arch/x86/kernel/rtc.c

   1 /*
   2  * RTC related functions
   3  */
   4 #include <linux/acpi.h>
   5 #include <linux/bcd.h>
   6 #include <linux/mc146818rtc.h>
   7
   8 #include <asm/time.h>
   9 #include <asm/vsyscall.h>
  10
  11 #ifdef CONFIG_X86_32
  12 /*
  13  * This is a special lock that is owned by the CPU and holds the index
  14  * register we are working with.  It is required for NMI access to the
  15  * CMOS/RTC registers.  See include/asm-i386/mc146818rtc.h for details.
  16  */
  17 volatile unsigned long cmos_lock = 0;
  18 EXPORT_SYMBOL(cmos_lock);
  19 #endif
  20
  21 /* For two digit years assume time is always after that */
  22 #define CMOS_YEARS_OFFS 2000
  23
  24 DEFINE_SPINLOCK(rtc_lock);
  25 EXPORT_SYMBOL(rtc_lock);
  26
  27 /*
  28  * In order to set the CMOS clock precisely, set_rtc_mmss has to be
  29  * called 500 ms after the second nowtime has started, because when
  30  * nowtime is written into the registers of the CMOS clock, it will
  31  * jump to the next second precisely 500 ms later. Check the Motorola
  32  * MC146818A or Dallas DS12887 data sheet for details.
  33  *
  34  * BUG: This routine does not handle hour overflow properly; it just
  35  *      sets the minutes. Usually you'll only notice that after reboot!
  36  */
  37 int mach_set_rtc_mmss(unsigned long nowtime)
  38 {
  39         int retval = 0;
  40         int real_seconds, real_minutes, cmos_minutes;
  41         unsigned char save_control, save_freq_select;
  42
  43          /* tell the clock it's being set */
  44         save_control = CMOS_READ(RTC_CONTROL);
  45         CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
  46
  47         /* stop and reset prescaler */
  48         save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
  49         CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
  50
  51         cmos_minutes = CMOS_READ(RTC_MINUTES);
  52         if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  53                 BCD_TO_BIN(cmos_minutes);
  54
  55         /*
  56          * since we're only adjusting minutes and seconds,
  57          * don't interfere with hour overflow. This avoids
  58          * messing with unknown time zones but requires your
  59          * RTC not to be off by more than 15 minutes
  60          */
  61         real_seconds = nowtime % 60;
  62         real_minutes = nowtime / 60;
  63         /* correct for half hour time zone */
  64         if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
  65                 real_minutes += 30;
  66         real_minutes %= 60;
  67
  68         if (abs(real_minutes - cmos_minutes) < 30) {
  69                 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  70                         BIN_TO_BCD(real_seconds);
  71                         BIN_TO_BCD(real_minutes);
  72                 }
  73                 CMOS_WRITE(real_seconds,RTC_SECONDS);
  74                 CMOS_WRITE(real_minutes,RTC_MINUTES);
  75         } else {
  76                 printk(KERN_WARNING
  77                        "set_rtc_mmss: can't update from %d to %d\n",
  78                        cmos_minutes, real_minutes);
  79                 retval = -1;
  80         }
  81
  82         /* The following flags have to be released exactly in this order,
  83          * otherwise the DS12887 (popular MC146818A clone with integrated
  84          * battery and quartz) will not reset the oscillator and will not
  85          * update precisely 500 ms later. You won't find this mentioned in
  86          * the Dallas Semiconductor data sheets, but who believes data
  87          * sheets anyway ...                           -- Markus Kuhn
  88          */
  89         CMOS_WRITE(save_control, RTC_CONTROL);
  90         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
  91
  92         return retval;
  93 }
  94
  95 unsigned long mach_get_cmos_time(void)
  96 {
  97         unsigned int status, year, mon, day, hour, min, sec, century = 0;
  98
  99         /*
 100          * If UIP is clear, then we have >= 244 microseconds before
 101          * RTC registers will be updated.  Spec sheet says that this
 102          * is the reliable way to read RTC - registers. If UIP is set
 103          * then the register access might be invalid.
 104          */
 105         while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
 106                 cpu_relax();
 107
 108         sec = CMOS_READ(RTC_SECONDS);
 109         min = CMOS_READ(RTC_MINUTES);
 110         hour = CMOS_READ(RTC_HOURS);
 111         day = CMOS_READ(RTC_DAY_OF_MONTH);
 112         mon = CMOS_READ(RTC_MONTH);
 113         year = CMOS_READ(RTC_YEAR);
 114
 115 #if defined(CONFIG_ACPI) && defined(CONFIG_X86_64)
 116         /* CHECKME: Is this really 64bit only ??? */
 117         if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
 118             acpi_gbl_FADT.century)
 119                 century = CMOS_READ(acpi_gbl_FADT.century);
 120 #endif
 121
 122         status = CMOS_READ(RTC_CONTROL);
 123         WARN_ON_ONCE((RTC_ALWAYS_BCD && (status & RTC_DM_BINARY));
 124
 125         if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) {
 126                 BCD_TO_BIN(sec);
 127                 BCD_TO_BIN(min);
 128                 BCD_TO_BIN(hour);
 129                 BCD_TO_BIN(day);
 130                 BCD_TO_BIN(mon);
 131                 BCD_TO_BIN(year);
 132         }
 133
 134         if (century) {
 135                 BCD_TO_BIN(century);
 136                 year += century * 100;
 137                 printk(KERN_INFO "Extended CMOS year: %d\n", century * 100);
 138         } else
 139                 year += CMOS_YEARS_OFFS;
 140
 141         return mktime(year, mon, day, hour, min, sec);
 142 }
 143
 144 /* Routines for accessing the CMOS RAM/RTC. */
 145 unsigned char rtc_cmos_read(unsigned char addr)
 146 {
 147         unsigned char val;
 148
 149         lock_cmos_prefix(addr);
 150         outb_p(addr, RTC_PORT(0));
 151         val = inb_p(RTC_PORT(1));
 152         lock_cmos_suffix(addr);
 153         return val;
 154 }
 155 EXPORT_SYMBOL(rtc_cmos_read);
 156
 157 void rtc_cmos_write(unsigned char val, unsigned char addr)
 158 {
 159         lock_cmos_prefix(addr);
 160         outb_p(addr, RTC_PORT(0));
 161         outb_p(val, RTC_PORT(1));
 162         lock_cmos_suffix(addr);
 163 }
 164 EXPORT_SYMBOL(rtc_cmos_write);
 165
 166 static int set_rtc_mmss(unsigned long nowtime)
 167 {
 168         int retval;
 169         unsigned long flags;
 170
 171         spin_lock_irqsave(&rtc_lock, flags);
 172         retval = set_wallclock(nowtime);
 173         spin_unlock_irqrestore(&rtc_lock, flags);
 174
 175         return retval;
 176 }
 177
 178 /* not static: needed by APM */
 179 unsigned long read_persistent_clock(void)
 180 {
 181         unsigned long retval, flags;
 182
 183         spin_lock_irqsave(&rtc_lock, flags);
 184         retval = get_wallclock();
 185         spin_unlock_irqrestore(&rtc_lock, flags);
 186
 187         return retval;
 188 }
 189
 190 int update_persistent_clock(struct timespec now)
 191 {
 192         return set_rtc_mmss(now.tv_sec);
 193 }
 194
 195 unsigned long long native_read_tsc(void)
 196 {
 197         return __native_read_tsc();
 198 }
 199 EXPORT_SYMBOL(native_read_tsc);
 200