src/lib/rtc.c

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2
   3 /*
   4  * From U-Boot 2016.05
   5  */
   6
   7 #include <console/console.h>
   8 #include <rtc.h>
   9
  10 #define FEBRUARY                2
  11 #define STARTOFTIME             1970
  12 #define SECDAY                  86400L
  13 #define SECYR                   (SECDAY * 365)
  14 #define LEAP_YEAR(year)         (((year) % 4 == 0 && (year) % 100 != 0) || (year) % 400 == 0)
  15 #define DAYS_IN_YEAR(a)         (LEAP_YEAR(a) ? 366 : 365)
  16 #define DAYS_IN_MONTH(a)        (month_days[(a) - 1])
  17
  18 static const char *const weekdays[] = {
  19         "Sun", "Mon", "Tues", "Wednes", "Thurs", "Fri", "Satur"
  20 };
  21
  22 /* Zeller's rule */
  23 static int rtc_calc_weekday(struct rtc_time *tm)
  24 {
  25         /* In Zeller's rule, January and February are treated as if they
  26            are months 13 and 14 of the previous year (March is still month 3) */
  27         const int zyear = ((tm->mon < 3) ? tm->year - 1 : tm->year);
  28         const int q = tm->mday;
  29         const int m = (tm->mon < 3) ? tm->mon + 12 : tm->mon;
  30         const int K = zyear % 100;
  31         const int J = zyear / 100;
  32
  33         /*
  34          * Because of the way the modulo operator works with negative numbers,
  35          * the traditional formulation of Zeller's rule must be modified
  36          * slightly to make the numerator positive (i.e., add 5J instead of
  37          * subtracting 2J).  Also subtract 1 so that Sunday is day 0.
  38          */
  39         const int h = (q + (13 * (m + 1)) / 5
  40                        + K + (K / 4) + (J / 4) + (5 * J) - 1) % 7;
  41
  42         tm->wday = h;
  43         return 0;
  44 }
  45
  46 int rtc_to_tm(int tim, struct rtc_time *tm)
  47 {
  48         int month_days[12] = {
  49                 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
  50         };
  51         register int i;
  52         register long hms, day;
  53
  54         day = tim / SECDAY;
  55         hms = tim % SECDAY;
  56
  57         /* Hours, minutes, seconds are easy */
  58         tm->hour = hms / 3600;
  59         tm->min = (hms % 3600) / 60;
  60         tm->sec = (hms % 3600) % 60;
  61
  62         /* Number of years in days */
  63         for (i = STARTOFTIME; day >= DAYS_IN_YEAR(i); i++)
  64                 day -= DAYS_IN_YEAR(i);
  65         tm->year = i;
  66
  67         /* Number of months in days left */
  68         if (LEAP_YEAR(tm->year))
  69                 DAYS_IN_MONTH(FEBRUARY) = 29;
  70         for (i = 1; day >= DAYS_IN_MONTH(i); i++)
  71                 day -= DAYS_IN_MONTH(i);
  72         DAYS_IN_MONTH(FEBRUARY) = 28;
  73         tm->mon = i;
  74
  75         /* Days are what is left over (+1) from all that */
  76         tm->mday = day + 1;
  77
  78         /* Determine the day of week */
  79         return rtc_calc_weekday(tm);
  80 }
  81
  82 /*
  83  * Converts Gregorian date to seconds since 1970-01-01 00:00:00.
  84  * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
  85  * => year=1980,  mon=12,  day=31,  hour=23,  min=59,  sec=59.
  86  *
  87  * [For the Julian calendar (which was used in Russia before 1917,
  88  * Britain & colonies before 1752,  anywhere else before 1582,
  89  * and is still in use by some communities) leave out the
  90  * -year / 100 + year / 400 terms,  and add 10.]
  91  *
  92  * This algorithm was first published by Gauss (I think).
  93  *
  94  * WARNING: this function will overflow on 2106-02-07 06:28:16 on
  95  * machines where long is 32-bit! (However, as time_t is signed, we
  96  * will already get problems at other places on 2038-01-19 03:14:08)
  97  */
  98 unsigned long rtc_mktime(const struct rtc_time *tm)
  99 {
 100         int mon = tm->mon;
 101         int year = tm->year;
 102         int days, hours;
 103
 104         mon -= 2;
 105         if (0 >= (int)mon) {    /* 1..12 -> 11, 12, 1..10 */
 106                 mon += 12;      /* Puts Feb last since it has leap day */
 107                 year -= 1;
 108         }
 109
 110         days = (unsigned long)(year / 4 - year / 100 + year / 400 +
 111                                367 * mon / 12 + tm->mday) +
 112                                year * 365 - 719499;
 113         hours = days * 24 + tm->hour;
 114         return (hours * 60 + tm->min) * 60 + tm->sec;
 115 }
 116
 117 void rtc_display(const struct rtc_time *tm)
 118 {
 119         printk(BIOS_INFO, "Date: %5d-%02d-%02d (%sday)  Time: %2d:%02d:%02d\n",
 120                tm->year,  tm->mon,  tm->mday,
 121                (tm->wday < 0 || tm->wday > 6) ? "unknown " : weekdays[tm->wday],
 122                tm->hour,  tm->min,  tm->sec);
 123 }
 124
 125 static int rtc_month_days(unsigned int month, unsigned int year)
 126 {
 127         int month_days[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
 128
 129         return month_days[month] + (LEAP_YEAR(year) && month == 2);
 130 }
 131
 132 int rtc_invalid(const struct rtc_time *tm)
 133 {
 134         if (tm->sec > 59 || tm->min > 59 || tm->hour > 23 || tm->mon == 0 || tm->mon > 12 ||
 135             tm->year < 1970 || tm->mday > rtc_month_days(tm->mon - 1, tm->year))
 136                 return 1;
 137         else
 138                 return 0;
 139 }