1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * Copyright (C) 2014-15 Synopsys, Inc. (www.synopsys.com)
4 */
5
6 #ifndef __ASM_BARRIER_H
7 #define __ASM_BARRIER_H
8
9 #ifdef CONFIG_ISA_ARCV2
10
11 /*
12 * ARCv2 based HS38 cores are in-order issue, but still weakly ordered
13 * due to micro-arch buffering/queuing of load/store, cache hit vs. miss ...
14 *
15 * Explicit barrier provided by DMB instruction
16 * - Operand supports fine grained load/store/load+store semantics
17 * - Ensures that selected memory operation issued before it will complete
18 * before any subsequent memory operation of same type
19 * - DMB guarantees SMP as well as local barrier semantics
20 * (asm-generic/barrier.h ensures sane smp_*mb if not defined here, i.e.
21 * UP: barrier(), SMP: smp_*mb == *mb)
22 * - DSYNC provides DMB+completion_of_cache_bpu_maintenance_ops hence not needed
23 * in the general case. Plus it only provides full barrier.
24 */
25
26 #define mb() asm volatile("dmb 3\n" : : : "memory")
27 #define rmb() asm volatile("dmb 1\n" : : : "memory")
28 #define wmb() asm volatile("dmb 2\n" : : : "memory")
29
30 #else
31
32 /*
33 * ARCompact based cores (ARC700) only have SYNC instruction which is super
34 * heavy weight as it flushes the pipeline as well.
35 * There are no real SMP implementations of such cores.
36 */
37
38 #define mb() asm volatile("sync\n" : : : "memory")
39
40 #endif
41
42 #include <asm-generic/barrier.h>
43
44 #endif
45
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.