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6d4518d76f
Patch from Peter Teichmann Currently, if the kernels HZ value is greater than 100, delays with the udelay function are too short. This can cause trouble for instance with the zd1201 usb wlan driver. This patch suggests a solution that keeps the overhead small and maintains (hopefully) sufficient resolution. Signed-off-by: Peter Teichmann Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
45 lines
1.2 KiB
C
45 lines
1.2 KiB
C
/*
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* Copyright (C) 1995-2004 Russell King
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*
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* Delay routines, using a pre-computed "loops_per_second" value.
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*/
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#ifndef __ASM_ARM_DELAY_H
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#define __ASM_ARM_DELAY_H
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#include <asm/param.h> /* HZ */
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extern void __delay(int loops);
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/*
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* This function intentionally does not exist; if you see references to
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* it, it means that you're calling udelay() with an out of range value.
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*
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* With currently imposed limits, this means that we support a max delay
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* of 2000us. Further limits: HZ<=1000 and bogomips<=3355
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*/
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extern void __bad_udelay(void);
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/*
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* division by multiplication: you don't have to worry about
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* loss of precision.
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*
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* Use only for very small delays ( < 1 msec). Should probably use a
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* lookup table, really, as the multiplications take much too long with
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* short delays. This is a "reasonable" implementation, though (and the
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* first constant multiplications gets optimized away if the delay is
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* a constant)
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*/
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extern void __udelay(unsigned long usecs);
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extern void __const_udelay(unsigned long);
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#define MAX_UDELAY_MS 2
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#define udelay(n) \
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(__builtin_constant_p(n) ? \
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((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \
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__const_udelay((n) * ((2199023U*HZ)>>11))) : \
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__udelay(n))
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#endif /* defined(_ARM_DELAY_H) */
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