/*
* linux/arch/alpha/kernel/time.c
*
* Copyright (C) 1991, 1992, 1995 Linus Torvalds
*
* This file contains the PC-specific time handling details:
* reading the RTC at bootup, etc..
* 1994-07-02 Alan Modra
* fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime
* 1995-03-26 Markus Kuhn
* fixed 500 ms bug at call to set_rtc_mmss, fixed DS12887
* precision CMOS clock update
*/
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <asm/segment.h>
#include <asm/io.h>
#include <asm/hwrpb.h>
#include <linux/mc146818rtc.h>
#include <linux/timex.h>
#define TIMER_IRQ 0
extern struct hwrpb_struct *hwrpb;
static int set_rtc_mmss(unsigned long);
/*
* Shift amount by which scaled_ticks_per_cycle is scaled. Shifting
* by 48 gives us 16 bits for HZ while keeping the accuracy good even
* for large CPU clock rates.
*/
#define FIX_SHIFT 48
/* lump static variables together for more efficient access: */
static struct {
__u32 last_time; /* cycle counter last time it got invoked */
__u32 max_cycles_per_tick; /* more makes us think we lost an interrupt */
unsigned long scaled_ticks_per_cycle; /* ticks/cycle * 2^48 */
long last_rtc_update; /* last time the cmos clock got updated */
} state;
static inline __u32 rpcc(void)
{
__u32 result;
asm volatile ("rpcc %0" : "r="(result));
return result;
}
/*
* timer_interrupt() needs to keep up the real-time clock,
* as well as call the "do_timer()" routine every clocktick
*/
void timer_interrupt(struct pt_regs * regs)
{
__u32 delta, now;
now = rpcc();
delta = now - state.last_time;
state.last_time = now;
if (delta > state.max_cycles_per_tick) {
int i, missed_ticks;
missed_ticks = ((delta * state.scaled_ticks_per_cycle) >> FIX_SHIFT) - 1;
for (i = 0; i < missed_ticks; ++i) {
do_timer(regs);
}
}
do_timer(regs);
/*
* If we have an externally synchronized Linux clock, then update
* CMOS 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_state != TIME_BAD && xtime.tv_sec > state.last_rtc_update + 660 &&
xtime.tv_usec > 500000 - (tick >> 1) &&
xtime.tv_usec < 500000 + (tick >> 1))
if (set_rtc_mmss(xtime.tv_sec) == 0)
state.last_rtc_update = xtime.tv_sec;
else
state.last_rtc_update = xtime.tv_sec - 600; /* do it again in 60 s */
}
/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
* Assumes input in normal date format, i.e. 1980-12-31 23:59:59
* => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
*
* [For the Julian calendar (which was used in Russia before 1917,
* Britain & colonies before 1752, anywhere else before 1582,
* and is still in use by some communities) leave out the
* -year/100+year/400 terms, and add 10.]
*
* This algorithm was first published by Gauss (I think).
*
* WARNING: this function will overflow on 2106-02-07 06:28:16 on
* machines were long is 32-bit! (However, as time_t is signed, we
* will already get problems at other places on 2038-01-19 03:14:08)
*/
static inline unsigned long mktime(unsigned int year, unsigned int mon,
unsigned int day, unsigned int hour,
unsigned int min, unsigned int sec)
{
if (0 >= (int) (mon -= 2)) { /* 1..12 -> 11,12,1..10 */
mon += 12; /* Puts Feb last since it has leap day */
year -= 1;
}
return (((
(unsigned long)(year/4 - year/100 + year/400 + 367*mon/12 + day) +
year*365 - 719499
)*24 + hour /* now have hours */
)*60 + min /* now have minutes */
)*60 + sec; /* finally seconds */
}
void time_init(void)
{
unsigned int year, mon, day, hour, min, sec;
int i;
/* The Linux interpretation of the CMOS clock register contents:
* When the Update-In-Progress (UIP) flag goes from 1 to 0, the
* RTC registers show the second which has precisely just started.
* Let's hope other operating systems interpret the RTC the same way.
*/
/* read RTC exactly on falling edge of update flag */
for (i = 0 ; i < 1000000 ; i++) /* may take up to 1 second... */
if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)
break;
for (i = 0 ; i < 1000000 ; i++) /* must try at least 2.228 ms */
if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
break;
do { /* Isn't this overkill ? UIP above should guarantee consistency */
sec = CMOS_READ(RTC_SECONDS);
min = CMOS_READ(RTC_MINUTES);
hour = CMOS_READ(RTC_HOURS);
day = CMOS_READ(RTC_DAY_OF_MONTH);
mon = CMOS_READ(RTC_MONTH);
year = CMOS_READ(RTC_YEAR);
} while (sec != CMOS_READ(RTC_SECONDS));
if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
{
BCD_TO_BIN(sec);
BCD_TO_BIN(min);
BCD_TO_BIN(hour);
BCD_TO_BIN(day);
BCD_TO_BIN(mon);
BCD_TO_BIN(year);
}
#ifdef ALPHA_PRE_V1_2_SRM_CONSOLE
/*
* The meaning of life, the universe, and everything. Plus
* this makes the year come out right on SRM consoles earlier
* than v1.2.
*/
year -= 42;
#endif
if ((year += 1900) < 1970)
year += 100;
xtime.tv_sec = mktime(year, mon, day, hour, min, sec);
xtime.tv_usec = 0;
if (HZ > (1<<16)) {
extern void __you_loose (void);
__you_loose();
}
state.last_time = rpcc();
state.scaled_ticks_per_cycle = ((unsigned long) HZ << FIX_SHIFT) / hwrpb->cycle_freq;
state.max_cycles_per_tick = (2 * hwrpb->cycle_freq) / HZ;
state.last_rtc_update = 0;
}
/*
* We could get better timer accuracy by using the alpha
* time counters or something. Now this is limited to
* the HZ clock frequency.
*/
void do_gettimeofday(struct timeval *tv)
{
unsigned long flags;
save_flags(flags);
cli();
*tv = xtime;
restore_flags(flags);
}
void do_settimeofday(struct timeval *tv)
{
cli();
xtime = *tv;
time_state = TIME_BAD;
time_maxerror = 0x70000000;
time_esterror = 0x70000000;
sti();
}
/*
* 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.
*/
static int set_rtc_mmss(unsigned long nowtime)
{
int retval = 0;
int real_seconds, real_minutes, cmos_minutes;
unsigned char save_control, save_freq_select;
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)
real_minutes += 30; /* correct for half hour time zone */
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
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);
return retval;
}
