arch/arm/lib/delay.S

   1 /*
   2  *  linux/arch/arm/lib/delay.S
   3  *
   4  *  Copyright (C) 1995, 1996 Russell King
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10 #include <linux/linkage.h>
  11 #include <asm/assembler.h>
  12                 .text
  13
  14 LC0:            .word   loops_per_jiffy
  15
  16 /*
  17  * 0 <= r0 <= 2000
  18  */
  19 ENTRY(__udelay)
  20                 mov     r2,     #0x6800
  21                 orr     r2, r2, #0x00db
  22                 mul     r0, r2, r0
  23 ENTRY(__const_udelay)                           @ 0 <= r0 <= 0x01ffffff
  24                 ldr     r2, LC0
  25                 ldr     r2, [r2]                @ max = 0x0fffffff
  26                 mov     r0, r0, lsr #11         @ max = 0x00003fff
  27                 mov     r2, r2, lsr #11         @ max = 0x0003ffff
  28                 mul     r0, r2, r0              @ max = 2^32-1
  29                 movs    r0, r0, lsr #6
  30                 RETINSTR(moveq,pc,lr)
  31
  32 /*
  33  * loops = (r0 * 0x10c6 * 100 * loops_per_jiffy) / 2^32
  34  *
  35  * Oh, if only we had a cycle counter...
  36  */
  37
  38 @ Delay routine
  39 ENTRY(__delay)
  40                 subs    r0, r0, #1
  41 #if 0
  42                 RETINSTR(movls,pc,lr)
  43                 subs    r0, r0, #1
  44                 RETINSTR(movls,pc,lr)
  45                 subs    r0, r0, #1
  46                 RETINSTR(movls,pc,lr)
  47                 subs    r0, r0, #1
  48                 RETINSTR(movls,pc,lr)
  49                 subs    r0, r0, #1
  50                 RETINSTR(movls,pc,lr)
  51                 subs    r0, r0, #1
  52                 RETINSTR(movls,pc,lr)
  53                 subs    r0, r0, #1
  54                 RETINSTR(movls,pc,lr)
  55                 subs    r0, r0, #1
  56 #endif
  57                 bhi     __delay
  58                 RETINSTR(mov,pc,lr)