aboutsummaryrefslogtreecommitdiff
path: root/arch/x86_64/kernel/time.c
diff options
context:
space:
mode:
Diffstat (limited to 'arch/x86_64/kernel/time.c')
-rw-r--r--arch/x86_64/kernel/time.c64
1 files changed, 47 insertions, 17 deletions
diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index 0e3b60e1ac5..fb8c809b4cd 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -26,6 +26,10 @@
#include <linux/sysdev.h>
#include <linux/bcd.h>
#include <linux/kallsyms.h>
+#include <linux/acpi.h>
+#ifdef CONFIG_ACPI
+#include <acpi/achware.h> /* for PM timer frequency */
+#endif
#include <asm/8253pit.h>
#include <asm/pgtable.h>
#include <asm/vsyscall.h>
@@ -396,6 +400,10 @@ static irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
(offset - vxtime.last)*(NSEC_PER_SEC/HZ) / hpet_tick;
vxtime.last = offset;
+#ifdef CONFIG_X86_PM_TIMER
+ } else if (vxtime.mode == VXTIME_PMTMR) {
+ lost = pmtimer_mark_offset();
+#endif
} else {
offset = (((tsc - vxtime.last_tsc) *
vxtime.tsc_quot) >> 32) - (USEC_PER_SEC / HZ);
@@ -898,6 +906,13 @@ void __init time_init(void)
hpet_period;
cpu_khz = hpet_calibrate_tsc();
timename = "HPET";
+#ifdef CONFIG_X86_PM_TIMER
+ } else if (pmtmr_ioport) {
+ vxtime_hz = PM_TIMER_FREQUENCY;
+ timename = "PM";
+ pit_init();
+ cpu_khz = pit_calibrate_tsc();
+#endif
} else {
pit_init();
cpu_khz = pit_calibrate_tsc();
@@ -923,35 +938,50 @@ void __init time_init(void)
}
/*
+ * Make an educated guess if the TSC is trustworthy and synchronized
+ * over all CPUs.
+ */
+static __init int unsynchronized_tsc(void)
+{
+#ifdef CONFIG_SMP
+ if (oem_force_hpet_timer())
+ return 1;
+ /* Intel systems are normally all synchronized. Exceptions
+ are handled in the OEM check above. */
+ if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
+ return 0;
+ /* All in a single socket - should be synchronized */
+ if (cpus_weight(cpu_core_map[0]) == num_online_cpus())
+ return 0;
+#endif
+ /* Assume multi socket systems are not synchronized */
+ return num_online_cpus() > 1;
+}
+
+/*
* Decide after all CPUs are booted what mode gettimeofday should use.
*/
void __init time_init_gtod(void)
{
char *timetype;
- /*
- * AMD systems with more than one CPU don't have fully synchronized
- * TSCs. Always use HPET gettimeofday for these, although it is slower.
- * Intel SMP systems usually have synchronized TSCs, so use always
- * the TSC.
- *
- * Exceptions:
- * IBM Summit2 checked by oem_force_hpet_timer().
- * AMD dual core may also not need HPET. Check me.
- *
- * Can be turned off with "notsc".
- */
- if (num_online_cpus() > 1 &&
- boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
- notsc = 1;
- /* Some systems will want to disable TSC and use HPET. */
- if (oem_force_hpet_timer())
+ if (unsynchronized_tsc())
notsc = 1;
if (vxtime.hpet_address && notsc) {
timetype = "HPET";
vxtime.last = hpet_readl(HPET_T0_CMP) - hpet_tick;
vxtime.mode = VXTIME_HPET;
do_gettimeoffset = do_gettimeoffset_hpet;
+#ifdef CONFIG_X86_PM_TIMER
+ /* Using PM for gettimeofday is quite slow, but we have no other
+ choice because the TSC is too unreliable on some systems. */
+ } else if (pmtmr_ioport && !vxtime.hpet_address && notsc) {
+ timetype = "PM";
+ do_gettimeoffset = do_gettimeoffset_pm;
+ vxtime.mode = VXTIME_PMTMR;
+ sysctl_vsyscall = 0;
+ printk(KERN_INFO "Disabling vsyscall due to use of PM timer\n");
+#endif
} else {
timetype = vxtime.hpet_address ? "HPET/TSC" : "PIT/TSC";
vxtime.mode = VXTIME_TSC;