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/* Copyright (c) 2009, Code Aurora Forum. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * 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.
* * Neither the name of Code Aurora nor
* the names of its contributors may be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NON-INFRINGEMENT ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER 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.
*
*/
/*
* Part of this this code is based on the standard ARM spinlock
* implementation (asm/spinlock.h) found in the 2.6.29 kernel.
*/
#ifndef __ASM__ARCH_QC_REMOTE_SPINLOCK_H
#define __ASM__ARCH_QC_REMOTE_SPINLOCK_H
#include <linux/types.h>
#include <linux/spinlock.h>
typedef struct {
volatile uint32_t lock;
} raw_remote_spinlock_t;
typedef raw_remote_spinlock_t *_remote_spinlock_t;
#define remote_spin_lock_id_t uint32_t
static inline void __raw_remote_ex_spin_lock(raw_remote_spinlock_t *lock)
{
unsigned long tmp;
__asm__ __volatile__(
"1: ldrex %0, [%1]\n"
" teq %0, #0\n"
" strexeq %0, %2, [%1]\n"
" teqeq %0, #0\n"
" bne 1b"
: "=&r" (tmp)
: "r" (&lock->lock), "r" (1)
: "cc");
smp_mb();
}
static inline void __raw_remote_ex_spin_unlock(raw_remote_spinlock_t *lock)
{
smp_mb();
__asm__ __volatile__(
" str %1, [%0]\n"
:
: "r" (&lock->lock), "r" (0)
: "cc");
}
static inline void __raw_remote_swp_spin_lock(raw_remote_spinlock_t *lock)
{
unsigned long tmp;
__asm__ __volatile__(
"1: swp %0, %2, [%1]\n"
" teq %0, #0\n"
" bne 1b"
: "=&r" (tmp)
: "r" (&lock->lock), "r" (1)
: "cc");
smp_mb();
}
static inline void __raw_remote_swp_spin_unlock(raw_remote_spinlock_t *lock)
{
smp_mb();
__asm__ __volatile__(
" str %1, [%0]"
:
: "r" (&lock->lock), "r" (0)
: "cc");
}
int _remote_spin_lock_init(remote_spin_lock_id_t id, _remote_spinlock_t *lock);
/* Only use SWP-based spinlocks for ARM11 apps processors where the LDREX/STREX
* instructions are unable to lock shared memory for exclusive access. */
#if defined(CONFIG_ARCH_MSM_ARM11)
#define _remote_spin_lock(lock) __raw_remote_swp_spin_lock(*lock)
#define _remote_spin_unlock(lock) __raw_remote_swp_spin_unlock(*lock)
#else
#define _remote_spin_lock(lock) __raw_remote_ex_spin_lock(*lock)
#define _remote_spin_unlock(lock) __raw_remote_ex_spin_unlock(*lock)
#endif /* CONFIG_ARCH_MSM_ARM11 */
/* Grabbing a local spin lock before going for a remote lock has several
* advantages:
* 1. Get calls to preempt enable/disable and IRQ save/restore for free.
* 2. For UP kernel, there is no overhead.
* 3. Reduces the possibility of executing the remote spin lock code. This is
* especially useful when the remote CPUs' mutual exclusion instructions
* don't work with the local CPUs' instructions. In such cases, one has to
* use software based mutex algorithms (e.g. Lamport's bakery algorithm)
* which could get expensive when the no. of contending CPUs is high.
* 4. In the case of software based mutex algorithm the exection time will be
* smaller since the no. of contending CPUs is reduced by having just one
* contender for all the local CPUs.
* 5. Get most of the spin lock debug features for free.
* 6. The code will continue to work "gracefully" even when the remote spin
* lock code is stubbed out for debug purposes or when there is no remote
* CPU in some board/machine types.
*/
typedef struct {
spinlock_t local;
_remote_spinlock_t remote;
} remote_spinlock_t;
#define remote_spin_lock_init(lock,id) \
do { \
spin_lock_init(&((lock)->local)); \
_remote_spin_lock_init(id, &((lock)->remote)); \
} while (0)
#define remote_spin_lock(lock) \
do { \
spin_lock(&((lock)->local)); \
_remote_spin_lock(&((lock)->remote)); \
} while (0)
#define remote_spin_unlock(lock) \
do { \
_remote_spin_unlock(&((lock)->remote)); \
spin_unlock(&((lock)->local)); \
} while (0)
#define remote_spin_lock_irqsave(lock, flags) \
do { \
spin_lock_irqsave(&((lock)->local), flags); \
_remote_spin_lock(&((lock)->remote)); \
} while (0)
#define remote_spin_unlock_irqrestore(lock, flags) \
do { \
_remote_spin_unlock(&((lock)->remote)); \
spin_unlock_irqrestore(&((lock)->local), flags); \
} while (0)
#endif /* __ASM__ARCH_QC_REMOTE_SPINLOCK_H */
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