1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3 * Queued spinlock
4 *
5 * (C) Copyright 2013-2015 Hewlett-Packard Development Company, L.P.
6 *
7 * Authors: Waiman Long <waiman.long@hp.com>
8 */
9 #ifndef __ASM_GENERIC_QSPINLOCK_TYPES_H
10 #define __ASM_GENERIC_QSPINLOCK_TYPES_H
11
12 #include <linux/types.h>
13
14 typedef struct qspinlock {
15 union {
16 atomic_t val;
17
18 /*
19 * By using the whole 2nd least significant byte for the
20 * pending bit, we can allow better optimization of the lock
21 * acquisition for the pending bit holder.
22 */
23 #ifdef __LITTLE_ENDIAN
24 struct {
25 u8 locked;
26 u8 pending;
27 };
28 struct {
29 u16 locked_pending;
30 u16 tail;
31 };
32 #else
33 struct {
34 u16 tail;
35 u16 locked_pending;
36 };
37 struct {
38 u8 reserved[2];
39 u8 pending;
40 u8 locked;
41 };
42 #endif
43 };
44 } arch_spinlock_t;
45
46 /*
47 * Initializier
48 */
49 #define __ARCH_SPIN_LOCK_UNLOCKED { { .val = ATOMIC_INIT(0) } }
50
51 /*
52 * Bitfields in the atomic value:
53 *
54 * When NR_CPUS < 16K
55 * 0- 7: locked byte
56 * 8: pending
57 * 9-15: not used
58 * 16-17: tail index
59 * 18-31: tail cpu (+1)
60 *
61 * When NR_CPUS >= 16K
62 * 0- 7: locked byte
63 * 8: pending
64 * 9-10: tail index
65 * 11-31: tail cpu (+1)
66 */
67 #define _Q_SET_MASK(type) (((1U << _Q_ ## type ## _BITS) - 1)\
68 << _Q_ ## type ## _OFFSET)
69 #define _Q_LOCKED_OFFSET 0
70 #define _Q_LOCKED_BITS 8
71 #define _Q_LOCKED_MASK _Q_SET_MASK(LOCKED)
72
73 #define _Q_PENDING_OFFSET (_Q_LOCKED_OFFSET + _Q_LOCKED_BITS)
74 #if CONFIG_NR_CPUS < (1U << 14)
75 #define _Q_PENDING_BITS 8
76 #else
77 #define _Q_PENDING_BITS 1
78 #endif
79 #define _Q_PENDING_MASK _Q_SET_MASK(PENDING)
80
81 #define _Q_TAIL_IDX_OFFSET (_Q_PENDING_OFFSET + _Q_PENDING_BITS)
82 #define _Q_TAIL_IDX_BITS 2
83 #define _Q_TAIL_IDX_MASK _Q_SET_MASK(TAIL_IDX)
84
85 #define _Q_TAIL_CPU_OFFSET (_Q_TAIL_IDX_OFFSET + _Q_TAIL_IDX_BITS)
86 #define _Q_TAIL_CPU_BITS (32 - _Q_TAIL_CPU_OFFSET)
87 #define _Q_TAIL_CPU_MASK _Q_SET_MASK(TAIL_CPU)
88
89 #define _Q_TAIL_OFFSET _Q_TAIL_IDX_OFFSET
90 #define _Q_TAIL_MASK (_Q_TAIL_IDX_MASK | _Q_TAIL_CPU_MASK)
91
92 #define _Q_LOCKED_VAL (1U << _Q_LOCKED_OFFSET)
93 #define _Q_PENDING_VAL (1U << _Q_PENDING_OFFSET)
94
95 #endif /* __ASM_GENERIC_QSPINLOCK_TYPES_H */
96
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