/*      $NetBSD: mutex.h,v 1.19 2023/07/13 07:46:43 mrg Exp $   */

/*-
* Copyright (c) 2002, 2007 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Jason R. Thorpe and Andrew Doran.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/

#ifndef _HPPA_MUTEX_H_
#define _HPPA_MUTEX_H_

/*
* The HPPA mutex implementation is troublesome, because HPPA lacks
* a compare-and-set operation, yet there are many SMP HPPA machines
* in circulation.  SMP for spin mutexes is easy - we don't need to
* know who owns the lock.  For adaptive mutexes, we need an owner
* field and additional interlock
*/

#ifndef __ASSEMBLER__

#include <sys/types.h>

#ifdef __MUTEX_PRIVATE
#include <machine/lock.h>
#include <machine/intr.h>
#endif

struct kmutex {
       union {
               /*
                * Only the 16 bytes aligned word of __cpu_simple_lock_t will
                * be used. It's 16 bytes to simplify the allocation.
                * See hppa/lock.h
                */
#ifdef __MUTEX_PRIVATE
               struct {
                       __cpu_simple_lock_t     mtxu_lock;      /* 0-15 */
                       volatile uint32_t       mtxs_owner;     /* 16-19 */
                       ipl_cookie_t            mtxs_ipl;       /* 20-23 */
                       volatile uint8_t        mtxs_waiters;   /* 24 */

                       /* For LOCKDEBUG */
                       uint8_t                 mtxs_dodebug;   /* 25 */
               } s;
#endif
               uint8_t                 mtxu_pad[32];   /* 0 - 32 */
       } u;
} __aligned (16);
#endif

#ifdef __MUTEX_PRIVATE

#define __HAVE_MUTEX_STUBS      1

#define mtx_lock        u.s.mtxu_lock
#define mtx_owner       u.s.mtxs_owner
#define mtx_ipl         u.s.mtxs_ipl
#define mtx_waiters     u.s.mtxs_waiters
#define mtx_dodebug     u.s.mtxs_dodebug

/* Magic constants for mtx_owner */
#define MUTEX_ADAPTIVE_UNOWNED          0xffffff00
#define MUTEX_SPIN_FLAG                 0xffffff10
#define MUTEX_UNOWNED_OR_SPIN(x)        (((x) & 0xffffffef) == 0xffffff00)

#if !defined(__ASSEMBLER__) && defined(_KERNEL)

static inline uintptr_t
MUTEX_OWNER(uintptr_t owner)
{
       return owner;
}

static inline int
MUTEX_OWNED(uintptr_t owner)
{
       return owner != MUTEX_ADAPTIVE_UNOWNED;
}

static inline int
MUTEX_SET_WAITERS(struct kmutex *mtx, uintptr_t owner)
{
       __sync();               /* formerly mb_read */
       mtx->mtx_waiters = 1;
       __sync();               /* formerly mb_memory */
       return mtx->mtx_owner != MUTEX_ADAPTIVE_UNOWNED;
}

static inline int
MUTEX_HAS_WAITERS(const volatile struct kmutex *mtx)
{
       return mtx->mtx_waiters != 0;
}

static inline void
MUTEX_INITIALIZE_SPIN(struct kmutex *mtx, bool dodebug, int ipl)
{
       mtx->mtx_ipl = makeiplcookie(ipl);
       mtx->mtx_dodebug = dodebug;
       mtx->mtx_owner = MUTEX_SPIN_FLAG;
       __cpu_simple_lock_init(&mtx->mtx_lock);
}

static inline void
MUTEX_INITIALIZE_ADAPTIVE(struct kmutex *mtx, bool dodebug)
{
       mtx->mtx_dodebug = dodebug;
       mtx->mtx_owner = MUTEX_ADAPTIVE_UNOWNED;
       __cpu_simple_lock_init(&mtx->mtx_lock);
}

static inline void
MUTEX_DESTROY(struct kmutex *mtx)
{
       mtx->mtx_owner = 0xffffffff;
}

static inline bool
MUTEX_DEBUG_P(const volatile struct kmutex *mtx)
{
       return mtx->mtx_dodebug != 0;
}

static inline int
MUTEX_SPIN_P(const uintptr_t owner)
{
       return owner == MUTEX_SPIN_FLAG;
}

static inline int
MUTEX_ADAPTIVE_P(const uintptr_t owner)
{
       return owner != MUTEX_SPIN_FLAG;
}

/* Acquire an adaptive mutex */
static inline int
MUTEX_ACQUIRE(struct kmutex *mtx, uintptr_t curthread)
{
       if (!__cpu_simple_lock_try(&mtx->mtx_lock))
               return 0;
       mtx->mtx_owner = curthread;
       return 1;
}

/* Release an adaptive mutex */
static inline void
MUTEX_RELEASE(struct kmutex *mtx)
{
       mtx->mtx_owner = MUTEX_ADAPTIVE_UNOWNED;
       __cpu_simple_unlock(&mtx->mtx_lock);
       mtx->mtx_waiters = 0;
}

static inline void
MUTEX_CLEAR_WAITERS(struct kmutex *mtx)
{
       mtx->mtx_waiters = 0;
}

#endif  /* !__ASSEMBLER__ && _KERNEL */

#endif  /* __MUTEX_PRIVATE */

#endif /* _HPPA_MUTEX_H_ */