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linux/arch/alpha/kernel/time.c

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/*
* linux/arch/alpha/kernel/time.c
*
* Copyright (C) 1991, 1992, 1995, 1999, 2000 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
* 1997-09-10 Updated NTP code according to technical memorandum Jan '96
* "A Kernel Model for Precision Timekeeping" by Dave Mills
* 1997-01-09 Adrian Sun
* use interval timer if CONFIG_RTC=y
* 1997-10-29 John Bowman (bowman@math.ualberta.ca)
* fixed tick loss calculation in timer_interrupt
* (round system clock to nearest tick instead of truncating)
* fixed algorithm in time_init for getting time from CMOS clock
* 1999-04-16 Thorsten Kranzkowski (dl8bcu@gmx.net)
* fixed algorithm in do_gettimeofday() for calculating the precise time
* from processor cycle counter (now taking lost_ticks into account)
* 2000-08-13 Jan-Benedict Glaw <jbglaw@lug-owl.de>
* Fixed time_init to be aware of epoches != 1900. This prevents
* booting up in 2048 for me;) Code is stolen from rtc.c.
* 2003-06-03 R. Scott Bailey <scott.bailey@eds.com>
* Tighten sanity in time_init from 1% (10,000 PPM) to 250 PPM
*/
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/ioport.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/bcd.h>
#include <linux/profile.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/hwrpb.h>
#include <asm/8253pit.h>
#include <linux/mc146818rtc.h>
#include <linux/time.h>
#include <linux/timex.h>
#include "proto.h"
#include "irq_impl.h"
static int set_rtc_mmss(unsigned long);
DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);
#define TICK_SIZE (tick_nsec / 1000)
/*
* 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 {
/* cycle counter last time it got invoked */
__u32 last_time;
/* ticks/cycle * 2^48 */
unsigned long scaled_ticks_per_cycle;
/* last time the CMOS clock got updated */
time_t last_rtc_update;
/* partial unused tick */
unsigned long partial_tick;
} state;
unsigned long est_cycle_freq;
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
*/
irqreturn_t timer_interrupt(int irq, void *dev)
{
unsigned long delta;
__u32 now;
long nticks;
#ifndef CONFIG_SMP
/* Not SMP, do kernel PC profiling here. */
profile_tick(CPU_PROFILING);
#endif
write_seqlock(&xtime_lock);
/*
* Calculate how many ticks have passed since the last update,
* including any previous partial leftover. Save any resulting
* fraction for the next pass.
*/
now = rpcc();
delta = now - state.last_time;
state.last_time = now;
delta = delta * state.scaled_ticks_per_cycle + state.partial_tick;
state.partial_tick = delta & ((1UL << FIX_SHIFT) - 1);
nticks = delta >> FIX_SHIFT;
while (nticks > 0) {
do_timer(1);
#ifndef CONFIG_SMP
update_process_times(user_mode(get_irq_regs()));
#endif
nticks--;
}
/*
* 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 (ntp_synced()
&& xtime.tv_sec > state.last_rtc_update + 660
&& xtime.tv_nsec >= 500000 - ((unsigned) TICK_SIZE) / 2
&& xtime.tv_nsec <= 500000 + ((unsigned) TICK_SIZE) / 2) {
int tmp = set_rtc_mmss(xtime.tv_sec);
state.last_rtc_update = xtime.tv_sec - (tmp ? 600 : 0);
}
write_sequnlock(&xtime_lock);
return IRQ_HANDLED;
}
void __init
common_init_rtc(void)
{
unsigned char x;
/* Reset periodic interrupt frequency. */
x = CMOS_READ(RTC_FREQ_SELECT) & 0x3f;
/* Test includes known working values on various platforms
where 0x26 is wrong; we refuse to change those. */
if (x != 0x26 && x != 0x25 && x != 0x19 && x != 0x06) {
printk("Setting RTC_FREQ to 1024 Hz (%x)\n", x);
CMOS_WRITE(0x26, RTC_FREQ_SELECT);
}
/* Turn on periodic interrupts. */
x = CMOS_READ(RTC_CONTROL);
if (!(x & RTC_PIE)) {
printk("Turning on RTC interrupts.\n");
x |= RTC_PIE;
x &= ~(RTC_AIE | RTC_UIE);
CMOS_WRITE(x, RTC_CONTROL);
}
(void) CMOS_READ(RTC_INTR_FLAGS);
outb(0x36, 0x43); /* pit counter 0: system timer */
outb(0x00, 0x40);
outb(0x00, 0x40);
outb(0xb6, 0x43); /* pit counter 2: speaker */
outb(0x31, 0x42);
outb(0x13, 0x42);
init_rtc_irq();
}
/* Validate a computed cycle counter result against the known bounds for
the given processor core. There's too much brokenness in the way of
timing hardware for any one method to work everywhere. :-(
Return 0 if the result cannot be trusted, otherwise return the argument. */
static unsigned long __init
validate_cc_value(unsigned long cc)
{
static struct bounds {
unsigned int min, max;
} cpu_hz[] __initdata = {
[EV3_CPU] = { 50000000, 200000000 }, /* guess */
[EV4_CPU] = { 100000000, 300000000 },
[LCA4_CPU] = { 100000000, 300000000 }, /* guess */
[EV45_CPU] = { 200000000, 300000000 },
[EV5_CPU] = { 250000000, 433000000 },
[EV56_CPU] = { 333000000, 667000000 },
[PCA56_CPU] = { 400000000, 600000000 }, /* guess */
[PCA57_CPU] = { 500000000, 600000000 }, /* guess */
[EV6_CPU] = { 466000000, 600000000 },
[EV67_CPU] = { 600000000, 750000000 },
[EV68AL_CPU] = { 750000000, 940000000 },
[EV68CB_CPU] = { 1000000000, 1333333333 },
/* None of the following are shipping as of 2001-11-01. */
[EV68CX_CPU] = { 1000000000, 1700000000 }, /* guess */
[EV69_CPU] = { 1000000000, 1700000000 }, /* guess */
[EV7_CPU] = { 800000000, 1400000000 }, /* guess */
[EV79_CPU] = { 1000000000, 2000000000 }, /* guess */
};
/* Allow for some drift in the crystal. 10MHz is more than enough. */
const unsigned int deviation = 10000000;
struct percpu_struct *cpu;
unsigned int index;
cpu = (struct percpu_struct *)((char*)hwrpb + hwrpb->processor_offset);
index = cpu->type & 0xffffffff;
/* If index out of bounds, no way to validate. */
if (index >= ARRAY_SIZE(cpu_hz))
return cc;
/* If index contains no data, no way to validate. */
if (cpu_hz[index].max == 0)
return cc;
if (cc < cpu_hz[index].min - deviation
|| cc > cpu_hz[index].max + deviation)
return 0;
return cc;
}
/*
* Calibrate CPU clock using legacy 8254 timer/counter. Stolen from
* arch/i386/time.c.
*/
#define CALIBRATE_LATCH 0xffff
#define TIMEOUT_COUNT 0x100000
static unsigned long __init
calibrate_cc_with_pit(void)
{
int cc, count = 0;
/* Set the Gate high, disable speaker */
outb((inb(0x61) & ~0x02) | 0x01, 0x61);
/*
* Now let's take care of CTC channel 2
*
* Set the Gate high, program CTC channel 2 for mode 0,
* (interrupt on terminal count mode), binary count,
* load 5 * LATCH count, (LSB and MSB) to begin countdown.
*/
outb(0xb0, 0x43); /* binary, mode 0, LSB/MSB, Ch 2 */
outb(CALIBRATE_LATCH & 0xff, 0x42); /* LSB of count */
outb(CALIBRATE_LATCH >> 8, 0x42); /* MSB of count */
cc = rpcc();
do {
count++;
} while ((inb(0x61) & 0x20) == 0 && count < TIMEOUT_COUNT);
cc = rpcc() - cc;
/* Error: ECTCNEVERSET or ECPUTOOFAST. */
if (count <= 1 || count == TIMEOUT_COUNT)
return 0;
return ((long)cc * PIT_TICK_RATE) / (CALIBRATE_LATCH + 1);
}
/* 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. */
static unsigned long __init
rpcc_after_update_in_progress(void)
{
do { } while (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP));
do { } while (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
return rpcc();
}
void __init
time_init(void)
{
unsigned int year, mon, day, hour, min, sec, cc1, cc2, epoch;
unsigned long cycle_freq, tolerance;
long diff;
/* Calibrate CPU clock -- attempt #1. */
if (!est_cycle_freq)
est_cycle_freq = validate_cc_value(calibrate_cc_with_pit());
cc1 = rpcc();
/* Calibrate CPU clock -- attempt #2. */
if (!est_cycle_freq) {
cc1 = rpcc_after_update_in_progress();
cc2 = rpcc_after_update_in_progress();
est_cycle_freq = validate_cc_value(cc2 - cc1);
cc1 = cc2;
}
cycle_freq = hwrpb->cycle_freq;
if (est_cycle_freq) {
/* If the given value is within 250 PPM of what we calculated,
accept it. Otherwise, use what we found. */
tolerance = cycle_freq / 4000;
diff = cycle_freq - est_cycle_freq;
if (diff < 0)
diff = -diff;
if ((unsigned long)diff > tolerance) {
cycle_freq = est_cycle_freq;
printk("HWRPB cycle frequency bogus. "
"Estimated %lu Hz\n", cycle_freq);
} else {
est_cycle_freq = 0;
}
} else if (! validate_cc_value (cycle_freq)) {
printk("HWRPB cycle frequency bogus, "
"and unable to estimate a proper value!\n");
}
/* From John Bowman <bowman@math.ualberta.ca>: allow the values
to settle, as the Update-In-Progress bit going low isn't good
enough on some hardware. 2ms is our guess; we haven't found
bogomips yet, but this is close on a 500Mhz box. */
__delay(1000000);
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);
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);
}
/* PC-like is standard; used for year >= 70 */
epoch = 1900;
if (year < 20)
epoch = 2000;
else if (year >= 20 && year < 48)
/* NT epoch */
epoch = 1980;
else if (year >= 48 && year < 70)
/* Digital UNIX epoch */
epoch = 1952;
printk(KERN_INFO "Using epoch = %d\n", epoch);
if ((year += epoch) < 1970)
year += 100;
xtime.tv_sec = mktime(year, mon, day, hour, min, sec);
xtime.tv_nsec = 0;
wall_to_monotonic.tv_sec -= xtime.tv_sec;
wall_to_monotonic.tv_nsec = 0;
if (HZ > (1<<16)) {
extern void __you_loose (void);
__you_loose();
}
state.last_time = cc1;
state.scaled_ticks_per_cycle
= ((unsigned long) HZ << FIX_SHIFT) / cycle_freq;
state.last_rtc_update = 0;
state.partial_tick = 0L;
/* Startup the timer source. */
alpha_mv.init_rtc();
}
/*
* Use the cycle counter to estimate an displacement from the last time
* tick. Unfortunately the Alpha designers made only the low 32-bits of
* the cycle counter active, so we overflow on 8.2 seconds on a 500MHz
* part. So we can't do the "find absolute time in terms of cycles" thing
* that the other ports do.
*/
void
do_gettimeofday(struct timeval *tv)
{
unsigned long flags;
unsigned long sec, usec, seq;
unsigned long delta_cycles, delta_usec, partial_tick;
do {
seq = read_seqbegin_irqsave(&xtime_lock, flags);
delta_cycles = rpcc() - state.last_time;
sec = xtime.tv_sec;
usec = (xtime.tv_nsec / 1000);
partial_tick = state.partial_tick;
} while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
#ifdef CONFIG_SMP
/* Until and unless we figure out how to get cpu cycle counters
in sync and keep them there, we can't use the rpcc tricks. */
delta_usec = 0;
#else
/*
* usec = cycles * ticks_per_cycle * 2**48 * 1e6 / (2**48 * ticks)
* = cycles * (s_t_p_c) * 1e6 / (2**48 * ticks)
* = cycles * (s_t_p_c) * 15625 / (2**42 * ticks)
*
* which, given a 600MHz cycle and a 1024Hz tick, has a
* dynamic range of about 1.7e17, which is less than the
* 1.8e19 in an unsigned long, so we are safe from overflow.
*
* Round, but with .5 up always, since .5 to even is harder
* with no clear gain.
*/
delta_usec = (delta_cycles * state.scaled_ticks_per_cycle
+ partial_tick) * 15625;
delta_usec = ((delta_usec / ((1UL << (FIX_SHIFT-6-1)) * HZ)) + 1) / 2;
#endif
usec += delta_usec;
if (usec >= 1000000) {
sec += 1;
usec -= 1000000;
}
tv->tv_sec = sec;
tv->tv_usec = usec;
}
EXPORT_SYMBOL(do_gettimeofday);
int
do_settimeofday(struct timespec *tv)
{
time_t wtm_sec, sec = tv->tv_sec;
long wtm_nsec, nsec = tv->tv_nsec;
unsigned long delta_nsec;
if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
return -EINVAL;
write_seqlock_irq(&xtime_lock);
/* The offset that is added into time in do_gettimeofday above
must be subtracted out here to keep a coherent view of the
time. Without this, a full-tick error is possible. */
#ifdef CONFIG_SMP
delta_nsec = 0;
#else
delta_nsec = rpcc() - state.last_time;
delta_nsec = (delta_nsec * state.scaled_ticks_per_cycle
+ state.partial_tick) * 15625;
delta_nsec = ((delta_nsec / ((1UL << (FIX_SHIFT-6-1)) * HZ)) + 1) / 2;
delta_nsec *= 1000;
#endif
nsec -= delta_nsec;
wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
set_normalized_timespec(&xtime, sec, nsec);
set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
ntp_clear();
write_sequnlock_irq(&xtime_lock);
clock_was_set();
return 0;
}
EXPORT_SYMBOL(do_settimeofday);
/*
* 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 won't notice until after reboot!
*/
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;
/* irq are locally disabled here */
spin_lock(&rtc_lock);
/* Tell the clock it's being set */
save_control = CMOS_READ(RTC_CONTROL);
CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
/* Stop and reset prescaler */
save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
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;
}
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