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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/arch/arm/lib/delay-loop.S
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/* SPDX-License-Identifier: GPL-2.0-only */

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/*

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 *  linux/arch/arm/lib/delay.S

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 *

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 *  Copyright (C) 1995, 1996 Russell King

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 */

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#include <linux/linkage.h>

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#include <linux/cfi_types.h>

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#include <asm/assembler.h>

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#include <asm/delay.h>

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#ifdef CONFIG_ARCH_RPC

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		.arch	armv4

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#endif

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		.text

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.LC0:		.word	loops_per_jiffy

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.LC1:		.word	UDELAY_MULT

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/*

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 * loops = r0 * HZ * loops_per_jiffy / 1000000

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 *

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 * r0  <= 2000

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 * HZ  <= 1000

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 */

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SYM_TYPED_FUNC_START(__loop_udelay)

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		ldr	r2, .LC1

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		mul	r0, r2, r0		@ r0 = delay_us * UDELAY_MULT

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		b	__loop_const_udelay

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SYM_FUNC_END(__loop_udelay)

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SYM_TYPED_FUNC_START(__loop_const_udelay)	@ 0 <= r0 <= 0xfffffaf0

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		ldr	r2, .LC0

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		ldr	r2, [r2]

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		umull	r1, r0, r2, r0		@ r0-r1 = r0 * loops_per_jiffy

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		adds	r1, r1, #0xffffffff	@ rounding up ...

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		adcs	r0, r0, r0		@ and right shift by 31

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		reteq	lr

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		b	__loop_delay

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SYM_FUNC_END(__loop_const_udelay)

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		.align 3

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@ Delay routine

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SYM_TYPED_FUNC_START(__loop_delay)

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		subs	r0, r0, #1

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#if 0

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		retls	lr

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		subs	r0, r0, #1

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		retls	lr

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		subs	r0, r0, #1

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		retls	lr

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		subs	r0, r0, #1

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		retls	lr

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		subs	r0, r0, #1

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		retls	lr

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		subs	r0, r0, #1

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		retls	lr

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		subs	r0, r0, #1

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		retls	lr

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		subs	r0, r0, #1

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#endif

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		bhi	__loop_delay

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		ret	lr

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SYM_FUNC_END(__loop_delay)

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