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include/asm-ppc/delay.h
1.91 KB
1da177e4c
Linux-2.6.12-rc2
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#ifdef __KERNEL__
#ifndef _PPC_DELAY_H
#define _PPC_DELAY_H
#include <asm/param.h>
/*
* Copyright 1996, Paul Mackerras.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
extern unsigned long loops_per_jiffy;
extern void __delay(unsigned int loops);
/*
* Note that 19 * 226 == 4294 ==~ 2^32 / 10^6, so
* loops = (4294 * usecs * loops_per_jiffy * HZ) / 2^32.
*
* The mulhwu instruction gives us loops = (a * b) / 2^32.
* We choose a = usecs * 19 * HZ and b = loops_per_jiffy * 226
* because this lets us support a wide range of HZ and
* loops_per_jiffy values without either a or b overflowing 2^32.
* Thus we need usecs * HZ <= (2^32 - 1) / 19 = 226050910 and
* loops_per_jiffy <= (2^32 - 1) / 226 = 19004280
* (which corresponds to ~3800 bogomips at HZ = 100).
* -- paulus
*/
#define __MAX_UDELAY (226050910UL/HZ) /* maximum udelay argument */
#define __MAX_NDELAY (4294967295UL/HZ) /* maximum ndelay argument */
extern __inline__ void __udelay(unsigned int x)
{
unsigned int loops;
__asm__("mulhwu %0,%1,%2" : "=r" (loops) :
"r" (x), "r" (loops_per_jiffy * 226));
__delay(loops);
}
extern __inline__ void __ndelay(unsigned int x)
{
unsigned int loops;
__asm__("mulhwu %0,%1,%2" : "=r" (loops) :
"r" (x), "r" (loops_per_jiffy * 5));
__delay(loops);
}
extern void __bad_udelay(void); /* deliberately undefined */
extern void __bad_ndelay(void); /* deliberately undefined */
#define udelay(n) (__builtin_constant_p(n)? \
((n) > __MAX_UDELAY? __bad_udelay(): __udelay((n) * (19 * HZ))) : \
__udelay((n) * (19 * HZ)))
#define ndelay(n) (__builtin_constant_p(n)? \
((n) > __MAX_NDELAY? __bad_ndelay(): __ndelay((n) * HZ)) : \
__ndelay((n) * HZ))
#endif /* defined(_PPC_DELAY_H) */
#endif /* __KERNEL__ */
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