1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __ASM_ARM_CMPXCHG_H
3 #define __ASM_ARM_CMPXCHG_H
4
5 #include <linux/irqflags.h>
6 #include <linux/prefetch.h>
7 #include <asm/barrier.h>
8 #include <linux/cmpxchg-emu.h>
9
10 #if defined(CONFIG_CPU_SA1100) || defined(CONFIG_CPU_SA110)
11 /*
12 * On the StrongARM, "swp" is terminally broken since it bypasses the
13 * cache totally. This means that the cache becomes inconsistent, and,
14 * since we use normal loads/stores as well, this is really bad.
15 * Typically, this causes oopsen in filp_close, but could have other,
16 * more disastrous effects. There are two work-arounds:
17 * 1. Disable interrupts and emulate the atomic swap
18 * 2. Clean the cache, perform atomic swap, flush the cache
19 *
20 * We choose (1) since its the "easiest" to achieve here and is not
21 * dependent on the processor type.
22 *
23 * NOTE that this solution won't work on an SMP system, so explcitly
24 * forbid it here.
25 */
26 #define swp_is_buggy
27 #endif
28
29 static inline unsigned long
30 __arch_xchg(unsigned long x, volatile void *ptr, int size)
31 {
32 extern void __bad_xchg(volatile void *, int);
33 unsigned long ret;
34 #ifdef swp_is_buggy
35 unsigned long flags;
36 #endif
37 #if __LINUX_ARM_ARCH__ >= 6
38 unsigned int tmp;
39 #endif
40
41 prefetchw((const void *)ptr);
42
43 switch (size) {
44 #if __LINUX_ARM_ARCH__ >= 6
45 #ifndef CONFIG_CPU_V6 /* MIN ARCH >= V6K */
46 case 1:
47 asm volatile("@ __xchg1\n"
48 "1: ldrexb %0, [%3]\n"
49 " strexb %1, %2, [%3]\n"
50 " teq %1, #0\n"
51 " bne 1b"
52 : "=&r" (ret), "=&r" (tmp)
53 : "r" (x), "r" (ptr)
54 : "memory", "cc");
55 break;
56 case 2:
57 asm volatile("@ __xchg2\n"
58 "1: ldrexh %0, [%3]\n"
59 " strexh %1, %2, [%3]\n"
60 " teq %1, #0\n"
61 " bne 1b"
62 : "=&r" (ret), "=&r" (tmp)
63 : "r" (x), "r" (ptr)
64 : "memory", "cc");
65 break;
66 #endif
67 case 4:
68 asm volatile("@ __xchg4\n"
69 "1: ldrex %0, [%3]\n"
70 " strex %1, %2, [%3]\n"
71 " teq %1, #0\n"
72 " bne 1b"
73 : "=&r" (ret), "=&r" (tmp)
74 : "r" (x), "r" (ptr)
75 : "memory", "cc");
76 break;
77 #elif defined(swp_is_buggy)
78 #ifdef CONFIG_SMP
79 #error SMP is not supported on this platform
80 #endif
81 case 1:
82 raw_local_irq_save(flags);
83 ret = *(volatile unsigned char *)ptr;
84 *(volatile unsigned char *)ptr = x;
85 raw_local_irq_restore(flags);
86 break;
87
88 case 4:
89 raw_local_irq_save(flags);
90 ret = *(volatile unsigned long *)ptr;
91 *(volatile unsigned long *)ptr = x;
92 raw_local_irq_restore(flags);
93 break;
94 #else
95 case 1:
96 asm volatile("@ __xchg1\n"
97 " swpb %0, %1, [%2]"
98 : "=&r" (ret)
99 : "r" (x), "r" (ptr)
100 : "memory", "cc");
101 break;
102 case 4:
103 asm volatile("@ __xchg4\n"
104 " swp %0, %1, [%2]"
105 : "=&r" (ret)
106 : "r" (x), "r" (ptr)
107 : "memory", "cc");
108 break;
109 #endif
110 default:
111 /* Cause a link-time error, the xchg() size is not supported */
112 __bad_xchg(ptr, size), ret = 0;
113 break;
114 }
115
116 return ret;
117 }
118
119 #define arch_xchg_relaxed(ptr, x) ({ \
120 (__typeof__(*(ptr)))__arch_xchg((unsigned long)(x), (ptr), \
121 sizeof(*(ptr))); \
122 })
123
124 #include <asm-generic/cmpxchg-local.h>
125
126 #if __LINUX_ARM_ARCH__ < 6
127 /* min ARCH < ARMv6 */
128
129 #ifdef CONFIG_SMP
130 #error "SMP is not supported on this platform"
131 #endif
132
133 #define arch_xchg arch_xchg_relaxed
134
135 /*
136 * cmpxchg_local and cmpxchg64_local are atomic wrt current CPU. Always make
137 * them available.
138 */
139 #define arch_cmpxchg_local(ptr, o, n) ({ \
140 (__typeof(*ptr))__generic_cmpxchg_local((ptr), \
141 (unsigned long)(o), \
142 (unsigned long)(n), \
143 sizeof(*(ptr))); \
144 })
145
146 #define arch_cmpxchg64_local(ptr, o, n) __generic_cmpxchg64_local((ptr), (o), (n))
147
148 #include <asm-generic/cmpxchg.h>
149
150 #else /* min ARCH >= ARMv6 */
151
152 extern void __bad_cmpxchg(volatile void *ptr, int size);
153
154 /*
155 * cmpxchg only support 32-bits operands on ARMv6.
156 */
157
158 static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
159 unsigned long new, int size)
160 {
161 unsigned long oldval, res;
162
163 prefetchw((const void *)ptr);
164
165 switch (size) {
166 #ifdef CONFIG_CPU_V6 /* ARCH == ARMv6 */
167 case 1:
168 oldval = cmpxchg_emu_u8((volatile u8 *)ptr, old, new);
169 break;
170 #else /* min ARCH > ARMv6 */
171 case 1:
172 do {
173 asm volatile("@ __cmpxchg1\n"
174 " ldrexb %1, [%2]\n"
175 " mov %0, #0\n"
176 " teq %1, %3\n"
177 " strexbeq %0, %4, [%2]\n"
178 : "=&r" (res), "=&r" (oldval)
179 : "r" (ptr), "Ir" (old), "r" (new)
180 : "memory", "cc");
181 } while (res);
182 break;
183 case 2:
184 do {
185 asm volatile("@ __cmpxchg1\n"
186 " ldrexh %1, [%2]\n"
187 " mov %0, #0\n"
188 " teq %1, %3\n"
189 " strexheq %0, %4, [%2]\n"
190 : "=&r" (res), "=&r" (oldval)
191 : "r" (ptr), "Ir" (old), "r" (new)
192 : "memory", "cc");
193 } while (res);
194 break;
195 #endif
196 case 4:
197 do {
198 asm volatile("@ __cmpxchg4\n"
199 " ldrex %1, [%2]\n"
200 " mov %0, #0\n"
201 " teq %1, %3\n"
202 " strexeq %0, %4, [%2]\n"
203 : "=&r" (res), "=&r" (oldval)
204 : "r" (ptr), "Ir" (old), "r" (new)
205 : "memory", "cc");
206 } while (res);
207 break;
208 default:
209 __bad_cmpxchg(ptr, size);
210 oldval = 0;
211 }
212
213 return oldval;
214 }
215
216 #define arch_cmpxchg_relaxed(ptr,o,n) ({ \
217 (__typeof__(*(ptr)))__cmpxchg((ptr), \
218 (unsigned long)(o), \
219 (unsigned long)(n), \
220 sizeof(*(ptr))); \
221 })
222
223 static inline unsigned long __cmpxchg_local(volatile void *ptr,
224 unsigned long old,
225 unsigned long new, int size)
226 {
227 unsigned long ret;
228
229 switch (size) {
230 #ifdef CONFIG_CPU_V6 /* min ARCH == ARMv6 */
231 case 1:
232 case 2:
233 ret = __generic_cmpxchg_local(ptr, old, new, size);
234 break;
235 #endif
236 default:
237 ret = __cmpxchg(ptr, old, new, size);
238 }
239
240 return ret;
241 }
242
243 #define arch_cmpxchg_local(ptr, o, n) ({ \
244 (__typeof(*ptr))__cmpxchg_local((ptr), \
245 (unsigned long)(o), \
246 (unsigned long)(n), \
247 sizeof(*(ptr))); \
248 })
249
250 static inline unsigned long long __cmpxchg64(unsigned long long *ptr,
251 unsigned long long old,
252 unsigned long long new)
253 {
254 unsigned long long oldval;
255 unsigned long res;
256
257 prefetchw(ptr);
258
259 __asm__ __volatile__(
260 "1: ldrexd %1, %H1, [%3]\n"
261 " teq %1, %4\n"
262 " teqeq %H1, %H4\n"
263 " bne 2f\n"
264 " strexd %0, %5, %H5, [%3]\n"
265 " teq %0, #0\n"
266 " bne 1b\n"
267 "2:"
268 : "=&r" (res), "=&r" (oldval), "+Qo" (*ptr)
269 : "r" (ptr), "r" (old), "r" (new)
270 : "cc");
271
272 return oldval;
273 }
274
275 #define arch_cmpxchg64_relaxed(ptr, o, n) ({ \
276 (__typeof__(*(ptr)))__cmpxchg64((ptr), \
277 (unsigned long long)(o), \
278 (unsigned long long)(n)); \
279 })
280
281 #define arch_cmpxchg64_local(ptr, o, n) arch_cmpxchg64_relaxed((ptr), (o), (n))
282
283 #endif /* __LINUX_ARM_ARCH__ >= 6 */
284
285 #endif /* __ASM_ARM_CMPXCHG_H */
286
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