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atomic.h

/*
 * Atomic operations that C can't guarantee us.  Useful for
 * resource counting etc.
 *
 * But use these as seldom as possible since they are slower than
 * regular operations.
 *
 * Copyright (C) 2004-2006 Atmel Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#ifndef __ASM_AVR32_ATOMIC_H
#define __ASM_AVR32_ATOMIC_H

#include <linux/types.h>
#include <asm/system.h>

#define ATOMIC_INIT(i)  { (i) }

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

/*
 * atomic_sub_return - subtract the atomic variable
 * @i: integer value to subtract
 * @v: pointer of type atomic_t
 *
 * Atomically subtracts @i from @v. Returns the resulting value.
 */
static inline int atomic_sub_return(int i, atomic_t *v)
{
      int result;

      asm volatile(
            "/* atomic_sub_return */\n"
            "1:   ssrf  5\n"
            "     ld.w  %0, %2\n"
            "     sub   %0, %3\n"
            "     stcond      %1, %0\n"
            "     brne  1b"
            : "=&r"(result), "=o"(v->counter)
            : "m"(v->counter), "rKs21"(i)
            : "cc");

      return result;
}

/*
 * atomic_add_return - add integer to atomic variable
 * @i: integer value to add
 * @v: pointer of type atomic_t
 *
 * Atomically adds @i to @v. Returns the resulting value.
 */
static inline int atomic_add_return(int i, atomic_t *v)
{
      int result;

      if (__builtin_constant_p(i) && (i >= -1048575) && (i <= 1048576))
            result = atomic_sub_return(-i, v);
      else
            asm volatile(
                  "/* atomic_add_return */\n"
                  "1:   ssrf  5\n"
                  "     ld.w  %0, %1\n"
                  "     add   %0, %3\n"
                  "     stcond      %2, %0\n"
                  "     brne  1b"
                  : "=&r"(result), "=o"(v->counter)
                  : "m"(v->counter), "r"(i)
                  : "cc", "memory");

      return result;
}

/*
 * atomic_sub_unless - sub 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.
 *
 * If the atomic value v is not equal to u, this function subtracts a
 * from v, and returns non zero. If v is equal to u then it returns
 * zero. This is done as an atomic operation.
*/
static inline int atomic_sub_unless(atomic_t *v, int a, int u)
{
      int tmp, result = 0;

      asm volatile(
            "/* atomic_sub_unless */\n"
            "1:   ssrf  5\n"
            "     ld.w  %0, %3\n"
            "     cp.w  %0, %5\n"
            "     breq  1f\n"
            "     sub   %0, %4\n"
            "     stcond      %2, %0\n"
            "     brne  1b\n"
            "     mov   %1, 1\n"
            "1:"
            : "=&r"(tmp), "=&r"(result), "=o"(v->counter)
            : "m"(v->counter), "rKs21"(a), "rKs21"(u), "1"(result)
            : "cc", "memory");

      return result;
}

/*
 * 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.
 *
 * If the atomic value v is not equal to u, this function adds a to v,
 * and returns non zero. If v is equal to u then it returns zero. This
 * is done as an atomic operation.
*/
static inline int atomic_add_unless(atomic_t *v, int a, int u)
{
      int tmp, result;

      if (__builtin_constant_p(a) && (a >= -1048575) && (a <= 1048576))
            result = atomic_sub_unless(v, -a, u);
      else {
            result = 0;
            asm volatile(
                  "/* atomic_add_unless */\n"
                  "1:   ssrf  5\n"
                  "     ld.w  %0, %3\n"
                  "     cp.w  %0, %5\n"
                  "     breq  1f\n"
                  "     add   %0, %4\n"
                  "     stcond      %2, %0\n"
                  "     brne  1b\n"
                  "     mov   %1, 1\n"
                  "1:"
                  : "=&r"(tmp), "=&r"(result), "=o"(v->counter)
                  : "m"(v->counter), "r"(a), "ir"(u), "1"(result)
                  : "cc", "memory");
      }

      return result;
}

/*
 * atomic_sub_if_positive - conditionally subtract integer from atomic variable
 * @i: integer value to subtract
 * @v: pointer of type atomic_t
 *
 * Atomically test @v and subtract @i if @v is greater or equal than @i.
 * The function returns the old value of @v minus @i.
 */
static inline int atomic_sub_if_positive(int i, atomic_t *v)
{
      int result;

      asm volatile(
            "/* atomic_sub_if_positive */\n"
            "1:   ssrf  5\n"
            "     ld.w  %0, %2\n"
            "     sub   %0, %3\n"
            "     brlt  1f\n"
            "     stcond      %1, %0\n"
            "     brne  1b\n"
            "1:"
            : "=&r"(result), "=o"(v->counter)
            : "m"(v->counter), "ir"(i)
            : "cc", "memory");

      return result;
}

#define atomic_xchg(v, new)   (xchg(&((v)->counter), new))
#define atomic_cmpxchg(v, o, n)     (cmpxchg(&((v)->counter), (o), (n)))

#define atomic_sub(i, v)      (void)atomic_sub_return(i, v)
#define atomic_add(i, v)      (void)atomic_add_return(i, v)
#define atomic_dec(v)         atomic_sub(1, (v))
#define atomic_inc(v)         atomic_add(1, (v))

#define atomic_dec_return(v)  atomic_sub_return(1, v)
#define atomic_inc_return(v)  atomic_add_return(1, v)

#define atomic_sub_and_test(i, v) (atomic_sub_return(i, v) == 0)
#define atomic_inc_and_test(v) (atomic_add_return(1, v) == 0)
#define atomic_dec_and_test(v) (atomic_sub_return(1, v) == 0)
#define atomic_add_negative(i, v) (atomic_add_return(i, v) < 0)

#define atomic_inc_not_zero(v)      atomic_add_unless(v, 1, 0)
#define atomic_dec_if_positive(v) atomic_sub_if_positive(1, v)

#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-long.h>

#endif /*  __ASM_AVR32_ATOMIC_H */

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