/*
* include/asm-xtensa/spinlock.h
*
* 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) 2001 - 2005 Tensilica Inc.
*/
#ifndef _XTENSA_SPINLOCK_H
#define _XTENSA_SPINLOCK_H
#include <asm/barrier.h>
#include <asm/processor.h>
/*
* spinlock
*
* There is at most one owner of a spinlock. There are not different
* types of spinlock owners like there are for rwlocks (see below).
*
* When trying to obtain a spinlock, the function "spins" forever, or busy-
* waits, until the lock is obtained. When spinning, presumably some other
* owner will soon give up the spinlock making it available to others. Use
* the trylock functions to avoid spinning forever.
*
* possible values:
*
* 0 nobody owns the spinlock
* 1 somebody owns the spinlock
*/
#define arch_spin_is_locked(x) ((x)->slock != 0)
static inline void arch_spin_lock(arch_spinlock_t *lock)
{
unsigned long tmp;
__asm__ __volatile__(
" movi %0, 0\n"
" wsr %0, scompare1\n"
"1: movi %0, 1\n"
" s32c1i %0, %1, 0\n"
" bnez %0, 1b\n"
: "=&a" (tmp)
: "a" (&lock->slock)
: "memory");
}
/* Returns 1 if the lock is obtained, 0 otherwise. */
static inline int arch_spin_trylock(arch_spinlock_t *lock)
{
unsigned long tmp;
__asm__ __volatile__(
" movi %0, 0\n"
" wsr %0, scompare1\n"
" movi %0, 1\n"
" s32c1i %0, %1, 0\n"
: "=&a" (tmp)
: "a" (&lock->slock)
: "memory");
return tmp == 0 ? 1 : 0;
}
static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
unsigned long tmp;
__asm__ __volatile__(
" movi %0, 0\n"
" s32ri %0, %1, 0\n"
: "=&a" (tmp)
: "a" (&lock->slock)
: "memory");
}
/*
* rwlock
*
* Read-write locks are really a more flexible spinlock. They allow
* multiple readers but only one writer. Write ownership is exclusive
* (i.e., all other readers and writers are blocked from ownership while
* there is a write owner). These rwlocks are unfair to writers. Writers
* can be starved for an indefinite time by readers.
*
* possible values:
*
* 0 nobody owns the rwlock
* >0 one or more readers own the rwlock
* (the positive value is the actual number of readers)
* 0x80000000 one writer owns the rwlock, no other writers, no readers
*/
static inline void arch_write_lock(arch_rwlock_t *rw)
{
unsigned long tmp;
__asm__ __volatile__(
" movi %0, 0\n"
" wsr %0, scompare1\n"
"1: movi %0, 1\n"
" slli %0, %0, 31\n"
" s32c1i %0, %1, 0\n"
" bnez %0, 1b\n"
: "=&a" (tmp)
: "a" (&rw->lock)
: "memory");
}
/* Returns 1 if the lock is obtained, 0 otherwise. */
static inline int arch_write_trylock(arch_rwlock_t *rw)
{
unsigned long tmp;
__asm__ __volatile__(
" movi %0, 0\n"
" wsr %0, scompare1\n"
" movi %0, 1\n"
" slli %0, %0, 31\n"
" s32c1i %0, %1, 0\n"
: "=&a" (tmp)
: "a" (&rw->lock)
: "memory");
return tmp == 0 ? 1 : 0;
}
static inline void arch_write_unlock(arch_rwlock_t *rw)
{
unsigned long tmp;
__asm__ __volatile__(
" movi %0, 0\n"
" s32ri %0, %1, 0\n"
: "=&a" (tmp)
: "a" (&rw->lock)
: "memory");
}
static inline void arch_read_lock(arch_rwlock_t *rw)
{
unsigned long tmp;
unsigned long result;
__asm__ __volatile__(
"1: l32i %1, %2, 0\n"
" bltz %1, 1b\n"
" wsr %1, scompare1\n"
" addi %0, %1, 1\n"
" s32c1i %0, %2, 0\n"
" bne %0, %1, 1b\n"
: "=&a" (result), "=&a" (tmp)
: "a" (&rw->lock)
: "memory");
}
/* Returns 1 if the lock is obtained, 0 otherwise. */
static inline int arch_read_trylock(arch_rwlock_t *rw)
{
unsigned long result;
unsigned long tmp;
__asm__ __volatile__(
" l32i %1, %2, 0\n"
" addi %0, %1, 1\n"
" bltz %0, 1f\n"
" wsr %1, scompare1\n"
" s32c1i %0, %2, 0\n"
" sub %0, %0, %1\n"
"1:\n"
: "=&a" (result), "=&a" (tmp)
: "a" (&rw->lock)
: "memory");
return result == 0;
}
static inline void arch_read_unlock(arch_rwlock_t *rw)
{
unsigned long tmp1, tmp2;
__asm__ __volatile__(
"1: l32i %1, %2, 0\n"
" addi %0, %1, -1\n"
" wsr %1, scompare1\n"
" s32c1i %0, %2, 0\n"
" bne %0, %1, 1b\n"
: "=&a" (tmp1), "=&a" (tmp2)
: "a" (&rw->lock)
: "memory");
}
#endif /* _XTENSA_SPINLOCK_H */
