x86/tsc: Split native_calibrate_cpu() into early and late parts

During early boot TSC and CPU frequency can be calibrated using MSR, CPUID,
and quick PIT calibration methods. The other methods PIT/HPET/PMTIMER are
available only after ACPI is initialized.

Split native_calibrate_cpu() into early and late parts so they can be
called separately during early and late tsc calibration.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: steven.sistare@oracle.com
Cc: daniel.m.jordan@oracle.com
Cc: linux@armlinux.org.uk
Cc: schwidefsky@de.ibm.com
Cc: heiko.carstens@de.ibm.com
Cc: john.stultz@linaro.org
Cc: sboyd@codeaurora.org
Cc: hpa@zytor.com
Cc: douly.fnst@cn.fujitsu.com
Cc: peterz@infradead.org
Cc: prarit@redhat.com
Cc: feng.tang@intel.com
Cc: pmladek@suse.com
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: linux-s390@vger.kernel.org
Cc: boris.ostrovsky@oracle.com
Cc: jgross@suse.com
Cc: pbonzini@redhat.com
Link: https://lkml.kernel.org/r/20180719205545.16512-26-pasha.tatashin@oracle.com

diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index c4368ff73652ab4b01f162dbf59137fe2481a59d..88140e4f229226c8b7763998cb2d9c2668f48b60 100644 (file)
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -40,6 +40,7 @@ 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 9277ae9b68b3f3c08eda2ec376b72a59949459af..60586779b02cf292f5603ff6c81feba3d0ba74dc 100644 (file)
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -680,30 +680,17 @@ static unsigned long cpu_khz_from_cpuid(void)
        return eax_base_mhz * 1000;
 }
 
-/**
- * native_calibrate_cpu - calibrate the cpu on boot
+/*
+ * calibrate cpu using pit, hpet, and ptimer methods. They are available
+ * later in boot after acpi is initialized.
  */
-unsigned long native_calibrate_cpu(void)
+static unsigned long pit_hpet_ptimer_calibrate_cpu(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;
        int hpet = is_hpet_enabled(), i, loopmin;
 
-       fast_calibrate = cpu_khz_from_cpuid();
-       if (fast_calibrate)
-               return fast_calibrate;
-
-       fast_calibrate = cpu_khz_from_msr();
-       if (fast_calibrate)
-               return fast_calibrate;
-
-       local_irq_save(flags);
-       fast_calibrate = quick_pit_calibrate();
-       local_irq_restore(flags);
-       if (fast_calibrate)
-               return fast_calibrate;
-
        /*
         * Run 5 calibration loops to get the lowest frequency value
         * (the best estimate). We use two different calibration modes
@@ -846,6 +833,37 @@ unsigned long native_calibrate_cpu(void)
        return tsc_pit_min;
 }
 
+/**
+ * native_calibrate_cpu_early - can calibrate the cpu early in boot
+ */
+unsigned long native_calibrate_cpu_early(void)
+{
+       unsigned long flags, fast_calibrate = cpu_khz_from_cpuid();
+
+       if (!fast_calibrate)
+               fast_calibrate = cpu_khz_from_msr();
+       if (!fast_calibrate) {
+               local_irq_save(flags);
+               fast_calibrate = quick_pit_calibrate();
+               local_irq_restore(flags);
+       }
+       return fast_calibrate;
+}
+
+
+/**
+ * native_calibrate_cpu - calibrate the cpu
+ */
+unsigned long native_calibrate_cpu(void)
+{
+       unsigned long tsc_freq = native_calibrate_cpu_early();
+
+       if (!tsc_freq)
+               tsc_freq = pit_hpet_ptimer_calibrate_cpu();
+
+       return tsc_freq;
+}
+
 void recalibrate_cpu_khz(void)
 {
 #ifndef CONFIG_SMP