1 files changed, 166 insertions, 0 deletions

diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
new file mode 100644
index 000000000000..45bf54d9f4c5
--- /dev/null
+++ b/arch/x86/kernel/rtc.c
@@ -0,0 +1,166 @@
+/*
+ * RTC related functions
+ */
+#include <linux/bcd.h>
+#include <linux/mc146818rtc.h>
+
+#include <asm/time.h>
+
+/*
+ * In order to set the CMOS clock precisely, set_rtc_mmss has to be
+ * called 500 ms after the second nowtime has started, because when
+ * nowtime is written into the registers of the CMOS clock, it will
+ * jump to the next second precisely 500 ms later. Check the Motorola
+ * MC146818A or Dallas DS12887 data sheet for details.
+ *
+ * BUG: This routine does not handle hour overflow properly; it just
+ *      sets the minutes. Usually you'll only notice that after reboot!
+ */
+int mach_set_rtc_mmss(unsigned long nowtime)
+{
+        int retval = 0;
+        int real_seconds, real_minutes, cmos_minutes;
+        unsigned char save_control, save_freq_select;
+
+        save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being set */
+        CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
+
+        save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset prescaler */
+        CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
+
+        cmos_minutes = CMOS_READ(RTC_MINUTES);
+        if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
+                BCD_TO_BIN(cmos_minutes);
+
+        /*
+         * since we're only adjusting minutes and seconds,
+         * don't interfere with hour overflow. This avoids
+         * messing with unknown time zones but requires your
+         * RTC not to be off by more than 15 minutes
+         */
+        real_seconds = nowtime % 60;
+        real_minutes = nowtime / 60;
+        if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
+                real_minutes += 30;             /* correct for half hour time zone */
+        real_minutes %= 60;
+
+        if (abs(real_minutes - cmos_minutes) < 30) {
+                if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
+                        BIN_TO_BCD(real_seconds);
+                        BIN_TO_BCD(real_minutes);
+                }
+                CMOS_WRITE(real_seconds,RTC_SECONDS);
+                CMOS_WRITE(real_minutes,RTC_MINUTES);
+        } else {
+                printk(KERN_WARNING
+                       "set_rtc_mmss: can't update from %d to %d\n",
+                       cmos_minutes, real_minutes);
+                retval = -1;
+        }
+
+        /* The following flags have to be released exactly in this order,
+         * otherwise the DS12887 (popular MC146818A clone with integrated
+         * battery and quartz) will not reset the oscillator and will not
+         * update precisely 500 ms later. You won't find this mentioned in
+         * the Dallas Semiconductor data sheets, but who believes data
+         * sheets anyway ...                           -- Markus Kuhn
+         */
+        CMOS_WRITE(save_control, RTC_CONTROL);
+        CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
+
+        return retval;
+}
+
+unsigned long mach_get_cmos_time(void)
+{
+        unsigned int year, mon, day, hour, min, sec;
+
+        do {
+                sec = CMOS_READ(RTC_SECONDS);
+                min = CMOS_READ(RTC_MINUTES);
+                hour = CMOS_READ(RTC_HOURS);
+                day = CMOS_READ(RTC_DAY_OF_MONTH);
+                mon = CMOS_READ(RTC_MONTH);
+                year = CMOS_READ(RTC_YEAR);
+        } while (sec != CMOS_READ(RTC_SECONDS));
+
+        if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
+                BCD_TO_BIN(sec);
+                BCD_TO_BIN(min);
+                BCD_TO_BIN(hour);
+                BCD_TO_BIN(day);
+                BCD_TO_BIN(mon);
+                BCD_TO_BIN(year);
+        }
+
+        year += 1900;
+        if (year < 1970)
+                year += 100;
+
+        return mktime(year, mon, day, hour, min, sec);
+}
+
+DEFINE_SPINLOCK(rtc_lock);
+EXPORT_SYMBOL(rtc_lock);
+
+/*
+ * This is a special lock that is owned by the CPU and holds the index
+ * register we are working with.  It is required for NMI access to the
+ * CMOS/RTC registers.  See include/asm-i386/mc146818rtc.h for details.
+ */
+volatile unsigned long cmos_lock = 0;
+EXPORT_SYMBOL(cmos_lock);
+
+/* Routines for accessing the CMOS RAM/RTC. */
+unsigned char rtc_cmos_read(unsigned char addr)
+{
+        unsigned char val;
+
+        lock_cmos_prefix(addr);
+        outb_p(addr, RTC_PORT(0));
+        val = inb_p(RTC_PORT(1));
+        lock_cmos_suffix(addr);
+        return val;
+}
+EXPORT_SYMBOL(rtc_cmos_read);
+
+void rtc_cmos_write(unsigned char val, unsigned char addr)
+{
+        lock_cmos_prefix(addr);
+        outb_p(addr, RTC_PORT(0));
+        outb_p(val, RTC_PORT(1));
+        lock_cmos_suffix(addr);
+}
+EXPORT_SYMBOL(rtc_cmos_write);
+
+static int set_rtc_mmss(unsigned long nowtime)
+{
+        int retval;
+        unsigned long flags;
+
+        /* gets recalled with irq locally disabled */
+        /* XXX - does irqsave resolve this? -johnstul */
+        spin_lock_irqsave(&rtc_lock, flags);
+        retval = set_wallclock(nowtime);
+        spin_unlock_irqrestore(&rtc_lock, flags);
+
+        return retval;
+}
+
+/* not static: needed by APM */
+unsigned long read_persistent_clock(void)
+{
+        unsigned long retval;
+        unsigned long flags;
+
+        spin_lock_irqsave(&rtc_lock, flags);
+        retval = get_wallclock();
+        spin_unlock_irqrestore(&rtc_lock, flags);
+
+        return retval;
+}
+
+int update_persistent_clock(struct timespec now)
+{
+        return set_rtc_mmss(now.tv_sec);
+}