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cpufreq: speedstep-lib: Use monotonic clock

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Wall time obtained from do_gettimeofday is susceptible to sudden jumps due to
user setting the time or due to NTP.

Monotonic time is constantly increasing time better suited for comparing two
timestamps.

Signed-off-by: Abhilash Jindal <klock.android@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Abhilash Jindal 2015-08-11 12:01:22 -04:00 committed by Rafael J. Wysocki
parent 309d0631cc
commit 72e624de6e
1 changed files with 4 additions and 5 deletions
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9
drivers/cpufreq/speedstep-lib.c
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@ -386,7 +386,7 @@ unsigned int speedstep_get_freqs(enum speedstep_processor processor,
unsigned int prev_speed;
unsigned int ret = 0;
unsigned long flags;
struct timeval tv1, tv2;
ktime_t tv1, tv2;
if ((!processor) || (!low_speed) || (!high_speed) || (!set_state))
return -EINVAL;
@ -415,14 +415,14 @@ unsigned int speedstep_get_freqs(enum speedstep_processor processor,
/* start latency measurement */
if (transition_latency)
do_gettimeofday(&tv1);
tv1 = ktime_get();
/* switch to high state */
set_state(SPEEDSTEP_HIGH);
/* end latency measurement */
if (transition_latency)
do_gettimeofday(&tv2);
tv2 = ktime_get();
*high_speed = speedstep_get_frequency(processor);
if (!*high_speed) {
@ -442,8 +442,7 @@ unsigned int speedstep_get_freqs(enum speedstep_processor processor,
set_state(SPEEDSTEP_LOW);
if (transition_latency) {
*transition_latency = (tv2.tv_sec - tv1.tv_sec) * USEC_PER_SEC +
tv2.tv_usec - tv1.tv_usec;
*transition_latency = ktime_to_us(ktime_sub(tv2, tv1));
pr_debug("transition latency is %u uSec\n", *transition_latency);
/* convert uSec to nSec and add 20% for safety reasons */