1 files changed, 227 insertions, 0 deletions
diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h
new file mode 100644
index 000000000..3ea4112c8
--- /dev/null
+++ b/arch/arc/include/asm/cmpxchg.h
@@ -0,0 +1,227 @@
+/*
+ * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __ASM_ARC_CMPXCHG_H
+#define __ASM_ARC_CMPXCHG_H
+
+#include <linux/types.h>
+
+#include <asm/barrier.h>
+#include <asm/smp.h>
+
+#ifdef CONFIG_ARC_HAS_LLSC
+
+static inline unsigned long
+__cmpxchg(volatile void *ptr, unsigned long expected, unsigned long new)
+{
+	unsigned long prev;
+
+	/*
+	 * Explicit full memory barrier needed before/after as
+	 * LLOCK/SCOND thmeselves don't provide any such semantics
+	 */
+	smp_mb();
+
+	__asm__ __volatile__(
+	"1:	llock   %0, [%1]	\n"
+	"	brne    %0, %2, 2f	\n"
+	"	scond   %3, [%1]	\n"
+	"	bnz     1b		\n"
+	"2:				\n"
+	: "=&r"(prev)	/* Early clobber, to prevent reg reuse */
+	: "r"(ptr),	/* Not "m": llock only supports reg direct addr mode */
+	  "ir"(expected),
+	  "r"(new)	/* can't be "ir". scond can't take LIMM for "b" */
+	: "cc", "memory"); /* so that gcc knows memory is being written here */
+
+	smp_mb();
+
+	return prev;
+}
+
+#elif !defined(CONFIG_ARC_PLAT_EZNPS)
+
+static inline unsigned long
+__cmpxchg(volatile void *ptr, unsigned long expected, unsigned long new)
+{
+	unsigned long flags;
+	int prev;
+	volatile unsigned long *p = ptr;
+
+	/*
+	 * spin lock/unlock provide the needed smp_mb() before/after
+	 */
+	atomic_ops_lock(flags);
+	prev = *p;
+	if (prev == expected)
+		*p = new;
+	atomic_ops_unlock(flags);
+	return prev;
+}
+
+#else /* CONFIG_ARC_PLAT_EZNPS */
+
+static inline unsigned long
+__cmpxchg(volatile void *ptr, unsigned long expected, unsigned long new)
+{
+	/*
+	 * Explicit full memory barrier needed before/after
+	 */
+	smp_mb();
+
+	write_aux_reg(CTOP_AUX_GPA1, expected);
+
+	__asm__ __volatile__(
+	"	mov r2, %0\n"
+	"	mov r3, %1\n"
+	"	.word %2\n"
+	"	mov %0, r2"
+	: "+r"(new)
+	: "r"(ptr), "i"(CTOP_INST_EXC_DI_R2_R2_R3)
+	: "r2", "r3", "memory");
+
+	smp_mb();
+
+	return new;
+}
+
+#endif /* CONFIG_ARC_HAS_LLSC */
+
+#define cmpxchg(ptr, o, n) ({				\
+	(typeof(*(ptr)))__cmpxchg((ptr),		\
+				  (unsigned long)(o),	\
+				  (unsigned long)(n));	\
+})
+
+/*
+ * atomic_cmpxchg is same as cmpxchg
+ *   LLSC: only different in data-type, semantics are exactly same
+ *  !LLSC: cmpxchg() has to use an external lock atomic_ops_lock to guarantee
+ *         semantics, and this lock also happens to be used by atomic_*()
+ */
+#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
+
+
+#ifndef CONFIG_ARC_PLAT_EZNPS
+
+/*
+ * xchg (reg with memory) based on "Native atomic" EX insn
+ */
+static inline unsigned long __xchg(unsigned long val, volatile void *ptr,
+				   int size)
+{
+	extern unsigned long __xchg_bad_pointer(void);
+
+	switch (size) {
+	case 4:
+		smp_mb();
+
+		__asm__ __volatile__(
+		"	ex  %0, [%1]	\n"
+		: "+r"(val)
+		: "r"(ptr)
+		: "memory");
+
+		smp_mb();
+
+		return val;
+	}
+	return __xchg_bad_pointer();
+}
+
+#define _xchg(ptr, with) ((typeof(*(ptr)))__xchg((unsigned long)(with), (ptr), \
+						 sizeof(*(ptr))))
+
+/*
+ * xchg() maps directly to ARC EX instruction which guarantees atomicity.
+ * However in !LLSC config, it also needs to be use @atomic_ops_lock spinlock
+ * due to a subtle reason:
+ *  - For !LLSC, cmpxchg() needs to use that lock (see above) and there is lot
+ *    of  kernel code which calls xchg()/cmpxchg() on same data (see llist.h)
+ *    Hence xchg() needs to follow same locking rules.
+ *
+ * Technically the lock is also needed for UP (boils down to irq save/restore)
+ * but we can cheat a bit since cmpxchg() atomic_ops_lock() would cause irqs to
+ * be disabled thus can't possibly be interrpted/preempted/clobbered by xchg()
+ * Other way around, xchg is one instruction anyways, so can't be interrupted
+ * as such
+ */
+
+#if !defined(CONFIG_ARC_HAS_LLSC) && defined(CONFIG_SMP)
+
+#define xchg(ptr, with)			\
+({					\
+	unsigned long flags;		\
+	typeof(*(ptr)) old_val;		\
+					\
+	atomic_ops_lock(flags);		\
+	old_val = _xchg(ptr, with);	\
+	atomic_ops_unlock(flags);	\
+	old_val;			\
+})
+
+#else
+
+#define xchg(ptr, with)  _xchg(ptr, with)
+
+#endif
+
+#else /* CONFIG_ARC_PLAT_EZNPS */
+
+static inline unsigned long __xchg(unsigned long val, volatile void *ptr,
+				   int size)
+{
+	extern unsigned long __xchg_bad_pointer(void);
+
+	switch (size) {
+	case 4:
+		/*
+		 * Explicit full memory barrier needed before/after
+		 */
+		smp_mb();
+
+		__asm__ __volatile__(
+		"	mov r2, %0\n"
+		"	mov r3, %1\n"
+		"	.word %2\n"
+		"	mov %0, r2\n"
+		: "+r"(val)
+		: "r"(ptr), "i"(CTOP_INST_XEX_DI_R2_R2_R3)
+		: "r2", "r3", "memory");
+
+		smp_mb();
+
+		return val;
+	}
+	return __xchg_bad_pointer();
+}
+
+#define xchg(ptr, with) ({				\
+	(typeof(*(ptr)))__xchg((unsigned long)(with),	\
+			       (ptr),			\
+			       sizeof(*(ptr)));		\
+})
+
+#endif /* CONFIG_ARC_PLAT_EZNPS */
+
+/*
+ * "atomic" variant of xchg()
+ * REQ: It needs to follow the same serialization rules as other atomic_xxx()
+ * Since xchg() doesn't always do that, it would seem that following defintion
+ * is incorrect. But here's the rationale:
+ *   SMP : Even xchg() takes the atomic_ops_lock, so OK.
+ *   LLSC: atomic_ops_lock are not relevant at all (even if SMP, since LLSC
+ *         is natively "SMP safe", no serialization required).
+ *   UP  : other atomics disable IRQ, so no way a difft ctxt atomic_xchg()
+ *         could clobber them. atomic_xchg() itself would be 1 insn, so it
+ *         can't be clobbered by others. Thus no serialization required when
+ *         atomic_xchg is involved.
+ */
+#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
+
+#endif