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);
30 ida_simple_remove(&rtc_ida, rtc->id);
34 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
35 /* Result of the last RTC to system clock attempt. */
36 int rtc_hctosys_ret = -ENODEV;
38 /* IMPORTANT: the RTC only stores whole seconds. It is arbitrary
39 * whether it stores the most close value or the value with partial
40 * seconds truncated. However, it is important that we use it to store
41 * the truncated value. This is because otherwise it is necessary,
42 * in an rtc sync function, to read both xtime.tv_sec and
43 * xtime.tv_nsec. On some processors (i.e. ARM), an atomic read
44 * of >32bits is not possible. So storing the most close value would
45 * slow down the sync API. So here we have the truncated value and
46 * the best guess is to add 0.5s.
49 static void rtc_hctosys(struct rtc_device *rtc)
53 struct timespec64 tv64 = {
54 .tv_nsec = NSEC_PER_SEC >> 1,
57 err = rtc_read_time(rtc, &tm);
59 dev_err(rtc->dev.parent,
60 "hctosys: unable to read the hardware clock\n");
64 tv64.tv_sec = rtc_tm_to_time64(&tm);
66 #if BITS_PER_LONG == 32
67 if (tv64.tv_sec > INT_MAX) {
73 err = do_settimeofday64(&tv64);
75 dev_info(rtc->dev.parent, "setting system clock to %ptR UTC (%lld)\n",
76 &tm, (long long)tv64.tv_sec);
79 rtc_hctosys_ret = err;
83 #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
85 * On suspend(), measure the delta between one RTC and the
86 * system's wall clock; restore it on resume().
89 static struct timespec64 old_rtc, old_system, old_delta;
91 static int rtc_suspend(struct device *dev)
93 struct rtc_device *rtc = to_rtc_device(dev);
95 struct timespec64 delta, delta_delta;
98 if (timekeeping_rtc_skipsuspend())
101 if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
104 /* snapshot the current RTC and system time at suspend*/
105 err = rtc_read_time(rtc, &tm);
107 pr_debug("%s: fail to read rtc time\n", dev_name(&rtc->dev));
111 ktime_get_real_ts64(&old_system);
112 old_rtc.tv_sec = rtc_tm_to_time64(&tm);
115 * To avoid drift caused by repeated suspend/resumes,
116 * which each can add ~1 second drift error,
117 * try to compensate so the difference in system time
118 * and rtc time stays close to constant.
120 delta = timespec64_sub(old_system, old_rtc);
121 delta_delta = timespec64_sub(delta, old_delta);
122 if (delta_delta.tv_sec < -2 || delta_delta.tv_sec >= 2) {
124 * if delta_delta is too large, assume time correction
125 * has occurred and set old_delta to the current delta.
129 /* Otherwise try to adjust old_system to compensate */
130 old_system = timespec64_sub(old_system, delta_delta);
136 static int rtc_resume(struct device *dev)
138 struct rtc_device *rtc = to_rtc_device(dev);
140 struct timespec64 new_system, new_rtc;
141 struct timespec64 sleep_time;
144 if (timekeeping_rtc_skipresume())
147 rtc_hctosys_ret = -ENODEV;
148 if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
151 /* snapshot the current rtc and system time at resume */
152 ktime_get_real_ts64(&new_system);
153 err = rtc_read_time(rtc, &tm);
155 pr_debug("%s: fail to read rtc time\n", dev_name(&rtc->dev));
159 new_rtc.tv_sec = rtc_tm_to_time64(&tm);
162 if (new_rtc.tv_sec < old_rtc.tv_sec) {
163 pr_debug("%s: time travel!\n", dev_name(&rtc->dev));
167 /* calculate the RTC time delta (sleep time)*/
168 sleep_time = timespec64_sub(new_rtc, old_rtc);
171 * Since these RTC suspend/resume handlers are not called
172 * at the very end of suspend or the start of resume,
173 * some run-time may pass on either sides of the sleep time
174 * so subtract kernel run-time between rtc_suspend to rtc_resume
175 * to keep things accurate.
177 sleep_time = timespec64_sub(sleep_time,
178 timespec64_sub(new_system, old_system));
180 if (sleep_time.tv_sec >= 0)
181 timekeeping_inject_sleeptime64(&sleep_time);
186 static SIMPLE_DEV_PM_OPS(rtc_class_dev_pm_ops, rtc_suspend, rtc_resume);
187 #define RTC_CLASS_DEV_PM_OPS (&rtc_class_dev_pm_ops)
189 #define RTC_CLASS_DEV_PM_OPS NULL
192 /* Ensure the caller will set the id before releasing the device */
193 static struct rtc_device *rtc_allocate_device(void)
195 struct rtc_device *rtc;
197 rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
201 device_initialize(&rtc->dev);
204 * Drivers can revise this default after allocating the device.
205 * The default is what most RTCs do: Increment seconds exactly one
206 * second after the write happened. This adds a default transport
207 * time of 5ms which is at least halfways close to reality.
209 rtc->set_offset_nsec = NSEC_PER_SEC + 5 * NSEC_PER_MSEC;
212 rtc->max_user_freq = 64;
213 rtc->dev.class = rtc_class;
214 rtc->dev.groups = rtc_get_dev_attribute_groups();
215 rtc->dev.release = rtc_device_release;
217 mutex_init(&rtc->ops_lock);
218 spin_lock_init(&rtc->irq_lock);
219 init_waitqueue_head(&rtc->irq_queue);
221 /* Init timerqueue */
222 timerqueue_init_head(&rtc->timerqueue);
223 INIT_WORK(&rtc->irqwork, rtc_timer_do_work);
225 rtc_timer_init(&rtc->aie_timer, rtc_aie_update_irq, rtc);
227 rtc_timer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, rtc);
229 hrtimer_init(&rtc->pie_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
230 rtc->pie_timer.function = rtc_pie_update_irq;
231 rtc->pie_enabled = 0;
236 static int rtc_device_get_id(struct device *dev)
238 int of_id = -1, id = -1;
241 of_id = of_alias_get_id(dev->of_node, "rtc");
242 else if (dev->parent && dev->parent->of_node)
243 of_id = of_alias_get_id(dev->parent->of_node, "rtc");
246 id = ida_simple_get(&rtc_ida, of_id, of_id + 1, GFP_KERNEL);
248 dev_warn(dev, "/aliases ID %d not available\n", of_id);
252 id = ida_simple_get(&rtc_ida, 0, 0, GFP_KERNEL);
257 static void rtc_device_get_offset(struct rtc_device *rtc)
264 * If RTC driver did not implement the range of RTC hardware device,
265 * then we can not expand the RTC range by adding or subtracting one
268 if (rtc->range_min == rtc->range_max)
271 ret = device_property_read_u32(rtc->dev.parent, "start-year",
274 rtc->start_secs = mktime64(start_year, 1, 1, 0, 0, 0);
275 rtc->set_start_time = true;
279 * If user did not implement the start time for RTC driver, then no
280 * need to expand the RTC range.
282 if (!rtc->set_start_time)
285 range_secs = rtc->range_max - rtc->range_min + 1;
288 * If the start_secs is larger than the maximum seconds (rtc->range_max)
289 * supported by RTC hardware or the maximum seconds of new expanded
290 * range (start_secs + rtc->range_max - rtc->range_min) is less than
291 * rtc->range_min, which means the minimum seconds (rtc->range_min) of
292 * RTC hardware will be mapped to start_secs by adding one offset, so
293 * the offset seconds calculation formula should be:
294 * rtc->offset_secs = rtc->start_secs - rtc->range_min;
296 * If the start_secs is larger than the minimum seconds (rtc->range_min)
297 * supported by RTC hardware, then there is one region is overlapped
298 * between the original RTC hardware range and the new expanded range,
299 * and this overlapped region do not need to be mapped into the new
300 * expanded range due to it is valid for RTC device. So the minimum
301 * seconds of RTC hardware (rtc->range_min) should be mapped to
302 * rtc->range_max + 1, then the offset seconds formula should be:
303 * rtc->offset_secs = rtc->range_max - rtc->range_min + 1;
305 * If the start_secs is less than the minimum seconds (rtc->range_min),
306 * which is similar to case 2. So the start_secs should be mapped to
307 * start_secs + rtc->range_max - rtc->range_min + 1, then the
308 * offset seconds formula should be:
309 * rtc->offset_secs = -(rtc->range_max - rtc->range_min + 1);
311 * Otherwise the offset seconds should be 0.
313 if (rtc->start_secs > rtc->range_max ||
314 rtc->start_secs + range_secs - 1 < rtc->range_min)
315 rtc->offset_secs = rtc->start_secs - rtc->range_min;
316 else if (rtc->start_secs > rtc->range_min)
317 rtc->offset_secs = range_secs;
318 else if (rtc->start_secs < rtc->range_min)
319 rtc->offset_secs = -range_secs;
321 rtc->offset_secs = 0;
325 * rtc_device_unregister - removes the previously registered RTC class device
327 * @rtc: the RTC class device to destroy
329 static void rtc_device_unregister(struct rtc_device *rtc)
331 mutex_lock(&rtc->ops_lock);
333 * Remove innards of this RTC, then disable it, before
334 * letting any rtc_class_open() users access it again
336 rtc_proc_del_device(rtc);
337 cdev_device_del(&rtc->char_dev, &rtc->dev);
339 mutex_unlock(&rtc->ops_lock);
340 put_device(&rtc->dev);
343 static void devm_rtc_release_device(struct device *dev, void *res)
345 struct rtc_device *rtc = *(struct rtc_device **)res;
347 rtc_nvmem_unregister(rtc);
350 rtc_device_unregister(rtc);
352 put_device(&rtc->dev);
355 struct rtc_device *devm_rtc_allocate_device(struct device *dev)
357 struct rtc_device **ptr, *rtc;
360 id = rtc_device_get_id(dev);
364 ptr = devres_alloc(devm_rtc_release_device, sizeof(*ptr), GFP_KERNEL);
370 rtc = rtc_allocate_device();
377 devres_add(dev, ptr);
380 rtc->dev.parent = dev;
381 dev_set_name(&rtc->dev, "rtc%d", id);
388 ida_simple_remove(&rtc_ida, id);
391 EXPORT_SYMBOL_GPL(devm_rtc_allocate_device);
393 int __rtc_register_device(struct module *owner, struct rtc_device *rtc)
395 struct rtc_wkalrm alrm;
399 dev_dbg(&rtc->dev, "no ops set\n");
404 rtc_device_get_offset(rtc);
406 /* Check to see if there is an ALARM already set in hw */
407 err = __rtc_read_alarm(rtc, &alrm);
408 if (!err && !rtc_valid_tm(&alrm.time))
409 rtc_initialize_alarm(rtc, &alrm);
411 rtc_dev_prepare(rtc);
413 err = cdev_device_add(&rtc->char_dev, &rtc->dev);
415 dev_warn(rtc->dev.parent, "failed to add char device %d:%d\n",
416 MAJOR(rtc->dev.devt), rtc->id);
418 dev_dbg(rtc->dev.parent, "char device (%d:%d)\n",
419 MAJOR(rtc->dev.devt), rtc->id);
421 rtc_proc_add_device(rtc);
423 rtc->registered = true;
424 dev_info(rtc->dev.parent, "registered as %s\n",
425 dev_name(&rtc->dev));
427 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
428 if (!strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE))
434 EXPORT_SYMBOL_GPL(__rtc_register_device);
437 * devm_rtc_device_register - resource managed rtc_device_register()
438 * @dev: the device to register
439 * @name: the name of the device (unused)
440 * @ops: the rtc operations structure
441 * @owner: the module owner
443 * @return a struct rtc on success, or an ERR_PTR on error
445 * Managed rtc_device_register(). The rtc_device returned from this function
446 * are automatically freed on driver detach.
447 * This function is deprecated, use devm_rtc_allocate_device and
448 * rtc_register_device instead
450 struct rtc_device *devm_rtc_device_register(struct device *dev,
452 const struct rtc_class_ops *ops,
453 struct module *owner)
455 struct rtc_device *rtc;
458 rtc = devm_rtc_allocate_device(dev);
464 err = __rtc_register_device(owner, rtc);
470 EXPORT_SYMBOL_GPL(devm_rtc_device_register);
472 static int __init rtc_init(void)
474 rtc_class = class_create(THIS_MODULE, "rtc");
475 if (IS_ERR(rtc_class)) {
476 pr_err("couldn't create class\n");
477 return PTR_ERR(rtc_class);
479 rtc_class->pm = RTC_CLASS_DEV_PM_OPS;
483 subsys_initcall(rtc_init);