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_DELAY_H
  11 #define _ASM_DELAY_H
  12
  13 #include <linux/config.h>
  14
  15 extern __inline__ void
  16 __delay(unsigned long loops)
  17 {
  18         __asm__ __volatile__ (
  19                 ".set\tnoreorder\n"
  20                 "1:\tbnez\t%0,1b\n\t"
  21                 "subu\t%0,1\n\t"
  22                 ".set\treorder"
  23                 :"=r" (loops)
  24                 :"0" (loops));
  25 }
  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 __inline__ void __udelay(unsigned long usecs, unsigned long lps)
  38 {
  39         unsigned long lo;
  40
  41         usecs *= 0x000010c6;            /* 2**32 / 1000000 */
  42         __asm__("multu\t%2,%3"
  43                 :"=h" (usecs), "=l" (lo)
  44                 :"r" (usecs),"r" (lps));
  45         __delay(usecs);
  46 }
  47
  48 #ifdef CONFIG_SMP
  49 #define __udelay_val cpu_data[smp_processor_id()].udelay_val
  50 #else
  51 #define __udelay_val loops_per_sec
  52 #endif
  53
  54 #define udelay(usecs) __udelay((usecs),__udelay_val)
  55
  56 #endif /* _ASM_DELAY_H */