ARM: 5897/1: spinlock: don't use deprecated barriers on ARMv7

On ARMv7, the use of the cp15 operations for barriers is deprecated
in favour of the isb, dsb, and dmb instructions.  Change the locking
functions to use the appropriate type of dsb for the architecture
being built for.

Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/spinlock.h

@@ -5,6 +5,22 @@
 #error SMP not supported on pre-ARMv6 CPUs
 #endif
 
+static inline void dsb_sev(void)
+{
+#if __LINUX_ARM_ARCH__ >= 7
+	__asm__ __volatile__ (
+		"dsb\n"
+		"sev"
+	);
+#elif defined(CONFIG_CPU_32v6K)
+	__asm__ __volatile__ (
+		"mcr p15, 0, %0, c7, c10, 4\n"
+		"sev"
+		: : "r" (0)
+	);
+#endif
+}
+
 /*
  * ARMv6 Spin-locking.
  *
@@ -69,13 +85,11 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
 
 	__asm__ __volatile__(
 "	str	%1, [%0]\n"
-#ifdef CONFIG_CPU_32v6K
-"	mcr	p15, 0, %1, c7, c10, 4\n" /* DSB */
-"	sev"
-#endif
 	:
 	: "r" (&lock->lock), "r" (0)
 	: "cc");
+
+	dsb_sev();
 }
 
 /*
@@ -132,13 +146,11 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
 
 	__asm__ __volatile__(
 	"str	%1, [%0]\n"
-#ifdef CONFIG_CPU_32v6K
-"	mcr	p15, 0, %1, c7, c10, 4\n" /* DSB */
-"	sev\n"
-#endif
 	:
 	: "r" (&rw->lock), "r" (0)
 	: "cc");
+
+	dsb_sev();
 }
 
 /* write_can_lock - would write_trylock() succeed? */
@@ -188,14 +200,12 @@ static inline void arch_read_unlock(arch_rwlock_t *rw)
 "	strex	%1, %0, [%2]\n"
 "	teq	%1, #0\n"
 "	bne	1b"
-#ifdef CONFIG_CPU_32v6K
-"\n	cmp	%0, #0\n"
-"	mcreq   p15, 0, %0, c7, c10, 4\n"
-"	seveq"
-#endif
 	: "=&r" (tmp), "=&r" (tmp2)
 	: "r" (&rw->lock)
 	: "cc");
+
+	if (tmp == 0)
+		dsb_sev();
 }
 
 static inline int arch_read_trylock(arch_rwlock_t *rw)