From bb8985586b7a906e116db835c64773b7a7d51663 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 17 Aug 2008 21:05:42 -0400 Subject: x86, um: ... and asm-x86 move Signed-off-by: Al Viro Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/timer.h | 66 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 66 insertions(+) create mode 100644 arch/x86/include/asm/timer.h (limited to 'arch/x86/include/asm/timer.h') diff --git a/arch/x86/include/asm/timer.h b/arch/x86/include/asm/timer.h new file mode 100644 index 00000000000..d0babce4b47 --- /dev/null +++ b/arch/x86/include/asm/timer.h @@ -0,0 +1,66 @@ +#ifndef ASM_X86__TIMER_H +#define ASM_X86__TIMER_H +#include +#include +#include + +#define TICK_SIZE (tick_nsec / 1000) + +unsigned long long native_sched_clock(void); +unsigned long native_calibrate_tsc(void); + +#ifdef CONFIG_X86_32 +extern int timer_ack; +extern int recalibrate_cpu_khz(void); +#endif /* CONFIG_X86_32 */ + +extern int no_timer_check; + +#ifndef CONFIG_PARAVIRT +#define calibrate_tsc() native_calibrate_tsc() +#endif + +/* 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!" + */ + +DECLARE_PER_CPU(unsigned long, cyc2ns); + +#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */ + +static inline unsigned long long __cycles_2_ns(unsigned long long cyc) +{ + return cyc * per_cpu(cyc2ns, smp_processor_id()) >> CYC2NS_SCALE_FACTOR; +} + +static inline unsigned long long cycles_2_ns(unsigned long long cyc) +{ + unsigned long long ns; + unsigned long flags; + + local_irq_save(flags); + ns = __cycles_2_ns(cyc); + local_irq_restore(flags); + + return ns; +} + +#endif /* ASM_X86__TIMER_H */ -- cgit v1.2.3