device *rtc)
399 struct rtc_wkalrm alrm;
403 dev_dbg(&rtc->dev, "no ops set\n");
408 rtc_device_get_offset(rtc);
410 /* Check to see if there is an ALARM already set in hw */
411 err = __rtc_read_alarm(rtc, &alrm);
412 if (!err && !rtc_valid_tm(&alrm.time))
413 rtc_initialize_alarm(rtc, &alrm);
415 rtc_dev_prepare(rtc);
417 err = cdev_device_add(&rtc->char_dev, &rtc->dev);
419 dev_warn(rtc->dev.parent, "failed to add char device %d:%d\n",
420 MAJOR(rtc->dev.devt), rtc->id);
422 dev_dbg(rtc->dev.parent, "char device (%d:%d)\n",
423 MAJOR(rtc->dev.devt), rtc->id);
425 rtc_proc_add_device(rtc);
427 rtc->registered = true;
428 dev_info(rtc->dev.parent, "registered as %s\n",
429 dev_name(&rtc->dev));
431 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
432 if (!strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE))
438 EXPORT_SYMBOL_GPL(__rtc_register_device);
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
447 * @return a struct rtc on success, or an ERR_PTR on error
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
454 struct rtc_device *devm_rtc_device_register(struct device *dev,
456 const struct rtc_class_ops *ops,
457 struct module *owner)
459 struct rtc_device *rtc;
462 rtc = devm_rtc_allocate_device(dev);
468 err = __rtc_register_device(owner, rtc);
474 EXPORT_SYMBOL_GPL(devm_rtc_device_register);
476 static int __init rtc_init(void)
478 rtc_class = class_create(THIS_MODULE, "rtc");
479 if (IS_ERR(rtc_class)) {
480 pr_err("couldn't create class\n");
481 return PTR_ERR(rtc_class);
483 rtc_class->pm = RTC_CLASS_DEV_PM_OPS;
487 subsys_initcall(rtc_init);