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Linux/arch/openrisc/include/asm/cmpxchg.h

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  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 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 __xchg(volatile void *ptr, unsigned long with,
151                 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 xchg(ptr, with)                                                 \
165         ({                                                              \
166                 (__typeof__(*(ptr))) __xchg((ptr),                      \
167                                             (unsigned long)(with),      \
168                                             sizeof(*(ptr)));            \
169         })
170 
171 #endif /* __ASM_OPENRISC_CMPXCHG_H */
172 

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