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 #ifdef CONFIG_ACPI
 116         if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
 117             acpi_gbl_FADT.century)
 118                 century = CMOS_READ(acpi_gbl_FADT.century);
 119 #endif
 120
 121         status = CMOS_READ(RTC_CONTROL);
 122         WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY));
 123
 124         if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) {
 125                 BCD_TO_BIN(sec);
 126                 BCD_TO_BIN(min);
 127                 BCD_TO_BIN(hour);
 128                 BCD_TO_BIN(day);
 129                 BCD_TO_BIN(mon);
 130                 BCD_TO_BIN(year);
 131         }
 132
 133         if (century) {
 134                 BCD_TO_BIN(century);
 135                 year += century * 100;
 136                 printk(KERN_INFO "Extended CMOS year: %d\n", century * 100);
 137         } else
 138                 year += CMOS_YEARS_OFFS;
 139
 140         return mktime(year, mon, day, hour, min, sec);
 141 }
 142
 143 /* Routines for accessing the CMOS RAM/RTC. */
 144 unsigned char rtc_cmos_read(unsigned char addr)
 145 {
 146         unsigned char val;
 147
 148         lock_cmos_prefix(addr);
 149         outb(addr, RTC_PORT(0));
 150         val = inb(RTC_PORT(1));
 151         lock_cmos_suffix(addr);
 152         return val;
 153 }
 154 EXPORT_SYMBOL(rtc_cmos_read);
 155
 156 void rtc_cmos_write(unsigned char val, unsigned char addr)
 157 {
 158         lock_cmos_prefix(addr);
 159         outb(addr, RTC_PORT(0));
 160         outb(val, RTC_PORT(1));
 161         lock_cmos_suffix(addr);
 162 }
 163 EXPORT_SYMBOL(rtc_cmos_write);
 164
 165 static int set_rtc_mmss(unsigned long nowtime)
 166 {
 167         int retval;
 168         unsigned long flags;
 169
 170         spin_lock_irqsave(&rtc_lock, flags);
 171         retval = set_wallclock(nowtime);
 172         spin_unlock_irqrestore(&rtc_lock, flags);
 173
 174         return retval;
 175 }
 176
 177 /* not static: needed by APM */
 178 unsigned long read_persistent_clock(void)
 179 {
 180         unsigned long retval, flags;
 181
 182         spin_lock_irqsave(&rtc_lock, flags);
 183         retval = get_wallclock();
 184         spin_unlock_irqrestore(&rtc_lock, flags);
 185
 186         return retval;
 187 }
 188
 189 int update_persistent_clock(struct timespec now)
 190 {
 191         return set_rtc_mmss(now.tv_sec);
 192 }
 193
 194 unsigned long long native_read_tsc(void)
 195 {
 196         return __native_read_tsc();
 197 }
 198 EXPORT_SYMBOL(native_read_tsc);
 199