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/*

 * This file is subject to the terms and conditions of the GNU General Public

 * License.  See the file "COPYING" in the main directory of this archive

 * for more details.

 *

 * Copyright (C) 1996  Linus Torvalds

 * Copyright (C) 1998, 99, 2000, 01  Ralf Baechle

 * Copyright (C) 1999, 2000, 01  Silicon Graphics, Inc.

 * Copyright (C) 2000, 01 MIPS Technologies, Inc.

 */

#ifndef _ASM_SEMAPHORE_H

#define _ASM_SEMAPHORE_H

#include <linux/compiler.h>

#include <linux/config.h>

#include <linux/spinlock.h>

#include <linux/wait.h>

#include <linux/rwsem.h>

#include <asm/atomic.h>

struct semaphore {

#ifdef __MIPSEB__

        atomic_t count;

        atomic_t waking;

#else

        atomic_t waking;

        atomic_t count;

#endif

        wait_queue_head_t wait;

#if WAITQUEUE_DEBUG

        long __magic;

#endif

} __attribute__((aligned(8)));

#if WAITQUEUE_DEBUG

# define __SEM_DEBUG_INIT(name) , .__magic = (long)&(name).__magic

#else

# define __SEM_DEBUG_INIT(name)

#endif

#define __SEMAPHORE_INITIALIZER(name,_count) {                          \

        .count  = ATOMIC_INIT(_count),                                  \

        .waking = ATOMIC_INIT(0),                                        \

        .wait   = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)            \

        __SEM_DEBUG_INIT(name)                                          \

}

#define __MUTEX_INITIALIZER(name) __SEMAPHORE_INITIALIZER(name, 1)

#define __DECLARE_SEMAPHORE_GENERIC(name,count) \

        struct semaphore name = __SEMAPHORE_INITIALIZER(name, count)

#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name, 1)

#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)

static inline void sema_init (struct semaphore *sem, int val)

{

        atomic_set(&sem->count, val);

        atomic_set(&sem->waking, 0);

        init_waitqueue_head(&sem->wait);

#if WAITQUEUE_DEBUG

        sem->__magic = (long)&sem->__magic;

#endif

}

static inline void init_MUTEX (struct semaphore *sem)

{

        sema_init(sem, 1);

}

static inline void init_MUTEX_LOCKED (struct semaphore *sem)

{

        sema_init(sem, 0);

}

#ifndef CONFIG_CPU_HAS_LLDSCD

/*

 * On machines without lld/scd we need a spinlock to make the manipulation of

 * sem->count and sem->waking atomic.

 */

extern spinlock_t semaphore_lock;

#endif

extern void __down_failed(struct semaphore * sem);

extern int  __down_failed_interruptible(struct semaphore * sem);

extern void __up_wakeup(struct semaphore * sem);

static inline void down(struct semaphore * sem)

{

        int count;

#if WAITQUEUE_DEBUG

        CHECK_MAGIC(sem->__magic);

#endif

        count = atomic_dec_return(&sem->count);

        if (unlikely(count < 0))

                __down_failed(sem);

}

/*

 * Interruptible try to acquire a semaphore.  If we obtained

 * it, return zero.  If we were interrupted, returns -EINTR

 */

static inline int down_interruptible(struct semaphore * sem)

{

        int count;

#if WAITQUEUE_DEBUG

        CHECK_MAGIC(sem->__magic);

#endif

        count = atomic_dec_return(&sem->count);

        if (unlikely(count < 0))

                return __down_failed_interruptible(sem);

        return 0;

}

#ifdef CONFIG_CPU_HAS_LLDSCD

/*

 * down_trylock returns 0 on success, 1 if we failed to get the lock.

 *

 * We must manipulate count and waking simultaneously and atomically.

 * Here, we do this by using lld/scd on the pair of 32-bit words.

 *

 * Pseudocode:

 *

 *   Decrement(sem->count)

 *   If(sem->count >=0) {

 *      Return(SUCCESS)                 // resource is free

 *   } else {

 *      If(sem->waking <= 0) {          // if no wakeup pending

 *         Increment(sem->count)        // undo decrement

 *         Return(FAILURE)

 *      } else {

 *         Decrement(sem->waking)       // otherwise "steal" wakeup

 *         Return(SUCCESS)

 *      }

 *   }

 */

static inline int down_trylock(struct semaphore * sem)

{

        long ret, tmp, tmp2, sub;

#if WAITQUEUE_DEBUG

        CHECK_MAGIC(sem->__magic);

#endif

        __asm__ __volatile__(

        "       .set    mips3                   # down_trylock          \n"

        "0:     lld     %1, %4                                          \n"

        "       dli     %3, 0x0000000100000000  # count -= 1            \n"

        "       dsubu   %1, %3                                          \n"

        "       li      %0, 0                   # ret = 0               \n"

        "       bgez    %1, 2f                  # if count >= 0         \n"

        "       sll     %2, %1, 0               # extract waking        \n"

        "       blez    %2, 1f                  # if waking < 0 -> 1f   \n"

        "       daddiu  %1, %1, -1              # waking -= 1           \n"

        "       b       2f                                              \n"

        "1:     daddu   %1, %1, %3              # count += 1            \n"

        "       li      %0, 1                   # ret = 1               \n"

        "2:     scd     %1, %4                                          \n"

        "       beqz    %1, 0b                                          \n"

        "       sync                                                    \n"

        "       .set    mips0                                           \n"

        : "=&r"(ret), "=&r"(tmp), "=&r"(tmp2), "=&r"(sub)

        : "m"(*sem)

        : "memory");

        return ret;

}

/*

 * Note! This is subtle. We jump to wake people up only if

 * the semaphore was negative (== somebody was waiting on it).

 */

static inline void up(struct semaphore * sem)

{

        unsigned long tmp, tmp2;

        int count;

#if WAITQUEUE_DEBUG

        CHECK_MAGIC(sem->__magic);

#endif

        /*

         * We must manipulate count and waking simultaneously and atomically.

         * Otherwise we have races between up and __down_failed_interruptible

         * waking up on a signal.

         */

        __asm__ __volatile__(

        "       .set    mips3                                   \n"

        "       sync                    # up                    \n"

        "1:     lld     %1, %3                                  \n"

        "       dsra32  %0, %1, 0       # extract count to %0   \n"

        "       daddiu  %0, 1           # count += 1            \n"

        "       slti    %2, %0, 1       # %3 = (%0 <= 0)        \n"

        "       daddu   %1, %2          # waking += %3          \n"

        "       dsll32 %1, %1, 0        # zero-extend %1        \n"

        "       dsrl32 %1, %1, 0                                \n"

        "       dsll32  %2, %0, 0       # Reassemble union      \n"

        "       or      %1, %2          # from count and waking \n"

        "       scd     %1, %3                                  \n"

        "       beqz    %1, 1b                                  \n"

        "       .set    mips0                                   \n"

        : "=&r"(count), "=&r"(tmp), "=&r"(tmp2), "+m"(*sem)

        :

        : "memory");

        if (unlikely(count <= 0))

                __up_wakeup(sem);

}

#else

/*

 * Non-blockingly attempt to down() a semaphore.

 * Returns zero if we acquired it

 */

static inline int down_trylock(struct semaphore * sem)

{

        unsigned long flags;

        int count, waking;

        int ret = 0;

#if WAITQUEUE_DEBUG

        CHECK_MAGIC(sem->__magic);

#endif

        spin_lock_irqsave(&semaphore_lock, flags);

        count = atomic_read(&sem->count) - 1;

        atomic_set(&sem->count, count);

        if (unlikely(count < 0)) {

                waking = atomic_read(&sem->waking);

                if (waking <= 0) {

                        atomic_set(&sem->count, count + 1);

                        ret = 1;

                } else {

                        atomic_set(&sem->waking, waking - 1);

                        ret = 0;

                }

        }

        spin_unlock_irqrestore(&semaphore_lock, flags);

        return ret;

}

/*

 * Note! This is subtle. We jump to wake people up only if

 * the semaphore was negative (== somebody was waiting on it).

 */

static inline void up(struct semaphore * sem)

{

        unsigned long flags;

        int count, waking;

#if WAITQUEUE_DEBUG

        CHECK_MAGIC(sem->__magic);

#endif

        /*

         * We must manipulate count and waking simultaneously and atomically.

         * Otherwise we have races between up and __down_failed_interruptible

         * waking up on a signal.

         */

        spin_lock_irqsave(&semaphore_lock, flags);

        count = atomic_read(&sem->count) + 1;

        waking = atomic_read(&sem->waking);

        if (count <= 0)

                waking++;

        atomic_set(&sem->count, count);

        atomic_set(&sem->waking, waking);

        spin_unlock_irqrestore(&semaphore_lock, flags);

        if (unlikely(count <= 0))

                __up_wakeup(sem);

}

#endif /* CONFIG_CPU_HAS_LLDSCD */

static inline int sem_getcount(struct semaphore *sem)

{

        return atomic_read(&sem->count);

}

#endif /* _ASM_SEMAPHORE_H */