From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
The generic atomic.h used cmpxchg to implement the atomic
operations, it will cause daul loop to reduce the forward
guarantee. The patch implement csky custom atomic operations with
ldex/stex instructions for the best performance.
Important reference comment by Rutland:
8e86f0b409a4 ("arm64: atomics: fix use of acquire + release for
full barrier semantics")
Link: https://lore.kernel.org/linux-riscv/CAJF2gTSAxpAi=LbAdu7jntZRUa=-dJwL0VfmDfBV5MHB=rcZ-w@xxxxxxxxxxxxxx/T/#m27a0f1342995deae49ce1d0e1f2683f8a181d6c3
Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
---
Changes in V2:
- Fixup use of acquire + release for barrier semantics by Rutland.
---
arch/csky/include/asm/atomic.h | 130 +++++++++++++++++++++++++++++++++
1 file changed, 130 insertions(+)
create mode 100644 arch/csky/include/asm/atomic.h
diff --git a/arch/csky/include/asm/atomic.h b/arch/csky/include/asm/atomic.h
new file mode 100644
index 000000000000..2e1a22f55ea1
--- /dev/null
+++ b/arch/csky/include/asm/atomic.h
@@ -0,0 +1,130 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __ASM_CSKY_ATOMIC_H
+#define __ASM_CSKY_ATOMIC_H
+
+#ifdef CONFIG_SMP
+# include <asm-generic/atomic64.h>
+
+#include <asm/cmpxchg.h>
+#include <asm/barrier.h>
+
+#define __atomic_acquire_fence() __smp_acquire_fence()
+
+#define __atomic_release_fence() __smp_release_fence()
+
+static __always_inline int arch_atomic_read(const atomic_t *v)
+{
+ return READ_ONCE(v->counter);
+}
+static __always_inline void arch_atomic_set(atomic_t *v, int i)
+{
+ WRITE_ONCE(v->counter, i);
+}
+
+#define ATOMIC_OP(op, asm_op, I) \
+static __always_inline \
+void arch_atomic_##op(int i, atomic_t *v) \
+{ \
+ unsigned long tmp; \
+ __asm__ __volatile__ ( \
+ "1: ldex.w %0, (%2) \n" \
+ " " #op " %0, %1 \n" \
+ " stex.w %0, (%2) \n" \
+ " bez %0, 1b \n" \
+ : "=&r" (tmp) \
+ : "r" (I), "r" (&v->counter) \
+ : "memory"); \
+}
+
+ATOMIC_OP(add, add, i)
+ATOMIC_OP(sub, add, -i)
+ATOMIC_OP(and, and, i)
+ATOMIC_OP( or, or, i)
+ATOMIC_OP(xor, xor, i)
+
+#undef ATOMIC_OP
+
+#define ATOMIC_FETCH_OP(op, asm_op, I) \
+static __always_inline \
+int arch_atomic_fetch_##op##_relaxed(int i, atomic_t *v) \
+{ \
+ register int ret, tmp; \
+ __asm__ __volatile__ ( \
+ "1: ldex.w %0, (%3) \n" \
+ " mov %1, %0 \n" \
+ " " #op " %0, %2 \n" \
+ " stex.w %0, (%3) \n" \
+ " bez %0, 1b \n" \
+ : "=&r" (tmp), "=&r" (ret) \
+ : "r" (I), "r"(&v->counter) \
+ : "memory"); \
+ return ret; \
+}
+
+#define ATOMIC_OP_RETURN(op, asm_op, c_op, I) \
+static __always_inline \
+int arch_atomic_##op##_return_relaxed(int i, atomic_t *v) \
+{ \
+ return arch_atomic_fetch_##op##_relaxed(i, v) c_op I; \
+}
+
+#define ATOMIC_OPS(op, asm_op, c_op, I) \
+ ATOMIC_FETCH_OP( op, asm_op, I) \
+ ATOMIC_OP_RETURN(op, asm_op, c_op, I)
+
+ATOMIC_OPS(add, add, +, i)
+ATOMIC_OPS(sub, add, +, -i)
+
+#define arch_atomic_fetch_add_relaxed arch_atomic_fetch_add_relaxed
+#define arch_atomic_fetch_sub_relaxed arch_atomic_fetch_sub_relaxed
+
+#define arch_atomic_add_return_relaxed arch_atomic_add_return_relaxed
+#define arch_atomic_sub_return_relaxed arch_atomic_sub_return_relaxed
+
+#undef ATOMIC_OPS
+#undef ATOMIC_OP_RETURN
+
+#define ATOMIC_OPS(op, asm_op, I) \
+ ATOMIC_FETCH_OP(op, asm_op, I)
+
+ATOMIC_OPS(and, and, i)
+ATOMIC_OPS( or, or, i)
+ATOMIC_OPS(xor, xor, i)
+
+#define arch_atomic_fetch_and_relaxed arch_atomic_fetch_and_relaxed
+#define arch_atomic_fetch_or_relaxed arch_atomic_fetch_or_relaxed
+#define arch_atomic_fetch_xor_relaxed arch_atomic_fetch_xor_relaxed
+
+#undef ATOMIC_OPS
+
+#undef ATOMIC_FETCH_OP
+
+#define ATOMIC_OP() \
+static __always_inline \
+int arch_atomic_xchg_relaxed(atomic_t *v, int n) \
+{ \
+ return __xchg_relaxed(n, &(v->counter), 4); \
+} \
+static __always_inline \
+int arch_atomic_cmpxchg_relaxed(atomic_t *v, int o, int n) \
+{ \
+ return __cmpxchg_relaxed(&(v->counter), o, n, 4); \
+}
+
+#define ATOMIC_OPS() \
+ ATOMIC_OP()
+
+ATOMIC_OPS()
+
+#define arch_atomic_xchg_relaxed arch_atomic_xchg_relaxed
+#define arch_atomic_cmpxchg_relaxed arch_atomic_cmpxchg_relaxed
+
+#undef ATOMIC_OPS
+#undef ATOMIC_OP
+
+#else
+# include <asm-generic/atomic.h>
+#endif
+
+#endif /* __ASM_CSKY_ATOMIC_H */
--
2.25.1
