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/* MN10300 RTC management
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/mc146818rtc.h>
#include <linux/bcd.h>
#include <linux/timex.h>
#include <asm/rtc-regs.h>
#include <asm/rtc.h>
DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);
/*
* Read the current RTC time
*/
void read_persistent_clock(struct timespec *ts)
{
struct rtc_time tm;
mc146818_set_time(&tm);
ts->tv_nsec = 0;
ts->tv_sec = mktime(tm.tm_year, tm.tm_mon, tm.tm_mday,
tm.tm_hour, tm.tm_min, tm.tm_sec);
/* if rtc is way off in the past, set something reasonable */
if (ts->tv_sec < 0)
ts->tv_sec = mktime(2009, 1, 1, 12, 0, 0);
}
/*
* In order to set the CMOS clock precisely, set_rtc_mmss has to be called 500
* ms after the second nowtime has started, because when nowtime is written
* into the registers of the CMOS clock, it will jump to the next second
* precisely 500 ms later. Check the Motorola MC146818A or Dallas DS12887 data
* sheet for details.
*
* BUG: This routine does not handle hour overflow properly; it just
* sets the minutes. Usually you'll only notice that after reboot!
*/
static int set_rtc_mmss(unsigned long nowtime)
{
unsigned char save_control, save_freq_select;
int retval = 0;
int real_seconds, real_minutes, cmos_minutes;
/* gets recalled with irq locally disabled */
spin_lock(&rtc_lock);
save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being
* set */
CMOS_WRITE(save_control | RTC_SET, RTC_CONTROL);
save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset
* prescaler */
CMOS_WRITE(save_freq_select | RTC_DIV_RESET2, RTC_FREQ_SELECT);
cmos_minutes = CMOS_READ(RTC_MINUTES);
if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
cmos_minutes = bcd2bin(cmos_minutes);
/*
* since we're only adjusting minutes and seconds,
* don't interfere with hour overflow. This avoids
* messing with unknown time zones but requires your
* RTC not to be off by more than 15 minutes
*/
real_seconds = nowtime % 60;
real_minutes = nowtime / 60;
if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1)
/* correct for half hour time zone */
real_minutes += 30;
real_minutes %= 60;
if (abs(real_minutes - cmos_minutes) < 30) {
if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
real_seconds = bin2bcd(real_seconds);
real_minutes = bin2bcd(real_minutes);
}
CMOS_WRITE(real_seconds, RTC_SECONDS);
CMOS_WRITE(real_minutes, RTC_MINUTES);
} else {
printk_once(KERN_NOTICE
"set_rtc_mmss: can't update from %d to %d\n",
cmos_minutes, real_minutes);
retval = -1;
}
/* The following flags have to be released exactly in this order,
* otherwise the DS12887 (popular MC146818A clone with integrated
* battery and quartz) will not reset the oscillator and will not
* update precisely 500 ms later. You won't find this mentioned in
* the Dallas Semiconductor data sheets, but who believes data
* sheets anyway ... -- Markus Kuhn
*/
CMOS_WRITE(save_control, RTC_CONTROL);
CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
spin_unlock(&rtc_lock);
return retval;
}
int update_persistent_clock(struct timespec now)
{
return set_rtc_mmss(now.tv_sec);
}
/*
* calibrate the TSC clock against the RTC
*/
void __init calibrate_clock(void)
{
unsigned char status;
/* make sure the RTC is running and is set to operate in 24hr mode */
status = RTSRC;
RTCRB |= RTCRB_SET;
RTCRB |= RTCRB_TM_24HR;
RTCRB &= ~RTCRB_DM_BINARY;
RTCRA |= RTCRA_DVR;
RTCRA &= ~RTCRA_DVR;
RTCRB &= ~RTCRB_SET;
}
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