1 /* 2 * include/asm-xtensa/atomic.h 3 * 4 * Atomic operations that C can't guarantee us. Useful for resource counting.. 5 * 6 * This file is subject to the terms and conditions of the GNU General Public 7 * License. See the file "COPYING" in the main directory of this archive 8 * for more details. 9 * 10 * Copyright (C) 2001 - 2008 Tensilica Inc. 11 */ 12 13 #ifndef _XTENSA_ATOMIC_H 14 #define _XTENSA_ATOMIC_H 15 16 #include <linux/stringify.h> 17 #include <linux/types.h> 18 19 #ifdef __KERNEL__ 20 #include <asm/processor.h> 21 #include <asm/cmpxchg.h> 22 #include <asm/barrier.h> 23 24 #define ATOMIC_INIT(i) { (i) } 25 26 /* 27 * This Xtensa implementation assumes that the right mechanism 28 * for exclusion is for locking interrupts to level EXCM_LEVEL. 29 * 30 * Locking interrupts looks like this: 31 * 32 * rsil a15, TOPLEVEL 33 * <code> 34 * wsr a15, PS 35 * rsync 36 * 37 * Note that a15 is used here because the register allocation 38 * done by the compiler is not guaranteed and a window overflow 39 * may not occur between the rsil and wsr instructions. By using 40 * a15 in the rsil, the machine is guaranteed to be in a state 41 * where no register reference will cause an overflow. 42 */ 43 44 /** 45 * atomic_read - read atomic variable 46 * @v: pointer of type atomic_t 47 * 48 * Atomically reads the value of @v. 49 */ 50 #define atomic_read(v) ACCESS_ONCE((v)->counter) 51 52 /** 53 * atomic_set - set atomic variable 54 * @v: pointer of type atomic_t 55 * @i: required value 56 * 57 * Atomically sets the value of @v to @i. 58 */ 59 #define atomic_set(v,i) ((v)->counter = (i)) 60 61 #if XCHAL_HAVE_S32C1I 62 #define ATOMIC_OP(op) \ 63 static inline void atomic_##op(int i, atomic_t * v) \ 64 { \ 65 unsigned long tmp; \ 66 int result; \ 67 \ 68 __asm__ __volatile__( \ 69 "1: l32i %1, %3, 0\n" \ 70 " wsr %1, scompare1\n" \ 71 " " #op " %0, %1, %2\n" \ 72 " s32c1i %0, %3, 0\n" \ 73 " bne %0, %1, 1b\n" \ 74 : "=&a" (result), "=&a" (tmp) \ 75 : "a" (i), "a" (v) \ 76 : "memory" \ 77 ); \ 78 } \ 79 80 #define ATOMIC_OP_RETURN(op) \ 81 static inline int atomic_##op##_return(int i, atomic_t * v) \ 82 { \ 83 unsigned long tmp; \ 84 int result; \ 85 \ 86 __asm__ __volatile__( \ 87 "1: l32i %1, %3, 0\n" \ 88 " wsr %1, scompare1\n" \ 89 " " #op " %0, %1, %2\n" \ 90 " s32c1i %0, %3, 0\n" \ 91 " bne %0, %1, 1b\n" \ 92 " " #op " %0, %0, %2\n" \ 93 : "=&a" (result), "=&a" (tmp) \ 94 : "a" (i), "a" (v) \ 95 : "memory" \ 96 ); \ 97 \ 98 return result; \ 99 } 100 101 #else /* XCHAL_HAVE_S32C1I */ 102 103 #define ATOMIC_OP(op) \ 104 static inline void atomic_##op(int i, atomic_t * v) \ 105 { \ 106 unsigned int vval; \ 107 \ 108 __asm__ __volatile__( \ 109 " rsil a15, "__stringify(TOPLEVEL)"\n"\ 110 " l32i %0, %2, 0\n" \ 111 " " #op " %0, %0, %1\n" \ 112 " s32i %0, %2, 0\n" \ 113 " wsr a15, ps\n" \ 114 " rsync\n" \ 115 : "=&a" (vval) \ 116 : "a" (i), "a" (v) \ 117 : "a15", "memory" \ 118 ); \ 119 } \ 120 121 #define ATOMIC_OP_RETURN(op) \ 122 static inline int atomic_##op##_return(int i, atomic_t * v) \ 123 { \ 124 unsigned int vval; \ 125 \ 126 __asm__ __volatile__( \ 127 " rsil a15,"__stringify(TOPLEVEL)"\n" \ 128 " l32i %0, %2, 0\n" \ 129 " " #op " %0, %0, %1\n" \ 130 " s32i %0, %2, 0\n" \ 131 " wsr a15, ps\n" \ 132 " rsync\n" \ 133 : "=&a" (vval) \ 134 : "a" (i), "a" (v) \ 135 : "a15", "memory" \ 136 ); \ 137 \ 138 return vval; \ 139 } 140 141 #endif /* XCHAL_HAVE_S32C1I */ 142 143 #define ATOMIC_OPS(op) ATOMIC_OP(op) ATOMIC_OP_RETURN(op) 144 145 ATOMIC_OPS(add) 146 ATOMIC_OPS(sub) 147 148 ATOMIC_OP(and) 149 ATOMIC_OP(or) 150 ATOMIC_OP(xor) 151 152 #undef ATOMIC_OPS 153 #undef ATOMIC_OP_RETURN 154 #undef ATOMIC_OP 155 156 /** 157 * atomic_sub_and_test - subtract value from variable and test result 158 * @i: integer value to subtract 159 * @v: pointer of type atomic_t 160 * 161 * Atomically subtracts @i from @v and returns 162 * true if the result is zero, or false for all 163 * other cases. 164 */ 165 #define atomic_sub_and_test(i,v) (atomic_sub_return((i),(v)) == 0) 166 167 /** 168 * atomic_inc - increment atomic variable 169 * @v: pointer of type atomic_t 170 * 171 * Atomically increments @v by 1. 172 */ 173 #define atomic_inc(v) atomic_add(1,(v)) 174 175 /** 176 * atomic_inc - increment atomic variable 177 * @v: pointer of type atomic_t 178 * 179 * Atomically increments @v by 1. 180 */ 181 #define atomic_inc_return(v) atomic_add_return(1,(v)) 182 183 /** 184 * atomic_dec - decrement atomic variable 185 * @v: pointer of type atomic_t 186 * 187 * Atomically decrements @v by 1. 188 */ 189 #define atomic_dec(v) atomic_sub(1,(v)) 190 191 /** 192 * atomic_dec_return - decrement atomic variable 193 * @v: pointer of type atomic_t 194 * 195 * Atomically decrements @v by 1. 196 */ 197 #define atomic_dec_return(v) atomic_sub_return(1,(v)) 198 199 /** 200 * atomic_dec_and_test - decrement and test 201 * @v: pointer of type atomic_t 202 * 203 * Atomically decrements @v by 1 and 204 * returns true if the result is 0, or false for all other 205 * cases. 206 */ 207 #define atomic_dec_and_test(v) (atomic_sub_return(1,(v)) == 0) 208 209 /** 210 * atomic_inc_and_test - increment and test 211 * @v: pointer of type atomic_t 212 * 213 * Atomically increments @v by 1 214 * and returns true if the result is zero, or false for all 215 * other cases. 216 */ 217 #define atomic_inc_and_test(v) (atomic_add_return(1,(v)) == 0) 218 219 /** 220 * atomic_add_negative - add and test if negative 221 * @v: pointer of type atomic_t 222 * @i: integer value to add 223 * 224 * Atomically adds @i to @v and returns true 225 * if the result is negative, or false when 226 * result is greater than or equal to zero. 227 */ 228 #define atomic_add_negative(i,v) (atomic_add_return((i),(v)) < 0) 229 230 #define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n))) 231 #define atomic_xchg(v, new) (xchg(&((v)->counter), new)) 232 233 /** 234 * __atomic_add_unless - add unless the number is a given value 235 * @v: pointer of type atomic_t 236 * @a: the amount to add to v... 237 * @u: ...unless v is equal to u. 238 * 239 * Atomically adds @a to @v, so long as it was not @u. 240 * Returns the old value of @v. 241 */ 242 static __inline__ int __atomic_add_unless(atomic_t *v, int a, int u) 243 { 244 int c, old; 245 c = atomic_read(v); 246 for (;;) { 247 if (unlikely(c == (u))) 248 break; 249 old = atomic_cmpxchg((v), c, c + (a)); 250 if (likely(old == c)) 251 break; 252 c = old; 253 } 254 return c; 255 } 256 257 #endif /* __KERNEL__ */ 258 259 #endif /* _XTENSA_ATOMIC_H */ 260