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>

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 66cef33c4ec7b4595c80d978c40808833ef8fb86..926a51cb7e52cdf90f52e17cc27a827067515dbe 100644 (file)
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -576,8 +576,17 @@ unsigned int cpufreq_policy_transition_delay_us(struct cpufreq_policy *policy)
 
        latency = policy->cpuinfo.transition_latency / NSEC_PER_USEC;
        if (latency) {
+               unsigned int max_delay_us = 2 * MSEC_PER_SEC;
+
+               /*
+                * 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 (< 10
+                * For platforms that can change the frequency very fast (< 2
                 * us), the above formula gives a decent transition delay. But
                 * for platforms where transition_latency is in milliseconds, it
                 * 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
                 * the frequency.
                 */
-               return min(latency * LATENCY_MULTIPLIER, (unsigned int)(2 * MSEC_PER_SEC));
+               return min(latency * LATENCY_MULTIPLIER, max_delay_us);
        }
 
        return LATENCY_MULTIPLIER;