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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 | /* * Smp timebase synchronization for ppc. * * Copyright (C) 2003 Samuel Rydh (samuel@ibrium.se) * */ #include <linux/kernel.h> #include <linux/sched.h> #include <linux/smp.h> #include <linux/unistd.h> #include <linux/init.h> #include <asm/atomic.h> #include <asm/smp.h> #include <asm/time.h> #define NUM_ITER 300 enum { kExit=0, kSetAndTest, kTest }; static struct { volatile u64 tb; volatile u64 mark; volatile int cmd; volatile int handshake; int filler[2]; volatile int ack; int filler2[7]; volatile int race_result; } *tbsync; static volatile int running; static void __devinit enter_contest(u64 mark, long add) { while (get_tb() < mark) tbsync->race_result = add; } void __devinit smp_generic_take_timebase(void) { int cmd; u64 tb; unsigned long flags; local_irq_save(flags); while (!running) barrier(); rmb(); for (;;) { tbsync->ack = 1; while (!tbsync->handshake) barrier(); rmb(); cmd = tbsync->cmd; tb = tbsync->tb; mb(); tbsync->ack = 0; if (cmd == kExit) break; while (tbsync->handshake) barrier(); if (cmd == kSetAndTest) set_tb(tb >> 32, tb & 0xfffffffful); enter_contest(tbsync->mark, -1); } local_irq_restore(flags); } static int __devinit start_contest(int cmd, long offset, int num) { int i, score=0; u64 tb; u64 mark; tbsync->cmd = cmd; local_irq_disable(); for (i = -3; i < num; ) { tb = get_tb() + 400; tbsync->tb = tb + offset; tbsync->mark = mark = tb + 400; wmb(); tbsync->handshake = 1; while (tbsync->ack) barrier(); while (get_tb() <= tb) barrier(); tbsync->handshake = 0; enter_contest(mark, 1); while (!tbsync->ack) barrier(); if (i++ > 0) score += tbsync->race_result; } local_irq_enable(); return score; } void __devinit smp_generic_give_timebase(void) { int i, score, score2, old, min=0, max=5000, offset=1000; printk("Synchronizing timebase\n"); /* if this fails then this kernel won't work anyway... */ tbsync = kzalloc( sizeof(*tbsync), GFP_KERNEL ); mb(); running = 1; while (!tbsync->ack) barrier(); printk("Got ack\n"); /* binary search */ for (old = -1; old != offset ; offset = (min+max) / 2) { score = start_contest(kSetAndTest, offset, NUM_ITER); printk("score %d, offset %d\n", score, offset ); if( score > 0 ) max = offset; else min = offset; old = offset; } score = start_contest(kSetAndTest, min, NUM_ITER); score2 = start_contest(kSetAndTest, max, NUM_ITER); printk("Min %d (score %d), Max %d (score %d)\n", min, score, max, score2); score = abs(score); score2 = abs(score2); offset = (score < score2) ? min : max; /* guard against inaccurate mttb */ for (i = 0; i < 10; i++) { start_contest(kSetAndTest, offset, NUM_ITER/10); if ((score2 = start_contest(kTest, offset, NUM_ITER)) < 0) score2 = -score2; if (score2 <= score || score2 < 20) break; } printk("Final offset: %d (%d/%d)\n", offset, score2, NUM_ITER ); /* exiting */ tbsync->cmd = kExit; wmb(); tbsync->handshake = 1; while (tbsync->ack) barrier(); tbsync->handshake = 0; kfree(tbsync); tbsync = NULL; running = 0; } |