linux/arch/ia64/kernel/time.c
Tony Luck c47953cfc6 [IA64] s/scalibility/scalability/
Previous spelling patch from Simon Arlott broke one spot that
didn't need fixing (reported by Simon within 35 minutes of the
patch ... but not until after I'd applied to GIT and pushed :-(

Signed-off-by: Tony Luck <tony.luck@intel.com>
2007-05-14 15:57:39 -07:00

311 lines
8.4 KiB
C

/*
* linux/arch/ia64/kernel/time.c
*
* Copyright (C) 1998-2003 Hewlett-Packard Co
* Stephane Eranian <eranian@hpl.hp.com>
* David Mosberger <davidm@hpl.hp.com>
* Copyright (C) 1999 Don Dugger <don.dugger@intel.com>
* Copyright (C) 1999-2000 VA Linux Systems
* Copyright (C) 1999-2000 Walt Drummond <drummond@valinux.com>
*/
#include <linux/cpu.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/profile.h>
#include <linux/sched.h>
#include <linux/time.h>
#include <linux/interrupt.h>
#include <linux/efi.h>
#include <linux/profile.h>
#include <linux/timex.h>
#include <asm/machvec.h>
#include <asm/delay.h>
#include <asm/hw_irq.h>
#include <asm/ptrace.h>
#include <asm/sal.h>
#include <asm/sections.h>
#include <asm/system.h>
volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */
#ifdef CONFIG_IA64_DEBUG_IRQ
unsigned long last_cli_ip;
EXPORT_SYMBOL(last_cli_ip);
#endif
static struct time_interpolator itc_interpolator = {
.shift = 16,
.mask = 0xffffffffffffffffLL,
.source = TIME_SOURCE_CPU
};
static irqreturn_t
timer_interrupt (int irq, void *dev_id)
{
unsigned long new_itm;
if (unlikely(cpu_is_offline(smp_processor_id()))) {
return IRQ_HANDLED;
}
platform_timer_interrupt(irq, dev_id);
new_itm = local_cpu_data->itm_next;
if (!time_after(ia64_get_itc(), new_itm))
printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
ia64_get_itc(), new_itm);
profile_tick(CPU_PROFILING);
while (1) {
update_process_times(user_mode(get_irq_regs()));
new_itm += local_cpu_data->itm_delta;
if (smp_processor_id() == time_keeper_id) {
/*
* Here we are in the timer irq handler. We have irqs locally
* disabled, but we don't know if the timer_bh is running on
* another CPU. We need to avoid to SMP race by acquiring the
* xtime_lock.
*/
write_seqlock(&xtime_lock);
do_timer(1);
local_cpu_data->itm_next = new_itm;
write_sequnlock(&xtime_lock);
} else
local_cpu_data->itm_next = new_itm;
if (time_after(new_itm, ia64_get_itc()))
break;
/*
* Allow IPIs to interrupt the timer loop.
*/
local_irq_enable();
local_irq_disable();
}
do {
/*
* If we're too close to the next clock tick for
* comfort, we increase the safety margin by
* intentionally dropping the next tick(s). We do NOT
* update itm.next because that would force us to call
* do_timer() which in turn would let our clock run
* too fast (with the potentially devastating effect
* of losing monotony of time).
*/
while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
new_itm += local_cpu_data->itm_delta;
ia64_set_itm(new_itm);
/* double check, in case we got hit by a (slow) PMI: */
} while (time_after_eq(ia64_get_itc(), new_itm));
return IRQ_HANDLED;
}
/*
* Encapsulate access to the itm structure for SMP.
*/
void
ia64_cpu_local_tick (void)
{
int cpu = smp_processor_id();
unsigned long shift = 0, delta;
/* arrange for the cycle counter to generate a timer interrupt: */
ia64_set_itv(IA64_TIMER_VECTOR);
delta = local_cpu_data->itm_delta;
/*
* Stagger the timer tick for each CPU so they don't occur all at (almost) the
* same time:
*/
if (cpu) {
unsigned long hi = 1UL << ia64_fls(cpu);
shift = (2*(cpu - hi) + 1) * delta/hi/2;
}
local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
ia64_set_itm(local_cpu_data->itm_next);
}
static int nojitter;
static int __init nojitter_setup(char *str)
{
nojitter = 1;
printk("Jitter checking for ITC timers disabled\n");
return 1;
}
__setup("nojitter", nojitter_setup);
void __devinit
ia64_init_itm (void)
{
unsigned long platform_base_freq, itc_freq;
struct pal_freq_ratio itc_ratio, proc_ratio;
long status, platform_base_drift, itc_drift;
/*
* According to SAL v2.6, we need to use a SAL call to determine the platform base
* frequency and then a PAL call to determine the frequency ratio between the ITC
* and the base frequency.
*/
status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
&platform_base_freq, &platform_base_drift);
if (status != 0) {
printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
} else {
status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
if (status != 0)
printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
}
if (status != 0) {
/* invent "random" values */
printk(KERN_ERR
"SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
platform_base_freq = 100000000;
platform_base_drift = -1; /* no drift info */
itc_ratio.num = 3;
itc_ratio.den = 1;
}
if (platform_base_freq < 40000000) {
printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
platform_base_freq);
platform_base_freq = 75000000;
platform_base_drift = -1;
}
if (!proc_ratio.den)
proc_ratio.den = 1; /* avoid division by zero */
if (!itc_ratio.den)
itc_ratio.den = 1; /* avoid division by zero */
itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%u/%u, "
"ITC freq=%lu.%03luMHz", smp_processor_id(),
platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
if (platform_base_drift != -1) {
itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
printk("+/-%ldppm\n", itc_drift);
} else {
itc_drift = -1;
printk("\n");
}
local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
local_cpu_data->itc_freq = itc_freq;
local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
+ itc_freq/2)/itc_freq;
if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
itc_interpolator.frequency = local_cpu_data->itc_freq;
itc_interpolator.drift = itc_drift;
#ifdef CONFIG_SMP
/* On IA64 in an SMP configuration ITCs are never accurately synchronized.
* Jitter compensation requires a cmpxchg which may limit
* the scalability of the syscalls for retrieving time.
* The ITC synchronization is usually successful to within a few
* ITC ticks but this is not a sure thing. If you need to improve
* timer performance in SMP situations then boot the kernel with the
* "nojitter" option. However, doing so may result in time fluctuating (maybe
* even going backward) if the ITC offsets between the individual CPUs
* are too large.
*/
if (!nojitter) itc_interpolator.jitter = 1;
#endif
register_time_interpolator(&itc_interpolator);
}
/* Setup the CPU local timer tick */
ia64_cpu_local_tick();
}
static struct irqaction timer_irqaction = {
.handler = timer_interrupt,
.flags = IRQF_DISABLED | IRQF_IRQPOLL,
.name = "timer"
};
void __devinit ia64_disable_timer(void)
{
ia64_set_itv(1 << 16);
}
void __init
time_init (void)
{
register_percpu_irq(IA64_TIMER_VECTOR, &timer_irqaction);
efi_gettimeofday(&xtime);
ia64_init_itm();
/*
* Initialize wall_to_monotonic such that adding it to xtime will yield zero, the
* tv_nsec field must be normalized (i.e., 0 <= nsec < NSEC_PER_SEC).
*/
set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
}
/*
* Generic udelay assumes that if preemption is allowed and the thread
* migrates to another CPU, that the ITC values are synchronized across
* all CPUs.
*/
static void
ia64_itc_udelay (unsigned long usecs)
{
unsigned long start = ia64_get_itc();
unsigned long end = start + usecs*local_cpu_data->cyc_per_usec;
while (time_before(ia64_get_itc(), end))
cpu_relax();
}
void (*ia64_udelay)(unsigned long usecs) = &ia64_itc_udelay;
void
udelay (unsigned long usecs)
{
(*ia64_udelay)(usecs);
}
EXPORT_SYMBOL(udelay);
static unsigned long long ia64_itc_printk_clock(void)
{
if (ia64_get_kr(IA64_KR_PER_CPU_DATA))
return sched_clock();
return 0;
}
static unsigned long long ia64_default_printk_clock(void)
{
return (unsigned long long)(jiffies_64 - INITIAL_JIFFIES) *
(1000000000/HZ);
}
unsigned long long (*ia64_printk_clock)(void) = &ia64_default_printk_clock;
unsigned long long printk_clock(void)
{
return ia64_printk_clock();
}
void __init
ia64_setup_printk_clock(void)
{
if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT))
ia64_printk_clock = ia64_itc_printk_clock;
}