drivers/rtc/rtc-mc146818-lib.c

   1 #include <linux/bcd.h>
   2 #include <linux/delay.h>
   3 #include <linux/export.h>
   4 #include <linux/mc146818rtc.h>
   5
   6 #ifdef CONFIG_ACPI
   7 #include <linux/acpi.h>
   8 #endif
   9
  10 /*
  11  * Returns true if a clock update is in progress
  12  */
  13 static inline unsigned char mc146818_is_updating(void)
  14 {
  15         unsigned char uip;
  16         unsigned long flags;
  17
  18         spin_lock_irqsave(&rtc_lock, flags);
  19         uip = (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
  20         spin_unlock_irqrestore(&rtc_lock, flags);
  21         return uip;
  22 }
  23
  24 unsigned int mc146818_get_time(struct rtc_time *time)
  25 {
  26         unsigned char ctrl;
  27         unsigned long flags;
  28         unsigned char century = 0;
  29
  30 #ifdef CONFIG_MACH_DECSTATION
  31         unsigned int real_year;
  32 #endif
  33
  34         /*
  35          * read RTC once any update in progress is done. The update
  36          * can take just over 2ms. We wait 20ms. There is no need to
  37          * to poll-wait (up to 1s - eeccch) for the falling edge of RTC_UIP.
  38          * If you need to know *exactly* when a second has started, enable
  39          * periodic update complete interrupts, (via ioctl) and then
  40          * immediately read /dev/rtc which will block until you get the IRQ.
  41          * Once the read clears, read the RTC time (again via ioctl). Easy.
  42          */
  43         if (mc146818_is_updating())
  44                 mdelay(20);
  45
  46         /*
  47          * Only the values that we read from the RTC are set. We leave
  48          * tm_wday, tm_yday and tm_isdst untouched. Even though the
  49          * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
  50          * by the RTC when initially set to a non-zero value.
  51          */
  52         spin_lock_irqsave(&rtc_lock, flags);
  53         time->tm_sec = CMOS_READ(RTC_SECONDS);
  54         time->tm_min = CMOS_READ(RTC_MINUTES);
  55         time->tm_hour = CMOS_READ(RTC_HOURS);
  56         time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH);
  57         time->tm_mon = CMOS_READ(RTC_MONTH);
  58         time->tm_year = CMOS_READ(RTC_YEAR);
  59 #ifdef CONFIG_MACH_DECSTATION
  60         real_year = CMOS_READ(RTC_DEC_YEAR);
  61 #endif
  62 #ifdef CONFIG_ACPI
  63         if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
  64             acpi_gbl_FADT.century)
  65                 century = CMOS_READ(acpi_gbl_FADT.century);
  66 #endif
  67         ctrl = CMOS_READ(RTC_CONTROL);
  68         spin_unlock_irqrestore(&rtc_lock, flags);
  69
  70         if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  71         {
  72                 time->tm_sec = bcd2bin(time->tm_sec);
  73                 time->tm_min = bcd2bin(time->tm_min);
  74                 time->tm_hour = bcd2bin(time->tm_hour);
  75                 time->tm_mday = bcd2bin(time->tm_mday);
  76                 time->tm_mon = bcd2bin(time->tm_mon);
  77                 time->tm_year = bcd2bin(time->tm_year);
  78                 century = bcd2bin(century);
  79         }
  80
  81 #ifdef CONFIG_MACH_DECSTATION
  82         time->tm_year += real_year - 72;
  83 #endif
  84
  85         if (century)
  86                 time->tm_year += (century - 19) * 100;
  87
  88         /*
  89          * Account for differences between how the RTC uses the values
  90          * and how they are defined in a struct rtc_time;
  91          */
  92         if (time->tm_year <= 69)
  93                 time->tm_year += 100;
  94
  95         time->tm_mon--;
  96
  97         return RTC_24H;
  98 }
  99 EXPORT_SYMBOL_GPL(mc146818_get_time);
 100
 101 /* Set the current date and time in the real time clock. */
 102 int mc146818_set_time(struct rtc_time *time)
 103 {
 104         unsigned long flags;
 105         unsigned char mon, day, hrs, min, sec;
 106         unsigned char save_control, save_freq_select;
 107         unsigned int yrs;
 108 #ifdef CONFIG_MACH_DECSTATION
 109         unsigned int real_yrs, leap_yr;
 110 #endif
 111         unsigned char century = 0;
 112
 113         yrs = time->tm_year;
 114         mon = time->tm_mon + 1;   /* tm_mon starts at zero */
 115         day = time->tm_mday;
 116         hrs = time->tm_hour;
 117         min = time->tm_min;
 118         sec = time->tm_sec;
 119
 120         if (yrs > 255)  /* They are unsigned */
 121                 return -EINVAL;
 122
 123         spin_lock_irqsave(&rtc_lock, flags);
 124 #ifdef CONFIG_MACH_DECSTATION
 125         real_yrs = yrs;
 126         leap_yr = ((!((yrs + 1900) % 4) && ((yrs + 1900) % 100)) ||
 127                         !((yrs + 1900) % 400));
 128         yrs = 72;
 129
 130         /*
 131          * We want to keep the year set to 73 until March
 132          * for non-leap years, so that Feb, 29th is handled
 133          * correctly.
 134          */
 135         if (!leap_yr && mon < 3) {
 136                 real_yrs--;
 137                 yrs = 73;
 138         }
 139 #endif
 140
 141 #ifdef CONFIG_ACPI
 142         if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
 143             acpi_gbl_FADT.century) {
 144                 century = (yrs + 1900) / 100;
 145                 yrs %= 100;
 146         }
 147 #endif
 148
 149         /* These limits and adjustments are independent of
 150          * whether the chip is in binary mode or not.
 151          */
 152         if (yrs > 169) {
 153                 spin_unlock_irqrestore(&rtc_lock, flags);
 154                 return -EINVAL;
 155         }
 156
 157         if (yrs >= 100)
 158                 yrs -= 100;
 159
 160         if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY)
 161             || RTC_ALWAYS_BCD) {
 162                 sec = bin2bcd(sec);
 163                 min = bin2bcd(min);
 164                 hrs = bin2bcd(hrs);
 165                 day = bin2bcd(day);
 166                 mon = bin2bcd(mon);
 167                 yrs = bin2bcd(yrs);
 168                 century = bin2bcd(century);
 169         }
 170
 171         save_control = CMOS_READ(RTC_CONTROL);
 172         CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
 173         save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
 174         CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
 175
 176 #ifdef CONFIG_MACH_DECSTATION
 177         CMOS_WRITE(real_yrs, RTC_DEC_YEAR);
 178 #endif
 179         CMOS_WRITE(yrs, RTC_YEAR);
 180         CMOS_WRITE(mon, RTC_MONTH);
 181         CMOS_WRITE(day, RTC_DAY_OF_MONTH);
 182         CMOS_WRITE(hrs, RTC_HOURS);
 183         CMOS_WRITE(min, RTC_MINUTES);
 184         CMOS_WRITE(sec, RTC_SECONDS);
 185 #ifdef CONFIG_ACPI
 186         if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
 187             acpi_gbl_FADT.century)
 188                 CMOS_WRITE(century, acpi_gbl_FADT.century);
 189 #endif
 190
 191         CMOS_WRITE(save_control, RTC_CONTROL);
 192         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
 193
 194         spin_unlock_irqrestore(&rtc_lock, flags);
 195
 196         return 0;
 197 }
 198 EXPORT_SYMBOL_GPL(mc146818_set_time);