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x86: merge the TSC cpu-freq code
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Unify the TSC cpufreq code.

Signed-off-by: Alok N Kataria <akataria@vmware.com>
Signed-off-by: Dan Hecht <dhecht@vmware.com>
Cc: Dan Hecht <dhecht@vmware.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Alok Kataria authored and Ingo Molnar committed Jul 9, 2008
1 parent bfc0f59 commit 2dbe06f
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Showing 3 changed files with 114 additions and 227 deletions.
114 changes: 114 additions & 0 deletions arch/x86/kernel/tsc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
#include <linux/module.h>
#include <linux/timer.h>
#include <linux/acpi_pmtmr.h>
#include <linux/cpufreq.h>

#include <asm/hpet.h>

Expand Down Expand Up @@ -215,3 +216,116 @@ int recalibrate_cpu_khz(void)
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 */
113 changes: 0 additions & 113 deletions arch/x86/kernel/tsc_32.c
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Original file line number Diff line number Diff line change
Expand Up @@ -18,119 +18,6 @@
extern int tsc_unstable;
extern int tsc_disabled;

/* 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;

/*
* Start smoothly with the new frequency:
*/
sched_clock_idle_wakeup_event(0);
local_irq_restore(flags);
}

#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 struct clocksource clocksource_tsc;
Expand Down
114 changes: 0 additions & 114 deletions arch/x86/kernel/tsc_64.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -16,120 +16,6 @@
extern int tsc_unstable;
extern int tsc_disabled;

/* 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

/*
* Make an educated guess if the TSC is trustworthy and synchronized
* over all CPUs.
Expand Down

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