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