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      1 /*	$NetBSD: barrier.h,v 1.21 2023/02/25 12:23:36 riastradh 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 Taylor R. Campbell.
      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 #ifndef _ASM_BARRIER_H_
     33 #define _ASM_BARRIER_H_
     34 
     35 #include <sys/atomic.h>
     36 
     37 #include <linux/compiler.h>
     38 
     39 #ifdef _KERNEL_OPT
     40 #include "opt_multiprocessor.h"
     41 #else
     42 #define	MULTIPROCESSOR	1	/* safer to assume multiprocessor */
     43 #endif
     44 
     45 /*
     46  * I/O memory barriers.  drm uses these to order memory operations on
     47  * normal or write-combining/prefetchable, or uncacheable I/O
     48  * operations, for coordination between the CPU and I/O devices.
     49  *
     50  * In NetBSD, this is normally done with bus_space_barrier, but Linux
     51  * doesn't pass around the bus space tag and handle needed for that.
     52  */
     53 #if defined(__aarch64__)
     54 #include <arm/cpufunc.h>
     55 #define	mb()	dsb(sy)
     56 #define	wmb()	dsb(st)
     57 #define	rmb()	dsb(ld)
     58 #elif defined(__arm__)
     59 #include <arm/cpufunc.h>
     60 #define	mb()	dsb()
     61 #define	wmb()	mb()
     62 #define	rmb()	mb()
     63 #elif defined(__i386__) || defined(__x86_64__)
     64 #include <x86/cpufunc.h>
     65 #define	mb()	x86_mfence()
     66 #define	wmb()	x86_sfence()
     67 #define	rmb()	x86_lfence()
     68 #elif defined(__powerpc__)
     69 #define	mb()	__asm __volatile ("eieio" ::: "memory")
     70 #define	wmb()	mb()
     71 #define	rmb()	mb()
     72 #elif defined(__sparc__) || defined(__sparc64__)
     73 #ifdef __sparc64__
     74 #define	mb()	__asm __volatile ("membar #MemIssue" ::: "memory")
     75 #else
     76 #define	mb()	membar_sync()	/* ldstub */
     77 #endif
     78 #define	wmb()	mb()		/* XXX could maybe be __insn_barrier in TSO */
     79 #define	rmb()	mb()		/* XXX could maybe be __insn_barrier in TSO */
     80 #elif defined(__mips__)
     81 #include <mips/locore.h>
     82 #define	mb()	wbflush()
     83 #define	wmb()	mb()
     84 #define	rmb()	mb()
     85 #elif defined(__alpha__)
     86 #include <machine/alpha_cpu.h>
     87 #define	mb()	alpha_mb()
     88 #define	wmb()	alpha_wmb()
     89 #define	rmb()	mb()
     90 #else
     91 #error Missing Linux memory-mapped I/O barriers for this architecture.
     92 #endif
     93 
     94 /*
     95  * MP memory barriers.  drm uses these to order memory operations on
     96  * normal memory for coordination between CPUs.  Aliases for NetBSD's
     97  * membar_*.
     98  */
     99 #ifdef MULTIPROCESSOR
    100 #  define	smp_mb				membar_sync
    101 #  define	smp_wmb				membar_producer
    102 #  define	smp_rmb				membar_consumer
    103 #  define	smp_mb__before_atomic		membar_release
    104 #  define	smp_mb__after_atomic		membar_acquire
    105 #else
    106 #  define	smp_mb()			__insn_barrier()
    107 #  define	smp_wmb()			__insn_barrier()
    108 #  define	smp_rmb()			__insn_barrier()
    109 #  define	smp_mb__before_atomic()		__nothing
    110 #  define	smp_mb__after_atomic()		__nothing
    111 #endif
    112 
    113 #endif  /* _ASM_BARRIER_H_ */
    114