arch/arm/lib/delay-loop.S

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  *  linux/arch/arm/lib/delay.S
   4  *
   5  *  Copyright (C) 1995, 1996 Russell King
   6  */
   7 #include <linux/linkage.h>
   8 #include <linux/cfi_types.h>
   9 #include <asm/assembler.h>
  10 #include <asm/delay.h>
  11
  12 #ifdef CONFIG_ARCH_RPC
  13                 .arch   armv4
  14 #endif
  15
  16                 .text
  17
  18 .LC0:           .word   loops_per_jiffy
  19 .LC1:           .word   UDELAY_MULT
  20
  21 /*
  22  * loops = r0 * HZ * loops_per_jiffy / 1000000
  23  *
  24  * r0  <= 2000
  25  * HZ  <= 1000
  26  */
  27
  28 SYM_TYPED_FUNC_START(__loop_udelay)
  29                 ldr     r2, .LC1
  30                 mul     r0, r2, r0              @ r0 = delay_us * UDELAY_MULT
  31                 b       __loop_const_udelay
  32 SYM_FUNC_END(__loop_udelay)
  33
  34 SYM_TYPED_FUNC_START(__loop_const_udelay)       @ 0 <= r0 <= 0xfffffaf0
  35                 ldr     r2, .LC0
  36                 ldr     r2, [r2]
  37                 umull   r1, r0, r2, r0          @ r0-r1 = r0 * loops_per_jiffy
  38                 adds    r1, r1, #0xffffffff     @ rounding up ...
  39                 adcs    r0, r0, r0              @ and right shift by 31
  40                 reteq   lr
  41                 b       __loop_delay
  42 SYM_FUNC_END(__loop_const_udelay)
  43
  44                 .align 3
  45
  46 @ Delay routine
  47 SYM_TYPED_FUNC_START(__loop_delay)
  48                 subs    r0, r0, #1
  49 #if 0
  50                 retls   lr
  51                 subs    r0, r0, #1
  52                 retls   lr
  53                 subs    r0, r0, #1
  54                 retls   lr
  55                 subs    r0, r0, #1
  56                 retls   lr
  57                 subs    r0, r0, #1
  58                 retls   lr
  59                 subs    r0, r0, #1
  60                 retls   lr
  61                 subs    r0, r0, #1
  62                 retls   lr
  63                 subs    r0, r0, #1
  64 #endif
  65                 bhi     __loop_delay
  66                 ret     lr
  67 SYM_FUNC_END(__loop_delay)