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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
Atsushi Nemoto8f9a2b32006-09-07 01:00:22 +090011#ifdef __KERNEL__
12
Linus Torvalds1da177e2005-04-16 15:20:36 -070013#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
Ralf Baechle49a89ef2007-10-11 23:46:15 +010051static inline cycles_t get_cycles(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -070052{
53 return read_c0_count();
54}
55
Atsushi Nemoto8f9a2b32006-09-07 01:00:22 +090056#endif /* __KERNEL__ */
57
Linus Torvalds1da177e2005-04-16 15:20:36 -070058#endif /* _ASM_TIMEX_H */