LXR linux/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
  20DEFINE_SPINLOCK(rtc_lock);
  21EXPORT_SYMBOL(rtc_lock);
  22
  23/*
  24 * Read the current RTC time
  25 */
  26void 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 */
  51static 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
 112int 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 */
 120void __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}
 133