atomic.h
/*
* include/asm-xtensa/atomic.h
*
* Atomic operations that C can't guarantee us. Useful for resource counting..
*
* 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_ATOMIC_H
#define _XTENSA_ATOMIC_H
#include <linux/stringify.h>
typedef struct { volatile int counter; } atomic_t;
#ifdef __KERNEL__
#include <asm/processor.h>
#include <asm/system.h>
#define ATOMIC_INIT(i) { (i) }
/*
* This Xtensa implementation assumes that the right mechanism
* for exclusion is for locking interrupts to level 1.
*
* Locking interrupts looks like this:
*
* rsil a15, 1
* <code>
* wsr a15, PS
* rsync
*
* Note that a15 is used here because the register allocation
* done by the compiler is not guaranteed and a window overflow
* may not occur between the rsil and wsr instructions. By using
* a15 in the rsil, the machine is guaranteed to be in a state
* where no register reference will cause an overflow.
*/
/**
* atomic_read - read atomic variable
* @v: pointer of type atomic_t
*
* Atomically reads the value of @v.
*/
#define atomic_read(v) ((v)->counter)
/**
* atomic_set - set atomic variable
* @v: pointer of type atomic_t
* @i: required value
*
* Atomically sets the value of @v to @i.
*/
#define atomic_set(v,i) ((v)->counter = (i))
/**
* atomic_add - add integer to atomic variable
* @i: integer value to add
* @v: pointer of type atomic_t
*
* Atomically adds @i to @v.
*/
static inline void atomic_add(int i, atomic_t * v)
{
unsigned int vval;
__asm__ __volatile__(
"rsil a15, "__stringify(LOCKLEVEL)"\n\t"
"l32i %0, %2, 0 \n\t"
"add %0, %0, %1 \n\t"
"s32i %0, %2, 0 \n\t"
"wsr a15, "__stringify(PS)" \n\t"
"rsync \n"
: "=&a" (vval)
: "a" (i), "a" (v)
: "a15", "memory"
);
}
/**
* atomic_sub - subtract the atomic variable
* @i: integer value to subtract
* @v: pointer of type atomic_t
*
* Atomically subtracts @i from @v.
*/
static inline void atomic_sub(int i, atomic_t *v)
{
unsigned int vval;
__asm__ __volatile__(
"rsil a15, "__stringify(LOCKLEVEL)"\n\t"
"l32i %0, %2, 0 \n\t"
"sub %0, %0, %1 \n\t"
"s32i %0, %2, 0 \n\t"
"wsr a15, "__stringify(PS)" \n\t"
"rsync \n"
: "=&a" (vval)
: "a" (i), "a" (v)
: "a15", "memory"
);
}
/*
* We use atomic_{add|sub}_return to define other functions.
*/
static inline int atomic_add_return(int i, atomic_t * v)
{
unsigned int vval;
__asm__ __volatile__(
"rsil a15,"__stringify(LOCKLEVEL)"\n\t"
"l32i %0, %2, 0 \n\t"
"add %0, %0, %1 \n\t"
"s32i %0, %2, 0 \n\t"
"wsr a15, "__stringify(PS)" \n\t"
"rsync \n"
: "=&a" (vval)
: "a" (i), "a" (v)
: "a15", "memory"
);
return vval;
}
static inline int atomic_sub_return(int i, atomic_t * v)
{
unsigned int vval;
__asm__ __volatile__(
"rsil a15,"__stringify(LOCKLEVEL)"\n\t"
"l32i %0, %2, 0 \n\t"
"sub %0, %0, %1 \n\t"
"s32i %0, %2, 0 \n\t"
"wsr a15, "__stringify(PS)" \n\t"
"rsync \n"
: "=&a" (vval)
: "a" (i), "a" (v)
: "a15", "memory"
);
return vval;
}
/**
* atomic_sub_and_test - subtract value from variable and test result
* @i: integer value to subtract
* @v: pointer of type atomic_t
*
* Atomically subtracts @i from @v and returns
* true if the result is zero, or false for all
* other cases.
*/
#define atomic_sub_and_test(i,v) (atomic_sub_return((i),(v)) == 0)
/**
* atomic_inc - increment atomic variable
* @v: pointer of type atomic_t
*
* Atomically increments @v by 1.
*/
#define atomic_inc(v) atomic_add(1,(v))
/**
* atomic_inc - increment atomic variable
* @v: pointer of type atomic_t
*
* Atomically increments @v by 1.
*/
#define atomic_inc_return(v) atomic_add_return(1,(v))
/**
* atomic_dec - decrement atomic variable
* @v: pointer of type atomic_t
*
* Atomically decrements @v by 1.
*/
#define atomic_dec(v) atomic_sub(1,(v))
/**
* atomic_dec_return - decrement atomic variable
* @v: pointer of type atomic_t
*
* Atomically decrements @v by 1.
*/
#define atomic_dec_return(v) atomic_sub_return(1,(v))
/**
* atomic_dec_and_test - decrement and test
* @v: pointer of type atomic_t
*
* Atomically decrements @v by 1 and
* returns true if the result is 0, or false for all other
* cases.
*/
#define atomic_dec_and_test(v) (atomic_sub_return(1,(v)) == 0)
/**
* atomic_inc_and_test - increment and test
* @v: pointer of type atomic_t
*
* Atomically increments @v by 1
* and returns true if the result is zero, or false for all
* other cases.
*/
#define atomic_inc_and_test(v) (atomic_add_return(1,(v)) == 0)
/**
* atomic_add_negative - add and test if negative
* @v: pointer of type atomic_t
* @i: integer value to add
*
* Atomically adds @i to @v and returns true
* if the result is negative, or false when
* result is greater than or equal to zero.
*/
#define atomic_add_negative(i,v) (atomic_add_return((i),(v)) < 0)
#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
/**
* atomic_add_unless - add unless the number is a given value
* @v: pointer of type atomic_t
* @a: the amount to add to v...
* @u: ...unless v is equal to u.
*
* Atomically adds @a to @v, so long as it was not @u.
* Returns non-zero if @v was not @u, and zero otherwise.
*/
static __inline__ int atomic_add_unless(atomic_t *v, int a, int u)
{
int c, old;
c = atomic_read(v);
for (;;) {
if (unlikely(c == (u)))
break;
old = atomic_cmpxchg((v), c, c + (a));
if (likely(old == c))
break;
c = old;
}
return c != (u);
}
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
static inline void atomic_clear_mask(unsigned int mask, atomic_t *v)
{
unsigned int all_f = -1;
unsigned int vval;
__asm__ __volatile__(
"rsil a15,"__stringify(LOCKLEVEL)"\n\t"
"l32i %0, %2, 0 \n\t"
"xor %1, %4, %3 \n\t"
"and %0, %0, %4 \n\t"
"s32i %0, %2, 0 \n\t"
"wsr a15, "__stringify(PS)" \n\t"
"rsync \n"
: "=&a" (vval), "=a" (mask)
: "a" (v), "a" (all_f), "1" (mask)
: "a15", "memory"
);
}
static inline void atomic_set_mask(unsigned int mask, atomic_t *v)
{
unsigned int vval;
__asm__ __volatile__(
"rsil a15,"__stringify(LOCKLEVEL)"\n\t"
"l32i %0, %2, 0 \n\t"
"or %0, %0, %1 \n\t"
"s32i %0, %2, 0 \n\t"
"wsr a15, "__stringify(PS)" \n\t"
"rsync \n"
: "=&a" (vval)
: "a" (mask), "a" (v)
: "a15", "memory"
);
}
/* Atomic operations are already serializing */
#define smp_mb__before_atomic_dec() barrier()
#define smp_mb__after_atomic_dec() barrier()
#define smp_mb__before_atomic_inc() barrier()
#define smp_mb__after_atomic_inc() barrier()
#include <asm-generic/atomic.h>
#endif /* __KERNEL__ */
#endif /* _XTENSA_ATOMIC_H */
