From: "Andi Kleen" <[email protected]>
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: <[email protected]>
Signed-off-by: Andi Kleen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
25-akpm/arch/x86_64/kernel/setup.c | 5 ++++-
25-akpm/arch/x86_64/kernel/time.c | 5 +++--
25-akpm/include/asm-x86_64/cpufeature.h | 1 +
3 files changed, 8 insertions(+), 3 deletions(-)
diff -puN arch/x86_64/kernel/setup.c~x86_64-support-constantly-ticking-tscs arch/x86_64/kernel/setup.c
--- 25/arch/x86_64/kernel/setup.c~x86_64-support-constantly-ticking-tscs 2005-04-12 03:21:23.473568376 -0700
+++ 25-akpm/arch/x86_64/kernel/setup.c 2005-04-12 03:21:23.479567464 -0700
@@ -855,6 +855,8 @@ static void __init init_intel(struct cpu
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
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,
diff -puN arch/x86_64/kernel/time.c~x86_64-support-constantly-ticking-tscs arch/x86_64/kernel/time.c
--- 25/arch/x86_64/kernel/time.c~x86_64-support-constantly-ticking-tscs 2005-04-12 03:21:23.474568224 -0700
+++ 25-akpm/arch/x86_64/kernel/time.c 2005-04-12 03:21:23.480567312 -0700
@@ -614,6 +614,9 @@ static int time_cpufreq_notifier(struct
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
lpj = &boot_cpu_data.loops_per_jiffy;
#endif
-
-
if (!ref_freq) {
ref_freq = freq->old;
loops_per_jiffy_ref = *lpj;
diff -puN include/asm-x86_64/cpufeature.h~x86_64-support-constantly-ticking-tscs include/asm-x86_64/cpufeature.h
--- 25/include/asm-x86_64/cpufeature.h~x86_64-support-constantly-ticking-tscs 2005-04-12 03:21:23.475568072 -0700
+++ 25-akpm/include/asm-x86_64/cpufeature.h 2005-04-12 03:21:23.481567160 -0700
@@ -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 */
_
-
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