/*
 * 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/cmpxchg.h>

#define ATOMIC_INIT(i)  { (i) }

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

#define ATOMIC_OP_RETURN(op, asm_op, asm_con)                           \
static inline int __atomic_##op##_return(int i, atomic_t *v)            \
{                                                                       \
        int result;                                                     \
                                                                        \
        asm volatile(                                                   \
                "/* atomic_" #op "_return */\n"                         \
                "1:     ssrf    5\n"                                    \
                "       ld.w    %0, %2\n"                               \
                "       " #asm_op "     %0, %3\n"                       \
                "       stcond  %1, %0\n"                               \
                "       brne    1b"                                     \
                : "=&r" (result), "=o" (v->counter)                     \
                : "m" (v->counter), #asm_con (i)                        \
                : "cc");                                                \
                                                                        \
        return result;                                                  \
}

ATOMIC_OP_RETURN(sub, sub, rKs21)
ATOMIC_OP_RETURN(add, add, r)

#undef ATOMIC_OP_RETURN

/*
 * Probably found the reason why we want to use sub with the signed 21-bit
 * limit, it uses one less register than the add instruction that can add up to
 * 32-bit values.
 *
 * Both instructions are 32-bit, to use a 16-bit instruction the immediate is
 * very small; 4 bit.
 *
 * sub 32-bit, type IV, takes a register and subtracts a 21-bit immediate.
 * add 32-bit, type II, adds two register values together.
 */
#define IS_21BIT_CONST(i)                                               \
        (__builtin_constant_p(i) && ((i) >= -1048575) && ((i) <= 1048576))

/*
 * 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)
{
        if (IS_21BIT_CONST(i))
                return __atomic_sub_return(-i, v);

        return __atomic_add_return(i, v);
}

/*
 * 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)
{
        if (IS_21BIT_CONST(i))
                return __atomic_sub_return(i, v);

        return __atomic_add_return(-i, v);
}

/*
 * __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 the old value of @v.
*/
static inline int __atomic_add_unless(atomic_t *v, int a, int u)
{
        int tmp, old = atomic_read(v);

        if (IS_21BIT_CONST(a)) {
                asm volatile(
                        "/* __atomic_sub_unless */\n"
                        "1:     ssrf    5\n"
                        "       ld.w    %0, %2\n"
                        "       cp.w    %0, %4\n"
                        "       breq    1f\n"
                        "       sub     %0, %3\n"
                        "       stcond  %1, %0\n"
                        "       brne    1b\n"
                        "1:"
                        : "=&r"(tmp), "=o"(v->counter)
                        : "m"(v->counter), "rKs21"(-a), "rKs21"(u)
                        : "cc", "memory");
        } else {
                asm volatile(
                        "/* __atomic_add_unless */\n"
                        "1:     ssrf    5\n"
                        "       ld.w    %0, %2\n"
                        "       cp.w    %0, %4\n"
                        "       breq    1f\n"
                        "       add     %0, %3\n"
                        "       stcond  %1, %0\n"
                        "       brne    1b\n"
                        "1:"
                        : "=&r"(tmp), "=o"(v->counter)
                        : "m"(v->counter), "r"(a), "ir"(u)
                        : "cc", "memory");
        }

        return old;
}

#undef IS_21BIT_CONST

/*
 * 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_dec_if_positive(v) atomic_sub_if_positive(1, v)

#endif /*  __ASM_AVR32_ATOMIC_H */