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cpufreq: Honour transition_latency over transition_delay_us 

Some platforms like Arm's Juno can have a high transition latency that
can be larger than the 2ms cap introduced. If a driver reports
a transition_latency that is higher than the cap, then use it as-is.

Update comment s/10/2/ to reflect the new cap of 2ms.

Reported-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Qais Yousef <qyousef@layalina.io>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Qais Yousef 2024-02-27 23:34:52 +00:00 committed by Rafael J. Wysocki
parent d394abcb12
commit a755d0e2d4
1 changed files with 11 additions and 2 deletions
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13
drivers/cpufreq/cpufreq.c
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@ -576,8 +576,17 @@ unsigned int cpufreq_policy_transition_delay_us(struct cpufreq_policy *policy)
latency = policy->cpuinfo.transition_latency / NSEC_PER_USEC; latency = policy->cpuinfo.transition_latency / NSEC_PER_USEC;
if (latency) { if (latency) {
unsigned int max_delay_us = 2 * MSEC_PER_SEC;
/* /*
* For platforms that can change the frequency very fast (< 10 * If the platform already has high transition_latency, use it
* as-is.
*/
if (latency > max_delay_us)
return latency;
/*
* For platforms that can change the frequency very fast (< 2
* us), the above formula gives a decent transition delay. But * us), the above formula gives a decent transition delay. But
* for platforms where transition_latency is in milliseconds, it * for platforms where transition_latency is in milliseconds, it
* ends up giving unrealistic values. * ends up giving unrealistic values.
@ -586,7 +595,7 @@ unsigned int cpufreq_policy_transition_delay_us(struct cpufreq_policy *policy)
* a reasonable amount of time after which we should reevaluate * a reasonable amount of time after which we should reevaluate
* the frequency. * the frequency.
*/ */
return min(latency * LATENCY_MULTIPLIER, (unsigned int)(2 * MSEC_PER_SEC)); return min(latency * LATENCY_MULTIPLIER, max_delay_us);
} }
return LATENCY_MULTIPLIER; return LATENCY_MULTIPLIER;