forked from Minki/linux
539eb11e6e
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 <johnstul@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
50 lines
1.1 KiB
C
50 lines
1.1 KiB
C
/*
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* linux/include/asm-i386/tsc.h
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*
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* i386 TSC related functions
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*/
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#ifndef _ASM_i386_TSC_H
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#define _ASM_i386_TSC_H
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#include <linux/config.h>
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#include <asm/processor.h>
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/*
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* Standard way to access the cycle counter on i586+ CPUs.
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* Currently only used on SMP.
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*
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* If you really have a SMP machine with i486 chips or older,
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* compile for that, and this will just always return zero.
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* That's ok, it just means that the nicer scheduling heuristics
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* won't work for you.
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*
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* We only use the low 32 bits, and we'd simply better make sure
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* that we reschedule before that wraps. Scheduling at least every
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* four billion cycles just basically sounds like a good idea,
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* regardless of how fast the machine is.
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*/
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typedef unsigned long long cycles_t;
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extern unsigned int cpu_khz;
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extern unsigned int tsc_khz;
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static inline cycles_t get_cycles(void)
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{
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unsigned long long ret = 0;
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#ifndef CONFIG_X86_TSC
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if (!cpu_has_tsc)
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return 0;
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#endif
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#if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC)
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rdtscll(ret);
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#endif
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return ret;
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}
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extern void tsc_init(void);
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extern void mark_tsc_unstable(void);
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#endif
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