LXR linux/arch/unicore32/include/asm/delay.h

   1/*
   2 * linux/arch/unicore32/include/asm/delay.h
   3 *
   4 * Code specific to PKUnity SoC and UniCore ISA
   5 *
   6 * Copyright (C) 2001-2010 GUAN Xue-tao
   7 *
   8 * This program is free software; you can redistribute it and/or modify
   9 * it under the terms of the GNU General Public License version 2 as
  10 * published by the Free Software Foundation.
  11 *
  12 * Delay routines, using a pre-computed "loops_per_second" value.
  13 */
  14#ifndef __UNICORE_DELAY_H__
  15#define __UNICORE_DELAY_H__
  16
  17#include <asm/param.h>  /* HZ */
  18
  19extern void __delay(int loops);
  20
  21/*
  22 * This function intentionally does not exist; if you see references to
  23 * it, it means that you're calling udelay() with an out of range value.
  24 *
  25 * With currently imposed limits, this means that we support a max delay
  26 * of 2000us. Further limits: HZ<=1000 and bogomips<=3355
  27 */
  28extern void __bad_udelay(void);
  29
  30/*
  31 * division by multiplication: you don't have to worry about
  32 * loss of precision.
  33 *
  34 * Use only for very small delays ( < 1 msec).  Should probably use a
  35 * lookup table, really, as the multiplications take much too long with
  36 * short delays.  This is a "reasonable" implementation, though (and the
  37 * first constant multiplications gets optimized away if the delay is
  38 * a constant)
  39 */
  40extern void __udelay(unsigned long usecs);
  41extern void __const_udelay(unsigned long);
  42
  43#define MAX_UDELAY_MS 2
  44
  45#define udelay(n)                                                       \
  46        (__builtin_constant_p(n) ?                                      \
  47          ((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() :              \
  48                        __const_udelay((n) * ((2199023U*HZ)>>11))) :    \
  49          __udelay(n))
  50
  51#endif /* __UNICORE_DELAY_H__ */
  52
  53