From 539eb11e6e904f2cd4f62908cc5e44d724879721 Mon Sep 17 00:00:00 2001 From: john stultz Date: Mon, 26 Jun 2006 00:25:10 -0700 Subject: [PATCH] Time: i386 Conversion - part 2: Rework TSC Support As part of the i386 conversion to the generic timekeeping infrastructure, this introduces a new tsc.c file. The code in this file replaces the TSC initialization, management and access code currently in timer_tsc.c (which will be removed) that we want to preserve. The code also introduces the following functionality: o tsc_khz: like cpu_khz but stores the TSC frequency on systems that do not change TSC frequency w/ CPU frequency o check/mark_tsc_unstable: accessor/modifier flag for TSC timekeeping usability o minor cleanups to calibration math. This patch also includes a one line __cpuinitdata fix from Zwane Mwaikambo. Signed-off-by: John Stultz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-i386/tsc.h | 49 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 49 insertions(+) create mode 100644 include/asm-i386/tsc.h (limited to 'include/asm-i386/tsc.h') diff --git a/include/asm-i386/tsc.h b/include/asm-i386/tsc.h new file mode 100644 index 000000000000..97b828ce31e0 --- /dev/null +++ b/include/asm-i386/tsc.h @@ -0,0 +1,49 @@ +/* + * linux/include/asm-i386/tsc.h + * + * i386 TSC related functions + */ +#ifndef _ASM_i386_TSC_H +#define _ASM_i386_TSC_H + +#include +#include + +/* + * Standard way to access the cycle counter on i586+ CPUs. + * Currently only used on SMP. + * + * If you really have a SMP machine with i486 chips or older, + * compile for that, and this will just always return zero. + * That's ok, it just means that the nicer scheduling heuristics + * won't work for you. + * + * We only use the low 32 bits, and we'd simply better make sure + * that we reschedule before that wraps. Scheduling at least every + * four billion cycles just basically sounds like a good idea, + * regardless of how fast the machine is. + */ +typedef unsigned long long cycles_t; + +extern unsigned int cpu_khz; +extern unsigned int tsc_khz; + +static inline cycles_t get_cycles(void) +{ + unsigned long long ret = 0; + +#ifndef CONFIG_X86_TSC + if (!cpu_has_tsc) + return 0; +#endif + +#if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC) + rdtscll(ret); +#endif + return ret; +} + +extern void tsc_init(void); +extern void mark_tsc_unstable(void); + +#endif -- cgit v1.2.3