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Subject[PATCH v4 09/24] openrisc: add optimized atomic operations
Date
From: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>

Using the l.lwa and l.swa atomic instruction pair.
Most openrisc processor cores provide these instructions now. If the
instructions are not available emulation is provided.

Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
[shorne@gmail.com: remove OPENRISC_HAVE_INST_LWA_SWA config suggesed by
Alan Cox https://lkml.org/lkml/2014/7/23/666]
[shorne@gmail.com: expand to implement all ops suggested by Peter
Zijlstra https://lkml.org/lkml/2017/2/20/317]
Signed-off-by: Stafford Horne <shorne@gmail.com>
---
arch/openrisc/include/asm/Kbuild | 1 -
arch/openrisc/include/asm/atomic.h | 126 +++++++++++++++++++++++++++++++++++++
include/asm-generic/atomic.h | 2 +
3 files changed, 128 insertions(+), 1 deletion(-)
create mode 100644 arch/openrisc/include/asm/atomic.h

diff --git a/arch/openrisc/include/asm/Kbuild b/arch/openrisc/include/asm/Kbuild
index 15e6ed5..1cedd63 100644
--- a/arch/openrisc/include/asm/Kbuild
+++ b/arch/openrisc/include/asm/Kbuild
@@ -1,7 +1,6 @@

header-y += ucontext.h

-generic-y += atomic.h
generic-y += auxvec.h
generic-y += barrier.h
generic-y += bitsperlong.h
diff --git a/arch/openrisc/include/asm/atomic.h b/arch/openrisc/include/asm/atomic.h
new file mode 100644
index 0000000..146e166
--- /dev/null
+++ b/arch/openrisc/include/asm/atomic.h
@@ -0,0 +1,126 @@
+/*
+ * Copyright (C) 2014 Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
+ *
+ * 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.
+ */
+
+#ifndef __ASM_OPENRISC_ATOMIC_H
+#define __ASM_OPENRISC_ATOMIC_H
+
+#include <linux/types.h>
+
+/* Atomically perform op with v->counter and i */
+#define ATOMIC_OP(op) \
+static inline void atomic_##op(int i, atomic_t *v) \
+{ \
+ int tmp; \
+ \
+ __asm__ __volatile__( \
+ "1: l.lwa %0,0(%1) \n" \
+ " l." #op " %0,%0,%2 \n" \
+ " l.swa 0(%1),%0 \n" \
+ " l.bnf 1b \n" \
+ " l.nop \n" \
+ : "=&r"(tmp) \
+ : "r"(&v->counter), "r"(i) \
+ : "cc", "memory"); \
+}
+
+/* Atomically perform op with v->counter and i, return the result */
+#define ATOMIC_OP_RETURN(op) \
+static inline int atomic_##op##_return(int i, atomic_t *v) \
+{ \
+ int tmp; \
+ \
+ __asm__ __volatile__( \
+ "1: l.lwa %0,0(%1) \n" \
+ " l." #op " %0,%0,%2 \n" \
+ " l.swa 0(%1),%0 \n" \
+ " l.bnf 1b \n" \
+ " l.nop \n" \
+ : "=&r"(tmp) \
+ : "r"(&v->counter), "r"(i) \
+ : "cc", "memory"); \
+ \
+ return tmp; \
+}
+
+/* Atomically perform op with v->counter and i, return orig v->counter */
+#define ATOMIC_FETCH_OP(op) \
+static inline int atomic_fetch_##op(int i, atomic_t *v) \
+{ \
+ int tmp, old; \
+ \
+ __asm__ __volatile__( \
+ "1: l.lwa %0,0(%2) \n" \
+ " l." #op " %1,%0,%3 \n" \
+ " l.swa 0(%2),%1 \n" \
+ " l.bnf 1b \n" \
+ " l.nop \n" \
+ : "=&r"(old), "=&r"(tmp) \
+ : "r"(&v->counter), "r"(i) \
+ : "cc", "memory"); \
+ \
+ return old; \
+}
+
+ATOMIC_OP_RETURN(add)
+ATOMIC_OP_RETURN(sub)
+
+ATOMIC_FETCH_OP(add)
+ATOMIC_FETCH_OP(sub)
+ATOMIC_FETCH_OP(and)
+ATOMIC_FETCH_OP(or)
+ATOMIC_FETCH_OP(xor)
+
+ATOMIC_OP(and)
+ATOMIC_OP(or)
+ATOMIC_OP(xor)
+
+#undef ATOMIC_FETCH_OP
+#undef ATOMIC_OP_RETURN
+#undef ATOMIC_OP
+
+#define atomic_add_return atomic_add_return
+#define atomic_sub_return atomic_sub_return
+#define atomic_fetch_add atomic_fetch_add
+#define atomic_fetch_sub atomic_fetch_sub
+#define atomic_fetch_and atomic_fetch_and
+#define atomic_fetch_or atomic_fetch_or
+#define atomic_fetch_xor atomic_fetch_xor
+#define atomic_and atomic_and
+#define atomic_or atomic_or
+#define atomic_xor atomic_xor
+
+/*
+ * Atomically add a to v->counter as long as v is not already u.
+ * Returns the original value at v->counter.
+ *
+ * This is often used through atomic_inc_not_zero()
+ */
+static inline int __atomic_add_unless(atomic_t *v, int a, int u)
+{
+ int old, tmp;
+
+ __asm__ __volatile__(
+ "1: l.lwa %0, 0(%2) \n"
+ " l.sfeq %0, %4 \n"
+ " l.bf 2f \n"
+ " l.add %1, %0, %3 \n"
+ " l.swa 0(%2), %1 \n"
+ " l.bnf 1b \n"
+ " l.nop \n"
+ "2: \n"
+ : "=&r"(old), "=&r" (tmp)
+ : "r"(&v->counter), "r"(a), "r"(u)
+ : "cc", "memory");
+
+ return old;
+}
+#define __atomic_add_unless __atomic_add_unless
+
+#include <asm-generic/atomic.h>
+
+#endif /* __ASM_OPENRISC_ATOMIC_H */
diff --git a/include/asm-generic/atomic.h b/include/asm-generic/atomic.h
index 9ed8b98..3f38eb0 100644
--- a/include/asm-generic/atomic.h
+++ b/include/asm-generic/atomic.h
@@ -223,6 +223,7 @@ static inline void atomic_dec(atomic_t *v)
#define atomic_xchg(ptr, v) (xchg(&(ptr)->counter, (v)))
#define atomic_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), (old), (new)))

+#ifndef __atomic_add_unless
static inline int __atomic_add_unless(atomic_t *v, int a, int u)
{
int c, old;
@@ -231,5 +232,6 @@ static inline int __atomic_add_unless(atomic_t *v, int a, int u)
c = old;
return c;
}
+#endif

#endif /* __ASM_GENERIC_ATOMIC_H */
--
2.9.3
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