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[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>
This commit is contained in:
Andi Kleen 2005-04-16 15:25:05 -07:00 committed by Linus Torvalds
parent dc37db4d8c
commit c29601e9c1
3 changed files with 8 additions and 3 deletions
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5
arch/x86_64/kernel/setup.c
View File

@ -855,6 +855,8 @@ static void __init init_intel(struct cpuinfo_x86 *c)
if (c->x86 == 15)
c->x86_cache_alignment = c->x86_clflush_size * 2;
if (c->x86 >= 15)
set_bit(X86_FEATURE_CONSTANT_TSC, &c->x86_capability);
}
void __init get_cpu_vendor(struct cpuinfo_x86 *c)
@ -1055,7 +1057,8 @@ static int show_cpuinfo(struct seq_file *m, void *v)
NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
/* Other (Linux-defined) */
"cxmmx", "k6_mtrr", "cyrix_arr", "centaur_mcr", NULL, NULL, NULL, NULL,
"cxmmx", NULL, "cyrix_arr", "centaur_mcr", "k8c+",
"constant_tsc", NULL, NULL,
NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,

5
arch/x86_64/kernel/time.c
View File

@ -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;

1
include/asm-x86_64/cpufeature.h
View File

@ -62,6 +62,7 @@
#define X86_FEATURE_CYRIX_ARR (3*32+ 2) /* Cyrix ARRs (= MTRRs) */
#define X86_FEATURE_CENTAUR_MCR (3*32+ 3) /* Centaur MCRs (= MTRRs) */
#define X86_FEATURE_K8_C (3*32+ 4) /* C stepping K8 */
#define X86_FEATURE_CONSTANT_TSC (3*32+5) /* TSC runs at constant rate */
/* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */
#define X86_FEATURE_XMM3 (4*32+ 0) /* Streaming SIMD Extensions-3 */