From 4e653e04cc1c3553af539ffc81fb56d83d83c733 Mon Sep 17 00:00:00 2001
From: Michael Hennerich <michael.hennerich@analog.com>
Date: Wed, 4 Feb 2009 16:49:45 +0800
Subject: [PATCH] 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>
---
arch/blackfin/include/asm/delay.h | 11 +++++------
1 file 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
--
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