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Commit 72e624de authored by Abhilash Jindal's avatar Abhilash Jindal Committed by Rafael J. Wysocki
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cpufreq: speedstep-lib: Use monotonic clock 



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: default avatarAbhilash Jindal <klock.android@gmail.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 309d0631

drivers/cpufreq/speedstep-lib.c

+4 −5
Original line number Diff line number Diff line
@@ -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 */