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);
40 mutex_destroy(&rtc->ops_lock);
44 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
45 /* Result of the last RTC to system clock attempt. */
46 int rtc_hctosys_ret = -ENODEV;
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.
59 static void rtc_hctosys(struct rtc_device *rtc)
63 struct timespec64 tv64 = {
64 .tv_nsec = NSEC_PER_SEC >> 1,
67 err = rtc_read_time(rtc, &tm);
69 dev_err(rtc->dev.parent,
70 "hctosys: unable to read the hardware clock\n");
74 tv64.tv_sec = rtc_tm_to_time64(&tm);
76 #if BITS_PER_LONG == 32
77 if (tv64.tv_sec > INT_MAX) {
83 err = do_settimeofday64(&tv64);
85 dev_info(rtc->dev.parent, "setting system clock to %ptR UTC (%lld)\n",
86 &tm, (long long)tv64.tv_sec);
89 rtc_hctosys_ret = err;
93 #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
95 * On suspend(), measure the delta between one RTC and the
96 * system's wall clock; restore it on resume().
99 static struct timespec64 old_rtc, old_system, old_delta;
101 static int rtc_suspend(struct device *dev)
103 struct rtc_device *rtc = to_rtc_device(dev);
105 struct timespec64 delta, delta_delta;
108 if (timekeeping_rtc_skipsuspend())
111 if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
114 /* snapshot the current RTC and system time at suspend*/
115 err = rtc_read_time(rtc, &tm);
117 pr_debug("%s: fail to read rtc time\n", dev_name(&rtc->dev));
121 ktime_get_real_ts64(&old_system);
122 old_rtc.tv_sec = rtc_tm_to_time64(&tm);
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.
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) {
134 * if delta_delta is too large, assume time correction
135 * has occurred and set old_delta to the current delta.
139 /* Otherwise try to adjust old_system to compensate */
140 old_system = timespec64_sub(old_system, delta_delta);
146 static int rtc_resume(struct device *dev)
148 struct rtc_device *rtc = to_rtc_device(dev);
150 struct timespec64 new_system, new_rtc;
151 struct timespec64 sleep_time;
154 if (timekeeping_rtc_skipresume())
157 rtc_hctosys_ret = -ENODEV;
158 if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
161 /* snapshot the current rtc and system time at resume */
162 ktime_get_real_ts64(&new_system);
163 err = rtc_read_time(rtc, &tm);
165 pr_debug("%s: fail to read rtc time\n", dev_name(&rtc->dev));
169 new_rtc.tv_sec = rtc_tm_to_time64(&tm);
172 if (new_rtc.tv_sec < old_rtc.tv_sec) {
173 pr_debug("%s: time travel!\n", dev_name(&rtc->dev));
177 /* calculate the RTC time delta (sleep time)*/
178 sleep_time = timespec64_sub(new_rtc, old_rtc);
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.
187 sleep_time = timespec64_sub(sleep_time,
188 timespec64_sub(new_system, old_system));
190 if (sleep_time.tv_sec >= 0)
191 timekeeping_inject_sleeptime64(&sleep_time);
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)
199 #define RTC_CLASS_DEV_PM_OPS NULL
202 /* Ensure the caller will set the id before releasing the device */
203 static struct rtc_device *rtc_allocate_device(void)
205 struct rtc_device *rtc;
207 rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
211 device_initialize(&rtc->dev);
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.
219 rtc->set_offset_nsec = NSEC_PER_SEC + 5 * NSEC_PER_MSEC;
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;
227 mutex_init(&rtc->ops_lock);
228 spin_lock_init(&rtc->irq_lock);
229 init_waitqueue_head(&rtc->irq_queue);
231 /* Init timerqueue */
232 timerqueue_init_head(&rtc->timerqueue);
233 INIT_WORK(&rtc->irqwork, rtc_timer_do_work);
235 rtc_timer_init(&rtc->aie_timer, rtc_aie_update_irq, rtc);
237 rtc_timer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, rtc);
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;
243 set_bit(RTC_FEATURE_ALARM, rtc->features);
248 static int rtc_device_get_id(struct device *dev)
250 int of_id = -1, id = -1;
253 of_id = of_alias_get_id(dev->of_node, "rtc");
254 else if (dev->parent && dev->parent->of_node)
255 of_id = of_alias_get_id(dev->parent->of_node, "rtc");
258 id = ida_simple_get(&rtc_ida, of_id, of_id + 1, GFP_KERNEL);
260 dev_warn(dev, "/aliases ID %d not available\n", of_id);
264 id = ida_simple_get(&rtc_ida, 0, 0, GFP_KERNEL);
269 static void rtc_device_get_offset(struct rtc_device *rtc)
276 * If RTC driver did not implement the range of RTC hardware device,
277 * then we can not expand the RTC range by adding or subtracting one
280 if (rtc->range_min == rtc->range_max)
283 ret = device_property_read_u32(rtc->dev.parent, "start-year",
286 rtc->start_secs = mktime64(start_year, 1, 1, 0, 0, 0);
287 rtc->set_start_time = true;
291 * If user did not implement the start time for RTC driver, then no
292 * need to expand the RTC range.
294 if (!rtc->set_start_time)
297 range_secs = rtc->range_max - rtc->range_min + 1;
300 * If the start_secs is larger than the maximum seconds (rtc->range_max)
301 * supported by RTC hardware or the maximum seconds of new expanded
302 * range (start_secs + rtc->range_max - rtc->range_min) is less than
303 * rtc->range_min, which means the minimum seconds (rtc->range_min) of
304 * RTC hardware will be mapped to start_secs by adding one offset, so
305 * the offset seconds calculation formula should be:
306 * rtc->offset_secs = rtc->start_secs - rtc->range_min;
308 * If the start_secs is larger than the minimum seconds (rtc->range_min)
309 * supported by RTC hardware, then there is one region is overlapped
310 * between the original RTC hardware range and the new expanded range,
311 * and this overlapped region do not need to be mapped into the new
312 * expanded range due to it is valid for RTC device. So the minimum
313 * seconds of RTC hardware (rtc->range_min) should be mapped to
314 * rtc->range_max + 1, then the offset seconds formula should be:
315 * rtc->offset_secs = rtc->range_max - rtc->range_min + 1;
317 * If the start_secs is less than the minimum seconds (rtc->range_min),
318 * which is similar to case 2. So the start_secs should be mapped to
319 * start_secs + rtc->range_max - rtc->range_min + 1, then the
320 * offset seconds formula should be:
321 * rtc->offset_secs = -(rtc->range_max - rtc->range_min + 1);
323 * Otherwise the offset seconds should be 0.
325 if (rtc->start_secs > rtc->range_max ||
326 rtc->start_secs + range_secs - 1 < rtc->range_min)
327 rtc->offset_secs = rtc->start_secs - rtc->range_min;
328 else if (rtc->start_secs > rtc->range_min)
329 rtc->offset_secs = range_secs;
330 else if (rtc->start_secs < rtc->range_min)
331 rtc->offset_secs = -range_secs;
333 rtc->offset_secs = 0;
336 static void devm_rtc_unregister_device(void *data)
338 struct rtc_device *rtc = data;
340 mutex_lock(&rtc->ops_lock);
342 * Remove innards of this RTC, then disable it, before
343 * letting any rtc_class_open() users access it again
345 rtc_proc_del_device(rtc);
346 cdev_device_del(&rtc->char_dev, &rtc->dev);
348 mutex_unlock(&rtc->ops_lock);
351 static void devm_rtc_release_device(void *res)
353 struct rtc_device *rtc = res;
355 put_device(&rtc->dev);
358 struct rtc_device *devm_rtc_allocate_device(struct device *dev)
360 struct rtc_device *rtc;
363 id = rtc_device_get_id(dev);
367 rtc = rtc_allocate_device();
369 ida_simple_remove(&rtc_ida, id);
370 return ERR_PTR(-ENOMEM);
374 rtc->dev.parent = dev;
375 dev_set_name(&rtc->dev, "rtc%d", id);
377 err = devm_add_action_or_reset(dev, devm_rtc_release_device, rtc);
383 EXPORT_SYMBOL_GPL(devm_rtc_allocate_device);
385 int __devm_rtc_register_device(struct module *owner, struct rtc_device *rtc)
387 struct rtc_wkalrm alrm;
391 dev_dbg(&rtc->dev, "no ops set\n");
395 if (!rtc->ops->set_alarm)
396 clear_bit(RTC_FEATURE_ALARM, rtc->features);
399 rtc_device_get_offset(rtc);
401 /* Check to see if there is an ALARM already set in hw */
402 err = __rtc_read_alarm(rtc, &alrm);
403 if (!err && !rtc_valid_tm(&alrm.time))
404 rtc_initialize_alarm(rtc, &alrm);
406 rtc_dev_prepare(rtc);
408 err = cdev_device_add(&rtc->char_dev, &rtc->dev);
410 dev_warn(rtc->dev.parent, "failed to add char device %d:%d\n",
411 MAJOR(rtc->dev.devt), rtc->id);
413 dev_dbg(rtc->dev.parent, "char device (%d:%d)\n",
414 MAJOR(rtc->dev.devt), rtc->id);
416 rtc_proc_add_device(rtc);
418 dev_info(rtc->dev.parent, "registered as %s\n",
419 dev_name(&rtc->dev));
421 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
422 if (!strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE))
426 return devm_add_action_or_reset(rtc->dev.parent,
427 devm_rtc_unregister_device, rtc);
429 EXPORT_SYMBOL_GPL(__devm_rtc_register_device);
432 * devm_rtc_device_register - resource managed rtc_device_register()
433 * @dev: the device to register
434 * @name: the name of the device (unused)
435 * @ops: the rtc operations structure
436 * @owner: the module owner
438 * @return a struct rtc on success, or an ERR_PTR on error
440 * Managed rtc_device_register(). The rtc_device returned from this function
441 * are automatically freed on driver detach.
442 * This function is deprecated, use devm_rtc_allocate_device and
443 * rtc_register_device instead
445 struct rtc_device *devm_rtc_device_register(struct device *dev,
447 const struct rtc_class_ops *ops,
448 struct module *owner)
450 struct rtc_device *rtc;
453 rtc = devm_rtc_allocate_device(dev);
459 err = __devm_rtc_register_device(owner, rtc);
465 EXPORT_SYMBOL_GPL(devm_rtc_device_register);
467 static int __init rtc_init(void)
469 rtc_class = class_create(THIS_MODULE, "rtc");
470 if (IS_ERR(rtc_class)) {
471 pr_err("couldn't create class\n");
472 return PTR_ERR(rtc_class);
474 rtc_class->pm = RTC_CLASS_DEV_PM_OPS;
478 subsys_initcall(rtc_init);