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BACKPORT: tsc: provide monotonic timer

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Implement the timer_monotonic_get() using the TSC.

Change-Id: I2c09ba2a2e96861255c7bf38291d9f4df004dcc4
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/49751
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
This commit is contained in:
Aaron Durbin 2013-04-29 22:22:55 -05:00 • committed by ChromeBot
commit d04b40cfcf
2 changed files with 44 additions and 0 deletions
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7
src/cpu/x86/Kconfig
View file

@ -25,6 +25,13 @@ config UDELAY_TSC
bool
default n
config TSC_MONOTONIC_TIMER
def_bool n
depends on UDELAY_TSC
select HAVE_MONOTONIC_TIMER
help
Expose monotonic time using the TSC.
config UDELAY_TIMER2
bool
default n

37
src/cpu/x86/tsc/delay_tsc.c
View file

@ -164,3 +164,40 @@ void udelay(unsigned us)
count = rdtscll();
}
}
#if CONFIG_TSC_MONOTONIC_TIMER
#include <timer.h>
static struct monotonic_counter {
int initialized;
struct mono_time time;
uint64_t last_value;
} mono_counter;
void timer_monotonic_get(struct mono_time *mt)
{
uint64_t current_tick;
uint64_t ticks_elapsed;
if (!mono_counter.initialized) {
init_timer();
mono_counter.last_value = rdtscll();
mono_counter.initialized = 1;
}
current_tick = rdtscll();
ticks_elapsed = current_tick - mono_counter.last_value;
/* Update current time and tick values only if a full tick occurred. */
if (ticks_elapsed >= clocks_per_usec) {
uint64_t usecs_elapsed;
usecs_elapsed = ticks_elapsed / clocks_per_usec;
mono_time_add_usecs(&mono_counter.time, (long)usecs_elapsed);
mono_counter.last_value = current_tick;
}
/* Save result. */
*mt = mono_counter.time;
}
#endif