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      1 /*	$NetBSD: mutex.h,v 1.7 2024/11/25 22:04:14 skrll Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2002, 2007 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Jason R. Thorpe and Andrew Doran.
      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 _RISCV_MUTEX_H_
     33 #define	_RISCV_MUTEX_H_
     34 
     35 #include <sys/types.h>
     36 
     37 #ifndef __MUTEX_PRIVATE
     38 
     39 struct kmutex {
     40 	uintptr_t	mtx_pad1;
     41 };
     42 
     43 #else	/* __MUTEX_PRIVATE */
     44 
     45 #include <sys/cdefs.h>
     46 
     47 #include <sys/param.h>
     48 
     49 #include <machine/intr.h>
     50 
     51 struct kmutex {
     52 	volatile uintptr_t	mtx_owner;
     53 };
     54 
     55 #ifdef _KERNEL
     56 
     57 #ifdef _LP64
     58 #define MTX_ASMOP_SFX ".d"		// doubleword atomic op
     59 #else
     60 #define MTX_ASMOP_SFX ".w"		// word atomic op
     61 #endif
     62 
     63 #define	MTX_LOCK			__BIT(8)	// just one bit
     64 #define	MTX_IPL				__BITS(7,4)	// only need 4 bits
     65 
     66 #undef MUTEX_SPIN_IPL			// override <sys/mutex.h>
     67 #define	MUTEX_SPIN_IPL(a)		riscv_mutex_spin_ipl(a)
     68 #define	MUTEX_INITIALIZE_SPIN_IPL(a,b)	riscv_mutex_initialize_spin_ipl(a,b)
     69 #define MUTEX_SPINBIT_LOCK_INIT(a)	riscv_mutex_spinbit_lock_init(a)
     70 #define MUTEX_SPINBIT_LOCK_TRY(a)	riscv_mutex_spinbit_lock_try(a)
     71 #define MUTEX_SPINBIT_LOCKED_P(a)	riscv_mutex_spinbit_locked_p(a)
     72 #define MUTEX_SPINBIT_LOCK_UNLOCK(a)	riscv_mutex_spinbit_lock_unlock(a)
     73 
     74 static inline ipl_cookie_t
     75 riscv_mutex_spin_ipl(kmutex_t *__mtx)
     76 {
     77 	return (ipl_cookie_t){._spl = __SHIFTOUT(__mtx->mtx_owner, MTX_IPL)};
     78 }
     79 
     80 static inline void
     81 riscv_mutex_initialize_spin_ipl(kmutex_t *__mtx, int ipl)
     82 {
     83 	__mtx->mtx_owner = (__mtx->mtx_owner & ~MTX_IPL)
     84 	    | __SHIFTIN(ipl, MTX_IPL);
     85 }
     86 
     87 static inline void
     88 riscv_mutex_spinbit_lock_init(kmutex_t *__mtx)
     89 {
     90 	__mtx->mtx_owner &= ~MTX_LOCK;
     91 }
     92 
     93 static inline bool
     94 riscv_mutex_spinbit_locked_p(const kmutex_t *__mtx)
     95 {
     96 	return (__mtx->mtx_owner & MTX_LOCK) != 0;
     97 }
     98 
     99 static inline bool
    100 riscv_mutex_spinbit_lock_try(kmutex_t *__mtx)
    101 {
    102 	uintptr_t __old;
    103 	__asm __volatile(
    104 		"amoor" MTX_ASMOP_SFX ".aq\t%0, %1, (%2)"
    105 	   :	"=r"(__old)
    106 	   :	"r"(MTX_LOCK), "r"(__mtx));
    107 	return (__old & MTX_LOCK) == 0;
    108 }
    109 
    110 static inline void
    111 riscv_mutex_spinbit_lock_unlock(kmutex_t *__mtx)
    112 {
    113 	__asm __volatile(
    114 		"amoand" MTX_ASMOP_SFX ".rl\tx0, %0, (%1)"
    115 	   ::	"r"(~MTX_LOCK), "r"(__mtx));
    116 }
    117 
    118 #endif /* _KERNEL */
    119 
    120 #if 0
    121 #define	__HAVE_MUTEX_STUBS		1
    122 #define	__HAVE_SPIN_MUTEX_STUBS		1
    123 #endif
    124 #define	__HAVE_SIMPLE_MUTEXES		1
    125 
    126 #endif	/* __MUTEX_PRIVATE */
    127 
    128 #endif /* _RISCV_MUTEX_H_ */
    129