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/*
* 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) { \
loongson_llsc_mb(); \
__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) \
: __LLSC_CLOBBER); \
} 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 __always_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) { \
loongson_llsc_mb(); \
__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) \
: __LLSC_CLOBBER); \
loongson_llsc_mb(); \
} 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 __always_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);
loongson_llsc_mb();
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");
loongson_llsc_mb();
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) { \
smp_mb__before_llsc(); \
__res = __cmpxchg64((ptr), __old, __new); \
smp_llsc_mb(); \
} 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 */
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