1 files changed, 135 insertions, 0 deletions
diff --git a/arch/riscv/include/asm/spinlock.h b/arch/riscv/include/asm/spinlock.h
new file mode 100644
index 000000000..f4f7fa1b7
--- /dev/null
+++ b/arch/riscv/include/asm/spinlock.h
@@ -0,0 +1,135 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2015 Regents of the University of California
+ * Copyright (C) 2017 SiFive
+ */
+
+#ifndef _ASM_RISCV_SPINLOCK_H
+#define _ASM_RISCV_SPINLOCK_H
+
+#include <linux/kernel.h>
+#include <asm/current.h>
+#include <asm/fence.h>
+
+/*
+ * Simple spin lock operations.  These provide no fairness guarantees.
+ */
+
+/* FIXME: Replace this with a ticket lock, like MIPS. */
+
+#define arch_spin_is_locked(x)	(READ_ONCE((x)->lock) != 0)
+
+static inline void arch_spin_unlock(arch_spinlock_t *lock)
+{
+	smp_store_release(&lock->lock, 0);
+}
+
+static inline int arch_spin_trylock(arch_spinlock_t *lock)
+{
+	int tmp = 1, busy;
+
+	__asm__ __volatile__ (
+		"	amoswap.w %0, %2, %1\n"
+		RISCV_ACQUIRE_BARRIER
+		: "=r" (busy), "+A" (lock->lock)
+		: "r" (tmp)
+		: "memory");
+
+	return !busy;
+}
+
+static inline void arch_spin_lock(arch_spinlock_t *lock)
+{
+	while (1) {
+		if (arch_spin_is_locked(lock))
+			continue;
+
+		if (arch_spin_trylock(lock))
+			break;
+	}
+}
+
+/***********************************************************/
+
+static inline void arch_read_lock(arch_rwlock_t *lock)
+{
+	int tmp;
+
+	__asm__ __volatile__(
+		"1:	lr.w	%1, %0\n"
+		"	bltz	%1, 1b\n"
+		"	addi	%1, %1, 1\n"
+		"	sc.w	%1, %1, %0\n"
+		"	bnez	%1, 1b\n"
+		RISCV_ACQUIRE_BARRIER
+		: "+A" (lock->lock), "=&r" (tmp)
+		:: "memory");
+}
+
+static inline void arch_write_lock(arch_rwlock_t *lock)
+{
+	int tmp;
+
+	__asm__ __volatile__(
+		"1:	lr.w	%1, %0\n"
+		"	bnez	%1, 1b\n"
+		"	li	%1, -1\n"
+		"	sc.w	%1, %1, %0\n"
+		"	bnez	%1, 1b\n"
+		RISCV_ACQUIRE_BARRIER
+		: "+A" (lock->lock), "=&r" (tmp)
+		:: "memory");
+}
+
+static inline int arch_read_trylock(arch_rwlock_t *lock)
+{
+	int busy;
+
+	__asm__ __volatile__(
+		"1:	lr.w	%1, %0\n"
+		"	bltz	%1, 1f\n"
+		"	addi	%1, %1, 1\n"
+		"	sc.w	%1, %1, %0\n"
+		"	bnez	%1, 1b\n"
+		RISCV_ACQUIRE_BARRIER
+		"1:\n"
+		: "+A" (lock->lock), "=&r" (busy)
+		:: "memory");
+
+	return !busy;
+}
+
+static inline int arch_write_trylock(arch_rwlock_t *lock)
+{
+	int busy;
+
+	__asm__ __volatile__(
+		"1:	lr.w	%1, %0\n"
+		"	bnez	%1, 1f\n"
+		"	li	%1, -1\n"
+		"	sc.w	%1, %1, %0\n"
+		"	bnez	%1, 1b\n"
+		RISCV_ACQUIRE_BARRIER
+		"1:\n"
+		: "+A" (lock->lock), "=&r" (busy)
+		:: "memory");
+
+	return !busy;
+}
+
+static inline void arch_read_unlock(arch_rwlock_t *lock)
+{
+	__asm__ __volatile__(
+		RISCV_RELEASE_BARRIER
+		"	amoadd.w x0, %1, %0\n"
+		: "+A" (lock->lock)
+		: "r" (-1)
+		: "memory");
+}
+
+static inline void arch_write_unlock(arch_rwlock_t *lock)
+{
+	smp_store_release(&lock->lock, 0);
+}
+
+#endif /* _ASM_RISCV_SPINLOCK_H */