release/src-rt-6.x.4708/linux/linux-2.6.36/arch/mn10300/kernel/rtc.c

   1 /* MN10300 RTC management
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11 #include <linux/kernel.h>
  12 #include <linux/module.h>
  13 #include <linux/init.h>
  14 #include <linux/mc146818rtc.h>
  15 #include <linux/bcd.h>
  16 #include <linux/timex.h>
  17 #include <asm/rtc-regs.h>
  18 #include <asm/rtc.h>
  19
  20 DEFINE_SPINLOCK(rtc_lock);
  21 EXPORT_SYMBOL(rtc_lock);
  22
  23 /* time for RTC to update itself in ioclks */
  24 static unsigned long mn10300_rtc_update_period;
  25
  26 void read_persistent_clock(struct timespec *ts)
  27 {
  28         struct rtc_time tm;
  29
  30         get_rtc_time(&tm);
  31
  32         ts->tv_sec = mktime(tm.tm_year, tm.tm_mon, tm.tm_mday,
  33                       tm.tm_hour, tm.tm_min, tm.tm_sec);
  34         ts->tv_nsec = 0;
  35 }
  36
  37 /*
  38  * In order to set the CMOS clock precisely, set_rtc_mmss has to be called 500
  39  * ms after the second nowtime has started, because when nowtime is written
  40  * into the registers of the CMOS clock, it will jump to the next second
  41  * precisely 500 ms later.  Check the Motorola MC146818A or Dallas DS12887 data
  42  * sheet for details.
  43  *
  44  * BUG: This routine does not handle hour overflow properly; it just
  45  *      sets the minutes. Usually you'll only notice that after reboot!
  46  */
  47 static int set_rtc_mmss(unsigned long nowtime)
  48 {
  49         unsigned char save_control, save_freq_select;
  50         int retval = 0;
  51         int real_seconds, real_minutes, cmos_minutes;
  52
  53         /* gets recalled with irq locally disabled */
  54         spin_lock(&rtc_lock);
  55         save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being
  56                                                 * set */
  57         CMOS_WRITE(save_control | RTC_SET, RTC_CONTROL);
  58
  59         save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset
  60                                                         * prescaler */
  61         CMOS_WRITE(save_freq_select | RTC_DIV_RESET2, RTC_FREQ_SELECT);
  62
  63         cmos_minutes = CMOS_READ(RTC_MINUTES);
  64         if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  65                 cmos_minutes = bcd2bin(cmos_minutes);
  66
  67         /*
  68          * since we're only adjusting minutes and seconds,
  69          * don't interfere with hour overflow. This avoids
  70          * messing with unknown time zones but requires your
  71          * RTC not to be off by more than 15 minutes
  72          */
  73         real_seconds = nowtime % 60;
  74         real_minutes = nowtime / 60;
  75         if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1)
  76                 /* correct for half hour time zone */
  77                 real_minutes += 30;
  78         real_minutes %= 60;
  79
  80         if (abs(real_minutes - cmos_minutes) < 30) {
  81                 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  82                         real_seconds = bin2bcd(real_seconds);
  83                         real_minutes = bin2bcd(real_minutes);
  84                 }
  85                 CMOS_WRITE(real_seconds, RTC_SECONDS);
  86                 CMOS_WRITE(real_minutes, RTC_MINUTES);
  87         } else {
  88                 printk(KERN_WARNING
  89                        "set_rtc_mmss: can't update from %d to %d\n",
  90                        cmos_minutes, real_minutes);
  91                 retval = -1;
  92         }
  93
  94         /* The following flags have to be released exactly in this order,
  95          * otherwise the DS12887 (popular MC146818A clone with integrated
  96          * battery and quartz) will not reset the oscillator and will not
  97          * update precisely 500 ms later. You won't find this mentioned in
  98          * the Dallas Semiconductor data sheets, but who believes data
  99          * sheets anyway ...                           -- Markus Kuhn
 100          */
 101         CMOS_WRITE(save_control, RTC_CONTROL);
 102         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
 103         spin_unlock(&rtc_lock);
 104
 105         return retval;
 106 }
 107
 108 int update_persistent_clock(struct timespec now)
 109 {
 110         return set_rtc_mmss(now.tv_sec);
 111 }
 112
 113 /*
 114  * calibrate the TSC clock against the RTC
 115  */
 116 void __init calibrate_clock(void)
 117 {
 118         unsigned long count0, counth, count1;
 119         unsigned char status;
 120
 121         /* make sure the RTC is running and is set to operate in 24hr mode */
 122         status = RTSRC;
 123         RTCRB |= RTCRB_SET;
 124         RTCRB |= RTCRB_TM_24HR;
 125         RTCRA |= RTCRA_DVR;
 126         RTCRA &= ~RTCRA_DVR;
 127         RTCRB &= ~RTCRB_SET;
 128
 129         /* work out the clock speed by counting clock cycles between ends of
 130          * the RTC update cycle - track the RTC through one complete update
 131          * cycle (1 second)
 132          */
 133         startup_timestamp_counter();
 134
 135         while (!(RTCRA & RTCRA_UIP)) {}
 136         while ((RTCRA & RTCRA_UIP)) {}
 137
 138         count0 = TMTSCBC;
 139
 140         while (!(RTCRA & RTCRA_UIP)) {}
 141
 142         counth = TMTSCBC;
 143
 144         while ((RTCRA & RTCRA_UIP)) {}
 145
 146         count1 = TMTSCBC;
 147
 148         shutdown_timestamp_counter();
 149
 150         MN10300_TSCCLK = count0 - count1; /* the timers count down */
 151         mn10300_rtc_update_period = counth - count1;
 152         MN10300_TSC_PER_HZ = MN10300_TSCCLK / HZ;
 153 }