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 /* last time the RTC got updated */
  24 static long last_rtc_update;
  25
  26 /* time for RTC to update itself in ioclks */
  27 static unsigned long mn10300_rtc_update_period;
  28
  29 /*
  30  * read the current RTC time
  31  */
  32 unsigned long __init get_initial_rtc_time(void)
  33 {
  34         struct rtc_time tm;
  35
  36         get_rtc_time(&tm);
  37
  38         return mktime(tm.tm_year, tm.tm_mon, tm.tm_mday,
  39                       tm.tm_hour, tm.tm_min, tm.tm_sec);
  40 }
  41
  42 /*
  43  * In order to set the CMOS clock precisely, set_rtc_mmss has to be called 500
  44  * ms after the second nowtime has started, because when nowtime is written
  45  * into the registers of the CMOS clock, it will jump to the next second
  46  * precisely 500 ms later.  Check the Motorola MC146818A or Dallas DS12887 data
  47  * sheet for details.
  48  *
  49  * BUG: This routine does not handle hour overflow properly; it just
  50  *      sets the minutes. Usually you'll only notice that after reboot!
  51  */
  52 static int set_rtc_mmss(unsigned long nowtime)
  53 {
  54         unsigned char save_control, save_freq_select;
  55         int retval = 0;
  56         int real_seconds, real_minutes, cmos_minutes;
  57
  58         /* gets recalled with irq locally disabled */
  59         spin_lock(&rtc_lock);
  60         save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being
  61                                                 * set */
  62         CMOS_WRITE(save_control | RTC_SET, RTC_CONTROL);
  63
  64         save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset
  65                                                         * prescaler */
  66         CMOS_WRITE(save_freq_select | RTC_DIV_RESET2, RTC_FREQ_SELECT);
  67
  68         cmos_minutes = CMOS_READ(RTC_MINUTES);
  69         if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  70                 BCD_TO_BIN(cmos_minutes);
  71
  72         /*
  73          * since we're only adjusting minutes and seconds,
  74          * don't interfere with hour overflow. This avoids
  75          * messing with unknown time zones but requires your
  76          * RTC not to be off by more than 15 minutes
  77          */
  78         real_seconds = nowtime % 60;
  79         real_minutes = nowtime / 60;
  80         if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1)
  81                 /* correct for half hour time zone */
  82                 real_minutes += 30;
  83         real_minutes %= 60;
  84
  85         if (abs(real_minutes - cmos_minutes) < 30) {
  86                 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  87                         BIN_TO_BCD(real_seconds);
  88                         BIN_TO_BCD(real_minutes);
  89                 }
  90                 CMOS_WRITE(real_seconds, RTC_SECONDS);
  91                 CMOS_WRITE(real_minutes, RTC_MINUTES);
  92         } else {
  93                 printk(KERN_WARNING
  94                        "set_rtc_mmss: can't update from %d to %d\n",
  95                        cmos_minutes, real_minutes);
  96                 retval = -1;
  97         }
  98
  99         /* The following flags have to be released exactly in this order,
 100          * otherwise the DS12887 (popular MC146818A clone with integrated
 101          * battery and quartz) will not reset the oscillator and will not
 102          * update precisely 500 ms later. You won't find this mentioned in
 103          * the Dallas Semiconductor data sheets, but who believes data
 104          * sheets anyway ...                           -- Markus Kuhn
 105          */
 106         CMOS_WRITE(save_control, RTC_CONTROL);
 107         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
 108         spin_unlock(&rtc_lock);
 109
 110         return retval;
 111 }
 112
 113 void check_rtc_time(void)
 114 {
 115         /* the RTC clock just finished ticking over again this second
 116          * - if we have an externally synchronized Linux clock, then update
 117          *   RTC clock accordingly every ~11 minutes. set_rtc_mmss() has to be
 118          *   called as close as possible to 500 ms before the new second starts.
 119          */
 120         if ((time_status & STA_UNSYNC) == 0 &&
 121             xtime.tv_sec > last_rtc_update + 660 &&
 122             xtime.tv_nsec / 1000 >= 500000 - ((unsigned) TICK_SIZE) / 2 &&
 123             xtime.tv_nsec / 1000 <= 500000 + ((unsigned) TICK_SIZE) / 2
 124             ) {
 125                 if (set_rtc_mmss(xtime.tv_sec) == 0)
 126                         last_rtc_update = xtime.tv_sec;
 127                 else
 128                         /* do it again in 60s */
 129                         last_rtc_update = xtime.tv_sec - 600;
 130         }
 131 }
 132
 133 /*
 134  * calibrate the TSC clock against the RTC
 135  */
 136 void __init calibrate_clock(void)
 137 {
 138         unsigned long count0, counth, count1;
 139         unsigned char status;
 140
 141         /* make sure the RTC is running and is set to operate in 24hr mode */
 142         status = RTSRC;
 143         RTCRB |= RTCRB_SET;
 144         RTCRB |= RTCRB_TM_24HR;
 145         RTCRA |= RTCRA_DVR;
 146         RTCRA &= ~RTCRA_DVR;
 147         RTCRB &= ~RTCRB_SET;
 148
 149         /* work out the clock speed by counting clock cycles between ends of
 150          * the RTC update cycle - track the RTC through one complete update
 151          * cycle (1 second)
 152          */
 153         startup_timestamp_counter();
 154
 155         while (!(RTCRA & RTCRA_UIP)) {}
 156         while ((RTCRA & RTCRA_UIP)) {}
 157
 158         count0 = TMTSCBC;
 159
 160         while (!(RTCRA & RTCRA_UIP)) {}
 161
 162         counth = TMTSCBC;
 163
 164         while ((RTCRA & RTCRA_UIP)) {}
 165
 166         count1 = TMTSCBC;
 167
 168         shutdown_timestamp_counter();
 169
 170         MN10300_TSCCLK = count0 - count1; /* the timers count down */
 171         mn10300_rtc_update_period = counth - count1;
 172         MN10300_TSC_PER_HZ = MN10300_TSCCLK / HZ;
 173 }