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Merge branch 'x86-tsc-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 

* 'x86-tsc-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  x86: Check tsc available/disabled in the delayed init function
  x86: Improve TSC calibration using a delayed workqueue
  x86: Make tsc=reliable override boot time stability checks
This commit is contained in:
Linus Torvalds 2011-01-06 11:08:14 -08:00
parent 4f00b901d4 a8760eca6c
commit d7a5a18190
2 changed files with 96 additions and 9 deletions
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9
Documentation/kernel-parameters.txt
View File

@ -2461,12 +2461,13 @@ and is between 256 and 4096 characters. It is defined in the file
to facilitate early boot debugging.
See also Documentation/trace/events.txt
tsc= Disable clocksource-must-verify flag for TSC.
tsc= Disable clocksource stability checks for TSC.
Format: <string>
[x86] reliable: mark tsc clocksource as reliable, this
disables clocksource verification at runtime.
Used to enable high-resolution timer mode on older
hardware, and in virtualized environment.
disables clocksource verification at runtime, as well
as the stability checks done at bootup. Used to enable
high-resolution timer mode on older hardware, and in
virtualized environment.
[x86] noirqtime: Do not use TSC to do irq accounting.
Used to run time disable IRQ_TIME_ACCOUNTING on any
platforms where RDTSC is slow and this accounting

96
arch/x86/kernel/tsc.c
View File

@ -872,6 +872,9 @@ __cpuinit int unsynchronized_tsc(void)
if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
return 0;
if (tsc_clocksource_reliable)
return 0;
/*
* Intel systems are normally all synchronized.
* Exceptions must mark TSC as unstable:
@ -879,14 +882,92 @@ __cpuinit int unsynchronized_tsc(void)
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 1;
}
return tsc_unstable;
return 0;
}
static void __init init_tsc_clocksource(void)
static void tsc_refine_calibration_work(struct work_struct *work);
static DECLARE_DELAYED_WORK(tsc_irqwork, tsc_refine_calibration_work);
/**
* tsc_refine_calibration_work - Further refine tsc freq calibration
* @work - ignored.
*
* This functions uses delayed work over a period of a
* second to further refine the TSC freq value. Since this is
* timer based, instead of loop based, we don't block the boot
* process while this longer calibration is done.
*
* If there are any calibration anomolies (too many SMIs, etc),
* or the refined calibration is off by 1% of the fast early
* calibration, we throw out the new calibration and use the
* early calibration.
*/
static void tsc_refine_calibration_work(struct work_struct *work)
{
static u64 tsc_start = -1, ref_start;
static int hpet;
u64 tsc_stop, ref_stop, delta;
unsigned long freq;
/* Don't bother refining TSC on unstable systems */
if (check_tsc_unstable())
goto out;
/*
* Since the work is started early in boot, we may be
* delayed the first time we expire. So set the workqueue
* again once we know timers are working.
*/
if (tsc_start == -1) {
/*
* Only set hpet once, to avoid mixing hardware
* if the hpet becomes enabled later.
*/
hpet = is_hpet_enabled();
schedule_delayed_work(&tsc_irqwork, HZ);
tsc_start = tsc_read_refs(&ref_start, hpet);
return;
}
tsc_stop = tsc_read_refs(&ref_stop, hpet);
/* hpet or pmtimer available ? */
if (!hpet && !ref_start && !ref_stop)
goto out;
/* Check, whether the sampling was disturbed by an SMI */
if (tsc_start == ULLONG_MAX || tsc_stop == ULLONG_MAX)
goto out;
delta = tsc_stop - tsc_start;
delta *= 1000000LL;
if (hpet)
freq = calc_hpet_ref(delta, ref_start, ref_stop);
else
freq = calc_pmtimer_ref(delta, ref_start, ref_stop);
/* Make sure we're within 1% */
if (abs(tsc_khz - freq) > tsc_khz/100)
goto out;
tsc_khz = freq;
printk(KERN_INFO "Refined TSC clocksource calibration: "
"%lu.%03lu MHz.\n", (unsigned long)tsc_khz / 1000,
(unsigned long)tsc_khz % 1000);
out:
clocksource_register_khz(&clocksource_tsc, tsc_khz);
}
static int __init init_tsc_clocksource(void)
{
if (!cpu_has_tsc || tsc_disabled > 0)
return 0;
if (tsc_clocksource_reliable)
clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
/* lower the rating if we already know its unstable: */
@ -894,8 +975,14 @@ static void __init init_tsc_clocksource(void)
clocksource_tsc.rating = 0;
clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
}
clocksource_register_khz(&clocksource_tsc, tsc_khz);
schedule_delayed_work(&tsc_irqwork, 0);
return 0;
}
/*
* We use device_initcall here, to ensure we run after the hpet
* is fully initialized, which may occur at fs_initcall time.
*/
device_initcall(init_tsc_clocksource);
void __init tsc_init(void)
{
@ -949,6 +1036,5 @@ void __init tsc_init(void)
mark_tsc_unstable("TSCs unsynchronized");
check_system_tsc_reliable();
init_tsc_clocksource();
}