Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
+16
-18
-4
arch/x86/kernel/hpet.c
-4
arch/x86/kernel/hpet.c
+16
-14
arch/x86/kernel/tsc.c
+16
-14
arch/x86/kernel/tsc.c
···
297
297
298
298
__setup("tsc=", tsc_setup);
299
299
300
-
#define MAX_RETRIES 5
301
-
#define SMI_TRESHOLD 50000
300
+
#define MAX_RETRIES 5
301
+
#define TSC_DEFAULT_THRESHOLD 0x20000
302
302
303
303
/*
304
-
* Read TSC and the reference counters. Take care of SMI disturbance
304
+
* Read TSC and the reference counters. Take care of any disturbances
305
305
*/
306
306
static u64 tsc_read_refs(u64 *p, int hpet)
307
307
{
308
308
u64 t1, t2;
309
+
u64 thresh = tsc_khz ? tsc_khz >> 5 : TSC_DEFAULT_THRESHOLD;
309
310
int i;
310
311
311
312
for (i = 0; i < MAX_RETRIES; i++) {
···
316
315
else
317
316
*p = acpi_pm_read_early();
318
317
t2 = get_cycles();
319
-
if ((t2 - t1) < SMI_TRESHOLD)
318
+
if ((t2 - t1) < thresh)
320
319
return t2;
321
320
}
322
321
return ULLONG_MAX;
···
704
703
* zero. In each wait loop iteration we read the TSC and check
705
704
* the delta to the previous read. We keep track of the min
706
705
* and max values of that delta. The delta is mostly defined
707
-
* by the IO time of the PIT access, so we can detect when a
708
-
* SMI/SMM disturbance happened between the two reads. If the
706
+
* by the IO time of the PIT access, so we can detect when
707
+
* any disturbance happened between the two reads. If the
709
708
* maximum time is significantly larger than the minimum time,
710
709
* then we discard the result and have another try.
711
710
*
712
711
* 2) Reference counter. If available we use the HPET or the
713
712
* PMTIMER as a reference to check the sanity of that value.
714
713
* We use separate TSC readouts and check inside of the
715
-
* reference read for a SMI/SMM disturbance. We dicard
714
+
* reference read for any possible disturbance. We dicard
716
715
* disturbed values here as well. We do that around the PIT
717
716
* calibration delay loop as we have to wait for a certain
718
717
* amount of time anyway.
···
745
744
if (ref1 == ref2)
746
745
continue;
747
746
748
-
/* Check, whether the sampling was disturbed by an SMI */
747
+
/* Check, whether the sampling was disturbed */
749
748
if (tsc1 == ULLONG_MAX || tsc2 == ULLONG_MAX)
750
749
continue;
751
750
···
1269
1268
*/
1270
1269
static void tsc_refine_calibration_work(struct work_struct *work)
1271
1270
{
1272
-
static u64 tsc_start = -1, ref_start;
1271
+
static u64 tsc_start = ULLONG_MAX, ref_start;
1273
1272
static int hpet;
1274
1273
u64 tsc_stop, ref_stop, delta;
1275
1274
unsigned long freq;
···
1284
1283
* delayed the first time we expire. So set the workqueue
1285
1284
* again once we know timers are working.
1286
1285
*/
1287
-
if (tsc_start == -1) {
1286
+
if (tsc_start == ULLONG_MAX) {
1287
+
restart:
1288
1288
/*
1289
1289
* Only set hpet once, to avoid mixing hardware
1290
1290
* if the hpet becomes enabled later.
1291
1291
*/
1292
1292
hpet = is_hpet_enabled();
1293
-
schedule_delayed_work(&tsc_irqwork, HZ);
1294
1293
tsc_start = tsc_read_refs(&ref_start, hpet);
1294
+
schedule_delayed_work(&tsc_irqwork, HZ);
1295
1295
return;
1296
1296
}
1297
1297
···
1302
1300
if (ref_start == ref_stop)
1303
1301
goto out;
1304
1302
1305
-
/* Check, whether the sampling was disturbed by an SMI */
1306
-
if (tsc_start == ULLONG_MAX || tsc_stop == ULLONG_MAX)
1307
-
goto out;
1303
+
/* Check, whether the sampling was disturbed */
1304
+
if (tsc_stop == ULLONG_MAX)
1305
+
goto restart;
1308
1306
1309
1307
delta = tsc_stop - tsc_start;
1310
1308
delta *= 1000000LL;