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 <mjon...@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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
