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 # define CMOS_YEARS_OFFS 1900
  13 /*
  14  * This is a special lock that is owned by the CPU and holds the index
  15  * register we are working with.  It is required for NMI access to the
  16  * CMOS/RTC registers.  See include/asm-i386/mc146818rtc.h for details.
  17  */
  18 volatile unsigned long cmos_lock = 0;
  19 EXPORT_SYMBOL(cmos_lock);
  20 #else
  21 /*
  22  * x86-64 systems only exists since 2002.
  23  * This will work up to Dec 31, 2100
  24  */
  25 # define CMOS_YEARS_OFFS 2000
  26 #endif
  27
  28 DEFINE_SPINLOCK(rtc_lock);
  29 EXPORT_SYMBOL(rtc_lock);
  30
  31 /*
  32  * In order to set the CMOS clock precisely, set_rtc_mmss has to be
  33  * called 500 ms after the second nowtime has started, because when
  34  * nowtime is written into the registers of the CMOS clock, it will
  35  * jump to the next second precisely 500 ms later. Check the Motorola
  36  * MC146818A or Dallas DS12887 data sheet for details.
  37  *
  38  * BUG: This routine does not handle hour overflow properly; it just
  39  *      sets the minutes. Usually you'll only notice that after reboot!
  40  */
  41 int mach_set_rtc_mmss(unsigned long nowtime)
  42 {
  43         int retval = 0;
  44         int real_seconds, real_minutes, cmos_minutes;
  45         unsigned char save_control, save_freq_select;
  46
  47          /* tell the clock it's being set */
  48         save_control = CMOS_READ(RTC_CONTROL);
  49         CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
  50
  51         /* stop and reset prescaler */
  52         save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
  53         CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
  54
  55         cmos_minutes = CMOS_READ(RTC_MINUTES);
  56         if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  57                 BCD_TO_BIN(cmos_minutes);
  58
  59         /*
  60          * since we're only adjusting minutes and seconds,
  61          * don't interfere with hour overflow. This avoids
  62          * messing with unknown time zones but requires your
  63          * RTC not to be off by more than 15 minutes
  64          */
  65         real_seconds = nowtime % 60;
  66         real_minutes = nowtime / 60;
  67         /* correct for half hour time zone */
  68         if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
  69                 real_minutes += 30;
  70         real_minutes %= 60;
  71
  72         if (abs(real_minutes - cmos_minutes) < 30) {
  73                 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  74                         BIN_TO_BCD(real_seconds);
  75                         BIN_TO_BCD(real_minutes);
  76                 }
  77                 CMOS_WRITE(real_seconds,RTC_SECONDS);
  78                 CMOS_WRITE(real_minutes,RTC_MINUTES);
  79         } else {
  80                 printk(KERN_WARNING
  81                        "set_rtc_mmss: can't update from %d to %d\n",
  82                        cmos_minutes, real_minutes);
  83                 retval = -1;
  84         }
  85
  86         /* The following flags have to be released exactly in this order,
  87          * otherwise the DS12887 (popular MC146818A clone with integrated
  88          * battery and quartz) will not reset the oscillator and will not
  89          * update precisely 500 ms later. You won't find this mentioned in
  90          * the Dallas Semiconductor data sheets, but who believes data
  91          * sheets anyway ...                           -- Markus Kuhn
  92          */
  93         CMOS_WRITE(save_control, RTC_CONTROL);
  94         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
  95
  96         return retval;
  97 }
  98
  99 unsigned long mach_get_cmos_time(void)
 100 {
 101         unsigned int year, mon, day, hour, min, sec, century = 0;
 102
 103         /*
 104          * If UIP is clear, then we have >= 244 microseconds before
 105          * RTC registers will be updated.  Spec sheet says that this
 106          * is the reliable way to read RTC - registers. If UIP is set
 107          * then the register access might be invalid.
 108          */
 109         while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
 110                 cpu_relax();
 111
 112         sec = CMOS_READ(RTC_SECONDS);
 113         min = CMOS_READ(RTC_MINUTES);
 114         hour = CMOS_READ(RTC_HOURS);
 115         day = CMOS_READ(RTC_DAY_OF_MONTH);
 116         mon = CMOS_READ(RTC_MONTH);
 117         year = CMOS_READ(RTC_YEAR);
 118
 119 #if defined(CONFIG_ACPI) && defined(CONFIG_X86_64)
 120         /* CHECKME: Is this really 64bit only ??? */
 121         if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
 122             acpi_gbl_FADT.century)
 123                 century = CMOS_READ(acpi_gbl_FADT.century);
 124 #endif
 125
 126         if (RTC_ALWAYS_BCD || !(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY)) {
 127                 BCD_TO_BIN(sec);
 128                 BCD_TO_BIN(min);
 129                 BCD_TO_BIN(hour);
 130                 BCD_TO_BIN(day);
 131                 BCD_TO_BIN(mon);
 132                 BCD_TO_BIN(year);
 133         }
 134
 135         if (century) {
 136                 BCD_TO_BIN(century);
 137                 year += century * 100;
 138                 printk(KERN_INFO "Extended CMOS year: %d\n", century * 100);
 139         } else {
 140                 year += CMOS_YEARS_OFFS;
 141                 if (year < 1970)
 142                         year += 100;
 143         }
 144
 145         return mktime(year, mon, day, hour, min, sec);
 146 }
 147
 148 /* Routines for accessing the CMOS RAM/RTC. */
 149 unsigned char rtc_cmos_read(unsigned char addr)
 150 {
 151         unsigned char val;
 152
 153         lock_cmos_prefix(addr);
 154         outb_p(addr, RTC_PORT(0));
 155         val = inb_p(RTC_PORT(1));
 156         lock_cmos_suffix(addr);
 157         return val;
 158 }
 159 EXPORT_SYMBOL(rtc_cmos_read);
 160
 161 void rtc_cmos_write(unsigned char val, unsigned char addr)
 162 {
 163         lock_cmos_prefix(addr);
 164         outb_p(addr, RTC_PORT(0));
 165         outb_p(val, RTC_PORT(1));
 166         lock_cmos_suffix(addr);
 167 }
 168 EXPORT_SYMBOL(rtc_cmos_write);
 169
 170 static int set_rtc_mmss(unsigned long nowtime)
 171 {
 172         int retval;
 173         unsigned long flags;
 174
 175         spin_lock_irqsave(&rtc_lock, flags);
 176         retval = set_wallclock(nowtime);
 177         spin_unlock_irqrestore(&rtc_lock, flags);
 178
 179         return retval;
 180 }
 181
 182 /* not static: needed by APM */
 183 unsigned long read_persistent_clock(void)
 184 {
 185         unsigned long retval, flags;
 186
 187         spin_lock_irqsave(&rtc_lock, flags);
 188         retval = get_wallclock();
 189         spin_unlock_irqrestore(&rtc_lock, flags);
 190
 191         return retval;
 192 }
 193
 194 int update_persistent_clock(struct timespec now)
 195 {
 196         return set_rtc_mmss(now.tv_sec);
 197 }
 198
 199 unsigned long long native_read_tsc(void)
 200 {
 201         return __native_read_tsc();
 202 }
 203 EXPORT_SYMBOL(native_read_tsc);
 204