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#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <asm/timer.h>
#ifdef CONFIG_HPET_TIMER
/*
* HPET memory read is slower than tsc reads, but is more dependable as it
* always runs at constant frequency and reduces complexity due to
* cpufreq. So, we prefer HPET timer to tsc based one. Also, we cannot use
* timer_pit when HPET is active. So, we default to timer_tsc.
*/
#endif
/* list of timers, ordered by preference, NULL terminated */
static struct init_timer_opts* __initdata timers[] = {
#ifdef CONFIG_X86_CYCLONE_TIMER
&timer_cyclone_init,
#endif
#ifdef CONFIG_HPET_TIMER
&timer_hpet_init,
#endif
#ifdef CONFIG_X86_PM_TIMER
&timer_pmtmr_init,
#endif
&timer_tsc_init,
&timer_pit_init,
NULL,
};
static char clock_override[10] __initdata;
static int __init clock_setup(char* str)
{
if (str)
strlcpy(clock_override, str, sizeof(clock_override));
return 1;
}
__setup("clock=", clock_setup);
/* The chosen timesource has been found to be bad.
* Fall back to a known good timesource (the PIT)
*/
void clock_fallback(void)
{
cur_timer = &timer_pit;
}
/* iterates through the list of timers, returning the first
* one that initializes successfully.
*/
struct timer_opts* __init select_timer(void)
{
int i = 0;
/* find most preferred working timer */
while (timers[i]) {
if (timers[i]->init)
if (timers[i]->init(clock_override) == 0)
return timers[i]->opts;
++i;
}
panic("select_timer: Cannot find a suitable timer\n");
return NULL;
}
int read_current_timer(unsigned long *timer_val)
{
if (cur_timer->read_timer) {
*timer_val = cur_timer->read_timer();
return 0;
}
return -1;
}
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