1 /*
2 * This file is subject to the terms and conditions of the GNU General Public
3 * License. See the file "COPYING" in the main directory of this archive
4 * for more details.
5 *
6 * Copyright (C) 2003, 06, 07 by Ralf Baechle (ralf@linux-mips.org)
7 */
8 #ifndef __ASM_CMPXCHG_H
9 #define __ASM_CMPXCHG_H
10
11 #include <linux/bug.h>
12 #include <linux/irqflags.h>
13 #include <asm/asm.h>
14 #include <asm/compiler.h>
15 #include <asm/sync.h>
16
17 /*
18 * These functions doesn't exist, so if they are called you'll either:
19 *
20 * - Get an error at compile-time due to __compiletime_error, if supported by
21 * your compiler.
22 *
23 * or:
24 *
25 * - Get an error at link-time due to the call to the missing function.
26 */
27 extern unsigned long __cmpxchg_called_with_bad_pointer(void)
28 __compiletime_error("Bad argument size for cmpxchg");
29 extern unsigned long __cmpxchg64_unsupported(void)
30 __compiletime_error("cmpxchg64 not available; cpu_has_64bits may be false");
31 extern unsigned long __xchg_called_with_bad_pointer(void)
32 __compiletime_error("Bad argument size for xchg");
33
34 #define __xchg_asm(ld, st, m, val) \
35 ({ \
36 __typeof(*(m)) __ret; \
37 \
38 if (kernel_uses_llsc) { \
39 __asm__ __volatile__( \
40 " .set push \n" \
41 " .set noat \n" \
42 " .set push \n" \
43 " .set " MIPS_ISA_ARCH_LEVEL " \n" \
44 " " __SYNC(full, loongson3_war) " \n" \
45 "1: " ld " %0, %2 # __xchg_asm \n" \
46 " .set pop \n" \
47 " move $1, %z3 \n" \
48 " .set " MIPS_ISA_ARCH_LEVEL " \n" \
49 " " st " $1, %1 \n" \
50 "\t" __stringify(SC_BEQZ) " $1, 1b \n" \
51 " .set pop \n" \
52 : "=&r" (__ret), "=" GCC_OFF_SMALL_ASM() (*m) \
53 : GCC_OFF_SMALL_ASM() (*m), "Jr" (val) \
54 : __LLSC_CLOBBER); \
55 } else { \
56 unsigned long __flags; \
57 \
58 raw_local_irq_save(__flags); \
59 __ret = *m; \
60 *m = val; \
61 raw_local_irq_restore(__flags); \
62 } \
63 \
64 __ret; \
65 })
66
67 extern unsigned long __xchg_small(volatile void *ptr, unsigned long val,
68 unsigned int size);
69
70 static __always_inline
71 unsigned long __arch_xchg(volatile void *ptr, unsigned long x, int size)
72 {
73 switch (size) {
74 case 1:
75 case 2:
76 return __xchg_small(ptr, x, size);
77
78 case 4:
79 return __xchg_asm("ll", "sc", (volatile u32 *)ptr, x);
80
81 case 8:
82 if (!IS_ENABLED(CONFIG_64BIT))
83 return __xchg_called_with_bad_pointer();
84
85 return __xchg_asm("lld", "scd", (volatile u64 *)ptr, x);
86
87 default:
88 return __xchg_called_with_bad_pointer();
89 }
90 }
91
92 #define arch_xchg(ptr, x) \
93 ({ \
94 __typeof__(*(ptr)) __res; \
95 \
96 /* \
97 * In the Loongson3 workaround case __xchg_asm() already \
98 * contains a completion barrier prior to the LL, so we don't \
99 * need to emit an extra one here. \
100 */ \
101 if (__SYNC_loongson3_war == 0) \
102 smp_mb__before_llsc(); \
103 \
104 __res = (__typeof__(*(ptr))) \
105 __arch_xchg((ptr), (unsigned long)(x), sizeof(*(ptr))); \
106 \
107 smp_llsc_mb(); \
108 \
109 __res; \
110 })
111
112 #define __cmpxchg_asm(ld, st, m, old, new) \
113 ({ \
114 __typeof(*(m)) __ret; \
115 \
116 if (kernel_uses_llsc) { \
117 __asm__ __volatile__( \
118 " .set push \n" \
119 " .set noat \n" \
120 " .set push \n" \
121 " .set "MIPS_ISA_ARCH_LEVEL" \n" \
122 " " __SYNC(full, loongson3_war) " \n" \
123 "1: " ld " %0, %2 # __cmpxchg_asm \n" \
124 " bne %0, %z3, 2f \n" \
125 " .set pop \n" \
126 " move $1, %z4 \n" \
127 " .set "MIPS_ISA_ARCH_LEVEL" \n" \
128 " " st " $1, %1 \n" \
129 "\t" __stringify(SC_BEQZ) " $1, 1b \n" \
130 " .set pop \n" \
131 "2: " __SYNC(full, loongson3_war) " \n" \
132 : "=&r" (__ret), "=" GCC_OFF_SMALL_ASM() (*m) \
133 : GCC_OFF_SMALL_ASM() (*m), "Jr" (old), "Jr" (new) \
134 : __LLSC_CLOBBER); \
135 } else { \
136 unsigned long __flags; \
137 \
138 raw_local_irq_save(__flags); \
139 __ret = *m; \
140 if (__ret == old) \
141 *m = new; \
142 raw_local_irq_restore(__flags); \
143 } \
144 \
145 __ret; \
146 })
147
148 extern unsigned long __cmpxchg_small(volatile void *ptr, unsigned long old,
149 unsigned long new, unsigned int size);
150
151 static __always_inline
152 unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
153 unsigned long new, unsigned int size)
154 {
155 switch (size) {
156 case 1:
157 case 2:
158 return __cmpxchg_small(ptr, old, new, size);
159
160 case 4:
161 return __cmpxchg_asm("ll", "sc", (volatile u32 *)ptr,
162 (u32)old, new);
163
164 case 8:
165 /* lld/scd are only available for MIPS64 */
166 if (!IS_ENABLED(CONFIG_64BIT))
167 return __cmpxchg_called_with_bad_pointer();
168
169 return __cmpxchg_asm("lld", "scd", (volatile u64 *)ptr,
170 (u64)old, new);
171
172 default:
173 return __cmpxchg_called_with_bad_pointer();
174 }
175 }
176
177 #define arch_cmpxchg_local(ptr, old, new) \
178 ((__typeof__(*(ptr))) \
179 __cmpxchg((ptr), \
180 (unsigned long)(__typeof__(*(ptr)))(old), \
181 (unsigned long)(__typeof__(*(ptr)))(new), \
182 sizeof(*(ptr))))
183
184 #define arch_cmpxchg(ptr, old, new) \
185 ({ \
186 __typeof__(*(ptr)) __res; \
187 \
188 /* \
189 * In the Loongson3 workaround case __cmpxchg_asm() already \
190 * contains a completion barrier prior to the LL, so we don't \
191 * need to emit an extra one here. \
192 */ \
193 if (__SYNC_loongson3_war == 0) \
194 smp_mb__before_llsc(); \
195 \
196 __res = arch_cmpxchg_local((ptr), (old), (new)); \
197 \
198 /* \
199 * In the Loongson3 workaround case __cmpxchg_asm() already \
200 * contains a completion barrier after the SC, so we don't \
201 * need to emit an extra one here. \
202 */ \
203 if (__SYNC_loongson3_war == 0) \
204 smp_llsc_mb(); \
205 \
206 __res; \
207 })
208
209 #ifdef CONFIG_64BIT
210 #define arch_cmpxchg64_local(ptr, o, n) \
211 ({ \
212 BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
213 arch_cmpxchg_local((ptr), (o), (n)); \
214 })
215
216 #define arch_cmpxchg64(ptr, o, n) \
217 ({ \
218 BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
219 arch_cmpxchg((ptr), (o), (n)); \
220 })
221 #else
222
223 # include <asm-generic/cmpxchg-local.h>
224 # define arch_cmpxchg64_local(ptr, o, n) __generic_cmpxchg64_local((ptr), (o), (n))
225
226 # ifdef CONFIG_SMP
227
228 static inline unsigned long __cmpxchg64(volatile void *ptr,
229 unsigned long long old,
230 unsigned long long new)
231 {
232 unsigned long long tmp, ret;
233 unsigned long flags;
234
235 /*
236 * The assembly below has to combine 32 bit values into a 64 bit
237 * register, and split 64 bit values from one register into two. If we
238 * were to take an interrupt in the middle of this we'd only save the
239 * least significant 32 bits of each register & probably clobber the
240 * most significant 32 bits of the 64 bit values we're using. In order
241 * to avoid this we must disable interrupts.
242 */
243 local_irq_save(flags);
244
245 asm volatile(
246 " .set push \n"
247 " .set " MIPS_ISA_ARCH_LEVEL " \n"
248 /* Load 64 bits from ptr */
249 " " __SYNC(full, loongson3_war) " \n"
250 "1: lld %L0, %3 # __cmpxchg64 \n"
251 " .set pop \n"
252 /*
253 * Split the 64 bit value we loaded into the 2 registers that hold the
254 * ret variable.
255 */
256 " dsra %M0, %L0, 32 \n"
257 " sll %L0, %L0, 0 \n"
258 /*
259 * Compare ret against old, breaking out of the loop if they don't
260 * match.
261 */
262 " bne %M0, %M4, 2f \n"
263 " bne %L0, %L4, 2f \n"
264 /*
265 * Combine the 32 bit halves from the 2 registers that hold the new
266 * variable into a single 64 bit register.
267 */
268 # if MIPS_ISA_REV >= 2
269 " move %L1, %L5 \n"
270 " dins %L1, %M5, 32, 32 \n"
271 # else
272 " dsll %L1, %L5, 32 \n"
273 " dsrl %L1, %L1, 32 \n"
274 " .set noat \n"
275 " dsll $at, %M5, 32 \n"
276 " or %L1, %L1, $at \n"
277 " .set at \n"
278 # endif
279 " .set push \n"
280 " .set " MIPS_ISA_ARCH_LEVEL " \n"
281 /* Attempt to store new at ptr */
282 " scd %L1, %2 \n"
283 /* If we failed, loop! */
284 "\t" __stringify(SC_BEQZ) " %L1, 1b \n"
285 "2: " __SYNC(full, loongson3_war) " \n"
286 " .set pop \n"
287 : "=&r"(ret),
288 "=&r"(tmp),
289 "=" GCC_OFF_SMALL_ASM() (*(unsigned long long *)ptr)
290 : GCC_OFF_SMALL_ASM() (*(unsigned long long *)ptr),
291 "r" (old),
292 "r" (new)
293 : "memory");
294
295 local_irq_restore(flags);
296 return ret;
297 }
298
299 # define arch_cmpxchg64(ptr, o, n) ({ \
300 unsigned long long __old = (__typeof__(*(ptr)))(o); \
301 unsigned long long __new = (__typeof__(*(ptr)))(n); \
302 __typeof__(*(ptr)) __res; \
303 \
304 /* \
305 * We can only use cmpxchg64 if we know that the CPU supports \
306 * 64-bits, ie. lld & scd. Our call to __cmpxchg64_unsupported \
307 * will cause a build error unless cpu_has_64bits is a \
308 * compile-time constant 1. \
309 */ \
310 if (cpu_has_64bits && kernel_uses_llsc) { \
311 smp_mb__before_llsc(); \
312 __res = __cmpxchg64((ptr), __old, __new); \
313 smp_llsc_mb(); \
314 } else { \
315 __res = __cmpxchg64_unsupported(); \
316 } \
317 \
318 __res; \
319 })
320
321 # else /* !CONFIG_SMP */
322 # define arch_cmpxchg64(ptr, o, n) arch_cmpxchg64_local((ptr), (o), (n))
323 # endif /* !CONFIG_SMP */
324 #endif /* !CONFIG_64BIT */
325
326 #endif /* __ASM_CMPXCHG_H */
327
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