1/* $NetBSD: sync_bool_compare_and_swap_1.S,v 1.1 2013/11/08 22:42:52 matt Exp $ */
2
3/*-
4 * Copyright (c) 2013 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Matt Thomas <matt@3am-software.com>
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32#include "atomic_op_asm.h"
33
34#if defined(_ARM_ARCH_6)
35/*
36 * ARMv6 has load-exclusive/store-exclusive which works for both user
37 * and kernel.
38 */
39ENTRY_NP(__sync_bool_compare_and_swap_1)
40	mov	ip, r0			/* we need r0 for return value */
41	mov	r0, #0			/* assume no match */
421:
43	ldrexb	r3, [ip]		/* load old value */
44	cmp	r3, r1			/*   compare? */
45#ifdef __thumb__
46	bne	2f
47#else
48	RETc(ne)			/*     return if different */
49#endif
50	strexb	r0, r2, [ip]		/* store new value */
51	cmp	r0, #0			/*   succeed? */
52	bne	1b			/*     nope, try again. */
53	mov	r0, #1			/* it was a success */
54#ifdef _ARM_ARCH_7
55	dsb				/* data synchronization barrier */
56#else
57	mcr	p15, 0, r3, c7, c10, 4	/* data synchronization barrier */
58#endif
592:	RET				/* return. */
60END(__sync_bool_compare_and_swap_1)
61
62#endif /* _ARM_ARCH_6 */
63