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m68k: Implement ndelay() based on the existing udelay() logic
Add a ndelay macro modeled after the Coldfire udelay(). The ISP1160 driver needs a 150ns delay, so we need to have ndelay(). Signed-off-by: Michael Schmitz <schmitz@debian.org> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
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@ -92,5 +92,28 @@ static inline void __udelay(unsigned long usecs)
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#define udelay(n) (__builtin_constant_p(n) ? \
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((n) > 20000 ? __bad_udelay() : __const_udelay(n)) : __udelay(n))
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/*
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* nanosecond delay:
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*
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* ((((HZSCALE) >> 11) * (loops_per_jiffy >> 11)) >> 6) is the number of loops
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* per microsecond
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*
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* 1000 / ((((HZSCALE) >> 11) * (loops_per_jiffy >> 11)) >> 6) is the number of
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* nanoseconds per loop
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*
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* So n / ( 1000 / ((((HZSCALE) >> 11) * (loops_per_jiffy >> 11)) >> 6) ) would
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* be the number of loops for n nanoseconds
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*/
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/*
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* The simpler m68k and ColdFire processors do not have a 32*32->64
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* multiply instruction. So we need to handle them a little differently.
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* We use a bit of shifting and a single 32*32->32 multiply to get close.
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* This is a macro so that the const version can factor out the first
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* multiply and shift.
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*/
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#define HZSCALE (268435456 / (1000000 / HZ))
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#define ndelay(n) __delay(DIV_ROUND_UP((n) * ((((HZSCALE) >> 11) * (loops_per_jiffy >> 11)) >> 6), 1000));
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#endif /* defined(_M68K_DELAY_H) */
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