/*
 * 1,2 and 4 byte cmpxchg and xchg implementations for OpenRISC.
 *
 * Copyright (C) 2014 Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
 * Copyright (C) 2017 Stafford Horne <shorne@gmail.com>
 *
 * This file is licensed under the terms of the GNU General Public License
 * version 2.  This program is licensed "as is" without any warranty of any
 * kind, whether express or implied.
 *
 * Note:
 * The portable implementations of 1 and 2 byte xchg and cmpxchg using a 4
 * byte cmpxchg is sourced heavily from the sh and mips implementations.
 */

#ifndef __ASM_OPENRISC_CMPXCHG_H
#define __ASM_OPENRISC_CMPXCHG_H

#include  <linux/bits.h>
#include  <linux/compiler.h>
#include  <linux/types.h>

#define __HAVE_ARCH_CMPXCHG 1

static inline unsigned long cmpxchg_u32(volatile void *ptr,
                unsigned long old, unsigned long new)
{
        __asm__ __volatile__(
                "1:     l.lwa %0, 0(%1)         \n"
                "       l.sfeq %0, %2           \n"
                "       l.bnf 2f                \n"
                "        l.nop                  \n"
                "       l.swa 0(%1), %3         \n"
                "       l.bnf 1b                \n"
                "        l.nop                  \n"
                "2:                             \n"
                : "=&r"(old)
                : "r"(ptr), "r"(old), "r"(new)
                : "cc", "memory");

        return old;
}

static inline unsigned long xchg_u32(volatile void *ptr,
                unsigned long val)
{
        __asm__ __volatile__(
                "1:     l.lwa %0, 0(%1)         \n"
                "       l.swa 0(%1), %2         \n"
                "       l.bnf 1b                \n"
                "        l.nop                  \n"
                : "=&r"(val)
                : "r"(ptr), "r"(val)
                : "cc", "memory");

        return val;
}

static inline u32 cmpxchg_small(volatile void *ptr, u32 old, u32 new,
                                int size)
{
        int off = (unsigned long)ptr % sizeof(u32);
        volatile u32 *p = ptr - off;
#ifdef __BIG_ENDIAN
        int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
#else
        int bitoff = off * BITS_PER_BYTE;
#endif
        u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
        u32 load32, old32, new32;
        u32 ret;

        load32 = READ_ONCE(*p);

        while (true) {
                ret = (load32 & bitmask) >> bitoff;
                if (old != ret)
                        return ret;

                old32 = (load32 & ~bitmask) | (old << bitoff);
                new32 = (load32 & ~bitmask) | (new << bitoff);

                /* Do 32 bit cmpxchg */
                load32 = cmpxchg_u32(p, old32, new32);
                if (load32 == old32)
                        return old;
        }
}

/* xchg */

static inline u32 xchg_small(volatile void *ptr, u32 x, int size)
{
        int off = (unsigned long)ptr % sizeof(u32);
        volatile u32 *p = ptr - off;
#ifdef __BIG_ENDIAN
        int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
#else
        int bitoff = off * BITS_PER_BYTE;
#endif
        u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
        u32 oldv, newv;
        u32 ret;

        do {
                oldv = READ_ONCE(*p);
                ret = (oldv & bitmask) >> bitoff;
                newv = (oldv & ~bitmask) | (x << bitoff);
        } while (cmpxchg_u32(p, oldv, newv) != oldv);

        return ret;
}

/*
 * This function doesn't exist, so you'll get a linker error
 * if something tries to do an invalid cmpxchg().
 */
extern unsigned long __cmpxchg_called_with_bad_pointer(void)
        __compiletime_error("Bad argument size for cmpxchg");

static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
                unsigned long new, int size)
{
        switch (size) {
        case 1:
        case 2:
                return cmpxchg_small(ptr, old, new, size);
        case 4:
                return cmpxchg_u32(ptr, old, new);
        default:
                return __cmpxchg_called_with_bad_pointer();
        }
}

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

/*
 * This function doesn't exist, so you'll get a linker error if
 * something tries to do an invalidly-sized xchg().
 */
extern unsigned long __xchg_called_with_bad_pointer(void)
        __compiletime_error("Bad argument size for xchg");

static inline unsigned long
__arch_xchg(volatile void *ptr, unsigned long with, int size)
{
        switch (size) {
        case 1:
        case 2:
                return xchg_small(ptr, with, size);
        case 4:
                return xchg_u32(ptr, with);
        default:
                return __xchg_called_with_bad_pointer();
        }
}

#define arch_xchg(ptr, with)                                            \
        ({                                                              \
                (__typeof__(*(ptr))) __arch_xchg((ptr),                 \
                                                 (unsigned long)(with), \
                                                 sizeof(*(ptr)));       \
        })

#endif /* __ASM_OPENRISC_CMPXCHG_H */