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 #include <asm/mrst.h>
  16
  17 #ifdef CONFIG_X86_32
  18 /*
  19  * This is a special lock that is owned by the CPU and holds the index
  20  * register we are working with.  It is required for NMI access to the
  21  * CMOS/RTC registers.  See include/asm-i386/mc146818rtc.h for details.
  22  */
  23 volatile unsigned long cmos_lock;
  24 EXPORT_SYMBOL(cmos_lock);
  25 #endif /* CONFIG_X86_32 */
  26
  27 /* For two digit years assume time is always after that */
  28 #define CMOS_YEARS_OFFS 2000
  29
  30 DEFINE_SPINLOCK(rtc_lock);
  31 EXPORT_SYMBOL(rtc_lock);
  32
  33 /*
  34  * In order to set the CMOS clock precisely, set_rtc_mmss has to be
  35  * called 500 ms after the second nowtime has started, because when
  36  * nowtime is written into the registers of the CMOS clock, it will
  37  * jump to the next second precisely 500 ms later. Check the Motorola
  38  * MC146818A or Dallas DS12887 data sheet for details.
  39  *
  40  * BUG: This routine does not handle hour overflow properly; it just
  41  *      sets the minutes. Usually you'll only notice that after reboot!
  42  */
  43 int mach_set_rtc_mmss(unsigned long nowtime)
  44 {
  45         int real_seconds, real_minutes, cmos_minutes;
  46         unsigned char save_control, save_freq_select;
  47         unsigned long flags;
  48         int retval = 0;
  49
  50         spin_lock_irqsave(&rtc_lock, flags);
  51
  52          /* tell the clock it's being set */
  53         save_control = CMOS_READ(RTC_CONTROL);
  54         CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
  55
  56         /* stop and reset prescaler */
  57         save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
  58         CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
  59
  60         cmos_minutes = CMOS_READ(RTC_MINUTES);
  61         if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  62                 cmos_minutes = bcd2bin(cmos_minutes);
  63
  64         /*
  65          * since we're only adjusting minutes and seconds,
  66          * don't interfere with hour overflow. This avoids
  67          * messing with unknown time zones but requires your
  68          * RTC not to be off by more than 15 minutes
  69          */
  70         real_seconds = nowtime % 60;
  71         real_minutes = nowtime / 60;
  72         /* correct for half hour time zone */
  73         if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
  74                 real_minutes += 30;
  75         real_minutes %= 60;
  76
  77         if (abs(real_minutes - cmos_minutes) < 30) {
  78                 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  79                         real_seconds = bin2bcd(real_seconds);
  80                         real_minutes = bin2bcd(real_minutes);
  81                 }
  82                 CMOS_WRITE(real_seconds, RTC_SECONDS);
  83                 CMOS_WRITE(real_minutes, RTC_MINUTES);
  84         } else {
  85                 printk_once(KERN_NOTICE
  86                        "set_rtc_mmss: can't update from %d to %d\n",
  87                        cmos_minutes, real_minutes);
  88                 retval = -1;
  89         }
  90
  91         /* The following flags have to be released exactly in this order,
  92          * otherwise the DS12887 (popular MC146818A clone with integrated
  93          * battery and quartz) will not reset the oscillator and will not
  94          * update precisely 500 ms later. You won't find this mentioned in
  95          * the Dallas Semiconductor data sheets, but who believes data
  96          * sheets anyway ...                           -- Markus Kuhn
  97          */
  98         CMOS_WRITE(save_control, RTC_CONTROL);
  99         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
 100
 101         spin_unlock_irqrestore(&rtc_lock, flags);
 102
 103         return retval;
 104 }
 105
 106 unsigned long mach_get_cmos_time(void)
 107 {
 108         unsigned int status, year, mon, day, hour, min, sec, century = 0;
 109         unsigned long flags;
 110
 111         spin_lock_irqsave(&rtc_lock, flags);
 112
 113         /*
 114          * If UIP is clear, then we have >= 244 microseconds before
 115          * RTC registers will be updated.  Spec sheet says that this
 116          * is the reliable way to read RTC - registers. If UIP is set
 117          * then the register access might be invalid.
 118          */
 119         while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
 120                 cpu_relax();
 121
 122         sec = CMOS_READ(RTC_SECONDS);
 123         min = CMOS_READ(RTC_MINUTES);
 124         hour = CMOS_READ(RTC_HOURS);
 125         day = CMOS_READ(RTC_DAY_OF_MONTH);
 126         mon = CMOS_READ(RTC_MONTH);
 127         year = CMOS_READ(RTC_YEAR);
 128
 129 #ifdef CONFIG_ACPI
 130         if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
 131             acpi_gbl_FADT.century)
 132                 century = CMOS_READ(acpi_gbl_FADT.century);
 133 #endif
 134
 135         status = CMOS_READ(RTC_CONTROL);
 136         WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY));
 137
 138         spin_unlock_irqrestore(&rtc_lock, flags);
 139
 140         if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) {
 141                 sec = bcd2bin(sec);
 142                 min = bcd2bin(min);
 143                 hour = bcd2bin(hour);
 144                 day = bcd2bin(day);
 145                 mon = bcd2bin(mon);
 146                 year = bcd2bin(year);
 147         }
 148
 149         if (century) {
 150                 century = bcd2bin(century);
 151                 year += century * 100;
 152                 printk(KERN_INFO "Extended CMOS year: %d\n", century * 100);
 153         } else
 154                 year += CMOS_YEARS_OFFS;
 155
 156         return mktime(year, mon, day, hour, min, sec);
 157 }
 158
 159 /* Routines for accessing the CMOS RAM/RTC. */
 160 unsigned char rtc_cmos_read(unsigned char addr)
 161 {
 162         unsigned char val;
 163
 164         lock_cmos_prefix(addr);
 165         outb(addr, RTC_PORT(0));
 166         val = inb(RTC_PORT(1));
 167         lock_cmos_suffix(addr);
 168
 169         return val;
 170 }
 171 EXPORT_SYMBOL(rtc_cmos_read);
 172
 173 void rtc_cmos_write(unsigned char val, unsigned char addr)
 174 {
 175         lock_cmos_prefix(addr);
 176         outb(addr, RTC_PORT(0));
 177         outb(val, RTC_PORT(1));
 178         lock_cmos_suffix(addr);
 179 }
 180 EXPORT_SYMBOL(rtc_cmos_write);
 181
 182 int update_persistent_clock(struct timespec now)
 183 {
 184         return x86_platform.set_wallclock(now.tv_sec);
 185 }
 186
 187 /* not static: needed by APM */
 188 void read_persistent_clock(struct timespec *ts)
 189 {
 190         unsigned long retval;
 191
 192         retval = x86_platform.get_wallclock();
 193
 194         ts->tv_sec = retval;
 195         ts->tv_nsec = 0;
 196 }
 197
 198
 199 static struct resource rtc_resources[] = {
 200         [0] = {
 201                 .start  = RTC_PORT(0),
 202                 .end    = RTC_PORT(1),
 203                 .flags  = IORESOURCE_IO,
 204         },
 205         [1] = {
 206                 .start  = RTC_IRQ,
 207                 .end    = RTC_IRQ,
 208                 .flags  = IORESOURCE_IRQ,
 209         }
 210 };
 211
 212 static struct platform_device rtc_device = {
 213         .name           = "rtc_cmos",
 214         .id             = -1,
 215         .resource       = rtc_resources,
 216         .num_resources  = ARRAY_SIZE(rtc_resources),
 217 };
 218
 219 static __init int add_rtc_cmos(void)
 220 {
 221 #ifdef CONFIG_PNP
 222         static const char * const  const ids[] __initconst =
 223             { "PNP0b00", "PNP0b01", "PNP0b02", };
 224         struct pnp_dev *dev;
 225         struct pnp_id *id;
 226         int i;
 227
 228         pnp_for_each_dev(dev) {
 229                 for (id = dev->id; id; id = id->next) {
 230                         for (i = 0; i < ARRAY_SIZE(ids); i++) {
 231                                 if (compare_pnp_id(id, ids[i]) != 0)
 232                                         return 0;
 233                         }
 234                 }
 235         }
 236 #endif
 237         if (of_have_populated_dt())
 238                 return 0;
 239
 240         /* Intel MID platforms don't have ioport rtc */
 241         if (mrst_identify_cpu())
 242                 return -ENODEV;
 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);