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Index: sys/x86/x86/tsc.c
===================================================================
--- sys/x86/x86/tsc.c
+++ sys/x86/x86/tsc.c
@@ -32,12 +32,14 @@
#include "opt_clock.h"
#include <sys/param.h>
+#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/cpu.h>
#include <sys/eventhandler.h>
#include <sys/limits.h>
#include <sys/malloc.h>
-#include <sys/systm.h>
+#include <sys/proc.h>
+#include <sys/sched.h>
#include <sys/sysctl.h>
#include <sys/time.h>
#include <sys/timetc.h>
@@ -134,14 +136,11 @@
}
/*
- * Calculate TSC frequency using information from the CPUID leaf 0x15
- * 'Time Stamp Counter and Nominal Core Crystal Clock'. If leaf 0x15
- * is not functional, as it is on Skylake/Kabylake, try 0x16 'Processor
- * Frequency Information'. Leaf 0x16 is described in the SDM as
- * informational only, but if 0x15 did not work, and TSC calibration
- * is disabled, it is the best we can get at all. It should still be
- * an improvement over the parsing of the CPU model name in
- * tsc_freq_intel(), when available.
+ * Calculate TSC frequency using information from the CPUID leaf 0x15 'Time
+ * Stamp Counter and Nominal Core Crystal Clock'. If leaf 0x15 is not
+ * functional, as it is on Skylake/Kabylake, try 0x16 'Processor Frequency
+ * Information'. Leaf 0x16 is described in the SDM as informational only, but
+ * we can use this value until late calibration is complete.
*/
static bool
tsc_freq_cpuid(uint64_t *res)
@@ -167,8 +166,8 @@
return (false);
}
-static void
-tsc_freq_intel(void)
+static bool
+tsc_freq_intel_brand(uint64_t *res)
{
char brand[48];
u_int regs[4];
@@ -205,7 +204,7 @@
i = 1000000;
break;
default:
- return;
+ return (false);
}
#define C2D(c) ((c) - '0')
if (p[1] == '.') {
@@ -221,16 +220,17 @@
freq *= i * 1000000;
}
#undef C2D
- tsc_freq = freq;
+ *res = freq;
+ return (true);
}
}
+ return (false);
}
static void
probe_tsc_freq(void)
{
- uint64_t tmp_freq, tsc1, tsc2;
- int no_cpuid_override;
+ uint64_t tsc1, tsc2;
if (cpu_power_ecx & CPUID_PERF_STAT) {
/*
@@ -287,50 +287,47 @@
break;
}
- if (tsc_skip_calibration) {
- if (tsc_freq_cpuid(&tmp_freq))
- tsc_freq = tmp_freq;
- else if (cpu_vendor_id == CPU_VENDOR_INTEL)
- tsc_freq_intel();
- if (tsc_freq == 0)
- tsc_disabled = 1;
- } else {
+ if (tsc_freq_cpuid(&tsc_freq)) {
+ /*
+ * If possible, use the value obtained from CPUID as the initial
+ * frequency. This will be refined later during boot but is
+ * good enough for now. The 8254 PIT is not functional on some
+ * newer platforms anyway, so don't delay our boot for what
+ * might be a garbage result. Late calibration is required if
+ * the initial frequency was obtained from CPUID.16H, as the
+ * derived value may be off by as much as 1%.
+ */
if (bootverbose)
- printf("Calibrating TSC clock ... ");
- tsc1 = rdtsc();
- DELAY(1000000);
- tsc2 = rdtsc();
- tsc_freq = tsc2 - tsc1;
-
+ printf("Early TSC frequency %juHz derived from CPUID\n",
+ (uintmax_t)tsc_freq);
+ } else if (tsc_skip_calibration) {
/*
- * If the difference between calibrated frequency and
- * the frequency reported by CPUID 0x15/0x16 leafs
- * differ significantly, this probably means that
- * calibration is bogus. It happens on machines
- * without 8254 timer. The BIOS rarely properly
- * reports it in FADT boot flags, so just compare the
- * frequencies directly.
+ * Try to parse the brand string to obtain the nominal TSC
+ * frequency.
*/
- if (tsc_freq_cpuid(&tmp_freq) && qabs(tsc_freq - tmp_freq) >
- uqmin(tsc_freq, tmp_freq)) {
- no_cpuid_override = 0;
- TUNABLE_INT_FETCH("machdep.disable_tsc_cpuid_override",
- &no_cpuid_override);
- if (!no_cpuid_override) {
- if (bootverbose) {
- printf(
- "TSC clock: calibration freq %ju Hz, CPUID freq %ju Hz%s\n",
- (uintmax_t)tsc_freq,
- (uintmax_t)tmp_freq,
- no_cpuid_override ? "" :
- ", doing CPUID override");
- }
- tsc_freq = tmp_freq;
- }
+ if (cpu_vendor_id == CPU_VENDOR_INTEL &&
+ tsc_freq_intel_brand(&tsc_freq)) {
+ if (bootverbose)
+ printf(
+ "Early TSC frequency %juHz derived from brand string\n",
+ (uintmax_t)tsc_freq);
+ } else {
+ tsc_disabled = 1;
}
+ } else {
+ /*
+ * Calibrate against the 8254 PIT. This is a rough estimate and
+ * will be refined later in tsc_calib().
+ */
+ tsc1 = rdtsc_ordered();
+ DELAY(100000);
+ tsc2 = rdtsc_ordered();
+ tsc_freq = (tsc2 - tsc1) * 10;
+ if (bootverbose)
+ printf(
+ "Early TSC frequency %juHz calibrated from 8254 PIT\n",
+ (uintmax_t)tsc_freq);
}
- if (bootverbose)
- printf("TSC clock: %ju Hz\n", (intmax_t)tsc_freq);
}
void
@@ -372,13 +369,18 @@
break;
}
#endif
-
+
probe_tsc_freq();
/*
* Inform CPU accounting about our boot-time clock rate. This will
* be updated if someone loads a cpufreq driver after boot that
* discovers a new max frequency.
+ *
+ * The frequency may also be updated after late calibration is complete;
+ * however, we register the TSC as the ticker now to avoid switching
+ * counters after much of the kernel has already booted and potentially
+ * sampled the CPU clock.
*/
if (tsc_freq != 0)
set_cputicker(rdtsc, tsc_freq, !tsc_is_invariant);
@@ -656,11 +658,62 @@
if (tsc_freq != 0) {
tsc_timecounter.tc_frequency = tsc_freq >> shift;
tsc_timecounter.tc_priv = (void *)(intptr_t)shift;
- tc_init(&tsc_timecounter);
+
+ /*
+ * Timecounter registration is deferred until after late
+ * calibration is finished.
+ */
}
}
SYSINIT(tsc_tc, SI_SUB_SMP, SI_ORDER_ANY, init_TSC_tc, NULL);
+static void
+tsc_update_freq(uint64_t new_freq)
+{
+ atomic_store_rel_64(&tsc_freq, new_freq);
+ atomic_store_rel_64(&tsc_timecounter.tc_frequency,
+ new_freq >> (int)(intptr_t)tsc_timecounter.tc_priv);
+}
+
+/*
+ * Perform late calibration of the TSC frequency once ACPI-based timecounters
+ * are available.
+ */
+static void
+tsc_calib(void *arg __unused)
+{
+ sbintime_t t_start, t_end;
+ uint64_t freq_khz, tsc_start, tsc_end;
+ register_t flags;
+ int cpu;
+
+ flags = intr_disable();
+ cpu = curcpu;
+ tsc_start = rdtsc_ordered();
+ t_start = sbinuptime();
+ intr_restore(flags);
+
+ DELAY(1000000);
+
+ thread_lock(curthread);
+ sched_bind(curthread, cpu);
+
+ flags = intr_disable();
+ tsc_end = rdtsc_ordered();
+ t_end = sbinuptime();
+ intr_restore(flags);
+
+ sched_unbind(curthread);
+ thread_unlock(curthread);
+
+ freq_khz = (SBT_1S / 1024) * (tsc_end - tsc_start) / (t_end - t_start);
+
+ tsc_update_freq(freq_khz * 1024);
+ 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)
{
@@ -752,9 +805,7 @@
/* Total setting for this level gives the new frequency in MHz. */
freq = (uint64_t)level->total_set.freq * 1000000;
- atomic_store_rel_64(&tsc_freq, freq);
- tsc_timecounter.tc_frequency =
- freq >> (int)(intptr_t)tsc_timecounter.tc_priv;
+ tsc_update_freq(freq);
}
static int
@@ -767,14 +818,10 @@
if (freq == 0)
return (EOPNOTSUPP);
error = sysctl_handle_64(oidp, &freq, 0, req);
- if (error == 0 && req->newptr != NULL) {
- atomic_store_rel_64(&tsc_freq, freq);
- atomic_store_rel_64(&tsc_timecounter.tc_frequency,
- freq >> (int)(intptr_t)tsc_timecounter.tc_priv);
- }
+ if (error == 0 && req->newptr != NULL)
+ tsc_update_freq(freq);
return (error);
}
-
SYSCTL_PROC(_machdep, OID_AUTO, tsc_freq,
CTLTYPE_U64 | CTLFLAG_RW | CTLFLAG_NEEDGIANT,
0, 0, sysctl_machdep_tsc_freq, "QU",

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