From: Mischa Jonker <Mischa.Jonker@synopsys.com>
To: Vineet.Gupta1@synopsys.com, linux-kernel@vger.kernel.org
Cc: Mischa Jonker <Mischa.Jonker@synopsys.com>
Subject: [PATCH] ARC: Fix __udelay parentheses
Date: Wed, 28 Aug 2013 20:29:48 +0200 [thread overview]
Message-ID: <1377714588-2144-1-git-send-email-mjonker@synopsys.com> (raw)
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;
__delay(loops);
}
--
1.7.9.5
next reply other threads:[~2013-08-28 18:30 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-28 18:29 Mischa Jonker [this message]
2013-08-28 18:45 ` Joe Perches
2013-08-28 18:53 ` Mischa Jonker
2013-08-28 19:01 ` Joe Perches
2013-08-28 19:12 ` Mischa Jonker
2013-08-29 1:43 ` Joe Perches
2013-08-29 5:55 ` Vineet Gupta
2013-08-29 6:01 ` Joe Perches
2013-08-29 6:24 ` Vineet Gupta
2013-08-29 6:37 ` Joe Perches
2013-08-29 6:49 ` Vineet Gupta
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