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authorRoss Biro <ross.biro@gmail.com>2006-01-11 22:43:51 +0100
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-11 19:04:52 -0800
commit79c62cf1789f935280138b412bb750be84aec747 (patch)
tree24c522ed0dd3dba942f1db43048205b0973aa7c8 /arch/x86_64/lib
parente4e94072d9c3b19662537cbd5e2d37bcaeed3d9b (diff)
downloadlinux-linaro-stable-79c62cf1789f935280138b412bb750be84aec747.tar.gz
[PATCH] x86_64: Make udelay more accurate
The attempt to avoid overflow in __delay caused varying precision on different CPUs depending on differences in the CPU speed. We should be able to do this multiplication with out overflowing provided the cpu is running at less than about 128 GHz. xloops < 20000 * 0x10c6. loops_per_jiffy * HZ <= cpu_clock_speed. So if the cpu clock speed < 2^64/(20000 * 0x10c6) = 2^64/ 51E6CC0 < 2^64/2^27 = 2^37 = 128G we will not overflow the calculation. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch/x86_64/lib')
-rw-r--r--arch/x86_64/lib/delay.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86_64/lib/delay.c b/arch/x86_64/lib/delay.c
index 841bd738a189..03c460cbdd1c 100644
--- a/arch/x86_64/lib/delay.c
+++ b/arch/x86_64/lib/delay.c
@@ -39,7 +39,7 @@ void __delay(unsigned long loops)
inline void __const_udelay(unsigned long xloops)
{
- __delay(((xloops * cpu_data[raw_smp_processor_id()].loops_per_jiffy) >> 32) * HZ);
+ __delay((xloops * HZ * cpu_data[raw_smp_processor_id()].loops_per_jiffy) >> 32);
}
void __udelay(unsigned long usecs)