1 /* 2 * 1,2 and 4 byte cmpxchg and xchg implementations for OpenRISC. 3 * 4 * Copyright (C) 2014 Stefan Kristiansson <stefan.kristiansson@saunalahti.fi> 5 * Copyright (C) 2017 Stafford Horne <shorne@gmail.com> 6 * 7 * This file is licensed under the terms of the GNU General Public License 8 * version 2. This program is licensed "as is" without any warranty of any 9 * kind, whether express or implied. 10 * 11 * Note: 12 * The portable implementations of 1 and 2 byte xchg and cmpxchg using a 4 13 * byte cmpxchg is sourced heavily from the sh and mips implementations. 14 */ 15 16 #ifndef __ASM_OPENRISC_CMPXCHG_H 17 #define __ASM_OPENRISC_CMPXCHG_H 18 19 #include <linux/bits.h> 20 #include <linux/compiler.h> 21 #include <linux/types.h> 22 23 #define __HAVE_ARCH_CMPXCHG 1 24 25 static inline unsigned long cmpxchg_u32(volatile void *ptr, 26 unsigned long old, unsigned long new) 27 { 28 __asm__ __volatile__( 29 "1: l.lwa %0, 0(%1) \n" 30 " l.sfeq %0, %2 \n" 31 " l.bnf 2f \n" 32 " l.nop \n" 33 " l.swa 0(%1), %3 \n" 34 " l.bnf 1b \n" 35 " l.nop \n" 36 "2: \n" 37 : "=&r"(old) 38 : "r"(ptr), "r"(old), "r"(new) 39 : "cc", "memory"); 40 41 return old; 42 } 43 44 static inline unsigned long xchg_u32(volatile void *ptr, 45 unsigned long val) 46 { 47 __asm__ __volatile__( 48 "1: l.lwa %0, 0(%1) \n" 49 " l.swa 0(%1), %2 \n" 50 " l.bnf 1b \n" 51 " l.nop \n" 52 : "=&r"(val) 53 : "r"(ptr), "r"(val) 54 : "cc", "memory"); 55 56 return val; 57 } 58 59 static inline u32 cmpxchg_small(volatile void *ptr, u32 old, u32 new, 60 int size) 61 { 62 int off = (unsigned long)ptr % sizeof(u32); 63 volatile u32 *p = ptr - off; 64 #ifdef __BIG_ENDIAN 65 int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE; 66 #else 67 int bitoff = off * BITS_PER_BYTE; 68 #endif 69 u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff; 70 u32 load32, old32, new32; 71 u32 ret; 72 73 load32 = READ_ONCE(*p); 74 75 while (true) { 76 ret = (load32 & bitmask) >> bitoff; 77 if (old != ret) 78 return ret; 79 80 old32 = (load32 & ~bitmask) | (old << bitoff); 81 new32 = (load32 & ~bitmask) | (new << bitoff); 82 83 /* Do 32 bit cmpxchg */ 84 load32 = cmpxchg_u32(p, old32, new32); 85 if (load32 == old32) 86 return old; 87 } 88 } 89 90 /* xchg */ 91 92 static inline u32 xchg_small(volatile void *ptr, u32 x, int size) 93 { 94 int off = (unsigned long)ptr % sizeof(u32); 95 volatile u32 *p = ptr - off; 96 #ifdef __BIG_ENDIAN 97 int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE; 98 #else 99 int bitoff = off * BITS_PER_BYTE; 100 #endif 101 u32 bitmask = ((0x1 << size * BITS_PER_BYTE) - 1) << bitoff; 102 u32 oldv, newv; 103 u32 ret; 104 105 do { 106 oldv = READ_ONCE(*p); 107 ret = (oldv & bitmask) >> bitoff; 108 newv = (oldv & ~bitmask) | (x << bitoff); 109 } while (cmpxchg_u32(p, oldv, newv) != oldv); 110 111 return ret; 112 } 113 114 /* 115 * This function doesn't exist, so you'll get a linker error 116 * if something tries to do an invalid cmpxchg(). 117 */ 118 extern unsigned long __cmpxchg_called_with_bad_pointer(void) 119 __compiletime_error("Bad argument size for cmpxchg"); 120 121 static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, 122 unsigned long new, int size) 123 { 124 switch (size) { 125 case 1: 126 case 2: 127 return cmpxchg_small(ptr, old, new, size); 128 case 4: 129 return cmpxchg_u32(ptr, old, new); 130 default: 131 return __cmpxchg_called_with_bad_pointer(); 132 } 133 } 134 135 #define arch_cmpxchg(ptr, o, n) \ 136 ({ \ 137 (__typeof__(*(ptr))) __cmpxchg((ptr), \ 138 (unsigned long)(o), \ 139 (unsigned long)(n), \ 140 sizeof(*(ptr))); \ 141 }) 142 143 /* 144 * This function doesn't exist, so you'll get a linker error if 145 * something tries to do an invalidly-sized xchg(). 146 */ 147 extern unsigned long __xchg_called_with_bad_pointer(void) 148 __compiletime_error("Bad argument size for xchg"); 149 150 static inline unsigned long 151 __arch_xchg(volatile void *ptr, unsigned long with, int size) 152 { 153 switch (size) { 154 case 1: 155 case 2: 156 return xchg_small(ptr, with, size); 157 case 4: 158 return xchg_u32(ptr, with); 159 default: 160 return __xchg_called_with_bad_pointer(); 161 } 162 } 163 164 #define arch_xchg(ptr, with) \ 165 ({ \ 166 (__typeof__(*(ptr))) __arch_xchg((ptr), \ 167 (unsigned long)(with), \ 168 sizeof(*(ptr))); \ 169 }) 170 171 #endif /* __ASM_OPENRISC_CMPXCHG_H */ 172