1 /* 2 * Atomic xchg and cmpxchg operations. 3 * 4 * This file is subject to the terms and conditions of the GNU General Public 5 * License. See the file "COPYING" in the main directory of this archive 6 * for more details. 7 * 8 * Copyright (C) 2001 - 2005 Tensilica Inc. 9 */ 10 11 #ifndef _XTENSA_CMPXCHG_H 12 #define _XTENSA_CMPXCHG_H 13 14 #ifndef __ASSEMBLY__ 15 16 #include <linux/bits.h> 17 #include <linux/stringify.h> 18 19 /* 20 * cmpxchg 21 */ 22 23 static inline unsigned long 24 __cmpxchg_u32(volatile int *p, int old, int new) 25 { 26 #if XCHAL_HAVE_S32C1I 27 __asm__ __volatile__( 28 " wsr %2, scompare1\n" 29 " s32c1i %0, %1, 0\n" 30 : "+a" (new) 31 : "a" (p), "a" (old) 32 : "memory" 33 ); 34 35 return new; 36 #else 37 __asm__ __volatile__( 38 " rsil a15, "__stringify(TOPLEVEL)"\n" 39 " l32i %0, %1, 0\n" 40 " bne %0, %2, 1f\n" 41 " s32i %3, %1, 0\n" 42 "1:\n" 43 " wsr a15, ps\n" 44 " rsync\n" 45 : "=&a" (old) 46 : "a" (p), "a" (old), "r" (new) 47 : "a15", "memory"); 48 return old; 49 #endif 50 } 51 /* This function doesn't exist, so you'll get a linker error 52 * if something tries to do an invalid cmpxchg(). */ 53 54 extern void __cmpxchg_called_with_bad_pointer(void); 55 56 static __inline__ unsigned long 57 __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size) 58 { 59 switch (size) { 60 case 4: return __cmpxchg_u32(ptr, old, new); 61 default: __cmpxchg_called_with_bad_pointer(); 62 return old; 63 } 64 } 65 66 #define cmpxchg(ptr,o,n) \ 67 ({ __typeof__(*(ptr)) _o_ = (o); \ 68 __typeof__(*(ptr)) _n_ = (n); \ 69 (__typeof__(*(ptr))) __cmpxchg((ptr), (unsigned long)_o_, \ 70 (unsigned long)_n_, sizeof (*(ptr))); \ 71 }) 72 73 #include <asm-generic/cmpxchg-local.h> 74 75 static inline unsigned long __cmpxchg_local(volatile void *ptr, 76 unsigned long old, 77 unsigned long new, int size) 78 { 79 switch (size) { 80 case 4: 81 return __cmpxchg_u32(ptr, old, new); 82 default: 83 return __cmpxchg_local_generic(ptr, old, new, size); 84 } 85 86 return old; 87 } 88 89 /* 90 * cmpxchg_local and cmpxchg64_local are atomic wrt current CPU. Always make 91 * them available. 92 */ 93 #define cmpxchg_local(ptr, o, n) \ 94 ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\ 95 (unsigned long)(n), sizeof(*(ptr)))) 96 #define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n)) 97 #define cmpxchg64(ptr, o, n) cmpxchg64_local((ptr), (o), (n)) 98 99 /* 100 * xchg_u32 101 * 102 * Note that a15 is used here because the register allocation 103 * done by the compiler is not guaranteed and a window overflow 104 * may not occur between the rsil and wsr instructions. By using 105 * a15 in the rsil, the machine is guaranteed to be in a state 106 * where no register reference will cause an overflow. 107 */ 108 109 static inline unsigned long xchg_u32(volatile int * m, unsigned long val) 110 { 111 #if XCHAL_HAVE_S32C1I 112 unsigned long tmp, result; 113 __asm__ __volatile__( 114 "1: l32i %1, %2, 0\n" 115 " mov %0, %3\n" 116 " wsr %1, scompare1\n" 117 " s32c1i %0, %2, 0\n" 118 " bne %0, %1, 1b\n" 119 : "=&a" (result), "=&a" (tmp) 120 : "a" (m), "a" (val) 121 : "memory" 122 ); 123 return result; 124 #else 125 unsigned long tmp; 126 __asm__ __volatile__( 127 " rsil a15, "__stringify(TOPLEVEL)"\n" 128 " l32i %0, %1, 0\n" 129 " s32i %2, %1, 0\n" 130 " wsr a15, ps\n" 131 " rsync\n" 132 : "=&a" (tmp) 133 : "a" (m), "a" (val) 134 : "a15", "memory"); 135 return tmp; 136 #endif 137 } 138 139 #define xchg(ptr,x) \ 140 ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr)))) 141 142 static inline u32 xchg_small(volatile void *ptr, u32 x, int size) 143 { 144 int off = (unsigned long)ptr % sizeof(u32); 145 volatile u32 *p = ptr - off; 146 #ifdef __BIG_ENDIAN 147 int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE; 148 #else 149 int bitoff = off * BITS_PER_BYTE; 150 #endif 151 u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff; 152 u32 oldv, newv; 153 u32 ret; 154 155 do { 156 oldv = READ_ONCE(*p); 157 ret = (oldv & bitmask) >> bitoff; 158 newv = (oldv & ~bitmask) | (x << bitoff); 159 } while (__cmpxchg_u32(p, oldv, newv) != oldv); 160 161 return ret; 162 } 163 164 /* 165 * This only works if the compiler isn't horribly bad at optimizing. 166 * gcc-2.5.8 reportedly can't handle this, but I define that one to 167 * be dead anyway. 168 */ 169 170 extern void __xchg_called_with_bad_pointer(void); 171 172 static __inline__ unsigned long 173 __xchg(unsigned long x, volatile void * ptr, int size) 174 { 175 switch (size) { 176 case 1: 177 return xchg_small(ptr, x, 1); 178 case 2: 179 return xchg_small(ptr, x, 2); 180 case 4: 181 return xchg_u32(ptr, x); 182 default: 183 __xchg_called_with_bad_pointer(); 184 return x; 185 } 186 } 187 188 #endif /* __ASSEMBLY__ */ 189 190 #endif /* _XTENSA_CMPXCHG_H */ 191