55 lines
1.6 KiB
C
55 lines
1.6 KiB
C
/*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Copyright (C) 1998, 1999, 2003 by Ralf Baechle
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*/
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#ifndef _ASM_TIMEX_H
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#define _ASM_TIMEX_H
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#include <asm/mipsregs.h>
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/*
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* This is the frequency of the timer used for Linux's timer interrupt.
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* The value should be defined as accurate as possible or under certain
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* circumstances Linux timekeeping might become inaccurate or fail.
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*
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* For many system the exact clockrate of the timer isn't known but due to
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* the way this value is used we can get away with a wrong value as long
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* as this value is:
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*
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* - a multiple of HZ
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* - a divisor of the actual rate
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*
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* 500000 is a good such cheat value.
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*
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* The obscure number 1193182 is the same as used by the original i8254
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* time in legacy PC hardware; the chip unfortunately also found in a
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* bunch of MIPS systems. The last remaining user of the i8254 for the
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* timer interrupt is the RM200; it's a very standard system so there is
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* no reason to make this a separate architecture.
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*/
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#include <timex.h>
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/*
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* Standard way to access the cycle counter.
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* Currently only used on SMP for scheduling.
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*
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* Only the low 32 bits are available as a continuously counting entity.
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* But this only means we'll force a reschedule every 8 seconds or so,
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* which isn't an evil thing.
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*
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* We know that all SMP capable CPUs have cycle counters.
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*/
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typedef unsigned int cycles_t;
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static inline cycles_t get_cycles (void)
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{
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return read_c0_count();
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}
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#endif /* _ASM_TIMEX_H */
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