xref: /openbmc/linux/arch/arm64/include/asm/cmpxchg.h (revision b34e08d5)
1 /*
2  * Based on arch/arm/include/asm/cmpxchg.h
3  *
4  * Copyright (C) 2012 ARM Ltd.
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  * GNU General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License
16  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
17  */
18 #ifndef __ASM_CMPXCHG_H
19 #define __ASM_CMPXCHG_H
20 
21 #include <linux/bug.h>
22 
23 #include <asm/barrier.h>
24 
25 static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
26 {
27 	unsigned long ret, tmp;
28 
29 	switch (size) {
30 	case 1:
31 		asm volatile("//	__xchg1\n"
32 		"1:	ldxrb	%w0, %2\n"
33 		"	stlxrb	%w1, %w3, %2\n"
34 		"	cbnz	%w1, 1b\n"
35 			: "=&r" (ret), "=&r" (tmp), "+Q" (*(u8 *)ptr)
36 			: "r" (x)
37 			: "memory");
38 		break;
39 	case 2:
40 		asm volatile("//	__xchg2\n"
41 		"1:	ldxrh	%w0, %2\n"
42 		"	stlxrh	%w1, %w3, %2\n"
43 		"	cbnz	%w1, 1b\n"
44 			: "=&r" (ret), "=&r" (tmp), "+Q" (*(u16 *)ptr)
45 			: "r" (x)
46 			: "memory");
47 		break;
48 	case 4:
49 		asm volatile("//	__xchg4\n"
50 		"1:	ldxr	%w0, %2\n"
51 		"	stlxr	%w1, %w3, %2\n"
52 		"	cbnz	%w1, 1b\n"
53 			: "=&r" (ret), "=&r" (tmp), "+Q" (*(u32 *)ptr)
54 			: "r" (x)
55 			: "memory");
56 		break;
57 	case 8:
58 		asm volatile("//	__xchg8\n"
59 		"1:	ldxr	%0, %2\n"
60 		"	stlxr	%w1, %3, %2\n"
61 		"	cbnz	%w1, 1b\n"
62 			: "=&r" (ret), "=&r" (tmp), "+Q" (*(u64 *)ptr)
63 			: "r" (x)
64 			: "memory");
65 		break;
66 	default:
67 		BUILD_BUG();
68 	}
69 
70 	smp_mb();
71 	return ret;
72 }
73 
74 #define xchg(ptr,x) \
75 	((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))
76 
77 static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
78 				      unsigned long new, int size)
79 {
80 	unsigned long oldval = 0, res;
81 
82 	switch (size) {
83 	case 1:
84 		do {
85 			asm volatile("// __cmpxchg1\n"
86 			"	ldxrb	%w1, %2\n"
87 			"	mov	%w0, #0\n"
88 			"	cmp	%w1, %w3\n"
89 			"	b.ne	1f\n"
90 			"	stxrb	%w0, %w4, %2\n"
91 			"1:\n"
92 				: "=&r" (res), "=&r" (oldval), "+Q" (*(u8 *)ptr)
93 				: "Ir" (old), "r" (new)
94 				: "cc");
95 		} while (res);
96 		break;
97 
98 	case 2:
99 		do {
100 			asm volatile("// __cmpxchg2\n"
101 			"	ldxrh	%w1, %2\n"
102 			"	mov	%w0, #0\n"
103 			"	cmp	%w1, %w3\n"
104 			"	b.ne	1f\n"
105 			"	stxrh	%w0, %w4, %2\n"
106 			"1:\n"
107 				: "=&r" (res), "=&r" (oldval), "+Q" (*(u16 *)ptr)
108 				: "Ir" (old), "r" (new)
109 				: "cc");
110 		} while (res);
111 		break;
112 
113 	case 4:
114 		do {
115 			asm volatile("// __cmpxchg4\n"
116 			"	ldxr	%w1, %2\n"
117 			"	mov	%w0, #0\n"
118 			"	cmp	%w1, %w3\n"
119 			"	b.ne	1f\n"
120 			"	stxr	%w0, %w4, %2\n"
121 			"1:\n"
122 				: "=&r" (res), "=&r" (oldval), "+Q" (*(u32 *)ptr)
123 				: "Ir" (old), "r" (new)
124 				: "cc");
125 		} while (res);
126 		break;
127 
128 	case 8:
129 		do {
130 			asm volatile("// __cmpxchg8\n"
131 			"	ldxr	%1, %2\n"
132 			"	mov	%w0, #0\n"
133 			"	cmp	%1, %3\n"
134 			"	b.ne	1f\n"
135 			"	stxr	%w0, %4, %2\n"
136 			"1:\n"
137 				: "=&r" (res), "=&r" (oldval), "+Q" (*(u64 *)ptr)
138 				: "Ir" (old), "r" (new)
139 				: "cc");
140 		} while (res);
141 		break;
142 
143 	default:
144 		BUILD_BUG();
145 	}
146 
147 	return oldval;
148 }
149 
150 static inline unsigned long __cmpxchg_mb(volatile void *ptr, unsigned long old,
151 					 unsigned long new, int size)
152 {
153 	unsigned long ret;
154 
155 	smp_mb();
156 	ret = __cmpxchg(ptr, old, new, size);
157 	smp_mb();
158 
159 	return ret;
160 }
161 
162 #define cmpxchg(ptr, o, n) \
163 ({ \
164 	__typeof__(*(ptr)) __ret; \
165 	__ret = (__typeof__(*(ptr))) \
166 		__cmpxchg_mb((ptr), (unsigned long)(o), (unsigned long)(n), \
167 			     sizeof(*(ptr))); \
168 	__ret; \
169 })
170 
171 #define cmpxchg_local(ptr, o, n) \
172 ({ \
173 	__typeof__(*(ptr)) __ret; \
174 	__ret = (__typeof__(*(ptr))) \
175 		__cmpxchg((ptr), (unsigned long)(o), \
176 			  (unsigned long)(n), sizeof(*(ptr))); \
177 	__ret; \
178 })
179 
180 #define cmpxchg64(ptr,o,n)		cmpxchg((ptr),(o),(n))
181 #define cmpxchg64_local(ptr,o,n)	cmpxchg_local((ptr),(o),(n))
182 
183 #define cmpxchg64_relaxed(ptr,o,n)	cmpxchg_local((ptr),(o),(n))
184 
185 #endif	/* __ASM_CMPXCHG_H */
186