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-rw-r--r--arch/x86/kernel/tsc.c42
1 files changed, 29 insertions, 13 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 424093b157d3..599e58168631 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -15,6 +15,7 @@
#include <asm/vgtod.h>
#include <asm/time.h>
#include <asm/delay.h>
+#include <asm/hypervisor.h>
unsigned int cpu_khz; /* TSC clocks / usec, not used here */
EXPORT_SYMBOL(cpu_khz);
@@ -31,6 +32,7 @@ static int tsc_unstable;
erroneous rdtsc usage on !cpu_has_tsc processors */
static int tsc_disabled = -1;
+static int tsc_clocksource_reliable;
/*
* Scheduler clock - returns current time in nanosec units.
*/
@@ -98,6 +100,15 @@ int __init notsc_setup(char *str)
__setup("notsc", notsc_setup);
+static int __init tsc_setup(char *str)
+{
+ if (!strcmp(str, "reliable"))
+ tsc_clocksource_reliable = 1;
+ return 1;
+}
+
+__setup("tsc=", tsc_setup);
+
#define MAX_RETRIES 5
#define SMI_TRESHOLD 50000
@@ -352,9 +363,15 @@ unsigned long native_calibrate_tsc(void)
{
u64 tsc1, tsc2, delta, ref1, ref2;
unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX;
- unsigned long flags, latch, ms, fast_calibrate;
+ unsigned long flags, latch, ms, fast_calibrate, tsc_khz;
int hpet = is_hpet_enabled(), i, loopmin;
+ tsc_khz = get_hypervisor_tsc_freq();
+ if (tsc_khz) {
+ printk(KERN_INFO "TSC: Frequency read from the hypervisor\n");
+ return tsc_khz;
+ }
+
local_irq_save(flags);
fast_calibrate = quick_pit_calibrate();
local_irq_restore(flags);
@@ -731,24 +748,21 @@ static struct dmi_system_id __initdata bad_tsc_dmi_table[] = {
{}
};
-/*
- * Geode_LX - the OLPC CPU has a possibly a very reliable TSC
- */
+static void __init check_system_tsc_reliable(void)
+{
#ifdef CONFIG_MGEODE_LX
-/* RTSC counts during suspend */
+ /* RTSC counts during suspend */
#define RTSC_SUSP 0x100
-
-static void __init check_geode_tsc_reliable(void)
-{
unsigned long res_low, res_high;
rdmsr_safe(MSR_GEODE_BUSCONT_CONF0, &res_low, &res_high);
+ /* Geode_LX - the OLPC CPU has a possibly a very reliable TSC */
if (res_low & RTSC_SUSP)
- clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
-}
-#else
-static inline void check_geode_tsc_reliable(void) { }
+ tsc_clocksource_reliable = 1;
#endif
+ if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE))
+ tsc_clocksource_reliable = 1;
+}
/*
* Make an educated guess if the TSC is trustworthy and synchronized
@@ -783,6 +797,8 @@ static void __init init_tsc_clocksource(void)
{
clocksource_tsc.mult = clocksource_khz2mult(tsc_khz,
clocksource_tsc.shift);
+ if (tsc_clocksource_reliable)
+ clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
/* lower the rating if we already know its unstable: */
if (check_tsc_unstable()) {
clocksource_tsc.rating = 0;
@@ -843,7 +859,7 @@ void __init tsc_init(void)
if (unsynchronized_tsc())
mark_tsc_unstable("TSCs unsynchronized");
- check_geode_tsc_reliable();
+ check_system_tsc_reliable();
init_tsc_clocksource();
}