Author: kib
Date: Wed Apr 29 10:53:35 2020
New Revision: 360455
URL: https://svnweb.freebsd.org/changeset/base/360455
Log:
MFC r359997:
Improve TSC calibration logic.
Modified:
stable/12/sys/x86/x86/tsc.c
Directory Properties:
stable/12/ (props changed)
Modified: stable/12/sys/x86/x86/tsc.c
==============================================================================
--- stable/12/sys/x86/x86/tsc.c Wed Apr 29 05:11:17 2020 (r360454)
+++ stable/12/sys/x86/x86/tsc.c Wed Apr 29 10:53:35 2020 (r360455)
@@ -82,8 +82,8 @@ SYSCTL_INT(_machdep, OID_AUTO, disable_tsc, CTLFLAG_RD
"Disable x86 Time Stamp Counter");
static int tsc_skip_calibration;
-SYSCTL_INT(_machdep, OID_AUTO, disable_tsc_calibration, CTLFLAG_RDTUN |
- CTLFLAG_NOFETCH, &tsc_skip_calibration, 0,
+SYSCTL_INT(_machdep, OID_AUTO, disable_tsc_calibration, CTLFLAG_RDTUN,
+ &tsc_skip_calibration, 0,
"Disable TSC frequency calibration");
static void tsc_freq_changed(void *arg, const struct cf_level *level,
@@ -230,7 +230,6 @@ probe_tsc_freq(void)
u_int regs[4];
uint64_t tmp_freq, tsc1, tsc2;
int no_cpuid_override;
- uint16_t bootflags;
if (cpu_high >= 6) {
do_cpuid(6, regs);
@@ -291,30 +290,13 @@ probe_tsc_freq(void)
break;
}
- if (!TUNABLE_INT_FETCH("machdep.disable_tsc_calibration",
- &tsc_skip_calibration)) {
- /*
- * User did not give the order about calibration.
- * If he did, we do not try to guess.
- *
- * Otherwise, if ACPI FADT reports that the platform
- * is legacy-free and CPUID provides TSC frequency,
- * use it. The calibration could fail anyway since
- * ISA timer can be absent or power gated.
- */
- if (acpi_get_fadt_bootflags(&bootflags) &&
- (bootflags & ACPI_FADT_LEGACY_DEVICES) == 0 &&
- tsc_freq_cpuid(&tmp_freq)) {
- printf("Skipping TSC calibration since no legacy "
- "devices reported by FADT and CPUID works\n");
- tsc_skip_calibration = 1;
- }
- }
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 (bootverbose)
printf("Calibrating TSC clock ... ");
@@ -328,8 +310,9 @@ probe_tsc_freq(void)
* the frequency reported by CPUID 0x15/0x16 leafs
* differ significantly, this probably means that
* calibration is bogus. It happens on machines
- * without 8254 timer and with BIOS not properly
- * reporting it in FADT boot flags.
+ * without 8254 timer. The BIOS rarely properly
+ * reports it in FADT boot flags, so just compare the
+ * frequencies directly.
*/
if (tsc_freq_cpuid(&tmp_freq) && qabs(tsc_freq - tmp_freq) >
uqmin(tsc_freq, tmp_freq)) {
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