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kernel/linux-imx6_3.14.28/arch/arm/lib/delay-loop.S 1.34 KB
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  /*
   *  linux/arch/arm/lib/delay.S
   *
   *  Copyright (C) 1995, 1996 Russell King
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   */
  #include <linux/linkage.h>
  #include <asm/assembler.h>
  #include <asm/delay.h>
  		.text
  
  .LC0:		.word	loops_per_jiffy
  .LC1:		.word	UDELAY_MULT
  
  /*
   * r0  <= 2000
   * lpj <= 0x01ffffff (max. 3355 bogomips)
   * HZ  <= 1000
   */
  
  ENTRY(__loop_udelay)
  		ldr	r2, .LC1
  		mul	r0, r2, r0
  ENTRY(__loop_const_udelay)			@ 0 <= r0 <= 0x7fffff06
  		mov	r1, #-1
  		ldr	r2, .LC0
  		ldr	r2, [r2]		@ max = 0x01ffffff
  		add	r0, r0, r1, lsr #32-14
  		mov	r0, r0, lsr #14		@ max = 0x0001ffff
  		add	r2, r2, r1, lsr #32-10
  		mov	r2, r2, lsr #10		@ max = 0x00007fff
  		mul	r0, r2, r0		@ max = 2^32-1
  		add	r0, r0, r1, lsr #32-6
  		movs	r0, r0, lsr #6
  		moveq	pc, lr
  
  /*
   * loops = r0 * HZ * loops_per_jiffy / 1000000
   */
  		.align 3
  
  @ Delay routine
  ENTRY(__loop_delay)
  		subs	r0, r0, #1
  #if 0
  		movls	pc, lr
  		subs	r0, r0, #1
  		movls	pc, lr
  		subs	r0, r0, #1
  		movls	pc, lr
  		subs	r0, r0, #1
  		movls	pc, lr
  		subs	r0, r0, #1
  		movls	pc, lr
  		subs	r0, r0, #1
  		movls	pc, lr
  		subs	r0, r0, #1
  		movls	pc, lr
  		subs	r0, r0, #1
  #endif
  		bhi	__loop_delay
  		mov	pc, lr
  ENDPROC(__loop_udelay)
  ENDPROC(__loop_const_udelay)
  ENDPROC(__loop_delay)