x86: Perform late TSC calibration before LAPIC timer calibration
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
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@ -28,6 +28,7 @@ void i8254_init(void);
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void i8254_delay(int);
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void clock_init(void);
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void lapic_calibrate(void);
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void tsc_calibrate(void);
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/*
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* Driver to clock driver interface.
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@ -413,6 +413,7 @@ cpu_initclocks(void)
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td = curthread;
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tsc_calibrate();
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lapic_calibrate_timer();
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cpu_initclocks_bsp();
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CPU_FOREACH(i) {
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@ -428,6 +429,7 @@ cpu_initclocks(void)
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sched_unbind(td);
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thread_unlock(td);
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#else
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tsc_calibrate();
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lapic_calibrate_timer();
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cpu_initclocks_bsp();
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#endif
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@ -695,23 +695,27 @@ tsc_update_freq(uint64_t new_freq)
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/*
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* Perform late calibration of the TSC frequency once ACPI-based timecounters
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* are available.
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* are available. At this point timehands are not set up, so we read the
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* highest-quality timecounter directly rather than using (s)binuptime().
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*/
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static void
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tsc_calib(void *arg __unused)
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void
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tsc_calibrate(void)
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{
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sbintime_t t_start, t_end;
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struct timecounter *tc;
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uint64_t freq_khz, tsc_start, tsc_end;
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u_int t_start, t_end;
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register_t flags;
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int cpu;
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if (tsc_disabled)
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return;
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tc = atomic_load_ptr(&timecounter);
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flags = intr_disable();
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cpu = curcpu;
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tsc_start = rdtsc_ordered();
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t_start = sbinuptime();
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t_start = tc->tc_get_timecount(tc) & tc->tc_counter_mask;
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intr_restore(flags);
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DELAY(1000000);
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@ -721,19 +725,23 @@ tsc_calib(void *arg __unused)
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flags = intr_disable();
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tsc_end = rdtsc_ordered();
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t_end = sbinuptime();
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t_end = tc->tc_get_timecount(tc) & tc->tc_counter_mask;
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intr_restore(flags);
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sched_unbind(curthread);
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thread_unlock(curthread);
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freq_khz = (SBT_1S / 1024) * (tsc_end - tsc_start) / (t_end - t_start);
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if (t_end <= t_start) {
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/* Assume that the counter has wrapped around at most once. */
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t_end += (uint64_t)tc->tc_counter_mask + 1;
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}
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tsc_update_freq(freq_khz * 1024);
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freq_khz = tc->tc_frequency * (tsc_end - tsc_start) / (t_end - t_start);
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tsc_update_freq(freq_khz);
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tc_init(&tsc_timecounter);
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set_cputicker(rdtsc, tsc_freq, !tsc_is_invariant);
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}
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SYSINIT(tsc_calib, SI_SUB_CLOCKS + 1, SI_ORDER_ANY, tsc_calib, NULL);
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void
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resume_TSC(void)
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