Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* |
2 | * Smp timebase synchronization for ppc. | |
3 | * | |
4 | * Copyright (C) 2003 Samuel Rydh (samuel@ibrium.se) | |
5 | * | |
6 | */ | |
7 | ||
8 | #include <linux/config.h> | |
9 | #include <linux/kernel.h> | |
10 | #include <linux/sched.h> | |
11 | #include <linux/smp.h> | |
12 | #include <linux/unistd.h> | |
13 | #include <linux/init.h> | |
14 | #include <asm/atomic.h> | |
15 | #include <asm/smp.h> | |
16 | #include <asm/time.h> | |
17 | ||
18 | #define NUM_ITER 300 | |
19 | ||
20 | enum { | |
21 | kExit=0, kSetAndTest, kTest | |
22 | }; | |
23 | ||
24 | static struct { | |
25 | volatile long tb; | |
26 | volatile long mark; | |
27 | volatile int cmd; | |
28 | volatile int handshake; | |
29 | int filler[3]; | |
30 | ||
31 | volatile int ack; | |
32 | int filler2[7]; | |
33 | ||
34 | volatile int race_result; | |
35 | } *tbsync; | |
36 | ||
37 | static volatile int running; | |
38 | ||
39 | static void __devinit | |
40 | enter_contest( long mark, long add ) | |
41 | { | |
42 | while( (long)(mftb() - mark) < 0 ) | |
43 | tbsync->race_result = add; | |
44 | } | |
45 | ||
46 | void __devinit | |
47 | smp_generic_take_timebase( void ) | |
48 | { | |
49 | int cmd; | |
50 | long tb; | |
51 | ||
52 | local_irq_disable(); | |
53 | while( !running ) | |
54 | ; | |
55 | rmb(); | |
56 | ||
57 | for( ;; ) { | |
58 | tbsync->ack = 1; | |
59 | while( !tbsync->handshake ) | |
60 | ; | |
61 | rmb(); | |
62 | ||
63 | cmd = tbsync->cmd; | |
64 | tb = tbsync->tb; | |
65 | tbsync->ack = 0; | |
66 | if( cmd == kExit ) | |
67 | return; | |
68 | ||
69 | if( cmd == kSetAndTest ) { | |
70 | while( tbsync->handshake ) | |
71 | ; | |
72 | asm volatile ("mttbl %0" :: "r" (tb & 0xfffffffful) ); | |
73 | asm volatile ("mttbu %0" :: "r" (tb >> 32) ); | |
74 | } else { | |
75 | while( tbsync->handshake ) | |
76 | ; | |
77 | } | |
78 | enter_contest( tbsync->mark, -1 ); | |
79 | } | |
80 | local_irq_enable(); | |
81 | } | |
82 | ||
83 | static int __devinit | |
84 | start_contest( int cmd, long offset, long num ) | |
85 | { | |
86 | int i, score=0; | |
87 | long tb, mark; | |
88 | ||
89 | tbsync->cmd = cmd; | |
90 | ||
91 | local_irq_disable(); | |
92 | for( i=-3; i<num; ) { | |
93 | tb = (long)mftb() + 400; | |
94 | tbsync->tb = tb + offset; | |
95 | tbsync->mark = mark = tb + 400; | |
96 | ||
97 | wmb(); | |
98 | ||
99 | tbsync->handshake = 1; | |
100 | while( tbsync->ack ) | |
101 | ; | |
102 | ||
103 | while( (long)(mftb() - tb) <= 0 ) | |
104 | ; | |
105 | tbsync->handshake = 0; | |
106 | enter_contest( mark, 1 ); | |
107 | ||
108 | while( !tbsync->ack ) | |
109 | ; | |
110 | ||
111 | if ((tbsync->tb ^ (long)mftb()) & 0x8000000000000000ul) | |
112 | continue; | |
113 | if( i++ > 0 ) | |
114 | score += tbsync->race_result; | |
115 | } | |
116 | local_irq_enable(); | |
117 | return score; | |
118 | } | |
119 | ||
120 | void __devinit | |
121 | smp_generic_give_timebase( void ) | |
122 | { | |
123 | int i, score, score2, old, min=0, max=5000, offset=1000; | |
124 | ||
125 | printk("Synchronizing timebase\n"); | |
126 | ||
127 | /* if this fails then this kernel won't work anyway... */ | |
128 | tbsync = kmalloc( sizeof(*tbsync), GFP_KERNEL ); | |
129 | memset( tbsync, 0, sizeof(*tbsync) ); | |
130 | mb(); | |
131 | running = 1; | |
132 | ||
133 | while( !tbsync->ack ) | |
134 | ; | |
135 | ||
136 | printk("Got ack\n"); | |
137 | ||
138 | /* binary search */ | |
139 | for( old=-1 ; old != offset ; offset=(min+max)/2 ) { | |
140 | score = start_contest( kSetAndTest, offset, NUM_ITER ); | |
141 | ||
142 | printk("score %d, offset %d\n", score, offset ); | |
143 | ||
144 | if( score > 0 ) | |
145 | max = offset; | |
146 | else | |
147 | min = offset; | |
148 | old = offset; | |
149 | } | |
150 | score = start_contest( kSetAndTest, min, NUM_ITER ); | |
151 | score2 = start_contest( kSetAndTest, max, NUM_ITER ); | |
152 | ||
153 | printk( "Min %d (score %d), Max %d (score %d)\n", min, score, max, score2 ); | |
154 | score = abs( score ); | |
155 | score2 = abs( score2 ); | |
156 | offset = (score < score2) ? min : max; | |
157 | ||
158 | /* guard against inaccurate mttb */ | |
159 | for( i=0; i<10; i++ ) { | |
160 | start_contest( kSetAndTest, offset, NUM_ITER/10 ); | |
161 | ||
162 | if( (score2=start_contest(kTest, offset, NUM_ITER)) < 0 ) | |
163 | score2 = -score2; | |
164 | if( score2 <= score || score2 < 20 ) | |
165 | break; | |
166 | } | |
167 | printk("Final offset: %d (%d/%d)\n", offset, score2, NUM_ITER ); | |
168 | ||
169 | /* exiting */ | |
170 | tbsync->cmd = kExit; | |
171 | wmb(); | |
172 | tbsync->handshake = 1; | |
173 | while( tbsync->ack ) | |
174 | ; | |
175 | tbsync->handshake = 0; | |
176 | kfree( tbsync ); | |
177 | tbsync = NULL; | |
178 | running = 0; | |
179 | } |