summaryrefslogtreecommitdiff
path: root/arch/openrisc/include/asm/cmpxchg.h
blob: f9cd43a39d72612decb2c7cfecbfabe38daeba12 (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
/*
 * 1,2 and 4 byte cmpxchg and xchg implementations for OpenRISC.
 *
 * Copyright (C) 2014 Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
 * Copyright (C) 2017 Stafford Horne <shorne@gmail.com>
 *
 * This file is licensed under the terms of the GNU General Public License
 * version 2.  This program is licensed "as is" without any warranty of any
 * kind, whether express or implied.
 *
 * Note:
 * The portable implementations of 1 and 2 byte xchg and cmpxchg using a 4
 * byte cmpxchg is sourced heavily from the sh and mips implementations.
 */

#ifndef __ASM_OPENRISC_CMPXCHG_H
#define __ASM_OPENRISC_CMPXCHG_H

#include  <linux/bits.h>
#include  <linux/compiler.h>
#include  <linux/types.h>

#define __HAVE_ARCH_CMPXCHG 1

static inline unsigned long cmpxchg_u32(volatile void *ptr,
		unsigned long old, unsigned long new)
{
	__asm__ __volatile__(
		"1:	l.lwa %0, 0(%1)		\n"
		"	l.sfeq %0, %2		\n"
		"	l.bnf 2f		\n"
		"	 l.nop			\n"
		"	l.swa 0(%1), %3		\n"
		"	l.bnf 1b		\n"
		"	 l.nop			\n"
		"2:				\n"
		: "=&r"(old)
		: "r"(ptr), "r"(old), "r"(new)
		: "cc", "memory");

	return old;
}

static inline unsigned long xchg_u32(volatile void *ptr,
		unsigned long val)
{
	__asm__ __volatile__(
		"1:	l.lwa %0, 0(%1)		\n"
		"	l.swa 0(%1), %2		\n"
		"	l.bnf 1b		\n"
		"	 l.nop			\n"
		: "=&r"(val)
		: "r"(ptr), "r"(val)
		: "cc", "memory");

	return val;
}

static inline u32 cmpxchg_small(volatile void *ptr, u32 old, u32 new,
				int size)
{
	int off = (unsigned long)ptr % sizeof(u32);
	volatile u32 *p = ptr - off;
#ifdef __BIG_ENDIAN
	int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
#else
	int bitoff = off * BITS_PER_BYTE;
#endif
	u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
	u32 load32, old32, new32;
	u32 ret;

	load32 = READ_ONCE(*p);

	while (true) {
		ret = (load32 & bitmask) >> bitoff;
		if (old != ret)
			return ret;

		old32 = (load32 & ~bitmask) | (old << bitoff);
		new32 = (load32 & ~bitmask) | (new << bitoff);

		/* Do 32 bit cmpxchg */
		load32 = cmpxchg_u32(p, old32, new32);
		if (load32 == old32)
			return old;
	}
}

/* xchg */

static inline u32 xchg_small(volatile void *ptr, u32 x, int size)
{
	int off = (unsigned long)ptr % sizeof(u32);
	volatile u32 *p = ptr - off;
#ifdef __BIG_ENDIAN
	int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
#else
	int bitoff = off * BITS_PER_BYTE;
#endif
	u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
	u32 oldv, newv;
	u32 ret;

	do {
		oldv = READ_ONCE(*p);
		ret = (oldv & bitmask) >> bitoff;
		newv = (oldv & ~bitmask) | (x << bitoff);
	} while (cmpxchg_u32(p, oldv, newv) != oldv);

	return ret;
}

/*
 * This function doesn't exist, so you'll get a linker error
 * if something tries to do an invalid cmpxchg().
 */
extern unsigned long __cmpxchg_called_with_bad_pointer(void)
	__compiletime_error("Bad argument size for cmpxchg");

static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
		unsigned long new, int size)
{
	switch (size) {
	case 1:
	case 2:
		return cmpxchg_small(ptr, old, new, size);
	case 4:
		return cmpxchg_u32(ptr, old, new);
	default:
		return __cmpxchg_called_with_bad_pointer();
	}
}

#define cmpxchg(ptr, o, n)						\
	({								\
		(__typeof__(*(ptr))) __cmpxchg((ptr),			\
					       (unsigned long)(o),	\
					       (unsigned long)(n),	\
					       sizeof(*(ptr)));		\
	})

/*
 * This function doesn't exist, so you'll get a linker error if
 * something tries to do an invalidly-sized xchg().
 */
extern unsigned long __xchg_called_with_bad_pointer(void)
	__compiletime_error("Bad argument size for xchg");

static inline unsigned long __xchg(volatile void *ptr, unsigned long with,
		int size)
{
	switch (size) {
	case 1:
	case 2:
		return xchg_small(ptr, with, size);
	case 4:
		return xchg_u32(ptr, with);
	default:
		return __xchg_called_with_bad_pointer();
	}
}

#define xchg(ptr, with) 						\
	({								\
		(__typeof__(*(ptr))) __xchg((ptr),			\
					    (unsigned long)(with),	\
					    sizeof(*(ptr)));		\
	})

#endif /* __ASM_OPENRISC_CMPXCHG_H */