/* 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);
/* last time the RTC got updated */
static long last_rtc_update;
/* time for RTC to update itself in ioclks */
static unsigned long mn10300_rtc_update_period;
/*
* read the current RTC time
*/
unsigned long __init get_initial_rtc_time(void)
{
struct rtc_time tm;
get_rtc_time(&tm);
return mktime(tm.tm_year, tm.tm_mon, tm.tm_mday,
tm.tm_hour, tm.tm_min, tm.tm_sec);
}
/*
* 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)
BCD_TO_BIN(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) {
BIN_TO_BCD(real_seconds);
BIN_TO_BCD(real_minutes);
}
CMOS_WRITE(real_seconds, RTC_SECONDS);
CMOS_WRITE(real_minutes, RTC_MINUTES);
} else {
printk(KERN_WARNING
"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;
}
void check_rtc_time(void)
{
/* the RTC clock just finished ticking over again this second
* - if we have an externally synchronized Linux clock, then update
* RTC clock accordingly every ~11 minutes. set_rtc_mmss() has to be
* called as close as possible to 500 ms before the new second starts.
*/
if ((time_status & STA_UNSYNC) == 0 &&
xtime.tv_sec > last_rtc_update + 660 &&
xtime.tv_nsec / 1000 >= 500000 - ((unsigned) TICK_SIZE) / 2 &&
xtime.tv_nsec / 1000 <= 500000 + ((unsigned) TICK_SIZE) / 2
) {
if (set_rtc_mmss(xtime.tv_sec) == 0)
last_rtc_update = xtime.tv_sec;
else
/* do it again in 60s */
last_rtc_update = xtime.tv_sec - 600;
}
}
/*
* calibrate the TSC clock against the RTC
*/
void __init calibrate_clock(void)
{
unsigned long count0, counth, count1;
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;
RTCRA |= RTCRA_DVR;
RTCRA &= ~RTCRA_DVR;
RTCRB &= ~RTCRB_SET;
/* work out the clock speed by counting clock cycles between ends of
* the RTC update cycle - track the RTC through one complete update
* cycle (1 second)
*/
startup_timestamp_counter();
while (!(RTCRA & RTCRA_UIP)) {}
while ((RTCRA & RTCRA_UIP)) {}
count0 = TMTSCBC;
while (!(RTCRA & RTCRA_UIP)) {}
counth = TMTSCBC;
while ((RTCRA & RTCRA_UIP)) {}
count1 = TMTSCBC;
shutdown_timestamp_counter();
MN10300_TSCCLK = count0 - count1; /* the timers count down */
mn10300_rtc_update_period = counth - count1;
MN10300_TSC_PER_HZ = MN10300_TSCCLK / HZ;
}
