/*
* This code largely moved from arch/i386/kernel/timer/timer_tsc.c
* which was originally moved from arch/i386/kernel/time.c.
* See comments there for proper credits.
*/
#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 <asm/delay.h>
#include <asm/tsc.h>
#include <asm/delay.h>
#include <asm/io.h>
#include "mach_timer.h"
/*
* 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;
int tsc_disable __cpuinitdata = 0;
#ifdef CONFIG_X86_TSC
static int __init tsc_setup(char *str)
{
printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
"cannot disable TSC.\n");
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)
{
tsc_disable = 1;
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;
static inline int check_tsc_unstable(void)
{
return tsc_unstable;
}
void mark_tsc_unstable(void)
{
tsc_unstable = 1;
}
EXPORT_SYMBOL_GPL(mark_tsc_unstable);
/* Accellerators 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 percision, 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!"
*/
static unsigned long cyc2ns_scale __read_mostly;
#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
static inline void set_cyc2ns_scale(unsigned long cpu_khz)
{
cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz;
}
static inline unsigned long long cycles_2_ns(unsigned long long cyc)
{
return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR;
}
/*
* Scheduler clock - returns current time in nanosec units.
*/
unsigned long long sched_clock(void)
{
unsigned long long this_offset;
/*
* in the NUMA case we dont use the TSC as they are not
* synchronized across all CPUs.
*/
#ifndef CONFIG_NUMA
if (!cpu_khz || check_tsc_unstable())
#endif
/* 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);
}
static unsigned long calculate_cpu_khz(void)
{
unsigned long long start, end;
unsigned long count;
u64 delta64;
int i;
unsigned long flags;
local_irq_save(flags);
/* run 3 times to ensure the cache is warm */
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)
goto err;
delta64 = end - start;
/* cpu freq too fast: */
if (delta64 > (1ULL<<32))
goto err;
/* cpu freq too slow: */
if (delta64 <= CALIBRATE_TIME_MSEC)
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);
void __init tsc_init(void)
{
if (!cpu_has_tsc || tsc_disable)
return;
cpu_khz = calculate_cpu_khz();
tsc_khz = cpu_khz;
if (!cpu_khz)
return;
printk("Detected %lu.%03lu MHz processor.\n",
(unsigned long)cpu_khz / 1000,
(unsigned long)cpu_khz % 1000);
set_cyc2ns_scale(cpu_khz);
use_tsc_delay();
}
#ifdef CONFIG_CPU_FREQ
static unsigned int cpufreq_delayed_issched = 0;
static unsigned int cpufreq_init = 0;
static struct work_struct cpufreq_delayed_get_work;
static void handle_cpufreq_delayed_get(void *v)
{
unsigned int cpu;
for_each_online_cpu(cpu)
cpufreq_get(cpu);
cpufreq_delayed_issched = 0;
}
/*
* if we notice cpufreq oddness, schedule a call to cpufreq_get() as it tries
* to verify the CPU frequency the timing core thinks the CPU is running
* at is still correct.
*/
static inline void cpufreq_delayed_get(void)
{
if (cpufreq_init && !cpufreq_delayed_issched) {
cpufreq_delayed_issched = 1;
printk(KERN_DEBUG "Checking if CPU frequency changed.\n");
schedule_work(&cpufreq_delayed_get_work);
}
}
/*
* 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 = 0;
static unsigned long loops_per_jiffy_ref = 0;
static unsigned long cpu_khz_ref = 0;
static int
time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data)
{
struct cpufreq_freqs *freq = data;
if (val != CPUFREQ_RESUMECHANGE && val != CPUFREQ_SUSPENDCHANGE)
write_seqlock_irq(&xtime_lock);
if (!ref_freq) {
if (!freq->old){
ref_freq = freq->new;
goto end;
}
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);
/*
* TSC based sched_clock turns
* to junk w/ cpufreq
*/
mark_tsc_unstable();
}
}
}
end:
if (val != CPUFREQ_RESUMECHANGE && val != CPUFREQ_SUSPENDCHANGE)
write_sequnlock_irq(&xtime_lock);
return 0;
}
static struct notifier_block time_cpufreq_notifier_block = {
.notifier_call = time_cpufreq_notifier
};
static int __init cpufreq_tsc(void)
{
int ret;
INIT_WORK(&cpufreq_delayed_get_work, handle_cpufreq_delayed_get, NULL);
ret = cpufreq_register_notifier(&time_cpufreq_notifier_block,
CPUFREQ_TRANSITION_NOTIFIER);
if (!ret)
cpufreq_init = 1;
return ret;
}
core_initcall(cpufreq_tsc);
#endif
/* clock source code */
static unsigned long current_tsc_khz = 0;
static int tsc_update_callback(void);
static cycle_t read_tsc(void)
{
cycle_t ret;
rdtscll(ret);
return ret;
}
static struct clocksource clocksource_tsc = {
.name = "tsc",
.rating = 300,
.read = read_tsc,
.mask = CLOCKSOURCE_MASK(64),
.mult = 0, /* to be set */
.shift = 22,
.update_callback = tsc_update_callback,
.is_continuous = 1,
};
static int tsc_update_callback(void)
{
int change = 0;
/* check to see if we should switch to the safe clocksource: */
if (clocksource_tsc.rating != 0 && check_tsc_unstable()) {
clocksource_tsc.rating = 0;
clocksource_reselect();
change = 1;
}
/* only update if tsc_khz has changed: */
if (current_tsc_khz != tsc_khz) {
current_tsc_khz = tsc_khz;
clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
clocksource_tsc.shift);
change = 1;
}
return change;
}
static int __init dmi_mark_tsc_unstable(struct dmi_system_id *d)
{
printk(KERN_NOTICE "%s detected: marking TSC unstable.\n",
d->ident);
mark_tsc_unstable();
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"),
},
},
{}
};
#define TSC_FREQ_CHECK_INTERVAL (10*MSEC_PER_SEC) /* 10sec in MS */
static struct timer_list verify_tsc_freq_timer;
/* XXX - Probably should add locking */
static void verify_tsc_freq(unsigned long unused)
{
static u64 last_tsc;
static unsigned long last_jiffies;
u64 now_tsc, interval_tsc;
unsigned long now_jiffies, interval_jiffies;
if (check_tsc_unstable())
return;
rdtscll(now_tsc);
now_jiffies = jiffies;
if (!last_jiffies) {
goto out;
}
interval_jiffies = now_jiffies - last_jiffies;
interval_tsc = now_tsc - last_tsc;
interval_tsc *= HZ;
do_div(interval_tsc, cpu_khz*1000);
if (interval_tsc < (interval_jiffies * 3 / 4)) {
printk("TSC appears to be running slowly. "
"Marking it as unstable\n");
mark_tsc_unstable();
return;
}
out:
last_tsc = now_tsc;
last_jiffies = now_jiffies;
/* set us up to go off on the next interval: */
mod_timer(&verify_tsc_freq_timer,
jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL));
}
/*
* Make an educated guess if the TSC is trustworthy and synchronized
* over all CPUs.
*/
static __init int unsynchronized_tsc(void)
{
/*
* Intel systems are normally all synchronized.
* Exceptions must mark TSC as unstable:
*/
if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
return 0;
/* assume multi socket systems are not synchronized: */
return num_possible_cpus() > 1;
}
static int __init init_tsc_clocksource(void)
{
if (cpu_has_tsc && tsc_khz && !tsc_disable) {
/* check blacklist */
dmi_check_system(bad_tsc_dmi_table);
if (unsynchronized_tsc()) /* mark unstable if unsynced */
mark_tsc_unstable();
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;
init_timer(&verify_tsc_freq_timer);
verify_tsc_freq_timer.function = verify_tsc_freq;
verify_tsc_freq_timer.expires =
jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL);
add_timer(&verify_tsc_freq_timer);
return clocksource_register(&clocksource_tsc);
}
return 0;
}
module_init(init_tsc_clocksource);
