LXR uboot/lib/rtc-lib.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * rtc and date/time utility functions
   4 *
   5 * Copyright (C) 2005-06 Tower Technologies
   6 * Author: Alessandro Zummo <a.zummo@towertech.it>
   7 *
   8 * U-Boot rtc_time differs from Linux rtc_time:
   9 * - The year field takes the actual value, not year - 1900.
  10 * - January is month 1.
  11 */
  12
  13#include <common.h>
  14#include <rtc.h>
  15#include <linux/math64.h>
  16
  17static const unsigned char rtc_days_in_month[] = {
  18        31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
  19};
  20
  21#define LEAPS_THRU_END_OF(y) ((y) / 4 - (y) / 100 + (y) / 400)
  22
  23/*
  24 * The number of days in the month.
  25 */
  26int rtc_month_days(unsigned int month, unsigned int year)
  27{
  28        return rtc_days_in_month[month] + (is_leap_year(year) && month == 1);
  29}
  30
  31/*
  32 * rtc_to_tm - Converts u64 to rtc_time.
  33 * Convert seconds since 01-01-1970 00:00:00 to Gregorian date.
  34 *
  35 * This function is copied from rtc_time64_to_tm() in the Linux kernel.
  36 * But in U-Boot January is month 1 and we do not subtract 1900 from the year.
  37 */
  38void rtc_to_tm(u64 time, struct rtc_time *tm)
  39{
  40        unsigned int month, year, secs;
  41        int days;
  42
  43        days = div_u64_rem(time, 86400, &secs);
  44
  45        /* day of the week, 1970-01-01 was a Thursday */
  46        tm->tm_wday = (days + 4) % 7;
  47
  48        year = 1970 + days / 365;
  49        days -= (year - 1970) * 365
  50                + LEAPS_THRU_END_OF(year - 1)
  51                - LEAPS_THRU_END_OF(1970 - 1);
  52        while (days < 0) {
  53                year -= 1;
  54                days += 365 + is_leap_year(year);
  55        }
  56        tm->tm_year = year; /* Not year - 1900 */
  57        tm->tm_yday = days + 1;
  58
  59        for (month = 0; month < 11; month++) {
  60                int newdays;
  61
  62                newdays = days - rtc_month_days(month, year);
  63                if (newdays < 0)
  64                        break;
  65                days = newdays;
  66        }
  67        tm->tm_mon = month + 1; /* January = 1 */
  68        tm->tm_mday = days + 1;
  69
  70        tm->tm_hour = secs / 3600;
  71        secs -= tm->tm_hour * 3600;
  72        tm->tm_min = secs / 60;
  73        tm->tm_sec = secs - tm->tm_min * 60;
  74
  75        /* Zero unused fields */
  76        tm->tm_isdst = 0;
  77}
  78