[PATCH 1/9] x86: Add a native_perf_sched_clock_from_tsc

[Andi Kleen <andi@firstfloor.org>]

From: Andi Kleen <ak@linux.intel.com>

PEBSv3 has a raw TSC time stamp in its memory buffer that
later needs to to be converted to perf_clock. Add a
native_sched_clock_from_tsc() that works the same
as native_sched_clock, but starts with an already given TSC
value.

Right now I ignore paravirt for this. It will just get
the native clock. But there isn't para virtualized PEBS anyways.

Cc: tglx@linutronix.de
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 arch/x86/include/asm/tsc.h | 1 +
 arch/x86/kernel/tsc.c      | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index 94605c0..aad56eb 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -51,6 +51,7 @@ extern int unsynchronized_tsc(void);
 extern int check_tsc_unstable(void);
 extern int check_tsc_disabled(void);
 extern unsigned long native_calibrate_tsc(void);
+extern unsigned long long native_sched_clock_from_tsc(u64 tsc);
 
 extern int tsc_clocksource_reliable;
 
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 5054497..c16afd5 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -296,6 +296,14 @@ u64 native_sched_clock(void)
 	return cycles_2_ns(tsc_now);
 }
 
+/*
+ * Generate a sched_clock if you already have a TSC value.
+ */
+u64 native_sched_clock_from_tsc(u64 tsc)
+{
+	return cycles_2_ns(tsc);
+}
+
 /* We need to define a real function for sched_clock, to override the
    weak default version */
 #ifdef CONFIG_PARAVIRT
-- 
1.9.3