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