1/*
2 * Copyright 2011 Tilera Corporation. All Rights Reserved.
3 *
4 *   This program is free software; you can redistribute it and/or
5 *   modify it under the terms of the GNU General Public License
6 *   as published by the Free Software Foundation, version 2.
7 *
8 *   This program is distributed in the hope that it will be useful, but
9 *   WITHOUT ANY WARRANTY; without even the implied warranty of
10 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
11 *   NON INFRINGEMENT.  See the GNU General Public License for
12 *   more details.
13 *
14 * 64-bit SMP ticket spinlocks, allowing only a single CPU anywhere
15 * (the type definitions are in asm/spinlock_types.h)
16 */
17
18#ifndef _ASM_TILE_SPINLOCK_64_H
19#define _ASM_TILE_SPINLOCK_64_H
20
21/* Shifts and masks for the various fields in "lock". */
22#define __ARCH_SPIN_CURRENT_SHIFT	17
23#define __ARCH_SPIN_NEXT_MASK		0x7fff
24#define __ARCH_SPIN_NEXT_OVERFLOW	0x8000
25
26/*
27 * Return the "current" portion of a ticket lock value,
28 * i.e. the number that currently owns the lock.
29 */
30static inline u32 arch_spin_current(u32 val)
31{
32	return val >> __ARCH_SPIN_CURRENT_SHIFT;
33}
34
35/*
36 * Return the "next" portion of a ticket lock value,
37 * i.e. the number that the next task to try to acquire the lock will get.
38 */
39static inline u32 arch_spin_next(u32 val)
40{
41	return val & __ARCH_SPIN_NEXT_MASK;
42}
43
44/* The lock is locked if a task would have to wait to get it. */
45static inline int arch_spin_is_locked(arch_spinlock_t *lock)
46{
47	u32 val = lock->lock;
48	return arch_spin_current(val) != arch_spin_next(val);
49}
50
51/* Bump the current ticket so the next task owns the lock. */
52static inline void arch_spin_unlock(arch_spinlock_t *lock)
53{
54	wmb();  /* guarantee anything modified under the lock is visible */
55	__insn_fetchadd4(&lock->lock, 1U << __ARCH_SPIN_CURRENT_SHIFT);
56}
57
58void arch_spin_unlock_wait(arch_spinlock_t *lock);
59
60void arch_spin_lock_slow(arch_spinlock_t *lock, u32 val);
61
62/* Grab the "next" ticket number and bump it atomically.
63 * If the current ticket is not ours, go to the slow path.
64 * We also take the slow path if the "next" value overflows.
65 */
66static inline void arch_spin_lock(arch_spinlock_t *lock)
67{
68	u32 val = __insn_fetchadd4(&lock->lock, 1);
69	u32 ticket = val & (__ARCH_SPIN_NEXT_MASK | __ARCH_SPIN_NEXT_OVERFLOW);
70	if (unlikely(arch_spin_current(val) != ticket))
71		arch_spin_lock_slow(lock, ticket);
72}
73
74/* Try to get the lock, and return whether we succeeded. */
75int arch_spin_trylock(arch_spinlock_t *lock);
76
77/* We cannot take an interrupt after getting a ticket, so don't enable them. */
78#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
79
80/*
81 * Read-write spinlocks, allowing multiple readers
82 * but only one writer.
83 *
84 * We use fetchadd() for readers, and fetchor() with the sign bit
85 * for writers.
86 */
87
88#define __WRITE_LOCK_BIT (1 << 31)
89
90static inline int arch_write_val_locked(int val)
91{
92	return val < 0;  /* Optimize "val & __WRITE_LOCK_BIT". */
93}
94
95/**
96 * read_can_lock - would read_trylock() succeed?
97 * @lock: the rwlock in question.
98 */
99static inline int arch_read_can_lock(arch_rwlock_t *rw)
100{
101	return !arch_write_val_locked(rw->lock);
102}
103
104/**
105 * write_can_lock - would write_trylock() succeed?
106 * @lock: the rwlock in question.
107 */
108static inline int arch_write_can_lock(arch_rwlock_t *rw)
109{
110	return rw->lock == 0;
111}
112
113extern void __read_lock_failed(arch_rwlock_t *rw);
114
115static inline void arch_read_lock(arch_rwlock_t *rw)
116{
117	u32 val = __insn_fetchaddgez4(&rw->lock, 1);
118	if (unlikely(arch_write_val_locked(val)))
119		__read_lock_failed(rw);
120}
121
122extern void __write_lock_failed(arch_rwlock_t *rw, u32 val);
123
124static inline void arch_write_lock(arch_rwlock_t *rw)
125{
126	u32 val = __insn_fetchor4(&rw->lock, __WRITE_LOCK_BIT);
127	if (unlikely(val != 0))
128		__write_lock_failed(rw, val);
129}
130
131static inline void arch_read_unlock(arch_rwlock_t *rw)
132{
133	__insn_mf();
134	__insn_fetchadd4(&rw->lock, -1);
135}
136
137static inline void arch_write_unlock(arch_rwlock_t *rw)
138{
139	__insn_mf();
140	__insn_exch4(&rw->lock, 0);  /* Avoid waiting in the write buffer. */
141}
142
143static inline int arch_read_trylock(arch_rwlock_t *rw)
144{
145	return !arch_write_val_locked(__insn_fetchaddgez4(&rw->lock, 1));
146}
147
148static inline int arch_write_trylock(arch_rwlock_t *rw)
149{
150	u32 val = __insn_fetchor4(&rw->lock, __WRITE_LOCK_BIT);
151	if (likely(val == 0))
152		return 1;
153	if (!arch_write_val_locked(val))
154		__insn_fetchand4(&rw->lock, ~__WRITE_LOCK_BIT);
155	return 0;
156}
157
158#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
159#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
160
161#endif /* _ASM_TILE_SPINLOCK_64_H */
162