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         unsigned long flags;
  46         int retval = 0;
  47
  48         spin_lock_irqsave(&rtc_lock, flags);
  49
  50          /* tell the clock it's being set */
  51         save_control = CMOS_READ(RTC_CONTROL);
  52         CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
  53
  54         /* stop and reset prescaler */
  55         save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
  56         CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
  57
  58         cmos_minutes = CMOS_READ(RTC_MINUTES);
  59         if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  60                 cmos_minutes = bcd2bin(cmos_minutes);
  61
  62         /*
  63          * since we're only adjusting minutes and seconds,
  64          * don't interfere with hour overflow. This avoids
  65          * messing with unknown time zones but requires your
  66          * RTC not to be off by more than 15 minutes
  67          */
  68         real_seconds = nowtime % 60;
  69         real_minutes = nowtime / 60;
  70         /* correct for half hour time zone */
  71         if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
  72                 real_minutes += 30;
  73         real_minutes %= 60;
  74
  75         if (abs(real_minutes - cmos_minutes) < 30) {
  76                 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  77                         real_seconds = bin2bcd(real_seconds);
  78                         real_minutes = bin2bcd(real_minutes);
  79                 }
  80                 CMOS_WRITE(real_seconds, RTC_SECONDS);
  81                 CMOS_WRITE(real_minutes, RTC_MINUTES);
  82         } else {
  83                 printk_once(KERN_NOTICE
  84                        "set_rtc_mmss: can't update from %d to %d\n",
  85                        cmos_minutes, real_minutes);
  86                 retval = -1;
  87         }
  88
  89         /* The following flags have to be released exactly in this order,
  90          * otherwise the DS12887 (popular MC146818A clone with integrated
  91          * battery and quartz) will not reset the oscillator and will not
  92          * update precisely 500 ms later. You won't find this mentioned in
  93          * the Dallas Semiconductor data sheets, but who believes data
  94          * sheets anyway ...                           -- Markus Kuhn
  95          */
  96         CMOS_WRITE(save_control, RTC_CONTROL);
  97         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
  98
  99         spin_unlock_irqrestore(&rtc_lock, flags);
 100
 101         return retval;
 102 }
 103
 104 unsigned long mach_get_cmos_time(void)
 105 {
 106         unsigned int status, year, mon, day, hour, min, sec, century = 0;
 107         unsigned long flags;
 108
 109         spin_lock_irqsave(&rtc_lock, flags);
 110
 111         /*
 112          * If UIP is clear, then we have >= 244 microseconds before
 113          * RTC registers will be updated.  Spec sheet says that this
 114          * is the reliable way to read RTC - registers. If UIP is set
 115          * then the register access might be invalid.
 116          */
 117         while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
 118                 cpu_relax();
 119
 120         sec = CMOS_READ(RTC_SECONDS);
 121         min = CMOS_READ(RTC_MINUTES);
 122         hour = CMOS_READ(RTC_HOURS);
 123         day = CMOS_READ(RTC_DAY_OF_MONTH);
 124         mon = CMOS_READ(RTC_MONTH);
 125         year = CMOS_READ(RTC_YEAR);
 126
 127 #ifdef CONFIG_ACPI
 128         if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
 129             acpi_gbl_FADT.century)
 130                 century = CMOS_READ(acpi_gbl_FADT.century);
 131 #endif
 132
 133         status = CMOS_READ(RTC_CONTROL);
 134         WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY));
 135
 136         spin_unlock_irqrestore(&rtc_lock, flags);
 137
 138         if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) {
 139                 sec = bcd2bin(sec);
 140                 min = bcd2bin(min);
 141                 hour = bcd2bin(hour);
 142                 day = bcd2bin(day);
 143                 mon = bcd2bin(mon);
 144                 year = bcd2bin(year);
 145         }
 146
 147         if (century) {
 148                 century = bcd2bin(century);
 149                 year += century * 100;
 150                 printk(KERN_INFO "Extended CMOS year: %d\n", century * 100);
 151         } else
 152                 year += CMOS_YEARS_OFFS;
 153
 154         return mktime(year, mon, day, hour, min, sec);
 155 }
 156
 157 /* Routines for accessing the CMOS RAM/RTC. */
 158 unsigned char rtc_cmos_read(unsigned char addr)
 159 {
 160         unsigned char val;
 161
 162         lock_cmos_prefix(addr);
 163         outb(addr, RTC_PORT(0));
 164         val = inb(RTC_PORT(1));
 165         lock_cmos_suffix(addr);
 166
 167         return val;
 168 }
 169 EXPORT_SYMBOL(rtc_cmos_read);
 170
 171 void rtc_cmos_write(unsigned char val, unsigned char addr)
 172 {
 173         lock_cmos_prefix(addr);
 174         outb(addr, RTC_PORT(0));
 175         outb(val, RTC_PORT(1));
 176         lock_cmos_suffix(addr);
 177 }
 178 EXPORT_SYMBOL(rtc_cmos_write);
 179
 180 int update_persistent_clock(struct timespec now)
 181 {
 182         return x86_platform.set_wallclock(now.tv_sec);
 183 }
 184
 185 /* not static: needed by APM */
 186 void read_persistent_clock(struct timespec *ts)
 187 {
 188         unsigned long retval;
 189
 190         retval = x86_platform.get_wallclock();
 191
 192         ts->tv_sec = retval;
 193         ts->tv_nsec = 0;
 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         static const char *ids[] __initconst =
 227             { "PNP0b00", "PNP0b01", "PNP0b02", };
 228         struct pnp_dev *dev;
 229         struct pnp_id *id;
 230         int i;
 231
 232         pnp_for_each_dev(dev) {
 233                 for (id = dev->id; id; id = id->next) {
 234                         for (i = 0; i < ARRAY_SIZE(ids); i++) {
 235                                 if (compare_pnp_id(id, ids[i]) != 0)
 236                                         return 0;
 237                         }
 238                 }
 239         }
 240 #endif
 241         if (of_have_populated_dt())
 242                 return 0;
 243
 244         platform_device_register(&rtc_device);
 245         dev_info(&rtc_device.dev,
 246                  "registered platform RTC device (no PNP device found)\n");
 247
 248         return 0;
 249 }
 250 device_initcall(add_rtc_cmos);