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Diffstat (limited to 'arch/i386/kernel/timers/timer.c')
-rw-r--r--arch/i386/kernel/timers/timer.c66
1 files changed, 66 insertions, 0 deletions
diff --git a/arch/i386/kernel/timers/timer.c b/arch/i386/kernel/timers/timer.c
new file mode 100644
index 000000000000..a3d6a288088b
--- /dev/null
+++ b/arch/i386/kernel/timers/timer.c
@@ -0,0 +1,66 @@
1#include <linux/init.h>
2#include <linux/kernel.h>
3#include <linux/string.h>
4#include <asm/timer.h>
5
6#ifdef CONFIG_HPET_TIMER
7/*
8 * HPET memory read is slower than tsc reads, but is more dependable as it
9 * always runs at constant frequency and reduces complexity due to
10 * cpufreq. So, we prefer HPET timer to tsc based one. Also, we cannot use
11 * timer_pit when HPET is active. So, we default to timer_tsc.
12 */
13#endif
14/* list of timers, ordered by preference, NULL terminated */
15static struct init_timer_opts* __initdata timers[] = {
16#ifdef CONFIG_X86_CYCLONE_TIMER
17 &timer_cyclone_init,
18#endif
19#ifdef CONFIG_HPET_TIMER
20 &timer_hpet_init,
21#endif
22#ifdef CONFIG_X86_PM_TIMER
23 &timer_pmtmr_init,
24#endif
25 &timer_tsc_init,
26 &timer_pit_init,
27 NULL,
28};
29
30static char clock_override[10] __initdata;
31
32static int __init clock_setup(char* str)
33{
34 if (str)
35 strlcpy(clock_override, str, sizeof(clock_override));
36 return 1;
37}
38__setup("clock=", clock_setup);
39
40
41/* The chosen timesource has been found to be bad.
42 * Fall back to a known good timesource (the PIT)
43 */
44void clock_fallback(void)
45{
46 cur_timer = &timer_pit;
47}
48
49/* iterates through the list of timers, returning the first
50 * one that initializes successfully.
51 */
52struct timer_opts* __init select_timer(void)
53{
54 int i = 0;
55
56 /* find most preferred working timer */
57 while (timers[i]) {
58 if (timers[i]->init)
59 if (timers[i]->init(clock_override) == 0)
60 return timers[i]->opts;
61 ++i;
62 }
63
64 panic("select_timer: Cannot find a suitable timer\n");
65 return NULL;
66}