include/asm-sparc/atomic.h

/* atomic.h: These still suck, but the I-cache hit rate is higher.
 *
 * Copyright (C) 1996 David S. Miller (davem@caip.rutgers.edu)
 * Copyright (C) 2000 Anton Blanchard (anton@linuxcare.com.au)
 */

#ifndef __ARCH_SPARC_ATOMIC__
#define __ARCH_SPARC_ATOMIC__

#include <linux/config.h>

typedef struct { volatile int counter; } atomic_t;

#ifdef __KERNEL__
#ifndef CONFIG_SMP

#define ATOMIC_INIT(i)  { (i) }
#define atomic_read(v)          ((v)->counter)
#define atomic_set(v, i)        (((v)->counter) = i)

#else
/* We do the bulk of the actual work out of line in two common
 * routines in assembler, see arch/sparc/lib/atomic.S for the
 * "fun" details.
 *
 * For SMP the trick is you embed the spin lock byte within
 * the word, use the low byte so signedness is easily retained
 * via a quick arithmetic shift.  It looks like this:
 *
 *	----------------------------------------
 *	| signed 24-bit counter value |  lock  |  atomic_t
 *	----------------------------------------
 *	 31                          8 7      0
 */

#define ATOMIC_INIT(i)	{ (i << 8) }

static __inline__ int atomic_read(atomic_t *v)
{
	int ret = v->counter;

	while(ret & 0xff)
		ret = v->counter;

	return ret >> 8;
}

#define atomic_set(v, i)	(((v)->counter) = ((i) << 8))
#endif

static __inline__ int __atomic_add(int i, atomic_t *v)
{
	register volatile int *ptr asm("g1");
	register int increment asm("g2");

	ptr = &v->counter;
	increment = i;

	__asm__ __volatile__(
	"mov	%%o7, %%g4\n\t"
	"call	___atomic_add\n\t"
	" add	%%o7, 8, %%o7\n"
	: "=&r" (increment)
	: "0" (increment), "r" (ptr)
	: "g3", "g4", "g7", "memory", "cc");

	return increment;
}

static __inline__ int __atomic_sub(int i, atomic_t *v)
{
	register volatile int *ptr asm("g1");
	register int increment asm("g2");

	ptr = &v->counter;
	increment = i;

	__asm__ __volatile__(
	"mov	%%o7, %%g4\n\t"
	"call	___atomic_sub\n\t"
	" add	%%o7, 8, %%o7\n"
	: "=&r" (increment)
	: "0" (increment), "r" (ptr)
	: "g3", "g4", "g7", "memory", "cc");

	return increment;
}

#define atomic_add(i, v) ((void)__atomic_add((i), (v)))
#define atomic_sub(i, v) ((void)__atomic_sub((i), (v)))

#define atomic_dec_return(v) __atomic_sub(1, (v))
#define atomic_inc_return(v) __atomic_add(1, (v))

#define atomic_sub_and_test(i, v) (__atomic_sub((i), (v)) == 0)
#define atomic_dec_and_test(v) (__atomic_sub(1, (v)) == 0)

#define atomic_inc(v) ((void)__atomic_add(1, (v)))
#define atomic_dec(v) ((void)__atomic_sub(1, (v)))

#define atomic_add_negative(i, v) (__atomic_add((i), (v)) < 0)

/* 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()

#endif /* !(__KERNEL__) */

#endif /* !(__ARCH_SPARC_ATOMIC__) */