Date: Wed, 29 Dec 2021 15:47:01 GMT From: Mark Johnston <markj@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: 13dbf9da686c - stable/13 - x86: Perform late TSC calibration before LAPIC timer calibration Message-ID: <202112291547.1BTFl1DZ001470@gitrepo.freebsd.org>
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The branch stable/13 has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=13dbf9da686c1c3ea1a1e197b932ea3abdf27a43 commit 13dbf9da686c1c3ea1a1e197b932ea3abdf27a43 Author: Mark Johnston <markj@FreeBSD.org> AuthorDate: 2021-12-06 15:42:19 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2021-12-29 15:39:22 +0000 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 Sponsored by: The FreeBSD Foundation (cherry picked from commit 553af8f1ec71d397b5b4fd5876622b9269936e63) --- sys/x86/include/clock.h | 1 + sys/x86/isa/clock.c | 2 ++ sys/x86/x86/tsc.c | 26 +++++++++++++++++--------- 3 files changed, 20 insertions(+), 9 deletions(-) diff --git a/sys/x86/include/clock.h b/sys/x86/include/clock.h index d492196bac85..83c8351ed31c 100644 --- a/sys/x86/include/clock.h +++ b/sys/x86/include/clock.h @@ -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. diff --git a/sys/x86/isa/clock.c b/sys/x86/isa/clock.c index 2eb1c343f4db..513174626892 100644 --- a/sys/x86/isa/clock.c +++ b/sys/x86/isa/clock.c @@ -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 diff --git a/sys/x86/x86/tsc.c b/sys/x86/x86/tsc.c index 53e2c7dcfe42..6debe3ecca6d 100644 --- a/sys/x86/x86/tsc.c +++ b/sys/x86/x86/tsc.c @@ -693,23 +693,27 @@ 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); @@ -719,19 +723,23 @@ 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; + } + + freq_khz = tc->tc_frequency * (tsc_end - tsc_start) / (t_end - t_start); - tsc_update_freq(freq_khz * 1024); + 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)
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