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// SPDX-License-Identifier: GPL-2.0
#include <linux/rtc.h>
#include <linux/time.h>
/**
* rtc_set_ntp_time - Save NTP synchronized time to the RTC
* @now: Current time of day
* @target_nsec: pointer for desired now->tv_nsec value
*
* Replacement for the NTP platform function update_persistent_clock64
* that stores time for later retrieval by rtc_hctosys.
*
* Returns 0 on successful RTC update, -ENODEV if a RTC update is not
* possible at all, and various other -errno for specific temporary failure
* cases.
*
* -EPROTO is returned if now.tv_nsec is not close enough to *target_nsec.
*
* If temporary failure is indicated the caller should try again 'soon'
*/
int rtc_set_ntp_time(struct timespec64 now, unsigned long *target_nsec)
{
struct rtc_device *rtc;
struct rtc_time tm;
struct timespec64 to_set;
int err = -ENODEV;
bool ok;
rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE);
if (!rtc)
goto out_err;
if (!rtc->ops || (!rtc->ops->set_time && !rtc->ops->set_mmss64 &&
!rtc->ops->set_mmss))
goto out_close;
/* Compute the value of tv_nsec we require the caller to supply in
* now.tv_nsec. This is the value such that (now +
* set_offset_nsec).tv_nsec == 0.
*/
set_normalized_timespec64(&to_set, 0, -rtc->set_offset_nsec);
*target_nsec = to_set.tv_nsec;
/* The ntp code must call this with the correct value in tv_nsec, if
* it does not we update target_nsec and return EPROTO to make the ntp
* code try again later.
*/
ok = rtc_tv_nsec_ok(rtc->set_offset_nsec, &to_set, &now);
if (!ok) {
err = -EPROTO;
goto out_close;
}
rtc_time64_to_tm(to_set.tv_sec, &tm);
/* rtc_hctosys exclusively uses UTC, so we call set_time here, not
* set_mmss.
*/
err = rtc_set_time(rtc, &tm);
out_close:
rtc_class_close(rtc);
out_err:
return err;
}
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