/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2003, 06, 07 by Ralf Baechle (ralf@linux-mips.org)
 */
#ifndef __ASM_CMPXCHG_H
#define __ASM_CMPXCHG_H

#include <linux/bug.h>
#include <linux/irqflags.h>
#include <asm/compiler.h>
#include <asm/war.h>

/*
 * Using a branch-likely instruction to check the result of an sc instruction
 * works around a bug present in R10000 CPUs prior to revision 3.0 that could
 * cause ll-sc sequences to execute non-atomically.
 */
#if R10000_LLSC_WAR
# define __scbeqz "beqzl"
#else
# define __scbeqz "beqz"
#endif

/*
 * These functions doesn't exist, so if they are called you'll either:
 *
 * - Get an error at compile-time due to __compiletime_error, if supported by
 *   your compiler.
 *
 * or:
 *
 * - Get an error at link-time due to the call to the missing function.
 */
extern unsigned long __cmpxchg_called_with_bad_pointer(void)
        __compiletime_error("Bad argument size for cmpxchg");
extern unsigned long __cmpxchg64_unsupported(void)
        __compiletime_error("cmpxchg64 not available; cpu_has_64bits may be false");
extern unsigned long __xchg_called_with_bad_pointer(void)
        __compiletime_error("Bad argument size for xchg");

#define __xchg_asm(ld, st, m, val)                                      \
({                                                                      \
        __typeof(*(m)) __ret;                                           \
                                                                        \
        if (kernel_uses_llsc) {                                         \
                __asm__ __volatile__(                                   \
                "       .set    push                            \n"     \
                "       .set    noat                            \n"     \
                "       .set    push                            \n"     \
                "       .set    " MIPS_ISA_ARCH_LEVEL "         \n"     \
                "1:     " ld "  %0, %2          # __xchg_asm    \n"     \
                "       .set    pop                             \n"     \
                "       move    $1, %z3                         \n"     \
                "       .set    " MIPS_ISA_ARCH_LEVEL "         \n"     \
                "       " st "  $1, %1                          \n"     \
                "\t" __scbeqz " $1, 1b                          \n"     \
                "       .set    pop                             \n"     \
                : "=&r" (__ret), "=" GCC_OFF_SMALL_ASM() (*m)           \
                : GCC_OFF_SMALL_ASM() (*m), "Jr" (val)                  \
                : "memory");                                            \
        } else {                                                        \
                unsigned long __flags;                                  \
                                                                        \
                raw_local_irq_save(__flags);                            \
                __ret = *m;                                             \
                *m = val;                                               \
                raw_local_irq_restore(__flags);                         \
        }                                                               \
                                                                        \
        __ret;                                                          \
})

extern unsigned long __xchg_small(volatile void *ptr, unsigned long val,
                                  unsigned int size);

static inline unsigned long __xchg(volatile void *ptr, unsigned long x,
                                   int size)
{
        switch (size) {
        case 1:
        case 2:
                return __xchg_small(ptr, x, size);

        case 4:
                return __xchg_asm("ll", "sc", (volatile u32 *)ptr, x);

        case 8:
                if (!IS_ENABLED(CONFIG_64BIT))
                        return __xchg_called_with_bad_pointer();

                return __xchg_asm("lld", "scd", (volatile u64 *)ptr, x);

        default:
                return __xchg_called_with_bad_pointer();
        }
}

#define xchg(ptr, x)                                                    \
({                                                                      \
        __typeof__(*(ptr)) __res;                                       \
                                                                        \
        smp_mb__before_llsc();                                          \
                                                                        \
        __res = (__typeof__(*(ptr)))                                    \
                __xchg((ptr), (unsigned long)(x), sizeof(*(ptr)));      \
                                                                        \
        smp_llsc_mb();                                                  \
                                                                        \
        __res;                                                          \
})

#define __cmpxchg_asm(ld, st, m, old, new)                              \
({                                                                      \
        __typeof(*(m)) __ret;                                           \
                                                                        \
        if (kernel_uses_llsc) {                                         \
                __asm__ __volatile__(                                   \
                "       .set    push                            \n"     \
                "       .set    noat                            \n"     \
                "       .set    push                            \n"     \
                "       .set    "MIPS_ISA_ARCH_LEVEL"           \n"     \
                "1:     " ld "  %0, %2          # __cmpxchg_asm \n"     \
                "       bne     %0, %z3, 2f                     \n"     \
                "       .set    pop                             \n"     \
                "       move    $1, %z4                         \n"     \
                "       .set    "MIPS_ISA_ARCH_LEVEL"           \n"     \
                "       " st "  $1, %1                          \n"     \
                "\t" __scbeqz " $1, 1b                          \n"     \
                "       .set    pop                             \n"     \
                "2:                                             \n"     \
                : "=&r" (__ret), "=" GCC_OFF_SMALL_ASM() (*m)           \
                : GCC_OFF_SMALL_ASM() (*m), "Jr" (old), "Jr" (new)              \
                : "memory");                                            \
        } else {                                                        \
                unsigned long __flags;                                  \
                                                                        \
                raw_local_irq_save(__flags);                            \
                __ret = *m;                                             \
                if (__ret == old)                                       \
                        *m = new;                                       \
                raw_local_irq_restore(__flags);                         \
        }                                                               \
                                                                        \
        __ret;                                                          \
})

extern unsigned long __cmpxchg_small(volatile void *ptr, unsigned long old,
                                     unsigned long new, unsigned int size);

static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
                                      unsigned long new, unsigned int size)
{
        switch (size) {
        case 1:
        case 2:
                return __cmpxchg_small(ptr, old, new, size);

        case 4:
                return __cmpxchg_asm("ll", "sc", (volatile u32 *)ptr,
                                     (u32)old, new);

        case 8:
                /* lld/scd are only available for MIPS64 */
                if (!IS_ENABLED(CONFIG_64BIT))
                        return __cmpxchg_called_with_bad_pointer();

                return __cmpxchg_asm("lld", "scd", (volatile u64 *)ptr,
                                     (u64)old, new);

        default:
                return __cmpxchg_called_with_bad_pointer();
        }
}

#define cmpxchg_local(ptr, old, new)                                    \
        ((__typeof__(*(ptr)))                                           \
                __cmpxchg((ptr),                                        \
                          (unsigned long)(__typeof__(*(ptr)))(old),     \
                          (unsigned long)(__typeof__(*(ptr)))(new),     \
                          sizeof(*(ptr))))

#define cmpxchg(ptr, old, new)                                          \
({                                                                      \
        __typeof__(*(ptr)) __res;                                       \
                                                                        \
        smp_mb__before_llsc();                                          \
        __res = cmpxchg_local((ptr), (old), (new));                     \
        smp_llsc_mb();                                                  \
                                                                        \
        __res;                                                          \
})

#ifdef CONFIG_64BIT
#define cmpxchg64_local(ptr, o, n)                                      \
  ({                                                                    \
        BUILD_BUG_ON(sizeof(*(ptr)) != 8);                              \
        cmpxchg_local((ptr), (o), (n));                                 \
  })

#define cmpxchg64(ptr, o, n)                                            \
  ({                                                                    \
        BUILD_BUG_ON(sizeof(*(ptr)) != 8);                              \
        cmpxchg((ptr), (o), (n));                                       \
  })
#else

# include <asm-generic/cmpxchg-local.h>
# define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))

# ifdef CONFIG_SMP

static inline unsigned long __cmpxchg64(volatile void *ptr,
                                        unsigned long long old,
                                        unsigned long long new)
{
        unsigned long long tmp, ret;
        unsigned long flags;

        /*
         * The assembly below has to combine 32 bit values into a 64 bit
         * register, and split 64 bit values from one register into two. If we
         * were to take an interrupt in the middle of this we'd only save the
         * least significant 32 bits of each register & probably clobber the
         * most significant 32 bits of the 64 bit values we're using. In order
         * to avoid this we must disable interrupts.
         */
        local_irq_save(flags);

        asm volatile(
        "       .set    push                            \n"
        "       .set    " MIPS_ISA_ARCH_LEVEL "         \n"
        /* Load 64 bits from ptr */
        "1:     lld     %L0, %3         # __cmpxchg64   \n"
        /*
         * Split the 64 bit value we loaded into the 2 registers that hold the
         * ret variable.
         */
        "       dsra    %M0, %L0, 32                    \n"
        "       sll     %L0, %L0, 0                     \n"
        /*
         * Compare ret against old, breaking out of the loop if they don't
         * match.
         */
        "       bne     %M0, %M4, 2f                    \n"
        "       bne     %L0, %L4, 2f                    \n"
        /*
         * Combine the 32 bit halves from the 2 registers that hold the new
         * variable into a single 64 bit register.
         */
#  if MIPS_ISA_REV >= 2
        "       move    %L1, %L5                        \n"
        "       dins    %L1, %M5, 32, 32                \n"
#  else
        "       dsll    %L1, %L5, 32                    \n"
        "       dsrl    %L1, %L1, 32                    \n"
        "       .set    noat                            \n"
        "       dsll    $at, %M5, 32                    \n"
        "       or      %L1, %L1, $at                   \n"
        "       .set    at                              \n"
#  endif
        /* Attempt to store new at ptr */
        "       scd     %L1, %2                         \n"
        /* If we failed, loop! */
        "\t" __scbeqz " %L1, 1b                         \n"
        "       .set    pop                             \n"
        "2:                                             \n"
        : "=&r"(ret),
          "=&r"(tmp),
          "=" GCC_OFF_SMALL_ASM() (*(unsigned long long *)ptr)
        : GCC_OFF_SMALL_ASM() (*(unsigned long long *)ptr),
          "r" (old),
          "r" (new)
        : "memory");

        local_irq_restore(flags);
        return ret;
}

#  define cmpxchg64(ptr, o, n) ({                                       \
        unsigned long long __old = (__typeof__(*(ptr)))(o);             \
        unsigned long long __new = (__typeof__(*(ptr)))(n);             \
        __typeof__(*(ptr)) __res;                                       \
                                                                        \
        /*                                                              \
         * We can only use cmpxchg64 if we know that the CPU supports   \
         * 64-bits, ie. lld & scd. Our call to __cmpxchg64_unsupported  \
         * will cause a build error unless cpu_has_64bits is a          \
         * compile-time constant 1.                                     \
         */                                                             \
        if (cpu_has_64bits && kernel_uses_llsc)                         \
                __res = __cmpxchg64((ptr), __old, __new);               \
        else                                                            \
                __res = __cmpxchg64_unsupported();                      \
                                                                        \
        __res;                                                          \
})

# else /* !CONFIG_SMP */
#  define cmpxchg64(ptr, o, n) cmpxchg64_local((ptr), (o), (n))
# endif /* !CONFIG_SMP */
#endif /* !CONFIG_64BIT */

#undef __scbeqz

#endif /* __ASM_CMPXCHG_H */