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