Branch data     Line data    Source code

       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                 :            :  */
      21                 :          0 : int rtc_set_ntp_time(struct timespec64 now, unsigned long *target_nsec)
      22                 :            : {
      23                 :          0 :         struct rtc_device *rtc;
      24                 :          0 :         struct rtc_time tm;
      25                 :          0 :         struct timespec64 to_set;
      26                 :          0 :         int err = -ENODEV;
      27                 :          0 :         bool ok;
      28                 :            : 
      29                 :          0 :         rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE);
      30         [ #  # ]:          0 :         if (!rtc)
      31                 :          0 :                 goto out_err;
      32                 :            : 
      33   [ #  #  #  # ]:          0 :         if (!rtc->ops || !rtc->ops->set_time)
      34                 :          0 :                 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                 :          0 :         set_normalized_timespec64(&to_set, 0, -rtc->set_offset_nsec);
      41                 :          0 :         *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                 :          0 :         ok = rtc_tv_nsec_ok(rtc->set_offset_nsec, &to_set, &now);
      48         [ #  # ]:          0 :         if (!ok) {
      49                 :          0 :                 err = -EPROTO;
      50                 :          0 :                 goto out_close;
      51                 :            :         }
      52                 :            : 
      53                 :          0 :         rtc_time64_to_tm(to_set.tv_sec, &tm);
      54                 :            : 
      55                 :          0 :         err = rtc_set_time(rtc, &tm);
      56                 :            : 
      57                 :          0 : out_close:
      58                 :          0 :         rtc_class_close(rtc);
      59                 :          0 : out_err:
      60                 :          0 :         return err;
      61                 :            : }