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/* MN10300 spinlock support
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#ifndef _ASM_SPINLOCK_H
#define _ASM_SPINLOCK_H
#include <linux/atomic.h>
#include <asm/barrier.h>
#include <asm/processor.h>
#include <asm/rwlock.h>
#include <asm/page.h>
/*
* Simple spin lock operations. There are two variants, one clears IRQ's
* on the local processor, one does not.
*
* We make no fairness assumptions. They have a cost.
*/
#define arch_spin_is_locked(x) (*(volatile signed char *)(&(x)->slock) != 0)
static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
asm volatile(
" bclr 1,(0,%0) \n"
:
: "a"(&lock->slock)
: "memory", "cc");
}
static inline int arch_spin_trylock(arch_spinlock_t *lock)
{
int ret;
asm volatile(
" mov 1,%0 \n"
" bset %0,(%1) \n"
" bne 1f \n"
" clr %0 \n"
"1: xor 1,%0 \n"
: "=d"(ret)
: "a"(&lock->slock)
: "memory", "cc");
return ret;
}
static inline void arch_spin_lock(arch_spinlock_t *lock)
{
asm volatile(
"1: bset 1,(0,%0) \n"
" bne 1b \n"
:
: "a"(&lock->slock)
: "memory", "cc");
}
static inline void arch_spin_lock_flags(arch_spinlock_t *lock,
unsigned long flags)
{
int temp;
asm volatile(
"1: bset 1,(0,%2) \n"
" beq 3f \n"
" mov %1,epsw \n"
"2: mov (0,%2),%0 \n"
" or %0,%0 \n"
" bne 2b \n"
" mov %3,%0 \n"
" mov %0,epsw \n"
" nop \n"
" nop \n"
" bra 1b\n"
"3: \n"
: "=&d" (temp)
: "d" (flags), "a"(&lock->slock), "i"(EPSW_IE | MN10300_CLI_LEVEL)
: "memory", "cc");
}
#ifdef __KERNEL__
/*
* Read-write spinlocks, allowing multiple readers
* but only one writer.
*
* NOTE! it is quite common to have readers in interrupts
* but no interrupt writers. For those circumstances we
* can "mix" irq-safe locks - any writer needs to get a
* irq-safe write-lock, but readers can get non-irqsafe
* read-locks.
*/
/**
* read_can_lock - would read_trylock() succeed?
* @lock: the rwlock in question.
*/
#define arch_read_can_lock(x) ((int)(x)->lock > 0)
/**
* write_can_lock - would write_trylock() succeed?
* @lock: the rwlock in question.
*/
#define arch_write_can_lock(x) ((x)->lock == RW_LOCK_BIAS)
/*
* On mn10300, we implement read-write locks as a 32-bit counter
* with the high bit (sign) being the "contended" bit.
*/
static inline void arch_read_lock(arch_rwlock_t *rw)
{
#if 0 //def CONFIG_MN10300_HAS_ATOMIC_OPS_UNIT
__build_read_lock(rw, "__read_lock_failed");
#else
{
atomic_t *count = (atomic_t *)rw;
while (atomic_dec_return(count) < 0)
atomic_inc(count);
}
#endif
}
static inline void arch_write_lock(arch_rwlock_t *rw)
{
#if 0 //def CONFIG_MN10300_HAS_ATOMIC_OPS_UNIT
__build_write_lock(rw, "__write_lock_failed");
#else
{
atomic_t *count = (atomic_t *)rw;
while (!atomic_sub_and_test(RW_LOCK_BIAS, count))
atomic_add(RW_LOCK_BIAS, count);
}
#endif
}
static inline void arch_read_unlock(arch_rwlock_t *rw)
{
#if 0 //def CONFIG_MN10300_HAS_ATOMIC_OPS_UNIT
__build_read_unlock(rw);
#else
{
atomic_t *count = (atomic_t *)rw;
atomic_inc(count);
}
#endif
}
static inline void arch_write_unlock(arch_rwlock_t *rw)
{
#if 0 //def CONFIG_MN10300_HAS_ATOMIC_OPS_UNIT
__build_write_unlock(rw);
#else
{
atomic_t *count = (atomic_t *)rw;
atomic_add(RW_LOCK_BIAS, count);
}
#endif
}
static inline int arch_read_trylock(arch_rwlock_t *lock)
{
atomic_t *count = (atomic_t *)lock;
atomic_dec(count);
if (atomic_read(count) >= 0)
return 1;
atomic_inc(count);
return 0;
}
static inline int arch_write_trylock(arch_rwlock_t *lock)
{
atomic_t *count = (atomic_t *)lock;
if (atomic_sub_and_test(RW_LOCK_BIAS, count))
return 1;
atomic_add(RW_LOCK_BIAS, count);
return 0;
}
#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
#define _raw_spin_relax(lock) cpu_relax()
#define _raw_read_relax(lock) cpu_relax()
#define _raw_write_relax(lock) cpu_relax()
#endif /* __KERNEL__ */
#endif /* _ASM_SPINLOCK_H */
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