Messages in this thread | | | Date | Mon, 25 Feb 2019 14:39:55 +0530 | From | Viresh Kumar <> | Subject | Re: [PATCH V2 4/5] cpufreq: Register notifiers with the PM QoS framework |
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On 25-02-19, 08:58, Qais Yousef wrote: > On 02/25/19 10:01, Viresh Kumar wrote: > > > > + min = dev_pm_qos_read_value(cpu_dev, DEV_PM_QOS_MIN_FREQUENCY); > > > > + max = dev_pm_qos_read_value(cpu_dev, DEV_PM_QOS_MAX_FREQUENCY); > > > > + > > > > + if (min > new_policy->min) > > > > + new_policy->min = min; > > > > + if (max < new_policy->max) > > > > + new_policy->max = max;
> And this is why we need to check here if the PM QoS value doesn't conflict with > the current min/max, right? Until the current notifier code is removed they > could trip over each others.
No. The above if/else block is already removed as part of patch 5/5. It was required because of conflict between userspace specific min/max and qos min/max, which are migrated to use qos by patc 5/5.
The cpufreq notifier mechanism already lets users play with min/max and that is already safe from conflicts.
> It would be nice to add a comment here about PM QoS managing and remembering > values
I am not sure if that would add any value. Some documentation update may be useful for people looking for details though, that I shall do after all the changes get in and things become a bit stable.
> and that we need to be careful that both mechanisms don't trip over > each others until this transient period is over.
The second mechanism will die very very soon once this is merged, migrating them shouldn't be a big challenge AFAICT. I didn't attempt that because I didn't wanted to waste time updating things in case this version also doesn't make sense to others.
> I have a nit too. It would be nice to explicitly state this is > CPU_{MIN,MAX}_FREQUENCY. I can see someone else adding {MIN,MAX}_FREQUENCY for > something elsee (memory maybe?)
This is not CPU specific, but any device. The same interface shall be used by devfreq as well, who wanted to use freq-constraints initially.
> Although I looked at the previous series briefly, but this one looks more > compact and easier to follow, so +1 for that.
Thanks for looking into this Qais.
-- viresh
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