metag: Atomics, locks and bitops

Add header files to implement Meta hardware thread locks (used by some
other atomic operations), atomics, spinlocks, and bitops.

There are 2 main types of atomic primitives for metag (in addition to
IRQs off on UP):
 - LOCK instructions provide locking between hardware threads.
 - LNKGET/LNKSET instructions provide load-linked/store-conditional
   operations allowing for lighter weight atomics on Meta2

LOCK instructions allow for hardware threads to acquire voluntary or
exclusive hardware thread locks:
 - LOCK0 releases exclusive and voluntary lock from the running hardware
   thread.
 - LOCK1 acquires the voluntary hardware lock, blocking until it becomes
   available.
 - LOCK2 implies LOCK1, and additionally acquires the exclusive hardware
   lock, blocking all other hardware threads from executing.

Signed-off-by: James Hogan <james.hogan@imgtec.com>

1 files changed, 42 insertions, 0 deletions

diff --git a/arch/metag/include/asm/cmpxchg_irq.h b/arch/metag/include/asm/cmpxchg_irq.h
new file mode 100644
index 000000000000..649573168b05
--- /dev/null
+++ b/arch/metag/include/asm/cmpxchg_irq.h
@@ -0,0 +1,42 @@
+#ifndef __ASM_METAG_CMPXCHG_IRQ_H
+#define __ASM_METAG_CMPXCHG_IRQ_H
+
+#include <linux/irqflags.h>
+
+static inline unsigned long xchg_u32(volatile u32 *m, unsigned long val)
+{
+	unsigned long flags, retval;
+
+	local_irq_save(flags);
+	retval = *m;
+	*m = val;
+	local_irq_restore(flags);
+	return retval;
+}
+
+static inline unsigned long xchg_u8(volatile u8 *m, unsigned long val)
+{
+	unsigned long flags, retval;
+
+	local_irq_save(flags);
+	retval = *m;
+	*m = val & 0xff;
+	local_irq_restore(flags);
+	return retval;
+}
+
+static inline unsigned long __cmpxchg_u32(volatile int *m, unsigned long old,
+					  unsigned long new)
+{
+	__u32 retval;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	retval = *m;
+	if (retval == old)
+		*m = new;
+	local_irq_restore(flags);       /* implies memory barrier  */
+	return retval;
+}
+
+#endif /* __ASM_METAG_CMPXCHG_IRQ_H */