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 /*
  24  * Read the current RTC time
  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_nsec = 0;
  33         ts->tv_sec = mktime(tm.tm_year, tm.tm_mon, tm.tm_mday,
  34                             tm.tm_hour, tm.tm_min, tm.tm_sec);
  35
  36         /* if rtc is way off in the past, set something reasonable */
  37         if (ts->tv_sec < 0)
  38                 ts->tv_sec = mktime(2009, 1, 1, 12, 0, 0);
  39 }
  40
  41 /*
  42  * In order to set the CMOS clock precisely, set_rtc_mmss has to be called 500
  43  * ms after the second nowtime has started, because when nowtime is written
  44  * into the registers of the CMOS clock, it will jump to the next second
  45  * precisely 500 ms later.  Check the Motorola MC146818A or Dallas DS12887 data
  46  * sheet for details.
  47  *
  48  * BUG: This routine does not handle hour overflow properly; it just
  49  *      sets the minutes. Usually you'll only notice that after reboot!
  50  */
  51 static int set_rtc_mmss(unsigned long nowtime)
  52 {
  53         unsigned char save_control, save_freq_select;
  54         int retval = 0;
  55         int real_seconds, real_minutes, cmos_minutes;
  56
  57         /* gets recalled with irq locally disabled */
  58         spin_lock(&rtc_lock);
  59         save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being
  60                                                 * set */
  61         CMOS_WRITE(save_control | RTC_SET, RTC_CONTROL);
  62
  63         save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset
  64                                                         * prescaler */
  65         CMOS_WRITE(save_freq_select | RTC_DIV_RESET2, RTC_FREQ_SELECT);
  66
  67         cmos_minutes = CMOS_READ(RTC_MINUTES);
  68         if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
  69                 cmos_minutes = bcd2bin(cmos_minutes);
  70
  71         /*
  72          * since we're only adjusting minutes and seconds,
  73          * don't interfere with hour overflow. This avoids
  74          * messing with unknown time zones but requires your
  75          * RTC not to be off by more than 15 minutes
  76          */
  77         real_seconds = nowtime % 60;
  78         real_minutes = nowtime / 60;
  79         if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1)
  80                 /* correct for half hour time zone */
  81                 real_minutes += 30;
  82         real_minutes %= 60;
  83
  84         if (abs(real_minutes - cmos_minutes) < 30) {
  85                 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
  86                         real_seconds = bin2bcd(real_seconds);
  87                         real_minutes = bin2bcd(real_minutes);
  88                 }
  89                 CMOS_WRITE(real_seconds, RTC_SECONDS);
  90                 CMOS_WRITE(real_minutes, RTC_MINUTES);
  91         } else {
  92                 printk_once(KERN_NOTICE
  93                        "set_rtc_mmss: can't update from %d to %d\n",
  94                        cmos_minutes, real_minutes);
  95                 retval = -1;
  96         }
  97
  98         /* The following flags have to be released exactly in this order,
  99          * otherwise the DS12887 (popular MC146818A clone with integrated
 100          * battery and quartz) will not reset the oscillator and will not
 101          * update precisely 500 ms later. You won't find this mentioned in
 102          * the Dallas Semiconductor data sheets, but who believes data
 103          * sheets anyway ...                           -- Markus Kuhn
 104          */
 105         CMOS_WRITE(save_control, RTC_CONTROL);
 106         CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
 107         spin_unlock(&rtc_lock);
 108
 109         return retval;
 110 }
 111
 112 int update_persistent_clock(struct timespec now)
 113 {
 114         return set_rtc_mmss(now.tv_sec);
 115 }
 116
 117 /*
 118  * calibrate the TSC clock against the RTC
 119  */
 120 void __init calibrate_clock(void)
 121 {
 122         unsigned char status;
 123
 124         /* make sure the RTC is running and is set to operate in 24hr mode */
 125         status = RTSRC;
 126         RTCRB |= RTCRB_SET;
 127         RTCRB |= RTCRB_TM_24HR;
 128         RTCRB &= ~RTCRB_DM_BINARY;
 129         RTCRA |= RTCRA_DVR;
 130         RTCRA &= ~RTCRA_DVR;
 131         RTCRB &= ~RTCRB_SET;
 132 }