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-rw-r--r--arch/mn10300/kernel/rtc.c173
1 files changed, 173 insertions, 0 deletions
diff --git a/arch/mn10300/kernel/rtc.c b/arch/mn10300/kernel/rtc.c
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+/* MN10300 RTC management
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/mc146818rtc.h>
+#include <linux/bcd.h>
+#include <linux/timex.h>
+#include <asm/rtc-regs.h>
+#include <asm/rtc.h>
+
+DEFINE_SPINLOCK(rtc_lock);
+EXPORT_SYMBOL(rtc_lock);
+
+/* last time the RTC got updated */
+static long last_rtc_update;
+
+/* time for RTC to update itself in ioclks */
+static unsigned long mn10300_rtc_update_period;
+
+/*
+ * read the current RTC time
+ */
+unsigned long __init get_initial_rtc_time(void)
+{
+ struct rtc_time tm;
+
+ get_rtc_time(&tm);
+
+ return mktime(tm.tm_year, tm.tm_mon, tm.tm_mday,
+ tm.tm_hour, tm.tm_min, tm.tm_sec);
+}
+
+/*
+ * 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!
+ */
+static int set_rtc_mmss(unsigned long nowtime)
+{
+ unsigned char save_control, save_freq_select;
+ int retval = 0;
+ int real_seconds, real_minutes, cmos_minutes;
+
+ /* gets recalled with irq locally disabled */
+ spin_lock(&rtc_lock);
+ 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)
+ /* correct for half hour time zone */
+ real_minutes += 30;
+ 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);
+ spin_unlock(&rtc_lock);
+
+ return retval;
+}
+
+void check_rtc_time(void)
+{
+ /* the RTC clock just finished ticking over again this second
+ * - if we have an externally synchronized Linux clock, then update
+ * RTC clock accordingly every ~11 minutes. set_rtc_mmss() has to be
+ * called as close as possible to 500 ms before the new second starts.
+ */
+ if ((time_status & STA_UNSYNC) == 0 &&
+ xtime.tv_sec > last_rtc_update + 660 &&
+ xtime.tv_nsec / 1000 >= 500000 - ((unsigned) TICK_SIZE) / 2 &&
+ xtime.tv_nsec / 1000 <= 500000 + ((unsigned) TICK_SIZE) / 2
+ ) {
+ if (set_rtc_mmss(xtime.tv_sec) == 0)
+ last_rtc_update = xtime.tv_sec;
+ else
+ /* do it again in 60s */
+ last_rtc_update = xtime.tv_sec - 600;
+ }
+}
+
+/*
+ * calibrate the TSC clock against the RTC
+ */
+void __init calibrate_clock(void)
+{
+ unsigned long count0, counth, count1;
+ unsigned char status;
+
+ /* make sure the RTC is running and is set to operate in 24hr mode */
+ status = RTSRC;
+ RTCRB |= RTCRB_SET;
+ RTCRB |= RTCRB_TM_24HR;
+ RTCRA |= RTCRA_DVR;
+ RTCRA &= ~RTCRA_DVR;
+ RTCRB &= ~RTCRB_SET;
+
+ /* work out the clock speed by counting clock cycles between ends of
+ * the RTC update cycle - track the RTC through one complete update
+ * cycle (1 second)
+ */
+ startup_timestamp_counter();
+
+ while (!(RTCRA & RTCRA_UIP)) {}
+ while ((RTCRA & RTCRA_UIP)) {}
+
+ count0 = TMTSCBC;
+
+ while (!(RTCRA & RTCRA_UIP)) {}
+
+ counth = TMTSCBC;
+
+ while ((RTCRA & RTCRA_UIP)) {}
+
+ count1 = TMTSCBC;
+
+ shutdown_timestamp_counter();
+
+ MN10300_TSCCLK = count0 - count1; /* the timers count down */
+ mn10300_rtc_update_period = counth - count1;
+ MN10300_TSC_PER_HZ = MN10300_TSCCLK / HZ;
+}