/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __ASM_SPINLOCK_H
#define __ASM_SPINLOCK_H

#include <asm/barrier.h>
#include <asm/ldcw.h>
#include <asm/processor.h>
#include <asm/spinlock_types.h>

static inline void arch_spin_val_check(int lock_val)
{
        if (IS_ENABLED(CONFIG_LIGHTWEIGHT_SPINLOCK_CHECK))
                asm volatile(   "andcm,= %0,%1,%%r0\n"
                                ".word %2\n"
                : : "r" (lock_val), "r" (__ARCH_SPIN_LOCK_UNLOCKED_VAL),
                        "i" (SPINLOCK_BREAK_INSN));
}

static inline int arch_spin_is_locked(arch_spinlock_t *x)
{
        volatile unsigned int *a;
        int lock_val;

        a = __ldcw_align(x);
        lock_val = READ_ONCE(*a);
        arch_spin_val_check(lock_val);
        return (lock_val == 0);
}

static inline void arch_spin_lock(arch_spinlock_t *x)
{
        volatile unsigned int *a;

        a = __ldcw_align(x);
        do {
                int lock_val_old;

                lock_val_old = __ldcw(a);
                arch_spin_val_check(lock_val_old);
                if (lock_val_old)
                        return; /* got lock */

                /* wait until we should try to get lock again */
                while (*a == 0)
                        continue;
        } while (1);
}

static inline void arch_spin_unlock(arch_spinlock_t *x)
{
        volatile unsigned int *a;

        a = __ldcw_align(x);
        /* Release with ordered store. */
        __asm__ __volatile__("stw,ma %0,0(%1)"
                : : "r"(__ARCH_SPIN_LOCK_UNLOCKED_VAL), "r"(a) : "memory");
}

static inline int arch_spin_trylock(arch_spinlock_t *x)
{
        volatile unsigned int *a;
        int lock_val;

        a = __ldcw_align(x);
        lock_val = __ldcw(a);
        arch_spin_val_check(lock_val);
        return lock_val != 0;
}

/*
 * Read-write spinlocks, allowing multiple readers but only one writer.
 * Unfair locking as Writers could be starved indefinitely by Reader(s)
 *
 * The spinlock itself is contained in @counter and access to it is
 * serialized with @lock_mutex.
 */

/* 1 - lock taken successfully */
static inline int arch_read_trylock(arch_rwlock_t *rw)
{
        int ret = 0;
        unsigned long flags;

        local_irq_save(flags);
        arch_spin_lock(&(rw->lock_mutex));

        /*
         * zero means writer holds the lock exclusively, deny Reader.
         * Otherwise grant lock to first/subseq reader
         */
        if (rw->counter > 0) {
                rw->counter--;
                ret = 1;
        }

        arch_spin_unlock(&(rw->lock_mutex));
        local_irq_restore(flags);

        return ret;
}

/* 1 - lock taken successfully */
static inline int arch_write_trylock(arch_rwlock_t *rw)
{
        int ret = 0;
        unsigned long flags;

        local_irq_save(flags);
        arch_spin_lock(&(rw->lock_mutex));

        /*
         * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
         * deny writer. Otherwise if unlocked grant to writer
         * Hence the claim that Linux rwlocks are unfair to writers.
         * (can be starved for an indefinite time by readers).
         */
        if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
                rw->counter = 0;
                ret = 1;
        }
        arch_spin_unlock(&(rw->lock_mutex));
        local_irq_restore(flags);

        return ret;
}

static inline void arch_read_lock(arch_rwlock_t *rw)
{
        while (!arch_read_trylock(rw))
                cpu_relax();
}

static inline void arch_write_lock(arch_rwlock_t *rw)
{
        while (!arch_write_trylock(rw))
                cpu_relax();
}

static inline void arch_read_unlock(arch_rwlock_t *rw)
{
        unsigned long flags;

        local_irq_save(flags);
        arch_spin_lock(&(rw->lock_mutex));
        rw->counter++;
        arch_spin_unlock(&(rw->lock_mutex));
        local_irq_restore(flags);
}

static inline void arch_write_unlock(arch_rwlock_t *rw)
{
        unsigned long flags;

        local_irq_save(flags);
        arch_spin_lock(&(rw->lock_mutex));
        rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
        arch_spin_unlock(&(rw->lock_mutex));
        local_irq_restore(flags);
}

#endif /* __ASM_SPINLOCK_H */