root/arch/unicore32/include/asm/delay.h

INCLUDED FROM

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * linux/arch/unicore32/include/asm/delay.h
   4  *
   5  * Code specific to PKUnity SoC and UniCore ISA
   6  *
   7  * Copyright (C) 2001-2010 GUAN Xue-tao
   8  *
   9  * Delay routines, using a pre-computed "loops_per_second" value.
  10  */
  11 #ifndef __UNICORE_DELAY_H__
  12 #define __UNICORE_DELAY_H__
  13 
  14 #include <asm/param.h>  /* HZ */
  15 
  16 extern void __delay(int loops);
  17 
  18 /*
  19  * This function intentionally does not exist; if you see references to
  20  * it, it means that you're calling udelay() with an out of range value.
  21  *
  22  * With currently imposed limits, this means that we support a max delay
  23  * of 2000us. Further limits: HZ<=1000 and bogomips<=3355
  24  */
  25 extern void __bad_udelay(void);
  26 
  27 /*
  28  * division by multiplication: you don't have to worry about
  29  * loss of precision.
  30  *
  31  * Use only for very small delays ( < 1 msec).  Should probably use a
  32  * lookup table, really, as the multiplications take much too long with
  33  * short delays.  This is a "reasonable" implementation, though (and the
  34  * first constant multiplications gets optimized away if the delay is
  35  * a constant)
  36  */
  37 extern void __udelay(unsigned long usecs);
  38 extern void __const_udelay(unsigned long);
  39 
  40 #define MAX_UDELAY_MS 2
  41 
  42 #define udelay(n)                                                       \
  43         (__builtin_constant_p(n) ?                                      \
  44           ((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() :              \
  45                         __const_udelay((n) * ((2199023U*HZ)>>11))) :    \
  46           __udelay(n))
  47 
  48 #endif /* __UNICORE_DELAY_H__ */
  49