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 #include <linux/platform_device.h>
   8 #include <linux/pnp.h>
   9
  10 #include <asm/time.h>
  11 #include <asm/vsyscall.h>
  12
  13 #ifdef CONFIG_X86_32
  14 /*
  15  * This is a special lock that is owned by the CPU and holds the index
  16  * register we are working with.  It is required for NMI access to the
  17  * CMOS/RTC registers.  See include/asm-i386/mc146818rtc.h for details.
  18  */
  19 volatile unsigned long cmos_lock = 0;
  20 EXPORT_SYMBOL(cmos_lock);
  21 #endif
  22
  23 /* For two digit years assume time is always after that */
  24 #define CMOS_YEARS_OFFS 2000
  25
  26 DEFINE_SPINLOCK(rtc_lock);
  27 EXPORT_SYMBOL(rtc_lock);
  28
  29 /*
  30  * In order to set the CMOS clock precisely, set_rtc_mmss has to be
  31  * called 500 ms after the second nowtime has started, because when
  32  * nowtime is written into the registers of the CMOS clock, it will
  33  * jump to the next second precisely 500 ms later. Check the Motorola
  34  * MC146818A or Dallas DS12887 data sheet for details.
  35  *
  36  * BUG: This routine does not handle hour overflow properly; it just
  37  *      sets the minutes. Usually you'll only notice that after reboot!
  38  */
  39 int mach_set_rtc_mmss(unsigned long nowtime)
  40 {
  41         int retval = 0;
  42         int real_seconds, real_minutes, cmos_minutes;
  43         unsigned char save_control, save_freq_select;
  44
  45          /* tell the clock it's being set */
  46         save_control = CMOS_READ(RTC_CONTROL);
  47         CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
  48
  49         /* stop and reset prescaler */
  50         save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
  51         CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
  52
  53         cmos_minutes = CMOS_READ(RTC_MINUTES);
  54         if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  55                 BCD_TO_BIN(cmos_minutes);
  56
  57         /*
  58          * since we're only adjusting minutes and seconds,
  59          * don't interfere with hour overflow. This avoids
  60          * messing with unknown time zones but requires your
  61          * RTC not to be off by more than 15 minutes
  62          */
  63         real_seconds = nowtime % 60;
  64         real_minutes = nowtime / 60;
  65         /* correct for half hour time zone */
  66         if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
  67                 real_minutes += 30;
  68         real_minutes %= 60;
  69
  70         if (abs(real_minutes - cmos_minutes) < 30) {
  71                 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  72                         BIN_TO_BCD(real_seconds);
  73                         BIN_TO_BCD(real_minutes);
  74                 }
  75                 CMOS_WRITE(real_seconds,RTC_SECONDS);
  76                 CMOS_WRITE(real_minutes,RTC_MINUTES);
  77         } else {
  78                 printk(KERN_WARNING
  79                        "set_rtc_mmss: can't update from %d to %d\n",
  80                        cmos_minutes, real_minutes);
  81                 retval = -1;
  82         }
  83
  84         /* The following flags have to be released exactly in this order,
  85          * otherwise the DS12887 (popular MC146818A clone with integrated
  86          * battery and quartz) will not reset the oscillator and will not
  87          * update precisely 500 ms later. You won't find this mentioned in
  88          * the Dallas Semiconductor data sheets, but who believes data
  89          * sheets anyway ...                           -- Markus Kuhn
  90          */
  91         CMOS_WRITE(save_control, RTC_CONTROL);
  92         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
  93
  94         return retval;
  95 }
  96
  97 unsigned long mach_get_cmos_time(void)
  98 {
  99         unsigned int status, year, mon, day, hour, min, sec, century = 0;
 100
 101         /*
 102          * If UIP is clear, then we have >= 244 microseconds before
 103          * RTC registers will be updated.  Spec sheet says that this
 104          * is the reliable way to read RTC - registers. If UIP is set
 105          * then the register access might be invalid.
 106          */
 107         while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
 108                 cpu_relax();
 109
 110         sec = CMOS_READ(RTC_SECONDS);
 111         min = CMOS_READ(RTC_MINUTES);
 112         hour = CMOS_READ(RTC_HOURS);
 113         day = CMOS_READ(RTC_DAY_OF_MONTH);
 114         mon = CMOS_READ(RTC_MONTH);
 115         year = CMOS_READ(RTC_YEAR);
 116
 117 #ifdef CONFIG_ACPI
 118         if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
 119             acpi_gbl_FADT.century)
 120                 century = CMOS_READ(acpi_gbl_FADT.century);
 121 #endif
 122
 123         status = CMOS_READ(RTC_CONTROL);
 124         WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY));
 125
 126         if (RTC_ALWAYS_BCD || !(status & 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
 142         return mktime(year, mon, day, hour, min, sec);
 143 }
 144
 145 /* Routines for accessing the CMOS RAM/RTC. */
 146 unsigned char rtc_cmos_read(unsigned char addr)
 147 {
 148         unsigned char val;
 149
 150         lock_cmos_prefix(addr);
 151         outb(addr, RTC_PORT(0));
 152         val = inb(RTC_PORT(1));
 153         lock_cmos_suffix(addr);
 154         return val;
 155 }
 156 EXPORT_SYMBOL(rtc_cmos_read);
 157
 158 void rtc_cmos_write(unsigned char val, unsigned char addr)
 159 {
 160         lock_cmos_prefix(addr);
 161         outb(addr, RTC_PORT(0));
 162         outb(val, RTC_PORT(1));
 163         lock_cmos_suffix(addr);
 164 }
 165 EXPORT_SYMBOL(rtc_cmos_write);
 166
 167 static int set_rtc_mmss(unsigned long nowtime)
 168 {
 169         int retval;
 170         unsigned long flags;
 171
 172         spin_lock_irqsave(&rtc_lock, flags);
 173         retval = set_wallclock(nowtime);
 174         spin_unlock_irqrestore(&rtc_lock, flags);
 175
 176         return retval;
 177 }
 178
 179 /* not static: needed by APM */
 180 unsigned long read_persistent_clock(void)
 181 {
 182         unsigned long retval, flags;
 183
 184         spin_lock_irqsave(&rtc_lock, flags);
 185         retval = get_wallclock();
 186         spin_unlock_irqrestore(&rtc_lock, flags);
 187
 188         return retval;
 189 }
 190
 191 int update_persistent_clock(struct timespec now)
 192 {
 193         return set_rtc_mmss(now.tv_sec);
 194 }
 195
 196 unsigned long long native_read_tsc(void)
 197 {
 198         return __native_read_tsc();
 199 }
 200 EXPORT_SYMBOL(native_read_tsc);
 201
 202
 203 static struct resource rtc_resources[] = {
 204         [0] = {
 205                 .start  = RTC_PORT(0),
 206                 .end    = RTC_PORT(1),
 207                 .flags  = IORESOURCE_IO,
 208         },
 209         [1] = {
 210                 .start  = RTC_IRQ,
 211                 .end    = RTC_IRQ,
 212                 .flags  = IORESOURCE_IRQ,
 213         }
 214 };
 215
 216 static struct platform_device rtc_device = {
 217         .name           = "rtc_cmos",
 218         .id             = -1,
 219         .resource       = rtc_resources,
 220         .num_resources  = ARRAY_SIZE(rtc_resources),
 221 };
 222
 223 static __init int add_rtc_cmos(void)
 224 {
 225 #ifdef CONFIG_PNP
 226         if (!pnp_platform_devices)
 227                 platform_device_register(&rtc_device);
 228 #else
 229         platform_device_register(&rtc_device);
 230 #endif /* CONFIG_PNP */
 231         return 0;
 232 }
 233 device_initcall(add_rtc_cmos);