1 /*
2 * This program is free software; you can redistribute it and/or modify it
3 * under the terms of the GNU General Public License version 2 as published by
4 * the Free Software Foundation.
5 *
6 */
7 #include <linux/rtc.h>
8 #include <linux/time.h>
9
10 /**
11 * rtc_set_ntp_time - Save NTP synchronized time to the RTC
12 * @now: Current time of day
13 * @target_nsec: pointer for desired now->tv_nsec value
14 *
15 * Replacement for the NTP platform function update_persistent_clock64
16 * that stores time for later retrieval by rtc_hctosys.
17 *
18 * Returns 0 on successful RTC update, -ENODEV if a RTC update is not
19 * possible at all, and various other -errno for specific temporary failure
20 * cases.
21 *
22 * -EPROTO is returned if now.tv_nsec is not close enough to *target_nsec.
23 *
24 * If temporary failure is indicated the caller should try again 'soon'
25 */
rtc_set_ntp_time(struct timespec64 now,unsigned long * target_nsec)26 int rtc_set_ntp_time(struct timespec64 now, unsigned long *target_nsec)
27 {
28 struct rtc_device *rtc;
29 struct rtc_time tm;
30 struct timespec64 to_set;
31 int err = -ENODEV;
32 bool ok;
33
34 rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE);
35 if (!rtc)
36 goto out_err;
37
38 if (!rtc->ops || (!rtc->ops->set_time && !rtc->ops->set_mmss64 &&
39 !rtc->ops->set_mmss))
40 goto out_close;
41
42 /* Compute the value of tv_nsec we require the caller to supply in
43 * now.tv_nsec. This is the value such that (now +
44 * set_offset_nsec).tv_nsec == 0.
45 */
46 set_normalized_timespec64(&to_set, 0, -rtc->set_offset_nsec);
47 *target_nsec = to_set.tv_nsec;
48
49 /* The ntp code must call this with the correct value in tv_nsec, if
50 * it does not we update target_nsec and return EPROTO to make the ntp
51 * code try again later.
52 */
53 ok = rtc_tv_nsec_ok(rtc->set_offset_nsec, &to_set, &now);
54 if (!ok) {
55 err = -EPROTO;
56 goto out_close;
57 }
58
59 rtc_time64_to_tm(to_set.tv_sec, &tm);
60
61 /* rtc_hctosys exclusively uses UTC, so we call set_time here, not
62 * set_mmss.
63 */
64 err = rtc_set_time(rtc, &tm);
65
66 out_close:
67 rtc_class_close(rtc);
68 out_err:
69 return err;
70 }
71