1 /*
2  * Queued spinlock
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License as published by
6  * the Free Software Foundation; either version 2 of the License, or
7  * (at your option) any later version.
8  *
9  * This program is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12  * GNU General Public License for more details.
13  *
14  * (C) Copyright 2013-2015 Hewlett-Packard Development Company, L.P.
15  *
16  * Authors: Waiman Long <waiman.long@hp.com>
17  */
18 #ifndef __ASM_GENERIC_QSPINLOCK_TYPES_H
19 #define __ASM_GENERIC_QSPINLOCK_TYPES_H
20 
21 /*
22  * Including atomic.h with PARAVIRT on will cause compilation errors because
23  * of recursive header file incluson via paravirt_types.h. So don't include
24  * it if PARAVIRT is on.
25  */
26 #ifndef CONFIG_PARAVIRT
27 #include <linux/types.h>
28 #include <linux/atomic.h>
29 #endif
30 
31 typedef struct qspinlock {
32 	union {
33 		atomic_t val;
34 
35 		/*
36 		 * By using the whole 2nd least significant byte for the
37 		 * pending bit, we can allow better optimization of the lock
38 		 * acquisition for the pending bit holder.
39 		 */
40 #ifdef __LITTLE_ENDIAN
41 		struct {
42 			u8	locked;
43 			u8	pending;
44 		};
45 		struct {
46 			u16	locked_pending;
47 			u16	tail;
48 		};
49 #else
50 		struct {
51 			u16	tail;
52 			u16	locked_pending;
53 		};
54 		struct {
55 			u8	reserved[2];
56 			u8	pending;
57 			u8	locked;
58 		};
59 #endif
60 	};
61 } arch_spinlock_t;
62 
63 /*
64  * Initializier
65  */
66 #define	__ARCH_SPIN_LOCK_UNLOCKED	{ { .val = ATOMIC_INIT(0) } }
67 
68 /*
69  * Bitfields in the atomic value:
70  *
71  * When NR_CPUS < 16K
72  *  0- 7: locked byte
73  *     8: pending
74  *  9-15: not used
75  * 16-17: tail index
76  * 18-31: tail cpu (+1)
77  *
78  * When NR_CPUS >= 16K
79  *  0- 7: locked byte
80  *     8: pending
81  *  9-10: tail index
82  * 11-31: tail cpu (+1)
83  */
84 #define	_Q_SET_MASK(type)	(((1U << _Q_ ## type ## _BITS) - 1)\
85 				      << _Q_ ## type ## _OFFSET)
86 #define _Q_LOCKED_OFFSET	0
87 #define _Q_LOCKED_BITS		8
88 #define _Q_LOCKED_MASK		_Q_SET_MASK(LOCKED)
89 
90 #define _Q_PENDING_OFFSET	(_Q_LOCKED_OFFSET + _Q_LOCKED_BITS)
91 #if CONFIG_NR_CPUS < (1U << 14)
92 #define _Q_PENDING_BITS		8
93 #else
94 #define _Q_PENDING_BITS		1
95 #endif
96 #define _Q_PENDING_MASK		_Q_SET_MASK(PENDING)
97 
98 #define _Q_TAIL_IDX_OFFSET	(_Q_PENDING_OFFSET + _Q_PENDING_BITS)
99 #define _Q_TAIL_IDX_BITS	2
100 #define _Q_TAIL_IDX_MASK	_Q_SET_MASK(TAIL_IDX)
101 
102 #define _Q_TAIL_CPU_OFFSET	(_Q_TAIL_IDX_OFFSET + _Q_TAIL_IDX_BITS)
103 #define _Q_TAIL_CPU_BITS	(32 - _Q_TAIL_CPU_OFFSET)
104 #define _Q_TAIL_CPU_MASK	_Q_SET_MASK(TAIL_CPU)
105 
106 #define _Q_TAIL_OFFSET		_Q_TAIL_IDX_OFFSET
107 #define _Q_TAIL_MASK		(_Q_TAIL_IDX_MASK | _Q_TAIL_CPU_MASK)
108 
109 #define _Q_LOCKED_VAL		(1U << _Q_LOCKED_OFFSET)
110 #define _Q_PENDING_VAL		(1U << _Q_PENDING_OFFSET)
111 
112 #endif /* __ASM_GENERIC_QSPINLOCK_TYPES_H */
113