// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Generic implementation of 64-bit atomics using spinlocks,
 * useful on processors that don't have 64-bit atomic instructions.
 *
 * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
 */
#include <linux/types.h>
#include <linux/cache.h>
#include <linux/spinlock.h>
#include <linux/init.h>
#include <linux/export.h>
#include <linux/atomic.h>

/*
 * We use a hashed array of spinlocks to provide exclusive access
 * to each atomic64_t variable.  Since this is expected to used on
 * systems with small numbers of CPUs (<= 4 or so), we use a
 * relatively small array of 16 spinlocks to avoid wasting too much
 * memory on the spinlock array.
 */
#define NR_LOCKS        16

/*
 * Ensure each lock is in a separate cacheline.
 */
static union {
        arch_spinlock_t lock;
        char pad[L1_CACHE_BYTES];
} atomic64_lock[NR_LOCKS] __cacheline_aligned_in_smp = {
        [0 ... (NR_LOCKS - 1)] = {
                .lock =  __ARCH_SPIN_LOCK_UNLOCKED,
        },
};

static inline arch_spinlock_t *lock_addr(const atomic64_t *v)
{
        unsigned long addr = (unsigned long) v;

        addr >>= L1_CACHE_SHIFT;
        addr ^= (addr >> 8) ^ (addr >> 16);
        return &atomic64_lock[addr & (NR_LOCKS - 1)].lock;
}

s64 generic_atomic64_read(const atomic64_t *v)
{
        unsigned long flags;
        arch_spinlock_t *lock = lock_addr(v);
        s64 val;

        local_irq_save(flags);
        arch_spin_lock(lock);
        val = v->counter;
        arch_spin_unlock(lock);
        local_irq_restore(flags);
        return val;
}
EXPORT_SYMBOL(generic_atomic64_read);

void generic_atomic64_set(atomic64_t *v, s64 i)
{
        unsigned long flags;
        arch_spinlock_t *lock = lock_addr(v);

        local_irq_save(flags);
        arch_spin_lock(lock);
        v->counter = i;
        arch_spin_unlock(lock);
        local_irq_restore(flags);
}
EXPORT_SYMBOL(generic_atomic64_set);

#define ATOMIC64_OP(op, c_op)                                           \
void generic_atomic64_##op(s64 a, atomic64_t *v)                        \
{                                                                       \
        unsigned long flags;                                            \
        arch_spinlock_t *lock = lock_addr(v);                           \
                                                                        \
        local_irq_save(flags);                                          \
        arch_spin_lock(lock);                                           \
        v->counter c_op a;                                              \
        arch_spin_unlock(lock);                                         \
        local_irq_restore(flags);                                       \
}                                                                       \
EXPORT_SYMBOL(generic_atomic64_##op);

#define ATOMIC64_OP_RETURN(op, c_op)                                    \
s64 generic_atomic64_##op##_return(s64 a, atomic64_t *v)                \
{                                                                       \
        unsigned long flags;                                            \
        arch_spinlock_t *lock = lock_addr(v);                           \
        s64 val;                                                        \
                                                                        \
        local_irq_save(flags);                                          \
        arch_spin_lock(lock);                                           \
        val = (v->counter c_op a);                                      \
        arch_spin_unlock(lock);                                         \
        local_irq_restore(flags);                                       \
        return val;                                                     \
}                                                                       \
EXPORT_SYMBOL(generic_atomic64_##op##_return);

#define ATOMIC64_FETCH_OP(op, c_op)                                     \
s64 generic_atomic64_fetch_##op(s64 a, atomic64_t *v)                   \
{                                                                       \
        unsigned long flags;                                            \
        arch_spinlock_t *lock = lock_addr(v);                           \
        s64 val;                                                        \
                                                                        \
        local_irq_save(flags);                                          \
        arch_spin_lock(lock);                                           \
        val = v->counter;                                               \
        v->counter c_op a;                                              \
        arch_spin_unlock(lock);                                         \
        local_irq_restore(flags);                                       \
        return val;                                                     \
}                                                                       \
EXPORT_SYMBOL(generic_atomic64_fetch_##op);

#define ATOMIC64_OPS(op, c_op)                                          \
        ATOMIC64_OP(op, c_op)                                           \
        ATOMIC64_OP_RETURN(op, c_op)                                    \
        ATOMIC64_FETCH_OP(op, c_op)

ATOMIC64_OPS(add, +=)
ATOMIC64_OPS(sub, -=)

#undef ATOMIC64_OPS
#define ATOMIC64_OPS(op, c_op)                                          \
        ATOMIC64_OP(op, c_op)                                           \
        ATOMIC64_FETCH_OP(op, c_op)

ATOMIC64_OPS(and, &=)
ATOMIC64_OPS(or, |=)
ATOMIC64_OPS(xor, ^=)

#undef ATOMIC64_OPS
#undef ATOMIC64_FETCH_OP
#undef ATOMIC64_OP

s64 generic_atomic64_dec_if_positive(atomic64_t *v)
{
        unsigned long flags;
        arch_spinlock_t *lock = lock_addr(v);
        s64 val;

        local_irq_save(flags);
        arch_spin_lock(lock);
        val = v->counter - 1;
        if (val >= 0)
                v->counter = val;
        arch_spin_unlock(lock);
        local_irq_restore(flags);
        return val;
}
EXPORT_SYMBOL(generic_atomic64_dec_if_positive);

s64 generic_atomic64_cmpxchg(atomic64_t *v, s64 o, s64 n)
{
        unsigned long flags;
        arch_spinlock_t *lock = lock_addr(v);
        s64 val;

        local_irq_save(flags);
        arch_spin_lock(lock);
        val = v->counter;
        if (val == o)
                v->counter = n;
        arch_spin_unlock(lock);
        local_irq_restore(flags);
        return val;
}
EXPORT_SYMBOL(generic_atomic64_cmpxchg);

s64 generic_atomic64_xchg(atomic64_t *v, s64 new)
{
        unsigned long flags;
        arch_spinlock_t *lock = lock_addr(v);
        s64 val;

        local_irq_save(flags);
        arch_spin_lock(lock);
        val = v->counter;
        v->counter = new;
        arch_spin_unlock(lock);
        local_irq_restore(flags);
        return val;
}
EXPORT_SYMBOL(generic_atomic64_xchg);

s64 generic_atomic64_fetch_add_unless(atomic64_t *v, s64 a, s64 u)
{
        unsigned long flags;
        arch_spinlock_t *lock = lock_addr(v);
        s64 val;

        local_irq_save(flags);
        arch_spin_lock(lock);
        val = v->counter;
        if (val != u)
                v->counter += a;
        arch_spin_unlock(lock);
        local_irq_restore(flags);

        return val;
}
EXPORT_SYMBOL(generic_atomic64_fetch_add_unless);