xref: /openbmc/linux/arch/xtensa/include/asm/cmpxchg.h (revision 3d3337de)
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/stringify.h>
17 
18 /*
19  * cmpxchg
20  */
21 
22 static inline unsigned long
23 __cmpxchg_u32(volatile int *p, int old, int new)
24 {
25 #if XCHAL_HAVE_S32C1I
26 	__asm__ __volatile__(
27 			"       wsr     %2, scompare1\n"
28 			"       s32c1i  %0, %1, 0\n"
29 			: "+a" (new)
30 			: "a" (p), "a" (old)
31 			: "memory"
32 			);
33 
34 	return new;
35 #else
36 	__asm__ __volatile__(
37 			"       rsil    a15, "__stringify(LOCKLEVEL)"\n"
38 			"       l32i    %0, %1, 0\n"
39 			"       bne     %0, %2, 1f\n"
40 			"       s32i    %3, %1, 0\n"
41 			"1:\n"
42 			"       wsr     a15, ps\n"
43 			"       rsync\n"
44 			: "=&a" (old)
45 			: "a" (p), "a" (old), "r" (new)
46 			: "a15", "memory");
47 	return old;
48 #endif
49 }
50 /* This function doesn't exist, so you'll get a linker error
51  * if something tries to do an invalid cmpxchg(). */
52 
53 extern void __cmpxchg_called_with_bad_pointer(void);
54 
55 static __inline__ unsigned long
56 __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size)
57 {
58 	switch (size) {
59 	case 4:  return __cmpxchg_u32(ptr, old, new);
60 	default: __cmpxchg_called_with_bad_pointer();
61 		 return old;
62 	}
63 }
64 
65 #define cmpxchg(ptr,o,n)						      \
66 	({ __typeof__(*(ptr)) _o_ = (o);				      \
67 	   __typeof__(*(ptr)) _n_ = (n);				      \
68 	   (__typeof__(*(ptr))) __cmpxchg((ptr), (unsigned long)_o_,	      \
69 	   			        (unsigned long)_n_, sizeof (*(ptr))); \
70 	})
71 
72 #include <asm-generic/cmpxchg-local.h>
73 
74 static inline unsigned long __cmpxchg_local(volatile void *ptr,
75 				      unsigned long old,
76 				      unsigned long new, int size)
77 {
78 	switch (size) {
79 	case 4:
80 		return __cmpxchg_u32(ptr, old, new);
81 	default:
82 		return __cmpxchg_local_generic(ptr, old, new, size);
83 	}
84 
85 	return old;
86 }
87 
88 /*
89  * cmpxchg_local and cmpxchg64_local are atomic wrt current CPU. Always make
90  * them available.
91  */
92 #define cmpxchg_local(ptr, o, n)				  	       \
93 	((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
94 			(unsigned long)(n), sizeof(*(ptr))))
95 #define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
96 #define cmpxchg64(ptr, o, n)    cmpxchg64_local((ptr), (o), (n))
97 
98 /*
99  * xchg_u32
100  *
101  * Note that a15 is used here because the register allocation
102  * done by the compiler is not guaranteed and a window overflow
103  * may not occur between the rsil and wsr instructions. By using
104  * a15 in the rsil, the machine is guaranteed to be in a state
105  * where no register reference will cause an overflow.
106  */
107 
108 static inline unsigned long xchg_u32(volatile int * m, unsigned long val)
109 {
110 #if XCHAL_HAVE_S32C1I
111 	unsigned long tmp, result;
112 	__asm__ __volatile__(
113 			"1:     l32i    %1, %2, 0\n"
114 			"       mov     %0, %3\n"
115 			"       wsr     %1, scompare1\n"
116 			"       s32c1i  %0, %2, 0\n"
117 			"       bne     %0, %1, 1b\n"
118 			: "=&a" (result), "=&a" (tmp)
119 			: "a" (m), "a" (val)
120 			: "memory"
121 			);
122 	return result;
123 #else
124 	unsigned long tmp;
125 	__asm__ __volatile__(
126 			"       rsil    a15, "__stringify(LOCKLEVEL)"\n"
127 			"       l32i    %0, %1, 0\n"
128 			"       s32i    %2, %1, 0\n"
129 			"       wsr     a15, ps\n"
130 			"       rsync\n"
131 			: "=&a" (tmp)
132 			: "a" (m), "a" (val)
133 			: "a15", "memory");
134 	return tmp;
135 #endif
136 }
137 
138 #define xchg(ptr,x) \
139 	((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))
140 
141 /*
142  * This only works if the compiler isn't horribly bad at optimizing.
143  * gcc-2.5.8 reportedly can't handle this, but I define that one to
144  * be dead anyway.
145  */
146 
147 extern void __xchg_called_with_bad_pointer(void);
148 
149 static __inline__ unsigned long
150 __xchg(unsigned long x, volatile void * ptr, int size)
151 {
152 	switch (size) {
153 		case 4:
154 			return xchg_u32(ptr, x);
155 	}
156 	__xchg_called_with_bad_pointer();
157 	return x;
158 }
159 
160 #endif /* __ASSEMBLY__ */
161 
162 #endif /* _XTENSA_CMPXCHG_H */
163