drivers/rtc/systohc.c

   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  *
  14  * Replacement for the NTP platform function update_persistent_clock64
  15  * that stores time for later retrieval by rtc_hctosys.
  16  *
  17  * Returns 0 on successful RTC update, -ENODEV if a RTC update is not
  18  * possible at all, and various other -errno for specific temporary failure
  19  * cases.
  20  *
  21  * If temporary failure is indicated the caller should try again 'soon'
  22  */
  23 int rtc_set_ntp_time(struct timespec64 now)
  24 {
  25         struct rtc_device *rtc;
  26         struct rtc_time tm;
  27         int err = -ENODEV;
  28
  29         if (now.tv_nsec < (NSEC_PER_SEC >> 1))
  30                 rtc_time64_to_tm(now.tv_sec, &tm);
  31         else
  32                 rtc_time64_to_tm(now.tv_sec + 1, &tm);
  33
  34         rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE);
  35         if (rtc) {
  36                 /* rtc_hctosys exclusively uses UTC, so we call set_time here,
  37                  * not set_mmss. */
  38                 if (rtc->ops &&
  39                     (rtc->ops->set_time ||
  40                      rtc->ops->set_mmss64 ||
  41                      rtc->ops->set_mmss))
  42                         err = rtc_set_time(rtc, &tm);
  43                 rtc_class_close(rtc);
  44         }
  45
  46         return err;
  47 }