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
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commit
d7a5a18190
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@ -2461,12 +2461,13 @@ and is between 256 and 4096 characters. It is defined in the file
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to facilitate early boot debugging.
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See also Documentation/trace/events.txt
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tsc= Disable clocksource-must-verify flag for TSC.
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tsc= Disable clocksource stability checks for TSC.
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Format: <string>
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[x86] reliable: mark tsc clocksource as reliable, this
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disables clocksource verification at runtime.
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Used to enable high-resolution timer mode on older
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hardware, and in virtualized environment.
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disables clocksource verification at runtime, as well
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as the stability checks done at bootup. Used to enable
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high-resolution timer mode on older hardware, and in
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virtualized environment.
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[x86] noirqtime: Do not use TSC to do irq accounting.
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Used to run time disable IRQ_TIME_ACCOUNTING on any
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platforms where RDTSC is slow and this accounting
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@ -872,6 +872,9 @@ __cpuinit int unsynchronized_tsc(void)
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if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
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return 0;
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if (tsc_clocksource_reliable)
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return 0;
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/*
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* Intel systems are normally all synchronized.
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* Exceptions must mark TSC as unstable:
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@ -879,14 +882,92 @@ __cpuinit int unsynchronized_tsc(void)
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if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
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/* assume multi socket systems are not synchronized: */
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if (num_possible_cpus() > 1)
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tsc_unstable = 1;
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return 1;
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}
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return tsc_unstable;
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return 0;
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}
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static void __init init_tsc_clocksource(void)
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static void tsc_refine_calibration_work(struct work_struct *work);
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static DECLARE_DELAYED_WORK(tsc_irqwork, tsc_refine_calibration_work);
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/**
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* tsc_refine_calibration_work - Further refine tsc freq calibration
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* @work - ignored.
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*
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* This functions uses delayed work over a period of a
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* second to further refine the TSC freq value. Since this is
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* timer based, instead of loop based, we don't block the boot
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* process while this longer calibration is done.
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*
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* If there are any calibration anomolies (too many SMIs, etc),
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* or the refined calibration is off by 1% of the fast early
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* calibration, we throw out the new calibration and use the
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* early calibration.
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*/
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static void tsc_refine_calibration_work(struct work_struct *work)
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{
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static u64 tsc_start = -1, ref_start;
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static int hpet;
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u64 tsc_stop, ref_stop, delta;
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unsigned long freq;
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/* Don't bother refining TSC on unstable systems */
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if (check_tsc_unstable())
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goto out;
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/*
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* Since the work is started early in boot, we may be
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* delayed the first time we expire. So set the workqueue
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* again once we know timers are working.
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*/
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if (tsc_start == -1) {
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/*
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* Only set hpet once, to avoid mixing hardware
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* if the hpet becomes enabled later.
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*/
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hpet = is_hpet_enabled();
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schedule_delayed_work(&tsc_irqwork, HZ);
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tsc_start = tsc_read_refs(&ref_start, hpet);
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return;
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}
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tsc_stop = tsc_read_refs(&ref_stop, hpet);
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/* hpet or pmtimer available ? */
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if (!hpet && !ref_start && !ref_stop)
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goto out;
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/* Check, whether the sampling was disturbed by an SMI */
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if (tsc_start == ULLONG_MAX || tsc_stop == ULLONG_MAX)
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goto out;
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delta = tsc_stop - tsc_start;
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delta *= 1000000LL;
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if (hpet)
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freq = calc_hpet_ref(delta, ref_start, ref_stop);
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else
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freq = calc_pmtimer_ref(delta, ref_start, ref_stop);
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/* Make sure we're within 1% */
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if (abs(tsc_khz - freq) > tsc_khz/100)
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goto out;
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tsc_khz = freq;
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printk(KERN_INFO "Refined TSC clocksource calibration: "
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"%lu.%03lu MHz.\n", (unsigned long)tsc_khz / 1000,
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(unsigned long)tsc_khz % 1000);
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out:
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clocksource_register_khz(&clocksource_tsc, tsc_khz);
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}
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static int __init init_tsc_clocksource(void)
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{
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if (!cpu_has_tsc || tsc_disabled > 0)
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return 0;
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if (tsc_clocksource_reliable)
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clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
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/* lower the rating if we already know its unstable: */
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@ -894,8 +975,14 @@ static void __init init_tsc_clocksource(void)
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clocksource_tsc.rating = 0;
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clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
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}
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clocksource_register_khz(&clocksource_tsc, tsc_khz);
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schedule_delayed_work(&tsc_irqwork, 0);
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return 0;
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}
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/*
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* We use device_initcall here, to ensure we run after the hpet
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* is fully initialized, which may occur at fs_initcall time.
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*/
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device_initcall(init_tsc_clocksource);
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void __init tsc_init(void)
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{
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@ -949,6 +1036,5 @@ void __init tsc_init(void)
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mark_tsc_unstable("TSCs unsynchronized");
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check_system_tsc_reliable();
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init_tsc_clocksource();
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}
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