include/asm-mips/delay.h

   1 /* $Id: delay.h,v 1.2 1999/01/04 16:09:20 ralf Exp $
   2  *
   3  * This file is subject to the terms and conditions of the GNU General Public
   4  * License.  See the file "COPYING" in the main directory of this archive
   5  * for more details.
   6  *
   7  * Copyright (C) 1994 by Waldorf Electronics
   8  * Copyright (C) 1995 - 1998 by Ralf Baechle
   9  */
  10 #ifndef __ASM_MIPS_DELAY_H
  11 #define __ASM_MIPS_DELAY_H
  12
  13 extern __inline__ void __delay(int loops)
  14 {
  15         __asm__ __volatile__ (
  16                 ".set\tnoreorder\n"
  17                 "1:\tbnez\t%0,1b\n\t"
  18                 "subu\t%0,1\n\t"
  19                 ".set\treorder"
  20                 :"=r" (loops)
  21                 :"0" (loops));
  22 }
  23
  24 /*
  25  * division by multiplication: you don't have to worry about
  26  * loss of precision.
  27  *
  28  * Use only for very small delays ( < 1 msec).  Should probably use a
  29  * lookup table, really, as the multiplications take much too long with
  30  * short delays.  This is a "reasonable" implementation, though (and the
  31  * first constant multiplications gets optimized away if the delay is
  32  * a constant)
  33  */
  34 extern __inline__ void __udelay(unsigned long usecs, unsigned long lps)
  35 {
  36         usecs *= 0x000010c6;            /* 2**32 / 1000000 */
  37         __asm__("multu\t%0,%2\n\t"
  38                 "mfhi\t%0"
  39                 :"=r" (usecs)
  40                 :"0" (usecs),"r" (lps));
  41         __delay(usecs);
  42 }
  43
  44 #ifdef __SMP__
  45 #define __udelay_val cpu_data[smp_processor_id()].udelay_val
  46 #else
  47 #define __udelay_val loops_per_sec
  48 #endif
  49
  50 #define udelay(usecs) __udelay((usecs),__udelay_val)
  51
  52 #endif /* __ASM_MIPS_DELAY_H */