Messages in this thread | | | Subject | Re: [PATCH] ARC: Fix __udelay parentheses | From | Joe Perches <> | Date | Wed, 28 Aug 2013 11:45:39 -0700 |
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On Wed, 2013-08-28 at 20:29 +0200, Mischa Jonker wrote: > Make sure that usecs is casted to long long, to ensure that the > (usecs * 4295 * HZ) multiplication is 64 bit. > > Initially, the (usecs * 4295 * HZ) part was done as a 32 bit > multiplication, with the result casted to 64 bit. This led to some bits > falling off. > > Signed-off-by: Mischa Jonker <mjonker@synopsys.com> > --- > arch/arc/include/asm/delay.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arc/include/asm/delay.h b/arch/arc/include/asm/delay.h > index 442ce5d..8d35fe1 100644 > --- a/arch/arc/include/asm/delay.h > +++ b/arch/arc/include/asm/delay.h > @@ -56,8 +56,8 @@ static inline void __udelay(unsigned long usecs) > /* (long long) cast ensures 64 bit MPY - real or emulated > * HZ * 4295 is pre-evaluated by gcc - hence only 2 mpy ops > */ > - loops = ((long long)(usecs * 4295 * HZ) * > - (long long)(loops_per_jiffy)) >> 32; > + loops = (((long long) usecs) * 4295 * HZ * > + (long long) loops_per_jiffy) >> 32;
Shouldn't this be unsigned long long or u64?
Why is it >> 32 again?
The comment above it doesn't seem to match the code.
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