summaryrefslogtreecommitdiffstats
path: root/arch/xtensa/include/asm/spinlock.h
blob: 3bb49681ee242803e13c1ef1eae81011a33a98b4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
/*
 * include/asm-xtensa/spinlock.h
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2001 - 2005 Tensilica Inc.
 */

#ifndef _XTENSA_SPINLOCK_H
#define _XTENSA_SPINLOCK_H

#include <asm/barrier.h>
#include <asm/processor.h>

/*
 * spinlock
 *
 * There is at most one owner of a spinlock.  There are not different
 * types of spinlock owners like there are for rwlocks (see below).
 *
 * When trying to obtain a spinlock, the function "spins" forever, or busy-
 * waits, until the lock is obtained.  When spinning, presumably some other
 * owner will soon give up the spinlock making it available to others.  Use
 * the trylock functions to avoid spinning forever.
 *
 * possible values:
 *
 *    0         nobody owns the spinlock
 *    1         somebody owns the spinlock
 */

#define arch_spin_is_locked(x) ((x)->slock != 0)

#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)

static inline void arch_spin_lock(arch_spinlock_t *lock)
{
	unsigned long tmp;

	__asm__ __volatile__(
			"       movi    %0, 0\n"
			"       wsr     %0, scompare1\n"
			"1:     movi    %0, 1\n"
			"       s32c1i  %0, %1, 0\n"
			"       bnez    %0, 1b\n"
			: "=&a" (tmp)
			: "a" (&lock->slock)
			: "memory");
}

/* Returns 1 if the lock is obtained, 0 otherwise. */

static inline int arch_spin_trylock(arch_spinlock_t *lock)
{
	unsigned long tmp;

	__asm__ __volatile__(
			"       movi    %0, 0\n"
			"       wsr     %0, scompare1\n"
			"       movi    %0, 1\n"
			"       s32c1i  %0, %1, 0\n"
			: "=&a" (tmp)
			: "a" (&lock->slock)
			: "memory");

	return tmp == 0 ? 1 : 0;
}

static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
	unsigned long tmp;

	__asm__ __volatile__(
			"       movi    %0, 0\n"
			"       s32ri   %0, %1, 0\n"
			: "=&a" (tmp)
			: "a" (&lock->slock)
			: "memory");
}

/*
 * rwlock
 *
 * Read-write locks are really a more flexible spinlock.  They allow
 * multiple readers but only one writer.  Write ownership is exclusive
 * (i.e., all other readers and writers are blocked from ownership while
 * there is a write owner).  These rwlocks are unfair to writers.  Writers
 * can be starved for an indefinite time by readers.
 *
 * possible values:
 *
 *   0          nobody owns the rwlock
 *  >0          one or more readers own the rwlock
 *                (the positive value is the actual number of readers)
 *  0x80000000  one writer owns the rwlock, no other writers, no readers
 */

#define arch_write_can_lock(x)  ((x)->lock == 0)

static inline void arch_write_lock(arch_rwlock_t *rw)
{
	unsigned long tmp;

	__asm__ __volatile__(
			"       movi    %0, 0\n"
			"       wsr     %0, scompare1\n"
			"1:     movi    %0, 1\n"
			"       slli    %0, %0, 31\n"
			"       s32c1i  %0, %1, 0\n"
			"       bnez    %0, 1b\n"
			: "=&a" (tmp)
			: "a" (&rw->lock)
			: "memory");
}

/* Returns 1 if the lock is obtained, 0 otherwise. */

static inline int arch_write_trylock(arch_rwlock_t *rw)
{
	unsigned long tmp;

	__asm__ __volatile__(
			"       movi    %0, 0\n"
			"       wsr     %0, scompare1\n"
			"       movi    %0, 1\n"
			"       slli    %0, %0, 31\n"
			"       s32c1i  %0, %1, 0\n"
			: "=&a" (tmp)
			: "a" (&rw->lock)
			: "memory");

	return tmp == 0 ? 1 : 0;
}

static inline void arch_write_unlock(arch_rwlock_t *rw)
{
	unsigned long tmp;

	__asm__ __volatile__(
			"       movi    %0, 0\n"
			"       s32ri   %0, %1, 0\n"
			: "=&a" (tmp)
			: "a" (&rw->lock)
			: "memory");
}

static inline void arch_read_lock(arch_rwlock_t *rw)
{
	unsigned long tmp;
	unsigned long result;

	__asm__ __volatile__(
			"1:     l32i    %1, %2, 0\n"
			"       bltz    %1, 1b\n"
			"       wsr     %1, scompare1\n"
			"       addi    %0, %1, 1\n"
			"       s32c1i  %0, %2, 0\n"
			"       bne     %0, %1, 1b\n"
			: "=&a" (result), "=&a" (tmp)
			: "a" (&rw->lock)
			: "memory");
}

/* Returns 1 if the lock is obtained, 0 otherwise. */

static inline int arch_read_trylock(arch_rwlock_t *rw)
{
	unsigned long result;
	unsigned long tmp;

	__asm__ __volatile__(
			"       l32i    %1, %2, 0\n"
			"       addi    %0, %1, 1\n"
			"       bltz    %0, 1f\n"
			"       wsr     %1, scompare1\n"
			"       s32c1i  %0, %2, 0\n"
			"       sub     %0, %0, %1\n"
			"1:\n"
			: "=&a" (result), "=&a" (tmp)
			: "a" (&rw->lock)
			: "memory");

	return result == 0;
}

static inline void arch_read_unlock(arch_rwlock_t *rw)
{
	unsigned long tmp1, tmp2;

	__asm__ __volatile__(
			"1:     l32i    %1, %2, 0\n"
			"       addi    %0, %1, -1\n"
			"       wsr     %1, scompare1\n"
			"       s32c1i  %0, %2, 0\n"
			"       bne     %0, %1, 1b\n"
			: "=&a" (tmp1), "=&a" (tmp2)
			: "a" (&rw->lock)
			: "memory");
}

#define arch_read_lock_flags(lock, flags)	arch_read_lock(lock)
#define arch_write_lock_flags(lock, flags)	arch_write_lock(lock)

#endif	/* _XTENSA_SPINLOCK_H */