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 */
26int 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
66out_close:
67	rtc_class_close(rtc);
68out_err:
69	return err;
70}