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Commit 03821f45 authored by Pavel Tatashin's avatar Pavel Tatashin Committed by Thomas Gleixner
Browse files

x86/tsc: Split native_calibrate_cpu() into early and late parts 



During early boot TSC and CPU frequency can be calibrated using MSR, CPUID,
and quick PIT calibration methods. The other methods PIT/HPET/PMTIMER are
available only after ACPI is initialized.

Split native_calibrate_cpu() into early and late parts so they can be
called separately during early and late tsc calibration.

Signed-off-by: default avatarPavel Tatashin <pasha.tatashin@oracle.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: steven.sistare@oracle.com
Cc: daniel.m.jordan@oracle.com
Cc: linux@armlinux.org.uk
Cc: schwidefsky@de.ibm.com
Cc: heiko.carstens@de.ibm.com
Cc: john.stultz@linaro.org
Cc: sboyd@codeaurora.org
Cc: hpa@zytor.com
Cc: douly.fnst@cn.fujitsu.com
Cc: peterz@infradead.org
Cc: prarit@redhat.com
Cc: feng.tang@intel.com
Cc: pmladek@suse.com
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: linux-s390@vger.kernel.org
Cc: boris.ostrovsky@oracle.com
Cc: jgross@suse.com
Cc: pbonzini@redhat.com
Link: https://lkml.kernel.org/r/20180719205545.16512-26-pasha.tatashin@oracle.com
parent 46457ea4

arch/x86/include/asm/tsc.h

+1 −0
Original line number Diff line number Diff line
@@ -40,6 +40,7 @@ extern int unsynchronized_tsc(void); 
extern int check_tsc_unstable(void);

extern void mark_tsc_async_resets(char *reason);

extern unsigned long native_calibrate_cpu(void);

extern unsigned long native_calibrate_cpu_early(void);

extern unsigned long native_calibrate_tsc(void);

extern unsigned long long native_sched_clock_from_tsc(u64 tsc);

arch/x86/kernel/tsc.c

+36 −18
Original line number Diff line number Diff line
@@ -680,30 +680,17 @@ static unsigned long cpu_khz_from_cpuid(void) 
	return eax_base_mhz * 1000;

}



/**

 * native_calibrate_cpu - calibrate the cpu on boot

/*

 * calibrate cpu using pit, hpet, and ptimer methods. They are available

 * later in boot after acpi is initialized.

 */

unsigned long native_calibrate_cpu(void)

static unsigned long pit_hpet_ptimer_calibrate_cpu(void)

{

	u64 tsc1, tsc2, delta, ref1, ref2;

	unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX;

	unsigned long flags, latch, ms, fast_calibrate;

	unsigned long flags, latch, ms;

	int hpet = is_hpet_enabled(), i, loopmin;



	fast_calibrate = cpu_khz_from_cpuid();

	if (fast_calibrate)

		return fast_calibrate;



	fast_calibrate = cpu_khz_from_msr();

	if (fast_calibrate)

		return fast_calibrate;



	local_irq_save(flags);

	fast_calibrate = quick_pit_calibrate();

	local_irq_restore(flags);

	if (fast_calibrate)

		return fast_calibrate;



	/*

	 * Run 5 calibration loops to get the lowest frequency value

	 * (the best estimate). We use two different calibration modes
@@ -846,6 +833,37 @@ unsigned long native_calibrate_cpu(void) 
	return tsc_pit_min;

}



/**

 * native_calibrate_cpu_early - can calibrate the cpu early in boot

 */

unsigned long native_calibrate_cpu_early(void)

{

	unsigned long flags, fast_calibrate = cpu_khz_from_cpuid();



	if (!fast_calibrate)

		fast_calibrate = cpu_khz_from_msr();

	if (!fast_calibrate) {

		local_irq_save(flags);

		fast_calibrate = quick_pit_calibrate();

		local_irq_restore(flags);

	}

	return fast_calibrate;

}





/**

 * native_calibrate_cpu - calibrate the cpu

 */

unsigned long native_calibrate_cpu(void)

{

	unsigned long tsc_freq = native_calibrate_cpu_early();



	if (!tsc_freq)

		tsc_freq = pit_hpet_ptimer_calibrate_cpu();



	return tsc_freq;

}



void recalibrate_cpu_khz(void)

{

#ifndef CONFIG_SMP