LXR linux/drivers/rtc/systohc.c

   1// SPDX-License-Identifier: GPL-2.0
   2#include <linux/rtc.h>
   3#include <linux/time.h>
   4
   5/**
   6 * rtc_set_ntp_time - Save NTP synchronized time to the RTC
   7 * @now: Current time of day
   8 * @target_nsec: pointer for desired now->tv_nsec value
   9 *
  10 * Replacement for the NTP platform function update_persistent_clock64
  11 * that stores time for later retrieval by rtc_hctosys.
  12 *
  13 * Returns 0 on successful RTC update, -ENODEV if a RTC update is not
  14 * possible at all, and various other -errno for specific temporary failure
  15 * cases.
  16 *
  17 * -EPROTO is returned if now.tv_nsec is not close enough to *target_nsec.
  18 *
  19 * If temporary failure is indicated the caller should try again 'soon'
  20 */
  21int rtc_set_ntp_time(struct timespec64 now, unsigned long *target_nsec)
  22{
  23        struct rtc_device *rtc;
  24        struct rtc_time tm;
  25        struct timespec64 to_set;
  26        int err = -ENODEV;
  27        bool ok;
  28
  29        rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE);
  30        if (!rtc)
  31                goto out_err;
  32
  33        if (!rtc->ops || !rtc->ops->set_time)
  34                goto out_close;
  35
  36        /* Compute the value of tv_nsec we require the caller to supply in
  37         * now.tv_nsec.  This is the value such that (now +
  38         * set_offset_nsec).tv_nsec == 0.
  39         */
  40        set_normalized_timespec64(&to_set, 0, -rtc->set_offset_nsec);
  41        *target_nsec = to_set.tv_nsec;
  42
  43        /* The ntp code must call this with the correct value in tv_nsec, if
  44         * it does not we update target_nsec and return EPROTO to make the ntp
  45         * code try again later.
  46         */
  47        ok = rtc_tv_nsec_ok(rtc->set_offset_nsec, &to_set, &now);
  48        if (!ok) {
  49                err = -EPROTO;
  50                goto out_close;
  51        }
  52
  53        rtc_time64_to_tm(to_set.tv_sec, &tm);
  54
  55        err = rtc_set_time(rtc, &tm);
  56
  57out_close:
  58        rtc_class_close(rtc);
  59out_err:
  60        return err;
  61}
  62