locking/atomic: atomic: simplify ifdeffery

Now that asm-generic/atomic.h is only used by architectures without any
architecture-specific atomic definitions, we know that there will be no
architecture-specific implementations to override, and can remove the
ifdeffery this has previously required, bringing it into line with
asm-generic/atomic64.h.

At the same time, we can implement atomic_add() and atomic_sub()
directly using ATOMIC_OP(), since we know architectures won't provide
atomic_add_return() or atomic_sub_return().

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210525140232.53872-9-mark.rutland@arm.com

include/asm-generic/atomic.h

@@ -93,65 +93,27 @@ static inline int atomic_fetch_##op(int i, atomic_t *v)			\
 
 #endif /* CONFIG_SMP */
 
-#ifndef atomic_add_return
 ATOMIC_OP_RETURN(add, +)
-#endif
-
-#ifndef atomic_sub_return
 ATOMIC_OP_RETURN(sub, -)
-#endif
 
-#ifndef atomic_fetch_add
 ATOMIC_FETCH_OP(add, +)
-#endif
-
-#ifndef atomic_fetch_sub
 ATOMIC_FETCH_OP(sub, -)
-#endif
-
-#ifndef atomic_fetch_and
 ATOMIC_FETCH_OP(and, &)
-#endif
-
-#ifndef atomic_fetch_or
 ATOMIC_FETCH_OP(or, |)
-#endif
-
-#ifndef atomic_fetch_xor
 ATOMIC_FETCH_OP(xor, ^)
-#endif
 
-#ifndef atomic_and
+ATOMIC_OP(add, +)
+ATOMIC_OP(sub, -)
 ATOMIC_OP(and, &)
-#endif
-
-#ifndef atomic_or
 ATOMIC_OP(or, |)
-#endif
-
-#ifndef atomic_xor
 ATOMIC_OP(xor, ^)
-#endif
 
 #undef ATOMIC_FETCH_OP
 #undef ATOMIC_OP_RETURN
 #undef ATOMIC_OP
 
-#ifndef atomic_read
-#define atomic_read(v)	READ_ONCE((v)->counter)
-#endif
-
-#define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
-
-static inline void atomic_add(int i, atomic_t *v)
-{
-	atomic_add_return(i, v);
-}
-
-static inline void atomic_sub(int i, atomic_t *v)
-{
-	atomic_sub_return(i, v);
-}
+#define atomic_read(v)			READ_ONCE((v)->counter)
+#define atomic_set(v, i)		WRITE_ONCE(((v)->counter), (i))
 
 #define atomic_xchg(ptr, v)		(xchg(&(ptr)->counter, (v)))
 #define atomic_cmpxchg(v, old, new)	(cmpxchg(&((v)->counter), (old), (new)))