#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/timer.h>
#include <linux/acpi_pmtmr.h>
#include <linux/cpufreq.h>
#include <asm/hpet.h>
unsigned int cpu_khz; /* TSC clocks / usec, not used here */
EXPORT_SYMBOL(cpu_khz);
unsigned int tsc_khz;
EXPORT_SYMBOL(tsc_khz);
/*
* TSC can be unstable due to cpufreq or due to unsynced TSCs
*/
int tsc_unstable;
/* native_sched_clock() is called before tsc_init(), so
we must start with the TSC soft disabled to prevent
erroneous rdtsc usage on !cpu_has_tsc processors */
int tsc_disabled = -1;
/*
* Scheduler clock - returns current time in nanosec units.
*/
u64 native_sched_clock(void)
{
u64 this_offset;
/*
* Fall back to jiffies if there's no TSC available:
* ( But note that we still use it if the TSC is marked
* unstable. We do this because unlike Time Of Day,
* the scheduler clock tolerates small errors and it's
* very important for it to be as fast as the platform
* can achive it. )
*/
if (unlikely(tsc_disabled)) {
/* No locking but a rare wrong value is not a big deal: */
return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
}
/* read the Time Stamp Counter: */
rdtscll(this_offset);
/* return the value in ns */
return cycles_2_ns(this_offset);
}
/* We need to define a real function for sched_clock, to override the
weak default version */
#ifdef CONFIG_PARAVIRT
unsigned long long sched_clock(void)
{
return paravirt_sched_clock();
}
#else
unsigned long long
sched_clock(void) __attribute__((alias("native_sched_clock")));
#endif
int check_tsc_unstable(void)
{
return tsc_unstable;
}
EXPORT_SYMBOL_GPL(check_tsc_unstable);
#ifdef CONFIG_X86_TSC
int __init notsc_setup(char *str)
{
printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
"cannot disable TSC completely.\n");
tsc_disabled = 1;
return 1;
}
#else
/*
* disable flag for tsc. Takes effect by clearing the TSC cpu flag
* in cpu/common.c
*/
int __init notsc_setup(char *str)
{
setup_clear_cpu_cap(X86_FEATURE_TSC);
return 1;
}
#endif
__setup("notsc", notsc_setup);
#define MAX_RETRIES 5
#define SMI_TRESHOLD 50000
/*
* Read TSC and the reference counters. Take care of SMI disturbance
*/
static u64 __init tsc_read_refs(u64 *pm, u64 *hpet)
{
u64 t1, t2;
int i;
for (i = 0; i < MAX_RETRIES; i++) {
t1 = get_cycles();
if (hpet)
*hpet = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF;
else
*pm = acpi_pm_read_early();
t2 = get_cycles();
if ((t2 - t1) < SMI_TRESHOLD)
return t2;
}
return ULLONG_MAX;
}
/**
* tsc_calibrate - calibrate the tsc on boot
*/
static unsigned int __init tsc_calibrate(void)
{
unsigned long flags;
u64 tsc1, tsc2, tr1, tr2, delta, pm1, pm2, hpet1, hpet2;
int hpet = is_hpet_enabled();
unsigned int tsc_khz_val = 0;
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();
while ((inb(0x61) & 0x20) == 0);
tr2 = get_cycles();
tsc2 = tsc_read_refs(&pm2, hpet ? &hpet2 : NULL);
local_irq_restore(flags);
/*
* Preset the result with the raw and inaccurate PIT
* calibration value
*/
delta = (tr2 - tr1);
do_div(delta, 50);
tsc_khz_val = delta;
/* hpet or pmtimer available ? */
if (!hpet && !pm1 && !pm2) {
printk(KERN_INFO "TSC calibrated against PIT\n");
goto out;
}
/* Check, whether the sampling was disturbed by an SMI */
if (tsc1 == ULLONG_MAX || tsc2 == ULLONG_MAX) {
printk(KERN_WARNING "TSC calibration disturbed by SMI, "
"using PIT calibration result\n");
goto out;
}
tsc2 = (tsc2 - tsc1) * 1000000LL;
if (hpet) {
printk(KERN_INFO "TSC calibrated against HPET\n");
if (hpet2 < hpet1)
hpet2 += 0x100000000ULL;
hpet2 -= hpet1;
tsc1 = ((u64)hpet2 * hpet_readl(HPET_PERIOD));
do_div(tsc1, 1000000);
} else {
printk(KERN_INFO "TSC calibrated against PM_TIMER\n");
if (pm2 < pm1)
pm2 += (u64)ACPI_PM_OVRRUN;
pm2 -= pm1;
tsc1 = pm2 * 1000000000LL;
do_div(tsc1, PMTMR_TICKS_PER_SEC);
}
do_div(tsc2, tsc1);
tsc_khz_val = tsc2;
out:
return tsc_khz_val;
}
unsigned long native_calculate_cpu_khz(void)
{
return tsc_calibrate();
}
#ifdef CONFIG_X86_32
/* Only called from the Powernow K7 cpu freq driver */
int recalibrate_cpu_khz(void)
{
#ifndef CONFIG_SMP
unsigned long cpu_khz_old = cpu_khz;
if (cpu_has_tsc) {
cpu_khz = calculate_cpu_khz();
tsc_khz = cpu_khz;
cpu_data(0).loops_per_jiffy =
cpufreq_scale(cpu_data(0).loops_per_jiffy,
cpu_khz_old, cpu_khz);
return 0;
} else
return -ENODEV;
#else
return -ENODEV;
#endif
}
EXPORT_SYMBOL(recalibrate_cpu_khz);
#endif /* CONFIG_X86_32 */
/* Accelerators for sched_clock()
* convert from cycles(64bits) => nanoseconds (64bits)
* basic equation:
* ns = cycles / (freq / ns_per_sec)
* ns = cycles * (ns_per_sec / freq)
* ns = cycles * (10^9 / (cpu_khz * 10^3))
* ns = cycles * (10^6 / cpu_khz)
*
* Then we use scaling math (suggested by george@mvista.com) to get:
* ns = cycles * (10^6 * SC / cpu_khz) / SC
* ns = cycles * cyc2ns_scale / SC
*
* And since SC is a constant power of two, we can convert the div
* into a shift.
*
* We can use khz divisor instead of mhz to keep a better precision, since
* cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
* (mathieu.desnoyers@polymtl.ca)
*
* -johnstul@us.ibm.com "math is hard, lets go shopping!"
*/
DEFINE_PER_CPU(unsigned long, cyc2ns);
void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
{
unsigned long long tsc_now, ns_now;
unsigned long flags, *scale;
local_irq_save(flags);
sched_clock_idle_sleep_event();
scale = &per_cpu(cyc2ns, cpu);
rdtscll(tsc_now);
ns_now = __cycles_2_ns(tsc_now);
if (cpu_khz)
*scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz;
sched_clock_idle_wakeup_event(0);
local_irq_restore(flags);
}
#ifdef CONFIG_CPU_FREQ
/* Frequency scaling support. Adjust the TSC based timer when the cpu frequency
* changes.
*
* RED-PEN: On SMP we assume all CPUs run with the same frequency. It's
* not that important because current Opteron setups do not support
* scaling on SMP anyroads.
*
* Should fix up last_tsc too. Currently gettimeofday in the
* first tick after the change will be slightly wrong.
*/
static unsigned int ref_freq;
static unsigned long loops_per_jiffy_ref;
static unsigned long tsc_khz_ref;
static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
void *data)
{
struct cpufreq_freqs *freq = data;
unsigned long *lpj, dummy;
if (cpu_has(&cpu_data(freq->cpu), X86_FEATURE_CONSTANT_TSC))
return 0;
lpj = &dummy;
if (!(freq->flags & CPUFREQ_CONST_LOOPS))
#ifdef CONFIG_SMP
lpj = &cpu_data(freq->cpu).loops_per_jiffy;
#else
lpj = &boot_cpu_data.loops_per_jiffy;
#endif
if (!ref_freq) {
ref_freq = freq->old;
loops_per_jiffy_ref = *lpj;
tsc_khz_ref = tsc_khz;
}
if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) ||
(val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
(val == CPUFREQ_RESUMECHANGE)) {
*lpj = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new);
tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new);
if (!(freq->flags & CPUFREQ_CONST_LOOPS))
mark_tsc_unstable("cpufreq changes");
}
set_cyc2ns_scale(tsc_khz_ref, freq->cpu);
return 0;
}
static struct notifier_block time_cpufreq_notifier_block = {
.notifier_call = time_cpufreq_notifier
};
static int __init cpufreq_tsc(void)
{
cpufreq_register_notifier(&time_cpufreq_notifier_block,
CPUFREQ_TRANSITION_NOTIFIER);
return 0;
}
core_initcall(cpufreq_tsc);
#endif /* CONFIG_CPU_FREQ */
