ARM: 7687/1: atomics: don't use exclusives for atomic64 read/set with LPAE

To ease page table updates with 64-bit descriptors, CPUs implementing
LPAE are required to implement ldrd/strd as atomic operations.

This patch uses these accessors instead of the exclusive variants when
performing atomic64_{read,set} on LPAE systems.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 24 insertions, 0 deletions

diff --git a/arch/arm/include/asm/atomic.h b/arch/arm/include/asm/atomic.h
index c79f61faa3a5..da1c77d39327 100644
--- a/arch/arm/include/asm/atomic.h
+++ b/arch/arm/include/asm/atomic.h
@@ -243,6 +243,29 @@ typedef struct {
 
 #define ATOMIC64_INIT(i) { (i) }
 
+#ifdef CONFIG_ARM_LPAE
+static inline u64 atomic64_read(const atomic64_t *v)
+{
+        u64 result;
+
+        __asm__ __volatile__("@ atomic64_read\n"
+"       ldrd    %0, %H0, [%1]"
+        : "=&r" (result)
+        : "r" (&v->counter), "Qo" (v->counter)
+        );
+
+        return result;
+}
+
+static inline void atomic64_set(atomic64_t *v, u64 i)
+{
+        __asm__ __volatile__("@ atomic64_set\n"
+"       strd    %2, %H2, [%1]"
+        : "=Qo" (v->counter)
+        : "r" (&v->counter), "r" (i)
+        );
+}
+#else
 static inline u64 atomic64_read(const atomic64_t *v)
 {
         u64 result;
@@ -269,6 +292,7 @@ static inline void atomic64_set(atomic64_t *v, u64 i)
         : "r" (&v->counter), "r" (i)
         : "cc");
 }
+#endif
 
 static inline void atomic64_add(u64 i, atomic64_t *v)
 {