1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
|
/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 2006 by Ralf Baechle (ralf@linux-mips.org)
*/
#ifndef __ASM_BARRIER_H
#define __ASM_BARRIER_H
#include <asm/addrspace.h>
/*
* Sync types defined by the MIPS architecture (document MD00087 table 6.5)
* These values are used with the sync instruction to perform memory barriers.
* Types of ordering guarantees available through the SYNC instruction:
* - Completion Barriers
* - Ordering Barriers
* As compared to the completion barrier, the ordering barrier is a
* lighter-weight operation as it does not require the specified instructions
* before the SYNC to be already completed. Instead it only requires that those
* specified instructions which are subsequent to the SYNC in the instruction
* stream are never re-ordered for processing ahead of the specified
* instructions which are before the SYNC in the instruction stream.
* This potentially reduces how many cycles the barrier instruction must stall
* before it completes.
* Implementations that do not use any of the non-zero values of stype to define
* different barriers, such as ordering barriers, must make those stype values
* act the same as stype zero.
*/
/*
* Completion barriers:
* - Every synchronizable specified memory instruction (loads or stores or both)
* that occurs in the instruction stream before the SYNC instruction must be
* already globally performed before any synchronizable specified memory
* instructions that occur after the SYNC are allowed to be performed, with
* respect to any other processor or coherent I/O module.
*
* - The barrier does not guarantee the order in which instruction fetches are
* performed.
*
* - A stype value of zero will always be defined such that it performs the most
* complete set of synchronization operations that are defined.This means
* stype zero always does a completion barrier that affects both loads and
* stores preceding the SYNC instruction and both loads and stores that are
* subsequent to the SYNC instruction. Non-zero values of stype may be defined
* by the architecture or specific implementations to perform synchronization
* behaviors that are less complete than that of stype zero. If an
* implementation does not use one of these non-zero values to define a
* different synchronization behavior, then that non-zero value of stype must
* act the same as stype zero completion barrier. This allows software written
* for an implementation with a lighter-weight barrier to work on another
* implementation which only implements the stype zero completion barrier.
*
* - A completion barrier is required, potentially in conjunction with SSNOP (in
* Release 1 of the Architecture) or EHB (in Release 2 of the Architecture),
* to guarantee that memory reference results are visible across operating
* mode changes. For example, a completion barrier is required on some
* implementations on entry to and exit from Debug Mode to guarantee that
* memory effects are handled correctly.
*/
/*
* stype 0 - A completion barrier that affects preceding loads and stores and
* subsequent loads and stores.
* Older instructions which must reach the load/store ordering point before the
* SYNC instruction completes: Loads, Stores
* Younger instructions which must reach the load/store ordering point only
* after the SYNC instruction completes: Loads, Stores
* Older instructions which must be globally performed when the SYNC instruction
* completes: Loads, Stores
*/
#define STYPE_SYNC 0x0
/*
* Ordering barriers:
* - Every synchronizable specified memory instruction (loads or stores or both)
* that occurs in the instruction stream before the SYNC instruction must
* reach a stage in the load/store datapath after which no instruction
* re-ordering is possible before any synchronizable specified memory
* instruction which occurs after the SYNC instruction in the instruction
* stream reaches the same stage in the load/store datapath.
*
* - If any memory instruction before the SYNC instruction in program order,
* generates a memory request to the external memory and any memory
* instruction after the SYNC instruction in program order also generates a
* memory request to external memory, the memory request belonging to the
* older instruction must be globally performed before the time the memory
* request belonging to the younger instruction is globally performed.
*
* - The barrier does not guarantee the order in which instruction fetches are
* performed.
*/
/*
* stype 0x10 - An ordering barrier that affects preceding loads and stores and
* subsequent loads and stores.
* Older instructions which must reach the load/store ordering point before the
* SYNC instruction completes: Loads, Stores
* Younger instructions which must reach the load/store ordering point only
* after the SYNC instruction completes: Loads, Stores
* Older instructions which must be globally performed when the SYNC instruction
* completes: N/A
*/
#define STYPE_SYNC_MB 0x10
#ifdef CONFIG_CPU_HAS_SYNC
#define __sync() \
__asm__ __volatile__( \
".set push\n\t" \
".set noreorder\n\t" \
".set mips2\n\t" \
"sync\n\t" \
".set pop" \
: /* no output */ \
: /* no input */ \
: "memory")
#else
#define __sync() do { } while(0)
#endif
#define __fast_iob() \
__asm__ __volatile__( \
".set push\n\t" \
".set noreorder\n\t" \
"lw $0,%0\n\t" \
"nop\n\t" \
".set pop" \
: /* no output */ \
: "m" (*(int *)CKSEG1) \
: "memory")
#ifdef CONFIG_CPU_CAVIUM_OCTEON
# define OCTEON_SYNCW_STR ".set push\n.set arch=octeon\nsyncw\nsyncw\n.set pop\n"
# define __syncw() __asm__ __volatile__(OCTEON_SYNCW_STR : : : "memory")
# define fast_wmb() __syncw()
# define fast_rmb() barrier()
# define fast_mb() __sync()
# define fast_iob() do { } while (0)
#else /* ! CONFIG_CPU_CAVIUM_OCTEON */
# define fast_wmb() __sync()
# define fast_rmb() __sync()
# define fast_mb() __sync()
# ifdef CONFIG_SGI_IP28
# define fast_iob() \
__asm__ __volatile__( \
".set push\n\t" \
".set noreorder\n\t" \
"lw $0,%0\n\t" \
"sync\n\t" \
"lw $0,%0\n\t" \
".set pop" \
: /* no output */ \
: "m" (*(int *)CKSEG1ADDR(0x1fa00004)) \
: "memory")
# else
# define fast_iob() \
do { \
__sync(); \
__fast_iob(); \
} while (0)
# endif
#endif /* CONFIG_CPU_CAVIUM_OCTEON */
#ifdef CONFIG_CPU_HAS_WB
#include <asm/wbflush.h>
#define mb() wbflush()
#define iob() wbflush()
#else /* !CONFIG_CPU_HAS_WB */
#define mb() fast_mb()
#define iob() fast_iob()
#endif /* !CONFIG_CPU_HAS_WB */
#define wmb() fast_wmb()
#define rmb() fast_rmb()
#if defined(CONFIG_WEAK_ORDERING)
# ifdef CONFIG_CPU_CAVIUM_OCTEON
# define __smp_mb() __sync()
# define __smp_rmb() barrier()
# define __smp_wmb() __syncw()
# else
# define __smp_mb() __asm__ __volatile__("sync" : : :"memory")
# define __smp_rmb() __asm__ __volatile__("sync" : : :"memory")
# define __smp_wmb() __asm__ __volatile__("sync" : : :"memory")
# endif
#else
#define __smp_mb() barrier()
#define __smp_rmb() barrier()
#define __smp_wmb() barrier()
#endif
#if defined(CONFIG_WEAK_REORDERING_BEYOND_LLSC) && defined(CONFIG_SMP)
#define __WEAK_LLSC_MB " sync \n"
#else
#define __WEAK_LLSC_MB " \n"
#endif
#define smp_llsc_mb() __asm__ __volatile__(__WEAK_LLSC_MB : : :"memory")
#ifdef CONFIG_CPU_CAVIUM_OCTEON
#define smp_mb__before_llsc() smp_wmb()
#define __smp_mb__before_llsc() __smp_wmb()
/* Cause previous writes to become visible on all CPUs as soon as possible */
#define nudge_writes() __asm__ __volatile__(".set push\n\t" \
".set arch=octeon\n\t" \
"syncw\n\t" \
".set pop" : : : "memory")
#else
#define smp_mb__before_llsc() smp_llsc_mb()
#define __smp_mb__before_llsc() smp_llsc_mb()
#define nudge_writes() mb()
#endif
#define __smp_mb__before_atomic() __smp_mb__before_llsc()
#define __smp_mb__after_atomic() smp_llsc_mb()
/*
* Some Loongson 3 CPUs have a bug wherein execution of a memory access (load,
* store or pref) in between an ll & sc can cause the sc instruction to
* erroneously succeed, breaking atomicity. Whilst it's unusual to write code
* containing such sequences, this bug bites harder than we might otherwise
* expect due to reordering & speculation:
*
* 1) A memory access appearing prior to the ll in program order may actually
* be executed after the ll - this is the reordering case.
*
* In order to avoid this we need to place a memory barrier (ie. a sync
* instruction) prior to every ll instruction, in between it & any earlier
* memory access instructions. Many of these cases are already covered by
* smp_mb__before_llsc() but for the remaining cases, typically ones in
* which multiple CPUs may operate on a memory location but ordering is not
* usually guaranteed, we use loongson_llsc_mb() below.
*
* This reordering case is fixed by 3A R2 CPUs, ie. 3A2000 models and later.
*
* 2) If a conditional branch exists between an ll & sc with a target outside
* of the ll-sc loop, for example an exit upon value mismatch in cmpxchg()
* or similar, then misprediction of the branch may allow speculative
* execution of memory accesses from outside of the ll-sc loop.
*
* In order to avoid this we need a memory barrier (ie. a sync instruction)
* at each affected branch target, for which we also use loongson_llsc_mb()
* defined below.
*
* This case affects all current Loongson 3 CPUs.
*/
#ifdef CONFIG_CPU_LOONGSON3_WORKAROUNDS /* Loongson-3's LLSC workaround */
#define loongson_llsc_mb() __asm__ __volatile__(__WEAK_LLSC_MB : : :"memory")
#else
#define loongson_llsc_mb() do { } while (0)
#endif
#include <asm-generic/barrier.h>
#endif /* __ASM_BARRIER_H */
|
