#include <linux/sched.h>
#include <linux/clocksource.h>
#include <linux/workqueue.h>
#include <linux/cpufreq.h>
#include <linux/jiffies.h>
#include <linux/init.h>
#include <linux/dmi.h>
#include <linux/percpu.h>
#include <asm/delay.h>
#include <asm/tsc.h>
#include <asm/io.h>
#include <asm/timer.h>
#include "mach_timer.h"
/* 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 */
static int tsc_disabled = -1;
/*
* On some systems the TSC frequency does not
* change with the cpu frequency. So we need
* an extra value to store the TSC freq
*/
unsigned int tsc_khz;
EXPORT_SYMBOL_GPL(tsc_khz);
#ifdef CONFIG_X86_TSC
static int __init tsc_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
*/
static int __init tsc_setup(char *str)
{
setup_clear_cpu_cap(X86_FEATURE_TSC);
return 1;
}
#endif
__setup("notsc", tsc_setup);
/*
* code to mark and check if the TSC is unstable
* due to cpufreq or due to unsynced TSCs
*/
static int tsc_unstable;
int check_tsc_unstable(void)
{
return tsc_unstable;
}
EXPORT_SYMBOL_GPL(check_tsc_unstable);
/* 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);
static 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;
/*
* Start smoothly with the new frequency:
*/
sched_clock_idle_wakeup_event(0);
local_irq_restore(flags);
}
/*
* Scheduler clock - returns current time in nanosec units.
*/
unsigned long long native_sched_clock(void)
{
unsigned long long 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
unsigned long native_calculate_cpu_khz(void)
{
unsigned long long start, end;
unsigned long count;
u64 delta64 = (u64)ULLONG_MAX;
int i;
unsigned long flags;
local_irq_save(flags);
/* run 3 times to ensure the cache is warm and to get an accurate reading */
for (i = 0; i < 3; i++) {
mach_prepare_counter();
rdtscll(start);
mach_countup(&count);
rdtscll(end);
/*
* Error: ECTCNEVERSET
* 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..
*/
if (count <= 1)
continue;
/* cpu freq too slow: */
if ((end - start) <= CALIBRATE_TIME_MSEC)
continue;
/*
* We want the minimum time of all runs in case one of them
* is inaccurate due to SMI or other delay
*/
delta64 = min(delta64, (end - start));
}
/* cpu freq too fast (or every run was bad): */
if (delta64 > (1ULL<<32))
goto err;
delta64 += CALIBRATE_TIME_MSEC/2; /* round for do_div */
do_div(delta64,CALIBRATE_TIME_MSEC);
local_irq_restore(flags);
return (unsigned long)delta64;
err:
local_irq_restore(flags);
return 0;
}
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);
#ifdef CONFIG_CPU_FREQ
/*
* if the CPU frequency is scaled, TSC-based delays will need a different
* loops_per_jiffy value to function properly.
*/
static unsigned int ref_freq;
static unsigned long loops_per_jiffy_ref;
static unsigned long cpu_khz_ref;
static int
time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data)
{
struct cpufreq_freqs *freq = data;
if (!ref_freq) {
if (!freq->old){
ref_freq = freq->new;
return 0;
}
ref_freq = freq->old;
loops_per_jiffy_ref = cpu_data(freq->cpu).loops_per_jiffy;
cpu_khz_ref = cpu_khz;
}
if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) ||
(val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
(val == CPUFREQ_RESUMECHANGE)) {
if (!(freq->flags & CPUFREQ_CONST_LOOPS))
cpu_data(freq->cpu).loops_per_jiffy =
cpufreq_scale(loops_per_jiffy_ref,
ref_freq, freq->new);
if (cpu_khz) {
if (num_online_cpus() == 1)
cpu_khz = cpufreq_scale(cpu_khz_ref,
ref_freq, freq->new);
if (!(freq->flags & CPUFREQ_CONST_LOOPS)) {
tsc_khz = cpu_khz;
set_cyc2ns_scale(cpu_khz, freq->cpu);
/*
* TSC based sched_clock turns
* to junk w/ cpufreq
*/
mark_tsc_unstable("cpufreq changes");
}
}
}
return 0;
}
static struct notifier_block time_cpufreq_notifier_block = {
.notifier_call = time_cpufreq_notifier
};
static int __init cpufreq_tsc(void)
{
return cpufreq_register_notifier(&time_cpufreq_notifier_block,
CPUFREQ_TRANSITION_NOTIFIER);
}
core_initcall(cpufreq_tsc);
#endif
/* clock source code */
static unsigned long current_tsc_khz;
static struct clocksource clocksource_tsc;
/*
* We compare the TSC to the cycle_last value in the clocksource
* structure to avoid a nasty time-warp issue. This can be observed in
* a very small window right after one CPU updated cycle_last under
* xtime lock and the other CPU reads a TSC value which is smaller
* than the cycle_last reference value due to a TSC which is slighty
* behind. This delta is nowhere else observable, but in that case it
* results in a forward time jump in the range of hours due to the
* unsigned delta calculation of the time keeping core code, which is
* necessary to support wrapping clocksources like pm timer.
*/
static cycle_t read_tsc(void)
{
cycle_t ret;
rdtscll(ret);
return ret >= clocksource_tsc.cycle_last ?
ret : clocksource_tsc.cycle_last;
}
static struct clocksource clocksource_tsc = {
.name = "tsc",
.rating = 300,
.read = read_tsc,
.mask = CLOCKSOURCE_MASK(64),
.mult = 0, /* to be set */
.shift = 22,
.flags = CLOCK_SOURCE_IS_CONTINUOUS |
CLOCK_SOURCE_MUST_VERIFY,
};
void mark_tsc_unstable(char *reason)
{
if (!tsc_unstable) {
tsc_unstable = 1;
printk("Marking TSC unstable due to: %s.\n", reason);
/* Can be called before registration */
if (clocksource_tsc.mult)
clocksource_change_rating(&clocksource_tsc, 0);
else
clocksource_tsc.rating = 0;
}
}
EXPORT_SYMBOL_GPL(mark_tsc_unstable);
static int __init dmi_mark_tsc_unstable(const struct dmi_system_id *d)
{
printk(KERN_NOTICE "%s detected: marking TSC unstable.\n",
d->ident);
tsc_unstable = 1;
return 0;
}
/* List of systems that have known TSC problems */
static struct dmi_system_id __initdata bad_tsc_dmi_table[] = {
{
.callback = dmi_mark_tsc_unstable,
.ident = "IBM Thinkpad 380XD",
.matches = {
DMI_MATCH(DMI_BOARD_VENDOR, "IBM"),
DMI_MATCH(DMI_BOARD_NAME, "2635FA0"),
},
},
{}
};
/*
* Make an educated guess if the TSC is trustworthy and synchronized
* over all CPUs.
*/
__cpuinit int unsynchronized_tsc(void)
{
if (!cpu_has_tsc || tsc_unstable)
return 1;
/* Anything with constant TSC should be synchronized */
if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
return 0;
/*
* Intel systems are normally all synchronized.
* Exceptions must mark TSC as unstable:
*/
if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
/* assume multi socket systems are not synchronized: */
if (num_possible_cpus() > 1)
tsc_unstable = 1;
}
return tsc_unstable;
}
/*
* Geode_LX - the OLPC CPU has a possibly a very reliable TSC
*/
#ifdef CONFIG_MGEODE_LX
/* RTSC counts during suspend */
#define RTSC_SUSP 0x100
static void __init check_geode_tsc_reliable(void)
{
unsigned long res_low, res_high;
rdmsr_safe(MSR_GEODE_BUSCONT_CONF0, &res_low, &res_high);
if (res_low & RTSC_SUSP)
clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
}
#else
static inline void check_geode_tsc_reliable(void) { }
#endif
void __init tsc_init(void)
{
int cpu;
if (!cpu_has_tsc || tsc_disabled > 0)
return;
cpu_khz = calculate_cpu_khz();
tsc_khz = cpu_khz;
if (!cpu_khz) {
mark_tsc_unstable("could not calculate TSC khz");
return;
}
/* now allow native_sched_clock() to use rdtsc */
tsc_disabled = 0;
printk("Detected %lu.%03lu MHz processor.\n",
(unsigned long)cpu_khz / 1000,
(unsigned long)cpu_khz % 1000);
/*
* Secondary CPUs do not run through tsc_init(), so set up
* all the scale factors for all CPUs, assuming the same
* speed as the bootup CPU. (cpufreq notifiers will fix this
* up if their speed diverges)
*/
for_each_possible_cpu(cpu)
set_cyc2ns_scale(cpu_khz, cpu);
use_tsc_delay();
/* Check and install the TSC clocksource */
dmi_check_system(bad_tsc_dmi_table);
unsynchronized_tsc();
check_geode_tsc_reliable();
current_tsc_khz = tsc_khz;
clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
clocksource_tsc.shift);
/* lower the rating if we already know its unstable: */
if (check_tsc_unstable()) {
clocksource_tsc.rating = 0;
clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
}
clocksource_register(&clocksource_tsc);
}
