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author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 22:20:36 (GMT) |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 22:20:36 (GMT) |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /include/asm-mips/timex.h | |
download | linux-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.xz |
Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'include/asm-mips/timex.h')
-rw-r--r-- | include/asm-mips/timex.h | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/include/asm-mips/timex.h b/include/asm-mips/timex.h new file mode 100644 index 0000000..98aa737 --- /dev/null +++ b/include/asm-mips/timex.h @@ -0,0 +1,54 @@ +/* + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file "COPYING" in the main directory of this archive + * for more details. + * + * Copyright (C) 1998, 1999, 2003 by Ralf Baechle + */ +#ifndef _ASM_TIMEX_H +#define _ASM_TIMEX_H + +#include <asm/mipsregs.h> + +/* + * This is the frequency of the timer used for Linux's timer interrupt. + * The value should be defined as accurate as possible or under certain + * circumstances Linux timekeeping might become inaccurate or fail. + * + * For many system the exact clockrate of the timer isn't known but due to + * the way this value is used we can get away with a wrong value as long + * as this value is: + * + * - a multiple of HZ + * - a divisor of the actual rate + * + * 500000 is a good such cheat value. + * + * The obscure number 1193182 is the same as used by the original i8254 + * time in legacy PC hardware; the chip unfortunately also found in a + * bunch of MIPS systems. The last remaining user of the i8254 for the + * timer interrupt is the RM200; it's a very standard system so there is + * no reason to make this a separate architecture. + */ + +#include <timex.h> + +/* + * Standard way to access the cycle counter. + * Currently only used on SMP for scheduling. + * + * Only the low 32 bits are available as a continuously counting entity. + * But this only means we'll force a reschedule every 8 seconds or so, + * which isn't an evil thing. + * + * We know that all SMP capable CPUs have cycle counters. + */ + +typedef unsigned int cycles_t; + +static inline cycles_t get_cycles (void) +{ + return read_c0_count(); +} + +#endif /* _ASM_TIMEX_H */ |