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| author | Michael Hennerich <michael.hennerich@analog.com> | 2009-02-04 16:49:45 +0800 |
|---|---|---|
| committer | Bryan Wu <cooloney@kernel.org> | 2009-02-04 16:49:45 +0800 |
| commit | 4e653e04cc1c3553af539ffc81fb56d83d83c733 (patch) | |
| tree | 6d5ab0a6e8033901ccb6c193daa15f0c20e008ab | |
| parent | 972de7d9292439c9429c301cf377fbf56b6e654e (diff) | |
| download | linux-4e653e04cc1c3553af539ffc81fb56d83d83c733.tar.gz | |
Blackfin arch: Fix udelay implementation
Avoid possible overflow during 32*32->32 multiplies. Reported-by: Marco Reppenhagen <marco.reppenhagen@auerswald.de> Signed-off-by: Michael Hennerich <michael.hennerich@analog.com> Signed-off-by: Bryan Wu <cooloney@kernel.org>
| -rw-r--r-- | arch/blackfin/include/asm/delay.h | 11 |
1 files changed, 5 insertions, 6 deletions
diff --git a/arch/blackfin/include/asm/delay.h b/arch/blackfin/include/asm/delay.h index 0889c3abb593..47f98c5067b5 100644 --- a/arch/blackfin/include/asm/delay.h +++ b/arch/blackfin/include/asm/delay.h @@ -47,16 +47,15 @@ static inline void __delay(unsigned long loops) #include <linux/param.h> /* needed for HZ */ /* - * Use only for very small delays ( < 1 msec). Should probably use a - * lookup table, really, as the multiplications take much too long with - * short delays. This is a "reasonable" implementation, though (and the - * first constant multiplications gets optimized away if the delay is - * a constant) + * close approximation borrowed from m68knommu to avoid 64-bit math */ + +#define HZSCALE (268435456 / (1000000/HZ)) + static inline void udelay(unsigned long usecs) { extern unsigned long loops_per_jiffy; - __delay(usecs * loops_per_jiffy / (1000000 / HZ)); + __delay((((usecs * HZSCALE) >> 11) * (loops_per_jiffy >> 11)) >> 6); } #endif |