1 /*
2 * 1,2 and 4 byte cmpxchg and xchg implementations for OpenRISC.
3 *
4 * Copyright (C) 2014 Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
5 * Copyright (C) 2017 Stafford Horne <shorne@gmail.com>
6 *
7 * This file is licensed under the terms of the GNU General Public License
8 * version 2. This program is licensed "as is" without any warranty of any
9 * kind, whether express or implied.
10 *
11 * Note:
12 * The portable implementations of 1 and 2 byte xchg and cmpxchg using a 4
13 * byte cmpxchg is sourced heavily from the sh and mips implementations.
14 */
15
16 #ifndef __ASM_OPENRISC_CMPXCHG_H
17 #define __ASM_OPENRISC_CMPXCHG_H
18
19 #include <linux/bits.h>
20 #include <linux/compiler.h>
21 #include <linux/types.h>
22
23 #define __HAVE_ARCH_CMPXCHG 1
24
25 static inline unsigned long cmpxchg_u32(volatile void *ptr,
26 unsigned long old, unsigned long new)
27 {
28 __asm__ __volatile__(
29 "1: l.lwa %0, 0(%1) \n"
30 " l.sfeq %0, %2 \n"
31 " l.bnf 2f \n"
32 " l.nop \n"
33 " l.swa 0(%1), %3 \n"
34 " l.bnf 1b \n"
35 " l.nop \n"
36 "2: \n"
37 : "=&r"(old)
38 : "r"(ptr), "r"(old), "r"(new)
39 : "cc", "memory");
40
41 return old;
42 }
43
44 static inline unsigned long xchg_u32(volatile void *ptr,
45 unsigned long val)
46 {
47 __asm__ __volatile__(
48 "1: l.lwa %0, 0(%1) \n"
49 " l.swa 0(%1), %2 \n"
50 " l.bnf 1b \n"
51 " l.nop \n"
52 : "=&r"(val)
53 : "r"(ptr), "r"(val)
54 : "cc", "memory");
55
56 return val;
57 }
58
59 static inline u32 cmpxchg_small(volatile void *ptr, u32 old, u32 new,
60 int size)
61 {
62 int off = (unsigned long)ptr % sizeof(u32);
63 volatile u32 *p = ptr - off;
64 #ifdef __BIG_ENDIAN
65 int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
66 #else
67 int bitoff = off * BITS_PER_BYTE;
68 #endif
69 u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
70 u32 load32, old32, new32;
71 u32 ret;
72
73 load32 = READ_ONCE(*p);
74
75 while (true) {
76 ret = (load32 & bitmask) >> bitoff;
77 if (old != ret)
78 return ret;
79
80 old32 = (load32 & ~bitmask) | (old << bitoff);
81 new32 = (load32 & ~bitmask) | (new << bitoff);
82
83 /* Do 32 bit cmpxchg */
84 load32 = cmpxchg_u32(p, old32, new32);
85 if (load32 == old32)
86 return old;
87 }
88 }
89
90 /* xchg */
91
92 static inline u32 xchg_small(volatile void *ptr, u32 x, int size)
93 {
94 int off = (unsigned long)ptr % sizeof(u32);
95 volatile u32 *p = ptr - off;
96 #ifdef __BIG_ENDIAN
97 int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
98 #else
99 int bitoff = off * BITS_PER_BYTE;
100 #endif
101 u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff;
102 u32 oldv, newv;
103 u32 ret;
104
105 do {
106 oldv = READ_ONCE(*p);
107 ret = (oldv & bitmask) >> bitoff;
108 newv = (oldv & ~bitmask) | (x << bitoff);
109 } while (cmpxchg_u32(p, oldv, newv) != oldv);
110
111 return ret;
112 }
113
114 /*
115 * This function doesn't exist, so you'll get a linker error
116 * if something tries to do an invalid cmpxchg().
117 */
118 extern unsigned long __cmpxchg_called_with_bad_pointer(void)
119 __compiletime_error("Bad argument size for cmpxchg");
120
121 static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
122 unsigned long new, int size)
123 {
124 switch (size) {
125 case 1:
126 case 2:
127 return cmpxchg_small(ptr, old, new, size);
128 case 4:
129 return cmpxchg_u32(ptr, old, new);
130 default:
131 return __cmpxchg_called_with_bad_pointer();
132 }
133 }
134
135 #define arch_cmpxchg(ptr, o, n) \
136 ({ \
137 (__typeof__(*(ptr))) __cmpxchg((ptr), \
138 (unsigned long)(o), \
139 (unsigned long)(n), \
140 sizeof(*(ptr))); \
141 })
142
143 /*
144 * This function doesn't exist, so you'll get a linker error if
145 * something tries to do an invalidly-sized xchg().
146 */
147 extern unsigned long __xchg_called_with_bad_pointer(void)
148 __compiletime_error("Bad argument size for xchg");
149
150 static inline unsigned long
151 __arch_xchg(volatile void *ptr, unsigned long with, int size)
152 {
153 switch (size) {
154 case 1:
155 case 2:
156 return xchg_small(ptr, with, size);
157 case 4:
158 return xchg_u32(ptr, with);
159 default:
160 return __xchg_called_with_bad_pointer();
161 }
162 }
163
164 #define arch_xchg(ptr, with) \
165 ({ \
166 (__typeof__(*(ptr))) __arch_xchg((ptr), \
167 (unsigned long)(with), \
168 sizeof(*(ptr))); \
169 })
170
171 #endif /* __ASM_OPENRISC_CMPXCHG_H */
172
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