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authorLinus Torvalds <torvalds@linux-foundation.org>2019-01-27 11:57:46 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-01-27 11:57:46 -0800
commit351e1aa6cb4b136e3f772605071d7a8db3c5b4e0 (patch)
tree1a91db374d7432fab6ec9057ca7da32c45b09a57
parentf907bb4c326d145c13504db184f38557d169f4bc (diff)
parentd999c0ec2498e54b9328db6b2c1037710025add1 (diff)
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
-rw-r--r--arch/x86/kernel/hpet.c4
-rw-r--r--arch/x86/kernel/tsc.c30
2 files changed, 16 insertions, 18 deletions
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index b0acb22e5a46..dfd3aca82c61 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -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
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index e9f777bfed40..3fae23834069 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -297,15 +297,16 @@ static int __init tsc_setup(char *str)
__setup("tsc=", tsc_setup);
-#define MAX_RETRIES 5
-#define SMI_TRESHOLD 50000
+#define MAX_RETRIES 5
+#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;