arch/arm/lib/delay-loop.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 #include <asm/delay.h>
  13                 .text
  14
  15 .LC0:           .word   loops_per_jiffy
  16 .LC1:           .word   UDELAY_MULT
  17
  18 /*
  19  * r0  <= 2000
  20  * lpj <= 0x01ffffff (max. 3355 bogomips)
  21  * HZ  <= 1000
  22  */
  23
  24 ENTRY(__loop_udelay)
  25                 ldr     r2, .LC1
  26                 mul     r0, r2, r0
  27 ENTRY(__loop_const_udelay)                      @ 0 <= r0 <= 0x7fffff06
  28                 mov     r1, #-1
  29                 ldr     r2, .LC0
  30                 ldr     r2, [r2]                @ max = 0x01ffffff
  31                 add     r0, r0, r1, lsr #32-14
  32                 mov     r0, r0, lsr #14         @ max = 0x0001ffff
  33                 add     r2, r2, r1, lsr #32-10
  34                 mov     r2, r2, lsr #10         @ max = 0x00007fff
  35                 mul     r0, r2, r0              @ max = 2^32-1
  36                 add     r0, r0, r1, lsr #32-6
  37                 movs    r0, r0, lsr #6
  38                 moveq   pc, lr
  39
  40 /*
  41  * loops = r0 * HZ * loops_per_jiffy / 1000000
  42  */
  43
  44 @ Delay routine
  45 ENTRY(__loop_delay)
  46                 subs    r0, r0, #1
  47 #if 0
  48                 movls   pc, lr
  49                 subs    r0, r0, #1
  50                 movls   pc, lr
  51                 subs    r0, r0, #1
  52                 movls   pc, lr
  53                 subs    r0, r0, #1
  54                 movls   pc, lr
  55                 subs    r0, r0, #1
  56                 movls   pc, lr
  57                 subs    r0, r0, #1
  58                 movls   pc, lr
  59                 subs    r0, r0, #1
  60                 movls   pc, lr
  61                 subs    r0, r0, #1
  62 #endif
  63                 bhi     __loop_delay
  64                 mov     pc, lr
  65 ENDPROC(__loop_udelay)
  66 ENDPROC(__loop_const_udelay)
  67 ENDPROC(__loop_delay)