133 lines
3.9 KiB
C
133 lines
3.9 KiB
C
/* MN10300 RTC management
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*
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* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/mc146818rtc.h>
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#include <linux/bcd.h>
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#include <linux/timex.h>
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#include <asm/rtc-regs.h>
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#include <asm/rtc.h>
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DEFINE_SPINLOCK(rtc_lock);
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EXPORT_SYMBOL(rtc_lock);
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/*
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* Read the current RTC time
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*/
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void read_persistent_clock(struct timespec *ts)
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{
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struct rtc_time tm;
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get_rtc_time(&tm);
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ts->tv_nsec = 0;
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ts->tv_sec = mktime(tm.tm_year, tm.tm_mon, tm.tm_mday,
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tm.tm_hour, tm.tm_min, tm.tm_sec);
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/* if rtc is way off in the past, set something reasonable */
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if (ts->tv_sec < 0)
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ts->tv_sec = mktime(2009, 1, 1, 12, 0, 0);
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}
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/*
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* In order to set the CMOS clock precisely, set_rtc_mmss has to be called 500
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* ms after the second nowtime has started, because when nowtime is written
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* into the registers of the CMOS clock, it will jump to the next second
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* precisely 500 ms later. Check the Motorola MC146818A or Dallas DS12887 data
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* sheet for details.
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*
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* BUG: This routine does not handle hour overflow properly; it just
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* sets the minutes. Usually you'll only notice that after reboot!
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*/
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static int set_rtc_mmss(unsigned long nowtime)
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{
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unsigned char save_control, save_freq_select;
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int retval = 0;
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int real_seconds, real_minutes, cmos_minutes;
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/* gets recalled with irq locally disabled */
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spin_lock(&rtc_lock);
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save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being
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* set */
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CMOS_WRITE(save_control | RTC_SET, RTC_CONTROL);
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save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset
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* prescaler */
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CMOS_WRITE(save_freq_select | RTC_DIV_RESET2, RTC_FREQ_SELECT);
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cmos_minutes = CMOS_READ(RTC_MINUTES);
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if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
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cmos_minutes = bcd2bin(cmos_minutes);
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/*
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* since we're only adjusting minutes and seconds,
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* don't interfere with hour overflow. This avoids
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* messing with unknown time zones but requires your
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* RTC not to be off by more than 15 minutes
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*/
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real_seconds = nowtime % 60;
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real_minutes = nowtime / 60;
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if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1)
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/* correct for half hour time zone */
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real_minutes += 30;
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real_minutes %= 60;
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if (abs(real_minutes - cmos_minutes) < 30) {
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if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
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real_seconds = bin2bcd(real_seconds);
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real_minutes = bin2bcd(real_minutes);
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}
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CMOS_WRITE(real_seconds, RTC_SECONDS);
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CMOS_WRITE(real_minutes, RTC_MINUTES);
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} else {
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printk_once(KERN_NOTICE
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"set_rtc_mmss: can't update from %d to %d\n",
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cmos_minutes, real_minutes);
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retval = -1;
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}
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/* The following flags have to be released exactly in this order,
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* otherwise the DS12887 (popular MC146818A clone with integrated
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* battery and quartz) will not reset the oscillator and will not
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* update precisely 500 ms later. You won't find this mentioned in
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* the Dallas Semiconductor data sheets, but who believes data
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* sheets anyway ... -- Markus Kuhn
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*/
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CMOS_WRITE(save_control, RTC_CONTROL);
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CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
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spin_unlock(&rtc_lock);
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return retval;
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}
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int update_persistent_clock(struct timespec now)
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{
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return set_rtc_mmss(now.tv_sec);
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}
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/*
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* calibrate the TSC clock against the RTC
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*/
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void __init calibrate_clock(void)
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{
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unsigned char status;
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/* make sure the RTC is running and is set to operate in 24hr mode */
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status = RTSRC;
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RTCRB |= RTCRB_SET;
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RTCRB |= RTCRB_TM_24HR;
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RTCRB &= ~RTCRB_DM_BINARY;
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RTCRA |= RTCRA_DVR;
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RTCRA &= ~RTCRA_DVR;
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RTCRB &= ~RTCRB_SET;
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}
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