arm64: implement spinlocks

We put this off, as it wasn't necessary without smp. Now it
is. Only need to do this for arm64, as we've already done it
already for arm.
Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

config/config-arm64.mak

@@ -9,6 +9,7 @@ kernel_offset = 0x80000
 
 cstart.o = $(TEST_DIR)/cstart64.o
 cflatobjs += lib/arm64/processor.o
+cflatobjs += lib/arm64/spinlock.o
 
 # arm64 specific tests
 tests =

lib/arm64/asm/spinlock.h

@@ -5,11 +5,7 @@ struct spinlock {
 	int v;
 };
 
-static inline void spin_lock(struct spinlock *lock __unused)
-{
-}
-static inline void spin_unlock(struct spinlock *lock __unused)
-{
-}
+extern void spin_lock(struct spinlock *lock);
+extern void spin_unlock(struct spinlock *lock);
 
 #endif /* _ASMARM64_SPINLOCK_H_ */

lib/arm64/spinlock.c

+/*
+ * spinlocks
+ *
+ * Copyright (C) 2015, Red Hat Inc, Andrew Jones <drjones@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.
+ */
+#include <asm/spinlock.h>
+#include <asm/barrier.h>
+#include <asm/mmu.h>
+
+void spin_lock(struct spinlock *lock)
+{
+	u32 val, fail;
+
+	smp_mb();
+
+	if (!mmu_enabled()) {
+		lock->v = 1;
+		return;
+	}
+
+	do {
+		asm volatile(
+		"1:	ldaxr	%w0, [%2]\n"
+		"	cbnz	%w0, 1b\n"
+		"	mov	%0, #1\n"
+		"	stxr	%w1, %w0, [%2]\n"
+		: "=&r" (val), "=&r" (fail)
+		: "r" (&lock->v)
+		: "cc" );
+	} while (fail);
+	smp_mb();
+}
+
+void spin_unlock(struct spinlock *lock)
+{
+	if (mmu_enabled())
+		asm volatile("stlrh wzr, [%0]" :: "r" (&lock->v));
+	else
+		lock->v = 0;
+	smp_mb();
+}