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1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
4 */
5
6#ifndef __ASM_ARC_CMPXCHG_H
7#define __ASM_ARC_CMPXCHG_H
8
9#include <linux/build_bug.h>
10#include <linux/types.h>
11
12#include <asm/barrier.h>
13#include <asm/smp.h>
14
15#ifdef CONFIG_ARC_HAS_LLSC
16
17/*
18 * if (*ptr == @old)
19 * *ptr = @new
20 */
21#define __cmpxchg(ptr, old, new) \
22({ \
23 __typeof__(*(ptr)) _prev; \
24 \
25 __asm__ __volatile__( \
26 "1: llock %0, [%1] \n" \
27 " brne %0, %2, 2f \n" \
28 " scond %3, [%1] \n" \
29 " bnz 1b \n" \
30 "2: \n" \
31 : "=&r"(_prev) /* Early clobber prevent reg reuse */ \
32 : "r"(ptr), /* Not "m": llock only supports reg */ \
33 "ir"(old), \
34 "r"(new) /* Not "ir": scond can't take LIMM */ \
35 : "cc", \
36 "memory"); /* gcc knows memory is clobbered */ \
37 \
38 _prev; \
39})
40
41#define arch_cmpxchg_relaxed(ptr, old, new) \
42({ \
43 __typeof__(ptr) _p_ = (ptr); \
44 __typeof__(*(ptr)) _o_ = (old); \
45 __typeof__(*(ptr)) _n_ = (new); \
46 __typeof__(*(ptr)) _prev_; \
47 \
48 switch(sizeof((_p_))) { \
49 case 4: \
50 _prev_ = __cmpxchg(_p_, _o_, _n_); \
51 break; \
52 default: \
53 BUILD_BUG(); \
54 } \
55 _prev_; \
56})
57
58#else
59
60#define arch_cmpxchg(ptr, old, new) \
61({ \
62 volatile __typeof__(ptr) _p_ = (ptr); \
63 __typeof__(*(ptr)) _o_ = (old); \
64 __typeof__(*(ptr)) _n_ = (new); \
65 __typeof__(*(ptr)) _prev_; \
66 unsigned long __flags; \
67 \
68 BUILD_BUG_ON(sizeof(_p_) != 4); \
69 \
70 /* \
71 * spin lock/unlock provide the needed smp_mb() before/after \
72 */ \
73 atomic_ops_lock(__flags); \
74 _prev_ = *_p_; \
75 if (_prev_ == _o_) \
76 *_p_ = _n_; \
77 atomic_ops_unlock(__flags); \
78 _prev_; \
79})
80
81#endif
82
83/*
84 * xchg
85 */
86#ifdef CONFIG_ARC_HAS_LLSC
87
88#define __arch_xchg(ptr, val) \
89({ \
90 __asm__ __volatile__( \
91 " ex %0, [%1] \n" /* set new value */ \
92 : "+r"(val) \
93 : "r"(ptr) \
94 : "memory"); \
95 _val_; /* get old value */ \
96})
97
98#define arch_xchg_relaxed(ptr, val) \
99({ \
100 __typeof__(ptr) _p_ = (ptr); \
101 __typeof__(*(ptr)) _val_ = (val); \
102 \
103 switch(sizeof(*(_p_))) { \
104 case 4: \
105 _val_ = __arch_xchg(_p_, _val_); \
106 break; \
107 default: \
108 BUILD_BUG(); \
109 } \
110 _val_; \
111})
112
113#else /* !CONFIG_ARC_HAS_LLSC */
114
115/*
116 * EX instructions is baseline and present in !LLSC too. But in this
117 * regime it still needs use @atomic_ops_lock spinlock to allow interop
118 * with cmpxchg() which uses spinlock in !LLSC
119 * (llist.h use xchg and cmpxchg on sama data)
120 */
121
122#define arch_xchg(ptr, val) \
123({ \
124 __typeof__(ptr) _p_ = (ptr); \
125 __typeof__(*(ptr)) _val_ = (val); \
126 \
127 unsigned long __flags; \
128 \
129 atomic_ops_lock(__flags); \
130 \
131 __asm__ __volatile__( \
132 " ex %0, [%1] \n" \
133 : "+r"(_val_) \
134 : "r"(_p_) \
135 : "memory"); \
136 \
137 atomic_ops_unlock(__flags); \
138 _val_; \
139})
140
141#endif
142
143#endif
1/*
2 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 */
8
9#ifndef __ASM_ARC_CMPXCHG_H
10#define __ASM_ARC_CMPXCHG_H
11
12#include <linux/types.h>
13
14#include <asm/barrier.h>
15#include <asm/smp.h>
16
17#ifdef CONFIG_ARC_HAS_LLSC
18
19static inline unsigned long
20__cmpxchg(volatile void *ptr, unsigned long expected, unsigned long new)
21{
22 unsigned long prev;
23
24 /*
25 * Explicit full memory barrier needed before/after as
26 * LLOCK/SCOND thmeselves don't provide any such semantics
27 */
28 smp_mb();
29
30 __asm__ __volatile__(
31 "1: llock %0, [%1] \n"
32 " brne %0, %2, 2f \n"
33 " scond %3, [%1] \n"
34 " bnz 1b \n"
35 "2: \n"
36 : "=&r"(prev) /* Early clobber, to prevent reg reuse */
37 : "r"(ptr), /* Not "m": llock only supports reg direct addr mode */
38 "ir"(expected),
39 "r"(new) /* can't be "ir". scond can't take LIMM for "b" */
40 : "cc", "memory"); /* so that gcc knows memory is being written here */
41
42 smp_mb();
43
44 return prev;
45}
46
47#elif !defined(CONFIG_ARC_PLAT_EZNPS)
48
49static inline unsigned long
50__cmpxchg(volatile void *ptr, unsigned long expected, unsigned long new)
51{
52 unsigned long flags;
53 int prev;
54 volatile unsigned long *p = ptr;
55
56 /*
57 * spin lock/unlock provide the needed smp_mb() before/after
58 */
59 atomic_ops_lock(flags);
60 prev = *p;
61 if (prev == expected)
62 *p = new;
63 atomic_ops_unlock(flags);
64 return prev;
65}
66
67#else /* CONFIG_ARC_PLAT_EZNPS */
68
69static inline unsigned long
70__cmpxchg(volatile void *ptr, unsigned long expected, unsigned long new)
71{
72 /*
73 * Explicit full memory barrier needed before/after
74 */
75 smp_mb();
76
77 write_aux_reg(CTOP_AUX_GPA1, expected);
78
79 __asm__ __volatile__(
80 " mov r2, %0\n"
81 " mov r3, %1\n"
82 " .word %2\n"
83 " mov %0, r2"
84 : "+r"(new)
85 : "r"(ptr), "i"(CTOP_INST_EXC_DI_R2_R2_R3)
86 : "r2", "r3", "memory");
87
88 smp_mb();
89
90 return new;
91}
92
93#endif /* CONFIG_ARC_HAS_LLSC */
94
95#define cmpxchg(ptr, o, n) ((typeof(*(ptr)))__cmpxchg((ptr), \
96 (unsigned long)(o), (unsigned long)(n)))
97
98/*
99 * atomic_cmpxchg is same as cmpxchg
100 * LLSC: only different in data-type, semantics are exactly same
101 * !LLSC: cmpxchg() has to use an external lock atomic_ops_lock to guarantee
102 * semantics, and this lock also happens to be used by atomic_*()
103 */
104#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
105
106
107#ifndef CONFIG_ARC_PLAT_EZNPS
108
109/*
110 * xchg (reg with memory) based on "Native atomic" EX insn
111 */
112static inline unsigned long __xchg(unsigned long val, volatile void *ptr,
113 int size)
114{
115 extern unsigned long __xchg_bad_pointer(void);
116
117 switch (size) {
118 case 4:
119 smp_mb();
120
121 __asm__ __volatile__(
122 " ex %0, [%1] \n"
123 : "+r"(val)
124 : "r"(ptr)
125 : "memory");
126
127 smp_mb();
128
129 return val;
130 }
131 return __xchg_bad_pointer();
132}
133
134#define _xchg(ptr, with) ((typeof(*(ptr)))__xchg((unsigned long)(with), (ptr), \
135 sizeof(*(ptr))))
136
137/*
138 * xchg() maps directly to ARC EX instruction which guarantees atomicity.
139 * However in !LLSC config, it also needs to be use @atomic_ops_lock spinlock
140 * due to a subtle reason:
141 * - For !LLSC, cmpxchg() needs to use that lock (see above) and there is lot
142 * of kernel code which calls xchg()/cmpxchg() on same data (see llist.h)
143 * Hence xchg() needs to follow same locking rules.
144 *
145 * Technically the lock is also needed for UP (boils down to irq save/restore)
146 * but we can cheat a bit since cmpxchg() atomic_ops_lock() would cause irqs to
147 * be disabled thus can't possibly be interrpted/preempted/clobbered by xchg()
148 * Other way around, xchg is one instruction anyways, so can't be interrupted
149 * as such
150 */
151
152#if !defined(CONFIG_ARC_HAS_LLSC) && defined(CONFIG_SMP)
153
154#define xchg(ptr, with) \
155({ \
156 unsigned long flags; \
157 typeof(*(ptr)) old_val; \
158 \
159 atomic_ops_lock(flags); \
160 old_val = _xchg(ptr, with); \
161 atomic_ops_unlock(flags); \
162 old_val; \
163})
164
165#else
166
167#define xchg(ptr, with) _xchg(ptr, with)
168
169#endif
170
171#else /* CONFIG_ARC_PLAT_EZNPS */
172
173static inline unsigned long __xchg(unsigned long val, volatile void *ptr,
174 int size)
175{
176 extern unsigned long __xchg_bad_pointer(void);
177
178 switch (size) {
179 case 4:
180 /*
181 * Explicit full memory barrier needed before/after
182 */
183 smp_mb();
184
185 __asm__ __volatile__(
186 " mov r2, %0\n"
187 " mov r3, %1\n"
188 " .word %2\n"
189 " mov %0, r2\n"
190 : "+r"(val)
191 : "r"(ptr), "i"(CTOP_INST_XEX_DI_R2_R2_R3)
192 : "r2", "r3", "memory");
193
194 smp_mb();
195
196 return val;
197 }
198 return __xchg_bad_pointer();
199}
200
201#define xchg(ptr, with) ((typeof(*(ptr)))__xchg((unsigned long)(with), (ptr), \
202 sizeof(*(ptr))))
203
204#endif /* CONFIG_ARC_PLAT_EZNPS */
205
206/*
207 * "atomic" variant of xchg()
208 * REQ: It needs to follow the same serialization rules as other atomic_xxx()
209 * Since xchg() doesn't always do that, it would seem that following defintion
210 * is incorrect. But here's the rationale:
211 * SMP : Even xchg() takes the atomic_ops_lock, so OK.
212 * LLSC: atomic_ops_lock are not relevant at all (even if SMP, since LLSC
213 * is natively "SMP safe", no serialization required).
214 * UP : other atomics disable IRQ, so no way a difft ctxt atomic_xchg()
215 * could clobber them. atomic_xchg() itself would be 1 insn, so it
216 * can't be clobbered by others. Thus no serialization required when
217 * atomic_xchg is involved.
218 */
219#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
220
221#endif