include/asm-mips/delay.h

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 1994 by Waldorf Electronics
   7  * Copyright (C) 1995 - 1998, 2001 by Ralf Baechle
   8  */
   9 #ifndef _ASM_DELAY_H
  10 #define _ASM_DELAY_H
  11
  12 #include <linux/config.h>
  13 #include <linux/param.h>
  14
  15 extern unsigned long loops_per_jiffy;
  16
  17 extern __inline__ void
  18 __delay(unsigned long loops)
  19 {
  20         __asm__ __volatile__ (
  21                 ".set\tnoreorder\n"
  22                 "1:\tbnez\t%0,1b\n\t"
  23                 "subu\t%0,1\n\t"
  24                 ".set\treorder"
  25                 :"=r" (loops)
  26                 :"0" (loops));
  27 }
  28
  29 /*
  30  * Division by multiplication: you don't have to worry about
  31  * loss of precision.
  32  *
  33  * Use only for very small delays ( < 1 msec).  Should probably use a
  34  * lookup table, really, as the multiplications take much too long with
  35  * short delays.  This is a "reasonable" implementation, though (and the
  36  * first constant multiplications gets optimized away if the delay is
  37  * a constant)
  38  */
  39 extern __inline__ void __udelay(unsigned long usecs, unsigned long lpj)
  40 {
  41         unsigned long lo;
  42
  43         /*
  44          * Excessive precission?  Probably ...
  45          */
  46         usecs *= (unsigned long) (((0x8000000000000000ULL / (500000 / HZ)) +
  47                                    0x80000000ULL) >> 32);
  48         __asm__("multu\t%2,%3"
  49                 :"=h" (usecs), "=l" (lo)
  50                 :"r" (usecs),"r" (lpj));
  51         __delay(usecs);
  52 }
  53
  54 #ifdef CONFIG_SMP
  55 #define __udelay_val cpu_data[smp_processor_id()].udelay_val
  56 #else
  57 #define __udelay_val loops_per_jiffy
  58 #endif
  59
  60 #define udelay(usecs) __udelay((usecs),__udelay_val)
  61
  62 #endif /* _ASM_DELAY_H */