powerpc: atomic: Implement acquire/release/relaxed variants for xchg

Implement xchg{,64}_relaxed and atomic{,64}_xchg_relaxed, based on these
_relaxed variants, release/acquire variants and fully ordered versions
can be built.

Note that xchg{,64}_relaxed and atomic_{,64}_xchg_relaxed are not
compiler barriers.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

2 files changed, 32 insertions, 39 deletions

diff --git a/arch/powerpc/include/asm/atomic.h b/arch/powerpc/include/asm/atomic.h
index a35c27709e05..a19fcdc318ee 100644
--- a/arch/powerpc/include/asm/atomic.h
+++ b/arch/powerpc/include/asm/atomic.h
@@ -177,6 +177,7 @@ static __inline__ int atomic_dec_return_relaxed(atomic_t *v)
 
 #define atomic_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))
 #define atomic_xchg(v, new) (xchg(&((v)->counter), new))
+#define atomic_xchg_relaxed(v, new) xchg_relaxed(&((v)->counter), (new))
 
 /**
  * __atomic_add_unless - add unless the number is a given value
@@ -444,6 +445,7 @@ static __inline__ long atomic64_dec_if_positive(atomic64_t *v)
 
 #define atomic64_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))
 #define atomic64_xchg(v, new) (xchg(&((v)->counter), new))
+#define atomic64_xchg_relaxed(v, new) xchg_relaxed(&((v)->counter), (new))
 
 /**
  * atomic64_add_unless - add unless the number is a given value
diff --git a/arch/powerpc/include/asm/cmpxchg.h b/arch/powerpc/include/asm/cmpxchg.h
index d1a8d93cccfd..17c7e14b37ca 100644
--- a/arch/powerpc/include/asm/cmpxchg.h
+++ b/arch/powerpc/include/asm/cmpxchg.h
@@ -9,21 +9,20 @@
 /*
  * Atomic exchange
  *
- * Changes the memory location '*ptr' to be val and returns
+ * Changes the memory location '*p' to be val and returns
  * the previous value stored there.
  */
+
 static __always_inline unsigned long
-__xchg_u32(volatile void *p, unsigned long val)
+__xchg_u32_local(volatile void *p, unsigned long val)
 {
         unsigned long prev;
 
         __asm__ __volatile__(
-        PPC_ATOMIC_ENTRY_BARRIER
 "1:     lwarx   %0,0,%2 \n"
         PPC405_ERR77(0,%2)
 "       stwcx.  %3,0,%2 \n\
         bne-    1b"
-        PPC_ATOMIC_EXIT_BARRIER
         : "=&r" (prev), "+m" (*(volatile unsigned int *)p)
         : "r" (p), "r" (val)
         : "cc", "memory");
@@ -31,42 +30,34 @@ __xchg_u32(volatile void *p, unsigned long val)
         return prev;
 }
 
-/*
- * Atomic exchange
- *
- * Changes the memory location '*ptr' to be val and returns
- * the previous value stored there.
- */
 static __always_inline unsigned long
-__xchg_u32_local(volatile void *p, unsigned long val)
+__xchg_u32_relaxed(u32 *p, unsigned long val)
 {
         unsigned long prev;
 
         __asm__ __volatile__(
-"1:     lwarx   %0,0,%2 \n"
-        PPC405_ERR77(0,%2)
-"       stwcx.  %3,0,%2 \n\
-        bne-    1b"
-        : "=&r" (prev), "+m" (*(volatile unsigned int *)p)
+"1:     lwarx   %0,0,%2\n"
+        PPC405_ERR77(0, %2)
+"       stwcx.  %3,0,%2\n"
+"       bne-    1b"
+        : "=&r" (prev), "+m" (*p)
         : "r" (p), "r" (val)
-        : "cc", "memory");
+        : "cc");
 
         return prev;
 }
 
 #ifdef CONFIG_PPC64
 static __always_inline unsigned long
-__xchg_u64(volatile void *p, unsigned long val)
+__xchg_u64_local(volatile void *p, unsigned long val)
 {
         unsigned long prev;
 
         __asm__ __volatile__(
-        PPC_ATOMIC_ENTRY_BARRIER
 "1:     ldarx   %0,0,%2 \n"
         PPC405_ERR77(0,%2)
 "       stdcx.  %3,0,%2 \n\
         bne-    1b"
-        PPC_ATOMIC_EXIT_BARRIER
         : "=&r" (prev), "+m" (*(volatile unsigned long *)p)
         : "r" (p), "r" (val)
         : "cc", "memory");
@@ -75,18 +66,18 @@ __xchg_u64(volatile void *p, unsigned long val)
 }
 
 static __always_inline unsigned long
-__xchg_u64_local(volatile void *p, unsigned long val)
+__xchg_u64_relaxed(u64 *p, unsigned long val)
 {
         unsigned long prev;
 
         __asm__ __volatile__(
-"1:     ldarx   %0,0,%2 \n"
-        PPC405_ERR77(0,%2)
-"       stdcx.  %3,0,%2 \n\
-        bne-    1b"
-        : "=&r" (prev), "+m" (*(volatile unsigned long *)p)
+"1:     ldarx   %0,0,%2\n"
+        PPC405_ERR77(0, %2)
+"       stdcx.  %3,0,%2\n"
+"       bne-    1b"
+        : "=&r" (prev), "+m" (*p)
         : "r" (p), "r" (val)
-        : "cc", "memory");
+        : "cc");
 
         return prev;
 }
@@ -99,14 +90,14 @@ __xchg_u64_local(volatile void *p, unsigned long val)
 extern void __xchg_called_with_bad_pointer(void);
 
 static __always_inline unsigned long
-__xchg(volatile void *ptr, unsigned long x, unsigned int size)
+__xchg_local(volatile void *ptr, unsigned long x, unsigned int size)
 {
         switch (size) {
         case 4:
-                return __xchg_u32(ptr, x);
+                return __xchg_u32_local(ptr, x);
 #ifdef CONFIG_PPC64
         case 8:
-                return __xchg_u64(ptr, x);
+                return __xchg_u64_local(ptr, x);
 #endif
         }
         __xchg_called_with_bad_pointer();
@@ -114,25 +105,19 @@ __xchg(volatile void *ptr, unsigned long x, unsigned int size)
 }
 
 static __always_inline unsigned long
-__xchg_local(volatile void *ptr, unsigned long x, unsigned int size)
+__xchg_relaxed(void *ptr, unsigned long x, unsigned int size)
 {
         switch (size) {
         case 4:
-                return __xchg_u32_local(ptr, x);
+                return __xchg_u32_relaxed(ptr, x);
 #ifdef CONFIG_PPC64
         case 8:
-                return __xchg_u64_local(ptr, x);
+                return __xchg_u64_relaxed(ptr, x);
 #endif
         }
         __xchg_called_with_bad_pointer();
         return x;
 }
-#define xchg(ptr,x)                                                          \
-  ({                                                                         \
-     __typeof__(*(ptr)) _x_ = (x);                                           \
-     (__typeof__(*(ptr))) __xchg((ptr), (unsigned long)_x_, sizeof(*(ptr))); \
-  })
-
 #define xchg_local(ptr,x)                                                    \
   ({                                                                         \
      __typeof__(*(ptr)) _x_ = (x);                                           \
@@ -140,6 +125,12 @@ __xchg_local(volatile void *ptr, unsigned long x, unsigned int size)
                 (unsigned long)_x_, sizeof(*(ptr)));                         \
   })
 
+#define xchg_relaxed(ptr, x)                                            \
+({                                                                      \
+        __typeof__(*(ptr)) _x_ = (x);                                   \
+        (__typeof__(*(ptr))) __xchg_relaxed((ptr),                      \
+                        (unsigned long)_x_, sizeof(*(ptr)));            \
+})
 /*
  * Compare and exchange - if *p == old, set it to new,
  * and return the old value of *p.