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

#include <linux/irqflags.h>
#include <linux/prefetch.h>
#include <asm/barrier.h>

#if defined(CONFIG_CPU_SA1100) || defined(CONFIG_CPU_SA110)
/*
 * On the StrongARM, "swp" is terminally broken since it bypasses the
 * cache totally.  This means that the cache becomes inconsistent, and,
 * since we use normal loads/stores as well, this is really bad.
 * Typically, this causes oopsen in filp_close, but could have other,
 * more disastrous effects.  There are two work-arounds:
 *  1. Disable interrupts and emulate the atomic swap
 *  2. Clean the cache, perform atomic swap, flush the cache
 *
 * We choose (1) since its the "easiest" to achieve here and is not
 * dependent on the processor type.
 *
 * NOTE that this solution won't work on an SMP system, so explcitly
 * forbid it here.
 */
#define swp_is_buggy
#endif

static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
{
        extern void __bad_xchg(volatile void *, int);
        unsigned long ret;
#ifdef swp_is_buggy
        unsigned long flags;
#endif
#if __LINUX_ARM_ARCH__ >= 6
        unsigned int tmp;
#endif

        prefetchw((const void *)ptr);

        switch (size) {
#if __LINUX_ARM_ARCH__ >= 6
#ifndef CONFIG_CPU_V6 /* MIN ARCH >= V6K */
        case 1:
                asm volatile("@ __xchg1\n"
                "1:     ldrexb  %0, [%3]\n"
                "       strexb  %1, %2, [%3]\n"
                "       teq     %1, #0\n"
                "       bne     1b"
                        : "=&r" (ret), "=&r" (tmp)
                        : "r" (x), "r" (ptr)
                        : "memory", "cc");
                break;
        case 2:
                asm volatile("@ __xchg2\n"
                "1:     ldrexh  %0, [%3]\n"
                "       strexh  %1, %2, [%3]\n"
                "       teq     %1, #0\n"
                "       bne     1b"
                        : "=&r" (ret), "=&r" (tmp)
                        : "r" (x), "r" (ptr)
                        : "memory", "cc");
                break;
#endif
        case 4:
                asm volatile("@ __xchg4\n"
                "1:     ldrex   %0, [%3]\n"
                "       strex   %1, %2, [%3]\n"
                "       teq     %1, #0\n"
                "       bne     1b"
                        : "=&r" (ret), "=&r" (tmp)
                        : "r" (x), "r" (ptr)
                        : "memory", "cc");
                break;
#elif defined(swp_is_buggy)
#ifdef CONFIG_SMP
#error SMP is not supported on this platform
#endif
        case 1:
                raw_local_irq_save(flags);
                ret = *(volatile unsigned char *)ptr;
                *(volatile unsigned char *)ptr = x;
                raw_local_irq_restore(flags);
                break;

        case 4:
                raw_local_irq_save(flags);
                ret = *(volatile unsigned long *)ptr;
                *(volatile unsigned long *)ptr = x;
                raw_local_irq_restore(flags);
                break;
#else
        case 1:
                asm volatile("@ __xchg1\n"
                "       swpb    %0, %1, [%2]"
                        : "=&r" (ret)
                        : "r" (x), "r" (ptr)
                        : "memory", "cc");
                break;
        case 4:
                asm volatile("@ __xchg4\n"
                "       swp     %0, %1, [%2]"
                        : "=&r" (ret)
                        : "r" (x), "r" (ptr)
                        : "memory", "cc");
                break;
#endif
        default:
                /* Cause a link-time error, the xchg() size is not supported */
                __bad_xchg(ptr, size), ret = 0;
                break;
        }

        return ret;
}

#define arch_xchg_relaxed(ptr, x) ({                                    \
        (__typeof__(*(ptr)))__xchg((unsigned long)(x), (ptr),           \
                                   sizeof(*(ptr)));                     \
})

#include <asm-generic/cmpxchg-local.h>

#if __LINUX_ARM_ARCH__ < 6
/* min ARCH < ARMv6 */

#ifdef CONFIG_SMP
#error "SMP is not supported on this platform"
#endif

#define arch_xchg arch_xchg_relaxed

/*
 * cmpxchg_local and cmpxchg64_local are atomic wrt current CPU. Always make
 * them available.
 */
#define arch_cmpxchg_local(ptr, o, n) ({                                \
        (__typeof(*ptr))__generic_cmpxchg_local((ptr),                  \
                                                (unsigned long)(o),     \
                                                (unsigned long)(n),     \
                                                sizeof(*(ptr)));        \
})

#define arch_cmpxchg64_local(ptr, o, n) __generic_cmpxchg64_local((ptr), (o), (n))

#include <asm-generic/cmpxchg.h>

#else   /* min ARCH >= ARMv6 */

extern void __bad_cmpxchg(volatile void *ptr, int size);

/*
 * cmpxchg only support 32-bits operands on ARMv6.
 */

static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
                                      unsigned long new, int size)
{
        unsigned long oldval, res;

        prefetchw((const void *)ptr);

        switch (size) {
#ifndef CONFIG_CPU_V6   /* min ARCH >= ARMv6K */
        case 1:
                do {
                        asm volatile("@ __cmpxchg1\n"
                        "       ldrexb  %1, [%2]\n"
                        "       mov     %0, #0\n"
                        "       teq     %1, %3\n"
                        "       strexbeq %0, %4, [%2]\n"
                                : "=&r" (res), "=&r" (oldval)
                                : "r" (ptr), "Ir" (old), "r" (new)
                                : "memory", "cc");
                } while (res);
                break;
        case 2:
                do {
                        asm volatile("@ __cmpxchg1\n"
                        "       ldrexh  %1, [%2]\n"
                        "       mov     %0, #0\n"
                        "       teq     %1, %3\n"
                        "       strexheq %0, %4, [%2]\n"
                                : "=&r" (res), "=&r" (oldval)
                                : "r" (ptr), "Ir" (old), "r" (new)
                                : "memory", "cc");
                } while (res);
                break;
#endif
        case 4:
                do {
                        asm volatile("@ __cmpxchg4\n"
                        "       ldrex   %1, [%2]\n"
                        "       mov     %0, #0\n"
                        "       teq     %1, %3\n"
                        "       strexeq %0, %4, [%2]\n"
                                : "=&r" (res), "=&r" (oldval)
                                : "r" (ptr), "Ir" (old), "r" (new)
                                : "memory", "cc");
                } while (res);
                break;
        default:
                __bad_cmpxchg(ptr, size);
                oldval = 0;
        }

        return oldval;
}

#define arch_cmpxchg_relaxed(ptr,o,n) ({                                \
        (__typeof__(*(ptr)))__cmpxchg((ptr),                            \
                                      (unsigned long)(o),               \
                                      (unsigned long)(n),               \
                                      sizeof(*(ptr)));                  \
})

static inline unsigned long __cmpxchg_local(volatile void *ptr,
                                            unsigned long old,
                                            unsigned long new, int size)
{
        unsigned long ret;

        switch (size) {
#ifdef CONFIG_CPU_V6    /* min ARCH == ARMv6 */
        case 1:
        case 2:
                ret = __generic_cmpxchg_local(ptr, old, new, size);
                break;
#endif
        default:
                ret = __cmpxchg(ptr, old, new, size);
        }

        return ret;
}

#define arch_cmpxchg_local(ptr, o, n) ({                                \
        (__typeof(*ptr))__cmpxchg_local((ptr),                          \
                                        (unsigned long)(o),             \
                                        (unsigned long)(n),             \
                                        sizeof(*(ptr)));                \
})

static inline unsigned long long __cmpxchg64(unsigned long long *ptr,
                                             unsigned long long old,
                                             unsigned long long new)
{
        unsigned long long oldval;
        unsigned long res;

        prefetchw(ptr);

        __asm__ __volatile__(
"1:     ldrexd          %1, %H1, [%3]\n"
"       teq             %1, %4\n"
"       teqeq           %H1, %H4\n"
"       bne             2f\n"
"       strexd          %0, %5, %H5, [%3]\n"
"       teq             %0, #0\n"
"       bne             1b\n"
"2:"
        : "=&r" (res), "=&r" (oldval), "+Qo" (*ptr)
        : "r" (ptr), "r" (old), "r" (new)
        : "cc");

        return oldval;
}

#define arch_cmpxchg64_relaxed(ptr, o, n) ({                            \
        (__typeof__(*(ptr)))__cmpxchg64((ptr),                          \
                                        (unsigned long long)(o),        \
                                        (unsigned long long)(n));       \
})

#define arch_cmpxchg64_local(ptr, o, n) arch_cmpxchg64_relaxed((ptr), (o), (n))

#endif  /* __LINUX_ARM_ARCH__ >= 6 */

#endif /* __ASM_ARM_CMPXCHG_H */