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/*
* linux/arch/i386/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
* 1996-05-03 Ingo Molnar
* fixed time warps in do_[slow|fast]_gettimeoffset()
* 1997-09-10 Updated NTP code according to technical memorandum Jan '96
* "A Kernel Model for Precision Timekeeping" by Dave Mills
* 1998-09-05 (Various)
* More robust do_fast_gettimeoffset() algorithm implemented
* (works with APM, Cyrix 6x86MX and Centaur C6),
* monotonic gettimeofday() with fast_get_timeoffset(),
* drift-proof precision TSC calibration on boot
* (C. Scott Ananian <cananian@alumni.princeton.edu>, Andrew D.
* Balsa <andrebalsa@altern.org>, Philip Gladstone <philip@raptor.com>;
* ported from 2.0.35 Jumbo-9 by Michael Krause <m.krause@tu-harburg.de>).
* 1998-12-16 Andrea Arcangeli
* Fixed Jumbo-9 code in 2.1.131: do_gettimeofday was missing 1 jiffy
* because was not accounting lost_ticks.
* 1998-12-24 Copyright (C) 1998 Andrea Arcangeli
* Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
* serialize accesses to xtime/lost_ticks).
*/
#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 <linux/interrupt.h>
#include <linux/time.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <asm/io.h>
#include <asm/smp.h>
#include <asm/irq.h>
#include <asm/msr.h>
#include <asm/delay.h>
#include <asm/mpspec.h>
#include <asm/uaccess.h>
#include <asm/processor.h>
#include <linux/mc146818rtc.h>
#include <linux/timex.h>
#include <linux/config.h>
#include <asm/fixmap.h>
#include <asm/cobalt.h>
/*
* for x86_do_profile()
*/
#include <linux/irq.h>
unsigned long cpu_khz; /* Detected as we calibrate the TSC */
/* Number of usecs that the last interrupt was delayed */
static int delay_at_last_interrupt;
static unsigned long last_tsc_low; /* lsb 32 bits of Time Stamp Counter */
/* Cached *multiplier* to convert TSC counts to microseconds.
* (see the equation below).
* Equal to 2^32 * (1 / (clocks per usec) ).
* Initialized in time_init.
*/
unsigned long fast_gettimeoffset_quotient;
extern rwlock_t xtime_lock;
extern unsigned long wall_jiffies;
spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;
static inline unsigned long do_fast_gettimeoffset(void)
{
register unsigned long eax, edx;
/* Read the Time Stamp Counter */
rdtsc(eax,edx);
/* .. relative to previous jiffy (32 bits is enough) */
eax -= last_tsc_low; /* tsc_low delta */
/*
* Time offset = (tsc_low delta) * fast_gettimeoffset_quotient
* = (tsc_low delta) * (usecs_per_clock)
* = (tsc_low delta) * (usecs_per_jiffy / clocks_per_jiffy)
*
* Using a mull instead of a divl saves up to 31 clock cycles
* in the critical path.
*/
__asm__("mull %2"
:"=a" (eax), "=d" (edx)
:"rm" (fast_gettimeoffset_quotient),
"0" (eax));
/* our adjusted time offset in microseconds */
return delay_at_last_interrupt + edx;
}
#define TICK_SIZE tick
spinlock_t i8253_lock = SPIN_LOCK_UNLOCKED;
extern spinlock_t i8259A_lock;
#ifndef CONFIG_X86_TSC
/* This function must be called with interrupts disabled
* It was inspired by Steve McCanne's microtime-i386 for BSD. -- jrs
*
* However, the pc-audio speaker driver changes the divisor so that
* it gets interrupted rather more often - it loads 64 into the
* counter rather than 11932! This has an adverse impact on
* do_gettimeoffset() -- it stops working! What is also not
* good is that the interval that our timer function gets called
* is no longer 10.0002 ms, but 9.9767 ms. To get around this
* would require using a different timing source. Maybe someone
* could use the RTC - I know that this can interrupt at frequencies
* ranging from 8192Hz to 2Hz. If I had the energy, I'd somehow fix
* it so that at startup, the timer code in sched.c would select
* using either the RTC or the 8253 timer. The decision would be
* based on whether there was any other device around that needed
* to trample on the 8253. I'd set up the RTC to interrupt at 1024 Hz,
* and then do some jiggery to have a version of do_timer that
* advanced the clock by 1/1024 s. Every time that reached over 1/100
* of a second, then do all the old code. If the time was kept correct
* then do_gettimeoffset could just return 0 - there is no low order
* divider that can be accessed.
*
* Ideally, you would be able to use the RTC for the speaker driver,
* but it appears that the speaker driver really needs interrupt more
* often than every 120 us or so.
*
* Anyway, this needs more thought.... pjsg (1993-08-28)
*
* If you are really that interested, you should be reading
* comp.protocols.time.ntp!
*/
static unsigned long do_slow_gettimeoffset(void)
{
int count;
static int count_p = LATCH; /* for the first call after boot */
static unsigned long jiffies_p = 0;
/*
* cache volatile jiffies temporarily; we have IRQs turned off.
*/
unsigned long jiffies_t;
/* gets recalled with irq locally disabled */
spin_lock(&i8253_lock);
/* timer count may underflow right here */
outb_p(0x00, 0x43); /* latch the count ASAP */
count = inb_p(0x40); /* read the latched count */
/*
* We do this guaranteed double memory access instead of a _p
* postfix in the previous port access. Wheee, hackady hack
*/
jiffies_t = jiffies;
count |= inb_p(0x40) << 8;
/* VIA686a test code... reset the latch if count > max + 1 */
if (count > LATCH) {
outb_p(0x34, 0x43);
outb_p(LATCH & 0xff, 0x40);
outb(LATCH >> 8, 0x40);
count = LATCH - 1;
}
spin_unlock(&i8253_lock);
/*
* avoiding timer inconsistencies (they are rare, but they happen)...
* there are two kinds of problems that must be avoided here:
* 1. the timer counter underflows
* 2. hardware problem with the timer, not giving us continuous time,
* the counter does small "jumps" upwards on some Pentium systems,
* (see c't 95/10 page 335 for Neptun bug.)
*/
/* you can safely undefine this if you don't have the Neptune chipset */
#define BUGGY_NEPTUN_TIMER
if( jiffies_t == jiffies_p ) {
if( count > count_p ) {
/* the nutcase */
int i;
spin_lock(&i8259A_lock);
/*
* This is tricky when I/O APICs are used;
* see do_timer_interrupt().
*/
i = inb(0x20);
spin_unlock(&i8259A_lock);
/* assumption about timer being IRQ0 */
if (i & 0x01) {
/*
* We cannot detect lost timer interrupts ...
* well, that's why we call them lost, don't we? :)
* [hmm, on the Pentium and Alpha we can ... sort of]
*/
count -= LATCH;
} else {
#ifdef BUGGY_NEPTUN_TIMER
/*
* for the Neptun bug we know that the 'latch'
* command doesnt latch the high and low value
* of the counter atomically. Thus we have to
* substract 256 from the counter
* ... funny, isnt it? :)
*/
count -= 256;
#else
printk("do_slow_gettimeoffset(): hardware timer problem?\n");
#endif
}
}
} else
jiffies_p = jiffies_t;
count_p = count;
count = ((LATCH-1) - count) * TICK_SIZE;
count = (count + LATCH/2) / LATCH;
return count;
}
static unsigned long (*do_gettimeoffset)(void) = do_slow_gettimeoffset;
#else
#define do_gettimeoffset() do_fast_gettimeoffset()
#endif
/*
* This version of gettimeofday has microsecond resolution
* and better than microsecond precision on fast x86 machines with TSC.
*/
void do_gettimeofday(struct timeval *tv)
{
unsigned long flags;
unsigned long usec, sec;
read_lock_irqsave(&xtime_lock, flags);
usec = do_gettimeoffset();
{
unsigned long lost = jiffies - wall_jiffies;
if (lost)
usec += lost * (1000000 / HZ);
}
sec = xtime.tv_sec;
usec += xtime.tv_usec;
read_unlock_irqrestore(&xtime_lock, flags);
while (usec >= 1000000) {
usec -= 1000000;
sec++;
}
tv->tv_sec = sec;
tv->tv_usec = usec;
}
void do_settimeofday(struct timeval *tv)
{
write_lock_irq(&xtime_lock);
/*
* This is revolting. We need to set "xtime" correctly. However, the
* value in this location is the value at the most recent update of
* wall time. Discover what correction gettimeofday() would have
* made, and then undo it!
*/
tv->tv_usec -= do_gettimeoffset();
tv->tv_usec -= (jiffies - wall_jiffies) * (1000000 / HZ);
while (tv->tv_usec < 0) {
tv->tv_usec += 1000000;
tv->tv_sec--;
}
xtime = *tv;
time_adjust = 0; /* stop active adjtime() */
time_status |= STA_UNSYNC;
time_maxerror = NTP_PHASE_LIMIT;
time_esterror = NTP_PHASE_LIMIT;
write_unlock_irq(&xtime_lock);
}
/*
* 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)
{
int retval = 0;
int real_seconds, real_minutes, cmos_minutes;
unsigned char save_control, save_freq_select;
/* 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)
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 {
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;
}
/* last time the cmos clock got updated */
static long last_rtc_update;
int timer_ack;
/*
* timer_interrupt() needs to keep up the real-time clock,
* as well as call the "do_timer()" routine every clocktick
*/
static inline void do_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
#ifdef CONFIG_X86_IO_APIC
if (timer_ack) {
/*
* Subtle, when I/O APICs are used we have to ack timer IRQ
* manually to reset the IRR bit for do_slow_gettimeoffset().
* This will also deassert NMI lines for the watchdog if run
* on an 82489DX-based system.
*/
spin_lock(&i8259A_lock);
outb(0x0c, 0x20);
/* Ack the IRQ; AEOI will end it automatically. */
inb(0x20);
spin_unlock(&i8259A_lock);
}
#endif
#ifdef CONFIG_VISWS
/* Clear the interrupt */
co_cpu_write(CO_CPU_STAT,co_cpu_read(CO_CPU_STAT) & ~CO_STAT_TIMEINTR);
#endif
do_timer(regs);
/*
* In the SMP case we use the local APIC timer interrupt to do the
* profiling, except when we simulate SMP mode on a uniprocessor
* system, in that case we have to call the local interrupt handler.
*/
#ifndef CONFIG_X86_LOCAL_APIC
if (!user_mode(regs))
x86_do_profile(regs->eip);
#else
if (!using_apic_timer)
smp_local_timer_interrupt(regs);
#endif
/*
* 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_status & STA_UNSYNC) == 0 &&
xtime.tv_sec > last_rtc_update + 660 &&
xtime.tv_usec >= 500000 - ((unsigned) tick) / 2 &&
xtime.tv_usec <= 500000 + ((unsigned) tick) / 2) {
if (set_rtc_mmss(xtime.tv_sec) == 0)
last_rtc_update = xtime.tv_sec;
else
last_rtc_update = xtime.tv_sec - 600; /* do it again in 60 s */
}
#ifdef CONFIG_MCA
if( MCA_bus ) {
/* The PS/2 uses level-triggered interrupts. You can't
turn them off, nor would you want to (any attempt to
enable edge-triggered interrupts usually gets intercepted by a
special hardware circuit). Hence we have to acknowledge
the timer interrupt. Through some incredibly stupid
design idea, the reset for IRQ 0 is done by setting the
high bit of the PPI port B (0x61). Note that some PS/2s,
notably the 55SX, work fine if this is removed. */
irq = inb_p( 0x61 ); /* read the current state */
outb_p( irq|0x80, 0x61 ); /* reset the IRQ */
}
#endif
}
static int use_tsc;
/*
* This is the same as the above, except we _also_ save the current
* Time Stamp Counter value at the time of the timer interrupt, so that
* we later on can estimate the time of day more exactly.
*/
static void timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
int count;
/*
* Here we are in the timer irq handler. We just have irqs locally
* disabled but we don't know if the timer_bh is running on the other
* CPU. We need to avoid to SMP race with it. NOTE: we don' t need
* the irq version of write_lock because as just said we have irq
* locally disabled. -arca
*/
write_lock(&xtime_lock);
if (use_tsc)
{
/*
* It is important that these two operations happen almost at
* the same time. We do the RDTSC stuff first, since it's
* faster. To avoid any inconsistencies, we need interrupts
* disabled locally.
*/
/*
* Interrupts are just disabled locally since the timer irq
* has the SA_INTERRUPT flag set. -arca
*/
/* read Pentium cycle counter */
rdtscl(last_tsc_low);
spin_lock(&i8253_lock);
outb_p(0x00, 0x43); /* latch the count ASAP */
count = inb_p(0x40); /* read the latched count */
count |= inb(0x40) << 8;
spin_unlock(&i8253_lock);
count = ((LATCH-1) - count) * TICK_SIZE;
delay_at_last_interrupt = (count + LATCH/2) / LATCH;
}
do_timer_interrupt(irq, NULL, regs);
write_unlock(&xtime_lock);
}
/* not static: needed by APM */
unsigned long get_cmos_time(void)
{
unsigned int year, mon, day, hour, min, sec;
int i;
spin_lock(&rtc_lock);
/* 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);
}
spin_unlock(&rtc_lock);
if ((year += 1900) < 1970)
year += 100;
return mktime(year, mon, day, hour, min, sec);
}
static struct irqaction irq0 = { timer_interrupt, SA_INTERRUPT, 0, "timer", NULL, NULL};
/* ------ Calibrate the TSC -------
* Return 2^32 * (1 / (TSC clocks per usec)) for do_fast_gettimeoffset().
* Too much 64-bit arithmetic here to do this cleanly in C, and for
* accuracy's sake we want to keep the overhead on the CTC speaker (channel 2)
* output busy loop as low as possible. We avoid reading the CTC registers
* directly because of the awkward 8-bit access mechanism of the 82C54
* device.
*/
#define CALIBRATE_LATCH (5 * LATCH)
#define CALIBRATE_TIME (5 * 1000020/HZ)
static unsigned long __init calibrate_tsc(void)
{
/* 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 */
{
unsigned long startlow, starthigh;
unsigned long endlow, endhigh;
unsigned long count;
rdtsc(startlow,starthigh);
count = 0;
do {
count++;
} while ((inb(0x61) & 0x20) == 0);
rdtsc(endlow,endhigh);
last_tsc_low = endlow;
/* Error: ECTCNEVERSET */
if (count <= 1)
goto bad_ctc;
/* 64-bit subtract - gcc just messes up with long longs */
__asm__("subl %2,%0\n\t"
"sbbl %3,%1"
:"=a" (endlow), "=d" (endhigh)
:"g" (startlow), "g" (starthigh),
"0" (endlow), "1" (endhigh));
/* Error: ECPUTOOFAST */
if (endhigh)
goto bad_ctc;
/* Error: ECPUTOOSLOW */
if (endlow <= CALIBRATE_TIME)
goto bad_ctc;
__asm__("divl %2"
:"=a" (endlow), "=d" (endhigh)
:"r" (endlow), "0" (0), "1" (CALIBRATE_TIME));
return endlow;
}
/*
* The CTC wasn't reliable: we got a hit on the very first read,
* or the CPU was so fast/slow that the quotient wouldn't fit in
* 32 bits..
*/
bad_ctc:
return 0;
}
void __init time_init(void)
{
extern int x86_udelay_tsc;
xtime.tv_sec = get_cmos_time();
xtime.tv_usec = 0;
/*
* If we have APM enabled or the CPU clock speed is variable
* (CPU stops clock on HLT or slows clock to save power)
* then the TSC timestamps may diverge by up to 1 jiffy from
* 'real time' but nothing will break.
* The most frequent case is that the CPU is "woken" from a halt
* state by the timer interrupt itself, so we get 0 error. In the
* rare cases where a driver would "wake" the CPU and request a
* timestamp, the maximum error is < 1 jiffy. But timestamps are
* still perfectly ordered.
* Note that the TSC counter will be reset if APM suspends
* to disk; this won't break the kernel, though, 'cuz we're
* smart. See arch/i386/kernel/apm.c.
*/
/*
* Firstly we have to do a CPU check for chips with
* a potentially buggy TSC. At this point we haven't run
* the ident/bugs checks so we must run this hook as it
* may turn off the TSC flag.
*
* NOTE: this doesnt yet handle SMP 486 machines where only
* some CPU's have a TSC. Thats never worked and nobody has
* moaned if you have the only one in the world - you fix it!
*/
dodgy_tsc();
if (cpu_has_tsc) {
unsigned long tsc_quotient = calibrate_tsc();
if (tsc_quotient) {
fast_gettimeoffset_quotient = tsc_quotient;
use_tsc = 1;
/*
* We could be more selective here I suspect
* and just enable this for the next intel chips ?
*/
x86_udelay_tsc = 1;
#ifndef do_gettimeoffset
do_gettimeoffset = do_fast_gettimeoffset;
#endif
/* report CPU clock rate in Hz.
* The formula is (10^6 * 2^32) / (2^32 * 1 / (clocks/us)) =
* clock/second. Our precision is about 100 ppm.
*/
{ unsigned long eax=0, edx=1000;
__asm__("divl %2"
:"=a" (cpu_khz), "=d" (edx)
:"r" (tsc_quotient),
"0" (eax), "1" (edx));
printk("Detected %lu.%03lu MHz processor.\n", cpu_khz / 1000, cpu_khz % 1000);
}
}
}
#ifdef CONFIG_VISWS
printk("Starting Cobalt Timer system clock\n");
/* Set the countdown value */
co_cpu_write(CO_CPU_TIMEVAL, CO_TIME_HZ/HZ);
/* Start the timer */
co_cpu_write(CO_CPU_CTRL, co_cpu_read(CO_CPU_CTRL) | CO_CTRL_TIMERUN);
/* Enable (unmask) the timer interrupt */
co_cpu_write(CO_CPU_CTRL, co_cpu_read(CO_CPU_CTRL) & ~CO_CTRL_TIMEMASK);
/* Wire cpu IDT entry to s/w handler (and Cobalt APIC to IDT) */
setup_irq(CO_IRQ_TIMER, &irq0);
#else
setup_irq(0, &irq0);
#endif
}
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