[PATCH v2 10/23] openrisc: add spinlock implementation

[Stafford Horne]

From: Stefan Kristiansson <stefan.kristiansson@xxxxxxxxxxxxx>

Heavily based on the ARM implementation, this adds
ticket spinlock support for OpenRISC.

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@xxxxxxxxxxxxx>
[shorne@xxxxxxxxx: fix tabs vs space checkpatch warning]
Signed-off-by: Stafford Horne <shorne@xxxxxxxxx>
---
 arch/openrisc/include/asm/spinlock.h       | 232 ++++++++++++++++++++++++++++-
 arch/openrisc/include/asm/spinlock_types.h |  28 ++++
 2 files changed, 259 insertions(+), 1 deletion(-)
 create mode 100644 arch/openrisc/include/asm/spinlock_types.h

diff --git a/arch/openrisc/include/asm/spinlock.h b/arch/openrisc/include/asm/spinlock.h
index fd00a3a..adf62a6 100644
--- a/arch/openrisc/include/asm/spinlock.h
+++ b/arch/openrisc/include/asm/spinlock.h
@@ -9,6 +9,9 @@
  * Copyright (C) 2003 Matjaz Breskvar <phoenix@xxxxxxxxx>
  * Copyright (C) 2010-2011 Jonas Bonn <jonas@xxxxxxxxxxxx>
  * et al.
+ * Copyright (C) 2014 Stefan Kristiansson <stefan.kristiansson@xxxxxxxxxxxxx>
+ *
+ * Ticket spinlocks, based on the ARM implementation.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -19,6 +22,233 @@
 #ifndef __ASM_OPENRISC_SPINLOCK_H
 #define __ASM_OPENRISC_SPINLOCK_H
 
-#error "or32 doesn't do SMP yet"
+#include <asm/spinlock_types.h>
+
+#define arch_spin_unlock_wait(lock) \
+	do { while (arch_spin_is_locked(lock)) cpu_relax(); } while (0)
+
+#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
+
+static inline void arch_spin_lock(arch_spinlock_t *lock)
+{
+	u32 newval;
+	arch_spinlock_t lockval;
+
+	__asm__ __volatile__(
+		"1:	l.lwa	%0, 0(%2)	\n"
+		"	l.add	%1, %0, %3	\n"
+		"	l.swa	0(%2), %1	\n"
+		"	l.bnf	1b		\n"
+		"	 l.nop			\n"
+		: "=&r" (lockval), "=&r" (newval)
+		: "r" (&lock->slock), "r" (1 << TICKET_SHIFT)
+		: "cc", "memory");
+
+	while (lockval.tickets.next != lockval.tickets.owner)
+		lockval.tickets.owner = ACCESS_ONCE(lock->tickets.owner);
+
+	smp_mb();
+}
+
+static inline int arch_spin_trylock(arch_spinlock_t *lock)
+{
+	unsigned long contended, tmp;
+	u32 slock;
+
+	/* contended = (lock->tickets.owner != lock->tickets.next) */
+	__asm__ __volatile__(
+		"1:	l.lwa	%0, 0(%3)	\n"
+		"	l.srli	%1, %0, 16	\n"
+		"	l.andi	%2, %0, 0xffff	\n"
+		"	l.sfeq	%1, %2		\n"
+		"	l.bnf	1f		\n"
+		"	 l.ori	%1, r0, 1	\n"
+		"	l.add	%0, %0, %4	\n"
+		"	l.swa	0(%3), %0	\n"
+		"	l.bnf	1b		\n"
+		"	 l.ori	%1, r0, 0	\n"
+		"1:				\n"
+		: "=&r" (slock), "=&r" (contended), "=&r" (tmp)
+		: "r" (&lock->slock), "r" (1 << TICKET_SHIFT)
+		: "cc", "memory");
+
+	if (!contended) {
+		smp_mb();
+		return 1;
+	} else {
+		return 0;
+	}
+}
+
+static inline void arch_spin_unlock(arch_spinlock_t *lock)
+{
+	smp_mb();
+	lock->tickets.owner++;
+}
+
+static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
+{
+	return lock.tickets.owner == lock.tickets.next;
+}
+
+static inline int arch_spin_is_locked(arch_spinlock_t *lock)
+{
+	return !arch_spin_value_unlocked(ACCESS_ONCE(*lock));
+}
+
+static inline int arch_spin_is_contended(arch_spinlock_t *lock)
+{
+	struct __raw_tickets tickets = ACCESS_ONCE(lock->tickets);
+
+	return (tickets.next - tickets.owner) > 1;
+}
+#define arch_spin_is_contended	arch_spin_is_contended
+
+/*
+ * RWLOCKS
+ *
+ *
+ * Write locks are easy - we just set bit 31.  When unlocking, we can
+ * just write zero since the lock is exclusively held.
+ */
+
+static inline void arch_write_lock(arch_rwlock_t *rw)
+{
+	unsigned long tmp;
+
+	__asm__ __volatile__(
+		"1:	l.lwa	%0, 0(%1)	\n"
+		"	l.sfeqi	%0, 0		\n"
+		"	l.bnf	1f		\n"
+		"	 l.nop			\n"
+		"	l.swa	0(%1), %2	\n"
+		"	l.bnf	1b		\n"
+		"	 l.nop			\n"
+		"1:				\n"
+		: "=&r" (tmp)
+		: "r" (&rw->lock), "r" (0x80000000)
+		: "cc", "memory");
+
+	smp_mb();
+}
+
+static inline int arch_write_trylock(arch_rwlock_t *rw)
+{
+	unsigned long contended;
+
+	__asm__ __volatile__(
+		"1:	l.lwa	%0, 0(%1)	\n"
+		"	l.sfeqi	%0, 0		\n"
+		"	l.bnf	1f		\n"
+		"	 l.nop			\n"
+		"	l.swa	 0(%1), %2	\n"
+		"	l.bnf	1b		\n"
+		"	 l.nop			\n"
+		"1:				\n"
+		: "=&r" (contended)
+		: "r" (&rw->lock), "r" (0x80000000)
+		: "cc", "memory");
+
+	if (!contended) {
+		smp_mb();
+		return 1;
+	} else {
+		return 0;
+	}
+}
+
+static inline void arch_write_unlock(arch_rwlock_t *rw)
+{
+	smp_mb();
+	rw->lock = 0;
+}
+
+/* write_can_lock - would write_trylock() succeed? */
+#define arch_write_can_lock(x)		(ACCESS_ONCE((x)->lock) == 0)
+
+/*
+ * Read locks are a bit more hairy:
+ *  - Exclusively load the lock value.
+ *  - Increment it.
+ *  - Store new lock value if positive, and we still own this location.
+ *    If the value is negative, we've already failed.
+ *  - If we failed to store the value, we want a negative result.
+ *  - If we failed, try again.
+ * Unlocking is similarly hairy.  We may have multiple read locks
+ * currently active.  However, we know we won't have any write
+ * locks.
+ */
+static inline void arch_read_lock(arch_rwlock_t *rw)
+{
+	unsigned long tmp;
+
+	__asm__ __volatile__(
+		"1:	l.lwa		%0, 0(%1)	\n"
+		"	l.sfltsi	%0, -1		\n"
+		"	l.bf		1b		\n"
+		"	 l.addi		%0, %0, 1	\n"
+		"	l.swa		0(%1), %0	\n"
+		"	l.bnf		1b		\n"
+		"	 l.nop				\n"
+		: "=&r" (tmp)
+		: "r" (&rw->lock)
+		: "cc", "memory");
+
+	smp_mb();
+}
+
+static inline void arch_read_unlock(arch_rwlock_t *rw)
+{
+	unsigned long tmp;
+
+	smp_mb();
+
+	__asm__ __volatile__(
+		"1:	l.lwa	%0, 0(%1)	\n"
+		"	l.addi	%0, %0, -1	\n"
+		"	l.swa	0(%1), %0	\n"
+		"	l.bnf	1b		\n"
+		"	 l.nop			\n"
+		: "=&r" (tmp)
+		: "r" (&rw->lock)
+		: "cc", "memory");
+
+}
+
+static inline int arch_read_trylock(arch_rwlock_t *rw)
+{
+	unsigned long contended;
+
+	__asm__ __volatile__(
+		"1:	l.lwa		%0, 0(%1)	\n"
+		"	l.sfltsi	%0, -1		\n"
+		"	l.bf		1f		\n"
+		"	 l.addi		%0, %0, 1	\n"
+		"	l.swa		0(%1), %0	\n"
+		"	l.bnf		1b		\n"
+		"	 l.nop				\n"
+		"1:					\n"
+		: "=&r" (contended)
+		: "r" (&rw->lock)
+		: "cc", "memory");
+
+	/* If the lock is negative, then it is already held for write. */
+	if (contended < 0x80000000) {
+		smp_mb();
+		return 1;
+	} else {
+		return 0;
+	}
+}
+
+/* read_can_lock - would read_trylock() succeed? */
+#define arch_read_can_lock(x)		(ACCESS_ONCE((x)->lock) < 0x80000000)
+
+#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
+#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
+
+#define arch_spin_relax(lock)	cpu_relax()
+#define arch_read_relax(lock)	cpu_relax()
+#define arch_write_relax(lock)	cpu_relax()
 
 #endif
diff --git a/arch/openrisc/include/asm/spinlock_types.h b/arch/openrisc/include/asm/spinlock_types.h
new file mode 100644
index 0000000..bc0de48
--- /dev/null
+++ b/arch/openrisc/include/asm/spinlock_types.h
@@ -0,0 +1,28 @@
+#ifndef __ASM_SPINLOCK_TYPES_H
+#define __ASM_SPINLOCK_TYPES_H
+
+#ifndef __LINUX_SPINLOCK_TYPES_H
+# error "please don't include this file directly"
+#endif
+
+#define TICKET_SHIFT	16
+
+typedef struct {
+	union {
+		u32 slock;
+		struct __raw_tickets {
+			u16 next;
+			u16 owner;
+		} tickets;
+	};
+} arch_spinlock_t;
+
+#define __ARCH_SPIN_LOCK_UNLOCKED	{ { 0 } }
+
+typedef struct {
+	u32 lock;
+} arch_rwlock_t;
+
+#define __ARCH_RW_LOCK_UNLOCKED		{ 0 }
+
+#endif
-- 
2.9.3