Commit 539eb11e authored by john stultz's avatar john stultz Committed by Linus Torvalds
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[PATCH] Time: i386 Conversion - part 2: Rework TSC Support



As part of the i386 conversion to the generic timekeeping infrastructure, this
introduces a new tsc.c file.  The code in this file replaces the TSC
initialization, management and access code currently in timer_tsc.c (which
will be removed) that we want to preserve.

The code also introduces the following functionality:

o tsc_khz: like cpu_khz but stores the TSC frequency on systems that do not
  change TSC frequency w/ CPU frequency

o check/mark_tsc_unstable: accessor/modifier flag for TSC timekeeping
  usability

o minor cleanups to calibration math.

This patch also includes a one line __cpuinitdata fix from Zwane Mwaikambo.
Signed-off-by: default avatarJohn Stultz <johnstul@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 8d016ef1
......@@ -7,7 +7,7 @@ extra-y := head.o init_task.o vmlinux.lds
obj-y := process.o semaphore.o signal.o entry.o traps.o irq.o \
ptrace.o time.o ioport.o ldt.o setup.o i8259.o sys_i386.o \
pci-dma.o i386_ksyms.o i387.o bootflag.o \
quirks.o i8237.o topology.o alternative.o i8253.o
quirks.o i8237.o topology.o alternative.o i8253.o tsc.o
obj-y += cpu/
obj-y += timers/
......
......@@ -79,10 +79,12 @@ int __init get_memcfg_numaq(void)
return 1;
}
static int __init numaq_dsc_disable(void)
static int __init numaq_tsc_disable(void)
{
printk(KERN_DEBUG "NUMAQ: disabling TSC\n");
tsc_disable = 1;
if (num_online_nodes() > 1) {
printk(KERN_DEBUG "NUMAQ: disabling TSC\n");
tsc_disable = 1;
}
return 0;
}
core_initcall(numaq_dsc_disable);
arch_initcall(numaq_tsc_disable);
......@@ -1575,6 +1575,7 @@ void __init setup_arch(char **cmdline_p)
conswitchp = &dummy_con;
#endif
#endif
tsc_init();
}
static __init int add_pcspkr(void)
......
......@@ -32,10 +32,6 @@ static unsigned long hpet_last;
static struct timer_opts timer_tsc;
#endif
static inline void cpufreq_delayed_get(void);
int tsc_disable __devinitdata = 0;
static int use_tsc;
/* Number of usecs that the last interrupt was delayed */
static int delay_at_last_interrupt;
......@@ -144,30 +140,6 @@ static unsigned long long monotonic_clock_tsc(void)
return base + cycles_2_ns(this_offset - last_offset);
}
/*
* 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 (!use_tsc)
#endif
/* no locking but a rare wrong value is not a big deal */
return jiffies_64 * (1000000000 / HZ);
/* Read the Time Stamp Counter */
rdtscll(this_offset);
/* return the value in ns */
return cycles_2_ns(this_offset);
}
static void delay_tsc(unsigned long loops)
{
unsigned long bclock, now;
......@@ -231,136 +203,6 @@ static void mark_offset_tsc_hpet(void)
}
#endif
#ifdef CONFIG_CPU_FREQ
#include <linux/workqueue.h>
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 lost ticks, 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 "Losing some ticks... 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;
#ifndef CONFIG_SMP
static unsigned long fast_gettimeoffset_ref = 0;
static unsigned int cpu_khz_ref = 0;
#endif
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;
#ifndef CONFIG_SMP
fast_gettimeoffset_ref = fast_gettimeoffset_quotient;
cpu_khz_ref = cpu_khz;
#endif
}
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);
#ifndef CONFIG_SMP
if (cpu_khz)
cpu_khz = cpufreq_scale(cpu_khz_ref, ref_freq, freq->new);
if (use_tsc) {
if (!(freq->flags & CPUFREQ_CONST_LOOPS)) {
fast_gettimeoffset_quotient = cpufreq_scale(fast_gettimeoffset_ref, freq->new, ref_freq);
set_cyc2ns_scale(cpu_khz);
}
}
#endif
}
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);
#else /* CONFIG_CPU_FREQ */
static inline void cpufreq_delayed_get(void) { return; }
#endif
int recalibrate_cpu_khz(void)
{
#ifndef CONFIG_SMP
unsigned int cpu_khz_old = cpu_khz;
if (cpu_has_tsc) {
local_irq_disable();
init_cpu_khz();
local_irq_enable();
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);
static void mark_offset_tsc(void)
{
unsigned long lost,delay;
......@@ -451,9 +293,6 @@ static void mark_offset_tsc(void)
clock_fallback();
}
/* ... but give the TSC a fair chance */
if (lost_count > 25)
cpufreq_delayed_get();
} else
lost_count = 0;
/* update the monotonic base value */
......@@ -578,23 +417,6 @@ static int tsc_resume(void)
return 0;
}
#ifndef CONFIG_X86_TSC
/* 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;
}
#else
static int __init tsc_setup(char *str)
{
printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
"cannot disable TSC.\n");
return 1;
}
#endif
__setup("notsc", tsc_setup);
......
/*
* 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/workqueue.h>
#include <linux/cpufreq.h>
#include <linux/jiffies.h>
#include <linux/init.h>
#include <asm/tsc.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 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);
}
#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
......@@ -369,6 +369,11 @@ static void acpi_processor_idle(void)
t2 = inl(acpi_fadt.xpm_tmr_blk.address);
/* Get end time (ticks) */
t2 = inl(acpi_fadt.xpm_tmr_blk.address);
#ifdef CONFIG_GENERIC_TIME
/* TSC halts in C2, so notify users */
mark_tsc_unstable();
#endif
/* Re-enable interrupts */
local_irq_enable();
set_thread_flag(TIF_POLLING_NRFLAG);
......@@ -409,6 +414,10 @@ static void acpi_processor_idle(void)
ACPI_MTX_DO_NOT_LOCK);
}
#ifdef CONFIG_GENERIC_TIME
/* TSC halts in C3, so notify users */
mark_tsc_unstable();
#endif
/* Re-enable interrupts */
local_irq_enable();
set_thread_flag(TIF_POLLING_NRFLAG);
......
......@@ -15,7 +15,9 @@
#ifndef _MACH_TIMER_H
#define _MACH_TIMER_H
#define CALIBRATE_LATCH (5 * LATCH)
#define CALIBRATE_TIME_MSEC 30 /* 30 msecs */
#define CALIBRATE_LATCH \
((CLOCK_TICK_RATE * CALIBRATE_TIME_MSEC + 1000/2)/1000)
static inline void mach_prepare_counter(void)
{
......
......@@ -2,6 +2,7 @@
#define __ASM_MACH_MPPARSE_H
#include <mach_apic.h>
#include <asm/tsc.h>
extern int use_cyclone;
......@@ -29,6 +30,7 @@ static inline int mps_oem_check(struct mp_config_table *mpc, char *oem,
(!strncmp(productid, "VIGIL SMP", 9)
|| !strncmp(productid, "EXA", 3)
|| !strncmp(productid, "RUTHLESS SMP", 12))){
mark_tsc_unstable();
use_cyclone = 1; /*enable cyclone-timer*/
setup_summit();
return 1;
......@@ -42,6 +44,7 @@ static inline int acpi_madt_oem_check(char *oem_id, char *oem_table_id)
if (!strncmp(oem_id, "IBM", 3) &&
(!strncmp(oem_table_id, "SERVIGIL", 8)
|| !strncmp(oem_table_id, "EXA", 3))){
mark_tsc_unstable();
use_cyclone = 1; /*enable cyclone-timer*/
setup_summit();
return 1;
......
......@@ -7,6 +7,7 @@
#define _ASMi386_TIMEX_H
#include <asm/processor.h>
#include <asm/tsc.h>
#ifdef CONFIG_X86_ELAN