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Do not access ISA timer if BIOS reports that there is no legacy

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devices present.

On at least one machine where it would matter since the ISA timer is
power gated when booted in the UEFI mode, BIOS still reports that the
legacy devices are present.  That is, user still have to manually
disable TSC calibration on such machines.  Hopefully it will be more
useful in the future.

Discussed with:	Ben Widawsky <benjamin.widawsky@intel.com>
Reviewed by:	royger
Sponsored by:	The FreeBSD Foundation
Differential revision:	https://reviews.freebsd.org/D16004
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2018-06-25 11:24:26 +00:00
parent 28ebccd5fa
commit ce3bf75015
1 changed files with 24 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

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

@ -50,6 +50,7 @@ __FBSDID("$FreeBSD$");
#include <machine/specialreg.h>
#include <x86/vmware.h>
#include <dev/acpica/acpi_hpet.h>
#include <contrib/dev/acpica/include/acpi.h>
#include "cpufreq_if.h"
@ -81,8 +82,9 @@ SYSCTL_INT(_machdep, OID_AUTO, disable_tsc, CTLFLAG_RDTUN, &tsc_disabled, 0,
"Disable x86 Time Stamp Counter");
static int tsc_skip_calibration;
SYSCTL_INT(_machdep, OID_AUTO, disable_tsc_calibration, CTLFLAG_RDTUN,
&tsc_skip_calibration, 0, "Disable TSC frequency calibration");
SYSCTL_INT(_machdep, OID_AUTO, disable_tsc_calibration, CTLFLAG_RDTUN |
CTLFLAG_NOFETCH, &tsc_skip_calibration, 0,
"Disable TSC frequency calibration");
static void tsc_freq_changed(void *arg, const struct cf_level *level,
int status);
@ -213,6 +215,7 @@ probe_tsc_freq(void)
{
u_int regs[4];
uint64_t tsc1, tsc2;
uint16_t bootflags;
if (cpu_high >= 6) {
do_cpuid(6, regs);
@ -272,6 +275,25 @@ 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()) {
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())
;