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1/*
2 * RTC subsystem, base class
3 *
4 * Copyright (C) 2005 Tower Technologies
5 * Author: Alessandro Zummo <a.zummo@towertech.it>
6 *
7 * class skeleton from drivers/hwmon/hwmon.c
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
12*/
13
14#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>
20
21#include "rtc-core.h"
22
23
24static DEFINE_IDR(rtc_idr);
25static DEFINE_MUTEX(idr_lock);
26struct class *rtc_class;
27
28static void rtc_device_release(struct device *dev)
29{
30 struct rtc_device *rtc = to_rtc_device(dev);
31 mutex_lock(&idr_lock);
32 idr_remove(&rtc_idr, rtc->id);
33 mutex_unlock(&idr_lock);
34 kfree(rtc);
35}
36
37#if defined(CONFIG_PM) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
38
39/*
40 * On suspend(), measure the delta between one RTC and the
41 * system's wall clock; restore it on resume().
42 */
43
44static struct timespec old_rtc, old_system, old_delta;
45
46
47static int rtc_suspend(struct device *dev, pm_message_t mesg)
48{
49 struct rtc_device *rtc = to_rtc_device(dev);
50 struct rtc_time tm;
51 struct timespec delta, delta_delta;
52 if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
53 return 0;
54
55 /* snapshot the current RTC and system time at suspend*/
56 rtc_read_time(rtc, &tm);
57 getnstimeofday(&old_system);
58 rtc_tm_to_time(&tm, &old_rtc.tv_sec);
59
60
61 /*
62 * To avoid drift caused by repeated suspend/resumes,
63 * which each can add ~1 second drift error,
64 * try to compensate so the difference in system time
65 * and rtc time stays close to constant.
66 */
67 delta = timespec_sub(old_system, old_rtc);
68 delta_delta = timespec_sub(delta, old_delta);
69 if (abs(delta_delta.tv_sec) >= 2) {
70 /*
71 * if delta_delta is too large, assume time correction
72 * has occured and set old_delta to the current delta.
73 */
74 old_delta = delta;
75 } else {
76 /* Otherwise try to adjust old_system to compensate */
77 old_system = timespec_sub(old_system, delta_delta);
78 }
79
80 return 0;
81}
82
83static int rtc_resume(struct device *dev)
84{
85 struct rtc_device *rtc = to_rtc_device(dev);
86 struct rtc_time tm;
87 struct timespec new_system, new_rtc;
88 struct timespec sleep_time;
89
90 if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
91 return 0;
92
93 /* snapshot the current rtc and system time at resume */
94 getnstimeofday(&new_system);
95 rtc_read_time(rtc, &tm);
96 if (rtc_valid_tm(&tm) != 0) {
97 pr_debug("%s: bogus resume time\n", dev_name(&rtc->dev));
98 return 0;
99 }
100 rtc_tm_to_time(&tm, &new_rtc.tv_sec);
101 new_rtc.tv_nsec = 0;
102
103 if (new_rtc.tv_sec <= old_rtc.tv_sec) {
104 if (new_rtc.tv_sec < old_rtc.tv_sec)
105 pr_debug("%s: time travel!\n", dev_name(&rtc->dev));
106 return 0;
107 }
108
109 /* calculate the RTC time delta (sleep time)*/
110 sleep_time = timespec_sub(new_rtc, old_rtc);
111
112 /*
113 * Since these RTC suspend/resume handlers are not called
114 * at the very end of suspend or the start of resume,
115 * some run-time may pass on either sides of the sleep time
116 * so subtract kernel run-time between rtc_suspend to rtc_resume
117 * to keep things accurate.
118 */
119 sleep_time = timespec_sub(sleep_time,
120 timespec_sub(new_system, old_system));
121
122 timekeeping_inject_sleeptime(&sleep_time);
123 return 0;
124}
125
126#else
127#define rtc_suspend NULL
128#define rtc_resume NULL
129#endif
130
131
132/**
133 * rtc_device_register - register w/ RTC class
134 * @dev: the device to register
135 *
136 * rtc_device_unregister() must be called when the class device is no
137 * longer needed.
138 *
139 * Returns the pointer to the new struct class device.
140 */
141struct rtc_device *rtc_device_register(const char *name, struct device *dev,
142 const struct rtc_class_ops *ops,
143 struct module *owner)
144{
145 struct rtc_device *rtc;
146 struct rtc_wkalrm alrm;
147 int id, err;
148
149 if (idr_pre_get(&rtc_idr, GFP_KERNEL) == 0) {
150 err = -ENOMEM;
151 goto exit;
152 }
153
154
155 mutex_lock(&idr_lock);
156 err = idr_get_new(&rtc_idr, NULL, &id);
157 mutex_unlock(&idr_lock);
158
159 if (err < 0)
160 goto exit;
161
162 id = id & MAX_ID_MASK;
163
164 rtc = kzalloc(sizeof(struct rtc_device), GFP_KERNEL);
165 if (rtc == NULL) {
166 err = -ENOMEM;
167 goto exit_idr;
168 }
169
170 rtc->id = id;
171 rtc->ops = ops;
172 rtc->owner = owner;
173 rtc->irq_freq = 1;
174 rtc->max_user_freq = 64;
175 rtc->dev.parent = dev;
176 rtc->dev.class = rtc_class;
177 rtc->dev.release = rtc_device_release;
178
179 mutex_init(&rtc->ops_lock);
180 spin_lock_init(&rtc->irq_lock);
181 spin_lock_init(&rtc->irq_task_lock);
182 init_waitqueue_head(&rtc->irq_queue);
183
184 /* Init timerqueue */
185 timerqueue_init_head(&rtc->timerqueue);
186 INIT_WORK(&rtc->irqwork, rtc_timer_do_work);
187 /* Init aie timer */
188 rtc_timer_init(&rtc->aie_timer, rtc_aie_update_irq, (void *)rtc);
189 /* Init uie timer */
190 rtc_timer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, (void *)rtc);
191 /* Init pie timer */
192 hrtimer_init(&rtc->pie_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
193 rtc->pie_timer.function = rtc_pie_update_irq;
194 rtc->pie_enabled = 0;
195
196 /* Check to see if there is an ALARM already set in hw */
197 err = __rtc_read_alarm(rtc, &alrm);
198
199 if (!err && !rtc_valid_tm(&alrm.time))
200 rtc_initialize_alarm(rtc, &alrm);
201
202 strlcpy(rtc->name, name, RTC_DEVICE_NAME_SIZE);
203 dev_set_name(&rtc->dev, "rtc%d", id);
204
205 rtc_dev_prepare(rtc);
206
207 err = device_register(&rtc->dev);
208 if (err) {
209 put_device(&rtc->dev);
210 goto exit_kfree;
211 }
212
213 rtc_dev_add_device(rtc);
214 rtc_sysfs_add_device(rtc);
215 rtc_proc_add_device(rtc);
216
217 dev_info(dev, "rtc core: registered %s as %s\n",
218 rtc->name, dev_name(&rtc->dev));
219
220 return rtc;
221
222exit_kfree:
223 kfree(rtc);
224
225exit_idr:
226 mutex_lock(&idr_lock);
227 idr_remove(&rtc_idr, id);
228 mutex_unlock(&idr_lock);
229
230exit:
231 dev_err(dev, "rtc core: unable to register %s, err = %d\n",
232 name, err);
233 return ERR_PTR(err);
234}
235EXPORT_SYMBOL_GPL(rtc_device_register);
236
237
238/**
239 * rtc_device_unregister - removes the previously registered RTC class device
240 *
241 * @rtc: the RTC class device to destroy
242 */
243void rtc_device_unregister(struct rtc_device *rtc)
244{
245 if (get_device(&rtc->dev) != NULL) {
246 mutex_lock(&rtc->ops_lock);
247 /* remove innards of this RTC, then disable it, before
248 * letting any rtc_class_open() users access it again
249 */
250 rtc_sysfs_del_device(rtc);
251 rtc_dev_del_device(rtc);
252 rtc_proc_del_device(rtc);
253 device_unregister(&rtc->dev);
254 rtc->ops = NULL;
255 mutex_unlock(&rtc->ops_lock);
256 put_device(&rtc->dev);
257 }
258}
259EXPORT_SYMBOL_GPL(rtc_device_unregister);
260
261static int __init rtc_init(void)
262{
263 rtc_class = class_create(THIS_MODULE, "rtc");
264 if (IS_ERR(rtc_class)) {
265 printk(KERN_ERR "%s: couldn't create class\n", __FILE__);
266 return PTR_ERR(rtc_class);
267 }
268 rtc_class->suspend = rtc_suspend;
269 rtc_class->resume = rtc_resume;
270 rtc_dev_init();
271 rtc_sysfs_init(rtc_class);
272 return 0;
273}
274
275static void __exit rtc_exit(void)
276{
277 rtc_dev_exit();
278 class_destroy(rtc_class);
279 idr_destroy(&rtc_idr);
280}
281
282subsys_initcall(rtc_init);
283module_exit(rtc_exit);
284
285MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
286MODULE_DESCRIPTION("RTC class support");
287MODULE_LICENSE("GPL");
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);
24struct class *rtc_class;
25
26static 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 kfree(rtc);
32}
33
34#ifdef CONFIG_RTC_HCTOSYS_DEVICE
35/* Result of the last RTC to system clock attempt. */
36int rtc_hctosys_ret = -ENODEV;
37#endif
38
39#if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
40/*
41 * On suspend(), measure the delta between one RTC and the
42 * system's wall clock; restore it on resume().
43 */
44
45static struct timespec64 old_rtc, old_system, old_delta;
46
47static int rtc_suspend(struct device *dev)
48{
49 struct rtc_device *rtc = to_rtc_device(dev);
50 struct rtc_time tm;
51 struct timespec64 delta, delta_delta;
52 int err;
53
54 if (timekeeping_rtc_skipsuspend())
55 return 0;
56
57 if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
58 return 0;
59
60 /* snapshot the current RTC and system time at suspend*/
61 err = rtc_read_time(rtc, &tm);
62 if (err < 0) {
63 pr_debug("%s: fail to read rtc time\n", dev_name(&rtc->dev));
64 return 0;
65 }
66
67 ktime_get_real_ts64(&old_system);
68 old_rtc.tv_sec = rtc_tm_to_time64(&tm);
69
70 /*
71 * To avoid drift caused by repeated suspend/resumes,
72 * which each can add ~1 second drift error,
73 * try to compensate so the difference in system time
74 * and rtc time stays close to constant.
75 */
76 delta = timespec64_sub(old_system, old_rtc);
77 delta_delta = timespec64_sub(delta, old_delta);
78 if (delta_delta.tv_sec < -2 || delta_delta.tv_sec >= 2) {
79 /*
80 * if delta_delta is too large, assume time correction
81 * has occurred and set old_delta to the current delta.
82 */
83 old_delta = delta;
84 } else {
85 /* Otherwise try to adjust old_system to compensate */
86 old_system = timespec64_sub(old_system, delta_delta);
87 }
88
89 return 0;
90}
91
92static int rtc_resume(struct device *dev)
93{
94 struct rtc_device *rtc = to_rtc_device(dev);
95 struct rtc_time tm;
96 struct timespec64 new_system, new_rtc;
97 struct timespec64 sleep_time;
98 int err;
99
100 if (timekeeping_rtc_skipresume())
101 return 0;
102
103 rtc_hctosys_ret = -ENODEV;
104 if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
105 return 0;
106
107 /* snapshot the current rtc and system time at resume */
108 ktime_get_real_ts64(&new_system);
109 err = rtc_read_time(rtc, &tm);
110 if (err < 0) {
111 pr_debug("%s: fail to read rtc time\n", dev_name(&rtc->dev));
112 return 0;
113 }
114
115 new_rtc.tv_sec = rtc_tm_to_time64(&tm);
116 new_rtc.tv_nsec = 0;
117
118 if (new_rtc.tv_sec < old_rtc.tv_sec) {
119 pr_debug("%s: time travel!\n", dev_name(&rtc->dev));
120 return 0;
121 }
122
123 /* calculate the RTC time delta (sleep time)*/
124 sleep_time = timespec64_sub(new_rtc, old_rtc);
125
126 /*
127 * Since these RTC suspend/resume handlers are not called
128 * at the very end of suspend or the start of resume,
129 * some run-time may pass on either sides of the sleep time
130 * so subtract kernel run-time between rtc_suspend to rtc_resume
131 * to keep things accurate.
132 */
133 sleep_time = timespec64_sub(sleep_time,
134 timespec64_sub(new_system, old_system));
135
136 if (sleep_time.tv_sec >= 0)
137 timekeeping_inject_sleeptime64(&sleep_time);
138 rtc_hctosys_ret = 0;
139 return 0;
140}
141
142static SIMPLE_DEV_PM_OPS(rtc_class_dev_pm_ops, rtc_suspend, rtc_resume);
143#define RTC_CLASS_DEV_PM_OPS (&rtc_class_dev_pm_ops)
144#else
145#define RTC_CLASS_DEV_PM_OPS NULL
146#endif
147
148/* Ensure the caller will set the id before releasing the device */
149static struct rtc_device *rtc_allocate_device(void)
150{
151 struct rtc_device *rtc;
152
153 rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
154 if (!rtc)
155 return NULL;
156
157 device_initialize(&rtc->dev);
158
159 /* Drivers can revise this default after allocating the device. */
160 rtc->set_offset_nsec = NSEC_PER_SEC / 2;
161
162 rtc->irq_freq = 1;
163 rtc->max_user_freq = 64;
164 rtc->dev.class = rtc_class;
165 rtc->dev.groups = rtc_get_dev_attribute_groups();
166 rtc->dev.release = rtc_device_release;
167
168 mutex_init(&rtc->ops_lock);
169 spin_lock_init(&rtc->irq_lock);
170 init_waitqueue_head(&rtc->irq_queue);
171
172 /* Init timerqueue */
173 timerqueue_init_head(&rtc->timerqueue);
174 INIT_WORK(&rtc->irqwork, rtc_timer_do_work);
175 /* Init aie timer */
176 rtc_timer_init(&rtc->aie_timer, rtc_aie_update_irq, rtc);
177 /* Init uie timer */
178 rtc_timer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, rtc);
179 /* Init pie timer */
180 hrtimer_init(&rtc->pie_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
181 rtc->pie_timer.function = rtc_pie_update_irq;
182 rtc->pie_enabled = 0;
183
184 return rtc;
185}
186
187static int rtc_device_get_id(struct device *dev)
188{
189 int of_id = -1, id = -1;
190
191 if (dev->of_node)
192 of_id = of_alias_get_id(dev->of_node, "rtc");
193 else if (dev->parent && dev->parent->of_node)
194 of_id = of_alias_get_id(dev->parent->of_node, "rtc");
195
196 if (of_id >= 0) {
197 id = ida_simple_get(&rtc_ida, of_id, of_id + 1, GFP_KERNEL);
198 if (id < 0)
199 dev_warn(dev, "/aliases ID %d not available\n", of_id);
200 }
201
202 if (id < 0)
203 id = ida_simple_get(&rtc_ida, 0, 0, GFP_KERNEL);
204
205 return id;
206}
207
208static void rtc_device_get_offset(struct rtc_device *rtc)
209{
210 time64_t range_secs;
211 u32 start_year;
212 int ret;
213
214 /*
215 * If RTC driver did not implement the range of RTC hardware device,
216 * then we can not expand the RTC range by adding or subtracting one
217 * offset.
218 */
219 if (rtc->range_min == rtc->range_max)
220 return;
221
222 ret = device_property_read_u32(rtc->dev.parent, "start-year",
223 &start_year);
224 if (!ret) {
225 rtc->start_secs = mktime64(start_year, 1, 1, 0, 0, 0);
226 rtc->set_start_time = true;
227 }
228
229 /*
230 * If user did not implement the start time for RTC driver, then no
231 * need to expand the RTC range.
232 */
233 if (!rtc->set_start_time)
234 return;
235
236 range_secs = rtc->range_max - rtc->range_min + 1;
237
238 /*
239 * If the start_secs is larger than the maximum seconds (rtc->range_max)
240 * supported by RTC hardware or the maximum seconds of new expanded
241 * range (start_secs + rtc->range_max - rtc->range_min) is less than
242 * rtc->range_min, which means the minimum seconds (rtc->range_min) of
243 * RTC hardware will be mapped to start_secs by adding one offset, so
244 * the offset seconds calculation formula should be:
245 * rtc->offset_secs = rtc->start_secs - rtc->range_min;
246 *
247 * If the start_secs is larger than the minimum seconds (rtc->range_min)
248 * supported by RTC hardware, then there is one region is overlapped
249 * between the original RTC hardware range and the new expanded range,
250 * and this overlapped region do not need to be mapped into the new
251 * expanded range due to it is valid for RTC device. So the minimum
252 * seconds of RTC hardware (rtc->range_min) should be mapped to
253 * rtc->range_max + 1, then the offset seconds formula should be:
254 * rtc->offset_secs = rtc->range_max - rtc->range_min + 1;
255 *
256 * If the start_secs is less than the minimum seconds (rtc->range_min),
257 * which is similar to case 2. So the start_secs should be mapped to
258 * start_secs + rtc->range_max - rtc->range_min + 1, then the
259 * offset seconds formula should be:
260 * rtc->offset_secs = -(rtc->range_max - rtc->range_min + 1);
261 *
262 * Otherwise the offset seconds should be 0.
263 */
264 if (rtc->start_secs > rtc->range_max ||
265 rtc->start_secs + range_secs - 1 < rtc->range_min)
266 rtc->offset_secs = rtc->start_secs - rtc->range_min;
267 else if (rtc->start_secs > rtc->range_min)
268 rtc->offset_secs = range_secs;
269 else if (rtc->start_secs < rtc->range_min)
270 rtc->offset_secs = -range_secs;
271 else
272 rtc->offset_secs = 0;
273}
274
275/**
276 * rtc_device_unregister - removes the previously registered RTC class device
277 *
278 * @rtc: the RTC class device to destroy
279 */
280static void rtc_device_unregister(struct rtc_device *rtc)
281{
282 mutex_lock(&rtc->ops_lock);
283 /*
284 * Remove innards of this RTC, then disable it, before
285 * letting any rtc_class_open() users access it again
286 */
287 rtc_proc_del_device(rtc);
288 cdev_device_del(&rtc->char_dev, &rtc->dev);
289 rtc->ops = NULL;
290 mutex_unlock(&rtc->ops_lock);
291 put_device(&rtc->dev);
292}
293
294static void devm_rtc_release_device(struct device *dev, void *res)
295{
296 struct rtc_device *rtc = *(struct rtc_device **)res;
297
298 rtc_nvmem_unregister(rtc);
299
300 if (rtc->registered)
301 rtc_device_unregister(rtc);
302 else
303 put_device(&rtc->dev);
304}
305
306struct rtc_device *devm_rtc_allocate_device(struct device *dev)
307{
308 struct rtc_device **ptr, *rtc;
309 int id, err;
310
311 id = rtc_device_get_id(dev);
312 if (id < 0)
313 return ERR_PTR(id);
314
315 ptr = devres_alloc(devm_rtc_release_device, sizeof(*ptr), GFP_KERNEL);
316 if (!ptr) {
317 err = -ENOMEM;
318 goto exit_ida;
319 }
320
321 rtc = rtc_allocate_device();
322 if (!rtc) {
323 err = -ENOMEM;
324 goto exit_devres;
325 }
326
327 *ptr = rtc;
328 devres_add(dev, ptr);
329
330 rtc->id = id;
331 rtc->dev.parent = dev;
332 dev_set_name(&rtc->dev, "rtc%d", id);
333
334 return rtc;
335
336exit_devres:
337 devres_free(ptr);
338exit_ida:
339 ida_simple_remove(&rtc_ida, id);
340 return ERR_PTR(err);
341}
342EXPORT_SYMBOL_GPL(devm_rtc_allocate_device);
343
344int __rtc_register_device(struct module *owner, struct rtc_device *rtc)
345{
346 struct rtc_wkalrm alrm;
347 int err;
348
349 if (!rtc->ops) {
350 dev_dbg(&rtc->dev, "no ops set\n");
351 return -EINVAL;
352 }
353
354 rtc->owner = owner;
355 rtc_device_get_offset(rtc);
356
357 /* Check to see if there is an ALARM already set in hw */
358 err = __rtc_read_alarm(rtc, &alrm);
359 if (!err && !rtc_valid_tm(&alrm.time))
360 rtc_initialize_alarm(rtc, &alrm);
361
362 rtc_dev_prepare(rtc);
363
364 err = cdev_device_add(&rtc->char_dev, &rtc->dev);
365 if (err)
366 dev_warn(rtc->dev.parent, "failed to add char device %d:%d\n",
367 MAJOR(rtc->dev.devt), rtc->id);
368 else
369 dev_dbg(rtc->dev.parent, "char device (%d:%d)\n",
370 MAJOR(rtc->dev.devt), rtc->id);
371
372 rtc_proc_add_device(rtc);
373
374 rtc->registered = true;
375 dev_info(rtc->dev.parent, "registered as %s\n",
376 dev_name(&rtc->dev));
377
378 return 0;
379}
380EXPORT_SYMBOL_GPL(__rtc_register_device);
381
382/**
383 * devm_rtc_device_register - resource managed rtc_device_register()
384 * @dev: the device to register
385 * @name: the name of the device (unused)
386 * @ops: the rtc operations structure
387 * @owner: the module owner
388 *
389 * @return a struct rtc on success, or an ERR_PTR on error
390 *
391 * Managed rtc_device_register(). The rtc_device returned from this function
392 * are automatically freed on driver detach.
393 * This function is deprecated, use devm_rtc_allocate_device and
394 * rtc_register_device instead
395 */
396struct rtc_device *devm_rtc_device_register(struct device *dev,
397 const char *name,
398 const struct rtc_class_ops *ops,
399 struct module *owner)
400{
401 struct rtc_device *rtc;
402 int err;
403
404 rtc = devm_rtc_allocate_device(dev);
405 if (IS_ERR(rtc))
406 return rtc;
407
408 rtc->ops = ops;
409
410 err = __rtc_register_device(owner, rtc);
411 if (err)
412 return ERR_PTR(err);
413
414 return rtc;
415}
416EXPORT_SYMBOL_GPL(devm_rtc_device_register);
417
418static int __init rtc_init(void)
419{
420 rtc_class = class_create(THIS_MODULE, "rtc");
421 if (IS_ERR(rtc_class)) {
422 pr_err("couldn't create class\n");
423 return PTR_ERR(rtc_class);
424 }
425 rtc_class->pm = RTC_CLASS_DEV_PM_OPS;
426 rtc_dev_init();
427 return 0;
428}
429subsys_initcall(rtc_init);