172 lines
4 KiB
C
172 lines
4 KiB
C
/*
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* 1,2 and 4 byte cmpxchg and xchg implementations for OpenRISC.
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*
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* Copyright (C) 2014 Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
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* Copyright (C) 2017 Stafford Horne <shorne@gmail.com>
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*
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* This file is licensed under the terms of the GNU General Public License
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* version 2. This program is licensed "as is" without any warranty of any
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* kind, whether express or implied.
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*
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* Note:
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* The portable implementations of 1 and 2 byte xchg and cmpxchg using a 4
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* byte cmpxchg is sourced heavily from the sh and mips implementations.
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*/
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#ifndef __ASM_OPENRISC_CMPXCHG_H
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#define __ASM_OPENRISC_CMPXCHG_H
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#include <linux/bits.h>
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#include <linux/compiler.h>
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#include <linux/types.h>
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#define __HAVE_ARCH_CMPXCHG 1
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static inline unsigned long cmpxchg_u32(volatile void *ptr,
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unsigned long old, unsigned long new)
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{
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__asm__ __volatile__(
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"1: l.lwa %0, 0(%1) \n"
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" l.sfeq %0, %2 \n"
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" l.bnf 2f \n"
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" l.nop \n"
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" l.swa 0(%1), %3 \n"
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" l.bnf 1b \n"
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" l.nop \n"
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"2: \n"
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: "=&r"(old)
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: "r"(ptr), "r"(old), "r"(new)
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: "cc", "memory");
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return old;
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}
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static inline unsigned long xchg_u32(volatile void *ptr,
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unsigned long val)
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{
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__asm__ __volatile__(
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"1: l.lwa %0, 0(%1) \n"
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" l.swa 0(%1), %2 \n"
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" l.bnf 1b \n"
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" l.nop \n"
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: "=&r"(val)
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: "r"(ptr), "r"(val)
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: "cc", "memory");
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return val;
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}
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static inline u32 cmpxchg_small(volatile void *ptr, u32 old, u32 new,
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int size)
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{
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int off = (unsigned long)ptr % sizeof(u32);
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volatile u32 *p = ptr - off;
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#ifdef __BIG_ENDIAN
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int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
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#else
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int bitoff = off * BITS_PER_BYTE;
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#endif
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u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
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u32 load32, old32, new32;
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u32 ret;
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load32 = READ_ONCE(*p);
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while (true) {
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ret = (load32 & bitmask) >> bitoff;
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if (old != ret)
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return ret;
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old32 = (load32 & ~bitmask) | (old << bitoff);
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new32 = (load32 & ~bitmask) | (new << bitoff);
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/* Do 32 bit cmpxchg */
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load32 = cmpxchg_u32(p, old32, new32);
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if (load32 == old32)
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return old;
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}
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}
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/* xchg */
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static inline u32 xchg_small(volatile void *ptr, u32 x, int size)
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{
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int off = (unsigned long)ptr % sizeof(u32);
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volatile u32 *p = ptr - off;
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#ifdef __BIG_ENDIAN
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int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
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#else
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int bitoff = off * BITS_PER_BYTE;
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#endif
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u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
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u32 oldv, newv;
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u32 ret;
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do {
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oldv = READ_ONCE(*p);
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ret = (oldv & bitmask) >> bitoff;
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newv = (oldv & ~bitmask) | (x << bitoff);
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} while (cmpxchg_u32(p, oldv, newv) != oldv);
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return ret;
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}
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/*
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* This function doesn't exist, so you'll get a linker error
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* if something tries to do an invalid cmpxchg().
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*/
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extern unsigned long __cmpxchg_called_with_bad_pointer(void)
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__compiletime_error("Bad argument size for cmpxchg");
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static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
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unsigned long new, int size)
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{
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switch (size) {
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case 1:
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case 2:
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return cmpxchg_small(ptr, old, new, size);
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case 4:
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return cmpxchg_u32(ptr, old, new);
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default:
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return __cmpxchg_called_with_bad_pointer();
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}
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}
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#define cmpxchg(ptr, o, n) \
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({ \
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(__typeof__(*(ptr))) __cmpxchg((ptr), \
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(unsigned long)(o), \
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(unsigned long)(n), \
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sizeof(*(ptr))); \
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})
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/*
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* This function doesn't exist, so you'll get a linker error if
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* something tries to do an invalidly-sized xchg().
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*/
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extern unsigned long __xchg_called_with_bad_pointer(void)
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__compiletime_error("Bad argument size for xchg");
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static inline unsigned long __xchg(volatile void *ptr, unsigned long with,
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int size)
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{
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switch (size) {
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case 1:
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case 2:
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return xchg_small(ptr, with, size);
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case 4:
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return xchg_u32(ptr, with);
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default:
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return __xchg_called_with_bad_pointer();
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}
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}
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#define xchg(ptr, with) \
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({ \
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(__typeof__(*(ptr))) __xchg((ptr), \
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(unsigned long)(with), \
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sizeof(*(ptr))); \
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})
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#endif /* __ASM_OPENRISC_CMPXCHG_H */
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