Hexagon: Add locking types and functions

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+/*
+ * Spinlock support for the Hexagon architecture
+ *
+ * Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved.
+ *
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+#ifndef _ASM_SPINLOCK_H
+#define _ASM_SPINLOCK_H
+
+#include <asm/irqflags.h>
+
+/*
+ * This file is pulled in for SMP builds.
+ * Really need to check all the barrier stuff for "true" SMP
+ */
+
+/*
+ * Read locks:
+ * - load the lock value
+ * - increment it
+ * - if the lock value is still negative, go back and try again.
+ * - unsuccessful store is unsuccessful.  Go back and try again.  Loser.
+ * - successful store new lock value if positive -> lock acquired
+ */
+static inline void arch_read_lock(arch_rwlock_t *lock)
+{
+	__asm__ __volatile__(
+		"1:	R6 = memw_locked(%0);\n"
+		"	{ P3 = cmp.ge(R6,#0); R6 = add(R6,#1);}\n"
+		"	{ if !P3 jump 1b; }\n"
+		"	memw_locked(%0,P3) = R6;\n"
+		"	{ if !P3 jump 1b; }\n"
+		:
+		: "r" (&lock->lock)
+		: "memory", "r6", "p3"
+	);
+
+}
+
+static inline void arch_read_unlock(arch_rwlock_t *lock)
+{
+	__asm__ __volatile__(
+		"1:	R6 = memw_locked(%0);\n"
+		"	R6 = add(R6,#-1);\n"
+		"	memw_locked(%0,P3) = R6\n"
+		"	if !P3 jump 1b;\n"
+		:
+		: "r" (&lock->lock)
+		: "memory", "r6", "p3"
+	);
+
+}
+
+/*  I think this returns 0 on fail, 1 on success.  */
+static inline int arch_read_trylock(arch_rwlock_t *lock)
+{
+	int temp;
+	__asm__ __volatile__(
+		"	R6 = memw_locked(%1);\n"
+		"	{ %0 = #0; P3 = cmp.ge(R6,#0); R6 = add(R6,#1);}\n"
+		"	{ if !P3 jump 1f; }\n"
+		"	memw_locked(%1,P3) = R6;\n"
+		"	{ %0 = P3 }\n"
+		"1:\n"
+		: "=&r" (temp)
+		: "r" (&lock->lock)
+		: "memory", "r6", "p3"
+	);
+	return temp;
+}
+
+static inline int arch_read_can_lock(arch_rwlock_t *rwlock)
+{
+	return rwlock->lock == 0;
+}
+
+static inline int arch_write_can_lock(arch_rwlock_t *rwlock)
+{
+	return rwlock->lock == 0;
+}
+
+/*  Stuffs a -1 in the lock value?  */
+static inline void arch_write_lock(arch_rwlock_t *lock)
+{
+	__asm__ __volatile__(
+		"1:	R6 = memw_locked(%0)\n"
+		"	{ P3 = cmp.eq(R6,#0);  R6 = #-1;}\n"
+		"	{ if !P3 jump 1b; }\n"
+		"	memw_locked(%0,P3) = R6;\n"
+		"	{ if !P3 jump 1b; }\n"
+		:
+		: "r" (&lock->lock)
+		: "memory", "r6", "p3"
+	);
+}
+
+
+static inline int arch_write_trylock(arch_rwlock_t *lock)
+{
+	int temp;
+	__asm__ __volatile__(
+		"	R6 = memw_locked(%1)\n"
+		"	{ %0 = #0; P3 = cmp.eq(R6,#0);  R6 = #-1;}\n"
+		"	{ if !P3 jump 1f; }\n"
+		"	memw_locked(%1,P3) = R6;\n"
+		"	%0 = P3;\n"
+		"1:\n"
+		: "=&r" (temp)
+		: "r" (&lock->lock)
+		: "memory", "r6", "p3"
+	);
+	return temp;
+
+}
+
+static inline void arch_write_unlock(arch_rwlock_t *lock)
+{
+	smp_mb();
+	lock->lock = 0;
+}
+
+static inline void arch_spin_lock(arch_spinlock_t *lock)
+{
+	__asm__ __volatile__(
+		"1:	R6 = memw_locked(%0);\n"
+		"	P3 = cmp.eq(R6,#0);\n"
+		"	{ if !P3 jump 1b; R6 = #1; }\n"
+		"	memw_locked(%0,P3) = R6;\n"
+		"	{ if !P3 jump 1b; }\n"
+		:
+		: "r" (&lock->lock)
+		: "memory", "r6", "p3"
+	);
+
+}
+
+static inline void arch_spin_unlock(arch_spinlock_t *lock)
+{
+	smp_mb();
+	lock->lock = 0;
+}
+
+static inline unsigned int arch_spin_trylock(arch_spinlock_t *lock)
+{
+	int temp;
+	__asm__ __volatile__(
+		"	R6 = memw_locked(%1);\n"
+		"	P3 = cmp.eq(R6,#0);\n"
+		"	{ if !P3 jump 1f; R6 = #1; %0 = #0; }\n"
+		"	memw_locked(%1,P3) = R6;\n"
+		"	%0 = P3;\n"
+		"1:\n"
+		: "=&r" (temp)
+		: "r" (&lock->lock)
+		: "memory", "r6", "p3"
+	);
+	return temp;
+}
+
+/*
+ * SMP spinlocks are intended to allow only a single CPU at the lock
+ */
+#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
+#define arch_spin_unlock_wait(lock) \
+	do {while (arch_spin_is_locked(lock)) cpu_relax(); } while (0)
+#define arch_spin_is_locked(x) ((x)->lock != 0)
+
+#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
+#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
+
+#endif

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