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MIPS: Fix mdelay(1) for 64bit kernel with HZ == 1000

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mdelay(1) (i.e. udelay(1000)) does not work correctly due to overflow.
    
1000 * 0x004189374BC6A7f0 = 0x10000000000000180 (>= 2**64)
    
0x004189374BC6A7ef (0x004189374BC6A7f0 - 1) is OK and it is exactly
same as catchall case (0x8000000000000000UL / (500000 / HZ)).
    
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Atsushi Nemoto 2005-11-30 13:33:26 +09:00 committed by
parent 6c35585273
commit f12555d24c
1 changed files with 2 additions and 4 deletions
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6
include/asm-mips/delay.h
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@ -52,13 +52,11 @@ static inline void __udelay(unsigned long usecs, unsigned long lpj)
unsigned long lo;
/*
* The common rates of 1000 and 128 are rounded wrongly by the
* catchall case for 64-bit. Excessive precission? Probably ...
* The rates of 128 is rounded wrongly by the catchall case
* for 64-bit. Excessive precission? Probably ...
*/
#if defined(CONFIG_64BIT) && (HZ == 128)
usecs *= 0x0008637bd05af6c7UL; /* 2**64 / (1000000 / HZ) */
#elif defined(CONFIG_64BIT) && (HZ == 1000)
usecs *= 0x004189374BC6A7f0UL; /* 2**64 / (1000000 / HZ) */
#elif defined(CONFIG_64BIT)
usecs *= (0x8000000000000000UL / (500000 / HZ));
#else /* 32-bit junk follows here */