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Subject[PATCH v15 26/26] x86/tsc: use tsc_calibrate_cpu_early and pit_hpet_ptimer_calibrate_cpu
Date
Early in boot enable tsc_calibrate_cpu_early and switch to
tsc_calibrate_cpu() only later. Do this unconditionally, because it is
unknown what methods other cpus will use to calibrate once they are
onlined.

If by the time tsc_init() is called tsc frequency is still unknown do only
pit_hpet_ptimer_calibrate_cpu to calibrate, as this function contails the
only methods that had not been called earlier in boot.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
---
arch/x86/include/asm/tsc.h | 1 -
arch/x86/kernel/tsc.c | 25 +++++++++++++++++++------
arch/x86/kernel/x86_init.c | 2 +-
3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index 88140e4f2292..eb5bbfeccb66 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -39,7 +39,6 @@ extern void mark_tsc_unstable(char *reason);
extern int unsynchronized_tsc(void);
extern int check_tsc_unstable(void);
extern void mark_tsc_async_resets(char *reason);
-extern unsigned long native_calibrate_cpu(void);
extern unsigned long native_calibrate_cpu_early(void);
extern unsigned long native_calibrate_tsc(void);
extern unsigned long long native_sched_clock_from_tsc(u64 tsc);
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 60586779b02c..02e416b87ac1 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -854,7 +854,7 @@ unsigned long native_calibrate_cpu_early(void)
/**
* native_calibrate_cpu - calibrate the cpu
*/
-unsigned long native_calibrate_cpu(void)
+static unsigned long native_calibrate_cpu(void)
{
unsigned long tsc_freq = native_calibrate_cpu_early();

@@ -1374,13 +1374,19 @@ static int __init init_tsc_clocksource(void)
*/
device_initcall(init_tsc_clocksource);

-static bool __init determine_cpu_tsc_frequencies(void)
+static bool __init determine_cpu_tsc_frequencies(bool early)
{
/* Make sure that cpu and tsc are not already calibrated */
WARN_ON(cpu_khz || tsc_khz);

- cpu_khz = x86_platform.calibrate_cpu();
- tsc_khz = x86_platform.calibrate_tsc();
+ if (early) {
+ cpu_khz = x86_platform.calibrate_cpu();
+ tsc_khz = x86_platform.calibrate_tsc();
+ } else {
+ /* We should not be here with non-native cpu calibration */
+ WARN_ON(x86_platform.calibrate_cpu != native_calibrate_cpu);
+ cpu_khz = pit_hpet_ptimer_calibrate_cpu();
+ }

/*
* Trust non-zero tsc_khz as authorative,
@@ -1419,7 +1425,7 @@ void __init tsc_early_init(void)
{
if (!boot_cpu_has(X86_FEATURE_TSC))
return;
- if (!determine_cpu_tsc_frequencies())
+ if (!determine_cpu_tsc_frequencies(true))
return;
loops_per_jiffy = get_loops_per_jiffy();

@@ -1431,6 +1437,13 @@ void __init tsc_early_init(void)

void __init tsc_init(void)
{
+ /*
+ * native_calibrate_cpu_early can only calibrate using methods that are
+ * available early in boot.
+ */
+ if (x86_platform.calibrate_cpu == native_calibrate_cpu_early)
+ x86_platform.calibrate_cpu = native_calibrate_cpu;
+
if (!boot_cpu_has(X86_FEATURE_TSC)) {
setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
return;
@@ -1438,7 +1451,7 @@ void __init tsc_init(void)

if (!tsc_khz) {
/* We failed to determine frequencies earlier, try again */
- if (!determine_cpu_tsc_frequencies()) {
+ if (!determine_cpu_tsc_frequencies(false)) {
mark_tsc_unstable("could not calculate TSC khz");
setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
return;
diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
index 3ab867603e81..2792b5573818 100644
--- a/arch/x86/kernel/x86_init.c
+++ b/arch/x86/kernel/x86_init.c
@@ -109,7 +109,7 @@ struct x86_cpuinit_ops x86_cpuinit = {
static void default_nmi_init(void) { };

struct x86_platform_ops x86_platform __ro_after_init = {
- .calibrate_cpu = native_calibrate_cpu,
+ .calibrate_cpu = native_calibrate_cpu_early,
.calibrate_tsc = native_calibrate_tsc,
.get_wallclock = mach_get_cmos_time,
.set_wallclock = mach_set_rtc_mmss,
--
2.18.0
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