From 9dcb3bd61b8bf49741a32fcad73e56d2c7dcb0f6 Mon Sep 17 00:00:00 2001 From: Dave Jones Date: Mon, 5 Jan 2004 18:16:28 +0000 Subject: [PATCH] [CPUFREQ] on P4s no TSC adjustment is necessary From Dominik Brodowski --- arch/i386/kernel/timers/timer_tsc.c | 35 ++++++++++++++++++++++------- 1 file changed, 27 insertions(+), 8 deletions(-) diff --git a/arch/i386/kernel/timers/timer_tsc.c b/arch/i386/kernel/timers/timer_tsc.c index be9a2a533dd1e..3b081f1b82054 100644 --- a/arch/i386/kernel/timers/timer_tsc.c +++ b/arch/i386/kernel/timers/timer_tsc.c @@ -306,9 +306,17 @@ static void mark_offset_tsc_hpet(void) } #endif + #ifdef CONFIG_CPU_FREQ +/* If the CPU frequency is scaled, TSC-based delays will need a different + * loops_per_jiffy value to function properly. An exception to this + * are modern Intel Pentium 4 processors, where the TSC runs at a constant + * speed independent of frequency scaling. + */ + static unsigned int ref_freq = 0; static unsigned long loops_per_jiffy_ref = 0; +static unsigned int variable_tsc = 1; #ifndef CONFIG_SMP static unsigned long fast_gettimeoffset_ref = 0; @@ -333,12 +341,15 @@ time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) || (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) { - cpu_data[freq->cpu].loops_per_jiffy = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new); + if (variable_tsc) + cpu_data[freq->cpu].loops_per_jiffy = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new); #ifndef CONFIG_SMP if (use_tsc) { - fast_gettimeoffset_quotient = cpufreq_scale(fast_gettimeoffset_ref, freq->new, ref_freq); cpu_khz = cpufreq_scale(cpu_khz_ref, ref_freq, freq->new); - set_cyc2ns_scale(cpu_khz/1000); + if (variable_tsc) { + fast_gettimeoffset_quotient = cpufreq_scale(fast_gettimeoffset_ref, freq->new, ref_freq); + set_cyc2ns_scale(cpu_khz/1000); + } } #endif } @@ -350,7 +361,19 @@ time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, static struct notifier_block time_cpufreq_notifier_block = { .notifier_call = time_cpufreq_notifier }; -#endif + + +static int __init cpufreq_tsc(void) +{ + /* P4 and above CPU TSC freq doesn't change when CPU frequency changes*/ + if ((boot_cpu_data.x86 >= 15) && (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)) + variable_tsc = 0; + + return cpufreq_register_notifier(&time_cpufreq_notifier_block, CPUFREQ_TRANSITION_NOTIFIER); +} +core_initcall(cpufreq_tsc); + +#endif static int __init init_tsc(char* override) @@ -392,10 +415,6 @@ static int __init init_tsc(char* override) * some CPU's have a TSC. Thats never worked and nobody has * moaned if you have the only one in the world - you fix it! */ - -#ifdef CONFIG_CPU_FREQ - cpufreq_register_notifier(&time_cpufreq_notifier_block, CPUFREQ_TRANSITION_NOTIFIER); -#endif count2 = LATCH; /* initialize counter for mark_offset_tsc() */ -- 2.53.0