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cvmx-spinlock.h

/***********************license start***************
 * Author: Cavium Networks
 *
 * Contact: support@caviumnetworks.com
 * This file is part of the OCTEON SDK
 *
 * Copyright (c) 2003-2008 Cavium Networks
 *
 * This file is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, Version 2, as
 * published by the Free Software Foundation.
 *
 * This file is distributed in the hope that it will be useful, but
 * AS-IS and WITHOUT ANY WARRANTY; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, TITLE, or
 * NONINFRINGEMENT.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this file; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 * or visit http://www.gnu.org/licenses/.
 *
 * This file may also be available under a different license from Cavium.
 * Contact Cavium Networks for more information
 ***********************license end**************************************/

/**
 * Implementation of spinlocks for Octeon CVMX.  Although similar in
 * function to Linux kernel spinlocks, they are not compatible.
 * Octeon CVMX spinlocks are only used to synchronize with the boot
 * monitor and other non-Linux programs running in the system.
 */

#ifndef __CVMX_SPINLOCK_H__
#define __CVMX_SPINLOCK_H__

#include "cvmx-asm.h"

/* Spinlocks for Octeon */

/* define these to enable recursive spinlock debugging */
/*#define CVMX_SPINLOCK_DEBUG */

/**
 * Spinlocks for Octeon CVMX
 */
00048 typedef struct {
      volatile uint32_t value;
} cvmx_spinlock_t;

/* note - macros not expanded in inline ASM, so values hardcoded */
#define  CVMX_SPINLOCK_UNLOCKED_VAL  0
#define  CVMX_SPINLOCK_LOCKED_VAL    1

#define CVMX_SPINLOCK_UNLOCKED_INITIALIZER  {CVMX_SPINLOCK_UNLOCKED_VAL}

/**
 * Initialize a spinlock
 *
 * @lock:   Lock to initialize
 */
static inline void cvmx_spinlock_init(cvmx_spinlock_t *lock)
{
      lock->value = CVMX_SPINLOCK_UNLOCKED_VAL;
}

/**
 * Return non-zero if the spinlock is currently locked
 *
 * @lock:   Lock to check
 * Returns Non-zero if locked
 */
static inline int cvmx_spinlock_locked(cvmx_spinlock_t *lock)
{
      return lock->value != CVMX_SPINLOCK_UNLOCKED_VAL;
}

/**
 * Releases lock
 *
 * @lock:   pointer to lock structure
 */
static inline void cvmx_spinlock_unlock(cvmx_spinlock_t *lock)
{
      CVMX_SYNCWS;
      lock->value = 0;
      CVMX_SYNCWS;
}

/**
 * Attempts to take the lock, but does not spin if lock is not available.
 * May take some time to acquire the lock even if it is available
 * due to the ll/sc not succeeding.
 *
 * @lock:   pointer to lock structure
 *
 * Returns 0: lock successfully taken
 *         1: lock not taken, held by someone else
 * These return values match the Linux semantics.
 */

static inline unsigned int cvmx_spinlock_trylock(cvmx_spinlock_t *lock)
{
      unsigned int tmp;

      __asm__ __volatile__(".set noreorder         \n"
                       "1: ll   %[tmp], %[val] \n"
                  /* if lock held, fail immediately */
                       "   bnez %[tmp], 2f     \n"
                       "   li   %[tmp], 1      \n"
                       "   sc   %[tmp], %[val] \n"
                       "   beqz %[tmp], 1b     \n"
                       "   li   %[tmp], 0      \n"
                       "2:                     \n"
                       ".set reorder           \n" :
                  [val] "+m"(lock->value), [tmp] "=&r"(tmp)
                       : : "memory");

      return tmp != 0;        /* normalize to 0 or 1 */
}

/**
 * Gets lock, spins until lock is taken
 *
 * @lock:   pointer to lock structure
 */
static inline void cvmx_spinlock_lock(cvmx_spinlock_t *lock)
{
      unsigned int tmp;

      __asm__ __volatile__(".set noreorder         \n"
                       "1: ll   %[tmp], %[val]  \n"
                       "   bnez %[tmp], 1b     \n"
                       "   li   %[tmp], 1      \n"
                       "   sc   %[tmp], %[val] \n"
                       "   beqz %[tmp], 1b     \n"
                       "   nop                \n"
                       ".set reorder           \n" :
                  [val] "+m"(lock->value), [tmp] "=&r"(tmp)
                  : : "memory");

}

/** ********************************************************************
 * Bit spinlocks
 * These spinlocks use a single bit (bit 31) of a 32 bit word for locking.
 * The rest of the bits in the word are left undisturbed.  This enables more
 * compact data structures as only 1 bit is consumed for the lock.
 *
 */

/**
 * Gets lock, spins until lock is taken
 * Preserves the low 31 bits of the 32 bit
 * word used for the lock.
 *
 *
 * @word:  word to lock bit 31 of
 */
static inline void cvmx_spinlock_bit_lock(uint32_t *word)
{
      unsigned int tmp;
      unsigned int sav;

      __asm__ __volatile__(".set noreorder         \n"
                       ".set noat              \n"
                       "1: ll    %[tmp], %[val]  \n"
                       "   bbit1 %[tmp], 31, 1b    \n"
                       "   li    $at, 1      \n"
                       "   ins   %[tmp], $at, 31, 1  \n"
                       "   sc    %[tmp], %[val] \n"
                       "   beqz  %[tmp], 1b     \n"
                       "   nop                \n"
                       ".set at              \n"
                       ".set reorder           \n" :
                  [val] "+m"(*word), [tmp] "=&r"(tmp), [sav] "=&r"(sav)
                       : : "memory");

}

/**
 * Attempts to get lock, returns immediately with success/failure
 * Preserves the low 31 bits of the 32 bit
 * word used for the lock.
 *
 *
 * @word:  word to lock bit 31 of
 * Returns 0: lock successfully taken
 *         1: lock not taken, held by someone else
 * These return values match the Linux semantics.
 */
static inline unsigned int cvmx_spinlock_bit_trylock(uint32_t *word)
{
      unsigned int tmp;

      __asm__ __volatile__(".set noreorder\n\t"
                       ".set noat\n"
                       "1: ll    %[tmp], %[val] \n"
                  /* if lock held, fail immediately */
                       "   bbit1 %[tmp], 31, 2f     \n"
                       "   li    $at, 1      \n"
                       "   ins   %[tmp], $at, 31, 1  \n"
                       "   sc    %[tmp], %[val] \n"
                       "   beqz  %[tmp], 1b     \n"
                       "   li    %[tmp], 0      \n"
                       "2:                     \n"
                       ".set at              \n"
                       ".set reorder           \n" :
                  [val] "+m"(*word), [tmp] "=&r"(tmp)
                  : : "memory");

      return tmp != 0;        /* normalize to 0 or 1 */
}

/**
 * Releases bit lock
 *
 * Unconditionally clears bit 31 of the lock word.  Note that this is
 * done non-atomically, as this implementation assumes that the rest
 * of the bits in the word are protected by the lock.
 *
 * @word:  word to unlock bit 31 in
 */
static inline void cvmx_spinlock_bit_unlock(uint32_t *word)
{
      CVMX_SYNCWS;
      *word &= ~(1UL << 31);
      CVMX_SYNCWS;
}

#endif /* __CVMX_SPINLOCK_H__ */

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