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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Smp timebase synchronization for ppc.
4 *
5 * Copyright (C) 2003 Samuel Rydh (samuel@ibrium.se)
6 *
7 */
8
9#include <linux/kernel.h>
10#include <linux/sched.h>
11#include <linux/smp.h>
12#include <linux/unistd.h>
13#include <linux/slab.h>
14#include <linux/atomic.h>
15#include <asm/smp.h>
16#include <asm/time.h>
17
18#define NUM_ITER 300
19
20enum {
21 kExit=0, kSetAndTest, kTest
22};
23
24static struct {
25 volatile u64 tb;
26 volatile u64 mark;
27 volatile int cmd;
28 volatile int handshake;
29 int filler[2];
30
31 volatile int ack;
32 int filler2[7];
33
34 volatile int race_result;
35} *tbsync;
36
37static volatile int running;
38
39static void enter_contest(u64 mark, long add)
40{
41 while (get_tb() < mark)
42 tbsync->race_result = add;
43}
44
45void smp_generic_take_timebase(void)
46{
47 int cmd;
48 u64 tb;
49 unsigned long flags;
50
51 local_irq_save(flags);
52 while (!running)
53 barrier();
54 rmb();
55
56 for (;;) {
57 tbsync->ack = 1;
58 while (!tbsync->handshake)
59 barrier();
60 rmb();
61
62 cmd = tbsync->cmd;
63 tb = tbsync->tb;
64 mb();
65 tbsync->ack = 0;
66 if (cmd == kExit)
67 break;
68
69 while (tbsync->handshake)
70 barrier();
71 if (cmd == kSetAndTest)
72 set_tb(tb >> 32, tb & 0xfffffffful);
73 enter_contest(tbsync->mark, -1);
74 }
75 local_irq_restore(flags);
76}
77
78static int start_contest(int cmd, long offset, int num)
79{
80 int i, score=0;
81 u64 tb;
82 u64 mark;
83
84 tbsync->cmd = cmd;
85
86 local_irq_disable();
87 for (i = -3; i < num; ) {
88 tb = get_tb() + 400;
89 tbsync->tb = tb + offset;
90 tbsync->mark = mark = tb + 400;
91
92 wmb();
93
94 tbsync->handshake = 1;
95 while (tbsync->ack)
96 barrier();
97
98 while (get_tb() <= tb)
99 barrier();
100 tbsync->handshake = 0;
101 enter_contest(mark, 1);
102
103 while (!tbsync->ack)
104 barrier();
105
106 if (i++ > 0)
107 score += tbsync->race_result;
108 }
109 local_irq_enable();
110 return score;
111}
112
113void smp_generic_give_timebase(void)
114{
115 int i, score, score2, old, min=0, max=5000, offset=1000;
116
117 pr_debug("Software timebase sync\n");
118
119 /* if this fails then this kernel won't work anyway... */
120 tbsync = kzalloc( sizeof(*tbsync), GFP_KERNEL );
121 mb();
122 running = 1;
123
124 while (!tbsync->ack)
125 barrier();
126
127 pr_debug("Got ack\n");
128
129 /* binary search */
130 for (old = -1; old != offset ; offset = (min+max) / 2) {
131 score = start_contest(kSetAndTest, offset, NUM_ITER);
132
133 pr_debug("score %d, offset %d\n", score, offset );
134
135 if( score > 0 )
136 max = offset;
137 else
138 min = offset;
139 old = offset;
140 }
141 score = start_contest(kSetAndTest, min, NUM_ITER);
142 score2 = start_contest(kSetAndTest, max, NUM_ITER);
143
144 pr_debug("Min %d (score %d), Max %d (score %d)\n",
145 min, score, max, score2);
146 score = abs(score);
147 score2 = abs(score2);
148 offset = (score < score2) ? min : max;
149
150 /* guard against inaccurate mttb */
151 for (i = 0; i < 10; i++) {
152 start_contest(kSetAndTest, offset, NUM_ITER/10);
153
154 if ((score2 = start_contest(kTest, offset, NUM_ITER)) < 0)
155 score2 = -score2;
156 if (score2 <= score || score2 < 20)
157 break;
158 }
159 pr_debug("Final offset: %d (%d/%d)\n", offset, score2, NUM_ITER );
160
161 /* exiting */
162 tbsync->cmd = kExit;
163 wmb();
164 tbsync->handshake = 1;
165 while (tbsync->ack)
166 barrier();
167 tbsync->handshake = 0;
168 kfree(tbsync);
169 tbsync = NULL;
170 running = 0;
171}
1/*
2 * Smp timebase synchronization for ppc.
3 *
4 * Copyright (C) 2003 Samuel Rydh (samuel@ibrium.se)
5 *
6 */
7
8#include <linux/kernel.h>
9#include <linux/sched.h>
10#include <linux/smp.h>
11#include <linux/unistd.h>
12#include <linux/slab.h>
13#include <linux/atomic.h>
14#include <asm/smp.h>
15#include <asm/time.h>
16
17#define NUM_ITER 300
18
19enum {
20 kExit=0, kSetAndTest, kTest
21};
22
23static struct {
24 volatile u64 tb;
25 volatile u64 mark;
26 volatile int cmd;
27 volatile int handshake;
28 int filler[2];
29
30 volatile int ack;
31 int filler2[7];
32
33 volatile int race_result;
34} *tbsync;
35
36static volatile int running;
37
38static void enter_contest(u64 mark, long add)
39{
40 while (get_tb() < mark)
41 tbsync->race_result = add;
42}
43
44void smp_generic_take_timebase(void)
45{
46 int cmd;
47 u64 tb;
48 unsigned long flags;
49
50 local_irq_save(flags);
51 while (!running)
52 barrier();
53 rmb();
54
55 for (;;) {
56 tbsync->ack = 1;
57 while (!tbsync->handshake)
58 barrier();
59 rmb();
60
61 cmd = tbsync->cmd;
62 tb = tbsync->tb;
63 mb();
64 tbsync->ack = 0;
65 if (cmd == kExit)
66 break;
67
68 while (tbsync->handshake)
69 barrier();
70 if (cmd == kSetAndTest)
71 set_tb(tb >> 32, tb & 0xfffffffful);
72 enter_contest(tbsync->mark, -1);
73 }
74 local_irq_restore(flags);
75}
76
77static int start_contest(int cmd, long offset, int num)
78{
79 int i, score=0;
80 u64 tb;
81 u64 mark;
82
83 tbsync->cmd = cmd;
84
85 local_irq_disable();
86 for (i = -3; i < num; ) {
87 tb = get_tb() + 400;
88 tbsync->tb = tb + offset;
89 tbsync->mark = mark = tb + 400;
90
91 wmb();
92
93 tbsync->handshake = 1;
94 while (tbsync->ack)
95 barrier();
96
97 while (get_tb() <= tb)
98 barrier();
99 tbsync->handshake = 0;
100 enter_contest(mark, 1);
101
102 while (!tbsync->ack)
103 barrier();
104
105 if (i++ > 0)
106 score += tbsync->race_result;
107 }
108 local_irq_enable();
109 return score;
110}
111
112void smp_generic_give_timebase(void)
113{
114 int i, score, score2, old, min=0, max=5000, offset=1000;
115
116 pr_debug("Software timebase sync\n");
117
118 /* if this fails then this kernel won't work anyway... */
119 tbsync = kzalloc( sizeof(*tbsync), GFP_KERNEL );
120 mb();
121 running = 1;
122
123 while (!tbsync->ack)
124 barrier();
125
126 pr_debug("Got ack\n");
127
128 /* binary search */
129 for (old = -1; old != offset ; offset = (min+max) / 2) {
130 score = start_contest(kSetAndTest, offset, NUM_ITER);
131
132 pr_debug("score %d, offset %d\n", score, offset );
133
134 if( score > 0 )
135 max = offset;
136 else
137 min = offset;
138 old = offset;
139 }
140 score = start_contest(kSetAndTest, min, NUM_ITER);
141 score2 = start_contest(kSetAndTest, max, NUM_ITER);
142
143 pr_debug("Min %d (score %d), Max %d (score %d)\n",
144 min, score, max, score2);
145 score = abs(score);
146 score2 = abs(score2);
147 offset = (score < score2) ? min : max;
148
149 /* guard against inaccurate mttb */
150 for (i = 0; i < 10; i++) {
151 start_contest(kSetAndTest, offset, NUM_ITER/10);
152
153 if ((score2 = start_contest(kTest, offset, NUM_ITER)) < 0)
154 score2 = -score2;
155 if (score2 <= score || score2 < 20)
156 break;
157 }
158 pr_debug("Final offset: %d (%d/%d)\n", offset, score2, NUM_ITER );
159
160 /* exiting */
161 tbsync->cmd = kExit;
162 wmb();
163 tbsync->handshake = 1;
164 while (tbsync->ack)
165 barrier();
166 tbsync->handshake = 0;
167 kfree(tbsync);
168 tbsync = NULL;
169 running = 0;
170}