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
  19 extern 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  */
  28 extern 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  */
  40 extern void __udelay(unsigned long usecs);
  41 extern 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