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
23 static DEFINE_IDA(rtc_ida);
24 struct class *rtc_class;
25
rtc_device_release(struct device * dev)26 static void rtc_device_release(struct device *dev)
27 {
28 struct rtc_device *rtc = to_rtc_device(dev);
29 struct timerqueue_head *head = &rtc->timerqueue;
30 struct timerqueue_node *node;
31
32 mutex_lock(&rtc->ops_lock);
33 while ((node = timerqueue_getnext(head)))
34 timerqueue_del(head, node);
35 mutex_unlock(&rtc->ops_lock);
36
37 cancel_work_sync(&rtc->irqwork);
38
39 ida_simple_remove(&rtc_ida, rtc->id);
40 kfree(rtc);
41 }
42
43 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
44 /* Result of the last RTC to system clock attempt. */
45 int 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
rtc_hctosys(struct rtc_device * rtc)58 static 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
87 err_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
98 static struct timespec64 old_rtc, old_system, old_delta;
99
rtc_suspend(struct device * dev)100 static 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
rtc_resume(struct device * dev)145 static 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
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)
197 #else
198 #define RTC_CLASS_DEV_PM_OPS NULL
199 #endif
200
201 /* Ensure the caller will set the id before releasing the device */
rtc_allocate_device(void)202 static struct rtc_device *rtc_allocate_device(void)
203 {
204 struct rtc_device *rtc;
205
206 rtc = kzalloc(sizeof(*rtc), GFP_KERNEL);
207 if (!rtc)
208 return NULL;
209
210 device_initialize(&rtc->dev);
211
212 /* Drivers can revise this default after allocating the device. */
213 rtc->set_offset_nsec = NSEC_PER_SEC / 2;
214
215 rtc->irq_freq = 1;
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;
220
221 mutex_init(&rtc->ops_lock);
222 spin_lock_init(&rtc->irq_lock);
223 init_waitqueue_head(&rtc->irq_queue);
224
225 /* Init timerqueue */
226 timerqueue_init_head(&rtc->timerqueue);
227 INIT_WORK(&rtc->irqwork, rtc_timer_do_work);
228 /* Init aie timer */
229 rtc_timer_init(&rtc->aie_timer, rtc_aie_update_irq, rtc);
230 /* Init uie timer */
231 rtc_timer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, rtc);
232 /* Init pie timer */
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;
236
237 return rtc;
238 }
239
rtc_device_get_id(struct device * dev)240 static int rtc_device_get_id(struct device *dev)
241 {
242 int of_id = -1, id = -1;
243
244 if (dev->of_node)
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");
248
249 if (of_id >= 0) {
250 id = ida_simple_get(&rtc_ida, of_id, of_id + 1, GFP_KERNEL);
251 if (id < 0)
252 dev_warn(dev, "/aliases ID %d not available\n", of_id);
253 }
254
255 if (id < 0)
256 id = ida_simple_get(&rtc_ida, 0, 0, GFP_KERNEL);
257
258 return id;
259 }
260
rtc_device_get_offset(struct rtc_device * rtc)261 static void rtc_device_get_offset(struct rtc_device *rtc)
262 {
263 time64_t range_secs;
264 u32 start_year;
265 int ret;
266
267 /*
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
270 * offset.
271 */
272 if (rtc->range_min == rtc->range_max)
273 return;
274
275 ret = device_property_read_u32(rtc->dev.parent, "start-year",
276 &start_year);
277 if (!ret) {
278 rtc->start_secs = mktime64(start_year, 1, 1, 0, 0, 0);
279 rtc->set_start_time = true;
280 }
281
282 /*
283 * If user did not implement the start time for RTC driver, then no
284 * need to expand the RTC range.
285 */
286 if (!rtc->set_start_time)
287 return;
288
289 range_secs = rtc->range_max - rtc->range_min + 1;
290
291 /*
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;
299 *
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;
308 *
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);
314 *
315 * Otherwise the offset seconds should be 0.
316 */
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;
324 else
325 rtc->offset_secs = 0;
326 }
327
328 /**
329 * rtc_device_unregister - removes the previously registered RTC class device
330 *
331 * @rtc: the RTC class device to destroy
332 */
rtc_device_unregister(struct rtc_device * rtc)333 static void rtc_device_unregister(struct rtc_device *rtc)
334 {
335 mutex_lock(&rtc->ops_lock);
336 /*
337 * Remove innards of this RTC, then disable it, before
338 * letting any rtc_class_open() users access it again
339 */
340 rtc_proc_del_device(rtc);
341 cdev_device_del(&rtc->char_dev, &rtc->dev);
342 rtc->ops = NULL;
343 mutex_unlock(&rtc->ops_lock);
344 put_device(&rtc->dev);
345 }
346
devm_rtc_release_device(struct device * dev,void * res)347 static void devm_rtc_release_device(struct device *dev, void *res)
348 {
349 struct rtc_device *rtc = *(struct rtc_device **)res;
350
351 rtc_nvmem_unregister(rtc);
352
353 if (rtc->registered)
354 rtc_device_unregister(rtc);
355 else
356 put_device(&rtc->dev);
357 }
358
devm_rtc_allocate_device(struct device * dev)359 struct rtc_device *devm_rtc_allocate_device(struct device *dev)
360 {
361 struct rtc_device **ptr, *rtc;
362 int id, err;
363
364 id = rtc_device_get_id(dev);
365 if (id < 0)
366 return ERR_PTR(id);
367
368 ptr = devres_alloc(devm_rtc_release_device, sizeof(*ptr), GFP_KERNEL);
369 if (!ptr) {
370 err = -ENOMEM;
371 goto exit_ida;
372 }
373
374 rtc = rtc_allocate_device();
375 if (!rtc) {
376 err = -ENOMEM;
377 goto exit_devres;
378 }
379
380 *ptr = rtc;
381 devres_add(dev, ptr);
382
383 rtc->id = id;
384 rtc->dev.parent = dev;
385 dev_set_name(&rtc->dev, "rtc%d", id);
386
387 return rtc;
388
389 exit_devres:
390 devres_free(ptr);
391 exit_ida:
392 ida_simple_remove(&rtc_ida, id);
393 return ERR_PTR(err);
394 }
395 EXPORT_SYMBOL_GPL(devm_rtc_allocate_device);
396
__rtc_register_device(struct module * owner,struct rtc_device * rtc)397 int __rtc_register_device(struct module *owner, struct rtc_device *rtc)
398 {
399 struct rtc_wkalrm alrm;
400 int err;
401
402 if (!rtc->ops) {
403 dev_dbg(&rtc->dev, "no ops set\n");
404 return -EINVAL;
405 }
406
407 rtc->owner = owner;
408 rtc_device_get_offset(rtc);
409
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);
414
415 rtc_dev_prepare(rtc);
416
417 err = cdev_device_add(&rtc->char_dev, &rtc->dev);
418 if (err)
419 dev_warn(rtc->dev.parent, "failed to add char device %d:%d\n",
420 MAJOR(rtc->dev.devt), rtc->id);
421 else
422 dev_dbg(rtc->dev.parent, "char device (%d:%d)\n",
423 MAJOR(rtc->dev.devt), rtc->id);
424
425 rtc_proc_add_device(rtc);
426
427 rtc->registered = true;
428 dev_info(rtc->dev.parent, "registered as %s\n",
429 dev_name(&rtc->dev));
430
431 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
432 if (!strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE))
433 rtc_hctosys(rtc);
434 #endif
435
436 return 0;
437 }
438 EXPORT_SYMBOL_GPL(__rtc_register_device);
439
440 /**
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
446 *
447 * @return a struct rtc on success, or an ERR_PTR on error
448 *
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
453 */
devm_rtc_device_register(struct device * dev,const char * name,const struct rtc_class_ops * ops,struct module * owner)454 struct rtc_device *devm_rtc_device_register(struct device *dev,
455 const char *name,
456 const struct rtc_class_ops *ops,
457 struct module *owner)
458 {
459 struct rtc_device *rtc;
460 int err;
461
462 rtc = devm_rtc_allocate_device(dev);
463 if (IS_ERR(rtc))
464 return rtc;
465
466 rtc->ops = ops;
467
468 err = __rtc_register_device(owner, rtc);
469 if (err)
470 return ERR_PTR(err);
471
472 return rtc;
473 }
474 EXPORT_SYMBOL_GPL(devm_rtc_device_register);
475
rtc_init(void)476 static int __init rtc_init(void)
477 {
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);
482 }
483 rtc_class->pm = RTC_CLASS_DEV_PM_OPS;
484 rtc_dev_init();
485 return 0;
486 }
487 subsys_initcall(rtc_init);
488