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Diffstat (limited to 'arch/mips/include/asm/cmpxchg.h')
-rw-r--r--arch/mips/include/asm/cmpxchg.h104
1 files changed, 98 insertions, 6 deletions
diff --git a/arch/mips/include/asm/cmpxchg.h b/arch/mips/include/asm/cmpxchg.h
index 638de0c25249..f345a873742d 100644
--- a/arch/mips/include/asm/cmpxchg.h
+++ b/arch/mips/include/asm/cmpxchg.h
@@ -36,6 +36,8 @@
*/
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");
@@ -204,12 +206,102 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
cmpxchg((ptr), (o), (n)); \
})
#else
-#include <asm-generic/cmpxchg-local.h>
-#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
-#ifndef CONFIG_SMP
-#define cmpxchg64(ptr, o, n) cmpxchg64_local((ptr), (o), (n))
-#endif
-#endif
+
+# 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