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x86: Perform late TSC calibration before LAPIC timer calibration

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This ensures that LAPIC calibration is done using the correct tsc_freq
value, i.e., the one associated with the TSC timecounter.  It does mean
though that TSC calibration cannot use sbinuptime() to read the
reference timecounter, as timehands are not yet set up.

Reviewed by:	kib, jhb
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D33209
This commit is contained in:
Mark Johnston 2021-12-06 10:42:19 -05:00
parent 62d09b46ad
commit 553af8f1ec
3 changed files with 20 additions and 9 deletions
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1
sys/x86/include/clock.h
View File

@ -28,6 +28,7 @@ void i8254_init(void);
void i8254_delay(int);
void clock_init(void);
void lapic_calibrate(void);
void tsc_calibrate(void);
/*
* Driver to clock driver interface.

2
sys/x86/isa/clock.c
View File

@ -413,6 +413,7 @@ cpu_initclocks(void)
td = curthread;
tsc_calibrate();
lapic_calibrate_timer();
cpu_initclocks_bsp();
CPU_FOREACH(i) {
@ -428,6 +429,7 @@ cpu_initclocks(void)
sched_unbind(td);
thread_unlock(td);
#else
tsc_calibrate();
lapic_calibrate_timer();
cpu_initclocks_bsp();
#endif

26
sys/x86/x86/tsc.c
View File

@ -695,23 +695,27 @@ tsc_update_freq(uint64_t new_freq)
/*
* Perform late calibration of the TSC frequency once ACPI-based timecounters
* are available.
* are available. At this point timehands are not set up, so we read the
* highest-quality timecounter directly rather than using (s)binuptime().
*/
static void
tsc_calib(void *arg __unused)
void
tsc_calibrate(void)
{
sbintime_t t_start, t_end;
struct timecounter *tc;
uint64_t freq_khz, tsc_start, tsc_end;
u_int t_start, t_end;
register_t flags;
int cpu;
if (tsc_disabled)
return;
tc = atomic_load_ptr(&timecounter);
flags = intr_disable();
cpu = curcpu;
tsc_start = rdtsc_ordered();
t_start = sbinuptime();
t_start = tc->tc_get_timecount(tc) & tc->tc_counter_mask;
intr_restore(flags);
DELAY(1000000);
@ -721,19 +725,23 @@ tsc_calib(void *arg __unused)
flags = intr_disable();
tsc_end = rdtsc_ordered();
t_end = sbinuptime();
t_end = tc->tc_get_timecount(tc) & tc->tc_counter_mask;
intr_restore(flags);
sched_unbind(curthread);
thread_unlock(curthread);
freq_khz = (SBT_1S / 1024) * (tsc_end - tsc_start) / (t_end - t_start);
if (t_end <= t_start) {
/* Assume that the counter has wrapped around at most once. */
t_end += (uint64_t)tc->tc_counter_mask + 1;
}
tsc_update_freq(freq_khz * 1024);
freq_khz = tc->tc_frequency * (tsc_end - tsc_start) / (t_end - t_start);
tsc_update_freq(freq_khz);
tc_init(&tsc_timecounter);
set_cputicker(rdtsc, tsc_freq, !tsc_is_invariant);
}
SYSINIT(tsc_calib, SI_SUB_CLOCKS + 1, SI_ORDER_ANY, tsc_calib, NULL);
void
resume_TSC(void)