arch/x86/kernel/rtc.c

   1 /*
   2  * RTC related functions
   3  */
   4 #include <linux/platform_device.h>
   5 #include <linux/mc146818rtc.h>
   6 #include <linux/acpi.h>
   7 #include <linux/bcd.h>
   8 #include <linux/pnp.h>
   9 #include <linux/of.h>
  10
  11 #include <asm/vsyscall.h>
  12 #include <asm/x86_init.h>
  13 #include <asm/time.h>
  14
  15 #ifdef CONFIG_X86_32
  16 /*
  17  * This is a special lock that is owned by the CPU and holds the index
  18  * register we are working with.  It is required for NMI access to the
  19  * CMOS/RTC registers.  See include/asm-i386/mc146818rtc.h for details.
  20  */
  21 volatile unsigned long cmos_lock;
  22 EXPORT_SYMBOL(cmos_lock);
  23 #endif /* CONFIG_X86_32 */
  24
  25 /* For two digit years assume time is always after that */
  26 #define CMOS_YEARS_OFFS 2000
  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 real_seconds, real_minutes, cmos_minutes;
  44         unsigned char save_control, save_freq_select;
  45         int retval = 0;
  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                 cmos_minutes = bcd2bin(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                         real_seconds = bin2bcd(real_seconds);
  75                         real_minutes = bin2bcd(real_minutes);
  76                 }
  77                 CMOS_WRITE(real_seconds, RTC_SECONDS);
  78                 CMOS_WRITE(real_minutes, RTC_MINUTES);
  79         } else {
  80                 printk_once(KERN_NOTICE
  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 status, 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 #ifdef CONFIG_ACPI
 120         if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
 121             acpi_gbl_FADT.century)
 122                 century = CMOS_READ(acpi_gbl_FADT.century);
 123 #endif
 124
 125         status = CMOS_READ(RTC_CONTROL);
 126         WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY));
 127
 128         if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) {
 129                 sec = bcd2bin(sec);
 130                 min = bcd2bin(min);
 131                 hour = bcd2bin(hour);
 132                 day = bcd2bin(day);
 133                 mon = bcd2bin(mon);
 134                 year = bcd2bin(year);
 135         }
 136
 137         if (century) {
 138                 century = bcd2bin(century);
 139                 year += century * 100;
 140                 printk(KERN_INFO "Extended CMOS year: %d\n", century * 100);
 141         } else
 142                 year += CMOS_YEARS_OFFS;
 143
 144         return mktime(year, mon, day, hour, min, sec);
 145 }
 146
 147 /* Routines for accessing the CMOS RAM/RTC. */
 148 unsigned char rtc_cmos_read(unsigned char addr)
 149 {
 150         unsigned char val;
 151
 152         lock_cmos_prefix(addr);
 153         outb(addr, RTC_PORT(0));
 154         val = inb(RTC_PORT(1));
 155         lock_cmos_suffix(addr);
 156
 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(addr, RTC_PORT(0));
 165         outb(val, RTC_PORT(1));
 166         lock_cmos_suffix(addr);
 167 }
 168 EXPORT_SYMBOL(rtc_cmos_write);
 169
 170 int update_persistent_clock(struct timespec now)
 171 {
 172         unsigned long flags;
 173         int retval;
 174
 175         spin_lock_irqsave(&rtc_lock, flags);
 176         retval = x86_platform.set_wallclock(now.tv_sec);
 177         spin_unlock_irqrestore(&rtc_lock, flags);
 178
 179         return retval;
 180 }
 181
 182 /* not static: needed by APM */
 183 void read_persistent_clock(struct timespec *ts)
 184 {
 185         unsigned long retval, flags;
 186
 187         spin_lock_irqsave(&rtc_lock, flags);
 188         retval = x86_platform.get_wallclock();
 189         spin_unlock_irqrestore(&rtc_lock, flags);
 190
 191         ts->tv_sec = retval;
 192         ts->tv_nsec = 0;
 193 }
 194
 195 unsigned long long native_read_tsc(void)
 196 {
 197         return __native_read_tsc();
 198 }
 199 EXPORT_SYMBOL(native_read_tsc);
 200
 201
 202 static struct resource rtc_resources[] = {
 203         [0] = {
 204                 .start  = RTC_PORT(0),
 205                 .end    = RTC_PORT(1),
 206                 .flags  = IORESOURCE_IO,
 207         },
 208         [1] = {
 209                 .start  = RTC_IRQ,
 210                 .end    = RTC_IRQ,
 211                 .flags  = IORESOURCE_IRQ,
 212         }
 213 };
 214
 215 static struct platform_device rtc_device = {
 216         .name           = "rtc_cmos",
 217         .id             = -1,
 218         .resource       = rtc_resources,
 219         .num_resources  = ARRAY_SIZE(rtc_resources),
 220 };
 221
 222 static __init int add_rtc_cmos(void)
 223 {
 224 #ifdef CONFIG_PNP
 225         static const char *ids[] __initconst =
 226             { "PNP0b00", "PNP0b01", "PNP0b02", };
 227         struct pnp_dev *dev;
 228         struct pnp_id *id;
 229         int i;
 230
 231         pnp_for_each_dev(dev) {
 232                 for (id = dev->id; id; id = id->next) {
 233                         for (i = 0; i < ARRAY_SIZE(ids); i++) {
 234                                 if (compare_pnp_id(id, ids[i]) != 0)
 235                                         return 0;
 236                         }
 237                 }
 238         }
 239 #endif
 240         if (of_have_populated_dt())
 241                 return 0;
 242
 243         platform_device_register(&rtc_device);
 244         dev_info(&rtc_device.dev,
 245                  "registered platform RTC device (no PNP device found)\n");
 246
 247         return 0;
 248 }
 249 device_initcall(add_rtc_cmos);