[PATCH] x86_64: Support constantly ticking TSCs

On Intel Noconas the TSC ticks with a constant frequency.  Don't scale the
factor used by udelay when cpufreq changes the frequency.

This generalizes an earlier patch by Intel for this. 

Cc: <venkatesh.pallipadi@intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index 3bafe438fa75..c7a1b50b4af3 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -614,6 +614,9 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
         struct cpufreq_freqs *freq = data;
         unsigned long *lpj, dummy;
 
+        if (cpu_has(&cpu_data[freq->cpu], X86_FEATURE_CONSTANT_TSC))
+                return 0;
+
         lpj = &dummy;
         if (!(freq->flags & CPUFREQ_CONST_LOOPS))
 #ifdef CONFIG_SMP
@@ -622,8 +625,6 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
         lpj = &boot_cpu_data.loops_per_jiffy;
 #endif
 
-
-
         if (!ref_freq) {
                 ref_freq = freq->old;
                 loops_per_jiffy_ref = *lpj;