Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * Smp timebase synchronization for ppc. | |
3 | * | |
4 | * Copyright (C) 2003 Samuel Rydh (samuel@ibrium.se) | |
5 | * | |
6 | */ | |
7 | ||
1da177e4 LT |
8 | #include <linux/kernel.h> |
9 | #include <linux/sched.h> | |
10 | #include <linux/smp.h> | |
11 | #include <linux/unistd.h> | |
5a0e3ad6 | 12 | #include <linux/slab.h> |
60063497 | 13 | #include <linux/atomic.h> |
1da177e4 LT |
14 | #include <asm/smp.h> |
15 | #include <asm/time.h> | |
16 | ||
17 | #define NUM_ITER 300 | |
18 | ||
19 | enum { | |
20 | kExit=0, kSetAndTest, kTest | |
21 | }; | |
22 | ||
23 | static struct { | |
8ad200d7 PM |
24 | volatile u64 tb; |
25 | volatile u64 mark; | |
1da177e4 LT |
26 | volatile int cmd; |
27 | volatile int handshake; | |
8ad200d7 | 28 | int filler[2]; |
1da177e4 LT |
29 | |
30 | volatile int ack; | |
31 | int filler2[7]; | |
32 | ||
33 | volatile int race_result; | |
34 | } *tbsync; | |
35 | ||
36 | static volatile int running; | |
37 | ||
cad5cef6 | 38 | static void enter_contest(u64 mark, long add) |
1da177e4 | 39 | { |
8ad200d7 | 40 | while (get_tb() < mark) |
1da177e4 LT |
41 | tbsync->race_result = add; |
42 | } | |
43 | ||
cad5cef6 | 44 | void smp_generic_take_timebase(void) |
1da177e4 LT |
45 | { |
46 | int cmd; | |
8ad200d7 | 47 | u64 tb; |
467c3780 | 48 | unsigned long flags; |
1da177e4 | 49 | |
467c3780 | 50 | local_irq_save(flags); |
8ad200d7 PM |
51 | while (!running) |
52 | barrier(); | |
1da177e4 LT |
53 | rmb(); |
54 | ||
8ad200d7 | 55 | for (;;) { |
1da177e4 | 56 | tbsync->ack = 1; |
8ad200d7 PM |
57 | while (!tbsync->handshake) |
58 | barrier(); | |
1da177e4 LT |
59 | rmb(); |
60 | ||
61 | cmd = tbsync->cmd; | |
62 | tb = tbsync->tb; | |
8ad200d7 | 63 | mb(); |
1da177e4 | 64 | tbsync->ack = 0; |
8ad200d7 PM |
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); | |
1da177e4 | 73 | } |
467c3780 | 74 | local_irq_restore(flags); |
1da177e4 LT |
75 | } |
76 | ||
cad5cef6 | 77 | static int start_contest(int cmd, long offset, int num) |
1da177e4 LT |
78 | { |
79 | int i, score=0; | |
8ad200d7 | 80 | u64 tb; |
9a06c3b1 | 81 | u64 mark; |
1da177e4 LT |
82 | |
83 | tbsync->cmd = cmd; | |
84 | ||
85 | local_irq_disable(); | |
8ad200d7 PM |
86 | for (i = -3; i < num; ) { |
87 | tb = get_tb() + 400; | |
1da177e4 LT |
88 | tbsync->tb = tb + offset; |
89 | tbsync->mark = mark = tb + 400; | |
90 | ||
91 | wmb(); | |
92 | ||
93 | tbsync->handshake = 1; | |
8ad200d7 PM |
94 | while (tbsync->ack) |
95 | barrier(); | |
1da177e4 | 96 | |
8ad200d7 PM |
97 | while (get_tb() <= tb) |
98 | barrier(); | |
1da177e4 | 99 | tbsync->handshake = 0; |
8ad200d7 | 100 | enter_contest(mark, 1); |
1da177e4 | 101 | |
8ad200d7 PM |
102 | while (!tbsync->ack) |
103 | barrier(); | |
1da177e4 | 104 | |
8ad200d7 | 105 | if (i++ > 0) |
1da177e4 LT |
106 | score += tbsync->race_result; |
107 | } | |
108 | local_irq_enable(); | |
109 | return score; | |
110 | } | |
111 | ||
cad5cef6 | 112 | void smp_generic_give_timebase(void) |
1da177e4 LT |
113 | { |
114 | int i, score, score2, old, min=0, max=5000, offset=1000; | |
115 | ||
a6a8e009 | 116 | pr_debug("Software timebase sync\n"); |
1da177e4 LT |
117 | |
118 | /* if this fails then this kernel won't work anyway... */ | |
f8485350 | 119 | tbsync = kzalloc( sizeof(*tbsync), GFP_KERNEL ); |
1da177e4 LT |
120 | mb(); |
121 | running = 1; | |
122 | ||
8ad200d7 PM |
123 | while (!tbsync->ack) |
124 | barrier(); | |
1da177e4 | 125 | |
a6a8e009 | 126 | pr_debug("Got ack\n"); |
1da177e4 LT |
127 | |
128 | /* binary search */ | |
8ad200d7 PM |
129 | for (old = -1; old != offset ; offset = (min+max) / 2) { |
130 | score = start_contest(kSetAndTest, offset, NUM_ITER); | |
1da177e4 | 131 | |
a6a8e009 | 132 | pr_debug("score %d, offset %d\n", score, offset ); |
1da177e4 LT |
133 | |
134 | if( score > 0 ) | |
135 | max = offset; | |
136 | else | |
137 | min = offset; | |
138 | old = offset; | |
139 | } | |
8ad200d7 PM |
140 | score = start_contest(kSetAndTest, min, NUM_ITER); |
141 | score2 = start_contest(kSetAndTest, max, NUM_ITER); | |
1da177e4 | 142 | |
a6a8e009 BH |
143 | pr_debug("Min %d (score %d), Max %d (score %d)\n", |
144 | min, score, max, score2); | |
8ad200d7 PM |
145 | score = abs(score); |
146 | score2 = abs(score2); | |
1da177e4 LT |
147 | offset = (score < score2) ? min : max; |
148 | ||
149 | /* guard against inaccurate mttb */ | |
8ad200d7 PM |
150 | for (i = 0; i < 10; i++) { |
151 | start_contest(kSetAndTest, offset, NUM_ITER/10); | |
1da177e4 | 152 | |
8ad200d7 | 153 | if ((score2 = start_contest(kTest, offset, NUM_ITER)) < 0) |
1da177e4 | 154 | score2 = -score2; |
8ad200d7 | 155 | if (score2 <= score || score2 < 20) |
1da177e4 LT |
156 | break; |
157 | } | |
a6a8e009 | 158 | pr_debug("Final offset: %d (%d/%d)\n", offset, score2, NUM_ITER ); |
1da177e4 LT |
159 | |
160 | /* exiting */ | |
161 | tbsync->cmd = kExit; | |
162 | wmb(); | |
163 | tbsync->handshake = 1; | |
8ad200d7 PM |
164 | while (tbsync->ack) |
165 | barrier(); | |
1da177e4 | 166 | tbsync->handshake = 0; |
8ad200d7 | 167 | kfree(tbsync); |
1da177e4 LT |
168 | tbsync = NULL; |
169 | running = 0; | |
170 | } |