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