1/* 2 * This file is subject to the terms and conditions of the GNU General Public 3 * License. See the file "COPYING" in the main directory of this archive 4 * for more details. 5 * 6 * Copyright (C) 1998, 1999, 2003 by Ralf Baechle 7 */ 8#ifndef _ASM_TIMEX_H 9#define _ASM_TIMEX_H 10 11#ifdef __KERNEL__ 12 13#include <asm/mipsregs.h> 14 15/* 16 * This is the frequency of the timer used for Linux's timer interrupt. 17 * The value should be defined as accurate as possible or under certain 18 * circumstances Linux timekeeping might become inaccurate or fail. 19 * 20 * For many system the exact clockrate of the timer isn't known but due to 21 * the way this value is used we can get away with a wrong value as long 22 * as this value is: 23 * 24 * - a multiple of HZ 25 * - a divisor of the actual rate 26 * 27 * 500000 is a good such cheat value. 28 * 29 * The obscure number 1193182 is the same as used by the original i8254 30 * time in legacy PC hardware; the chip unfortunately also found in a 31 * bunch of MIPS systems. The last remaining user of the i8254 for the 32 * timer interrupt is the RM200; it's a very standard system so there is 33 * no reason to make this a separate architecture. 34 */ 35 36#include <timex.h> 37 38/* 39 * Standard way to access the cycle counter. 40 * Currently only used on SMP for scheduling. 41 * 42 * Only the low 32 bits are available as a continuously counting entity. 43 * But this only means we'll force a reschedule every 8 seconds or so, 44 * which isn't an evil thing. 45 * 46 * We know that all SMP capable CPUs have cycle counters. 47 */ 48 49typedef unsigned int cycles_t; 50 51static inline cycles_t get_cycles (void) 52{ 53 return read_c0_count(); 54} 55 56#endif /* __KERNEL__ */ 57 58#endif /* _ASM_TIMEX_H */ 59