Commit 4e653e04 authored by Michael Hennerich's avatar Michael Hennerich Committed by Bryan Wu

Blackfin arch: Fix udelay implementation

Avoid possible overflow during 32*32->32 multiplies.
Reported-by: default avatarMarco Reppenhagen <marco.reppenhagen@auerswald.de>
Signed-off-by: default avatarMichael Hennerich <michael.hennerich@analog.com>
Signed-off-by: default avatarBryan Wu <cooloney@kernel.org>
parent 972de7d9
...@@ -47,16 +47,15 @@ static inline void __delay(unsigned long loops) ...@@ -47,16 +47,15 @@ static inline void __delay(unsigned long loops)
#include <linux/param.h> /* needed for HZ */ #include <linux/param.h> /* needed for HZ */
/* /*
* Use only for very small delays ( < 1 msec). Should probably use a * close approximation borrowed from m68knommu to avoid 64-bit math
* 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)
*/ */
#define HZSCALE (268435456 / (1000000/HZ))
static inline void udelay(unsigned long usecs) static inline void udelay(unsigned long usecs)
{ {
extern unsigned long loops_per_jiffy; extern unsigned long loops_per_jiffy;
__delay(usecs * loops_per_jiffy / (1000000 / HZ)); __delay((((usecs * HZSCALE) >> 11) * (loops_per_jiffy >> 11)) >> 6);
} }
#endif #endif
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