From 2dbe06faf37b39f9ecffc054dd173b2a1dc2adcd Mon Sep 17 00:00:00 2001 From: Alok Kataria Date: Tue, 1 Jul 2008 11:43:31 -0700 Subject: x86: merge the TSC cpu-freq code Unify the TSC cpufreq code. Signed-off-by: Alok N Kataria Signed-off-by: Dan Hecht Cc: Dan Hecht Signed-off-by: Ingo Molnar --- arch/x86/kernel/tsc.c | 114 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 114 insertions(+) (limited to 'arch/x86/kernel/tsc.c') diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index e6ee14533c7..595f78a2221 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -4,6 +4,7 @@ #include #include #include +#include #include @@ -215,3 +216,116 @@ int recalibrate_cpu_khz(void) EXPORT_SYMBOL(recalibrate_cpu_khz); #endif /* CONFIG_X86_32 */ + +/* Accelerators for sched_clock() + * convert from cycles(64bits) => nanoseconds (64bits) + * basic equation: + * ns = cycles / (freq / ns_per_sec) + * ns = cycles * (ns_per_sec / freq) + * ns = cycles * (10^9 / (cpu_khz * 10^3)) + * ns = cycles * (10^6 / cpu_khz) + * + * Then we use scaling math (suggested by george@mvista.com) to get: + * ns = cycles * (10^6 * SC / cpu_khz) / SC + * ns = cycles * cyc2ns_scale / SC + * + * And since SC is a constant power of two, we can convert the div + * into a shift. + * + * We can use khz divisor instead of mhz to keep a better precision, since + * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits. + * (mathieu.desnoyers@polymtl.ca) + * + * -johnstul@us.ibm.com "math is hard, lets go shopping!" + */ + +DEFINE_PER_CPU(unsigned long, cyc2ns); + +void set_cyc2ns_scale(unsigned long cpu_khz, int cpu) +{ + unsigned long long tsc_now, ns_now; + unsigned long flags, *scale; + + local_irq_save(flags); + sched_clock_idle_sleep_event(); + + scale = &per_cpu(cyc2ns, cpu); + + rdtscll(tsc_now); + ns_now = __cycles_2_ns(tsc_now); + + if (cpu_khz) + *scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz; + + sched_clock_idle_wakeup_event(0); + local_irq_restore(flags); +} + +#ifdef CONFIG_CPU_FREQ + +/* Frequency scaling support. Adjust the TSC based timer when the cpu frequency + * changes. + * + * RED-PEN: On SMP we assume all CPUs run with the same frequency. It's + * not that important because current Opteron setups do not support + * scaling on SMP anyroads. + * + * Should fix up last_tsc too. Currently gettimeofday in the + * first tick after the change will be slightly wrong. + */ + +static unsigned int ref_freq; +static unsigned long loops_per_jiffy_ref; +static unsigned long tsc_khz_ref; + +static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, + void *data) +{ + 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 + lpj = &cpu_data(freq->cpu).loops_per_jiffy; +#else + lpj = &boot_cpu_data.loops_per_jiffy; +#endif + + if (!ref_freq) { + ref_freq = freq->old; + loops_per_jiffy_ref = *lpj; + tsc_khz_ref = tsc_khz; + } + if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) || + (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) || + (val == CPUFREQ_RESUMECHANGE)) { + *lpj = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new); + + tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new); + if (!(freq->flags & CPUFREQ_CONST_LOOPS)) + mark_tsc_unstable("cpufreq changes"); + } + + set_cyc2ns_scale(tsc_khz_ref, freq->cpu); + + return 0; +} + +static struct notifier_block time_cpufreq_notifier_block = { + .notifier_call = time_cpufreq_notifier +}; + +static int __init cpufreq_tsc(void) +{ + cpufreq_register_notifier(&time_cpufreq_notifier_block, + CPUFREQ_TRANSITION_NOTIFIER); + return 0; +} + +core_initcall(cpufreq_tsc); + +#endif /* CONFIG_CPU_FREQ */ -- cgit v1.2.3