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x86_64: Consolidate tsc calibration 

Move the TSC calibration code to tsc.c. Reimplement it so the
pm timer can be used as a reference as well.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
This commit is contained in:
Thomas Gleixner 2007-10-12 23:04:06 +02:00 committed by Thomas Gleixner
parent 89b2bbd69b
commit d371698efd
4 changed files with 96 additions and 80 deletions
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49
arch/x86/kernel/hpet_64.c
View File

@ -184,55 +184,6 @@ int hpet_reenable(void)
return hpet_timer_stop_set_go(hpet_tick);
}
/*
* calibrate_tsc() calibrates the processor TSC in a very simple way, comparing
* it to the HPET timer of known frequency.
*/
#define TICK_COUNT 100000000
#define SMI_THRESHOLD 50000
#define MAX_TRIES 5
/*
* Some platforms take periodic SMI interrupts with 5ms duration. Make sure none
* occurs between the reads of the hpet & TSC.
*/
static void __init read_hpet_tsc(int *hpet, int *tsc)
{
int tsc1, tsc2, hpet1, i;
for (i = 0; i < MAX_TRIES; i++) {
tsc1 = get_cycles_sync();
hpet1 = hpet_readl(HPET_COUNTER);
tsc2 = get_cycles_sync();
if ((tsc2 - tsc1) < SMI_THRESHOLD)
break;
}
*hpet = hpet1;
*tsc = tsc2;
}
unsigned int __init hpet_calibrate_tsc(void)
{
int tsc_start, hpet_start;
int tsc_now, hpet_now;
unsigned long flags;
local_irq_save(flags);
read_hpet_tsc(&hpet_start, &tsc_start);
do {
local_irq_disable();
read_hpet_tsc(&hpet_now, &tsc_now);
local_irq_restore(flags);
} while ((tsc_now - tsc_start) < TICK_COUNT &&
(hpet_now - hpet_start) < TICK_COUNT);
return (tsc_now - tsc_start) * 1000000000L
/ ((hpet_now - hpet_start) * hpet_period / 1000);
}
#ifdef CONFIG_HPET_EMULATE_RTC
/* HPET in LegacyReplacement Mode eats up RTC interrupt line. When, HPET
* is enabled, we support RTC interrupt functionality in software.

33
arch/x86/kernel/time_64.c
View File

@ -292,35 +292,6 @@ static unsigned int __init tsc_calibrate_cpu_khz(void)
return pmc_now * tsc_khz / (tsc_now - tsc_start);
}
/*
* pit_calibrate_tsc() uses the speaker output (channel 2) of
* the PIT. This is better than using the timer interrupt output,
* because we can read the value of the speaker with just one inb(),
* where we need three i/o operations for the interrupt channel.
* We count how many ticks the TSC does in 50 ms.
*/
static unsigned int __init pit_calibrate_tsc(void)
{
unsigned long start, end;
unsigned long flags;
spin_lock_irqsave(&i8253_lock, flags);
outb((inb(0x61) & ~0x02) | 0x01, 0x61);
outb(0xb0, 0x43);
outb((PIT_TICK_RATE / (1000 / 50)) & 0xff, 0x42);
outb((PIT_TICK_RATE / (1000 / 50)) >> 8, 0x42);
start = get_cycles_sync();
while ((inb(0x61) & 0x20) == 0);
end = get_cycles_sync();
spin_unlock_irqrestore(&i8253_lock, flags);
return (end - start) / 50;
}
#define PIT_MODE 0x43
#define PIT_CH0 0x40
@ -376,14 +347,14 @@ void __init time_init(void)
if (hpet_use_timer) {
/* set tick_nsec to use the proper rate for HPET */
tick_nsec = TICK_NSEC_HPET;
tsc_khz = hpet_calibrate_tsc();
timename = "HPET";
} else {
pit_init();
tsc_khz = pit_calibrate_tsc();
timename = "PIT";
}
tsc_calibrate();
cpu_khz = tsc_khz;
if (cpu_has(&boot_cpu_data, X86_FEATURE_CONSTANT_TSC) &&
boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&

90
arch/x86/kernel/tsc_64.c
View File

@ -6,7 +6,9 @@
#include <linux/time.h>
#include <linux/acpi.h>
#include <linux/cpufreq.h>
#include <linux/acpi_pmtmr.h>
#include <asm/hpet.h>
#include <asm/timex.h>
static int notsc __initdata = 0;
@ -118,6 +120,94 @@ core_initcall(cpufreq_tsc);
#endif
#define MAX_RETRIES 5
#define SMI_TRESHOLD 50000
/*
* Read TSC and the reference counters. Take care of SMI disturbance
*/
static unsigned long __init tsc_read_refs(unsigned long *pm,
unsigned long *hpet)
{
unsigned long t1, t2;
int i;
for (i = 0; i < MAX_RETRIES; i++) {
t1 = get_cycles_sync();
if (hpet)
*hpet = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF;
else
*pm = acpi_pm_read_early();
t2 = get_cycles_sync();
if ((t2 - t1) < SMI_TRESHOLD)
return t2;
}
return ULONG_MAX;
}
/**
* tsc_calibrate - calibrate the tsc on boot
*/
void __init tsc_calibrate(void)
{
unsigned long flags, tsc1, tsc2, tr1, tr2, pm1, pm2, hpet1, hpet2;
int hpet = is_hpet_enabled();
local_irq_save(flags);
tsc1 = tsc_read_refs(&pm1, hpet ? &hpet1 : NULL);
outb((inb(0x61) & ~0x02) | 0x01, 0x61);
outb(0xb0, 0x43);
outb((CLOCK_TICK_RATE / (1000 / 50)) & 0xff, 0x42);
outb((CLOCK_TICK_RATE / (1000 / 50)) >> 8, 0x42);
tr1 = get_cycles_sync();
while ((inb(0x61) & 0x20) == 0);
tr2 = get_cycles_sync();
tsc2 = tsc_read_refs(&pm2, hpet ? &hpet2 : NULL);
local_irq_restore(flags);
/*
* Preset the result with the raw and inaccurate PIT
* calibration value
*/
tsc_khz = (tr2 - tr1) / 50;
/* hpet or pmtimer available ? */
if (!hpet && !pm1 && !pm2) {
printk(KERN_INFO "TSC calibrated against PIT\n");
return;
}
/* Check, whether the sampling was disturbed by an SMI */
if (tsc1 == ULONG_MAX || tsc2 == ULONG_MAX) {
printk(KERN_WARNING "TSC calibration disturbed by SMI, "
"using PIT calibration result\n");
return;
}
tsc2 = (tsc2 - tsc1) * 1000000L;
if (hpet) {
printk(KERN_INFO "TSC calibrated against HPET\n");
if (hpet2 < hpet1)
hpet2 += 0x100000000;
hpet2 -= hpet1;
tsc1 = (hpet2 * hpet_readl(HPET_PERIOD)) / 1000000;
} else {
printk(KERN_INFO "TSC calibrated against PM_TIMER\n");
if (pm2 < pm1)
pm2 += ACPI_PM_OVRRUN;
pm2 -= pm1;
tsc1 = (pm2 * 1000000000) / PMTMR_TICKS_PER_SEC;
}
tsc_khz = tsc2 / tsc1;
}
/*
* Make an educated guess if the TSC is trustworthy and synchronized
* over all CPUs.

4
include/asm-x86/tsc.h
View File

@ -72,4 +72,8 @@ int check_tsc_unstable(void);
extern void check_tsc_sync_source(int cpu);
extern void check_tsc_sync_target(void);
#ifdef CONFIG_X86_64
extern void tsc_calibrate(void);
#endif
#endif