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