locking/atomic, arch/hexagon: Implement atomic_fetch_{add,sub,and,or,xor}()

Implement FETCH-OP atomic primitives, these are very similar to the
existing OP-RETURN primitives we already have, except they return the
value of the atomic variable _before_ modification.

This is especially useful for irreversible operations -- such as
bitops (because it becomes impossible to reconstruct the state prior
to modification).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-hexagon@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/hexagon/include/asm/atomic.h

@@ -110,7 +110,7 @@ static inline void atomic_##op(int i, atomic_t *v)			\
 	);								\
 }									\
 
-#define ATOMIC_OP_RETURN(op)							\
+#define ATOMIC_OP_RETURN(op)						\
 static inline int atomic_##op##_return(int i, atomic_t *v)		\
 {									\
 	int output;							\
@@ -127,16 +127,39 @@ static inline int atomic_##op##_return(int i, atomic_t *v)		\
 	return output;							\
 }
 
-#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_OP_RETURN(op)
+#define ATOMIC_FETCH_OP(op)						\
+static inline int atomic_fetch_##op(int i, atomic_t *v)			\
+{									\
+	int output, val;						\
+									\
+	__asm__ __volatile__ (						\
+		"1:	%0 = memw_locked(%2);\n"			\
+		"	%1 = "#op "(%0,%3);\n"				\
+		"	memw_locked(%2,P3)=%1;\n"			\
+		"	if !P3 jump 1b;\n"				\
+		: "=&r" (output), "=&r" (val)				\
+		: "r" (&v->counter), "r" (i)				\
+		: "memory", "p3"					\
+	);								\
+	return output;							\
+}
+
+#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_OP_RETURN(op) ATOMIC_FETCH_OP(op)
 
 ATOMIC_OPS(add)
 ATOMIC_OPS(sub)
 
-ATOMIC_OP(and)
-ATOMIC_OP(or)
-ATOMIC_OP(xor)
+#undef ATOMIC_OPS
+#define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_FETCH_OP(op)
+
+#define atomic_fetch_or atomic_fetch_or
+
+ATOMIC_OPS(and)
+ATOMIC_OPS(or)
+ATOMIC_OPS(xor)
 
 #undef ATOMIC_OPS
+#undef ATOMIC_FETCH_OP
 #undef ATOMIC_OP_RETURN
 #undef ATOMIC_OP