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/export.h>
   9 #include <linux/pnp.h>
  10 #include <linux/of.h>
  11
  12 #include <asm/vsyscall.h>
  13 #include <asm/x86_init.h>
  14 #include <asm/time.h>
  15
  16 #ifdef CONFIG_X86_32
  17 /*
  18  * This is a special lock that is owned by the CPU and holds the index
  19  * register we are working with.  It is required for NMI access to the
  20  * CMOS/RTC registers.  See include/asm-i386/mc146818rtc.h for details.
  21  */
  22 volatile unsigned long cmos_lock;
  23 EXPORT_SYMBOL(cmos_lock);
  24 #endif /* CONFIG_X86_32 */
  25
  26 /* For two digit years assume time is always after that */
  27 #define CMOS_YEARS_OFFS 2000
  28
  29 DEFINE_SPINLOCK(rtc_lock);
  30 EXPORT_SYMBOL(rtc_lock);
  31
  32 /*
  33  * In order to set the CMOS clock precisely, set_rtc_mmss has to be
  34  * called 500 ms after the second nowtime has started, because when
  35  * nowtime is written into the registers of the CMOS clock, it will
  36  * jump to the next second precisely 500 ms later. Check the Motorola
  37  * MC146818A or Dallas DS12887 data sheet for details.
  38  *
  39  * BUG: This routine does not handle hour overflow properly; it just
  40  *      sets the minutes. Usually you'll only notice that after reboot!
  41  */
  42 int mach_set_rtc_mmss(unsigned long nowtime)
  43 {
  44         int real_seconds, real_minutes, cmos_minutes;
  45         unsigned char save_control, save_freq_select;
  46         int retval = 0;
  47
  48          /* tell the clock it's being set */
  49         save_control = CMOS_READ(RTC_CONTROL);
  50         CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
  51
  52         /* stop and reset prescaler */
  53         save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
  54         CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
  55
  56         cmos_minutes = CMOS_READ(RTC_MINUTES);
  57         if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  58                 cmos_minutes = bcd2bin(cmos_minutes);
  59
  60         /*
  61          * since we're only adjusting minutes and seconds,
  62          * don't interfere with hour overflow. This avoids
  63          * messing with unknown time zones but requires your
  64          * RTC not to be off by more than 15 minutes
  65          */
  66         real_seconds = nowtime % 60;
  67         real_minutes = nowtime / 60;
  68         /* correct for half hour time zone */
  69         if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
  70                 real_minutes += 30;
  71         real_minutes %= 60;
  72
  73         if (abs(real_minutes - cmos_minutes) < 30) {
  74                 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  75                         real_seconds = bin2bcd(real_seconds);
  76                         real_minutes = bin2bcd(real_minutes);
  77                 }
  78                 CMOS_WRITE(real_seconds, RTC_SECONDS);
  79                 CMOS_WRITE(real_minutes, RTC_MINUTES);
  80         } else {
  81                 printk_once(KERN_NOTICE
  82                        "set_rtc_mmss: can't update from %d to %d\n",
  83                        cmos_minutes, real_minutes);
  84                 retval = -1;
  85         }
  86
  87         /* The following flags have to be released exactly in this order,
  88          * otherwise the DS12887 (popular MC146818A clone with integrated
  89          * battery and quartz) will not reset the oscillator and will not
  90          * update precisely 500 ms later. You won't find this mentioned in
  91          * the Dallas Semiconductor data sheets, but who believes data
  92          * sheets anyway ...                           -- Markus Kuhn
  93          */
  94         CMOS_WRITE(save_control, RTC_CONTROL);
  95         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
  96
  97         return retval;
  98 }
  99
 100 unsigned long mach_get_cmos_time(void)
 101 {
 102         unsigned int status, year, mon, day, hour, min, sec, century = 0;
 103
 104         /*
 105          * If UIP is clear, then we have >= 244 microseconds before
 106          * RTC registers will be updated.  Spec sheet says that this
 107          * is the reliable way to read RTC - registers. If UIP is set
 108          * then the register access might be invalid.
 109          */
 110         while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
 111                 cpu_relax();
 112
 113         sec = CMOS_READ(RTC_SECONDS);
 114         min = CMOS_READ(RTC_MINUTES);
 115         hour = CMOS_READ(RTC_HOURS);
 116         day = CMOS_READ(RTC_DAY_OF_MONTH);
 117         mon = CMOS_READ(RTC_MONTH);
 118         year = CMOS_READ(RTC_YEAR);
 119
 120 #ifdef CONFIG_ACPI
 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         status = CMOS_READ(RTC_CONTROL);
 127         WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY));
 128
 129         if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) {
 130                 sec = bcd2bin(sec);
 131                 min = bcd2bin(min);
 132                 hour = bcd2bin(hour);
 133                 day = bcd2bin(day);
 134                 mon = bcd2bin(mon);
 135                 year = bcd2bin(year);
 136         }
 137
 138         if (century) {
 139                 century = bcd2bin(century);
 140                 year += century * 100;
 141                 printk(KERN_INFO "Extended CMOS year: %d\n", century * 100);
 142         } else
 143                 year += CMOS_YEARS_OFFS;
 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(addr, RTC_PORT(0));
 155         val = inb(RTC_PORT(1));
 156         lock_cmos_suffix(addr);
 157
 158         return val;
 159 }
 160 EXPORT_SYMBOL(rtc_cmos_read);
 161
 162 void rtc_cmos_write(unsigned char val, unsigned char addr)
 163 {
 164         lock_cmos_prefix(addr);
 165         outb(addr, RTC_PORT(0));
 166         outb(val, RTC_PORT(1));
 167         lock_cmos_suffix(addr);
 168 }
 169 EXPORT_SYMBOL(rtc_cmos_write);
 170
 171 int update_persistent_clock(struct timespec now)
 172 {
 173         unsigned long flags;
 174         int retval;
 175
 176         spin_lock_irqsave(&rtc_lock, flags);
 177         retval = x86_platform.set_wallclock(now.tv_sec);
 178         spin_unlock_irqrestore(&rtc_lock, flags);
 179
 180         return retval;
 181 }
 182
 183 /* not static: needed by APM */
 184 void read_persistent_clock(struct timespec *ts)
 185 {
 186         unsigned long retval, flags;
 187
 188         spin_lock_irqsave(&rtc_lock, flags);
 189         retval = x86_platform.get_wallclock();
 190         spin_unlock_irqrestore(&rtc_lock, flags);
 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);