Commit 351e1aa6 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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

Pull x86 timer fixes from Thomas Gleixner:
 "Two commits which were missed to be sent during the merge window.

   - The TSC calibration fix turns out to be more urgent as recent
     Skylake-X systems seem to have massive trouble with calibration
     disturbance. This should go back into stable for that reason and it
     the risk of breakage is rather low.

   - Drop an unused define"

* 'x86-timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/hpet: Remove unused FSEC_PER_NSEC define
  x86/tsc: Make calibration refinement more robust
parents f907bb4c d999c0ec

arch/x86/kernel/hpet.c

+0 −4
Original line number Diff line number Diff line
@@ -21,10 +21,6 @@ 


#define HPET_MASK			CLOCKSOURCE_MASK(32)



/* FSEC = 10^-15

   NSEC = 10^-9 */

#define FSEC_PER_NSEC			1000000L



#define HPET_DEV_USED_BIT		2

#define HPET_DEV_USED			(1 << HPET_DEV_USED_BIT)

#define HPET_DEV_VALID			0x8

arch/x86/kernel/tsc.c

+16 −14
Original line number Diff line number Diff line
@@ -298,14 +298,15 @@ static int __init tsc_setup(char *str) 
__setup("tsc=", tsc_setup);



#define MAX_RETRIES		5

#define SMI_TRESHOLD    50000

#define TSC_DEFAULT_THRESHOLD	0x20000



/*

 * Read TSC and the reference counters. Take care of SMI disturbance

 * Read TSC and the reference counters. Take care of any disturbances

 */

static u64 tsc_read_refs(u64 *p, int hpet)

{

	u64 t1, t2;

	u64 thresh = tsc_khz ? tsc_khz >> 5 : TSC_DEFAULT_THRESHOLD;

	int i;



	for (i = 0; i < MAX_RETRIES; i++) {
@@ -315,7 +316,7 @@ static u64 tsc_read_refs(u64 *p, int hpet) 
		else

			*p = acpi_pm_read_early();

		t2 = get_cycles();

		if ((t2 - t1) < SMI_TRESHOLD)

		if ((t2 - t1) < thresh)

			return t2;

	}

	return ULLONG_MAX;
@@ -703,15 +704,15 @@ static unsigned long pit_hpet_ptimer_calibrate_cpu(void) 
	 * zero. In each wait loop iteration we read the TSC and check

	 * the delta to the previous read. We keep track of the min

	 * and max values of that delta. The delta is mostly defined

	 * by the IO time of the PIT access, so we can detect when a

	 * SMI/SMM disturbance happened between the two reads. If the

	 * by the IO time of the PIT access, so we can detect when

	 * any disturbance happened between the two reads. If the

	 * maximum time is significantly larger than the minimum time,

	 * then we discard the result and have another try.

	 *

	 * 2) Reference counter. If available we use the HPET or the

	 * PMTIMER as a reference to check the sanity of that value.

	 * We use separate TSC readouts and check inside of the

	 * reference read for a SMI/SMM disturbance. We dicard

	 * reference read for any possible disturbance. We dicard

	 * disturbed values here as well. We do that around the PIT

	 * calibration delay loop as we have to wait for a certain

	 * amount of time anyway.
@@ -744,7 +745,7 @@ static unsigned long pit_hpet_ptimer_calibrate_cpu(void) 
		if (ref1 == ref2)

			continue;



		/* Check, whether the sampling was disturbed by an SMI */

		/* Check, whether the sampling was disturbed */

		if (tsc1 == ULLONG_MAX || tsc2 == ULLONG_MAX)

			continue;
@@ -1268,7 +1269,7 @@ static DECLARE_DELAYED_WORK(tsc_irqwork, tsc_refine_calibration_work); 
 */

static void tsc_refine_calibration_work(struct work_struct *work)

{

	static u64 tsc_start = -1, ref_start;

	static u64 tsc_start = ULLONG_MAX, ref_start;

	static int hpet;

	u64 tsc_stop, ref_stop, delta;

	unsigned long freq;
@@ -1283,14 +1284,15 @@ static void tsc_refine_calibration_work(struct work_struct *work) 
	 * delayed the first time we expire. So set the workqueue

	 * again once we know timers are working.

	 */

	if (tsc_start == -1) {

	if (tsc_start == ULLONG_MAX) {

restart:

		/*

		 * 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);

		schedule_delayed_work(&tsc_irqwork, HZ);

		return;

	}
@@ -1300,9 +1302,9 @@ static void tsc_refine_calibration_work(struct work_struct *work) 
	if (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;

	/* Check, whether the sampling was disturbed */

	if (tsc_stop == ULLONG_MAX)

		goto restart;



	delta = tsc_stop - tsc_start;

	delta *= 1000000LL;

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